1. Diabetes Centre, Isala Clinics, Zwolle, the Netherlands
2. Department of Medicine, University Medical Centre Groningen, Groningen, the Netherlands
3. Langerhans Medical Research Group, Zwolle, the Netherlands
4. Department of Biomedical Engineering, University Medical Centre Groningen, Groningen, the Netherlands
5. Department of General Practice, University Medical Centre Groningen and University of Groningen, Groningen, the Netherlands
6. Department of Medicine, University of Groningen, Groningen, the Netherlands