An unexplored brain-gut microbiota axis in stroke

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.

Genetically supported causality between gut microbiota, immune cells, and ischemic stroke: a two-sample Mendelian randomization study

Background

Previous studies have highlighted a robust correlation between gut microbiota/immune cells and ischemic stroke (IS). However, the precise nature of their causal relationship remains uncertain. To address this gap, our study aims to meticulously investigate the causal association between gut microbiota/immune cells and the likelihood of developing IS, employing a two-sample Mendelian randomization (MR) analysis.

Methods

Our comprehensive analysis utilized summary statistics from genome-wide association studies (GWAS) on gut microbiota, immune cells, and IS. The primary MR method employed was the inverse variance-weighted (IVW) approach. To address potential pleiotropy and identify outlier genetic variants, we incorporated the Mendelian randomization pleiotropy residual sum and outlier (MR-PRESSO) technique, along with MR-Egger regression. Heterogeneity was assessed using Cochran's Q-test. Additionally, leave-one-out analysis was conducted to pinpoint any individual genetic variant influencing the observed causal associations. Finally, a reverse MR analysis was performed to explore the potential of reverse causation.

Results

Our investigation revealed four gut microbial taxa and 16 immune cells with a significant causal relationship with IS (p < 0.05). Notably, two bacterial features and five immunophenotypes were strongly associated with a lower IS risk: genus.Barnesiella.id.944 (OR: 0.907, 95% CI: 0.836-0.983, p = 0.018), genus.LachnospiraceaeNK4A136group.id.11319 (OR: 0.918, 95% CI: 0.853-0.983, p = 0.988), Activated & resting Treg % CD4++ (OR: 0.977, 95% CI: 0.956-0.998, p = 0.028). Additionally, significant associations between IS risk and two bacterial features along with eleven immunophenotypes were observed: genus.Paraprevotella.id.962 (OR: 1.106, 95% CI: 1.043-1.172, p < 0.001), genus.Streptococcus.id.1853 (OR: 1.119, 95% CI: 1.034-1.210, p = 0.005), CD127 on granulocyte (OR: 1.039, 95% CI: 1.009-1.070, p = 0.011). Our analyses did not reveal heterogeneity based on the Cochrane's Q-test (p > 0.05) nor indicate instances of horizontal pleiotropy according to MR-Egger and MR-PRESSO analyses (p > 0.05). Furthermore, the robustness of our MR results was confirmed through leave-one-out analysis.

Conclusion

Our study provides further evidence supporting the potential association between gut microbiota and immune cells in relation to IS, shedding light on the underlying mechanisms that may contribute to this condition. These findings lay a solid foundation for future investigations into targeted prevention strategies.

Gut Bacteria Provide Genetic and Molecular Reporter Systems to Identify Specific Diseases

With genetic information gained from next-generation sequencing (NGS) and genome-wide association studies (GWAS), it is now possible to select for genes that encode reporter molecules that may be used to detect abnormalities such as alcohol-related liver disease (ARLD), cancer, cognitive impairment, multiple sclerosis (MS), diabesity, and ischemic stroke (IS). This, however, requires a thorough understanding of the gut-brain axis (GBA), the effect diets have on the selection of gut microbiota, conditions that influence the expression of microbial genes, and human physiology. Bacterial metabolites such as short-chain fatty acids (SCFAs) play a major role in gut homeostasis, maintain intestinal epithelial cells (IECs), and regulate the immune system, neurological, and endocrine functions. Changes in butyrate levels may serve as an early warning of colon cancer. Other cancer-reporting molecules are colibactin, a genotoxin produced by polyketide synthetase-positive Escherichia coli strains, and spermine oxidase (SMO). Increased butyrate levels are also associated with inflammation and impaired cognition. Dysbiosis may lead to increased production of oxidized low-density lipoproteins (OX-LDLs), known to restrict blood vessels and cause hypertension. Sudden changes in SCFA levels may also serve as a warning of IS. Early signs of ARLD may be detected by an increase in regenerating islet-derived 3 gamma (REG3G), which is associated with changes in the secretion of mucin-2 (Muc2). Pro-inflammatory molecules such as cytokines, interferons, and TNF may serve as early reporters of MS. Other examples of microbial enzymes and metabolites that may be used as reporters in the early detection of life-threatening diseases are reviewed.

Stroke Related Brain-Heart Crosstalk: Pathophysiology, Clinical Implications, and Underlying Mechanisms

The emergence of acute ischemic stroke (AIS) induced cardiovascular dysfunctions as a bidirectional interaction has gained paramount importance in understanding the intricate relationship between the brain and heart. Post AIS, the ensuing cardiovascular dysfunctions encompass a spectrum of complications, including heart attack, congestive heart failure, systolic or diastolic dysfunction, arrhythmias, electrocardiographic anomalies, hemodynamic instability, cardiac arrest, among others, all of which are correlated with adverse outcomes and mortality. Mounting evidence underscores the intimate crosstalk between the heart and the brain, facilitated by intricate physiological and neurohumoral complex networks. The primary pathophysiological mechanisms contributing to these severe cardiac complications involve the hypothalamic-pituitary-adrenal (HPA) axis, sympathetic and parasympathetic hyperactivity, immune and inflammatory responses, and gut dysbiosis, collectively shaping the stroke-related brain-heart axis. Ongoing research endeavors are concentrated on devising strategies to prevent AIS-induced cardiovascular dysfunctions. Notably, labetalol, nicardipine, and nitroprusside are recommended for hypertension control, while β-blockers are employed to avert chronic remodeling and address arrhythmias. However, despite these therapeutic interventions, therapeutic targets remain elusive, necessitating further investigations into this complex challenge. This review aims to delineate the state-of-the-art pathophysiological mechanisms in AIS through preclinical and clinical research, unraveling their intricate interplay within the brain-heart axis, and offering pragmatic suggestions for managing AIS-induced cardiovascular dysfunctions.

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.

Multiorgan talks in the presence of brain injury

PURPOSE OF REVIEW

The brain is the command center of the rest of the body organs. The normal multiorgan talks between the brain and the rest of the body organs are essential for the normal body homeostasis. In the presence of brain injury, the disturbed talks between the brain and the rest of body organs will result in several pathological conditions. The aim of this review is to present the most recent findings for the pathological conditions that would result from the impaired multiorgan talks in the presence of brain injury.

RECENT FINDINGS

The brain injury such as in acute ischemic stroke, subarachnoid hemorrhage and traumatic brain injury will result in cascade of pathological talks between the brain and the rest of body organs. These pathological talks could result in pathological conditions such as cardiomyopathy, acute lung and kidney injuries, impaired liver functions, and impaired gut barrier permeability as well.

SUMMARY

Better understanding of the pathological conditions that could result from the impaired multiorgan talks in the presence of brain injury will open the doors for precise targeted therapies in the future for myriad of pathological conditions.

Interactions between gut microbiota and polyphenols: A mechanistic and metabolomic review

BACKGROUND

Polyphenols are a class of naturally sourced compounds with widespread distribution and an extensive array of bioactivities. However, due to their complex constituents and weak absorption, a convincing explanation for their remarkable bioactivity remains elusive for a long time. In recent years, interaction with gut microbiota is hypothesized to be a reasonable explanation of the potential mechanisms for natural compounds especially polyphenols.

OBJECTIVES

This review aims to present a persuasive explanation for the contradiction between the limited bioavailability and the remarkable bioactivities of polyphenols by examining their interactions with gut microbiota.

METHODS

We assessed literatures published before April 10, 2023, from several databases, including Scopus, PubMed, Google Scholar, and Web of Science. The keywords used include "polyphenols", "gut microbiota", "short-chain fatty acids", "bile acids", "trimethylamine N-oxide", "lipopolysaccharides" "tryptophan", "dopamine", "intestinal barrier", "central nervous system", "lung", "anthocyanin", "proanthocyanidin", "baicalein", "caffeic acid", "curcumin", "epigallocatechin-3-gallate", "ferulic acid", "genistein", "kaempferol", "luteolin", "myricetin", "naringenin", "procyanidins", "protocatechuic acid", "pterostilbene", "quercetin", "resveratrol", etc. RESULTS: The review first demonstrates that polyphenols significantly alter gut microbiota diversity (α- and β-diversity) and the abundance of specific microorganisms. Polyphenols either promote or inhibit microorganisms, with various factors influencing their effects, such as dosage, treatment duration, and chemical structure of polyphenols. Furthermore, the review reveals that polyphenols regulate several gut microbiota metabolites, including short-chain fatty acids, dopamine, trimethylamine N-oxide, bile acids, and lipopolysaccharides. Polyphenols affect these metabolites by altering gut microbiota composition, modifying microbial enzyme activity, and other potential mechanisms. The changed microbial metabolites induced by polyphenols subsequently trigger host responses in various ways, such as acting as intestinal acid-base homeostasis regulators and activating on specific target receptors. Additionally, polyphenols are transformed into microbial derivatives by gut microbiota and these polyphenols' microbial derivatives have many potential advantages (e.g., increased bioactivity, improved absorption). Lastly, the review shows polyphenols maintain intestinal barrier, central nervous system, and lung function homeostasis by regulating gut microbiota.

CONCLUSION

The interaction between polyphenols and gut microbiota provides a credible explanation for the exceptional bioactivities of polyphenols. This review aids our understanding of the underlying mechanisms behind the bioactivity of polyphenols.

Unraveling mechanistic insights into the role of microbiome in neurogenic hypertension: A comprehensive review

Neurogenic hypertension, a complex and multifactorial cardiovascular disorder, is known to be influenced by various genetic, environmental, and lifestyle factors. In recent years, there has been growing interest in the role of the gut microbiome in hypertension pathogenesis. The bidirectional communication between the gut microbiota and the central nervous system, known as the microbiota-gut-brain axis, has emerged as a crucial mechanism through which the gut microbiota exerts its influence on neuroinflammation, immune responses, and blood pressure regulation. Recent studies have shown how the microbiome has a substantial impact on a variety of physiological functions, such as cardiovascular health. The increased sympathetic activity to the gut may cause microbial dysbiosis, increased permeability of the gut, and increased inflammatory reactions by altering a number of intestinal bacteria producing short-chain fatty acids (SCFAs) and the concentrations of lipopolysaccharide (LPS) in the plasma. Collectively, these microbial metabolic and structural compounds stimulate sympathetic stimulation, which may be an important stage in the onset of hypertension. The result is an upsurge in peripheral and central inflammatory response. In addition, it has recently been shown that a link between the immune system and the gut microbiota might play a significant role in hypertension. The therapeutic implications of the gut microbiome including probiotic usage, prebiotics, dietary modifications, and fecal microbiota transplantation in neurogenic hypertension have also been found. A large body of research suggests that probiotic supplementation might help reduce chronic inflammation and hypertension that have an association with dysbiosis in the gut microbiota. Overall, this review sheds light on the intricate interplay between the gut microbiome and neurogenic hypertension, providing valuable insights for both researchers and clinicians. As our knowledge of the microbiome's role in hypertension expands, novel therapeutic strategies and diagnostic biomarkers may pave the way for more effective management and prevention of this prevalent cardiovascular disorder. Exploring the potential of the microbiome in hypertension offers an exciting avenue for future research and offers opportunities for precision medicine and improved patient care.

The gastrointestinal-brain-microbiota axis: a promising therapeutic target for ischemic stroke

Ischemic stroke is a highly complex systemic disease characterized by intricate interactions between the brain and gastrointestinal tract. While our current understanding of these interactions primarily stems from experimental models, their relevance to human stroke outcomes is of considerable interest. After stroke, bidirectional communication between the brain and gastrointestinal tract initiates changes in the gastrointestinal microenvironment. These changes involve the activation of gastrointestinal immunity, disruption of the gastrointestinal barrier, and alterations in gastrointestinal microbiota. Importantly, experimental evidence suggests that these alterations facilitate the migration of gastrointestinal immune cells and cytokines across the damaged blood-brain barrier, ultimately infiltrating the ischemic brain. Although the characterization of these phenomena in humans is still limited, recognizing the significance of the brain-gastrointestinal crosstalk after stroke offers potential avenues for therapeutic intervention. By targeting the mutually reinforcing processes between the brain and gastrointestinal tract, it may be possible to improve the prognosis of ischemic stroke. Further investigation is warranted to elucidate the clinical relevance and translational potential of these findings.

Plasmon-activated water as a therapeutic strategy in Alzheimer's disease by altering gut microbiota

Gut microbiota (GM) are involved in the pathophysiology of Alzheimer's disease (AD) and might correlate to the machinery of the gut-brain axis. Alteration of the GM profiles becomes a potential therapy strategy in AD. Here, we found that plasmon-activated water (PAW) therapy altered GM profile and reduced AD symptoms in APPswe/PS1dE9 transgenic mice (AD mice). GM profile showed the difference between AD and WT mice. PAW therapy in AD mice altered GM profile and fecal microbiota transplantation (FMT) reproduced GM profile in AD mice. PAW therapy and FMT in AD mice reduced cognitive decline and amyloid accumulation by novel object recognition (NOR) test and amyloid PET imaging. Immunofluorescent staining and western blot analysis of β-amyloid (Aβ) and phosphorylated (p)-tau in the brain of AD mice were reduced in PAW therapy and FMT. The inflammatory markers, interleukin (IL)-6, IL-1β, and tumor necrosis factor (TNF)-α and pro-inflammatory indicator of arginase-1/CD86 ratio were also reduced. Furthermore, immunohistochemistry (IHC) analysis of occludin and claudin-5 in the intestine and AXL in the brain were increased to correlate with the abundant GM in PAW therapy and FMT. Our results showed the machinery of gut-brain axis, and PAW might be a potential therapeutic strategy in AD.

The central role of peripheral inflammation in ischemic stroke

Stroke pathology and its treatments conventionally focus on the brain. Probing inflammation, a critical secondary cell death mechanism in stroke, has been largely relegated to the brain. To this end, peripheral inflammation has emerged as an equally potent contributor to the onset and progression of stroke secondary cell death. Here, we review novel concepts on peripheral organs displaying robust inflammatory response to stroke. These inflammation-plagued organs include the spleen, cervical lymph nodes, thymus, bone marrow, gastrointestinal system, and adrenal glands, likely converging their inflammatory effects through B and T-cells. Recognizing the significant impact of this systemic inflammation, we also discuss innovative stroke therapeutics directed at sequestration of peripheral inflammation. This review paper challenges the paradigm of a brain-centered disease pathology and treatment and offers a peripheral approach to our stroke understanding.

Microbiota-gut-brain axis impairment in the pathogenesis of stroke: implication as a potent therapeutic target

The human microbiota-gut-brain axis has an enormous role in the maintenance of homeostasis and health. Over the last two decades, it has received concerted research attention and focus due to a rapidly emerging volume of evidence that has established that impairment within the microbiota-gut-brain axis contributes to the development and progression of various diseases. Stroke is one of the entities identified to be associated with microbiota-gut-brain axis impairment. Currently, there are still limitations in the clinical treatment of stroke, and the presence of a non-nervous factor from gut microbiota that can alter the course of stroke presents a novel strategy towards the search for a therapeutic silver bullet against stroke. Hence, the aim herein, was to focus on the involvement of microbiota-gut-brain axis impairment in the pathogenesis stroke as well as elucidate its implications as a potent therapeutic target against stroke. The findings of studies to date have revealed and extended the role microbiota-gut-brain axis impairment in the pathogenesis of stroke, and studies have identified from both clinical and pre-clinical perspectives targets within the microbiota-gut-brain axis and successfully modulated the outcome of stroke. It was concluded that the microbiota-gut-brain axis stands as potent target to salvage the neurons in the ischemic penumbra for the treatment of stroke. Assessment of the microbiota profile and its metabolites status holds enormous clinical potentials as a non-invasive indicator for the early diagnosis and prognosis of stroke.

Global cerebral ischemia followed by long-term reperfusion promotes neurodegeneration, oxidative stress, and inflammation in the small intestine in Wistar rats

AIMS

Brain ischemia and reperfusion may occur in several clinical conditions that have high rates of mortality and disability, compromising an individual's quality of life. Brain injury can affect organs beyond the brain, such as the gastrointestinal tract. The present study investigated the effects of cerebral ischemia on the ileum and jejunum during a chronic reperfusion period by examining oxidative stress, inflammatory parameters, and the myenteric plexus in Wistar rats.

MAIN METHODS

Ischemia was induced by the four-vessel occlusion model for 15 min with 52 days of reperfusion. Oxidative stress and inflammatory markers were evaluated using biochemical techniques. Gastrointestinal transit time was evaluated, and immunofluorescence techniques were used to examine morpho-quantitative aspects of myenteric neurons.

KEY FINDINGS

Brain ischemia and reperfusion promoted inflammation, characterized by increases in myeloperoxidase and N-acetylglycosaminidase activity, oxidative stress, and lipid hydroperoxides, decreases in superoxide dismutase and catalase activity, a decrease in levels of reduced glutathione, neurodegeneration in the gut, and slow gastrointestinal transit.

SIGNIFICANCE

Chronic ischemia and reperfusion promoted a slow gastrointestinal transit time, oxidative stress, and inflammation and neurodegeneration in the small intestine in rats. These findings indicate that the use of antioxidant and antiinflammatory molecules even after a long period of reperfusion may be useful to alleviate the consequences of this pathology.

Gut microbiota-derived melatonin from Puerariae Lobatae Radix-resistant starch supplementation attenuates ischemic stroke injury via a positive microbial co-occurrence pattern

Ischemic stroke is closely associated with gut microbiota dysbiosis and intestinal barrier dysfunction. Prebiotic intervention could modulate the intestinal microbiota, thus considered a practical strategy for neurological disorders. Puerariae Lobatae Radix-resistant starch (PLR-RS) is a potential novel prebiotic; however, its role in ischemic stroke remains unknown. This study aimed to clarify the effects and underlying mechanisms of PLR-RS in ischemic stroke. Middle cerebral artery occlusion surgery was performed to establish a model of ischemic stroke in rats. After gavage for 14 days, PLR-RS attenuated ischemic stroke-induced brain impairment and gut barrier dysfunction. Moreover, PLR-RS rescued gut microbiota dysbiosis and enriched Akkermansia and Bifidobacterium. We transplanted the fecal microbiota from PLR-RS-treated rats into rats with ischemic stroke and found that the brain and colon damage were also ameliorated. Notably, we found that PLR-RS promoted the gut microbiota to produce a higher level of melatonin. Intriguingly, exogenous gavage of melatonin attenuated ischemic stroke injury. In particular, melatonin attenuated brain impairment via a positive co-occurrence pattern in the intestinal microecology. Specific beneficial bacteria served as leaders or keystone species to promoted gut homeostasis, such as Enterobacter, Bacteroidales_S24-7_group, Prevotella_9, Ruminococcaceae and Lachnospiraceae. Thus, this new underlying mechanism could explain that the therapeutic efficacy of PLR-RS on ischemic stroke at least partly attributed to gut microbiota-derived melatonin. In summary, improving intestinal microecology by prebiotic intervention and melatonin supplementation in the gut were found to be effective therapies for ischemic stroke.

The Bridge Between Ischemic Stroke and Gut Microbes: Short-Chain Fatty Acids

Short-chain fatty acids (SCFAs) are monocarboxylates produced by the gut microbiota (GM) and result from the interaction between diet and GM. An increasing number of studies about the microbiota-gut-brain axis (MGBA) indicated that SCFAs may be a crucial mediator in the MGBA, but their roles have not been fully clarified. In addition, there are few studies directly exploring the role of SCFAs as a potential regulator of microbial targeted interventions in ischemic stroke, especially for clinical studies. This review summarizes the recent studies concerning the relationship between ischemic stroke and GM and outlines the role of SCFAs as a bridge between them. The potential mechanisms by which SCFAs affect ischemic stroke are described. Finally, the beneficial effects of SFCAs-mediated therapeutic measures such as diet, dietary supplements (e.g., probiotics and prebiotics), fecal microbiota transplantation, and drugs on ischemic brain injury are also discussed.

Neuroprotective Strategies for Ischemic Stroke-Future Perspectives

Ischemic stroke is the main cause of death and the most common cause of acquired physical disability worldwide. Recent demographic changes increase the relevance of stroke and its sequelae. The acute treatment for stroke is restricted to causative recanalization and restoration of cerebral blood flow, including both intravenous thrombolysis and mechanical thrombectomy. Still, only a limited number of patients are eligible for these time-sensitive treatments. Hence, new neuroprotective approaches are urgently needed. Neuroprotection is thus defined as an intervention resulting in the preservation, recovery, and/or regeneration of the nervous system by interfering with the ischemic-triggered stroke cascade. Despite numerous preclinical studies generating promising data for several neuroprotective agents, successful bench-to-bedside translations are still lacking. The present study provides an overview of current approaches in the research field of neuroprotective stroke treatment. Aside from "traditional" neuroprotective drugs focusing on inflammation, cell death, and excitotoxicity, stem-cell-based treatment methods are also considered. Furthermore, an overview of a prospective neuroprotective method using extracellular vesicles that are secreted from various stem cell sources, including neural stem cells and bone marrow stem cells, is also given. The review concludes with a short discussion on the microbiota-gut-brain axis that may serve as a potential target for future neuroprotective therapies.

Interventional strategies for ischemic stroke based on the modulation of the gut microbiota

The microbiota-gut-brain axis connects the brain and the gut in a bidirectional manner. The organism's homeostasis is disrupted during an ischemic stroke (IS). Cerebral ischemia affects the intestinal flora and microbiota metabolites. Microbiome dysbiosis, on the other hand, exacerbates the severity of IS outcomes by inducing systemic inflammation. Some studies have recently provided novel insights into the pathogenesis, efficacy, prognosis, and treatment-related adverse events of the gut microbiome in IS. In this review, we discussed the view that the gut microbiome is of clinical value in personalized therapeutic regimens for IS. Based on recent non-clinical and clinical studies on stroke, we discussed new therapeutic strategies that might be developed by modulating gut bacterial flora. These strategies include dietary intervention, fecal microbiota transplantation, probiotics, antibiotics, traditional Chinese medication, and gut-derived stem cell transplantation. Although the gut microbiota-targeted intervention is optimistic, some issues need to be addressed before clinical translation. These issues include a deeper understanding of the potential underlying mechanisms, conducting larger longitudinal cohort studies on the gut microbiome and host responses with multiple layers of data, developing standardized protocols for conducting and reporting clinical analyses, and performing a clinical assessment of multiple large-scale IS cohorts. In this review, we presented certain opportunities and challenges that might be considered for developing effective strategies by manipulating the gut microbiome to improve the treatment and prevention of ischemic stroke.

Stroke and the risk of gastrointestinal disorders: A Mendelian randomization study

Background

The issue of whether a stroke is causally related to gastrointestinal disorders was still not satisfactorily understood. Therefore, we investigated if there is a connection between stroke and the most prevalent gastrointestinal disorders, including peptic ulcer disease (PUD), gastroesophageal reflux disease (GERD), irritable bowel syndrome (IBS), and inflammatory bowel disease (IBD).

Methods

We applied two-sample Mendelian randomization to investigate relationships with gastrointestinal disorders. We obtained genome-wide association study (GWAS) summary data of any stroke, ischemic stroke, and its subtypes from the MEGASTROKE consortium. From the International Stroke Genetics Consortium (ISGC) meta-analysis, we acquired GWAS summary information on intracerebral hemorrhage (ICH), including all ICH, deep ICH, and lobar ICH. Several sensitivity studies were performed to identify heterogeneity and pleiotropy, while inverse-variance weighted (IVW) was utilized as the most dominant estimate.

Results

No evidence for an effect of genetic predisposition to ischemic stroke and its subtypes on gastrointestinal disorders were found in IVW. The complications of deep ICH are a higher risk for PUD and GERD. Meanwhile, lobar ICH has a higher risk of complications for PUD.

Conclusion

This study provides proof of the presence of a brain-gut axis. Among the complications of ICH, PUD and GERD were more common and associated with the site of hemorrhage.

Network pharmacology approach to investigate the multitarget mechanisms of Zhishi Rhubarb Soup on acute cerebral infarction

CONTEXT

Zhishi Rhubarb Soup (ZRS) is a traditional Chinese medicine formula used in the clinic to treat acute cerebral infarction (ACI) for many years. However, the exact mechanism of the treatment remains unclear.

OBJECTIVE

This study elucidates the multitarget mechanisms underlying the effects of ZRS on ACI using network pharmacology analysis and verify its effect by performing animal experiments.

MATERIALS AND METHODS

Using the network pharmacology approach, the multiple components, critical targets and potential mechanisms of ZRS against ACI were investigated. Six herbal names of ZRS and 'acute cerebral infarction' were used as keywords to search the relevant databases. In addition, we established the MCAO model to verify the results of network pharmacology enrichment analysis. ZRS (10 g crude drug/kg) was gavaged once per day for 7 consecutive days beginning 3 h after model establishment. After ZRS treatment, TTC staining, Western blot analysis, IHC and ELISA were conducted to further explore the mechanism of ZRS intervention in ACI.

RESULTS

The network pharmacology approach identified 69 key targets, 10 core genes and 169 signalling pathways involved in the treatment of ACI with ZRS. In vivo experiment showed that ZRS treatment significantly reduced cerebral infarction volume (42.76%). It also reduced the expression level of AGE, RAGE and P65; and inhibited the expression of inflammatory MMP-9 and IFN-γ.

CONCLUSIONS

This study demonstrated that ZRS improved cerebral ischaemic injury by inhibiting neuroinflammation partly via the AGE-RAGE signalling pathway. It provides a theoretical basis for the clinical application of ZRS in the treatment of ACI.

Intestinal flora induces depression by mediating the dysregulation of cerebral cortex gene expression and regulating the metabolism of stroke patients

Post-stroke depression (PSD) is a common cerebrovascular complication characterized by complex pathogenesis and poor treatment effects. Here, we tested the influence of differentially expressed genes (DEGs), non-targeted metabolites, and intestinal microbes on the occurrence and development of PSD. We acquired gene expression profiles for stroke patients, depression patients, and healthy controls from the Gene Expression Omnibus database. After screening for DEGs using differential expression analysis, we identified common DEGs in stroke and depression patients that were considered to form the molecular basis of PSD. Functional enrichment analysis of DEGs also revealed that the majority of biological functions were closely related to metabolism, immunity, the nervous system, and microorganisms, and we also collected blood and stool samples from healthy controls, stroke patients, and PSD patients and performed 16S rDNA sequencing and untargeted metabolomics. After evaluating the quality of the sequencing data, we compared the diversity of the metabolites and intestinal flora within and between groups. Metabolic pathway enrichment analysis was used to identify metabolic pathways that were significantly involved in stroke and PSD, and a global metabolic network was constructed to explore the pathogenesis of PSD. Additionally, we constructed a global regulatory network based on 16S rDNA sequencing, non-targeted metabolomics, and transcriptomics to explore the pathogenesis of PSD through correlation analysis. Our results suggest that intestinal flora associates the dysregulation of cerebral cortex gene expression and could potentially promote the occurrence of depression by affecting the metabolism of stroke patients. Our findings may be helpful in identifying new targets for the prevention and treatment of PSD.

Uncovering the characteristics of the gut microbiota in patients with acute ischemic stroke and phlegm-heat syndrome

Growing evidence has indicated that the characteristics of gut microbiota are associated with acute ischemic stroke (AIS). Phlegm-heat syndrome (PHS), a specific pathological state of the AIS, is one of the common traditional Chinese syndromes of stroke. The long duration of PHS in patients with AIS could lead to poor clinical outcomes. Gut microbiota characteristics in patients with both AIS and PHS, and their relationship remains unknown. This study was designed to investigate the alterations in gut microbiota in patients with AIS and PHS through a cross-sectional study. Fecal samples were collected from 10 patients with AIS and non-PHS (ntAIS), 7 patients with AIS and PHS (tAIS), and 10 healthy controls (HC). Samples were profiled via Illumina sequencing of the 16S rRNA V3-V4. Stroke severity was assessed at admission by the National Institutes of Health Stroke Scale (NIHSS) and modified Rankin scale (mRS); their correlation with gut microbiota was investigated. The alpha-diversity of the bacterial communities was significantly higher in the fecal samples of patients with tAIS than in patients with ntAIS (Shannon index, P = 0.037). In addition, the combined tAIS and ntAIS group (tntAIS) exhibited higher microbiotic diversity when compared with HC (chao1, P = 0.019). The structure of intestinal microbiota was effectively distinguished between the tAIS and ntAIS group (ANOSIM, r = 0.337, P = 0.007). Additionally, the gut microbiota structure was significantly different between the tntAIS and HC groups (ANOSIM, r = 0.217, P = 0.005). The genera, Ruminococcaceae_ UCG_002 and Christensenellaceae_R-7_group, were implicated in the discrimination of PHS from non-PHS. The order Lactobacillales and family Lachnospiraceae were significantly negatively correlated with NIHSS and mRS at admission (P < 0.05). By contrast, the order Desulfovibrionales, families Christensenellaceae and Desulfovibrionaceae, and genera Ruminococcaceae UCG-014 and Ruminococcaceae UCG-002 were significantly positively correlated with NIHSS and mRS at admission (P < 0.05). This study is the first to profile the characteristics of gut microbiota in patients with AIS and PHS, compared with those with non-PHS. The genera, Ruminococcaceae_ UCG_002 and Christensenellaceae_R-7_group, may be objective indicators of this traditional Chinese medicine (TCM) syndrome in AIS. Furthermore, it provides a microbe-inspired biological basis for TCM syndrome differentiation.

Systemic immune responses after ischemic stroke: From the center to the periphery

Ischemic stroke is a leading cause of disability and death. It imposes a heavy economic burden on individuals, families and society. The mortality rate of ischemic stroke has decreased with the help of thrombolytic drug therapy and intravascular intervention. However, the nerve damage caused by ischemia-reperfusion is long-lasting and followed by multiple organ dysfunction. In this process, the immune responses manifested by systemic inflammatory responses play an important role. It begins with neuroinflammation following ischemic stroke. The large number of inflammatory cells released after activation of immune cells in the lesion area, along with the deactivated neuroendocrine and autonomic nervous systems, link the center with the periphery. With the activation of systemic immunity and the emergence of immunosuppression, peripheral organs become the second “battlefield” of the immune response after ischemic stroke and gradually become dysfunctional and lead to an adverse prognosis. The purpose of this review was to describe the systemic immune responses after ischemic stroke. We hope to provide new ideas for future research and clinical treatments to improve patient outcomes and quality of life.

Diet-microbiome-gut-brain nexus in acute and chronic brain injury

In recent years, appreciation for the gut microbiome and its relationship to human health has emerged as a facilitator of maintaining healthy physiology and a contributor to numerous human diseases. The contribution of the microbiome in modulating the gut-brain axis has gained significant attention in recent years, extensively studied in chronic brain injuries such as Epilepsy and Alzheimer’s Disease. Furthermore, there is growing evidence that gut microbiome also contributes to acute brain injuries like stroke(s) and traumatic brain injury. Microbiome-gut-brain communications are bidirectional and involve metabolite production and modulation of immune and neuronal functions. The microbiome plays two distinct roles: it beneficially modulates immune system and neuronal functions; however, abnormalities in the host’s microbiome also exacerbates neuronal damage or delays the recovery from acute injuries. After brain injury, several inflammatory changes, such as the necrosis and apoptosis of neuronal tissue, propagates downward inflammatory signals to disrupt the microbiome homeostasis; however, microbiome dysbiosis impacts the upward signaling to the brain and interferes with recovery in neuronal functions and brain health. Diet is a superlative modulator of microbiome and is known to impact the gut-brain axis, including its influence on acute and neuronal injuries. In this review, we discussed the differential microbiome changes in both acute and chronic brain injuries, as well as the therapeutic importance of modulation by diets and probiotics. We emphasize the mechanistic studies based on animal models and their translational or clinical relationship by reviewing human studies.

Effect of Electroacupuncture on Short-Chain Fatty Acids in Peripheral Blood after Middle Cerebral Artery Occlusion/Reperfusion in Rats Based on Gas Chromatography–Mass Spectrometry

Previous fundamental and clinical research has shown that electroacupuncture (EA) at the acupoints of Quchi (LI11) and Zusanli (ST36) can successfully alleviate motor dysfunction following stroke. Additionally, it has been discovered that gut microbiota and their metabolites play an essential role in stroke. However, the relationship between the metabolites of gut microbiota and the efficacy of EA is still unclear. Therefore, the aim of this study was to evaluate the mechanism of EA at LI11 and ST36 in the treatment of motor dysfunction after middle cerebral artery occlusion/reperfusion (MCAO/R) in model rats by comparing the differences and correlation between different short-chain fatty acids (SCFAs) and the recovery of motor function. The results indicated that EA at LI11 and ST36 acupoints enhanced the neurological function, motor function, and infarct volume of MCAO/R rats. The levels of acetic acid, propionic acid, and total SCFAs were considerably lower in the MCAO/R group than in the sham group (P < 0.05). Acetic acid, propionic acid, and total SCFA concentrations were substantially higher in the MCAO/R + EA group than in the MCAO/R group (P < 0.05). Finally, Pearson correlation analysis revealed that the propionic acid concentration was substantially favorably connected with the duration on the rotarod (r = 0.633 and P < 0.05) and highly negatively correlated with the modified neurological severity score (mNSS) (r = −0.698 and P < 0.05) and the percentage of cerebral infarct volume (r = −0.729 and P < 0.05). Taken together, these findings indicate that the increase in propionic acid may be one of the mechanisms and targets of EA at LI11 and ST36 acupoints to improve poststroke motor dysfunction in MCAO/R rats.

The clinical and mechanistic roles of bile acids in depression, Alzheimer's disease, and stroke

The burden of neurological and neuropsychiatric disorders continues to grow with significant impacts on human health and social economy worldwide. Increasing clinical and preclinical evidences have implicated that bile acids (BAs) are involved in the onset and progression of neurological and neuropsychiatric diseases. Here, we summarized recent studies of BAs in three types of highly prevalent brain disorders, depression, Alzheimer's disease, and stroke. The shared and specific BA profiles were explored and potential markers associated with disease development and progression were summarized. The mechanistic roles of BAs were reviewed with focuses on inflammation, gut-brain-microbiota axis, cellular apoptosis. We also discussed future perspectives for the prevention and treatment of neurological and neuropsychiatric disorders by targeting BAs and related molecules and gut microbiota. Our understanding of BAs and their roles in brain disorders is still evolving. A large number of questions still need to be addressed on the emerging crosstalk among central, peripheral, intestine and their contribution to brain and mental health. This article is protected by copyright. All rights reserved.

Peripheral Organ Injury After Stroke

Stroke is a disease with high incidence, mortality and disability rates. It is also the main cause of adult disability in developed countries. Stroke is often caused by small emboli on the inner wall of the blood vessels supplying the brain, which can lead to arterial embolism, and can also be caused by cerebrovascular or thrombotic bleeding. With the exception of recombinant tissue plasminogen activator (rt-PA), which is a thrombolytic drug used to recanalize the occluded artery, most treatments have been demonstrated to be ineffective. Stroke can also induce peripheral organ damage. Most stroke patients have different degrees of injury to one or more organs, including the lung, heart, kidney, spleen, gastrointestinal tract and so on. In the acute phase of stroke, severe inflammation occurs in the brain, but there is strong immunosuppression in the peripheral organs, which greatly increases the risk of peripheral organ infection and aggravates organ damage. Nonneurological complications of stroke can affect treatment and prognosis, may cause serious short-term and long-term consequences and are associated with prolonged hospitalization and increased mortality. Many of these complications are preventable, and their adverse effects can be effectively mitigated by early detection and appropriate treatment with various medical measures. This article reviews the pathophysiological mechanism, clinical manifestations and treatment of peripheral organ injury after stroke.

Therapeutic Effect of Buyang Huanwu Decoction on the Gut Microbiota and Hippocampal Metabolism in a Rat Model of Cerebral Ischemia

Buyang Huanwu decoction (BHD) is a well-known Chinese herbal prescription. It has been widely used in the clinical treatment of cerebral ischemia (CI) in China. However, the mechanism underlying the treatment of CI with BHD remains to be elucidated. In this study, we combined microbiomic and metabolomic strategies to explore the therapeutic effects of BHD on middle cerebral artery occlusion (MCAO) in rats. Our results showed that BHD could effectively improve neurological severity scores and alleviate neuronal damage in rats with MCAO. BHD could also reduce the level of peripheral proinflammatory cytokines and inhibit neuroinflammation. 16S rRNA sequencing showed that BHD could increase the relative abundances of the genera Lactobacillus, Faecalibacterium, Ruminococcaceae_UCG-002, etc., while decreasing the relative abundances of the genera Escherichia-Shigella, Klebsiella, Streptococcus, Coprococcus_2, Enterococcus, etc. Untargeted metabolomic analysis of hippocampal samples showed that 17 significantly differentially abundant metabolites and 9 enriched metabolic pathways were linked with BHD treatment. We also found that the regulatory effects of BHD on metabolites were correlated with the differentially abundant microbial taxa. The predicted function of the gut microbiota and the metabolic pathway enrichment results showed that purine metabolism, glutamatergic synapses, arginine and proline metabolism, and alanine, aspartic acid and glutamate metabolism were involved in the effects of BHD. These pathways may be related to pathological processes such as excitotoxicity, neuroinflammation, and energy metabolism disorder in CI. In summary, these findings suggest that regulation of hippocampal metabolism and of the composition and function of the gut microbiota may be important mechanisms underlying the effect of BHD in the treatment of CI.

Gut Dysbiosis Is Associated With the Severity of Cryptogenic Stroke and Enhanced Systemic Inflammatory Response

Studies implicate that gut dysbiosis is related with many neurological diseases. However, the potential role of gut dysbiosis in cryptogenic stroke (CS) has not been elucidated yet. In this study, a high prevalence of gastrointestinal (GI) dysfunction and gut inflammation with increased intestinal permeability have been found in CS patients compared with normal controls (NCs). The systemic inflammation in CS patients was also identified by measuring the levels of plasma C-reactive protein (CRP), lipopolysaccharide (LPS), LPS-binding protein (LBP), and white blood cells (WBC) count. Using 16S rRNA sequencing, we found increased alpha diversity, accompanied by a higher abundance of Enterobacteriaceae, Streptococcaceae, and Lactobacillaceae at the family level and Escherichia–Shigella, Streptococcus, Lactobacillus, and Klebsilla at the genus level in the intestinal microbiota of CS patients compared to NCs. Our results showed that the abundance of Klebsilla was positively correlated with the systemic inflammation, the National Institutes of Health Stroke Scale (NIHSS) scores, and the infarct volumes. In conclusion, gut dysbiosis in CS patients was associated with the severity of CS and the systemic inflammation. Maintaining the intestinal homeostasis may be a potential strategy for the treatment of CS.

The Influence of Gut Dysbiosis in the Pathogenesis and Management of Ischemic Stroke

Recent research on the gut microbiome has revealed the influence of gut microbiota (GM) on ischemic stroke pathogenesis and treatment outcomes. Alterations in the diversity, abundance, and functions of the gut microbiome, termed gut dysbiosis, results in dysregulated gut–brain signaling, which induces intestinal barrier changes, endotoxemia, systemic inflammation, and infection, affecting post-stroke outcomes. Gut–brain interactions are bidirectional, and the signals from the gut to the brain are mediated by microbially derived metabolites, such as trimethylamine N-oxide (TMAO) and short-chain fatty acids (SCFAs); bacterial components, such as lipopolysaccharide (LPS); immune cells, such as T helper cells; and bacterial translocation via hormonal, immune, and neural pathways. Ischemic stroke affects gut microbial composition via neural and hypothalamic–pituitary–adrenal (HPA) pathways, which can contribute to post-stroke outcomes. Experimental and clinical studies have demonstrated that the restoration of the gut microbiome usually improves stroke treatment outcomes by regulating metabolic, immune, and inflammatory responses via the gut–brain axis (GBA). Therefore, restoring healthy microbial ecology in the gut may be a key therapeutic target for the effective management and treatment of ischemic stroke.

Diet-Induced High Serum Levels of Trimethylamine-N-oxide Enhance the Cellular Inflammatory Response without Exacerbating Acute Intracerebral Hemorrhage Injury in Mice

Trimethylamine-N-oxide (TMAO), an intestinal flora metabolite of choline, may aggravate atherosclerosis by inducing a chronic inflammatory response and thereby promoting the occurrence of cerebrovascular diseases. Knowledge about the influence of TMAO-related inflammatory response on the pathological process of acute stroke is limited. This study was designed to explore the effects of TMAO on neuroinflammation, brain injury severity, and long-term neurologic function in mice with acute intracerebral hemorrhage (ICH). We fed mice with either a regular chow diet or a chow diet supplemented with 1.2% choline pre- and post-ICH. In this study, we measured serum levels of TMAO with ultrahigh-performance liquid chromatography-tandem mass spectrometry at 24 h and 72 h post-ICH. The expression level of P38-mitogen-protein kinase (P38-MAPK), myeloid differentiation factor 88 (MyD88), high-mobility group box1 protein (HMGB1), and interleukin-1β (IL-1β) around hematoma was examined by western blotting at 24 h. Microglial and astrocyte activation and neutrophil infiltration were examined at 72 h. The lesion was examined on days 3 and 28. Neurologic deficits were examined for 28 days. A long-term choline diet significantly increased serum levels of TMAO compared with a regular diet at 24 h and 72 h after sham operation or ICH. Choline diet-induced high serum levels of TMAO did not enhance the expression of P38-MAPK, MyD88, HMGB1, or IL-1β at 24 h. However, it did increase the number of activated microglia and astrocytes around the hematoma at 72 h. Contrary to our expectations, it did not aggravate acute or long-term histologic damage or neurologic deficits after ICH. In summary, choline diet-induced high serum levels of TMAO increased the cellular inflammatory response probably by activating microglia and astrocytes. However, it did not aggravate brain injury or worsen long-term neurologic deficits. Although TMAO might be a potential risk factor for cerebrovascular diseases, this exploratory study did not support that TMAO is a promising target for ICH therapy.

Gut microbiome in neuropsychiatric disorders

ABSTRACT Background: Neuropsychiatric disorders are a significant cause of death and disability worldwide. The mechanisms underlying these disorders include a constellation of structural, infectious, immunological, metabolic, and genetic etiologies. Advances in next-generation sequencing techniques have demonstrated that the composition of the enteric microbiome is dynamic and plays a pivotal role in host homeostasis and several diseases. The enteric microbiome acts as a key mediator in neuronal signaling via metabolic, neuroimmune, and neuroendocrine pathways. Objective: In this review, we aim to present and discuss the most current knowledge regarding the putative influence of the gut microbiome in neuropsychiatric disorders. Methods: We examined some of the preclinical and clinical evidence and therapeutic strategies associated with the manipulation of the gut microbiome. Results: targeted taxa were described and grouped from major studies to each disease. Conclusions: Understanding the complexity of these ecological interactions and their association with susceptibility and progression of acute and chronic disorders could lead to novel diagnostic biomarkers based on molecular targets. Moreover, research on the microbiome can also improve some emerging treatment choices, such as fecal transplantation, personalized probiotics, and dietary interventions, which could be used to reduce the impact of specific neuropsychiatric disorders. We expect that this knowledge will help physicians caring for patients with neuropsychiatric disorders.

Stroke-induced immunosuppression: implications for the prevention and prediction of post-stroke infections

Stroke produces a powerful inflammatory cascade in the brain, but also a suppression of the peripheral immune system, which is also called stroke-induced immunosuppression (SIIS). The main processes that lead to SIIS are a shift from a lymphocyte phenotype T-helper (Th) 1 to a Th2 phenotype, a decrease of the lymphocyte counts and NK cells in the blood and spleen, and an impairment of the defense mechanisms of neutrophils and monocytes. The direct clinical consequence of SIIS in stroke patients is an increased susceptibility to stroke-associated infections, which is enhanced by clinical factors like dysphagia. Among these infections, stroke-associated pneumonia (SAP) is the one that accounts for the highest impact on stroke outcome, so research is focused on its early diagnosis and prevention. Biomarkers indicating modifications in SIIS pathways could have an important role in the early prediction of SAP, but currently, there are no individual biomarkers or panels of biomarkers that are accurate enough to be translated to clinical practice. Similarly, there is still no efficient therapy to prevent the onset of SAP, and clinical trials testing prophylactic antibiotic treatment and β-blockers have failed. However, local immunomodulation could open up a new research opportunity to find a preventive therapy for SAP. Recent studies have focused on the pulmonary immune changes that could be caused by stroke similarly to other acquired brain injuries. Some of the traits observed in animal models of stroke include lung edema and inflammation, as well as inflammation of the bronchoalveolar lavage fluid.

Could the Gut Microbiota Serve as a Therapeutic Target in Ischemic Stroke?

The brain-gut axis is a relatively recent discovery of a two-way regulation system between the gut and brain, suggesting that the gut microbiota may be a promising targeted prevention and treatment strategy for patients with a high risk of acute cerebral ischemia/reperfusion injury. There are many risk factors for ischemic stroke, and many studies have shown that the gut microbiota affects the absorption and metabolism of the body, as well as the risk factors of stroke, such as blood pressure, blood glucose, blood lipids, and atherosclerosis, either directly or indirectly. Furthermore, the gut microbiota can affect the occurrence and prognosis of ischemic stroke by regulating risk factors or immune responses. Therefore, this study aimed to collect evidence of the interaction between gut microbiota and ischemic stroke, summarize the interaction mechanism between the two, and explore the gut microbiota as a new targeted prevention and treatment strategy for patients with high ischemic risk.

Rebuilding Microbiome for Mitigating Traumatic Brain Injury: Importance of Restructuring the Gut-Microbiome-Brain Axis

Traumatic brain injury (TBI) is a damage to the brain from an external force that results in temporary or permanent impairment in brain functions. Unfortunately, not many treatment options are available to TBI patients. Therefore, knowledge of the complex interplay between gut microbiome (GM) and brain health may shed novel insights as it is a rapidly expanding field of research around the world. Recent studies show that GM plays important roles in shaping neurogenerative processes such as blood-brain-barrier (BBB), myelination, neurogenesis, and microglial maturation. In addition, GM is also known to modulate many aspects of neurological behavior and cognition; however, not much is known about the role of GM in brain injuries. Since GM has been shown to improve cellular and molecular functions via mitigating TBI-induced pathologies such as BBB permeability, neuroinflammation, astroglia activation, and mitochondrial dysfunction, herein we discuss how a dysbiotic gut environment, which in fact, contributes to central nervous system (CNS) disorders during brain injury and how to potentially ward off these harmful effects. We further opine that a better understanding of GM-brain (GMB) axis could help assist in designing better treatment and management strategies in future for the patients who are faced with limited options.

Intestinal Barrier Dysfunction Participates in the Pathophysiology of Ischemic Stroke

The gastrointestinal tract is a major organ for the body to absorb nutrients, water and electrolytes. At the same time, it is a tight barrier to resist the invasion of harmful substances and maintain the homeostasis of the internal environment. Destruction of the intestinal barrier is linked to the digestive system, cardiovascular system, endocrine system and other systemic diseases. Mounting evidence suggests that ischemic stroke not only changes the intestinal microbes, but also increases the permeability of the intestinal barrier, leading to bacterial translocation, infection, and even sepsis. The intestinal barrier, as part of the gut-brain axis, has also been proven to participate in the pathophysiological process of ischemic stroke. However, little attention has been paid to it. Since ischemic stroke is a major public health issue worldwide, there is an urgent need to know more about the disease for better prevention, treatment and prognosis. Therefore, understanding the pathophysiological relationship between ischemic stroke and the intestinal barrier will help researchers further uncover the pathophysiological mechanism of ischemic stroke and provide a novel therapeutic target for the treatment of ischemic stroke. Here, we review the physiology and pathology between ischemic stroke and intestinal barrier based on related articles published in the past ten years about the relationship between ischemic stroke, stroke risk factors and intestinal flora, intestinal barrier, and discuss the following parts: the intestinal barrier; possible mechanisms of intestinal barrier destruction in ischemic stroke; intestinal barrier destruction caused by stroke-related risk factors; intestinal barrier dysfunction in ischemic stroke; targeting the intestinal barrier to improve stroke; conclusions and perspectives.

Intestinal Flora: A Pivotal Role in Investigation of Traditional Chinese Medicine

Intestinal flora is essential for maintaining host health and plays a unique role in transforming Traditional Chinese Medicine (TCM). TCM, as a bodyguard, has saved countless lives and maintained human health in the long history, especially in this COVID-19 pandemic. Pains of diseases have been removed from the effective TCM therapy, such as TCM preparation, moxibustion, and acupuncture. With the development of life science and technology, the wisdom and foresight of TCM has been more displayed. Furthermore, TCM has been also inherited and developed in innovation to better realize the modernization and globalization. Nowadays, intestinal flora transforming TCM and TCM targeted intestinal flora treating diseases have been important findings in life science. More and more TCM researches showed the significance of intestinal flora. Intestinal flora is also a way to study TCM to elucidate the profound theory of TCM. Processing, compatibility, and properties of TCM are well demonstrated by intestinal flora. Thus, it is no doubt that intestinal flora is a core in TCM study. The interaction between intestinal flora and TCM is so crucial for host health. Therefore, it is necessary to sum up the latest results in time. This paper systematically depicted the profile of TCM and the importance of intestinal flora in host. What is more, we comprehensively summarized and discussed the latest progress of the interplay between TCM and intestinal flora to better reveal the core connotation of TCM.

Gut dysbiosis in stroke and its implications on Alzheimer's disease-like cognitive dysfunction

Various neurological disorders, such as stroke and Alzheimer's disease (AD), involve neuroinflammatory responses. The advent of the gut‐brain axis enhances our understanding of neurological disease progression and secondary cell death. Gut microbiomes, especially those associated with inflammation, may reflect the dysbiosis of both the brain and the gut, opening the possibility to utilize inflammatory microbiomes as biomarkers and therapeutic targets. The gut‐brain axis may serve as a contributing factor to disease pathology and offer innovative approaches in cell‐based regenerative medicine for the treatment of neurological diseases. In reviewing the pathogenesis of stroke and AD, we also discuss the effects of gut microbiota on cognitive decline and brain pathology. Although the underlying mechanism of primary cell death from either disease is clearly distinct, both may be linked to gut‐microbial dysfunction as a consequential aberration that is unique to each disease. Targeting peripheral cell death pathways that exacerbate disease symptoms, such as those arising from the gut, coupled with conventional central therapeutic approach, may improve stroke and AD outcomes.

The Role of Gut Microbiota in an Ischemic Stroke

The intestinal microbiome, the largest reservoir of microorganisms in the human body, plays an important role in neurological development and aging as well as in brain disorders such as an ischemic stroke. Increasing knowledge about mediators and triggered pathways has contributed to a better understanding of the interaction between the gut-brain axis and the brain-gut axis. Intestinal bacteria produce neuroactive compounds and can modulate neuronal function, which affects behavior after an ischemic stroke. In addition, intestinal microorganisms affect host metabolism and immune status, which in turn affects the neuronal network in the ischemic brain. Here we discuss the latest results of animal and human research on two-way communication along the gut-brain axis in an ischemic stroke. Moreover, several reports have revealed the impact of an ischemic stroke on gut dysfunction and intestinal dysbiosis, highlighting the delicate play between the brain, intestines and microbiome after this acute brain injury. Despite our growing knowledge of intestinal microflora in shaping brain health, host metabolism, the immune system and disease progression, its therapeutic options in an ischemic stroke have not yet been fully utilized. This review shows the role of the gut microflora-brain axis in an ischemic stroke and assesses the potential role of intestinal microflora in the onset, progression and recovery post-stroke.

Sex differences in stroke outcome correspond to rapid and severe changes in gut permeability in adult Sprague-Dawley rats

BACKGROUND

Sex differences in experimental stroke outcomes are well documented, such that adult males have a greater infarct volume, increased stroke-induced mortality, and more severe sensory-motor impairment. Based on recent evidence that the gut is an early responder to stroke, the present study tested the hypothesis that sex differences in stroke severity will be accompanied by rapid and greater permeability of the gut-blood barrier and gut dysbiosis in males as compared to females.

METHOD

Male and female Sprague-Dawley rats (5-7 months of age) were subject to endothelin (ET)-1-induced middle cerebral artery occlusion (MCAo). Sensory-motor tests were conducted pre- and 2 days after MCAo. Gut permeability was assessed in serum samples using biomarkers of gut permeability as well as functional assays using size-graded dextrans. Histological analysis of the gut was performed with H&E staining, periodic acid-Schiff for mucus, and immunohistochemistry for the tight junction protein, ZO-1. Fecal samples obtained pre- and post-stroke were analyzed for bacterial taxa and short-chain fatty acids (SCFAs).

RESULTS

After stroke, males displayed greater mortality, worse sensory-motor deficit, and higher serum levels of proinflammatory cytokines IL-17A, MCP-1, and IL-5 as compared to females. MCAo-induced gut permeability was rapid and severe in males as indicated by dextran extravasation from the gut to the blood in the hyperacute (< 2 h) and early acute (2 days) phase of stroke. This was accompanied by dysmorphology of the gut villi and dysregulation of the tight junction protein ZO-1 in the acute phase. Fecal 16s sequencing showed no differences in bacterial diversity in the acute phase of stroke. Predictive modeling indicated that markers of gut permeability were associated with acute sensory-motor impairment and infarct volume.

CONCLUSIONS

These data show that extensive leakiness of the gut barrier is associated with severe post-stroke disability and suggest that reinforcing this barrier may improve stroke outcomes.

Occult Blood in Feces Is Associated With an Increased Risk of Ischemic Stroke and Myocardial Infarction: A Nationwide Population Study

Background

Although occult hemoglobin in feces is universally valued as a screening tool for colorectal cancer (CRC), only few studies investigated the clinical meaning of fecal immunochemical test (FIT) in other diseases. We evaluated the clinical utility of FIT in patients with cardiovascular diseases (namely, ischemic stroke and myocardial infarction [MI]).

Methods and Results

Using the National Health Insurance database, participants (aged >50 years) with CRC screening records from 2009 to 2012 were screened and followed up. Subjects with a history of cardiovascular diseases and CRC were excluded. Ischemic stroke, MI, and other comorbidities were defined by International Classification of Diseases, Tenth Revision (ICD‐10), codes. Age, sex, smoking, alcohol consumption, regular exercise, diabetes mellitus, hypertension, dyslipidemia, and body mass index were adjusted in a multivariate analysis. A total of 6 277 446 subjects were eligible for analysis. During the mean 6.79 years of follow‐up, 168 570 participants developed ischemic stroke, 105 983 developed MI, and 11 253 deaths were observed. A multivariate‐adjusted model revealed that the risk of ischemic stroke was higher in the FIT‐positive population (adjusted hazard ratio [HR], 1.09; 95% CI, 1.07–1.11). Similarly, FIT‐positive subjects were at an increased risk of MI (adjusted HR, 1.09; 95% CI, 1.06–1.12). Moreover, increased all‐cause mortality was observed in the FIT‐positive population (adjusted HR, 1.15; 95% CI, 1.07–1.23). The increased risk remained consistent in the stratified analysis on anemia and CRC status.

Conclusions

Positive FIT findings were associated with ischemic stroke, MI, and mortality. Occult blood in feces may offer more clinical information than its well‐known conventional role in CRC screening.

Oxidative Stress at the Crossroads of Aging, Stroke and Depression

Epidemiologic studies have shown that in the aging society, a person dies from stroke every 3 minutes and 42 seconds, and vast numbers of people experience depression around the globe. The high prevalence and disability rates of stroke and depression introduce enormous challenges to public health. Accumulating evidence reveals that stroke is tightly associated with depression, and both diseases are linked to oxidative stress (OS). This review summarizes the mechanisms of OS and OS-mediated pathological processes, such as inflammation, apoptosis, and the microbial-gut-brain axis in stroke and depression. Pathological changes can lead to neuronal cell death, neurological deficits, and brain injury through DNA damage and the oxidation of lipids and proteins, which exacerbate the development of these two disorders. Additionally, aging accelerates the progression of stroke and depression by overactive OS and reduced antioxidant defenses. This review also discusses the efficacy and safety of several antioxidants and antidepressants in stroke and depression. Herein, we propose a crosstalk between OS, aging, stroke, and depression, and provide potential therapeutic strategies for the treatment of stroke and depression.

Dysbiosis is one of the risk factor for stroke and cognitive impairment and potential target for treatment

More than 50 million people have various forms of cognitive impairment basically caused by neurodegenerative diseases, such as Alzheimer's, Parkinson's, and cerebrovascular diseases as well as stroke. Often these conditions coexist and exacerbate one another. The damaged area in post-stroke dementia may lead to neurodegenerative lesions. Gut microbiome functions like an endocrine organ by generating bioactive metabolites that can directly or indirectly impact human physiology. An alteration in the composition and function of intestinal flora, i.e. gut dysbiosis, is implicated in neurodegenerative and cerebrovascular diseases. Additionally, gut dysbiosis may accelerate the progression of cognitive impairment. Dysbiosis may result from obesity; metabolic disorders, cardiovascular disease, and sleep disorders, Lack of physical activity is associated with dysbiosis as well. These may coexist in various patterns in older people, enhancing the risk, incidence, and progression of cerebrovascular lesions, neurodegenerative disorders, and cognitive impairment, creating a vicious circle. Recently, it has been reported that several metabolites produced by gut microbiota (e.g., trimethylamine/trimethylamine N-oxide, short-chain fatty acids, secondary bile acids) may be linked to neurodegenerative and cerebrovascular diseases. New treatment modalities, including prebiotic and probiotics, may normalize the gut microbiota composition, change the brain-gut barrier, and decrease the risk of the pathology development. Fecal microbiota transplantation, sometimes in combination with other methods, is used for remodeling and replenishing the symbiotic gut microbiome. This promising field of research is associated with basic findings of bidirectional communication between body organs and gut microbiota that creates new possibilities of pharmacological treatments of many clinical conditions. The authors present the role of gut microbiota in physiology, and the novel therapeutic targets in modulation of intestinal microbiota Personalized therapies based on their personal genome make up could offer benefits by modulating microbiota cross-talk with brain and cardiovascular system. A healthy lifestyle, including pre and probiotic nutrition is generally recommended. Prevention may also be enhanced by correcting gut dysbiosis resulting a reduced risk of post-stroke cognitive impairment including dementia.

The microbiota-microglia axis in central nervous system disorders

The innate immune system in the central nervous system (CNS) is mainly represented by specialized tissue-resident macrophages, called microglia. In the past years, various species-, host- and tissue-specific as well as environmental factors were recognized that essentially affect microglial properties and functions in the healthy and diseased brain. Host microbiota are mostly residing in the gut and contribute to microglial activation states, for example, via short-chain fatty acids (SCFAs) or aryl hydrocarbon receptor (AhR) ligands. Thereby, the gut microorganisms are deemed to influence numerous CNS diseases mediated by microglia. In this review, we summarize recent findings of the interaction between the host microbiota and the CNS in health and disease, where we specifically highlight the resident gut microbiota as a crucial environmental factor for microglial function as what we coin "the microbiota-microglia axis."

Microbial Peer Pressure: The Role of the Gut Microbiota in Hypertension and Its Complications

There is increasing evidence of the influence of the gut microbiota on hypertension and its complications, such as chronic kidney disease, stroke, heart failure, and myocardial infarction. This is not surprising considering that the most common risk factors for hypertension, such as age, sex, medication, and diet, can also impact the gut microbiota. For example, sodium and fermentable fiber have been studied in relation to both hypertension and the gut microbiota. By combining second- and, now, third-generation sequencing with metabolomics approaches, metabolites, such as short-chain fatty acids and trimethylamine N-oxide, and their producers, have been identified and are now known to affect host physiology and the cardiovascular system. The receptors that bind these metabolites have also been explored with positive findings-examples include known short-chain fatty acid receptors, such as G-protein coupled receptors GPR41, GPR43, GPR109a, and OLF78 in mice. GPR41 and OLF78 have been shown to have inverse roles in blood pressure regulation, whereas GPR43 and GPR109A have to date been demonstrated to impact cardiac function. New treatment options in the form of prebiotics (eg, dietary fiber), probiotics (eg, Lactobacillus spp.), and postbiotics (eg, the short-chain fatty acids acetate, propionate, and butyrate) have all been demonstrated to be beneficial in lowering blood pressure in animal models, but the underlying mechanisms remain poorly understood and translation to hypertensive patients is still lacking. Here, we review the evidence for the role of the gut microbiota in hypertension, its risk factors, and cardiorenal complications and identify future directions for this exciting and fast-evolving field.

Brain-heart interaction after acute ischemic stroke

Early detection of cardiovascular dysfunctions directly caused by acute ischemic stroke (AIS) has become paramount. Researchers now generally agree on the existence of a bidirectional interaction between the brain and the heart. In support of this theory, AIS patients are extremely vulnerable to severe cardiac complications. Sympathetic hyperactivity, hypothalamic-pituitary-adrenal axis, the immune and inflammatory responses, and gut dysbiosis have been identified as the main pathological mechanisms involved in brain-heart axis dysregulation after AIS. Moreover, evidence has confirmed that the main causes of mortality after AIS include heart attack, congestive heart failure, hemodynamic instability, left ventricular systolic dysfunction, diastolic dysfunction, arrhythmias, electrocardiographic anomalies, and cardiac arrest, all of which are more or less associated with poor outcomes and death. Therefore, intensive care unit admission with continuous hemodynamic monitoring has been proposed as the standard of care for AIS patients at high risk for developing cardiovascular complications. Recent trials have also investigated possible therapies to prevent secondary cardiovascular accidents after AIS. Labetalol, nicardipine, and nitroprusside have been recommended for the control of hypertension during AIS, while beta blockers have been suggested both for preventing chronic remodeling and for treating arrhythmias. Additionally, electrolytic imbalances should be considered, and abnormal rhythms must be treated. Nevertheless, therapeutic targets remain challenging, and further investigations might be essential to complete this complex multi-disciplinary puzzle. This review aims to highlight the pathophysiological mechanisms implicated in the interaction between the brain and the heart and their clinical consequences in AIS patients, as well as to provide specific recommendations for cardiovascular management after AIS.

Hypothesis and Theory: A Pathophysiological Concept of Stroke-Induced Acute Phase Response and Increased Intestinal Permeability Leading to Secondary Brain Damage

Gut integrity impairment leading to increased intestinal permeability (IP) is hypothesized to be a trigger of critically illness. Approximately 15-20% of human ischemic stroke (IS) victims require intensive care, including patients with impaired level of consciousness or a high risk for developing life-threatening cerebral edema. Local and systemic inflammatory reactions are a major component of the IS pathophysiology and can significantly aggravate brain tissue damage. Intracerebral inflammatory processes following IS have been well studied. Until now, less is known about systemic inflammatory responses and IS consequences apart from a frequently observed post-IS immunosuppression. Here, we provide a hypothesis of a crosstalk between systemic acute phase response (APR), IP and potential secondary brain damage during acute and subacute IS stages supported by preliminary experimental data. Alterations of the acute phase proteins (APPs) C-reactive protein and lipopolysaccharide-binding protein and serum level changes of antibodies directed against Escherichia coli-cell extract antigen (IgA-, IgM-, and IgG-anti-E. coli) were investigated at 1, 2, and 7 days following IS in ten male sheep. We found an increase of both APPs as well as a decrease of all anti-E. coli antibodies within 48 h following IS. This may indicate an early systemic APR and increased IP, and underlines the importance of the increasingly recognized gut-brain axis and of intestinal antigen release for systemic immune responses in acute and subacute stroke stages.

Protective Effect of Tong-Qiao-Huo-Xue Decoction on Inflammatory Injury Caused by Intestinal Microbial Disorders in Stroke Rats

Tong-Qiao-Huo-Xue Decoction (TQHXD) is a classic traditional Chinese medicine prescription for treating cerebral ischemia. The purpose of this study was to investigate the effect of TQHXD on intervening inflammatory response of ischemic stroke by regulating intestinal flora and repairing the intestinal barrier. A rat model of cerebral ischemia was established using middle cerebral artery occlusion (MCAO) and behavioral scores were performed. Additionally, the high throughput 16S ribosomal DNA (rDNA) sequence of intestinal bacteria in fecal samples of rat was also carried out. Our results showed that TQHXD could change the main components of intestinal flora in stroke rats, and reduced the excessive increase of Bacteroidetes, and also regulated the abnormal changes of abundance of some flora as well. In addition, the intestinal epithelial barrier was damaged after stroke, allowing bacterial metabolites to enter the blood, while TQHXD had an improved effect on this phenomenon. Meanwhile, pathological changes in the brain tissue and infarct volume were also alleviated by TQHXD. Due to the disorder of the intestinal flora and the destruction of the barrier, the peripheral immune imbalance caused an inflammatory reaction. TQHXD improved the imbalance of T cells, and inhibited the inflammatory response. Finally, the therapeutic transplantation of fecal microbiota also improved the outcome of stroke in rats. Our presented results suggest that TQHXD may improve the gut microbiota disorder and its induced inflammatory response after stroke, which could be a new target and mechanism for the treatment of stroke.

Gut microbiota and neuroinflammation in pathogenesis of hypertension: A potential role for hydrogen sulfide

Inflammation and gut dysbiosis are hallmarks of hypertension (HTN). Hydrogen sulfide (H2S) is an important freely diffusing molecule that modulates the function of neural, cardiovascular and immune systems, and circulating levels of H2S are reduced in animals and humans with HTN. While most research to date has focused on H₂S produced endogenously by the host, H2S is also produced by the gut bacteria and may affect the host homeostasis. Here, we review an association between neuroinflammation and gut dysbiosis in HTN, with special emphasis on a potential role of H2S in this interplay.

The Role of Oxidative Stress in Common Risk Factors and Mechanisms of Cardio-Cerebrovascular Ischemia and Depression

The public health sector faces a huge challenge as a result of the high prevalence and burden of disability caused by ischemic cardio-cerebrovascular disease (CVD) and depression. Although studies have explored the underlying mechanisms and potential therapies to address conditions, there is no treatment breakthrough, especially for depression which is highly influenced by social stressors. However, accumulating evidence reveals that CVD and depression are correlated and share common risk factors, particularly obesity, diabetes, and hypertension. They also share common mechanisms, including oxidative stress (OS), inflammation and immune response, cell death signaling pathway, and microbiome-gut-brain axis. This review summarizes the relationship between ischemic CVD and depression and describes the interactions among common risk factors and mechanisms for these two diseases. In addition, we propose that OS mediates the crosstalk between these diseases. We also reveal the potential of antioxidants to ameliorate OS-related injuries.