Minimal model analyses of insulin sensitivity and glucose‐dependent glucose disposal in black and white Americans: a study of persons at risk for type 2 diabetes

Abstract

Abstract. We have examined the impact of race and positive family history of type 2 diabetes on glucose/insulin dynamics and the two components of glucose disposal in healthy, first‐degree relatives of black and white American patients with type 2 diabetes mellitus who are at a greater risk from the disease and their healthy control subjects. Seventeen black and 15 white relatives were studied. Twenty‐two black people and 24 white people, without family history of type 2 diabetes, served as healthy control subjects. Standard oral glucose tolerance test (OGTT) and tolbutamide‐modified frequent sampling intravenous glucose tolerance (FSIGT) tests were performed in each subject. Insulin sensitivity index (S I ) and glucose effectiveness (S G ) were calculated using the MINI‐MOD method described by Bergman et al . Mean fasting and post‐stimulation serum glucose levels were not significantly different in the black and white relatives. However, mean serum insulin responses to oral and/or intravenous stimulation were significantly greater in the blacks than whites, irrespective of positive family history of diabetes. The mean S I was significantly ( P < 0·02) lower (52%) in the black (3·67±0·56) than the white [7·50±1·93 times 10 ‐4 min ‐1 (mUl) ‐1 ] relatives. Comparing the healthy controls, the mean S I was significantly ( P < 0·02) lower (51%) in black than white controls (4·84±0·78 vs. 9·71±1·27 times 10min ‐1 (mUl) ‐1 ]. Mean S G and K G were greater ( P < ·05) in the blacks than whites, irrespective of family history of diabetes. In summary, the present study demonstrates that non‐diabetic black people manifest insulin resistant and hyperinsulinaemia, irrespective of family history of diabetes, when compared to white people. We speculate that these metabolic changes could play a potential role in the higher prevalence of type 2 diabetes in the black Americans.