Insights into diet-associated oxidative pathomechanisms in inflammatory bowel disease and protective effects of functional amino acids.

There has been a substantial rise in the incidence and prevalence of clinical patients presenting with inflammatory bowel disease (IBD), which includes Crohn's disease and ulcerative colitis. Accumulating evidence has corroborated the view that dietary factors (particularly diets with high levels of saturated fat or sugar) are involved in the development and progression of IBD, which is predominately associated with changes in the composition of the gut microbiota and an increase in the generation of reactive oxygen species. Notably, the ecological imbalance of the gut microbiome exacerbates oxidative stress and inflammatory responses, leading to perturbations of the intestinal redox balance and immunity, as well as mucosal integrity. Recent findings have revealed that functional amino acids, including L-glutamine, glycine, L-arginine, L-histidine, L-tryptophan, and hydroxyproline, are effectively implicated in the maintenance of intestinal redox and immune homeostasis. These amino acids and their metabolites have oxygen free-radical scavenging and inflammation-relieving properties, and they participate in modulation of the microbial community and the metabolites in the gut. The principal focus of this article is a review of recent advances in the oxidative pathomechanisms of IBD development and progression in relation to dietary factors, with a particular emphasis on the redox and signal transduction mechanisms of host cells in response to unbalanced diets and enterobacteria. In addition, an update on current understanding of the protective effects of functional amino acids against IBD, together with the underlying mechanisms for this protection, have been provided.