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)