Dietary L-Tryptophan Modulates the Structural and Functional Composition of the Intestinal Microbiome in Weaned Piglets

Abstract

Background: Intestinal microbiota plays an important role in regulating metabolism, physiology, and immune response of the host. L-Tryptophan (Trp) are metabolized by several genera of bacteria. It remains largely unknown whether Trp can regulate the composition and diversity of the intestinal microbiota and contribute to intestinal homeostasis.Methods: A total of 126 weaning piglets were fed a corn- and soybean meal-based diet supplemented with 0, 0.2, or 0.4% Trp for 4 weeks. The intestinal microbiota was measured by using bacterial 16S rRNA gene-based high-throughput sequencing methods. Metabolites of Trp and short-chain fatty acids (SCFAs) in the hindgut were determined by high-performance liquid chromatography and gas chromatography, respectively. The mRNA levels for aromatic hydrocarbon receptor (AhR), tumor necrotic factor-α (TNF-α), interleukin-8 (IL-8), and protein abundances of tight junction proteins were determined.Results: Compared with the control group, Trp supplementation enhanced piglet growth performance and markedly altered the intestinal microbial composition as evidenced by enhanced alpha and beta diversity in the microbiome (P < 0.05). The abundances of Prevotella, Roseburia, and Succinivibrio genera were enriched, but those of Clostridium sensu stricto and Clostridium XI, opportunistic pathogens, were decreased with dietary Trp supplementation. Analysis of metabolic pathways indicated enhanced indole alkaloid biosynthesis and Trp metabolism, which was validated by elevated concentrations of 3-indoleacetic acid and indole in the intestinal contents of Trp-supplemented piglets (P < 0.05). These changes in Trp metabolites were correlated with activation of AhR and cytochrome p4501 A1 (CYP1A1) in cecum and colonic tissues, and with a decrease in the intestinal mucosal IL-8 mRNA level. Moreover, the protein abundances for zonula occluden (ZO)-1 and occludin were upregulated by Trp supplementation in colonic tissues.Conclusion: Dietary Trp supplementation altered intestinal microbial composition and diversity, improved intestinal mucosal barrier function, activated AhR signaling, and downregulated expression of inflammatory cytokines in the large intestine of weaned piglets. These results indicate a crosstalk between dietary Trp and intestine in nutrition, microbial metabolism, and mucosal immunity.

Dietary Tryptophan Modulate the Composition of the Ileum and Cecum microbiota in Weaned Piglets after Lipopolysaccharide Challenge

“…Interesting, we found dietary 0.2% Trp alleviated the decrease of alpha diversity in ileum microbiota challenged by LPS, but dietary 0.4% has no effect on the reduction of diversity in ileum microbiota caused by LPS. This result consistent with a previous study, which reported the richness and diversity of gut microbiota in 0.2% Trp group higher than that in control and 0.4% Trp groups [19]. These results indicated that the addition of 0.2% Trp to the diet has improved regulation of ileum microbiota diversity than 0.4% Trp treatments regardless of whether the piglets are challenged by LPS.…”

“…Some previous studies have shown that dietary Trp level could regulate feed intake [15], growth [16], intestinal integrity [17] and oxidative stress [14] of pigs. Interestingly, recent studies reported that dietary Trp altered intestinal microbial composition and diversity, improved intestinal barrier and downregulated expression of inflammatory cytokines in the intestine of weaned piglets [18,19]. In addition, increasing dietary tryptophan level could improve feed intake and growth performance of weanling pigs orally challenged with Escherichia coli K88 [16].…”

Administration of encapsulated L-tryptophan improves duodenal starch digestion and increases gastrointestinal hormones secretions in beef cattle

“…In other words, starch digestion in the small intestines of ruminants can be modulated by the environment inside of the small intestine. It is while a similar phenomenon was previously reported in broiler chicks [11] and weaned piglets [12]. Therefore, any attempts to improve α-amylase activity in duodenal fluids could help starch digestion, which is also targeted in the present study.…”

Gut-Microbial and -Metabolomic Signatures in the Prevention of Non-Alcoholic Fatty Liver Disease by Lactobacillus Lactis and Pediococcus Pentosaceus

“…Indeed, a growing evidence implicates gut microbiota-derived metabolites as active modulators, encompassing diet, microorganisms, and the host, attributed to causal functionality, including SCFAs and tryptophan metabolites [19,25]. Tryptophan metabolites in particular have been shown to affect the development of NAFLD by altering the composition of the gut microbiota [5,26]. Indole compounds are major products of tryptophan-derived metabolites, and include indole-3-acrylic acid, indole-3-acetic acid, and indole-3-propionic acid [5,7,20].…”