Nanodelivery Optimization of IDO1 Inhibitors in Tumor Immunotherapy: Challenges and Strategies.

Tryptophan (Trp) metabolism plays a vital role in cancer immunity. Indoleamine 2.3-dioxygenase 1 (IDO1), is a crucial enzyme in the metabolic pathway by which Trp is degraded to kynurenine (Kyn). IDO1-mediated Trp metabolites can inhibit tumor immunity and facilitate immune evasion by cancer cells; thus, targeting IDO1 is a potential tumor immunotherapy strategy. Recently, numerous IDO1 inhibitors have been introduced into clinical trials as immunotherapeutic agents for cancer treatment. However, drawbacks such as low oral bioavailability, slow onset of action, and high toxicity are associated with these drugs. With the continuous development of nanotechnology, medicine is gradually entering an era of precision healthcare. Nanodrugs carried by inorganic, lipid, and polymer nanoparticles (NPs) have shown great potential for tumor therapy, providing new ways to overcome tumor diversity and improve therapeutic efficacy. Compared to traditional drugs, nanomedicines offer numerous significant advantages, including a prolonged half-life, low toxicity, targeted delivery, and responsive release. Moreover, based on the physicochemical properties of these nanomaterials (eg, photothermal, ultrasonic response, and chemocatalytic properties), various combination therapeutic strategies have been developed to synergize the effects of IDO1 inhibitors and enhance their anticancer efficacy. This review is an overview of the mechanism by which the Trp-IDO1-Kyn pathway acts in tumor immune escape. The classification of IDO1 inhibitors, their clinical applications, and barriers for translational development are discussed, the use of IDO1 inhibitor-based nanodrug delivery systems as combination therapy strategies is summarized, and the issues faced in their clinical application are elucidated. We expect that this review will provide guidance for the development of IDO1 inhibitor-based nanoparticle nanomedicines that can overcome the limitations of current treatments, improve the efficacy of cancer immunotherapy, and lead to new breakthroughs in the field of cancer immunotherapy.

Biopharmaceutical studies of a novel sedative sublingual lozenge based on glycine and tryptophan: A rationale for mucoadhesive agent selection.

Effective sedative drugs are in great demand due to increasing incidence of nervous disorders. The present work was aimed to develop a novel sublingual sedative drug based on glycine and L-tryptophan amino acids. Carbopol and different hydroxypropyl methylcellulose species were alternatively tested as mucoadhesive agents intended to prolong tryptophan sublingual release time. A model lipid medium of fully hydrated L-α-dimyristoylphosphatidylcholine was used for optimal mucoadhesive agents selection. Simultaneous processes of drug release and diffusion in lipid medium were first investigated involving both experimental and theoretical approaches. Individual substances, their selected combinations as well as different drug formulations were consecutively examined. Application of kinetic differential scanning calorimetry method allowed us to reveal a number of specific drug-excipient effects. Lactose was found to essentially facilitate tryptophan release and provide its ability to get into the bloodstream simultaneously with glycine, which is necessary to achieve glycine-tryptophan synergism. Introduction of a mucoadhesive agent into the formulation was shown to change kinetics of drug-membrane interactions variously depending on viscosity grade. Among the mucoadhesive agents, hydroxypropyl methylcellulose species K4M and E4M were shown to further accelerate drug release, therefore they were selected as optimal. Thus, effectiveness of the novel sedative drug was provided by including some excipients, such as lactose and the selected mucoadhesive agent species. A dynamic mathematical model was developed properly describing release and diffusion in lipid medium of various drug substances. Our study clearly showed applicability of a lipid medium to meet challenges such as drug-excipient interactions and optimization of drug formulations.

Cathepsin B-Activatable Bioactive Peptide Nanocarrier for High-Efficiency Immunotherapy of Asthma.

Introduction: Asthma, a chronic respiratory disease closely associated with inflammation, presents ongoing treatment challenges. IALLIPF (le-Ala-Leu-Leu-Ile-Pro-Phe) is one of millet prolamins peptides (MPP) which shows anti-oxidant bioactivity by reducing the production of reactive oxygen species (ROS). Tryptophan (Trp, W) is an amino acid that has been demonstrated to possess anti-inflammatory effects. We introduce a novel cathepsin B-activatable bioactive peptides nanocarrier, PEG-IALLIPF-GFLG-W (MPP-Trp), designed for immunotherapy of asthma. Methods: MPP-Trp is synthesized, purified, and its characteristics are investigated by dynamic light scattering (DLS) and transmission electron microscopy (TEM). The yield of nitric oxide (NO) and pro-inflammatory cytokines (TNF-α, IL-6 and IL-1ß) are examined to evaluate anti-inflammatory effects of IALLIPF, Trp and MPP-Trp. The immunomodulatory effects of IALLIPF, Trp and MPP-Trp on Th1/Th2 cell populations and cytokines are investigated by flow cytometry, qRT-PCR and ELISA assays. We explore the therapeutic effect of MPP-Trp in the mouse model of asthma by the analysis of lung histology and ELISA. It is necessary to study the biocompatibility of MPP-Trp by CCK8 assay and histopathologic analysis using hematoxylin and eosin (HE) staining. Results: In asthmatic peripheral blood mononuclear cells (PBMCs), IALLIPF, Trp and MPP-Trp are able to significantly alleviate inflammation by inhibiting the yield of nitric oxide (NO) and pro-inflammatory cytokines (TNF-α, IL-6 and IL-1ß), especially MPP-Trp. MPP-Trp significantly upregulates Th1 cell levels while notably reducing Th2 cell levels. Furthermore, MPP-Trp effectively elevates the expression and production of interferon-gamma (IFN-γ), an essential cytokine from Th1 cells. Additionally, MPP-Trp markedly diminishes the mRNA expression and levels of key asthma pathogenesis cytokines, such as interleukin-4 (IL-4), interleukin-13 (IL-13), and interleukin-5 (IL-5), in asthma PBMCs. MPP-Trp ameliorates pulmonary pathological alterations and significantly inhibits OVA-induced inflammation in mice with asthma. It has little influence on the cell viability in Asthma-PBMCs treated with various concentrations or durations of MPP-Trp. No pathological changes, including in the heart, liver, spleen, lung, and kidney tissues, are observed in non-sensitized and non-challenged mice treated with MPP-Trp (20 mg/kg). Discussion: Our research demonstrates that MPP-Trp has immunomodulatory effects on Th1/Th2 cell populations, essential in managing asthma. It considerably alleviates OVA-induced asthma by shifting the immune response towards a Th1-dominant profile, thereby reducing Th2-driven inflammation. Therefore, this novel bioactive peptide nanocarrier, MPP-Trp, holds promise as a candidate for asthma immunotherapy.

Targeting Divergent Pathways in the Nutritional Management of Depression.

The nutritional management of depression has long been discussed, due to the perceived benefit of a nutritional product having less side effects than pharmaceutical agents. Candidate nutrients for managing depression include vitamin D, B vitamins, tryptophan, branch chain amino acids, probiotics, omega-3 fatty acids, folate/methylfolate (also known as vitamin B9), and s-adenosylmethionine. This paper provides a narrative review of three nutrients which have significant scientific support for the management of depression. A deficiency in each nutrient is associated with depression, and interventional studies indicate that the correction of the nutritional deficiency may provide clinical benefit. We present epidemiological evidence, a mechanistic explanation and a review of interventional studies for these nutrients. Finally, relevant nutritional guidelines are presented with their conclusion for the role of each nutrient in the management of depression.

Intraduodenal calcium enhances the effects of L-tryptophan to stimulate gut hormone secretion and suppress energy intake in healthy males: a randomized, crossover, clinical trial.

BACKGROUND: In humans, intraduodenal infusion of L-tryptophan (Trp) increases plasma concentrations of gastrointestinal hormones and stimulates pyloric pressures, both key determinants of gastric emptying and associated with potent suppression of energy intake. The stimulation of gastrointestinal hormones by Trp has been shown, in preclinical studies, to be enhanced by extracellular calcium and mediated in part by the calcium-sensing receptor. OBJECTIVES: This study aim was to determine whether intraduodenal calcium can enhance the effects of Trp to stimulate gastrointestinal hormones and pyloric pressures and, if so, whether it is associated with greater suppression of energy intake, in healthy males. METHODS: Fifteen males with normal weight (mean ± standard deviation; age: 26 ± 7 years; body mass index: 22 ± 2 kg/m2), received on 3 separate occasions, 150-min intraduodenal infusions of 0, 500, or 1000 mg calcium (Ca), each combined with Trp (load: 0.1 kcal/min, with submaximal energy intake-suppressant effects) from t = 75-150 min, in a randomized, double-blind, crossover study. Plasma concentrations of GI hormones [gastrin, cholecystokinin, glucose-dependent insulinotropic polypeptide (GIP), glucagon-like peptide (GLP)-1, and peptide tyrosine-tyrosine (PYY)], and Trp and antropyloroduodenal pressures were measured throughout. Immediately postinfusions (t = 150-180 min), energy intake at a standardized buffet-style meal was quantified. RESULTS: In response to calcium alone, both 500- and 1000-mg doses stimulated PYY, while only the 1000-mg dose stimulated GLP-1 and pyloric pressures (all P < 0.05). The 1000-mg dose also enhanced the effects of Trp to stimulate cholecystokinin and GLP-1, and both doses stimulated PYY but, surprisingly, reduced the stimulation of GIP (all P < 0.05). Both doses substantially and dose dependently enhanced the effects of Trp to suppress energy intake (Ca-0+Trp: 1108 ± 70 kcal; Ca-500+Trp: 961 ± 90 kcal; and Ca-1000+Trp: 922 ± 96 kcal; P < 0.05). CONCLUSIONS: Intraduodenal administration of calcium enhances the effect of Trp to stimulate plasma cholecystokinin, GLP-1, and PYY and suppress energy intake in healthy males. These findings have potential implications for novel nutrient-based approaches to energy intake regulation in obesity. The trial was registered at the Australian New Zealand Clinical Trial Registry (www.anzctr.org.au) as ACTRN12620001294943).

Sleep Patterns and Tryptophan Consumption among Students at Spanish Universities: The Unihcos Project.

The objective of this cross-sectional study was to explore sleep patterns and the potential relationship between sleep and tryptophan intake among Spanish university students. A total of 11,485 students self-reported their sleep and dietary patterns and habits. Tryptophan intake was calculated using a food intake matrix and results were presented as quartiles of total intake. Short sleep duration prevalence was 51.0%, with males exhibiting a significantly higher frequency. A total of 55.0% of participants presented inadequate sleep efficiency, with males again presenting a higher rate. Median tryptophan intake was 692.16 ± 246.61 mg/day, 731.84 ± 246.86 mg/day in males and 677.24 ± 244.87 mg/day in females (p = 0.001). Dietary tryptophan intake below the first quartile (<526.43 mg/day) was associated with a higher risk of short sleep duration in males (1.26; 95%CI: 1.02-1.55) and females (1.19; 95%CI: 1.05-1.34) and with the Athens Insomnia Scale insomnia in males (2.56; 95%CI: 1.36-4.82) and females (1.47; 95%CI: 1.10-2.05). Regarding academic specializations, females in the humanities field showed a higher risk of Athens Insomnia Scale insomnia due to low tryptophan intake (Q1: 3.15; 95% CI: 1.04-9.55 and Q2: 3.41; 95%CI: 1.01-11.5). In summary, lower tryptophan consumption appears to be associated with poorer sleep quality in Spanish university students; however, other social factors affecting students may also influence sleep quality. These findings have important implications for nutritional recommendations aimed at enhancing tryptophan intake to improve sleep quality.

Oral tryptophan activates duodenal aryl hydrocarbon receptor in healthy subjects: a crossover randomized controlled trial.

Tryptophan is an essential amino acid transformed by host and gut microbial enzymes into metabolites that regulate mucosal homeostasis through aryl hydrocarbon receptor (AhR) activation. Alteration of tryptophan metabolism has been associated with chronic inflammation; however, whether tryptophan supplementation affects the metabolite repertoire and AhR activation under physiological conditions in humans is unknown. We performed a randomized, double blind, placebo-controlled, crossover study in 20 healthy volunteers. Subjects on a low tryptophan background diet were randomly assigned to a 3-wk l-tryptophan supplementation (3 g/day) or placebo, and after a 2-wk washout switched to opposite interventions. We assessed gastrointestinal and psychological symptoms by validated questionnaires, AhR activation by cell reporter assay, tryptophan metabolites by liquid chromatography and high-resolution mass spectrometry, cytokine production in isolated monocytes by ELISA, and microbiota profile by 16S rRNA Illumina technique. Oral tryptophan supplementation was well tolerated, with no changes in gastrointestinal or psychological scores. Compared with placebo, tryptophan increased AhR activation capacity by duodenal contents, but not by feces. This was paralleled by higher urinary and plasma kynurenine metabolites and indoles. Tryptophan had a modest impact on fecal microbiome profiles and no significant effect on cytokine production. At the doses used in this study, oral tryptophan supplementation in humans induces microbial indole and host kynurenine metabolic pathways in the small intestine, known to be immunomodulatory. The results should prompt tryptophan intervention strategies in inflammatory conditions of the small intestine where the AhR pathway is impaired.NEW & NOTEWORTHY We demonstrate that in healthy subjects, orally administered tryptophan activates microbial indole and host kynurenine pathways in the small intestine, the primary metabolic site for dietary components, and the richest source of immune cells along the gut. This study provides novel insights in how to optimally activate immunomodulatory AhR pathways and indole metabolism in the small intestine, serving as basis for future therapeutic trials using l-tryptophan supplementation in chronic inflammatory conditions affecting the small intestine.

Dopamine receptor D2 confers colonization resistance via microbial metabolites.

The gut microbiome has major roles in modulating host physiology. One such function is colonization resistance, or the ability of the microbial collective to protect the host against enteric pathogens1-3, including enterohaemorrhagic Escherichia coli (EHEC) serotype O157:H7, an attaching and effacing (AE) food-borne pathogen that causes severe gastroenteritis, enterocolitis, bloody diarrhea and acute renal failure4,5 (haemolytic uremic syndrome). Although gut microorganisms can provide colonization resistance by outcompeting some pathogens or modulating host defence provided by the gut barrier and intestinal immune cells6,7, this phenomenon remains poorly understood. Here, we show that activation of the neurotransmitter receptor dopamine receptor D2 (DRD2) in the intestinal epithelium by gut microbial metabolites produced upon dietary supplementation with the essential amino acid L-tryptophan protects the host against Citrobacter rodentium, a mouse AE pathogen that is widely used as a model for EHEC infection8,9. We further find that DRD2 activation by these tryptophan-derived metabolites decreases expression of a host actin regulatory protein involved in C. rodentium and EHEC attachment to the gut epithelium via formation of actin pedestals. Our results reveal a noncanonical colonization resistance pathway against AE pathogens that features an unconventional role for DRD2 outside the nervous system in controlling actin cytoskeletal organization in the gut epithelium. Our findings may inspire prophylactic and therapeutic approaches targeting DRD2 with dietary or pharmacological interventions to improve gut health and treat gastrointestinal infections, which afflict millions globally.

Tryptophan intake and pancreatic cancer: findings from a case-control study.

BACKGROUND: Pancreatic cancer is a leading cause of cancer-related death worldwide. Tryptophan plays a vital role in cell growth and maintenance as a building block of protein and coordination of organismal responses to environmental and dietary cues. Animal model study showed that dietary tryptophan improved treatment response in those who received chemotherapy or immune checkpoint inhibitors. Limited data are available assessing the association between tryptophan intake and risk of pancreatic cancer. We aimed to evaluate this association in a case-control study in Vietnam. METHODS: We analyzed data from a case-control study, including 3759 cancer cases and 2995 control subjects of whom 37 with pancreatic cancer cases. Tryptophan intake was derived from food frequency questionnaire. Unconditional logistic regression was used to calculate odds ratios (ORs) and 95% confidence intervals (CIs) for different levels of tryptophan intake with pancreatic cancer risk. RESULTS: Overall, tryptophan intake was inversely associated with pancreatic cancer risk in a dose-dependent manner. The ORs and 95% CIs of pancreatic cancer were 0.51 (0.29-0.92) for continuous scale, 0.27 (0.10-0.73) for tertile 2 and 0.34 (0.11-1.06) for tertile 3, compared with tertile 1 (the lowest intake) ( Ptrend = 0.02). In stratified analysis, this inverse association pattern was present among those with BMI < 23 kg/m 2 and ever drinkers. CONCLUSION: A diet with a higher intake of tryptophan was significantly associated with a lower incidence of pancreatic cancer among Vietnamese population. These suggest that dietary modification may be an effective strategy for primary prevention of pancreatic cancer development.

The Modulatory Activity of Tryptophan Displaying Nanodevices on Macrophage Activation for Preventing Acute Lung Injury.

Macrophages play an important role in the initiation, progression and resolution of inflammation in many human diseases. Effective regulation of their activation and immune responses could be a promising therapeutic strategy to manage various inflammatory conditions. Nanodevices that naturally target macrophages are ideal agents to regulate immune responses of macrophages. Here we described a special tryptophan (Trp)-containing hexapeptide-coated gold nanoparticle hybrid, PW, which had unique immunomodulatory activities on macrophages. The Trp residues enabled PW higher affinity to cell membranes, and contributed to inducing mild pro-inflammatory responses of NF-κB/AP-1 activation. However, in the presence of TLR stimuli, PW exhibited potent anti-inflammatory activities through inhibiting multiple TLR signaling pathways. Mechanistically, PW was internalized primarily through micropinocytosis pathway into macrophages and attenuated the endosomal acidification process, and hence preferentially affected the endosomal TLR signaling. Interestingly, PW could induce the expression of the TLR negative regulator IRAK-M, which may also contribute to the observed TLR inhibitory activities. In two acute lung injury (ALI) mouse models, PW could effectively ameliorate lung inflammation and protect lung from injuries. This work demonstrated that nanodevices with thoughtful design could serve as novel immunomodulatory agents to manage the dysregulated inflammatory responses for treating many chronic and acute inflammatory conditions, such as ALI.

Discovery and Preclinical Pharmacology of an Oral Bromodomain and Extra-Terminal (BET) Inhibitor Using Scaffold-Hopping and Structure-Guided Drug Design.

Inhibition of the bromodomain and extra-terminal (BET) family of adaptor proteins is an attractive strategy for targeting transcriptional regulation of key oncogenes, such as c-MYC. Starting with the screening hit 1, a combination of structure-activity relationship and protein structure-guided drug design led to the discovery of a differently oriented carbazole 9 with favorable binding to the tryptophan, proline, and phenylalanine (WPF) shelf conserved in the BET family. Identification of an additional lipophilic pocket and functional group optimization to optimize pharmacokinetic (PK) properties culminated in the discovery of 18 (BMS-986158) with excellent potency in binding and functional assays. On the basis of its favorable PK profile and robust in vivo activity in a panel of hematologic and solid tumor models, BMS-986158 was selected as a candidate for clinical evaluation.

Dietary Tryptophan Supplementation Alters Fat and Glucose Metabolism in a Low-Birthweight Piglet Model.

Low birthweight (LBW) is associated with metabolic complications, such as glucose and lipid metabolism disturbances in early life. The objective of this study was to assess: (1) the effect of dietary tryptophan (Trp) on glucose and fat metabolism in an LBW piglet model, and (2) the role peripheral 5-hydroxytryptamine type 3 (5HT3) receptors in regulating the feeding behavior in LBW piglets fed with Trp-supplemented diets. Seven-day-old piglets were assigned to 4 treatments: normal birthweight-0%Trp (NBW-T0), LBW-0%Trp (LBW-T0), LBW-0.4%Trp (LBW-T0.4), and LBW-0.8%Trp (LBW-T0.8) for 3 weeks. Compared to LBW-T0, the blood glucose was decreased in LBW-T0.8 at 60 min following the meal test, and the triglycerides were lower in LBW-T0.4 and LBW-T0.8. Relative to LBW-T0, LBW-T0.8 had a lower transcript and protein abundance of hepatic glucose transporter-2, a higher mRNA abundance of glucokinase, and a lower transcript of phosphoenolpyruvate carboxykinase. LBW-T0.4 tended to have a lower protein abundance of sodium-glucose co-transporter 1 in the jejunum. In comparison with LBW-T0, LBW-T0.4 and LBW-T0.8 had a lower transcript of hepatic acetyl-CoA carboxylase, and LBW-T0.4 had a higher transcript of 3-hydroxyacyl-CoA dehydrogenase. Blocking 5-HT3 receptors with ondansetron reduced the feed intake in all groups, with a transient effect on LBW-T0, but more persistent effect on LBW-T0.8 and NBW-T0. In conclusion, Trp supplementation reduced the hepatic lipogenesis and gluconeogenesis, but increased the glycolysis in LBW piglets. Peripheral serotonin is likely involved in the regulation of feeding behavior, particularly in LBW piglets fed diets supplemented with a higher dose of Trp.

Safety, Tolerability, Pharmacokinetics, and Pharmacodynamics of Macimorelin in Children with Suspected Growth Hormone Deficiency: An Open-Label, Group Comparison, Dose-Escalation Trial.

BACKGROUND/AIMS: Diagnosis of growth hormone deficiency (GHD) in children requires the use of provocative growth hormone (GH) stimulation tests, which can have limited reliability and are potentially contraindicated in some patients. This is the first paediatric study to test the safety, tolerability, and pharmacokinetics (PK)/pharmacodynamics (PD) of macimorelin, an oral GH secretagogue, approved for diagnosis of adult GHD. METHODS: In this open-label, group comparison, single-dose escalation trial (EudraCT 2018-001988-23), sequential cohorts of patients (C1-C3) received ascending single doses of macimorelin: 0.25 (C1), 0.5 (C2), and 1.0 (C3) mg/kg. Primary endpoints were safety and tolerability, and secondary endpoints were PK/PD. RESULTS: Twenty-four patients aged between 2 and <18 with suspected GHD participated in the study. No macimorelin-related adverse events were reported, and macimorelin was well tolerated. Plasma macimorelin concentrations increased with dose: mean areas under the curve were 6.69 (C1), 18.02 (C2), and 30.92 (C3) h × ng/mL; mean maximum concentrations were 3.46 (C1), 8.13 (C2), and 12.87 (C3) ng/mL. GH concentration increased following macimorelin administration: mean times of maximum measured concentration were 52.5 (C1), 37.5 (C2), and 37.5 (C3) min. CONCLUSION: All 3 doses of macimorelin had excellent safety and tolerability with PK/PD profiles in expected ranges. These results support the use of 1.0 mg/mL macimorelin in a Phase 3 test validation trial in children.

The efficacy of indoximod upon stimulation with pro-inflammatory cytokines in triple-negative breast cancer cells.

BACKGROUND: Indoleamine 2,3-dioxygenase (IDO) inhibition has received much attention in cancer immunotherapy due to its role in immune escape in cancer cells. Additionally, changes in the pro-inflammatory cytokine levels can affect tumor growth and metastasis as well as the effectiveness of immunotherapy. The purpose of this study was for the first time to determine the effects of indoximod as an IDO inhibitor on triple-negative breast cancer (TNBC) and to assess the link between the efficacy of indoximod and IFN-γ or TNF-α stimulation. METHODS: The cytotoxic and apoptotic effects of indoximod alone or IFN-γ or TNF-α induction to mimic an inflammatory environment were evaluated by WST-1, Annexin V, cell cycle analysis, and acridine orange (AO)/ethidium bromide (EtBr) staining. Furthermore, the expression levels of IDO1 and PD-L1 expression were analyzed by RT-PCR. RESULTS: Our results demonstrated that indoximod significantly decreased the TNBC cell viability through apoptotic cell death (p < .05). The combination of indoximod and TNF-α was more effective than indoximod and IFN-γ stimulation or indoximod alone in TNBC cells. Additionally, PD-L1 expression level was significantly up-regulated after treatment with indoximod and TNF-α or IFN-γ combinations (p < .05). CONCLUSIONS: Indoximod exhibited a therapeutic potential in TNBC cells and pro-inflammatory cytokines could affect the effectiveness of indoximod. However, further studies are required to identify the role of the IDO-associated signaling pathways, the molecular mechanisms of indoximod induced apoptotic cell death, and the relationship between IDO inhibition by IDO inhibitors and pro-inflammatory cytokine levels.

Effects of Tyrosine and Tryptophan Supplements on the Vital Indicators in Mice Differently Prone to Diet-Induced Obesity.

We studied the effects of the addition of large neutral amino acids, such as tyrosine (Tyr) and tryptophan (Trp), in mice DBA/2J and tetrahybrid mice DBCB receiving a high-fat, high-carbohydrate diet (HFCD) for 65 days. The locomotor activity, anxiety, muscle tone, mass of internal organs, liver morphology, adipokines, cytokines, and biochemical indices of animals were assessed. The Tyr supplementation potentiated increased anxiety in EPM and contributed to a muscle tone increase, a decrease in the AST/ALT ratio, and an increase in protein anabolism in both mice strains. Tyr contributed to a decrease in liver fatty degeneration and ALT reduction only in DBCB that were sensitive to the development of obesity. The addition of Trp caused an increase in muscle tone and potentiated an increase in anxiety with age in animals of both genotypes. Trp had toxic effects on the livers of mice, which was manifested in increased fatty degeneration in DBCB, edema, and the appearance of micronuclei in DBA/2J. The main identified effects of Tyr on mice are considered in the light of its modulating effect on the dopamine neurotransmitter metabolism, while for the Trp supplement, effects were presumably associated with the synthesis of its toxic metabolites by representatives of the intestinal microflora.

5-Methoxytryptophan attenuates postinfarct cardiac injury by controlling oxidative stress and immune activation.

AIMS: Myocardial infarction (MI) remains a major cause of heart failure. 5-Methoxytryptophan (5-MTP), a 5-methoxyindole metabolite of L-tryptophan, exerts anti-inflammatory and antifibrotic effects, but MI impairs the biosynthesis of cardiac 5-MTP. Therefore, we evaluated the effect of exogenous 5-MTP administration on rescuing post-MI cardiac injury. METHODS AND RESULTS: After a detailed pharmacokinetic analysis of 5-MTP, Sprague Dawley rats that had undergone left anterior descending coronary artery ligation received intraperitoneal administration of either 17 mg/kg 5-MTP or saline at 0.5 and 24 h after MI. Cardiac systolic function, infarction size, and fibrosis were evaluated using echocardiography, triphenyltetrazolium chloride staining, and Masson trichrome staining, respectively. Myocardial apoptosis was analyzed by staining for caspase-3 and cardiac troponin I. 5-MTP treatment decreased the infarct area and myocardial apoptosis; attenuated systolic dysfunction and left ventricular dilatation; and reduced cardiomyocyte hypertrophy, myocardial fibrosis, and infarct expansion. Crucially, 5-MTP alleviated oxidative stress by preserving mitochondrial antioxidant enzymes and downregulating reactive oxygen species-generating NADPH oxidase isoforms and endothelin-1. Consequently, 5-MTP-treated MI rat hearts exhibited lower levels of chemokines and cytokines, namely interleukin (IL)-1ß, IL-18, IL-6, C-C motif chemokine ligand (CCL)-2, and CCL5, accompanied by reduced infiltration of CD11b+ cells and CD4+ T cells. Notably, 5-MTP protected against H2O2-induced damage in HL-1 cardiomyocytes and human umbilical vein endothelial cells in vitro. CONCLUSION: 5-MTP prevented post-MI cardiac injury by promoting mitochondrial stabilization and controlling redox imbalance. This cytoprotective effect ameliorated macrophage and T-cell infiltration, thus reducing the infarct size, attenuating fibrosis, and restoring myocardial function.

Oxytocin levels in response to pituitary provocation tests in healthy volunteers.

OBJECTIVE: Oxytocin, secreted into circulation through the posterior pituitary, regulates lactation, weight, and socio-behavioral functioning. Oxytocin deficiency has been suggested in patients with hypopituitarism; however, diagnostic testing for oxytocin deficiency has not been developed. The aim of this study was to investigate known pituitary provocation tests to stimulate plasma oxytocin. DESIGN: Sixty-five healthy volunteers underwent either the hypertonic saline or arginine infusion test, known to stimulate copeptin, or the oral macimorelin test, known to stimulate growth hormone. Plasma oxytocin was measured before and once plasma sodium level ≥ 150 mmol/L for the hypertonic saline, after 60 min for the arginine infusion, and after 45 min for the oral macimorelin test (expected peak of copeptin and growth hormone levels, respectively). Primary outcome was a change from basal to stimulated oxytocin levels using paired t-tests. RESULTS: As expected, copeptin increased in response to hypertonic saline and arginine infusion (P < 0.001), and growth hormone increased to oral macimorelin (P < 0.001). Oxytocin increased in response to hypertonic saline infusion from 0.4 (0.2) to 0.6 pg/mL (0.3) (P = 0.003) but with a high variance. There was no change to arginine infusion (P = 0.4), and a trend to lower stimulated levels to oral macimorelin (P = 0.05). CONCLUSION: Neither the arginine infusion nor the oral macimorelin test stimulates plasma oxytocin levels, whereas there was an increase with high variance upon hypertonic saline infusion. As a predictable rise in most participants is required for a reliable pituitary provocation test, none of the investigated pituitary provocation tests can be recommended diagnostically to identify patients with an oxytocin deficiency.

Ameliorative Effect of Dietary Tryptophan on Neurodegeneration and Inflammation in d-Galactose-Induced Aging Mice with the Potential Mechanism Relying on AMPK/SIRT1/PGC-1α Pathway and Gut Microbiota.

Dietary tryptophan affects intestinal homeostasis and neurogenesis, whereas the underlying mechanism and the reciprocal interaction between tryptophan and gut microbiota in aging are unclear. This investigation was performed to determine the effect and mechanism of tryptophan on intestinal- and neuro- health in aging. In present study, the 0.4% tryptophan diet significantly ameliorated the oxidative stress and inflammation in the aging mice, potentially through the regulation of 5'-adenosine monophosphate (AMP)-activated protein kinase (AMPK) and nuclear factor κB (NF-κB) pathways. The 0.4% tryptophan diet increased the levels of indoles in colon contents, which indicated the potential contribution of tryptophan metabolites. Microbiome analysis revealed that the 0.4% tryptophan diet raised the relative abundance of Akkermansia in aging. The ameliorated effect of 0.4% tryptophan on neurodegeneration and neuroinflammation was summarized to potentially rely on the brain-derived neurotrophic factor- (BDNF) and NF-κB-related pathways. These findings provide the research evidence for the beneficial effect of tryptophan on aging.