Kornelis J J van Hateren1, Gijs W D Landman2, Nanne Kleefstra3. 1. Diabetes Centre, Isala, Zwolle, The Netherlands. 2. Diabetes Centre, Isala, Zwolle, The Netherlands; Department of Internal Medicine, Gelre Hospital, Apeldoorn, The Netherlands. 3. Diabetes Centre, Isala, Zwolle, The Netherlands; Department of Internal Medicine, University of Groningen and University Medical Center Groningen, Groningen, The Netherlands; Langerhans Medical Research Group, Zwolle, The Netherlands.