1. Salk Institute for Biological Studies, La Jolla, California 92037, USA
2. University of Minnesota, Division of Diabetes, Endocrinology and Metabolism, Minneapolis, Minnesota 55455, USA
3. University of California, San Diego, Division of Cardiovascular Diseases, Department of Medicine, 9434 Medical Center Drive, La Jolla, California 92037, USA
4. New York Nutrition Obesity Research Center, Division of Endocrinology, Department of Medicine, Columbia University Irving Medical Center; New York, New York 10032, USA