Prenatal stress-induced alterations in major physiological systems correlate with gut microbiota composition in adulthood

Microbial reconstitution reverses prenatal stress-induced cognitive impairment and synaptic deficits in rat offspring

Stress during pregnancy is often linked with increased incidents of neurodevelopmental disorders, including cognitive impairment. Here, we report that stress during pregnancy leads to alterations in the intestinal flora, which negatively affects the cognitive function of offspring. Cognitive impairment in stressed offspring can be reproduced by transplantation of cecal contents of stressed pregnant rats (ST) to normal pregnant rats. In addition, gut microbial dysbiosis results in an increase of β-guanidinopropionic acid in the blood, which leads to an activation of the adenosine monophosphate-activated protein kinase (AMPK) and signal transducer and activator of transcription 3 (STAT3) in the fetal brain. Moreover, β-guanidinopropionic acid supplementation in pregnant rats can reproduce pregnancy stress-induced enhanced glial differentiation of the fetal brain, resulting in impaired neural development. Using probiotics to reconstruct maternal microbiota can correct the cognitive impairment in the offspring of pregnant stressed rats. These findings suggest that microbial reconstitution reverses gestational stress-induced cognitive impairment and synaptic deficits in male rat offspring.

Absence of association between maternal adverse events and long-term gut microbiome outcomes in the Australian autism biobank

Introduction

Maternal immune activation (MIA) and prenatal maternal stress (MatS) are well-studied risk factors for psychiatric conditions such as autism and schizophrenia. Animal studies have proposed the gut microbiome as a mechanism underlying this association and have found that risk factor-related gut microbiome alterations persist in the adult offspring. In this cross-sectional study, we assessed whether maternal immune activation and prenatal maternal stress were associated with long-term gut microbiome alterations in children using shotgun metagenomics.

Methods

This cross-sectional study included children diagnosed with autism (N = 92), siblings without a diagnosis (N = 42), and unrelated children (N = 40) without a diagnosis who were recruited into the Australian Autism Biobank and provided a faecal sample. MIA exposure was inferred from self-reported data and included asthma/allergies, complications during pregnancy triggering an immune response, auto-immune conditions, and acute inflammation. Maternal stress included any of up to 9 stressful life events during pregnancy, such as divorce, job loss, and money problems. Data were analysed for a total of 174 children, of whom 63 (36%) were born to mothers with MIA and 84 (48%) were born to mothers who experienced maternal stress during pregnancy (where 33 [19%] experienced both). Gut microbiome data was assessed using shotgun metagenomic sequencing of the children's faecal samples.

Results

In our cohort, MIA, but not MatS, was associated with ASD. Variance component analysis revealed no associations between any of the gut microbiome datasets and neither MIA nor MatS. After adjusting for age, sex, diet and autism diagnosis, there was no significant difference between groups for bacterial richness, α-diversity or β-diversity. We found no significant differences in species abundance in the main analyses. However, when stratifying the cohort by age, we found that Faecalibacterium prausnitzii E was significantly decreased in MIA children aged 11-17.

Discussion

Consistent with previous findings, we found that children who were born to mothers with MIA were more likely to be diagnosed with autism. Unlike within animal studies, we found negligible microbiome differences associated with MIA and maternal stress. Given the current interest in the microbiome-gut-brain axis, researchers should exercise caution in translating microbiome findings from animal models to human contexts and the clinical setting.

Early Life Adversity, Microbiome, and Inflammatory Responses

Early life adversity has a profound impact on physical and mental health. Because the central nervous and immune systems are not fully mature at birth and continue to mature during the postnatal period, a bidirectional interaction between the central nervous system and the immune system has been hypothesized, with traumatic stressors during childhood being pivotal in priming individuals for later adult psychopathology. Similarly, the microbiome, which regulates both neurodevelopment and immune function, also matures during childhood, rendering this interaction between the brain and the immune system even more complex. In this review, we provide evidence for the role of the immune response and the microbiome in the deleterious effects of early life adversity, both in humans and rodent models.

Prenatal stress impacts foetal neurodevelopment: Temporal windows of gestational vulnerability

Prenatal maternal stressors ranging in severity from everyday occurrences/hassles to the experience of traumatic events negatively impact neurodevelopment, increasing the risk for the onset of psychopathology in the offspring. Notably, the timing of prenatal stress exposure plays a critical role in determining the nature and severity of subsequent neurodevelopmental outcomes. In this review, we evaluate the empirical evidence regarding temporal windows of heightened vulnerability to prenatal stress with respect to motor, cognitive, language, and behavioural development in both human and animal studies. We also explore potential temporal windows whereby several mechanisms may mediate prenatal stress-induced neurodevelopmental effects, namely, excessive hypothalamic-pituitary-adrenal axis activity, altered serotonin signalling and sympathetic-adrenal-medullary system, changes in placental function, immune system dysregulation, and alterations of the gut microbiota. While broadly defined developmental windows are apparent for specific psychopathological outcomes, inconsistencies arise when more complex cognitive and behavioural outcomes are considered. Novel approaches to track molecular markers reflective of the underlying aetiologies throughout gestation to identify tractable biomolecular signatures corresponding to critical vulnerability periods are urgently required.

Biogeography of intestinal mucus-associated microbiome: Depletion of genus Pseudomonas is associated with depressive-like behaviors in female cynomolgus macaques

INTRODUCTION

Depression is a debilitating and poorly understood mental disorder. There is an urgency to explore new potential biological mechanisms of depression and the gut microbiota is a promising research area.

OBJECTIVES

Our study was aim to understand regional heterogeneity and potential molecular mechanisms underlying depression induced by dysbiosis of mucus-associated microbiota.

METHODS

Here, we only selected female macaques because they are more likely to form a natural social hierarchy in a harem-like environment. Because high-ranking macaques rarely displayed depressive-like behaviors, we selected seven monkeys from high-ranking individuals as control group (HC) and the same number of low-ranking ones as depressive-like group (DL), which displayed significant depressive-like behaviors. Then, we collected mucus from the duodenum, jejunum, ileum, cecum and colon of DL and HC monkeys for shotgun metagenomic sequencing, to profile the biogeography of mucus-associated microbiota along duodenum to colon.

RESULTS

Compared with HC, DL macaques displayed noticeable depressive-like behaviors such as longer duration of huddle and sit alone behaviors (negative emotion behaviors), and fewer duration of locomotion, amicable and ingestion activities (positive emotion behaviors). Moreover, the alpha diversity index (Chao) could predict aforementioned depressive-like behaviors along duodenum to colon. Further, we identified that genus Pseudomonas was consistently decreased in DL group throughout the entire intestinal tract except for the jejunum. Specifically, there were 10, 18 and 28 decreased Pseudomonas spp. identified in ileum, cecum and colon, respectively. Moreover, a bacterial module mainly composed of Pseudomonas spp. was positively associated with three positive emotion behaviors. Functionally, Pseudomonaswas mainly involved in microbiota derived lipid metabolisms such as PPAR signaling pathway, cholesterol metabolism, and fat digestion and absorption.

CONCLUSION

Different regions of intestinal mucus-associated microbiota revealed that depletion of genus Pseudomonas is associated with depressive-like behaviors in female macaques, which might induce depressive phenotypes through regulating lipid metabolism.

A gut (microbiome) feeling about addiction: Interactions with stress and social systems

In recent years, an increasing attention has given to the intricate and diverse connection of microorganisms residing in our gut and their impact on brain health and central nervous system disease. There has been a shift in mindset to understand that drug addiction is not merely a condition that affects the brain, it is now being recognized as a disorder that also involves external factors such as the intestinal microbiota, which could influence vulnerability and the development of addictive behaviors. Furthermore, stress and social interactions, which are closely linked to the intestinal microbiota, are powerful modulators of addiction. This review delves into the mechanisms through which the microbiota-stress-immune axis may shape drug addiction and social behaviors. This work integrates preclinical and clinical evidence that demonstrate the bidirectional communication between stress, social behaviors, substance use disorders and the gut microbiota, suggesting that gut microbes might modulate social stress having a significance in drug addiction.

How gut microbiota may impact ocular surface homeostasis and related disorders

Changes in the bacterial flora in the gut, also described as gut microbiota, are readily acknowledged to be associated with several systemic diseases, especially those with an inflammatory, neuronal, psychological or hormonal factor involved in the pathogenesis and/or the perception of the disease. Maintaining ocular surface homeostasis is also based on all these four factors, and there is accumulating evidence in the literature on the relationship between gut microbiota and ocular surface diseases. The mechanisms involved are mostly interconnected due to the interaction of central and peripheral neuronal networks, inflammatory effectors and the hormonal system. A better understanding of the influence of the gut microbiota on the maintenance of ocular surface homeostasis, and on the onset or persistence of ocular surface disorders could bring new insights and help elucidate the epidemiology and pathology of ocular surface dynamics in health and disease. Revealing the exact nature of these associations could be of paramount importance for developing a holistic approach using highly promising new therapeutic strategies targeting ocular surface diseases.

Affective Symptoms in Pregnancy are Associated with the Vaginal Microbiome

Composition of the vaginal microbiome in pregnancy is associated with adverse maternal, obstetric, and child health outcomes. Identifying the sources of individual differences in the vaginal microbiome is therefore of considerable clinical and public health interest. The current study tested the hypothesis that vaginal microbiome composition during pregnancy is associated with an individual's experience of affective symptoms and stress exposure. Data were based on a prospective longitudinal study of a diverse and medically healthy community sample of 275 mother-infant pairs. Affective symptoms and stress exposure and select measures of associated biomarkers (diurnal salivary cortisol, serum measures of sex hormones) were collected at each trimester; self-report, clinical, and medical records were used to collect detailed data on socio-demographic factors and health behavior, including diet and sleep. Vaginal microbiome samples were collected in the third trimester (34-40 weeks) and characterized by 16S rRNA sequencing. Identified taxa were clustered into three community state types (CST1-3) based on dissimilarity of vaginal microbiota composition. Results indicate that depressive symptoms during pregnancy were reliably associated with individual taxa and CST3 in the third trimester. Prediction of functional potential from 16S taxonomy revealed a differential abundance of metabolic pathways in CST1-3 and individual taxa, including biosynthetic pathways for the neuroactive metabolites, serotonin and dopamine. With the exception of bioavailable testosterone, no significant associations were found between symptoms- and stress-related biomarkers and CSTs. Our results provide further evidence of how prenatal psychological distress during pregnancy alters the maternal-fetal microbiome ecosystem that may be important for understanding maternal and child health outcomes.

Association between gut microbiota and male infertility: a two-sample Mendelian randomization study

Previous research has confirmed the significant association between gut microbiota (GM) and male infertility (MI), but the causality between them remains unclear. This study aims to investigate the causal relationship between GM and MI using Mendelian randomization (MR) and provide supplementary information for the optimization of future randomized controlled trials (RCTs). Instrumental variables for 211 GM taxa were obtained from genome-wide association studies (GWAS), and inverse variance weighted (IVW) method was used as the main analysis method for two-sample MR analysis to assess the impact of GM on the risk of MI. Four methods were used to test for horizontal pleiotropy and heterogeneity of MR results to ensure the reliability of the MR findings. A total of 50 single-nucleotide polymorphisms (SNPs) closely related to GM were included, and ultimately identified 1 family and 4 general are causally associated with MI. Among them, Anaerotruncus (OR = 1.96, 95% CI 1.31-3.40, P = 0.016) is significantly associated with increased MI risk. Furthermore, we used four MR methods to evaluate the causality, and the results supported these findings. The leave-one-out analysis showed stable results with no instrumental variables exerting strong influence on the results. The causal direction indicated a positive effect, and the effects of heterogeneity and horizontal pleiotropy on the estimation of causal effect were minimized. We confirmed a causal relationship between GM taxa and MI, providing new insights into the mechanisms underlying GM-mediated MI.

The gut microbiome modulates the susceptibility to traumatic stress in a sex-dependent manner

Post-traumatic stress disorder (PTSD), a psychological condition triggered by exposure to extreme or chronic stressful events, exhibits a sex bias in incidence and clinical manifestations. Emerging research implicates the gut microbiome in the pathogenesis of PTSD and its roles in stress susceptibility. However, it is unclear whether differential gut microbiota contribute to PTSD susceptibility in male and female rats. Here, we utilized the single prolonged stress animal model and employed unsupervised machine learning to classify stressed animals into stress-susceptible subgroups and stress-resilient subgroups. Subsequently, using 16S V3-V4 rDNA sequencing, we investigated the differential gut microbiota alterations between susceptible and resilient individuals in male and female rats. Our findings revealed distinct changes in gut microbiota composition between the sexes at different taxonomic levels. Furthermore, the abundance of Parabacteroides was lower in rats that underwent SPS modeling compared to the control group. In addition, the abundance of Tenericutes in the stress-susceptible subgroup was higher than that in the control group and stress-resilient subgroup, suggesting that Tenericutes may be able to characterize stress susceptibility. What is particularly interesting here is that Cyanobacteria may be particularly associated with anti-anxiety effects in male rats. This study underscores sex-specific variations in gut microbiota composition in response to stress and sex differences should be taken into account when using macrobiotics for neuropsychiatric treatment, highlighting potential targets for PTSD therapeutic interventions.

The Interaction between Stress and Inflammatory Bowel Disease in Pediatric and Adult Patients

Background: Inflammatory bowel diseases (IBDs) have seen an exponential increase in incidence, particularly among pediatric patients. Psychological stress is a significant risk factor influencing the disease course. This review assesses the interaction between stress and disease progression, focusing on articles that quantified inflammatory markers in IBD patients exposed to varying degrees of psychological stress. Methods: A systematic narrative literature review was conducted, focusing on the interaction between IBD and stress among adult and pediatric patients, as well as animal subjects. The research involved searching PubMed, Scopus, Medline, and Cochrane Library databases from 2000 to December 2023. Results: The interplay between the intestinal immunity response, the nervous system, and psychological disorders, known as the gut-brain axis, plays a major role in IBD pathophysiology. Various types of stressors alter gut mucosal integrity through different pathways, increasing gut mucosa permeability and promoting bacterial translocation. A denser microbial load in the gut wall emphasizes cytokine production, worsening the disease course. The risk of developing depression and anxiety is higher in IBD patients compared with the general population, and stress is a significant trigger for inducing acute flares of the disease. Conclusions: Further large studies should be conducted to assess the relationship between stressors, psychological disorders, and their impact on the course of IBD. Clinicians involved in the medical care of IBD patients should aim to implement stress reduction practices in addition to pharmacological therapies.

Adolescence, the Microbiota-Gut-Brain Axis, and the Emergence of Psychiatric Disorders

Second only to early life, adolescence is a period of dramatic change and growth. For the developing young adult, this occurs against a backdrop of distinct environmental challenges and stressors. A significant body of work has identified an important role for the microbiota-gut-brain (MGB) axis in the development and function of the brain. Given that the MGB axis is both highly plastic during the teenage years and vulnerable to environmental stressors, more attention needs to be drawn to its potential role in the emergence of psychiatric illnesses, many of which first manifest during adolescence. Here, we review the current literature surrounding the developing microbiome, enteric nervous system, vagus nerve, and brain during the adolescent period. We also examine preclinical and clinical research involving the MGB axis during this dynamic developmental window and argue that more research is needed to further understand the role of the MGB in the pathogenesis of brain disorders. Greater understanding of the adolescent MGB axis will open up the exciting potential for new microbial-based therapeutics for the treatment of these often-refractory psychiatric illnesses.

Stressed to the Core: Inflammation and Intestinal Permeability Link Stress-Related Gut Microbiota Shifts to Mental Health Outcomes

Stress levels are surging, alongside the incidence of stress-related psychiatric disorders. Perhaps a related phenomenon, especially in urban areas, the human gut contains fewer bacterial species than ever before. Although the functional implications of this absence are unclear, one consequence may be reduced stress resilience. Preclinical and clinical evidence has shown how stress exposure can alter the gut microbiota and their metabolites, affecting host physiology. Also, stress-related shifts in the gut microbiota jeopardize tight junctions of the gut barrier. In this context, bacteria and bacterial products can translocate from the gut to the bloodstream, lymph nodes, and other organs, thereby modifying systemic inflammatory responses. Heightened circulating inflammation can be an etiological factor in stress-related psychiatric disorders, including some cases of depression. In this review, we detail preclinical and clinical evidence that traces these brain-to-gut-to-brain pathways that underlie stress-related psychiatric disorders and potentially affect their responsivity to conventional psychiatric medications. We also review evidence for interventions that modulate the gut microbiota (e.g., antibiotics, probiotics, prebiotics) to reduce stress responses and psychiatric symptoms. Lastly, we discuss challenges to translation and opportunities for innovations that could impact future psychiatric clinical practice.

Stress in the microbiome-immune crosstalk

The gut microbiota exerts a mutualistic interaction with the host in a fragile ecosystem and the host intestinal, neural, and immune cells. Perturbations of the gastrointestinal track composition after stress have profound consequences on the central nervous system and the immune system. Reciprocally, brain signals after stress affect the gut microbiota highlighting the bidirectional communication between the brain and the gut. Here, we focus on the potential role of inflammation in mediating stress-induced gut-brain changes and discuss the impact of several immune cells and inflammatory molecules of the gut-brain dialogue after stress. Understanding the impact of microbial changes on the immune system after stress might provide new avenues for therapy.

Maternal stress during the third trimester of pregnancy and the neonatal microbiome

OBJECTIVES

Preliminary research suggests that maternal prenatal stress may alter the development of the fetal microbiome and resulting microbial composition after birth. However, the findings of existing studies are mixed and inconclusive. The purpose of this exploratory study was to assess whether maternal stress during pregnancy is associated with the overall number and diversity of various microbial species in the infant gut microbiome or the abundance of specific bacterial taxa.

METHODS

Fifty-one women were recruited during their third trimester of pregnancy. The women completed a demographic questionnaire and Cohen's Perceived Stress Scale at recruitment. A stool sample was collected from their neonate at one month of age. Data on potential confounders, such as gestational age and mode of delivery, were extracted from medical records to control for their effects. 16s rRNA gene sequencing was used to identify the diversity and abundance of microbial species, along with multiple linear regression models to examine the effects of prenatal stress on microbial diversity. We employed negative binomial generalized linear models to test for differential expression of various microbial taxa among infants exposed to prenatal stress and those not exposed to prenatal stress.

RESULTS

More severe symptoms of prenatal stress were associated with a greater diversity of microbial species in the gut microbiome of neonates (β = .30, p = .025). Certain microbial taxa, such as Lactobacillus and Bifidobacterium, were enriched among infants exposed to greater maternal stress in utero, while others, such as Bacteroides and Enterobacteriaceae, were depleted in contrast to infants exposed to less stress.

CONCLUSIONS

Findings suggest that mild to moderate stress exposure in utero could be associated with a microbial environment in early life that is more optimally prepared to thrive in a stressful postnatal environment. Adaptation of gut microbiota under conditions of stress may involve upregulation of bacterial species, including certain protective microorganisms (e.g. Bifidobacterium), as well as downregulation of potential pathogens (e.g. Bacteroides) via epigenetic or other processes within the fetal/neonatal gut-brain axis. However, further research is needed to understand the trajectory of microbial diversity and composition as infant development proceeds and the ways in which both the structure and function of the neonatal microbiome may mediate the relationship between prenatal stress and health outcomes over time. These studies may eventually yield microbial markers and gene pathways that are biosignatures of risk or resilience and inform targets for probiotics or other therapies in utero or during the postnatal period.

Long-term and trimester-specific effects of prenatal stress on the child gut microbiota

OBJECTIVE

Stress is common among pregnant individuals and is associated with an altered gut microbiota composition in infants. It is unknown if these compositional changes persist into the preschool years when the gut microbiota reaches an adult-like composition. This study aimed to investigate if indicators of prenatal stress (i.e., psychological distress and stress-related physiology) are associated with children's gut microbiota composition and metabolites at 3-4 years of age.

METHODS

Maternal-child pairs (n = 131) were from the Alberta Pregnancy Outcomes and Nutrition (APrON) cohort. Each trimester, psychological distress was measured as symptoms of anxiety (Symptom Checklist-90-R) and depressed mood (Edinburgh Postnatal Depression Scale), whereas salivary cortisol was quantified as a measure of stress-related physiology. Child stool samples were collected at 3-4 years to evaluate gut microbiota composition using 16S rRNA gene sequencing and fecal metabolome using liquid chromatography with tandem mass spectrometry (LC-MS/MS). Associations between prenatal distress and cortisol with the gut microbiota were determined using Pearson and Spearman correlations and corrected for multiple testing. Associations between prenatal distress and cortisol with the fecal metabolome were assessed using Metaboanalyst.

RESULTS

Symptoms of depressed mood during the 2nd and 3rd trimesters and anxiety during the 2nd trimester of pregnancy were associated with increased alpha diversity of the child's gut microbiota. Cortisol levels during the 1st trimester were also associated with increased Faith PD diversity (r = 0.32), whereas cortisol levels during the 2nd trimester were associated with reduced Shannon diversity (r = -0.27). Depression scores during the 2nd and 3rd trimesters were associated with reductions in the relative abundances of Eggerthella, Parasutterella, and increases in Ruminococcaceae (rs = -0.28, rs = -0.32, rs = 0.32, respectively), as well as the fecal metabolome (e.g., branched-chain amino acid metabolism). Cortisol levels during the 2nd trimester correlated with 7 bacterial taxa, whereas 1st-trimester cortisol levels were associated with the child's fecal metabolome.

CONCLUSIONS

Prenatal distress and cortisol were associated with both child gut microbiota composition and fecal metabolome at preschool age. Understanding these associations may allow for the identification of microbiota-targeted interventions to support child developmental outcomes affected by prenatal stress.

The impact of acute and chronic stress on gastrointestinal physiology and function: a microbiota-gut-brain axis perspective

The physiological consequences of stress often manifest in the gastrointestinal tract. Traumatic or chronic stress is associated with widespread maladaptive changes throughout the gut, although comparatively little is known about the effects of acute stress. Furthermore, these stress-induced changes in the gut may increase susceptibility to gastrointestinal disorders and infection, and impact critical features of the neural and behavioural consequences of the stress response by impairing gut-brain axis communication. Understanding the mechanisms behind changes in enteric nervous system circuitry, visceral sensitivity, gut barrier function, permeability, and the gut microbiota following stress is an important research objective with pathophysiological implications in both neurogastroenterology and psychiatry. Moreover, the gut microbiota has emerged as a key aspect of physiology sensitive to the effects of stress. In this review, we focus on different aspects of the gastrointestinal tract including gut barrier function as well as the immune, humoral and neuronal elements involved in gut-brain communication. Furthermore, we discuss the evidence for a role of stress in gastrointestinal disorders. Existing gaps in the current literature are highlighted, and possible avenues for future research with an integrated physiological perspective have been suggested. A more complete understanding of the spatial and temporal dynamics of the integrated host and microbial response to different kinds of stressors in the gastrointestinal tract will enable full exploitation of the diagnostic and therapeutic potential in the fast-evolving field of host-microbiome interactions.

Male infertility risk and gut microbiota: a Mendelian randomization study

Background

In recent decades, the decline of male sperm quality has become a worldwide phenomenon, with sperm quality of critical importance for the ability to conceive naturally. Recent studies suggest that male fertility function is closely linked to the gut microbiota, however, the cause-and-effect association between the gut microbiota and male infertility risk is currently unclear.

Methods

We performed one two-sample Mendelian randomization (MR) study, which uses summary data on human gut microbiota from the MiBioGen consortium as factors of exposure. FinnGen Consortium R8 data was used to obtain GWAS data for male infertility. To evaluate cause-and-effect associations linking gut microbiota and male infertility risk with multiple Mendelian randomization methods, we included inverse variance weighted (IVW), MR-Egger, and Maximum Likelihood (ML) Ratio. The heterogeneity of instrumental variables was evaluated through Cochran's Q, Rucker's Q, and leave-one-out analysis methods.

Results

We found a positive association between Allisonella, Anaerotruncus, Barnesiella, Intestinibacter, and Lactococcus with male infertility risk according to the MR analysis results. Bacteroides Romboutsia, Ruminococcaceae (NK4A2140group), and Ruminococcaceae (UCG011) play a protective function in male infertility pathogenesis.

Conclusion

It was found that gut microbiota and infertility are causally related in this study. In subsequent studies, there is a need to build a larger and more comprehensive GWAS database on male infertility, which will reveal the underlying mechanisms for gut microbiota and male infertility. There is a need for randomized controlled trials for validating the protective effect of the associated gut microbiota against male infertility risk, and for exploring the associated mechanisms.

Overview of the Gut Microbiome

The human gastrointestinal tract is home to trillions of microorganisms-collectively referred to as the gut microbiome-that maintain a symbiotic relationship with their host. This diverse community of microbes grows and changes as we do, with developmental, lifestyle, and environmental factors all shaping microbiome community structure. Increasing evidence suggests this relationship is bidirectional, with the microbiome also influencing host physiological processes. For example, changes in the gut microbiome have been shown to alter neurodevelopment and have lifelong effects on the brain and behavior. Age-related changes in gut microbiome composition have also been linked to inflammatory changes in the brain, perhaps increasing susceptibility to neurological disease. Indeed, associations between gut dysbiosis and many age-related neurological diseases-including Parkinson's disease, Alzheimer's disease, multiple sclerosis, and amyotrophic lateral sclerosis-have been reported. Further, microbiome manipulation in animal models of disease highlights a potential role for the gut microbiome in disease development and progression. Although much remains unknown, these associations open up an exciting new world of therapeutic targets, potentially allowing for improved quality of life for a wide range of patient populations.

The long-term gut bacterial signature of a wild primate is associated with a timing effect of pre- and postnatal maternal glucocorticoid levels

BACKGROUND

During development, elevated levels of maternal glucocorticoids (GCs) can have detrimental effects on offspring morphology, cognition, and behavior as well as physiology and metabolism. Depending on the timing of exposure, such effects may vary in strength or even reverse in direction, may alleviate with age, or may concern more stable and long-term programming of phenotypic traits. Maternal effects on gut bacterial diversity, composition, and function, and the persistence of such effects into adulthood of long-lived model species in the natural habitats remain underexplored.

RESULTS

In a cross-sectional sample of infant, juvenile, and adult Assamese macaques, the timing of exposure to elevated maternal GCs during ontogeny was associated with the gut bacterial community of the offspring. Specifically, naturally varying maternal GC levels during early but not late gestation or lactation were associated with reduced bacterial richness. The overall effect of maternal GCs during early gestation on the gut bacterial composition and function exacerbated with offspring age and was 10 times stronger than the effect associated with exposure during late prenatal or postnatal periods. Instead, variation in maternal GCs during the late prenatal or postnatal period had less pronounced or less stable statistical effects and therefore a weaker effect on the entire bacterial community composition, particularly in adult individuals. Finally, higher early prenatal GCs were associated with an increase in the relative abundance of several potential pro-inflammatory bacteria and a decrease in the abundance of Bifidobacterium and other anti-inflammatory taxa, an effect that exacerbated with age.

CONCLUSIONS

In primates, the gut microbiota can be shaped by developmental effects with strong timing effects on plasticity and potentially detrimental consequences for adult health. Together with results on other macaque species, this study suggests potential detrimental developmental effects similar to rapid inflammaging, suggesting that prenatal exposure to high maternal GC concentrations is a common cause underlying both phenomena. Our findings await confirmation by metagenomic functional and causal analyses and by longitudinal studies of long-lived, ecologically flexible primates in their natural habitat, including developmental effects that originate before birth. Video Abstract.

Effects of Unconventional Work and Shift Work on the Human Gut Microbiota and the Potential of Probiotics to Restore Dysbiosis

The work environment is a factor that can significantly influence the composition and functionality of the gut microbiota of workers, in many cases leading to gut dysbiosis that will result in serious health problems. The aim of this paper was to provide a compilation of the different studies that have examined the influence of jobs with unconventional work schedules and environments on the gut microbiota of workers performing such work. As a possible solution, probiotic supplements, via modulation of the gut microbiota, can moderate the effects of sleep disturbance on the immune system, as well as restore the dysbiosis produced. Rotating shift work has been found to be associated with an increase in the risk of various metabolic diseases, such as obesity, metabolic syndrome, and type 2 diabetes. Sleep disturbance or lack of sleep due to night work is also associated with metabolic diseases. In addition, sleep disturbance induces a stress response, both physiologically and psychologically, and disrupts the healthy functioning of the gut microbiota, thus triggering an inflammatory state. Other workers, including military, healthcare, or metallurgy workers, as well as livestock farmers or long-travel seamen, work in environments and schedules that can significantly affect their gut microbiota.

Current Understanding of the Roles of Gut-Brain Axis in the Cognitive Deficits Caused by Perinatal Stress Exposure

The term 'perinatal environment' refers to the period surrounding birth, which plays a crucial role in brain development. It has been suggested that dynamic communication between the neuro-immune system and gut microbiota is essential in maintaining adequate brain function. This interaction depends on the mother's status during pregnancy and/or the newborn environment. Here, we show experimental and clinical evidence that indicates that the perinatal period is a critical window in which stress-induced immune activation and altered microbiota compositions produce lasting behavioral consequences, although a clear causative relationship has not yet been established. In addition, we discuss potential early treatments for preventing the deleterious effect of perinatal stress exposure. In this sense, early environmental enrichment exposure (including exercise) and melatonin use in the perinatal period could be valuable in improving the negative consequences of early adversities. The evidence presented in this review encourages the realization of studies investigating the beneficial role of melatonin administration and environmental enrichment exposure in mitigating cognitive alteration in offspring under perinatal stress exposure. On the other hand, direct evidence of microbiota restoration as the main mechanism behind the beneficial effects of this treatment has not been fully demonstrated and should be explored in future studies.

Stress, inflammation, microbiome and depression

Psychiatric disorders are mental illnesses involving changes in mood, cognition and behavior. Their prevalence has rapidly increased in the last decades. One of the most prevalent psychiatric disorders is major depressive disorder (MDD), a debilitating disease lacking efficient treatments. Increasing evidence shows that microbial and immunological changes contribute to the pathophysiology of depression and both are modulated by stress. This bidirectional relationship constitutes the brain-gut axis involving various neuroendocrine, immunological, neuroenterocrine and autonomic pathways. The present review covers the most recent findings on the relationships between stress, the gut microbiome and the inflammatory response and their contribution to depression.

The mediating role of gut microbiota in the associations of prenatal maternal combined exposure to lead and stress with neurodevelopmental deficits in young rats

Prenatal single and combined exposure to lead (Pb) and stress (Ps) impairs neurodevelopment. Prenatal single exposure to Pb or Ps affects the composition of intestinal microbiota, and bidirectional communication between gut microbiota and central nervous system has been well recognized. However, whether gut microbiota mediated the effects of prenatal Pb+Ps co-exposure on neurodevelopmental deficits remains unclear. This study established rat models with prenatal single and combined exposure to Ps and Pb. We investigated the effects of such prenatal single and combined exposure on hippocampal structures using morphological analyses, on learning/memory using the Morris-water-maze test, and on fecal microbiota using 16S rRNA sequencing. The mediating roles of gut microbiota were analyzed using the bootstrap method. The study found both single and combined exposure affected hippocampal ultra-structures and spatial learning/memory, and the most significant impairments were observed in the Pb+Ps group. Prenatal Pb+Ps co-exposure decreased fecal microbial alpha/beta-diversity. Significantly lower levels of B/F-ratio, class-Bacteroidia, order-Bacteroidales, and family-S24-7, and significantly higher levels of class-Bacilli, order-Lactobacillales, family-Lactobacillaceae, and genus-Lactobacillus were observed in the co-exposure group, compared with the controls. Increased relative abundances of genus-Helicobacter mediated the detrimental effect of prenatal Ps+Pb co-exposure on learning/memory [β (95%CI) for the total and indirect effects: - 10.70 (-19.19, -2.21) and - 4.65(-11.07, -1.85)], accounting for 43.47% of the total effect. As a result, increased relative abundances of genus-Lactobacillus alleviated the adverse effects of the co-exposure on learning/memory, and the alleviation effect accounted for 44.55% of the direct effect [β (95%CI) for the direct and indirect effects: - 0.28(-0.48, -0.08) and 0.13(0.01, 0.41)]. This study suggested that prenatal combined exposure to Pb and Ps induced more impairments in offspring gut microbiota and neurodevelopment than single exposure, and alterations in fecal microbiome may mediate the developmental neurotoxicity induced by such prenatal co-exposure.

The importance of gut-brain axis and use of probiotics as a treatment strategy for multiple sclerosis

It has been shown that the dysbiosis of the gut's microbes substantially impacts CNS illnesses, including Alzheimer's, Parkinson's, autism, and autoimmune diseases like multiple sclerosis (MS). MS is a CNS-affected autoimmune demyelination condition. Through a two-way communication pathway known as the gut-brain axis, gut microbes communicate with the CNS. When there is a disruption in the gut microbiome, cytokines and other immune cells are secreted, which affects the BBB and gastrointestinal permeability. Recent research using animal models has revealed that the gut microbiota may greatly influence the pathophysiology of EAE/MS. Any change in the gut might increase inflammatory cytokinesand affect the quantity of SCFAs, and other metabolites that cause neuroinflammation and demyelination. In- vivo and in-vitro studies have concluded that probiotics affect the immune system and can be utilized to treat gastrointestinal dysbiosis. Any alteration in the gut microbial composition caused by probiotic intake may serve as a preventive and treatment strategy for MS. The major goal of this review is to emphasize an overview of recent research on the function of gut microbiota in the onset of MS and how probiotics have a substantial impact on gastrointestinal disruption in MS and other neuro disorders. It will be easier to develop new therapeutic approaches, particularly probiotic-based supplements, for treating multiple sclerosis (MS) if we know the link between the gut and CNS.

Understanding the Connection between Gut Homeostasis and Psychological Stress

Long-term exposure to adverse life events that provoke acute or chronic psychological stress (hereinafter "stress") can negatively affect physical health and even increase susceptibility to psychological illnesses, such as anxiety and depression. As a part of the hypothalamic-pituitary-adrenal axis, corticotropin-releasing factor (CRF) released from the hypothalamus is primarily responsible for the stress response. Typically, CRF disrupts the gastrointestinal system and leads to gut microbiota dysbiosis, thereby increasing risk of functional gastrointestinal diseases, such as irritable bowel syndrome. Furthermore, CRF increases oxidative damage to the colon and triggers immune responses involving mast cells, neutrophils, and monocytes. CRF even affects the differentiation of intestinal stem cells (ISCs), causing enterochromaffin cells to secrete excessive amounts of 5-hydroxytryptamine (5-HT). Therefore, stress is often accompanied by damage to the intestinal epithelial barrier function, followed by increased intestinal permeability and bacterial translocation. There are multi-network interactions between the gut microbiota and stress, and gut microbiota may relieve the effects of stress on the body. Dietary intake of probiotics can provide energy for ISCs through glycolysis, thereby alleviating the disruption to homeostasis caused by stress, and it significantly bolsters the intestinal barrier, alleviates intestinal inflammation, and maintains endocrine homeostasis. Gut microbiota also directly affect the synthesis of hormones and neurotransmitters, such as CRF, 5-HT, dopamine, and norepinephrine. Moreover, the Mediterranean diet enhances the stress resistance to some extent by regulating the intestinal flora. This article reviews recent research on how stress damages the gut and microbiota, how the gut microbiota can improve gut health by modulating injury due to stress, and how the diet relieves stress injury by interfering with intestinal microflora. This review gives insight into the potential role of the gut and its microbiota in relieving the effects of stress via the gut-brain axis.

[The regulatory role of gut microbiota in inflammation in depression and anxiety]

Numerous studies have identified the important role of the gut microbiota in maintaining of the CNS normal functioning and in the pathogenesis of mental disorders as one of the systems regulating the bidirectional communication between the gut and the brain. The microbiota has been found to be involved in the modulation of inflammation as well as in the development and function of the immune and nervous systems. It is assumed that in multicellular organisms, the nervous and immune systems have evolved together with the microbiota, being in interaction with it, in order to optimize the body's ability to adapt to a wide range of environmental stresses in order to maintain the constancy of its homeostasis. Normally, microbes live in stable communities, while under conditions of even mild or chronic social stress, significant shifts in the composition of the microbiota occur, which lead to the development of dysbiosis associated with changes in microbiota metabolites, which can lead to the formation of physiology and behavior characteristic of stress and depression. Microbes influence the activation of peripheral immune cells that regulate the response to neuroinflammation, brain damage, autoimmune responses, and neurogenesis. The review provides a brief overview of the normal gut microbiota, describes the factors influencing the state of the microbiota, and also discusses recent discoveries concerning the regulatory effect of the gut microbiota on CNS functions, the immune system, and inflammation in the pathogenesis of depression and anxiety.

Pubertal consumption of R. badensis subspecies acadiensis modulates LPS-induced immune responses and gut microbiome dysbiosis in a sex-specific manner

Puberty is a critical period of development characterized by significant brain remodeling and increased vulnerability to immune challenges. Exposure to an immune challenge such as LPS during puberty can result in inflammation and gut dysbiosis which may lead to altered brain functioning and psychiatric illnesses later in life. However, treatment with probiotics during puberty has been found to mitigate LPS-induced peripheral and central inflammation, prevent LPS-induced changes to the gut microbiota and protect against enduring behavioural disorders in a sex-specific manner. Recent findings from our laboratory revealed that pubertal R. badensis subspecies acadiensis (R. badensis subsp. acadiensis) treatment prevents LPS-induced depression-like behavior and alterations in 5HT1A receptor expression in a sex-specific manner. However, the underlying mechanism remains unclear. Thus, the aim of this study was to gain mechanistic insights and to investigate the ability of R. badensis subsp. acadiensis consumption during puberty to mitigate the effects of LPS treatment on the immune system and the gut microbiome. Our results revealed that pubertal treatment with R. badensis subsp. acadiensis reduced sickness behaviors in females more than males in a time-specific manner. It also mitigated LPS-induced increases in pro-inflammatory cytokines in the blood and in TNFα mRNA expression in the prefrontal cortex and the hippocampus of female mice. There were sex-dependent differences in microbiome composition that persisted after LPS injection or R. badensis subsp. acadiensis consumption. R. badensis subsp. acadiensis had greater impact on the microbiota of male mice but female microbiota's were more responsive to LPS treatment. This suggested that female mice microbiota's may be more prone to modulation by this probiotic. These findings emphasize the sex-specific effects of probiotic use during puberty on the structure of the gut microbiome and the immune system and highlight the critical role of gut colonization with probiotics during adolescence on immunomodulation and prevention of the enduring effects of infections.

Role of Brain-Gut-Microbiota Axis in Depression: Emerging Therapeutic Avenues

The human gut microbiota plays a significant role in the pathophysiology of central nervous system-related diseases. Recent studies suggest correlations between the altered gut microbiota and major depressive disorder (MDD). It is proposed that normalization of the gut microbiota alleviates MDD. The imbalance of brain-gut-microbiota axis also results in dysregulation of the hypothalamicpituitary- adrenal (HPA) axis. This imbalance has a crucial role in the pathogenesis of depression. Treatment strategies with certain antibiotics lead to the depletion of useful microbes and thereby induce depression like effects in subjects. Microbiota is also involved in the synthesis of various neurotransmitters (NTs) like 5-hydroxy tryptamine (5-HT; serotonin), norepinephrine (NE) and dopamine (DA). In addition to NTs, the gut microbiota also has an influence on brain derived neurotrophic factor (BDNF) levels. Recent research findings have exhibited that transfer of stress prone microbiota in mice is also responsible for depression and anxiety-like behaviour in animals. The use of probiotics, prebiotics, synbiotics and proper diet have shown beneficial effects in the regulation of depression pathogenesis. Moreover, transplantation of fecal microbiota from depressed individuals to normal subjects also induces depression-like symptoms. With the precedence of limited therapeutic benefits from monoamine targeting drugs, the regulation of brain-gut microbiota is emerging as a new treatment modality for MDDs. In this review, we elaborate on the significance of brain-gut-microbiota axis in the progression of MDD, particularly focusing on the modulation of the gut microbiota as a mode of treating MDD.

The Role of Gut Dysbiosis in the Pathophysiology of Neuropsychiatric Disorders

Mounting evidence shows that the complex gut microbial ecosystem in the human gastrointestinal (GI) tract regulates the physiology of the central nervous system (CNS) via microbiota and the gut-brain (MGB) axis. The GI microbial ecosystem communicates with the brain through the neuroendocrine, immune, and autonomic nervous systems. Recent studies have bolstered the involvement of dysfunctional MGB axis signaling in the pathophysiology of several neurodegenerative, neurodevelopmental, and neuropsychiatric disorders (NPDs). Several investigations on the dynamic microbial system and genetic-environmental interactions with the gut microbiota (GM) have shown that changes in the composition, diversity and/or functions of gut microbes (termed "gut dysbiosis" (GD)) affect neuropsychiatric health by inducing alterations in the signaling pathways of the MGB axis. Interestingly, both preclinical and clinical evidence shows a positive correlation between GD and the pathogenesis and progression of NPDs. Long-term GD leads to overstimulation of hypothalamic-pituitary-adrenal (HPA) axis and the neuroimmune system, along with altered neurotransmitter levels, resulting in dysfunctional signal transduction, inflammation, increased oxidative stress (OS), mitochondrial dysfunction, and neuronal death. Further studies on the MGB axis have highlighted the significance of GM in the development of brain regions specific to stress-related behaviors, including depression and anxiety, and the immune system in the early life. GD-mediated deregulation of the MGB axis imbalances host homeostasis significantly by disrupting the integrity of the intestinal and blood-brain barrier (BBB), mucus secretion, and gut immune and brain immune functions. This review collates evidence on the potential interaction between GD and NPDs from preclinical and clinical data. Additionally, we summarize the use of non-therapeutic modulators such as pro-, pre-, syn- and post-biotics, and specific diets or fecal microbiota transplantation (FMT), which are promising targets for the management of NPDs.

Differences in gut microbes in captive pangolins and the effects of captive breeding

Intestinal microorganisms are crucial for health and have a significant impact on biological processes, such as metabolism, immunity, and neural regulation. Although pangolin are protected animals in China and listed as critically endangered (CR) level by The International Union for Conservation of Nature (IUCN), the population of wild pangolins has decreased sharply in recent decades. Captive breeding has been adopted to protect pangolins, but the survival is low due to gastrointestinal infections, diarrhea, and parasitic infections. Studies on intestinal microbes in pangolins may reveal the relationship between intestinal microorganisms and health and assist protection. To explore the relationship between intestinal microorganisms and pangolin health, blood parameters and intestinal microorganisms of 10 pangolins (two Manis pentadactyla and eight Manis javanica) were studied at the Shenzhen Wildlife Rescue Center. There is difference among adult Sunda pangolins (M. javanica), adult Chinese pangolins (M. pentadactyla) and sub-adult Sunda pangolins (M. javanica) in intestinal microbial composition, diversity and phenotypic diversity, which suggested that adult Sunda pangolins occupied more diversity and proportion of microbial species to resist environmental pressure than the others. Due to the captive breeding serum cortisol of pangolins was increased, and the intestinal microbial structure changed, which may affect immunity. This study provides a scientific basis for the rescue of pangolins through artificial breeding.

Gut Microbiota Dysbiosis Induced by a High-Fat Diet Increases Susceptibility to Atrial Fibrillation

BACKGROUND

Obesity is a significant risk factor for atrial fibrillation (AF), and the gut microbiota is closely related to obesity-induced diseases. However, whether the gut microbiota is involved in regulating obesity-induced AF has not been studied. This study investigated whether gut microbiota dysbiosis affects obesity-related AF.

METHODS

Fecal microbes derived from normal diet (ND)-fed and high-fat diet (HD)-fed mice were transplanted into those fed normally. Morphologic, biochemical, functional, histologic, electrophysiological studies, molecular analysis, 16S rRNA gene amplicon sequencing, and RNA-sequencing were performed.

RESULTS

Transplantation of the HD gut microbes in ND-maintained (THD) mice led to a significant increase in the susceptibility to AF. Gut microbiota analysis showed a significant increase in Desulfovibrionaceae, which generated metabolic endotoxemia in THD mice. Transplantation with HD microbes also resulted in significantly increased levels of circulating lipopolysaccharide (LPS), significant disruption in the histologic architecture of the intestinal tissue, and significantly increased proinflammatory cytokines in the left atrium, indicating that atrial inflammation likely contributed to AF susceptibility. RNA-sequencing showed that the THD group had enhanced activation of ferroptosis and TLR4/NF-κB/NLRP3 inflammasome signalling pathway. Inhibiting the ferroptosis or NLRP3 inflammasome signalling pathway significantly improved atrial fibrosis and reduced susceptibility to obesity-related gut dysbiosis-induced AF.

CONCLUSIONS

This study provides evidence showing an original causal role of gut microbiota dysbiosis in the pathogenesis of obesity-related AF, which showed elevated LPS and dysregulation of atrial pathologic remodelling by activating ferroptosis and the TLR4/NF-κB/NLRP3 inflammasome signalling pathway.

Identification of bacterial lipopeptides as key players in IBS

OBJECTIVES

Clinical studies revealed that early-life adverse events contribute to the development of IBS in adulthood. The aim of our study was to investigate the relationship between prenatal stress (PS), gut microbiota and visceral hypersensitivity with a focus on bacterial lipopeptides containing γ-aminobutyric acid (GABA).

DESIGN

We developed a model of PS in mice and evaluated, in adult offspring, visceral hypersensitivity to colorectal distension (CRD), colon inflammation, barrier function and gut microbiota taxonomy. We quantified the production of lipopeptides containing GABA by mass spectrometry in a specific strain of bacteria decreased in PS, in PS mouse colons, and in faeces of patients with IBS and healthy volunteers (HVs). Finally, we assessed their effect on PS-induced visceral hypersensitivity.

RESULTS

Prenatally stressed mice of both sexes presented visceral hypersensitivity, no overt colon inflammation or barrier dysfunction but a gut microbiota dysbiosis. The dysbiosis was distinguished by a decreased abundance of Ligilactobacillus murinus, in both sexes, inversely correlated with visceral hypersensitivity to CRD in mice. An isolate from this bacterial species produced several lipopeptides containing GABA including C14AsnGABA. Interestingly, intracolonic treatment with C14AsnGABA decreased the visceral sensitivity of PS mice to CRD. The concentration of C16LeuGABA, a lipopeptide which inhibited sensory neurons activation, was decreased in faeces of patients with IBS compared with HVs.

CONCLUSION

PS impacts the gut microbiota composition and metabolic function in adulthood. The reduced capacity of the gut microbiota to produce GABA lipopeptides could be one of the mechanisms linking PS and visceral hypersensitivity in adulthood.

Gut Microbiota across Normal Gestation and Gestational Diabetes Mellitus: A Cohort Analysis

The prevalence of gestational diabetes mellitus (GDM) is a global public health concern. The mechanism that leads to glucose tolerance beyond normal physiological levels to pathogenic conditions remains incompletely understood, and it is speculated that the maternal microbiome may play an important role. This study analyzes the gut microbiota composition in each trimester of weight-matched women with and without GDM and examines possible bacterial genera associations with GDM. This study followed 56 pregnant women with GDM and 59 without admitted to the outpatient clinic during their first/second or third trimester of gestation. They were submitted to a standardized questionnaire, dietary recalls, clinical examination, biological sample collection, and molecular profiling of fecal microbiota. Women with GDM were older and had a higher number of pregnancies than normal-tolerant ones. There was no difference in alpha diversity, and the groups did not differ regarding the overall microbiota structure. A higher abundance of Bacteroides in the GDM group was found. A positive correlation between Christensenellaceae and Intestinobacter abundances with one-hour post-challenge plasma glucose and a negative correlation between Enterococcus and two-hour plasma glucose levels were observed. Bifidobacterium and Peptococcus abundances were increased in the third gestational trimester for both groups. The gut microbiota composition was not dependent on the presence of GDM weight-matched women throughout gestation. However, some genera abundances showed associations with glucose metabolism. Our findings may therefore encourage a deeper understanding of physiological and pathophysiological changes in the microbiota throughout pregnancy, which could have further implications for diseases prevention.

Individual Nutrition Is Associated with Altered Gut Microbiome Composition for Adults with Food Insecurity

Diet is widely recognized as a key contributor to human gut microbiome composition and function. However, overall nutrition can be difficult to compare across a population with varying diets. Moreover, the role of food security in the relationship with overall nutrition and the gut microbiome is unclear. This study aims to investigate the association between personalized nutrition scores, variation in the adult gut microbiome, and modification by food insecurity. The data originate from the Survey of the Health of Wisconsin and the Wisconsin Microbiome Study. Individual nutrition scores were assessed using My Nutrition Index (MNI), calculated using data from food frequency questionnaires, and additional health history and demographic surveys. Food security and covariate data were measured through self-reported questionnaires. The gut microbiome was assessed using 16S amplicon sequencing of DNA extracted from stool samples. Associations, adjusted for confounding and interaction by food security, were estimated using Weighted Quantile Sum (WQS) regression models with Random Subset and Repeated Holdout extensions (WQSRSRH), with bacterial taxa used as components in the weighted index. Of 643 participants, the average MNI was 66.5 (SD = 31.9), and 22.8% of participants were food insecure. Increased MNI was significantly associated with altered gut microbial composition (β = 2.56, 95% CI = 0.52−4.61), with Ruminococcus, Oscillospira, and Blautia among the most heavily weighted of the 21 genera associated with the MNI score. In the stratified interaction WQSRSRH models, the bacterial taxa most heavily weighted in the association with MNI differed by food security, but the level of association between MNI and the gut microbiome was not significantly different. More bacterial genera are important in the association with higher nutrition scores for people with food insecurity versus food security, including Streptococcus, Parabacteroides Faecalibacterium, and Desulfovibrio. Individual nutrition scores are associated with differences in adult gut microbiome composition. The bacterial taxa most associated with nutrition vary by level of food security. While further investigation is needed, results showed a higher nutrition score was associated with a wider range of bacterial taxa for food insecure vs. secure, suggesting nutritional quality in food insecure individuals is important in maintaining health and reducing disparities.

Changes in intestinal microflora and its metabolites underlie the cognitive impairment in preterm rats

Background

The brain development of preterm infants is easily affected by various adverse extrauterine factors and complications, resulting in abnormal neurological and cognitive development. Recent studies have found that there is a significant correlation between intestinal microbial changes and cognitive behavior. Nevertheless, the correlation between the cognitive impairment and abnormal changes of intestinal microflora in the preterm newborn has been rarely elucidated.

Aim

To analyze the differences of fecal intestinal flora, short chain fatty acids (SCFAs) and microbiota-gut-brain axis (MGBA)-related serum factors between preterm birth with and without cognitive impairment.

Methods

Healthy female rats (body weight 410 ± 40 g) of 16-17 days of gestation were selected for the establishment of preterm cognitive impairment model and screened by Morris water maze navigation experiments. The pathological change of rat hippocampus was confirmed by HE staining. The abundance of fecal intestinal microflora was determined by 16sRNA sequencing, while the contents of fecal SCFAs were examined by gas chromatography.

Results

Compared with the control group, the cognitive impairment group had decreased abundance and diversity of intestinal microflora and increased abundance of Proteobacteria at the level of phylum. While the abundances of Alistipes, Bacteroides, Prevotella, and Lactobacillus decreased significantly at the level of order, family, and genus, the abundances of Staphylococcaceae, Enterococci, Psychrobacter, and Oligella increased significantly. Moreover, the levels of total SCFAs and acetic acid in the disease group were significantly lower. The fecal abundance of acetic acid was positively correlated with that of Lactobacillaceae or Peptostreptococcaceae, and negatively correlated with that of Aerococcaceae, and Alcaligenaceae in disease rats. Furthermore, cognitive impairment caused significantly decreased levels of 5-HT, GABA, and BDNF, and increased levels of GR, CRH, IL-6, and TNF-α in rat blood.

Conclusion

Alterations in intestinal microflora structure and the abundances of SCFAs contributed substantially to the cognitive impairment in preterm rats, which was associated with significant changes in MGBA-related soluble factors.

Contribution of hippocampal BDNF/CREB signaling pathway and gut microbiota to emotional behavior impairment induced by chronic unpredictable mild stress during pregnancy in rats offspring

Background

Numerous studies have shown that exposure to prenatal maternal stress (PMS) is associated with various psychopathological outcomes of offspring. The accumulating evidence linking bacteria in the gut and neurons in the brain (the microbiota-gut-brain axis) has been aconsensus; however, there is a lack of research on the involvement mechanism of gut microbiota in the regulation of the BDNF/CREB signaling pathway in the hippocampus of prenatally stressed offspring.

Methods

Pregnant rats were subjected to chronic unpredictable mild stress (CUMS) to establish the prenatal maternal stress model. The body weight was measured and the behavioral changes were recorded. Offspring were tested to determine emotional state using sucrose preference test (SPT), open-field test (OFT) and suspended tail test (STT). Gut microbiota was evaluated by sequencing the microbial 16S rRNA V3-V4 region, and the interactive analysis of bacterial community structure and diversity was carried out. The expression of hippocampal BDNF, TrkB and CREB mRNA and proteins were respectively measured using RT-PCR and Western blotting.

Results

Prenatal maternal stress increased maternal plasma corticosterone levels, slowed maternal weight gain and caused depression-like behaviors (all P < 0.05). In offspring, prenatal maternal stress increased plasma corticosterone levels (P < 0.05) and emotional behavior changes (depression-like state) were observed (P < 0.05). The species abundance, diversity and composition of the offspring's gut microbiota changed after the maternal stress during pregnancy (P < 0.05). Compared with the control group's offspring, the species abundance of Lactobacillaceae was dropped, while the abundance of the Muribaculaceae species abundance was risen. Concurrent, changes in the hippocampal structure of the offspring and decreases in expression of BDNF/CREB signaling were noted (P < 0.05).

Conclusions

Prenatal maternal stress leads to high corticosterone status and abnormal emotion behavior of offspring, which may be associated with the abnormal BDNF/CREB signaling in hippocampus of offspring caused by the change of gut microbiota composition.

ACTH(6-9)-Pro-Gly-Pro ameliorates anxiety-like and depressive-like behaviour and gut mucosal microbiota composition in rats under conditions of chronic restraint stress

The effects of the peptide ACTH(6-9)-Pro-Gly-Pro at doses of 5; 50; 500 μg/kg on the Wistar rats' behaviour and gut mucosal microbiota composition under conditions of chronic immobilization stress (CRS) were studied. CRS increased anxiety-like and depressive-like behaviour, disturbances in locomotor activity and gut dysbiosis. Administration of ACTH(6-9)-Pro-Gly-Pro showed many phenotypic results. Peptide demonstrated anti-depressant activity at doses of 5 and 500 μg/kg by a decrease in the total immobile time in the FST. ACTH(6-9)-Pro-Gly-Pro administered at a dose of 50 μg/kg resulted in an anxiolytic effect which is shown by an increase in the time in the open arms of EPM (p < 0.05) and a decrease in the time in the closed arms (p < 0.05). Moreover, the peptide led to a decrease in alpha- and beta-diversity of the gut microbiota (p < 0.01). Correlation and linear regression analysis demonstrated central mechanisms of ACTH(6-9)-Pro-Gly-Pro anxiolytic activity and both central and peripheral ones in an anti-depressant effect. In this way, peptide ACTH(6-9)-Pro-Gly-Pro could prevent the development of behavioural disturbances and gut dysbiosis caused by chronic restraint stress.

The Microbiome and Gut Endocannabinoid System in the Regulation of Stress Responses and Metabolism

The endocannabinoid system, with its receptors and ligands, is present in the gut epithelium and enteroendocrine cells, and is able to modulate brain functions, both indirectly through circulating gut-derived factors and directly through the vagus nerve, finally acting on the brain’s mechanisms regarding metabolism and behavior. The gut endocannabinoid system also regulates gut motility, permeability, and inflammatory responses. Furthermore, microbiota composition has been shown to influence the activity of the endocannabinoid system. This review examines the interaction between microbiota, intestinal endocannabinoid system, metabolism, and stress responses. We hypothesize that the crosstalk between microbiota and intestinal endocannabinoid system has a prominent role in stress-induced changes in the gut-brain axis affecting metabolic and mental health. Inter-individual differences are commonly observed in stress responses, but mechanisms underlying resilience and vulnerability to stress are far from understood. Both gut microbiota and the endocannabinoid system have been implicated in stress resilience. We also discuss interventions targeting the microbiota and the endocannabinoid system to mitigate metabolic and stress-related disorders.

Psychological stress disrupts intestinal epithelial cell function and mucosal integrity through microbe and host-directed processes

Psychological stress alters the gut microbiota and predisposes individuals to increased risk for enteric infections and chronic bowel conditions. Intestinal epithelial cells (IECs) are responsible for maintaining homeostatic interactions between the gut microbiota and its host. In this study, we hypothesized that disruption to colonic IECs is a key factor underlying stress-induced disturbances to intestinal homeostasis. Conventionally raised (CONV-R) and germ-free (GF) mice were exposed to a social disruption stressor (Str) to ascertain how stress modifies colonic IECs, the mucosal layer, and the gut microbiota. RNA sequencing of IECs isolated from CONV-R mice revealed a robust pro-inflammatory (Saa1, Il18), pro-oxidative (Duox2, Nos2), and antimicrobial (Reg3b/g) transcriptional profile as a result of Str. This response occurred concomitant to mucus layer thinning and signs of microbial translocation. In contrast to their CONV-R counterparts, IECs from GF mice or mice treated with broad spectrum antibiotics exhibited no detectable transcriptional changes in response to Str. Nevertheless, IECs from Str-exposed GF mice exhibited an altered response to ex vivo bacterial challenge (increased dual Oxidase-2 [Duox2] and nitric oxide synthase-2 (Nos2)), indicating that STR primes host IEC pro-oxidative responses. In CONV-R mice stress-induced increases in colonic Duox2 and Nos2 (ROS generating enzymes) strongly paralleled changes to microbiome composition and function, evidencing Str-mediated ROS production as a primary factor mediating gut-microbiota dysbiosis. In conclusion, a mouse model of social stress disrupts colonic epithelial and mucosal integrity, a response dependent on an intact microbiota and host stress signals. Together these preclinical findings may provide new insight into mechanisms of stress-associated bowel pathologies in humans.

Maternal stress and the maternal microbiome have sex-specific effects on offspring development and aggressive behavior in Siberian hamsters (Phodopus sungorus)

The gut microbiome, a community of commensal, symbiotic and pathogenic bacteria, fungi, and viruses, interacts with many physiological systems to affect behavior. Prenatal experiences, including exposure to maternal stress and different maternal microbiomes, are important sources of organismal variation that can affect offspring development. These physiological systems do not act in isolation and can have long-term effects on offspring development and behavior. Here we investigated the interactive effects of maternal stress and manipulations of the maternal microbiome on offspring development and social behavior using Siberian hamsters, Phodopus sungorus. We exposed pregnant females to either a social stressor, antibiotics, both the social stressor and antibiotics, or no treatment (i.e., control) over the duration of their pregnancy and quantified male and female offspring growth, gut microbiome composition and diversity, stress-induced cortisol concentrations, and social behavior. Maternal antibiotic exposure altered the gut microbial communities of male and female offspring. Maternal treatment also had sex-specific effects on aspects of offspring development and aggressive behavior. Female offspring produced by stressed mothers were more aggressive than other female offspring. Female, but not male, offspring produced by mothers exposed to the combined treatment displayed low levels of aggression, suggesting that alteration of the maternal microbiome attenuated the effects of prenatal stress in a sex-specific manner. Maternal treatment did not affect non-aggressive behavior in offspring. Collectively, our study offers insight into how maternal systems can interact to affect offspring in sex-specific ways and highlights the important role of the maternal microbiome in mediating offspring development and behavior.

Recent Advances in Understanding the Structure and Function of the Human Microbiome

Trillions of microbes live within our bodies in a deep symbiotic relationship. Microbial populations vary across body sites, driven by differences in the environment, immunological factors, and interactions between microbial species. Major advances in genome sequencing enable a better understanding of microbiome composition. However, most of the microbial taxa and species of the human microbiome are still unknown. Without revealing the identity of these microbes as a first step, we cannot appreciate their role in human health and diseases. A shift in the microbial balance, termed dysbiosis, is linked to a broad range of diseases from simple colitis and indigestion to cancer and dementia. The last decade has witnessed an explosion in microbiome research that led to a better understanding of the microbiome structure and function. This understanding leads to potential opportunities to develop next-generation microbiome-based drugs and diagnostic biomarkers. However, our understanding is limited given the highly personalized nature of the microbiome and its complex and multidirectional interactions with the host. In this review, we discuss: (1) our current knowledge of microbiome structure and factors that shape the microbial composition, (2) recent associations between microbiome dysbiosis and diseases, and (3) opportunities of new microbiome-based therapeutics. We analyze common themes, promises, gaps, and challenges of the microbiome research.

Investigating the potential of fish oil as a nutraceutical in an animal model of early life stress

Background: Early life stress is a key predisposing factor for depression and anxiety disorders. Selective serotonin re-uptake inhibitors (SSRI) are frequently used as the first line of pharmacology treatment for depression but have several negative qualities, i.e. a delay or absence of effectiveness and negative side-effects. Therefore, there is a growing need for new nutraceutical-based strategies to blunt the effects of adverse-life events.Objectives: This study aimed to use the maternal separation model in rats to test the efficacy of fish oil dietary supplementation, on its own and in conjunction with the SSRI anti-depressant fluoxetine, as a treatment for depressive and anxiety-like symptoms associated with early life stress.Methods: Behavioural tests (open field test, elevated plus maze test and forced swim test) and biochemical markers (corticosterone, BDNF, brain fatty acids and short chain fatty acids) were used to analyse the effects of the dietary treatments. Gut microbial communities and relating metabolites (SCFA) were analysed to investigate possible changes in the microbiota-gut-brain axis.Results: Maternally separated rats showed depressive-like behaviours in the forced swim and open field tests. These behaviours were prevented significantly by fluoxetine administration and in part by fish oil supplementation. Associated biochemical changes reported include altered brain fatty acids, significantly lower plasma corticosterone levels (AUC) and reduced brain stem serotonin turnover, compared to untreated, maternally separated (MS) rats. Untreated MS animals had significantly lower ratios of SCFA producers such as Caldicoprobacteraceae, Streptococcaceae, Rothia, Lachnospiraceae_NC2004_group, and Ruminococcus_2, along with significantly reduced levels of total SCFA compared to non-separated animals. Compared to untreated MS animals, animals fed fish oil had significantly higher Bacteroidetes and Prevotellaceae and reduced levels of butyrate, while fluoxetine treatment resulted in significantly higher levels of Neochlamydia, Lachnoclostridium, Acetitomaculum and Stenotrophomonas and, acetate and propionate.Conclusion: Despite the limitations in extrapolating from animal behavioural data and the notable differences in pharmacokinetics between rodents and humans, the results of this study provide a further advancement into the understanding of some of the complex systems within which nutraceuticals and pharmaceuticals effect the microbiota-gut-brain axis.

One Giant Leap from Mouse to Man: The Microbiota-Gut-Brain Axis in Mood Disorders and Translational Challenges Moving towards Human Clinical Trials

The microbiota–gut–brain axis is a bidirectional communication pathway that enables the gut microbiota to communicate with the brain through direct and indirect signaling pathways to influence brain physiology, function, and even behavior. Research has shown that probiotics can improve several aspects of health by changing the environment within the gut, and several lines of evidence now indicate a beneficial effect of probiotics on mental and brain health. Such evidence has prompted the arrival of a new term to the world of biotics research: psychobiotics, defined as any exogenous influence whose effect on mental health is bacterially mediated. Several taxonomic changes in the gut microbiota have been reported in neurodevelopmental disorders, mood disorders such as anxiety and depression, and neurodegenerative disorders such as Alzheimer’s disease. While clinical evidence supporting the role of the gut microbiota in mental and brain health, and indeed demonstrating the beneficial effects of probiotics is rapidly accumulating, most of the evidence to date has emerged from preclinical studies employing different animal models. The purpose of this review is to focus on the role of probiotics and the microbiota–gut–brain axis in relation to mood disorders and to review the current translational challenges from preclinical to clinical research.

WORKbiota: A Systematic Review about the Effects of Occupational Exposure on Microbiota and Workers' Health

The characterization of human microbiota and the impact of its modifications on the health of individuals represent a current topic of great interest for the world scientific community. Scientific evidence is emerging regarding the role that microbiota has in the onset of important chronic illnesses. Since individuals spend most of their life at work, occupational exposures may have an impact on the organism’s microbiota. The purpose of this review is to explore the influence that different occupational exposures have on human microbiota in order to set a new basis for workers’ health protection and disease prevention. The literature search was performed in PubMed, Cochrane, and Scopus. A total of 5818 references emerged from the online search, and 31 articles were included in the systematic review (26 original articles and 5 reviews). Exposure to biological agents (in particular direct contact with animals) was the most occupational risk factor studied, and it was found involved in modifications of the microbiota of workers. Changes in microbiota were also found in workers exposed to chemical agents or subjected to work-related stress and altered dietary habits caused by specific microclimate characteristics or long trips. Two studies evaluated the role of microbiota changes on the development of occupational lung diseases. Occupational factors can interface with the biological rhythms of the bacteria of the microbiota and can contribute to its modifications and to the possible development of diseases. Future studies are needed to better understand the role of the microbiota and its connection with occupational exposure to promote projects for the prevention and protection of global health.

A metaproteomic-based gut microbiota profiling in children affected by autism spectrum disorders

During the last decade, the evidences on the relationship between neurodevelopmental disorders and the microbial communities of the intestinal tract have considerably grown. Particularly, the role of gut microbiota (GM) ecology and predicted functions in Autism Spectrum Disorders (ASD) has been especially investigated by 16S rRNA targeted and shotgun metagenomics, trying to assess disease signature and their correlation with cognitive impairment or gastrointestinal (GI) manifestations of the disease. Herein we present a metaproteomic approach to point out the microbial gene expression profiles, their functional annotations, and the taxonomic distribution of gut microbial communities in ASD children. We pursued a LC-MS/MS based investigation, to compare the GM profiles of patients with those of their respective relatives and aged-matched controls, providing a quantitative evaluation of bacterial metaproteins by SWATH analysis. All data were managed by a multiple step bioinformatic pipeline, including network analysis. In particular, comparing ASD subjects with CTRLs, up-regulation was found for some metaproteins associated with Clostridia and with carbohydrate metabolism (glyceraldehyde-3-phosphate and glutamate dehydrogenases), while down-regulation was observed for others associated with Bacteroidia (SusC and SusD family together with the TonB dependent receptor). Moreover, network analysis highlighted specific microbial correlations among ASD subgroups characterized by different functioning levels and GI symptoms. SIGNIFICANCE: To the best of our knowledge, this study represents the first metaproteomic investigation on the gut microbiota of ASD children compared with relatives and age-matched CTRLs. Remarkably, the applied SWATH methodology allowed the attribution of differentially regulated functions to specific microbial taxa, offering a novel and complementary point of view with respect to previous studies.

Host phenotype and microbiome vary with infection status, parasite genotype, and parasite microbiome composition

A growing literature demonstrates the impact of helminths on their host gut microbiome. We investigated whether the stickleback host microbiome depends on eco-evolutionary variables by testing the impact of exposure to the cestode parasite Schistocephalus solidus with respect to infection success, host genotype, parasite genotype, and parasite microbiome composition. We observed constitutive differences in the microbiome of sticklebacks of different origin, and those differences increased when sticklebacks exposed to the parasite resisted infection. In contrast, the microbiome of successfully infected sticklebacks varied with parasite genotype. More specifically, we revealed that the association between microbiome and immune gene expression increased in infected individuals and varied with parasite genotype. In addition, we showed that S. solidus hosts a complex endo- microbiome and that bacterial abundance in the parasite correlates with expression of host immune genes. Within this comprehensive analysis we demonstrated that (i) parasites contribute to modulating the host microbiome through both successful and unsuccessful infection, (ii) when infection is successful, the host microbiome varies with parasite genotype due to genotype-dependent variation in parasite immunomodulation, and (iii) the parasite-associated microbiome is distinct from its host's and impacts the host immune response to infection.

Altered stress responses in adults born by Caesarean section

Birth by Caesarean-section (C-section), which increases the risk for metabolic and immune disorders, disrupts the normal initial microbial colonisation of the gut, in addition to preventing early priming of the stress and immune-systems.. Animal studies have shown there are enduring psychological processes in C-section born mice. However, the long-term impact of microbiota-gut-brain axis disruptions due to birth by C-section on psychological processes in humans is unknown. Forty age matched healthy young male university students born vaginally and 36 C-section delivered male students were recruited. Participants underwent an acute stressor, the Trier social stress test (TSST), during a term-time study visit. A subset of participants also completed a study visit during the university exam period, representing a naturalistic stressor. Participants completed a battery of cognitive tests and self-report measures assessing mood, anxiety, and perceived stress. Saliva, blood, and stool samples were collected for analysis of cortisol, peripheral immune profile, and the gut microbiota. Young adults born by C-section exhibit increased psychological vulnerability to acute stress and a prolonged period of exam-related stress. They did not exhibit an altered salivary cortisol awakening response to the TSST, but their measures of positive affect were significantly lower than controls throughout the procedure. Both C-section and vaginally-delivered participants performed equally well on cognitive assessments. Most of the initial effects of delivery mode on the gut microbiome did not persist into adulthood as the gut microbiota profile showed modest changes in composition in adult vaginally-delivered and C-sectioned delivered subjects. From an immune perspective, concentrations of IL-1β and 1L-10 were higher in C-section participants. These data confirm that there is a potential enduring effect of delivery mode on the psychological responses to acute stress during early adulthood. The mental health implications of these observations require further study regarding policies on C-section use.

Gut Microbiota Linked with Reduced Fear of Humans in Red Junglefowl Has Implications for Early Domestication

Domestication of animals can lead to profound phenotypic modifications within short evolutionary time periods, and for many species behavioral selection is likely at the forefront of this process. Animal studies have strongly implicated that the gut microbiome plays a major role in host behavior and cognition through the microbiome-gut-brain axis. Consequently, herein, it is hypothesized that host gut microbiota may be one of the earliest phenotypes to change as wild animals were domesticated. Here, the gut microbiome community in two selected lines of red junglefowl that are selected for either high or low fear of humans up to eight generations is examined. Microbiota profiles reveal taxonomic differences in gut bacteria known to produce neuroactive compounds between the two selection lines. Gut-brain module analysis by means of genome-resolved metagenomics identifies enrichment in the microbial synthesis and degradation potential of metabolites associated with fear extinction and reduces anxiety-like behaviors in low fear fowls. In contrast, high fear fowls are enriched in gut-brain modules from the butyrate and glutamate pathways, metabolites associated with fear conditioning. Overall, the results identify differences in the composition and functional potential of the gut microbiota across selection lines that may provide insights into the mechanistic explanations of the domestication process.