Alanyl-glutamine but not glycyl-glutamine improved the proliferation of enterocytes as glutamine substitution in vitro
Abstract
The synthetic dipeptides alanyl-glutamine (Ala-Gln) and glycyl-glutamine (Gly-Gln) are used as Gln substitution to provide energy source in the gastrointestinal tract due to their high solubility and stability. This study aimed to investigate the effects of Gln, Ala-Gln and Gly-Gln on mitochondrial respiration and protein turnover of enterocytes. Intestinal porcine epithelial cells (IPEC-J2) were cultured for 2 days in Dulbecco’s modified Eagle’s-F12 Ham medium (DMEM-F12) containing 2.5 mM Gln, Ala-Gln or Gly-Gln. Results from 5-ethynyl-2′-deoxyuridine incorporation and flow cytometry analysis indicated that there were no differences in proliferation between free Gln and Ala-Gln-treated cells, whereas Gly-Gln treatment inhibited the cell growth compared with Gln treatment. Significantly lower mRNA expressions of Sp1 and PepT1 were also observed in Gly-Gln-treated cells than that of Ala-Gln treatment. Ala-Gln treatment increased the basal respiration and ATP production, compared with free Gln and Gly-Gln treatments. There were no differences in protein turnover between free Gln and Ala-Gln-treated cells, but Gly-Gln treatment reduced protein synthesis and increased protein degradation. Ala-Gln treatment stimulated mTOR activation whereas Gly-Gln decreased mTOR phosphorylation and increased the UB protein expression compared with free Gln treatment. These results indicate that Ala-Gln has the very similar functional profile to free Gln in porcine enterocytes in vitro and can be substituted Gln as energy and protein sources in the gastrointestinal tract.
Publisher URL: https://link.springer.com/article/10.1007/s00726-017-2460-z
DOI: 10.1007/s00726-017-2460-z
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