Gut-Microbiota-Brain Axis and Its Effect on Neuropsychiatric Disorders With Suspected Immune Dysregulation

The Efficacy of Fecal Transplantation and Bifidobacterium Supplementation in Ameliorating Propionic Acid-Induced Behavioral and Biochemical Autistic Features in Juvenile Male Rats

Gut microbiota plays a major role in neurological disorders, including autism. Modulation of the gut microbiota through fecal microbiota transplantation (FMT) or probiotic administration, such as Bifidobacteria, is suggested to alleviate autistic symptoms; however, their effects on the brain are not fully examined. We tested both approaches in a propionic acid (PPA) rodent model of autism as treatment strategies. Autism was induced in Sprague-Dawley rats by administering PPA orally (250 mg/kg) for 3 days. Animals were later treated with either saline, FMT, or Bifidobacteria for 22 days. Control animals were treated with saline throughout the study. Social behavior and selected brain biochemical markers related to stress hormones, inflammation, and oxidative stress were assessed. PPA treatment induced social impairments, which was rescued by the treatments. In the brain, Bifidobacteria treatment increased oxytocin relative to control and PPA groups. Moreover, Bifidobacteria treatment rescued the PPA-induced increase in IFN-γ levels. Both treatments increased GST levels, which was diminished by the PPA treatment. These findings indicate the potential of gut microbiota-targeted therapeutics in ameliorating behavioral deficit and underlying neural biochemistry.

Gut Microbiome Composition Linked to Inflammatory Factors and Cognitive Functions in First-Episode, Drug-Naive Major Depressive Disorder Patients

OBJECTIVE

The microbiota-gut-brain axis, especially the inflammatory pathway, may play a critical role in the pathogenesis of cognitive impairment in major depressive disorder (MDD). However, studies on the microbiota-inflammatory-cognitive function axis in MDD are lacking. The aim of the present study was to analyze the gut microbiota composition and explore the correlation between gut microbiota and inflammatory factors, cognitive function in MDD patients.

METHOD

Study participants included 66 first-episode, drug naïve MDD patients as well as 43 healthy subjects (HCs). The composition of fecal microbiota was evaluated using16S rRNA sequencing and bioinformatics analysis. The cytokines such as hs-CRP, IL-1β, IL-6, IL-10, and TNF-α in peripheral blood were detected via enzyme linked immunosorbent assay (ELISA); assessment of cognitive functions was performed using the Color Trail Test (CTT), The Repeatable Battery for the Assessment of Neuropsychological Status (RBANS) and the Stroop Color-Word Test (SCWT).

RESULTS

We found that compared with HCs, MDD patients had cognitive impairments and showed different α-diversity and β-diversity of gut microbiota composition. LDA effect size (LEfSe) analysis found MDD have higher Deinococcaceae and lower Bacteroidaceae, Turicibacteraceae, Clostridiaceae and Barnesiellaceae at family level. Deinococcus and Odoribacter was higher in the MDD group, however, Bacteroides, Alistipes, Turicibacter, Clostridium, Roseburia, and Enterobacter were lower at genus level. Furthermore, In MDD patients, the Bacteroidaceae and Bacteroides were both positively correlated with hsCRP, CCT1, CCT2. Alistipes was positively correlated with IL-6, Word time, Color time, Word-Color time, Color-Word time and negatively correlated with Delayed Memory, Total score and Standardized score. Turicibacteraceae and Turicibacter were both negatively correlated with IL-1β and IL-6.

CONCLUSION

The present findings confirm that the gut microbiota in MDD patients have altered gut microbes that are closely associated with inflammatory factors and cognitive function in MDD patients.

Gut Microbiota Alteration Is Associated With Cognitive Deficits in Genetically Diabetic (Db/db) Mice During Aging

Recent studies have revealed that the microbiota may be implicated in diabetes-related cognitive dysfunction. However, the relationship between gut microbiota and cognitive dysfunction during the progression of type 2 diabetes remains elusive. We used 16S rRNA sequencing combined with conventional behavioral tests to explore the longitudinal changes of gut microbiota and cognition in diabetic db/db mice (leptin receptor knockout mice) and their wild-type littermates at different ages. Prussian blue staining was performed to detect the microhemorrhage in the brain, and immunofluorescent study was applied to analyze microglia activation. Moreover, a Meso Scale Discovery kit was used to determine the cytokine levels in the brain. Db/db mice exhibited age dependent pathological characteristics, including cognitive deficits, neuron damage, spontaneous hemorrhages and neuroinflammation. Furthermore, we observed that the diversity and composition of gut microbiota significantly differed between the wild-type and db/db mice during aging. We found that compared to age-matched wild-type mice, genus Helicobacter was significant higher in db/db mice at 18 and 26 weeks. Correlation analysis revealed that Helicobacter is positively associated with Iba-1 positive cells and TNF-α expression. Collectively, our longitudinal study suggests that diabetic cognitive impairment during aging is associated with abnormal gut microbiota composition, which may play a role in the regulation of neuroinflammation.

Targeting NF-κB pathway by dietary lignans in inflammation: expanding roles of gut microbiota and metabolites

Inflammation is a major factor affecting human health. Nuclear factor-kappa B (NF-κB) plays a vital role in the development of inflammation, and the promoters of most inflammatory cytokine genes have NF-κB-binding sites. Targeting NF-κB could be an exciting route for the prevention and treatment of inflammatory diseases. As important constituents of natural plants, lignans are proved to have numerous biological functions. There are growing pieces of evidence demonstrate that lignans have the potential anti-inflammatory activities. In this work, the type, structure and source of lignans and the influence on mitigating the inflammation are systematically summarized. This review focuses on the targeting NF-κB signaling pathway in the inflammatory response by different lignans and their molecular mechanisms. Lignans also regulate gut microflora and change gut microbial metabolites, which exert novel pathway to prevent NF-κB activation. Taken together, lignans target NF-κB with various mechanisms to inhibit inflammatory cytokine expressions in the inflammatory response. It will provide a scientific theoretical basis for further research on the anti-inflammatory effects of lignans and the development of functional foods.

Gut Microbiota Metabolites in Major Depressive Disorder-Deep Insights into Their Pathophysiological Role and Potential Translational Applications

The gut microbiota is a complex and dynamic ecosystem essential for the proper functioning of the organism, affecting the health and disease status of the individuals. There is continuous and bidirectional communication between gut microbiota and the host, conforming to a unique entity known as "holobiont". Among these crosstalk mechanisms, the gut microbiota synthesizes a broad spectrum of bioactive compounds or metabolites which exert pleiotropic effects on the human organism. Many of these microbial metabolites can cross the blood-brain barrier (BBB) or have significant effects on the brain, playing a key role in the so-called microbiota-gut-brain axis. An altered microbiota-gut-brain (MGB) axis is a major characteristic of many neuropsychiatric disorders, including major depressive disorder (MDD). Significative differences between gut eubiosis and dysbiosis in mental disorders like MDD with their different metabolite composition and concentrations are being discussed. In the present review, the main microbial metabolites (short-chain fatty acids -SCFAs-, bile acids, amino acids, tryptophan -trp- derivatives, and more), their signaling pathways and functions will be summarized to explain part of MDD pathophysiology. Conclusions from promising translational approaches related to microbial metabolome will be addressed in more depth to discuss their possible clinical value in the management of MDD patients.

Lactiplantibacillus plantarum DMDL 9010 alleviates dextran sodium sulfate (DSS)-induced colitis and behavioral disorders by facilitating microbiota-gut-brain axis balance

Previous studies have found that probiotic supplements can ameliorate mental behavioral disorders. This study investigated the effects of Lactiplantibacillus plantarum DMDL 9010 (LP9010) intake on the depression-like behavior induced by dextran sodium sulfate (DSS) and its possible mechanism. Male C57BL/6N mice were fed with DSS to establish the model of ulcerative colitis. LP9010 intake reduced the DSS-induced inflammatory response, and repaired intestinal barrier damage, as well as lightened depression-like behavior. LP9010 supplementation also inhibited neuroinflammation by up-regulating the levels of neurotransmitters, especially 5-HT, NE, DA, and 5-HIAA. Moreover, the intake of LP9010 reorganized the gut microbiome by increasing the relative abundance of Bacteroidetes and Firmicutes, and decreasing the relative abundance of Proteobacteria and Verrucomicrobia. Furthermore, treatment with LP9010 increased the levels of short-chain fatty acids, such as butyric acid and propionic acid. In conclusion, LP9010 intake was a promising probiotic intervention strategy for the prevention of colitis-induced behavioral disorders through the microbiota-gut-brain axis.

The Gut Microbiota-Brain Axis: A New Frontier on Neuropsychiatric Disorders

Alzheimer's disease (AD) is a progressive and incurable neurodegenerative disorder of integrative areas of the brain, characterized by cognitive decline and disability resulting in negative impacts on the family of the patients and the health care services worldwide. AD involves oxidative stress, neuroinflammation and accelerated apoptosis, accompanied by deposition of amyloid-β peptide plaques and tau protein-based neurofibrillary tangles in the central nervous system. Among the multiple factors that contribute to the onset and evolution of this disease, aging stands out. That is why the prevalence of this disease has increased due to the constant increase in life expectancy. In the hope of finding new, more effective methods to slow the progression of this disease, over the last two decades, researchers have promoted "omics"-based approaches that include the gut microbiota and their reciprocal interactions with different targets in the body. This scientific advance has also led to a better understanding of brain compartments and the mechanisms that affect the integrity of the blood-brain barrier. This review aims to discuss recent advances related to the gut-brain-microbiota axis in AD. Furthermore, considering that AD involves psychiatric symptoms, this review also focuses on the psychiatric factors that interact with this axis (an issue that has not yet been sufficiently addressed in the literature).

Fecal Microbiota Transplantation in Autism Spectrum Disorder

Autism spectrum disorder (ASD) is a group of neurodevelopmental disorders that begin in infancy. In recent years, the incidence of ASD in the world is increasing year by year. At present, the etiology and pathogenesis of ASD are not clear, and effective treatments are still lacking. In addition to neurobehavioral symptoms, children with ASD often have obvious gastrointestinal symptoms. Gut microbiota is a large microbial community in the human gut, which is closely related to the nervous system and can affect brain development and behavior through the neuroendocrine, neuroimmune and autonomic nervous systems, forming a microbiota-gut-brain axis connection. Recent studies have shown that children with ASD have significant gut microbiota and metabolic disorders, and fecal microbiota transplantation (FMT) is expected to improve ASD-related symptoms by regulating gut microbiota and metabolism. This review paper will therefore focus on FMT in the treatment of ASD, and FMT is effective in improving gastrointestinal and neurobehavioral symptoms in children with ASD.

Intersection of Epigenetic and Immune Alterations: Implications for Fetal Alcohol Spectrum Disorder and Mental Health

Prenatal alcohol exposure can impact virtually all body systems, resulting in a host of structural, neurocognitive, and behavioral abnormalities. Among the adverse impacts associated with prenatal alcohol exposure are alterations in immune function, including an increased incidence of infections and alterations in immune/neuroimmune parameters that last throughout the life-course. Epigenetic patterns are also highly sensitive to prenatal alcohol exposure, with widespread alcohol-related alterations to epigenetic profiles, including changes in DNA methylation, histone modifications, and miRNA expression. Importantly, epigenetic programs are crucial for immune system development, impacting key processes such as immune cell fate, differentiation, and activation. In addition to their role in development, epigenetic mechanisms are emerging as attractive candidates for the biological embedding of environmental factors on immune function and as mediators between early-life exposures and long-term health. Here, following an overview of the impact of prenatal alcohol exposure on immune function and epigenetic patterns, we discuss the potential role for epigenetic mechanisms in reprogramming of immune function and the consequences for health and development. We highlight a range of both clinical and animal studies to provide insights into the array of immune genes impacted by alcohol-related epigenetic reprogramming. Finally, we discuss potential consequences of alcohol-related reprogramming of immune/neuroimmune functions and their effects on the increased susceptibility to mental health disorders. Overall, the collective findings from animal models and clinical studies highlight a compelling relationship between the immune system and epigenetic pathways. These findings have important implications for our understanding of the biological mechanisms underlying the long-term and multisystem effects of prenatal alcohol exposure, laying the groundwork for possible novel interventions and therapeutic strategies to treat individuals prenatally exposed to alcohol.

An In Vitro Approach to Studying the Microbial Community and Impact of Pre and Probiotics under Anorexia Nervosa Related Dietary Restrictions

Individuals with anorexia nervosa (AN) often suffer psychological and gastrointestinal problems consistent with a dysregulated gut microbial community. Psychobiotics have been postulated to modify microbiota and improve mental well-being and gut symptoms, but there is currently a lack of evidence for such approaches in AN. The aim of this study was to use an in vitro colonic model to evaluate the impact of dietary restrictions associated with AN on the intestinal ecosystem and to assess the impact of pre and probiotic intervention. Bacteriology was quantified using flow cytometry combined with fluorescence in situ hybridisation and metabolic end products (including neurotransmitters) by gas chromatography and liquid chromatography mass spectrometry Consistent with previous research, the nutritional changes significantly reduced total microbiota and metabolites compared with healthy conditions. Pre and probiotic supplementation on restricted conditions enhanced the microbial community and modulated metabolic activity to resemble that of a healthy diet. The model system indicates that nutritional changes associated with AN can impact the microbial community, and that these changes can, at least in part, be restored through the use of pre and probiotic interventions.

Correlation between Gut Microbiota and Six Facets of Neuroticism in Korean Adults

A person high in neuroticism is more likely to experience anxiety, stress, worry, fear, anger, and depression. Previous studies have shown that the gut microbiota can influence personality and mental disorders, including stress, anxiety, and depression, through the gut-brain axis. Here, we investigated the correlations between the sub-facet of neuroticism and gut microbiota using the Revised NEO Personality Inventory and the 16S rRNA gene sequencing data 784 adults. We found that the high anxiety and vulnerability group showed significantly lower richness in microbial diversity than a group with low anxiety and vulnerability. In beta diversity, there was a significant difference between the low and high groups of anxiety, self-consciousness, impulsiveness, and vulnerability. In taxonomic compositions, Haemophilus belonging to Gammaproteobacteria was correlated with the Neuroticism domain as well as N1 anxiety and N6 vulnerability facets. The high N1 anxiety and N6 vulnerability group was correlated with a low abundance of Christensenellaceae belonging to Firmicutes Clostridia. High N4 self-consciousness was correlated with a low abundance of Alistipes and Sudoligranulum. N5 impulsiveness was correlated with a low abundance of Oscillospirales. Our findings will contribute to uncovering the potential link between the gut microbiota and neuroticism, and the elucidation of the correlations of the microbiome-gut-brain axis with behavioral changes and psychiatric cases in the general population.

Vitamin A Deficiency Exacerbates Gut Microbiota Dysbiosis and Cognitive Deficits in Amyloid Precursor Protein/Presenilin 1 Transgenic Mice

Vitamin A deficiency (VAD) plays an essential role in the pathogenesis of Alzheimer’s disease (AD). However, the specific mechanism by which VAD aggravates cognitive impairment is still unknown. At the intersection of microbiology and neuroscience, the gut-brain axis is undoubtedly contributing to the formation and function of neurological systems, but most of the previous studies have ignored the influence of gut microbiota on the cognitive function in VAD. Therefore, we assessed the effect of VAD on AD pathology and the decline of cognitive function in AD model mice and determined the role played by the intestinal microbiota in the process. Twenty 8-week-old male C57BL/6J amyloid precursor protein/presenilin 1 (APP/PS1) transgenic mice were randomly assigned to either a vitamin A normal (VAN) or VAD diet for 45 weeks. Our results show that VAD aggravated the behavioral learning and memory deficits, reduced the retinol concentration in the liver and the serum, decreased the transcription of vitamin A (VA)-related receptors and VA-related enzymes in the cortex, increased amyloid-β peptides (Aβ40 and Aβ42) in the brain and gut, upregulate the translation of beta-site APP-cleaving enzyme 1 (BACE1) and phosphorylated Tau in the cortex, and downregulate the expression of brain-derived neurotrophic factor (BDNF) and γ-aminobutyric acid (GABA) receptors in the cortex. In addition, VAD altered the composition and functionality of the fecal microbiota as exemplified by a decreased abundance of Lactobacillus and significantly different α- and β-diversity. Of note, the functional metagenomic prediction (PICRUSt analysis) indicated that GABAergic synapse and retinol metabolism decreased remarkably after VAD intervention, which was in line with the decreased expression of GABA receptors and the decreased liver and serum retinol. In summary, the present study provided valuable facts that VAD exacerbated the morphological, histopathological, molecular biological, microbiological, and behavioral impairment in the APP/PS1 transgenic mice, and the intestinal microbiota may play a key mediator role in this mechanism.

The Microbiota-Gut-Brain Axis During Heat Stress in Chickens: A Review

Heat stress is a global issue for the poultry industries with substantial annual economic losses and threats to bird health and welfare. When chickens are exposed to high ambient temperatures, like other species they undergo multiple physiological alterations, including behavioral changes, such as cessation of feeding, initiation of a stress signaling cascade, and intestinal immune, and inflammatory responses. The brain and gut are connected and participate in bidirectional communication via the nervous and humoral systems, this network collectively known as the gut-brain axis. Moreover, heat stress not only induces hyperthermia and oxidative stress at the gut epithelium, leading to impaired permeability and then susceptibility to infection and inflammation, but also alters the composition and abundance of the microbiome. The gut microflora, primarily via bacterially derived metabolites and hormones and neurotransmitters, also communicate via similar pathways to regulate host metabolic homeostasis, health, and behavior. Thus, it stands to reason that reshaping the composition of the gut microbiota will impact intestinal health and modulate host brain circuits via multiple reinforcing and complementary mechanisms. In this review, we describe the structure and function of the microbiota-gut-brain axis, with an emphasis on physiological changes that occur in heat-stressed poultry.

The role of the host microbiome in autism and neurodegenerative disorders and effect of epigenetic procedures in the brain functions

Autism Spectrum Disorder (ASD) is a severe neurological/neurodegenerative syndrome that results in cognitive and communication disorders. The degree of dysbiosis is related to the severity of ASD signs. The gut is conferred with a variety of sensory receptors that cooperate with effector systems including the endocrine, nervous and gut immune systems of the intestine. Gut dysbiosis causes amplified inflammation, the launch of the HPA axis, changed levels of neurotransmitters and bacterial metabolites; these may donate to abnormal signaling throughout the Vagus nerve in ASD. Decreased integrity of the gastrointestinal barrier led to extreme leakage of substances as of the intestine in early life and inflammation followed by disruption of BBB integrity maybe increase the risk of ASD. Microbiota, by controlling the barrier permeability, regulate the quantity and types of bioactive materials that are transferred from the intestine to the brain. Exposure to metabolites and microbial products regulate significant procedures in the CNS, including glial cell role, myelination, synaptic pruning, and play a role in neurobehavioral, neurodegenerative, psychiatric, and metabolic syndrome.

Vancomycin-Induced Changes in Host Immunity and Behavior: Comparative Genomic and Metagenomic Analysis in C57BL/6 and BALB/c Mice

BACKGROUND

The consequence of treatment with antibiotics on the gut microbiota can be destructive. The antibiotics, however, can be utilized to understand the role of gut microbiota on the host physiology.

AIM

Earlier, we reported the efficacy of vancomycin in gut microbiota perturbation. We continued to understand the effect of restoration kinetics of perturbed gut microbiota on the immunity and behavior of Th1 (C57BL/6)- and Th2 (BALB/c)-biased mice.

METHODS

We studied restoration kinetics of the gut microbiota for two months following the withdrawal of vancomycin treatment in both mice strains. We analyzed cecal microbiome composition, different behavioral assays, and expression of select genes associated with stress and barrier function in gut and brain.

RESULTS

Metagenomic analysis of gut microbiota revealed that the treatment with vancomycin caused a significant decrease in the relative abundance of Firmicutes and Bacteroidetes phyla with a time-dependent increase in Proteobacteria and Verrucomicrobia phyla. Maximum restoration (> 70%) of gut microbiota happened by the 15th day of withdrawal of vancomycin. BALB/c mice showed a more efficient restoration of gut microbiota compared to C57BL/6 mice. We established the correlation patterns of gut microbiota alteration and its effect on (a) the behavior of mice, (b) expression of key brain molecules, and (c) immunity-related genes.

CONCLUSIONS

The results revealed that the gut microbiome profiling, behavior, and immune responses varied significantly between Th1- and Th2-biased mice. By withdrawing the treatment with vancomycin of major gut microbes, important physiological and behavioral changes of both mice strains returned to the normal (untreated control) level.

The immune system and autism spectrum disorder: association and therapeutic challenges

Autism spectrum disorder (ASD) is a neurodevelopmental disorder, affecting communication and behavior. Historically, ASD had been described as a purely psychiatric disorder with genetic factors playing the most critical role. Recently, a growing body of literature has been emphasizing the importance of environmental and immunological factors in its pathogenesis, with the autoimmune process attracting the most attention. This study provides a review of the autoimmune involvement in the pathogenesis of ASD. The\r\nmicrobiome, the representative of the innate immune system in the central nervous system (CNS), plays a critical role in triggering inflammation. Besides, a bidirectional communicational pathway between the CNS and the intestine called the gut‑brain‑axis is linked to the development of ASD. Moreover, the higher plasma level of pro‑inflammatory cytokines in ASD patients and the higher prevalence of autoimmune disorders in the first‑degree family members of affected persons are other clues of the immune system involvement in\r\nthe pathogenesis of ASD. Furthermore, some anti‑inflammatory drugs, including resveratrol and palmitoylethanolamide have shown promising effects by relieving the manifestations of ASD. Although considerable advances have been made in elucidating the role of autoimmunity in the ASD pathogenesis, further studies with stronger methodologies are needed to apply the knowledge to the definitive treatment of ASD.

Microbiome-Specific Statistical Modeling Identifies Interplay Between Gastrointestinal Microbiome and Neurobehavioral Outcomes in Patients With Autism: A Case Control Study

Autism Spectrum Disorder (ASD) is a neurodevelopmental disorder with unclear mechanisms of pathogenesis. Gastrointestinal microbiome alterations were found to correlate with ASD core symptoms, but its specific role in ASD pathogenesis has not been determined. In this study, we used a case-control strategy that simultaneously compared the ASD gastrointestinal microbiome with that from age-sex matched controls and first-degree relative controls, using a statistical framework accounting for confounders such as age. Enterobacteriaceae (including Escherichia/Shigella) and Phyllobacterium were significantly enriched in the ASD group, with their relative abundances all following a pattern of ASD > first degree relative control > healthy control, consistent with our hypothesis of living environment and shared microbial and immunological exposures as key drivers of ASD gastrointestinal microbiome dysbiosis. Using multivariable omnibus testing, we identified clinical factors including ADOS scores, dietary habits, and gastrointestinal symptoms that covary with overall microbiome structure within the ASD cohort. A microbiome-specific multivariate modeling approach (MaAsLin2) demonstrated microbial taxa, such as Lachnoclostridium and Tyzzerella, are significantly associated with ASD core symptoms measured by ADOS. Finally, we identified alterations in predicted biological functions, including tryptophan and tyrosine biosynthesis/metabolism potentially relevant to the pathophysiology of the gut-brain-axis. Overall, our results identified gastrointestinal microbiome signature changes in patients with ASD, highlighted associations between gastrointestinal microbiome and clinical characteristics related to the gut-brain axis and identified contributors to the heterogeneity of gastrointestinal microbiome within the ASD population.

Bacterial Translocation Associates With Aggression in Schizophrenia Inpatients

Objective: Accumulating evidence indicates that inflammation abnormalities may contribute to aggression behaviors in psychotic patients, however, the possible sources of inflammation remain elusive. We aimed to evaluate the associations among aggression, inflammation, and bacterial translocation (BT) in aggression-affected schizophrenia (ScZ) inpatients with 2 weeks of antipsychotics discontinuation.

Methods: Serum specimens collected from 112 aggression and 112 non-aggression individuals with ScZ and 56 healthy adults were used for quantifications of inflammation- or BT-related biomarkers. Aggression severity was assessed by Modified Overt Aggression Scale (MOAS).

Results: Proinflammation phenotype dominated and leaky gut-induced BT occurred only in cases with ScZ with a history of aggression, and the MOAS score positively related to levels of C-reactive protein, interleukin (IL)-6, IL-1β, and tumor necrosis factor-α. Furthermore, serum levels of BT-derived lipopolysaccharide (LPS), as well as LPS-responded soluble CD14, were not only positively correlated with levels of above proinflammation mediators but also the total MOAS score and subscore for aggression against objects or others.

Conclusion: Our results collectively demonstrate the presence of leaky gut and further correlate BT-derived LPS and soluble CD14 to onset or severity of aggression possibly by driving proinflammation response in inpatients with ScZ, which indicates that BT may be a novel anti-inflammation therapeutic target for aggression prophylaxis.

Inflammation, Anxiety, and Stress in Attention-Deficit/Hyperactivity Disorder

Attention-deficit/hyperactivity disorder (ADHD) is a prevalent and serious neurodevelopmental disorder characterized by symptoms of inattention and/or hyperactivity/impulsivity. Chronic and childhood stress is involved in ADHD development, and ADHD is highly comorbid with anxiety. Similarly, inflammatory diseases and a pro-inflammatory state have been associated with ADHD. However, while several works have studied the relationship between peripheral inflammation and stress in affective disorders such as depression or bipolar disorder, fewer have explored this association in ADHD. In this narrative review we synthetize evidence showing an interplay between stress, anxiety, and immune dysregulation in ADHD, and we discuss the implications of a potential disrupted neuroendocrine stress response in ADHD. Moreover, we highlight confounding factors and limitations of existing studies on this topic and critically debate multidirectional hypotheses that either suggest inflammation, stress, or anxiety as a cause in ADHD pathophysiology or inflammation as a consequence of this disease. Untangling these relationships will have diagnostic, therapeutic and prognostic implications for ADHD patients.

Gut microbiota and neuropsychiatric disorders: Implications for neuroendocrine-immune regulation

Recently, increasing evidence has shown gut microbiota dysbiosis might be implicated in the physiological mechanisms of neuropsychiatric disorders. Altered microbial community composition, diversity and distribution traits have been reported in neuropsychiatric disorders. However, the exact pathways by which the intestinal microbiota contribute to neuropsychiatric disorders remain largely unknown. Given that the onset and progression of neuropsychiatric disorders are characterized with complicated alterations of neuroendocrine and immunology, both of which can be continually affected by gut microbiota via "microbiome-gut-brain axis". Thus, we assess the complicated crosstalk between neuroendocrine and immunological regulation might underlie the mechanisms of gut microbiota associated with neuropsychiatric disorders. In this review, we summarized clinical and preclinical evidence on the role of the gut microbiota in neuropsychiatry disorders, especially in mood disorders and neurodevelopmental disorders. This review may elaborate the potential mechanisms of gut microbiota implicating in neuroendocrine-immune regulation and provide a comprehensive understanding of physiological mechanisms for neuropsychiatric disorders.

Gut microbiota and probiotic therapy in ADHD: A review of current knowledge

Attention deficit hyperactivity disorder (ADHD) is a common neurodevelopmental disorder characterized by inattention, impulsivity and hyperactivity. The etiology of the disorder is multi-factorial, with a main focus on genetic factors. However, emerging research shows the involvement of changes and imbalances in the intestinal microbiota. Evidence for the influence of gut microbiota on brain development and neurogenesis is clear. We present a review of emerging research on the microbiota in the ADHD population. The aim of this study was to summarize the current state of knowledge on ADHD, to identify gaps in knowledge, as well as to indicate the directions of new research. Thanks to the researchers that would be possible to better understand the complexity of ADHD etiology, especially the role of the intestinal microbiota in the pathogenesis of the disorder. Pubmed, Scopus and Google Scholar databases were used while writing the review. Numerous studies show that probiotic supplementation can have a positive effect on the course of neurodevelopmental disorders, including ADHD. Unfortunately, clinical studies that were identified are mostly inconclusive, and more high-quality research is needed to produce robust evidence for therapy based on interventions targeting microbiota.

Effect of Chaihu-jia-Longgu-Muli decoction on withdrawal symptoms in rats with methamphetamine-induced conditioned place preference

Traditional Chinese medicine detoxification prescription Chaihu-jia-Longgu-Muli decoction (CLMD) relieves depressive symptoms in patients withdrawing from methamphetamine. In the present study, we assessed the effects of CLMD on methamphetamine withdrawal in rats. A methamphetamine-intoxicated rat model was established. Rats were randomly divided into the control, model, high-dosage, medium-dosage, and low-dosage groups, receiving high, medium, and low doses of CLMD, respectively. Weekly body weight measurements revealed that rats treated with methamphetamine had the lowest body weight. The conditioned place preference (CPP) experiment revealed that methamphetamine-intoxicated rats stayed significantly longer in the drug-paired chamber than the control rats. However, after administering high-dosage CLMD, the amount of time the rats spent in the drug-paired chamber was significantly less than that of the model rats. Our open-field test revealed that the model group had lower crossing and rearing scores than the control group. Additionally, rats that received CLMD treatment exhibited higher crossing and rearing scores than the model rats. Striatal dopamine (DA), 5-hydroxytryptamine (5-HT), and endorphins (β-EP) and serum interleukin (IL)-1α and IL-2 concentrations were estimated. Rats in the model group had lower striatal DA, 5-HT, and β-EP and higher serum IL-1α and IL-2 concentrations than those in the control group. High-dosage CLMD administration significantly changed the concentrations of these molecules, such that they approached normal concentrations. In general, CLMD could prevent the development of methamphetamine-induced withdrawal symptoms in rats by increasing the DA, 5-HT, and β-EP and lowering the IL-1α and IL-2 concentrations.

A bidirectional relationship between anxiety, depression and gastrointestinal symptoms in Parkinson's disease

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Gastrointestinal (GI) and mood symptoms are common in Parkinson’s disease.

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Depression and anxiety are bidirectional risk factors for GI distress.

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Association between GI and mood symptoms may reflect disrupted Gut-Brain axis.

Introduction

Anxiety, depression and gastrointestinal (GI) symptoms are common non-motor symptoms in Parkinson’s disease (PD). Past studies provide evidence of a disrupted microbiome-gut-brain axis in PD, which is associated with certain motor and non-motor symptoms in PD. Additionally, there is evidence of a bidirectional association between mental health and gut health among individuals with GI disorders. The current study examined the bidirectional association between GI symptoms and anxiety/depression among individuals newly diagnosed with PD.

Methods

We conducted a secondary data analysis of the Parkinson’s Progression Markers Initiative. This included 487 individuals newly diagnosed with PD and followed for up to 5 years. Participants completed questionnaires of anxiety, depression and GI symptoms (Scales for Outcomes in Parkinson’s Disease Autonomic; SCOPA-AUT) at each annual visit. Multilevel models examined the bidirectional-lagged relationship between GI symptoms and anxiety/depression.

Results

Models provided evidence for a bidirectional relationship between GI symptoms and anxiety/depression. Specifically, more severe GI symptoms predicted more severe anxious/depressive symptoms within the same year and at the following year. There was also evidence of the inverse directionality, meaning that more severe anxiety/depression predicted more severe GI symptoms concurrently and in the following year.

Discussion

Findings provide preliminary evidence for a cyclical relationship among gut health and mental health in PD. Future studies are needed to examine if the microbiome-gut-brain axis plays a mechanistic role.

The brain-gut axis in gastrointestinal cancers

Recent developments have given more credence into the brain-gut-microbiota axis and its role in the development of tumor genesis. The microbiota have multiple functions including maintenance of the epithelial barrier, immune response, digestion, cortisol regulation, and control of neurotransmitters and their metabolism [e.g., serotonin, dopamine, noradrenaline and gamma-Aminobutyric Acid (GABA)]. Changes in gut microbiota can interfere with homeostasis leading to dysbiosis microbiota, which is linked to colorectal cancer. Microbiota composition can cause pronounced effect on medical interventions including medications, chemotherapy, and radiation. Altered primary immune system is associated with microbiota disassociation and development of colorectal cancer. This article reviews the current research in brain-gut axis with focus on microbiota and its role in the development of gastrointestinal cancers. We conducted a literature review on PubMed, Cochrane, and Science direct using English language. We begin by reviewing the brain-gut axis and its function and then discuss its effect on the development of gastrointestinal cancers. We reviewed 70 manuscripts and found association between microbiota dysfunction and development of colorectal cancers predisposing to psychiatric manifestations. Lasting disturbances in the microbiota can lead to systemic inflammation with implications on disease development or treatment modifications. These disruptions of the intestinal flora can play an important role in the pathogenesis of cancers. Most psychological reactions to cancer are similar across cancer types but each cancer when examined individually has its own unique features associated with it. Correlation between fear of recurrence and the level of pathological distress is viewed as an indicator of overall adjustment to cancer survival.

Chaihu-Shugan-San (Shihosogansan) alleviates restraint stress-generated anxiety and depression in mice by regulating NF-κB-mediated BDNF expression through the modulation of gut microbiota

BACKGROUND

Chaihu-Shugan-San (CSS, named Shihosogansan in Korean), a Chinese traditional medicine, is frequently used to treat anxiety and depression. Psychiatric disorders including depression are associated with gut dysbiosis. Therefore, to comprehend gut microbiota-involved anti-depressive effect of CSS, we examined its effect on restraint stress (RS)-induced depression and gut dysbiosis in mice METHODS: CSS was extracted with water in boiling water bath and freeze-dried. Anxiety and depression was induced in C57BL/6 mice by exposure to RS. Anxiety- and depression-like behaviors were measured in the light/dark transition and elevated plus maze tasks, forced swimming test, and tail suspension test. Biomarkers were assayed by using the enzyme-linked immunosorbent assay and immunoblotting. The gut microbiota composition was analyzed by Illumina iSeq sequencer.

RESULTS

CSS significantly reduced the RS-induced anxiety- and depression-like behaviors in mice. CSS suppressed the RS-induced activation of NF-κB and expression of interleukin (IL)-6 and increased the RS-suppressed expression of brain-derived neurotrophic factor (BDNF). Furthermore, CSS suppressed the RS-induced IL-6 and corticosterone level in the blood and IL-6 expression and myeloperoxidase activity in the colon. CSS decreased the RS-induced γ-Proteobacteria population in gut microbiota, while the RS-suppressed Lactobacillaceae, Prevotellaceae, and AC160630_f populations increased. Fecal transplantation of vehicle-treated control or RS/CSS-treated mice into RS-exposed mice significantly mitigated RS-induced anxity- and depression-like behaviors, suppressed the NF-κB activation in the hippocampus and colon, and reduced the IL-6 and corticosterone levels in the blood. These fecal microbiota transplantations suppressed RS-induced Desulfovibrionaceae and γ-Proteobacteria populations and increased RS-suppressed Lactobacillaceae and Prevotellaceae poulation in the gut microbiota.

CONCLUSIONS

CSS alleviated anxiety and depression by inducing NF-κB-involved BDNF expression through the regulation of gut inflammation and microbiota.

PACAP orchestration of stress-related responses in neural circuits

Pituitary adenylate cyclase activating polypeptide (PACAP) is a pleiotropic polypeptide that can activate G protein-coupled PAC1, VPAC1, and VPAC2 receptors, and has been implicated in stress signaling. PACAP and its receptors are widely distributed throughout the nervous system and other tissues and can have a multitude of effects. Human and animal studies suggest that PACAP plays a role responding to a variety of threats and stressors. Here we review the roles of PACAP in several regions of the central nervous system (CNS) as they relate to several behavioral functions. For example, in the bed nucleus of the stria terminalis (BNST), PACAP is upregulated following chronic stress and may drive anxiety-like behavior. PACAP can also influence both the consolidation and expression of fear memories, as demonstrated by studies in several fear-related areas, such as the amygdala, hippocampus, and prefrontal cortex. PACAP can also mediate the emotional component of pain, as PACAP in the central nucleus of the amygdala (CeA) is able to decrease pain sensitivity thresholds. Outside of the central nervous system, PACAP may drive glucocorticoid release via enhanced hypothalamic-pituitary-adrenal axis activity and may participate in infection-induced stress responses. Together, this suggests that PACAP exerts effects on many stress-related systems and may be an important driver of emotional behavior.

Role of microbes in the pathogenesis of neuropsychiatric disorders

Microbes inhabit different anatomical sites of the human body including oral cavity, gut, and skin. A growing literature highlights how microbiome variation is associated with human health and disease. There is strong evidence of bidirectional communication between gut and brain mediated by neurotransmitters and microbial metabolites. Here, we review the potential involvement of microbes residing in the gut and in other body sites in the pathogenesis of eight neuropsychiatric disorders, discussing findings from animal and human studies. The data reported provide a comprehensive overview of the current state of the microbiome research in neuropsychiatry, including hypotheses about the mechanisms underlying the associations reported and the translational potential of probiotics and prebiotics.

Gut microbiota mediates cognitive impairment in young mice after multiple neonatal exposures to sevoflurane

Multiple exposures to anesthesia may increase the risk of cognitive impairment in young children. However, the mechanisms underlying this neurodevelopmental disorder remain elusive. In this study, we investigated alteration of the gut microbiota after multiple neonatal exposures to the anesthetic sevoflurane and the potential role of microbiota alteration on cognitive impairment using a young mice model. Multiple neonatal sevoflurane exposures resulted in obvious cognitive impairment symptoms and altered gut microbiota composition. Fecal transplantation experiments confirmed that alteration of the microbiota was responsible for the cognitive disorders in young mice. Microbiota profiling analysis identified microbial taxa that showed consistent differential abundance before and after fecal microbiota transplantation. Several of the differentially abundant taxa are associated with memory and/or health of the host, such as species of Streptococcus, Lachnospiraceae, and Pseudoflavonifractor. The results reveal that abnormal composition of the gut microbiota is a risk factor for cognitive impairment in young mice after multiple neonatal exposures to sevoflurane and provide insight into a potential therapeutic strategy for sevoflurane-related neurotoxicity.

Dysregulated metabolism and behaviors by disrupting gut microbiota in prenatal and neonatal mice

The live microbiota ecosystem in the intestine plays a critical role in maintaining the normal physiological and psychological functions in both animals and human beings. However, the chronic effect of microbiota disturbances during prenatal and neonatal developing periods on animal's health remains less studied. In the current study, pregnant ICR mice were fed with an antibiotic diet (7-g nebacitin [bacitracin-neomycin sulphate 2:1]/kg standard diet) from day 14 of conception, and their offspring were provided with the same diet till the termination of the experiments. Dams treated with antibiotics showed increased body weight along with enlarged gut. Antibiotic-treated offspring revealed decreased bodyweight, increased food, water, and sucrose intake. Administration of antibiotics affected corticosterone responsivity to acute 20 min restraint challenge in male pups. In behavior tests, female pups showed decreased movement in open field while male pups revealed decreased latency to open arms in elevated plus maze test and immobility time in tail suspension test. Together, these results suggested that early antibiotic exposure may impact on the food intake, body weight gain, and emotional behavior regulation in mice.

Chronic Stress-Induced Depression and Anxiety Priming Modulated by Gut-Brain-Axis Immunity

Chronic stress manifests as depressive- and anxiety-like behavior while recurrent stress elicits disproportionate behavioral impairments linked to stress-induced immunological priming. The gut-brain-microbiota-axis is a promising therapeutic target for stress-induced behavioral impairments as it simultaneously modulates peripheral and brain immunological landscapes. In this study, a combination of probiotics and prebiotics, known as a synbiotic, promoted behavioral resilience to chronic and recurrent stress by normalizing gut microbiota populations and promoting regulatory T cell (Treg) expansion through modulation of ileal innate lymphoid cell (ILC)3 activity, an impact reflecting behavioral responses better than limbic brain region neuroinflammation. Supporting this conclusion, a multivariate machine learning model correlatively predicted a cross-tissue immunological signature of stress-induced behavioral impairment where the ileal Treg/T helper17 cell ratio associated to hippocampal chemotactic chemokine and prefrontal cortex IL-1β production in the context of stress-induced behavioral deficits. In conclusion, stress-induced behavioral impairments depend on the gut-brain-microbiota-axis and through ileal immune regulation, synbiotics attenuate the associated depressive- and anxiety-like behavior.

Role of Polyphenols on Gut Microbiota and the Ubiquitin-Proteasome System in Neurodegenerative Diseases

Today, neurodegenerative diseases have become a remarkable public health challenge due to their direct relation with aging. Accordingly, understanding the molecular and cellular mechanisms occurring in the pathogenesis of them is essential. Both protein aggregations as a result of the ubiquitin-proteasome system (UPS) inefficiency and gut microbiota alternation are the main pathogenic hallmarks. Polyphenols upregulating this system may decrease the developing rate of neurodegenerative diseases. Most of the dietary intake of polyphenols is converted into other microbial metabolites, which have completely different biological properties from the original polyphenols and should be thoroughly investigated. Herein, several prevalent neurodegenerative diseases are pinpointed to explain the role of gut microbiota alternations and the role of molecular changes, especially UPS down-regulation in their pathogenesis. Some of the most important polyphenols found in our diet are explained along with their microbial metabolites in the body.

The interaction between tea polyphenols and host intestinal microorganisms: an effective way to prevent psychiatric disorders

Tea polyphenols (TP) are the most bioactive components in tea extracts. It has been reported that TP can regulate the composition and the function of the intestinal flora. Meanwhile, intestinal microorganisms improve the bioavailability of TP, and the corresponding metabolites of TP can regulate intestinal micro-ecology and promote human health more effectively. The dysfunction of the microbiota-gut-brain axis is the main pathological basis of depression, and its abnormality may be the direct cause and potential influencing factor of psychiatric disorders. The interrelationship between TP and intestinal microorganisms is discussed in this review, which will enable us to better evaluate the potential preventive effects of TP on psychiatric disorders by modulating host intestinal microorganisms.

Mechanism and therapeutic strategies of depression after myocardial infarction

Depression resulted as an important factor associated with the myocardial infarction (MI) prognosis. Patients with MI also have a higher risk for developing depression. Although the issue of depression after MI has become a matter of clinical concern, the molecular mechanism underlying depression after MI remains unclear, whereby several strategies suggested have not got ideal effects, such as selective serotonin reuptake inhibitors. In this review, we summarized and discussed the occurrence mechanism of depression after MI, such as 5-hydroxytryptamine (5-HT) dysfunction, altered hypothalamus-pituitary-adrenal (HPA) axis function, gut microbiota imbalance, exosomal signal transduction, and inflammation. In addition, we offered a succinct overview of treatment, as well as some promising molecules especially from natural products for the treatment of depression after MI.

Gastrointestinal involvement of autism spectrum disorder: focus on gut microbiota

INTRODUCTION

Autism spectrum disorder (ASD) is a neurodevelopmental disorder typical of early age, characterized by impaired communication, social interaction, and repetitive behaviors. ASD patients frequently suffer from gastrointestinal (GI) symptoms. Neuro-psychological functions, intestinal homeostasis, and functional GI disturbances are modulated by the gut microbiota through the so-called 'microbiota-gut-brain axis'.

AREAS COVERED

Literature regarding GI symptoms among the ASD community as well as the involvement and modulation of the gut microbiota in GI disturbances of ASD patients was searched. Constipation, diarrhea, reflux, abdominal bloating, pain, and discomfort are reported with variable prevalence. ASD is characterized by a reduction of Bacteroidetes/Firmicutes, of the abundance of Bacteroidetes and other imbalances. ASD patients with GI symptoms present microbial changes with plausible relation with deficiency of digestive enzymes, carbohydrate malabsorption, selective eating, bacterial toxins, serotonin metabolism, and inflammation. The strategies to mitigate the GI distress through the gut microbiota modulation comprise antimicrobials, probiotics, prebiotics, fecal microbiota transplantation, and dietary intervention.

EXPERT OPINION

The modulation of the gut microbiota in ASD individuals with GI disturbances seems a promising target for the future medicine. A standardization of the research strategies for large-scale studies together with a focus on poorly explored fields is necessary to strengthen this hypothesis.

Disruption of circadian rhythm and risk of autism spectrum disorder: role of immune-inflammatory, oxidative stress, metabolic and neurotransmitter pathways

Circadian rhythms in most living organisms are regulated by light and synchronized to an endogenous biological clock. The circadian clock machinery is also critically involved in regulating and fine-tuning neurodevelopmental processes. Circadian disruption during embryonic development can impair crucial phases of neurodevelopment. This can contribute to neurodevelopmental disorders like autism spectrum disorder (ASD) in the offspring. Increasing evidence from studies showing abnormalities in sleep and melatonin as well as genetic and epigenetic changes in the core elements of the circadian pathway indicate a pivotal role of circadian disruption in ASD. However, the underlying mechanistic basis through which the circadian pathways influence the risk and progression of ASD are yet to be fully discerned. Well-recognized mechanistic pathways in ASD include altered immune-inflammatory, nitro oxidative stress, neurotransmission and synaptic plasticity, and metabolic pathways. Notably, all these pathways are under the control of the circadian clock. It is thus likely that a disrupted circadian clock will affect the functioning of these pathways. Herein, we highlight the possible mechanisms through which aberrations in the circadian clock might affect immune-inflammatory, nitro-oxidative, metabolic pathways, and neurotransmission, thereby driving the neurobiological sequelae leading to ASD.

Immunoregulation and antidepressant effect of ketamine

Major depressive disorder (MDD) is a common mental health disorder that brings severe disease burden worldwide. Traditional antidepressants are mainly targeted at monoamine neurotransmitters, with low remission rates and high recurrence rates. Ketamine is a noncompetitive glutamate N-methyl-d-aspartate receptor (NMDAR) antagonist, and its rapid and powerful antidepressant effects have come to light. Its antidepressant mechanism is still unclarified. Research found that ketamine had not only antagonistic effect on NMDAR but also strong immunomodulatory effect, both of which were closely related to the pathophysiology of MDD. Although there are many related studies, they are relatively heterogeneous. Therefore, this review mainly describes the immune mechanisms involved in MDD and how ketamine plays an antidepressant role by regulating peripheral and central immune system, including peripheral inflammatory cytokines, central microglia, and astrocytes. This review summarizes the related research, finds out the deficiencies of current research, and provides ideas for future research and the development of novel antidepressants.

Bidirectional communication between mast cells and the gut-brain axis in neurodegenerative diseases: Avenues for therapeutic intervention

Although the global incidence of neurodegenerative diseases has been steadily increasing, especially in adults, there are no effective therapeutic interventions. Neurodegeneration is a heterogeneous group of disorders that is characterized by the activation of immune cells in the central nervous system (CNS) (e.g., mast cells and microglia) and subsequent neuroinflammation. Mast cells are found in the brain and the gastrointestinal tract and play a role in "tuning" neuroimmune responses. The complex bidirectional communication between mast cells and gut microbiota coordinates various dynamic neuro-cellular responses, which propagates neuronal impulses from the gastrointestinal tract into the CNS. Numerous inflammatory mediators from degranulated mast cells alter intestinal gut permeability and disrupt blood-brain barrier, which results in the promotion of neuroinflammatory processes leading to neurological disorders, thereby offsetting the balance in immune-surveillance. Emerging evidence supports the hypothesis that gut-microbiota exert a pivotal role in inflammatory signaling through the activation of immune and inflammatory cells. Communication between inflammatory cytokines and neurocircuits via the gut-brain axis (GBA) affects behavioral responses, activates mast cells and microglia that causes neuroinflammation, which is associated with neurological diseases. In this comprehensive review, we focus on what is currently known about mast cells and the gut-brain axis relationship, and how this relationship is connected to neurodegenerative diseases. We hope that further elucidating the bidirectional communication between mast cells and the GBA will not only stimulate future research on neurodegenerative diseases but will also identify new opportunities for therapeutic interventions.

From the Role of Microbiota in Gut-Lung Axis to SARS-CoV-2 Pathogenesis

Severe acute respiratory syndrome-coronavirus 2 (SARS-CoV-2) is responsible for the outbreak of a new viral respiratory infection. It has been demonstrated that the microbiota has a crucial role in establishing immune responses against respiratory infections, which are controlled by a bidirectional cross-talk, known as the “gut-lung axis.” The effects of microbiota on antiviral immune responses, including dendritic cell (DC) function and lymphocyte homing in the gut-lung axis, have been reported in the recent literature. Additionally, the gut microbiota composition affects (and is affected by) the expression of angiotensin-converting enzyme-2 (ACE2), which is the main receptor for SARS-CoV-2 and contributes to regulate inflammation. Several studies demonstrated an altered microbiota composition in patients infected with SARS-CoV-2, compared to healthy individuals. Furthermore, it has been shown that vaccine efficacy against viral respiratory infection is influenced by probiotics pretreatment. Therefore, the importance of the gut microbiota composition in the lung immune system and ACE2 expression could be valuable to provide optimal therapeutic approaches for SARS-CoV-2 and to preserve the symbiotic relationship of the microbiota with the host.

Association of food hypersensitivity in children with the risk of autism spectrum disorder: a meta-analysis

This meta-analysis was performed to clarify the association between food hypersensitivity in children and autism spectrum disorder (ASD) in detail. Relevant studies published in 8 databases before March 2020 were retrieved and screened according to established inclusion criteria. The odds ratio (OR) with the 95% confidence interval (CI) was pooled to estimate the effect. Subgroup analyses were performed in terms of publication year, study design, location, sample size, definition of food hypersensitivity, definition of ASD, and study quality score. Furthermore, we stratified studies by participant sex and age to perform a more detailed analysis. This meta-analysis included 12 published articles with 434,809 subjects. A significant association was observed between food hypersensitivity and the risk of ASD (OR = 2.792, 95% CI: 2.081-3.746). The risk of ASD among girls and subjects younger than 12 with food hypersensitivity may be greater than that among boys and those older than 12. The results of sensitivity analysis and publication bias analysis show that the association is relatively stable.Conclusion: Our results showed a positive association between food hypersensitivity and autism spectrum disorder, and girls and subjects younger than 12 may be more sensitive to this association. The role of food hypersensitivity in the onset of ASD deserves more attention. What is Known: • Food hypersensitivity is a term used to describe food allergies and food intolerance. • ASD is a group of neurodevelopmental disorders that are characterized by deficits in social interaction, repetitive or stereotypic behavior, and verbal communication disorder. • The prevalence rates of ASD and food hypersensitivity in the developed world are increasing. What is New: • In this work, we reviewed and analyzed the available data and studies and found a positive association between food hypersensitivity and ASD. • Girls and children younger than 12 may be more sensitive to have ASD than boys and children older than 12.

Unravelling the potential of gut microbiota in sustaining brain health and their current prospective towards development of neurotherapeutics

Increasing incidences of neurological disorders, such as Parkinson's disease (PD), multiple sclerosis (MS), Alzheimer's disease (AD) and amyotrophic lateral sclerosis (ALS) are being reported, but an insight into their pathology remains elusive. Findings have suggested that gut microbiota play a major role in regulating brain functions through the gut-brain axis. A unique bidirectional communication between gut microbiota and maintenance of brain health could play a pivotal role in regulating incidences of neurodegenerative diseases. Contrarily, the present life style with changing food habits and disturbed circadian rhythm may contribute to gut homeostatic imbalance and dysbiosis leading to progression of several neurological disorders. Therefore, dysbiosis, as a primary factor behind intestinal disorders, may also augment inflammation, intestinal and blood-brain barrier permeability through microbiota-gut-brain axis. This review primarily focuses on the gut-brain axis functions, specific gut microbial population, metabolites produced by gut microbiota, their role in regulating various metabolic processes and role of gut microbiota towards development of neurodegenerative diseases. However, several studies have reported a decrease in abundance of a specific gut microbial population and a corresponding increase in other microbial family, with few findings revealing some contradictions. Reports also showed that colonization of gut microbiota isolated from patients suffering from neurodegenerative disease leads to the development of enhance pathological outcomes in animal models. Hence, a systematic understanding of the dominant role of specific gut microbiome towards development of different neurodegenerative diseases could possibly provide novel insight into the use of probiotics and microbial transplantation as a substitute approach for treating/preventing such health maladies.

The Contribution of Gut Microbiota-Brain Axis in the Development of Brain Disorders

Different bacterial families colonize most mucosal tissues in the human organism such as the skin, mouth, vagina, respiratory, and gastrointestinal districts. In particular, the mammalian intestine hosts a microbial community of between 1,000 and 1,500 bacterial species, collectively called "microbiota." Co-metabolism between the microbiota and the host system is generated and the symbiotic relationship is mutually beneficial. The balance that is achieved between the microbiota and the host organism is fundamental to the organization of the immune system. Scientific studies have highlighted a direct correlation between the intestinal microbiota and the brain, establishing the existence of the gut microbiota-brain axis. Based on this theory, the microbiota acts on the development, physiology, and cognitive functions of the brain, although the mechanisms involved have not yet been fully interpreted. Similarly, a close relationship between alteration of the intestinal microbiota and the onset of several neurological pathologies has been highlighted. This review aims to point out current knowledge as can be found in literature regarding the connection between intestinal dysbiosis and the onset of particular neurological pathologies such as anxiety and depression, autism spectrum disorder, and multiple sclerosis. These disorders have always been considered to be a consequence of neuronal alteration, but in this review, we hypothesize that these alterations may be non-neuronal in origin, and consider the idea that the composition of the microbiota could be directly involved. In this direction, the following two key points will be highlighted: (1) the direct cross-talk that comes about between neurons and gut microbiota, and (2) the degree of impact of the microbiota on the brain. Could we consider the microbiota a valuable target for reducing or modulating the incidence of certain neurological diseases?

The Hygiene Hypothesis and New Perspectives-Current Challenges Meeting an Old Postulate

During its 30 years history, the Hygiene Hypothesis has shown itself to be adaptable whenever it has been challenged by new scientific developments and this is a still a continuously ongoing process. In this regard, the mini review aims to discuss some selected new developments in relation to their impact on further fine-tuning and expansion of the Hygiene Hypothesis. This will include the role of recently discovered classes of innate and adaptive immune cells that challenges the old Th1/Th2 paradigm, the applicability of the Hygiene Hypothesis to newly identified allergy/asthma phenotypes with diverse underlying pathomechanistic endotypes, and the increasing knowledge derived from epigenetic studies that leads to better understanding of mechanisms involved in the translation of environmental impacts on biological systems. Further, we discuss in brief the expansion of the Hygiene Hypothesis to other disease areas like psychiatric disorders and cancer and conclude that the continuously developing Hygiene Hypothesis may provide a more generalized explanation for health burden in highly industrialized countries also relation to global changes.

The Role of Intestinal Flora in the Regulation of Bone Homeostasis

Intestinal flora located within the intestinal tract comprises a large number of cells, which are referred to as the second gene pool of the human body and form a complex symbiotic relationship with the host. The knowledge of the complex interaction between the intestinal flora and various life activities of the host is a novel and rapidly expanding field. Recently, many studies are being conducted on the relationship between the intestinal flora and bone homeostasis and indicate that the intestinal flora can regulate bone homeostasis via the host immune, metabolic, and endocrine systems. What’s more, based on several clinical and preclinical pieces of evidence, changing the composition and function of the host intestinal flora through the application of probiotics, prebiotics, and fecal microbiota transplantation is being considered to be a potential novel target for the regulation of bone homeostasis. Here, we searched relevant literature and reviewed the role of the intestinal flora in the regulation of bone homeostasis and its modulating interventions.

Translational Approaches with Antioxidant Phytochemicals against Alcohol-Mediated Oxidative Stress, Gut Dysbiosis, Intestinal Barrier Dysfunction, and Fatty Liver Disease

Emerging data demonstrate the important roles of altered gut microbiomes (dysbiosis) in many disease states in the peripheral tissues and the central nervous system. Gut dysbiosis with decreased ratios of Bacteroidetes/Firmicutes and other changes are reported to be caused by many disease states and various environmental factors, such as ethanol (e.g., alcohol drinking), Western-style high-fat diets, high fructose, etc. It is also caused by genetic factors, including genetic polymorphisms and epigenetic changes in different individuals. Gut dysbiosis, impaired intestinal barrier function, and elevated serum endotoxin levels can be observed in human patients and/or experimental rodent models exposed to these factors or with certain disease states. However, gut dysbiosis and leaky gut can be normalized through lifestyle alterations such as increased consumption of healthy diets with various fruits and vegetables containing many different kinds of antioxidant phytochemicals. In this review, we describe the mechanisms of gut dysbiosis, leaky gut, endotoxemia, and fatty liver disease with a specific focus on the alcohol-associated pathways. We also mention translational approaches by discussing the benefits of many antioxidant phytochemicals and/or their metabolites against alcohol-mediated oxidative stress, gut dysbiosis, intestinal barrier dysfunction, and fatty liver disease.

The interplay between gut microbiota and autism spectrum disorders: A focus on immunological pathways

Autism spectrum disorders (ASD) are a group of neurodevelopmental disorders characterized by impairments in social and cognitive activities, stereotypical and repetitive behaviors and restricted areas of interest. A remarkable proportion of ASD patients represent immune dysregulation as well as gastrointestinal complications. Hence, a novel concept has recently emerged, addressing the possible intercommunication between the brain, the immune system, the gut and its commensals. Here, we provide an overview of how gut microbes and their metabolites are associated with neurobehavioral features of ASD through various immunologic mechanisms. Moreover, we discuss the potential therapeutic options that could modify these features.

Gut microbiota dysbiosis is associated with worse emotional states in HIV infection

The biological mechanisms underlying emotional distress in HIV infection are likely to be complex but remain understudied. We investigated whether dysbiotic signatures in the gut microbiome of persons living with HIV (PLWH) are associated with their emotional status. We retrospectively examined the gut microbiome and clinical evaluation of 129 adults (94 PLWH and 35 HIV-) enrolled at UC San Diego's HIV Neurobehavioral Research Program. A subset of participants (32 PLWH vs. 13 HIV-) underwent an emotional assessment using the NIH Toolbox Emotion Battery summarized by three composite scores (negative affect, social satisfaction, and psychological well-being). We then sequenced the 16S rDNA V3-V4 regions from stool and performed taxonomic assignment using CLC Microbial Genomics Module. The gut microbiota profiles were evaluated in relation to participants' emotional assessment. All analyses were done in R statistical software. We found that the relative abundance of aerotolerant bacteria was significantly higher in PLWH (p < 0.01) and was associated with a lifetime major depression diagnosis independently of HIV status (p = 0.05). Moreover, PLWH experienced significantly worse psychological well-being (p = 0.02), less social satisfaction (p = 0.03), and more negative affect (p = 0.02). Higher levels of aerotolerant bacteria were associated with worse psychological well-being (rho = -0.35, p = 0.02), less social satisfaction (r = - 0.42, p < 0.01), and more negative affect (rho = 0.46, p < 0.01). The association of aerotolerant bacteria with social satisfaction and negative affect was independent of HIV status (p < 0.05, for both). The over-representation of aerotolerant bacteria in the gut may reflect worse oxidative stress and barrier defects and may contribute to emotional distress during HIV infection.