1. Division of Internal Medicine, Department of Diabetes, Endocrinology and Metabolism, Shinshu University School of Medicine , Matsumoto 390-8621 , Japan
2. Diabetes Center, Aizawa Hospital , Matsumoto 390-8510 , Japan
3. Department of Endocrinology, Metabolism and Nephrology, Graduate School of Medicine, Nippon Medical School , Tokyo 113-8603 , Japan