Study shows gene variant raises obesity risk
An international team of researchers has found a connection between a variation in a gene active in the central nervous system (CNS) and an increased risk for obesity. The study, published in the journal Public Library of Science (PLoS) Genetics, adds weight to past findings that our genes play a major role in what we want to eat and how much of it, and in our susceptibility to obesity. The research is part of the EU-funded EUROSPAN ('European special populations research network: quantifying and harnessing genetic variation for gene discovery') project, which is supported under the Sixth Framework Programme (FP6) to the tune of EUR 2.4 million. For this latest study, 34 European and US research institutions discovered that people who have inherited the gene variant neurexin 3 (NRXN3) have a 10% to 15% increased chance of being obese versus people who do not have the variant. 'Obesity is a major health concern worldwide. In the past two years, genome-wide association studies of DNA (deoxyribonucleic acid) markers known as SNPs (single nucleotide polymorphisms) have identified two novel genetic factors that may help scientists better understand why some people may be more susceptible to obesity,' the authors write. 'We uncovered a new gene influencing waist circumference, the NRXN3, which has been previously implicated in studies of addiction and reward behaviour.' Data from eight studies were used to carry out the research. These studies, which focused on genes and body weight, included over 31,000 people of European origin, aged 45 to 76. According to the researchers, the subjects represented a broad range of health behaviours and dietary habits. The researchers noted the NRXN3 gene variant has been linked to alcohol dependence, cocaine addiction and illegal substance abuse. By evaluating more than 2 million regions of the human genome, the team found that NRXN3 can predict the tendency of people to become obese. The gene variant was found in 20% of the subjects assessed, they said. 'We've known for a long time that obesity is an inherited trait, but specific genes linked to it have been difficult to find,' explained Professor Robert Kaplan of Department of Epidemiology and Population Health at the Albert Einstein College of Medicine in the US. 'A lot of factors - the types and quantity of foods you eat, how much you exercise, and how you metabolise 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.' Professor Kaplan pointed out that NRXN3 is the third obesity-linked gene to be identified. An important factor to consider is that all three genes are very active in encoding brain proteins. 'Considering how many factors are involved in obesity, it is interesting that research is increasingly pointing to the brain as being very important in its development,' he remarked. The prevention and treatment of obesity could be possible with the identification of obesity genes. '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,' Professor Kaplan said. 'Also, we may eventually see drugs that target the molecular pathways through which obesity genes exert their influence.'