Intestinal Barrier Dysfunction Participates in the Pathophysiology of Ischemic Stroke

Blueberry extract for the treatment of ischaemic stroke through regulating the gut microbiota and kynurenine metabolism

Although the gut microbiota and kynurenine (KYN) metabolism have significant protective effects against ischaemic stroke (IS), the exact mechanism has yet to be fully elucidated. Combined serum metabolomics and 16S rRNA gene sequencing were used to reveal the differences between the gut microbiota and metabolites in rats treated with or without blueberry extract. Faecal microbiota transplantation (FMT) was employed to validate the protective role of the gut microbiota in IS. Furthermore, the interaction between Prevotella and IS was also confirmed in patients. Rats with IS experienced neurological impairments accompanied by an impaired intestinal barrier and disturbed intestinal flora, which further contributed to heightened inflammatory responses. Furthermore, Prevotella played a critical role in IS pathophysiology, and a positive correlation between Prevotella and KYN was detected. The role of KYN metabolism in IS was further demonstrated by the finding that IDO was significantly upregulated and that the use of the IDO inhibitor, attenuated KYN metabolic pathway activity and ameliorated neurological damage in rats with IS. Prevotella intervention also significantly improved stroke symptoms and decreasing KYN levels in rats with IS. FMT showed that the beneficial effects of blueberry extract on IS involve gut bacteria, especially Prevotella, which were confirmed by microbiological analyses conducted on IS patients. Moreover, blueberry extract led to significant changes in kynurenic acid levels and tryptophan and IDO levels through interactions with Prevotella. Our study demonstrates for the first time that blueberry extract could modulate "intestinal microecology-KYN metabolism" to improve IS.

Microbiota-derived short-chain fatty acids mediate the effects of dengzhan shengmai in ameliorating cerebral ischemia via the gut-brain axis

ETHNOPHARMACOLOGICAL RELEVANCE

Dengzhan shengmai (DZSM) formula, composed of four herbal medicines (Erigeron breviscapus, Panax ginseng, Schisandra chinensis, and Ophiopogon japonicus), is widely used in the recovery period of ischemic cerebrovascular diseases; however, the associated molecular mechanism remains unclear.

AIM OF THE STUDY

The purpose of this study was to uncover the links between the microbiota-gut-brain axis and the efficacy of DZSM in ameliorating cerebral ischemic diseases.

MATERIALS AND METHODS

The effects of DZSM on the gut microbiota community and bacteria-derived short-chain fatty acid (SCFA) production were evaluated in vivo using a rat model of cerebral ischemia and in vitro through the anaerobic incubation with fresh feces derived from model animals. Subsequently, the mechanism underlying the role of SCFAs in the DZSM-mediated treatment of cerebral ischemia was explored.

RESULTS

We found that DZSM treatment significantly altered the composition of the gut microbiota and markedly enhanced SCFA production. The consequent increase in SCFA levels led to the upregulation of the expression of monocarboxylate transporters and facilitated the transportation of intestinal SCFAs into the brain, thereby inhibiting the apoptosis of neurocytes via the regulation of the PI3K/AKT/caspase-3 pathway. The increased intestinal SCFA levels also contributed to the repair of the 2VO-induced disruption of gut barrier integrity and inhibited the translocation of lipopolysaccharide from the intestine to the brain, thus attenuating neuroinflammation. Consequently, cerebral neuropathy and oxidative stress were significantly improved in 2VO model rats, leading to the amelioration of cerebral ischemia-induced cognitive dysfunction. Finally, fecal microbiota transplantation could reproduce the beneficial effects of DZSM on SCFA production and cerebral ischemia.

CONCLUSIONS

Our findings suggested that SCFAs mediate the effects of DZSM in ameliorating cerebral ischemia via the gut microbiota-gut-brain axis.

Risk factors for small intestinal bacterial overgrowth in patients with acute ischaemic stroke

Introduction. The intestinal flora has become a promising new target in acute ischaemic stroke (AIS), and small intestinal bacterial overgrowth (SIBO) is a common pathological condition of the intestinal flora. Recently, the lactose hydrogen-methane breath test has emerged as a non-invasive and economical method for the detection of SIBO in AIS patients. Exploring the prevalence of SIBO and its associated risk factors will provide a clinical basis for the association between intestinal flora and AIS.Hypothesis/Gap Statement. Given that the prevalence of SIBO and its risk factors in patients with AIS remain to be studied, there is a need to investigate them.Aim. This study aimed to investigate the prevalence and risk factors of SIBO in patients with AISMethodology. Eighty patients tested for SIBO using the lactulose hydrogen-methane breath test were evaluated. Patients were divided into SIBO-positive and SIBO-negative groups according to the presence or absence of SIBO, respectively. The baseline characteristics and clinical biochemical indicators of the patients were compared between the two groups. The independent risk factors and predictive value of SIBO in AIS patients were determined using multivariate logistic regression and receiver operating characteristic (ROC) curve analyses.Results. Of the 80 consecutive patients with AIS, 23 (28.8 %) tested positive for SIBO. Triglyceride (TG) and homocysteine (Hcy) levels were identified as independent risk factors for SIBO in patients with AIS using multivariate logistic regression analysis (P<0.005). ROC curve analysis showed that the area under the curve (AUC) of TG was 0.690 (95 % CI 0.577-0.789, P=0.002). The sensitivity, specificity and optimal cut-off values were 95.7 %, 35.1 % and 1.14 mmol l^-1, respectively. The AUC of Hcy was 0.676 (95 % CI 0.562-0.776, P=0.01). The sensitivity, specificity and optimal cut-off values were 73.9 %, 59.7 % and 14.1 µmol^-1, respectively. When TG and Hcy levels were combined, the AUC increased to 0.764 (95 % CI 0.656-0.852, P<0.001). The specificity and sensitivity were 61.4 and 82.6 %, respectively. This showed that the combined detection of TG and Hcy levels had a higher predictive valueConclusion. The prevalence of SIBO in patients with AIS was 28.8 %. TG and Hcy levels are independent risk factors for SIBO in patients with AIS. Both markers had good predictive value for the occurrence of SIBO. In the future, we should actively utilize these indicators to prevent intestinal flora imbalance and the occurrence of SIBO.

Inflammasome-Regulated Pyroptotic Cell Death in Disruption of the Gut-Brain Axis After Stroke

Approximately 50% of stroke survivors experience gastrointestinal complications. The innate immune response plays a role in changes to the gut-brain axis after stroke. The purpose of this study is to examine the importance of inflammasome-mediated pyroptosis in disruption of the gut-brain axis after experimental stroke. B6129 mice were subjected to a closed-head photothrombotic stroke. We examined the time course of inflammasome protein expression in brain and intestinal lysate using western blot analysis at 1-, 3-, and 7-days post-injury for caspase-1, interleukin-1β, nod-like receptor protein 3 (NLRP3), and apoptosis speck-like protein containing a caspase-recruiting domain (ASC) and gasdermin-D (GSDMD) cleavage. In a separate group of mice, we processed brain tissue 24 and 72 h after thrombotic stroke for immunohistochemical analysis of neuronal and endothelial cell pyroptosis. We examined intestinal tissue for morphological changes and pyroptosis of macrophages. We performed behavioral tests and assessed gut permeability changes to confirm functional changes after stroke. Our data show that thrombotic stroke induces inflammasome activation in the brain and intestinal tissue up to 7-day post-injury as well as pyroptosis of neurons, cerebral endothelial cells, and intestinal macrophages. We found that thrombotic stroke leads to neurocognitive and motor function deficits as well as increased gut permeability. Finally, the adoptive transfer of serum-derived EVs from stroke mice into naive induced inflammasome activation in intestinal tissues. Taken together, these results provide novel information regarding possible mechanisms underlying gut complications after stroke and the identification of new therapeutic targets for reducing the widespread consequences of ischemic brain injury.

Ischemic Stroke Impacts the Gut Microbiome, Ileal Epithelial and Immune Homeostasis

Ischemic stroke critically impacts neurovascular homeostasis, potentially resulting in neurological disorders. However, the mechanisms through which stroke-induced inflammation modifies the molecular and metabolic circuits, particularly in ileal epithelial cells (iECs), currently remain elusive. Using multiomic approaches, we illustrated that stroke impaired the ileal microbiome and associated metabolites, leading to increased inflammatory signals and altered metabolites, potentially deteriorating the iEC homeostasis. Bulk transcriptomic and metabolomic profiling demonstrated that stroke enhanced fatty acid oxidation while reducing the tricarboxylic acid (TCA) cycle in iECs within the first day after stroke. Intriguingly, single-cell RNA sequencing analysis revealed that stroke dysregulated cell-type-specific gene responses within iECs and reduced frequencies of goblet and tuft cells. Additionally, stroke augmented interleukin-17A+ γδ T cells but decreased CD4+ T cells in the ileum. Collectively, our findings provide a comprehensive overview of stroke-induced intestinal dysbiosis and unveil responsive gene programming within iECs with implications for disease development.