Intermuscular Adipose Tissue and Metabolic Associations in HIV Infection

Intermuscular adipose tissue (IMAT) is associated with metabolic abnormalities similar to those associated with visceral adipose tissue (VAT). Increased IMAT has been found in obese human immunodeficiency virus (HIV)‐infected women. We hypothesized that IMAT, like VAT, would be similar or increased in HIV‐infected persons compared with healthy controls, despite decreases in subcutaneous adipose tissue (SAT) found in HIV infection. In the second FRAM (Study of Fat Redistribution and Metabolic Change in HIV infection) exam, we studied 425 HIV‐infected subjects and 211 controls (from the Coronary Artery Risk Development in Young Adults study) who had regional AT and skeletal muscle (SM) measured by magnetic resonance imaging (MRI). Multivariable linear regression identified factors associated with IMAT and its association with metabolites. Total IMAT was 51% lower in HIV‐infected participants compared with controls (P = 0.003). The HIV effect was attenuated after multivariable adjustment (to ?28%, P < 0.0001 in men and ?3.6%, P = 0.70 in women). Higher quantities of leg SAT, upper‐trunk SAT, and VAT were associated with higher IMAT in HIV‐infected participants, with weaker associations in controls. Stavudine use was associated with lower IMAT and SAT, but showed little relationship with VAT. In multivariable analyses, regional IMAT was associated with insulin resistance and triglycerides (TGs). Contrary to expectation, IMAT is not increased in HIV infection; after controlling for demographics, lifestyle, VAT, SAT, and SM, HIV⁺ men have lower IMAT compared with controls, whereas values for women are similar. Stavudine exposure is associated with both decreased IMAT and SAT, suggesting that IMAT shares cellular origins with SAT.     

Associations of visceral and liver fat with the metabolic syndrome across the spectrum of obesity: the AGES-Reykjavik study

Visceral adipose tissue (VAT) is a key pathogenic fat depot in the metabolic syndrome (MetS), but liver fat (LF) may also play an important role. We evaluated associations of VAT and LF with MetS in normal weight, overweight, and obese men and women (BMI <25, 25-29.9, and ≥30 kg/m2, respectively). This analysis included 2,495 participants from the Age, Gene/Environment Susceptibility (AGES)-Reykjavik study with computed tomography measurements for VAT and LF. MetS was defined by ≥3 of the following: larger abdominal circumference, hypertension, elevated triglyceride (TG), low high-density lipoprotein (HDL), impaired fasting glucose (IFG), and microalbuminuria. We estimated the odds of MetS per 1-s.d. increase in VAT and LF, adjusting for key covariates. VAT was associated with an increased odds of MetS in normal weight, overweight, and obese women (odds ratios (OR) = 2.78, 1.63, and 1.43, respectively; all P < 0.01) that diminished in magnitude with increasing BMI (VAT × BMI class interaction P < 0.001). In men, VAT was related to MetS only among the overweight (OR = 1.69, P < 0.01). LF was associated with MetS in the overweight and obese groups in women (OR = 1.38 and 1.45; both P < 0.001) and in men (OR = 1.38, P = 0.01; and OR = 1.27, P = 0.10), but not in the normal weight groups. These BMI-specific relationships persisted when both fat depots were included in the model. VAT and LF were associated with MetS independently of each other, and these relationships were modified by BMI class such that, VAT was the more important depot at lower levels of obesity and LF at higher levels. Importantly, fatty liver may be a novel metabolic risk factor in overweight and obese individuals.     

Adiposity and hand osteoarthritis: the Netherlands Epidemiology of Obesity study

Introduction

Obesity, usually characterized by the body mass index (BMI), is a risk factor for hand osteoarthritis (OA). We investigated whether adipose tissue and abdominal fat distribution are associated with hand OA.

Methods

The Netherlands Epidemiology of Obesity (NEO) study is a population-based cohort aged 45 to 65 years, including 5315 participants (53% women, median BMI 29.9 kg/m²). Fat percentage and fat mass (FM) (kg) were estimated using bioelectrical impedance analysis. The waist-to-hip ratio (WHR) was calculated. In 1721 participants, visceral adipose tissue (VAT) and subcutaneous adipose tissue (SAT) (cm²) were assessed using abdominal MR imaging. Hand OA was defined according to the ACR criteria.Odds ratios (OR) with 95% confidence intervals (CI) were calculated for the association of fat percentage, FM, WHR, VAT and SAT with hand OA using logistic regression analyses per standard deviation, stratified by sex and adjusted for age.

Results

Hand OA was present in 8% of men and 20% of women. Fat percentage was associated with hand OA in men (OR 1.34 (95% CI 1.11 to 1.61)) and women (OR 1.26 (1.05 to 1.51)), as was FM. WHR was associated with hand OA in men (OR 1.45 (1.13 to 1.85)), and to a lesser extent in women (OR 1.17 (1.00 to 1.36)). Subgroup analysis revealed that VAT was associated with hand OA in men (OR1.33 (1.01 to 1.75)). This association increased after additional adjustment for FM (OR 1.51 (1.13 to 2.03)).

Conclusions

Fat percentage, FM and WHR were associated with hand OA. VAT was associated with hand OA in men, suggesting involvement of visceral fat in hand OA.     

Serum Leptin in Elderly People: Associations with Sex Hormones,Insulin, and Adipose Tissue Volumes

BAUMGARTNER, RICHARD N., ROBERT R. ROSS, DEBRA L. WATERS, WILLIAM M. BROOKS, JOHN E. MORLEY, GEORGE D. MONTOYA, AND PHILIP J. GARRY. Serum leptin in elderly people: associations with sex hormones, insulin, and adipose tissue volumes. Obes Res. Objective There are few data for associations of serum leptin with body fat, fat distribution, sex hormones, or fasting insulin in elderly adults. We hypothesized that the sex difference in serum leptin concentrations would disappear after adjustment for subcutaneous, but not visceral body fat. Serum leptin would not be associated with sex hormone concentrations or serum fasting insulin after adjusting for body fat and fat distribution. Research Methods and Procedures Subcutaneous adipose tissue (SAT) and visceral adipose tissue (VAT) volumes were measured using magnetic resonance imaging in a cross-sectional sample of 56 nondiabetic, elderly men and women aged 64 years to 94 years. Serum leptin, sex hormones (testosterone and estrone), sex hormone-binding globulin, and fasting insulin were also measured. Nine women were taking hormone replacement, and five men were clinically hypogonadal. Results Leptin was significantly associated with both SAT and VAT in each sex. Adjustment for SAT reduced the sex difference in leptin by 56%, but adjustment for VAT increased the difference by 25%. Leptin was not associated with serum estrone or hormone replacement therapy in the women, but had a significant, negative association with testosterone in the men that was independent of SAT, but not VAT. Leptin was significantly associated with fasting insulin in both sexes independent of age, sex hormones, sex hormone-binding globulin, VAT and SAT. Discussion Sex difference in serum leptin is partly explained by different amounts of SAT. Studies including both men and women should adjust for SAT rather than total body fat that includes VAT. The sex difference in serum leptin is not due to estrogen, but may be partly explained by testosterone. Testosterone is negatively associated with leptin in men, but the association is confounded with VAT. Leptin is associated with fasting insulin in non-diabetic elderly men and women independent of body fat, fat distribution. or sex hormones.     

Impacts of Visceral Adipose Tissue and Subcutaneous Adipose Tissue on Metabolic Risk Factors in Middle‐aged Japanese

Regional fat distribution rather than overall fat volume has been considered to be important to understanding the link between obesity and metabolic disorders. We aimed to evaluate the independent associations of visceral adipose tissue (VAT) and subcutaneous adipose tissue (SAT) with metabolic risk factors in apparently healthy middle‐aged Japanese. Participants were 1,119 men and 854 women aged 38–60 years who were not taking medications for diabetes, hypertension, or dyslipidemia. VAT and SAT were measured by use of computed tomography (CT) scanning. VAT and SAT were significantly and positively correlated with each other in men (r = 0.531, P < 0.001) and women (r = 0.589, P < 0.001). In multiple regression analyses, either measure of abdominal adiposity (VAT or SAT) was positively associated with blood pressure, fasting plasma glucose, and log triglyceride (P < 0.001) and inversely with high‐density lipoprotein (HDL)‐cholesterol (P < 0.001). When VAT and SAT were simultaneously included in the model, the association of VAT with triglycerides was maintained (P < 0.001) but that of SAT was lost. The same was true for HDL‐cholesterol in women. For fasting plasma glucose, the association with VAT was strong (P < 0.001) and the borderline association with SAT was maintained (P = 0.060 in men and P = 0.020 in women). Both VAT and SAT were independently associated with blood pressure (P < 0.001). Further adjustment for anthropometric indices resulted in the independent association only with VAT for all risk factors. In conclusion, impacts of VAT and SAT differed among risk factors. VAT showed dominant impacts on triglyceride concentrations in both genders and on HDL‐cholesterol in women, while SAT also had an independent association with blood pressure.     

Visceral and Subcutaneous Adiposity and Brachial Artery Vasodilator Function

Endothelial dysfunction may link obesity to cardiovascular disease (CVD). We tested the hypothesis that visceral abdominal tissue (VAT) as compared with subcutaneous adipose tissue (SAT) is more related to endothelium‐dependent vasodilation. Among Framingham Offspring and Third Generation cohorts (n = 3,020, mean age 50 years, 47% women), we used multivariable linear regression adjusted for CVD and its risk factors to relate computed tomography (CT)‐assessed VAT and SAT, BMI, and waist circumference (WC), with brachial artery measures. In multivariable‐adjusted models, BMI, WC, VAT, and SAT were positively related to baseline artery diameter and baseline mean flow velocity (all P < 0.001), but not hyperemic mean flow velocity. In multivariable‐adjusted models, BMI (P = 0.002), WC (P = 0.001), and VAT (P = 0.01), but not SAT (P = 0.24) were inversely associated with percentage of flow‐mediated dilation (FMD%). However, there was little incremental increase in the proportion of variability explained by VAT (R² = 0.266) as compared to SAT (R² = 0.265), above and beyond traditional risk factors. VAT, but not SAT was associated with FMD% after adjusting for clinical covariates. Nevertheless, the differential association with VAT as compared to SAT was minimal.     

Genome-wide association for abdominal subcutaneous and visceral adipose reveals a novel locus for visceral fat in women

Body fat distribution, particularly centralized obesity, is associated with metabolic risk above and beyond total adiposity. We performed genome-wide association of abdominal adipose depots quantified using computed tomography (CT) to uncover novel loci for body fat distribution among participants of European ancestry. Subcutaneous and visceral fat were quantified in 5,560 women and 4,997 men from 4 population-based studies. Genome-wide genotyping was performed using standard arrays and imputed to ~2.5 million Hapmap SNPs. Each study performed a genome-wide association analysis of subcutaneous adipose tissue (SAT), visceral adipose tissue (VAT), VAT adjusted for body mass index, and VAT/SAT ratio (a metric of the propensity to store fat viscerally as compared to subcutaneously) in the overall sample and in women and men separately. A weighted z-score meta-analysis was conducted. For the VAT/SAT ratio, our most significant p-value was rs11118316 at LYPLAL1 gene (p = 3.1 × 10E-09), previously identified in association with waist-hip ratio. For SAT, the most significant SNP was in the FTO gene (p = 5.9 × 10E-08). Given the known gender differences in body fat distribution, we performed sex-specific analyses. Our most significant finding was for VAT in women, rs1659258 near THNSL2 (p = 1.6 × 10-08), but not men (p = 0.75). Validation of this SNP in the GIANT consortium data demonstrated a similar sex-specific pattern, with observed significance in women (p = 0.006) but not men (p = 0.24) for BMI and waist circumference (p = 0.04 [women], p = 0.49 [men]). Finally, we interrogated our data for the 14 recently published loci for body fat distribution (measured by waist-hip ratio adjusted for BMI); associations were observed at 7 of these loci. In contrast, we observed associations at only 7/32 loci previously identified in association with BMI; the majority of overlap was observed with SAT. Genome-wide association for visceral and subcutaneous fat revealed a SNP for VAT in women. More refined phenotypes for body composition and fat distribution can detect new loci not previously uncovered in large-scale GWAS of anthropometric traits.     

Abdominal Subcutaneous and Visceral Adipose Tissue and Insulin Resistance in the Framingham Heart Study

Insulin resistance is associated with central obesity and an increased risk of cardiovascular disease. Our objective is to examine the association between abdominal subcutaneous (SAT) and visceral adipose tissue (VAT) and insulin resistance, to determine which fat depot is a stronger correlate of insulin resistance, and to assess whether there was an interaction between SAT, VAT, and age, sex, or BMI. Participants without diabetes from the Framingham Heart Study (FHS), who underwent multidetector computed tomography to assess SAT and VAT (n = 3,093; 48% women; mean age 50.4 years; mean BMI 27.6 kg/m²), were evaluated. Insulin resistance was measured using the homeostasis model and defined as HOMA_IR ≥75th percentile. Logistic regression models, adjusted for age, sex, smoking, alcohol, menopausal status, and hormone replacement therapy use, were used to assess the association between fat measures and insulin resistance. The odds ratio (OR) for insulin resistance per standard deviation increase in SAT was 2.5 (95% confidence interval (CI): 2.2–2.7; P < 0.0001), whereas the OR for insulin resistance per standard deviation increase in VAT was 3.5 (95% CI: 3.1–3.9; P < 0.0001). Overall, VAT was a stronger correlate of insulin resistance than SAT (P < 0.0001 for SAT vs. VAT comparison). After adjustment for BMI, the OR of insulin resistance for VAT was 2.2 (95% CI: 1.9–2.5; P < 0.0001). We observed an interaction between VAT and BMI for insulin (P interaction = 0.0004), proinsulin (P interaction = 0.003), and HOMA_IR (P interaction = 0.003), where VAT had a stronger association in obese individuals. In conclusion, SAT and VAT are both correlates of insulin resistance; however, VAT is a stronger correlate of insulin resistance than SAT.     

Visceral and not subcutaneous abdominal adiposity reduction drives the benefits of a 1-year lifestyle modification program

Excess visceral adipose tissue (VAT) is associated with an increased cardiometabolic risk. The study examined whether changes in cardiometabolic risk markers after a 1-year lifestyle intervention in viscerally obese men were associated with changes in VAT or with changes in subcutaneous abdominal adipose tissue (SAT). The relative contributions of changes in global adiposity vs. changes in cardiorespiratory fitness to changes in VAT were also quantified. One hundred and forty four men were selected on the basis of an increased waist circumference (≥ 90 cm) associated with dyslipidemia (triglycerides ≥ 1.69 and/or high-density lipoprotein (HDL)-cholesterol <1.03 mmol/l); 117 men completed the 1-year intervention which consisted in a healthy eating, physical activity/exercise program. Body weight, body composition, and fat distribution were assessed by anthropometry and dual-energy X-ray absorptiometry (DEXA)/computed tomography. Cardiorespiratory fitness, plasma adipokine/inflammatory markers, fasting lipoprotein-lipid profile, and oral glucose tolerance test (OGTT) were assessed. VAT volume decreased by 26%, cardiorespiratory fitness improved by 20% (P < 0.0001) after 1 year. Plasma adipokine/inflammatory markers, lipids/lipoproteins, and glucose homeostasis were improved. One-year changes in triglyceride (r = 0.29), apolipoprotein B (r = 0.21), 120-min OGTT-glucose (r = 0.27), and fasting insulin (r = 0.27) levels correlated with changes in VAT (all P < 0.05) after adjustment for changes in SAT. Using a multilinear regression model, VAT reduction was independently associated with SAT reduction and with improvement in cardiorespiratory fitness (R(2) = 0.58, P < 0.0001). Therefore, this healthy eating-physical activity/exercise program improved the cardiometabolic risk profile of viscerally obese men in relation to the reduction of VAT. Furthermore, the reduction in VAT was independently related to the reduction in global adiposity and to the improvement in cardiorespiratory fitness.     

Femoral-gluteal subcutaneous and intermuscular adipose tissues have independent and opposing relationships with CVD risk.

Femoral-gluteal adipose tissue (AT) may be cardioprotective through fatty acids uptake. Femoral-gluteal AT has previously been defined as leg fat measured by dual energy x-ray absorptiometry (DXA); however, subcutaneous adipose tissue (SAT) and intermuscular adipose tissue (IMAT) are inseparable using DXA. This study investigated the independent relationships between femoral-gluteal SAT, femoral-gluteal IMAT, and cardiovascular disease (CVD) risk factors [fasting serum measures of glucose, total cholesterol (TC), high density lipoprotein cholesterol (HDLC), triglycerides (TG) and insulin] and whether race differences exist in femoral-gluteal AT distribution. Adult Caucasians (56 men and 104 women), African-Americans (37 men and 76 women), and Asians (11 men and 35 women) had total AT (TAT) including femoral-gluteal AT (upper leg SAT and IMAT) and visceral AT (VAT) by magnetic resonance imaging (MRI). General linear models identified the independent effects of femoral-gluteal SAT and femoral-gluteal IMAT on each risk factor after covarying for TAT, VAT, age, race, sex, and two-way interactions. Femoral-gluteal IMAT and glucose (P < 0.05) were positively associated independent of VAT. There were also significant inverse associations between femoral-gluteal SAT and insulin (P < 0.01) and TG (P < 0.05), although the addition of VAT rendered these effects nonsignificant, possibly due to collinearity. Asian women had less femoral-gluteal SAT and greater VAT than Caucasians and African-Americans (P < 0.05) and Asian and African-American men had greater femoral-gluteal IMAT than Caucasians, adjusted for age and TAT (P < 0.05 for both). Femoral-gluteal SAT and femoral-gluteal IMAT distribution varies by sex and race, and these two components have independent and opposing relationships with CVD risk factors.     

Subdivisions of subcutaneous abdominal adipose tissue and insulin resistance

Whereas truncal (central) adiposity is strongly associated with the insulin resistant metabolic syndrome, it is uncertain whether this is accounted for principally by visceral adiposity (VAT). Several recent studies find as strong or stronger association between subcutaneous abdominal adiposity (SAT) and insulin resistance. To reexamine the issue of truncal adipose tissue depots, we performed cross-sectional abdominal computed tomography, and we undertook the novel approach of partitioning SAT into the plane superficial to the fascia within subcutaneous adipose tissue (superficial SAT) and that below this fascia (deep SAT), as well as measurement of VAT. Among 47 lean and obese glucose-tolerant men and women, insulin-stimulated glucose utilization, measured by euglycemic clamp, was strongly correlated with both VAT and deep SAT (r = -0.61 and -0.64, respectively; both P < 0.001), but not with superficial SAT (r = -0.29, not significant). Also, VAT and deep SAT followed a highly congruent pattern of associations with glucose and insulin area under the curve (75-g oral glucose tolerance test), mean arterial blood pressure, apoprotein-B, high-density lipoprotein cholesterol, and triglyceride. Superficial SAT had markedly weaker association with all these parameters and instead followed the pattern observed for thigh subcutaneous adiposity. We conclude that there are two functionally distinct compartments of adipose tissue within abdominal subcutaneous fat and that the deep SAT has a strong relation to insulin resistance.     

Incidental physical activity and sedentary behavior are not associated with abdominal adipose tissue in inactive adults

The aim was to determine the association between objectively measured incidental physical activity (IPA) (i.e.,nonpurposeful activity accrued through activities of daily living) and sedentary behavior (SED) with abdominal obesity in a sample of inactive men and women. Participants were inactive, abdominally obese men (n = 42; waist circumference (WC) ≥102 cm) and women (n = 84; WC ≥88 cm) recruited from Kingston, Canada. Physical activity and SED were determined by accelerometry over 7 days and summarized as IPA (accelerometer counts per min (cpm) >100), light physical activity (LPA; cpm 100-1951), sporadic moderate-to-vigorous physical activity (MVPA; cpm ≥1,952, accumulated in bouts <10 consecutive minutes) and SED (cpm <100). Magnetic resonance imaging was used to acquire measures of abdominal obesity, visceral adipose tissue (VAT), and subcutaneous adipose tissue (ASAT). Participants spent on average 310.2 ± 102.6 min/d in IPA and 627.8 ± 86.9 min/d in SED. Neither IPA nor SED was associated with any measure of abdominal obesity (P > 0.1). Similarly, LPA was not a significant predictor of abdominal obesity whereas sporadic MVPA was negatively associated with VAT (P < 0.05) after control for age and sex. In this study, neither IPA nor SED was associated with abdominal obesity among inactive men and women.     

Associations of visceral and abdominal subcutaneous adipose tissue with markers of cardiac and metabolic risk in obese adults

Objective : Visceral (VAT) and abdominal subcutaneous (SAT) adipose tissues contribute to obesity but may have different metabolic and atherosclerosis risk profiles. We sought to determine the associations of abdominal VAT and SAT mass with markers of cardiac and metabolic risk in a large, multiethnic, population‐based cohort of obese adults. Design and Methods : Among obese participants in the Dallas Heart Study, we examined the cross‐sectional associations of abdominal VAT and SAT mass, assessed by magnetic resonance imaging (MRI) and indexed to body surface area (BSA), with circulating biomarkers of insulin resistance, dyslipidemia, and inflammation (n = 942); and with aortic plaque and liver fat by MRI and coronary calcium by computed tomography (n = 1200). Associations of VAT/BSA and SAT/BSA were examined after adjustment for age, sex, race, menopause, and body mass index. Results : In multivariable models, VAT significantly associated with the homeostasis model assessment of insulin resistance (HOMA‐IR), lower adiponectin, smaller LDL and HDL particle size, larger VLDL size, and increased LDL and VLDL particle number (p < 0.001 for each). VAT also associated with prevalent diabetes, metabolic syndrome, hepatic steatosis, and aortic plaque (p < 0.001 for each). VAT independently associated with C‐reactive protein but not with any other inflammatory biomarkers tested. In contrast, SAT associated with leptin and inflammatory biomarkers, but not with dyslipidemia or atherosclerosis. Associations between SAT and HOMA‐IR were significant in univariable analyses but attenuated after multivariable adjustment. Conclusion : VAT associated with an adverse metabolic, dyslipidemic, and atherogenic obesity phenotype. In contrast, SAT demonstrated a more benign phenotype, characterized by modest associations with inflammatory biomarkers and leptin, but no independent association with dyslipidemia, insulin resistance, or atherosclerosis in obese individuals. These findings suggest that abdominal fat distribution defines distinct obesity sub‐phenotypes with heterogeneous metabolic and atherosclerosis risk.     

Depot-specific regulation of glucose uptake and insulin sensitivity in HIV-lipodystrophy

Altered fat distribution is associated with insulin resistance in HIV, but little is known about regional glucose metabolism in fat and muscle depots in this patient population. The aim of the present study was to quantify regional fat, muscle, and whole body glucose disposal in HIV-infected men with lipoatrophy. Whole body glucose disposal was determined by hyperinsulinemic clamp technique (80 mU x m(-2) x min(-1)) in 6 HIV-infected men and 5 age/weight-matched healthy volunteers. Regional glucose uptake in muscle and subcutaneous (SAT) and visceral adipose tissue (VAT) was quantified in fasting and insulin-stimulated states using 2-deoxy-[18F]fluoro-D-glucose positron emission tomography. HIV-infected subjects with lipoatrophy had significantly increased glucose uptake into SAT (3.8 +/- 0.4 vs. 2.3 +/- 0.5 micromol x kg tissue(-1) x min(-1), P < 0.05) in the fasted state. Glucose uptake into VAT did not differ between groups. VAT area was inversely related with whole body glucose disposal, insulin sensitivity, and muscle glucose uptake during insulin stimulation. VAT area was highly predictive of whole body glucose disposal (r2 = 0.94, P < 0.0001). This may be mediated by adiponectin, which was significantly associated with VAT area (r = -0.75, P = 0.008), and whole body glucose disposal (r = 0.80, P = 0.003). This is the first study to directly demonstrate increased glucose uptake in subcutaneous fat of lipoatrophic patients, which may partially compensate for loss of SAT. Furthermore, we demonstrate a clear relationship between VAT and glucose metabolism in multiple fat and muscle depots, suggesting the critical importance of this depot in the regulation of glucose and highlighting the significant potential role of adiponectin in this process.     

Visceral and Subcutaneous Adiposity and Adiponectin in Middle‐aged Japanese Men: The ERA JUMP Study

Adiponectin is reduced in obesity and has been suggested to play an important role in modulation of atherosclerosis. We studied the relationship between visceral (VAT) and subcutaneous (SAT) adipose tissue and serum adiponectin concentrations in Japanese men. Participants were 304 randomly selected community-based Japanese men aged 40–49 without a prior history of cardiovascular disease. Participants were grouped according to tertiles of serum adiponectin. In multiple linear regression analysis including age, pack years of smoking, and alcohol intake as covariates, log-transformed adiponectin was inversely associated with both VAT and SAT when these two obesity measures were included separately in the models. However, log-transformed adiponectin was inversely associated with VAT (standardized β estimate = −0.465; P < 0.0001) and positively associated with SAT (standardized β estimate = 1.277; P = 0.03), when these were included concomitantly in the model. In conclusion, VAT and SAT had differential associations with serum adiponectin concentrations.     

Visceral fat, waist circumference, and BMI: impact of race/ethnicity

Objective: BMI and waist circumference are used to define risk from excess body fat. Limited data in women suggest that there may be racial/ethnic differences in visceral adipose tissue (VAT) at a given BMI or waist circumference. This study tested the hypothesis that racial/ethnic differences exist in both men and women in the relationship of anthropometric measures of body composition and computed tomography (CT)‐determined VAT or subcutaneous adipose tissue (SAT). Methods and Procedures: Subjects included 66 African American, 72 Hispanic, and 47 white men and women, aged ≥ 45. Waist circumference and BMI were measured using standard methods. Total abdominal and L4L5 VAT and SAT were measured using CT. Results: Among both men and women, groups did not differ in waist circumference or BMI. White men had greater L4L5 VAT than African‐American men, and both white and Hispanic men had greater total VAT than African‐American men. Among women, Hispanics and whites had greater L4L5 VAT than African Americans, and Hispanics had greater total VAT than African Americans. The slope of the linear relationship between BMI or waist circumference and VAT was lower in African Americans than in Hispanics and/or whites. Discussion: Middle‐aged and older African‐American men and women had lower VAT despite similar BMI and waist circumference measurements. Altered relationships between anthropometric measures and VAT may have implications for defining metabolic risk in different populations. Different waist circumference or BMI cutoff points may be necessary to adequately reflect risk in different racial/ethnic groups.     

Both Subcutaneous and Visceral Adipose Tissue Correlate Highly with Insulin Resistance in African Americans

Objective: The contribution of visceral adipose tissue (VAT) to insulin resistance is well‐established; however, the role of subcutaneous abdominal adipose tissue (SAT) in insulin resistance remains controversial. Sex may determine which of these two components of abdominal obesity is more strongly related to insulin resistance and its consequences. The aim of this study was to determine whether both VAT and SAT contribute to insulin resistance in African Americans and to examine the effects of sex on this relationship. Research Methods and Procedures: This was a cross‐sectional study of 78 nondiabetic African‐American volunteers (44 men, 35 women; age 33.8 ± 7.3 years; BMI 30.9 ± 7.4 kg/m²). VAT and SAT volumes were measured using serial computerized tomography slices from the dome of the diaphragm to the iliac crest. The insulin sensitivity index (S_I) was determined from the minimal model using data obtained from the frequently sampled intravenous glucose tolerance test. Results: In men, both VAT and SAT were negatively correlated with S_I (r for both correlations = ?0.57; p < 0.01). In women, the correlation coefficient between VAT and S_I was ?0.50 (p < 0.01) and between SAT and S_I was ?0.67 (p < 0.01). In women, the correlation coefficient for S_I with SAT was significantly greater than the correlation coefficient with VAT (p = 0.02). Discussion: Both SAT and VAT are strongly correlated with insulin resistance in African Americans. For African‐American women, SAT may have a greater effect than VAT on insulin resistance.     

Impact of Race/Ethnicity on the Relationship Between Visceral Fat and Inflammatory Biomarkers

The purpose of this study was to determine whether racial/ethnic differences exist in the relationship between visceral adipose tissue (VAT) and selected inflammatory biomarkers. Subjects included 136 African‐American, 133 Hispanic, and 100 white men and women, aged ≥45. Waist circumference and BMI were measured using standard methods. Total VAT, and VAT and subcutaneous adipose tissue (SAT) at the L4L5 spinal level were measured using computed tomography. Interleukin‐6 (IL‐6), C‐reactive protein (CRP), and fibrinogen were measured from fasting blood samples. Results revealed that waist circumference and BMI were similar among groups but African Americans had significantly lower L4L5 VAT compared with Hispanics and whites. Despite lower VAT, African‐American men had similar concentrations of inflammatory biomarkers. On the other hand, African‐American women had higher CRP and IL‐6 than white women, and higher fibrinogen than both Hispanic and white women. After controlling for L4L5 VAT, L4L5 SAT, and age, African‐American women had higher concentrations of IL‐6 and fibrinogen. Stratified analyses for CRP indicated that L4L5 SAT was associated with CRP in African‐American and white women after controlling for L4L5 VAT and age, but that the reverse was not true. These data indicate that African Americans had lower VAT but similar or higher concentrations of inflammatory biomarkers. African‐American women consistently displayed greater inflammation compared with whites, even after controlling for VAT or SAT.     

Elevation in cardiovascular disease risk in South Asians is mediated by differences in visceral adipose tissue

South Asians have a higher risk for cardiovascular disease (CVD) that remains largely unexplained. We hypothesized that the increased CVD risk in South Asians compared to Europeans is mediated through higher levels of visceral adipose tissue (VAT) in South Asians compared to total body fat and subcutaneous abdominal adipose tissue (SAT). South Asians (207) and Europeans (201) underwent assessment for demographics, body fat, and risk factors. Linear regression models were created by sex for each risk factor to explore mediation effects of total body fat, SAT, and VAT adjusted for age, income, smoking, and BMI (menopausal status for women). Mediation was based on changes in the ethnicity β coefficient due to additional adjustment for our adipose variable of interest and the Sobel test for mediation. South Asians had worse lipid, glucose, insulin, and C-reactive protein (CRP) levels than Europeans after adjusting for confounders. Most of these differences remained even after further adjustment by either total body fat or SAT. In contrast, VAT attenuated the ethnic differences in risk factors by 16%-52%. After adjusting for VAT, there were no longer ethnic differences in total cholesterol (TC), LDL-C, TC/HDL-C, glucose, and diastolic blood pressure (BP) in men, and in HDL-C, triglycerides (TG), TC/HDL-C, and homeostasis model (HOMA) in women, and VAT was a significant mediator for these risk factors. Higher levels of risk factors for CVD in South Asians are predominantly because of the unique phenotype of South Asians having greater VAT than Europeans even at the same BMI.     

Dietary patterns,abdominal visceral adipose tissue,and cardiometabolic risk factors in African Americans: The Jackson heart study

Objective:

To examine the relative association of abdominal visceral adipose tissue (VAT) with cardiometabolic risk factors between African and European Americans.

Design and Methods:

We conducted a cross‐sectional study of 2035 African Americans from Jackson Heart Study (JHS) and 3170 European Americans from Framingham Heart Study (FHS) who underwent computed tomography assessment of VAT and subcutaneous adipose tissue (SAT). The FHS participants were weighted to match the age distribution of the JHS participants and the metabolic risk factors were examined by study groups in relation to VAT.

Results:

JHS participants had higher rates of obesity, hypertension, diabetes and metabolic syndrome than FHS participants (all p = 0.001). The associations were weaker in JHS women for VAT with blood pressure, triglycerides, HDL‐C, and total cholesterol (p_interaction = 0.03 to 0.001) than FHS women. In contrast, JHS men had stronger associations for VAT with high triglycerides, low HDL, and metabolic syndrome (all p_interaction = 0.001) compared to FHS men. Similar associations and gender patterns existed for SAT with most metabolic risk factors.

Conclusions:

The relative association between VAT and cardiometabolic risk factors is weaker in JHS women compared to FHS women, whereas stronger association with triglycerides and HDL were observed in JHS men.