Two-sample Mendelian Randomization Research Articles

Causal Link between Gut Microbiota and Infertility: A Two-sample Bidirectional Mendelian Randomization Study

Causal Link between Gut Microbiota and Infertility: A Two-sample Bidirectional Mendelian Randomization Study

Inflammatory bowel disease and risk of ophthalmic inflammation-related diseases: a two-sample Mendelian randomization study

AIM: To investigate the causal effect of inflammatory bowel disease (IBD) on ocular inflammation using Mendelian randomization (MR) analysis. METHODS: Genetic instruments associated with inflammatory bowel disease (IBD), ulcerative colitis (UC), and Crohn's disease (CD) were derived from the largest genome-wide association studies (GWAS) published to date. The FinnGen research project was utilized to identify genetic risk variants associated with conjunctivitis, keratitis, iridocyclitis, chorioretinitis, episcleritis, and optic neuritis. All participants were of European ancestry. Three methods which included inverse variance weighting (IVW), weighted median (WM), and MR-Egger regression were performed to estimate the causal association in this study. IVW took the inverse variance of each study as the weight to calculate the weighted average of effect sizes, to summarize the effect sizes of multiple independent studies, which could provide the most precise estimated results. IVW was used as the primary outcome, while WM and MR-Egger were used to improve the estimation of IVW. RESULTS: A nominal causal effect of genetically predicted IBD on risk of non-infectious conjunctivitis, keratitis, iridocyclitis, and optic neuritis, but not on chorioretinitis or episcleritis. After Bonferroni correction, the results showed that genetically predicted UC was significantly associated with an increased risk of iridocyclitis (IVW: OR, 1.17; 95%CI, 1.10-1.24, P=2.54×10-7). CD was significantly associated with conjunctivitis (IVW: OR, 1.05; 95%CI, 1.03-1.08, P=3.20×10-5), keratitis (IVW: OR, 1.06; 95%CI, 1.02-1.09; P=1.13×10-3), and iridocyclitis (IVW: OR, 1.09; 95%CI, 1.04-1.14; P=1.43×10-4). CONCLUSION: IBD causally poses a risk of inflammation of conjunctiva, cornea, Iris-ciliary body complex, and optic neuritis. CD is more closely associated with the eye inflammation than UC. These impliy that the relationship of IBD and different parts of the eye structure are different, and provide novel evidence linking based on the association of the gut-eye axis.

Pre-diagnosis blood DNA methylation profiling of twin pairs discordant for breast cancer points to the importance of environmental risk factors

Abstract Background Assessment of breast cancer (BC) risk generally relies on mammography, family history, reproductive history, and genotyping of major mutations. However, assessing the impact of environmental factors, such as lifestyle, health-related behavior, or external exposures, is still challenging. DNA methylation (DNAm), capturing both genetic and environmental effects, presents a promising opportunity. Previous studies have identified associations and predicted the risk of BC using DNAm in blood; however, these studies did not distinguish between genetic and environmental contributions to these DNAm sites. In this study, associations between DNAm and BC are assessed using paired twin models, which control for shared genetic and environmental effects, allowing testing for associations between DNAm and non-shared environmental exposures and behavior. Results Pre-diagnosis blood samples of 32 monozygotic (MZ) and 76 dizygotic (DZ) female twin pairs discordant for BC were collected at the mean age of 56.0 years, with the mean age at diagnosis 66.8 years and censoring 75.2 years. We identified 212 CpGs (p < 6.4*10–8) and 15 DMRs associated with BC risk across all pairs using paired Cox proportional hazard models. All but one of the BC risks associated with CpGs were hypomethylated, and 198/212 CpGs had their DNAm associated with BC risk independent of genetic effects. According to previous literature, at least five of the top CpGs were related to estrogen signaling. Following a comprehensive two-sample Mendelian randomization analysis, we found evidence supporting a dual causal impact of DNAm at cg20145695 (gene body of NXN, rs480351) with increased risk for estrogen receptor positive BC and decreased risk for estrogen receptor negative BC. Conclusion While causal effects of DNAm on BC risk are rare, most of the identified CpGs associated with the risk of BC appear to be independent of genetic effects. This suggests that DNAm could serve as a valuable biomarker for environmental risk factors for BC, and may offer potential benefits as a complementary tool to current risk assessment procedures.

Proteomic and phosphoproteomic identified structural and functional changes in the aorta associate with age-dependent hypertension in male Sprague Dawley rats.

Guillain-Barré syndrome (GBS) and cardiovascular diseases (CVDs) have been observed to have a potential association, with GBS potentially leading to cardiovascular complications. However, these observational studies may be influenced by confounding factors. This study aimed to assess the causal relationship between GBS and CVDs, including heart failure (HF), atrial fibrillation (AF), and coronary artery disease (CAD), using a two-sample bidirectional Mendelian randomization (MR) analysis. Datasets for GBS and CVDs were retrieved from the United Kingdom Biobank and analyzed using selected instrumental variables (IVs) related to genetic variations. Sensitivity tests, including heterogeneity and horizontal pleiotropy tests, were conducted to ensure the reliability of the selected IVs. The analysis results were then visualized to illustrate the causal relationships. The study identified genetic variants as IVs for both GBS and CVDs. MR analysis revealed a significant causal effect of GBS on the increased risk of HF (Inverse variance weighted [IVW], p<0.05), but no significant causal relationship was found between GBS and AF or CAD. Similarly, no causal effect of CVDs on the occurrence of GBS was observed. Sensitivity analyses indicated no significant heterogeneity or horizontal pleiotropy, supporting the robustness of the results. This bidirectional MR analysis suggests a causal relationship between GBS and an increased risk of HF but not with AF or CAD, nor was a reverse causal effect of CVDs on GBS observed. These findings underscore the importance of considering cardiovascular complications, particularly HF, in the clinical management of patients with GBS in European populations.

Bidirectional Mendelian randomization links gut microbiota to primary biliary cholangitis.

Primary biliary cholangitis (PBC) and gut microbiota (GM) are epidemiologically correlated but the causal inter-relationships remain poorly understood. We aim to explore the causal relationships between GM and PBC. Using the MiBioGen consortium, GWAS data for GM at the species level and the largest publicly available PBC GWAS data to date, we performed a bidirectional two-sample Mendelian randomization by the inverse variance weighted, MR-Egger, weighted median, weighted model and MR-PRESSO to elucidate the potential causal role of GM in PBC. To measure the heterogeneity of instrumental variables (IV), Cochran's Q statistic and MR-Egger intercept test were used. Genetically instrumented order Coriobacteriales (odds ratio [OR] = 2.18, 95% confidence interval [CI] 1.30-3.66, P = 0.004) significantly increased the risk for PBC, while genetically driven class Deltaproteobacteria (OR = 0.52, 95% CI 0.36-0.74, P = 0.002) causally decrease the NAFLD risk. Reverse MR analysis showed no significant association between PBC and the two specific GM. However, it indicated that PBC progression significantly increases the abundance of the class Bacteroidia, order Bacteroidales, and phylum Bacteroidetes (OR = 1.02, 95% CI 1.002-1.03, P = 0.026), while decreasing the abundance of the genus Lachnospiraceae UCG010 (OR = 0.98, 95% CI 0.96-0.995, P = 0.026). Our study demonstrated that genetically driven order Coriobacteriales and class Deltaproteobacteria were causally related to PBC risk. This causality provided a new perspective on ameliorating PBC by modulating GM. Our study demonstrated that genetically driven order Coriobacteriales and class Deltaproteobacteria were causally related to PBC risk. PBC was causally related to the abundance of four GM taxa(class Bacteroidia, order Bacteroidales, phylum Bacteroidetes and genus Lachnospiraceae UCG010). This causality provided a new perspective on ameliorating PBC by modulating GM.

Multidimensional Plasma Lipids Affect Preeclampsia/Eclampsia: A Mendelian Randomization Study.

Circulating lipids play a crucial role during pregnancy and may impact various pregnancy-related diseases. This study employed a two-sample Mendelian randomization (MR) framework to investigate the causal relationship between alterations in multidimensional plasma lipid levels and the risk of preeclampsia or eclampsia, offering deeper insight into this association. The inverse variance weighted (IVW) method was utilized as the main analysis. Summary statistics from plasma lipidomics of 7174 Finnish individuals and summary data on preeclampsia/eclampsia from the FinnGen consortium involving 219 817 European participants were employed. Sensitivity analyses were conducted to evaluate heterogeneity and pleiotropy. The study identified 17 lipid species from a total of 179 lipid species associated with susceptibility to preeclampsia/eclampsia. Notably, ten species, including six triacylglycerols (TAGs) (50:1, 48:1, 56:4, 49:2, 48:2, 54:3), a diacylglycerol (DAG) (16:1_18:1), and three sphingomyelins (SMs) (d36:1, d34:1, d38:1), were found to increase the risk of preeclampsia/eclampsia. Conversely, seven species, including five phosphatidylcholines (PCs) (16:1_20:4, O-18:1_20:4, 18:1_20:4, 16:0_20:4, 17:0_20:4) and two phosphatidylethanolamines (PEAs) (18:0_20:4, 16:0_20:4), all containing arachidonic acid (ARA) in the sn-2 position, were associated with a reduced risk of preeclampsia/eclampsia (all p < 0.05). The results of thestratified analysis were consistent with these findings. Furthermore, reverse MR analysis indicated that preeclampsia/eclampsia does not causally affect plasma levels of these lipids. Our findings established a causal relationship between specific plasma lipid species and modulation of preeclampsia/eclampsia risk, providing improved resolution for risk assessment and potential therapeutic targets in the disease.

Association of B cells and the risk of Esophageal cancer: a bidirectional two-sample mendelian randomization study.

Currently, research on the role of B cells in esophageal cancer (EC) is limited, and existing studies on their impact are controversial. Therefore, this study was conducted to elucidate the complex causal relationship between B cells and EC, expand the understanding of esophageal cancer immunology. Bidirectional two-sample Mendelian randomization (MR) was performed to assess the causal relationships between 190 B cell phenotypes and EC. To complement the MR analysis, Bayesian Weighted Mendelian Randomization (BWMR) was employed, and sensitivity analyses were conducted to evaluate the robustness of the findings. Positive results were further validated in independent cohorts of esophageal cancer studies. In addition, RNA sequencing (RNA-seq) data from The Cancer Genome Atlas (TCGA) were utilized for validation, incorporating B cell-related gene expression analysis and functional enrichment analysis to support the MR findings. In the primary analysis, significant causal relationships were observed between 5 B cell types and the risk of EC; the onset of EC was causally linked to 3 B cell phenotypes. Validation in other cohorts revealed that 4 outcomes aligned with the primary analysis, included were CD19 on IgD + CD38-, CD20 on IgD- CD27-, CD20 on IgD- CD38br, and CD38 on PB/PC. Further validation using RNA-seq data showed that CD38 mRNA was significantly overexpressed in EC tissues, whereas CD19 and MS4A1 mRNA levels did not differ significantly between tumor and normal tissues. Functional enrichment analysis revealed that CD19, MS4A1, and CD38 are involved in multiple tumor-related immune pathways, suggesting their pivotal role in regulating the tumor immune microenvironment. Our study suggests a potential connection between B cell phenotypes and EC through bidirectional two-sample MR combined with BWMR analysis, providing a preliminary basis for future research.

The Gut Microbiota and Its Metabolites and Their Association with the Risk of Autoimmune Thyroid Disease: A Mendelian Randomization Study

Objectives: Observational research shows associations of the gut microbiota and its metabolites with autoimmune thyroid disease (AITD), but the causality is undetermined. Methods: Two-sample Mendelian randomization (MR) was employed to analyze the association of the gut microbiota and its metabolites with AITD. A total of 119 gut microbiotas and nine fecal/circulating metabolites were the exposures. AITD, Graves’ disease (GD), and Hashimoto’s thyroiditis (HT) were the outcomes. Inverse-variance weighting (IVW) was primarily used to assess causality; Cochran’s Q was used to assess heterogeneity. Sensitivity analyses (weighted median, MRPRESSO regression, MRPRESSO intercept, MRPRESSO global, Steiger filtering, leave-one-out) were conducted to assess causal estimate robustness. Multivariable MR (MVMR) was used to estimate the effects of body mass index (BMI) and alcohol consumption frequency on causality. Results: The outcomes were potentially causally associated with 22 gut microbiotas and three metabolites. After multiple-test correction, 3-indoleglyoxylic acid retained significant causality with AITD (IVW: odds ratio [OR] = 1.09, 95% confidence interval [CI] = 1.05–1.14, p = 2.43 × 10−5, FDR = 0.009). The sensitivity analyses were confirmatory (weighted median: OR = 1.06, 95% CI = 1.01–1.12, p = 0.025; MRPRESSO: OR = 1.09, 95% CI = 1.15–1.14, p = 0.001). MVMR revealed no confounding effects on this association (BMI: OR = 1.21, 95% CI =1.08–1.35, p = 0.001; drinks/week: OR = 1.22, 95% CI = 1.04–1.43, p = 0.014). Conclusions: MR revealed no significant causal effects of the gut microbiota on the outcomes. However, MR revealed the causal effects of 3-indoleglyoxylic acid on the risk of AITD.

Role of CD38 in mediating the effect of Bacillus on acute pancreatitis: a study of mediated Mendelian randomization

BackgroundSome studies suggest a potential link between intestinal flora and acute pancreatitis (AP). However, the causal relationships between specific intestinal flora and AP, and the possible mediating role of immune cell traits, remain unclear.MethodsA genome-wide association study (GWAS) involving 5,959 participants was conducted to identify genetic instrumental variables associated with 473 intestinal flora taxa. Summary statistics for AP were obtained from the UK Biobank. Immune cell traits were also identified using large-scale GWAS summary data. We employed a two-sample bidirectional Mendelian randomization (MR) approach to investigate the causal relationships between intestinal flora, immune cell traits, and AP, with inverse variance weighting (IVW) as the primary statistical method. Sensitivity analyses, including the MR-Egger intercept test, Cochran’s Q test, MR-PRESSO test, and leave-one-out test, were conducted to assess the robustness of our findings. Additionally, we explored whether immune cell traits mediate the pathway from intestinal flora to AP.Results11 positive and 11 negative causal relationships were identified between genetic susceptibility in intestinal flora and AP. Furthermore, 19 positive and 9 negative causal relationships were observed between immune cell traits and AP. Notably, CD38 mediated the causal relationship between Bacillus C and AP.ConclusionsThis study is the first to uncover novel causal relationships between various intestinal flora and acute pancreatitis, emphasizing the mediating role of immune cell traits in the pathway from intestinal flora to AP. It also provides new evidence supporting the conditional pathogenicity of the Bacillus genus.

Exploring genetic associations between immune cells and hypertensive disorder of pregnancy using Mendelian randomization.

Observational epidemiological studies suggested that immunological dysregulation and inflammation play a significant role in the placental and renal dysfunction that leads to maternal hypertension. The immunophenotypes' possible causalities with hypertensive disease of pregnancy remain ambiguous. We performed two-sample Mendelian randomization (MR) analyses to comprehensively investigate the causal effect of immunophenotypes on hypertensive disorder of pregnancy (HDP). The large-scale genome-wide association studies (GWASs) data on immunological traits was taken from public catalog for 731 immunophenotypes. The summarized GWAS data in 4 types of HDP were retrieved from FinnGen database, including 811,605 Finnish individuals. The primary analysis was the inverse variance weighted (IVW) method, supplemented by conducting sensitivity analysis. To confirm whether cardiovascular proteins mediated the causal effect of immune cells on HDP, we additionally executed a mediation MR study. After looking into genetically predicted immunophenotype biomarkers, we discovered 14 highly correlative immunophenotypes and 104 suggestive possible factors. The IVW analysis indicated that HLA DR on myeloid DC, HLA DR on plasmacytoid DC, and HLA DR on DC had a significant association with pre-eclampsia/eclampsia (PE), whereas CD4+ CD8dim AC and CD4+ CD8dim % leukocyte were protective against gestational hypertension (GH). All of HDP in our study had no statistically significant impact on immune cells, according to reverse MR analysis. The mediating role of LOX-1between HLA DR on plasmacytoid DC and chronic hypertension prior to pregnancy was validated. This study showed that many immunophenotypes are implicated in HDP. Furthermore, the level of LOX-1 mediated the pathophysiology relationship between HLA DR on plasmacytoid dendritic cells and chronic hypertension prior to pregnancy.

Gut Microbiota’s role in lipoma development: evidence from mendelian randomization

BackgroundLipoma, a benign tumor derived from mesenchymal tissue, significantly affects patients’ physical and psychological wellbeing. Increasing evidence points to a strong link between the gut microbiome (GM) and lipoma incidence. This study utilizes Mendelian Randomization (MR) to assess the potential causal relationships between the GM and lipoma development.MethodsWe conducted a two-sample MR analysis using genome-wide association study (GWAS) data from MiBioGen and FinnGen to explore the causal relationship between GM and lipoma. The GM dataset included 18,340 participants with 14,587 single nucleotide polymorphisms (SNPs), while the lipoma dataset comprised 412,181 participants with 21,306,349 SNPs. We employed 5 MR methods: Inverse Variance Weighted (IVW), Weighted Median, Simple Mode, MR-Egger, and Weighted Mode. Additional assessments included Cochran’s Q test for result heterogeneity, PRESSO analysis for horizontal pleiotropy, and sensitivity analyses through scatter plots, leave-one-out analyses, funnel plots, and forest plots.ResultsThe IVW method identified 18 gene predictors trans-genus associated with lipoma risk. Protective effects against benign lipoma (BL) were observed in the Eubacterium rectale group, Desulfovibrio, Ruminococcus1, Clostridium sensu stricto1, and Lachnospiraceae UCG001; conversely, Lachnospiraceae UCG008 was linked to increased BL risk. Desulfovibrio provided protection against TS-BL; however, the Family XIII AD3011 group, Eubacterium coprostanoligenes group, Lachnospiraceae NK4A136 group, and Parasutterella were associated with an increased TS-BL risk. The Clostridium innocuum group, Eubacterium rectale group, Anaerotruncus, Ruminiclostridium6, and Lachnospiraceae UCG001 offered protection against LS-BL, while Lachnospiraceae UCG008 was linked to an increased LS-BL risk. The Eubacterium brachy group, Odoribacter, Butyricimonas, Subdoligranulum, and Clostridium sensu stricto1 were protective against HFNS-BL; Ruminococcaceae UCG005 was associated with an increased HFNS-BL risk.ConclusionCompared to malignant tumors, research on lipomas has been relatively limited. This study, through MR analysis, provided new evidence of a causal relationship between specific GM and the development of lipomas. Certain gut bacterial species may act as protective or harmful factors in lipoma formation, offering new avenues for future treatment strategies. However, additional research is required to unravel the complexity of how GM influences the pathogenesis of lipomas.

Potential Drug Targets for Diabetic Retinopathy Identified Through Mendelian Randomization Analysis.

This study aimed to investigate the causal effect of plasma proteins on diabetic retinopathy (DR) risk and identify potential drug targets for this disease. Two-sample Mendelian randomization was performed to explore potential drug targets for DR. A total of 734 proteins were selected as instrumental variables. The Steiger filtering test and colocalization analysis were conducted to determine the causal direction and genetic pleiotropy. Plasma proteins from the decode study were used to validate the findings. Eleven plasma proteins were associated with DR risk. Genetically predicted high levels of CCL3L1 (odds ratio [OR] = 0.582; 95% confidence interval [CI], 0.343-0.986; P = 0.044), PAM (OR = 0.782; 95% CI, 0.652-0.937; P = 0.008), GP1BA (OR = 0.793; 95% CI, 0.632-0.994; P = 0.044), GALNT16 (OR = 0.832; 95% CI, 0.727-0.952; P = 0.008), POGLUT1 (OR = 0.836; 95% CI = 0.703-0.995; P = 0.043), and DKK3 (OR = 0.859; 95% CI, 0.777-0.950; P = 0.003) have the protective effect on DR risk. Genetically predicted high levels of GFRA2 (OR = 1.104; 95% CI, 1.028-1.187; P = 0.007), PATE4 (OR = 1.405; 95% CI, 1.060-1.860; P = 0.018), GSTA1 (OR = 1.464; 95% CI, 1.163-1.842; P = 0.001), SIRPG (OR = 1.600, 95% CI, 1.244-2.057; P = 2.51E-04), and MAPK13 (OR = 1.731; 95% CI, 1.233-2.431; P = 0.002) were associated with an increased risk of DR. However, the colocalization analysis results suggested that SIRPG and GP1BA have a shared causal variant with DR. CCL3L1, PAM, GALNT16, POGLUT1, DKK3, GFRA2, PATE4, GSTA1, and MAPK13 were associated with DR risk and were identified as potential drug targets for DR. The present study has highlighted the role of CCL3L1, PAM, GALNT16, POGLUT1, DKK3, GFRA2, PATE4, GSTA1, and MAPK13 in the development of DR.

Allergic Diseases and T2DM:A Bidirectional Multivariable Mendelian Randomization Study and Mediation Analysis

Background Clinical studies involving observation have uncovered a mutual relationship between allergic disorders and diabetes, yet the precise causal link remains undetermined. Methods We conducted two-sample bidirectional Mendelian randomization analyses using single nucleotide polymorphisms (SNPs) associated with allergic conditions (asthma, allergic rhinitis, atopic dermatitis) from genome-wide studies and SNPs related to type 2 diabetes from FinnGen. Initially, we evaluated the causal link between allergic disorders and type 2 diabetes through a univariate Mendelian randomization study, incorporating inverse variance weighting, MR-Egger, and the weighted median estimator. To address potential confounding, we employed multivariate Mendelian randomization. Finally, we validated mediators influencing the correlation between asthma and type 2 diabetes. Results The Inverse variance weighte method showed that asthma genetically increased the risk of type 2 diabetes (Asthma- type 2 diabetes: β(95%CI)＝0.892(0.152～1.632), P = 0.018). Allergic rhinitis and type 2 diabetes exhibit a mutual protective effect: β(95% CI)＝-1.333(-2.617 to -0.049), P = 0.042；type 2 diabetes - Allergic rhinitis: β(95%CI)＝-0.002(-0.004 to -0.000), P = 0.018). The Multivariable Mendelian randomization study results showed that after after excluding confounding factors, asthma still demonstrates statistical significance in relation to type 2 diabetes. Through mediation analysis, it was discovered that lung function and the percentage of monocytes in leukocytes exert an inhibitory effect on the mediation between asthma and type 2 diabetes. Conclusion The Multivariable Mendelian randomization study indicates asthma as a risk factor for type 2 diabetes.Lung function, and the percentage of monocytes in leukocytes, play an inhibitory role in asthma and type 2 diabetes mediating effects.

Genetically Predicted Immune Cell-Mediated Effect of Lipid Metabolism on Allergic Diseases: A Two-Step, Mediation Mendelian Randomization Study.

An increasing number of studies have demonstrated that dynamic changes in lipid species can affect allergic diseases; however, the causal relationship and mediating role of immune cells remain unclear. We conducted a bidirectional two-sample mendelian randomization (MR) analysis using genome-wide association study (GWAS) data on 179 lipid species (n = 7,174) and three types of allergic diseases including allergic rhinitis (AR) (n = 370,158), allergic asthma (n = 219,753), and allergic conjunctivitis (n = 377,277). The principal model used was the inverse variance-weighted approach, and a series of sensitivity analyses were conducted to ensure the robustness of the results. We used a two-step MR approach to assess whether the causal effect was mediated by immune cells (n = 3,757). Sterol ester and sphingomyelin played pathogenic roles in allergic asthma, AR, and allergic conjunctivitis; however, the effective subtypes differed. Among them, CD45RA- CD4+ mature T cells and CCR2 on CD14+ CD16+ monocytes affected the promoting impact of sterol ester's metabolism on allergic asthma and AR with different mediating proportions, while the role of sphingomyelin may not involve the immune cells. Moreover, we observed that HLA-DR on CD33- HLA DR+ myeloid cells, CD11b on CD66b++ myeloid cells, and IgD+ CD38- B cells played the most mediating effect of phosphatidylethanolamine (O-18:2_20:4) in allergic asthma, phosphatidylinositol (16:0_18:1) in AR, and phosphatidylethanolamine (18:0_18:2) in allergic conjunctivitis. This MR study provides evidence for specific lipid species associated with the risk of allergic diseases, especially sterol esters, and identifies the immune cells that mediate this causal relationship.

Large-scale genome-wide association studies identified causal relationship between multiple blood biomarkers and risk of acute pancreatitis.

Observational studies have shown that there is a connection between blood biomarkers and the occurrence of acute pancreatitis (AP). Nevertheless, the causal relationships are still not clear. The purpose of this study was to evaluate causal association between biomarkers and AP. A bidirectional two-sample Mendelian randomization (MR) analysis was applied to investigate the causal association between blood biomarkers and AP. Summary statistics obtained from genome-wide association studies were utilized for this analysis. The primary statistical approach employed was the inverse variance weighted (IVW) method, complemented by sensitivity analyses aimed at assessing heterogeneity and pleiotropy. Furthermore, a multivariable MR (MVMR) analysis was performed to adjust for confounders. A total of 11 red blood cell (RBC) traits, 6 white blood cell traits, platelet count, and 30 blood biomarkers were analyzed in this study. Genetically predicted RBC count (IVW odds ratio [OR]=1.144, P=0.004), the high light scatter reticulocyte count (HLSR) (OR=1.127, P=0.022), blood glucose (BG) (OR=1.480, P=0.019), and leptin (OR=1.234, P=0.050) were suggestively associated with an increased risk of AP. Reverse MR analysis showed no causal effect of AP on RBC, HLSR, BG, and leptin (IVW P>0.05). Sensitivity analyses and MVMR analysis still supported the earlier causality. Our findings provide evidence of a suggestive association between RBC count, HLSR, BG, and leptin with an increased susceptibility to AP. These findings aid in our comprehension of the cause of AP and may be used as potential prognostic markers or predictors of severity with AP.

The causal relationships between iron status and sarcopenia in Europeans: a bidirectional two-sample Mendelian randomization study.

Previous studies have indicated potential associations between metals, lifestyle factors, and sarcopenia. However, the specific causal relationships between iron status, lifestyle factors, and sarcopenia remain unclear. Therefore, we conducted a bidirectional two-sample Mendelian Randomization (MR) approach to investigate these relationships. The exposure variables included iron status, living alone, coffee intake, alcohol taken with meals, and moderate physical activity, while the outcome variable was sarcopenia, assessed by grip strength in both hands and usual walking pace. We employed the Weighted Median (WM), the Inverse Variance-Weighted (IVW), and other MR methods to explore these problems for analysis. Simultaneously, we conducted a bidirectional MR analysis to assess whether sarcopenia has a reverse causal relationship with internal iron status. In our present research, we found serum iron (P = 0.033), ferritin (P = 0.001), transferrin saturation (P = 0.029) and coffee intake (P = 0.002) revealed a negative trend for sarcopenia, living alone (P = 0.022) and alcohol taken with meal (P = 0.006) showed a opposite trend for sarcopenia. Whereas sarcopenia showed negative trend for ferritin (P = 0.041) and transferrin saturation (P = 0.043), showed the opposite trend for transferrin (P = 0.021). Our study suggested that higher serum iron levels might reduce the risk of sarcopenia. Moreover, living alone and alcohol consumption might increase the sarcopenia risk, while coffee intake and moderate physical activity could reduce the sarcopenia risk.

Assessing the causal associations of atrial fibrillation with serum uric acid level and gout: insights from a bidirectional mendelian randomization study.

Numerous observational studies consistently highlight a strong association between serum uric acid (sUA) levels and atrial fibrillation (AF). However, the causal relationship and the direction of this association remain elusive, despite extensive research efforts. This study aimed to investigate the bidirectional causal relationships between sUA, gout, and the risk of AF using the two-sample Mendelian randomization (MR) approach. We conducted a comprehensive analysis utilizing publicly available genome-wide association studies (GWAS) summary statistics, employing stringent criteria to meticulously select genetic variants associated with sUA, gout, and AF. Our primary analytical approach was the inverse-variance weighted (IVW) method, complemented by some sensitivity analyses, including MR-Egger, weighted median, simple mode, and weighted mode, to estimate the causal effects. To identify potential violations, we conducted Egger regression and leave-one-SNP-out analyses. We assessed the strength of instrumental variables using F values to evaluate weak instruments. Additionally, we referenced the Phenoscanner database to exclude single nucleotide polymorphisms (SNPs) associated with confounding factors or outcomes. Our forward Mendelian randomization analysis suggests that there is no causal relationship between UA levels/gout from different populations and the risk of AF [IVW OR 1.03, 95% CI: 0.97-1.08; p = 0.335; IVW OR 0.99, 95% CI: 0.97-1.02; p = 0.583; and IVW OR 1.07, 95% CI: 0.84-1.37; p = 0.575], respectively. We did not detect significant heterogeneity or potential pleiotropy, and we also excluded the possibility of weak instrumental variables. Furthermore, we did not find any reverse causal effects of AF on sUA levels and gout risk. Our findings challenge the widely held belief that lowering urate levels is uniformly effective in reducing the risk of atrial fibrillation (AF). Our study fails to substantiate the existence of a causal link between uric acid (UA) levels or gout and the development of AF, regardless of direction.

Dietary habit and risk of rheumatoid arthritis: a mendelian randomization study identifying protective and risk factors.

Dietary habit significantly contributes to the initiation and progression of rheumatoid arthritis (RA). Dietary choices intersect with a range of clinical and societal factors. The utilization of cross-sectional methodologies in numerous studies poses a challenge in establishing definitive causality for the noted associations. Moreover, within identical food categories, specific items may elicit diverse effects on the pathogenesis of RA, and the correlation between several prevalent food items or beverages and RA remains inadequately explored. We performed a two-sample Mendelian Randomization (MR) study to evaluate the causal impact of 27 distinct dietary habits and RA susceptibility. These dietary-related phenotypes encompass both the relative intake of the four macronutrients (fat, protein, carbohydrates, and sugar) and 23 specific single food intake. Several filtering steps were employed to select eligible genetic instruments strongly associated with each of the traits. The random-effects inverse-variance weighted, weighted median, and MR-Egger methods were employed for MR estimations. Sensitivity analyses and power calculations were executed to ensure the robustness of our study. After rigorous single-nucleotide polymorphism (SNP) filtering procedures, 611 SNPs were included in our ongoing investigations. The consumption of dried fruit, bread, and alcohol emerged as protective factors, while beef, processed meat, and coffee intake were identified as risk factors. The robustness of our study was confirmed through the outcomes of sensitivity analysis and power calculation. The ongoing investigations furnish evidence that accentuates the influence of diet on RA disease activity, underscoring the importance of delineating the optimal nutritional lifestyle for RA patients.

Genetic Influence of the Brain on Muscle Structure: A Mendelian Randomization Study of Sarcopenia.

The association between brain and sarcopenia has not been clarified. We aim to investigate the causal association between brain structure, function, gene expression and sarcopenia-related traits. All participants were Europeans. GWAS data of Brain Imaging Data Structure (BIDs) was from the UK Biobank. Gene expression in 13 brain regions was acquired from the GTEx Consortium. The sarcopenia-related traits, including appendicular lean mass (ALM), whole body lean mass (WBLM), grip strength and sarcopenia diagnosed by the European Working Group on Sarcopenia in Older People (EWGSOP) or Foundation for the National Institutes of Health (FNIH), were from the IEU website. The inverse variance weighted (IVW), MR Egger, weighted median, weighted mode and Wald ratio methods were used for a two-sample Mendelian randomization (MR) analysis between brain structures and sarcopenia-related traits. The summary-data-based MR (SMR) was used to investigate brain genes causally influencing sarcopenia. We calculated the F-value, odds ratio with 95% CI and p-value. For the sensitivity analysis, the heterogeneity I2 statistic, Cochrane's Q test, Egger's intercept test, MR-PRESSO and the leave-one-out sensitivity test were used. Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway, protein-protein interaction (PPI), transcription factor interaction prediction and miRNA interaction prediction analysis were used to reveal potential signalling pathways and mechanisms. We included 3144 imaging phenotypes from 8428 participants in BIDs data. One hundred forty-one BIDs were identified to causally influence ALM, 160 BIDs showed significant causal effect on the WBLM, and 86 BIDs showed significant causal effect on grip strength. There were 48 or 32 BIDs causally associated with sarcopenia diagnosed by the EWGSOP or FNIH criteria respectively. After FDR correction, there were 35 BIDs showing causal effect on the ALM, 28 BIDs showing causal effect on the WBLM and 7 BIDs showing causal effect on grip strength (p < 0.05). Twelve to forty-eight genes in different brain regions showed causal effect on all the five sarcopenia-related traits. MMP24-AS1, HLA-DRB6, HLA-DQA2, DDX42, BAG6, NUSAP1, LINC00940, NME1-NME2 and AS3MT in the amygdala region showed detrimental effect on all the five sarcopenia-related traits, whereas HLA-DRB1, HLA-DQB1-AS1 and C6ORF3 showed protective effect (p < 0.05). The gene enrichment analysis indicated these screened genes was mainly enriched in immune-related signalling. We discovered the causal effect of BIDs and brain gene expression on sarcopenia. The positive genes were mainly enriched in immune-related signalling, suggesting an immune-based cross-organ regulation mechanism of brain-muscle axis.

Association between copper and Achilles tendon disease: a two-sample Mendelian randomization study

BackgroundThere is a clear association between micronutrients and Achilles tendon disease (AT). An increase in micronutrients may alleviate AT symptoms and have a therapeutic effect. The aim of this study is to clarify the causal relationship between 15 micronutrients (copper, zinc, magnesium, vitamins A, C, E, D, B6, B12, folic acid, carotene, iron, selenium, calcium, and potassium) and AT.MethodsWe employed the Mendelian randomization (MR) method to analyze the causal effects of micronutrients on the risk of AT. The SNPs related to micronutrients were obtained from a large-scale genome-wide association study (GWAS) of circulating micronutrients in European populations. Outcome data were obtained from a meta-analysis of AT in European-ancestry participants from the Finnish FINNGEN BIOBANK. The main analysis was conducted using the inverse variance weighting (IVW) method, with additional sensitivity and pleiotropy analyses performed.ResultsInverse variance weighting results indicated a causal relationship between copper and AT (P = 0.003, OR = 0.899, 95% CI = 0.839–0.964). Sensitivity analysis validated the robustness and reliability of this finding.ConclusionThis study revealed a causal relationship between copper and AT, with copper serving as a protective factor. This provides evidence of the causality between copper and AT, offering new insights for clinical research and therapeutic approaches in AT.