The bidirectional gut-brain-microbiota axis as a potential nexus between traumatic brain injury, inflammation, and disease

Bidirectional regulation of the brain-gut-microbiota axis following traumatic brain injury

JOURNAL/nrgr/04.03/01300535-202508000-00002/figure1/v/2024-09-30T120553Z/r/image-tiff Traumatic brain injury is a prevalent disorder of the central nervous system. In addition to primary brain parenchymal damage, the enduring biological consequences of traumatic brain injury pose long-term risks for patients with traumatic brain injury; however, the underlying pathogenesis remains unclear, and effective intervention methods are lacking. Intestinal dysfunction is a significant consequence of traumatic brain injury. Being the most densely innervated peripheral tissue in the body, the gut possesses multiple pathways for the establishment of a bidirectional "brain-gut axis" with the central nervous system. The gut harbors a vast microbial community, and alterations of the gut niche contribute to the progression of traumatic brain injury and its unfavorable prognosis through neuronal, hormonal, and immune pathways. A comprehensive understanding of microbiota-mediated peripheral neuroimmunomodulation mechanisms is needed to enhance treatment strategies for traumatic brain injury and its associated complications. We comprehensively reviewed alterations in the gut microecological environment following traumatic brain injury, with a specific focus on the complex biological processes of peripheral nerves, immunity, and microbes triggered by traumatic brain injury, encompassing autonomic dysfunction, neuroendocrine disturbances, peripheral immunosuppression, increased intestinal barrier permeability, compromised responses of sensory nerves to microorganisms, and potential effector nuclei in the central nervous system influenced by gut microbiota. Additionally, we reviewed the mechanisms underlying secondary biological injury and the dynamic pathological responses that occur following injury to enhance our current understanding of how peripheral pathways impact the outcome of patients with traumatic brain injury. This review aimed to propose a conceptual model for future risk assessment of central nervous system-related diseases while elucidating novel insights into the bidirectional effects of the "brain-gut-microbiota axis."

Probiotic therapy modulates the brain-gut-liver microbiota axis in a mouse model of traumatic brain injury

The interplay between gut microbiota and host health is crucial for maintaining the overall health of the body and brain, and it is even more crucial how changes in the bacterial profile can influence the aftermath of traumatic brain injury (TBI). We studied the effects of probiotic treatment after TBI to identify potential changes in hepatic lipid species relevant to brain function. Bioinformatic analysis of the gut microbiota indicated a significant increase in the Firmicutes/Bacteroidetes ratio in the probiotic-treated TBI group compared to sham and untreated TBI groups. Although strong correlations between gut bacteria and hepatic lipids were found in sham mice, TBI disrupted these links, and probiotic treatment did not fully restore them. Probiotic treatment influenced systemic glucose metabolism, suggesting altered metabolic regulation. Behavioral tests confirmed memory improvement in probiotic-treated TBI mice. While TBI reduced hippocampal mRNA expression of CaMKII and CREB, probiotics reversed these effects yet did not alter BDNF mRNA levels. Elevated pro-inflammatory markers TNF-α and IL1-β in TBI mice were not significantly affected by probiotic treatment, pointing to different mechanisms underlying the probiotic benefits. In summary, our study suggests that TBI induces dysbiosis, alters hepatic lipid profiles, and preemptive administration of Lactobacillus helveticus and Bifidobacterium longum probiotics can counter neuroplasticity deficits and memory impairment. Altogether, these findings highlight the potential of probiotics for attenuating TBI's detrimental cognitive and metabolic effects through gut microbiome modulation and hepatic lipidomic alteration, laying the groundwork for probiotics as a potential TBI therapy.

Evaluating genetic insights into ulcerative colitis and anxiety: Limitations and future directions

We reviewed the study by He et al, which investigates the genetic correlation between ulcerative colitis (UC) and anxiety using bidirectional Mendelian randomization. This study reveals a genetic link between UC and anxiety, diverging from prior research associating higher anxiety with Crohn’s disease. While the study's use of large-scale genome-wide association studies data is commendable, it faces limitations such as single nucleotide polymorphism selection biases, lack of multiple testing corrections, and a reliance on European populations. Future research should address these limitations, incorporate diverse populations, and explore psychotherapeutic interventions to improve UC management and patient outcomes.

From gut to brain: unveiling probiotic effects through a neuroimaging perspective-A systematic review of randomized controlled trials

The gut-brain axis, a bidirectional communication network between the gastrointestinal system and the brain, significantly influences mental health and behavior. Probiotics, live microorganisms conferring health benefits, have garnered attention for their potential to modulate this axis. However, their effects on brain function through gut microbiota modulation remain controversial. This systematic review examines the effects of probiotics on brain activity and functioning, focusing on randomized controlled trials using both resting-state and task-based functional magnetic resonance imaging (fMRI) methodologies. Studies investigating probiotic effects on brain activity in healthy individuals and clinical populations (i.e., major depressive disorder and irritable bowel syndrome) were identified. In healthy individuals, task-based fMRI studies indicated that probiotics modulate brain activity related to emotional regulation and cognitive processing, particularly in high-order areas such as the amygdala, precuneus, and orbitofrontal cortex. Resting-state fMRI studies revealed changes in connectivity patterns, such as increased activation in the Salience Network and reduced activity in the Default Mode Network. In clinical populations, task-based fMRI studies showed that probiotics could normalize brain function in patients with major depressive disorder and irritable bowel syndrome. Resting-state fMRI studies further suggested improved connectivity in mood-regulating networks, specifically in the subcallosal cortex, amygdala and hippocampus. Despite promising findings, methodological variability and limited sample sizes emphasize the need for rigorous, longitudinal research to clarify the beneficial effects of probiotics on the gut-brain axis and mental health.

The role of nutrition in mild traumatic brain injury rehabilitation for service members and veterans

BACKGROUND

Veterans Affairs and the Department of Defense (DOD) acknowledge that nutrition may be a modifier of mild traumatic brain injury (TBI) sequelae. Military clinicians are considering nutritional supplements and dietary interventions when managing patients with mild TBI. Therefore, clinicians should be familiar with the current evidence for nutritional interventions in mild TBI and special considerations related to the military lifestyle.

OBJECTIVE

This narrative review aims to summarize the existing evidence surrounding the role of special diets and select nutrients in mild TBI outcomes, gut microbiota changes, and special considerations for Service members and Veterans recovering from mild TBI.

METHODS

We conducted a literature review in PubMed and Google Scholar limited to nutritional interventions and nine topics with primary focus on mild TBI, although we included some articles related to moderate-to-severe TBI where relevant: 1) ketogenic diet, 2) Mediterranean-DASH Intervention for Neurodegenerative Delay (MIND) diet, 3) omega-3 fatty acids, 4) creatine, 5) vitamin D, 6) weight management, 7) gut microbiota, 8) caffeine, and 9) alcohol. We summarized key findings and safety factors where appropriate for each intervention. We also identified nutritional supplement safety and operational rations considerations and areas in need of further research.

RESULTS

Preclinical studies and early human trials suggest that the specific nutrients and diets discussed in the current article may offer neuroprotection or benefit during mild TBI rehabilitation. Omega-3 fatty acids, creatine, and vitamin D are generally safe when taken within recommended guidelines.

CONCLUSION

More evidence is needed to support nutritional recommendations for enhancing neuroprotection and mitigating mild TBI symptoms in humans. The DOD's Warfighter Nutrition Guide recommends a whole food diet rich in antioxidants, phytonutrients, omega-3 fatty acids, micronutrients, probiotics, and fiber to optimize long-term health and performance.

Critical Knowledge Gaps and Future Priorities Regarding the Intestinal Barrier Damage After Traumatic Brain Injury

The analysis aims to provide a comprehensive understanding of the current landscape of research on the Intestinal barrier damage after traumatic brain injury (TBI), elucidate specific mechanisms, and address knowledge gaps to help guide the development of targeted therapeutic interventions and improve outcomes for individuals with TBI. A total of 2756 relevant publications by 13,778 authors affiliated within 3198 institutions in 79 countries were retrieved from the Web of Science. These publications have been indexed by 1139 journals and cited 158, 525 references. The most productive author in this field was Sikiric P, and the University of Pittsburgh was identified as the most influential institution. The United States was found to be the leading country in terms of article output and held a dominant position in this field. The International Journal of Molecular Sciences was identified as a major source of publications in this area. In terms of collaboration, the cooperation between the United States and China was found to be the most extensive among countries, institutions, and authors, indicating a high level of influence in this field. Keyword co-occurrence network analysis revealed several hotspots in this field, including the microbiome-gut-brain axis, endoplasmic reticulum stress, cellular autophagy, ischemia-reperfusion, tight junctions, and intestinal permeability. The analysis of keyword citation bursts suggested that ecological imbalance and gut microbiota may be the forefront of future research. The findings of this study can serve as a reference and guiding perspective for future research in this field.

Exposure to hexafluoropropylene oxide trimer acid (HFPO-TA) impairs 5-HT metabolism by impacting the brain-gut axis in mice

Hexafluoropropylene oxide trimer acid (HFPO-TA) has been found to cause hepatotoxicity, lipotoxicity, and cytotoxicity. However, the effects of HFPO-TA exposure on nervous system toxicity are still unclear. Here, six-week-old male C57BL/6J mice were treated with 2, 20, and 200 μg/L HFPO-TA for six weeks. The untargeted transcriptome analysis was employed to identify differentially expressed mRNAs in the tissue of mouse hippocampi. Then, the levels of neurotransmitters were detected by ELISA analysis in hippocampal and colonic tissues. Real-time quantitative PCR and western blotting analysis were performed to detect the expression of genes associated with modulation of serotonin (5-HT) metabolism and blood-brain barrier. HFPO-TA exposure reduced the mRNA and protein expression of several tight junction protein-coded genes, including Occludin, Claudin-1, and ZO-1, in mice hippocampi, indicating that the blood-brain barrier was disrupted. Moreover, HFPO-TA exposure elevated the expression of neuroinflammatory factors, including TNF-α, IL-6, IL-1β, TGF-α, and TGF-β. Analysis of hippocampal transcriptomics suggested that HFPO-TA exposure would impair 5-HT generation and metabolic pathways. In keeping with this prediction, our findings confirmed that the levels of several neurotransmitters, including tryptophan (TRP), 5-HT, 5-HTP, and 5-HIAA, were all impaired by HFPO-TA exposure in the serum, colon, and hippocampus, as was the colonic and hippocampal expression of TRP and 5-HT metabolism-related genes such as SERT, MAO-A, and IDO. These results suggest that HFPO-TA nervous system toxicity in mice may be partly modulated by the brain-gut axis and that HFPO-TA exposure may negatively impact human mental health.

Prevotella copri transplantation promotes neurorehabilitation in a mouse model of traumatic brain injury

BACKGROUND

The gut microbiota plays a critical role in regulating brain function through the microbiome-gut-brain axis (MGBA). Dysbiosis of the gut microbiota is associated with neurological impairment in Traumatic brain injury (TBI) patients. Our previous study found that TBI results in a decrease in the abundance of Prevotella copri (P. copri). P. copri has been shown to have antioxidant effects in various diseases. Meanwhile, guanosine (GUO) is a metabolite of intestinal microbiota that can alleviate oxidative stress after TBI by activating the PI3K/Akt pathway. In this study, we investigated the effect of P. copri transplantation on TBI and its relationship with GUO-PI3K/Akt pathway.

METHODS

In this study, a controlled cortical impact (CCI) model was used to induce TBI in adult male C57BL/6J mice. Subsequently, P. copri was transplanted by intragastric gavage for 7 consecutive days. To investigate the effect of the GUO-PI3K/Akt pathway in P. copri transplantation therapy, guanosine (GUO) was administered 2 h after TBI for 7 consecutive days, and PI3K inhibitor (LY294002) was administered 30 min before TBI. Various techniques were used to assess the effects of these interventions, including quantitative PCR, neurological behavior tests, metabolite analysis, ELISA, Western blot analysis, immunofluorescence, Evans blue assays, transmission electron microscopy, FITC-dextran permeability assay, gastrointestinal transit assessment, and 16 S rDNA sequencing.

RESULTS

P. copri abundance was significantly reduced after TBI. P. copri transplantation alleviated motor and cognitive deficits tested by the NSS, Morris's water maze and open field test. P. copri transplantation attenuated oxidative stress and blood-brain barrier damage and reduced neuronal apoptosis after TBI. In addition, P. copri transplantation resulted in the reshaping of the intestinal flora, improved gastrointestinal motility and intestinal permeability. Metabolomics and ELISA analysis revealed a significant increase in GUO levels in feces, serum and injured brain after P. copri transplantation. Furthermore, the expression of p-PI3K and p-Akt was found to be increased after P. copri transplantation and GUO treatment. Notably, PI3K inhibitor LY294002 treatment attenuated the observed improvements.

CONCLUSIONS

We demonstrate for the first time that P. copri transplantation can improve GI functions and alter gut microbiota dysbiosis after TBI. Additionally, P. copri transplantation can ameliorate neurological deficits, possibly via the GUO-PI3K/Akt signaling pathway after TBI.

Effect of prednisolone in a kindling model of epileptic seizures in rats on cytokine and intestinal microbiota diversity

Epilepsy is a neurological disease characterized by spontaneous and recurrent seizures. Epileptic seizures can be initiated and facilitated by inflammatory mechanisms. As the dysregulation of the immune system would be involved in epileptogenesis, it is suggested that anti-inflammatory medications could impact epileptic seizures. These medications could potentially have a side effect by altering the structure and composition of the intestinal microbiota. These changes can disrupt microbial homeostasis, leading to dysbiosis and potentially exacerbating intestinal inflammation. We hypothesize that prednisolone may affect the development of epileptic seizures, potentially influencing the diversity of the intestinal microbiota and the regulation of pro-inflammatory cytokines in intestinal tissue. This study aimed to evaluate the effects of prednisolone treatment on epileptic seizures and investigate the effect of this drug on the bacterial diversity of the intestinal microbiota and markers of inflammatory processes in intestinal tissue. We used Male Wistar rat littermates (n = 31, 90-day-old) divided into four groups: positive control treated with 2 mg/kg of diazepam (n = 6), negative control treated with 0.9 g% sodium chloride (n = 6), and the remaining two groups were subjected to treatment with prednisolone, with one receiving 1 mg/kg (n = 9) and the other 5 mg/kg (n = 10). All administrations were performed intraperitoneally (i.p.) over 14 days. To induce the chronic model of epileptic seizures, we administered pentylenetetrazole (PTZ) 25 mg/kg i.p. on alternate days. Seizure latency (n = 6 - 10) and TNF-α and IL-1β concentrations from intestinal samples were measured by ELISA (n = 6 per group), and intestinal microbiota was evaluated with intergenic ribosomal RNA (rRNA) spacer (RISA) analysis (n = 6 per group). The prednisolone treatment demonstrated an increase in the latency time of epileptic seizures and TNF-α and IL-1β concentrations compared to controls. There was no statistically significant difference in intestinal microbiota diversity between the different treatments. However, there was a strong positive correlation between microbial diversity and TNF-α and IL-1β concentrations. The administration of prednisolone yields comparable results to diazepam on increasing latency between seizures, exhibiting promise for its use in clinical studies. Although there were no changes in intestinal microbial diversity, the increase in the TNF-α and IL-1β cytokines in intestinal tissue may be linked to immune system signaling pathways involving the intestinal microbiota. Additional research is necessary to unravel the intricacies of these pathways and to understand their implications for clinical practice.

From Gut to Brain: Uncovering Potential Serum Biomarkers Connecting Inflammatory Bowel Diseases to Neurodegenerative Diseases

Inflammatory bowel diseases (IBDs) are characterized by chronic gastrointestinal inflammation due to abnormal immune responses to gut microflora. The gut-brain axis is disrupted in IBDs, leading to neurobiological imbalances and affective symptoms. Systemic inflammation in IBDs affects the brain's inflammatory response system, hormonal axis, and blood-brain barrier integrity, influencing the gut microbiota. This review aims to explore the association between dysregulations in the gut-brain axis, serum biomarkers, and the development of cognitive disorders. Studies suggest a potential association between IBDs and the development of neurodegeneration. The mechanisms include systemic inflammation, nutritional deficiency, GBA dysfunction, and the effect of genetics and comorbidities. The objective is to identify potential correlations and propose future research directions to understand the impact of altered microbiomes and intestinal barrier functions on neurodegeneration. Serum levels of vitamins, inflammatory and neuronal damage biomarkers, and neuronal growth factors have been investigated for their potential to predict the development of neurodegenerative diseases, but current results are inconclusive and require more studies.

Importance of good hosting: reviewing the bi-directionality of the microbiome-gut-brain-axis

Gut microorganisms have been shown to significantly impact on central function and studies that have associated brain disorders with specific bacterial genera have advocated an anomalous gut microbiome as the pathophysiological basis of several psychiatric and neurological conditions. Thus, our knowledge of brain-to-gut-to microbiome communication in this bidirectional axis seems to have been overlooked. This review examines the known mechanisms of the microbiome-to-gut-to-brain axis, highlighting how brain-to-gut-to-microbiome signaling may be key to understanding the cause of disrupted gut microbial communities. We show that brain disorders can alter the function of the brain-to-gut-to-microbiome axis, which will in turn contribute to disease progression, while the microbiome-to gut-to brain direction presents as a more versatile therapeutic axis, since current psychotropic/neurosurgical interventions may have unwanted side effects that further cause disruption to the gut microbiome. A consideration of the brain-to-gut-to-microbiome axis is imperative to better understand how the microbiome-gut-brain axis overall is involved in brain illnesses, and how it may be utilized as a preventive and therapeutic tool.

Early-life stress and the gut microbiome: A comprehensive population-based investigation

Early-life stress (ELS) has been robustly associated with a range of poor mental and physical health outcomes. Recent studies implicate the gut microbiome in stress-related mental, cardio-metabolic and immune health problems, but research on humans is scarce and thus far often based on small, selected samples, often using retrospective reports of ELS. We examined associations between ELS and the human gut microbiome in a large, population-based study of children. ELS was measured prospectively from birth to 10 years of age in 2,004 children from the Generation R Study. We studied overall ELS, as well as unique effects of five different ELS domains, including life events, contextual risk, parental risk, interpersonal risk, and direct victimization. Stool microbiome was assessed using 16S rRNA sequencing at age 10 years and data were analyzed at multiple levels (i.e. α- and β-diversity indices, individual genera and predicted functional pathways). In addition, we explored potential mediators of ELS-microbiome associations, including diet at age 8 and body mass index at 10 years. While no associations were observed between overall ELS (composite score of five domains) and the microbiome after multiple testing correction, contextual risk - a specific ELS domain related to socio-economic stress, including risk factors such as financial difficulties and low maternal education - was significantly associated with microbiome variability. This ELS domain was associated with lower α-diversity, with β-diversity, and with predicted functional pathways involved, amongst others, in tryptophan biosynthesis. These associations were in part mediated by overall diet quality, a pro-inflammatory diet, fiber intake, and body mass index (BMI). These results suggest that stress related to socio-economic adversity - but not overall early life stress - is associated with a less diverse microbiome in the general population, and that this association may in part be explained by poorer diet and higher BMI. Future research is needed to test causality and to establish whether modifiable factors such as diet could be used to mitigate the negative effects of socio-economic adversity on the microbiome and related health consequences.

The protective effects of statins in traumatic brain injury

Traumatic brain injury (TBI), often referred to as the "silent epidemic", is the most common cause of mortality and morbidity worldwide among all trauma-related injuries. It is associated with considerable personal, medical, and economic consequences. Although remarkable advances in therapeutic approaches have been made, current treatments and clinical management for TBI recovery still remain to be improved. One of the factors that may contribute to this gap is that existing therapies target only a single event or pathology. However, brain injury after TBI involves various pathological mechanisms, including inflammation, oxidative stress, blood-brain barrier (BBB) disruption, ionic disturbance, excitotoxicity, mitochondrial dysfunction, neuronal necrosis, and apoptosis. Statins have several beneficial pleiotropic effects (anti-excitotoxicity, anti-inflammatory, anti-oxidant, anti-thrombotic, immunomodulatory activity, endothelial and vasoactive properties) in addition to promoting angiogenesis, neurogenesis, and synaptogenesis in TBI. Supposedly, using agents such as statins that target numerous and diverse pathological mechanisms, may be more effective than a single-target approach in TBI management. The current review was undertaken to investigate and summarize the protective mechanisms of statins against TBI. The limitations of conducted studies and directions for future research on this potential therapeutic application of statins are also discussed.

Pathophysiology of acute lung injury in patients with acute brain injury: the triple-hit hypothesis

It has been convincingly demonstrated in recent years that isolated acute brain injury (ABI) may cause severe dysfunction of peripheral extracranial organs and systems. Of all potential target organs and systems, the lung appears to be the most vulnerable to damage after ABI. The pathophysiology of the bidirectional brain-lung interactions is multifactorial and involves inflammatory cascades, immune suppression, and dysfunction of the autonomic system. Indeed, the systemic effects of inflammatory mediators in patients with ABI create a systemic inflammatory environment ("first hit") that makes extracranial organs vulnerable to secondary procedures that enhance inflammation, such as mechanical ventilation (MV), surgery, and infections ("second hit"). Moreover, accumulating evidence supports the knowledge that gut microbiota constitutes a critical superorganism and an organ on its own, potentially modifying various physiological functions of the host. Furthermore, experimental and clinical data suggest the existence of a communication network among the brain, gastrointestinal tract, and its microbiome, which appears to regulate immune responses, gastrointestinal function, brain function, behavior, and stress responses, also named the "gut-microbiome-brain axis." Additionally, recent research evidence has highlighted a crucial interplay between the intestinal microbiota and the lungs, referred to as the "gut-lung axis," in which alterations during critical illness could result in bacterial translocation, sustained inflammation, lung injury, and pulmonary fibrosis. In the present work, we aimed to further elucidate the pathophysiology of acute lung injury (ALI) in patients with ABI by attempting to develop the "double-hit" theory, proposing the "triple-hit" hypothesis, focused on the influence of the gut-lung axis on the lung. Particularly, we propose, in addition to sympathetic hyperactivity, blast theory, and double-hit theory, that dysbiosis and intestinal dysfunction in the context of ABI alter the gut-lung axis, resulting in the development or further aggravation of existing ALI, which constitutes the "third hit."

Current state of neuroprotective therapy using antibiotics in human traumatic brain injury and animal models

TBI is a leading cause of death and disability in young people and older adults worldwide. There is no gold standard treatment for TBI besides surgical interventions and symptomatic relief. Post-injury infections, such as lower respiratory tract and surgical site infections or meningitis are frequent complications following TBI. Whether the use of preventive and/or symptomatic antibiotic therapy improves patient mortality and outcome is an ongoing matter of debate. In contrast, results from animal models of TBI suggest translational perspectives and support the hypothesis that antibiotics, independent of their anti-microbial activity, alleviate secondary injury and improve neurological outcomes. These beneficial effects were largely attributed to the inhibition of neuroinflammation and neuronal cell death. In this review, we briefly outline current treatment options, including antibiotic therapy, for patients with TBI. We then summarize the therapeutic effects of the most commonly tested antibiotics in TBI animal models, highlight studies identifying molecular targets of antibiotics, and discuss similarities and differences in their mechanistic modes of action.

Fecal microbiota transplantation unveils sex-specific differences in a controlled cortical impact injury mouse model

Introduction

Contusion type of traumatic brain injury (TBI) is a major cause of locomotor disability and mortality worldwide. While post-TBI deleterious consequences are influenced by gender and gut dysbiosis, the sex-specific importance of commensal gut microbiota is underexplored after TBI. In this study, we investigated the impact of controlled cortical impact (CCI) injury on gut microbiota signature in a sex-specific manner in mice.

Methods

We depleted the gut microflora of male and female C57BL/6 mice using antibiotic treatment. Thereafter, male mice were colonized by the gut microbiota of female mice and vice versa, employing the fecal microbiota transplantation (FMT) method. CCI surgery was executed using a stereotaxic impactor (Impact One™). For the 16S rRNA gene amplicon study, fecal boli of mice were collected at 3 days post-CCI (dpi).

Results and discussion

CCI-operated male and female mice exhibited a significant alteration in the genera of Akkermansia, Alistipes, Bacteroides, Clostridium, Lactobacillus, Prevotella, and Ruminococcus. At the species level, less abundance of Lactobacillus helveticus and Lactobacillus hamsteri was observed in female mice, implicating the importance of sex-specific bacteriotherapy in CCI-induced neurological deficits. FMT from female donor mice to male mice displayed an increase in genera of Alistipes, Lactobacillus, and Ruminococcus and species of Bacteroides acidifaciens and Ruminococcus gnavus. Female FMT-recipient mice from male donors showed an upsurge in the genus Lactobacillus and species of Lactobacillus helveticus, Lactobacillus hamsteri, and Prevotella copri. These results suggest that the post-CCI neurological complications may be influenced by the differential gut microbiota perturbation in male and female mice.

Investigating metabolic dysregulation in serum of triple transgenic Alzheimer's disease male mice: implications for pathogenesis and potential biomarkers

Alzheimer's disease (AD) is a multifactorial neurodegenerative disease that lacks convenient and accessible peripheral blood diagnostic markers and effective drugs. Metabolic dysfunction is one of AD risk factors, which leaded to alterations of various metabolites in the body. Pathological changes of the brain can be reflected in blood metabolites that are expected to explain the disease mechanisms or be candidate biomarkers. The aim of this study was to investigate the changes of targeted metabolites within peripheral blood of AD mouse model, with the purpose of exploring the disease mechanism and potential biomarkers. Targeted metabolomics was used to quantify 256 metabolites in serum of triple transgenic AD (3 × Tg-AD) male mice. Compared with controls, 49 differential metabolites represented dysregulation in purine, pyrimidine, tryptophan, cysteine and methionine and glycerophospholipid metabolism. Among them, adenosine, serotonin, N-acetyl-5-hydroxytryptamine, and acetylcholine play a key role in regulating neural transmitter network. The alteration of S-adenosine-L-homocysteine, S-adenosine-L-methionine, and trimethylamine-N-oxide in AD mice serum can served as indicator of AD risk. The results revealed the changes of metabolites in serum, suggesting that metabolic dysregulation in periphery in AD mice may be related to the disturbances in neuroinhibition, the serotonergic system, sleep function, the cholinergic system, and the gut microbiota. This study provides novel insights into the dysregulation of several key metabolites and metabolic pathways in AD, presenting potential avenues for future research and the development of peripheral biomarkers.

Diet-gut microbiome interaction and ferulic acid bioavailability: implications on neurodegenerative disorders

PURPOSE OF THE REVIEW

Ferulic acid (FA), which occurs naturally as the feruloylated sugar ester in grains, fruits, and vegetables, is critical for combating oxidative stress and alleviating neurodegenerative diseases resulting from free radical-generated protein aggregates in brain cells. However, FA cannot be absorbed in conjugated form. Therefore, strategies to improve the bioavailability of FA are gaining more importance. Ferulic acid esterases (FAE) of the gut microbiota are critical enzymes that facilitate FA release from feruloylated sugar ester conjugates and influence systemic health. This review provides insight into a nutrition-based approach to preventing neurodegenerative disorders such as Alzheimer's and Parkinson's by altering the diversity of FAE-producing gut microbiota.

RECENT FINDINGS

The human gut is a niche for a highly dense microbial population. Nutrient components and the quality of food shape the gut microbiota. Microbiota-diet-host interaction primarily involves an array of enzymes that hydrolyse complex polysaccharides and release covalently attached moieties, thereby increasing their bio-accessibility. Moreover, genes encoding polysaccharide degrading enzymes are substrate inducible, giving selective microorganisms a competitive advantage in scavenging nutrients. Nutraceutical therapy using specific food components holds promise as a prophylactic agent and as an adjunctive treatment strategy in neurotherapeutics, as it results in upregulation of polysaccharide utilisation loci containing fae genes in the gut microbiota, thereby increasing the release of FA and other antioxidant molecules and combat neurodegenerative processes.

Making migraine easier to stomach: the role of the gut-brain-immune axis in headache disorders

BACKGROUND AND PURPOSE

Headache disorders place a significant burden on the healthcare system, being the leading cause of disability in those under 50 years. Novel studies have interrogated the relationship between headache disorders and gastrointestinal dysfunction, suggesting a link between the gut-brain-immune (GBI) axis and headache pathogenesis. Although the exact mechanisms driving the complex relationship between the GBI axis and headache disorders remain unclear, there is a growing appreciation that a healthy and diverse microbiome is necessary for optimal brain health.

METHODS

A literature search was performed through multiple reputable databases in search of Q1 journals within the field of headache disorders and gut microbiome research and were critically and appropriately evaluated to investigate and explore the following; the role of the GBI axis in dietary triggers of headache disorders and the evidence indicating that diet can be used to alleviate headache severity and frequency. The relationship between the GBI axis and post-traumatic headache is then synthesized. Finally, the scarcity of literature regarding paediatric headache disorders and the role that the GBI axis plays in mediating the relationship between sex hormones and headache disorders are highlighted.

CONCLUSIONS

There is potential for novel therapeutic targets for headache disorders if understanding of the GBI axis in their aetiology, pathogenesis and recovery is increased.

Plasma D-dimer levels are a biomarker for in-hospital complications and long-term mortality in patients with traumatic brain injury

Introduction

Traumatic brain injury (TBI) is a major health concern worldwide. D-dimer levels, commonly used in the diagnosis and treatment of neurological diseases, may be associated with adverse events in patients with TBI. However, the relationship between D-dimer levels, TBI-related in-hospital complications, and long-term mortality in patients with TBI has not been investigated. Here, examined whether elevated D-dimer levels facilitate the prediction of in-hospital complications and mortality in patients with TBI.

Methods

Overall, 1,338 patients with TBI admitted to our institute between January 2016 and June 2022 were retrospectively examined. D-dimer levels were assessed within 24 h of admission, and propensity score matching was used to adjust for baseline characteristics.

Results

Among the in-hospital complications, high D-dimer levels were associated with electrolyte metabolism disorders, pulmonary infections, and intensive care unit admission (p < 0.05). Compared with patients with low (0.00-1.54 mg/L) D-dimer levels, the odds of long-term mortality were significantly higher in all other patients, including those with D-dimer levels between 1.55 mg/L and 6.35 mg/L (adjusted hazard ratio [aHR] 1.655, 95% CI 0.9632.843), 6.36 mg/L and 19.99 mg/L (aHR 2.38, 95% CI 1.416-4.000), and >20 mg/L (aHR 3.635, 95% CI 2.195-6.018; p < 0.001). D-dimer levels were positively correlated with the risk of death when the D-dimer level reached 6.82 mg/L.

Conclusion

Overall, elevated D-dimer levels at admission were associated with adverse outcomes and may predict poor prognosis in patients with TBI. Our findings will aid in the acute diagnosis, classification, and management of TBI.

"Sentinel or accomplice": gut microbiota and microglia crosstalk in disorders of gut-brain interaction

Abnormal brain-gut interaction is considered the core pathological mechanism behind the disorders of gut-brain interaction (DGBI), in which the intestinal microbiota plays an important role. Microglia are the "sentinels" of the central nervous system (CNS), which participate in tissue damage caused by traumatic brain injury, resist central infection and participate in neurogenesis, and are involved in the occurrence of various neurological diseases. With in-depth research on DGBI, we could find an interaction between the intestinal microbiota and microglia and that they are jointly involved in the occurrence of DGBI, especially in individuals with comorbidities of mental disorders, such as irritable bowel syndrome (IBS). This bidirectional regulation of microbiota and microglia provides a new direction for the treatment of DGBI. In this review, we focus on the role and underlying mechanism of the interaction between gut microbiota and microglia in DGBI, especially IBS, and the corresponding clinical application prospects and highlight its potential to treat DGBI in individuals with psychiatric comorbidities.

Gut Microbiota Regulates Epigenetic Remodelling in the Amygdala: A Role in Repeated Mild Traumatic Brain Injury (rMTBI)-Induced Anxiety

Gut microbiota serves in the development and maintenance of phenotype. However, the underlying mechanisms are still in its infancy. The current study shows epigenetic remodelling in the brain as a causal mechanism in the gut microbiota-brain axis. Like in trauma patients, gut dysbiosis and anxiety were comorbid in adult male Wistar rats subjected to repeated mild traumatic brain injuries (rMTBI). rMTBI caused epigenetic dysregulation of brain-derived neurotrophic factor (Bdnf) expression in the amygdala, owing to the formation of transcriptional co-repressor complex due to dynamic interaction between histone deacetylase and DNA methylation modification at the Bdnf gene promoter. The probiosis after faecal microbiota transplantation (FMT) from healthy naïve rats or by administration of single strain probiotic (SSP), Lactobacillus rhamnosus GG (LGG), recuperated rMTBI-induced anxiety. Concurrently, LGG infusion or naïve FMT also dislodged rMTBI-induced co-repressor complex resulting in the normalization of Bdnf expression and neuronal plasticity as measured by Golgi-Cox staining. Furthermore, sodium butyrate, a short-chain fatty acid, produced neurobehavioural effects similar to naïve FMT or LGG administration. Interestingly, the gut microbiota from rMTBI-exposed rats per se was able to provoke anxiety in naïve rats in parallel with BDNF deficits. Therefore, gut microbiota seems to be causally linked with the chromatin remodelling necessary for neuroadaptations via neuronal plasticity which drives experience-dependent behavioural manifestations.

Bowel dysfunctions after acquired brain injury: a scoping review

Bowel dysfunction is a common consequence of neurological diseases and has a major impact on the dignity and quality of life of patients. Evidence on neurogenic bowel is focused on spinal cord injury and multiple sclerosis; few studies have focused on patients with acquired brain injury (ABI). Neurogenic bowel dysfunction is related to a lifelong condition derived from central neurological disease, which further increases disability and social deprivation. The manifestations of neurogenic bowel dysfunction include fecal incontinence and constipation. Almost two out of three patients with central nervous system disorder have bowel impairment. This scoping review aims to comprehend the extent and type of evidence on bowel dysfunction after ABI and present conservative treatment. For this scoping review, the PCC (population, concept, and context) framework was used: patients with ABI and bowel dysfunction; evaluation and treatment; and intensive/extensive rehabilitation path. Ten full-text articles were included in the review. Oral laxatives are the most common treatment. The Functional Independence Measure (FIM) subscale is the most common scale used to assess neurogenic bowel disease (60%), followed by the Rome II and III criteria, and the colon transit time is used to test for constipation; however, no instrumental methods have been used for incontinence. An overlapping between incontinence and constipation, SCI and ABI increase difficulties to manage NBD. The need for a consensus between the rehabilitative and gastroenterological societies on the diagnosis and medical care of NBD.

Systematic review registration

Open Science Framework on August 16, 2022 https://doi.org/10.17605/OSF.IO/NEQMA.

Multiorgan talks in the presence of brain injury

PURPOSE OF REVIEW

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

RECENT FINDINGS

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

SUMMARY

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

Fecal microbial transplantation limits neural injury severity and functional deficits in a pediatric piglet traumatic brain injury model

Pediatric traumatic brain injury (TBI) is a leading cause of death and disability in children. Due to bidirectional communication between the brain and gut microbial population, introduction of key gut bacteria may mitigate critical TBI-induced secondary injury cascades, thus lessening neural damage and improving functional outcomes. The objective of this study was to determine the efficacy of a daily fecal microbial transplant (FMT) to alleviate neural injury severity, prevent gut dysbiosis, and improve functional recovery post TBI in a translational pediatric piglet model. Male piglets at 4-weeks of age were randomly assigned to Sham + saline, TBI + saline, or TBI + FMT treatment groups. A moderate/severe TBI was induced by controlled cortical impact and Sham pigs underwent craniectomy surgery only. FMT or saline were administered by oral gavage daily for 7 days. MRI was performed 1 day (1D) and 7 days (7D) post TBI. Fecal and cecal samples were collected for 16S rRNA gene sequencing. Ipsilateral brain and ileum tissue samples were collected for histological assessment. Gait and behavior testing were conducted at multiple timepoints. MRI showed that FMT treated animals demonstrated decreased lesion volume and hemorrhage volume at 7D post TBI as compared to 1D post TBI. Histological analysis revealed improved neuron and oligodendrocyte survival and restored ileum tissue morphology at 7D post TBI in FMT treated animals. Microbiome analysis indicated decreased dysbiosis in FMT treated animals with an increase in multiple probiotic Lactobacilli species, associated with anti-inflammatory therapeutic effects, in the cecum of the FMT treated animals, while non-treated TBI animals showed an increase in pathogenic bacteria, associated with inflammation and disease such in feces. FMT mediated enhanced cellular and tissue recovery resulted in improved motor function including stride and step length and voluntary motor activity in FMT treated animals. Here we report for the first time in a highly translatable pediatric piglet TBI model, the potential of FMT treatment to significantly limit cellular and tissue damage leading to improved functional outcomes following a TBI.

Microbiota-gut-brain axis mechanisms in the complex network of bipolar disorders: potential clinical implications and translational opportunities

Bipolar disorders (BD) represent a severe leading disabling mental condition worldwide characterized by episodic and often progressive mood fluctuations with manic and depressive stages. The biological mechanisms underlying the pathophysiology of BD remain incompletely understood, but it seems that there is a complex picture of genetic and environmental factors implicated. Nowadays, gut microbiota is in the spotlight of new research related to this kind of psychiatric disorder, as it can be consistently related to several pathophysiological events observed in BD. In the context of the so-called microbiota-gut-brain (MGB) axis, it is shown to have a strong influence on host neuromodulation and endocrine functions (i.e., controlling the synthesis of neurotransmitters like serotonin or mediating the activation of the hypothalamic-pituitary-adrenal axis), as well as in modulation of host immune responses, critically regulating intestinal, systemic and brain inflammation (neuroinflammation). The present review aims to elucidate pathophysiological mechanisms derived from the MGB axis disruption and possible therapeutic approaches mainly focusing on gut microbiota in the complex network of BD. Understanding the mechanisms of gut microbiota and its bidirectional communication with the immune and other systems can shed light on the discovery of new therapies for improving the clinical management of these patients. Besides, the effect of psychiatric drugs on gut microbiota currently used in BD patients, together with new therapeutical approaches targeting this ecosystem (dietary patterns, probiotics, prebiotics, and other novelties) will also be contemplated.

Host-Microbiome Interactions: Tryptophan Metabolism and Aromatic Hydrocarbon Receptors after Traumatic Brain Injury

Traumatic brain injury refers to the damage caused to intracranial tissues by an external force acting on the head, leading to both immediate and prolonged harmful effects. Neuroinflammatory responses play a critical role in exacerbating the primary injury during the acute and chronic phases of TBI. Research has demonstrated that numerous neuroinflammatory responses are mediated through the "microbiota-gut-brain axis," which signifies the functional connection between the gut microbiota and the brain. The aryl hydrocarbon receptor (AhR) plays a vital role in facilitating communication between the host and microbiota through recognizing specific ligands produced directly or indirectly by the microbiota. Tryptophan (trp), an indispensable amino acid in animals and humans, represents one of the key endogenous ligands for AhR. The metabolites of trp have significant effects on the functioning of the central nervous system (CNS) through activating AHR signalling, thereby establishing bidirectional communication between the gut microbiota and the brain. These interactions are mediated through immune, metabolic, and neural signalling mechanisms. In this review, we emphasize the co-metabolism of tryptophan in the gut microbiota and the signalling pathway mediated by AHR following TBI. Furthermore, we discuss the impact of these mechanisms on the underlying processes involved in traumatic brain injury, while also addressing potential future targets for intervention.

Pre-traumatic antibiotic-induced microbial depletion reduces neuroinflammation in acute murine traumatic brain injury

The connection between dysbiosis of the gut microbiome and diseases and injuries of the brain has attracted considerable interest in recent years. Interestingly, antibiotic-induced microbial dysbiosis has been implicated in the pathogenesis of traumatic brain injury (TBI), while early administration of antibiotics associates with improved survival in TBI patients. In animal models of TBI, short- or long-term administration of antibiotics, both peri- or post-operatively, were shown to induce gut microbiome dysbiosis but also anti-inflammatory and neuroprotective effects. However, the acute consequences of microbial dysbiosis on TBI pathogenesis after discontinuation of antibiotic treatment are elusive. In this study, we tested whether pre-traumatic antibiotic-induced microbial depletion by vancomycin, amoxicillin, and clavulanic acid affects pathogenesis during the acute phase of TBI in adult male C57BL/6 mice. Pre-traumatic microbiome depletion did not affect neurological deficits over 72 h post injury (hpi) and brain histopathology, including numbers of activated astrocytes and microglia, at 72 hpi. However, astrocytes and microglia were smaller after pre-traumatic microbiome depletion compared to vehicle treatment at 72hpi, indicating less inflammatory activation. Accordingly, TBI-induced gene expression of the inflammation markers Interleukin-1β, complement component C3, translocator protein TSPO and the major histocompatibility complex MHC2 was attenuated in microbiome-depleted mice along with reduced Immunoglobulin G extravasation as a proxy of blood-brain barrier (BBB) impairment. These results suggest that the gut microbiome contributes to early neuroinflammatory responses to TBI but does not have a significant impact on brain histopathology and neurological deficits.

Risk assessment model for sleep disturbance based on gastrointestinal myoelectrical activity in middle-aged and elderly people

Background

Sleep disturbance has become a considerable factor affecting the quality of life for middle-aged and elderly people; however, there are still many obstacles to screening sleep disturbance for those people. Given the growing awareness of the association between gastrointestinal function and sleep disturbance, our study aims to predict the risk of sleep disturbance using gastrointestinal electrophysiological signals.

Methods

The Pittsburgh Sleep Quality Index and gastrointestinal electrophysiological signals of 914 participants in western China were used to establish the model. Demographic characteristics and routine blood test were collected as covariates. Participants were randomly assigned into two sets with a 7:3 ratio for training and validation. In the training set, the least absolute shrinkage and selection operator (LASSO) regression and stepwise logistic regression were used, respectively for variables selection and optimization. To assess the model performance, receiver operator characteristic (ROC) curve, calibration curve and decision curve analysis (DCA) were utilized. Then, validation was performed.

Results

Thirteen predictors were chosen from 46 variables by LASSO regression. Then, age, gender, percentage of normal slow wave and electrical spreading rate on the pre-meal gastric channel, dominant power ratio on the post-meal gastric channel, coupling percent and dominant frequency on the post-meal intestinal channel were the seven predictors reserved by logistic regression. The area under ROC curve was 0.65 in the training set and 0.63 in the validation set, both exhibited moderate predictive ability. Furthermore, by overlapping the DCA results of two data-sets, there might be clinical net benefit if 0.35 was used as reference threshold for high risk of sleep disturbance.

Conclusion

The model performs a worthy predictive potency for sleep disturbance, which not only provides clinical evidence for the association of gastrointestinal function with sleep disturbance, but also can be considered as an auxiliary assessment for screening sleep disturbance.

Fructus gardeniae ameliorates anxiety-like behaviors induced by sleep deprivation via regulating hippocampal metabolomics and gut microbiota

Fructus gardeniae (FG) is a traditional Chinese medicine and health food for thousands of years of application throughout Chinese history and is still widely used in clinical Chinese medicine. FG has a beneficial impact on anxiety, depression, insomnia, and psychiatric disorders; however, its mechanism of action requires further investigation. This study aimed to investigate the effects and mechanisms of FG on sleep deprivation (SD)-induced anxiety-like behavior in rats. A model of SD-induced anxiety-like behavior in rats was established by intraperitoneal injection of p-chlorophenylalanine (PCPA). This was accompanied by neuroinflammation and metabolic abnormalities in the hippocampus and disturbance of intestinal microbiota. However reduced SD-induced anxiety-like behavior and decreased levels of pro-inflammatory cytokines including TNF-α and IL-1β were observed in the hippocampus of rats after 7 days of FG intervention. In addition, metabolomic analysis demonstrated that FG was able to modulate levels of phosphatidylserine 18, Phosphatidylinositol 18, sn-glycero-3-phosphocholine, deoxyguanylic acid, xylose, betaine and other metabolites in the hippocampus. The main metabolic pathways of hippocampal metabolites after FG intervention involve carbon metabolism, glycolysis/gluconeogenesis, pentose phosphate, and glycerophospholipid metabolism. 16S rRNA sequencing illustrated that FG ameliorated the dysbiosis of gut microbiota in anxious rats, mainly increased the abundance of Muribaculaceae and Lactobacillus, and decreased the abundance of Lachnospiraceae_NK4A136_group. In addition, the correlation analysis demonstrated that there was a close relationship between hippocampal metabolites and intestinal microbiota. In conclusion, FG improved the anxiety behavior and inhibited of neuroinflammation in sleep-deprived rats, and the mechanism may be related to the FG regulation of hippocampal metabolites and intestinal microflora composition.

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.

TRAUMATIC BRAIN INJURY-INDUCED INFLAMMATION AND GASTROINTESTINAL MOTILITY DYSFUNCTION

ABSTRACT

Background: Traumatic brain injury (TBI) is a significant cause of morbidity and mortality in the United States, with an annual cost of 60 billion dollars. There is evidence suggesting that in the post-TBI period, the gastrointestinal tract plays a central role in driving organ and immune dysfunction and may be the source of increased circulating proinflammatory mediators. In this study, we examined systemic inflammation and bacterial dysbiosis in patients who sustained a TBI with or without polytrauma. Using a mouse model of TBI, we further show how neuroinflammation after TBI is potentially linked to disruptions in gut homeostasis such as intestinal transit and inflammation. Methods: During a study of trauma patients performed from September 1, 2018, to September 1, 2019, at a single, level 1 trauma center, TBI patients aged 21 to 95 years were enrolled. Patients were categorized as TBI based on evidence of acute abnormal findings on head computed tomographic scan, which was a combination of isolated TBI and TBI with polytrauma. Blood and stool samples were collected between 24 h and 3 days after admission. Twelve plasma samples and 10 fecal samples were used for this study. Healthy control samples were obtained from a healthy control biobank. We examined systemic inflammation and bacterial changes in patients who sustained a TBI. In addition, TBI was induced in 9- to 10-week-old male mice; we assessed neuroinflammation, and intestine transit (motility) and bacterial changes 24 h after TBI. Results: When compared with healthy controls, TBI patients had increased systemic inflammation as evidenced by increased levels of IFN-γ and MCP-1 and a trend toward an increase of IL-6 and IL-8 ( P = 0.0551 and P = 0.0549), respectively. The anti-inflammatory cytokine, IL-4, was also decreased in TBI patients. Although there was a trend of an increase in copy number of Enterobacteriaceae and a decrease in copy number of Lactobacillus in both patients and mice after TBI, these trends were not found to be significantly different. However, TBI significantly increased the copy number of another potential pathogenic bacteria Bilophila wadsworthia in TBI patients compared with healthy controls. After a moderate TBI, mice had increased expression of TNF-α, IL-6 and IL-1β, CXCL1, s100a9, and Ly6G and decreased IL-10 in the brain lesion after TBI. This accompanied decreased transit and increased TNF-α in the small intestine of mice after TBI. Conclusions: Our findings suggest that TBI increases systemic inflammation, intestinal dysfunction, and neuroinflammation. More studies are needed to confirm whether changes in intestinal motility play a role in post-TBI neuroinflammation and cognitive deficit.

Spinal Cord-Gut-Immune Axis and its Implications Regarding Therapeutic Development for Spinal Cord Injury

Spinal cord injury (SCI) affects ∼1,300,000 people living in the United States. Most research efforts have been focused on reversing paralysis, as this is arguably the most defining feature of SCI. The damage caused by SCI, however, extends past paralysis and includes other debilitating outcomes including immune dysfunction and gut dysbiosis. Recent efforts are now investigating the pathophysiology of and developing therapies for these more distal manifestations of SCI. One exciting avenue is the spinal cord-gut-immune axis, which proposes that gut dysbiosis amplifies lesion inflammation and impairs SCI recovery. This review will highlight the most recent findings regarding gut and immune dysfunction following SCI, and discuss how the central nervous system (CNS), gut, and immune system all coalesce to form a bidirectional axis that can impact SCI recovery. Finally, important considerations regarding how the spinal cord-gut-immune axis fits within the larger framework of therapeutic development (i.e., probiotics, fecal transplants, dietary modifications) will be discussed, emphasizing the lack of interdepartmental investigation and the missed opportunity to maximize therapeutic benefit in SCI.

The Effects of Perioperative Probiotics on Postoperative Gastrointestinal Function in Patients with Brain Tumors: A Randomized, Placebo-Controlled Study

The incidence of postoperative gastrointestinal dysfunction among neurosurgical patients is as high as 80%. Probiotics help to maintain gastrointestinal barrier defense, provide competitive adherence to mucus and epithelial cells, and regulate gastrointestinal motility. Therefore, the purpose of this study was to investigate whether probiotics enhance gastrointestinal health after craniotomy in patients with brain tumors. This study was a 15-day, prospective, randomized, double-blind, placebo-controlled trial for patients being treated with elective craniotomy for brain tumors. Participants were randomly divided into the probiotics group (4 g probiotics, twice daily) and placebo group. The primary outcome was the time of first stool after surgery. The secondary outcomes included assessments of the gastrointestinal function, changes in gastrointestinal permeability and clinical outcomes. We enrolled a total of 200 participants (probiotics: 100; placebo: 100) and followed the principles of intention-to-treat analysis. The time of first stool and flatus were significantly shorter in the probiotics group compared to the placebo group (P < 0.001, respectively). No significant trends were observed for any other of the secondary outcome variables. Our findings suggest that probiotics can improve the gastrointestinal mobility of patients received craniotomy, and this improvement cannot be explained by changes in gastrointestinal permeability.

A bibliometric analysis of the role of microbiota in trauma

Introduction

Over the last several decades, the gut microbiota has been implicated in the formation and stabilization of health, as well as the development of disease. With basic and clinical experiments, scholars are gradually understanding the important role of gut microbiota in trauma, which may offer novel ideas of treatment for trauma patients. In this study, we purposed to summarize the current state and access future trends in gut microbiota and trauma research.

Methods

We retrieved relevant documents and their published information from the Web of Science Core Collection (WoSCC). Bibliometrix package was responsible for the visualized analysis.

Results

Totally, 625 documents were collected and the number of annual publications kept increasing, especially from 2016. China published the most documents while the USA had the highest local citations. The University of Colorado and Food & Function are respectively the top productive institution and journal, as PLOS One is the most local cited journal. With the maximum number of articles and local citations, Deitch EA is supported to be the most contributive author. Combining visualized analysis of keywords and documents and literature reading, we recognized two key topics: bacteria translocation in trauma and gut microbiota's effect on inflammation in injury, especially in nervous system injury.

Discussion

The impact of gut microbiota on molecular and pathological mechanism of inflammation is the focus now. In addition, the experiments of novel therapies based on gut microbiota's impact on trauma are being carried out. We hope that this study can offer a birds-eye view of this field and promote the gradual improvement of it.

Change of gut microbiome structure in preterm infants with hypoxic ischemic encephalopathy induced by apnea

BACKGROUND

Since a high incidence of mortality and morbidity is induced by preterm birth, it is important to understand how hypoxic ischemic encephalopathy (HIE) in preterm infants alters gut microbiota development.

METHODS

We analyzed 89 stools from 30 term newborns (NNG), 30 preterm infants without apnea (PG) and 29 preterm infants with definite diagnosis of apnea (PAG) by 16S rRNA gene sequencing in this study.

RESULTS

The data showed that species richness and diversity in PG and PAG were significantly lower compared with NNG. This study investigated the difference in bacteria and relative abundance between NNG, PG and PAG. The abundance of Klebsiella and Streptococcus strains were markedly increased, while Clostridium was significantly decreased in PAG compared with PG. The most notable exceptions included Klebsiella pneumoniae and Escherichia coli, which were markedly increased in PG and PAG, and these provide the main bacterial source of dopamine and serotonin production. This study also revealed that Lactobacillus and Bifidobacterium were markedly increased in PG and PAG, and these are the main source of GABA production for bacteria.

CONCLUSION

The present study confirmed that apnea had a uniform effect on species richness and diversity. However, it cannot be established whether the abundance and difference of these bacterial genera and species directly affect the occurrence and development of preterm infants with HIE by secreting intestinal neurotransmitters.

The Interplay Between Gut Microbiota and Central Nervous System

This review highlights the relationships between gastrointestinal microorganisms and the brain. The gut microbiota communicates with the central nervous system through nervous, endocrine, and immune signalling mechanisms. Our brain can modulate the gut microbiota structure and function through the autonomic nervous system, and possibly through neurotransmitters which directly act on bacterial gene expression. In this context, oxidative stress is one the main factors involved in the dysregulation of the gut-brain axis and consequently in neurodegenerative disorders. Several factors influence the susceptibility to oxidative stress by altering the antioxidant status or free oxygen radical generation. Amongst these, of interest is alcohol, a commonly used substance which can negatively influence the central nervous system and gut microbiota, with a key role in the development of neurodegenerative disorder. The role of "psychobiotics" as a novel contrast strategy for preventing and treating disorders caused due to alcohol use and abuse has been investigated.

The role of the microbiota-gut-brain axis in long-term neurodegenerative processes following traumatic brain injury

Traumatic brain injury (TBI) can be a devastating and debilitating disease to endure. Due to improvements in clinical practice, declining mortality rates have led to research into the long-term consequences of TBI. For example, the incidence and severity of TBI have been associated with an increased susceptibility of developing neurodegenerative disorders, such as Parkinson's or Alzheimer's disease. However, the mechanisms linking this alarming association are yet to be fully understood. Recently, there has been a groundswell of evidence implicating the microbiota-gut-brain axis in the pathogenesis of these diseases. Interestingly, survivors of TBI often report gastrointestinal complaints and animal studies have demonstrated gastrointestinal dysfunction and dysbiosis following injury. Autonomic dysregulation and chronic inflammation appear to be the main driver of these pathologies. Consequently, this review will explore the potential role of the microbiota-gut-brain axis in the development of neurodegenerative diseases following TBI.

Interactions between gut microbes and NLRP3 inflammasome in the gut-brain axis

The role of the gut-brain axis in maintaining the brain's and gut's homeostasis has been gradually recognized in recent years. The connection between the gut and the brain takes center stage. In this scenario, the nucleotide-binding oligomerization domain leucine-rich repeat and pyrin domain-containing protein 3 (NLRP3) inflammasome promotes inflammatory cell recruitment. It plays a crucial role in coordinating host physiology and immunity. Recent evidence shows how vital the gut-brain axis is for maintaining brain and gut homeostasis. However, more research is needed to determine the precise causal link between changed gut microbiota structure and NLRP3 activation in pathogenic circumstances. This review examines the connection between gut microbiota and the NLRP3 inflammasome. We describe how both dynamically vary in clinical cases and the external factors affecting both. Finally, we suggest that the crosstalk between the gut microbiota and NLRP3 is involved in signaling in the gut-brain axis, which may be a potential pathological mechanism for CNS diseases and intestinal disorders.

Brain-gut-liver axis: Chronic psychological stress promotes liver injury and fibrosis via gut in rats

Background

The effect of chronic psychological stress on hepatitis and liver fibrosis is concerned. However, its mechanism remains unclear. We investigated the effect and mechanism of chronic psychological stress in promoting liver injury and fibrosis through gut.

Methods

Sixty male SD rats were randomly assigned to 6 groups. Rat models of chronic psychological stress (4 weeks) and liver fibrosis (8 weeks) were established. The diversity of gut microbiota in intestinal feces, permeability of intestinal mucosa, pathologies of intestinal and liver tissues, collagen fibers, protein expressions of toll-like receptor 4 (TLR4), myeloid differentiation factor 88 (MyD88), nuclear factor kappa β (NF-κβ), tumor necrosis factor α (TNF-α) and interleukin 1 (IL-1) in liver tissue, liver function and coagulation function in blood and lipopolysaccharide (LPS) in portal vein blood were detected and analyzed.

Results

The diversities and abundances of gut microbiota were significant differences in rats among each group. The pathological lesions of intestinal and liver tissues, decreased expression of occludin protein in intestinal mucosa, deposition of collagen fibers and increased protein expression of TLR4, MyD88, NF-κβ, TNF-α and IL-1 in liver tissue, increased LPS level in portal vein blood, and abnormalities of liver function and coagulation function, were observed in rats exposed to chronic psychological stress or liver fibrosis. There were significant differences with normal rats. When the dual intervention factors of chronic psychological stress and liver fibrosis were superimposed, the above indicators were further aggravated.

Conclusion

Chronic psychological stress promotes liver injury and fibrosis, depending on changes in the diversity of gut microbiota and increased intestinal permeability caused by psychological stress, LPS that enters liver and acts on TLR4, and active LPS-TLR4 pathway depend on MyD88. It demonstrates the possibility of existence of brain-gut-liver axis.

Gut microbiome and neurosurgery: Implications for treatment

Introduction

The aim of this review is to summarize the current understanding of the gut-brain axis (GBA), its impact on neurosurgery, and its implications for future treatment.

Background

An abundance of research has established the existence of a collection of pathways between the gut microbiome and the central nervous system (CNS), commonly known as the GBA. Complicating this relationship, the gut microbiome bacterial diversity appears to change with age, antibiotic exposure and a number of external and internal factors.

Methods

In this paper, we present the current understanding of the key protective and deleterious roles the gut microbiome plays in the pathogenesis of several common neurosurgical concerns.

Results

Specifically, we examine how spinal cord injury, traumatic brain injury and stroke may cause gut microbial dysbiosis. Furthermore, this link appears to be bidirectional as gut dysbiosis contributes to secondary CNS injury in each of these ailment settings. This toxic cycle may be broken, and the future secondary damage rescued by timely, therapeutic, gut microbiome modification. In addition, a robust gut microbiome appears to improve outcomes in brain tumour treatment. There are several primary routes by which microbiome dysbiosis may be ameliorated, including faecal microbiota transplant, oral probiotics, bacteriophages, genetic modification of gut microbiota and vagus nerve stimulation.

Conclusion

The GBA represents an important component of patient care in the field of neurosurgery. Future research may illuminate ideal methods of therapeutic microbiome modulation in distinct pathogenic settings.

Mapping trends and hotspot regarding gastrointestinal microbiome and neuroscience: A bibliometric analysis of global research (2002-2022)

BACKGROUND

Scholars have long understood that gastrointestinal microorganisms are intimately related to human disorders. The literature on research involving the gut microbiome and neuroscience is emerging. This study exposed the connections between gut microbiota and neuroscience methodically and intuitively using bibliometrics and visualization. This study's objectives were to summarize the knowledge structure and identify emerging trends and potential hotspots in this field.

MATERIALS AND METHODS

On October 18, 2022, a literature search was conducted utilizing the Web of Science Core Collection (WoSCC) database for studies on gut microbiota and neuroscience studies from 2002 to 2022 (August 20, 2022). VOSviewer and CiteSpace V software was used to conduct the bibliometrics and visualization analysis.

RESULTS

From 2002 to 2022 (August 20, 2022), 2,275 publications in the WoSCC database satisfied the criteria. The annual volume of publications has rapidly emerged in recent years (2016-2022). The most productive nation (n = 732, 32.18%) and the hub of inter-country cooperation (links: 38) were the United States. University College Cork had the most research papers published in this area, followed by McMaster University and Harvard Medical School. Cryan JF, Dinan TG, and Clarke G were key researchers with considerable academic influence. The journals with the most publications are "Neurogastroenterology and Motility" and "Brain Behavior and Immunity." The most cited article and co-cited reference was Cryan JF's 2012 article on the impact of gut microbiota on the brain and behavior. The current research hotspot includes gastrointestinal microbiome, inflammation, gut-brain axis, Parkinson's disease (PD), and Alzheimer's disease (AD). The research focus would be on the "gastrointestinal microbiome, inflammation: a link between obesity, insulin resistance, and cognition" and "the role of two important theories of the gut-brain axis and microbial-gut-brain axis in diseases." Burst detection analysis showed that schizophrenia, pathology, and psychiatric disorder may continue to be the research frontiers.

CONCLUSION

Research on "gastrointestinal microbiome, inflammation: a link between obesity, insulin resistance, and cognition" and "the role of two important theories of the gut-brain axis and microbial-gut-brain axis in diseases" will continue to be the hotspot. Schizophrenia and psychiatric disorder will be the key research diseases in the field of gut microbiota and neuroscience, and pathology is the key research content, which is worthy of scholars' attention.

Traumatic brain injury alters the gut-derived serotonergic system and associated peripheral organs

Most efforts to understand the pathology of traumatic brain injury (TBI) have been centered on the brain, ignoring the role played by systemic physiology. Gut-derived serotonin is emerging as a major regulator of systemic homeostasis involving various organs and tissues throughout the body. Here, we shed light on the roles occupied by gut-derived serotonin and its downstream metabolic targets in the systemic pathogenesis of TBI. Male C57BL/6J mice were subjected to a fluid percussion injury (FPI) and RT-qPCR was used to examine mRNA levels in intestine, liver, and adipose tissue. In the intestinal tract, TBI transiently downregulated enteric neuronal markers Chat and Nos1 in the duodenum and colon, and altered colonic genes related to synthesis and degradation of serotonin, favoring an overall serotonin downregulation. There also was a decrease in serotonin fluorescence intensity in the colonic mucosa and reduced circulating blood serotonin levels, with concurrent alterations in serotonin-associated gene expression in downstream tissues after TBI (i.e., upregulation of serotonin receptor Htr2a and dysregulation of genes associated with lipid metabolism in liver and adipose). Levels of commensal bacterial species were also altered in the gut and were associated with TBI-mediated changes in the colonic serotonin system. Our findings suggest that TBI alters peripheral serotonin homeostasis, which in turn may impact gastrointestinal function, gut microbiota, and systemic energy balance. These data highlight the importance of building an integrative view of the role of systemic physiology in TBI pathogenesis to assist in the development of effective TBI treatments.

Establishment and evaluation of a prediction model for acute gastrointestinal injury in patients with prolonged disorder of consciousness

Objective

To establish a prediction model for acute gastrointestinal injury (AGI) in patients with prolonged disorder of consciousness (pDOC) and to evaluate and apply the prediction model. 

Methods

The clinical data of 165 patients with pDOC admitted to the hyperbaric oxygen department from January 2021 to December 2021 were retrospectively reviewed, and the patients were divided into an AGI group (n = 91) and an N-AGI group (n = 74) according to whether AGI occurred. A prediction model was built by fitting multiple independent influencing factors through logistic regression. The receiver operating characteristic (ROC) curve was used to evaluate the predictive value of the model, the Hosmer–Lemeshow (H–L) test was used to evaluate the goodness-of-fit of the model, and the ROC curve and calibration curve were drawn to evaluate the predictive performance. A nomogram was plotted to visualize the prediction model.

Results

According to the multivariate logistic regression analysis results, the prediction model was finally constructed with the CRS-R score, DAO, PCT, ALB, and I-FABP, and a nomogram was generated. The area under the ROC curve (AUC) of the prediction model was 0.931, the sensitivity was 83.5%, and the specificity was 93.2%. The data were divided into 5 groups for the H–L test (χ² = 2.54, P = 0.468 > 0.05) and into 10 groups for the H–L test (χ² = 9.98, P = 0.267 > 0.05). A calibration curve was drawn based on the test results, indicating that the prediction model has a good goodness-of-fit and good prediction stability.

Conclusion

The prediction model for AGI in pDOC patients constructed in this study can be used in clinical practice and is helpful to predict the occurrence of AGI in pDOC patients.

POSTINJURY FECAL MICROBIOME TRANSPLANT DECREASES LESION SIZE AND NEUROINFLAMMATION IN TRAUMATIC BRAIN INJURY

ABSTRACT

Background: Traumatic brain injury (TBI) is an underrecognized public health threat. The constitutive activation of microglia after TBI has been linked to long-term neurocognitive deficits and the progression of neurodegenerative disease. Evolving evidence indicates a critical role for the gut-brain axis in this process. Specifically, TBI has been shown to induce the depletion of commensal gut bacteria. The resulting gut dysbiosis is associated with neuroinflammation and disease. Hypothesis: We hypothesized that fecal microbiota transplantation would attenuate microglial activation and improve neuropathology after TBI. Methods: C57Bl/6 mice were subjected to severe TBI (n = 10) or sham injury (n = 10) via an open-head controlled cortical impact. The mice underwent fecal microbiota transplantation (FMT) or vehicle alone via oral gavage once weekly for 4 weeks after injury. At 59 days after TBI, mice underwent three-dimensional, contrast-enhanced magnetic resonance imaging. Following imaging, mice were killed, brains harvested at 60 DPI, and CD45+ cells isolated via florescence-activated cell sorting. cDNA libraries were prepared using the 10x Genomics Chromium Single Cell 3' Reagent kit followed by sequencing on a HiSeq4000 instrument, and computational analysis was performed. Results: Fecal microbiota transplantation resulted in a >marked reduction of ventriculomegaly (P < 0.002) and preservation of white matter connectivity at 59 days after TBI (P < 0.0001). In addition, microglia from FMT-treated mice significantly reduced inflammatory gene expression and enriched pathways involving the heat-shock response compared with mice treated with vehicle alone. Conclusions: We hypothesized that restoring gut microbial community structure via FMT would attenuate microglial activation and reduce neuropathology after TBI. Our data demonstrated significant preservation of cortical volume and white matter connectivity after an injury compared with mice treated with vehicle alone. This preservation of neuroanatomy after TBI was associated with a marked reduction in inflammatory gene expression within the microglia of FMT-treated mice. Microglia from FMT-treated mice enriched pathways in the heat-shock response, which is known to play a neuroprotective role in TBI and other neurodegenerative disease processes.

The Brain–Gut Axis in Traumatic Brain Injury: Implications for Nutrition Support

Purpose of Review

Early enteral nutrition improves outcomes following traumatic brain injury (TBI). This can prove difficult due to TBI-induced feeding intolerance secondary to disruption of the brain-gut axis, a network composed of central nervous system (CNS) input, autonomic signaling, and immunologic regulation that controls gut and CNS homeostasis. Here, we discuss the pathophysiology of brain–gut axis dysregulation and outline nutrition strategies in patients with TBI.

Recent Findings

Feeding intolerance following TBI is multifactorial; complex signaling between the CNS, sympathetic nervous system, parasympathetic nervous system, and enteric nervous system that controls gut homeostasis is disrupted within hours post-injury. This has profound effects on the immune system and gut microbiome, further complicating post-TBI recovery. Despite this disruption, calorie and protein requirements increase considerably following TBI, and early nutritional supplementation improves survival following TBI. Enteral nutrition has proven more efficacious than parenteral nutrition in TBI patients and should be initiated within 48 hours following admission. Immune-fortified nutrition reduces CNS and gut inflammation and may improve outcomes in TBI patients.

Summary

Although autonomic dysregulation of the brain–gut axis results in feeding intolerance following TBI, early enteral nutrition is of paramount importance. Enteral nutrition reduces post-TBI inflammation and enhances immunologic and gut function. When feasible, enteral nutrition should be initiated within 48 hours following injury.

Prognostic Significance of Plasma Insulin Level for Deep Venous Thrombosis in Patients with Severe Traumatic Brain Injury in Critical Care

BACKGROUND

Whether insulin resistance underlies deep venous thrombosis (DVT) development in patients with severe traumatic brain injury (TBI) is unclear. In this study, the association between plasma insulin levels and DVT was analyzed in patients with severe TBI.

METHODS

A prospective observational study of 73 patients measured insulin, glucose, glucagon-like peptide 1 (GLP-1), inflammatory factors, and hematological profiles within four preset times during the first 14 days after TBI. Ultrasonic surveillance of DVT was tracked. Two-way analysis of variance was used to determine the factors that discriminated between patients with and without DVT or with and without insulin therapy. Partial correlations of insulin level with all the variables were conducted separately in patients with DVT or patients without DVT. Factors associated with DVT were analyzed by multivariable logistic regression. Neurological outcomes 6 months after TBI were assessed.

RESULTS

Among patients with a mean (± standard deviation) age of 53 (± 16 years), DVT developed in 20 patients (27%) on median 10.4 days (range 4-22), with higher Acute Physiology and Chronic Health Evaluation II scores but similar Sequential Organ Failure Assessment scores and TBI severity. Patients with DVT were more likely to receive insulin therapy than patients without DVT (60% vs. 28%; P = 0.012); hence, they had higher 14-day insulin levels. However, insulin levels were comparable between patients with DVT and patients without DVT in the subgroups of patients with insulin therapy (n = 27) and patients without insulin therapy (n = 46). The platelet profile significantly discriminated between patients with and without DVT. Surprisingly, none of the coagulation profiles, blood cell counts, or inflammatory mediators differed between the two groups. Patients with insulin therapy had significantly higher insulin (P = 0.006), glucose (P < 0.001), and GLP-1 (P = 0.01) levels and were more likely to develop DVT (60% vs. 15%; P < 0.001) along with concomitant platelet depletion. Insulin levels correlated with glucose, GLP-1 levels, and platelet count exclusively in patients without DVT. Conversely, in patients with DVT, insulin correlated negatively with GLP-1 levels (P = 0.016). Age (P = 0.01) and elevated insulin levels at days 4-7 (P = 0.04) were independently associated with DVT. Patients with insulin therapy also showed worse Glasgow Outcome Scale scores (P = 0.001).

CONCLUSIONS

Elevated insulin levels in the first 14 days after TBI may indicate insulin resistance, which is associated with platelet hyperactivity, and thus increasing the risk of DVT.

Recombinant Human Annexin A5 Alleviated Traumatic-Brain-Injury Induced Intestinal Injury by Regulating the Nrf2/HO-1/HMGB1 Pathway

Aims: Annexin A5 (ANXA5) exhibited potent antithrombotic, antiapoptotic, and anti-inflammatory properties in a previous study. The role of ANXA5 in traumatic brain injury (TBI)-induced intestinal injury is not fully known. Main methods: Recombinant human ANXA5 (50 µg/kg) or vehicle (PBS) was administered to mice via the tail vein 30 min after TBI. Mouse intestine tissue was gathered for hematoxylin and eosin staining 0.5 d, 1 d, 2 d, and 7 d after modeling. Intestinal Western blotting, immunofluorescence, TdT-mediated dUTP nick-end labeling staining, and enzyme-linked immunosorbent assays were performed 2 days after TBI. A series of kits were used to assess lipid peroxide indicators such as malonaldehyde, superoxide dismutase activity, and catalase activity. Key findings: ANXA5 treatment improved the TBI-induced intestinal mucosa injury at different timepoints and significantly increased the body weight. It significantly reduced apoptosis and matrix metalloproteinase-9 and inhibited the degradation of tight-junction-associated protein in the small intestine. ANXA5 treatment improved intestinal inflammation by regulating inflammation-associated factors. It also mitigated the lipid peroxidation products 4-HNE, 8-OHDG, and malonaldehyde, and enhanced the activity of the antioxidant enzymes, superoxide dismutase and catalase. Lastly, ANXA5 significantly enhanced nuclear factor E2-related factor 2 (Nrf2) and hemeoxygenase-1, and decreased high mobility group box 1 (HMGB1). Significance: Collectively, the results suggest that ANXA5 inhibits TBI-induced intestinal injury by restraining oxidative stress and inflammatory responses. The mechanisms involved sparking the Nrf2/hemeoxygenase-1-induced antioxidant system and suppressing the HMGB1 pathway. ANXA5 may be an attractive therapeutic candidate for protecting against TBI-induced intestinal injury.