There is a growing burden of cardiovascular disease associated with HF worldwide. Patients with chronic HF have a 1-year mortality rate of 7.2% and a 1-year hospitalization rate of 31.9%, while patients with acute HF have 17.4% and 43.9%, respectively[20]. Although the N-terminal fragment of NT-pro-BNP is a potential marker of heart failure as outlined in the European guidelines from 2008[21], circulating diagnostic biomarkers-microRNAs have their advantages. Unlike mRNAs, microRNAs are stable at room temperature and remain so after repeated freeze-thawing[8]. The present study analyzed the circulating miRNA signature of patients with HFrEF. The results of a genome-wide microarray followed by an independent qRT-PCR analysis demonstrated that two plasma microRNAs (miR 378 and miR 195-5p) were significantly downregulated while ten circulating miRNAs (miR 21-3p, miR 21-5p, miR 106b-5p, miR 23a-3p, miR 208a-3p, miR 1-3p, miR 126-5p, miR 133a-3p, miR 133b and miR 223-3p) were remarkably upregulated in HFrEF patients compared with their hypertensive controls. The AUC of all differentially expressed miRNAs was more significant than 0.70, except for miR-21-5p and miR-22a-3p. ROC analysis revealed that the combination of miR 133a-3p, miR 106b-5p, miR 1-3p, miR 133b, and miR 378 had similar discriminatory abilities in identifying HFrEF as NT-proBNP, which is an acknowledged biomarker. Drawing ROC curves for these miRNA biomarker candidates were used to determine the cut-off points for these biomarker candidates. It should be noted that the cut-off values here were change-fold, which was a relative ratio. The absolute quantification of miRNA is challenging to define and is greatly influenced by each batch's reagents, operation, and other factors. Therefore, the diagnostic value of miRNA may be somewhat affected in practical operation. The absolute RT-qPCR method, on the other hand, is capable of determining the exact number of copies of a miRNA.The signal in an unknown sample is compared to a standard curve to achieve this[22]. Recently, digital RT-PCR has been used to quantify miRNA absolute levels. Digital PCR has the inherent advantage over conventional PCR in that it does not require external calibration (standard curves) or normalization in order to estimate the concentration of an unknown target[22].
It is reported that the overexpression of miR-133a significantly decreased fibrosis in rats with chronic heart failure by inhibiting the serine/threonine kinase Akt[23]. MiR-133 overexpression also suppresses the expression of multiple genes in fibroblasts, concurrently activating cardiac reprogram[24]. MiR-378 plays a dual role in suppressing cardiac hypertrophy and fibrosis through a paracrine mechanism[24]. In our study, some of these diagnostic candidate miRNAs are also associated with the LVEF (miR 133a-5p, miR 1-3p, miR 106b-5p, miR 126-5p, and miR 195-5p) and other echocardiographic parameters(LAD, LVDd, LVDs, IVSd, and PAP), which predicts that these miRNAs may be involved in myocardial hypertrophy or myocardial remodeling and deserve further investigation.
Further, we made a bioinformatic analysis of these HFrEF diagnostic candidates. It was determined that these five candidate miRNAs target 130 genes that are co-expressed using the miRWALK2.0 software. GO analysis demonstrated that the overlapping differentially expressed genes were dramatically concentrated in the organelle. As part of the KEGG analysis, we investigated whether there were any common enriched pathways related to pathophysiological processes associated with heart failure. We found support for some familiar pathway enrichment results with heart failure for the Mitogen-activated protein kinas (MAPK) signaling pathway, ErbB signaling pathway, and TGF-beta signaling pathway.
MAPK signaling cascades are critical regulators of cardiac hypertrophic response[25]. Liang reported that inhibiting p38 MAPK can reduce cardiomyocyte growth in response to hypertrophic stimuli[26]. In addition, chronic activation of the p38 MAPK pathway has been demonstrated to induce hypertrophic responses in cultured cardiomyocytes[27, 28].
Animal models have demonstrated significant changes within the cardiac NRG-1/ErbB pathway during the progression of chronic HF. In the early stages of the disease, NRG-1/ErbB expression is elevated and declines just after the pump fails[29, 30].
It has been demonstrated that the TGFβ signaling pathway plays a role in cardiac remodeling[31]. Increased TGFβ1 expression is instrumental in heart hypertrophy[32] and cardiomyocyte apoptosis[32]. It is also reported that there is a climacteric link between miR-34a, cardiovascular fibrosis, and Smad4/TGFβ1 signaling pathway[33].
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Our study has some limitations: 1) the number of patients was relatively small, which reduced our statistical power. Therefore, more extensive studies should be conducted to confirm the diagnostic value of miRNAs. 2) it is skeptical whether these circulating miRNAs are released from cardiomyocytes, fibroblasts, macrophages, or even by non-cardiovascular tissues due to the secondary consequence of HF.