Microbiota modulate behavioral and physiological abnormalities associated with neurodevelopmental disorders

Integrated metabolome and microbiome strategy reveals the therapeutic effect of nervonic acid on Alzheimer's disease rats

Alzheimer's disease (AD) is a complex neurodegenerative disease. Nervonic acid is a component of breast milk and is also found in fish oil and specific vegetable oils. Studies have shown that nervonic acid is essential for the development of the human nervous system. In this study, Morris water maze (MWM) test and pathological analysis showed that nervonic acid could improve cognitive deficits and brain nerve damage in AD rats. Then, through sequencing, we found that nervonic acid increased the abundance of beneficial bacteria such as Lactobacillus and Bacteroides, and decreased the abundance of Pseudomonadaceae_Pseudomonas. Not only that, nervonic acid also regulates the production of short-chain fatty acids (SCFA) and the levels of 29 fecal metabolites, and affects the metabolism of linoleic acid, α-linolenic acid, arachidonic acid, and sphingolipid. Finally, we verified the regulatory effect of nervonic acid on metabolic enzyme activity.

The brain-gut microbiota network (BGMN) is correlated with symptom severity and neurocognition in patients with schizophrenia

The association between the human brain and gut microbiota, known as the "brain-gut-microbiota axis", is involved in the neuropathological mechanisms of schizophrenia (SZ); however, its association patterns and correlations with symptom severity and neurocognition are still largely unknown. In this study, 43 SZ patients and 55 normal controls (NCs) were included, and resting-state functional magnetic resonance imaging (rs-fMRI) and gut microbiota data were acquired for each participant. First, the brain features of brain images and functional brain networks were computed from rs-fMRI data; the gut features of gut microbiota abundance and the gut microbiota network were computed from gut microbiota data. Second, we propose a novel methodology to construct an individual brain-gut microbiota network (BGMN) for each participant by combining the brain and gut features via multiple strategies. Third, discriminative models between SZ patients and NCs were built using the connectivity matrices of the BGMN as input features. Moreover, the correlations between the most discriminative features and the scores of symptom severity and neurocognition were analyzed in SZ patients. The results showed that the best discriminative model between SZ patients and NCs was achieved using the connectivity matrices of the BGMN when all the brain and gut features were integrated, with an accuracy of 0.90 and an area under the curve value of 0.97. The most discriminative features were related primarily to the genera Faecalibacterium and Collinsella, in which the genus Faecalibacterium was linked to the visual system and subcortical cortices and the genus Collinsella was linked to the default network and subcortical cortices. Furthermore, parts of the most discriminative features were significantly correlated with the scores of neurocognition in the SZ patients. The methodology for constructing individual BGMNs proposed in this study can help us reveal the associations between the brain and gut microbiota and understand the neuropathology of SZ.

Exploring the neurotoxic effects of microbial metabolites: A potential link between p-Cresol and autism spectrum disorders?

Autism spectrum disorder (ASD) is a neurodevelopmental disorder with a complex etiology, including genetic and environmental factors. A growing body of evidence (preclinical and clinical studies) implicates a potential role of gut microbiome dysregulation in ASD pathophysiology. This review focuses on the microbial metabolite p-Cresol, produced by certain gut bacteria such as Clostridium, and its potential role in ASD. The review summarizes studies investigating the gut microbiome composition in ASD patients, particularly the increased abundance of Clostridium species and associated gastrointestinal symptoms. The potential neurotoxic effects of p-Cresol are explored, including its influence on neurotransmitter metabolism (especially dopamine), neuroinflammation, and brain development. The mechanistic findings from the preclinical studies of p-Cresol's induction of ASD-like behaviors and its impact on the dopaminergic system are discussed. Literature studies indicated increased levels of p-Cresol in the urine of patients with ASD. This increasing evidence suggests that p-Cresol may serve as a crucial biomarker for understanding the relationship between gut microbiota and ASD, opening avenues for potential diagnostic and therapeutic interventions.

Gut microbiota metabolites, secretory immunoglobulin A and Bayley-III cognitive scores in children from the CHILD Cohort Study

Background

Dysbiosis of the gut microbiota has been demonstrated in neurodevelopmental disorders but the underlying mechanisms that may explain these associations are poorly understood. Gut secretory immunoglobulin A (SIgA) binds pathogenic microbes, preventing mucosal penetration. Gut microbes also influence SIgA production and its binding characteristics through short-chain fatty acid (SCFA) metabolites, allowing them to regulate the immune response. Serum IgA deficiency has been noted in children with autism spectrum disorders (ASD). In this study, we aimed to determine whether SIgA level in infancy is associated with gut microbiota taxonomy and metabolites, and neurodevelopmental outcomes in preschool children.

Methods

For a subsample of 178 children from the Canadian CHILD Cohort Study, gut microbiota of fecal samples collected at 3-4 months and 12 months was profiled using 16S rRNA sequencing. Gut bacterial metabolites levels and SIgA level were measured by nuclear magnetic resonance (NMR) based metabolomics and SIgA enzyme-linked immunosorbent assay at 3-4 months, respectively. Bayley-III Scale of Infant Development was assessed at 12 and 24 months. We evaluated direct relationships in multiple linear regression models and putative causal relationships in statistical mediation models.

Results

Propionate and butyrate levels at 3-4 months were associated with decreased Bayley cognitive score at 24 months (p-values: 0.01 and 0.02, respectively) in adjusted multiple linear regression models, but when we investigated an indirect relationship mediated by decreased SIgA level at 3-4 months, it did not reach statistical significance (p-values: 0.18 and 0.20, respectively). Lactate level at 3-4 months was associated with increased Bayley cognitive score at 24 months in adjusted multiple linear regression models (p-value: 0.01), but the statistical model mediated by increased SIgA level at 3-4 months did not reach statistical significance neither (p-value: 0.20).

Conclusions

Our study contributes to growing evidence that neurodevelopment is influenced by the infant gut microbiota and that it might involve SIgA level, but larger studies are required.

Short-chain fatty acids in Huntington's disease: Mechanisms of action and their therapeutic implications

Huntington's disease (HD) is a progressive neurodegenerative disorder characterized by motor dysfunction, cognitive decline, and emotional instability, primarily resulting from the abnormal accumulation of mutant huntingtin protein. Growing research highlights the role of intestinal microbiota and their metabolites, particularly short-chain fatty acids (SCFAs), in modulating HD progression. SCFAs, including acetate, propionate, and butyrate, are produced by gut bacteria through dietary fiber fermentation and are recognized for their neuroprotective properties. Evidence suggests that SCFAs regulate neuroinflammation, neuronal communication, and metabolic functions within the central nervous system (CNS). In HD, these compounds may support neuronal health, reduce oxidative stress, and enhance blood-brain barrier (BBB) integrity. Their mechanisms of action involve binding to G-protein-coupled receptors (GPCRs) and modulating gene expression through epigenetic pathways, underscoring their therapeutic potential. This analysis examines the significance of SCFAs in HD, emphasizing the gut-brain axis and the benefits of dietary interventions aimed at modifying gut microbiota composition and promoting SCFA production. Further research into these pathways may pave the way for novel HD management strategies and improved therapeutic outcomes.

The microbiome as a modulator of neurological health across the maternal-offspring interface

The maternal microbiome is emerging as an important factor that influences the neurological health of mothers and their children. Recent studies highlight how microbial communities in the maternal gut can shape early-life development in ways that inform long-term health trajectories. Research on the neurodevelopmental effects of maternal microbiomes is expanding our understanding of the microbiome-gut-brain axis to include signaling across the maternal-offspring unit during the perinatal period. In this Review, we synthesize existing literature on how the maternal microbiome modulates brain function and behavior in both mothers and their developing offspring. We present evidence from human and animal studies showing that the maternal microbiome interacts with environmental factors to impact risk for neurodevelopmental abnormalities. We further discuss molecular and cellular mechanisms that facilitate maternal-offspring crosstalk for neuromodulation. Finally, we consider how advancing understanding of these complex interactions could lead to microbiome-based interventions for promoting maternal and offspring health.

Single-cell delineation of the microbiota-gut-brain axis: Probiotic intervention in Chd8 haploinsufficient mice

Emerging research underscores the gut microbiome's impact on the nervous system via the microbiota-gut-brain axis, yet comprehensive insights remain limited. Using a CHD8-haploinsufficient model for autism spectrum disorder (ASD), we explored host-gut microbiota interactions by constructing a single-cell transcriptome atlas of brain and intestinal tissues in wild-type and mutant mice across three developmental stages. CHD8 haploinsufficiency caused delayed development of radial glial precursors and excitatory neural progenitors in the E14.5 brain, inflammation in the adult brain, immunodeficiency, and abnormal intestinal development. Selective CHD8 knockdown in intestinal epithelial cells generated Chd8ΔIEC mice, which exhibited normal sociability but impaired social novelty recognition. Probiotic intervention with Lactobacillus murinus selectively rescued social deficits in Chd8ΔIEC mice, with single-cell transcriptome analysis revealing underlying mechanisms. This study provides a detailed single-cell transcriptomic dataset of ASD-related neural and intestinal changes, advancing our understanding of the gut-brain axis and offering potential therapeutic strategies for ASD.

Quinoa Ethanol Extract Ameliorates Cognitive Impairments Induced by Hypoxia in Mice: Insights into Antioxidant Defense and Gut Microbiome Modulation

Quinoa, rich in pharmacologically active ingredients, possesses the potential benefit in preventing cognitive impairments induced by hypoxia. In this study, the efficacy of quinoa ethanol extracts (QEE) consumption (200 and 500 mg/kg/d, respectively) against hypobaric hypoxia (HH)-induced cognitive deficits in mice was investigated. QEE significantly ameliorated hypoxic stress induced by HH, as evidenced by improvements in baseline indices and reductions in hypoxia-inducible factor 1α levels. Furthermore, QEE enhanced antioxidant defense mechanisms, alleviated neuroinflammation in brain regions associated with memory, and improved HH-induced cognitive impairments by modulating the cyclic adenosine monophosphate response element-binding protein/brain-derived neurotrophic factor signaling pathway. Higher doses generally yielded more effective outcomes than lower doses. QEE also significantly reshaped the gut microbiome structure of HH mice, inhibited gut barrier damage, and reduced lipopolysaccharide migration, thereby increasing short-chain fatty acids (SCFAs) levels. Our findings suggest that QEE may be a promising strategy for preventing hypoxia-induced cognitive impairments by maintaining gut microbiome stability and increasing SCFAs levels.

Polysaccharides from Astragalus membranaceus Bunge alleviate LPS-induced neuroinflammation in mice by modulating microbe-metabolite-brain axis and MAPK/NF-κB signaling pathway

Neuroinflammation can lead to various neurodegenerative disorders, resulting in irreversible neurological dysfunction. Astragalus membranaceus Bunge polysaccharides (APS) present great potential in alleviating neuroinflammation; however, the specific mechanism underlying its neuroprotective effect remains unclear, leading to uncertain prospects for pharmaceutical applications. This study aims to elucidate the mechanism underlying APS-mediated inhibition of neuroinflammation in mice induced by lipopolysaccharide (LPS) through regulation of metabolic function, intestinal flora composition, and cell signaling transduction. Results indicated that APS pretreatment effectively mitigated LPS-induced brain damage. Metabolomics analysis revealed that APS pretreatment also regulated the metabolic disturbances induced by LPS through targeting five specific metabolic pathways. This regulation was supported by notable alterations in nine metabolite markers. Furthermore, APS pretreatment significantly modulated the abundance of four taxa of gut microbes (i.e., Romboutsia, Rikenella, Dubosiella, Odoribacter) closely associated with regulations in eleven metabolic and signaling pathways. Additionally, transcriptome analysis and Western blotting unveiled that APS pretreatment exerted a neuroprotective effect by modulating the MAPK/NF-κB signaling pathway. Our findings provide insights into the potential mechanisms underlying the neuroprotective effects of APS while establishing a solid foundation for future utilization of APS.

Akkermansia muciniphila identified as key strain to alleviate gut barrier injury through Wnt signaling pathway

As the largest mucosal surface, the gut has built a physical, chemical, microbial, and immune barrier to protect the body against pathogen invasion. The disturbance of gut microbiota aggravates pathogenic bacteria invasion and gut barrier injury. Fecal microbiota transplantation (FMT) is a promising treatment for microbiome-related disorders, where beneficial strain engraftment is a significant factor influencing FMT outcomes. The aim of this research was to explore the effect of FMT on antibiotic-induced microbiome-disordered (AIMD) models infected with enterotoxigenic Escherichia coli (ETEC). We used piglet, mouse, and intestinal organoid models to explore the protective effects and mechanisms of FMT on ETEC infection. The results showed that FMT regulated gut microbiota and enhanced the protection of AIMD piglets against ETEC K88 challenge, as demonstrated by reduced intestinal pathogen colonization and alleviated gut barrier injury. Akkermansia muciniphila (A. muciniphila) and Bacteroides fragilis (B. fragilis) were identified as two strains that may play key roles in FMT. We further investigated the alleviatory effects of these two strains on ETEC infection in the AIMD mice model, which revealed that A. muciniphila and B. fragilis relieved ETEC-induced intestinal inflammation by maintaining the proportion of Treg/Th17 cells and epithelial damage by moderately activating the Wnt/β-catenin signaling pathway, while the effect of A. muciniphila was better than B. fragilis. We, therefore, identified whether A. muciniphila protected against ETEC infection using basal-out and apical-out intestinal organoid models. A. muciniphila did protect the intestinal stem cells and stimulate the proliferation and differentiation of intestinal epithelium, and the protective effects of A. muciniphila were reversed by Wnt inhibitor. FMT alleviated ETEC-induced gut barrier injury and intestinal inflammation in the AIMD model. A. muciniphila was identified as a key strain in FMT to promote the proliferation and differentiation of intestinal stem cells by mediating the Wnt/β-catenin signaling pathway.

Psychobiotics and the gut-brain axis: advances in metabolite quantification and their implications for mental health

Psychobiotics are live microorganisms that, when administered in adequate amounts, confer mental health benefits to the host. Several clinical studies have demonstrated significant mental health benefits from psychobiotic administration, making them an emerging topic in food science. Certain strains of Lactobacillus, Bifidobacterium, Streptococcus, Escherichia, and Enterococcus species are known for their ability to modulate the gut-brain axis and provide mental health benefits. Proposed action mechanisms include the production of neuroactive compounds or their precursors, which may cross the blood-brain barrier, or transported by their extracellular vesicles. However, there is a lack of in vivo evidence directly confirming these mechanisms, although indirect evidence from recent studies suggest potential pathways for further investigation. To advance our understanding, it is crucial to study these mechanisms within the host, with accurate quantification of neuroactive compounds and/or their precursors being key in such studies. Current quantification methods, however, face challenges, such as low sensitivity for detecting trace metabolites and limited specificity due to interference from other compounds, impacting the reliability of measurements. This review discusses the emerging field of psychobiotics, their potential action mechanisms, neuroactive compound estimation techniques, and perspectives for improvement in quantifying neuroactive compounds and/or precursors within the host.

Multi-level analysis of gut microbiome extracellular vesicles-host interaction reveals a connection to gut-brain axis signaling

Microbiota-released extracellular vesicles (MEVs) have emerged as a key player in intercellular signaling. However, their involvement in the gut-brain axis has been poorly investigated. We hypothesize that MEVs cross host cellular barriers and deliver their cargoes of bioactive compounds to the brain. In this study, we aimed to investigate the cargo capacity of MEVs for bioactive metabolites and their interactions with the host cellular barriers. First, we conducted a multi-omics profiling of MEVs' contents from ex vivo and stool samples. Metabolomics analysis identified various neuro-related compounds encapsulated within MEVs, such as arachidonyl-dopamine, gabapentin, glutamate, and N-acylethanolamines. Metaproteomics unveiled an enrichment of enzymes involved in neuronal metabolism, primarily in the glutamine/glutamate/gamma-aminobutyric acid (GABA) pathway. These neuro-related proteins and metabolites were correlated with Bacteroides spp. We isolated 18 Bacteroides strains and assessed their GABA production capacity in extracellular vesicles (EVs) and culture supernatant. A GABA-producing Bacteroides finegoldii, released EVs with a high GABA content (4 µM) compared to Phocaeicola massiliensis. Upon testing the capacity of MEVs to cross host barriers, MEVs exhibited a dose-dependent paracellular transport and were endocytosed by Caco-2 and hCMEC/D3 cells. Exposure of Caco-2 cells to MEVs did not alter expression of genes related to intestinal barrier integrity, while affected immune pathways and cell apoptosis process as revealed by RNA-seq analyses. In vivo, MEVs biodistributed across mice organs, including the brain, liver, stomach, and spleen. Our results highlight the ability of MEVs to cross the intestinal and blood-brain barriers to deliver their cargoes to distant organs, with potential implication for the gut-brain axis.

IMPORTANCE

Microbiota-released extracellular vesicles (MEVs) have emerged as a key player in intercellular signaling. In this study, a multi-level analysis revealed presence of a diverse array of biologically active molecules encapsulated within MEVs, including neuroactive metabolites, such as arachidonyl-dopamine, gabapentin, glutamate, and N-acylethanolamines, and gamma-aminobutyric acid (GABA). Metaproteomics also unveiled an enrichment of neural-related proteins, mainly the glutamine/glutamate/GABA pathway. MEVs were able to cross epithelial and blood-brain barriers in vitro. RNA-seq analyses showed that MEVs stimulate several immune pathways while suppressing cell apoptosis process. Furthermore, MEVs were able to traverse the intestinal barriers and reach distal organs, including the brain, thereby potentially influencing brain functionality and contributing to mental and behavior.

Microbial Trojan Horses: Virulence Factors as Key Players in Neurodegenerative Diseases

Changes in population demographics indicate that the elderly population will reach 2.1 billion worldwide by 2050. In parallel, there will be an increase in neurodegenerative diseases such as Alzheimer's and Parkinson's. This review explores dysbiosis occurring in these pathologies and how virulence factors contribute to the worsening or development of clinical conditions, and it summarizes existing and potential ways to combat microorganisms related to these diseases. Microbiota imbalances can contribute to the progression of neurodegenerative diseases by increasing intestinal permeability, exchanging information through innervation, and even acting as a Trojan horse affecting immune cells. The microorganisms of the microbiota produce virulence factors to protect themselves from host defenses, many of which contribute to neurodegenerative diseases. These virulence factors are expressed according to the genetic composition of each microorganism, leading to a wide range of factors to be considered. Among the main virulence factors are LPS, urease, curli proteins, amyloidogenic proteins, VacA, and CagA. These factors can also be packed into bacterial outer membrane vesicles, which transport proteins, RNA, and DNA, enabling distal communication that impacts various diseases, including Alzheimer's and Parkinson's.

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.

The neuroimmune connectome in health and disease

The nervous and immune systems have complementary roles in the adaptation of organisms to environmental changes. However, the mechanisms that mediate cross-talk between the nervous and immune systems, called neuroimmune interactions, are poorly understood. In this Review, we summarize advances in the understanding of neuroimmune communication, with a principal focus on the central nervous system (CNS): its response to immune signals and the immunological consequences of CNS activity. We highlight these themes primarily as they relate to neurological diseases, the control of immunity, and the regulation of complex behaviours. We also consider the importance and challenges linked to the study of the neuroimmune connectome, which is defined as the totality of neuroimmune interactions in the body, because this provides a conceptual framework to identify mechanisms of disease pathogenesis and therapeutic approaches. Finally, we discuss how the latest techniques can advance our understanding of the neuroimmune connectome, and highlight the outstanding questions in the field.

Biotransport and toxic effects of micro- and nanoplastics in fish model and their potential risk to humans: A review

The growing body of scientific evidence suggests that micro- and nanoplastics (MPs/NPs) pose a significant threat to aquatic ecosystems and human health. These particles can enter organisms through ingestion, inhalation, dermal contact, and trophic transfer. Exposure can directly affect multiple organs and systems (respiratory, digestive, neurological, reproductive, urinary, cardiovascular) and activate extensive intracellular signaling, inducing cytotoxicity involving mechanisms such as membrane disruption, extracellular polymer degradation, reactive oxygen species (ROS) production, DNA damage, cellular pore blockage, lysosomal instability, and mitochondrial depolarization. This review focuses on current research examining the in vivo and in vitro toxic effects of MPs/NPs on aquatic organisms, particularly fish, in relation to particulate toxicity aspects (such as particle transport mechanisms and structural modifications). Meanwhile, from the perspectives of the food chain and environmental factors, it emphasizes the comprehensive threats of MPs/NPs to human health in terms of both direct and indirect toxicity. Additionally, future research needs and strategies are discussed to aid in mitigating the potential risks of particulate plastics as carriers of toxic trace elements to human health.

Maternal pre- and postnatal stress and maternal and infant gut microbiota features

BACKGROUND

Maternal stress can have short and long term adverse (mental) health effects for the mother and her child. Previous evidence suggests that the gut microbiota may be a potential mediator and moderator for the effects of stress via various pathways. This study explored the maternal microbiota trajectory during pregnancy as well as the association between pre- and postnatal maternal stress and features of the maternal and infant gut microbiota during and after pregnancy. In line with previous research, we hypothesized that maternal stress would be positively related to maternal and infant microbiota volatility and that infants of highly stressed mothers would show a relative increase in Proteobacteria and a relative decrease in Bifidobacterium.

METHODS

We collected maternal stool samples at 18 and 32 weeks of pregnancy and 8 months postpartum. Infant stools samples were obtained at 2, 6 and 12 weeks and 8 months postpartum. All samples were analyzed using shotgun metagenome sequencing. We also collected several measures of maternal stress (self-reported depression, anxiety, and stress, and hair cortisol and cortisone), most at the same time points as the microbiota samples.

RESULTS

Our data indicated that the maternal microbiota does not undergo drastic changes from the second to the third trimester of pregnancy but that the postpartum microbiota differs significantly from the prenatal microbiota. Furthermore, we identified associations between several stress measures and maternal and infant gut microbiota features at different time points including positive and negative associations with alpha diversity, beta diversity and individual microbial phyla and species relative abundances. Also, the maternal stress composite score, the perceived stress score and the log-ratio of hair cortisol and cortisone were all positively associated with infant microbiota volatility.

CONCLUSION

Our study provides evidence that maternal prenatal and postnatal stress is related to both the maternal and the infant microbiota. Collectively, this and previous studies indicate that maternal stress does not uniformly associate with most gut microbial features. Instead, the associations are highly time point specific. Regarding infant microbiota volatility, we have consistently found a positive association between stress and infant microbiota volatility. This warrants future research investigating this link in more depth.

Unraveling the Connections: Eating Issues, Microbiome, and Gastrointestinal Symptoms in Autism Spectrum Disorder

Autism spectrum disorder (ASD) is a neurodevelopmental condition characterized by challenges in social communication, restricted interests, and repetitive behaviors. It is also associated with a high prevalence of eating disorders, gastrointestinal (GI) symptoms, and alterations in gut microbiota composition. One of the most pressing concerns is food selectivity. Various eating disorders, such as food neophobia, avoidant/restrictive food intake disorder (ARFID), specific dietary patterns, and poor-quality diets, are commonly observed in this population, often leading to nutrient deficiencies. Additionally, gastrointestinal problems in children with ASD are linked to imbalances in gut microbiota and immune system dysregulation. The aim of this narrative review is to identify previous associations between the gut-brain axis and gastrointestinal problems in ASD. We discuss the impact of the "microbiome-gut-brain axis", a bidirectional connection between gut microbiota and brain function, on the development and symptoms of ASD. In gastrointestinal problems associated with ASD, a 'vicious cycle' may play a significant role: ASD symptoms contribute to the prevalence of ARFID, which in turn leads to microbiota degradation, ultimately worsening ASD symptoms. Current data suggest a link between gastrointestinal problems in ASD and the microbiota, but the amount of evidence is limited. Further research is needed, targeting the correlation of a patient's microbiota status, dietary habits, and disease course.

Beyond digestion: Exploring how the gut microbiota modulates human social behaviors

For a long time, traditional medicine has acknowledged the gut's impact on general health. Contemporary science substantiates this association through investigations of the gut microbiota, the extensive community of microorganisms inhabiting our gastrointestinal system. These microscopic residents considerably improve digestive processes, nutritional absorption, immunological function, and pathogen defense. Nevertheless, a variety of gastrointestinal and extra-intestinal disorders can result from dysbiosis, an imbalance of the microbial composition of the gut microbiota. A groundbreaking discovery is the gut-brain axis, a complex communication network that links the enteric and central nervous system (CNS). This bidirectional communication allows the brain to influence gut activities and vice versa, impacting mental health and mood disorders like anxiety and depression. The gut microbiota can influence this communication by creating neurotransmitters and short-chain fatty acids, among other biochemical processes. These factors may affect our mental state, our ability to regulate our emotions, and the hypothalamic-pituitary-adrenal (HPA) axis. This study aimed to explore the complex interrelationships between the brain and the gut microbiota. We also conducted a thorough examination of the existing understanding in the area of how microbiota affects social behaviors, including emotions, stress responses, and cognitive functions. We also explored the potential of interventions that focus on the connection between the gut and the brain, such as using probiotics to treat diseases of the CNS. This research opens up new possibilities for addressing mental health and neurological conditions in an innovative manner.

Gut dysbiosis as a driver of neuroinflammation in attention-deficit/hyperactivity disorder: A review of current evidence

There is mounting evidence for the involvement of the immune system, neuroinflammation and disturbed gut microbiota, or dysbiosis, in attention-deficit/hyperactivity disorder (ADHD). Gut dysbiosis is strongly implicated in many physical, autoimmune, neurological, and neuropsychiatric conditions, however knowledge of its particular pathogenic role in ADHD is sparse. As such, this narrative review examines and synthesizes the available evidence related to inflammation, dysbiosis, and neural processes in ADHD. Minimal differences in microbiota diversity measures between cases and controls were found, however many relative abundance differences were observed at all classification levels (phylum to strain). Compositional differences of taxa important to key gut-brain axis pathways, in particular Bacteroides species and Faecalibacterium, may contribute to inflammation, brain functioning differences, and symptoms, in ADHD. We have identified one possible model of ADHD etiopathogenesis involving systemic inflammation, an impaired blood-brain barrier, and neural disturbances as downstream consequences of gut dysbiosis. Nevertheless, studies conducted to date have varied degrees of methodological rigour and involve diverse participant characteristics and analytical techniques, highlighting a need for additional research.

Regulatory effects of Lactobacillus zhachilii HBUAS52074T on depression-like behavior induced by chronic social defeat stress in mice: modulation of the gut microbiota

The gut microbiome has emerged as a growing focus of research and public health interest, leading to the frequent exploration of probiotic dietary supplements as potential treatments for various disorders, such as anxiety and depression. In the present report, changes in inflammation and microbiome composition were assessed in model mice exhibiting depressive-like behaviors that were exposed to the probiotic Lactobacillus zhachilii HBUAS52074T. It was found that L. zhachilii HBUAS52074T alleviated the severity of depressive-like behaviors while increasing serum 5-HT concentrations. Moreover, L. zhachilii HBUAS52074T modulated the composition of the gut microbiota, resulting in a decrease in the abundance of Prevotella and an increase in the abundance of Lactobacillus. Additionally, supplementation with L. zhachilii HBUAS52074T enhanced intestinal barrier function and reduced inflammation in peripheral blood, as well as in the hippocampal and prefrontal cortical tissues. Correlational analyses indicated that the abundance of Lactobacillus was positively correlated with the social interaction ratio, time spent in the center, entries into the center, as well as serum 5-HT and serum IL-10 levels but negatively correlated with immobility time. Overall, chronic social defeat stress was found to be associated with inflammation and the exacerbation of depressive-like behaviors. The above findings suggested that L. zhachilii HBUAS52074T supplementation was sufficient to alter the parameters. Collectively, these data suggest that L. zhachilii HBUAS52074T, derived from naturally fermented foods, may possess therapeutic potential for the treatment of depression.

Identification of Bacterial Lipopolysaccharide-Associated Genes and Molecular Subtypes in Autism Spectrum Disorder

Background

Autism spectrum disorder (ASD) is a complex neurodevelopmental condition marked by diverse symptoms affecting social interaction, communication, and behavior. This research aims to explore bacterial lipopolysaccharide (LPS)- and immune-related (BLI) molecular subgroups in ASD to enhance understanding of the disorder.

Methods

We analyzed 89 control samples and 157 ASD samples from the GEO database, identifying BLI signatures using least absolute shrinkage and selection operator regression (LASSO) and logistic regression machine learning algorithms. A nomogram prediction model was developed based on these signatures, and we performed Gene Set Enrichment Analysis (GSEA), Gene Set Variation Analysis (GSVA), and immune cell infiltration analysis to assess the impact of BLI subtypes and their underlying mechanisms.

Results

Our findings revealed 17 differentially expressed BLI genes in children with ASD, with BLNK, MAPK8, PRKCQ, and TNFSF12 identified as potential biomarkers. The nomogram demonstrated high diagnostic accuracy for ASD. We delineated two distinct molecular subtypes (Cluster 1 and Cluster 2), with GSVA indicating that Cluster 2 showed upregulation of immune- and inflammation-related pathways. This cluster exhibited increased levels of antimicrobial agents, chemokines, cytokines, and TNF family cytokines, alongside activation of bacterial lipoprotein-related pathways. A significant correlation was found between these pathways and distinct immune cell subtypes, suggesting a potential mechanism for neuroinflammation and immune cell infiltration in ASD.

Conclusion

Our research highlights the role of BLI-associated genes in the immune responses of individuals with ASD, indicating their contribution to the disorder's typification. The interplay between bacterial components, genetic predisposition, and immune dysregulation offers new insights for understanding ASD and developing personalized interventions.

Investigation of Clostridium butyricum on atopic dermatitis based on gut microbiota and TLR4/MyD88/ NF-κB signaling pathway

BACKGROUND

Probiotics, as common regulators of the gut microbiota, have been used in research to alleviate clinical symptoms of atopic dermatitis (AD).

OBJECTIVE

Our research team has previously identified a potential relieving effect of Clostridium butyricum on the treatment of AD, but the specific mechanism of how Clostridium butyricum alleviates AD has not yet been confirmed.

METHODS

In this study, we explored the relieving effect of Clostridium butyricum on AD through in vivo and in vitro experiments. AD mice induced by 2,4-dinitrofluorobenzene (DNFB) were orally administered with 1 × 108 CFU of Clostridium butyricum for three consecutive weeks.

RESULTS

Oral administration of Clostridium butyricum reduced ear swelling, alleviated back skin lesions, decreased mast cell and inflammatory cell infiltration, and regulated the levels of inflammation-related cytokines. Clostridium butyricum activated the intestinal immune system through the TLR4/MyD88/NF-κB signaling pathway, suppressed the expression of inflammatory factors IL-10 and IL-13, and protected the damaged intestinal mucosa.

CONCLUSION

Clostridium butyricum administration improved the diversity and abundance of the gut microbiota, enhanced the functionality of the immune system, and protected the epidermal barrier.

Age-Related Changes in Gut Health and Behavioral Biomarkers in a Beagle Dog Population

The gut and the gut microbiome communicate with the nervous system through the gut-brain axis via neuroimmune and neuroendocrine mechanisms. Despite existing research, studies exploring this link in aging dogs are limited. This study aims to examine multiple blood and fecal biomarkers of intestinal health, along with various behavioral indicators based on saliva, blood, observations, and activity, in different age populations (junior: <2 y.o.; adult: 2-7 y.o.; senior: >7 y.o.) of thirty-seven Beagle dogs. In our study, Bacteroides were significantly higher in senior dogs. The relative abundance of Faecalibacterium and Blautia showed age-related trends, higher in senior and junior dogs, respectively. Fecal short-chain fatty acid concentration, especially acetate, increased with age, while propionate was higher in junior dogs. For the behavioral indicators we considered, blood thyroxine concentration, playing, exploring, and total activity were higher in junior dogs. The differences observed between the biomarkers of gut health and behavior, particularly those significant for the age correlations, emphasize the importance of considering age-related factors when studying the gut microbiome and behavior. However, further research is needed to better understand the mechanisms and specific pathways involved in the relationship between the studied biomarkers and age.

The human gut Bacteroides eggerthii expresses a new galactofuranose-containing lipooligosaccharide with weak immunostimulatory properties

Lipopolysaccharides (LPS) decorating the cell surface of Gram-negative bacteria exhibit nuanced functionalities linked to their precise structural composition. However, despite their critical role in health and disease, information on the structure and function of LPS from members of the human gut microbiota is still limited. Here, we deciphered the complete structure of the LPS isolated from the human gut bacterium Bacteroides eggerthii 1_2_48FAA. We showed that B. eggerthii 1_2_48FAA produces an R-type LPS (or lipooligosaccharide, LOS) composed of a heterogeneous mixture of tetra- and penta-acylated lipid A species with different degree of phosphorylation, and a compact galactofuranose-containing core oligosaccharide. Using in vitro human cell lines, we showed that B. eggerthii 1_2_48FAA LOS acts as a weak activator of TLR4-mediated signaling. Moreover, we observed that expression of maturation markers CD40, CD80 and CD86 on monocytes-derived dendritic cells upon B. eggerthii 1_2_48FAA LOS exposure was significantly lower compared to pro-inflammatory Escherichia coli LPS. Taken together, these data provide new structural and biological insights into LPS from gut bacteria, underscoring the importance of structural features in modulating host immunity.

Beyond nutrition: The emerging therapeutic potential landscape of breast milk-derived extracellular vesicles

Breastfeeding is widely recognized for its essential nutritional benefits and broader biological impacts. Beyond providing infants with a balanced mix of vitamins, proteins, and fats critical for growth and development, breast milk contains bioactive extracellular vesicles (BMEVs). These membrane-bound particles, rich in proteins, lipids, and nucleic acids, play a pivotal role in immune modulation, intercellular communication, and the overall development of the infant's immune system. This review explores the emerging therapeutic potential of BMEVs, highlighting their capacity to modulate recipient cell functions, influence immune responses, and contribute to overall infant health. Preclinical evidence suggests that these vesicles can prevent and manage conditions such as necrotizing enterocolitis, allergies, and viral infections, which are common in early childhood. Furthermore, BMEVs offer promise as vehicles for targeted drug delivery, enhancing the efficacy of therapeutic interventions. Despite the growing body of evidence, challenges such as the need for standardized isolation methods, characterization techniques, and larger-scale clinical studies persist, hindering the translation of this research into clinical practice. This review addresses these challenges and discusses future directions, emphasizing the need for comprehensive mechanistic studies to fully realize the potential of BMEVs as novel therapeutic agents and biomarkers of health. Ultimately, these vesicles represent a promising frontier in maternal and child health, with potential applications extending far beyond traditional nutrition. By harnessing their unique properties, BMEVs could revolutionize infant care, offering new strategies for disease prevention and innovative therapeutic interventions that enhance infant health outcomes.

Unravelling the critical role of neuroinflammation in epilepsy-associated neuropsychiatric comorbidities: A review

Epilepsy is a complex neurological disorder characterized not only by seizures but also by significant neuropsychiatric comorbidities, affecting approximately one-third of those diagnosed. This review explores the intricate relationship between epilepsy and its associated psychiatric and cognitive disturbances, with a focus on the role of inflammation. Recent definitions of epilepsy emphasize its multifaceted nature, linking it to neurobiological, psychiatric, cognitive, and social deficits. Inflammation has emerged as a critical factor influencing both seizure activity and neuropsychiatric outcomes in epilepsy patients. This paper critically examines how dysregulated inflammatory pathways disrupt neurotransmitter transmission and contribute to depression, mood disorders, and anxiety prevalent among individuals with epilepsy. It also evaluates current therapeutic approaches and underscores the potential of anti-inflammatory therapies in managing epilepsy and related neuropsychiatric conditions. Additionally, the review highlights the importance of the anti-inflammatory effects of anti-seizure medications, antidepressants, and antipsychotics and their therapeutic implications for mood disorders. Also, the role of ketogenic diet in managing epilepsy and its psychiatric comorbidities is briefly presented. Furthermore, it briefly discusses the role of the gut-brain axis in maintaining neurological health and how its dysregulation is associated with epilepsy. The review concludes that inflammation plays a pivotal role in linking epilepsy with its neuropsychiatric comorbidities, suggesting that targeted anti-inflammatory interventions may offer promising therapeutic strategies. Future research should focus on longitudinal studies comparing outcomes between epileptic patients with and without neuropsychiatric comorbidities, the development of diagnostic tools, and the exploration of novel anti-inflammatory treatments to better manage these complex interactions.

Microbiota and social behavior alterations in a mouse model of down syndrome: Modulation by a synbiotic treatment

Sex differences in the composition and functionality of gut microbiota are an emerging field of interest in neurodevelopmental disorders, as they may help in understanding the phenotypic disparities between males and females. This study aimed to characterize sex-related specific alterations in gut microbiota composition in a mouse model of Down syndrome (Ts65Dn mice, TS mice) through the sequencing of the PCR-amplified 16S ribosomal DNA fraction. Moreover, it intended to examine whether the modulation of gut microbiota by the administration of a synbiotic (SYN) treatment would be beneficial for the behavioral alterations observed in male and female TS mice. Our results show that male, but not female, TS mice exhibit alterations in beta diversity compared to their wild-type (WT) littermates. Sex-dependent differences are also observed in the relative abundance of the classes Bacilli and Clostridia. Administering the SYN effectively counteracts hypersociability in females, and normalizes the overall abundance of Bacilli, specifically by increasing Lactobacillaceae. On the contrary, it rescues emotional recognition deficits in male TS mice and increases the relative abundance of the families Lactobacillaceae, Streptococcaceae and Atopobiaceae. In addition, a metagenome KEGG analysis of differentially enriched pathways shows relevant changes in the cofactor biosynthesis and the amino acid synthesis categories. Finally, following SYN treatment, both male and female TS mice exhibit a robust increase in propionic acid levels compared to WT littermates. These findings suggest sex-specific mechanisms that could link gut microbiota composition with behavior in TS mice, and underscore the potential of targeted gut microbiota interventions to modulate social abnormalities in neurodevelopmental disorders.

Influential articles in autism and gut microbiota: bibliometric profile and research trends

Objective

Autism spectrum disorder (ASD) is a common neurodevelopmental disorder. Increasing evidence suggests that it is potentially related to gut microbiota, but no prior bibliometric analysis has been performed to explore the most influential works in the relationships between ASD and gut microbiota. In this study, we conducted an in-depth analysis of the most-cited articles in this field, aiming to provide insights to the existing body of research and guide future directions.

Methods

A search strategy was constructed and conducted in the Web of Science database to identify the 100 most-cited papers in ASD and gut microbiota. The Biblioshiny package in R was used to analyze and visualize the relevant information, including citation counts, country distributions, authors, journals, and thematic analysis. Correlation and comparison analyses were performed using SPSS software.

Results

The top 100 influential manuscripts were published between 2000 and 2021, with a total citation of 40,662. The average number of citations annually increased over the years and was significantly correlated to the year of publication (r = 0.481, p < 0.01, Spearman's rho test). The United States was involved in the highest number of publications (n = 42). The number of publications in the journal was not significantly related to the journal's latest impact factor (r = 0.016, p > 0.05, Spearman's rho test). Co-occurrence network and thematic analysis identified several important areas, such as microbial metabolites of short-chain fatty acids and overlaps with irritable bowel syndrome.

Conclusion

This bibliometric analysis provides the key information of the most influential studies in the area of ASD and gut microbiota, and suggests the hot topics and future directions. The findings of this study can serve as a valuable reference for researchers and policymakers, guiding the development and implementation of the scientific research strategies in this area.

The influence of seminal microbiota on human testicular steroidogenesis: a prospective study

OBJECTIVE

Preclinical evidence has demonstrated that gut microbiota composition can influence steroid hormone biosynthesis and spermatogenesis. This study aims to investigate the association of seminal microbiota and testicular steroidogenesis.

PATIENTS AND METHODS

One hundred adult eugonadal men were consecutively enrolled. The seminal concentration of Lactobacilli, anaerobic and facultative bacteria, as well as serum levels of luteinizing hormone (LH), follicle-stimulating hormone (FSH), and total testosterone (TT) were evaluated. Unadjusted and adjusted multi-regression models were built to evaluate the relationship between seminal Lactobacilli, anaerobic and facultative bacteria, and Lactobacilli/total bacteria ratio, and serum LH, FSH, and TT. The concentrations of seminal Lactobacilli, anaerobic, and facultative bacteria predictive of serum TT values in the lowest quartile (< 3.8 ng/mL) were calculated.

RESULTS

TT levels were weakly and positively correlated with seminal Lactobacillus concentration (r = 0.33; p = 0.001), with seminal Lactobacilli/total bacteria ratio (r = 0.89; p < 0.001), and negatively with anaerobic and facultative bacteria (r = - 0.69; p < 0.001). Opposite correlations were found for gonadotropin concentrations. These data persisted after adjustment for confounding factors. Seminal concentration of Lactobacilli ≤ 0.1 × 106/mL (AUC 0.917, 95% CI: 0.845 to 0.963), of anaerobic and facultative bacteria > 2 × 104/mL (AUC 0.924, 95% CI: 0.853 to 0.967), or a Lactobacilli/total bacteria ratio ≤ 90% (AUC 0.910, 95% CI: 0.837 to 0.958) were found to predict serum TT level < 3.8 ng/mL with a sensitivity of 92.0% and a specificity of 88.0%.

CONCLUSION

A relationship between the composition of the seminal microbiota and testicular steroidogenesis seems to exist. The mechanisms underlying this association are still unknown.

Microbiota-neuroepithelial signalling across the gut-brain axis

Research over the past two decades has established a remarkable ability of the gut microbiota to modulate brain activity and behaviour. Conversely, signals from the brain can influence the composition and function of the gut microbiota. This bidirectional communication across the gut microbiota-brain axis, involving multiple biochemical and cellular mediators, is recognized as a major brain-body network that integrates cues from the environment and the body's internal state. Central to this network is the gut sensory system, formed by intimate connections between chemosensory epithelial cells and sensory nerve fibres, that conveys interoceptive signals to the central nervous system. In this Review, we provide a broad overview of the pathways that connect the gut and the brain, and explore the complex dialogue between microorganisms and neurons at this emerging intestinal neuroepithelial interface. We highlight relevant microbial factors, endocrine cells and neural mechanisms that govern gut microbiota-brain interactions and their implications for gastrointestinal and neuropsychiatric health.

The microbiome's influence on the neurobiology of opioid addiction and brain connectivity

BACKGROUND

Opioids are the most effective and potent analgesics available for acute pain management. With no viable alternative for treating chronic or post operative pain, it is not surprising that over 10 million people misuse opioids. This study explores the developmental influence of the microbiome on resistance to opioid addictive behavior and functional connectivity.

METHODS

Female germ free reared (GFR) mice were compared to wild-type (WT) mice, before and after conventionalization using conditioned place preference (CPP) with oxycodone (OXY) exposure. Functional connectivity data were collected providing site-specific analysis for over 140 different brain areas.

RESULTS

GFR mice showed significant reduction in CPP after OXY exposure. When GFR mice are conventionalized CPP reward behavior mirrors WT mice. Functional connectivity data shows significant differences across several brain regions e.g., thalamus, hippocampus, and sensory cortices between GFR and WT before and after conventionalization. Prior to conventionalization GFR mice showed hyperconnectivity that became less organized and more global after conventionalization. Sequencing of the fecal microbiome of the GFR mice before conventionalization showed an absence of normal murine gut microbiome members, but the presence of Corynebacterium, Staphylococcus, Paenibacillus, and Turicibacter.

CONCLUSION

The implications suggest the microbiome has a direct impact on the development of reward seeking behavior. With the widespread number of opioid receptors found in the gut, studying the interaction between the microbiota and substance use disorder may lead to a better understanding of the mechanisms that lead to the development of addiction as well as potential treatments.

Gut microbiota transfer from the preclinical maternal immune activation model of autism is sufficient to induce sex-specific alterations in immune response and behavioural outcomes

The gut microbiome plays a vital role in health and disease, including neurodevelopmental disorders like autism spectrum disorder (ASD). ASD affects 4:1 males-to-females, and sex differences are apparent in gut microbiota composition among ASD individuals and in animal models of this condition, such as the maternal immune activation (MIA) mouse model. However, few studies have included sex as a biological variable when assessing the role of gut microbiota in mediating ASD symptoms. Using the MIA model of ASD, we assessed whether gut microbiota contributes to the sex differences in the presentation of ASD-like behaviors. Gut microbiota transplantation from MIA or vehicle/control male and female mice into healthy, otherwise unmanipulated, 4-week-old C57Bl/6 mice was performed for 6 treatments over 12 days. Colonization with male, but not female, MIA microbiota was sufficient to reduce sociability, decrease microbiota diversity and increase neuroinflammation with more pronounced deficits in male recipients. Colonization with both male and female donor microbiota altered juvenile ultrasonic vocalizations and anxiety-like behavior in recipients of both sexes, and there was an accompanied change in the gut microbiota and serum cytokine IL-4 and IL-7 levels of all recipients of MIA gut microbiota. In addition to the increases in gut microbes associated with pathological states, the female donor microbiota profile also had increases in gut microbes with known neural protective effects (e.g., Lactobacillus and Rikenella). These results suggest that gut reactivity to environmental insults, such as in the MIA model, may play a role in shaping the sex disparity in ASD development.

IUPHAR review: Targeted therapies of signaling pathways based on the gut microbiome in autism spectrum disorders: Mechanistic and therapeutic applications

Autism spectrum disorders (ASD) are complex neurodevelopmental disorders characterized by impairments in social interaction, communication and repetitive activities. Gut microbiota significantly influences behavior and neurodevelopment by regulating the gut-brain axis. This review explores gut microbiota-influenced treatments for ASD, focusing on their therapeutic applications and mechanistic insights. In addition, this review discusses the interactions between gut microbiota and the immune, metabolic and neuroendocrine systems, focusing on crucial microbial metabolites including short-chain fatty acids (SCFAs) and several neurotransmitters. Furthermore, the review explores various therapy methods including fecal microbiota transplantation, dietary modifications, probiotics and prebiotics and evaluates their safety and efficacy in reducing ASD symptoms. The discussion shows the potential of customized microbiome-based therapeutics and the integration of multi-omics methods to understand the underlying mechanisms. Moreover, the review explores the intricate relationship between gut microbiota and ASD, aiming to develop innovative therapies that utilize the gut microbiome to improve the clinical outcomes of ASD patients. Microbial metabolites such as neurotransmitter precursors, tryptophan metabolites and SCFAs affect brain development and behavior. Symptoms of ASD are linked to changes in these metabolites. Dysbiosis in the gut microbiome may impact neuroinflammatory processes linked to autism, negatively affecting immune signaling pathways. Research indicates that probiotics and prebiotics can improve gut microbiota and alleviate symptoms in ASD patients. Fecal microbiota transplantation may also improve behavioral symptoms and restore gut microbiota balance. The review emphasizes the need for further research on gut microbiota modification as a potential therapeutic approach for ASD, highlighting its potential in clinical settings.

Phlorizin ameliorates cognitive and behavioral impairments via the microbiota-gut-brain axis in high-fat and high-fructose diet-induced obese male mice

The long-term high-fat, high-sugar diet exacerbates type 2 diabetes mellitus (T2DM)-related cognitive impairments. Phlorizin, a well-studied natural compound found in apples and other plants, is recognized for its bioactive properties, including modulation of glucose and lipid metabolism. Despite its established role in mitigating metabolic disorders, the neuroprotective effects of phlorizin, particularly against diabetes-related cognitive dysfunction, have not been fully elucidated. Therefore, the present study aimed to investigate the effect of dietary supplementation of phlorizin on high-fat and high-fructose diet (HFFD)-induced cognitive dysfunction and evaluate the crucial role of the microbiota-gut-brain axis. We found that dietary supplementation of phlorizin for 14 weeks effectively prevented glucolipid metabolism disorder, spatial learning impairment, and memory impairment in HFFD mice. In addition, phlorizin improved the HFFD-induced decrease in synaptic plasticity, neuroinflammation, and excessive activation of microglia in the hippocampus. Transcriptomics analysis shows that the protective effect of phlorizin on cognitive impairment was associated with increased expression of neurotransmitters and synapse-related genes in the hippocampus. Phlorizin treatment alleviated colon microbiota disturbance, mainly manifested by an increase in gut microbiota diversity and the abundance of short-chain fatty acid (SCFA)-producing bacteria. The level of microbial metabolites, including SCFA, inosine 5'-monophosphate (IMP), and D (-)-beta-hydroxybutyric acid (BHB) were also significantly increased after phlorizin treatment. Integrating multiomics analysis observed tight connections between phlorizin-regulated genes, microbiota, and metabolites. Furthermore, removal of the gut microbiota via antibiotics treatment diminished the protective effect of phlorizin against HFFD-induced cognitive impairment, underscoring the critical role of the gut microbiota in mediating cognitive behavior. Importantly, supplementation with SCFA and BHB alone mimicked the regulatory effects of phlorizin on cognitive function. Therefore, phlorizin shows promise as a potential nutritional therapy for addressing cognitive impairment associated with metabolic disorders. Further research is needed to explore its effectiveness in preventing and alleviating neurodegenerative diseases.

Gut microbiome-gut brain axis-depression: interconnection

OBJECTIVES

The relationship between the gut microbiome and mental health, particularly depression, has gained significant attention. This review explores the connection between microbial metabolites, dysbiosis, and depression. The gut microbiome, comprising diverse microorganisms, maintains physiological balance and influences health through the gut-brain axis, a communication pathway between the gut and the central nervous system.

METHODS

Dysbiosis, an imbalance in the gut microbiome, disrupts this axis and worsens depressive symptoms. Factors like diet, antibiotics, and lifestyle can cause this imbalance, leading to changes in microbial composition, metabolism, and immune responses. This imbalance can induce inflammation, disrupt neurotransmitter regulation, and affect hormonal and epigenetic processes, all linked to depression.

RESULTS

Microbial metabolites, such as short-chain fatty acids and neurotransmitters, are key to gut-brain communication, influencing immune regulation and mood. The altered production of these metabolites is associated with depression. While progress has been made in understanding the gut-brain axis, more research is needed to clarify causative relationships and develop new treatments. The emerging field of psychobiotics and microbiome-targeted therapies shows promise for innovative depression treatments by harnessing the gut microbiome's potential.

CONCLUSIONS

Epigenetic mechanisms, including DNA methylation and histone modifications, are crucial in how the gut microbiota impacts mental health. Understanding these mechanisms offers new prospects for preventing and treating depression through the gut-brain axis.

Alterations of oral microbiota in young children with autism: Unraveling potential biomarkers for early detection

OBJECTIVES

This study investigated the oral microbiota in young children with autism spectrum disorder (ASD) to determine possible alterations in microbial composition and identify potential biomarkers for early detection.

METHODS

Dental plaque samples from 25 children with ASD (aged 3-6 years; M = 4.79, SD = 0.83) and 30 age- and sex-matched typically developing (TD) children were analyzed using 16S rRNA sequencing.

RESULTS

The results showed lower bacterial diversity in children with ASD compared to controls, with distinct microbial compositions in the ASD and TD groups. Six discriminatory species (Microbacterium flavescens, Leptotrichia sp. HMT-212, Prevotella jejuni, Capnocytophaga leadbetteri, Leptotrichia sp. HMT-392, and Porphyromonas sp. HMT-278) were identified in the oral microbiota of ASD children, while five discriminatory species (Fusobacterium nucleatum subsp. polymorphum, Schaalia sp. HMT-180, Leptotrichia sp. HMT-498, Actinomyces gerencseriae, and Campylobacter concisus) were identified in TD controls. A model generated by random forest and leave-one-out cross-validation achieved an accuracy of 0.813. Receiver operating characteristic analysis yielded a sensitivity of 0.778, a specificity of 0.857, and an AUC (area under curve) of 0.937 (95 % CI: 0.82 - 1.00) for differentiating children with and without ASD.

CONCLUSION

The present study has unveiled significant disparities in the oral microbial composition between ASD and TD children.

SIGNIFICANCE

These findings contribute to understanding the microbiome-brain connection in ASD and its implications for early detection and management. Further research is needed to validate these oral bacterial biomarkers and explore their mechanistic association with ASD pathophysiology.

The involvement of the microbiota-gut-brain axis in the pathophysiology of mood disorders and therapeutic implications

INTRODUCTION

There is a growing body of evidence implicating gut-brain axis dysfunction in the pathophysiology of mood disorders. Accordingly, gut microbiota has become a promising target for the development of biomarkers and novel therapeutics for bipolar and depressive disorders.

AREAS COVERED

We describe the observed changes in the gut microbiota of patients with mood disorders and discuss the available studies assessing microbiota-based strategies for their treatment.

EXPERT OPINION

Microbiota-targeted interventions, such as symbiotics, prebiotics, paraprobiotics, and fecal microbiota transplants seem to attenuate the severity of depressive symptoms. The available results must be seen as preliminary and need to be replicated and/or confirmed in larger and independent studies, also considering the pathophysiological and clinical heterogeneity of mood disorders.

Gut microbial 'TNFα-sphingolipids-steroid hormones' axis in children with autism spectrum disorder: an insight from meta-omics analysis

BACKGROUND

Autism spectrum disorder (ASD) is a persistent neurodevelopmental disorder affecting brains of children. Mounting evidences support the associations between gut microbial dysbiosis and ASD, whereas detailed mechanisms are still obscure.

METHODS

Here we probed the potential roles of gut microbiome in ASD using fecal metagenomics and metabolomics.

RESULTS

Children with ASD were found to be associated with augmented serum cytokines milieu, especially TNFα. Metagenomic analysis generated 29 differential species and 18 dysregulated functional pathways such as Bifidobacterium bifidum, Segatella copri, and upregulated 'Sphingolipid metabolism' in children with ASD. Metabolomics revealed steroid hormone dysgenesis in children with ASD with lower abundances of metabolites such as estriol, estradiol and deoxycorticosterone. A three-way association analysis showed positive correlations between TNFα and microbial function potentials such as 'Bacterial toxins' and 'Lysosome', indicating the contribution of microbial dysbiosis to neuroinflammation. TNFα also correlated positively with 'Sphingolipid metabolism', which further showed negative correlations with metabolites estriol and deoxycorticosterone. Such results, in consistent with current findings, revealed the contribution of increased TNFα to upregulated sphingolipid metabolism, which further impaired steroid hormone biosynthesis.

CONCLUSION

Our study proposed the gut microbial 'TNFα-sphingolipids-steroid hormones' axis in children with ASD, which may provide new perspectives for developing gut microbiome-based treatments in the future.

Gut Microbiota: An Important Participant in Childhood Obesity

Increasing prevalence of childhood obesity has emerged as a critical global public health concern. Recent studies have challenged the previous belief that obesity was solely a result of excessive caloric intake. Alterations in early-life gut microbiota can contribute to childhood obesity through their influence on nutrient absorption and metabolism, initiation of inflammatory responses, and regulation of gut-brain communication. The gut microbiota is increasingly acknowledged to play a crucial role in human health, as certain beneficial bacteria have been scientifically proven to possess the capacity to reduce body fat content and enhance intestinal barrier function and their metabolic products to exhibit anti-inflammatory effect. Examples of such microbes include bifidobacteria, Akkermansia muciniphila, and Lactobacillus reuteri. In contrast, an increase in Enterobacteriaceae and propionate-producing bacteria (Prevotellaceae and Veillonellaceae) has been implicated in the induction of low-grade systemic inflammation and disturbances in lipid metabolism, which can predispose individuals to obesity. Studies have demonstrated that modulating the gut microbiota through diet, lifestyle changes, prebiotics, probiotics, or fecal microbiota transplantation may contribute to gut homeostasis and the management of obesity and its associated comorbidities. This review aimed to elucidate the impact of alterations in gut microbiota composition during early life on childhood obesity and explores the mechanisms by which gut microbiota contributes to the pathogenesis of obesity and specifically focused on recent advances in using short-chain fatty acids for regulating gut microbiota and ameliorating obesity. Additionally, it aimed to discuss the therapeutic strategies for childhood obesity from the perspective of gut microbiota, aiming to provide a theoretical foundation for interventions targeting pediatric obesity based on gut microbiota.

Role of oral-gut-brain axis in psychiatric and neurological disorders

The oral cavity and gut are two important microbial habitats in the human body, harboring the most ecologically rich and taxonomically diverse microbial communities in humans, which play a key role in microbiome related diseases. In recent years, the emerging concept of the oral-gut-brain axis has attracted widespread attention in the fields of neuroscience, digestive science, and microbiology. It is not only an anatomical description, but also a comprehensive concept that covers multiple physiological functions and pathological mechanisms. Simply put, the oral-gut-brain axis refers to the complex network that connects the mouth, gut, and brain tightly together through neural connections and hormonal and immune pathways. With the deepening of research on the oral-gut-brain axis theory, more and more evidence shows that it plays an important role in depression, Parkinson's disease, and other neurodegenerative diseases. This article reviews the recent progress in research of the oral-gut-brain axis in psychiatric and neurological diseases.

Annual Research Review: Micronutrients and their role in the treatment of paediatric mental illness

The aim of this narrative review is to summarize evidence relating the importance of nutrient intake from diet and supplementation for paediatric mental health. We begin by reviewing several mechanisms by which nutrients maximize brain health, including enabling metabolic reactions to occur, supporting mitochondrial function, reducing inflammation and assisting with detoxification. Circumstances that may contribute to an individual requiring additional nutrients beyond what are available in the diet, such as consumption of nutritionally depleted food, individual differences in biological need, long-term medication use and gut-brain health needs are then reviewed. These factors underpin the importance of tackling deficiencies relative to individual metabolic requirements with a broad spectrum of micronutrients, as opposed to a single nutrient approach, to address personal metabolic needs and/or environmentally induced nutrient depletions. The evidence for treating psychological symptoms with supplementary micronutrients is presented, summarizing research using broad-spectrum micronutrients in the treatment of mental health issues including aggression, autism spectrum disorder, attention-deficit/hyperactivity disorder and emotional dysregulation, often with medium between-group effect sizes compared with placebo, with clinically meaningful changes. The breadth and consistency of the findings highlight the importance of receiving a complete foundation of nutrients to optimize brain health; however, the small number of studies identifies the importance of future work to replicate these preliminary findings. Documented safety in 8-week randomized controlled trials with open-label extensions up to 16 weeks and longer-term follow-up for 1.5-5 years in smaller samples provide reassurance that this treatment approach does not result in serious adverse events. We provide recommendations for future research including consistency in micronutrient interventions, scalable delivery models, effectiveness and implementation studies and the need to investigate these interventions in the prevention and management of less-studied childhood psychiatric conditions.

The therapeutic effects of probiotics on core and associated behavioral symptoms of autism spectrum disorders: a systematic review and meta-analysis

BACKGROUND

We aimed at investigating the efficacies of probiotics in alleviating the core and associated symptoms of autism spectrum disorder (ASD).

METHODS

Randomized placebo-controlled trials were identified from major electronic databases from inception to Nov 2023. The outcomes of interests including improvements in the total and associated symptoms of ASD were quantitatively expressed as effect size (ES) based on standardized mean difference (SMD) with 95% confidence interval (CI).

RESULTS

Ten studies with 522 participants (mean age = 8.11) were included in this meta-analysis. The primary results revealed significant improvement in total symptoms in the probiotics group compared with the controls (SMD = - 0.19, p = 0.03, ten studies, n = 522) but not the core symptoms (i.e., repetitive restricted behaviors, As affiliations 3 and 5 are same, we have deleted the duplicate affiliations and renumbered accordingly. Please check and confirm.problems with social behaviors/communication). Subgroup analyses demonstrated improvement in total symptoms in probiotics users relative to their controls only in studies using multiple-strain probiotics (SMD = - 0.26, p = 0.03, five studies, n = 288) but not studies using single-strain regimens. Secondary results showed improvement in adaptation (SMD = 0.37, p = 0.03, three studies, n = 139) and an improvement trend in anxiety symptoms in the probiotics group compared with controls (SMD = - 0.29, 95% CI - 0.60 to 0.02, p = 0.07, three studies, n = 163) but failed to demonstrate greater improvement in the former regarding symptoms of irritability/aggression, hyperactivity/impulsivity, inattention, and parental stress.

CONCLUSIONS

Our study supported probiotics use against the overall behavioral symptoms of ASD, mainly in individuals receiving multiple-strain probiotics as supplements. However, our results showed that probiotics use was only associated with improvement in adaptation and perhaps anxiety, but not core symptoms, highlighting the impact of adaptation on quality of life rather than just the core symptoms. Nevertheless, the limited number of included trials warrants further large-scale clinical investigations.

An evaluation of in utero polycyclic aromatic hydrocarbon exposure on the neonatal meconium microbiome

INTRODUCTION

In utero exposure to environmental polycyclic aromatic hydrocarbon (PAH) is associated with neurodevelopmental impairments[1-8], prematurity[9-12] and low birthweight[9,13-15]. The gut microbiome serves as an intermediary between self and external environment; therefore, exploring the impact of PAH on microbiota may elucidate their role in disease. Here, we evaluated the effect of in utero PAH exposure on meconium microbiome.

METHODS

We evaluated 49 mother-child dyads within Fair Start Birth Cohort with full term delivery and adequate meconium sampling. Prenatal PAH was measured using personal active samplers worn for 48 h during third trimester. Post-processing, 35 samples with adequate biomass were evaluated for association between tertile of PAH exposure (high (H) vs low/medium (L/M)) and microbiome diversity.

RESULTS

No significant differences were observed in alpha diversity metrics, Chao1 and Shannon index, between exposure groups for total PAH. However, alpha diversity metrics were negatively associated with log benzo[a]anthracene (BaA) and log chrysene (Chry) with high exposure, but positively associated with log benzo[a]pyrene (BaP) with low/medium exposure. After adjustment for birthweight and sex, alpha diversity metrics were negatively associated with log BaA, BaP, Chry, Indeno (Zhang et al., 2021; Perera et al., 2018)pyrene (IcdP) and total PAH with high exposure. Conversely, with low/medium exposure, alpha diversity metrics positively correlated with log BaP and benzo[b]fluoranthane (BbF). No significant difference in beta diversity was observed across groups using UniFrac, weighted UniFrac, or Bray-Curtis methods. Differential expression analysis showed differentially abundant taxa between exposure groups.

CONCLUSION

Bacterial taxa were detectable in 35/49 (71%) meconium samples. Altered alpha diversity metrics and differentially abundant taxa between groups suggest in utero PAH exposure may impede early colonization. Sample size is limited, but these findings provide supporting evidence for wider scale research. Research on long-term impact of prenatal PAH exposure on childhood health outcomes is ongoing. Differential effects of specific PAHs need further evaluation.

Associations between pre- and post-natal exposure to phthalate and DINCH metabolites and gut microbiota in one-year old children

The gut microbiota is a collection of symbiotic microorganisms in the gastrointestinal tract. Its sensitivity to chemicals with widespread exposure, such as phthalates, is little known. We aimed to investigate the impact of perinatal exposure to phthalates on the infant gut microbiota at 12 months of age. Within SEPAGES cohort (Suivi de l'Exposition à la Pollution Atmosphérique durant la Grossesse et Effet sur la Santé), we assessed 13 phthalate metabolites and 2 di(isononyl) cyclohexane-1,2-dicarboxylate (DINCH) metabolites in repeated urine samples collected in pregnant women and their offspring. We obtained stool samples from 356 children at 12 months of age and sequenced the V3-V4 region of the 16S rRNA gene, allowing gut bacterial profiling. We used single-chemical (linear regressions) and mixture (BKMR, Bayesian Kernel Machine Regression) models to examine associations of phthalates and DINCH metabolites, with gut microbiota indices of α-diversity (specific richness and Shannon diversity) and the relative abundances of the most abundant microbiota phyla and genera. After correction for multiple testing, di(2-ethylhexyl) phthalate (ΣDEHP), diethyl phthalate (DEP) and bis(2-propylheptyl) phthalate (DPHP) metabolites 12-month urinary concentrations were associated with higher Shannon α-diversity of the child gut microbiota in single-chemical models. The multiple-chemical model (BKMR) suggested higher α-diversity with exposure to the phthalate mixture at 12 months, driven by the same phthalates. There were no associations between phthalate and DINCH exposure biomarkers at other time points and α-diversity after correction for multiple testing. ΣDEHP metabolites concentration at 12 months was associated with higher Coprococcus genus. Finally, ΣDEHP exposure at 12 months tended to be associated with higher phylum Firmicutes, an association not maintained after correction for multiple testing. Infancy exposure to phthalate might disrupt children's gut microbiota. The observed associations were cross-sectional, so that reverse causality cannot be excluded.

Early antibiotic exposure and risk of psychiatric and neurocognitive outcomes: systematic review and meta-analysis

BACKGROUND

The prenatal and early-life periods pose a crucial neurodevelopmental window whereby disruptions to the intestinal microbiota and the developing brain may have adverse impacts. As antibiotics affect the human intestinal microbiome, it follows that early-life antibiotic exposure may be associated with later-life psychiatric or neurocognitive outcomes.

AIMS

To explore the association between early-life (in utero and early childhood (age 0-2 years)) antibiotic exposure and the subsequent risk of psychiatric and neurocognitive outcomes.

METHOD

A search was conducted using Medline, PsychINFO and Excerpta Medica databases on 20 November 2023. Risk of bias was assessed using the Newcastle-Ottawa scale, and certainty was assessed using the grading of recommendations, assessment, development and evaluation (GRADE) certainty assessment.

RESULTS

Thirty studies were included (n = 7 047 853 participants). Associations were observed between in utero antibiotic exposure and later development of autism spectrum disorder (ASD) (odds ratio 1.09, 95% CI: 1.02-1.16) and attention-deficit hyperactivity disorder (ADHD) (odds ratio 1.19, 95% CI: 1.11-1.27) and early-childhood exposure and later development of ASD (odds ratio 1.19, 95% CI: 1.01-1.40), ADHD (odds ratio 1.33, 95% CI: 1.20-1.48) and major depressive disorder (MDD) (odds ratio 1.29, 95% CI: 1.04-1.60). However, studies that used sibling control groups showed no significant association between early-life exposure and ASD or ADHD. No studies in MDD used sibling controls. Using the GRADE certainty assessment, all meta-analyses but one were rated very low certainty, largely owing to methodological and statistical heterogeneity.

CONCLUSIONS

While there was weak evidence for associations between antibiotic use in early-life and later neurodevelopmental outcomes, these were attenuated in sibling-controlled subgroup analyses. Thus, associations may be explained by genetic and familial confounding, and studies failing to utilise sibling-control groups must be interpreted with caution. PROSPERO ID: CRD42022304128.

Gut microbiota regulate insomnia-like behaviors via gut-brain metabolic axis

Sleep interacts reciprocally with the gut microbiota. However, mechanisms of the gut microbe-brain metabolic axis that are responsible for sleep behavior have remained largely unknown. Here, we showed that the absence of the gut microbiota can alter sleep behavior. Sleep deprivation reduced butyrate levels in fecal content and the hypothalamus in specific pathogen-free mice but not in germ-free mice. The microbial metabolite butyrate can promote sleep by modulating orexin neuronal activity in the lateral hypothalamic area in mice. Insomnia patients had lower serum butyrate levels and a deficiency in butyrate-producing species within the gut microbiota. Transplantation of the gut microbiota from insomnia patients to germ-free mice conferred insomnia-like behaviors, accompanied by a decrease in serum butyrate levels. The oral administration of butyrate rescued sleep disturbances in recipient mice. Overall, these findings reveal the causal role of microbial metabolic pathways in modulating insomnia-like behaviors, suggesting potential therapeutic strategies for treating sleep disorders.

Linking Gut Microbiota, Oral Microbiota, and Serum Metabolites in Insomnia Disorder: A Preliminary Study

Purpose

Despite recent findings suggesting an altered gut microbiota in those suffering from insomnia disorder (ID), research into the gut microbiota, oral microbiota, serum metabolites, and their interactions in patients with ID is sparse.

Patients and Methods

We collected a total of 114 fecal samples, 133 oral cavity samples and 20 serum samples to characterize the gut microbiota, oral microbiota and serum metabolites in a cohort of 76 ID patients (IDs) and 59 well-matched healthy controls (HCs). We assessed the microbiota as potentially biomarkers for ID for ID by 16S rDNA sequencing and elucidated the interactions involving gut microbiota, oral microbiota and serum metabolites in ID in conjunction with untargeted metabolomics.

Results

Gut and oral microbiota of IDs were dysbiotic. Gut and oral microbial biomarkers could be used to differentiate IDs from HCs. Eleven significantly altered serum metabolites, including adenosine, phenol, and phenol sulfate, differed significantly between groups. In multi-omics analyses, adenosine showed a positive correlation with genus_Lachnospira (p=0.029) and total sleep time (p=0.016). Additionally, phenol and phenol sulphate had a negative correlation with genus_Coprococcus (p=0.0059; p=0.0059) and a positive correlation with Pittsburgh Sleep Quality Index (p=0.006; p=0.006) and Insomnia Severity Index (p=0.021; p=0.021).

Conclusion

Microbiota and serum metabolite changes in IDs are strongly correlated with clinical parameters, implying mechanistic links between altered bacteria, serum metabolites and ID. This study offers novel perspective into the interaction among gut microbiota, oral microbiota, and serum metabolites for ID.

An Update on Microbial Interventions in Autism Spectrum Disorder with Gastrointestinal Symptoms

In the United States, autism spectrum disorder (ASD) affects 1 in 33 children and is characterized by atypical social interactions, communication difficulties, and intense, restricted interests. Microbial dysbiosis in the gastrointestinal (GI) tract is frequently observed in individuals with ASD, potentially contributing to behavioral manifestations and correlating with worsening severity. Moreover, dysbiosis may contribute to the increased prevalence of GI comorbidities in the ASD population and exacerbate immune dysregulation, further worsening dysbiosis. Over the past 25 years, research on the impact of microbial manipulation on ASD outcomes has gained substantial interest. Various approaches to microbial manipulation have been preclinically and clinically tested, including antibiotic treatment, dietary modifications, prebiotics, probiotics, and fecal microbiota transplantation. Each method has shown varying degrees of success in reducing the severity of ASD behaviors and/or GI symptoms and varying long-term efficacy. In this review, we discuss these microbiome manipulation methods and their outcomes. We also discuss potential microbiome manipulation early in life, as this is a critical period for neurodevelopment.

An Investigation into the Relationship of Circulating Gut Microbiome Molecules and Inflammatory Markers with the Risk of Incident Dementia in Later Life

The gut microbiome may be involved in the occurrence of dementia primarily through the molecular mechanisms of producing bioactive molecules and promoting inflammation. Epidemiological evidence linking gut microbiome molecules and inflammatory markers to dementia risk has been mixed, and the intricate interplay between these groups of biomarkers suggests that their joint investigation in the context of dementia is warranted. We aimed to simultaneously investigate the association of circulating levels of selected gut microbiome molecules and inflammatory markers with dementia risk. This case-cohort epidemiological study included 805 individuals (83 years, 66% women) free of dementia at baseline. Plasma levels of 19 selected gut microbiome molecules comprising lipopolysaccharide, short-chain fatty acids, and indole-containing tryptophan metabolites as well as four inflammatory markers measured at baseline were linked to incident all-cause (ACD) and Alzheimer's disease dementia (AD) in binary outcomes and time-to-dementia analyses. Independent of several covariates, seven gut microbiome molecules, 5-hydroxyindole-3-acetic acid, indole-3-butyric acid, indole-3-acryloylglycine, indole-3-lactic acid, indole-3-acetic acid methyl ester, isobutyric acid, and 2-methylbutyric acid, but no inflammatory markers discriminated incident dementia cases from non-cases. Furthermore, 5-hydroxyindole-3-acetic acid (hazard ratio: 0.58; 0.36-0.94, P = 0.025) was associated with time-to-ACD. These molecules underpin gut microbiome-host interactions in the development of dementia and they may be crucial in its prevention and intervention strategies. Future larger epidemiological studies are needed to confirm our findings, specifically in exploring the repeatedly measured circulating levels of these molecules and investigating their causal relationship with dementia risk.