Causal Relationship Between Lung Function and Atrial Fibrillation: A Two Sample Univariable and Multivariable, Bidirectional Mendelian Randomization Study

Genetic Causal Relationship Between Systemic Lupus Erythematosus and Malignant Tumors of the Female Reproductive System: A GWAS Analysis in European Populations

Background: Systemic lupus erythematosus (SLE) is a multisystem autoimmune disease that primarily affects women of reproductive age. Existing studies have demonstrated complex associations between SLE and various diseases, but its genetic relationship with malignant tumors of the female reproductive system has not been fully elucidated. This study is aimed at exploring the potential genetic associations and shared molecular basis between SLE and female reproductive system malignancies using genome-wide association studies (GWASs) and cross-trait analysis. Methods: We selected genetic variants significantly associated with SLE (p < 5 × 10-8) from large-scale GWAS databases as genetic instruments and applied various statistical methods to analyze the associations between SLE and cervical cancer, endometrial cancer, ovarian cancer, vulvar cancer, vaginal cancer, and uterine cancer. The primary analysis was conducted using inverse variance weighting (IVW), supplemented by Egger regression, weighted median, and weighted mode methods. To control for potential confounders, we performed multivariable analysis while including BMI, estradiol, and CRP as covariates. Additionally, cross-trait analysis using the association analysis based on subset (ASSET) method was employed to identify shared genetic variants and their effect directions between SLE and uterine cancer. Results: Genetic association analysis showed a significant negative association between SLE and endometrial cancer (OR = 0.972, 95% CI [0.946-0.998], p = 0.038), suggesting that SLE may be associated with a reduced risk of endometrial cancer. For uterine cancer, the weighted median method also indicated a marginally significant negative association (OR = 0.955, 95% CI [0.912-1.000], p = 0.049). Multivariable analysis further confirmed that the protective association between SLE and endometrial cancer remained significant after controlling for BMI, estradiol, and CRP (OR = 0.96, 95% CI [0.93-0.99], p = 0.014). However, no significant association was observed between SLE and cervical cancer, ovarian cancer, vulvar cancer, or vaginal cancer. Cross-trait analysis identified 193 shared genetic variants between SLE and endometrial cancer and 71 shared variants between SLE and uterine cancer, with rs2442719 and rs3131004 showing consistent effect directions in both comparisons. Conclusion: This study provides genetic epidemiological evidence suggesting that SLE may have a protective effect against endometrial and uterine cancers and identifies potential shared genetic bases. These findings offer new insights into the relationship between SLE and gynecological tumors and may provide references for the prevention and treatment of related diseases.

The role of inflammatory factors in mediating the causal effects of type 1 diabetes mellitus on idiopathic pulmonary fibrosis: A two-step Mendelian randomization study

While recent studies suggested a potential causal link between type 1 diabetes mellitus (T1DM) but not type 2 diabetes mellitus (T2DM) and idiopathic pulmonary fibrosis (IPF), the involved mechanism remains unclear. Here, using a Mendelian randomization (MR) approach, we verified the causal relationship between the two types of diabetes mellitus and IPF and investigated the possible role of inflammation in the association between diabetes mellitus and IPF. Based on genome-wide association study (GWAS) summary data of T1DM, T2DM, and IPF, the univariable MR, multivariable MR (MVMR), and mediation MR were successively used to analyze the causal relationship. Inverse variance weighted was used as the main method to infer the causal effect, together with a series of sensitivity analyses. The univariable MR showed that only T1DM increased the risk of IPF, and there was no significant causal relationship between T2DM and IPF. The MVMR further verified that there was an independent direct causal effect of T1DM on IPF. Further mediation analysis showed that this effect was partly mediated by increasing C-X-C motif chemokine ligand 10 (CXCL10) and interleukin-12 subunit beta (IL-12B). In conclusion, T1DM is related to an increased risk of IPF. Notably, the causal effect was partially mediated by CXCL10 and IL-12B. Hence, monitoring T1DM patients may help in the early detection and prevention of IPF.

Circulating levels of vitamins and risk of lymphoma: insights from a two-sample Mendelian randomization

BACKGROUND

To explore the genetic causal association between lymphoma and the circulating levels of vitamins through Mendelian randomization (MR).

RESEARCH DESIGN AND METHODS

We performed MR analysis using publicly available genome-wide association study (GWAS) summary data. Seven indicators related to the circulating levels of vitamins (vitamin D, vitamin C, vitamin B6, vitamin B12, folic acid, vitamin E, and carotene) served as exposures, while lymphoma was the outcome. The genetic causal association between these circulating levels of vitamin indicators and lymphoma was assessed using the inverse variance weighted (IVW) method.

RESULTS

Based on IVW method, vitamin B12 (OR = 0.48; 95% CI: 0.28-5.19; p = 0.018) and folic acid (OR = 0.62; 95% CI: 0.40-0.96; p = 0.032) both showed substantial evidence of a relationship with lymphoma. Moreover, the Weighted median method similarly indicated potential evidence of an association between vitamin B12 (OR = 0.40; 95% CI: 0.18-0.90; p = 0.027) and lymphoma. The Simple mode, and Weighted mode methods showed no potential genetic causal association (p > 0.05 in the two analyses).

CONCLUSIONS

This study suggests a potential association between folic acid and vitamin B12 and lymphoma. Further research is required to assess the reproducibility of this finding in different contexts and to gain deeper insights into the potential underlying mechanisms.

No genetic causal association between iron status and pulmonary artery hypertension: Insights from a two-sample Mendelian randomization

To explore the genetic causal association between pulmonary artery hypertension (PAH) and iron status through Mendelian randomization (MR), we conducted MR analysis using publicly available genome-wide association study (GWAS) summary data. Five indicators related to iron status (serum iron, ferritin, total iron binding capacity (TIBC), soluble transferrin receptor (sTfR), and transferrin saturation) served as exposures, while PAH was the outcome. The genetic causal association between these iron status indicators and PAH was assessed using the inverse variance weighted (IVW) method. Cochran's Q statistic was employed to evaluate heterogeneity. We assessed pleiotropy using MR-Egger regression and MR-Presso test. Additionally, we validated our results using the Weighted median, Simple mode, and Weighted mode methods. Based on the IVW method, we found no causal association between iron status (serum iron, ferritin, TIBC, sTfR, and transferrin saturation) and PAH (p β > 0.05). The Weighted median, Simple mode, and Weighted mode methods showed no potential genetic causal association (p β > 0.05 in the three analyses). Additionally, no heterogeneity or horizontal pleiotropy was detected in any of the analyses. Our results show that there are no genetic causal association between iron status and PAH.

Ischemic Stroke and Cerebral Microbleeds: A Two-Sample Bidirectional Mendelian Randomization Study

INTRODUCTION

Recent observational studies have reported the association between ischemic stroke (IS) and cerebral microbleeds (CMBs). Whether this reflects a causal association remains to be established. Herein, we adopted a two-sample bidirectional Mendelian randomization (MR) analysis to comprehensively evaluate the causal association of IS and CMBs.

METHODS

The summary-level genome-wide association studies (GWASs) data of IS were obtained from the GIGASTROKE consortium (62,100 European ancestry cases and 1,234,808 European ancestry controls). All IS cases could be further divided into large-vessel atherosclerosis stroke (LVS, n = 6399), cardio-embolic stroke (CES, n = 10,804) and small-vessel occlusion stroke (SVS, n = 6811). Meanwhile, we used publicly available summary statistics from published GWASs of CMBs (3556 of the 25,862 European participants across 2 large initiatives). A bidirectional MR analysis was conducted using inverse-variance weighting (IVW) as the major outcome, whereas MR-Egger and weighted median (WM) were used to complement the IVW estimates as they can provide more robust estimates in a broader set of scenarios but are less efficient (wider CIs). A Bonferroni-corrected threshold of p < 0.0125 was considered significant, and p values between 0.0125 and 0.05 were considered suggestive of evidence for a potential association.

RESULTS

We detected that higher risk of IS [IVW odds ratio (OR) 1.47, 95% confidence interval (CI) 1.04-2.07, p = 0.03] and SVS (IVW OR 1.62, 95% CI 1.07-2.47, p = 0.02) were significantly associated with CMBs. Reverse MR analyses found no significant evidence for a causal effect of CMBs on IS and its subtypes.

CONCLUSIONS

Our study provides potential evidence that IS and SVS are causally linked to increased risk of CMBs. Further research is needed to determine the mechanisms of association between IS and CMBs.

Genetic association and causal inference between lung function and venous thromboembolism

BACKGROUND

Previous studies have indicated that lower lung function is related to a higher risk of venous thromboembolism (VTE). However, causal inferences may be affected by confounders, coheritability or reverse causality. We aimed to explore the causal association between lung function and VTE.

METHODS

Summary data from public genome-wide association studies (GWAS) for lung function and VTE were obtained from published meta-analysis studies and the FinnGen consortium, respectively. Independent genetic variables significantly related to exposure were filtered as proxy instruments. We adopted linkage disequilibrium score regression (LDSC) and two-sample Mendelian randomization (MR) analyses to infer the genetic backgrounds and causal associations between different lung functions and VTE events.

RESULTS

LDSC showed a genetic correlation between forced expiratory volume in one second (FEV1) and deep vein thrombosis (DVT) (rg = - 0.189, P = 0.005). In univariate MR (UVMR), there was suggestive evidence for causal associations of genetically predicted force vital capacity (FVC) with DVT (odds ratio (OR) 0.774; 95% confidence interval (CI) 0.641-0.934) via forwards analysis and genetically predicted pulmonary embolism (PE) with FVC (OR 0.989; 95% CI 0.979-0.999) via reverse analysis. Multivariate MR (MVMR) analyses of lung function-specific SNPs suggested no significant direct effects of lung function on VTE, and vice versa. Of note is the borderline causal effect of PE on FEV1 (OR 0.921; 95% CI 0.848-1.000).

CONCLUSIONS

Our findings identified a coheritability of FEV1 (significant) and FVC (suggestive) with DVT. There was no convincing causal relationship between lung function and the risk of VTE events. The borderline causal effect of PE on FEV1 and the significant genetic correlation of FEV1 with DVT may have clinical implications for improving the quality of existing prevention and intervention strategies.

A Mild Causal Relationship Between Tea Consumption and Obesity in General Population: A Two-Sample Mendelian Randomization Study

Evidence from observational studies for the effect of tea consumption on obesity is inconclusive. This study aimed to verify the causal association between tea consumption and obesity through a two-sample Mendelian randomization (MR) analysis in general population-based datasets. The genetic instruments, single nucleotide polymorphisms (SNPs) associated with tea consumption habits, were obtained from genome-wide association studies (GWAS): UK Biobank, Nurses' Health Study, Health Professionals Follow-up Study, and Women's Genome Health Study. The effect of the genetic instruments on obesity was analyzed using the UK Biobank dataset (among ∼500,000 participants). The causal relationship between tea consumption and obesity was analyzed by five methods of MR analyses: inverse variance weighted (IVW) method, MR-Egger regression method, weighted median estimator (WME), weighted mode, and simple mode. Ninety-one SNPs were identified as genetic instruments in our study. A mild causation was found by IVW (odds ratio [OR] = 0.998, 95% confidence interval [CI] = 0.996 to 1.000, p = 0.049]), which is commonly used in two-sample MR analysis, indicating that tea consumption has a statistically significant but medically weak effect on obesity control. However, the other four approaches did not show significance. Since there was no heterogeneity and pleiotropy in this study, the IVW approach has the priority of recommendation. Further studies are needed to clarify the effects of tea consumption on obesity-related health problems in detail.

Mendelian Randomization Study of Causal Relationship between Omega-3 Fatty Acids and Risk of Lung Cancer

Objective

Evidence suggests that omega-3 fatty acid intake exerts a protective effect on lung cancer, but its causal association with risk of lung cancer remains uncertain. This study attempts to clarify the causal effect of omega-3 fatty acids on lung cancer utilizing genome-wide association study (GWAS) data with Mendelian randomization (MR) approach.

Methods

This study acquired omega-3 fatty acid data from the UK Biobank and data of lung cancer patients from the Consortium and International Lung Cancer Consortium (ILCCO). Single-nucleotide polymorphisms (SNPs) associated with omega-3 fatty acids were screened as instrumental variables (IVs) in line with the criteria of p < 5E - 8, linkage disequilibrium R ² > 0.001 and distance < 10000 kb. Through inverse variance weighted (IVW), MR-Egger, weighted median, simple mode, and weighted mode, causal association between omega-3 fatty acids and risk of lung cancer was evaluated. Cochran's Q test was applied for a heterogeneity test. The pleiotropy and horizontal pleiotropy among IVs were evaluated via MR-Egger regression intercept analysis.

Results

Totally, 42 SNPs associated with omega-3 fatty acids were identified as IVs. According to the results of IVW (OR (95% CI): 0.899 (0.817, 0.990), p = 0.03), MR-Egger (OR (95% CI): 0.856 (0.750, 0.977), p = 0.026), weighted median (OR (95% CI): 0.899 (0.817, 0.990), p = 0.001), simple mode (OR (95% CI): 0.901 (-0.678, 1.199), p = 0.478), and weighted mode (OR (95% CI): 0.859 (0.782, 0.944), p = 0.003), omega-3 fatty acids showed a causal association with low risk of lung cancer. No genetic pleiotropy or horizontal pleiotropy was found according to MR-Egger regression intercept analysis.

Conclusion

Our findings provide sufficient evidence that omega-3 fatty acids are causal protective factors of lung cancer. Despite this, further work is required for elucidating the potential mechanisms.