Epidemiological evidence suggests that low levels of serum vitamin D are a possible risk factor for the development of multiple sclerosis (MS).1 The exact mechanisms by which vitamin D exerts its effects on MS risk are not well understood. The paper by Lin et al² identifies novel protein kinase C polymorphisms associated with 25 hydroxy vitamin D levels in MS patients.

Vitamin D is derived from the diet and from endogenous production in the skin. Vitamin D is akin to a pro-drug: it must be hydroxylated to the 25 hydroxy vitamin D metabolite in the liver and then to the active 1, 25 dihydroxy vitamin D form that binds the vitamin D receptor. Several cytochrome P450 enzymes including CYP2R1, CYP2D11 and CYP2D25 can catalyse the 25-hydroxylation reaction3 …