CONJUGATED LINOLEIC-ACID MODULATES HEPATIC LIPID-COMPOSITION IN MICE

Conjugated linoleic acid (CLA) is a chemoprotective fatty acid that in hibits mammary, colon, forestomach, and skin carcinogenesis in experim ental animals. We hypothesize that the ubiquitous chemoprotective acti ons of dietary CLA in extrahepatic tissues are dependent upon its role in modulating fatty acid composition and metabolism in liver, the maj or organ for lipid metabolism. This study begins to evaluate the role of CLA in lipid metabolism by determining the modulation of fatty acid composition by CLA. Female SENCAR mice were fed semipurified diets co ntaining 0.0% (Diet A), 0.5% (Diet B), 1.0% (Diet C), or 1.5% (Diet D) CLA (by weight) for six weeks. Mice fed Diets B, C, and D exhibited l ower body weights and elevated amounts of extractable total lipid in l ivers compared with mice fed diets without CLA (Diet A). Analyses of t he fatty acid composition of liver by gas chromatography revealed that dietary CLA was incorporated into neutral and phospholipids at the ex pense of linoleate in Diets B, C, and D; oleate increased and arachido nate decreased in neutral lipids of CLA diet groups. In addition, incr easing dietary CLA was associated with reduced linoleate in hepatic ph ospholipids. In an in vitro assay, CLA was desaturated to an unidentif ied 18:3 product to a similar extent as linoleate conversion to gamma- linolenate (9.88, and 13.63%, respectively). These data suggest that C LA may affect metabolic interconversion of fatty acids in liver that m ay ultimately result in modified fatty acid composition and arachidona te-derived eicosanoid production in extrahepatic tissues. In addition to determining how dietary CLA modulates eicosanoid synthesis, further work is needed to identify enzymatic products that may result from de saturation of CLA.