August 28, 2008

Study Suggests Missing Gene May Impair Appetite Control

By Nanci Hellmich

Some obese children and adults who eat excessively may be missing a gene for a brain chemical involved in controlling appetite, according to a study in today's New England Journal of Medicine.

Low levels of the chemical are also linked to long-term memory loss and difficulties in sensing pain.

Researchers at the National Institutes of Health examined 33 children and adults with a rare condition in which groups of genes have been deleted. Called WAGR syndrome, the genetic aberration is found in about 250 people in the USA.

Half of the people studied lacked one of two genes for a brain chemical called brain-derived neurotrophic factor (BDNF). The ones missing the gene had low blood levels of the chemical. By age 10, all of those missing the gene were obese and reported a strong tendency to overeat. Those who had two working copies of the BDNF gene were no more likely to be obese in childhood or to report unusually high levels of overeating than the general population.

Scientists suspected that people within the group had abnormalities with the gene, and they believe a larger segment of the population has the same problem.

The missing gene may explain why some people can't seem to control their eating or lose weight, says Jack Yanovski, head of the Unit on Growth and Obesity at NIH's Eunice Kennedy Shriver National Institute of Child Health and Human Development.

"We suspect that BDNF has important issues in many parts of the brain, including memory and ability to sense pain," he says.

Yanovski says the brain chemical works in combination with other chemicals in the body, including the hormone leptin, to regulate appetite and body weight. More research needs to be done so scientists can develop obesity drugs to treat people who don't make enough BDNF, he says.

"BDNF is just a small part of the puzzle explaining why some folks have trouble maintaining a normal weight." (c) Copyright 2008 USA TODAY, a division of Gannett Co. Inc. <>