DIFFERENTIAL-EFFECTS OF AMBIENT BLOOD-GLUCOSE LEVEL AND DEGREE OF OBESITY ON BASAL SERUM C-PEPTIDE LEVEL AND THE C-PEPTIDE RESPONSE TO GLUCOSE AND GLUCAGON IN NON-INSULIN-DEPENDENT DIABETES-MELLITUS

We studied basal, glucose-and glucagon-induced insulin secretion in no n-insulin-dependent diabetes mellitus (NIDDM) patients in relation to body mass index (BMI) and fasting serum glucose (FBS) level. A total o f 46 NIDDM patients and 22 control subjects with varying degrees of BM I and FBS were given 100 g of oral glucose and 1 mg of intravenous glu cagon on separate days. C-peptide response to glucose, but not basal s erum C-peptide and C-peptide response to glucagon, was significantly l ower in NIDDM than in controls (P < 0.001). FBS was inversely correlat ed with C-peptide response to glucose in NIDDM patients (r = -0.67, P < 0.001), but not with basal C-peptide level and C-peptide response to glucagon. On the other hand, BMI was positively correlated with basal serum C-peptide level both in NIDDM (r = 0.60, P < 0.001) and in cont rol subjects (r = 0.74, P < 0.001). In 15 poorly controlled NIDDM pati ents, the tests were repeated after insulin treatment for 10-14 days. C-peptide response to glucose significantly increased, but not to a le vel in control subjects, after glycemic control. Basal serum C-peptide level and the C-peptide response to glucagon decreased after glycemic control to significantly lower levels than those in the baseline and those in control subjects. These results suggest that beta cell secret ory reserve is reduced in moderate to severe NIDDM patients. (C) 1997 Elsevier Science Ireland Ltd.