Roles of Dietary Amino Acids and Their Metabolites in Pathogenesis of Inflammatory Bowel Disease

Table 2

Application of partial AAs in inflammatory bowel disease therapies.

AAs	Dose	Administration method	Models	Major functions and effects	Ref.
Tryptophan	88 mg/kg⋅BW⋅day	Intragastric infusion	Piglets	Amelioration of clinical symptoms; reduction of gut permeability and cell apoptosis; inhibition of the production of inflammatory cytokines (TNF-α, IL-6, IFN-γ, IL-12p40, IL-1β, and ICAM-1)	[35]
Melatonin	20 mg/kg⋅BW⋅day	Intragastric infusion	Rats	Antioxidant; inhibition of the production of inflammatory cytokines (TNF-α, COX-2, SOD, and NF-κB); accelerating healing of gastric ulcer	[36]
Glutamine	25% of the total nitrogen	Dietary	Mice	Anti-inflammation; reduction of expression of PSGL-1, LFA-1, and CCR9 by Th cells	[37]
Glutamate	12 μg Glu/0.3 μL saline	Microinjection	Rats	Neurotransmitter; inhibition of T-cell response and inflammation	[38]
Methionine	0.12% L-Met	Dietary	Piglets	Protection of the small-intestinal mucosa	[39]
Cysteine	144 mg/kg⋅BW⋅day	Intragastric infusion	Piglets	Reduction of intestinal permeability and cell apoptosis; inhibition of the local expression of inflammatory mediators (IL-6, TNF-α, IL-12p40, and IL-1β)	[40]
Histidine	Not mentioned	Dietary	Mice	Reduction of histologic damage, colon weight, IL-6, and TNF-α production; inhibition of NF-κB	[41]
Arginine	1% (wt/vol) solution	Drinking water	Mice	Improvement of the clinical parameters and body weight loss; reduction of the colonic permeability; reduction of the proinflammatory cytokine and chemokine expression	[42]
Glycine	5% Gly	Dietary	Rats	Diarrhea amelioration; prevention of the increases of IL-1β and TNF-α	[43]
Taurine	30 mM	Rectal administration	Rats	Anti-inflammation; inhibiting NF-κB activity	[44]
	2%	Drinking water	Mice	Inhibitory effects on the secretion of MIP-2; cytoprotective functions on the epithelial barrier	[45]

TNF-α, tumor necrosis factor-α; IL, interleukin; IFN-γ, interferon-γ; ICAM-1, intracellular adhesion molecule-1; PSGL-1, P-selectin glycoprotein ligand-1; LFA-1, leukocyte function-associated antigen-1; CCR9, C-C chemokine receptor type 9; MIP-2, macrophage inflammatory protein 2.