SNAT2介导的猪小肠氨基酸感应机制研究

Amino acids are preferential nutrients for the small intestine and play important roles in intestinal mucosal renewal and barrier function. How to sense the nutritional information of amino acids by small intestine has become a hot topic studied in the field of nutrition. Some amino acid transporters may act as receptors and regulate cellular amino acids contents and therefore modulate cellular downstream signaling of amino acid receptor. We previously showed that some amino acids can regulate the expression levels of SNAT2 and other genes related to amino acids sensing. Therefore, the project is conduct to reveal the mechanisms of amino acids transport mediated by SNAT2 in intestinal mucosa and epithelial cells by Ussing chamber and radioisotopiac trace and analysis the pathway of amino acids chemosensing and study cellular GCN2 and mTOR signaling pathway mediated by SNAT2 in small intestine using PCR Array; and then validate the pathway of amino acids sensing mediated by SNAT2 by study the effects of inhibiting SNAT2 on amino acids nutrient sensing signaling in vivo of pigs. The aim is to elucidate the chemosensory mechanism of amino acids mediated by SNAT2, providing the theory basis for nutritional regulation of intestinal amino acid in pigs, which is significant for improving amino acids utilization and controlling intestinal diseases.

氨基酸是小肠优先利用的重要营养物质，对肠道黏膜更新和屏障功能起着重要作用。小肠如何感应氨基酸营养信息已成为营养研究领域的热点问题。某些氨基酸转运载体能通过转运过程调节细胞内氨基酸浓度，调控细胞内氨基酸受体下游信号，发挥着转运载体和受体的双重功能。我们前期的研究发现，很多氨基酸能调控SNAT2和细胞内氨基酸感应相关基因表达。因此，本项目拟采用Ussing Chamber技术和同位素示踪法，研究猪肠上皮细胞SNAT2介导的氨基酸转运机制；采用PCR Array等技术解析小肠SNAT2介导的氨基酸化学感应途径，研究SNAT2介导的GCN2和mTORC1信号通路；研究体内抑制仔猪SNAT2对肠道氨基酸营养感应信号的影响，验证SNAT2介导的氨基酸营养感应途径。项目旨在阐明SNAT2介导的小肠氨基酸营养感应机制，为仔猪肠道氨基酸营养调控提供理论依据，对提高氨基酸利用率、控制相关疾病具有重要意义。

项目研究了仔猪肠道SNAT2组织分布和发育性变化及其调控机制，发现SNAT2在仔猪小肠各段均有表达，十二指肠中表达量最高。SNAT2 mRNA的哺乳期发育性变化规律在小肠各段并不相同，断奶应激对SNAT2表达有较大影响，其mRNA和蛋白水平均显著降低，为进一步研究肠道中SNAT2介导的氨基酸利用和信号转导机制提供基础。采用PCR Array解析猪肠道SNAT2介导的mTORC1信号通路，发现SNAT2在肠上皮细胞增殖和蛋白合成过程中发挥重要作用，SNAT2抑制后mTOR相关的一些基因的表达受到显著影响，这些基因大部分集中在mTORC1信号通路的上游。发现仔猪哺乳期灌服腐胺和NCG显著提高了空肠和回肠黏膜SNAT2的蛋白表达水平，灌服脯氨酸和NCG显著提高了空肠黏膜氨基酸转运感应相关基因（PAT1、CasR、PLCβ2和T1R3）的 mRNA表达水平，NCG还显著上调了mTOR信号通路相关基因（MAP4K3和PIK3C3）的mRNA水平。项目阐明了SNAT2介导的小肠氨基酸营养感应机制，为仔猪肠道氨基酸营养调控提供理论依据，对提高氨基酸利用率、控制相关疾病具有重要意义。项目第一标注发表SCI收录论文14篇，CSCD收录论文4篇，国际会议报告1个。研究结果作为重要成果获2016年度国家自然科学奖二等奖和2014-2015 年度中华农业科技奖一等奖。项目培养博士研究生2名，硕士研究生2名。项目负责人晋升为研究员，入选第三批中组部万人计划科技领军人才；2名参与人员分别晋升为副研究员和副教授。