Mechanisms of HDL reduction after probucol. Changes in HDL subfractions and increased reverse cholesteryl ester transfer.

Treatment with probucol, a widely used lipid-lowering agent, is associated with a significant reduction of high density lipoprotein (HDL) cholesterol levels, but with an apparently improved removal of cholesteryl esters from tissues (e.g., from tendon xanthomas). The effects of probucol (500 mg twice daily) on HDL subfraction distribution and cholesteryl ester transfer activity were tested in 12 patients with stable type II hyperlipidemia [low density lipoprotein (LDL) cholesterol greater than 180 mg/dl] after a placebo-controlled cross-over trial. Probucol significantly lowered total cholesterol (-13.8%), LDL cholesterol (-9.1%), and HDL cholesterol (-30%). By rate zonal ultracentrifugation, a marked reduction of HDL2 cholesterol (-68%) was shown, whereas changes in HDL3 were less significant (-21%). These findings were confirmed by polyacrylamide gradient gel electrophoresis, typically showing a reduction or disappearance of HDL2b particles and the prevalence of particles in the HDL3a range. Cholesteryl ester transfer from HDL to lower density lipoproteins was significantly increased (30%) in all patients. These findings suggest that, in addition to the well-documented in vitro changes (prevention of LDL peroxidation and macrophage uptake), probucol characteristically modifies HDL particle distribution in vivo, and is associated with a significant increase of cholesteryl ester transfer activity.