The Relationship between Level of Glutamic Acid Decarboxylase Antibodies and β-cell Function in the Capacity to Release Insulin Determined by Loading Glucagon in Patients with IDDM and SPIDDM

Abstract

There have been reports that a high level of GAD antibodies is associated with a low risk of clinical disease in at-risk relatives. Therefore we studied the relationships between residual β-cell function and the titer of glutamic acid decarboxylase antibodies in patients with IDDM and SPIDDM. Residual β-cell function was evaluated by the C-peptide immunoreactivity response to loading by glucagon, and the titer of GAD-Ab was determined with RIA Kits. We found that the C-peptide immunoreactivity respone to glucagon loading was positively correlated with the titer of GAD antibodies in IDDM patients with 5-years duration of diabetes (γ=0.43, p<0.05), but not in IDDM patients with duration of diabetes over 6 years. In SPIDDM patients, we found no relationship between the titer of GAD-Ab and the capacity to release insulin.