Rethinking Healthcare

Wheels Keep On Turning: missing gene gives mice super endurance

Posting in Energy

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.

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

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Janet Fang

Contributing Editor

Janet Fang has written for Nature, Discover and the Point Reyes Light. She is currently a lab technician at Lamont-Doherty Earth Observatory. She holds degrees from the University of California, Berkeley and Columbia University. She is based in New York. Follow her on Twitter. Disclosure