Psychological stress-induced microbial metabolite indole-3-acetate disrupts intestinal cell lineage commitment

Unraveling cysteinyl leukotrienes and their receptors in inflammation through the brain-gut-lung axis

Cysteinyl leukotrienes (CysLTs), as potent lipid inflammatory mediators, play a pivotal role in systemic multi-organ inflammation and inter-organ communication through interactions with their receptors (CysLTRs). However, However, the function of CysLT3R is unclear and lacks a network of cross-organ metabolite interactions, and the clinical use of leukotriene receptor antagonists (LTRAs) has certain limitations. This review systematically synthesizes existing evidence and proposes future directions by clarifying receptor subtype specificity, optimizing targeted therapies, exploring CysLTs' applications in neuroimmunology, and elucidating the dual roles of CysLTs in chronic inflammation. It is indicated that CysLTs activate eosinophils, mast cells, and airway tuft cells, driving type 2 immune responses and mucus secretion in the lungs, thereby exacerbating respiratory diseases such as asthma. In the nervous system, CysLTs aggravate neurodegenerative disorders like cerebral ischemia and Alzheimer's disease by disrupting the blood-brain barrier, promoting glial activation, and inducing neuronal damage. In the gut, CysLTs regulate anti-helminth immunity via the tuft cell-ILC2 pathway and collaborate with prostaglandin D2 (PGD2) to modulate bile excretion and mucosal protection. Furthermore, CysLTs mediate communication through the gut-lung and gut-brain axes via metabolites such as succinate, contributing to cross-organ inflammatory regulation. In conclusion, this review highlights the complex roles of CysLTs in chronic inflammation, providing a theoretical foundation for precise intervention in multi-organ inflammatory diseases, which provides a theoretical framework for precision interventions in multi-organ inflammatory diseases and inspires interdisciplinary breakthroughs.

Pawsitive impact: How pet contact ameliorates adult inflammatory stress responses in individuals raised in an urban environment

BACKGROUND

Individuals raised in an urban environment (URBANs) show an exaggerated inflammatory response to the Trier Social Stress Test (TSST) compared with individuals raised in a rural environment (RURALs). The underlying mechanisms are unclear but may relate to childhood animal contact. As an exaggerated immune (re)activity plays a causal role in the pathogenesis of stress-associated disorders, these findings might explain the higher prevalence of stress-associated disorders in urban vs. rural areas.

METHODS

We recruited physically and emotionally healthy male URBANs, raised in a city with more than 40,000 residents either in the absence (noPETs) or presence (PETs) of household pets. Participants were individually exposed to the TSST, and before and after the TSST, blood and saliva were collected for assessment of different stress-related parameters. An additional saliva sample before the TSST was collected for salivary microbiome analysis. Heart rate (HR) and HR variability (HRV) were recorded continuously. Mental and physical health status, early-life and perceived life stress, current animal contact, and subjective strain induced by TSST exposure were assessed using validated questionnaires.

RESULTS

Here we show that adult healthy male noPETs vs. PETs still reported less animal contact during adulthood and were characterized by deficits in their immunoregulatory and intestinal barrier function, which under basal conditions did not translate into a chronic low-grade inflammatory state. This was different under acute psychosocial stress conditions. Exposure to the TSST resulted in a facilitated mobilization of particularly neutrophil granulocytes in noPETs vs. PETs, accompanied by an enhanced pro- and compromised anti-inflammatory systemic stress response.

CONCLUSION

Together, the presence of pets seems to reduce the risk for URBANs to develop stress-associated disorders later in life (i.e., primary prevention) by facilitating immunoregulatory and barrier functions, in turn preventing an overshooting immune activation in response to acute stressors and chronic low-grade inflammation in response to repeated/chronic stressors.

Milk peptides alleviate irritable bowel syndrome by suppressing colonic mast cell activation and prostaglandin E2 production in mice

This study aimed to investigate the effect of milk peptides on irritable bowel syndrome (IBS). The mice were intragastrally administered with casein or whey protein hydrolysates at a dose of 1 g/kg body weight/day for 24 days and were subjected to Citrobacter rodentium infection and water avoidance stress from day 7 to 24. Results indicated that casein and whey protein hydrolysates effectively reduced diarrhea, anxiety, and visceral hypersensitivity in IBS mice. Casein and whey protein hydrolysates regulated gut microbiota composition and increased the abundance of short-chain fatty acid-producing bacteria, such as Alloprevotella and Alistipes. Whey protein hydrolysate significantly increased the mRNA levels of zonula occludens-1 (ZO-1) and claudin-1 in the colon, while casein hydrolysate significantly improved the mRNA levels of occludin. Casein and whey protein hydrolysates both decreased the levels of pro-inflammatory cytokines including interleukin-6 (IL-6), interleukin-1β (IL-1β), and tumor necrosis factor-α (TNF-α), while increased the level of anti-inflammatory cytokine interleukin-10 (IL-10). Importantly, casein and whey protein hydrolysates significantly reduced colonic mast cell activation and decreased prostaglandin E2 (PGE2) production. Moreover, three novel casein-derived cyclooxygenase-2 (COX2)-inhibitory peptides RGPF, FPK, and NPW were identified with IC50 values of 0.36 ± 0.03, 0.64 ± 0.01, and 1.10 ± 0.09 mM, respectively and predicted to form hydrogen bonds and hydrophobic interactions with the residues of the active site of COX2. This study highlighted the potential of milk peptides as bioactive ingredients in functional foods for managing IBS.

Microbiota-neuroepithelial signalling across the gut-brain axis

Research over the past two decades has established a remarkable ability of the gut microbiota to modulate brain activity and behaviour. Conversely, signals from the brain can influence the composition and function of the gut microbiota. This bidirectional communication across the gut microbiota-brain axis, involving multiple biochemical and cellular mediators, is recognized as a major brain-body network that integrates cues from the environment and the body's internal state. Central to this network is the gut sensory system, formed by intimate connections between chemosensory epithelial cells and sensory nerve fibres, that conveys interoceptive signals to the central nervous system. In this Review, we provide a broad overview of the pathways that connect the gut and the brain, and explore the complex dialogue between microorganisms and neurons at this emerging intestinal neuroepithelial interface. We highlight relevant microbial factors, endocrine cells and neural mechanisms that govern gut microbiota-brain interactions and their implications for gastrointestinal and neuropsychiatric health.

Intestinal epithelial cells in health and disease

This comprehensive review delves into the pivotal role of intestinal epithelial cells in the context of various diseases. It provides an in-depth analysis of the diverse types and functions of these cells, explores the influence of multiple signaling pathways on their differentiation, and elucidates their critical roles in a spectrum of diseases. The significance of the gastrointestinal tract in maintaining overall health is extremely important and cannot be exaggerated. This complex and elongated organ acts as a crucial link between the internal and external environments, making it vulnerable to various harmful influences. Preserving the normal structure and function of the gut is essential for well-being. Intestinal epithelial cells serve as the primary defense mechanism within the gastrointestinal tract and play a crucial role in preventing harmful substances from infiltrating the body. As the main components of the digestive system, they not only participate in the absorption and secretion of nutrients and the maintenance of barrier function but also play a pivotal role in immune defense. Therefore, the health of intestinal epithelial cells is of vital importance for overall health.

Psychological stress-induced systemic corticosterone directly sabotages intestinal stem cells and exacerbates colitis

Psychological stress has profound impacts on the gastrointestinal tract via the brain‒gut axis. However, its effects on intestinal stem cells (ISCs) and the resulting implication for intestinal homeostasis remain poorly understood. Here, we observed a notable reduction in both the quantity and proliferative capacity of ISCs under chronic stress conditions, driven by elevated levels of corticosterone resulting from activation of the hypothalamic‒pituitary‒adrenal (HPA) axis. Mechanistically, corticosterone directly interacts with its receptor, nuclear receptor subfamily 3 group c member 1 (NR3C1), leading to increased expression of FKBP prolyl isomerase 5 (FKBP5) in ISCs. Subsequently, FKBP5 negatively regulates AKT activation by facilitating its dephosphorylation at Ser473, ultimately enhancing nuclear translocation of forkhead box O (FoxO) and inhibiting ISC proliferative activity. Consequently, ISC dysfunction contributes to the stress-driven exacerbation of DSS-induced colitis. Collectively, these findings reveal an intrinsic brain-to-gut regulatory pathway whereby psychological stress impairs ISC activity via corticosterone elevation, providing a mechanistic explanation for stress-enhanced susceptibility to colitis.

Vagal pathway activation links chronic stress to decline in intestinal stem cell function

Chronic stress adversely affects intestinal health, but the specific neural pathways linking the brain to intestinal tissue are not fully understood. Here, we show that chronic stress-induced activation of the central amygdala-dorsal motor nucleus of the vagus (CeA-DMV) pathway accelerates premature aging and impairs the stemness of intestinal stem cells (ISCs). This pathway influences ISC function independently of the microbiota, the hypothalamic-pituitary-adrenal (HPA) axis, the immune response, and the sympathetic nervous system (SNS). Under chronic stress, DMV-mediated vagal activation prompts cholinergic enteric neurons to release acetylcholine (ACh), which engages ISCs via the M3 muscarinic acetylcholine receptor (CHRM3). This interaction activates the p38 mitogen-activated protein kinase (MAPK) pathway, triggering growth arrest and mitochondrial fragmentation, thereby accelerating an aging-like decline in ISCs. Together, our findings provide insights into an alternative neural mechanism that links stress to intestinal dysfunction. Strategies targeting the DMV-associated vagal pathway represent potential therapeutic approaches for stress-induced intestinal diseases.

A Gut Microbial Metabolite Alleviates Stress-Induced Neurobehavioral Dysfunction in an Alzheimer's Disease Model

Chronic psychological stress is a known risk factor for neurodegenerative disorders like Alzheimer's disease (AD), but its role in AD neuropathology remains unclear. Using the water-avoidance stress model in the APP/PS1 preclinical mouse model of AD, we investigate how chronic stress exacerbates neurobehavioral dysfunction and cognitive impairment and explore the neuroprotective potential of indole-3-propionate (IPA), a microbiome-derived metabolite, in mitigating these effects. Our findings show that psychological stress leads to depression- and anxiety-like behaviors, as indicated by reduced grooming and exploration behaviors; however, these effects are ameliorated by IPA supplementation. Stress also disrupts the gut microbiome and promotes intestinal inflammation. While IPA does not significantly alter microbiome composition, it mitigates inflammation by normalizing IL-17a and TGF-β gene expression and reducing TNF-⍺ and IL-6 protein levels. Although stress has a limited effect on hippocampal inflammation, IPA suppresses low-grade neuroinflammation by downregulating IL-1β, TNF-⍺, IL-6, and MCP-1 protein levels. Additionally, IPA treatment tends to reduce hippocampal amyloid-β plaques. These findings highlight the detrimental effects of chronic psychosocial stress on AD pathology and suggest that IPA may confer neuroprotection through the gut-immune-brain axis, supporting the therapeutic potential of microbial metabolites in mitigating cognitive decline.

Restraint Stress Disrupted Intestinal Homeostasis via 5-HT/HTR7/Wnt/β-Catenin/NF-kB Signaling

Stress may aggravate the development of inflammatory bowel disease and irritable bowel syndrome, in which the number of enterochromaffin (EC) cells and 5-hydroxytryptamine (5-HT) levels are abnormal, but the underlying mechanism remains largely unresolved. In this study, we discovered that restraint stress triggered the expression of Tph1, which led to 5-HT production. The 5-HT signaling then increased intestinal permeability, downregulated the expression of tight junction proteins, reduced the number of goblet cells and their ability to secrete mucin, promoted the expression of inflammatory cytokines, and ultimately damaged the intestinal mucosal barrier. Mechanistically, the 5-HT receptor HTR7 was highly expressed in the intestine. It interacted with 5-HT to initiate the Wnt/β-catenin signaling pathway, inducing an increase in intestinal EC cells and further promoting 5-HT secretion. Additionally, the activation of the Wnt/β-catenin signaling pathway could initiate the NF-κB signaling pathway and induce the expression of inflammatory cytokines. Blocking the 5-HT signal in mice inhibited the activation of the Wnt/β-catenin signal, thereby alleviating intestinal inflammation. Our findings revealed a novel role for 5-HT in intestinal inflammatory diseases and represent a potential new therapeutic target.

Gut microbiota derived indole-3-acetic acid ameliorates precancerous inflammatory intestinal milieu to inhibit tumorigenesis through IL-35

BACKGROUND

Gut microbiota can significantly alter the risk or progression of cancer by maintaining gut immune system homeostasis. However, the exact mechanism by which the gut microbiota and its metabolites influence colorectal tumorigenesis is unclear.

METHODS

The roles of tryptophan metabolite indole-3-acetic acid (IAA) in inflammation and tumor development were investigated in dextran sodium sulfate (DSS) and azoxymethane (AOM)-DSS mouse models with or without IAA supplementation and with or without Lactobacillus reuteri-produced IAA. Pregnane X receptor (PXR) knockout (KO) mice and aryl hydrocarbon receptor KO mice were used to explore the mechanism by which IAA regulates interleukin (IL)-35 expression. IL-35+ immune cells were stimulated in vitro and analyzed by flow cytometry. Additionally, metabolites were analyzed by liquid chromatography-mass spectrometry.

RESULTS

We found that IAA, a metabolite of tryptophan produced in the gut by L. reuteri, can inhibit the development of colitis by inducing IL-35 expression in immunosuppressant cells. HuREG3αIECtg mice had high levels of intestinal microbiota-derived IAA, and these mice were resistant to AOM-DSS-induced cancer. Patients with colorectal cancer also had low peripheral blood levels of IAA. Further studies revealed that IAA-producing L. reuteri alleviated colitis symptoms and inhibited colon tumors by inducing macrophages, T cells, and B cells to produce IL-35. Finally, PXR KO completely abolished the effects of IAA on immune cells.

CONCLUSION

We demonstrate that gut microbiota-derived IAA can improve the precancerous colon inflammatory environment through IL-35, thereby inhibiting tumorigenesis, suggesting that IAA may be a preventive factor for colitis-related cancers.

Statin therapy associated Lactobacillus intestinalis attenuates pancreatic fibrosis through remodeling intestinal homeostasis

Chronic pancreatitis (CP) is characterized by irreversible fibrotic destruction and impaired pancreatic function. CP disrupts lipid metabolism and causes the imbalance of gut microbiota which in turn exacerbates pancreatic fibrosis. Statins alter gut microbiota and exert anti-inflammatory effects, but its role in CP has not been fully elucidated. Here, we found that statins-associated higher abundance of Lactobacillus intestinalis (L.intestinalis) maintained gut homeostasis that restrained bacteria translocation from gut to the pancreas, which eventually aggravated pancreatic fibrosis through inhibiting CD8+T cells-dependent immunity. Fecal microbiota transplantation (FMT) or L.intestinalis administration inhibited the infiltration of CD8+T cells and macrophages that delayed CP progression. L.intestinalis restrained the recruitment of M1 macrophages and limited the release of Ccl2/7 in the colon, which prevented epithelial damage and epithelial barrier dysfunction through blocking Ccl2/7-Ccr1 signaling. Our findings elucidate that the utilization of statin therapy or supplementation of L.intestinalis can be potential approach for the therapies of CP.

Decreased gut microbiome-derived indole-3-propionic acid mediates the exacerbation of myocardial ischemia/reperfusion injury following depression via the brain-gut-heart axis

Despite the increasing recognition of the interplay between depression and cardiovascular disease (CVD), the precise mechanisms by which depression contributes to the pathogenesis of cardiovascular disease remain inadequately understood. The involvement of gut microbiota and their metabolites to health and disease susceptibility has been gaining increasing attention. In this study, it was found that depression exacerbated cardiac injury, impaired cardiac function (EF%: P < 0.01; FS%: P < 0.05), hindered long-term survival (P < 0.01), and intensified adverse cardiac remodeling (WGA: P < 0.01; MASSON: P < 0.0001) after myocardial ischemia/reperfusion (MI/R) in mice. Then we found that mice receiving microbiota transplants from chronic social defeat stress (CSDS) mice exhibited worse cardiac function (EF%: P < 0.01; FS%: P < 0.01) than those receiving microbiota transplants from non-CSDS mice after MI/R injury. Moreover, impaired tryptophan metabolism due to alterations in gut microbiota composition and structure was observed in the CSDS mice. Mechanistically, we analyzed the metabolomics of fecal and serum samples from CSDS mice and identified indole-3-propionic acid (IPA) as a protective agent for cardiomyocytes against ferroptosis after MI/R via NRF2/System xc-/GPX4 axis, played a role in mediating the detrimental influence of depression on MI/R. Our findings provide new insights into the role of the gut microbiota and IPA in depression and CVD, forming the basis of intervention strategies aimed at mitigating the deterioration of cardiac function following MI/R in patients experiencing depression.

Job Stress Can Lead to Intestinal Inflammation and Subsequent Gut-Originated Extraoral Halitosis

OBJECTIVES

Reports on stress-associated halitosis are scarce and have only focused on intraoral halitosis. This work aimed to study stress-associated extraoral halitosis (EOH) and further investigate its potential association with stress-induced intestinal inflammation.

METHODS

This retrospective study included 664 white-collar employees with self-reported stress-associated halitosis. They underwent the organoleptic score (OLS) to assess halitosis, modified Brief Job Stress Questionnaire (BJSQ) score to assess job stress, OralChroma breath test to measure volatile sulfur compounds (VSCs) in breath, and hydrogen/methane breath test (HMBT) and nitric oxide breath test (NOBT) to detect intestinal inflammation. They were classified into high-stress and low-stress groups based on their modified BJSQ score.

RESULTS

Totally, 106 eligible patients were identified as having stress-associated EOH, and 61 of them had high stress. Additionally, 70 (66.04%) and 73 (68.87%) of them tested positive for HMB and NOBT, respectively. Dimethyl sulfide (DMS) was found to be the predominant VSC in breath. High-stress patients had significantly higher positivity rates for HMBT and NOBT, OLS, and exhaled DMS levels compared to low-stress patients. HMBT-positive patients and NOBT-positive patients had significantly higher OLS and exhaled DMS levels compared to their respective negative counterparts.

CONCLUSIONS

Job stress can lead to intestinal inflammation and subsequent gut-originated EOH.

Stress, microbiota, and the gut-brain axis in mental and digestive health

The prevailing mind-body dualism in contemporary medicine, rooted in reductionism and the fragmentation of knowledge, has impeded the development of a conceptual model that can adequately address the complexity of illnesses. Integrating biomedical data into a cohesive model that considers the mind-body-context interconnections is essential. This integration is not merely theoretical; rather, it has significant clinical implications. This is exemplified by chronic stress-related mental and digestive disorders. The onset and development of these disorders are intimately linked to chronic psychological stress via the brain-gut-microbiota axis. The present article examines the evidence and mechanisms indicating that stress is a primary factor and a potentiator of symptom severity in common mental health and digestive diseases, with a particular focus on human studies. However, due to space limitations, only a very general overview of preventive and therapeutic clinical strategies is provided. It is hoped that the recurring phrase, "Everything that happens to you is due to stress," will become more comprehensible to the physician after reading this manuscript.

Effects of psychological stress on inflammatory bowel disease via affecting the microbiota-gut-brain axis

ABSTRACT

Inflammatory bowel disease (IBD) is an idiopathic intestinal inflammatory condition with chronic and relapsing manifestations and is characterized by a disturbance in the interplay between the intestinal microbiota, the gut, and the brain. The microbiota-gut-brain axis involves interactions among the nervous system, the neuroendocrine system, the gut microbiota, and the host immune system. Increasing published data indicate that psychological stress exacerbates the severity of IBD due to its negative effects on the microbiota-gut-brain axis, including alterations in the stress response of the hypothalamic-pituitary-adrenal (HPA) axis, the balance between the sympathetic nervous system and vagus nerves, the homeostasis of the intestinal flora and metabolites, and normal intestinal immunity and permeability. Although the current evidence is insufficient, psychotropic agents, psychotherapies, and interventions targeting the microbiota-gut-brain axis show the potential to improve symptoms and quality of life in IBD patients. Therefore, further studies that translate recent findings into therapeutic approaches that improve both physical and psychological well-being are needed.

Optimized oxygen therapy improves sleep deprivation-induced cardiac dysfunction through gut microbiota

Adequate sleep is of paramount importance for relieving stress and restoring mental vigor. However, the adverse physiological and pathological responses resulting from sleep insufficiency or sleep deprivation (SD) are becoming increasingly prevalent. Currently, the impact of sleep deficiency on gut microbiota and microbiota-associated human diseases, especially cardiac diseases, remains controversial. Here, we employed the following methods: constructed an experimental sleep-deprivation model in mice; conducted 16S rRNA sequencing to investigate the changes in gut microbiota; through fecal microbiota transplantation (FMT) experiments, transplanted fecal microbiota from sleep-deprived mice to other mice; established an environment with a 30% oxygen concentration to explore the therapeutic effects of oxygen therapy on gut microbiota-associated cardiac fibrosis and dysfunction; and utilized transcriptome data to study the underlying mechanisms of oxygen therapy. The results revealed that: sleep-deprived mice exhibited weakness, depression-like behaviors, and dysfunction in multiple organs. Pathogenic cardiac hypertrophy and fibrosis occurred in sleep-deprived mice, accompanied by poor ejection fraction and fractional shortening. 16S rRNA sequencing indicated that sleep deprivation induced pathogenic effects on gut microbiota, and similar phenomena were also observed in mice that received fecal microbiota from sleep-deprived mice in the FMT experiments. The environment with a 30% oxygen concentration effectively alleviated the pathological impacts on cardiac function. Transcriptome data showed that oxygen therapy targeted several hypoxia-dependent pathways and inhibited the production of cardiac collagen. In conclusion, these results demonstrate the significance of sufficient sleep for gut microbiota and may represent a potential therapeutic strategy, where the oxygen environment exerts a protective effect on insomniacs through gut microbiota.

3-HKA Promotes Vascular Remodeling After Stroke by Modulating the Activation of A1/A2 Reactive Astrocytes

Ischemic stroke is the most common cerebrovascular disease and the leading cause of permanent disability worldwide. Recent studies have shown that stroke development and prognosis are closely related to abnormal tryptophan metabolism. Here, significant downregulation of 3-hydroxy-kynurenamine (3-HKA) in stroke patients and animal models is identified. Supplementation with 3-HKA improved long-term neurological recovery, reduced infarct volume, and increased ipsilateral cerebral blood flow after distal middle cerebral artery occlusion (MCAO). 3-HKA promoted angiogenesis, functional blood vessel formation, and blood-brain barrier (BBB) repair. Moreover, 3-HKA inhibited A1-like (neurotoxic) astrocyte activation but promoted A2-like (neuroprotective) astrocyte polarization. Proteomic analysis revealed that 3-HKA inhibited AIM2 inflammasome activation after stroke, and co-labeling studies indicated that AIM2 expression typically increased in astrocytes at 7 and 14 days after stroke. Consistently, in co-cultures of primary mouse brain microvascular endothelial cells and astrocytes, 3-HKA promoted angiogenesis after oxygen-glucose deprivation (OGD). AIM2 overexpression in astrocytes abrogated 3-HKA-driven vascular remodeling in vitro and in vivo, suggesting that 3-HKA may regulate astrocyte-mediated vascular remodeling by impeding AIM2 inflammasome activation. In conclusion, 3-HKA may promote post-stroke vascular remodeling by regulating A1/A2 astrocyte activation, thereby improving long-term neurological recovery, suggesting that supplementation with 3-HKA may be an efficient therapy for stroke.

Dachaihu decoction ameliorates abnormal behavior by regulating gut microbiota in rats with propionic acid-induced autism

Background

Autism spectrum disorder (ASD) is an early-onset neurodevelopmental disorder, usually accompanied by gut microbiota dysregulation. Gut microbiota homeostasis is considered effective for ASD. Reportedly, Dachaihu decoction (DCHD) can efficiently regulate gut microbiota and inflammation. However, the mechanisms underlying the effects of DCHD in the treatment of ASD remain unclear.

Objective

This study investigated the potential effects and mechanisms of DCHD in treating ASD.

Methods

In the animal experiment, propionic acid was administered to construct an ASD rat model. The ASD rats were treated with DCHD, and the efficacy was assessed using the behavioral detections, such as open field test, elevated plus maze test, novel object recognition test. Additionally, the levels of IL-6, TNF-α, IL-10, T-SOD, MDA, GSH and CAT were determined using kits, and histological staining was used to evaluate brain morphology. Moreover, tight junction proteins (ZO-1 and occludin) expression levels were evaluated using RT-qPCR, whereas Iba1 expression level was assessed by immunofluorescence staining. The 16S rRNA sequencing and metabolomic analysis of feces revealed the potential targets of DCHD against ASD. In a small human trail, the clinical scales ADOS-2 and Autism Behavior Checklist (ABC) assessed autism severity. Gastrointestinal problems and brain function were evaluated based on food intolerance and event-related potential, respectively.

Results

DCHD significantly improved autism-like behaviors and increased antioxidant enzyme activity, decreased inflammation and enhanced the intestinal barrier by the animal experiment. Furthermore, the DCHD treatment altered the gut microbiota profile, with increased probiotics Adlercreutzia, Parvibacter, Turicibacter, and Christensenellaceae. Further, DCHD increased the beneficial metabolite indole-3-acetate and decreased the cognitive impairment-related metabolites asymmetric dimethylarginine and homogentisic acid. Meanwhile, the small clinical trial revealed that DCHD significantly alleviated the core symptoms of ASD, with decreased ADOS-2 and ABC scale scores. DCHD also decreased the levels of specific egg white/yolk and milk IgG antibodies and shortened the MMN and P3b latencies.

Conclusion

This study demonstrated that DCHD may alleviate ASD via inhibiting oxidative stress, reducing inflammation, and modulating the gut microbiota in rats. Combined with human trial, DCHD may be a promising drug for treating ASD. This study provides a scientific rationale for treating mental disorders related to gut microbiota dysbiosis.

Ginsenoside Rg1 enriches gut microbial indole-3-acetic acid to alleviate depression-like behavior in mice via oxytocin signaling

BACKGROUND AND PURPOSE

Although a large collection of data has shown that ginsenosides, the major active ingredients from Ginseng, have neuroprotective and anti-depressant effect, the mechanism of action is incompletely understood. This study aims to elucidate the antidepressant mechanism of ginsenoside Rg1 (Rg1), a poorly absorbed ginsenoside, from the perspective of gut microbe to brain signaling.

METHODS

A mouse model of depression was induced by unpredictable mild stress (UMS). Behavioral and neurochemical tests were conducted to evaluate the effect and mechanism of Rg1 on depressive behavior. Non-target and target metabolomics were performed to identify the signaling metabolites underlying the antidepressant efficacy of Rg1. Gut microbial structure was analyzed by 16S rRNA sequencing and the potential functional strains associated with Rg1 action were investigated by in vitro bacterial culture. Chemical intervention was used to explore the mechanism of Rg1 and signaling metabolite.

RESULTS

Rg1 improved UMS-induced despair, anxiety-like and social avoidance behaviors in mice, which were accompanied by increased hypothalamic oxytocin secretion and restored neural proliferation in the hippocampus. Metabolomic analysis of the gut-brain axis revealed that Rg1 increased the concentration of serum and brain indole-3-acetic acid (IAA), a bacterial metabolite that was partially attributed to the enrichment of Lactobacillus murinus in the gut microbiome. Oral supplementation of IAA mimicked the anti-depressant action of Rg1, while oxytocin receptor antagonist abrogated the anti-depressant effects of both Rg1 and IAA.

CONCLUSION

Our work provides a new gut-to-brain signaling mechanism for the antidepressant effects of Rg1. In particular, Rg1 enriches the abundance of Lactobacillus murinus, which in turn increases the level of brain IAA and potentiates hypothalamic oxytocin signal. These findings suggest a promising pathway for producing antidepressant effects through gut-brain crosstalk.

The Value of PHQ-9 and GAD-7 for Screening Emotional Disorders in IBS-D and the Specificity of the Gut Flora Associated with Emotional Comorbidity: Preliminary Findings

Background

To identify irritable bowel syndrome with diarrhea (IBS-D) combined with anxiety and/or depression through a psychological screening tool and to further explore the relationships between patients with comorbidities and gut microbiota.

Methods

The GAD-7, SAS, PHQ-9 and SDS were administered to evaluate anxiety and depression. Faeces were subsequently collected from 44 patients with emotional disorders (IBS-EDs), 22 patients without emotional disorders (IBS-nEDs) and 18 healthy controls (HCs) via 16S rRNA sequencing, depending on the participants' wishes. The differences in gut microbiota among different groups were analysed. Spearman analysis was conducted at the genus level and was based on psychological assessment scores. Patients with IBS-D were recruited from December 2020 to November 2022.

Results

This study included 124 outpatients with IBS-D. According to the GAD-7 and SAS scores, 40.3% and 19.3% of the participants, respectively, had anxiety (P < 0.05). Similarly, a significantly greater percentage of participants had depression according to the PHQ-9 than according to the SDS (61.3% vs 33.1%) (P < 0.05). Overall, approximately 66.1% of the participants had emotional disorders (anxiety and/or depression) according to the GAD-7 and PHQ-9. Correlation analysis revealed that the abundances of Eubacterium_hallii_group, Monoglobus and Lachnoclostridium were closely related to the PHQ-9 scores and that the abundances of Subdoligranulum and Holdemanella were closely related to the GAD-7 scores.

Conclusion

In comparison to the SAS and SDS, both the GAD-7 and PHQ-9 identified a greater number of individuals with emotional disorders within the IBS-D population. Furthermore, our findings demonstrated that Lachnoclostridium is not only a biomarker for IBS-ED patients but also that its abundance changes are related to PHQ-9 scores, which may provide insights for further brain gut investigations.

Microbiota-gut-brain axis: Natural antidepressants molecular mechanism

BACKGROUND

Major depressive disorder (MDD) is a severe mental health condition characterized by persistent depression, impaired cognition, and reduced activity. Increasing evidence suggests that gut microbiota (GM) imbalance is closely linked to the emergence and advancement of MDD, highlighting the potential significance of regulating the "Microbiota-Gut-Brain" (MGB) axis to impact the development of MDD. Natural products (NPs), characterized by broad biological activities, low toxicity, and multi-target characteristics, offer unique advantages in antidepressant treatment by regulating MGB axis.

PURPOSE

This review was aimed to explore the intricate relationship between the GM and the brain, as well as host responses, and investigated the mechanisms underlying the MGB axis in MDD development. It also explored the pharmacological mechanisms by which NPs modulate MGB axis to exert antidepressant effects and addressed current research limitations. Additionally, it proposed new strategies for future preclinical and clinical applications in the MDD domain.

METHODS

To study the effects and mechanism by which NPs exert antidepressant effects through mediating the MGB axis, data were collected from Web of Science, PubMed, ScienceDirect from initial establishment to March 2024. NPs were classified and summarized by their mechanisms of action.

RESULTS

NPs, such as flavonoids,alkaloids,polysaccharides,saponins, terpenoids, can treat MDD by regulating the MGB axis. Its mechanism includes balancing GM, regulating metabolites and neurotransmitters such as SCAFs, 5-HT, BDNF, inhibiting neuroinflammation, improving neural plasticity, and increasing neurogenesis.

CONCLUSIONS

NPs display good antidepressant effects, and have potential value for clinical application in the prevention and treatment of MDD by regulating the MGB axis. However, in-depth study of the mechanisms by which antidepressant medications affect MGB axis will also require considerable effort in clinical and preclinical research, which is essential for the development of effective antidepressant treatments.

Indole-3-Carboxaldehyde Alleviates LPS-Induced Intestinal Inflammation by Inhibiting ROS Production and NLRP3 Inflammasome Activation

Indole-3-carboxaldehyde (IAld) is a tryptophan (Trp) metabolite derived from gut microbiota, which has a potential protective effect on intestinal inflammatory diseases. Abnormal activation of NOD-like receptor family pyrin domain-containing 3 (NLRP3) inflammasome is an important cause of intestinal inflammation. However, the effect and mechanism of IAld on NLRP3 inflammasome activation remain unclear. Here, we found that IAld inhibited the activation of the NLRP3 inflammasome in intestinal epithelial cells, and effectively prevented intestinal epithelial barrier injury caused by lipopolysaccharide (LPS) stimulation. Mechanistically, we demonstrated that IAld activated the aryl hydrocarbon receptor (AhR), subsequently prevented reactive oxygen species (ROS) production, maintained mitochondrial membrane potential, and blocked the NF-κB/NLRP3 inflammatory pathway in intestinal epithelial cells. Also, the AhR-specific inhibitor CH-223191 effectively blocked the IAld-induced NLRP3 inhibition and intestinal epithelial barrier repairment. In addition, in vivo results showed that IAld prevented pro-inflammatory mediator production and intestinal inflammatory damage in LPS-induced mice, which is related to AhR activation and NLRP3 inflammasome inhibition. Collectively, our study unveiled that IAld is an effective endogenous antioxidant and suggested the AhR as a potential treatment target for NLRP3-induced intestinal inflammatory diseases.

Emerging chemophysiological diversity of gut microbiota metabolites

Human physiology is profoundly influenced by the gut microbiota, which generates a wide array of metabolites. These microbiota-derived compounds serve as signaling molecules, interacting with various cellular targets in the gastrointestinal tract and distant organs, thereby impacting our immune, metabolic, and neurobehavioral systems. Recent advancements have unveiled unique physiological functions of diverse metabolites derived from tryptophan (Trp) and bile acids (BAs). This review highlights the emerging chemophysiological diversity of these metabolites and discusses the role of chemical and biological tools in analyzing and therapeutically manipulating microbial metabolism and host targets, with the aim of bridging the chemical diversity with physiological complexity in host-microbe molecular interactions.

Gut microbiota-derived indole-3-acetic acid suppresses high myopia progression by promoting type I collagen synthesis

High myopia (HM) is a leading cause of blindness worldwide with currently no effective interventions available. A major hurdle lies in its often isolated perception as a purely ocular morbidity, disregarding potential systemic implications. Recent evidence suggests the existence of a gut-eye axis; however, the role of gut microbiota in the pathogenesis of HM remains largely unexplored. Herein, we provide a potential crosstalk among HM's gut dysbiosis, microbial metabolites, and scleral remodeling. Utilizing 16S rRNA gene sequencing, we observed an altered gut microbiota profile in HM patients with a significant reduction in probiotic abundance compared with healthy controls. Subsequent targeted metabolic profiling revealed a notable decrease in plasma levels of the gut microbiota-derived metabolite indole-3-acetic acid (3-IAA) among HM patients, which is closely associated with the reduced probiotics, both negatively correlated with HM severity. Genetic analyses determined that gut microbiota are causally associated with myopia risk. Importantly, when mice subjected to HM modeling receive fecal microbiota transplantation from healthy donors, there is an increase in 3-IAA plasma levels and simultaneous retardation of HM progression along with better maintenance of collagen type I alpha 1 (COL1A1) expression in the sclera. Furthermore, 3-IAA gavage achieves similar effects. Mechanistic investigations confirm the transcriptional activation of COL1A1 by 3-IAA via promoting the enrichment of SP1 to its promoter. Together, our findings provide novel insights into the gut microbiota-eye axis in the pathogenesis of HM and propose new strategies for HM intervention by remodeling the gut microbiota and indole supplementation.

Fasting-mimicking diet remodels gut microbiota and suppresses colorectal cancer progression

The progression of colorectal cancer is closely associated with diet. Fasting-mimicking diet (FMD) is a promising type of dietary intervention that have beneficial effects in the prevention and treatment of various cancers. We investigated the therapeutic effect of 4-day FMD against colorectal cancer in mice through immune cell analysis, microbiota composition analysis and anti-PD-1 treatment. These FMD cycles effectively suppressed colorectal cancer growth, reduced cell proliferation and angiogenesis, increased tumor-infiltration lymphocytes especially CD8+T cells. FMD stimulated protective gut microbiota, especially Lactobacillus. Supplementation of Lactobacillus johnsonii induced similar results as FMD intervention, which also suppressed tumor growth and increased CD45+ and CD8+ T cells. Additionally, FMD synthesizing with anti-PD-1 therapy effectively inhibited CRC progression. These findings suggest that Lactobacillus. johnsonii is necessary for the anticancer process of FMD in CRC. FMD through its effects on both gut microbiota and immune system, effectively suppressed colorectal cancer progression in mouse model.

DNA metabarcoding technology for the identification of the fecal microbiome in patients with chronic stress

In the latest research, the concept of stress is associated with the deregulation of several biological systems sensitive to stress, such as the immune system, the microbiome, the endocrine system and neuroanatomical substrates. The objective of the research was to identify the fecal microbiome in patients diagnosed with chronic stress and in healthy patients through a metabarcoding analysis. The methodology used fecal samples collected from 20 patients with stress and 20 healthy patients. For the diagnosis of stress, psychological tools previously validated by external researchers were used. For metabarcoding analysis, metagenomic DNA extraction was performed from the fecal samples. Next Generation Illumina genetic sequencing targeting the 16S rDNA gene was then performed, followed by bioinformatic analysis using QUIME II software. The results, at the psychological test level, 20 people with chronic stress were diagnosed, on the other hand, at the metabarcoding level, specifically at the Gender level, the Asteroleplasma bacteria present only in the 20 healthy patients was molecularly identified. On the other hand, the bacteria Alistipes and Bifidobacterium were identified with greater predominance in the 20 patients with stress. Concluding, the bacteria Alistipes and Bifidobacterium are candidates as possible markers of the intestinal microbiome in patients with chronic stress, and the bacteria Asteroleplasma are candidates as a bacterial marker of the intestinal microbiome in healthy people. Finally, the identification of the microbiome in patients with stress opens a new path to understanding stress and its relationship to dysregulation with the microbiome.

Microbial metabolite steers intestinal stem cell fate under stress

Recently in Cell Metabolism, Wei et al.1 unveiled a brain-to-gut pathway that conveys psychological stress to intestinal epithelial cells, leading to their dysfunction. This gut-brain axis involves a microbial metabolite, indole-3-acetate (IAA), as a niche signal that hampers mitochondrial respiration to skew intestinal stem cell (ISC) fate.

Psychobiotics and the Microbiota-Gut-Brain Axis: Where Do We Go from Here?

The bidirectional relationship between the gut microbiota and the nervous system is known as the microbiota-gut-brain axis (MGBA). The MGBA controls the complex interactions between the brain, the enteric nervous system, the gut-associated immune system, and the enteric neuroendocrine systems, regulating key physiological functions such as the immune response, sleep, emotions and mood, food intake, and intestinal functions. Psychobiotics are considered tools with the potential to modulate the MGBA through preventive, adjunctive, or curative approaches, but their specific mechanisms of action on many aspects of health are yet to be characterized. This narrative review and perspectives article highlights the key paradigms needing attention as the scope of potential probiotics applications in human health increases, with a growing body of evidence supporting their systemic beneficial effects. However, there are many limitations to overcome before establishing the extent to which we can incorporate probiotics in the management of neuropsychiatric disorders. Although this article uses the term probiotics in a general manner, it remains important to study probiotics at the strain level in most cases.

The role of microbial indole metabolites in tumor

The gut microbiota can produce a variety of microbial-derived metabolites to influence tumor development. Tryptophan, an essential amino acid in the human body, can be converted by microorganisms via the indole pathway to indole metabolites such as Indole-3-Lactic Acid (ILA), Indole-3-Propionic Acid (IPA), Indole Acetic Acid (IAA) and Indole-3-Aldehyde (IAld). Recent studies have shown that indole metabolites play key roles in tumor progression, and they can be used as adjuvant regimens for tumor immunotherapy or chemotherapy. Here, we summarize recent findings on the common microbial indole metabolites and provide a review of the mechanisms of different indole metabolites in the tumor microenvironment. We further discuss the limitations of current indole metabolite research and future possibilities. It is expected that microbial indole metabolites will provide new strategies for clinical therapy.