Dietary trans-10,cis-12 conjugated linoleic acid induces hyperinsulinemia and fatty liver in the mouse |
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Authors: | Clément Lionel Poirier Hélène Niot Isabelle Bocher Virginie Guerre-Millo Michèle Krief Stéphane Staels Bart Besnard Philippe |
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Institution: | Physiologie de la Nutrition, Ecole Nationale Supérieure de Biologie Appliquée à la Nutrition et à l'Alimentation (ENSBANA) FRE2328 CNRS-CESG/Université de Bourgogne F-21000, Dijon, France. |
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Abstract: | 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 gamma (PPARgamma), 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 PPARalpha, beta/delta, and gamma 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. |
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