A brain chemical associated with long term memory may also have a hand in regulating how much people eat, according to a study released Wednesday.
The chemical, "brain derived neurotrophic factor" (BDNF), may also help control appetite and weight, studies of laboratory animals suggest. The National Institutes of Health study shows that the chemical plays a role in regulating weight in humans as well.
The study was published in the New England Journal of Medicine. Researchers discovered the influence of the chemical while studying children with a rare genetic disorder called WAGR syndrome, which affects one in 500,000 to 1 million people.
WAGR stands for the symptoms seen in people with the condition: Wilms tumor, a tumor of the kidneys; aniridia, absence of the iris; genital and urinary tract abnormalities; and mental retardation.
The researchers found that some with the syndrome are missing copies of the gene for BDNF. Those lacking the gene had unusually large appetites and a strong tendency towards obesity.
"This is a promising new lead in the search for biological pathways that contribute to obesity," Duane Alexander, director of the NIH's Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD) said. "This finding may eventually lead to the development of new drugs to regulate appetite in people who have not had success with other treatments."
People with WAGR syndrome lack genes on chromosome 11. Researchers analyzed the chromosome in 33 patients. Nineteen patients were missing all or large parts of one copy of the gene for BDNF. By the time they reached 10, all of these patients were obese and tended to overeat.
Patients who had two working copies of the gene were no more likely to develop childhood onset obesity, than the general population.
Dr. Jack A. Yanovski of NICHD's Unit on Growth and Obesity, and one of the authors of the study, said BDNF most likely works in combination with other substances, such as leptin, a hormone that signals hunger. Yanovski said leptin triggers the release of BDNF in the hypothalamus, a part of the brain that controls eating.
Studies of the relationship between BDNF and leptin could lead to new drugs for treating obesity, he said.
