Gut microbiota and major depressive disorder: A bidirectional Mendelian randomization

Causal effects between gut microbiota and endometriosis: a two-sample Mendelian randomisation study

BACKGROUND

Previous observational evidence has indicated the potential involvement of the gut microbiota (GM) in the development of endometriosis. However, the causal relationship of the association remains to be investigated.

METHOD

Genome-wide association study (GWAS) data of GM was obtained from the MiBioGen consortium, and GWAS for endometriosis data was from the FinnGen consortium. Initially, a two-sample Mendelian randomisation (MR) analysis was performed to identify specific bacteria associated with endometriosis. Inverse variance-weighted (IVW) was used as the main MR analysis to infer causal relationships. The other four popular MR methods including MR-Egger regression, weighted mode, weighted median, and simple mode were used for secondary confirmation. Subsequently, these selected bacteria were employed as exposure to investigate their causal effects on six sub-types of endometriosis. Furthermore, reverse MR analysis was implemented to evaluate the reverse causal effects. Cochran's Q statistics was used to test the heterogeneity of instrumental variables (IVs); MR-Egger regression was used to test horizontal pleiotropy; MR-PRESSO and leave-one-out sensitivity analysis were applied to find significant outliers.

RESULT

A total of 1131 single nucleotide polymorphisms (SNPs) were collected as IVs for 196 GM taxa with endometriosis as the outcome. We identified 12 causal relationships between endometriosis and GM taxa including 1 phylum, 3 families, 2 orders, and 6 genera (Rikenellaceae RC9 gut group, Eubacterium ruminantium group, Faecalibacterium, Peptococcus, Clostridium sensu stricto 1, and Ruminococcaceae UCG005). Utilizing the Bonferroni method, we identified phylum Cyanobacteria as the strongest associated GM taxa. Subsequently, 6 significant causal effects were uncovered between the 12 selected specific GM and 6 sub-types of endometriosis. Meanwhile, no reverse causal relationship was found. Further, no horizontal pleiotropy and no significant outliers were detected in the sensitive analysis.

CONCLUSIONS

This MR analysis revealed significant causal effects between GM and endometriosis and phylum Cyanobacteria had the strongest association.

Balancing the mind: Toward a complete picture of the interplay between gut microbiota, inflammation and major depressive disorder

The intricate interplay existing between gut microbiota and homeostasis extends to the realm of the brain, where emerging research underscores the significant impact of the microbiota on mood regulation and overall neurological well-being and vice-versa, with inflammation playing a pivotal role in mediating these complex interactions. This comprehensive review explores the complex interplay between inflammation, alterations in gut microbiota, and their impact on major depressive disorder (MDD). It provides a cohesive framework for the puzzle pieces of this triad, emphasizing recent advancements in understanding the gut microbiota and inflammatory states' contribution to the depressive features. Two directions of communication between the gut and the brain in depression are discussed, with inflammation serving as a potential modulator. Therapeutic implications were discussed as well, drawing insights from interventional studies on the effects of probiotics on gut bacterial composition and depressive symptoms. Ultimately, this review will attempt to provide a complete and valuable framework for future research and therapeutic interventions in MDD.

Causal associations between intermediate very-low-density lipoprotein cholesterol-to-total lipids ratio and peptic ulcer: A bidirectional Mendelian randomization study

BACKGROUND

Previous epidemiologic investigations have consistently demonstrated a strong association between the ratio of cholesterol to total lipids in medium very-low-density lipoprotein (VLDL) and the occurrence of peptic ulcers (PU). However, the precise causal relationship between these factors remains ambiguous. Consequently, this study aims to elucidate the potential correlation between the ratio of cholesterol to total lipids in medium VLDL and the incidence of peptic ulcer.

AIM

To investigate the ratio of cholesterol to total lipids in medium very-low-density lipoprotein (VLDL) association with PU via genetic methods, guiding future clinical research.

METHODS

Genome-wide association study (GWAS) datasets for the ratio of cholesterol to total lipids in intermediate VLDL and peptic ulcer were retrieved from the IEU OpenGWAS project (https://gwas.mrcieu.ac.uk). For the forward Mendelian randomization (MR) analysis, 72 single nucleotide polymorphisms (SNPs) were identified as instrumental variables. These SNPs were selected based on their association with the ratio of cholesterol to total lipids in intermediate VLDL, with peptic ulcer as the outcome variable. Conversely, for the inverse MR analysis, no SNPs were identified with peptic ulcer as the exposure variable and the ratio of cholesterol to total lipids in intermediate VLDL as the outcome. All MR analyses utilized inverse variance weighted (IVW) as the primary analytical method. Additionally, weighted median and MR-Egger methods were employed as supplementary analytical approaches to assess causal effects. Egger regression was used as a supplementary method to evaluate potential directional pleiotropy. Heterogeneity and multiplicity tests were conducted using the leave-one-out method to evaluate result stability and mitigate biases associated with multiple testing.

RESULTS

The genetically predicted ratio of cholesterol to total lipids in medium VLDL was significantly associated with an elevated risk of peptic ulcer (IVW: OR = 2.557, 95%CI = 1.274-5.132, P = 0.008). However, no causal association of peptic ulcer with the ratio of cholesterol to total lipids in medium VLDL was observed in the inverse Mendelian randomization analysis.

CONCLUSION

In conclusion, our study reveals a significant association between the ratio of cholesterol to total lipids in medium VLDL and an elevated risk of peptic ulcers. However, further validation through laboratory investigations and larger-scale studies is warranted to strengthen the evidence and confirm the causal relationship between these factors.

Exploring the bidirectional causal association between Sleep Apnea Syndrome and Depression: A Mendelian randomization study involving gut microbiota, serum metabolites, and inflammatory factors

OBJECTIVE

This study aimed to investigate the potential causal association between Sleep Apnea Syndrome (SAS) and Depression, focusing on the roles of gut microbiota, serum metabolites, and inflammatory factors in these conditions.

METHODS

Mendelian Randomization (MR) analysis was performed using data from genome-wide association studies to assess 211 types of gut microbiota, 1400 serum metabolites, and 91 inflammatory factors as potential contributing factors. Causal inference was conducted using the Inverse Variance Weighted (IVW) method, with additional robustness checks through Cochran's Q test, MR-Egger regression intercept test, MR-PRESSO global test, and leave-one-out analysis.

RESULTS

The MR analysis indicated a positive correlation between the risk of SAS and Depression (OR = 1.12, 95 % CI: 1.05-1.19, P < 0.001), with a reciprocal analysis showing a similar positive correlation between Depression and the risk of SAS (OR = 1.19, 95 % CI: 1.07-1.31, P = 0.001). Additionally, causal associations were identified between 15 types of gut microbiota, 36 serum metabolites, and 2 inflammatory factors with SAS, and between 11 types of gut microbiota, 23 serum metabolites, and 3 inflammatory factors with Depression (IVW, all P < 0.05). The robustness of these findings was confirmed through the MR-Egger regression intercept test and MR-PRESSO global test.

CONCLUSION

This study provides epidemiological evidence of a bidirectional causal association between SAS and Depression, emphasizing the potential roles of gut microbiota, serum metabolites, and inflammatory factors in the pathogenesis of these disorders. These findings may inform the development of new therapeutic strategies.

Associations Between Gut Microbiota and Alcohol Abuse: A Mendelian Randomisation and Bioinformatics Study

Alcohol abuse, also known as Alcohol Use Disorder (AUD), is a substance dependency psychiatric disorder. We aimed to establish a causal relationship between specific gut microbiota and alcohol abuse using Mendelian Randomisation (MR) and bioinformatics methods. We acquired summary data of genome-wide association studies (GWAS) for gut microbiota and alcohol abuse from the Mibiogen and Finngen databases, respectively. We conducted MR analyses using various methodologies and mapped the single nucleotide polymorphisms (SNPs) to genes via the FUMA GWAS platform. We further performed multiple enrichment analyses and a Multi-variable Mendelian Randomisation (MVMR) approach to examine whether gut microbiota influences alcohol abuse by modulating neurotransmitter-related amino acids. The MR analysis revealed an inverse relationship between the genus Eubacterium ventriosum group and the Porphyromonadaceae family with alcohol abuse. Gene enrichment analysis showed that these genes are expressed in brain tissue and are involved in addictive disorders, psychiatric conditions, immunological processes, neurotransmitter synthesis and synaptic regulation. MVMR analysis suggested that the Porphyromonadaceae family as well as genus Eubacterium ventriosum group may suppress alcohol abuse through the metabolism of neurotransmitter-related amino acids, especially Tryptophan. The MR analysis and bioinformatics investigations indicate that the genus Eubacterium ventriosum group and Porphyromonadaceae family confer a protective effect against alcohol abuse, potentially through the modulation of synaptic function.

Anorexia and bulimia in relation to ulcerative colitis: a Mendelian randomization study

Background

Evidence for anorexia and bulimia in relation to the risk of ulcerative colitis (UC) is limited and inconsistent. The objective of this research was to utilize bi-directional, two-sample Mendelian randomization (MR) analysis to predict the causal association between anorexia nervosa and bulimia nervosa with UC.

Methods

The genome-wide association studies (GWAS) provided data for anorexia and bulimia from the UK Biobank, utilizing single-nucleotide polymorphisms (SNP) as instrumental variables. Additionally, genetic associations with UC were collected from various sources including the FinnGen Biobank, the UK Biobank and the International Inflammatory Bowel Disease Genetics Consortium (IIBDGC). The main analytical approach utilized in this study was the inverse-variance-weighted (IVW) method. To evaluate horizontal pleiotropy, the researchers conducted MR-Egger regression and MR-PRESSO global test analyses. Additionally, heterogeneity was assessed using the Cochran's Q test.

Results

This study found a negative association between genetically predicted bulimia (OR = 0.943, 95% CI: 0.893-0.996; p = 0.034) and the risk of UC in the IIBDGC dataset, indicating that individuals with bulimia have approximately a 5.7% lower risk of developing UC. No association was observed in the other two datasets. Conversely, genetically predicted anorexia was not found to be causally associated with UC. In bi-directional Mendelian randomization, UC from the IIBDGC dataset was negatively associated with the risk of anorexia (OR = 0.877, 95% CI: 0.797-0.965; p = 0.007), suggesting that UC patients have approximately a 12.3% lower risk of developing anorexia, but not causally associated with bulimia.

Conclusion

Genetically predicted bulimia may have a negative association with the onset of UC, while genetically predicted anorexia does not show a causal relationship with the development of UC. Conversely, genetically predicted UC may have a negative association with the development of anorexia.

Gut microbiome and major depressive disorder: insights from two-sample Mendelian randomization

BACKGROUND

Existing evidence suggests that alterations in the gut microbiome are closely associated with major depressive disorder (MDD). We aimed to reveal the causal relationships between MDD and various microbial taxa in the gut.

METHODS

We used the two-sample Mendelian randomization (TSMR) to explore the bidirectional causal effects between gut microbiota and MDD. The genome-wide association studies summary results of gut microbiota were obtained from two large consortia, the MibioGen consortium and the Dutch Microbiome Project, which we analyzed separately.

RESULTS

Our TSMR analysis identified 10 gut bacterial taxa that were protective against MDD, including phylum Actinobacteria, order Clostridiales, and family Bifidobacteriaceae (OR: 0.96 ∼ 0.98). Ten taxa were associated with an increased risk of MDD, including phyla Firmicutes and Proteobacteria, class Actinobacteria, and genus Alistipes (OR: 1.01 ∼ 1.09). On the other hand, MDD may decrease the abundance of 12 taxa, including phyla Actinobacteria and Firmicutes, families Bifidobacteriaceae and Defluviitaleaceae (OR: 0.63 ∼ 0.88). MDD may increase the abundance of 8 taxa, including phylum Bacteroidetes, genera Parabacteroides, and Bacteroides (OR: 1.12 ∼ 1.43).

CONCLUSIONS

Our study supports that there are mutual causal relationships between certain gut microbiota and the development of MDD suggesting that gut microbiota may be targeted in the treatment of MDD.

Dissecting the association between gut microbiota, body mass index and specific depressive symptoms: a mediation Mendelian randomisation study

Background

Observational studies highlight the association between gut microbiota (GM) composition and depression; however, evidence for the causal relationship between GM and specific depressive symptoms remains lacking.

Aims

We aimed to evaluate the causal relationship between GM and specific depressive symptoms as well as the mediating role of body mass index (BMI).

Methods

We performed a two-sample Mendelian randomisation (MR) analysis using genetic variants associated with GM and specific depressive symptoms from genome-wide association studies. The mediating role of BMI was subsequently explored using mediation analysis via two-step MR.

Results

MR evidence suggested the Bifidobacterium genus (β=-0.03; 95% CI -0.05 to -0.02; p<0.001 and β=-0.03; 95% CI -0.05 to -0.02; p<0.001) and Actinobacteria phylum (β=-0.04; 95% CI -0.06 to -0.02; p<0.001 and β=-0.03; 95% CI -0.05 to -0.03; p=0.001) had protective effects on both anhedonia and depressed mood. The Actinobacteria phylum also had protective effects on appetite changes (β=-0.04; 95% CI -0.06 to -0.01; p=0.005), while the Family XI had an antiprotective effect (β=0.03; 95% CI 0.01 to 0.04; p<0.001). The Bifidobacteriaceae family (β=-0.01; 95% CI -0.02 to -0.01; p=0.001) and Actinobacteria phylum (β=-0.02; 95% CI -0.03 to -0.01; p=0.001) showed protective effects against suicidality. The two-step MR analysis revealed that BMI also acted as a mediating moderator between the Actinobacteria phylum and appetite changes (mediated proportion, 34.42%) and that BMI partially mediated the effect of the Bifidobacterium genus (14.14% and 8.05%) and Actinobacteria phylum (13.10% and 8.31%) on both anhedonia and depressed mood.

Conclusions

These findings suggest a potential therapeutic effect of Actinobacteria and Bifidobacterium on both depression and obesity. Further studies are required to translate these findings into clinical practice.

Gut microbiota, skin microbiota, and alopecia areata: A Mendelian randomization study

BACKGROUND

Observational studies have shown an association between skin microbiota and alopecia areata (AA), but the causal connection remains ambiguous.

METHODS

We obtained data on skin microbiota and AA from summary statistics of Genome-Wide Association Studies and applied statistical methods from Mendelian randomization (MR) to assess causal relationships. Additionally, we investigated whether the skin microbiota acts as a mediator in the pathway from gut microbiota to AA.

RESULTS

In the MR analysis of KORA FF4 and AA, the inverse-variance weighting method indicated that Corynebacterium (odds ratio [OR] = 0.82, 95% confidence interval [CI]: 0.70-0.96, p = 0.02) and asv037 (OR = 0.87, 95% CI: 0.76-0.99, p = 0.05) exerted protective effects, while Betaproteobacteria (OR = 1.21, 95% CI: 1.01-1.44, p = 0.03), asv015 (OR = 1.27, 95% CI: 1.05-1.54, p = 0.02), and Burkholderiales (OR = 1.20, 95% CI: 1.04-1.38, p = 0.01) were identified as risk factors in AA. In the MR analysis of PopGen and AA, asv001 (OR = 1.12, 95% CI: 1.01-1.24, p = 0.04), asv054 (OR = 1.13, 95% CI: 1.01-1.25, p = 0.03), and asv059 (OR = 1.14, 95% CI: 1.02-1.27, p = 0.02) were found to potentially increase the risk in AA. Furthermore, in the influence of gut microbiota on AA, the skin microbiota did not act as a mediator.

CONCLUSION

Our analysis suggests potential causal relationships between certain skin microbiota and AA, revealing insights into its pathogenesis and potential intervention strategies.

Gut microbiota and postpartum depression: a Mendelian randomization study

Background

Increasing evidence suggests a correlation between intestinal microbiota and the gut-brain axis; however, the causal relationship between gut microbiota and postpartum depression (PPD) remains unclear.

Methods

In this study, a two-sample Mendelian randomization (MR) design was employed to analyze the GWAS data of gut microorganisms from the Mibiogen database and PPD data from the UK biobank. Various statistical methods, including inverse variance weighted, MR-Egger, weighted median, weighted model, and MR-PRESSO, were utilized to investigate the causal relationship between gut microbiota and PPD. Additionally, sensitivity analysis was conducted to assess the robustness of the findings.

Results

Through MR analysis, it was found that phylum Actinobacteria (P=0.014, OR=0.971, 95% CI=0.948-0.994) and genus Holdemanella (P=0.023, OR=0.979, 95% CI=0.961-0.997) have protective effects on PPD, while the other two unknown genera, genus Unknown Ids 2001 (P=0.025, OR=0.972,95% CI=0.947-0.996), and genus Unknown Ids 2755 (P=0.012, OR=0.977, 95% CI=0.959-0.995) also has a protective effect on PPD. The sensitivity analysis results indicate that there is no heterogeneity or horizontal pleiotropy.

Conclusion

This study has identified a causal association between Actinomycetota, Holdemanella, and PDD through MR analysis. These findings offer significant contributions to the development of personalized treatment approaches for PPD, encompassing interventions such as dietary modifications or microbiome interventions.

Electroacupuncture intervention alleviates depressive-like behaviors and regulates gut microbiome in a mouse model of depression

Electroacupuncture (EA) is a neuroregulatory therapy for depression. Nonetheless, the effects of EA on the gut microbiome in mice models of depression are not well established. Here, using a chronic unpredictable mild stress (CUMS) model in mice, we evaluated the antidepressant effects of EA and changes in gut microbiota with behavioral tests and 16S rRNA gene sequencing. The results found that EA increased the time spent in the center area of the open-field test and the percentage of sucrose preference and reduced the immobility time in the tail suspension test in CUMS-treated mice. Furthermore, the genus Lachnoclostridium, Ruminococcaceae_UCG-002 and Rikenellaceae_RC9_gut_group were enriched in the CUMS group, which was positively correlated with depressive-like behaviors. Whereas phylum Actinobacteria and genus Allobaculum, Bifidobacterium, Dubosiella, Rikenella and Ileibacterium were enriched in the EA and CUMS + EA groups, all of which were negatively correlated with depressive-like behaviors. This study characterizes gut microbiota under EA treatment and provides new insights into the association of anti-depressive-like effects of EA and gut microbiota.

Relationship between plasma brain-derived neurotrophic factor levels and neurological disorders: An investigation using Mendelian randomisation

Background

Altered brain-derived neurotrophic factor (BDNF) concentrations have been detected in the central nervous system tissues and peripheral blood. These alterations are associated with a series of neurological disorders.

Objective

To investigate the potential causal relationships between genetically determined plasma BDNF levels and various neurological diseases using a two-sample Mendelian randomisation study.

Methods

We selected single nucleotide polymorphisms strongly related to plasma BDNF levels as instrumental variables. Within the Mendelian randomisation framework, we used summary-level statistics for exposure (plasma BDNF levels) and outcomes (neurological disorders).

Results

We observed suggestive evidence of a relation between higher plasma BDNF levels and less risk of nontraumatic intracranial haemorrhage (nITH) (odds ratio [OR] = 0.861, 95 % confidence interval [CI]: 0.774-0.958, P = 0.006, PFDR = 0.078), epilepsy (OR = 0.927, 95 % CI: 0.880-0.976, P = 0.004, PFDR = 0.078), focal epilepsy (OR = 0.928, 95 % CI: 0.874-0.986, P = 0.016, PFDR = 0.139), and non-lesional focal epilepsy (OR = 0.981, 95 % CI: 0.964-0.999, P = 0.041, PFDR = 0.267). Combined with the UK Biobank dataset, the association of plasma BDNF levels with nITH remained significant (OR = 0.88, 95 % CI: 0.81-0.96, P < 0.01). The combined analysis of three consortium datasets demonstrated a considerable impact of plasma BDNF on epilepsy (OR = 0.94, 95 % CI: 0.90-0.98, P < 0.01) and a suggestive impact on focal epilepsy (OR = 0.94, 95 % CI: 0.89-0.99, P = 0.02). However, there was no apparent correlation between plasma BDNF levels and other neurological disorders or related subtypes.

Conclusions

Our study supports a possible causal relationship between elevated plasma BDNF levels and a reduced risk of nITH, epilepsy, and focal epilepsy.

Gut microbiota and cognitive performance: A bidirectional two-sample Mendelian randomization

PURPOSE

Previous studies have suggested a potential association between gut microbiota and neurological and psychiatric disorders. However, the causal relationship between gut microbiota and cognitive performance remains uncertain.

METHODS

A two-sample Mendelian randomization (MR) study used SNPs linked to gut microbiota (n = 18,340) and cognitive performance (n = 257,841) from recent GWAS data. Inverse-variance weighted (IVW), MR Egger, weighted median, simple mode, and weighted mode were employed. Heterogeneity was assessed via Cochran's Q test for IVW. Results were shown with funnel plots. Outliers were detected through leave-one-out method. MR-PRESSO and MR-Egger intercept tests were conducted to address horizontal pleiotropy influence.

LIMITATIONS

Limited to European populations, generic level, and potential confounding factors.

RESULTS

IVW analysis revealed detrimental effects on cognitive perfmance associated with the presence of genus Blautia (P = 0.013, 0.966[0.940-0.993]), Catenibacterium (P = 0.035, 0.977[0.956-0.998]), Oxalobacter (P = 0.043, 0.979[0.960-0.999]). Roseburia (P < 0.001, 0.935[0.906-0.965]), in particular, remained strongly negatively associated with cognitive performance after Bonferroni correction. Conversely, families including Bacteroidaceae (P = 0.043, 1.040[1.001-1.081]), Rikenellaceae (P = 0.047, 1.026[1.000-1.053]), along with genera including Paraprevotella (P = 0.044, 1.020[1.001-1.039]), Ruminococcus torques group (P = 0.016, 1.062[1.011-1.115]), Bacteroides (P = 0.043, 1.040[1.001-1.081]), Dialister (P = 0.027, 1.039[1.004-1.074]), Paraprevotella (P = 0.044, 1.020[1.001-1.039]) and Ruminococcaceae UCG003 (P = 0.007, 1.040[1.011-1.070]) had a protective effect on cognitive performance.

CONCLUSIONS

Our results suggest that interventions targeting specific gut microbiota may offer a promising avenue for improving cognitive function in diseased populations. The practical application of these findings has the potential to enhance cognitive performance, thereby improving overall quality of life.

Genetic analysis of the causal relationship between gut microbiota and intervertebral disc degeneration: a two-sample Mendelian randomized study

PURPOSE

Several recent studies have reported a possible association between gut microbiota and intervertebral disc degeneration; however, no studies have shown a causal relationship between gut microbiota and disc degeneration. This study was dedicated to investigate the causal relationship between the gut microbiota and intervertebral disc degeneration and the presence of potentially bacterial traits using two-sample Mendelian randomization.

METHODS

A two-sample Mendelian randomization study was performed using the summary statistics of the gut microbiota from the largest available genome-wide association study meta-analysis conducted by the MiBioGen consortium. Summary statistics of intervertebral disc degeneration were obtained from the FinnGen consortium R8 release data. Five basic methods and MR-PRESSO were used to examine causal associations. The results of the study were used to examine the causal association between gut microbiota and intervertebral disc degeneration. Cochran's Q statistics were used to quantify the heterogeneity of instrumental variables.

RESULTS

By using Mendelian randomization analysis, 10 bacterial traits potentially associated with intervertebral disc degeneration were identified: genus Eubacterium coprostanoligenes group, genus Lachnoclostridium, unknown genus id.2755, genus Marvinbryantia, genus Ruminococcaceae UCG003, family Rhodospirillaceae, unknown genus id.959, order Rhodospirillales, genus Lachnospiraceae NK4A136 grou, genus Eubacterium brachy group.

CONCLUSION

This Mendelian Randomization study found a causal effect between 10 gut microbiota and intervertebral disc degeneration, and we summarize the possible mechanisms of action in the context of existing studies. However, additional research is essential to fully understand the contribution of genetic factors to the dynamics of gut microbiota and its impact on disc degeneration.

Improving precision management of anxiety disorders: a Mendelian randomization study targeting specific gut microbiota and associated metabolites

Background

There is growing evidence of associations between the gut microbiota and anxiety disorders, where changes in gut microbiotas may affect brain function and behavior via the microbiota-gut-brain axis. However, population-level studies offering a higher level of evidence for causality are lacking. Our aim was to investigate the specific gut microbiota and associated metabolites that are closely related to anxiety disorders to provide mechanistic insights and novel management perspectives for anxiety disorders.

Method

This study used summary-level data from publicly available Genome-Wide Association Studies (GWAS) for 119 bacterial genera and the phenotype "All anxiety disorders" to reveal the causal effects of gut microbiota on anxiety disorders and identify specific bacterial genera associated with anxiety disorders. A two-sample, bidirectional Mendelian randomization (MR) design was deployed, followed by comprehensive sensitivity analyses to validate the robustness of results. We further conducted multivariable MR (MVMR) analysis to investigate the potential impact of neurotransmitter-associated metabolites, bacteria-associated dietary patterns, drug use or alcohol consumption, and lifestyle factors such as smoking and physical activity on the observed associations.

Results

Bidirectional MR analysis identified three bacterial genera causally related to anxiety disorders: the genus Eubacterium nodatum group and genus Ruminococcaceae UCG011 were protective, while the genus Ruminococcaceae UCG011 was associated with an increased risk of anxiety disorders. Further MVMR suggested that a metabolite-dependent mechanism, primarily driven by tryptophan, tyrosine, phenylalanine, glycine and cortisol, which is consistent with previous research findings, probably played a significant role in mediating the effects of these bacterial genera to anxiety disorders. Furthermore, modifying dietary pattern such as salt, sugar and processed meat intake, and adjusting smoking state and physical activity levels, appears to be the effective approaches for targeting specific gut microbiota to manage anxiety disorders.

Conclusion

Our findings offer potential avenues for developing precise and effective management approaches for anxiety disorders by targeting specific gut microbiota and associated metabolites.

Causal associations between human gut microbiota and osteomyelitis: a Mendelian randomization study

Background

Recent studies have emphasized the role of gut microbiota in the onset and progression of osteomyelitis. However, the exact types of gut microbiota and their mechanisms of action remain unclear. Additionally, there is a lack of theoretical support for treatments that improve osteomyelitis by altering the gut microbiota.

Methods

In our study, we utilized the largest genome-wide association study (GWAS) meta-analysis to date from the MiBioGen consortium, involving 13,400 participants. The GWAS data for osteomyelitis were sourced from the UK Biobank, which included 4,836 osteomyelitis cases and 486,484 controls. We employed a two-sample Mendelian randomization framework for a detailed investigation into the causal relationship between gut microbiota and osteomyelitis. Our methods included inverse variance weighting, MR-Egger, weighted median, and weighted mode approaches. Additionally, we applied Cochran's Q statistic to assess the heterogeneity of the instrumental variable.

Results

At the class level, Bacilli and Bacteroidia were positively correlated with the risk of osteomyelitis. At the order level, only Bacteroidales showed a positive association with osteomyelitis. At the genus level, an increased abundance of Butyricimonas, Coprococcus3, and Tyzzerella3 was positively associated with the risk of osteomyelitis, whereas Lachnospira was negatively associated. Sensitivity analyses showed no evidence of heterogeneity or pleiotropy.

Conclusion

This study reveals that classes Bacilli and Bacteroidia, order Bacteroidales, and genera Butyricimonas, Coprococcus3, and Tyzzerella3 are implicated in increasing the risk of osteomyelitis, while the genus Lachnospira is associated with a reduced risk. Future investigations are warranted to elucidate the precise mechanisms through which these specific bacterial groups influence the pathophysiology of osteomyelitis.

Causal association between gut microbiota and hyperemesis gravidarum: a two-sample Mendelian randomization study

Background

Observational studies have reported an association between the gut microbiota (GM) and hyperemesis gravidarum (HG). However, the causal relationship is unclear. In this study, Mendelian randomization (MR) was used to infer causal relationships between GM and HG.

Methods

Inverse-variance weighted MR was performed using summary statistics for genetic variants from genome-wide association studies (GWAS). Sensitivity analyses were performed to validate the MR results and assess the robustness of the causal inference. Reverse MR analysis was performed for bacterial taxa that were causally linked to the HG risk in the forward MR analysis to evaluate reverse causality.

Results

MR analysis revealed that the genera Defluviitaleaceae UCG011, Ruminococcus1, Ruminococcus2, Turicibacter, and unknowngenus and phylum Verrucomicrobiota are positively associated with the risk of HG. Additionally, the genus Coprococcus2 was related to a decreased risk of HG. Sensitivity studies validated the strength and reliability of the link between the composition of the GM and HG. No evidence for reverse causality from HG to identified bacterial taxa was found.

Conclusion

Our MR analysis provided novel insight into the association between GM and HG. In particular, our results indicated that targeting the GM could serve as an effective therapeutic strategy for HG.

Associations Between Brain-Gut Axis and Psychological Distress in Fibromyalgia: A Microbiota and Magnetic Resonance Imaging Study

An altered brain-gut axis is suspected to be one of the pathomechanisms in fibromyalgia (FM). This cross-sectional study investigated the associations among altered microbiota, psychological distress, and brain functional connectivity (FC) in FM. We recruited 25 FM patients and 25 healthy people in the present study. Psychological distress was measured using standardized questionnaires. Microbiota analysis was performed on the participants' stools. Functional magnetic resonance imaging data were acquired, and seed-based resting-state FC (rs-FC) analysis was conducted with the salience network nodes as seeds. Linear regression and mediation analyses evaluated microbiota, symptoms, and rs-FCs associations. We found altered microbiota diversity in FM, of which Phascolarctobacterium and Lachnoclostridium taxa increased the most and Faecalibacterium taxon decreased the most compared to controls. The Phascolarctobacterium abundance significantly predicted Beck depression inventory (BDI-II) scores in FM (β = 6.83; P = .033). Rs-FCs from salience network nodes were reduced in FM, of which rs-FCs from the right lateral rostral prefrontal cortex (RPFC) to the lateral occipital cortex, superior division right (RPFC-sLOC) could be predicted by BDI-II scores in patients (β = -.0064; P = .0054). In addition, the BDI-II score was a mediator in the association between Phascolarctobacterium abundance and rs-FCs of RPFC-sLOC (ab = -.06; 95% CI: -.16 to -9.10-3). In conclusion, microbial dysbiosis might be associated with altered neural networks mediated by psychological distress in FM, emphasizing the critical role of the brain-gut axis in FM's non-pain symptoms and supporting further analysis of mechanism-targeted therapies to reduce FM symptoms. PERSPECTIVE: Our study suggests microbial dysbiosis might be associated with psychological distress and the altered salience network, supporting the role of brain-gut axis dysfunction in fibromyalgia pathomechanisms. Further targeting therapies for microbial dysbiosis should be investigated to manage fibromyalgia patients in the future.

Association between gut microbiota and Hirschsprung disease: a bidirectional two-sample Mendelian randomization study

Background

Several studies have pointed to the critical role of gut microbiota (GM) and their metabolites in Hirschsprung disease (HSCR) pathogenesis. However, the detailed causal relationship between GM and HSCR remains unknown.

Methods

In this study, we used two-sample Mendelian randomization (MR) analysis to investigate the causal relationship between GM and HSCR, based on the MiBioGen Consortium's genome-wide association study (GWAS) and the GWAS Catalog's HSCR data. Reverse MR analysis was performed subsequently, and the sensitivity analysis, Cochran's Q-test, MR pleiotropy residual sum, outlier (MR-PRESSO), and the MR-Egger intercept were used to analyze heterogeneity or horizontal pleiotropy. 16S rDNA sequencing and targeted mass spectrometry were developed for initial validation.

Results

In the forward MR analysis, inverse-variance weighted (IVW) estimates suggested that Eggerthella (OR: 2.66, 95%CI: 1.23-5.74, p = 0.01) was a risk factor for HSCR, while Peptococcus (OR: 0.37, 95%CI: 0.18-0.73, p = 0.004), Ruminococcus2 (OR: 0.32, 95%CI: 0.11-0.91, p = 0.03), Clostridiaceae1 (OR: 0.22, 95%CI: 0.06-0.78, p = 0.02), Mollicutes RF9 (OR: 0.27, 95%CI: 0.09-0.8, p = 0.02), Ruminococcaceae (OR: 0.16, 95%CI: 0.04-0.66, p = 0.01), and Paraprevotella (OR: 0.45, 95%CI: 0.21-0.98, p = 0.04) were protective factors for HSCR, which had no heterogeneity or horizontal pleiotropy. However, reverse MR analysis showed that HSCR (OR: 1.02, 95%CI: 1-1.03, p = 0.049) is the risk factor for Eggerthella. Furthermore, some of the above microbiota and short-chain fatty acids (SCFAs) were altered in HSCR, showing a correlation.

Conclusion

Our analysis established the relationship between specific GM and HSCR, identifying specific bacteria as protective or risk factors. Significant microbiota and SCFAs were altered in HSCR, underlining the importance of further study and providing new insights into the pathogenesis and treatment.

The bidirectional interaction between antidepressants and the gut microbiota: are there implications for treatment response?

This review synthesizes the evidence on associations between antidepressant use and gut microbiota composition and function, exploring the microbiota's possible role in modulating antidepressant treatment outcomes. Antidepressants exert an influence on measures of gut microbial diversity. The most consistently reported differences were in β-diversity between those exposed to antidepressants and those not exposed, with longitudinal studies supporting a potential causal association. Compositional alterations in antidepressant users include an increase in the Bacteroidetes phylum, Christensenellaceae family, and Bacteroides and Clostridium genera, while a decrease was found in the Firmicutes phylum, Ruminococcaceae family, and Ruminococcus genus. In addition, antidepressants attenuate gut microbial differences between depressed and healthy individuals, modulate microbial serotonin transport, and influence microbiota's metabolic functions. These include lyxose degradation, peptidoglycan maturation, membrane transport, and methylerythritol phosphate pathways, alongside gamma-aminobutyric acid metabolism. Importantly, baseline increased α-diversity and abundance of the Roseburia and Faecalibacterium genera, in the Firmicutes phylum, are associated with antidepressant response, emerging as promising biomarkers. This review highlights the potential for gut microbiota as a predictor of treatment response and emphasizes the need for further research to elucidate the mechanisms underlying antidepressant-microbiota interactions. More homogeneous studies and standardized techniques are required to confirm these initial findings.

Causal relationship between gut microbiome and sex hormone-binding globulin: A bidirectional two-sample Mendelian randomization study

PROBLEM

Currently, there is a variety of evidence linking the gut microbiota to changes in sex hormones. In contrast, the causal relationship between SHBG, a carrier of sex hormones, and the gut microbiota is unclear.

METHOD OF STUDY

Bidirectional two-sample Mendelian randomization (MR) analysis was used to detect the causal effect between SHBG and the gut microbiome. Summary statistics of genome-wide association studies (GWASs) for the gut microbiome and SHBG were obtained from public datasets. Inverse-variance weighting (IVW), weighted median, weighted mode, MR-Egger and simple mode methods were used to operate the MR analysis. F-statistics and sensitivity analyses performed to evaluate bias and reliability.

RESULTS

When we set gut microbiome as exposure and SHBG as outcome, we identified nine causal relationships. In males, Coprobacter (PIVW = 2.01 × 10-6 ), Ruminococcus2 (PIVW = 3.40 × 10-5 ), Barnesiella (PIVW = 2.79 × 10-2 ), Actinobacteria (PIVW = 3.25 × 10-2 ) and Eubacterium fissicatena groups (PIVW = 3.64 × 10-2 ) were associated with lower SHBG levels; Alphaproteobacteria (PIVW = 1.61 × 10-2 ) is associated with higher SHBG levels. In females, Lachnoclostridium (PIVW = 9.75 × 10-3 ) and Defluviitaleaceae UCG011 (PIVW = 3.67 × 10-2 ) were associated with higher SHBG levels; Victivallaceae (PIVW = 2.23 × 10-2 ) was associated with lower SHBG levels. According to the results of reverse MR analysis, three significant causal effect of SHBG was found on gut microbiota. In males, Dorea (PIVW = 4.17 × 10-2 ) and Clostridiales (PIVW = 4.36 × 10-2 ) were associated with higher SHBG levels. In females, Lachnoclostridium (PIVW = 7.44 × 10-4 ) was associated with higherr SHBG levels. No signifcant heterogeneity of instrumental variables or horizontal pleiotropy was found in bidirectional two-sample MR analysis.

CONCLUSIONS

This study may provide new insights into the causal relationship between the gut microbiome and sex hormone-binding protein levels, as well as new treatment and prevention strategies for diseases such as abnormal changes in sex hormones.

Potential causal association between gut microbiome and posttraumatic stress disorder

BACKGROUND

The causal effects of gut microbiome and the development of posttraumatic stress disorder (PTSD) are still unknown. This study aimed to clarify their potential causal association using mendelian randomization (MR).

METHODS

The summary-level statistics for gut microbiome were retrieved from a genome-wide association study (GWAS) of the MiBioGen consortium. As to PTSD, the Freeze 2 datasets were originated from the Psychiatric Genomics Consortium Posttraumatic Stress Disorder Working Group (PGC-PTSD), and the replicated datasets were obtained from FinnGen consortium. Single nucleotide polymorphisms meeting MR assumptions were selected as instrumental variables. The inverse variance weighting (IVW) method was employed as the main approach, supplemented by sensitivity analyses to evaluate potential pleiotropy and heterogeneity and ensure the robustness of the MR results. We also performed reverse MR analyses to explore PTSD's causal effects on the relative abundances of specific features of the gut microbiome.

RESULTS

In Freeze 2 datasets from PGC-PTSD, eight bacterial traits revealed a potential causal association between gut microbiome and PTSD (IVW, all P < 0.05). In addition, Genus.Dorea and genus.Sellimonas were replicated in FinnGen datasets, in which eight bacterial traits revealed a potential causal association between gut microbiome and the occurrence of PTSD. The heterogeneity and pleiotropy analyses further supported the robustness of the IVW findings, providing additional evidence for their reliability.

CONCLUSION

Our study provides the potential causal impact of gut microbiomes on the development of PTSD, shedding new light on the understanding of the dysfunctional gut-brain axis in this disorder. Our findings present novel evidence and call for investigations to confirm the association between their links, as well as to illuminate the underlying mechanisms.

Gut microbiota and risk of endocarditis: a bidirectional Mendelian randomization study

Background

The associations between gut microbiota and cardiovascular disease have been reported in previous studies. However, the relationship between gut microbiota and endocarditis remains unclear.

Methods

A bidirectional Mendelian randomization (MR) study was performed to detect the association between gut microbiota and endocarditis. Inverse variance weighted (IVW) method was considered the main result. Simultaneously, heterogeneity and pleiotropy tests were conducted.

Results

Our study suggests that family Victivallaceae (p = 0.020), genus Eubacterium fissicatena group (p = 0.047), genus Escherichia Shigella (p = 0.024), genus Peptococcus (p = 0.028) and genus Sellimonas (p = 0.005) play protective roles in endocarditis. Two microbial taxa, including genus Blautia (p = 0.006) and genus Ruminococcus2 (p = 0.024) increase the risk of endocarditis. At the same time, endocarditis has a negative effect on genus Eubacterium fissicatena group (p = 0.048). Besides, no heterogeneity or pleiotropy was found in this study.

Conclusion

Our study emphasized the certain role of specific gut microbiota in patients with endocarditis and clarified the negative effect of endocarditis on gut microbiota.

The Associations of Vitamin D with Ovarian Reserve Markers and Depression: A Narrative Literature Review

Since the identification of vitamin D receptors in both the female reproductive tract and the central nervous system, further data have shown that vitamin D is involved in the processes of reproductive and mental health. This paper reviews current research on the associations of vitamin D with ovarian reserve markers and depression and discusses the potential role of vitamin D in their relationships. There have been numerous studies reporting that vitamin D was significantly related to ovarian reserve markers and depression in basic or clinical research, but some observational and interventional clinical studies have shown inconsistent results. Nevertheless, recent meta-analyses of interventional studies have provided promising results showing that vitamin D supplementation significantly improves ovarian reserve metrics, especially in a subgroup of women with normal or diminished ovarian reserve, and decreases depressive symptoms and risk. The demonstration of an association of vitamin D with both ovarian reserve and depression could suggest that vitamin D may be another important key in explaining female reproductive depression. Larger-scale studies in standardized settings will be needed in order to gain further insight into the role of vitamin D in female reproduction and depression.

Co-Housing and Fecal Microbiota Transplantation: Technical Support for TCM Herbal Treatment of Extra-Intestinal Diseases Based on Gut Microbial Ecosystem Remodeling

Dysregulation of the gut microbial ecosystem (GME) (eg, alterations in the gut microbiota, gut-derived metabolites, and gut barrier) may contribute to the onset and progression of extra-intestinal diseases. Previous studies have found that Traditional Chinese Medicine herbs (TCMs) play an important role in manipulating the GME, but a prominent obstacle in current TCM research is the causal relationship between GME and disease amelioration. Encouragingly, co-housing and fecal microbiota transplantation (FMT) provide evidence-based support for TCMs to treat extra-intestinal diseases by targeting GME. In this review, we documented the principles, operational procedures, applications and limitations of the key technologies (ie, co-housing and FMT); furthermore, we provided evidence that TCM works through the GME, especially the gut microbiota (eg, SCFA- and BSH-producing bacteria), the gut-derived metabolites (eg, IS, pCS, and SCFAs), and intestinal barrier to alleviate extra-intestinal diseases. This will be beneficial in constructing microecological pathways for TCM treatment of extra-intestinal diseases in the future.

Association between gut microbiota and endometriosis: a two-sample Mendelian randomization study

Background

Recent studies have shown that an imbalance in gut microbiota (GM) may not always be associated with endometriosis (EMS). To investigate this further, we conducted a two-sample Mendelian randomization study.

Methods

MR analysis was performed on genome-wide association study (GWAS) summary statistics of GM and EMS. Specifically, the MiBioGen microbiota GWAS (N = 18,340) was used as exposure. The FinnGen study GWAS (8,288 EMS cases and 68,969 controls) was used as outcome. We primarily used the inverse variance weighted (IVW) method to analyze the correlation and conducted a sensitivity analysis to verify its reliability.

Results

(1) MR analysis: The results of the IVW method confirmed that a total of 8 GM taxa were related to the risk of EMS. Class-Melainabacteria (p = 0.036), family-Ruminococcaceae (p = 0.037), and genus-Eubacteriumruminantium (p = 0.015) had a protective effect on EMS, whereas order-Bacillales (p = 0.046), family-Prevotellaceae (p = 0.027), genus-Anaerotruncus (p = 0.025), genus-Olsenella (p = 0.036) and genus-RuminococcaceaeUCG002 (p = 0.035) could increase the risk of EMS. (2) Sensitivity analysis: Cochrane's Q test (p > 0.05), MR-Egger intercept method (p > 0.05), and leave-one-out method confirmed the robustness of MR results.

Conclusion

This study performed a MR analysis on two large national databases and identified the association between 8 GM taxa and EMS. These taxa could potentially be utilized for indirectly diagnosing EMS and could lead to novel perspectives in research regarding the pathogenesis, diagnosis, and treatment of EMS.

The cause and effect of gut microbiota in development of inflammatory disorders of the breast

BACKGROUND

Inflammatory disorders of the breast (IDB) damages the interests of women and children and hinders the progress of global health seriously. Several studies had offered clues between gut microbiota (GM) and inflammatory disorders of the breast (IDB). The gut-mammary gland axis also implied a possible contribution of the GM to IDB. However, the causality between them is still elusive.

METHODS

The data of two-sample Mendelian randomization (MR) study related to the composition of GM (n = 18,340) and IDB (n = 177,446) were accessed from openly available genome-wide association studies (GWAS) database. As the major analytical method, inverse variance weighted (IVW) was introduced and several sensitive analytical methods were conducted to verify results.

RESULTS

Inverse variance weighted revealed Eubacterium rectale group (OR = 1.87, 95% CI: 1.02-3.43, p = 4.20E-02), Olsenella (OR = 1.29, 95% CI: 1.02-1.64, p = 3.30E-02), Ruminiclostridium-6 (OR = 1.53, 95% CI: 1.08-2.14, p = 1.60E-02) had an anti-protective effect on IDB. Peptococcus (OR = 0.75, 95% CI: 0.60-0.94, p = 1.30E-02) had a protective effect on IDB. The results were credible through a series of test.

CONCLUSIONS

We revealed causality between IDB and GM taxa, exactly including Ruminiclostridium-6, Eubacterium rectale group, Olsenella and Peptococcus. These genera may become novel biomarkers and supply new viewpoint for probiotic treatment. However, these findings warrant further test owing to the insufficient evidences.

Association between gut microbiota and primary ovarian insufficiency: a bidirectional two-sample Mendelian randomization study

Background

Recent studies have indicated a potential correlation between intestinal bacteria and primary ovarian insufficiency (POI). However, the causal relationship between the gut microbiota (GM) and POI remains unclear.

Methods

A bidirectional two-sample Mendelian randomization (MR) study was conducted to investigate the relationship between the GM and POI. Data on the GM were based on the MiBioGen consortium's summary statistics from the most comprehensive genome-wide association study meta-analysis to date (n=13,266), and POI data were obtained from the R8 release of the FinnGen consortium, containing a total of 424 cases and 181,796 controls. A variety of analytical methods, including inverse variance weighting, maximum likelihood, MR-Egger, weighted median, and constrained maximum likelihood and model averaging and Bayesian information criterion, were utilized to explore the connection between the GM and POI. The Cochran's Q statistics were used to evaluate the heterogeneity of instrumental variables. The MR-Egger and MR-pleiotropy residual sum and outlier (PRESSO) methods were used to identify the horizontal pleiotropy of instrumental variables. The MR Steiger test was used to evaluate the strength of causal relationships. A reverse MR study was performed to investigate the causal relationship between POI and the targeted GMs which were indicated to have a causal relationship with POI in the forward MR evaluation.

Results

The inverse variance weighted analysis indicated that Eubacterium (hallii group) (odds ratio [OR]=0.49, 95% confidence interval [CI]: 0.26-0.9, P=0.022) and Eubacterium (ventriosum group) (OR=0.51, 95% CI: 0.27-0.97, P=0.04) had protective effects on POI, and Intestinibacter (OR=1.82, 95% CI: 1.04-3.2, P=0.037) and Terrisporobacter (OR=2.47, 95% CI: 1.14-5.36, P=0.022) had detrimental effects on POI. Results of the reverse MR analysis indicated that POI had no significant influence on the four GMs. No significant heterogeneity or horizontal pleiotropy was observed in the performance of the instrumental variables.

Conclusion

This bidirectional two-sample MR study revealed a causal link between Eubacterium (hallii group), Eubacterium (ventriosum group), Intestinibacter, and Terrisporobacter and POI. Additional clinical trials are needed to gain a clearer understanding of the beneficial or detrimental effects of the GMs on POI and their mechanisms of action.

Causal associations between human gut microbiota and cholelithiasis: a mendelian randomization study

Background

There was some evidence that gut microbiota was closely related to cholelithiasis, but the causal relationship between them remained unclear. In this study, we try to use Two-sample Mendelian randomization (MR) to clarify the potential causal relationship between gut microbiota and cholelithiasis.

Methods

Summary Genome-Wide Association Studies (GWAS) statistical data for gut microbiota was obtained from MiBioGen, and the data of cholelithiasis was obtained from UK Biobank (UKB). Two-sample MR analyses were performed to assess causalities between gut microbiota and cholelithiasis mainly using the inverse-variance weighted (IVW) method. Sensitivity analyses were used to determine the robustness of the MR results. Reverse MR analyses were performed to examine the reverse causal association.

Results

Our research results, based primarily on the IVW method, support the existence of a causal relationship between nine gut microbial taxa and cholelithiasis. We observed a positive association between Genus Butyrivibrio (p=0.032), Genus Lachnospiraceae_UCG_001 (p=0.015), Genus Ruminococcaceae_NK4A214_group (p=0.003), Genus Ruminococcaceae_UCG_011 (p=0.010) and cholelithiasis, while Order Rhodospirillales (p=0.031), Genus Actinomyces (p=0.010), Genus Phascolarctobacterium (p=0.036), Genus Rikenellaceae_RC9_gutgroup (p=0.023), Genus Ruminococcaceae_UCG_013 (p=0.022) may be associated with a reduced risk of cholelithiasis. We did not find a reverse causal relationship between cholelithiasis and 9 specific gut microbial taxa.

Conclusions

This is the first mendelian randomization study to explore the causalities between specific gut microbiota taxa and cholelithiasis, which may provide new ideas and a theoretical basis for the prevention and treatment of cholelithiasis in the future.

Causal effects of gut microbiota on the risk of periodontitis: a two-sample Mendelian randomization study

Introduction

The oral cavity and the gut tract are interconnected, and both contain abundant natural microbiota. Gut microbiota may interact with oral flora and participate in the development of periodontitis. However, the specific role of certain gut microbiota taxa for periodontitis has not been investigated. Mendelian Randomization is an ideal method to explore causal relationships avoiding reverse causality and potential confounding factors. Thus, we conducted a two-sample Mendelian Randomization study to comprehensively reveal the potential genetic causal effect of gut microbiota on periodontitis.

Methods

SNPs strongly associated with 196 gut microbiota taxa (18,340 individuals) were selected as instrument variables, and periodontitis (17,353 periodontitis cases and 28,210 controls) was used as the outcome. The causal effect was analyzed via random effect inverse variance-weighted, weighted median, and MR-Egger. The sensitivity analyses were conducted using Cochran's Q tests, funnel plots, leave-one-out analyses, and MR-Egger intercept tests.

Results

Nine gut microbiota taxa (Prevotella 7, Lachnospiraceae UCG-008, Enterobacteriales, Pasteurellales, Enterobacteriaceae, Pasteurellaceae, Bacteroidales S24.7 group, Alistipes, and Eisenbergiella) are predicted to play a causal role in enhancing the risk of periodontitis (p< 0.05). Besides, two gut microbiota taxa (Butyricicoccus and Ruminiclostridium 6) have potentially inhibitive causal effects on the risk of periodontitis (p< 0.05). No significant estimation of heterogeneity or pleiotropy is detected.

Conclusion

Our study demonstrates the genetic causal effect of 196 gut microbiota taxa on periodontitis and provides guidance for the clinical intervention of periodontitis.

Young adults with major depression show altered microbiome

There is growing basic and clinical evidence that major depressive disorder (MDD) is associated with gut microbiome alterations, but clinical studies have tended not to adjust for confounding factors. And few studies on the gut microbiome focused on young adults with MDD. Here we performed a pilot study to compare the gut microbiome of young adults with MDD with healthy controls. Shotgun metagenomic sequencing was performed on stool samples obtained from 40 young adults with MDD and 42 healthy controls. After controlling for confounding factors including sex, age, BMI, alcohol or cigarette consumption, bowel movement quality, exercise or defecation frequency, we compared microbiome diversity between groups, identified differentially abundant taxa, and further compared functional differences through gut-brain and gut-metabolic module analysis. There were no significant differences in overall gut microbiome structure and function in young adults with MDD compared with controls. Abundance of Sutterellaceae and species belonging to Clostridium, Eubacterium, and Ruminococcus were significantly different between groups. The cysteine degradation I pathway was increased in MDD. After controlling for most confounding factors, this pilot study provides new evidence on the specific, often subtle gut dysbiosis affecting young adults with depression.

Exploration of the Gut Microbiome in Thai Patients with Major Depressive Disorder Shows a Specific Bacterial Profile with Depletion of the Ruminococcus Genus as a Putative Biomarker

Maes et al. (2008) published the first paper demonstrating that major depressive disorder (MDD) is accompanied by abnormalities in the microbiota-gut-brain axis, as evidenced by elevated serum IgM/IgA to lipopolysaccharides (LPS) of Gram-negative bacteria, such as Morganella morganii and Klebsiella Pneumoniae. The latter aberrations, which point to increased gut permeability (leaky gut), are linked to activated neuro-immune and oxidative pathways in MDD. To delineate the profile and composition of the gut microbiome in Thai patients with MDD, we examined fecal samples of 32 MDD patients and 37 controls using 16S rDNA sequencing, analyzed α- (Chao1 and Shannon indices) and β-diversity (Bray-Curtis dissimilarity), and conducted linear discriminant analysis (LDA) effect size (LEfSe) analysis. Neither α- nor β-diversity differed significantly between MDD and controls. Rhodospirillaceae, Hungatella, Clostridium bolteae, Hungatella hathewayi, and Clostridium propionicum were significantly enriched in MDD, while Gracillibacteraceae family, Lutispora, and Ruminococcus genus, Ruminococcus callidus, Desulfovibrio piger, Coprococcus comes, and Gemmiger were enriched in controls. Contradictory results have been reported for all these taxa, with the exception of Ruminococcus, which is depleted in six different MDD studies (one study showed increased abundance), many medical disorders that show comorbidities with MDD, and animal MDD models. Our results may suggest a specific profile of compositional gut dysbiosis in Thai MDD patients, with increases in some pathobionts and depletion of some beneficial microbiota. The results suggest that depletion of Ruminococcus may be a more universal biomarker of MDD that may contribute to increased enteral LPS load, LPS translocation, and gut-brain axis abnormalities.

Different roles of microbiota and genetics in the prediction of treatment response in major depressive disorder

The roles of gut microbiota and susceptibility genes in patients with major depression disorder (MDD) are not well understood. Examining the microbiome and host genetics might be helpful for clinical decision-making. Patients with MDD were recruited in this study and subsequently treated for eight weeks. We identified the differences between the population with a response after two weeks and those with a response after eight weeks. The factors that were significantly correlated with efficacy were used to predict the treatment response. The differences in the importance of microbiota and genetics in prediction were analyzed. Our study identified rs58010457 as a potentially key locus affecting the treatment effect. Different microbiota and enriched pathways might play different roles in the response after two and eight weeks. We found that the area under the curve (AUC) value was greater than 0.8 for both random forest models. The contribution of different components to the AUC was evaluated by removing genetic information, microbiota abundance, and pathway data. The gut microbiome was an important predictor of the response after eight weeks, while genetics was an important predictor of the response after two weeks. These results suggested a dynamic effect of interaction among genetics and gut microbes on treatment. Furthermore, these results provide new guidance for clinical decisions: in cases of inadequate treatment effects after two weeks, the composition of the intestinal flora can be improved by diet therapy, which could ultimately affect the efficacy.

Antioxidant and Anti-Inflammatory Effects of Carotenoids in Mood Disorders: An Overview

Depression has a multifactorial etiology comprising family history and unemployment. This review aims to summarize the evidence available for the antioxidant and anti-inflammatory effects of carotenoids in mood disorders. This review article’s methodologies were based on a search of the PubMed database for all linked published papers. Epidemiological studies indicate that a diet rich in vegetables, fruits, nuts, fish, and olive oil may prevent the development of depression. Antioxidant supplementation has been found to combat various stress-induced psychiatric disorders, including depression and anxiety. A growing body of evidence indicates that carotenoids have both antioxidant and anti-inflammatory. Studies also suggest that poor dietary intake, particularly low intakes of fruit and vegetables and high intakes of fast food and other convenience foods, may increase the risk of developing depression. Thus, dietary interventions have the potential to help mitigate the risk of mental health decline in both the general population and those with mood disorders. Considering that carotenoids have both antioxidant and anti-inflammatory effects, it is expected that they might exert a promising antidepressant effect. Nevertheless, further studies (including interventional and mechanistic studies) assessing the effect of carotenoids on preventing and alleviating depression symptoms are needed.

The gut microbiota links disease to human genome evolution

A large number of studies have established a causal relationship between the gut microbiota and human disease. In addition, the composition of the microbiota is substantially influenced by the human genome. Modern medical research has confirmed that the pathogenesis of various diseases is closely related to evolutionary events in the human genome. Specific regions of the human genome known as human accelerated regions (HARs) have evolved rapidly over several million years since humans diverged from a common ancestor with chimpanzees, and HARs have been found to be involved in some human-specific diseases. Furthermore, the HAR-regulated gut microbiota has undergone rapid changes during human evolution. We propose that the gut microbiota may serve as an important mediator linking diseases to human genome evolution.

The relationship between major depression and migraine: A bidirectional two-sample Mendelian randomization study

Background

Previous epidemiological and other studies have shown an association between major depressive disorder (MDD) and migraine. However, the causal relationship between them remains unclear. Therefore, this study aimed to investigate the causal relationship between MDD and migraine using a bidirectional, two-sample Mendelian randomization (MR) approach.

Methods

Data on MDD and migraine, including subtypes with aura migraine (MA) and without aura migraine (MO), were gathered from a publicly available genome-wide association study (GWAS). Single nucleotide polymorphisms (SNPs) utilized as instrumental variables (IVs) were then screened by adjusting the intensity of the connection and removing linkage disequilibrium. To explore causal effects, inverse variance weighting (IVW) was used as the primary analysis method, with weighted median, MR-Egger, simple mode, and weighted mode used as supplementary analytic methods. Furthermore, heterogeneity and pleiotropy tests were carried out. Cochran's Q-test with IVW and MR-Egger was used to assess heterogeneity. Pleiotropy testing was carried out using the MR-Egger intercept and MR-PRESSO analysis methods. A leave-one-out analysis was also used to evaluate the stability of the findings. Finally, we used migraine (MA and MO) levels to deduce reverse causality with MDD risk.

Results

Random effects IVW results were (MDD-Migraine: odds ratio (OR), 1.606, 95% confidence interval (CI), 1.324-1.949, p = 1.52E-06; MDD-MA: OR, 1.400, 95%CI, 1.067-1.8378, p = 0.015; MDD-MO: OR, 1.814, 95%CI, 1.277-2.578, p = 0.0008), indicating a causal relationship between MDD levels and increased risk of migraine (including MA and MO). In the inverse MR analysis, the findings were all negative, while in sensitivity analyses, the results were robust except for the study of MA with MDD.

Conclusion

Our study confirms a causal relationship between MDD levels and increased risk of migraine, MA, and MO. There was little evidence in the reverse MR analysis to suggest a causal genetic relationship between migraine (MA and MO) and MDD risk levels.

Circulating metabolites and depression: a bidirectional Mendelian randomization

Background

Studies have shown an association between depression and circulating metabolites, but the causal relationship between them has not been elucidated. The purpose of this study was to elucidate the causal relationship between circulating metabolites and depression and to explore the role of circulating metabolites in depression.

Methods

In this study, the top single-nucleotide polymorphisms (SNPs) associated with circulating metabolites (n = 24,925) and depression (n = 322,580) were obtained based on the publicly available genome-wide association study using two-sample Mendelian randomization (MR). SNP estimates were summarized through inverse variance weighted, MR Egger, weighted median, MR pleiotropy residual sum and outlier, and "leave-one-out" methods.

Results

Apolipoprotein A-I (OR 0.990, 95% CI 981-0.999) and glutamine (OR 0.985, 95% CI 0.972-0.997) had protective causal effects on depression, whereas acetoacetate (OR 1.021, 95% CI 1.009-1.034), glycoproteins (OR 1.005, 95% CI 1.000-1.009), isoleucine (OR 1.013, 95% CI 1.002-1.024), and urea (OR 1.020, 95% CI 1.000-1.039) had an anti-protective effect on depression. Reversed MR showed no effect of depression on the seven circulating metabolites.

Conclusion

In this study, MR analysis showed that apolipoprotein A-I and glutamine had a protective effect on depression, and acetoacetate, glycoprotein, isoleucine, glucose, and urea may be risk factors for depression. Therefore, further research must be conducted to translate the findings into practice.