GLUT2介导肠道T1R2/T1R3调控奶山羊小肠葡萄糖吸收的分子机制

葡萄糖吸收能力不足限制了淀粉在奶山羊小肠的利用效率。申请人前期研究发现增加过瘤胃淀粉可提高奶山羊血液葡萄糖浓度和生产性能，同时回肠黏膜葡萄糖转运载体2（GLUT2）和甜味受体的表达量上调。本项目提出假设：小肠甜味受体的激活可通过下游信号通路影响GLUT2的表达和定位，进而促进小肠葡萄糖吸收，提高淀粉在奶山羊小肠的利用效率。本项目拟在明确甜味受体和GLUT2在奶山羊小肠不同部位的表达及定位规律后，通过构建GLUT2持续定位于小肠上皮细胞顶膜的稳定超表达细胞，探明GLUT2在奶山羊小肠葡萄糖吸收中的作用；利用基因超表达、RNA干扰、抑制剂、激活剂等分子生物学技术，明确奶山羊小肠甜味受体调控GLUT2表达和定位的分子机制及其对葡萄糖吸收的影响；进而通过在体试验进行机理验证，最终揭示GLUT2在奶山羊小肠葡萄糖吸收中的作用及其调控机制，为改善奶山羊能量利用效率的营养调控措施提供理论依据。

The utilization efficiency of starch in small intestine of dairy goats is limited by the low capacity to uptake glucose from the lumen of small intestine to epithelial cell. Our previous studies showed that increasing postruminal starch increased the blood glucose concentration and growth performance of dairy goats with the increased glucose transporter 2 (GLUT2) and sweet receptor expression in ileal mucosa. Therefore, we hypothesize that activation of sweet receptor will improve the expression and localization of GLUT2, thereby enhance glucose absorption and starch utilization in dairy goats. Based on the expression patterns and localization of sweet receptor and GLUT2 in small intestine of dairy goats, the present project will clarify the role of GLUT2 in small intestinal glucose absorption of dairy goats by the establishment of GLUT2 overexpression cells that the GLUT2 is constantly localized in the apical membrane of intestinal epithelial cells. Then with overexpression, RNA interference, inhibitor, and activator techniques, this study will explore the molecular mechanism of GLUT2 expression and localization by sweet receptor and its effect on glucose absorption. Finally, this project will reveal and validate in vivo the role of GLUT2 in small intestinal glucose absorption of dairy goats and its regulatory mechanism. The implementation of this project will provide a sound theoretical basis for the nutritional regulation strategy of energy utilization efficiency in dairy goats.