Akkermansia muciniphila inhibits tryptophan metabolism via the AhR/ß-catenin signaling pathway to counter the progression of colorectal cancer.

Akkermansia muciniphila (A. muciniphila), a gram-negative anaerobic bacterium, is selectively decreased in the fecal microbiota of patients with colorectal cancer (CRC), but its molecular mechanism in CRC development remains inconclusive. In this study, we first confirmed the inhibitory effect of A. muciniphila on CRC formation and analyzed the metabolic role of intestinal flora in human Polyps, A-CRA (advanced colorectal adenoma) and CRC samples. To better clarify the role of A. muciniphila in CRC development, a pseudo-germ-free (GF) azoxymethane (AOM)/dextran sulfate sodium (DSS) mouse model was established, followed by infection with or without A. muciniphila. Metabolomic analysis and RNA-seq analysis showed tryptophan-mediated aryl hydrocarbon receptor (AhR) was significantly down-regulated in A. muciniphila-infected CRC mice. Then, mice with intestinal specific AhR deficiency (AhRfl/fl Cre) were generated and were used in 2 murine models: AOM/DSS treatment as a model of carcinogen-induced colon cancer and a genetically induced model using ApcMin/+ mice. Notably, AhR deficiency inhibited CRC growth in the AOM/DSS and ApcMin/+ mouse model. Moreover, AhR deficiency inhibited, rather than enhanced, tumor formation and tumor-derived organoids in Apc-deficient cells both in vivo and in vitro by activating Wnt/ß-catenin signaling and TCF4/LEF1-dependent transcription. Furthermore, the antitumor effectiveness of A. muciniphila was abolished either in a human colon cancer tumor model induced by subcutaneous transplantation of AhR-silenced CRC cells, or AhR-deficienty spontaneous colorectal cancer model. In conclusion, supplementation with A. muciniphila. protected mice from CRC development by specifically inhibiting tryptophan-mediated AhR/ß-catenin signaling.

Gut Microbiota-Derived Tryptophan Metabolite Indole-3-aldehyde Ameliorates Aortic Dissection.

Tryptophan, an essential dietary amino acid, is metabolized into various metabolites within both gut microbiota and tissue cells. These metabolites have demonstrated potential associations with panvascular diseases. However, the specific relationship between tryptophan metabolism, particularly Indole-3-aldehyde (3-IAId), and the occurrence of aortic dissection (AD) remains unclear. 3-IAId showed an inverse association with advanced atherosclerosis, a risk factor for AD. In this study, we employed a well-established ß-aminopropionitrile monofumarate (BAPN)-induced AD murine model to investigate the impact of 3-IAId treatment on the progression of AD. Our results reveal compelling evidence that the administration of 3-IAId significantly mitigated aortic dissection and rupture rates (BAPN + 3-IAId vs. BAPN, 45% vs. 90%) and led to a notable reduction in mortality rates (BAPN + 3-IAId vs. BAPN, 20% vs. 55%). Furthermore, our study elucidates that 3-IAId exerts its beneficial effects by inhibiting the phenotype transition of vascular smooth muscle cells (VSMCs) from a contractile to a synthetic state. It also mitigates extracellular matrix degradation, attenuates macrophage infiltration, and suppresses the expression of inflammatory cytokines, collectively contributing to the attenuation of AD development. Our findings underscore the potential of 3-IAId as a promising intervention strategy for the prevention of thoracic aortic dissection, thus providing valuable insights into the realm of vascular disease management.

5-Methoxytryptophan ameliorates endotoxin-induced acute lung injury in vivo and in vitro by inhibiting NLRP3 inflammasome-mediated pyroptosis through the Nrf2/HO-1 signaling pathway.

BACKGROUND AND AIM: Endotoxin-induced acute lung injury (ALI) is a complicated and fatal condition with no specific or efficient clinical treatments. 5-Methoxytryptophan (5-MTP), an endogenous metabolite of tryptophan, was revealed to block systemic inflammation. However, the specific mechanism by which 5-MTP affects ALI still needs to be clarified. The purpose of this study was to determine whether 5-MTP protected the lung by inhibiting NLRP3 inflammasome-mediated pyroptosis through the Nrf2/HO-1 signaling pathway. METHODS AND RESULTS: We used lipopolysaccharide (LPS)-stimulated C57BL/6 J mice and MH-S alveolar macrophages to create models of ALI, and 5-MTP (100 mg/kg) administration attenuated pathological lung damage in LPS-exposed mice, which was associated with decreased inflammatory cytokines and oxidative stress levels, upregulated protein expression of Nrf2 and HO-1, and suppressed Caspase-1 activation and NLRP3-mediated pyroptosis protein levels. Moreover, Nrf2-deficient mice or MH-S cells were treated with 5-MTP to further confirm the protective effect of the Nrf2/HO-1 pathway on lung damage. We found that Nrf2 deficiency partially eliminated the beneficial effect of 5-MTP on reducing oxidative stress levels and inflammatory responses and abrogating the inhibition of NLRP3-mediated pyroptosis induced by LPS. CONCLUSION: These findings suggested that 5-MTP could effectively ameliorate ALI by inhibiting NLRP3-mediated pyroptosis via the Nrf2/HO-1 signaling pathway.

Tolerable Upper Intake Level for Individual Amino Acids in Humans: A Narrative Review of Recent Clinical Studies.

Individual amino acids are widely popular as supplements because of various perceived and real health benefits. However, currently, there are no recommendations set by national health agencies for tolerable upper intake levels (UL) for amino acids because of a lack of well-conducted human dose-response trials. In the past decade, under the initiative of the International Council on Amino Acid Science, a nonprofit organization, a series of UL human clinical studies were conducted. The goal of this narrative review is to summarize the studies on 6 essential amino acids (leucine, tryptophan, methionine, lysine, histidine, and phenylalanine), 2 nonessential amino acids (arginine and serine), and 2 nonproteinogenic amino acids (ornithine and citrulline) and provide the first set of ULs. A brief background of the concept of the DRI framework of UL, the concept of UL for amino acids, and a perspective of the results are also provided. The data suggest that in relatively healthy adult individuals, the tested amino acids are well tolerated, and ULs, or the no-observed-adverse-effect-level (NOAEL), lowest-observed-adverse-effect-level (LOAEL), can be determined. The ULs were for leucine-young (35 g/d), tryptophan (4.5 g/d), and leucine-elderly (30 g/d); NOAEL and LOAEL for methionine at 3.2 and 6.4 g/d, respectively; NOAEL for arginine (30 g/d); NOAEL and LOAEL for lysine at 6 and 7.5 g/d, respectively; NOAEL and LOAEL for histidine at 8 and 12 g/d, respectively; and NOAEL for phenylalanine (12 g/d), serine (12 g/d), ornithine (12 g/d) and citrulline (24 g/d). This first set of human UL data are hoped to help national and international agencies set safety standards for supplemental amino acids.

Saussurea involucrata oral liquid regulates gut microbiota and serum metabolism during alleviation of collagen-induced arthritis in rats.

Saussurea involucrata oral liquid (SIOL) can clinically relieve symptoms, such as joint pain and swelling, and morning stiffness, in patients with rheumatoid arthritis (RA). However, the mechanism of action remains unclear. This study used a combination of gut microbiota and serum metabolomics analysis to investigate the effects and potential mechanisms of SIOL intervention on rats with RA induced by type II bovine collagen and Freund's complete adjuvant. Results showed that SIOL treatment consequently improved the degree of ankle joint swelling, joint histopathological changes, joint pathological score, and expression of serum-related inflammatory cytokines (interleukin (IL)-1ß, IL-4, IL-6, IL-10, and tumor necrosis factor-α) in RA model rats. 16 S rRNA sequencing results showed that SIOL increased the relative richness of the Lactobacillus and Bacteroides genus and decreased the relative richness of Romboutsia, Alloprevotella, Blautia, and Helicobacter genus. Serum nontargeted metabolomic results indicated that SIOL could regulate metabolites related to metabolic pathways, such as glycine, serine, threonine, galactose, cysteine, and methionine metabolism. Spearman correlation analysis showed that the regulatory effects of SIOL on the tricarboxylic acid (TCA) cycle, phenylalanine metabolism, phenylalanine, tyrosine, and tryptophan biosynthesis, and glyoxylate and dicarboxylate metabolism pathways were correlated with changes in the richness of the Lactobacillus, Romboutsia, Bacteroides, and Alloprevotella genus in the gut microbiome. In conclusion, this study revealed the ameliorative effects of SIOL on RA and suggested that the therapeutic effects of SIOL on RA may be related to the regulation of the community richness of the Lactobacillus, Romboutsia, Bacteroides, and Alloprevotella genus, thereby improving the TCA cycle; phenylalanine metabolism; phenylalanine, tyrosine, and tryptophan biosynthesis, and glyoxylate and dicarboxylate metabolism-related pathways.

Lizhong Decoction Ameliorates Ulcerative Colitis in Mice via Regulation of Plasma and Urine Metabolic Profiling.

OBJECTIVE: To elucidate the mechanism of Lizhong Decoction (LZD) in treating dextran sodium sulfate (DSS)-induced colitis in mice based on metabonomics. METHODS: Thirty-six mice were randomly divided into 6 groups, including normal, model, low- (1.365 g/kg), medium- (4.095 g/kg) and high dose (12.285 g/kg) LZD and salazosulfadimidine (SASP) groups, 6 mice in each group. Colitis model mice were induced by DSS admistration for 7 days, and treated with low, medium and high dose LZD extract and positive drug SASP. Metabolic comparison of DSS-induced colitis and normal mice was investigated by using ultra-performance liquid chromatography coupled to quadrupole time-of-flight mass (UPLC-Q-TOF/MS) combined with Metabolynx™ software. RESULTS: The metabolic profiles of plasma and urine in colitis mice were distinctly ameliorated after LZD treatment (P<0.05). Potential biomarkers (9 in serum and 4 in urine) were screened and tentatively identified. The endogenous metabolites were mainly involved in primary bile acid, sphingolipid, linoleic acid, arachidonic acid, amino acids (alanine, aspartate, and glutamate), butanoate and glycerophospholipid metabolism in plasma, and terpenoid backbone biosynthesis, glycerophospholipid and tryptophan metabolism in urine. After LZD treatment, these markers notably restored to normal levels. CONCLUSIONS: The study revealed the underlying mechanism of LZD on amelioration of ulcerative colitis based on metabonomics, which laid a foundation for further exploring the pathological and physiological mechanism, early diagnosis, and corresponding drug development of colitis.

Thorough QT/QTc Study Evaluating the Effect of Macimorelin on Cardiac Safety Parameters in Healthy Participants.

Macimorelin is an orally active growth hormone secretagogue indicated for the diagnosis of adult growth hormone deficiency. The primary objective of this study was to evaluate the effect of macimorelin on the baseline and placebo-corrected mean QT interval using Fridericia's formula (ΔΔQTcF). Secondary objectives were to determine QTcF for moxifloxacin; evaluate the effects of macimorelin on other cardiac intervals (PR, QRS, RR), heart rate, and electrocardiogram morphology parameters; characterize pharmacokinetics; and assess safety of macimorelin. The phase 1 thorough QT/QTc study, designed according to the International Council for Harmonisation E14 guideline, was a randomized, placebo-controlled, double-blind, 3-way complete crossover study comparing the effect of macimorelin 2.0 mg/kg with placebo and moxifloxacin 400 mg (positive control). Data were collected over a 3-month span from male (n=36) and female participants (n=24) aged 18 to 55 years with body mass index between 18.5 and 30.0 kg/m2 . Fifty-six participants received all 3 treatments. The ΔΔQTcF for macimorelin showed a prolongation with a maximum mean value of 9.61 milliseconds (2-sided 90% confidence interval, 7.81 milliseconds and 11.41 milliseconds) at 4 hours after dosing. The 2-sided 90% confidence interval of this value also exceeded the 10 millisecond threshold at 3 hours after dosing. Assay sensitivity was confirmed with moxifloxacin. Other electrocardiogram parameters evaluated were not influenced by macimorelin. Macimorelin did not raise other safety concerns and was well tolerated. In summary, a single supratherapeutic dose of macimorelin prolonged cardiac repolarization according to the regulatory guideline.

Inconsistencies in the Nutrition Management of Glutaric Aciduria Type 1: An International Survey.

Glutaric aciduria type 1 (GA-1) is a cerebral organic aciduria characterized by striatal injury and progressive movement disorder. Nutrition management shifted from a general restriction of intact protein to targeted restriction of lysine and tryptophan. Recent guidelines advocate for a low-lysine diet using lysine-free, tryptophan-reduced medical foods. GA-1 guideline recommendations for dietary management of patients over the age of six are unclear, ranging from avoiding excessive intake of intact protein to counting milligrams of lysine intake. A 22-question survey on the nutrition management of GA-1 was developed with the goal of understanding approaches to diet management for patients identified by newborn screening under age six years compared to management after diet liberalization, as well as to gain insight into how clinicians define diet liberalization. Seventy-six responses (25% of possible responses) to the survey were received. Nutrition management with GA-1 is divergent among surveyed clinicians. There was congruency among survey responses to the guidelines, but there is still uncertainty about how to counsel patients on diet optimization and when diet liberalization should occur. Ongoing clinical research and better understanding of the natural history of this disease will help establish stronger recommendations from which clinicians can best counsel families.

Hypothesis: Metabolic targeting of 5-aminolevulinate synthase by tryptophan and inhibitors of heme utilisation by tryptophan 2,3-dioxygenase as potential therapies of acute hepatic porphyrias.

Metabolic targeting of liver 5-aminolevulinate synthase (5-ALAS) by inhibition of heme utilisation by tryptophan (Trp) 2,3-dioxygenase (TDO) or the use of tryptophan is proposed as a therapy of acute hepatic porphyrias. 5-ALAS, the rate-limiting enzyme of heme biosynthesis, is under negative feedback control by a small regulatory heme pool in the hepatic cytosol. Acute porphyric attacks, precipitated by fasting, certain hormones and some drugs, involve induction of 5-ALAS secondarily to depletion of the above pool, and the resultant elevation of 5-ALA levels initiates the abdominal and neurological symptoms of attacks. By utilising the regulatory heme, cytosolic TDO undermines the feedback control, thus allowing 5-ALAS induction to occur, e.g. upon glucocorticoid induction of TDO during fasting (starvation) and exogenous glucocorticoid administration. Currently, glucose therapy is the preferred strategy for reversing moderate attacks induced by fasting (calorie restriction), with more severe attacks being treated by intravenous heme preparations. Reversal of fasting-induced attacks by glucose is explained by the previously demonstrated reversal of increased heme utilisation by TDO. Inhibitors of this utilisation are therefore potential therapeutic targets in acute attacks and also for maintenance of a symptomless state. Existing TDO inhibitors other than glucose include allopurinol, nicotinamide and recently developed potent inhibitors such as LM10 used in cancer therapy. Based on studies in rats, the hypothesis predicts that the safety or otherwise of drugs in the hepatic porphyrias is determined by their ability to inhibit TDO utilisation of heme under basal conditions or after glucocorticoid induction or heme activation of TDO, in parallel with reciprocal changes in 5-ALAS induction. Tryptophan is also proposed as a potential therapy of acute attacks either alone or as an adjunct to the recently proposed 5-ALAS1 gene silencing. Trp increases heme biosynthesis by enhancing 5-ALA dehydratase activity and, based on a Trp-5-ALA model presented herein, Trp offers several advantages over heme therapy, namely rapid conversion of 5-ALA into heme, a greatly enhanced heme availability, a near complete inhibition of 5-ALAS induction, assumed rapid clearance of 5-ALA and hence accelerated resolution of symptoms of attacks, and finally provision of the neuroprotective metabolite kynurenic acid to neutralise the neurological symptoms. The hypothesis also addresses heme regulation in species lacking the TDO free apoenzyme and its glucocorticoid induction mechanism and proposes detailed assessment of heme biosynthesis in these species. Detailed proposals for testing the hypothesis are presented.

Negative effects on newborn piglets caused by excess dietary tryptophan in the morning in sows.

BACKGROUND: This study investigated the effect of dynamic feeding models of dietary tryptophan on sows' performance during late pregnancy. RESULTS: The average piglet birth weight and live farrowing rate from sows consuming a high-low tryptophan diet (0.39% Trp in the morning and 0.13% Trp in the afternoon) were decreased compared with those fed a 2×tryptophan diet (0.26% Trp in the morning and afternoon). Compared with the 2×tryptophan group, sow serum kynurenic acid and the newborn liver n-6:n-3 polyunsaturated fatty acid ratio were significantly higher, and sow serum taurine and newborn serum taurine, phosphoserine, cysteine and proline were lower in the high-low tryptophan diet group. Eighty-eight genes were differentially expressed in newborn piglets' livers between the 2×tryptophan and high-low groups. Genes related to cytotoxic effector regulation (major histocompatibility complex class I proteins), NADH oxidation, reactive oxygen species (ROS) metabolism and tissue development were differentially expressed between these two groups. CONCLUSION: Together, the results provide information on new biomarkers in serum or liver and provide novel insights into variations in the fetal liver during exogenous stimulus response and biological processes of ROS metabolism in fetuses during late pregnancy caused by a single excessive tryptophan ingestion daily in the morning. © 2018 Society of Chemical Industry.

Macimorelin as a Diagnostic Test for Adult GH Deficiency.

Purpose: The diagnosis of adult GH deficiency (AGHD) is challenging and often requires confirmation with a GH stimulation test (GHST). The insulin tolerance test (ITT) is considered the reference standard GHST but is labor intensive, can cause severe hypoglycemia, and is contraindicated for certain patients. Macimorelin, an orally active GH secretagogue, could be used to diagnose AGHD by measuring stimulated GH levels after an oral dose. Materials and Methods: The present multicenter, open-label, randomized, two-way crossover trial was designed to validate the efficacy and safety of single-dose oral macimorelin for AGHD diagnosis compared with the ITT. Subjects with high (n = 38), intermediate (n = 37), and low (n = 39) likelihood for AGHD and healthy, matched controls (n = 25) were included in the efficacy analysis. Results: After the first test, 99% of macimorelin tests and 82% of ITTs were evaluable. Using GH cutoff levels of 2.8 ng/mL for macimorelin and 5.1 ng/mL for ITTs, the negative agreement was 95.38% (95% CI, 87% to 99%), the positive agreement was 74.32% (95% CI, 63% to 84%), sensitivity was 87%, and specificity was 96%. On retesting, the reproducibility was 97% for macimorelin (n = 33). In post hoc analyses, a GH cutoff of 5.1 ng/mL for both tests resulted in 94% (95% CI, 85% to 98%) negative agreement, 82% (95% CI, 72% to 90%) positive agreement, 92% sensitivity, and 96% specificity. No serious adverse events were reported for macimorelin. Conclusions: Oral macimorelin is a simple, well-tolerated, reproducible, and safe diagnostic test for AGHD with accuracy comparable to that of the ITT. A GH cutoff of 5.1 ng/mL for the macimorelin test provides an excellent balance between sensitivity and specificity.

Effects of Intragastric Administration of Tryptophan on the Blood Glucose Response to a Nutrient Drink and Energy Intake, in Lean and Obese Men.

Tryptophan stimulates plasma cholecystokinin and pyloric pressures, both of which slow gastric emptying. Gastric emptying regulates postprandial blood glucose. Tryptophan has been reported to decrease energy intake. We investigated the effects of intragastric tryptophan on the glycaemic response to, and gastric emptying of, a mixed-nutrient drink, and subsequent energy intake. Lean and obese participants (n = 16 each) received intragastric infusions of 1.5 g ("Trp-1.5g") or 3.0 g ("Trp-3.0g") tryptophan, or control, and 15 min later consumed a mixed-nutrient drink (56 g carbohydrates). Gastric emptying (13C-acetate breath-test), blood glucose, plasma C-peptide, glucagon, cholecystokinin and tryptophan concentrations were measured (t = 0-60 min). Energy intake was assessed between t = 60-90 min. In lean individuals, Trp-3.0g, but not Trp-1.5g, slowed gastric emptying, reduced C-peptideAUC and increased glucagonAUC (all P < 0.05), but did not significantly decrease the blood glucose response to the drink, stimulate cholecystokinin or reduce mean energy intake, compared with control. In obese individuals, Trp-3.0g, but not Trp-1.5g, tended to slow gastric emptying (P = 0.091), did not affect C-peptideAUC, increased glucagonAUC (P < 0.001) and lowered blood glucose at t = 30 min (P < 0.05), and did not affect cholecystokinin or mean energy intake. In obese individuals, intragastrically administered tryptophan may reduce postprandial blood glucose by slowing gastric emptying; the lack of effect on mean energy intake requires further investigation.

Metabolomic association between venous thromboembolism in critically ill trauma patients and kynurenine pathway of tryptophan metabolism.

OBJECTIVE: Incidence of venous thromboembolism (VTE) in critically ill patients remains unacceptably high despite widespread use of thromboprophylaxis. A systems biology approach may be useful in understanding disease pathology and predicting response to treatment. Metabolite profile under specific environmental conditions provides the closest link to phenotype, but the relationship between metabolomics and risk of VTE in critically ill patients is unknown. In this study, metabolomics signatures are compared in patients with and without VTE. DESIGN: Multicenter case-control study using prospectively collected data from the Inflammation and Host Response to Injury program, with pathway and in silico gene expression analyses. SETTING: Eight level 1 US trauma centers. PATIENTS: Critically ill adults with blunt trauma who developed VTE within the first 28 days of hospitalization compared to patients without VTE (N-VTE). INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: Patients included in the study (n = 20 VTE, n = 20 N-VTE) were mean age of 34 years, injury severity score of 35, and VTE diagnosed a median of 10.5 days after admission. Global metabolomics revealed two kynurenine metabolites, N-formylkynurenine (AUC = 0.77; 95% CI: 0.59-0.89) and 5-hydroxy-N-formylkynurenine (AUC = 0.80; 95% CI:0.63-0.90) significantly discriminated VTE and N-VTE; ratio between N-formylkynurenine/5-hydroxy-N-formylkynurenine improved predictive power (AUC = 0.87; 95% CI: 0.74-0.95). In the pathway analysis, tryptophan was the only significant metabolic pathway including N-formylkynurenine and 5-hydroxy-N-formylkynurenine (p < 0.001), and 8 proteins directly or indirectly interacted with these metabolites in the interaction network analysis. Of the 8 genes tested in the in silico gene expression analyses, KYNU (p < 0.001), CCBL1 (p < 0.001), and CCBL2 (p = 0.001) were significantly different between VTE and N-VTE, controlling for age and sex. CONCLUSIONS: Two novel kynurenine metabolites in the tryptophan pathway associated with hospital-acquired VTE, and 3 candidate genes were identified via pathway and interaction network analyses. Future studies are warranted to validate these findings in diverse populations using a multi-omics approach.

Dietary Tryptophan Restriction Dose-Dependently Modulates Energy Balance, Gut Hormones, and Microbiota in Obesity-Prone Rats.

OBJECTIVE: To determine the effects of graded dietary restriction of tryptophan on food intake, energy expenditure, body composition, gut hormones, and select fecal bacterial populations in obesity-prone rats. METHODS: Obesity-prone rats were randomized to isocaloric diets with varying degrees of tryptophan restriction: control (100% requirements), 70% tryptophan (70TRP), 40% tryptophan (40TRP), or 10% tryptophan (10TRP) for 21 days. The sympathetic system was challenged with a subcutaneous injection of propranolol on days 15 to 17. Measurements included food intake, energy expenditure, body composition, metabolic hormones, and fecal concentrations of select bacteria. RESULTS: Moderate tryptophan restriction (70TRP) induced thermogenesis without altering body composition, whereas severe degrees of restriction (40TRP, 10TRP) produced profound hypophagia and decreased energy expenditure and body weight. The thermogenic effects of moderate tryptophan restriction were sympathetically mediated. Severe tryptophan restriction decreased fasting circulating concentrations of glucose, insulin, C-peptide, and leptin, but increased glucagon, pancreatic polypeptide, and glucagon-like peptide-1. Severe tryptophan restriction decreased fecal concentrations of Enterobacteriaceae, Lactobacillus, Bacteroides, and Clostridium coccoides while increasing Roseburia groups. CONCLUSIONS: Our findings demonstrate that dietary tryptophan restriction dose-dependently modulates energy balance, with severe restriction causing hypophagia and weight loss and moderate restriction promoting sympathetically driven thermogenesis as well as concurrent changes in gut microbiota and hormones.

Association between habitual tryptophan intake and depressive symptoms in young and middle-aged women.

BACKGROUND: The intake of tryptophan, the precursor of serotonin, is assumed to affect serotonin availability and depression onset. Nevertheless, a definitive relationship between dietary tryptophan intake and depressive symptoms has not been established. We examined the association between tryptophan intake and depressive symptoms screened in a group of 4272 first-year female dietetic students and 3651 their mothers. METHODS: Dietary tryptophan intake during the preceding month was assessed with a validated, self-administered diet history questionnaire. Depressive symptoms were assessed with the Center for Epidemiologic Studies Depression Scale (CES-D) using two cutoff scores: CES-D score ≥ 16 and CES-D score ≥ 19 (the optimal cutoff score for Japanese people). The multivariate adjusted prevalence ratio (PR) and 95% confidence interval (CI) for depressive symptoms were calculated using Poisson regression analysis. RESULTS: The prevalence of depressive symptoms (CES-D score ≥ 16) was 50.0% for young women and 26.5% for middle-aged women. The adjusted PR (95% CI) for depressive symptoms in the highest versus lowest quintile of tryptophan intake was 0.84 (0.75, 0.93) in young women (P for trend < 0.0001) and 0.83 (0.64, 1.01) in middle-aged women (P for trend < 0.0001). These associations were stable even when depressive symptoms were defined as a CES-D score ≥ 19. LIMITATIONS: This is a cross-sectional study. Depressive symptoms were assessed using a self-reported questionnaire. CONCLUSIONS: This cross-sectional study showed that a higher tryptophan intake was independently associated with a lower prevalence of depressive symptoms in young Japanese women.

Structure determination of disease associated peak AAA from l-Tryptophan implicated in the eosinophilia-myalgia syndrome.

The eosinophilia-myalgia syndrome (EMS) outbreak of 1989 that occurred in the USA and elsewhere was caused by the ingestion of l-Tryptophan (L-Trp) solely manufactured by the Japanese company Showa Denko K.K. (SD). Six compounds present in the SD L-Trp were reported to be case-associated contaminants. However, "one" of these compounds, Peak AAA has remained structurally uncharacterized, despite the fact that it was described as "the only statistically significant (p=0.0014) contaminant". Here, we employ on-line microcapillary-high performance liquid chromatography-electrospray ionization mass spectrometry (LC-MS), and tandem mass spectrometry (MS/MS) to determine that Peak AAA is in fact two structurally related isomers. Peak AAA1 and Peak AAA2 differed in LC retention times, and were determined by accurate mass-LC-MS to both have a protonated molecular ion (MH+) of mass 343.239Da (Da), corresponding to a molecular formula of C21H30N2O2, and possessing eight degrees of unsaturation (DoU) for the non-protonated molecule. By comparing the LC-MS and LC-MS-MS retention times and spectra with authentic synthetic standards, Peak AAA1 was identified as the intermolecular condensation product of L-Trp with anteiso 7-methylnonanoic acid, to afford (S)-2-amino-3-(2-((S,E)-7-methylnon-1-en-1-yl)-1H-indol-3-yl)propanoic acid. Peak AAA2 was determined to be a condensation product of L-Trp with decanoic acid, which produced (S)-2-amino-3-(2-((E)-dec-1-en-1-yl)-1H-indol-3-yl)propanoic acid.

A Perspective on the Safety of Supplemental Tryptophan Based on Its Metabolic Fates.

Over the past 50 y, tryptophan has been ingested in amounts well in excess of its dietary requirement. This use is based on extensive findings that ingesting tryptophan increases brain tryptophan concentrations, which stimulates the synthesis and release of the neurotransmitter serotonin, from which it is derived. Such increases in serotonin function may improve mood and sleep. However, tryptophan ingestion has other effects, such as increasing serotonin production in the gut, increasing serotonin concentrations in blood, stimulating the production of the hormone melatonin (a tryptophan metabolite), stimulating tryptophan metabolism via the kynurenine pathway, and possibly stimulating the production of tryptophan metabolites in the gut microbiome. Several of the kynurenine metabolites have actions on excitatory glutamate receptors in the gut and brain and on cells of the immune system. In addition, metabolites of tryptophan produced by colonic bacteria are reported to cause adverse effects in some species. This review examines each of these tryptophan pathways to determine if any of the metabolites increase after tryptophan ingestion, and if so, whether effects are seen on target body functions. In this regard, recent research suggests that it may be useful to examine kynurenine pathway metabolites and some microbial tryptophan metabolites to determine whether supplemental tryptophan consumption increases their concentrations in the body and amplifies their actions.

The Importance of Quality Specifications in Safety Assessments of Amino Acids: The Cases of l-Tryptophan and l-Citrulline.

The increasing consumption of amino acids from a wide variety of sources, including dietary supplements, natural health products, medical foods, infant formulas, athletic and work-out products, herbal medicines, and other national and international categories of nutritional and functional food products, increases the exposure to amino acids to amounts far beyond those normally obtained from the diet, thereby necessitating appropriate and robust safety assessments of these ingredients. Safety assessments of amino acids, similar to all food constituents, largely rely on the establishment of an upper limit [Tolerable Upper Intake Level (UL)] considered to be a guide for avoiding high intake, above which adverse or toxic effects might occur. However, reliable ULs have been difficult or impossible to define for amino acids because of inadequate toxicity studies in animals and scarce or missing clinical data, as well as a paucity or absence of adverse event reporting data. This review examines 2 amino acids that have been associated with in-market adverse events to show how quality specifications might have helped prevent the adverse clinical outcomes. We further highlight the importance of various factors that should be incorporated into an overall safety assessment of these and other amino acids. In addition to the traditional reliance on the established UL, well-defined quality specifications, review of synthesis and production strategies, potential interactions with drugs, contraindications with certain disease states, and cautionary use within certain age groups should all be taken into consideration.

Proposals for Upper Limits of Safe Intake for Arginine and Tryptophan in Young Adults and an Upper Limit of Safe Intake for Leucine in the Elderly.

On the basis of research presented during the 9th Amino Acid Assessment Workshop, a No Observed Adverse Effect Level (NOAEL) for diet-added arginine (added mostly in the form of dietary supplements) of 30 g/d and an upper limit of safe intake (ULSI) for diet-added tryptophan (added mostly in the form of dietary supplements) of 4.5 g/d have been proposed. Both recommendations apply to healthy young adults. The total dietary leucine ULSI proposed for elderly individuals is 500 mg · kg-1 · d-1 All 3 recommendations are relevant only to high-quality amino acid-containing products with specifications corresponding to those listed in the US Pharmacopeia Because the above amino acids are extensively utilized as dietary supplements for various real or perceived benefits, such as vasodilation, spermatogenesis, sleep, mood regulation, or muscle recovery, the above safety recommendations will have an important impact on regulatory and nutritional practices.