Glutamine peptide does not improve gut barrier function and mucosal immunity in total parenteral nutrition

In two separate experiments, three groups of 10 (first experiment) and 12 (second experiment) rats each were catheterized for the long term via the right jugular vein and fed one of the following dietary regimens for 7 days while in individual metabolism cages. The rat food control groups were fed powdered rat food. The total parenteral nutrition (TPN) formula for one group was enriched with the stable dipeptide L-alanyl-L-glutamine (ALA-GLN) equivalent to a 1% or 2% glutamine concentration. For the control TPN groups, the dipeptide was replaced by isonitrogenous amounts of alanine (ALA). In both experiments, bacterial translocation was promoted to a similar extent by the ALA-GLN and ALA TPN formulas compared with the rat food groups. Bacterial overgrowth in the cecum and intestinal atrophy, quantitated by the mucosal protein content, did not differ between ALA-GLN and ALA groups. The nitrogen balances of the three groups showed similar values in the second experiment. The secretory immunoglobulin A was measured in washings of the jejunum and ileum (soluble fraction) and in the homogenates of the gut mucosa (insoluble fraction). The secretory immunoglobulin A values of both fractions showed no difference between the ALA and ALA-GLN groups, irrespective of whether they were normalized for gut segment length or corrected for mucosal protein content. In conclusion from these results, the supplementation of TPN with glutamine does not seem to improve gut barrier function or mucosal immunity in unstressed rats.