Decreased expression of microRNA miR‐133 but not miR‐1 is associated with impaired cardiac performance

MicroRNAs (miRs) post‐transcriptionally regulate gene expression. miR‐1 and miR‐133 can evoke opposing effects on apoptosis in cardiomyocytes with miR‐1 acting pro‐apoptotically and miR‐133 anti‐apoptotically. In 86 patients undergoing coronary artery bypass grafting (CABG), we tested the hypothesis that cardiac miR‐1 and miR‐133 expression are associated with altered cardiac performance. Cardiac index and vascular pressures were determined during general anesthesia and right atrial appendages were obtained during cannulation for extracorporal circulation. miR expression was quantified by RNase protection assay and by Real‐Time PCR. Decreased miR‐133 expression was significantly associated with diminished exercise performance as indicated by worsened NYHA functional class (p=0.0045), and higher pulmonary artery occlusion pressures (p=0.0042). Furthermore, patients with NT‐proBNP concentrations >1800 pg/ml showed a 60% decrease in miR‐133 expression compared to patients with concentrations <300 pg/ml (p=0.036). In contrast, no association could be detected between miR‐1 expression and variables of cardiac performance. This study shows for the first time a link between decreased miR‐133 expression and development of cardiac failure in CABG patients, possibly indicating a role of miR‐133 in regulating cell fate by inhibiting apoptosis.