A review of the immunomodulatory role of dietary tryptophan in livestock and poultry

Abstract

Tryptophan, a nutritionally essential amino acid, is active in the regulation of immune responses in animals. The products of tryptophan metabolism, such as indoleamine 2,3-dioxygenase, kynurenine, quinolinic acid, and melatonin, may improve immunity in an organism and induce anti-inflammatory responses. The immune tolerance processes mediated by tryptophan metabolites are not well understood. Recent studies have reported that the enzymes that break down tryptophan through the kynurenine metabolic pathway are found in numerous cell types, including immunocytes. Moreover, some tryptophan metabolites have been shown to play a role in the inhibition of T lymphocyte proliferation, elevation of immunoglobulin levels in the blood, and promotion of antigen-presenting organization in tissues. This review summarizes the effects and mechanisms of tryptophan and metabolites in immune functions in livestock and poultry. It also highlights the areas in which our understanding of the role(s) of tryptophan is incomplete and suggests possible future research that might prove of benefit to livestock and poultry producers.

Effect of dietary tryptophan supplementation on growth performance, immune response and anti‐oxidant status of broiler chickens from 7 to 21 days

“…Stress has strong correlation with production performance in broiler. Tryptophan is major precursor of serotonin and had a significant role in the modulation of biological function and diminished stress (Bai et al, ). The catalase, glutathione reductase, glutathione peroxidase and ARE are the main parameters used to evaluate the anti‐oxidative status in the enzymatic system, while total anti‐oxidant status and total oxidant status represent enzymatic and non‐enzymatic systems for oxidative stress.…”

“…Tryptophan deficiency leads to depressed body weight gain (BWG), lowered feed intake and poor feed conversion ratio (FCR) along with compromised antibody status (Mozhdeh et al, ). Tryptophan is a structural component of protein as well as a major precursor of serotonin and melatonin hormones which plays an important role in maintenance of normal physiological processes, for example, tissue synthesis, feed intake, growth performance, FCR and immunity in broiler chickens (Bai et al, ). Further, Trp is also involved in niacin biosynthesis in poultry (Richard et al, ).…”

Targeting regulation of tryptophan metabolism for colorectal cancer therapy: a systematic review

“…It is an important functional amino acid with a variety of nutritional and physiological functions. 1 It is indicated that many diseases are associated with TRP metabolism disorders, such Huntington's disease, 3 and gastrointestinal diseases 4 to name a few, also, miscarriage. 2 In recent years, a large number of studies have shown that tumor growth is closely related to TRP metabolism.…”

Evaluation of the role of whey with dodder oxymel on mild to moderate psoriasis: A double-blind, randomized controlled trial

“…Also, apart from its effect on the heart, liver, kidney, and intestines, giant dodder (aftimon) has potent anti-inflammatory, anti-pruritus, and anti-allergic properties. It also has an inhibitory effect on insulin-like growth factor signalling pathway, which inhibits the hyperproliferation of keratinocytes [19,20,[37][38][39]. According to the results of this study, it seems that whey and dodder oxymel, with its additional effect on the immune system, reduction of inflammation, inhibition of cytotoxin secretion, increase in glutathione and serotonin, and subsequent reduction of depression, would improve psoriasis and increase the life expectancy of the patients.…”