ALTERATIONS IN THE HDL SYSTEM AFTER RAPID PLASMA-CHOLESTEROL REDUCTION BY LDL-APHERESIS

Changes in high density lipoprotein (HDL) subfraction structure and composition were analyzed during and after extracorporeal removal of apo B containing lipoproteins in seven familial hypercholesterolemic (FH) patients. After the apheretic procedure, carried out with dextran-sulfate-cellulose columns, the plasma levels of very low density lipoproteins (VLDL), low density lipoproteins (LDL), and HDL decreased by 72%, 50%, and 19%, respectively. The free cholesterol to esterified cholesterol ratio in plasma increased, with a 26% drop in the lecithin: cholesterol acyl transferase (LCAT) activity. In the ensuing 24 hours, VLDL, HDL, and LCAT activity approached the pretreatment levels. During this phase, possibly as a consequence of increased cholesterol esterification and exchange of cholesteryl esters for triglycerides between HDL and VLDL, HDL2a particles were detected in plasma. However, these metabolic changes did not result in clearcut modifications in the HDL2-HDL3 subfraction distribution. These findings clearly demonstrate that rapid changes in the plasma VLDL-LDL levels affect several processes involved in the HDL metabolism, but confirm that the HDL system, in spite of a considerable plasticity, displays a marked stability of the HDL2-HDL3 subfraction distribution.