The physiological impact of regular endurance training can be visualized over time and is often used to prevent cardiovascular disease, diabetes, obesity and other such conditions. However, how these changes occur at the molecular level and their impact on a genomic scale lack complete resolution. Now, investigators from the Karolinska Institutet report on their recent findings that show how endurance training changes the activity of thousands of genes and gives rise to a multitude of altered DNA and RNA copies.
The Swedish researchers were able to analyze RNA in muscle tissue before and after endurance training. They found approximately 3400 RNA variants, associated with 2600 genes, that changed in response to training. One implication of the study is that exercise can induce the same gene to increase the production of one RNA variant and reduce that of another. According to the researchers, this can mean that genes can change function as a result of exercise and, for example, start to promote the production of certain protein variants over others.
“In this study, 23 individuals trained one leg for three months,” the authors wrote. “Nine months later, 12 of the same subjects trained both legs in a second training period. Skeletal muscle biopsies were obtained from both legs before and after both training periods. RNA sequencing analysis of all 119 skeletal muscle biopsies showed that training altered the expression of 3,404 gene isoforms, mainly associated with oxidative ATP production. Fifty-four genes had isoforms that changed in opposite directions. Training altered expression of 34 novel transcripts, all with protein-coding potential.”
The findings from the study were published recently in PLoS Genetics in an article entitled “The Impact of Endurance Training on Human Skeletal Muscle Memory, Global Isoform Expression and Novel Transcripts.”
“It has not been previously shown that training changes the expression of genes in this particular way,” explained lead study author Maléne Lindholm, Ph.D., postdoctoral researcher in the Karolinska Institutet's Department of Physiology and Pharmacology. “The study also provides new basic information about how the body adapts to regular endurance training and what role many of our genes play in the adaptation.”
Interestingly, the researchers found that the changed genetic activity in the previously trained leg was no longer present when exercise resumed. However, the repeated response to training was somewhat different in the trained and previously untrained legs in the second training period, which suggests that the exercise could have left other lasting impacts.
“We were looking for any residual effects of previous training, a kind of muscle memory as it were, and trying to find out if this could influence the response to repeated training,” Dr. Lindholm noted.
The Karolinska team was excited by their findings and believe that this study has great importance toward the fundamental understanding of how muscles operate and how we adapt to endurance training.
“The results can also contribute to the future optimization of training effects in different individuals,” Dr. Lindholm concluded. “In the long run, it is conceivably of some significance to the possibility of preventing cardiovascular disease and the development of new, more precise drugs for people who, for whatever reason, are unable to exercise.”