Emerging role of circANRIL expression in peripheral blood mononuclear cells as a promising liquid biopsy diagnostic biomarker for coronary artery disease

Background: Long-non-coding RNAs (lncRNAs) are increasingly recognized to play major roles in coronary artery disease (CAD). ANRIL, a well-known lncRNA is located on the 9p21.3 locus which is the first reported CAD risk locus. This study aimed to evaluate the association of ANRIL and its transcript variants expressions with susceptibility to CAD as well as to investigate the impact of 9p21.3 locus single nucleotid polymorphisms (SNPs) on their expressions in adipose tissues and peripheral blood mononuclear cells (PBMCs) of Tanzanian study cohort. Methods: : Expressions of ANRIL, and its variants; circANRIL (hsa_circ_0008574), NR003529, EU741058 and DQ485454 were detected by qRT-PCR in visceral adipose tissues (VAT) (epicardial adipose tissue (EAT) and mediastinal adipose tissue(MAT)), subcutaneous adipose tissue (SAT) and PBMCs of patients undergoing coronary artery bypass grafting due to CAD and non-CAD patients undergoing heart valve surgery. Five SNPs encompassing the 9p21.3 risk locus were genotyped in a cohort of 200 CAD patients an 220 non-CAD patients using qRT-PCR and their impact on gene expressions were further evaluated. Results: : ANRIL expression was significantly up-regulated, while the expression of circANRIL significantly down-regulated in CAD patients compared to non-CAD patients. Also, increased circANRIL expression was determined to be significantly inversely associated with the severity of CAD. Moreover, rs10757278 and rs10811656 polymorphisms were significantly associated with expressions of ANRIL, EU741058, NR003529 and circANRIL in VAT and PBMCs. Decreased circANRIL levels were correlated with aggressive clinical characteristics. Moreover, the random forest model was evaluated to feature importance of CAD prediction. Accordingly, the receiver operating characteristics(ROC) curve analysis was evaluated and the result suggested that circANRIL has high diagnostic accuracy. The area under the ROC curve (AUC) was 0.9808, the optimal cut‐off value was 0.33, with a sensitivity of 1.0 and a specificity of 0.88. Conclusion: We report the first data demonstating the presence of, ANRIL and its transcript variants expressions in adipose tissues and PBMCs of CAD patients and the strong association between ANRIL expression and CAD. circANRIL having a synergetic effect with ANRIL plays a protective role in CAD pathogenesis. Therefore, altered circANRIL expression may become a potential diagnostic biomarker for early CAD diagnosis in Tanzania.