Offspring of Two Diabetic Parents: Differential Serum Insulin Responses to Intravenous Glucose and Tolbutamide1

Abstract

Intravenous glucose tolerance tests and intravenous tolbutamide tests were performed in 14 non-obese male offspring of 2 diabetic parents and 25 non-obese male controls of comparable age. Blood glucose and plasma free fatty acid responses were similar in both groups during the 2 tests, as were the serum insulin levels during the tolbutamide test. The serum insulin response during the glucose tolerance test was significantly lower during the first 30 min in the prediabetics. There was a significant relationship between serum insulin and blood glucose during the glucose tolerance test in each group; comparisons revealed a significantly lower insulin-glucose relationship in the prediabetics. The magnitude of the insulin response during the tolbutamide test was correlated with that observed during the glucose tolerance test in the normals, but this correlation was no longer present in the prediabetics. These findings suggest that the beta cell of genetic prediabetics exhibits a defective glucose responsive mechanism for insulin secretion but that the tolbutamide responsive mechanism is normal.