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L-Tryptophan

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• Associations between plasma tryptophan and indole-3-propionic acid levels and mortality in patients with coronary artery disease - Am J Clin Nutr 2022 Jun 21 - "CAD patients with the highest quartile of tryptophan and IPA levels had multivariable-adjusted hazard ratios of 0.62 (95% confidence interval [CI], 0.43, 0.89) and 0.71 (95% CI 0.50, 0.99), respectively, for cardiovascular mortality and 0.67 (95% CI, 0.50, 0.90) and 0.75 (95%CI 0.57, 0.99), respectively, for all-cause mortality compared with that in CAD patients in the lowest quartile. After multivariable adjustments, one standard deviation increase in the continuous plasma tryptophan and IPA levels were respectively associated with 16% and 14% decreases in the risk of cardiovascular mortality and with 13% and 14% decreases in the risk of all-cause mortality"
  • 3-Indolepropionic acid - Wikipedia - "3-Indolepropionic acid (IPA), or indole-3-propionic acid, is a potent neuroprotective antioxidant, plant auxin, and natural product in humans that is being studied for therapeutic use in Alzheimer's disease.[2][3][4][5] It is endogenously produced by human microbiota and has only been detected in vivo when the species Clostridium sporogenes is present in the gastrointestinal tract.[4][5][6] As of April 2016, C. sporogenes, which uses tryptophan to synthesize IPA, is the only species of bacteria known to synthesize IPA in vivo at levels which are subsequently detectable in the blood plasma of the host" - See tryptophan at Amazon.com.
• Tryptophan Supplementation Increases the Production of Microbial-Derived AhR Agonists in an In Vitro Simulator of Intestinal Microbial Ecosystem - J Agric Food Chem 2022 Mar 28 - "The aryl hydrocarbon receptor (AhR) plays an important role in intestinal homeostasis, and some microbial metabolites of tryptophan are known AhR agonists. In this study, we assessed the impact of tryptophan supplementation on the formation of tryptophan metabolites, AhR activation, and microbiota composition in the simulator of the human intestinal microbial ecosystem (SHIME) ... Tryptophan supplementation induced most microbial changes in the transverse colon including increased relative abundance of lactobacillus. We conclude that tryptophan supplementation leads to increased formation of AhR agonists in the colon"
• Effects of dietary tryptophan on muscle growth, protein synthesis, and antioxidant capacity in hybrid catfish Pelteobagrus vachelli♀ × Leiocassis longirostris - Br J Nutr 2021 Jul 29 - "Trp improved muscle growth, protein synthesis as well as antioxidant capacity, which might be partly related to myogenic regulatory factors (MRFs), IGFs/PIK3Ca/AKT/TOR, and Keap1/Nrf2 signaling pathways"
• The impact of tryptophan supplementation on sleep quality: a systematic review, meta-analysis, and meta-regression - Nutr Rev 2021 May 3 - "Results from the study suggested that Trp supplementation can shorten wake after sleep onset (-81.03 min/g, P = 0.017; SMD, -1.08 min [95%CI, -1.89 to -0.28]). In addition, the group receiving ≥1 g Trp supplementation had a shorter wake after sleep onset than the group with Trp < 1g supplementation (Trp <1 g vs Trp ≥1 g: 56.55 vs 28.91 min; P = 0.001) ... Conclusion: Trp supplementation, especially at ≥1 g can help improve sleep quality"
• Dietary intake of tryptophan tied emotion-related impulsivity in humans - Int J Vitam Nutr Res. 2019 Oct 4:1-8 - "Three Factor Impulsivity Index, TFI ... Correlational analyses indicated that higher tryptophan intake was associated with significantly lower scores on two out of three subscales of the TFI, Pervasive Influence of Feelings scores r = -.502, p < .010, and (lack-of) Follow-Through scores, r = -.407, p < .050. ... Findings provide further evidence that emotion-related impulsivity is correlated to serotonergic indices, even when considering only food habits. It also suggests the need for more research on whether tryptophan supplements might be beneficial for impulsive persons suffering from a psychological disorder"
• Low serum tryptophan predicts higher mortality in cardiovascular disease - Eur J Clin Invest. 2015 Jan 13 - "After adjustments for cardiovascular risk factors and other possible confounders, the hazard ratio (with 95% CI) in the first tryptophan quartile of the study population was 1.51 (1.19-1.90; p=0.0006) for total mortality, 1.41 (1.05-1.89; p=0.0224) for cardiovascular and 1.79 (1.20-2.67; p=0.0042) for non-cardiovascular mortality, respectively, thus indicating a significantly higher risk of death in patients with tryptophan concentrations <34 μmol/L ... Low serum tryptophan in CAD patients is associated with immune activation and indicates reduced life expectancy"