Glutamine regulates the homeostasis of intestinal immune system at the cellular level

Glutamine is the most abundant amino acid in the human and many other mammalian plasmas. Glutamine operates at multiple levels within intestinal cells, including intestinal epithelial cells, goblet cells, paneth cells, and immune cells in the intestinal mucosa, demonstrating its role in fostering both innate and adaptive immunity and its connections with the gut microbiome. This review introduces the potential mechanisms by which the glutamine functions as an intermediary between the gut microbiota and immune system, through changes in the intestinal microbiota and activation of toll-like receptors (TLRs) as well as the mTOR signaling pathway. Glutamine supplementation could increased proliferation and differentiation of T cells, as well as stimulation of secretory IgA (sIgA) secretion, thus contributing to a strengthened intestinal immune response. Studying the glutamine functions among the gut microbiota and immune system will provide ideas and perspectives for maintaining and maximizing intestinal health.