1. Department of Medicine, Harvard Medical School, Research Program in Men's Health: Aging and Metabolism, Boston Claude D. Pepper Older Americans Independence Center, Brigham and Women's Hospital , Boston, MA 02115 , USA
2. Department of Integrative Physiology and Medicine, University of Colorado Boulder, Boulder, CO 80309 , USA
3. Department of Pharmacology, Mitchell Cancer Institute, College of Medicine, University of Southern Alabama , Mobile, AL 36688 , USA
4. Department of Medicine, Division of Endocrinology, Diabetes and Metabolism, Cedars-Sinai Medical Center , Los Angeles, CA 90048 , USA
5. Department of Physiology, Institute for Diabetes, Obesity & Metabolism, Perelman School of Medicine, University of Pennsylvania , Philadelphia, PA 19104 , USA