The Vagus Nerve at the Interface of the Microbiota-Gut-Brain Axis

Modulation of anxiety-like behavior in galactooligosaccharide-fed mice: A potential role for bacterial tryptophan metabolites and reduced microglial reactivity

Prebiotic galactooligosaccharides (GOS) reduce anxiety-like behaviors in mice and humans. However, the biological pathways behind these behavioral changes are not well understood. To begin to study these pathways, we utilized C57BL/6 mice that were fed a standard diet with or without GOS supplementation for 3 weeks prior to testing on the open field. After behavioral testing, colonic contents and serum were collected for bacteriome (16S rRNA gene sequencing, colonic contents only) and metabolome (UPLC-MS, colonic contents and serum data) analyses. As expected, GOS significantly reduced anxiety-like behavior (i.e., increased time in the center) and decreased cytokine gene expression (Tnfa and Ccl2) in the prefrontal cortex. Notably, time in the center of the open field was significantly correlated with serum methyl-indole-3-acetic acid (methyl-IAA). This metabolite is a methylated form of indole-3-acetic acid (IAA) that is derived from bacterial metabolism of tryptophan. Sequencing analyses showed that GOS significantly increased Lachnospiraceae UCG006 and Akkermansia; these taxa are known to metabolize both GOS and tryptophan. To determine the extent to which methyl-IAA can affect anxiety-like behavior, mice were intraperitoneally injected with methyl-IAA. Mice given methyl-IAA had a reduction in anxiety-like behavior in the open field, along with lower Tnfa in the prefrontal cortex. Methyl-IAA was also found to reduce TNF-α (as well as CCL2) production by LPS-stimulated BV2 microglia. Together, these data support a novel pathway through which GOS reduces anxiety-like behaviors in mice and suggests that the bacterial metabolite methyl-IAA reduces microglial cytokine and chemokine production, which in turn reduces anxiety-like behavior.

Understanding the impact of the gut microbiome on opioid use disorder: Pathways, mechanisms, and treatment insights

The widespread use of opioids for chronic pain management not only poses a significant public health issue but also contributes to the risk of tolerance, dependence, and addiction, leading to opioid use disorder (OUD), which affects millions globally each year. Recent research has highlighted a potential bidirectional relationship between the gut microbiome and OUD. This emerging perspective is critical, especially as the opioid epidemic intensifies, emphasizing the need to investigate how OUD may alter gut microbiome dynamics and vice versa. Understanding these interactions could reveal new insights into the mechanisms of addiction and tolerance, as well as provide novel approaches for managing and potentially mitigating OUD impacts. This comprehensive review explores the intricate bidirectional link through the gut-brain axis, focusing on how opiates influence microbial composition, functional changes, and gut mucosal integrity. By synthesizing current findings, the review aims to inspire new strategies to combat the opioid crisis and leverage microbiome-centred interventions for preventing and treating OUD.

Gut Microbiota Mediates Neuroinflammation in Alzheimer's Disease: Unraveling Key Factors and Mechanistic Insights

The gut microbiota, the complex community of microorganisms that inhabit the gastrointestinal tract, has emerged as a key player in the pathogenesis of neurodegenerative disorders, including Alzheimer's disease (AD). AD is characterized by progressive cognitive decline and neuronal loss, associated with the accumulation of amyloid-β plaques, neurofibrillary tangles, and neuroinflammation in the brain. Increasing evidence suggests that alterations in the composition and function of the gut microbiota, known as dysbiosis, may contribute to the development and progression of AD by modulating neuroinflammation, a chronic and maladaptive immune response in the central nervous system. This review aims to comprehensively analyze the current role of the gut microbiota in regulating neuroinflammation and glial cell function in AD. Its objective is to deepen our understanding of the pathogenesis of AD and to discuss the potential advantages and challenges of using gut microbiota modulation as a novel approach for the diagnosis, treatment, and prevention of AD.

The role of gut-derived short-chain fatty acids in Parkinson's disease

The emerging function of short-chain fatty acids (SCFAs) in Parkinson's disease (PD) has been investigated in this article. SCFAs, which are generated via the fermentation of dietary fiber by gut microbiota, have been associated with dysfunction of the gut-brain axis and, neuroinflammation. These processes are integral to the development of PD. This article examines the potential therapeutic implications of SCFAs in the management of PD, encompassing their capacity to modulate gastrointestinal permeability, neuroinflammation, and neuronal survival, by conducting an extensive literature review. As a whole, this article emphasizes the potential therapeutic utility of SCFAs as targets for the management and treatment of PD.

Fluoxetine attenuates the anxiolytic effects of the probiotic VSL#3 in a stress-vulnerable genetic line of aves in the chick social-separation stress test, a dual screening assay

Anxiety disorders represent one of the most common and debilitating illnesses worldwide. However, the development of novel therapeutics for anxiety disorders has lagged compared to other mental illnesses. A growing body of research suggests the gut microbiota plays a role in the etiopathology of anxiety disorders and may, therefore, serve as a novel target for their treatment through the use of probiotics. The use of dietary supplements like probiotics is increasing and their interaction with pharmacotherapies is not well understood. Utilizing the chick social-separation stress test, the primary aim of this study was to evaluate the commercially-available multi-strain probiotic found in VSL#3 for potential anxiolytic-like and/or antidepressant-like effects in the stress-vulnerable Black Australorp genetic line. A secondary aim was to evaluate the interaction between probiotics and the SSRI fluoxetine. Animals were treated with either saline, probiotics, fluoxetine, or probiotics + fluoxetine for 8 days prior to exposure to a 90-min isolation stressor that produces both a panic-like (i.e., anxiety-like) state followed by a state of behavioral despair (i.e., depression-like). The 8-day probiotic regimen produced anxiolytic-like effects but did not attenuate behavioral despair. Fluoxetine failed to significantly alter behavior in either of the two phases. Moreover, the combination of fluoxetine with probiotics attenuated the anxiolytic-like effects of probiotics. The fluoxetine + probiotics combination had no effect on behavioral despair. The results of the current study align with other preclinical studies and some clinical trials suggesting probiotics may offer beneficial effects on anxiety. Investigations examining the anxiolytic-like mechanism of probiotics are needed before any conclusions can be made. Additionally, as the use of probiotics becomes more popular, research on the interactions between probiotic-microbiota and psychotropic medications is necessary.

Role of stress and early-life stress in the pathogeny of inflammatory bowel disease

Numerous preclinical and clinical studies have shown that stress is one of the main environmental factor playing a significant role in the pathogeny and life-course of bowel diseases. However, stressful events that occur early in life, even during the fetal life, leave different traces within the central nervous system, in area involved in stress response and autonomic network but also in emotion, cognition and memory regulation. Early-life stress can disrupt the prefrontal-amygdala circuit thus favoring an imbalance of the autonomic nervous system and the hypothalamic-pituitary adrenal axis, resulting in anxiety-like behaviors. The down regulation of vagus nerve and cholinergic anti-inflammatory pathway favors pro-inflammatory conditions. Recent data suggest that emotional abuse at early life are aggravating risk factors in inflammatory bowel disease. This review aims to unravel the mechanisms that explain the consequences of early life events and stress in the pathophysiology of inflammatory bowel disease and their mental co-morbidities. A review of therapeutic potential will also be covered.

Umbelliprenin attenuates comorbid behavioral disorders in acetic acid-induced colitis in mice: mechanistic insights into hippocampal oxidative stress and neuroinflammation

Inflammatory bowel disease (IBD) is often accompanied by psychiatric disorders. Emerging evidence suggests that neuroinflammation and oxidative stress contribute to the psychiatric symptoms associated with IBD. Umbelliprenin (UMB) possesses several pharmacological properties, including anti-inflammatory and antioxidant effects. This study aimed to investigate the protective effects of UMB on comorbid behavioral disorders in a mouse model of experimental colitis, focusing on its potential anti-neuroinflammatory and antioxidant activities. After inducing colitis with acetic acid, male NMRI mice were treated for 7 consecutive days with UMB, saline, or dexamethasone. Behavioral assessments included the forced swimming test (FST), splash test, open field test (OFT), and elevated plus maze (EPM). Histopathological changes in the colon were evaluated, and total antioxidant capacity (TAC), malondialdehyde (MDA) levels, and the expression of inflammatory genes (TNFα, IL1β, and TLR4) were measured in the hippocampus. Colitis was associated with increased immobility time in the FST, reduced entries and time spent in the open arms of the EPM, decreased grooming behavior in the splash test, and reduced time spent in the central zone of the OFT. Colitis also resulted in a reduction in TAC and an increase in MDA levels and inflammatory gene expression in the hippocampus. UMB treatment mitigated the behavioral disorders associated with colitis, reduced neuroinflammation and oxidative stress in the hippocampus, and alleviated histopathological alterations in the colon. In conclusion, UMB may reduce behavioral disorders induced by colitis by decreasing oxidative stress and neuroinflammation in the hippocampus.

Gut microbiota: the indispensable player in neurodegenerative diseases

As one of the most urgent social and health problems in the world, neurodegenerative diseases have always been of interest to researchers. However, the pathological mechanisms and therapeutic approaches are not achieved. In addition to the established roles of oxidative stress, inflammation and immune response, changes of gut microbiota are also closely related to the pathogenesis of neurodegenerative diseases. Gut microbiota is the central player of the gut-brain axis, the dynamic bidirectional communication pathway between gut microbiota and central nervous system, and emerging insights have confirmed its indispensability in the development of neurodegenerative diseases. In this review, we discuss the complex relationship between gut microbiota and the central nervous system from the perspective of the gut-brain axis; review the mechanism of microbiota for the modulation different neurodegenerative diseases and discuss how different dietary patterns affect neurodegenerative diseases via gut microbiota; and prospect the employment of gut microbiota in the therapeutic approach to those diseases. © 2024 Society of Chemical Industry.

Electroacupuncture remodels gut microbiota and metabolites in mice with perioperative neurocognitive impairment

Gut microbiota and metabolites are considered key factors in the pathogenesis of perioperative neurocognitive disorders (PND), and the brain-gut axis may be a promising target for PND treatment. Electroacupuncture has been shown to improve a wide range of neurological disorders and to restore function to the gastrointestinal tract. Thus, we hypothesized whether electroacupuncture could remodel gut microbiota and neuroinflammation induced by anesthesia/surgery. First, we observed electroacupuncture at acupoints GV20, LI4 and PC6 significantly improved memory in behavioral tests. Next, we found electroacupuncture decreased the levels of inflammatory factors (NSE, S-100β, IL-6, etc.) in the hippocampus, indicating that nerve inflammation was blocked by electroacupuncture. Furthermore, via 16S rRNA sequence analysis and LC-MS analysis, the gut microbiota and its metabolites were appropriately restored after electroacupuncture treatment. Additionally, we further confirmed the restorative effect of electroacupuncture on PND by fecal transplantation. In conclusion, the role of electroacupuncture in improving cognitive function and protecting neurons may be related to the modulation of gut microbiota and their metabolite dysregulation, thereby inhibiting neuroinflammation in PND mice.

The ketogenic diet mitigates opioid-induced hyperalgesia by restoring short-chain fatty acids-producing bacteria in the gut

ABSTRACT

Opioids are commonly prescribed to patients with chronic pain. Chronic opioid usage comes with a slew of serious side effects, including opioid-induced hyperalgesia (OIH). The patients with long-term opioid treatment experience paradoxical increases in nociceptive hypersensitivity, namely, OIH. Currently, treatment options for OIH are extremely lacking. In this study, we show that the ketogenic diet recovers the abnormal pain behavior caused by chronic morphine treatment in male mice, and we further show that the therapeutic effect of the ketogenic diet is mediated through gut microbiome. Our 16S rRNA sequencing demonstrates that chronic morphine treatment causes changes in mouse gut microbiota, specifically a decrease in short-chain fatty acids-producing bacteria, and the sequencing data also show that the ketogenic diet rescues those bacteria in the mouse gut. More importantly, we show that supplementation with short-chain fatty acids (butyrate, propionate, and acetate) can delay the onset of OIH, indicating that short-chain fatty acids play a direct role in the development of OIH. Our findings suggest that gut microbiome could be targeted to treat OIH, and the ketogenic diet can be used as a complementary approach for pain relief in patients with chronic opioid treatment. We only used male mice in this study, and thus, our findings cannot be generalized to both sexes.

Deciphering the microbial map and its implications in the therapeutics of neurodegenerative disorder

Every facet of biological anthropology, including development, ageing, diseases, and even health maintenance, is influenced by gut microbiota's significant genetic and metabolic capabilities. With current advancements in sequencing technology and with new culture-independent approaches, researchers can surpass older correlative studies and develop mechanism-based studies on microbiome-host interactions. The microbiota-gut-brain axis (MGBA) regulates glial functioning, making it a possible target for the improvement of development and advancement of treatments for neurodegenerative diseases (NDDs). The gut-brain axis (GBA) is accountable for the reciprocal communication between the gastrointestinal and central nervous system, which plays an essential role in the regulation of physiological processes like controlling hunger, metabolism, and various gastrointestinal functions. Lately, studies have discovered the function of the gut microbiome for brain health-different microbiota through different pathways such as immunological, neurological and metabolic pathways. Additionally, we review the involvement of the neurotransmitters and the gut hormones related to gut microbiota. We also explore the MGBA in neurodegenerative disorders by focusing on metabolites. Further, targeting the blood-brain barrier (BBB), intestinal barrier, meninges, and peripheral immune system is investigated. Lastly, we discuss the therapeutics approach and evaluate the pre-clinical and clinical trial data regarding using prebiotics, probiotics, paraprobiotics, fecal microbiota transplantation, personalised medicine, and natural food bioactive in NDDs. A comprehensive study of the GBA will felicitate the creation of efficient therapeutic approaches for treating different NDDs.

Microbiota-gut-brain axis in health and neurological disease: Interactions between gut microbiota and the nervous system

Along with mounting evidence that gut microbiota and their metabolites migrate endogenously to distal organs, the 'gut-lung axis,' 'gut-brain axis,' 'gut-liver axis' and 'gut-renal axis' have been established. Multiple animal recent studies have demonstrated gut microbiota may also be a key susceptibility factor for neurological disorders such as Alzheimer's disease, Parkinson's disease and autism. The gastrointestinal tract is innervated by the extrinsic sympathetic and vagal nerves and the intrinsic enteric nervous system, and the gut microbiota interacts with the nervous system to maintain homeostatic balance in the host gut. A total of 1507 publications on the interactions between the gut microbiota, the gut-brain axis and neurological disorders are retrieved from the Web of Science to investigate the interactions between the gut microbiota and the nervous system and the underlying mechanisms involved in normal and disease states. We provide a comprehensive overview of the effects of the gut microbiota and its metabolites on nervous system function and neurotransmitter secretion, as well as alterations in the gut microbiota in neurological disorders, to provide a basis for the possibility of targeting the gut microbiota as a therapeutic agent for neurological disorders.

Disturbances of the gut microbiota-derived tryptophan metabolites as key actors in vagotomy-induced mastitis in mice

Previous studies have demonstrated that gut microbiota dysbiosis promotes the development of mastitis. The interaction of the vagus nerve and gut microbiota endows host homeostasis and regulates disease development, but whether the vagus nerve participates in the pathogenesis of mastitis is unclear. Here, vagotomized mice exhibit disruption of the blood-milk barrier and mammary gland inflammation. Notably, mastitis and barrier damage caused by vagotomy are dependent on the gut microbiota, as evidenced by antibiotic treatment and fecal microbiota transplantation. Vagotomy significantly alters the gut microbial composition and tryptophan metabolism and reduces the 5-hydroxyindole acetic acid (5-HIAA) level. Supplementation with 5-HIAA alleviates vagotomy-induced mastitis, which is associated with the activation of the aryl hydrocarbon receptor (AhR) and subsequent inhibition of the NF-κB pathway. Collectively, our findings indicate the important role of the vagus-mediated gut-mammary axis in the pathogenesis of mastitis and imply a potential strategy for the treatment of mastitis by targeting the vagus-gut microbiota interaction.

Oral Administration of Probiotic Bifidobacterium breve Ameliorates Tonic-Clonic Seizure in a Pentylenetetrazole-Induced Kindling Mouse Model via Integrin-Linked Kinase Signaling

Epilepsy is a chronic neurological disorder characterized by recurrent seizures that affects over 70 million people worldwide. Although many antiepileptic drugs that block seizures are available, they have little effect on preventing and curing epilepsy, and their side effects sometimes lead to serious morbidity. Therefore, prophylactic agents with anticonvulsant properties and no adverse effects need to be identified. Recent studies on probiotic administration have reported a variety of beneficial effects on the central nervous system via the microbiota-gut-brain axis. In this study, we investigated the effects of the oral administration of Bifidobacterium breve strain A1 [MCC1274] (B. breve A1) on tonic-clonic seizure in a pentylenetetrazole (PTZ)-induced kindling mouse (KD mouse) model. We found that the oral administration of B. breve A1 every other day for 15 days significantly reduced the seizure score, which gradually increased with repetitive injections of PTZ in KD mice. The administration of B. breve A1, but not saline, to KD mice significantly increased the level of Akt Ser473 phosphorylation (p-Akt) in the hippocampus; this increase was maintained for a minimum of 24 h after PTZ administration. Treatment of B. breve A1-administered KD mice with the selective inhibitor of integrin-linked kinase (ILK) Cpd22 significantly increased the seizure score and blocked the antiepileptic effect of B. breve A1. Moreover, Cpd22 blocked the B. breve A1-induced increase in hippocampal p-Akt levels. These results suggest that the ILK-induced phosphorylation of Akt Ser473 in the hippocampus might be involved in the antiepileptic effect of B. breve A1.

GSK3β Substrate-competitive Inhibitors Regulate the gut Homeostasis and Barrier Function to Inhibit Neuroinflammation in Scopolamine-induced Alzheimer's Disease Model Mice

Alzheimer's disease (AD) is a neurodegenerative disease mainly characterized by cognitive impairment. Glycogen synthase kinase 3 (GSK3β) is a potential therapeutic target against AD. Isoorientin (ISO), a GSK3β substrate competitive inhibitor, plays anti-AD effects in in vitro and in vivo AD model. TFGF-18 is an ISO synthetic analog with improved potency, but its neuroprotective effect in vivo remains to be elucidated, and the underlying mechanisms of GSK3β inhibitor against AD need to be clarified. This study investigated the TFGF-18 and ISO effects on gut homeostasis and neuroinflammation in scopolamine (SCOP)-induced AD mice. And the protection on barrier function was observed in in vitro blood-brain barrier (BBB) model of mouse brain microvascular endothelial cells (bEnd.3). The results show that TFGF-18 and ISO improved cognitive function in SCOP-induced mice, and inhibited cholinergic system disorders and inflammation in the brain and intestine, decreased the level of lipopolysaccharides (LPS) in serum and intestine, protected the diversity and balance of intestinal microbiome, increased the expressions of tight junction protein (ZO-1, occludin), brain derived neurotrophic factor (BDNF) and glial cell-derived neurotrophic factor (GDNF) in the mouse brain and intestine. In addition, TFGF-18 and ISO protected against barrier damage in LPS-stimulated BBB model of bEnd.3 cells in vitro. TFGF-18 and ISO increased the ratio of p-GSK3β/GSK3β, suppressed toll-like receptors 4 (TLR-4) expression and nuclear factor kappa-B (NF-κB) activation in vivo and in vitro, and increased the expressions of β-catenin, nuclear factor erythroid 2-related factor 2 (Nrf2) and heme oxygenase-1 (HO-1) in vitro. In conclusion, The GSK3β inhibitors TFGF-18 and ISO modulate the gut homeostasis and barrier function to inhibit neuroinflammation and attenuate cognitive impairment by regulating NF-κB, β-catenin and Nrf2/HO-1 pathways.

Neuromicrobiology Comes of Age: The Multifaceted Interactions between the Microbiome and the Nervous System

The past decade has seen an explosion in our knowledge about the interactions between gut microbiota, the central nervous system, and the immune system. The gut-brain axis has recently gained much attention due to its role in regulating host physiology. This review explores recent findings concerning potential pathways linking the gut-brain axis to the initiation, pathophysiology, and development of neurological disorders. Our objective of this work is to uncover causative factors and pinpoint particular pathways and therapeutic targets that may facilitate the translation of experimental animal research into practical applications for human patients. We highlight three distinct yet interrelated mechanisms: (1) disruptions of both the intestinal and blood-brain barriers, (2) persistent neuroinflammation, and (3) the role of the vagus nerve.

Transcutaneous vagus nerve stimulation: a bibliometric study on current research hotspots and status

Background

Transcutaneous Vagal Nerve Stimulation (tVNS) has been used as a promising noninvasive neuromodulation technique for the treatment of various systems.The aim of this study was to analyze the research hotspots and future directions of tVNS in the 21st century by using bibliometric methods.

Methods

The study object was the literature related to tVNS from the Web of Science database from 2000 to May 2024. In order to measure and analyze the number of literature issuance, institutions, authors, countries, keywords, co-citations, and journals of publication, we used VOSviewer, Citespace, Bibliometrix R-package, and Scimago Graphica software. A narrative review of the current research content of tVNS was conducted to gain a better understanding of the current state of the field.

Results

A total of 569 papers were included in the study. The results show that from 2000 to 2024, the number of publications shows an increasing trend year by year, involving a total of 326 research institutions. The United States, China, and Germany are the major research centers. The study identified 399 keywords, which roughly formed 11 natural clusters, revealing that the current hotspots of related research are mainly reflected in 3 areas: intervention efficacy on nervous system diseases, mechanism of action of tVNS, and stimulation mode of tVNS. The top 10 most cited references focus on research into the mechanism of action of tVNS.

Conclusion

The efficacy and safety of tVNS have been confirmed in previous studies, but a standardized tVNS treatment protocol has not yet been developed, and most clinical studies have small sample sizes and lack multicenter and multidisciplinary collaboration. Currently, tVNS is used in the treatment of neurological diseases, psychiatric diseases, cardiovascular diseases, and some autoimmune diseases. It is expected that future research in this field will continue to focus on the application of tVNS in central nervous system diseases and the exploration of related mechanisms, and at the same time, with the rise of non-invasive neuromodulation technology, the application of tVNS in other diseases also has great potential for development.

Impacts of microbiota and its metabolites through gut-brain axis on pathophysiology of major depressive disorder

Major depressive disorder (MDD) is characterized by a high rate of recurrence and disability, which seriously affects the quality of life of patients. That's why a deeper understanding of the mechanisms of MDD pathology is an urgent task, and some studies have found that intestinal symptoms accompany people with MDD. The microbiota-gut-brain axis is the bidirectional communication between the gut microbiota and the central nervous system, which was found to have a strong association with the pathogenesis of MDD. Previous studies have focused more on the communication between the gut and the brain through neuroendocrine, neuroimmune and autonomic pathways, and the role of gut microbes and their metabolites in depression is unclear. Metabolites of intestinal microorganisms (e.g., tryptophan, kynurenic acid, indole, and lipopolysaccharide) can participate in the pathogenesis of MDD through immune and inflammatory pathways or by altering the permeability of the gut and blood-brain barrier. In addition, intestinal microbes can communicate with intestinal neurons and glial cells to affect the integrity and function of intestinal nerves. However, the specific role of gut microbes and their metabolites in the pathogenesis of MDD is not well understood. Hence, the present review summarizes how gut microbes and their metabolites are directly or indirectly involved in the pathogenesis of MDD.

Impact of acute stress on the canine gut microbiota

There is growing evidence that a relationship exists between mental and emotional wellbeing and the gut microbiota. Little is known regarding how the microbiota reacts to repeated acute stress events in dogs, and whether it is a predictor of stress response. In this study, we explored the impact on the gut microbiota and digestive health with two common events many pet dogs find stressful. Twenty healthy adult dogs, living within a colony, were exposed to either car travel or separation three times across eight-week intervals. Faecal samples were collected 24 h before, within 24 h, and 24-48 h after. Faecal quality and pH, and microbiota diversity and composition were analysed in context with wider published work on physiological stress measures. No significant changes were observed in faecal quality or pH with either stress event at any timepoint, indicating all pets remained in good digestive health. Microbiota analysis demonstrated no significant impact on alpha or beta diversity with either stressor. Microbial signatures previously linked to stress were not identified in these dogs and no changes were observed in the functional gut composition. Irrespective of whether the pet was considered "stressed" (i.e., exhibited an increase in serum cortisol), there was no effect on the microbiota and no taxa were predictive of stress response. Collectively, this work demonstrates, for this population, certain acute stress events have no meaningful impact on the canine gut microbiota, and it has no impact on the associated stress response.

Postoperative delayed gastric emptying: may gut microbiota play a role?

Postoperative delayed gastric emptying is a prevalent complication following surgical procedures, imposing heavy physical and financial burdens on patients. However, current treatment options remain suboptimal. In recent years, an increasing number of studies have highlighted that the gut microbiota and its metabolites are closely associated with postoperative complications. Various factors can disrupt the gut microbiome after surgery. This review discusses the potential mechanisms by which the gut microbiota and their metabolites may contribute to the pathogenesis of postoperative delayed gastric emptying. However, the current knowledge base is limited in terms of fully understanding the exact mechanisms involved. It is therefore evident that further research is required to fully elucidate the role of the gut microbiome in postoperative delayed gastric emptying, with the aim of uncovering new possibilities for preventive measures and therapeutic treatments.

An ingestible, battery-free, tissue-adhering robotic interface for non-invasive and chronic electrostimulation of the gut

Ingestible electronics have the capacity to transform our ability to effectively diagnose and potentially treat a broad set of conditions. Current applications could be significantly enhanced by addressing poor electrode-tissue contact, lack of navigation, short dwell time, and limited battery life. Here we report the development of an ingestible, battery-free, and tissue-adhering robotic interface (IngRI) for non-invasive and chronic electrostimulation of the gut, which addresses challenges associated with contact, navigation, retention, and powering (C-N-R-P) faced by existing ingestibles. We show that near-field inductive coupling operating near 13.56 MHz was sufficient to power and modulate the IngRI to deliver therapeutically relevant electrostimulation, which can be further enhanced by a bio-inspired, hydrogel-enabled adhesive interface. In swine models, we demonstrated the electrical interaction of IngRI with the gastric mucosa by recording conductive signaling from the subcutaneous space. We further observed changes in plasma ghrelin levels, the "hunger hormone," while IngRI was activated in vivo, demonstrating its clinical potential in regulating appetite and treating other endocrine conditions. The results of this study suggest that concepts inspired by soft and wireless skin-interfacing electronic devices can be applied to ingestible electronics with potential clinical applications for evaluating and treating gastrointestinal conditions.

The gut microbiota-brain axis in neurological disorders

Previous studies have shown a bidirectional communication between human gut microbiota and the brain, known as the microbiota-gut-brain axis (MGBA). The MGBA influences the host's nervous system development, emotional regulation, and cognitive function through neurotransmitters, immune modulation, and metabolic pathways. Factors like diet, lifestyle, genetics, and environment shape the gut microbiota composition together. Most research have explored how gut microbiota regulates host physiology and its potential in preventing and treating neurological disorders. However, the individual heterogeneity of gut microbiota, strains playing a dominant role in neurological diseases, and the interactions of these microbial metabolites with the central/peripheral nervous systems still need exploration. This review summarizes the potential role of gut microbiota in driving neurodevelopmental disorders (autism spectrum disorder and attention deficit/hyperactivity disorder), neurodegenerative diseases (Alzheimer's and Parkinson's disease), and mood disorders (anxiety and depression) in recent years and discusses the current clinical and preclinical gut microbe-based interventions, including dietary intervention, probiotics, prebiotics, and fecal microbiota transplantation. It also puts forward the current insufficient research on gut microbiota in neurological disorders and provides a framework for further research on neurological disorders.

Microbiome composition and central serotonergic activity in patients with depression and type 1 diabetes

The role of gut-brain axis functioning gains growing attention in research on the pathophysiology of major depressive disorders. Here, especially consequences of altered microbiota composition on tryptophan metabolism resulting in altered serotonergic neurotransmission in the central nervous system (CNS) have reached a central position. Previous research, however, mainly focused on either microbiota and peripheral serotonin levels or central serotonergic neurotransmission. The present study aimed to combine the analysis of microbiota composition and central serotonergic activity using a valid neurophysiological indicator. We recruited 19 adult patients with type 1 diabetes and depression (D + D; 7 males), 19 patients with type 1 diabetes (D-; 7 male), and 20 healthy participants (HC; 7 males). Next to the analysis of fecal microbiota regarding α- and β-diversity, the loudness dependence of auditory evoked potential (LDAEP) was investigated, a non-invasive measurement of central serotonergic activity. High α-diversity was associated with high LDAEP, i.e., low serotonergic activity, in patients with diabetes and additional depression. Furthermore, relative abundances of bacterial families belonging to Bacteroidetes, Proteobacteria and Firmicutes were shown to have an impact on central serotonergic activity. This finding was supported by a tendency indicating an association of central serotonergic activity with the Bacteroidetes-Firmicutes ratio in both patients' groups. Together, this data suggests that the guts' microbiota composition might play an important role in regulating the central serotonergic activity in the brain.

Probiotics and the microbiota-gut-brain axis in neurodegeneration: Beneficial effects and mechanistic insights

Neurodegenerative diseases (NDs) are a group of heterogeneous disorders with a high socioeconomic burden. Although pharmacotherapy is currently the principal therapeutic approach for the management of NDs, mounting evidence supports the notion that the protracted application of available drugs would abate their dopaminergic outcomes in the long run. The therapeutic application of microbiome-based modalities has received escalating attention in biomedical works. In-depth investigations of the bidirectional communication between the microbiome in the gut and the brain offer a multitude of targets for the treatment of NDs or maximizing the patient's quality of life. Probiotic administration is a well-known microbial-oriented approach to modulate the gut microbiota and potentially influence the process of neurodegeneration. Of note, there is a strong need for further investigation to map out the mechanistic prospects for the gut-brain axis and the clinical efficacy of probiotics. In this review, we discuss the importance of microbiome modulation and hemostasis via probiotics, prebiotics, postbiotics and synbiotics in ameliorating pathological neurodegenerative events. Also, we meticulously describe the underlying mechanism of action of probiotics and their metabolites on the gut-brain axis in different NDs. We suppose that the present work will provide a functional direction for the use of probiotic-based modalities in promoting current practical treatments for the management of neurodegenerative-related diseases.

Electrical stimulation of the dorsal motor nucleus of the vagus in male mice can regulate inflammation without affecting the heart rate

BACKGROUND

The vagus nerve plays an important role in neuroimmune interactions and in the regulation of inflammation. A major source of efferent vagus nerve fibers that contribute to the regulation of inflammation is the brainstem dorsal motor nucleus of the vagus (DMN), as recently shown using optogenetics. In contrast to optogenetics, electrical neuromodulation has broad therapeutic implications. However, the anti-inflammatory effectiveness of electrical stimulation of the DMN (eDMNS) and the possible heart rate (HR) alterations associated with this approach have not been investigated. Here, we examined the effects of eDMNS on HR and cytokine levels in mice administered with lipopolysaccharide (LPS, endotoxin) and in mice subjected to cecal ligation and puncture (CLP) sepsis.

METHODS

Anesthetized male 8-10-week-old C57BL/6 mice on a stereotaxic frame were subjected to eDMNS using a concentric bipolar electrode inserted into the left or right DMN or sham stimulation. eDMNS (500, 250 or 50 μA at 30 Hz, for 1 min) was performed and HR recorded. In endotoxemia experiments, sham or eDMNS utilizing 250 μA or 50 μA was performed for 5 mins and was followed by LPS (0.5 mg/kg) i.p. administration. eDMNS was also applied in mice with cervical unilateral vagotomy or sham operation. In CLP experiments sham or left eDMNS was performed immediately post CLP. Cytokines and corticosterone were analyzed 90 mins after LPS administration or 24 h after CLP. CLP survival was monitored for 14 days.

RESULTS

Either left or right eDMNS at 500 μA and 250 μA decreased HR, compared with baseline pre-stimulation. This effect was not observed at 50 μA. Left side eDMNS at 50 μA, compared with sham stimulation, significantly decreased serum and splenic levels of the pro-inflammatory cytokine TNF and increased serum levels of the anti-inflammatory cytokine IL-10 during endotoxemia. The anti-inflammatory effect of eDMNS was abrogated in mice with unilateral vagotomy and was not associated with serum corticosterone alterations. Right side eDMNS in endotoxemic mice suppressed serum TNF and increased serum IL-10 levels but had no effects on splenic cytokines. In mice with CLP, left side eDMNS suppressed serum IL-6, as well as splenic IL-6 and increased splenic IL-10 and significantly improved the survival rate of CLP mice.

CONCLUSIONS

For the first time we show that a regimen of eDMNS which does not cause bradycardia alleviates LPS-induced inflammation. These eDMNS anti-inflammatory effects require an intact vagus nerve and are not associated with corticosteroid alterations. eDMNS also decreases inflammation and improves survival in a model of polymicrobial sepsis. These findings are of interest for further studies exploring bioelectronic anti-inflammatory approaches targeting the brainstem DMN.

Advances in gut-brain organ chips

The brain and gut are sensory organs responsible for sensing, transmitting, integrating, and responding to signals from the internal and external environment. In-depth analysis of brain-gut axis interactions is important for human health and disease prevention. Current research on the brain-gut axis primarily relies on animal models. However, animal models make it difficult to study disease mechanisms due to inherent species differences, and the reproducibility of experiments is poor because of individual animal variations, which leads to a significant limitation of real-time sensory responses. Organ-on-a-chip platforms provide an innovative approach for disease treatment and personalized research by replicating brain and gut ecosystems in vitro. This enables a precise understanding of their biological functions and physiological responses. In this article, we examine the history and most current developments in brain, gut, and gut-brain chips. The importance of these systems for understanding pathophysiology and developing new drugs is emphasized throughout the review. This article also addresses future directions and present issues with the advancement and application of gut-brain-on-a-chip technologies.

Exploring Mechanism of Electroacupuncture in Modulating Neuroinflammation Based on Intestinal Flora and Its Metabolites

Neuroinflammatory responses play an important role in the pathogenesis of various diseases, particularly those affecting the central nervous system. Inhibition of neuroinflammation is a crucial therapeutic strategy for the management of central nervous system disorders. The intestinal microbial-gut-brain axis serves as a key regulatory pathway that modulates neuroinflammatory processes. Intestinal flora metabolites such as short-chain fatty acids, indoles and their derivatives, lipopolysaccharides, trimethylamine oxide, and secondary bile acids exert direct or indirect effects on neuroinflammation. Studies have shown that electroacupuncture (EA) modulates the composition of the intestinal microbiota and its metabolites, while also suppressing neuroinflammation by targeting the TLR4/NF- κ B, NLRP3/caspase-1, and microglial cell M2-type transformation pathways. This review discusses the mechanisms by which EA regulates neuroinflammation via intestinal microbiota and its metabolites, providing information and a foundation for further investigation of the precise therapeutic mechanisms of EA in neurological disorders.

The Role of Intestinal Microbiota and Probiotics Supplementation in Multiple Sclerosis Management

Multiple sclerosis (MS) is a neurological autoimmune disorder predominantly afflicting young adults. The etiology of MS is intricate, involving a variety of environmental and genetic factors. Current research increasingly focuses on the substantial contribution of gut microbiota in MS pathogenesis. The commensal microbiota resident within the intestinal milieu assumes a central role within the intricate network recognized as the gut-brain axis (GBA), wielding beneficial impact in neurological and psychological facets. As a result, the modulation of gut microbiota is considered a pivotal aspect in the management of neural disorders, including MS. Recent investigations have unveiled the possibility of using probiotic supplements as a promising strategy for exerting a positive impact on the course of MS. This therapeutic approach operates through several mechanisms, including the reinforcement of gut epithelial integrity, augmentation of the host's resistance against pathogenic microorganisms, and facilitation of mucosal immunomodulatory processes. The present study comprehensively explains the gut microbiome's profound influence on the central nervous system (CNS). It underscores the pivotal role played by probiotics in forming the immune system and modulating neurotransmitter function. Furthermore, the investigation elucidates various instances of probiotic utilization in MS patients, shedding light on the potential therapeutic advantages afforded by this intervention.

Intersecting Pathways: The Role of Metabolic Dysregulation, Gastrointestinal Microbiome, and Inflammation in Acute Ischemic Stroke Pathogenesis and Outcomes

Acute ischemic stroke (AIS) remains a major cause of mortality and long-term disability worldwide, driven by complex and multifaceted etiological factors. Metabolic dysregulation, gastrointestinal microbiome alterations, and systemic inflammation are emerging as significant contributors to AIS pathogenesis. This review addresses the critical need to understand how these factors interact to influence AIS risk and outcomes. We aim to elucidate the roles of dysregulated adipokines in obesity, the impact of gut microbiota disruptions, and the neuroinflammatory cascade initiated by lipopolysaccharides (LPS) in AIS. Dysregulated adipokines in obesity exacerbate inflammatory responses, increasing AIS risk and severity. Disruptions in the gut microbiota and subsequent LPS-induced neuroinflammation further link systemic inflammation to AIS. Advances in neuroimaging and biomarker development have improved diagnostic precision. Here, we highlight the need for a multifaceted approach to AIS management, integrating metabolic, microbiota, and inflammatory insights. Potential therapeutic strategies targeting these pathways could significantly improve AIS prevention and treatment. Future research should focus on further elucidating these pathways and developing targeted interventions to mitigate the impacts of metabolic dysregulation, microbiome imbalances, and inflammation on AIS.

The Relationship between Canine Behavioral Disorders and Gut Microbiome and Future Therapeutic Perspectives

Canine behavioral disorders have become one of the most common concerns and challenging issues among dog owners. Thus, there is a great demand for knowledge about various factors affecting dogs' emotions and well-being. Among them, the gut-brain axis seems to be particularly interesting, especially since in many instances the standard treatment or behavioral therapies insufficiently improve animal behavior. Therefore, to face this challenge, the search for novel therapeutic methods is highly required. Existing data show that mammals' gut microbiome, immune system, and nervous system are in continuous communication and influence animal physiology and behavior. This review aimed to summarize and discuss the most important scientific evidence on the relationship between mental disorders and gut microbiota in dogs, simultaneously presenting comparable outcomes in humans and rodent models. A comprehensive overview of crucial mechanisms of the gut-brain axis is included. This refers especially to the neurotransmitters crucial for animal behavior, which are regulated by the gut microbiome, and to the main microbial metabolites-short-chain fatty acids (SCFAs). This review presents summarized data on gut dysbiosis in relation to the inflammation process within the organism, as well as the activation of the hypothalamic-pituitary-adrenal (HPA) axis. All of the above mechanisms are presented in this review in strict correlation with brain and/or behavioral changes in the animal. Additionally, according to human and laboratory animal studies, the gut microbiome appears to be altered in individuals with mental disorders; thus, various strategies to manipulate the gut microbiota are implemented. This refers also to the fecal microbiome transplantation (FMT) method, based on transferring the fecal matter from a donor into the gastrointestinal tract of a recipient in order to modulate the gut microbiota. In this review, the possible effects of the FMT procedure on animal behavioral disorders are discussed.

Interoceptive Processing in Functional Gastrointestinal Disorders

Functional gastrointestinal disorders (FGIDs) are characterized by chronic gastrointestinal symptoms in the absence of overt pathology and affect a significant percentage of the worldwide population. They are commonly accompanied by co-morbid psychiatric symptomatology and are associated with significant suffering and great healthcare services utilization. There is growing evidence that dysregulation of the gut-brain axis and disturbances in the processing of afferent interoceptive signals lie at the heart of these disorders. In this context, the aim of the current review was to detect and critically review original articles focusing on the role of interoception in the pathophysiology of FGIDs. Our search yielded 38 relevant studies. FGID patients displayed increased visceral sensitivity, enhanced attention to gastrointestinal interoceptive cues, and greater emotional arousal when coping with gut-derived sensations. Neuroimaging studies have shown significant structural and functional changes in regions of the interoceptive network, while molecular and genetic studies have revealed significant associations between interoceptive signaling and deficits in excitatory neurotransmission, altered endocrine and immune physiological pathways, and aberrant expression of transient receptor potential channel genes. Finally, there were emerging data suggesting that interoception-based interventions may reduce physical symptoms and improve quality of life and should be integrated into FGID clinical management practices.

Acupuncture influences multiple diseases by regulating gut microbiota

Acupuncture, an important green and side effect-free therapy in traditional Chinese medicine, is widely use both domestically and internationally. Acupuncture can interact with the gut microbiota and influence various diseases, including metabolic diseases, gastrointestinal diseases, mental disorders, nervous system diseases, and other diseases. This review presents a thorough analysis of these interactions and their impacts and examines the alterations in the gut microbiota and the potential clinical outcomes following acupuncture intervention to establish a basis for the future utilization of acupuncture in clinical treatments.

Association of Postexercise Vagal Dysfunction With Protein-Energy Wasting and Noncardiovascular Outcomes in Patients Receiving Hemodialysis: A Retrospective Cohort Study

OBJECTIVE

Postexercise vagal dysfunction is linked to noncardiovascular mortality in hemodialysis patients, but the mechanism is unknown. This study aimed to determine the association of cardiovagal neuropathy with systemic inflammation, protein-energy wasting, and noncardiovascular hospitalization.

METHODS

This 2-center retrospective cohort study analyzed data from 280 hemodialysis patients who underwent exercise test. Patients were assessed for heart rate (HR) recovery (bpm) for 1 minute after exercise, a marker of vagal function, and were divided into 3 categories (Low: ≤ 6, Mid: 7-11, High: ≥ 12 bpm). We followed 1-year changes in the systemic inflammation-based prognostic score (Glasgow Prognostic Score [GPS]), body weight, and creatinine generation rate (CGR), an indicator of muscle mass, as well as 2-year hospitalization.

RESULTS

The HR recovery category was associated with serum C-reactive protein and albumin levels and GPS. After 1 year, the low HR recovery category was associated with worsening in GPS (low, 0 [0-0.5]; mid, 0 [0-1]; high, 0 [0-0]), weight (low, 100.0 [96.1-102.5]; mid, 101.3 [98.9-105.0]; high, 100.5 [98.2-102.9]%), and CGR (low, 97.0 [88.5-111.4]; mid, 110.2 [90.9-124.8]; high, 106.2 [95.5-115.5]%), and the correlations with GPS and CGR remained consistent after adjusting for confounders such as exercise capacity and hospitalization during the follow-up period. There were 117 patients hospitalized. Compared to the high HR recovery category, the mid (hazard ratio: 1.8, 95% confidence interval [CI]: 1.1-3.1, P = .02) and low (hazard ratio: 2.4, 95% CI: 1.5-4.0, P = .001) categories were independently associated with an increased risk of all-cause hospitalization. For noncardiovascular disease hospitalization, the low HR recovery category was independently associated with increased risk of hospitalization (hazard ratio: 2.1, 95% CI: 1.2-3.7, P = .007).

CONCLUSIONS

Vagal neuropathy in this population can contribute to adverse outcomes associated with systemic inflammation and protein-energy wasting.

Oligosaccharides from black ginseng innovatively prepared by low-temperature steam-heating process ameliorate cognitive impairment in Alzheimer's disease mice via the Keap-1/Nrf2 pathway

BACKGROUND

Our objective in this study was to evaluate the effectiveness of oligosaccharides extracted from black ginseng (OSBG), innovatively prepared by a low-temperature steam-heating process, in the improvement of learning and memory impairment in mice, as well as the mechanism(s).

RESULTS

Eight carbohydrates involving isomaltose and maltotetraose were detected in black gensing; monosaccharide residues including mannose and rhamnose were also discovered. OSBG-treated mice showed significant amelioration in recognition and spatial memory deficits compared to the scopolamine group. OSBG could decrease acetylcholinesterase activity in a tissue-dependent fashion but not in a dose-dependent manner. Furthermore, in contrast, OSBG administration resulted in significant upregulation superoxide dismutase, glutathione, glutathione peroxidase (GPx), and Kelch-like ECH-associated protein 1, downregulation of malondialdehyde and nuclear factor erythroid 2-related factor 2 in the tissues. Finally, at the genus level, we observed that the OSBG interventions increased the relative abundance of probiotics (e.g., Barnesiella, Staphylococcus, Clostridium_XlVb) and decreased pernicious bacteria such as Eisenbergiella and Intestinimonas, compared to the Alzheimer's disease mouse model group. Herein, our results demonstrate that OSBG restores the composition of the scopolamine-induced intestinal microbiota in mice, providing homeostasis of gut microbiota and providing evidence for microbiota-regulated therapeutic potential.

CONCLUSION

Our results showed for the first time a clear role for OSBG in improving scopolamine-induced memory impairment by inhibiting cholinergic dysfunction in a tissue-dependent manner. Additionally, OSBG administration relieved oxidative stress by activating the Keap-1/Nrf2 pathway and modulating the gut microbiota. Collectively, OSBG may be a promising target for neuroprotective antioxidants for improving memory and cognition in Alzheimer's disease patients. © 2024 Society of Chemical Industry.

Gut Microbiota Metabolite Messengers in Brain Function and Pathology at a View of Cell Type-Based Receptor and Enzyme Reaction

The human gastrointestinal (GI) tract houses a diverse microbial community, known as the gut microbiome comprising bacteria, viruses, fungi, and protozoa. The gut microbiome plays a crucial role in maintaining the body's equilibrium and has recently been discovered to influence the functioning of the central nervous system (CNS). The communication between the nervous system and the GI tract occurs through a two-way network called the gut-brain axis. The nervous system and the GI tract can modulate each other through activated neuronal cells, the immune system, and metabolites produced by the gut microbiome. Extensive research both in preclinical and clinical realms, has highlighted the complex relationship between the gut and diseases associated with the CNS, such as Alzheimer's disease, Parkinson's disease, and amyotrophic lateral sclerosis. This review aims to delineate receptor and target enzymes linked with gut microbiota metabolites and explore their specific roles within the brain, particularly their impact on CNS-related diseases.

Rebalancing the Gut: Glucagon-Like Peptide-1 Agonists as a Strategy for Obesity and Metabolic Health

Obesity significantly impacts gut microbial composition, exacerbating metabolic dysfunction and weight gain. Traditional treatment methods often fall short, underscoring the need for innovative approaches. Glucagon-like peptide-1 (GLP-1) agonists have emerged as promising agents in obesity management, demonstrating significant potential in modulating gut microbiota. These agents promote beneficial bacterial populations, such as Bacteroides, Lactobacillus, and Bifidobacterium, while reducing harmful species like Enterobacteriaceae. By influencing gut microbiota composition, GLP-1 agonists enhance gut barrier integrity, reducing permeability and systemic inflammation, which are hallmarks of metabolic dysfunction in obesity. Additionally, GLP-1 agonists improve metabolic functions by increasing the production of short-chain fatty acids like butyrate, propionate, and acetate, which serve as energy sources for colonocytes, modulate immune responses, and enhance the production of gut hormones that regulate appetite and glucose homeostasis. By increasing microbial diversity, GLP-1 agonists create a more resilient gut microbiome capable of resisting pathogenic invasions and maintaining metabolic balance. Thus, by shifting the gut microbiota toward a healthier profile, GLP-1 agonists help disrupt the vicious cycle of obesity-induced gut dysbiosis and inflammation. This review highlights the intricate relationship between obesity, gut microbiota, and GLP-1 agonists, providing valuable insights into their combined role in effective obesity treatment and metabolic health enhancement.

Peyer's Patch: Possible target for modulating the Gut-Brain-Axis through microbiota

The gastrointestinal (GI) tract and the brain form bidirectional nervous, immune, and endocrine communications known as the gut-brain axis. Several factors can affect this axis; among them, various studies have focused on the microbiota and imply that alterations in microbiota combinations can influence both the brain and GI. Also, many studies have shown that the immune system has a vital role in varying gut microbiota combinations. In the current paper, we will review the multidirectional effects of gut microbiota, immune system, and nervous system on each other. Specifically, this review mainly focuses on the impact of Peyer's patches as a critical component of the gut immune system on the gut-brain axis through affecting the gut's microbial composition. In this way, some factors were discussed as proposed elements of missing gaps in this field.

Neuroimmune response and oxidative stress in the prefrontal cortex mediate seizure susceptibility in experimental colitis in male mice

Inflammatory bowel disease (IBD) is a chronic gastrointestinal disorder. Oxidative stress and inflammatory responses have a vital role in the pathophysiology of IBD as well as seizure. IBD is associated with extraintestinal manifestations. This study aimed to explore the relationship between colitis and susceptibility to seizures, with a focus on the roles of neuroinflammation and oxidative stress in acetic acid-induced colitis in mice. Forty male Naval Medical Research Institute mice were divided into four groups: control, colitis, pentylenetetrazole (PTZ), and colitis + PTZ. Colitis was induced by intrarectal administration of acetic acid, and seizures were induced by intravenous injection of PTZ 7 days postcolitis induction. Following the measurement of latency to seizure, the mice were killed, and their colons and prefrontal cortex (PFC) were dissected. Gene expression of inflammatory markers including interleukin-1β, tumor necrosis factor-alpha, NOD-like receptor protein 3, and toll-like receptor 4, as well as total antioxidant capacity (TAC), malondialdehyde (MDA), and nitrite levels were measured in the colon and PFC. Histopathological evaluations were performed on the colon samples. Data were analyzed by t-test or one-way variance analysis. Colitis decreased latency to seizure, increased gene expression of inflammatory markers, and altered levels of MDA, nitrite, and TAC in both the colon and PFC. Simultaneous induction of colitis and seizure exacerbated the neuroimmune response and oxidative stress in the PFC and colon. Results concluded that neuroinflammation and oxidative stress in the PFC at least partially mediate the comorbid decrease in seizure latency in mice with colitis.

Coprococcus eutactus screened from healthy adolescent attenuates chronic restraint stress-induced depression-like changes in adolescent mice: Potential roles in the microbiome and neurotransmitter modulation

The onset of depression commonly occurs in adolescence; therefore, depressive prevention and intervention are pivotal during this period. It is becoming evident that neurotransmitter imbalance and gut microbiota dysbiosis are prominent causes of depression. However, the underlying links and mechanisms remain poorly understood. In this study, with 16S ribosomal RNA gene sequencing, genus Coprococcus markedly differentiated between the healthy and unmedicated depressive adolescents. Based on this, transplantation of Coprococcus eutactus (C.e.) was found to dramatically ameliorate the chronic restraint stress (CRS) induced depression-like changes and prevent synaptic loss and glial-stimulated neuroinflammation in mice. The Ultra-high performance liquid chromatography tandem mass spectrometry analysis (UHPLC-MS/MS) further showed that neurotoxic neurotransmitters in kynurenine pathway (KP) such as 3-hydroxykynurenine (3-HK) and 3-hydroxyanthranilic acid (3-HAA) decreased in mouse brains, mechanistically deciphering the transfer of the tryptophan metabolic pathway to serotonin metabolic signaling in the brain after C.e. treatment, which was also verified in the colon. Molecularly, blockage of KP activities mediated by C.e. was ascribed to the restraint of the limit-step enzymes responsible for kynurenine, 3-HK, and quinolinic acid generation. In the colon, C.e. treatment significantly recovered goblet cells and mucus secretion in CRS mice which may ascribe to the rebalance of the disordered gut microbiota, especially Akkermansia, Roseburia, Rikenella, Blautia, and Alloprevotella. Taken together, the current study reveals for the first time the beneficial effects and potential mechanisms of C.e. in ameliorating CRS-induced depression, unraveling the direct links between C.e. treatment and neurotransmitter rebalance, which may provide efficacious therapeutic avenues for adolescent depressive intervention.

Analgesic Effect of Auricular Vagus Nerve Stimulation on Oxaliplatin-induced Peripheral Neuropathic Pain in a Rodent Model

Cancer chemotherapy often triggers peripheral neuropathy in patients, leading to neuropathic pain in the extremities. While previous research has explored various nerve stimulation to alleviate chemotherapy-induced peripheral neuropathy (CIPN), evidence on the effectiveness of noninvasive auricular vagus nerve stimulation (aVNS) remains uncertain. This study aimed to investigate the efficacy of non-invasive aVNS in relieving CIPN pain. To induce CIPN in experimental animals, oxaliplatin was intraperitoneally administered to rats (6 mg/kg). Mechanical and cold allodynia, the representative symptoms of neuropathic pain, were evaluated using the von Frey test and acetone test, respectively. The CIPN animals were randomly assigned to groups and treated with aVNS (5 V, square wave) at different frequencies (2, 20, or 100 Hz) for 20 minutes. Results revealed that 20 Hz aVNS exhibited the most pronounced analgesic effect, while 2 or 100 Hz aVNS exhibited weak effects. Immunohistochemistry analysis demonstrated increased c-Fos expression in the locus coeruleus (LC) in the brain of CIPN rats treated with aVNS compared to sham treatment. To elucidate the analgesic mechanisms involving the adrenergic descending pathway, α1-, α2-, or β-adrenergic receptor antagonists were administered to the spinal cord before 20 Hz aVNS. Only the β-adrenergic receptor antagonist, propranolol, blocked the analgesic effect of aVNS. These findings suggest that 20 Hz aVNS may effectively alleviate CIPN pain through β-adrenergic receptor activation.

Enteric neuropathy and the vagus nerve: Therapeutic implications

Enteric neuropathies are characterized by abnormalities of gut innervation, which includes the enteric nervous system, inducing severe gut dysmotility among other dysfunctions. Most of the gastrointestinal tract is innervated by the vagus nerve, the efferent branches of which have close interconnections with the enteric nervous system and whose afferents are distributed throughout the different layers of the digestive wall. The vagus nerve is a key element of the autonomic nervous system, involved in the stress response, at the interface of the microbiota-gut-brain axis, has anti-inflammatory and prokinetic properties, modulates intestinal permeability, and has a significant capacity of plasticity and regeneration. Targeting these properties of the vagus nerve, with vagus nerve stimulation (or non-stimulation/ pharmacological methods), could be of interest in the therapeutic management of enteric neuropathies.

From Skin and Gut to the Brain: The Infectious Journey of the Human Commensal Fungus Malassezia and Its Neurological Consequences

The human mycobiome encompasses diverse communities of fungal organisms residing within the body and has emerged as a critical player in shaping health and disease. While extensive research has focused on the skin and gut mycobiome, recent investigations have pointed toward the potential role of fungal organisms in neurological disorders. Among those fungal organisms, the presence of the commensal fungus Malassezia in the brain has created curiosity because of its commensal nature and primary association with the human skin and gut. This budding yeast is responsible for several diseases, such as Seborrheic dermatitis, Atopic dermatitis, Pityriasis versicolor, Malassezia folliculitis, dandruff, and others. However recent findings surprisingly show the presence of Malassezia DNA in the brain and have been linked to diseases like Alzheimer's disease, Parkinson's disease, Multiple sclerosis, and Amyotrophic lateral sclerosis. The exact role of Malassezia in these disorders is unknown, but its ability to infect human cells, travel through the bloodstream, cross the blood-brain barrier, and reside along with the lipid-rich neuronal cells are potential mechanisms responsible for pathogenesis. This also includes the induction of pro-inflammatory cytokines, disruption of the blood-brain barrier, gut-microbe interaction, and accumulation of metabolic changes in the brain environment. In this review, we discuss these key findings from studies linking Malassezia to neurological disorders, emphasizing the complex and multifaceted nature of these cases. Furthermore, we discuss potential mechanisms through which Malassezia might contribute to the development of neurological conditions. Future investigations will open up new avenues for our understanding of the fungal gut-brain axis and how it influences human behavior. Collaborative research efforts among microbiologists, neuroscientists, immunologists, and clinicians hold promise for unraveling the enigmatic connections between human commensal Malassezia and neurological disorders.

Faecal microbiota transplantation (FMT) in Norwegian outpatients with mild to severe myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS): protocol for a 12-month randomised double-blind placebo-controlled trial

INTRODUCTION

The observed alteration of the intestinal microbiota in patients with myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) and the effect of transferring a healthy gut flora from a faecal donor using a faecal microbiota transplantation (FMT) will be explored in this trial.

METHODS AND ANALYSIS

This is a protocol for a randomised, double-blind, placebo-controlled, parallel-group, single-centre trial, with 12 months follow-up. 80 participants will be included and randomised (1:1:2) to either donor FMT (from two different donors) or placebo (autologous FMT). Participants will be included by the International Clinical Criteria for ME/CFS. The clinical measures of ME/CFS and disease activity include Modified DePaul Questionnaire, Fatigue Severity Scale (FSS), Hospital Anxiety and Depression Scale (HADS), 36-Item Short Form Health Survey (SF-36), ROMA IV criteria, Food Frequency Questionnaire, Repeatable Battery for the Assessment of Neuropsychological Status, heart rate variability testing and reports on the use of antibiotics and food supplements, as well as biobanking of blood, urine and faeces.The primary endpoint is proportion with treatment success in FSS score in donor versus autologous FMT group 3 months after treatment. Treatment success is defined as an FSS improvement of more than 1.2 points from baseline at 3 months after treatment. Adverse events will be registered throughout the study.

ETHICS AND DISSEMINATION

The Regional Committee for Medical Research Ethics Northern Norway has approved the study. The study has commenced in May 2019. Findings will be disseminated in international peer-reviewed journal(s), submitted to relevant conferences, and trial participants will be informed via phone calls.

TRIAL REGISTRATION NUMBER

NCT03691987.

Zeolite and Neurodegenerative Diseases

Neurodegenerative diseases (NDs), characterized by progressive degeneration and death of neurons, are strongly related to aging, and the number of people with NDs will continue to rise. Alzheimer's disease (AD) and Parkinson's disease (PD) are the most common NDs, and the current treatments offer no cure. A growing body of research shows that AD and especially PD are intricately related to intestinal health and the gut microbiome and that both diseases can spread retrogradely from the gut to the brain. Zeolites are a large family of minerals built by [SiO4]4- and [AlO4]5- tetrahedrons joined by shared oxygen atoms and forming a three-dimensional microporous structure holding water molecules and ions. The most widespread and used zeolite is clinoptilolite, and additionally, mechanically activated clinoptilolites offer further improved beneficial effects. The current review describes and discusses the numerous positive effects of clinoptilolite and its forms on gut health and the gut microbiome, as well as their detoxifying, antioxidative, immunostimulatory, and anti-inflammatory effects, relevant to the treatment of NDs and especially AD and PD. The direct effects of clinoptilolite and its activated forms on AD pathology in vitro and in vivo are also reviewed, as well as the use of zeolites as biosensors and delivery systems related to PD.

Rejuvenating fecal microbiota transplant enhances peripheral nerve repair in aged mice by modulating endoneurial inflammation

Peripheral nerve injury (PNI) resulting from trauma or neuropathies can cause significant disability, and its prognosis deteriorates with age. Emerging evidence suggests that gut dysbiosis and reduced fecal short-chain fatty acids (SCFAs) contribute to an age-related systemic hyperinflammation (inflammaging), which hinders nerve recovery after injury. This study thus aimed to evaluate the pro-regenerative effects of a rejuvenating fecal microbiota transplant (FMT) in a preclinical PNI model using aged mice. Aged C57BL/6 mice underwent bilateral crush injuries to their sciatic nerves. Subsequently, they either received FMT from young donors at three and four days after the injury or retained their aged gut microbiota. We analyzed gut microbiome composition and SCFA concentrations in fecal samples. The integrity of the ileac mucosal barrier was assessed by immunofluorescence staining of Claudin-1. Flow cytometry was utilized to examine immune cells and cytokine production in the ileum, spleen, and sciatic nerve. Various assessments, including behavioural tests, electrophysiological studies, and morphometrical analyses, were conducted to evaluate peripheral nerve function and repair following injury. Rejuvenating FMT reversed age-related gut dysbiosis by increasing Actinobacteria, especially Bifidobacteriales genera. This intervention also led to an elevation of gut SCFA levels and mitigated age-related ileac mucosal leakiness in aged recipients. Additionally, it augmented the number of T-helper 2 (Th2) and regulatory T (Treg) cells in the ileum and spleen, with the majority being positive for anti-inflammatory interleukin-10 (IL-10). In sciatic nerves, rejuvenating FMT resulted in increased M2 macrophage counts and a higher IL-10 production by IL-10+TNF-α- M2 macrophage subsets. Ultimately, restoring a youthful gut microbiome in aged mice led to improved nerve repair and enhanced functional recovery after PNI. Considering that FMT is already a clinically available technique, exploring novel translational strategies targeting the gut microbiome to enhance nerve repair in the elderly seems promising and warrants further evaluation.

Kefir as a therapeutic agent in clinical research: a scoping review

Increasing research has been conducted on the role of probiotics in disease treatment. Kefir, a safe, low-cost probiotic fermented milk drink, has been investigated in many in vitro and animal studies, although parameters for human therapeutic dose or treatment time have not yet been determined. Here we perform a scoping review of clinical studies that have used kefir as a therapeutic agent, compiling the results for perspectives to support and direct further research. This review was based on Joanna Briggs Institute guidelines, including studies on the effects of kefir-fermented milk in humans. Using the term KEFIR, the main international databases were searched for studies published in English, Spanish or Portuguese until 9 March 2022. A total of 5835 articles were identified in the four databases, with forty-four eligible for analysis. The research areas were classified as metabolic syndrome and type 2 diabetes, gastrointestinal health/disorders, maternal/child health and paediatrics, dentistry, oncology, women's and geriatric health, and dermatology. The many study limitations hampered generalisation of the results. The small sample sizes, methodological variation and differences in kefir types, dosage and treatment duration prevented clear conclusions about its benefits for specific diseases. We suggest using a standard therapeutic dose of traditionally prepared kefir in millilitres according to body weight, making routine consumption more feasible. The studies showed that kefir is safe for people without serious illnesses.

Applied physiology: gut microbiota and antimicrobial therapy

The gut microbiota plays an important role in maintaining human health and in the pathogenesis of several diseases. Antibiotics are among the most commonly prescribed drugs and have a significant impact on the structure and function of the gut microbiota. The understanding that a healthy gut microbiota prevents the development of many diseases has also led to its consideration as a potential therapeutic target. At the same time, any factor that alters the gut microbiota becomes important in this approach. Exercise and antibacterial therapy have a direct effect on the microbiota. The review reflects the current state of publications on the mechanisms of intestinal bacterial involvement in the pathogenesis of cardiovascular, metabolic, and neurodegenerative diseases. The physiological mechanisms of the influence of physical activity on the composition of the gut microbiota are considered. The mechanisms of the common interface between exercise and antibacterial therapy will be considered using the example of several socially important diseases. The aim of the study is to show the physiological relationship between the effects of exercise and antibiotics on the gut microbiota.

Gut-brain axis in the pathogenesis of sepsis-associated encephalopathy

The gut-brain axis is a bidirectional communication network linking the gut and the brain, overseeing digestive functions, emotional responses, body immunity, brain development, and overall health. Substantial research highlights a connection between disruptions of the gut-brain axis and various psychiatric and neurological conditions, including depression and Alzheimer's disease. Given the impact of the gut-brain axis on behavior, cognition, and brain diseases, some studies have started to pay attention to the role of the axis in sepsis-associated encephalopathy (SAE), where cognitive impairment is the primary manifestation. SAE emerges as the primary and earliest form of organ dysfunction following sepsis, potentially leading to acute cognitive impairment and long-term cognitive decline in patients. Notably, the neuronal damage in SAE does not stem directly from the central nervous system (CNS) infection but rather from an infection occurring outside the brain. The gut-brain axis is posited as a pivotal factor in this process. This review will delve into the gut-brain axis, exploring four crucial pathways through which inflammatory signals are transmitted and elevate the incidence of SAE. These pathways encompass the vagus nerve pathway, the neuroendocrine pathway involving the hypothalamic-pituitary-adrenal (HPA) axis and serotonin (5-HT) regulation, the neuroimmune pathway, and the microbial regulation. These pathways can operate independently or collaboratively on the CNS to modulate brain activity. Understanding how the gut affects and regulates the CNS could offer the potential to identify novel targets for preventing and treating this condition, ultimately enhancing the prognosis for individuals with SAE.

Gut Microbiota Mediate the Neuroprotective Effect of Oolong Tea Polyphenols in Cognitive Impairment Induced by Circadian Rhythm Disorder

Oolong tea polyphenols (OTP) have attracted wide attention due to their ability to reduce inflammatory response, regulate gut microbiota, and improve cognitive function. However, exactly how the gut microbiota modulates nervous system activity is still an open question. We previously expounded that supplementing with OTP alleviated neuroinflammation in circadian rhythm disorder (CRD) mice. Here, we showed that OTP can relieve microglia activation by reducing harmful microbial metabolites lipopolysaccharide (LPS) that alleviate CRD-induced cognitive decline. Mechanistically, OTP suppressed the inflammation response by regulating the gut microbiota composition, including upregulating the relative abundance of Muribaculaceae and Clostridia_UCG-014 and downregulating Desulfovibrio, promoting the production of short-chain fatty acids (SCFAs). Moreover, the use of OTP alleviated intestinal barrier damage and decreased the LPS transport to the serum. These results further inhibited the activation of microglia, thus alleviating cognitive impairment by inhibiting neuroinflammation, neuron damage, and neurotoxicity metabolite glutamate elevation. Meanwhile, OTP upregulated the expression of synaptic plasticity-related protein postsynaptic density protein 95 (PSD-95) and synaptophysin (SYN) by elevating the brain-derived neurotrophic factor (BDNF) level. Taken together, our findings suggest that the OTP has the potential to prevent CRD-induced cognition decline by modulating gut microbiota and microbial metabolites.

Revitalizing the Gut Microbiome in Chronic Kidney Disease: A Comprehensive Exploration of the Therapeutic Potential of Physical Activity

Both physical inactivity and disruptions in the gut microbiome appear to be prevalent in patients with chronic kidney disease (CKD). Engaging in physical activity could present a novel nonpharmacological strategy for enhancing the gut microbiome and mitigating the adverse effects associated with microbial dysbiosis in individuals with CKD. This narrative review explores the underlying mechanisms through which physical activity may favorably modulate microbial health, either through direct impact on the gut or through interorgan crosstalk. Also, the development of microbial dysbiosis and its interplay with physical inactivity in patients with CKD are discussed. Mechanisms and interventions through which physical activity may restore gut homeostasis in individuals with CKD are explored.