A supplementary infusion of glucose-dependent insulinotropic polypeptide (GIP) with a meal does not significantly improve the β cell response or glucose tolerance in type 2 diabetes mellitus

Abstract

Newly diagnosed, previously untreated patients with type 2 diabetes mellitus ( n = 6) were studied on two separate days after overnight fasts. On each day they were given a 500-kcal mixed meal plus an infusion of either porcine glucose-dependent insulinotropic polypeptide (GIP) (0.75 pmol/kg/min) or control solution (CS) from 0 to 30 min in random order. Frequent measurements of plasma glucose, C-peptide, insulin and GIP concentrations were made. Fasting GIP levels were similar on both days. During the meal plus GIP infusion plasma GIP levels increased from a basal value of 7.6 ± 1.5 pmol/l to a peak of 88.6 ± 5.4 pmol/l at 30 min. Following the meal and infusion of CS GIP increased from a fasting level of 10.3 ± 1.2 pmol/l to a significantly lower peak of 58.0 ± 8.3 pmol/l at 60 min. During the meal plus GIP infusion GIP levels were higher at 10–45 min and at 90 min ( P < 0.05−0.001). Fasting and postprandial glucose, C-peptide and insulin levels were, however, similar on both study days. A supplementary infusion of porcine GIP with a mixed meal did not significantly alter the β cell response or glucose tolerance in this group of patients with type 2 diabetes mellitus.