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

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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.