for National Geographic News
Although athletes at the Beijing Olympics have been subjected to some of the most aggressive testing ever for performance-enhancing drugs, no case of so-called gene doping has yet been detected.
But experts say Oympic athletes may soon be able to genetically enhance their muscles to be faster, stronger, and better able to recover after workouts—if they aren't already.
Gene doping uses techniques similar to gene therapies developed to treat muscle-wasting diseases, such as muscular dystrophy.
Injected into an athlete, a harmless virus could carry a performance-enhancing gene and splice it into a muscle cell, said Theodore Friedmann, a gene therapy researcher at the University of California, San Diego (quick genetics overview).
A synthetic virus called Repoxygen, for example, has been used this way in animal tests to insert a gene for erythropoietin (EPO), a hormone that tells the body to make more red blood cells, which carry oxygen to muscles.
EPO is important in the treatment of anemia, and it's also a favorite doping agent for cyclists, runners, and cross-country skiers.
Athletes are well aware of Repoxygen's potential: A German coach was accused of trying to obtain it before the 2006 Winter Olympics.
Gene-doping may also work by modifying genes that are already in an athlete's cells but whose functioning he or she might want to control.
It's not a new concept. Many ordinary drugs can have this effect, as can daily activities.
"Training and athletic workouts probably do their work at least partly by modifying the expression of genes," Friedmann said.
Cheating Delayed?
A few years ago it was believed that wholesale gene doping was just around the corner. But clinical trials of legitimate gene-therapy methods have run into hitches.
"There have been deaths," Friedmann said. And an otherwise successful attempt to cure severe combined immunodeficiency disorder—the so-called bubble-baby syndrome—was halted when some of the children developed leukemia.
Also the gene-therapy viruses that might lend themselves to cheating don't work as easily as had been hoped.
The problem is that the human immune system tries to fight them off, said H. Lee Sweeney, a physiology professor at the University of Pennsylvania.
"That's caused most of the trials to stop," Sweeney said.
In future tests patients may have to be hospitalized during treatment, with their immune systems suppressed.
"I'm not sure an athlete is going to be willing to be put in the hospital for six weeks right in the middle of their training," Sweeney said.
"Naked" DNA
Less ambitious forms of gene doping may be right around the corner, though.
Dispensing with the troublesome virus-based delivery system, this type of doping would inject "naked" DNA directly into a muscle.
Nearby cells would take up some of the DNA, and if that DNA controls an important hormone, like EPO or human growth hormone (HGH), it might be enough to do the job.
It's not so different from injecting EPO or HGH directly, but it would save money, because it would only have to be done once.
"You could probably get a molecular-biology major to make it for you for a couple hundred dollars," Sweeney said.
Testing for this type of doping would be easy, though, since the athlete's body would still carry too much of the hormone.
Testing for full-blown gene doping will be more difficult. Just be safe, the International Olympic Committee is hanging on to Olympians' genetic samples for eight years, in case testing methods catch up with currently indetectable doping methods.
For its part, the World Anti-Doping Authority is working on a test to determine the expression of all 25,000 of the human body's genes, looking for abnormal patterns, said the University of California's Friedmann, who chairs the agency's genetics panel.
But sports authorities may eventually have to accept gene doping as a fact of life, scientists say.
The same techniques that could create superathletes will likely also help ordinary people stay fitter and healthier.
"I think [gene therapy] will change the way we all live and how health care treats the average person," the University of Pennsylvania's Sweeney said.
"You can't legislate it out of sport, because you'd be depriving people of a standard of care."
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