Background: The impact of the anti-inflammatory and immunomodulatory actions of Vitamin D on the duration of partial clinical remission (PR) in youth with type 1 diabetes (T1D) is unclear. Objective: To determine the effect of adjunctive ergocalciferol on residual β-cell function (RBCF) and PR in youth with newly-diagnosed T1D who were maintained on a standardized insulin treatment protocol. Hypothesis: Ergocalciferol supplementation increases RBCF and prolongs PR. Methods: A 12-month randomized, double-blind, placebo-controlled trial of 50,000 IU of ergocalciferol per week for 2 months, and then once every 2 weeks for 10 months, versus placebo in 36 subjects of ages 10-21years(y), with T1D ofmonths, and a stimulated C-peptide (SCP) level of ≥0.2nmol/L (≥0.6ng/mL). The ergocalciferol group had 18 randomized subjects (10m/ 8f), mean age 13.3±2.8y; while the control group had 18 subjects (14m/4f), age 14.3±2.9y. Results: The ergocalciferol treatment group had significantly higher serum 25-hydroxyvitamin D at 6 months (p=0.01) and 9 months (p=0.02) than the placebo group. At 12 months, the ergocalciferol group had a significantly lower serum TNF-α concentration (p=0.03). There were no significant differences between the groups at each timepoint from baseline to 12 months for SCP concentration (p=0.08), HbA1c (p=0.09), insulin-dose-adjusted A1c (IDAA1c), or total daily dose of insulin. Temporal trends for rising HbA1c (p=0.044) and IDAA1c (p=0.015) were significantly blunted in the ergocalciferol group. Conclusions: Ergocalciferol significantly reduced serum TNF-α concentration and the rates of increase in both A1c and IDAA1c suggesting a protection of RBCF and PR in youth with newly-diagnosed T1D
