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Regular exercise can induce epigenetic changes, new research on twins indicates. In this innovative study, scientists compared the genetics of twins who were raised together through childhood but went on to live separately as adults. After reaching adulthood, many of the pairs differed from each other on measures of physical activity, neighborhood walkability, and body mass index. This difference, the researchers found, was reflected in epigenetic profiles.

The Washington State University study, published today in Scientific Reports, found that active twins had epigenetic markers linked to lowered metabolic syndrome, a condition that can lead to heart disease, stroke and type 2 diabetes. More physically active siblings also had lower signs of metabolic disease, measured by waist size and body mass index.

Since identical twins have the same genetics, the study suggests that markers of metabolic disease are influenced by how people interact with their environment and not just the genes they inherited.

“The findings provide a molecular mechanism for the link between physical activity and metabolic disease,” said Michael Skinner, WSU biologist and the study’s corresponding author. “Physical exercise is known to reduce the susceptibility to obesity, but now it looks like exercise through epigenetics is affecting a lot of cell types, many of them involved in metabolic disease.”

Epigenetics describes “molecular modifications on DNA that can regulate gene activity are independent of DNA sequence and mitotically stable.” The field has expanded dramatically in the last 20 years, and seems to be maturing after going through the inevitable hype, disappointment, and post-all-that phases.

In this study, the researchers collected cheek swabs of 70 pairs of identical twins who also participated in an exercise study through the Washington State Twin Registry. A team led by WSU Professor and Registry Director Glenn Duncan collected data on the twins at several different points in time from 2012 to 2019. They used fitness trackers to measure physical activity and measured the participants’ waistlines and body mass indexes. The twins also answered survey questions about their lifestyle and neighborhoods.

Many of the twin pairs were found to be discordant—they differed from each other on measures of physical activity, neighborhood walkability and body mass index.

An analysis by Skinner’s lab of the cells in the discordant twins’ cheek swabs revealed epigenetic differences too. The twin in the discordant pair with a high level of physical activity, defined as more than 150 minutes a week of exercise, had epigenetic alterations in areas called DNA methylation regions that correlated with reduced body mass index and waist circumference. Those regions are also associated with over fifty genes that have already been identified as specific to vigorous physical activity and metabolic risk factors.

Scientists have previously noted that the majority of identical twins develop different diseases as they get older even though they have the same genes. Epigenetics may help explain the reason why, said Skinner.

“If genetics and DNA sequence were the only driver for biology, then essentially twins should have the same diseases. But they don’t,” said Skinner. “So that means there has to be an environmental impact on the twins that is driving the development of disease.”

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