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

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 x 10(-4) min(-1) (mU 1)(-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 x 10 min(-1) (mU 1)(-1)]. Mean S-G and K-G were greater (P < 0.05) 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.