Wednesday, May 4, 2016

Are labradors genetically prone to obesity?

I wonder if Bosca has the POMC deletion...

UPDATE: You can listen to a podcast about this with Vet Talk Video & Podcasts with Brian and Kaye here.

Why are Labradors always presenting with gastrointestinal foreign bodies? Any vet will tell you that the odd dog will skip the odd meal occasionally, but when a lab skips a meal you tend to worry. And by meal, I mean anything. Because it doesn’t have to be food for a lab to eat it. They’re notorious for ingesting socks, undies, plastic bags, food in containers, balls, toys – you name it, someone has likely surgically removed it from the inside ofa Labrador.

There may be a genetic basis for this amazing appetite. According to a paper published in CellMetabolism this week, Labs and flat coated retrievers (the latter being a less common breed) have a gene alteration linked to canine obesity. The genetic alteration was found to be more frequent in assistance dogs, suggesting that these dogs may have been selected because they’re more food motivated and thus more trainable.

The lead author on the study is a veterinarian and geneticist at Cambridge University who studied human obesity before moving onto dogs. The team looked at 15 obese labs and 18 lean labs, and looked for three obesity-related genes already found in humans. They found a deletion in a gene, POMC, in more of the obese than the lean dogs. They hypothesised that this deletion hindered a dog’s ability to produce neuropeptides responsible for stopping hunger after a meal. 

Which might explain why, on the day that I discharged him hospital following surgery to remove some rocks he ate, one of my Labrador patients went home, busted into the fridge, at 1kg of cheese, a 1 litre tub of yoghurt and 8 Tim Tams. Remarkably, this impressive, high-fat binge led neither to vomiting or pancreatitis.

They then looked at a larger sample of 310 labs, and found some interesting things. Not all dogs with the DNA variation were obese – and not all obese dogs had the variation. But, in general, the variation was associated with greater body weight and (as reported by owners) a bigger appetite: more begging, more scavenging, more sad eyes when owner’s eat.

But not all labs are affected. They found the POMC deletion in 23 per cent of 411 labs sampled in the US and UK. Of 38 other breeds studied, the POMC deletion only occurred in flat coated retrievers. Strikingly, it occurred in 76 per cent of assistance dogs.

The million dollar question (especially when there may be implications in the human market) is whether scientists can invent a drug to switch this gene off. Eliminating obesity would certainly improve the welfare of dogs, but what would it mean for assistance dogs? Would they be harder to train? And what about obese labs that don't have the POMC deletion? Watch this space.

Reference

Raffan et al. A deletion in the canine POMC gene is associated with weight and appetite in obesity prone Labrador retriever dogsCell Metabolism, 2016 DOI: 10.1016/j.cmet.2016.04.012

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