Long-term endurance training alters the epigenetic pattern of the human skeletal muscle, according to new research from the Karolinska Institutet in Sweden, published in the journal Epigenetics.
Epigenetics are temporary biochemical changes in the genome caused by environmental influences. The researchers behind the new study explain that if genes are the “hardware” of cells, then epigenetics are their “software.”
In particular, the researchers were interested in a type of epigenetic change called methylation. In methylation, a methyl group – molecules that reside within genes – is either added to or subtracted from a DNA molecule base without it affecting the original DNA sequence.
In the study, 23 healthy young men and women performed supervised one-legged cycling, with the untrained leg acting as a control.
The participants took part in 45-minute training sessions conducted four times each week during a 3-month period. Performance was measured in both legs before and after the training sessions, and biopsies were taken of skeletal muscle, where methylation and the activity of more than 20,000 genes were measured.
In the participants’ trained legs, the researchers found strong associations between the change in activity of 4,000 genes and epigenetic methylation.
Genomic regions subject to increased methylation also featured carbohydrate metabolism and adaptation of the skeletal muscle. Genomic regions that had a decreasing degree of methylation, however, were associated with inflammation.
A key finding of the study was that the majority of epigenetic changes occurred in “enhancers,” which are regulatory regions of the genome.
“We found that endurance training in a coordinated fashion affects thousands of DNA methylation sites and genes associated to improvement in muscle function and health,” says Prof. Carl Johan Sundberg, principal investigator at the Karolinska Institutet’s Department of Physiology and Pharmacology.
He continues:
“This could be of great importance for the understanding and treatment of many common diseases such as diabetes and cardiovascular disease, but also for how to maintain a good muscle function throughout life. Interestingly, we also saw that there were epigenetic differences between male and female skeletal muscle, which may be of importance to develop gender specific therapies in the future.”
Prof. Sundberg says that although it is well established that inactivity is bad for health and regular physical activity improves quality of life and life expectancy, the exact mechanisms behind the positive effects of training have been unclear.
“This study indicates that epigenetics is an important part in skeletal muscle adaptation to endurance training,” he concludes.
In 2013, Medical News Today reported on a study by researchers at Lund University in Sweden that also looked at epigenetic methylation and exercise.
The Lund researchers found that epigenetic changes occurred in 7,000 genes in their overweight but relatively healthy participants while performing aerobic exercises. Genes that are linked to type 2 diabetes and obesity also underwent epigenetic changes, the Lund researchers reported.
Tina Rönn, associate researcher at Lund University, said this “suggests that altered DNA methylation as a result of physical activity could be one of the mechanisms of how these genes affect the risk of disease.”