Constrained maximum likelihood-based Mendelian randomization robust to both correlated and uncorrelated pleiotropic effects

Effects of different types of milk consumption on Crohn's disease and the mediating effects of amino acids: A Mendelian randomization study

Dietary therapy is a common adjunctive treatment for Crohn's disease (CD). However, previous studies have presented conflicting views on whether dairy products should be included in dietary therapy. This controversy may be due to confounding factors. Thus, this study employed Mendelian randomization to investigate the effects of consumption of 6 different dairy products on CD. In addition, the mediating effects of 8 amino acids were explored. Three sensitivity analysis methods were employed to exclude horizontal pleiotropy and heterogeneity, ensuring the robustness of the conclusions. Ultimately, the study found that whole milk consumption can reduce the risk of CD (odds ratio = 0.504, 95% CI: 0.324-0.784). Mediation analysis demonstrated that serum isoleucine (mediation effect: -0.265, 95%CI: -0.533 to -0.068) and valine (mediation effect: -0.083, 95%CI: -0.198 to -0.002) are influenced by full-cream milk and modulate the onset of CD, with mediation effects accounting for 38.685% and 12.083%, respectively.

Genetically Predicted Frailty Index Is Associated With Increased Risk of Multiple Metabolic Diseases: 175 226 European Participants in a Mendelian Randomization Study

BACKGROUND

A relationship between frailty index (FI) and metabolic diseases (MDs) has been reported in previous observational studies. However, the causality between them remains unclear. This study aimed to examine the causal effect of FI on MDs.

METHODS

We performed a bidirectional two-sample Mendelian randomization (MR) study. A recent large-scale genome-wide association study (GWAS) provided available data associated with FI, and summary statistics on eight MDs were collected from the IEU OpenGWAS database. Inverse variance weighted (IVW) was used as the main analysis to estimate causal effects, together with MR pleiotropy residual sum and outlier (MR-PRESSO), MR-Egger, Cochran's Q test, pleiotropy test, leave-one-out method, and MR Steiger analysis were used in the sensitivity analyses.

RESULTS

Our MR study demonstrated for the first time that elevated FI was causally associated with an increased risk of MDs including obesity (odds ratio [OR] = 1.78; 95% confidence interval [CI]: 1.17-2.70; p = 0.0075), T2DM (OR = 1.67; 95% CI: 1.24-2.24; p = 6.95 × 10-4), gout (OR = 2.45; 95% CI: 1.29-4.64; p = 0.006), hypothyroidism (OR = 1.96; 95% CI: 1.47-2.60; p = 3.47 × 10-6), and HTN (OR = 2.17; 95% CI: 1.72-2.74; p = 5.25 × 10-11). However, no causal association was found between FI and osteoporosis, vitamin D deficiency, and hyperthyroidism.

CONCLUSIONS

Our findings support a causal relationship between FI and multiple MDs. This is crucial for the prevention of associated MDs in patients with frailty.

Association between sex steroid hormones and α-klotho: Results from the NHANES 2013-2016 and Mendelian randomization study

PURPOSE

This study aimed to explore the association and causal links between sex steroid hormones and the anti-aging protein α-Klotho, extending to investigate the mediation effects of potential mediators.

METHODS

Based on data from the National Health and Nutrition Examination Survey (NHANES) 2013-2016, this study performed weighted multivariable-adjusted logistic regression to evaluate the association between sex steroid hormones and α-Klotho. Then, utilizing summary data from genome-wide association studies (GWAS), a bidirectional two-sample Mendelian randomization (MR) was conducted to assess the causal relationship between sex steroid hormones and α-Klotho. Finally, mediation analysis was conducted to delineate the influence of five identified potential mediators on the sex steroid hormones-α-Klotho association.

RESULTS

In men, significant positive correlations with α-Klotho were consistent across both unadjusted and fully adjusted models for total testosterone (TT), bio-available testosterone (Bio-T), estradiol (E2) and sex hormone-binding globulin (SHBG) (Model 3: TT: β = 3.54, 95 % CI: 1.63-5.44, P = 0.0003; Bio-T: β = 1.74, 95 % CI: 0.73-2.74, P = 0.0007; E2: β = 0.25, 95 % CI: 0.11-0.38, P = 0.0003; SHBG: β = 0.95, 95 % CI: 0.63-1.27, P < 0.0001); In premenopausal women, we detected a potential nonlinear relationship between TT levels and α-Klotho, with α-Klotho levels rising to a peak at a TT level of 72.2 ng/mL, after which they declined. Furthermore, results from MR analyses reaffirmed positive associations of TT and Bio-T with α-Klotho in men (TT: β = 3.54, 95 % CI: 1.63-5.44, P = 0.0003; Bio-T: β = 1.74, 95 % CI: 0.73-2.74, P = 0.0007). Finally, significant mediation effects were observed for uric acid (β = 0.27, 95 % CI: 0.15-0.67, P < 0.0001) and creatinine (β = 0.05, 95 % CI: 0.01-0.16, P = 0.0060), accounting for 26.7 % and 5.23 % of the total mediation effect, respectively.

CONCLUSION

In conclusion, our results demonstrate that both TT and Bio-T enhance the expression of α-Klotho in men. The positive association observed may be partly mediated by uric acid and creatinine.

The causal association between plasma caffeine and frailty: A two-sample mendelian randomization study

BACKGROUND

Frailty is one of the most common and challenging consequences of aging, which negatively affects older adults, their families, and society. Caffeine has been shown to be associated with a reduced risk of frailty by observational studies, yet its causal relationship with frailty remains to be tested using more robust methods.

AIMS

This study aimed to explore the causal association between plasma caffeine and frailty using a two-sample Mendelian Randomization (MR) analysis.

METHODS

Single nucleotide polymorphisms related to plasma caffeine concentrations were selected as instrumental variables. Data on the Frailty Index (FI) were sourced from the UK Biobank and TwinGen meta-analysis (n = 175,226), while data on the Fried Frailty Score (FFS) were obtained from the UK Biobank (n = 386,565). The causal association between plasma caffeine levels and frailty was tested using five MR methods, with the inverse-variance weighted method as the primary approach.

RESULTS

Our results consistently showed significantly negative associations between genetically predicted plasma caffeine with FI (β = -0.050, 95 % CI:0.077 to -0.023, P < 0.001) and FFS (β = -0.049, 95 % CI:0.064 to -0.034, P < 0.001). These results remained robust in further sensitivity analyses using a leave-one-out approach.

CONCLUSION

Our findings confirm a causal relationship between plasma caffeine and frailty and suggest that increasing plasma caffeine levels may help prevent and reduce the risk of frailty.

SFRP2 mediates Epstein-Barr virus and bladder cancer risk: a Mendelian randomization study and colocalization analysis

Studies suggest a possible association between Epstein-Barr virus (EBV) infection and bladder cancer (BCa) risk, though this remains unclear. Secreted frizzled-related protein (sFRP) is also linked to BCa, with some DNA viruses potentially regulating its expression. This study used Mendelian randomization (MR) and colocalization analysis to explore the causal relationship between EBV infection, BCa risk, and the mediating role of sFRP. We first performed a two-sample MR study to assess the causal relationship between 5 EBV-related antibodies (AEB-IgG, EA-D, EBNA-1, VCA-p18, ZEBRA) and BCa using the Finnish Consortium's R11 dataset, validated with R10. Reverse MR analysis followed. For significant results, multivariable MR (MVMR) was applied to adjust for confounding risk factors. A two-step MR explored the potential mediating role of 3 sFRPs (sFRP1, sFRP2, sFRP3) between positive exposures and BCa. Colocalization analysis were conducted for positive exposures, mediators, and BCa, with multiple sensitivity analyses confirming the robustness of the results. The two-sample Mendelian randomization study found that EBNA-1 (OR = 1.15, 95% CI: 1.01-1.30; p = 0.039) and VCA-p18 (OR = 1.36, 95% CI: 1.13-1.64; p = 0.001) may increase BCa risk, with only VCA-p18 (P_fdr = 0.006) showing a significant effect after False Discovery Rate (FDR) correction. The Finnish Consortium R10 replication study yielded similar results, and reverse MR analysis did not suggest reverse causality. After MVMR adjusted for relevant confounders, VCA-p18 (OR = 1.40, 95% CI: 1.13-1.74; p = 0.002) still significantly increased BCa risk. Two-step MR identified sFRP2 as a mediator, with VCA-p18 down-regulating sFRP2 expression to elevate BCa risk. Colocalization analysis suggested a shared causal variant (nearby gene HLA-DQA1) between VCA-p18 and BCa (PPH4 = 65.44%). Multiple sensitivity analyses confirmed the robustness of the results. Our study suggests that EBV infection (VCA-p18 antibody) may increase the risk of BCa by lowering sFRP2 levels. Additionally, EBNA-1 antibodies may also contribute to an elevated risk of BCa. We hope these findings will provide new insights for future research on the association between EBV and BCa.

Multilayer analysis of ethnically diverse blood and urine biomarkers for breast cancer risk and prognosis

Breast cancer (BC) is one of the most common malignancies among women globally, characterized by complex pathogenesis involving various biomarkers present in blood and urine. To enhance understanding of the genetic associations between biomarkers and BC via multidimensional, cross ethnic investigations. Based on GWAS data of 35 blood and urine biomarkers from European populations, we adopted multiple analysis strategies including univariable Mendelian randomization (MR) analysis, reverse MR analysis, sensitivity analysis and multivariate MR to identify potential biomarkers associated with BC risk and survival. Our initial analysis included 122,977 BC and 105,974 controls of European ancestry. Building upon these findings, we conducted cross ethnic validation by applying the same analyses to East Asian populations using data from the IEU GWAS database, which included 5,552 BC and 89,731 controls. This step allowed us to investigate the universality and heterogeneity of our identified biomarkers across different ancestries. Subsequently, utilizing clinical laboratory detection data from multiple regions in China, we performed differential analyses and survival assessments on these potential biomarkers to evaluate their clinical relevance and utility. Notably, we leveraged Luzhou's clinical data to integrate HDL-C with conventional tumor markers (CEA, CA125, CA153) into a machine learning model, comparing its diagnostic efficacy against tumor marker combination. Our study validated associations of ALP, HDL-C, TG, SHBG, and IGF-1 with BC risk, reinforcing the reliability of these findings. Moreover, notable interethnic disparities emerged in the association between HDL-C and BC risk, where in HDL-C demonstrates a contrasting role: acting as a genetic protective agent against BC and suggesting promise as an auxiliary diagnostic marker in East Asian populations, yet inversely, it serves as a genetic dangerous predictor in European populations. Analyzing BC subtypes, we identified associations of HDL-C, TG, SHBG, and CRP with ER+BC, while ER-BC showed associations with GLU, urinary creatinine and microalbuminuria, underscoring subtype-specific genetic characteristics critical for personalized prevention and treatment strategies. Overall, this comprehensive study, by traversing the intricate landscape of genetic associations across ethnic boundaries and employing advanced analytical methodologies, not only uncovers the complex interplay between key biomarkers and BC susceptibility but also highlights the significance of ethnic-specific differences in the role of HDL-C. By enhancing the diagnostic power of a tailored biomarker panel through machine learning, this study contributes to the advancement of precision medicine in BC, offering strategies tailored to the unique genetic profiles and biomarker patterns across diverse populations.

Plasma proteins and herpes simplex virus infection: a proteome-wide Mendelian randomization study

Proteomics plays a pivotal role in clinical diagnostics and monitoring. We conducted proteome-wide Mendelian randomization (MR) study to estimate the causal association between plasma proteins and Herpes simplex virus (HSV) infection. Data for 2,923 plasma protein levels were obtained from a large-scale protein quantitative trait loci study involving 54,219 individuals, conducted by the UK Biobank Pharma Proteomics Project. HSV-associated SNPs were derived from the FinnGen study, which included a total of 400,098 subjects infected with HSV. MR analysis was performed to assess the links between protein levels and the risk of HSV infection. Furthermore, a Phenome-wide MR analysis was utilized to explore potential alternative indications or predict adverse drug events. Finally, we evaluated the impact of 1,949 plasma proteins on HSV infection, identifying 48 proteins that were negatively associated with HSV infection and 54 proteins that were positively associated. Genetically higher HLA-E levels were significantly associated with increased HSV infection risk (OR = 1.39, 95% CI: 1.17-1.65, P = 2.13 × 10-4, while ULBP2 showed a significant negative association with HSV infection risk (OR = 0.81, 95% CI: 0.73-0.90, P = 6.25 × 10-5) in the primary analysis. No significant heterogeneity or pleiotropy was observed in any of the results. Additionally, we found a suggestive association of Lymphotoxin-beta, SMOC1, MICB_MICA, ASGR1, and ANXA10 with HSV infection risk (P < 0.003). In Phenome-wide MR analysis, HLA-E was associated with 214 phenotypes (PFDR < 0.10) while ULBP2 did not show significant associations with any diseases after FDR adjustment. The comprehensive MR analysis established a causal link between multiple plasma proteins and HSV infection, emphasizing the roles of HLA-E and ULBP2. These results provide new insights into the biological mechanisms of HSV and support the potential for early intervention and treatment strategies, although further research is needed to validate these plasma protein biomarkers.

Genetic colocalization of cathepsins H, D, and L1 with Alzheimer's disease: Implications for biomarker and therapeutic target discovery

BACKGROUND

Cathepsins, a family of lysosomal proteases, have been implicated in Alzheimer's disease (AD) pathogenesis through their involvement in amyloid-β protein precursor processing and neuroinflammation. However, the specific roles of different cathepsins in AD remain unclear.

OBJECTIVE

This study aimed to investigate the genetic associations and potential causal relationships between cathepsins and AD, using Mendelian randomization (MR) to explore their roles as biomarkers and therapeutic targets.

METHODS

A two-sample MR analysis was conducted using genome-wide association study data for AD and cathepsins. Genetic variants associated with cathepsin expression were used as instrumental variables. Forward MR assessed the causal effect of cathepsins on AD, while reverse MR explored the impact of AD on cathepsin levels. Colocalization analysis was performed to identify shared genetic variants between cathepsins and AD.

RESULTS

Cathepsin H was significantly associated with an increased risk of AD (p = 0.0034, OR = 1.04), with consistent results across multiple MR methods. Colocalization analysis revealed a significant genetic overlap between Cathepsin L1 and AD (PP.H4 = 100%), suggesting a shared genetic basis.

CONCLUSIONS

Cathepsin H may be a potential risk factor for AD, while Cathepsin L1 shows promise as a therapeutic target and biomarker due to its genetic overlap with AD. Further research is needed to explore the mechanisms by which these cathepsins influence AD progression and to assess their therapeutic potential in diverse populations.

Genetic evidence identifies a causal relationship between EBV infection and multiple myeloma risk

BACKGROUND

Previous observational studies have suggested a potential association between Epstein-Barr virus (EBV) infection and the development of multiple myeloma (MM), but this relationship is not clear. Therefore, we conducted a systematic Mendelian randomization (MR) analysis to investigate the causal relationship between EBV infection and the risk of MM, while exploring the possible mediating role of immune cells in this association.

METHODS

The study first conducted a two-sample MR analysis using the MM R11 dataset from the FinnGen Consortium to evaluate the causal relationship between five EBV infection-related antibodies (AEB-IgG, EA-D, EBNA-1, VCA-p18, and ZEBRA) and MM, with validation in the MM R10 dataset. A reverse MR analysis was then performed. For significant results, multivariable MR (MVMR) was used to adjust for the effects of confounding risk factors. Next, a two-step MR mediation analysis was applied to investigate the potential mediating role of 731 immune cell types between positive exposure and MM. Multiple sensitivity analyses were conducted to assess the robustness of the findings.

RESULTS

A two-sample MR study found that EBNA-1 antibodies (OR = 1.36, 95% CI: 1.06-1.73; P = 0.015) were associated with an increased risk of MM, with similar results observed in the FinnGen Consortium R10 replication study. Although the association did not remain statistically significant after false discovery rate (FDR) adjustment (P_fdr = 0.075), further adjustment for relevant confounders using multivariable MR (MVMR) demonstrated that EBNA-1 antibodies (OR = 1.33, 95% CI: 1.01-1.75; P = 0.041) were still significantly associated with an increased risk of MM. Reverse MR analysis indicated no causal effect of MM on EBV-related antibodies. A two-sample MR analysis involving 731 immune cell phenotypes identified 27 potential mediating cell types. Ultimately, two-step MR confirmed that HLA-DR on myeloid dendritic cells (HLA-DR⁺ mDC) serves as a mediating factor, with EBNA-1 antibodies downregulating HLA-DR⁺ mDC, thereby increasing MM risk. Multiple sensitivity analyses supported the robustness of these findings.

CONCLUSION

The findings of this study suggest that EBNA-1 antibodies may increase the risk of MM by downregulating HLA-DR⁺ mDC. This indicates that chronic EBV infection may contribute to an elevated risk of MM. We hope these results provide new insights for future research on the prevention and treatment of MM.

Mendelian randomization analysis revealed a gut microbiota-eye axis in acute anterior uveitis

BACKGROUND

Observational studies suggest that gut microbiome (GM) may contribute to acute anterior uveitis (AAU) development, but causality remains unclear. This study was conducted to test whether specific GM taxa were causally associated with AAU.

METHODS

The GM data were obtained from the DMP, which included 7738 individuals' faecal samples and an analysis of host genotype-taxa abundance associations. The AAU data were derived from the FinnGen Consortium (8624 cases and 473,095 controls). We primarily employed the inverse-variance weighted method, complemented by supplementary sensitivity analyses.

RESULTS

Higher abundance of Lachnospiraceae noname (OR = 0.86, 95% CI 0.81-0.91, P = 5.7 × 10-8), Alistipes finegoldii (OR = 0.87, 95% CI 0.78-0.96, P = 0.008), Erysipelotrichaceae (OR = 0.90, 95% CI 0.81-0.99, P = 0.037), Erysipelotrichia (OR = 0.90, 95% CI 0.81-0.99, P = 0.037), Erysipelotrichales (OR = 0.90, 95% CI 0.81-0.99, P = 0.037), and Bacteroides ovatus (OR = 0.93, 95% CI 0.87-1.00, P = 0.039) predicted a lower AAU risk. Conversely, higher abundance of Bifidobacterium catenulatum (OR = 1.06, 95% CI: 1.02-1.10, P = 0.005), Bacteroides coprocola (OR = 1.11, 95% CI: 1.02-1.21, P = 0.014), Parabacteroides unclassified (OR = 1.12, 95% CI 1.03-1.22, P = 0.010), and Prevotella (OR = 1.15, 95% CI: 1.01-1.29, P = 0.029) predicted a higher AAU risk. The results also showed a reverse causation from AAU to Bifidobacterium catenulatum (OR = 1.39, 95% CI: 1.03-1.86, P = 0.005).

CONCLUSION

This study suggests that specific GM is causally associated with AAU risk, warranting more mechanistic validation and clinical trials.

Genetically predicted inflammatory proteins mediate the association between gut microbiota and renal cell carcinoma

BACKGROUND

Studies have indicated a potential relationship between gut microbiota and renal cell carcinoma. However, the causal relationship between various types of gut microbiota and renal cell carcinoma, as well as the role of inflammatory protein as mediators, remains unclear.

METHODS

This study aimed to identify the relationship between gut microbiota, inflammatory protein, and renal cell cancer through a large-scale genome-wide association study (GWAS) utilizing pooled data. We employed Mendelian randomization (MR) to investigate the causal relationship among these variables. Inverse variance weighting (IVW) was utilized as the primary statistical method. Furthermore, we examined the mediating role of inflammatory protein in the pathway through which gut microbiota influences the development of renal cell cancer.

RESULTS

The analysis revealed 12 positive causal relationships and 15 negative causal relationships between the genetic liability of gut microbiota and renal cell cancer. Furthermore, there were three positive causal relationships and one negative causal relationship between inflammatory proteins and renal cell cancer. There were two axes of relationships in which gut microbiota promote the development of renal cell cancer. through inflammatory proteins acting as mediators.

CONCLUSIONS

Gut microbiota and inflammatory protein were causally related to renal cell cancer, and inflammatory protein were intermediary factors in the pathway between gut microbiota and renal cell cancer.

Insomnia and Female Reproductive Diseases: A Cross-Sectional and Mendelian Randomization Study

Background

Insomnia is increasingly emerging as a significant concern in public health, with a longstanding emphasis on its relationship with overall well-being. Nevertheless, few research has been devoted to investigating the relationship between insomnia and female reproductive health.

Methods

In our study, we conducted a Mendelian randomization (MR) study to estimate the causal relationship between insomnia and female reproductive diseases. A total of 268 independent genetic variants associated with insomnia at the genome-wide significance level (P < 5×10-8) were used as instrumental variables. Summary-level data were obtained from the UK Biobank and Finn Gen study, including ovarian cysts, polycystic ovarian syndrome (PCOS), endometriosis, premature ovarian insufficiency (POI), ovarian cancer (OC), uterine fibroids, endometrial cancer (EC) and female infertility. We performed logistic regression to assess the associations between insomnia and the risk of OC and EC by using data from the National Health and Nutrition Examination Survey (NHANES) 2013-2014.

Results

Our research reveals that genetic liability to insomnia constitutes a risk factor for ovarian cysts (odds ratio [OR]: 1.44, 95% confidence interval [CI]: 1.21-1.72, P< 0.05), PCOS (OR: 1.67, 95% CI: 1.44-1.94, P< 0.05), and endometriosis (OR: 1.43, 95% CI: 1.16-1.76, P< 0.05). However, we found no statistically significant associations between insomnia and POI, OC, uterine fibroids, EC, or female infertility. Additionally, body mass index (BMI) was found to mediate about 10% of the effect of the insomnia on ovarian cysts and PCOS. Moreover, in cross-sectional study, insomnia was not associated with OC and EC.

Conclusion

Our study provides causal evidence that genetically predicted insomnia increases the risk of ovarian cysts, PCOS, and endometriosis. Accordingly, the potential significance of weight control and good sleep in keeping fit need to be emphasized.

Rheumatoid arthritis and risk of hearing impairment: A genetic correlation and bidirectional Mendelian randomization study

Prior research has indicated a connection between rheumatoid arthritis (RA) and hearing impairment (HI), although there is disagreement among researchers. An extensive assessment of the causal relationship between RA and HI was the aim of this Mendelian randomization (MR) study. We examined summary-level data from RA and HL genome-wide association studies using inverse variance weighted (IVW) analysis. We further supplemented the results with weighted median (WM), MR-Egger, MR-RAPS, and maximum likelihood techniques. We used sensitivity analyses to check the accuracy of the MR analysis results. Genetically, higher RA substantially increases the likelihood of HI (IVW: P = 8.78 × 10-03, odds ratio (OR) = 1.014, 95% confidence interval (CI): 1.003-1.024). Sensitivity analysis reveals a consistent direction of the association using the following methods: Bayesian MR (P = 8.72 × 10-03, OR = 1.014, 95% CI: 1.004-1.025), MR robust adjustment profile score (P = 2.31 × 10-02, OR = 1.013, 95% CI: 1.002-1.024), maximum likelihood method (P = 2.70 × 10-02, OR = 1.014, 95% CI: 0.996-1.026), WM (P = 1.35 × 10-01, OR = 1.012, 95% CI: 0.996-1.029), and MR-Egger (P = 1.41 × 10-01, OR = 1.011, 95% CI: 0.996-1.027). Despite not achieving statistical significance, the WM and MR-Egger approaches offered reliable guidance. Moreover, we replicated our results on other datasets and obtained similar results (IVW: P = 8.71 × 10-03, OR = 1.016, 95% CI: 1.004-1.028), indicating the validity of our results. Our study provides evidence linking RA to a higher risk of HI. In order to gain more insight into treatments that change the disease or prevent hearing loss, audiological testing is necessary for the diagnosis and follow-up of individuals with RA.

Causal role of plasma liposome in diabetic retinopathy: mendelian randomization (MR) study

BACKGROUND

Research indicates that there may be an association between plasma lipidome levels and the incidence of diabetic retinopathy (DR) in patients. However, the potential causality of this relationship is yet to be determined. To investigate this matter further, we employed a two-sample Mendelian randomization (MR) analysis to comprehensively assess the causality between lipidome levels and DR.

METHODS

Summary statistics for lipid levels and DR were obtained from the Genome-Wide Association Studies (GWAS) Catalog database and the FinnGen Consortium, respectively. We conducted a two-sample MR analysis, and statistical analysis were performed using the inverse variance weighted (IVW) with the addition of the MR-Egger, weighted median (WM), constrained maximum likelihood and model averaging (cML-MA) to test for causal associations between lipid levels and DR. Heterogeneity was checked using Cochran's Q statistic. The MR Pleiotropy Residual Sum and Outlier (MR-PRESSO) global test and the MR-Egger regression were used to detect horizontal pleiotropy. The robustness of our findings was assessed using leave-one-out and funnel plots. To further assess the reliability of the results, linkage disequilibrium score regressions, colocalization analysis and reverse MR analysis were also performed.

RESULTS

Analysis of the pooled MR results and after correction for the false discovery rate (FDR) revealed that five lipid levels were associated with DR risk. Phosphatidylcholine (16:0_16:0) levels [OR = 0.869 (0.810 to 0.933), Pfdr = 0.006], phosphatidylcholine (16:0_20:2) levels [OR = 0.893 (0.834 to 0.956), Pfdr = 0.043] and phosphatidylethanolamine (18:0_20:4) levels [OR = 0.906 (0.863 to 0.951), Pfdr = 0.006] were protective against DR, whereas sphingomyelin (d36:1) levels [OR = 1.120 (1.061 to 1.183), Pfdr = 0.006], and sphingomyelin (d40:1) levels [OR = 1.081 (1.031 to 1.134), Pfdr = 0.043] were associated with a greater risk of DR. Further sensitivity analysis did not reveal heterogeneity or horizontal pleiotropy.

CONCLUSION

In summary, genetic evidence suggests a causal relationship between the levels of specific lipid levels and DR. These findings may provide valuable insights into the causal relationships between lipid levels and DR, potentially informing future prevention and treatment strategies.

Exploring the Relationship Between Sporadic Creutzfeldt-Jakob Disease and Gut Microbiota Through a Mendelian Randomization Study

Observational studies have shown gut microbiota changes in sporadic Creutzfeldt-Jakob disease patients, but the causal relationship remains unknown. We aimed to determine any causal links between gut microbiota and this prion disease. Using Mendelian randomization analysis, we examined the causal relationship between gut microbiota composition and sporadic Creutzfeldt-Jakob disease. Data on gut microbiota (N = 18,340) and disease cases (5208) were obtained. Various analysis methods were used, including inverse variance weighted, Mendelian randomization-Egger, weighted median, simple mode, and weighted mode. In addition, MR-PRESSO was used to evaluate horizontal pleiotropy and detect outliers. Pleiotropy and heterogeneity were assessed, and reverse analysis was conducted. Negative associations were found between sporadic Creutzfeldt-Jakob disease and family Defluviitaleaceae, family Ruminococcaceae, genus Butyricicoccus, genus Desulfovibrio, and genus Eubacterium nodatum. Genus Lachnospiraceae UCG010 showed a positive correlation. Reverse analysis indicated genetic associations between the disease and decreased levels of family Peptococcaceae, genus Faecalibacterium, and genus Phascolarctobacterium, as well as increased levels of genus Butyrivibrio. No pleiotropy, heterogeneity, outliers, or weak instrument bias were observed. This study revealed bidirectional causal effects between specific gut microbiota components and sporadic Creutzfeldt-Jakob disease. Certain components demonstrated inhibitory effects on disease pathogenesis, while others were positively associated with the disease. Modulating gut microbiota may provide new insights into prion disease therapies. Further research is needed to clarify mechanisms and explore treatments for sporadic Creutzfeldt-Jakob disease.

Genetically Predicted Vascular Proteins and Risk of Intracranial Aneurysms: A Mendelian Randomization Study

The relationship between vascular proteins (VPs) and intracranial aneurysms (IAs) has not been fully elucidated. We used Mendelian randomization (MR) analysis to explore the effect of VPs on IAs. Dataset of aneurysmal subarachnoid hemorrhage (aSAH) [5140 cases and 71,934 controls] and unruptured intracranial aneurysm (uIA) [2070 cases and 71,934 controls] were obtained from individuals of European ancestry. Univariate MR was used to explore the associations between 90 VPs and IAs. Then, we performed multivariate MR (MVMR) to further investigate the identified VP-to-IA estimates. Two-sample MR showed that TNFSF14 was inversely associated with aSAH (odds ratio [OR] = 0.831, 95% CI: 0.713-0.969, p = 0.018). IL-16 (OR = 1.218, 95% CI: 1.032-1.438, p = 0.020) and AgRP (OR = 1.394, 95% CI: 1.048-1.855, p = 0.023) were positively associated with aSAH. HBEGF (OR = 0.642, 95% CI: 0.461-0.894, p = 0.009), MCP-1 (OR = 1.537, 95% CI: 1.007-2.344, p = 0.046), and CX3CL1 (OR = 0.762, 95% CI: 0.581-0.999, 0.049 < p < 0.050) were associated with uIA risk. The MVMR showed that the TNFSF14-to-aSAH estimate remained statistically significant after adjustment for past tobacco smoking, alcohol consumption, systolic blood pressure and body mass index. Our study indicated that low serum TNFSF14 levels might be a potential risk factor for IA rupture. Five VPs (HBEGF, MCP-1, IL-6, CX3CL1, and AgRP) are associated with the risk of IAs (both uIA and aSAH).

Effect of different types of milk consumption on Gout and the mediating effect of branched chain amino acids (BCAAs): a Mendelian randomization study

Numerous studies have shown that dietary factors can reduce the risk of developing gout, while changes in serum amino acids also impact gout risk. However, current research lacks insights into how dairy products with varying fat content influence serum amino acids and gout risk, as well as the mediating effects of amino acids. This study employed Mendelian randomization (MR) to analyze the association between 3 milk consumption phenotypes with different fat contents and gout. We found that only whole milk was associated with a reduced risk of gout, whereas no association was observed with the other 2 milk types. Subsequent mediation analysis revealed that isoleucine played a mediating role, with a mediation effect of -0.198 (95% CI: -0.354 to -0.072), accounting for 66.32% of the total effect, and the mediation effect was significant (P = 0.006).

Unbiased causal inference with Mendelian randomization and covariate-adjusted GWAS data

Mendelian randomization (MR) facilitates causal inference with observational data using publicly available genome-wide association study (GWAS) results. In a GWAS, one or more heritable covariates may be adjusted for to estimate the direct effects of SNPs on a focal trait or to improve statistical power, which may introduce collider bias in SNP-trait association estimates, thus affecting downstream MR analyses. Numerical studies suggested that using covariate-adjusted GWAS summary data might introduce bias in univariable Mendelian randomization (UVMR), which can be mitigated by multivariable Mendelian randomization (MVMR). However, it remains unclear and even mysterious why/how MVMR works; a rigorous theory is needed to explain and substantiate the above empirical observation. In this paper, we derive some analytical results when multiple covariates are adjusted for in the GWAS of exposure and/or the GWAS of outcome, thus supporting and explaining the empirical results. Our analytical results offer insights to how bias arises in UVMR and how it is avoided in MVMR, regardless of whether collider bias is present. We also consider applying UVMR or MVMR methods after collider-bias correction. We conducted extensive simulations to demonstrate that with covariate-adjusted GWAS summary data, MVMR had an advantage over UVMR by producing nearly unbiased causal estimates; however, in some situations it is advantageous to apply UVMR after bias correction. In real data analyses of the GWAS data with body mass index (BMI) being adjusted for metabolomic principal components, we examined the causal effect of BMI on blood pressure, confirming the above points.

Prospective Investigation Unravels Plasma Proteomic Links to Dementia

Investigating plasma proteomic signatures of dementia offers insights into its pathology, aids biomarker discovery, supports disease monitoring, and informs drug development. Here, we analyzed data from 48,367 UK Biobank participants with proteomic profiling. Using Cox and generalized linear models, we examined the longitudinal associations between proteomic signatures and dementia-related phenotypes. Mendelian randomization analysis was employed to identify causal associations, and machine learning algorithms were applied to develop protein-based models for dementia prediction. We identified 74 proteins significantly associated with the risk of various types of dementia and cognitive functions after Bonferroni correction. Among these, strong associations were observed for growth/differentiation factor 15 (GDF15), glial fibrillary acidic protein (GFAP), and neurofilament light polypeptide (NEFL), across all types of dementia. Additionally, 15 proteins demonstrated significant associations with neuroimaging-defined dementia endophenotypes. Two-sample Mendelian randomization analyses further substantiated causal relationships between dementia-associated proteins and Alzheimer's disease, particularly involving GDF15, proto-oncogene tyrosine-protein kinase receptor Ret (RET), and GFAP. Moreover, we identified three protein modules associated with dementia, primarily linked to immune system processes, angiogenesis, and energy metabolism, providing insights into potential biological pathways underlying the disease. Furthermore, we proposed a ten-protein panel capable of forecasting dementia over a median follow-up period of 8.6 years, achieving an area under the curve (AUC) of 0.857 (95% confidence interval (CI), 0.837-0.876). Our results revealed dementia-associated plasma proteomic signatures, and their causal relationships, notably GDF15-RET signaling with Alzheimer's disease, and proposed a promising protein panel for high-risk dementia screening.

Genetic variation reveals the therapeutic potential of BRSK2 in idiopathic pulmonary fibrosis

BACKGROUND

Current research underscores the need to better understand the pathogenic mechanisms and treatment strategies for idiopathic pulmonary fibrosis (IPF). This study aimed to identify key targets involved in the progression of IPF.

METHODS

We employed Mendelian randomization (MR) with three genome-wide association studies and four quantitative trait loci datasets to identify key driver genes for IPF. Prioritized targets were evaluated for respiratory insufficiency and transplant-free survival. The therapeutic efficacy of the core gene was validated in cellular and animal models. Additionally, we conducted a comprehensive evaluation of therapeutic value, pathogenic mechanisms, and safety through phenome-wide association study (PheWAS), mediation analysis, transcriptomic analyses, shared causal variant exploration, DNA methylation MR, and protein interactions.

RESULTS

Multiple MR results revealed that BRSK2 has a significant pathogenic impact on IPF at both transcriptional and translational levels, with a lung tissue-specific association (OR = 1.596; CI, 1.300-1.961; Pval = 8.290 × 10 - 6). BRSK2 was associated with IPF progression driven by high-risk factors, with mediation effects ranging from 34.452 to 69.665%. Elevated BRSK2 expression in peripheral blood mononuclear cells correlated with reduced pulmonary function, while increased circulating BRSK2 levels suggested respiratory failure and shorter transplant-free survival in IPF patients. BRSK2 silencing attenuated lung fibrosis progression in cellular and animal models. Transcriptomic integration identified PSMB1, CTSD, and CTSH as significant downstream effectors of BRSK2, with PSMB1 showing robust shared causal variant support (PPH4 = 0.800). Colocalization analysis and phenotype scan deepened the pathogenic association of BRSK2 with IPF, while methylation MR analysis highlighted the critical role of epigenetic regulation in BRSK2-driven IPF pathogenesis. PheWAS revealed no significant drug-related toxicities for BRSK2, and its therapeutic potential was further underscored by protein interaction analyses.

CONCLUSIONS

BRSK2 is identified as a critical pathogenic factor in IPF, with strong potential as a therapeutic target. Future studies should focus on its translational implications and the development of targeted therapies to improve patient outcomes.

Association between serum iron status and gout: results from the NHANES and Mendelian randomization study

Aims. Previous observational studies have provided inconsistent evidence for the association between serum iron status and the risk of gout. Moreover, it remains uncertain whether the observed association is causal or due to confounding or reverse causality. This research aimed to investigate the association of serum iron status indicators with the risk of gout and to further examine the causal relationship by the Mendelian randomization (MR) method. Methods. We first conducted a cross-sectional study from the National Health and Nutrition Examination Survey 2017-2018, including a total of 4635 participants. The association of serum iron status indicators with gout risk was evaluated using a multivariable logistic regression model. Furthermore, a two-sample MR study using genetic data from large-scale genome-wide association studies of serum iron status indicators (246 139 individuals) and gout (discovery: 13 179 cases and 75 0634 controls; replication: 5292 cases and 368 788 controls; 2115 cases and 67 259 controls) was conducted to infer causality. Inverse-variance-weighting (IVW) was applied as the main method of MR analysis. A series of sensitivity analyses were used to evaluate the robustness of their relationship. Results. In the cross-sectional study, there was no significant relationship between serum iron status indicators and gout risk. However, IVW results showed that genetically predicted serum iron and transferrin saturation (TSAT) were significantly associated with the increased risk of gout in the discovery analysis [odds ratio (OR): 1.21; 95% confidence interval (CI): 1.10-1.32; P = 9.80 × 10-5 for serum iron and OR: 1.16; 95% CI: 1.08-1.25; P = 7.14 × 10-5 for TSAT]. The replication analysis provided similar results compared with the discovery analysis. Conclusion. Our study provides support for potential causal associations between serum iron and the altered risk of gout. Further investigations are warranted to elucidate the biological processes through which iron influences susceptibility to gout.

Effect of different types of milk consumption on type 2 diabetes and the mediating effect of amino acids: a Mendelian randomization study of East Asian population

There is currently a lack of research examining the association between the consumption of different dairy products and type 2 diabetes (T2D) in East Asian populations. To address this gap, the present study employs Mendelian randomization (MR) to investigate the potential impact of 3 different types of milk consumption (including whole milk, semi-skim milk, and skim milk) on the risk of developing T2D. The results indicate that both whole milk and skim milk are associated with an increased risk of T2D (whole milk: OR = 1.022, 95% confidence interval [CI]: 1.001-1.044, P = 0.042, skim milk: OR = 1.023, 95% CI: 1.007-1.039, P = 0.005). Mediation analysis reveals that asparagine acts as a mediator between skim milk consumption and T2D, with a mediation effect of 0.003 (95% CI: 0.000 to 0.008), accounting for 14.269% of the total effect.

Immunological Insights into the Causal Link Between Arthritis, Osteoarthritis, and Frailty: An Integrated Analytical Study

Background: Previous observational studies have observed associations between rheumatoid arthritis (RA), knee osteoarthritis (KOA), hip osteoarthritis (HOA), and frailty, but the causal relationships remain unestablished. Objective: This study aimed to evaluate the causal relationships between RA, KOA, HOA, KneeHipOA, and frailty using Mendelian randomization (MR) and bioinformatics analysis. Methods: We performed two-sample MR to test for causality between RA, KOA, HOA, KneeHipOA, and frailty. Subsequently, we combined our results in a meta-analysis and conducted multiple sensitivity analyses (MR-Egger, weighted median, constrained maximum likelihood and model averaging (cML-MA), and Bayesian weighted MR (BWMR)). We further explored the role of circulating immune cells and the effects of RA and OA-related gene expression on frailty. Results: Genetically determined RA, KOA, HOA, and KneeHipOA were correlated with a higher risk of frailty. The results of multivariate MR analyses were consistent with those of two-sample MR. Gene Ontology enrichment analysis and Kyoto Encyclopedia of Genes and Genomes analysis indicated that RA and OA-related genes were primarily enriched in various immune responses. Our findings suggested that increases in monocyte cell AC, eosinophil cell AC, and neutrophil cell AC were associated with a higher risk of frailty. Conclusion: This research provides evidence supporting the associations between RA, KOA, HOA, KneeHipOA, and frailty. It also highlights the significant role of circulating immune cells in the development of frailty, indicating the importance of frailty management from an immunological perspective.

A semi-empirical Bayes approach for calibrating weak instrumental bias in sex-specific Mendelian randomization studies

Strong sex differences exist in sleep phenotypes and also cardiovascular diseases (CVDs). However, sex-specific causal effects of sleep phenotypes on CVD-related outcomes have not been thoroughly examined. Mendelian randomization (MR) analysis is a useful approach for estimating the causal effect of a risk factor on an outcome of interest when interventional studies are not available. We first conducted sex-specific genome-wide association studies (GWASs) for suboptimal-sleep phenotypes (insomnia, obstructive sleep apnea (OSA), short and long sleep durations, and excessive daytime sleepiness) utilizing the Million Veteran Program (MVP) dataset. We then developed a semi-empirical Bayesian framework that (i) calibrates variant-phenotype effect estimates by leveraging information across sex groups, and (ii) applies shrinkage sex-specific effect estimates in MR analysis, to alleviate weak instrumental bias when sex groups are analyzed in isolation. Simulation studies demonstrate that the causal effect estimates derived from our framework are substantially more efficient than those obtained through conventional methods. We estimated the causal effects of sleep phenotypes on CVD-related outcomes using sex-specific GWAS data from the MVP and All of Us. Significant sex differences in causal effects were observed, particularly between OSA and chronic kidney disease, as well as long sleep duration on several CVD-related outcomes. By applying shrinkage estimates for instrumental variable selection, we identified multiple sex-specific significant causal relationships between OSA and CVD-related phenotypes.

Investigating causal relationships of blood and urine biomarkers with urological cancer risks: a mendelian randomization study and colocalization analyses

Background: Establishing the causal links between biomarkers and cancer enhances understanding of risk factors and facilitates the discovery of therapeutic targets. To this end, we used Mendelian randomization (MR) and colocalization analysis to explore the causal relationship of blood and urinary biomarkers (BUBs) with urological cancers (UCs). Methods: First, we used a two-sample MR study to explore the causal relationship between 33 BUBs and 4 UCs, while we performed reverse Mendelian randomization. After Bonferroni correction, for BUB and UC with significant causality we confirmed the direct causality by multivariate MR adjusting for relevant risk factors. We also applied two-step MR analysis to further explore the possible mediators between BUB and UC with significant causality, while colocalization analysis was performed for BUB, UC and possible mediators. Sensitivity analysis were performed to assess the robustness of the results. Results: A two-sample MR study found that there were 8 BUBs of CA, IGF-1, LPA, TP, CRE, BILD, TBIL and NAP with potential causality with some UCs (p<0.05), but after Bonferroni correction only IGF-1 had a significant causality with PCa (OR = 1.14, 95% CI: 1.06-1.23; p=0.0006<0.05/33). Moreover, the causal relationship between IGF-1 and PCa remained significant (P<0.05) after adjusting for relevant risk factors in the multivariate MR study. The two-step MR study found SHBG to be a mediator between IGF-1 and PCa, and the colocalization analysis found that there was a common causal variant (nearby gene TNS3) between IGF-1 and SHBG (PPH4=93.21%), which further confirmed the mediating effect of SHBG. Conclusion: Strong evidence from our study suggests that IGF-1 increases the risk of PCa by decreasing SHBG levels, and in addition some BUBs were found to have a potential causal relationship with UCs.

Exploring pleiotropy in Mendelian randomisation analyses: What are genetic variants associated with 'cigarette smoking initiation' really capturing?

Genetic variants used as instruments for exposures in Mendelian randomisation (MR) analyses may have horizontal pleiotropic effects (i.e., influence outcomes via pathways other than through the exposure), which can undermine the validity of results. We examined the extent of this using smoking behaviours as an example. We first ran a phenome-wide association study in UK Biobank, using a smoking initiation genetic instrument. From the most strongly associated phenotypes, we selected those we considered could either plausibly or not plausibly be caused by smoking. We examined associations between genetic instruments for smoking initiation, smoking heaviness and lifetime smoking and these phenotypes in UK Biobank and the Avon Longitudinal Study of Parents and Children (ALSPAC). We conducted negative control analyses among never smokers, including children. We found evidence that smoking-related genetic instruments were associated with phenotypes not plausibly caused by smoking in UK Biobank and (to a lesser extent) ALSPAC. We observed associations with phenotypes among never smokers. Our results demonstrate that smoking-related genetic risk scores are associated with unexpected phenotypes that are less plausibly downstream of smoking. This may reflect horizontal pleiotropy in these genetic risk scores, and we would encourage researchers to exercise caution this when using these and genetic risk scores for other complex behavioural exposures. We outline approaches that could be taken to consider this and overcome issues caused by potential horizontal pleiotropy, for example, in genetically informed causal inference analyses (e.g., MR) it is important to consider negative control outcomes and triangulation approaches, to avoid arriving at incorrect conclusions.

A Novel One-Sample Mendelian Randomization Approach for Count-Type Outcomes That Is Robust to Correlated and Uncorrelated Pleiotropic Effects

We propose two novel one-sample Mendelian randomization (MR) approaches to causal inference from count-type health outcomes, tailored to both equidispersion and overdispersion conditions. Selecting valid single-nucleotide polymorphisms (SNPs) as instrumental variables (IVs) poses a key challenge for MR approaches, as it requires meeting the necessary IV assumptions. To bolster the proposed approaches by addressing violations of IV assumptions, we incorporate a process for removing invalid SNPs that violate the assumptions. In simulations, our proposed approaches demonstrate robustness to the violations, delivering valid estimates, and interpretable type-I errors and statistical power. This increases the practical applicability of the models. We applied the proposed approaches to evaluate the causal effect of fetal hemoglobin (HbF) on the vaso-occlusive crisis and acute chest syndrome (ACS) events in patients with sickle cell disease (SCD) and revealed the causal relation between HbF and ACS events in these patients. We also developed a user-friendly Shiny web application to facilitate researchers' exploration of causal relations.

IL-20RA is Associated with the Risk of Diabetic Microangiopathy: A Bidirectional Mendelian Randomization Analysis and Clinical Validation

Objective

Studies have demonstrated a link between chronic inflammatory responses and diabetic microangiopathy, which include diabetic nephropathy, diabetic retinopathy, and diabetic neuropathy. However, it remains unclear whether there is a causal association between circulating inflammatory cytokines and the development of diabetic microvascular complications. This study aimed to investigate whether altered genetically predicted concentrations of circulating inflammatory cytokines were associated with the development of diabetic microvascular complications using two-sample Mendelian randomization (MR) analysis and clinical validation.

Methods

Pooled data on diabetic nephropathy, diabetic retinopathy, diabetic neuropathy, and 91 circulating inflammatory cytokines were obtained from publicly available databases. The analysis was conducted mainly using the inverse variance weighting (IVW) method and the results were assessed based on the odds ratio (OR) and 95% confidence interval (CI). In addition, the stability and reliability of the results were verified using the leave-one-out method, heterogeneity tests, and horizontal pleiotropy. Finally, ELISA and RT-qPCR were utilized to assess the expression of relevant inflammatory cytokines associated with diabetic microvascular complications.

Results

Mendelian randomization analysis identified a total of 9 circulating inflammatory cytokines that exhibit causal associations with the diabetic microangiopathy, with IL-20RA being a common risk factor for all three conditions. Clinical studies have found elevated plasma IL-20RA concentrations in patients with diabetic peripheral neuropathy, and RT-qPCR testing of peripheral blood mononuclear cells revealed significantly higher IL-20RA mRNA expression in patients with diabetic peripheral neuropathy as compared to normal individuals.

Conclusion

This study highlights the potential role of specific inflammatory cytokines in the development of diabetic microangiopathy (diabetic nephropathy, diabetic retinopathy and diabetic neuropathy). Additionally, IL-20RA emerges as a potential common risk factor for three diabetic microvascular complications. These findings may provide novel insights into early prevention and new therapeutic strategies for diabetic microvascular complications.

Association between depression and vascular aging: a comprehensive analysis of predictive value and mortality risks

BACKGROUND

Depression is a significant global health concern, projected to become the leading disease burden. Vascular burden has been implicated in the pathogenesis of depression. Conversely, whether depression independently influences the process of vascular aging is unknown. This study aims to investigate the mutual relationship between vascular age and depression.

METHODS

Utilizing data from the National Health and Nutrition Examination Survey (NHANES), the study included 27,764 participants after exclusions. Depression was assessed using the Patient Health Questionnaire (PHQ-9). Vascular aging was assessed by estimated pulse wave velocity (ePWV) and the heart age/vascular age (HVA) based on Framingham Risk Score (FRS). The study employed weighted logistic regression and Cox proportional hazards models to analyze the association between vascular age and depression as well as its mortality risk. Mendelian randomization was utilized to explore the causal associations.

RESULTS

Individuals with depression exhibited a higher risk of an advanced vascular age over their chronological age. Mendelian randomization analysis indicated a causal relationship between depression and arterial stiffness. A significant association was found between vascular age and depression incidence with odds ratios ranging from 1.10 to 1.38. As vascular age increased, the risk of mortality in individuals with depression increased by 22 % and 46 %, respectively.

LIMITATIONS

The study design limits the exploration of the dynamic relationship between changes in vascular age and depression due to the single timepoint measurement.

CONCLUSION

This study highlights the bidirectional relationship between depression and vascular age. Vascular age is a significant biomarker for the risk and prognosis of depression, while depression may contribute to vascular aging, which underscores the importance of integrated strategies for managing both vascular health and depression.

Omega-3 Fatty Acids as Protective Factors for Age-Related Macular Degeneration: Prospective Cohort and Mendelian Randomization Analyses

PURPOSE

Epidemiologic studies and clinical trials have reported inconsistent findings regarding omega-3 fatty acids' protective role in age-related macular degeneration (AMD). We investigated their association in a prospective cohort and examined causality using Mendelian randomization (MR) analyses.

DESIGN

Prospective cohort study and 2-sample MR analyses.

PARTICIPANTS

The cohort included 258 350 AMD-free individuals of European descent from the UK Biobank. Mendelian randomization analyses used genome-wide association study data on plasma omega-3 and docosahexaenoic acid (DHA) (UK Biobank, n = 115 006) and AMD (dry, wet, and any; FinnGen, n = 208 690-209 122).

METHODS

Cox regression assessed the association between plasma omega-3 and DHA levels and AMD incidence, adjusting for systemic covariates and AMD polygenetic risk score (PRS). Interaction effects of AMD genetic risk (PRS, complement factor H and age-related maculopathy susceptibility 2 genotypes), and plasma omega-3 and DHA levels were tested. For MR analyses, we used random-effect inverse-variance weighted model as primary, with 5 sensitivity models. Causality was considered significant if P < 0.05 in the primary model and at least 2 sensitivity models.

MAIN OUTCOME MEASURES

Risk of AMD.

RESULTS

Over 12.9 years, 5068 people (1.9%) demonstrated AMD. Higher plasma levels (in millimoles per liter) of omega-3 (hazard ratio [HR], 0.80; 95% confidence interval [CI], 0.72-0.95; P = 0.006) and DHA (HR, 0.65; 95% CI, 0.44-0.96; P = 0.029) were associated with lower risk of receiving an AMD diagnosis. Mendelian randomization showed genetic predisposition to higher plasma omega-3 levels reduced the risk of dry AMD (odds ratio [OR], 0.83; 95% CI, 0.73-0.96; P = 0.010), wet AMD (OR, 0.76; 95% CI, 0.65-0.88; P < 0.001), and any AMD (OR, 0.82; 95% CI, 0.74-0.92; P < 0.001). Similar results were found for plasma DHA levels (wet AMD:OR, 0.79; 95% CI, 0.65-0.96; P = 0.017; any AMD: OR, 0.84; 95% CI, 0.72-0.98; P = 0.030). No significant interaction was found between omega-3 and DHA levels and AMD genetic risk (all P > 0.05).

CONCLUSIONS

Both the prospective and MR analyses suggest omega-3 and DHA may protect against AMD, supporting the need for further clinical trials to test their effectiveness in AMD prevention and treatment.

FINANCIAL DISCLOSURE(S)

Proprietary or commercial disclosure may be found in the Footnotes and Disclosures at the end of this article.

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

Previous research has confirmed the significant association between gut microbiota (GM) and male infertility (MI), but the causality between them remains unclear. This study aims to investigate the causal relationship between GM and MI using Mendelian randomization (MR) and provide supplementary information for the optimization of future randomized controlled trials (RCTs). Instrumental variables for 211 GM taxa were obtained from genome-wide association studies (GWAS), and inverse variance weighted (IVW) method was used as the main analysis method for two-sample MR analysis to assess the impact of GM on the risk of MI. Four methods were used to test for horizontal pleiotropy and heterogeneity of MR results to ensure the reliability of the MR findings. A total of 50 single-nucleotide polymorphisms (SNPs) closely related to GM were included, and ultimately identified 1 family and 4 general are causally associated with MI. Among them, Anaerotruncus (OR = 1.96, 95% CI 1.31-3.40, P = 0.016) is significantly associated with increased MI risk. Furthermore, we used four MR methods to evaluate the causality, and the results supported these findings. The leave-one-out analysis showed stable results with no instrumental variables exerting strong influence on the results. The causal direction indicated a positive effect, and the effects of heterogeneity and horizontal pleiotropy on the estimation of causal effect were minimized. We confirmed a causal relationship between GM taxa and MI, providing new insights into the mechanisms underlying GM-mediated MI.

Exploring the causal effect of complement and IgA nephropathy-a Mendelian randomization study

IgA nephropathy, one of the most common primary glomerulonephritis worldwide, is still under investigation for its precise etiology. The widely accepted theory is the 'four-hit model' and subsequent complement and inflammatory responses. Recent studies have reported correlations between specific complement components and IgA nephropathy. However, the causal effects of genetically predicted complement components on IgA nephropathy require further elucidation. Our study aimed to determine the causal relationship between genetic predictors of complement and IgA nephropathy using the Mendelian randomization method. The primary analysis was initially conducted, examining heterogeneity and horizontal pleiotropy tests in each subgroup. Complement components with positive results were further analyzed using the MR-PRESSO test and co-localization analysis. Subsequently, the positive results were further analyzed using the cML-MA method to validate the previous studies. Finally, a Bi‑directional analysis was performed, providing a brief evaluation of the causal effect of IgA nephropathy on complement components. We found a causal effect between C1QBP, C3b, C3d, C2, and C7 and IgA nephropathy, but did not identify any reverse causality. Results from co-localization analysis suggest intricate pathway interactions between the complement system and IgA nephropathy. Our findings provide possible directions for subsequent complement research, which will contribute to further exploration of the etiology of IgA nephropathy.

Allergic disease and keratoconus: A two-sample univariable and multivariable Mendelian randomization study

Background

There is accumulating evidence that allergy is a risk factor for keratoconus. Nonetheless the association between allergic disease and keratoconus remains controversial. We performed a two-sample Mendelian randomization (MR) study to determine the putative causal association of 4 allergic diseases (allergic conjunctivitis, allergic asthma, allergic rhinitis and atopic dermatitis) with keratoconus.

Methods

Summary statistics were obtained from genome-wide association studies (GWAS) of allergic conjunctivitis (AC) (20,958 cases and 356,319 controls), allergic asthma (AA) (9631 cases and 210,122 controls), allergic rhinitis (AR) (11,009 cases and 359,149 controls), atopic dermatitis (AD) (13,473 cases and 336,589 controls), keratoconus (KC) (2116 cases and 24,626 controls) and 91 circulating inflammatory cytokines (n = 14,824). Two-sample univariable and multivariable MR analyses were performed. A two-step MR was then applied to determine whether systemic inflammatory cytokines mediated the effect of allergic disease on keratoconus.

Results

The causal odds ratio (OR) estimate of genetically determined KC was 1.66 (95% CI: 1.32-2.08; P < 0.001) for AC, 1.29 (95% CI: 1.10-1.51, P = 0.0014) for AA, 1.39 (95% CI: 1.15-1.68; P < 0.001) for AR and 1.30 (95% CI: 1.17-1.45, P < 0.001) for AD. Multivariable MR indicated a suggestive association between AC and KC after conditioning on other allergic diseases (OR 1.61; 95% CI: 1.10-2.34; P adjusted = 0.054). Two-step MR revealed that the effect was not mediated by systemic inflammatory cytokines.

Conclusions

Our findings provide evidence of a potential causal relationship between AC and KC. The effect of AC on KC may be mediated via other systemic inflammatory cytokines not included in the present study, or by alternative mechanisms. These findings may offer insight for prevention and intervention strategies to lower the risk of KC in patients with AC.

Unraveling shared and unique genetic causal relationship between gut microbiota and four types of uterine-related diseases: Bidirectional Mendelian inheritance approaches to dissect the "Gut-Uterus Axis"

BACKGROUND

The gut microbiota has emerged as a pivotal factor in the etiology of uterine-related diseases. This study aims to elucidate the genetic causal link between gut microbiota composition and these conditions, focusing on the systemic impact and uterine pathology to better understand the "Gut-Uterus Axis."

METHODS

We utilized pooled data from two different GWAS databases, including data from 209 gut microbiota traits and data from four uterus-related diseases. Bidirectional Mendelian Randomization (MR) approaches, incorporating Bayesian weighting and traditional inverse variance weighting (IVW) methods, were employed to explore causal relationships. The robustness of findings was ensured through sensitivity analyses, outlier testing, and MR-PRESSO analysis.

RESULTS

Seventeen significant associations were identified between gut microbiota traits and uterine-related diseases, suggesting potential causal links. These associations were consistent across sensitivity analyses, affirming the reliability of our results. Conversely, reverse MR analyses did not reveal statistically significant associations between uterine diseases and bacterial traits, indicating a unidirectional influence of gut microbiota on uterine health. These findings highlight the complex interplay within the "Gut-Uterus Axis."

CONCLUSION

This research establishes a causal relationship between gut microbiota and uterine diseases, advocating for targeted interventions to mitigate associated risks. It underscores the interconnectedness of gut and reproductive health, promoting a holistic approach to management and treatment within the "Gut-Uterus Axis".

Proteome-Wide Mendelian Randomisation Identifies Causal Links of Plasma Proteins With Periodontitis

OBJECTIVE

Periodontitis is a complex and multifactorial disease and it is challenging to decipher its underlying causes and mechanisms. This study attempted to explore potential circulating proteins in connection to periodontitis through proteome-wide Mendelian randomisation (MR).

METHODS

We analysed 1722 circulating proteins to identify prospective drug targets for tackling periodontitis, using the genomic dataset from the FinnGen study. Two-sample MR was conducted to evaluate the bidirectional relationship between circulating proteins and periodontitis risk. A dataset from the UK Biobank was used to validate the findings. Single-cell analysis was performed to assess the cellular expression of the identified proteins within gingival tissues.

RESULTS

MR analyses found that genetically predicted circulating levels of von Willebrand factor A domain-containing 1 (von Willebrand factor A domain containing 1 [VWA1], odds ratios: 0.94, 95% CI 0.92-0.97, P = 1.28 × 10-5) were inversely associated with periodontitis. In contrast, the level of growth differentiation factor 15 (growth differentiation factor 15 [GDF15], odds ratios: 1.05, 95% CI 1.02-1.07, P = 2.12 × 10-5) might be associated with an increased risk of periodontitis. Single-cell analysis indicated that VWA1 was primarily expressed in endothelial cells of healthy gingival tissues, while the main source of GDF15 was not derived from periodontal cells.

CONCLUSIONS

The present study suggests that certain plasma proteins like VWA1 and GDF15 may be potentially indicative of the risk and susceptibility to periodontitis. These proteins could possibly be the potential therapeutic targets for treating periodontitis, and further investigation is highly warranted.

Causal associations of Helicobacter pylori infection and metabolic syndrome: insights from a two-sample Mendelian randomization study

BACKGROUND

Helicobacter pylori (Hp) infection and metabolic syndrome (MetS) have a high prevalence of co-morbidities and both pose a significant threat to human health and survival. It has been suggested that Hp infection affects the development of MetS in the host, but the causal relationship between the two has not been confirmed.

METHODS

We conducted a two-sample Mendelian randomization study to investigate the causal effect of Hp infection with MetS and its components. Summary statistics for exposure factors (Hp infection) were obtained from the GWAS Catalog (anti-Hp IgG, n = 8,735; Hp VacA antibody levels, n = 1,571; Hp GroEL antibody levels, n = 2,716; Hp OMP antibody levels, n = 2,640). Summary statistics for outcome factors (MetS) were obtained from the most comprehensive genome-wide association study (GWAS) currently available (n = 291,107) as well as from the components of MetS: fasting glucose (n = 46,186), hypertension (n = 461,880), serum triglycerides (n = 115,082), waist circumference (n = 21,949), and high-density lipoprotein (n = 400, 754). The inverse-variance weighted (IVW) method was used as the primary MR method and the robustness of the results was assessed through sensitivity analyses.

RESULTS

MR analysis showed that anti-Hp IgG levels were positively correlated with waist circumference (β = 0.08, P = 0.012), and GroEL antibody levels showed an opposite correlation with HDL levels (β= -0.03, P = 0.025) and TG (β = 0.02, P = 0.045). In contrast, OMP antibodies levels were positively correlated with both HDL and FBG (β = 0.064, P = 0.037 and β = 0.09, P = 0.003). In the estimation of IVW as the main causal method, VacA antibody level was positively associated with hypertension level and negatively associated with TG (β = 0.02, P = 0.008 and β= -0.02, P = 0.007). Meanwhile, the results of sensitivity analyses showed no heterogeneity or significant level pleiotropy.

CONCLUSIONS

Our study suggests that there is a causal effect between Hp infection and Mets diagnosis and its composition, and further studies are needed to understand the mechanism of its influence.

The causal relationship between type 2 diabetes mellitus and isolated REM sleep behavior disorder: results from multivariable and network Mendelian randomization analysis

Objectives

To investigate the causal relationship between type 2 diabetes mellitus (T2DM, exposure) and isolated REM sleep behavior disorder (iRBD, outcome).

Methods

Genome-wide association study (GWAS) data for iRBD comprised 9,447 samples, including 1,061 iRBD cases from the International RBD Study Group. Initially, we performed linkage disequilibrium score regression (LDSC) to explore the genetic correlation between T2DM and iRBD. Then the two-sample univariate MR (UVMR) analysis was conducted to examine the effects of T2DM and blood sugar metabolism-related factors on iRBD. Subsequently, we applied multivariable MR (MVMR) methods to further adjust for confounders. Lastly, we executed a network MR analysis, with cytokines and immune cell characteristics as potential mediators, aiming to investigate indirect effect of T2DM on iRBD.

Results

Results from LDSC suggest a genetic correlation between T2DM and iRBD (rg=0.306, P=0.029). UVMR analysis indicates that both T2DM (Odds Ratio [95% Confidence Interval] = 1.19 [1.03, 1.37], P = 0.017) and high blood glucose levels (1.55 [1.04, 2.30], P = 0.032) are risk factors for iRBD. Even after adjusting for confounders in MVMR, the association between T2DM and iRBD remains robust. Finally, results from network MR analysis suggest that T2DM may indirectly promote the development of iRBD by reducing levels of Stromal Cell-Derived Factor 2 in circulation and by increasing BAFF-receptor expression in IgD- CD38- B cells.

Conclusions

T2DM may promote the onset of iRBD by influencing immune-inflammatory responses. Our findings provide valuable insights and directions for understanding the pathogenesis of iRBD, identifying high-risk groups, and discovering new therapeutic targets.

Causality between autoimmune diseases and schizophrenia: a bidirectional Mendelian randomization study

BACKGROUND

Observational studies have shown a link between autoimmune diseases and schizophrenia, with conflicting conclusions. Due to the existence of confounding factors, the causal link between autoimmune diseases and schizophrenia is still unknown.

METHOD

We conducted a comprehensive Mendelian randomization (MR) analysis of schizophrenia and ten common autoimmune diseases in individuals of European descent using genome-wide association studies (GWASs). To evaluate the relationships between autoimmune diseases and schizophrenia, inverse variance weighted, MR-RAPS, Bayesian weighted MR, constrained maximum likelihood, debiased IVW, MR-Egger, and weighted median were utilized. Several sensitivity analyses were performed to ensure the reliability of the study's results.

RESULTS

Our findings reveal that genetically predicted ankylosing spondylitis is related to an increased risk of schizophrenia, whereas celiac disease, type 1 diabetes, and systemic lupus erythematosus are associated with a lower risk of schizophrenia. In the reverse MR analysis, our study indicated that genetically predicted schizophrenia is linked to higher risks of ankylosing spondylitis, Crohn's disease, ulcerative colitis, inflammatory bowel disease, and psoriasis. Neither multiple sclerosis nor rheumatoid arthritis have been linked to schizophrenia, and vice versa.

CONCLUSION

Despite contradicting some other observational reports, this study showed support for a causal link between autoimmune diseases and schizophrenia. To gain a better understanding of the mechanisms underlying the development of immune-mediated schizophrenia, additional research is required to identify potential mechanisms identified in observational studies.

Causal impact of gut microbiota on five liver diseases: insights from mendelian randomization and single-cell RNA sequencing

Background

Liver disease is among the top ten causes of death globally. With studies suggesting a link between gut microbiota (GM) and liver disease.

Method

We selected summary statistics data from the largest available whole-genome association study (n = 13,266) of GM by the MiBioGen consortium as the exposure, and obtained liver disease-related data from IEU Open GWAS and The NHGRI-EBI GWAS Catalog. A two-sample Mendelian Randomization (MR) analysis employing various methods, to establish the causal relationship between GM and five liver diseases. Meanwhile, single-cell RNA sequencing data were used to examine Prevotella-related genes expression under healthy and disease liver.

Results

The IVW analysis indicate a causal relationship between GM and liver diseases, with Prevotella exhibiting a protective effect in all five liver diseases: Alcoholic liver disease (OR:0.81,95% confidence interval:0.66-1.00,P IVW = 0.0494); Cirrhosis (OR: 0.85,95% confidence interval: 0.73-0.99,P IVW = 0.0397); Hepatic failure, not elsewhere classified (OR:0.60,95% confidence interval:0.37-0.95,P IVW = 0.0305); Benign neoplasm:Liver (OR:0.39,95% confidence interval:0.2-0.75,P IVW = 0.0046); Malignant neoplasm of liver, primary (OR:0.41, 95% confidence interval:0.18-0.93,P IVW = 0.0334). The single-cell results suggest differential expression of Prevotella-related genes between liver disease patients and healthy individuals.

Conclusion

Our MR results show a causal relationship between the GM and liver disease. Prevotella displays a notable protective effect. This finding may enhance the precision of GM-based therapies and offer new insights for clinical research.

Impact of elevated CO2 on soil microbiota: A meta-analytical review of carbon and nitrogen metabolism

In the face of 21st-century challenges driven by population growth and resource depletion, understanding the intricacies of climate change is crucial for environmental sustainability. This review systematically explores the interaction between rising atmospheric CO2 concentrations and soil microbial populations, with possible feedback effects on climate change and terrestrial carbon (C) cycling through a meta-analytical approach. Furthermore, it investigates the enzymatic activities related to carbon acquisition, gene expression patterns governing carbon and nitrogen metabolism, and metagenomic and meta-transcriptomic dynamics in response to elevated CO2 levels. The study reveals that elevated CO2 levels substantially influence soil microbial communities, increasing microbial biomass C and respiration rate by 15 % and upregulating genes involved in carbon and nitrogen metabolism by 12 %. Despite a 14 % increase in C-acquiring enzyme activity, there is a 5 % decrease in N-acquiring enzyme activity, indicating complex microbial responses to CO2 changes. Additionally, fungal marker ratios increase by 14 % compared to bacterial markers, indicating potential ecosystem changes. However, the current inadequacy of data on metagenomic and meta-transcriptomic processes underscores the need for further research. Understanding soil microbial feedback mechanisms is crucial for elucidating the role of rising CO2 levels in carbon sequestration and climate regulation. Consequently, future research should prioritize a comprehensive elucidation of soil microbial carbon cycling, greenhouse gas emission dynamics, and their underlying drivers.

Causal associations of Sjögren's syndrome with cardiovascular disease: A two-sample Mendelian randomization study

Study objectives

Observational and cohort studies have associated Sjögren's syndrome (SS) with various types of cardiovascular disease (CVD), yet causal relationships have not been established. We employed Mendelian randomization (MR) to investigate potential causal links between SS and CVD in the general population.

Methods

We conducted a two-sample MR analysis using data from four distinct sources for 11 genome-wide significant single nucleotide polymorphisms (SNPs) associated with SS and data for 13 types of CVD sourced from FinnGen, IEU OpenGWAS, and GWAS catalog. The inverse variance weighted method was selected as the primary analytical approach, complemented by various sensitivity analyses.

Results

MR analyses provide evidence of a significantly increased risk of ischemic stroke associated with genetically predicted SS (odds ratio [OR], 1.0237; 95 % CI, 1.0096 to 1.0379; p = 0.0009), as well as suggestive evidence of a potential causal relationship between SS and an increased risk of chronic heart failure (OR, 1.0302; 95 % CI, 1.0020 to 1.0592; p = 0.0355). Sensitivity analyses reinforced these associations, demonstrating robustness and consistency across multiple statistical methods. The secondary analysis, conducted after outlier correction using MR-PRESSO and RadialMR methods, reaffirmed these associations and also indicated a suggestive causal link between SS and non-rheumatic valvular heart disease (OR, 1.0251; 95 % CI, 1.0021 to 1.0486; p = 0.0323).

Conclusions

This study demonstrates that genetically predicted SS is a potential causative risk factor for ischemic stroke, chronic heart failure, and non-rheumatic valvular heart disease on a large-scale population. However, further research incorporating ancestral diversity is required to confirm a causal relationship between SS and CVD.

Causal associations and shared genetic etiology of neurodegenerative diseases with epigenetic aging and human longevity

The causative mechanisms underlying the genetic relationships of neurodegenerative diseases with epigenetic aging and human longevity remain obscure. We aimed to detect causal associations and shared genetic etiology of neurodegenerative diseases with epigenetic aging and human longevity. We obtained large-scale genome-wide association study summary statistics data for four measures of epigenetic age (GrimAge, PhenoAge, IEAA, and HannumAge) (N = 34,710), multivariate longevity (healthspan, lifespan, and exceptional longevity) (N = 1,349,462), and for multiple neurodegenerative diseases (N = 6618-482,730), including Lewy body dementia, Alzheimer's disease (AD), Parkinson's disease, amyotrophic lateral sclerosis, and multiple sclerosis. Main analyses were conducted using multiplicative random effects inverse-variance weighted Mendelian randomization (MR), and conditional/conjunctional false discovery rate (cond/conjFDR) approach. Shared genomic loci were functionally characterized to gain biological understanding. Evidence showed that AD patients had 0.309 year less in exceptional longevity (IVW beta = -0.309, 95% CI: -0.38 to -0.24, p = 1.51E-19). We also observed suggestively significant causal evidence between AD and GrimAge age acceleration (IVW beta = -0.10, 95% CI: -0.188 to -0.013, p = 0.02). Following the discovery of polygenic overlap, we identified rs78143120 as shared genomic locus between AD and GrimAge age acceleration, and rs12691088 between AD and exceptional longevity. Among these loci, rs78143120 was novel for AD. In conclusion, we observed that only AD had causal effects on epigenetic aging and human longevity, while other neurodegenerative diseases did not. The genetic overlap between them, with mixed effect directions, suggested complex shared genetic etiology and molecular mechanisms.

Multivariate genomic analysis of 5 million people elucidates the genetic architecture of shared components of the metabolic syndrome

Metabolic syndrome (MetS) is a complex hereditary condition comprising various metabolic traits as risk factors. Although the genetics of individual MetS components have been investigated actively through large-scale genome-wide association studies, the conjoint genetic architecture has not been fully elucidated. Here, we performed the largest multivariate genome-wide association study of MetS in Europe (nobserved = 4,947,860) by leveraging genetic correlation between MetS components. We identified 1,307 genetic loci associated with MetS that were enriched primarily in brain tissues. Using transcriptomic data, we identified 11 genes associated strongly with MetS. Our phenome-wide association and Mendelian randomization analyses highlighted associations of MetS with diverse diseases beyond cardiometabolic diseases. Polygenic risk score analysis demonstrated better discrimination of MetS and predictive power in European and East Asian populations. Altogether, our findings will guide future studies aimed at elucidating the genetic architecture of MetS.

Causal relationships between gut microbiota and polycystic ovarian syndrome: A bidirectional Mendelian randomization study

INTRODUCTION

Previous studies have established a link between gut microbiota and polycystic ovary syndrome (PCOS), but little is known about their precise causal relationship. Therefore, this study aims to explore whether there are precise causal relationships between gut microbiota and PCOS.

MATERIAL AND METHODS

We performed a bidirectional two-sample Mendelian randomization (MR) analysis. Datasets were from the largest published meta-analysis on gut microbiota composition and the FinnGen cohort of the IEU Open Genome-Wide Association Study Project database. Inverse variance weighted (IVW), MR-Egger, constrained maximum likelihood-based Mendelian randomization, weighted median, weighted mode, and simple mode were used. Cochran's Q and MR-Egger intercept tests were employed to measure the heterogeneity.

RESULTS

A total of 211 gut microbiota taxa were identified in MR analysis. Nine taxa of bacteria, including Alphaproteobacteria (0.55, 0.30-0.99, p = 0.04), Bacilli (1.76, 1.07-2.91, p = 0.03), Bilophila (0.42, 0.23-0.77, p < 0.01), Blautia (0.16, 0.03-0.79, p = 0.02), Burkholderiales (2.37, 1.22-4.62, p = 0.01), Candidatus Soleaferrea (0.65, 0.43-0.98, p = 0.04), Cyanobacteria (0.51, 0.31-0.83, p = 0.01), Holdemania (0.53, 0.35-0.81, p < 0.01), and Lachnospiraceae (1.86, 1.04-3.35, p = 0.03), were found to be associated with PCOS in the above MR methods included at least IVW method. Cochran's Q statistics and MR-Egger intercept test suggested no significant heterogeneity. In addition, 69 taxa were shown significant for at least the IVW method in reverse MR analysis, of these, 25 had a positive correlation, and 37 had a negative correlation. Additionally, Alphaproteobacteria and Lachnospiraceae (0.95, 0.91-0.98, p < 0.01; 0.97, 0.94-0.99, p = 0.02, respectively) were shown a bidirected causally association with PCOS.

CONCLUSIONS

Our study provides evidence of the bidirectional causal association between gut microbiota and PCOS from a genetic perspective.

Cysteine cathepsins and autoimmune diseases: A bidirectional Mendelian randomization

Cysteine cathepsins are proteolytic enzymes crucial in various physiological and pathological processes, primarily operating within lysosomes. Their functions include protein degradation, immune system regulation, and involvement in various diseases. While some cysteine cathepsins play important roles in the immune system, their connection to autoimmune diseases remains unclear. This study proposes using Mendelian randomization to explore the causal relationship between cysteine cathepsins and autoimmune diseases. Single nucleotide polymorphisms (SNPs) for cysteine cathepsins were obtained from a publicly available genome-wide association study (GWAS) dataset, while outcome SNP data were sourced from 10 separate GWAS datasets. Mendelian randomization (MR) analysis employed the Wald ratio (WR) and inverse variance weighted (IVW) approach as primary methods, supplemented by the weighted median and MR-Egger methods. Heterogeneity was assessed using Cochran Q test, and sensitivity analysis was conducted using the MR-PRESSO method. The association strength between exposure and outcome was evaluated using odds ratios (OR) with 95% confidence intervals (CI). The study identified a potential positive correlation between elevated cathepsin B and psoriasis (Wald ratio OR = 1.449, 95% CI: 1.053-1.993, P = .0227). Elevated cathepsin F was potentially linked to ulcerative colitis (WR OR = 1.073, 95% CI: 1.021-1.127, P = .0056), ankylosing spondylitis (WR OR = 1.258, 95% CI: 1.082-1.463, P = .0029), and primary biliary cholangitis(PBC) (WR OR = 1.958, 95% CI: 1.326-2.889, P = .0007). Conversely, cathepsin H appeared protective against celiac disease (WR OR = 0.881, 95% CI: 0.838-0.926, P = 6.5e-7), though elevated levels may increase the risk of type 1 diabetes (IVW OR = 1.121, 95% CI: 1.053-1.194, P = .0003) and PBC (WR OR = 1.792, 95% CI: 1.062-3.024, P = .0288). Cathepsin Z was also associated with an increased risk of type 1 diabetes (IVW OR = 1.090, 95% CI: 1.006-1.181, P = .0349). The MR analysis suggests potential risks of cathepsin B with psoriasis, cathepsin F with ulcerative colitis, ankylosing spondylitis, and PBC, and cathepsin Z with type 1 diabetes. Conversely, cathepsin H may protect against celiac disease but could increase the risk of type 1 diabetes and PBC.

Serum iron status and the risk of female infertility in European populations: A two-sample Mendelian randomization study

The relationship between iron status and female infertility has been observed in several studies, yet its causal nature remains ambiguous. We employed univariate Mendelian randomization (MR) analyses to explore the potential causal connection between these 2 factors. For our analysis, genetic instrumental variables pertaining to iron status were selected using data from the Iron Status Genetics Consortium, encompassing 48,972 individuals of European descent from 19 cohorts (11 discovery and 8 replication). For female infertility data, we referred to FinnGen Consortium Release 9, which includes 11,442 cases and 107,564 controls. Our MR approach utilized both a conservative strategy (involving single nucleotide polymorphisms pertinent to general iron status) and a liberal strategy (encompassing single nucleotide polymorphisms linked to any iron status indicator). The conservative approach relied on inverse variance-weighted methods, whereas the liberal strategy integrated inverse variance weighted with MR-Egger regression, the weighted median approach, and simple mode techniques. The conservative strategy did not reveal a significant link between iron status and female infertility risk. Conversely, the liberal strategy indicated a positive correlation specifically between serum iron levels and female infertility risk (odds ratio from MR: 1.225; 95% confidence interval: 1.064-1.410; P = .030), while no significant associations were found for other iron indicators (P > 0.05). Our MR investigation suggests a potential positive association between serum iron levels and the risk of female infertility, while other iron markers do not appear to significantly influence this risk. These findings highlight the need for further research into the possible connection between serum iron status and female infertility risk.

Exploring the potential link between gut microbiota and chronic kidney disease in causality: A 2-sample Mendelian randomization study

Increasing evidence indicates a significant correlation between gut microbiota (GM) and susceptibility to chronic kidney disease (CKD). However, causal relationship presence remains uncertain. Mendelian randomization (MR) was applied to evaluate potential causal relation from GM to CKD. Genomic association analysis aggregates publicly online databases, utilizing Genome-Wide Association Study (GWAS) database focused on GM and CKD. For examination of potential causal connection from GM to CKD, a 2-way, 2-sample Mendelian randomization (MR) method was applied. Sensitivity analyses were utilized to scrutinize for heterogeneity, horizontal pleiotropy, MR outcomes resilience. Result from inverse variance weighting (IVW) method revealed that 10 microbiotas such as Porphyromonadaceae (OR = 1.351, 95% CI: 1.114-1.638, P = .002), Dorea (OR = 1.236, 95% CI: 1.040-1.468, P = .016), Ruminococcus torques group (OR = 1.290, 95% CI: 1.035-1.608, P = .024) are potential CKD risk factors. Five microbiotas, including the Prevotellaceae (OR = 0.814, 95% CI: 0.719-0.922, P = .001) are potential CKD protective factors. Sensitivity analyses reveal no horizontal pleiotropy or heterogeneity. Additionally, reverse MR results unveiled potential relation between CKD and disorders in 3 microbiotas, including Senegalimassilia. According to the investigation, MR method was employed to delve into reciprocal causal connection from GM to CKD. Our findings identified 15 types of GM causally linked to CKD, as well as CKD demonstrating causal associations with 3 types of GM. Further exploration of these associated GM types is hopeful to raise novel insights, for CKD preventing and early monitoring.

Hypertensive disorders of pregnancy and stroke: a univariate and multivariate Mendelian randomization study

Background

Hypertensive disorders of pregnancy (HDP) are associated with an increased risk of stroke later in life in multiparous women. However, causality of these associations remains unclear. This study employed 2-sample univariate and multivariate Mendelian randomization (MR) to assess the causal connection between HDP and stroke.

Methods

Genetic variants for HDP and two subtypes were identified from recent large-scale genome-wide association studies and the FinnGen consortium. Stroke summary data were obtained from the MEGASTROKE consortium. The primary analytical approach for univariate MR was the inverse variance weighting method. Sensitivity analyses incorporated methods such as MR-Egger regression, weighted median, and maximum likelihood to ascertain the robustness of the results. Additionally, multivariable MR analyses were conducted to account for potential associative effects of hypertension and type 2 diabetes.

Results

Genetically predicted HDP was associated with a high risk of large artery atherosclerosis (odds ratio [OR]=1.50, 95% confidence interval [CI]: 1.17-1.91, P=1.13×10-3) and small vessel stroke (OR=1.29, 95% CI: 1.20-1.50, P=1.52×10-3). HDP may also correlate with ischemic stroke (OR=1.13, 95% CI: 1.04-1.23, P=4.99×10-3) and stroke (OR=1.11, 95% CI: 1.03-1.20, P=8.85×10-3). An elevated risk of small vessel stroke (OR=1.20, 95% CI: 1.01-1.43, P=3.74×10-2) and large artery atherosclerosis (OR=1.22, 95% CI: 1.01-1.47, P=4.07×10-2) may be related with genetically predicted susceptibility to gestational hypertension. Genetically predicted susceptibility to preeclampsia or eclampsia may be associated with an increased risk of stroke (OR = 1.10, 95% CI: 1.02-1.19, P = 1.16×10-2) and ischemic stroke (OR = 1.10, 95% CI: 1.02-1.20, P = 1.84×10-2). Type 2 diabetes mellitus and hypertension were identified as significant factors contributing to the association between HDP and stroke.

Conclusions

This study provides genetic evidence supporting an association between HDP and increased stroke risk bolstering HDP as a cerebrovascular risk factor.

Exploring the association between skin microbiota and inflammatory skin diseases: a two-sample Mendelian randomization analysis

Dysbiosis in the skin microbiome is closely associated with various inflammatory skin diseases. However, current research on the causal relationship between the skin microbiome and inflammatory skin diseases lacks comprehensive and detailed investigation. We used a two-sample Mendelian randomization (MR) approach to explore associations between the skin microbiome and seven inflammatory skin diseases, including acne, atopic dermatitis, erysipelas, vitiligo, psoriasis, rosacea, and urticaria. The GWAS summary data for the skin microbiome was derived from 647 participants in two German population-based cohorts, and for the inflammatory skin diseases, they were sourced from the FinnGen consortium. Our primary MR analysis method was the inverse variance weighted (IVW) method, complemented by alternatives like MR-Egger regression, weighted median estimation, and constrained maximum likelihood. Sensitivity analyses, including Cochran's Q test, MR-Egger intercept test, and MR-PRESSO outlier detection, were conducted to validate and stabilize our findings. We identified significant causal relationships between the skin microbiome and seven inflammatory skin diseases: acne, atopic dermatitis, erysipelas, vitiligo, psoriasis, rosacea, and urticaria, with 7, 6, 9, 1, 7, 4, and 7 respective causal relationships for each disease. These relationships comprise 20 protective and 14 risk causal relationships. We applied the false discovery rate correction to these results. Sensitivity analysis revealed no significant pleiotropy or heterogeneity. Our study revealed both beneficial and detrimental causal relationships between diverse skin microbiota and inflammatory skin diseases. Additionally, the ecological niche of the skin microbiome was crucial to its functional impact. This research provided new insights into how skin microbiota impacted skin diseases and the development of therapeutic strategies.

Multi-Ancestry Causal Association between Rheumatoid Arthritis and Interstitial Lung Disease: A Bidirectional Two-Sample Mendelian Randomization Study

Background: Rheumatoid arthritis (RA) is associated with diverse extra-articular manifestations, including interstitial lung disease (ILD). No previous studies have examined the bidirectional relationship between RA and ILD using the Mendelian randomization (MR) analyses. Therefore, we aimed to investigate this subject using a two-sample bidirectional MR method. Methods: We performed bidirectional two-sample MR using summary statistics from genome-wide association studies (GWASs). The data are publicly available, de-identified, and from European (EUR) and East Asian (EAS) ancestries. Results: A total of 474,450 EUR participants and 351,653 EAS participants were included for either forward or reverse MR analysis. In our primary analysis, we found significant evidence of an increased risk of ILD associated with RA among individuals of EUR ancestry (ORMR-cML = 1.08; 95% confidence interval [CI] = 1.03-1.14; p = 0.003) and EAS ancestry (ORMR-cML = 1.37; 95% CI = 1.23-1.54; p < 0.001). Additionally, the reverse MR showed significant evidence of an increased risk of RA associated with ILD among those of EUR ancestry (ORMR-cML = 1.12; 95% CI = 1.05-1.19; p < 0.001). However, only one instrumental variable was selected in the EAS ILD GWAS, and there was no increased risk of RA associated with ILD in those of EAS ancestry (ORMR-cML = 1.02; 95% CI = 0.91-1.14; p = 0.740). Conclusions: Our findings indicate that RA and ILD have a bidirectional causal inference when using the MR analysis of GWAS datasets. The findings are only relevant for genetic predisposition; thus, further research is needed to determine the impact of non-genetic predispositions.