Small Intestinal Co‐Perfusion of Alanyl‐Glutamine and Free Glutamine with fMLP Bacterial Peptide Resulted in a Diminished Inflammatory Response in Parenterally and Sow‐Fed Neonatal Piglets
Authors: Trevors Alexander R. , Nosworthy Matthew G. , Bertolo Robert F. , Brunton Janet A. 
Published: November 2023

Small peptide absorption in the intestine is mediated by the transporter PepT1, which is also capable of transporting bacterial peptides such as formyl‐methionyl‐leucyl‐phenylalanine (fMLP). Previously, we demonstrated that fMLP induced mucosal inflammation during an intestinal perfusion experiment. Co‐perfusion of fMLP with the dipeptide cysteinyl‐glycine ameliorated the response as indicated by reduced myeloperoxidase activity and lower TNF‐α concentration in mucosal tissue. The objective of this study was to assess the interactions of alanyl‐glutamine or free alanine and glutamine with fMLP in a similar intestinal perfusion experiment; however, this time we employed a single‐pass perfusion model as opposed to re‐circulating the perfusion buffers to ensure constant exposure to fMLP. Piglets (10 d old) were assigned to either a total parenteral nutrition diet (TPN, n=6) for 4 full days to induce intestinal atrophy, or left to suckle on the sow (SF, n=6). Piglets subsequently underwent an intestinal perfusion procedure under anesthesia. Five 10 cm segments of intestine were isolated and left in situ, beginning at 50 cm proximal to the ileocecal valve; the isolated segments were each separated by 30 cm. The segments were perfused with one of the following: 1) 10 μM fMLP, 2) 5 mM alanyl‐glutamine, 3) 5 mM of each alanine + glutamine, 4) 5 mM alanyl‐glutamine + 10 μM fMLP, or 5) 5 mM of each alanine + glutamine + 10 μM fMLP. All perfusion solutions also contained 3H‐fMLP to measure uptake and were perfused continuously for 3 h at a rate of 1 mL/min. Myeloperoxidase activity in intestinal mucosa was higher in the TPN pigs compared to SF pigs (P<0.05), but was not affected by any of the treatments. Furthermore, there were no differences in mucosal TNF‐α concentrations in response to fMLP perfusion or diet. Intestinal morphology also did not differ between methods of feeding or perfusion treatments. Measuring 3H‐fMLP disappearance from the perfusion buffers indicated that approximately 25% of fMLP was taken up by the intestine, regardless of treatments. Interestingly, we hypothesized that the single‐pass model should facilitate a greater inflammatory response to fMLP compared to the recirculating model from our previous work. Studies with glutamine supplementation in a number of models have demonstrated an immunomodulatory role in the small intestine, in part by enhancing mucosal integrity via tight junctions, or by mediating the cytokine cascade. Evidence of fMLP uptake without changes in TNF‐α concentration or myeloperoxidase activity suggests that glutamine, delivered either enterally to the mucosa or absorbed and supplied via the systemic circulation, may provide protection against bacterial peptide‐induced inflammation in the neonatal gut.

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Canadian Institutes of Health Research, Research & Development Corporation of Newfoundland and Labrador