25(OH) Vitamin D Levels and Severity of Type 1 Diabetes in Youth and Adults With Recent-Onset Disease

To test 25-hydroxy vitamin D (25(OH)D) levels among subjects with new-onset type 1 diabetes (T1D) and their association with fasting and stimulated C-peptide at study entry in an open-label randomized trial.

We conducted a post hoc secondary analysis of the POSEIDON trial (a Pilot, Safety and Feasibility Trial of High-Dose Omega-3 fatty acids and High-Dose Cholecalciferol Supplementation in Type 1 Diabetes). Eligibility criteria included age 6 to 65 years, T1D of up to 10 years duration, presence of at least 1 islet autoantibody, and stimulated C-peptide ≥0.066 pmol/mL. A total of 18 subjects with new-onset T1D (defined as ≤180 days duration) with paired 25(OH)D levels and a 4-hour mixed meal tolerance test (MMTT) at screening were included.

25(OH)D levels were directly associated with fasting C-peptide (r = 0.589; 95% CI 0.154-0.833; P = .01) but no significant associations were found with MMTT stimulated C-peptide. Ten subjects had 25(OH)D levels <30 ng/mL (56%) and fasting C-peptide was significantly lower compared to those with 25(OH)D levels >30 ng/mL (0.22 ± 0.14 vs 0.41 ± 0.09 pmol/mL; P < .006).

25(OH)D levels were directly associated with fasting C-peptide in youth and adults with newly diagnosed T1D. Low 25(OH)D levels may be associated with more aggressive autoimmunity in patients at risk for T1D potentially leading to a lower beta-cell mass at T1D clinical onset, but larger studies are required to validate these results.