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Inhibition of soluble epoxide hydrolase modulates inflammation and autophagy in obese adipose tissue and liver: Role for omega-3 epoxides
Abstract
Significance
Our study demonstrates that stabilization of cytochrome P-450 epoxides derived from omega-3 polyunsaturated fatty acids through inhibition of the inactivating enzyme soluble epoxide hydrolase (sEH) exerts beneficial actions in counteracting metabolic disorders associated with obesity. In addition, our study sheds more light on the role of sEH in cellular homeostasis by providing evidence that omega-3 epoxides and sEH inhibition regulate autophagy and endoplasmic reticulum stress in insulin-sensitive tissues, especially the liver. Therefore, administration of a sEH inhibitor is a promising strategy to prevent obesity-related comorbidities.
... In a tumor mouse model, it was shown, that low dose sEH-inhibition led to an increase in n-3 DHAderived 19,20-EDP and thereby reduced tumor angiogenesis and cell invasion and thus inhibition of tumor growth . Furthermore, a protective effect in obesity and obesityrelated comorbidities, such as fatty liver disease, of n-3 epoxy PUFA was found in animal models (López-Vicario et al., 2015). The beneficial effects of n-3 PUFA regarding to cancer and its complications are probably due to their anti-inflammatory and pro-resolution mediators (Freitas and Campos, 2019). ...
... When taking into account the different levels of the precursor n-3 PUFAs EPA and DHA we were able to establish that EPA is metabolized by CYP enzymes to a similar extent as AA, while DHA utilization was higher, leading to significantly increased levels of the 19,20-metabolites derived from DHA during sorafenib treatment ( Figures 2E, 5B). Given that previous data from mouse models show inhibition of tumor angiogenesis and reduced cell invasion by increasing 19,20-EDP and to dampen and alleviate inflammation in the liver (López-Vicario et al., 2015), this could be a beneficial effect of sorafenib that could be harnessed in HCC therapy by supplementing DHA. ...
... Another explanation would be that sorafenib may have more complex effects on PUFA-derived metabolites in humans, with increased formation of epoxy-PUFAs. We did not analyse expression of sEH directly, therefore there is a possibility of increased sEH expression, as described in an animal models of high fat diet induced liver disease (López-Vicario et al., 2015) which might compensate for an inhibitory effect of sorafenib. Interestingly, in our pilot study we found an increase of 8,9-EET, 11,12-EET and 14,15-EET levels in HCC patients treated with sorafenib (Leineweber et al., 2020) while we found a significant increase only of 5,6-EET and 8,9-EET levels here. ...
Hepatocellular carcinoma (HCC) is a leading cause of cancer death, and medical treatment options are limited. The multikinase inhibitor sorafenib was the first approved drug widely used for systemic therapy in advanced HCC. Sorafenib might affect polyunsaturated fatty acids (PUFA)-derived epoxygenated metabolite levels, as it is also a potent inhibitor of the soluble epoxide hydrolase (sEH), which catalyzes the conversion of cytochrome-P450 (CYP)-derived epoxide metabolites derived from PUFA, such as omega-6 arachidonic acid (AA) and omega-3 docosahexaenoic acid (DHA), into their corresponding dihydroxy metabolites. Experimental studies with AA-derived epoxyeicosatrienoic acids (EETs) have shown that they can promote tumor growth and metastasis, while DHA-derived 19,20-epoxydocosapentaenoic acid (19,20-EDP) was shown to have anti-tumor activity in mice. In this study, we found a significant increase in EET levels in 43 HCC patients treated with sorafenib and a trend towards increased levels of DHA-derived 19,20-EDP. We demonstrate that the effect of sorafenib on CYP- metabolites led to an increase of 19,20-EDP and its dihydroxy metabolite, whereas DHA plasma levels decreased under sorafenib treatment. These data indicate that specific supplementation with DHA could be used to increase levels of the epoxy compound 19,20-EDP with potential anti-tumor activity in HCC patients receiving sorafenib therapy.
... Aging is a biological process that increases the risk for almost all health-related adverse phenotypes [28][29][30][31][32][33]35,37], while BMI is a measure of obesity, which has been linked to an increased risk for cardiometabolic disorders and death [28,31,32,39,40]. While the relationships of sEH with obesity [9,[41][42][43][44][45][46][47][48][49] and age [50][51][52] have been indirectly assessed in several animal studies, how age and BMI affect sEH in adult women has not been directly examined. ...
... BMI is a well-studied risk factor for cardiometabolic disorders [28,31,32,39,40]. Several studies found that sEH expression and activity were increased in obese humans, in mice, and during adipogenesis [9,[42][43][44][45][46][47][48][49]. Our earlier work has shown that a EPHX2 polymorphism, rs2291635, moderated the association between BMI increase and cholesterol levels [91]. ...
... Our earlier work has shown that a EPHX2 polymorphism, rs2291635, moderated the association between BMI increase and cholesterol levels [91]. In this study, despite significant BMI differences between HW and AN groups, BMI was positively correlated with sEH expression and activity in both groups, consistent with previous findings that higher BMI is linked to a higher level of sEH [9,[42][43][44][45][46][47][48][49]. ...
The metabolism of bioactive oxylipins by soluble epoxide hydrolase (sEH) plays an important role in inflammation, and sEH may be a risk modifier in various human diseases and disorders. The relationships that sEH has with the risk factors of these diseases remain elusive. Herein, sEH protein expression and activity in white blood cells were characterized before and after a high-fat meal in healthy women (HW) and women with anorexia nervosa (AN). sEH expression and sEH activity were significantly correlated and increased in both groups two hours after consumption of the study meal. Fasting sEH expression and activity were positively associated with body mass index (BMI) in both groups, while an inverse association with age was found in AN only (p value < 0.05). sEH was not associated with anxiety or depression in either group at the fasting timepoint. While the anxiety score decreased after eating in both groups, a higher fasting sEH was associated with a lower postprandial anxiety decrease in HW (p value < 0.05). sEH characterization using direct measurements verified the relationship between the protein expression and in vivo activity of this important oxylipin modulator, while a well-controlled food challenge study design using HW and a clinical control group of women with disordered eating elucidated sEH’s role in the health of adult women.
... fat-1 gene from Caenorhabditis elegans that allows endogenous conversion of omega-6 into omega-3-PUFA. [17][18][19] Fat-1 mice possess a high omega-3-PUFA content in cell membrane phospholipids, evading any confounding factor inherent to the supplementation of PUFAs through the diet. In addition, fat-1 mice are endogenously enriched with omega-3-derived lipid autacoids. ...
... Hemizygous fat-1 mice were generated and backcrossed onto a C57BL/6 background and genotyped by capillary electrophoresis as previously described [17,19] and as detailed in the online Supporting Information (SI). All animal studies were conducted in accordance with the criteria of the Investigation and Ethics Committee of the University of Barcelona (Barcelona, Spain) following the EU laws governing the use of experimental animals. ...
... The results of the current study also provide a mechanistic basis by which fat-1 mice are resistant to obesity-induced hepatic steatosis, insulin resistance, inflammation in insulin-sensitive tissues (white adipose tissue [WAT] and liver), and liver fibrosis. [18,19] Our findings might also explain why animals endogenously enriched with omega-3-PUFAs are protected against alcohol-induced liver injury, [40] a condition characterized by widespread mitochondrial damage. [41] Our study also provides some mechanistic insights beyond the liver cells as to why omega-3-PUFA-enriched animals have a reduced risk for noncommunicable diseases including metabolic disease, colon inflammation-triggered injury, pancreatitis, acute lung injury, inflammatory burden during preterm birth, vascular inflammation, and neuroinflammatory injury among others in which loss of mitochondria function is common. ...
Background&aim:
Injury to hepatocyte mitochondria is common in metabolic dysfunction-associated fatty liver disease. Here, we investigated whether changes in the content of essential fatty acid-derived lipid autacoids affect hepatocyte mitochondrial bioenergetics and metabolic efficiency.
Approach&results:
The study was performed in transgenic mice for the fat-1 gene, which allows the endogenous replacement of the membrane omega-6-polyunsaturated fatty acid (PUFA) composition by omega-3-PUFA. Transmission electron microscopy revealed that hepatocyte mitochondria of fat-1 mice had more abundant intact cristae and higher mitochondrial aspect ratio. Fat-1 mice had increased expression of oxidative phosphorylation complexes I and II and translocases of both inner (TIM44) and outer (TOM20) mitochondrial membranes. Fat-1 mice also showed increased mitofusin-2 and reduced DRP1 phosphorylation, which mediate mitochondrial fusion and fission, respectively. Mitochondria of fat-1 mice exhibited enhanced oxygen consumption rate, fatty acid β-oxidation and energy substrate utilization as determined by high-resolution respirometry, [1-14 C]-oleate oxidation and NADH/FADH2 production, respectively. Untargeted lipidomics identified a rich hepatic omega-3-PUFA composition and a specific docosahexaenoic acid (DHA)-enriched lipid fingerprint in fat-1 mice. Targeted lipidomics uncovered a higher content of DHA-derived lipid autacoids, namely resolvin D1 and maresin 1, which rescued hepatocytes from TNFα-induced mitochondrial dysfunction, unblocked the tricarboxylic acid cycle flux and metabolic utilization of long-chain acyl-carnitines, amino acids and carbohydrates. Importantly, fat-1 mice were protected against mitochondrial injury induced by obesogenic and fibrogenic insults.
Conclusion:
Our data uncover the importance of a lipid membrane composition rich in DHA and its lipid autacoid derivatives to have optimal hepatic mitochondrial and metabolic efficiency.
... For example, many investigations have identified positive outcomes in ameliorating lung inflammation/disease via therapeutic administration of SPM (Croasdell et al., 19502016;Seki et al., 19502010;Aoki et al., 2008;Haworth et al., 2011;Hsiao et al., 2013;Miyata and Arita, 2015;Kim et al., 2016), including our own previous studies identifying beneficial effects of the DHA-derived SPM maresin-1 in reducing the lung inflammatory effects of acute and repetitive organic dust exposure (Nordgren et al., 2013;Nordgren et al., 2015). While SPM can potently inhibit inflammation while promoting tissue repair, these bioactive metabolites are quickly deactivated by subsequent metabolism (Lopez-Vicario et al., 2015;Basil and Levy, 2016). Thus, another therapeutic strategy to leverage these endogenous inflammation resolution pathways is to combine ω-3 PUFA supplementation with pharmacologic inhibition of enzymes responsible for the deactivation of SPM. ...
... One such strategy has been the use of inhibitors of the sEH enzyme to prevent the deactivation of the cytochrome P450 family of SPM, thereby potentiating their protective effects (Guedes et al., 2013;Ulu et al., 2013;Ulu et al., 2014;Yang et al., 2015;Ulu et al., 2016;Zhou et al., 2016;Goswami et al., 2017;Zhou et al., 2017;Yang et al., 2020;Zhang et al., 2020). Previous studies have found enhanced protective effects of ω-3 PUFA when used in combination with inhibitors of sEH such as TPPU (Wang et al., 2012;Lopez-Vicario et al., 2015;Yang et al., 2015;Zhou et al., 2016;Zhou et al., 2017). This enzyme deactivates the epoxide SPM (e.g., 19, 20-EDP; produced through CYP450 metabolism) into less active diol forms (e.g., 19 (20)-DiHDPA). ...
... This enzyme deactivates the epoxide SPM (e.g., 19, 20-EDP; produced through CYP450 metabolism) into less active diol forms (e.g., 19 (20)-DiHDPA). A recent study in a model of metabolic disease identified that a sEH inhibitor enhanced the protective effects identified in Fat-1 mice vs. WT mice (Lopez-Vicario et al., 2015), while previous studies also identify beneficial effects of sEH inhibition in murine models of acute lung injury (Zhou et al., 2017), pulmonary fibrosis (Zhou et al., 2016), asthma (Yang et al., 2015), and COPD (Wang et al., 2012). Corroborating these previous reports, when we utilized TPPU in the experiments described herein, we found that addition of TPPU lowered all outcomes examined in the DE-exposed animals, suggesting that TPPU not only enhanced the effects of ω-3 fatty acids as in Fat-1 + DE + TPPU animals, but also showed efficacy independent of the Fat-1 genotype. ...
In agriculture industries, workers are at increased risk for developing pulmonary diseases due to inhalation of agricultural dusts, particularly when working in enclosed confinement facilities. Agricultural dusts inhalation leads to unresolved airway inflammation that precedes the development and progression of lung disease. We have previously shown beneficial effects of the omega-3 polyunsaturated fatty acid (ω-3 PUFA) DHA in protecting against the negative inflammatory effects of repetitive dust exposure in the lung. Dietary manipulation of pulmonary disease risk is an attractive and timely approach given the contribution of an increased ω-6 to ω-3 PUFA ratio to low grade inflammation and chronic disease in the Western diet. To prevent any confounding factors that comes with dietary supplementation of ω-3 PUFA (different sources, purity, dose, and duration), we employed a Fat-1 transgenic mouse model that convert ω-6 PUFA to ω-3 PUFA, leading to a tissue ω-6 to ω-3 PUFA ratio of approximately 1:1. Building on our initial findings, we hypothesized that attaining elevated tissue levels of ω-3 PUFA would attenuate agricultural dust-induced lung inflammation and its resolution. To test this hypothesis, we compared wild-type (WT) and Fat-1 transgenic mice in their response to aqueous extracts of agricultural dust (DE). We also used a soluble epoxide hydrolase inhibitor (sEH) to potentiate the effects of ω-3 PUFA, since sEH inhibitors have been shown to stabilize the anti-inflammatory P450 metabolites derived from both ω-3 and ω-6 PUFA and promote generation of specialized pro-resolving lipid mediators from ω-3 PUFA. Over a three-week period, mice were exposed to a total of 15 intranasal instillations of DE obtained from swine confinement buildings in the Midwest. We observed genotype and sex-specific differences between the WT vs. Fat-1 transgenic mice in response to repetitive dust exposure, where three-way ANOVA revealed significant main effects of treatment, genotype, and sex. Also, Fat-1 transgenic mice displayed reduced lymphoid aggregates in the lung following DE exposure as compared to WT animals exposed to DE, suggesting improved resilience to the DE-induced inflammatory effects. Overall, our data implicate a protective role of ω-3 FA in the lung following repetitive dust exposure.
... EpFAs are regulated in part by being metabolized to vicinal diols mostly by the soluble epoxide hydrolase (sEH) [1]. The sEH is now a therapeutic target for several diseases [8][9][10][11][12][13][14][15]. Unlike EpFAs, the vicinal diols are mostly reported as largely fewer active metabolites of the beneficial epoxides or for their putative toxicity and pro-inflammation effects [16]. ...
... The main difficulty in analyzing fatty acid vicinal diols is the presence of numerous regioisomers. For example, four possible regioisomeric diols are formed from ARA-i.e., 5,6-DiHETrE, 8,11,and 14,-which have different biological activities. These regioisomers make a difficult analytical problem even more complicated. ...
... EpFAs are very important signaling mediators in a variety of biological processes The sEH, expressed in almost every organ, is the primary enzyme that degrades these chemicals in vivo, by degrading the EpFAs to their corresponding and usually less-active vicinal diols [1]. The pharmacological inhibition of sEH for stabilizing EpFAs is considered for the Molecules 2022, 27, 283 7 of 11 treatment of numerous diseases [8][9][10][11][12][13][14][15]. Using purified EpFAs regioisomers, it was shown that sEH has selectivity among the different regioisomers of these natural epoxides [35,36]. ...
Vicinal diols are important signaling metabolites of various inflammatory diseases, and some of them are potential biomarkers for some diseases. Utilizing the rapid reaction between diol and 6-bromo-3-pyridinylboronic acid (BPBA), a selective and sensitive approach was established to profile these vicinal diols using liquid chromatography-post column derivatization coupled with double precursor ion scan-mass spectrometry (LC-PCD-DPIS-MS). After derivatization, all BPBA-vicinal-diol esters gave a pair of characteristic isotope ions resulting from 79Br and 81Br. The unique isotope pattern generated two characteristic fragment ions of m/z 200 and 202. Compared to a traditional offline derivatization technique, the new LC-PCD-DPIS-MS method retained the capacity of LC separation. In addition, it is more sensitive and selective than a full scan MS method. As an application, an in vitro study of the metabolism of epoxy fatty acids by human soluble epoxide hydrolase was tested. These vicinal-diol metabolites of individual regioisomers from different types of polyunsaturated fatty acids were easily identified. The limit of detection (LOD) reached as low as 25 nM. The newly developed LC-PCD-DPIS-MS method shows significant advantages in improving the selectivity and therefore can be employed as a powerful tool for profiling vicinal-diol compounds from biological matrices.
... Omega-3 fatty acids can be metabolized by CYP enzymes into epoxy omega-3 derivatives, i.e., EEQ and EDP, that will inhibit tumor growth and metastasis by suppressing tumor angiogenesis [30]. However, epoxy omega-3 EEQ/EDP are unstable and will be further hydrolyzed into inactive diols by sEH [56]. sEH is a cytosolic enzyme that catalyzes the rapid hydration of EEQ and EDP by adding water to these epoxygenated fatty acids (EpFAs) and converting them into inactive or less active 1,2-diols [56,57]. ...
... However, epoxy omega-3 EEQ/EDP are unstable and will be further hydrolyzed into inactive diols by sEH [56]. sEH is a cytosolic enzyme that catalyzes the rapid hydration of EEQ and EDP by adding water to these epoxygenated fatty acids (EpFAs) and converting them into inactive or less active 1,2-diols [56,57]. Xia et al. reported [58] that a combination of use omega-3 fatty acids and sEH inhibition is a strategy with high potential for pancreatic cancer treatment and prevention. ...
Lung cancer is the leading cause of cancer death worldwide. Polycyclic aromatic hydrocarbons (PAHs) are metabolized by the cytochrome P450 (CYP)1A and 1B1 to DNA-reactive metabolites, which could lead to mutations in critical genes, eventually resulting in cancer. Omega-3 fatty acids, such as eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), are beneficial against cancers. In this investigation, we elucidated the mechanisms by which omega-3 fatty acids EPA and DHA will attenuate PAH-DNA adducts and lung carcinogenesis and tumorigenesis mediated by the PAHs BP and MC. Adult wild-type (WT) (A/J) mice, Cyp1a1-null, Cyp1a2-null, or Cyp1b1-null mice were exposed to PAHs benzo[a]pyrene (BP) or 3-methylcholanthrene (MC), and the effects of omega-3 fatty acid on PAH-mediated lung carcinogenesis and tumorigenesis were studied. The major findings were as follows: (i) omega-3 fatty acids significantly decreased PAH-DNA adducts in the lungs of each of the genotypes studied; (ii) decreases in PAH-DNA adduct levels by EPA/DHA was in part due to inhibition of CYP1B1; (iii) inhibition of soluble epoxide hydrolase (sEH) enhanced the EPA/DHA-mediated prevention of pulmonary carcinogenesis; and (iv) EPA/DHA attenuated PAH-mediated carcinogenesis in part by epigenetic mechanisms. Taken together, our results suggest that omega-3 fatty acids have the potential to be developed as cancer chemo-preventive agents in people.
... Inhibiting sEH, either through genetic deletion or pharmacological intervention, leads to elevated levels of EETs, resulting in a spectrum of protective effects (5), so sEH has emerged as a potential pharmacological target for kidney diseases. Moreover, sEH exerts regulatory effects on renal diseases through mechanisms involving oxidative stress, inflammation, endoplasmic reticulum (ER) stress, and autophagy (6)(7)(8). This intricate interplay between sEH, EETs, and their impact on renal physiology and pathology forms a critical nexus in understanding and potentially intervening in various renal-associated diseases. ...
... It can be found that these labeled elements do play a significant role in the development and maturation evolution of autophagosomes. This finding is the same as the increased autophagy behavior that has been reported due to symptoms of sEH deficiency (8,60). With the continuous demonstration of experimental phenomena, autophagic cells play a great role in regulating kidney function and ensuring kidney function. ...
In recent years, numerous experimental studies have underscored the pivotal role of soluble epoxide hydrolase (sEH) in renal diseases, demonstrating the reno-protective effects of sEH inhibitors. The nexus between sEH and renal-associated diseases has garnered escalating attention. This review endeavors to elucidate the potential molecular mechanisms of sEH in renal diseases and emphasize the critical role of sEH inhibitors as a prospective treatment modality. Initially, we expound upon the correlation between sEH and Epoxyeicosatrienoic acids (EETs) and also addressing the impact of sEH on other epoxy fatty acids, delineate prevalent EPHX2 single nucleotide polymorphisms (SNPs) associated with renal diseases, and delve into sEH-mediated potential mechanisms, encompassing oxidative stress, inflammation, ER stress, and autophagy. Subsequently, we delineate clinical research pertaining to sEH inhibition or co-inhibition of sEH with other inhibitors for the regulation of renal-associated diseases, covering conditions such as acute kidney injury, chronic kidney diseases, diabetic nephropathy, and hypertension-induced renal injury. Our objective is to validate the potential role of sEH inhibitors in the treatment of renal injuries. We contend that a comprehensive comprehension of the salient attributes of sEH, coupled with insights from clinical experiments, provides invaluable guidance for clinicians and presents promising therapeutic avenues for patients suffering from renal diseases.
... In addition, evidence suggests that specialized pro-resolving mediators (SPM), derived from n-3 PUFA via LOX action, could regulate inflammation resolution (4). This supports the concept of n-3 PUFA derived inflammation-dampening oxylipins (n-3 IDOs) (25)(26)(27). In contrast, n-6 PUFA metabolites may have opposite or neutral effects (28). ...
... In contrast, EETs help dilate arteries and reduce inflammation, but their sEH products may negate the protective effects (59). Given the experimental data implicating n-3 PUFA derived inflammation-dampening oxylipins in the alleviation of metabolic liver disease (25)(26)(27)60), our data presented here support a concept of optimizing n-3 PUFA levels by identifying individuals with fatty acid imbalance and evidence of excess inflammation, rebalancing oxylipin profiles could significantly impact outcomes. This could alleviate metabolic disease-associated inflammation due to increased n-3 inflammation dampening oxylipin (n-3 IDO) formation with increased TGs, and liver fat, in patients with T2DM. ...
Objective
Dyslipidemia, in particular elevated triglycerides (TGs) contribute to increased cardiovascular risk in type 2 diabetes mellitus (T2DM). In this pilot study we aimed to assess how increased TGs affect hepatic fat as well as polyunsaturated fatty acid (PUFA) metabolism and oxylipin formation in T2DM patients.
Methods
40 patients with T2DM were characterized analyzing routine lipid blood parameters, as well as medical history and clinical characteristics. Patients were divided into a hypertriglyceridemia (HTG) group (TG ≥ 1.7mmol/l) and a normal TG group with TGs within the reference range (TG < 1.7mmol/l). Profiles of PUFAs and their oxylipins in plasma were measured by gas chromatography and liquid chromatography/tandem mass spectrometry. Transient elastography (TE) was used to assess hepatic fat content measured as controlled attenuation parameter (CAP) (in dB/m) and the degree of liver fibrosis measured as stiffness (in kPa).
Results
Mean value of hepatic fat content measured as CAP as well as body mass index (BMI) were significantly higher in patients with high TGs as compared to those with normal TGs, and correlation analysis showed higher concentrations of TGs with increasing CAP and BMI scores in patients with T2DM. There were profound differences in plasma oxylipin levels between these two groups. Cytochrome P450 (CYP) and lipoxygenase (LOX) metabolites were generally more abundant in the HTG group, especially those derived from arachidonic acid (AA), eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA), γ-linolenic acid (γ-LA), and α-linolenic acid (α-LA), and a strong correlation between TG levels and plasma metabolites from different pathways was observed.
Conclusions
In adult patients with T2DM, elevated TGs were associated with increased liver fat and BMI. Furthermore, these patients also had significantly higher plasma levels of CYP- and LOX- oxylipins, which could be a novel indicator of increased inflammatory pathway activity, as well as a novel target to dampen this activity.
... The fat-1 mouse is a transgenic animal model able to produce n-3 PUFA endogenously due to introduction of an ω-3 FA desaturase-1 (fat-1) [32]. It has previously been shown, by us and others, that expression of the fat-1 gene and subsequent increase of endogenous n-3 PUFA protects mice from inflammation as well as tumorigenesis in the colon [33][34][35][36][37][38] and the liver [39][40][41][42][43][44][45][46][47]. ...
... This was accompanied by highly notable increases of established inflammation-dampening n-3 PUFA-derived oxylipins in fat-1 colons, especially from EPA such as 15-HEPE and 17,18-EEQ, as previously shown by us in both healthy and colitis-affected mice [16,54]. Particularly, the epoxy compounds 19,20-EDP and 17,18-EEQ are established mediators to alleviate liver inflammation [41]. While we cannot show that these oxylipins are directly responsible for the lower inflammatory phenotype in the liver, we speculate that these oxylipin mediators have systemic effects to dampen concomitant liver inflammation and oxidative damage in the fat-1 mice with colitis, leading to a healthier phenotype after DSS-induced colitis compared to control mice and fewer signs of oxidative damage. ...
Inflammatory bowel disease (IBD) is an immune-mediated gut dysfunction, which might also be associated with an inflammatory phenotype in the liver. It is known that the nutritional intake of omega-3 polyunsaturated fatty acids (n-3 PUFA) is inversely correlated to the severity and occurrence of IBD. In order to investigate whether n-3 PUFA can also reduce liver inflammation and oxidative liver damage due to colon inflammation, we explored the dextran sulfate sodium (DSS)-induced colitis model in wild-type and fat-1 mice with endogenously increased n-3 PUFA tissue content. Besides confirming previous data of alleviated DSS-induced colitis in the fat-1 mouse model, the increase of n-3 PUFA also resulted in a significant reduction of liver inflammation and oxidative damage in colitis-affected fat-1 mice as compared to wild-type littermates. This was accompanied by a remarkable increase of established inflammation-dampening n-3 PUFA oxylipins, namely docosahexaenoic acid-derived 19,20-epoxydocosapentaenoic acid and eicosapentaenoic acid-derived 15-hydroxyeicosapentaenoic acid and 17,18-epoxyeicosatetraenoic acid. Taken together, these observations demonstrate a strong inverse correlation between the anti-inflammatory lipidome derived from n-3 PUFA and the colitis-triggered inflammatory changes in the liver by reducing oxidative liver stress.
... Although our data clearly demonstrates that nutritional stess in the form of WD feeding is associated with reduced liver mitophagy, the underlying mechanism for this effect remains a major outstanding question. One possibility is that reduced mitophagy results from a generalized loss of macroautophagy, which has been reported in models of obesity-associated fatty liver [50][51][52] . Notably, reduced macroautophagy in these reports occurred in extreme models of genetic obesity (ob/ob or db/db) or after long-term high-fat diet feeding of 16 weeks or more [50][51][52] . ...
... One possibility is that reduced mitophagy results from a generalized loss of macroautophagy, which has been reported in models of obesity-associated fatty liver [50][51][52] . Notably, reduced macroautophagy in these reports occurred in extreme models of genetic obesity (ob/ob or db/db) or after long-term high-fat diet feeding of 16 weeks or more [50][51][52] . Whether macroautophagy is reduced in response to short-term dietary stress, such as six weeks where we first observed reduced mitophagy here in mito-Keima mice, remains untested to our knowledge. ...
Nonalcoholic fatty liver disease (NAFLD) encompasses a spectrum of pathologies that includes steatosis, steatohepatitis (NASH) and fibrosis and is strongly associated with insulin resistance and type 2 diabetes. Changes in mitochondrial function are implicated in the pathogenesis of NAFLD, particularly in the transition from steatosis to NASH. Mitophagy is a mitochondrial quality control mechanism that allows for the selective removal of damaged mitochondria from the cell via the autophagy pathway. While past work demonstrated a negative association between liver fat content and rates of mitophagy, when changes in mitophagy occur during the pathogenesis of NAFLD and whether such changes contribute to the primary endpoints associated with the disease are currently poorly defined. We therefore undertook the studies described here to establish when alterations in mitophagy occur during the pathogenesis of NAFLD, as well as to determine the effects of genetic inhibition of mitophagy via conditional deletion of a key mitophagy regulator, PARKIN, on the development of steatosis, insulin resistance, inflammation and fibrosis. We find that loss of mitophagy occurs early in the pathogenesis of NAFLD and that loss of PARKIN accelerates the onset of key NAFLD disease features. These observations suggest that loss of mitochondrial quality control in response to nutritional stress may contribute to mitochondrial dysfunction and the pathogenesis of NAFLD.
... In adipose tissues, ATM frequencies were increased by DSS (Appendix Fig S1A), which resulted in an increased presence of crown-like structures, however, this was comparable between wild-type and Atg7 Ad mice. EpFA can alter macrophage polarization and increase tissue-resident macrophage marker expression such as CD206 (Lopez-Vicario et al, 2015). In line with reduced EpFA levels in the adipose tissue, Atg7 Ad ATMs had a slightly reduced CD206 expression (Appendix Fig S1B) but remained the predominant type of macrophage in the tissue. ...
... Increasing evidence suggests that macrophages are regulated by oxylipins in their environment. Indeed, increased presence of omega-3-derived EpFA achieved either through inhibition of EPHX2 or through supplementation has been shown to promote CD206 expression and IL-10 secretion (Lopez-Vicario et al, 2015;McDougle et al, 2017). In line with the reduced presence of EpFA in Atg7-deficient adipose tissue, we found these two hallmarks of anti-inflammatory macrophages were equally decreased. ...
Lipids play a major role in inflammatory diseases by altering inflammatory cell functions, either through their function as energy substrates or as lipid mediators such as oxylipins. Autophagy, a lysosomal degradation pathway that limits inflammation, is known to impact on lipid availability, however, whether this controls inflammation remains unexplored. We found that upon intestinal inflammation visceral adipocytes upregulate autophagy and that adipocyte-specific loss of the autophagy gene Atg7 exacerbates inflammation. While autophagy decreased lipolytic release of free fatty acids, loss of the major lipolytic enzyme Pnpla2/Atgl in adipocytes did not alter intestinal inflammation, ruling out free fatty acids as anti-inflammatory energy substrates. Instead, Atg7-deficient adipose tissues exhibited an oxylipin imbalance, driven through an NRF2-mediated upregulation of Ephx1. This shift reduced secretion of IL-10 from adipose tissues, which was dependent on the cytochrome P450-EPHX pathway, and lowered circulating levels of IL-10 to exacerbate intestinal inflammation. These results suggest an underappreciated fat-gut crosstalk through an autophagy-dependent regulation of anti-inflammatory oxylipins via the cytochrome P450-EPHX pathway, indicating a protective effect of adipose tissues for distant inflammation.
... The authors concluded that enhanced autophagy may contribute to the maintenance of adipose tissue homeostasis [111]. Another study demonstrated that biologically active derivatives of PUFA may also contribute to autophagy regulation in adipose tissue and the liver [112]. Cytochrome P450 (CYP) epoxygenases catalyze the reaction of epoxides synthesis from PUFAs. ...
... Arachidonic acid (AA) is converted into epoxyeicosatrienoic acids (EETs), which act as autocrine or paracrine factors involved in the regulation of inflammation, hyperalgesia, and tissue regeneration, whereas omega-3 PUFAs EPA and DHA are converted into epoxyeicosatetraenoic (EEQs) and epoxydocosapentaenoic (EDPs) acids, respectively. Using fat-1 transgenic mice (capable of producing n-3 fatty acids from the n-6 type, leading to abundant n-3 fatty acids in their organs and tissues, without the need of a dietary n-3 supply), this research group demonstrated that inhibition of soluble epoxide hydrolase (sHE) leads to down-regulation of ER-stress and decreased autophagy in adipose tissue [112]. On the other hand, in livers from obese fat-1 mice, hepatic ER stress was attenuated in the presence of sEH inhibitor but autophagy was restored. ...
A high-fat diet is one of the causative factors of obesity. The dietary profile of fatty acids is also an important variable in developing obesity, as saturated fatty acids are more obesogenic than monounsaturated and polyunsaturated fatty acids. Overweight and obesity are inseparably connected with the excess of adipose tissue in the body, characterized by hypertrophy and hyperplasia of fat cells, which increases the risk of developing metabolic syndrome. Changes observed within hypertrophic adipocytes result in elevated oxidative stress, unfolded protein accumulation, and increased endoplasmic reticulum (ER) stress. One of the processes involved in preservation of cellular homeostasis is autophagy, which is defined as an intracellular lysosome-dependent degradation system that serves to recycle available macromolecules and eliminate damaged organelles. In obesity, activation of autophagy is increased and the process appears to be regulated by different types of dietary fatty acids. This review describes the role of autophagy in adipose tissue and summarizes the current understanding of the effects of saturated and unsaturated fatty acids in autophagy modulation in adipocytes.
... Although our data clearly demonstrates that nutritional stess in the form of WD feeding is associated with reduced liver mitophagy, the underlying mechanism for this effect remains a major outstanding question. One possibility is that reduced mitophagy results from a generalized loss of macroautophagy, which has been reported in models of obesity-associated fatty liver [49][50][51] . Notably, reduced macroautophagy in these reports occurred in extreme models of genetic obesity (ob/ob or db/db) or after long-term high-fat diet feeding of 16 weeks or more [49][50][51] . ...
... One possibility is that reduced mitophagy results from a generalized loss of macroautophagy, which has been reported in models of obesity-associated fatty liver [49][50][51] . Notably, reduced macroautophagy in these reports occurred in extreme models of genetic obesity (ob/ob or db/db) or after long-term high-fat diet feeding of 16 weeks or more [49][50][51] . Whether macroautophagy is reduced in response to short-term dietary stress, such as six weeks where we rst observed reduced mitophagy here in mito-Keima mice, remains untested to our knowledge. ...
Nonalcoholic fatty liver disease (NAFLD) encompasses a spectrum of pathologies that includes steatosis, steatohepatitis (NASH) and fibrosis and is strongly associated with insulin resistance and type 2 diabetes. Changes in mitochondrial function are implicated in the pathogenesis of NAFLD, particularly in the transition from steatosis to NASH. Mitophagy is a mitochondrial quality control mechanism that allows for the selective removal of damaged mitochondria from the cell via the autophagy pathway. While past work demonstrated a negative association between liver fat content and rates of mitophagy, when changes in mitophagy occur during the pathogenesis of NAFLD and whether such changes contribute to the primary endpoints associated with the disease are currently poorly defined. We therefore undertook the studies described here to establish when alterations in mitophagy occur during the pathogenesis of NAFLD, as well as to determine the effects of genetic inhibition of mitophagy via conditional deletion of a key mitophagy regulator, PARKIN, on the development of steatosis, insulin resistance, inflammation and fibrosis. We find that loss of mitophagy occurs early in the pathogenesis of NAFLD and that loss of PARKIN hastens the onset but not severity of key NAFLD disease features. These observations suggest that loss of mitochondrial quality control in response to nutritional stress may contribute to mitochondrial dysfunction and the pathogenesis of NAFLD.
... For example, 14, 15-EET protects cardiomyocytes during starvation by regulating autophagy [34]. The sEH inhibitor t-TUCB downregulates ER stress and increases hepatic autophagy in metabolic diseases [35]. Additionally, the pulmonary autophagy induced by cigarette smoke is reportedly attenuated in sEH-deficient mice [36]. ...
... This was also observed in vitro. Our results were consistent with those of previous studies showing that AUDA attenuates myocardial ischemia-reperfusion injury [47], prevents apoptosis [48,49], and increases autophagy [34,35]. Overall, these results demonstrate that sEH inhibition exerts beneficial effects against DCM. ...
Background:
Many patients with diabetes die from diabetic cardiomyopathy (DCM); however, effective strategies for the prevention or treatment of DCM have not yet been clarified.
Methods:
Leptin receptor-deficient (db/db) mice were treated with either the soluble epoxide hydrolase (sEH) inhibitor AUDA or vehicle alone. A virus carrying Nrf2 shRNA was used to manipulate Nrf2 expression in db/db mice. Cardiac structures and functions were analyzed using echocardiography and hemodynamic examinations. Primary cardiomyocytes cultured under high glucose and high fat (HGHF) conditions were used to conduct in vitro loss-of-function assays after culture in the presence or absence of AUDA (1 μM). Fluorescence microscopy-based detection of mCherry-GFP-LC3 was performed to assess autophagic flux.
Results:
The sEH inhibitor AUDA significantly attenuated ventricular remodeling and ameliorated cardiac dysfunction in db/db mice. Interestingly, AUDA upregulated Nrf2 expression and promoted its nuclear translocation in db/db mice and the HGHF-treated cardiomyocytes. Additionally, AUDA increased autophagy and decreased apoptosis in db/db mice heart. Furthermore, the administration of AUDA promoted autophagic flux and elevated LC3-II protein level in the presence of bafilomycin A1. However, AUDA-induced autophagy was abolished, and the antiapoptotic effect was partially inhibited upon Nrf2 knockdown.
Conclusion:
Our findings suggest that the sEH inhibitor AUDA attenuates cardiac remodeling and dysfunction in DCM via increasing autophagy and reducing apoptosis, which is relevant to activate Nrf2 signaling pathway.
... 10 By blocking sEH activity, sEH inhibitors prevent the degradation of EpFAs and potentially limit production of DhFAs, which are generally considered to be biologically inactive, less active, or, in some cases, deleterious. 11,12 A recent study from our group found that heavy-drinking individuals with severe ALD had elevated plasma levels of the linoleic acidederived DhFAs 9,10-DiHOME and 12,13-DiHOME and, subsequently, corresponding elevated DhFA/EpFA ratios (an indirect marker of increased sEH activity), compared with healthy control subjects or patients who were heavy drinkers with or without mild liver injury. 13 Studies in experimental animal models of ALD showed that genetic ablation of liver sEH ameliorated ethanol (EtOH)-induced hepatic steatosis, injury, inflammation, and oxidative and endoplasmic reticulum (ER) stress. ...
... Inhibition of the hydrolase, expressed in heart, liver, and [101][102][103]105]; LTA4H inhibitors/FXR agonists ref [108]; FABP1 inhibitors/FXR agonists ref [109]. kidney, reduces inflammation and has been demonstrated useful in the treatment of inflammatory pathologies [86,87]. Dual sHE inhibitors and FXR agonists might hold promise in the treatment of NASH [88]. ...
The farnesoid-x-receptor (FXR) and the G protein bile acid activated receptor (GPBAR)1 are two bile acid activated receptors highly expressed in entero-hepatic, immune, adipose and cardiovascular tissues. FXR and GPBAR1 are clinically validated targets in the treatment of metabolic disorders and FXR agonists are currently trialled in patients with non-alcoholic steato-hepatitis (NASH). Results of these trials, however, have raised concerns over safety and efficacy of selective FXR ligands suggesting that the development of novel agent designed to impact on multiple targets might have utility in the treatment of complex, multigenic, disorders. Harnessing on FXR and GPBAR1 agonists, several novel hybrid molecules have been developed, including dual FXR and GPBAR1 agonists and antagonists, while exploiting the flexibility of FXR agonists toward other nuclear receptors, dual FXR and peroxisome proliferators-activated receptors (PPARs) and liver-X-receptors (LXRs) and Pregnane-X-receptor (PXR) agonists have been reported. In addition, modifications of FXR agonists has led to the discovery of dual FXR agonists and fatty acid binding protein (FABP)1 and Leukotriene B4 hydrolase (LTB4H) inhibitors. The GPBAR1 binding site has also proven flexible to accommodate hybrid molecules functioning as GPBAR1 agonist and cysteinyl leukotriene receptor (CYSLTR)1 antagonists, as well as dual GPBAR1 agonists and retinoid-related orphan receptor (ROR)γt antagonists, dual GPBAR1 agonist and LXR antagonists and dual GPBAR1 agonists endowed with inhibitory activity on dipeptidyl peptidase 4 (DPP4). In this review we have revised the current landscape of FXR and GPBAR1 based hybrid agents focusing on their utility in the treatment of metabolic associated liver disorders.
... white adipose tissue (WAT) of patients might be due to a lower intake of DHA and EPA (32). In addition, the upregulation levels of SPM metabolizing enzymes such as 15-PGDH and eicosanoid oxidoreductases in obese WAT was also associated with the inadequate SPM levels (15,33). Therefore, the findings of our study and of previous studies suggest that the effects of RvD1 and RvD2 on T2DM risk should be further investigated in overweight/ obese populations. ...
Background
Although cellular and animal studies have reported that resolvin D1 (RvD1) and resolvin D2 (RvD2) are mechanisms involved in the development of type 2 diabetes mellitus (T2DM), the impact of RvD1 and RvD2 on the risk of T2DM at a population level remains unclear.
Methods
We included 2755 non-diabetic adults from a community-based cohort in China and followed them for seven years. Cox proportional hazards model was used to estimate hazard ratios (HRs) and 95% confidence intervals (CIs) for the association of RvD1 and RvD2 with T2DM probability. Time-dependent receiver operator characteristics (ROC) curve was used to evaluate the predictive performance of RvD1 and RvD2 for the risk of T2DM based on the Chinese CDC T2DM prediction model (CDRS).
Results
A total of 172 incident T2DM cases were identified. Multivariate-adjusted HRs (95% CI) for T2DM across quartiles of RvD1 levels (Q1, Q2, Q3 and Q4) were 1.00, 1.64 (1.03-2.63), 1.80 (1.13-2.86) and 1.61 (1.01-2.57), respectively. Additionally, body mass index (BMI) showed a significant effect modification in the association of RvD1 with incident T2DM ( P interaction = 0.026). After multivariate adjustment, the HR (95% CI) for T2DM in the fourth compared with the first quartile of RvD2 was 1.94 (95% CI: 1.24-3.03). Time-dependent ROC analysis showed that the area under time-dependent ROC curves of the “CDRS+RvD1+RvD2” model for the 3-, 5- and 7-year risk of T2DM were 0.842, 0.835 and 0.828, respectively.
Conclusions
Higher RvD1 and RvD2 levels are associated with a higher risk of T2DM at the population level.
... One mode of action for TPPU and other sEH inhibitors is believed to involve skewing of the cytochrome P450 (CYP) w-6 metabolite profile to favor antiinflammatory/pro-resolving epoxy fatty acids (EpFAs) over proinflammatory or less active dihydroxy fatty acids (DiHFAs; vicinal diols) generated because of sEH activity. Furthermore, there is intriguing but limited evidence in preclinical models that suggests there is enhanced efficacy in anti-inflammatory effects when w-3s are combined with pharmacologic inhibition of sEH (42)(43)(44)(45)(46). ...
Introduction
Lipopolysaccharide (LPS)-accelerated autoimmune glomerulonephritis (GN) in NZBWF1 mice is a preclinical model potentially applicable for investigating lipidome-modulating interventions against lupus. LPS can be expressed as one of two chemotypes: smooth LPS (S-LPS) or rough LPS (R-LPS) which is devoid of O-antigen polysaccharide sidechain. Since these chemotypes differentially affect toll-like receptor 4 (TLR4)-mediated immune cell responses, these differences may influence GN induction.
Methods
We initially compared the effects of subchronic intraperitoneal (i.p.) injection for 5 wk with 1) Salmonella S-LPS, 2) Salmonella R-LPS, or 3) saline vehicle (VEH) (Study 1) in female NZBWF1 mice. Based on the efficacy of R-LPS in inducing GN, we next used it to compare the impact of two lipidome-modulating interventions, ω-3 polyunsaturated fatty acid (PUFA) supplementation and soluble epoxide hydrolase (sEH) inhibition, on GN (Study 2). Specifically, effects of consuming ω-3 docosahexaenoic acid (DHA) (10 g/kg diet) and/or the sEH inhibitor 1-(4-trifluoro-methoxy-phenyl)-3-(1-propionylpiperidin-4-yl) urea (TPPU) (22.5 mg/kg diet ≈ 3 mg/kg/day) on R-LPS triggering were compared.
Results
In Study 1, R-LPS induced robust elevations in blood urea nitrogen, proteinuria, and hematuria that were not evident in VEH- or S-LPS-treated mice. R-LPS-treated mice further exhibited kidney histopathology including robust hypertrophy, hyperplasia, thickened membranes, lymphocytic accumulation containing B and T cells, and glomerular IgG deposition consistent with GN that was not evident in VEH- or SLPS-treated groups. R-LPS but not S-LPS induced spleen enlargement with lymphoid hyperplasia and inflammatory cell recruitment in the liver. In Study 2, resultant blood fatty acid profiles and epoxy fatty acid concentrations reflected the anticipated DHA- and TPPU-mediated lipidome changes, respectively. The relative rank order of R-LPS-induced GN severity among groups fed experimental diets based on proteinuria, hematuria, histopathologic scoring, and glomerular IgG deposition was: VEH/CON< R-LPS/DHA ≈ R-LPS/TPPU<<< R-LPS/TPPU+DHA ≈ R-LPS/CON. In contrast, these interventions had modest-to- negligible effects on R-LPS-induced splenomegaly, plasma antibody responses, liver inflammation, and inflammation-associated kidney gene expression.
Discussion
We show for the first time that absence of O-antigenic polysaccharide in R-LPS is critical to accelerated GN in lupus-prone mice. Furthermore, intervention by lipidome modulation through DHA feeding or sEH inhibition suppressed R-LPS-induced GN; however, these ameliorative effects were greatly diminished upon combining the treatments.
... Autophagy is inhibited in Ephx2 deficiency mouse model 44 . EETs protect the heart and liver by autophagy regulation 45,46 . Our previous study has shown that TPPU can significantly increase angiogenesis, and reduce acinar cell apoptosis and histological damage in ir-injured mice 47 . ...
Inflammation-induced autophagy is a double-edged sword. Dysfunction of autophagy impairs the differentiation capacity of mesenchymal stem cells and enhances inflammation-induced bone loss. Tooth extraction with periodontal and/or endodontic lesions exacerbates horizontal and vertical resorption of alveolar bone during the healing period. Alveolar socket preservation (ASP) procedure following tooth extraction has important clinical implications for future prosthodontic treatments. Studies have shown that epoxyeicosatrienoic acids (EETs) have significant anti-inflammatory effects and participate in autophagy. However, whether EETs can minimize alveolar bone resorption and contribute to ASP by regulating autophagy levels under inflammatory conditions remain elusive. Here, we figured out that LPS-induced inflammatory conditions increased the inflammatory cytokine and inhibited osteogenic differentiation of human dental pulp stem cells (hDPSCs), and led to excessive autophagy of hDPSCs. Moreover, we identified that increased EETs levels using TPPU, a soluble epoxide hydrolase inhibitor, reversed these negative outcomes. We further demonstrated the potential of TPPU to promote early healing of extraction sockets and ASP, and speculated that it was related to autophagy. Taken together, these results suggest that targeting inhibition of soluble epoxide hydrolase using TPPU plays a protective role in the differentiation and autophagy of mesenchymal stem cells and provides potential feasibility for applying TPPU for ASP, especially under inflammatory conditions.
... However, sEH also hydrolyzes other polyunsaturated fatty acid epoxides (EpFA), namely epoxyeicosatetranoic (EEQ) and epoxydocosapentaenoic (EDP) acids, into their less active diols 36 . Studies into these omega-3 epoxides in the brain and cerebral vasculature in particular remains sparse, although they do also demonstrate vasoactive and antiinflammatory properties in other organ systems [37][38][39][40][41][42][43][44] , which may contribute to the phenotype observed here. Further study into omega-3 epoxide levels in Tie2hsEH mice, and their functions in brain physiology is required. ...
Soluble epoxide hydrolase (sEH) is upregulated in microvascular endothelium of human brain with vascular cognitive impairment (VCI). Transgenic endothelial expression of human sEH in mice (Tie2hsEH) induces endothelial dysfunction (ED), a pathogenetic mechanism of VCI. We sought to determine if endothelial upregulation of sEH is sufficient to cause cognitive impairment, and if cognitive impairment due to chronic hypoperfusion induced by unilateral common carotid artery occlusion (CCAO) is exacerbated in Tie2hsEH mice. Behavioral performance was assessed by the open field, rotarod, novel object, Morris water maze and fear conditioning tests. Cerebral blood flow and brain morphology were evaluated by MRI, and inflammatory changes investigated using immunohistochemistry and flow cytometry. We demonstrate that transgenic endothelial expression of sEH is sufficient to induce cognitive impairment, associated with leukocyte infiltration, brain atrophy and accelerated, age-dependent ventriculomegaly, identifying ED and sEH upregulation as potential underlying mechanisms and therapeutic targets for VCI.
... Epoxidized fatty acids with a 3-membered ring ether are highly reactive lipids; for instance, arachidonic acid-derived epoxidized fatty acids (epoxyeicosanoid; EET) have several functions that affect various processes, such as angiogenesis and anti-inflammation, which contribute to the maintenance of homeostasis [22][23][24] . On the other hand, ω-3 fatty acids are known to have bioprotective effects including cardioprotection [25][26][27] , and in recent years it has been revealed that their epoxy compounds exert strong unique physiological effects such as anti-inflammatory, vasodilatory, and tumorsuppressive effects [28][29][30][31][32][33][34] . Interestingly, the anti-fibrotic action and improvement of PH exerted by ω-3 epoxides observed in this study could not be confirmed when ω-3 fatty acids (EPA and DHA) were administered at the same dose, suggesting that these functions were Fig. 2 Hypoxic PH is exacerbated in Pafah2 KO mice. ...
Pulmonary hypertension is a fatal rare disease that causes right heart failure by elevated pulmonary arterial resistance. There is an unmet medical need for the development of therapeutics focusing on the pulmonary vascular remodeling. Bioactive lipids produced by perivascular inflammatory cells might modulate the vascular remodeling. Here, we show that ω-3 fatty acid-derived epoxides (ω-3 epoxides) released from mast cells by PAF-AH2, an oxidized phospholipid-selective phospholipase A2, negatively regulate pulmonary hypertension. Genetic deletion of Pafah2 in mice accelerate vascular remodeling, resulting in exacerbation of hypoxic pulmonary hypertension. Treatment with ω-3 epoxides suppresses the lung fibroblast activation by inhibiting TGF-β signaling. In vivo ω-3 epoxides supplementation attenuates the progression of pulmonary hypertension in several animal models. Furthermore, whole-exome sequencing for patients with pulmonary arterial hypertension identifies two candidate pathogenic variants of Pafah2. Our findings support that the PAF-AH2-ω-3 epoxide production axis could be a promising therapeutic target for pulmonary hypertension. Pulmonary hypertension is a fatal disease that causes right heart failure due to pulmonary artery stenosis. Here, the authors find that ω-3 epoxides produced by the phospholipase PAF-AH2 in mast cells regulate pulmonary vascular remodeling.
... This is consistent with the oxylipin profile showing elevated DiHOMEs from burned mice, suggesting higher activity of the sEH enzyme in response to burn and the importance of inhibiting the formation of these metabolites. Furthermore, animals with higher omega-3 fatty acid epoxides demonstrate an antiinflammatory phenotype; however, the biological activity of the omega-3 diols has not been investigated (44). Thus, it is uncertain whether the antiinflammatory profile is a result of the increased epoxides or decreased inflammatory diols. ...
Significance
Oxylipins alter immune cell function and potentially drive pathophysiology in burn and sepsis patients. Past and recent data reveal a correlation between increased systemic EpOME levels and reduced survival in human burn trauma and sepsis. This work extends these studies and provides evidence that the downstream sEH-derived metabolites, DiHOMEs, are driving worsening outcomes by altering the immune response. Inhibiting DiHOME metabolite formation with the sEH inhibitor, 1-trifluoromethoxyphenyl-3-(1-propionylpiperidin-4-yl) urea (TPPU), restored immune function by increasing immune cell survival and function. These data support the hypothesis that sEH-derived linoleic acid diols are responsible for increased mortality in burn and sepsis patients and also provide a rationale for testing the therapeutic blockage of DiHOME generation in burn and sepsis patients to improve their outcomes.
Background
Obesity drives maladaptive changes in the white adipose tissue (WAT) which can progressively cause insulin resistance, type 2 diabetes mellitus (T2DM) and metabolic dysfunction-associated liver disease (MASLD). Obesity-mediated loss of WAT homeostasis can trigger liver steatosis through dysregulated lipid pathways such as those related to polyunsaturated fatty acid (PUFA)-derived oxylipins. However, the exact relationship between oxylipins and metabolic syndrome remains elusive and cross-tissue dynamics of oxylipins are ill-defined.
Methods
We quantified PUFA-related oxylipin species in the omental WAT, liver biopsies and plasma of 88 patients undergoing bariatric surgery (female N = 79) and 9 patients (female N = 4) undergoing upper gastrointestinal surgery, using UPLC-MS/MS. We integrated oxylipin abundance with WAT phenotypes (adipogenesis, adipocyte hypertrophy, macrophage infiltration, type I and VI collagen remodelling) and the severity of MASLD (steatosis, inflammation, fibrosis) quantified in each biopsy. The integrative analysis was subjected to (i) adjustment for known risk factors and, (ii) control for potential drug-effects through UPLC-MS/MS analysis of metformin-treated fat explants ex vivo.
Findings
We reveal a generalized down-regulation of cytochrome P450 (CYP)-derived diols during obesity conserved between the WAT and plasma. Notably, epoxide:diol ratio, indicative of soluble epoxide hydrolyse (sEH) activity, increases with WAT inflammation/fibrosis, hepatic steatosis and T2DM. Increased 12,13-EpOME:DiHOME in WAT and liver is a marker of worsening metabolic syndrome in patients with obesity.
Interpretation
These findings suggest a dampened sEH activity and a possible role of fatty acid diols during metabolic syndrome in major metabolic organs such as WAT and liver. They also have implications in view of the clinical trials based on sEH inhibition for metabolic syndrome.
Funding
10.13039/100010269Wellcome Trust (PS3431_WMIH); 10.13039/100016017Duke-NUS (Intramural Goh Cardiovascular Research Award (Duke-NUS-GCR/2022/0020); 10.13039/501100001349National Medical Research Council (OFLCG22may-0011); 10.13039/100000066National Institute of Environmental Health Sciences (Z01 ES025034); 10.13039/501100013342NIHR Imperial Biomedical Research Centre.
Globally, the incidence of diabetes mellitus (DM) and Alzheimer's disease (AD) is increasing year by year, causing a huge economic and social burden, and their pathogenesis and aetiology have been proven to have a certain correlation. In recent years, more and more studies have shown that vacuolar adenosine triphosphatases (v‐ATPases) in eukaryotes, which are biomolecules regulating lysosomal acidification and glycolipid metabolism, play a key role in DM and AD. This article describes the role of v‐ATPase in DM and AD, including its role in glycolysis, insulin secretion and insulin resistance (IR), as well as its relationship with lysosomal acidification, autophagy and β‐amyloid (Aβ). In DM, v‐ATPase is involved in the regulation of glucose metabolism and IR. v‐ATPase is closely related to glycolysis. On the one hand, v‐ATPase affects the rate of glycolysis by affecting the secretion of insulin and changing the activities of key glycolytic enzymes hexokinase (HK) and phosphofructokinase 1 (PFK‐1). On the other hand, glucose is the main regulator of this enzyme, and the assembly and activity of v‐ATPase depend on glucose, and glucose depletion will lead to its decomposition and inactivation. In addition, v‐ATPase can also regulate free fatty acids, thereby improving IR. In AD, v‐ATPase can not only improve the abnormal brain energy metabolism by affecting lysosomal acidification and autophagy but also change the deposition of Aβ by affecting the production and degradation of Aβ. Therefore, v‐ATPase may be the bridge between DM and AD.
Perfluorooctanesulfonate (PFOS) is a widespread environmental pollutant with a long half-life and clearly negative outcomes on metabolic diseases such as fatty liver disease and diabetes. Male and female Cyp2b-null and humanized CYP2B6-transgenic (hCYP2B6-Tg) mice were treated with 0, 1, or 10 mg/kg/day PFOS for 21 days, and surprisingly it was found that PFOS was retained at greater concentrations in the serum and liver of hCYP2B6-Tg mice than those of Cyp2b-null mice, with greater differences in the females. Thus, Cyp2b-null and hCYP2B6-Tg mice provide new models for investigating individual mechanisms for PFOS bioaccumulation and toxicity. Overt toxicity was greater in hCYP2B6-Tg mice (especially females) as measured by mortality; however, steatosis occurred more readily in Cyp2b-null mice despite the lower PFOS liver concentrations. Targeted lipidomics and transcriptomics from PFOS-treated Cyp2b-null and hCYP2B6-Tg mouse livers were performed and compared to PFOS retention and serum markers of toxicity using PCA. Several oxylipins, including prostaglandins, thromboxanes, and docosahexaenoic acid metabolites, are associated or inversely associated with PFOS toxicity. Both lipidomics and transcriptomics indicate PFOS toxicity is associated with PPAR activity in all models. GO terms associated with reduced steatosis were sexually dimorphic with lipid metabolism and transport increased in females and circadian rhythm associated genes increased in males. However, we cannot rule out that steatosis was initially protective from PFOS toxicity. Moreover, several transporters are associated with increased retention, probably due to increased uptake. The strongest associations are the organic anion transport proteins (Oatp1a4-6) genes and a long-chain fatty acid transport protein (fatp1), enriched in female hCYP2B6-Tg mice. PFOS uptake was also reduced in cultured murine hepatocytes by OATP inhibitors. The role of OATP1A6 and FATP1 in PFOS transport has not been tested. In summary, Cyp2b-null and hCYP2B6-Tg mice provided unique models for estimating the importance of novel mechanisms in PFOS retention and toxicity.
Hepatic steatosis is an early stage in the progression of non-alcoholic fatty liver disease (NAFLD) and can lead to the development of non-alcoholic steatohepatitis (NASH), a major cause of liver-related morbidity and mortality. Identification of dietary components that can alleviate hepatic steatosis is crucial for developing effective therapeutic strategies for NAFLD. Recently, we demonstrated the impact of lipids extracted from the marine red alga Susabinori (Pyropia yezoensis) in a murine model of type 2-diabete (db/db). We found that Susabinori lipids (SNL), abundant in eicosapentaenoic acid (EPA)-containing polar lipids, protected against obesity-induced hepatic steatosis in db/db mice. To understand the specific genes or biological pathways underlying the effects of SNL, we conducted RNA-Seq analysis of the hepatic transcriptome. By performing comparative analysis of differentially expressed genes between normal mice and db/db mice consuming a control diet, as well as SNL-fed db/db mice, we identified the 15 SNL-dependent up-regulated genes that were down-regulated in db/db mice but up-regulated by SNL feeding. Gene ontology and pathway analysis on these 15 genes demonstrated a significant association with the metabolisms of arachidonic acid (AA) and linoleic acid (LA). Furthermore, we observed alterations in the expression levels of monoacylglycerol lipase (Magl) and fatty acid-binding protein 4 (Fabp4) in the SNL-fed db/db mice, both of which are implicated in AA and LA metabolism. Additionally , the livers of SNL-fed db/db mice exhibited reduced levels of AA and LA, but a high accumulation of EPA. In conclusion, the SNL diet might affect the metabolisms of AA and LA, which contribute to the improvement of hepatic steatosis. Our findings provide insights into the molecular mechanisms underlying the beneficial effects of SNL.
SARS-CoV-2 mediated infection instigated a scary pandemic state since 2019. They created havoc comprising death, imbalanced social structures, and a wrecked global economy. During infection, the inflammation and associated cytokine storm generate a critical pathological situation in the human body, especially in the lungs. By the passage of time of infection, inflammatory disorders, and multiple organ damage happen which might lead to death, if not treated properly. Until now, many pathological parameters have been used to understand the progress of the severity of COVID-19 but with limited success. Bioactive lipid mediators have the potential of initiating and resolving inflammation in any disease. The connection between lipid storm and inflammatory states of SARS-CoV-2 infection has surfaced and got importance to understand and mitigate the pathological states of COVID-19. As the role of eicosanoids in COVID-19 infection is not well defined, available information regarding this issue has been accumulated to address the possible network of eicosanoids related to the initiation of inflammation, promotion of cytokine storm, and resolution of inflammation, and highlight possible strategies for treatment and drug discovery related to SARS-CoV-2 infection in this study. Understanding the involvement of eicosanoids in exploration of cellular events provoked by SARS-CoV-2 infection has been summarized as an important factor to deescalate any upcoming catastrophe imposed by the lethal variants of this micro-monster. Additionally, this study also recognized the eicosanoid based drug discovery, treatment, and strategies for managing the severity of SARS-COV-2 infection.
Translation failure occurs when a treatment shown to be safe and effective in one type of population does not produce the same result in another. We are currently in a crisis involving the translatability of preclinical studies to human populations. Animal trials are no better than a coin toss at predicting the safety and efficacy of drugs in human trials, and the high failure rate of drugs entering human trials suggests that most of the suffering of laboratory animals is futile, creating no commensurate benefit for human patients. Here, I argue that animal ethics committees have a role to play in getting us out of this crisis. Inadequate representation is a known contributor to translation failures and is a matter of both scientific and ethical concern. Ethical review committees have the authority to address it by reprioritising the values already enshrined in their guiding principles.
Nonalcoholic fatty liver disease (NAFLD) is a chronic liver disease affecting up to 30% of the general adult population. NAFLD encompasses a histological spectrum ranging from pure steatosis to non-alcoholic steatohepatitis (NASH). NASH can progress to cirrhosis and is becoming the most common indication for liver transplantation, as a result of increasing disease prevalence and of the absence of approved treatments. Lipidomic readouts of liver blood and urine samples from experimental models and from NASH patients disclosed an abnormal lipid composition and metabolism. Collectively, these changes impair organelle function and promote cell damage, necro-inflammation and fibrosis, a condition termed lipotoxicity. We will discuss the lipid species and metabolic pathways leading to NASH development and progression to cirrhosis, as well as and those species that can contribute to inflammation resolution and fibrosis regression. We will also focus on emerging lipid-based therapeutic opportunities, including specialized proresolving lipid molecules and macrovesicles contributing to cell-to-cell communication and NASH pathophysiology.
Maternal obesity leads to obstetric complications and a high prevalence of metabolic anomalies in the offspring. Among various contributing factors for maternal obesity-evoked health sequelae, developmental programming is considered as one of the leading culprit factors for maternal obesity-associated chronic comorbidities. Although a unified theory is still lacking to systematically address multiple unfavorable postnatal health sequelae, a cadre of etiological machineries have been put forward, including lipotoxicity, inflammation, oxidative stress, autophagy/mitophagy defect, and cell death. Hereinto, autophagy and mitophagy play an essential housekeeping role in the clearance of long-lived, damaged, and unnecessary cell components to maintain and restore cellular homeostasis. Defective autophagy/mitophagy has been reported in maternal obesity and negatively impacts fetal development and postnatal health. This review will provide an update on metabolic disorders in fetal development and postnatal health issues evoked by maternal obesity and/or intrauterine overnutrition and discuss the possible contribution of autophagy/mitophagy in metabolic diseases. Moreover, relevant mechanisms and potential therapeutic strategies will be discussed in an effort to target autophagy/mitophagy and metabolic disturbances in maternal obesity.
Chronic and heavy alcohol consumption is commonly observed in alcohol use disorder (AUD). AUD often leads to alcohol-associated organ injury, including alcohol-associated liver disease (ALD). Approximately 10–20% of patients with AUD progress to ALD. Progression of ALD from the development phase to more advanced states involve the interplay of several pathways, including nutritional alterations. Multiple pathologic processes have been identified in the progression and severity of ALD. However, there are major gaps in the characterization and understanding of the clinical presentation of early-stage ALD as assessed by clinical markers and laboratory measures. Several Institutions and Universities, including the University of Louisville, in collaboration with the National Institutes of Health, have published a series of manuscripts describing early-stage ALD over the past decade. Here, we comprehensively describe early-stage ALD using the liver injury and drinking history markers, and the laboratory biomarkers (with a focus on nutrition status) that are uniquely involved in the development and progression of early-stage ALD.
The term ‘autophagy’ literally translates to ‘self-eating’ and alterations to autophagy have been identified as one of the several molecular changes that occur with aging in a variety of species. Autophagy and aging, have a complicated and multifaceted relationship that has recently come to light thanks to breakthroughs in our understanding of the various substrates of autophagy on tissue homoeostasis. Several studies have been conducted to reveal the relationship between autophagy and age-related diseases. The present review looks at a few new aspects of autophagy and speculates on how they might be connected to both aging and the onset and progression of disease. Additionally, we go over the most recent preclinical data supporting the use of autophagy modulators as age-related illnesses including cancer, cardiovascular and neurodegenerative diseases, and metabolic dysfunction. It is crucial to discover important targets in the autophagy pathway in order to create innovative therapies that effectively target autophagy. Natural products have pharmacological properties that can be therapeutically advantageous for the treatment of several diseases and they also serve as valuable sources of inspiration for the development of possible new small-molecule drugs. Indeed, recent scientific studies have shown that several natural products including alkaloids, terpenoids, steroids, and phenolics, have the ability to alter a number of important autophagic signalling pathways and exert therapeutic effects, thus, a wide range of potential targets in various stages of autophagy have been discovered. In this review, we summarised the naturally occurring active compounds that may control the autophagic signalling pathways.
The seminal discovery that cytochrome P450 enzymes (CYPs) can oxidize polyunsaturated fatty acids (PUFAs) sparked a new area of research aimed at discovering the role of these metabolites in cardiac physiology and pathophysiology. CYPs metabolize arachidonic acid, an ω-6 PUFA, to alcohols and epoxides with the latter providing cardioprotection following myocardial infarction, hypertrophy, and diabetes-induced cardiomyopathy through their anti-inflammatory, vasodilatory and antioxidant properties. Despite their protective properties, the use of EETs as therapeutic agents is hampered mainly by their rapid hydrolysis to less active vicinal diols by soluble epoxide hydrolase (sEH). Several approaches have been investigated to prolong EET signaling effects using small molecule sEH inhibitors, chemically and biologically stable analogs of EETs and more recently, through the development of an sEH vaccine. Alternatively, research investigating the cardioprotective outcomes of ω-3 PUFAs, eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), mainly focused on dietary intake or supplementation studies. EPA and DHA have overlapping but distinct effects on myocardial function and merit separate studies to fully understand their mechanism of cardiac protection. In contrast to EETs, relatively fewer studies examined the protective mechanisms of EPA and DHA derived epoxides to determine if some protective effects are in part due to the CYP mediated downstream metabolites. The actions of CYPs on PUFAs generate potent oxylipins utilizing diverse cardioprotective mechanisms and the extent of their full potential will be important for the future development of therapeutics to prevent or treat cardiovascular disease.
The cytochrome P450 (CYP) soluble epoxide hydrolase (sEH) pathway generates a large number of biologically active epoxides and diols from a range of ω-3 and ω-6 polyunsaturated fatty acids (PUFAs). While epoxides of arachidonic acid or epoxyeicosatrienoic acids are probably the best studied of these mediators, epoxides of linoleic acid as well as the fish oils; docosahexaenoic acid and eicosapentaenoic acid have also been attributed signaling actions. Cell and tissue levels of the PUFA epoxides are largely determined by the sEH and in many cases inflammation and chronic diseases, e.g., cardiovascular disease, diabetes and Alzheimer's disease, have been associated with increased sEH expression and the accelerated conversion of PUFA epoxides to their corresponding diols. In low concentrations, the diols act to influence stem and progenitor cells as well as brown adipose tissue but in high concentrations, they tend to have pro-inflammatory and cytotoxic effects that promote disease progression. This review outlines some of the actions to the PUFA epoxides and diols in physiology and pathophysiology as well as the beneficial effects associates with sEH inhibition.
The incidence of heart failure (HF) is generally preceded by cardiac hypertrophy (CH), which is the enlargement of cardiac myocytes in response to stress. During CH, the metabolism of arachidonic acid (AA), which is present in the cell membrane phospholipids, is modulated. Metabolism of AA gives rise to hydroxyeicosatetraenoic acids (HETEs) and epoxyeicosatrienoic acids (EETs) via cytochrome P450 (CYP) ω-hydroxylases and CYP epoxygenases, respectively. A plethora of studies demonstrated the involvement of CYP-mediated AA metabolites in the pathogenesis of CH. Also, inflammation is known to be a characteristic hallmark of CH. In this review, our aim is to highlight the impact of inflammation on CYP-derived AA metabolites and CH. Inflammation is shown to modulate the expression of various CYP ω-hydroxylases and CYP epoxygenases and their respective metabolites in the heart. In general, HETEs such as 20-HETE and mid-chain HETEs are pro-inflammatory, while EETs are characterized by their anti-inflammatory and cardioprotective properties. Several mechanisms are implicated in inflammation-induced CH, including the modulation of NF-κB and MAPK. This review demonstrated the inflammatory modulation of cardiac CYPs and their metabolites in the context of CH and the anti-inflammatory strategies that can be employed in the treatment of CH and HF.
A hepatic crown-like structure (hCLS) formed by macrophages accumulating around lipid droplets and dead cells in the liver is a unique feature of nonalcoholic steatohepatitis (NASH) that triggers progression of liver fibrosis. As hCLS plays a key role in the progression of NASH fibrosis, hCLS formation has emerged as a potential therapeutic target. n-3 polyunsaturated fatty acids (n-3 PUFAs) have potential suppressive effects on NASH fibrosis; however, the mechanisms underlying this effect are poorly understood. Here, we report that n-3 PUFA-enriched Fat-1 transgenic mice are resistant to hCLS formation and liver fibrosis in a NASH model induced by a combination of high-fat diet, CCl4 and a Liver X receptor (LXR) agonist. Liquid chromatography-tandem mass spectrometry-based mediator lipidomics revealed that the amount of endogenous n-3 PUFA-derived metabolites, such as 17,18-dihydroxyeicosatetraenoic acid (17,18-diHETE), and 19,20-epoxy docosapentaenoic acid (19,20-EpDPE), was significantly elevated in Fat-1 mice, along with hCLS formation. In particular, DHA-derived 19,20-EpDPE produced by Cyp4f18 attenuated the hCLS formation and liver fibrosis in a G protein-coupled receptor 120 (GPR120)-dependent manner. These results indicated that 19,20-EpDPE is an endogenous active metabolite that mediates the preventive effect of n-3 PUFAs against NASH fibrosis.
Aflatoxin B1 (AFB1) contamination in food and feed leads to severe global health problems. Acting as the frontier immunological barrier, the intestinal mucosa is constantly challenged by exposure to foodborne toxins such as AFB1 via contaminated diets, but the detailed toxic mechanism and endogenous regulators of AFB1 toxicity are still unclear. Here, we showed that AFB1 disrupted intestinal immune function by suppressing macrophages, especially M2 macrophages, and antimicrobial peptide-secreting Paneth cells. Using an oxylipinomics approach, we identified that AFB1 immunotoxicity is associated with decreased epoxy fatty acids, notably epoxyeicosatrienoic acids, and increased soluble epoxide hydrolase (sEH) levels in the intestine. Furthermore, sEH deficiency or inhibition rescued the AFB1-compromised intestinal immunity by restoring M2 macrophages as well as Paneth cells and their-derived lysozyme and α-defensin-3 in mice. Altogether, our study demonstrates that AFB1 exposure impairs intestinal immunity, at least in part, in a sEH-mediated way. Moreover, the present study supports the potential application of pharmacological intervention by inhibiting the sEH enzyme in alleviating intestinal immunotoxicity and associated complications caused by AFB1 global contamination.
Epoxyeicosatrienoic acids (EETs) are arachidonic acid metabolites with biological effects, including anti-apoptotic, anti-inflammatory, and anti-fibrotic functions. Soluble epoxide hydrolase (sEH)-mediated hydrolysis of EETs to dihydroxyeicosatrienoic acids (DHET) attenuates these effects. Recent studies have demonstrated inhibition of sEH prevents renal tubulointerstitial fibrosis and inflammation in chronic kidney disease (CKD) model. Given the pathophysiological role of the EET pathway in CKD, we investigated if administration of EETs regioisomers and/or sEH inhibition will promote anti-fibrotic and reno-protective effects in renal fibrosis following UUO. EETs administration abolished tubulointerstitial fibrogenesis, as demonstrated by reduced fibroblast activation and collagen deposition after UUO. Inflammatory response was prevented as demonstrated by decreased neutrophil and macrophage infiltration and expression of cytokines in EETs-administered UUO kidneys. EETs administration and/or sEH inhibition significantly reduced M1 macrophage markers while M2 macrophage markers were highly upregulated. Furthermore, UUO-induced oxidative stress, tubular injury, and apoptosis were all downregulated following EETs administration. Combined EETs administration and sEH inhibition however, had no additive effect in attenuating inflammation and renal interstitial fibrogenesis after UUO. Taken together, our findings provide a mechanistic understanding of how EETs prevent kidney fibrogenesis during obstructive nephropathy, and suggest EETs treatment as a potential therapeutic strategy to treat fibrotic diseases.
Metabolic syndrome (MetS), a cluster of metabolic abnormalities composed of central obesity, elevated blood pressure, glucose disturbances, hypercholesterolemia and dyslipidaemia, has increasingly become a public health problem in the 21st century worldwide. The dysfunction of telomeres, the repetitive DNA with highly conserved sequences (5′-TTAGGG-3′), is remarkably correlated with organismal aging, even suggesting a causal relationship with metabolic disorders. The health benefits of n-3 polyunsaturated fatty acids (PUFAs) in multiple disorders are associated with telomere length in evidence, which have recently drawn wide attention. However, functional targets and pathways for the associations of n-3 PUFAs and telomere with MetS remain scare. Few studies have summarized the role of n-3 PUFAs in DNA damage repair pathways, anti-inflammatory pathways, and redox balance, linking with telomere biology, and other potential telomere-related signaling pathways. This review aims to (i) elucidate how n-3 PUFAs ameliorate telomere attrition in the context of anti-oxidation and anti-inflammation; (ii) unravel the role of n-3 PUFAs in modulating telomere-related neuron dysfunction and regulating the neuro-endocrine-immunological network in MetS; (iii) epidemiologically implicate the associations of metabolic disorders and n-3 PUFAs with telomere length; and (iv) suggest promising biochemical approaches and advancing methodologies to overcome the inter-variation problem helpful for future research.
Background:
Long-term parenteral nutrition (PN) can lead to intestinal failure-associated liver disease (IFALD). Omega-3 polyunsaturated fatty acids (n-3 PUFA) eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) were shown to prevent IFALD. EPA- and DHA-derived oxylipins could contribute to this protective effect.
Methods:
We analyzed the effect of parenteral fish oil on oxylipins in patients with chronic intestinal failure on PN (n=8). Patients first received no fish oil for 8 weeks and were then switched to a PN with 25% of fats as fish oil for another 8 weeks. Fatty acid (FA) profiles of red blood cells, PUFA-derived oxylipins generated by cyclooxygenase (COX), lipoxygenase (LOX) and cytochrome P450 (CYP) pathways, inflammatory markers and liver function were assessed before and during fish oil PN.
Results:
EPA + DHA in erythrocytes (the Omega-3 Index) was high with a median of 11.96% at baseline and decreased to 9.57% without fish oil in the PN. Addition of fish oil in the PN increased the median Omega-3-Index to 12.75%. EPA- and DHA-derived CYP- and LOX-dependent metabolites increased significantly with fish oil in the PN, with less pronounced changes in arachidonic acid and its oxylipins. There were no significant changes of inflammation and liver function parameters.
Conclusions:
This study shows that fish oil-containing PN leads to primarily CYP and LOX-dependent n-3 PUFA derived inflammation dampening oxylipins (n-3 IDOs) arising from EPA and DHA. Within this short (16 week) study there were no significant changes in inflammation and clinical readout parameters. This article is protected by copyright. All rights reserved.
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The global population of people over the age of 65 is increasing and expected to reach 1.5 billion by 2050. While aging is associated with a number of chronic illnesses including dementia, the underlying contribution of alcohol misuse in the elderly is understudied. Long-term chronic alcohol misuse can lead to alcohol-associated liver disease, consisting of a spectrum of pathologies including steatosis and cirrhosis; liver disease can be rapidly accelerated by non-resolving inflammation. Despite this knowledge, the mechanistic underpinnings of dysregulated host immunity and accelerated liver disease progression in the aged by alcohol is unknown. Alcohol misuse in the elderly is on the rise and aging is associated with progressive increases in pro-inflammatory cytokine production. The goals of current study are to characterize bioactive lipid mediators of inflammation by making use of a murine model of ethanol-induced liver disease in 3-month old and 20-month old mice by quantitatively profiling selected oxylipins in liver, brain and plasma. Following chronic ethanol exposure, liver injury, steatosis, and senescence markers were robustly increased in aged mice compared to young adult mice. Expression of proinflammatory cytokines and lipid metabolizing enzymes were increased in liver by both age and ethanol feeding. Lipoxygenase-derived lipid metabolites 9- and 13-hydroxy-octadecadienoic acid and 15-hydroxyeicosatetraenoic acid were increased in liver and plasma in ethanol-fed aged mice and positively correlated with liver injury. In plasma, 9,10-dihydroxy-octadecenoic acid/epoxy‐octadecenoic acid plasma ratios correlated with liver injury in ethanol-fed aged mice. Finally, 15-hydroxyeicosatetraenoic acid and 9,10-dihydroxy-octadecenoic acid positively correlated between liver and plasma. Importantly, leukotriene E4, 9,10-dihydroxy-octadecenoic acid and 15-hydroxyeicosatetraenoic acid increased lipid accumulation and ER stress in cultured AML12 hepatocytes. These data highlight the complexity of lipid metabolite networks but identify key mediators that may be used for diagnostic and prognostic markers in early stages of alcohol-related liver disease in patients of all ages.
Alcohol consumption and high caloric diet are leading causes of progressive fatty liver disease. Genetic variant rs738409 in patatin-like phospholipase domain-containing protein 3 (PNPLA3 rs738409 C>G) has been repeatedly described as one of the major risk loci for alcoholic liver cirrhosis (ALC) and hepatocellular carcinoma (HCC) in humans, however, the mechanism behind this association is incompletely understood. We generated mice carrying the rs738409 variant (PNPLA3 I148M) in order to detect genotype-phenotype relationships in mice upon chow and alcohol-high fat/high sugar diet (EtOH/WD). We could clearly demonstrate that the presence of rs738409 per se is sufficient to induce spontaneous development of steatosis after one year in mice on a chow diet, whereas in the setting of unhealthy diet feeding, PNPLA3 I148M did not affect hepatic inflammation or fibrosis, but induced a striking lipid remodelling, microvesicular steatosis and protected from HCC formation. Using shot gun lipidomics, we detected a striking restoration of reduced long chain-polyunsaturated fatty acids (LC-PUFA)-containing TGs, docosapentaenoic acid (C22:5 n3) and omega-3-derived eicosanoids (5-HEPE, 20-HEPE, 19,20-EDP, 21-HDHA) in PNPLA3 I148M mice upon EtOH/WD. At the molecular level, PNPLA3 I148M modulated enzymes for fatty acid and TG transport and metabolism. These findings suggest (dietary) lipids as an important and independent driver of hepatic tumorigenesis. Genetic variant in PNPLA3 exerted protective effects in mice, conflicting with findings in humans. Species-related differences in physiology and metabolism should be taken into account when modelling unhealthy human lifestyle, as genetic mouse models may not always allow for translation of insight gained in humans.
Background
Specialized pro-resolving mediators (SPM), synthesized from polyunsaturated fatty acids (PUFA), resolve inflammation and return damaged tissue to homeostasis. Thus, increasing metabolites of the SPM biosynthetic pathway may have potential health benefits for select clinical populations such as those with obesity that display dysregulation of SPM metabolism. However, bioavailability of SPMs and their metabolic intermediates in humans with obesity remains unclear.
Objectives
The primary objective was to determine if a marine oil supplement increased specific metabolites of the SPM biosynthetic pathway in adults with obesity. The second objective was to determine if the supplement changed the relative abundance of key immune cell populations. Finally, given the critical role of antibodies in inflammation, we determined if ex vivo CD19 + B cell antibody production was modified by marine oil intervention.
Methods
Twenty-three subjects, median age of 56y and BMI of 33.1, consumed 2 g/d of a marine oil supplement for 28–30 days. The supplement was particularly enriched with 18-hydroxyeicosapentaenoic, 14-hydroxydocosahexaenoic, and 17-hydroxydocosahexaenoic acids. Blood was collected pre/post supplementation for plasma mass spectrometry oxylipin and fatty acid analyses, flow cytometry, and B cell isolation. Paired T-tests/Wilcoxon tests were used for statistical analyses.
Results
Relative to pre-intervention, the supplement increased six different hydroxyeicosapentaenoic and hydroxydocosahexaenoic acids accompanied by changes in plasma PUFAs. Resolvin E1 and docosapentaenoic acid-derived maresin 1 levels were respectively increased 3.5 and 4.7-fold upon intervention. The supplement did not increase the concentration of D-series resolvins and had no effect on the abundance of immune cells. Ex vivo B cell IgG but not IgM levels were lowered post-supplementation.
Conclusions
A marine oil supplement increased select SPMs and their metabolic intermediates in adults with obesity. Additional studies are needed to determine if increased levels of specific SPMs control the resolution of inflammation in humans with obesity. This trial was registered at clinicaltrials.gov (NCT04701138).
Background
Intermittent fasting (IF) activates autophagy in cardiac muscle and pancreatic islets. We examined the effect of IF on markers of autophagy in liver and skeletal muscle in mice and in humans.
Methods
Ten-week-old C57BL/6J male mice were ad-libitum fed a high-fat (HFD) or chow diet for 8 weeks, before randomisation to AL or IF (24h fast, 3 non-consecutive days per week) for 8 weeks (8-16/group). Tissue was collected in the fed or 22h fasted state. Fifty women (51±2y, 31.8±4.3 kg/m²) were randomly assigned to one of two IF protocols (24h fast, 3 non-consecutive days per week) and fed at 70% (IF70) or 100% (IF100) of energy requirements for 8 weeks. Vastus lateralis muscle was collected at 8am following 12h and 24h fasts. Microtubule associated protein light chain 1 (Map1lc3b), Beclin1 (Becn1), Sequestosome 1 (Sqstm1/p62), and Lysosomal associated membrane protein 2 (Lamp2) were assessed by qPCR and LC3, BECLIN1 and LAMP1 by immunoblotting.
Results
Fasting increased hepatic LC3I protein and Map1lc3b mRNA levels in IF mice fed chow or HFD. LAMP1 protein and Beclin1 mRNA levels were also increased by fasting, but only in chow-fed mice. IF did not activate markers of autophagy in mouse muscle. In humans, a 24h fast increased SQSTM1. BECLIN1, SQSTM1 and LAMP2 mRNA levels were decreased in IF70 following a 12h overnight fast only.
Conclusion
Markers of autophagy in liver, but not in muscle, were elevated in response to IF in mice. In humans, autophagy markers in muscle were reduced, likely in response to weight loss.
Retinopathy of prematurity (ROP) is a leading cause of childhood blindness worldwide. Neovascularization of retina in ROP eyes is a result of complex mechanisms that involve plethora of risk factors; however, the exact pathophysiology is still not clear. Even in the absence of risk factors, the disease progress to severe conditions. Thus, understanding the role of cellular molecules/events involved in ROP pathogenesis is very important to check the disease progression. Many studies have focused on investigating the role of cellular macromolecules and oxidative stress in ROP and their functional validations. The aim of this chapter is to discuss the role of various genes, RNA, proteins, lipids, and oxidative stress in physiological mechanism of normal retinal vascularization and various pathological changes that can lead to neovascularization of retina. The identification of such molecular mechanisms involved in neovascularization can help to find out novel therapeutic targets for an effective disease management.KeywordsRetinaROPGeneticsAbnormal angiogenesisCandidate genesmiRNAOxidative stressGrowth factors
The mechanisms whereby fish oil rich in EPA and DHA promotes BAT thermogenesis and WAT browning are not fully understood. Thus, this study aimed to investigate the effects of cytochrome P450 (CYP) epoxygenase-derived EPA and DHA oxylipins 17,18-EpETE and 19,20-EpDPE on BAT thermogenesis and WAT browning and explore the underlying mechanism. Stromal vascular cells (SVCs) were subjected to 17,18-EpETE or 19,20-EpDPE treatment and mice were treated with the CYP epoxygenase inhibitor, the thermogenic marker genes were detected and the involvement of GPR120 and AMPKα were assessed. The in vitro results indicated that 17,18-EpETE and 19,20-EpDPE induced brown and beige adipocyte thermogenesis, with increased expression of thermogenic marker gene UCP1 in differentiated SVCs. Meanwhile, the expression of GPR120 and phosphorylation of AMPKα were increased in response to these two oxylipins. However, the inhibition of GPR120 and AMPKα inhibited the promotion of adipocyte thermogenesis. In addition, in the presence of CYP epoxygenase inhibitor MS-PPOH, EPA and DHA had no effect on increasing UCP1 expression in differentiated SVCs. Consistent with the in vitro results, the in vivo findings demonstrated that fish oil had no body fat-lowering effects and no effects on enhancing energy metabolism, iBAT thermogenesis and iWAT browning in mice fed HFD after intraperitoneal injection of CYP epoxygenase inhibitor SKF-525A. Moreover, fish oil had no effect on the elevation of GPR120 expression and activation of AMPKα in iBAT and iWAT in mice fed HFD after intraperitoneal injection of SKF-525A. In summary, our results showed that CYP epoxygenase-derived EPA and DHA oxylipins 17,18-EpETE and 19,20-EpDPE promoted BAT thermogenesis and WAT browning through the GPR120-AMPKα signaling pathway, which might contribute to the thermogenic and anti-obesity effects of fish oil.
The soluble epoxide hydrolase (sEH) enzyme is a major regulator of bioactive lipids. The enzyme is highly expressed in liver and kidney and modulates levels of endogenous epoxy-fatty acids, which have pleiotropic biological effects including limiting inflammation, neuroinflammation, and hypertension. It has been hypothesized that inhibiting sEH has beneficial effects on limiting obesity and metabolic disease as well. There is a body of literature published on these effects, but typically only male subjects have been included. Here, we investigate the role of sEH in both male and female mice and use a global sEH knockout mouse model to compare the effects of diet and diet-induced obesity. The results demonstrate that sEH activity in the liver is modulated by high-fat diets more in male than in female mice. In addition, we characterized the sEH activity in high fat content tissues and demonstrated the influence of diet on levels of bioactive epoxy-fatty acids. The sEH KO animals had generally increased epoxy-fatty acids compared to wild-type mice but gained less body weight on higher-fat diets. Generally, proinflammatory prostaglandins and triglycerides were also lower in livers of sEH KO mice fed HFD. Thus, sEH activity, prostaglandins, and triglycerides increase in male mice on high-fat diet but are all limited by sEH ablation. Additionally, these changes also occur in female mice though at a different magnitude and are also improved by knockout of the sEH enzyme.
Objective
Omega-6 and omega-3 oxylipins are known to play a role in inflammation and cardiometabolic diseases in preclinical models. The associations between plasma levels of omega-6 and omega-3 polyunsaturated fatty acid–derived oxylipins and body composition and cardiometabolic risk factors in young adults were assessed.
Methods
Body composition, brown adipose tissue, traditional serum cardiometabolic risk factors, inflammatory markers, and a panel of 83 oxylipins were analyzed in 133 young adults (age 22.1[SD 2.2] years, 67% women).
Results
Plasma levels of four omega-6 oxylipins (15-HeTrE, 5-HETE, 14,15-EpETrE, and the oxidative stress–derived 8,12-iso-iPF2α-VI) correlated positively with adiposity, prevalence of metabolic syndrome, fatty liver index, and homeostatic model assessment of insulin resistance index and lipid parameters. By contrast, the plasma levels of three omega-3 oxylipins (14,15-DiHETE, 17,18-DiHETE, and 19,20-DiHDPA) were negatively correlated with adiposity, prevalence of metabolic syndrome, fatty liver index, homeostatic model assessment of insulin resistance index, and lipid parameters. The panel of seven oxylipins predicted adiposity better than traditional inflammatory markers such as interferon gamma or tumor necrosis factor-alpha. Pathway analyses revealed that individuals with obesity had higher plasma levels of omega-6 and lower plasma levels of omega-3 oxylipins than normal-weight individuals.
Conclusion
Plasma levels of seven omega-6 and omega-3 oxylipins may have utility as early markers of cardiometabolic risk in young adults.
Advances in our understanding of the mechanisms that bring about the resolution of acute inflammation have uncovered a new genus of pro-resolving lipid mediators that include the lipoxin, resolvin, protectin and maresin families, collectively called specialized pro-resolving mediators. Synthetic versions of these mediators have potent bioactions when administered in vivo. In animal experiments, the mediators evoke anti-inflammatory and novel pro-resolving mechanisms, and enhance microbial clearance. Although they have been identified in inflammation resolution, specialized pro-resolving mediators are conserved structures that also function in host defence, pain, organ protection and tissue remodelling. This Review covers the mechanisms of specialized pro-resolving mediators and omega-3 essential fatty acid pathways that could help us to understand their physiological functions.
: Mediators of anti-hypertensive actions of docosahexaenoic acid (DHA) are largely unknown. The omega-3 epoxide of DHA, 19, 20-EDP (epoxydocosapentaenoic acid) is metabolized by soluble epoxide hydrolase (sEH), which also metabolizes the anti-inflammatory and anti-hypertensive arachidonic acid (ARA) epoxides, EETs (epoxyeicosatrienoic acids). Based in part on plasma levels of EDPs following a DHA-rich diet, we hypothesized that 19, 20-EDP contributes to the anti-hypertensive actions of DHA in angiotensin-II dependent hypertension. Treatment individually with 19, 20-EDP, and a potent sEH inhibitor (sEHI) TPPU (1-trifluoromethoxyphenyl-3-(1-propionylpiperidin-4-yl) urea) significantly lowered blood pressure (BP) as compared to angiotensin-II infused animals. The largest reduction in BP was obtained with the combination of 19, 20-EDP and TPPU, which was more efficacious than the combination of 14, 15-EET and TPPU. Oxylipin profiling revealed that 19, 20-EDP and 14, 15-EET infusion affected mostly metabolites of the P450 pathway but also renal levels of prostaglandin-E2. Our findings suggest that 19, 20- EDP is a mediator of the anti-hypertensive effects of DHA in angiotensin-II dependent hypertension. It appears that 19, 20- EDP requires metabolic stabilization with a sEHI to be most effective in lowering BP, although both TPPU and 19, 20- EDP are so effective on their own that demonstrating additive or synergistic interactions is difficult.
Background and purpose: Soluble epoxide hydrolase (sEH) diminishes vasodilatory and neuroprotective effects of epoxyeicosatrienoic acids by hydrolyzing them to inactive dihydroxy metabolites. The primary goals of this study were to investigate the effects of acute sEH inhibition by t-AUCB on infarct volume, functional outcome, and changes in cerebral blood flow (CBF) in a rat model of ischemic stroke. Methods: Focal cerebral ischemia was induced in rats for 90 min followed by reperfusion. At the end of 24 h after reperfusion rat were euthanized for infarct volume assessment by TTC staining. Brain cortical sEH activity was assessed by UPLC-MS/MS. Functional outcome at 24, and 48 h after reperfusion was evaluated by arm flexion, and sticky-tape tests. Changes in CBF were assessed by ASL-MRI at baseline, during ischemia, and at 180 min after reperfusion. Neuroprotective effects of t-AUCB were evaluated in primary rat neuronal cultures by Cytotox-Flour kit and Propidium Iodide staining. Results: t-AUCB significantly reduced cortical infarct volume by 35% (14.5±2.7% vs 41.5±4.5%), elevated cumulative EETs/DHETs ratio in brain cortex by two fold (4.40±1.89 vs 1.97±0.85), and improved functional outcome in arm-flexion test (day 1: 3.28±0.5 s vs 7.50±0.9 s; day 2: 1.71±0.4 s vs 5.28±0.5 s) when compared to the vehicle-treated group. t-AUCB significantly reduced neuronal cell death in a dose dependent manner (vehicle:70.9±7.1% vs t-AUCB0.1µM: 58±5.11% vs t-AUCB0.5µM: 39.9±5.8%). Conclusions: These findings suggest that t-AUCB may exert its neuroprotective effects by affecting multiple components of neurovascular unit including neurons, astrocytes and microvascular flow.
Epoxyeicosatrienoic acids (EETs), lipid mediators produced by cytochrome P450 epoxygenases, regulate inflammation, angiogenesis, and vascular tone. Despite pleiotropic effects on cells, the role of these epoxyeicosanoids in normal organ and tissue regeneration remains unknown. EETs are produced predominantly in the endothelium. Normal organ and tissue regeneration require an active paracrine role of the microvascular endothelium, which in turn depends on angiogenic growth factors. Thus, we hypothesize that endothelial cells stimulate organ and tissue regeneration via production of bioactive EETs. To determine whether endothelial-derived EETs affect physiologic tissue growth in vivo, we used genetic and pharmacological tools to manipulate endogenous EET levels. We show that endothelial-derived EETs play a critical role in accelerating tissue growth in vivo, including liver regeneration, kidney compensatory growth, lung compensatory growth, wound healing, corneal neovascularization, and retinal vascularization. Administration of synthetic EETs recapitulated these results, whereas lowering EET levels, either genetically or pharmacologically, delayed tissue regeneration, demonstrating that pharmacological modulation of EETs can affect normal organ and tissue growth. We also show that soluble epoxide hydrolase inhibitors, which elevate endogenous EET levels, promote liver and lung regeneration. Thus, our observations indicate a central role for EETs in organ and tissue regeneration and their contribution to tissue homeostasis.
Soluble epoxide hydrolase (sEH) is a cytosolic enzyme whose inhibition has beneficial effects in cardiovascular, inflammatory,
and metabolic diseases in murine models. Mice with targeted deletion or pharmacological inhibition of sEH exhibit improved
insulin signaling in liver and adipose tissue. Herein, we assessed the role of sEH in regulating endoplasmic reticulum (ER)
stress in liver and adipose tissue. We report that sEH expression was increased in the livers and adipose tissue of mice fed
a high fat diet, the adipose tissue of overweight humans, and palmitate-treated cells. Importantly, sEH deficiency or inhibition
in mice attenuated chronic high fat diet-induced ER stress in liver and adipose tissue. Similarly, pharmacological inhibition
of sEH in HepG2 cells and 3T3-L1 adipocytes mitigated chemical-induced ER stress and activation of JNK, p38, and cell death.
In addition, insulin signaling was enhanced in HepG2 cells treated with sEH substrates and attenuated in cells treated with
sEH products. In summary, these findings demonstrate that sEH is a physiological modulator of ER stress and a potential target
for mitigating complications associated with obesity.
Epidemiological and preclinical evidence supports that omega-3 dietary fatty acids (fish oil) reduce the risks of macular degeneration and cancers, but the mechanisms by which these omega-3 lipids inhibit angiogenesis and tumorigenesis are poorly understood. Here we show that epoxydocosapentaenoic acids (EDPs), which are lipid mediators produced by cytochrome P450 epoxygenases from omega-3 fatty acid docosahexaenoic acid, inhibit VEGF- and fibroblast growth factor 2-induced angiogenesis in vivo, and suppress endothelial cell migration and protease production in vitro via a VEGF receptor 2-dependent mechanism. When EDPs (0.05 mg⋅kg(-1)⋅d(-1)) are coadministered with a low-dose soluble epoxide hydrolase inhibitor, EDPs are stabilized in circulation, causing ∼70% inhibition of primary tumor growth and metastasis. Contrary to the effects of EDPs, the corresponding metabolites derived from omega-6 arachidonic acid, epoxyeicosatrienoic acids, increase angiogenesis and tumor progression. These results designate epoxyeicosatrienoic acids and EDPs as unique endogenous mediators of an angiogenic switch to regulate tumorigenesis and implicate a unique mechanistic linkage between omega-3 and omega-6 fatty acids and cancers.
Objectives:
Autophagy is a highly regulated process that has an important role in the control of a wide range of cellular functions, such as organelle recycling, nutrient availability and tissue differentiation. A recent study has shown an increased autophagic activity in the adipose tissue of obese subjects, and a role for autophagy in obesity-associated insulin resistance was proposed. Body mass reduction is the most efficient approach to tackle insulin resistance in over-weight subjects; however, the impact of weight loss in adipose tissue autophagy is unknown.
Subjects:
Adipose tissue autophagy was evaluated in mice and humans.
Results:
First, a mouse model of diet-induced obesity and diabetes was maintained on a 15-day, 40% caloric restriction. At baseline, markers of autophagy were increased in obese mice as compared with lean controls. Upon caloric restriction, autophagy increased in the lean mice, whereas it decreased in the obese mice. The reintroduction of ad libitum feeding was sufficient to rapidly reduce autophagy in the lean mice and increase autophagy in the obese mice. In the second part of the study, autophagy was evaluated in the subcutaneous adipose tissue of nine obese-non-diabetic and six obese-diabetic subjects undergoing bariatric surgery for body mass reduction. Specimens were collected during the surgery and approximately 1 year later. Markers of systemic inflammation, such as tumor necrosis factor-1α, interleukin (IL)-6 and IL-1β were evaluated. As in the mouse model, human obesity was associated with increased autophagy, and body mass reduction led to an attenuation of autophagy in the adipose tissue.
Conclusion:
Obesity and caloric overfeeding are associated with the defective regulation of autophagy in the adipose tissue. The studies in obese-diabetic subjects undergoing improved metabolic control following calorie restriction suggest that autophagy and inflammation are regulated independently.
The presence of epoxyeicosatrienoic acids (EETs) in tissues and their metabolism by soluble epoxide hydrolase (sEH) to 1,2-diols were first reported 30 years ago. However, appreciation of their importance in cell biology and physiology has greatly accelerated over the past decade with the discovery of metabolically stable inhibitors of sEH, the commercial availability of EETs, and the development of analytical methods for the quantification of EETs and their diols. Numerous roles of EETs in regulatory biology now are clear, and the value of sEH inhibition in various animal models of disease has been demonstrated. Here, we review these results and discuss how the pharmacological stabilization of EETs and other natural epoxy-fatty acids could lead to possible disease therapies. Expected final online publication date for the Annual Review of Pharmacology and Toxicology Volume 53 is January 06, 2013. Please see http://www.annualreviews.org/catalog/pubdates.aspx for revised estimates.
Non-alcoholic fatty liver disease is associated with obesity and considered an inflammatory disease. Soluble epoxide hydrolase (sEH) is a major enzyme hydrolyzing epoxyeicosatrienoic acids and attenuates their cardiovascular protective and anti-inflammatory effects. We examined whether sEH inhibition can protect against high-fat (HF)-diet-induced fatty liver in mice and the underlying mechanism. Compared with wild-type littermates, sEH-null mice showed lower diet-induced lipid accumulation in liver, as seen by Oil-red O staining and triglycerides levels. We studied the effect of sEH inhibition on diet-induced fatty liver by feeding C57BL/6 mice an HF diet for 8 weeks (short-term) or 16 weeks (long-term) and administering t-AUCB, a selective sEH inhibitor. sEH inhibition had no effect on the HF-diet-increased body and adipose tissue weight or impaired glucose tolerance but alleviated the diet-induced hepatic steatosis. Adenovirus-mediated overexpression of sEH in liver increased the level of triglycerides in liver and the hepatic inflammatory response. Surprisingly, the induced expression of sEH in liver occurred only with the long-term but not short-term HF diet, which suggests a secondary effect of HF diet on regulating sEH expression. Furthermore, sEH inhibition attenuated the HF-diet-induced increase in plasma levels of proinflammatory cytokines and their mRNA upregulation in adipose tissue, which was accompanied by increased macrophage infiltration. Therefore, sEH inhibition could alleviate HF-diet-induced hepatic steatosis, which might involve its anti-inflammatory effect in adipose tissue and direct inhibition in liver. sEH may be a therapeutic target for HF-diet-induced hepatic steatosis in inhibiting systemic inflammation.
In 2008 we published the first set of guidelines for standardizing research in autophagy. Since then, research on this topic has continued to accelerate, and many new scientists have entered the field. Our knowledge base and relevant new technologies have also been expanding. Accordingly, it is important to update these guidelines for monitoring autophagy in different organisms. Various reviews have described the range of assays that have been used for this purpose. Nevertheless, there continues to be confusion regarding acceptable methods to measure autophagy, especially in multicellular eukaryotes. A key point that needs to be emphasized is that there is a difference between measurements that monitor the numbers or volume of autophagic elements (e.g., autophagosomes or autolysosomes) at any stage of the autophagic process vs. those that measure flux through the autophagy pathway (i.e., the complete process); thus, a block in macroautophagy that results in autophagosome accumulation needs to be differentiated from stimuli that result in increased autophagic activity, defined as increased autophagy induction coupled with increased delivery to, and degradation within, lysosomes (in most higher eukaryotes and some protists such as Dictyostelium) or the vacuole (in plants and fungi). In other words, it is especially important that investigators new to the field understand that the appearance of more autophagosomes does not necessarily equate with more autophagy. In fact, in many cases, autophagosomes accumulate because of a block in trafficking to lysosomes without a concomitant change in autophagosome biogenesis, whereas an increase in autolysosomes may reflect a reduction in degradative activity. Here, we present a set of guidelines for the selection and interpretation of methods for use by investigators who aim to examine macroautophagy and related processes, as well as for reviewers who need to provide realistic and reasonable critiques of papers that are focused on these processes. These guidelines are not meant to be a formulaic set of rules, because the appropriate assays depend in part on the question being asked and the system being used. In addition, we emphasize that no individual assay is guaranteed to be the most appropriate one in every situation, and we strongly recommend the use of multiple assays to monitor autophagy. In these guidelines, we consider these various methods of assessing autophagy and what information can, or cannot, be obtained from them. Finally, by discussing the merits and limits of particular autophagy assays, we hope to encourage technical innovation in the field.
Non-alcoholic fatty liver disease (NAFLD) is a frequent accompaniment of obesity and insulin resistance. With the prevalence approaching 85% in obese populations, new therapeutic approaches to manage NAFLD are warranted. A systematic search of the literature was conducted for studies pertaining to the effect of omega-3 polyunsaturated fatty acid (PUFA) supplementation on NAFLD in humans. Primary outcome measures were liver fat and liver function tests: alanine aminotransferase (ALT) and aspartate aminotransferase [1]. Data were pooled and meta-analyses conducted using a random effects model. Nine eligible studies, involving 355 individuals given either omega-3 PUFA or control treatment were included. Beneficial changes in liver fat favoured PUFA treatment (effect size=-0.97, 95% CI: -0.58 to -1.35, p<0.001). A benefit of PUFA vs. control was also observed for AST (effect size=-0.97, 95% CI: -0.13 to -1.82, p=0.02). There was a trend towards favouring PUFA treatment on ALT but this was not significant (effect size=-0.56, 95% CI: -1.16 to 0.03, p=0.06). Sub-analyses of only randomised control trials (RCTs) showed a significant benefit for PUFA vs. control on liver fat (effect size=-0.96, 95% CI: -0.43 to -1.48, p<0.001), but not for ALT (p=0.74) or AST (p=0.28). There was significant heterogeneity between studies. The pooled data suggest that omega-3 PUFA supplementation may decrease liver fat, however, the optimal dose is currently not known. Well designed RCTs which quantify the magnitude of effect of omega-3 PUFA supplementation on liver fat are needed.
Although short-term incubation of hepatocytes with oleic acid (OA) stimulates secretion of apolipoprotein B100 (apoB100), exposure to higher doses of OA for longer periods inhibits secretion in association with induction of endoplasmic reticulum (ER) stress. Palmitic acid (PA) induces ER stress, but its effects on apoB100 secretion are unclear. Docosahexaenoic acid (DHA) inhibits apoB100 secretion, but its effects on ER stress have not been studied. We compared the effects of each of these fatty acids on ER stress and apoB100 secretion in McArdle RH7777 (McA) cells: OA and PA induced ER stress and inhibited apoB100 secretion at higher doses; PA was more potent because it also increased the synthesis of ceramide. DHA did not induce ER stress but was the most potent inhibitor of apoB100 secretion, acting via stimulation of autophagy. These unique effects of each fatty acid were confirmed when they were infused into C57BL6J mice. Our results suggest that when both increased hepatic secretion of VLDL apoB100 and hepatic steatosis coexist, reducing ER stress might alleviate hepatic steatosis but at the expense of increased VLDL secretion. In contrast, increasing autophagy might reduce VLDL secretion without causing steatosis.
Eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) protect against cardiovascular disease by largely unknown mechanisms. We tested the hypothesis that EPA and DHA may compete with arachidonic acid (AA) for the conversion by cytochrome P450 (CYP) enzymes, resulting in the formation of alternative, physiologically active, metabolites. Renal and hepatic microsomes, as well as various CYP isoforms, displayed equal or elevated activities when metabolizing EPA or DHA instead of AA. CYP2C/2J isoforms converting AA to epoxyeicosatrienoic acids (EETs) preferentially epoxidized the ω-3 double bond and thereby produced 17,18-epoxyeicosatetraenoic (17,18-EEQ) and 19,20-epoxydocosapentaenoic acid (19,20-EDP) from EPA and DHA. We found that these ω-3 epoxides are highly active as antiarrhythmic agents, suppressing the Ca(2+)-induced increased rate of spontaneous beating of neonatal rat cardiomyocytes, at low nanomolar concentrations. CYP4A/4F isoforms ω-hydroxylating AA were less regioselective toward EPA and DHA, catalyzing predominantly ω- and ω minus 1 hydroxylation. Rats given dietary EPA/DHA supplementation exhibited substantial replacement of AA by EPA and DHA in membrane phospholipids in plasma, heart, kidney, liver, lung, and pancreas, with less pronounced changes in the brain. The changes in fatty acids were accompanied by concomitant changes in endogenous CYP metabolite profiles (e.g. altering the EET/EEQ/EDP ratio from 87:0:13 to 27:18:55 in the heart). These results demonstrate that CYP enzymes efficiently convert EPA and DHA to novel epoxy and hydroxy metabolites that could mediate some of the beneficial cardiovascular effects of dietary ω-3 fatty acids.
Beneficial physiological effects of long-chain n-3 polyunsaturated fatty acids are widely accepted but the mechanism(s) by which these fatty acids act remains unclear. Herein, we report the presence, distribution, and regulation of the levels of n-3 epoxy-fatty acids by soluble epoxide hydrolase (sEH) and a direct antinociceptive role of n-3 epoxy-fatty acids, specifically those originating from docosahexaenoic acid (DHA). The monoepoxides of the C18:1 to C22:6 fatty acids in both the n-6 and n-3 series were prepared and the individual regioisomers purified. The kinetic constants of the hydrolysis of the pure regioisomers by sEH were measured. Surprisingly, the best substrates are the mid-chain DHA epoxides. We also demonstrate that the DHA epoxides are present in considerable amounts in the rat central nervous system. Furthermore, using an animal model of pain associated with inflammation, we show that DHA epoxides, but neither the parent fatty acid nor the corresponding diols, selectively modulate nociceptive pathophysiology. Our findings support an important function of epoxy-fatty acids in the n-3 series in modulating nociceptive signaling. Consequently, the DHA and eicosapentaenoic acid epoxides may be responsible for some of the beneficial effects associated with dietary n-3 fatty acid intake.
The relative balance between the quantity of white and brown adipose tissue can profoundly affect lipid storage and whole-body energy homeostasis. However, the mechanisms regulating the formation, expansion, and interconversion of these 2 distinct types of fat remain unknown. Recently, the lysosomal degradative pathway of macroautophagy has been identified as a regulator of cellular differentiation, suggesting that autophagy may modulate this process in adipocytes. The function of autophagy in adipose differentiation was therefore examined in the current study by genetic inhibition of the critical macroautophagy gene autophagy-related 7 (Atg7). Knockdown of Atg7 in 3T3-L1 preadipocytes inhibited lipid accumulation and decreased protein levels of adipocyte differentiation factors. Knockdown of Atg5 or pharmacological inhibition of autophagy or lysosome function also had similar effects. An adipocyte-specific mouse knockout of Atg7 generated lean mice with decreased white adipose mass and enhanced insulin sensitivity. White adipose tissue in knockout mice had increased features of brown adipocytes, which, along with an increase in normal brown adipose tissue, led to an elevated rate of fatty acid, beta-oxidation, and a lean body mass. Autophagy therefore functions to regulate body lipid accumulation by controlling adipocyte differentiation and determining the balance between white and brown fat.
As of 2004, >73 million people were prescribed antiinflammatory medication. Despite the extensive number of current products, many people still suffer from their diseases or the pharmacological properties (side effects) of the medications. Therefore, developing therapeutic strategies to treat inflammation remains an important endeavor. Here, we demonstrate that the soluble epoxide hydrolase (sEH) is a key pharmacologic target for treating acute systemic inflammation. Lipopolysaccharide-induced mortality, systemic hypotension, and histologically evaluated tissue injury were substantially diminished by administration of urea-based, small-molecule inhibitors of sEH to C57BL/6 mice. Moreover, sEH inhibitors decreased plasma levels of proinflammatory cytokines and nitric oxide metabolites while promoting the formation of lipoxins, thus supporting inflammatory resolution. These data suggest that sEH inhibitors have therapeutic efficacy in the treatment and management of acute inflammatory diseases.
• cyclooxygenase
• lipoxin A4
• lipoxygenase
• proinflammatory mediators
• epoxygenase
In 2008 we published the first guidelines paper for monitoring autophagy and interpreting the data resulting from the various assays used in our field. The guidelines paper was substantially expanded and updated in 2012. Based on the number of citations, and on comments from many users, I think it is accurate to say that the guidelines have been very useful for many researchers. Because the field continues to undergo rapid development, it is necessary to update the guidelines once again.
Insulin resistance and nonalcoholic steatohepatitis (NASH), characterized by hepatic steatosis combined with inflammation, are major sequelae of obesity. Currently, lifestyle modification (i.e., weight loss) is the first-line therapy for NASH. However, weight loss resolves steatosis but not inflammation. In this study, we tested the ability of resolvin D1 (RvD1), an anti-inflammatory and proresolving molecule, to promote the resolution initiated by calorie restriction in obese mice with NASH. Calorie restriction reduced adipose and liver weight (-56 and -13%, respectively; P<0.001), serum leptin and resistin levels, hepatic steatosis, and insulin resistance. In addition to these, mice receiving RvD1 during the dietary intervention showed increased adiponectin expression at both the mRNA and protein levels and reduced liver macrophage infiltration (-15%, P<0.01). Moreover, RvD1 skewed macrophages from an M1- to an M2-like anti-inflammatory phenotype, induced a specific hepatic miRNA signature (i.e., miR-219-5p and miR-199a-5p), and reduced inflammatory adipokine mRNA and protein expression and macrophage innate immune response. In precision-cut liver slices (PCLSs), which override the influence of circulating factors, RvD1 attenuated hypoxia-induced mRNA and protein expression of COX-2, IL-1β, IL-6, and CCR7. Of note, RvD1 anti-inflammatory actions were absent in macrophage-depleted PCLSs. In summary, RvD1 acts as a facilitator of the hepatic resolution process by reducing the inflammatory component of obesity-induced NASH.-Rius, B., Titos, E., Morán-Salvador, E., López-Vicario, C., García-Alonso, V., González-Périz, A., Arroyo, V., Clària, J. Resolvin D1 primes the resolution process initiated by calorie restriction in obesity-induced steatohepatitis.
Studies performed in the liver in the 1960s led to the identification of lysosomes and the discovery of autophagy, the process by which intracellular proteins and organelles are degraded in lysosomes. Early studies in hepatocytes also uncovered how nutritional status regulates autophagy and how various circulating hormones modulate the activity of this catabolic process in the liver. The intensive characterization of hepatic autophagy over the years has revealed that lysosome-mediated degradation is important not only for maintaining liver homeostasis in normal physiological conditions, but also for an adequate response of this organ to stressors such as proteotoxicity, metabolic dysregulation, infection and carcinogenesis. Autophagic malfunction has also been implicated in the pathogenesis of common liver diseases, suggesting that chemical manipulation of this process might hold potential therapeutic value. In this Review-intended as an introduction to the topic of hepatic autophagy for clinical scientists-we describe the different types of hepatic autophagy, their role in maintaining homeostasis in a healthy liver and the contribution of autophagic malfunction to liver disease.
Objective:
The mechanisms underlying non-alcoholic steatohepatitis (NASH) are not completely elucidated. In the current study we integrated gene expression profiling of liver biopsies from NASH patients with translational studies in mouse models of steatohepatitis and pharmacological interventions in isolated hepatocytes to identify new molecular targets in NASH.
Design and results:
Using oligonucleotide microarray analysis we identified a significant enrichment of genes involved in the multi-step catalysis of long-chain polyunsaturated fatty acids, namely, Δ-5 desaturase (Δ5D) and Δ6D in NASH. Increased expression of Δ5D and Δ6D at both mRNA and protein level were confirmed in livers from mice with high-fat diet-induced obesity and NASH. Gas chromatography analysis revealed impaired desaturation fluxes toward the ω-6 and ω-3 pathways resulting in increased ω-6 to ω-3 ratio and reduced ω-3 index in human and mouse fatty livers. Restoration of hepatic ω-3 content in transgenic fat-1 mice expressing an ω-3 desaturase, which allows the endogenous conversion of ω-6 into ω-3 fatty acids, produced a significant reduction in hepatic insulin resistance, steatosis, macrophage infiltration, necroinflammation and lipid peroxidation, accompanied by attenuated expression of genes involved in inflammation, fatty acid uptake and lipogenesis. These results were mostly reproduced by feeding obese mice with an exogenous ω-3-enriched diet. A combined Δ5D/Δ6D inhibitor, CP-24879, significantly reduced intracellular lipid accumulation and inflammatory injury in hepatocytes. Interestingly, CP-24879 exhibited superior antisteatotic and anti-inflammatory actions in fat-1 and ω-3-treated hepatocytes.
Conclusions:
These findings indicate that impaired hepatic fatty acid desaturation and unbalanced ω-6 to ω-3 ratio play a role in the pathogenesis of NASH.
Autophagy, an evolutionary conserved process aimed at recycling damaged organelles and protein aggregates in the cell, also modulates proinflammatory cytokine production in peripheral blood mononuclear cells. Because adipose tissue inflammation accompanied by elevated levels of proinflammatory cytokines is characteristic for the development of obesity, we hypothesized that modulation of autophagy alters adipose tissue inflammatory gene expression and secretion. We tested our hypothesis using ex vivo and in vivo studies of human and mouse adipose tissue. Levels of the autophagy marker LC3 were elevated in sc adipose tissue of obese vs. lean human subjects and positively correlated to both systemic insulin resistance and morphological characteristics of adipose tissue inflammation. Similarly, autophagic activity levels were increased in adipose tissue of obese and insulin resistant animals as compared with lean mice. Inhibition of autophagy by 3-methylalanine in human and mouse adipose tissue explants led to a significant increase in IL-1β, IL-6, and IL-8 mRNA expression and protein secretion. Noticeably, the enhancement in IL-1β, IL-6, and keratinocyte-derived chemoattractant (KC) by inhibition of autophagy was more robust in the presence of obesity. Similar results were obtained by blocking autophagy using small interfering RNA targeted to ATG7 in human Simpson-Golabi-Behmel syndrome adipocytes. Our results demonstrate that autophagy activity is up-regulated in the adipose tissue of obese individuals and inhibition of autophagy enhances proinflammatory gene expression both in adipocytes and adipose tissue explants. Autophagy may function to dampen inflammatory gene expression and thereby limit excessive inflammation in adipose tissue during obesity.
17(R),18(S)-epoxyeicosatetraenoic acid [17(R),18(S)-EETeTr], a cytochrome P450 epoxygenase metabolite of eicosapentaenoic acid (EPA), exerts negative chronotropic effects and protects neonatal rat cardiomyocytes against Ca(2+)-overload with EC(50) ≈ 1-2 nM. Structure-activity studies revealed that a cis-Δ(11,12)- or Δ(14,15)-olefin and a 17(R),18(S)-epoxide are minimal structural elements for antiarrhythmic activity whereas antagonist activity was often associated with the combination of a Δ(14,15)-olefin and a 17(S),18(R)-epoxide. Compared with natural material, the agonist and antagonist analogues are chemically and metabolically more robust and several show promise as templates for future development of clinical candidates.
Omega-3 fatty acids (omega-3 FAs), DHA and EPA, exert anti-inflammatory effects, but the mechanisms are poorly understood. Here, we show that the G protein-coupled receptor 120 (GPR120) functions as an omega-3 FA receptor/sensor. Stimulation of GPR120 with omega-3 FAs or a chemical agonist causes broad anti-inflammatory effects in monocytic RAW 264.7 cells and in primary intraperitoneal macrophages. All of these effects are abrogated by GPR120 knockdown. Since chronic macrophage-mediated tissue inflammation is a key mechanism for insulin resistance in obesity, we fed obese WT and GPR120 knockout mice a high-fat diet with or without omega-3 FA supplementation. The omega-3 FA treatment inhibited inflammation and enhanced systemic insulin sensitivity in WT mice, but was without effect in GPR120 knockout mice. In conclusion, GPR120 is a functional omega-3 FA receptor/sensor and mediates potent insulin sensitizing and antidiabetic effects in vivo by repressing macrophage-induced tissue inflammation.
Autophagy is a homeostatic process involved in the bulk degradation of cytoplasmic components, including damaged organelles and proteins. In both genetic and dietary models of obesity, we observed a severe downregulation of autophagy, particularly in Atg7 expression levels in liver. Suppression of Atg7 both in vitro and in vivo resulted in defective insulin signaling and elevated ER stress. In contrast, restoration of the Atg7 expression in liver resulted in dampened ER stress, enhanced hepatic insulin action, and systemic glucose tolerance in obese mice. The beneficial action of Atg7 restoration in obese mice could be completely prevented by blocking a downstream mediator, Atg5, supporting its dependence on autophagy in regulating insulin action. Our data demonstrate that autophagy is an important regulator of organelle function and insulin signaling and that loss of autophagy is a critical component of defective insulin action seen in obesity.
Soluble epoxide hydrolase (sEH) inhibitors have been shown to effectively increase the levels of epoxyeicosatrienoic acids and reduce the levels of dihydroxyeicosatrienoic acids, which may be translated to therapeutic potentials for multiple disease indications. It has been claimed that sEH inhibitors can be used to treat hypertension, diabetes, stroke, dyslipidemia, pain, immunological disorders, eye diseases, neurological diseases and other indications.
A comprehensive synopsis of patent literature on sEH inhibitors is provided.
A total of more than 100 patent publications describing multiple classes of sEH inhibitors are analyzed. These include amides, ureas, thioamides, thioureas, carbamates, acyl hydrazones, chalcone oxdies, etc. In addition to selected in vitro and in vivo data of representative sEH inhibitors, a wide range of proposed applications of sEH inhibitors are also summarized.
Several sEH inhibitors with potent in vitro and in vivo target inhibition appear promising, including one Phase II clinical candidate. The clinical evaluation will be critical to assess the proclaimed therapeutic utility of sEH inhibition.
Obesity is an increasingly important public health issue reaching epidemic proportions. Visceral obesity has been defined as an important element of the metabolic syndrome and expansion of the visceral fat mass has been shown to contribute to the development of insulin resistance and cardiovascular disease. To identify novel contributors to cardiovascular and metabolic abnormalities in obesity, we analyzed the adipose proteome and identified soluble epoxide hydrolase (sEH) in the epididymal fat pad from C57BL/6J mice that received either a regular diet or a "western diet." sEH was synthesized in adipocytes and expression levels increased upon differentiation of 3T3-L1 preadipocytes. Although normalized sEH mRNA and protein levels did not differ in the fat pads from mice receiving a regular or a "western diet," total adipose sEH activity was higher in the obese mice, even after normalization for body weight. Furthermore, peroxisome proliferator-activated receptor gamma (PPARgamma) agonists increased the expression of sEH in mature 3T3-L1 adipocytes in vitro and in adipose tissue in vivo. Considering the established role for sEH in inflammation, cardiovascular diseases, and lipid metabolism, and the suggested involvement of sEH in the development of type 2 diabetes, our study has identified adipose sEH as a potential novel therapeutic target that might affect the development of metabolic and cardiovascular abnormalities in obesity.
Animal studies suggest that increased consumption of the long-chain omega-3 polyunsaturated fatty acids, eicosapentaenoic acid and docosahexaenoic acid, can protect against the development of obesity in animals exposed to an obesogenic diet and reduce body fat when already obese. There is also evidence that increased intakes of these fatty acids can reduce body fat in humans, but human studies are relatively few and have generally been conducted over short time periods with small sample sizes, making it difficult to draw definitive conclusions. Reported reductions in body fat may result from appetite-suppressing effects, adipocyte apoptosis and changes of gene expression in skeletal muscle, heart, liver, intestine and adipose tissues that suppress fat deposition and increase fat oxidation and energy expenditure. We conclude that increased intakes of long-chain omega-3 fatty acids may improve body composition, but longer-term human studies are needed to confirm efficacy and determine whether increasing omega-3 intakes might be an effective strategy to combat obesity.
Omega-3-polyunsaturated fatty acids (omega-3-PUFAs) have well-documented protective effects that are attributed not only to eicosanoid inhibition but also to the formation of novel biologically active lipid mediators (i.e., resolvins and protectins). In this study, we examined their effects on ob/ob mice, an obesity model of insulin resistance and fatty liver disease. Dietary intake of omega-3-PUFAs had insulin-sensitizing actions in adipose tissue and liver and improved insulin tolerance in obese mice. Genes involved in insulin sensitivity (PPARgamma), glucose transport (GLUT-2/GLUT-4), and insulin receptor signaling (IRS-1/IRS-2) were up-regulated by omega-3-PUFAs. Moreover, omega-3-PUFAs increased adiponectin, an anti-inflammatory and insulin-sensitizing adipokine, and induced AMPK phosphorylation, a fuel-sensing enzyme and a gatekeeper of the energy balance. Concomitantly, hepatic steatosis was alleviated by omega-3-PUFAs. A lipidomic analysis with liquid chromatography/mass spectrometry/mass spectrometry revealed that omega-3-PUFAs inhibited the formation of omega-6-PUFA-derived eicosanoids, while triggering the formation of omega-3-PUFA-derived resolvins and protectins. Moreover, representative members of these lipid mediators, namely resolvin E1 and protectin D1, mimicked the insulin-sensitizing and antisteatotic effects of omega-3-PUFAs and induced adiponectin expression to a similar extent that of rosiglitazone, a member of the thiazolidinedione family of antidiabetic drugs. Taken together, these findings uncover beneficial actions of omega-3-PUFAs and their bioactive lipid autacoids in preventing obesity-induced insulin resistance and hepatic steatosis.
Elevated serum-free fatty acid (FFA) levels induce insulin resistance in whole animals and humans. To understand the direct mechanism by which FFAs impact insulin-responsive tissue, we have used our previously developed in vitro model of long-chain saturated fatty acids (LCSFA)-induced insulin resistance in adipocytes. In addition to explanted rat adipocytes, we now demonstrate that overnight exposure of 3T3-L1 adipocytes to 1 mM individually of the LCSFA palmitate, myristate, and stearate, leads to an approximately 50% inhibition of insulin-induced glucose transport. Insulin resistance can be accomplished at 0.3 mM palmitate, which is within the range ofpalmitate found in diabetic and obese individuals. This inhibition was noted within 4 h of exposure to FFA, which is comparable to in vivo lipid infusion studies. Initial LCSFA-induced resistance is specific to glucose transport and does not affect insulin stimulation of glucose incorporation into glycogen. In 3T3-L1 adipocytes overexpressing the EGF receptor, LCSFA exposure also specifically inhibited EGF-induced GLUT4-mediated glucose transport, but not EGF-induced glycogen synthesis. We find that LCSFA treatment did not impair insulin stimulation of GLUT4 translocation or exofacial presentation on the cell surface as determined by trypsin accessibility. Our results suggest that the initial direct effect of elevated LCSFA is to impair activation of GLUT4 transporter activity and that this effect is specific for glucose transport.
Mammals cannot naturally produce omega-3 (n-3) fatty acids--beneficial nutrients found mainly in fish oil--from the more abundant omega-6 (n-6) fatty acids and so they must rely on a dietary supply. Here we show that mice engineered to carry a fat-1 gene from the roundworm Caenorhabditis elegans can add a double bond into an unsaturated fatty-acid hydrocarbon chain and convert n-6 to n-3 fatty acids. This results in an abundance of n-3 and a reduction in n-6 fatty acids in the organs and tissues of these mice, in the absence of dietary n-3. As well as presenting an opportunity to investigate the roles played by n-3 fatty acids in the body, our discovery indicates that this technology might be adapted to enrich n-3 fatty acids in animal products such as meat, milk and eggs.
Epoxyeicosatrienoic acids (EETs), which function primarily as autocrine and paracrine mediators in the cardiovascular and renal systems, are synthesized from arachidonic acid by cytochrome P-450 epoxygenases. They activate smooth muscle large-conductance Ca(2+)-activated K(+) channels, producing hyperpolarization and vasorelaxation. EETs also have anti-inflammatory effects in the vasculature and kidney, stimulate angiogenesis, and have mitogenic effects in the kidney. Many of the functional effects of EETs occur through activation of signal transduction pathways and modulation of gene expression, events probably initiated by binding to a putative cell surface EET receptor. However, EETs are rapidly taken up by cells and are incorporated into and released from phospholipids, suggesting that some functional effects may occur through a direct interaction between the EET and an intracellular effector system. In this regard, EETs and several of their metabolites activate peroxisome proliferator-activated receptor alpha (PPARalpha) and PPARgamma, suggesting that some functional effects may result from PPAR activation. EETs are metabolized primarily by conversion to dihydroxyeicosatrienoic acids (DHETs), a reaction catalyzed by soluble epoxide hydrolase (sEH). Many potentially beneficial actions of EETs are attenuated upon conversion to DHETs, which do not appear to be essential under routine conditions. Therefore, sEH is considered a potential therapeutic target for enhancing the beneficial functions of EETs.
Autophagy regulates adipose mass and differentiation in mice
- R Singh
- Singh R