Microbiota-Gut-Brain Axis: New Therapeutic Opportunities

Lacticaseibacillus rhamnosus KY16 Improves Depression by Promoting Intestinal Secretion of 5-HTP and Altering the Gut Microbiota

Increasing research suggests a connection between gut microbiota and depressive disorders. Targeted changes to the intestinal flora may contribute to alleviating anxiety and depression. This study aimed to identify probiotics that could attenuate stress-induced abnormal behavior and explore potential mechanisms. The administration of LR.KY16 significantly reduced stress-induced abnormal behaviors and physiological dysfunction. The mechanism may be via regulating the structure of the intestinal microbiota in mice, increasing the abundance of Akkermansia muciniphila, prompting enterochromaffin cells to secrete 5-HTP in the gut, which enters the brain through the bloodstream and promotes the synthesis of 5-HT in the brain, and then activates brain-derived neurotrophic factor (BDNF)/tyrosine kinase receptor B (TrkB) through the 5-HT1A receptor. In addition, LR.KY16 also increased the expression of claudin-7, occludin, and zonula occludens-1 (ZO-1) in the colon, inhibited microglial M1 polarization, and inhibited systemic inflammation.

Contrasting the pharmacokinetic performance and gut microbiota effects of an amorphous solid dispersion and lipid nanoemulsion for a poorly water-soluble anti-psychotic

Increasing attention is being afforded to understanding the bidirectional relationship that exists between oral drugs and the gut microbiota. Often overlooked, however, is the impact that pharmaceutical excipients exert on the gut microbiota. Subsequently, in this study, we contrasted the pharmacokinetic performance and gut microbiota interactions between two commonly employed formulations for poorly soluble compounds, namely 1) an amorphous solid dispersion (ASD) stabilised by poly(vinyl pyrrolidone) K-30, and 2) a lipid nanoemulsion (LNE) comprised of medium chain glycerides and lecithin. The poorly soluble antipsychotic, lurasidone, was formulated with ASD and LNE due to its rate-limiting dissolution, poor oral bioavailability, and significant food effect. Both the ASD and LNE were shown to facilitate lurasidone supersaturation within in vitro dissolution studies simulating the gastrointestinal environment. This translated into profound improvements in oral pharmacokinetics in rats, with the ASD and LNE exerting comparable ∼ 2.5-fold improvements in lurasidone bioavailability, compared to the pure drug. The oral formulations imparted contrasting effects on the gut microbiota, with the LNE depleting the richness and abundance of the microbial ecosystem, as evidenced through reductions in alpha diversity (Chao1 index) and operational taxonomical units (OTUs). In contrast, the ASD exerted a 'gut neutral' effect, whereby a mild enrichment of alpha diversity and OTUs was observed. Importantly, this suggests that ASDs are effective solubility-enhancing formulations that can be used without comprising the integrity of the gut microbiota - an integral consideration in the treatment of mental health disorders, such as schizophrenia, due to the role of the gut microbiota in regulating mood and cognition.

The gut microbiota-immune-brain axis in a wild vertebrate: dynamic interactions and health impacts

The gut microbiota-immune-brain axis is a feedback network which influences diverse physiological processes and plays a pivotal role in overall health and wellbeing. Although research in humans and laboratory mice has shed light into the associations and mechanisms governing this communication network, evidence of such interactions in wild, especially in young animals, is lacking. We therefore investigated these interactions during early development in a population of common buzzards (Buteo buteo) and their effects on individual condition. In a longitudinal study, we used a multi-marker approach to establish potential links between the bacterial and eukaryotic gut microbiota, a panel of immune assays and feather corticosterone measurements as a proxy for long-term stress. Using Bayesian structural equation modeling, we found no support for feedback between gut microbial diversity and immune or stress parameters. However, we did find strong relationships in the feedback network. Immunity was negatively correlated with corticosterone levels, and microbial diversity was positively associated with nestling body condition. Furthermore, corticosterone levels and eukaryotic microbiota diversity decreased with age while immune activity increased. The absence of conclusive support for the microbiota-immune-brain axis in common buzzard nestlings, coupled with the evidence for stress mediated immunosuppression, suggests a dominating role of stress-dominated maturation of the immune system during early development. Confounding factors inherent to wild systems and developing animals might override associations known from adult laboratory model subjects. The positive association between microbial diversity and body condition indicates the potential health benefits of possessing a diverse and stable microbiota.

Fecal microbiota transplantation ameliorates high-fat diet-induced memory impairment in mice

Gut dysbiosis is linked to metabolic and neurodegenerative diseases and comprises a plausible link between high-fat diet (HFD) and brain dysfunction. Here we show that gut microbiota modulation by either antibiotic treatment for 5 weeks or a brief 3-day fecal microbiota transplantation (FMT) regimen from low-fat (control) diet-fed mice decreased weight gain, adipose tissue hypertrophy, and glucose intolerance induced by HFD in C57BL/6 male mice. Notably, gut microbiota modulation by FMT completely reversed impaired recognition memory induced by HFD, whereas modulation by antibiotics had less pronounced effect. Improvement in recognition memory by FMT was accompanied by decreased HFD-induced astrogliosis in the hippocampal cornu ammonis region. Gut microbiome composition analysis indicated that HFD diminished microbiota diversity compared to control diet, whereas FMT partially restored the phyla diversity. Our findings reinforce the role of the gut microbiota on HFD-induced cognitive impairment and suggest that modulating the gut microbiota may be an effective strategy to prevent metabolic and cognitive dysfunction associated with unfavorable dietary patterns.

Gut microbiota: the indispensable player in neurodegenerative diseases

As one of the most urgent social and health problems in the world, neurodegenerative diseases have always been of interest to researchers. However, the pathological mechanisms and therapeutic approaches are not achieved. In addition to the established roles of oxidative stress, inflammation and immune response, changes of gut microbiota are also closely related to the pathogenesis of neurodegenerative diseases. Gut microbiota is the central player of the gut-brain axis, the dynamic bidirectional communication pathway between gut microbiota and central nervous system, and emerging insights have confirmed its indispensability in the development of neurodegenerative diseases. In this review, we discuss the complex relationship between gut microbiota and the central nervous system from the perspective of the gut-brain axis; review the mechanism of microbiota for the modulation different neurodegenerative diseases and discuss how different dietary patterns affect neurodegenerative diseases via gut microbiota; and prospect the employment of gut microbiota in the therapeutic approach to those diseases. © 2024 Society of Chemical Industry.

Influence of human gut microbiome on the healthy and the neurodegenerative aging

The gut microbiome plays a crucial role in host health throughout the lifespan by influencing brain function during aging. The microbial diversity of the human gut microbiome decreases during the aging process and, as a consequence, several mechanisms increase, such as oxidative stress, mitochondrial dysfunction, inflammatory response, and microbial gut dysbiosis. Moreover, evidence indicates that aging and neurodegeneration are closely related; consequently, the gut microbiome may serve as a novel marker of lifespan in the elderly. In this narrative study, we investigated how the changes in the composition of the gut microbiome that occur in aging influence to various neuropathological disorders, such as mild cognitive impairment (MCI), dementia, Alzheimer's disease (AD), and Parkinson's disease (PD); and which are the possible mechanisms that govern the relationship between the gut microbiome and cognitive impairment. In addition, several studies suggest that the gut microbiome may be a potential novel target to improve hallmarks of brain aging and to promote healthy cognition; therefore, current and future therapeutic interventions have been also reviewed.

The gut microbiome: an important role in neurodegenerative diseases and their therapeutic advances

There are complex interactions between the gut and the brain. With increasing research on the relationship between gut microbiota and brain function, accumulated clinical and preclinical evidence suggests that gut microbiota is intimately involved in the pathogenesis of neurodegenerative diseases (NDs). Increasingly studies are beginning to focus on the association between gut microbiota and central nervous system (CNS) degenerative pathologies to find potential therapies for these refractory diseases. In this review, we summarize the changes in the gut microbiota in Alzheimer's disease, Parkinson's disease, multiple sclerosis, and amyotrophic lateral sclerosis and contribute to our understanding of the function of the gut microbiota in NDs and its possible involvement in the pathogenesis. We subsequently discuss therapeutic approaches targeting gut microbial abnormalities in these diseases, including antibiotics, diet, probiotics, and fecal microbiota transplantation (FMT). Furthermore, we summarize some completed and ongoing clinical trials of interventions with gut microbes for NDs, which may provide new ideas for studying NDs.

Role of inflammatory cytokines and the gut microbiome in vascular dementia: insights from Mendelian randomization analysis

Background

Both inflammatory cytokines and the gut microbiome are susceptibility factors for vascular dementia (VaD). The trends in the overall changes in the dynamics of inflammatory cytokines and in the composition of the gut microbiome are influenced by a variety of factors, making it difficult to fully explain the different effects of both on the different subtypes of VaD. Therefore, this Mendelian randomization (MR) study identified the inflammatory cytokines and gut microbiome members that influence the risk of developing VaD and their causal effects, and investigated whether inflammatory cytokines are gut microbiome mediators affecting VaD.

Methods

We obtained pooled genome-wide association study (GWAS) data for 196 gut microbiota and 41 inflammatory cytokines and used GWAS data for six VaD subtypes, namely, VaD (mixed), VaD (multiple infarctions), VaD (other), VaD (subcortical), VaD (sudden onset), and VaD (undefined). We used the inverse-variance weighted (IVW) method as the primary MR analysis method. We conducted sensitivity analyses and reverse MR analyses to examine reverse causal associations, enhancing the reliability and stability of the conclusions. Finally, we used multivariable MR (MVMR) analysis to assess the direct causal effects of inflammatory cytokines and the gut microbiome on the risk of VaD, and performed mediation MR analysis to explore whether inflammatory factors were potential mediators.

Results

Our two-sample MR study revealed relationships between the risk of six VaD subtypes and inflammatory cytokines and the gut microbiota: 7 inflammatory cytokines and 14 gut microbiota constituents were positively correlated with increased VaD subtype risk, while 2 inflammatory cytokines and 11 gut microbiota constituents were negatively correlated with decreased VaD subtype risk. After Bonferroni correction, interleukin-18 was correlated with an increased risk of VaD (multiple infarctions); macrophage migration inhibitory factor was correlated with an increased risk of VaD (sudden onset); interleukin-4 was correlated with a decreased risk of VaD (other); Ruminiclostridium 6 and Bacillales were positively and negatively correlated with the risk of VaD (undefined), respectively; Negativicutes and Selenomonadales were correlated with a decreased risk of VaD (mixed); and Melainabacteria was correlated with an increased risk of VaD (multiple infarctions). Sensitivity analyses revealed no multilevel effects or heterogeneity and no inverse causality between VaD and inflammatory cytokines or the gut microbiota. The MVMR results further confirmed that the causal effects of Negativicutes, Selenomonadales, and Melainabacteria on VaD remain significant. Mediation MR analysis showed that inflammatory cytokines were not potential mediators.

Conclusion

This study helps us to better understand the pathological mechanisms of VaD and suggests the potential value of targeting increases or decreases in inflammatory cytokines and gut microbiome members for VaD prevention and intervention.

Gut microbiota is necessary for pair-housing to protect against post-stroke depression in mice

The goal of this study is to investigate the role of microbiota-gut-brain axis involved in the protective effect of pair-housing on post-stroke depression (PSD). PSD model was induced by occluding the middle cerebral artery (MCAO) plus restraint stress for four weeks. At three days after MCAO, the mice were restrained 2 h per day. For pair-housing (PH), each mouse was pair housed with a healthy isosexual cohabitor for four weeks. While in the other PH group, their drinking water was replaced with antibiotic water. On day 35 to day 40, anxiety- and depression-like behaviors (sucrose consumption, open field test, forced swim test, and tail-suspension test) were conducted. Results showed pair-housed mice had better performance on anxiety- and depression-like behaviors than the PSD mice, and the richness and diversity of intestinal flora were also improved. However, drinking antibiotic water reversed the effects of pair-housing. Furthermore, pair-housing had an obvious improvement in gut barrier disorder and inflammation caused by PSD. Particularly, they showed significant decreases in CD8 lymphocytes and mRNA levels of pro-inflammatory cytokines (TNF-a, IL-1β and IL-6), while IL-10 mRNA was upregulated. In addition, pair-housing significantly reduced activated microglia and increased Nissl's body in the hippocampus of PSD mice. However, all these improvements were worse in the pair-housed mice administrated with antibiotic water. We conclude that pair-housing significantly improves PSD in association with enhanced functions of microbiota-gut-brain axis, and homeostasis of gut microbiota is indispensable for the protective effect of pair-housing on PSD.

Exploring the Potential of Probiotics and Prebiotics in Major Depression: From Molecular Function to Clinical Therapy

Major depressive disorder (MDD) represents a complex and challenging mental health condition with multifaceted etiology. Recent research exploring the gut-brain axis has shed light on the potential influence of gut microbiota on mental health, offering novel avenues for therapeutic intervention. This paper reviews current evidence on the role of prebiotics and probiotics in the context of MDD treatment. Clinical studies assessing the effects of prebiotic and probiotic interventions have demonstrated promising results, showcasing improvements in depression symptoms and metabolic parameters in certain populations. Notably, prebiotics and probiotics have shown the capacity to modulate inflammatory markers, cortisol levels, and neurotransmitter pathways linked to MDD. However, existing research presents varied outcomes, underscoring the need for further investigation into specific microbial strains, dosage optimization, and long-term effects. Future research should aim at refining personalized interventions, elucidating mechanisms of action, and establishing standardized protocols to integrate these interventions into clinical practice. While prebiotics and probiotics offer potential adjunctive therapies for MDD, continued interdisciplinary efforts are vital to harnessing their full therapeutic potential and reshaping the landscape of depression treatment paradigms.

Can exercise benefits be harnessed with drugs? A new way to combat neurodegenerative diseases by boosting neurogenesis

Adult hippocampal neurogenesis (AHN) is affected by multiple factors, such as enriched environment, exercise, ageing, and neurodegenerative disorders. Neurodegenerative disorders can impair AHN, leading to progressive neuronal loss and cognitive decline. Compelling evidence suggests that individuals engaged in regular exercise exhibit higher production of proteins that are essential for AHN and memory. Interestingly, specific molecules that mediate the effects of exercise have shown effectiveness in promoting AHN and cognition in different transgenic animal models. Despite these advancements, the precise mechanisms by which exercise mimetics induce AHN remain partially understood. Recently, some novel exercise molecules have been tested and the underlying mechanisms have been proposed, involving intercommunications between multiple organs such as muscle-brain crosstalk, liver-brain crosstalk, and gut-brain crosstalk. In this review, we will discuss the current evidence regarding the effects and potential mechanisms of exercise mimetics on AHN and cognition in various neurological disorders. Opportunities, challenges, and future directions in this research field are also discussed.

'It takes a village': deciphering the role of the gut microbiome in the health and performance of military personnel

The human gut microbiome can be impacted by a range of environmental and lifestyle factors including diet, antibiotics, physical fitness and acute and chronic stressors. There is also evidence to suggest that specific compositional and/or functional features of the gut microbiome are mediators of aspects of health and performance including disease susceptibility, cognitive and physical states and the immune response. Therefore, understanding microbe-to-microbe and nutrient-to-microbe interactions in the gut and how they interact with host biology (eg, via the gut-brain axis) could enable better design of interventions aimed at modulating the gut microbiome to improve the health and performance of the military. Accordingly, this review summarises a thematic session hosted at the 6th International Conference on Soldier Physical Performance which provided an overview of military-relevant research related to the gut microbiome. It articulates a timely opportunity to leverage this rapidly advancing area to improve personnel health and military performance.

Neuroinflammation, neurodegeneration and alteration of spatial memory in BALB/c mice through ampicillin-induced gut dysbiosis; NOS2 and NFL involvement in a microbiota-gut-brain axis model

We aimed to investigate ampicillin (AMP) mechanisms in microbiota-gut-brain axis. We evaluated its effect on two gut and brain regions and behavioral performances. We administred AMP (1 g/l) to BALB/c mice for 21 days. Then, we analyzed body weigth change, stool consistency scoring, gut length, intestinal microbiota composition, nitric oxide synthase 2 (NOS2) expression and tissue integrity. We subsequently evaluated NOS2, GFAP, CD68 and NFL cerebral expression and spatial memory.Interestingly, our data showed gut microbiota disruption, NOS2 upregulation and tissue damage, associated to cerebral NOS2, GFAP, CD68 and NFL over-expression and behavioral alteration. Antiobiotic therapy should be prescribed with great caution.

Rapid Microbial Profiling through Multimodal Biosensors for Transversal Analysis

The intricate interactions between host and microbial communities hold significant implications for biology and medicine. However, traditional microbial profiling methods face limitations in processing time, measurement of absolute abundance, detection of low biomass, discrimination between live and dead cells, and functional analysis. This study introduces a rapid multimodal microbial characterization platform, Multimodal Biosensors for Transversal Analysis (MBioTA), for capturing the taxonomy, viability, and functional genes of the microbiota. The platform incorporates single cell biosensors, scalable microwell arrays, and automated image processing for rapid transversal analysis in as few as 2 h. The multimodal biosensors simultaneously characterize the taxon, viability, and functional gene expression of individual cells. By automating the image processing workflow, the single cell analysis techniques enable the quantification of bacteria with sensitivity down to 0.0075%, showcasing its capability in detecting low biomass samples. We illustrate the applicability of the MBioTA platform through the transversal analysis of the gut microbiota composition, viability, and functionality in a familial Alzheimer's disease mouse model. The effectiveness, rapid turnaround, and scalability of the MBioTA platform will facilitate its application from basic research to clinical diagnostics, potentially revolutionizing our understanding and management of diseases associated with microbe-host interactions.

Transplant of fecal microbiota from healthy young mice relieves cognitive defects in late-stage diabetic mice by reducing metabolic disorders and neuroinflammation

Fecal microbiota transplant (FMT) is becoming as a promising area of interest for treating refractory diseases. In this study, we investigated the effects of FMT on diabetes-associated cognitive defects in mice as well as the underlying mechanisms. Fecal microbiota was prepared from 8-week-aged healthy mice. Late-stage type 1 diabetics (T1D) mice with a 30-week history of streptozotocin-induced diabetics were treated with antibiotics for 7 days, and then were transplanted with bacterial suspension (100 μL, i.g.) once a day for 14 days. We found that FMT from healthy young mice significantly alleviated cognitive defects of late-stage T1D mice assessed in Morris water maze test. We revealed that FMT significantly reduced the relative abundance of Gram-negative bacteria in the gut microbiota and enhanced intestinal barrier integrity, mitigating LPS translocation into the bloodstream and NLRP3 inflammasome activation in the hippocampus, thereby reducing T1D-induced neuronal loss and astrocytic proliferation. FMT also reshaped the metabolic phenotypes in the hippocampus of T1D mice especially for alanine, aspartate and glutamate metabolism. Moreover, we showed that application of aspartate (0.1 mM) significantly inhibited NLRP3 inflammasome activation and IL-1β production in BV2 cells under a HG/LPS condition. We conclude that FMT can effectively relieve T1D-associated cognitive decline via reducing the gut-brain metabolic disorders and neuroinflammation, providing a potential therapeutic approach for diabetes-related brain disorders in clinic.

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.

Periodontal Inflammation and Dysbiosis Relate to Microbial Changes in the Gut

Periodontal disease (PerioD) is a chronic inflammatory disease of dysbiotic etiology. Animal models and few human data showed a relationship between oral bacteria and gut dysbiosis. However, the effect of periodontal inflammation and subgingival dysbiosis on the gut is unknown. We hypothesized that periodontal inflammation and its associated subgingival dysbiosis contribute to gut dysbiosis even in subjects free of known gut disorders. We evaluated and compared elderly subjects with Low and High periodontal inflammation (assessed by Periodontal Inflamed Surface Area (PISA)) for stool and subgingival derived bacteria (assayed by 16S rRNA sequencing). The associations between PISA/subgingival dysbiosis and gut dysbiosis and bacteria known to produce short-chain fatty acid (SCFA) were assessed. LEfSe analysis showed that, in Low PISA, species belonging to Lactobacillus, Roseburia, and Ruminococcus taxa and Lactobacillus zeae were enriched, while species belonging to Coprococcus, Clostridiales, and Atopobium were enriched in High PISA. Regression analyses showed that PISA associated with indicators of dysbiosis in the gut mainly reduced abundance of SCFA producing bacteria (Radj = -0.38, p = 0.03). Subgingival bacterial dysbiosis also associated with reduced levels of gut SCFA producing bacteria (Radj = -0.58, p = 0.002). These results suggest that periodontal inflammation and subgingival microbiota contribute to gut bacterial changes.

Current Aspects of Selected Factors to Modulate Brain Health and Sports Performance in Athletes

This review offers a comprehensive evaluation of current aspects related to nutritional strategies, brain modulation, and muscle recovery, focusing on their applications and the underlying mechanisms of physiological adaptation for promoting a healthy brain, not only in athletes but also for recreationally active and inactive individuals. We propose that applying the rule, among others, of good sleep, regular exercise, and a properly balanced diet, defined as "SPARKS", will have a beneficial effect on the function and regeneration processes of the gut-brain-muscle axis. However, adopting the formula, among others, of poor sleep, stress, overtraining, and dysbiosis, defined as "SMOULDER", will have a detrimental impact on the function of this axis and consequently on human health as well as on athletes. Understanding these dynamics is crucial for optimizing brain health and cognitive function. This review highlights the significance of these factors for overall well-being, suggesting that adopting the "SPARKS" approach may benefit not only athletes but also older adults and individuals with health conditions.

Integrated oral microgel system ameliorates renal fibrosis by hitchhiking co-delivery and targeted gut flora modulation

BACKGROUND

Renal fibrosis is a progressive process associated with chronic kidney disease (CKD), contributing to impaired kidney function. Active constituents in traditional Chinese herbs, such as emodin (EMO) and asiatic acid (AA), exhibit potent anti-fibrotic properties. However, the oral administration of EMO and AA results in low bioavailability and limited kidney accumulation. Additionally, while oral probiotics have been accepted for CKD treatment through gut microbiota modulation, a significant challenge lies in ensuring their viability upon administration. Therefore, our study aims to address both renal fibrosis and gut microbiota imbalance through innovative co-delivery strategies.

RESULTS

In this study, we developed yeast cell wall particles (YCWPs) encapsulating EMO and AA self-assembled nanoparticles (NPYs) and embedded them, along with Lactobacillus casei Zhang, in chitosan/sodium alginate (CS/SA) microgels. The developed microgels showed significant controlled release properties for the loaded NPYs and prolonged the retention time of Lactobacillus casei Zhang (L. casei Zhang) in the intestine. Furthermore, in vivo biodistribution showed that the microgel-carried NPYs significantly accumulated in the obstructed kidneys of rats, thereby substantially increasing the accumulation of EMO and AA in the impaired kidneys. More importantly, through hitchhiking delivery based on yeast cell wall and positive modulation of gut microbiota, our microgels with this synergistic strategy of therapeutic and modulatory interactions could regulate the TGF-β/Smad signaling pathway and thus effectively ameliorate renal fibrosis in unilateral ureteral obstruction (UUO) rats.

CONCLUSION

In conclusion, our work provides a new strategy for the treatment of renal fibrosis based on hitchhiking co-delivery of nanodrugs and probiotics to achieve synergistic effects of disease treatment and targeted gut flora modulation.

Brain-gut photobiomodulation restores cognitive alterations in chronically stressed mice through the regulation of Sirt1 and neuroinflammation

BACKGROUND

Chronic stress is an important risk factor for the development of major depressive disorder (MDD). Recent studies have shown microbiome dysbiosis as one of the pathogenic mechanisms associated with MDD. Thus, it is important to find novel non-pharmacological therapeutic strategies that can modulate gut microbiota and brain activity. One such strategy is photobiomodulation (PBM), which involves the non-invasive use of light.

OBJECTIVE/HYPOTHESIS

Brain-gut PBM could have a synergistic beneficial effect on the alterations induced by chronic stress.

METHODS

We employed the chronic unpredictable mild stress (CUMS) protocol to induce a depressive-like state in mice. Subsequently, we administered brain-gut PBM for 6 min per day over a period of 3 weeks. Following PBM treatment, we examined behavioral, structural, molecular, and cellular alterations induced by CUMS.

RESULTS

We observed that the CUMS protocol induces profound behavioral alterations and an increase of sirtuin1 (Sirt1) levels in the hippocampus. We then combined the stress protocol with PBM and found that tissue-combined PBM was able to rescue cognitive alterations induced by CUMS. This rescue was accompanied by a restoration of hippocampal Sirt1 levels, prevention of spine density loss in the CA1 of the hippocampus, and the modulation of the gut microbiome. PBM was also effective in reducing neuroinflammation and modulating the morphology of Iba1-positive microglia.

LIMITATIONS

The molecular mechanisms behind the beneficial effects of tissue-combined PBM are not fully understood.

CONCLUSIONS

Our results suggest that non-invasive photobiomodulation of both the brain and the gut microbiome could be beneficial in the context of stress-induced MDD.

Dihydroartemisinin Protects Mice from CUMS-induced Depression-like Behaviors by Regulating Gut Microbes

Depression is one of the most common forms of psychopathology, which is associated with gut microbiota dysfunction. Dihydroartemisinin (DHA) has been shown to regulate gut microbiota and ameliorate neuropathies, but whether it can be used to treat depression remains unclear. Our study found that DHA treatment raised the preference for sugar water in chronic unpredictable mild stress (CUMS)-induced mice and reduced the immobility time in open field, forced swimming and tail suspension experiments, and promoted doublecortin expression. Additionally, DHA up-regulated the diversity and richness of intestinal microbiota in depression-like mice, and restored the abnormal abundance of microbiota induced by CUMS, such as Turicibacter, Lachnospiraceae, Erysipelotrichaceae, Erysipelatoclostridium, Eubacterium, Psychrobacter, Atopostipes, Ileibacterium, Coriobacteriacea, Alistipes, Roseburia, Rikenella, Eggerthellaceae, Ruminococcus, Tyzzerella, and Clostridia. Furthermore, KEGG pathway analysis revealed that gut microbiota involved in the process of depression may be related to glucose metabolism, energy absorption and transport, and AMPK signaling pathway. These results indicated that DHA may play a protective role in CUMS-induced depression by mediating gut-microbiome.

Unveiling the neuroprotective properties of isoflavones: current evidence, molecular mechanisms and future perspectives

Neurodegenerative diseases encompass a wide range of debilitating and incurable brain disorders characterized by the progressive deterioration of the nervous system's structure and function. Isoflavones, which are naturally occurring polyphenolic phytochemicals, have been found to regulate various cellular signaling pathways associated with the nervous system. The main objective of this comprehensive review is to explore the neuroprotective effects of isoflavones, elucidate the underlying mechanisms, and assess their potential for treating neurodegenerative disorders. Relevant data regarding isoflavones and their impact on neurodegenerative diseases were gathered from multiple library databases and electronic sources, including PubMed, Google Scholar, Web of Science, and Science Direct. Numerous isoflavones, including genistein, daidzein, biochanin A, and formononetin, have exhibited potent neuroprotective properties against various neurodegenerative diseases. These compounds have been found to modulate neurotransmitters, which in turn contributes to their ability to protect against neurodegeneration. Both in vitro and in vivo experimental studies have provided evidence of their neuroprotection mechanisms, which involve interactions with estrogenic receptors, antioxidant effects, anti-inflammatory properties, anti-apoptotic activity, and modulation of neural plasticity. This review aims to provide current insights into the neuroprotective characteristics of isoflavones and shed light on their potential therapeutic applications in future clinical scenarios.

Restraint Stress-Induced Neutrophil Inflammation Contributes to Concurrent Gastrointestinal Injury in Mice

Psychological stress increases risk of gastrointestinal tract diseases. However, the mechanism behind stress-induced gastrointestinal injury is not well understood. The objective of our study is to elucidate the putative mechanism of stress-induced gastrointestinal injury and develop an intervention strategy. To achieve this, we employed the restraint stress mouse model, a well-established method to study the pathophysiological changes associated with psychological stress in mice. By orally administering gut-nonabsorbable Evans blue dye and monitoring its plasma levels, we were able to track the progression of gastrointestinal injury in live mice. Additionally, flow cytometry was utilized to assess the viability, death, and inflammatory status of splenic leukocytes, providing insights into the stress-induced impact on the innate immune system associated with stress-induced gastrointestinal injury. Our findings reveal that neutrophils represent the primary innate immune leukocyte lineage responsible for stress-induced inflammation. Splenic neutrophils exhibited elevated expression levels of the pro-inflammatory cytokine IL-1, cellular reactive oxygen species, mitochondrial burden, and cell death following stress challenge compared to other innate immune cells such as macrophages, monocytes, and dendritic cells. Regulated cell death analysis indicated that NETosis is the predominant stress-induced cell death response among other analyzed regulated cell death pathways. NETosis culminates in the formation and release of neutrophil extracellular traps, which play a crucial role in modulating inflammation by binding to pathogens. Treatment with the NETosis inhibitor GSK484 rescued stress-induced neutrophil extracellular trap release and gastrointestinal injury, highlighting the involvement of neutrophil extracellular traps in stress-induced gastrointestinal inflammation. Our results suggest that neutrophil NETosis could serve as a promising drug target for managing psychological stress-induced gastrointestinal injuries.

Association of gut microbiota with cerebral cortical thickness: A Mendelian randomization study

BACKGROUND

The causal relationship between gut microbiota and cerebral cortex development remains unclear. We aimed to scrutinize the plausible causal impact of gut microbiota on cortical thickness via Mendelian randomization (MR) study.

METHODS

Genome-wide association study (GWAS) data for 196 gut microbiota phenotypes (N = 18,340) were obtained as exposures, and GWAS data for cortical thickness-related traits (N = 51,665) were selected as outcomes. Inverse variance weighted was used as the main estimate method. A series of sensitivity analyses was used to test the robustness of the estimates including Cochran's Q test, MR-Egger intercept analysis, Steiger filtering, scatter plot funnel plot and leave-one-out analysis.

RESULTS

Genetic prediction of high Bacillales (β = 0.005, P = 0.032) and Lactobacillales (β = 0.010, P = 0.012) abundance was associated with a potential increase in global cortical thickness. For specific functional brain subdivisions, genetically predicted order Lactobacillales would potentially increase the thickness of the fusiform (β = 0.014, P = 0.016) and supramarginal (β = 0.017, P = 0.003). Meanwhile, order Bacillales would increase the thickness of fusiform (β = 0.007, P = 0.039), insula (β = 0.011, P = 0.003), rostralanteriorcingulate (β = 0.014, P = 0.002) and supramarginal (β = 0.006, P = 0.043). No significant estimates of heterogeneity or pleiotropy were found.

CONCLUSIONS

Through MR studies, we discovered genetic prediction of the Lactobacillales and Bacillales orders potentially linked to cortical thickness, affirming gut microbiota may enhance brain structure. Genetically predicted supramarginal and fusiform may be potential targets.

The effects of heavy metal exposure on brain and gut microbiota: A systematic review of animal studies

The gut-brain axis is a crucial interface between the central nervous system and the gut microbiota. Recent evidence shows that exposure to environmental contaminants, such as heavy metals, can cause dysbiosis in gut microbiota, which may affect the gut-brain communication, impacting aspects of brain function and behavior. This systematic review of the literature aims to evaluate whether deleterious effects on brain function due to heavy metal exposure could be mediated by changes in the gut microbiota profile. Animal studies involving exposure to heavy metals and a comparison with a control group that evaluated neuropsychological outcomes and/or molecular outcomes along with the analysis of microbiota composition were reviewed. The authors independently assessed studies for inclusion, extracted data and assessed risk of bias using the protocol of Systematic Review Center for Laboratory Animal Experimentation (SYRCLE) for preclinical studies. A search in 3 databases yielded 16 eligible studies focused on lead (n = 10), cadmium (n = 1), mercury (n = 3), manganese (n = 1), and combined exposure of lead and manganese (n = 1). The animal species were rats (n = 7), mice (n = 4), zebrafish (n = 3), carp (n = 1) and fruit fly (n = 1). Heavy metals were found to adversely affect cognitive function, behavior, and neuronal morphology. Moreover, heavy metal exposure was associated with changes in the abundance of specific bacterial phyla, such as Firmicutes and Proteobacteria, which play crucial roles in gut health. In some studies, these alterations were correlated with learning and memory impairments and mood disorders. The interplay of heavy metals, gut microbiota, and brain suggests that heavy metals can induce direct brain alterations and indirect effects through the microbiota, contributing to neurotoxicity and the development of neuropsychological disorders. However, the small number of papers under review makes it difficult to draw definitive conclusions. Further research is warranted to unravel the underlying mechanisms and evaluate the translational implications for human health.

Potential neuroprotective benefits of plant-based fermented foods in Alzheimer's disease: an update on preclinical evidence

Alzheimer's disease (AD) currently lacks effective treatments, making its prevention a critical focus. While accumulating evidence supports that plant-based fermented foods may contribute to AD prevention, the neuroprotective effect of plant-based fermented foods on AD has not been comprehensively reviewed. In this study, we conducted a systematic review of preclinical studies on the efficacy of plant-based fermented foods in AD. The literature search was based on databases including PubMed, Embase, Web of Science, and Scopus. The PICO approach was employed for report inclusion, and each report was assessed for risk of bias using the SYRCLE's RoB tool. From the analysis of 25 retrieved reports, we extracted essential details, including bibliographic information, animal models and characteristics, sources of plant-based fermented foods, dosages, administration routes, durations, and outcome measures. Our findings indicate that plant-based fermented foods may positively impact acute and long-term cognitive function, as well as beta-amyloid-mediated neurodegeneration. This review sheds light on the potential neuroprotective benefits of plant-based fermented foods for various AD-related aspects, including oxidative stress, synaptotoxicity, neuroinflammation, tau hyperphosphorylation, dysfunctional amyloidogenic pathways, and cognitive deficits, as observed in rodent models of AD. However, the small number of studies obtained from our literature search and the finding that many of them were of moderate methodological quality suggest the need for further investigation to substantiate the beneficial potential of this class of functional food for the management of AD.

Gut microbiota-host lipid crosstalk in Alzheimer's disease: implications for disease progression and therapeutics

Trillions of intestinal bacteria in the human body undergo dynamic transformations in response to physiological and pathological changes. Alterations in their composition and metabolites collectively contribute to the progression of Alzheimer's disease. The role of gut microbiota in Alzheimer's disease is diverse and complex, evidence suggests lipid metabolism may be one of the potential pathways. However, the mechanisms that gut microbiota mediate lipid metabolism in Alzheimer's disease pathology remain unclear, necessitating further investigation for clarification. This review highlights the current understanding of how gut microbiota disrupts lipid metabolism and discusses the implications of these discoveries in guiding strategies for the prevention or treatment of Alzheimer's disease based on existing data.

Advances in molecular mechanisms and therapeutic strategies for central nervous system diseases based on gut microbiota imbalance

BACKGROUD

Central nervous system (CNS) diseases pose a serious threat to human health, but the regulatory mechanisms and therapeutic strategies of CNS diseases need to be further explored. It has been demonstrated that the gut microbiota (GM) is closely related to CNS disease. GM structure disorders, abnormal microbial metabolites, intestinal barrier destruction and elevated inflammation exist in patients with CNS diseases and promote the development of CNS diseases. More importantly, GM remodeling alleviates CNS pathology to some extent.

AIM OF REVIEW

Here, we have summarized the regulatory mechanism of the GM in CNS diseases and the potential treatment strategies for CNS repair based on GM regulation, aiming to provide safer and more effective strategies for CNS repair from the perspective of GM regulation.

KEY SCIENTIFIC CONCEPTS OF REVIEW

The abundance and composition of GM is closely associated with the CNS diseases. On the basis of in-depth analysis of GM changes in mice with CNS disease, as well as the changes in its metabolites, therapeutic strategies, such as probiotics, prebiotics, and FMT, may be used to regulate GM balance and affect its microbial metabolites, thereby promoting the recovery of CNS diseases.

Hepatopancreatic metabolic disorders and their implications in the development of Alzheimer's disease and vascular dementia

Dementia has been faced with significant public health challenges and economic burdens that urges the need to develop safe and effective interventions. In recent years, an increasing number of studies have focused on the relationship between dementia and liver and pancreatic metabolic disorders that result in diseases such as diabetes, obesity, hypertension and dyslipidemia. Previous reports have shown that there is a plausible correlation between pathologies caused by hepatopancreatic dysfunctions and dementia. Glucose, insulin and IGF-1 metabolized in the liver and pancreas probably have an important influence on the pathophysiology of the most common dementias: Alzheimer's and vascular dementia. This current review highlights recent studies aimed at identifying convergent mechanisms, such as insulin resistance and other diseases, linked to altered hepatic and pancreatic metabolism, which are capable of causing brain changes that ultimately lead to dementia.

Correlation between the gut microbiome and neurodegenerative diseases: a review of metagenomics evidence

A growing body of evidence suggests that the gut microbiota contributes to the development of neurodegenerative diseases via the microbiota-gut-brain axis. As a contributing factor, microbiota dysbiosis always occurs in pathological changes of neurodegenerative diseases, such as Alzheimer's disease, Parkinson's disease, and amyotrophic lateral sclerosis. High-throughput sequencing technology has helped to reveal that the bidirectional communication between the central nervous system and the enteric nervous system is facilitated by the microbiota's diverse microorganisms, and for both neuroimmune and neuroendocrine systems. Here, we summarize the bioinformatics analysis and wet-biology validation for the gut metagenomics in neurodegenerative diseases, with an emphasis on multi-omics studies and the gut virome. The pathogen-associated signaling biomarkers for identifying brain disorders and potential therapeutic targets are also elucidated. Finally, we discuss the role of diet, prebiotics, probiotics, postbiotics and exercise interventions in remodeling the microbiome and reducing the symptoms of neurodegenerative diseases.

Gut microbiota and type 2 diabetes mellitus: a focus on the gut-brain axis

Type 2 diabetes mellitus (T2DM) has become one of the most serious public healthcare challenges, contributing to increased mortality and disability. In the past decades, significant progress has been made in understanding the pathogenesis of T2DM. Mounting evidence suggested that gut microbiota (GM) plays a significant role in the development of T2DM. Communication between the GM and the brain is a complex bidirectional connection, known as the "gut-brain axis," via the nervous, neuroendocrine, and immune systems. Gut-brain axis has an essential impact on various physiological processes, including glucose metabolism, food intake, gut motility, etc. In this review, we provide an outline of the gut-brain axis. We also highlight how the dysbiosis of the gut-brain axis affects glucose homeostasis and even results in T2DM.

Alterations of the gut microbiota in patients with schizophrenia

Introduction

Schizophrenia is a complex psychiatric disorder, of which molecular pathogenesis remains largely unknown. Accumulating evidence suggest that gut microbiota may affect brain function via the complex gut-brain axis, which may be a potential contributor to schizophrenia. However, the alteration of gut microbiota showed high heterogeneity across different studies. Therefore, this study aims to identify the consistently altered gut microbial taxa associated with schizophrenia.

Methods

We conducted a systematic search and synthesis of the up-to-date human gut microbiome studies on schizophrenia, and performed vote counting analyses to identify consistently changed microbiota. Further, we investigated the effects of potential confounders on the alteration of gut microbiota.

Results

We obtained 30 available clinical studies, and found that there was no strong evidence to support significant differences in α-diversity and β-diversity between schizophrenic patients and healthy controls. Among 428 differential gut microbial taxa collected from original studies, we found that 8 gut microbial taxa were consistently up-regulated in schizophrenic patients, including Proteobacteria, Gammaproteobacteria, Lactobacillaceae, Enterobacteriaceae, Lactobacillus, Succinivibrio, Prevotella and Acidaminococcus. While 5 taxa were consistently down-regulated in schizophrenia, including Fusicatenibacter, Faecalibacterium, Roseburia, Coprococcus and Anaerostipes.

Discussion

These findings suggested that gut microbial changes in patients with schizophrenia were characterized by the depletion of anti-inflammatory butyrate-producing genera, and the enrichment of certain opportunistic bacteria genera and probiotics. This study contributes to further understanding the role of gut microbiota in schizophrenia, and developing microbiota-based diagnosis and therapy for schizophrenia.

The function of the gut microbiota-bile acid-TGR5 axis in diarrhea-predominant irritable bowel syndrome

Imbalanced gut microbiota (GM) and abnormal fecal bile acid (BA) are thought to be the key factors for diarrhea-predominant irritable bowel syndrome (IBS-D), but the underlying mechanism remains unclear. Herein, we explore the influence of the GM-BA-Takeda G-protein-coupled receptor 5 (TGR5) axis on IBS-D. Twenty-five IBS-D patients and fifteen healthy controls were recruited to perform BA-related metabolic and metagenomic analyses. Further, the microbiota-humanized IBS-D rat model was established by fecal microbial transplantation (FMT) to investigate the GM-BA-TGR5 axis effects on the colonic barrier and visceral hypersensitivity (VH) in IBS-D. Finally, we used chenodeoxycholic acid (CDCA), an important BA screened out by metabolome, to evaluate whether it affected diarrhea and VH via the TGR5 pathway. Clinical research showed that GM associated with bile salt hydrolase (BSH) activity such as Bacteroides ovatus was markedly reduced in the GM of IBS-D, accompanied by elevated total and primary BA levels. Moreover, we found that CDCA not only was increased as the most important primary BA in IBS-D patients but also could induce VH through upregulating TGR5 in the colon and ileum of normal rats. TGR5 inhibitor could reverse the phenotype, depression-like behaviors, pathological change, and level of fecal BSH in a microbiota-humanized IBS-D rat model. Our findings proved that human-associated FMT could successfully induce the IBS-D rat model, and the imbalanced GM-BA-TGR5 axis may promote colonic mucosal barrier dysfunction and enhance VH in IBS-D.

IMPORTANCE

Visceral hypersensitivity and intestinal mucosal barrier damage are important factors that cause abnormal brain-gut interaction in diarrhea-predominant irritable bowel syndrome (IBS-D). Recently, it was found that the imbalance of the gut microbiota-bile acid axis is closely related to them. Therefore, understanding the structure and function of the gut microbiota and bile acids and the underlying mechanisms by which they shape visceral hypersensitivity and mucosal barrier damage in IBS-D is critical. An examination of intestinal feces from IBS-D patients revealed that alterations in gut microbiota and bile acid metabolism underlie IBS-D and symptom onset. We also expanded beyond existing knowledge of well-studied gut microbiota and bile acid and found that Bacteroides ovatus and chenodeoxycholic acid may be potential bacteria and bile acid involved in the pathogenesis of IBS-D. Moreover, our data integration reveals the influence of the microbiota-bile acid-TGR5 axis on barrier function and visceral hypersensitivity.

Gut microbiota and its metabolites in Alzheimer's disease: from pathogenesis to treatment

Introduction

An increasing number of studies have demonstrated that altered microbial diversity and function (such as metabolites), or ecological disorders, regulate bowel-brain axis involvement in the pathophysiologic processes in Alzheimer's disease (AD). The dysregulation of microbes and their metabolites can be a double-edged sword in AD, presenting the possibility of microbiome-based treatment options. This review describes the link between ecological imbalances and AD, the interactions between AD treatment modalities and the microbiota, and the potential of interventions such as prebiotics, probiotics, synbiotics, fecal microbiota transplantation, and dietary interventions as complementary therapeutic strategies targeting AD pathogenesis and progression.

Survey methodology

Articles from PubMed and china.com on intestinal flora and AD were summarized to analyze the data and conclusions carefully to ensure the comprehensiveness, completeness, and accuracy of this review.

Conclusions

Regulating the gut flora ecological balance upregulates neurotrophic factor expression, regulates the microbiota-gut-brain (MGB) axis, and suppresses the inflammatory responses. Based on emerging research, this review explored novel directions for future AD research and clinical interventions, injecting new vitality into microbiota research development.

Fermented foods: Harnessing their potential to modulate the microbiota-gut-brain axis for mental health

Over the past two decades, whole food supplementation strategies have been leveraged to target mental health. In addition, there has been increasing attention on the ability of gut microbes, so called psychobiotics, to positively impact behaviour though the microbiota-gut-brain axis. Fermented foods offer themselves as a combined whole food microbiota modulating intervention. Indeed, they contain potentially beneficial microbes, microbial metabolites and other bioactives, which are being harnessed to target the microbiota-gut-brain axis for positive benefits. This review highlights the diverse nature of fermented foods in terms of the raw materials used and type of fermentation employed, and summarises their potential to shape composition of the gut microbiota, the gut to brain communication pathways including the immune system and, ultimately, modulate the microbiota-gut-brain axis. Throughout, we identify knowledge gaps and challenges faced in designing human studies for investigating the mental health-promoting potential of individual fermented foods or components thereof. Importantly, we also suggest solutions that can advance understanding of the therapeutic merit of fermented foods to modulate the microbiota-gut-brain axis.

Probiotic, prebiotic, synbiotic and fermented food supplementation in psychiatric disorders: A systematic review of clinical trials

The use of probiotics, prebiotics, synbiotics or fermented foods can modulate the gut-brain axis and constitute a potentially therapeutic intervention in psychiatric disorders. This systematic review aims to identify current evidence regarding these interventions in the treatment of patients with DSM/ICD psychiatric diagnoses. Forty-seven articles from 42 studies met the inclusion criteria. Risk of bias was assessed in all included studies. Major depression was the most studied disorder (n = 19 studies). Studies frequently focused on schizophrenia (n = 11) and bipolar disorder (n = 5) and there were limited studies in anorexia nervosa (n = 4), ADHD (n = 3), Tourette (n = 1), insomnia (n = 1), PTSD (n = 1) and generalized anxiety disorder (n = 1). Except in MDD, current evidence does not clarify the role of probiotics and prebiotics in the treatment of mental illness. Several studies point to an improvement in the immune and inflammatory profile (e.g. CRP, IL6), which may be a relevant mechanism of action of the therapeutic response identified in these studies. Future research should consider lifestyle and dietary habits of patients as possible confounders that may influence inter-individual treatment response.

The probiotic SLAB51 as agent to counteract BPA toxicity on zebrafish gut microbiota -liver-brain axis

A plethora of studies have so far described the toxic effects of bisphenol A (BPA) on organism health, highlighting the urgent need to find new strategies not only to reduce the presence of this toxicant but also to counteract its adverse effects. In this context, probiotics emerged as a potential tool since they promote organism welfare. Using a multidisciplinary approach, this study explores the effects of SLAB51 dietary administration to counteract BPA toxicity using zebrafish as a model. Adult males and females were maintained under standard conditions (control group; C), exposed for 28 days via the water to an environmental relevant dose of BPA (10 μg/L; BPA), dietary treated with SLAB51 (109 CFU/g of body weight; P) and co-treated with BPA plus SLAB51 (BPA + P). In the gut, exposure to BPA resulted in altered architecture in both males and females, with females also experiencing an increase of pathogenic bacterial species. Co-administration of BPA + P led to the restoration of normal gut architecture, favored beneficial bacteria colonization, and decreased the abundance of pathogenic species. In the liver, male BPA exposure led to steatosis and glycogen depletion, which was partially mitigated by SLAB51 co-administration. In contrast, in females exposed to BPA, the lack of steatosis along with the greater glycogen depletion, suggested an increase in energy demand as supported by the metabolomic phenotype. The analysis of liver metabolites in BPA + P males revealed increased levels of anserine and reduced levels of glutamine, which could lie behind the counteraction of the brain histopathological damage caused by BPA. In BPA + P females, a reduction of retinoic acid was found in the liver, suggesting an increase in retinoids responsible for BPA detoxification. Overall, these results demonstrate that SLAB51 exerts its beneficial effects on the gut microbiota-brain-liver axis through distinct molecular pathways, effectively mitigating the pleiotropic toxicity of BPA.

Probiotics as modulators of gut-brain axis for cognitive development

Various microbial communities reside in the gastrointestinal tract of humans and play an important role in immunity, digestion, drug metabolism, intestinal integrity, and protection from pathogens. Recent studies have revealed that the gut microbiota (GM) is involved in communication with the brain, through a bidirectional communication network known as the gut-brain axis. This communication involves humoral, immunological, endocrine, and neural pathways. Gut dysbiosis negatively impacts these communication pathways, leading to neurological complications and cognitive deficits. Both pre-clinical and clinical studies have demonstrated that probiotics can restore healthy GM, reduce intestinal pH, and reduce inflammation and pathogenic microbes in the gut. Additionally, probiotics improve cell-to-cell signaling and increase blood-brain-derived neurotrophic factors. Probiotics emerge as a potential approach for preventing and managing neurological complications and cognitive deficits. Despite these promising findings, the safety concerns and possible risks of probiotic usage must be closely monitored and addressed. This review article provides a brief overview of the role and significance of probiotics in cognitive health.

Existing and Future Strategies to Manipulate the Gut Microbiota With Diet as a Potential Adjuvant Treatment for Psychiatric Disorders

Nutrition and diet quality play key roles in preventing and slowing cognitive decline and have been linked to multiple brain disorders. This review compiles available evidence from preclinical studies and clinical trials on the impact of nutrition and interventions regarding major psychiatric conditions and some neurological disorders. We emphasize the potential role of diet-related microbiome alterations in these effects and highlight commonalities between various brain disorders related to the microbiome. Despite numerous studies shedding light on these findings, there are still gaps in our understanding due to the limited availability of definitive human trial data firmly establishing a causal link between a specific diet and microbially mediated brain functions and symptoms. The positive impact of certain diets on the microbiome and cognitive function is frequently ascribed with the anti-inflammatory effects of certain microbial metabolites or a reduction of proinflammatory microbial products. We also critically review recent research on pro- and prebiotics and nondietary interventions, particularly fecal microbiota transplantation. The recent focus on diet in relation to brain disorders could lead to improved treatment outcomes with combined dietary, pharmacological, and behavioral interventions.

Transcutaneous Auricular Vagus Nerve Stimulation to Improve Emotional State

Emotional experiences are a part of our lives. The maladaptive functioning of an individual's emotional field can lead to emotional disturbances of various kinds, such as anxiety and depression. Currently, there is an increasing prevalence of emotional disorders that cause great human suffering and high socioeconomic costs. Emotional processing has a biological basis. The major neuroscientific theories of emotion are based on biological functioning, and all of them take into account the anatomy and function of the tenth cranial nerve: the vagus nerve. The vagus nerve connects the subdiaphragmatic and supradiaphragmatic areas and modulates emotional processing as the basis of interoceptive functioning. Auricular vagus nerve stimulation is a new and innovative neuromodulation technique based on the function of the vagus nerve. Several interventions have shown that this new neurostimulation technique is a very promising resource for treating emotional disorders. In this paper, we summarise three neuroscientific theories of emotion, explain what transcutaneous auricular nerve stimulation is, and present arguments for its use and continued research.

Association between healthy eating and depression symptoms among Chinese older adults: A cross-sectional study based on the Chinese Longitudinal Healthy Longevity survey

Introduction

This study aimed to assess the relationship between the healthy eating index (HEI) and depression symptoms in an older adult population using the Chinese Longevity Health Survey.

Methods

The HEI was constructed based on the frequency of intake of 13 dietary variables, with higher scores indicating better diet quality. Depression symptoms was assessed by the Center for Epidemiologic Studies Depression-10 scale. We used multivariate binary logistic regression to explore the association between the HEI and depression symptoms and reported as odds ratio (OR) and 95 % confidence interval (95 % CI).

Results

A total of 12,078 older adults were included. The average HEI for this group of older adults was 26.4 ± 7.1. After adjusting for covariates, compared with participants in the lowest quartile of a healthy eating index, those in the second to the fourth quartile group had a 0.93- (95 % CI: 0.83 to 1.03), 0.84- (95 % CI: 0.75 to 0.95) and 0.69- (95 % CI: 0.62 to 0.77) fold risk of depression symptoms, respectively. Restricted cubic spline curves showed that the risk of depression symptoms decreased with increasing HEI, especially above 26, and for each unit increase in the HEI, the risk of depression symptoms in older adults decreased by 3 % (OR = 0.97; 95 % CI: 0.96 to 0.99).

Conclusions

This study found an association between higher levels of the HEI and reduced risk of depression symptoms in older Chinese adults. This result emphasizes the need to focus on dietary diversity in older adults to promote healthy aging.

Akkermansia muciniphila Improves Depressive-Like Symptoms by Modulating the Level of 5-HT Neurotransmitters in the Gut and Brain of Mice

Accumulating evidence has suggested that the gut microbiome plays an important role in depression. Akkermansia muciniphila (AKK), a next-generation probiotic, shows a beneficial effect on immune and metabolic homeostasis. The relative abundance of AKK was found negatively correlated with depressive symptoms in both clinical and pre-clinical studies. To evaluate the potential antidepressant effect of AKK and explore the possible mechanism, we used chronic alcohol exposure and chronic unpredictable mild stress (CUMS) to induce depressive-like behaviors in mice. We found that oral AKK administration significantly reduced the immobility time in the force swimming test (FST) and tail suspension test (TST) in the mice with chronic alcohol exposure and the CUMS mice. The sucrose preference in the mice receiving AKK was significantly increased in the sucrose preference test (SPT). More importantly, AKK implantation significantly increased the level of 5-HT in the gut and PFC of both the alcohol exposure mice and the CUMS mice. Furthermore, AKK had inhibited the expression of SERT in the gut but not in the brain for both NIAAA and the CUMS model mice. Interestingly, the expression of cFos in enteric nerves in the gut significantly decreased after AKK administration. In conclusion, our study demonstrated the antidepressant effect of AKK in mice exposed to alcohol exposure and CUMS, with the potential mechanism that AKK implantation might lead to an increased level of 5-HT and inhibited SERT expression in the gut, and might alter the gut-to-brain signal through suppression of enteric nerves activation.

Fibre-rich diet attenuates chemotherapy-related neuroinflammation in mice

The gastrointestinal microbiota has received increasing recognition as a key mediator of neurological conditions with neuroinflammatory features, through its production of the bioactive metabolites, short-chain fatty acids (SCFAs). Although neuroinflammation is a hallmark shared by the neuropsychological complications of chemotherapy (including cognitive impairment, fatigue and depression), the use of microbial-based therapeutics has not previously been studied in this setting. Therefore, we aimed to investigate the effect of a high fibre diet known to modulate the microbiota, and its associated metabolome, on neuroinflammation caused by the common chemotherapeutic agent 5-fluorouracil (5-FU). Twenty-four female C57Bl/6 mice were treated with 5-FU (400 mg/kg, intraperitoneal, i.p.) or vehicle control, with or without a high fibre diet (constituting amylose starch; 4.7 % crude fibre content), given one week prior to 5-FU and until study completion (16 days after 5-FU). Faecal pellets were collected longitudinally for 16S rRNA gene sequencing and terminal SCFA concentrations of the caecal contents were quantified using gas chromatography-mass spectrometry (GC-MS). Neuroinflammation was determined by immunofluorescent analysis of astrocyte density (GFAP). The high fibre diet significantly altered gut microbiota composition, increasing the abundance of Bacteroidaceae and Akkermansiaceae (p < 0.0001 and p = 0.0179) whilst increasing the production of propionate (p = 0.0097). In the context of 5-FU, the diet reduced GFAP expression in the CA1 region of the hippocampus (p < 0.0001) as well as the midbrain (p = 0.0216). Astrocyte density negatively correlated with propionate concentrations and the abundance of Bacteroidaceae and Akkermansiaceae, suggesting a relationship between neuroinflammatory and gastrointestinal markers in this model. This study provides the first evidence of the neuroprotective effects of fibre via dietary intake in alleviating the neuroimmune changes seen in response to systemically administered 5-FU, indicating that the microbiota-gut-brain axis is a targetable mediator to reduce the neurotoxic effects of chemotherapy treatment.

Intravenous transplantation of bone marrow-derived mesenchymal stem cells improved behavioral deficits and altered fecal microbiota composition of BTBR mice

AIMS

It is recognized that autism spectrum disorder (ASD) is a highly complex neurodevelopmental disorder with communication deficits as well as multiple social barriers. The core symptoms of ASD are not treatable with current therapeutics. Therefore, finding new treatment strategies for ASD is urgently needed. Mesenchymal stem cells (MSC) have been shown to be a promising therapeutic approach in previous studies. However, the underlying mechanisms of MSC treatment for ASD through gut microbiota remain unclear and require further investigation.

MAIN METHODS

BTBR mice were used as ASD model and then randomly assigned to the human bone marrow-derived mesenchymal stem cell (hBMMSC) intravenous treatment group or vehicle treatment group. C57BL/6J (C57) mice served as control. Multiple social behavioral tests were performed during the 6-week period and fecal samples were collected at different time points for 16 s rRNA sequencing analysis.

KEY FINDINGS

The administration of hBMMSC improved social deficits of BTBR mice in the open field test (OFT), light-dark box test (LBT), novel object recognition (NOR), and free social test (FST), while also significantly reducing stereotypic behaviors. Additionally, hBMMSC administration notably reversed the alterations of microbiota abundance in BTBR mice, particularly the Firmicutes/Bacteroidetes ratio. Several specific differential taxa were further selected and showed a correlation with the prognosis and behavioral scores of ASD.

SIGNIFICANCE

Overall, intravenous treatment with hBMMSC had a beneficial impact on ASD by ameliorating social deficits and modifying microbiota compositions. This outcome indicates that hBMMSC intravenous transplantation could be a promising therapeutic strategy for enhancing ASD symptoms improvements.

Microbiota-Gut-Brain Axis and Antidepressant Treatment

In the treatment of depressive disorders, conventional antidepressant therapy has been the mainstay of clinical management, along with well-established nonpharmacological interventions such as various kinds of psychotherapy. Over the last 2 decades, there has been considerable interest in the role of the gastrointestinal system and its microbiota on brain function, behavior, and mental health. Components of what is referred to as the microbiota-gut-brain axis have been uncovered, and further research has elicited functional capabilities such as "gut-brain modules." Some studies have found associations with compositional alterations of gut microbiota in patients with depressive disorders and individuals experiencing symptoms of depression. Regarding the pathogenesis and neurobiology of depression itself, there appears to be a multifactorial contribution, in addition to the theories involving deficits in catecholaminergic and monoamine neurotransmission. Interestingly, there is evidence to suggest that antidepressants may play a role in modulating the gut microbiota, thereby possibly having an impact on the microbiota-gut-brain axis in this manner. The development of prebiotics, probiotics, and synbiotics has led to studies investigating not only their impact on the microbiota but also their therapeutic value in mental health. These psychobiotics have the potential to be used as therapeutic adjuncts in the treatment of depression. Regarding future directions, and in an attempt to further understand the role of the microbiota-gut-brain axis in depression, more studies such as those involving fecal microbiota transplantation will be required. In addition to recent findings, it is also suggested that more research will have to be undertaken to elicit whether specific strains of gut organisms are linked to depression. In terms of further investigation of the therapeutic potential of prebiotics, probiotics, and synbiotics as adjuncts to antidepressant treatment, we also expect there to be more research targeting specific microorganisms, as well as a strong focus on the effects of specific prebiotic fibers from an individualized (personalized) point of view.

Restraint stress-associated gastrointestinal injury and implications from the Evans blue-fed restraint stress mouse model

The association between stress and gastrointestinal (GI) tract diseases is well established, while the exact mechanism remains elusive. As a result, it is urgent to establish mouse models to investigate restraint stress-associated GI leakage, but current models have their limitations. A new Evans blue-fed restraint mouse model has recently been developed that allows researchers to study restraint stress-associated GI leakage in live animals. This review article will focus on this model, including its mechanisms, clinical implications, and applications for studying restraint stress-associated GI injury. Recent findings from studies using this model will also be highlighted, along with their potential for diagnosis and treatment. The article aims to discuss about current research and provide recommendations for further study, ultimately improving our understanding of the link between stress and GI injury and improving patient outcomes.

Variety of Serotonin Levels in Pediatric Gastrointestinal Disorders

(1) Serotonin primarily regulates our emotions. A complex process, which includes dysfunctions in gastrointestinal motility and deregulation of the gene responsible for serotonin reuptake (SERT), is implicated in the pathophysiology of irritable bowel syndrome (IBS). This also encompasses changes in intestinal microbiota, the response to stress, the intricate interplay between the brain and the digestive tract, heightened sensitivity to visceral stimuli, and low-grade inflammation. This paper aims to investigate the effectiveness of probiotic therapy in managing gastrointestinal and neuropsychiatric symptoms related to serotonin levels, with a focus on individuals with serotonin deficiency and those with normal serotonin levels experiencing gastrointestinal disorders. (2) The study involved 135 pediatric patients aged 5-18 years with gastrointestinal disturbances, including constipation, diarrhea, and other symptoms, such as nausea, flatulence, feeling full, or gastrointestinal pain. (3) Serotonin testing was performed, and administering probiotics appeared to be effective in addressing serotonin deficiency and other gastrointestinal disorders. (4) Serotonin's pivotal role in regulating neurotransmitter secretion and its impact on neuropsychiatric health, coupled with gender differences and age-related declines, underscore the complexity of their influence on gastrointestinal and neuropsychiatric conditions.

Microbiota Composition and Probiotics Supplementations on Sleep Quality-A Systematic Review and Meta-Analysis

The gut microbiota (GM) plays a crucial role in human health. The bidirectional interaction between GM and the central nervous system may occur via the microbiota-gut-brain axis, possibly regulating the sleep/wake cycle. Recent reports highlight associations between intestinal dysbiosis and sleep disorders, suggesting that probiotics could ameliorate this condition. However, data are poor and inconsistent. The aim of this quantitative metanalytic study is to assess the GM composition in sleep disturbances and evaluate probiotics' effectiveness for managing sleep disorders. A systematic review was carried out until July 2022 in online databases, limiting the literature research to human studies and English language articles. No significant GM diversity between patients with sleep disturbances versus healthy controls was found, revealed by α-diversity, while β-diversity is missing due to lack of proper reporting. However, probiotics supplementation significantly reduced the self-assessed parameter of sleep quality and disturbances Pittsburgh Sleep Quality Index (PSQI) score compared with the placebo. No difference in the Epworth Sleepiness Scale (ESS) score was found. While available data suggest that GM diversity is not related to sleep disturbances, probiotics administration strongly improves sleep quality as a subjective perception. However, heterogeneity of data reporting in the scientific literature should be considered as a limitation.