Gut microbiota, metabolism and psychopathology: A critical review and novel perspectives

The identification of metabolites from gut microbiota in coronary heart disease via network pharmacology

Although the gut microbial metabolites exhibit potential effects on coronary heart disease (CHD), the underlying mechanism remains unclear. In this study, the active gut microbial metabolites acting on CHD and their potential mechanisms of action were explored through a network pharmacological approach. We collected a total of 208 metabolites from the gutMgene database and 726 overlapping targets from the similarity ensemble approach (SEA) and SwissTargetPrediction (STP) database, and ultimately identified 610 targets relevant to CHD. In conjunction with the gutMGene database, we identified 12 key targets. The targets of exogenous substances were removed, and 10 core targets involved in CHD were eventually retained. The microbiota-metabolites-targets-signalling pathways network analysis revealed that C-type lectin receptor signalling pathway, Lachnospiraceae, Escherichia, mitogen-activated protein kinase 1, prostaglandin-endoperoxidase synthase 2, phenylacetylglutamine and alcoholic acid are notable components of CHD and play important roles in the development of CHD. The results of molecular docking experiments demonstrated that AKT1-glycocholic acid and PTGS2-phenylacetylglutamine complexes may act on C-type lectin receptor signalling pathways. In this study, the key substances and potential mechanisms of gut microbial metabolites were analysed via network pharmacological methods, and a scientific basis and comprehensive idea were provided for the effects of gut microbial metabolites on CHD.

Probiotic and prebiotic interventions in eating disorders: A narrative review

AIMS

The review aimed to summarise and discuss findings focused on therapeutic probiotic and prebiotic interventions in eating disorders (ED).

METHODS

Using PubMed/MEDLINE, Cochrane Library, and Web of Science all published studies were retrieved until February 2023, following PRISMA guidelines. From the 111 initial studies, 5 met the inclusion criteria for this review.

RESULTS

All studies included in this narrative review were focused on anorexia nervosa (AN). Three longitudinal, randomised, controlled trials aimed to evaluate interventions with probiotics (Lactobacillus reuteri, yoghurt with Lactobacillus, and Streptococcus) in children and adolescents. These studies primarily emphasised medical outcomes and anthropometric measures following the administration of probiotics. However, the findings yielded mixed results in terms of short-term weight gain or alterations in specific immunological parameters. With a lower level of evidence, supplementation with synbiotics (probiotic + prebiotic) has been associated with improvements in microbiota diversity and attenuation of inflammatory responses.

CONCLUSIONS

Research on probiotics and prebiotics in ED is limited, primarily focussing on anorexia nervosa (AN). Their use in AN regarding medical and anthropometric outcomes needs further confirmation and future research should be warranted to assess their impact on psychological and ED symptomatology, where there is a notable gap in the existing literature.

Alterations in Vagal Tone Are Associated with Changes in the Gut Microbiota of Adults with Anxiety and Depression Symptoms: Analysis of Fecal Metabolite Profiles

Accumulating evidence suggests that interactions between the brain and gut microbiota significantly impact brain function and mental health. In the present study, we aimed to investigate whether young, healthy adults without psychiatric diagnoses exhibit differences in metabolic stool and microbiota profiles based on depression/anxiety scores and heart rate variability (HRV) parameters. Untargeted nuclear magnetic resonance-based metabolomics was used to identify fecal metabolic profiles. Results were subjected to multivariate analysis through principal component analysis (PCA) and partial least squares discriminant analysis (PLS-DA), and the metabolites were identified through VIP score. Metabolites separating asymptomatic and symptomatic groups were acetate, valine, and glutamate, followed by sugar regions, glutamine, acetone, valerate, and acetoacetate. The main metabolites identified in high vagal tone (HVT) and low vagal tone (LVT) groups were acetate, valerate, and glutamate, followed by propionate and butyrate. In addition to the metabolites identified by the PLS-DA test, significant differences in aspartate, sarcosine, malate, and methionine were observed between the groups. Levels of acetoacetate were higher in both symptomatic and LVT groups. Valerate levels were significantly increased in the symptomatic group, while isovalerate, propionate, glutamate, and acetone levels were significantly increased in the LVT group. Furthermore, distinct abundance between groups was only confirmed for the Firmicutes phylum. Differences between participants with high and low vagal tone suggest that certain metabolites are involved in communication between the vagus nerve and the brain.

Importance of good hosting: reviewing the bi-directionality of the microbiome-gut-brain-axis

Gut microorganisms have been shown to significantly impact on central function and studies that have associated brain disorders with specific bacterial genera have advocated an anomalous gut microbiome as the pathophysiological basis of several psychiatric and neurological conditions. Thus, our knowledge of brain-to-gut-to microbiome communication in this bidirectional axis seems to have been overlooked. This review examines the known mechanisms of the microbiome-to-gut-to-brain axis, highlighting how brain-to-gut-to-microbiome signaling may be key to understanding the cause of disrupted gut microbial communities. We show that brain disorders can alter the function of the brain-to-gut-to-microbiome axis, which will in turn contribute to disease progression, while the microbiome-to gut-to brain direction presents as a more versatile therapeutic axis, since current psychotropic/neurosurgical interventions may have unwanted side effects that further cause disruption to the gut microbiome. A consideration of the brain-to-gut-to-microbiome axis is imperative to better understand how the microbiome-gut-brain axis overall is involved in brain illnesses, and how it may be utilized as a preventive and therapeutic tool.

Combined effect of seasons and life history in an anuran strengthens the response and relationship between their physiology and gut microbiota

Gut microbiota impact host physiology, though simultaneous investigations in ectothermic vertebrates are rare. Particularly, amphibians may exhibit more complex interactions between host physiology and the effects of gut microbiota due to the combination of seasonal changes and complex life histories. In this study, we assessed the relationships among food resources, gut bacterial communities, and host physiology in frogs (Phelophylax nigromaculatus), taking into account seasonal and life history variations. We found that food sources were not correlated with physiological parameters but had some relationships with the gut bacterial community. Variations in gut bacterial community and host physiology were influenced by the combined effects of seasonal differences and life history, though mostly driven by seasonal differences. An increase in Firmicutes was associated with higher fat content, reflecting potential fat storage in frogs during the non-breeding season. The increase in Bacteroidetes resulted in lower fat content in adult frogs and decreased immunity in juvenile frogs during the breeding season, demonstrating a direct link. Our results suggest that the gut microbiome may act as a link between food conditions and physiological status, and that the combined effect of seasons and life history could reinforce the relationship between gut microbiota and physiological status in ectothermic animals. While food sources may influence the gut microbiota of ectotherms, we contend that temperature-correlated seasonal variation, which predominately influences most ectotherms, is a significant factor.

Gut microbiome diversity and function during hibernation and spring emergence in an aquatic frog

The gut microbiota maintains a deeply symbiotic relationship with host physiology, intricately engaging with both internal (endogenous) and external (exogenous) factors. Anurans, especially those in temperate regions, face the dual challenges of significant external influences like hibernation and complex internal variances tied to different life histories. In our research, we sought to determine whether different life stages (juvenile versus adult) of the Japanese wrinkled frog (Glandirana rugosa) lead to distinct shifts in gut bacterial communities during winter (hibernation) and its subsequent transition to spring. As hypothesized, we observed a more pronounced variability in the gut bacterial diversity and abundance in juvenile frogs compared to their adult counterparts. This suggests that the gut environment may be more resilient or stable in adult frogs during their hibernation period. However, this pronounced difference was confined to the winter season; by spring, the diversity and abundance of gut bacteria in both juvenile and adult frogs aligned closely. Specifically, the variance in gut bacterial diversity and composition between winter and spring appears to mirror the frogs' ecological adaptations. During the hibernation period, a dominance of Proteobacteria suggests an emphasis on supporting intracellular transport and maintaining homeostasis, as opposed to active metabolism in the frogs. Conversely, come spring, an uptick in bacterial diversity coupled with a dominance of Firmicutes and Bacteroidetes points to an upsurge in metabolic activity post-hibernation, favoring enhanced nutrient assimilation and energy metabolism. Our findings highlight that the relationship between the gut microbiome and its host is dynamic and bidirectional. However, the extent to which changes in gut bacterial diversity and composition contribute to enhancing hibernation physiology in frogs remains an open question, warranting further investigation.

The role of intestinal microecology in inflammatory bowel disease and colorectal cancer: A review

Intestinal microecology is a dominant and complex microecological system in human body. Generally, intestinal microecosystem consists of normal symbiotic flora and its living environment (including intestinal epithelial tissue and intestinal mucosal immune system). Commensal flora is the core component of microecology. Both structures of intestinal mucosa and functions of immune system are essential to maintain homeostasis of intestinal microecosystem. Under normal conditions, intestinal microorganisms and intestinal mucosa coordinate with each other to promote host immunity. When certain factors in the intestine are altered, such as disruption of the intestinal barrier causing dysbiosis of the intestinal flora, the immune system of the host intestinal mucosa makes a series of responses, which leads to the development of intestinal inflammation and promotes colorectal cancer. In this review, to further understand the relationship between intestinal microecology and intestinal diseases, we systematically elaborate the composition of the intestinal mucosal immune system, analyze the relationship between intestinal flora and mucosal immune system, and the role of intestinal flora on intestinal inflammatory diseases and colorectal cancer.

Advancing our understanding of the influence of drug induced changes in the gut microbiome on bone health

The gut microbiome has been implicated in a multitude of human diseases, with emerging evidence linking its microbial diversity to osteoporosis. This review article will explore the molecular mechanisms underlying perturbations in the gut microbiome and their influence on osteoporosis incidence in individuals with chronic diseases. The relationship between gut microbiome diversity and bone density is primarily mediated by microbiome-derived metabolites and signaling molecules. Perturbations in the gut microbiome, induced by chronic diseases can alter bacterial diversity and metabolic profiles, leading to changes in gut permeability and systemic release of metabolites. This cascade of events impacts bone mineralization and consequently bone mineral density through immune cell activation. In addition, we will discuss how orally administered medications, including antimicrobial and non-antimicrobial drugs, can exacerbate or, in some cases, treat osteoporosis. Specifically, we will review the mechanisms by which non-antimicrobial drugs disrupt the gut microbiome's diversity, physiology, and signaling, and how these events influence bone density and osteoporosis incidence. This review aims to provide a comprehensive understanding of the complex interplay between orally administered drugs, the gut microbiome, and osteoporosis, offering new insights into potential therapeutic strategies for preserving bone health.

Tadpole growth rates and gut bacterial community: Dominance of developmental stages over temperature variations

Tadpoles present an intriguing model system for studying the regulation and selection of gut microbiota. They offer a unique perspective to enhance our understanding of host-microbiota interactions, given their capacity to alter the dynamics of the gut microbial community by interacting with multiple environmental factors within a complex life cycle. In this study, we comprehensively investigated variations in growth rate and gut bacterial community in relation to temperature differences during the complex process of amphibian metamorphosis. Higher temperatures prompted tadpoles to metamorphose more rapidly than at lower temperatures, but the impact on size and weight was minimal. Differences in temperature were not associated with gut bacterial diversity, but they did affect certain aspects of beta diversity and bacterial composition. However, the developmental stage invoked greater heterogeneity than temperature in gut bacterial diversity, composition, and functional groups. These findings suggest that inherent biological systems exert stronger control over an organism's homeostasis and variation than the external environment. Although results may vary based on the magnitude or type of environmental factors, metamorphosis in tadpoles greatly influences their biology, potentially dominating microbial interactions.

Intergenerational and early life associations of the gut microbiome and stress-related symptomatology among Black American mothers and children

Recent evidence suggests that maternal childhood adversity may have an intergenerational impact, with children of adversity-exposed mothers exhibiting elevated symptoms of psychopathology. At the same time, many children demonstrate resilience to these intergenerational effects. Among the variety of factors that likely contribute to resilience, the composition of the gut microbiome may play a role in buffering the negative impacts of trauma and stress. The current prospective cohort study tested the novel hypothesis that offspring gut microbiome composition is a potential moderator in the relationship between maternal exposure to childhood adversity and offspring symptomatology (i.e., internalizing, externalizing, and posttraumatic stress symptoms). Maternal childhood adversity was self-reported during pregnancy via the Childhood Trauma Questionnaire and Adverse Childhood Experiences (ACEs) survey, and offspring symptomatology was assessed with the Child Behavior Checklist/1.5-5 when offspring were 2-4 years old. Offspring fecal samples were collected between these timepoints (i.e., during 6- to 24-month follow-up visits) for microbiome sequencing. Results indicated that maternal ACEs and the relative abundances of Bifidobacterium, Lactobacillus, and Prevotella were associated with offspring symptomatology. However, there was little evidence that microbial abundance moderated the association between maternal adversity and offspring symptoms. Overall, these findings further our understanding of how the gut microbiome associates with psychopathology, and informs future studies aimed at targeting modifiable factors that may buffer the intergenerational effects of childhood adversity.

Dietary Patterns and Gut Microbiota Changes in Inflammatory Bowel Disease: Current Insights and Future Challenges

Inflammatory bowel disease (IBD) is a result of a complex interplay between genes, host immune response, gut microbiota, and environmental factors. As one of the crucial environmental factors, diet plays a pivotal role in the modulation of gut microbiota community and the development of IBD. In this review, we present an overview of dietary patterns involved in the pathogenesis and management of IBD, and analyze the associated gut microbial alterations. A Westernized diet rich in protein, fats and refined carbohydrates tends to cause dysbiosis and promote IBD progression. Some dietary patterns have been found effective in obtaining IBD clinical remission, including Crohn's Disease Exclusion Diet (CDED), Mediterranean diet (MD), Anti-Inflammatory Diet (AID), the low-"Fermentable Oligo-, Di-, Mono-saccharides and Polyols" (FODMAP) diet, Specific Carbohydrate Diet (SCD), and plant-based diet, etc. Overall, many researchers have reported the role of diet in regulating gut microbiota and the IBD disease course. However, more prospective studies are required to achieve consistent and solid conclusions in the future. This review provides some recommendations for studies exploring novel and potential dietary strategies that prevent IBD.

Effects of Chronic Bifidobacteria Administration in Adult Male Rats on Plasma Metabolites: A Preliminary Metabolomic Study

Probiotics are live microorganisms distributed in the gastrointestinal tract that confer health benefits to the host when administered in adequate amounts. Bifidobacteria have been widely tested as a therapeutic strategy in the prevention and treatment of a broad spectrum of gastrointestinal disorders as well as in the regulation of the "microbiota-gut-brain axis". Metabolomic techniques can provide details in the study of molecular metabolic mechanisms involved in Bifidobacteria function through the analysis of metabolites that positively contribute to human health. This study was focused on the effects of the chronic assumption of a mixture of Bifidobacteria in adult male rats using a metabolomic approach. Plasma samples were collected at the end of treatment and analyzed with a gas chromatography-mass spectrometry (GC-MS) platform. Partial least square discriminant analysis (PLS-DA) was performed to compare the metabolic pattern in control and probiotic-treated rats. Our results show, in probiotic-treated animals, an increase in metabolites involved in the energetic cycle, such as glucose, erythrose, creatinine, taurine and glycolic acid, as well as 3-hydroxybutyric acid. This is an important metabolite of short-chain fatty acids (SCFA) with multitasking roles in energy circuit balance, and it has also been proposed to have a key role in the prevention and treatment of neurodegenerative diseases.

Platelet-To-Lymphocyte and Neutrophil-To-Lymphocyte Ratios Predict Intestinal Injury in Male Heroin Addicts

Objective

To explore the potential link between gut damage and proinflammatory cytokines in heroin-dependent patients.

Methods

We retrospectively analyzed and compared partial blood counts and biomarkers of intestinal injury and their potential correlations in 38 male heroin abuse patients and 29 healthy male participants. In addition, we compared and assessed proinflammatory cytokines and immune cells in 10 heroin abuse patients and 10 healthy participants.

Results

Neutrophil counts, platelets/lymphocytes (PLR), neutrophils/lymphocytes (NLR), gut injury biomarkers, and proinflammatory cytokines, CD19+B in patients compared with healthy subjects' cells increased significantly. The number of lymphocytes, CD3 CD4 T cells, and CD3 CD8 T cells decreased in patients compared to healthy individuals. When distinguishing between heroin addicts and healthy people, ROC/AUC analysis showed that a cutoff of 142.42 for PLR and 2.18 for NLR yielded a sensitivity of 65% and 85% and a specificity of 96.5% and 89.7%, respectively (p = 0.001, p < 0.001). For predicting intestinal injury, ROC/AUC analysis showed that a cutoff of 135.7 for PLR and 0.15 for NLR yielded a sensitivity of 52% and 60% and a specificity of 82% and 86.4%, respectively (p = 0.003, p = 0.009). Male heroin addicts are subject to intestinal injury and present with increased proinflammatory cytokine levels.

Conclusion

NLR and PLR are possible indirect biomarkers for heroin dependence based on intestinal injury.

Moving beyond descriptive studies: harnessing metabolomics to elucidate the molecular mechanisms underpinning host-microbiome phenotypes

Advances in technology and software have radically expanded the scope of metabolomics studies and allow us to monitor a broad transect of central carbon metabolism in routine studies. These increasingly sophisticated tools have shown that many human diseases are modulated by microbial metabolism. Despite this, it remains surprisingly difficult to move beyond these statistical associations and identify the specific molecular mechanisms that link dysbiosis to the progression of human disease. This difficulty stems from both the biological intricacies of host-microbiome dynamics as well as the analytical complexities inherent to microbiome metabolism research. The primary objective of this review is to examine the experimental and computational tools that can provide insights into the molecular mechanisms at work in host-microbiome interactions and to highlight the undeveloped frontiers that are currently holding back microbiome research from fully leveraging the benefits of modern metabolomics.

Gut Microbiome: A Brief Review on Its Role in Schizophrenia and First Episode of Psychosis

There is a growing body of evidence highlighting the role of gut microbiota as a biological basis of psychiatric disorders. The existing literature suggest that cognitive and emotional activities can be influenced by microbes through the microbiota–gut–brain axis and implies an association between alterations in the gut microbiome and several psychiatric conditions, such as autism, depression, bipolar disorder and psychosis. The aim of this review is to summarise recent findings and provide concise updates on the latest progress of the role of gut microbiota in the development and maintenance of psychiatric symptoms in schizophrenia and the first episode of psychosis. Despite the lack of consistent findings in regard to specific microbiome changes related to psychosis, the emerging literature reports significant differences in the gut microbiome of schizophrenic subjects compared to healthy controls and increasingly outlines the significance of an altered microbiome composition in the pathogenesis, development, symptom severity and prognosis of psychosis. Further human studies are, however, required, which should focus on identifying the drivers of microbiota changes in psychosis and establish the direction of causality between psychosis and microbiome alterations.

Associations between self-reported psychological symptom severity and gut microbiota: further support for the microgenderome

BACKGROUND

Research into the brain-gut-microbiota axis (BGMA) continues to reveal associations between gut microbiota (GM) and psychological symptom expression, inspiring new ways of conceptualising psychological disorders. However, before GM modulation can be touted as a possible auxiliary treatment option, more research is needed as inconsistencies in previous findings regarding these associations are prevalent. Additionally, the concept of the microgenderome, which proposes that GM may interact with sex hormones, has received limited attention in studies using human samples to date. However, such research has demonstrated sex specific associations between GM and psychological symptom expression.

METHOD

This cross-sectional retrospective study explores associations between GM species (identified through faecal microbial analysis) and symptom severity across four psychological domains (Depressive, Neurocognitive, Stress and Anxiety, and Sleep and Fatigue) for males (N = 1143) and females (N = 3467) separately.

RESULTS

GM species from several genera including Bifidobacterium, Clostridium, Enterococcus, and Leuconostoc were found to be differentially associated with psychological symptom severity for males and females. As such, the findings of the current study provide support for the concept of the microgenderome.

CONCLUSION

While further research is needed before their implementation in psychological treatment plans, the current findings suggest that modulation of GM at the species level may hold promise as auxiliary diagnostic or treatment options. These findings may give further insight into a client's presenting problem from a more holistic, multidisciplinary perspective. The clear sex divergence in associations between GM and symptoms give insight into sex discrepancies in susceptibility to psychological disorders.

Drugs and bugs: Negative affect, psychostimulant use and withdrawal, and the microbiome

BACKGROUND AND OBJECTIVES

A growing body of literature demonstrates that the human microbiota plays a crucial role in health and disease states, as well as in the body's response to stress. In addition, the microbiome plays a role in psychological well-being and regulating negative affect. Regulation of negative affect is a factor in psychostimulant abuse disorders. We propose a risk chain in which stress leads to negative affect that places an individual at risk to develop or relapse to psychostimulant abuse disorder. Stress, negative affect, and psychostimulant use all alter the gut microbiome.

METHODS

This review brings together the literature on affective disorders, stress, and psychostimulant abuse disorders to assess possible modulatory actions of the gut-brain axis to regulate these conditions.

RESULTS

Studies reviewed across the various disciplines suggest that the dysbiosis resulting from drug use, drug withdrawal, or stress may cause an individual to be more susceptible to addiction and relapse. Probiotics and prebiotics reduce stress and negative affect.

SCIENTIFIC SIGNIFICANCE

Treatment during the withdrawal phase of psychostimulant abuse disorder, when the microbiome is altered, may ameliorate the symptoms of stress and negative affect leading to a reduced risk of relapse to psychostimulant use.

Gut microbial changes of patients with psychotic and affective disorders: A systematic review

BACKGROUND

Many diverse inflammatory pathophysiologic mechanisms have been linked to mental disorders, and through the past decade an increasing interest in the gut microbiota and its relation to mental health has been arising. We aimed to systematically review studies of alterations in gut microbiota of patients suffering from psychotic disorders, bipolar disorder or depression compared to healthy controls.

METHODS

We systematically searched the databases CENTRAL, PubMed, EMBASE, PsycINFO and LILACS. Primary outcome was to compare the gut microbiota of patients suffering from psychotic disorders, bipolar disorder or depression with healthy controls.

RESULTS

We identified 17 studies, covering 744 patients and 620 healthy controls. The most consistent microbiota changes were a tendency towards higher abundance of Actinobacteria and lower abundance of Firmicutes at the phylum level, lower abundance of Lachnospiraceae at family level and lower abundance of Faecalibacterium at genus level for the mental disorders overall. However, we found that all studies had risk of bias and that the included studies displayed great variability in methods of storage, analysis of the fecal samples, reporting of results and statistics used.

CONCLUSION

Due to the many limitations of the included studies the findings should be interpreted with caution. Larger studies (especially of schizophrenia and major depressive disorder) are needed, but it is also of great importance to gather information of and control for factors that influence the result of a microbiota analysis including body mass index (BMI), smoking, alcohol consumption, diet habits, antibiotics, sample handling, wet laboratory methods and statistics.

Understanding the role of gut microbiota in the pathogenesis of schizophrenia

Schizophrenia is a chronic mental disorder with marked symptoms of hallucination, delusion, and impaired cognitive behaviors. Although multidimensional factors have been associated with the development of schizophrenia, the principal cause of the disorder remains debatable. Microbiome involvement in the etiology of schizophrenia has been widely researched due to the advancement in sequencing technologies. This review describes the contribution of the gut microbiome in the development of schizophrenia that is facilitated by the gut-brain axis. The gut microbiota is connected to the gut-brain axis via several pathways and mechanisms, that are discussed in this review. The role of the oral microbiota, probiotics and prebiotics in shaping the gut microbiota are also highlighted. Lastly, future perspectives for microbiome research in schizophrenia are addressed.

High-Resolution Metabolomics of 50 Neurotransmitters and Tryptophan Metabolites in Feces, Serum, and Brain Tissues Using UHPLC-ESI-Q Exactive Mass Spectrometry

Recent evidence indicates that tryptophan metabolites and neurotransmitters are potential mediators of the microbiome-gut-brain interaction. Here, a high-resolution ultra-high performance liquid chromatography-electrospray ionization tandem mass spectrometry (UHPLC-ESI-MS/MS) assay was developed and validated for quantifying 50 neurotransmitters, tryptophan metabolites, and bacterial indole derivatives in mouse serum, feces, and brain. The lower limit of quantitation for the 50 compounds ranged from 0.5 to 100 nmol/L, and sample preparation procedures were adapted for individual compounds to allow quantitation within linearity of the assay with a correlation coefficient >0.99. Reproducibility was tested by intra- and interday precision and accuracy of analysis: intra- and interday precision at the lower limit of quantitation was less than 20% for all compounds, with over two-thirds of the compounds achieving an interday precision below 10%, while the interday accuracy at the lower limit of quantitation ranged from 82.3 to 128.0% for all compounds. The analyte recovery was assessed based on sample-spiked stable-isotope-labeling standards, illustrating a need to consider matrix-specific recovery discrepancies when performing interorgan comparison. Carryover was evaluated by intermittent solvent blank injection. The assay was successfully applied to determining the concentration profiles of neurotransmitter and tryptophan metabolites in serum, feces, and brain of conventionally raised specific pathogen-free (SPF) C57BL/6 mice. Our method may serve as a useful analytical resource for investigating the roles of tryptophan metabolism and neurotransmitter signaling in host-microbiota interaction.

Shotgun metagenomics reveals both taxonomic and tryptophan pathway differences of gut microbiota in major depressive disorder patients

BACKGROUND

The microbiota-gut-brain axis, especially the microbial tryptophan (Trp) biosynthesis and metabolism pathway (MiTBamp), may play a critical role in the pathogenesis of major depressive disorder (MDD). However, studies on the MiTBamp in MDD are lacking. The aim of the present study was to analyze the gut microbiota composition and the MiTBamp in MDD patients.

METHODS

We performed shotgun metagenomic sequencing of stool samples from 26 MDD patients and 29 healthy controls (HCs). In addition to the microbiota community and the MiTBamp analyses, we also built a classification based on the Random Forests (RF) and Boruta algorithm to identify the gut microbiota as biomarkers for MDD.

RESULTS

The Bacteroidetes abundance was strongly reduced whereas that of Actinobacteria was significantly increased in the MDD patients compared with the abundance in the HCs. Most noteworthy, the MDD patients had increased levels of Bifidobacterium, which is commonly used as a probiotic. Four Kyoto Encyclopedia of Genes and Genomes (KEGG) orthologies (KOs) (K01817, K11358, K01626, K01667) abundances in the MiTBamp were significantly lower in the MDD group. Furthermore, we found a negative correlation between the K01626 abundance and the HAMD scores in the MDD group. Finally, RF classification at the genus level can achieve an area under the receiver operating characteristic curve of 0.890.

CONCLUSIONS

The present findings enabled a better understanding of the changes in gut microbiota and the related Trp pathway in MDD. Alterations of the gut microbiota may have the potential as biomarkers for distinguishing MDD patients form HCs.

Gut Biofactory-Neurocompetent Metabolites within the Gastrointestinal Tract. A Scoping Review

The gut microbiota have gained much scientific attention recently. Apart from unravelling the taxonomic data, we should understand how the altered microbiota structure corresponds to functions of this complex ecosystem. The metabolites of intestinal microorganisms, especially bacteria, exert pleiotropic effects on the human organism and contribute to the host systemic balance. These molecules play key roles in regulating immune and metabolic processes. A subset of them affect the gut brain axis signaling and balance the mental wellbeing. Neurotransmitters, short chain fatty acids, tryptophan catabolites, bile acids and phosphatidylcholine, choline, serotonin, and L-carnitine metabolites possess high neuroactive potential. A scoping literature search in PubMed/Embase was conducted up until 20 June 2020, using three major search terms "microbiota metabolites" AND "gut brain axis" AND "mental health". This review aimed to enhance our knowledge regarding the gut microbiota functional capacity, and support current and future attempts to create new compounds for future clinical interventions.

Lactobacillus paracasei PS23 decelerated age-related muscle loss by ensuring mitochondrial function in SAMP8 mice

Sarcopenia is a common impairment in the elderly population responsible for poor outcomes later in life; it can be caused by age-related alternations. Only a few strategies have been reported to reduce sarcopenia. Lactobacillus paracasei PS23 (LPPS23) has been reported to delay some age-related disorders. Therefore, here we investigated whether LPPS23 decelerates age-related muscle loss and its underlying mechanism. Female senescence-accelerated mouse prone-8 (SAMP8) mice were divided into three groups (n=6 each): non-aging (16-week-old), control (28-week-old), and PS23 (28-week-old) groups. The control and PS23 groups were given saline and LPPS23, respectively. We evaluated the effects of LPPS23 by analyzing body weight and composition, muscle strength, protein uptake, mitochondrial function, reactive oxygen species (ROS), antioxidant enzymes, and inflammation-related cytokines. LPPS23 significantly attenuated age-related decreases of muscle mass and strength. Compared to the control group, the non-aging and PS23 groups exhibited higher mitochondrial function, IL10, antioxidant enzymes, and protein uptake. Moreover, inflammatory cytokines and ROS were lower in the non-aging and PS23 groups than the control group. Taken together, LPPS23 extenuated sarcopenia progression during aging; this effect might have been enacted by preserving the mitochondrial function via reducing age-related inflammation and ROS and by retaining protein uptake in the SAMP8 mice.

Role of intestinal microbiota and metabolites in inflammatory bowel disease

Objective:

The metabolites produced by the gut microbiota are of interest to scientists. The objective of this review was to provide an updated summary of progress regarding the microbiota and their metabolites and influences on the pathogenesis of inflammatory bowel disease (IBD).

Data sources:

The author retrieved information from the PubMed database up to January 2018, using various combinations of search terms, including IBD, microbiota, and metabolite.

Study selection:

Both clinical studies and animal studies of intestinal microbiota and metabolites in IBD were selected. The information explaining the possible pathogenesis of microbiota in IBD was organized.

Results:

In IBD patients, the biodiversity of feces/mucosa-associated microbiota is decreased, and the probiotic microbiota is also decreased, whereas the pathogenic microbiota are increased. The gut microbiota may be a target for diagnosis and treatment of IBD. Substantial amounts of data support the view that the microbiota and their metabolites play pivotal roles in IBD by affecting intestinal permeability and the immune response.

Conclusions:

This review highlights the advances in recent gut microbiota research and clarifies the importance of the gut microbiota in IBD pathogenesis. Future research is needed to study the function of altered bacterial community compositions and the roles of metabolites.

Hair regrowth following fecal microbiota transplantation in an elderly patient with alopecia areata: A case report and review of the literature

BACKGROUND

Alopecia areata is a hair loss disease associated with genetics, autoimmunity, and other factors. There is an intriguing link between alopecia areata and gut dysbiosis. Fecal microbiota transplantation (FMT) has been recommended to treat Clostridium difficile (previously known as Clostridioides difficile) infection, and has also shown potentials in the treatment of inflammatory bowel disease, irritable bowel syndrome, and non-alcohol fatty liver disease.

CASE SUMMARY

An 86-year-old man, with a history of sigmoid colon carcinoma, suffered from recurrent abdominal pain and distension, and diarrhea for six months, with inappetence. At admission, he was also diagnosed with depression. Upon physical examination, the patient presented with a 1.5 cm × 2.0 cm alopecia areata on his right occiput. Due to the negative results of laboratory testing, capsule endoscopy, and colonoscopy, the patient was diagnosed with noninfectious diarrhea, depressive disorder, and patchy alopecia areata. Considering that noninfectious diarrhea in the elderly patient was mainly caused by gut dysbiosis, he was given six rounds of FMT. His diarrhea improved remarkably one month after FMT, with improved appetite and disappearance of abdominal pain, distension, and depressive symptoms. Surprisingly, he reported new hair growth on the affected region of his scalp, with some of his white hair gradually turning to black, without taking any other therapies for alopecia areata before and after FMT.

CONCLUSION

FMT might act as a potential therapy for patients who suffer from alopecia areata. Large and well-designed studies are required to confirm the role of FMT in alopecia areata.

Diabesity and mood disorders: Multiple links through the microbiota-gut-brain axis

The global prevalence of diabesity is on the rise, and the clinical, social and economic health burden arising from this epidemic is aggravated by a significant co-morbidity of diabesity with neuropsychiatric disease, particularly depression. Importantly, not only is the prevalence of mood disorders elevated in patients with type 2 diabetes, depressed patients are also more prone to develop diabetes. This reciprocal relationship calls for a molecular and systemic analysis of diabesity-brain interactions to guide preventive and therapeutic strategies. The analysis we are presenting in this review is modelled on the microbiota-gut-brain axis, which provides the brain with information from the gut not only via the nervous system, but also via a continuous stream of microbial, endocrine, metabolic and immune messages. This communication network offers important clues as to how obesity and diabetes could target the brain to provoke neuropsychiatric disease. There is emerging evidence that the gut microbiota is orchestrating a multiplicity of bodily functions that are intimately related to the immune, metabolic and nervous systems and that gut dysbiosis spoils the homeostasis between these systems. In our article we highlight two groups of molecular links that seem to have a significant bearing on the impact of diabesity on the brain. On the one hand, we focus on microbiota-related metabolites such as short-chain fatty acids, tryptophan metabolites, immune stimulants and endocannabinoids that are likely to play a mediator role. On the other hand, we discuss signalling molecules that operate primarily in the brain, specifically neuropeptide Y, brain-derived neurotrophic factor and γ-amino butyric acid, that are disturbed by microbial factors, obesity and diabetes and are relevant to mental illness. Finally, we address the usefulness of diet-related interventions to suspend the deleterious relationship between diabesity and mood disorders.

The Probiotic Effectiveness in Preventing Experimental Colitis Is Correlated With Host Gut Microbiota

Current evidence to support extensive use of probiotics in inflammatory bowel disease is limited and factors that contribute to the inconsistent effectiveness of clinical probiotic therapy are not completely known. Here, we used Bifidobacterium longum JDM 301 as a model probiotic to study potential factors that may influence the effect of probiotics in experimental colitis. We found that the effect of B. longum JDM 301 in tempering experimental colitis varied across individual mice even with the same genetic background. The probiotic efficacy was highly correlated with the host gut microbial community features. Consumption of a diet rich in fat could exacerbate mucosal injury-induced colitis but could not change the host responsiveness to B. longum JDM 301 treatment, suggesting of potential mechanistic differences between regulating colitis pathogenesis, and modulating probiotic efficacies by the gut microbiota. Together, our results suggest that personalized microbiome features may modify the probiotic therapeutic effect and support the idea of personalized probiotic medicine in inflammatory bowel disease.