CLAREMONT, Calif.–A team of Brazilian scientists pursuing a study that began at the Keck Graduate Institute discovered a gene regulator that keeps hearts healthy even under intense exercise, providing a medical explanation for why exercise is good for the heart.

“Now, we’re beginning to get to the molecular basis of why exercise is good for you,” said Dr. Ian Phillips, KGI’s Norris Professor of Applied Life Sciences, in whose lab the research on the gene regulator called MicroRNA 29 began.

“It’s well known that athletes get large hearts and they remain healthy while people with large hearts, who are not athletes, are in big trouble,” Phillips said. “But we’ve never known before why they were different.”

Edilamar de Oliveira, a biochemistry professor in the Physical Education School at the University of Sao Paulo, worked with Phillips while doing postdoctoral studies at KGI from 2007-09.

Applying what she learned about MicroRNAs to her research on physical training and cardiac hypertrophy after returning to Brazil, she found MicroRNAs act as brakes on specific genes, inhibiting what proteins those genes produce.

De Oliveira and her team found that rats that trained like athletes, two and three times a day on a 10-week regimen involving swimming, showed much higher levels of MicroRNA 29 than sedentary rats.

Even though the athletic rats’ hearts were enlarged, they did not develop an excess of collagen fibers, which interferes with the heart’s ability to pump effectively, according to Phillips, adding that bad hearts are full of collagen while healthy hearts have very little.

According to KGI, one of the Claremont Colleges, the discovery has broad implications for individuals with heart disease and congestive heart failure.

The findings appear in the latest issue of the journal Physiological Genomics.