Human Omental Adipose Tissue Research Articles

Increase in Circulating and Adipose Tissue Expression of Secretory Leukocyte Peptidase Inhibitor (SLPI) with Obesity and Diabetes

Objective: We have recently identified secretory leukocyte peptidase inhibitor (SLPI), a component of the in- nate host defence in human omental adipose tissue. The objective of this study was to determine if the SLPI secreted by adipose tissue is regulated by changes in obesity. Materials/Methods: Circulating SLPI was measured in lean/overweight (n = 13), obese (n = 10) and obese diabetic (n = 11) male volunteers. SLPI gene expression was measured in subcutaneous adipose tissue fat biopsies from these volun- teers using real time PCR. The regulation of SLPI was further explored in the human SGBS adipocyte cell line. Results: Circulating SLPI shows a small but significant increase in obese (11%; p ≤ 0.05) and obese diabetic volunteers (16%; p ≤ 0.001) when compared with lean/overweight volunteers. There was a corresponding increase in SLPI mRNA in the adipose tissue of obese (800%; p ≤ 0.01) and obese diabetic volunteers (500%; p≤ 0.001) compared with lean/overweight volunteers. In differentiated human adipocytes, SLPI mRNA is increased by IL-6 (10ng/ml; 318%; p ≤ 0.05), TNFalpha (1ng/ml; 279%; p ≤ 0.005), LPS (100ng/ml; 318%; p ≤ 0.05), insulin (1mM; 321%; p ≤ 0.05) and glu- cose (5 mM; 246%; p ≤ 0.05) while in the preadipocytes SLPI mRNA is decreased by TNF alpha (10ng/ml; 30%; p ≤ 0.05) and LPS (100ng/ml; 42%; p ≤ 0.05) compared to untreated preadipocytes. Conclusions: Circulating SLPI and SLPI gene expression in subcutaneous adipose tissue increases with obesity where it may play a local role in the regulation of the low grade inflammatory response associated with obesity.

The ghrelin O-acyltransferase–ghrelin system reduces TNF-α-induced apoptosis and autophagy in human visceral adipocytes

Proinflammatory and proapoptotic cytokines such as TNF-α are upregulated in human obesity. We evaluated the association between ghrelin isoforms (acylated and desacyl ghrelin) and TNF-α in obesity and obesity-associated type 2 diabetes, as well as the potential role of ghrelin in the control of apoptosis and autophagy in human adipocytes. Plasma concentrations of the ghrelin isoforms and TNF-α were measured in 194 participants. Ghrelin and ghrelin O-acyltransferase (GOAT) levels were analysed by western-blot, immunohistochemistry and real-time PCR in 53 biopsies of human omental adipose tissue. We also determined the effect of acylated and desacyl ghrelin (10 to 1,000 pmol/l) on TNF-α-induced apoptosis and autophagy-related molecules in omental adipocytes. Circulating concentrations of acylated ghrelin and TNF-α were increased, whereas desacyl ghrelin levels were decreased in obesity-associated type 2 diabetes. Ghrelin and GOAT were produced in omental and subcutaneous adipose tissue. Visceral adipose tissue from obese patients with type 2 diabetes showed higher levels of GOAT, increased adipocyte apoptosis and increased expression of the autophagy-related genes ATG5, BECN1 and ATG7. In differentiating human omental adipocytes, incubation with acylated and desacyl ghrelin reduced TNF-α-induced activation of caspase-8 and caspase-3, and cell death. In addition, acylated ghrelin reduced the basal expression of the autophagy-related genes ATG5 and ATG7, while desacyl ghrelin inhibited the TNF-α-induced increase of ATG5, BECN1 and ATG7 expression. Apoptosis and autophagy are upregulated in human visceral adipose tissue of patients with type 2 diabetes. Acylated and desacyl ghrelin reduce TNF-α-induced apoptosis and autophagy in human visceral adipocytes.

Using Gene Expression to Predict Differences in the Secretome of Human Omental vs. Subcutaneous Adipose Tissue

The objective of this study was to characterize differences in the secretome of human omental compared with subcutaneous adipose tissue using global gene expression profiling. Gene expression was measured using Affymetrix microarrays (Affymetrix, Santa Clara, CA) in subcutaneous and omental adipose tissue in two independent experiments (n = 5 and n = 3 independent subjects; n = 16 arrays in total, 2 for each subject). Predictive bioinformatic algorithms were employed to identify secreted proteins. Microarray analysis identified 22 gene probe sets whose expression was significantly different with a fold change (FC) greater than 5 in expression in both experiments between omental and subcutaneous adipose tissue. Using bioinformatic predictive programs 11 of these 22 probe sets potentially coded for secreted proteins. Pathway network analysis of the secreted proteins showed that three of the proteins are part of a common pathway network. These proteins gremlin 1 (GREM1), pleiotrophin (PTN), and secretory leukocyte peptidase inhibitor (SLPI) are expressed respectively 43×, 23×, and 5× in omental adipose tissue relative to subcutaneous adipose tissue as determined by real-time PCR. The presence of GREM1, PTN, and SLPI protein in human adipose tissue was confirmed by western blotting. All three proteins are expressed in the human Simpson-Golabi-Behmel syndrome (SGBS) preadipocyte cell line. The expression of GREM1, PTN, and SLPI changed with the differentiation of the preadipocytes into mature adipocytes. Gene expression coupled with predictive bioinformatic algorithms have identified several genes coding for secreted proteins which are expressed differently in omental adipose tissue compared to subcutaneous adipose tissue proving a valid alternative approach to help further define the adipocyte secretome.

Depot-specific expression of caveolin-1 in human adipose tissue and their relationship with obesity and insulin resistance

To explore the depot-specific mRNA and protein expression of caveolin-1 (CAV-1) in human subcutaneous and omental adipose tissues and analyze their relationship with obesity and insulin resistance. A total of 41 subjects with normal glucose regulation were recruited. Among them, there were 29 cases with normal body mass index (BMI) and 12 cases with BMI ≥ 24 kg/m(2). All were scheduled to undergone selective abdominal operations. The levels of fasting insulin (FINS) were measured by chemiluminescence enzyme-linked immunosorbent assay (ELISA) kit. Fasting plasma glucose (FPG) was tested by glucose oxidase and home model insulin resistance index (HOMA-IR) calculated. Real-time polymerase chain reaction (RT-PCR) and Western blotting were employed to assess the relative mRNA and protein expression of caveolin-1 in subcutaneous and omental adipose tissues. And the mRNA and protein expression of caveolin-1 from different fat depots were compared and their correlations with BMI and HOMA-IR analyzed. (1) FINS and HOMA-IR were significantly higher in the overweight and obesity group than those in the normal BMI group (FINS: (8.82 ± 3.79) mU/L vs (6.43 ± 4.38) mU/L, P < 0.05, HOMA-1R: 1.91 ± 0.85 vs 1.36 ± 0.72, P < 0.05). (2) The normal BMI group patients had the higher expression levels of caveolin-1 mRNA in omental adipose tissue than overweight counterparts (2.84 ± 0.86 vs 1.02 ± 0.36, P < 0.01). But the difference in subcutaneous adipose tissue was not significant (P > 0.05). (3) The caveolin-1 protein expression in omental adipose tissue of the normal BMI group was higher than that of overweight patients (1.68 ± 0.67 vs 0.73 ± 0.29, P < 0.05). And the difference between two groups was not significant (P > 0.05). (4)The expressions of caveolin-1 mRNA in omental adipose tissue were negatively correlated with BMI, waist circumstance, triglyceride and HOMA-IR (r = -0.441, -0.615, -0.539, -0.688, P < 0.05). No correlations were found between the expressions of caveolin-1 mRNA in subcutaneous adipose tissue with BMI, waist circumstance and HOMA-IR (P > 0.05). Differential depot-specific expressions of caveolin-1 are present in human subcutaneous and omental adipose tissues. A low expression of caveolin-1 in omental adipose tissue may contribute to the pathogenesis of obesity and insulin resistance.

Effects of type 5-phosphodiesterase inhibition on energy metabolism and mitochondrial biogenesis in human adipose tissue ex vivo

An excess of adipose tissue (AT) in obese individuals is linked to increased cardiovascular risk and mitochondria have been shown to be defective in the muscle and AT of patients with metabolic disorders such as obesity and Type 2 diabetes. Nitric oxide (NO) generated by endothelial NO synthase (eNOS) plays a role in mitochondrial biogenesis through cyclic-GMP (cGMP). AT harbors the whole molecular signaling pathway of NO, together with type 5-phosphodiesterase (PDE- 5), the main cGMP catabolising enzyme. Our aim was to evaluate the effect of the modulation of NO pathway, through PDE-5 inhibition, on energy metabolism and mitochondria biogenesis in human omental AT. Cultured human omental AT was stimulated with PDE-5 inhibitor, vardenafil, at different concentration for 24 and 72 h. Analysis of the expression of both key-regulator genes of adipocyte metabolism and mitochondria-biogenesis markers was performed. We found an increased gene expression of peroxisome proliferator-activated receptor-γ (PPAR-γ), adiponectin, and proliferator- activated receptor gamma coactivator-1 α (PGC-1α) after a 24-h stimulation with vardenafil at the lowest concentration employed compared to controls (p<0.05). After 72 h of stimulation, a significant increase of mitochondrial DNA was found compared to control samples (p<0.05). Our data suggest that PDE-5 inhibition could have an impact on mitochondrial content of human AT suggesting a positive effect on energy metabolism and adding new elements in the comprehension of AT pathophysiology.

Attenuated metabolism is a hallmark of obesity as revealed by comparative proteomic analysis of human omental adipose tissue

Obesity is recognized as an epidemic health problem worldwide. In humans, the accumulation of omental rather than subcutaneous fat appears to be tightly linked to insulin resistance, type 2 diabetes and cardiovascular disease. Differences in gene expression profiles in the adipose tissue comparing non-obese and obese subjects have been well documented. However, to date, no comparative proteomic studies based on omental fat have investigated the influence of obesity in protein expression. In this work, we searched for proteins differentially expressed in the omental fat of non-obese and obese subjects using 2D-DIGE and MS. Forty-four proteins, several of which were further studied by immunoblotting and immunostaining analyses, showed significant differences in the expression levels in the two groups of subjects. Our findings reveal a clearly distinctive proteomic profile between obese and non-obese subjects which emphasizes: i) reduced metabolic activity in the obese fat, since most down-regulated proteins were engaged in metabolic pathways; and ii) morphological and structural cell changes in the obese fat, as revealed by the functions exerted by most up-regulated proteins. Interestingly, transketolase and aminoacylase-1 represent newly described molecules involved in the pathophysiology of obesity, thus opening up new possibilities in the study of obesity.

Histone Deacetylase 9 Is a Negative Regulator of Adipogenic Differentiation

Differentiation of preadipocytes into mature adipocytes capable of efficiently storing lipids is an important regulatory mechanism in obesity. Here, we examined the involvement of histone deacetylases (HDACs) and histone acetyltransferases (HATs) in the regulation of adipogenesis. We find that among the various members of the HDAC and HAT families, only HDAC9 exhibited dramatic down-regulation preceding adipogenic differentiation. Preadipocytes from HDAC9 gene knock-out mice exhibited accelerated adipogenic differentiation, whereas HDAC9 overexpression in 3T3-L1 preadipocytes suppressed adipogenic differentiation, demonstrating its direct role as a negative regulator of adipogenesis. HDAC9 expression was higher in visceral as compared with subcutaneous preadipocytes, negatively correlating with their potential to undergo adipogenic differentiation in vitro. HDAC9 localized in the nucleus, and its negative regulation of adipogenesis segregates with the N-terminal nuclear targeting domain, whereas the C-terminal deacetylase domain is dispensable for this function. HDAC9 co-precipitates with USF1 and is recruited with USF1 at the E-box region of the C/EBPα gene promoter in preadipocytes. Upon induction of adipogenic differentiation, HDAC9 is down-regulated, leading to its dissociation from the USF1 complex, whereas p300 HAT is up-regulated to allow its association with USF1 and accumulation at the E-box site of the C/EBPα promoter in differentiated adipocytes. This reciprocal regulation of HDAC9 and p300 HAT in the USF1 complex is associated with increased C/EBPα expression, a master regulator of adipogenic differentiation. These findings provide new insights into mechanisms of adipogenic differentiation and document a critical regulatory role for HDAC9 in adipogenic differentiation through a deacetylase-independent mechanism.

FTO mRNA Expression in Extremely Obese and Type 2 Diabetic Human Omental and Subcutaneous Adipose Tissues

Fat mass and obesity-associated protein (FTO) gene expression is known to correlate with obesity. Our aim was to investigate the FTO gene expression in paired omental and subcutaneous human adipose tissues from morbid and obese patients. To understand the role of CD68-positive macrophages in adipose tissues, the correlation with adiposity parameters such as adipocyte diameter and adipocyte radius was also measured. Drug and adiposity correlations were also analyzed. Paired omental and subcutaneous adipose tissue were excised during elective surgery from morbidly obese (n = 9) and obese (n = 5) patients. FTO expressions were determined by quantitative PCR. Tissue sections were analyzed for their CD68 protein expressions by immunuhistochemistry. Omental and subcutaneous adipose tissue FTO gene expression levels were not found to differ significantly among morbidly obese and obese study groups. Serum aspartate aminotransferase e and alanine transaminase levels were found to be in negative correlation with subcutaneous fat tissue FTO expression rate. Antidiabetic drug use was found to be in correlation with adiposity. Both subcutaneous and omental fat cell diameters were found to have correlation with antidiabetic drug use. Omental fat cell diameter was found to enlarge together with omental CD68 protein expression. Subcutaneous macrophage number decreased while omental fat cell radius increased. Omental macrophage number was found in correlation with subcutaneous macrophage number. Antidiabetic therapy was found to increase adiposity in omental and subcutaneous fat. Further research is needed with larger samples to explore the exact role of FTO in obesity.

Abstract LB-291: Central obesity drives oesophageal tumor cell growth through VEGF-mediated mechanisms

Abstract Introduction: Obesity is a risk-factor for both esophageal/colorectal adenocarcinoma. Adipose tissue is an endocrine organ secreting numerous factors, including Vascular Endothelial Growth Factor (VEGF). VEGF was identified to be up-regulated in cancer cells by affymetrix-array following co-culture with human omental adipose tissue (OAT). An understanding of the mechanisms driving obesity-related disease is needed to uncover pathways and develop new targets for therapy. In this study, we aimed to investigate the effect of OAT-derived VEGF on tumor growth and the potential of bevacizumab to block this effect. Methods: Matched subcutaneous and omental adipose tissue, serum and tumor were harvested from oesophageal/colorectal cancer patients undergoing resective surgery. VEGF was quantified in adipose conditioned media (ACM) and serum by ELISA. Proliferation of esophageal (OE33, JH-ESO) and colorectal (HCT15, SW480) cells following culture with ACM was assessed by BrdU assay. The protective effect of ACM on chemotherapy (cisplatin and 5FU) induced death was assessed. The effect of bevacizumab in attenuating these effects was also examined. VEGF and VEGF receptor 2 (KDR) expression was assessed in tumor tissue by qPCR. In a 200-patient tissue microarray, VEGF and VEGFR expression was related to clinico-pathological parameters and obesity status. Results: ACM from omental adipose tissue of obese patients significantly (p&amp;lt;0.05) increased proliferation in oesophageal (313%) and colorectal (424%) adenocarcinoma cell lines relative to omental adipose tissue from non-obese cancer patients (180% and 157% respectively). Interestingly, this effect was not observed in ACM from matched subcutaneous depots indicating that omental adipose tissue is more pro-tumor and metabolically active. Omental ACM from obese patients contained significantly higher levels of VEGF (p&amp;lt;0.05). In our patient cohort, serum VEGF was significantly elevated in centrally obese relative to normal weight cancer patients (determined by CT). There was a significant (p&amp;lt;0.05) higher expression of VEGF and KDR expression in esophageal tumours from centrally obese patients. The expression of KDR was higher in the leading edge of tumors from patients classified as obese, and was associated with decreased survival and increased nodal involvement. ACM from omental adipose tissue protected against 5FU-induced cell death (P&amp;lt;0.01), an effect which could be blocked by treatment with bevacizumab. Conclusion: VEGF from OAT increased proliferation in oesophageal/colorectal cancer cells. VEGF and KDR expression in oesophageal cancer was higher in centrally obese patients. ACM protected against chemotherapy-induced death, an effect that was mediated through VEGF. These findings suggest anti-VEGF strategies are warrented in obesity-associated malignancies, alone or in combination with conventional chemotherapies. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr LB-291. doi:10.1158/1538-7445.AM2011-LB-291

Adiponectin Gene Polymorphisms and Type 2 Diabetes among Singaporean Chinese Adults

Background: Adiponectin is the most abundant circulating adipokine in human that regulates insulin actions. Association of adiponectin gene variations with type 2 diabetes (T2DM) has been reported albeit predominantly in non-Asian populations. Additionally, proof of variant functionality beyond statistical association is often unavailable. We studied six common (minor allele frequency ?0.05) adiponectin single nucleotide polymorphisms (SNPs) in Singaporean Chinese adults with follow-up functional genetic experiments. Methods: In a case-control study (N=588), genotyping of six common adiponectin haplotype tagging SNPs [-3964A>G(rs822396), +45T>G(rs2241766), 276C>A(rs1501299), 973G>A(rs3774262), 4551G>C(rs1063539) and 5852G>A(rs6444175)] was performed using Taqman genotyping assay. Allele-dependent differential efficiency of mRNA expression was tested with quantitative real time PCR using human subcutaneous and omental adipose tissues. Results: Distributions of genotypes for all SNPs among controls were consistent with Hardy-Weinberg Equilibrium. Single locus, genotyped-based analysis suggested borderline significant (P=0.07) association between an exon- 2 coding-synonymous +45T>G(rs2241766) and T2DM. We demonstrated that the relative mRNA expression of adiponectin gene was ~80% lower among carriers of minor G allele in human subcutaneous adipose tissue (N=43, p G(rs2241766) and T2DM among Singaporean Chinese adults. Functional experiments in both human subcutaneous and omental adipose tissue suggested that polymorphisms in +45T>G(rs2241766) may be associated with differential allelic expression.

Depot-specific expression of retinol-binding protein 4 in human adipose tissue and their relationship with obesity and insulin resistance

To explore the depot-specific mRNA and protein expression of retinol-binding protein 4 (RBP4) in human subcutaneous and omental adipose tissue and investigate their relationship with the serum RBP4 levels, obesity and insulin resistance. A total of 41 subjects with normal glucose regulation were recruited. Among them, there were 29 cases with normal body mass index (BMI) and 12 cases with BMI ≥ 24 kg/m(2). All were prepared to undergone a selective abdominal surgery. The levels of serum RBP4 and fasting insulin (FINS) were measured by ELISA (enzyme-linked immunosorbent assay) and chemiluminescence ELISA kit respectively. Fasting plasma glucose (FPG) was tested by glucose oxidase and the home model insulin resistance index (HOMA-IR) calculated. Real-time PCR (RT-PCR) and Western blot were employed to assess the relative mRNA and protein expression of RBP4 in subcutaneous and omental adipose tissues. The mRNA and protein expression of RBP4 from different fat depots were compared and their correlations with BMI, the serum RBP4 concentrations and HOMA-IR analyzed. (1) The serum concentrations of RBP4, FINS and HOMA-IR were significantly higher in overweight and obesity group than those in the normal BMI group [RBP4: (39.61 ± 1.57) mg/L vs (33.40 ± 1.28) mg/L, P < 0.01; FINS: (8.82 ± 3.79) mU/L vs (6.43 ± 4.38) mU/L, P < 0.05; HOMA-IR: 1.91 ± 0.85 vs 1.36 ± 0.72, P < 0.05]. (2) The expression levels of RBP4 mRNA and protein were significantly higher in omental adipose tissues than those in subcutaneous adipose tissue [mRNA: (5.88 ± 2.37) vs (2.07 ± 1.66), P < 0.01; protein: (0.76 ± 0.18 vs 0.15 ± 0.07, P < 0.05] and these depots difference in both groups (P < 0.05). Moreover, the overweight patients had the higher expression levels of RBP4 mRNA and protein in omental adipose tissue than normal BMI group (mRNA: 7.52 ± 0.58 vs 4.37 ± 0.45, P < 0.01; protein: 0.92 ± 0.23 vs 0.57 ± 0.13, P < 0.05). (3) The expressions of both RBP4 mRNA and protein in the omental adipose tissue were positively correlated with BMI, waist circumstance, serum concentrations of RBP4, FINS and HOMA-IR. The expression of was negatively correlated with HOMA-IR (r = -0.635, P < 0.05) in subcutaneous adipose tissue. No correlations were found between the expressions of RBP4 mRNA and protein in subcutaneous adipose tissue with BMI, waist circumstance, serum RBP4 and FINS concentrations. There is depot-specific expression of RBP4 in human subcutaneous and omental adipose tissues. A high expression of RBP4 in omental adipose tissue and an elevated level of serum RBP4 may contribute to the pathogenesis of obesity and IR.

Phosphoprotein enriched in diabetes gene product (Ped/pea-15) is increased in omental adipose tissue of women with the polycystic ovary syndrome: ex vivo regulation of ped/pea-15 by glucose, insulin and metformin

Polycystic ovary syndrome (PCOS), the commonest endocrine disorder in women, is characterized by an altered steroid milieu and is associated with insulin resistance and type 2 diabetes mellitus (T2DM). Phosphoprotein enriched in diabetes gene product (Ped/pea-15) regulates glucose metabolism and is increased in T2DM. Our novel data indicate that Ped/pea-15 mRNA expression and protein levels are significantly increased in omental adipose tissue (AT) from PCOS women compared to matched controls (p < 0.01); Ped/pea-15 levels in subcutaneous AT were not significantly different. Furthermore, Ped/pea-15 mRNA expression and protein levels were higher in omental compared to subcutaneous AT in PCOS subjects (p < 0.01); however, in control subjects, this was not significant. Glucose was predictive of omental AT Ped/pea-15 mRNA expression (p = 0.045). Importantly, glucose and insulin increased whereas metformin significantly decreased Ped/pea-15 levels in human omental AT explants. Our findings should serve to promote further research on Ped/pea-15 biology.

The anti-adipogenic effect of angiotensin II on human preadipose cells involves ERK1,2 activation and PPARG phosphorylation

Despite the importance of adipocyte formation for adipose tissue physiology, current knowledge about the mechanisms that regulate the recruitment of progenitor cells to undergo adipogenic differentiation is limited. A role for locally generated angiotensin II emerged from studies with human and murine cells. Preadipose cells from different human fat depots show reduced response to adipogenic stimuli when exposed to angiotensin II. This investigation sought to gain an insight into the intracellular mechanisms involved in the anti-adipogenic response of human preadipose cells from omental fat to angiotensin II. Its effect was evaluated on cells stimulated to adipogenic differentiation in vitro, by assessment of glycerol-3-phosphate dehydrogenase activity and expression of early markers of adipogenesis. Extracellular signal-regulated kinase(1,2) (ERK(1,2)) pathway activation was inferred from the phosphorylated to total ERK(1,2) ratio determined by western blot. Exposure to angiotensin II throughout the 10-day differentiation period resulted in a reduced adipogenic response. A similar anti-adipogenic effect was observed when this hormone was present during the first 48 h of induction to differentiation. Angiotensin II treatment had no consequences on CCAAT/enhancer-binding protein beta and peroxisome proliferator-activated receptor gamma (PPARG) induction, but increased the phosphorylated form of the key adipogenic regulator PPARG. Upon angiotensin II exposure, a raise of phosphorylated ERK(1,2) was determined, which was more prominent 8-20 h after induction of adipogenesis (when controls reached negligible values). Chemical inhibition of ERK(1,2) phosphorylation prevented angiotensin II-dependent reduction in adipogenesis. These results support the participation of the mitogen-activated protein kinase/ERK(1,2) pathway in the anti-adipogenic effect of angiotensin II on preadipose cells from human omental adipose tissue.

Expression of endoplasmic reticulum stress markers in omental adipose tissue from obese patients

The expressions of endoplasmic retieulum stress markers,including heavy-chain binding protein(Bip),inositol requiting enzymel(IRE1),PKR-like endoplasmic reticulum kinase(PERK),and oxygen-regulated protein(ORP150),were increased in omental adipose tissue in obese patients[1.4(1.4)vs0.9(0.6).2.0±0.8 vs 1.3±0.8,2.4(2.9)vs 1.5(1.2),1.6(2.6)vs 0.6(0.5),all P<0.05].PERK and ORP150 were correlated with body mass index.Bip,ORP150,X-box binding protein(XBP1),and IRE1 were correlated with the expressions of tumor necrosis factor-α and interleukin-6.The results suggest that endoplasmic reticulum stress may be activated in human omental adipose tissue and the expressions of stress markers seem to be correlated with local inflammation. Key words: Obesity; Endoplasmic reticulum stress; Inflammation; Insulin resistance

Regulation of adipokine production in human adipose tissue by propionic acid

Dietary fibre (DF) has been shown to be protective for the development of obesity, insulin resistance and type 2 diabetes. Short-chain fatty acids, produced by colonic fermentation of DF might mediate this beneficial effect. Adipose tissue plays a key role in the regulation of energy homeostasis, therefore, we investigated the influence of the short-chain fatty acid propionic acid (PA) on leptin, adiponectin and resistin production by human omental (OAT) and subcutaneous adipose tissue (SAT). As PA has been shown to be a ligand for G-protein coupled receptor (GPCR) 41 and 43, we investigated the role of GPCR's in PA signalling. Human OAT and SAT explants were obtained from gynaecological patients who underwent surgery. Explants were incubated for 24 h with PA. Adipokine secretion and mRNA expression were determined using ELISA and RT-PCR respectively. We found that PA significantly stimulated leptin mRNA expression and secretion by OAT and SAT, whereas it had no effect on adiponectin. Furthermore, PA reduced resistin mRNA expression. Leptin induction, but not resistin reduction, was abolished by inhibition of Gi/o-coupled GPCR signalling. Moreover, GPCR41 and GPCR43 mRNA levels were considerably higher in SAT than in OAT. We demonstrate that PA stimulates expression of the anorexigenic hormone leptin and reduces the pro-inflammatory factor resistin in human adipose tissue depots. This suggests that PA is involved in regulation of human energy metabolism and inflammation and in this way may influence the development of obesity and type 2 diabetes.

Pro-inflammatory CD11c+CD206+ adipose tissue macrophages are associated with insulin resistance in human obesity.

OBJECTIVEInsulin resistance and other features of the metabolic syndrome have been causally linked to adipose tissue macrophages (ATMs) in mice with diet-induced obesity. We aimed to characterize macrophage phenotype and function in human subcutaneous and omental adipose tissue in relation to insulin resistance in obesity.RESEARCH DESIGN AND METHODSAdipose tissue was obtained from lean and obese women undergoing bariatric surgery. Metabolic markers were measured in fasting serum and ATMs characterized by immunohistology, flow cytometry, and tissue culture studies.RESULTSATMs comprised CD11c+CD206+ cells in “crown” aggregates and solitary CD11c−CD206+ cells at adipocyte junctions. In obese women, CD11c+ ATM density was greater in subcutaneous than omental adipose tissue and correlated with markers of insulin resistance. CD11c+ ATMs were distinguished by high expression of integrins and antigen presentation molecules; interleukin (IL)-1β, -6, -8, and -10; tumor necrosis factor-α; and CC chemokine ligand-3, indicative of an activated, proinflammatory state. In addition, CD11c+ ATMs were enriched for mitochondria and for RNA transcripts encoding mitochondrial, proteasomal, and lysosomal proteins, fatty acid metabolism enzymes, and T-cell chemoattractants, whereas CD11c− ATMs were enriched for transcripts involved in tissue maintenance and repair. Tissue culture medium conditioned by CD11c+ ATMs, but not CD11c− ATMs or other stromovascular cells, impaired insulin-stimulated glucose uptake by human adipocytes.CONCLUSIONSThese findings identify proinflammatory CD11c+ ATMs as markers of insulin resistance in human obesity. In addition, the machinery of CD11c+ ATMs indicates they metabolize lipid and may initiate adaptive immune responses.

Expression of genes related to glucocorticoid action in human subcutaneous and omental adipose tissue

Adipose tissue glucocorticoid action relies on local enzymatic interconversion and glucocorticoid receptor (GR) availability. 11β-Hydroxysteroid dehydrogenase type 1 (11β-HSD1), 2 (11β-HSD2) and hexose-6-phosphate dehydrogenase (H6PDH) are likely involved in glucocorticoid activation/inactivation within adipose tissue. We examined adipose tissue mRNA expression of genes related to glucocorticoid action and their association with total and visceral adiposity. Messenger RNA was measured in paired subcutaneous and omental fat samples obtained from 56 women (age: 47.3 ± 4.8 years, BMI: 27.1 ± 5.2 kg/m 2) undergoing gynaecological surgery. Expression levels of 11β-HSD2, H6PDH and GRα were higher in omental adipose tissue while 11β-HSD1 expression was similar between fat compartments. Subcutaneous and omental 11β-HSD1 mRNA abundances were positively associated with total and visceral adiposity whereas omental H6PDH mRNA abundance was negatively associated with these measures. Only omental 11β-HSD1 mRNA expression remained significantly associated with visceral adipose tissue area following statistical adjustment for fat mass, age and menopausal status. Omental 11β-HSD1 mRNA expression explained 19.1% of the variance in visceral adipose tissue area. Omental fat tissue 11β-HSD-1 protein and cortisol levels were higher in visceral obese women, supporting findings obtained with 11β-HSD-1 mRNA. These results suggest that among the transcripts examined only omental 11β-HSD1 is independently associated with visceral obesity in women.

Characterization of gene expression and adipokine secretion during differentiation of primary cultured human omental preadipocytes

Stromal preadipocytes from human omental adipose tissues were isolated with enzyme-digesting method,and cultured for inducing differentiation.Preadipocyte factor-1 was abundant during preadipoeyte stage,whereas lipoprotein lipase and PPARγ2 mRNA were rapidly up-regulated at early stage of differentiation and CCAAT/enhancer binding protein expression was increased rather late.In addition,resistin expression and secretion was primarily detectable in preadipocytes,leptin was gradually increased during adipogenesis,whereas adiponectin appeared specifically in mature adipocytes.Insulin-like growth factor-Ⅰ secretion was remarkably detected in both preadipocytes and mature adipocytes. Key words: Omental adipose tissue; Preadipocyte; Primary cell culture; Adipokine

The inflammatory response seen when human omental adipose tissue explants are incubated in primary culture is not dependent upon albumin and is primarily in the nonfat cells

BackgroundThe present studies were designed to investigate the changes in gene expression during in vitro incubation of human visceral omental adipose tissue explants as well as fat cells and nonfat cells derived from omental fat.MethodsAdipose tissue was obtained from extremely obese women undergoing bariatric surgery. Explants of the tissue as well as fat cells and the nonfat cells derived by digestion with collagenase were incubated for 20 minutes to 48 h. The expression of interleukin 1β [IL-1β], tumor necrosis factor α [TNFα], interleukin 8 [IL-8], NFκB1p50 subunit, hypoxia-inducible factor 1α [HIF1α], omentin/intelectin, and 11β-hydroxysteroid dehydrogenase 1 [11β-HSD1] mRNA were measured by qPCR as well as the release of IL-8 and TNFα.ResultsThere was an inflammatory response at 2 h in explants of omental adipose tissue that was reduced but not abolished in the absence of albumin from the incubation buffer for IL-8, IL-1β and TNFα. There was also an inflammatory response with regard to upregulation of HIF1α and NFκB1 gene expression that was unaffected whether albumin was present or absent from the medium. In the nonfat cells derived by a 2 h collagenase digestion of omental fat there was an inflammatory response comparable but not greater than that seen in tissue. The exception was HIF1α where the marked increase in gene expression was primarily seen in intact tissue. The inflammatory response was not seen with respect to omentin/intelectin. Over a subsequent 48 h incubation there was a marked increase in IL-8 mRNA expression and IL-8 release in adipose tissue explants that was also seen to the same extent in the nonfat cells incubated in the absence of fat cells.ConclusionThe marked inflammatory response seen when human omental adipose tissue is incubated in vitro is reduced but not abolished in the presence of albumin with respect to IL-1β, TNFα, IL-8, and is primarily in the nonfat cells of adipose tissue.

Release of Inflammatory Mediators by Human Adipose Tissue Is Enhanced in Obesity and Primarily by the Nonfat Cells: A Review

This paper considers the role of putative adipokines that might be involved in the enhanced inflammatory response of human adipose tissue seen in obesity. Inflammatory adipokines [IL-6, IL-10, ACE, TGFβ1, TNFα, IL-1β, PAI-1, and IL-8] plus one anti-inflammatory [IL-10] adipokine were identified whose circulating levels as well as in vitro release by fat are enhanced in obesity and are primarily released by the nonfat cells of human adipose tissue. In contrast, the circulating levels of leptin and FABP-4 are also enhanced in obesity and they are primarily released by fat cells of human adipose tissue. The relative expression of adipokines and other proteins in human omental as compared to subcutaneous adipose tissue as well as their expression in the nonfat as compared to the fat cells of human omental adipose tissue is also reviewed. The conclusion is that the release of many inflammatory adipokines by adipose tissue is enhanced in obese humans.