Aneurysmal Subarachnoid Hemorrhage Onset Alters Pyruvate Metabolism in Poor-Grade Patients and Clinical Outcome Depends on More: A Cerebrospinal Fluid Metabolomic Study

Intestinal flora influences the progression of subarachnoid hemorrhage by affecting peripheral and central inflammatory pathways

Subarachnoid hemorrhage (SAH) is a debilitating condition that leaves survivors with neurological disability for the rest of their lives. No effective treatment for early brain injury (EBI) has been developed. Gut microbiome (GM) impact the host immune system and can influence disease processes in several organs, including the brain. However, it remains unclear whether the GM has an impact on the outcome of SAH brain injury. Here, we wondered whether microbiota could relieve the injury. We changed the microbiota of 8-week-old male rats by administering antibiotic-containing water for 2 weeks. Composition of the GM was profiled by using 16S rRNA. We induced SAH by puncture the internal carotid artery of control rats and rats with altered GM. Additionally, we studied inflammatory cells using HE stains, Intestinal lymphocyte flow cytometry, and Neuroinflammatory factor WB. SAH was significantly averted by alterations in GM using antibiotics. The altered GM significantly increased the intestinal and intracranial inflammation after SAH. This was manifested by Mosin (MSN) inflammatory cytokines. Our findings demonstrated that the brain injury following SAH is associated with GM.

Transcriptomics and metabolomics reveal hypothalamic metabolic characteristics and key genes after subarachnoid hemorrhage in rats

Subarachnoid hemorrhage (SAH) is a serious hemorrhagic event with high mortality and morbidity. Multiple injurious events produced by SAH can lead to a series of pathophysiologic processes in the hypothalamus that can severely impact patients' life. These pathophysiologic processes usually result in physiologic derangements and dysfunction of the brain and multiple organs. This dysfunction involved multiple dimensions of the genome and metabolome. In our study, we induced the SAH model in rats to obtain hypothalamic tissue and serum. The samples were subsequently analyzed by transcriptomics and metabolomics. Next, the functional enrichment analysis of the differentially expressed genes and metabolites were performed by GO and KEGG pathway analysis. Through transcriptomic analysis of hypothalamus samples, 263 up-regulated differential genes, and 207 down-regulated differential genes were identified in SAH groups compared to Sham groups. In the KEGG pathway analysis, a large number of differential genes were found to be enriched in IL-17 signaling pathway, PI3K-Akt signaling pathway, and bile secretion. Liquid chromatography-mass spectrometry metabolomics technology was conducted on the serum of SAH rats and identified 11 up-regulated and 26 down-regulated metabolites in positive ion model, and 1 up-regulated and 10 down-regulated metabolites in negative ion model. KEGG pathways analysis showed that differentially expressed metabolites were mainly enriched in pathways of bile secretion and primary bile acid biosynthesis. We systematically depicted the neuro- and metabolism-related biomolecular changes occurring in the hypothalamus after SAH by performing transcriptomics and metabolomics studies. These biomolecular changes may provide new insights into hypothalamus-induced metabolic changes and gene expression after SAH.

Ferroptosis in early brain injury after subarachnoid hemorrhage: review of literature

Spontaneous subarachnoid hemorrhage (SAH), mainly caused by ruptured intracranial aneurysms, is a serious acute cerebrovascular disease. Early brain injury (EBI) is all brain injury occurring within 72 h after SAH, mainly including increased intracranial pressure, decreased cerebral blood flow, disruption of the blood-brain barrier, brain edema, oxidative stress, and neuroinflammation. It activates cell death pathways, leading to neuronal and glial cell death, and is significantly associated with poor prognosis. Ferroptosis is characterized by iron-dependent accumulation of lipid peroxides and is involved in the process of neuron and glial cell death in early brain injury. This paper reviews the research progress of ferroptosis in early brain injury after subarachnoid hemorrhage and provides new ideas for future research.

CSF metabolomics alterations after aneurysmal subarachnoid hemorrhage: what do we know?

PURPOSE

The purpose of this mini review is to describe metabolomics in cerebrospinal fluid (CSF) and its potential in aneurysmal subarachnoid hemorrhage (aSAH). In brain injury, patients' micro dialysis enables detecting biochemical change in brain tissue. Indicators for ischemia were detected such as lactate, pyruvate, glucose, and glutamate. In aSAH patients, the pathophysiology and the factor for poor outcome are not completely understood yet. Routine use of biomarkers in CSF, particularly in aSAH patients, is still lacking.

METHODS

This mini review was performed on the role of metabolomics alterations after aneurysmal subarachnoid hemorrhage.

RESULTS

We identified five clinical studies that addressed metabolomics in patients with aneurysmal subarachnoid hemorrhage.

CONCLUSION

There is increasing evidence suggesting that biomarkers can give insight in the pathogenesis and can serve as an outcome predictor. In this mini review, we present a brief overview of metabolomics profiling in neuroscience and wish to discuss the predictive and therapeutic value in aSAH patients.

Metabolomic Analysis in Neurocritical Care Patients

Metabolomics is the analytical study of metabolites in biological matrices using high-throughput profiling. Traditionally, the metabolome has been studied to identify various biomarkers for the diagnosis and pathophysiology of disease. Over the last decade, metabolomic research has grown to include the identification of prognostic markers, the development of novel treatment strategies, and the prediction of disease severity. In this review, we summarized the available evidence on the use of metabolome profiling in neurocritical care populations. Specifically, we focused on aneurysmal subarachnoid hemorrhage, traumatic brain injury, and intracranial hemorrhage to identify the gaps in the current literature and to provide direction for future studies. A primary literature search of the Medline and EMBASE databases was conducted. Upon removing duplicate studies, abstract screening and full-text screening were performed. We screened 648 studies and extracted data from 17 studies. Based on the current evidence, the utility of metabolomic profiling has been limited due to inconsistencies amongst studies and a lack of reproducible data. Studies identified various biomarkers for diagnosis, prognosis, and treatment modification. However, studies evaluated and identified different metabolites, resulting in an inability to compare the study results. Future research towards addressing the gaps in the current literature, including reproducing data on the use of specific metabolite panels, is needed.

Additive prognostic impact of the cerebrospinal fluid arginine/ornithine ratio to established clinical scores in aneurysmal subarachnoid hemorrhage

Cerebrospinal fluid (CSF) metabolites are increasingly recognized as prognostic factors in aneurysmal subarachnoid hemorrhage (SAH). The CSF arginine/ornithine ratio (Arg/Orn) was shown to predict cerebral vasospasms and clinical outcome in SAH. The additive prognostic value of Arg/Orn over established prognostic scores has not been investigated. CSF Arg/Orn and the established prognostic scores SAH, FRESH, SAH-PDS, HAIR, Rosen-McDonald, Hunt and Hess, WFNS and modified Fisher scale were determined in a prospective cohort of patients with aneurysmal SAH. Logistic regression models to predict a favorable outcome, defined as a modified Rankin Scale score of 0-3 at 3  months follow-up, were constructed for each score, both with and without the addition of Arg/Orn. The impact of Arg/Orn was assessed comparing logistic regression models containing the respective score with and without Arg/Orn with the likelihood ratio chi-squared test. CSF Arg/Orn and clinical scores were determined in 38 SAH patients. Arg/Orn was an independent predictor of clinical outcome when added to established prognostic scores (p < 0.05) with the exception of HAIR (p = 0.078). All models were significantly improved if Arg/Orn was added as a covariable (p < 0.05). The results of this study confirm Arg/Orn as an independent prognostic factor and its addition improves established prognostic models in SAH.

Metabolomics as a potential tool for monitoring patients with aneurysmal subarachnoid hemorrhage

Metabolomics has evolved into a particularly useful tool to study interactions between metabolites and serves as an aid in unraveling the complexity of entire metabolomes. Nonetheless, it is increasingly viewed as a methodology with practical applications in the clinical setting, where identifying and quantifying biomarkers of interest could prove useful for diagnostics. Starting from a concise overview of the most prominent analytical techniques employed in metabolomics, herein we present a review of its application in studies of brain metabolism and cerebrovascular diseases, paying most attention to its uses in researching aneurysmal subarachnoid hemorrhage. Both animal models and human studies are considered, and metabolites identified as potential biomarkers are highlighted.

Cerebrospinal fluid metabolic profiling reveals divergent modulation of pentose phosphate pathway by midazolam, propofol and dexmedetomidine in patients with subarachnoid hemorrhage: a cohort study

BACKGROUND

Agitation is common in subarachnoid hemorrhage (SAH), and sedation with midazolam, propofol and dexmedetomidine is essential in agitation management. Previous research shows the tendency of dexmedetomidine and propofol in improving long-term outcome of SAH patients, whereas midazolam might be detrimental. Brain metabolism derangement after SAH might be interfered by sedatives. However, how sedatives work and whether the drugs interfere with patient outcome by altering cerebral metabolism is unclear, and the comprehensive view of how sedatives regulate brain metabolism remains to be elucidated.

METHODS

For cerebrospinal fluid (CSF) and extracellular space of the brain exchange instantly, we performed a cohort study, applying CSF of SAH patients utilizing different sedatives or no sedation to metabolomics. Baseline CSF metabolome was corrected by selecting patients of the same SAH and agitation severity. CSF components were analyzed to identify the most affected metabolic pathways and sensitive biomarkers of each sedative. Markers might represent the outcome of the patients were also investigated.

RESULTS

Pentose phosphate pathway was the most significantly interfered (upregulated) pathway in midazolam (p = 0.0000107, impact = 0.35348) and propofol (p = 0.00000000000746, impact = 0.41604) groups. On the contrary, dexmedetomidine decreased levels of sedoheptulose 7-phosphate (p = 0.002) and NADP (p = 0.024), and NADP is the key metabolite and regulator in pentose phosphate pathway. Midazolam additionally augmented purine synthesis (p = 0.00175, impact = 0.13481) and propofol enhanced pyrimidine synthesis (p = 0.000203, impact = 0.20046), whereas dexmedetomidine weakened pyrimidine synthesis (p = 0.000000000594, impact = 0.24922). Reduced guanosine diphosphate (AUC of ROC 0.857, 95%CI 0.617-1, p = 0.00506) was the significant CSF biomarker for midazolam, and uridine diphosphate glucose (AUC of ROC 0.877, 95%CI 0.631-1, p = 0.00980) for propofol, and succinyl-CoA (AUC of ROC 0.923, 95%CI 0.785-1, p = 0.000810) plus adenosine triphosphate (AUC of ROC 0.908, 95%CI 0.6921, p = 0.00315) for dexmedetomidine. Down-regulated CSF succinyl-CoA was also associated with favorable outcome (AUC of ROC 0.708, 95% CI: 0.524-0.865, p = 0.029333).

CONCLUSION

Pentose phosphate pathway was a crucial target for sedatives which alter brain metabolism. Midazolam and propofol enhanced the pentose phosphate pathway and nucleotide synthesis in poor-grade SAH patients, as presented in the CSF. The situation of dexmedetomidine was the opposite. The divergent modulation of cerebral metabolism might further explain sedative pharmacology and how sedatives affect the outcome of SAH patients.

Plasma Amino Acids May Improve Prediction Accuracy of Cerebral Vasospasm after Aneurysmal Subarachnoid Haemorrhage

Aneurysmal subarachnoid haemorrhages (aSAH) account for 5% of strokes and continues to place a great burden on patients and their families. Cerebral vasospasm (CVS) is one of the main causes of death after aSAH, and is usually diagnosed between day 3 and 14 after bleeding. Its pathogenesis remains poorly understood. To verify whether plasma concentration of amino acids have prognostic value in predicting CVS, we analysed data from 35 patients after aSAH (median age 55 years, IQR 39-62; 20 females, 57.1%), and 37 healthy volunteers (median age 50 years, IQR 38-56; 19 females, 51.4%). Fasting peripheral blood samples were collected on postoperative day one and seven. High performance liquid chromatography-mass spectrometry (HPLC-MS) analysis was performed. The results showed that plasma from patients after aSAH featured a distinctive amino acids concentration which was presented in both principal component analysis and direct comparison. No significant differences were noted between postoperative day one and seven. A total of 18 patients from the study group (51.4%) developed CVS. Hydroxyproline (AUC = 0.7042, 95%CI 0.5259-0.8826, p = 0.0248) and phenylalanine (AUC = 0.6944, 95%CI 0.5119-0.877, p = 0.0368) presented significant CVS prediction potential. Combining the Hunt-Hess Scale and plasma levels of hydroxyproline and phenylalanine provided the model with the best predictive performance and the lowest leave-one-out cross-validation of performance error. Our results suggest that plasma amino acids may improve sensitivity and specificity of Hunt-Hess scale in predicting CVS.

Arginase-1 Released into CSF After Aneurysmal Subarachnoid Hemorrhage Decreases Arginine/Ornithine Ratio: a Novel Prognostic Biomarker

We hypothesized that the enzyme arginase-1 is released into the cerebrospinal fluid (CSF) during red blood cell lysis and contributes to dysregulated metabolism of the nitric oxide (NO) precursor L-arginine during aneurysmal subarachnoid hemorrhage (SAH). This prospective case-control study included 43 patients with aneurysmal SAH and ventricular drainage for clinical reasons. Longitudinal CSF samples (99) were obtained in the course of SAH. Patients were dichotomized regarding the occurrence of cerebral vasospasm syndrome (CVS) (N = 19). Arginase-1 and the amino acids L-arginine and L-ornithine were quantified in CSF. Outcome assessments included delayed cerebral ischemia (DCI) and functional status after 3 months using the modified Rankin Scale (mRS). Arginase-1 was released into the CSF of SAH patients whereas this enzyme was undetectable in controls. Compared to patients without CVS, arginase-1 levels were higher in CVS patients until day 14 after clinical event. The well-known surrogate parameter for arginase acitivity, the L-arginine to L-ornithine ratio (Arg/Orn), correlated with CSF arginase-1 levels. Arg/Orn was reduced in patients with CVS from disease onset (days 1-3, p = 0.0009) until day 14. Logistic regression analysis of early Arg/Orn was predictive for CVS (p = 0.008) and DCI (p = 0.035), independent of age, Hunt and Hess grade, and intraventricular blood. Arg/Orn < 2.71 at disease onset predicted CVS with a sensitivity of 86.7% and specificity of 72.2%. Arg/Orn ≥ 2.71 predicted excellent functional outcome. We propose a novel mechanism contributing to NO deprivation during SAH: arginase-1 is released from erythrocytes into the CSF, leading to L-arginine consumption and reduced NO bioavailability. Furthermore, Arg/Orn is a robust predictor for occurrence of CVS, DCI, and functional outcome 3 months after aneurysmal SAH. Our data provide a novel prognostic biomarker and may contribute to the development of novel therapeutic strategies in SAH. Clinical Trial Registration-URL: http://www.drks.de . Unique identifier: DRKS00015293, date of registration: 13.09.2018.

Cerebrospinal fluid metabolomics: detection of neuroinflammation in human central nervous system disease

The high morbidity and mortality of neuroinflammatory diseases drives significant interest in understanding the underlying mechanisms involved in the innate and adaptive immune response of the central nervous system (CNS). Diagnostic biomarkers are important to define treatable neuroinflammation. Metabolomics is a rapidly evolving research area offering novel insights into metabolic pathways, and elucidation of reliable metabolites as biomarkers for diseases. This review focuses on the emerging literature regarding the detection of neuroinflammation using cerebrospinal fluid (CSF) metabolomics in human cohort studies. Studies of classic neuroinflammatory disorders such as encephalitis, CNS infection and multiple sclerosis confirm the utility of CSF metabolomics. Additionally, studies in neurodegeneration and neuropsychiatry support the emerging potential of CSF metabolomics to detect neuroinflammation in common CNS diseases such as Alzheimer's disease and depression. We demonstrate metabolites in the tryptophan-kynurenine pathway, nitric oxide pathway, neopterin and major lipid species show moderately consistent ability to differentiate patients with neuroinflammation from controls. Integration of CSF metabolomics into clinical practice is warranted to improve recognition and treatment of neuroinflammation.

Fluid metabolic pathways after subarachnoid hemorrhage

Aneurysmal subarachnoid hemorrhage (aSAH) is a devastating cerebrovascular disease with high mortality and morbidity. In recent years, a large number of studies have focused on the mechanism of early brain injury (EBI) and delayed cerebral ischemia (DCI), including vasospasm, neurotoxicity of hematoma and neuroinflammatory storm, after aSAH. Despite considerable efforts, no novel drugs have significantly improved the prognosis of patients in phase III clinical trials, indicating the need to further re-examine the multifactorial pathophysiological process that occurs after aSAH. The complex pathogenesis is reflected by the destruction of the dynamic balance of the energy metabolism in the nervous system after aSAH, which prevents the maintenance of normal neural function. This review focuses on the fluid metabolic pathways of the central nervous system (CNS), starting with ruptured aneurysms, and discusses the dysfunction of blood circulation, cerebrospinal fluid (CSF) circulation and the glymphatic system during disease progression. It also proposes a hypothesis on the metabolic disorder mechanism and potential therapeutic targets for aSAH patients.

Ifenprodil Improves Long-Term Neurologic Deficits Through Antagonizing Glutamate-Induced Excitotoxicity After Experimental Subarachnoid Hemorrhage

Excessive glutamate leading to excitotoxicity worsens brain damage after SAH and contributes to long-term neurological deficits. The drug ifenprodil is a non-competitive antagonist of GluN1-GluN2B N-methyl-d-aspartate (NMDA) receptor, which mediates excitotoxic damage in vitro and in vivo. Here, we show that cerebrospinal fluid (CSF) glutamate level within 48 h was significantly elevated in aSAH patients who later developed poor outcome. In rat SAH model, ifenprodil can improve long-term sensorimotor and spatial learning deficits. Ifenprodil attenuates experimental SAH-induced neuronal death of basal cortex and hippocampal CA1 area, cellular and mitochondrial Ca²⁺ overload of basal cortex, blood-brain barrier (BBB) damage, and cerebral edema of early brain injury. Using in vitro models, ifenprodil declines the high-concentration glutamate-mediated intracellular Ca²⁺ increase and cell apoptosis in primary cortical neurons, reduces the high-concentration glutamate-elevated endothelial permeability in human brain microvascular endothelial cell (HBMEC). Altogether, our results suggest ifenprodil improves long-term neurologic deficits through antagonizing glutamate-induced excitotoxicity.

The physiopathology of spontaneous hemorrhagic stroke: a systematic review

Hemorrhagic stroke (HS) is a major cause of death and disability worldwide, despite being less common, it presents more aggressively and leads to more severe sequelae than ischemic stroke. There are two types of HS: Intracerebral Hemorrhage (ICH) and Subarachnoid Hemorrhage (SAH), differing not only in the site of bleeding, but also in the mechanisms responsible for acute and subacute symptoms. This is a systematic review of databases in search of works of the last five years relating to the comprehension of both kinds of HS. Sixty two articles composed the direct findings of the recent literature and were further characterized to construct the pathophysiology in the order of events. The road to the understanding of the spontaneous HS pathophysiology is far from complete. Our findings show specific and individual results relating to the natural history of the disease of ICH and SAH, presenting common and different risk factors, distinct and similar clinical manifestations at onset or later days to weeks, and possible complications for both.

Low-Dose IL-2 Treatment Affords Protection against Subarachnoid Hemorrhage Injury by Expanding Peripheral Regulatory T Cells

Subarachnoid hemorrhage (SAH) is considered a devastating disease, leaving survivors with lifelong neurological impairment. With increased knowledge that regulatory T cells (Tregs) provide protection against stroke, novel agents which could expand Treg populations have been assessed in terms of the potential clinical neuroprotection effect. Using a rat SAH model, we investigated the number variation of Tregs induced by SAH and the protective effect of low-dose interleukin-2 (IL-2) treatment on the SAH model. We observed that the number of peripheral Tregs significantly decreased soon after SAH, accompanying with reactivity recovery after 3 days. Our results also revealed that low-dose IL-2 treatment not only elevated Tregs numbers but significantly reduced neuronal injury and improved neurological functions up to 21 days (d) after SAH. Furthermore, compared with PBS-treatment group, cerebral proinflammatory factors and peripheral neutrophils were significantly suppressed by low-dose IL-2 after SAH. Therefore, the results suggest that low-dose IL-2 treatment is a novel and clinically feasible immunotherapy to improve long-term outcomes after SAH, perhaps via up-regulating Treg population to suppress neuroinflammation induced by SAH.

Using Cerebral Metabolites to Guide Precision Medicine for Subarachnoid Hemorrhage: Lactate and Pyruvate

Subarachnoid hemorrhage (SAH) is one of the deadliest types of strokes with high rates of morbidity and permanent injury. Fluctuations in the levels of cerebral metabolites following SAH can be indicators of brain injury severity. Specifically, the changes in the levels of key metabolites involved in cellular metabolism, lactate and pyruvate, can be used as a biomarker for patient prognosis and tailor treatment to an individual’s needs. Here, clinical research is reviewed on the usefulness of cerebral lactate and pyruvate measurements as a predictive tool for SAH outcomes and their potential to guide a precision medicine approach to treatment.