Tryptophan has drawn wide attention due to its involvement in improving intestinal immune defense directly and indirectly by regulating metabolic pathways. The study aims to elucidate the potential modulating roles of
tryptophan to protect against intestinal
inflammation and elucidate the underlying molecular mechanisms. The protective effects of
tryptophan against intestinal
inflammation are examined in the
lipopolysaccharide (LPS)-induced inflammatory model. We first found that
tryptophan markedly (p < 0.01) inhibited proinflammatory
cytokines production and nuclear factor κB (NF-κB) pathway activation upon LPS challenge. Next, we demonstrated that
tryptophan (p < 0.05) attenuated LPS-caused intestinal mucosal barrier damage by increasing the number of goblet cells,
mucins, and
antimicrobial peptides (AMPs) in the ileum of mice. In addition,
tryptophan (p < 0.05) inhibited LPS-induced autophagic flux through the
AMP-activated protein kinase (AMPK)-
sirtuin 1 (
SIRT1) pathway in the intestinal systems to maintain autophagy homeostasis. Meanwhile,
tryptophan also reshaped the gut microbiota composition in LPS-challenge mice by increasing the abundance of
short-chain fatty acid (SCFA)-producing bacteria such as Acetivibrio (0.053 ± 0.017 to 0.21 ± 0.0041%). Notably, dietary
tryptophan resulted in the activation of metabolic pathways during the inflammatory response. Furthermore, exogenous treatment of
tryptophan metabolites
kynurenine (Kyn) and
5-HT in porcine intestinal epithelial cells (IPEC-J2 cells) reproduced similar protective effects as
tryptophan to attenuate LPS-induced intestinal
inflammation through regulating the AMPK-SIRT1-autophagy. Taken together, the present study indicates that
tryptophan exhibits intestinal protective and immunoregulatory effects resulting from the activation of metabolic pathways, maintenance of gut mucosal barrier integrity, microbiota composition, and AMPK-SIRT1-autophagy level.