[Show abstract][Hide abstract] ABSTRACT: Background:
Obesity is associated with changes in fat cell gene expression and metabolism. What drives these changes is not well understood. We aimed to explore fat cell epigenetics, i.e., DNA methylation, as one mediator of gene regulation, in obese women. The global DNA methylome for abdominal subcutaneous fat cells was compared between 15 obese case (BMI 41.4 ± 4.4 kg/m(2), mean ± SD) and 14 never-obese control women (BMI 25.2 ± 2.5 kg/m(2)). Global array-based transcriptome analysis was analyzed for subcutaneous white adipose tissue (WAT) from 11 obese and 9 never-obese women. Limma was used for statistical analysis.
We identified 5529 differentially methylated DNA sites (DMS) for 2223 differentially expressed genes between obese cases and never-obese controls (false discovery rate <5 %). The 5529 DMS displayed a median difference in beta value of 0.09 (range 0.01 to 0.40) between groups. DMS were under-represented in CpG islands and in promoter regions, and over-represented in open sea-regions and gene bodies. The 2223 differentially expressed genes with DMS were over-represented in key fat cell pathways: 31 of 130 (25 %) genes linked to "adipogenesis" (adjusted P = 1.66 × 10(-11)), 31 of 163 (19 %) genes linked to "insulin signaling" (adjusted P = 1.91 × 10(-9)), and 18 of 67 (27 %) of genes linked to "lipolysis" (P = 6.1 × 10(-5)). In most cases, gene expression and DMS displayed reciprocal changes in obese women. Furthermore, among 99 candidate genes in genetic loci associated with body fat distribution in genome-wide association studies (GWAS); 22 genes displayed differential expression accompanied by DMS in obese versus never-obese women (P = 0.0002), supporting the notion that a significant proportion of gene loci linked to fat distribution are epigenetically regulated.
Subcutaneous WAT from obese women is characterized by congruent changes in DNA methylation and expression of genes linked to generation, distribution, and metabolic function of fat cells. These alterations may contribute to obesity-associated metabolic disturbances such as insulin resistance in women.
[Show abstract][Hide abstract] ABSTRACT: In humans, Cidea (cell death-inducing DNA fragmentation factor alpha-like effector A) is highly but variably expressed in white fat, and expression correlates with metabolic health. Here we generate transgenic mice expressing human Cidea in adipose tissues (aP2-hCidea mice) and show that Cidea is mechanistically associated with a robust increase in adipose tissue expandability. Under humanized conditions (thermoneutrality, mature age and prolonged exposure to high-fat diet), aP2-hCidea mice develop a much more pronounced obesity than their wild-type littermates. Remarkably, the malfunctioning of visceral fat normally caused by massive obesity is fully overcome-perilipin 1 and Akt expression are preserved, tissue degradation is prevented, macrophage accumulation is decreased and adiponectin expression remains high. Importantly, the aP2-hCidea mice display enhanced insulin sensitivity. Our data establish a functional role for Cidea and suggest that, in humans, the association between Cidea levels in white fat and metabolic health is not only correlative but also causative.
[Show abstract][Hide abstract] ABSTRACT: Dysregulated expression of metabolic and inflammatory genes is a prominent consequence of obesity causing insulin resistance and type 2 diabetes. Finding causative factors is essential to understanding progression of these pathologies and discovering new therapeutic targets. The transcription factor V-maf musculoaponeurotic fibrosarcoma oncogene homologue B (MAFB) is highly expressed in human white adipose tissue (WAT). However, its role in the regulation of WAT function is elusive. We aimed to characterise MAFB expression and function in human WAT in the context of obesity and insulin resistance.
MAFB mRNA expression was evaluated in human WAT from seven cohorts with large inter-individual variation in BMI and metabolic features. Insulin-induced adipocyte lipogenesis and lipolysis were measured and correlated with MAFB expression. MAFB regulation during adipogenesis and the effects of MAFB suppression in human adipocytes was investigated. MAFB regulation by TNF-α was examined in human primary adipocytes and THP-1 monocytes/macrophages.
MAFB expression in human adipocytes is upregulated during adipogenesis, increases with BMI in WAT, correlates with adverse metabolic features and is decreased after weight loss. MAFB downregulation decreases proinflammatory gene expression in adipocytes and interferes with TNF-α effects. Interestingly, MAFB is differentially regulated by TNF-α in adipocytes (suppressed) and THP-1 cells (upregulated). Further, MAFB is primarily expressed in WAT macrophages/monocytes and its expression correlates with macrophage and inflammatory markers.
Our findings indicate that MAFB is a regulator and a marker of adipose tissue inflammation, a process that subsequently causes insulin resistance.
[Show abstract][Hide abstract] ABSTRACT: MicroRNAs (miRNAs) are post-transcriptional regulators of gene expression. In white adipose tissue (WAT), recent studies suggest that miRNA levels are altered in various metabolic diseases, including obesity.
To determine whether adipocyte-expressed miRNAs altered by obesity can regulate adiponectin expression/secretion in fat cells.
Eleven miRNAs previously shown to be altered in obese human WAT were overexpressed in human in vitro differentiated adipocytes followed by assessments of adiponectin levels in conditioned media.
Cohort study (n=56) in academic hospital.
Subcutaneous WAT was obtained from non-obese and obese individuals.
Protein and mRNA levels of adiponectin.
Out of the eleven investigated miRNAs, three (miR-193b/-126/-26a) increased adiponectin secretion when overexpressed in human adipocytes. However, in human WAT only miR-193b expression correlated with adiponectin gene expression and HOMAIR.. Moreover, qPCR of miR-193b in both WAT and isolated adipocytes showed a significant association with serum adiponectin levels. Overexpression of miR-193b altered the gene expression of seven known adiponectin regulators. 3'-UTR reporter assays confirmed binding to cAMP responsive element binding protein 5 (CREB5), nuclear receptor interacting protein 1 (NRIP1) and nuclear transcription factor Y, alpha (NF-YA). The effects of miR-193b on NF-YA expression were confirmed at the protein level. Transfection with individual miRNA target protectors selective for NF-YA and NRIP1 abolished the stimulatory effect of miR-193b on adiponectin secretion.
In human adipocytes, miR-193b controls adiponectin production via pathways involving NF-YA and possibly NRIP1.
The Journal of Clinical Endocrinology and Metabolism 05/2015; 100(8):jc20151530. DOI:10.1210/jc.2015-1530 · 6.21 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Visceral fat accumulation is associated with metabolic disease. It is therefore relevant to study factors that regulate adipose tissue distribution. Recent data shows that overeating saturated fatty acids promotes greater visceral fat storage than overeating unsaturated fatty acids. Visceral adiposity is observed in states of hypercortisolism, and the enzyme 11-β-hydroxysteroid-dehydrogenase type 1 (11β-hsd1) is a major regulator of cortisol activity by converting inactive cortisone to cortisol in adipose tissue. We hypothesized that tissue fatty acid composition regulates body fat distribution through local effects on the expression of 11β-hsd1 and its corresponding gene (HSD11B1) resulting in altered cortisol activity.
Visceral- and subcutaneous adipose tissue biopsies were collected during Roux-en-Y gastric bypass surgery from 45 obese women (BMI; 41 ± 4 kg/m(2)). The fatty acid composition of each biopsy was measured and correlated to the mRNA levels of HSD11B1. 11β-hsd1 protein levels were determined in a subgroup (n = 12) by western blot analysis. Our main finding was that tissue saturated fatty acids (e.g. palmitate) were associated with increased 11β-hsd1 gene- and protein-expression in visceral but not subcutaneous adipose tissue.
The present study proposes a link between HSD11B1 and saturated fatty acids in visceral, but not subcutaneous adipose tissue. Nutritional regulation of visceral fat mass through HSD11B1 is of interest for the modulation of metabolic risk and warrants further investigation.
Lipids in Health and Disease 05/2015; 14(1):42. DOI:10.1186/s12944-015-0042-1 · 2.22 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Background:
Cancer cachexia (CC) is linked to poor prognosis. Although the mechanisms promoting this condition are not known, several circulating proteins have been proposed to contribute. We analyzed the plasma proteome in cancer subjects in order to identify factors associated with cachexia.
Plasma was obtained from a screening cohort of 59 patients, newly diagnosed with suspected gastrointestinal cancer, with (n = 32) or without (n = 27) cachexia. Samples were subjected to proteomic profiling using 760 antibodies (targeting 698 individual proteins) from the Human Protein Atlas project. The main findings were validated in a cohort of 93 patients with verified and advanced pancreas cancer.
Only six proteins displayed differential plasma levels in the screening cohort. Among these, Carnosine Dipeptidase 1 (CNDP1) was confirmed by sandwich immunoassay to be lower in CC (p = 0.008). In both cohorts, low CNDP1 levels were associated with markers of poor prognosis including weight loss, malnutrition, lipid breakdown, low circulating albumin/IGF1 levels and poor quality of life. Eleven of the subjects in the discovery cohort were finally diagnosed with non-malignant disease but omitting these subjects from the analyses did not have any major influence on the results.
In gastrointestinal cancer, reduced plasma levels of CNDP1 associate with signs of catabolism and poor outcome. These results, together with recently published data demonstrating lower circulating CNDP1 in subjects with glioblastoma and metastatic prostate cancer, suggest that CNDP1 may constitute a marker of aggressive cancer and CC.
PLoS ONE 04/2015; 10(4):e0123566. DOI:10.1371/journal.pone.0123566 · 3.23 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Genome-wide association studies have implicated PLEXIN D1 (PLXND1) in body fat distribution and type 2 diabetes. However, a role for PLXND1 in regional adiposity and insulin resistance is unknown. Here we use in vivo imaging and genetic analysis in zebrafish to show that Plxnd1 regulates body fat distribution and insulin sensitivity. Plxnd1 deficiency in zebrafish induced hyperplastic morphology in visceral adipose tissue (VAT) and reduced lipid storage. In contrast, subcutaneous adipose tissue (SAT) growth and morphology were unaffected, resulting in altered body fat distribution and a reduced VAT:SAT ratio in zebrafish. A VAT-specific role for Plxnd1 appeared conserved in humans, as PLXND1 mRNA was positively associated with hypertrophic morphology in VAT, but not SAT. In zebrafish plxnd1 mutants, the effect on VAT morphology and body fat distribution was dependent on induction of the extracellular matrix protein collagen type V alpha 1 (col5a1). Furthermore, after high-fat feeding, zebrafish plxnd1 mutant VAT was resistant to expansion, and excess lipid was disproportionately deposited in SAT, leading to an even greater exacerbation of altered body fat distribution. Plxnd1-deficient zebrafish were protected from high-fat-diet-induced insulin resistance, and human VAT PLXND1 mRNA was positively associated with type 2 diabetes, suggesting a conserved role for PLXND1 in insulin sensitivity. Together, our findings identify Plxnd1 as a novel regulator of VAT growth, body fat distribution, and insulin sensitivity in both zebrafish and humans.
Proceedings of the National Academy of Sciences 03/2015; 112(14). DOI:10.1073/pnas.1416412112 · 9.67 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Obese subjects have increased number of enlarged fat cells which are reduced in size but not number in post-obesity. We performed DNA methylation profiling in fat cells with the aim of identifying differentially methylated DNA sites (DMS) linked to adipose hyperplasia (many small fat cells) in post-obesity.
Genome-wide DNA methylation was analyzed in abdominal subcutaneous fat cells from 16 women examined two years after gastric bypass surgery at a post-obese state (BMI 26±2 kg/m(2), mean±s.d.) and 14 never-obese women (BMI 25±2 kg/m(2)). Gene expression was analyzed in subcutaneous adipose tissue from 9 women in each group. In a secondary analysis, we examined DNA methylation and expression of adipogenesis genes in 15 and 11 obese women, respectively.
The average degree of DNA methylation of all analyzed CpG-sites was lower in fat cells from post-obese as compared to never-obese women (P=0.014). 8,504 CpG sites were differentially methylated in fat cells from post-obese versus never-obese women (false discovery rate 1%). DMS were under-represented in CpG-islands and surrounding shores. The 8,504 DMS mapped to 3,717 unique genes; these genes were over-represented in cell differentiation pathways. Notably, 27% of genes linked to adipogenesis (i.e. 35 of 130) displayed DMS (adjusted P=10(-8)) in post-obese versus never-obese women. Next, we explored DNA methylation and expression of genes linked to adipogenesis in more detail in adipose tissue samples. DMS annotated to adipogenesis genes were not accompanied by differential gene expression in post-obese compared to never-obese women. In contrast, adipogenesis genes displayed differential DNA methylation accompanied by altered expression in obese women,Conclusions:Global CpG hypomethylation and overrepresentation of DMS in adipogenesis genes in fat cells may contribute to adipose hyperplasia in post-obese women.International Journal of Obesity accepted article preview online, 18 March 2015. doi:10.1038/ijo.2015.31.
International journal of obesity (2005) 03/2015; 39(6). DOI:10.1038/ijo.2015.31 · 5.00 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: MicroRNAs (miRNAs) are small noncoding RNAs that regulate gene expression and, therefore, biological processes in different tissues. A major function of miRNAs in adipose tissue is to stimulate or inhibit the differentiation of adipocytes, and to regulate specific metabolic and endocrine functions. Numerous miRNAs are present in human adipose tissue; however, the expression of only a few is altered in individuals with obesity and type 2 diabetes mellitus or are differentially expressed in various adipose depots. In humans, obesity is associated with chronic low-grade inflammation that is regulated by signal transduction networks, in which miRNAs, either directly or indirectly (through regulatory elements such as transcription factors), influence the expression and secretion of inflammatory proteins. In addition to their diverse effects on signalling, miRNAs and transcription factors can interact to amplify the inflammatory effect. Although additional miRNA signal networks in human adipose tissue are not yet known, similar regulatory circuits have been described in brown adipose tissue in mice. miRNAs can also be secreted from fat cells into the circulation and serve as markers of disturbed adipose tissue function. Given their role in regulating transcriptional networks, miRNAs in adipose tissue might offer tangible targets for treating metabolic disorders.
[Show abstract][Hide abstract] ABSTRACT: Although it is generally accepted that cellular differentiation requires changes to transcriptional networks, dynamic regulation of promoters and enhancers at specific sets of genes has not been previously studied en masse. Exploiting the fact that active promoters and enhancers are transcribed, we simultaneously measured their activity in 19 human and 14 mouse time courses covering a wide range of cell types and biological stimuli. Enhancer RNAs, then messenger RNAs encoding transcription factors, dominated the earliest responses. Binding sites for key lineage transcription factors were simultaneously overrepresented in enhancers and promoters active in each cellular system. Our data support a highly generalizable model in which enhancer transcription is the earliest event in successive waves of transcriptional change during cellular differentiation or activation.
[Show abstract][Hide abstract] ABSTRACT: Background:
Cross-sectional studies show that white adipose tissue hypertrophy (few, large adipocytes), in contrast to hyperplasia (many, small adipocytes), associates with insulin resistance and increased risk of developing type 2 diabetes. We investigated if baseline adipose cellularity could predict improvements in insulin sensitivity following weight loss.
Plasma samples and subcutaneous abdominal adipose biopsies were examined in 100 overweight or obese individuals before and 10 weeks after a hypocaloric diet (7±3% weight loss) and in 61 obese subjects before and 2 years after gastric by-pass surgery (33±9% weight loss). The degree of adipose tissue hypertrophy or hyperplasia (termed the morphology value) in each individual was calculated on the basis of the relationship between fat cell volume and total fat mass. Insulin sensitivity was determined by homeostasis model assessment-estimated insulin resistance (HOMAIR).
In both cohorts at baseline, subjects with hypertrophy displayed significantly higher fasting plasma insulin and HOMAIR values than subjects with hyperplasia (P<0.0001), despite similar total fat mass. Plasma insulin and HOMAIR were normalized in both cohorts following weight loss. The improvement (delta insulin or delta HOMAIR) was more pronounced in individuals with hypertrophy, irrespective of whether adipose morphology was used as a continuous (P=0.0002-0.027) or nominal variable (P=0.002-0.047). Absolute adipocyte size associated (although weaker than morphology) with HOMAIR improvement only in the surgery cohort. Anthropometric measures at baseline (fat mass, body mass index, waist-to-hip ratio or waist circumference) showed no significant association with delta insulin or delta HOMAIR.
In contrast to anthropometric variables or fat cell size, subcutaneous adipose morphology predicts improvement in insulin sensitivity following both moderate and pronounced weight loss in overweight/obese subjects.
International journal of obesity (2005) 02/2015; 39(6). DOI:10.1038/ijo.2015.18 · 5.00 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Recently developed high-throughput sequencing technology shows power to detect low-frequency disease-causing variants by deep sequencing of all known exons. We used exome sequencing to identify variants associated with morbid obesity. DNA from 100 morbidly obese adult subjects and 100 controls were pooled (n=10/pool), subjected to exome capture, and subsequent sequencing. At least 100 million sequencing reads were obtained from each pool. After several filtering steps and comparisons of observed frequencies of variants between obese and non-obese control pools, we systematically selected 144 obesity-enriched non-synonymous, splicing site or 5' upstream single-nucleotide variants for validation. We first genotyped 494 adult subjects with morbid obesity and 496 controls. Five obesity-associated variants (nominal P-value<0.05) were subsequently genotyped in 1425 morbidly obese and 782 controls. Out of the five variants, only rs62623713:A>G (NM_001040709:c.A296G:p.E99G) was confirmed. rs62623713 showed strong association with body mass index (beta=2.13 (1.09, 3.18), P=6.28 × 10(-5)) in a joint analysis of all 3197 genotyped subjects and had an odds ratio of 1.32 for obesity association. rs62623713 is a low-frequency (2.9% minor allele frequency) non-synonymous variant (E99G) in exon 4 of the synaptophysin-like 2 (SYPL2) gene. rs62623713 was not covered by Illumina or Affymetrix genotyping arrays used in previous genome-wide association studies. Mice lacking Sypl2 has been reported to display reduced body weight. In conclusion, using exome sequencing we identified a low-frequency coding variant in the SYPL2 gene that was associated with morbid obesity. This gene may be involved in the development of excess body fat.European Journal of Human Genetics advance online publication, 19 November 2014; doi:10.1038/ejhg.2014.255.
European journal of human genetics: EJHG 11/2014; 23(9). DOI:10.1038/ejhg.2014.255 · 4.35 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Background:
Cardiovascular disease is associated with multiple risk factors including stiff arteries and large adipocytes. Whether the latter two are interrelated is unknown. We aimed to determine whether arterial stiffness is associated with fat cell size and number in subcutaneous or visceral white adipose tissue (WAT).
A cross-sectional study of 120 obese subjects scheduled for bariatric surgery in whom WAT mass and distribution was assessed by dual-X-ray absorptiometry. Biopsies from visceral (greater omentum) and subcutaneous (abdominal) WAT were obtained to calculate fat cell volume and number. Arterial stiffness was determined as aortic pulse wave velocity (PWV).
Visceral adipocyte volume, but not number, was strongly (P<0.0001) and positively correlated with PWV, explaining 20% of the inter-individual variations in this parameter. This relationship remained significant after correction for clinical confounders. PWV correlated positively (r=0.38, P<0.0001) with visceral (but not subcutaneous) WAT mass. Furthermore, PWV was also positively associated with subcutaneous adipocyte volume (r=0.20, P=0.031) and negatively with fat cell number (r=-0.26, P=0.006). However, the relationships between PWV and visceral WAT mass or subcutaneous fat cell size/number became non-significant when controlling for visceral fat cell volume. In a multiple regression analysis to determine the factors that explain variations in PWV, only visceral fat cell volume, age, pulse rate and diastolic blood pressure entered the model, together explaining 42% of the variation in PWV.
Visceral fat cell volume was the only WAT parameter that constituted an independent and significant, positive regressor for arterial stiffness determined by PWV. Although a causal relationship is not established, visceral fat cell volume may explain the well-known correlation between central fat mass, arterial stiffness and cardiovascular risk, at least in severely/morbidly obese subjects.
International journal of obesity (2005) 07/2014; 39(2). DOI:10.1038/ijo.2014.118 · 5.00 Impact Factor