Identification of bidirectional causal links between gut microbiota and narcolepsy type 1 using Mendelian randomization

Roles of cerebrospinal fluid metabolites in mediating the relationship between cathepsins and narcolepsy type 1: A comprehensive Mendelian randomization analysis

INTRODUCTION

To investigate the potential causal relationship between cathepsins and Narcolepsy Type 1 (NT1), along with the mediating influence of cerebrospinal fluid metabolites.

METHOD

We performed a comprehensive Mendelian randomization (MR) analysis using genome-wide association studies (GWAS) data. Data on nine plasma cathepsins and 338 cerebrospinal fluid metabolites were sourced from the IEU OpenGWAS database, and NT1 were obtained from the FinnGen consortium's R10 release. Univariate MR (UVMR), multivariate MR (MVMR) and gene co-localization analyses were used to explore the potential causal relationship between cathepsins and NT1. In addition, mediation analyses were performed to explore the role of cerebrospinal fluid metabolites in mediating the relationship.

RESULT

In UVMR study, we identified a significant positive association between genetically elevated levels of plasma cathepsin B (OR = 2.022, 95 % CI: 1.456-2.809, p < 0.01) and cathepsin F (OR = 0.676, 95 % CI: 0.473-0.966, p = 0.031) with NT1. However, in the MVMR analysis, only cathepsin B maintained a consistent effect (OR = 1.920, 95 % CI: 1.378-2.675, p < 0.001). Subsequent co-localization analysis indicated shared causal variants between cathepsin B and NT1, further highlighting the robustness of our findings. Additionally, mediation MR revealed that the association between cathepsin B and NT1 was mediated by sphingomyelin and 1-(1-alkenyl-palmitoyl1)-2-propenoyl-gpc, accounting for 2.6 % and 4.7 % of the effect, respectively.

CONCLUSION

Our findings suggest a probable causal relationship between increased cathepsin B levels and NT1, with the potential of cerebrospinal fluid fatty acid metabolism disorder playing a mediating role in the development of this association. This indicates the potential of cathepsin B as a promising biomarker for NT1, highlighting significant implications for the diagnosis and treatment of this condition.

Appraising the Effects of Gut Microbiota on Insomnia Risk Through Genetic Causal Analysis

BackgroundInsomnia is a common neurological disorder that exhibits connections with the gut microbiota; however, the exact causal relationship remains unclear. MethodsWe conducted a Mendelian randomization (MR) study to systematically evaluate the causal effects of genus-level gut microbiota on insomnia risk in individuals of European ancestry. Summary-level datasets on gut microbiota were sourced from the genome-wide association study (GWAS) of MiBioGen, while datasets on insomnia were obtained from the GWAS of Neale Lab and FinnGen. The primary analytical approach used was the inverse-variance weighted (IVW) method, supplemented by MR-Egger, maximum likelihood, MR-robust adjusted profile score, and weighted median. Sensitivity analyses were conducted to ensure robustness. ResultsThe microbial taxa Enterorhabdus, Family XIII AD3011 group, Paraprevotella, and Lachnospiraceae UCG004 were associated with an increased risk of insomnia, whereas Coprococcus1, Coprobacter, Desulfovibrio, Flavonifractor, Olsenella, Odoribacter, and Oscillibacter were linked to a decreased risk. Regarding the insomnia phenotype characterized by trouble falling asleep, the microbial taxon Eisenbergiella was correlated with an increased risk, while Haemophilus and the Eubacterium brachy group were associated with a reduced risk. Furthermore, for the insomnia phenotype characterized by waking too early, the microbial taxa Family XIII UCG001, Lachnospiraceae FCS020 group, and Olsenella were linked to an increased risk, whereas the Eubacterium brachy group and Victivallis were associated with a lower risk. The results remained robust across all sensitivity analyses. ConclusionOur MR study identified multiple genus-level gut microbial taxa that may exhibit potential causal effects on insomnia from a genetic perspective. These findings provide evidence supporting the theory of the microbiota-gut-brain axis and offer new insights into potential prevention and therapeutic targets for insomnia.

Effect of probiotic supplementation combined with bismuth-containing quadruple therapy on gut microbiota during Helicobacter pylori eradication: a randomized, double-blind, placebo-controlled trial

Background

Helicobacter pylori (H. pylori) eradication has been reported to affect gut microbiota distribution. This study aimed to evaluate the effect of probiotic supplementation on the gastrointestinal microbiota during eradication and the efficacy of bismuth-containing quadruple therapy.

Methods

One hundred treatment-naïve H. pylori-positive patients were randomly assigned 1:1 to receive 14-day bismuth-containing quadruple therapy (esomeprazole, bismuth, amoxicillin, and clarithromycin) combined with the probiotic (Bifidobacterium animalism subsp. lactis BLa80) or placebo. The Gastrointestinal Symptom Rating Scale (GSRS) was completed before and after treatment. Stool samples were collected for 16S rRNA gene sequencing at weeks 0, 2, and 10.

Results

No significant difference in the eradication rate was observed between the two groups. The incidence of adverse events, especially nausea (p = 0.029), was lower in the probiotic group. After treatment, the GSRS score decreased significantly in the probiotic group (p = 0.039). The gut microbiota underwent considerable changes immediately following eradication treatment, predominantly characterized by an increase in Proteobacteria at the expense of commensal Firmicutes and Bacteroidota, but gradually returned to baseline after eight weeks. By week 10, beneficial genera such as Lachnoclostridium, Parasutterella, Hungatella, and Akkermansia were notably enriched in the probiotic group. Additionally, the correlation networks in the probiotic group were closer to their initial levels at week 10 compared to the placebo group.

Conclusion

Disturbances in the gut microbiota following H. pylori treatment appeared to be temporary, and probiotic supplementation could mitigate antibiotic-induced alterations in the gut microbiota. This study also provided evidence supporting the effectiveness of probiotics in alleviating gastrointestinal symptoms.

Possible roles of neuropeptide/transmitter and autoantibody modulation in emotional problems and aggression

The theoretical foundations of understanding psychiatric disorders are undergoing changes. Explaining behaviour and neuroendocrine cell communication leaning towards immunology represents a different approach compared to previous models for understanding complex central nervous system processes. One such approach is the study of immunoglobulins or autoantibodies, and their effect on peptide hormones in the neuro-endocrine system. In the present review, we provide an overview of the literature on neuropeptide/transmitter and autoantibody modulation in psychiatric disorders featuring emotional problems and aggression, including associated illness behaviour. Finally, we discuss the role of psycho-immunology as a growing field in the understanding of psychiatric disorders, and that modulation and regulation by IgG autoAbs represent a relatively new subcategory in psycho-immunology, where studies are currently being conducted.

Gut microbiota and sleep: Interaction mechanisms and therapeutic prospects

Sleep is crucial for wellness, and emerging research reveals a profound connection to gut microbiota. This review explores the bidirectional relationship between gut microbiota and sleep, exploring the mechanisms involved and the therapeutic opportunities it presents. The gut-brain axis serves as a conduit for the crosstalk between gut microbiota and the central nervous system, with dysbiosis in the microbiota impairing sleep quality and vice versa. Diet, circadian rhythms, and immune modulation all play a part. Specific gut bacteria, like Lactobacillus and Bifidobacterium, enhance sleep through serotonin and gamma-aminobutyric acid production, exemplifying direct microbiome influence. Conversely, sleep deprivation reduces beneficial bacteria, exacerbating dysbiosis. Probiotics, prebiotics, postbiotics, and fecal transplants show therapeutic potential, backed by animal and human research, yet require further study on safety and long-term effects. Unraveling this intricate link paves the way for tailored sleep therapies, utilizing microbiome manipulation to improve sleep and health. Accelerated research is essential to fully tap into this promising field for sleep disorder management.

Anorexia nervosa and bulimia nervosa: a Mendelian randomization study of gut microbiota

Background

Anorexia nervosa (AN) and bulimia nervosa (BN) poses a significant challenge to global public health. Despite extensive research, conclusive evidence regarding the association between gut microbes and the risk of AN and BN remains elusive. Mendelian randomization (MR) methods offer a promising avenue for elucidating potential causal relationships.

Materials and methods

Genome-wide association studies (GWAS) datasets of AN and BN were retrieved from the OpenGWAS database for analysis. Independent single nucleotide polymorphisms closely associated with 196 gut bacterial taxa from the MiBioGen consortium were identified as instrumental variables. MR analysis was conducted utilizing R software, with outlier exclusion performed using the MR-PRESSO method. Causal effect estimation was undertaken employing four methods, including Inverse variance weighted. Sensitivity analysis, heterogeneity analysis, horizontal multivariate analysis, and assessment of causal directionality were carried out to assess the robustness of the findings.

Results

A total of 196 bacterial taxa spanning six taxonomic levels were subjected to analysis. Nine taxa demonstrating potential causal relationships with AN were identified. Among these, five taxa, including Peptostreptococcaceae, were implicated as exerting a causal effect on AN risk, while four taxa, including Gammaproteobacteria, were associated with a reduced risk of AN. Similarly, nine taxa exhibiting potential causal relationships with BN were identified. Of these, six taxa, including Clostridiales, were identified as risk factors for increased BN risk, while three taxa, including Oxalobacteraceae, were deemed protective factors. Lachnospiraceae emerged as a common influence on both AN and BN, albeit with opposing effects. No evidence of heterogeneity or horizontal pleiotropy was detected for significant estimates.

Conclusion

Through MR analysis, we revealed the potential causal role of 18 intestinal bacterial taxa in AN and BN, including Lachnospiraceae. It provides new insights into the mechanistic basis and intervention targets of gut microbiota-mediated AN and BN.