The aim of this study was to compare the associations of adiposity with insulin sensitivity and β-cell function between African Americans (AA) and European Americans (EA) during different periods of their lives. The study cohort included 168 healthy, normoglycemic AA and EA girls and women aged 7-12 years (prepubertal), 18-32 years (premenopausal), and 40-70 years (postmenopausal). Results showed that the inverse association of adiposity with insulin sensitivity was significant among EA but not AA. Adiposity appeared stimulatory to β-cell function in younger subjects and EA, but inhibitory in postmenopausal women and especially in AA postmenopausal women. The association in AA postmenopausal women was independent of insulin sensitivity, therefore suggesting a direct effect of adipose tissue on β-cell function. Moreover, the authors found that within postmenopausal women, adiposity was adversely related to insulin sensitivity among EA, but to insulin secretion among AA. Regarding abdominal fat distribution, abdominal subcutaneous adipose tissue and intra-abdominal (visceral) adipose tissue were inversely associated with insulin sensitivity among EA, but not in AA. In addition, β-cell function was positively associated with both subcutaneous adipose tissue and intra-abdominal adipose tissue in a positive way among EA and negatively among AA. Thus, these results suggest that the association bewteen adiposity and insulin secretion is altered by age and differs as a function of ethnic background.
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