Addiction Gene Linked to Common ObesityMonday, June 29, 2009
Hedonic hyperphagia (overeating controlled by reward rather than need for calories) often underlies excess caloric intake. As the reward centres that regulate drug and other forms of addiction are the same that are stimulated by highly palatable foods, it is not surprising that genes associated with substance and other addictions may also be linked with obesity.
This assumption finds new support in a study published this month in PLoS Genetics by Nancy Heard-Costa from Boston University School of Medicine on behalf of the CHARGE (Cohorts for Heart and Aging Research in Genome Epidemiology) consortium .
The researchers performed genetic analyses on more than 30,000 subjects participating in 8 large cohort studies, including the Age, Gene/Environment Susceptibility-Reykjavik Study (AGES- Reykjavik Study), the Atherosclerosis Risk in Communities Study (ARIC), the Cardiovascular Health Study (CHS), the European Special Population Network consortium (EUROSPAN), the Family Heart Study, the Framingham Heart Study, Old Order Amish (OOA), and the Rotterdam Study (RS).
Genetic loci studied included those identified in previous studies as well as new candidate loci for abdominal fat deposition.
In addition to confirming significant associations with the previously reported FTO and MC4R genes, the researchers found a novel locus in the NRXN3 gene associated with waist circumference, BMI and obesity.
NRNX3 has previously been associated with addiction (alcohol dependence, cocaine addiction, and illegal substance abuse) and is part of a family of central nervous adhesion molecules, which are highly expressed in sub-cortical regions of the brain in involved with learning and reward training.
Although the odds ratio for obesity per copy of the implicated G Allele was only 1.13, this small effect at a population level can be substantial.
More importantly, this finding clearly supports the notion that some individuals may be more susceptible to obesity because of an increased genetic predisposition to reward-seeking behaviours, that obviously include seeking out highly-palatable (addictive) foods.
Punitive approaches to drug addictions have not worked – neither will punitive approaches to obesity resulting from hedonic overeating.