1. Second Department of Internal Medicine, Diabetes Centre, Diabetic Foot Clinic, Democritus University of Thrace, Alexandroupolis, Greece
2. Institute for Clinical Diabetology, German Diabetes Center, Leibniz Center for Diabetes Research, Heinrich Heine University, Düsseldorf, Germany
3. Department of Endocrinology and Diabetology, Medical Faculty, Heinrich Heine University, Düsseldorf, Germany