Search

Glucocorticoids promote fat accumulation in visceral compared to subcutaneous depots, but the molecular mechanisms involved remain poorly understood. To identify long-term changes in gene expression that are differentially sensitive or responsive to glucocorticoids in these depots, paired samples of human omental (Om) and abdominal subcutaneous (Abdsc) adipose tissues obtained from obese women during elective surgery were cultured with the glucocorticoid receptor agonist dexamethasone (Dex, 0, 1, 10, 25 and 1000 nM) for 7 days. Dex regulated 32% of the 19,741 genes on the array, while 53% differed by Depot and 2.5% exhibited a Depot*Dex concentration interaction. Gene set enrichment analysis showed Dex regulation of the expected metabolic and inflammatory pathways in both depots. Cluster analysis of the 460 transcripts that exhibited an interaction of Depot and Dex concentration revealed sets of mRNAs for which the responses to Dex differed in magnitude, sensitivity or direction between the two depots as well as mRNAs that responded to Dex only in one depot. These transcripts were also clearly depot different in fresh adipose tissue and are implicated in processes that could affect adipose tissue distribution or functions (e.g. adipogenesis, triacylglycerol synthesis and storage, insulin action). Elucidation of the mechanisms underlying the depot differences in the effect of Dex on the expression of specific genes and pathways that regulate adipose function may offer novel insights into understanding the biology of visceral adipose tissues and their links to metabolic health., Competing Interests: The authors have declared that no competing interests exist.

Objective: Growth hormone (GH) administration reduces abdominal, but not lower body, fat mass. To gain insight into the underlying mechanisms, this study examined the expression of the GH receptor (GHR) and some of its targets in abdominal and gluteal adipose tissue., Methods: GHR and GH targets in the lipolytic pathway were assessed (quantitative PCR/Western blotting) in adipose aspirates from premenopausal women [n = 15, age 26.9 ± 6.1 years, body mass index (BMI) 28.0 ± 6.8 kg/m(2) ] and men (n = 28, age 29.2 ± 7.0 years, BMI 26.9 ± 3.7 kg/m(2) )., Results: GHR mRNA expression was lower in the gluteal depot when compared with the abdominal depot (P = 0.01). Abdominal GHR correlated negatively with age and BMI, whereas gluteal GHR was associated with lower waist-to-hip ratio (WHR), that is, pear shape. In both sites, GHR mRNA correlated strongly with genes important for the regulation of lipolysis: adipose tissue triglyceride lipase (ATGL), hormone-sensitive lipase, perilipin, and CIDEA (all P < 0.001), independently of BMI, WHR, age, and sex. GHR protein was lower in the gluteal fat when compared with the abdominal fat (P = 0.03) and correlated with ATGL protein in the gluteal depot (P < 0.001)., Conclusions: GHR levels correlate with levels of lipases and lipid droplet-associated proteins crucial for lipolysis. Thus, higher GHR expression in the abdominal depot when compared with the gluteal depot may underlie the in vivo effect of GH to specifically reduce abdominal adipose tissue mass., (© 2016 The Obesity Society.)

Objective: Lower body fat is associated with diminishing cardiometabolic risk. Physiological differences between gluteofemoral and abdominal subcutaneous adipocyte functions are known, but the molecular basis for depot differences in adipocyte function is poorly understood. The objective of this study was to identify depot differences in microRNA (miRNA) expression in human abdominal and gluteofemoral subcutaneous adipose tissues and their implication in gene regulation.Methods: Abdominal and gluteofemoral adipose tissue aspirates obtained from 18 participants (9 male and 9 female, age 30 ± 1.5 y, BMI 27.3 ± 1.23 kg/m2 ) were analyzed for miRNA expression profiles by next-generation DNA sequencing. The raw reads were mapped to miRBase 17, and differentially expressed miRNAs were confirmed by qRT-PCR. The hsa-mimic-miR196a was transfected into cultured abdominal preadipocytes isolated from five women with obesity. Target gene expression was evaluated by RT-qPCR.Results: Among the 640 miRNAs detected in adipose tissue, miR196a2, miR196a1, miR196b, and miR204 showed a higher expression in the gluteofemoral depot (fold change = 2.7, 2.3, 1.7, and 2.3, respectively) independent of sex. Bioinformatic analyses and human primary preadipocyte transfection with miR196 suggested that the differentially expressed miRNAs could directly or indirectly modulate homeobox (HOX) gene expression.Conclusions: The miR196 gene family could play an important role in the regulation of HOX gene expression in subcutaneous adipose tissue and in fat distribution variation. [ABSTRACT FROM AUTHOR]

Glucocorticoids (GC) are powerful regulators of adipocyte differentiation, metabolism, and endocrine function and promote the development of upper body obesity, especially visceral fat stores. To provide a comprehensive understanding of how GC affect adipose tissue and adipocyte function, we analyzed patterns of gene expression (HG U95 Affymetrix arrays) after culture of abdominal subcutaneous (Abd sc) and omental (Om) adipose tissues from severely obese subjects (3 F, 1 M) in the presence of insulin or insulin (7 nM) plus dexamethasone (Dex, 25 nM) for 7 days. About 20% (561 genes in Om and 569 genes in sc) of 2,803 adipose expressed genes were affected by long-term GC. While most of the genes (90%) were commonly regulated by Dex in both depots, 26 in Om and 34 in Abd sc were affected by Dex in only one depot. 60% of the commonly upregulated genes were involved in metabolic pathways and were expressed mainly in adipocytes. Dex suppressed genes in immune/inflammatory (IL-6, IL-8, and MCP-1, expressed in nonadipocytes) and proapoptotic pathways, yet induced genes related to the acute-phase response (SAA, factor D, haptoglobin, and RBP4, expressed in adipocytes) and stress/defense response. Functional classification analysis showed that Dex also induced expression levels of 22 transcription factors related to insulin action and lipogenesis (LXRα, STAT5α, SREBP1, and FoxO1) and immunity/adipogenesis (TSC22D3) while suppressing 17 transcription factors in both depots. Overall, these studies reveal the powerful effects of GC on gene networks that regulate many key functions in human adipose tissue. [ABSTRACT FROM AUTHOR]

Central obesity and the accumulation of visceral fat are risk factors for the development of type 2 diabetes and cardiovascular disease. Omentin is a protein expressed and secreted from visceral but not subcutaneous adipose tissue that increases insulin sensitivity in human adipocytes. To determine the impact of obesity-dependent insulin resistance on the regulation of two omentin isoforms, gene expression and plasma levels were measured in lean, overweight, and obese subjects. Omentin 1 was shown to be the major circulating isoform in human plasma. Lean subjects had significantly higher plasma omentin 1 levels than obese and overweight subjects. In addition, higher plasma omentin 1 levels were detected in women compared with men. Plasma omentin 1 levels were inversely correlated with BMI, waist circumference, leptin levels, and insulin resistance as measured by homeostasis model assessment and positively correlated with adiponectin and HDL levels. Both omentin 1 and omentin 2 gene expression were decreased with obesity and were highly correlated with each other in visceral adipose tissue. In summary, decreased omentin levels are associated with increasing obesity and insulin resistance. Therefore, omentin levels may be predictive of the metabolic consequences or co-morbidities associated with obesity. Diabetes 56:1655-1661, 2007 [ABSTRACT FROM AUTHOR]

Glucocorticoids (GC) are powerful modulators of adipose tissue function, and GC action varies in human visceral and sc adipose tissues. To establish if alterations in GC action are secondary to alterations in its receptor, and post-receptor events, we assessed the tissue-specific expression of glucocorticoid receptor (GR) translational isoforms (A-D). Direct GR isoforms exert diverse and partially non-overlapping effects of GC on gene expression. GRA/B (94-91kDa) and GR D (54 kDa) were major translational isoforms expressed in human adipose tissue. The expression of the more transcriptionally active A/B form was higher in subcutaneous than omentum, while D form was similar (n=5). Because GC action is regulated by inflammatory cytokines in other cell types and tumor necrosis factor alpha (TNF) expression in adipose tissue is increased in human obesity, we examined whether TNF modulates glucocorticoid receptor expression and activity in human adipose tissue. TNF treatment (3 ng/ml, 2d) of subcutaneous adipose tissue fragments in organ culture increased GRα expression levels but simultaneously increased GRα phosphorylational at serine 226 (+82% in ratio to total GR p<0.05, n=4), a post-translational modification known to decrease GR activity. In addition, TNF decreased GR serine 211 phosphorylation (ligand dependent) (ratio to total, +8.9 fold without TNF vs. +4.5 fold with TNF, n=3) and attenuated the magnitude of GC effects on key target genes (glucocortieoid induced leucine zipper (GILZ) and PEPCK). TNF also decreased sensitivity and responsiveness to stimulatory effects of GC on lipoprotein lipase (LPL) activity. These effects on LPL were partially blocked by a JNK inhibitor (SP600125, 25 µM) while p38 or ERK1/2 inhibitors were ineffective. Collectively, these data indicate TNF regulates the expression and activity of the GR in human adipose tissue at translational and post-translational levels. Further, depot- and/or obesity-related differences in TNF in obesity may regulate GR activity. [ABSTRACT FROM AUTHOR]

Adipose tissue development is tightly regulated by altering gene expression. MicroRNAs are strong posttranscriptional regulators of mammalian differentiation. We hypothesized that microRNAs might influence human adipogenesis by targeting specific adipogenic factors. We identified microRNAs that showed varying abundance during the differentiation of human preadipocytes into adipocytes. Among them, miR-130 strongly affected adipocyte differentiation, as overexpressing miR-130 impaired adipogenesis and reducing miR-130 enhanced adipogenesis. A key effector of miR-130 actions was the protein peroxisome proliferator-activated receptor γ (PPARγ), a major regulator of adipogenesis. Interestingly, miR-130 potently repressed PPARγ expression by targeting both the PPARγ mRNA coding and 3' untranslated regions. Adipose tissue from obese women contained significantly lower miR-130 and higher PPARγ mRNA levels than that from nonobese women. Our findings reveal that miR-130 reduces adipogenesis by repressing PPARγ biosynthesis and suggest that perturbations in this regulation is linked to human obesity. [ABSTRACT FROM AUTHOR]

Retinol binding protein 4 (RBP4) was overexpressed in adipose tissue of Glut4 KO mice, and elevated RBP4 has been associated with insulin resistance in mouse and human studies. To determine the relationship between RBP4 and obesity, insulin resistance, and other markers of insulin resistance in humans, RBP4 gene expression measured by real-time RT-PCR and blood levels measured by ELISA and Western blotting were studied in adipose tissue and muscle of 85 non-diabetic humans over a wide range of BMI (19-55 Kg/m²) and S[sub I] (1.02-26.77 x 10[sup -5] x min[sup -1]/pM), and RBP4 expression was also measured from visceral (VAT) and subcutaneous adipose tissue (SAT) from 16 surgical patients. RBP4 expression was 3-fold higher in SAT vs VAT (p<0.005), and RBP4 was 7-fold higher in the adipocyte (vs stromal) fraction, and undetectable in preadipocytes. Neither SAT RBP4 expression nor blood RBP4 level showed a significant relationship with BMI or S[sub I]. However, there was a strong positive correlation between RBP4 mRNA and the inflammation markers MCP1 (r=0.42, p<0.0001) and CD68 (r=0.46, p<0.0001)). Adipose GLUT4 mRNA was also highly associated with RBP4 (r=0.53, p<0.0001). These relationships remained significant after adjustment for BMI and St. Impaired glucose tolerant subjects were treated with pioglitazone, resulting in an increase in S[sub 1] along with a 60% increase in RBP4 expression, but no change in plasma RBP4. The in vitro treatment of cultured adipocytes with pioglitazone yielded a similar increase in RBP4 mRNA. Hence, RBP4 expression in humans was not significantly associated with obesity or insulin resistance, and actually increased with TZD treatment. However, RBP4 was associated with inflammatory markers and GLUT 4 expression, suggesting a complex role in metabolic syndrome. [ABSTRACT FROM AUTHOR]