Why exercise helps the heart

"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"