Thursday, October 20, 2005

A Germ, An Eating Disorder

I saw a woman yesterday whose eating disorder had left its imprint on her temples, literally. There were carved out hollows where her temples would have been. At her age, much of this bone loss is probably irreplaceable.

Eating disorders have complex roots. Women who starve themselves, or who binge and purge, don't do it solely to acquire the lithe figure of a celebrity. There are myriad psychological and biochemical forces that lead to this behavior.

Now, there's one more:

Anorexia nervosa and bulimia may have an autoimmune component.
(Published in the October 11 issue of the Proceedings of the National Academy of Sciences. You can view the abstract here.)

Researchers in Sweden found unusual levels of autoantibodies (antibodies that attack the body's own cells instead of fighting invading organisms) in subjects with eating disorders. The autoantibodies were attacking a small protein (α-melanocyte-stimulating hormone) that operates in the nervous system to control appetite. It's also involved in the stress response.

Why were these autoantibodies present?
The authors speculated that some microorganism, a bacteria or virus, may be to blame. Microorganisms are known to protect themselves from attack by camouflaging to look like one of our body's proteins. Our immune system can sometimes see through their costume, attacking both the real protein along with the disguised germ.

Their work sheds light on the causes of other psychiatric disorders, notably obsessive-compulsive disorder (OCD). It also paves a way for new therapies. That's good news for younger sufferers, but people past their mid-thirties whose bone integrity has been compromised by an eating disorder aren't likely to experience a skeletal windfall.

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