Effect of 1, 25 dihydroxy v itamin D3 on T Helper 17 (TH17) cell pathways in diarrhea associated irritable bowel syndrome

Purpose: To investigate the effect of 1, 25-dihydroxyvitamin D3 (1,25-(OH)2D3) on T-Helper 17 (TH17) cell pathways in diarrhea-associated irritable bowel syndrome (IBS-D). Methods: 120 children with IBS-D were treated with Smecta alone and Smecta in addition to 1,25-(OH)2D3 in Hangzhou Ninth Peoples Hospital, Hangzhou, China. Blood samples were taken to determine the levels of 1,25-(OH)2D3, IL-17, IFN-γ, IL-23, and IL-6, as well as Th17 cell ratio. Furthermore, IL-17 and RORγt expressions were evaluated. Results: Serum 1,25-(OH)2D3 levels decreased in IBS-D patients and were negatively correlated with IL-17 levels in serum and Th17 cells in peripheral blood. Treatment with 1,25-(OH)2D3 significantly reduced serum IFN-γ, IL-17, IL-23 and IL-6 levels in IBS-D patients (p < 0.05). Percentage of Th17 cells, and IL-17 and RORγt expression levels were significantly reduced in IBS-D patients after 1,25-(OH)2D3 treatment (p < 0.05). Conclusion: This study shows that 1,25-(OH)2D3 reduces serum IFN-γ, IL-17, IL-23, IL-6 levels, Th17 cells and RORγt expression in IBS-D patients. Additional studies with larger sample sizes are required to validate these findings.