Metabolism of trans Acids in the Rat: Influence of the Geometric Isomers of Linoleic Acid on the Structure of Liver Triglycerides and Lecithins

Abstract

Studies were made on the structures of the liver lecithins and triglycerides of essential fatty acid (EFA)-deficient male rats of the Sprague-Dawley strain fed 5% supplements of cis, cis-linoleate, cis-9, trans-12-linoleate or trans-9, trans-12-linoleate or various mixtures of each of these compounds with cis, cis-linoleate or linolenate for 18 to 20 days. Enzymatic hydrolysis of lecithins with phospholipase A and triglycerides with pancreatic lipase showed that the cis, cis and cis-9, trans-12 isomers of linoleic acid were esterified predominately in the secondary positions, and that the trans, trans isomer was esterified predominately in the primary positions in these compounds. The precise positional arrangement of the geometric isomers of linoleic acid, as well as of other fatty acids, in any single molecular species, was influenced not only by the position to which they were directed dominantly but also by the relative degree that the other fatty acids were directed into the same position. The saturated fatty acids were esterified predominately in the primary positions in all molecular species; the trans, trans isomer of linoleic acid was esterified predominately in the primary positions in all molecular species except those containing saturated fatty acids. The cis, cis isomer of linoleic acid was esterified predominately in the β-position in all molecular species, except when it was associated with arachidonic acid which was esterified predominately in the β-position in all molecular species in which it was a constituent. Oleic acid and cis-9, trans-12-linoleic acid were distributed in the β-position with saturated or trans, trans-linoleic acid, and in the α-position with all other polyunsaturated fatty acids.