Fig. 1.

Elevated miR-33a represses the expression of ABCA1, leading to decreased HDL formation. Under normal circumstances, ABCA1 moves cholesterol and phospholipids from the inner to the outer leaflet of the macrophage membrane, thereby facilitating HDL formation. During the progression of atherosclerosis, aberrantly elevated miR-33a represses ABCA1 expression. Under conditions of decreased expression of ABCA1, the cholesterol efflux cannot function properly, resulting in decreased HDL formation. miR-33a might be secreted into plasma or transported to the liver via microvesicles, Ago2 or HDL