Presentation of acute events in patients with atherosclerosis remains unpredictable even after controlling for classical risk factors. MicroRNAs (miRNAs) measured in liquid biopsies could be good candidate biomarkers to improve risk prediction. Here, we hypothesized that miRNAs could predict atherosclerotic plaque progression and clinical event presentation in familial hypercholesterolemia (FH) patients.
Circulating miRNAs (plasma, exosomes, microvesicles) were investigated by TaqMan Array and RT-qPCR assays. Patients with genetic diagnosis of FH and healthy relatives from the SAFEHEART cohort were included. A differential signature of 10 miRNA was obtained by comparing two extreme phenotypes consisting of FH-patients suffering a cardiovascular event (CVE) within a 8-year follow-up period (FH-CVE, N=42) and non-FH hypercholesterolemic relatives from the same cohort, matched for age and treatment, without CVE during the same period (nFH-nCVE, N=30). The validation studies included two independent groups of patients with FH-background (Discovery-Group, N=89, Validation-Group N=196), developing a future CVE (FH-CVE) or not (FH-nCVE) within the same time period of follow-up. Of the 10 miRNAs initially selected, miR-133a was significantly higher in FH-CVE than in FH-nCVE patients. ROC-analysis confirmed miR-133a as the best microRNA for predicting CVE in FH-patients (0.76±0.054; P<0.001). Furthermore, Kaplan-Meier and COX-analysis showed that high plasma miR-133a levels associated to the higher risk of presenting a CVE within the next 8 years (HR: 3.89 [95%CI: 1.88-8.07], P<0.001). In silico analysis of curate biological interactions related miR-133a with target genes involved in regulation of the cell-membrane lipid-receptor LRP6 and inflammatory cytokines (CXCL8, IL6, TNF). These predictions were experimentally proven in human macrophages and endothelial cells transfected with agomiR-133a.
Elevated levels of miR-133a in the circulation anticipate those FH-patients that are going to present a clinical CVE within the next 2 years (average). Mechanistically, miR-133a is directly related with lipid- and inflammatory-signalling in key cells for atherosclerosis progression.
The present study in patients with familial hypercholesterolemia shows that epigenetic markers can allow the identification of those patients that are going to present an acute clinical event within the next two years (average). There are currently few prognostic biomarkers able to identify subjects at risk of developing major acute cardiovascular events. Here, by using a non-targeted approach of miRNA-discovery, we show for first time that plasma levels of miR-133a have prognostic value to predict incident cardiovascular events in patients with familial hypercholesterolemia treated as per guidelines. Future studies with larger independent cohorts are needed to validate the prognostic value of miR-133a in the general population.

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