1 Department of Physiology, Rodent Metabolic Phenotyping Core, and Institute for Diabetes, Obesity, and Metabolism, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania. Electronic address: ptitc@pennmedicine.upenn.edu.
2 Department of Physiology, Rodent Metabolic Phenotyping Core, and Institute for Diabetes, Obesity, and Metabolism, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania. Electronic address: baur@pennmedicine.upenn.edu.