Alteration in the Temporal Organisation of Insulin Secretion in Type 2 (non-insulin-dependent) Diabetic Patients Under Continuous Enteral Nutrition

Concomitant oscillations of plasma glucose, insulin and C-peptide levels with a period of about 80 min between peak levels have been identified in normal man. To determine whether these oscillations persist in Type 2 (non-insulin-dependent) diabetic patients, peripheral plasma levels of glucose, insulin and C-peptide were measured at 10 min intervals over 12 h in six patients and in six matched control subjects during continuous enteral nutrition (90 kcal.h-1;50% carbohydrate, 35% fat, 15% protein). The insulin secretion rate was estimated from peripheral C-peptide levels using an open two-compartment model. For the control subjects, mean plasma glucose, insulin and insulin secretion profiles rose sharply and then attained a steady-state; in contrast, for the diabetic patients, the mean insulin and insulin secretion profiles were characterized by a slow ascending trend throughout the day. Mean glucose levels rose sharply and reached higher levels than in the control subjects. The individual 12 h profiles revealed synchronous oscillations of plasma glucose, plasma insulin, and insulin secretion in the control subjects. In the diabetic patients, the number of plasma insulin and insulin secretion pulses was significantly lower; they had a smaller amplitude and were less frequently associated with the glucose pulses. However, plasma glucose levels had a similar oscillatory pattern in the diabetic patients compared with the control subjects, albeit with a higher absolute amplitude. The poor association between glucose and insulin secretion pulses in the diabetic patients suggests that insulin pulses are insufficient to account for the glucose pulses.(ABSTRACT TRUNCATED AT 250 WORDS)