1. Institute of Anatomy II, Medical Faculty, Heinrich-Heine University, Düsseldorf, Germany
2. Institute for Clinical Diabetology, German Diabetes Center, Düsseldorf
3. German Center for Diabetes Research (DZD), München-Neuherberg, Germany
4. Department of Endocrinology and Diabetology, Medical Faculty, Heinrich-Heine University, Düsseldorf, Germany