MICROSOMAL TRIACYLGLYCEROL SYNTHESIS AND DIACYLGLYCEROL CONCENTRATION IN THE LIVER OF RATS FED WITH SOYBEAN AND EGG-YOLK PHOSPHOLIPIDS

Diets containing 10% soybean oil, soybean phospholipid and egg yolk phospholipid decreased rat liver microsomal diacylglycerol acyltransferase activity when measured with an endogenous diacylglycerol substrate relative to that in rats fed with a low-fat diet (0.5% soybean oil). Although no significant difference was detected in the enzyme activity among the rats fed with the diets containing 10% lipids, the extent of the decrease was more prominent with two kinds of phospholipids compared to soybean oil. When the enzyme activity was measured with an exogenous dioleoylglycerol substrate dispersed in ethanol, it was also significantly depressed by the diets containing 10% phospholipids and soybean oil, but to a much lesser extent. Dietary phospholipids reduced the microsomal concentration of diacylglycerol to a value less than one-third that in the animals fed with a low-fat diet. Soybean oil also decreased this parameter, but to a lesser extent. In addition, soybean and egg yolk phospholipids compared to soybean oil were more effective in reducing the triacylglycerol concentration in the liver. It seemed that dietary phospholipid compared to soybean oil exerted a more potent triacylglycerol lowering effect by modifying the concentration of microsomal diacylglycerol available for triacylglycerol synthesis in the liver.