Study Promises
Benefits of Exercise in a Pill
By Alexis Madrigal
Wired Science
July 31, 2008
Working out is tough. So why not skip the exercise and pop a
few endurance-boosting pills?
That dream, cherished by millions of sedentary couch
potatoes, just got a little bit closer. Today, researchers are reporting that
an experimental drug can mimic the results of an exercise regimen -- with no
exercise required. After four weeks of taking the pill, mice who hadn't worked
out displayed a 44 percent increase in their running endurance.
"It’s tricking the muscle into ‘believing’ it’s been
exercised daily," said the study's lead researcher, Ronald Evans of the
Salk Institute, in a release. "It’s basically the couch potato experiment,
and it proves you can have a pharmacologic equivalent to exercise."
Human muscle enhancement has already shown considerable
success. Steroids easily facilitate the creation of bulky muscles. But that
type of muscle-building doesn't necessarily help you run a 10k, and
endurance-based exercise tends to yield more health benefits than strength
training. If drugs like this work in humans, it could prove a boon to an aging
and increasingly overweight American population.
But not all researchers are convinced that "exercise in
a pill" is actually possible.
"Physical activity is so important for maintaining the
health of the human body in almost every human organ system," said Darrell
Neufer, a professor of sports medicine specializing
in cellular energy systems at
Neufer cited a 2000 paper by BYU
and
Until this study, only high doses of resveratol,
a possible anti-aging drug and metabolic enhancer, had shown promise increasing
endurance by enhancing mitochondrial function. But resveratol
works by stimulating an entirely different set of proteins and could have a
wider range of effects, for good or ill.
The new work, which appears today in the journal Cell, tries
to tackle the cellular energy problem that we call fatigue directly, by
activating the enzyme AMPK with a long-known drug called AICAR.
Scientists believe that AMPK is an important regulator of
the cell's metabolism. In that energy system, ATP is used to power cellular
action, such as the muscle contractions associated with running. In the
process, ATP breaks down into another substance called AMP. As that happens,
British researchers have shown that AMPK acts to crank up ATP production.
The drug, AICAR, mimics AMP, effectively tricking the body
into thinking that it needs more energy and to begin producing more ATP -- making
more energy available for cellular action.
In other words, if ATP is the "molecular currency"
of cellular energy transfer, AMPK is the mint that can print more money, and
the drug is a kind of forged note from the Treasury Secretary ordering the mint
to begin printing more bills.
Neufer, however, questioned the
novelty of the research around AICAR, saying that the compound has long been
linked to the creation of mitochondria -- cells' engines -- which, in turn,
create more ATP.
"The bottom line is that the main finding is not a
particularly new finding," Neufer said.
"I'm surprised that this got into such a high-profile journal."
Still, the molecules Evans is studying have athletic
authorities worried because they appear to increase endurance among trained
athletes. In the same Cell paper, the researchers showed that, using a separate
drug, they could increase the levels of a protein called PPAR-delta, which
resulted in a 68 percent endurance gain for exercise-trained mice.
Evans is already working with the World Anti-Doping Agency
to find a way to test for this new kind of doping. It won't be ready by this
year's summer Olympics, but the test could be ready in time to retroactively
test the blood samples from athletes who compete in the 2008 games.
Neufer agreed that human athletes
need to be cautious about trying to obtain pharmacological help.
"Right now you have no way to target the drug to
specific cell types. By giving Aicar systemically,
you'd be activating the signaling pathway in every cell of the body," he
said. "Without knowing what impacts that might have that would be a
dangerous thing to do."
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