Gut microbiota alterations in schizophrenia might be related to stress exposure: Findings from the machine learning analysis

Dysbiosis is associated with the behavioral phenotype observed in the triple-hit Wisket rat model of schizophrenia

Comorbidities between gastrointestinal diseases and psychiatric disorders have been widely reported, with the gut-brain axis implicated as a potential biological basis. Thus, dysbiosis may play an important role in the etiology of schizophrenia, which is barely detected. Triple-hit Wisket model rats exhibit various schizophrenia-like behavioral phenotypes. The present study aimed to compare the diversity and abundance of gut microbiota in Wisket model and control rats; furthermore, to correlate the microbial taxonomic profiles to indices of behavioral change. Tail-flick and Ambitus tests were used to assess acute heat pain sensitivity, and record exploration and locomotor activity along with motivation in young adult, control and Wisket model rats. Fecal microbiota composition was profiled by deep sequencing of bacterial 16S rRNA, and it was correlated to behavioral phenotype. Wisket rats exhibited significantly decreased pain sensitivity, lower locomotor activity and exploration, and impaired motivation compared with controls. No significant differences were observed in bacterial alpha diversity between the groups; however, clear differences in community structure were observed. Wisket rats showed decreases in several genera of Firmicutes and Saccharimonas, and increases in Bacteriodetes and Helicobacter phyla compared with controls. Correlation analysis revealed significant associations between the microbiota profile and the behavioral phenotype. This is the first demonstration that fecal microbiota composition is markedly altered in a triple-hit schizophrenia rat model, suggesting the contribution of the microbiota-gut-brain axis in the development of the schizophrenia-like behavioral phenotype. Thus targeting the gut microbiota may be a novel approach to treat such impairments.

Understanding the Impact of the Gut Microbiome on Mental Health: A Systematic Review

Mental health is a serious issue, with mental health disorders affecting millions of people globally. Gut microbiota has received considerable attention because of its potential role in the pathogenesis of mental health disorders. This systematic review synthesized 15 studies exploring the effects of the gut microbiome on depression, anxiety, schizophrenia, and bipolar disorder, with qualitative and quantitative insights. The studies were conducted in different countries and employed various methods including 16S rRNA sequencing and metagenomic analysis with sample sizes varying from 50 to 600. Some of the key findings were that depression was associated with reduced microbial diversity and high levels of Firmicutes, and anxiety was associated with low levels of short-chain fatty acid (SCFA)-producing bacteria and high levels of Proteobacteria. Schizophrenia was related to endotoxemia and a reduction in the Lactobacillus count whereas bipolar disorder displayed a shift in the Firmicutes/Bacteroidetes ratio. Of interest, probiotics and dietary changes were as effective as drug treatment leading to symptom alleviation in many patients. It was found that depression was linked to less diverse gut bacteria while anxiety was associated with an increase in inflammatory bacteria. People with bipolar disorder were also found to have different gut bacteria patterns. This review also emphasizes the importance of the gut microbiota in the pathophysiology of mental disorders and the promising value of targeting microbiomes in pharmacological treatment approaches.

Reproducible gut microbial signatures in bipolar and schizophrenia spectrum disorders: A metagenome-wide study

BACKGROUND

Numerous studies report gut microbiome variations in bipolar disorder (BD) and schizophrenia spectrum disorders (SSD) compared to healthy individuals, though, there is limited consensus on which specific bacteria are associated with these disorders.

METHODS

In this study, we performed a comprehensive metagenomic shotgun sequencing analysis in 103 Dutch patients with BD/SSD and 128 healthy controls matched for age, sex, body mass index and income, while accounting for diet quality, transit time and technical confounders. To assess the replicability of the findings, we used two validation cohorts (total n = 203), including participants from a distinct population with a different metagenomic isolation protocol.

RESULTS

The gut microbiome of the patients had a significantly different β-diversity, but not α-diversity nor neuroactive potential compared to healthy controls. Initially, twenty-six bacterial taxa were identified as differentially abundant in patients. Among these, the previously reported genera Lachnoclostridium and Eggerthella were replicated in the validation cohorts. Employing the CoDaCoRe learning algorithm, we identified two bacterial balances specific to BD/SSD, which demonstrated an area under the receiver operating characteristic curve (AUC) of 0.77 in the test dataset. These balances were replicated in the validation cohorts and showed a positive association with the severity of psychiatric symptoms and antipsychotic use. Last, we showed a positive association between the relative abundance of Klebsiella and Klebsiella pneumoniae with antipsychotic use and between the Anaeromassilibacillus and lithium use.

CONCLUSIONS

Our findings suggest that microbial balances could be a reproducible method for identifying BD/SSD-specific microbial signatures, with potential diagnostic and prognostic applications. Notably, Lachnoclostridium and Eggerthella emerge as frequently occurring bacteria in BD/SSD. Last, our study reaffirms the previously established link between Klebsiella and antipsychotic medication use and identifies a novel association between Anaeromassilibacillus and lithium use.

Long-term Environmental Enrichment Normalizes Schizophrenia-like Abnormalities and Promotes Hippocampal Slc6a4 Promoter Demethylation in Mice Submitted to a Two-hit Model

Here, we explored the impact of prolonged environmental enrichment (EE) on behavioral, neurochemical, and epigenetic changes in the serotonin transporter gene in mice subjected to a two-hit schizophrenia model. The methodology involved administering the viral mimetic PolyI:C to neonatal Swiss mice as a first hit during postnatal days (PND) 5-7, or a sterile saline solution as a control. At PND21, mice were randomly assigned either to standard environment (SE) or EE housing conditions. Between PND35-44, the PolyI:C-treated group was submitted to various unpredictable stressors, constituting the second hit. Behavioral assessments were conducted on PND70, immediately after the final EE exposure. Following the completion of behavioral assessments, we evaluated the expression of proteins in the hippocampus that are indicative of microglial activation, such as Iba-1, as well as related to neurogenesis, including doublecortin (Dcx). We also performed methylation analysis on the serotonin transporter gene (Slc6a4) to investigate alterations in serotonin signaling. The findings revealed that EE for 50 days mitigated sensorimotor gating deficits and working memory impairments in two-hit mice and enhanced their locomotor and exploratory behaviors. EE also normalized the overexpression of hippocampal Iba-1 and increased the expression of hippocampal Dcx. Additionally, we observed hippocampal demethylation of the Slc6a4 gene in the EE-exposed two-hit group, indicating epigenetic reprogramming. These results contribute to the growing body of evidence supporting the protective effects of long-term EE in counteracting behavioral disruptions caused by the two-hit schizophrenia model, pointing to enhanced neurogenesis, diminished microglial activation, and epigenetic modifications of serotonergic pathways as underlying mechanisms.

Novel Insights into Psychosis and Antipsychotic Interventions: From Managing Symptoms to Improving Outcomes

For the past 70 years, the dopamine hypothesis has been the key working model in schizophrenia. This has contributed to the development of numerous inhibitors of dopaminergic signaling and antipsychotic drugs, which led to rapid symptom resolution but only marginal outcome improvement. Over the past decades, there has been limited research on the quantifiable pathological changes in schizophrenia, including premature cellular/neuronal senescence, brain volume loss, the attenuation of gamma oscillations in electroencephalograms, and the oxidation of lipids in the plasma and mitochondrial membranes. We surmise that the aberrant activation of the aryl hydrocarbon receptor by toxins derived from gut microbes or the environment drives premature cellular and neuronal senescence, a hallmark of schizophrenia. Early brain aging promotes secondary changes, including the impairment and loss of mitochondria, gray matter depletion, decreased gamma oscillations, and a compensatory metabolic shift to lactate and lactylation. The aim of this narrative review is twofold: (1) to summarize what is known about premature cellular/neuronal senescence in schizophrenia or schizophrenia-like disorders, and (2) to discuss novel strategies for improving long-term outcomes in severe mental illness with natural senotherapeutics, membrane lipid replacement, mitochondrial transplantation, microbial phenazines, novel antioxidant phenothiazines, inhibitors of glycogen synthase kinase-3 beta, and aryl hydrocarbon receptor antagonists.

Associations of gut microbiota alterations with clinical, metabolic, and immune-inflammatory characteristics of chronic schizophrenia

The present study had the following aims: 1) to compare gut microbiota composition in patients with schizophrenia and controls and 2) to investigate the association of differentially abundant bacterial taxa with markers of inflammation, intestinal permeability, lipid metabolism, and glucose homeostasis as well as clinical manifestation. A total of 115 patients with schizophrenia during remission of positive and disorganization symptoms, and 119 controls were enrolled. Altogether, 32 peripheral blood markers were assessed. A higher abundance of Eisenbergiella, Family XIII AD3011 group, Eggerthella, Hungatella, Lactobacillus, Olsenella, Coprobacillus, Methanobrevibacter, Ligilactobacillus, Eubacterium fissicatena group, and Clostridium innocuum group in patients with schizophrenia was found. The abundance of Paraprevotella and Bacteroides was decreased in patients with schizophrenia. Differentially abundant genera were associated with altered levels of immune-inflammatory markers, zonulin, lipid profile components, and insulin resistance. Moreover, several correlations of differentially abundant genera with cognitive impairment, higher severity of negative symptoms, and worse social functioning were observed. The association of Methanobrevibacter abundance with the level of negative symptoms, cognition, and social functioning appeared to be mediated by the levels of interleukin-6 and RANTES. In turn, the association of Hungatella with the performance of attention was mediated by the levels of zonulin. The findings indicate that compositional alterations of gut microbiota observed in patients with schizophrenia correspond with clinical manifestation, intestinal permeability, subclinical inflammation, lipid profile alterations, and impaired glucose homeostasis. Subclinical inflammation and impaired gut permeability might mediate the association of gut microbiota alterations with psychopathological symptoms and cognitive impairment.

Lactobacillus plantarum 24-7 improves postoperative bloating and hard stools by modulating intestinal microbiota in patients with congenital heart disease: a randomized controlled trial

Gastrointestinal symptoms are a common postoperative complication in patients with congenital heart disease (CHD), affecting their postoperative recovery. Probiotic intervention may be a promising therapeutic approach to alleviate postoperative gastrointestinal symptoms. This study aimed to evaluate the potential of Lactobacillus plantarum 24-7 (L. plantarum 24-7) in mitigating postoperative gastrointestinal symptoms and promoting patient recovery. Adult CHD patients scheduled for surgical intervention were recruited. One hundred and twenty patients were randomized and received L. plantarum or placebo intervention twice daily for ten days. Gastrointestinal symptoms were assessed utilizing the Gastrointestinal Symptom Rating Scale (GSRS). Various postoperative variables were analyzed across both groups. Alterations in gut microbiota were evaluated through 16S rRNA sequencing. 112 patients completed the study, with 55 in the probiotic group and 57 in the placebo group. While the disparity in overall postoperative GSRS scores between the two groups did not reach statistical significance (P = 0.067), marked differences were observed in bloating (P = 0.004) and hard stool (P = 0.030) scores. Furthermore, individuals within the probiotic group exhibited lower postoperative neutrophil counts (P = 0.007) and concurrently higher lymphocyte counts (P = 0.001). Variations in the diversity and composition of postoperative gut microbiota were discerned between the probiotic and placebo groups. Remarkably, no probiotic-related adverse events were documented. Supplementation with L. plantarum was well-tolerated and demonstrated partial efficacy in ameliorating gastrointestinal symptoms in postoperative CHD patients. Modulating the gut microbiota may be a potential mechanism by which L. plantarum exerts clinical benefits.

Potential for New Therapeutic Approaches by Targeting Lactate and pH Mediated Epigenetic Dysregulation in Major Mental Diseases

Multiple lines of evidence have shown that lactate-mediated pH alterations in the brains of patients with neuropsychiatric diseases such as schizophrenia (SCZ), Alzheimer's disease (AD) and autism may be attributed to mitochondrial dysfunction and changes in energy metabolism. While neuronal activity is associated with reduction in brain pH, astrocytes are responsible for rebalancing the pH to maintain the equilibrium. As lactate level is the main determinant of brain pH, neuronal activities are impacted by pH changes due to the binding of protons (H+) to various types of proteins, altering their structure and function in the neuronal and non-neuronal cells of the brain. Lactate and pH could affect diverse types of epigenetic modifications, including histone lactylation, which is linked to histone acetylation and DNA methylation. In this review, we discuss the importance of pH homeostasis in normal brain function, the role of lactate as an essential epigenetic regulatory molecule and its contributions to brain pH abnormalities in neuropsychiatric diseases, and shed light on lactate-based and pH-modulating therapies in neuropsychiatric diseases by targeting epigenetic modifications. In conclusion, we attempt to highlight the potentials and challenges of translating lactate-pH-modulating therapies to clinics for the treatment of neuropsychiatric diseases.

Causal association between gut microbiota and fibromyalgia: a Mendelian randomization study

Background

Fibromyalgia (FM) is a syndrome characterized by chronic and widespread musculoskeletal pain. A number of studies have implied a potential association between gut microbiota and FM. However, the casual association between gut microbiota and FM remains unknown.

Method

Mendelian randomization (MR) study was conducted using the summary statistics of genetic variants from the genome-wide association study (GWAS). Inverse variance weighted (IVW), combined with MR-Egger and weighted median were used to investigate the causal association between 119 gut microbiota genera and FM. Sensitivity analyses were performed on the MR results, including heterogeneity test, leave-one-out test and pleiotropy test.

Results

A total of 1,295 single nucleotide polymorphism (SNPs) were selected as instrumental variables (IVs), with no significant heterogeneity and pleiotropy according to the sensitivity analyses. Five gut microbiota genera were found to have significant casual association with FM. Coprococcus2 (OR = 2.317, p-value = 0.005, 95% CI: 1.289-4.167), Eggerthella (OR = 1.897, p-value = 0.001, 95% CI: 1.313-2.741) and Lactobacillus (OR = 1.576, p-value =0.020, 95% CI: 1.073-2.315) can increase the risk of FM. FamillyXIIIUCG001 (OR = 0.528, p-value = 0.038, 95% CI: 0.289-0.964) and Olsenella (OR = 0.747, p-value = 0.050, 95% CI: 0.557-1.000) can decrease the risk of FM.

Conclusion

This MR study found that gut microbiota is casually associated with FM. New insights into the mechanisms of FM mediated by gut microbiota are provided.