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.

Transcriptomic Analyses Reveal the Protective Immune Regulation of Conjugated Linoleic Acids in Sheep Ruminal Epithelial Cells

“…Due to the continuous production of CLA during the ruminal microbial biohydrogenation process, ruminal epithelial cells are directly exposed to a certain amount of CLA (Masur et al, 2016), and the positive immunoregulatory effect of CLA on gastrointestinal barrier health has been extensively verified in both animal and human studies (Chen et al, 2019;Coelho et al, 2019). Considering that the rumen immune system must continuously face challenges from antigens of lysed dead microbial cells or LPS from the shedding gram-negative bacteria within the rumen, we hypothesized that CLA may contribute to the immune response of the ruminal epithelium.…”

“…Among the broad range of CLA isomers, cis-9, trans-11 CLA and trans-10, cis-12-CLA have been the most studied bioactive isomers (Bruen et al, 2017), and many healthy characteristics have been associated with the results of interactions between these two major isomers, such as anti-obesogenic, anti-carcinogenic, anti-inflammatory and immune enhancement properties (Kim et al, 2016;Viladomiu et al, 2016;Garibay-Nieto et al, 2017). Previous studies on ruminants found that the addition of cis-9, trans-11 CLA and trans-10, cis-12 CLA can modify the fatty acid profile of sheep's milk and beef (Schiavon et al, 2011;Pellattiero et al, 2015), affect the fatty acid metabolism pathways in ovine ruminal epithelial cells (Masur et al, 2016) and lower the milk fat content and improve the energy balance in dairy cows during early lactation (Qin et al, 2018). Basiricò et al (2017) also found that supplementation of cis-9, trans-11 CLA and trans-10, cis-12 CLA protected bovine mammary epithelial cells against H 2 O 2 -induced oxidative damage.…”