The effects of calcitriol and nicotinamide on residual pancreatic β‐cell function in patients with recent‐onset Type 1 diabetes (IMDIAB XI)

BACKGROUND: A number of recent studies underline the importance of vitamin D in the pathogenesis of Type 1 diabetes (T1D). AIMS: The aim of this study was to investigate whether supplementation with the active form of vitamin D (calcitriol) in subjects with recent-onset T1D protects residual pancreatic beta-cell function and improves glycaemic control (HbA(1c) and insulin requirement). METHODS: In this open-label randomized trial, 70 subjects with recent-onset T1D, mean age 13.6 years +/- 7.6 sd were randomized to calcitriol (0.25 microg on alternate days) or nicotinamide (25 mg/kg daily) and followed up for 1 year. Intensive insulin therapy was implemented with three daily injections of regular insulin + NPH insulin at bedtime. RESULTS: No significant differences were observed between calcitriol and nicotinamide groups in respect of baseline/stimulated C-peptide or HbA1c 1 year after diagnosis, but the insulin dose at 3 and 6 months was significantly reduced in the calcitriol group. CONCLUSIONS: At the dosage used, calcitriol has a modest effect on residual pancreatic beta-cell function and only temporarily reduces the insulin dose.