INSULIN-SECRETION AND SENSITIVITY IN BLACK VERSUS WHITE PREPUBERTAL HEALTHY-CHILDREN

We had previously demonstrated greater insulin secretion and lower ins ulin sensitivity in black pubertal adolescents compared with whites. T his study aimed to investigate whether similar black/white differences are present in the prepubertal period or are characteristics of the p ubertal period. Twelve black and 11 white healthy prepubertal children , matched for age, body mass index, and Tanner I pubertal development, underwent a 2-h hyperglycemic clamp (225 mg/dL). Physical fitness was assessed by maximal oxygen consumption (VO2max) measurement during gr aded bicycle ergometry, and resting energy expenditure was measured by indirect calorimetry after overnight fast. Fasting and first phase in sulin concentrations were higher in blacks than in whites [14.7 +/- 1. 3 vs. 10.4 +/- 1.2 (P = 0.02) and 76.9 +/- 6.8 vs. 52.1 +/- 6.4 mu U/m L (P = 0.016)]. There were no differences in second phase insulin leve ls and insulin sensitivity index. Both maximal oxygen consumption (VO2 max) and resting energy expenditure were lower in black children, wher eas insulin-like growth factor I was higher. After controlling. for th ese differences, race contributed significantly to basal insulin, but not to first phase insulin. In summary, previously reported black/whit e differences in insulin secretion and sensitivity during adolescence may have their origin in early childhood manifested as hyperinsulinemi a. However, genetic (race) vs. environmental factors (physical activit y/fitness and energy balance) should be carefully scrutinized as poten tial factors responsible for such differences.