No Effect of the 1α,25-Dihydroxyvitamin D(3) on β-Cell Residual Function and Insulin Requirement in Adults With New-Onset Type 1 Diabetes

OBJECTIVE: To determine whether daily intake of 1α,25-dihydroxyvitamin D(3) [1,25(OH)(2)D(3)] is safe and improves β-cell function in patients with recently diagnosed type 1 diabetes. RESEARCH DESIGN AND METHODS: Safety was assessed in an open study of 25 patients aged 18–39 years with recent-onset type 1 diabetes who received 0.25 μg 1,25(OH)(2)D(3) daily for 9 months. An additional 40 patients were randomly assigned to 0.25 μg 1,25(OH)(2)D(3) or placebo daily for 9 months and followed for a total of 18 months for safety, β-cell function, insulin requirement, and glycemic control. RESULTS: Safety assessment showed values in the normal range in nearly all patients, regardless of whether they received 1,25(OH)(2)D(3) or placebo. No differences in AUC C-peptide, peak C-peptide, and fasting C-peptide after a mixed-meal tolerance test between the treatment and placebo groups were observed at 9 and 18 months after study entry, with ∼40% loss for each parameter over the 18-month period. A1C and daily insulin requirement were similar between treatment and placebo groups throughout the study follow-up period. CONCLUSIONS: Treatment with 1,25(OH)(2)D(3) at a daily dose of 0.25 μg was safe but did not reduce loss of β-cell function.