‘Couch potato’ tendencies may be genetic

Scientists claim to have found a gene responsible for some 'couch potatoes'. Picture: TSPL

TURNING into a “couch potato” and spending the day on the sofa may be down to simple genetics, according to new research by scientists in Scotland and China.

Researchers have made a key genetic discovery which could explain why some people are more likely than others to spend the day lazing about and taking no active exercise.

It was revealed today that a mutation in a gene, which has a critical role in the brain, may explain why some people are less inclined to exercise and are more likely to put on weight and develop health problems.

Their study - published in the journal PLOS Genetics - also raised the prospect of a “personalised pill” being developed in the future that could reverse the problem and help transform the lives of the inactive across the globe.

Mice

The discovery was made after scientists from Aberdeen University and the Chinese Academy of Sciences at the Institute of Genetics and Developmental Biology in Beijing compared “normal” mice with mice that had a mutation in a gene called SLC35D3.

An Aberdeen University spokeswoman explained: “The researchers discovered that SLC35D3 produces a protein which plays a key signalling role in the brain’s dopamine system – this system is involved in a range of functions including regulation of physical activity levels.

“However mice with this gene mutated had far fewer of this type of dopamine receptor on their brain cell surfaces. Instead, the dopamine receptors were stuck within the cell. This meant that their signalling process was not functioning properly. However, treating the mice with a drug that activates dopamine receptors reversed the problem – the mice became more active and lost their excess weight.”

Professor Wei Li, of the IGDB, led the study. He said: “We discovered that mice with this gene mutation were typical couch potatoes. They walked only about a third as much as a normal mouse, and when they did move they walked more slowly.

“The mice became fat and they also developed other symptoms similar to a condition in people called ‘metabolic syndrome’ - a medical term for those with a combination of risk factors related to diabetes, high blood pressure and obesity.”

Prof Li added: “What was of particular interest was that when we gave the mice a drug that acted on the dopamine signalling system, the genetic defect could be overcome and the mice became more active and thinner.”

Very rare

The researchers then screened 400 overweight and obese Chinese patients with metabolic syndrome and found mutations in the SLC35D3 gene in two of them. As the mice could be treated using a drug that acted on the dopamine receptor, the scientists suggest that in the future people with metabolic syndrome could possibly be screened to see if they have the relevant mutations. If so, perhaps drugs could be offered as a treatment.

Prof Li said: “We are really excited about these findings. A long-standing prescription in combating obesity is to mind your mouth and move your legs. However, genetics contributes to the reluctance to move in some obese people. Medical treatments will in the future be tailored to fit a person’s individual genetic make-up. ”

Professor John Speakman, who works between Aberdeen University of Aberdeen and the IGDB, stressed: “Although only about one in about 200 people may have these ‘rare’ mutations, there are a very large number of people worldwide that have metabolic syndrome. Consequently the population of sufferers that may benefit from being treated with dopamine receptor drugs runs into many millions of patients.

“The work is a perfect example of successful translational work – from great basic science to an important potential clinical application.”