Genes linked to obesity in both humans and labradors identified

Researchers have identified multiple genes that influence obesity in both humans and labrador retrievers, providing new insights into the genetic basis of weight gain.

Obesity is a growing issue in both humans and pets, with around half of pet dogs being overweight. The new study, published in Science by researchers at the University of Cambridge, highlights the role of genetics in obesity, and shows that some individuals and animals are biologically predisposed to overeating. Understanding these genetic mechanisms could inform targeted obesity treatments and interventions in both veterinary and human medicine.

'Studying the dogs showed us something really powerful: owners of slim dogs are not morally superior,' said Dr Eleanor Raffan from the University of Cambridge, senior author of the study. '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.'

The researchers conducted a genome-wide association study (GWAS) using DNA from 241 labrador retrievers, comparing their genetic profiles with their body condition scores, a measure of obesity. They identified multiple genes linked to obesity, with the DENND1B gene showing the strongest association with obesity. Dogs carrying a specific variant of this gene had approximately eight percent more body fat than those without it.

The study also found that dogs with a high genetic risk for obesity could still maintain a healthy weight if their owners enforced strict control over their diet and exercise, but with significantly more effort and vigilance required than for dogs with a lower genetic risk of obesity.

The researchers then examined human genetic data and found that variations in DENND1B were also associated with higher body mass index, a measure of obesity, in humans. They performed further experiments in human cell lines to investigate the function of the DENND1B protein. They found that DENND1B plays a key role in the leptin-melanocortin pathway, which regulates appetite and energy balance, by influencing the activity of another protein that controls hunger signals in the brain.

The findings indicate that some individuals are biologically predisposed to overeating. Based on the data from labradors, people with bigger appetites may be more likely to gain weight in environments where food is easily available, and will need to be more mindful of their eating habits to maintain a healthy weight.

'This work shows how similar dogs are to humans, genetically. Studying the dogs meant we had reason to focus on this particular gene [DENND1B], which has led to a big advance in understanding how our own brain controls our eating behaviour and energy use,' said Dr Raffan.