Abstract
High-cholesterol diet induced fatty liver in rats (SHR). Cholesterol ester and triacylglycerol accumulated in large amounts in liver, but the increases of these lipids in plasma were relatively small, suggesting that the step before the secretion of lipids from liver is limited under these conditions. Plasma cholesterol ester consisted of mainly arachidonate species in rats fed normal diet but oleate and linoleate esters increased significantly by feeding high-cholesterol diet. At the 2-position of phosphatidylcholine in plasma and liver, oleate and linoleate increased slightly by feeding high-cholesterol diet. The enzymatic bases for inducing such changes were examined. Microsomal glycerophosphate acyltransferase in liver increased 2 to 3-fold to meet the increased supply of oleate, the synthesis of which was stimulated by 10-fold increase in microsomal Δ9-desaturase activity. Endogenous cholesterol in microsomes increased 2-fold and the acyl-CoA: cholesterol acyltransferase activity also increased 3-fold whereas plasma lecithin: cholesterol acyltransferase activity was unchanged. Thus, the increase in cholesterol oleate was due mainly to the increases in acyl-CoA: cholesterol acyltransferase and Δ9-desaturase activities in liver.
