Comparison in inhibitory effects of lipolysis products on cholesterol esterification

The effects of lipolysis products (glycerol, free fatty acids and lysolecithin) on cholesterol esterification in LDL and HDL3 were studied. The effects of oleic acid, linoleic acid and EPA on cholesterol esterification in LDL and HDL3 were also compared. 14C-FC labeled lipoprotein, LCAT source (lipoprotein deficient plasma) and test substance were incubated at 37 degrees C, and cholesterol esterification rates were estimated. In LDL, glycerol and palmitic acid did not inhibit cholesterol esterification. The inhibition rates of cholesterol esterification by lysolecithin were same as those by linoleic acid in LDL and increased to 100% at 2.5 mM depending on the concentrations. The effects of oleic acid, linoleic acid, and EPA were compared. The inhibition rates of cholesterol esterification in LDL were highest by EPA, next by linoleic acid and lowest by oleic acid. In HDL3, glycerol did not inhibit cholesterol esterification. Palmitic acid inhibited cholesterol esterification in HDL3. The inhibition rates of cholesterol esterification by lysolecithin in HDL3 were always lower than those by linoleic acid. The inhibition rates by palmitic acid were almost same as those by lysolecithin in HDL3. The inhibition rates of cholesterol esterification by EPA were higher than those by linoleic acid in HDL3. The inhibition rates of cholesterol esterification by oleic acid were close to those by linoleic acid in HDL3. Polyunsaturated FA suppressed LCAT activities much stronger than saturated FA at physiological concentrations.