Lipoprotein Metabolism
Transport of lipids in blood via chylomicrons, VLDL, LDL, and HDL particles.
Overview
Lipoproteins transport hydrophobic lipids (cholesterol, triglycerides) through the aqueous blood. Dietary lipids are packaged into chylomicrons in the intestine. The liver produces VLDL, which delivers triglycerides to tissues via lipoprotein lipase (LPL) action, becoming IDL then LDL. LDL delivers cholesterol to tissues via LDLR. HDL mediates reverse cholesterol transport — ABCA1 effluxes cholesterol to lipid-poor apoA-I, LCAT esterifies it, and CETP can transfer it to VLDL/LDL. SR-BI on hepatocytes takes up HDL cholesterol.
Cellular Location
Intestine → Liver → Blood → Peripheral tissues
Clinical Significance
LDL cholesterol drives atherosclerosis; statins + PCSK9 inhibitors (evolocumab) dramatically lower LDL; HDL is atheroprotective; familial hypercholesterolemia = LDLR mutations; PCSK9 is a major drug target.
Key Molecules
Key Enzymes
Related Pathways
Cholesterol Biosynthesis (Mevalonate Pathway)
Multi-step synthesis of cholesterol from acetyl-CoA via the mevalonate pathway.
β-Oxidation of Fatty Acids
Sequential removal of 2-carbon units from fatty acids as acetyl-CoA.
Receptor-Mediated Endocytosis
Clathrin-coated pit internalization of receptor-ligand complexes.