Amino acid and dipeptide uptake in the piglet small intestine

Amino acids and oligopeptides are the end products of protein digestion. Amino acids are transported into the small intestine by several amino acid transporter systems, but di/tri peptides are carried solely by the intestinal peptide transporter 1 (PepT1), which is also capable of transporting bacterial peptide such as N-formyl-methionyl-leucyl-phenylalanine (fMLP). Studies have reported that PepT1 activity is preserved during situations like infection or parenteral nutrition, while free amino acid transporter activities decline. Previously we demonstrated that fMLP-induced mucosal inflammation during an intestinal perfusion experiment was ameliorated when co-perfused with cysteinyl-glycine. My first study investigated the impact of arginyl-glutamine on fMLP-induced inflammatory responses.

PepT1 is necessary for peptide transport, but its activity also appears to enhance free amino acid absorption via trans-stimulation of the Na+ independent amino acid transporter B0/+/AT antiporter. B0/+/AT transports cationic amino acids such as arginine and lysine. Previously we demonstrated significantly enhanced arginine uptake from in situ isolated small intestinal segments that were perfused with arginine and lysyl-lysine compared to arginine alone. We speculated that enhanced arginine uptake was facilitated by PepT-mediated uptake of lysyl-lysine, which increased intracellular lysine concentration as a result of lysyl-lysine hydrolysis. Higher intracellular lysine enhanced arginine uptake through the trans-stimulation of the B0/+antiporter. This study investigates whether the enhanced arginine uptake in the presence of lysyl-lysine can be abolished when co-perfused with the hydrolysis resistant dipeptide, glycyl-sarcosine. The findings of this research will contribute to the development of diets that will optimize the amino acid uptake during growth and periods of small intestinal stress such as weaning and infectious disease.