ABCA1 and atherosclerosis: miRNA-33 (miR-33) is composed of miR-33a and miR-33b, located in the SREBP2 and SREBP1 gene introns, respectively, and co-expressed under different stimulation conditions.368,369 miR-33 inhibits expression of the genes involved in cholesterol efflux and HDL synthesis, such as ABCA1 and ABCG1. 370 Studies have shown that inhibition of miR-33 induces hepatic ABCA1 expression, thereby increasing plasma HDL-C levels, and the inhibition also promotes RCT in macrophages and regression of atherosclerosis.371,372 In addition, some studies have investigated the role of miR-33 on VLDL/LDL metabolism.