High-density lipoprotein (HDL) (HDL)

High-density lipoprotein (HDL) particles, often called "good cholesterol," are small, dense lipoproteins (5-17 nm diameter) primarily composed of apolipoproteins (mainly apoA-I and apoA-II), phospholipids, free cholesterol, cholesteryl esters, and triglycerides, forming either discoidal or spherical structures. They originate as lipid-poor apoA-I discs via interaction with ABCA1 transporters on cells, maturing through LCAT esterification of cholesterol into spherical particles that facilitate reverse cholesterol transport (RCT) by effluxing cholesterol from peripheral tissues (via ABCA1/ABCG1) and delivering it to the liver for excretion. Beyond RCT, HDL exerts pleiotropic protective effects, including anti-oxidant, anti-inflammatory, and endothelial-protective functions, reducing atherosclerosis by removing lipids from artery walls and modulating immune responses. In disease, low HDL levels or dysfunctional HDL (e.g., in inflammation) strongly correlate with cardiovascular disease (CVD) risk, though pharmacologically raising HDL cholesterol has not proven cardioprotective in trials. HDL is dynamically remodeled by enzymes (e.g., LCAT, lipases) and transfer proteins (e.g., CETP, PLTP), existing as diverse subspecies differing in size, density, and cargo like microRNAs, which influence their functionality. Therapeutic efforts target HDL-raising (e.g., CETP inhibitors, apoA-I infusions) to enhance RCT, but challenges persist due to HDL's heterogeneity and context-dependent roles in CVD.

Other names

good cholesterolalpha-migrating HDL

Inhibition of cholesteryl ester transfer protein (CETP) to raise HDL levels and enhance reverse cholesterol transport. Promotion of cholesterol efflux via ABCA1 and ABCG1 transporters. Stabilization of HDL particle structure to improve anti-atherogenic functions.