Impact of HIV/simian immunodeficiency virus infection and viral proteins on adipose tissue fibrosis and adipogenesis

Visceral Adipose Tissue Attacks Beyond the Liver: Esophagogastric Junction as a New Target

Body fat distribution contributes to obesity-related metabolic and cardiovascular disorders. Visceral fat is more detrimental than subcutaneous fat. However, the mechanisms underlying visceral fat-mediated cardiometabolic dysregulation are not completely understood. Localized increases in expression of the renin angiotensin system (RAS) in adipose tissue (AT) may be implicated. We therefore investigated mRNA and protein expression of RAS components in visceral versus subcutaneous AT using paired samples from individuals undergoing surgery (N = 20, body mass index: 45.6 ± 6.2 kg/m2, and age: 44.6 ± 9.1 years). We also examined RAS-related proteins in AT obtained from individuals on renin angiotensin aldosterone system (RAAS) targeted drugs (N = 10, body mass index: 47.2 ± 9.3 kg/m2, and age: 53.3 ± 10.1 years). Comparison of protein expression between subcutaneous and visceral AT samples showed an increase in renin (p = 0.004) and no change in angiotensinogen (p = 0.987) expression in visceral AT. Among proteins involved in angiotensin peptide generation, angiotensin converting enzyme (p = 0.02) was increased in subcutaneous AT while chymase (p = 0.001) and angiotensin converting enzyme-2 (p = 0.001) were elevated in visceral fat. Furthermore, visceral fat expression of angiotensin II type-2 receptor (p = 0.007) and angiotensin II type-1 receptor (p = 0.031) was higher, and MAS receptor (p < 0.001) was lower. Phosphorylated-p53 (p = 0.147), AT fibrosis (p = 0.138) and average adipocyte size (p = 0.846) were similar in the two depots. Nonetheless, visceral AT showed increased mRNA expression of inflammatory (TNFα, p < 0.001; IL-6, p = 0.001) and oxidative stress markers (NOX2, p = 0.038; NOX4, p < 0.001). Of note, mRNA and protein expression of RAS components did not differ between subjects taking or not taking RAAS related drugs. In summary, several RAS related proteins are differentially expressed in subcutaneous versus visceral AT. This differential expression may not alter AngII but likely increases Ang1-7 generation in visceral fat. These potential differences in active angiotensin peptides and receptor expression in the two depots suggest that localized RAS may not be involved in differences in visceral vs subcutaneous AT function in obese individuals. Our findings do not support a role for localized RAS differences in visceral fat-mediated development of cardiovascular and metabolic pathology.

We examined the independent relationships among various visceral and abdominal subcutaneous adipose tissue (AT) depots, glucose tolerance, and insulin sensitivity in 89 obese men. Measurements included an oral glucose tolerance test (OGTT), glucose disposal by euglycemic clamp, and abdominal and nonabdominal (e.g., peripheral) AT by magnetic resonance imaging (MRI). OGTT glucose and glucose disposal rates were related (P < 0.05) to visceral AT (r = 0.50 and -0.41, respectively). These observations remained significant (P < 0.05) after control for nonabdominal and abdominal subcutaneous AT, and maximal O(2) consumption (VO(2 max)). Abdominal subcutaneous AT was not a significant correlate (P > 0.05) of any metabolic variable after control for nonabdominal and visceral AT and VO(2 max). Division of abdominal subcutaneous AT into deep and superficial depots and visceral AT into intra- and extraperitoneal AT depots did not alter the observed relationships. Further analysis matched two groups of men for abdominal subcutaneous AT but also for low and high visceral AT. Men with high visceral AT had higher OGTT glucose values and lower glucose disposal rates compared with those with low visceral AT values (P < 0.05). A similar analysis performed on two groups of men matched for visceral AT but also for high and low abdominal subcutaneous AT revealed no statistically different values for any metabolic variable (P > 0.10). In conclusion, visceral AT alone is a strong correlate of insulin resistance independent of nonabdominal and abdominal subcutaneous AT and cardiovascular fitness. Subdivision of visceral and abdominal subcutaneous AT by MRI did not provide additional insight into the relationship between abdominal obesity and metabolic risk in obese men.

Effect of Central Obesity on Prostate Specific Antigen Measured by Computerized Tomography: Related Markers and Prostate Volume

Visceral adipose tissue (VAT) compartments may confer increased metabolic risk. The incremental utility of measuring both visceral and subcutaneous abdominal adipose tissue (SAT) in association with metabolic risk factors and underlying heritability has not been well described in a population-based setting. Participants (n=3001) were drawn from the Framingham Heart Study (48% women; mean age, 50 years), were free of clinical cardiovascular disease, and underwent multidetector computed tomography assessment of SAT and VAT volumes between 2002 and 2005. Metabolic risk factors were examined in relation to increments of SAT and VAT after multivariable adjustment. Heritability was calculated using variance-components analysis. Among both women and men, SAT and VAT were significantly associated with blood pressure, fasting plasma glucose, triglycerides, and high-density lipoprotein cholesterol and with increased odds of hypertension, impaired fasting glucose, diabetes mellitus, and metabolic syndrome (P range < 0.01). In women, relations between VAT and risk factors were consistently stronger than in men. However, VAT was more strongly correlated with most metabolic risk factors than was SAT. For example, among women and men, both SAT and VAT were associated with increased odds of metabolic syndrome. In women, the odds ratio (OR) of metabolic syndrome per 1-standard deviation increase in VAT (OR, 4.7) was stronger than that for SAT (OR, 3.0; P for difference between SAT and VAT < 0.0001); similar differences were noted for men (OR for VAT, 4.2; OR for SAT, 2.5). Furthermore, VAT but not SAT contributed significantly to risk factor variation after adjustment for body mass index and waist circumference (P < or = 0.01). Among overweight and obese individuals, the prevalence of hypertension, impaired fasting glucose, and metabolic syndrome increased linearly and significantly across increasing VAT quartiles. Heritability values for SAT and VAT were 57% and 36%, respectively. Although both SAT and VAT are correlated with metabolic risk factors, VAT remains more strongly associated with an adverse metabolic risk profile even after accounting for standard anthropometric indexes. Our findings are consistent with the hypothesized role of visceral fat as a unique, pathogenic fat depot. Measurement of VAT may provide a more complete understanding of metabolic risk associated with variation in fat distribution.

Adipose tissue dysfunction is associated with inflammation, type 2 diabetes mellitus and vascular diseases. Visceral adipose tissue (VAT)-derived adipokines, which are released in the portal circulation may influence liver metabolism. (1) To estimate the contribution of VAT and subcutaneous adipose tissue (SAT) on adipokine levels by measuring differences in adipokine concentrations between the portal draining inferior mesenteric vein and the subclavian vein. (2) To determine the relation of both VAT and SAT quantity and composition to mesenteric and systemic concentrations of adipokines. Cross-sectional cohort study. A total of 32 patients undergoing abdominal aortic surgery. A panel of 18 adipokines was measured in perioperatively obtained blood samples from the subclavian vein and the inferior mesenteric vein. Adipocyte size, macrophage infiltration and capillary density were measured in subcutaneous and mesenteric adipose tissue biopsies; SAT and VAT areas were measured on computed tomography images. Serum interferon-γ-inducible protein 10 (IP-10) and hepatocyte growth factor (HGF) concentrations were significantly higher in the inferior mesenteric vein vs the subclavian vein. SAT area (β -18; 95% confidence interval (CI) -35 to -2), subcutaneous adipocyte size (β -488; 95% CI -938 to -38) and SAT macrophages quantity (β -1439; 95% CI -2387 to -491) were negatively associated with adiponectin levels in the systemic circulation. SAT area was related to systemic concentrations of leptin. Mesenteric adiponectin concentrations were related to VAT area (β -20; 95% CI -35 to -5) and visceral adipocyte size (β -1076; 95% CI -1624 to -527). VAT area, adipocyte size and capillary density were related to systemic adiponectin concentrations. SAT and VAT quantities as well as morphologic characteristics of both adipose tissue depots are related to systemic and mesenteric adipokine concentrations. There were no differences in adipokine concentrations between the mesenteric and subclavian vein, except for higher IP-10 and HGF concentrations in the inferior mesenteric vein, indicating a possible contribution of VAT to IP-10 and HGF levels.

Long-chain fatty acids (LCFAs) cross the plasma membrane via a protein-mediated mechanism involving one or more LCFA-binding proteins. Among these, FAT/CD36 has been identified as key LCFA transporter in the heart and skeletal muscle, where it is regulated acutely and chronically by insulin. In skeletal muscle, FAT/CD36 expression and/or subcellular distribution is altered in obesity and type 2 diabetes. There is limited information as to whether the expression of this protein is also altered in subcutaneous and/or visceral adipose tissue depots in human obesity or type 2 diabetes. To compare (a) the expression of FAT/CD36 in subcutaneous and visceral adipose tissue depots in lean, overweight, and obese individuals and in type 2 diabetics, (b) to determine whether the protein expression of FAT/CD36 in these depots is associated with the severity of insulin resistance (type 2 diabetes>obese>overweight/lean) and (c) whether FAT/CD36 protein expression in these adipose tissue depots is associated with alterations in circulating substrates and hormones. Subjects who were undergoing abdominal surgery and who were lean (n=10; three men, seven women), overweight (n=10; three men, seven women) or obese (n=7; one man, six women), or who had been diagnosed with type 2 diabetes (n=5; one man, four women) participated in this study. Subcutaneous and visceral adipose tissue samples, as well as blood samples, were obtained from the subjects while under general anesthesia. Adipose tissue samples were analyzed for FAT/CD36 using Western blotting. Serum samples were analyzed for glucose, insulin, FFA and leptin. BMI was also calculated. Subcutaneous adipose tissue FAT/CD36 expression was upregulated by +58, +76 and +150% in overweight, obese and type 2 diabetics, respectively. Relative to subcutaneous adipose tissue, visceral adipose tissue FAT/CD36 expression was upregulated in lean (+52%) and overweight subjects (+30%). In contrast, in obese subjects and type 2 diabetics, no difference in FAT/CD36 protein expression was observed between their subcutaneous and visceral adipose tissue depots (P>0.05). The subcutaneous adipose tissue FAT/CD36 expression (R=0.85) and the visceral adipose tissue FAT/CD36 expression (R=0.77) were associated with alteration in BMI and circulating glucose and insulin. Subcutaneous adipose tissue FAT/CD36 expression is upregulated in obesity and type 2 diabetes. As FAT/CD36 expression is not different in lean, overweight and obese subjects, and was only increased in type 2 diabetics, it appears that visceral adipose tissue FAT/CD36 may respond in a less dynamic manner to metabolic disturbances than subcutaneous adipose tissue FAT/CD36.

Dietary Fatty Acid Composition Is Associated with FTO Gene Expression in Human Visceral and Subcutaneous Adipose Tissues

The human obesity susceptibility gene, FTO, associates with body mass and obesity in humans through regulation of energy expenditure and intake. We aimed to determine how fatty acids in plasma and in diet associate with FTO gene expression in subcutaneous and visceral adipose tissues. In this study, 97 participants aged ≥ 18years were selected from patients admitted to the hospital for abdominal surgeries. Habitual dietary intake of participants was collected using a valid and reliable food frequency questionnaire (FFQ), from which the intake of fatty acids was quantified. Plasma fatty acids were assessed by gas-liquid chromatography. The mRNA expression of the FTO gene in visceral and subcutaneous adipose tissues obtained by biopsy was measured by Real-Time Quantitative Reverse Transcription PCR. Standardized β-coefficients were calculated by multivariable linear regression. After adjusting for age, homeostasis model insulin resistance index (HOMA-IR), and body mass index, total fatty acid intake was significantly associated with FTO gene expression in visceral (STZβ = 0.208, P = 0.037) and subcutaneous (STZβ = 0.236, P = 0.020) adipose tissues. Dietary intake of monounsaturated fatty acid (MUFA) and polyunsaturated fatty acids (PUFA) had positive significant associations with the expression of FTO in visceral (STZβ = 0.227, P = 0.023; STZβ = 0.346, P < 0.001, respectively) and subcutaneous (STZβ = 0.227, P = 0.026; STZβ = 0.274, P = 0.006, respectively) adipose tissues. There were no associations between plasma fatty acids and FTO mRNA expression in either subcutaneous or visceral adipose tissues. The weak association of dietary total fatty acids, MUFA, and PUFA with FTO gene expression in both adipose tissues may highlight the importance of dietary fatty acids composition along with total fat intake in relation to FTO gene expression.

Lower expression of adiponectin mRNA in visceral adipose tissue in lean and obese subjects

Increased Glucose Uptake in Visceral Versus Subcutaneous Adipose Tissue Revealed by PET Imaging

Introduction: Asian Indians show “thin fat phenotype” characterized by higher visceral adipose tissue(VAT) and lower subcutaneous adipose tissue(SAT) mass and their higher cardio-metabolic risk has been attributed to this fat distribution. However, the underlying molecular pathology and role of these adipose depots in the pathogenesis of T2D in them remains unknown.Hypothesis: The comparison of transcription profiles of abdominal VAT and SAT and their correlation with diabetes related intermediate phenotypic traits could shed some light on their role in the pathophysiology of diabetes.MethodologySubjects: 19 diabetics (M: F ratio, 8:11) and 16 age and BMI matched controls (M: F ratio 5:11) undergoing abdominal surgery (non-malignant and non-infective conditions).Clinical Parameters: Anthropometry, Serum glucose, insulin, HOMA-R, HbA1c, lipid profile, FFA, adipocytokines. Abdominal VAT, SAT and liver fat were estimated by MRI.Adipose tissue biopsy: SAT and VAT samples were taken during surgery. Genome-wide gene expression profiling of these biopsies was performed using Affymetrix GeneChipPrimeView® arrays. The data was submitted to NCBI-GEO (Accession # GSE78721). Selected genes were validated by qPCR. Gene set enrichment analysis (GSEA) for functional and Weighted Gene Correlation Analysis (WGCNA) for statistical comparison was done.Results:Diabetics had higher waist circumference (p=0.05), HOMA-R (p=0.0002), Visceral fat content (p=0.02) and adipocyte size (p=0.02)GSEA: diabetics vs. controls: In VAT 16 gene sets were upregulated (FDR < 25%) enriching various immune system and inflammation-related pathways. In SAT too, various inflammatory genes were upregulated however they were statistically non-significant (FDR > 25%). Moreover, 12 out of 16 significantly enriched pathways in VAT were among the top 20 pathways in SAT. GSEA in diabetics: VAT vs SAT: None of the gene sets were found significant at FDR < 25% which substantiated our hypothesis that overall pathophysioloigcal alteration in both depots are similar. WGCNA for statistical comparison of VAT and SAT depots The correlation between measures of average gene expression and overall connectivity between both depots was significantly positive. Several modules of co-expressed genes in both VAT and SAT showed positive as well as negative correlation with various intermediate phenotypic traits of diabetes. In both depots they enriched several pathways otherwise known to be associated with pathological adipose tissue like inflammation, adipogenesis etc.ConclusionsIn Asian Indians, diabetes pathology inflicts similar molecular alternations in VAT and SAT, which are more intense in the former. The role of both adipose depots in the pathophysiology of diabetes is along similar lines and they enrich several molecular pathways which are otherwise known to be implicated in pathological adipose tissue.

To study abdominal fat distribution in anorexia nervosa subjects and to assess the effects of initial weight regain on abdominal fat distribution. Longitudinal, clinical study. The baseline measurement was acquired within four days of admission to the eating disorders clinic. All patients were treated by re-feeding, reinforced by psychotherapy. Following weight regain of at least 5 kg, a second body fat distribution evaluation was performed. Of the 21 subjects evaluated at baseline, 14 achieved the goal of body weight regain and were retested. Fourteen subjects (age: 18-38 y; body mass index: 11.5-18.3; relative body weight: 54.9-88.3%). Total, subcutaneous and visceral abdominal adipose tissue areas at the L4-L5 level were evaluated by computed tomography. At baseline the subjects showed a higher proportion of visceral adipose tissue (% visceral adipose tissue = 55.3 +/- 26.1). A significant association was observed between body weight and both subcutaneous adipose tissue and total adipose tissue. A regain of body weight of 7.3 +/- 1.6 kg was accompanied by a significant increase in total adipose tissue, comprising both subcutaneous and visceral adipose tissue. The increase observed in subcutaneous adipose tissue, however, was significantly greater than for visceral adipose tissue (212.6% vs 116.8%, respectively, P < 0.01). The results of the current study show a higher proportion of visceral adipose tissue than subcutaneous adipose tissue in anorexia nervosa subjects. With regain of body weight there is a preferential regain of subcutaneous adipose tissue. These data demonstrate a redistribution of abdominal adipose tissue with weight regain in anorexia nervosa subjects.

Towards addressing questions related to HIV pathogenesis and vaccine design we are fortunate to have the availability of the SIV-infected rhesus macaque model. The strengths of this model which include a rapid rate of progression to AIDS and knowledge of the dose route and strain of the infecting virus complement studies in HIV-infected patients in which the reagents host genetics and access to samples are more extensive and better defined. Unfortunately there is currently still too little known about the antiviral immune responses in either system to directly and accurately compare their similarities and differences and to draw any definitive conclusions. Therefore the data and views presented herein will simply reflect what has recently been discovered in both humans and non-human primate studies. (excerpt)

Effects of Growth Hormone on Visceral Adipose Tissue and Dyslipidemia in HIV, an Erratum