1. Diabetes Centre, Isala, Zwolle, Netherlands
2. Department of Internal Medicine, University Medical Center Groningen, University of Groningen, Groningen, Netherlands
3. Department of Internal Medicine, Diakonessenhuis, Utrecht, Netherlands
4. Department of Internal Medicine, Isala, Zwolle, Netherlands
5. Department of Pathology and Medical Biology, University Medical Centter Groningen, University of Groningen, Groningen, Netherlands
6. Medical Research Group, Langerhans, Ommen, Netherlands