HughPickens.com writes 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. Scientists have known that certain genes become active or quieter as a result of exercise but they hadn't understood how those genes knew how to respond to exercise. Now the NYT reports that scientists at the Karolinska Institute in Stockholm have completed a study where they 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. 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 there were also changes within the exercised muscle cells' DNA. Using technology that analyses 480,000 positions throughout the genome, they could see that new methylation patterns had taken place in 7,000 genes (an individual has 20–25,000 genes). In a process known as DNA 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. In the exercised portions of the bodies, many of the methylation changes were on portions of the genome known as enhancers that can amplify the expression of proteins by genes. And gene expression was noticeably increased or changed in thousands of the muscle-cell genes that the researchers studied. 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. Many mysteries still remain but the message of the study is unambiguous. "Through endurance training — a lifestyle change that is easily available for most people and doesn't cost much money," says Sara Lindholm, "we can induce changes that affect how we use our genes and, through that, get healthier and more functional muscles that ultimately improve our quality of life."
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