1. Department of Internal Medicine I, Section of Endocrinology & Diabetes, University Hospital Schleswig-Holstein, 23538 Lübeck, Germany
2. Clinical Division of Endocrinology and Metabolism, Department of Medicine III, Medical University of Vienna, 1090 Vienna, Austria
3. Endokrinologikum Hannover, 30161 Hannover, Germany
4. Department of Biochemistry and Molecular Cell Biology, University Medical Center Hamburg-Eppendorf, 20246 Hamburg, Germany
5. Department of Internal Medicine I, Section of Nutritional Medicine and Institute of Nutritional Medicine, University Hospital Schleswig-Holstein, 23538 Lübeck, Germany
6. Department of Biomedical Imaging and Image-Guided Therapy, Division of Nuclear Medicine, Medical University of Vienna, Vienna, Austria
7. German Center for Diabetes Research (DZD), 85764 Neuherberg, Germany