L-Tryptophan

https://www.ncbi.nlm...pubmed/31144383
The role of inflammation and the gut microbiome in depression and anxiety.
Abstract
The study of the gut microbiome has increasingly revealed an important role in modulating brain function and mental health. In this review, we underscore specific pathways and mechanisms by which the gut microbiome can promote the development of mental disorders such as depression and anxiety. First, we review the involvement of the stress response and immune system activation in the development of depression and anxiety. Then, we examine germ-free murine models used to uncover the role of the gut microbiome in developing and modulating pertinent activity in the brain and the immune system. We also document multiple pathways by which stress-induced inflammation harms brain function and ultimately affects mental health, and review how probiotic and prebiotic treatments have shown to be beneficial. Lastly, we provide an overview of gut microbiome-derived compounds (short-chain fatty acids, tryptophan catabolites, microbial pattern recognition) and related mechanisms (vagal nerve activity and fecal microbiota transplants) involved in mediating the influence of the gut microbiome to mental health. Overall, a picture of the gut microbiome playing a facilitating role between stress response, inflammation, and depression, and anxiety is emerging. Future research is needed to firmly establish the microbiome's causal role, to further elucidate the mechanisms by which gut microbes influence brain function and mental health, and to possibly develop treatments that improve mental health through microbiotic targets.


https://www.ncbi.nlm...pubmed/31825083
Tryptophan Metabolism: A Link Between the Gut Microbiota and Brain.
Abstract
The gut-brain axis (GBA) is a bilateral communication network between the gastrointestinal (GI) tract and the central nervous system. The essential amino acid tryptophan contributes to the normal growth and health of both animals and humans and, importantly, exerts modulatory functions at multiple levels of the GBA. Tryptophan is the sole precursor of serotonin, which is a key monoamine neurotransmitter participating in the modulation of central neurotransmission and enteric physiological function. In addition, tryptophan can be metabolized into kynurenine, tryptamine, and indole, thereby modulating neuroendocrine and intestinal immune responses. The gut microbial influence on tryptophan metabolism emerges as an important driving force in modulating tryptophan metabolism. Here, we focus on the potential role of tryptophan metabolism in the modulation of brain function by the gut microbiota. We start by outlining existing knowledge on tryptophan metabolism, including serotonin synthesis and degradation pathways of the host, and summarize recent advances in demonstrating the influence of the gut microbiota on tryptophan metabolism. The latest evidence revealing those mechanisms by which the gut microbiota modulates tryptophan metabolism, with subsequent effects on brain function, is reviewed. Finally, the potential modulation of intestinal tryptophan metabolism as a therapeutic option for brain and GI functional disorders is also discussed.


https://www.ncbi.nlm...pubmed/31711278
Biomarkers in Drug Free Subjects with Depression : Correlation with Tryptophan.
Results show that levels of TRP, Se, Vit D, Mg, and serotonin were decreased in the depressed patient when compared to normal subjects. There is a direct correlation between TRP and Vit D, and TRP and Se while the inverse correlation between TRP and Mg, and TRP and serotonin in depressed subjects. The association among TRP and other biomarkers is non-significant.