MS is autoimmune and neurodegenerative disease of unknown etiology but has about a 25% genetic risk and multiple environmental risk factors. Since 2006 low vitamin D levels have been known to be one of the risk factors along with EBV infection, smoking and adolescent obesity.
Vitamin D insufficiency is one of the most studied environmental risk factors. Interestingly there is correlation in Caucasians but not in Blacks or Hispanics, suggesting genetic interaction with this environmental risk. In Caucasians, supplementing vitamin D helps prevent relapses and disability progression.
In a recent study, researchers in Vermont, studied animal models of MS to evalaute this. They found that response to vitamin D was sex specific and only present in females. It seemed to need estrogen to be protective.
They then looked at genetic mouse variants and vit D was only protective in certain genetic strains just like our patients.
This genetic and sex-dependent Vit D protective effect was accompanied by decrease in expression of proinflammatory genes in CD4 T effector cells including MHC class II genes interferon gamma and other genes involved in neuroinflammation.
Genetic background and sex also modulated expression of known Vit D metabolism genes which changed their response to vit D
Results suggest that the association between Vit D and MS susceptibility in mouse model is highly dependent on genetic background and sex of animals. This may give us new insights to responses in our patients to environmental triggers and disease modifying therapy because they may vary with sex and genetic backgrounds.
Nancy Nealon, MD