Racial differences in adiponectin in youth: relationship to visceral fat and insulin sensitivity

OBJECTIVE: The purpose of this study was to investigate 1) whether adiponectin is associated with insulin sensitivity independent of visceral adipose tissue in African-American and Caucasian youth and 2) whether adiponectin is associated with racial differences in insulin sensitivity. RESEARCH DESIGN AND METHODS: Total body fat was measured by dual-energy X-ray absorptiometry and abdominal adipose tissue with computed tomography. Insulin sensitivity was measured by a 3-h hyperinsulinemic-euglycemic clamp. RESULTS: Adiponectin was inversely associated (P < 0.01) with visceral adipose tissue, fasting insulin, and proinsulin and was positively related (P < 0.01) to insulin sensitivity after controlling for Tanner stage and sex independent of race. Stepwise multiple regression revealed that adiponectin was a strong independent predictor of insulin sensitivity, explaining 27% of the variance in insulin sensitivity. When subjects were categorized into tertiles of visceral adipose tissue and further low (< or = 50th) and high (>50th) adiponectin groups, insulin sensitivity was significantly different across the visceral adipose tissue groups (main effect, P < 0.01) in both races. However, within each visceral adipose tissue group, subjects with high adiponectin had higher insulin sensitivity (main effect, P < 0.05) than subjects with low adiponectin, independent of race. Racial differences in insulin sensitivity remained significant (P < 0.01) after controlling for leptin and visceral adipose tissue but not (P > 0.05) after additional adjustment for adiponectin. CONCLUSIONS: Adiponectin is associated with insulin sensitivity independent of visceral adipose tissue in both African-American and Caucasian youth. Low adiponectin in African-American youth may be a biological marker that predisposes them to a greater risk of insulin resistance.