US scientists believe they might be on track to develop a pill that gives humans some of the benefits of exercise without having to crack a sweat.
The Scripps Research Institute in Florida researchers found that injecting a drug could stimulate production of a protein called REV-ERB in mice, which helped to control their body clocks, lose weight and improve their cholesterol levels, even when fed a high fat diet.
They also found the mice used more oxygen throughout the day and expended about five percent more energy than a control group, even though they both moved the same amount.
Unsure of exactly how REV-ERB worked, the scientists bred a strain of mice that had little of that protein naturally in its cells.
Those mice had very few mitochondria, which are cellular structures that help the body convert oxygen to energy and are boosted by exercise.
As a result, the mice's oxygen capacity was about 60 percent lower than average and they became exhausted on a treadmill much quicker than a control group of normal mice.
But when the scientists injected certain mice muscles with the drug, their cells produced a lot more REV-ERB, which meant they generated more mitochondria and ran further on treadmills.
The drug "certainly seems to act as an exercise mimic", said co-author Thomas Burris from St. Louis University School of Medicine.
He said it's possible that the development could lead to a drug in the future to help people who can't exercise to get the benefits.
Professor Mark Hargreaves, from the department of physiology at the University of Melbourne, told ninemsn that scientists have long been looking for a way to help people get the benefits of exercise if they are unable to do it.
"There have been lots of studies looking at the fairly basic mechanisms for how the pathways that are activated in exercise might be activated by chemical agents," Professor Hargreaves said.
"Each time one of these basic studies comes out, the popular story is that this could lead to an exercise pill. These are exciting developments to help us understand the mechanisms of how some of these biological processes can be affected by exercise and by other agents."
Professor Hargreaves said it's unlikely a pill will ever be able to fully mimic all the benefits of exercise.
"If you think about the vast array of effects of exercise on all of the tissues of the body — the brain, the muscles, the heart, the fat cells — it's hard to imagine that a single pill could recapitulate many or all of the effects of exercise," he said.
Professor Matthew Watt, from the department of physiology at Monash University told ninemsn that it would be at least five to 10 years until a drug is available for humans to enhance mitochondrial function.
"This would be important for individuals that have an impaired capacity to exercise or a genetic predisposition to impaired mitochondrial function," he said.
"It could benefit people like the morbidly obese who find it difficult to move around, or the frail elderly, and also individuals with certain muscular issues. They all have an impaired mitochondrial function, so you could use a drug to enhance mitochondrial function to improve their metabolic health."
But Professor Hargreaves said a lot of research into potential side effects needs to be done before any such drugs would be available for humans.
The study was published in the journal Nature Medicine.
Source: New York Times Author: Kimberly Gillan; Approving editor: Rory Kinsella