Researchers at Case Western Reserve University have bred a 'mighty mice' that can run non-stop for up to six hours at 20 metres per minute, which is metabolically similar to Tour de France legend Lance Armstrong.
This special breed eats 60 percent more than normal mice, remains fitter, trimmer and lives longer than wild mice, according to an article in the Journal of Biological Chemistry.
Some female mighty mice have also had offspring at 2.5 years of age, an amazing feat because most mice do not reproduce after they are a year old.
"They are metabolically similar to Lance Armstrong biking up the Pyrenees. They utilize mainly fatty acids for energy and produce very little lactic acid," said Richard W. Hanson, senior author of the article.
The key to this remarkable energy metabolism is the over-expression of the gene for the enzyme phosphoenolypyruvate carboxykinases (PEPCK-C).
Parvin Hakimi, the article's co-author, developed the new line of PEKCK-C mice over the past five years as part of research to better understand the metabolic and physiological function of PEPCK-C in skeletal muscle and adipose tissue.
"From a very early age, the PEPCK-Cmus mice ran continuously in their cages," said Hakimi, adding that she could identify which mice were from this new line by simply watching their level of activity in the cage.
"It is remarkable that the over-expression of a single enzyme involved in a metabolic pathway should result in such a profound alteration in the phenotype of the mouse," Hakimi said.
"Understanding the biochemical mechanisms responsible for this repatterning of energy metabolism will keep us busy for some time to come," she added.