Reduced Insulin Response in Diabetes - a Quantitative or a Qualitative Problem?

The lacking or reduced insulin response to glucose infusion is typical of diabetes mellitus. Nevertheless it is possible to verify a significant increase of the serum insulin level in maturity onset diabetics following tolbutamide of glucagon injection when reaction to oral glucose administration is missing. We examined whether it is possible to obtain a stimulation of insulin secretion by maximum increase of the blood glucose level by intravenous administration of glucose. For this purpose 9 diabetic patients have been studied. The patients received 0.75 g glucose per kg of body weight initially and thereafter an infusion of 30 mg glucose per kg of body weight per minute during 30 minutes. Despite the blood glucose increase up to 1000mg/100 ml under intravenous infusion no stimulation of insulin secretion by the glucose took place. The same patients showed a significant insulin increase after stimulation with tolbutamide or glucagon. However, this response has been observed in patients also in cases where the oral stimulation with 100 g glucose did not result in any secretion whatever. This type of insulin secretion probably results from a complete alteration of the glucose receptor in respect of stimulation with glucose. Tolbutamide and glucagon receptors seem to be intact.