Fat Emulsions with Added Free Cholesterol or Fatty Acid Cholesteryl Esters

The fractional elimination rate of fat emulsions of soybean oil, emulsified with egg yolk phosphatides with 1% addition of cholesterol or various cholesteryl fatty acid esters, was studied in rabbits. The fractional removal rate k2%/min was the same after addition of free cholesterol or esters with fatty acids up to eight carbon esters. The k2 values were twice as high for emulsions with cholesteryl-stearate, three times higher with added cholesteryl-palmitate and four times higher when cholesteryl-linoleate was added. The triglyceride (TG) lipase activity was determined with human or rabbit post-heparin plasma and with purified bovine lipoprotein lipase. All these enzyme sources gave similar results. Addition of saturated cholesteryl esters did not affect the lipase activity, but addition of 1% cholesterol markedly decreased the lipase activity. Furthermore, addition of cholesteryl-linoleate and linolenate reduced post-heparin TG lipase activity.