A HIGHER PROINSULIN RESPONSE TO GLUCOSE LOADING PREDICTS DETERIORATING FASTING PLASMA-GLUCOSE AND WORSENING TO DIABETES IN SUBJECTS WITH IMPAIRED GLUCOSE-TOLERANCE

To evaluate the clinical significance of proinsulin determination, we measured glucose, insulin, C-peptide and proinsulin during 75-g oral g lucose loading in 59 patients. In a 2.5-year follow-up study of 37 sub jects with impaired glucose tolerance (IGT) at the initial test, 11 pa tients changed from IGT to a normal state and 5 patients showed worsen ing to overt Type 2 diabetes with elevation of fasting plasma glucose; 21 patients remained unchanged. Although our data showed that both fa sting (IGT: p=0.4523) and 120-min plasma glucose (IGT: p=0.8168) value s at the initial test were not significantly correlated with increased fasting plasma glucose levels in a 2.5-year follow-up study, subjects with a higher 120-min proinsulin response to glucose during the initi al OGTT showed a significant correlation (IcT: p<0.0001) with increase d fasting plasma glucose levels after follow-up period and developed T ype 2 diabetes. The present findings suggest that the proinsulin respo nse to glucose loading might be a useful indicator for predicting wors ening to diabetes in subjects with impaired glucose tolerance.