Ethnic differences in glucose effectiveness and disposition index in overweight/obese African American and white women with prediabetes: A study of compensatory mechanisms.

Objective: Prediabetes, a major precursor of type 2 diabetes, varies among ethnic populations. Therefore, we compared the pathophysiologic mechanisms of prediabetes in overweight/obese African American (AA) and White American (WA) women.

Subjects And Methods: We recruited 95 women (67 AA, 28 WA) with prediabetes. Standard OGTT and FSIVGTT were performed in each subject. Insulin sensitivity (Si), glucose effectiveness (Sg), beta cell function (acute insulin response to glucose (AIRg) and disposition index (DI: Si×AIRg) were calculated using Bergman's Minmod.

Results: Mean BMI was greater in AA vs WA with prediabetes (38.3±8.2vs 34.6±8.5kg/m, p=0.05). Mean fasting serum glucose, and insulin levels were lower in AA vs WA. Similarly, mean peak serum glucose levels were lower while peak insulin levels were higher at 30 and 60minutes in AA vs WA. In contrast, mean fasting and peak serum c-peptide levels at 60 and 90minutes were significantly lower in AA vs WA. Mean AIRg was higher but not significantly different in AA vs WA (633±520.92 vs 414.8±246.8, p=0.193). Although, Si (2.93±3.25vs 44 2.50±1.76 (×10×min [μU/ml]), p=0.448) was not different, DI was significantly higher in AA vs WA (1381±1126 vs 901.9±477.1, p=0.01). In addition, mean Sg was significantly higher in AAvs WA (2.51±1.17 vs 1.97±0.723 (×10/min), p=0.02).

Conclusions: We found that in overweight/obese prediabetic AA and WA women with similar Si, the mean Sg and DI were significantly higher in AA. We conclude that the pathophysiologic mechanisms of prediabetes differ in the overweight/obese AA and WA women.