340 Dietary conjugated linoleic acid modify gene expression in liver, muscles, and fat tissues of finishing pigs 1 N. Tous,* P. K. Theil,† 2 C. Lauridsen,† R. Lizardo,* B. Vilà,* and E. Esteve-Garcia* *Monogastric Nutrition, IRTA, Ctra. Reus-El Morell Km 4.5, E-43120 Constantí, Spain †Department of Animal Science, Faculty of Science and Technology, Aarhus University, Blichers Alle 20, DK-8830 Tjele, Denmark 1 This project was supported by MICINN (Ministerio de Ciencia e Innovación) in the project number AGL2007-65898-C02-02. Appreciation is expressed to INIA for the grant and Molimen (Spain) for supplying CLA source. 2 Corresponding author: peter.theil@agrsci.dk ABSTRACT: The aim of this study was to investigate underlying mechanisms of dietary conjugated linoleic acid (CLA) on lipid metabolism in various tissues of pigs. Sixteen gilts (73 ± 3 kg) were fed a control (containing sunflower oil) or an experimental diet in which 4% of sunflower oil was replaced by CLA, and slaughtered at an average BW of 117 ± 4.9 kg. Transcription of peroxisome proliferator-activated receptor alpha (PPARα), peroxisome proliferator- activated receptor gamma (PPARγ), fatty acid synthase (FAS), sterol regulatory element binding protein (SREBP1), acetyl-CoA carboxylase (ACC), lipoprotein lipase (LPL), delta-6-desaturase (D6D), and stearoyl CoA desaturase (SCD) were determined by real-time PCR in longissimus thoracis (LT) and semimembranosus (SM) muscles, LT subcutaneous and SM intermuscular fat, and in the liver. Fatty acid (FA) composition was analyzed using gas chromatography in these tissues, except for SM intermuscular fat. Dietary CLA increased PPARγ in LT muscle (P < 0.05), whereas CLA reduced PPARα transcription in all tissues studied (P < 0.05) with the exception of intermuscular fat. Transcription of genes related to FA synthesis was reduced by CLA in SM muscle and liver (SREBP1, both P < 0.1; ACC, P < 0.01 in SM; and FAS, P < 0.01 in liver), whereas CLA reduced (P < 0.05) LPL and D6D transcriptions in SM muscle and reduced (P < 0.05) SCD in liver but increased (P < 0.05) SCD in LT muscle and intermuscular fat. Saturated FA were increased in all studied tissues (P < 0.01), while monosaturated and polyunsaturated FA were reduced in a tissue-specific way by CLA. It was concluded that dietary CLA affected transcription of genes and fat metabolism in a tissue-specific manner. Key words: conjugated linoleic acid, intramuscular fat, lipid metabolism © 2012 American Society of Animal Science. All rights reserved. J. Anim. Sci. 2012.90:340–342 doi:10.2527/jas53768 INTRODUCTION Genetic selection has resulted in leaner pig carcasses, and more knowledge is needed to improve the eating quality of pork meat, which is associated with levels of intramuscular fat (IMF). Addition of conjugated linoleic acid (CLA) in feed is a potential way to increase IMF of pork meat while concomitantly reducing the subcutaneous fat (Morel et al., 2008). In a previous study, a reduction of whole body fatness without modification of IMF was observed by inclusion of CLA in pig diets and may potentially be caused by altered gene expression. The hypothesis of the present study was that dietary CLA affects transcription of genes related to lipid metabolism, and thereby influence fat metabolism and fat deposition within the carcass. At slaughter, fatty acid (FA) composition and transcription of selected genes was quantified as potential markers for lipid oxidation [peroxisome proliferator-activated receptor alpha (PPARα)], de novo fat synthesis [sterol regulatory element binding protein (SREBP1), fatty acid synthase (FAS), acetyl-CoA carboxylase (ACC)], FA uptake [lipoprotein lipase (LPL)], cell differentiation [peroxisome proliferator-activated receptor gamma (PPARγ)], and conversion of FA [delta-6-desaturase (D6D) and steroyl-CoA-desaturase (SCD)] in 2 different types of muscle [longissimus thoracis (LT) and semimembranosus (SM)], 2 different types of fat (LT subcutaneous and SM intermuscular fat), and liver. Published January 23, 2015