Effect of enteral nutrition on the intestinal microbiome and risk of death in ischemic stroke patients.

BACKGROUND: Studies have shown that the intestinal microbiome of stroke patients is significantly altered and that the degree of microbiota disturbance correlates with prognosis. Enteral nutrition (EN) can reshape the intestinal microbiome and is important for stroke patients with dysphagia. We aimed to describe the intestinal microbiome in patients with ischemic cerebral infarction receiving standard EN. METHODS: First, 17 healthy controls (HCs), 54 stroke patients with oral feeding (ON), and 50 stroke patients with EN were matched to investigate the changes in the intestinal microbiota with EN in the first week after admission and dynamic changes in the EN group in the second week. Second, we investigated the relationship between the intestinal microbiome and clinical characteristics in a larger sample of participants receiving EN (n = 147). Survival analysis was performed using Cox proportional hazards regression. The composition and structure of the intestinal microbiota were analyzed by 16S rRNA sequencing. RESULTS: Compared with the HC and ON groups, patients with EN exhibited significantly different compositions of the intestinal microbiota in the first week, including enrichment of the opportunistic pathogen Enterococcus and depletion of bacteria such as Lachnospiraceae, and Ruminococcus, which were further depleted in the second week. An increase in Parvimonas and Comamonas abundances was associated with an increased risk of 180-day mortality. CONCLUSIONS: The intestinal microbiota in ischemic stroke patients receiving EN is significantly altered, and specific strains of bacteria may be associated with prognosis and clinical indicators.

Fecal Transplantation from db/db Mice Treated with Sodium Butyrate Attenuates Ischemic Stroke Injury.

The complication of type 2 diabetes (T2D) exacerbates brain infarction in acute ischemic stroke (AIS). Because butyrate-producing bacteria are decreased in T2D and butyrate has been reported to be associated with attenuated brain injury in AIS, we hypothesize that administering butyrate could ameliorate T2D-associated exacerbation of brain infarction in AIS. Therefore, we first validated that Chinese AIS patients with T2D comorbidity have significantly lower levels of fecal butyrate-producing bacteria and butyrate than AIS patients without T2D. Then, we performed a 4-week intervention in T2D mice receiving either sodium butyrate (SB) or sodium chloride (NaCl) and found that SB improved the diabetic phenotype, altered the gut microbiota, and ameliorated brain injury after stroke. Fecal samples were collected from T2D mice after SB or NaCl treatment and were transplanted into antibiotic-treated C57BL/6 mice. After 2 weeks of transplantation, the gut microbiota profile and butyrate level of recipient mice were tested, and then the recipient mice were subjected to ischemic stroke. Stroke mice that received gut microbiota from SB-treated mice had a smaller cerebral infarct volume than mice that received gut microbiota from NaCl-treated mice. This protection was also associated with improvements in gut barrier function, reduced serum levels of lipopolysaccharide (LPS), LPS binding protein (LBP), and proinflammatory cytokines, and improvements in the blood-brain barrier. IMPORTANCE Ischemic stroke is a major global health burden, and T2D is a well-known comorbidity that aggravates brain injury after ischemic stroke. However, the underlying mechanism by which T2D exacerbates stroke injury has not been completely elucidated. A large amount of evidence suggests that the gut microbiota composition affects stroke outcomes. Our results showed that the gut microbiota of T2D aggravated brain injury after ischemic stroke and could be modified by SB to afford neuroprotection against stroke injury. These findings suggest that supplementation with SB is a potential therapeutic strategy for T2D patients with ischemic stroke.

Rapid gut dysbiosis induced by stroke exacerbates brain infarction in turn.

OBJECTIVE: Stroke is a leading cause of death and disability worldwide. Neuroprotective approaches have failed in clinical trials, thus warranting therapeutic innovations with alternative targets. The gut microbiota is an important contributor to many risk factors for stroke. However, the bidirectional interactions between stroke and gut microbiota remain largely unknown. DESIGN: We performed two clinical cohort studies to capture the gut dysbiosis dynamics after stroke and their relationship with stroke prognosis. Then, we used a middle cerebral artery occlusion model to explore gut dysbiosis post-stroke in mice and address the causative relationship between acute ischaemic stroke and gut dysbiosis. Finally, we tested whether aminoguanidine, superoxide dismutase and tungstate can alleviate post-stroke brain infarction by restoring gut dysbiosis. RESULTS: Brain ischaemia rapidly induced intestinal ischaemia and produced excessive nitrate through free radical reactions, resulting in gut dysbiosis with Enterobacteriaceae expansion. Enterobacteriaceae enrichment exacerbated brain infarction by enhancing systemic inflammation and is an independent risk factor for the primary poor outcome of patients with stroke. Administering aminoguanidine or superoxide dismutase to diminish nitrate generation or administering tungstate to inhibit nitrate respiration all resulted in suppressed Enterobacteriaceae overgrowth, reduced systemic inflammation and alleviated brain infarction. These effects were gut microbiome dependent and indicated the translational value of the brain-gut axis in stroke treatment. CONCLUSIONS: This study reveals a reciprocal relationship between stroke and gut dysbiosis. Ischaemic stroke rapidly triggers gut microbiome dysbiosis with Enterobacteriaceae overgrowth that in turn exacerbates brain infarction.

[Research progress of the effect of enteral nutrition on intestinal microecology in neurocritical ill patients].

The intestinal flora and the intestinal environment in which it resides together constitute the intestinal microecosystem,it is significantly disturbed in neurocritical ill patients, as manifested by the decrease of bacterial diversity, an increase of pathogen, and the destruction of the intestinal barrier. Appropriate enteral nutrition is effective in maintaining intestinal barrier stability, regulating intestinal immune function, inhibiting intestinal inflammation, and regulating specific intestinal microbiota and intestinal function. It is important for sustaining intestinal microecological balance, reducing clinical complications in patients, and is a new target for the treatment of neurocritical ill patients. This review elaborates the alteration of intestinal microecology and treatment options recommended by current clinical guidelines in neurocritical ill patients and summarizes the research progress of the effects of enteral nutrition and several nutritional additives on intestinal flora and intestinal functions, to provide a reference for the follow-up research.

Dysbiosis of Gut Microbiota and Short-Chain Fatty Acids in Acute Ischemic Stroke and the Subsequent Risk for Poor Functional Outcomes.

BACKGROUND: The intestinal microbiota and its metabolites have been reported to play an important role in stroke. Gut microbiota-originating short-chain fatty acids (SCFAs) modulate brain functions directly or indirectly through immune, endocrine, vagal, and other humoral pathways. However, relatively few investigations have evaluated the gut microbiome and SCFAs spectrum or their potential associations with stroke outcomes in acute ischemic stroke (AIS) patients with different stroke severities. METHODS: We used 16S rRNA gene sequencing and gas chromatography to compare the fecal microbial composition and SCFA spectrum between AIS patients (n = 140) and healthy controls (n = 92). Their associations with 90-day poor functional outcomes were evaluated by logistic regression models. RESULTS: We found that the intestinal microbiota distinguished AIS patients from healthy controls. A lack of SCFAs-producing bacteria and a low fecal SCFAs level defined dysbiosis in AIS patients, especially those with increased stroke severity. The SCFAs levels were negatively correlated with stroke severity and prognosis. Reduced SCFAs levels, especially acetate, were associated with an increased risk of 90-day poor functional outcomes even after adjustments. CONCLUSIONS: Dysbiosis of SCFAs-producing bacteria and SCFAs in AIS patients increased the subsequent risk for poor functional outcomes, indicating that SCFAs could be potential prognostic markers and therapeutic targets for stroke.

Dysbiosis of Gut Microbiota and Short-Chain Fatty Acids in Encephalitis: A Chinese Pilot Study.

Background: Encephalitis, the inflammation of the brain, may be caused by an infection or an autoimmune reaction. However, few researches were focused on the gut microbiome characteristics in encephalitis patients. Methods: A prospective observational study was conducted in an academic hospital in Guangzhou from February 2017 to February 2018. Patients with encephalitis were recruited. Fecal and serum samples were collected at admission. Healthy volunteers were enrolled from a community. Disease severity scores were recorded by specialized physicians, including Glasgow Coma Scale (GCS), Sequential Organ Failure Assessment (SOFA), and Acute Physiology and Chronic Health Evaluation-II (APACHE-II). 16S rRNA sequence was performed to analyze the gut microbiome, then the α-diversities and ß-diversities were estimated. Short-chain fatty acids (SCFAs) were extracted from fecal samples and determined by gas chromatography-mass spectrometry. Serum D-lactate (D-LA), intestinal fatty acid-binding protein (iFABP), lipopolysaccharide (LPS), and lipopolysaccharide-binding protein (LBP) were measured by enzyme-linked immunosorbent assay (ELISA). The associations among microbial indexes and clinical parameters were evaluated by Spearman correlation analysis. Results: In total, twenty-eight patients were recruited for analysis (median age 46 years; 82.1% male; median GCS 6.5; median SOFA 6.5; median APACHE-II 14.5). Twenty-eight age- and sex-matched healthy subjects were selected as controls. The ß-diversities between patients and healthy subjects were significantly different. The α-diversities did not show significant differences between these two groups. In the patient group, the abundances of Bacteroidetes, Proteobacteria, and Bacilli were significantly enriched. Accordingly, fecal SCFA levels were decreased in the patient group, whereas serum D-LA, iFABP, LPS, and LBP levels were increased compared with those in healthy subjects. Correlation analyses showed that disease severity had positive correlations with Proteobacteria and Akkermansia but negative correlations with Firmicutes, Clostridia, and Ruminococcaceae abundances. The cerebrospinal fluid albumin-to-serum albumin ratio (CSAR) was positively related to the α-diversity but negatively correlated with the fecal butyrate concentration. Conclusion: Gut microbiota disruption was observed in encephalitis patients, which manifested as pathogen dominance and health-promoting commensal depletion. Disease severity and brain damage may have associations with the gut microbiota or its metabolites. The causal relationship should be further explored in future studies.

Dynamic Changes and Prognostic Value of Gut Microbiota-Dependent Trimethylamine-N-Oxide in Acute Ischemic Stroke.

Background: Acute ischemic stroke (AIS) is an atherothrombotic disease. Trimethylamine-N-oxide (TMAO), a gut microbiota-dependent metabolite, has been shown to be proatherogenic and prothrombotic. However, the involvement of TMAO in AIS remains unclear. This study aimed to observe the dynamic changes of TMAO in AIS patients and identify the prognostic value of TMAO for major ischemic events and unfavorable functional outcomes. Methods: This study included 204 AIS patients and 108 healthy controls. Blood samples for TMAO analyses were drawn at admission, 2 and 7 days of admission. Logistic regression models and receiver operating characteristic curves were established to identify associations between TMAO levels and major ischemic events (ischemic stroke, myocardial infarction, or death from an ischemic vascular event), as well as unfavorable functional outcomes (modified Rankin Scale score ≥3), at 90 days and 12 months. Results: TMAO levels showed no significant changes before and within 24 h of AIS treatment (at admission) but decreased significantly thereafter. Elevated log2-transformed baseline TMAO levels were associated with increased risks of 90-day [odds ratio (OR), 2.62; 95% confidence interval (CI), 1.55-4.45; p < 0.001] and 12-month (OR, 3.59; 95% CI, 2.12-6.09; p < 0.001) major ischemic events, as well as 90-day (OR, 2.89; 95% CI, 1.46-5.71; p = 0.002) and 12-month (OR, 2.58; 95% CI, 1.50-4.46; p = 0.001) unfavorable functional outcomes, after adjustments for confounding factors. The areas under curve of baseline TMAO levels for predicting 90-day and 12-month major ischemic events were 0.72 (95% CI, 0.61-0.83; p < 0.001) and 0.76 (95% CI, 0.66-0.85; p < 0.001). Baseline TMAO levels improved the prognostic accuracy of conventional risk factors, National Institutes of Health Stroke Scale (NIHSS) score and N-terminal B-type natriuretic peptide (NT-proBNP) level. Conclusions: TMAO levels decreased with time since stroke onset. Elevated TMAO levels at an earlier period portended poor stroke outcomes, broadening the potential clinical utility of TMAO as an independent prognostic marker and therapeutic target.

Dysbiosis of the intestinal microbiota in neurocritically ill patients and the risk for death.

BACKGROUND: Despite the essential functions of the intestinal microbiota in human physiology, little has been reported about the microbiome in neurocritically ill patients. This investigation aimed to evaluate the characteristics of the gut microbiome in neurocritically ill patients and its changes after admission. Furthermore, we investigated whether the characteristics of the gut microbiome at admission were a risk factor for death within 180 days. METHODS: This prospective observational cohort study included neurocritically ill patients admitted to the neurological intensive care unit of a large university-affiliated academic hospital in Guangzhou. Faecal samples were collected within 72 h after admission (before antibiotic treatment) and serially each week. Healthy volunteers were recruited from a community in Guangzhou. The gut microbiome was monitored via 16S rRNA gene sequence analysis, and the associations with the clinical outcome were evaluated by a Cox proportional hazards model. RESULTS: In total, 98 patients and 84 age- and sex-matched healthy subjects were included in the analysis. Compared with healthy subjects, the neurocritically ill patients exhibited significantly different compositions of intestinal microbiota. During hospitalization, the α-diversity and abundance of Ruminococcaceae and Lachnospiraceae decreased significantly over time in patients followed longitudinally. The abundance of Enterobacteriaceae was positively associated with the modified Rankin Scale at discharge. In the multivariate Cox regression analysis, Christensenellaceae and Erysipelotrichaceae were associated with an increased risk of death. The increases in intestinal Enterobacteriales and Enterobacteriaceae during the first week in the neurological intensive care unit were associated with increases of 92% in the risk of 180-day mortality after adjustments. CONCLUSIONS: This analysis of the gut microbiome in 98 neurocritically ill patients indicates that the gut microbiota composition in these patients differs significantly from that in a healthy population and that the magnitude of this dysbiosis increases during hospitalization in a neurological intensive care unit. The gut microbiota characteristics seem to have an impact on patients' 180-day mortality. Gut microbiota analysis could hopefully predict outcome in the future.

Stroke Dysbiosis Index (SDI) in Gut Microbiome Are Associated With Brain Injury and Prognosis of Stroke.

Background: Significant dysbiosis occurs in the gut microbiome of stroke patients. Condensing these broad, complex changes into one index would greatly facilitate the clinical usage of gut microbiome data. Here, we formulated a gut microbiota index in patients with acute ischemic stroke based on their gut microbiota dysbiosis patterns and tested whether the index was correlated with brain injury and early outcome. Methods: A total of 104 patients with acute ischemic stroke and 90 healthy individuals were recruited, and their gut microbiotas were compared and to model a Stroke Dysbiosis Index (SDI), which representing stroke-associated dysbiosis patterns overall. Another 83 patients and 70 controls were recruited for validation. The association of SDI with stroke severity (National Institutes of Health Stroke Scale [NIHSS] score) and outcome (modified Rankin scale [mRS] score: favorable, 0-2; unfavorable, >2) at discharge was also assessed. A middle cerebral artery occlusion (MCAO) model was used in human flora-associated (HFA) animals to explore the causal relationship between gut dysbiosis and stroke outcome. Results: Eighteen genera were significantly different between stroke patients and healthy individuals. The SDI formula was devised based on these microbiome differences; SDI was significantly higher in stroke patients than in healthy controls. SDI alone discriminated stroke patients from controls with AUCs of 74.9% in the training cohort and 84.3% in the validation cohort. SDI was significantly and positively correlated with NIHSS score on admission and mRS score at discharge. Logistic regression analysis showed that SDI was an independent predictor of severe stroke (NIHSS ≥8) and early unfavorable outcome (mRS >2). Mice receiving fecal transplants from high-SDI patients developed severe brain injury with elevated IL-17+ γδ T cells in gut compared to mice receiving transplants from low-SDI patients (all P < 0.05). Conclusions: We developed an index to measure gut microbiota dysbiosis in stroke patients; this index was significantly correlated with patients' outcome and was causally related to outcome in a mouse model of stroke. Our model facilitates the potential clinical application of gut microbiota data in stroke and adds quantitative evidence linking the gut microbiota to stroke.

Higher Risk of Stroke Is Correlated With Increased Opportunistic Pathogen Load and Reduced Levels of Butyrate-Producing Bacteria in the Gut.

Objective: Gut microbiota is a newly identified risk factor for stroke, and there are no large prospective studies linking the baseline gut microbiome to long-term risk of stroke. We present here the correlation between the gut microbiota and stroke risk in people with no prior stroke history. Methods: A total of 141 participants aged ≥60 years without prior history of stroke were recruited and divided into low-risk, medium-risk, and high-risk groups based on known risk factors and whether they were suffering from chronic diseases. The composition of their gut microbiomes was compared using 16S rRNA gene amplicon next-generation-sequencing and Quantitative Insights into Microbial Ecology (QIIME) analysis. Levels of fecal short-chain fatty acids were measured using gas chromatography. Results: We found that opportunistic pathogens (e.g., Enterobacteriaceae and Veillonellaceae) and lactate-producing bacteria (e.g., Bifidobacterium and Lactobacillus) were enriched, while butyrate-producing bacteria (e.g., Lachnospiraceae and Ruminococcaceae) were depleted, in the high-risk group compared to the low-risk group. Butyrate concentrations were also lower in the fecal samples obtained from the high-risk group than from the low-risk group. The concentrations of other short-chain fatty acids (e.g., acetate, propionate, isobutyrate, isovalerate, and valerate) in the gut were comparable among the three groups. Conclusion: Participants at high risk of stroke were characterized by the enrichment of opportunistic pathogens, low abundance of butyrate-producing bacteria, and reduced concentrations of fecal butyrate. More researches into the gut microbiota as a risk factor in stroke should be carried out in the near future.

[Research progress of gut microbiota and microbiota-targeted therapy in critical ill patients].

OBJECTIVE: In physiological conditions, a diverse microbiota might enhance host defense. However, the gut microbiota of critically ill patients is characterized by lower diversity, lower abundances of key commensal genera, and overgrowth by one bacterial generation, a state known as dysbiosis. Increasing evidences indicate that microbiota-derived components can reach the systemic circulation from the gut and modulate immune homeostasis. Dysbiosis could have greater consequences for the critically ill patients and might contribute to poor outcome. In this review, we highlighted the crucial role of intestinal microbiota in systemic homeostasis in the critically ill patients and summarized emerging evidence in the field of microbiota-targeted therapies. This would provide new perspective for further establishing the causes and consequences of dysbiosis found in the critically ill patients as well as developing new strategies of intervention.