Section of Digestive Diseases, West Virginia Clinical and Translational Science Institute, West Virginia University Health Sciences Center, One Medical Center Drive, PO Box 9161, Morgantown, WV 26506, USA.
Dig Dis Sci. 2013 Mar;58(3):660-7. doi: 10.1007/s10620-012-2407-x. Epub 2013 Jan 24.
Short chain fatty acids (SCFA) are absorbed by carrier mediated uptake in the small intestine by pH-dependent SCFA/HCO3 (-) exchangers on the apical membrane of epithelial cells. Conventional assumption is that MCT1 mediates SCFA/HCO3 (-) exchange in the intestine. Further, due to the presence of multiple such anion exchangers, the identity of the intestinal SCFA/HCO3 (-) has been controversial.
The aim of this study was to determine the identities of the butyrate transporter in the intestinal epithelial cells (IEC-18).
IEC-18 cells were treated with specific siRNAs for MCT1 and MCT4, and butyrate and lactate uptake studies were performed.
Alpha-cyano-4-hydroxycinnamic acid inhibited lactate uptake but not butyrate uptake in IEC-18 cells, indicating that these two substrates are transported via two different transporter systems. MCT1 siRNA treatment abolished both MCT1 mRNA by more than 95 % and protein expression by 83 % as evidenced by RTQ-PCR and western blotting experiments. However, MCT1 siRNA treatment inhibited butyrate uptake upto 24 %, whereas it inhibited lactate uptake significantly by 70 %. Treatment with MCT4 siRNA inhibited MCT4 mRNA expression by 75 % and protein expression by 85 % in these cells. MCT4 siRNA inhibited butyrate uptake by 40 %. Further, several non-steroidal anti-inflammatory drugs (NSAIDs) are transported by the butyrate transporter. Finally, MCT4 siRNA inhibited salicylate uptake by 27 % indicating direct evidence for the transport of salicylate by MCT4.
These data indicate that MCT1 is the high affinity lactate transporter and MCT4 is the high affinity butyrate transporter in the intestinal epithelial cell line IEC-18.
短链脂肪酸 (SCFA) 通过上皮细胞顶膜上的 pH 依赖性 SCFA/HCO3 (-) 交换器，经载体介导摄取被小肠吸收。传统假设是 MCT1 介导肠道中的 SCFA/HCO3 (-) 交换。此外，由于存在多种阴离子交换器，肠道 SCFA/HCO3 (-) 的身份一直存在争议。
本研究旨在确定肠上皮细胞 (IEC-18) 中丁酸盐转运体的身份。
用 MCT1 和 MCT4 的特异性 siRNA 处理 IEC-18 细胞，并进行丁酸盐和乳酸盐摄取研究。
α-氰基-4-羟基肉桂酸抑制 IEC-18 细胞中的乳酸盐摄取，但不抑制丁酸盐摄取，表明这两种底物通过两种不同的转运体系统运输。MCT1 siRNA 处理使 MCT1 mRNA 减少 95%以上，蛋白表达减少 83%，这一点通过 RTQ-PCR 和 Western blot 实验得到证实。然而，MCT1 siRNA 处理仅抑制丁酸盐摄取 24%，而显著抑制乳酸盐摄取 70%。在这些细胞中，用 MCT4 siRNA 处理抑制 MCT4 mRNA 表达 75%，蛋白表达 85%。MCT4 siRNA 抑制丁酸盐摄取 40%。此外，几种非甾体抗炎药 (NSAIDs) 由丁酸盐转运体转运。最后，MCT4 siRNA 抑制水杨酸摄取 27%，表明水杨酸由 MCT4 直接转运的直接证据。
这些数据表明，MCT1 是肠上皮细胞系 IEC-18 中的高亲和力乳酸盐转运体，而 MCT4 是高亲和力丁酸盐转运体。
