title: L-Glutamine enhances enterocyte growth via activation of the mTOR signaling pathway independently of AMPK.
abstract: Neonates (including human infants) require L-glutamine (Gln) for optimal intestinal health. This study tested the hypothesis that Gln enhances enterocyte growth via both mammalian target of rapamycin (mTOR) and AMP-activated kinase (AMPK) signaling pathways. Intestinal porcine epithelial cells (IPEC-1) were cultured for 3 days in Gln-free Dulbecco's modified Eagle medium containing 0 or 2 mM Gln. To determine the role of mTOR and AMPK on cell growth, additional experiments were conducted where medium contained 2 mM Gln and 10 nM rapamycin (Rap, an inhibitor of mTOR) or 1 μM compound C (an inhibitor of AMPK). IPEC-1 cell growth increased with increasing concentrations of Gln from 0 to 2 mM. Compared with 0 mM Gln, 2 mM Gln increased (P < 0.05) the amounts of phosphorylated 4E-binding protein 1 (4E-BP1) and ribosomal protein S6 kinase (p70S6 kinase) proteins but did not affect abundances of total or phosphorylated AMPK protein. Gln also increased mRNA levels for Bcl-2, mTOR, p70S6 kinase, 4E-BP1, COX7C, ASCT2, ODC, SGLT-1, CFTR, Na(+)/K(+)-ATPase, HSP70, and ZO-1. Similarly, cells cultured with Rap and Gln exhibited higher (P < 0.05) abundances of phosphorylated 4E-BP1 and p70S6 kinase proteins than the Rap-only group, whereas abundances of phosphorylated mTOR and 4E-BP1 proteins were increased when AMPK was inhibited by compound C. Conversely, the amount of phosphorylated AMPK increased when mTOR was inhibited by Rap, suggesting a negative cross-talk between mTOR and AMPK. Collectively, these results indicate that Gln stimulates enterocyte growth by activating the mTOR signaling pathway independently of AMPK.
authors.affiliation: Hubei Collaborative Innovation Center for Animal Nutrition and Feed Safety, Hubei Key Laboratory of Animal Nutrition and Feed Science, Wuhan Polytechnic University, Wuhan, 430023, China.
authors.forename: Dan
authors.initials: D
authors.lastname: Yi
authors.forename: Yongqing
authors.initials: Y
authors.lastname: Hou
authors.forename: Lei
authors.initials: L
authors.lastname: Wang
authors.forename: Wanjin
authors.initials: W
authors.lastname: Ouyang
authors.forename: Minhui
authors.initials: M
authors.lastname: Long
authors.forename: Di
authors.initials: D
authors.lastname: Zhao
authors.forename: Binying
authors.initials: B
authors.lastname: Ding
authors.forename: Yulan
authors.initials: Y
authors.lastname: Liu
authors.forename: Guoyao
authors.initials: G
authors.lastname: Wu
mesh_terms: D055372:AMP-Activated Protein Kinases / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D049109:Cell Proliferation; D020895:Enterocytes / Q000166:cytology* / Q000378:metabolism*; D005973:Glutamine; D010766:Phosphorylation; D019893:Ribosomal Protein S6 Kinases / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction; D013552:Swine; D058570:TOR Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism*
chemical_list: D005973:Glutamine; D019893:Ribosomal Protein S6 Kinases; D058570:TOR Serine-Threonine Kinases; D055372:AMP-Activated Protein Kinases