1. Department of Medicine, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
2. Department of Internal Medicine, Division of Endocrinology, Diabetology, and Nephrology, University Hospital Tübingen, Tübingen, Germany
3. Institute of Diabetes Research and Metabolic Diseases, Helmholtz Center Munich, University Tübingen, Tübingen, Germany
4. German Center for Diabetes Research, University Tübingen, Tübingen, Germany