The PEPCK-Cmus mice eat about sixty percent more than the control mice, but remain fitter, trimmer and live and breed longer than wild mice in a control group.
These mice achieve excellence in a manner that seems to be very similar to the way that Lance Armstrong does it - he was born with specific capacities make him different from most people. For example, when he exercises, his body utilizes lactate more efficiently; it does not accumulate as it does in most bikers and runners.
"Armstrong's most unusual attribute may be his low lactate levels. During intense training, the levels of most racers range from 12 μL/kg to as much as 20 μL/kg; Armstrong is below 6 μL/kg."
Lactate is believed to be a useful fuel for the body. And what about the "mighty mice?"
"What is particularly dramatic is the difference in the concentrations of lactate in the blood," the researchers said. "At the beginning of exercise, the concentration of lactate was similar in two groups of mice, but by the end of the exercise period, the control group had elevated levels of blood lactate with little change in the levels in the PEPCK-Cmus mice."
The technical reason for their amazing physical feats? The over-expression of the gene for the enzyme phosphoenolypyruvate carboxykinases (PEPCK-C). The "mighty mice" are descended from founder lines that had an additional gene added. It is a chimeric gene; a copy of the cDNA for PEPCK-C was linked to the skeletal actin gene promoter, containing the 3'-end of the bovine growth hormone gene. The skeletal actin gene promoter directs expression of PEPCK-C exclusively to skeletal muscle. Various lines of PEPCK-Cmus mice expressed PEPCK-C at different levels, but one very active line of PEPCK-Cmus mice had levels of PEPCK-C activity of 9 units/gram skeletal muscle, compared to only 0.08 units/gram in the muscles of control animals.
Science fiction fans are long familiar with the idea of beings who have been engineered to be superior. For example, consider the eugenic "supermen" from Star Trek.
(Khan Noonien Singh - played by Ricardo Montalban)
Fans might also recall the Sauron Supermen from Niven and Pournelle's The Mote in God's Eye.
Mice are quickly acquiring other remarkable characteristics, thanks to hard-working researchers:
E.T. Mouse Hearts Glow
Researchers at Cornell have created mice whose heart muscles have been genetically engineered to fluoresce when the muscles contract (see photo).