Dengler F, Rackwitz R, Benesch F, Pfannkuche H, Gäbel G
Institute of Veterinary Physiology, University of Leipzig, Leipzig, Germany.
J Anim Physiol Anim Nutr (Berl). 2015 Apr;99(2):379-90. doi: 10.1111/jpn.12201. Epub 2014 May 8.
Butyrate modulates the differentiation, proliferation and gene expression profiles of various cell types. Ruminal epithelium is exposed to a high intraluminal concentration and inflow of n-butyrate. We aimed to investigate the influence of n-butyrate on the mRNA expression of proteins involved in the transmembranal transfer of n-butyrate metabolites and short-chain fatty acids in ruminal epithelium. N-butyrate-induced changes were compared with the effects of hypoxia because metabolite accumulation after O2 depletion is at least partly comparable to the accumulation of metabolites after n-butyrate exposure. Furthermore, in various tissues, O2 depletion modulates the expression of transport proteins that are also involved in the extrusion of metabolites derived from n-butyrate breakdown in ruminal epithelium. Sheep ruminal epithelia mounted in Ussing chambers were exposed to 50 mM n-butyrate or incubated under hypoxic conditions for 6 h. Electrophysiological measurements showed hypoxia-induced damage in the epithelia. The mRNA expression levels of monocarboxylate transporters (MCT) 1 and 4, anion exchanger (AE) 2, downregulated in adenoma (DRA), putative anion transporter (PAT) 1 and glucose transporter (GLUT) 1 were assessed by RT-qPCR. We also examined the mRNA expression of nuclear factor (NF) κB, cyclooxygenase (COX) 2, hypoxia-inducible factor (HIF) 1α and acyl-CoA oxidase (ACO) to elucidate the possible signalling pathways involved in the modulation of gene expression. The mRNA expression levels of MCT 1, MCT 4, GLUT 1, HIF 1α and COX 2 were upregulated after both n-butyrate exposure and hypoxia. ACO and PAT 1 were upregulated only after n-butyrate incubation. Upregulation of both MCT isoforms and NFκB after n-butyrate incubation could be detected on protein level as well. Our study suggests key roles for MCT 1 and 4 in the adaptation to an increased intracellular load of metabolites, whereas an involvement of PAT 1 in the transport of n-butyrate also seems possible.
丁酸盐可调节多种细胞类型的分化、增殖及基因表达谱。瘤胃上皮暴露于高腔内浓度及正丁酸流入环境中。我们旨在研究正丁酸对瘤胃上皮中正丁酸代谢产物及短链脂肪酸跨膜转运相关蛋白的mRNA表达的影响。将正丁酸诱导的变化与缺氧的影响进行比较，因为氧气耗尽后代谢产物的积累至少部分与正丁酸暴露后代谢产物的积累相当。此外，在各种组织中，氧气耗尽会调节转运蛋白的表达，这些转运蛋白也参与瘤胃上皮中正丁酸分解产生的代谢产物的排出。安装在尤斯灌流小室中的绵羊瘤胃上皮暴露于50 mM正丁酸或在缺氧条件下孵育6小时。电生理测量显示缺氧诱导上皮损伤。通过RT-qPCR评估单羧酸转运蛋白（MCT）1和4、阴离子交换蛋白（AE）2、腺瘤下调的阴离子转运蛋白（DRA）、推定阴离子转运蛋白（PAT）1和葡萄糖转运蛋白（GLUT）1的mRNA表达水平。我们还检测了核因子（NF）κB、环氧化酶（COX）2、缺氧诱导因子（HIF）1α和酰基辅酶A氧化酶（ACO）的mRNA表达，以阐明参与基因表达调节的可能信号通路。正丁酸暴露和缺氧后，MCT 1、MCT 4、GLUT 1、HIF 1α和COX 2的mRNA表达水平均上调。仅在正丁酸孵育后，ACO和PAT 1上调。在蛋白质水平也可检测到正丁酸孵育后MCT同工型和NFκB的上调。我们的研究表明，MCT 1和4在适应细胞内代谢产物负荷增加中起关键作用，而PAT 1也可能参与正丁酸的转运。
