New Evidence of Gut Microbiota Involvement in the Neuropathogenesis of Bipolar Depression by TRANK1 Modulation: Joint Clinical and Animal Data

Causal relationship between gut microbiota, lipids, and neuropsychiatric disorders: A Mendelian randomization mediation study

BACKGROUND

Numerous studies have shown an interconnection between the gut microbiota and the brain via the "gut-brain" axis. However, the causal relationships between gut microbiota, lipids, and neuropsychiatric disorders remain unclear. This study aimed to analyze potential associations among gut microbiota, lipids, and neuropsychiatric disorders-including AD, PD, ALS, MS, SCZ, MDD, and BD-using summary data from large-scale GWAS.

METHODS

Bidirectional Mendelian randomization (MR) with inverse variance weighting (IVW) was the primary method. Supplementary analyses included sensitivity analyses, Steiger tests, and Bayesian weighted MR (BWMR). Mediation analyses used two-step MR (TSMR) and multivariable MR (MVMR).

RESULTS

The analyses revealed 51 positive correlations (risk factors) (β > 0, P < 0.05) and 47 negative correlations (protective factors) (β < 0, P < 0.05) between gut microbiota and neuropsychiatric disorders. In addition, 35 positive correlations (β > 0, P < 0.05) and 22 negative correlations (β < 0, P < 0.05) between lipids and neuropsychiatric disorders were observed. Assessment of reverse causality with the seven neuropsychiatric disorders as exposures and the identified gut microbiota and lipids as outcomes revealed no evidence of reverse causality (P > 0.05). Mediation analysis indicated that the effect of the species Bacteroides plebeius on MDD is partially mediated through the regulation of phosphatidylcholine (16:0_20:4) levels (mediation proportion = 10.9 % [95 % CI = 0.0110-0.2073]).

CONCLUSION

This study provides evidence of a causal relationship between gut microbiota and neuropsychiatric disorders, suggesting lipids as mediators. These findings offer new insights into the mechanisms by which gut microbiota may influence neuropsychiatric disorders.

Changes in Type 1 Diabetes-Associated Gut Microbiota Aggravate Brain Ischemia Injury by Affecting Microglial Polarization Via the Butyrate-MyD88 Pathway in Mice

People with type 1 diabetes (T1D) have a significantly elevated risk of stroke, but the mechanism through which T1D worsens ischemic stroke remains unclear. This study was aimed at investigating the roles of T1D-associated changes in the gut microbiota in aggravating ischemic stroke and the underlying mechanism. Fecal 16SrRNA sequencing indicated that T1D mice and mice with transplantation of T1D mouse gut microbiota had lower relative abundance of butyric acid producers, f_Erysipelotrichaceae and g_Allobaculum, and lower content of butyric acid in feces. After middle cerebral artery occlusion (MCAO), these mice had poorer neurological outcomes and more severe inflammation, but higher expression of myeloid differentiation factor 88 (MyD88) in the ischemic penumbra; moreover, the microglia were inclined to polarize toward the pro-inflammatory type. Administration of butyrate to T1D mice in the drinking water alleviated the neurological damage after MCAO. Butyrate influenced the response and polarization of BV2 and decreased the production of inflammatory cytokines via MyD88 after oxygen-glucose deprivation/reoxygenation. Knocking down MyD88 in the brain alleviated neurological outcomes and decreased the concentrations of inflammatory cytokines in the brain after stroke in mice with transplantation of T1D mouse gut microbiota. Poor neurological outcomes and aggravated inflammatory responses of T1D mice after ischemic stroke may be partly due to differences in microglial polarization mediated by the gut microbiota-butyrate-MyD88 pathway. These findings provide new ideas and potential intervention targets for alleviating neurological damage after ischemic stroke in T1D.

Gut Microbiota and Mental Health: A Comprehensive Review of Gut-Brain Interactions in Mood Disorders

The human gut flora of trillions of bacteria is vital for general health and greatly influences digestion, immune system function, and brain development. Through neuronal, hormonal, and immunological channels, the gut-brain axis (GBA), a bidirectional communication network, links the gut microbiota to the central nervous system (CNS). This relationship has been linked to affective diseases, including depression and anxiety, as well as mental health issues. This review explores the intricate relationship between gut bacteria and mood disorders, focusing on how gut microbiota-host interactions, immune system modulation, and neurotransmitter control support mental health. The function of important microbial metabolites, including short-chain fatty acids (SCFAs), in preserving blood-brain barrier integrity and modulating neuroinflammation is covered in this review. It also examines the bidirectional impact between gut health and mental health, including how dysbiosis could aggravate mood disorders and how depressed states might change the composition of gut bacteria. Furthermore, we discuss how psychotropic drugs affect gut flora and consider other elements such as nutrition and lifestyle that affect gut microbiome composition. Potential paths for treating mood disorders through gut microbiota modification are presented as emerging treatment techniques, including probiotics, nutritional therapies, and precision medicine. The development of new therapeutic approaches for mood disorders depends on the awareness of the GBA. Gut bacteria significantly affect mental health through immune modulation, neurotransmitter generation, and other intricate processes. Future studies should concentrate on large, varied populations to better understand these interactions and to create customized treatments that combine gut microbiota modulation with conventional mental health therapies.

Effects of low-dose aspirin in bipolar disorder: study protocol for a randomised controlled trial (the A-Bipolar RCT)

INTRODUCTION

Accumulating data support the association between increased inflammation and bipolar disorder (BD), and preliminary data suggest that augmentation with low-dose aspirin (LDA) may protect against the onset and deterioration of BD via anti-inflammatory pathways. The A-bipolar randomised controlled trial (RCT) aims to investigate whether adding LDA to standard treatment improves day-to-day mood instability (MI) in BD.

METHODS AND ANALYSIS

A two-arm, triple-blind, parallel-group, superiority RCT including 250 patients with newly diagnosed BD treated at the Copenhagen Affective Disorder Clinic, Denmark. Participants are randomised 1:1 to either 150 mg of acetylsalicylic acid daily (LDA) or a placebo for six months in addition to their regular treatment. Mood instability, calculated from daily smartphone-based mood evaluations, is the primary outcome measure due to its internal validity as a real-life measure for patients and external validity as it reflects patients' illness severity and functioning. Analyses will be conducted as intention-to-treat analyses using a linear mixed model including time (categorical) and the time-treatment interaction as fixed effects and with an unstructured covariance pattern to account for repeated measurements on each study participant. The trial is Good Clinical Practice monitored.

ETHICS AND DISSEMINATION

The Danish Research Ethics Committee (H-21014515) and the data agency, Capital Region of Copenhagen (P-2021-576) approved the trial. Results will be published in peer-reviewed journals.

TRIAL REGISTRATION NUMBER

NCT05035316.

Gain of bipolar disorder-related lncRNA AP1AR-DT in mice induces depressive and anxiety-like behaviors by reducing Negr1-mediated excitatory synaptic transmission

BACKGROUND

Bipolar disorder is a complex polygenic disorder that is characterized by recurrent episodes of depression and mania, the heterogeneity of which is likely complicated by epigenetic modifications that remain to be elucidated.

METHODS

We performed transcriptomic analysis of peripheral blood RNA from monozygotic (MZ) twins discordant for bipolar disorder to identify disease-associated differentially expressed long noncoding RNAs (DE-lncRNAs), which were further validated in the PsychENCODE brain RNA-seq dataset. We then performed behavioral tests, electrophysiological assays, chromatin immunoprecipitation, and PCR to investigate the function of DE-lncRNAs in the mouse and cell models. Statistical analyses were performed using GraphPad Prism 9.0 or SPSS.

RESULTS

We identified a bipolar disorder-associated upregulated long non-coding RNA (lncRNA), AP1AR-DT. We observed that overexpression of AP1AR-DT in the mouse medial prefrontal cortex (mPFC) resulted in a reduction of both the total spine density and the spontaneous excitatory postsynaptic current (sEPSC) frequency of mPFC neurons as well as depressive and anxiety-like behaviors. A combination of the results of brain transcriptome analysis of AP1AR-DT overexpressing mice brains with the known genes associated with bipolar disorder revealed that NEGR1, which encodes neuronal growth regulator 1, is one of the AP1AR-DT targets and is reduced in vivo upon gain of AP1AR-DT in mice. We further demonstrated that overexpression of recombinant Negr1 in the mPFC neurons of AP1AR-DTOE mice ameliorates depressive and anxiety-like behaviors and normalizes the reduced excitatory synaptic transmission induced by the gain of AP1AR-DT. We finally identified that AP1AR-DT reduces NEGR1 expression by competing for the transcriptional activator NRF1 in the overlapping binding site of the NEGR1 promoter region.

CONCLUSIONS

The epigenetic and pathophysiological mechanism linking AP1AR-DT to the modulation of depressive and anxiety-like behaviors and excitatory synaptic function provides etiological implications for bipolar disorder.

Chinese Materia Medica in Treating Depression: The Role of Intestinal Microenvironment

Depression is a highly heterogeneous mental illness. Drug treatment is currently the main therapeutic strategy used in the clinic, but its efficacy is limited by the modulation of a single target, slow onset, and side effects. The gut-brain axis is of increasing interest because intestinal microenvironment disorders increase susceptibility to depression. In turn, depression affects intestinal microenvironment homeostasis by altering intestinal tissue structure, flora abundance and metabolism, hormone secretion, neurotransmitter transmission, and immune balance. Depression falls into the category of "stagnation syndrome" according to Traditional Chinese Medicine (TCM), which further specifies that "the heart governs the spirit and is exterior-interior with the small intestine". However, the exact mechanisms of the means by which the disordered intestinal microenvironment affects depression are still unclear. Here, we present an overview of how the Chinese materia medica (CMM) protects against depression by repairing intestinal microenvironment homeostasis. We review the past five years of research progress in classical antidepressant TCM formulae and single CMMs on regulating the intestinal microenvironment for the treatment of depression. We then analyze and clarify the multitarget functions of CMM in repairing intestinal homeostasis and aim to provide a new theoretical basis for CMM clinical application in the treatment of depression.

Epigenetic Aberrations in Major Psychiatric Diseases Related to Diet and Gut Microbiome Alterations

Nutrition and metabolism modify epigenetic signatures like histone acetylation and DNA methylation. Histone acetylation and DNA methylation in the central nervous system (CNS) can be altered by bioactive nutrients and gut microbiome via the gut-brain axis, which in turn modulate neuronal activity and behavior. Notably, the gut microbiome, with more than 1000 bacterial species, collectively contains almost three million functional genes whose products interact with millions of human epigenetic marks and 30,000 genes in a dynamic manner. However, genetic makeup shapes gut microbiome composition, food/nutrient metabolism, and epigenetic landscape, as well. Here, we first discuss the effect of changes in the microbial structure and composition in shaping specific epigenetic alterations in the brain and their role in the onset and progression of major mental disorders. Afterward, potential interactions among maternal diet/environmental factors, nutrition, and gastrointestinal microbiome, and their roles in accelerating or delaying the onset of severe mental illnesses via epigenetic changes will be discussed. We also provide an overview of the association between the gut microbiome, oxidative stress, and inflammation through epigenetic mechanisms. Finally, we present some underlying mechanisms involved in mediating the influence of the gut microbiome and probiotics on mental health via epigenetic modifications.

Therapeutic Prospect of New Probiotics in Neurodegenerative Diseases

Increasing clinical and preclinical evidence implicates gut microbiome (GM) dysbiosis as a key susceptibility factor for neurodegenerative disorders, including Alzheimer's disease (AD) and Parkinson's disease (PD). In recent years, neurodegenerative diseases have been viewed as being driven not solely by defects in the brain, and the role of GM in modulating central nervous system function via the gut-brain axis has attracted considerable interest. Encouraged by current GM research, the development of new probiotics may lead to tangible impacts on the treatment of neurodegenerative disorders. This review summarizes current understandings of GM composition and characteristics associated with neurodegenerative diseases and research demonstrations of key molecules from the GM that affect neurodegeneration. Furthermore, applications of new probiotics, such as Clostridium butyricum, Akkermansia muciniphila, Faecalibacterium prausnitzii, and Bacteroides fragilis, for the remediation of neurodegenerative diseases are discussed.

Gut microbiota decreased inflammation induced by chronic unpredictable mild stress through affecting NLRP3 inflammasome

Dysbiosis of the gut microbiota is associated with the development of depression, but the underlying mechanism remains unclear. The aim of this study was to determine the relationship between microbiota and NLRP3 inflammasome induced by chronic unpredictable mild stress (CUMS). Fecal transplantation (FMT) experiment was conducted to elucidate the potential mechanism. Levels of NLRP3 inflammasome, microbiota, inflammatory factors and tight junction proteins were measured. CUMS stimulation significantly increased the levels of NLRP3, Caspase-1 and ASC in brain and colon(p<0.05), decreased the levels of tight junction proteins Occludin and ZO-1 (p<0.05). Interestingly, increased NLRP3 inflammasome and inflammatory cytokines and decreased tight junction proteins were found in antibiotic-treated (Abx) rats received CUMS rat fecal microbiota transplantation. Furthermore, fecal microbiota transplantation altered the microbiota in Abx rats, which partially overlapped with that of the donor rats. Importantly, probiotic administration amended the alteration of microbiota induced by CUMS treatment, then reduced the levels of NLRP3 inflammasome and inflammatory factors. In conclusion, these findings suggested that depression-like behaviors induced by CUMS stimulation were related to altered gut microbiota, broke the intestinal barrier, promoted the expression of NLRP3 inflammasome and elevated inflammation. Therefore, improving the composition of microbiota via probiotic can attenuate inflammation by amending the microbiota and suppressing the activation of NLRP3 inflammasome, which is considered as a novel therapeutic strategy for depression.

The Brain-Gut-Microbiota Interplay in Depression: a key to design innovative therapeutic approaches

Depression is the most prevalent mental disorder in the world associated with huge socio-economic consequences. While depressive-related symptoms are well known, the molecular mechanisms underlying disease pathophysiology and progression remain largely unknown. The gut microbiota (GM) is emerging as a key regulator of the central nervous system homeostasis by exerting fundamental immune and metabolic functions. In turn, the brain influences the intestinal microbial composition through neuroendocrine signals, within the so-called gut microbiota-brain axis. The balance of this bidirectional crosstalk is important to ensure neurogenesis, preserve the integrity of the blood-brain barrier and avoid neuroinflammation. Conversely, dysbiosis and gut permeability negatively affect brain development, behavior, and cognition. Furthermore, although not fully defined yet, changes in the GM composition in depressed patients are reported to influence the pharmacokinetics of common antidepressants by affecting their absorption, metabolism, and activity. Similarly, neuropsychiatric drugs may shape in turn the GM with an impact on the efficacy and toxicity of the pharmacological intervention itself. Consequently, strategies aimed at re-establishing the correct homeostatic gut balance (i.e., prebiotics, probiotics, fecal microbiota transplantation, and dietary interventions) represent an innovative approach to improve the pharmacotherapy of depression. Among these, probiotics and the Mediterranean diet, alone or in combination with the standard of care, hold promise for clinical application. Therefore, the disclosure of the intricate network between GM and depression will give precious insights for innovative diagnostic and therapeutic approaches towards depression, with profound implications for drug development and clinical practice.

Is fecal microbiota transplantation a useful therapeutic intervention for psychiatric disorders? A narrative review of clinical and preclinical evidence

The therapeutic management of psychiatric disorders is currently confronted with a critical need to find new therapeutic interventions due to the high rates of non-responsivity or low responsivity in the key pathologies, e.g. schizophrenia spectrum disorders, alcohol use disorders, or major depressive disorder. The modulation of intestinal microbiota has been explored in various organic and psychiatric dysfunctions, with different degrees of success. However, this type of intervention may represent a helpful add-on at a conceptual level since it does not associate negative pharmacokinetics interactions, significant adverse events, or risk for non-adherence in the long term. Oral administration of pre-, pro-, or synbiotics, and especially the treatment with fecal microbiota transplantation (FMT), are methods still in their early research phase for patients with psychiatric disorders, therefore an exploration of data regarding the potential benefits and adverse events of FMT was considered necessary. In order to accomplish this purpose, the available results of research dedicated to each category of psychiatric disorders, starting with depressive and anxiety disorders, continuing with schizophrenia, substance use disorders, and finishing with disorders diagnosed during childhood, were presented in this paper. Seven clinical trials, 16 preclinical studies, three meta-analyses/systematic reviews, and six case reports, all of these representing ten distinct categories of psychiatric disorders or manifestations, have been reviewed. Mood disorders, anxiety disorders, and alcohol dependence have been the most extensively investigated clinical entities from the FMT efficacy and tolerability perspective, and reviewed data are generally promising. Based on the current status of research, FMT may be considered a helpful intervention in specific psychiatric pathologies. Still, this review showed that most of the information is derived from entirely preclinical studies. Therefore, clinical trials with sound methodology and more participants are needed to clarify FMT's benefits and risks in psychiatric disorders.

Gut Microbial Dysbiosis and Cognitive Impairment in Bipolar Disorder: Current Evidence

Recent studies have reported that the gut microbiota influences mood and cognitive function through the gut-brain axis, which is involved in the pathophysiology of neurocognitive and mental disorders, including Parkinson’s disease, Alzheimer’s disease, and schizophrenia. These disorders have similar pathophysiology to that of cognitive dysfunction in bipolar disorder (BD), including neuroinflammation and dysregulation of various neurotransmitters (i.e., serotonin and dopamine). There is also emerging evidence of alterations in the gut microbial composition of patients with BD, suggesting that gut microbial dysbiosis contributes to disease progression and cognitive impairment in BD. Therefore, microbiota-centered treatment might be an effective adjuvant therapy for BD-related cognitive impairment. Given that studies focusing on connections between the gut microbiota and BD-related cognitive impairment are lagging behind those on other neurocognitive disorders, this review sought to explore the potential mechanisms of how gut microbial dysbiosis affects cognitive function in BD and identify potential microbiota-centered treatment.

Gut Microbiota Research in Bipolar Disorder and Possible Implications for Precision Psychiatry: A Systematic Review

Bipolar disorder (BD) is a highly disabling condition with a chronic and relapsing nature. Despite the substantial socioeconomic burden associated with BD, there are still significant research gaps in risk stratification, diagnostic accuracy, and treatment selection, all key components of precision psychiatry. One possible strategy to increase the validity of precision psychiatry approaches in BD is to increase our knowledge of disorder-associated gut microbiota perturbations. To this end, we systematically reviewed the evidence on gut microbiota alterations in relation to precision psychiatry approaches on BD. We performed a systematic review on PubMed/MEDLINE and Web of Science to identify original articles investigating the possible clinical applications of microbiota analyses for pragmatic precision psychiatry in BD. A pearl growing strategy was employed to enlarge the scope of this review. The primary search strategy yielded one paper and an additional one was identified through reference tracking. The included studies were observational, with one study of good quality. The identified results justify the efforts devolved in this area of research and underscore the need to expand these investigations through additional larger and properly designed studies.