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 mu g 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 HbA(1c) 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.