Differences in insulin secretion and sensitivity of Caucasian and African American prepubertal children

Abstract

Objective: To investigate whether differences in body composition of African American children (AA) and Caucasian children (C) explain differences in insulin sensitivity and secretion. Study design: Prepubertal nondiabetic children (31 AA and 54 C) were studied; 84% were overweight. Participants underwent a 2-hour hyperglycemic clamp, to estimate insulin sensitivity (SIclamp) and secretion, and dual energy x-ray absorptiometry, to assess body composition. Results: AA had greater total body fat mass (P =.01), fasting, 1st phase, 2nd phase, and steady state insulin levels (P <.05). AA and C had similar glucose disposal rates, but AA had lower SIclamp (P <.05). Fasting, 1st phase, and steady state C-peptide were less in C (P <.05), whereas corresponding C-peptide/insulin ratios were higher (all P <.005). Insulin levels and SIclamp remained different in AA and C after adjustment for body fat or lean mass differences. Analyses restricted to only overweight AA and C showed similar trends. Conclusion: Prepubertal African American children have higher baseline and glucose-stimulated insulin and C-peptide levels, as well as reduced insulin sensitivity that is not entirely explained by differences in adiposity. The lower C-peptide/insulin molar ratio in AA suggests that they probably have lower hepatic insulin clearance than Caucasian children. (J Pediatr 2002;140:673-80)