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Weaning is a particularly vulnerable period associated with an increased prevalence of gastrointestinal infection, as the removal of maternal immune components coincides with the increased exposure to pathogens. Despite glutamine (Gln) has been shown to improve intestinal barrier function and immune function in both in vivo and in vitro models, supplementation during the vulnerable weaning period has received little attention. The objective of the present study was to determine the ability of dietary supplementation with Gln to improve immune and gastrointestinal function and defense against an enterotoxigenic Escherichia coli challenge in the early post-weaning period in a piglet model. As the development of a reproducible orally induced model of enterotoxigenic E. coli infection in the piglet has proved problematic, an in vivo closed intestinal loop model of enterotoxigenic E. coli infection was used to produce the early signs of E. coli infection. We randomized 21-d-old piglets (n = 20) to nutritionally complete isonitrogenous diets with or without Gln (4.4 %, w/w) for 2 weeks. Intestinal loops were isolated from anaesthetised pigs and inoculated with either saline or one of the two E. coli (K88AC or K88 wild-type)-containing solutions. Intestinal tissue was studied for permeability, cytokine expression, fluid secretion and tight-junction protein expression.
Animals receiving Gln supplementation had decreased potential difference (PD) and short-circuit current (Isc) in E. coli-inoculated intestinal loops (PD 0.628 (SEM 0.151) mV; Isc 13.0 (SEM 3.07) μA/cm2) compared with control-fed animals (PD 1.36 (SEM 0.227) mV; Isc 22.4 (SEM 2.24) μA/cm2). Intestinal tissue from control, but not from Gln-supplemented, animals responded to E. coli with a significant increase in mucosal cytokine mRNA (IL-1β, IL-6, transforming growth factor-β and IL-10). Tight-junction protein expression (claudin-1 and occludin) was reduced with exposure to E. coli in control-fed animals and was not influenced in Gln supplemented piglets.
In summary, the results of the present study suggest that Gln supplementation during the weaning period is useful in reducing early steps in weaning-related gastrointestinal infections by suppressing the inflammatory and regulatory cytokine response in the gut and decreasing damage to tight junction proteins and intestinal electrolyte movement.
JB Ewaschuk, GK Murdoch, IR Johnson, KL Madsen and CJ Field, 2011. British Journal of Nutrition, 106: 870-877.
