Metformin suppresses phenylephrine-induced hypertrophic responses by inhibiting p300-HAT activity in cardiomyocytes

Heart failure is the final pathway for a wide spectrum of myocardial stress, including hypertension and myocardial infarction. However, the potential effects of metformin on cardiac hypertrophy are still unclear. The purpose of this study was to investigate whether metformin leads to suppression of hypertrophic responses in cardiomyocytes. To investigate whether metformin inhibited p300-histone acetyltransferase (HAT), we performed an in vitro HAT assay. Metformin directly inhibited p300-mediated acetylation of histone-H3K9. To examine the effects of metformin on hypertrophic responses, cardiomyocytes prepared from neonatal rats were treated with metformin and stimulated with saline or phenylephrine (PE), a α1-adrenergic agonist for 48 h. PE stimulus showed an increase in cell size, myofibrillar organization, expression of the endogenous atrial natriuretic factor and brain natriuretic peptide genes, and acetylation of histone-H3K9 compared with saline-treated cells. These PE-induced changes were inhibited by metformin. Next, to examine the effect of metformin on p300-mediated hypertrophy, cardiomyocytes were transfected with expression vector of p300. Metformin significantly suppressed p300-induced hypertrophic responses and acetylation of histone-H3K9. The study demonstrates that metformin can suppress PE-induced and p300-mediated hypertrophic responses. Metformin may be useful for the treatment of patients with diabetes and heart failure.