Submitted to: Lipids Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/12/2004
Publication Date: 2/20/2004
Citation: Kelley, D.S., Bartolini, G.L., Warren, J.M., Simon, V.A., Mackey, B.E., Erickson, K.L. 2004. Contrasting effects of 110, c-12-, and c9, t11-conjugated linoleic acid isomers on fatty acid profiles of mouse liver lipids. Lipids. 39:135-141. Interpretive Summary: Conjugated linoleic acid or CLA refers to different forms of linoleic acid (the n-6 fatty acid found in vegetable oils) where the double bonds have shifted. More than a dozen isomers of CLA are known. Feeding a mixture of these isomers to humans and animal models affected several health parameters, including body composition and immune functions. It is not known which of the purified isomers of CLA alters liver lipids and their fatty acid composition. We examined the effects of feeding two purified isomers of CLA (c9, t11 and t10, c12) on the concentration of liver lipids and their fatty acid composition in mice. c9, t11 isomer did not alter the weight of total lipids and various lipid fractions, but it did alter the fatty acid composition of the lipids. t10, c12-CLA caused a four fold increase in the liver total lipids, which was largely due to the increase in triglycerides, although the cholesterol content was also increased; it also altered the fatty acid profile of the lipids. Effects of the two isomers on fatty acid composition of the lipids differed; c9, t11-CLA increased the concentration of linoleic acid, while t10, c12-CLA decreased it. Thus, the two isomers differ not only in their effects on the weights of total liver lipids and lipid fractions, but also on the fatty acid profile of the lipid fractions. These results emphasize the need to study the health effects of individual isomers of CLA.
Technical Abstract: The purpose of this study was to examine the effects of two purified isomers of CLA (c9, t11-CLA, and t10, c12-CLA) on the concentrations and fatty acid compositions of hepatic triglycerides, phospholipids, cholesterol esters, and free fatty acids. Eight week old, female mice (n=6/group) were fed either a control diet, or diets supplemented with 0.5% c9, t11-CLA or t10, c12-CLA isomers for eight weeks. Weights of total liver lipids and those of individual lipid fractions did not differ between the control and c9, t11-CLA groups. Livers from animals fed the t10, c12-CLA diet contained 4 times more lipids than in the control group; this was mainly due to an increase in triglyceride fractions (5 fold), but cholesterol (3 fold), cholesterol esters (3 fold) and free fatty acids (2 fold) were also significantly increased. Although c9, t11-CLA did not significantly alter the weights of liver lipids when compared to the control group, it caused significant decreases in the wt% of 18:1n9 and 18:1n7 in the triglyceride fraction, and significant increases in the 18:2n6 in the triglyceride, cholesterol esters and phospholipids fractions. On the other hand, t10, c12-CLA significantly increased the concentration of 18:1n9 and decreased that of 18:2n6 in all lipid fractions. Thus, the two isomers differ not only in their effects on the weights of total liver lipids and lipid fractions, but also on the fatty acid profile of the lipid fractions.