Contributions of intestinal hydrolase and nutrient transporter expression to the postnatal growth in pigs

猪的全身氮（N）利用率在哺乳期约为80%，然后在断奶过渡期下降到60%，在生长-肥育期变低（40-50%）。然而，在组织、器官、细胞和分子水平上，与出生后全身氮利用效率降低相关的生物学机制和因素还不是很清楚。小肠是一个代谢活跃的组织，饮食和动脉来源的氨基酸（AA）被肠道广泛利用，用于管腔中的微生物增殖和宿主粘膜代谢，包括代谢内源性N损失。小肠顶端水解酶和营养物质转运蛋白在宿主末端营养物质的消化吸收、保护性解毒以及能量营养物质如糖和AA在腔微生物和宿主之间的分配中起着重要作用。小肠基底外侧膜能量营养转运蛋白是在肠道和外周组织如骨骼肌之间分配能量营养物质的重要途径。 我的长期目标是了解机制，并确定与出生后小肠水解酶和营养转运蛋白表达的变化相关的因素，这些变化导致猪全身氮利用效率下降。我在未来五年的具体目标是调查出生后的变化，i）主要的顶端膜水解酶基因在小肠中的表达; ii）顶端膜己糖和AA转运蛋白基因在小肠中的表达;和iii）基底外侧己糖和AA转运蛋白基因在猪小肠中的表达。 一个集成的全身，细胞和分子研究工具将被用来研究目标基因的表达，并说明如何出生后编程和饮食类型的变化是负责整体增强肠道利用AA和降低效率的全身N利用。拟议的研究将提高我们在胃肠道生理学方面的知识，并导致营养和生物技术策略，以改善新生儿的生长和猪饲养中氮的利用效率。

Efficiency of whole body nitrogen (N) utilization is high at about 80% during the suckling, then drops to 60% during the weanling transition and becomes low during the growing-finishing phases (40-50%) in pigs. However, biological mechanisms and factors associated with the postnatal decreases in whole-body efficiency of N utilization are not very clear at the tissue, organ, cellular and molecular levels. The small intestine is a metabolic active tissue and both dietary and arterial sources of amino acids (AA) are extensively utilized by the intestine for microbial multiplication in the lumen and host mucosal metabolism including the metabolic endogenous N losses. Small intestinal apical hydrolases and nutrient transporters play important roles in the host terminal nutrient digestion and absorption, protective detoxification and partitioning of availability of energy nutrients such as sugars and AA between luminal microbes and the host. The small intestinal basolateral membrane energy nutrient transporters are essential to the partitioning of availability of the energy nutrients between the gut and the peripheral tissues such as skeletal muscle. My long-term goal is to understand mechanisms and identify factors associated with the postnatal changes of the small intestinal hydrolase and nutrient transporter expression being for the declining efficiency of whole-body N utilization in the pig. My specific objectives for the next five years are to investigate postnatal changes in i) the major apical membrane hydrolase gene expression in the small intestine; ii) apical membrane hexose and AA transporter gene expression in the small intestine; and iii) basolateral hexose and AA transporter gene expression in the small intestine of pigs. An integrated whole-body, cellular and molecular research tools will be used to study target gene expression and illustrate how postnatal programming and changes of diet types are responsible for an overall enhanced gut utilization of AA and the reduced efficiency of whole body N utilization. The proposed research will improve our knowledge in gastrointestinal physiology and lead to nutritional and biotechnology strategies for improving neonate growth and efficiency of nitrogen utilization in swine feeding.