1. Institute of Biochemistry II, Medical Faculty, University of Cologne, Köln, Germany
2. German Diabetic Centre, Department of Clinical Biochemistry and Pathobiochemistry,UKD, University of Düsseldorf, Düsseldorf, Germany
3. Department of General Pediatrics, UKD, University of Düsseldorf, Düsseldorf, Germany
4. Department of Anatomy I, Medical Faculty, University of Cologne, Köln, Germany
5. Center for Molecular Medicine Cologne, University of Cologne, Köln, Germany