title: Conjugated linoleic acids influence fatty acid metabolism in ovine ruminal epithelial cells.
abstract: Conjugated linoleic acids (CLA), particularly cis-9,trans-11 (c9t11) and trans-10,cis-12 (t10c12), are used as feed additives to adapt to constantly increasing demands on the performance of lactating cows. Under these feeding conditions, the rumen wall, and the rumen epithelial cells (REC) in particular, are directly exposed to high amounts of CLA. This study determined the effect of CLA on the fatty acid (FA) metabolism of REC and expression of genes known to be modulated by FA. Cultured REC were incubated with c9t11, t10c12, and the structurally similar FA linoleic acid (LA), oleic acid (OA), and trans-vaccenic acid (TVA) for 48 h at a concentration of 100 µM. Cellular FA levels were determined by gas chromatography. Messenger RNA expression levels of stearoyl-CoA desaturase (SCD) and monocarboxylate transporter (MCT) 1 and 4 were quantified by reverse transcription-quantitative PCR. Fatty acid evaluation revealed significant effects of CLA, LA, OA, and TVA on the amount of FA metabolites of β-oxidation and elongation and of metabolites related to desaturation by SCD. The observed changes in FA content point (among others) to the ability of REC to synthesize c9t11 from TVA endogenously. The mRNA expression levels of SCD identified a decrease after CLA, LA, OA, or TVA treatment. In line with the changes in mRNA expression, we found reduced amounts of C16:1n-7 cis-9 and C18:1n-9 cis-9, the main products of SCD. The expression of MCT1 mRNA increased after c9t11 and t10c12 treatment, and CLA c9t11 induced an upregulation of MCT4. Application of peroxisome proliferator-activated receptor (PPAR) α antagonist suggested that activation of PPARα is involved in the changes of MCT1, MCT4, and SCD mRNA expression induced by c9t11. Participation of PPARγ in the changes of MCT1 and SCD mRNA expression was shown by the application of the respective antagonist. The study demonstrates that exposure to CLA affects both FA metabolism and regulatory pathways within REC.
authors.affiliation: Institute of Veterinary Physiology, Faculty of Veterinary Medicine, University of Leipzig, Leipzig, 04103, Germany. Electronic address: franziska.masur@vetmed.uni-leipzig.de.
authors.forename: F
authors.initials: F
authors.lastname: Masur
authors.affiliation: Institute of Veterinary Physiology, Faculty of Veterinary Medicine, University of Leipzig, Leipzig, 04103, Germany.
authors.forename: F
authors.initials: F
authors.lastname: Benesch
authors.affiliation: Institute of Veterinary Physiology, Faculty of Veterinary Medicine, University of Leipzig, Leipzig, 04103, Germany.
authors.forename: H
authors.initials: H
authors.lastname: Pfannkuche
authors.affiliation: Institute of Physiological Chemistry, Faculty of Veterinary Medicine, University of Leipzig, Leipzig, 04103, Germany.
authors.forename: H
authors.initials: H
authors.lastname: Fuhrmann
authors.affiliation: Institute of Veterinary Physiology, Faculty of Veterinary Medicine, University of Leipzig, Leipzig, 04103, Germany.
authors.forename: G
authors.initials: G
authors.lastname: Gäbel
mesh_terms: D000818:Animals; D002478:Cells, Cultured; D004847:Epithelial Cells / Q000187:drug effects / Q000378:metabolism; D005227:Fatty Acids / Q000378:metabolism*; D005260:Female; D007774:Lactation / Q000187:drug effects; D044243:Linoleic Acids, Conjugated / Q000494:pharmacology*; D027501:Monocarboxylic Acid Transporters / Q000235:genetics; D009829:Oleic Acids; D047493:PPAR alpha / Q000502:physiology; D047495:PPAR gamma / Q000502:physiology; D012333:RNA, Messenger / Q000032:analysis / Q000378:metabolism; D012417:Rumen / Q000378:metabolism*; D012756:Sheep / Q000378:metabolism*; D013230:Stearoyl-CoA Desaturase / Q000235:genetics
chemical_list: D005227:Fatty Acids; D044243:Linoleic Acids, Conjugated; D027501:Monocarboxylic Acid Transporters; D009829:Oleic Acids; D047493:PPAR alpha; D047495:PPAR gamma; D012333:RNA, Messenger; D013230:Stearoyl-CoA Desaturase; C050413:11-octadecenoic acid
keywords: conjugated linoleic acid; monocarboxylate transporter; peroxisome proliferator-activated receptor; rumen epithelium; stearoyl-CoA desaturase