A New Gene, NRXN3, Is Associated with Obesity

Neurexin 3 Links Genetics and Food Addiction

Jul 3, 2009 Cecile Le Page

A new mutation in a gene that is active in the central nervous system and named neurexin 3 has been associated with increased risk for obesity.

Obesity is a major health concern and is constantly increasing in westernized countries. In USA, rates range from 18 to 33% in the adult population through the different states of the country. In Canada, more than 18% of the population is obese. Children are not exempt from this increasing phenomenon and the number of obese children has tripled in the past 20 years, now reaching 8% in Canada. Obesity is related to increased risk of several deadly diseases, such as cancer, diabetes and high blood pressure.

Obesity and Genetics

Obesity is estimated by the Body Mass Index (BMI) measure, which is the ratio of body weight (in kg) to height squared (in m²). When the BMI is between 25 and 30, people are considered overweight, and when BMI is over 30 people are considered obese. Several environmental, social and familial factors have been implicated in the increased rate of obesity. Recent genetics research brings additional evidence that food addiction may be under the control of the genes and may influence the food addiction and obesity status of certain people.

NRXN3 and Addiction

A new international study, co-directed by Dr Robert Kaplan and Dr Kari North, and published online in PLoS Genetics (issue 6, e 1000539, 2009) shows that people who have inherited the genetic mutation in the neurexin gene 3 (NRXN3) have an up to 15 % increased risk of being obese compared with healthy people who do not have this particular mutation. The scientists analyzed eight different studies involving genes and body weight. In total, more than 31,000 people of European origin, with ages between 45 and 76, were included in these studies and represent a broad range of dietary habits.

The NRXN3 gene was previously associated with addictions such as alcohol dependence and cocaine addiction. In this new study, the researchers analyzed more than 2 million small regions of the human genome and found that the NRXN3 gene mutation is associated with the risk of becoming obese. The mutation was found in 20 percent of the people studied.

Application to Genetic Studies In Obesity Treatment

Identifying obesity genes could help in preventing the condition and lead to effective diagnosis and treatments. Genetic tests could be performed to identify people, early in their life, susceptible to develop eating disorders and food addiction. This may help warn them to watch their diet and to exercise.

The identification of genetic factors involved in obesity and food addiction could also result in pharmacological treatment of the disease by developing drugs that target protein encoded by mutant genes and thereby inhibiting their effect on the brain.

The copyright of the article A New Gene, NRXN3, Is Associated with Obesity in Genetics & Evolution is owned by Cecile Le Page. Permission to republish A New Gene, NRXN3, Is Associated with Obesity in print or online must be granted by the author in writing.

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