Anti-lipolytic effects of insulin in African American and white prepubertal boys.

OBJECTIVE Relative to whites, African Americans have lower circulating triglycerides (TG) and greater highdensity lipoprotein cholesterol. The metabolic basis for this difference is not known. This study was conducted to test the hypothesis that insulin-induced suppression of free fatty acids (FFA) results in lower serum TG in African American versus white prepubertal children. RESEARCH METHODS AND PROCEDURES Insulin, FFA, and TG were determined at baseline and during a frequently sampled, intravenous glucose tolerance test in eight African American and eight white prepubertal males pair-matched for whole-body insulin sensitivity. RESULTS Baseline TG was lower in African Americans (0.43 +/- 0.10 vs. 0.79 +/- 0.37 mM/L; mean +/- SD; p < 0.01). African Americans had higher peak insulin (218 +/- 102 vs. 100 +/- 30 pM/L; mean +/- SD; p < 0.01) and a greater acute insulin response (9282 +/- 4272 vs. 4230 +/- 1326 pM/L x 10 minutes; mean +/- SD; p < 0.05). FFA and TG values determined at the FFA nadir were lower in African Americans (0.26 +/- 0.02 vs. 0.30 +/- 0.03 mEq/L; mean +/- SD; p < 0.01 for FFA nadir and 0.49 +/- 0.07 vs. 0.77 +/- 0.33 mM/L; mean +/- SD; p < 0.05 for TG). Among all subjects, FFA nadir was correlated with peak insulin (r = -0.54; p < 0.05). After adjusting for FFA nadir, neither baseline nor postchallenge TG differed with ethnicity (p = 0.073 and 0.192, respectively). The ethnic difference in FFA nadir disappeared after adjusting for peak insulin (p = 0.073). DISCUSSION These data suggest that hyperinsulinemiainduced suppression of FFA among African Americans is a determinant of lower TG in this group.