Microbiota dysbiosis and functional outcome in acute ischemic stroke patients

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.

Intestinal Akkermansia muciniphila is Beneficial to Functional Recovery Following Ischemic Stroke

Recent studies have demonstrated the interaction between gut microbiota and brain on ischemic stroke, but the roles of gut microbiota in the pathophysiology of ischemic stroke remain largely unclear. In this study, we detected a significant increase of intestinal Akkermansia muciniphila (AKK) following ischemic stroke by a rose bengal photothrombosis model. To investigate the function and mechanism of AKK on ischemic stroke, we performed the AKK administration prior to stroke surgery. The results showed that mice treated with AKK gained significantly higher body weight and behaved better than those in PBS group at 3 days after ischemic stroke. Consistently, AKK administration remarkably decreased the infarct volumes as well as the density of degenerating neurons and apoptotic cells after ischemic stroke. Notably, AKK is a potential therapeutic target in immune-related disorders connected to the microbiota, and inflammation is crucially involved in the pathophysiological process of ischemic stroke. For the determination of underlying mechanisms of this protective effect, we investigated whether there are associations between AKK and neuroinflammation following ischemic stroke. The results suggested that AKK administration significantly reduced the activation of astrocytes and microglia but up-regulated multiple anti-inflammatory factors following ischemic stroke. Therefore, our study highlighted the beneficial roles of intestinal AKK on ischemic stroke and provided a new perspective for the treatment of ischemic stroke.

A prospective pilot study of gut microbiome in cerebral vasospasm and delayed cerebral ischemia after aneurysmal subarachnoid hemorrhage

A recent systematic review indicated that gut-microbiota-brain axis contributes to growth and rupture of intracranial aneurysms. However, gaps were detected in the role of intestinal microbiome in cerebral vasospasm (CVS) after aneurysmal subarachnoid hemorrhage (aSAH). This is the first pilot study aiming to test study feasibility and identify differences in gut microbiota between subjects with and without CVS following aSAH. A prospective nested case-control pilot study with 1:1 matching was conducted recruiting subjects with aSAH: cases with CVS; and controls without CVS based on the clinical picture and structured bedside transcranial Doppler (TCD). Fecal samples for microbiota analyses by means of 16S rRNA gene amplicon sequencing were collected within the first 96 h after ictus. Operational taxonomic unit tables were constructed, diversity metrics calculated, phylogenetic trees built, and differential abundance analysis (DAA) performed. At baseline, the groups did not differ significantly in basic demographic and aneurysm-related characteristics (p > 0.05). Alpha-diversity (richness and Shannon Index) was significantly reduced in cases of middle cerebral artery (MCA) vasospasm (p < 0.05). In DAA, relative abundance of genus Acidaminococcus was associated with MCA vasospasm (p = 0.00013). Two butyrate-producing genera, Intestinimonas and Butyricimonas, as well as [Clostridium] innocuum group had the strongest negative correlation with the mean blood flow velocity in anterior cerebral arteries (p < 0.01; rho = - 0.63; - 0.57, and - 0.57, respectively). In total, 16 gut microbial genera were identified to correlate with TCD parameters, and two intestinal genera correlated with outcome upon discharge. In this pilot study, we prove study feasibility and present the first preliminary evidence of gut microbiome signature associating with CVS as a significant cause of stroke in subjects with aSAH.

Vagus Nerve Suppression in Ischemic Stroke by Carotid Artery Occlusion: Implications for Metabolic Regulation, Cognitive Function, and Gut Microbiome in a Gerbil Model

The vagus nerve regulates metabolic homeostasis and mediates gut-brain communication. We hypothesized that vagus nerve dysfunction, induced by truncated vagotomy (VGX) or carotid artery occlusion (AO), would disrupt gut-brain communication and exacerbate metabolic dysregulation, neuroinflammation, and cognitive impairment. This study aimed to test the hypothesis in gerbils fed a high-fat diet. The gerbils were divided into four groups: AO with VGX (AO_VGX), AO without VGX (AO_NVGX), no AO with VGX (NAO_VGX), and no AO without VGX (NAO_NVGX). After 5 weeks on a high-fat diet, the neuronal cell death, neurological severity, hippocampal lipids and inflammation, energy/glucose metabolism, intestinal morphology, and fecal microbiome composition were assessed. AO and VGX increased the neuronal cell death and neurological severity scores associated with increased hippocampal lipid profiles and lipid peroxidation, as well as changes in the inflammatory cytokine expression and brain-derived neurotrophic factor (BDNF) levels. AO and VGX also increased the body weight, visceral fat mass, and insulin resistance and decreased the skeletal muscle mass. The intestinal morphology and microbiome composition were altered, with an increase in the abundance of Bifidobacterium and a decrease in Akkermansia and Ruminococcus. Microbial metagenome functions were also impacted, including glutamatergic synaptic activity, glycogen synthesis, and amino acid biosynthesis. Interestingly, the effects of VGX were not significantly additive with AO, suggesting that AO inhibited the vagus nerve activity, partly offsetting the effects of VGX. In conclusion, AO and VGX exacerbated the dysregulation of energy, glucose, and lipid metabolism, neuroinflammation, and memory deficits, potentially through the modulation of the gut-brain axis. Targeting the gut-brain axis by inhibiting vagus nerve suppression represents a potential therapeutic strategy for ischemic stroke.

Genetic evidence for a causal link between gut microbiota and arterial embolism and thrombosis: a two-sample Mendelian randomization study

Background

Previous research has hinted at a crucial link between gut microbiota and arterial embolism and thrombosis, yet the causal relationship remains enigmatic. To gain a deeper understanding, we aimed to comprehensively explore the causal relationship and elucidate the impact of the gut microbiota on the risk through a two-sample Mendelian randomization (MR) study.

Methods

Genetic instrumental variables for gut microbiota were identified from a genome-wide association study (GWAS) of 18,340 participants. Summary statistics for IBS were drawn from a GWAS including 1,076 cases and 381,997 controls. We used the inverse-variance weighted (IVW) method as the primary analysis. To test the robustness of our results, we further performed the weighted median method, MR-Egger regression, and MR pleiotropy residual sum and outlier test.

Results

We identified three bacterial traits that were associated with the risk of arterial embolism and thrombosis: odds ratio (OR): 1.58, 95% confidence interval (CI): 1.08-2.31, p = 0.017 for genus Catenibacterium; OR: 0.64, 95% CI: 0.42-0.96, p = 0.031 for genus Dialister; and OR: 2.08, 95% CI: 1.25-3.47, p = 0.005 for genus Odoribacter. The results of sensitivity analyses for these bacterial traits were consistent (P<0.05).

Conclusion

Our systematic analyses provided evidence to support a potential causal relationship between several gut microbiota taxa and the risk of arterial embolism and thrombosis. More studies are required to show how the gut microbiota affects the development of arterial embolism and thrombosis.

Identifying gut microbiota with high specificity for ischemic stroke with large vessel occlusion

Gut microbiota can regulate the metabolic and immunological aspects of ischemic stroke and modulate the treatment effects. The present study aimed to identify specific changes in gut microbiota in patients with large vessel occlusion (LVO) ischemic stroke and assess the potential association between gut microbiota and clinical features of ischemic stroke. A total of 63 CSVD patients, 64 cerebral small vessel disease (CSVD) patients, and 36 matching normal controls (NCs) were included in this study. The fecal samples were collected for all participants and analyzed for gut microbiota using 16S rRNA gene sequencing technology. The abundances of five gut microbiota, including genera Bifidobacterium, Butyricimonas, Blautia, and Dorea and species Bifidobacterium_longum, showed significant changes with high specificity in the LVO patients as compared to the NCs and CSVD patients. In LVO patients, the genera Bifidobacterium and Blautia and species Bifidobacterium_longum were significantly correlated with the National Institutes of Health Stroke Scale (NIHSS) scores at the admission and discharge of the patients. Serum triglyceride levels could significantly affect the association of the abundance of genus Bifidobacterium and species Bifidobacterium_longum with the NIHSS scores at admission and modified Rankin Scale (mRS) at discharge in LVO patients. The identification of five gut microbiota with high specificity were identified in the early stage of LVO stroke, which contributed to performed an effective clinical management for LVO ischemic stroke.

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.

Multiomics profiling of the therapeutic effect of Dan-deng-tong-nao capsule on cerebral ischemia-reperfusion injury

BACKGROUND

Stroke is a complex physiological process associated with intestinal flora dysbiosis and metabolic disorders. Dan-deng-tong-nao capsule (DDTN) is a traditional Chinese medicine used clinically to treat cerebral ischemia-reperfusion injury (CIRI) for many years. However, little is known about the effects of DDTN in the treatment of CIRI from the perspective of gut microbiota and metabolites.

PURPOSE

This study aimed to investigate the regulatory roles of DDTN in endogenous metabolism and gut microbiota in CIRI rats, thus providing a basis for clinical rational drug use and discovering natural products with potential physiological activities in DDTN for the treatment of CIRI.

METHODS

The chemical composition of DDTN in vitro and in vivo was investigated using ultra-high performance liquid chromatography-high resolution mass spectrometry (UHPLCHRMS), followed by target prediction using reverse molecular docking. Secondly, a biological evaluation of DDTN ameliorating neural damage in CIRI was performed at the whole animal level. Then, an integrated omics approach based on UHPLCHRMS and 16S rRNA sequencing was proposed to reveal the anti-CIRI effect and possible mechanism of DDTN. Finally, exploring the intrinsic link between changes in metabolite profiles, changes in the intestinal flora, and targets of components to reveal DDTN for the treatment of CIRI.

RESULTS

A total of 112 chemical components of DDTN were identified in vitro and 10 absorbed constituents in vivo. The efficacy of DDTN in the treatment of CIRI was confirmed by alleviating cerebral infarction and neurological deficits. After the DDTN intervention, 21 and 26 metabolites were significantly altered in plasma and fecal, respectively. Based on the fecal microbiome, a total of 36 genera were enriched among the different groups. Finally, the results of the network integration analysis showed that the 10 potential active ingredients of DDTN could mediate the differential expression of 24 metabolites and 6 gut microbes by targeting 25 target proteins.

CONCLUSION

This study was the first to outline the landscapes of metabolites as well as gut microbiota regulated by DDTN in CIRI rats using multi-omics data, and comprehensively revealed the systematic relationships among ingredients, targets, metabolites, and gut microbiota, thus providing new perspectives on the mechanism of DDTN in the treatment of CIRI.

Insights into the Mechanisms of Action of Akkermansia muciniphila in the Treatment of Non-Communicable Diseases

This comprehensive review delineates the extensive roles of Akkermansia muciniphila in various health domains, spanning from metabolic and inflammatory diseases to neurodegenerative disorders. A. muciniphila, known for its ability to reside in the mucous layer of the intestine, plays a pivotal role in maintaining gut integrity and interacting with host metabolic processes. Its influence extends to modulating immune responses and potentially easing symptoms across several non-communicable diseases, including obesity, diabetes, inflammatory bowel disease, and cancer. Recent studies highlight its capacity to interact with the gut-brain axis, suggesting a possible impact on neuropsychiatric conditions. Despite the promising therapeutic potential of A. muciniphila highlighted in animal and preliminary human studies, challenges remain in its practical application due to stability and cultivation issues. However, the development of pasteurized forms and synthetic mediums offers new avenues for its use in clinical settings, as recognized by regulatory bodies like the European Food Safety Authority. This narrative review serves as a crucial resource for understanding the broad implications of A. muciniphila across different health conditions and its potential integration into therapeutic strategies.

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.

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.

Modulation of intestinal metabolites by calorie restriction and its association with gut microbiota in a xenograft model of colorectal cancer

BACKGROUND

Colorectal cancer (CRC) is a common malignant tumor, and its occurrence and development are closely related to dysbiosis of gut microbes. Previously, we found calorie restriction altered the composition of the microbial community in a colorectal cancer mouse model and inhibited in vivo growth of CRC cells. Here, we aim to further investigate alteration in the intestinal metabolites and explore the interplay between gut microbiota and intestinal metabolites upon calorie restriction.

METHODS

Human colorectal cancer HCT116 cells were used to establish a colorectal cancer xenograft mouse model. The changes of intestinal metabolites in the ad libitum group and calorie restriction group were investigated through untargeted metabolomics analysis. The integrative analysis of gut microbiota and metabolites to elucidate the associations between gut microbiota and intestinal metabolites.

RESULTS

Compared with the mice in the ad libitum group, mice upon calorie restriction exhibited downregulation of Isoleucyl-Valine, and upregulation of D-Proline, 1-Palmitoylphosphatidylcholine, and 4-Trimethylammoniobutanoic acid. Additionally, an integrative analysis of gut microbiota and metabolites revealed that Lactobacillus, Parabacteroides and rC4-4 genus were upregulated in the calorie restriction group and positively correlated with D-Proline, 4-Trimethylammoniobutanoic acid or 1-Palmitoylphosphatidylcholine, while negatively correlated with Isoleucyl-Valine. In contrast, the Nitrospirae and Deferribacteres phylum exhibited opposite trends.

CONCLUSION

Calorie restriction affects the abundance of gut microbes such as Nitrospirae phylum and Lactobacillus genus in mouse model of colorectal cancer, leading to changes in the metabolites such as D-Proline、Isoleucyl-Valine, which contributes to the suppression of in vivo growth of CRC by calorie restriction.

The human gut microbiome in critical illness: disruptions, consequences, and therapeutic frontiers

With approximately 39 trillion cells and over 20 million genes, the human gut microbiome plays an integral role in both health and disease. Modern living has brought a widespread use of processed food and beverages, antimicrobial and immunomodulatory drugs, and invasive procedures, all of which profoundly disrupt the delicate homeostasis between the host and its microbiome. Of particular interest is the human gut microbiome, which is progressively being recognized as an important contributing factor in many aspects of critical illness, from predisposition to recovery. Herein, we describe the current understanding of the adverse impacts of standard intensive care interventions on the human gut microbiome and delve into how these microbial alterations can influence patient outcomes. Additionally, we explore the potential association between the gut microbiome and post-intensive care syndrome, shedding light on a previously underappreciated avenue that may enhance patient recuperation following critical illness. There is an impending need for future epidemiological studies to encompass detailed phenotypic analyses of gut microbiome perturbations. Interventions aimed at restoring the gut microbiome represent a promising therapeutic frontier in the quest to prevent and treat critical illnesses.

Microbiome signatures in ischemic stroke: A systematic review

Microbial structural changes and dysfunction play an important role in the development of cerebral ischemia. We searched PubMed, Embase, Web of Science, and Cochrane Library and conducted a systematic review to assess the relationship between the human microbiome and ischemic stroke. A total of 24 studies were included, and the intestinal bacterial communities detected in both stroke and healthy people were dominated by 4 main phyla, including Firmicutes, Bacteroidetes, Proteobacteria, and Actinobacteria. Significant diversity (alpha and beta) in patients with ischemic versus nonischemic stroke was observed in nine out of 18 studies, and 3 studies showed that the severity of ischemic stroke affected microbial diversity. The imbalance of bacteria that produce short-chain fatty acids (SCFAs) changes the bacterial metabolic pathway, and disorders in the level of bacterial metabolites (trimethylamine N-oxide TMAO) lead to significant changes in intestinal flora function, which may aggravate the severity of stroke and affect its prognosis. Further studies are needed to explore the relationship between the microbiome and ischemic stroke.

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.

Association analysis of the gut microbiota in predicting outcomes for patients with acute ischemic stroke and H-type hypertension

Introduction

H-type hypertension (HHTN) is a subtype of hypertension that tends to worsen the prognosis of acute ischemic stroke (AIS). Recent studies have highlighted the vital role of gut microbiota in both hypertension and AIS, but there is little available data on the relationship between gut microbiota and the progression of AIS patients with HHTN. In this study, we investigated the microbial signature of AIS patients with HHTN and identified characteristic bacteria as biomarkers for predicting prognosis.

Methods

AIS patients with HHTN (n = 150) and without HHTN (n = 50) were enrolled. All patients received a modified Rankin Scale (mRS) assessment at 3 months after discharge. Fecal samples were collected from the participants upon admission, including 150 AIS patients with HHTN, 50 AIS patients with non-HHTN, and 90 healthy subjects with HHTN. These samples were analyzed using 16S rRNA sequencing to characterize the bacterial taxa, predict functions, and conduct correlation analysis between specific taxa and clinical features.

Results

Our results showed that the composition of the gut microbiota in HHTN patients differed significantly from that in non-HHTN patients. The abundance of the genera Bacteroides, Escherichia-Shigella, Lactobacillus, Bifidobacterium, and Prevotella in AIS patients with HHTN was significantly increased compared to AIS patients without HHTN, while the genus Streptococcus, Faecalibacterium, and Klebsiella were significantly decreased. Moreover, Bacteroides, Lactobacillus, Bifidobacterium, and Klebsiella in AIS patients with HHTN were more abundant than healthy subjects with HHTN, while Escherichia-Shigella, Blautia, and Faecalibacterium were less abundant. Moreover, the genera Butyricicoccus, Rothia, and Family_XIII_UCG-001 were negatively connected with the NIHSS score, and the genera Butyricicoccus and Rothia were observed to be negatively associated with the mRS score. The genera Butyricicoccus, Romboutsia, and Terrisporobacter were associated with a poor prognosis, whereas the increase in Butyricimonas and Odoribacter was correlated with good outcomes. Generated by eight genera and clinical indexes, the area under the curve (AUC) value of the receiver operating characteristic (ROC) curve achieved 0.739 to effectively predict the prognosis of AIS patients with HHTN.

Conclusion

These findings revealed the microbial signature of AIS patients with HHTN and further provided potential microbial biomarkers for the clinical diagnosis of AIS patients with HHTN.

Case report: isolated prevotella intermedia causing intracranial infection detected using metagenomic next generation sequencing

BACKGROUND

Isolated Prevotella intermedia, a rare gram-negative, rod-shaped, anaerobic bacterium, is rarely detected in clinical practice. It has been associated with infections of the oral cavity and female genital tract, but has never been detected in cerebrospinal fluid (CSF) of patients in China. Accurate detection of causative pathogens is still an arduous task owing to the difficult conditions of anaerobic bacterial culture. Isolated Prevotella intermedia can be detected by metagenomic next generation sequencing (mNGS) of the CSF. Correct diagnosis and antibiotic treatment can help patients avoid life-threatening events.

CASE PRESENTATION

Herein, we describe the case of a 64-year-old Chinese woman who presented with typical features of meningoencephalitis. Routine CSF culture failed to identify the causative pathogen. Isolated Prevotella intermedia was detected by mNGS, and the patient was treated with antibacterial agents including ceftriaxone, vancomycin, moxifloxacin, meropenem, metronidazole, and linezolid. The patient underwent surgical treatment for abscess of left frontal parietal lobe, which was observed on magnetic resonance imaging (MRI) and was suspected to be caused by Prevotella intermedia. It was further confirmed that it was a secondary infection from the oral cavity, and the possible etiology might have been dental surgery. Treatment was rendered to the patient based on metagenomic test result, and her condition improved after two months.

CONCLUSIONS

This case highlights the role of mNGS in accurate diagnosis of patients with central nervous system infection. In particular, mNGS can be used to identify rare pathogens and confirm the diagnosis in patients with unknown etiology.

Bacterial extracellular vesicles - brain invaders? A systematic review

Introduction

Knowledge on the human gut microbiota in health and disease continues to rapidly expand. In recent years, changes in the gut microbiota composition have been reported as a part of the pathology in numerous neurodegenerative diseases. Bacterial extracellular vesicles (EVs) have been suggested as a novel mechanism for the crosstalk between the brain and gut microbiota, physiologically connecting the observed changes in the brain to gut microbiota dysbiosis.

Methods

Publications reporting findings on bacterial EVs passage through the blood-brain barrier were identified in PubMed and Scopus databases.

Results

The literature search yielded 138 non-duplicate publications, from which 113 records were excluded in title and abstract screening step. From 25 publications subjected to full-text screening, 8 were excluded. The resulting 17 publications were considered for the review.

Discussion

Bacterial EVs have been described with capability to cross the blood-brain barrier, but the mechanisms behind the crossing remain largely unknown. Importantly, very little data exists in this context on EVs secreted by the human gut microbiota. This systematic review summarizes the present evidence of bacterial EVs crossing the blood-brain barrier and highlights the importance of future research on gut microbiota-derived EVs in the context of gut-brain communication across the blood-brain barrier.

Alteration and clinical potential in gut microbiota in patients with cerebral small vessel disease

Background

Cerebral small vessel disease (CSVD) is a cluster of microvascular disorders with unclear pathological mechanisms. The microbiota-gut-brain axis is an essential regulatory mechanism between gut microbes and their host. Therefore, the compositional and functional gut microbiota alterations lead to cerebrovascular disease pathogenesis. The current study aims to determine the alteration and clinical value of the gut microbiota in CSVD patients.

Methods

Sixty-four CSVD patients and 18 matched healthy controls (HCs) were included in our study. All the participants underwent neuropsychological tests, and the multi-modal magnetic resonance imaging depicted the changes in brain structure and function. Plasma samples were collected, and the fecal samples were analyzed with 16S rRNA gene sequencing.

Results

Based on the alpha diversity analysis, the CSVD group had significantly decreased Shannon and enhanced Simpson compared to the HC group. At the genus level, there was a significant increase in the relative abundances of Parasutterella, Anaeroglobus, Megasphaera, Akkermansia, Collinsella, and Veillonella in the CSVD group. Moreover, these genera with significant differences in CSVD patients revealed significant correlations with cognitive assessments, plasma levels of the blood-brain barrier-/inflammation-related indexes, and structural/functional magnetic resonance imaging changes. Functional prediction demonstrated that lipoic acid metabolism was significantly higher in CSVD patients than HCs. Additionally, a composite biomarker depending on six gut microbiota at the genus level displayed an area under the curve of 0.834 to distinguish CSVD patients from HCs using the least absolute shrinkage and selection operator (LASSO) algorithm.

Conclusion

The evident changes in gut microbiota composition in CSVD patients were correlated with clinical features and pathological changes of CSVD. Combining these gut microbiota using the LASSO algorithm helped identify CSVD accurately.

Akkermansia muciniphila-Nlrp3 is involved in the neuroprotection of phosphoglycerate mutase 5 deficiency in traumatic brain injury mice

Introduction

Gut-microbiota-brain axis is a potential treatment to decrease the risk of chronic traumatic encephalopathy following traumatic brain injury (TBI). Phosphoglycerate mutase 5 (PGAM5), a mitochondrial serine/threonine protein phosphatase, resides in mitochondrial membrane and regulates mitochondrial homeostasis and metabolism. Mitochondria mediates intestinal barrier and gut microbiome.

Objectives

This study investigated the association between PGAM5 and gut microbiota in mice with TBI.

Methods

The controlled cortical impact injury was established in mice with genetically-ablated Pgam5 (Pgam5^-/-) or wild type, and WT male mice were treated with fecal microbiota transplantation (FMT) from male Pgam5^-/- mice or Akkermansia muciniphila (A. muciniphila). Then the gut microbiota abundance, blood metabolites, neurological function, and nerve injury were detected.

Results

Treated with antibiotics for suppressing gut microbiota in Pgam5^-/- mice partially relieved the role of Pgam5 deficiency in the improvement of initial inflammatory factors and motor dysfunction post-TBI. Pgam5 knockout exhibited an increased abundance of A. muciniphila in mice. FMT from male Pgam5^-/- mice enabled better maintenance of amino acid metabolism and peripherial environment than that in TBI-vehicle mice, which suppressed neuroinflammation and improved neurological deficits, and A. muciniphila was negatively associated with intestinal mucosal injury and neuroinflammation post-TBI. Moreover, A. muciniphila treatment ameliorated neuroinflammation and nerve injury by regulating Nlrp3 inflammasome activation in cerebral cortex with TBI.

Conclusion

Thus, the present study provides evidence that Pgam5 is involved in gut microbiota-mediated neuroinflammation and nerve injury, with A. muciniphila-Nlrp3 contributing to peripheral effects.

Common Signaling Pathways Involved in Alzheimer's Disease and Stroke: Two Faces of the Same Coin

Alzheimer's disease (AD) and stroke are two interrelated neurodegenerative disorders which are the leading cause of death and affect the neurons in the brain and central nervous system. Although amyloid-β aggregation, tau hyperphosphorylation, and inflammation are the hallmarks of AD, the exact cause and origin of AD are still undefined. Recent enormous fundamental discoveries suggest that the amyloid hypothesis of AD has not been proven and anti-amyloid therapies that remove amyloid deposition have not yet slowed cognitive decline. However, stroke, mainly ischemic stroke (IS), is caused by an interruption in the cerebral blood flow. Significant features of both disorders are the disruption of neuronal circuitry at different levels of cellular signaling, leading to the death of neurons and glial cells in the brain. Therefore, it is necessary to find out the common molecular mechanisms of these two diseases to understand their etiological connections. Here, we summarized the most common signaling cascades including autotoxicity, ApoE4, insulin signaling, inflammation, mTOR-autophagy, notch signaling, and microbiota-gut-brain axis, present in both AD and IS. These targeted signaling pathways reveal a better understanding of AD and IS and could provide a distinguished platform to develop improved therapeutics for these diseases.

The role of the probiotic Akkermansia muciniphila in brain functions: insights underpinning therapeutic potential

The role of Akkermansia muciniphila, one of the most abundant microorganisms of the intestinal microbiota, has been studied extensively in metabolic diseases, such as obesity and diabetes. It is considered a next-generation probiotic microorganism. Although its mechanism of action has not been fully elucidated, accumulating evidence indicates the important role of A. muciniphila in brain functions via the gut-brain axis and its potential as a therapeutic target in various neuropsychiatric disorders. However, only a limited number of studies, particularly clinical studies, have directly assessed the therapeutic effects of A. muciniphila interventions in these disorders. This is the first review to discuss the comprehensive mechanism of A. muciniphila in the gut-brain axis via the protection of the intestinal mucosal barrier and modulation of the immune system and metabolites, such as short-chain fatty acids, amino acids, and amino acid derivatives. Additionally, the role of A. muciniphila and its therapeutic potential in various neuropsychiatric disorders, including Alzheimer's disease and cognitive deficit, amyotrophic lateral sclerosis, Parkinson's disease, and multiple sclerosis, have been discussed. The review suggests the potential role of A. muciniphila in healthy brain functions.

Imbalance of Microbacterial Diversity Is Associated with Functional Prognosis of Stroke

Objectives

There is mounting evidence to suggest that the pathophysiology of stroke is greatly influenced by the microbiota of the gut and its metabolites, in particular short-chain fatty acids (SCFAs). The primary purpose of the study was to evaluate whether the levels of SCFAs and the gut microbiota are altered in poststroke patients and to examine the relationship between these alterations and the physical condition, intestinal health, pain, or nutritional status of patients.

Methods

Twenty stroke patients and twenty healthy controls were enrolled in the current study, and their demographics were matched. Gas chromatography was used to determine the fecal SCFAs, and 16S rRNA gene sequencing was used to evaluate their fecal microbiota. Microbial diversity and richness were examined using the diversity indices alpha and beta, and taxonomic analysis was utilized to determine group differences. The relationships between the gut microbiome and fecal SCFAs, discriminant bacteria, and poststroke clinical outcomes were analyzed.

Results

Less community richness (ACE and Chao) was observed in the poststroke patients (P < 0.05), but the differences between the poststroke group and the healthy control group in terms of species diversity (Shannon and Simpson) were not statistically significant. The makeup of the poststroke gut microbiota was distinct from that of the control group, as evidenced by beta diversity. Then, the relative abundances of the taxa in the poststroke and control groups were compared in order to identify the specific microbiota changes. At the level of phylum, the poststroke subjects showed a significant increase in the relative abundances of Akkermansiaceae, Fusobacteriota, Desulfobacterota, Ruminococcaceae, and Oscillospirales and a particularly noticeable decrease in the relative abundance of Acidobacteriota compared to the control subjects (P < 0.05). In regard to SCFA concentrations, lower levels of fecal acetic acid (P = 0.001) and propionic acid (P = 0.049) were found in poststroke subjects. Agathobacter was highly correlated with acetic acid level (r = 0.473, P = 0.002), whereas Fusobacteria (r = -0.371, P = 0.018), Flavonifractor (r = -0.334, P = 0.034), Desulfovibrio (r = -0.362, P = 0.018), and Akkermansia (r = -0.321, P = 0.043) were negatively related to acetic acid levels. Additionally, the findings of the correlation analysis revealed that Akkermansia (r = -0.356, P = 0.024), Desulfovibrio (r = -0.316, P = 0.047), and Alloprevotella (r = -0.366, P = 0.020) were significantly negatively correlated with high-density lipoprotein cholesterol. In addition, the Neurogenic Bowel Dysfunction score (r = 0.495, P = 0.026), Barthel index (r = -0.531, P = 0.015), Fugl-Meyer Assessment score (r = -0.565, P = 0.009), Visual Analogue Scale score (r = 0.605, P = 0.005), and Brief Pain Inventory score (r = 0.507, P = 0.023) were significantly associated with alterations of distinctive gut microbiota.

Conclusions

Stroke generates extensive and substantial alterations in the gut microbiota and SCFAs, according to our findings. The differences of intestinal flora and lower fecal SCFA levels are closely related to the physical function, intestinal function, pain, or nutritional status of poststroke patients. Treatment strategies aimed at modulating the gut microbiota and SCFAs may have the potential to enhance the clinical results of patients.

Altered gut microbiomes are associated with the symptomatic status of unruptured intracranial aneurysms

Background

Gut microbiome has recently been recognized as an important environmental factor affecting the occurrence and development of unruptured intracranial aneurysms (UIA). This study aimed to investigate the relationship between gut microbiome and symptomatic UIA, which is a predictor of instability and a high propensity to rupture.

Methods

A total of 132 patients including 86 asymptomatic UIA and 46 symptomatic UIA were recruited in the study. The composition of gut bacterial communities was determined by 16S ribosomal RNA gene sequencing. In addition, Phylogenetic Investigation of Communities by Reconstruction of Unobserved States (PICRUSt) was used to predict the functional composition of the gut microbiome.

Results

There is no difference in the fecal microbial alpha diversity between symptomatic and asymptomatic UIA, but gut microbiome composition changed significantly. At the order level, the relative abundance of Clostridiales was significantly enriched in the symptomatic compared with asymptomatic UIA (p = 0.043). In addition, similar alterations were observed at the family levels of Ruminococcaceae. The Linear discriminant analysis (LEfSe) revealed Fournierella, Ruthenibacterium, and Anaerotruncus as discriminative features in the symptomatic group. Notably, functional differences in gut microbiome of patients with symptomatic UIA included decreased propionate metabolism pathway and enrichment of peptidoglycan biosynthesis pathways.

Conclusion

The present study comprehensively characterizes gut microbiome in a large cohort of different risk statuses of UIA patients and demonstrates the potential biological function of gut microbiome involved in the development of UIA. It may provide additional benefits in guiding UIA management and improving patient outcomes.

Multi-omics reveals specific host metabolism-microbiome associations in intracerebral hemorrhage

Intracerebral hemorrhage (ICH) is the most devastating subtype of stroke, but effective prevention and treatment strategies are lacking. Recently, gut microbiome and its metabolitesis are considered to be an influencing factor of stroke. However, little is known about the effects of the gut microbiome on ICH and host metabolic activity. Therefore, we used 16S sequencing, macrogenomics sequencing and untargeted metabolomics to explore the differences in gut microbial-metabolome interactions between patients with intracerebral hemorrhage and healthy control populations. We found a significant decrease in the phylum of Firmicutes and a significant increase of Bacteroidetes in ICH patients. At the genus level, Streptococcus, Bifidobacterium, Akkermansia, and Lactobacillus were more abundant in ICH patients. Macrogenomic analysis revealed active glycosaminoglycan degradation, heme synthesis, galactose degradation, lipopolysaccharide core region synthesis, and beta-Lactam resistance in ICH patients. Serum untargeted metabolomic analysis combined with ROC curves showed that octanoylcarnitine, decanoylcarnitine, dodecanoylcarnitine, glyceric acid, pyruvic acid, aspartic acid, methylcysteine, pyroglutamic acid, 9E-tetradecenoic acid, N-Acetylneuraminic acid, and aconitic acid were the best markers for the diagnosis of ICH. Correlation analysis showed that microbiome enriched in the gut of ICH patients were significantly correlated with serum metabolites, revealing a close correlation between the gut microbiome of ICH patients and the host metabolome, and significant differences from the healthy population. microbiota-host co-metabolites including pyruvic acid and 9E-tetradecenoic acid is associated with the the National Institutes of Health Stroke Scale (NIHSS) scores. In conclusion, microbiome-related metabolites in ICH patients was associated with the severity of ICH, the microbiota-host co-metabolites may be a potential may be potential therapeutic targets.

Human Blood Bacteriome: Eubiotic and Dysbiotic States in Health and Diseases

The human gut microbiome is acknowledged as being associated with homeostasis and the pathogenesis of several diseases. Conventional culture techniques are limited in that they cannot culture the commensals; however, next-generation sequencing has facilitated the discovery of the diverse and delicate microbial relationship in body sites and blood. Increasing evidence regarding the blood microbiome has revolutionized the concept of sterility and germ theory in circulation. Among the types of microbial communities in the blood, bacteriomes associated with many health conditions have been thoroughly investigated. Blood bacterial profiles in healthy subjects are identified as the eubiotic blood bacteriome, whereas the dysbiotic blood bacteriome represents the change in bacterial characteristics in subjects with diseases showing deviations from the eubiotic profiles. The blood bacterial characteristics in each study are heterogeneous; thus, the association between eubiotic and dysbiotic blood bacteriomes and health and disease is still debatable. Thereby, this review aims to summarize and discuss the evidence concerning eubiotic and dysbiotic blood bacteriomes characterized by next-generation sequencing in human studies. Knowledge pertaining to the blood bacteriome will transform the concepts around health and disease in humans, facilitating clinical implementation in the near future.

Bacterial Signatures of Cerebral Thrombi in Large Vessel Occlusion Stroke

It is important to understand the microbial features of the cerebral thrombus and its clinical relevance in stroke patients, of which data were scarce. We aimed to investigate the microbial features of cerebral thrombi retrieved via thrombectomy in stroke patients with large vessel occlusion (LVO) and their correlations with 3-month mortality. In a prospective cohort study, thrombus samples were collected during mechanical thrombectomy in LVO stroke patients with successful revascularization at a tertiary hospital. Oral, fecal, and isolated plasma samples were collected within 12 h of admission. The microbial compositions of all samples were compared using 16S rRNA gene amplicon next-generation sequencing. Fluorescent in situ hybridization (FISH) was used to detect bacteria in thrombus samples. The primary outcome was 3-month mortality. Perioperative adverse events (AEs) within 48 h were also recorded. Bacterial DNA was detected in 96.2% of thrombus samples from 104 patients, and clusters of bacterial signals were seen in the thrombi with FISH. Compared with fecal and oral samples, the thrombus microbiota was mainly characterized by excessive enrichment of Proteobacteria, mainly originating from plasma. The bacterial concentrations, dominant bacteria, and distribution patterns differed in thrombi obtained from cardioembolic and large-artery atherosclerotic strokes. Higher abundances of Acinetobacter and Enterobacteriaceae were associated with a higher risk of perioperative AEs, and a higher abundance of Acinetobacter was independently associated with a higher risk of 90-day mortality. This study demonstrated the presence of bacteria in cerebral thrombi retrieved with thrombectomy in LVO strokes, with some bacteria associated with patients’ prognoses.

Candidate Phyla Radiation, an Underappreciated Division of the Human Microbiome, and Its Impact on Health and Disease

Candidate phyla radiation (CPR) is an emerging division of the bacterial domain within the human microbiota. Still poorly known, these microorganisms were first described in the environment in 1981 as "ultramicrobacteria" with a cell volume under 0.1 μm³ and were first associated with the human oral microbiota in 2007. The evolution of technology has been paramount for the study of CPR within the human microbiota. In fact, since these ultramicrobacteria have yet to be axenically cultured despite ongoing efforts, progress in imaging technology has allowed their observation and morphological description. Although their genomic abilities and taxonomy are still being studied, great strides have been made regarding their taxonomic classification, as well as their lifestyle. In addition, advancements in next-generation sequencing and the continued development of bioinformatics tools have allowed their detection as commensals in different human habitats, including the oral cavity and gastrointestinal and genital tracts, thus highlighting CPR as a nonnegligible part of the human microbiota with an impact on physiological settings. Conversely, several pathologies present dysbiosis affecting CPR levels, including inflammatory, mucosal, and infectious diseases. In this exhaustive review of the literature, we provide a historical perspective on the study of CPR, an overview of the methods available to study these organisms and a description of their taxonomy and lifestyle. In addition, their distribution in the human microbiome is presented in both homeostatic and dysbiotic settings. Future efforts should focus on developing cocultures and, if possible, axenic cultures to obtain isolates and therefore genomes that would provide a better understanding of these ultramicrobacteria, the importance of which in the human microbiome is undeniable.

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.

Intestinal Flora Composition Determines Microglia Activation and Improves Epileptic Episode Progress

In response to environmental stimuli, immune memory mediates the plasticity of myeloid cells. Immune training and immune tolerance are two aspects of plasticity. Microglia that are immunologically trained or immunologically tolerant are endowed with a tendency to differentiate into alternative dominant phenotypes (M1/M2). Male C57BL/6 mice (immune-training group, immune-tolerant group, and control group) were used to establish the kainic acid epilepsy model. The seizure grade, duration, latency, hippocampal potential, and energy density were used to evaluate seizures, and the changes in the polarization of microglia were detected by western blot. 16S rDNA sequencing showed that the abundance of Ruminococcus in the immune-tolerant group was the dominant flora. Our research connections Intestinal microorganisms, brain immune status, and epilepsy behavior together. Pro-inflammatory M1 phenotype and anti-inflammatory M2 phenotype mediate and enhance and suppress subsequent inflammation, respectively. We conclude that intestinal microorganisms influence the occurrence and development of epilepsy by regulating the polarization of microglia.

Correlation of Triglyceride-Rich Lipoprotein Cholesterol and Diabetes Mellitus in Stroke Patients

BACKGROUND

Previous studies have revealed that triglyceride-rich lipoprotein cholesterol (TRL-c) is closely related to diabetes mellitus (DM) in hypertensive patients. However, this relationship in stroke patients has not been reported. The aims of this study are to investigate the relationship between TRL-c and diabetes in adult Chinese stroke.

METHODS

Patients with stroke treated in the Department of Neurology of the Second Affiliated Hospital of Nanchang University from January 2019 to January 2021 were selected. TRL-c was calculated from total cholesterol minus (high-density and low-density lipoprotein). DM was diagnosed based on previous medical history (diagnosed by secondary hospitals or above) and/or current use of hypoglycemic drugs and/or intravenous blood glucose measurement (fasting blood glucose ≥7.0 mmol/L or nonfasting blood glucose > 11.1 mmol/L). The relationship between the TRL-c and DM was determined using multivariate logistic regression, smoothing curve fitting (penalized spline method), and subgroup analysis.

RESULTS

A total of 890 patients with stroke (age, 66.1 ± 11.8 years) were enrolled, including 329 females. Multivariate logistic regression analysis demonstrated that TRL-c had a positive association with DM (OR 1.88; 95% CI: 1.22 to 2.89). Strong linear associations of TRL-c with DM were confirmed by restricted cubic spline analysis. And the association between TRL-c and DM was consistent in the different subgroups.

CONCLUSION

Positive associations were found between TRL-c and DM in patients with stroke.