Wednesday, August 06, 2008

A Pill for Exercise?

The hype on this new study seems way overstated. From the New York Times:
For all who have wondered if they could enjoy the benefits of exercise without the pain of exertion, the answer may one day be yes — just take a pill that tricks the muscles into thinking they have been working out furiously.

Researchers at the Salk Institute in San Diego reported that they had found two drugs that did wonders for the athletic endurance of couch potato mice. One drug, known as Aicar, increased the mice’s endurance on a treadmill by 44 percent after just four weeks of treatment.

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Four years ago he found that PPAR-delta played a different role in muscle. Muscle fibers exist in two main forms. Type 1 fibers have copious numbers of mitochondria, which generate the cell’s energy and are therefore resistant to fatigue. Type 2 fibers have fewer mitochondria and tire easily. Athletes have lots of Type 1 fibers. People with obesity and diabetes have far fewer Type 1 and more Type 2 fibers.

Dr. Evans and his team found that the PPAR-delta protein remodeled the muscle, producing more of the high-endurance Type 1 fiber. They genetically engineered a strain of mice whose muscles produced extra amounts of PPAR-delta. These mice grew more Type 1 fibers and could run twice as far as on a treadmill as ordinary mice before collapsing.

Given that people cannot be engineered in this way, Dr. Evans wondered whether levels of the PPAR-delta protein could be raised by drugs. Pharmaceutical companies have long tried to manipulate PPAR-delta because of its role in fat metabolism, and Dr. Evans found several drugs were available, although they had been tested for different purposes.

In a report in the Friday issue of Cell, he described the two drugs that successfully activate the muscle-remodeling system in mice, generating more high-endurance Type 1 fiber. The drug GW1516 activates the PPAR-delta protein but the mice must also exercise to show increased endurance. It seems that PPAR-delta switches on one set of genes, and exercise another, and both are needed for endurance.

Aicar improves endurance without training. Dr. Evans believes that it both activates the PPAR-delta protein and mimics the effects of exercise, thus switching on both sets of genes needed for the endurance signal.
So they found that giving certain drugs to mice may ultimately have switched on certain genes that affect muscle endurance. We don't know that this drug would work in humans in the first place, let alone that the drug would have any of the many other benefits of exercise (decreased risk of many diseases, longer lifespan, better mood, improved cognitive performance, increased aerobic capacity, maintenance of bone mass, lowered blood pressure, etc.), let alone that it would do so without serious side effects. I'm not sure why, at this early point, this drug is being given publicity different from that of steroids.


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