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Gene Tied to Anorexia Nervosa

Researchers call discovery 'first crack' in disorder's genetic mystery

TUESDAY, Aug. 6, 2002 (HealthDayNews) -- Australian scientists have found a gene variant that contributes to anorexia nervosa in a large number of patients.

The gene variant, which the researchers call the "first major crack in the genetic mystery around anorexia," helps regulate the body's norepinephrine (or noradrenalin) system. This marks a sharp departure from previous research avenues; scientific detectives had previously assumed that the key to anorexia lay in the brain's serotonin system.

The findings appear in the August issue of Molecular Psychiatry.

"People have believed for a long time that anorexia nervosa had a genetic basis, and the issue has been how much is genetic and how much is environmental," says Dr. Ilene Fennoy, chief of pediatric endocrinology at St. Luke's Roosevelt Hospital Center in New York City. "That has major implications for how aggressively you pursue pharmaceutical interventions and even genetic interventions. Identifying a genetic locus is a very crucial piece of where one can go."

Anorexia nervosa is a psychiatric disorder that mainly affects young women. These women become obsessed with dieting and losing weight and often stop eating. Anorexia has the highest death rate of all psychiatric disorders.

Previously, researchers thought the signs of anorexia, including low blood pressure and low pulse, might be due to starvation.

"But now there's the possibility that it's not due to starvation but to the actual genetics of the way this chemical is handled," says Dr. Kenneth Nunn, senior clinical author of the study and a clinical associate professor in child psychiatry at Children's Hospital in Westmead, Australia. "One of the problems in anorexia is distinguishing between the cause and effect of starvation."

It appears that people with this genetic variation have problems in the way the chemical norepinephrine, which is involved in sending messages related to stress, is "recycled" or put back into circulation to be used again. As long as your body has enough fuel, the system works fine. But if you go on a diet and run out of fuel, the system goes into shut-down, Nunn says. "Then they don't want to eat and they have less fuel and it becomes a vicious cycle," he says.

"Normal" girls (and sometimes boys) can go on a diet and stop without much of a problem. Those with the genetic variation can't.

The unusual thing about this research is that treatments are available. "There are things we can do straight away," says Nunn.

One thing you can do is kick-start the norepinephrine system by making sure the patient's diet contains tyrosine, which can be broken down into the chemicals the body needs. Ironically, diet drinks may do the trick because they contain phenylalanine (used as a sweetener), which breaks down into tyrosine and in turn is eventually converted into norepinephrine.

Some of the newer antidepressants, such as reboxetine, target the norepinephrine system and may help combat the disorder. It's also possible that some of the drugs that target the serotonin system would help, the researchers say.

The findings may help in the effort to distinguish between different subtypes of anorexia.

Certainly, the study shifts the equation between genetic and environmental factors. "The evidence is slowly gathering," Nunn says. "We know that this is not a disease caused by bad parenting."

What To Do

For more information on anorexia nervosa, visit the National Alliance for the Mentally Ill or the National Association of Anorexia Nervosa and Associated Disorders.

SOURCES: Kenneth Nunn, M.D., clinical associate professor in child psychiatry, Children's Hospital, Westmead, Australia; Ilene Fennoy, M.D., chief of pediatric endocrinology, St. Luke's Roosevelt Hospital Center, New York City; August 2002 Molecular Psychiatry
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