Effects of dietary l-tryptophan supplementation on intestinal response to chronic unpredictable stress in broilers

Abstract

Stress has been recognized as a critical risk factor for gastrointestinal diseases in both humans and animals. However, nutritional strategies to attenuate stress-induced intestinal barrier function and underlying mechanisms remain largely unknown. This study tested the hypothesis that L-tryptophan enhanced intestinal barrier function by regulating mucosal serotonin metabolism in chronic unpredictable stress-exposed broilers. One-day-old male broilers (Arbor Acres) were fed a basal diet supplemented with or without L-tryptophan in the absence or presence of chronic unpredictable stress. Feed intake, body weight gain, plasma corticosterone and 5-hydroxytryptamine (5-HT), intestinal permeability, mucosal secretory IgA (sIgA), and mRNA levels for tryptophan hydroxylase 1 (TPH1), IL-1β, IL-6, TNF-α, IL-10, protein abundance for claudin-1, occludin, and ZO-1 were determined. Stress exposure led to elevated plasma corticosterone (P < 0.05), increased intestinal permeability (P < 0.05), reduced growth performance (P < 0.05), and decreased sIgA secretion compared with the controls. These effects were largely reversed (P < 0.05) by L-tryptophan supplementation. Western blot analysis showed that stress exposure resulted in decreased protein abundance for occludin, claudin-1, and ZO-1, which was attenuated by L-tryptophan. mRNA levels for IL-1β, IL-6, and TNF-α were increased, but those for IL-10 were decreased, in the jejunal tissue of broilers subjected to stress. This effect of stress on cytokine expression was abolished by L-tryptophan treatment. The effects of stress were associated with decreased plasma concentration of 5-HT (P < 0.05), and reduced (P < 0.05) mRNA levels for TPH1. L-Tryptophan supplementation markedly attenuated stress-induced alterations in 5-HT and TPH1 mRNA level in jejunal tissues of broilers. Collectively, these results indicate that L-tryptophan supplementation alleviates chronic unpredictable stress-induced intestinal barrier dysfunction by regulating 5-HT metabolism in broilers.

Dietary Supplementation with Lysine and Threonine Modulates the Performance and Plasma Metabolites of Broiler Chicken

“…Whether peripheral serotonin, particularly plasma serotonin, affects glucose and lipid metabolism as well as FCR in broiler chickens is unknown. A recent study showed that supplementation of broiler chicken diet with tryptophan may improve FCR under chronic and unpredictable stress, probably owing to serotonergic metabolism (Yue et al, 2017). Therefore, the metabolic role of peripheral serotonin has been identified in broilers in the present study.…”

Functions and Signaling Pathways of Amino Acids in Intestinal Inflammation

“…The supplementation of Trp inhibits Th1 differentiation in vivo [ 61 ]. And L-Trp supplementation decreases the destruction of intestinal barrier triggered by stress via modulating 5-HT metabolism in broilers [ 62 ]. Collectively, EAAs mainly exert anti-inflammatory roles by NF- κ B, CaSR, MAPK, and mTOR signaling pathway to restrain the expressions of proinflammatory cytokines.…”

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

“…Whereas oxidative stress puts harmful effects on membran fludity. The 5-HT has beneficial effects on the enzymatic and non-enzymatic anti-oxidant capacity (Dong, Azzam, Rao, Yu, & Zou, 2012;Yue, Guo, & Yang, 2017).…”