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SOMETHING as simple as eating a healthy diet could help people who suffer
from a common genetic disorder, according to new research.

Spinal Muscular Atrophy (SMA) is the most common genetic cause of infant
mortality worldwide, affecting about 1 in 6000 babies. It causes muscle weakness
and wasting, and kills most victims before they are two years old. But many
people survive to adulthood, despite the fact that most cases are caused by the
same mutation in a single gene.

It had been assumed that the varying fates of those affected were due to
other, as yet unknown, genes. But the new research suggests that one factor
determining the severity of symptoms could be how much folic acid and vitamin
B₁₂ a patient consumes—either through a healthy diet or by taking
vitamin pills.

The researchers emphasise that there have been no clinical studies to back up
the theory yet. “I don’t want anybody for a moment to get any sort of
sensational message from this. I’m not suggesting this is a cure. I wouldn’t
have even suggested it if there had been any obvious downside to taking these
supplements,” says Gideon Dreyfuss, a biochemist at the University of
Pennsylvania and co-author of the study.

SMA sufferers have a mutation in a gene responsible for making a protein
called SMN. All cells need SMN, but it’s especially important for motor
neurons—the nerve cells that carry signals to muscles. SMN interacts with
a number of other proteins in the neurons, helping them build the molecular
machinery needed to manufacture proteins and RNA. Because SMA sufferers don’t
have enough SMN protein, their motor neurons don’t work well. This in turn means
their muscles don’t receive the stimuli they need to function, so they waste
away.

Dreyfuss and his colleagues set out to determine exactly what the SMN protein
does. They noticed that SMN needs help to bind to other proteins and found that
before it can attach to its protein targets, they have to be “tagged” with a
chemical label called a methyl group. This is where folic acid and vitamin
B₁₂ come in, because the methyl groups originally come from folic acid,
through a pathway that requires vitamin B₁₂.

Since SMA sufferers are already short of the SMN protein, a lack of methyl
groups could hit them especially hard, making it even more difficult for SMN to
do its job. Dreyfuss says he’s discussing clinical trials with other researchers
to see if B₁₂ and folate supplements could help. Foods rich in folic
acid include green leafy vegetables such as broccoli and spinach, while meat and
dairy products provide vitamin B₁₂.

“Any kind of glimmer of hope is well worth pursuing,” says Kenneth H.
Fischbeck, a neurologist with the National Institutes of Health near Washington
DC. “You have to make a jump to say you’ll find a deficiency in people. On the
other hand, it is a benign treatment.”