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Thursday, Dec. 19, 2002

NATURAL SELECTIONS

Autoimmune disorder may kickstart anorexia in some


At the beginning of the Manic Street Preachers song "4st 7lbs," a girl is heard saying: "I eat too much to die. And not enough to stay alive. I'm sitting in the middle waiting."

The lyrics are about anorexia, written by Richey Edwards, who himself suffered from the disease, at one point surviving on a single bar of chocolate a day.

While anorexia means "loss of appetite," those suffering from it in fact have normal appetites, but they exercise extreme control over their eating.

Anorexics develop a distorted body image that can lead to life-threatening weight loss and amenorrhea (cessation of menstruation) in female sufferers. If the disorder and weight loss continue over several years, the patients suffer an increased risk of osteoporosis in later life.

Anorexia and bulimia (a related eating disorder characterized by binge-eating followed by vomiting) are most common in adolescent, middle-class girls (men are less likely to suffer from eating disorders). In Western countries, eating disorders affect, for instance, one in every 150 15-year-old girls. And 3 percent of women will be affected at some point during their lives.

The causes are as yet unknown, but are likely to vary from person to person.

However, research carried out in Sweden and published in the Proceedings of the National Academy of Sciences suggests that in some cases an autoimmune disorder may be partly to blame.

Autoimmune disorders occur when the body's immune system turns against itself. It is responsible for diseases such as rheumatoid arthritis, lupus and multiple sclerosis, and if the Swedish research is confirmed, anorexia and bulimia could join them.

Serguei Fetissov and colleagues, of the Karolinska Institute in Stockholm, analyzed blood serum from female patients diagnosed with anorexia, bulimia or both (individuals often suffer from both disorders at the same time). The blood of many of the patients contained antibodies that disrupt the body's regulation of food intake and body weight.

Fetissov wasn't just lucky to find the antibodies; he was testing a theory about neural control over eating.

Although the causes of anorexia and bulimia are unknown, "a body of data exists suggesting a primary neurobiological origin," write the authors. Fetissov and colleagues focused on the hypothalamus and the pituitary, regions of the brain that are known to play a central role in regulating our food intake.

Previous studies had shown that animals with damage to the lateral hypothalamus (the "hunger center" of the brain) lost weight, while rats with lesions in the ventromedial hypothalamus overate and became obese. Fetissov's team hypothesized that the hypothalamus and/or the pituitary of anorexic and bulimic women might be damaged, perhaps by the immune system.

If we become infected, say, by a virus, our body produces antibodies to attack the invaders. But in autoimmune disorders, the body produces antibodies primed to attack our own tissue. This is what Fetissov and his team found was happening in 74 percent of the 57 anorexic/bulimic women whose blood they screened.

The scientists found that these women (who were between the ages of 17 and 42) had antibodies that targeted proteins in the hypothalamus and the pituitary. These brain areas make proteins called neuropeptides that regulate the metabolism, and the antibodies in the affected women were attracted to cells making neuropeptides called alpha-MSH, ACTH and LHRH. The "auto-antibodies" might directly destroy, or disrupt, the brain signals that regulate body weight and food intake.

However, Fetissov was careful to emphasize that the causes of anorexia and bulimia are still, as yet, unknown. The same antibodies, for example, were also found in two out of 13 healthy women who were tested. So it can't just be the antibodies that cause eating disorders.

"I would like to emphasize that some apparently healthy individuals also had such auto-antibodies," Fetissov said.

The Swedish work does however suggest that the traditional view of eating disorders as being primarily behavioral and developmental problems might have to be modified.

Eating disorders often start around the time of exams, when adolescents face high levels of stress and feel pressured to match the expectations of their parents. Much blame is also put on the Western "culture of thinness" (although the culture of thinness in Japan -- where eating disorders are also common -- is at least as pervasive as in the West, if not more so). Young women, surrounded by images of beautiful, thin models, feel the pressure to diet.

While it seems reasonable that some of the blame for eating disorders be attributed to social pressure, if future research on antibodies supports Fetissov's ideas (the Swedish lab is planning to screen a larger group of patients), then we could have an entirely new way of looking at anorexia and bulimia, as well as new ways of treating them.

Until then, here's how Edwards -- who literally vanished soon after penning the words and has been missing for years -- finished his song about anorexia: "Yeah 4 stone 7, an epilogue of youth/Such beautiful dignity in self-abuse/I've finally come to understand life/Through staring blankly at my navel."

Rowan Hooper welcomes comments at rowhoop@gol.com


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