Alcohol Gene May Also be Obesity Gene

(Ivanhoe Newswire) – A new study adds to evidence that genes influence appetite and that the brain plays a key role in obesity.

After analyzing more than two million regions of the human genome, researchers found that the NRXN3 gene variant - previously associated with alcohol dependence, cocaine addiction, and illegal substance abuse - also predicts the tendency to become obese.

Robert Kaplan, Ph.D., associate professor of epidemiology and population health, helped direct the international study, which involved 34 research institutions. Albert Einstein College of Medicine of Yeshiva University played a major role in this study.

Since NRXN3 is active in the brain and also is implicated in addiction, these traits may share some neurologic underpinnings. "Although we don't have data to suggest a direct connection between drug abuse and obesity,” Dr. Kaplan is quoted as saying, “we can indirectly infer a link because both traits have this gene in common."

NRXN3 is the third obesity-associated gene to be identified. The fact that all three genes are highly active in encoding brain proteins is significant. "Considering how many factors are involved in obesity,” said Dr. Kaplan, “it is interesting that research is increasingly pointing to the brain as being very important in its development."

Dr. Kaplan and his U.S. and European colleagues found that people who have inherited the gene variant NRXN3 have a 10 to 15 percent greater risk of being obese than people who do not have the variant.
 
The researchers examined data from eight studies involving genes and body weight. These studies included more than 31,000 people of European origin, ages 45 to 76, representing a broad range of dietary habits and health behaviors. Altogether, researchers found the gene variant in 20 percent of the people studied.

"We've known for a long time that obesity is an inherited trait, but specific genes linked to it have been difficult to find," says Dr. Kaplan. "A lot of factors - the types and quantity of foods you eat, how much you exercise, and how you metabolize foods, for example - affect your body shape and size. So we are looking for genes that may have a small role to play in a complex situation."
 
Identifying obesity genes could help prevent the condition and lead to treatments for it.

"Someday we may be able to incorporate several obesity genes into a genetic test to identify people at risk of becoming obese and alert them to the need to watch their diet and to exercise," Dr. Kaplan said. "Also, we may eventually see drugs that target the molecular pathways through which obesity genes exert their influence."

SOURCE:  PLoS Genetics, June 26th, 2009

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