Clinical heterogeneity of adult Japanese diabetes depending on titers of glutamic acid decarboxylase autoantibodies

Aims/Introduction: We examined whether levels of glutamic acid decarboxylase autoantibodies (GADAb) might show the clinical heterogeneity of adult Japanese diabetes. Materials and Methods: In this cross‐sectional study, the serum levels of GADAb were measured in a total of 1857 consecutive adult diabetic patients aged 20 years or older. The patients with positive GADAb, arbitrarily defined as ≥1.5 U/mL, were divided into quartiles according to the number of patients. The age‐ and sex‐matched diabetic patients without GADAb were selected as a control group. Results: A total of 103 (5.5%) of the diabetic patients had GADAb, and showed higher HbA_1c and serum high‐density lipoprotein (HDL) cholesterol levels, lower body mass index (BMI), urinary C ‐ peptide immunoreactivity (CPR), serum triglycerides (TG) and uric acid (UA) levels, and lower prevalence of metabolic syndrome than the control group (P < 0.05). Quartiles 3 and 4 (i.e. GADAb ≥4.6 U/mL) showed a higher HbA_1c level, lower BMI, urinary CPR, serum TG and UA levels, quartile 2 (2.5 ≤ GADAb < 4.6 U/mL) showed a lower BMI level than the control group (P < 0.05). Among the clinical parameters, we observed significant upward trends for both HbA_1c and serum HDL cholesterol levels, and significant downward trends for BMI, serum TG and UA, urinary CPR levels, and prevalence of metabolic syndrome across GADAb quartiles (P < 0.05 for trend). Conclusions: These results show that the clinical phenotype of adult Japanese diabetes correlates with GADAb levels, and that patients with GADAb (≥2.5 U/mL) show different characteristics from those without GADAb, although further longitudinal studies are required. (J Diabetes Invest, doi: 10.1111/j.2040‐1124.2011.00190.x, 2011)