Obesity, Regional Fat Distribution, and Syndrome X in Obese BlackVersusWhite Adolescents: Race Differential in Diabetogenic and Atherogenic Risk Factors

Abstract

The incidence of type 2 diabetes mellitus in children is increasing with the increasing prevalence of obesity, particularly in African-American children. We hypothesized that African-American obese adolescents are more insulin resistant than their white peers, but have lower insulin secretion, thus increasing their risk of type 2 diabetes mellitus. The present study investigated insulin sensitivity and secretion, visceral adiposity (VAT), and cardiovascular disease (CVD) risk profile in black obese adolescents (BOA) vs. white obese adolescents (WOA). Twenty-four BOA and 26 WOA underwent a hyperinsulinemic-euglycemic clamp to assess insulin sensitivity, a hyperglycemic clamp to determine insulin secretion, dual energy x-ray absorptiometry for body composition and computed tomography scan at L4-L5 to measure VAT and sc abdominal adipose tissue. Fasting lipid and automated blood pressure measurements were obtained. The WOA and BOA groups were divided into low VAT and high VAT groups. BOA compared with WOA of similar body mass index and percent body fat had less visceral adiposity, lower hepatic glucose production, and lower lipid levels. Visceral adiposity was associated with lower insulin sensitivity in both groups [low vs. high VAT; BOA, 2.9 +/- 0.4 vs. 1.7 +/- 0.2 micromol/kg x min per pmol/liter (P = 0.016); WOA, 2.6 +/- 0.5 vs. 1.5 +/- 0.1 (P = 0.032)]. However, this was compensated by higher insulin secretion in whites (low VAT, 934.8 +/- 121.8; high VAT, 1590.6 +/- 232.8 pmol/liter; P = 0.037), but not in blacks (low VAT, 1398.9 +/- 214.0; high VAT, 1423.7 +/- 108.7 pmol/liter). Glucose disposition index (insulin sensitivity x first phase insulin) was lower in high VAT vs. low VAT BOA, but not in WOA. In each racial group, high VAT groups had elevation of systolic and diastolic blood pressure, but dyslipidemia was worse in WOA with high VAT. In conclusion, a given level of body mass index confers different metabolic risks for WOA vs. BOA. Although differences in fat patterning may help explain the more atherogenic risk profile in whites, the cause of the more diabetogenic insulin sensitivity/secretion profile in blacks remains unknown and needs to be investigated further.

Comparison of metabolic syndrome prevalence using six different definitions in overweight pre-pubertal children enrolled in a weight management study

“…It is likely that these ranges will need to be assay and population specific. 36,37 We agree with Lambert et al that the insulin resistance syndrome (IRS) of childhood, or pre-MS, may be a better name than MS in this age group.…”

Cardiorespiratory fitness and abdominal adiposity in youth

“…Abdominal adiposity is associated with numerous health risk in the pediatric (Bacha et al, 2003;Weiss et al, 2003) and adult populations (Ross et al, 2002;Hayashi et al, 2004). In adults, emerging evidence suggests that cardiorespiratory fitness (CRF) is associated with lower visceral and abdominal subcutaneous adipose tissue (AT) Janssen et al, 2004) independent of body mass index (BMI).…”

“…In that study (Nassis et al, 2005), total and abdominal fat was estimated by sum of skinfolds and CRF was indirectly assessed by 20 m shuttle run test. It is currently unknown whether CRF is associated with visceral AT, a strong independent predictor of insulin resistance and type 2 diabetes in youth (Bacha et al, 2003;Weiss et al, 2003).…”

Prediction of visceral fat area in Japanese adults: proposal of prediction method applicable in a field setting

“…Previous studies have been reported racial differences in regional fat distribution, intra-abdominal and subcutaneous abdominal adipose tissue patterns and metabolism (Berman et al, 2001;Raji et al, 2001;Weinsier et al, 2001;Bacha et al, 2003). Further examinations considering other populations will be required.…”