Josh Avila, M.S.
People like to place the blame on their genes for their lack of Herculean strength or Olympic endurance. But is this really fair? Do our genes actually have an effect on our ability to exercise?
Improvements in cardio-respiratory fitness made by increasing levels of physical activity have been shown to reduce the level of all-cause mortality regardless of baseline fitness levels. Research has shown that both initial exercise capacity and the response to exercise training are highly variable. The research also demonstrates that some individuals might not improve their fitness level with training. Therefore, these individuals might be at a higher risk of incidence for cardiovascular disease, metabolic syndrome, and certain cancers, including breast and colon cancer.
The marked differences in responses to exercise have led to these questions: Which genes might influence an individual’s variation in adaptations to exercise training? And, are these genes responsible for the differences?
Locating and identifying appropriate genes is a difficult task in humans due to the large populations of subjects and families needed and the inability to control their environment. As an alternative, the mouse has been adopted as a model for genetic studies because most human genes have an analogue in the mouse genome, therefore, the findings can be transferable back to humans. Mice also reproduce quickly, providing large litter sizes allowing for the amount of animals needed in a genetic study. There are numerous strains of inbred mice, and each mouse is genetically identical within a strain.
Mice from different strains can be trained to run on a rodent treadmill to find strains that consistently produce faster runners and those producing slower runners. By comparing multiple strains of inbred mice, the researchers reproduce the variation that is seen within the human population. This process is similar to the genome-wide association studies seen in humans in which researchers search for single-nucleotide polymorphisms (SNPs) or mutations in the DNA, associating a trait with a particular DNA region. These mutations are fairly stable with little change from generation to generation, allowing them to be helpful in mapping the genome. This allows researchers to identify genes that contribute to or are responsible for varying levels of adaptations to exercise.
What could this information mean? While it is unlikely that identifying genes associated with exercise response could turn you into the next Michael Phelps, the information could be very useful. If these genes are linked with disease susceptibility, eventually it may be possible to help individuals who suffer from diseases such as diabetes, heart disease and certain forms of cancer by designing a drug that would be able to interact with their genes to prevent or lessen a disease.
For readings related to this topic:
“Quantitative train loci for 6Jexercise training responses in FVB/NJ and C57BL/6J mice.”
“Quantitative trait loci for physical activity traits in mice.”