The potential role and mechanism of circRNA/miRNA axis in cholesterol synthesis

Cholesterol levels are an initiating risk factor for atherosclerosis. Many genes play a central role in cholesterol synthesis, including HMGCR, SQLE, HMGCS1, FDFT1, LSS, MVK, PMK, MVD, FDPS, CYP51, TM7SF2, LBR, MSMO1, NSDHL, HSD17B7, DHCR24, EBP, SC5D, DHCR7, IDI1/2. Especially, HMGCR, SQLE, FDFT1, LSS, FDPS, CYP51, and EBP are promising therapeutic targets for drug development due to many drugs have been approved and entered into clinical research by targeting these genes. However, new targets and drugs still need to be discovered. Interestingly, many small nucleic acid drugs and vaccines were approved for the market, including Inclisiran, Patisiran, Inotersen, Givosiran, Lumasiran, Nusinersen, Volanesorsen, Eteplirsen, Golodirsen, Viltolarsen, Casimersen, Elasomeran, Tozinameran. However, these agents are all linear RNA agents. Circular RNAs (circRNAs) may have longer half-lives, higher stability, lower immunogenicity, lower production costs, and higher delivery efficiency than these agents due to their covalently closed structures. CircRNA agents are developed by several companies, including Orna Therapeutics, Laronde, and CirCode, Therorna. Many studies have shown that circRNAs regulate cholesterol synthesis by regulating HMGCR, SQLE, HMGCS1, ACS, YWHAG, PTEN, DHCR24, SREBP-2, and PMK expression. MiRNAs are essential for circRNA-mediated cholesterol biosynthesis. Notable, the phase II trial for inhibiting miR-122 with nucleic acid drugs has been completed. Suppressing HMGCR, SQLE, and miR-122 with circRNA_ABCA1, circ-PRKCH, circEZH2, circRNA-SCAP, and circFOXO3 are the promising therapeutic target for drug development, specifically the circFOXO3. This review focuses on the role and mechanism of the circRNA/miRNA axis in cholesterol synthesis in the hope of providing knowledge to identify new targets.