Correlation of the Plasma Cholesterol-lowering Effect of Dietary Glycine with the Alteration of Hepatic Phospholipid Composition in Rats

Abstract

The plasma cholesterol-lowering effect of dietary glycine was investigated in relation to its influence on the free amino acid profiles in the liver and plasma and on the composition of phospholipids in liver microsomes of rats fed on a cholesterol-free diet. The plasma total and HDL cholesterol levels were significantly decreased by dietary supplementation with glycine and ethanolamine, but not with serine and threonine. The hepatic free ethanolamine concentration was enhanced by dietary supplementation with glycine as well as with ethanolamine, and there existed a significant Correlation between the hepatic free ethanolamine concentration and plasma total or HDL cholesterol level. Dietary supplementation with glycine significantly increased the content and proportion of phosphatidylethanolamine in liver microsomes and inversely decreased the proportion of phosphatidylcholine. The phospholipid composition of liver microsomes changed prior to the plasma total cholesterol level in response to glycine supplementation, suggesting that the alteration of phospholipid composition was not the result of an alteration of the plasma cholesterol level. From these results, it is suggested that the plasma cholesterol-lowering effect of dietary glycine might be associated with the alteration of microsomal phospholipid composition.