Why exercise helps the heart

BOSTON, Dec. 24 (UPI) -- Although doctors know exercise benefits the heart, U.S. researchers say they now have a better understanding of how it does so.

Bruce Spiegelman of Harvard Medical School in Boston says studies in mice suggest exercise turns on a genetic program that leads the heart to grow as heart muscle cells divide.

It appears that shift is driven in part by a single transcription factor -- a gene that controls other genes -- known to play important roles in other parts of the body, but this is the first evidence C/EBPb influences the heart, Spiegelman says.

"We've identified a pathway involved in beneficial cardiac hypertrophy -- the good kind of heart growth," Spiegelman says in a statement.

Researchers say the heart muscle adapts to increased pressure and volume by increasing in size both in a beneficial way during exercise, but also in a bad way due to high blood pressure.

The researchers sought to better understand these differences to quantify changes in the expression of transcription factors in the heart at the genome-wide level in both exercised mice and those who had their aortas surgically constricted, which increases heart size.

The findings are published in the journal Cell.