Metabolic fate of amino acids in the gut of the postnatal developing pig

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Efficiency of whole-body nitrogen (N) utilization for growth is high during the suckling and becomes low during the weaning transition and growing-finishing phases in pigs. However, 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 intestine is metabolic active and both enteral and arterial sources of amino acids (AA) are extensively utilized by the intestine for microbial catabolism and growth in the lumen, mucosal cellular catabolism and growth and the gastrointestinal metabolic endogenous losses as various nitrogenous compounds. Amino acid transporters are gateways in directing the AA fluxes across organs and tissues and these are highly regulated and coordinated at the whole body level. The long-term goal of my NSERC Discovery research program is to identify factors and to understand mechanisms that are associated with postnatal changes of the major pathways of AA utilization and metabolism responsible for the declining efficiency of the whole-body N utilization with emphasis on the gut in the pig. My specific objectives for the next five years are i) to investigate postnatal changes of AA utilization for microbial catabolism and growth in the lumen; ii) to examine cellular and molecular aspects of postnatal changes in the apical, mitochondrial inner membrane, and basolateral transport of neutral, e.g., glutamine, leucine and glycine, and acidic AA, e.g., glutamate in the small intestine; and iii) to study postnatal changes of AA catabolism and utilization for biosyntheses of cellular glutathione, proteins, RNA and DNA. Integrated research tools will be used to reveal how postnatal programming and changes of dietary 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 basic gastrointestinal physiology and protein nutrition and metabolism and train highly qualified personnel, leading to nutritional and biotechnological strategies for improving neonate growth and the efficiency of N utilization in pig feeding.