Differences between Basal and Postprandial Circadian Variation of Insulin Sensitivity in Healthy Subjects and Type 1 Diabetics

The circadian variation of basal and postprandial plasma glucose and insulin levels was analyzed in 10 healthy individuals and 10 type-1 diabetic patients treated with a glucose-controlled insulin infusion system. In both groups the postprandial glycemic response to identical low caloric mixed meals ingested at 8 a. m., 1 p. m., and 6 p. m. increased significantly in the course of the day. In contrast to findings in conventional insulin therapy mean postprandial insulin requirements of the diabetic patients increased from 8.5 ±3.0 IU for breakfast to 9.1 ± 2.0 for lunch and 10.9 ± 3.0 for dinner (p<0.01). Repeated studies with different test meals showed that in the diabetic patients the circadian deterioration of carbohydrate tolerance was reduced after a fiber rich meal with low glycemic effect and insulin requirements. In the healthy subjects basal insulin levels at 8 a. m. were 35% higher than at 1 and 6 p. m. (p<0.01). Basal insulin requirements of the diabetic patients increased significantly from a night value of 0.7 IU/h to 1.18 IU/h during the early morning and remained constant throughout day time.