Wheels Keep On Turning: missing gene gives mice super endurance

Mice engineered to lack a muscle contraction gene run 6 times farther than normal mice, a new study shows. This is not unlike the extra endurance of long-distance Olympians.
Written by Janet Fang, Contributor

And maybe people too.

Without a gene called IL-15Rα, mice can run in their exercise wheels for hours every night. Going nowhere still, but doing it with the fortitude of a marathon runner.

Previous studies have hinted that IL-15Rα might be important for muscle strength and contraction, but the gene has never been studied in a live animal.

So a team led by Tejvir Khurana of the University of Pennsylvania genetically engineered mice who lack IL-15Rα. And these mighty modified mice ran 6 times farther than normal mice each night, according to the sensors on their wheels.

After dissecting the mice’s muscles, the researchers found that they sported:

  • Increased numbers of mitochondria, the energy-generating power plants of our cells.
  • And more muscle fibers, which indicates that they tired less easily.
  • And when stimulated with electricity, the muscles contracted for longer than normal, taking longer to use up their energy stores.

Mice, like humans, have two types of muscles. ScienceNOW explains:

Fast-twitch muscles, such as the muscles in our fingers, allow more precise movements but tire faster, whereas slow-twitch muscles, like those in our back, are more resistant to fatigue but don't allow such precise movements. Removing the IL-15Rα gene, Khurana says, coaxed the mice's fast-twitch leg muscles to turn into slow-twitch muscles.

To study whether the gene affects human endurance, the team worked with Australian researchers to look at genetic samples from Olympians and other world-class athletes.

They found that certain variants of the IL-15Rα gene were more common in long-distance cyclists and rowers than they were in sprinters – suggesting that the most successful endurance athletes might have a variant that gives their muscles extra endurance.

The work raises the possibility that drugs blocking IL-15Rα could one day enhance endurance.

The study was published this week in The Journal of Clinical Investigation.

Via ScienceNOW.

Image by KevinMcCarthyPhoto via Flickr

This post was originally published on Smartplanet.com

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