Objectives MicroRNAs (miRNAs) play key roles in diverse biological and pathological processes, including the regulation of proliferation, apoptosis and cellular differentiation. Recently, circulating miRNAs have been proposed as potential biomarkers for cardiovascular disease. However, its value in the evaluation of perioperative myocardial injury has not yet been assessed. In the present study, we presumed that plasma concentrations of miR-499 may serve as a biomarker for identifying myocardial injury in cardiac surgery.
Methods Thirty two consecutive patients undergoing on pump coronary artery bypass grafting (CABG)were included in a prospective, randomised study using standardised operative procedures and myocardial protection. Serial plasma samples from patients were collected at 7 perioperative time points (preoperatively, 1, 3, 6, 12, 24, 48 h after declamping), and were tested for miRNAs and cardiac troponin I (cTnI). Total RNA were extracted from plasma with mirVana PARIS Kit. The levels of circulating musle-specific miR-499 were measured by TaqMan quantitative reverse transcription-PCR (qRT-PCR),and plasma cTnI concentrations were measured by electrochemiluminescence based methods on the Beckman ACCESS2 Analyser.
Results Our study showed that circulating miR-499 was highly elevated at 1, 3, 6h after declamping in CABG patients, 50-fold (P < 0.01), 100-fold (P < 0.01),and 50-fold (P < 0.01), respectively, as compared with the preoperative. And it gradually returned closer to normal at 48h (6-fold; P < 0.01). MiR-499 and cTnI exhibited the same trend. Importantly, miR-499 levels peaked as early as 1 h after declamping, whereas TnI peaked only 6 h after declamping. Indeed, peak plasma levels of miR-499 correlated significantly with peak level of cTnI (r = 0.648, P = 0.001), indicating the degree of myocardial damage.
Conclusions In this study, we reported the expression of circulating miR-499 in CABG. In comparison to the preoperative, interestingly, miR-499 plasma levels in patients with CABG up-regulated after the declamping. Importantly, an outstanding finding in this study is that miR-499 and cTnI exhibited the same trend. The plasma concentration of miR-499 showed a good correlation with the plasma concentration of cTnI, a classic marker of myocardial injury. The plasma concentration of miR-499 can be a potential indicator of myocardial injury in CABG. Thus, our results clearly hold out the hypothesis that miR-499 may be useful for identifying perioperative myocardial injury in CABG patients.