A two-sample mendelian randomization analysis investigates associations between gut microbiota and infertility

Bidirectional Mendelian randomization to explore the causal relationships between the gut microbiota and male reproductive diseases

Gut bacteria might play an important role in male reproductive disorders, such as male infertility and sperm abnormalities; however, their causal role is unclear. Herein, Mendelian randomization (MR)-Egger, weighted median, inverse variance weighting, Simple mode, and Weighted mode were used to test the causal relationship between gut microbes and male reproductive diseases. The MR results were validated using various metrics. The MR results were also consolidated using reverse causality speculation, conducted using two-way MR analysis and Steiger filtering. Biological function was analysed using enrichment analyses. The results suggested that eight intestinal microflorae were causally associated with male infertility. The Eubacterium oxidoreducens group was associated with an increased risk of male infertility, while the family Bacteroidaceae was negatively associated with male reproductive diseases. Eight intestinal microflorae were causally associated with abnormal spermatozoa. The family Streptococcaceae was associated with a high risk of abnormal spermatozoa, whereas the family Porphyromonadaceae was associated with a low risk of abnormal spermatozoa. No pleiotropy was observed, this study identified a high correlation between the gut flora and the likelihood of male reproductive diseases. Future research will attempt to advance microbial-focused treatments for such diseases.

Inflammatory cytokines may mediate the causal relationship between gut microbiota and male infertility: a bidirectional, mediating, multivariate Mendelian randomization study

Introduction

Studies have shown that the gut microbiota is associated with male infertility (MI). However, their causal relationship and potential mediators need more evidence to prove. We aimed to investigate the causal relationship between the gut microbiome and MI and the potential mediating role of inflammatory cytokines from a genetic perspective through a Mendelian randomization approach.

Methods

This study used data from genome-wide association studies of gut microbes (Mibiogen, n = 18, 340), inflammatory cytokines (NFBC1966, FYPCRS, FINRISK 1997 and 2002, n=13, 365), and male infertility (Finngen, n=120, 706) to perform two-way Mendelian randomization (MR), mediated MR, and multivariate MR(MVMR) analyses. In this study, the inverse variance weighting method was used as the primary analysis method, and other methods were used as supplementary analysis methods.

Results

In the present study, two gut microbes and two inflammatory cytokines were found to have a potential causal relationship with MI. Of the two gut microorganisms causally associated with male infertility, Anaerotruncus increased the risk of male infertility (odds ratio = 1.81, 95% confidence interval = 1.18-2.77, P = 0.0062), and Bacteroides decreased the risk of male infertility (odds ratio = 0.57, 95% confidence interval = 0.33-0.96, P = 0.0363). In addition, of the two inflammatory cytokines identified, hepatocyte growth factor(HGF) reduced the risk of male infertility (odds ratio = 0.50, 95% confidence interval = 0.35-0.71, P = 0.0001), Monocyte chemotactic protein 3 (MCP-3) increased the risk of male infertility (odds ratio = 1.28, 95% confidence interval = 1.03-1.61, P = 0.0039). Mediated MR analysis showed that HGF mediated the causal effect of Bacteroides on MI (mediated percentage 38.9%). Multivariate MR analyses suggest that HGF may be one of the pathways through which Bacteroides affects MI, with other unexplored pathways.

Conclusion

The present study suggests a causal relationship between specific gut microbiota, inflammatory cytokines, and MI. In addition, HGF may mediate the relationship between Bacteroides and MI.

The Potential Harmful Effects of Genetically Engineered Microorganisms (GEMs) on the Intestinal Microbiome and Public Health

Gut luminal dysbiosis and pathobiosis result in compositional and biodiversified alterations in the microbial and host co-metabolites. The primary mechanism of bacterial evolution is horizontal gene transfer (HGT), and the acquisition of new traits can be achieved through the exchange of mobile genetic elements (MGEs). Introducing genetically engineered microbes (GEMs) might break the harmonized balance in the intestinal compartment. The present objectives are: 1. To reveal the role played by the GEMs' horizontal gene transfers in changing the landscape of the enteric microbiome eubiosis 2. To expand on the potential detrimental effects of those changes on the human genome and health. A search of articles published in PubMed/MEDLINE, EMBASE, and Scielo from 2000 to August 2023 using appropriate MeSH entry terms was performed. The GEMs' horizontal gene exchanges might induce multiple human diseases. The new GEMs can change the long-term natural evolution of the enteric pro- or eukaryotic cell inhabitants. The worldwide regulatory authority's safety control of GEMs is not enough to protect public health. Viability, biocontainment, and many other aspects are only partially controlled and harmful consequences for public health should be avoided. It is important to remember that prevention is the most cost-effective strategy and primum non nocere should be the focus.

Genetic support of the causal association between gut microbiota and peripheral artery disease: a bidirectional Mendelian randomization study

BACKGROUND

The causal relationship between gut microbiota and peripheral artery disease (PAD) is still not clear. In this research, we employed the Mendelian randomization (MR) technique to explore the potential causal connection between 211 gut microbiota species and PAD. We also investigated whether the causal effects operate in both directions.

METHODS

We used Genome-wide Association Studies (GWAS) summary statistics data from the MiBioGen and FinnGen consortia to conduct a two-sample MR analysis to explore the causal link between gut microbiota and PAD. Sensitivity analysis is conducted to assess the robustness of the MR results. In addition to that, reverse MR analysis was performed to examine the inverse causal relationship.

RESULTS

The inverse variance weighted (IVW) method provided evidence supporting a causal relationship between 9 specific gut microbiota taxa and PAD. The study findings indicated that family Family XI (OR=1.11, CI 1.00-1.24, P=0.048), genus Lachnoclostridium (OR=1.24, 1.02-1.50, P=0.033), and genus Lachnospiraceae UCG001 (OR=1.17, 1.01-1.35, P=0.031) are risk factors associated with PAD. class Actinobacteria (OR=0.84, 0.72-0.99, P=0.034), family Acidaminococcaceae (OR=0.80, 0.66-0.98, P=0.029), genus Coprococcus2 (OR=0.79, 0.64-0.98, P=0.029), genus Ruminococcaceae UCG004 (OR=0.84, 0.72-0.99, P=0.032), genus Ruminococcaceae UCG010 (OR=0.74, 0.58-0.96, P=0.022), and order NB1n (OR=0.88, 0.79-0.98, P=0.02) may be associated with the risk factors of PAD. Moreover, our analysis did not uncover any evidence of a reverse causal relationship between PAD and the nine specific gut microbiota taxa investigated.

CONCLUSIONS

Our MR research has confirmed the potential causal relationship between gut microbiota and PAD while also identifying specific gut bacterial communities associated with PAD.