Vaccenic Acid in Tissue Lipids and its Positional Distribution in Glycerolipids of Rats Fed a Polyunsaturated Fat Diet

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Abstract
The distribution of vaccenic acid (cis-11-octadecenoic acid) was studied in the tissue lipids of rats, fed a diet supplemented with soybean oil, which contained very little (ca. 1%) vaccenic acid. Maximum proportions of vaccenic acid in the octadecenoic acids were found in the total lipids of heart, followed by those of liver, adipose tissue, and blood serum. In the triacylglycerols of heart, liver, and adipose tissue, vaccenic acid was preferentially esterified in the 1,3-positions, whereas oleic acid was almost equally distributed between the 1,3- and 2-positions. In the triacylglycerols of serum, vaccenic acid was preferentially esterified in the 2-position. In the phosphatidylcholines of heart, vaccenic acid predominated in the 2-position, whereas in serum it was most commonly found in the 1-position. In both tissues, oleic acid was equally distributed between 1- and 2-positions. In the phosphatidylcholines of liver, vaccenic acid was equally distributed between 1- and 2-positions, whereas oleic acid preferred the 1-position. Unesterified vaccenic and oleic acids in serum were derived mainly from the triacylglycerols of adipose tissue. The lipolytic enzymes did not appear to differentiate between triacylglycerols containing either of these acids. In the cholesteryl esters of liver, oleic acid predominated over vaccenic acid, which confirms the strong specificity of acyl-CoA:cholesterol-O-acyltransferase for oleoyl-CoA. In the cholesteryl esters of serum, the levels of vaccenic and oleic acids were similar to those in the 2-position of phosphatidylcholines of liver, which shows that lecithincholesterol-acyltransferase (LCAT) readily accepts each of these acids as substrate.

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