 Tritons
have produced some exceptional endurance athletes over the years,
but one
group training on campus takes the prize for being the most unusual.
They run on treadmills and swim in water baths
within a laboratory chamber.
They are a group of genetically enhanced “super mice” and
they are helping biologists
unravel some of the biochemical secrets of endurance.
UCSD researchers reported in the
August 24 issue of the online journal PloS that they
had transformed ordinary laboratory mice into the rodent equivalent
of Olympic endurance athletes. This was accomplished by deleting
a gene that allows mammalian muscles to switch from aerobic to
anaerobic metabolism when oxygen levels in the muscles run low.
Led by biology professor Randall
Johnson, researchers found that the inability of these genetically
modified mice to generate energy
through anaerobic metabolism, the biochemical process used for
short sprints or bursts of power, provided the mice instead with
an extraordinary
capacity for longer, sustained aerobic
endurance exercise.
But while these endurance-enhanced mice can run and swim to exhaustion
in laboratory tests for far longer periods than their normal counterparts,
the scientists discovered
that their super-endurance capabilities appear to be only temporary and came
at a high price. After four days of exercise tests, the gene-doped endurance
mice exhibited significantly more muscle damage than their normal counterparts.
“It’s a double-edged sword,” says
Johnson. “By changing the
way skeletal muscles respond to low-oxygen levels, we’ve developed
muscles that appear to be better adapted or trained for long bouts of submaximal
aerobic
exercise. But these muscles also become damaged more easily than normal muscles
during exercise and we don’t know why.”
The discovery has obvious importance for physiologists and others
who study muscle metabolism to maximize human endurance. But
it should also be of keen
interest
to medical researchers seeking treatments for human genetic disorders.
“Our studies demonstrate that exercise endurance in mice may be a model
for genetic factors in exercise and endurance in humans,” says Johnson.
The UCSD research team, which besides Johnson includes Steven Mason,
Richard Howlett, Matthew Kim, Mark Olfert, Michael Hogan, Wayne
McNulty and Peter
Wagner, is now training the mice to determine whether additional training
can help
the mice perform better and reduce muscle damage. If that’s the case, look
out. Blood doping and drug enhancement won’t be the only sources of controversy
at the Olympics. — Kim McDonald
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