Microbiome and immuno-metabolic dysregulation in patients with major depressive disorder with atypical clinical presentation

The microbiome's influence on obesity: mechanisms and therapeutic potential

In 2023, the World Obesity Atlas Federation concluded that more than 50% of the world's population would be overweight or obese within the next 12 years. At the heart of this epidemic lies the gut microbiota, a complex ecosystem that profoundly influences obesity-related metabolic health. Its multifaced role encompasses energy harvesting, inflammation, satiety signaling, gut barrier function, gut-brain communication, and adipose tissue homeostasis. Recognizing the complexities of the cross-talk between host physiology and gut microbiota is crucial for developing cutting-edge, microbiome-targeted therapies to address the global obesity crisis and its alarming health and economic repercussions. This narrative review analyzed the current state of knowledge, illuminating emerging research areas and their implications for leveraging gut microbial manipulations as therapeutic strategies to prevent and treat obesity and related disorders in humans. By elucidating the complex relationship between gut microflora and obesity, we aim to contribute to the growing body of knowledge underpinning this critical field, potentially paving the way for novel interventions to combat the worldwide obesity epidemic.

[The gastrointestinal microbiome - vision and mission]

The gastrointestinal microbiome influences physiological functions and is altered in a variety of diseases. The causality of "dysbiosis" in the pathogenesis is not always proven; association studies are often involved. Patients with IBD, bacteria, fungi, bacteriophages, and archaea show disease-typical patterns associated with metabolome disturbances. Fecal microbiome transfer (FMT) for treating various diseases is the subject of numerous clinical studies. Currently, recurrent Clostridioides difficile infection (rCDI) is the only confirmed indication recommended in medical guidelines. In Germany, the FMT is subject to the Medicines Act and may only be carried out as part of individual healing attempts or clinical studies. For patient safety, repeated donor screening, ideally with the construction of a chair bench, is necessary. This significantly limits the nationwide availability of the FMT in Germany. Microbiota-based therapeutics prepared from the stool of tested donors have recently been approved by the US Food and Drug Administration (FDA) for the prevention of rCDI. More microbiome-based medicines can be expected in the future.

Immuno-metabolic depression: from concept to implementation

Major depressive disorder is a common, disabling mental disorder characterized by extensive etiological and phenotypic heterogeneity. This heterogeneity makes treatment approaches imprecise and often ineffective. Insight into the underlying biological mechanisms underpinning depression and its subtypes may enable more personalized treatments. In this review, we provide an overview of immuno-metabolic depression and illustrate that significant immuno-metabolic dysregulations are present in about 20-30% of people with depression. Such immuno-metabolic depression is characterized by the clustering of 1) atypical, energy-related depressive symptoms such as hypersomnia, fatigue, hyperphagia, and possibly anhedonia, 2) systemic low-grade inflammation with elevated levels of e.g., C-reactive protein, cytokines and glycoprotein acetyls, and 3) metabolic abnormalities involving e.g., obesity, dyslipidaemia, insulin and leptin resistance. Persons with immuno-metabolic depression are at a higher risk for cardiometabolic diseases and seem to respond less well to standard antidepressant treatment. Interventions targeting inflammation, metabolism or lifestyle may be more effective treatment options for individuals with immuno-metabolic depression, in line with principles of precision psychiatry.

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.

SorCS2 is involved in promoting periodontitis-induced depression-like behaviour in mice

BACKGROUND

Emerging evidence supports the association between periodontitis and depression, although the mechanisms are unclear. This study investigated the role of SorCS2 in the pathogenesis of periodontitis-induced depression.

MATERIALS AND METHODS

An experimental periodontitis model was established using SorCS2 knockout mice and their wild-type littermates, and depression-like behaviour was evaluated. The expression of proBDNF signalling, neuronal activity, and glutamate-associated signalling pathways were further measured by western blotting and immunofluorescence. In addition, neuroinflammatory status, astrocytic and microglial markers, and the expression of corticosterone-related factors were measured by immunofluorescence, western blotting, and enzyme-linked immunosorbent assays.

RESULTS

SorCS2 deficiency alleviated periodontitis-induced depression-like behaviour in mice. Further results suggested that SorCS2 deficiency downregulated the expression of pro-BDNF and glutamate signalling and restored neuronal activities in mice with periodontitis. Neuroinflammation in the mouse hippocampus was triggered by experimental periodontitis but was not affected by SorCS2 deficiency. The levels of corticosterone and the expression of glucocorticoid receptors were also not altered.

CONCLUSION

Our study, for the first time, reveals the critical role of SorCS2 in the pathogenesis of periodontitis-induced depression. The underlying mechanism involves proBDNF and glutamate signalling in the hippocampus, providing a novel therapeutic target for periodontitis-associated depression.

Sex differences in the inflammation-depression link: A systematic review and meta-analysis

Major Depressive Disorder (MDD) is a heterogeneous disorder that affects twice as many women than men. Precluding advances in more tailored and efficacious treatments for depression is the lack of reliable biomarkers. While depression is linked to elevations in inflammatory immune system functioning, this relationship is not evident among all individuals with depression and may vary based on symptom subtypes and/or sex. This systematic review and meta-analysis examined whether inflammatory immune peripheral markers of depression are sex-specific. PRISMA guidelines were followed for the systematic review, and a comprehensive search strategy that identified studies from PubMed and PsycInfo was applied. Studies were included if they reported C-reactive protein (CRP), interleukin (IL)-6, tumor necrosis factor (TNF)-α and/or IL-1β for males and/or females among depressed and healthy adults. We identified 23 studies that satisfied these inclusion criteria. Random-effects meta-analysis models were fit, and measures of association were summarized between levels of circulating markers of inflammation in depressed and healthy males and females. Sex-based analyses revealed elevated levels of CRP among females with depression (Cohen's d = 0.19) relative to their healthy counterparts (p = 0.02), an effect not apparent among males (Cohen's d = -0.01). Similarly, levels of IL-6 were increased among females with depression compared to healthy controls (Cohen's d = 0.51; p = 0.04), but once again this was not found among males (Cohen's d = 0.16). While TNF-α levels were elevated among individuals with depression compared to controls (p = 0.01), no statistically significant sex differences were found. The meta-analysis for IL-1β resulted in only three articles, and thus, results are presented in the supplemental section. This meta-analysis advances our understanding of the unique involvement of inflammatory biomarkers in depression among men and women, which may help inform more tailored sex-specific treatment approaches in the future.

Gut microbiome, and immune cells mediated effect on depression: A two-step, two-sample Mendelian randomization analysis

BACKGROUND

The gut microbiota (GM) plays an important role in the development of immune-related diseases, and the immune response is one of the pathomechanisms of depression (Dep); whether the effect of GM on Dep is mediated by immune cells (ImC) is unclear.

OBJECTIVE

ImC may mediate the effect of GM on Dep. Our aim is to identify and quantify the role of immune characteristics as potential mediators.

METHODS

Pooled statistics for GM (n = 7738) and ImC (n = 3757) were obtained from publicly available genome-wide association studies (GWAS), and for Dep (n = 47,696) from the Finnish database R10. We used a mediated Mendelian randomization (MR) study to investigate the causal relationship between GM and Dep and the mediating role of ImC between GM and Dep associations.

RESULTS

The results showed that the genetically predicted GM was significantly correlated with both ImC as well as Dep. MR analysis identified five microbiomes that had significant causal effects on Dep (Methionine biosynthesis III, PWY-6737-Starch degradation V, Parasutterella excrementihominis, Parasutterella, and Lysine biosynthesis I). In addition, five of the 26 ImC trait significantly associated with GM were most closely associated with Dep (T cell %lymphocyte、CD28-CD127-CD25++CD8br AC、CD28-CD8br AC、CD27 receptor on peripheral blood plasma cells (CD27 on PB/PC) and CD11b receptor on mononuclear myeloid-derived suppressor cells (CD11b on Mo MDSC)). This mediated MR illustrates the causal role of methionine biosynthesis III on Dep (IVW: OR = 1.08, 95%CI [1.04,1.14], P = 0.001). And there was no strong evidence for a causal effect of depression on methionine biosynthesis III. In the B cell group, the proportion of CD27 on PB/PC mediated was 7.88 %(95%CI [-0.04,0.03]) of the total effect. This study further suggests that Dep patients should actively seek immunologic intervention therapy.

CONCLUSION

This MR study found that GM may play a causal role in Dep by mediating ImC. Our findings will help to understand the pathogenic mechanism of GM in Dep and the risk of immune mediation.

Gender-affirming hormonal therapy induces a gender-concordant fecal metagenome transition in transgender individuals

BACKGROUND

Limited data exists regarding gender-specific microbial alterations during gender-affirming hormonal therapy (GAHT) in transgender individuals. This study aimed to investigate the nuanced impact of sex steroids on gut microbiota taxonomy and function, addressing this gap. We prospectively analyzed gut metagenome changes associated with 12 weeks of GAHT in trans women and trans men, examining both taxonomic and functional shifts.

METHODS

Thirty-six transgender individuals (17 trans women, 19 trans men) provided pre- and post-GAHT stool samples. Shotgun metagenomic sequencing was used to assess the changes in gut microbiota structure and potential function following GAHT.

RESULTS

While alpha and beta diversity remained unchanged during transition, specific species, including Parabacteroides goldsteinii and Escherichia coli, exhibited significant abundance shifts aligned with affirmed gender. Overall functional metagenome analysis showed a statistically significant effect of gender and transition (R2 = 4.1%, P = 0.0115), emphasizing transitions aligned with affirmed gender, particularly in fatty acid-related metabolism.

CONCLUSIONS

This study provides compelling evidence of distinct taxonomic and functional profiles in the gut microbiota between trans men and women. GAHT induces androgenization in trans men and feminization in trans women, potentially impacting physiological and health-related outcomes.

TRIAL REGISTRATION

Clinicaltrials.gov NCT02185274.

Relationship between human oral microbiome dysbiosis and neuropsychiatric diseases: An updated overview

The role of the gut-brain axis in mental health disorders has been extensively studied. As the oral cavity is the starting point of the digestive tract, the role that the oral microbiota plays in mental health disorders has gained recent attention. Oral microbiota can enter the bloodstream and trigger inflammatory responses or translocate to the brain through the trigeminal nerve or olfactory system. Hence, the concept of the oral microbiota-brain axis has emerged. Several hypotheses have been suggested that the oral microbiota can enter the gastrointestinal tract and affect the gut-brain axis; however, literature describing oral-brain communication remains limited. This review summarizes the characteristics of oral microbiota and its mechanisms associated with mental health disorders. Through a comprehensive examination of the relationship between oral microbiota and various neuropsychiatric diseases, such as anxiety, depression, schizophrenia, autism spectrum disorder, epilepsy, Parkinson's disease, and dementia, this review seeks to identify promising avenues of future research.

A metabolomics perspective on the effect of environmental micro and nanoplastics on living organisms: A review

The increasing trend regarding the use of plastics has arisen an exponential concern on the fate of their derived products to the environment. Among these derivatives, microplastics and nanoplastics (MNPs) have been featured for their associated environmental impact due to their low molecular size and high surface area, which has prompted their ubiquitous transference among all environmental interfaces. Due to the heterogenous chemical composition of MNPs, the study of these particles has focused a high number of studies, as a result of the myriad of associated physicochemical properties that contribute to the co-transference of a wide range of contaminants, thus becoming a major challenge for the scientific community. In this sense, both primary and secondary MNPs are well-known to be adscribed to industrial and urbanized areas, from which they are massively released to the environment through a multiscale level, involving the atmosphere, hydrosphere, and lithosphere. Consequently, much research has been conducted on the understanding of the interconnection between those interfaces, that motivate the spread of these contaminants to biological systems, being mostly represented by the biosphere, especially phytosphere and, finally, the anthroposphere. These findings have highlighted the potential hazardous risk for human health through different mechanisms from the environment, requiring a much deeper approach to define the real risk of MNPs exposure. As a result, there is a gap of knowledge regarding the environmental impact of MNPs from a high-throughput perspective. In this review, a metabolomics-based overview on the impact of MNPs to all environmental interfaces was proposed, considering this technology a highly valuable tool to decipher the real impact of MNPs on biological systems, thus opening a novel perspective on the study of these contaminants.

Depressive symptoms and all-cause mortality among middle-aged and older people in China and associations with chronic diseases

Introduction

It remains unclear whether depressive symptoms are associated with increased all-cause mortality and to what extent depressive symptoms are associated with chronic disease and all-cause mortality. The study aims to explore the relationship between depressive symptoms and all-cause mortality, and how depressive symptoms may, in turn, affect all-cause mortality among Chinese middle-aged and older people through chronic diseases.

Methods

Data were collected from the China Health and Retirement Longitudinal Study (CHARLS). This cohort study involved 13,855 individuals from Wave 1 (2011) to Wave 6 (2020) of the CHARLS, which is a nationally representative survey that collects information from Chinese residents ages 45 and older to explore intrinsic mechanisms between depressive symptoms and all-cause mortality. The Center for Epidemiological Studies Depression Scale (CES-D-10) was validated through the CHARLS. Covariates included socioeconomic variables, living habits, and self-reported history of chronic diseases. Kaplan-Meier curves depicted mortality rates by depressive symptom levels, with Cox proportional hazards regression models estimating the hazard ratios (HRs) of all-cause mortality.

Results

Out of the total 13,855 participants included, the median (Q1, Q3) age was 58.00 (51.00, 63.00) years. Adjusted for all covariates, middle-aged and older adults with depressive symptoms had a higher all-cause mortality rate (HR = 1.20 [95% CI, 1.09-1.33]). An increased rate was observed for 55-64 years old (HR = 1.23 [95% CI, 1.03-1.47]) and more than 65 years old (HR = 1.32 [95% CI, 1.18-1.49]), agricultural Hukou (HR = 1.44, [95% CI, 1.30-1.59]), and nonagricultural workload (HR = 1.81 [95% CI, 1.61-2.03]). Depressive symptoms increased the risks of all-cause mortality among patients with hypertension (HR = 1.19 [95% CI, 1.00-1.40]), diabetes (HR = 1.41[95% CI, 1.02-1.95]), and arthritis (HR = 1.29 [95% CI, 1.09-1.51]).

Conclusion

Depressive symptoms raise all-cause mortality risk, particularly in those aged 55 and above, rural household registration (agricultural Hukou), nonagricultural workers, and middle-aged and older people with hypertension, diabetes, and arthritis. Our findings through the longitudinal data collected in this study offer valuable insights for interventions targeting depression, such as early detection, integrated chronic disease care management, and healthy lifestyles; and community support for depressive symptoms may help to reduce mortality in middle-aged and older people.

Gut microbiome in atypical depression

BACKGROUND

Recent studies showed that immunometabolic dysregulation is related to unipolar major depressive disorder (MDD) and that it more consistently maps to MDD patients endorsing an atypical symptom profile, characterized by energy-related symptoms including increased appetite, weight gain, and hypersomnia. Despite the documented influence of the microbiome on immune regulation and energy homeostasis, studies have not yet investigated microbiome differences among clinical groups in individuals with MDD.

METHODS

Fifteen MDD patients with atypical features according to the Diagnostic and Statistical Manual of Mental Disorders (DSM-5)-5, forty-four MDD patients not fulfilling the DSM-5 criteria for the atypical subtype, and nineteen healthy controls were included in the study. Participants completed detailed clinical assessment and stool samples were collected. Samples were sequenced for the prokaryotic 16S rRNA gene, in the V3-V4 variable regions. Only samples with no antibiotic exposure in the previous 12 months and a minimum of >2000 quality-filtered reads were included in the analyses.

RESULTS

There were no statistically significant differences in alpha- and beta-diversity between the MDD groups and healthy controls. However, within the atypical MDD group, there was an increase in the Verrucomicrobiota phylum, with Akkermansia as the predominant bacterial genus.

LIMITATIONS

Cross-sectional data, modest sample size, and significantly increased body mass index in the atypical MDD group.

CONCLUSIONS

There were no overall differences among the investigated groups. However, differences were found at several taxonomic levels. Studies in larger longitudinal samples with relevant confounders are needed to advance the understanding of the microbial influences on the clinical heterogeneity of depression.

Impact of Toxoplasma gondii and Human Microbiome on Suicidal Behavior: A Systematic Review

BACKGROUND

Suicide remains a persistent global health challenge, resisting widespread prevention efforts. According to previous findings, toxoplasmosis is particularly associated with altered decision making, which could lead to risk-taking behavior, thereby increasing the likelihood for suicidal behavior (SB). In addition, discussion about the role of microbiome in psychiatric disorders has emerged lately, which also makes it relevant to investigate its role in the context of SB. Therefore, two systematic reviews are integrated in this paper, and the existing knowledge is comprehensively summarized regarding the association between microbial pathogens and SB.

METHODS

We conducted a systematic search with keywords including SB and Toxoplasma gondii (Suicid* AND Toxoplasm*) and microbiome (Suicid* AND Microbiome AND Microbiota) throughout PubMed and Scopus to retrieve related studies up to 9 November 2023, identifying 24 eligible records. The subjects of the included studies had to have fulfilled the criteria of an SB disorder as defined by DSM-5, and death cases needed to have been defined as suicide.

RESULTS

Most studies reported significant association between toxoplasmosis and SB, suggesting a higher likelihood of SB in the infected population. Regarding the microbiome, only very few studies investigated an association between SB and alterations in the microbiome. Based on six included studies, there were some indications of a link between changes in the microbiome and SB.

CONCLUSION

The cognitive aspects of decision making in T. gondii-infected individuals with SB should be further investigated to unravel the underlying mechanisms. Further sufficiently powered studies are needed to establish a link between SB and alterations in the microbiome.

[Online phenotypes of depression symptoms are associated with polygenic risk scores of somatic diseases in a population-based cohort]

OBJECTIVE

To test an associations of online phenotypes of depressive symptoms with polygenic risk scores (PRS) for selected somatic diseases in a population-based cohort.

MATERIAL AND METHODS

Participants in a Russian population-based cohort (n=4520) underwent online phenotyping based on the originally developed questionnaire using DSM-5 criteria (DSM phenotypes) and the Hospital Anxiety and Depression Scale (HADS) questionnaire (HADS phenotypes). After DNA genotyping with microarrays, PRS were calculated using summary statistics from large-scale GWASs (mostly from UK Biobank) for irritable bowel syndrome (IBS), coronary heart disease (narrow and broad phenotypes) (CHD), ischemic stroke (IS),diabetes mellitus type 2 (DT2) and migraine (MG). Then we assessed associations of PRS for somatic diseases with online phenotypes of depressive symptoms in a population-based cohort.

RESULTS

Highly specific associations of PRS for somatic diseases with online phenotypes of depressive symptoms in a population cohort were identified: positive associations of PRS IBS with «DSM depression» (p=0.0035) and PRS CHD (narrow phenotype) with «DSM bipolar disorder» (p=0.0207), as well as a negative association of PRS IS with the symptomatic DSM phenotype «Hyperphagia» (p=0.0262). All the HADS phenotypes (clinical depression, subclinical depression, and HADS-D total score) showed a positive association with PRS for IBS and DT2, and at the same time were negatively associated with PRS IS. The DSM phenotype «Hypersomnia and hyperphagia» was positively associated with PRS for DT2 and IS, and negatively associated with PRS CHD (narrow phenotype). The DSM phenotypes «Subclinical Depression», «Hypersomnia», and «Anhedonia» showed exclusively negative associations with PRSs for DT2, IS, and IBS. Three maximum informative PRS by explained variance (PRS.R2) were found for the single DSM phenotype «Hypersomnia and hyperphagia»: PRS for IS and DT2 are positively associated and increase the risk of this phenotype, and PRS CHD (narrow phenotype) has a negative association and reduces the risk of this phenotype.

CONCLUSION

Our study confirmed the presence of possible genetic comorbidity of depression and chronic somatic diseases and showed different effectiveness of online phenotyping of depressive symptoms as markers of genetic risk of somatic diseases in the population cohort. Further research is needed to construct various versions of online phenotyping test systems for population-based screening of cohorts at high genetic risk for genetically comorbid diseases.