A team of researchers has identified multiple genes associated with obesity among labrador retrievers, a dog breed known for its insatiable appetite. In particular, the researchers looked at the DENND1B gene, which altered hunger signals among labradors, making them more prone to overeating. This gene, they said, was also linked to obesity in humans. The findings are described in the study, ‘Canine genome-wide association study identifies DENND1B as an obesity gene in dogs and humans’, which was published in the journal Science on March 6. It was carried out by researchers based at the University of Cambridge in England. How was the study carried out? The researchers examined DNA samples from 241 British labrador retrievers. They also collected information including the dogs’ body fat mass, how much dogs asked for food, and how strictly their owners controlled their diet. The researchers identified five obesity-associated genes, and then checked if these genes were also relevant to human obesity. They “looked at both large population-based studies, and at cohorts of patients with severe, early onset obesity where single genetic changes are suspected to cause the weight gain,” a press statement by the University of Cambridge said. What were the findings of the study? Among the five obesity-associated genes that the researchers had identified, the DENND1B gene was found to be most strongly associated with body mass and obesity in labradors. Dogs with a mutation in this gene had about 8% more body fat than those without it. The DENND1B gene is also found in humans, in whom it was also associated with higher body mass, the researchers found. Before this study of labrador genetics “no one suspected that [DENND1B] gene had anything to do with obesity”, Dr Eleanor Raffan, a researcher in the University of Cambridge’s Department of Physiology, Development and Neuroscience and the co-author of the study, told the BBC in an interview. The gene essentially interferes with a brain signalling pathway that helps regulate our appetite. Raffan said, “It alters the predisposition to weight gain because it's tweaking a system that is involved in regulating how hungry we feel and how much energy we burn off.” The researchers also found that the dog owners who strictly regulated their dogs’ diet and exercise managed to prevent even those with high genetic risk from becoming obese. However, much more attention and effort was required on the part of such dog owners. Similarly, humans with high genetic risk of obesity are more prone to weight gain. Why is this significant? The findings highlight the fact that obesity, both in dogs and humans, is not just a matter of will power. Yes, some people eat more, that is not completely by choice — they are genetically predisposed to it. Obesity is thus deeply connected with a complex interaction between genetics and the environment. In a press statement, Raffan said, “Owners of slim dogs are not morally superior. The same is true of slim people. If you have a high genetic risk of obesity, then when there’s lots of food available you’re prone to overeating and gaining weight unless you put a huge effort into not doing so.”
