Study points to brain chemical involved in obesity

By Will Dunham

WASHINGTON (Reuters) - Researchers studying people with a rare genetic disorder have identified a brain chemical that may play a role in appetite and obesity, a finding they say could lead to new drugs to help some obese people.

Previous animal studies had pointed to this chemical, known as BDNF, as helping to regulate appetite and weight, but the new study published on Wednesday in the New England Journal of Medicine is the first to show such a role in people.

"The importance of the finding is that it opens up another avenue for us to develop treatments that might help folks with obesity," said Dr. Jack Yanovski of the Eunice Kennedy Shriver National Institute of Child Health and Human Development, part of the U.S. National Institutes of Health.

A number of substances naturally occurring in the body, including the hormone leptin and neuropeptide Y, are known to affect appetite and obesity, and the findings about BDNF add to the understanding of factors underpinning obesity, he added.

BDNF, which stands for brain-derived neurotrophic factor, is already known to play a role in long-term memory.

"We're looking at a small part of what is really a large and complex puzzle," Yanovski, who helped lead the study, said in a telephone interview. "We guess there are probably about 300 genes that affect body weight in some form or another."

The study involved 33 people with WAGR (pronounced wagger) syndrome, a rare genetic condition that puts one at high risk for eye problems, certain cancer types and mental retardation.

Normally a person has two copies of the gene that controls BDNF. But the researchers found that most of the WAGR syndrome patients -- 19 of them -- were missing one copy of the gene, and thus had low blood levels of BDNF.

Every one of the 19 was obese by age 10 and had a strong tendency to overeat. The 14 other people who had two working copies of the gene were no more likely than the general population to be obese or overeat, the researchers said.

This strongly suggests BDNF is involved in controlling appetite and thus obesity, they said. The release of BDNF in the hypothalamus, a brain structure involved in regulating appetite, may be triggered indirectly by leptin, they added.

Yanovski said drugs that are based on improving low levels of BDNF could help certain obese people who have not had success with other treatments.

(Editing by Julie Steenhuysen and Cynthia Osterman)