A mutation contributing to Labrador obesity

A mutation in the gene POMC is associated with obesity and food motivation in Labrador dogs. It disrupts molecular signalling in the brain which usually control hunger. The mutation is more common in assistance dogs than pets.

In May 2016 the GOdogs team published findings from the study of obesity in Labradors in the journal Cell Metabolism.  The findings are summarised in the graphic on the right and discussed below.  There is also a page with more detail about the data here.

Why study Labrador obesity genetics?

Despite the fact that dog owners control their pets’ diet and exercise, some breeds of dog are more susceptible to obesity than others, suggesting the influence of genetic factors. Labradors are the most common breed of dog in the UK, USA and many other countries worldwide and the breed is known as being particularly obesity-prone.

What did we do?

We studied 310 pet and assistance dog Labradors. Independent veterinary professionals weighed the dogs and assessed their body condition score, and the scientists searched for mutations in three known obesity-related genes. The team also assessed ‘food motivation’ using a questionnaire in which owners reported their dog’s behaviour related to food.  (We previously published the validation of this questionnaire here.)

A mutation associated with obesity

We found that a variant of one gene in particular, known as POMC, was strongly associated with weight, obesity and appetite in Labradors and flatcoat retrievers. Around one in four (23%) Labradors in the UK carries at least one copy of the variant. In both breeds, for each copy of the gene carried, the dog was on average 1.9kg (4lb) heavier, an effect size particularly notable given the extent to which owners, rather than the dogs themselves, control the amount of food and exercise their dogs receive.

“This is a common genetic variant in Labradors and has a  significant effect on those dogs that carry it, so it is likely that this helps explain why Labradors are more prone to being overweight in comparison to other breeds,” explains Dr Eleanor Raffan. “However, it’s not the whole story – there are plenty of overweight and highly food-motivated Labradors without the mutation”.

The gene affected is known to be important in regulating how the brain recognises hunger and the feeling of being full after a meal.  “People who live with Labradors often say they are obsessed by food, and that would fit with what we know about this genetic change,” says Dr Raffan.

An effect on training?

It was also striking that the mutation was more common in Labradors selected as assistance dogs.  Senior co-author Dr Giles Yeo adds: “Labradors make particularly successful working and pet dogs because they are loyal, intelligent and eager to please, but importantly, they are also relatively easy to train. Food is often used as a reward during training, and carrying this variant may make dogs more motivated to work for a titbit.

“But it’s a double-edged sword – carrying the variant may make them more trainable, but it also makes them susceptible to obesity. This is something owners will need to be aware of so they can actively manage their dog’s weight.”

Benefits for humans

The team believe that a better understanding of the mechanisms behind the POMC gene, which is also found in humans, might have implications for the health of both Labradors and human.

Professor Stephen O’Rahilly, Co-Director of the Wellcome Trust-Medical Research Council Institute of Metabolic Science, says: “Common genetic variants affecting the POMC gene are associated with human body weight and there are even some rare obese people who lack a very similar part of the POMC gene to the one that is missing in the dogs. So further research in these obese Labradors may not only help the wellbeing of companion animals but also have important lessons for human health.”

The research was funded by the Wellcome Trust, the Medical Research Council and the Dogs Trust.

Interested?  Find out more.

Want to know why we think the mutation has the effect we see?  Or get into the nitty gritty of the data?  You can read more about the science behind our findings on the next page or by reading the original scientific paper.

Alternatively, listen to Eleanor talking about the results on BBC Radio 4’s Inside Science programme.

You might also be interested in coverage from the BBC, Science Daily and LiveScience websites.