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MicroRNAs: Emerging roles in lipid and lipoprotein metabolism
Abstract
MicroRNAs (miRNAs) regulate gene expression by binding to target mRNAs and control a wide range of biological functions. Recent reports have identified specific miRNAs as major regulators of fatty acid and cholesterol homeostasis. This review examines the biological function of various miRNAs and the emerging evidence linking specific miRNAs to critical pathways in lipid metabolism.
Disruption of lipid balance can lead to metabolic disturbances and thus tight regulation is required to maintain lipid homeostasis. Recent studies have shown key roles for miR-33 and miR-122 in regulation of lipid metabolism, and further evidence implicates miR-370 in regulation of miR-122. In addition, miRNAs involved in adipogenesis (miR-378/378* and miR-27) as well as newly discovered miRNAs such as miR-613, miR-302a, and miR-168 have now been implicated in regulation of lipid metabolism.
Growing evidence support key roles for miRNAs in regulating both cholesterol and fatty acid metabolism, leading to considerable interest in miRNAs as potential drug targets to modulate lipid and lipoprotein metabolism. MiRNA-based therapeutics hold considerable promise in the fight to curtail the growing epidemic of obesity and type 2 diabetes and the associated risk of atherosclerosis.
... Fatty acid β oxidation, atty acid and triacylglycerol biosynthesis [21,32] hsa-miR-378a Adipogenesis, fatty acid and triacylglycerol biosynthesis [7,14,32] of the process, except for the primer and the extracted RNA. Then, to 70 μL of the mix we added 50 µL of each RNA sample. ...
... Fatty acid β oxidation, atty acid and triacylglycerol biosynthesis [21,32] hsa-miR-378a Adipogenesis, fatty acid and triacylglycerol biosynthesis [7,14,32] of the process, except for the primer and the extracted RNA. Then, to 70 μL of the mix we added 50 µL of each RNA sample. ...
... Finally, the possibility exists for selective modification in the degradation rate of circulating exosomes, with subsequent exposure of the enclosed miRNAs to circulating ribonucleases, as a result of exercise-induced metabolite, hormonal or cytokine alterations. miR-33a has been shown to be involved in cholesterol and fatty acid metabolism in the liver of experimental animals [9,14,15,30,32]. Since we are not aware of any reports regarding effects of acute exercise on hepatic cholesterol metabolism and since changes in circulating cholesterol (if any) are attributed to peripheral effects, that is, activation of muscle lipoprotein lipase [24], we turned our attention to how the observed increase in hsa-miR-33a with exercise might affect fatty acid metabolism in the liver. ...
The response of micro-ribonucleic acid (miRNA) expression to exercise has not been studied in saliva, although saliva combines non-invasive collection with the largest number of miRNA species among biological fluids and tissues. Thus, the purpose of this study was to investigate the effect of acute exercise on the expression of 8 human saliva miRNAs involved in lipid metabolism. 19 healthy, physically active men (VO2max, 40.9±1.6 mL·kg(-1)·min(-1), mean±se) performed a 50-min interval exercise program on stationary bicycle (spinning). Saliva samples were collected before and after exercise for miRNA expression analysis by real-time polymerase chain reaction. Statistically significant (p<0.05) changes after exercise were found in 2 of the 8 miRNAs, namely, hsa-miR-33a (fold change, 7.66±2.94; p=0.012), which regulates cholesterol homeostasis and fatty acid metabolism in the liver, and hsa-miR-378a (fold change 0.79±0.11, p=0.048), which regulates energy homeostasis and affects lipogenesis and adipogenesis. These alterations may contribute to our understanding of physiological responses to exercise and the therapeutic potential of exercise against cardiovascular disease, obesity, and the metabolic syndrome. Moreover, our findings open the possibility of noninvasively studying miRNAs that regulate the function of specific organs.
© Georg Thieme Verlag KG Stuttgart · New York.
... 5,6 Micro-RNAs (mi-RNAs) are a group of naturally noncoding RNA molecules. They are approximately [19][20][21][22][23][24][25] nucleotides involved in the regulation of gene expression through RNA silencing via base pairing with the 3ʹuntranslated region (3ʹUTR) of specific mRNAs, 7,8 and fine-tuning in concert with the activity of thousands of genes and, thus, their protein synthesis. 9 Mi-RNAs are detectable in almost all body fluids like serum, plasma, and urine. ...
... 21 Mi-RNA -122 is the most expressed mi-RNA in adult human liver; it resembles about 70% of total mi-RNA, plays an important role in regulating total serum cholesterol and hepatic lipid metabolism, 22 appears to maintain the hepatic cell phenotype, and its inhibition decreases total serum cholesterol and fatty acid (FA) synthesis. 22,23 Moreover, mi-RNA-122 is implicated in NASH development, such as fatty acid synthase (FAS), 3-hydroxy-3-methylglutaryl-CoA reductase (HMGCR), sterol regulatory element-binding protein-1c (SREBP-1c), and sterol regulatory element-binding protein 2 (SREBP-2). 24 The mi-RNA-34a is known to be increased in fatty livers of diet-induced obese mice, 25 and it is implicated in the dysregulation of cholesterol metabolism by targeting the hepatic NAD-dependent deacetylase Sirtuin 1 (SIRT1), which is an important enzyme in the modulation of liver cell apoptosis, metabolic disease, and cancer. ...
Background: It remains essential for patient safety to develop non-invasive diagnostic tools
to diagnose non-alcoholic fatty liver rather than invasive techniques.
Aim: Our case-control study was to address the value of circulating miRNAs as a potential
non-invasive biomarker for the diagnosis of non-alcoholic fatty acid diseases (NAFLD) and
monitoring of disease progression.
Methods: Routine clinical assessment, laboratory tests, anthropometric study, and liver
biopsy results reported for 210 patients with NAFLD (124 patients of simple steatosis (SS)
and 86 of non-alcoholic steatohepatitis (NASH)). Apparently matched for age and gender,
healthy participants (n= 90) were enrolled as a control group. Serum samples were tested for
micro-RNAs (−122, −34a and −99a) by quantitative-PCR.
Results: By histopathology, 124 of the NAFLD group were of SS and 86 patients were of
NASH. Compared with the control subjects, both mi-RNA-122 and −34a levels were increased
in NAFLD (p< 001) and at a cut-off = 1.261, mi-RNA-122 had 92% sensitivity, 85% specificity
to differentiate NAFLD from healthy controls, while mi-RNA-99a were significantly decreased
in NAFLD patients with an observed decrease in disease severity, and at a cut-off = 0.46,
miRNA-99a had 94% sensitivity and 96% specificity to discriminate SS from NASH.
Conclusion: The integration of a circulating mi-RNA panel to diagnose NAFLD cases and
to discriminate between SS and NASH. Large-scale study is still needed to verify the other
mi-RNA profiles and their role in NAFLD pathogenesis and targeting therapy
... 5,6 Micro-RNAs (mi-RNAs) are a group of naturally noncoding RNA molecules. They are approximately [19][20][21][22][23][24][25] nucleotides involved in the regulation of gene expression through RNA silencing via base pairing with the 3ʹuntranslated region (3ʹUTR) of specific mRNAs, 7,8 and fine-tuning in concert with the activity of thousands of genes and, thus, their protein synthesis. 9 Mi-RNAs are detectable in almost all body fluids like serum, plasma, and urine. ...
... 21 Mi-RNA -122 is the most expressed mi-RNA in adult human liver; it resembles about 70% of total mi-RNA, plays an important role in regulating total serum cholesterol and hepatic lipid metabolism, 22 appears to maintain the hepatic cell phenotype, and its inhibition decreases total serum cholesterol and fatty acid (FA) synthesis. 22,23 Moreover, mi-RNA-122 is implicated in NASH development, such as fatty acid synthase (FAS), 3-hydroxy-3-methylglutaryl-CoA reductase (HMGCR), sterol regulatory element-binding protein-1c (SREBP-1c), and sterol regulatory element-binding protein 2 (SREBP-2). 24 The mi-RNA-34a is known to be increased in fatty livers of diet-induced obese mice, 25 and it is implicated in the dysregulation of cholesterol metabolism by targeting the hepatic NAD-dependent deacetylase Sirtuin 1 (SIRT1), which is an important enzyme in the modulation of liver cell apoptosis, metabolic disease, and cancer. ...
Background:
It remains essential for patient safety to develop non-invasive diagnostic tools to diagnose non-alcoholic fatty liver rather than invasive techniques.
Aim:
Our case-control study was to address the value of circulating miRNAs as a potential non-invasive biomarker for the diagnosis of non-alcoholic fatty acid diseases (NAFLD) and monitoring of disease progression.
Methods:
Routine clinical assessment, laboratory tests, anthropometric study, and liver biopsy results reported for 210 patients with NAFLD (124 patients of simple steatosis (SS) and 86 of non-alcoholic steatohepatitis (NASH)). Apparently matched for age and gender, healthy participants (n= 90) were enrolled as a control group. Serum samples were tested for micro-RNAs (-122, -34a and -99a) by quantitative-PCR.
Results:
By histopathology, 124 of the NAFLD group were of SS and 86 patients were of NASH. Compared with the control subjects, both mi-RNA-122 and -34a levels were increased in NAFLD (p< 001) and at a cut-off = 1.261, mi-RNA-122 had 92% sensitivity, 85% specificity to differentiate NAFLD from healthy controls, while mi-RNA-99a were significantly decreased in NAFLD patients with an observed decrease in disease severity, and at a cut-off = 0.46, miRNA-99a had 94% sensitivity and 96% specificity to discriminate SS from NASH.
Conclusion:
The integration of a circulating mi-RNA panel to diagnose NAFLD cases and to discriminate between SS and NASH. Large-scale study is still needed to verify the other mi-RNA profiles and their role in NAFLD pathogenesis and targeting therapy.
... It is well appreciated nowadays that miRNAs play important roles in atherogenesis [10]. It became understood that miRNAs are crucially involved in the regulation of cholesterol and lipoprotein homeostasis [11][12][13][14][15][16][17][18][19][20][21][22][23][24]. The complexities of interplay of different miRNAs in cholesterol and lipid homeostasis are highlighted in a number of comprehensive review articles [10][11][12][13][14][15][16][17][18][19][20][21][22][23][24]. ...
... It became understood that miRNAs are crucially involved in the regulation of cholesterol and lipoprotein homeostasis [11][12][13][14][15][16][17][18][19][20][21][22][23][24]. The complexities of interplay of different miRNAs in cholesterol and lipid homeostasis are highlighted in a number of comprehensive review articles [10][11][12][13][14][15][16][17][18][19][20][21][22][23][24]. ...
Chemokines play a significant role in initial and advanced steps of atherogenesis. In early steps, chemokines control the adhesion of leukocytes to endothelial cells (ECs) followed by transmigration of monocytes and their deposition in the intima where they differentiate to proinflammatory macrophages. Except proinflammatory activity, chemokines are responsible for homeostasis and homing of progenitor cells. Recently, microRNAs (miRs) were found to control expression and activity of chemokines in ECs, vascular smooth muscle cells (VSMCs), and macrophages at different steps of atherogenesis. Expression of the proatherogenic chemokine CXCL1 is suppressed by miR-181 that down-regulates nuclear transcription factor NF-kB stimulation in ECs therefore weakening the adhesiveness of the endothelium for monocytes. MiR-126 activates the endothelial production of a chemokine CXCL12 via self-multiplying feedback loop to promote re-endothelialization and support lesion stability. MiR-155 is proatherogenic by induction of the inflammatory chemokine CCL2 in macrophages. In fact, chemokines, their receptors, and relevant miRs form a complex network that exerts pro- and anti-inflammatory properties in vascular cells during different steps of atherogenic process. Obtaining a new knowledge about complicated relations between miRs and chemokines may create prerequisites for development of novel therapeutic approaches to treat atherogenesis.
... In recent years, miRNAs have attracted a lot of attention as regulators of cellular pathways involved in adipose tissue development, including proliferation, differentiation, apoptosis, and regulation of gene expression [12], MiRNAs are small, 22-nucleotide RNAs that act as regulatory and modifying factors in numerous pathways. Some miRNAs have been shown to have anti-adipogenic activities, with down-regulation in obesity, while others are pro-adipogenic agents that are up-regulated during adipocyte differentiation [13,14]. ...
Objectives:
Obesity is a major global health issue, resulting in significant costs and increased mortality rates. Finding effective treatments for obesity is therefore essential. This study investigated the combined effects of L-Carnitine (LC) and Conjugated Linoleic Acid (CLA) on weight loss and adipose tissue microRNA levels.
Subjects /methods:
Forty male Wistar rats weighing 150-200 g and about 8 weeks old were fed either a normal fat diet (NFD) or a high-fat diet (HFD) for 8 weeks. Afterwards, the HFD group was randomly divided into four subgroups: control, LC (200 mg kg-1), CLA (500 mg kg-1), and both (n = 8 in each group). The study lasted for an additional 4 weeks. The animals' weights were recorded regularly, and after 12 weeks, miRNAs were extracted from epididymal adipose tissue and analysed using real-time PCR. The miRNA expression levels of miR-27a and miR-143 were compared between groups using Kolmogorov-Smirnov and one-way ANOVA tests in SPSS software.
Results:
At the end of the first 8 weeks, the HFD group weighed significantly more than the NFD group. LC significantly decreased weight gain (4.2%) compared to the control group, whereas CLA alone (3.5%) or in combination with LC (3.1%) did not significantly slow weight gain. Real-time PCR results showed that the HFD group had higher miR-143 levels and lower miR-27a levels compared to the NFD group. LC and CLA increased miR-27a expression after 4 weeks, but their combination decreased miR-27a expression. CLA alone reduced miR-143 expression, whereas LC had almost no effect. Their combination also reduced miR-143 expression.
Conclusion:
CLA and LC, which are considered weight loss supplements, can potentially regulate metabolism and cellular pathways. However, their combination did not show a synergistic effect on weight loss, possibly due to the reduction in miR-27a expression. Further studies are needed to evaluate the effects of combined fat burners on obesity treatment.
... The integrative role of microRNAs (miRNAs)-small (22-nucleotide) noncoding RNAs that regulate genes by binding to the 3 -untranslated region (UTR) of target mRNA [27]-in lipid metabolism cannot be ignored. Recent studies have demonstrated the key role of miRNAs in regulating lipid metabolism and many important miRNAs, such as miR-33, miR-122, miR-370, and miR-27 [27,28]. Importantly, miR-122 plays a role in the regulation of fatty acid and triglyceride biosynthesis, such as fatty acid synthesis (FAS), and in controlling the levels of acetyl-CoA carboxylase 1 (ACC-1) and sterol regulatory elementbinding protein 1c (SREBP-1c) and the expression of many genes that regulate fatty acid β-oxidation [29]. ...
Background:
Lung cancer remains a leading cause of cancer-related death, with an annual global mortality rate of 18.4%. Despite advances in diagnostic and therapeutic technologies, non-small cell lung carcinoma (NSCLC) continues to be characterized by a poor prognosis. This may be associated with the enrichment of cancer stem cells (CSCs) and the development of chemoresistance-a double-edged challenge that continues to impede the improvement of long-term outcomes. Metabolic reprogramming is a new hallmark of cancer. Sterol regulatory element-binding proteins (SREBPs) play crucial regulatory roles in the synthesis and uptake of cholesterol, fatty acids, and phospholipids. Recent evidence has demonstrated that SREBP-1 is upregulated in several cancer types. However, its role in lung cancer remains unclear.
Objective:
This study investigated the role of SREBP-1 in NSCLC biology, progression, and therapeutic response and explored the therapeutic exploitability of SREBP-1 and SREBP-1-dependent oncometabolic signaling and miRNA epigenetic regulation.
Methods:
We analyzed SREBP-1 levels and biological functions in clinical samples and the human NSCLC cell lines H441 and A549 through shRNA-based knock down of SREBP function, cisplatin-resistant clone generation, immunohistochemical staining of clinical samples, and cell viability, sphere-formation, Western blot, and quantitative PCR assays. We conducted in-silico analysis of miRNA expression in NSCLC samples by using the Gene Expression Omnibus (GSE102286) database.
Results:
We demonstrated that SREBP-1 and SCAP are highly expressed in NSCLC and are positively correlated with the aggressive phenotypes of NSCLC cells. In addition, downregulation of the expression of tumor-suppressing hsa-miR-497-5p, which predictively targets SREBP-1, was observed. We also demonstrated that SREBP-1/SCAP/FASN lipogenic signaling plays a key role in CSCs-like and chemoresistant NSCLC phenotypes, especially because the fatostatin or shRNA targeting of SREBP-1 significantly suppressed the viability, cisplatin resistance, and cancer stemness of NSCLC cells and because treatment induced the expression of hsa-miR-497.
Conclusion:
Targeting the SREBP-1/hsa-miR-497 signaling axis is a potentially effective anticancer therapeutic strategy for NSCLC.
... Therefore, we focused on the relationship between polyphenols and miRNAs that may have an impact on liver disease and diseases caused by MAFLD (Fig. 2). [61][62][63][64] Lipid metabolism (cholesterol, VLDL, TG, HMGCR), carcinogenesis miRNA -10b [65] Lipid metabolism (PPAR-α) miRNA -33 [66][67][68] ABCA1 transport, ABCG1, Niemann Pick (NP) -C1, insulin signal pathway miRNA -34 [6,21,61,[69][70][71] AMPK phosphorylation, miR-34a/SIRT1/p53 activation, MAFLD progression, lipid metabolism miRNA -192 [72,73] MAFLD progression miRNA -214-5p [74] MAFLD progression miRNA -27a/b [75] Lipid metabolism miRNA -24 [76] Lipid metabolism (Insig1) miRNA -451 [77] Inflammation miRNA -1290, miRNA -27b-3p [78] Variable miRNA -192-5p [79] Lipid metabolism (SCD-1) ...
Metabolic-associated fatty liver disease (MAFLD) is a public health problem that is increasingly recognized, currently affecting up to a quarter of the world’s adult population. Although a biopsy is the current gold standard to diagnose MAFLD, there are potentially serious complications, making it inadequate. Thus far, noninvasive methods have not been able to determine the stage and the subtype of MAFLD. The development and prognosis of MAFLD are modulated by epigenetic factors, including microRNAs (miRNAs), which may be potential biomarkers for MAFLD. Polyphenols, found in many fruits and vegetables, may be useful, as they alter gene expression with epigenetic factors, such as miRNAs. This review presents an overview of the relationship between polyphenols and miRNAs in MAFLD. The literature suggests that miRNAs could be used as a diagnostic method for MAFLD, especially miRNA-122 and miRNA-34a. However, though it has been demonstrated that polyphenols may contribute to improving MAFLD, to our knowledge, no study to date has shown the relationship between polyphenols and miRNAs in MAFLD. The exact mechanisms of polyphenols on miRNAs in MAFLD remain unclear. Future studies may provide hope for diet therapy for MAFLD patients as well as the development of polyphenol-related foods or drugs that target miRNAs to treat MAFLD.
... MiRNAs form a big group of small non-coding RNAs with 19-23 nucleotides, which could bind to the 3′-UTR region of corresponding messenger RNAs (mRNAs) to suppress their protein expression [10][11][12]. MiRNAs have been observed to implicate in various cellular processes, such as cell apoptosis, lipid metabolisms, malignant transformations and cell differentiation [13][14][15]. For osteoarthritis, accumulative evidence suggests that many types of miRNAs could alleviate progressions of osteoarthritis, such as miR-140 [16], miR-130a [17], miR-16-5p [18] and so on [19][20][21]. ...
Background
Osteoarthritis (OA) is a commonly known prevalent joint disease, with limited therapeutic methods. This study aimed to investigate the functions of miRNA-132 (miR-132) in the modulation of PTEN/PI3K/AKT signaling pathway in the development and progression of osteoarthritis.
Methods
Eight male osteoarthritic patients and eight healthy males were recruited. Male Sprague Dawley (SD) rats were used for cellular experiments. QRT-PCR was performed to detect the expression levels of miR-132, PTEN, PI3K and AKT. MTT assay and apoptosis assay were carried out to measure the cell proliferation rate and cell apoptosis rate, respectively. Western blotting was employed to detect the protein expression of related RNAs and inflammatory factors.
Results
In osteoarthritic patients, the expression level of miR-132 was decreased, compared with that in the normal group. Over-expression of miR-132 elevated cell proliferation and decreased apoptosis of chondrocytes. Down-regulation of miR-132 decreased cell proliferation and induced apoptosis in chondrocytes. In addition, down-regulation of miR-132 promoted the expression of Bax protein and activated caspase-3/9, increased inflammation divisors. PTEN inhibitor antagonized the destructive effect of the miR-132 inhibitor on cell proliferation of chondrocytes. PI3K inhibitor increased the destructive effect of the miR-132 inhibitor on osteoarthritis.
Conclusion
In conclusion, miR-132 is an important regulator of osteoarthritis in chondrocytes through the PTEN/PI3K/AKT signaling pathway.
... About 100 different miRNAs are expressed differentially in cases of NASH in humans [103] and alterations in miRNA-29c, miRNA-34a, miRNA-200b and miRNA-155 are due to methyl-donor deficiencies [104]. In humans, miRNA-122 is largely expressed in hepatocytes but under expressed in NASH [104] and therefore is proposed to be the potential target for treatment of dyslipidemia [105] and high cholesterol [106]. Using adipocyte models, our group reported that twelve different adipocyte-derived miRNAs targeting peroxisome proliferator-activated receptor gamma (PPARγ) (miRNA-31, miRNA-130b and miRNA-23a), adipocyte differentiation (miRNA-143, miRNA-145, miRNA-146a, miRNA-125b, miRNA-222 and miRNA-221), CCAAT/enhancer-binding protein alpha (miRNA-31) and pathways of insulin resistance (miRNA-107 and miRNA-103a) were significantly altered due to low B12, thereby modulating adipocyte differentiation and physiology [41]. ...
Obesity is a worldwide epidemic responsible for 5% of global mortality. The risks of developing other key metabolic disorders like diabetes, hypertension and cardiovascular diseases (CVDs) are increased by obesity, causing a great public health concern. A series of epidemiological studies and animal models have demonstrated a relationship between the importance of vitamin B12 (B12) and various components of metabolic syndrome. High prevalence of low B12 levels has been shown in European (27%) and South Indian (32%) patients with type 2 diabetes (T2D). A longitudinal prospective study in pregnant women has shown that low B12 status could independently predict the development of T2D five years after delivery. Likewise, children born to mothers with low B12 levels may have excess fat accumulation which in turn can result in higher insulin resistance and risk of T2D and/or CVD in adulthood. However, the independent role of B12 on lipid metabolism, a key risk factor for cardiometabolic disorders, has not been explored to a larger extent. In this review, we provide evidence from pre-clinical and clinical studies on the role of low B12 status on lipid metabolism and insights on the possible epigenetic mechanisms including DNA methylation, micro-RNA and histone modifications. Although, there are only a few association studies of B12 on epigenetic mechanisms, novel approaches to understand the functional changes caused by these epigenetic markers are warranted.
... One of the key findings of this study is that CDKN2B-AS1 was highly expressed in atherosclerotic plaque tissues and HP-1 macrophage-derived foam cells, and promoted the progression of atherosclerosis in vivo. Current evidence points to the existence of noncoding RNA such as microRNA [25] and long non-coding RNA in blood and their participation in regulating circulation. lncRNAs are reported to play a key role in atherosclerosis occurrence, reflected by their functions in atherogenic cells including vascular smooth muscle cells, endothelial cells, and monocytes/macrophages [26]. ...
Background
Atherosclerosis involves a slow process of plaque formation on the walls of arteries, and comprises a leading cause of cardiovascular disease. Long non-coding RNAs (lncRNAs) have been implicated in the pathogenesis of atherosclerosis. In this study, we aim to explore the possible involvement of lncRNA ‘cyclin-dependent kinase inhibitor 2B antisense noncoding RNA’ (CDKN2B-AS1) and CDKN2B in the progression of atherosclerosis.
Methods
Initially, we quantified the expression of CDKN2B-AS1 in atherosclerotic plaque tissues and, in THP-1 macrophage-derived, and human primary macrophage (HPM)-derived foam cells. Next, we established a mouse model of atherosclerosis using apolipoprotein E knockout (ApoE−/−) mice, where lipid uptake, lipid accumulation, and macrophage reverse cholesterol transport (mRCT) were assessed, in order to explore the contributory role of CDKN2B-AS1 to the progression of atherosclerosis. RIP and ChIP assays were used to identify interactions between CDKN2B-AS1, CCCTC-binding factor (CTCF), enhancer of zeste homologue 2 (EZH2), and CDKN2B. Triplex formation was determined by RNA-DNA pull-down and capture assay as well as EMSA experiment.
Findings
CDKN2B-AS1 showed high expression levels in atherosclerosis, whereas CDKN2B showed low expression levels. CDKN2B-AS1 accelerated lipid uptake and intracellular lipid accumulation whilst attenuating mRCT in THP-1 macrophage-derived foam cells, HPM-derived foam cells, and in the mouse model. EZH2 and CTCF were found to bind to the CDKN2B promoter region. An RNA-DNA triplex formed by CDKN2B-AS1 and CDKN2B promoter was found to recruit EZH2 and CTCF in the CDKN2B promoter region and consequently inhibit CDKN2B transcription by accelerating histone methylation.
Interpretation
The results demonstrated that CDKN2B-AS1 promotes atherosclerotic plaque formation and inhibits mRCT in atherosclerosis by regulating CDKN2B promoter, and thereby could be a potential therapeutic target for atherosclerosis.
... It has been successively demonstrated that miRNAs exert crucial functions in various biological processes, such as animal growth and development, immune response, metabolic activity, and diseases [18,19]. Notably, increasing evidence has revealed that miRNAs participate in lipid metabolism [20,21]. It was proved that miR-24 could suppress TG content and lipid accumulation in HepG2 cells by targeting scavenger receptor B1 (SR-B1) gene, which regulates cholesterol trafficking and the selective transfer of cholesteryl ester [22]. ...
Accumulating evidence has shown that miR-34a serves as a posttranscriptional regulatory molecule of lipid metabolism in mammals. However, little studies about miR-34a on lipid metabolism in poultry have been reported until now. To gain insight into the biological functions and action mechanisms of miR-34a on hepatic lipid metabolism in poultry, we firstly investigated the expression pattern of miR-34a-5p, a member of miR-34a family, in liver of chicken, and determined its function in hepatocyte lipid metabolism by miR-34a-5p overexpression and inhibition, respectively. We then validated the interaction between miR-34a-5p and its target using dual-luciferase reporter assay, and explored the action mechanism of miR-34a-5p on its target by qPCR and Western blotting. Additionally, we looked into the function of the target gene on hepatocyte lipid metabolism by gain- and loss-of-function experiments. Our results indicated that miR-34a-5p showed a significantly higher expression level in livers in peak-laying hens than that in pre-laying hens. miR-34a-5p could increase the intracellular levels of triglycerides and total cholesterol in hepatocyte. Furthermore, miR-34a-5p functioned by inhibiting the translation of its target gene, long-chain acyl-CoA synthetase 1 (ACSL1), which negatively regulates hepatocyte lipid content. In conclusion, miR-34a-5p could increase intracellular lipid content by reducing the protein level, without influencing mRNA stability of the ACSL1 gene in chickens.
... miR-122 silencing induced the up-regulation of genes involved in lipids catabolism and favored lipogenesis in cellular models [10]. Opposite results were obtained after miR-122 over-expression [43] pointing out miR-122 as a promising therapeutic target in the treatment of hypercholesterolemia and other dyslipidemias [44]. ...
Nonalcoholic fatty liver disease (NAFLD) defines a wide pathological spectrum ranging from simple steatosis to nonalcoholic steatohepatitis (NASH) which may predispose to liver cirrhosis and hepatocellular carcinoma. It represents the leading cause of hepatic damage worldwide. Diagnosis of NASH still requires liver biopsy but due to the high prevalence of NAFLD, this procedure, which is invasive, is not practicable for mass screening. Thus, it is crucial to non-invasively identify NAFLD patients at higher risk of progression to NASH and fibrosis. It has been demonstrated that hepatic fat content and progressive liver damage have a strong heritable component. Therefore, genetic variants associated with NAFLD have been proposed as non-invasive markers to be used in clinical practice. However, genetic variability is not completely explained by these common variants and it is possible that many of the phenotypic differences result from gene-environment interactions. Indeed, NAFLD development and progression is also modulated by epigenetic factors, in particular microRNAs (miRNAs), which control at post-transcriptional level many complementary target mRNAs and whose dysregulation has been shown to have high prognostic and predictive value in NAFLD. The premise of the current review is to discuss the role of miRNAs as pathogenic factors, risk predictors and therapeutic targets in NAFLD.
... 14 From among numerous adipocyte miRNAs, miR-143 and miR-27, which are up-and downregulated (respectively) during adipocyte differentiation, were selected for further investigation. [16][17][18] The expression of miR-143 was reported to be increased in mice fed a high-fat diet, which in turn caused hyperinsulinemia and impaired glucose tolerance. On the other hand, in mice with reduced miR-143 level or activity, undesirable blood glucose changes were modified, and consequently, this microRNA was regarded as a potential candidate to be targeted in type 2 diabetes as well as obesity treatment. ...
Background:
Conjugated linoleic acid (CLA), which is an octadecadienoic acid isomer, is believed to play different positive physiological roles, such as lowering body fat. Due to some reported side effects of CLA, like lipodystrophy and impaired glucose metabolism, it is important to establish its safety by understanding detailed molecular mechanisms. One of these mechanisms may be the role of this dietary agent in modifying the function and activity of microRNAs (miRNAs).
Objectives:
The aim of the study was to investigate how adipocyte miR-27a and miR-143 expression may be influenced by CLA in obese rats.
Material and methods:
In this study, 24 male Wistar rats were randomly divided into normal-fat diet (NFD) and high-fat diet (HFD) groups. After 8 weeks, the rats were weighed and half of the diet-induced obese rats were randomly selected to receive 500 mg CLA per 1 kg body weight for 4 weeks. At the end of this period, epididymal fat was isolated to investigate the expression level of miRNAs by real-time polymerase chain reaction (RT-PCR).
Results:
After 12 weeks, the obese rats in the HFD group, compared with rats in the NFD group, demonstrated a significant decrease in the expression of miR-27a (p < 0.05) and a significant increase in the expression of miR-143 (p < 0.05). In the group which had received CLA for a 4-week period, these events were reversed. Moreover, the rats in this group gained less weight than other rats in HFD groups, although the difference was not statistically significant.
Conclusions:
In conclusion, this study demonstrated that CLA, as an anti-obesity agent, may minimize abnormal changes in miRNA expression in obesity. This suggests a new pathway for weight loss; however, further studies are needed.
... Knockout of miRNA-122 resulted in marked decreased levels of circulating cholesterol (25%-30%) [20,21]. A host of genes linked to cholesterol biosynthesis were also decreased through an as yet unknown mechanism [21,22], with a decrease in SWI/SNF (nucleosome remodeling complex) related matrix-associated actin-dependent regulator of chromatin subfamily d member 1 (Smarcd1/ Baf60a; a group of proteins that remodel the way DNA is packaged), reflecting the direct drugs include atorvastatin, fluvastatin, pravastatin, rosuvastatin. Steatosis: a pathological condition associated with metabolic dysfunction in which there is accumulation of lipid in hepatocytes. ...
Cardiovascular disease (CVD) is a major cause of death globally. Addressing cardiovascular risk factors, particularly dyslipidemia, represents the most robust clinical strategy towards reducing the CVD burden. Statins inhibit 3-hydroxy-3-methylglutaryl-CoA (HMG-CoA) reductase and represent the main therapeutic approach for lowering cholesterol and reducing plaque formation/rupture. The protective effects of statins extend beyond lowering cholesterol. MicroRNAs (miRNAs or miRs), small noncoding regulatory RNAs, likely mediate the positive pleiotropic effects of statins via modulation of lipid metabolism, enhancement of endothelial function, inhibition of inflammation, improvement of plaque stability, and immune regulation. miRNAs are implicated in statin-related interindividual variations in therapeutic response, directly via HMG-CoA reductase, or indirectly through targeting cytochrome P450 3A (CYP3A) functionality and proprotein convertase subtilisin/kexin type9 (PCSK9) biology.
... MicroRNAs are shown to be involved in cholesterol regulation and homeostasis (Sacco and Adeli, 2012;Vickers et al., 2014). Several miRNAs have been reported for their regulatory roles in cholesterol metabolism (Rotllan and Fernandez-Hernando, 2012), and some of these miRNA such as miR33 is particularly involved in brain cholesterol metabolism and implicated in related diseases (Jaouen and Gascon, 2016). ...
MiR-335-3p, a neuron-enriched microRNA, has been reported to be involved in aging and age related neurological diseases. However, the role of miR-335-3p in cholesterol metabolism of astrocytes, and whether it affects neuronal functions, particularly during aging process, largely remains unknown. In this study, we uncover that miR-335-3p is significantly increased in aged cultured astrocytes and aged hippocampal brains, accompanied by decreased cellular cholesterol and diminished expression of HMGCR and HMGCS1, both step-limiting enzymes in cholesterol synthesis pathway. We also demonstrate that miR-335-3p suppresses HMGCS1 post-transcriptionally by directly binding to its 3'UTR, and HMGCR through binding mediated by SFRS2. More importantly, aged mice with miR-335-3p deficiency in hippocampal brains exhibit improved learning and memory, accompanied by enhanced levels of PSD95. We further reveal that the level change of PSD95 is resulted from altered cholesterol metabolism. Our findings provide a novel insight into the regulatory role of miR-335-3p in cholesterol metabolism in astrocytes, and consequently cognitive functions during aging.
... Silencing of miR-122 is an early event during hepatocarcinogenesis from NASH, and miR-122 could be a novel molecular marker for evaluating the risk of HCC in patients with NASH [73]. It has been also proposed as a potential therapeutic target in the treatment of hypercholesterolemia and other dyslipidemias [66]. ...
Genetics and epigenetics play a key role in the development of several diseases, including nonalcoholic fatty liver disease (NAFLD). Family studies demonstrate that first degree relatives of patients with NAFLD are at a much higher risk of the disease than the general population. The development of the Genome Wide Association Study (GWAS) technology has allowed the identification of numerous genetic polymorphisms involved in the evolution of diseases (e.g.,PNPLA3,MBOAT7). On the other hand, epigenetic changes interact with inherited risk factors to determine an individual's susceptibility to NAFLD. Modifications of the histones amino-terminal ends are key factors in the maintenance of chromatin structure and gene expression (cAMP-responsive element binding protein H (CREBH) or SIRT1). Activation of SIRT1 showed potential against the physiological mechanisms related to NAFLD. Abnormal DNA methylation represents a starting point for cancer development in NAFLD patients. Besides, the evaluation of circulating miRNA profiles represents a promising approach to assess and non-invasively monitor liver disease severity. To date, there is no approved pharmacologic therapy for NAFLD and the current treatment remains weight loss with lifestyle modification and exercise. In this review, the status of research into relevant genetic and epigenetic modifiers of NAFLD progression will be discussed.
... Ils ont des rôles établis dans la croissance cellulaire, la prolifération cellulaire, la différenciation, l'apoptose, la cardiogenèse, le développement lymphocytaire, la réponse immunitaire, la différenciation adipocytaire, la sécrétion d'insuline, ils sont responsables de nombreuses voies de signalisation. Ils sont également impliqués dans plusieurs pathologies comme l'obésité, le cancer, l'athérosclérose, le diabète, les maladies cardiovasculaires, les infections virales, les désordres neurodégénératifs(169)(170)(171)(172).Les microARN régulent des voies métaboliques centrales qui jouent un rôle vital dans le maintien de la balance énergétique de l'organisme et l'homéostasie métabolique. Des thérapeutiques à base de microARN sont en train d'émerger et semble une stratégie viable pour traiter les maladies métaboliques. ...
L'hyperchylomicronémie est une maladie rare et complexe impliquant plusieurs gènes qui sont eux-mêmes fortement régulés par plusieurs mécanismes et dont les voies métaboliques sont étroitement dépendantes de facteurs environnementaux. La survenue de la pathologie due à la présence de variants ou d'une association de variants sur ces gènes n'est pas toujours clairement définie. Ce qui suggère l'intervention d'autres mécanismes mal élucidés dans le développement des hyperchylomicronémies et la régulation du métabolisme des triglycérides. Nous avons essayé d'appréhender certains mécanismes causals dans la survenue de l hyperchylomicronémie en lien avec la présence de variants sur les gènes régulateurs APOC3 et LMF1 du métabolisme des triglycérides. Le gène APOC3 présente le variant SstI (rs5128) en région 3' non codante associée significativement à l'hypertriglycéridémie dans notre cohorte, nous avons cherché à caractériser sa régulation post-transcriptionnelle éventuelle par des microARN hépatiques ou intestinaux. Nos résultats ne confirment pas l'hypothèse d'une régulation du variant SstI du gène APOC3 par un microARN hépatique ou intestinal ciblant directement l'extrémité 3'UTR du gène APOC3. Le gène LMF1, nouveau gène candidat pour étudier les mécanismes des hyperchylomicronémies, est encore peu investigué. Nous avons mis en place son diagnostic génétique au sein du laboratoire ainsi qu'une technique in vitro permettant d'évaluer l'impact de la présence de certains variants codants de LMF1 sur l'activité post héparinique de la lipoprotéine lipase (LPL) par mesure de la lipolyse des triglycérides des VLDL. Nous avons mis en évidence des activités LPL significativement diminuées suggérant une dysfonction de LMF1 en présence des variants p.Gly172Arg (rs201406396), p.Arg354Trp (rs143076454), p.Arg364Gln (rs35168378), et des deux variants non-sens déjà décrits p.Tyr439Ter (rs121909397) et p.Trp464Ter (rs587777626). Ces travaux permettent de confirmer l'effet fonctionnel des variants LMF1 sur la régulation de la sécrétion de la LPL. Nous avons également retrouvé dans notre cohorte de 385 patients 18 variants sur la région 3' non codante du gène LMF1. Pour les trois variants : c*231C>A (rs75476513), c*512G>A (rs117039680), et c*530G>A (rs139657279), les résultats in vitro suggèrent une régulation post transcriptionnelle par les microARN. Ce qui pourrait ainsi expliquer le mécanisme de l'association de ces variants non traduits à l'hypertriglycéridémie. Ainsi, des interrelations des multiples gènes impliqués dans le métabolisme des triglycérides et leurs régulations à plusieurs niveaux simultanés modulent le phénotype d'hyperchylomicronémie. Il est nécessaire d'étudier tous les mécanismes complexes impliqués dans la régulation de la triglycéridémie afin de mieux appréhender la physiopathologie et de développer de nouvelles cibles thérapeutiques
... Adipose tissues play a key role in maintaining the homeostasis of the body's energy metabolism by releasing an array of hormones and cytokines: adipocytokines. The current study revealed that the dysregulated miRNAs play important roles in glucose, as well as lipid metabolism (Table S1) [29,50,92]. These miRNAs, including miR-17-5p, -155-5p, -125b-5p, -30e-5p, -27a-5p, -221-3p, -199a-5p, -130b-3p, -181a-5p, -29a, -29b, interact with multiple transcription factors, such as PPARs (peroxisome proliferator activated receptors), including PPARG, also known as PPARγ, and adipocyte-enriched genes (GLUT4 (also known as SLC2A4), SOCS1, SOCS3, GRB2, INSR and PPARG), to regulate many aspects of the lipid and glucose metabolisms [90,93]. ...
MicroRNAs (miRNAs) are small noncoding RNAs that modulate the cellular transcriptome at the post-transcriptional level. miRNA plays important roles in different disease manifestation, including type 2 diabetes mellitus (T2DM). Many studies have characterized the changes of miRNAs in T2DM, a complex systematic disease; however, few studies have integrated these findings and explored the functional effects of the dysregulated miRNAs identified. To investigate the involvement of miRNAs in T2DM, we obtained and analyzed all relevant studies published prior to 18 October 2016 from various literature databases. From 59 independent studies that met the inclusion criteria, we identified 158 dysregulated miRNAs in seven different major sample types. To understand the functional impact of these deregulated miRNAs, we performed targets prediction and pathway enrichment analysis. Results from our analysis suggested that the altered miRNAs are involved in the core processes associated with T2DM, such as carbohydrate and lipid metabolisms, insulin signaling pathway and the adipocytokine signaling pathway. This systematic survey of dysregulated miRNAs provides molecular insights on the effect of deregulated miRNAs in different tissues during the development of diabetes. Some of these miRNAs and their mRNA targets may have diagnostic and/or therapeutic utilities in T2DM.
... Bo, Hu, Ma, Mo (Esau et al., 2004, Kajimoto et al., 2006, Xie et al., 2009, Jin et al., 2010, Li et al., 2011, Romao et al., 2011) miR-378 Targets PPARG expression through the MAPK1 pathway B, Mo (Gerin et al., 2010, Jin et al., 2010, John et al., 2012, Sacco and Adeli, 2012, Liu et al., 2015) Table 2. Effect of far-off and close-up feeding management on subcutaneous adipose tissue expression (back-transformed LSM and SEM) in grazing dairy cows during the transition period. Cows that were dried off at a lower BCS than optimal (0.75-1.00 unit lower) were overfed to quickly reach optimal calving BCS at 5wk prepartum, hence FastBCS, While animals that were dried closer to optimal (<0.25 unit than optimal) were fed to maintenance to slowly reach calving BCS at 5wk prepartum, hence SlowBCS 2 CU = close-up feeding management; Feed65, Feed90, and Feed120 were fed to reach 65, 90, and 120% of estimated ME requirements, respectively Table 3. ...
The common practice of increasing dietary energy density during the “close-up” dry period (last ~3 wk prepartum) has been recently associated with a higher incidence of metabolic disorders after calving. Despite these reports, over-feeding of metabolizable energy (ME) during the ‘far-off’, non-lactating period is a common management policy aimed at achieving optimum calving body condition score (BCS) in pasture-based systems, as cows are generally thinner than TMR cows at the end of lactation. Our hypothesis was that both far-off and close-up overfeeding influence the peripartum adipose tissue changes associated with energy balance and inflammatory state. Sixty mid-lactation, grazing dairy cows of mixed age and breed were randomly allocated to one of two groups that were managed through late lactation to achieve a low and high BCS (approximately 4.25 and 5.0 on a 10-point scale) at dry-off. The low BCS cows were then overfed ME to ensure that they achieved the same BCS as the higher BCS group by calving. Within each rate of BCS gain treatment, cows were offered either 65, 90, or 120% of their pre-calving ME requirements for three weeks pre-calving in a 2 x 3 factorial arrangement of treatments (i.e., 10 cows/treatment). Subcutaneous adipose tissue was collected via biopsy at -1, 1 and 4 wk relative to parturition. Quantitative PCR was used to measure mRNA and microRNA (miRNA) expression of targets related to adipogenesis and inflammation. Cows overfed in the far-off period had increased expression of miR-143 and miR-378 prepartum (-1 wk) indicating greater adipogenesis, consistent with their rapid gain in BCS following dry-off. Furthermore, the lower postpartum expression of IL6, TNF, TLR4, TLR9, and miR-145, and a higher abundance of miR-99a indicated lower body fat mobilization in early lactation in the same group. In the close-up period, feeding either 65 or 120% of ME requirements caused changes in FASN, IL1B, IL6R, TLR9, and the miRNA miR-143, miR-155, and miR-378. Their respective expression patterns indicate a tentative negative-feedback mechanism in metabolically compromised, feed-restricted cows, and a possible immune-related stimulation of lipolysis in apparently static adipocytes in overfed cows. Data from cows fed 90% of ME requirements indicate the existence of a balance between lipolytic (inflammatory-related) and anti-lipolytic signals, in order to prime the mobilization machinery in light of imminent lactation. Overall, results indicate that far-off dry cow nutrition influences peripartum adipose tissue metabolism, with neither strategy negatively affecting the physiological adaptation to lactation. Furthermore, to ensure a favorable transition, cows should be subjected to a small feed restriction in the close-up period, irrespective of far-off nutritional management.
... Recent reports have identified specific miRNAs as major regulators of lipid homeostasis and anti-atherosclerosis; and the best-characteristic one is miRNA-33 (miR-33) [6]. Although several recent findings reported that suppression of miR-33 is controversial in lipid metabolism and anti-atherosclerosis [7][8][9], more studies evidenced that inhibiting miR-33 could improve lipid profile and have atheroprotective properties. ...
Atherosclerosis is a chronic inflammatory disease with complex pathological processes. MicroRNA-33 (miR-33), a novel non-coding RNA that coexpresses with sterol regulatory element-binding proteins (SREBPs), affects macrophage actions to prevent atherosclerosis. Fibroblast growth factor 21 (FGF21) is an important regulator of lipid metabolism, especially for macrophage-related cholesterol export, but the mechanism is not fully studied. Interestingly, FGF21 has been evidenced to prevent atherosclerosis via inhibiting SREBP-2 expression. Therefore, we speculate that FGF21 may be a potential regulator for miR-33 with an aim of insight into novel anti-atherosclerotic mechanisms and research fields.
... Distinctive features of small RNAs are their length (20-30 nucleotides), as well as their association with Argonaute-2 proteins (2). MicroRNAs constitute a dominating class of small RNAs that regulate diverse cellular functions, including apoptosis (3), metabolism (4), as well as cell growth and differentiation (5,6). Due the pivotal role of miRNAs in biological processes, deregulation in miRNAs expression alters normal cell functions, hence participating in the development of human disease, including cancer. ...
MicroRNAs (miRNAs) constitute a dominating class of small RNAs that regulate diverse cellular functions. Due the pivotal role of miRNAs in biological processes, a deregulated miRNA expression is likely involved in human cancers. MicroRNAs possess tumor suppressor capability, as well as display oncogenic characteristics. Interestingly, miRNAs exist in various biological fluids as circulating entities. Changes in the profile of circulating miRNAs are indicative of pathophysiological conditions in human cancer. This concept has led to consider circulating miRNAs valid biomarkers in cancer diagnostics. Furthermore, current research promotes the use of miRNAs as a target in cancer therapy. However, miRNAs are an evolving research field. Although miRNAs have been demonstrated to be potentially valuable tools both in cancer diagnosis and treatment, a greater effort should be made to improve our understanding of miRNAs biology. This review describes the biology of microRNAs, emphasizing on the use of miRNAs in cancer diagnostics and therapy.
... These subcellular organelles are comprised of neutral lipids (i.e., triacylglycerol and cholesterol esters) that are membrane bound by phospholipids [6]. There are a number of miRNAs with emerging roles in regulating lipid metabolism by targeting genes in lipid pathways [7][8][9][10][11][12][13]. Kidney cancer is described as a metabolic disease in which the renal clear cell subtype is characterized by increased lipid droplets [14]; it has yet to be investigated whether miRNAs contribute to metabolic dysregulation in this disease. ...
Background
miRNAs can regulate cellular survival in various cancer cell types. Recent evidence implicates the formation of lipid droplets as a hallmark event during apoptotic cell death response. It is presently unknown whether MIR494, located at 14q32 which is deleted in renal cancers, reduces cell survival in renal cancer cells and if this process is accompanied by changes in the number of lipid droplets.
Methods
769-P renal carcinoma cells were utilized for this study. Control or MIR494 mimic was expressed in these cells following which cell viability (via crystal violet) and apoptotic cell numbers (via Annexin V/PI staining) were assessed. By western blotting, MIR494 cellular responses were validated using MIR494 antagomir and Argonaute 2 siRNA. Transmission electron microscopy (TEM) was performed in MIR494-transfected 769-P cells to identify ultrastructural changes. LipidTOX green neutral lipid staining and cholesterol measurements were conducted to assess accumulation of lipids droplets and total cholesterol levels, respectively, in MIR494 expressing 769-P cells. Indirect immunofluorescence and western analyses were also performed to examine changes in mitochondria organization. Co-transfection of MIR494 mimic with siRNA targeting LC3B and ATG7 was conducted to assess their contribution to formation of lipid droplets in MIR494-expressing cells.
Results
MIR494 expression reduces viability of 769-P renal cancer cells; this was accompanied by increased cleaved PARP (an apoptotic marker) and LC3B protein. Further, expression of MIR494 increased LC3B mRNA levels and LC3B promoter activity (2.01-fold; 50 % increase). Interestingly, expression of MIR494 markedly increased multilamellar bodies and lipid droplets (by TEM and validated by LipidTOX immunostaining) while reducing total cholesterol levels. Via immunocytochemistry, we observed increased LC3B-associated endogenous punctae upon MIR494 expression. In contrast to ATG7 siRNA, knockdown of LC3B reduced the numbers of lipid droplets in MIR494-expressing cells. Our results also identified that MIR494 expression altered the organization of mitochondria which was accompanied by co-localization with LC3B punctae, decreased PINK1 protein, and altered Drp1 intracellular distribution.
Conclusion
Collectively, our findings indicate that MIR494 reduces cell survival in 769-P renal cancer cells which is accompanied by increased lipid droplet formation (which occurs in a LC3B-dependent manner) and mitochondrial changes.
... By contrast, these authors found that overexpression of miR-185 resulted in increased insulin receptor substrate-2 (IRS-2) expression, improved insulin sensitivity and reduced steatosis [35]. Another prominent miRNA involved in the positive regulation of cholesterol and fatty acid biosynthesis is miR-33a/b [36,37]. Since inhibition of miR-33a/b enhances fatty acid oxidation and insulin signaling, it is a potential molecular target in the management of metabolic syndrome [38]. ...
Nonalcoholic fatty liver disease (NAFLD) has become the most common liver disorder. Strongly linked to obesity and diabetes, NAFLD has the characteristics of complex diseases with substantial heterogeneity. Accordingly, our ability to predict the risk of advanced NAFLD and provide efficient treatment may improve by a better understanding of the relationship between genotype and phenotype. MicroRNAs (miRNAs) play a major role in the fine-tuning of gene expression and they have recently emerged as novel biomarkers and therapeutic tools in the management of NAFLD. These short non-coding RNA sequences act by partial repression or degradation of targeted mRNAs. Deregulation of miRNAs has been associated with different stages of NAFLD, while their biological role in the pathogenesis remains to be fully understood. Systems biology analyses based on predicted target genes have associated hepatic miRNAs with molecular pathways involved in NAFLD progression such as cholesterol and lipid metabolism, insulin signaling, oxidative stress, inflammation, and pathways of cell survival and proliferation. Moreover, circulating miRNAs have been identified as promising noninvasive biomarkers of NAFLD and linked to disease severity. This rapidly growing field is likely to result in major advances in the pathomechanism, prognostication, and treatment of NAFLD.
... In this sense miR-122, the most expressed miRNA in human liver has been reported significantly under-expressed in NASH [37] , acting as a tumor-supressor in the liver [29,38] . It has been proposed as a potential therapeutic target in the treatment of hypercholesterolemia [39] or different dyslipidaemia [40] . Besides miR-122, other miRNAs have been demonstrated to be involved in NAFLD. ...
Non-alcoholic fatty liver disease (NAFLD) is an emerging health concern in both developed and non-developed world, encompassing from simple steatosis to non-alcoholic steatohepatitis (NASH), cirrhosis and liver cancer. Incidence and prevalence of this disease are increasing due to the socioeconomic transition and change to harmful diet. Currently, gold standard method in NAFLD diagnosis is liver biopsy, despite complications and lack of accuracy due to sampling error. Further, pathogenesis of NAFLD is not fully understood, but is well-known that obesity, diabetes and metabolic derangements played a major role in disease development and progression. Besides, gut microbioma and host genetic and epigenetic background could explain considerable interindividual variability. Knowledge that epigenetics, heritable events not caused by changes in DNA sequence, contribute to development of diseases has been a revolution in the last few years. Recently, evidences are accumulating revealing the important role of epigenetics in NAFLD pathogenesis and in NASH genesis. Histone modifications, changes in DNA methylation and aberrant profiles or microRNAs could boost development of NAFLD and transition into clinical relevant status. PNPLA3 genotype GG has been associated with a more progressive disease and epigenetics could modulate this effect. The impact of epigenetic on NAFLD progression could deserve further applications on therapeutic targets together with future non-invasive methods useful for the diagnosis and staging of NAFLD.
... Mitochondrial energy metabolism during brain ischemia-reperfusion injury is regulated by miRNAs [138]. (Table 1, lines 15 to 25). ...
Cerebral ischemia-reperfusion injury involves multiple independently fatal terminal pathways in the mitochondria. These pathways include the reactive oxygen species (ROS) generation caused by changes in mitochondrial membrane potential and calcium overload, resulting in apoptosis via cytochrome c (Cyt c) release. In addition, numerous microRNAs are associated with the overall process. In this review, we first briefly summarize the mitochondrial changes in cerebral ischemia-reperfusion and then describe the possible molecular mechanism of miRNA-regulated mitochondrial function, which likely includes oxidative stress and energy metabolism, as well as apoptosis. On the basis of the preceding analysis, we conclude that studies of microRNAs that regulate mitochondrial function will expedite the development of treatments for cerebral ischemia-reperfusion injury.
... MiRNAs regulate gene expression by binding to target mRNAs and control a wide range of biological functions. Recent reports have identified specific miRNAs as major regulators of fatty acid and cholesterol homeostasis [10]. NASH is associated with altered hepatic microRNA expression [11]. ...
Background and objective:
The short form augmenter of liver regeneration (sfALR) is a novel human hepatotrophic growth factor. The aim of this study was to investigate the potential role of sfALR in NAFLD.
Methods:
The free fatty acids (FFA) induced lipid accumulation in mouse liver parenchymal cells was examined by Oil Red O staining and triglyceride level determination. The cell cycle was determined by flow cytometry and the proliferation was assessed by CCK8. The expression levels of gfer, miR-122, srebp-1c, fas, dgat2, acc1 and Lrp1B were assessed by quantitative real-time PCR. Furthermore, the MAPK pathway was detected by western blot.
Results:
The results showed that sfALR could alleviate the lipid accumulation in mice both in vivo and in vitro. sfALR relieved the proliferation inhibition and G2 arrest of mouse liver parenchymal cells induced by FFAs. Free fatty acids affected gfer expression in a time-and dose-dependent way. And sfALR suppressed JNK activation, increased miR-122 level and reduced fatty acid synthesis-related gene expression.
Conclusion:
These findings suggested that sfALR could alleviate the severity of fatty liver in mice.
... miRNAs have emerged as important regulators of cell proliferation, inflammation and metabolism. Recent studies have shown that hepatic miRNAs may have an important impact on lipid and lipoprotein metabolism [21][22][23] . ...
Non-alcoholic fatty liver disease (NAFLD) is one of the most common liver diseases, but its underlying mechanism is poorly understood. Here we show that hepatocyte nuclear factor 4α (HNF4α), a liver-enriched nuclear hormone receptor, is markedly inhibited, whereas miR-34a is highly induced in patients with non-alcoholic steatohepatitis, diabetic mice and mice fed a high-fat diet. miR-34a is essential for HNF4α expression and regulates triglyceride accumulation in human and murine hepatocytes. miR-34a inhibits very low-density lipoprotein secretion and promotes liver steatosis and hypolipidemia in an HNF4α-dependent manner. As a result, increased miR-34a or reduced HNF4α expression in the liver attenuates the development of atherosclerosis in Apoe(-/-) or Ldlr(-/-) mice. These data indicate that the miR-34a-HNF4α pathway is activated under common conditions of metabolic stress and may have a role in the pathogenesis of NAFLD and in regulating plasma lipoprotein metabolism. Targeting this pathway may represent a novel approach for the treatment of NAFLD.
... Micro RNA 370 reduces β-oxidation of fatty acids but on the other hand increases the expression of another miRNA that results in increasing cholesterol synthesis and β-oxidation of fatty acids, thus promoting insulin resistance leading to T2D and CAD complication of DM [16]. This explains the obtained observations of positive correlation between miRNA370 and dyslipidemia in patients with T2D with CAD, and was also found in another study, where miRNA370 levels were increased in patients with hyperlipidemia and their expression correlated with CAD incidence [23]. Changing miRNA 370 levels in human hepatocytes resulted in changing β-oxidation of fatty acids and synthesis of TAG, which was linked to changes in the levels of fatty acid synthase and acetyl-CoA carboxylase [16]. ...
Background:
MicroRNAs (miRNAs) are small non coding RNAs with essential roles, of which any alteration leads to several conditions. Their roles in diabetes (DM) and its vascular complications have not been completely assessed.
Aim:
to study the association of two miRNAs; 9 and 370, with biochemical parameters of type 2 diabetic (T2D), dyslipidemia and coronary artery disease (CAD).
Subjects and methods:
Blood samples were taken from 200 subjects of both genders, in the Outpatient clinic of Al Qasr El-Einy teaching hospitals, in which levels of both miRNAs (using real time PCR) and routine parameters were measured. Subjects were divided over four groups, 50 in each group as follows; patients with T2D, patients with CAD, patients with T2D and CAD, and healthy control subjects.
Main outcome:
miRNA 9 levels were expected to be over expressed in diabetic patients, while miRNA 370 levels were expected to be over expressed in those suffering from CAD and their association with CAD complication of T2D.
Results:
miRNA 9 levels were significantly higher in T2D patients and T2D patients with CAD, (1.18±0.07, and 1.31±0.08 respectively), while miRNA 370 levels were significantly higher in T2D patients, CAD patients, and T2D patients with CAD (0.59±0.05, 1.00±0.05, and 1.20±0.06 respectively), compared to control group at p = 0.000. In addition both miRNAs were still significantly associated with each other even after conducting multiple regression analysis.
Conclusion:
This study associates the possible role of miRNAs in the diagnosis/prognosis of CAD complication of T2D.
This study investigated the role of the miR-871-5p/proliferator-activated receptor α (PGC1α) pathway in ameliorating hepatic steatosis. We examined miR-871-5p expression in liver tissues of ageing mice and AML12 senescent cells co-induced by low serum and palmitic acid (PA). Bioinformatics and multiple experiments were employed to validate the expression level of the target gene PGC1α for miR-871-5p. In this study, we aimed to investigate the potential role of miR-871-5p in regulating hepatic lipid deposition associated with ageing. To do so, we performed in vitro transfection of both miR-871-5p mimic and inhibitor into senescent hepatocytes. Our results showed that miR-871-5p could inhibit PGC1α expression and cause lipid deposition in the liver due to ageing. MiR-871-5p controls this process by regulating PGC1α / fatty acid β oxidation. H&E staining displayed the appearance of fat vacuoles in the livers of ageing mice, and fatty acid β oxidation-related genes (acyl-coenzyme A oxidase 1 carnitine palmitoyl transferase 1α (ACOX1), and peroxisome proliferator-activated receptor α (PPARα)) expression was significantly reduced. Lipogenic genes (sterol regulatory element binding protein 1C (SREBP-1C), fatty acid synthase (FASN)) expression level was increased in the livers of ageing mice. In AML12 cells co-induced by low serum and PA, miR-871-5p mimics decreased PGC1α expression and increased lipid droplet accumulation in senescent hepatocytes. Conversely, miR-871-5p inhibitor promoted PGC1α expression and reduced lipid deposition in senescent hepatocytes. Our findings suggest that inhibiting miR-871-5p could be crucial in ameliorating aging-associated hepatic steatosis. These findings offer valuable insights into the molecular mechanisms driving hepatic steatosis in ageing.
Metabolic-associated fatty liver disease (MAFLD) is a public health problem that is increasingly recognized, currently affecting up to a quarter of the world's adult population. Although a biopsy is the current gold standard to diagnose MAFLD, there are potentially serious complications, making it inadequate. Thus far, noninvasive methods have not been able to determine the stage and the subtype of MAFLD. The development and prognosis of MAFLD are modulated by epigenetic factors, including microRNAs (miRNAs), which may be potential biomarkers for MAFLD. Polyphenols, found in many fruits and vegetables, may be useful, as they alter gene expression with epigenetic factors, such as miRNAs. This review presents an overview of the relationship between polyphenols and miRNAs in MAFLD. The literature suggests that miRNAs could be used as a diagnostic method for MAFLD, especially miRNA-122 and miRNA-34a. However, though it has been demonstrated that polyphenols may contribute to improving MAFLD, to our knowledge, no study to date has shown the relationship between polyphenols and miRNAs in MAFLD. The exact mechanisms of polyphenols on miRNAs in MAFLD remain unclear. Future studies may provide hope for diet therapy for MAFLD patients as well as the development of polyphenol-related foods or drugs that target miRNAs to treat MAFLD.
Chondrocyte apoptosis contributes to osteoarthritis, while miR-146a is a critical player in chondrocyte apoptosis. Our bioinformatics analysis showed that miR-146a may bind with long non-coding RNA (lncRNA) CALML3 antisense RNA 1 (CALML3-AS1). Our study was therefore carried out to investigate the interactions between lncRNA CALML3-AS1 and miR-146a in osteoarthritis. This study included 66 osteoarthritis patients who were admitted at Shanxi People’s Hospital from July 2016 to June 2019. Transfections were performed to analyse gene interactions. RT-qPCR and Western blot were performed to determine the expression levels of gene and protein, respectively. Cell apoptosis of chondrocytes induced by lipopolysaccharide (LPS) was analysed by cell apoptosis assay. We found that CALML3-AS1 was downregulated, while miR-146a was upregulated in osteoarthritis. However, no significant correlation was found between them. In addition, overexpression of CALML3-AS1 or miR-146a did not affect the expression of each other. However, overexpression of CALML3-AS1 resulted in the upregulation of Smad family member 4 (Smad4), a downstream target of miR-146a. We also found that the expression of miR-146a and Smad4 were negatively correlated, while the correlation between CALML3-AS1 and smad4 was not significant. In cell apoptosis assay, overexpression of CALML3-AS1 and Smad4 resulted in decreased proliferation of chondrocytes. MiR-146a played an opposite role and reduced the effects of overexpression of CALML3-AS1 and Smad4. Therefore, CALML3-AS1 may regulate chondrocyte apoptosis by acting as a sponge for miR-146a to upregulate Smad4.
A type of evolutionarily conserved, noncoding, small, endogenous, single-stranded RNA, miRNAs are widely distributed in eukaryotes, where they participate in various biological processes as critical regulatory molecules. miR-1299 has mainly been investigated in cancers. miR-1299 is a tumor suppressor that regulates the expression of its target genes, activating or inhibiting the transcription of genes regulating biological activities including cell proliferation, migration, survival and programmed cell death. miR-1299 has become a hotspot in research of disease mechanisms and biomarkers; elucidation of the regulatory roles of miR-1299 in tumorigenesis, proliferation, apoptosis, invasion, migration and angiogenesis may provide a new perspective for understanding its biological functions as a tumor suppressor.
Fish, particularly marine species, are considered as the major source of long-chain polyunsaturated fatty acids (LC-PUFA) in the human diet. The extent to which fish can synthesize LC-PUFA varies with species and is regulated by dietary fatty acids and ambient salinity. Therefore, to enable fish to produce more LC-PUFA, comprehending the mechanisms underlying the regulation of LC-PUFA biosynthesis is necessary. Here, the regulatory roles of miR-145 were investigated in the marine teleost rabbitfish Siganus canaliculatus. The hepatic abundance of miR-145 was lower in rabbitfish reared in low salinity (10 ppt) in comparison with that of those cultured in seawater (32 ppt), while the opposite pattern was observed for the transcripts of the transcription factor hepatocyte nuclear factor 4 alpha (Hnf4α), known to affect rabbitfish LC-PUFA biosynthesis. Rabbitfish hnf4α was identified as a target of miR-145 by luciferase reporter assays, and overexpression of miR-145 in the S. canaliculatus hepatocyte line (SCHL) markedly reduced the expression of Hnf4α and its target genes involved in LC-PUFA biosynthesis, namely, Δ4 fads2, Δ6Δ5 fads2, and elovl5. The opposite pattern was observed when miR-145 was knocked down in SCHL cells, with these effects being attenuated by subsequent hnf4α knockdown. Moreover, increasing endogenous Hnf4α by the knockdown of miR-145 increased the expression of LC-PUFA biosynthesis genes and enhanced the synthesis of LC-PUFA in both SCHL cells and rabbitfish in vivo. This is the first report to identify miR-145 as a key effector of LC-PUFA biosynthesis by targeting hnf4α, providing a novel insight into the mechanisms of the regulation of LC-PUFA biosynthesis in vertebrates.
Milk fat is a main nutritional component of milk, and it has become one of the important traits of dairy cow breeding. Recently, there is increasing evidence that microRNAs (miRNA) play significant roles in the process of milk fat synthesis in the mammary gland. Primary bovine mammary epithelial cells (BMEC) were harvested from mid-lactation cows and cultured in DMEM/F-12 medium with 10% fetal bovine serum, 100 units/mL penicillin, 100 µg/mL streptomycin, 5 µg/mL bovine insulin, 1 µg/mL hydrocortisone, and 2 µg/mL bovine prolactin. We found that miR-34b mimic transfection in BMEC reduced the content of intracellular triacylglycerol (TAG) and lipid droplet accumulation via triacylglycerol assay and Oil Red O staining, meanwhile, overexpression of miR-34b inhibited mRNA expression of lipid metabolism-related genes such as peroxisome proliferator-activated receptor gamma (PPARγ), fatty acid synthase (FASN), fatty acid binding protein 4 (FABP4), and CCAAT enhancer binding protein alpha (C/EBPα). Whereas miR-34b inhibitor resulted in completely opposite results. Furthermore, q-PCR and western blot analysis revealed the mRNA and protein expression levels of DCP1A were downregulated in miR-34b mimic transfection group and upregulated in miR-34b inhibitor group. Moreover, luciferase reporter assays verified that DCP1A was the direct target of miR-34b and DCP1A gene silencing in BMEC inhibited TAG accumulation and suppressed lipid droplet formation. In conclusion, these findings revealed a novel miR-34b–DCP1A axis that has a significant role in regulating milk fat synthesis and suggested that miR-34b may be used to improve the beneficial ingredients in milk.
Increasing evidence has suggested that microRNAs (miRNAs) are critical regulators of tumorigenesis. MicroRNA-613 (miR-613) has recently been reported as a novel tumor-related miRNA that plays an important role in multiple cancers. However, the expression and functional significance of miR-613 in glioma remains unclear. In this study, we aimed to investigate the biological function of miR-613 in glioma. We found that miR-613 expression was frequently downregulated in glioma tissues and cell lines compared with normal controls. Overexpression of miR-613 impeded proliferation and colony formation and induced cell cycle arrest in G0/G1 phase, and also inhibited the invasive ability of glioma cells. By contrast, miR-613 inhibition had the opposite effects. Bioinformatic analysis and dual-luciferase reporter assays showed that miR-613 directly targets the 3'-untranslated region of cyclin-dependent kinase 14 (CDK14). Real-time quantitative PCR and Western blot analysis showed that CDK14 expression is negatively regulated by miR-613. In addition, miR-613 expression was inversely correlated with CDK14 expression in clinical glioma tissues. Moreover, overexpression of miR-613 decreased the protein expression of β-catenin and inhibited the activation of Wnt signaling. Importantly, the antitumor effects of miR-613 were significantly reversed by CDK14 overexpression. Overall, our results show that miR-613 inhibits glioma cell proliferation and invasion by downregulating CDK14, suggesting that miR-613 and CDK14 may serve as potential therapeutic targets for the treatment of glioma.
Lipotoxicity is considered one of the main causes of deterioration in β-cells function. Glucagon-like peptide-1 (GLP-1) has been revealed to protect and improve pancreatic β-cell function against lipotoxicity. However, the mechanism behind these is largely unknown. The aim of this study was to investigate the effects of GLP-1 on cholesterol-induced lipotoxicity in INS-1 cells and examine the underlying mechanisms. The cell viability was determined, and caspase-3 was used to assess the effects of GLP-1 on cholesterol-induced apoptosis. The alterations of miR-27a and ABCA1 resulting from incubation with cholesterol or GLP-1 were detected by real-time PCR and western blot. The inhibition and overexpression of miR-27a were established to explore the effects of a GLP-1-mediated decrease in miR-27a. Further, Oil red O staining and cholesterol measurement were used to detect lipid accumulation. The β-cells function was measured in glucose-stimulated insulin secretion. Our data shows that cholesterol significantly attenuated cell viability, promoted cell apoptosis, facilitated lipid accumulation, and impaired β-cells function, and these effects were significantly reversed by GLP-1. Furthermore, the results demonstrated that GLP-1 decreased miR-27a expression and increased the expression of ABCA1. In conclusion, GLP-1 may affect cholesterol accumulation and β-cells dysfunction by regulating the expression of miR-27a and ABCA1.
Diabetes is a severe condition worldwide. It is characterized by chronic hyperglycemia and is caused by defects in insulin production, secretion, and action. Both genetic and environmental factors contribute to the
development of type 1 and type 2 diabetes. The pathogenesis of diabetes is complex and the underlying molecular mechanisms are only partially understood. MicroRNAs (miRNAs) play a fundamental role in diabetes and its complications. This chapter focuses on the dysregulation of miRNAs involved in the regulation of pancreatic islet insulin production and secretion as well as action and signaling in peripheral tissues. The roles of miRNAs in the development of diabetic complications are also discussed. Modulating miRNA expression, by either upregulation or inhibition, holds a promise as a strategy for treating this metabolic disease.
MicroRNAs (miRNAs) are important gene regulators in both biological and pathological processes, including myocardial ischemia/reperfusion (I/R) injury. This study investigated the effect of miR-613 on I/R-induced cardiomyocyte apoptosis and its molecular mechanism of action. Hypoxia/reoxygenation (H/R) significantly increased the release of lactate dehydrogenase (LDH), levels of malondialdehyde (MDA), and cardiomyocyte apoptosis, but these effects were attenuated by an miR-613 mimic. Programmed cell death 10 (PDCD10) was identified as a target gene of miR-613. miR-613 significantly increased the phosphorylation of Akt (p-Akt). An miR-613 mimic lowered the level of expression of pro-apoptotic proteins, C/EBP homologous protein (CHOP), and phosphorylated c-Jun N-terminal kinase (p-JNK), and it up-regulated the expression of the anti-apoptotic protein B-cell lymphoma-2 (Bcl-2). All of these effects were reversed by restoration of PDCD10. Taken together, the current findings indicate that miR-613 inhibits I/R-induced cardiomyocyte apoptosis by targeting PDCD10 by regulating the PI3K/AKT signaling pathway.
Nonalcoholic fatty liver disease (NAFLD) has become a major health problem in developed countries and is commonly associated with many obesity-related health complications, including cardiovascular disease, type 2 diabetes, hyperlipidemia and hypertension. We hypothesized that the composition of fatty acids delivered to and stored within the liver is an important determinant of liver cell integrity, and probably an independent risk factor for the progression to the more severe form of NAFLD, mediated by low-grade chronic inflammation. Different mechanisms, including antioxidant, anti-inflammatory, presence of fiber, and antiestrogenic processes, have been proposed to explain the protective nature of certain dietary components, particularly, components of Mediterranean diet that could be an important therapeutic lifestyle change, which allows to avoid the development of metabolic diseases.
Background and aims:
Several studies suggest that cardiomyocyte-enriched miR-186 is involved in cardiac injury and myocardial infarction, and also plays an important role in atherosclerotic diseases, but the underlying mechanism is unknown. Cystathionine-γ-lyase (CSE) is the predominant enzyme to produce H2S in the cardiovascular system. Here, miR-186 was identified to bind to the 3'UTR of CSE. In this study, we aimed at exploring whether miR-186 affects lipid accumulation and secretion of pro-inflammatory cytokines by targeting CSE and its underlying mechanism in human THP-1 macrophages and peripheral blood monocyte-derived macrophages (PBMDM). PBMDM just as a control group for the comparison with the THP-1 macrophages.
Methods:
MiR-186 target genes, CSE 3'UTR sequence and free energy were predicted and analyzed by bioinformatics analyses and dual-luciferase reporter assays. The expression of CSE mRNA and protein were measured by real-time quantitative PCR and western blot analyses. The lipid accumulation in THP-1 macrophages was detected by high performance liquid chromatography (HPLC). The effects of miR-186 on secretion of IL-6, IL-1β and TNF-α were examined by ELISA. Endogenous H2S was detected by spectrophotometry. Using small interfering RNA (siRNA) approach to decrease the expression of CSE protein and mRNA.
Results:
We found that miR-186 directly inhibited CSE protein and mRNA expression through targeting CSE 3'UTR by bioinformatics analyses and dual-luciferase reporter assays. HPLC assays showed that miR-186 increased the lipid accumulation in human THP-1 macrophages. We also showed that miR-186 enhanced secretion of pro-inflammatory cytokines in human THP-1 macrophages. Using siRNA approach, we found that CSE siRNA could inhibit the miR-186 inhibitor-induced decrease in the expression of LPL protein and mRNA in human THP-1 macrophages, which was accompanied a decrease in the level of H2S.
Conclusions:
MicroRNA-186 promotes macrophage lipid accumulation and pro-inflammatory cytokine secretion by targeting cystathionine γ-lyase in THP-1 macrophages.
MiRNAs are short single-stranded non-coding RNAs that cause degradation or repression of target mRNAs by base pairing with their 3′-untranslated regions. Recent studies have shown that miRNAs play an important role in the occurrence and development of cerebral ischaemia, as well as exerting regulatory effects. Additionally, circulating miRNAs in peripheral blood, which are dysregulated following cerebral ischaemia, have recently been identified as useful biomarkers in diagnosis and prognosis of cerebral ischaemia. Single-nucleotide polymorphisms (SNPs) located in miRNA genes or target sites are likely to cause complex functional consequences by affecting miRNA biogenesis or target selection. Research on miRNA-SNPs is rapidly growing, and recent studies have identified a significant relationship between miRNAs and ischemic disease. We also address the latest advances in miRNA-based therapeutic approaches for ischemic disease. In conclusion, our review summarizes current research regarding miRNAs and cerebral ischaemia, focusing on the regulatory role of miRNAs in cerebral ischaemia, as well as the potential of miRNAs as biomarkers and therapeutic targets in cerebral ischaemia.
Salidroside is known for its pharmacological properties and in particular its antioxidation effects. In recent years, it has been recognized that salidroside plays an important role in treating diabetes. Accumulated evidence suggests that microRNAs may be involved in diabetic lipid disorders. We investigated how salidroside regulates lipid metabolism through miR-370 in vivo and in vitro. After 4 weeks of a high-fat diet, and intraperitoneal injection of streptozotocin (100mg/kg), type 2 diabetes was induced in male C56BL/6J mice. After 4 weeks, mice with fasting blood glucose levels above 7.8mmol/l were divided into five groups: those with diabetes mellitus, and those treated with 40mg/kg, 80mg/kg, and 160mg/kg salidroside, and metformin (480mg/kg), for a further 4 weeks. The hypoglycemic effects of salidroside were consistently demonstrated when measuring fasting blood glucose levels, observing insulin-sensitizing effects, and testing oral glucose tolerance. In addition to this, the expressions of miR-370, and related lipid protein expression in primary hepatocytes, were examined in primary type 2 diabetic mice. The present study has shown that the expression levels of miR-370, SREBP-1 and FAS-1 were significantly elevated in the liver of type 2 diabetic mice. In contrast, the elevated expression levels were reversed by salidroside. The addition of salidroside attenuated the effect of miR-370, and reduced the expression of these lipid metabolism proteins in primary hepatocytes. These findings demonstrate that salidroside can directly decrease the expression of miR-370 in type 2 diabetic mice, and particularly in primary hepatocytes, affecting lipid metabolism in the liver.
The main objective was to evaluate if different planes of maternal nutrition during late gestation and weaning age alter microRNA (miRNA) and target gene expression in offspring longissimus muscle (LM). Early (EW) and normal weaned (NW) Angus × Simmental calves (n = 30) born to cows that were grazing endophyte-infected tall fescue and red clover pastures with no supplement [low plane of nutrition (LPN)], or supplemented with 2.3 and 9.1 kg of dried distiller's grains with solubles and soy hulls [medium and high plane of nutrition (MPN, HPN), respectively] during the last 105 ± 11 days of gestation were used. Biopsies of LM were harvested at 78 (early weaning), 187 (normal weaning) and 354 days of age. Results indicate a role of pro-adipogenic miRNA in the control of adipogenesis in LM of NW-MPN steers between 78 and 187 days of age through upregulation of (1) miR-103 which inhibits CAV1, a protein that destabilizes INSR and leads to insulin resistance; (2) miR-143 which inhibits DLK1, a protein that inhibits adipocyte differentiation; and (3) miR-21 which impairs TGFBR2-induced inhibition of adipocyte differentiation. Among the studied anti-adipogenic miRNA, cow plane of nutrition resulted in downregulation of miR-34a expression in MPN steers compared with HPN and LPN at 78 days of age. Data for miR-34a provided a potential sign of epigenetic regulation of LM in beef offspring due to the cow plane of nutrition during late gestation.
Transcriptional regulation in salmonids with emphasis on lipid metabolism
in vitro and in vivo studies
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Schiller Vestergren, AnnaLotta (2014). Transcriptional regulation in salmonids with emphasis on lipid metabolism. Diss. (sammanfattning/summary) Uppsala : Sveriges lantbruksuniv., Acta Universitatis agriculturae Sueciae, 1652-6880 ; 2014:89
ISBN 978-91-576-8126-3
eISBN 978-91-576-8127-0
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Abstract
Fish is a vital source of valuable omega-3 (n-3) fatty acids (FA) in the human diet. With declining commercial fisheries, aquaculture fish constitute a growing proportion of human consumption. Sustainable development of aquaculture requires that the fish feed used is not solely based on fish meal and oil (FO), but also contains increasing levels of vegetable oil (VO). The replacement of FO with VO influences FA composition in fish tissues by decreasing n-3 long-chain polyunsaturated fatty acids (LCPUFAs) and the nutritional value for humans. Accordingly, the last decade of salmonid research has focused on increasing the amount of n-3 LCPUFAs in fish fed VO diets e.g. addition of bioactive compounds. This thesis examined the potential effects of bioactive compounds on lipid metabolism in salmonids. Genes involved in transcriptional regulation, uptake, β-oxidation, elongation and desaturation were shown to be affected by addition of bioactive compounds in both in vivo and in vitro experiments. Effects on FA composition were also observed, but no clear effect on docosahexaenoic acid (DHA) content. The discrepancies between increased gene expression of target genes in the desaturation and elongation cascade and the actual lack of response in FA content of eicosapentaenoic acid and docosahexaenoic acid may be the result of a combination of feedback regulation and post-transcriptional regulation, such as RNA silencing through microRNA (miRNA) repression. This thesis describes the miRNA transcriptome in liver tissue of Atlantic salmon post-smoltification and the tissue distribution of selected miRNAs in nine different somatic tissues of juvenile Atlantic salmon (Salmo salar) for the first time. The results expand the number of known Atlantic salmon miRNAs and provide a framework for understanding the n-3 LCPUFA pathway in Atlantic salmon.
Background:
Different technologies, such as quantitative real-time PCR or microarrays, have been developed to measure microRNA (miRNA) expression levels. Quantification of miRNA transcripts implicates data normalization using endogenous and exogenous reference genes for data correction. However, there is no consensus about an optimal normalization strategy. The choice of a reference gene remains problematic and can have a serious impact on the actual available transcript levels and, consequently, on the biological interpretation of data.
Content:
In this review article we discuss the reliability of the use of small RNAs, commonly reported in the literature as miRNA expression normalizers, and compare different strategies used for data normalization.
Summary:
A workflow strategy is proposed for normalization of miRNA expression data in an attempt to provide a basis for the establishment of a global standard procedure that will allow comparison across studies.
Radiotherapy is widely used in the treatment of nasopharyngeal carcinoma (NPC), whereas its effects on the NPC growth, survival, and metastases have not been completely evaluated. Here, we compared the detected metastatic NPC tissues after radiotherapy (m-NPC) to the resected primary NPC tissues prior to radiotherapy (p-NPC). We detected higher levels of Snail2 protein, but not mRNA in m-NPC, compared to p-NPC. In vitro, a modest irradiation on NPC cells resulted in significant cell death, but increased Snail2 protein, but mRNA levels in the surviving NPC cells. Bioinformatics analyses showed that miR-613, which was significantly decreased in NPC cells after irradiation, targeted the 3'-UTR of Snail2 mRNA to inhibit its translation. Moreover, miR-613 overexpression inhibited Snail2-mediated cell invasiveness, while miR-613 depletion increased Snail2-mediated cell invasiveness in NPC cells. Finally, we detected significantly lower levels of miR-613 in m-NPC, compared to p-NPC. Together our data suggest that although radiotherapy induced NPC cell death, it may increase Snail2-mediated NPC cell invasiveness through downregulating miR-613.
MicroRNAs (miRNAs) are important regulators and potential therapeutic targets of metabolic disease. In this study we show by in vivo administration of locked nucleic acid (LNA) inhibitors that suppression of endogenous miR-29 lowers plasma cholesterol levels by ~40%, commensurate with the effect of statins, and reduces fatty acid content in the liver by ~20%. Whole transcriptome sequencing of the liver reveals 883 genes dysregulated (612 down, 271 up) by inhibition of miR-29. The set of 612 down-regulated genes are most significantly over-represented in lipid synthesis pathways. Among the up-regulated genes are the anti-lipogenic deacetylase sirtuin 1 (Sirt1) and the anti-lipogenic transcription factor aryl hydrocarbon receptor (Ahr), the latter of which we demonstrate is a direct target of miR-29. In vitro radiolabeled acetate incorporation assays confirm that pharmacologic inhibition of miR-29 significantly reduces de novo cholesterol and fatty acid synthesis. Our findings indicate that miR-29 controls hepatic lipogenic programs, likely in part through regulation of Ahr and Sirt1, and therefore may represent a candidate therapeutic target for metabolic disorders such as dyslipidemia.
The global burden of cardiovascular disease is increasing despite therapeutic advances in medication and interventional technologies. Accumulated deoxyribonucleic acid (DNA) damage and subsequent repair pathways are now increasingly recognised as a causal factor in the initiation and progression of atherosclerosis. These molecular alterations have been shown to occur within affected vasculature, plaque microenvironment as well as in circulating cells. The DNA damage response (DDR) pathway is reliant on post-translational modification of sensing proteins which activate a signalling cascade to repair, if possible, DNA damaged sites in response to various environmental and physiological insults. This review summarises the current evidence for DNA damage in atherosclerosis, the key steps involved in the DDR pathway, DNA repair and their subsequent effects on atherosclerotic plaques, as well as the therapeutic options in managing DNA damage-induced atherosclerosis.
Copyright © 2015. Published by Elsevier Ltd.
Among different mechanisms that could lead to interindividual differences in obesity susceptibility, epigenetics has emerged, in the last years, as a potentially very important contributor. The role of epigenetics in obesity may be considered by different points of view. Several nutritional factors are, in fact, known to influence epigenetic phenomena including DNA methylation, histone modifications, noncoding RNA expression, and chromatin remodeling mechanisms, all of which significantly influence transcriptional regulatory pathways and phenotypic plasticity. Moreover, there are genes affecting metabolic processes related to weight control and obesity development whose expression is controlled by epigenetic mechanisms.
A number of evidences suggest that epigenetic phenomena may be important in obesity development due to the dysregulation of known imprinted genes which have an essential role in normal growth and development and by modulating gene expression regulation through promoter DNA methylation at specific loci and histone modifications involved in obesity-linked metabolic pathways. Early life exposure to environmental/nutritional factors affecting epigenetics is also involved in obesity development. While some evidences are quite solid in this field, much is to be learned for the better understanding of epigenetic regulation in obesity and even more in terms of therapeutic prospectives. One of the objectives for the research in this novel area relies on the ability of defining epigenetic regulatory processes in genes involved in obesity and in a deeper knowledge on how epigenetic phenomena may be modulated by nutritional/environmental factors. Indeed, one of the main challenges is defining the epigenetic marks involved in obesity development and more specifically, to identify those which are potentially more susceptible to be modified by nutritional/environmental factors for specific preventive and therapeutic approaches.
MicroRNAs (miRNAs) are small endogenous, non-coding RNAs that specifically bind to the 3′ untranslated region (3′UTR) of target
genes in animals. However, some recent studies have demonstrated that miRNAs also target the coding regions of mammalian genes.
Here, we show that miRNA-181a downregulates the expression of a large number of zinc finger genes (ZNFs). Bioinformatics analysis
revealed that these ZNFs contain many miR-181a seed-matched sites within their coding sequences (CDS). In particular, miR-181a
8-mer-matched sequences were mostly localized to the regions coding for the ZNF C2H2 domain. A series of reporter assays confirmed
that miR-181a inhibits the expression of ZNFs by directly targeting their CDS. These inhibitory effects might be due to the
multiple target sites located within the ZNF genes. In conclusion, our findings indicate that some miRNA species may regulate
gene family by targeting their coding regions, thus providing an important and novel perspective for decoding the complex
mechanism of miRNA/mRNA interplay.
Cellular imbalances of cholesterol and fatty acid metabolism result in pathological processes, including atherosclerosis and
metabolic syndrome. Recent work from our group and others has shown that the intronic microRNAs hsa-miR-33a and hsa-miR-33b are located within the sterol regulatory element-binding protein-2 and -1 genes, respectively, and regulate cholesterol homeostasis
in concert with their host genes. Here, we show that miR-33a and -b also regulate genes involved in fatty acid metabolism
and insulin signaling. miR-33a and -b target key enzymes involved in the regulation of fatty acid oxidation, including carnitine
O-octaniltransferase, carnitine palmitoyltransferase 1A, hydroxyacyl-CoA-dehydrogenase, Sirtuin 6 (SIRT6), and AMP kinase subunit-α.
Moreover, miR-33a and -b also target the insulin receptor substrate 2, an essential component of the insulin-signaling pathway
in the liver. Overexpression of miR-33a and -b reduces both fatty acid oxidation and insulin signaling in hepatic cell lines,
whereas inhibition of endogenous miR-33a and -b increases these two metabolic pathways. Together, these data establish that
miR-33a and -b regulate pathways controlling three of the risk factors of metabolic syndrome, namely levels of HDL, triglycerides,
and insulin signaling, and suggest that inhibitors of miR-33a and -b may be useful in the treatment of this growing health
concern.
Our previous studies have demonstrated that stable microRNAs (miRNAs) in mammalian serum and plasma are actively secreted from tissues and cells and can serve as a novel class of biomarkers for diseases, and act as signaling molecules in intercellular communication. Here, we report the surprising finding that exogenous plant miRNAs are present in the sera and tissues of various animals and that these exogenous plant miRNAs are primarily acquired orally, through food intake. MIR168a is abundant in rice and is one of the most highly enriched exogenous plant miRNAs in the sera of Chinese subjects. Functional studies in vitro and in vivo demonstrated that MIR168a could bind to the human/mouse low-density lipoprotein receptor adapter protein 1 (LDLRAP1) mRNA, inhibit LDLRAP1 expression in liver, and consequently decrease LDL removal from mouse plasma. These findings demonstrate that exogenous plant miRNAs in food can regulate the expression of target genes in mammals.
Cardiovascular disease (CVD) remains the leading cause of mortality in westernized countries, despite optimum medical therapy to lower LDL cholesterol. The pursuit of novel therapies to target this residual risk has focused on raising levels of HDL cholesterol in order to exploit its atheroprotective effects1. MicroRNAs have emerged as important post-transcriptional regulators of lipid metabolism, and are thus a new class of targets for therapeutic intervention2. MicroRNA-33a and b (miR-33a/b) are intronic microRNAs embedded in the sterol response element binding protein genes SREBF2 and SREBF13–5, respectively, that repress expression of the cholesterol transporter ABCA1, a key regulator of HDL biogenesis. Recent studies in mice suggest that antagonizing miR-33a may be an effective strategy for raising plasma HDL3–5 and protecting from atherosclerosis6, however extrapolation of these findings to humans is complicated by the fact that mice lack miR-33b which is present only in the SREBF1 gene of higher mammals. Here we show in African green monkeys that systemic delivery of an anti-miR oligonucleotide that targets both miR-33a and miR-33b increases hepatic expression of ABCA1 and induces a sustained increase in plasma HDL over 12 weeks. Notably, miR-33 antagonism in this non-human primate model also increased the expression of miR-33 target genes involved in the oxidation of fatty acids (CROT, CPT1A, HADHB, PRKAA1) and reduced genes involved in fatty acid synthesis (SREBF1, FASN, ACLY, ACACA), resulting in a marked suppression of plasma VLDL triglyceride levels, a finding not previously observed in mice. These data establish, in a model highly relevant to humans, that pharmacological inhibition of miR-33a and b is a promising therapeutic strategy to raise plasma HDL and lower VLDL triglycerides for the treatment of dyslipidemias that increase cardiovascular disease risk.
Our previous studies have demonstrated that stable microRNAs (miRNAs) in mammalian serum and plasma are actively secreted from tissues and cells and can serve as a novel class of biomarkers for diseases, and act as signaling molecules in intercellular communication. Here, we report the surprising finding that exogenous plant miRNAs are present in the sera and tissues of various animals and that these exogenous plant miRNAs are primarily acquired orally, through food intake. MIR168a is abundant in rice and is one of the most highly enriched exogenous plant miRNAs in the sera of Chinese subjects. Functional studies in vitro and in vivo demonstrated that MIR168a could bind to the human/mouse low-density lipoprotein receptor adapter protein 1 (LDLRAP1) mRNA, inhibit LDLRAP1 expression in liver, and consequently decrease LDL removal from mouse plasma. These findings demonstrate that exogenous plant miRNAs in food can regulate the expression of target genes in mammals.
MicroRNAs (miRNAs) are small 19-23 nucleotide RNA molecules that act as regulators of protein expression in eukaryotic cells by inducing the translational arrest and degrada- tion of messenger RNAs (1). They are potent drivers of differentiation and development (1), and their dysregulation has been linked to many diseases. Here, we present an overview of the known and proposed roles and effects of miRNAs in type 1 and type 2 diabetes (T1D and T2D), focusing on b-cell biology, insulin resistance, and diabetes complications. Specifically, we discuss miRNAs in b-cell biology, altered expression of miRNAs in adipose tissue in response to obesity, and miRNA dysfunction in organs and tissues that may be affected in later stages of the disease. Additionally, we propose a set of research directions that may yield novel diagnostic and therapeutic approaches for this chronic illness. T2D is characterized by hyperglycemia resultant from impaired insulin secretion and/or impaired insulin action
Defects in insulin signalling are among the most common and earliest defects that predispose an individual to the development of type 2 diabetes. MicroRNAs have been identified as a new class of regulatory molecules that influence many biological functions, including metabolism. However, the direct regulation of insulin sensitivity by microRNAs in vivo has not been demonstrated. Here we show that the expression of microRNAs 103 and 107 (miR-103/107) is upregulated in obese mice. Silencing of miR-103/107 leads to improved glucose homeostasis and insulin sensitivity. In contrast, gain of miR-103/107 function in either liver or fat is sufficient to induce impaired glucose homeostasis. We identify caveolin-1, a critical regulator of the insulin receptor, as a direct target gene of miR-103/107. We demonstrate that caveolin-1 is upregulated upon miR-103/107 inactivation in adipocytes and that this is concomitant with stabilization of the insulin receptor, enhanced insulin signalling, decreased adipocyte size and enhanced insulin-stimulated glucose uptake. These findings demonstrate the central importance of miR-103/107 to insulin sensitivity and identify a new target for the treatment of type 2 diabetes and obesity.
Plasma HDL levels have a protective role in atherosclerosis, yet clinical therapies to raise HDL levels have remained elusive. Recent advances in the understanding of lipid metabolism have revealed that miR-33, an intronic microRNA located within the SREBF2 gene, suppresses expression of the cholesterol transporter ABC transporter A1 (ABCA1) and lowers HDL levels. Conversely, mechanisms that inhibit miR-33 increase ABCA1 and circulating HDL levels, suggesting that antagonism of miR-33 may be atheroprotective. As the regression of atherosclerosis is clinically desirable, we assessed the impact of miR-33 inhibition in mice deficient for the LDL receptor (Ldlr-/- mice), with established atherosclerotic plaques. Mice treated with anti-miR33 for 4 weeks showed an increase in circulating HDL levels and enhanced reverse cholesterol transport to the plasma, liver, and feces. Consistent with this, anti-miR33-treated mice showed reductions in plaque size and lipid content, increased markers of plaque stability, and decreased inflammatory gene expression. Notably, in addition to raising ABCA1 levels in the liver, anti-miR33 oligonucleotides directly targeted the plaque macrophages, in which they enhanced ABCA1 expression and cholesterol removal. These studies establish that raising HDL levels by anti-miR33 oligonucleotide treatment promotes reverse cholesterol transport and atherosclerosis regression and suggest that it may be a promising strategy to treat atherosclerotic vascular disease.
Increased plasma concentrations of apolipoprotein B100 often present in patients with insulin resistance and confer increased risk for the development of atherosclerosis. Naturally occurring polyphenolic compounds including flavonoids have antiatherogenic properties. The aim of the current study was to evaluate the effect of the polymethoxylated flavonoid nobiletin on lipoprotein secretion in cultured human hepatoma cells (HepG2) and in a mouse model of insulin resistance and atherosclerosis.
Lipoprotein secretion was determined in HepG2 cells incubated with nobiletin or insulin. mRNA abundance was evaluated by quantitative real-time PCR, and Western blotting was used to demonstrate activation of cell signaling pathways. In LDL receptor-deficient mice (Ldlr(-/-)) fed a Western diet supplemented with nobiletin, metabolic parameters, gene expression, fatty acid oxidation, glucose homeostasis, and energy expenditure were documented. Atherosclerosis was quantitated by histological analysis.
In HepG2 cells, activation of mitogen-activated protein kinase-extracellular signal-related kinase signaling by nobiletin or insulin increased LDLR and decreased MTP and DGAT1/2 mRNA, resulting in marked inhibition of apoB100 secretion. Nobiletin, unlike insulin, did not induce phosphorylation of the insulin receptor or insulin receptor substrate-1 and did not stimulate lipogenesis. In fat-fed Ldlr(-/-) mice, nobiletin attenuated dyslipidemia through a reduction in VLDL-triglyceride (TG) secretion. Nobiletin prevented hepatic TG accumulation, increased expression of Pgc1α and Cpt1α, and enhanced fatty acid β-oxidation. Nobiletin did not activate any peroxisome proliferator-activated receptor (PPAR), indicating that the metabolic effects were PPAR independent. Nobiletin increased hepatic and peripheral insulin sensitivity and glucose tolerance and dramatically attenuated atherosclerosis in the aortic sinus.
Nobiletin provides insight into treatments for dyslipidemia and atherosclerosis associated with insulin-resistant states.
The nuclear receptor liver X receptor (LXR) is a ligand-dependent transcription factor that plays an important role in the metabolism and homeostasis of cholesterol, lipids, bile acids, and steroid hormones. MicroRNAs (miRNAs) are recently recognized important negative regulators of gene expression. In this report, we showed that miRNA hsa-miR-613 played an important role in the autoregulation of the human LXRα gene. hsa-miR-613 targeted the endogenous LXRα through its specific miRNA response element (613MRE) within the LXRα 3'-untranslated region. Interestingly and paradoxically, the expression of hsa-miR-613 itself was induced upon the activation of LXR. However, hsa-miR-613 did not appear to be a direct LXR target gene. Instead, the positive regulation of hsa-miR-613 by LXR was mediated by the sterol regulatory element binding protein (SREBP)-1c, a known LXR target gene. Promoter analysis revealed an SREBP response element in the hsa-miR-613 gene promoter. Treatment with insulin also induced the expression of hsa-miR-613 in an SREBP-1c-dependent manner, further supporting the role of SREBP-1c in the positive regulation of this miRNA species. Finally, the autoinduction of LXRα by a LXR agonist was enhanced when hsa-miR-613 was inhibited or SREBP-1c was down-regulated. hsa-miR-613 appeared to specifically target the human LXRα. We propose that the negative regulation mediated by hsa-miR-613 and SREBP-1c and the previously reported positive regulation mediated by an LXR response element in the LXRα gene promoter constitute a ying-yang mechanism to ensure a tight regulation of this nuclear receptor of many metabolic functions.
This study was performed to investigate the effect of microRNA-203 (miR-203) and ΔNp63 on cell proliferation and the functional connection between miR-203 and ΔNp63 in ESCC.
We employed 2 human ESCC cell lines, Eca109 and TE-1, as the model system. The effect of miR-203 and ΔNp63 on cell proliferation was determined in cells transfected with miR-203 mimic and ΔNp63 small interfering RNA (siRNA), respectively. The regulation of ΔNp63 expression in ESCC cells by miR-203 was studied by luciferase reporter assay, RT-PCR and western blot analysis in cells transfected with miR-203. The effect of ΔNp63 re-expression on miR-203 induced inhibition of cell proliferation was studied by cell proliferation assay in cells cotransfected with miR-203 and pcDNA-ΔNp63 plasmid (without the 3'-UTR of ΔNp63).
We found that both miR-203 and ΔNp63 siRNA signicantly inhibited cell proliferation in ESCC. MiR-203 could down-regulate endogenous ΔNp63 expression at the posttranscriptional level. Moreover, re-expression of ΔNp63 in cells transfected with miR-203 significantly attenuated the miR-203 induced inhibition of cell proliferation.
Our data implied that miR-203 could inhibit cell proliferation in human ESCC through ΔNp63-mediated signal pathway. Therefore, we propose that miR-203 might be used as a therapeutic agent for human ESCC.
MicroRNAs (miRNAs), small noncoding RNAs, are negative regulators of gene expression and play important roles in gene regulation in the heart. To examine the role of miRNAs in the expression of the two isoforms of the cardiac myosin heavy chain (MHC) gene, α- and β-MHC, which regulate cardiac contractility, endogenous miRNAs were downregulated in neonatal rat ventricular myocytes (NRVMs) using lentivirus-mediated small interfering RNA (siRNA) against Dicer, an essential enzyme for miRNA biosynthesis, and MHC expression levels were examined. As a result, Dicer siRNA could downregulate endogenous miRNAs simultaneously and the β-MHC gene but not α-MHC, which implied that specific miRNAs could upregulate the β-MHC gene. Among 19 selected miRNAs, miR-27a was found to most strongly upregulate the β-MHC gene but not α-MHC. Moreover, β-MHC protein was downregulated by silencing of endogenous miR-27a. Through a bioinformatics screening using TargetScan, we identified thyroid hormone receptor β1 (TRβ1), which negatively regulates β-MHC transcription, as a target of miR-27a. Moreover, miR-27a was demonstrated to modulate β-MHC gene regulation via thyroid hormone signaling and to be upregulated during the differentiation of mouse embryonic stem (ES) cells or in hypertrophic hearts in association with β-MHC gene upregulation. These findings suggested that miR-27a regulates β-MHC gene expression by targeting TRβ1 in cardiomyocytes.
The sterol regulatory element binding protein 2 (SREBP-2) and the liver X receptor (LXR) control antagonistic transcriptional programs that stimulate cellular cholesterol uptake and synthesis, and cholesterol efflux, respectively. The clinical importance of SREBP-2 is revealed in patients with hypercholesterolemia treated with statins, which reduce low-density lipoprotein (LDL) cholesterol levels by increasing hepatic expression of SREBP-2 and its target, the LDL receptor. Here we show that miR-33 is encoded within SREBP-2 and that both mRNAs are coexpressed. We also identify sequences in the 3' UTR of ABCA1 and ABCG1, sterol transporter genes both previously shown to be regulated by LXR, as targets for miR-33-mediated silencing. Our data show that LXR-dependent cholesterol efflux to both ApoAI and serum is ameliorated by miR-33 overexpression and, conversely, stimulated by miR-33 silencing. Finally, we show that ABCA1 mRNA and protein and plasma HDL levels decline after hepatic overexpression of miR-33, whereas they increase after hepatic miR-33 silencing. These results suggest novel ways to manage hypercholesterolemic patients.
MicroRNAs (miRNAs) are small noncoding RNAs that extensively regulate gene expression in animals, plants, and protozoa. miRNAs function posttranscriptionally by usually base-pairing to the mRNA 3'-untranslated regions to repress protein synthesis by mechanisms that are not fully understood. In this review, we describe principles of miRNA-mRNA interactions and proteins that interact with miRNAs and function in miRNA-mediated repression. We discuss the multiple, often contradictory, mechanisms that miRNAs have been reported to use, which cause translational repression and mRNA decay. We also address the issue of cellular localization of miRNA-mediated events and a role for RNA-binding proteins in activation or relief of miRNA repression.
Cholesterol metabolism is tightly regulated at the cellular level. Here we show that miR-33, an intronic microRNA (miRNA)
located within the gene encoding sterol-regulatory element–binding factor–2 (SREBF-2), a transcriptional regulator of cholesterol
synthesis, modulates the expression of genes involved in cellular cholesterol transport. In mouse and human cells, miR-33
inhibits the expression of the adenosine triphosphate–binding cassette (ABC) transporter, ABCA1, thereby attenuating cholesterol
efflux to apolipoprotein A1. In mouse macrophages, miR-33 also targets ABCG1, reducing cholesterol efflux to nascent high-density
lipoprotein (HDL). Lentiviral delivery of miR-33 to mice represses ABCA1 expression in the liver, reducing circulating HDL
levels. Conversely, silencing of miR-33 in vivo increases hepatic expression of ABCA1 and plasma HDL levels. Thus, miR-33
appears to regulate both HDL biogenesis in the liver and cellular cholesterol efflux.
microRNAs (miRNAs) are small noncoding RNAs that regulate cognate mRNAs at the post-transcriptional stage. Several studies have shown that miRNAs modulate gene expression in mammalian cells by base pairing to complementary sites in the 3'-untranslated region (3'-UTR) of the target mRNAs.
In the present study, miR-24 was found to target fas associated factor 1(FAF1) by binding to its amino acid coding sequence (CDS) region, thereby regulating apoptosis in DU-145 cells. This result supports an augmented model whereby animal miRNAs can exercise their effects through binding to the CDS region of the target mRNA. Transfection of miR-24 antisense oligonucleotide (miR-24-ASO) also induced apoptosis in HGC-27, MGC-803 and HeLa cells.
We found that miR-24 regulates apoptosis by targeting FAF1 in cancer cells. These findings suggest that miR-24 could be an effective drug target for treatment of hormone-insensitive prostate cancer or other types of cancers. Future work may further develop miR-24 for therapeutic applications in cancer biology.
Potential regulators of adipogenesis include microRNAs (miRNAs), small non-coding RNAs that have been recently shown related to adiposity and differentially expressed in fat depots. However, to date no study is available, to our knowledge, regarding miRNAs expression profile during human adipogenesis. Thereby, the aim of this study was to investigate whether miRNA pattern in human fat cells and subcutaneous adipose tissue is associated to obesity and co-morbidities and whether miRNA expression profile in adipocytes is linked to adipogenesis.
We performed a global miRNA expression microarray of 723 human and 76 viral mature miRNAs in human adipocytes during differentiation and in subcutaneous fat samples from non-obese (n = 6) and obese with (n = 9) and without (n = 13) Type-2 Diabetes Mellitus (DM-2) women. Changes in adipogenesis-related miRNAs were then validated by RT-PCR. Fifty of 799 miRNAs (6.2%) significantly differed between fat cells from lean and obese subjects. Seventy miRNAs (8.8%) were highly and significantly up or down-regulated in mature adipocytes as compared to pre-adipocytes. Otherwise, 17 of these 799 miRNAs (2.1%) were correlated with anthropometrical (BMI) and/or metabolic (fasting glucose and/or triglycerides) parameters. We identified 11 miRNAs (1.4%) significantly deregulated in subcutaneous fat from obese subjects with and without DM-2. Interestingly, most of these changes were associated with miRNAs also significantly deregulated during adipocyte differentiation.
The remarkable inverse miRNA profile revealed for human pre-adipocytes and mature adipocytes hints at a closely crosstalk between miRNAs and adipogenesis. Such candidates may represent biomarkers and therapeutic targets for obesity and obesity-related complications.
We previously observed that treatment of mice with a dominant negative form of cJun (dn-cJun) increased the expression of genes involved in lipid metabolism and modulated the expression of nine microRNAs (miR). To investigate the potential effect of these miRs on the expression of the genes of lipid metabolism, we performed studies in cultured HepG2 cells. Transfection of HepG2 cells with sense or antisense miR-370 or miR-122 upregulated and downregulated, respectively, the transcription factor sterol-regulatory element binding protein 1c (SREBP-1c) and the enzymes diacylglycerol acyltransferase-2 (DGAT2), fatty acid synthase (FAS), and acyl-CoA carboxylase 1 (ACC1) that regulate fatty acid and triglyceride biosynthesis. The other seven miRs identified by the miR array screening did not affect the expression of lipogenic genes. miR-370 upregulated the expression of miR-122. Furthermore, the effect of miR-370 on the expression of the lipogenic genes was abolished by antisense miR-122. miR-370 targets the 3' untranslated region (UTR) of Cpt1alpha, and it downregulated the expression of the carnitine palmitoyl transferase 1alpha (Cpt1alpha) gene as well as the rate of beta oxidation. Our data suggest that miR-370 acting via miR-122 may have a causative role in the accumulation of hepatic triglycerides by modulating initially the expression of SREBP-1c, DGAT2, and Cpt1alpha and, subsequently, the expression of other genes that affect lipid metabolism.
The liver-expressed microRNA-122 (miR-122) is essential for hepatitis C virus (HCV) RNA accumulation in cultured liver cells,
but its potential as a target for antiviral intervention has not been assessed. We found that treatment of chronically infected
chimpanzees with a locked nucleic acid (LNA)–modified oligonucleotide (SPC3649) complementary to miR-122 leads to long-lasting
suppression of HCV viremia, with no evidence of viral resistance or side effects in the treated animals. Furthermore, transcriptome
and histological analyses of liver biopsies demonstrated derepression of target mRNAs with miR-122 seed sites, down-regulation
of interferon-regulated genes, and improvement of HCV-induced liver pathology. The prolonged virological response to SPC3649
treatment without HCV rebound holds promise of a new antiviral therapy with a high barrier to resistance.
Obesity has emerged as a global health problem with more than 1.1 billion adults to be classified as overweight or obese, and is associated with type 2 diabetes, cardiovascular disease, and several cancers. Since obesity is characterized by an increased size and/or number of adipocytes, elucidating the molecular events governing adipogenesis is of utmost importance. Recent findings indicate that microRNAs (miRNAs) - small non-protein-coding RNAs that function as post-transcriptional gene regulators - are involved in the regulatory network of adipogenesis. Whereas only a single human miRNA is known so far to be functional in adipogenesis as pro-adipogenic, several mouse miRNAs have been identified very recently as adipogenic regulators, thereby stimulating demand for studying the functional role of miRNAs during adipogenesis in human. Here, we demonstrate that miR-27b abundance decreased during adipogenesis of human multipotent adipose-derived stem (hMADS) cells. Overexpression of miR-27b blunted induction of PPARgamma and C/EBPalpha, two key regulators of adipogenesis, during early onset of adipogenesis and repressed adipogenic marker gene expression and triglyceride accumulation at late stages. PPARgamma has a predicted and highly conserved binding site in its 3'UTR and was indeed confirmed to be a direct target of miR-27b. Thus, these results suggest that the anti-adipogenic effect of miR-27b in hMADS cells is due, at least in part, to suppression of PPARgamma.
MicroRNAs are important regulators of gene expression that control both physiological and pathological processes such as development and cancer. Although their mode of action has attracted great attention, the principles governing their expression and activity are only beginning to emerge. Recent studies have introduced a paradigm shift in our understanding of the microRNA biogenesis pathway, which was previously believed to be universal to all microRNAs. Maturation steps specific to individual microRNAs have been uncovered, and these offer a plethora of regulatory options after transcription with multiple proteins affecting microRNA processing efficiency. Here we review the recent advances in knowledge of the microRNA biosynthesis pathways and discuss their impact on post-transcriptional microRNA regulation during tumour development.
We investigated the regulation and involvement of microRNAs (miRNAs) in fat cell development and obesity.
Using miRNA microarrays, we profiled the expression of >370 miRNAs during adipogenesis of preadipocyte 3T3-L1 cells and adipocytes from leptin deficient ob/ob and diet-induced obese mice. Changes in key miRNAs were validated by RT-PCR. We further assessed the contribution of the chronic inflammatory environment in obese adipose tissue to the dysregulated miRNA expression by tumor necrosis factor (TNF)-alpha treatment of adipocytes. We functionally characterized two adipocyte-enriched miRNAs, miR-103 and miR-143, by a gain-of-function approach.
Similar miRNAs were differentially regulated during in vitro and in vivo adipogenesis. Importantly, miRNAs that were induced during adipogenesis were downregulated in adipocytes from both types of obese mice and vice versa. These changes are likely associated with the chronic inflammatory environment, since they were mimicked by TNF-alpha treatment of differentiated adipocytes. Ectopic expression of miR-103 or miR-143 in preadipocytes accelerated adipogenesis, as measured both by the upregulation of many adipogenesis markers and by an increase in triglyceride accumulation at an early stage of adipogenesis.
Our results provide the first experimental evidence for miR-103 function in adipose biology. The remarkable inverse regulatory pattern for many miRNAs during adipogenesis and obesity has important implications for understanding adipose tissue dysfunction in obese mice and humans and the link between chronic inflammation and obesity with insulin resistance.
MicroRNAs (miRNAs) are an abundant class of non-coding RNAs that are believed to be important in many biological processes through regulation of gene expression. The precise molecular function of miRNAs in mammals is largely unknown and a better understanding will require loss-of-function studies in vivo. Here we show that a novel class of chemically engineered oligonucleotides, termed 'antagomirs', are efficient and specific silencers of endogenous miRNAs in mice. Intravenous administration of antagomirs against miR-16, miR-122, miR-192 and miR-194 resulted in a marked reduction of corresponding miRNA levels in liver, lung, kidney, heart, intestine, fat, skin, bone marrow, muscle, ovaries and adrenals. The silencing of endogenous miRNAs by this novel method is specific, efficient and long-lasting. The biological significance of silencing miRNAs with the use of antagomirs was studied for miR-122, an abundant liver-specific miRNA. Gene expression and bioinformatic analysis of messenger RNA from antagomir-treated animals revealed that the 3' untranslated regions of upregulated genes are strongly enriched in miR-122 recognition motifs, whereas downregulated genes are depleted in these motifs. Analysis of the functional annotation of downregulated genes specifically predicted that cholesterol biosynthesis genes would be affected by miR-122, and plasma cholesterol measurements showed reduced levels in antagomir-122-treated mice. Our findings show that antagomirs are powerful tools to silence specific miRNAs in vivo and may represent a therapeutic strategy for silencing miRNAs in disease.
Vector-based RNA interference (RNAi) has emerged as a valuable tool for analysis of gene function. We have developed new RNA
polymerase II expression vectors for RNAi, designated SIBR vectors, based upon the non-coding RNA BIC. BIC contains the miR-155
microRNA (miRNA) precursor, and we find that expression of a short region of the third exon of mouse BIC is sufficient to
produce miR-155 in mammalian cells. The SIBR vectors use a modified miR-155 precursor stem–loop and flanking BIC sequences
to express synthetic miRNAs complementary to target RNAs. Like RNA polymerase III driven short hairpin RNA vectors, the SIBR
vectors efficiently reduce target mRNA and protein expression. The synthetic miRNAs can be expressed from an intron, allowing
coexpression of a marker or other protein with the miRNAs. In addition, intronic expression of a synthetic miRNA from a two
intron vector enhances RNAi. A SIBR vector can express two different miRNAs from a single transcript for effective inhibition
of two different target mRNAs. Furthermore, at least eight tandem copies of a synthetic miRNA can be expressed in a polycistronic
transcript to increase the inhibition of a target RNA. The SIBR vectors are flexible tools for a variety of RNAi applications.
Despite efforts spanning four decades, the therapeutic potential of thyroid hormone receptor (TR) agonists as lipid-lowering and anti-obesity agents remains largely unexplored in humans because of dose-limiting cardiac effects and effects on the thyroid hormone axis (THA), muscle metabolism, and bone turnover. TR agonists selective for the TRβ isoform exhibit modest cardiac sparing in rodents and primates but are unable to lower lipids without inducing TRβ-mediated suppression of the THA. Herein, we describe a cytochrome P450-activated prodrug of a phosphonate-containing TR agonist that exhibits increased TR activation in the liver relative to extrahepatic tissues and an improved therapeutic index. Pharmacokinetic studies in rats demonstrated that the prodrug (2R,4S)-4-(3-chlorophenyl)-2-[(3,5-dimethyl-4-(4′-hydroxy-3′-isopropylbenzyl)phenoxy)methyl]-2-oxido-[1,3,2]-dioxaphosphonane (MB07811) undergoes first-pass hepatic extraction and that cleavage of the prodrug generates the negatively charged TR agonist (3,5-dimethyl-4-(4′-hydroxy-3′-isopropylbenzyl)phenoxy)methylphosphonic acid (MB07344), which distributes poorly into most tissues and is rapidly eliminated in the bile. Enhanced liver targeting was further demonstrated by comparing the effects of MB07811 with 3,5,3′-triiodo-l-thyronine (T3) and a non-liver-targeted TR agonist, 3,5-dichloro-4-(4-hydroxy-3-isopropylphenoxy)phenylacetic acid (KB-141) on the expression of TR agonist-responsive genes in the liver and six extrahepatic tissues. The pharmacologic effects of liver targeting were evident in the normal rat, where MB07811 exhibited increased cardiac sparing, and in the diet-induced obese mouse, where, unlike KB-141, MB07811 reduced cholesterol and both serum and hepatic triglycerides at doses devoid of effects on body weight, glycemia, and the THA. These results indicate that targeting TR agonists to the liver has the potential to lower both cholesterol and triglyceride levels with an acceptable safety profile.
• cardiac sparing
• hepatic steatosis
• hyperlipidemia
• (2R,4S)-4-(3-chlorophenyl)-2-[(3,5-dimethyl-4-(4′-hydroxy-3′-isopropylbenzyl)-phenoxy)methyl]-2-oxido-[1,3,2]-dioxaphosphonane (MB07811)
• thyroid hormone axis
Insulin resistance is often associated with obesity and can precipitate type 2 diabetes. To date, most known approaches that improve insulin resistance must be preceded by the amelioration of obesity and hepatosteatosis. Here, we show that this provision is not mandatory; insulin resistance and hyperglycemia are improved by the modification of hepatic fatty acid composition, even in the presence of persistent obesity and hepatosteatosis. Mice deficient for Elovl6, the gene encoding the elongase that catalyzes the conversion of palmitate to stearate, were generated and shown to become obese and develop hepatosteatosis when fed a high-fat diet or mated to leptin-deficient ob/ob mice. However, they showed marked protection from hyperinsulinemia, hyperglycemia and hyperleptinemia. Amelioration of insulin resistance was associated with restoration of hepatic insulin receptor substrate-2 and suppression of hepatic protein kinase C epsilon activity resulting in restoration of Akt phosphorylation. Collectively, these data show that hepatic fatty acid composition is a new determinant for insulin sensitivity that acts independently of cellular energy balance and stress. Inhibition of this elongase could be a new therapeutic approach for ameliorating insulin resistance, diabetes and cardiovascular risks, even in the presence of a continuing state of obesity.
microRNAs (miRNAs) are small regulatory RNAs that are important in development and disease and therefore represent a potential new class of targets for therapeutic intervention. Despite recent progress in silencing of miRNAs in rodents, the development of effective and safe approaches for sequence-specific antagonism of miRNAs in vivo remains a significant scientific and therapeutic challenge. Moreover, there are no reports of miRNA antagonism in primates. Here we show that the simple systemic delivery of a unconjugated, PBS-formulated locked-nucleic-acid-modified oligonucleotide (LNA-antimiR) effectively antagonizes the liver-expressed miR-122 in non-human primates. Acute administration by intravenous injections of 3 or 10 mg kg(-1) LNA-antimiR to African green monkeys resulted in uptake of the LNA-antimiR in the cytoplasm of primate hepatocytes and formation of stable heteroduplexes between the LNA-antimiR and miR-122. This was accompanied by depletion of mature miR-122 and dose-dependent lowering of plasma cholesterol. Efficient silencing of miR-122 was achieved in primates by three doses of 10 mg kg(-1) LNA-antimiR, leading to a long-lasting and reversible decrease in total plasma cholesterol without any evidence for LNA-associated toxicities or histopathological changes in the study animals. Our findings demonstrate the utility of systemically administered LNA-antimiRs in exploring miRNA function in rodents and primates, and support the potential of these compounds as a new class of therapeutics for disease-associated miRNAs.
For every 1% increase in circulating HDL cholesterol (HDL-C), there is a 2% decrease in overall risk for development of coronary artery disease (Wilson PW. Am J Cardiol 1990;66:7A-10A). It has been found in mouse models of atherosclerosis that over expression of apoA1, which increases HDL levels, hinders plaque progression and promotes plaque regression (Plump AS, et al. Proc Natl Acad Sci USA 1994;91:9607-11 and Rong JX, et al. Circulation 2001;104:2447-52). Such evidence has stimulated an interest in therapies to raise HDL levels. Despite the fact HDL raising strategies may be effective therapy for atherosclerosis, the underlying mechanisms that contribute to HDL regulation and its manipulation for therapy remain poorly understood.
We demonstrate that mice lacking the oxysterol receptor, LXRα, lose their ability to respond normally to dietary cholesterol and are unable to tolerate any amount of cholesterol in excess of that which they synthesize de novo. When fed diets containing cholesterol, LXRα (−/−) mice fail to induce transcription of the gene encoding cholesterol 7α-hydroxylase (Cyp7a), the rate-limiting enzyme in bile acid synthesis. This defect is associated with a rapid accumulation of large amounts of cholesterol in the liver that eventually leads to impaired hepatic function. The regulation of several other crucial lipid metabolizing genes is also altered in LXRα (−/−) mice. These results demonstrate the existence of a physiologically significant feed-forward regulatory pathway for sterol metabolism and establish the role of LXRα as the major sensor of dietary cholesterol.
MicroRNAs (miRs) have recently emerged as a novel class of gene expression regulators. The number of studies documenting an altered miR expression pattern in cancer continues to expand rapidly. Critical information is continuously gained regarding how aberrantly expressed miRs contribute to carcinogenesis. Current studies provide evidence that analyses of miR expression patterns have potential clinical applications toward developing tumor biomarkers to identify the presence and dissemination of esophageal cancer, as well as to assess tumor chemosensitivity or radiosensitivity. The incidence of esophageal cancer is on the rise, and this disease continues to portend a poor prognosis. The current review addresses ways in which altered miR expression contributes to esophageal carcinogenesis, along with how recent discoveries may be applied clinically.
MicroRNAs modulate processes associated with cell cycle control and differentiation. Here we explored the potential of microRNAs in the modulation of hepatic lipid metabolism and the development of nonalcoholic fatty liver disease. MicroRNA profiles of hepatocytes from low-density lipoprotein (LDL) receptor knockout mice fed a chow diet or a hypertriglyceridemia/fatty liver-inducing Western-type diet (WTD) were determined using quantitative real-time polymerase chain reaction. Ninety-seven of 103 microRNAs measured were expressed by hepatocytes and low variability between hepatocyte pools was observed. Feeding WTD coincided with a marked fivefold decrease in the relative expression level of miR-216 (P<.05) and miR-302a (P<.01). Interestingly, an increased hepatic miR-216 expression was detected in response to fasting. MicroRNA/biological function linkage analysis suggested that the change in hepatocyte microRNA profiles in response to high dietary lipid levels is associated with changes in cell cycle control and proliferation. In accordance with a diminished miR-302a expression on the WTD, hepatocyte mRNA expression levels of miR-302a target genes ABCA1 and in particular ELOVL6 were increased in response to WTD (twofold to ninefold). This suggests a role for miR-302a in hepatic cholesterol, fatty acid and glucose metabolism. In conclusion, we have shown that fatty liver development in LDL receptor knockout mice is associated with a significant change in the hepatocyte microRNA profile, i.e., a fivefold decrease in miR-216 and miR-302a expression. Based upon our comparative gene and microRNA expression studies it is anticipated that miR-302a may prove to be a valuable therapeutic target in the regulation of hepatic fatty acid utilization and insulin resistance.
MicroRNAs (miRNAs) are genomically encoded small RNAs used by organisms to regulate the expression of proteins generated from messenger RNA transcripts. The in vivo requirement of specific miRNAs in mammals through targeted deletion remains unknown, and reliable prediction of mRNA targets is still problematic. Here, we show that miRNA biogenesis in the mouse heart is essential for cardiogenesis. Furthermore, targeted deletion of the muscle-specific miRNA, miR-1-2, revealed numerous functions in the heart, including regulation of cardiac morphogenesis, electrical conduction, and cell-cycle control. Analyses of miR-1 complementary sequences in mRNAs upregulated upon miR-1-2 deletion revealed an enrichment of miR-1 "seed matches" and a strong tendency for potential miR-1 binding sites to be located in physically accessible regions. These findings indicate that subtle alteration of miRNA dosage can have profound consequences in mammals and demonstrate the utility of mammalian loss-of-function models in revealing physiologic miRNA targets.
There is increasing evidence that microRNAs (miRNAs) play important roles in cell proliferation, apoptosis and differentiation that accompany inflammatory responses. However, whether microRNAs are associated with DC immuno-inflammatory responses with oxidized low density lipoprotein (oxLDL) stimulation is not yet known. Our study aims to explore the link of miRNAs with lipid-overload and immuno-inflammatory mechanism for atherosclerosis. In DCs transfected with microRNA-29a mimics or inhibitors, we showed that microRNA-29a plays an important role in proinflammatory cytokine secretion and scavenger receptor expression upon oxLDL-treatment. Furthermore, we suggest an additional explanation for the mechanism of microRNA-29a regulation of its functional target, lipoprotein lipase. We conclude that microRNA-29a could regulate pro-inflammatory cytokine secretion and scavenger receptor expression by targeting lipoprotein lipase in oxLDL-stimulated dendritic cells.
Although the role for microRNAs (miRNAs) in regulating multiple physiological processes including apoptosis, cell differentiation, and cancer is well established, the importance of these tiny RNAs in regulating lipid metabolism has only recently been uncovered. This review summarizes the evidence for a critical role of miRNAs in regulating lipid metabolism.
Lipid metabolism is tightly regulated at the cellular level. In addition to classic transcriptional regulation of cholesterol metabolism (e.g. by SREBP and LXR), members of a class of noncoding RNAs termed miRNAs have now been identified to be potent post-transcriptional regulators of lipid metabolism genes involved in cholesterol homeostasis and fatty acid oxidation. Several reports have recently shown that miR-33 regulates cholesterol efflux and HDL biogenesis by downregulating the expression of the ABC transporters, ABCA1 and ABCG1. In addition, miR-33 also inhibits the translation of several transcripts encoding proteins involved in fatty acid β-oxidation including CPT1a, CROT, and HADHB, thereby reducing fatty acid degradation. Other miRNAs including miR-122, miR-370, miR-335, and miR-378/378*, miR-27 and miR-125a-5p have been implicated in regulating cholesterol homeostasis, fatty acid metabolism and lipogenesis.
Recent advances in the understanding of the regulation of lipid metabolism indicate that miRNAs play major roles in regulating cholesterol and fatty acid metabolism. These new findings may open new avenues for the treatment of dyslipidemias.
Cholesterol metabolism is tightly regulated at the cellular level. In addition to classic transcriptional regulation of cholesterol metabolism (e.g. by SREBP and LXR), members of a class of non-coding RNAs termed microRNAs (miRNAs) have recently been identified to be potent post-transcriptional regulators of lipid metabolism genes, including cholesterol homeostasis. We and others have recently shown that miR-33 regulates cholesterol efflux and HDL biogenesis by downregulating the expression of the ABC transporters, ABCA1 and ABCG1. In addition to miR-33, miR-122 and miR-370 have been shown to play important roles in regulating cholesterol and fatty acid metabolism. These new data suggest important roles of microRNAs in the epigenetic regulation of cholesterol metabolism and have opened new avenues for the treatment of dyslipidemias.
miR-103 and miR-107, microRNAs hosted by pantothenate kinase genes, are proposed to regulate cellular lipid metabolism. microRNA-mediated regulation is complex, potentially affecting expression of the host gene, related enzymes within the same pathway, or apparently distinct targets. Using qRT-PCR, we demonstrate that miR-103 and miR-107 expression does not correlate with expression of host pantothenate kinase genes in mouse tissues. The miR-103/7 family thus provides an intriguing model for dissecting microRNA transcription, processing and coordinated function within host genes.
MicroRNAs (miRNAs) can influence lineage choice or affect critical developmental checkpoints during hematopoiesis. We examined the role of the p53-induced microRNA miR-34a in hematopoiesis by gain-of-function analysis in murine bone marrow. Constitutive expression of miR-34a led to a block in B cell development at the pro-B-cell-to-pre-B-cell transition, leading to a reduction in mature B cells. This block appeared to be mediated primarily by inhibited expression of the transcription factor Foxp1. Foxp1 was a direct target of miR-34a in a 3'-untranslated region (UTR)-dependent fashion. Knockdown of Foxp1 by siRNA recapitulated the B cell developmental phenotype induced by miR-34a, whereas cotransduction of Foxp1 lacking its 3' UTR with miR-34a rescued B cell maturation. Knockdown of miR-34a resulted in increased amounts of Foxp1 and mature B cells. These findings identify a role for miR-34a in connecting the p53 network with suppression of Foxp1, a known B cell oncogene.
In this study, we explored the roles of microRNAs in adipocyte differentiation and metabolism. We first knocked down Argonaute2 (Ago2), a key enzyme in the processing of micro-RNAs (miRNAs), to investigate a potential role for miRNAs in adipocyte differentiation and/or metabolism. Although we did not observe dramatic differences in adipogenesis between Ago2 knock-down and control 3T3-L1 cells, incorporation of [(14)C]glucose or acetate into triacylglycerol, and steady-state levels of triacyglycerol were all reduced, suggesting a role for miRNAs in adipocyte metabolism. To study roles of specific miRNAs in adipocyte biology, we screened for miRNAs that are differentially expressed between preadipocytes and adipocytes for the 3T3-L1 and ST2 cell lines. Distinct subsets of miRNAs decline or increase during adipocyte conversion, whereas most miRNAs are not regulated. One locus encoding two miRNAs, 378/378*, contained within the intron of PGC-1beta is highly induced during adipogenesis. When overexpressed in ST2 mesenchymal precursor cells, miRNA378/378* increases the size of lipid droplets and incorporation of [(14)C]acetate into triacylglycerol. Although protein and mRNA expression levels of C/EBPalpha, C/EBPbeta, C/EBPdelta, and PPARgamma1 are unchanged, microarray and quantitative RT-PCR analyses indicate that a set of lipogenic genes are upregulated, perhaps due to increased expression of PPARgamma2. Knock-down of miRNA378 and/or miRNA378* decreases accumulation of triacylglycerol. Interestingly, we made the unexpected finding that miRNA378/378* specifically increases transcriptional activity of C/EBPalpha and C/EBPbeta on adipocyte gene promoters.
MicroRNAs (miRNA) are mediators of post-transcriptional gene expression that likely regulate most biological pathways and networks. The study of miRNAs is a rapidly emerging field; recent findings have revealed a significant role for miRNAs in atherosclerosis and lipoprotein metabolism, which will be described in this review.
The discovery of miRNA gene regulatory mechanisms contributing to endothelial integrity, macrophage inflammatory response to atherogenic lipids, vascular smooth muscle-cell proliferation, and cholesterol synthesis are described. Furthermore, recent evidence suggests that miRNAs may play a role in mediating the beneficial pleiotropic effects observed with statin-based lipid-lowering therapies. New modifications to miRNA mimetics and inhibitors, increasing targeting efficacy and cellular uptake, will likely enable future therapies to exploit miRNA gene regulatory networks.
At this time, the applicability and full potential of miRNAs in clinical practice is unknown. Nonetheless, recent advances in miRNA delivery and inhibition hold great promise of a tremendous clinical impact in atherosclerosis and cholesterol regulation.
microRNAs (miRNAs) are non-coding small RNAs regulating gene expression, cell growth, and differentiation. Although several miRNAs have been implicated in cell growth and differentiation, it is barely understood their roles in adipocyte differentiation. In the present study, we reveal that miR-27a is involved in adipocyte differentiation by binding to the PPARgamma 3'-UTR whose sequence motifs are highly conserved in mammals. During adipogenesis, the expression level of miR-27a was inversely correlated with that of adipogenic marker genes such as PPARgamma and adiponectin. In white adipose tissue, miR-27a was more abundantly expressed in stromal vascular cell fraction than in mature adipocyte fraction. Ectopic expression of miR-27a in 3T3-L1 pre-adipocytes repressed adipocyte differentiation by reducing PPARgamma expression. Interestingly, the level of miR-27a in mature adipocyte fraction of obese mice was down-regulated than that of lean mice. Together, these results suggest that miR-27a would suppress adipocyte differentiation through targeting PPARgamma and thereby down-regulation of miR-27a might be associated with adipose tissue dysregulation in obesity.
MicroRNAs (miRNAs) represent a class of small, non-coding RNAs that negatively regulate gene expression via degradation or translational inhibition of their target mRNAs. Recent studies have identified that miR-145 is the most abundant miRNA in normal arteries and vascular smooth muscle cells (VSMCs), and its expression is significantly downregulated in dediffer-entiated VSMCs and atherosclerotic arteries. miR-145 plays a critical role in modulating VSMC phenotype. Because phenotypic modulation of VSMCs is an initial cellular event in the development of atherosclerosis, miRNAs, and miR-145 in particular, may represent new therapeutic targets for atherosclerosis.
1. MicroRNAs (miRNAs), the small non-coding RNAs of approximately 22 nucleotides, are now recognized as a very large family present throughout the genomes of plants and metazoans. These small transcripts modulate protein expression by binding to complementary or partially complementary target protein-coding mRNAs and targeting them for degradation or translational inhibition.
2. The discovery of miRNAs has revolutionized our understanding of the mechanisms that regulate gene expression, with the addition of an entirely novel level of regulatory control. Considerable information on miRNAs has been accumulated in this rapidly evolving research field. We now know that miRNAs play pivotal roles in diverse processes, such as development and differentiation, control of cell proliferation and death, stress response and metabolism. Indeed, aberrant miRNA expression has been documented in human disease as well as in animal models, with evidence for a causative role in tumourigenesis.
3. One of the most active fields of miRNA research is miRNA regulation of apoptosis, a programmed cell death implicated in many human diseases, such as cancer, Alzheimer’s disease, hypertrophy and heart failure. Thus far, nearly 30 of 500 human miRNAs have been validated experimentally to regulate apoptosis; this number is likely to increase with future studies.
4. The present review provides a comprehensive summary and analysis of the currently available data, focusing on the transcriptional controls, target genes and signalling pathways linking the apoptosis-regulating miRNAs and apoptotic cell death.
MicroRNAs (miRNAs) are involved in a plethora of important biological processes, from embryonic development to homeostasis in adult tissues. Recently, miRNAs have emerged as a class of epigenetic regulators of metabolism and energy homeostasis. We have investigated the role of miRNAs in the regulation of adipogenic differentiation. In this article, we demonstrate that the miR-27 gene family is downregulated during adipogenic differentiation. Overexpression of miR-27 specifically inhibited adipocyte formation, without affecting myogenic differentiation. We also found that expression of miR-27 resulted in blockade of expression of PPARgamma and C/EBPalpha, the two master regulators of adipogenesis. Importantly, expression of miR-27 was increased in fat tissue of obese mice and was regulated by hypoxia, an important extracellular stress associated with obesity. Our data strongly suggest that miR-27 represents a new class of adipogenic inhibitors and may play a role in the pathological development of obesity.
miRNAs silence gene expression by repressing translation and/or by promoting mRNA decay. In animal cells, degradation of partially complementary miRNA targets occurs via deadenylation by the CAF1-CCR4-NOT1 deadenylase complex, followed by decapping and subsequent exonucleolytic digestion. To determine how generally miRNAs trigger deadenylation, we compared mRNA expression profiles in D. melanogaster cells depleted of AGO1, CAF1, or NOT1. We show that approximately 60% of AGO1 targets are regulated by CAF1 and/or NOT1, indicating that deadenylation is a widespread effect of miRNA regulation. However, neither a poly(A) tail nor mRNA circularization are required for silencing, because mRNAs whose 3' ends are generated by a self-cleaving ribozyme are also silenced in vivo. We show further that miRNAs trigger mRNA degradation, even when binding by 40S ribosomal subunits is inhibited in cis. These results indicate that miRNAs promote mRNA decay by altering mRNP composition and/or conformation, rather than by directly interfering with the binding and function of ribosomal subunits.
lin-4 is essential for the normal temporal control of diverse postembryonic developmental events in C. elegans. lin-4 acts by negatively regulating the level of LIN-14 protein, creating a temporal decrease in LIN-14 protein starting in the first larval stage (L1). We have cloned the C. elegans lin-4 locus by chromosomal walking and transformation rescue. We used the C. elegans clone to isolate the gene from three other Caenorhabditis species; all four Caenorhabditis clones functionally rescue the lin-4 null allele of C. elegans. Comparison of the lin-4 genomic sequence from these four species and site-directed mutagenesis of potential open reading frames indicated that lin-4 does not encode a protein. Two small lin-4 transcripts of approximately 22 and 61 nt were identified in C. elegans and found to contain sequences complementary to a repeated sequence element in the 3' untranslated region (UTR) of lin-14 mRNA, suggesting that lin-4 regulates lin-14 translation via an antisense RNA-RNA interaction.
MicroRNAs (miRNAs) are a new class of noncoding RNAs, which are encoded as short inverted repeats in the genomes of invertebrates and vertebrates. It is believed that miRNAs are modulators of target mRNA translation and stability, although most target mRNAs remain to be identified. Here we describe the identification of 34 novel miRNAs by tissue-specific cloning of approximately 21-nucleotide RNAs from mouse. Almost all identified miRNAs are conserved in the human genome and are also frequently found in nonmammalian vertebrate genomes, such as pufferfish. In heart, liver, or brain, it is found that a single, tissue-specifically expressed miRNA dominates the population of expressed miRNAs and suggests a role for these miRNAs in tissue specification or cell lineage decisions. Finally, a miRNA was identified that appears to be the fruitfly and mammalian ortholog of C. elegans lin-4 stRNA.
We predict regulatory targets of vertebrate microRNAs (miRNAs) by identifying mRNAs with conserved complementarity to the seed (nucleotides 2-7) of the miRNA. An overrepresentation of conserved adenosines flanking the seed complementary sites in mRNAs indicates that primary sequence determinants can supplement base pairing to specify miRNA target recognition. In a four-genome analysis of 3' UTRs, approximately 13,000 regulatory relationships were detected above the estimate of false-positive predictions, thereby implicating as miRNA targets more than 5300 human genes, which represented 30% of our gene set. Targeting was also detected in open reading frames. In sum, well over one third of human genes appear to be conserved miRNA targets.
Current understanding of microRNA (miRNA) biology is limited, and antisense oligonucleotide (ASO) inhibition of miRNAs is a powerful technique for their functionalization. To uncover the role of the liver-specific miR-122 in the adult liver, we inhibited it in mice with a 2'-O-methoxyethyl phosphorothioate ASO. miR-122 inhibition in normal mice resulted in reduced plasma cholesterol levels, increased hepatic fatty-acid oxidation, and a decrease in hepatic fatty-acid and cholesterol synthesis rates. Activation of the central metabolic sensor AMPK was also increased. miR-122 inhibition in a diet-induced obesity mouse model resulted in decreased plasma cholesterol levels and a significant improvement in liver steatosis, accompanied by reductions in several lipogenic genes. These results implicate miR-122 as a key regulator of cholesterol and fatty-acid metabolism in the adult liver and suggest that miR-122 may be an attractive therapeutic target for metabolic disease.
To establish a unified working diagnostic tool for the metabolic syndrome (MetS) that is convenient to use in clinical practice and that can be used world-wide so that data from different countries can be compared. An additional aim was to highlight areas where more research into the MetS is needed.
The International Diabetes Federation (IDF) convened a workshop held 12-14 May 2004 in London, UK. The 21 participants included experts in the fields of diabetes, public health, epidemiology, lipidology, genetics, metabolism, nutrition and cardiology. There were participants from each of the five continents as well as from the World Health Organization (WHO) and the National Cholesterol Education Program-Third Adult Treatment Panel (ATP III). The workshop was sponsored by an educational grant from AstraZeneca Pharmaceuticals.
The consensus statement emerged following detailed discussions at the IDF workshop. After the workshop, a writing group produced a consensus statement which was reviewed and approved by all participants.
The IDF has produced a new set of criteria for use both epidemiologically and in clinical practice world-wide with the aim of identifying people with the MetS to clarify the nature of the syndrome and to focus therapeutic strategies to reduce the long-term risk of cardiovascular disease. Guidance is included on how to compensate for differences in waist circumference and in regional adipose tissue distribution between different populations. The IDF has also produced recommendations for additional criteria that should be included when studying the MetS for research purposes. Finally, the IDF has identified areas where more studies are currently needed; these include research into the aetiology of the syndrome.