1. Biology Research Laboratories; Mitsubishi Tanabe Pharma Corporation; Saitama 335-8505 Japan
2. Department of Diabetes, Endocrinology and Nutrition; Graduate School of Medicine; Kyoto University; Kyoto 606-8507 Japan
3. Department of Integrative and Systems Physiology; Faculty of Medical Sciences; University of Fukui; Fukui 910-1193 Japan
4. Department of Physiology and Biophysics; Graduate School of Medicine; Kyoto University; Kyoto 606-8501 Japan
5. Department of Life Science; Ritsumeikan University; Kusatsu, Shiga 525-8577 Japan