INSULIN RESPONSES TO INTRAVENOUS GLUCOSE, INTRAVENOUS ARGININE AND A HYPERGLYCEMIC CLAMP IN ICA-POSITIVE SUBJECTS WITH DIFFERENT DEGREES OFGLUCOSE-TOLERANCE

The relationship between altered insulin secretion and impaired glucos e tolerance was studied in 32 non-obese subjects aged 14-49 years with islet-cell antibodies (ICA) and fasting blood glucose below 7.9 mmol/ l, using oral (OGTT) and intravenous (IVGTT) glucose tolerance tests. Glucose tolerance was normal in 19 subjects, impaired (IGT) in 4 and s atisfied diabetic criteria in 9. Fifteen of these subjects and 8 ICA-n egative controls also underwent a hyperglyacemic clamp (10 mmol/l) and a glucose-potentiated IV arginine bolus. Acute insulin response to IV GTT and insulin and C-peptide responses to the hyperglycaemic clamp an d the arginine bolus were dramatically lower (p < 0.001) in diabetic a nd IGT subjects than in ICA-positive patients with normal glucose tole rance and control subjects. Insulin responses to the three tests were inversely correlated with plasma glucose levels and the area under the curve of OGTT. The correlations between the degree of glucose toleran ce and insulin responses to IVGTT, the hyperglycaemic clamp and the ar ginine bolus were virtually identical. It is concluded that insulin re sponses to the three stimuli were severely altered in ICA- positive pa tients with impaired glucose tolerance or asymptomatic diabetes, norma l in normotolerant ICA-positive subjects, and correlated with glucose tolerance.