It is estimated that the human genome encodes more than mature 2000 miRNAs (miRBase v. 22) according to GENCODE data (v. 29), including isoforms with slight variations. Circulating miRNAs are more stable and resistance to degradation by endogenous RNase activity than intracellular miRNAs, reside in microvesicles including exosomes, microparticles and apoptotic bodies, which may provide protection from RNase activity. The stability of circulating miRNAs has stimulated interest in their use as biomarkers for the diagnosis and prognosis of various diseases including CVD (13).
Nevertheless, the property of cTn and CKMB for early diagnosis of AMI is weak because the level of these biomarkers elevates late after MI. Thus, a biomarker that could be detected at the early stage of AMI with a better diagnostic value is needed to compensate for the deficiency of cTn and CKMB. B Wang et al., 2021, study aimed to compare the combined miRNAs could compensate for the deficiency of single miRNA in sensitivity or specificity for an optimal clinical value. Also the results displayed that some miRNAs reached peak time earlier and showed a shorter time window than the conventional biomarkers despite the different collection times of initial blood samples. Some of them were shown to be more valuable than classical biomarkers for the early diagnosis of AMI, and these miRNAs appeared to have the most potential biomarkers within 4 h of the onset of symptoms except miR-133a/b and miR-208b (14).
Muscle- and cardiac-specific miRNAs as miR-1, miR-133a/b and miR208a/b have already been described as deregulated in human MI in previous studies. In the present study, we evaluated miR133a and miR208b as potential circulating biomarkers for AMI. Increases in serum miR-133a level were observed in patients with evidence of cardiac injury (STEMI) after 8 h but unlike miR-208b level which remained elevated after 12 h. MiR-133a and miR-208b returned to baseline levels within 48 h after treatment.
Y Wexler et al.,2020, meta-data analysis comparing between different studies to determine the diagnostic value of miR-133a level whether it may serve as a biomarker for very early detection of AMI, and to evaluate the queried role that it may be useful in distinguishing STEMI from NSTEMI, as the commonly used biomarkers for the diagnosis of AMI, such as cardiac troponins and CK-MB-, were not effective at very early diagnosis of AMI (within 0–3 hours (15). It is approved in our study as well, as mir-133a started as its peak earlier at 8 hours and before miR-208b and clinical biomarkers TnI and CK-MB as well, their peaks at 12 hours.
It is known that miR-1, miR-133a, miR-133b, miR-206, miR-208a, miR-208b, and miR-499 are muscle-specific miRNAs. MiR-1, miR-133, and miR-208, being involved in heart development and disease. Among them, miR-133b and miR-206 are expressed only in skeletal muscle and miR-208a is expressed only in cardiac muscle. In this study, they showed upregulation of miR-208 levels and downregulation of miR-1 and miR-133 levels from autopsy samples of infarcted heart tissue from patients with MI (16).
In a larger cohort comprised of patients with acute coronary syndrome (ACS), the plasma miR-133a and miR-133b levels were independently associated with increased high sensitive cardiac troponin T (hsTnT) levels. MiR-133a levels were significantly associated with the risk of death, also reported fold increase of miR-133 level in plasma from AMI patients (17). A positive correlation was also reported in the elevated miR-133 and cTnI. This report also indicated that miR-133 may be superior to cardiac troponin I due to some confounding factors that may affect troponin I(TnI) levels. It shows up in the end-stage renal disease, the lower glomerular filtration would increase the troponin I level in the plasma (18). Commonly to our results, CK-MB and cTnI, achieved a peak of 15 ± 2.9 after 12 hours, 46.11 ± 7.602 12 hours, consecutively after the same onset.
In agreement with other related published reports (Kuwabara et al., 2011; C. Widera et al., 2011), related to the correlation between miR-133a level, CPK and TnT in CVD patients. Their results examined that the serum miR-133a Level was sensitive, and was significantly higher in ACS patients compared with non-ACS patients. The serum levels of these miR-133a peaked before 3 hours after chest pain was reported and decreased gradually thereafter, with no elevation of CPK and cTnT. MiR-133a expression levels decreased gradually expression levels decreased (18, 19).
In C. Widera et al., 2011, study including patient cohort with NSTEMI or STEMI, presented with higher levels of miR133a, and miR-208b compared with patients with unstable angina (UA) (18).
YU et al., 2018 study, investigated the expression of miR-133a level in patients with or without AMI following radical surgery for gastric cancer, and to explore its underlying mechanisms. The results suggested that patients with AMI exhibited significantly increased expression of endothelial injury markers and miR-133a compared with patients without AMI (20).
The same for the other MiRNAs in this study including 133a.The levels of the MiRNAs are decreased once the patients reached the hospital, might be used as a biomarker for AMI but it did not show any advantages over cTnT for AMI diagnosis. They are established biomarkers for the diagnosis of AMI and reflect infarct size. Compared with cTnI, cTnT is more specific and sensitive for the diagnosis of AMI compared to miRNAs in related studies. They performed ROC curve analyses to determine the diagnostic values of the four circulating miRNAs and to compare them with cTnT. They hypothesized that cTnT might be released from necrotic myocardium at the time of the AMI in patients prior to the onset of chest pain (3).
Corsten et al., 2010 study results indicated that the plasma levels of miR-208b in AMI patients, was increased more than 1000 times folds compared with healthy subjects. The changes in plasma level of miR-208b were consistent with cTnT, demonstared that miR-208b was released from injured cardiomyocytes like cTnT (21).
O Gidlöf et al., they demonstrated the levels of plasma miR-208b increased thousands fold in case of STEMI patients compared to healthy controls within 12 h after infarction, correlated with peak troponin I (cTnI), indicating a possible role for circulating miR-208b as a biomarker in diagnosis of STEMI at day 1(2).
Han et al., 2015, study, the plasma miRNA-208 level was significantly higher in AMI group within 12 hours of the MI onset than normal control group. Correlation analysis showed that miRNA-208 had significant correlation with cTnT, but not with CK-MB (23). In our study, miR-208b had significant correlation with CK-MB.
C Li et al., 2015 study aim to compare the expression of different miRNAs including miR-208b in AMI patients. MiR-208b was expressed at a high level in AMI compared to controls. MiR-208b was more effective in patients with NSTEMI. Though other studies there were no significance of the levels of plasma of miR-208b between STEMI and NSTEMI, including ours, especially STEMI (24).
X Liu et al.,2017 study involved 3 groups of the following, AMI patients divided to (one, two, three –vessel CAD), unstable angina (UA) patients, and controls were consecutively included in this study. The AMI patients who sustained percutaneous coronary intervention (PCI) were followed up at 6 months post-AMI. The concentration of miR-208b was significant in the AMI patients than in the other two groups, and it was positively correlated with the levels of CK-MB and cTnI, compared to our results. In addition, the miR-208b concentration in AMI patients with three vessel coronary artery disease (CAD) was higher than that of single- or two-vessel CAD AMI patients. Also, the miR-208b expression after PCI was significantly lower than before, except those with left ventricular remodeling/MACEs was higher after PCI (25).
In this pilot study, M Alavi-Moghaddam et al,.2018, they demonstrated the role of miR-208b as a candidate biomarker for AMI diagnosis and the potential of circulating miR-208b as a prognostic biomarker of 6-month survival in AMI patients (26).
K AGIANNITOPOULOS et al., 2018 study group consisted of Greek AMI patients and controls. All of the AMI patients were sustained a PCI. The relative expression of miR-208b and miR-499 were elevated in AMI patients compared to that of controls (27).
YQ Li ·et al., 2013 study, they demonstrated that circulating miR-208b levels was not significant between STEMI and NSTEMI patients. The same for the other MiRNAs in this study including 133a.The levels of the MiRNAs are decreased once the patients reached the hospital, might be used as a biomarker for AMI but it did not show any advantages over cTnT for AMI diagnosis. They were still trying to conform which more superior early diagnostic biomarker in case of MI case (28).
In other related published clinical studies (Peng et al., 2014; Boštjančič et al.,2018), they found that the expression of miR-133 was distinctly increased in STEMI and NSTEMI cases compared to non-AMI cases. E. Boštjančič et al.,2018, they demonstrated that miRNAs may contribute to the development of arrhythmias. Their studies included patients who had died after 24 h of MI and others after 1–7 days after MI. Some of them are proven ventricular fibrillation (VF) and others without VF. They were compared to healthy trauma victims were included as control. Their results suggested that in patients with MI with VF, were observed down-regulation of miR-133a/b, even stronger 2–7 days after MI. miR-208 was up-regulated in remote myocardium irrespective of the presence of VF (29).
B Wang et al,2021 systematic review, comparing miRNAs and Conventional Biomarkers as CK-MB and cTn, their results are different in several studies, regarding the potential cofounders such as single miRNA or combined miRNAs, sample size, collection time of samples and Detection Methods (30, 31).
Han et al., 2015, study, including AMI patients, the plasma miRNA-208 level was significantly higher in AMI group within 12 hours onset after than normal control group. Correlation analysis showed that miRNA-208 had significant correlation with cTnT, but not with CK-MB (15).