1. Department of Internal Medicine, Nagayama Clinic, Oyama 323-0032, Tochigi, Japan
2. Center of Diabetes, Endocrinology and Metabolism, Toho University, Sakura Medical Center, Sakura 285-0841, Chiba, Japan
3. Department of Diabetes and Metabolism, Chiba Kaihin Municipal Hospital, Chiba 261-0012, Chiba, Japan
4. Division of Diabetes, Metabolism and Endocrinology, Toho University Ohashi Medical Center, Meguro 153-8515, Tokyo, Japan