2 November 2007, 11:26 GMT
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Lab creates 'long-distance mouse'
Mice (Case Western Reserve University)
The modified mice: They were also found to be aggressive

One of the mice on a treadmill

A genetically modified "supermouse" which can run twice as far as a
normal rodent has been created by scientists working in the US.

It also lives longer, and breeds later in life compared with its
standard laboratory cousin.

The research has been conducted at Case Western Reserve University in
Cleveland, Ohio.

Details of the scientists' new transgenic animals are published in
the Journal of Biological Chemistry.

The mice were produced to study the biochemistry at play in
metabolism and could aid the understanding of human health and disease.

The GM rodents can run five to six kilometres at a speed of 20 meters
per minute on a treadmill, for up to six hours before stopping.

Mouse treadmill (Case Western Reserve University)
The performance was tested on rodent treadmills
"They are metabolically similar to Lance Armstrong biking up the
Pyrenees; they utilise mainly fatty acids for energy and produce very
little lactic acid," said Professor Richard Hanson, the senior author
on the journal article.

He told BBC News: "The muscles of these mice have many more
mitochondria. These are the little 'engines' in the cell that produce
energy. For some reason, the number of mitochondria are around 10
times more than we see in the muscle of their littermates."

The mice over-express a gene responsible for the enzyme
phosphoenolypyruvate carboxykinases (PEPCK-C). Normal expression is
in the liver, in the production of glucose.

The scientists found their new mice would eat twice as much as normal
mice - but weigh half as much. They could also give birth at three
years old - which in human terms is akin to an 80-year-old woman
giving birth.

Cover of Journal of Biological Chemistry
The research is featured in the Journal of Biological Chemistry
Other research groups have produced similar novel rodents by altering
different aspects of their genetics. One criticism of the work is
that it could open the door to abuse, with the spectre of athletes
resorting to gene therapy to try to improve their performance.

But Professor Hanson played this down. "Right now, this is impossible
to do - putting a gene into muscle. It's unethical. And I don't think
you'd want to do this. These animals are rather aggressive, we've
noticed."

Scientists say such work is more likely to help them understand human
conditions, such as those which lead to wasting of the muscles.