1. Department of Diabetes, Endocrinology and Hematology, Dokkyo Medical University Saitama Medical Center, Saitama 343-8555, Japan
2. Division of Diabetic Research, Clinical Research Institute, National Hospital Organization Kyoto Medical Center, Kyoto 612-8555, Japan
3. Division of Community and Family Medicine, Jichi Medical University, Tochigi 329-0498, Japan
4. Department of Diabetes, Metabolism and Endocrinology, Ichikawa Hospital, International University of Health and Welfare, Chiba 272-0827, Japan