A Comprehensive Review on the Role of the Gut Microbiome in Human Neurological Disorders

Pathogenesis, diagnosis, and treatment of epilepsy: electromagnetic stimulation-mediated neuromodulation therapy and new technologies

Epilepsy is a severe, relapsing, and multifactorial neurological disorder. Studies regarding the accurate diagnosis, prognosis, and in-depth pathogenesis are crucial for the precise and effective treatment of epilepsy. The pathogenesis of epilepsy is complex and involves alterations in variables such as gene expression, protein expression, ion channel activity, energy metabolites, and gut microbiota composition. Satisfactory results are lacking for conventional treatments for epilepsy. Surgical resection of lesions, drug therapy, and non-drug interventions are mainly used in clinical practice to treat pain associated with epilepsy. Non-pharmacological treatments, such as a ketogenic diet, gene therapy for nerve regeneration, and neural regulation, are currently areas of research focus. This review provides a comprehensive overview of the pathogenesis, diagnostic methods, and treatments of epilepsy. It also elaborates on the theoretical basis, treatment modes, and effects of invasive nerve stimulation in neurotherapy, including percutaneous vagus nerve stimulation, deep brain electrical stimulation, repetitive nerve electrical stimulation, in addition to non-invasive transcranial magnetic stimulation and transcranial direct current stimulation. Numerous studies have shown that electromagnetic stimulation-mediated neuromodulation therapy can markedly improve neurological function and reduce the frequency of epileptic seizures. Additionally, many new technologies for the diagnosis and treatment of epilepsy are being explored. However, current research is mainly focused on analyzing patients' clinical manifestations and exploring relevant diagnostic and treatment methods to study the pathogenesis at a molecular level, which has led to a lack of consensus regarding the mechanisms related to the disease.

Increased levels of Escherichia-Shigella and Klebsiella in the gut contribute to the responsivity of placebo analgesia

Placebo analgesia is observed in both humans and animals. Given the complexity of placebo analgesia involving a variety of neurobiological, psychological, and psychosocial processes, further investigation into its underlying mechanisms is essential. Gut microbiota has been implicated in the responsivity of placebo analgesia, but its precise role remains unknown and warrants further investigations. Here, we conducted a conditioning training model with chronic inflammatory pain induced by complete Freund's adjuvant (CFA) in mice, associating parecoxib with different cues. Hierarchical clustering analysis of placebo analgesia behaviors was employed to classify mice into responders and non-responders phenotypes. Approximately 40% of CFA mice undergoing conditioning training exhibited placebo analgesia. Notably, placebo analgesia responders displayed reduced anxiety-like behaviors. 16S rRNA results revealed a distinct composition of gut microbiota composition among the control, placebo analgesia non-responders and responders groups. Notably, levels of Escherichia Shigella and Klebsiella in the gut were increased considerably in the placebo analgesia responders as compared to both control and non-responders groups. In conclusion, placebo analgesia responders demonstrated marked analgesia, reduced anxiety-like behaviors, and increased levels of Escherichia-Shigella and Klebsiella, implying a potential linkage between gut microbiota and placebo analgesia.

Investigating the bacterial profiles of Lactobacillus, Bifidobacterium, Actinobacteria, Fusobacterium, Firmicutes, and Bacteroides in stool samples from patients with severe depression and healthy individuals

Depression is a multifaceted mental health disorder with complex etiology and significant global burden. Recent research indicates that the gut microbiota plays a role in the pathophysiology of depression, highlighting the potential role of specific bacterial species in influencing mood and cognitive function. In this study, we aimed to investigate the presence, copy numbers, and Ct values of selected bacterial species in stool samples from depressed patients (n=50) compared to control subjects (n=50). Our findings revealed significant differences in the abundance of Fusobacterium spp., Bifidobacterium spp., Lactobacillus spp., Bacteroidetes phylum, Firmicutes phylum, and Actinobacteria spp. between the two groups. Dysregulation of the gut microbiota, characterized by decreased presence of beneficial bacteria (e.g., Bifidobacterium spp., Lactobacillus spp.) and altered abundance of potentially pathogenic bacteria (e.g., Fusobacterium spp.), may contribute to the development or exacerbation of depression. These findings support the emerging concept of the gut-brain axis and its role in mental health. However, further research is needed to better understand the underlying mechanisms and explore the therapeutic potential of microbiota-targeted interventions for depression. Understanding the intricate interplay between the gut microbiota and depression could pave the way for novel treatment strategies and personalized approaches in mental health care.

Socioeconomic adversity, maternal nutrition, and the prenatal programming of offspring cognition and language at two years of age through maternal inflammation

Increasing rates of child neurodevelopmental vulnerability are a significant public health challenge. The adverse effect of socioeconomic adversity on offspring cognition may be mediated through elevated prenatal maternal systemic inflammation, but the role of modifiable antecedents such as maternal nutrition has not yet been clarified. This study aimed to examine (1) whether prenatal factors, with an emphasis on maternal nutrition, were associated with prenatal maternal systemic inflammation at 28 weeks' gestation, including the metabolomic marker glycoprotein acetyls (GlycA); (2) the extent to which the association between prenatal maternal nutrition and child cognition and language at age two years was mediated by elevated maternal inflammation in pregnancy; (3) the extent to which the associations between prenatal socioeconomic adversity and child neurodevelopment were mediated through prenatal maternal nutrition and GlycA levels. We used a prospective population-derived pre-birth longitudinal cohort study, the Barwon Infant Study (Barwon region of Victoria, Australia), where 1074 mother-child pairs were recruited by 28 weeks' gestation using an unselected sampling frame. Exposures included prenatal factors such as maternal diet measured by a validated food frequency questionnaire at 28 weeks' gestation and dietary patterns determined by principal component analysis. The main outcome measures were maternal inflammatory biomarkers (GlycA and hsCRP levels) at 28 weeks' gestation, and offspring Bayley-III cognition and language scores at age two years. Results showed that the 'modern wholefoods' and 'processed' maternal dietary patterns were independently associated with reduced and elevated maternal inflammation respectively (GlycA or hsCRP p < 0.001), and also with higher and reduced offspring Bayley-III scores respectively (cognition p ≤ 0.004, language p ≤ 0.009). Associations between dietary patterns and offspring cognition and language were partially mediated by higher maternal GlycA (indirect effect: cognition p ≤ 0.036, language p ≤ 0.05), but were less evident for hsCRP. The maternal dietary patterns mediated 22 % of the association between socioeconomic adversity (lower maternal education and/or lower household income vs otherwise) and poorer offspring cognition (indirect effect p = 0.001). Variation in prenatal GlycA levels that were independent of these dietary measures appeared less important. In conclusion, modifiable prenatal maternal dietary patterns were associated with adverse child neurocognitive outcomes through their effect on maternal inflammation (GlycA). Maternal diet may partially explain the association between socioeconomic adversity and child neurocognitive vulnerability. Maternal diet-by-inflammation pathways are an attractive target for future intervention studies.

Gut Microbiome variation in patients with early-stage mild-to-moderate intracerebral hemorrhage: A pilot study exploring therapeutic targets

BACKGROUND

The significant morbidity and mortality rates of acute intracerebral hemorrhage (ICH) are well-known around the world. The link between gut microbiota and different types of strokes is becoming more studied. The goal of this study was to look at the relationships between intestinal flora and early-stage mild-to-moderate ICH (emICH), and to provide a new perspective for adjunctive treatment of emICH.

METHODS

Fecal samples from 100 participants with emICH (n=50) and healthy individuals (n=50) in this study were collected as well as analyzed utilizing 16S rRNA gene amplicon sequencing in order to characterize the gut microbial community.

RESULTS

Distinct microbial communities are present within each group, with emICH patients exhibiting a diminished diversity and uniformity in their microbial profiles. A notable shift in the gut microbiota composition of emICH patients has been observed, characterized by an upsurge in pro-inflammatory microbes belonging to the Euryarchaeota phylum and a concurrent decline in beneficial Bacteroidetes species. Concurrently, significant associations and patterns among operational taxonomic units (OTUs) were identified in emICH patients. A panel of biomarkers (WAL_1855D, Methanobrevibacter, Streptococcus, Bacteroides, Coprococcus, Lachnospira) has been effectively utilized to distinguish emICH patients from healthy individuals, with an area under the curve (AUC) of 0.845. Additionally, an analysis using the Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway annotation uncovered several perturbed pathways in emICH patients, predominantly those related to metabolic processes and the inflammatory response. Moreover, predictive profiling of the microbiome's phenotypic traits suggests that emICH patients are likely to harbor a higher prevalence of Gram-negative bacteria and potential opportunistic pathogens compared to healthy controls.

CONCLUSIONS

The gut microbiota ecosystem of emICH patients is disrupted, characterized primarily by an increase in pro-inflammatory microbiota, elevated inflammatory signaling pathways, and metabolic dysregulation. Furthermore, microbiota modulation may be seen as a novel approach for the adjunctive treatment of emICH.

Gut microbiota as a potential therapeutic target for children with cerebral palsy and epilepsy

Gut microbiota (GM), the "second genome," exerts influence on human health by impacting brain function through the gut-brain axis. This interaction involves various mechanisms, including immune regulation, metabolites, and neuronal pathways. The application of the next-generation sequencing technology provides a revolutionary tool for the study of GM, which contributes to a deeper comprehension of the GM-host relationship. Children with cerebral palsy (CP), a common neurological disorder in children, are more likely to develop epilepsy, which can exacerbate CP symptoms, particularly those related to cognitive impairment and gastrointestinal tract, such as constipation. The current study identified specific changes in the GM of children with CP accompanied by epilepsy. Furthermore, both diet and oral microbiota have the potential to influence the composition of the GM. Interventions with probiotics and dietary fiber based on GM can improve constipation and cognition, and this approach may be a potential therapeutic strategy.

The effect of synbiotics in the treatment of drug-resistant epilepsy and the parental burden of caregivers: a single-arm pretest-posttest trial

BACKGROUND

In patients with drug-resistant epilepsy (DRE), the composition of the gut microbiome changes compared to drug-sensitive patients and healthy individuals. Synbiotics, a mixture of probiotics and prebiotics, aim to improve the balance of bacteria in the gut microbiome. This study aimed to assess the effect of synbiotics on the treatment of DRE and the burden on caregivers.

METHODS

This one-group pretest-posttest quasi-experimental study was conducted in Arak, Iran. Thirty children with DRE, diagnosed by a pediatric neurologist and meeting the inclusion criteria in 2021-22, were included in the study. In addition to anticonvulsant drugs, infants were administered PediLact at a dose of 5-15 drops per day for eight weeks, and KidiLact at a dose of one sachet per day for eight weeks for children aged 2-15 years. Both PediLact and KidiLact are synbiotics. To investigate the burden on caregivers (parents), the Zarit Caregiver Burden Interview was conducted. In addition, the number of epileptic seizures was assessed from mothers before and immediately after the intervention over one month.

RESULTS

The mean age of the participants in the study was 8.6 years (SD: 3.4). Eighteen participants (60%) were boys, and 12 (40%) were girls. The results of the study showed a statistically significant decrease in the mean burden on caregivers, from 34.20 (SD: 14.4) before the intervention to 30.26 (SD: 15.8) after the intervention (P = 0.017). The mean frequency of seizures decreased significantly, from 15.83 (SD: 12.9) before the intervention to 12.73 (SD: 12.8) after the intervention (P = 0.001). Following the intervention, the seizure frequency stopped in two patients, decreased by 50% in six patients, increased in one patient, and remained unchanged in 21 patients.

CONCLUSION

The results suggest that Symbiotics in DRE patients are associated with a lower parental burden of caregivers and seizure frequency. Well-designed randomized clinical trial studies are recommended to generate rigorous causal evidence and conclusions.

Investigating the mechanisms of inflammation and immune alterations in Parkinson's disease using spatial transcriptomics techniques

In recent years, overwhelming evidence has emphasized the crucial role of inflammation in the pathogenesis of PD. However, the exact mechanisms by which inflammation damages dopaminergic neurons in PD are still unclear. Therefore, we generated a MPTP-induced PD mouse model and performed spatial transcriptomic sequencing to provide more insight into the process of PD development at specific brain regions. Our results indicate that the pathological changes of PD are mainly manifested in the midbrain, especially in the substantia nigra region, with significant reductions in oligodendrocytes and Agt-labeled astrocytes and an increase in Gfap-labeled astrocytes. Macrophages displayed an increasing trend in the PD environment, indicating a pattern of immune modulation induced by PD. Moreover, pathway analysis revealed significant impairments in ion migration ability, abnormal Ca2+ channels, cAMP signaling, and synaptic damage in PD. Significant downregulation of Mt1 and Mt2 and upregulation of Atp1b2, Gpi1, and Cox6a1 in PD further underscored the occurrence of intense inflammation and immune alterations. On the basis of these findings, we have validated the significant accumulation of Ca2+ in the midbrain tissue in the PD environment by measuring its content. Additionally, we have demonstrated a close association between the reduction of dopaminergic neurons, represented by the midbrain region, and ferroptosis by evaluating the iron content, malondialdehyde (MDA) levels, and the protein expression of GPX4 and TH in the tissue. We propose the hypothesis that PD-related inflammation and immune changes can induce neuronal and oligodendrocyte damage through the induction of ferroptosis, thereby further accelerating the progression of PD.

Unravelling the neuroimmune nexus: insights into epilepsy pathology and the role of S100b protein in brain-gut axis modulation: a literature review

Epilepsy, a chronic neurological condition marked by recurrent, unprovoked seizures, involves complex pathophysiological mechanisms. Recent advancements have expanded our understanding from traditional neuronal dysfunction to include neuroimmune interactions and the influence of the brain-gut-bio-axis. This review explores the role of the S100b protein within these contexts, noted for its involvement in neuroinflammatory processes and as a potential biomarker. Furthermore, it discusses the emerging significance of the gut microbiome in modulating neuroimmune responses and seizure activity. The review integrates findings from recent studies, emphasizing the critical role of the S100b signalling pathway and the gut-brain axis in epilepsy pathology. The interplay between neuroimmune mechanisms and gut microbiota offers novel insights and potential therapeutic targets, underlining the need for further research to exploit these connections for clinical benefit.

Efficacy of bifidobacterium-related preparations on depression: the first meta-analysis

Currently, depression-induced suicide has emerged as the primary contributor to the worldwide burden of disability. However, the prevailing drug treatment not only suffers from delayed effectiveness and limited efficacy, but also there are withdrawal symptoms and rebound phenomenon. Consequently, there is an imperative to investigate safer and more efficient treatments to ameliorate the clinical manifestations of depression. At present, there is increased evidence that probiotics can improve the symptoms of depression, but the existing studies use many and mixed types of probiotics, and it is impossible to determine the specific efficacy of bifidobacteria in the treatment of depression. This review will systematically review the effects of bifidobacteria on the treatment effect of depression, Meta-analysis showed that Bifidobacterium-related preparations effectively improved depressive symptoms in patients with depression. This study represents the initial meta-analysis conducted on the use of bifidobacteria-related agents for treating depression. The objective was to determine the effect of bifidobacteria-related preparations on improving depressive symptoms. We found that Bifidobacterium and its related agents can effectively reduce depression scale scores in patients with depression, suggesting the need for further research into this potential strategy for the prevention and treatment of depression.

Microbiota-gut-brain axis in perioperative neurocognitive and depressive disorders: Pathogenesis to treatment

An increasing number of people undergo anesthesia and surgery. Perioperative neurocognitive and depressive disorders are common central nervous system complications with similar pathogeneses. These conditions pose a deleterious threat to human health and a significant societal burden. In recent years, numerous studies have focused on the role of the gut microbiota and its metabolites in the central nervous system via the gut-brain axis. Its involvement in perioperative neurocognitive and depressive disorders has attracted considerable attention. This review aimed to elucidate the role of the gut microbiota and its metabolites in the pathogenesis of perioperative neurocognitive and depressive disorders, as well as the value of targeted interventions and treatments.

Multi-omics insights into anti-colitis benefits of the synbiotic and postbiotic derived from wheat bran arabinoxylan and Limosilactobacillus reuteri

Exploring nutritional therapies that manipulate tryptophan metabolism to activate AhR signaling represents a promising approach for mitigating chronic colitis. Arabinoxylan is a bioactive constituent abundant in wheat bran. Here, we comprehensively investigated anti-colitis potentials of wheat bran arabinoxylan (WBAX), its synbiotic and postbiotic derived from WBAX and Limosilactobacillus reuteri WX-94 (i.e., a probiotic strain exhibiting tryptophan metabolic activity). WBAX fueled L. reuteri and promoted microbial conversion of tryptophan to AhR ligands during in vitro fermentation in the culture medium and in the fecal microbiota from type 2 diabetes. The WBAX postbiotic outperformed WBAX and its synbiotic in augmenting efficacy of tryptophan in restoring DSS-disturbed serum immune markers, colonic tight junction proteins and gene profiles involved in amino acid metabolism and FoxO signaling. The WBAX postbiotic remodeled gut microbiota and superiorly enhanced AhR ligands (i.e., indole metabolites and bile acids), alongside with elevation in colonic AhR and IL-22. Associations between genera and metabolites modified by the postbiotic and colitis in human were verified and strong binding capacities between metabolites and colitis-related targets were demonstrated by molecular docking. Our study advances the novel perspective of WBAX in manipulating tryptophan metabolism and anti-colitis potentials of WBAX postbiotic via promoting gut microbiota-dependent AhR signaling.

Explore the mechanisms of triterpenoids from Ganoderma lucidum in the protection against Alzheimer's disease via microbiota-gut-brain axis with the aid of network pharmacology

Ganoderma lucidum (Curtis) P. Karst.(G. lucidum) is a kind of fungi, which also a traditional Chinese medicine used for "wisdom growth" in China. Triterpenoids from G. lucidum (GLTs) are one of the main active ingredients. Based on the strategy of early intervention on Alzheimer's disease (AD) and the inextricable association between disordered gut microbiota and metabolites with AD, this study aimed to explore the mechanisms of GLTs in the protection against AD via microbiota-gut-brain axis with the aid of network pharmacology. In this study, LC-MS/MS was used to identify the main active ingredients of GLTs. Network pharmacology was used to predict the potential target and validated with Caco-2 cell model. D-galactose was used to induce the slow-onset AD on rats. Metabolomics methods basing on GC-MS combined with 16S rRNA sequencing technology was used to carry out microbiota-gut-metabolomics analysis in order to reveal the potential mechanisms of GLTs in the protection of AD. As results, GLTs showed a protection against AD effect on rats by intervening administration. The mechanisms were inextricably linked to GLTs interference with the balance of gut microbiota and metabolites. The main fecal metabolites involved were short-chain fatty acids and aromatic amino acid metabolites.

A comprehensive review on the pharmacological role of gut microbiome in neurodegenerative disorders: potential therapeutic targets

Neurological disorders, including Alzheimer and Parkinson's, pose significant challenges to public health due to their complex etiologies and limited treatment options. Recent advances in research have highlighted the intricate bidirectional communication between the gut microbiome and the central nervous system (CNS), revealing a potential therapeutic avenue for neurological disorders. Thus, this review aims to summarize the current understanding of the pharmacological role of gut microbiome in neurological disorders. Mounting evidence suggests that the gut microbiome plays a crucial role in modulating CNS function through various mechanisms, including the production of neurotransmitters, neuroactive metabolites, and immune system modulation. Dysbiosis, characterized by alterations in gut microbial composition and function, has been observed in many neurological disorders, indicating a potential causative or contributory role. Pharmacological interventions targeting the gut microbiome have emerged as promising therapeutic strategies for neurological disorders. Probiotics, prebiotics, antibiotics, and microbial metabolite-based interventions have shown beneficial effects in animal models and some human studies. These interventions aim to restore microbial homeostasis, enhance microbial diversity, and promote the production of beneficial metabolites. However, several challenges remain, including the need for standardized protocols, identification of specific microbial signatures associated with different neurological disorders, and understanding the precise mechanisms underlying gut-brain communication. Further research is necessary to unravel the intricate interactions between the gut microbiome and the CNS and to develop targeted pharmacological interventions for neurological disorders.

The Potential Role of Mitochondria in the Microbiota-Gut-Brain Axis: Implications for Brain Health

Mitochondria are crucial organelles that regulate cellular energy metabolism, calcium homeostasis, and oxidative stress responses, playing pivotal roles in brain development and neurodegeneration. Concurrently, the gut microbiota has emerged as a key modulator of brain physiology and pathology through the microbiota-gut-brain axis. Recent evidence suggests an intricate crosstalk between the gut microbiota and mitochondrial function, mediated by microbial metabolites that can influence mitochondrial activities in the brain. This review aims to provide a comprehensive overview of the emerging role of mitochondria as critical mediators in the microbiota-gut-brain axis, shaping brain health and neurological disease pathogenesis. We discuss how gut microbial metabolites such as short-chain fatty acids, secondary bile acids, tryptophan metabolites, and trimethylamine N-oxide can traverse the blood-brain barrier and modulate mitochondrial processes including energy production, calcium regulation, mitophagy, and oxidative stress in neurons and glial cells. Additionally, we proposed targeting the mitochondria through diet, prebiotics, probiotics, or microbial metabolites as a promising potential therapeutic approach to maintain brain health by optimizing mitochondrial fitness. Overall, further investigations into how the gut microbiota and its metabolites regulate mitochondrial bioenergetics, dynamics, and stress responses will provide valuable insights into the microbiota-gut-brain axis in both health and disease states.

Gut Microbiota Mediates Neuroinflammation in Alzheimer's Disease: Unraveling Key Factors and Mechanistic Insights

The gut microbiota, the complex community of microorganisms that inhabit the gastrointestinal tract, has emerged as a key player in the pathogenesis of neurodegenerative disorders, including Alzheimer's disease (AD). AD is characterized by progressive cognitive decline and neuronal loss, associated with the accumulation of amyloid-β plaques, neurofibrillary tangles, and neuroinflammation in the brain. Increasing evidence suggests that alterations in the composition and function of the gut microbiota, known as dysbiosis, may contribute to the development and progression of AD by modulating neuroinflammation, a chronic and maladaptive immune response in the central nervous system. This review aims to comprehensively analyze the current role of the gut microbiota in regulating neuroinflammation and glial cell function in AD. Its objective is to deepen our understanding of the pathogenesis of AD and to discuss the potential advantages and challenges of using gut microbiota modulation as a novel approach for the diagnosis, treatment, and prevention of AD.

A systematic framework for understanding the microbiome in human health and disease: from basic principles to clinical translation

The human microbiome is a complex and dynamic system that plays important roles in human health and disease. However, there remain limitations and theoretical gaps in our current understanding of the intricate relationship between microbes and humans. In this narrative review, we integrate the knowledge and insights from various fields, including anatomy, physiology, immunology, histology, genetics, and evolution, to propose a systematic framework. It introduces key concepts such as the 'innate and adaptive genomes', which enhance genetic and evolutionary comprehension of the human genome. The 'germ-free syndrome' challenges the traditional 'microbes as pathogens' view, advocating for the necessity of microbes for health. The 'slave tissue' concept underscores the symbiotic intricacies between human tissues and their microbial counterparts, highlighting the dynamic health implications of microbial interactions. 'Acquired microbial immunity' positions the microbiome as an adjunct to human immune systems, providing a rationale for probiotic therapies and prudent antibiotic use. The 'homeostatic reprogramming hypothesis' integrates the microbiome into the internal environment theory, potentially explaining the change in homeostatic indicators post-industrialization. The 'cell-microbe co-ecology model' elucidates the symbiotic regulation affecting cellular balance, while the 'meta-host model' broadens the host definition to include symbiotic microbes. The 'health-illness conversion model' encapsulates the innate and adaptive genomes' interplay and dysbiosis patterns. The aim here is to provide a more focused and coherent understanding of microbiome and highlight future research avenues that could lead to a more effective and efficient healthcare system.

Making waves: From tap to gut- exploring the impact of drinking water on gut microbiota

Drinking water (DW) harbours diverse microbial species and chemical attributes. Water comprises the greatest portion of our daily diet, ingested both on its own and used in the preparation of food. DW is our major source of liquids, which is vital to maintaining homeostasis, and can also supply essential minerals. Limited evidence suggests that DW plays a role in shaping the gut microbiome, which implies that it may impact human health. Despite its significant contribution to diet, DW is often overlooked in studies examining dietary influences on the gut microbiota. This perspective explores our current understanding of the link between DW and the gut microbiota - an area of human microbiome science that has been surprisingly understudied. Existing studies reveal links between DW source, microbiota composition, and gut health, emphasizing the need for comprehensive investigations. Understanding the interplay between DW and gut microbiota holds potential for tailored interventions to enhance human health.

The mechanisms, hallmarks, and therapies for brain aging and age-related dementia

Age-related cognitive decline and dementia are significant manifestations of brain aging. As the elderly population grows rapidly, the health and socio-economic impacts of cognitive dysfunction have become increasingly significant. Although clinical treatment of dementia has faced considerable challenges over the past few decades, with limited breakthroughs in slowing its progression, there has been substantial progress in understanding the molecular mechanisms and hallmarks of age-related dementia (ARD). This progress brings new hope for the intervention and treatment of this disease. In this review, we categorize the latest findings in ARD biomarkers into four stages based on disease progression: healthy brain, pre-clinical, mild cognitive impairment, and dementia. We then systematically summarize the most promising therapeutic approaches to prevent or slow ARD at four levels: genome and epigenome, organelle, cell, and organ and organism. We emphasize the importance of early prevention and detection, along with the implementation of combined treatments as multimodal intervention strategies, to address brain aging and ARD in the future.

Bile acid modulation by gut microbiota: a bridge to understanding cognitive health

The gut microbiota plays an important role in regulating the body's physiological system, and more recently its impact on bile acid metabolism and cognitive function has been investigated by many studies. In addition to their conventional function in fat digestion and absorption, bile acids are now considered crucial signaling molecules that control several metabolic processes and immunological responses. For this purpose, the authors conducted comprehensive research using relevant terms in an attempt to understand more about the gut microbiota and its impact on bile acid metabolism and cognitive health. The gut-brain axis refers to the network of routes through which gut bacteria communicate with the brain. Through its capacity to bio-transform primary bile acids into secondary bile acids, the gut microbiota plays a significant role in bile acid metabolism. Bile acids function as signaling molecules and act on the brain through nuclear and membrane-bound receptors, influencing neurotransmitter production, neuroinflammation, and neuroplasticity to modify this communication. Any dysregulation in this axis can result in cognitive dysfunction. The link between gut microbiota, bile acids, and cognitive health cannot be ignored. It is imperative to explore this link further by conducting large-scale trials to improve the cognitive health of patients with multiple comorbidities, especially those involving the gastrointestinal tract and nervous system.

Microbiome and metabolome analyses indicate variations in the gut microbiota that disrupt regulation of appetite

The mechanism connecting gut microbiota to appetite regulation is not yet fully understood. This study identifies specific microbial community and metabolites that may influence appetite regulation. In the initial phase of the study, mice were administered a broad-spectrum antibiotic cocktail (ABX) for 10 days. The treatment significantly reduced gut microbes and disrupted the metabolism of arginine and tryptophan. Consequently, ABX-treated mice demonstrated a notable reduction in feed consumption. The hypothalamic expression levels of CART and POMC, two key anorexigenic factors, were significantly increased, while orexigenic factors, such as NPY and AGRP, were decreased. Notably, the levels of appetite-suppressing hormone cholecystokinin in the blood were significantly elevated. In the second phase, control mice were maintained, while the ABX-treated mice received saline, probiotics, and short-chain fatty acids (SCFAs) for an additional 10 days to restore their gut microbiota. The microbiota reconstructed by probiotic and SCFA treatments were quite similar, while microbiota of the naturally recovering mice demonstrated greater resemblance to that of the control mice. Notably, the abundance of Akkermansia and Bacteroides genera significantly increased in the reconstructed microbiota. Moreover, microbiota reconstruction corrected the disrupted arginine and tryptophan metabolism and the abnormal peripheral hormone levels caused by ABX treatment. Among the groups, SCFA-treated mice had the highest feed intake and NPY expression. Our findings indicate that gut microbes, especially Akkermansia, regulate arginine and tryptophan metabolism, thereby influencing appetite through the microbe-gut-brain axis.

The gut microbiota improves the efficacy of immune-checkpoint inhibitor immunotherapy against tumors: From association to cause and effect

Immune-checkpoint inhibitors (ICIs), including anti-PD-1/PD-L1 therapeutic antibodies, have markedly enhanced survival across numerous cancer types. However, the limited number of patients with durable benefits creates an urgent need to identify response biomarkers and to develop novel strategies so as to improve response. It is widely recognized that the gut microbiome is a key mediator in shaping immunity. Additionally, the gut microbiome shows significant potential in predicting the response to and enhancing the efficacy of ICI immunotherapy against cancer. Recent studies encompassing mechanistic analyses and clinical trials of microbiome-based therapy have shown a cause-and-effect relationship between the gut microbiome and the modulation of the ICI immunotherapeutic response, greatly contributing to the establishment of novel strategies that will improve response and overcome resistance to ICI treatment. In this review, we outline the current state of research advances and discuss the future directions of utilizing the gut microbiome to enhance the efficacy of ICI immunotherapy against tumors.

Intestinal mycobiota dysbiosis associated inflammation activation in chronic schizophrenia

The microbiome-gut-brain axis is related to schizophrenia (SCZ). The role of intestinal mycobiota in SCZ has been under investigated. We present a half-year follow-up study involving 109 chronic SCZ patients and 77 healthy controls. Intestinal mycobiota was tested by internal transcribed spacer (ITS). Untargeted liquid chromatography-mass spectrometry (LC-MS) was used to measure fecal metabolites. Symptom severity was assessed using the Positive and Negative Syndrome Scale. Enterotype analysis showed that Candida-type patients exhibited severer positive symptoms and depression factors than Saccharomyces-type patients. Candida and its top species and operational taxonomic units (OTUs) were positively correlated with depression factors (all p=0.001). Fecal metabolites analysis showed that upregulated metabolites were associated with chronic inflammation (NF-κB pathway and T helper cell differentiation), downregulated metabolites were associated with glutamate metabolism, serotonergic and dopaminergic synapse. Procrustes analysis revealed significant correlation between intestinal mycobiota and fecal metabolites (M2=0.937, p<0.001). Metabolic module analysis showed that the top module, MEturquoise (associated with Th1 and Th2 cell differentiation), was negatively correlated with SCZ (r=-0.783, p<0.0001), positively correlated with Candida, Aspergillus, Trichosporon and Talaromyces (decreased in SCZ) and negatively correlated with Saccharomyces (increased in SCZ). We also found impairments of intestinal barrier in SCZ, characterized by increased in blood D-lactate (mucosa impairment marker) and decreased in blood mucin 2 (mucosal barrier protective protein). Serum levels of TNF-α was increased and showed stable high levels during treatment. This study suggests that mycobiota dysbiosis-related chronic inflammation and an impaired intestinal mucosal barrier are associated with chronic SCZ.

Impacts of microbiota and its metabolites through gut-brain axis on pathophysiology of major depressive disorder

Major depressive disorder (MDD) is characterized by a high rate of recurrence and disability, which seriously affects the quality of life of patients. That's why a deeper understanding of the mechanisms of MDD pathology is an urgent task, and some studies have found that intestinal symptoms accompany people with MDD. The microbiota-gut-brain axis is the bidirectional communication between the gut microbiota and the central nervous system, which was found to have a strong association with the pathogenesis of MDD. Previous studies have focused more on the communication between the gut and the brain through neuroendocrine, neuroimmune and autonomic pathways, and the role of gut microbes and their metabolites in depression is unclear. Metabolites of intestinal microorganisms (e.g., tryptophan, kynurenic acid, indole, and lipopolysaccharide) can participate in the pathogenesis of MDD through immune and inflammatory pathways or by altering the permeability of the gut and blood-brain barrier. In addition, intestinal microbes can communicate with intestinal neurons and glial cells to affect the integrity and function of intestinal nerves. However, the specific role of gut microbes and their metabolites in the pathogenesis of MDD is not well understood. Hence, the present review summarizes how gut microbes and their metabolites are directly or indirectly involved in the pathogenesis of MDD.

The breath volatilome is shaped by the gut microbiota

The gut microbiota is widely implicated in host health and disease, inspiring translational efforts to implement our growing body of knowledge in clinical settings. However, the need to characterize gut microbiota by its genomic content limits the feasibility of rapid, point-of-care diagnostics. The microbiota produces a diverse array of xenobiotic metabolites that disseminate into tissues, including volatile organic compounds (VOCs) that may be excreted in breath. We hypothesize that breath contains gut microbe-derived VOCs that inform the composition and metabolic state of the microbiota. To explore this idea, we compared the breath volatilome and fecal gut microbiomes of 27 healthy children and found that breath VOC composition is correlated with gut microbiomes. To experimentally interrogate this finding, we devised a method for capturing exhaled breath from gnotobiotic mice. Breath volatiles are then profiled by gas-chromatography mass-spectrometry (GC-MS). Using this novel methodology, we found that the murine breath profile is markedly shaped by the composition of the gut microbiota. We also find that VOCs produced by gut microbes in pure culture can be identified in vivo in the breath of mice monocolonized with the same bacteria. Altogether, our studies identify microbe-derived VOCs excreted in breath and support a mechanism by which gut bacterial metabolism directly contributes to the mammalian breath VOC profiles.

The impact of altered dietary adenine concentrations on the gut microbiota in Drosophila

The gut microbiota influences host metabolism and health, impacting diseases. Research into how diet affects gut microbiome dynamics in model organisms is crucial but underexplored. Herein, we examined how dietary adenine affects uric acid levels and the gut microbiota over five generations of Drosophila melanogaster. Wild-type W1118 flies consumed diets with various adenine concentrations (GC: 0%, GL: 0.05%, and GH: 0.10%), and their gut microbiota were assessed via Illumina MiSeq sequencing. Adenine intake significantly increased uric acid levels in the GH group > the GC group. Despite no significant differences in the alpha diversity indices, there were significant disparities in the gut microbiota health index (GMHI) and dysbiosis index (MDI) among the groups. Adenine concentrations significantly altered the diversity and composition of the gut microbiota. High adenine intake correlated with increased uric acid levels and microbial population shifts, notably affecting the abundances of Proteobacteria and Firmicutes. The gut microbiota phenotypes included mobile elements, gram-positive bacteria, biofilm-forming bacteria, and gram-negative bacteria. The significantly enriched KEGG pathways included ageing, carbohydrate metabolism, and the immune system. In conclusion, adenine intake increases uric acid levels, alters gut microbiota, and affects KEGG pathways in Drosophila across generations. This study highlights the impact of dietary adenine on uric acid levels and the gut microbiota, providing insights into intergenerational nutritional effects.

Healing from Within: How Gut Microbiota Predicts IBD Treatment Success-A Systematic Review

Recent research indicates that the microbiome has a significant impact on the progression of inflammatory bowel disease (IBD) and that creating therapies that change its composition could positively impact the outcomes of IBD treatment. This review summarizes the results of extensive studies that examined IBD patients undergoing several therapies, including anti-TNF medication, vedolizumab, ustekinumab, probiotics, and fecal microbiota transplantation (FMT), and the alterations in their gut microbiota's composition and function. The objective was to investigate the variety and effectiveness of microbial species in order to discover new biomarkers or therapeutic targets that could improve the outcome of treatment for these patients. This research aimed to offer useful insights into personalized medicine techniques for managing IBD. Beneficial bacteria such as Faecalibacterium prausnitzii and Roseburia have been consistently linked to favorable clinical outcomes, whereas pathogenic bacteria such as Escherichia coli and Clostridioides difficile are associated with worsening disease conditions. Although many studies have examined the role of gut microbiota in IBD, there is still a need for more targeted research on the connection between specific microbial communities and treatment outcomes. This study sought to address this gap by exploring the intricate relationship between the gut microbiota composition and the effectiveness of IBD medications.

The gut microbiota-brain axis in neurological disorders

Previous studies have shown a bidirectional communication between human gut microbiota and the brain, known as the microbiota-gut-brain axis (MGBA). The MGBA influences the host's nervous system development, emotional regulation, and cognitive function through neurotransmitters, immune modulation, and metabolic pathways. Factors like diet, lifestyle, genetics, and environment shape the gut microbiota composition together. Most research have explored how gut microbiota regulates host physiology and its potential in preventing and treating neurological disorders. However, the individual heterogeneity of gut microbiota, strains playing a dominant role in neurological diseases, and the interactions of these microbial metabolites with the central/peripheral nervous systems still need exploration. This review summarizes the potential role of gut microbiota in driving neurodevelopmental disorders (autism spectrum disorder and attention deficit/hyperactivity disorder), neurodegenerative diseases (Alzheimer's and Parkinson's disease), and mood disorders (anxiety and depression) in recent years and discusses the current clinical and preclinical gut microbe-based interventions, including dietary intervention, probiotics, prebiotics, and fecal microbiota transplantation. It also puts forward the current insufficient research on gut microbiota in neurological disorders and provides a framework for further research on neurological disorders.

Glaucoma and the Human Microbiome

PURPOSE OF REVIEW

To explore a view of the human microbiome as an interconnected, functional, dynamic system that may be linked to the pathogenesis and progression of glaucoma.

METHODS

A literature review was undertaken that included publications from 1966 to 2023.

RESULTS

Bacterial lipopolysaccharides (LPS) activate toll-like receptors (TLR) and mediate the human immune response. The LPS-TLR4 pathway is a potential avenue for the ocular, gut, and oral microbiomes to interface and/or influence ocular disease. Studies of gut dysbiosis have shown that alterations in the healthy microbiota can predispose the host to immune-mediated inflammatory and neurodegenerative conditions, while oral and ocular surface dysbiosis has been correlated with glaucoma. While developmental exposure to commensal microflora has shown to be necessary for the autoimmune and neurodegenerative responses to elevated intraocular pressure to take place, commensal bacterial products like short-chain fatty acids have regulatory effects protective against glaucoma.

SUMMARY

Alterations to human microbiotas have been associated with changes in intestinal permeability, gene regulation, immune cell differentiation, and neural functioning, which may predispose the host to glaucoma. Select microbes have been highlighted for their potential contributions to glaucoma disease progression or protection, raising the potential for microbiota-based treatment modalities. Current topical glaucoma treatments may disrupt the ocular surface microbiota, potentially having ramifications on host health. Further study of the relationships between human microbiome and glaucoma is needed.

Probiotics and the microbiota-gut-brain axis in neurodegeneration: Beneficial effects and mechanistic insights

Neurodegenerative diseases (NDs) are a group of heterogeneous disorders with a high socioeconomic burden. Although pharmacotherapy is currently the principal therapeutic approach for the management of NDs, mounting evidence supports the notion that the protracted application of available drugs would abate their dopaminergic outcomes in the long run. The therapeutic application of microbiome-based modalities has received escalating attention in biomedical works. In-depth investigations of the bidirectional communication between the microbiome in the gut and the brain offer a multitude of targets for the treatment of NDs or maximizing the patient's quality of life. Probiotic administration is a well-known microbial-oriented approach to modulate the gut microbiota and potentially influence the process of neurodegeneration. Of note, there is a strong need for further investigation to map out the mechanistic prospects for the gut-brain axis and the clinical efficacy of probiotics. In this review, we discuss the importance of microbiome modulation and hemostasis via probiotics, prebiotics, postbiotics and synbiotics in ameliorating pathological neurodegenerative events. Also, we meticulously describe the underlying mechanism of action of probiotics and their metabolites on the gut-brain axis in different NDs. We suppose that the present work will provide a functional direction for the use of probiotic-based modalities in promoting current practical treatments for the management of neurodegenerative-related diseases.

The association of dietary inflammatory index with sleep outcomes: A systematic review

Background

Sleep is a vital physiological process that plays a crucial role in various aspects of human health and well-being. Regarding the important role of diet on the sleep quality, the present study aimed to assess the association of dietary inflammatory index (DII) with the sleep outcomes and also to provide the potential mechanisms of action.

Methods

PubMed, Web of Science and Scopus databases and Google Scholar search engine were systematically searched for relevant studies related to DII and sleep outcomes using appropriate search terms until February 2024.

Results

From the initial systematic search of databases, 197 studies were retrieved. However, only 14 of them met the criteria for evaluation. Out of these, eleven studies indicated a significant correlation between higher DII scores and poor overall sleep quality and/or short/long sleep duration or its subscales. On the contrary, four studies did not find any proof of this association.

Conclusion

This systematic review indicated that following an anti-inflammatory diet could potentially lead to an improvement in the sleep outcomes. Well-designed clinical trials in the future will be necessary to provide a better understanding and quantification of this association.

Opioid Use and Gut Dysbiosis in Cancer Pain Patients

Opioids are commonly used for the management of severe chronic cancer pain. Their well-known pharmacological effects on the gastrointestinal system, particularly opioid-induced constipation (OIC), are the most common limiting factors in the optimization of analgesia, and have led to the wide use of laxatives and/or peripherally acting mu-opioid receptor antagonists (PAMORAs). A growing interest has been recently recorded in the possible effects of opioid treatment on the gut microbiota. Preclinical and clinical data, as presented in this review, showed that alterations of the gut microbiota play a role in modulating opioid-mediated analgesia and tolerability, including constipation. Moreover, due to the bidirectional crosstalk between gut bacteria and the central nervous system, gut dysbiosis may be crucial in modulating opioid reward and addictive behavior. The microbiota may also modulate pain regulation and tolerance, by activating microglial cells and inducing the release of inflammatory cytokines and chemokines, which sustain neuroinflammation. In the subset of cancer patients, the clinical meaning of opioid-induced gut dysbiosis, particularly its possible interference with the efficacy of chemotherapy and immunotherapy, is still unclear. Gut dysbiosis could be a new target for treatment in cancer patients. Restoring the physiological amount of specific gut bacteria may represent a promising therapeutic option for managing gastrointestinal symptoms and optimizing analgesia for cancer patients using opioids.

Effects of Different Cow-Milk Beta-Caseins on the Gut-Brain Axis: A Narrative Review of Preclinical, Animal, and Human Studies

The gut and brain communicate through bidirectional neural, endocrine, and immune signals to coordinate central nervous system activity with gastrointestinal function. Dysregulated inflammation can promote immune cell activation and increase entero-endocrine signaling and intestinal permeability; hence, a functional gut-brain axis is necessary for a healthy digestive system. The consumption of milk products can lead to gut discomfort via effects on gastrointestinal tract function and the inflammatory state, which, in turn, affect the brain. A1 β-casein and A2 β-casein are major components of bovine-milk protein, and their digestion may result in different physiological effects following the consumption of milk products. Peptides derived from A1 β-casein, such as β-casomorphins, may increase gut dysfunction and inflammation, thereby modulating the availability of bioactive metabolites in the bloodstream and contribute to changes in cognitive function. This narrative review examines the functional interrelationships between the consumption of cow-milk-derived β-caseins and their effect on the brain, immune system, and the gut, which together comprise the gut-brain axis.

Effects of salidroside on atherosclerosis: potential contribution of gut microbiota

Much research describes gut microbiota in atherosclerotic cardiovascular diseases (ASCVD) for that the composition of the intestinal microbiome or its metabolites can directly participate in the development of endothelial dysfunction, atherosclerosis and its adverse complications. Salidroside, a natural phenylpropane glycoside, exhibits promising biological activity against the progression of ASCVD. Recent studies suggested that the gut microbiota played a crucial role in mediating the diverse beneficial effects of salidroside on health. Here, we describe the protective effects of salidroside against the progression of atherosclerosis. Salidroside regulates the abundance of gut microbiotas and gut microbe-dependent metabolites. Moreover, salidroside improves intestinal barrier function and maintains intestinal epithelial barrier function integrity. In addition, salidroside attenuates the inflammatory responses exacerbated by gut microbiota disturbance. This review delves into how salidroside functions to ameliorate atherosclerosis by focusing on its interaction with gut microbiota, uncovering the potential roles of gut microbiota in the diverse biological impacts of salidroside.

Berberine alleviates Alzheimer's disease by regulating the gut microenvironment, restoring the gut barrier and brain-gut axis balance

BACKGROUND

Alzheimer's disease (AD) is the most common neurodegenerative disease. Intestinal flora and its metabolism play a significant role in ameliorating central nervous system disorders, including AD, through bidirectional interactions between the gut-brain axis. A naturally occurring alkaloid compound called berberine (BBR) has neuroprotective properties and prevents Aβ-induced microglial activation. Additionally, BBR can suppress the synthesis of Aβ and decrease BACE1 expression. However, it is still unclear if BBR therapy can alleviate AD by changing the gut flora.

PURPOSE

In this study, we examined whether a partial alleviation of AD could be achieved with BBR treatment and the molecular mechanisms involved.

METHODS

We did this by analyzing alterations in Aβ plaques, neurons, and related neuroinflammation-related markers in the brain and the transcriptome of the mouse brain. The relationship between the intestinal flora of 5xFAD model mice and BBR treatment was investigated using high-throughput sequencing analysis of 16S rRNA from mouse feces.

RESULTS

The findings demonstrated that treatment with BBR cleared Aβ plaques, alleviated neuroinflammation, and ameliorated spatial memory dysfunction in AD. BBR significantly alleviated intestinal inflammation, decreased intestinal permeability, and could improve intestinal microbiota composition in 5xFAD mice.

Impact of cadmium and diclofenac exposure on biochemical responses, transcriptome, gut microflora, and growth performance in grass carp (Ctenopharyngodonidella)

In recent years, the concentrations of cadmium (Cd) and diclofenac (DCF) in water have frequently exceeded the standard; however, the toxic effects of these two pollutants on grass carp under single and combined exposure are unknown. In this study, the concentrations of pollutants in different tissues were detected, and the toxicities of the two pollutants to grass carp under different exposure conditions were compared based on growth traits, biochemical responses, gut microbiome, and transcriptomes. Based on these findings, the brain showed the lowest levels of Cd and DCF accumulation. Oxidative stress and pathological damage were observed in the brain and intestines. Changes in the structure and abundance of the gut microflora affect the synthesis of neurotransmitters, such as GABA and steroids. Differentially expressed genes in the brain were enriched in circadian rhythm functions. The expression of PER, CLOCK,1L-1β, 1L-17, and other genes are related to the abundance of Akkermansia, which indicates that the disorder of gut microflora will affect the normal circadian rhythm of the brain. All indices in the recovery group showed an increasing trend. Overall, the toxicity of Cd and DCF showed antagonism, and a single exposure had a stronger effect on gut microorganisms and circadian rhythm, which provided a scientific basis for exploring the comprehensive effects of different pollutants.

Characterization of Gut Microbiota in Rats and Rhesus Monkeys After Methamphetamine Self-administration

Methamphetamine (MA) is one of the most abused drugs globally, but the mechanism of its addiction remains unclear. Several animal studies have shown that the gut microbiota (GM) influences addictive behaviors, but the pattern of GM changes during addiction in animals of different species remains unclear. The aim of this study was to explore the association between dynamic changes in GM and MA self-administration acquisition among two classical mammals, rhesus monkeys (Macaca mulatta) and rats, MA self-administration models. Male Sprague-Dawley rats and male rhesus monkeys were subjected to classical MA self-administration training, and fecal samples were collected before and after MA self-administration training, respectively. 16S rRNA sequencing was used for GM analyses. We found that GM changes were more pronounced in rats than in rhesus monkeys, as evidenced by more GM taxa producing significant differences before and after MA self-administration training in rats than in monkeys. We also found that the expression of the genus Clostridia_vadinBB60_group significantly decreased after MA self-administration training in both rats and rhesus monkeys. Lactobacillus changes were significantly negatively correlated with total MA uptake in rats (Pearson R =  - 0.666, p = 0.035; Spearman R =  - 0.721, p = 0.023), whereas its change was also highly negatively correlated with total MA uptake in rhesus monkeys (Pearson R =  - 0.882, p = 0.118; Spearman R =  - 1.000, p = 0.083), although this was not significant. These findings suggest that MA causes significant alterations in GM in both rhesus monkeys and rats and that the genus Lactobacillus might be a common therapeutic target for MA uptake prevention across the species.

Effect of probiotics on children with autism spectrum disorders: a meta-analysis

BACKGROUND

Researches have found that alteration of intestinal flora may be closely related to the development of autism spectrum disorder (ASD). However, whether probiotics supplementation has a protective effect on ASD remains controversial. This meta-analysis aimed to analyze the outcome of probiotics in the treatment of ASD children.

METHODS

The Pubmed, Cochrane Library, Web of Science and Embase were searched until Sep 2022. Randomized controlled trials (RCTs) relevant to the probiotics and placebo treatment on ASD children were screened. Quality assessment of the included RCTs was evaluated by the Cochrane collaboration's tool. The primary outcomes were ASD assessment scales, including ABC (aberrant behavior checklist) and CBCL (child behavior checklist) for evaluating the behavior improvement, SRS (social responsiveness scale) for social assessment, DQ (developmental quotient) for physical and mental development and CGI-I (clinical global impression improvement) for overall improvement. The secondary outcome was total 6-GSI (gastrointestinal severity index).

RESULTS

In total, 6 RCTs from 6 studies with 302 children were included in the systemic review. Total 6-GSI (MD=-0.59, 95%CI [-1.02,-0.17], P < 0.05) decreased significantly after oral administration of probiotics. Whereas, there was no statistical difference in ABC, CBCL, SRS, DQ and CGI-I between probiotics and placebo groups in ASD children.

CONCLUSION

Probiotics treatment could improve gastrointestinal symptoms, but there was no significant improvement in ASD.

Gut Microbiome Interactions with Oxidative Stress: Mechanisms and Consequences for Health

Understanding how gut flora interacts with oxidative stress has been the subject of significant research in recent years. There is much evidence demonstrating the existence of the microbiome-oxidative stress interaction. However, the biochemical basis of this interaction is still unclear. In this narrative review, possible pathways of the gut microbiota and oxidative stress interaction are presented, among which genetic underpinnings play an important role. Trimethylamine-N-oxide, mitochondria, short-chain fatty acids, and melatonin also appear to play roles. Moreover, the relationship between oxidative stress and the gut microbiome in obesity, metabolic syndrome, chronic ethanol consumption, dietary supplements, and medications is considered. An investigation of the correlation between bacterial community features and OS parameter changes under normal and pathological conditions might provide information for the determination of new research methods. Furthermore, such research could contribute to establishing a foundation for determining the linkers in the microbiome-OS association.

Microbiome and Metabolite Analysis Insight into the Potential of Shrimp Head Hydrolysate to Alleviate Depression-like Behaviour in Growth-Period Mice Exposed to Chronic Stress

Chronic stress (CS) endangers the physical and mental health of adolescents. Therefore, alleviating and preventing such negative health impacts are a top priority. This study explores the effect of feeding shrimp head hydrolysate (SHH) on gut microbiota, short-chain fatty acids (SCFAs), and neurotransmitters in growing C57BL/6 mice subjected to chronic unpredictable mild stress. Mice in the model group and three SHH groups were exposed to CS for 44 days, distilled water and SHH doses of 0.18, 0.45, 0.90 g/kg·BW were given respectively by gavage daily for 30 days from the 15th day. The results showed that SHH can significantly reverse depression-like behaviour, amino acids degradation, α diversity and β diversity, proportion of Firmicutes and Bacteroidota, abundance of genera such as Muribaculaceae, Bacteroides, Prevotellaceae_UCG-001, Parabacteroides and Alistipes, concentration of five short-chain fatty acids (SCFAs), 5-HT and glutamate induced by CS. Muribaculaceae and butyric acid may be a controlled target. This study highlights the potential and broad application of SHH as an active ingredient in food to combat chronic stress damage.

Comprehensive Analysis of Gut Microbiota Composition and Functional Metabolism in Children with Autism Spectrum Disorder and Neurotypical Children: Implications for Sex-Based Differences and Metabolic Dysregulation

This study aimed to investigate the gut microbiota composition in children with autism spectrum disorder (ASD) compared to neurotypical (NT) children, with a focus on identifying potential differences in gut bacteria between these groups. The microbiota was analyzed through the massive sequencing of region V3-V4 of the 16S RNA gene, utilizing DNA extracted from stool samples of participants. Our findings revealed no significant differences in the dominant bacterial phyla (Firmicutes, Bacteroidota, Actinobacteria, Proteobacteria, Verrucomicrobiota) between the ASD and NT groups. However, at the genus level, notable disparities were observed in the abundance of Blautia, Prevotella, Clostridium XI, and Clostridium XVIII, all of which have been previously associated with ASD. Furthermore, a sex-based analysis unveiled additional discrepancies in gut microbiota composition. Specifically, three genera (Megamonas, Oscilibacter, Acidaminococcus) exhibited variations between male and female groups in both ASD and NT cohorts. Particularly noteworthy was the exclusive presence of Megamonas in females with ASD. Analysis of predicted metabolic pathways suggested an enrichment of pathways related to amine and polyamine degradation, as well as amino acid degradation in the ASD group. Conversely, pathways implicated in carbohydrate biosynthesis, degradation, and fermentation were found to be underrepresented. Despite the limitations of our study, including a relatively small sample size (30 ASD and 31 NT children) and the utilization of predicted metabolic pathways derived from 16S RNA gene analysis rather than metagenome sequencing, our findings contribute to the growing body of evidence suggesting a potential association between gut microbiota composition and ASD. Future research endeavors should focus on validating these findings with larger sample sizes and exploring the functional significance of these microbial differences in ASD. Additionally, there is a critical need for further investigations to elucidate sex differences in gut microbiota composition and their potential implications for ASD pathology and treatment.

Mild cognitive impairment and microbiota: what is known and future perspectives

Mild cognitive impairment (MCI) is a heterogeneous condition definable as the intermediate clinical state between normal aging and dementia. As a pre-dementia condition, there is a recent growing interest in the identification of non-invasive markers able to predict the progression from MCI to a more advanced stage of the disease. Previous evidence showed the close link between gut microbiota and neurodegenerative diseases, such as Alzheimer's (AD) and Parkinson's disease (PD). Conversely, the actual relationship between gut microbiota and MCI is yet to be clarified. In this work, we provide an overview about the current knowledge regarding the role of gut microbiota in the context of MCI, also assessing the potential for microbiota-targeted therapies. Through the review of the most recent studies focusing on this topic, we found evidence of an increase of Bacteroidetes at phylum level and Bacteroides at genus level in MCI subjects with respect to healthy controls and patients with AD. Despite such initial evidence, the definitive identification of a typical microbiota profile associated with MCI is still far from being achieved. These preliminary results, however, are growingly encouraging research on the role of gut microbiota modulation in improving the cognitive status of pre-dementia subjects. To date, few studies evaluated the role of probiotics in MCI subjects, and they showed favorable results, although still biased by small sample size, heterogeneity of study design and short follow-up.

Neurotoxic mechanisms of mycotoxins: Focus on aflatoxin B1 and T-2 toxin

Aflatoxin B1 (AFB1) and T-2 toxin are commonly found in animal feed and stored grain, posing a serious threat to human and animal health. Mycotoxins can penetrate brain tissue by compromising the blood-brain barrier, triggering oxidative stress and neuroinflammation, and leading to oxidative damage and apoptosis of brain cells. The potential neurotoxic mechanisms of AFB1 and T-2 toxin were discussed by summarizing the relevant research reports from the past ten years. AFB1 and T-2 toxin cause neuronal damage in the cerebral cortex and hippocampus, leading to synaptic transmission dysfunction, ultimately impairing the nervous system function of the body. The toxic mechanism is related to excessive reactive oxygen species (ROS), oxidative stress, mitochondrial dysfunction, apoptosis, autophagy, and an exaggerated inflammatory response. After passing through the blood-brain barrier, toxins can directly affect glial cells, alter the activation state of microglia and astrocytes, thereby promoting brain inflammation, disrupting the blood-brain barrier, and influencing the synaptic transmission process. We discussed the diverse effects of various concentrations of toxins and different modes of exposure on neurotoxicity. In addition, toxins can also cross the placental barrier, causing neurotoxic symptoms in offspring, as demonstrated in various species. Our goal is to uncover the underlying mechanisms of the neurotoxicity of AFB1 and T-2 toxin and to provide insights for future research, including investigating the impact of mycotoxins on interactions between microglia and astrocytes.

Comparative Metabolomics and Microbiome Analysis of Ethanol versus OMNImet/gene•GUT Fecal Stabilization

Metabolites from feces provide important insights into the functionality of the gut microbiome. As immediate freezing is not always feasible in gut microbiome studies, there is a need for sampling protocols that provide the stability of the fecal metabolome and microbiome at room temperature (RT). Here, we investigated the stability of various metabolites and the microbiome (16S rRNA) in feces collected in 95% ethanol (EtOH) and commercially available sample collection kits with specific preservatives OMNImet•GUT/OMNIgene•GUT. To simulate field-collection scenarios, the samples were stored at different temperatures at varying durations (24 h + 4 °C, 24 h RT, 36 h RT, 48 h RT, and 7 days RT) and compared to aliquots immediately frozen at -80 °C. We applied several targeted and untargeted metabolomics platforms to measure lipids, polar metabolites, endocannabinoids, short-chain fatty acids (SCFAs), and bile acids (BAs). We found that SCFAs in the nonstabilized samples increased over time, while a stable profile was recorded in sample aliquots stored in 95% EtOH and OMNImet•GUT. When comparing the metabolite levels between aliquots stored at room temperature and at +4 °C, we detected several changes in microbial metabolites, including multiple BAs and SCFAs. Taken together, we found that storing samples at RT and stabilizing them in 95% EtOH yielded metabolomic results comparable to those from flash freezing. We also found that the overall composition of the microbiome did not vary significantly between different storage types. However, notable differences were observed in the α diversity. Altogether, the stability of the metabolome and microbiome in 95% EtOH provided results similar to those of the validated commercial collection kits OMNImet•GUT and OMNIgene•GUT, respectively.

The regulatory effect of polysaccharides on the gut microbiota and their effect on human health: A review

Polysaccharides with low toxicity and high biological activities are a kind of biological macromolecule. Recently, growing studies have confirmed that polysaccharides could improve obesity, diabetes, tumors, inflammatory bowel disease, hyperlipidemia, diarrhea, and liver-related diseases by changing the intestinal micro-environment. Moreover, polysaccharides could promote human health by regulating gut microbiota, enhancing production of short-chain fatty acids (SCFAs), improving intestinal mucosal barrier, regulating lipid metabolism, and activating specific signaling pathways. Notably, the biological activities of polysaccharides are closely related to their molecular weight, monosaccharide composition, glycosidic bond types, and regulation of gut microbiota. The intestinal microbiota can secrete glycoside hydrolases, lyases, and esterases to break down polysaccharides chains and generate monosaccharides, thereby promoting their absorption and utilization. The degradation of polysaccharides can produce SCFAs, further regulating the proportion of gut microbiota and achieving the effect of preventing and treating various diseases. This review aims to summarize the latest studies: 1) effect of polysaccharides structures on intestinal flora; 2) regulatory effect of polysaccharides on gut microbiota; 3) effects of polysaccharides on gut microbe-mediated diseases; 4) regulation of gut microbiota on polysaccharides metabolism. The findings are expected to provide important information for the development of polysaccharides and the treatment of diseases.

Perceived Taste and Olfactory Dysfunctions and Subsequent Stroke Risk

Background

Taste and olfactory dysfunction are commonly associated with neurodegenerative diseases and cardiovascular risk factors, but their specific associations with stroke risk remain uncertain.

Objectives

The purpose of this paper was to explore whether perceived taste and olfactory dysfunctions were associated with stroke risk.

Methods

Included were 85,656 participants (mean age 51.0 ± 15.3 years) of the Kailuan study. Perceived olfactory and taste dysfunctions were assessed via a questionnaire at baseline (in 2014-2016). Incident stroke cases were confirmed by review of medical records. Cox proportional hazards models were used to investigate associations of perceived olfactory and taste dysfunctions with stroke risk, and mediation analysis was used to estimate the mediating effect of chronic disease statuses.

Results

We documented 2,198 incident stroke cases during a mean of 5.6 years of follow-up. Perceived taste dysfunction was associated with a doubled risk of developing total stroke (adjusted HR: 2.03; 95% CI: 1.36-3.04; P < 0.001) even with adjustment of lifestyle factors, biomarkers (ie, blood lipids, blood glucose, blood pressure, and uric acid), and other potential confounders. However, perceived olfactory dysfunction (adjusted HR: 1.22; 95% CI: 0.79-1.90; P = 0.34) was not significantly associated with a high risk of total stroke. Similar results of both perceived taste and olfactory dysfunctions were observed for ischemic stroke. Presence of chronic diseases, including hypertension, diabetes, chronic kidney disease, and overweight/obesity, mediated 4% to 5% of the association of perceived taste dysfunction with both total stroke and ischemic stroke.

Conclusions

In this large cohort study, perceived taste dysfunction was associated with a high risk of developing stroke.

Combining fecal 16 S rRNA sequencing and spinal cord metabolomics analysis to explain the modulatory effect of PPARα on neuropathic pain

BACKGROUND

Existing evidence suggests that the composition of the gut microbiota is associated with neuropathic pain (NP), but the mechanistic link is elusive. Peroxisome proliferator-activated receptor α (PPARα) has been shown to be a pharmacological target for the treatment of metabolic disorders, and its expression is also involved in inflammatory regulation. The aim of this study was to investigate the important modulatory effects of PPARα on gut microbiota and spinal cord metabolites in mice subjected to chronic constriction injury.

METHODS

We analyzed fecal microbiota and spinal cord metabolic alterations in mice from the sham, CCI, GW7647 (PPARα agonist) and GW6471 (PPARα antagonist) groups by 16 S rRNA amplicon sequencing and untargeted metabolomics analysis. On this basis, the intestinal microbiota and metabolites that were significantly altered between treatment groups were analyzed in a combined multiomics analysis. We also investigated the effect of PPARα on the polarization fractionation of spinal microglia.

RESULTS

PPARα agonist significantly reduce paw withdrawal threshold and paw withdrawal thermal latency, while PPARα antagonist significantly increase paw withdrawal threshold and paw withdrawal thermal latency. 16 S rRNA gene sequencing showed that intraperitoneal injection of GW7647 or GW6471 significantly altered the abundance, homogeneity and composition of the gut microbiome. Analysis of the spinal cord metabolome showed that the levels of spinal cord metabolites were shifted after exposure to GW7647 or GW6471. Alterations in the composition of gut microbiota were significantly associated with the abundance of various spinal cord metabolites. The abundance of Licheniformes showed a significant positive correlation with nicotinamide, benzimidazole, eicosanoids, and pyridine abundance. Immunofluorescence results showed that intraperitoneal injection of GW7647 or GW6471 altered microglial activation and polarization levels.

CONCLUSION

Our study shows that PPARα can promote M2-type microglia polarization, as well as alter gut microbiota and metabolites in CCI mice. This study enhances our understanding of the mechanism of PPARα in the treatment of neuropathic pain.

Applied physiology: gut microbiota and antimicrobial therapy

The gut microbiota plays an important role in maintaining human health and in the pathogenesis of several diseases. Antibiotics are among the most commonly prescribed drugs and have a significant impact on the structure and function of the gut microbiota. The understanding that a healthy gut microbiota prevents the development of many diseases has also led to its consideration as a potential therapeutic target. At the same time, any factor that alters the gut microbiota becomes important in this approach. Exercise and antibacterial therapy have a direct effect on the microbiota. The review reflects the current state of publications on the mechanisms of intestinal bacterial involvement in the pathogenesis of cardiovascular, metabolic, and neurodegenerative diseases. The physiological mechanisms of the influence of physical activity on the composition of the gut microbiota are considered. The mechanisms of the common interface between exercise and antibacterial therapy will be considered using the example of several socially important diseases. The aim of the study is to show the physiological relationship between the effects of exercise and antibiotics on the gut microbiota.

Gut-brain axis in the pathogenesis of sepsis-associated encephalopathy

The gut-brain axis is a bidirectional communication network linking the gut and the brain, overseeing digestive functions, emotional responses, body immunity, brain development, and overall health. Substantial research highlights a connection between disruptions of the gut-brain axis and various psychiatric and neurological conditions, including depression and Alzheimer's disease. Given the impact of the gut-brain axis on behavior, cognition, and brain diseases, some studies have started to pay attention to the role of the axis in sepsis-associated encephalopathy (SAE), where cognitive impairment is the primary manifestation. SAE emerges as the primary and earliest form of organ dysfunction following sepsis, potentially leading to acute cognitive impairment and long-term cognitive decline in patients. Notably, the neuronal damage in SAE does not stem directly from the central nervous system (CNS) infection but rather from an infection occurring outside the brain. The gut-brain axis is posited as a pivotal factor in this process. This review will delve into the gut-brain axis, exploring four crucial pathways through which inflammatory signals are transmitted and elevate the incidence of SAE. These pathways encompass the vagus nerve pathway, the neuroendocrine pathway involving the hypothalamic-pituitary-adrenal (HPA) axis and serotonin (5-HT) regulation, the neuroimmune pathway, and the microbial regulation. These pathways can operate independently or collaboratively on the CNS to modulate brain activity. Understanding how the gut affects and regulates the CNS could offer the potential to identify novel targets for preventing and treating this condition, ultimately enhancing the prognosis for individuals with SAE.

Impact of menopause-associated frailty on traumatic brain injury

Navigating menopause involves traversing a complex terrain of hormonal changes that extend far beyond reproductive consequences. Menopausal transition is characterized by a decrease in estradiol-17β (E2), and the impact of menopause resonates not only in the reproductive system but also through the central nervous system, musculoskeletal, and gastrointestinal domains. As women undergo menopausal transition, they become more susceptible to frailty, amplifying the risk and severity of injuries, including traumatic brain injury (TBI). Menopause triggers a cascade of changes leading to a decline in muscle mass, accompanied by diminished tone and excitability, thereby restricting the availability of irisin, a crucial hormone derived from muscles. Concurrently, bone mass undergoes reduction, culminating in the onset of osteoporosis and altering the dynamics of osteocalcin, a hormone originating from bones. The diminishing levels of E2 during menopause extend their influence on the gut microbiota, resulting in a reduction in the availability of tyrosine, tryptophan, and serotonin metabolites, affecting neurotransmitter synthesis and function. Understanding the interplay between menopause, frailty, E2 decline, and the intricate metabolisms of bone, gut, and muscle is imperative when unraveling the nuances of TBI after menopause. The current review underscores the significance of accounting for menopause-associated frailty in the incidence and consequences of TBI. The review also explores potential mechanisms to enhance gut, bone, and muscle health in menopausal women, aiming to mitigate frailty and improve TBI outcomes.