Gut Microbiota Regulation of Tryptophan Metabolism in Health and Disease

Food-derived peptides with biological activity: from research to food applications.

Tryptophan- and arginine-rich antimicrobial peptides: structures and mechanisms of action.

The gut microbiota influences the health of the host, especially with regard to gut immune homeostasis and the intestinal immune response. In addition to serving as a nutrient enhancer, L-tryptophan (Trp) plays crucial roles in the balance between intestinal immune tolerance and gut microbiota maintenance. Recent discoveries have underscored that changes in the microbiota modulate the host immune system by modulating Trp metabolism. Moreover, Trp, endogenous Trp metabolites (kynurenines, serotonin, and melatonin), and bacterial Trp metabolites (indole, indolic acid, skatole, and tryptamine) have profound effects on gut microbial composition, microbial metabolism, the host's immune system, the host-microbiome interface, and host immune system-intestinal microbiota interactions. The aryl hydrocarbon receptor (AhR) mediates the regulation of intestinal immunity by Trp metabolites (as ligands of AhR), which is beneficial for immune homeostasis. Among Trp metabolites, AhR ligands consist of endogenous metabolites, including kynurenine, kynurenic acid, xanthurenic acid, and cinnabarinic acid, and bacterial metabolites, including indole, indole propionic acid, indole acetic acid, skatole, and tryptamine. Additional factors, such as aging, stress, probiotics, and diseases (spondyloarthritis, irritable bowel syndrome, inflammatory bowel disease, colorectal cancer), which are associated with variability in Trp metabolism, can influence Trp-microbiome-immune system interactions in the gut and also play roles in regulating gut immunity. This review clarifies how the gut microbiota regulates Trp metabolism and identifies the underlying molecular mechanisms of these interactions. Increased mechanistic insight into how the microbiota modulates the intestinal immune system through Trp metabolism may allow for the identification of innovative microbiota-based diagnostics, as well as appropriate nutritional supplementation of Trp to prevent or alleviate intestinal inflammation. Moreover, this review provides new insight regarding the influence of the gut microbiota on Trp metabolism. Additional comprehensive analyses of targeted Trp metabolites (including endogenous and bacterial metabolites) are essential for experimental preciseness, as the influence of the gut microbiota cannot be neglected, and may explain contradictory results in the literature.

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Impact of the Gut Microbiota on Intestinal Immunity Mediated by Tryptophan Metabolism

Biofabrication with chitosan.

The avian egg contains all of the necessary nutrients and growth factors required for the developing embryo, including antibodies that are transported from the blood of the hen into the egg yolk to provide immunity to the chick. Since the discovery of egg yolk antibodies, now called immunoglobulin Y (IgY), in the late 1800s, this process has been harnessed to produce antigen-specific yolk antibodies for numerous applications in the medical and research fields, including in areas such as diagnostics and proteomics. However, one of the most valuable and promising areas of IgY research is its use for passive immunization to treat and prevent human and animal diseases. The following review covers the key features and advantages of IgY and the production and purification of IgY from the egg yolk, as well as highlights some of the most promising applications of egg yolk antibodies in human and veterinary medicine.

Egg Yolk Antibodies for Passive Immunity

Fibrinolytic enzymes in Asian traditional fermented foods

Novel hen egg phosvitin phosphopeptides (PPP) with molecular masses of 1-3 kDa were prepared from tryptic hydrolysis following partial alkaline dephosphorylation. The phosvitin treated with various NaOH concentrations (0.05-0.4 N) resulted in different dephosphorylated proteins ranging from 17.5 to 96.3% of phosphate retention. The protein was digested into 10-20 amino acid peptides with trypsin. Calcium-binding properties of PPP were compared with those of commercial casein phosphopeptides in vitro. The PPP with 35% phosphate retention is shown to be effective for enhancing calcium binding capacity and inhibiting the formation of insoluble calcium phosphate. The results provide potential novel functional oilgophosphopeptides as nutraceuticals.

Preparation of novel functional oligophosphopeptides from hen egg yolk phosvitin.

The binding activities of IgG and IgE antibodies from egg-allergic patients to physically or chemically treated egg white proteins were examined and compared with those of rabbit anti-egg white IgG antibodies. The sera from eight patients and four rabbit antibodies were used in this study. The binding activities of human IgG antibody to partially denatured ovotransferrin (Tf), ovalbumin (OA), and lysozyme (Lys) forms were increased, whereas carboxymethylation (RCM) and heat treatment caused a dramatic decrease in the antigenicity of Tf and ovomucoid (OVM). Tf and OVM were major immunogenic antigens for the rabbit IgG response. Urea also caused Tf to exhibit greater rabbit IgG binding activity. In contrast, human and rabbit antibodies did not react with ovomucin. Partially denatured Tf and Lys also induced strong IgE binding activities. The allergenicity of Tf, OVM, and Lys was decreased by RCM, whereas OA retained its binding capacity. These results suggested that anti-OA IgE recognizes more sequential epitopes and that anti-OVM and Lys antibodies recognize both conformational and sequential epitopes. Tf and OVM were dominant allergens for the IgE antibodies of anaphylaxis patients, whereas IgE from atopic patients bound more strongly with OA and OVM.

Yoshinori Mine

Papers

Egg Yolk Antibodies for Passive Immunity

Fibrinolytic enzymes in Asian traditional fermented foods

Preparation of novel functional oligophosphopeptides from hen egg yolk phosvitin.

Comparative Studies on Antigenicity and Allergenicity of Native and Denatured Egg White Proteins

Heat induced gelling properties of soy protein isolates prepared from different defatted soybean flours