The Modulation Of Nitrogen Nutrient To Intestinal Nutrition Absorption And Mucosal Barrier Function

Sustainable development of the pig industry related to national economy,but the shortage of protein resources and nitrogen pollution are constraints to sustainable development of China’s pig industry.Pig production in our country,facing the problem that blind pursuit of growth rate and reference NRC standard of the US using a high level of dietary protein in our country causes the protein waste and environmental pollution.And because of the lack of quality protein raw material we had to use low-quality protein material and increasing the protein level to meet the needs of essential amino acids in pigs,resulting in waste of protein.Therefore,reducing nitrogen within reasonable limits is an important measure to ensure the healthy development of pig.This study main research that effect of appropriate to reduce dietary crude protein on pig’s intestinal development and function of nutrient absorption.Meanwhile test that effect of arginine on the intestinal epithelial cells function of barrier and nutrition uptake.Provide a theoretical basis for reducing feed nitrogen nutrients,provide a reference for the pig diet formulation process.We conducted the following studies:1)Nitrogen nutrients are important for the growth of pigs,as well as intestinal structure and mucosal barrier function.To evaluate the effects of dietary crude protein(CP)levels on the intestinal structure and nutrient absorption,two different CP levels(Low CP,Normal CP)were tested in pigs from 45 d to 160 d.The results demonstrated that reduction of CP level in suitable range would not influence the structure of intestinal villi(villus height and crypt depth)and the number of goblet cells(P>0.05),and would maintain the muc2 and E-cadherin mRNA expression levels in jejunum(P>0.05).We also found that reducing CP level would not affect the CAT-1 and ASCT1 expression in 45 to 160 days old pigs(P>0.05).Furthermore,the EAAT3,SGLT1 and GLUT2 mRNA expression levels in the jejunum could be increased significantly at certain age during the raising period(P<0.05,P<0.01).This study implied that the low LP we used was sufficient to maintain the intestinal mucosal structure and mucosal barrier function,andguarantee nutritional absorption,which would provide the basis for reducing nitrogen usage and emission for pig industry.2)The present study was conducted to investigate the extracellular concentrations of L-Arg regulating the barrier and nutrition uptake in IPEC-J2.The cells were cultured in Arg-free Dulbecco’s modified Eagle’s-F12 Ham medium containing 0.2 or 0.7 mM L-Arg.Our results showed that L-Arg enhanced IPEC-J2 growth with a maximal response at 0.2 mM.Addition of 0.2 or 0.7 mM L-Arg increased TEER,which was associated with greater expression of claudin-1 and mucl,in comparison with Arg-free group(P<0.05,P<0.01).Increasing extracellular concentrations of L-Arg from Arg-free to 0.7 mM dose dependently increased the expression levels of SGLT1 and GLUT2(P<0.05,P<0.01),while no remarkable effect on the uptake of glucose in the apical sides of the cell layer was found(P>0.05).Furthermore,supplementation of 0.2 mM L-Arg upregulated the expression of Slc7A1,Slc1A1 and Slc1A4 mRNA,and the uptake of other amino acids(e.g.Lys,His,Arg,Val,etc.)in 0.2 mM L-Arg group were higher than those in Arg-free and 0.7 mM L-Arg group(P<0.05,P<0.01).Collectively,we conclude that the L-Arg played a role in IPEC-J2’s barrier and uptake function,and 0.2 mM L-Arg was more suitable for the growth and development of IPEC-J2 than 0.7 mM L-Arg(commercial medium concentration).3)CAT1 as an important basic amino acid transporter,is the most important transport protein of y+ system.Previous studies have shown that the cationic amino acid transporters CAT1 and CAT3 mediate NMD A receptor activation-dependent changes in elaboration of neuronal processes via the mammalian target of rapamycin mTOR pathway.Experiment 3 was conducted in order to further study the role of the basic amino acid transporter CAT1 playing in intestinal epithelial cells and the mechanism of it in regulating intracellular signal transduction.We constructed CAT1-GFP fusion gene lentivirus expression vector to study how CAT1 participated in intracellular signal-regulated by overexpressing or interfering CAT1 in IPEC-J2.This study found that IPEC-J2 overexpressed or interfered CAT1 could cause expressing of epidermal growth factor receptor(EGFR)changed accordingly.However,the specific mechanism still needs further studies.