Genetic Obesity In Labrador RetrieversMonday, May 16, 2016
While much has been written on how the current obesity epidemic is not limited to humans but also includes house hold pets and zoo animals, some species appear to be more obesity prone than others.
Among dogs, which for centuries have been selectively bred to transform the wild type into all shapes, sizes and temperaments, some breeds likewise appear more prone to weight gain than others – these include labrador retrievers.
Now, a study by Eleanor Raffan and colleagues from Cambridge University, UK, in a paper published in Cell Metabolism, have identified a common deletion within the POMC gene that enhances appetite and feeding behaviour.
The 14 bp deletion in pro-opiomelanocortin (POMC) with an allele frequency of 12% disrupts the β-MSH and β-endorphin coding sequences and is associated with body weight (mean effect size 1.90 kg per deletion allele, equivalent to 0.33 SDs), adiposity, and greater food motivation.
Among another 39 dog breeds, the deletion was only found in the closely related flat-coat retriever (FCR), where it is similarly associated with body weight and food motivation.
The influence of this mutation on feeding behaviour is likely complex:
“It has been reported that owners of more highly food-motivated dogs make greater efforts to limit their dogs’ access to food. However, there is evidence to suggest dogs are able to influence both the type and quantity of food offered to them by their owners. It is possible that behavior changes related to the mutation are sufficient to lead to increased food intake (either by scavenging or soliciting owner-provided food).”
Interestingly, the mutation was found to be significantly more common in Labrador retrievers that had been selected to become assistance dogs than pets suggesting that there may be something about this deletion that positively influences temperament, making them best suited for this kind of work.
“Temperament and “trainability” are the main drivers for selection of assistance dogs, and “positive reinforcement” with food reward is a mainstay of puppy training. We therefore hypothesize that dogs carrying the POMC deletion may be more likely to be selected as assistance dogs.”
Overall, and this should come as no surprise, these findings show that mutations in the same system that regulates human weight and appetite (and perhaps temperament?) is found in obesity prone canines.
Which, incidentally, brings up the issue of selective breeding in humans – but that’s another story.