No Effect of the 1α,25-Dihydroxyvitamin D3 on β-Cell Residual Function and Insulin Requirement in Adults With New-Onset Type 1 Diabetes

OBJECTIVE - To determine whether daily intake of 1 alpha,25-dihydroxyvitamin D-3 [1,25(OH)(2)D-3] is safe and improves beta-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 mu g 1,25(OH)(2)D-3 daily for 9 months. An additional 40 patients were randomly assigned to 0.25 1, mu g 1,25(OH)(2)D-3 or placebo daily for 9 months and followed for a total of 18 months for safety, beta-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 similar to 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 mu g was safe but did not reduce loss of beta-cell function.