1. 1Geriatric Research, Education and Clinical Center, VA Palo Alto Health Care System, Palo Alto, California, USA
2. 2Division of Endocrinology, Gerontology and Metabolism, Stanford University, Stanford University, Stanford, California, USA
3. 3Stanford Diabetes Research Center, Stanford, California, USA
4. 4Jiangsu Key Laboratory for Molecular and Medical Biotechnology and College of Life Science, Nanjing Normal University, Nanjing, China