July 31, 2008 -- It may be possible to make a pill that captures the endurance-boosting effects of exercise, scientists report in Cell.
So far, they've tested two compounds in lab tests in mice. One of those compounds, called GW1516, boosted endurance in mice that exercised, but not in sedentary mice. The other compound, called AICAR, improved endurance in mice that didn't exercise at all.
Those compounds haven't yet been tested in people, and they're not on the market. But the researchers are already working on a drug test to screen for traces of GW1516 and AICAR in athletes' blood and urine.
Here's a quick look at the two compounds.
Back in 2004, the researchers -- who included professor Ronald M. Evans, PhD, of the Salk Institute for Biological Studies and the Howard Hughes Medical Institute in La Jolla, Calif. -- reported that they boosted endurance in mice by tweaking a mouse gene to boost the activity of a protein called PPAR-delta.
Evans' team then worked on getting the same result without genetic engineering. They squirted GW1516, which boosts PPAR-delta, into mice's mouths every day for a month.
At the end of the month, the mice ran 68% longer and 70% farther than when the experiment began -- but only if they had been running on exercise wheels daily while taking the drug. GW1516 didn't do anything for mice that weren't exercising.
Next, the scientists focused on another protein called AMPK. They gave sedentary mice a daily injection of AICAR, which boosts AMPK, for a month.
At the end of the month, those mice ran 23% longer and 44% farther than before starting AICAR treatment. That is, their endurance had improved without working out.
The results show that AMPK and PPAR-delta "can be targeted by orally active drugs to enhance training or even to increase endurance without exercise," write the researchers.
The mouse tests were all about skeletal muscles and endurance, not about the drugs' safety or ability to mimic the many other benefits of exercise, such as improving cardiovascular health and making some types of cancer less likely.