Effect of nifedipine retard on glucose-induced insulin response in patients with and without non—insulin-dependent diabetes mellitus and hypertension

Abstract

To study the long-term effects of nifedipine retard on insulin response to oral loading of 75-g glucose, insulin responses to oral glucose were assessed using the insulin area under the concentration—time curve (AUC) and the insulin secretion ratio (30-minute increments of plasma insulin to 30-minute increments of plasma glucose) during oral glucose tolerance tests (OGTTs). The tests were repeated before and after a nifedipine treatment period of 49 ± 3 months (mean ± SE) in 8 non—insulin-dependent diabetes mellitus (NIDDM) hypertensive and 12 nondiabetic hypertensive patients. We recruited 32 consecutive normotensive individuals (19 NIDDM patients and 13 nondiabetic individuals) as a control group, who received OGTTs twice at a mean interval of 43 ± months. They were matched for age; sex disribution; glycated hemoglobin A 1c (Hb A 1c) levels; fasting and 2-hour postglucose levels of plasma glucose during OGTTs; and, for diabetic patients, the type of diabetic medication. No statistically significant differences were noted between diabetic hypertensive and diabetic normotensive patients in changes over time in the insulin secretion ratio. The two diabetic groups of patients showed the same improvement in Hb A 1C and glucose AUC. Insulin AUC, however, increased by 156 ± 108 pmol × h/L in the hypertensive diabetic patients, whereas it decreased by 84 ± 42 pmol × h/L in normotensive NIDDM patients ( P = 0.02). In nondiabetic patients, Hb A 1c and glucose AUC increased to a similar extent in both hypertensive and normotensive individuals. Despite this, maximum insulin concentrations and insulin AUC increased by 90 ± 66 pmol/L and 168 ± 120 pmol × h/L, respectively, in hypertensive patients whereas they did not change in normotensive controls, although the differences between the two groups were not significant. At baseline, no statistically significant differences were noted in fasting and maximum concentrations of insulin, and insulin AUC between NIDDM hypertensive and NIDDM normotensive patients. In conclusion, the study indicated that long-term treatment with nifedipine retard was not associated with an adverse effect on insulin response to oral glucose loading in either diabetic or nondiabetic patients with hypertension.