出版社：American Society for Biochemistry and Molecular Biology
摘要：Conjugated linoleic acids (CLA) are a class of positional, geometric, conjugated dienoic isomers of linoleic acid (LA). Dietary CLA supplementation results in a dramatic decrease in body fat mass in mice, but also causes considerable liver steatosis. However, little is known of the molecular mechanisms leading to hepatomegaly. Although c9,t11 - and t10,c12 -CLA isomers are found in similar proportions in commercial preparations, the respective roles of these two molecules in liver enlargement has not been studied. We show here that mice fed a diet enriched in t10,c12 -CLA (0.4% w/w) for 4 weeks developed lipoatrophy, hyperinsulinemia, and fatty liver, whereas diets enriched in c9,t11 -CLA and LA had no significant effect. In the liver, dietary t10,c12 -CLA triggered the ectopic production of peroxisome proliferator-activated receptor γ (PPARγ), adipocyte lipid-binding protein and fatty acid transporter mRNAs and induced expression of the sterol responsive element-binding protein-1a and fatty acid synthase genes. In vitro transactivation assays demonstrated that t10,c12 - and c9,t11 -CLA were equally efficient at activating PPARα, β/δ, and γ and inhibiting liver-X-receptor. Thus, the specific effect of t10,c12 -CLA is unlikely to result from direct interaction with these nuclear receptors. Instead, t10,c12 -CLA-induced hyperinsulinemia may trigger liver steatosis, by inducing both fatty acid uptake and lipogenesis.
