1. Department of Medicine, Division of Endocrinology, Metabolism, and Molecular Medicine, Feinberg School of Medicine, Northwestern University, Chicago, IL 60611, USA.
2. Robert H. Lurie Cancer Center Metabolomics Core, Feinberg School of Medicine, Northwestern University, Chicago, IL 60611, USA.
3. Touchstone Diabetes Center, Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA.