Clinical Evaluation of Non-Insulin-Dependent Diabetes Mellitus Patients with Autoantibodies to Glutamic Acid Decarboxylase

We evaluated the frequency of antibodies to glutamic acid decarboxylase (GAD-Ab) in Japanese patients diagnosed initially as having non-insulin-dependent diabetes mellitus (NIDDM) and investigated a possible link between the presence of GAD-Ab and development of the insulin-dependent (ID) state. The population sample consisted of 583 Japanese NIDDM patients (age at onset >30 years) who were initially non-ketotic and did not require insulin treatment during at least 6 months of observation. GAD-Ab were measured using radioimmunoassay. The clinical characteristics of GAD-Ab +patients were carefully examined at four-year intervals from the onset of diabetes. We also examined the ID state by measuring the level of postprandial serum C-peptide and i.v. glucagon-stimulated serum C-peptide. The overall prevalence of GAD-Ab in Japanese NIDDM patients was 3.8%. The frequency of GAD-Ab +did not significantly decrease with a long history of diabetes. GAD-Ab +patients had a lower body mass index, compared with GAD-Ab −(20.8±2.9 vs 23.0±3.7, P