lipoproteina

Lipoproteins are macromolecular complexes composed of lipids and proteins that transport hydrophobic lipids through the aqueous environment of the bloodstream. They are classified by density, with chylomicrons being the least dense and HDL the most dense. Their core mainly contains triglycerides and cholesteryl esters, while the surface is a monolayer of phospholipids and free cholesterol, embedded with apolipoproteins that provide structural stability and receptor recognition.

The major classes include chylomicrons, very-low-density lipoproteins (VLDL), intermediate-density lipoproteins (IDL), low-density lipoproteins (LDL), and high-density lipoproteins (HDL). Chylomicrons form in enterocytes after dietary fat is absorbed and transport triglycerides to tissues; their remnants are cleared by the liver. VLDL is produced by the liver and carries endogenous triglycerides; as it loses triglycerides, it becomes IDL and then LDL, which is rich in cholesterol. HDL is involved in reverse cholesterol transport, picking up excess cholesterol from peripheral tissues and delivering it to the liver for excretion or recycling.

Apolipoproteins serve as key components of lipoproteins: ApoB-100 is essential for LDL and VLDL structure and receptor binding; ApoB-48 is produced in the intestine for chylomicrons; ApoA-I and ApoA-II are major proteins of HDL; ApoE mediates interactions with hepatic receptors for remnant clearance. Lipoprotein metabolism involves enzymes such as lipoprotein lipase, hepatic lipase, and the cholesteryl ester transfer protein (CETP). Clinical relevance includes associations between elevated LDL or reduced HDL and atherosclerotic cardiovascular disease, with lipid panels used for risk assessment and management strategies that include lifestyle changes and pharmacotherapy.