Study Links Genes in Labradors and Humans to Obesity Risk

In their study of British Labrador retrievers, scientists discovered several genes correlated with canine obesity that align with obesity-related genes in humans. The gene most strongly linked to obesity in Labradors is DENND1B, which also appears in humans and affects the leptin melanocortin pathway, a brain pathway vital for regulating energy balance.

Alongside DENND1B, four additional genes associated with obesity in dogs were linked to corresponding human genes, although these had a less pronounced effect.

Alyce McClellan, a joint first author of the study, noted that these genes do not appear to be straightforward targets for weight-loss drugs due to their influence on other crucial biological processes. She emphasized the role of fundamental brain pathways in appetite and weight control.

Natalie Wallis, another joint first author, stated that dogs at a higher genetic risk for obesity tended to show increased interest in food. The study measured how much dogs sought food from their owners and their eating preferences, revealing that these dogs exhibited signs of greater appetite, similar to people with a high genetic risk for obesity.

Owners who strictly managed their dogs' diets and exercise were able to prevent obesity in those genetically predisposed to it, though it required significant effort. Similarly, individuals with a genetic predisposition to obesity might not become obese if they adhere to a rigorous diet and exercise regimen, though they may have an increased propensity for weight gain.

The research found that no single gene dictated whether a dog was prone to obesity; rather, a combination of genetic variants influenced the risk.

The findings were published on March 6 in the journal 'Science'. Dr. Eleanor Raffan, the study's lead researcher, highlighted that the results indicate that the owners of slim dogs should not be viewed as morally superior, reflecting a similar dynamic with slim individuals. She explained that high genetic risk correlates with overeating when food is plentiful unless substantial effort is taken to control intake.

In the study, the obesity epidemic observed in dogs parallels the situation in humans, where approximately 40-60% of pet dogs are classified as overweight or obese, leading to various health issues. Dogs serve as an effective model for understanding human obesity due to their similar environmental influences and genetic similarity within breeds.

The researchers gathered information from dog owners, measuring body fat and food-seeking behavior while collecting saliva samples for DNA analysis. They connected the dogs' genetic data to their obesity status to identify relevant obesity-related genes.

Dogs carrying the DENND1B variant had about 8% more body fat than those without it. The team then explored whether these findings applied to human obesity through large population studies and cohorts with severe early-onset obesity linked to specific genetic changes.

The researchers also suggested that owners could manage their dogs' appetites by distributing daily food portions effectively, using puzzle feeders, or scattering food to prolong feeding times. Raffan remarked on the genetic similarities between dogs and humans, highlighting that understanding dog genetics has advanced insights into how our brains regulate eating behaviors and energy utilization.

Funding for the research was provided by several organizations, including Wellcome, the BBSRC, Dogs Trust, and others.