Genetic aspects of vitamin D receptor and metabolism in relation to the risk of multiple sclerosis

Recent findings suggest that polymorphisms in vitamin D pathway genes are candidates for association with multiple sclerosis susceptibility. It has been now well demonstrated that vitamin D has immunomodulatory functions that may be favorable for reduction of multiple sclerosis risk. Current research has been focused on identification of new variants of genes involved in vitamin D pathway, namely in vitamin D receptor and enzymes of vitamin D metabolism. These variants have been intensively studied as possible genetic predictors of both vitamin D levels and the risk of multiple sclerosis. Considering the findings available up-to-date, we may recognize two groups of genetic variants. The first group of genes was found to predict vitamin D levels but not the risk of multiple sclerosis. The second group of genetic variants is represented by promising genes predicting vitamin D levels as well as the risk of multiple sclerosis. A strong association with increased risk of the disease has been observed for a rare variant in the CYP27B1 gene encoding a vitamin D-activating enzyme. Observed interaction between genetic and epidemiological findings brings the rationale for supplementation trials of vitamin D. Although promising effects of vitamin D supplementation have emerged, the results obtained so far are inconclusive and the real therapeutic significance of vitamin D supplementation remains to be elucidated.