Microbiota, immunoregulatory old friends and psychiatric disorders

Airborne Exposure to Pollutants and Mental Health: A Review with Implications for United States Veterans

PURPOSE OF REVIEW

Inhalation of airborne pollutants in the natural and built environment is ubiquitous; yet, exposures are different across a lifespan and unique to individuals. Here, we reviewed the connections between mental health outcomes from airborne pollutant exposures, the biological inflammatory mechanisms, and provide future directions for researchers and policy makers. The current state of knowledge is discussed on associations between mental health outcomes and Clean Air Act criteria pollutants, traffic-related air pollutants, pesticides, heavy metals, jet fuel, and burn pits.

RECENT FINDINGS

Although associations between airborne pollutants and negative physical health outcomes have been a topic of previous investigations, work highlighting associations between exposures and psychological health is only starting to emerge. Research on criteria pollutants and mental health outcomes has the most robust results to date, followed by traffic-related air pollutants, and then pesticides. In contrast, scarce mental health research has been conducted on exposure to heavy metals, jet fuel, and burn pits. Specific cohorts of individuals, such as United States military members and in-turn, Veterans, often have unique histories of exposures, including service-related exposures to aircraft (e.g. jet fuels) and burn pits. Research focused on Veterans and other individuals with an increased likelihood of exposure and higher vulnerability to negative mental health outcomes is needed. Future research will facilitate knowledge aimed at both prevention and intervention to improve physical and mental health among military personnel, Veterans, and other at-risk individuals.

Conjugation of sulpiride with a cell penetrating peptide to augment the antidepressant efficacy and reduce serum prolactin levels

Depression ranks as the fourth most prevalent global disease, with suicide incidents occurring at a younger age. Sulpiride (SUL), an atypical antidepressant drug acting as a dopamine D2 receptor antagonist and possessing anti-inflammatory properties, exhibits limited ability to penetrate the blood brain barrier (BBB). This weak penetration hampers its inhibitory effect on prolactin release in the pituitary gland, consequently leading to hyperprolactinemia. In order to enhance the central nervous system efficacy of sulpiride and reduce serum prolactin levels, we covalently linked sulpiride to VPALR derived from the nuclear DNA repair protein ku70. In vivo study on depressive mice using intraperitoneal injection of VPALR-SUL demonstrated a significant increase in struggle time and total distance compared to those treated with only sulpiride while also reducing serum prolactin concentration. The pharmacokinetic study results showed that VPALR-SUL prolonged half-life and increased bioavailability. In conclusion, VPALR-SUL exhibited potential for enhancing sulpiride transport across the BBB, augmenting its antidepressant effects, and reducing serum prolactin levels. This study laid a foundation for improving sulpiride delivery and developing novel antidepressants.

A novel on-a-chip system with a 3D-bioinspired gut mucus suitable to investigate bacterial endotoxins dynamics

The possible pathogenic impact of pro-inflammatory molecules produced by the gut microbiota is one of the hypotheses considered at the basis of the biomolecular dialogue governing the microbiota-gut-brain axis. Among these molecules, lipopolysaccharides (LPS) produced by Gram-negative gut microbiota strains may have a potential key role due to their toxic effects in both the gut and the brain. In this work, we engineered a new dynamic fluidic system, the MINERVA device (MI-device), with the potential to advance the current knowledge of the biological mechanisms regulating the microbiota-gut molecular crosstalk. The MI-device supported the growth of bacteria that are part of the intestinal microbiota under dynamic conditions within a 3D moving mucus model, with features comparable to the physiological conditions (storage modulus of 80 ± 19 Pa, network mesh size of 41 ± 3 nm), without affecting their viability (∼ 109 bacteria/mL). The integration of a fluidically optimized and user-friendly design with a bioinspired microenvironment enabled the sterile extraction and quantification of the LPS produced within the mucus by bacteria (from 423 ± 34 ng/mL to 1785 ± 91 ng/mL). Compatibility with commercially available Transwell-like inserts allows the user to precisely control the transport phenomena that occur between the two chambers by selecting the pore density of the insert membrane without changing the design of the system. The MI-device is able to provide the flow of sterile medium enriched with LPS directly produced by bacteria, opening up the possibility of studying the effects of bacteria-derived molecules on cells in depth, as well as the assessment and characterization of their effects in a physiological or pathological scenario.

Microbiota Implications in Endocrine-Related Diseases: From Development to Novel Therapeutic Approaches

This comprehensive review article delves into the critical role of the human microbiota in the development and management of endocrine-related diseases. We explore the complex interactions between the microbiota and the endocrine system, emphasizing the implications of microbiota dysbiosis for the onset and progression of various endocrine disorders. The review aims to synthesize current knowledge, highlighting recent advancements and the potential of novel therapeutic approaches targeting microbiota-endocrine interactions. Key topics include the impact of microbiota on hormone regulation, its role in endocrine pathologies, and the promising avenues of microbiota modulation through diet, probiotics, prebiotics, and fecal microbiota transplantation. We underscore the importance of this research in advancing personalized medicine, offering insights for more tailored and effective treatments for endocrine-related diseases.

Sterile soil mitigates the intergenerational loss of gut microbial diversity and anxiety-like behavior induced by antibiotics in mice

The decline in gut microbial diversity in modern humans is closely associated with the rising prevalence of various diseases. It is imperative to investigate the underlying causes of gut microbial loss and restoring methods. Although the impact of non-perinatal antibiotic use on gut microbiota has been recognized, its intergenerational effects remain unexplored. Our previous research has highlighted soil in the farm environment as a key factor for gut microbiome health by restoring gut microbial diversity and balance. In this study, we investigated the intergenerational consequences of antibiotic exposure and the therapeutic potential of sterile soil. We treated C57BL/6 mice with vancomycin and streptomycin for 2 weeks continuously, followed by a 4-8 week withdrawal period before breeding. The process was repeated across 3 generations. Half of the mice in each generation received an oral sterile soil intervention. We assessed gut microbial diversity, anxiety behavior, microglial reactivity, and gut barrier integrity across generations. Antibiotic exposure led to a decrease in gut microbial diversity over generations, along with aggravated anxiety behavior, microgliosis, and altered intestinal tight junction protein expression. Oral sterile soil intervention restored gut microbial diversity in adult mice across generations, concomitantly rescuing abnormalities in behavior, microgliosis, and intestinal barrier integrity. In conclusion, this study simulated an important process of the progressive loss of gut microbiota diversity in modern humans and demonstrated the potential of sterile soil to reverse this process. This study provides a theoretical and experimental basis for research and interventions targeting multiple modern chronic diseases related to intestinal microorganisms.

Postpartum depression: aetiology, pathogenesis and the role of nutrients and dietary supplements in prevention and management

Postpartum depression (PPD) is a challenging psychological disorder faced by 10-30% of mothers across the globe. In India, it occurs among 22% of mothers. Its aetiology and pathophysiology aren't fully understood as of today but multiple theories on the interplay of hormones, neurotransmitters, genetics, epigenetics, nutrients, socio-environmental factors, etc. exist. Nutrients are not only essential for the synthesis of neurotransmitters, but they may also indirectly influence genomic pathways that methylate DNA, and there is evidence for molecular associations between nutritional quality and psychological well-being. Increased behavioural disorders have been attributed to macro- and micronutrient deficiencies, and dietary supplementation has been effective in treating several neuropsychiatric illnesses. Nutritional deficiencies occur frequently in women, especially during pregnancy and breastfeeding. The aim of this study was to perform a comprehensive literature review of evidence-based research in order to identify, gather and summarize existing knowledge on PPD's aetiology, pathophysiology, and the role of nutrients in its prevention as well as management. The possible mechanisms of action of nutrients are also presented here. Study findings show that the risk of depression increases when omega-3 fatty acid levels are low. Both fish oil and folic acid supplements have been used to effectively treat depression. Antidepressant efficacy is lowered by folate insufficiency. Folate, vitamin B12, iron, etc. deficiencies are more prevalent in depressed people than in non-depressed people. Serum cholesterol levels and plasma tryptophan levels are found to be inversely correlated with PPD. Serum vitamin D levels were associated inversely with perinatal depression. These findings highlight the importance of adequate nutrition in the antepartum period. Given that nutritional therapies can be affordable, safe, simple to use, and are typically well-accepted by patients, more focus should be placed on dietary variables in PPD.

Evolutionary Aspects of Diverse Microbial Exposures and Mental Health: Focus on "Old Friends" and Stress Resilience

The prevalence of inflammatory disease conditions, including allergies, asthma, and autoimmune disorders, increased during the latter half of the twentieth century, as societies transitioned from rural to urban lifestyles. A number of hypotheses have been put forward to explain the increasing prevalence of inflammatory disease in modern urban societies, including the hygiene hypothesis and the "Old Friends" hypothesis. In 2008, Rook and Lowry proposed, based on the evidence that increased inflammation was a risk factor for stress-related psychiatric disorders, that the hygiene hypothesis or "Old Friends" hypothesis may be relevant to psychiatric disorders. Since then, it has become more clear that chronic low-grade inflammation is a risk factor for stress-related psychiatric disorders, including anxiety disorders, mood disorders, and trauma- and stressor-related disorders, such as posttraumatic stress disorder (PTSD). Evidence now indicates that persons raised in modern urban environments without daily contact with pets, relative to persons raised in rural environments in proximity to farm animals, respond with greater systemic inflammation to psychosocial stress. Here we consider the possibility that increased inflammation in persons living in modern urban environments is due to a failure of immunoregulation, i.e., a balanced expression of regulatory and effector T cells, which is known to be dependent on microbial signals. We highlight evidence that microbial signals that can drive immunoregulation arise from phylogenetically diverse taxa but are strain specific. Finally, we highlight Mycobacterium vaccae NCTC 11659, a soil-derived bacterium with anti-inflammatory and immunoregulatory properties, as a case study of how single strains of bacteria might be used in a psychoneuroimmunologic approach for prevention and treatment of stress-related psychiatric disorders.

Psychophysiological Responses of Humans during Seed-Sowing Activity Using Soil Inoculated with Streptomyces rimosus

Electroencephalogram (EEG) responses and serum metabolite levels were used to investigate the effects of horticultural activities (seed-sowing) on the psychophysiological aspects of adults based on the presence or absence of the soil microorganism Streptomyces rimosus. In this case, 31 adults were subjected to seed-sowing activities using S. rimosus inoculated (experimental group) and medium (control group) soils. EEG was measured to analyze the resulting psychophysiological response, and blood samples (5 mL) were collected. The relative gamma power (RG), relative high beta (RHB), and SEF 50 and SEF 90 were significantly higher in the right than in the left occipital lobe (p < 0.05). In both occipital lobes, ratios of SMR to theta (RST), mid beta to theta (RMT), and SMR-mid beta to theta (RSMT) were high (p < 0.05). GC-TOF-MS-based serum metabolite analysis detected 33 metabolites. Compared to the control group, the experimental group showed a lower content of amino acids (except aspartic acid), lipids, and C6 sugar monomers after the activity (p < 0.05). Aminomalonic acid was decreased, and aspartic acid was increased (p < 0.05). This study confirmed a positive effect on improving the concentration and attention of adults when seed-sowing activity was performed using S. rimosus-inoculated soil.

Negative correlation between IL-1β, IL-12 and TNF-γ, and cortisol levels in patients with panic disorder

INTRODUCTION

Chronic exposure to stress is a major risk factor in anxiety disorders (ADs) and can be accompanied by an altered microbiome-gut-brain axis and a compromised immune system. In recent years, the study of inflammatory processes in AD has gained special attention. Continued stress causes the reactivity of the hypothalamic-pituitary-adrenal (HPA) axis, the alteration of the intestinal microbiota and the consequent release of pro-inflammatory cytokines, affecting the sensitivity to stress and the similar behavior of anxiety.

METHOD

The aim of the present study was to evaluate the interrelationships between measures of proinflammatory cytokines and cortisol in patients with panic disorder (PD).

RESULTS

The main results of the correlation analysis revealed that the levels of pro-inflammatory cytokines interleukin (IL)-1β, IL-12, and tumor necrosis factor gamma were negatively correlated with cortisol scores (area under the curve with respect to the ground).

CONCLUSIONS

These results suggest that the inflammatory response is associated with the reactivity of the HPA axis in patients with PD and may influence the maintenance of anxiety behavior.

Metabolomic Workflow for the Accurate and High-Throughput Exploration of the Pathways of Tryptophan, Tyrosine, Phenylalanine, and Branched-Chain Amino Acids in Human Biofluids

The modulation of host and dietary metabolites by gut microbiota (GM) is important for maintaining correct host physiology and in the onset of various pathologies. An ultrahigh-performance liquid chromatography-electrospray ionization-tandem mass spectrometry method was developed for the targeted quantitation in human plasma, serum, and urine of 89 metabolites resulting from human-GM cometabolism of dietary essential amino acids tryptophan, tyrosine, and phenylalanine as well as branched-chain amino acids. Ninety-six-well plate hybrid-SPE enables fast clean-up of plasma and serum. Urine was diluted and filtered. A 15 min cycle enabled the acquisition of 96 samples per day, with most of the metabolites stable in aqueous solution for up to 72 h. Calibration curves were specifically optimized to cover expected concentrations in biological fluids, and limits of detection were at the order of ppb. Matrix effects were in acceptable ranges, and analytical recoveries were in general greater than 80%. Inter and intraday precision and accuracy were satisfactory. We demonstrated its application in plasma and urine samples obtained from the same individual in the frame of an interventional study, allowing the quantitation of 51 metabolites. The method could be considered the reference for deciphering changes in human-gut microbial cometabolism in health and disease. Data are available via Metabolights with the identifier MTBLS4399.

Mycobacterium vaccae immunization in rats ameliorates features of age-associated microglia activation in the amygdala and hippocampus

Aging and reduced exposure to environmental microbes can both potentiate neuroinflammatory responses. Prior studies indicate that immunization with the immunoregulatory and anti-inflammatory bacterium, Mycobacterium vaccae (M. vaccae), in aged rats limits neuroimmune activation and cognitive impairments. However, the mechanisms by which M. vaccae immunization ameliorates age-associated neuroinflammatory “priming” and whether microglia are a primary target remain unclear. Here, we investigated whether M. vaccae immunization protects against microglia morphological changes in response to aging. Adult (3 mos) and aged (24 mos) Fisher 344 × Brown Norway rats were immunized with either M. vaccae or vehicle once every week for 3 weeks. Aging led to elevated Iba1 immunoreactivity, microglial density, and deramification of microglia processes in the hippocampus and amygdala but not other brain regions. Additionally, aged rats exhibited larger microglial somas in the dorsal hippocampus, suggestive of a more activated phenotype. Notably, M. vaccae treatment ameliorated indicators of microglia activation in both the amygdala and hippocampus. While changes in morphology appeared to be region-specific, gene markers indicative of microglia activation were upregulated by age and lowered in response to M. vaccae in all brain regions evaluated. Taken together, these data suggest that peripheral immunization with M. vaccae quells markers of age-associated microglia activation.

Salivary Microbiota Is Significantly Less Diverse in Patients with Chronic Spontaneous Urticaria Compared to Healthy Controls: Preliminary Results

Background: Because of the important role in regulating the immune system, increasing evidence suggests a possible implication of gut microbiota in Chronic spontaneous urticaria (CSU). Although the oral cavity is the first site of contact between microbiota and the immune system, the association between salivary microbiota and CSU has not yet been reported. Objective: This case-control study aimed to compare differences in salivary microbiota between CSU patients and healthy controls (HC). Twenty-three participants—13 patients with CSU and 10 HC were enrolled; salivary microbiota was determined by molecular approach targeting 16S ribosomal RNA. Terminal restriction fragment length polymorphism (T-RFLP) analysis was performed. Results: Alpha diversity of salivary microbiota in CSU patients was significantly reduced compared to HC, resulting in alteration of the community composition. Species richness determined via the Shannon index was significantly reduced in the CSU group. Conclusion: Dysbiosis of salivary microbiota may contribute to a dysregulated immune system in the development of CSU. To our knowledge, this was the first study that reported an alteration in salivary microbiota composition in CSU patients.

Technological tools and strategies for culturing human gut microbiota in engineered in vitro models

The gut microbiota directly impacts the pathophysiology of different human body districts. Consequently, microbiota investigation is an hot topic of research and its in vitro culture has gained extreme interest in different fields. However, the high sensitivity of microbiota to external stimuli, such as sampling procedure, and the physicochemical complexity of the gut environment make its in vitro culture a challenging task. New engineered microfluidic gut-on-a-chip devices have the potential to model some important features of the intestinal structure, but they are usually unable to sustain culture of microbiota over an extended period of time. The integration of gut-on-a-chip devices with bioreactors for continuous bacterial culture would lead to fast advances in the study of microbiota-host crosstalk. In this review, we summarize the main technologies for the continuous culture of microbiota as upstream systems to be coupled with microfluidic devices to study bacteria-host cells communication. The engineering of integrated microfluidic platforms, capable of sustaining both anaerobic and aerobic cultures, would be the starting point to unveil complex biological phenomena proper of the microbiota-host crosstalks, paving to way to multiple research and technological applications.

Immunization with a heat-killed bacterium, Mycobacterium vaccae NCTC 11659, prevents the development of cortical hyperarousal and a PTSD-like sleep phenotype after sleep disruption and acute stress in mice

STUDY OBJECTIVES

Sleep deprivation induces systemic inflammation that may contribute to stress vulnerability and other pathologies. We tested the hypothesis that immunization with heat-killed Mycobacterium vaccae NCTC 11659 (MV), an environmental bacterium with immunoregulatory and anti-inflammatory properties, prevents the negative impacts of 5 days of sleep disruption on stress-induced changes in sleep, behavior, and physiology in mice.

METHODS

In a 2 × 2 × 2 experimental design, male C57BL/6N mice were given injections of either MV or vehicle on days -17, -10, and -3. On days 1-5, mice were exposed to intermittent sleep disruption, whereby sleep was disrupted for 20 h per day. Immediately following sleep disruption, mice were exposed to 1-h social defeat stress or novel cage (control) conditions. Object location memory (OLM) testing was conducted 24 h after social defeat, and tissues were collected 6 days later to measure inflammatory markers. Sleep was recorded using electroencephalography (EEG) and electromyography (EMG) throughout the experiment.

RESULTS

In vehicle-treated mice, only the combination of sleep disruption followed by social defeat (double hit): (1) increased brief arousals and NREM beta (15-30 Hz) EEG power in sleep immediately post-social defeat compared to baseline; (2) induced an increase in the proportion of rapid-eye-movement (REM) sleep and number of state shifts for at least 5 days post-social defeat; and (3) induced hyperlocomotion and lack of habituation in the OLM task. Immunization with MV prevented most of these sleep and behavioral changes.

CONCLUSIONS

Immunization with MV ameliorates a stress-induced sleep and behavioral phenotype that shares features with human posttraumatic stress disorder.

Anxiolytic effects of administration of a commercially available prebiotic blend of galacto-oligosaccharides and beta glucans in Sprague-Dawley rats

Prebiotics are nondigestible food agents that stimulate the growth of bacteria in the gut, whereas probiotics are live microorganisms that replace or restore beneficial bacteria in the digestive tract. Both agents have been shown to have beneficial qualities within the microbiota-gut-brain axis, but the behavioural effects of prebiotics have been less studied than probiotics. Whereas several studies have shown that prebiotics reduce inflammation and modulate anxiety in animals that are injected with lipopolysacccharides or chronically stressed animals, respectively, it is not yet known how they affect a healthy organism. Here, we tested the behavioural effects of galacto-oligosaccharides and beta glucan as a commercially available prebiotic blend in healthy, naïve Sprague-Dawley rats. We used the open field test and elevated plus maze to assess anxiety-like behaviour in controls and in rats that ingested the prebiotic blend in their drinking water. We also used the Morris Water Maze to assess spatial memory performance in controls and prebiotic treated rats. Rats treated with prebiotics spent more time in the intermediate zone of the open field test and in the open arms of the elevated plus maze, and exhibited a shorter latency to enter each of these zones. No significant differences between groups were found in the Morris Water Maze. Our results suggest that whereas prebiotics significantly reduced anxiety-like behaviours, it had no effect on spatial memory performance. Altogether, our data indicate that commercially available prebiotic beta glucan blends have anxiolytic effects in healthy rats.

The Neuroprotective Effect of Tea Polyphenols on the Regulation of Intestinal Flora

Tea polyphenols (TPs) are the general compounds of natural polyhydroxyphenols extracted in tea. Although a large number of studies have shown that TPs have obvious neuroprotective and neuro repair effects, they are limited due to the low bioavailability in vivo. However, TPs can act indirectly on the central nervous system by affecting the “microflora–gut–brain axis”, in which the microbiota and its composition represent a factor that determines brain health. Bidirectional communication between the intestinal microflora and the brain (microbe–gut–brain axis) occurs through a variety of pathways, including the vagus nerve, immune system, neuroendocrine pathways, and bacteria-derived metabolites. This axis has been shown to influence neurotransmission and behavior, which is usually associated with neuropsychiatric disorders. In this review, we discuss that TPs and their metabolites may provide benefits by restoring the imbalance of intestinal microbiota and that TPs are metabolized by intestinal flora, to provide a new idea for TPs to play a neuroprotective role by regulating intestinal flora.

Exposure to airborne bacteria depends upon vertical stratification and vegetation complexity

Exposure to biodiverse aerobiomes supports human health, but it is unclear which ecological factors influence exposure. Few studies have investigated near-surface green space aerobiome dynamics, and no studies have reported aerobiome vertical stratification in different urban green spaces. We used columnar sampling and next generation sequencing of the bacterial 16S rRNA gene, combined with geospatial and network analyses to investigate urban green space aerobiome spatio-compositional dynamics. We show a strong effect of habitat on bacterial diversity and network complexity. We observed aerobiome vertical stratification and network complexity that was contingent on habitat type. Tree density, closer proximity, and canopy coverage associated with greater aerobiome alpha diversity. Grassland aerobiomes exhibited greater proportions of putative pathogens compared to scrub, and also stratified vertically. We provide novel insights into the urban ecosystem with potential importance for public health, whereby the possibility of differential aerobiome exposures appears to depend on habitat type and height in the airspace. This has important implications for managing urban landscapes for the regulation of aerobiome exposure.

Bovine Milk Oligosaccharides and Human Milk Oligosaccharides Modulate the Gut Microbiota Composition and Volatile Fatty Acid Concentrations in a Preclinical Neonatal Model

Milk oligosaccharides (OS) shape microbiome structure and function, but their relative abundances differ between species. Herein, the impact of the human milk oligosaccharides (HMO) (2′-fucosyllactose [2′FL] and lacto-N-neotetraose [LNnT]) and OS isolated from bovine milk (BMOS) on microbiota composition and volatile fatty acid (VFA) concentrations in ascending colon (AC) contents and feces was assessed. Intact male piglets received diets either containing 6.5 g/L BMOS (n = 12), 1.0 g/L 2′FL + 0.5 g/L LNnT (HMO; n = 12), both (HMO + BMOS; n = 10), or neither (CON; n = 10) from postnatal day (PND) 2 to 34. Microbiota were assessed by 16S rRNA gene sequencing and real-time PCR, and VFA were measured by gas chromatography. The microbiota was affected by OS in an intestine region-specific manner. BMOS reduced (p < 0.05) microbial richness in the AC, microbiota composition in the AC and feces, and acetate concentrations in AC, regardless of HMO presence. HMO alone did not affect overall microbial composition, but increased (p < 0.05) the relative proportion of specific taxa, including Blautia, compared to other groups. Bacteroides abundance was increased (p < 0.05) in the AC by BMOS and synergistically by BMOS + HMO in the feces. Distinct effects of HMO and BMOS suggest complementary and sometimes synergistic benefits of supplementing a complex mixture of OS to formula.

The gut reaction to couples' relationship troubles: A route to gut dysbiosis through changes in depressive symptoms

The gut microbiota plays a role in a wide range of diseases and disorders, with low microbial diversity and richness emerging as notable risk factors. This longitudinal study addressed the impact of marital quality (assessed by the Couples Satisfaction Index) on changes in depressive symptoms, and gut diversity, richness, and permeability. On two occasions an average of 90 days apart, 162 people provided stool and blood samples, and completed questionnaires. Depressive symptoms, assessed by the Center for Epidemiological Studies Depression Scale (CES-D), increased from visit 1 to visit 2 in those with clinically significant relationship problems, in contrast to the lack of change among their more satisfied counterparts. These changes in depression were consequential: the gut microbiota's diversity and richness decreased in tandem with the increase in depressive symptoms. Lower relationship satisfaction also foreshadowed increases in lipopolysaccharide binding protein from visit 1 to visit 2, reflecting greater translocation of bacterial endotoxin from the gut to blood circulation, a process that fuels inflammation. Lower diversity and richness provide a pathway from depressive symptoms and marital distress to subsequent health risk.

Gut microbiota dysbiosis in depressed women: The association of symptom severity and microbiota function

BACKGROUND

The association between abnormal gut microbiome composition and depression is well established. However, the composition and functional capacity of the gut microbiota regarding depressed women has been poorly addressed.

METHODS

Stool samples from 62 female patients with major depressive disorder (MDD) and 46 healthy controls (Con) were analyzed by 16S rRNA gene sequencing; Twenty fecal samples from the patient group and 21 fecal samples from the Con group were further analyzed by shotgun metagenomic sequencing. Psychiatric symptoms and psychological, social, and professional functioning was also assessed.

RESULTS

Phylum Bacteroidetes, proteobaeteria, and Fusobacteria were greatly enriched in patients with MDD, while the Firmicutes and Actinobacteria phyla were consistently higher in Con. Notably, 18 microbial markers were identified on a random forest model and achieve an area under the curve of 0.92 between patients with MDD and the Con group. Forty-five species and their associated function were identified with statistically significant differences between patients with MDD and the Con group.

LIMITATIONS

The number of recruited samples, especially samples enrolled for shotgun metagenomic sequencing was relatively small, and the stool samples were collected only at baseline, making it difficult to establish a causal association between changes in gut microbiota compositions and disease remission.

CONCLUSIONS

This study characterizes the gut microbiota and their related function in female MDD. The gut microbiota-based biomarkers may be helpful in diagnosis and the altered gut microbial metabolites may contribute to the pathogenesis of MDD in women, representing potential microbial targets.

Between a hygiene rock and a hygienic hard place: Avoiding SARS-CoV-2 while needing environmental exposures for immunity

Suboptimal understanding of concepts related to hygiene by the general public, clinicians and researchers is a persistent problem in health and medicine. Although hygiene is necessary to slow or prevent deadly pandemics of infectious disease such as coronavirus disease 2019 (COVID-19), hygiene can have unwanted effects. In particular, some aspects of hygiene cause a loss of biodiversity from the human body, characterized by the almost complete removal of intestinal worms (helminths) and protists. Research spanning more than half a century documents that this loss of biodiversity results in an increased propensity for autoimmune disease, allergic disorders, probably neuropsychiatric problems and adverse reactions to infectious agents. The differences in immune function between communities with and communities without helminths have become so pronounced that the reduced lethality of severe acute respiratory syndrome coronavirus 2 in low-income countries compared to high-income countries was predicted early in the COVID-19 pandemic. This prediction, based on the maladaptive immune responses observed in many cases of COVID-19 in high-income countries, is now supported by emerging data from low-income countries. Herein, hygiene is subdivided into components involving personal choice versus components instituted by community wide systems such as sewage treatment facilities and water treatment plants. The different effects of personal hygiene and systems hygiene are described, and appropriate measures to alleviate the adverse effects of hygiene without losing the benefits of hygiene are discussed. Finally, text boxes are provided to function as stand-alone, public-domain handouts with the goal of informing the public about hygiene and suggesting solutions for biomedical researchers and policy makers. Lay Summary: Hygiene related to sewer systems and other technology can have adverse effects on immune function, and is distinct from personal hygiene practices such as hand washing and social distancing. Dealing with the drawbacks of hygiene must be undertaken without compromising the protection from infectious disease imposed by hygiene.

The Holobiont Blindspot: Relating Host-Microbiome Interactions to Cognitive Biases and the Concept of the "Umwelt"

Cognitive biases can lead to misinterpretations of human and non-human biology and behavior. The concept of the Umwelt describes phylogenetic contrasts in the sensory realms of different species and has important implications for evolutionary studies of cognition (including biases) and social behavior. It has recently been suggested that the microbiome (the diverse network of microorganisms in a given environment, including those within a host organism such as humans) has an influential role in host behavior and health. In this paper, we discuss the host’s microbiome in relation to cognitive biases and the concept of the Umwelt. Failing to consider the role of host–microbiome (collectively termed a “holobiont”) interactions in a given behavior, may underpin a potentially important cognitive bias – which we refer to as the Holobiont Blindspot. We also suggest that microbially mediated behavioral responses could augment our understanding of the Umwelt. For example, the potential role of the microbiome in perception and action could be an important component of the system that gives rise to the Umwelt. We also discuss whether microbial symbionts could be considered in System 1 thinking – that is, decisions driven by perception, intuition and associative memory. Recognizing Holobiont Blindspots and considering the microbiome as a key factor in the Umwelt and System 1 thinking has the potential to advance studies of cognition. Furthermore, investigating Holobiont Blindspots could have important implications for our understanding of social behaviors and mental health. Indeed, the way we think about how we think may need to be revisited.

Vertical Stratification in Urban Green Space Aerobiomes

BACKGROUND

Exposure to a diverse environmental microbiome is thought to play an important role in "educating" the immune system and facilitating competitive exclusion of pathogens to maintain human health. Vegetation and soil are key sources of airborne microbiota--the aerobiome. A limited number of studies have attempted to characterize the dynamics of near surface green space aerobiomes, and no studies to date have investigated these dynamics from a vertical perspective. Vertical stratification in the aerobiome could have important implications for public health and for the design, engineering, and management of urban green spaces.

OBJECTIVES

The primary objectives of this study were to: a) assess whether significant vertical stratification in bacterial species richness and evenness (alpha diversity) of the aerobiome occurred in a parkland habitat in Adelaide, South Australia; b) assess whether significant compositional differences (beta diversity) between sampling heights occurred; and c) to preliminarily assess whether there were significant altitudinal differences in potentially pathogenic and beneficial bacterial taxa.

METHODS

We combined an innovative columnar sampling method at soil level, 0.0, 0.5, 1.0, and 2.0 m , using passive petri dish sampling to collect airborne bacteria. We used a geographic information system (GIS) to select study sites, and we used high-throughput sequencing of the bacterial 16S rRNA gene to assess whether significant vertical stratification of the aerobiome occurred.

RESULTS

Our results provide evidence of vertical stratification in both alpha and beta (compositional) diversity of airborne bacterial communities, with diversity decreasing roughly with height. We also found significant vertical stratification in potentially pathogenic and beneficial bacterial taxa.

DISCUSSION

Although additional research is needed, our preliminary findings point to potentially different exposure attributes that may be contingent on human height and activity type. Our results lay the foundations for further research into the vertical characteristics of urban green space aerobiomes and their implications for public health and urban planning. https://doi.org/10.1289/EHP7807.

Sex dependent effects of post-natal penicillin on brain, behavior and immune regulation are prevented by concurrent probiotic treatment

There is increasing awareness of the need to consider potential long-term effects of antibiotics on the health of children. In addition to being associated with immune and metabolic diseases, there is evidence that early-life antibiotic exposure can affect neurodevelopment. Here we investigated the effect of low dose of penicillin V on mice when administered for 1 week immediately prior to weaning. We demonstrated that exposure to the antibiotic during the pre-weaning period led to long-term changes in social behaviour, but not anxiety-like traits, in male mice only. The change in behaviour of males was associated with decreased hippocampal expression of AVPR1A and AVPR1B while expression of both receptors was increased in females. Spleens of male mice also showed an increase in the proportion of activated dendritic cells and a corresponding decrease in regulatory T cells with penicillin exposure. All changes in brain, behaviour and immune cell populations, associated with penicillin exposure, were absent in mice that received L. rhamnosus JB-1 supplementation concurrent with the antibiotic. Our study indicates that post-natal exposure to a clinically relevant dose of antibiotic has long-term, sex dependent effects on the CNS and may have implications for the development of neuropsychiatric disorders. Importantly, we also provide further evidence that probiotic based strategies may be of use in counteracting detrimental effects of early-life antibiotics on neurodevelopment.

Health impact of the Anthropocene: the complex relationship between gut microbiota, epigenetics, and human health, using obesity as an example

The growing prevalence of obesity worldwide poses a public health challenge in the current geological epoch, the Anthropocene. Global changes caused by urbanisation, loss of biodiversity, industrialisation, and land-use are happening alongside microbiota dysbiosis and increasing obesity prevalence. How alterations of the gut microbiota are associated with obesity and the epigenetic mechanism mediating this and other health outcome associations are in the process of being unveiled. Epigenetics is emerging as a key mechanism mediating the interaction between human body and the environment in producing disease. Evidence suggests that the gut microbiota plays a role in obesity as it contributes to different mechanisms, such as metabolism, body weight and composition, inflammatory responses, insulin signalling, and energy extraction from food. Consistently, obese people tend to have a different epigenetic profile compared to non-obese. However, evidence is usually scattered and there is a growing need for a structured framework to conceptualise this complexity and to help shaping complex solutions. In this paper, we propose a framework to analyse the observed associations between the alterations of microbiota and health outcomes and the role of epigenetic mechanisms underlying them using obesity as an example, in the current context of global changes within the Anthropocene.

Microbiota-Orientated Treatments for Major Depression and Schizophrenia

Background and significance. There is a need to develop new hypothesis-driven treatment for both both major depression (MD) and schizophrenia in which the risk of depression is 5 times higher than the general population. Major depression has been also associated with poor illness outcomes including pain, metabolic disturbances, and less adherence. Conventional antidepressants are partly effective, and 44% of the subjects remain unremitted under treatment. Improving MD treatment efficacy is thus needed to improve the SZ prognosis. Microbiota-orientated treatments are currently one of the most promising tracks. Method. This work is a systematic review synthetizing data of arguments to develop microbiota-orientated treatments (including fecal microbiota transplantation (FMT)) in major depression and schizophrenia. Results. The effectiveness of probiotic administration in MD constitutes a strong evidence for developing microbiota-orientated treatments. Probiotics have yielded medium-to-large significant effects on depressive symptoms, but it is still unclear if the effect is maintained following probiotic discontinuation. Several factors may limit MD improvement when using probiotics, including the small number of bacterial strains administered in probiotic complementary agents, as well as the presence of a disturbed gut microbiota that probably limits the probiotics’ impact. FMT is a safe technique enabling to improve microbiota in several gut disorders. The benefit/risk ratio of FMT has been discussed and has been recently improved by capsule administration. Conclusion. Cleaning up the gut microbiota by transplanting a totally new human gut microbiota in one shot, which is referred to as FMT, is likely to strongly improve the efficacy of microbiota-orientated treatments in MD and schizophrenia and maintain the effect over time. This hypothesis should be tested in future clinical trials.

Association of the Salivary Microbiome With Animal Contact During Early Life and Stress-Induced Immune Activation in Healthy Participants

The prevalence of stress-associated somatic and psychiatric disorders is increased in environments offering a narrow relative to a wide range of microbial exposure. Moreover, different animal and human studies suggest that an overreactive immune system not only accompanies stress-associated disorders, but might even be causally involved in their pathogenesis. In support of this hypothesis, we recently showed that urban upbringing in the absence of daily contact with pets, compared to rural upbringing in the presence of daily contact with farm animals, is associated with a more pronounced immune activation following acute psychosocial stressor exposure induced by the Trier Social Stress Test (TSST). Here we employed 16S rRNA gene sequencing to test whether this difference in TSST-induced immune activation between urban upbringing in the absence of daily contact with pets (n = 20) compared with rural upbringing in the presence of daily contact with farm animals (n = 20) is associated with differences in the composition of the salivary microbiome. Although we did not detect any differences in alpha or beta diversity measures of the salivary microbiome between the two experimental groups, statistical analysis revealed that the salivary microbial beta diversity was significantly higher in participants with absolutely no animal contact (n = 5, urban participants) until the age of 15 compared to all other participants (n = 35) reporting either daily contact with farm animals (n = 20, rural participants) or occasional pet contact (n = 15, urban participants). Interestingly, when comparing these urban participants with absolutely no pet contact to the remaining urban participants with occasional pet contact, the former also displayed a significantly higher immune, but not hypothalamic-pituitary-adrenal (HPA) axis or sympathetic nervous system (SNS) activation, following TSST exposure. In summary, we conclude that only urban upbringing with absolutely no animal contact had long-lasting effects on the composition of the salivary microbiome and potentiates the negative consequences of urban upbringing on stress-induced immune activation.

The connection between microbiome and schizophrenia

There has been an accumulation of knowledge about the human microbiome, some detailed investigations of the gastrointestinal microbiota and its functions, and the highlighting of complex interactions between the gut, the gut microbiota, and the central nervous system. That assumes the involvement of the microbiome in the pathogenesis of various CNS diseases, including schizophrenia. Given this information and the fact, that the gut microbiota is sensitive to internal and environmental influences, we have speculated that among the factors that influence the formation and composition of gut microbiota during life, possible key elements in the schizophrenia development chain are hidden where gut microbiota is a linking component. This article aims to describe and understand the developmental relationships between intestinal microbiota and the risk of developing schizophrenia.

Feeding Mode, but Not Prebiotics, Affects Colonic Microbiota Composition and Volatile Fatty Acid Concentrations in Sow-Reared, Formula-Fed, and Combination-Fed Piglets

BACKGROUND

Many infants consume both human milk and infant formula (combination-fed); however, little is known about how combination-feeding affects the gut microbiota or prebiotic fermentation compared to formula feeding.

OBJECTIVES

We investigated the impact of feeding mode and prebiotics on bacterial colonization and volatile fatty acid (VFA) concentrations.

METHODS

Newborn piglets (Large White and Landrace) were randomly assigned to 5 groups (n = 6/group): formula-fed (FF), formula-fed with prebiotics (FP), sow-reared (SR), combination-fed (CF), and combination-fed with prebiotics (CP). SR piglets remained with the sows 24 h/d. FF and FP were fed formula or formula with galactooligosaccharide and inulin (4 g/L in a 4:1 ratio). CF and CP were sow-reared for 5 d and then rotated between the sow and formula-feeding every 12 h. Ascending colon contents were collected at day 21. The microbiota was analyzed by pyrosequencing and denaturing gradient gel electrophoresis (DGGE). VFAs were determined by gas chromatography.

RESULTS

Distance-based redundancy analysis of DGGE and pyrosequencing data separated microbiota of FF from CF and SR. CF differed from SR by DGGE, but only a trend (P = 0.09) by pyrosequencing. Bacterial composition of CF was more similar to SR than FF. No bacterial genera in CF significantly differed from SR; however, 9 genera differed between CF and FF, including Lactobacillus, Clostridium XIVa, and Fusobacterium. VFA concentrations were similar between CF and SR, while isovalerate and isobutyrate were 2-fold greater (P < 0.05) in CF than FF. Neither microbiota nor VFA profile was affected by prebiotic supplementation.

CONCLUSIONS

Microbial colonization patterns and VFA profiles of CF piglets were more similar to SR piglets than FF piglets. Prebiotics did not affect piglet bacterial composition and/or VFA concentrations relative to the main feeding modes (FF and CF). Thus, partial exposure to breast milk can be beneficial for microbiota development of FF neonates.

The Possible Role of the Microbiota-Gut-Brain-Axis in Autism Spectrum Disorder

New research points to a possible link between autism spectrum disorder (ASD) and the gut microbiota as many autistic children have co-occurring gastrointestinal problems. This review focuses on specific alterations of gut microbiota mostly observed in autistic patients. Particularly, the mechanisms through which such alterations may trigger the production of the bacterial metabolites, or leaky gut in autistic people are described. Various altered metabolite levels were observed in the blood and urine of autistic children, many of which were of bacterial origin such as short chain fatty acids (SCFAs), indoles and lipopolysaccharides (LPS). A less integrative gut-blood-barrier is abundant in autistic individuals. This explains the leakage of bacterial metabolites into the patients, triggering new body responses or an altered metabolism. Some other co-occurring symptoms such as mitochondrial dysfunction, oxidative stress in cells, altered tight junctions in the blood-brain barrier and structural changes in the cortex, hippocampus, amygdala and cerebellum were also detected. Moreover, this paper suggests that ASD is associated with an unbalanced gut microbiota (dysbiosis). Although the cause-effect relationship between ASD and gut microbiota is not yet well established, the consumption of specific probiotics may represent a side-effect free tool to re-establish gut homeostasis and promote gut health. The diagnostic and therapeutic value of bacterial-derived compounds as new possible biomarkers, associated with perturbation in the phenylalanine metabolism, as well as potential therapeutic strategies will be discussed.

Altered Gut Microbiota Diversity and Composition in Chronic Urticaria

BACKGROUND

The pathogenesis of chronic urticaria (CU) is closely related to imbalances in immunity. The gastrointestinal microflora provides a vast and continuous stimulation for the immune system. However, the composition and diversity of gut microflora in CU patients are rarely reported.

METHODS

10 CU patients and 10 healthy individuals were selected in this study, and their intestinal microbiome was detected by 16S rRNA sequencing. The data were analyzed using R language software.

RESULTS

392 bacterial OTUs were common in the CU and healthy groups, but there were 159 OTUs particularly existing in the CU group, while 87 OTUs only were observed in healthy individuals. The bacterial diversity was reduced in CU patients compared with healthy individuals. The principal component analysis (PCA) and principal coordinate analysis (PCoA) revealed that the bacterial cluster in CU patients and the healthy controls were divided into different branches. Pathogenic strains including Escherichia coli were significantly higher in CU, while Faecalibacterium prausnitzii, Prevotella copri, and Bacteroides sp. were significantly lower in CU when compared with the healthy controls. CU patients with a high abundance of Escherichia coli had no ideal effect for probiotic therapy.

CONCLUSION

Our results demonstrated that the microbial composition was significantly different between CU patients and the healthy individual, which may be the reason leading to the various outcomes of probiotic treatment.

Developmental Trajectories of Early Life Stress and Trauma: A Narrative Review on Neurobiological Aspects Beyond Stress System Dysregulation

Early life stressors display a high universal prevalence and constitute a major public health problem. Prolonged psychoneurobiological alterations as sequelae of early life stress (ELS) could represent a developmental risk factor and mediate risk for disease, leading to higher physical and mental morbidity rates in later life. ELS could exert a programming effect on sensitive neuronal brain networks related to the stress response during critical periods of development and thus lead to enduring hyper- or hypo-activation of the stress system and altered glucocorticoid signaling. In addition, alterations in emotional and autonomic reactivity, circadian rhythm disruption, functional and structural changes in the brain, as well as immune and metabolic dysregulation have been lately identified as important risk factors for a chronically impaired homeostatic balance after ELS. Furthermore, human genetic background and epigenetic modifications through stress-related gene expression could interact with these alterations and explain inter-individual variation in vulnerability or resilience to stress. This narrative review presents relevant evidence from mainly human research on the ten most acknowledged neurobiological allostatic pathways exerting enduring adverse effects of ELS even decades later (hypothalamic-pituitary-adrenal axis, autonomic nervous system, immune system and inflammation, oxidative stress, cardiovascular system, gut microbiome, sleep and circadian system, genetics, epigenetics, structural, and functional brain correlates). Although most findings back a causal relation between ELS and psychobiological maladjustment in later life, the precise developmental trajectories and their temporal coincidence has not been elucidated as yet. Future studies should prospectively investigate putative mediators and their temporal sequence, while considering the potentially delayed time-frame for their phenotypical expression. Better screening strategies for ELS are needed for a better individual prevention and treatment.

Immunization with Mycobacterium vaccae induces an anti-inflammatory milieu in the CNS: Attenuation of stress-induced microglial priming, alarmins and anxiety-like behavior

Exposure to stressors induces anxiety- and depressive-like behaviors, which are mediated, in part, by neuroinflammatory processes. Recent findings demonstrate that treatment with the immunoregulatory and anti-inflammatory bacterium, Mycobacterium vaccae (M. vaccae), attenuates stress-induced exaggeration of peripheral inflammation and stress-induced anxiety-like behavioral responses. However, the effects of M. vaccae on neuroimmune processes have largely been unexplored. In the present study, we examined the effect of M. vaccae NCTC11659 on neuroimmune regulation, stress-induced neuroinflammatory processes and anxiety-like behavior. Adult male rats were immunized 3× with a heat-killed preparation of M. vaccae (0.1 mg, s.c.) or vehicle. M. vaccae induced an anti-inflammatory immunophenotype in hippocampus (increased interleukin (Il)4, Cd200r1, and Mrc1 mRNA expression) and increased IL4 protein 8 d after the last immunization. Central administration of recombinant IL4 recapitulated the effects of M. vaccae on Cd200r1 and Mrc1 mRNA expression. M. vaccae reduced basal levels of genes (Nlrp3 and Nfkbia) involved in microglial priming; thus, we explored the effects of M. vaccae on stress-induced hippocampal microglial priming and HMGB1, which mediates priming. We found that M. vaccae blocked stress-induced decreases in Cd200r1, increases in the alarmin HMGB1, and priming of the microglial response to immune challenge. Furthermore, M. vaccae prevented stress-induced increases in anxiety-like behavior. The present findings suggest that M. vaccae enhances immunomodulation in the CNS and mitigates the neuroinflammatory and behavioral effects of stress, which may underpin its capacity to impart a stress resilient phenotype.

Mechanisms underlying the effects of stress on tumorigenesis and metastasis (Review)

Stress is one of the fundamental survival mechanisms in nature. Although chronic or long-lasting stress can be detrimental to health, acute or short-term stress can have health benefits. The aim of the present review was to address the complexity and significance of stress in tumorigenesis. The review covers an evaluation of previously used and reported experimental animal models of stress, as well as the effects of stress on the neuroendocrine system, immune function, gut microbiota, and inflammation and multidrug resistance, all of which are closely associated with cancer occurrence, progression and treatment. The review concludes that understanding the efficacy of stress management (prevention and rehabilitation) is crucial to the development of comprehensive and individualized strategies for cancer prevention and treatment.

The protective effect of Lactobacillus and Bifidobacterium as the gut microbiota members against chronic urticaria

BACKGROUND

Chronic Urticaria is a common disorder which is defined by recurrent occurrence of wheals and sometimes angioedema. It has a notable influence on the patients' quality of life. Regulation of the immune system is one of the important roles of the gut microbiota. The effect of dysbiosis considering some members of gut microbiota in patients with chronic urticaria has been demonstrated in our previous study.

OBJECTIVE

Comparing the frequency and bacterial load of Lactobacillus, Bifidobacterium, and Bacteroides between patients with chronic urticaria and healthy controls.

METHODS

20 patients with chronic urticaria and 20 age and sex matched healthy individuals were included in the present study. Stool samples were analyzed for determining the frequency and bacterial load of Lactobacillus, Bifidobacterium, and Bacteroides genera.

RESULTS

There were no significant differences among the frequencies of detectable Lactobacillus, Bifidobacterium, or Bacteroides in stool samples of patients with chronic urticaria and healthy controls. The relative amounts of Lactobacillus and Bifidobacterium were significantly higher in fecal samples from controls compared to patients with chronic urticaria (P = 0.038 and 0.039, respectively).

CONCLUSION

It is the first study on the implication of Lactobacillus, Bifidobacterium, and Bacteroides genera as gut microbiota members in patients with chronic urticaria.

An Ontology Systems Approach on Human Brain Expression and Metaproteomics

Research in the last decade has shown growing evidence of the gut microbiota influence on brain physiology. While many mechanisms of this influence have been proposed in animal models, most studies in humans are the result of a pathology–dysbiosis association and very few have related the presence of certain taxa with brain substructures or molecular pathways. In this paper, we associated the functional ontologies in the differential expression of brain substructures from the Allen Brain Atlas database, with those of the metaproteome from the Human Microbiome Project. Our results showed several coherent clustered ontologies where many taxa could influence brain expression and physiology. A detailed analysis of psychobiotics showed specific slim ontologies functionally associated with substructures in the basal ganglia and cerebellar cortex. Some of the most relevant slim ontology groups are related to Ion transport, Membrane potential, Synapse, DNA and RNA metabolism, and Antigen processing, while the most relevant neuropathology found was Parkinson disease. In some of these cases, new hypothetical gut microbiota-brain interaction pathways are proposed.

Intestinal worms eating neuropsychiatric disorders? Apparently so

A number of factors in Western society, including inflammatory diets, sedentary lifestyles, vitamin D deficiency and chronic psychological stress, are known to induce inflammation and to be associated with neuropsychiatric disorders. One factor that is emerging as a potential inflammation inducing factor is biota depletion, or loss of biodiversity from the ecosystem of the human body as a result of industrialization. Originally known as the "hygiene hypothesis", biota alteration theory describes the effects of biota alteration on the human immune system. Work on this topic has pinpointed depletion of helminths as a key loss to the body's ecosystem in Western society, and suggests that some exposure to helminths, ubiquitous prior to the modern era, may be necessary for normal immune system development. Socio-medical studies of humans "self-treating" with helminths as well as limited studies in animal models strongly suggest that helminth therapy may be a productive approach toward treating a range of neuropsychiatric disorders, including chronic fatigue, migraine headaches, depression and anxiety disorders. However, helminth therapy faces some daunting hurdles, including the lack of a financial incentive for development, despite a tremendous potential market for the organisms. It is argued that benevolent donation for early trials as well as changes in regulatory policy to accommodate helminth therapy may be important for the field to develop. It is hoped that future success with some high-profile trials can propel the field, now dominated more by self-treatment than by clinical trials, forward into the main stream of medicine.

Gut dysbiosis and irritable bowel syndrome: The potential role of probiotics

OBJECTIVE

To discuss the role of gut dysbiosis in the development of irritable bowel syndrome (IBS) and the impact of probiotics as a potential therapeutic measure.

METHODS

PubMed was used to search for all of the studies published over the last 15 years using the key words: "irritable bowel syndrome" and "gut dysbiosis" or "probiotic". More than 800 articles were found, but only those published in English or providing evidence-based data were included in the evaluation.

RESULTS

IBS is a common disease for which no resolutive therapy is presently available. In recent years, strong evidence of a possible relationship between modifications of the gut microbiota composition and development of IBS has been collected. Moreover, the evidence showed that attempts to treat acute infectious and post-antibiotic gastroenteritis with some probiotics were significantly effective in a great number of patients, leading many experts to suggest the use of probiotics to address all of the clinical problems associated with IBS.

CONCLUSION

The available data are promising, but presently, a precise definition of which probiotic or which mixture of probiotics is effective cannot be made. Moreover, the dose and duration of treatment has not been established. Finally, we do not know whether probiotic treatment should be different according to the type of IBS. Further studies are needed before probiotics can be considered a reliable treatment for IBS.

Microbiota abnormalities and the therapeutic potential of probiotics in the treatment of mood disorders

Major depressive disorder (MDD) and bipolar disorder (BD) are among the leading causes of burden and disability worldwide. Despite intensified research efforts to improve the treatment options and remission rates in mood disorders, no disease modifying treatment exists for these disorders. Accumulating evidence implicates the involvement of the gut microbiota in processes relevant to etiopathology of central nervous system-based disorders. The objective of this article was to critically evaluate the evidence supporting the link between gastrointestinal microbiota and mood disorders and to discuss the potential benefits of using probiotics in the treatment of MDD and BD. The concept of psychobiotics, which is bacterial-based interventions with mental health benefit, is emerging in the field. On the other hand, while probiotics might potentially represent a significant advance, specific roles of microbiota in the pathophysiology of mood disorders still need further investigation along with intervention studies.

Production and Use of Hymenolepis diminuta Cysticercoids as Anti-Inflammatory Therapeutics

Helminthic therapy has shown considerable promise as a means of alleviating some inflammatory diseases that have proven resistant to pharmaceutical intervention. However, research in the field has been limited by a lack of availability to clinician scientists of a helminth that is relatively benign, non-communicable, affordable, and effectively treats disease. Previous socio-medical studies have found that some individuals self-treating with helminths to alleviate various diseases are using the rat tapeworm (cysticercoid developmental stage of Hymenolepis diminuta; HDC). In this study, we describe the production and use of HDCs in a manner that is based on reports from individuals self-treating with helminths, individuals producing helminths for self-treatment, and physicians monitoring patients that are self-treating. The helminth may fit the criteria needed by clinical scientists for clinical trials, and the methodology is apparently feasible for any medical center to reproduce. It is hoped that future clinical trials using this organism may shed light on the potential for helminthic therapy to alleviate inflammatory diseases. Further, it is hoped that studies with HDCs may provide a stepping stone toward population-wide restoration of the biota of the human body, potentially reversing the inflammatory consequences of biota depletion that currently affect Western society.

The Microbiome in Posttraumatic Stress Disorder and Trauma-Exposed Controls: An Exploratory Study

OBJECTIVE

Inadequate immunoregulation and elevated inflammation may be risk factors for posttraumatic stress disorder (PTSD), and microbial inputs are important determinants of immunoregulation; however, the association between the gut microbiota and PTSD is unknown. This study investigated the gut microbiome in a South African sample of PTSD-affected individuals and trauma-exposed (TE) controls to identify potential differences in microbial diversity or microbial community structure.

METHODS

The Clinician-Administered PTSD Scale for DSM-5 was used to diagnose PTSD according to Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition criteria. Microbial DNA was extracted from stool samples obtained from 18 individuals with PTSD and 12 TE control participants. Bacterial 16S ribosomal RNA gene V3/V4 amplicons were generated and sequenced. Microbial community structure, α-diversity, and β-diversity were analyzed; random forest analysis was used to identify associations between bacterial taxa and PTSD.

RESULTS

There were no differences between PTSD and TE control groups in α- or β-diversity measures (e.g., α-diversity: Shannon index, t = 0.386, p = .70; β-diversity, on the basis of analysis of similarities: Bray-Curtis test statistic = -0.033, p = .70); however, random forest analysis highlighted three phyla as important to distinguish PTSD status: Actinobacteria, Lentisphaerae, and Verrucomicrobia. Decreased total abundance of these taxa was associated with higher Clinician-Administered PTSD Scale scores (r = -0.387, p = .035).

CONCLUSIONS

In this exploratory study, measures of overall microbial diversity were similar among individuals with PTSD and TE controls; however, decreased total abundance of Actinobacteria, Lentisphaerae, and Verrucomicrobia was associated with PTSD status.

Cross Talk: The Microbiota and Neurodevelopmental Disorders

Humans evolved within a microbial ecosystem resulting in an interlinked physiology. The gut microbiota can signal to the brain via the immune system, the vagus nerve or other host-microbe interactions facilitated by gut hormones, regulation of tryptophan metabolism and microbial metabolites such as short chain fatty acids (SCFA), to influence brain development, function and behavior. Emerging evidence suggests that the gut microbiota may play a role in shaping cognitive networks encompassing emotional and social domains in neurodevelopmental disorders. Drawing upon pre-clinical and clinical evidence, we review the potential role of the gut microbiota in the origins and development of social and emotional domains related to Autism spectrum disorders (ASD) and schizophrenia. Small preliminary clinical studies have demonstrated gut microbiota alterations in both ASD and schizophrenia compared to healthy controls. However, we await the further development of mechanistic insights, together with large scale longitudinal clinical trials, that encompass a systems level dimensional approach, to investigate whether promising pre-clinical and initial clinical findings lead to clinical relevance.

Evolution, human-microbe interactions, and life history plasticity

A bacterium was once a component of the ancestor of all eukaryotic cells, and much of the human genome originated in microorganisms. Today, all vertebrates harbour large communities of microorganisms (microbiota), particularly in the gut, and at least 20% of the small molecules in human blood are products of the microbiota. Changing human lifestyles and medical practices are disturbing the content and diversity of the microbiota, while simultaneously reducing our exposures to the so-called old infections and to organisms from the natural environment with which human beings co-evolved. Meanwhile, population growth is increasing the exposure of human beings to novel pathogens, particularly the crowd infections that were not part of our evolutionary history. Thus some microbes have co-evolved with human beings and play crucial roles in our physiology and metabolism, whereas others are entirely intrusive. Human metabolism is therefore a tug-of-war between managing beneficial microbes, excluding detrimental ones, and channelling as much energy as is available into other essential functions (eg, growth, maintenance, reproduction). This tug-of-war shapes the passage of each individual through life history decision nodes (eg, how fast to grow, when to mature, and how long to live).

Mental Health in Allergic Rhinitis: Depression and Suicidal Behavior

A high proportion of suicides visit their medical provider in the month prior to death, but depression, suicidal thoughts, and substance use are seldom addressed. For the clinicians routinely treating a substantial patient population with allergic diseases, there are additional concerns, as allergy has been linked with both depression and suicidal behavior. While psychotropic medications may affect diagnosis of allergies, medications used to treat allergies impact mood and behavior. Thus, we present an overview of the overlap of allergic rhinitis with depression and suicidal behavior in adults, based on clinical and epidemiological data, and our research and clinical experience. In summary, we suggest: 1) inquiring among patients with allergies about personal and family history of depression, substance use disorders, suicidal ideation and attempts 2) increased mindfulness regarding the potential effects of allergy medications on mood and behavior; and 3) for people identified with certain types of depression or increased suicide risk, a systematic multilevel collaborative approach. While for practical reasons the majority of patients with depression will continue to be treated by general or family practitioners, the allergy-treating provider should always consider integrated care for bipolar, psychotic or suicidal depression and incomplete remission, or relapsing and highly recurrent course. While awaiting results of much needed basic and clinical research to guide clinical approach for patients with comorbid allergic rhinitis and depression, the simple steps recommended here are expected to improved clinical outcomes in depression, including, on a large scale, reduced premature deaths by suicide.

Interactions between the microbiota, immune and nervous systems in health and disease

The diverse collection of microorganisms that inhabit the gastrointestinal tract, collectively called the gut microbiota, profoundly influences many aspects of host physiology, including nutrient metabolism, resistance to infection and immune system development. Studies investigating the gut-brain axis demonstrate a critical role for the gut microbiota in orchestrating brain development and behavior, and the immune system is emerging as an important regulator of these interactions. Intestinal microbes modulate the maturation and function of tissue-resident immune cells in the CNS. Microbes also influence the activation of peripheral immune cells, which regulate responses to neuroinflammation, brain injury, autoimmunity and neurogenesis. Accordingly, both the gut microbiota and immune system are implicated in the etiopathogenesis or manifestation of neurodevelopmental, psychiatric and neurodegenerative diseases, such as autism spectrum disorder, depression and Alzheimer's disease. In this review, we discuss the role of CNS-resident and peripheral immune pathways in microbiota-gut-brain communication during health and neurological disease.

Gut microbiome in chronic kidney disease: challenges and opportunities

More than 100 trillion microbial cells that reside in the human gut heavily influence nutrition, metabolism, and immune function of the host. Gut dysbiosis, seen commonly in patients with chronic kidney disease (CKD), results from qualitative and quantitative changes in host microbiome profile and disruption of gut barrier function. Alterations in gut microbiota and a myriad of host responses have been implicated in progression of CKD, increased cardiovascular risk, uremic toxicity, and inflammation. We present a discussion of dysbiosis, various uremic toxins produced from dysbiotic gut microbiome, and their roles in CKD progression and complications. We also review the gut microbiome in renal transplant, highlighting the role of commensal microbes in alteration of immune responses to transplantation, and conclude with therapeutic interventions that aim to restore intestinal dysbiosis.

Impact of early gut microbiota on immune and metabolic development and function

Microbial colonization of the infant intestine occurs in the first two years of life. Symbiotic host and microbe interactions are critical for host metabolic and immune development. Emerging evidence indicates that early microbiota colonization may influence the occurrence of metabolic and immune diseases. Further understanding of the importance of environmental factors, including fetal microbial exposure, diet, delivery mode, pre- and probiotic consumption, and antibiotic use on immune and metabolic programming will provide new opportunities for the development of therapeutic and prophylactic measures to improve infant health and reduce the risk of disease in post-infancy years.