1 The Oxford Centre for Diabetes, Endocrinology, and Metabolism, Churchill Hospital, Oxford OX3 7LJ, UK.
2 Nuffield Department of Surgery, John Radcliffe Hospital, Oxford OX3 9DU, UK.
3 Department of Physiology, Anatomy, and Genetics, Oxford University, Oxford OX1 3PT, UK.
4 The Oxford Centre for Diabetes, Endocrinology, and Metabolism, Churchill Hospital, Oxford OX3 7LJ, UK. Electronic address: patrik.rorsman@ocdem.ox.ac.uk.