Short-Chain Fatty Acids Improve Poststroke Recovery via Immunological Mechanisms

Short-chain fatty acid on blood-brain barrier and glial function in ischemic stroke

Stroke is the second most common cause of death and one of the most common causes of disability worldwide. The intestine is home to several microorganisms that fulfill essential functions for the natural and physiological functioning of the human body. There is an interaction between the central nervous system (CNS) and the gastrointestinal system that enables bidirectional communication between them, the so-called gut-brain axis. Based on the gut-brain axis, there is evidence of a link between the gut microbiota and the regulation of microglial functions through glial activation. This interaction is partly due to the immunological properties of the microbiota and its connection with the CNS, such that metabolites produced by the microbiota can cross the gut barrier, enter the bloodstream and reach the CNS and significantly affect microglia, astrocytes and other cells of the immune system. Studies addressing the effects of short-chain fatty acids (SCFAs) on glial function and the BBB in ischemic stroke are still scarce. Therefore, this review aims to stimulate the investigation of these associations, as well as to generate new studies on this topic that can clarify the role of SCFAs after stroke in a more robust manner.

A gender perspective on diet, microbiome, and sex hormone interplay in cardiovascular disease

A unique interplay between body and environment embeds and reflects host-microbiome interactions that contribute to sex-differential disease susceptibility, symptomatology, and treatment outcomes. These differences derive from individual biological factors, such as sex hormone action, sex-divergent immune processes, X-linked gene dosage effects, and epigenetics, as well as from their interaction across the lifespan. The gut microbiome is increasingly recognized as a moderator of several body systems that are thus impacted by its function and composition. In humans, biological sex components further interact with gender-specific exposures such as dietary preferences, stressors, and life experiences to form a complex whole, requiring innovative methodologies to disentangle. Here, we summarize current knowledge of the interactions among sex hormones, gut microbiota, immune system, and vascular health and their relevance for sex-differential epidemiology of cardiovascular diseases. We outline clinical implications, identify knowledge gaps, and place emphasis on required future studies to address these gaps. In addition, we provide an overview of the caveats associated with conducting cardiovascular research that require consideration of sex/gender differences. While previous work has inspected several of these components separately, here we call attention to further translational utility of a combined perspective from cardiovascular translational research, gender medicine, and microbiome systems biology.

Intermittent fasting induced cerebral ischemic tolerance altered gut microbiome and increased levels of short-chain fatty acids to a beneficial phenotype

Preconditioning-induced cerebral ischemic tolerance is known to be a beneficial adaptation to protect the brain in an unavoidable event of stroke. We currently demonstrate that a short bout (6 weeks) of intermittent fasting (IF; 15 h fast/day) induces similar ischemic tolerance to that of a longer bout (12 weeks) in adult C57BL/6 male mice subjected to transient middle cerebral artery occlusion (MCAO). In addition, the 6 weeks IF regimen induced ischemic tolerance irrespective of age (3 months or 24 months) and sex. Mice subjected to transient MCAO following IF showed improved motor function recovery (rotarod and beam walk tests) between days 1 and 14 of reperfusion and smaller infarcts (T2-MRI) on day 1 of reperfusion compared with age/sex matched ad libitum (AL) controls. Diet influences the gut microbiome composition and stroke is known to promote gut bacterial dysbiosis. We presently show that IF promotes a beneficial phenotype of gut microbiome following transient MCAO compared with AL cohort. Furthermore, post-stroke levels of short-chain fatty acids (SCFAs), which are known to be neuroprotective, are higher in the fecal samples of the IF cohort compared with the AL cohort. Thus, our studies indicate the efficacy of IF in protecting the brain after stroke, irrespective of age and sex, probably by altering gut microbiome and SCFA production.

The communication mechanism of the gut-brain axis and its effect on central nervous system diseases: A systematic review

Gut microbiota is involved in intricate and active metabolic processes the host's brain function, especially its role in immune responses, secondary metabolism, and symbiotic connections with the host. Gut microbiota can promote the production of essential metabolites, neurotransmitters, and other neuroactive chemicals that affect the development and treatment of central nervous system diseases. This article introduces the relevant pathways and manners of the communication between the brain and gut, summarizes a comprehensive overview of the current research status of key gut microbiota metabolites that affect the functions of the nervous system, revealing those adverse factors that affect typical communication between the brain-gut axis, and outlining the efforts made by researchers to alleviate these neurological diseases through targeted microbial interventions. The relevant pathways and manners of communication between the brain and gut contribute to the experimental design of new treatment plans and drug development. The factors that may cause changes in gut microbiota and affect metabolites, as well as current intervention methods are summarized, which helps improve gut microbiota brain dialogue, prevent adverse triggering factors from interfering with the gut microbiota system, and minimize neuropathological changes.

Microglia in Microbiota-Gut-Brain Axis: A Hub in Epilepsy

There is growing concern about the role of the microbiota-gut-brain axis in neurological illnesses, and it makes sense to consider microglia as a critical component of this axis in the context of epilepsy. Microglia, which reside in the central nervous system, are dynamic guardians that monitor brain homeostasis. Microglia receive information from the gut microbiota and function as hubs that may be involved in triggering epileptic seizures. Vagus nerve bridges the communication in the axis. Essential axis signaling molecules, such as gamma-aminobutyric acid, 5-hydroxytryptamin, and short-chain fatty acids, are currently under investigation for their participation in drug-resistant epilepsy (DRE). In this review, we explain how vagus nerve connects the gut microbiota to microglia in the brain and discuss the emerging concepts derived from this interaction. Understanding microbiota-gut-brain axis in epilepsy brings hope for DRE therapies. Future treatments can focus on the modulatory effect of the axis and target microglia in solving DRE.

The impact of dysbiosis in oropharyngeal and gut microbiota on systemic inflammatory response and short-term prognosis in acute ischemic stroke with preceding infection

Background

Stroke is a devastating disease and ranks as the second leading cause of death and disability globally. Several studies have shown that preceding infection (PI) of upper respiratory tract are strongly associated with acute ischemic stroke (AIS). However, the clinical implications and underlying pathological mechanisms remain unclear.

Methods

In this study, 16S rRNA gene sequencing was employed to compare the structural characteristics of oropharyngeal and gut microbiota in AIS patients with or without PI and normal controls (NCs; 30 cases each), and systemic inflammatory markers were detected to explore the relationship between upper respiratory tract infections (URTIs) and subsequent stroke severity and functional outcome and the potential mechanism.

Results

We found that patients with AIS-PI exhibited elevated serum WBC, NE, CRP, and Hcy levels, as well as a higher 90-day mRS score. Oropharyngeal and gut microbiota analysis showed that AIS and AIS-PI patients exhibited increased microbial richness in sequence. Principal coordinate analysis of the microbiota demonstrated significant differences in microbiota composition among the three groups. In AIS-PI patients, Megamonas, Megasphaera, Ruminococcaceae UCG 004, Rothia, and Streptococcus were significantly enriched in the gut. Opportunistic pathogens, including Thermus, uncultured Veillonella sp., and Oribacterium sinu, were found to be significantly enriched in the oropharynx. The dysregulated microbiota were positively correlated with systemic inflammatory markers, stroke severity, and poor prognosis. In contrast, short-chain fatty acid-producing bacteria Eisenbergiella, bacterium NLAE, Fusicatenibacter, Ruminococcaceae, and Faecalibacterium were enriched in NCs. Their abundances were negatively correlated with systemic inflammatory markers, stroke severity and poor prognosis.

Conclusion

Our findings suggest that PIs of the upper respiratory tract may contribute to poor short-term functional outcome in AIS patients by causing disturbance of the oropharyngeal and gut microbiota and promoting elevated systemic inflammation levels.

Preclinical Evaluation of Sodium Butyrate's Potential to Reduce Alcohol Consumption: A Dose-Escalation Study in C57BL/6J Mice in Antibiotic-Enhanced Binge-Like Drinking Model

INTRODUCTION

In our earlier efforts to establish gut-brain axis during alcohol use disorder (AUD), we have demonstrated that supplementation of C57BL/6J male mice with 8 mg/mL sodium butyrate, a major short-chain fatty acid, in drinking water reduced ethanol intake and neuroinflammatory response in antibiotic (ABX)-enhanced voluntary binge-like alcohol consumption model, drinking in the dark (DID).

METHODS

To further evaluate the preclinical potential of SB, we have set a dose-escalation study in C57BL/6J male mice to test effects of ad libitum 20 mg/mL SB and 50 mg/mL SB and their combinations with ABX in the DID procedure for 4 weeks. Effects of these SB concentrations on ethanol consumption and bodily parameters were determined for the duration of the treatments. At the end of study, blood, liver, and intestinal tissues were collected to study any potential adverse effects ad to measure blood ethanol concentrations.

RESULTS

Increasing SB concentrations in the drinking water caused a loss in the protective effect against ethanol consumption and produced adverse effects on body and liver weights, reduced overall liquid intake. The hypothesis that these effects were due to aversion to SB smell/taste at these high concentrations were further tested in a follow up proof-of-concept study with intragastric gavage administration of SB. The higher gavage dose (320 mg/kg) caused reduction in ethanol consumption without any adverse effects.

CONCLUSION

Overall, these findings added more support for the therapeutic potential of SB in management of AUD, given a proper form of administration.

The gut-immune axis during hypertension and cardiovascular diseases

The gut-immune axis is a relatively novel phenomenon that provides mechanistic links between the gut microbiome and the immune system. A growing body of evidence supports it is key in how the gut microbiome contributes to several diseases, including hypertension and cardiovascular diseases (CVDs). Evidence over the past decade supports a causal link of the gut microbiome in hypertension and its complications, including myocardial infarction, atherosclerosis, heart failure, and stroke. Perturbations in gut homeostasis such as dysbiosis (i.e., alterations in gut microbial composition) may trigger immune responses that lead to chronic low-grade inflammation and, ultimately, the development and progression of these conditions. This is unsurprising, as the gut harbors one of the largest numbers of immune cells in the body, yet is a phenomenon not entirely understood in the context of cardiometabolic disorders. In this review, we discuss the role of the gut microbiome, the immune system, and inflammation in the context of hypertension and CVD, and consolidate current evidence of this complex interplay, whilst highlighting gaps in the literature. We focus on diet as one of the major modulators of the gut microbiota, and explain key microbial-derived metabolites (e.g., short-chain fatty acids, trimethylamine N-oxide) as potential mediators of the communication between the gut and peripheral organs such as the heart, arteries, kidneys, and the brain via the immune system. Finally, we explore the dual role of both the gut microbiome and the immune system, and how they work together to not only contribute, but also mitigate hypertension and CVD.

The influence of aging and the microbiome in multiple sclerosis and other neurologic diseases

The human gut microbiome is well-recognized as a key player in maintaining health. However, it is a dynamic entity that changes across the lifespan. How the microbial changes that occur in later decades of life shape host health or impact age-associated inflammatory neurological diseases such as multiple sclerosis (MS) is still unclear. Current understanding of the aging gut microbiome is largely limited to cross-sectional observational studies. Moreover, studies in humans are limited by confounding host-intrinsic and extrinsic factors that are not easily disentangled from aging. This review provides a comprehensive summary of existing literature on the aging gut microbiome and its known relationships with neurological diseases, with a specific focus on MS. We will also discuss preclinical animal models and human studies that shed light on the complex microbiota-host interactions that have the potential to influence disease pathology and progression in aging individuals. Lastly, we propose potential avenues of investigation to deconvolute features of an aging microbiota that contribute to disease, or alternatively promote health in advanced age.

Stress and the gut-brain axis: an inflammatory perspective

The gut-brain axis (GBA) plays a dominant role in maintaining homeostasis as well as contributes to mental health maintenance. The pathways that underpin the axis expand from macroscopic interactions with the nervous system, to the molecular signals that include microbial metabolites, tight junction protein expression, or cytokines released during inflammation. The dysfunctional GBA has been repeatedly linked to the occurrence of anxiety- and depressive-like behaviors development. The importance of the inflammatory aspects of the altered GBA has recently been highlighted in the literature. Here we summarize current reports on GBA signaling which involves the immune response within the intestinal and blood-brain barrier (BBB). We also emphasize the effect of stress response on altering barriers' permeability, and the therapeutic potential of microbiota restoration by probiotic administration or microbiota transplantation, based on the latest animal studies. Most research performed on various stress models showed an association between anxiety- and depressive-like behaviors, dysbiosis of gut microbiota, and disruption of intestinal permeability with simultaneous changes in BBB integrity. It could be postulated that under stress conditions impaired communication across BBB may therefore represent a significant mechanism allowing the gut microbiota to affect brain functions.

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.

From Gut Microbiomes to Infectious Pathogens: Neurological Disease Game Changers

Gut microbiota and infectious diseases affect neurological disorders, brain development, and function. Compounds generated in the gastrointestinal system by gut microbiota and infectious pathogens may mediate gut-brain interactions, which may circulate throughout the body and spread to numerous organs, including the brain. Studies shown that gut bacteria and disease-causing organisms may pass molecular signals to the brain, affecting neurological function, neurodevelopment, and neurodegenerative diseases. This article discusses microorganism-producing metabolites with neuromodulator activity, signaling routes from microbial flora to the brain, and the potential direct effects of gut bacteria and infectious pathogens on brain cells. The review also considered the neurological aspects of infectious diseases. The infectious diseases affecting neurological functions and the disease modifications have been discussed thoroughly. Recent discoveries and unique insights in this perspective need further validation. Research on the complex molecular interactions between gut bacteria, infectious pathogens, and the CNS provides valuable insights into the pathogenesis of neurodegenerative, behavioral, and psychiatric illnesses. This study may provide insights into advanced drug discovery processes for neurological disorders by considering the influence of microbial communities inside the human body.

Microglia contribute to neuronal synchrony despite endogenous ATP-related phenotypic transformation in acute mouse brain slices

Acute brain slices represent a workhorse model for studying the central nervous system (CNS) from nanoscale events to complex circuits. While slice preparation inherently involves tissue damage, it is unclear how microglia, the main immune cells and damage sensors of the CNS react to this injury and shape neuronal activity ex vivo. To this end, we investigated microglial phenotypes and contribution to network organization and functioning in acute brain slices. We reveal time-dependent microglial phenotype changes influenced by complex extracellular ATP dynamics through P2Y12R and CX3CR1 signalling, which is sustained for hours in ex vivo mouse brain slices. Downregulation of P2Y12R and changes of microglia-neuron interactions occur in line with alterations in the number of excitatory and inhibitory synapses over time. Importantly, functional microglia modulate synapse sprouting, while microglial dysfunction results in markedly impaired ripple activity both ex vivo and in vivo. Collectively, our data suggest that microglia are modulators of complex neuronal networks with important roles to maintain neuronal network integrity and activity. We suggest that slice preparation can be used to model time-dependent changes of microglia-neuron interactions to reveal how microglia shape neuronal circuits in physiological and pathological conditions.

Dietary complex probiotic supplementation changed the composition of intestinal short-chain fatty acids and improved the average daily gain of weaned piglets

Probiotics are a group of active microorganisms that form colonies within the body and alter the composition of the flora in a specific area to provide benefits to the host. In this study, a total of 96 Duroc × Landrace × Yorkshire weaned piglets with an initial body weight (BW) of 8.56 ± 0.53 kg were employed in a randomized complete block design for a 28-day experiment. Pigs were randomly divided into two treatment groups: the control group (CON) and the complex probiotic group (CON + 0.2% probiotics), respectively. The study found that through the 28-day experiment, the average daily gain (ADG) of the complex probiotic group was significantly higher than that of the CON (p < 0.05). However, compared with the CON, the feed conversion efficiency significantly decreased on days 0-14 (p < 0.05). The addition of dietary complex probiotic significantly increased the villus height (VH) of duodenum and ileum, acetate, propionate, butyrate, and total short-chain fatty acids (SCFAs) in feces, and decreased fecal methyl mercaptans, acetic acid, and CO2 (p < 0.05). It concluded that feeding weaned piglets 0.2% complex probiotic increased the VH of duodenum and ileum, as well as changed the content of SCFAs in feces. This ultimately led to an increase in ADG.

From Gut to Brain: Unraveling the Intricate Link Between Microbiome and Stroke

Stroke, a neurological disorder, is intricately linked to the gut microbiota, influencing microbial composition and elevating the risk of ischemic stroke. The neuroprotective impact of short-chain fatty acids (SCFAs) derived from dietary fiber fermentation contrasts with the neuroinflammatory effects of lipopolysaccharide (LPS) from gut bacteria. The pivotal role of the gut-brain axis, facilitating bidirectional communication between the gut and the brain, is crucial in maintaining gastrointestinal equilibrium and influencing cognitive functions. An in-depth understanding of the interplay among the gut microbiota, immune system, and neurological outcomes in stroke is imperative for devising innovative preventive and therapeutic approaches. Strategies such as dietary adjustments, probiotics, prebiotics, antibiotics, or fecal transplantation offer promise in modulating stroke outcomes. Nevertheless, comprehensive research is essential to unravel the precise mechanisms governing the gut microbiota's involvement in stroke and to establish effective therapeutic interventions. The initiation of large-scale clinical trials is warranted to assess the safety and efficacy of interventions targeting the gut microbiota in stroke management. Tailored strategies that reinstate eubiosis and foster a healthy gut microbiota hold potential for both stroke prevention and treatment. This review underscores the gut microbiota as a promising therapeutic target in stroke and underscores the need for continued research to delineate its precise role and develop microbiome-based interventions effectively.

The Involvement of Immune Cells Between Ischemic Stroke and Gut Microbiota

Ischemic stroke, a disease with high mortality and disability rate worldwide, currently has no effective treatment. The systemic inflammation response to the ischemic stroke, followed by immunosuppression in focal neurologic deficits and other inflammatory damage, reduces the circulating immune cell counts and multiorgan infectious complications such as intestinal and gut dysfunction dysbiosis. Evidence showed that microbiota dysbiosis plays a role in neuroinflammation and peripheral immune response after stroke, changing the lymphocyte populations. Multiple immune cells, including lymphocytes, engage in complex and dynamic immune responses in all stages of stroke and may be a pivotal moderator in the bidirectional immunomodulation between ischemic stroke and gut microbiota. This review discusses the role of lymphocytes and other immune cells, the immunological processes in the bidirectional immunomodulation between gut microbiota and ischemic stroke, and its potential as a therapeutic strategy for ischemic stroke.

Role of microglia in stroke

Microglia play key roles in the post-ischemic inflammatory response and damaged tissue removal reacting rapidly to the disturbances caused by ischemia and working to restore the lost homeostasis. However, the modified environment, encompassing ionic imbalances, disruption of crucial neuron-microglia interactions, spreading depolarization, and generation of danger signals from necrotic neurons, induce morphological and phenotypic shifts in microglia. This leads them to adopt a proinflammatory profile and heighten their phagocytic activity. From day three post-ischemia, macrophages infiltrate the necrotic core while microglia amass at the periphery. Further, inflammation prompts a metabolic shift favoring glycolysis, the pentose-phosphate shunt, and lipid synthesis. These shifts, combined with phagocytic lipid intake, drive lipid droplet biogenesis, fuel anabolism, and enable microglia proliferation. Proliferating microglia release trophic factors contributing to protection and repair. However, some microglia accumulate lipids persistently and transform into dysfunctional and potentially harmful foam cells. Studies also showed microglia that either display impaired apoptotic cell clearance, or eliminate synapses, viable neurons, or endothelial cells. Yet, it will be essential to elucidate the viability of engulfed cells, the features of the local environment, the extent of tissue damage, and the temporal sequence. Ischemia provides a rich variety of region- and injury-dependent stimuli for microglia, evolving with time and generating distinct microglia phenotypes including those exhibiting proinflammatory or dysfunctional traits and others showing pro-repair features. Accurate profiling of microglia phenotypes, alongside with a more precise understanding of the associated post-ischemic tissue conditions, is a necessary step to serve as the potential foundation for focused interventions in human stroke.

In vitro and in vivo fermentation models to study the function of dietary fiber in pig nutrition

The importance of dietary fiber (DF) in animal diets is increasing with the advancement of nutritional research. DF is fermented by gut microbiota to produce metabolites, which are important in improving intestinal health. This review is a systematic review of DF in pig nutrition using in vitro and in vivo models. The fermentation characteristics of DF and the metabolic mechanisms of its metabolites were summarized in an in vitro model, and it was pointed out that SCFAs and gases are the important metabolites connecting DF, gut microbiota, and intestinal health, and they play a key role in intestinal health. At the same time, some information about host-microbe interactions could have been improved through traditional animal in vivo models, and the most direct feedback on nutrients was generated, confirming the beneficial effects of DF on sow reproductive performance, piglet intestinal health, and growing pork quality. Finally, the advantages and disadvantages of different fermentation models were compared. In future studies, it is necessary to flexibly combine in vivo and in vitro fermentation models to profoundly investigate the mechanism of DF on the organism in order to promote the development of precision nutrition tools and to provide a scientific basis for the in-depth and rational utilization of DF in animal husbandry. KEY POINTS: • The fermentation characteristics of dietary fiber in vitro models were reviewed. • Metabolic pathways of metabolites and their roles in the intestine were reviewed. • The role of dietary fiber in pigs at different stages was reviewed.

Role of microbiota-gut-brain axis in natural aging-related alterations in behavior

Introduction

Aging is a complex, time-dependent biological process that involves a decline of overall function. Over the past decade, the field of intestinal microbiota associated with aging has received considerable attention. However, there is limited information surrounding microbiota-gut-brain axis (MGBA) to further reveal the mechanism of aging.

Methods

In this study, locomotory function and sensory function were evaluated through a series of behavioral tests.Metabolic profiling were determined by using indirect calorimetry.16s rRNA sequence and targeted metabolomics analyses were performed to investigate alterations in the gut microbiota and fecal short-chain fatty acids (SCFAs). The serum cytokines were detected by a multiplex cytokine assay.The expression of proinflammatory factors were detected by western blotting.

Results

Decreased locomotor activity, decreased pain sensitivity, and reduced respiratory metabolic profiling were observed in aged mice. High-throughput sequencing revealed that the levels of genus Lactobacillus and Dubosiella were reduced, and the levels of genus Alistipes and Bacteroides were increased in aged mice. Certain bacterial genus were directly associated with the decline of physiological behaviors in aged mice. Furthermore, the amount of fecal SCFAs in aged mice was decreased, accompanied by an upregulation in the circulating pro-inflammatory cytokines and increased expression of inflammatory factors in the brain.

Discussion

Aging-induced microbial dysbiosis was closely related with the overall decline in behavior, which may attribute to the changes in metabolic products, e.g., SCFAs, caused by an alteration in the gut microbiota, leading to inflammaging and contributing to neurological deficits. Investigating the MGBA might provide a novel viewpoint to exploring the pathogenesis of aging and expanding appropriate therapeutic targets.

Causal effects of gut microbiota on the prognosis of ischemic stroke: evidence from a bidirectional two-sample Mendelian randomization study

Background

Increasing research has implicated the possible effect of gut microbiota (GM) on the prognosis of ischemic stroke (IS). However, the precise causal relationship between GM and functional outcomes after IS remains unestablished.

Methods

Data on 211 GM taxa from the MiBioGen consortium and data on prognosis of IS from the Genetics of Ischemic Stroke Functional Outcome (GISCOME) network were utilized as summary-level data of exposure and outcome. Four kinds of Mendelian randomization (MR) methods were carried out to ascertain the causal effect of GM on functional outcomes following IS. A reverse MR analysis was performed on the positive taxa identified in the forward MR analysis to determine the direction of causation. In addition, we conducted a comparative MR analysis without adjusting the baseline National Institute of Health Stroke Scale (NIHSS) of post-stroke functional outcomes to enhance confidence of the results obtained in the main analysis.

Results

Four taxa were identified to be related to stroke prognosis in both main and comparative analyses. Specifically, genus Ruminococcaceae UCG005 and the Eubacterium oxidoreducens group showed significantly negative effects on stroke prognosis, while the genus Lachnospiraceae NK4A136 group and Lachnospiraceae UCG004 showed protective effects against stroke prognosis. The reverse MR analysis did not support a causal role of stroke prognosis in GM. No evidence of heterogeneity, horizontal pleiotropy, and outliers was found.

Conclusion

This MR study provided evidence that genetically predicted GM had a causal link with post-stroke outcomes. Specific gut microbiota taxa associated with IS prognosis were identified, which may be helpful to clarify the pathogenesis of ischemic stroke and making treatment strategies.

Role of the gut microbiota in complications after ischemic stroke

Ischemic stroke (IS) is a serious central nervous system disease. Post-IS complications, such as post-stroke cognitive impairment (PSCI), post-stroke depression (PSD), hemorrhagic transformation (HT), gastrointestinal dysfunction, cardiovascular events, and post-stroke infection (PSI), result in neurological deficits. The microbiota-gut-brain axis (MGBA) facilitates bidirectional signal transduction and communication between the intestines and the brain. Recent studies have reported alterations in gut microbiota diversity post-IS, suggesting the involvement of gut microbiota in post-IS complications through various mechanisms such as bacterial translocation, immune regulation, and production of gut bacterial metabolites, thereby affecting disease prognosis. In this review, to provide insights into the prevention and treatment of post-IS complications and improvement of the long-term prognosis of IS, we summarize the interaction between the gut microbiota and IS, along with the effects of the gut microbiota on post-IS complications.

Probiotic treatment causes sex-specific neuroprotection after traumatic brain injury in mice

Background

Recent studies have shed light on the potential role of gut dysbiosis in shaping traumatic brain injury (TBI) outcomes. Changes in the levels and types of Lactobacillus bacteria present might impact the immune system disturbances, neuroinflammatory responses, anxiety and depressive-like behaviors, and compromised neuroprotection mechanisms triggered by TBI.

Objective

This study aimed to investigate the effects of a daily pan-probiotic (PP) mixture in drinking water containing strains of Lactobacillus plantarum, L. reuteri, L. helveticus, L. fermentum, L. rhamnosus, L. gasseri, and L. casei, administered for either two or seven weeks before inducing TBI on both male and female mice.

Methods

Mice were subjected to controlled cortical impact (CCI) injury. Short-chain fatty acids (SCFAs) analysis was performed for metabolite measurements. The taxonomic profiles of murine fecal samples were evaluated using 16S rRNA V1-V3 sequencing analysis. Histological analyses were used to assess neuroinflammation and gut changes post-TBI, while behavioral tests were conducted to evaluate sensorimotor and cognitive functions.

Results

Our findings suggest that PP administration modulates the diversity and composition of the microbiome and increases the levels of SCFAs in a sex-dependent manner. We also observed a reduction of lesion volume, cell death, and microglial and macrophage activation after PP treatment following TBI in male mice. Furthermore, PP-treated mice show motor function improvements and decreases in anxiety and depressive-like behaviors.

Conclusion

Our findings suggest that PP administration can mitigate neuroinflammation and ameliorate motor and anxiety and depressive-like behavior deficits following TBI. These results underscore the potential of probiotic interventions as a viable therapeutic strategy to address TBI-induced impairments, emphasizing the need for gender-specific treatment approaches.

Dietary sodium butyrate positively modulated intestinal microbial community, but did not promote growth of largemouth bass (Micropterus salmoides)

This study investigated the effects of dietary sodium butyrate (NaB) on growth, serum biochemical indices, intestine histology, and gut microbiota of largemouth bass (Micropterus salmoides). A basal diet was formulated and used as the control diet (Con), and five additional diets were prepared by supplementing NaB (50%) in the basal diet at 2.0, 4.0, 8.0, 12.0, and 16.0 g/kg inclusion (NaB-2, NaB-4, NaB-8, NaB-12, and NaB-16 diets). Then, the six diets were fed to triplicate groups of largemouth bass juveniles (2.4 ± 0.1 g) for 8 weeks. NaB supplementation linearly and quadratically affected weight gain (WG) and feed intake (FI) (P < 0.05). The NaB-16 group displayed lower WG (- 6.8%) and FI than the Con group (P < 0.05), while no differences were found in WG and feed conversion ratio between the other NaB groups and Con group (P > 0.05). Serum alkaline phosphatase and lysozyme activities were higher in the NaB groups (P < 0.05), and D-lactate content was lower in the NaB-12 group (P < 0.05) than the control. Intestinal lipase activity in NaB-2, NaB-4 group, and villi width in NaB-8 group were also higher than those in the Con group (P < 0.05). Compared to the Con group, the intestinal abundances of Firmicutes and Mycoplasma were increased and the abundances of Proteobacteria, Achromobacter and Plesiomonas were decreased in NaB-4 and NaB-16 groups (P < 0.05). In conclusion, dietary NaB did not promote the growth of juvenile largemouth bass, but positively modulated the intestinal microbial community.

Protective effect of Tao Hong Si Wu Decoction against inflammatory injury caused by intestinal flora disorders in an ischemic stroke mouse model

BACKGROUND AND AIMS

Recent studies have shown that intestinal flora are involved in the pathological process of ischemic stroke (IS). The potential protective effect of the traditional Chinese prescription, Tao Hong Si Wu Decoction (THSWD), against inflammatory injury after IS and its underlying mechanisms of action were investigated in the current study.

METHODS

Fifty SPF(Specefic pathogen Free) male C57 mice were randomly assigned to sham operation, model, THSWD low-dose (6.5 g/kg), medium-dose (13 g/kg) and high-dose (26 g/kg) groups (10 mice per group). Mouse models of transient middle cerebral artery occlusion were prepared via thread embolism. Neurological function score, hematoxylin-eosin (HE) staining, immunohistochemistry, enzyme-linked immunosorbent assay (ELISA), 16S ribosomal DNA (rDNA) sequencing, quantitative reverse transcription PCR (qRT-PCR) and other methods were employed to elucidate the underlying molecular mechanisms.

RESULTS

Notably, THSWD induced a reduction in the neurological function score (P < 0.01) and neuronal injury in brain tissue, increase in protein expression of Claudin-5 and zonula occludens-1 (ZO-1) in brain tissue(P < 0.01), and decrease in serum lipopolysaccharide (LPS)(P < 0.01), diamine oxidase (DAO)(P < 0.01) and D-lactic acid(P < 0.01, P < 0.05) levels to a significant extent. THSWD also inhibited the levels of tumor necrosis factor-α (TNF-α)(P < 0.01) and interleukin - 1β (IL-1β)(P < 0.01) in brain tissue, and increased alpha and beta diversity in ischemic stroke mice, along with a certain reversal effect on different microflora. Finally, THSWD inhibited the polarization of microglia cells(P < 0.01) and decreased the protein and gene expression of toll-like receptor-4 (TLR-4)(P < 0.01, P < 0.05) and nuclear factor kappa B (NF-κB)(P < 0.01) in brain tissue.

CONCLUSION

Our data indicate that THSWD may interfere with inflammatory response in ischemic stroke by regulating intestinal flora and promoting intestinal barrier repair.

Unveiling the negative association of Faecalibacterium prausnitzii with ischemic stroke severity, impaired prognosis and pro-inflammatory markers

Background

The correlation between acute ischemic stroke (AIS) and gut microbiota has opened a promising avenue for improving stroke prognosis through the utilization of specific gut bacterial species. This study aimed to identify gut bacterial species in AIS patients and their correlation with stroke severity, 3-month prognosis, and inflammatory markers. Methods: We enrolled 59 AIS patients (from June 2021 to July 2022) and 31 age-matched controls with similar cerebrovascular risk profiles but no stroke history. Fecal samples were analyzed using 16 S rDNA V3-V4 sequencing to assess α and β diversity and identify significant microbiota differences. AIS cases were categorized based on the National Institute of Health Stroke Scale (NIHSS) scores and 3-month modified Rankin Scale (mRS) scores. Subgroup analyses were performed, and correlation analysis was used to examine associations between flora abundance, inflammatory markers and stroke outcome.

Results

Significant differences in β-diversity were observed between case and control groups (P < 0.01). Bacteroides dominated AIS samples, while Clostridia, Lachnospirales, Lachnospiraceae, Ruminococcaceae, Faecalibacterium, and Faecalibacterium prausnitzii were prominent in controls. Faecalibacterium and Faecalibacterium prausnitzii were significantly reduced in non-minor stroke and 3-month poor prognosis groups compared to controls, while this difference was less pronounced in patients with minor stroke and 3-month good prognosis. Both Faecalibacterium and Faecalibacterium prausnitzii were negatively correlated with the NIHSS score on admission (r = -0.48, -0.48, P < 0.01) and 3-month mRS score (r = -0.48, -0.44, P < 0.01). Additionally, they showed negative correlations with pro-inflammatory factors and positive correlations with anti-inflammatory factors (both P < 0.01).

Conclusions

Faecalibacterium prausnitzii is negatively associated with stroke severity, impaired prognosis, and pro-inflammatory markers, highlighting its potential application in AIS treatments.

Antibiotics treatment promotes vasculogenesis in the brain of glioma-bearing mice

In recent years, several studies described the close relationship between the composition of gut microbiota and brain functions, highlighting the importance of gut-derived metabolites in mediating neuronal and glial cells cross-talk in physiological and pathological condition. Gut dysbiosis may affects cerebral tumors growth and progression, but the specific metabolites involved in this modulation have not been identified yet. Using a syngeneic mouse model of glioma, we have investigated the role of dysbiosis induced by the administration of non-absorbable antibiotics on mouse metabolome and on tumor microenvironment. We report that antibiotics treatment induced: (1) alteration of the gut and brain metabolome profiles; (2) modeling of tumor microenvironment toward a pro-angiogenic phenotype in which microglia and glioma cells are actively involved; (3) increased glioma stemness; (4) trans-differentiation of glioma cells into endothelial precursor cells, thus increasing vasculogenesis. We propose glycine as a metabolite that, in ABX-induced dysbiosis, shapes brain microenvironment and contributes to glioma growth and progression.

Influence of the brain‑gut axis on neuroinflammation in cerebral ischemia‑reperfusion injury (Review)

Stroke, a debilitating cerebrovascular ailment, poses significant threats to human life and health. The intricate interplay between the gut‑brain‑microbiota axis (GBMA) and cerebral ischemia‑reperfusion has increasingly become a focal point of scientific exploration, emerging as a pivotal research avenue in stroke pathophysiology. In the present review, the authors delved into the nexus between the GBMA and neuroinflammation observed post‑stroke. The analysis underscored the pivotal roles of histone deacetylase 3 and neutrophil extracellular traps subsequent to stroke incidents. The influence of gut microbial compositions and their metabolites, notably short‑chain fatty acids and trimethylamine N‑oxide, on neuroinflammatory processes, was further elucidated. The involvement of immune cells, especially regulatory T‑cells, and the intricate signaling cascades including cyclic GMP‑AMP synthase/stimulator of interferon genes/Toll‑like receptor, further emphasized the complex regulatory mechanisms of GBMA in cerebral ischemia/reperfusion injury (CI/RI). Collectively, the present review offered a comprehensive perspective on the metabolic, immune and inflammatory modulations orchestrated by GBMA, augmenting the understanding of its role in neuroinflammation following CI/RI.

The role of gut microbiota in cerebrovascular disease and related dementia

In recent years, increasing evidence suggests that commensal microbiota may play an important role not only in health but also in disease including cerebrovascular disease. Gut microbes impact physiology, at least in part, by metabolizing dietary factors and host-derived substrates and then generating active compounds including toxins. The purpose of this current review is to highlight the complex interplay between microbiota, their metabolites. and essential functions for human health, ranging from regulation of the metabolism and the immune system to modulation of brain development and function. We discuss the role of gut dysbiosis in cerebrovascular disease, specifically in acute and chronic stroke phases, and the possible implication of intestinal microbiota in post-stroke cognitive impairment and dementia, and we identify potential therapeutic opportunities of targeting microbiota in this context. LINKED ARTICLES: This article is part of a themed issue From Alzheimer's Disease to Vascular Dementia: Different Roads Leading to Cognitive Decline. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v181.6/issuetoc.

Causal Associations Between Gut Microbiota and Cerebrovascular Diseases

BACKGROUND

Numerous studies suggest that the gut microbiota closely linked to cerebrovascular diseases, such as Intracranial aneurysm (IA) and aneurysmal subarachnoid hemorrhage (aSAH). Nevertheless, the confirmation of a definitive causal connection between gut microbiota, IA, and aSAH is still pending. The aim of our research is to explore the potential bidirectional causality among them.

METHODS

This bidirectional Mendelian Randomization (MR) study used single nucleotide polymorphisms linked to gut microbiota, IA, and aSAH from Genome-Wide Association Studies. The Inverse Variance Weighted (IVW) method was used to explore causality. To assess the robustness of the result, sensitivity analyses were further performed, including weighted-median method, MR-Egger regression, Maximum-likelihood method, MR pleiotropy residual sum and outlier test and leave-one-out analysis.

RESULTS

In the IVW method, the family Porphyromonadaceae (odds ratio [OR] 0.63; 95% CI 0.47-0.85; P: 0.002) and genus Bilophila (OR 0.66; 95% CI 0.50-0.86; P: 0.002) showed a significant negative association with the risk of IA. Similarly, the genus Bilophila (OR: 0.68; 95% CI: 0.50-0.93; P: 0.017) and genus Ruminococcus1 (OR: 0.48; 95% CI: 0.30-0.78; P: 0.003) were linked to reduced risk of aSAH. The sensitivity analysis yielded similar outcomes in the IVW approach. Through the adoption of reverse MR analysis, a potential correlation between IA and decreased abundance of genus Ruminococcus1 was identified (OR 0.94; 95% CI 0.90-0.99; P 0.024).

CONCLUSIONS

This MR analysis investigated the causal associations between gut microbiota, IA, and aSAH risks. The findings expanded current knowledge of the microbiota-gut-brain axis and offered novel perspectives on preventing and managing these conditions.

The role of short-chain fatty acids in central nervous system diseases: A bibliometric and visualized analysis with future directions

Background

Short-chain fatty acids (SCFAs) are thought to play a key role in the microbe-gut-brain axis and involve in the pathogenesis of a variety of neurological diseases. This study aimed to identify research hotspots and evolution trends in SCFAs in central nervous diseases (CNS) and examine current research trends.

Methods

The bibliometric analysis was performed using CiteSpace, and the results were visualized via network maps.

Results

From 2002 to 2022, 480 publications in the database met the criteria. On the country level, China produced the highest number of publications, while the United States had the highest centrality. On the institutional level, University College Cork contributed to the most publications, and John F. Cryan from this university was the key researcher with considerable academic influence. The article, the role of short-chain fatty acids in microbiota-gut-brain, written by Boushra Dalile et al., in 2019 was the most cited article. Furthermore, the journal Nutrients had the maximum number of publications, while Plos One was the most cited journal. "Gut microbiome", "SCFAs", and "central nervous system" were the three most frequent keywords. Among them, SCFAs had the highest centrality. "Animal model" was the keyword with the highest burst strength, with the latest burst keywords being "social behavior", "pathogenesis", and "insulin sensitive". In addition, the research topics on SCFAs in CNS diseases from 2002 to 2022 mainly focused on following aspects: SCFAs plays a key role in microbe-gut-brain crosstalk; The classification and definition of SCFAs in the field of CNS; Several CNS diseases that are closely related to SCFAs research; Mechanism and translational studies of SCFAs in the CNS diseases. And the hotspots over the past 5 years have gradually increased the attention to the therapeutic potential of SCFAs in the CNS diseases.

Conclusion

The research of SCFAs in CNS diseases is attracting growing attention. However, there is a lack of cooperation between countries and institutions, and additional measures are required to promote cooperation. The current evidence for an association between SCFAs and CNS diseases is preliminary and more work is needed to pinpoint the precise mechanism. Moreover, large-scale clinical trials are needed in the future to define the therapeutic potential of SCFAs in CNS diseases.

Therapeutic effect of Sanhua decoction on rats with middle cerebral artery occlusion and the associated changes in gut microbiota and short-chain fatty acids

Sanhua decoction (SHD), a traditional prescription, has long been used in treating ischemic stroke (IS). However, the therapeutic effect of SHD and the associated changes in gut microbiota and short-chain fatty acids (SCFAs) are uncertain. In this study, a rat model of IS was established by the middle cerebral artery occlusion (MCAO). By evaluating the cerebral infarct area and brain tissue pathology, it was found that SHD ameliorated IS-related symptoms in MCAO rats. Using 16S rRNA gene sequencing, we found that SHD reduced abnormally elevated Lactobacillus and opportunistic pathogens such as Desulfovibrio, but increased some beneficial bacteria that produce SCFAs, including Clostridia, Lachnospiraceae, Ruminococcaceae, and Coprococcus. KEGG analysis revealed that SHD regulates several pathways, including D-arginine and D-ornithine metabolism, polyketide sugar unit biosynthesis, and cyanoamino acid metabolism, which are significantly altered in MCAO rats. By gas chromatography-mass spectrometry detection of SCFAs, we found that fecal acetic acid, valeric acid, and caproic acid were significantly increased in MCAO rats, whereas propionic acid and isobutyric acid were decreased. SHD reversed the changes in acetic acid and propionic acid in the model rats and significantly increased fecal butyric acid. In addition, MCAO rats had significantly higher serum levels of acetic acid, butyric acid, isovaleric acid, and valeric acid, and lower levels of caproic acid. Altered serum levels of butyric acid, isovaleric acid, valeric acid, and caproic acid were restored, and the level of isobutyric acid was reduced after SHD administration. Spearman analysis revealed that cerebral infarct area had a strong correlation with Bifidobacterium, Desulfovibrio, Lachnospiraceae, Lactobacillus, acetic acid, valeric acid, and caproic acid. Overall, this study demonstrates for the first time that the effect of SHD on IS may be related to gut microbiota and SCFAs, providing a potential scientific explanation for the ameliorative effect of SHD on IS.

Efficacy of Fire-Needle Therapy in Improving Neurological Function Following Cerebral Infarction and Its Effect on Intestinal Flora Metabolites

Objective

This study was to investigate the mechanism of action and clinical efficacy of fire-needle therapy in improving neurological function in patients with acute cerebral infarction (identified as a wind-phlegm-blood stasis syndrome in traditional Chinese medicine).

Methods

We included patients diagnosed with acute cerebral infarction (wind-phlegm-blood stasis syndrome) admitted to the Encephalopathy and Acupuncture Center of the Second Affiliated Hospital of Tianjin University of Chinese Medicine. We randomly allocated them into the treatment and control groups, with 45 cases in each group. Acupuncture treatments that focused on regulating the mind and dredging the collaterals were used in the control group, while the treatment group additionally received fire-needle therapy. Our indicators included the National Institutes of Health Stroke Scale (NIHSS) scores, the Fugl-Meyer Assessment (FMA) scale, peripheral blood tumor necrosis factor-α (TNF-α), interleukin-17 (IL-17), hypersensitivity C-reactive protein (hs-CRP), and intestinal metabolites short-chain fatty acids (SCFAs). We measured these indicators before treatment and 14 days after treatment.

Results

The post-treatment NIHSS scores of the two groups were significantly reduced (P < 0.05), and the treatment group showed a more significant decline in the score when compared to the control group (P < 0.05). The treatment group showing significant improvement in the domains of reflex activity, mobility, cooperative movement, and finger movement (P < 0.05). Both groups showed a significant decrease in the IL-17 and hs-CRP levels (P < 0.05), with the treatment group demonstrating a significant declining trend when compared to the control group (P < 0.05). The levels of acetic acid, propionic acid, butyric acid, and valeric acid all increased significantly in the two groups (P < 0.05), with acetic acid and butyric acid increasing significantly in the treatment group when compared to the control group (P < 0.05). Clinical efficacy rate: 78.6% of patients in the treatment group had an excellent rate, whereas it was 30.0% in the control group, and the difference was statistically significant (P < 0.001).

Conclusion

Fire-needle therapy was effective in upregulating the SCFA content in patients with acute cerebral infarction (wind-phlegm-blood stasis syndrome), inhibiting the level of the inflammatory response, and improving the recovery of neurological functions.

Clinical registration number

Registration website link: https://www.chictr.org.cn. Registration date: 2022/9/27. Registration number: ChiCTR2200064122.

Gut microbial regulation of innate and adaptive immunity after traumatic brain injury

Acute care management of traumatic brain injury is focused on the prevention and reduction of secondary insults such as hypotension, hypoxia, intracranial hypertension, and detrimental inflammation. However, the imperative to balance multiple clinical concerns simultaneously often results in therapeutic strategies targeted to address one clinical concern causing unintended effects in other remote organ systems. Recently the bidirectional communication between the gastrointestinal tract and the brain has been shown to influence both the central nervous system and gastrointestinal tract homeostasis in health and disease. A critical component of this axis is the microorganisms of the gut known as the gut microbiome. Changes in gut microbial populations in the setting of central nervous system disease, including traumatic brain injury, have been reported in both humans and experimental animal models and can be further disrupted by off-target effects of patient care. In this review article, we will explore the important role gut microbial populations play in regulating brain-resident and peripheral immune cell responses after traumatic brain injury. We will discuss the role of bacterial metabolites in gut microbial regulation of neuroinflammation and their potential as an avenue for therapeutic intervention in the setting of traumatic brain injury.

Current understanding of the Alzheimer's disease-associated microbiome and therapeutic strategies

Alzheimer's disease (AD) is a fatal progressive neurodegenerative disease. Despite tremendous research efforts to understand this complex disease, the exact pathophysiology of the disease is not completely clear. Recently, anti-Aβ antibodies have been shown to remove amyloid from the brain and slow the clinical progression of mild dementia by ~30%. However, exploring alternative strategies is crucial to understanding and developing more effective therapeutic interventions. In recent years, the microbiota-gut-brain axis has received significant attention in the AD field. Numerous studies have suggested that alterations in the gut microbiota composition are associated with the progression of AD, and several underlying mechanisms have been proposed. However, studies in this area are still in their infancy, and many aspects of this field are just beginning to be explored and understood. Gaining a deeper understanding of the intricate interactions and signaling pathways involved in the microbiota-AD interaction is crucial for optimizing therapeutic strategies targeting gut microbiota to positively impact AD. In this review, we aim to summarize the current understanding of the microbiota-gut-brain axis in AD. We will discuss the existing evidence regarding the role of gut microbiota in AD pathogenesis, suggested underlying mechanisms, biological factors influencing the microbiome-gut-brain axis in AD, and remaining questions in the field. Last, we will discuss potential therapeutic approaches to recondition the community of gut microbiota to alleviate disease progression. An ongoing exploration of the gut-brain axis and the development of microbiota-based therapies hold the potential for advancing AD management in the future.

Fecal supernatants from dogs with idiopathic epilepsy activate enteric neurons

Introduction

Alterations in the composition and function of the gut microbiome have been reported in idiopathic epilepsy (IE), however, interactions of gut microbes with the enteric nervous system (ENS) in this context require further study. This pilot study examined how gastrointestinal microbiota (GIM), their metabolites, and nutrients contained in intestinal contents communicate with the ENS.

Methods

Fecal supernatants (FS) from healthy dogs and dogs with IE, including drug-naïve, phenobarbital (PB) responsive, and PB non-responsive dogs, were applied to cultured myenteric neurons to test their activation using voltage-sensitive dye neuroimaging. Additionally, the concentrations of short-chain fatty acids (SCFAs) in the FS were quantified.

Results

Our findings indicate that FS from all examined groups elicited neuronal activation. Notably, FS from PB non-responsive dogs with IE induced action potential discharge in a higher proportion of enteric neurons compared to healthy controls, which exhibited the lowest burst frequency overall. Furthermore, the highest burst frequency in enteric neurons was observed upon exposure to FS from drug-naïve dogs with IE. This frequency was significantly higher compared to that observed in PB non-responsive dogs with IE and showed a tendency to surpass that of healthy controls.

Discussion

Although observed disparities in SCFA concentrations across the various FS samples might be associated with the induced neuronal activity, a direct correlation remains elusive at this point. The obtained results hint at an involvement of the ENS in canine IE and set the basis for future studies.

Fibre-rich diet attenuates chemotherapy-related neuroinflammation in mice

The gastrointestinal microbiota has received increasing recognition as a key mediator of neurological conditions with neuroinflammatory features, through its production of the bioactive metabolites, short-chain fatty acids (SCFAs). Although neuroinflammation is a hallmark shared by the neuropsychological complications of chemotherapy (including cognitive impairment, fatigue and depression), the use of microbial-based therapeutics has not previously been studied in this setting. Therefore, we aimed to investigate the effect of a high fibre diet known to modulate the microbiota, and its associated metabolome, on neuroinflammation caused by the common chemotherapeutic agent 5-fluorouracil (5-FU). Twenty-four female C57Bl/6 mice were treated with 5-FU (400 mg/kg, intraperitoneal, i.p.) or vehicle control, with or without a high fibre diet (constituting amylose starch; 4.7 % crude fibre content), given one week prior to 5-FU and until study completion (16 days after 5-FU). Faecal pellets were collected longitudinally for 16S rRNA gene sequencing and terminal SCFA concentrations of the caecal contents were quantified using gas chromatography-mass spectrometry (GC-MS). Neuroinflammation was determined by immunofluorescent analysis of astrocyte density (GFAP). The high fibre diet significantly altered gut microbiota composition, increasing the abundance of Bacteroidaceae and Akkermansiaceae (p < 0.0001 and p = 0.0179) whilst increasing the production of propionate (p = 0.0097). In the context of 5-FU, the diet reduced GFAP expression in the CA1 region of the hippocampus (p < 0.0001) as well as the midbrain (p = 0.0216). Astrocyte density negatively correlated with propionate concentrations and the abundance of Bacteroidaceae and Akkermansiaceae, suggesting a relationship between neuroinflammatory and gastrointestinal markers in this model. This study provides the first evidence of the neuroprotective effects of fibre via dietary intake in alleviating the neuroimmune changes seen in response to systemically administered 5-FU, indicating that the microbiota-gut-brain axis is a targetable mediator to reduce the neurotoxic effects of chemotherapy treatment.

Potential Therapeutic Effects of Short-Chain Fatty Acids on Chronic Pain

The intestinal homeostasis maintained by the gut microbiome and relevant metabolites is essential for health, and its disturbance leads to various intestinal or extraintestinal diseases. Recent studies suggest that gut microbiome-derived metabolites short-chain fatty acids (SCFAs) are involved in different neurological disorders (such as chronic pain). SCFAs are produced by bacterial fermentation of dietary fibers in the gut and contribute to multiple host processes, including gastrointestinal regulation, cardiovascular modulation, and neuroendocrine-immune homeostasis. Although SCFAs have been implicated in the modulation of chronic pain, the detailed mechanisms that underlie such roles of SCFAs remain to be further investigated. In this review, we summarize currently available research data regarding SCFAs as a potential therapeutic target for chronic pain treatment and discuss several possible mechanisms by which SCFAs modulate chronic pain.

Gut Microbiota Ecological and Functional Modulation in Post-Stroke Recovery Patients: An Italian Study

Ischemic stroke (IS) can be caused by perturbations of the gut-brain axis. An imbalance in the gut microbiota (GM), or dysbiosis, may be linked to several IS risk factors and can influence the brain through the production of different metabolites, such as short-chain fatty acids (SCFAs), indole and derivatives. This study examines ecological changes in the GM and its metabolic activities after stroke. Fecal samples of 10 IS patients were compared to 21 healthy controls (CTRLs). GM ecological profiles were generated via 16S rRNA taxonomy as functional profiles using metabolomics analysis performed with a gas chromatograph coupled to a mass spectrometer (GC-MS). Additionally fecal zonulin, a marker of gut permeability, was measured using an enzyme-linked immuno assay (ELISA). Data were analyzed using univariate and multivariate statistical analyses and correlated with clinical features and biochemical variables using correlation and nonparametric tests. Metabolomic analyses, carried out on a subject subgroup, revealed a high concentration of fecal metabolites, such as SCFAs, in the GM of IS patients, which was corroborated by the enrichment of SCFA-producing bacterial genera such as Bacteroides, Christensellaceae, Alistipes and Akkermansia. Conversely, indole and 3-methyl indole (skatole) decreased compared to a subset of six CTRLs. This study illustrates how IS might affect the gut microbial milieu and may suggest potential microbial and metabolic biomarkers of IS. Expanded populations of Akkermansia and enrichment of acetic acid could be considered potential disease phenotype signatures.

The causal effects between gut microbiota and hemorrhagic stroke: a bidirectional two-sample Mendelian randomization study

Background

Recent studies have suggested that the composition of gut microbiota (GM) may change after intracerebral hemorrhage. However, the causal inference of GM and hemorrhagic stroke is unknown. Mendelian Randomization (MR) is an effective research method that removes confounding factors and investigates the causal relationship between exposure and outcome. This study intends to explore the causal relationship between GM and hemorrhagic stroke with the help of MR.

Methods

Univariable and multivariable MR analyses were performed using summary statistics of the GM (n = 18,340) in the MiBioGen consortium vs. the FinnGen consortium R9 summary statistics (intracerebral hemorrhage, subarachnoid hemorrhage, and nontraumatic intracranial hemorrhage). Causal associations between gut microbiota and hemorrhagic stroke were analyzed using inverse variance weighted, MR-Egger regression, weighted median, weighted mode, simple mode, and MR-PRESSO. Cochran's Q statistic, MR-Egger regression, and leave-one-out analysis were used to test for multiplicity and heterogeneity of instrumental variables. Separate reverse MR analyses were performed for microbiota found to be causally associated with hemorrhagic stroke in the forward MR analysis. Also, multivariate MR analyses were conducted after incorporating common confounders.

Results

Based on the results of univariable and multivariate MR analyses, Actinobacteria (phylum) (OR, 0.80; 95%CI, 0.66-0.97; p = 0.025) had a protective effect against hemorrhagic stroke, while Rikenellaceae RC9 gut group (genus) (OR, 0.81; 95%CI, 0.67-0.99; p = 0.039) had a potential protective effect. Furthermore, Dorea (genus) (OR, 1.77; 95%CI, 1.27-2.46; p = 0.001), Eisenbergiella (genus) (OR, 1.24; 95%CI, 1.05-1.48; p = 0.013) and Lachnospiraceae UCG008 (genus) (OR, 1.28; 95%CI, 1.01-1.62; p = 0.041) acted as potential risk factors for hemorrhagic stroke. The abundance of Dorea (genus) (β, 0.05; 95%CI, 0.002 ~ 0.101; p = 0.041) may increase, and that of Eisenbergiella (genus) (β, -0.072; 95%CI, -0.137 ~ -0.007; p = 0.030) decreased after hemorrhagic stroke according to the results of reverse MR analysis. No significant pleiotropy or heterogeneity was detected in any of the MR analyses.

Conclusion

There is a significant causal relationship between GM and hemorrhagic stroke. The prevention, monitoring, and treatment of hemorrhagic stroke through GM represent a promising avenue and contribute to a deeper understanding of the mechanisms underlying hemorrhagic stroke.

Spinal cord injury-induced gut dysbiosis influences neurological recovery partly through short-chain fatty acids

Spinal cord injury (SCI) can reshape gut microbial composition, significantly affecting clinical outcomes in SCI patients. However, mechanisms regarding gut-brain interactions and their clinical implications have not been elucidated. We hypothesized that short-chain fatty acids (SCFAs), intestinal microbial bioactive metabolites, may significantly affect the gut-brain axis and enhance functional recovery in a mouse model of SCI. We enrolled 59 SCI patients and 27 healthy control subjects and collected samples. Thereafter, gut microbiota and SCFAs were analyzed using 16 S rDNA sequencing and gas chromatography-mass spectrometry, respectively. We observed an increase in Actinobacteriota abundance and a decrease in Firmicutes abundance. Particularly, the SCFA-producing genera, such as Faecalibacterium, Megamonas, and Agathobacter were significantly downregulated among SCI patients compared to healthy controls. Moreover, SCI induced downregulation of acetic acid (AA), propionic acid (PA), and butyric acid (BA) in the SCI group. Fecal SCFA contents were altered in SCI patients with different injury course and injury segments. Main SCFAs (AA, BA, and PA) were administered in combination to treat SCI mice. SCFA supplementation significantly improved locomotor recovery in SCI mice, enhanced neuronal survival, promoted axonal formation, reduced astrogliosis, and suppressed microglial activation. Furthermore, SCFA supplementation downregulated NF-κB signaling while upregulating neurotrophin-3 expression following SCI. Microbial sequencing and metabolomics analysis showed that SCI patients exhibited a lower level of certain SCFAs and related bacterial strains than healthy controls. SCFA supplementation can reduce inflammation and enhance nourishing elements, facilitating the restoration of neurological tissues and the improvement of functional recuperation. Trial registration: This study was registered in the China Clinical Trial Registry ( www.chictr.org.cn ) on February 13, 2017 (ChiCTR-RPC-17010621).

Gut Microbiota in Ischemic Stroke: Role of Gut Bacteria-Derived Metabolites

Ischemic stroke (IS) remains a leading cause of death and long-term disability globally. Several mechanisms including glutamate excitotoxicity, calcium overload, neuroinflammation, oxidative stress, mitochondrial damage, and apoptosis are known to be involved in the pathogenesis of IS, but the underlying pathophysiology mechanisms of IS are not fully clarified. During the past decade, gut microbiota were recognized as a key regulator to affect the health of the host either directly or via their metabolites. Recent studies indicate that gut bacterial dysbiosis is closely related to hypertension, diabetes, obesity, dyslipidemia, and metabolic syndrome, which are the main risk factors for cardiovascular diseases. Increasing evidence indicates that IS can lead to perturbation in gut microbiota and increased permeability of the gut mucosa, known as "leaky gut," resulting in endotoxemia and bacterial translocation. In turn, gut dysbiosis and impaired intestinal permeability can alter gut bacterial metabolite signaling profile from the gut to the brain. Microbiota-derived products and metabolites, such as short-chain fatty acids (SCFAs), bile acids (BAs), trimethylamine N-oxide (TMAO), lipopolysaccharides (LPS), and phenylacetylglutamine (PAGln) can exert beneficial or detrimental effects on various extraintestinal organs, including the brain, liver, and heart. These metabolites have been increasingly acknowledged as biomarkers and mediators of IS. However, the specific role of the gut bacterial metabolites in the context of stroke remains incompletely understood. In-depth studies on these products and metabolites may provide new insight for the development of novel therapeutics for IS.

Gut microbiota and traumatic central nervous system injuries: Insights into pathophysiology and therapeutic approaches

Traumatic brain injury and spinal cord injury are two distinct but fundamentally similar types of acute insults to the central nervous system (CNS) that often culminate in death or cognitive and motor impairment. Over the past decade, researchers have tapped into research to discover the potential role being played by gut bacteria in CNS. After an acute CNS injury, the altered composition of the gut microbiota disturbs the balance of the bidirectional gut-brain axis, aggravating secondary CNS injury, motor dysfunctions, and cognitive deficits, which worsens the patient's prognosis. Some of the well-known therapeutic interventions which can also be used as adjuvant therapy for alleviating CNS injuries include, the use of pro and prebiotics, fecal microbiota transplantation, and microbial engineering. In this review, we aim to discuss the importance of gut microbes in our nervous system, anatomy, and signaling pathways involved in regulating the gut-brain axis, the alteration of the gut microbiome in CNS injuries, and the therapeutic strategies to target gut microbiomes in traumatic CNS injuries.

Akkermansia muciniphila supplementation prevents cognitive impairment in sleep-deprived mice by modulating microglial engulfment of synapses

The microbiome-gut-brain axis plays a crucial role in many neurological diseases, including mild cognitive impairment. Sleep deprivation (SD) induces cognitive decline accompanied by alterations in the gut microbiota. However, the role of gut microbiota alterations in SD-induced cognitive dysfunction and the underlying mechanisms remain unclear. Here, we found that dysbiosis of the gut microbiota following pretreatment with broad-spectrum antibiotics worsens SD-induced cognitive impairment in mice. Fecal microbiota transplantation from SD mice to healthy mice induced cognitive impairment. Additionally, the abundance of Akkermansia muciniphila (A. muciniphila) in the mouse gut microbiota was significantly reduced after 7 days of SD. A. muciniphila pretreatment alleviated cognitive dysfunction and prevented synaptic reduction in the hippocampus in SD mice. A. muciniphila pretreatment inhibited extensive microglial activation and synaptic engulfment in the hippocampus of SD mice. Metabolomics analysis revealed that A. muciniphila pretreatment increased the serum acetate and butanoic acid levels in SD mice. Finally, pretreatment with short-chain fatty acids (SCFAs) inhibited microglial synaptic engulfment and prevented neuronal synaptic loss in SD mice and primary microglia-neuron co-culture following LPS stimulation. Together, our findings illustrate that gut dysbiosis plays an essential role in SD-induced cognitive impairment by activating microglial engulfment at synapses. A. muciniphila supplementation may be a novel preventative strategy for SD-induced cognitive dysfunction, by increasing SCFAs production and maintaining microglial homeostasis.

Glyceryl triacetate promotes blood-brain barrier recovery after ischemic stroke through lipogenesis-mediated IL-33 in mice

BACKGROUND

Lipid metabolism has a crucial role in neural repair in neurodegenerative diseases. We recently revealed that lipogenesis-mediated interleukin-33 (IL-33) upregulation lead to blood-brain barrier (BBB) repair after ischemic stroke. However, manipulating the key enzyme fatty acid synthase (FASN) to enhance lipogenesis was very challenging. Glyceryl triacetate (GTA) was used as a donor of acetate and precursor of acetyl coenzyme A, the key substrate for de novo lipogenesis catalyzed by FASN. Therefore, we hypothesized that GTA would promote lipogenesis the peri-infarct after ischemic stroke and contribute to the BBB repair through IL-33.

METHODS

Middle cerebral artery occlusion (MCAO) was performed on C57BL mice and GTA was gavage administrated (4 g/kg) on day 2 and 4 after MCAO. Lipogenesis was evaluated by assessment of the protein level of FASN, lipid droplets, and fatty acid products through liquid chromatography-mass spectrometry in the peri-infarct area on day 3 after MCAO, respectively. BBB permeability was determined by extravasation of Evans blue, IgG and dextran, and levels of tight junction proteins in the peri-infarct area on day 7 after MCAO, respectively. Infarct size and neurological defects were assessed on day 7 after MCAO. Brain atrophy on day 30 and long-term sensorimotor abilities after MCAO were analyzed as well. The inhibitor of FASN, C75 and the virus-delivered FASN shRNA were used to evaluate the role of FASN-driven lipogenesis in GTA-improved BBB repair. Finally, the therapeutic potential of recombinant IL-33 on BBB repair and neurological recovery was evaluated.

RESULTS

We found that treatment with GTA increased the lipogenesis as evidenced by lipid droplets level and lauric acid content, but not the FASN protein level. Treatment with GTA increased the IL-33 level in the peri-infarct area and decreased the BBB permeability after MCAO. However, infarct size and neurological defect score were unchanged on day 7 after MCAO, while the long-term recovery of sensorimotor function and brain atrophy were improved by GTA. Inhibition of lipogenesis using C75 or FASN shRNA reversed the beneficial effect of GTA. Finally, exogenous IL-33 improved BBB repair and long-term functional recovery after stroke.

CONCLUSION

Collectively, we concluded that treatment with GTA improved the BBB repair and functional recovery after ischemic stroke, probably by the enhancement of lipogenesis and IL-33 expression.

Acidified drinking water improves motor function, prevents tremors and changes disease trajectory in Cln2R207X mice, a model of late infantile Batten disease

Batten disease is a group of mostly pediatric neurodegenerative lysosomal storage disorders caused by mutations in the CLN1-14 genes. We have recently shown that acidified drinking water attenuated neuropathological changes and improved motor function in the Cln1R151X and Cln3-/- mouse models of infantile CLN1 and juvenile CLN3 diseases. Here we tested if acidified drinking water has beneficial effects in Cln2R207X mice, a nonsense mutant model of late infantile CLN2 disease. Cln2R207X mice have motor deficits, muscle weakness, develop tremors, and die prematurely between 4 and 6 months of age. Acidified water administered to Cln2R207X male mice from postnatal day 21 significantly improved motor function, restored muscle strength and prevented tremors as measured at 3 months of age. Acidified drinking water also changed disease trajectory, slightly delaying the death of Cln2R207X males and females. The gut microbiota compositions of Cln2R207X and wild-type male mice were markedly different and acidified drinking water significantly altered the gut microbiota of Cln2R207X mice. This suggests that gut bacteria might contribute to the beneficial effects of acidified drinking water. Our study demonstrates that drinking water is a major environmental factor that can alter disease phenotypes and disease progression in rodent disease models.

Chrono-Gerontology: Integrating Circadian Rhythms and Aging in Stroke Research

Stroke is a significant public health concern for elderly individuals. However, the majority of pre-clinical studies utilize young and healthy rodents, which may result in failure of candidate therapies in clinical trials. In this brief review/perspective, the complex link between circadian rhythms, aging, innate immunity, and the gut microbiome to ischemic injury onset, progression, and recovery is discussed. Short-chain fatty acids and nicotinamide adenine dinucleotide+ (NAD+ ) production by the gut microbiome are highlighted as key mechanisms with profound rhythmic behavior, and it is suggested to boost them as prophylactic/therapeutic approaches. Integrating aging, its associated comorbidities, and circadian regulation of physiological processes into stroke research may increase the translational value of pre-clinical studies and help to schedule the optimal time window for existing practices to improve stroke outcome and recovery.

Gut microbiota and stroke: New avenues to improve prevention and outcome

Despite major recent therapeutic advances, stroke remains a leading cause of disability and death. Consequently, new therapeutic targets need to be found to improve stroke outcome. The deleterious role of gut microbiota alteration (often mentioned as "dysbiosis") on cardiovascular diseases, including stroke and its risk factors, has been increasingly recognized. Gut microbiota metabolites, such as trimethylamine-N-oxide, short chain fatty acids and tryptophan, play a key role. Evidence of a link between alteration of the gut microbiota and cardiovascular risk factors exists, with a possible causality link supported by several preclinical studies. Gut microbiota alteration also seems to be implicated at the acute phase of stroke, with observational studies showing more non-neurological complications, higher infarct size and worse clinical outcome in stroke patients with altered microbiota. Microbiota targeted strategies have been developed, including prebiotics/probiotics, fecal microbiota transplantation, short chain fatty acid and trimethylamine-N-oxide inhibitors. Research teams have been using different time windows and end-points for their studies, with various results. Considering the available evidence, it is believed that studies focusing on microbiota-targeted strategies in association with conventional stroke care should be conducted. Such strategies should be considered according to three therapeutic time windows: first, at the pre-stroke (primary prevention) or post-stroke (secondary prevention) phases, to enhance the control of cardiovascular risk factors; secondly, at the acute phase of stroke, to limit the infarct size and the systemic complications and enhance the overall clinical outcome; thirdly, at the subacute phase of stroke, to prevent stroke recurrence and promote neurological recovery.

Microbiota Metabolites and Immune Regulation Affect Ischemic Stroke Occurrence, Development, and Prognosis

The gut microbiota are not only related to the development and occurrence of digestive system disease, but also have a bidirectional relationship with nervous system diseases via the microbiota-gut-brain axis. At present, correlations between the gut microbiota and neurological diseases, including stroke, are one of the focuses of investigation and attention in the medical community. Ischemic stroke (IS) is a cerebrovascular disease accompanied by focal neurological deficit or central nervous system injury or death. In this review, we summarize the contemporary latest research on correlations between the gut microbiota and IS. Additionally, we discuss the mechanisms of gut microbiota implicated in IS and related to metabolite production and immune regulation. Moreover, the factors of gut microbiota that affecting IS occurrence, and research implicating the gut microbiota as potential therapeutic targets for IS, are highlighted. Our review highlights the evidential relationships and connections between the gut microbiota and IS pathogenesis and prognosis.

Ischaemic stroke patients present sex differences in gut microbiota

BACKGROUND

Gut microbiota plays a role in the pathophysiology of ischaemic stroke (IS) through the bidirectional gut-brain axis. Nevertheless, little is known about sex-specific microbiota signatures in IS occurrence.

METHODS

A total of 89 IS patients and 12 healthy controls were enrolled. We studied the taxonomic differences of the gut microbiota between men and women with IS by shotgun metagenomic sequencing. To evaluate the causal effect of several bacteria on IS risk, we performed a two-sample Mendelian randomisation (MR) with inverse-variance weighting (IVW) using genome-wide association analysis (GWAS) summary statistics from two cohorts of 5959 subjects with genetic and microbiota data and 1,296,908 subjects with genetic and IS data, respectively.

RESULTS

α-Diversity analysis measured using Observed Species (p = 0.017), Chao1 (p = 0.009) and Abundance-based Coverage Estimator (p = 0.012) indexes revealed that IS men have a higher species richness compared with IS women. Moreover, we found sex-differences in IS patients in relation to the phylum Fusobacteria, class Fusobacteriia, order Fusobacteriales and family Fusobacteriaceae (all Bonferroni-corrected p < 0.001). MR confirmed that increased Fusobacteriaceae levels in the gut are causally associated with an increased risk of IS (IVW p = 0.02, β = 0.32).

CONCLUSIONS

Our study is the first to indicate that there are gut microbiome differences between men and women with IS, identifying high levels of Fusobacteriaceae in women as a specific risk factor for IS. Incorporating sex stratification analysis is important in the design, analysis and interpretation of studies on stroke and the gut microbiota.

Gut Microbiota to Microglia: Microbiome Influences Neurodevelopment in the CNS

The brain is traditionally viewed as an immunologically privileged site; however, there are known to be multiple resident immune cells that influence the CNS environment and are reactive to extra-CNS signaling. Microglia are an important component of this system, which influences early neurodevelopment in addition to modulating inflammation and regenerative responses to injury and infection. Microglia are influenced by gut microbiome-derived metabolites, both as part of their normal function and potentially in pathological patterns that may induce neurodevelopmental disabilities or behavioral changes. This review aims to summarize the mounting evidence indicating that, not only is the Gut-Brain axis mediated by metabolites and microglia throughout an organism's lifetime, but it is also influenced prenatally by maternal microbiome and diet, which holds implications for both early neuropathology and neurodevelopment.