Coronary artery disease (CAD) is a major problem worldwide including Asian countries. Atherosclerosis and thrombosis underlying CAD involves multiple cell types[
1]. Various blood markers associated with CAD have been identified, but only a few have a diagnostic impact or important clinical implications that affect management[
2]. Therefore, biomarkers that can assess the risk for CAD and the early atherosclerotic process would be desirable. Circulating microRNAs (miRNAs) could be useful as biomarkers for various diseases including cancer[
3], acute myocardial infarction[
4], vascular diseases[
5] and heart failure[
6]. MiRNAs are a class of short (20-25 nt) single-stranded noncoding RNAs that regulate cellular functions through degradation and translational repression of mRNAs that contain complementary sequences. More than 1,000 human miRNAs are identified. In tissue miRNAs regulate the expression of genes involved in differentiation, growth, proliferation and apoptosis. MiRNAs regulate protein expressions as well[
7]. MiRNAs are found in tissues, plasma and other body fluids in a stable form that is protected from endogenous RNase activity[
3]. Thus, the signatures of miRNA in tissues and plasma may have a potential role in diagnosis, therapeutic efficacy and prognosis. In this study miRNA level in plasma of patients with angiographically significant CAD was compared to that of patients without angiographically significant CAD. Because endothelial dysfunction is involved in early processes of atherosclerosis and thrombosis[
8], vascular endothelium-enriched miRNA (miR-126)[
9] that can regulate angiogenesis was analyzed.