Although thought of as a psychological problem, the eating disorder anorexia nervosa often runs in families, suggesting that it has a genetic component. Now researchers have found two genes that help determine the risk of acquiring the disease. The results suggest that variations in genes involved in mood and appetite can put women at risk for anorexia.
People with anorexia, usually women, have a distorted body image, starve themselves, and tend to be perfectionists. Studies over the last decade have suggested that genes play a role. The risk of becoming anorexic is about half a percent in the general population, but in 2000, researchers found that the risk jumped 11-fold in people with anorexic family members. Family dynamics don't appear to explain the link: Psychiatrist Walter Kaye at the University of Pittsburgh and colleagues found a variation of a region on chromosome 1 that was common in people with the disease.
The fingered region contains between 100 and 300 genes, and Kaye and colleagues wanted to narrow that down. They found three candidate genes that they knew were involved in neural signaling for appetite, anxiety, and depression. By comparing the sequences of these genes in healthy versus anorexic people, the team found that anorexic women consistently had particular sequence variations in two of these three genes. Additional examination of the two genes in anoxeria-prone families gave the researchers a handle on which DNA sequence variations conferred the most risk. One of the genes codes for a protein that allows neurons to respond to serotonin, a neurotransmitter involved in mood. The other gene codes for an opioid receptor, which, among other things, is involved in appetite, the team reports in the May issue of Molecular Psychiatry.
By identifying serotonin and opioid receptors, the work suggests that the mood and appetite systems are disrupted by defective proteins in anorexia, says clinical researcher Michael Devlin of Columbia University in New York City. Researchers now have to figure out how those particular genetic abnormalities play into the disease, he says, and potentially use them to design therapies.