Causality of gut microbiome and hypertension: A bidirectional mendelian randomization study

Two cosmoses, one universe: a narrative review exploring the gut microbiome's role in the effect of urban risk factors on vascular ageing

In the face of rising global urbanisation, understanding how the associated environment and lifestyle impact public health is a cornerstone for prevention, research, and clinical practice. Cardiovascular disease is the leading cause of morbidity and mortality worldwide, with urban risk factors contributing greatly to its burden. The current narrative review adopts an exposome approach to explore the effect of urban-associated physical-chemical factors (such as air pollution) and lifestyle on cardiovascular health and ageing. In addition, we provide new insights into how these urban-related factors alter the gut microbiome, which has been associated with an increased risk of cardiovascular disease. We focus on vascular ageing, before disease onset, to promote preventative research and practice. We also discuss how urban ecosystems and social factors may interact with these pathways and provide suggestions for future research, precision prevention and management of vascular ageing. Most importantly, future research and decision-making would benefit from adopting an exposome approach and acknowledging the diverse and boundless universe of the microbiome.

Genetically proxied intestinal microbiota and risk of erectile dysfunction

BACKGROUND

The interaction between intestinal microbiota and erectile dysfunction (ED) is less investigated. This study was performed to explore the association between intestinal microbiota and ED.

METHODS

In this two-sample Mendelian randomization (MR) study, genetic variants of gut microbiota were obtained from MiBioGen consortium containing 18,340 individuals. Six methods including inverse variance weighting (IVW), MR-Egger, weighted median, maximum likelihood, MR robust adjusted profile score, and MR pleiotropy residual sum and outlier were used to investigate the causal links between intestinal microbiota and ED. Furthermore, reverse MR analysis was performed to exclude the causal impact of ED on gut microbiota.

RESULTS

As revealed by the IVW estimator, the risks of ED were raised by genetically proxied Lachnospiraceae (OR: 1.27), Lachnospiraceae NC2004 group (OR: 1.17), Oscillibacter (OR: 1.20), Senegalimassilia (OR: 1.32) (All P < 0.05) and Tyzzerella-3 (OR: 1.14, P < 0.05). It was observed that Ruminococcaceae UCG013 exerted protective effect against ED (OR: 0.77, P < 0.05). These results were consistent with other estimators in sensitivity analyses. In reverse MR analyses, genetic liability to ED did not alter the abundances of Lachnospiraceae, Lachnospiraceae NC2004 group, Oscillibacter, Senegalimassilia, Tyzzerella-3, and Ruminococcaceae UCG013 (All P > 0.05). No heterogeneity and pleiotropy were detected by Cochran's Q-test, MR-Egger, and global test (All P > 0.05).

CONCLUSIONS

This study provided novel evidence that genetically proxied Lachnospiraceae, Lachnospiraceae NC2004 group, Oscillibacter, Senegalimassilia, Tyzzerella-3, and Ruminococcaceae UCG013 had potentially causal effects on ED. Further studies are needed to clarify the biological mechanisms linking intestinal microbiota to ED.

Association between hypertension and pressure ulcer: A systematic review and meta-analysis

This review aims to systematically evaluate the association between hypertension and pressure ulcer (PU). PubMed, Embase, Web of Science, and Cochrane Library were searched for studies from their inception until September 12, 2023. Literature search, data extraction, and quality assessment were conducted independently by two researchers. The random-effects model was used to calculate the combined odds ratio (OR) and corresponding 95% confidence interval (CI) of hypertension in patients with PU; subgroup analyses were performed to explore the source of between-study heterogeneity; sensitivity analysis was used to test the robust of the combined result; and funnel plot and Egger's test were used to assess the publication bias. Finally, a total of 19 studies with 564 716 subjects were included; the overall pooled result showed no significant association between hypertension and risk of developing PU (OR = 1.15, 95% CI = 0.90-1.47, p = 0.27); and the sensitivity analysis and publication bias analysis showed robust of the combined result. Subgroup analysis indicated a significant association between hypertension and PU when the primary disease was COVID-19 (OR = 1.73, 95% CI = 1.35-2.22, p < 0.0001). No association between hypertension and PU was seen in subgroup analysis on the patient source and study design. In sum, there is no significantly statistical association between hypertension and the occurrence of PU in most cases, while the risk of PU significantly elevates among COVID-19 patients combined with hypertension regardless of patient source and study design.

Assessment of the causal relationship between gut microbiota and cardiovascular diseases: a bidirectional Mendelian randomization analysis

BACKGROUND

Previous studies have shown an association between gut microbiota and cardiovascular diseases (CVDs). However, the underlying causal relationship remains unclear. This study aims to elucidate the causal relationship between gut microbiota and CVDs and to explore the pathogenic role of gut microbiota in CVDs.

METHODS

In this two-sample Mendelian randomization study, we used genetic instruments from publicly available genome-wide association studies, including single-nucleotide polymorphisms (SNPs) associated with gut microbiota (n = 14,306) and CVDs (n = 2,207,591). We employed multiple statistical analysis methods, including inverse variance weighting, MR Egger, weighted median, MR pleiotropic residuals and outliers, and the leave-one-out method, to estimate the causal relationship between gut microbiota and CVDs. Additionally, we conducted multiple analyses to assess horizontal pleiotropy and heterogeneity.

RESULTS

GWAS summary data were available from a pooled sample of 2,221,897 adult and adolescent participants. Our findings indicated that specific gut microbiota had either protective or detrimental effects on CVDs. Notably, Howardella (OR = 0.955, 95% CI: 0.913-0.999, P = .05), Intestinibacter (OR = 0.908, 95% CI:0.831-0.993, P = .03), Lachnospiraceae (NK4A136 group) (OR = 0.904, 95% CI:0.841-0.973, P = .007), Turicibacter (OR = 0.904, 95% CI: 0.838-0.976, P = .01), Holdemania (OR, 0.898; 95% CI: 0.810-0.995, P = .04) and Odoribacter (OR, 0.835; 95% CI: 0.710-0.993, P = .04) exhibited a protective causal effect on atrial fibrillation, while other microbiota had adverse causal effects. Similar effects were observed with respect to coronary artery disease, myocardial infarction, ischemic stroke, and hypertension. Furthermore, reversed Mendelian randomization analyses revealed that atrial fibrillation and ischemic stroke had causal effects on certain gut microbiotas.

CONCLUSION

Our study underscored the importance of gut microbiota in the context of CVDs and lent support to the hypothesis that increasing the abundance of probiotics or decreasing the abundance of harmful bacterial populations may offer protection against specific CVDs. Nevertheless, further research is essential to translate these findings into clinical practice.

Genetically predicted causality between gut microbiota, blood metabolites, and intracerebral hemorrhage: a bidirectional Mendelian randomization study

Background

Recent research linked changes in the gut microbiota and serum metabolite concentrations to intracerebral hemorrhage (ICH). However, the potential causal relationship remained unclear. Therefore, the current study aims to estimate the effects of genetically predicted causality between gut microbiota, serum metabolites, and ICH.

Methods

Summary data from genome-wide association studies (GWAS) of gut microbiota, serum metabolites, and ICH were obtained separately. Gut microbiota GWAS (N = 18,340) were acquired from the MiBioGen study, serum metabolites GWAS (N = 7,824) from the TwinsUK and KORA studies, and GWAS summary-level data for ICH from the FinnGen R9 (ICH, 3,749 cases; 339,914 controls). A two-sample Mendelian randomization (MR) study was conducted to explore the causal effects between gut microbiota, serum metabolites, and ICH. The random-effects inverse variance-weighted (IVW) MR analyses were performed as the primary results, together with a series of sensitivity analyses to assess the robustness of the results. Besides, a reverse MR was conducted to evaluate the possibility of reverse causation. To validate the relevant findings, we further selected data from the UK Biobank for analysis.

Results

MR analysis results revealed a nominal association (p < 0.05) between 17 gut microbial taxa, 31 serum metabolites, and ICH. Among gut microbiota, the higher level of genus Eubacterium xylanophilum (odds ratio (OR): 1.327, 95% confidence interval (CI):1.154-1.526; Bonferroni-corrected p = 7.28 × 10-5) retained a strong causal relationship with a higher risk of ICH after the Bonferroni corrected test. Concurrently, the genus Senegalimassilia (OR: 0.843, 95% CI: 0.778-0.915; Bonferroni-corrected p = 4.10 × 10-5) was associated with lower ICH risk. Moreover, after Bonferroni correction, only two serum metabolites remained out of the initial 31 serum metabolites. One of the serum metabolites, Isovalerate (OR: 7.130, 95% CI: 2.648-19.199; Bonferroni-corrected p = 1.01 × 10-4) showed a very strong causal relationship with a higher risk of ICH, whereas the other metabolite was unidentified and excluded from further analysis. Various sensitivity analyses yielded similar results, with no heterogeneity or directional pleiotropy observed.

Conclusion

This two-sample MR study revealed the significant influence of gut microbiota and serum metabolites on the risk of ICH. The specific bacterial taxa and metabolites engaged in ICH development were identified. Further research is required in the future to delve deeper into the mechanisms behind these findings.

Putative causal relations among gut flora, serums metabolites and arrhythmia: a Mendelian randomization study

BACKGROUND

The pathogenesis of cardiac arrhythmias is multifaceted, encompassing genetic, environmental, hemodynamic, and various causative factors. Emerging evidence underscores a plausible connection between gut flora, serum metabolites, and specific types of arrhythmias. Recognizing the role of host genetics in shaping the microbiota, we employed two-sample Mendelian randomization analyses to investigate potential causal associations between gut flora, serum metabolites, and distinct arrhythmias.

METHODS

Mendelian randomization methods were deployed to ascertain causal relationships between 211 gut flora, 575 serum metabolites, and various types of arrhythmias. To ensure the reliability of the findings, five complementary Mendelian randomization methods, including inverse variance weighting methods, were employed. The robustness of the results was scrutinized through a battery of sensitivity analyses, incorporating the Cochran Q test, leave-one-out test, and MR-Egger intercept analysis.

RESULTS

Eighteen gut flora and twenty-six serum metabolites demonstrated associations with the risk of developing atrial fibrillation. Moreover, ten gut flora and fifty-two serum metabolites were linked to the risk of developing supraventricular tachycardia, while eight gut flora and twenty-five serum metabolites were associated with the risk of developing tachycardia. Additionally, six gut flora and twenty-one serum metabolites exhibited associations with the risk of developing bradycardia.

CONCLUSION

This study revealed the potential causal relationship that may exist between gut flora, serum metabolites and different cardiac arrhythmias and highlights the need for further exploration. This study provides new perspectives to enhance diagnostic and therapeutic strategies in the field of cardiac arrhythmias.

Causal effect between gut microbiota and pancreatic cancer: a two-sample Mendelian randomization study

BACKGROUND

Gut microbiota (GM) comprises a vast and diverse community of microorganisms, and recent studies have highlighted the crucial regulatory roles of various GM and their secreted metabolites in pancreatic cancer (PC). However, the causal relationship between GM and PC has yet to be confirmed.

METHODS

In the present study, we used two-sample Mendelian randomization (MR) analysis to investigate the causal effect between GM and PC, with genome-wide association study (GWAS) from MiBioGen consortium as an exposure factor and PC GWAS data from FinnGen as an outcome factor. Inverse variance weighted (IVW) was used as the primary method for this study.

RESULTS

At the genus level, we observed that Senegalimassilia (OR: 0.635, 95% CI: 0.403-0.998, P = 0.049) exhibited a protective effect against PC, while Odoribacter (OR:1.899, 95%CI:1.157-3.116, P = 0.011), Ruminiclostridium 9(OR:1.976,95%CI:1.128-3.461, P = 0.017), Ruminococcaceae (UCG011)(OR:1.433, 95%CI:1.072-1.916, P = 0.015), and Streptococcus(OR:1.712, 95%CI:1.071-1.736, P = 0.025) were identified as causative factors for PC. Additionally, sensitivity analysis, Cochran's Q test, the Mendelian randomization pleiotropy residual sum and outlier (MR-PRESSO), and MR-Egger regression indicated no heterogeneity, horizontal pleiotropy, or reverse causality between GM and PC.

CONCLUSIONS

Our analysis establishes a causal effect between specific GM and PC, which may provide new insights into the potential pathogenic mechanisms of GM in PC and the assignment of effective therapeutic strategies.

Multivariate Mendelian randomization provides no evidence for causal associations among both psoriasis and psoriatic arthritis, and skin cancer

Background

Some retrospective studies reported that psoriasis (PsO) and psoriatic arthritis (PsA) may have been associated with an elevated risk of skin cancer. The causal associations among them remain unclear.

Objectives

To evaluate the causal association of among both PsO and PsA, and skin cancer.

Methods

We performed large-scale two-sample and Multivariate Mendelian randomization analyses to examine whether there is a causal relationship between PsO and PsA, and skin cancer, encompassing basal cell carcinoma (BCC), cutaneous squamous cell carcinoma (cSCC), and cutaneous melanoma (CM).

Results

Genetically predicted PsO, per log-odds ratio increase, showed no significant association with the risk of BCC, cSCC, and CM. The odds ratios (with corresponding 95% confidence intervals) for BCC, cSCC, and CM were 1.00 (0.99,1.01) (PIvw = 0.990), 0.94(0.89, 1.00) (PIvw = 0.065), and 0.99 (0.98, 1.01) (PIvw = 0.239), respectively. PsA showed a significant association with a decreased risk of BCC, with odds ratios (with corresponding 95% confidence intervals) of 1.00 (1.00, 1.00) (PIvw = 0.214) and 1.00 (1.00, 1.00) (PIvw = 0.477), respectively. Univariate analysis of the FinnGen database demonstrated PsA did exhibit a significant association with the decrease risk of BCC, with an odds ratio of 0.94(0.90,0.99) (PIvw = 0.016). However, this association disappeared after other risk factors were adjusted.

Conclusions

Our findings suggest no causal association between PsO and PsA and the genetic risk of skin cancer. Further observational studies are required to elucidate the relationship among PsO, PsA, and skin cancer.

Investigating the gut microbiota's influence on psoriasis and psoriatic arthritis risk: a Mendelian randomization analysis

Background

Numerous investigations have revealed the interplay between gut microbiota (GM) and psoriasis (Ps) and psoriatic arthritis (PsA). However, the causal relationship between them remains unknown.

Methods

We curated a collection of genetic variants (P < 1 × 10-5) associated with GM (n = 18 340) derived from the MiBioGen study. To explore the intricate relationship between GM and Ps as well as PsA, we harnessed the comprehensive resources of the FinnGen database, encompassing a vast cohort of individuals, including 4510 Ps cases and 212 242 controls and 1637 PsA cases and 212 242 controls. Mendelian randomization (MR) was used, including an inverse variance weighting method, followed by a sensitivity analysis to verify the robustness of the results.

Results

For Ps, some bacterial taxa, including Lactococcus, Ruminiclostridium 5, and Eubacterium fissicatena, were identified as risk factors; but Odoribacter demonstrated a protective effect against Ps. In the case of PsA, Lactococcus, Verrucomicrobiales, Akkermansia, Coprococcus 1, and Verrucomicrobiaceae were identified as risk factors; Odoribacter and Rikenellaceae exhibited a protective effect against the development of PsA.

Conclusion

Our study establishes a causal link between the GM and Ps and PsA. These findings provide insights into the underlying mechanisms and suggest potential therapeutic targets.

Application of Compositional Data Analysis to Study the Relationship between Bacterial Diversity in Human Faeces and Sex, Age, and Weight

This work uses Compositional Data Analysis (CoDA) to examine the typical human faecal bacterial diversity in 39 healthy volunteers from the Andalusian region (Spain). Stool samples were subjected to high-throughput sequencing of the V3 and V4 regions of the 16S ribosomal RNA gene using Illumina MiSeq. The numbers of sequences per sample and their genus-level assignment were carried out using the Phyloseq R package. The alpha diversity indices of the faecal bacterial population were not influenced by the volunteer's sex (male or female), age (19-46 years), and weight (48.6-99.0 kg). To study the relationship between these variables and the faecal bacterial population, the ALDEx2 and coda4microbiome CoDA packages were used. Applying ALDEx2, a trend suggesting a connection between sex and the genera Senegalimassilia and Negatibacillus (slightly more abundant in females) and Desulfovibrio (more abundant in males) was found. Moreover, age was tentatively associated with Streptococcus, Tizzerella, and Ruminococaceae_UCG-003, while weight was linked to Senegalimassilia. The exploratory tool of the coda4microbiome package revealed numerous bacterial log-ratios strongly related to sex and, to a lesser extent, age and weight. Moreover, the cross-sectional analysis identified bacterial signature balances able to assign sex to samples regardless of controlling for volunteers' age or weight. Desulfovibrio, Faecalitalea, and Romboutsia were relevant in the numerator, while Coprococcus, Streptococcus, and Negatibacillus were prominent in the denominator; the greater presence of these could characterise the female sex. Predictions for age included Caproiciproducens, Coprobacter, and Ruminoclostridium in the numerator and Odoribacter, Ezakiella, and Tyzzerella in the denominator. The predictions depend on the relationship between both groups, but the abundance of the first group and scarcity of the second could be related to older individuals. However, the association of the faecal bacterial population with weight did not yield a satisfactory model, indicating scarce influence. These results demonstrate the usefulness of the CoDA methodology for studying metagenomics data and, specifically, human microbiota.