Background:Recent studies show that microRNA-145 (miRNA-145) might be an attractive tumor biomarker of considerable prognostic value,but little is known about their relationship with acute myocardial infarction (AMI).This study investigated the correlation between the level ofmiR-145 and AMI.Methods:One-hundred patients were divided into three groups:no coronary artery disease (CAD) group,non-ST segment elevation myocardial infarction group,and ST segment elevation myocardial infarction group.The plasma levels of miR-145 were quantified using real-time quantitative polymerase chain reaction.Logarithmic transformation of miRNA-145 levels (Ln_miRNA-145) was used for statistical analysis due to the skewed data distribution.Results:Plasma levels of miR-145 were significantly lower in patients with AMI compared to patients in the non-CAD group (-6.38 ± 0.11 vs.-4.47 ± 0.17,P ＜ 0.0001).Compared to those without heart failure,the levels of miR-145 were significantly lower in patients with heart failure (-6.91 ± 0.20 vs.-5.35 ± 0.13,P ＜ 0.0001).We also found that the lower plasma levels of miRNA-145 significantly correlated with increased serum levels of B-type natriuretic peptide (Spearman p =-0.60,P ＜ 0.0001),troponin T (Spearman p =-0.62,P ＜ 0.0001),and decreased ejection fraction (Spearman p =0.65,P ＜ 0.0001).In a multivariable linear regression analysis,AMI and heart failure were independently associated with lower Ln_miRNA-145 (estimate-0.99,standard error [SE] 0.28;P =0.001 and estimate-0.62,SE 0.21;P=0.004).Conclusions:Our results suggest that decreased plasma levels of miR-145 are associated with AMI.Circulating miR-145 may be useful in prognosticating cardiac function and the risk of developing heart failure.