Dietary conjugated linoleic acids promote fatty streak formation in the C57BL/6 mouse atherosclerosis model

Conjugated linoleic acids (CLA) are positional isomers of linoleic acid whi ch have been suggested by some to possess antiatherosclerotic properties. T o test this hypothesis, three groups of twenty C57BL/6 mice were fed on ath erogenic diets containing: 5 g CLA/kg, 2.5 g CLA + 2.5 g linoleic acid/kg o r 5g linoleic acid/kg. All diets were fed for 15 weeks and contained (g/kg) : triacylglycerol 145, free fatty acids 5, cholesterol 10 and cholic acid 5 . At the completion of the experimental period, when data from both groups fed on CLA were combined, dietary CLA did not produce significant differenc es in body weight, serum total cholesterol concentration or serum HDL-chole sterol concentration. However, mice receiving CLA developed a significantly higher serum HDL-cholesterol: total cholesterol ratio and a significantly lower serum triacylglycerol concentration than controls. Despite causing a serum lipoprotein profile considered to be less atherogenic, the addition o f CLA to the atherogenic diet increased the development of aortic fatty str eaks. Considering the increased atherogenesis associated with dietary CLA i n the present study, and the failure to demonstrate a significant beneficia l effect of CLA in other animal studies, there is currently no conclusive e vidence to support the hypothesis that CLA protect against atherogenesis.