Interaction of CD40L with CD40 triggers the induction of pro-inflammatory cytokines. It has been proposed that vitamin D deficiency might be an important factor which causes or aggregates autoimmune situations. The aim of the present study was to assess the effect of vitamin D on CD40L gene expression in patients with ulcerative colitis.

Ninety mild to moderate UC patients were randomized to receive a single injection of 7.5 mg cholecalciferol or 1 ml normal saline. At baseline and 90 days following the intervention RNA samples from whole blood were taken. Fold changes in CD40L mRNA expression were determined for each patient using the 2-ΔΔCq method. The data were analyzed using SPSS version 25.

Serum levels of vitamin D and calcium raised only in the vitamin D group (p<0.05). Relative to baselines, the CD40L gene expression fold change was significantly lower in the vitamin D group compared with the placebo group (Median ± IQR: 0.34 ± 0.30 vs 0.43 ± 1.20 respectively, p=0.016).

The results of this study show that vitamin D administration in mild to moderate ulcerative colitis patients leads to downregulation of the CD40L gene, which is an essential part of inflammatory pathways.