Fig. 4

The Process of HDL-Mediated Reverse Cholesterol Transport. The liver and intestines synthesize lipid-free ApoA-I, which initially acquires cholesterol and phospholipids from macrophages via ABCA1, forming nascent discoidal HDL. Subsequently, LCAT esterifies the cholesterol, rendering it fully hydrophobic and causing its migration to the core of the discoidal HDL, promoting its maturation into spherical HDL. Meanwhile, membrane proteins such as ABCG1 and SR-BI continue to transfer intracellular cholesterol to HDL, further aiding in HDL maturation. HDL2 and HDL3, the two subclasses of HDL, can interconvert. Next, HDL exchanges cholesteryl esters and triglycerides with VLDL and LDL in equimolar proportions. The final step of reverse cholesterol transport involves the selective uptake of cholesteryl esters from HDL particles by the hepatic SR-BI or the clearance of cholesteryl esters from VLDL and LDL via the LDL receptor (LDLR). (Adapted from “Icon Pack - Lipid”, by BioRender.com (2024). Retrieved from https://app.biorender.com/biorender-templates)