Glutamine and alanyl-glutamine promote crypt expansion and mTOR signaling in murine enteroids

摘要

L-Glutamine (Gin) is a key metabolic fuel for intestinal epithelial cell proliferation and survival and may be conditionally essential for gut homeostasis during catabolic states. We show that L-alanyl-L-glutamine (Ala-Gin), a stable Gin dipeptide, protects mice against jejunal crypt depletion in the setting of dietary protein and fat deficiency. Separately, we show that murine crypt cultures (enteroids) derived from the jejunum require Gin or Ala-Gin for maximal expansion. Once expanded, enteroids deprived of Gin display a gradual atrophy of cryptlike domains, with decreased epithelial proliferation, but stable proportions of Paneth and goblet cell differentiation, at 24 h. Replenishment of enteroid medium with Gin selectively activates mammalian target of rapamycin (mTOR) signaling pathways, rescues proliferation, and promotes crypt regeneration. Gin deprivation beyond 48 h leads to destabilization of enteroids but persistence of EGFP-Lgr5-positive intestinal stem cells with the capacity to regenerate enteroids upon Gin rescue. Collectively, these findings indicate that Gin deprivation induces a reversible quiescence of intestinal stem cells and provides new insights into nutritional regulation of intestinal epithelial homeostasis.