[Role of cholesterol esters in triglyceride transport]

Biosynthesis of cholesterol esters in the blood flow and their function are determined by the fact that these compounds are the sole endogenously synthesized molecules whose hydrophobicity is higher than that of triglycerides transferred by the blood. Within the structure of intermediate density lipoproteins, cholesterol esters substitute for triglycerides during association of apoprotein B-100 with the C-terminal lipid-binding domain. Substitution of the liquid-crystalline phase of triglycerides for the corresponding phase of cholesterol esters results in a significant alteration of the apoprotein B-100 conformation and the formation of low density lipoproteins. Within the structure of low density lipoproteins, the N-terminal domain (apoprotein B-100 ligand) acquires an active conformation and an ability to interact with cell membrane receptors, thereby facilitating their absorption of low density lipoproteins. Cholesterol synthesis in the blood is an independent step in triglyceride transport. Inhibition of cholesterol ester synthesis into high density lipoproteins and their conversion into intermediate density lipoproteins is unaccompanied by the acquisition by apoprotein B-100 of a final conformation or by the formation of low density lipoproteins. Remnants of intermediate density lipoproteins having an intermediate conformation of apoprotein B-100 and the inactive position of the domain ligand are accumulated in the blood. This results in the development of IIb type hyperlipoproteinemia. Resumption of conversion of cholesterol esters from high density lipoproteins into intermediate density lipoprotein remnants normalizes the triglyceride transport. The final conformation of apoprotein B-100 can be modelled by substituting triglycerides in intermediate density lipoprotein remnants for another substance whose hydrophobicity is similar to that of cholesterol esters (dolichol, probucol).(ABSTRACT TRUNCATED AT 250 WORDS)