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Differential expression of PEPT1 and PEPT2 mRNA in small intestine of Chinese Dongchuan pigs
A significant part of amino nitrogen in small intestine is absorbed in the form of oligopeptides rather than free amino acids, and the mammalian peptide transporters (PepT1 and PepT2) play a pivotal role in the process of absorbing. However, the distribution of PepT1 and PepT2 mRNA in small intestine of Dongchuan pigs, one high-quality local black pig breed in East China, was poorly studied. Therefore, the objective of this experiment was to investigate the expression of PepT1 and PepT2 mRNA in fattening Dongchuan pig’s small intestine, in order to study the mechanism of oligopeptide transporters and promote nutrition study about Dongchuan pig. Eight fattening Dongchuan pigs (72.55±1.22kg) were sacrificed and duodenum, jejunum, ileum tissue samples were obtained. Real-time PCR was used to measure the differential gene expression of PepT1 and PepT2 mRNA in intestinal segments, and the 2-ΔCt(ΔCt=Ct target gene-Ct housekeeping gene) method was used to calculate relative abundance of target genes with GAPDH as a housekeeping gene. One-way ANOVA showed small intestinal tissue specificity had significant effect on expression levels of both PepT1 mRNA (P<0.01) and PepT2 mRNA (P<0.05). The results showed that expression levels of PepT1 mRNA in jejunum (P<0.01) and ileum (P<0.05) were dramatically higher than that in duodenum. The expression trend of PepT1 mRNA was jejunum (1.18×10-2) > ileum (8.02×10-3) > duodenum (2.29×10-3). Meanwhile, expression level of PepT2 mRNA in duodenum was significantly higher than that in ileum (P<0.01). The expression trend of PepT2 mRNA was duodenum (1.54×10-3) > jejunum (9.06×10-4) > ileum (2.32×10-4). Further, mean expression level of PepT1 mRNA (7.37×10-3) in small intestine was nearly 7.5-fold change of PepT2 mRNA (9.77×10-4). To summarize, expression of PepT1 mRNA was more pronounced in distal segments of small intestine of Dongchuan pigs while PepT2 mRNA was mainly distributed in proximal intestinal tracts. Our results suggest that PepT1 might be the major intestinal oligopeptide transporter in distal segments of small intestine of Chinese Dongchuan pigs.
Keywords: Dongchuan pig; PepT1; PepT2