Administering 25-hydroxyvitamin D3 in vitamin D-deficient young type 1A diabetic patients reduces reactivity against islet autoantigens.

Background & Aims: We investigated whether improving 25-hydroxyvitamin D status in young type 1A diabetic patients reduces reactivity of peripheral blood mononuclear cells against islet autoantigens and associates with beta-cell functional changes.
Methods: Eight patients with 25-hydroxyvitamin D deficiency (<20 ng/ml), out of 15 consecutive young type 1A diabetic subjects received 25-hydroxyvitamin D3 to achieve and maintain levels above 50 ng/ml for up to one year. Peripheral blood mononuclear cell reactivity (Interferon-γ spots) against beta-cell autoantigens (glutamic acid decarboxylase 65-kD isoform, proinsulin and tyrosine phosphatase-like protein IA-2) and C-peptide during mixed meal were assessed before and after 25-hydroxyvitamin D3 replenishment.
Results: Target 25-hydroxyvitamin D blood levels were safely reached and maintained. Peripheral blood mononuclear cell reactivity against glutamic acid decarboxylase 65-kD isoform (3.8 ± 4.0 vs. 45 ± 16) and proinsulin (3.5 ± 3.2 vs. 75 ± 51) decreased significantly (p < 0.001 and p < 0.02) upon 25-hydroxyvitamin D3 replenishment, which was correlated with 25-hydroxyvitamin D concentrations. C-peptide values remained stable after one year of treatment.
Conclusions: Safely restored and maintained 25-hydroxyvitamin D levels associated with reduced peripheral blood mononuclear cell reactivity against beta-cell autoantigens with no significant decrease of beta-cell function in this cohort of patients.
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