kolesteroltransport

Kolesteroltransport refers to the physiological processes that distribute cholesterol and related lipids throughout the body. In humans, cholesterol circulates mainly in the blood bound to lipoproteins, particles that transport lipids and apolipoproteins that act as receptor ligands and enzyme cofactors.

Dietary cholesterol and fats are absorbed by enterocytes and packaged into chylomicrons, which enter the circulation. Lipoprotein lipase hydrolyzes triglycerides in chylomicrons, producing remnants cleared by the liver via apoE receptors. The liver also secretes very low density lipoprotein (VLDL); as triglycerides are removed, VLDL becomes IDL and then LDL, delivering cholesterol to cells via LDL receptors.

LDL particles carry cholesterol to peripheral tissues; uptake by LDL receptors provides cholesterol for membranes and steroid synthesis, or storage after esterification. HDL mediates reverse cholesterol transport: ApoA-I initiates cholesterol efflux via ABCA1, HDL forms and matures with LCAT, and SR-BI mediates hepatic uptake of cholesteryl esters.

Intracellular cholesterol trafficking involves NPC1 and NPC2 moving cholesterol from lysosomes to other organelles. Defects cause disorders such as Niemann-Pick type C. Clinically, high LDL and low HDL associate with atherosclerosis. Therapeutic strategies target synthesis, intestinal absorption, or receptor activity, including statins, ezetimibe, and PCSK9 inhibitors.