Lipolysis in African-American children: Is it a metabolic risk factor predisposing to obesity?

Rates of obesity and type 2 diabetes are higher in African-American (AA), c ompared with American white (AW), adults and children. It is not known whet her biologic and/or environmental differences are responsible for this raci al disparity. We and others have demonstrated that AA children are hyperins ulinemic, compared with their AW peers. This investigation tested the hypot hesis that hyperinsulinemia in AA children is associated with lower rates o f:lipolysis, which could be a risk factor for future obesity. Forty prepube rtal children (20 AA, and 20 AW) with comparable body composition (assessed by dual-energy x-ray absorptiometry) and visceral adiposity (evaluated wit h computed tomography scan) were studied. Total. body Lipolysis was measure d with [H-2(5)]glycerol after overnight fasting. Basal lipolysis was approximately 40% lower in AA vs. AW children, whether the data were expressed for total body(85.7 +/- 8.9 vs. 130.3 +/- 14.1 mu m ol/min, P = 0.011) or per-kilogram BW (2.4 +/- 0.2 vs. 3.8 +/- 0.4 mu mol/m in kg, P = 0.008 or per kilogram fat free mass (FFM) (3.3 +/- 0.3 vs. 5.2 /- 0.5 mu mol/min kg FFM, P = 0.004) or per kg fat mass (FM) (13.7 +/- 1.6 vs. 21.3 +/- 3.3 mu mol/min.kg FM, P = 0.046). Fasting insulin levels were higher in AA children (99.6 +/- 7.5 vs. 77.4 +/- 5.9 pmol/L, P = 0.032). Li polysis correlated positively with fat mass, percent body fat, and abdomina l fat mass. However, in multiple-regression analysis models after controlli ng for insulin and body composition, race remained a significant contributo r to the variance in lipolysis. In summary, the present study demonstrates that rates of lipolysis are sign ificantly lower in AA children, compared with their white peers. This may c onstitute an early metabolic phenotype that may mediate fat, trapping and s usceptibility to obesity in a specific environmental context of energy exce ss conducive to fat accretion.