Role of the Intestinal Microbiota in Host Responses to Stressor Exposure

A Cross Talking between the Gut Microbiota and Metabolites of Participants in a Confined Environment

Certain workplaces, like deep-sea voyages, subject workers to chronic psychological stress and circadian rhythm disorders due to confined environments and frequent shifts. In this study, participants lived in a strictly controlled confined environment, and we analyzed the effects of a confined environment on gut microbiota and metabolites. The results showed that living in confined environments can significantly alter both the gut microbiota and the gut metabolome, particularly affecting lipid metabolism pathways like glycerophospholipid metabolism. There was a significant reduction in the abundance of Faecalibacterium and Bacteroides, while Blautia, Bifidobacterium, and Collinsella showed significant increases. An association analysis revealed a strong correlation between changes in the gut microbiota and the metabolome. Four upregulated lipid metabolites may serve as biomarkers for damage induced by confined environments, and certain gut microbiota alterations, such as those involving Faecalibacterium and Bacteroides, could be potential psychobiotics or therapeutic targets for enhancing mental health in a confined environment.

Diversity Analysis of Intestinal Bifidobacteria in the Hohhot Population

(1) Background: Bifidobacterium plays a pivotal role within the gut microbiota, significantly affecting host health through its abundance and composition in the intestine. Factors such as age, gender, and living environment exert considerable influence on the gut microbiota, yet scant attention has been directed towards understanding the specific effects of these factors on the Bifidobacterium population. Therefore, this study focused on 98 adult fecal samples to conduct absolute and relative quantitative analyses of bifidobacteria. (2) Methods: Using droplet digital PCR and the PacBio Sequel II sequencing platform, this study sought to determine the influence of various factors, including living environment, age, and BMI, on the absolute content and biodiversity of intestinal bifidobacteria. (3) Results: Quantitative results indicated that the bifidobacteria content in the intestinal tract ranged from 106 to 109 CFU/g. Notably, the number of bifidobacteria in the intestinal tract of the school population surpassed that of the off-campus population significantly (p = 0.003). Additionally, the group of young people exhibited a significantly higher count of bifidobacteria than the middle-aged and elderly groups (p = 0.041). The normal-weight group displayed a significantly higher bifidobacteria count than the obese group (p = 0.027). Further analysis of the relative abundance of bifidobacteria under different influencing factors revealed that the living environment emerged as the primary factor affecting the intestinal bifidobacteria structure (p = 0.046, R2 = 2.411). Moreover, the diversity of bifidobacteria in the intestinal tract of college students surpassed that in the out-of-school population (p = 0.034). This was characterized by a notable increase in 11 strains, including B. longum, B. bifidum, and B. pseudolongum, in the intestinal tract of college students, forming a more intricate intestinal bifidobacteria interaction network. (4) Conclusions: In summary, this study elucidated the principal factors affecting intestinal bifidobacteria and delineated their characteristics of intestinal bifidobacteria in diverse populations. By enriching the theory surrounding gut microbiota and health, this study provides essential data support for further investigations into the intricate dynamics of the gut microbiota.

Lipids, Gut Microbiota, and the Complex Relationship with Alzheimer's Disease: A Narrative Review

Alzheimer's Disease (AD) is a multifactorial, progressive, and chronic neurodegenerative disorder associated with the aging process. Memory deficits, cognitive impairment, and motor dysfunction are characteristics of AD. It is estimated that, by 2050, 131.5 million people will have AD. There is evidence that the gastrointestinal microbiome and diet may contribute to the development of AD or act preventively. Communication between the brain and the intestine occurs through immune cells in the mucosa and endocrine cells, or via the vagus nerve. Aging promotes intestinal dysbiosis, characterized by an increase in pro-inflammatory pathogenic bacteria and a reduction in anti-inflammatory response-mediating bacteria, thus contributing to neuroinflammation and neuronal damage, ultimately leading to cognitive decline. Therefore, the microbiota-gut-brain axis has a significant impact on neurodegenerative disorders. Lipids may play a preventive or contributory role in the development of AD. High consumption of saturated and trans fats can increase cortisol release and lead to other chronic diseases associated with AD. Conversely, low levels of omega-3 polyunsaturated fatty acids may be linked to neurodegenerative diseases. Unlike other studies, this review aims to describe, in an integrative way, the interaction between the gastrointestinal microbiome, lipids, and AD, providing valuable insights into how the relationship between these factors affects disease progression, contributing to prevention and treatment strategies.

Role of intestinal microbiota in regulation of immune reactions of gut-associated lymphoid tissue under stress and following the modulation of its composition by antibiotics and probiotics administration

Over the past two decades, active study of the microbial ecosystem of the host organism gastrointestinal tract has led to the recognition of gut microbiome as a "key player" that carries a significant immune pressure and is responsible both for the course of physiological processes and for the development of pathological conditions in humans and animals. A vast number of bacteria living in the human gastrointestinal tract are considered as an organ functioning in dialogue in formation of immunological tolerance, the regulation of normal functional activity of the immune system and maintaining the intestinal mucosa homeostasis. However, disturbances in interaction between these physiological systems is closely related to the pathogenesis of different immune-mediated diseases. In turn, in a large number of works chronic social stress, along with the use of antibiotics, pre- and probiotics, is recognized as one of the leading factors modulating in the microbiota of the gastrointestinal tract. This review focuses on the role of the gut microbiome in the regulation of immune responses of GALT under stress and modulation of its composition by antibiotics and probiotics administration.

Probiotic supplements and stress-related occupational health outcomes: A scoping review

BACKGROUND

Prolonged and constant stress from work often leads to numerous adverse health effects. In recent years, interest in probiotics, living microorganisms that can benefit their host when consumed in adequate amounts, to aid health and well-being has increased. This scoping review is to systematically evaluate the current state of science on the effects of probiotic supplements on health, stress, and stress-related symptoms among working adults in occupational settings.

METHODS

We performed a systematic scoping review following the Arksey and O'Malley Framework. Studies that examined the effects of probiotics on workers' health and stress-related indicators/outcomes in occupational settings were included. A comprehensive search was performed from November 2021 to January 2022 using MEDLINE/PubMed, Cochrane Library, CINAHL, PsychInfo, Scopus, and Embase.

RESULTS

A total of 14 papers met the inclusion and exclusion criteria. Probiotics consisted primarily of Lactobacillus and/or Bifidobacterium strains in various forms and doses. Three out of eight studies reported statistical differences in inflammatory markers or stress hormone levels between probiotic and placebo groups. Three of six reported reduced respiratory tract infection incidents in the probiotic groups and three out of four studies reported no differences in anxiety and depression between groups. Lastly, three studies found that absenteeism and presentism were lower in probiotic groups compared with placebo groups.

CONCLUSION

The potential benefits of probiotics exist; however, the measurements of outcomes, the types of probiotics used, and the characteristics of the intervention varied across studies. Further research is needed focusing on probiotics' direct and indirect mechanisms of action on the stress response and the standardization of strains and dosing.

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.

Glutathione S-transferase (GST) and cortisol levels vs. microbiology of the digestive system of sheep during lambing

Background

During parturition, animals exhibit variation in hormone levels, homeostasis disturbance and dysfunction of the immune system as a result of stress. Glutathione S-transferase (GST) is responsible for the occurrence of oxidative stress in the cells. Cortisol is known as the stress hormone, but it is also involved in the metabolism of proteins, carbohydrates and metabolism processes led by adipose tissue. The aim of the this study was to determine how the levels of GST and cortisol change depending on the parity. Additionally, the influence of lambing on the microbiological composition of the digestive system and placenta in Olkuska sheep was investigated.

Methods

Eighteen ewes were selected for the experiment - primiparas (n = 9) and multiparas (n = 9), they were kept in the same environmental conditions, had the same diet and did not show any disease symptoms. Fecal samples were collected individually from each ewe (n = 18) and then bacterial DNA isolation was made, then qPCR analysis for Firmicutes, Bacteroidetes, Actinobacteria, Proteobacteria phyla and Lactobacillaceae family bacteria levels was performed. These samples were also used to analyze cortisol levels by ELISA test. In addition, placenta fragments were collected during delivery, and then the GST level from the tissue was tested.

Results

The analysis of the results showed a higher level of cortisol in primiparous sheep than in multiparous ones, as in the case of glutathione transferase. There were differences between both studied groups in the microbiological composition of the digestive system. In primiparous sheep, the levels of the tested microorganisms were significantly lower than in multiparous ones. A similar relationship occurred in the study of the placental microbiome.

Conclusion

The results show that sheep microbiome, cortisol and GST levels are different in primiparas and multiparas. The study conducted may constitute an introduction to further analyzes that would help positively affect the welfare and homeostasis of the female organism.

Probiotic Escherichia coli Ameliorates Antibiotic-Associated Anxiety Responses in Mice

Despite the beneficial actions of antibiotics against bacterial infections, the use of antibiotics is a crucial etiological factor influencing microbial dysbiosis-associated adverse outcomes in human health. Based on the assumption that gut microbial dysbiosis can provoke behavioral or psychological disorders, the present study evaluated anxiety-linked behavioral changes in a mouse model of streptomycin-induced dysbiosis. Measuring anxiety-like behavior using the light-dark box and elevated plus maze tests indicated that streptomycin treatment caused acute anxiety in mice. As an intervention for dysbiosis-associated distress, the probiotic strain Escherichia coli Nissle 1917 (EcN) was evaluated for its effects on streptomycin-induced behavioral changes in mice. EcN supplementation persistently ameliorated anxiety responses in mice with streptomycin-induced dysbiosis. As an outcome of anxiety, body weight changes were marginally affected by antibiotic treatment. However, mice supplemented with EcN displayed acute retardation of body weight gain, since EcN is known to reduce food intake and increase energy expenditure. Taken together, EcN treatment prominently counteracted streptomycin-induced anxiety in mice, with the metabolically beneficial retardation of body weight gain. The present model simulates psychological disorders in antibiotic users. As a promising intervention, EcN treatment can facilitate psychological relief under conditions of dysbiotic stress by blocking the pathologic gut-brain circuit.

Stress and the gut microbiota-brain axis

Stress is a nonspecific response of the body to any demand imposed upon it, disrupting the body homoeostasis and manifested with symptoms such as anxiety, depression or even headache. These responses are quite frequent in the present competitive world. The aim of this review is to explore the effect of stress on gut microbiota. First, we summarize evidence of where the microbiota composition has changed as a response to a stressful situation, and thereby the effect of the stress response. Likewise, we review different interventions that can modulate microbiota and could modulate the stress according to the underlying mechanisms whereby the gut-brain axis influences stress. Finally, we review both preclinical and clinical studies that provide evidence of the effect of gut modulation on stress. In conclusion, the influence of stress on gut microbiota and gut microbiota on stress modulation is clear for different stressors, but although the preclinical evidence is so extensive, the clinical evidence is more limited. A better understanding of the mechanism underlying stress modulation through the microbiota may open new avenues for the design of therapeutics that could boost the pursued clinical benefits. These new designs should not only focus on stress but also on stress-related disorders such as anxiety and depression, in both healthy individuals and different populations.

Exercise, diet and stress as modulators of gut microbiota: Implications for neurodegenerative diseases

The last decade has witnessed an exponentially growing interest in gut microbiota and the gut-brain axis in health and disease. Accumulating evidence from preclinical and clinical research indicate that gut microbiota, and their associated microbiomes, may influence pathogenic processes and thus the onset and progression of various diseases, including neurological and psychiatric disorders. In fact, gut dysbiosis (microbiota dysregulation) has been associated with a range of neurodegenerative diseases, including Alzheimer's, Parkinson's, Huntington's and motor neuron disease, as well as multiple sclerosis. The gut microbiota constitutes a dynamic microbial system constantly challenged by many biological variables, including environmental factors. Since the gut microbiota constitute a changeable and experience-dependent ecosystem, they provide potential therapeutic targets that can be modulated as new interventions for dysbiosis-related disorders, including neurodegenerative diseases. This article reviews the evidence for environmental modulation of gut microbiota and its relevance to brain disorders, exploring in particular the implications for neurodegenerative diseases. We will focus on three major environmental factors that are known to influence the onset and progression of those diseases, namely exercise, diet and stress. Further exploration of environmental modulation, acting via both peripheral (e.g. gut microbiota and associated metabolic dysfunction or 'metabolopathy') and central (e.g. direct effects on CNS neurons and glia) mechanisms, may lead to the development of novel therapeutic approaches, such as enviromimetics, for a wide range of neurological and psychiatric disorders.

The Preventive and Curative Effects of Lactobacillus reuteri NK33 and Bifidobacterium adolescentis NK98 on Immobilization Stress-Induced Anxiety/Depression and Colitis in Mice

The gut dysbiosis by stressors such as immobilization deteriorates psychiatric disorders through microbiota-gut-brain axis activation. To understand whether probiotics could simultaneously alleviate anxiety/depression and colitis, we examined their effects on immobilization stress (IS)-induced anxiety/depression and colitis in mice. The probiotics Lactobacillus reuteri NK33 and Bifidobacterium adolescentis NK98 were isolated from healthy human feces. Mice with anxiety/depression and colitis were prepared by IS treatment. NK33 and NK98 potently suppressed NF-κB activation in lipopolysaccharide (LPS)-induced BV-2 cells. Treatment with NK33 and/or NK98, which were orally gavaged in mice before or after IS treatment, significantly suppressed the occurrence and development of anxiety/depression, infiltration of Iba1⁺ and LPS⁺/CD11b⁺ cells (activated microglia) into the hippocampus, and corticosterone, IL-6, and LPS levels in the blood. Furthermore, they induced hippocampal BDNF expression while NF-κB activation was suppressed. NK33 and/or NK98 treatments suppressed IS-induced colon shortening, myeloperoxidase activity, infiltration of CD11b⁺/CD11c⁺ cells, and IL-6 expression in the colon. Their treatments also suppressed the IS-induced fecal Proteobacteria population and excessive LPS production. They also induced BDNF expression in LPS-induced SH-SY5Y cells in vitro. In conclusion, NK33 and NK98 synergistically alleviated the occurrence and development of anxiety/depression and colitis through the regulation of gut immune responses and microbiota composition.

Chronic stress-induced gut dysfunction exacerbates Parkinson's disease phenotype and pathology in a rotenone-induced mouse model of Parkinson's disease

Recent evidence provides support for involvement of the microbiota-gut-brain axis in Parkinson's disease (PD) pathogenesis. We propose that a pro-inflammatory intestinal milieu, due to intestinal hyper-permeability and/or microbial dysbiosis, initiates or exacerbates PD pathogenesis. One factor that can cause intestinal hyper-permeability and dysbiosis is chronic stress which has been shown to accelerate neuronal degeneration and motor deficits in Parkinsonism rodent models. We hypothesized that stress-induced intestinal barrier dysfunction and microbial dysbiosis lead to a pro-inflammatory milieu that exacerbates the PD phenotype in the low-dose oral rotenone PD mice model. To test this hypothesis, mice received unpredictable restraint stress (RS) for 12 weeks, and during the last six weeks mice also received a daily administration of low-dose rotenone (10 mg/kg/day) orally. The initial six weeks of RS caused significantly higher urinary cortisol, intestinal hyperpermeability, and decreased abundance of putative "anti-inflammatory" bacteria (Lactobacillus) compared to non-stressed mice. Rotenone alone (i.e., without RS) disrupted the colonic expression of the tight junction protein ZO-1, increased oxidative stress (N-tyrosine), increased myenteric plexus enteric glial cell GFAP expression and increased α-synuclein (α-syn) protein levels in the colon compared to controls. Restraint stress exacerbated these rotenone-induced changes. Specifically, RS potentiated rotenone-induced effects in the colon including: 1) intestinal hyper-permeability, 2) disruption of tight junction proteins (ZO-1, Occludin, Claudin1), 3) oxidative stress (N-tyrosine), 4) inflammation in glial cells (GFAP + enteric glia cells), 5) α-syn, 6) increased relative abundance of fecal Akkermansia (mucin-degrading Gram-negative bacteria), and 7) endotoxemia. In addition, RS promoted a number of rotenone-induced effects in the brain including: 1) reduced number of resting microglia and a higher number of dystrophic/phagocytic microglia as well as (FJ-C+) dying cells in the substantia nigra (SN), 2) increased lipopolysaccharide (LPS) reactivity in the SN, and 3) reduced dopamine (DA) and DA metabolites (DOPAC, HVA) in the striatum compared to control mice. Our findings support a model in which chronic stress-induced, gut-derived, pro-inflammatory milieu exacerbates the PD phenotype via a dysfunctional microbiota-gut-brain axis.

Immobilization stress-induced Escherichia coli causes anxiety by inducing NF-κB activation through gut microbiota disturbance

The present study aimed to understand the crosstalk between anxiety and gut microbiota. Exposure of mice to immobilization stress (IS) led to anxiety-like behaviors, increased corticosterone and tumor necrosis factor-α levels in the blood, increased nuclear factor (NF)-κB activation and microglia/monocyte populations in the hippocampus, and suppressed brain-derived neurotrophic factor (BDNF) expression in the hippocampus. Furthermore, IS exposure increased NF-κB activation and monocyte population in the colon and increased Proteobacteria and Escherichia coli populations in the gut microbiota and fecal and blood lipopolysaccharide (LPS) levels while decreasing the lactobacilli population. Oral administration of the fecal microbiota of mice treated with IS (FIS) or E. coli led to the increased NF-κB activation and monocyte population in the colon. These treatments increased blood corticosterone and LPS levels and anxiety-like behaviors, decreased BDNF expression, and induced NF-κB activation and microglia/monocyte populations in the hippocampus. Intraperitoneal injection of LPS purified from E. coli also led to anxiety and colitis in mice. Oral administration of commensal lactobacilli, particularly Lactobacillus johnsonii, attenuated IS- or E. coli-induced colitis and anxiety-like behaviors and biomarkers. These findings suggest that exposure to stressors can increase Proteobacteria populations and fecal LPS levels and cause gastrointestinal inflammation, resulting in the deterioration of anxiety through NF-κB activation. However, the amelioration of gastrointestinal inflammation by treatment with probiotics including L. johnsonii can alleviate anxiety.

Evidence for interplay among antibacterial-induced gut microbiota disturbance, neuro-inflammation, and anxiety in mice

The aim of the present study was to determine whether there is the mechanistic connection between antibacterial-dependent gut microbiota disturbance and anxiety. First, exposure of mice to ampicillin caused anxiety and colitis and increased the population of Proteobacteria, particularly Klebsiella oxytoca, in gut microbiota and fecal and blood lipopolysaccharide levels, while decreasing lactobacilli population including Lactobacillus reuteri. Next, treatments with fecal microbiota of ampicillin-treated mouse (FAP), K. oxytoca, or lipopolysaccharide isolated from K. oxytoca (KL) induced anxiety and colitis in mice and increased blood corticosterone, IL-6, and lipopolysaccharide levels. Moreover, these treatments also increased the recruitment of microglia (Iba1⁺), monocytes (CD11b⁺/CD45⁺), and dendritic cells (CD11b⁺/CD11c⁺) to the hippocampus, as well as the population of apoptotic neuron cells (caspase-3⁺/NeuN⁺) in the brain. Furthermore, ampicillin, K. oxytoca, and KL induced NF-κB activation and IL-1β and TNF-α expression in the colon and brain as well as increased gut membrane permeability. Finally, oral administration of L. reuteri alleviated ampicillin-induced anxiety and colitis. These results suggest that ampicillin exposure can cause anxiety through neuro-inflammation which can be induced by monocyte/macrophage-activated gastrointestinal inflammation and elevated Proteobacteria population including K. oxytoca, while treatment with lactobacilli suppresses it.

Obstructive Sleep Apnea-Induced Hypertension: Role of the Gut Microbiota

PURPOSE OF REVIEW

Obstructive sleep apnea (OSA) is a significant risk factor for systemic hypertension and other cardiovascular diseases. While this relationship has been firmly established, a detailed understanding of how OSA leads to hypertension is lacking. This review will examine the emerging idea that the gut microbiota plays a role in the development of hypertension, including that associated with OSA.

RECENT FINDINGS

Disruption of the normal composition of the gut microbiota, termed dysbiosis, has been identified in a number of metabolic and cardiovascular diseases, including diabetes, obesity, and atherosclerosis. Recently, a number of studies have demonstrated gut dysbiosis in various animal models of hypertension as well as in hypertensive patients. Evidence is now emerging that gut dysbiosis plays a causal role in the development of OSA-induced hypertension. In this review, we will examine the evidence that gut dysbiosis plays a role in OSA-induced hypertension. We will discuss potential mechanisms linking OSA to gut dysbiosis, examine how gut dysbiosis may be linked to hypertension, and highlight how this understanding may be utilized for the development of future therapeutics.

Revisiting Metchnikoff: Age-related alterations in microbiota-gut-brain axis in the mouse

Over the last decade, there has been increased interest in the role of the gut microbiome in health including brain health. This is by no means a new theory; Elie Metchnikoff proposed over a century ago that targeting the gut by consuming lactic acid bacteria such as those in yogurt, could improve or delay the onset of cognitive decline associated with ageing. However, there is limited information characterising the relationship between the behavioural and physiological sequelae of ageing and alterations in the gut microbiome. To this end, we assessed the behavioural, physiological and caecal microbiota profile of aged male mice. Older mice (20-21months old) exhibited deficits in spatial memory and increases in anxiety-like behaviours compared to younger mice (2-3months old). They also exhibited increased gut permeability, which was directly correlated with elevations in peripheral pro-inflammatory cytokines. Furthermore, stress exacerbated the gut permeability of aged mice. Examination of the caecal microbiota revealed significant increases in phylum TM7, family Porphyromonadaceae and genus Odoribacter of aged mice. This represents a shift of aged microbiota towards a profile previously associated with inflammatory disease, particularly gastrointestinal and liver disorders. Furthermore, Porphyromonadaceae, which has also been associated with cognitive decline and affective disorders, was directly correlated with anxiety-like behaviour in aged mice. These changes suggest that changes in the gut microbiota and associated increases in gut permeability and peripheral inflammation may be important mediators of the impairments in behavioural, affective and cognitive functions seen in ageing.

Obstructive Sleep Apnea-Induced Hypertension: Role of the Gut Microbiota

PURPOSE OF REVIEW

Obstructive sleep apnea (OSA) is a significant risk factor for systemic hypertension and other cardiovascular diseases. While this relationship has been firmly established, a detailed understanding of how OSA leads to hypertension is lacking. This review will examine the emerging idea that the gut microbiota plays a role in the development of hypertension, including that associated with OSA.

RECENT FINDINGS

Disruption of the normal composition of the gut microbiota, termed dysbiosis, has been identified in a number of metabolic and cardiovascular diseases, including diabetes, obesity, and atherosclerosis. Recently, a number of studies have demonstrated gut dysbiosis in various animal models of hypertension as well as in hypertensive patients. Evidence is now emerging that gut dysbiosis plays a causal role in the development of OSA-induced hypertension. In this review, we will examine the evidence that gut dysbiosis plays a role in OSA-induced hypertension. We will discuss potential mechanisms linking OSA to gut dysbiosis, examine how gut dysbiosis may be linked to hypertension, and highlight how this understanding may be utilized for the development of future therapeutics.