Obese Subcutaneous Adipose Tissue Research Articles

CABLES1 expression is reduced in human subcutaneous adipose tissue in obesity and type 2 diabetes but may not directly impact adipocyte glucose and lipid metabolism

ABSTRACT Cdk5 and Abl enzyme substrate 1 (CABLES1) is a cell cycle regulator that has previously been identified as a candidate gene for obesity-related phenotypes, but little is known about its role in adipose tissue metabolism. In this study, we explore the role of CABLES1 in obesity and type 2 diabetes (T2D) in human subcutaneous adipose tissue (SAT). We performed gene expression analysis of SAT obtained from subjects with and without T2D, and from a second validation cohort consisting of subjects without T2D. We used CRISPR/Cas9 genome editing to perform CABLES1 loss-of-function studies in human primary preadipocytes and assessed them functionally after differentiation. CABLES1 gene expression in SAT was decreased in T2D by almost 25%, and inversely associated with insulin resistance markers and hyperglycaemia. mRNA levels were reduced with increasing BMI and negatively correlated with obesity markers. We found that adipocytes are likely the main CABLES1-expressing cell type in SAT, but CABLES1 depletion in adipocytes caused no phenotypical changes in regards to differentiation, glucose uptake, or expression of key genes of adipocyte function. These findings suggest that CABLES1 gene expression in SAT might be altered in obesity and T2D as a consequence of metabolic dysregulation rather than being a causal factor.

Transcriptional characterization of subcutaneous adipose tissue in obesity affected women highlights metabolic dysfunction and implications for lncRNAs

Obesity is a complex disease with multifactorial causes, and its prevalence is becoming a serious health crisis. For this reason, there is a crucial need to identify novel targets and players. With this aim in mind, we analyzed via RNA-sequencing the subcutaneous adipose tissue of normal weight and obesity-affected women, highlighting the differential expression in the two tissues. We specifically focused on long non-coding RNAs, as 6 of these emerged as dysregulated in the diseased-tissue (COL4A2-AS2, RPS21-AS, PELATON, ITGB2-AS1, ACER2-AS and CTEPHA1). For each of them, we performed both a thorough in silico dissection and in vitro validation, to predict their function during adipogenesis. We report the lncRNAs expression during adipose derived stem cells differentiation to adipocytes as model of adipogenesis and their potential modulation by adipogenesis-related transcription factors (C/EBPs and PPARγ). Moreover, inhibiting CTEPHA1 expression we investigated its impact on adipogenesis-related transcription factors, showing its significative dysregulation of C/EBPα expression. Lastly, we dissected the subcellular localization, pathway involvement and disease-correlation for coding differentially expressed genes. Together, these findings highlight a transcriptional deregulation at the basis of obesity, impacted by both coding and long non-coding RNAs.

Dysregulation of endocannabinoid concentrations in human subcutaneous adipose tissue in obesity and modulation by omega-3 polyunsaturated fatty acids.

Obesity is believed to be associated with a dysregulated endocannabinoid system which may reflect enhanced inflammation. However, reports of this in human white adipose tissue (WAT) are limited and inconclusive. Marine long-chain omega-3 polyunsaturated fatty acids (LC n-3 PUFAs) have anti-inflammatory actions and therefore may improve obesity-associated adipose tissue inflammation. Therefore, fatty acid (FA) concentrations, endocannabinoid concentrations, and gene expression were assessed in subcutaneous WAT (scWAT) biopsies from healthy normal weight individuals (BMI 18.5-25 kg/m2) and individuals living with metabolically healthy obesity (BMI 30-40 kg/m2) prior to and following a 12-week intervention with 3 g fish oil/day (1.1 g eicosapentaenoic acid (EPA) + 0.8 g DHA) or 3 g corn oil/day (placebo). WAT from individuals living with metabolically healthy obesity had higher n-6 PUFAs and EPA, higher concentrations of two endocannabinoids (anandamide (AEA) and eicosapentaenoyl ethanolamide (EPEA)), higher expression of phospholipase A2 Group IID (PLA2G2D) and phospholipase A2 Group IVA (PLA2G4A), and lower expression of CNR1. In response to fish oil intervention, WAT EPA increased to a similar extent in both BMI groups, and WAT DHA increased by a greater extent in normal weight individuals. WAT EPEA and docosahexaenoyl ethanolamide (DHEA) increased in normal weight individuals only and WAT 2-arachidonyl glycerol (2-AG) decreased in individuals living with metabolically healthy obesity only. Altered WAT fatty acid, endocannabinoid, and gene expression profiles in metabolically healthy obesity at baseline may be linked. WAT incorporates n-3 PUFAs when their intake is increased which affects the endocannabinoid system; however, effects appear greater in normal weight individuals than in those living with metabolically healthy obesity.

Testosterone is sequestered in dysfunctional adipose tissue, modifying androgen-responsive genes.

The recognized association between male hypogonadism and obesity has multifactorial implications on adipose tissue (AT) physiology. The fat solubility of testosterone (T) suggests a sequestration process in fat depots, leading to reduced circulating levels of T in obesity. Several evidence suggest that steroids play a two-sided inhibitory role on adipogenesis by locally decreasing lipid accumulation and by stimulating lipolysis. The current study investigates T trafficking and activity in dysfunctional AT. Samples of subcutaneous AT (SAT) were obtained from explants from lipoaspirate plastic surgery in six obese and six normal weight male patients. Experimental procedures on both SAT explants and insulin-resistant (IR) 3T3-L1 adipocytes were performed, including real-time PCR and mass-spectrometry quantification. A significant deregulation of gene responsiveness to androgens in IR cells and obese SAT was observed (all p < 0.05), together with reduced T release after adrenergic stimulation (-10% compared with -55% in lean SAT, p = 0.021). Higher concentrations of intracellular T and estradiol in obese SAT were also observed (2.4 vs. 1.3 ng/g, p = 0.013 and 0.075 vs. 0.22 ng/g, p = 0.004, respectively). Testosterone accumulation resulted in even lower expression in androgen-responsive genes involved in lipolytic and anti-adipogenic pathways from both in vitro and ex vivo experiments. These results suggest an altered response of dysfunctional fat cells to testosterone stimulation, which normally favors lipolysis and induces an anti-adipogenic effect. The considerable reduction of lipolytic T release after adrenergic stimulation in obese SAT contributes to AT dysfunction, in a feedforward loop further reducing T levels in obese hypogonadal males.

Vitamin D release across abdominal adipose tissue in lean and obese men: The effect of ß-adrenergic stimulation.

Obesity is characterized by a blunted lipolytic response in abdominal subcutaneous adipose tissue (SAT) and low circulating vitamin D levels. Here we investigated whether an impaired SAT lipolytic response coincides with an impaired SAT vitamin D release in eight lean and six obese men. 25‐hydroxyvitamin D3 [25(OH)D3] and 1,25‐dihydroxyvitamin D3 [1,25(OH)2D3] fluxes across SAT were measured using arterio‐venous blood sampling in combination with AT blood flow measurements after an overnight fast and during 1‐hr intravenous infusion of the non‐selective ß‐adrenergic agonist isoprenaline (20 ng·kg FFM−1·min−1). 1,25(OH)2D3 was released across abdominal SAT during isoprenaline infusion in lean [−0.01 (−0.04 to 0.00) pmol*100 g tissue−1*min−1, p = .017 vs. zero flux], but not in obese men [0.01 (0.00 to 0.02) pmol*100 g tissue−1*min−1, p = .116 vs. zero flux], and accompanied by an impaired isoprenaline‐induced lipolytic response in abdominal SAT of obese versus lean men. Isoprenaline had no significant effects on net 25(OH)D3 release across abdominal SAT and plasma vitamin D metabolites in lean and obese men. To conclude, a blunted isoprenaline‐mediated lipolysis is accompanied by reduced release of 1,25(OH)2D3 vitamin D across abdominal SAT in obesity.

Mechanisms for secretion of antibodies with “anti-self” reactivity by the human obese adipose tissue

Abstract We have shown that the human obese subcutaneous adipose tissue(SAT)contributes to systemic and B cell intrinsic inflammation and increased secretion of autoimmune antibodies. Immune cells are recruited to the SAT by chemokines released by both adipocytes and infiltrating immune cells. We have identified several mechanisms responsible for the release of “self” antigens in the human obese SAT, induction of class switch and production of autoimmune antibodies, such as hypoxia, NK cell cytotoxicity and DNA damage, which induce cell death and further release of pro-inflammatory cytokines. All these processes, in the context of an inflammatory environment like the obese SAT, stimulate the production of autoimmune IgG antibodies which have been described to be pathogenic. We have identified “self” antigens that stimulate the secretion of autoimmune antibodies in cultures of SAT-derived immune cells, using a Protein G immunoprecipitation protocol to purify the autoantibodies, combined with mass spectrometry. Results show that around 25% of these “self” antigens are found at high frequency in all the individuals evaluated so far in independent experiments. Moreover, &amp;gt;90% of these “self” antigens (lipid and protein antigens, DNA, RNA) are cytoplasmic, nuclear or membrane-associated. These results allow the identification of novel pathways to manipulate in order to decrease pathogenic immune responses during aging.

Immunophenotyping of Human B Lymphocytes in Blood and in Adipose Tissue.

The human obese subcutaneous adipose tissue (SAT) contributes to systemic and B cell intrinsic inflammation, reduced B cell responses, and increased secretion of autoimmune antibodies. Immune cells are recruited to the SAT by chemokines released by both adipocytes and infiltrating immune cells. We describe here the characterization of B lymphocytes from the SAT and blood (control) of obese females undergoing weight reduction surgeries (breast reduction or panniculectomy). We show how to isolate the immune cells from the blood and SAT, how to characterize B cells and their subsets, and how to measure markers of activation and/or transcription factors in SAT-derived B cells and B cell subsets. We also show how to evaluate other immune cell types infiltrating the SAT, including T cells, NK cells, monocyte/macrophages, in order to measure relative proportions of these cell types as compared to the blood.

Obese subcutaneous adipose tissue impairs human myogenesis, particularly in old skeletal muscle, via resistin-mediated activation of NF\u03baB

Adiposity and adipokines are implicated in the loss of skeletal muscle mass with age and in several chronic disease states. The aim of this study was to determine the effects of human obese and lean subcutaneous adipose tissue secretome on myogenesis and metabolism in skeletal muscle cells derived from both young (18–30 yr) and elderly (>65 yr) individuals. Obese subcutaneous adipose tissue secretome impaired the myogenesis of old myoblasts but not young myoblasts. Resistin was prolifically secreted by obese subcutaneous adipose tissue and impaired myotube thickness and nuclear fusion by activation of the classical NFκB pathway. Depletion of resistin from obese adipose tissue secretome restored myogenesis. Inhibition of the classical NFκB pathway protected myoblasts from the detrimental effect of resistin on myogenesis. Resistin also promoted intramyocellular lipid accumulation in myotubes and altered myotube metabolism by enhancing fatty acid oxidation and increasing myotube respiration and ATP production. In conclusion, resistin derived from human obese subcutaneous adipose tissue impairs myogenesis of human skeletal muscle, particularly older muscle, and alters muscle metabolism in developing myotubes. These findings may have important implications for the maintenance of muscle mass in older people with chronic inflammatory conditions, or older people who are obese or overweight.

Secretion of autoimmune antibodies in the human subcutaneous adipose tissue.

The adipose tissue (AT) contributes to systemic and B cell intrinsic inflammation, reduced B cell responses and secretion of autoimmune antibodies. In this study we show that adipocytes in the human obese subcutaneous AT (SAT) secrete several pro-inflammatory cytokines and chemokines, which contribute to the establishment and maintenance of local and systemic inflammation, and consequent suboptimal immune responses in obese individuals, as we have previously shown. We also show that pro-inflammatory chemokines recruit immune cells expressing the corresponding receptors to the SAT, where they also contribute to local and systemic inflammation, secreting additional pro-inflammatory mediators. Moreover, we show that the SAT generates autoimmune antibodies. During the development of obesity, reduced oxygen and consequent hypoxia and cell death lead to further release of pro-inflammatory cytokines, “self” protein antigens, cell-free DNA and lipids. All these stimulate class switch and the production of autoimmune IgG antibodies which have been described to be pathogenic. In addition to hypoxia, we have measured cell cytotoxicity and DNA damage mechanisms, which may also contribute to the release of “self” antigens in the SAT. All these processes are significantly elevated in the SAT as compared to the blood. We definitively found that fat-specific IgG antibodies are secreted by B cells in the SAT and that B cells express mRNA for the transcription factor T-bet and the membrane marker CD11c, both involved in the production of autoimmune IgG antibodies. Finally, the SAT also expresses RNA for cytokines known to promote Germinal Center formation, isotype class switch, and plasma cell differentiation. Our results show novel mechanisms for the generation of autoimmune antibody responses in the human SAT and allow the identification of new pathways to possibly manipulate in order to reduce systemic inflammation and autoantibody production in obese individuals.

Open Surgical and Needle Biopsy to Study Abdominal Subcutaneous Adipose Tissue in Obesity

Open Surgical and Needle Biopsy to Study Abdominal Subcutaneous Adipose Tissue in Obesity

Multi-omics Integrative Investigation of Fatty Acid Metabolism in Obese and Lean Subcutaneous Tissue.

White adipose tissue (WAT) plays a central role in whole-body energy homeostasis through storage and release of fatty acids. A deeper understanding of the complex and highly integrated pathways regulating WAT fatty acid metabolism, and how they are altered with obesity, is necessary for diagnostic and therapeutic innovations in nutritional disorders. In this multi-omics study, we investigated the influence of obesity on fatty acid metabolism in human subcutaneous adipose tissue (SAT) using an approach that integrated transcriptomic, peptidomic, and fatty acid analyses. Notably, all analyses were conducted in the same adipose tissue sample from each participant, thus minimizing the chance of spurious results. In a sample of SAT from the periumbilical abdominal region of obese (n = 11, mean body mass index [BMI] = 35.0 ± 1.2 kg/m2) and lean subjects (n = 9, mean BMI = 22.1 ± 0.5 kg/m2), we found that obese SAT tended to have higher relative amounts of specific monounsaturated fatty acids and n-6 polyunsaturated fatty acids, and lower amounts of saturated fatty acids (p < 0.05). These changes were associated with differential regulation of lipogenic and lipolytic pathways in obese SAT. Fatty acid analysis showed changes in estimated fatty acid desaturase and elongase activities between lean and obese SAT (p < 0.05). Biomarkers of lipogenesis (e.g., fatty acid synthase protein) were differentially regulated between lean and obese SAT. These changes were noted in conjunction with increases in extracellular matrix remodeling proteins. Transcriptomic data revealed that the key regulators of lipolysis were reduced in obese SAT. This integrative multi-omics analysis collectively shows that obese SAT has a distinct fatty acid signature compared to lean SAT and the pathways underlying fatty acid metabolism are broadly regulated at the level of gene expression and protein abundance.

A self-sustained loop of inflammation-driven inhibition of beige adipogenesis in obesity.

In obesity, white adipose tissue (AT) inflammation is associated with reduced beige adipogenesis, a thermogenic and energy-dissipating function mediated by uncoupling protein-1 (UCP1)-expressing beige adipocytes. Here, we dissected an inflammation-driven inhibitory mechanism of beige adipogenesis in obesity that required direct adhesive interactions between macrophages and adipocytes mediated, respectively, by α4 integrin and its counter-receptor VCAM-1, the expression of which was upregulated in obesity. This adhesive interaction reciprocally and concomitantly modulated inflammatory activation in macrophages and Erk–dependent downregulation of UCP1 in adipocytes. Genetic or pharmacologic inactivation of α4 integrin in mice resulted in elevated UCP1 expression and beige adipogenesis of the subcutaneous AT in obesity. Our findings, established in both mouse and human systems, reveal a self-sustained cycle of inflammation-driven impairment of beige adipogenesis in obesity.

DNA methylation map in circulating leukocytes mirrors subcutaneous adipose tissue methylation pattern: a genome-wide analysis from non-obese and obese patients

The characterization of the epigenetic changes within the obesity-related adipose tissue will provide new insights to understand this metabolic disorder, but adipose tissue is not easy to sample in population-based studies. We aimed to evaluate the capacity of circulating leukocytes to reflect the adipose tissue-specific DNA methylation status of obesity susceptibility. DNA samples isolated from subcutaneous adipose tissue and circulating leukocytes were hybridized in the Infinium HumanMethylation 450 BeadChip. Data were compared between samples from obese (n = 45) and non-obese (n = 8–10) patients by Wilcoxon-rank test, unadjusted for cell type distributions. A global hypomethylation of the differentially methylated CpG sites (DMCpGs) was observed in the obese subcutaneous adipose tissue and leukocytes. The overlap analysis yielded a number of genes mapped by the common DMCpGs that were identified to reflect the obesity state in the leukocytes. Specifically, the methylation levels of FGFRL1, NCAPH2, PNKD and SMAD3 exhibited excellent and statistically significant efficiencies in the discrimination of obesity from non-obesity status (AUC > 0.80; p < 0.05) and a great correlation between both tissues. Therefore, the current study provided new and valuable DNA methylation biomarkers of obesity-related adipose tissue pathogenesis through peripheral blood analysis, an easily accessible and minimally invasive biological material instead of adipose tissue.

Interleukin-17A Differentially Induces Inflammatory and Metabolic Gene Expression in the Adipose Tissues of Lean and Obese Mice.

The functions of interleukin-17A (IL-17A) in adipose tissues and adipocytes have not been well understood. In the present study, male mice were fed with a regular diet (n = 6, lean mice) or a high-fat diet (n = 6, obese mice) for 30 weeks. Subcutaneous adipose tissue (SAT) and visceral adipose tissue (VAT) were analyzed for IL-17A levels. SAT and VAT were treated with IL-17A and analyzed for inflammatory and metabolic gene expression. Mouse 3T3-L1 pre-adipocytes were differentiated into adipocytes, followed with IL-17A treatment and analysis for inflammatory and metabolic gene expression. We found that IL-17A levels were higher in obese SAT than lean SAT; the basal expression of inflammatory and metabolic genes was different between SAT and VAT and between lean and obese adipose tissues. IL-17A differentially induced expression of inflammatory and metabolic genes, such as tumor necrosis factor α, Il-6, Il-1β, leptin, and glucose transporter 4, in adipose tissues of lean and obese mice. IL-17A also differentially induced expression of inflammatory and metabolic genes in pre-adipocytes and adipocytes, and IL-17A selectively activated signaling pathways in adipose tissues and adipocytes. These findings suggest that IL-17A differentially induces inflammatory and metabolic gene expression in the adipose tissues of lean and obese mice.

DNA methylation and gene expression patterns in adipose tissue differ significantly within young adult monozygotic BMI-discordant twin pairs.

Little is known about epigenetic alterations associated with subcutaneous adipose tissue (SAT) in obesity. Our aim was to study genome-wide DNA methylation and gene expression differences in SAT in monozygotic (MZ) twin pairs who are discordant for body mass index (BMI). This design completely matches lean and obese groups for genetic background, age, gender and shared environment. 14We analyzed DNA methylome and gene expression from SAT, together with body composition (magnetic resonance imaging/spectroscopy) and glucose tolerance test, lipids and C-reactive protein from 26 rare BMI-discordant (intrapair difference in BMI ⩾3 kg m(-2)) MZ twin pairs identified from 10 birth cohorts of young adult Finnish twins. We found 17 novel obesity-associated genes that were differentially methylated across the genome between heavy and lean co-twins. Nine of them were also differentially expressed. Pathway analyses indicated that dysregulation of SAT in obesity includes a paradoxical downregulation of lipo/adipogenesis and upregulation of inflammation and extracellular matrix remodeling. Furthermore, CpG sites whose methylation correlated with metabolically harmful fat depots (intra-abdominal and liver fat) also correlated with measures of insulin resistance, dyslipidemia and low-grade inflammation, thus suggesting that epigenetic alterations in SAT are associated with the development of unhealthy obesity. This is the first study in BMI-discordant MZ twin pairs reporting genome-wide DNA methylation and expression profiles in SAT. We found a number of novel genes and pathways whose methylation and expression patterns differ within the twin pairs, suggesting that the pathological adaptation of SAT to obesity is, at least in part, epigenetically regulated.

Investigations of the human endocannabinoid system in two subcutaneous adipose tissue depots in lean subjects and in obese subjects before and after weight loss

Endocannabinoids (ECs) have a role in obesity by affecting appetite and through peripheral effects. Obesity is associated with a dysregulation of the endocannabinoid system (ECS). We aimed to determine the ECS in subcutaneous adipose tissue (AT) in obese subject and investigate the influence of diet-induced weight loss on this system. The obese study participants underwent a 12 weeks diet regimen resulting in 10-12% weight loss. All study participants underwent fasting blood samples and AT biopsies from abdomen and gluteal region, the obese subjects both before and after weight loss. A total of 21 healthy obese individuals (10 men/11 women, age 39.5 ± 1.6 years, body mass index (BMI): 37.5 ± 0.8 kg m(-2)) and 21 age- and gender-matched lean subjects (BMI: 23.8 ± 0.4 kg m(-2)) were studied. The activity of ECS in AT was determined by measuring arachidonoyl glycerol (2-AG) and N-arachidonoylethanolamine/anandamide in AT by mass spectrometry and gene expressions of enzymes and receptors involved in the ECS. The EC, 2-AG was reduced in obese individuals in the gluteal AT depot (P<0.01). Moreover, 2-AG increased in both depots in the obese subjects following weight loss (P<0.05). The gene expression of the CB1 was either not affected by the obese state (in the gluteal AT depot) or reduced (in the abdominal depot, P<0.05) and significantly affected by weight loss. The expression of the degrading enzymes FAAH, FAAH2, MGL and MGL2 was differently affected by obesity, AT depot and weight loss. We found reduced levels of 2-AG in subcutaneous AT in obesity, which increased after weight loss. In abdominal AT, the low CB1 expression was normalised after weight loss, whereas in gluteal AT the CB1 expression was reduced after weight loss. These findings support the concept of a dysregulated ECS in AT in association with obesity.

11β-Hydroxysteroid Dehydrogenase Type 1 is Overexpressed in Subcutaneous Adipose Tissue of Morbidly Obese Patients

11beta-Hydroxysteroid dehydrogenase type 1 (11beta-HSD1) enzyme catalyzes interconversion of inactive cortisone to active cortisol. Its expression in adipose tissue has been associated with obesity and some of its metabolic disorders. Controversies regarding which fat depots [subcutaneous adipose tissue (SAT) or visceral adipose tissue (VAT)] have higher expression still remain. The aim of this work was to evaluate 11beta-HSD1 expression in SAT and VAT of obese patients and evaluate its association to metabolic features of metabolic syndrome. In 32 morbidly obese patients, paired samples of SAT and VAT were collected. All patients, 40.2+/-12.3 years and 36.7+/-3.8 body mass index (BMI), underwent sleeve gastrectomy or laparoscopic gastric bypass. Gene expression of 11beta-HSD1 in adipose tissue samples were determined by real-time reverse transcriptase polymerase chain reaction. Spearman correlation test was used to evaluate relationships between 11beta-HSD1 levels and clinical and biochemical parameters. 11beta-HSD1 mRNA levels were higher in SAT than in VAT, with median expression levels of 11.4 arbitrary units (AU) and 7.8 AU, respectively (p=0.03). SAT 11beta-HSD1 mRNA were correlated with VAT mRNA levels (r=-0.6, p=0.018) and hip circumference (r=0.66, p=0.018). SAT 11beta-HSD1 levels increase parallel according to BMI category. We did not find a correlation between SAT or VAT with fasting glucose (r=0.15, p=NS), total cholesterol (r=0.13, p=NS), triglycerides (r=0.04, p=NS), and high-density lipoprotein (r=-0.16, p=NS). However, SAT expression in patients with features of MS was higher than those without features of MS. Our results demonstrate that SATs express higher 11beta-HSD1 mRNA levels than VAT. This finding highlights the importance of SAT in obesity and its possible role on metabolic disorders associated with obesity.

Expression of TNF-α protein in omental and subcutaneous adipose tissue in obesity

Background During the last several years the role of adipose tissue in contributing to obesity-associated cardiovascular and metabolic risk has gained much attention. Aim To examine the expression of TNF-α protein in omental and subcutaneous adipose tissue in correlation with plasma PAI-1 and other clinical parameters in obesity subjects. Material and methods Paired biopsies of omental and subcutaneous fat were collected during surgery in 32 obesity subjects. The expression of TNF-α protein in omental and subcutaneous fat was quantified by using Western blot method, and correlations with plasma PAI-1, homeostasis model assessment insulin resistance (HOMA-IR) and lipid were investigated. Results TNF-α protein expression was higher in omental than in subcutaneous adipose tissue ( P < 0.01). Significant positive linear correlations were found between TNF-α protein in omental adipose tissue and plasma PAI-1 in obesity subjects. TNF-α protein in omental fat was positively associated with HOMA-IR, triglycerides and negatively with HDL-cholesterol. Conclusion TNF-α expression in omental adipose tissue could play a key role in contributing to cardiovascular risk in central obesity subjects.

Protein Array Reveals Differentially Expressed Proteins in Subcutaneous Adipose Tissue in Obesity

Many adipokines, inflammatory cytokines, and other proteins produced by adipose tissue have been shown to be involved in the development of obesity-related insulin resistance. Nevertheless, new factors that play an important role in these processes are still emerging. Therefore, we screened the level of 120 different proteins in biopsies of subcutaneous adipose tissue (ScAT) of lean and obese subjects. All studied volunteers (12 obese with BMI >30 and 6 lean with BMI <25 kg/m(2)) were young, clinically healthy, and drug-naive males with normal glucose tolerance. The ScAT was obtained by a needle biopsy from the umbilical region. Protein levels were assessed in adipose tissue lysates using protein arrays; mRNA levels were determined with the aid of real-time reverse transcription-polymerase chain reaction (RT-PCR). The obese subjects had higher fasting plasma glucose (although within the normal range) and insulin levels, increased high sensitivity C-reactive protein (hsCRP) in circulation, and decreased in vivo insulin action. Using the protein array technique, it was shown that of 120 proteins measured, 27 showed higher levels (leptin, HGF, EGF-R, FGF-6, IGF-1sR, Fas/Apo-1, ENA-78, PARC, lymphotactin, HCC-4, IL-10, IL-1a, IL-1R1, IL-1R4, IL-12p70, angiopoietin-2, Axl, Dtk, MIF, MIP-1a, -1b, -3b, MSP-a, osteoprotegerin, TECK, TIMP-1, -2) and only one (RANTES) showed a lower level in ScAT of obese subjects when compared with the lean controls (p < 0.05). The real-time RT-PCR confirmed the results of protein arrays for leptin, MIF, MIP-1a, TIMP-2, adiponectin, IL-6, and TNF-alpha but not for RANTES. To our knowledge, this is the first protein array data on a very early dysregulation of ScAT protein levels in insulin-resistant obese, but apparently healthy, subjects with normal glucose tolerance.

Mitogen-Activated Protein Kinases, Inhibitory-κB Kinase, and Insulin Signaling in Human Omental Versus Subcutaneous Adipose Tissue in Obesity

MAPKs and inhibitory-kappaB kinase (IKK) were suggested to link various conditions thought to develop in adipose tissue in obesity (oxidative, endoplasmic reticulum stress, inflammation) with insulin resistance. Yet whether in obesity these kinases are affected in a fat-depot-differential manner is unknown. We assessed the expression and phosphorylation of these kinases in paired omental and abdominal-sc fat biopsies from 48 severely obese women (body mass index > 32 kg/m(2)). Protein and mRNAs of p38MAPK, ERK, c-Jun kinase-1, and IKKbeta were increased 1.5-2.5-fold in omental vs. sc fat. The phosphorylated (activated) forms of these kinases were also increased to similar magnitudes as the total expression. However, phosphorylation of insulin receptor substrate-1 on Ser312 (equivalent of murine Ser307) was not increased in omental, compared with sc, fat. Consistently, fat tissue fragments stimulated with insulin demonstrated that tyrosine phosphorylation and signal transduction to Akt/protein kinase B in omental fat was not inferior to that observable in sc fat. Comparison with lean women (body mass index 23.2 +/- 2.9 kg/m(2)) revealed similar ERK2 and IKKbeta expression and phosphorylation in both fat depots. However, as compared with lean controls, obese women exhibited 480 and 270% higher amount of the phosphorylated forms of p38MAPK and c-Jun kinase, respectively, in omental, but not sc, fat, and this expression level correlated with clinical parameters of glycemia and insulin sensitivity. Increased expression of stress-activated kinases and IKK and their phosphorylated forms in omental fat occurs in obesity, potentially contributing to differential roles of omental and sc fat in the pathophysiology of obesity.