Findings on changes in the expression of gene regulators or transcription factors in the cardiomyocytes of exercised mice provide insight into how the heart grows larger in response to physical activity (Boström P et al. Cell. 2010;143:1072-1083).
Investigators at the Dana-Farber Cancer Institute and Harvard Medical School in Boston found mice that swam experienced changes in 175 transcription factors, including the factors C/EBPβ and CITED4.
Experiments in animals and cell culture showed that the decline in C/EBPβ leads to changes consistent with those that follow endurance exercise, including an increase in heart muscle size and proliferation. This proliferation was mediated, at least in part, by increased CITED4. Mice with reduced C/EBPβ levels were resistant to heart failure when the researchers induced stress on the heart.
Hampton T. Exercise and the Heart. JAMA. 2011;305(5):458. doi:10.1001/jama.2011.52