A batch of 500 ‘super mice’ has been created by genetically modifying normal mice. These super mice are capable of “running five to six kilometres at a speed of 20 meters per minute on a treadmill for up to six hours before stopping.” In other tests, the super mice were required to run on an inclined treadmill alongside normal mice. The normal mice lasted for an average of 19 mins where as the super mice kept running for 39 minutes. On an inclined surface, the level of exertion is quite high and normally the anaerobic respiration would be utilised to provide the energy. However, that also means that eventually excess levels of lactate acid would build up in the muscles. There are two ways to counter this; either oxygenate the muscle cells or remove lactate through Gluconeogenesis. Gluconeogenesis mainly occurs in the liver and can convert lactate into glucose (used for energy in muscles). On the other hand, glycolysis is the process of releasing energy from glucose and converting it into pyruvate. An important enzyme in this process is Phosphoenolpyruvate carboxykinase (PEPCK), which commonly found in the liver . It works by converting Oxaloacetate (another intermediate compound in the conversion of lactate to glucose) into a product that allows the production of glucose. The scientists modified the gene for production of PEPCK enzyme by inserting skeletal actin gene promoter, which directs the enzyme to be produced in large amounts in the muscles. It was seen that super mice had PEPCK levels at 9 units/gram of muscle, compared to only 0.08 units/gram for normal mice. Thus, super mice have very low levels of lactate because of their ‘efficient’ metabolism. They also utilised fatty acids for energy. Amazingly, they also had prolonged lives (3 years vs. 2 years for average lab mice). The researchers did notice increased aggressiveness, however.
Case Western Reserve University (2007, November 2). Genetically Engineered 'Mighty Mouse' Can Run 6 Kilometers Without Stopping. ScienceDaily. Retrieved May 15, 2009, from http://www.sciencedaily.com /releases/2007/11/071101162739.htm
