What’s social, playful, and more likely to gain weight if it has a particular gene variant? Both humans and Labradors, apparently.
Researchers in the UK have identified variants, or “versions,” of genes associated with obesity in British Labrador Retrievers. The bad news is that they found variants of the same gene, also linked to excessive weight gain, in humans. The good news is that both Labradors and people with the offending variants can prevent weight gain by following a strict diet and workout routine, according to the study published March 6 in the journal Science.
“By studying dogs we could measure their desire for food separately to the control owners exerted over their dog’s diet and exercise. In human studies, it’s harder to study how genetically driven appetite requires greater willpower to remain slim, as both are affecting the one person,” lead author Eleanor Raffan, a veterinary surgeon and researcher at the University of Cambridge, said in a university statement.
The team measured body fat, determined “greediness” levels, and collected saliva samples from 241 Labradors. They then compared each dog’s body fat to the genetic information revealed by its saliva samples to pinpoint which genetic components were most likely linked to canine obesity.
While all dogs have a gene called DENND1B, the researchers discovered that those with a particular variant of DENND1B—called rs24430444—had approximately 8% more body fat than those without it. While the researchers also identified other genes similarly linked to canine obesity, the DENND1B variant had the strongest association.
“We measured how much dogs pestered their owners for food and whether they were fussy eaters. Dogs at high genetic risk of obesity [carrying the gene variants linked to obesity] showed signs of having higher appetite, as has also been shown for people at high genetic risk of obesity,” explained Natalie Wallis, co-author of the study. Wallis is a researcher in the University of Cambridge’s department of physiology, development, and neuroscience.
In fact, Wallis and her colleagues revealed that DENND1B, along with four other genes they’d linked to canine obesity, were also implicated in human obesity. DENND1B is involved in the brain’s leptin melanocortin pathway, a network of neurons that regulates the body’s energy balance.
Unfortunately, “these genes are not immediately obvious targets for weight-loss drugs, because they control other key biological processes in the body that should not be interfered with. But the results emphasise the importance of fundamental brain pathways in controlling appetite and body weight,” said Alyce McClellan, a biologist from University of Cambridge who also participated in the study.
However, the team also noted that owners who imposed a strict eating and exercise regimen on dogs carrying the DENND1B variant were able to prevent obesity in their pets, though it required significantly more effort.
“Studying the dogs showed us something really powerful: 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,” said Raffan. In other words, humans with the DENND1B variant linked to obesity are not predestined to gain weight, but it will be much harder for them to keep it off compared to others due to their hypothesized genetic predisposition.
“This work shows how similar dogs are to humans genetically,” she added. “Studying the dogs meant we had reason to focus on this particular gene, which has led to a big advance in understanding how our own brain controls our eating behaviour and energy use.”
So the next time you admonish your Lab for begging, remember that you might have more in common than you think!
