1. Department of Medicine, Division of Endocrinology, Metabolism and Molecular Medicine, Northwestern University School of Medicine, Chicago, Illinois;
2. Department of Medicine, Division of Diabetes, Endocrinology & Metabolism, Baylor College of Medicine, Houston, Texas;
3. Department of Internal Medicine, Touchstone Diabetes Center, University of Texas Southwestern Medical Center, Dallas, Texas;
4. National Institutes of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, North Carolina.