Ethnic and sex differences in visceral,subcutaneous, and total body fat in children and adolescents

Objective: This study investigated ethnic and sex differences in the distribution of fat during childhood and adolescence. Design and Methods : A cross‐sectional sample (n = 382), aged 5–18 years, included African American males (n = 84), White males (n = 96), African American females (n = 118), and White females (n = 84). Measures for total body fat (TBF) mass and abdominal adipose tissue (total volume and L4‐L5 cross‐sectional area) for both subcutaneous adipose tissue (SAT) and visceral adipose tissue (VAT) depots were assessed by dual‐energy X‐ray absorptiometry and magnetic resonance image, respectively. Analyses of covariance (ANCOVAs) were used to determine ethnic and sex differences in TBF (adjusted for age) and ethnic and sex differences in SAT and VAT (adjusted for both age and TBF). Results: Age‐adjusted TBF was greater in African Americans (P = 0.017) and females (P < 0.0001) compared with Whites and males, respectively. In age‐ and TBF‐adjusted ANCOVAs, no differences were found in the SAT. The VAT volume was, however, greater in Whites (P < 0.0001) and males (P < 0.0001) compared with African Americans and females, respectively. Similar patterns were observed in SAT and VAT area at L4‐L5. Conclusions: The demonstrated ethnic and sex differences are important confounders in the prevalence of obesity and in the assignment of disease risk in children and adolescents.     

Adiponectin and leptin in African Americans

Objective: African Americans (AAs) have less visceral and more subcutaneous fat than whites, thus the relationship of adiponectin and leptin to body fat and insulin sensitivity in AA may be different from that in whites. Methods and Procedures: Sixty‐nine non‐diabetic AA (37 men and 32 women), aged 33 ± 1 year participated. The percent fat was determined by dual‐energy X‐ray absorptiometry, abdominal visceral adipose tissue (VAT) and subcutaneous adipose tissue (SAT) volume by computerized tomography (CT), and insulin sensitivity by homeostasis model assessment (HOMA). Results: VAT was greater in men (1,619 ± 177 cm³ vs. 1,022 ± 149 cm³; P = 0.01); women had a higher percentage of body fat (34.1 ± 1.4 vs. 24.0 ± 1.2; P < 0.0001), adiponectin (15.8 ± 1.2 μg/ml vs. 10.4 ± 0.8 μg/ml; P = 0.0004) and leptin (23.2 ± 15.8 ng/ml vs. 9.2 ± 7.2 ng/ml; P < 0.0001). SAT and HOMA did not differ because of the sex. Adiponectin negatively correlated with VAT (r = ?0.41, P < 0.05) in men, and with VAT (r = ?0.55, P < 0.01), and SAT (r = ?0.35, P < 0.05) in women. Adiponectin negatively correlated with HOMA in men (r = ?0.38, P < 0.05) and women (r = ?0.44, P < 0.05). In multiple regression, sex (P = 0.02), HOMA (P = 0.03) and VAT (P = 0.003) were significant predictors of adiponectin (adj R ² = 0.38, P < 0.0001). Leptin positively correlated with VAT, SAT, percent fat and HOMA in men (r = 0.79, r = 0.86, r = 0.89, and r = 0.53; P < 0.001) and women (r = 0.62, r = 0.75, r = 0.83, and r = 0.55; P < 0.01). In multiple regression VAT (P = 0.04), percent body fat (P < 0.0001) and sex (P = 0.01), but not HOMA were significant predictors of serum leptin (adj R ²= 0.82, P < 0.0001). Discussion: The relationship of adiponectin and leptin to body fat content and distribution in AA is dependent on sex. Although VAT and insulin sensitivity are significant determinants of adiponectin, VAT and percent body fat determine leptin.     

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.     

Comparison of Regional Fat Distribution and Health Risk Factors in Middle‐Aged White and African American Women: The Healthy Transitions Study

Objective: Both ethnicity and menopause appear to influence intra‐abdominal fat distribution. This study evaluated intra‐abdominal fat distribution and obesity‐related health risks in perimenopausal white and African American women. Research Methods and Procedures: Baseline data from a longitudinal study of changes in body composition and energy balance during menopause are reported. Healthy women (55 African Americans and 103 whites) who were on no medication and had at least five menstrual cycles in the previous 6 months were recruited. Body composition was assessed by DXA, and visceral adipose tissue (VAT) and subcutaneous adipose tissue (SAT) were assessed by computed tomography scan. SAT was divided into deep and superficial layers demarcated by the fascia superficialis. Results: African American women were slightly younger (46.7 ± 0.2 vs. 47.7 ± 0.2 years, p = 0.002) and fatter (42.4% ± 1.0% vs. 39.4% ± 0.8% body fat, p = 0.02) than white women. In unadjusted data, African Americans had significantly more total abdominal fat and total, deep, and superficial SAT than whites. After adjustment for percent body fat and age, only total and superficial SAT remained significantly higher in African Americans. VAT although slightly less in African American women, did not differ significantly by race. In multiple regression analysis, VAT was the strongest predictor of serum lipids, glucose, and insulin in women of both races, although superficial SAT was significantly associated with fasting glucose in whites. Conclusions: Middle‐aged African American women have larger SAT depots, adjusted for total body fatness, but do not differ from white women with regard to VAT. The complexity of the relationship between abdominal fat and metabolic risk is increased by ethnic differences in such associations.     

Adipose tissue R2* signal is increased in subjects with obesity: A preliminary MRI study

Objective : Circulating and adipose tissue markers of iron overload are increased in subjects with obesity. The aim is to study iron signals in adipose tissue. Methods: Adipose tissue R2* values and hepatic iron concentration (HIC) were evaluated using magnetic resonance imaging (MRI) in 23 middle‐aged subjects with obesity and 20 subjects without obesity. Results: Subcutaneous (SAT) and visceral adipose tissue (VAT) R2* were increased in subjects with obesity (P = 0.004 and P = 0.008) and correlated significantly and positively with HIC in all subjects. Strikingly, most of the associations of liver iron with metabolic parameters were replicated with SAT and VAT R2*. BMI, waist circumference, fat mass, HOMA value, and C‐reactive protein positively correlated with HIC and SAT and VAT R2*. BMI or percent fat mass (but not insulin resistance) contributed independently to 26.8‐34.8% of the variance in sex‐ and age‐adjusted SAT or VAT R2* (β > 0.40, P < 0.005). Within subjects with obesity, total cholesterol independently contributed to 14.8% of sex‐ and age‐adjusted VAT iron variance (β = 0.50, P = 0.025). Conclusions: Increased R2* in adipose tissue, which might indicate iron content, runs in parallel to liver iron stores of subjects with obesity. VAT iron seems also associated with serum cholesterol within subjects with obesity.     

The Human Visceral Fat Depot Has a Unique Inflammatory Profile

Obesity can be considered as a low‐grade inflammatory condition, strongly linked to adverse metabolic outcomes. Obesity‐associated adipose tissue inflammation is characterized by infiltration of macrophages and increased cytokine and chemokine production. The distribution of adipose tissue impacts the outcomes of obesity, with the accumulation of fat in visceral adipose tissue (VAT) and deep subcutaneous adipose tissue (SAT), but not superficial SAT, being linked to insulin resistance. We hypothesized that the inflammatory gene expression in deep SAT and VAT is higher than in superficial SAT. A total of 17 apparently healthy women (BMI: 29.3±5.5 kg/m²) were included in the study. Body fat (dual‐energy X‐ray absorptiometry) and distribution (computed tomography) were measured, and insulin sensitivity, blood lipids, and blood pressure were determined. Inflammation‐related differences in gene expression (real‐time PCR) from VAT, superficial and deep SAT biopsies were analyzed using univariate and multivariate data analyses. Using multivariate discrimination analysis, VAT appeared as a distinct depot in adipose tissue inflammation, while the SAT depots had a similar pattern, with respect to gene expression. A significantly elevated (P < 0.01) expression of the CC chemokine receptor 2 (CCR2) and macrophage migration inhibitory factor (MIF) in VAT contributed strongly to the discrimination. In conclusion, the human adipose tissue depots have unique inflammatory patterns, with CCR2 and MIF distinguishing between VAT and the SAT depots.     

A Single mri Slice Does Not Accurately Predict Visceral and Subcutaneous Adipose Tissue Changes During Weight Loss

Earlier cross‐sectional studies found that a single magnetic resonance imaging (MRI) slice predicts total visceral and subcutaneous adipose tissue (VAT and SAT) volumes well. We sought to investigate the accuracy of trunk single slice imaging in estimating changes of total VAT and SAT volume in 123 overweight and obese subjects who were enrolled in a 24‐week CB‐1R inverse agonist clinical trial (weight change, ?7.7 ± 5.3 kg; SAT change, ?5.4 ± 4.9 l, VAT change, ?0.8 ± 1.0 l). VAT and SAT volumes at baseline and 24 weeks were derived from whole‐body MRI images. The VAT area 5–10 cm above L₄—L₅ (A_+5–10) (R² = 0.59–0.70, P < 0.001) best predicted changes in VAT volume but the strength of these correlations was significantly lower than those at baseline (R² = 0.85–0.90, P < 0.001). Furthermore, the L₄—L₅ slice poorly predicted VAT volume changes (R² = 0.24–0.29, P < 0.001). Studies will require 44–69% more subjects if (A_+5–10) is used and 243–320% more subjects if the L₄—L₅ slice is used for equivalent power of multislice total volume measurements of VAT changes. Similarly, single slice imaging predicts SAT loss less well than cross‐sectional SAT (R² = 0.31–0.49 vs. R² = 0.52–0.68, P < 0.05). Results were the same when examined in men and women separately. A single MRI slice 5–10 cm above L₄—L₅ is more powerful than the traditionally used L₄—L₅ slice in detecting VAT changes, but in general single slice imaging poorly predicts VAT and SAT changes during weight loss. For certain study designs, multislice imaging may be more cost‐effective than single slice imaging in detecting changes for VAT and SAT.     

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.     

Differential Effects of Abdominal Adipose Tissue Distribution on Insulin Sensitivity in Black and White South African Women

Black South African women are more insulin resistant than BMI‐matched white women. The objective of the study was to characterize the determinants of insulin sensitivity in black and white South African women matched for BMI. A total of 57 normal‐weight (BMI 18–25 kg/m²) and obese (BMI > 30 kg/m²) black and white premenopausal South African women underwent the following measurements: body composition (dual‐energy X‐ray absorptiometry), body fat distribution (computerized tomography (CT)), insulin sensitivity (S_I, frequently sampled intravenous glucose tolerance test), dietary intake (food frequency questionnaire), physical activity (Global Physical Activity Questionnaire), and socioeconomic status (SES, demographic questionnaire). Black women were less insulin sensitive (4.4 ± 0.8 vs. 9.5 ± 0.8 and 3.0 ± 0.8 vs. 6.0 ± 0.8 × 10^?5/min/(pmol/l), for normal‐weight and obese women, respectively, P < 0.001), but had less visceral adipose tissue (VAT) (P = 0.051), more abdominal superficial subcutaneous adipose tissue (SAT) (P = 0.003), lower SES (P < 0.001), and higher dietary fat intake (P = 0.001) than white women matched for BMI. S_I correlated with deep and superficial SAT in both black (R = ?0.594, P = 0.002 and R = 0.495, P = 0.012) and white women (R = ?0.554, P = 0.005 and R = ?0.546, P = 0.004), but with VAT in white women only (R = ?0.534, P = 0.005). In conclusion, body fat distribution is differentially associated with insulin sensitivity in black and white women. Therefore, the different abdominal fat depots may have varying metabolic consequences in women of different ethnic origins.     

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.     

Dietary fat and weight gain among women in the Nurses' Health Study

Objective: To assess the association of dietary fat and weight gain among adult women and to investigate whether offspring of overweight parents have a greater predisposition to weight gain due to intake of dietary fat. Research Methods and Procedures: This was an 8‐year follow‐up of 41,518 women in the Nurses’ Health Study (NHS), a population‐based, prospective cohort. The women were 41 to 68 years of age, free of cardiovascular disease, cancer, and diabetes in 1986 when “baseline” weight and diet were assessed. Eight years later (1994), changes in weight and dietary intake were assessed. Linear regression models were used to relate change in weight to fat intake and change in fat intake, using the percentage of energy from carbohydrate as the comparison, adjusted for age, BMI in 1986, leisure time physical activity, time spent sitting, percent of calories from protein, and change in percentage of calories from protein. Results: Overall, there was a weak positive association between total fat intake (β = 0.11) and weight gain. Increases in monosaturated and polyunsaturated fat were not associated with weight gain, but increases in animal fat, saturated fat, and trans fat had a positive association with weight change. There was not strong evidence of effect modification by parental weight status (p = 0.7 to 0.8 for percentage of calories from total fat, animal fat, and vegetable fat); however, the associations were stronger among the overweight compared with leaner women (p < 0.05 for percentage of calories from each type of fat). Among overweight women, for every one percentage increase in percentage of calories from trans fat, women gained an additional 2.3 lb (95% confidence interval, 1.80 to 2.86). Conclusion: Our results show that, overall, percent of calories from fat has only a weak positive association with weight gain; however, percentage of calories from animal, saturated, and trans fat has stronger associations. There was no clear evidence that the diet‐weight gain association was stronger among offspring of overweight parents, but dietary fat was associated with greater weight gain among overweight women.     

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.     

Circulating levels of persistent organic pollutants in relation to visceral and subcutaneous adipose tissue by abdominal MRI

Objective:

We and others have shown relationships between circulating levels of persistent organic pollutants (POPs) and different measures of obesity in both cross‐sectional and prospective studies. Since viscerally located fat seems to be the most harmful type, we investigated whether plasma POP levels were more closely related to visceral adipose tissue (VAT) than to subcutaneous adipose tissue (SAT).

Design and Methods:

Thousand hundred and sixteen subjects aged 70 years were investigated in the Prospective Investigation of the Vasculature in Uppsala Seniors (PIVUS) study; 23 POPs were analyzed using high‐resolution gas chromatography/high‐resolution mass spectrometry. Abdominal magnetic resonance imaging, measuring VAT and SAT, respectively, was performed in a representative subsample of 287 subjects.

Results:

The less chlorinated polychlorinated biphenyl (PCB) congeners (105 and 118), and the pesticides dichlorodiphenyldichloroethylene (DDE), hexachlorobenzene (HCB), and trans‐nonachlordane (TNC) were positively related to both VAT and SAT, whereas the more highly chlorinated PCBs (153, 156, 157, 169, 170, 180, 194, 206, and 209) were inversely related to both VAT and SAT. PCB189 was related to the VAT/SAT ratio in an inverted U‐shaped manner (P = 0.0008).

Conclusions:

In conclusion, the results were in accordance with our previous studies using waist circumference and fat mass as obesity measure. However, the novel finding that PCB189 was related to the VAT/SAT ratio deserves further investigation since exposure to this PCB congener, which has previously been linked to diabetes development, might thereby play a role in the distribution of abdominal adipose tissue.     

Genome‐wide Association Study and Follow‐up Analysis of Adiposity Traits in Hispanic Americans: The IRAS Family Study

We investigated candidate genomic regions associated with computed tomography (CT)–derived measures of adiposity in Hispanics from the Insulin Resistance Atherosclerosis Study Family Study (IRASFS). In 1,190 Hispanic individuals from 92 families 3 from the San Luis Valley, Colorado and San Antonio, Texas, we measured CT‐derived visceral adipose tissue (VAT), subcutaneous adipose tissue (SAT), and visceral:subcutaneous ratio (VSR). A genome‐wide association study (GWAS) was completed using the Illumina HumanHap 300 BeadChip (～317K single‐nucleotide polymorphisms (SNPs)) in 229 individuals from the San Antonio site (stage 1). In total, 297 SNPs with evidence for association with VAT, SAT, or VSR, adjusting for age and sex (P < 0.001), were genotyped in the remaining 961 Hispanic samples. The entire Hispanic cohort (n = 1,190) was then tested for association, adjusting for age, sex, site of recruitment, and admixture estimates (stage 2). In stage 3, additional SNPs were genotyped in four genic regions showing evidence of association in stage 2. Several SNPs were associated in the GWAS (P < 1 × 10^?5) and were confirmed to be significantly associated in the entire Hispanic cohort (P < 0.01), including: rs7543757 for VAT, rs4754373 and rs11212913 for SAT, and rs4541696 and rs4134351 for VSR. Numerous SNPs were associated with multiple adiposity phenotypes. Targeted analysis of four genes whose SNPs were significant in stage 2 suggests candidate genes for influencing the distribution (RGS6) and amount of adiposity (NGEF). Several candidate loci, including RGS6 and NGEF, are associated with CT‐derived adipose fat measures in Hispanic Americans in a three‐stage genetic association study.     

Association of Pericardial Fat With Liver Fat and Insulin Sensitivity After Diet‐Induced Weight Loss in Overweight Women

Pericardial adipose tissue (PAT) is positively associated with fatty liver and obesity‐related insulin resistance. Because PAT is a well‐known marker of visceral adiposity, we investigated the impact of weight loss on PAT and its relationship with liver fat and insulin sensitivity independently of body fat distribution. Thirty overweight nondiabetic women (BMI 28.2–46.8 kg/m², 22–41 years) followed a 14.2 ± 4‐weeks low‐calorie diet. PAT, abdominal subcutaneous (SAT), and visceral fat volumes (VAT) were measured by magnetic resonance imaging (MRI), total fat mass, trunk, and leg fat by dual‐energy X‐ray absorptiometry and intrahepatocellular lipids (IHCL) by (¹)H‐magnetic resonance spectroscopy. Euglycemic hyperinsulinemic clamp (M) and homeostasis model assessment of insulin resistance (HOMA_IR) were used to assess insulin sensitivity or insulin resistance. At baseline, PAT correlated with VAT (r = 0.82; P < 0.001), IHCL (r = 0.46), HOMA_IR (r = 0.46), and M value (r = ?0.40; all P < 0.05). During intervention, body weight decreased by ?8.5%, accompanied by decreases of ?12% PAT, ?13% VAT, ?44% IHCL, ?10% HOMA2‐%B, and +24% as well as +15% increases in HOMA2‐%S and M, respectively. Decreases in PAT were only correlated with baseline PAT and the loss in VAT (r = ?0.56; P < 0.01; r = 0.42; P < 0.05) but no associations with liver fat or indexes of insulin sensitivity were observed. Improvements in HOMA_IR and HOMA2‐%B were only related to the decrease in IHCL (r = 0.62, P < 0.01; r = 0.65, P = 0.002) and decreases in IHCL only correlated with the decrease in VAT (r = 0.61, P = 0.004). In conclusion, cross‐sectionally PAT is correlated with VAT, liver fat, and insulin resistance. Longitudinally, the association between PAT and insulin resistance was lost suggesting no causal relationship between the two.     

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.     

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.     

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.     

Obesity Is Accompanied by Disturbances in Peripheral Glucocorticoid Metabolism and Changes in FA Recycling

The glucocorticoid activating enzyme 11β‐hydroxysteroid dehydrogenase type 1 (11βHSD1) is of major interest in obesity‐related morbidity. Alterations in tissue‐specific cortisol levels may influence lipogenetic and gluco/glyceroneogenetic pathways in fat and liver. We analyzed the expression and activity of 11βHSD1 as well as the expression of phosphoenolpyruvate carboxykinase (PEPCK), sterol regulatory element binding protein (SREBP), and fatty acid synthase (FAS) in adipose and liver and investigated putative associations between 11βHSD1 and energy metabolism genes. A total of 33 obese women (mean BMI 44.6) undergoing gastric bypass surgery were enrolled. Subcutaneous adipose tissue (SAT), omental fat (omental adipose tissue (OmAT)), and liver biopsies were collected during the surgery. 11βHSD1 gene expression was higher in SAT vs. OmAT (P = 0.013), whereas the activity was higher in OmAT (P = 0.009). The SAT 11βHSD1 correlated with waist circumference (P = 0.045) and was an independent predictor for the OmAT area in a linear regression model. Energy metabolism genes had AT depot–specific expression; higher leptin and SREBP in SAT than OmAT, but higher PEPCK in OmAT than SAT. The expression of 11βHSD1 correlated with PEPCK in both AT depots (P = 0.05 for SAT and P = 0.0001 for OmAT). Hepatic 11βHSD1 activity correlated negatively with abdominal adipose area (P = 0.002) and expression positively with PEPCK (P = 0.003). In human obesity, glucocorticoid regeneration in the SAT is associated with central fat accumulation indicating that the importance of this specific fat depot is underestimated. Central fat accumulation is negatively associated with hepatic 11βHSD1 activity. A disturbance in peripheral glucocorticoid metabolism is associated with changes in genes involved in fatty acid (FA) recycling in adipose tissue (AT).     

Analysis of FTO gene variants with measures of obesity and glucose homeostasis in the IRAS Family Study

Multiple studies have identified FTO gene variants associated with measures of adiposity in European-derived populations. The objective of the study was to determine whether FTO variants were associated with adiposity, including visceral and subcutaneous adipose tissue (VAT, SAT), and glucose homeostasis measures in the Insulin Resistance Atherosclerosis Family Study (IRASFS). A total of 27 SNPs in FTO intron 1, including SNPs prominent in the literature (rs9939609, rs8050136, rs1121980, rs17817449, rs1421085, and rs3751812), were genotyped in 1,424 Hispanic Americans and 604 African Americans. Multiple SNPs were associated with BMI and SAT (P values ranging from 0.001 to 0.033), and trending or associated with waist circumference (P values ranging from 0.008 to 0.099) in the Hispanic Americans. No association was observed with VAT, illustrating that FTO variants are associated with overall fat mass instead of specific fat depots. For the glucose homeostasis measures, variants were associated with fasting insulin but, consistent with other studies, after BMI adjustment, no evidence of association remained. The lack of association of FTO SNPs with insulin sensitivity is consistent with the lack of association with VAT, since these traits are strongly correlated. In the African Americans, only rs8050136 and rs9939609 were associated with BMI and WAIST (P values of 0.011 and 0.034), and associated or trending towards association with SAT (P values of 0.038 and 0.058). These results confirm that FTO variants are associated with adiposity measures, predisposing individuals to obesity by increasing overall fat mass in Hispanic Americans and to a lesser degree in African Americans.