Sunshine and Multiple Sclerosis – The Role of Vitamin D (Part 2)

By Brett Drummond

In part one of this series, we discussed that geographical studies indicated that MS is more prevalent the further you moved away from the equator and that this was thought to be due to Vitamin D deficiency caused by low levels of sunlight exposure. This is the strongest environmental link known to date. However, we also know that there is a genetic component to MS. In this article, we look at a genetic risk that can be associated with Vitamin D.

A large population study of more than 12,000 people (including 43 families whose genetic history included four or more people affected by MS) identified a rare version of a gene to be present at significant levels in people with MS compared to healthy individuals. This gene was a variant of CYP27B1 – the gene responsible for an enzyme that performs the last step in the conversion of sunlight to biologically active Vitamin D. People with one copy of this mutant version of the gene have lower levels of Vitamin D. However, people with two copies of the mutant gene (we inherit two copies of each gene – one from Mum and one from Dad), develop a genetic form of rickets (a disease caused by Vitamin D deficiency).

To further highlight this link, researchers then investigated cases where healthy parents had had a child that developed MS. From 3,000 families, they found 35 parents that carried a single copy of the mutant form of the CYP27B1 gene. In every one of these 35 cases, the child that developed MS had inherited the ‘bad’ version of the gene. The researchers were quoted as saying that the possibility that the child developing MS was unrelated to inheriting the mutated gene was ‘billions to one against’.

These studies provide further evidence as to the potential role of Vitamin D as a factor in the development of MS, as containing a mutant gene that decreases Vitamin D levels is found more often in people with MS. Not only can low levels of Vitamin D be part of the environmental causes of MS, it may also result from genetic causes. Identifying a version of a gene that leads to low levels of Vitamin D and MS could enhance our ability to assess an individual’s potential risk of developing MS (particularly if other family members are affected). In terms of treatment, it opens the door for a potential gene therapy approach and reinforces the possibility of using Vitamin D supplementation.