Short-chain fatty acid fermentation products of the gut microbiome: implications in autism spectrum disorders

Probiotics in autism spectrum disorders: a systematic review of clinical studies and future directions

CONTEXT

It is hypothesized that gut dysbiosis, a typical feature of patients with autism spectrum disorder (ASD), could be involved in the origin of this neurodevelopmental disorder. Therefore, the use of probiotics to restore gastrointestinal (GI) equilibrium might be a promising therapeutic strategy due to its capacity to balance the gut-brain axis and behavioral responses.

OBJECTIVE

To summarize current knowledge on the use of probiotics to treat core clinical ASD symptoms and concomitant GI signs, compare the design of published studies with those of ongoing trials, assess the near future of this field, and provide recommendations for improving novel studies.

DATA SOURCES

The literature search was conducted in February 2020 and updated in March 2021, using a broad range of bibliographic and clinical trial-specific databases.

DATA EXTRACTION

Data were extracted using a standardized form, and articles reporting on 28 clinical studies (already published or still ongoing) were included. The risk of bias in clinical studies was evaluated using the Cochrane Collaboration Risk of Bias Assessment tool for randomized trials and the Risk of Bias in Nonrandomized Studies-Interventions tool for nonrandomized trials.

RESULTS

The results suggest that probiotics improve ASD-like social deficits, GI symptoms, and gut microbiota profile. However, inconsistencies among studies and their methodological limitations make it difficult to draw any conclusions regarding the efficacy of probiotics in ASD. This review provides specific suggestions for future research to improve the quality of the studies.

CONCLUSIONS

Although ongoing studies have improved designs, the available knowledge does not permit solid conclusions to be made regarding the efficacy of probiotics in ameliorating the symptoms (psychiatric and/or GI) associated with ASD. Thus, more high-quality research and new approaches are needed to design effective probiotic strategies for ASD.

Role of Probiotics in Depression: Connecting Dots of Gut-Brain-Axis Through Hypothalamic-Pituitary Adrenal Axis and Tryptophan/Kynurenic Pathway involving Indoleamine-2,3-dioxygenase

Depression is one of the most disabling mental disorders worldwide and characterized by symptoms including worthlessness, anhedonia, sleep, and appetite disturbances. Recently, studies have suggested that tryptophan (Trp) metabolism plays a key role in depressed mood through serotonin and kynurenine pathway involving enzyme tryptophan 5-monooxygenase (TPH) and indoleamine-2,3-dioxygenase (IDO) respectively. Moreover, during neuroinflammation, IDO is activated by proinflammatory cytokines and affects neurogenesis, cognition, disturbed hypothalamic-pituitary-adrenal (HPA) axis, and gut homeostasis by altering the gut bacteria and its metabolites like Trp derivatives. Furthermore, over the decades, researchers have focused on understanding communication between the human microbiome, especially gut microbiota, and mental health, called gut-brain-axis (GBA), particularly through Trp metabolism. Supplementation of probiotics in depression has gained attention from researchers and clinicians. However, there is limited information about probiotics supplementation on depression involving enzyme IDO and kynurenine pathway metabolites. This review discussed the potential role of probiotics in depression through the tryptophan/kynurenine pathway.

Microbiota and Autism: A Review on Oral and Gut Microbiome Analysis Through 16S rRNA Sequencing

Autism spectrum disorder (ASD) is a complex neurodevelopmental condition with multifactorial etiologies, including genetic, environmental, and microbiological factors. In recent years, increasing attention has been given to the role of the gut microbiota in ASD. Emerging evidence suggests that gut microbiota dysbiosis may influence the central nervous system through the gut-brain axis, potentially impacting behavior and neurodevelopment. The use of 16S rRNA gene sequencing has become a pivotal tool in profiling the microbial communities associated with ASD, offering valuable insights into bacterial diversity, composition, and potential functional roles. This review aims to provide a comprehensive analysis of current findings on the relationship between the gut and oral microbiota with ASD, and a particular focus on studies utilizing 16S rRNA sequencing. We will explore how gut microbiome alterations may contribute to ASD pathophysiology, discuss the limitations of existing research, and propose future directions for the integration of microbiome analysis in ASD diagnostics and treatment strategies. These findings underscore the potential role of microbiota in modulating ASD symptoms. The data suggest that specific bacterial taxa are consistently altered in ASD, which may have implications for understanding the gut-brain axis and its influence on neurodevelopment.

Cutibacterium Acnes induces Alzheimer's disease-like pathology in brains of wistar rats through structural changes associated with microtubules

BACKGROUND

Cutibacterium acnes(C. acnes), a Gram-positive anaerobe and a dominant bacterium species in the sebaceous follicles of the face was detected in the brain of Alzheimer's disease (AD) patients. It has been found that C. acnes activates non-specifically the innate immune system by producing proinflammatory cytokines and can participate in brain inflammation. We hypothesise that C. acnes could influence the brain through the structural alteration in axons and dendrites of neurons.

METHODS

In this regard, the hippocampus of rats was infected with C. acnes, and memory retention, amyloid-β (Aβ1-42) deposition, hyperphosphorylated tau protein (p-Tau) formation, and expression levels of MAP2 and β-tubulin proteins in the hippocampus tissues were investigated.

RESULTS

C. acnes-infected rats displayed memory deficits and Aβ1-42 deposits were detected in their hippocampus tissue up to 7 days post-infection. C. acnes was neurotoxic and exerted detrimental effects on MAP2 and β-tubulin proteins, which are required for normal neuronal function. An elevated level of p-Tau was also identified in infected animals.

CONCLUSION

Based on these results, we propose that C. acnes infection of the brain participates in the initiation of the pathogenesis of sporadic AD through degeneration of axons and dendrites.

Amelioration of propionic acid-induced autism-like behaviors in rats by fenofibrate: A focus on reduction of brain galectin-3 levels

INTRODUCTION

Autism spectrum disorder (ASD) is a neurodevelopmental disorder characterized by impaired social interactions and repetitive behaviors. This study examines the effects of fenofibrate on a propionic acid (PPA)-induced rat model of ASD, focusing on behavioral changes, inflammatory markers, and histological findings.

MATERIALS AND METHODS

Thirty male Wistar rats were divided into three groups: a control group, a group receiving PPA and saline, and a group treated with PPA and fenofibrate for 15 days. Behavioral assessments, including the three-chamber sociability test, open-field test, and passive avoidance learning, were conducted. Biochemical analyses measured TNF-α, NGF, IL-17, IL-2, and galectin-3 levels in brain tissues. Histological evaluations focused on Purkinje neuron counts in the cerebellum and neuronal changes in the CA1 and CA3 regions of the hippocampus, along with glial fibrillary acidic protein (GFAP) levels.

RESULTS

Fenofibrate treatment significantly improved behavioral outcomes, reducing autism-like behaviors compared to the PPA/saline group. Biochemically, the PPA/saline group showed elevated levels of malondialdehyde, TNF-α, IL-2, IL-17, and galectin-3, which were reduced following fenofibrate treatment. Histologically, the PPA/saline group exhibited fewer, dysmorphic Purkinje neurons and increased glial activity in the CA1 region, both of which were ameliorated by fenofibrate treatment.

CONCLUSION

Fenofibrate shows promise in mitigating autism-like behaviors in a rat model of ASD, likely due to its antioxidative and neuroprotective properties, which contribute to preserving neuronal integrity and reducing inflammation.

Alcohol consumption during pregnancy differentially affects the fecal microbiota of dams and offspring

Microbiota imbalances are linked to inflammation and disease, as well as neurodevelopmental conditions where they may contribute to behavioral, physiological, and central nervous system dysfunction. By contrast, the role of the microbiota in Fetal Alcohol Spectrum Disorder (FASD), the group of neurodevelopmental conditions that can occur following prenatal alcohol exposure (PAE), has not received similar attention. Here we utilized a rodent model of alcohol consumption during pregnancy to characterize the impact of alcohol on the microbiota of dam-offspring dyads. Overall, bacterial diversity decreased in alcohol-consuming dams and community composition differed from that of controls in alcohol-consuming dams and their offspring. Bacterial taxa and predicted biochemical pathway composition were also altered with alcohol consumption/exposure; however, there was minimal overlap between the changes in dams and offspring. These findings illuminate the potential importance of the microbiota in the pathophysiology of FASD and support investigation into novel microbiota-based interventions.

In vitro study of potential prebiotic properties of monovarietal extra virgin olive oils

Olive oil, essential ingredient of the Mediterranean diet, is attracting a growing interest due to increasing evidence on its beneficial effects on human health. This study investigated whether extra virgin olive oil (EVOO) possess prebiotic properties. Twenty different monovarietal EVOO samples from 5 Marche region cultivars (Italy) were studied. The prebiotic activity of EVOOs was assessed monitoring the selective stimulation of gut bacterial species and the short chain fatty acids (SCFAs) production, using an in vitro fermentation system. All EVOOs selectively stimulated Lactobacillus spp., with a stronger activity than that observed in the inulin fermentation (positive control). Also, the bifidobacteria population increased; this bifidogenic stimulation was of EVOOs from Raggia cultivar. SCFAs appeared significantly higher after 24 h in all EVOO fermentations than in the control. Acetic and propionic acids production was particularly stimulated. Overall, most of the investigated EVOOs had a potential prebiotic activity, similar or stronger than inulin.

Could the Propionic Acid Treatment in Combination with Metformin be Safe for the Small Intestine of Diabetic Rats?

BACKGROUND

Effects of propionic acid (PA) on the cellular and molecular processes in the small intestine under type 2 diabetes mellitus (T2DM)-induced endoplasmic reticulum (ER) stress remain incompletely studied.

OBJECTIVES

The aim of the study was to assess the state of unfolded protein response (UPR) system in the small intestine of diabetic rats and to explore PA's influence on metformin treatment.

METHODS

Male Wistar rats were divided into 1) control and 2) T2DM groups, and groups receiving (14 days, orally) 3) metformin (60 mg/kg), 4) PA (60 mg/kg), and 5) PA+metformin. Western blotting, RT-PCR, and transmission electron microscopy were performed.

RESULTS

We found that T2DM induced elevation of ER intermembrane space and UPR overactivation based on increased GRP78, ATF6 and PERK levels in small intestine. Metformin treatment led to a further UPR activation. PA supplementation partially restored enterocytes functioning via normalization of ATF6 and PERK content, while IRE1 level reached the maximum value, compared to all groups. The most pronounced effect of adaptation to the T2DMinduced ER stress was observed after combined metformin and PA action. In particular, decreased ER intermembrane space in enterocytes was detected compared to separate metformin and PA administration, which was accompanied by restored GRP78, PERK and IRE1 levels.

CONCLUSION

Our study proves the safety of additional therapy with propionic acid in combination with metformin for the functional state of small intestine. Due to its ability to modulate UPR signaling, PA may be considered a safe and perspective candidate for supportive therapy in T2DM, especially for neuroprotection.

Microbial short-chain fatty acids regulate drug seeking and transcriptional control in a model of cocaine seeking

Cocaine use disorder represents a public health crisis with no FDA-approved medications for its treatment. A growing body of research has detailed the important connections between the brain and the resident population of bacteria in the gut, the gut microbiome, in psychiatric disease models. Acute depletion of gut bacteria results in enhanced reward in a mouse cocaine place preference model, and repletion of bacterially-derived short-chain fatty acid (SCFA) metabolites reverses this effect. However, the role of the gut microbiome and its metabolites in modulating cocaine-seeking behavior after prolonged abstinence is unknown. Given that relapse prevention is the most clinically challenging issue in treating substance use disorders, studies examining the effects of microbiome manipulations in relapse-relevant models are critical. Here, male Sprague-Dawley rats received either untreated water or antibiotics to deplete the gut microbiome and its metabolites. Rats were trained to self-administer cocaine and subjected to either within-session threshold testing to evaluate motivation for cocaine or 21 days of abstinence followed by a cue-induced cocaine-seeking task to model relapse behavior. Microbiome depletion did not affect cocaine acquisition on an fixed-ratio 1 schedule. However, microbiome-depleted rats exhibited significantly enhanced motivation for low dose cocaine on a within-session threshold task. Similarly, microbiome depletion increased cue-induced cocaine-seeking following prolonged abstinence and altered transcriptional regulation in the nucleus accumbens. In the absence of a normal microbiome, repletion of bacterially-derived SCFA metabolites reversed the behavioral and transcriptional changes associated with microbiome depletion. These findings suggest that gut bacteria, via their metabolites, are key regulators of drug-seeking behaviors, positioning the microbiome as a potential translational research target.

Advances in the Treatment of Autism Spectrum Disorder: Current and Promising Strategies

Autism spectrum disorder (ASD) is an umbrella term for developmental disorders characterized by social and communication impairments, language difficulties, restricted interests, and repetitive behaviors. Current management approaches for ASD aim to resolve its clinical manifestations based on the type and severity of the disability. Although some medications like risperidone show potential in regulating ASD-associated symptoms, a comprehensive treatment strategy for ASD is yet to be discovered. To date, identifying appropriate therapeutic targets and treatment strategies remains challenging due to the complex pathogenesis associated with ASD. Therefore, a comprehensive approach must be tailored to target the numerous pathogenetic pathways of ASD. From currently viable and basic treatment strategies, this review explores the entire field of advancements in ASD management up to cutting-edge modern scientific research. A novel systematic and personalized treatment approach is suggested, combining the available medications and targeting each symptom accordingly. Herein, summarize and categorize the most appropriate ways of modern ASD management into three distinct categories: current, promising, and prospective strategies.

Microbiota-gut-brain axis: interplay between microbiota, barrier function and lymphatic system

The human gastrointestinal tract, boasting the most diverse microbial community, harbors approximately 100 trillion microorganisms comprising viruses, bacteria, fungi, and archaea. The profound genetic and metabolic capabilities of the gut microbiome underlie its involvement in nearly every facet of human biology, from health maintenance and development to aging and disease. Recent recognition of microbiota - gut - brain axis, referring to the bidirectional communication network between gut microbes and their host, has led to a surge in interdisciplinary research. This review begins with an overview of the current understandings regarding the influence of gut microbes on intestinal and blood-brain barrier integrity. Subsequently, we discuss the mechanisms of the microbiota - gut - brain axis, examining the role of gut microbiota-related neural transmission, metabolites, gut hormones and immunity. We propose the concept of microbiota-mediated multi-barrier modulation in the potential treatment in gastrointestinal and neurological disorders. Furthermore, the role of lymphatic network in the development and maintenance of barrier function is discussed, providing insights into lesser-known conduits of communication between the microbial ecosystem within the gut and the brain. In the final section, we conclude by describing the ongoing frontiers in understanding of the microbiota - gut - brain axis's impact on human health and disease.

Gut microbiota functional profiling in autism spectrum disorders: bacterial VOCs and related metabolic pathways acting as disease biomarkers and predictors

Background

Autism spectrum disorder (ASD) is a multifactorial neurodevelopmental disorder. Major interplays between the gastrointestinal (GI) tract and the central nervous system (CNS) seem to be driven by gut microbiota (GM). Herein, we provide a GM functional characterization, based on GM metabolomics, mapping of bacterial biochemical pathways, and anamnestic, clinical, and nutritional patient metadata.

Methods

Fecal samples collected from children with ASD and neurotypical children were analyzed by gas-chromatography mass spectrometry coupled with solid phase microextraction (GC-MS/SPME) to determine volatile organic compounds (VOCs) associated with the metataxonomic approach by 16S rRNA gene sequencing. Multivariate and univariate statistical analyses assessed differential VOC profiles and relationships with ASD anamnestic and clinical features for biomarker discovery. Multiple web-based and machine learning (ML) models identified metabolic predictors of disease and network analyses correlated GM ecological and metabolic patterns.

Results

The GM core volatilome for all ASD patients was characterized by a high concentration of 1-pentanol, 1-butanol, phenyl ethyl alcohol; benzeneacetaldehyde, octadecanal, tetradecanal; methyl isobutyl ketone, 2-hexanone, acetone; acetic, propanoic, 3-methyl-butanoic and 2-methyl-propanoic acids; indole and skatole; and o-cymene. Patients were stratified based on age, GI symptoms, and ASD severity symptoms. Disease risk prediction allowed us to associate butanoic acid with subjects older than 5 years, indole with the absence of GI symptoms and low disease severity, propanoic acid with the ASD risk group, and p-cymene with ASD symptoms, all based on the predictive CBCL-EXT scale. The HistGradientBoostingClassifier model classified ASD patients vs. CTRLs by an accuracy of 89%, based on methyl isobutyl ketone, benzeneacetaldehyde, phenyl ethyl alcohol, ethanol, butanoic acid, octadecane, acetic acid, skatole, and tetradecanal features. LogisticRegression models corroborated methyl isobutyl ketone, benzeneacetaldehyde, phenyl ethyl alcohol, skatole, and acetic acid as ASD predictors.

Conclusion

Our results will aid the development of advanced clinical decision support systems (CDSSs), assisted by ML models, for advanced ASD-personalized medicine, based on omics data integrated into electronic health/medical records. Furthermore, new ASD screening strategies based on GM-related predictors could be used to improve ASD risk assessment by uncovering novel ASD onset and risk predictors.

Revealing the beneficial effects of a dairy infant formula on the gut microbiota of early childhood children with autistic spectrum disorder using static and SHIME® fermentation models

This study evaluated the impact of the Milnutri Profutura® (MNP) dairy infant formula on the gut microbiota of early childhood children (three to five years) with Autistic Spectrum Disorder (ASD) using static fermentation (time zero, 24, and 48 h) and the Simulator of the Human Intestinal Microbiol Ecosystem (SHIME®) (time zero, 72 h, and 7 days). The relative abundance of selected intestinal bacterial groups, pH values, organic acids, and sugars were verified at time zero, 24, and 48 h using flow cytometry and measurements. In addition, the diversity and changes in the gut microbiota, and the amounts of acetic, butyric, and propionic acids and ammonium ions (NH4+) in fermentation using the SHIME® were measured at time zero, 72 h, and 7 days. MNP increased Lactobacillus/Enterococcus and Bifidobacterium populations and decreased Bacteroides/Prevotella, Clostridium histolyticum and Eubacterium rectale/Clostridium coccoides populations (p < 0.05) at 24 and 48 h of static fermentation, showing a positive prebiotic activity score (65.18 ± 0.07). The pH, fructose and glucose decreased, while lactic, butyric, and propionic acids increased (p < 0.05) at 48 h of static fermentation. MNP increased (p < 0.05) the Firmicutes phylum during the fermentation in SHIME®. MNP decreased the diversity at 72 h of fermentation, mostly by the increase (p < 0.05) in the Lactobacillus genus. Microbial groups considered harmful such as Lachnospiraceae, Negativicoccus, and Lachnoclostridium were inhibited after administration with MNP. Propionic and butyric acids increased at 72 h and NH4+ decreased (p < 0.05) at the end of fermentation with MNP. The results indicate MNP as an infant formula which may benefit the gut microbiota of children with ASD.

Propionic and valproic acids have an impact on bacteria viability, proton flux and ATPase activity

Short-chain fatty acids like propionic (PPA) and valproic acids (VP) can alter gut microbiota, which is suggested to play a role in development of autism spectrum disorders (ASD). In this study we investigated the role of various concentrations of PPA and VP in gut enteric gram-negative Escherichia coli K12 and gram-positive Enterococcus hirae ATCC 9790 bacteria growth properties, ATPase activity and proton flux. The specific growth rate (µ) was 0.24 h-1 and 0.82 h-1 in E. coli and E. hirae, respectively. Different concentrations of PPA reduced the value of µ similarly in both strains. PPA affects membrane permeability only in E. hirae. PPA decreased DCCD-sensitive ATPase activity in the presence of K+ ions by 20% in E. coli and 40% in E. hirae suggesting the importance of the FOF1-K+ transport system in the regulation of PPA-disrupted homeostasis. Moreover, the H+ flux during PPA consumption could be the protective mechanism for enteric bacteria. VP has a selective effect on the µ depending on bacteria. The overwhelming effect of VP was detected on the K+-promoted ATPase activity in E. hirae. Taken together it can be suggested that PPA and VP have a disruptive effect on E. coli and E. hirae growth, viability, bioenergetic and biochemical properties, which are connected with the alteration of FOF1-ATPase activity and H+ flux rate or direction.

Gut microbiota regulates blood-cerebrospinal fluid barrier function and Aβ pathology

Accumulating evidence indicates that gut microbiota dysbiosis is associated with increased blood-brain barrier (BBB) permeability and contributes to Alzheimer's disease (AD) pathogenesis. In contrast, the influence of gut microbiota on the blood-cerebrospinal fluid (CSF) barrier has not yet been studied. Here, we report that mice lacking gut microbiota display increased blood-CSF barrier permeability associated with disorganized tight junctions (TJs), which can be rescued by recolonization with gut microbiota or supplementation with short-chain fatty acids (SCFAs). Our data reveal that gut microbiota is important not only for the establishment but also for the maintenance of a tight barrier. Also, we report that the vagus nerve plays an important role in this process and that SCFAs can independently tighten the barrier. Administration of SCFAs in AppNL-G-F mice improved the subcellular localization of TJs at the blood-CSF barrier, reduced the β-amyloid (Aβ) burden, and affected microglial phenotype. Altogether, our results suggest that modulating the microbiota and administering SCFAs might have therapeutic potential in AD via blood-CSF barrier tightening and maintaining microglial activity and Aβ clearance.

Unveiling sex-based differences in developing propionic acid-induced features in mice as a rodent model of ASD

Background

Males are more likely to develop autism as a neurodevelopmental disorder than females are, although the mechanisms underlying male vulnerability are not fully understood. Therefore, studying the role of autism etiologies considering sex differences in the propionic acid (PPA) rodent model of autism would build greater understanding of how females are protected from autism spectrum disorder, which may be used as a treatment strategy for males with autism.

Objectives

This study aimed to investigate the sex differences in oxidative stress, glutamate excitotoxicity, neuroinflammation, and gut microbiota impairment as etiological mechanisms for many neurological diseases, with specific reference to autism.

Method

Forty albino mice were divided into four groups of 10 animals each with two control and two treated groups of both sexes received only phosphate-buffered saline or a neurotoxic dose of PPA (250 mg/kg body weight) for 3 days, respectively. Biochemical markers of energy metabolism, oxidative stress, neuroinflammation, and excitotoxicity were measured in mouse brain homogenates, whereas the presence of pathogenic bacteria was assessed in mouse stool samples. Furthermore, the repetitive behavior, cognitive ability, and physical-neural coordination of the animals were examined.

Results

Collectively, selected variables related to oxidative stress, glutamate excitotoxicity, neuroinflammation, and gut bacteria were impaired concomitantly with altered behavior in PPA-induced rodent model, with males being more susceptible than females.

Conclusion

This study explains the role of sex in the higher vulnerability of males to develop autistic biochemical and behavioral features compared with females. Female sex hormones and the higher detoxification capacity and higher glycolytic flux in females serve as neuroprotective contributors in a rodent model of autism.

Zebrafish (Danio rerio) as a translational model for neuro-immune interactions in the enteric nervous system in autism spectrum disorders

Autism spectrum disorders (ASD) affect about 1% of the population and are strongly associated with gastrointestinal diseases creating shortcomings in quality of life. Multiple factors contribute to the development of ASD and although neurodevelopmental deficits are central, the pathogenesis of the condition is complex and the high prevalence of intestinal disorders is poorly understood. In agreement with the prominent research establishing clear bidirectional interactions between the gut and the brain, several studies have made it evident that such a relation also exists in ASD. Thus, dysregulation of the gut microbiota and gut barrier integrity may play an important role in ASD. However, only limited research has investigated how the enteric nervous system (ENS) and intestinal mucosal immune factors may impact on the development of ASD-related intestinal disorders. This review focuses on the mechanistic studies that elucidate the regulation and interactions between enteric immune cells, residing gut microbiota and the ENS in models of ASD. Especially the multifaceted properties and applicability of zebrafish (Danio rerio) for the study of ASD pathogenesis are assessed in comparison to studies conducted in rodent models and humans. Advances in molecular techniques and in vivo imaging, combined with genetic manipulation and generation of germ-free animals in a controlled environment, appear to make zebrafish an underestimated model of choice for the study of ASD. Finally, we establish the research gaps that remain to be explored to further our understanding of the complexity of ASD pathogenesis and associated mechanisms that may lead to intestinal disorders.

Short-chain fatty and carboxylic acid changes associated with fecal microbiota transplant communally influence microglial inflammation

The intestinal microbiota has been proposed to influence human mental health and cognition through the gut-brain axis. Individuals experiencing recurrent Clostridioides difficile infection (rCDI) frequently report depressive symptoms, which are improved after fecal microbiota transplantation (FMT); however, mechanisms underlying this association are poorly understood. Short-chain fatty acids and carboxylic acids (SCCA) produced by the intestinal microbiota cross the blood brain barrier and have been proposed to contribute to gut-brain communication. We hypothesized that changes in serum SCCA measured before and after successful FMT for rCDI influences the inflammatory response of microglia, the resident immune cells of the central nervous system. Serum SCCA were quantified using gas chromatography-mass spectroscopy from 38 patients who participated in a randomized trial comparing oral capsule-vs colonoscopy-delivered FMT for rCDI, and quality of life was assessed by SF-36 at baseline, 4, and 12 weeks after FMT treatment. Successful FMT was associated with improvements in mental and physical health, as well as significant changes in a number of circulating SCCA, including increased butyrate, 2-methylbutyrate, valerate, and isovalerate, and decreased 2-hydroxybutyrate. Primary cultured microglia were treated with SCCA and the response to a pro-inflammatory stimulus was measured. Treatment with a combination of SCCA based on the post-FMT serum profile, but not single SCCA species, resulted in significantly reduced inflammatory response including reduced cytokine release, reduced nitric oxide release, and accumulation of intracellular lipid droplets. This suggests that both levels and diversity of SCCA may be an important contributor to gut-brain communication.

Differences of gut microbiota and behavioral symptoms between two subgroups of autistic children based on γδT cells-derived IFN-γ Levels: A preliminary study

Background

Autism Spectrum Disorders (ASD) are defined as a group of pervasive neurodevelopmental disorders, and the heterogeneity in the symptomology and etiology of ASD has long been recognized. Altered immune function and gut microbiota have been found in ASD populations. Immune dysfunction has been hypothesized to involve in the pathophysiology of a subtype of ASD.

Methods

A cohort of 105 ASD children were recruited and grouped based on IFN-γ levels derived from ex vivo stimulated γδT cells. Fecal samples were collected and analyzed with a metagenomic approach. Comparison of autistic symptoms and gut microbiota composition was made between subgroups. Enriched KEGG orthologues markers and pathogen-host interactions based on metagenome were also analyzed to reveal the differences in functional features.

Results

The autistic behavioral symptoms were more severe for children in the IFN-γ-high group, especially in the body and object use, social and self-help, and expressive language performance domains. LEfSe analysis of gut microbiota revealed an overrepresentation of Selenomonadales, Negatiyicutes, Veillonellaceae and Verrucomicrobiaceae and underrepresentation of Bacteroides xylanisolvens and Bifidobacterium longum in children with higher IFN-γ level. Decreased metabolism function of carbohydrate, amino acid and lipid in gut microbiota were found in the IFN-γ-high group. Additional functional profiles analyses revealed significant differences in the abundances of genes encoding carbohydrate-active enzymes between the two groups. And enriched phenotypes related to infection and gastroenteritis and underrepresentation of one gut-brain module associated with histamine degradation were also found in the IFN-γ-High group. Results of multivariate analyses revealed relatively good separation between the two groups.

Conclusions

Levels of IFN-γ derived from γδT cell could serve as one of the potential candidate biomarkers to subtype ASD individuals to reduce the heterogeneity associated with ASD and produce subgroups which are more likely to share a more similar phenotype and etiology. A better understanding of the associations among immune function, gut microbiota composition and metabolism abnormalities in ASD would facilitate the development of individualized biomedical treatment for this complex neurodevelopmental disorder.

The gut microbiota and endometriosis: From pathogenesis to diagnosis and treatment

Endometriosis is a common gynecological disease, that often leads to pain and infertility. At present, the specific pathogenesis of endometriosis has not been clarified, but it may be closely related to an imbalance of sex hormones in the body, ectopic hyperplasia stimulated by immune inflammation, and invasion and escape based on tumor characteristics. Gut microbiota is associated with many inflammatory diseases. With the further study of the gut microbiota, people are paying increasing attention to its relationship with endometriosis. Studies have shown that there is an association between the gut microbiota and endometriosis. The specific ways and mechanisms by which the gut microbiota participates in endometriosis may involve estrogen, immune inflammation, and tumor characteristics, among others. Therefore, in the future, regulating gut microbiota disorders in various ways can help in the treatment of endometriosis patients. This study reviewed the research on the gut microbiota and endometriosis in order to provide ideas for clinical diagnosis and treatment.

Gastrointestinal symptoms have a minor impact on autism spectrum disorder and associations with gut microbiota and short-chain fatty acids

Children with autism spectrum disorder (ASD) experience gastrointestinal (GI) issues more frequently and severely than children who are typically developing (TD). The connections between gastrointestinal problems, microbiota, and short-chain fatty acids (SCFAs) in ASD are still being debated. We enrolled 90 children, 45 of whom were diagnosed with ASD, and examined the impact of GI disorders on ASD. The six-item GI Severity Index questionnaire was used to evaluate gastrointestinal symptoms, while the Social Responsiveness Scale was used to evaluate autism symptoms. Further, the Children’s Sleep Habits Questionnaire and the Children’s Eating Behavior Questionnaire are used to assess sleep and eating disorders in children. We assessed fecal microbiota by 16S rRNA gene sequencing, and SCFA concentrations by gas chromatography/mass spectrometry. The results revealed that children with ASD exhibited a high rate of gastrointestinal issues (78%), as well as higher rates of social impairment and poor sleeping habits, compared to TD children. However, GI disturbances have a minor impact on autism. In addition, the levels of propionic acid, butyric acid, and valeric acid were significantly higher in the ASD group. Besides, the ASD, TD, and GI subgroups possessed distinct microbiome profiles. These findings suggest that gastrointestinal disturbances have no discernible effect on the core symptoms of autism. Although autism may not cause an increase in GI symptoms directly, alterations in metabolites, such as SCFAs, may cause GI symptoms.

The promotion mechanism of prebiotics for probiotics: A review

Prebiotics and probiotics play a positive role in promoting human nutrition and health. Prebiotics are compounds that cannot be digested by the host, but can be used and fermented by probiotics, so as to promote the reproduction and metabolism of intestinal probiotics for the health of body. It has been confirmed that probiotics have clinical or health care functions in preventing or controlling intestinal, respiratory, and urogenital infections, allergic reaction, inflammatory bowel disease, irritable bowel syndrome and other aspects. However, there are few systematic summaries of these types, mechanisms of action and the promotion relationship between prebiotics and probiotic. Therefore, we summarized the various types of prebiotics and probiotics, their individual action mechanisms, and the mechanism of prebiotics promoting probiotics in the intestinal tract. It is hoped this review can provide new ideas for the application of prebiotics and probiotics in the future.

Restoration of Cathepsin D Level via L-Serine Attenuates PPA-Induced Lysosomal Dysfunction in Neuronal Cells

L-serine is a non-essential amino acid endogenously produced by astrocytes and is abundant in human diets. Beneficial roles of the metabolic products from L-serine in various conditions in the brain including neuronal development have been reported. Through several preclinical studies, L-serine treatment was also shown to offer beneficial therapeutic effects for brain damage such as ischemic stroke, amyotrophic lateral sclerosis, and Parkinson’s disease. Despite evidence for the value of L-serine in the clinic, however, its beneficial effects on the propionic acid (PPA)-induced neuronal toxicity and underlying mechanisms of L-serine-mediated neuroprotection are unknown. In this study, we observed that PPA-induced acidic stress induces abnormal lipid accumulation and functional defects in lysosomes of hippocampal neurons. L-serine treatment was able to rescue the structure and function of lysosomes in PPA-treated hippocampal neuronal cells. We further identified that L-serine suppressed the formation of lipid droplets and abnormal lipid membrane accumulations inside the lysosomes in PPA-treated hippocampal neuronal cells. Taken together, these findings indicate that L-serine can be utilized as a neuroprotective agent for the functionality of lysosomes through restoration of cathepsin D in disease conditions.

Shifts in the intestinal microflora of meat rabbits in response to glucocorticoids

BACKGROUND

As major stress hormones, glucocorticoids can directly or indirectly affect the intestinal microflora, although few studies have focused on changes in the composition of the intestinal microflora. In this study, rabbits were randomly divided into two groups: gavage administration with saline, and the same doses of dexamethasone (1 mg kg^-1 ). After 7 days, the microbial diversity of the jejunum contents was analysed.

RESULTS

The gut microflora richness and diversity had no significant difference between the two groups. The proportions of Firmicutes and Bacteroidetes were the most abundant in the jejunum of meat rabbits. Dexamethasone injection led to a change in the structure of the gut microflora composition, and we found that there were six biomarkers with linear discriminant analysis score >4 (Firmicutes, Caproiciproducens, Clostridiales, Clostridia, Psychrobacter, and Psychrobacter faecalis), moreover, the results of this study provide new insight into alleviating the effects of stress on meat rabbits.

CONCLUSION

It was concluded that glucocorticoids caused changes in the composition of intestinal microflora. © 2022 Society of Chemical Industry.

Effect of Electroacupuncture on Short-Chain Fatty Acids in Peripheral Blood after Middle Cerebral Artery Occlusion/Reperfusion in Rats Based on Gas Chromatography–Mass Spectrometry

Previous fundamental and clinical research has shown that electroacupuncture (EA) at the acupoints of Quchi (LI11) and Zusanli (ST36) can successfully alleviate motor dysfunction following stroke. Additionally, it has been discovered that gut microbiota and their metabolites play an essential role in stroke. However, the relationship between the metabolites of gut microbiota and the efficacy of EA is still unclear. Therefore, the aim of this study was to evaluate the mechanism of EA at LI11 and ST36 in the treatment of motor dysfunction after middle cerebral artery occlusion/reperfusion (MCAO/R) in model rats by comparing the differences and correlation between different short-chain fatty acids (SCFAs) and the recovery of motor function. The results indicated that EA at LI11 and ST36 acupoints enhanced the neurological function, motor function, and infarct volume of MCAO/R rats. The levels of acetic acid, propionic acid, and total SCFAs were considerably lower in the MCAO/R group than in the sham group (P < 0.05). Acetic acid, propionic acid, and total SCFA concentrations were substantially higher in the MCAO/R + EA group than in the MCAO/R group (P < 0.05). Finally, Pearson correlation analysis revealed that the propionic acid concentration was substantially favorably connected with the duration on the rotarod (r = 0.633 and P < 0.05) and highly negatively correlated with the modified neurological severity score (mNSS) (r = −0.698 and P < 0.05) and the percentage of cerebral infarct volume (r = −0.729 and P < 0.05). Taken together, these findings indicate that the increase in propionic acid may be one of the mechanisms and targets of EA at LI11 and ST36 acupoints to improve poststroke motor dysfunction in MCAO/R rats.

Age-dependent effects of gut microbiota metabolites on brain resident macrophages

In recent years, development of age-related diseases, such as Alzheimer's and Parkinson's disease, as well as other brain disorders, including anxiety, depression, and schizophrenia have been shown to be associated with changes in the gut microbiome. Several factors can induce an alteration in the bacterial composition of the host's gastrointestinal tract. Besides dietary changes and frequent use of antibiotics, the microbiome is also profoundly affected by aging. Levels of microbiota-derived metabolites are elevated in older individuals with age-associated diseases and cognitive defects compared to younger, healthy age groups. The identified metabolites with higher concentration in aged hosts, which include choline and trimethylamine, are known risk factors for age-related diseases. While the underlying mechanisms and pathways remain elusive for the most part, it has been shown, that these metabolites are able to trigger the innate immunity in the central nervous system by influencing development and activation status of brain-resident macrophages. The macrophages residing in the brain comprise parenchymal microglia and non-parenchymal macrophages located in the perivascular spaces, meninges, and the choroid plexus. In this review, we highlight the impact of age on the composition of the microbiome and microbiota-derived metabolites and their influence on age-associated diseases caused by dysfunctional brain-resident macrophages.

Potential health benefits of lowering gas production and bifidogenic effect of the blends of polydextrose with inulin in a human gut model

Polydextrose is a nutrient supplement, which is widely applied in the food industry. The use of polydextrose in combination with prebiotics and probiotics has recently increased, whereas the fermentation properties of its blend have not yet been fully revealed. We evaluated the metabolic profile of polydextrose, inulin, and their blends by a batch in vitro fermentation of fifteen human fecal inocula. After 24 h of fermentation, polydextrose increased the production of gas, ammonia, and several short chain fatty acids, including propionate and butyrate, when compared to its blends, inulin, and fructo-oligosaccharides. Furthermore, polydextrose had the slowest degradation rate of all the carbohydrates tested, consistent with its partial fermentation in the distal colon. The 16S rRNA gene sequencing analysis of the gut microbiome exhibited significantly increased relative abundance of Clostridium_XVIII, Megamonas, Mitsuokella, and Erysipelotrichaceae_incertae_sedis in polydextrose compared to other carbohydrates. On the other hand, the blends of polydextrose and inulin (1:1 or 2:1) showed reduced gas production and similar bifidogenicity to inulin alone. The blends not only had similar alpha-diversity and PCoA to inulin but also had a similar abundance of beneficial bacteria, such as Faecalibacterium and Roseburia, suggesting potential health benefits. Also their low gas production was likely due to the abundance of Faecalibacterium and Anaerostipes, which were negatively correlated with gas production. Additionally, our in vitro fermentation model shows advantages in the large-scale assessment of fermentation performance.

Deviated and early unsustainable stunted development of gut microbiota in children with autism spectrum disorder

OBJECTIVE

Recent studies have provided insights into the gut microbiota in autism spectrum disorder (ASD); however, these studies were restricted owing to limited sampling at the unitary stage of childhood. Herein, we aimed to reveal developmental characteristics of gut microbiota in a large cohort of subjects with ASD combined with interindividual factors impacting gut microbiota.

DESIGN

A large cohort of 773 subjects with ASD (aged 16 months to 19 years), 429 neurotypical (NT) development subjects (aged 11 months to 15 years) were emolyed to determine the dynamics change of gut microbiota across different ages using 16S rRNA sequencing.

RESULT

In subjects with ASD, we observed a distinct but progressive deviation in the development of gut microbiota characterised by persistently decreased alpha diversity, early unsustainable immature microbiota, altered aboudance of 20 operational taxonomic units (OTUs), decreased taxon detection rate and 325 deregulated microbial metabolic functions with age-dependent patterns. We further revealed microbial relationships that have changed extensively in ASD before 3 years of age, which were associated with the severity of behaviour, sleep and GI symptoms in the ASD group. This analysis demonstrated that a signature of the combination of 2 OTUs, Veillonella and Enterobacteriaceae, and 17 microbial metabolic functions efficiently discriminated ASD from NT subjects in both the discovery (area under the curve (AUC)=0.86), and validation 1 (AUC=0.78), 2 (AUC=0.82) and 3 (AUC=0.67) sets.

CONCLUSION

Our large cohort combined with clinical symptom analysis highlights the key regulator of gut microbiota in the pathogenesis of ASD and emphasises the importance of monitoring and targeting the gut microbiome in future clinical applications of ASD.

Role of the Gut-Brain Axis, Gut Microbial Composition, Diet, and Probiotic Intervention in Parkinson's Disease

Parkinson's disease (PD) is the second-most prevalent neurodegenerative or neuropsychiatric disease, affecting 1% of seniors worldwide. The gut microbiota (GM) is one of the key access controls for most diseases and disorders. Disturbance in the GM creates an imbalance in the function and circulation of metabolites, resulting in unhealthy conditions. Any dysbiosis could affect the function of the gut, consequently disturbing the equilibrium in the intestine, and provoking pro-inflammatory conditions in the gut lumen, which send signals to the central nervous system (CNS) through the vagus enteric nervous system, possibly disturbing the blood-brain barrier. The neuroinflammatory conditions in the brain cause accumulation of α-syn, and progressively develop PD. An important aspect of understanding and treating the disease is access to broad knowledge about the influence of dietary supplements on GM. Probiotics are live microorganisms which, when administered in adequate amounts, confer a health benefit on the host. Probiotic supplementation improves the function of the CNS, and improves the motor and non-motor symptoms of PD. Probiotic supplementation could be an adjuvant therapeutic method to manage PD. This review summarizes the role of GM in health, the GM-brain axis, the pathogenesis of PD, the role of GM and diet in PD, and the influence of probiotic supplementation on PD. The study encourages further detailed clinical trials in PD patients with probiotics, which aids in determining the involvement of GM, intestinal mediators, and neurological mediators in the treatment or management of PD.

The impact of maternal high-fat diet on offspring neurodevelopment

A maternal high-fat diet affects offspring neurodevelopment with long-term consequences on their brain health and behavior. During the past three decades, obesity has rapidly increased in the whole human population worldwide, including women of reproductive age. It is known that maternal obesity caused by a high-fat diet may lead to neurodevelopmental disorders in their offspring, such as autism spectrum disorder, attention deficit hyperactivity disorder, anxiety, depression, and schizophrenia. A maternal high-fat diet can affect offspring neurodevelopment due to inflammatory activation of the maternal gut, adipose tissue, and placenta, mirrored by increased levels of pro-inflammatory cytokines in both maternal and fetal circulation. Furthermore, a maternal high fat diet causes gut microbial dysbiosis further contributing to increased inflammatory milieu during pregnancy and lactation, thus disturbing both prenatal and postnatal neurodevelopment of the offspring. In addition, global molecular and cellular changes in the offspring's brain may occur due to epigenetic modifications including the downregulation of brain-derived neurotrophic factor (BDNF) expression and the activation of the endocannabinoid system. These neurodevelopmental aberrations are reflected in behavioral deficits observed in animals, corresponding to behavioral phenotypes of certain neurodevelopmental disorders in humans. Here we reviewed recent findings from rodent models and from human studies to reveal potential mechanisms by which a maternal high-fat diet interferes with the neurodevelopment of the offspring.

Role of Gut Microbiome in Autism Spectrum Disorder and Its Therapeutic Regulation

Autism spectrum disorder (ASD) is a neurological disorder that affects normal brain development. The recent finding of the microbiota-gut-brain axis indicates the bidirectional connection between our gut and brain, demonstrating that gut microbiota can influence many neurological disorders such as autism. Most autistic patients suffer from gastrointestinal (GI) symptoms. Many studies have shown that early colonization, mode of delivery, and antibiotic usage significantly affect the gut microbiome and the onset of autism. Microbial fermentation of plant-based fiber can produce different types of short-chain fatty acid (SCFA) that may have a beneficial or detrimental effect on the gut and neurological development of autistic patients. Several comprehensive studies of the gut microbiome and microbiota-gut-brain axis help to understand the mechanism that leads to the onset of neurological disorders and find possible treatments for autism. This review integrates the findings of recent years on the gut microbiota and ASD association, mainly focusing on the characterization of specific microbiota that leads to ASD and addressing potential therapeutic interventions to restore a healthy balance of gut microbiome composition that can treat autism-associated symptoms.

Gut Microbes Regulate Innate Immunity and Epilepsy

Epilepsy is a common chronic brain disease. There are many clinical methods to control epileptic seizures, such as anti-seizure medications (ASMs) or surgical removal of epileptogenic lesions. However, the pathophysiology of epilepsy is still unknown, making it difficult to control or prevent it. The host’s immune system monitors gut microbes, interacts with microbes through pattern recognition receptors such as Toll-like receptors (TLRs) and NOD-like receptors (NLRs) expressed by innate immune cells, and activates immune responses in the body to kill pathogens and balance the relationship between microbes and host. In addition, inflammatory responses induced by the innate immune system are seen in animal models of epilepsy and temporal lobe epilepsy brain tissue to combat pathogens or injuries. This review summarizes the potential relationship between gut microbes, innate immunity, and epilepsy based on recent research to provide more hints for researchers to explore this field further.

Protective Effects of Bee Pollen on Multiple Propionic Acid-Induced Biochemical Autistic Features in a Rat Model

Autism spectrum disorders (ASDs) are neurodevelopmental disorders that clinically presented as impaired social interaction, repetitive behaviors, and weakened communication. The use of bee pollen as a supplement rich in amino acids amino acids, vitamins, lipids, and countless bioactive substances may lead to the relief of oxidative stress, neuroinflammation, glutamate excitotoxicity, and impaired neurochemistry as etiological mechanisms autism. Thirty young male Western albino rats were randomly divided as: Group I-control; Group II, in which autism was induced by the oral administration of 250 mg propionic acid/kg body weight/day for three days followed by orally administered saline until the end of experiment and Group III, the bee pollen-treated group, in which the rats were treated with 250 mg/kg body weight of bee pollen for four weeks before autism was induced as described for Group II. Markers related to oxidative stress, apoptosis, inflammation, glutamate excitotoxicity, and neurochemistry were measured in the brain tissue. Our results indicated that while glutathione serotonin, dopamine, gamma-aminobutyric acid (GABA), GABA/Glutamate ratio, and vitamin C were significantly reduced in propionic acid-treated group (p < 0.05), glutamate, IFN-γ, IL-1A, IL-6, caspase-3, and lipid peroxide levels were significantly elevated (p < 0.05). Bee pollen supplementation demonstrates protective potency presented as amelioration of most of the measured variables with significance range between (p < 0.05)−(p < 0.001).

The function of gut microbiota in immune-related neurological disorders: a review

This review provides an overview of the importance of microbiota in the regulation of gut–brain communication in immune-related neurological disorders. The gastrointestinal (GI) tract hosts a diverse abundance of microbiota, referred to as gut microbiota. The gut microbiota plays a role in the maintenance of GI tract homeostasis and is likely to have multiple effects on brain development and function. The bidirectional communication between the gut microbiota and the brain is termed the microbiota–gut–brain axis. This communication between the intestine and the brain appears to affect human health and behavior, as certain animal studies have demonstrated the association between alterations in the gut microbiota and neurological disorders. Most insights about the microbiota–gut–brain axis come from germ-free animal models, which reveal the importance of gut microbiota in neural function. To date, many studies have observed the impact of the gut microbiota in patients with neurological disorders. Although many studies have investigated the microbiota–gut–brain axis, there are still limitations in translating this research to humans given the complexities of the relationship between the gut microbiota and the brain. In this review, we discuss emerging evidence of how the microbiota–gut–brain axis regulates brain development and function through biological networks, as well as the possible contribution of the microbiota–gut–brain axis in immune-related neurological disorders.

Selective Probiotic Treatment Positively Modulates the Microbiota-Gut-Brain Axis in the BTBR Mouse Model of Autism

Recent studies have shown promise for the use of probiotics in modulating behaviour through the microbiota–gut–brain axis. In the present study, we assessed the impact of two probiotic strains in mitigating autism-related symptomology in the BTBR T⁺ Itpr3^tf/J mouse model of autism spectrum disorder (ASD). Male juvenile BTBR mice were randomized into: (1) control, (2) Lr probiotic (1 × 10⁹ CFU/mL Lacticaseibacillus rhamnosus HA-114), and (3) Ls probiotic groups (1 × 10⁹ CFU/mL Ligilactobacillus salivarius HA-118) (n = 18–21/group), receiving treatments in drinking water for 4 weeks. Gut microbiota profiling by 16S rRNA showed Lr, but not Ls supplementation, to increase microbial richness and phylogenetic diversity, with a rise in potential anti-inflammatory and butyrate-producing taxa. Assessing serum and brain metabolites, Lr and Ls supplementation produced distinct metabolic profiles, with Lr treatment elevating concentrations of potentially beneficial neuroactive compounds, such as 5-aminovaleric acid and choline. As mitochondrial dysfunction is often observed in ASD, we assessed mitochondrial oxygen consumption rates in the prefrontal cortex and hippocampus. No differences were observed for either treatment. Both Lr and Ls treatment reduced behavioural deficits in social novelty preference. However, no changes in hyperactivity, repetitive behaviour, and sociability were observed. Results show Lr to impart positive changes along the microbiota–gut–brain axis, exhibiting beneficial effects on selected behaviour, gut microbial diversity, and metabolism in BTBR mice.

Intestinal Microbiota-Derived Short Chain Fatty Acids in Host Health and Disease

Intestinal microbiota has its role as an important component of human physiology. It produces metabolites that module key functions to establish a symbiotic crosstalk with their host. Among them, short chain fatty acids (SCFAs), produced by intestinal bacteria during the fermentation of partially and non-digestible polysaccharides, play key roles in regulating colon physiology and changing intestinal environment. Recent research has found that SCFAs not only influence the signal transduction pathway in the gut, but they also reach tissues and organs outside of the gut, through their circulation in the blood. Growing evidence highlights the importance of SCFAs level in influencing health maintenance and disease development. SCFAs are probably involved in the management of host health in a complicated (positive or negative) way. Here, we review the current understanding of SCFAs effects on host physiology and discuss the potential prevention and therapeutics of SCFAs in a variety of disorders. It provides a systematic theoretical basis for the study of mechanisms and precise intake level of SCFAs to promote human health.

The Use of Probiotic Therapy in Metabolic and Neurological Diseases

The human gut is home to trillions of microbes that interact with host cells to influence and contribute to body functions. The number of scientific studies focusing on the gut microbiome has exponentially increased in recent years. Studies investigating factors that may potentially affect the gut microbiome and may be used for therapeutic purposes in diseases where dysbioses in the gut microbiome have been shown are of particular interest. This review compiles current evidence available in the scientific literature on the use of probiotics to treat metabolic diseases and autism spectrum disorders (ASDs) to analyze the efficacy of probiotics in these diseases. To do this, we must first define the healthy gut microbiome before looking at the interplay between the gut microbiome and diseases, and how probiotics affect this interaction. In metabolic diseases, such as obesity and diabetes, probiotic supplementation positively impacts pathological parameters. Conversely, the gut–brain axis significantly impacts neurodevelopmental disorders such as ASDs. However, manipulating the gut microbiome and disease symptoms using probiotics has less pronounced effects on neurodevelopmental diseases. This may be due to a more complex interplay between genetics and the environment in these diseases. In conclusion, the use of microbe-based probiotic therapy may potentially have beneficial effects in ameliorating the pathology of various diseases. Validation of available data for the development of personalized treatment regimens for affected patients is still required.

Understanding the Role of the Gut Microbiome in Brain Development and Its Association With Neurodevelopmental Psychiatric Disorders

The gut microbiome has a tremendous influence on human physiology, including the nervous system. During fetal development, the initial colonization of the microbiome coincides with the development of the nervous system in a timely, coordinated manner. Emerging studies suggest an active involvement of the microbiome and its metabolic by-products in regulating early brain development. However, any disruption during this early developmental process can negatively impact brain functionality, leading to a range of neurodevelopment and neuropsychiatric disorders (NPD). In this review, we summarize recent evidence as to how the gut microbiome can influence the process of early human brain development and its association with major neurodevelopmental psychiatric disorders such as autism spectrum disorders, attention-deficit hyperactivity disorder, and schizophrenia. Further, we discuss how gut microbiome alterations can also play a role in inducing drug resistance in the affected individuals. We propose a model that establishes a direct link of microbiome dysbiosis with the exacerbated inflammatory state, leading to functional brain deficits associated with NPD. Based on the existing research, we discuss a framework whereby early diet intervention can boost mental wellness in the affected subjects and call for further research for a better understanding of mechanisms that govern the gut-brain axis may lead to novel approaches to the study of the pathophysiology and treatment of neuropsychiatric disorders.

Molecular interactions between the intestinal microbiota and the host

The intestine is the most densely colonized region of the body, inhabited by a diverse community of microbes. The functional significance of the intestinal microbiota is not yet fully understood, but it is known that the microbiota is implicated in numerous physiological processes of the host, such as metabolism, nutrition, the immune system, and regulation of behavior and mood. This article reviews recent findings on how bacteria of the intestinal microbiota interact with the host.

Microbiota‐microbiota and microbiota‐host interactions are mediated by direct cell contact and by metabolites either produced by bacteria or produced by the host or the environment and metabolized by bacteria. Among them are short‐chain fatty, including butyrate, propionate, and acetate. Other examples include polyamines, linoleic acid metabolites, tryptophan metabolites, trimethylamine‐N‐oxide, vitamins, and secondary bile acids. These metabolites are involved in regulating the cell cycle, neurobiological signaling, cholesterol and bile acid metabolism, immune responses, and responses to antioxidants. Understanding the host‐microbiota pathways and their modulation will allow the identification of individualized therapeutic targets for many diseases. This overview helps to facilitate and promote further research in this field.

Evidence for long-lasting alterations in the fecal microbiota following prenatal alcohol exposure

BACKGROUND

There is growing evidence that the gut microbiota can be shaped by early-life experiences/exposures, with long-term consequences for brain, behavior, and health. Changes in the gut microbiota have also been identified in neurodevelopmental disorders including Autism Spectrum Disorder and schizophrenia. In contrast, no studies to date have investigated whether the gut microbiota is altered in individuals with Fetal Alcohol Spectrum Disorder (FASD), the neurodevelopmental disorder that results from prenatal alcohol exposure (PAE). The current study was designed to assess the impact of PAE on the fecal microbiota.

METHODS

We used a rodent model in which pregnant Sprague-Dawley rats were provided with an EtOH-containing diet or a control diet throughout gestation. Fecal samples were collected from adult male and female animals and 16s rRNA sequencing was performed.

RESULTS

Overall, PAE rats showed greater richness of bacterial species, with community structure investigations demonstrating distinct clustering by prenatal treatment. In addition, prenatal treatment and sex-specific alterations were observed for many specific microbes. For example, in males, Bacteroides and Bifidobacterium, and in females, Faecalitalea and Proteus, differed in abundance between PAE and control rats.

CONCLUSIONS

Taken together, these results show for the first time that PAE has a long-lasting and sex-specific impact on the fecal microbiota. Further research is needed that considers fetal microbiota in the development of new interventions in FASD.

A Computational Framework for Studying Gut-Brain Axis in Autism Spectrum Disorder

Introduction

The integrity of the intestinal epithelium is crucial for human health and is harmed in autism spectrum disorder (ASD). An aberrant gut microbial composition resulting in gut-derived metabolic toxins was found to damage the intestinal epithelium, jeopardizing tissue integrity. These toxins further reach the brain via the gut-brain axis, disrupting the normal function of the brain. A mechanistic understanding of metabolic disturbances in the brain and gut is essential to design effective therapeutics and early intervention to block disease progression. Herein, we present a novel computational framework integrating constraint based tissue specific metabolic (CBM) model and whole-body physiological pharmacokinetics (PBPK) modeling for ASD. Furthermore, the role of gut microbiota, diet, and oxidative stress is analyzed in ASD.

Methods

A representative gut model capturing host-bacteria and bacteria-bacteria interaction was developed using CBM techniques and patient data. Simultaneously, a PBPK model of toxin metabolism was assembled, incorporating multi-scale metabolic information. Furthermore, dynamic flux balance analysis was performed to integrate CBM and PBPK. The effectiveness of a probiotic and dietary intervention to improve autism symptoms was tested on the integrated model.

Results

The model accurately highlighted critical metabolic pathways of the gut and brain that are associated with ASD. These include central carbon, nucleotide, and vitamin metabolism in the host gut, and mitochondrial energy and amino acid metabolisms in the brain. The proposed dietary intervention revealed that a high-fiber diet is more effective than a western diet in reducing toxins produced inside the gut. The addition of probiotic bacteria Lactobacillus acidophilus, Bifidobacterium longum longum, Akkermansia muciniphila, and Prevotella ruminicola to the diet restores gut microbiota balance, thereby lowering oxidative stress in the gut and brain.

Conclusion

The proposed computational framework is novel in its applicability, as demonstrated by the determination of the whole-body distribution of ROS toxins and metabolic association in ASD. In addition, it emphasized the potential for developing novel therapeutic strategies to alleviate autism symptoms. Notably, the presented integrated model validates the importance of combining PBPK modeling with COBRA -specific tissue details for understanding disease pathogenesis.

Therapeutic Effects of a Novel Form of Biotin on Propionic Acid-Induced Autistic Features in Rats

Magnesium biotinate (MgB) is a novel biotin complex with superior absorption and anti-inflammatory effects in the brain than D-Biotin. This study aimed to investigate the impact of different doses of MgB on social behavior deficits, learning and memory alteration, and inflammatory markers in propionic acid (PPA)-exposed rats. In this case, 35 Wistar rats (3 weeks old) were distributed into five groups: 1, Control; 2, PPA treated group; 3, PPA+MgBI (10 mg, HED); 4, PPA+MgBII (100 mg, HED); 5, PPA+MgBIII (500 mg, HED). PPA was given subcutaneously at 500 mg/kg/day for five days, followed by MgB for two weeks. PPA-exposed rats showed poor sociability and a high level of anxiety-like behaviors and cognitive impairments (p < 0.001). In a dose-dependent manner, behavioral and learning-memory disorders were significantly improved by MgB supplementation (p < 0.05). PPA decreased both the numbers and the sizes of Purkinje cells in the cerebellum. However, MgB administration increased the sizes and the densities of Purkinje cells. MgB improved the brain and serum Mg, biotin, serotonin, and dopamine concentrations, as well as antioxidant enzymes (CAT, SOD, GPx, and GSH) (p < 0.05). In addition, MgB treatment significantly regulated the neurotoxicity-related cytokines and neurotransmission-related markers. For instance, MgB significantly decreased the expression level of TNF-α, IL-6, IL-17, CCL-3, CCL-5, and CXCL-16 in the brain, compared to the control group (p < 0.05). These data demonstrate that MgB may ameliorate dysfunctions in social behavior, learning and memory and reduce the oxidative stress and inflammation indexes of the brain in a rat model.

Alteration of Gut Microbiota: New Strategy for Treating Autism Spectrum Disorder

Autism spectrum disorder (ASD) is defined as a complex heterogeneous disorder and characterized by stereotyped behavior and deficits in communication and social interactions. The emerging microbial knowledge has pointed to a potential link between gut microbiota dysbiosis and ASD. Evidence from animal and human studies showed that shifts in composition and activity of the gut microbiota may causally contribute to the etiopathogenesis of core symptoms in the ASD individuals with gastrointestinal tract disturbances and act on microbiota-gut-brain. In this review, we summarized the characterized gut bacterial composition of ASD and the involvement of gut microbiota and their metabolites in the onset and progression of ASD; the possible underlying mechanisms are also highlighted. Given this correlation, we also provide an overview of the microbial-based therapeutic interventions such as probiotics, antibiotics, fecal microbiota transplantation therapy, and dietary interventions and address their potential benefits on behavioral symptoms of ASD. The precise contribution of altering gut microbiome to treating core symptoms in the ASD needs to be further clarified. It seemed to open up promising avenues to develop microbial-based therapies in ASD.

The Microbiota-Gut-Brain Axis and Epilepsy

Honoured as the second genome in humans, the gut microbiota is involved in a constellation of physiological and pathological processes, including those related to the central nervous system. The communication between the gut microbiota and the brain is realized by a complex bidirectional connection, known as the "microbiota-gut-brain axis", via neuroendocrine, immunological, and direct neural mechanisms. Recent studies indicate that gut dysfunction/dysbiosis is presumably involved in the pathogenesis of and susceptibility to epilepsy. In addition, the reconstruction of the intestinal microbiome through, for example, faecal microbiota transplantation, probiotic intervention, and a ketogenic diet, has exhibited beneficial effects on drug-resistant epilepsy. The purposes of this review are to provide a brief overview of the microbiota-gut-brain axis and to synthesize what is known about the involvement of the gut microbiota in the pathogenesis and treatment of epilepsy, to bring new insight into the pathophysiology of epilepsy and to present a preliminary discussion of novel therapeutic options for epilepsy based on the gut microbiota.

Dynamic and Systemic Perspective in Autism Spectrum Disorders: A Change of Gaze in Research Opens to A New Landscape of Needs and Solutions

The first step for a harmonious bio-psycho-social framework in approaching autism spectrum disorders (ASD) is overcoming the conflict between the biological and the psychosocial perspective. Biological research can provide clues for a correct approach to clinical practice, assuming that it would lead to the conceptualization of a pathogenetic paradigm able to account for epidemiologic and clinical findings. The upward trajectory in ASD prevalence and the systemic involvement of other organs besides the brain suggest that the epigenetic paradigm is the most plausible one. The embryo-fetal period is the crucial window of opportunity for keeping neurodevelopment on the right tracks, suggesting that women's health in pregnancy should be a priority. Maladaptive molecular pathways beginning in utero, in particular, a vicious circle between the immune response, oxidative stress/mitochondrial dysfunction, and dysbiosis-impact neurodevelopment and brain functioning across the lifespan and are the basis for progressive multisystemic disorders that account for the substantial health loss and the increased mortality in ASD. Therefore, the biological complexity of ASD and its implications for health requires the enhancement of clinical skills on these topics, to achieve an effective multi-disciplinary healthcare model. Well-balanced training courses could be a promising starting point to make a change.

Crosstalk between peripheral and the brain-resident immune components in epilepsy

Epilepsy is one of the most common neurology diseases. It is characterized by recurrent, spontaneous seizures and accompanied by various comorbidities which can significantly affect a person's life. Accumulating evidence indicates an essential pathophysiological role for neuroinflammation in epilepsy, which involves activation of microglia and astrocytes, recruitment of peripheral leukocytes into the central nervous system, and release of some inflammatory mediators, including pro-inflammatory factors and anti-inflammatory cytokines. There is complex crosstalk between the central nervous system and peripheral immune responses associated with the progression of epilepsy. This review provides an update of current knowledge about the contribution of this crosstalk associated with epilepsy. Additionally, how gut microbiota is involved in epilepsy and its possible influence on crosstalk is also discussed. Such recent advances in understanding suggest innovative methods for targeting the molecules correlated with the crosstalk and may provide a better prognosis for patients diagnosed with epilepsy.

Effect of Propionic Acid on Diabetes-Induced Impairment of Unfolded Protein Response Signaling and Astrocyte/Microglia Crosstalk in Rat Ventromedial Nucleus of the Hypothalamus

Background

The aim was to investigate the influence of propionic acid (PA) on the endoplasmic reticulum (ER), unfolded protein response (UPR) state, and astrocyte/microglia markers in rat ventromedial hypothalamus (VMH) after type 2 diabetes mellitus (T2DM).

Methods

Male Wistar rats were divided: (1) control, (2) T2DM, and groups that received the following (14 days, orally): (3) metformin (60 mg/kg), (4) PA (60 mg/kg), and (5) PA+metformin. Western blotting, RT-PCR, transmission electron microscopy, and immunohistochemical staining were performed.

Results

We found T2DM-associated enlargement of ER cisterns, while drug administration slightly improved VMH ultrastructural signs of damage. GRP78 level was 2.1-fold lower in T2DM vs. control. Metformin restored GRP78 to control, while PA increased it by 2.56-fold and metformin+PA—by 3.28-fold vs. T2DM. PERK was elevated by 3.61-fold in T2DM, after metformin—by 4.98-fold, PA—5.64-fold, and metformin+PA—3.01-fold vs. control. A 2.45-fold increase in ATF6 was observed in T2DM. Metformin decreased ATF6 content vs. T2DM. Interestingly, PA exerted a more pronounced lowering effect on ATF6, while combined treatment restored ATF6 to control. IRE1 increased in T2DM (2.4-fold), metformin (1.99-fold), and PA (1.45-fold) groups vs. control, while metformin+PA fully normalized its content. The Iba1 level was upregulated in T2DM (5.44-fold) and metformin groups (6.88-fold). Despite PA treatment leading to a further 8.9-fold Iba1 elevation, PA+metformin caused the Iba1 decline vs. metformin and PA treatment. GFAP level did not change in T2DM but rose in metformin and PA groups vs. control. PA+metformin administration diminished GFAP vs. PA. T2DM-induced changes were associated with dramatically decreased ZO-1 levels, while PA treatment increased it almost to control values.

Conclusions

T2DM-induced UPR imbalance, activation of microglia, and impairments in cell integrity may trigger VMH dysfunction. Drug administration slightly improved ultrastructural changes in VMH, normalized UPR, and caused an astrocyte activation. PA and metformin exerted beneficial effects for counteracting diabetes-induced ER stress in VMH.

Comparative Study on the Exacerbating Effects of Casein-Rich vs. Gluten-Rich Diets on Biochemical-Induced Features in Rodent Model of Autism

In relation to dietary intervention in individuals with autism spectrum disorder (ASD), certain food constituents especially gluten and casein are recognized to be challenging and should be restricted. In this study, levels of glutathione S-transferase, glutathione, lipid peroxides, serotonin (5-HT), interleukin-6 (IL-6), glutamate, and gamma aminobutyric acid (GABA) were measured in the brain homogenates of ASD rodent model. Rats were treated either with single dose clindamycin (30 mg/kg) or with propionic acid (PPA) (250 mg/kg) for 3 days and then fed a standard diet, casein-rich diet (CRD), or gluten-rich diet (GRD). The obtained data demonstrates that clindamycin and PPA induced oxidative stress, which was slightly affected by CRD. A marked increase in the proinflammatory cytokine (IL-6) concentration found in clindamycin- and PPA-treated groups was lower in CRD fed rats. Both CRDs and GRDs produced similar trends in glutamate levels. 5-HT levels were higher in the clindamycin- and PPA-treated groups and increased with a GRD but were less affected by a CRD. CRD could be less deleterious compared to GRD. Although the underlying cause of gastrointestinal symptoms in patients with ASD is not exactly known, the most widely accepted one is the opioid theory which is related to GRD and CRD.

The role of microbiota in autism spectrum disorder: A bibliometric analysis based on original articles

BACKGROUND

Gastrointestinal (GI) symptoms can be observed in autism spectrum disorder (ASD) children. It is suggested that the gut microbiota and its metabolites are associated, not only with GI symptoms, but also with behaviors of ASD. The aim of this study was to explore the development context, research hotspots and frontiers of gut microbiota and ASD from January 1, 1980 to April 1, 2022 by bibliometric analysis.

MATERIALS AND METHODS

Publications of ASD and gut microbiota research from 1 January 1980 to 1 April 2022 were retrieved from the Web of Science Core Collection (WoSCC). Publications and citations trends were analyzed by Excel 2010. CiteSpace was used to analyze countries/regions, authors, institutes, references, and keywords and to visualize the knowledge map.

RESULTS

A total of 1027 studies were retrieved, and 266 original articles were included after screening. The most published countries and institutes were the United States and King Saud University. Afaf El-Aansary published the most articles, while Finegold SM had the highest co-citations. Hotspots and emerging trends in this area may be indicated by co-cited references and keywords and their clusters, including "gut-brain axis," "behavior," "chain fatty acid," "brain," "feces," "propionic acid," "clostridium perfringens," and "species clostridium innocuum."

CONCLUSION

The United States dominants the research in this field, which focuses on the alterations of gut microbiota composition and its metabolites, among which the roles of the genus Clostridium and metabolites of short-chain fatty acids, especially propionic acid, are priorities. Fecal microbiota transplantation (FMT) is a promising complementary therapy. In general, research in this area is sparse, but it still has great research prospects.

The Emerging Role of the Gut-Brain-Microbiota Axis in Neurodevelopmental Disorders

Autism spectrum disorder (ASD; autism) is a prevalent neurodevelopmental disorder associated with changes in gut-brain axis communication. Gastrointestinal (GI) symptoms are experienced by a large proportion of individuals diagnosed with autism. Several mutations associated with autism modify cellular communication via neuronal synapses. It has been suggested that modifications to the enteric nervous system, an intrinsic nervous system of the GI tract, could contribute to GI dysfunction. Changes in gut motility, permeability, and the mucosal barrier as well as shifts in the large population of microbes inhabiting the GI tract could contribute to GI symptoms. Preclinical research has demonstrated that mice expressing the well-studied R451C missense mutation in Nlgn3 gene, which encodes cell adhesion protein neuroligin-3 at neuronal synapses, exhibit GI dysfunction. Specifically, NL3^R451C mice show altered colonic motility and faster small intestinal transit. As well as dysmotility, macrophages located within the gut-associated lymphoid tissue of the NL3^R451C mouse caecum show altered morphology, suggesting that neuro-inflammation pathways are modified in this model. Interestingly, NL3^R451C mice maintained in a shared environment demonstrate fecal microbial dysbiosis indicating a role for the nervous system in regulating gut microbial populations. To better understand host-microbe interactions, further clarification and comparison of clinical and animal model profiles of dysbiosis should be obtained, which in turn will provide better insights into the efforts taken to design personalized microbial therapies. In addition to changes in neurophysiological measures, the mucosal component of the GI barrier may contribute to GI dysfunction more broadly in individuals diagnosed with a wide range of neurological disorders. As the study of GI dysfunction advances to encompass multiple components of the gut-brain-microbiota axis, findings will help understand future directions such as microbiome engineering and optimisation of the mucosal barrier for health.