The gut microbiota is associated with psychiatric symptom severity and treatment outcome among individuals with serious mental illness

Associations between specific dietary patterns, gut microbiome composition, and incident subthreshold depression in Chinese young adults

INTRODUCTION

The interplay between influential factors and the incidence of subthreshold depression (SD) in young adults remains poorly understood.

OBJECTIVES

This study sought to understand the dietary habits, gut microbiota composition, etc. among individuals with SD in young adults and to investigate their association with SD occurrence.

METHODS

Employing a cross-sectional approach, 178 individuals with SD, aged 18-32 years, were matched with 114 healthy counterparts. SD status was evaluated using the Zung Self-rating Depression Scale (SDS), Zung Self-rating Anxiety Scale (SAS), Beck Depression Inventory 2nd version (BDI-II), the 17-item Hamilton Rating Scales of Depression (HAMD-17), and Pittsburgh Sleep Quality Index (PSQI). Metagenomic sequencing was utilized to identify fecal microbial profiles. Dietary patterns were discerned via factor analysis of a 25-item food frequency questionnaire (FFQ). Logistic regression analysis and mediation analysis were performed to explore the potential links between gut microbiota, dietary patterns, and incident SD.

RESULTS

Data on dietary habits were available for 292 participants (mean [SD] age, 22.1 [2.9] years; 216 [73.9 %] female). Logistic regression analysis revealed that dietary patterns Ⅰ (odds ratio [OR], 0.34; 95 % CI, 0.15-0.75) and IV (OR, 0.39; 95 % CI, 0.17-0.86 and OR, 0.39; 95 % CI, 0.18-0.84) were associated with reduced risk of SD. Distinct microbial profiles were observed in young adults with SD, marked by increased microbial diversity and taxonomic alterations. Moreover, mediation analysis suggested Veillonella atypica as a potential mediator linking SDS or BDI-II scores with a healthy dietary pattern rich in bean products, coarse grains, nuts, fruits, mushrooms, and potatoes (β = 0.25, 95 % CI: 0.02-0.78 and β = 0.18, 95 % CI: 0.01-0.54).

CONCLUSIONS

Our findings highlight the complex interplay between dietary patterns, gut microbiota, and the risk of developing SD in young adults, underscoring the potential for dietary interventions and microbiome modulation in mental health promotion.

Impacts of microbiota and its metabolites through gut-brain axis on pathophysiology of major depressive disorder

Major depressive disorder (MDD) is characterized by a high rate of recurrence and disability, which seriously affects the quality of life of patients. That's why a deeper understanding of the mechanisms of MDD pathology is an urgent task, and some studies have found that intestinal symptoms accompany people with MDD. The microbiota-gut-brain axis is the bidirectional communication between the gut microbiota and the central nervous system, which was found to have a strong association with the pathogenesis of MDD. Previous studies have focused more on the communication between the gut and the brain through neuroendocrine, neuroimmune and autonomic pathways, and the role of gut microbes and their metabolites in depression is unclear. Metabolites of intestinal microorganisms (e.g., tryptophan, kynurenic acid, indole, and lipopolysaccharide) can participate in the pathogenesis of MDD through immune and inflammatory pathways or by altering the permeability of the gut and blood-brain barrier. In addition, intestinal microbes can communicate with intestinal neurons and glial cells to affect the integrity and function of intestinal nerves. However, the specific role of gut microbes and their metabolites in the pathogenesis of MDD is not well understood. Hence, the present review summarizes how gut microbes and their metabolites are directly or indirectly involved in the pathogenesis of MDD.

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.

Differences in bacterial taxa between treatment-naive patients with major depressive disorder and non-affected controls may be related to a proinflammatory profile

BACKGROUND

Major depressive disorder (MDD) is characterized by sadness and anhedonia, but also physical symptoms such as changes in appetite and weight. Gut microbiota has been hypothesized to be involved in MDD through gut-brain axis signaling. Moreover, antidepressants display antibacterial properties in the gastrointestinal tract. The aim of this study was to compare the gut microbiota and systemic inflammatory profile of young patients with MDD before and after initiation of antidepressant treatment and/or psychotherapy in comparison with a non-depressed control group (nonMDD).

METHODS

Fecal and blood samples were collected at baseline and at follow-up after four and twelve weeks, respectively. Patients started treatment immediately after collection of the baseline samples. The gut microbiota was characterized by 16 S rRNA gene sequencing targeting the hypervariable V4 region. Plasma levels of 49 unique immune markers were assessed using Mesoscale.

RESULTS

In total, 27 MDD patients and 32 nonMDD controls were included in the study. The gut microbiota in the baseline samples of MDD versus nonMDD participants did not differ regarding α- or β-diversity. However, there was a higher relative abundance of the genera Ruminococcus gnavus group, and a lower relative abundance of the genera Desulfovibrio, Tyzzerella, Megamonas, Olsenella, Gordonibacter, Allisonella and Rothia in the MDD group compared to the nonMDD group. In the MDD group, there was an increase in the genera Rothia, Desulfovibrio, Gordinobacteer and Lactobacillus, while genera belonging to the Firmicutes phylum were found depleted at twelve weeks follow-up compared to baseline. In the MDD group, IL-7, IL-8 and IL-17b levels were elevated compared to the nonMDD group at baseline. Furthermore, MDI score in the MDD group was found to correlate with Bray-Curtis dissimilarity at baseline, and several inflammatory markers at both baseline and after initiation of antidepressant treatment.

CONCLUSION

Several bacterial taxa differed between the MDD group and the nonMDD group at baseline and changed in relative abundance during antidepressant treatment and/or psychotherapy. The MDD group was furthermore found to have a pro-inflammatory profile compared to the nonMDD group at baseline. Further studies are required to investigate the gut microbiota and pro-inflammatory profile of patients with MDD.

Priming of microglia with dysfunctional gut microbiota impairs hippocampal neurogenesis and fosters stress vulnerability of mice

BACKGROUND

Mental disorders may be involved in neuroinflammatory processes that are triggered by gut microbiota. How gut microbiota influence microglia-mediated sensitivity to stress remains unclear. Here we explored in an animal model of depression whether disruption of the gut microbiome primes hippocampal microglia, thereby impairing neurogenesis and sensitizing to stress.

METHODS

Male C57BL/6J mice were exposed to chronic unpredictable mild stress (CUMS) for 4 weeks, and effects on gut microbiota were assessed using 16S rRNA sequencing. Fecal microbiota was transplanted from control or CUMS mice into naïve animals. The depression-like behaviors of recipients were evaluated in a forced swimming test and sucrose preference test. The morphology and phenotype of microglia in the hippocampus of recipients were examined using immunohistochemistry, quantitative PCR, and enzyme-linked immunosorbent assays. The recipients were treated with lipopolysaccharide or chronic stress exposure, and effects were evaluated on behavior, microglial responses and hippocampal neurogenesis. Finally, we explored the ability of minocycline to reverse the effects of CUMS on hippocampal neurogenesis and stress sensitivity in recipients.

RESULTS

CUMS altered the gut microbiome, leading to higher relative abundance of some bacteria (Helicobacter, Bacteroides, and Desulfovibrio) and lower relative abundance of some bacteria (Lactobacillus, Bifidobacterium, and Akkermansia). Fecal microbiota transplantation from CUMS mice to naïve animals induced microglial priming in the dentate gyrus of recipients. This microglia showed hyper-ramified morphology, and became more sensitive to LPS challenge or chronic stress, which characterized by more significant morphological changes and inflammatory responses, as well as impaired hippocampal neurogenesis and increased depressive-like behaviors. Giving minocycline to recipients reversed these effects of fecal transplantation.

CONCLUSIONS

These findings suggest that gut microbiota from stressed animals can induce microglial priming in the dentate gyrus, which is associated with a hyper-immune response to stress and impaired hippocampal neurogenesis. Remodeling the gut microbiome or inhibiting microglial priming may be strategies to reduce sensitivity to stress.

Synbiotics as potent functional food: recent updates on therapeutic potential and mechanistic insight

Synbiotics are the specific mixtures of prebiotics with probiotics intended to give health benefits to the host by stabilizing and supporting the gut microbiota.The prebiotic substance used in the synbiotics selectively favors the growth and metabolite production of probiotics. Gut microbiome dysbiosis may lead to generation and progression of various chronic diseases. Synbiotics act synergistically to modulate the gut ecosystem for improvement of metabolic health of the host. Probiotics have been found promising against various diseases being safer, effective, as an alternative or combinatorial therapy. Specific combinations of probiotics with suitable prebiotic substrate as synbiotics, may be the more effective therapeutic agents that can provide all benefits of probiotics as well as prebiotics. Though, effective combinations, dosage, mechanism of action, safety, cost effectiveness and other clinical investigations are required to be established along with other relevant aspects. Synbiotics have the potential to be functional food of importance in future. Present review summarizes the mechanistic overview of synbiotics related to gut microbiota, therapeutic potential and promising health benefits for human illnesses according to the available literature. In present scenario, synbiotics are more promising future alternatives as therapeutics to maintain healthy microbiota inside the host gut which directly affects the onset or development ofrelated disorders or diseases.

Lactobacillus rhamnosus Attenuates Cisplatin-Induced Intestinal Mucositis in Mice via Modulating the Gut Microbiota and Improving Intestinal Inflammation

Lactobacillus rhamnosus (LBS) is a well-documented probiotic strain in oncology and has a pivotal role in clinical applications. Here, we have investigated the protective effect of Lactobacillus rhamnosus on intestinal mucositis induced by cisplatin (CP) and explored the underlying mechanisms targeting inflammatory proteins, as well as the histological changes in the intestinal tissue of mice, in addition, the bacterial strains that may be related to the health-enhancing properties. BALB/c mice were pre-treated with or without LBS via oral gavage, followed by mucositis induction with cisplatin. Our results revealed that the LBS-treated groups significantly attenuated proinflammatory cytokine levels (IL-1β, IL-6, and TNF-α) compared to the CP group. Furthermore, LBS mitigated the damaged tight junction integrity caused by CP via up-regulating the levels of claudin, occludin, ZO-1, and mucin-2 protein (MUC-2). Finally, the 16S rRNA fecal microbiome genomic analysis showed that LBS administration enhanced the growth of beneficial bacteria, i.e., Firmicutes and Lachnospiraceae, while the relative abundance of the opportunistic bacteria Bacteroides and Proteobacteria decreased. Collectively, LBS was found to beneficially modulate microbial composition structure and functions and enrich the ecological diversity in the gut.

Reproducible microbiome composition signatures of anxiety and depressive symptoms

The gut microbiome is a significant contributor to mental health, with growing evidence linking its composition to anxiety and depressive disorders. Gut microbiome composition is associated with signs of anxiety and depression both in clinically diagnosed mood disorders and subclinically in the general population and may be influenced by dietary fibre intake and the presence of chronic pain. We provide an update of current evidence on the role of gut microbiome composition in depressive and anxiety disorders or symptoms by reviewing available studies. Analysing data from three independent cohorts (osteoarthritis 1 (OA1); n = 46, osteoarthritis 2 (OA2); n = 58, and healthy controls (CON); n = 67), we identified microbial composition signatures of anxiety and depressive symptoms at genus level and cross-validated our findings performing meta-analyses of our results with results from previously published studies. The genera Bifidobacterium (fixed-effect beta (95% CI) = -0.22 (-0.34, -0.10), p = 3.90e-04) and Lachnospiraceae NK4A136 group (fixed-effect beta (95% CI) = -0.09 (-0.13, -0.05), p = 2.53e-06) were found to be the best predictors of anxiety and depressive symptoms, respectively, across our three cohorts and published literature taking into account demographic and lifestyle covariates, such as fibre intake. The association with anxiety was robust in accounting for heterogeneity between cohorts and supports previous observations of the potential prophylactic effect of Bifidobacterium against anxiety symptoms.

Review of microbiota gut brain axis and innate immunity in inflammatory and infective diseases

The microbiota gut brain (MGB) axis has been shown to play a significant role in the regulation of inflammatory and infective diseases. Exploring the structure and communication mode of MGB axis is crucial for understanding its role in diseases, and studying the signaling pathways and regulatory methods of MGB axis regulation in diseases is also of profound significance for future clinical research. This article reviews the composition, communication mechanism of MGB axis and its role in inflammatory and infective diseases, including Parkinson's disease (PD), Alzheimer's disease (AD), multiple sclerosis (MS), autism spectrum disorder (ASD), depression, psoriasis, irritable bowel syndrome (IBS), and inflammatory bowel diseases (IBD). In addition, our investigation delved into the regulatory functions of the inflammasome, IFN-I, NF-κB, and PARK7/DJ-1 innate immune signaling pathway in the context of inflammatory and infective diseases. Ultimately, we discussed the efficacy of various interventions, including fecal microbiota transplantation (FMT), antibiotics, probiotics, prebiotics, synbiotics, and postbiotics, in the management of inflammatory and infective diseases. Understanding the role and mechanism of the MGB axis might make positive effects in the treatment of inflammatory and infective diseases.

Platelets bridging the gap between gut dysbiosis and neuroinflammation in stress-linked disorders: A narrative review

In this narrative review, we examine the association between gut dysbiosis, neuroinflammation, and stress-linked disorders, including depression, anxiety, and post-traumatic stress disorder (PTSD), and investigate whether tryptophan (TRP) metabolism and platelets play a role in this association. The mechanisms underlying the aetiology of stress-linked disorders are complex and not yet completely understood. However, a potential link between chronic inflammation and these disorders may potentially be found in TRP metabolism and platelets. By critically analysing existing literature on platelets, the gut microbiome, and stress-linked disorders, we hope to elicit the role of platelets in mediating the effects on serotonin (5-HT) levels and neuroinflammation. We have included studies specifically investigating platelets and TRP metabolism in relation to inflammation, neuroinflammation and neuropsychiatric disorders. Alteration in microbial composition due to stress could contribute to increased intestinal permeability, facilitating the translocation of microbial products, and triggering the release of pro-inflammatory cytokines. This causes platelets to become hyperactive and secrete 5-HT into the plasma. Increased levels of pro-inflammatory cytokines may also lead to increased permeability of the blood-brain barrier (BBB), allowing inflammatory mediators entry into the brain, affecting the balance of TRP metabolism products, such as 5-HT, kynurenic acid (KYNA), and quinolinic acid (QUIN). These alterations may contribute to neuroinflammation and possible neurological damage. Furthermore, platelets can cross the compromised BBB and interact with astrocytes and neurons, leading to the secretion of 5-HT and pro-inflammatory factors, exacerbating inflammatory conditions in the brain. The mechanisms underlying neuroinflammation resulting from peripheral inflammation are still unclear, but the connection between the brain and gut through the bloodstream could be significant. Identifying peripheral biomarkers and mechanisms in the plasma that reflect neuroinflammation may be important. This review serves as a foundation for further research on the association between the gut microbiome, blood microbiome, and neuropsychiatric disorders. The integration of these findings with protein and metabolite markers in the blood may expand our understanding of the subject.

Pharmacomicrobiomics of Antidepressants in Depression: A Systematic Review

This systematic review evaluated the animal and human evidence for pharmacomicrobiomics (PMx) interactions of antidepressant medications. Studies of gut microbiota effects on functional and behavioral effects of antidepressants in human and animal models were identified from PubMed up to December 2022. Risk of bias was assessed, and results are presented as a systematic review following PRISMA guidelines. A total of 28 (21 animal, 7 human) studies were included in the review. The reviewed papers converged on three themes: (1) Antidepressants can alter the composition and metabolites of gut microbiota, (2) gut microbiota can alter the bioavailability of certain antidepressants, and (3) gut microbiota may modulate the clinical or modeled mood modifying effects of antidepressants. The majority (n = 22) of studies had at least moderate levels of bias present. While strong evidence is still lacking to understand the clinical role of antidepressant PMx in human health, there is evidence for interactions among antidepressants, microbiota changes, microbiota metabolite changes, and behavior. Well-controlled studies of the mediating and moderating effects of baseline and treatment-emergent changes in microbiota on therapeutic and adverse responses to antidepressants are needed to better establish a potential role of PMx in personalizing antidepressant treatment selection and response prediction.

Leveraging the microbiome to understand clinical heterogeneity in depression: findings from the T-RAD study

Alterations in the gut microbiome have been linked to a variety of mental illnesses including anxiety and depression. This study utilized advanced bioinformatics tools that integrated both the compositional and community nature of gut microbiota to investigate how gut microbiota influence clinical symptoms in a sample of participants with depression. Gut microbiota of 179 participants with major depressive disorder (MDD) in the Texas Resilience Against Depression (T-RAD) study were analyzed by 16S rRNA gene sequencing of stool samples. Severity of anxiety, depression, and anhedonia symptoms were assessed with General Anxiety Disorder - 7 item scale, Patient Health 9-item Questionnaire, and Dimensional Anhedonia Rating Scale, respectively. Using weighted correlation network analysis, a data-driven approach, three co-occurrence networks of bacterial taxa were identified. One of these co-occurrence networks was significantly associated with clinical features including depression and anxiety. The hub taxa associated with this co-occurrence module -one Ruminococcaceae family taxon, one Clostridiales vadinBB60 group family taxon, and one Christencenellaceae family taxon- were connected to several additional butyrate-producing bacteria suggesting that deficits in butyrate production may contribute to clinical symptoms. Therefore, by considering the community nature of the gut microbiome in a real world clinical sample, this study identified a gut microbial co-occurrence network that was significantly associated with clinical anxiety in a cohort of depressed individuals.

Features of gut microbiota and short-chain fatty acids in patients with first-episode depression and their relationship with the clinical symptoms

Objective

To compare the differences in gut microbiota and short-chain fatty acids (SCFAs; metabolites of gut microbiota) in the serum of patients with first-episode depression and the healthy population and to analyze the relationship between gut microbiota and metabolite SCFAs and the clinical symptoms of major depressive disorder (MDD).

Methods

A total of 45 patients with first-episode depression and 22 healthy volunteers were chosen to complete relevant scale evaluations, and feces samples and venous blood samples were collected. The 16S RNA method was used to analyze the intestinal microflora and the characteristics of serum SCFAs detection by ELISA kit, as well as the intestinal flora, SCFAs content and their correlation with MDD clinical indicators.

Results

The abundance of Akkermansia, Megamonas, Prevotellaceae NK3B31 group, and butyrate-producing bacteria, Lachnospira, Subdoligranulum, Blautia, and Dialister, and acetate-producing bacteria, Streptococcus, in the gut microbiota of the MDD group was lower than that in the control (C) group. The abundance of Parasutterella in the MDD group was higher than that in the C group. Dialister negatively correlated with all measured clinical symptoms (r < 0, P < 0.05). The serum SCFA content in the MDD group was higher than that in the C group, and the content positively correlated with the Hamilton anxiety scale scores (r = 0.584, P < 0.05).

Conclusion

The results demonstrated that the MDD group differed from the C group in terms of gut microbiota and SCFAs in the serum and that the change in certain intestinal bacteria might participate in the pathogenic mechanism of MDD.

History of childhood physical abuse is associated with gut microbiota diversity among adult psychiatric inpatients

BACKGROUND

Traumatic life events are associated with the development of psychiatric and chronic medical illnesses. This exploratory study examined the relationship between traumatic life events and the gut microbiota among adult psychiatric inpatients.

METHODS

105 adult psychiatric inpatients provided clinical data and a single fecal sample shortly after admission. A modified version of the Stressful Life Events Screening Questionnaire was used to quantify history of traumatic life events. 16S rRNA gene sequencing was used to analyze the gut microbial community.

RESULTS

Gut microbiota diversity was not associated with overall trauma score or any of the three trauma factor scores. Upon item-level analysis, history of childhood physical abuse was uniquely associated with beta diversity. Linear Discriminant Analysis Effect Size (LefSe) analyses revealed that childhood physical abuse was associated with abundance of distinct bacterial taxa associated with inflammation.

LIMITATIONS

This study did not account for dietary differences, though diet was highly restricted as all participants were psychiatric inpatients. Absolute variance accounted for by the taxa was small though practically meaningful. The study was not powered for full subgroup analysis based on race and ethnicity.

CONCLUSIONS

This study is among the first to demonstrate a relationship between childhood physical abuse and gut microbiota composition among adult psychiatric patients. These findings suggest that early childhood adverse events may have long-conferred systemic consequences. Future efforts may target the gut microbiota for the prevention and/or treatment of psychiatric and medical risk associated with traumatic life events.

PRO-DEMET Randomized Controlled Trial on Probiotics in Depression—Pilot Study Results

There is a pressing need to identify new treatment options for depression and its comorbidities. Depression often coexists with metabolic complications, and the two may share a pathophysiological overlap, including inflammation and microbiota changes. Microbiota interventions (e.g., probiotics) may represent a safe and easy-to-use treatment option as an adjunctive therapy in patients only partially responsive to pharmacologic treatment. (1) Objective: The paper presents the results of a feasibility and pilot study. The study is an internal part of a randomized controlled trail (RCT) of the effect of probiotic supplementation on psychometric, anthropometric, metabolic, and inflammatory parameters in adult patients with depressive disorders depending on the presence of metabolic syndrome. (2) Methods: The trial has a four-arm, parallel-group, prospective, randomized, double-blind, controlled design. Sixty participants received a probiotic preparation containing Lactobacillus helveticus Rosell®-52 and Bifidobacterium longum Rosell®-175 over 60 days. The feasibility of the study design was assessed, as well as the rates of recruitment, eligibility, consent, and study completion. The following were assessed: depressive, anxiety and stress symptoms, quality of life, blood pressure, body mass index and waist circumference, complete blood count with differential, serum levels of C-reactive protein, high-density lipoprotein cholesterol, triglycerides, fasting glucose, some secondary markers of inflammation and metabolic health, as well as noninvasive biomarkers of liver fibrosis (APRI and FIB-4). (3) Results: The study was found to be generally feasible. The eligibility rate was 52% of recruited participants with 80% completing the study protocol. No differences in sociodemographic or anthropometric factors or basic laboratory findings were found between the placebo and probiotic group at the start of the intervention period. Importantly, the proportion of recruited participants fulfilling the criteria of metabolic syndrome was too low. (4) Conclusions: Whilst the whole study protocol was feasible, some different timepoint procedures require modification. The major weakness of the recruitment methods was that the percentage of metabolic arms participants was insufficient. Overall, the full RCT design on probiotics in depression with vs. without metabolic syndrome was shown to be feasible with little modification.

Differential co-expression networks of the gut microbiota are associated with depression and anxiety treatment resistance among psychiatric inpatients

BACKGROUND

Comorbid anxiety and depression are common and are associated with greater disease burden than either alone. Our recent efforts have identified an association between gut microbiota dysfunction and severity of anxiety and depression. In this follow-up, we applied Differential Co-Expression Analysis (DiffCoEx) to identify potential gut microbiota biomarker(s) candidates of treatment resistance among psychiatric inpatients.

METHODS

In a sample of convenience, 100 psychiatric inpatients provided clinical data at admission and discharge; fecal samples were collected early during the hospitalization. Whole genome shotgun sequencing methods were used to process samples. DiffCoEx was used to identify clusters of microbial features significantly different based on treatment resistance status. Once overlapping features were identified, a knowledge-mining tool was used to review the literature using a list of microbial species/pathways and a select number of medical subject headlines (MeSH) terms relevant for depression, anxiety, and brain-gut-axis dysregulation. Network analysis used overlapping features to identify microbial interactions that could impact treatment resistance.

RESULTS

DiffCoEx analyzed 10,403 bacterial features: 43/44 microbial features associated with depression treatment resistance overlapped with 43/114 microbial features associated with anxiety treatment resistance. Network analysis resulted in 8 biological interactions between 16 bacterial species. Clostridium perfringens evidenced the highest connection strength (0.95). Erysipelotrichaceae bacterium 6_1_45 has been most widely examined, is associated with inflammation and dysbiosis, but has not been associated with depression or anxiety.

CONCLUSION

DiffCoEx potentially identified gut bacteria biomarker candidates of depression and anxiety treatment-resistance. Future efforts in psychiatric microbiology should examine the mechanistic relationship of identified pro-inflammatory species, potentially contributing to a biomarker-based algorithm for treatment resistance.

IgA-Biome Profiles Correlate with Clinical Parkinson's Disease Subtypes

BACKGROUND

Parkinson's disease is a heterogeneous neurodegenerative disorder with distinctive gut microbiome patterns suggesting that interventions targeting the gut microbiota may prevent, slow, or reverse disease progression and severity.

OBJECTIVE

Because secretory IgA (SIgA) plays a key role in shaping the gut microbiota, characterization of the IgA-Biome of individuals classified into either the akinetic rigid (AR) or tremor dominant (TD) Parkinson's disease clinical subtypes was used to further define taxa unique to these distinct clinical phenotypes.

METHODS

Flow cytometry was used to separate IgA-coated and -uncoated bacteria from stool samples obtained from AR and TD patients followed by amplification and sequencing of the V4 region of the 16 S rDNA gene on the MiSeq platform (Illumina).

RESULTS

IgA-Biome analyses identified significant alpha and beta diversity differences between the Parkinson's disease phenotypes and the Firmicutes/Bacteroides ratio was significantly higher in those with TD compared to those with AR. In addition, discriminant taxa analyses identified a more pro-inflammatory bacterial profile in the IgA+ fraction of those with the AR clinical subclass compared to IgA-Biome analyses of those with the TD subclass and with the taxa identified in the unsorted control samples.

CONCLUSION

IgA-Biome analyses underscores the importance of the host immune response in shaping the gut microbiome potentially affecting disease progression and presentation. In the present study, IgA-Biome analyses identified a unique proinflammatory microbial signature in the IgA+ fraction of those with AR that would have otherwise been undetected using conventional microbiome analysis approaches.

Toward a Deeper Understanding of Gut Microbiome in Depression: The Promise of Clinical Applicability

The emergence of the coronavirus disease 2019 pandemic has dramatically increased the global prevalence of depression. Unfortunately, antidepressant drugs benefit only a small minority of patients. Thus, there is an urgent need to develop new interventions. Accumulating evidence supports a causal relationship between gut microbiota dysbiosis and depression. To advance microbiota-based diagnostics and therapeutics of depression, a comprehensive overview of microbial alterations in depression is presented to identify effector microbial biomarkers. This procedure generated 215 bacterial taxa from humans and 312 from animal models. Compared to controls, depression shows significant differences in β-diversity, but no changes in microbial richness and diversity. Additionally, species-specific microbial changes are identified like increased Eggerthella in humans and decreased Acetatifactor in rodent models. Moreover, a disrupted microbiome balance and functional changes, characterized by an enrichment of pro-inflammatory bacteria (e.g., Desulfovibrio and Escherichia/Shigella) and depletion of anti-inflammatory butyrate-producing bacteria (e.g., Bifidobacterium and Faecalibacterium) are consistently shared across species. Confounding effects of geographical region, depression type, and intestinal segments are also investigated. Ultimately, a total of 178 species and subspecies probiotics are identified to alleviate the depressive phenotypes. Current findings provide a foundation for developing microbiota-based diagnostics and therapeutics and advancing microbiota-oriented precision medicine for depression.

Association between Depression, Anxiety Symptoms and Gut Microbiota in Chinese Elderly with Functional Constipation

This study aimed to investigate the relationship between anxiety, depression, and gut microbiota in elderly patients with FC.

METHODS

in this cross-sectional study, a total of 198 elderly participants (85 male and 113 female) aged over 60 years were recruited. The study was conducted in Changsha city, China. The participants completed an online questionnaire, including The Patient Health Questionnaire-9 (PHQ-9), Generalized Anxiety Disorder-7 (GAD-7), The Patient Assessment of Symptoms (PAC-SYM), and The Patient Assessment of Quality of Life (PAC-QoL). We selected the 16S rDNA V3 + V4 region as the amplification region and sequenced the gut microbiota using the Illumina Novaseq PE250 high-throughput sequencing platform.

RESULTS

in total, 30.3% of patients with constipation had depression, while 21.3% had anxiety. The relative abundance of intestinal microbiota in the normal group was higher than that in the anxiety and depression group. According to LEfSe analysis, the relative abundance of g_Peptoniphilus and g_Geobacter in the people without depression and anxiety was higher. The relative abundance of g_Pseudoramibacter-Eubacterium and g_Candidatus-Solibacter in the depression group was lower, and the relative abundance of g_Bacteroides and g_Paraprevotella, g_Cc_115 in the anxiety group was higher. In addition, according to the correlation analysis, g_Aquicella and g_Limnohabitans were negatively correlated with constipation symptoms, anxiety, and depression.

CONCLUSIONS

this study found that gut microbiota composition may be associated with a higher incidence of anxiety and depression in patients with FC, thus providing insight into the mechanisms that ameliorate mood disorders in patients with FC.

Integrated Module of Multidimensional Omics for Peripheral Biomarkers (iMORE) in patients with major depressive disorder: rationale and design of a prospective multicentre cohort study

INTRODUCTION

Major depressive disorder (MDD) represents a worldwide burden on healthcare and the response to antidepressants remains limited. Systems biology approaches have been used to explore the precision therapy. However, no reliable biomarker clinically exists for prognostic prediction at present. The objectives of the Integrated Module of Multidimensional Omics for Peripheral Biomarkers (iMORE) study are to predict the efficacy of antidepressants by integrating multidimensional omics and performing validation in a real-world setting. As secondary aims, a series of potential biomarkers are explored for biological subtypes.

METHODS AND ANALYSIS

iMore is an observational cohort study in patients with MDD with a multistage design in China. The study is performed by three mental health centres comprising an observation phase and a validation phase. A total of 200 patients with MDD and 100 healthy controls were enrolled. The protocol-specified antidepressants are selective serotonin reuptake inhibitors and serotonin-norepinephrine reuptake inhibitors. Clinical visits (baseline, 4 and 8 weeks) include psychiatric rating scales for symptom assessment and biospecimen collection for multiomics analysis. Participants are divided into responders and non-responders based on treatment response (>50% reduction in Montgomery-Asberg Depression Rating Scale). Antidepressants' responses are predicted and biomarkers are explored using supervised learning approach by integration of metabolites, cytokines, gut microbiomes and immunophenotypic cells. The accuracy of the prediction models constructed is verified in an independent validation phase.

ETHICS AND DISSEMINATION

The study was approved by the ethics committee of Shanghai Mental Health Center (approval number 2020-87). All participants need to sign a written consent for the study entry. Study findings will be published in peer-reviewed journals.

TRIAL REGISTRATION NUMBER

NCT04518592.

Association Between Gut Microbiota and Depressive Symptoms: A Cross-Sectional Population-Based Study in South Korea

OBJECTIVE

This study aimed to investigate the association between gut microbiota and depressive symptoms in a large population cohort of Korean adults.

METHODS

Overall, 1238 participants were included in the study. Participants were categorized into depressed or non-depressed groups, based on the depressive symptoms reported on the Center for Epidemiologic Studies Rating Scale for Depression, with a cutoff score of 16, and their fecal microbiota was profiled using 16S ribosomal RNA gene sequencing. Several alpha and beta diversity measures were also estimated. The association between depressive symptoms and gut microbiota was analyzed using generalized linear models. The inferred function of the metagenomes was compared between the two groups.

RESULTS

There were no consistent differences in alpha and beta diversity between the depressed and non-depressed groups. However, the continuous measure of depressive symptoms was inversely associated with one of four measures of alpha diversity (Shannon's diversity, p = .021). We also found a substantial difference between the depressed and non-depressed groups in the Bray-Curtis dissimilarity among the four beta diversity indices ( p = .004). Participants whose depressive symptoms exceeded a clinical cutoff score had a lower relative abundance of the genus Faecalibacterium when compared with controls (coefficient = -0.025, q = 0.047). However, the depressed group had a significantly higher abundance of the genus Oscillospira than did the non-depressed group (coefficient = 0.002, q = 0.023).

CONCLUSIONS

Our findings contribute to the identification of potential relationships between the gut microbiota and depressive symptoms and provide useful insights for developing microbiota-based interventions for patients with depressive symptoms.

Remodeling of microbiota gut-brain axis using psychobiotics in depression

Depression is a multifaceted psychiatric disorder mainly orchestrated by dysfunction of neuroendocrine, neurochemical, immune, and metabolic systems. The interconnection of gut microbiota perturbation with the central nervous system disorders has been well documented in recent times. Indeed, alteration of commensal intestinal microflora is noted in several psychiatric disorders such as anxiety and depression, which are presumed to be routed through the enteric nervous system, autonomic nervous system, endocrine, and immune system. This review summarises the new mechanisms underlying the crosstalk between gut microbiota and brain involved in the management of depression. Depression-induced changes in the commensal intestinal microbiota are majorly linked with the disruption of gut integrity, hyperinflammation, and modulation of short-chain fatty acids, neurotransmitters, kynurenine metabolites, endocannabinoids, brain-derived neurotropic factors, hypothalamic-pituitary-adrenal axis, and gut peptides. The restoration of gut microbiota with prebiotics, probiotics, postbiotics, synbiotics, and fermented foods (psychobiotics) has gained a considerable attention for the management of depression. Recent evidence also propose the role of gut microbiota in the process of treatment-resistant depression. Thus, remodeling of the microbiota-gut-brain axis using psychobiotics appears to be a promising therapeutic approach for the reversal of psychiatric disorders, and it is imperative to decipher the underlying mechanisms for gut-brain crosstalk.

Sex-specific relationships of the infant microbiome and early-childhood behavioral outcomes

BACKGROUND

A link between the gut microbiome and behavior is hypothesized, but most previous studies are cross-sectional or in animal models. The modifying role of host sex is poorly characterized. We aimed to identify sex-specific prospective associations between the early-life gut microbiome and preschool-age neurobehavior.

METHODS

In a prospective cohort, gut microbiome diversity and taxa were estimated with 16S rRNA sequencing at 6 weeks, 1 year, and 2 years. Species and gene pathways were inferred from metagenomic sequencing at 6 weeks and 1 year. When subjects were 3 years old, parents completed the Behavioral Assessment System for Children, second edition (BASC-2). A total of 260 children contributed 523 16S rRNA and 234 metagenomics samples to analysis. Models adjusted for sociodemographic characteristics.

RESULTS

Higher diversity at 6 weeks was associated with better internalizing problems among boys, but not girls [β_Boys = -1.86 points/SD Shannon diversity; 95% CI (-3.29, -0.42), p_Boys = 0.01, β_Girls = 0.22 (-1.43, 1.87), p_Girls = 0.8, p_interaction = 0.06]. Among other taxa-specific associations, Bifidobacterium at 6 weeks was associated with Adaptive Skills scores in a sex-specific manner. We observed relationships between functional features and BASC-2 scores, including vitamin B6 biosynthesis pathways and better Depression scores.

CONCLUSIONS

This study advances our understanding of microbe-host interactions with implications for childhood behavioral health.

IMPACT

This is one of the first studies to examine the early-life microbiome and neurobehavior, and the first to examine prospective sex-specific associations. Infant and early-childhood microbiomes relate to neurobehavior including anxiety, depression, hyperactivity, and social behaviors in a time- and sex-specific manner. Our findings suggest future studies should evaluate whether host sex impacts the relationship between the gut microbiome and behavioral health outcomes.

A comprehensive approach to predicting weight gain and therapy response in psychopharmacologically treated major depressed patients: A cohort study protocol

Background

A subgroup of patients with Major Depressive Disorder shows signs of low-grade inflammation and metabolic abberances, while antidepressants can induce weight gain and subsequent metabolic disorders, and lacking antidepressant response is associated with inflammation.

Objectives

A comprehensive investigation of patient phenotypes and their predictive capability for weight gain and treatment response after psychotropic treatment will be performed. The following factors will be analyzed: inflammatory and metabolic markers, gut microbiome composition, lifestyle indicators (eating behavior, physical activity, chronotype, patient characteristics (childhood adversity among others), and polygenic risk scores.

Methods

Psychiatric inpatients with at least moderate Major Depressive Disorder will be enrolled in a prospective, observational, naturalistic, monocentric study using stratified sampling. Ethical approval was obtained. Primary outcomes at 4 weeks will be percent weight change and symptom score change on the Montgomery Asberg Depression Rating Scale. Both outcomes will also be binarized into clinically relevant outcomes at 5% weight gain and 50% symptom score reduction. Predictors for weight gain and treatment response will be tested using multiple hierachical regression for continuous outcomes, and multiple binary logistic regression for binarized outcomes. Psychotropic premedication, current medication, eating behavior, baseline BMI, age, and sex will be included as covariates. Further, a comprehensive analysis will be carried out using machine learning. Polygenic risk scores will be added in a second step to estimate the additional variance explained by genetic markers. Sample size calculation yielded a total amount of N = 171 subjects.

Discussion

Patient and physician expectancies regarding the primary outcomes and non-random sampling may affect internal validity and external validity, respectively. Through the prospective and naturalistic design, results will gain relevance to clinical practice. Examining the predictive value of patient profiles for weight gain and treatment response during pharmacotherapy will allow for targeted adjustments before and concomitantly to the start of treatment.

Potential of Probiotics as an Adjunct for Patients with Major Depressive Disorder

Major depressive disorder (MDD) is an enfeebling disease with a lifetime incidence of 20%. While accumulating studies implicate a correlation between the disease and gut microbiota, data show that not every patient responded to probiotic treatments. To comprehensively assess the potential role of probiotics in MDD, this study first summarizes the current pathological hypothesis of the disease from a life-stage perspective, focuses on the potential role of "depression gut microbiota." Currently available managements are then briefly summarized and novel bio-materials having potential therapeutic effects on MDD are also evaluated. To harness the positive effect of probiotics, prebiotics, and postbiotics, clinical evidence and their applications on MDD patients are listed. Factors that may counteract the pre/probiotic applications, such as diet, physiology, gender difference, and use of antibiotics and antidepressants are also discussed. The endocannabinoid (eCBs) system may be promising targets for probiotic therapy. More evidence is needed to demonstrate the hierarchical factors in the complex network driving the disease, and probiotic can be one promising adjunct for patients with MDD.

The gut microbiome and mental health: advances in research and emerging priorities

The gut microbiome exerts a considerable influence on human neurophysiology and mental health. Interactions between intestinal microbiology and host regulatory systems have now been implicated both in the development of psychiatric conditions and in the efficacy of many common therapies. With the growing acceptance of the role played by the gut microbiome in mental health outcomes, the focus of research is now beginning to shift from identifying relationships between intestinal microbiology and pathophysiology, and towards using this newfound insight to improve clinical outcomes. Here, we review recent advances in our understanding of gut microbiome-brain interactions, the mechanistic underpinnings of these relationships, and the ongoing challenge of distinguishing association and causation. We set out an overarching model of the evolution of microbiome-CNS interaction and examine how a growing knowledge of these complex systems can be used to determine disease susceptibility and reduce risk in a targeted manner.

The 4E approach to the human microbiome: Nested interactions between the gut-brain/body system within natural and built environments

The complexity of the human mind and its interaction with the environment is one of the main epistemological debates throughout history. Recent ideas, framed as the 4E perspective to cognition, highlight that human experience depends causally on both cerebral and extracranial processes, but also is embedded in a particular sociomaterial context and is a product of historical accumulation of trajectory changes throughout life. Accordingly, the human microbiome is one of the most intriguing actors modulating brain function and physiology. Here, we present the 4E approach to the Human Microbiome for understanding mental processes from a broader perspective, encompassing one's body physiology and environment throughout their lifespan, interconnected by microbiome community structure and dynamics. We review evidence supporting the approach theoretically and motivates the study of the global set of microbial ecosystem networks encountered by a person across their lifetime (from skin to gut to natural and built environments). We furthermore trace future empirical implementation of the approach. We finally discuss novel research opportunities and clinical interventions aimed toward developing low-cost/high-benefit integrative and personalized bio-psycho-socio-environmental treatments for mental health and including the brain-gut-microbiome axis.

The effect of ultraviolet radiation on the incidence and severity of major mental illness using birth month, birth year, and sunspot data

Background and objectives

The evaluation of the severity of patients afflicted with major mental illness (MMI) has been problematic because of confounding variables and genetic variability. There have been multiple studies that suggest several human diseases, especially schizophrenia, are predisposed to be born in certain months or seasons. This observation implied an epigenetic effect of sunlight, likely ultraviolet radiation (UVR), which is damaging to DNA, especially in an embryo. This paper outlines a method to evaluate the severity of schizophrenia (SZ), bipolar disorder (BPD), and schizoaffective disorder (SZ-AFF) using the month/year of birth of those affected compared to the month/year of birth of the general population (GP).

Relevance

Our previous research found that more intense UVR (equal to or greater than 90 sunspot number (SSN)) had a negative effect on the average human lifespan. Also, human birth rates vary in frequency by month of birth reflecting variables like availability of food, sunlight, and other unknown epigenetic factors. We wanted to see if the patient month of birth varied from the average birth months of the general population and if UVR has an epigenetic effect promoting these diseases.

Methods

We obtained the month and year of birth of 1,233 patients admitted over a 15-year period to Maine's largest state psychiatric hospital and counted the months of birth for each diagnosis of SZ, BPD, and SZ-AFF, and compared these results to the general population's birth months of 4,265,555 persons from U. S. Census Year 2006. The number of patients in each month was normalized to August and compared with the normalized birth months of the general population (GP). Plots of the normalized months were considered rates of change (e.g., derivatives) and their respective integrals gave domains of each mental illness relative to the GP. Normalizing the GP to unity was then related to the factor 1.28, e.g., 28% more entropy, deduced from the Sun's fractal dimension imprinted on biological organisms.

Results

The percent of patients meeting our criterion for severity: SZ = 27%; BPD = 26%; SZ-AFF = 100%.

Conclusions

High UVR intensity or a rapid increase in UVR in early gestation are likely epigenetic triggers of major mental illness. BPD is more epigenetically affected than SZ or SZ-AFF disorders. We found that 52% of 1,233 patients comprised the core function of a tertiary-care psychiatric hospital. Also, mental illness exacerbated when the median SSN doubled. This work also validates the Kraeplinian dichotomy.

What is new in this research

This paper offers a new paradigm for evaluating the severity of MMI and supports significant epigenetic effects from UVR.

Metagenomic analysis reveals gut bacterial signatures for diagnosis and treatment outcome prediction in bipolar depression

BACKGROUND

We aimed to characterize gut microbial alterations in depressed patients with bipolar disorder (BD) following quetiapine monotherapy and explored its potential for disease diagnosis and outcome prediction.

METHODS

Fecal samples were obtained from 60 healthy individuals and 62 patients in acute depressive episodes. All patients received one-month quetiapine treatment after enrollment. The structure of gut microbiota was measured with metagenomic sequencing, and its correlation with clinical profiles and brain function as indicated by resting-state functional magnetic resonance imaging was analyzed. Random forest models based on bacterial species were constructed to distinguish patients from controls, and responders from non-responders, respectively.

RESULTS

BD patients displayed specific alterations in gut microbial diversity and composition. Quetiapine treatment increased the diversity of microbial communities and changed the composition. The abundance of Clostridium bartlettii was negatively associated with age, baseline depression severity, while positively associated with spontaneous neural oscillation in the hippocampus. Tree-based classification models for (1) patients and controls and (2) responders and non-responders showed an area under the curve of 0.733 and 0.800, respectively.

CONCLUSION

Our findings add new evidence to the existing literature regarding gut dysbiosis in BD and reveal the potential of microbe-based biomarkers for disease diagnosis and treatment outcome prediction.

The Developing Microbiome From Birth to 3 Years: The Gut-Brain Axis and Neurodevelopmental Outcomes

The volume and breadth of research on the role of the microbiome in neurodevelopmental and neuropsychiatric disorders has expanded greatly over the last decade, opening doors to new models of mechanisms of the gut-brain axis and therapeutic interventions to reduce the burden of these outcomes. Studies have highlighted the window of birth to 3 years as an especially sensitive window when interventions may be the most effective. Harnessing the powerful gut-brain axis during this critical developmental window clarifies important investigations into the microbe-human connection and the developing brain, affording opportunities to prevent rather than treat neurodevelopmental disorders and neuropsychiatric illness. In this review, we present an overview of the developing intestinal microbiome in the critical window of birth to age 3; and its prospective relationship with neurodevelopment, with particular emphasis on immunological mechanisms. Next, the role of the microbiome in neurobehavioral outcomes (such as autism, anxiety, and attention-deficit hyperactivity disorder) as well as cognitive development are described. In these sections, we highlight the importance of pairing mechanistic studies in murine models with large scale epidemiological studies that aim to clarify the typical health promoting microbiome in early life across varied populations in comparison to dysbiosis. The microbiome is an important focus in human studies because it is so readily alterable with simple interventions, and we briefly outline what is known about microbiome targeted interventions in neurodevelopmental outcomes. More novel examinations of known environmental chemicals that adversely impact neurodevelopmental outcomes and the potential role of the microbiome as a mediator or modifier are discussed. Finally, we look to the future and emphasize the need for additional research to identify populations that are sensitive to alterations in their gut microbiome and clarify how interventions might correct and optimize neurodevelopmental outcomes.

The Role of the Gut Microbiota in the Development and Progression of Major Depressive and Bipolar Disorder

A growing number of studies in rodents indicate a connection between the intestinal microbiota and the brain, but comprehensive human data is scarce. Here, we systematically reviewed human studies examining the connection between the intestinal microbiota and major depressive and bipolar disorder. In this review we discuss various changes in bacterial abundance, particularly on low taxonomic levels, in terms of a connection with the pathophysiology of major depressive and bipolar disorder, their use as a diagnostic and treatment response parameter, their health-promoting potential, as well as novel adjunctive treatment options. The diversity of the intestinal microbiota is mostly decreased in depressed subjects. A consistent elevation of phylum Actinobacteria, family Bifidobacteriaceae, and genus Bacteroides, and a reduction of family Ruminococcaceae, genus Faecalibacterium, and genus Roseburia was reported. Probiotics containing Bifidobacterium and/or Lactobacillus spp. seemed to improve depressive symptoms, and novel approaches with different probiotics and synbiotics showed promising results. Comparing twin studies, we report here that already with an elevated risk of developing depression, microbial changes towards a “depression-like” microbiota were found. Overall, these findings highlight the importance of the microbiota and the necessity for a better understanding of its changes contributing to depressive symptoms, potentially leading to new approaches to alleviate depressive symptoms via alterations of the gut microbiota.

The impact of the Th17:Treg axis on the IgA-Biome across the glycemic spectrum

Secretory IgA (SIgA) is released into mucosal surfaces where its function extends beyond that of host defense to include the shaping of resident microbial communities by mediating exclusion/inclusion of respective microbes and regulating bacterial gene expression. In this capacity, SIgA acts as the fulcrum on which host immunity and the health of the microbiota are balanced. We recently completed an analysis of the gut and salivary IgA-Biomes (16S rDNA sequencing of SIgA-coated/uncoated bacteria) in Mexican-American adults that identified IgA-Biome differences across the glycemic spectrum. As Th17:Treg ratio imbalances are associated with gut microbiome dysbiosis and chronic inflammatory conditions such as type 2 diabetes, the present study extends our prior work by examining the impact of Th17:Treg ratios (pro-inflammatory:anti-inflammatory T-cell ratios) and the SIgA response (Th17:Treg-SIgA axis) in shaping microbial communities. Examining the impact of Th17:Treg ratios (determined by epigenetic qPCR lymphocyte subset quantification) on the IgA-Biome across diabetes phenotypes identified a proportional relationship between Th17:Treg ratios and alpha diversity in the stool IgA-Biome of those with dysglycemia, significant changes in community composition of the stool and salivary microbiomes across glycemic profiles, and genera preferentially abundant by T-cell inflammatory phenotype. This is the first study to associate epigenetically quantified Th17:Treg ratios with both the larger and SIgA-fractionated microbiome, assess these associations in the context of a chronic inflammatory disease, and offers a novel frame through which to evaluate mucosal microbiomes in the context of host responses and inflammation.

The effect of interventions targeting gut microbiota on depressive symptoms: a systematic review and meta-analysis

BACKGROUND

Despite their popularity, the efficacy of interventions targeting gut microbiota to improve depressive symptoms is unknown. Our objective is to summarize the effect of microbiome-targeting interventions on depressive symptoms.

METHODS

We conducted a systematic review and meta-analysis. We searched MEDLINE, Embase, PsycINFO, Database of Abstracts of Reviews of Effects, Cochrane Database of Systematic Reviews and the Cochrane Controlled Register of Trials from inception to Mar. 5, 2021. We included studies that evaluated probiotic, prebiotic, synbiotic, paraprobiotic or fecal microbiota transplant interventions in an adult population (age ≥ 18 yr) with an inactive or placebo comparator (defined by the absence of active intervention). Studies must have measured depressive symptoms with a validated scale, and used a randomized controlled trial study design. We conducted a random effects meta-analysis of change scores, using standardized mean difference as the measure of effect.

RESULTS

Sixty-two studies formed the final data set, with 50 included in the meta-analysis. Probiotic, prebiotic, and synbiotic interventions on depressive symptoms showed statistically significant benefits. In the single studies evaluating each of fecal microbiota transplant and paraprobiotic interventions, neither showed a statistically significant benefit.

INTERPRETATION

Despite promising findings of benefit of probiotic, prebiotic and synbiotic interventions for depressive symptoms in study populations, there is not yet strong enough evidence to favour inclusion of these interventions in treatment guidelines for depression. Critical questions about species administered, dosage and timing relative to other antidepressant medications remain to be answered.

STUDY REGISTRATION

PROSPERO no. 143178.

The role of microbiota-gut-brain axis in neuropsychiatric and neurological disorders

Emerging evidence indicates that the gut microbiota play a crucial role in the bidirectional communication between the gut and the brain suggesting that the gut microbes may shape neural development, modulate neurotransmission and affect behavior, and thereby contribute to the pathogenesis and/or progression of many neurodevelopmental, neuropsychiatric, and neurological conditions. This review summarizes recent data on the role of microbiota-gut-brain axis in the pathophysiology of neuropsychiatric and neurological disorders including depression, anxiety, schizophrenia, autism spectrum disorders, Parkinson's disease, migraine, and epilepsy. Also, the involvement of microbiota in gut disorders co-existing with neuropsychiatric conditions is highlighted. We discuss data from both in vivo preclinical experiments and clinical reports including: (1) studies in germ-free animals, (2) studies exploring the gut microbiota composition in animal models of diseases or in humans, (3) studies evaluating the effects of probiotic, prebiotic or antibiotic treatment as well as (4) the effects of fecal microbiota transplantation.

How we decide what to eat: Toward an interdisciplinary model of gut-brain interactions

Everyday dietary decisions have important short‐term and long‐term consequences for health and well‐being. How do we decide what to eat, and what physiological and neurobiological systems are involved in those decisions? Here, we integrate findings from thus‐far separate literatures: (a) the cognitive neuroscience of dietary decision‐making, and (b) growing evidence of gut–brain interactions and especially influences of the gut microbiome on diet and health outcomes. We review findings that suggest that dietary decisions and food consumption influence nutrient sensing, homeostatic signaling in the gut, and the composition of the gut microbiome. In turn, the microbiome can influence host health and behavior. Through reward signaling pathways, the microbiome could potentially affect food and drink decisions. Such bidirectional links between gut microbiome and the brain systems underlying dietary decision‐making may lead to self‐reinforcing feedback loops that determine long‐term dietary patterns, body mass, and health outcomes.

This article is categorized under:

Economics > Individual Decision‐Making

Psychology > Brain Function and Dysfunction

Psychology > Reasoning and Decision Making

Gastrointestinal Symptoms During Depressive Episodes in 3256 Patients with Major Depressive Disorders: Findings from the NSSD

BACKGROUND

Little is known how often depressive episodes are accompanied by gastrointestinal symptoms in major depressive disorders (MDD). The authors sought to determine the frequency and clinical correlates of gastrointestinal symptoms during episodes of depressive disorder.

METHODS

3,256 MDD patients from the National Survey on Symptomatology of Depression (NSSD), which was designed to investigate the magnitude of symptoms of current major depressive episodes in China, were enrolled and assessed for gastrointestinal symptoms in this study. Illness characteristics were compared in patients with a different frequency of gastrointestinal symptoms. Pearson correlation analysis and multiple linear regression analysis were employed to investigate the associations between gastrointestinal symptoms and psychological characteristics in the patients.

RESULTS

More than 70% of the subjects with depressive episodes had concomitant gastrointestinal symptoms. A higher frequency of gastrointestinal symptoms was associated with an increased risk of suicide ideation, suicide attempts, anxious mood, depressed mood, insomnia, feeling a failure, poor concentration, body pain, hopelessness, anger, and irritability. Pearson correlation analysis indicated moderate but significant associations between gastrointestinal symptoms and psychological characteristics (p<0.001). Multiple linear regression analysis showed that suicide ideation (β=0.161, p<0.001), anxiety mood (β=0.166, p = 0.006), insomnia (β =0.262, p<0.001), anger (β=0.144, p<0.001), feeling a failure (β =0.365, p<0.001), and body pain (β=0.581 p<0.001) were independently associated with gastrointestinal symptoms in MDD patients.

CONCLUSION

Gastrointestinal symptoms were one of the most prevalent clinical presentations of MDD. The associations between gastrointestinal symptoms and psychological characteristics may prove useful in expanding our understanding of how gastrointestinal symptoms contributes to MDD.

The Influence of Probiotic Supplementation on Depressive Symptoms, Inflammation, and Oxidative Stress Parameters and Fecal Microbiota in Patients with Depression Depending on Metabolic Syndrome Comorbidity-PRO-DEMET Randomized Study Protocol

There is a huge need to search for new treatment options and potential biomarkers of therapeutic response to antidepressant treatment. Depression and metabolic syndrome often coexist, while a pathophysiological overlap, including microbiota changes, may play a role. The paper presents a study protocol that aims to assess the effect of probiotic supplementation on symptoms of depression, anxiety and stress, metabolic parameters, inflammatory and oxidative stress markers, as well as fecal microbiota in adult patients with depressive disorders depending on the co-occurrence of metabolic syndrome. The trial will be a four-arm, parallel-group, prospective, randomized, double-blind, controlled design that will include 200 participants and will last 20 weeks (ClinicalTrials.gov identifier: NCT04756544). The probiotic preparation will contain Lactobacillus helveticus Rosell^®-52, Bifidobacterium longum Rosell^®-175. We will assess the level of depression, anxiety and stress, quality of life, blood pressure, body mass index and waist circumference, white blood cells count, serum levels of C-reactive protein, high-density lipoprotein (HDL) cholesterol, triglycerides, fasting glucose, fecal microbiota composition and the level of some fecal microbiota metabolites, as well as serum inflammatory markers and oxidative stress parameters. The proposed trial may establish a safe and easy-to-use adjunctive treatment option in a subpopulation of depressive patients only partially responsive to pharmacologic therapy.

Mining microbes for mental health: Determining the role of microbial metabolic pathways in human brain health and disease

There is increasing knowledge regarding the role of the microbiome in modulating the brain and behaviour. Indeed, the actions of microbial metabolites are key for appropriate gut-brain communication in humans. Among these metabolites, short-chain fatty acids, tryptophan, and bile acid metabolites/pathways show strong preclinical evidence for involvement in various aspects of brain function and behaviour. With the identification of neuroactive gut-brain modules, new predictive tools can be applied to existing datasets. We identified 278 studies relating to the human microbiota-gut-brain axis which included sequencing data. This spanned across psychiatric and neurological disorders with a small number also focused on normal behavioural development. With a consistent bioinformatics pipeline, thirty-five of these datasets were reanalysed from publicly available raw sequencing files and the remainder summarised and collated. Among the reanalysed studies, we uncovered evidence of disease-related alterations in microbial metabolic pathways in Alzheimer's Disease, schizophrenia, anxiety and depression. Amongst studies that could not be reanalysed, many sequencing and technical limitations hindered the discovery of specific biomarkers of microbes or metabolites conserved across studies. Future studies are warranted to confirm our findings. We also propose guidelines for future human microbiome analysis to increase reproducibility and consistency within the field.

Analysis of gut microbiota and intestinal integrity markers of inpatients with major depressive disorder

Previous studies have reported on the relationship between gut microbiota and major depressive disorder (MDD). However, there remain gaps in literature concerning the role of the intestinal barrier and microflora in the pathogenesis of depression. This study analyzes the potential causative relationship between gut microbiota and inflammatory and gut integrity markers and clinical symptoms in inpatients with depressive episodes. Sixteen inpatients (50% females) being treated with escitalopram (5-20 mg daily) in standardized conditions were included in the study. The composition of fecal microbiota was evaluated at baseline and endpoint using 16S rRNA sequencing. A significant correlation between depression severity was found, as measured with HDRS24 (Hamilton Depression Rating Scale-24 item), and the following abundance in bacteria: positive correlation with Paraprevotella (r = 0.80, q = 0.012), strong, negative correlations with Clostridiales (r = -0.70, q = 0.016), Clostridia (r = -0.71, q = 0.026), Firmicutes (r = -0.67. q = 0.032), and the RF32 order (r = -0.70, p = 0.016) in the Alphaproteobacteria (r = -0.66, q = 0.031). After six weeks of treatment, clinical outcomes were found to have a negative correlation with levels of plasma intestinal fatty acid-binding protein (IFABP) at the beginning of the study. Still they had a positive correlation with changes in fecal calprotectin during hospitalization. In conclusion, gut microbiota was associated with the severity of depressive symptoms. However, these findings do not serve as predictors of symptomatic improvement during antidepressant treatment in inpatient treatment for MDD. In turn, intestinal integrity and inflammation markers were associated with the response to treatment of patients with MDD and symptom severity. Additional studies are needed to confirm and extend these findings.

Major Depressive Disorder and gut microbiota - Association not causation. A scoping review

One very promising hypothesis of Major Depressive Disorder (MDD) pathogenesis is the gut-brain axis (GBA) dysfunction, which can lead to subclinical inflammation, hypothalamic-pituitary (HPA) axis dysregulation, and altered neural, metabolic and endocrine pathways. One of the most important parts of GBA is gut microbiota, which was shown to regulate different functions in the central nervous system (CNS). The purpose of this scoping review was to present the current state of research on the relationship between MDD and gut microbiota and extract causal relationships. Further, we presented the relationship between the use of probiotics and antidepressants, and the microbiota changes. We evaluated the data from 27 studies aimed to investigate microbial fingerprints associated with depression phenotype. We abstracted data from 16 and 11 observational and clinical studies, respectively; the latter was divided into trials evaluating the effects of psychiatric treatment (n = 3) and probiotic intervention (n = 9) on the microbiome composition and function. In total, the data of 1187 individuals from observational studies were assessed. In clinical studies, there were 490 individuals analysed. In probiotic studies, 220 and 218 patients with MDD received the intervention and non-active study comparator, respectively. It was concluded that in MDD, the microbiota is altered. Although the mechanism of this relationship is unknown, we hypothesise that the taxonomic changes observed in patients with MDD are associated with bacterial proinflammatory activity, reduced Schort Chain Fatty Acids (SCFAs) production, impaired intestinal barrier integrity and neurotransmitter production, impaired carbohydrates, tryptophane and glutamate metabolic pathways. However, only in few publications this effect was confirmed by metagenomic, metabolomic analysis, or by assessment of immunological parameters or intestinal permeability markers. Future research requires standardisation process starting from patient selection, material collection, DNA sequencing, and bioinformatic analysis. We did not observe whether antidepressive medications influence on gut microbiota, but the use of psychobiotics in patients with MDD has great prospects; however, this procedure requires also standardisation and thorough mechanistic research. The microbiota should be treated as an environmental element, which considers the aetiopathogenesis of the disease and provides new possibilities for monitoring and treating patients with MDD.

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.

Crosstalk between Gut and Brain in Alzheimer's Disease: The Role of Gut Microbiota Modulation Strategies

The gut microbiota (GM) represents a diverse and dynamic population of microorganisms and about 100 trillion symbiotic microbial cells that dwell in the gastrointestinal tract. Studies suggest that the GM can influence the health of the host, and several factors can modify the GM composition, such as diet, drug intake, lifestyle, and geographical locations. Gut dysbiosis can affect brain immune homeostasis through the microbiota–gut–brain axis and can play a key role in the pathogenesis of neurodegenerative diseases, including dementia and Alzheimer’s disease (AD). The relationship between gut dysbiosis and AD is still elusive, but emerging evidence suggests that it can enhance the secretion of lipopolysaccharides and amyloids that may disturb intestinal permeability and the blood–brain barrier. In addition, it can promote the hallmarks of AD, such as oxidative stress, neuroinflammation, amyloid-beta formation, insulin resistance, and ultimately the causation of neural death. Poor dietary habits and aging, along with inflammatory responses due to dysbiosis, may contribute to the pathogenesis of AD. Thus, GM modulation through diet, probiotics, or fecal microbiota transplantation could represent potential therapeutics in AD. In this review, we discuss the role of GM dysbiosis in AD and potential therapeutic strategies to modulate GM in AD.

Gut Microbiome Composition Associated With Major Depressive Disorder and Sleep Quality

The microbiota-gut-brain axis plays a critical role in the pathogenesis of major depressive disorder (MDD) and related subclinical symptoms. However, studies on the gut microbiota in MDD are inconsistent, and data on MDD's effects on sleep are lacking. This study aimed to analyze the gut microbiota composition and sleep quality of patients with MDD. We performed 16S rRNA sequencing of stool samples from 36 patients with MDD and 45 healthy controls (HC). Sleep quality was assessed using the Pittsburgh Sleep Quality Index, depressive severity with the Hamilton Depression Scale, and insomnia severity using the Insomnia Severity Index. Forty-eight microbiota targets showed significant differences between MDD and HC. In MDD, six microbiota targets were associated with the severity of depression, 11 with sleep quality, and 3 with sleep severity. At the genus level, Dorea was simultaneously related to depression and sleep quality, while Intestinibacter was more closely related to sleep problems. Coprococcus and Intestinibacter were associated with sleep quality independent of the severity of depression. In conclusion, the present findings enable a better understanding of the relationship between gut microbiota and MDD-related symptoms. Gut microbiota alterations may become potential biomarkers and/or treatment targets for sleep quality in MDD.

Impact of Diabetes on the Gut and Salivary IgA Microbiomes

Mucosal surfaces like those present in the lung, gut, and mouth interface with distinct external environments. These mucosal gateways are not only portals of entry for potential pathogens but also homes to microbial communities that impact host health. Secretory immunoglobulin A (SIgA) is the single most abundant acquired immune component secreted onto mucosal surfaces and, via the process of immune exclusion, shapes the architecture of these microbiomes. Not all microorganisms at mucosal surfaces are targeted by SIgA; therefore, a better understanding of the SIgA-coated fraction may identify the microbial constituents that stimulate host immune responses in the context of health and disease. Chronic diseases like type 2 diabetes are associated with altered microbial communities (dysbiosis) that in turn affect immune-mediated homeostasis. 16S rRNA gene sequencing of SIgA-coated/uncoated bacteria (IgA-Biome) was conducted on stool and saliva samples of normoglycemic participants and individuals with prediabetes or diabetes (n = 8/group). These analyses demonstrated shifts in relative abundance in the IgA-Biome profiles between normoglycemic, prediabetic, or diabetic samples distinct from that of the overall microbiome. Differences in IgA-Biome alpha diversity were apparent for both stool and saliva, while overarching bacterial community differences (beta diversity) were also observed in saliva. These data suggest that IgA-Biome analyses can be used to identify novel microbial signatures associated with diabetes and support the need for further studies exploring these communities. Ultimately, an understanding of the IgA-Biome may promote the development of novel strategies to restructure the microbiome as a means of preventing or treating diseases associated with dysbiosis at mucosal surfaces.

Identification of a Signaling Mechanism by Which the Microbiome Regulates Th17 Cell-Mediated Depressive-Like Behaviors in Mice

OBJECTIVE

Microbiota dysbiosis has been linked to major depressive disorder, but the mechanisms whereby the microbiota modulates mood remain poorly understood. The authors tested whether specific changes in the microbiome modulate depressive-like behaviors.

METHODS

Stools from learned helpless, non-learned helpless, and non-shocked mice were analyzed by V4 16S RNA sequencing to identify gut bacteria associated with learned helplessness and to quantify the level of the quorum-sensing molecule autoinducer-2 (AI-2). T cells were analyzed by flow cytometry, and serum amyloid proteins (SAA) were analyzed by quantitative real-time polymerase chain reaction. Fecal transfer approach and administration of oleic acid and AI-2 were used to determine the effects of the microbiome and quorum-sensing molecules on depressive-like behaviors.

RESULTS

Mice deficient in segmented filamentous bacteria (SFB) were resilient to the induction of depressive-like behavior, and were resensitized when SFB was reintroduced in the gut. SFB produces the quorum-sensing AI-2 and promotes the production of SAA1 and SAA2 by the host, which increases T helper 17 (Th17) cell production. Th17 cells were required to promote depressive-like behaviors by AI-2, as AI-2 administration did not promote susceptibility to depressive-like behaviors or SAA1 and SAA2 production in Th17-deficient mice after stress. Oleic acid, an AI-2 inhibitor, exhibited antidepressant properties, reducing depressive-like behavior, intestinal SAA1 and SAA2 production, and hippocampal Th17 cell accumulation. Stool samples from 10 people with current depressive symptoms and 10 matched healthy control subjects were analyzed as well. Patients with current major depressive disorder exhibited increased fecal interleukin 17A, SAA, and SFB levels.

CONCLUSIONS

The study results reveal a novel mechanism by which bacteria alter mood.

The Bidirectional Relationship of Depression and Inflammation: Double Trouble

Depression represents the number one cause of disability worldwide and is often fatal. Inflammatory processes have been implicated in the pathophysiology of depression. It is now well established that dysregulation of both the innate and adaptive immune systems occur in depressed patients and hinder favorable prognosis, including antidepressant responses. In this review, we describe how the immune system regulates mood and the potential causes of the dysregulated inflammatory responses in depressed patients. However, the proportion of never-treated major depressive disorder (MDD) patients who exhibit inflammation remains to be clarified, as the heterogeneity in inflammation findings may stem in part from examining MDD patients with varied interventions. Inflammation is likely a critical disease modifier, promoting susceptibility to depression. Controlling inflammation might provide an overall therapeutic benefit, regardless of whether it is secondary to early life trauma, a more acute stress response, microbiome alterations, a genetic diathesis, or a combination of these and other factors.

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.