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Born to Run: Thirty-six reasons why some rodents are omre into exercise.

FEELING THE URGE to skip the gym today? Blame your DNA.

An investigation by MU veterinary medicine professor Frank Booth and post-doctoral researcher Michael Roberts has determined that some rodents are more genetically prone to physical activity than others, a finding that could further our understanding of why some humans are more exercise averse than others.

The study, published in the April 3 issue of theĀ American Journal of Physiology: Regulatory, Integrative and Comparative Physiology, began with Booth and Roberts observing how willingly rats placed in running-wheel-equipped cages used those wheels during a six-day period. They then separated the most energetic runners from the loafers and began a breeding program: active with active, languid with languid.

Ten generations later, the researchers noted, those original traits had become much more pronounced. Rats in the “running rat” line chose to hit the wheel 10 times more often than their more indolent cousins.

The next, crucial step in the investigation involved determining levels of mitochondria in rats’ muscle cells, comparing measures of body compositions, and conducting RNA deep sequencing. “While we found minor differences in the body composition and levels of mitochondria in muscle cells of the rats, the most important thing we identified were the genetic differences between the two lines of rats,” says Roberts. “Out of more than 17,000 different genes in one part of the brain, we identified 36 genes that may play a role in predisposition to physical activity motivation.” Having identified these specific genes, Booth and Roberts will now try to pin down the effect each gene has on motivation to exercise.

“We have shown that it is possible to be genetically predisposed to being lazy,” Booth says. “This could be an important step in identifying additional causes for obesity in humans, especially considering dramatic increases in childhood obesity in the United States. It would be very useful to know if a person is genetically predisposed to having a lack of motivation to exercise, because that could potentially make them more likely to grow obese.”

Rat standing on mini-treadmill.

Illustration by Blake Dinsdale

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