1. Diabetes Centre, Isala Clinics, Zwolle, Netherlands
2. Department of General Practice, University of Groningen, UMCG, Groningen, Netherlands
3. Department of Internal Medicine, University of Groningen, UMCG, Groningen, Netherlands
4. Medical Research Group, Langerhans, Zwolle, Netherlands
5. Department of Internal Medicine, Isala Clinics, Zwolle, Netherlands