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NOVA scienceNOW: Marathon Mouse

Program Overview


Scientists have developed a drug that can give a total couch potato mouse the muscles of a marathon runner—with none of the training. By using drugs that trick a muscle cell into thinking that it's been working hard—even when it hasn't, scientists can mimic the effects of a rigorous exercise program. At least in mice. The rest of us are going to have to keep exercising until the drugs are proven to be safe.

This NOVA scienceNOW segment:

  • Notes that it is the mitochondria inside a cell that burn fuel (i.e., sugar and fat) and supply it energy.

  • Explains that the muscle cells of endurance athletes have far more mitochondria than those of people who do little or no endurance training. Furthermore, endurance muscle draws on fat as its primary energy source. Compared to sugar—a cell's standard energy source, fat provides far more energy. With more energy available, endurance muscles can keep going for much longer than other kinds of muscle.

  • Details how exercise stimulates muscle cells to make more mitochondria. This effect can be duplicated by drugs that increase the activity of genes that stimulate mitochondria production.

  • Traces scientist Ron Evan's hunt for the genes involved in promoting the development of endurance muscles. Through genetic engineering, Evans activated fat-burning genes in mice, resulting in thin mice with exceptional endurance. However, he programmed these mice when they were still embryos; the challenge became finding a drug that could produce this effect in adult mice.

  • Points out that when a cell burns fuel, it creates waste products. Evans learned that the build up of these waste products tells the cell to make more mitochondria.

  • Reports that the breakthrough came when Evans found a drug that mimicked the effects of endurance training. It significantly increased the amount of mitochondria and produced larger mitochondria and more blood vessels to supply muscle cells with oxygen.

  • Cautions that this drug has not yet been tested in humans, so nobody knows how it will affect people.

  • Notes that if the drug could be used safely, it could be a valuable therapy for people who are hospitalized, unable to exercise, or suffer the ill effects of aging—all situations that can cause a significant decline in strength, muscle mass, and blood supply to the muscles.

  • Raises the concern that this drug might be abused, especially by athletes. To discourage doping, Evans has developed a blood test to detect his drug.

Taping Rights: Can be used up to one year after the program is taped off the air.

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NOVA scienceNOW: Marathon Mouse
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