Muscles that do nothing can keep you warm and thin

Muscles that burn energy without contracting have yielded new clues about how the body retains a constant temperature ? and they may provide new targets for combating obesity.

Traditionally, the body's main thermostat was thought to be brown fat. It raids the body's white fat stores in cold conditions to burn energy and keep the body warm.

Muscles also play a role in keeping the body warm by contracting and triggering the shiver response ? but this is only a short-term fix because prolonged shivering damages muscles. Now it seems that muscles have another way to turn up the heat.

"Our findings demonstrate for the first time that muscle, which accounts for 40 per cent of body weight in humans, can generate heat independent of shivering," says Muthu Periasamy of Ohio State University in Columbus.

Surviving the chill

Through experiments on mice that had their usual thermostat ? brown fat ? surgically removed, Periasamy and his colleagues proved that a protein called sarcolipin helps muscle cells keep the body warm by burning energy, almost like an idling motor car, even if the muscles do not contract.

All of the mice had their brown fat removed, but some of them had been genetically engineered to lack sarcolipin too. These rodents could not survive when held at 4 ?C, and died of hypothermia within 10 hours. By contrast, mice that could make sarcolipin were able to survive the chilly temperatures and maintained their core body temperature ? despite having no brown fat.

Periasamy also showed that an inability to make sarcolipin made mice 33 per cent heavier than normal when fed a high-fat diet. This suggests that idling muscles might also help combat obesity by burning off excess energy. The search is now on for drugs that perform the same role, triggering idling muscles to burn off excess fat.

"The most interesting finding is that mice unable to make sarcolipin are more susceptible to obesity," says Andy Whittle of the University of Cambridge, who is testing spicy dietary treatments to ramp up the fat-burning activity of brown fat. "The research demonstrates that muscle is an important component even in mice, which have comparatively more brown fat than humans. In humans, burning fat in muscle is likely to be even more important for proper energy balance."

Journal reference: Nature Medicine, DOI: 10.1038/nm.2897

If you would like to reuse any content from New Scientist, either in print or online, please contact the syndication department first for permission. New Scientist does not own rights to photos, but there are a variety of licensing options available for use of articles and graphics we own the copyright to.

Have your say

Only subscribers may leave comments on this article. Please log in.

Only personal subscribers may leave comments on this article

Subscribe now to comment.

All comments should respect the New Scientist House Rules. If you think a particular comment breaks these rules then please use the "Report" link in that comment to report it to us.

If you are having a technical problem posting a comment, please contact technical support.

Source: http://feeds.newscientist.com/c/749/f/10897/s/233c23be/l/0L0Snewscientist0N0Carticle0Cdn22250A0Emuscles0Ethat0Edo0Enothing0Ecan0Ekeep0Eyou0Ewarm0Eand0Ethin0Bhtml0DDCMP0FOTC0Erss0Gnsref0Fonline0Enews/story01.htm

micah true kansas vs ohio state winning mega million numbers bruce weber boston globe google maps 8 bit mirror mirror