Superpowered: The genetically-engineered mice can eat 60 per cent more than normal lab mice (pictured), but remain slim and fit. The mighty mice live longer, and some females were able to reproduce much later in life than other mice.
Credit: AFP
WASHINGTON, DC: Geneticists have engineered a line of "mighty mice" whose human equivalent would have similar abilities to the U.S. bicycling champion Lance Armstrong, they say.
The breed of mice can run at a speed of 20 meters per minute for up to six hours without stopping – covering six kilometres – said biochemist Richard Hanson of Case Western Reserve University in Cleveland, Ohio.
"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 Hanson, the senior author of the article which was published in the Journal of Biological Chemistry.
See a remarkable video here of one of the mice out-competing a normal mouse on a treadmill.
Slim, fit and long-lived
The genetically engineered mice can eat 60 per cent more than wild mice in a control group, but remain slim and fit. These "mighty mice" live longer, and some females were able to reproduce much later in life than other mice.
The authors noted that some "have had offspring at 2.5 years of age – an amazing feat considering most mice do not reproduce after they are one year old."
Hanson said the strength of the mice was made possible by the fact that they produce very little lactic acid, which forms during intense exercise.
The U.S. scientists have bred 500 of the mice, which also showed more aggression than other mice, over the past five years as part of a project aimed at unlocking the metabolic and physiological function of PEPCK-C in muscles and tissues. The key to their unusual traits is the over-expression of the gene that influence production of the enzyme PEPCK-C (phosphoenolypyruvate carboxykinases), said Hanson.
The transgenic mice are descended from six founder lines that "contain a chimeric gene in which a copy of the cDNA for PEPCK-C was linked to the skeletal actin gene promoter," the study said.
On the run
The resulting mice showed different levels of PEPCK-C in their muscles, but one particularly active group had levels of PEPCK-C activity of nine units per gram of skeletal muscle, compared to just 0.08 units per gram in the muscles of control mice.
"From a very early age, the 'PEPCK-Cmus' mice ran continuously in their cages," said Parvin Hakimi, a researcher in the Hanson lab. The mighty mice primarily relied on "fatty acids as a source of energy during exercise, while the control animals rapidly switched from fatty acid metabolism to using muscle glycogen (carbohydrates) as a fuel; this dramatically raised the blood lactate levels," she said.
The PEPCK-C enzyme was first discovered at the medical school of Case Western Reserve University in 1955.
