Department of Physiology and Pharmacology, Karolinska Institute, Stockholm, Sweden. The Charles Bronfman Institute for Personalized Medicine, Icahn School of Medicine at Mount Sinai, New York, New York; The Mindich Child Health and Development Institute, Icahn School of Medicine at Mount Sinai, New York, New York. Diabetes Research Group, Translational and Clinical Research Institute, Faculty of Clinical Medical Sciences, Newcastle University, 4(th) Floor William Leech Building, Framlington Place, Newcastle upon Tyne, NE2 4HH, UK. Department of Physiology and Pharmacology, Karolinska Institute, Stockholm, Sweden; Department of Molecular Medicine and Surgery, Karolinska Institutet, Stockholm, Sweden; Novo Nordisk Foundation Center for Basic Metabolic Research, University of Copenhagen, Copenhagen, Denmark. Electronic address: juleen.zierath@ki.se.