The role of microbiota in the pathogenesis of schizophrenia and major depressive disorder and the possibility of targeting microbiota as a treatment option

Nutritional Strategies in Major Depression Disorder: From Ketogenic Diet to Modulation of the Microbiota-Gut-Brain Axis

Major depressive disorder (MDD) is a leading cause of disability worldwide. While traditional pharmacological treatments are effective for many cases, a significant proportion of patients do not achieve full remission or experience side effects. Nutritional interventions hold promise as an alternative or adjunctive approach, especially for treatment-resistant depression. This review examines the potential role of nutrition in managing MDD through addressing biological deficits and modulating pathways relevant to its pathophysiology. Specifically, it explores the ketogenic diet and gut microbiome modulation through various methods, including probiotics, prebiotics, synbiotics, postbiotics, and fecal microbiota transplantation. Numerous studies link dietary inadequacies to increased MDD risk and deficiencies in nutrients like omega-3 s, vitamins D and B, magnesium, and zinc. These deficiencies impact neurotransmitters, inflammation, and other biological factors in MDD. The gut-brain axis also regulates mood, stress response, and immunity, and disruptions are implicated in MDD. While medications aid acute symptoms, nutritional strategies may improve long-term outcomes by preventing relapse and promoting sustained remission. This comprehensive review aims to provide insights into nutrition's multifaceted relationship with MDD and its potential for developing more effective integrated treatment approaches.

Exploring the Potential of Probiotics and Prebiotics in Major Depression: From Molecular Function to Clinical Therapy

Major depressive disorder (MDD) represents a complex and challenging mental health condition with multifaceted etiology. Recent research exploring the gut-brain axis has shed light on the potential influence of gut microbiota on mental health, offering novel avenues for therapeutic intervention. This paper reviews current evidence on the role of prebiotics and probiotics in the context of MDD treatment. Clinical studies assessing the effects of prebiotic and probiotic interventions have demonstrated promising results, showcasing improvements in depression symptoms and metabolic parameters in certain populations. Notably, prebiotics and probiotics have shown the capacity to modulate inflammatory markers, cortisol levels, and neurotransmitter pathways linked to MDD. However, existing research presents varied outcomes, underscoring the need for further investigation into specific microbial strains, dosage optimization, and long-term effects. Future research should aim at refining personalized interventions, elucidating mechanisms of action, and establishing standardized protocols to integrate these interventions into clinical practice. While prebiotics and probiotics offer potential adjunctive therapies for MDD, continued interdisciplinary efforts are vital to harnessing their full therapeutic potential and reshaping the landscape of depression treatment paradigms.

Intricate role of intestinal microbe and metabolite in schizophrenia

BACKGROUND

The brain-gut axis has gained increasing attention due to its contribution to the etiology of various central nervous system disorders. This study aims to elucidate the hypothesis that schizophrenia is associated with disturbances in intestinal microflora and imbalance in intestinal metabolites. By exploring the intricate relationship between the gut and the brain, with the goal of offering fresh perspectives and valuable insights into the potential contribution of intestinal microbial and metabolites dysbiosis to the etiology of schizophrenia.

METHODS

In this study, we used a 16S ribosomal RNA (16S rRNA) gene sequence-based approach and an untargeted liquid chromatography-mass spectrometry-based metabolic profiling approach to measure the gut microbiome and microbial metabolites from 44 healthy controls, 41 acute patients, and 39 remission patients, to evaluate whether microbial dysbiosis and microbial metabolite biomarkers were linked with the severity of schizophrenic symptoms.

RESULTS

Here, we identified 20 dominant disturbances in the gut microbial composition of patients compared with healthy controls, with 3 orders, 4 families, 9 genera, and 4 species. Several unique bacterial taxa associated with schizophrenia severity. Compared with healthy controls, 145 unusual microflora metabolites were detected in the acute and remission groups, which were mainly involved in environmental information processing, metabolism, organismal systems, and human diseases in the Kyoto encyclopedia of genes and genomes pathway. The Sankey diagram showed that 4 abnormal intestinal and 4 anomalous intestinal microbial metabolites were associated with psychiatric clinical symptoms.

CONCLUSIONS

These findings suggest a possible interactive influence of the gut microbiota and their metabolites on the pathophysiology of schizophrenia.

The Gut-Brain Axis in Schizophrenia: The Implications of the Gut Microbiome and SCFA Production

Schizophrenia, a severe mental illness affecting about 1% of the population, manifests during young adulthood, leading to abnormal mental function and behavior. Its multifactorial etiology involves genetic factors, experiences of adversity, infection, and gene-environment interactions. Emerging research indicates that maternal infection or stress during pregnancy may also increase schizophrenia risk in offspring. Recent research on the gut-brain axis highlights the gut microbiome's potential influence on central nervous system (CNS) function and mental health, including schizophrenia. The gut microbiota, located in the digestive system, has a significant role to play in human physiology, affecting immune system development, vitamin synthesis, and protection against pathogenic bacteria. Disruptions to the gut microbiota, caused by diet, medication use, environmental pollutants, and stress, may lead to imbalances with far-reaching effects on CNS function and mental health. Of interest are short-chain fatty acids (SCFAs), metabolic byproducts produced by gut microbes during fermentation. SCFAs can cross the blood-brain barrier, influencing CNS activity, including microglia and cytokine modulation. The dysregulation of neurotransmitters produced by gut microbes may contribute to CNS disorders, including schizophrenia. This review explores the potential relationship between SCFAs, the gut microbiome, and schizophrenia. Our aim is to deepen the understanding of the gut-brain axis in schizophrenia and to elucidate its implications for future research and therapeutic approaches.

Comparison of gut microbiome profile in patients with schizophrenia and healthy controls - A plausible non-invasive biomarker?

The human gut microbiome regulates brain function through the microbiome-gut-brain axis and is implicated in several neuropsychiatric disorders. However, the relationship between the gut microbiome and the pathogenesis of schizophrenia (SCZ) is poorly defined, and very few studies have examined the effect of antipsychotic treatment response. We aim to study the differences in the gut microbiota among drug-naïve (DN SCZ) and risperidone-treated SCZ patients (RISP SCZ), compared to healthy controls (HCs). We recruited a total of 60 participants, from the clinical services of a large neuropsychiatric hospital, which included DN SCZ, RISP SCZ and HCs (n = 20 each). Fecal samples were analyzed using 16s rRNA sequencing in this cross-sectional study. No significant differences were found in taxa richness (alpha diversity) but microbial composition differed between SCZ patients (both DN and RISP) and HCs (PERMANOVA, p = 0.02). Linear Discriminant Analysis Effect Size (LEfSe) and Random Forest model identified the top six genera, which significantly differed in abundance between the study groups. A specific genus-level microbial panel of Ruminococcus, UCG005, Clostridium_sensu_stricto_1 and Bifidobacterium could discriminate SCZ patients from HCs with an area under the curve (AUC) of 0.79, HCs vs DN SCZ (AUC: 0.68), HCs vs RISP SCZ (AUC: 0.93) and DN SCZ vs RISP SCZ (AUC: 0.87). Our study identified distinct microbial signatures that could aid in the differentiation of DN SCZ, RISP SCZ, and HCs. Our findings contribute to a better understanding of the role of the gut microbiome in SCZ pathophysiology and suggest potential targeted interventions.

Probiotics as a Tool for Regulating Molecular Mechanisms in Depression: A Systematic Review and Meta-Analysis of Randomized Clinical Trials

Depression is one of the main mental disorders. Pharmacological treatment of depression is often associated with delayed effects or insufficient efficacy. Consequently, there is a need to discover new therapeutic methods to cope with depression faster and more effectively. Several lines of evidence indicate that the use of probiotic therapy reduces depressive symptoms. Nonetheless, the exact mechanisms linking the gut microbiota and the central nervous system, as well as the potential mechanisms of action for probiotics, are still not entirely clarified. The aim of this review was to systematically summarize the available knowledge according to PRISMA guidelines on the molecular mechanisms linking probiotics and healthy populations with subclinical depression or anxiety symptoms, as well as depressed patients with or without comorbid somatic illnesses. The standardized mean difference (SMD) with 95% confidence intervals (CI) was calculated. Twenty records were included. It has been found that probiotic administration is linked to a significant increase in BDNF levels during probiotic treatment compared to the placebo (SMD = 0.37, 95% CI [0.07, 0.68], p = 0.02) when considering the resolution of depressive symptoms in depressed patients with or without comorbid somatic illnesses. CRP levels were significantly lower (SMD = -0.47, 95% CI [0.75, -0.19], p = 0.001), and nitric oxide levels were significantly higher (SMD = 0.97, 95% CI [0.58, 1.36], p < 0.0001) in probiotic-treated patients compared to the placebo, however, only among depressed patients with somatic co-morbidities. There were no significant differences in IL-1β, IL-6, IL-10, TNF-α, and cortisol levels after probiotic administration between the intervention and control groups (all p > 0.05). Firm conclusions on the effectiveness of probiotics and their possible association with inflammatory markers in the healthy population (only with subclinical depressive or anxiety symptoms) cannot be drawn. The advent of clinical trials examining the long-term administration of probiotics could evaluate the long-term effectiveness of probiotics in treating depression and preventing its recurrence.

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.

The Role of Gut Microbiota—Gut—Brain Axis in Perioperative Neurocognitive Dysfunction

With the aging of the world population and advances in medical and health technology, more and more elderly patients are undergoing anesthesia and surgery, and perioperative neurocognitive dysfunction (PND) is receiving increasing attention. The latest definition of PND, published simultaneously in November 2018 in 6 leading journals in the field of anesthesiology, clarifies that PND includes preoperatively cognitive impairment, postoperative delirium, delayed neurocognitive recovery, and postoperative cognitive dysfunction and meets the diagnostic criteria for neurocognitive impairment in the Diagnostic and Statistical Manual of Mental Disorders -fifth edition (DSM-5). The time frame for PND includes preoperatively and within 12 months postoperatively. Recent studies have shown that gut microbiota regulates central nervous function and behavior through the gut microbiota - gut - brain axis, but the role of the axis in the pathogenesis of PND remains unclear. Therefore, this article reviews the mechanism of the role of gut microbiota-gut-brain axis in PND, so as to help explore reasonable early treatment strategies.

Altered Intestinal Permeability Biomarkers in Schizophrenia: A Possible Link with Subclinical Inflammation

Background and Purpose

Emerging studies have shown that gut-derived endotoxins might play a role in intestinal and systemic inflammation. Although the significance of intestinal permeability in modulating the pathogenesis of Schizophrenia (SCZ) is recognized, not much data on the specific role of intestinal permeability biomarkers, viz., zonulin, lipopolysaccharide-binding protein (LBP), and intestinal alkaline phosphatase (IAP) in SCZ is available. Therefore, we measured the plasma levels of zonulin, LBP, and IAP and its correlation with neutrophil-to-lymphocyte ratio (NLR); a marker of systemic inflammation in patients with SCZ.

Methods

We recruited 60 individuals, patients with SCZ (n = 40) and healthy controls (n = 20), from a large tertiary neuropsychiatry center. Plasma levels of zonulin, IAP, and LBP were quantified by enzyme-linked immunosorbent assay.

Results

Plasma levels of both LBP and zonulin were significantly increased (P <0.05), whereas the IAP levels (P <0.05) were significantly decreased in patients with SCZ compared to healthy controls. Pearson correlation analysis revealed that zonulin and LBP had a significant positive correlation with NLR, and IAP negatively correlated with NLR. Individuals with SCZ had higher independent odds of zonulin [odds ratio (OR): 10.32, 95% CI: 1.85-57.12], LBP [OR: 1.039, 95% CI: 1.02-1.07], and IAP [OR: 0.643, 95% CI: 0.471-0.879], even after adjusting for potential confounders.

Conclusion

Our study demonstrates an association of zonulin, LBP, and IAP in Asian Indian SCZ patients and correlates with NLR. Our results indicate that low-grade inflammation induced by metabolic endotoxemia might be implicated in the pathoetiology of SCZ.

The Zonulin-transgenic mouse displays behavioral alterations ameliorated via depletion of the gut microbiota

The gut-brain axis hypothesis suggests that interactions in the intestinal milieu are critically involved in regulating brain function. Several studies point to a gut-microbiota-brain connection linking an impaired intestinal barrier and altered gut microbiota composition to neurological disorders involving neuroinflammation. Increased gut permeability allows luminal antigens to cross the gut epithelium, and via the blood stream and an impaired blood-brain barrier (BBB) enters the brain impacting its function. Pre-haptoglobin 2 (pHP2), the precursor protein to mature HP2, is the first characterized member of the zonulin family of structurally related proteins. pHP 2 has been identified in humans as the thus far only endogenous regulator of epithelial and endothelial tight junctions (TJs). We have leveraged the Zonulin-transgenic mouse (Ztm) that expresses a murine pHP2 (zonulin) to determine the role of increased gut permeability and its synergy with a dysbiotic intestinal microbiota on brain function and behavior. Here we show that Ztm mice display sex-dependent behavioral abnormalities accompanied by altered gene expression of BBB TJs and increased expression of brain inflammatory genes. Antibiotic depletion of the gut microbiota in Ztm mice downregulated brain inflammatory markers ameliorating some anxiety-like behavior. Overall, we show that zonulin-dependent alterations in gut permeability and dysbiosis of the gut microbiota are associated with an altered BBB integrity, neuroinflammation, and behavioral changes that are partially ameliorated by microbiota depletion. Our results suggest the Ztm model as a tool for the study of the cross-talk between the microbiome/gut and the brain in the context of neurobehavioral/neuroinflammatory disorders.

Schizophrenia, the gut microbiota, and new opportunities from optogenetic manipulations of the gut-brain axis

Schizophrenia research arose in the twentieth century and is currently rapidly developing, focusing on many parallel research pathways and evaluating various concepts of disease etiology. Today, we have relatively good knowledge about the generation of positive and negative symptoms in patients with schizophrenia. However, the neural basis and pathophysiology of schizophrenia, especially cognitive symptoms, are still poorly understood. Finding new methods to uncover the physiological basis of the mental inabilities related to schizophrenia is an urgent task for modern neuroscience because of the lack of specific therapies for cognitive deficits in the disease. Researchers have begun investigating functional crosstalk between NMDARs and GABAergic neurons associated with schizophrenia at different resolutions. In another direction, the gut microbiota is getting increasing interest from neuroscientists. Recent findings have highlighted the role of a gut-brain axis, with the gut microbiota playing a crucial role in several psychopathologies, including schizophrenia and autism.

There have also been investigations into potential therapies aimed at normalizing altered microbiota signaling to the enteric nervous system (ENS) and the central nervous system (CNS). Probiotics diets and fecal microbiota transplantation (FMT) are currently the most common therapies. Interestingly, in rodent models of binge feeding, optogenetic applications have been shown to affect gut colony sensitivity, thus increasing colonic transit. Here, we review recent findings on the gut microbiota–schizophrenia relationship using in vivo optogenetics. Moreover, we evaluate if manipulating actors in either the brain or the gut might improve potential treatment research. Such research and techniques will increase our knowledge of how the gut microbiota can manipulate GABA production, and therefore accompany changes in CNS GABAergic activity.

Gut Microbial Metabolite Short-Chain Fatt Acids Partially Reverse Surgery and Anesthesia-Induced Behavior Deficits in C57BL/6J Mice

Accumulating evidence has demonstrated that damages of gut microbiota are strongly associated with central nervous system (CNS) diseases, such as perioperative neurocognitive disorders (PND). The present study investigated the role of gut microbial metabolite short-chain fatty acids (SCFAs) in surgery-induced cognitive deficits and neuroinflammation in the hippocampus. Adult male C57BL/6J mice received either SCFA mixture or saline orally for 4 weeks, and then partial hepatectomy was performed. The fecal supernatant of surgical mice was transplanted to normal mice for 3 weeks. The Morris water maze (MWM) and open-field tests were used to evaluate behavioral performance on postoperative or post-transplantation days 3 and 7. In the MWM test, pretreatment with exogenous SCFAs partially reversed surgery-induced impairments in crossing times and the time spent in the target quadrant on postoperative day 3 (p < 0.05, p < 0.05, respectively). In the open-field test, compared with the surgical mice, exogenous SCFA administration prior to surgery partially improved the locomotor activity (p < 0.05) and anxiety-like behavior (p < 0.05) on postoperative day 3. Surgical trauma and anesthesia enhanced ionized calcium-binding adapter molecule 1 (Iba-1) expression (p < 0.001), increased the levels of interleukin (IL)-1β (p < 0.001) and IL-6 (p < 0.001), and inhibited SCFA production (p < 0.001) on postoperative day 3. The expression of the brain-derived neurotrophic factor (BDNF) was also decreased (p < 0.001). Overall, surgical trauma and anesthesia exacerbated cognitive impairment, enhanced neuroinflammatory responses, and inhibited SCFA production. Pretreatment with SCFAs attenuated these effects partially by reversing microglial overactivation, inhibiting neuroinflammatory responses, and enhancing BDNF expression.

Gut microbiota shape B cell in health and disease settings

Recent accumulating evidence supports the hypothesis that the intricate interaction between gut microbiota and the immune system profoundly affects health and disease in humans and mice. In this context, microbiota plays an important role in educating and shaping the host immune system which, in turn, regulates gut microbiota diversity and function to maintain homeostasis. Studies have demonstrated that intestinal microbiota participates in shaping B cells in health and disease settings. Herein, we review the recent progress in understanding how microbiota regulates B-cell development, focusing on early-life B-cell repertoire generation in GALT and how microbial products, including microbial antigens and metabolites, affect B-cell activation and differentiation to ultimately regulate B-cell function. We also discuss the interaction between gut microbiota and B cells under pathogenic conditions and highlight new approaches that can be applied to treat various diseases.

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.

Evaluation of 16S rRNA primer sets for characterisation of microbiota in paediatric patients with autism spectrum disorder

intestinal microbiota is becoming a significant marker that reflects differences between health and disease status also in terms of gut-brain axis communication. Studies show that children with autism spectrum disorder (ASD) often have a mix of gut microbes that is distinct from the neurotypical children. Various assays are being used for microbiota investigation and were considered to be universal. However, newer studies showed that protocol for preparing DNA sequencing libraries is a key factor influencing results of microbiota investigation. The choice of DNA amplification primers seems to be the crucial for the outcome of analysis. In our study, we have tested 3 primer sets to investigate differences in outcome of sequencing analysis of microbiota in children with ASD. We found out that primers detected different portion of bacteria in samples especially at phylum level; significantly higher abundance of Bacteroides and lower Firmicutes were detected using 515f/806r compared to 27f/1492r and 27f*/1495f primers. So, the question is whether a gold standard of Firmicutes/Bacteroidetes ratio is a valuable and reliable universal marker, since two primer sets towards 16S rRNA can provide opposite information. Moreover, significantly higher relative abundance of Proteobacteria was detected using 27f/1492r. The beta diversity of sample groups differed remarkably and so the number of observed bacterial genera.

Targeting the microbiome-gut-brain axis for improving cognition in schizophrenia and major mood disorders: A narrative review

Cognitive impairment has been consistently found to be a core feature of serious mental illnesses such as schizophrenia and major mood disorders (major depression and bipolar disorder). In recent years, a great effort has been made in elucidating the biological causes of cognitive deficits and the search for new biomarkers of cognition. Microbiome and gut-brain axis (MGB) hormones have been postulated to be potential biomarkers of cognition in serious mental illnesses. The main aim of this review was to synthesize current evidence on the association of microbiome and gut-brain hormones on cognitive processes in schizophrenia and major mood disorders and the association of MGB hormones with stress and the immune system. Our review underscores the role of the MGB axis on cognitive aspects of serious mental illnesses with the potential use of agents targeting the gut microbiota as cognitive enhancers. However, the current evidence for clinical trials focused on the MGB axis as cognitive enhancers in these clinical populations is scarce. Future clinical trials using probiotics, prebiotics, antibiotics, or faecal microbiota transplantation need to consider potential mechanistic pathways such as the HPA axis, the immune system, or gut-brain axis hormones involved in appetite control and energy homeostasis.

Effectiveness of Probiotic, Prebiotic, and Synbiotic Supplementation to Improve Perinatal Mental Health in Mothers: A Systematic Review and Meta-Analysis

Introduction: There is an emerging interest in modulating the gut microbiota to target the gut-brain axis and improve maternal mental health in the perinatal period. This systematic review evaluated the effectiveness of prebiotics, probiotics, and synbiotics supplementation during pregnancy to reduce the risk of maternal mental health problems in the perinatal period. Methods: Electronic biomedical databases and clinical trial registries were searched from database inception through August 2020 to identify randomized controlled clinical trials (RCTs) evaluating the effect of probiotic, prebiotic, or synbiotic supplements administered to women during pregnancy on measures of perinatal depression, anxiety, and other mental health outcomes. Study selection, risk of bias appraisal, and data extraction were independently performed by two reviewers. Pooled mean differences (MD) and odds ratios (pOR) with 95% confidence intervals (CI) were calculated in random-effects meta-analyses for the outcomes of interest in the review. Results: From 3,868 studies identified through the search strategy, three RCTs of low risk of bias involving 713 participants were included, all three testing probiotics. There were no differences between probiotics and control groups in the mean depression scores (MD -0.46; 95% CI -2.16, 1.25) at end of follow-up. Although statistical significance was not achieved, probiotics showed an advantage in the proportion of participants scoring below an established cut-off for depression (pOR 0.68; 95% CI 0.43, 1.07). Compared to placebo, probiotics in pregnancy reduced anxiety symptoms (MD -0.99; 95% CI -1.80, -0.18); however, this advantage was not translated in a reduction in the proportion of participants scoring above an established cut-off for anxiety (pOR 0.65; 95% CI 0.23, 1.85). There were no differences between probiotics and control groups in global mental health scores at end of follow-up (MD 1.09; 95% CI -2.04, 4.22). Conclusion: There is limited but promising evidence about the effectiveness of probiotics during pregnancy to reduce anxiety symptoms and reduce the proportion of women scoring ABOVE a cut-off depression score. There is a lack of RCT evidence supporting prebiotics and synbiotics supplementation for similar purposes in the perinatal period. More research is needed before prebiotics, probiotics, and synbiotics are recommended to support maternal mental health and well-being in the perinatal period. Systematic Review Registration: PROSPERO, CRD42019137158.

Gut Microbiota: A Perspective for Psychiatrists

There is mounting evidence that the trillions of microbes that inhabit our gut are a substantial contributing factor to mental health and, equally, to the progression of neuropsychiatric disorders. The extraordinary complexity of the gut ecosystem, and how it interacts with the intestinal epithelium to manifest physiological changes in the brain to influence mood and behaviour, has been the subject of intense scientific scrutiny over the last 2 decades. To further complicate matters, we each harbour a unique microbiota community that is subject to change by a number of factors including diet, exercise, stress, health status, genetics, medication, and age, amongst others. The microbiota-gut-brain axis is a dynamic matrix of tissues and organs including the gastrointestinal (GI) microbiota, immune cells, gut tissue, glands, the autonomic nervous system (ANS), and the brain that communicate in a complex multidirectional manner through a number of anatomically and physiologically distinct systems. Long-term perturbations to this homeostatic environment may contribute to the progression of a number of disorders by altering physiological processes including hypothalamic-pituitary-adrenal axis activation, neurotransmitter systems, immune function, and the inflammatory response. While an appropriate, co-ordinated physiological response, such as an immune or stress response, is necessary for survival, a dysfunctional response can be detrimental to the host, contributing to the development of a number of central nervous system disorders.

A review on preventive role of ketogenic diet (KD) in CNS disorders from the gut microbiota perspective

The gut microbiota plays an important role in neurological diseases via the gut-brain axis. Many factors such as diet, antibiotic therapy, stress, metabolism, age, geography and genetics are known to play a critical role in regulating the colonization pattern of the microbiota. Recent studies have shown the role of the low carbohydrate, adequate protein, and high fat "ketogenic diet" in remodeling the composition of the gut microbiome and thereby facilitating protective effects in various central nervous system (CNS) disorders. Gut microbes are found to be involved in the pathogenesis of various CNS disorders like epilepsy, Parkinson's disease (PD), Alzheimer's disease (AD), autism spectrum disorders (ASDs), multiple sclerosis (MS), amyotrophic lateral sclerosis (ALS) and stress, anxiety and depression. In vivo studies have shown an intricate link between gut microbes and KD and specific microbes/probiotics proved useful in in vivo CNS disease models. In the present review, we discuss the gut-brain bidirectional axis and the underlying mechanism of KD-based therapy targeting gut microbiome in in vivo animal models and clinical studies in neurological diseases. Also, we tried to infer how KD by altering the microbiota composition contributes towards the protective role in various CNS disorders. This review helps to uncover the mechanisms that are utilized by the KD and gut microbiota to modulate gut-brain axis functions and may provide novel opportunities to target therapies to the gut to treat neurologic disorders.

Probiotics and the Microbiota-Gut-Brain Axis: Focus on Psychiatry

PURPOSE OF REVIEW

Probiotics are living bacteria, which when ingested in adequate amounts, confer health benefits. Gut microbes are suggested to play a role in many psychiatric disorders and could be a potential therapeutic target. Between the gut and the brain, there is a bi-directional communication pathway called the microbiota-gut-brain axis. The purpose of this review is to examine data from recent interventional studies focusing on probiotics and the gut-brain axis for the treatment of depression, anxiety and schizophrenia.

RECENT FINDINGS

Probiotics are likely to improve depression but not schizophrenia. Regarding anxiety, there is only one trial which showed an effect of a multispecies probiotic. However, determinants like the duration of treatment, dosage and interactions have not been thoroughly investigated and deserve more scientific attention. Microbiome-based therapies such as probiotics could be cautiously recommended for depression to enhance beneficial bacteria in the gut and to improve mood through the gut-brain axis.

Probiotics and prebiotics: focus on psychiatric disorders - a systematic review

CONTEXT

The gut-brain axis and microbial dysbiosis may play a role in psychiatric diseases. In this view, the gut microbiota has been considered a potential therapeutic target using probiotics and prebiotics.

OBJECTIVE

This systematic review aims to find the existing clinical evidence that may justify the use of probiotics or prebiotics in psychiatric patients.

DATA SOURCES

PRISMA guidelines were followed for a systematic literature review of randomized controlled trials that assessed the effect of prebiotics or probiotics in patients diagnosed with a classified psychiatric disorder.

DATA EXTRACTION

From a total of 212 studies screened, 11 were included in the final systematic review. Quality assessment of the included trials was assessed by the Jadad scale.

RESULTS

Probiotics seem to offer some benefit in major depressive disorder and Alzheimer's disease. One study showed that probiotics reduced rehospitalization in patients with acute mania. In autism spectrum disorders, the results were controversial; however a single study found that early administration of probiotics showed a preventive role. No benefits were found for patients with schizophrenia. In most studies, no major adverse effects were reported.

CONCLUSIONS

Although recent findings in specific psychiatric disorders are encouraging, the use of prebiotics and probiotics in clinical practice stills lacks sufficiently robust evidence.

Altered gut microbiota associated with symptom severity in schizophrenia

BACKGROUND

The gut microbiome and microbiome-gut-brain (MGB) axis have been receiving increasing attention for their role in the regulation of mental behavior and possible biological basis of psychiatric disorders. With the advance of next-generation sequencing technology, characterization of the gut microbiota in schizophrenia (SZ) patients can provide rich clues for the diagnosis and prevention of SZ.

METHODS

In this study, we compared the differences in the fecal microbiota between 82 SZ patients and 80 demographically matched normal controls (NCs) by 16S rRNA sequencing and analyzed the correlations between altered gut microbiota and symptom severity.

RESULTS

The alpha diversity showed no significant differences between the NC and SZ groups, but the beta diversity revealed significant community-level separation in microbiome composition between the two groups (pseudo-F =3.337, p < 0.001, uncorrected). At the phylum level, relatively more Actinobacteria and less Firmicutes (p < 0.05, FDR corrected) were found in the SZ group. At the genus level, the relative abundances of Collinsella, Lactobacillus, Succinivibrio, Mogibacterium, Corynebacterium, undefined Ruminococcus and undefined Eubacterium were significantly increased, whereas the abundances of Adlercreutzia, Anaerostipes, Ruminococcus and Faecalibacterium were decreased in the SZ group compared to the NC group (p < 0.05, FDR corrected). We performed PICRUSt analysis and found that several metabolic pathways differed significantly between the two groups, including the Polyketide sugar unit biosynthesis, Valine, Leucine and Isoleucine biosynthesis, Pantothenate and CoA biosynthesis, C5-Branched dibasic acid metabolism, Phenylpropanoid biosynthesis, Ascorbate and aldarate metabolism, Nucleotide metabolism and Propanoate metabolism pathways (p < 0.05, FDR corrected). Among the SZ group, the abundance of Succinivibrio was positively correlated with the total Positive and Negative Syndrome Scale (PANSS) scores (r = 0.24, p < 0.05, uncorrected) as well as the general PANSS scores (r = 0.22, p < 0.05, uncorrected); Corynebacterium was negatively related to the negative scores of PANSS (r = 0.22, p < 0.05, uncorrected).

CONCLUSIONS

Our findings provided evidence of altered gut microbial composition in SZ group. In addition, we found that Succinvibrio and Corynebacterium were associated with the severity of symptoms for the first time, which may provide some new biomarkers for the diagnosis of SZ.

Zonulin-Dependent Intestinal Permeability in Children Diagnosed with Mental Disorders: A Systematic Review and Meta-Analysis

Worldwide, up to 20% of children and adolescents experience mental disorders, which are the leading cause of disability in young people. Research shows that serum zonulin levels are associated with increased intestinal permeability (IP), affecting neural, hormonal, and immunological pathways. This systematic review and meta-analysis aimed to summarize evidence from observational studies on IP in children diagnosed with mental disorders. The review follows the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. A systematic search of the Cochrane Library, PsycINFO, PubMed, and the Web of Science identified 833 records. Only non-intervention (i.e., observational) studies in children (<18 years) diagnosed with mental disorders, including a relevant marker of intestinal permeability, were included. Five studies were selected, with the risk of bias assessed according to the Newcastle–Ottawa scale (NOS). Four articles were identified as strong and one as moderate, representing altogether 402 participants providing evidence on IP in children diagnosed with attention deficit and hyperactivity disorder (ADHD), autism spectrum disorder (ASD), and obsessive–compulsive disorder (OCD). In ADHD, elevated serum zonulin levels were associated with impaired social functioning compared to controls. Children with ASD may be predisposed to impair intestinal barrier function, which may contribute to their symptoms and clinical outcome compared to controls. Children with ASD, who experience gastro-intestinal (GI) symptoms, seem to have an imbalance in their immune response. However, in children with OCD, serum zonulin levels were not significantly different compared to controls, but serum claudin-5, a transmembrane tight-junction protein, was significantly higher. A meta-analysis of mean zonulin plasma levels of patients and control groups revealed a significant difference between groups (p = 0.001), including the four studies evaluating the full spectrum of the zonulin peptide family. Therefore, further studies are required to better understand the complex role of barrier function, i.e., intestinal and blood–brain barrier, and of inflammation, to the pathophysiology in mental and neurodevelopmental disorders. This review was PROSPERO preregistered, (162208).

Anesthesia and surgery induce cognitive dysfunction in elderly male mice: the role of gut microbiota

It is well known that the incidence of postoperative cognitive dysfunction (POCD) is high in elderly patients. The pathogenesis and therapeutic mechanisms of POCD, however, have not yet been completely elucidated. The effects of gut microbiota, particularly in terms of regulating brain function, have gradually attracted increasing attention. In this study, we investigated the potential role of gut microbiota in POCD in aged male mice and attempted to determine whether alterations in gut microbiota would be helpful in the diagnosis of POCD. POCD and non-POCD mice were classified by hierarchical cluster analysis of behavioral results. Additionally, α- and β-diversity of gut microbiota showed a differential profile between the groups. In total, 24 gut bacteria were significantly altered in POCD mice compared with those in non-POCD mice, in which 13 gut bacteria were significantly correlated with escape latency in the Morris water maze test (MWMT). Remarkably, receiver operating characteristic curves revealed that the Dehalobacteriaceae family and Dehalobacterium genus are potentially important bacteria for the diagnosis of POCD. These findings indicate that alterations in the composition of gut microbiota are probably involved in the pathogenesis of POCD in aged mice. Novel therapeutic strategies regulating specific gut bacteria may be helpful for the prevention and treatment of POCD.

Mitochondria could be a potential key mediator linking the intestinal microbiota to depression

The intestinal microbiota has been reported to affect depression, a common mental condition with severe health-related consequences. However, what mediates the effect of the intestinal microbiota on depression has not been well elucidated. We summarize the roles of the mitochondria in eliciting beneficial effects on the gut microbiota to ameliorate symptoms of depression. It is well known that mitochondria play a key role in depression. An important pathogenic factor, namely inflammatory response, may adversely impact mitochondrial functionality to maintain cellular homeostasis. Dysfunction of mitochondria not only affects neuronal function but also reduces neuron cell numbers. We posit that the intestinal microbiota could affect neuronal mitochondrial function through short-chain fatty acids such as butyrate. Brain inflammatory processes could also be affected through the modulation of gut permeability and blood lipopolysaccharide levels. Aberrant mitochondria functionality coupled to adverse cellular homeostasis could be a key mediator for the effect of the intestinal microbiota on the progression of depression.

Lithium Preparations in Psychiatry, Addiction Medicine and Neurology. Part II. Biochemical Mechanisms of Its Action

Lithium is the first and the lightest in the series of alkali metals, to which, in addition to lithium, two very biologically important elements – sodium and potassium, as well as trace elements rubidium and cesium, belong. Despite its formal affiliation to the group of alkali metals, lithium, like many other chemical elements of the «atypical» second period of the periodic table (for example, boron), is more similar in its chemical properties not to its counterparts in the group, but to its «diagonal brother» – magnesium. As we will show in this article, the diagonal chemical similarity between lithium and magnesium is of great importance for understanding the mechanisms of its intracellular biochemical action. At the same time, the intragroup chemical similarity of lithium with sodium and potassium is more important for understanding the mechanisms of its absorption, its distribution in the body and its excretion. Despite the 70 years that have passed since John Cade’s discovery of the antimanic effect of lithium, the mechanisms of its therapeutic action are still not completely understood. In the end, it turns out that the mechanism of the therapeutic action of lithium is extremely complex, multicomponent, unique and not imitable. Certain aspects of the mechanism of its action may be compatible with the mechanisms of action of other mood stabilizers, or with the mechanisms of action of so-called «lithium-mimetics», such as ebselen. However, no other drug to date failed to fully reproduce the biochemical effect of lithium on the body.

A Mechanistic Model of Gut-Brain Axis Perturbation and High-Fat Diet Pathways to Gut Microbiome Homeostatic Disruption, Systemic Inflammation, and Type 2 Diabetes

Type 2 diabetes (T2D) is a highly prevalent metabolic disease, affecting nearly 10% of the American population. Although the etiopathogenesis of T2D remains poorly understood, advances in DNA sequencing technologies have allowed for sophisticated interrogation of the human microbiome, providing insight into the role of the gut microbiome in the development and progression of T2D. An emerging body of research reveals that gut-brain axis (GBA) perturbations and a high-fat diet (HFD), along with other modifiable and nonmodifiable risk factors, contribute to gut microbiome homeostatic imbalance. Homeostatic imbalance or disruption increases gut wall permeability and facilitates translocation of endotoxins (lipopolysaccharides) into the circulation with resultant systemic inflammation. Chronic, low-grade systemic inflammation ensues with pro-inflammatory pathways activated, contributing to obesity, insulin resistance (IR), pancreatic β-cell decline, and, thereby, T2D. While GBA perturbations and HFD are implicated in provoking these conditions, prior mechanistic models have tended to examine HFD and GBA pathways exclusively without considering their shared pathways to T2D. Addressing this gap, this article proposes a mechanistic model informed by animal and human studies to advance scientific understanding of (1) modifiable and nonmodifiable risk factors for gut microbiome homeostatic disruption, (2) HFD and GBA pathways contributing to homeostatic disruption, and (3) shared GBA and HFD pro-inflammatory pathways to obesity, IR, β-cell decline, and T2D. The proposed mechanistic model, based on the extant literature, proposes a framework for studying the complex relationships of the gut microbiome to T2D to advance study in this promising area of research.

Schizophrenia and gut-flora related epigenetic factors

BACKGROUND

Schizophrenia (SZ) is a complex psychiatric disorder and the exact mechanisms that underpin SZ remain poorly understood despite decades of research. Genetic, epigenetic, and environmental factors are all considered to play a role. The importance of gut flora and its influence on the central nervous system has been recognized in recent years. We hypothesize that gut flora may be a converging point where environmental factors interact with epigenetic factors and contribute to SZ pathogenesis.

AIM

To summarize the current understanding of genetic and epigenetic factors and the possible involvement of gut flora in the pathogenesis of schizophrenia.

RESULTS

We searched PubMed and Medline with a combination of the key words schizophrenia, microbiome, epigenetic factors to identify studies of genetic and epigenetic factors in the pathogenesis of schizophrenia. Numerous genes that encode key proteins in neuronal signaling pathways have been linked to SZ. Epigenetic modifications, particularly, methylation and acetylation profiles, have been found to differ in individuals that present with SZ from those that don't. Gut flora may affect epigenetic modifications by regulation of key metabolic pathway molecules, including methionine, florate, biotin, and metabolites that are acetyl group donors. Despite a lack of direct studies on the subject, it is possible that gut flora may influence genetic and epigenetic expression and thereby contribute to the pathogenesis of SZ.

CONCLUSION

Gut flora is sensitive to both internal and environmental stimuli and the synthesis of some key molecules that participate in the epigenetic modulation of gene expression. Therefore, it is possible that gut flora is a converging point where environmental factors interact with genetic and epigenetic factors in the pathogenesis of SZ.

The gut microbiome from patients with schizophrenia modulates the glutamate-glutamine-GABA cycle and schizophrenia-relevant behaviors in mice

Schizophrenia (SCZ) is a devastating mental disorder with poorly defined underlying molecular mechanisms. The gut microbiome can modulate brain function and behaviors through the microbiota-gut-brain axis. Here, we found that unmedicated and medicated patients with SCZ had a decreased microbiome α-diversity index and marked disturbances of gut microbial composition versus healthy controls (HCs). Several unique bacterial taxa (e.g., Veillonellaceae and Lachnospiraceae) were associated with SCZ severity. A specific microbial panel (Aerococcaceae, Bifidobacteriaceae, Brucellaceae, Pasteurellaceae, and Rikenellaceae) enabled discriminating patients with SCZ from HCs with 0.769 area under the curve. Compared to HCs, germ-free mice receiving SCZ microbiome fecal transplants had lower glutamate and higher glutamine and GABA in the hippocampus and displayed SCZ-relevant behaviors similar to other mouse models of SCZ involving glutamatergic hypofunction. Together, our findings suggest that the SCZ microbiome itself can alter neurochemistry and neurologic function in ways that may be relevant to SCZ pathology.

Altered gut metabolome contributes to depression-like behaviors in rats exposed to chronic unpredictable mild stress

The gut microbiota has been increasingly correlated with depressive disorder. It was recently shown that the transplantation of the gut microbiota from depressed patients to animals can produce depressive-like behaviors, suggesting that the gut microbiota plays a causal role in the development of depression. In addition, metabolic disorder, which is strongly associated with depression, is exacerbated by changes in the composition of the gut microbiota and is alleviated by treatment with antidepressants. However, the key players and pathways that link the gut microbiota to the pathogenesis of depression remain largely unknown. To evaluate the relationships between depression and metabolic disorders in feces and plasma, we monitored changes in fecal and plasma metabolomes during the development of depressive-like behaviors in rats exposed to chronic unpredictable mild stress (CUMS). In these animals, the fecal metabolome was altered first and subjected to changes in the plasma metabolome. Changes in the abundance of fecal metabolites were associated with depressive-like behaviors and with altered levels of neurotransmitters in the hippocampus. Furthermore, the analysis of the fecal metabolome and the fecal microbiota in CUMS rats demonstrated consistent changes in the levels of several amino acids, including L-threonine, isoleucine, alanine, serine, tyrosine, and oxidized proline. Finally, we observed significant correlations between these amino acids and the altered fecal microbiota. The results of this study suggest that changes in amino acid metabolism by the gut microbiota contribute to changes in circulating amino acids and are associated with the behavior indices of depression.

Intestinal Sensing by Gut Microbiota: Targeting Gut Peptides

There are more than 2 billion overweight and obese individuals worldwide, surpassing for the first time, the number of people affected by undernutrition. Obesity and its comorbidities inflict a heavy burden on the global economies and have become a serious threat to individuals' wellbeing with no immediate cure available. The causes of obesity are manifold, involving several factors including physiological, metabolic, neural, psychosocial, economic, genetics and the environment, among others. Recent advances in genome sequencing and metagenomic profiling have added another dimension to this complexity by implicating the gut microbiota as an important player in energy regulation and the development of obesity. As such, accumulating evidence demonstrate the impact of the gut microbiota on body weight, adiposity, glucose, lipid metabolism, and metabolic syndrome. This also includes the role of microbiota as a modulatory signal either directly or through its bioactive metabolites on intestinal lumen by releasing chemosensing factors known to have a major role in controlling food intake and regulating body weight. The importance of gut signaling by microbiota signaling is further highlighted by the presence of taste and nutrient receptors on the intestinal epithelium activated by the microbial degradation products as well as their role in release of peptides hormones controlling appetite and energy homeostasis. This review present evidence on how gut microbiota interacts with intestinal chemosensing and modulates the release and activity of gut peptides, particularly GLP-1 and PYY.

Microbiome-The Missing Link in the Gut-Brain Axis: Focus on Its Role in Gastrointestinal and Mental Health

The central nervous system (CNS) and the human gastrointestinal (GI) tract communicate through the gut-brain axis (GBA). Such communication is bi-directional and involves neuronal, endocrine, and immunological mechanisms. There is mounting data that gut microbiota is the source of a number of neuroactive and immunocompetent substances, which shape the structure and function of brain regions involved in the control of emotions, cognition, and physical activity. Most GI diseases are associated with altered transmission within the GBA that are influenced by both genetic and environmental factors. Current treatment protocols for GI and non-GI disorders may positively or adversely affect the composition of intestinal microbiota with a diverse impact on therapeutic outcome(s). Alterations of gut microbiota have been associated with mood and depressive disorders. Moreover, mental health is frequently affected in GI and non-GI diseases. Deregulation of the GBA may constitute a grip point for the development of diagnostic tools and personalized microbiota-based therapy. For example, next generation sequencing (NGS) offers detailed analysis of microbiome footprints in patients with mental and GI disorders. Elucidating the role of stem cell⁻host microbiome cross talks in tissues in GBA disorders might lead to the development of next generation diagnostics and therapeutics. Psychobiotics are a new class of beneficial bacteria with documented efficacy for the treatment of GBA disorders. Novel therapies interfering with small molecules involved in adult stem cell trafficking are on the horizon.

Faecal Short Chain Fatty Acids Profile is Changed in Polish Depressive Women

Short chain fatty acids (SCFAs) being produced during fermentation of non-digestible polysaccharides are regulatory compounds with the potential to influence inflammatory, as well as emotional state and cognition through the gut⁻brain axis. We analyzed the association between stool concentration of SCFAs (acetic acid (C 2:0), propionic acid (C 3:0), isobutyric acid (C 4:0 i), butyric acid (C 4:0 n), isovaleric acid (C 5:0 i) valeric acid (C 5:0 n), isocaproic acid (C 6:0 i), caproic acid, and (C 6:0 n) heptanoic acid (C 7:0)) and depressive symptoms among women and looked for the potential confounders of microbiota byproduct synthesis. We enrolled 116 women aged 52.0 ± 4.7 years and recognized depression in 47 (40.52%). To analyze the emotional state, Beck's Depression Inventory (BDI) was used. We assessed SCFAs content by means of gas chromatography. Fiber intake was estimated using parts of food frequency questionnaire. The content of acetic acid was significantly lowered compared to non-depressed women (median {IQR}: 29.49 {20.81} vs. 34.99 {19.55}, p = 0.04). A tendency toward decreased level of propionic acid was noticed (median {IQR}: 16.88 {9.73} vs. 21.64 {12.17}, p = 0.07), while the concentration of isocaproic acid was significantly increased in (median {IQR}: 0.89 {1.15} vs. 0.56 {0.95}, p < 0.01) comparison to matched healthy subjects. We found negative correlations between acetate, propionate, and Beck's score (r = -0.2, p = 0.03; r = -0.21, p = 0.02, respectively). Statistically significant correlations between acetate and propionate and BDI somatic score (r = -0.21, p = 0.01; r = -0.17, p = 0.03), as well as correlations regarding isocaproic and both cognitive/affective (r = 0.37, p = 0.0001) and somatic (r = 9.37, p < 0.001) scores were found. Women who declared current usage of lipid-lowering and thyroid drugs in the past, had higher content of C6:0-i (Users; median {IQR}: 1.91 {3.62} vs. non-users; 0.55 {0.67}; p = 0.0048).and lower of C2:0 (Users; median {IQR}: 23.07 {12.80} vs. non users 33.73 {21.44}; p = 0.041), respectively. No correlations regarding SCFAs concentration and fiber intake were found. We concluded that SCFAs may potentially contribute to depression phenotype, however, due to the small size of groups suffering from moderately heavy (n = 5) and severe (n = 7) depression, the conclusion should be treated with caution. Pharmacotherapy of hyperlipidemia and thyroid disease might affect SCFAs synthesis. Studies with more participants are required.

Antipsychotics, Metabolic Adverse Effects, and Cognitive Function in Schizophrenia

Cognitive impairment is a core symptom domain of schizophrenia. The effect of antipsychotics, the cornerstone of treatment in schizophrenia, on this domain is not fully clear. There is some evidence suggesting that antipsychotics may partially improve cognitive function, and that this improvement may vary depending on the specific cognitive domain. However, this research is confounded by various factors, such as age, duration/stage of illness, medication adherence, and extrapyramidal side effects that complicate the relationship between antipsychotics and cognitive improvement. Furthermore, antipsychotics-particularly the second generation, or "atypical" antipsychotics-can induce serious metabolic side effects, such as obesity, dyslipidemia and type 2 diabetes, illnesses which themselves have been linked to impairments in cognition. Thus, the inter-relationships between cognition and metabolic side effects are complex, and this review aims to examine them in the context of schizophrenia and antipsychotic treatment. The review also speculates on potential mechanisms underlying cognitive functioning and metabolic risk in schizophrenia. We conclude that the available literature examining the inter-section of antipsychotics, cognition, and metabolic effects in schizophrenia is sparse, but suggests a relationship between metabolic comorbidity and worse cognitive function in patients with schizophrenia. Further research is required to determine if there is a causal connection between the well-recognized metabolic adverse effects of antipsychotics and cognitive deficits over the course of the illness of schizophrenia, as well as, to determine underlying mechanisms. In addition, findings from this review highlight the importance of monitoring metabolic disturbances in parallel with cognition, as well as, the importance of interventions to minimize metabolic abnormalities for both physical and cognitive health.

Deciphering microbiome and neuroactive immune gene interactions in schizophrenia

The body's microbiome represents an actively regulated network of novel mechanisms that potentially underlie the etiology and pathophysiology of a wide range of diseases. For complex brain disorders such as schizophrenia, understanding the cellular and molecular pathways that intersect the bidirectional gut-brain axis is anticipated to lead to new methods of treatment. The means by which the microbiome might differ across neuropsychiatric and neurological disorders are not known. Brain disorders as diverse as schizophrenia, major depression, Parkinson's disease and multiple sclerosis appear to share a common pathology of an imbalanced community of commensal microbiota, often measured in terms of a leaky gut phenotype accompanied by low level systemic inflammation. While environmental factors associated with these disease states might contribute to intestinal pathologies, products from a perturbed microbiome may also directly promote specific signs, symptoms and etiologies of individual disorders. We hypothesize that in schizophrenia, it is the putatively unique susceptibility related to genes that modulate the immune system and the gut-brain pleiotropy of these genes which leads to a particularly neuropathological response when challenged by a microbiome in dysbiosis. Consequences from exposure to this dysbiosis may occur during pre- or post-natal time periods and thus may interfere with normal neurodevelopment in those who are genetically predisposed. Here, we review the evidence from the literature which supports the idea that the intersection of the microbiome and immune gene susceptibility in schizophrenia is relevant etiologically and for disease progression. Figuring prominently at both ends of the gut-brain axis and at points in between are proteins encoded by genes found in the major histocompatibility complex (MHC), including select MHC as well as non-MHC complement pathway genes.

Adjunctive probiotic microorganisms to prevent rehospitalization in patients with acute mania: A randomized controlled trial

OBJECTIVE

Immunological abnormalities play a role in the pathophysiology of mania and have been associated with relapse. Probiotic organisms such as Lactobacilli and Bifidobacteria modulate inflammation in humans and animal models. The trial examined whether the administration of probiotic organisms prevents psychiatric rehospitalizations in patients recently discharged following hospitalization for mania.

METHODS

Patients hospitalized for mania (N = 66) were randomized after discharge to receive 24 weeks of adjunctive probiotics (Lactobacillus rhamnosus strain GG and Bifidobacterium animalis subsp. lactis strain Bb12) or adjunctive placebo in a parallel two-group design format. The effect of treatment group on the risk of rehospitalization was calculated using Cox regression models. The modulating effect of systemic inflammation was measured employing an inflammation score based on immunoglobulin levels directed at previously defined antigens.

RESULTS

During the 24-week observation period there were a total of 24 rehospitalizations in the 33 individuals who received placebo and eight rehospitalizations in the 33 individuals who received the probiotics (z = 2.63, P = .009). Hazard functions indicated that the administration of the probiotics was associated with a significant advantage in time to all psychiatric rehospitalizations (hazard ratio [HR] = 0.26, 95% confidence interval [CI] 0.10, .69; P = .007). Probiotic treatment also resulted in fewer days rehospitalized (mean 8.3 vs 2.8 days for placebo and probiotic treatment, respectively; χ²  = 5.17, P = .017). The effect of the probiotic treatment on the prevention of rehospitalization was increased in individuals with elevated levels of systemic inflammation at baseline.

CONCLUSION

Probiotic supplementation is associated with a lower rate of rehospitalization in patients who have been recently discharged following hospitalization for mania.

Proteomics and the microbiome: pitfalls and potential

Introduction: Human symbiotic microbiota are now known to play important roles in human health and disease. Significant progress in our understanding of the human microbiome has been driven by recent technological advances in the fields of genomics, transcriptomics, and proteomics. As a complementary method to metagenomics, proteomics is enabling detailed protein profiling of the microbiome to decipher its structure and function and to analyze its relationship with the human body. Fecal proteomics is being increasingly applied to discover and validate potential health and disease biomarkers, and Therapeutic Goods Administration (TGA)-approved instrumentation and a range of clinical assays are being developed that will collectively play key roles in advancing personalized medicine. Areas covered: This review will introduce the complexity of the microbiome and its role in health and disease (in particular the gastrointestinal tract or gut microbiome), discuss current genomic and proteomic methods for studying this system, including the discovery of potential biomarkers, and outline the development of clinically accepted protocols leading to personalized medicine. Expert commentary: Recognition of the important role the microbiome plays in both health and disease is driving current research in this key area. A proteogenomics approach will be essential to unravel the biologies underlying this complex network.