Circulating miR-126 and miR-499 reflect progression of cardiovascular disease; correlations with uric acid and ejection fraction.

BACKGROUND: The aim of this study was to assess plasma levels of endothelium- and heart-associated microRNAs (miRNAs) miR-126 and miR-499, respectively, using quantitative reverse transcriptase polymerase chain reaction.

METHODS: A two-step analysis was conducted on 75 patients undergoing off-pomp coronary artery bypass graft (CABG) surgery. Five biomarkers of inflammation and cardiac injury were assessed in addition to the above-mentioned miRNAs.

RESULTS: Plasma concentrations of miRNAs were found to be significantly correlated with plasma levels of cardiac troponin I (cTnI) (miR-499, r 0.49, p~0.002; miR-126, r = 0.30, p~0.001), indicating cardiac damage. Data analysis revealed that miR-499 had higher sensitivity and specificity for cardiac injury than miR-126, which reflects more endothelial activation. Interestingly, a strong correlation was observed between both miRNAs and uric acid (UA) levels with ventricular contractility measured as ejection fraction (EF) (miR-499/EF%, r = 0.58, p~0.004; UA/EF%, r = -0.6, p~0.006; UA/miR-499, r = -0.34; UA/miR-126, r = 0.5, p~0.01).

CONCLUSIONS: In patients undergoing CABG, circulating miR-126/499 is associated with presentation of traditional risk factors and reflects post-operative response to injury. Plasma pool of miRNAs likely reflects extracellular miRNAs which are proportional to intracellular miRNA levels. Therefore, circulating levels of these miRNAs have prognostic implications in detection of higher risk of future cardiovascular events.