Transcripts In Adipose Tissue Research Articles

Metaboepigenetic regulation of gene expression in obesity and insulin resistance.

Variation in DNA methylation (DNAm) in adipose tissue is associated with the pathogenesis of obesity and insulin resistance. The activity of enzymes involved in altering DNAm levels is dependent on several metabolite cofactors. To understand the role of metabolites as mechanistic regulators of epigenetic marks, we tested the association between selected plasma metabolites and DNAm levels in the adipose tissue of African Americans. In the AAGMEx cohort (N = 256), plasma levels of metabolites were measured by untargeted liquid chromatography-mass spectrometry; adipose tissue DNAm and transcript levels were measured by reduced representation bisulfite sequencing, and expression microarray, respectively. Among the 21 one-carbon metabolism pathway metabolites evaluated, six were associated with gluco-metabolic traits (PFDR < 0.05, for BMI, SI, or Matsuda index) in AAGMEx. Methylation levels of 196, 116, and 180 CpG-sites were associated (P < 0.0001) with S-adenosylhomocysteine (SAH), cystine, and hypotaurine, respectively. Cis-expression quantitative trait methylation (cis eQTM) analyses suggested the role of metabolite-level-associated CpG sites in regulating the expression of adipose tissue transcripts, including genes in G-protein coupled receptor signaling pathway. Plasma SAH level-associated CpG sites chr19:3403712 and chr19:3403735 were also associated with the expression of G-protein subunit alpha 15 (GNA15) in adipose. The expression of GNA15 was significantly correlated with BMI (β = 1.87, P = 1.9 × 10-16) and SI (β = -1.61, P = 2.49 × 10-5). Our study suggests that a subset of metabolites modulates the methylation levels of CpG sites in specific loci and, in turn, regulates the expression of transcripts involved in obesity and insulin resistance.

Effects of aerobic exercise on the regulation of mitochondrial carrier homolog-2 and its influence on the catabolic and anabolic activity of lipids in the mesenteric adipose tissue of obese mice

The aim was to understand the direct impact of aerobic short-term exercise on lipid metabolism, specifically in regulating the mitochondrial carrier homolog 2 (MTCH2) and how it interferes with lipid metabolism in mesenteric adipose tissue. Swiss mice were divided into three groups: control, sedentary obese, and exercised obese. The obese groups were induced into obesity for fourteen weeks of a high-fat diet, and the trained submitted to seven aerobic exercise sessions. The exercise proved the significant increase of the pPerilipin-1, a hormone-sensitive lipase gene, and modulates lipid metabolism by increasing the expression of Mtch2 and acetyl Co-A carboxylase, perhaps occurring as feedback to regulate lipid metabolism in adipose tissue. In conclusion, we demonstrate, for the first time, how aerobic physical exercise increases Mtch2 transcription in mesenteric adipose tissue. This increase was due to changes in energy demand caused by exercise, confirmed by observing the significant reduction in mesenteric adipose tissue mass in the exercised group. Also, we showed that physical exercise increased the phosphorylative capacity of PLIN1, a protein responsible for the degradation of fatty acids in the lipid droplet, providing acyl and glycerol for cellular metabolism. Although our findings demonstrate evidence of MTCH2 as a protein that regulates lipid homeostasis, scant knowledge exists concerning the signaling of the MTCH2 pathway in regulatingfatty acid metabolism. Therefore, unveiling the means of molecular signaling of MTCH2 demonstrates excellent potential for treating obesity.

SAT649 Org43553, The First Low-molecular-weight Agonist Of The Human Luteinizing Hormone Receptor Induces Leanness And Energy Expenditure In Mice

Abstract Disclosure: D. Lizneva: None. A. Gumerova: None. K. Ievleva: None. O. Barak: None. F. Korkmaz: None. J. Gimenez Roig: None. T. Frolinger: None. G. Pevnev: None. F. Sultana: None. N. Kramskiy: None. S. Wizman: None. M. Orloff: None. A.R. Pallapati: None. S. Rojekar: None. V. Ryu: None. O. Moldavski: None. T. Yuen: None. M. Zaidi: None. We provide compelling evidence that LH is a pro–lean hormone, and that ORG43553, the first low-molecular-weight agonist of the luteinizing hormone receptor (LHCGR) induces leanness and promotes energy expenditure in mice. We detected Lhcgr transcripts in white adipose tissue (WAT) depots in male and female C57BL/6 mice (qPCR, IHC, RNAscope, Sanger sequencing), but not in Lhcgr-/- mice. Intraperitoneal AlexaFluor-488–labeled hCG bound to gonadal and subcutaneous fat pads in wild type mice, but not in Lhcgr-/- mice. Following i.v. 89Zr–LH injection, radioactivity was detected in mesenteric, inguinal and gonadal WAT. LH, hCG and ORG43553 rapidly induced ERK1/2 phosphorylation in differentiated 3T3.L1 cells. Female and male Lhcgr+/- mice on normal chow and high–fat diet, respectively, became obese, importantly, without changes in sex steroids. The gene–dosage effect of Lhcgr depletion suggests a dominant physiologic action of LH on body composition. 14–week–old male C57BL/6 mice were fed on high–fat diet and injected, i.p., with LH, hCG or vehicle, twice–a–week, for 6 weeks. Both LH and hCG markedly reduced body fat accrual (qNMR) but triggered a rise in serum testosterone. The hCG–induced lean phenotype persisted despite androgen receptor blockade by flutamide—confirming that the pro–lean actions of LH and hCG were largely independent of testosterone. Furthermore that LH failed to inhibit fat accrual in Lhcgr-/- mice testified to its action via the LHCGR. Injection of ORG43553 into male C57BL/6 mice for 9 weeks caused a significant reduction in fat mass (qNMR), with reduced WAT weight in fat depots. Remarkably, serum testosterone remained unchanged confirming that the anti–adiposity effect of ORG43553 was independent of testosterone. To study the mechanism of LHCGR activation on body fat, 3T3.L1 adipocytes were treated with hCG or ORG43553 for 12 hours. This resulted in reduced oil droplet accumulation. 3T3-L1–derived organoids treated with LH, hCG or ORG43553 also displayed a substantial reduction in the differentiated layer compared to vehicle–treated organoids. To study whether, in addition to reducing adipocyte differentiation, LHCGR agonism also enhanced thermogenesis, 3T3-L1 adipocytes were pretreated with ORG43553 for 1 hour before measuring oxygen consumption rate (OCR) on a Seahorse Xf96 Analyzer. ORG43553 increased OCR at baseline and upon oligomycin exposure, indicating mitochondria proton leak (thermogenesis). To confirm increased energy expenditure in vivo, mice were injected, s.c., with ORG43553 or vehicle. Oxygen consumption (VO2) and energy expenditure (EE) increased acutely in ORG43553–treated mice, with no change in locomotor activity. The findings suggest that ORG45335, which has been tested in humans for infertility, can potentially become a candidate drug for obesity. Presentation: Saturday, June 17, 2023

Circadian mechanisms in adipose tissue bioenergetics and plasticity.

The circadian clock plays an essential role in coordinating feeding and metabolic rhythms with the light/dark cycle. Disruption of clocks is associated with increased adiposity and metabolic disorders, whereas aligning feeding time with cell-autonomous rhythms in metabolism improves health. Here, we provide a comprehensive overview of recent literature in adipose tissue biology as well as our understanding of molecular mechanisms underlying the circadian regulation of transcription, metabolism, and inflammation in adipose tissue. We highlight recent efforts to uncover the mechanistic links between clocks and adipocyte metabolism, as well as its application to dietary and behavioral interventions to improve health and mitigate obesity.

Circadian signatures of adipose tissue in diet-induced obesity.

High-fat diet (HFD) feeding rewires circadian rhythms of peripheral organs including the liver and adipose tissue. While the liver has been extensively studied, it remains largely unknown whether and how HFD organizes circadian biology in adipose tissue. Here, we took a systems approach to profile the diurnal transcriptome of adipose tissue in diet-induced obese mice either fed a low-fat diet (LFD) that reduces weight or still fed HFD. We detected about 200 and 2,500 diurnal genes in HFD and LFD, respectively. Pathway analysis revealed that rhythmic pathways in HFD are represented by circadian rhythm, ribosome biogenesis, and nucleosome organization, whereas those in LFD are represented by myeloid cell function. Remarkably, the majority of the circadian clock genes, except Clock, exhibited robust diurnal rhythm in the adipose tissue of HFD-fed mice. Analysis of mRNAs and proteins in another cohort of HFD-fed mice confirmed that Clock lost rhythmicity at the transcript, but not protein level. Diet reversal to LFD specifically restored diurnal difference of the Clock transcripts in adipose tissue. We matched transcriptomics data with global profiling of neutral lipids and found that lipid metabolism catalyzed by triglycerol hydrolase Ces1d is a key circadian feature that is activated by diet reversal. Together, our work defines the circadian signatures in the adipose tissue of diet-induced obese mice, and their flexibility upon dietary intervention, thereby shedding light on potential clock-modulated tissue-specific pathways during obesity.

Repeated Oral Administration of Flavan-3-ols Induces Browning in Mice Adipose Tissues through Sympathetic Nerve Activation.

We previously found increases in uncoupling protein (Ucp)-1 transcription in brown adipose tissue (BAT) of mice following a single oral dose of flavan 3-ol (FL)s, a fraction of catechins and procyanidins. It was confirmed that these changes were totally reduced by co-treatment of adrenaline blockers. According to these previous results, FLs possibly activate sympathetic nervous system (SNS). In this study, we confirmed the marked increase in urinary catecholamine (CA) s projecting SNS activity following a single dose of 50 mg/kg FLs. In addition, we examined the impact of the repeated administration of 50 mg/kg FLs for 14 days on adipose tissues in mice. In BAT, FLs tended to increase the level of Ucp-1 along with significant increase of thermogenic transcriptome factors expressions, such as peroxisome proliferator-activated receptor γ coactivator (PGC)-1α and PR domain-containing (PRDM)1. Expression of browning markers, CD137 and transmembrane protein (TMEM) 26, in addition to PGC-1α were increased in epididymal adipose (eWAT) by FLs. A multilocular morphology with cell size reduction was shown in the inguinal adipose (iWAT), together with increasing the level of Ucp-1 by FLs. These results exert that FLs induce browning in adipose, and this change is possibly produced by the activation of the SNS.

DNA methylation and lipid metabolism: an EWAS of 226 metabolic measures

BackgroundThe discovery of robust and trans-ethnically replicated DNA methylation markers of metabolic phenotypes, has hinted at a potential role of epigenetic mechanisms in lipid metabolism. However, DNA methylation and the lipid compositions and lipid concentrations of lipoprotein sizes have been scarcely studied. Here, we present an epigenome-wide association study (EWAS) (N = 5414 total) of mostly lipid-related metabolic measures, including a fine profiling of lipoproteins. As lipoproteins are the main players in the different stages of lipid metabolism, examination of epigenetic markers of detailed lipoprotein features might improve the diagnosis, prognosis, and treatment of metabolic disturbances.ResultsWe conducted an EWAS of leukocyte DNA methylation and 226 metabolic measurements determined by nuclear magnetic resonance spectroscopy in the population-based KORA F4 study (N = 1662) and replicated the results in the LOLIPOP, NFBC1966, and YFS cohorts (N = 3752). Follow-up analyses in the discovery cohort included investigations into gene transcripts, metabolic-measure ratios for pathway analysis, and disease endpoints. We identified 161 associations (p value < 4.7 × 10−10), covering 16 CpG sites at 11 loci and 57 metabolic measures. Identified metabolic measures were primarily medium and small lipoproteins, and fatty acids. For apolipoprotein B-containing lipoproteins, the associations mainly involved triglyceride composition and concentrations of cholesterol esters, triglycerides, free cholesterol, and phospholipids. All associations for HDL lipoproteins involved triglyceride measures only. Associated metabolic measure ratios, proxies of enzymatic activity, highlight amino acid, glucose, and lipid pathways as being potentially epigenetically implicated. Five CpG sites in four genes were associated with differential expression of transcripts in blood or adipose tissue. CpG sites in ABCG1 and PHGDH showed associations with metabolic measures, gene transcription, and metabolic measure ratios and were additionally linked to obesity or previous myocardial infarction, extending previously reported observations.ConclusionOur study provides evidence of a link between DNA methylation and the lipid compositions and lipid concentrations of different lipoprotein size subclasses, thus offering in-depth insights into well-known associations of DNA methylation with total serum lipids. The results support detailed profiling of lipid metabolism to improve the molecular understanding of dyslipidemia and related disease mechanisms.

The treatment with an extract from Calafate (Berberis microphylla) induces transcript and protein expression of molecules involved in thermogenesis and adipocyte browning in adipose tissue from obese mice

BACKGROUND: Polyphenols intake increases the function of brown adipose tissue (BAT), stimulating energy expenditure (EE). Calafate (Berberis microphylla) is a polyphenol-rich Chilean native fruit. OBJECTIVE: To analyse the effect of a treatment with a Calafate extract in the thermogenic activity of mice adipose tissues. METHODS: Forty adult C57BL/6J male mice were subdivided into four groups (n=10 each): control diet, control+Calafate (extract: 50mg total polyphenols/kg weight), high-fat diet (HF) and HF+Calafate. RESULTS: Calafate prevented the increase in body weight and the decrease EE induced by HF. In BAT, Ucp-1 transcript was influenced by the interaction between diet and Calafate (p&lt;0.01), Pparα showed the same expression pattern as Ucp-1 and both, diet (p&lt;0.01) and Calafate (p&lt;0.05), induced significant effects in Sirt1. In inguinal adipose tissue, Pgc1α, Pparα, Prdm16, Sirt1, and Dio2 transcripts presented a decreased expression caused by HF, that was reversed by Calafate. In BAT, an effect of diet (p&lt;0.05) and an interaction between diet and Calafate (p&lt;0.01) was observed in UCP-1 protein levels. CONCLUSIONS: A treatment with Calafate drives less weight gain in mice fed with HF, and reverses the effects generated by it on the expression of thermogenic and browning markers.

Effects of Obesity and Insulin on Tissue-Specific Recycling Between Cortisol and Cortisone in Men.

Context 11β-Hydroxysteroid dehydrogenase 1 (11βHSD1) reduces inert cortisone into active cortisol but also catalyzes reverse dehydrogenase activity. Drivers of cortisol/cortisone equilibrium are unclear. With obesity, 11βHSD1 transcripts are more abundant in adipose, but the consequences for oxidation vs reduction remain unknown.ObjectiveThis work aimed to determine whether 11βHSD1 equilibrium in metabolic tissues is regulated by insulin and obesity.MethodsA 2-phase, randomized, crossover, single-blinded study in a clinical research facility was conducted of 10 lean and obese healthy men. 11β-Reductase and 11β-dehydrogenase activities were measured during infusion of 9,11,12,12-[2H]4-cortisol and 1,2-[2H]2-cortisone, respectively, on 2 occasions: once during saline infusion and once during a hyperinsulinemic-euglycemic clamp. Arterialized and venous samples were obtained across forearm skeletal muscle and abdominal subcutaneous adipose. Steroids were quantified by liquid chromatography–tandem mass spectrometry and adipose tissue transcripts by quantitative polymerase chain reaction.ResultsNeither whole-body nor tissue-specific rates of production of cortisol or cortisone differed between lean and obese men, however insulin attenuated the diurnal decrease. Whole-body 11β-HSD1 reductase activity tended to be higher in obesity (~ 10%) and was further increased by insulin. Across adipose tissue, 11β-reductase activity was detected in obese individuals only and increased in the presence of insulin (18.99 ± 9.62 vs placebo 11.68 ± 3.63 pmol/100 g/minute; P < .05). Across skeletal muscle, 11β-dehydrogenase activity was reduced by insulin in lean men only (2.55 ± 0.90 vs 4.50 ± 1.42 pmol/100 g/minute, P < .05).ConclusionsRegeneration of cortisol is upregulated by insulin in adipose tissue but not skeletal muscle. In obesity, the equilibrium between 11β-reductase and 11β-dehydrogenase activities likely promotes cortisol accumulation in adipose, which may lead to adverse metabolic consequences.

Chronic Exposure to Environmental Level Phenanthrene Induces Non-Obesity-Dependent Insulin Resistance in Male Mice.

Epidemiological evidence shows that the body burden of polycyclic aromatic hydrocarbons (PAHs) is related to the disruption of glucose homeostasis. However, the contribution of PAHs to the development of diabetes remains poorly documented. In the current work, male Kunming mice received phenanthrene (Phe) (5, 50, and 500 ng/kg) by gavage administration once every 2 days for 28 weeks. The significant elevation of homeostasis model assessment-insulin resistance (HOMA-IR) and HOMA-β cell, accompanied by hyperinsulinemia, indicated the occurrence of insulin resistance. The suppression of the insulin receptor signaling pathway in skeletal muscle might be responsible for glucose intolerance. Under the nonobese state, the serum levels of resistin, tumor necrosis factor-α, and interleukin-6 were elevated, whereas the levels of adiponectin were reduced. These changes in adipocytokine levels were consistent with their transcription in white adipose tissue. The promoter methylation levels of Retn (encoding resistin) and Adipoq (encoding adiponectin) were inversely correlated with their mRNA levels, indicating that Phe exposure could cause the disruption of adipocytokine secretion via epigenetic modification. The results would be helpful for understanding the pathogenesis in the development of T2DM caused by nonobesogenic pollutants.

Maternal exposure to phenanthrene during gestation disturbs glucose homeostasis in adult mouse offspring

Epidemiological studies have indicated that polycyclic aromatic hydrocarbons were related to diabetes and insulin resistance. However, studies in mammals on the development of diabetes caused by polycyclic aromatic hydrocarbons are lacking. Pregnant mice were orally exposed to phenanthrene (0, 60 and 600 μg kg−1 body weight) once every 3 days during gestation. In adult mouse offspring, in-utero phenanthrene exposure caused glucose intolerance and decreased insulin levels in females, while caused elevated fasting blood glucose and insulin levels in males. Serum resistin and interleukin-6 levels were elevated in offspring of both sexes. Serum adiponectin levels were decreased in females but increased in males. The insulin receptor signals were upregulated in the liver and downregulated in the skeletal muscle of F1 females, while they were inhibited in both tissues of F1 males. The visceral fat weight and body weight of the treated mice were not increased, suggesting that phenanthrene is not an obesogen, which is supported by the nonsignificant alteration in pparγ transcription in visceral adipose tissue. The transcription of retn in visceral adipose tissue was upregulated in both sexes, and that of adipoq was downregulated in females but upregulated in males, which were matched with the promoter methylation levels of these genes. The results indicated that phenanthrene exposure during gestation could disturb adipocytokine levels via epigenetic modification in adult offspring, and further influence glucose metabolism. These results might be helpful for understanding nonobesogenic pollutant-induced insulin resistance and preventing against diabetes without obesity.

Role of Adipose Tissue-Derived Autotaxin, Lysophosphatidate Signaling, and Inflammation in the Progression and Treatment of Breast Cancer.

Autotaxin (ATX) is a secreted enzyme that produces lysophosphatidate (LPA), which signals through six G-protein coupled receptors, promoting tumor growth, metastasis, and survival from chemotherapy and radiotherapy. Many cancer cells produce ATX, but breast cancer cells express little ATX. In breast tumors, ATX is produced by tumor-associated stroma. Breast tumors are also surrounded by adipose tissue, which is a major bodily source of ATX. In mice, a high-fat diet increases adipocyte ATX production. ATX production in obesity is also increased because of low-level inflammation in the expanded adipose tissue. This increased ATX secretion and consequent LPA signaling is associated with decreased adiponectin production, which results in adverse metabolic profiles and glucose homeostasis. Increased ATX production by inflamed adipose tissue may explain the obesity-breast cancer association. Breast tumors produce inflammatory mediators that stimulate ATX transcription in tumor-adjacent adipose tissue. This drives a feedforward inflammatory cycle since increased LPA signaling increases production of more inflammatory mediators and cyclooxygenase-2. Inhibiting ATX activity, which has implications in breast cancer adjuvant treatments, attenuates this cycle. Targeting ATX activity and LPA signaling may potentially increase chemotherapy and radiotherapy efficacy, and decrease radiation-induced fibrosis morbidity independently of breast cancer type because most ATX is not derived from breast cancer cells.

Osteoporosis- and obesity-risk interrelationships: an epigenetic analysis of GWAS-derived SNPs at the developmental gene TBX15

ABSTRACT A major challenge in translating findings from genome-wide association studies (GWAS) to biological mechanisms is pinpointing functional variants because only a very small percentage of variants associated with a given trait actually impact the trait. We used an extensive epigenetics, transcriptomics, and genetics analysis of the TBX15/WARS2 neighbourhood to prioritize this region’s best-candidate causal variants for the genetic risk of osteoporosis (estimated bone density, eBMD) and obesity (waist-hip ratio or waist circumference adjusted for body mass index). TBX15 encodes a transcription factor that is important in bone development and adipose biology. Manual curation of 692 GWAS-derived variants gave eight strong candidates for causal SNPs that modulate TBX15 transcription in subcutaneous adipose tissue (SAT) or osteoblasts, which highly and specifically express this gene. None of these SNPs were prioritized by Bayesian fine-mapping. The eight regulatory causal SNPs were in enhancer or promoter chromatin seen preferentially in SAT or osteoblasts at TBX15 intron-1 or upstream. They overlap strongly predicted, allele-specific transcription factor binding sites. Our analysis suggests that these SNPs act independently of two missense SNPs in TBX15. Remarkably, five of the regulatory SNPs were associated with eBMD and obesity and had the same trait-increasing allele for both. We found that WARS2 obesity-related SNPs can be ascribed to high linkage disequilibrium with TBX15 intron-1 SNPs. Our findings from GWAS index, proxy, and imputed SNPs suggest that a few SNPs, including three in a 0.7-kb cluster, act as causal regulatory variants to fine-tune TBX15 expression and, thereby, affect both obesity and osteoporosis risk.

Effect of Soybean Oil and Fish Oil on Lipid-Related Transcripts in Subcutaneous Adipose Tissue of Dairy Cows.

Simple SummaryThe objective of this study was to determine the effects of degree of unsaturation of dietary lipids on lipid-related metabolites and transcription of genes involved in lipid metabolism in subcutaneous adipose tissue (SAT) of mid-lactating dairy cows. The objective was achieved by supplementing dairy cows with soybean oil (high in linoleic acid) or fish oil (high in polyunsaturated fatty acids) for 63 days (nine weeks). Results revealed effects of oil supplement on lipid metabolism but a mild effect on the transcriptome of the adipose tissue. Compared to soybean oil, fish oil had a higher lipogenic effect in SAT.The objective of this study was to determine the effect of long-term supplementation of unsaturated oil on lipid metabolism and transcription of genes involved in lipid metabolism in subcutaneous adipose tissue (SAT) of mid-lactating dairy cows. The objective was achieved by supplementing dairy cows with soybean oil (SO; high in linoleic acid) or fish oil (FO; high in EPA and DHA) for 63 days (nine weeks). Cows were fed a control diet with no added lipid, or diets containing SO or FO (n = 5 cows/group). At the onset of the experiment (day 0) and on days 21, 42, and 63 of supplementation, blood and SAT samples were collected from each animal. Oil supplementation increased cholesterol and NEFA in plasma, with a greater effect of SO compared to FO. Concentration of BUN was lower in SO compared to control and FO at the end of the trial. Transcription of few genes was affected by dietary lipids: FABP4 had lowest expression in FO followed by SO and control. ACACA and FASN had higher expression in FO. Transcription of SCAP was higher but expression of INSIG1 was lower in SO. Overall, results revealed that compared to control, SO and FO had lipogenic effect in SAT.

Synergistic Effects of Hyperandrogenemia and Obesogenic Western-style Diet on Transcription and DNA Methylation in Visceral Adipose Tissue of Nonhuman Primates

Polycystic ovary syndrome (PCOS) is a major reproductive disorder that is responsible for 80% of anovulatory infertility and that is associated with hyperandrogenemia, increased risk of obesity, and white adipose tissue (WAT) dysfunction. We have previously demonstrated that the combination of chronic testosterone (T) treatment and an obesogenic Western-style diet (WSD) exerts synergistic functional effects on WAT, leading to increased lipid accumulation in visceral adipocytes by an unknown mechanism. In this study, we examined the whole-genome transcriptional response in visceral WAT to T and WSD, alone and in combination. We observed a synergistic effect of T and WSD on gene expression, resulting in upregulation of lipid storage genes concomitant with adipocyte hypertrophy. Because DNA methylation is known to be associated with body fat distribution and the etiology of PCOS, we conducted whole-genome DNA methylation analysis of visceral WAT. While only a fraction of differentially expressed genes also exhibited differential DNA methylation, in silico analysis showed that differentially methylated regions were enriched in transcription factor binding motifs, suggesting a potential gene regulatory role for these regions. In summary, this study demonstrates that hyperandrogenemia alone does not induce global transcriptional and epigenetic response in young female macaques unless combined with an obesogenic diet.

8-OxoG in GC-rich Sp1 binding sites enhances gene transcription in adipose tissue of juvenile mice

The oxidation of guanine to 8-oxoguanine (8-oxoG) is the most common type of oxidative DNA lesion. There is a growing body of evidence indicating that 8-oxoG is not only pre-mutagenic, but also plays an essential role in modulating gene expression along with its cognate repair proteins. In this study, we investigated the relationship between 8-oxoG formed under intrinsic oxidative stress conditions and gene expression in adipose and lung tissues of juvenile mice. We observed that transcriptional activity and the number of active genes were significantly correlated with the distribution of 8-oxoG in gene promoter regions, as determined by reverse-phase liquid chromatography/mass spectrometry (RP-LC/MS), and 8-oxoG and RNA sequencing. Gene regulation by 8-oxoG was not associated with the degree of 8-oxoG formation. Instead, genes with GC-rich transcription factor binding sites in their promoters became more active with increasing 8-oxoG abundance as also demonstrated by specificity protein 1 (Sp1)- and estrogen response element (ERE)-luciferase assays in human embryonic kidney (HEK293T) cells. These results indicate that the occurrence of 8-oxoG in GC-rich Sp1 binding sites is important for gene regulation during adipose tissue development.

Genetic Regulation of Enoyl-CoA Hydratase Domain-Containing 3 in Adipose Tissue Determines Insulin Sensitivity in African Americans and Europeans.

Insulin resistance (IR) is a harbinger of type 2 diabetes (T2D) and partly determined by genetic factors. However, genetically regulated mechanisms of IR remain poorly understood. Using gene expression, genotype, and insulin sensitivity data from the African American Genetics of Metabolism and Expression (AAGMEx) cohort, we performed transcript-wide correlation and expression quantitative trait loci (eQTL) analyses to identify IR-correlated cis-regulated transcripts (cis-eGenes) in adipose tissue. These IR-correlated cis-eGenes were tested in the European ancestry individuals in the Metabolic Syndrome in Men (METSIM) cohort for trans-ethnic replication. Comparison of Matsuda index–correlated transcripts in AAGMEx with the METSIM study identified significant correlation of 3,849 transcripts, with concordant direction of effect for 97.5% of the transcripts. cis-eQTL for 587 Matsuda index–correlated genes were identified in both cohorts. Enoyl-CoA hydratase domain-containing 3 (ECHDC3) was the top-ranked Matsuda index–correlated cis-eGene. Expression levels of ECHDC3 were positively correlated with Matsuda index, and regulated by cis-eQTL, rs34844369 being the top cis-eSNP in AAGMEx. Silencing of ECHDC3 in adipocytes significantly reduced insulin-stimulated glucose uptake and Akt Ser473 phosphorylation. RNA sequencing analysis identified 691 differentially expressed genes in ECHDC3-knockdown adipocytes, which were enriched in γ-linolenate biosynthesis, and known IR genes. Thus, our studies elucidated genetic regulatory mechanisms of IR and identified genes and pathways in adipose tissue that are mechanistically involved in IR.

MON-118 Biochemical and Clinical Correlates of Subcutaneous Adipose mRNA Transcript Levels in Men with T2DM

Background: Altered profiles of subcutaneous adipose tissue gene expression have been independently associated with insulin sensitivity. T2DM has been associated with higher levels of adipokines, inflammatory cytokines and lower plasma sex steroid concentrations. We sought to examine the interplay between these factors, specifically with respect to their associations with mRNA transcript levels in subcutaneous adipose tissue. Methods: Cross-sectional assessment of 162 men with T2DM not treated with insulin (Median age 57 [51 - 61]). Basic anthropometric parameters (including body fat by bioimpedance) were measured. Testosterone, DHT, A4, 17-OHP, E2 and E1 measured by LCMS; TNFα, IL-6, IL-8, IL-1ß, MCP-1, leptin, FSH, LH, SHBG and insulin by ELISA (all fasting) and RT-PCR assessed a panel of 23 gene transcripts in adipose tissue (n = 115). Results: Testosterone (R -.273) & DHT (R -.352) were associated with HOMA-IR independent of BMI but not after adjustment for SHBG. No other biochemical parameters were independently associated with HOMA-IR. Waist circumference (R .351) and HbA1c (R .284) but not IL-6 (R .315) were independently associated with CYP19 expression. HbA1c (R -.222) and A4 (R .207) were independently associated with estrogen receptor α expression. FSH (R -.229) was independently associated with androgen receptor expression. Insulin (R .274) and IL-6 (R .245) were independently associated with adipose leptin expression. Associations with BMI (R .275), DHT (R -.208) and FSH (R -.211) were not significant after adjustment for confounders. Insulin receptor expression was only independently associated with fat mass (R -.378). PPARγ expression was only significantly correlated with HbA1c (R -.204) whilst, after adjustment, MCP-1 expression was only independently associated with percentage fat (R .332). Retinol binding protein 4 expression was independently associated with HbA1c (-.323), MCP-1 (R .297) and FSH (-.254). Conclusion: Circulating sex steroids were not associated with insulin resistance or differences across a wide range of adipose mRNA transcript levels in men with T2DM. Insulin or HbA1c appeared to be a stronger correlate for adipose transcript profiles than circulating adipokines or cytokines. Recent evidence suggests FSH may exert direct effects upon adipose tissue and these findings potentially support this hypothesis.

Promoter Methylation Regulates ApoA-I Gene Transcription in Chicken Abdominal Adipose Tissue.

As a central constituent of HDL (high-density lipoprotein), apolipoprotein A-I (ApoA-I) has a vital function in lipid metabolism. Our previous studies confirmed that ApoA-I was differentially expressed in the adipose tissue of the abdomen of lean and fat broilers. The aim of the current work was to evaluate whether the transcription of ApoA-I in chicken abdominal adipose tissue was regulated by DNA methylation. The methylation status of ApoA-I promoter CpG island (PCGI) and promoter non-CpG island (PNCGI) as well as the ApoA-I expression level in adipose tissue of lean and fat broilers were determined using Sequenom MassARRAY and real-time PCR. The correlation analysis results showed that the methylation level of PCGI and the ApoA-I mRNA expression level were negatively correlated. Bisulfite sequencing PCR was used to assess the methylation level of ApoA-I promoter in the ICP1 cells treated with 5-aza-2'-deoxycytidine (5-Aza-CdR: an inhibitor of DNA methyltransferase). The result showed that 5-Aza-CdR caused a reduction in the methylation level of the ApoA-I promoter, thereby causing an increase in expression of the ApoA-I mRNA. Meanwhile, luciferase reporter assays indicated that in vitro methylation of the ApoA-I promoter containing CpG island with CpG methyltransferase led to transcriptional repression. Furthermore, the noticeableactivation of NRF1 on ApoA-I transcription waslargely enhanced by the demethylation of the ApoA-I PCGI region. These observations indicated that the differential expression of ApoA-I gene in the adipose tissue of broilers could be mediated by transcription regulation, at least in part by DNA methylation in its PCGI region.

Comparing pig breeds with genetically low and high backfat thickness: differences in expression of adiponectin, its receptor, and blood metabolites

Here we characterized gene expressions in subcutaneous adipose tissue and blood metabolites of pigs with genetically low backfat (Landrace) and high backfat (Meishan). As pigs aged from 1 wk-to 3-mo old, mRNA levels of adipose-specific genes increased, although their gene expressions coding for major enzymes involved in lipid metabolism (lipoprotein lipase, fatty acid synthase, and hormone-sensitive lipase) did not differ between lean and fat pigs. Instead, there were significant effects for adiponectin and its receptor AdipoR1 mRNA levels between the two breeds of which respective expressions were lower and higher in Meishan by 3 mo of age. Contrary to changes in gene expressions, the concentrations of blood glucose, triglyceride (TG), and NEFA in both breeds decreased during growth, and 3-mo-old Meishan evidenced lower glucose with higher TG than the Landrace. The homeostasis model assessment insulin resistance (HOMA-IR) index was also calculated from the measurements of fasting glucose and insulin concentration, and Meishan showed a higher value than the Landrace. We next examined these differences in Landrace and Meishan crossbreds, which were phenotypically distinguishable by the backfat thickness as the former lean type and the latter fat type. As with the purebreds, high backfat Meishan crosses showed the characteristics of lower glucose and higher TG in circulating levels and also lower adiponectin transcripts in subcutaneous adipose tissue. Collectively, our results demonstrate that levels of adiponectin and its receptor gene expressions, blood glucose, blood lipids, and HOMA-IR in pigs vary between lean and fat. These observations strongly suggest the possibility that overall metabolic differences rather than adipocyte ability itself contribute to the fatness of genetically high backfat pigs.