Peripheral tissues take up more cholesterol from VLDL than they require, and export the surplus onto HDL for return to the liver for catabolism. HDL are secreted from the liver as a lipid-poor protein, and take up cholesterol from tissues by the action of lecithin—cholesterol acyltransferase at the lipoprotein surface.
Much of the cholesterol in HDL is transferred to chylomicron remnants and LDL, for receptor-mediated uptake into the liver. However, cholesterol-rich HDL can also bind to a liver receptor that has esterase activity, permitting uptake of cholesterol into the liver. The apoprotein is not internalized, as occurs with chylomicron remnants and LDL, but is released back into the circulation when most of the lipid has been removed.
Was this article helpful?