INCREASED INSULIN-RESISTANCE AND INSULIN-SECRETION IN NONDIABETIC AFRICAN-AMERICANS AND HISPANICS COMPARED WITH NON-HISPANIC WHITES - THE INSULIN-RESISTANCE ATHEROSCLEROSIS STUDY

The etiology of NIDDM is still controversial, with both insulin resist ance and decreased insulin secretion postulated as potential important factors, African-Americans and Hispanics have a two- to threefold exc ess risk of developing NIDDM compared with non-Hispanic whites, Yet li ttle is known concerning the prevalence of insulin resistance and secr etion defects in minorities, especially in African-Americans in popula tion-based studies, Fasting and 2-h post-glucose load glucose and insu lin levels, insulin-mediated glucose disposal (insulin sensitivity ind ex) (S-I), glucose effectiveness (S-G), and first-phase insulin respon se (acute insulin response [AIR]) were determined in nondiabetic Afric an-Americans (n = 288), Hispanics (n = 363), and non-Hispanic whites ( n = 435) as part of the Insulin Resistance Atherosclerosis Study, Subj ects received a standard 2-h oral glucose tolerance test on the first day and an insulin-modified frequently sampled intravenous glucose tol erance test on the second day, African-Americans and Hispanics were mo re obese than non-Hispanic whites, Both African-Americans and Hispanic s had higher fasting and 2-h insulin concentrations and AIR but lower S-I than non-Hispanic whites, No ethnic difference was observed in S-G . After further adjustments for obesity, body fat distribution, and be havioral factors, African-Americans continued to have higher fasting a nd 2-h insulin levels and AIR, but lower S-I, than non-Hispanic whites , In contrast, after adjustment for these covariates, no significant e thnic differences in S-I or fasting insulin levels were observed betwe en Hispanics and non-Hispanic whites, Hispanics continued to have high er 2-h insulin levels and AIRs than those in non-Hispanic whites, In t his report, the association between S-I and upper body adiposity (wais t-to-hip ratio) was similar in each ethnic group, Both nondiabetic Afr ican-Americans and Hispanics have increased insulin resistance and hig her AIR than nondiabetic non-Hispanic whites, suggesting that greater insulin resistance may be in large part responsible for the higher pre valence of NIDDM in these minority groups, However, in Hispanics, the greater insulin resistance may be due to greater adiposity and other b ehavioral factors.