Genetically modified they run twice as much as normal. All thanks to a protein that can also be stimulated by a new study drug. Will it be the doping of the future?
|The rides with mice were fashionable in England in the last century. Today doping could also affect this discipline.|
They can run as Halle Gelbrselassie or the best Kenyan marathoners, but they are doped "athletes". It is not the last Olympic scandal, but the results of a research by the Salk Institute of La Jolla in San Diego (California), which produced a new species of "marathon runners", able to run twice as much as normal ones. All thanks to a small modification of the genes that allows to considerably increase the resistance.
The objective of the research, as even the most nefarious scientist can easily imagine, was not so much to create super athletes for the Olympics of Topolinia, as it was to study the genes involved in obesity and fat metabolism. By chance, the researchers led by Ronald Evans have discovered the way to transform mice into cross-country skiers.
Resist, resist, resist. The key to everything is a protein called PPARdelta that plays a fundamental role in burning fat and fighting obesity. Its activity favors the reduction of the accumulation of fat reserves. In the body, however, the fat is burned mainly by the muscles with red fibers (also called resistant fibers or slow contraction) which give the athletes resistance and are very present in the muscles of the marathon runners. The other main muscle fibers are those called pale (or fast) fibers, fed above all by sugars and responsible for jerks and speed. The slow fibers are aerobic, while the fast ones are anaerobic.
Running to eat. The researchers created a genetically modified mouse to produce high levels of PPARdelta in the muscles. As was presumably, genetically modified mice, subjected to a hyper-fatty diet for 97 days, are only one-third fatter than the other mice. But surprisingly the composition of their muscles has changed: the slow fibers are doubled. "These mice are genetically more fit - Evans explains - and behave like trained athletes". Tested, they are capable of running almost twice (92 percent more) than normal mice.
The future of doping. Can increasing PPARdelta levels in humans have the same effects on the composition of muscle fibers? No one knows it yet. The proportion between slow and fast fibers makes the difference between a sprinter and a cross-country skier and in some way it can be changed with training. But a drug that directly activates the PPARdelta protein is being tested to lower cholesterol. It could be used in the future as a form of doping. The first conclusions of Evans, in fact, confirm that the drug has many effects similar to those found in mice and could serve to increase the resistance of the athletes.
(News updated August 26, 2004)