1. Department of Endocrinology and Metabolism, Renji Hospital, School of Medicine, Shanghai Jiaotong University, Shanghai 200127, P. R. China
2. Department of Medicine, Northwestern University Feinberg School of Medicine, Chicago, Illinois 60611, USA
3. Department of Preventive Medicine, Northwestern University Feinberg School of Medicine, Chicago, Illinois 60611, USA
4. Sarah W. Stedman Nutrition and Metabolism Center, Duke University School of Medicine, Durham, North Carolina 27705, USA
5. Duke Molecular Physiology Institute, Durham, North Carolina 27701, USA
6. Department of Medicine, Duke University School of Medicine, Durham, North Carolina 27707, USA