new research reports that the answer may lie, in part, in our DNA. Exercise, a new study finds, changes the shape and functioning of our genes, an important stop on the way to improved health and fitness.
The human genome is astonishingly complex and dynamic, with genes constantly turning on or off, depending on what biochemical signals they receive from the body. When genes are turned on, they express proteins that prompt physiological responses elsewhere in the body.
Scientists know that certain genes become active or quieter as a result of exercise. But they hadn’t understood how those genes know how to respond to exercise.
Enter epigenetics, a process by which the operation of genes is changed, but not the DNA itself.
Epigenetic changes occur on the outside of the gene, mainly through a process called methylation. In methylation, clusters of atoms, called methyl groups, attach to the outside of a gene like microscopic mollusks and make the gene more or less able to receive and respond to biochemical signals from the body.
Scientists know that methylation patterns change in response to lifestyle.
Eating certain diets or being exposed to pollutants, for instance, can change methylation patterns on some of the genes in our DNA and affect what proteins those genes express. Depending on which genes are involved, it may also affect our health and risk for disease.
Far less has been known about exercise and methylation. A few small studies have found that a single bout of exercise leads to immediate changes in the methylation patterns of certain genes in muscle cells. But whether longer-term, regular physical training affects methylation, or how it does, has been unclear.
So for a study published this month in Epigenetics, scientists at the Karolinska Institute in Stockholm recruited 23 young and healthy men and women, brought them to the lab for a series of physical performance and medical tests, including a muscle biopsy, and then asked them to exercise half of their lower bodies for three months.
so many aspects of our lives affect our methylation patterns, making it difficult to isolate the effects of exercise from those of diet or other behaviors.
The Karolinska scientists overturned that obstacle by the simple expedient of having their volunteers bicycle using only one leg, leaving the other unexercised. In effect, each person became his or her own control group.
Both legs would undergo methylation patterns influenced by his or her entire life; but only the pedaling leg would show changes related to exercise.
The volunteers pedaled one-legged at a moderate pace for 45 minutes, four times per week for three months. Then the scientists repeated the muscle biopsies and other tests with each volunteer.
Not surprisingly, the volunteers’ exercised leg was more powerful now than the other, showing that the exercise had resulted in physical improvements.
But the changes within the muscle cells’ DNA were more intriguing. Using sophisticated genomic analysis, the researchers determined that more than 5,000 sites on the genome of muscle cells from the exercised leg now featured new methylation patterns.
But the changes were significant and not found in the unexercised leg.
This means that epigenetic changes are only local, unlike the genetics/genes of an individual, which are the same in every cell.
This also leads to some uncertainties:
It’s unknown, for example, whether the genetic changes she and her colleagues observed would linger if someone quits exercising
Most of the genes in question are known to play a role in energy metabolism, insulin response and inflammation within muscles. In other words, they affect how healthy and fit our muscles — and bodies — become.