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The Pudgy Lab

Labrador retrievers may be more susceptible to weight gain because of a deletion in their pro-opiomelanocortin (POMC) gene, according to a University of Cambridge-led research team.

Cambridge's Stephen O'Rahilly and his colleagues studied a cohort of 310 Labrador retrievers, both pets and assistance dogs, as they report in Cell Metabolism this week. By examining a subset of dogs' coding sequences, the researchers uncovered three candidate obesity genes. The POMC gene, they note, harbored 11 novel variants, but one — a 14 base-pair deletion — was found in two-thirds of obese labs and in two out of 18 lean labs. In the wider cohort, the researchers found that this POMC deletion was associated with higher body weight. The mutation, they report, isn't present some three dozen other breeds, but is present in flat-coat retrievers, with which labs share a common ancestor. There, too, it was linked with higher weight.

This POMC mutation, O'Rahilly and his colleagues note, affects the production of β-MSH and β-endorphin, both of which have been linked with energy homeostasis.

This, Cambridge's Eleanor Raffan tells the Guardian could explain in part why labs make good assistance dogs. Such training involves treats and food-motivated dogs may do better in that process.

"Food is often used as a reward during training, and carrying this variant may make dogs more motivated to work for a tidbit," co-author Giles Yeo from Cambridge tells New Scientist.

People with mutations affecting POMC are constantly hungry and become obese at a young age, New Scientist adds, and this suggests that studying labs may also help understand weight gain in people.