ANTIBODY TO THE MR-65,000 ISOFORM OF GLUTAMIC-ACID DECARBOXYLASE ARE DETECTED IN NON-INSULIN-DEPENDENT DIABETES IN JAPANESE

It was recently reported that antibodies against glutamic acid decarbo xylase (GADAb) have a high positive predictive value for insulin-depen dency in non-insulin-dependent diabetic (NIDDM) patients. We studied 2 89 patients classified at onset as having NIDDM. Patients positive for GAD65Ab had a disease onset at a younger age, lower body mass index ( BMI) and lower serum C-peptide concentration, and were more often trea ted with insulin. Among 73 insulin-treated patients, patients with low er C-peptide level (n=30, C-peptide less than or equal to 0.9 ng/ml) s howed a higher frequency of GAD65Ab (46.7%) than patients with normal C-peptide (n=53, C-peptide>0.9; 7.5%, P<0.0001). The 206 remaining non -insulin-treated patients were divided into 48 short-duration (less th an 5 years from diagnosis) and 158 long-duration patients, Frequency o f GAD65Ab in short-duration patients (10.4%) was significantly higher than that in long-duration patients (3.2%, P<0.05). Among short-durati on patients, there was no significant difference in C-peptide levels b etween GAD65-positive and negative patients (2.175 and 2.226 ng/ml). I n conclusion, GAD65Ab, a marker of insulin deficiency, may predict the development of insulin dependency in non-insulin-dependent Japanese d iabetic patients before serum C-peptide concentration decreases. (C) 1 996 Academic Press Limited