Scientists Create 'Endurance' Mouse
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SCIENTISTS CREATE 'ENDURANCE' MOUSE
By Kate Tobin
August 14, 2002
BOSTON, Massachusetts (CNN) -- Mighty Mouse lives, and the "new age" version
is downright buff.
Researchers say they have created a transgenic mouse with muscles like a
marathoner, capable of enduring rigorous exercise for extended periods of
While so far the research has only been conducted on mice, scientists say
they expect the techniques they've developed to treat the mouse muscle will
also work on humans. Doctors say the discovery may one day lead to new
treatments for people who are bedridden or have degenerative muscle disease,
and could prove to be a wonder drug for endurance athletes like long
distance runners or cross country skiers.
Bruce Spiegelman and colleagues at the Dana-Farber Cancer Institute
identified a biochemical called PGC-1 that operates as a molecular switch,
converting so-called "fast-twitch" muscle, which is strong but tires
quickly, into high-endurance "slow-twitch" muscle.
"PGC-1 appears to be the switch, or a major component of it, that enables
your body's muscles to adjust to the demands being put on them," said
Spiegelman. "Understanding how this system works could make it possible to
develop a drug to manipulate this system."
Muscle is made up of a combination of different types of fibers. Endurance
athletes train long and hard to build up slow-twitch muscle fibers, called
Type I fibers, which are long and lean and can keep pumping for long periods
of aerobic exercise. Sprinters or weightlifters, on the other hand, have
muscle rich in fast-twitch, Type II fibers. These muscles are bulkier and
stronger but tire quickly.
To create the endurance mouse, Spiegelman's group bioengineered PGC-1 into
mouse muscle tissue. They expected that it would promote the development of
cellular power plants called mitochondria, which fuel the growth and
development of slow-twitch muscle fiber. But they were surprised to find
that PGC-1 appeared to be converting Type II fast-twitch fibers into Type I
The muscle itself actually changed color, taking on a reddish hue
characteristic of oxygen-rich tissue. Further, in an endurance test at a
Texas laboratory, the bioengineered muscle turned out to contract
efficiently two and a half times longer than regular muscle.
Spiegelman cautions that there is still five to 10 years of work to be done
before PGC-1 based treatments will be available.
The research is published in this week's edition of the journal Nature.
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