Regulation of Exercise-Dependent Cardiac Growth by MicroRNAs




Johnson, Brett A.

Journal Title

Journal ISSN

Volume Title


Content Notes


The heart is an adaptive organ which undergoes pathological or physiological remodeling in response to a variety of stimuli to meet the demands of the body. Chronic exercise training promotes a physiological remodeling response in which the heart increases in size to match loading demands. In this thesis, I present my studies on the function of microRNAs during exercise-induced cardiac remodeling. First, I show the expression of muscle-specific microRNA (miRNA), miR-499, is down-regulated by voluntary free-wheel running in hearts of mice. I hypothesized the reduction of miR-499 may be required for exercise-induced cardiac hypertrophy. I found forced cardiac over-expression of miR-499 was associated with diminished physiological cardiac growth, whereas genetic deletion and antimiR mediated inhibition of miR-499 caused enhanced physiological growth following exercise. I also explored the mechanism by which miR-499 represses exercise-induced cardiac growth. I determined the repressive effects of miR-499 are mediated through regulation of IGF-1/PI-3K/Akt and beta-catenin signaling pathways, which drive physiological growth of the heart. I demonstrated the effects of miR-499 on physiological cardiac growth are mediated, at least in part, through repression of a network of genes including p85-alpha, Rictor, Lin7c and Fzd4. Collectively, the results of my thesis research identify miR-499 as a pivotal regulator of exercise-induced cardiac hypertrophy.

General Notes

Table of Contents


Related URI