Researchers have expressed concern about athletes' use of genetic tools in the 'next generation' of illegal doping, and have stressed the importance of developing reliable new detection tests to stop them. Writing in the journal Science, Theodore Friedmann and colleagues at the University of California warn that 'the time is right to look at how advances in genetics are affecting sport'. The authors highlight the dangers of using imperfect and 'highly risky' genetic techniques, which may have not yet been tested in humans.
Traditional doping tests rely on the chemical and molecular detection of agents such as steroids or foreign proteins in the blood, but gene-based boosts cannot currently be detected. The authors describe how genetic doping methods 'are likely to produce broad metabolic, genetic and proteomic changes'. They advise that, rather than detecting the immediate evidence of doping, new tests should aim to identify more widespread changes in the body by analysing alterations in gene expression and protein production, which can't be easily hidden.
Recent advances in gene therapy for degenerative and inherited diseases have led to the availability of tools which could also be used to enhance traits such as athletic performance. For example, boosting expression of a gene called 'peroxisomal proliferator-activated receptor delta' (PPAR-δ), which regulates energy utilisation and increases the production of particular types of muscle fibres, has been shown to increase endurance in animals - the so-called 'marathon mice'. Another gene likely to be targeted is the insulin-like growth factor (IGF-1) receptor, which has been demonstrated to enhance muscle function when over-expressed in rats.
The World Anti-Doping Agency (WADA), which funds international research into doping detection, added gene doping to its list of banned substances and methods in 2004. However, in 2006 a German athletics coach was caught trying to obtain Repoxygen, an experimental gene therapy agent that boosts expression of the erythropoietin gene, enhancing red blood cell production and increasing the amount of oxygen delivered to the muscles. In 2008 a Chinese doctor reportedly offered stem cell injections to a journalist posing as a swimming coach at the Olympics in Beijing. Although there is no evidence that either of these agents have actually been tried by athletes yet, WADA's former chairperson noted that 'you would have to be blind not to see that the next generation of doping will be genetic.'
Although the tests are currently limited to animal studies, and further work is needed, it is thought that samples taken from athletes competing now could be stored for re-examination in the future. Friedman also acknowledged the ethical and privacy issues raised by genetic testing, but said 'that's kind of the cost of being an elite athlete.'