'Mendelian randomization': an approach for exploring causal relations in epidemiology

A practical guide for nephrologist peer reviewers: understanding and appraising Mendelian randomization studies

Identifying risk factors for disease onset and progression has been a core focus in nephrology research. Mendelian Randomization (MR) has emerged as a powerful genetic epidemiological approach, utilizing genome-wide association studies (GWAS) to establish causal relationships between modifiable risk factors and kidney disease outcomes. MR uses genetic variants as instrumental variables to infer causal relationships between exposures and disease outcomes. This method leverages the natural randomization of genetic variants to balance confounders, akin to matched cohorts in observational research. The rapid increase in MR studies on kidney disease poses challenges for journals and peer reviewers, especially clinicians unfamiliar with the methodology. High-quality MR studies use strong, well-validated genetic instruments with clear biological relevance, thoroughly testing for pleiotropy and confounding factors using methods like MR-Egger. Sensitivity analyses, such as MR-PRESSO, should ensure findings remain consistent across various assumptions. Effect sizes with confidence intervals should be reported and discussed within established biological mechanisms. Additionally, limitations must be transparently addressed, with recommendations for replication in future studies, to strengthen findings. This article guides readers in understanding MR application in nephrology and identifying high-quality MR studies, helping peers avoid pitfalls while seizing new opportunities in advancing kidney disease research.

Triangulated evidence provides no support for bidirectional causal pathways between diet/physical activity and depression/anxiety

BACKGROUND

Previous studies (various designs) present contradicting insights on the potential causal effects of diet/physical activity on depression/anxiety (and vice versa). To clarify this, we employed a triangulation framework including three methods with unique strengths/limitations/potential biases to examine possible bidirectional causal effects of diet/physical activity on depression/anxiety.

METHODS

Study 1: 3-wave longitudinal study (n = 9,276 Dutch University students). Using random intercept cross-lagged panel models to study temporal associations. Study 2: cross-sectional study (n = 341 monozygotic and n = 415 dizygotic Australian adult twin pairs). Using a co-twin control design to separate genetic/environmental confounding. Study 3: Mendelian randomization utilizing data (European ancestry) from genome-wide association studies (n varied between 17,310 and 447,401). Using genetic variants as instrumental variables to study causal inference.

RESULTS

Study 1 did not provide support for bidirectional causal effects between diet/physical activity and symptoms of depression/anxiety. Study 2 did provide support for causal effects between fruit/vegetable intake and symptoms of depression/anxiety, mixed support for causal effects between physical activity and symptoms of depression/anxiety, and no support for causal effects between sweet/savoury snack intake and symptoms of depression/anxiety. Study 3 provides support for a causal effect from increased fruit intake to the increased likelihood of anxiety. No support was found for other pathways. Adjusting the analyses including diet for physical activity (and vice versa) did not change the conclusions in any study.

CONCLUSIONS

Triangulating the evidence across the studies did not provide compelling support for causal effects of diet/physical activity on depression/anxiety or vice versa.

Genetically Supported Causality Between Micronutrients and Sleep Behaviors: A Two-Sample Mendelian Randomization Study

BACKGROUND

Sleep behaviors, defined by the total duration of sleep and chronotype, significantly influence overall health. Compromised sleep quality, which is often manifested through reduced sleep duration and the prevalence of insomnia, has been found to be associated with micronutrient deficiencies. Nonetheless, the existence of a causal relationship between micronutrient levels and sleep behaviors remains to be established.

METHODS

A two-sample Mendelian randomization (MR) analysis, utilizing data from genome-wide association studies (GWAS), was employed to examine the associations between 15 micronutrients (copper; calcium; carotene; folate; iron; magnesium; potassium; selenium; vitamins A, B12, B6, C, D, and E; and zinc) and various sleep behaviors, including short and long sleep durations, insomnia, and chronotype. Furthermore, multivariable MR (MVMR) analysis was performed to address potential confounding due to the interrelationships among micronutrients and to discern potential causal relationships.

RESULTS

The MR analysis identified a causal association between folate levels and chronotype (odds ratio [OR] = 1.09; 95% confidence interval [CI]: 1.01-1.17; p = 0.02), indicating a tendency toward morningness. Conversely, vitamin B6 (OR = 0.91; 95% CI: 0.86-0.96; p = 1.05 × 10-3) and vitamin D (OR = 0.94; 95% CI: 0.88-1.00; p = 0.03) showed inverse associations with chronotype, indicative of a preference for eveningness. MVMR analysis confirmed the positive association between folate (OR = 1.286, 95% CI = 1.124-1.472, p < 0.001) and chronotype and a negative association with vitamin B6 (OR = 0.750, 95% CI = 0.648-0.868, p < 0.001). No causal relationships were established between micronutrient levels and either sleep duration or insomnia.

CONCLUSIONS

Elevated folate levels correlate with morning-type preferences ("morning birds"), while higher concentrations of vitamin B6 are associated with evening-type preferences ("evening owls").

Insights into drug adverse reactions prediction through Mendelian randomization: a review

Adverse drug reactions pose a significant threat to patient safety and public health and often become apparent only after widespread clinical use. Mendelian randomization (MR) analysis is a valuable tool that can be used to infer causality by using genetic variants as instrumental variables, which can predict the occurrence of adverse drug reactions before they occur. Compared with traditional observational studies, MR Analysis can reduce the potential bias of confounding factors. This article reviews the principles of MR Analysis and its application in the prediction of adverse drug reactions, the challenges and future directions, and summarizes how to harness the power of this innovative epidemiological method to put us at the forefront of improving drug safety assessment and personalized medicine.

Causal associations between osteoporosis and HBV infection across Asian and European populations: evidence from Mendelian randomization and colocalization analysis

Introduction

Clinical studies have demonstrated a potential association between chronic hepatitis caused by hepatitis B virus (HBV) infection and osteoporosis. However, the causal relationship between HBV infection and osteoporosis remains to be determined.

Methods

We investigated whether HBV infection is causally associated with osteoporosis using Mendelian randomization (MR) in East Asian and European populations, respectively. The data we utilized were obtained from the genome-wide association studies (GWAS) database. Various MR methods, including inverse variance weighted (IVW), MR Egger, weighted median, simple median and simple mode were employed to estimate the association between HBV infection and osteoporosis. Heterogeneity analysis and sensitivity tests were performed to ensure the robustness of the results. Bayesian co-localization (coloc) analysis was also applied to calculate the posterior probability of causal variants and to identify common genetic variants between HBV infection and osteoporosis.

Results

MR analysis indicated that HBV infection increased the risk of osteoporosis onset in two East Asian cohort (IVW, OR = 1.058, 95% CI = 1.021 to 1.097, P = 0.002 and OR = 1.067, 95% CI = 1.029 to 1.106, P < 0.001). However, a clear effect of genetic susceptibility to HBV on the enhanced risk of osteoporosis was not observed in two European cohort (IVW, OR = 1.000, 95% CI = 0.999 to 1.001, P = 0.171 and OR = 1.003, 95% CI = 0.981 to 1.025, P = 0.780). Additional MR methods and sensitivity analyses further validated the reliability and robustness of our results. Bayesian co-localization analysis revealed co-localization of HBV infection and osteoporosis on STAT4 at rs11889341based on East Asian GWAS data.

Conclusions

Our study identified a causal relationship between HBV infection and osteoporosis in East Asian and European populations. These results provided strong evidence that HBV infection augmented the risk of developing osteoporosis in East Asian populations and provided novel therapeutic targets.

Causal relationships between immune cells, inflammatory factors, and preeclampsia: A two-step, two-sample mendelian randomization study

BACKGROUND

Preeclampsia (PE) is a complex hypertensive disorder that occurs during pregnancy, with the immune system playing a key role. Although immune modulation is implicated in PE progression, the roles of specific immune cells and inflammatory mediators remain unclear.

METHODS

We conducted a two-sample, two-step Mendelian randomization (MR) analysis, primarily using the inverse-variance weighted method, to investigate the causal effect of immune cell traits on PE. Additionally, we assessed the potential mediation effects of inflammatory factors.

RESULTS

The MR analyses revealed that 22 immune cell traits exert protective effects against PE, whereas 19 are associated with an increased risk. Additionally, four inflammatory factors were suggested to be linked to PE. Mediation analysis identified the absolute count (AC) of CD33 + HLA DR+ cells, including the CD14 - subset, as causally related to PE. Both the total effect of the CD33 + HLA DR+ AC (odds ratio [OR] = 0.977, 95 % confidence interval [CI], 0.960-0.994; P = 0.010) and the effect of CD33 + HLA DR+ CD14 - cells (OR = 0.977, 95 % CI, 0.963-0.991; P = 0.001) were significant. These effects were partially mediated by STAM-binding protein levels, contributing 16.7 % and 15.0 % to the total effects of the CD33 + HLA DR+ AC and CD33 + HLA DR+ CD14 - AC, respectively.

CONCLUSION

This study establishes a causal relationship between specific immune cells and PE, potentially mediated by inflammatory factors, highlighting the importance of these traits in PE pathogenesis. Further research is needed to validate these findings based on larger, more diverse cohorts.

Mendelian Randomization Study on hs-CRP and Dyslipidemia in Koreans: Identification of Novel SNP rs76400217

High-sensitivity C-reactive protein (hs-CRP) is a marker of systemic inflammation and is associated with developing dyslipidemia. However, the causality between hs-CRP and dyslipidemia remains unresolved. This study aimed to investigate the relationship between hs-CRP concentrations and dyslipidemia and to explore the potential causal link using Mendelian randomization (MR) analysis. A nested case-control study was conducted with 1174 participants, and genotype data were analyzed using the Korean Chip. A genome-wide association study (GWAS) identified rs76400217 as a suitable instrumental variable (IV) due to its significant association with hs-CRP (p < 10-8). Logistic regression models, adjusted for confounders, were used to evaluate the association between hs-CRP and dyslipidemia. An MR analysis was performed using a two-stage least squares (2SLS) method, with rs76400217 as the IV to assess causality. Logistic regression showed a significant association between hs-CRP concentrations and dyslipidemia (OR 2.08, 95% CI: 1.81-2.39, p < 0.001). This association remained significant after adjusting for factors such as age, sex, alcohol consumption, and BMI. The MR analysis using rs76400217 as the IV confirmed the strong associations with hs-CRP concentrations (p < 0.001) in all models, but the causality between hs-CRP and dyslipidemia was not statistically significant. Thus, no evidence of a causal relationship between hs-CRP and the risk of dyslipidemia was found in the Korean population. The strong association observed between hs-CRP and dyslipidemia may be due to other contributing factors rather than a direct cause.

Causal Association Between Childhood Body Mass Index and Phlebitis and Thrombophlebitis: An Analysis Using Mendelian Randomization

Background: Research has indicated a link between obesity and a greater likelihood of venous disorders. However, the specific relationship between obesity in children and conditions such as phlebitis and thrombophlebitis remains undetermined. To explore this, we undertook a two-sample Mendelian randomization (MR) study to investigate the possible causal impact of childhood body mass index (BMI) on the development of phlebitis and thrombophlebitis. Methods: This study utilized genome-wide association studies data from European populations. Childhood BMI was assessed in a sample of 39,620 individuals, while data on phlebitis and thrombophlebitis were obtained from 1613 cases and 335,586 controls. We selected 16 single nucleotide polymorphisms significantly associated with childhood BMI as instrumental variables (IVs). The inverse variance weighting (IVW) method was applied as the primary approach, with weighted median, MR-Egger regression, and weighted mode methods used as complementary analyses. Results: The IVW analysis indicates a significant causal link between childhood BMI and the occurrence of phlebitis and thrombophlebitis (Beta = 0.002739, Standard error (SE) = 0.000740, p = 0.0002147). Results from the weighted median method (Beta = 0.002446, SE = 0.001046, p = 0.01933) aligned with the IVW findings. However, the MR-Egger and weighted mode analyses did not show a significant association (p = 0.1051 and p = 0.2525, respectively). Leave-one-out sensitivity tests and heterogeneity assessments were performed, revealing no evidence of horizontal pleiotropy. Conclusion: The findings from the MR analysis suggest a potential causal relationship between childhood BMI and an elevated risk of phlebitis and thrombophlebitis. This study provides new insights into the impact of childhood obesity on venous health, emphasizing the need for early intervention and prevention strategies.

Causal Relationships Between 4 Exposure Factors and Rotator Cuff Syndrome Using Mendelian Randomization Analysis

Background

Although previous studies have investigated the risk factors for rotator cuff syndrome (RCS), there remains controversy due to uncontrolled and uncertain confounding factors in their analyses.

Purpose

To perform Mendelian randomization (MR) analysis using single-nucleotide polymorphisms to investigate the causal relationship between RCS and 4 risk factors: type 2 diabetes mellitus (T2DM), high blood pressure (HBP), body mass index (BMI), and low high-density lipoprotein cholesterol (HDL-C).

Study Design

Descriptive epidemiology study.

Methods

Genome-wide association study (GWAS) data for T2DM (ebi-a-GCST006867), BMI (ieu-b-40), HBP (finn-b-I9_HYPTENS), HDL-C (ieu-b-109), and RCS (ukb-b-50) were obtained from the IEU Open GWAS Project. The dataset of each risk factor was combined with the dataset of RCS, generating 4 datasets. Potential confounders and single-nucleotide polymorphisms related to RCS were excluded from these datasets. The causal relationships between the exposure factors and RCS were analyzed using 5 regression models: MR-Egger, weighted median estimate (WME), inverse-variance weighting (IVW), simple mode, and weighted mode. Heterogeneity in the causal effects was assessed using MR-Egger regression and IVW analyses. Sensitivity analyses were performed to determine the stability of the results.

Results

The MR-Egger regression intercepts for T2DM, BMI, HBP, and HDL-C showed no horizontal pleiotropic effects. The results of the Cochran Q test showed P values of .075 and .080 for BMI in the MR-Egger regression and IVW models, respectively, indicating the absence of heterogeneity between BMI and RCS. The results of the weighted median estimate and IVW regression analyses showed a significant causal association between BMI and RCS, with odds ratios of 1.002 (95% CI, 1-1.004; P = .038) and 1.003 (95% CI, 1.001-1.005; P = .0003), respectively. No significant associations were found for T2DM, HDL-C, or HBP.

Conclusion

In the present study, BMI was positively associated with the risk of developing RCS, while T2DM, HBP, and low HDL-C were not associated with RCS development.

Hypertension and 28-day mortality in sepsis patients: An observational and mendelian randomization study

BACKGROUND

Predicting and reducing the 28-day mortality in sepsis remains a challenge in this research field.

OBJECTIVE

This study aimed to explore the association between hypertension and 28-day mortality in sepsis.

METHODS

This study is a cross-sectional approach with Mendelian Randomization (MR). We used GWAS data for hypertension as the exposure and 28-day mortality in sepsis as the outcome and employed the main inverse variance weighted method along with other supplementary MR techniques to verify the causal association between hypertension and 28-day mortality in sepsis. We used sensitivity analyses to ensure the robustness of the research findings. Finally, we utilized clinical data from the Medical Information Mart for Intensive Care-IV database to assess the risk association between hypertension and 28-day mortality in sepsis using difference analysis and multivariate logistic regression analysis.

RESULTS

According to MR, hypertension increased the 28-day mortality in sepsis in both two datasets (FinnGen: odds ratio [OR] = 1.61, 95 % confidence interval [CI] = 1.15-2.26, p = 0.006; Medical Research Council-Integrative Epidemiological Unit: OR = 160, 95 % CI = 2.76-9250, p = 0.014). In our observational study, we included a total of 2012 sepsis patients, of which 60.5 % were male, and the average age was 55.4 years. By applying univariate and multivariate logistic regression models (univariate analysis p = 0.02, multivariate analysis p = 0.02), we observed a significantly increased risk of 28-day mortality due to hypertension in sepsis patients.

CONCLUSION

This study confirmed the causal relationship between hypertension and the 28-day mortality in sepsis.

Genetic evidence linking retinol to birth weight: A two-sample Mendelian randomization study

This study aims to clarify the potential causal effects of dietary antioxidant vitamins on pregnancy outcomes (miscarriage, preterm labor, and birth weight) using Mendelian randomization (MR). Our instrumental variables (IVs) were single-nucleotide polymorphisms (SNPs) linked to retinol, vitamin C, carotene, and vitamin E (P < 5×10-6). The summary statistics for miscarriage, preterm labor, and birth weight were extracted from genome-wide association studies (GWASs), with a sample size of 56,172, 5480, and 261,932, respectively. The present MR study primarily used the inverse-variance weighted method, with additional sensitivity analyses conducted to evaluate the robustness of the findings. We found that retinol was closely related to the birth weight (β=0.091, 95 %CI: 0.009-0.172, P=0.028), and sensitivity analyses showed similar results (MR-RAPS: OR=1.101, 95 %CI: 1.027-1.180; maximum likelihood: OR=1.098, 95 %CI: 1.011-1.194). While the relationship of retinol with miscarriage or preterm labor was not statistically significant. Additionally, our study did not reveal an association between the carotene, vitamin E, and vitamin C and pregnancy-related outcomes, miscarriage, preterm labor, and birth weight (all P > 0.05). In conclusion, our findings indicated a causal effect between retinol and birth weight and suggested that maintaining retinol at normal levels during pregnancy can prevent low birth weight. Therefore, it would be beneficial to measure retinol levels in pregnant women and to supplement with vitamin A in cases of deficiency, as these could be valuable strategies for improving pregnancy outcomes.

Mendelian randomization study of inflammatory bowel disease and type 1 diabetes

PURPOSE

Our purpose was to investigate and test the causal relationship between type 1 diabetes (T1D) and inflammatory bowel disease (IBD) and its major phenotypes, including ulcerative colitis (UC) and Crohn's disease (CD), in two large datasets.

METHODS

We obtained IBD samples from the largest publicly available genome-wide association study (GWAS), as well as the FinnGen database and the publicly accessible IEU GWAS database of T1D. We employed a two-sample Mendelian randomization approach to assess bidirectional causality using the inverse variance weighting (IVW) method as the primary outcome.

RESULTS

Genetic predisposition to T1D was associated with reduced risk of IBD (IVW: odds ratio (OR), 0.867; 95% confidence interval (CI), [0.852, 0.883]; P < 0.001), UC (OR = 0.879 [0.823, 0.939], P < 0.001), and CD (OR = 0.925 [0.872, 0.981], P = 0.009). The republication results found IBD genetically possessed negative association with T1D (OR = 0.781 [0.684, 0.891], P < 0.001). Additionally, a meta-analysis of results was conducted to prove the strong evidence between T1D and CD (OR = 0.95 [0.91, 0.98]; p = 0.01).

CONCLUSIONS

This study first demonstrated a causal effect of TID on the reduced risk of CD in the mendelian randomization study.

Appraising non-linear association between pre-diagnostic platelet counts and cancer survival outcomes: observational and genetic analysis

Previous studies have reported inconsistent associations between platelet count (PLT) and cancer survival. However, whether there is linear causal effect merits in-depth investigations. We conducted a cohort study using the UK Biobank and a two-sample Mendelian randomization (MR) analysis. PLT levels were measured prior to cancer diagnosis. We adopted overall survival (OS) as the primary outcome. Cox models were utilized to estimate the effects of PLTs on survival outcomes at multiple lag times for cancer diagnosis. We employed 34 genetic variants as PLT proxies for MR analysis. Linear and non-linear effects were modeled. Prognostic effects of gene expression harboring the instrumental variants were also investigated. A total of 65 471 cancer patients were included. We identified a significant association between elevated PLTs (per 100 × 109/L) and inferior OS (HR: 1.07; 95% CI: 1.04-1.10; p < .001). Similar significant associations were observed for several cancer types. We further observed a U-shaped relationship between PLTs and cancer survival (p < .001). Our MR analysis found null evidence to support a causal association between PLTs and overall cancer survival (HR: 1.000; 95% CI: 0.998-1.001; p = .678), although non-linear MR analysis unveiled a potential greater detrimental effect at lower PLT range. Expression of eleven PLT-related genes were associated with cancer survival. Early detection of escalated PLTs indicated possible occult cancer development and inferior subsequent survival outcomes. The observed associations could potentially be non-linear. However, PLT is less likely to be a promising therapeutic target.

Effects of Sjogren's Syndrome on essential hypertension: a two-sample mendelian randomization study

BACKGROUND

Sjogren's Syndrome (SS) plays important roles in the development of essential hypertension. Nevertheless, with the limitation of reverse causality and confounder in observational studies, such a relationship remains unclear. We aimed to assess the causal relationship of SS and hypertension by the Mendelian randomization (MR) approach.

METHODS

We used MR to investigate a causal association between SS and essential hypertension. Inverse variance weighted (IVW), MR Egger regression, Maximum likelihood, Weighted median, and MR pleiotropy residual sum and outlier test (MR-PRESSO) were used in this MR analysis.

RESULTS

In this study, we found that the ratio of IVW is 1.00024 (95% CI: 1.00013- 1.00036, P=0.0387), This result was also confirmed by sensitivity analysis methods such as Maximum likelihood is 1.00025 (95% CI: 1.00013-1.00037, P=0.036), MR Egger is 1.00071 (95% CI: 1.00047-1.00095, P=0.0045), and Weighted median is 1.00040 (95% CI: 1.00021- 1.00059, P=0.0322). And MR-Egger intercept method revealed the absence of horizontal pleiotropy in this investigation (P>0.05). The Cochran's Q Test indicated an absence of heterogeneity among them (P>0.05). Heterogeneity and horizontal pleiotropy tests further demonstrate that the results of MR are relatively stable. The above results all suggest that pSS may promote the risk of hypertension.

CONCLUSIONS

Our study provides evidence of a causal relationship of SS and hypertension. It is suggested to pay attention to early screening for hypertension, reduce disability and mortality rates, and improve patient prognosis in patients with SS.

No causal relationship between ankylosing spondylitis and Parkinson's disease: Insights from Mendelian randomization studies

Background

Retrospective cohort and cross-sectional studies have indicated an association between ankylosing spondylitis (AS) and Parkinson's disease (PD). However, owing the multitude of limitations, a consistent conclusion has not been determined. Furthermore, whether a causal relationship exists between these two diseases remains unclear.

Methods

We conducted a two-way Mendelian randomization (MR) analysis using genome-wide association study data. For patients with PD, we utilised data from the ieu-b-7 database, whereas for patients with AS, we employed the three databases with the largest sample sizes for a combined analysis. These databases included ebi-a-GCST005529, finn-b-M13 ANKYLOSPON, and finn-b-M13 ANKYLOSPON STRICT. Our primary method of analysis was inverse variance weighting (IVW), supplemented by four other effective methods, to comprehensively infer a potential causal relationship between AS and PD. Additionally, we conduct various sensitivity analyses to assess the robustness of our estimates.

Results

Based on our IVW MR analysis, no significant causal relationship between AS and PD was observed (odds ratio [OR] = 1.01, 95 % confidence interval [CI] = 0.99-1.03, P = 0.26). Additionally, our reverse MR analysis found no evidence supporting a significant causal relationship between PD and AS (OR = 0.93, 95 % CI = 0.85-1.01, P = 0.068). These results were substantiated by comprehensive sensitivity analyses that indicated minimal bias in the causal estimates.

Conclusion

In contrast to numerous existing clinical studies, this study failed to provide evidence supporting a significant impact of AS on PD risk, or vice versa. Further investigations regarding the potential causal mechanisms linking AS and PD are warranted.

Is there a genetic relationship between blood glucose and osteoarthritis? A mendelian randomization study

OBJECTIVE

The relationship between blood glucose levels and osteoarthritis (OA) is unclear. This study aimed to investigate the genetic causal relationship between blood glucose-related traits and OA.

METHODS

We first performed univariate Mendelian randomization (UVMR) analyses using published genome-wide association study (GWAS) datasets with fasting glucose (FG), 2 h-glucose post-challenge glucose (2hGlu), and glycosylated hemoglobin (HbA1c) as exposures, and hip osteoarthritis (HOA) and knee osteoarthritis (KOA) as outcomes; then, we performed inverse analyses of them. We used Inverse-variance weighted (IVW) analysis as the primary analysis, and sensitivity analyses were performed. Moreover, we performed multivariate Mendelian randomization (MVMR) to estimate the independent effect of exposure on outcome after adjusting for body mass index (BMI). Summarized data for blood glucose-related traits were obtained from the MAGIC Consortium study of the glucose trait genome and for OA from the UK Biobank and arcOGEN. Summarized data for BMI were obtained from the GIANT Consortium meta-analysis of individuals of European ancestry. A two-sided p value < 0.05 in UVMR was considered suggestive of significance when p < 0.0167 (Bonferroni correction p = 0.05/3 exposures) was considered statistically significant.

RESULTS

We found significant negative genetic causality of FG for HOA and KOA, and these associations remained significant after we adjusted for the effect of BMI [odds ratios (ORs) of 0.829 (0.687-0.999, p = 0.049) and 0.741 (0.570-0.964, p = 0.025)]. HbA1c also had an independent negative genetic causal effect on HOA after adjustment for BMI [0.665 (0.463-0.954, p = 0.027)]. At the same time, there was no evidence of reverse genetic causality of OA on blood glucose-related traits.

CONCLUSION

We further elucidated the relationship between blood glucose-related traits and OA by adjusting for the effect of BMI from a genetic causal perspective. This study provides new insights to further clarify the relationship between blood glucose levels and OA, as well as the pathogenesis, etiology and genetics of OA.

Causal role of the pyrimidine deoxyribonucleoside degradation superpathway mediation in Guillain-Barré Syndrome via the HVEM on CD4 + and CD8 + T cells

Immune system regulation is a key indicator of the gut microbiota (GM) influencing disease development. The causal role of the GM in Guillain-Barré syndrome (GBS) and whether it can be mediated by immune cells is unknown. Genome-wide association study (GWAS) summary statistics for the GM were obtained from the Dutch Microbiota Project (n = 7,738) and the FINRISK 2002 (FR02) cohort (n = 5,959). Inverse variance weighting method (IVW) were used as the main method to evaluate the causal relationship between GM and GBS. Subsequently, the mediating effects of 731 immune traits were evaluated. Additionally, we also executed the Bayesian Weighting algorithm for verification. Mendelian randomization (MR) analysis determined the protective effect of the pyrimidine deoxyribonucleoside degradation superpathway on GBS (IVW: P = 0.0019, OR = 0.4508). It is worth noting that in the causal effects of pyrimidine deoxyribonucleoside degradation superpathway on GBS, the mediated proportions of herpesvirus entry mediator (HVEM) ( HVEM on CM CD4 + , HVEM on naive CD4 + , HVEM on CD45RA - CD4 + , HVEM on CM CD8br) in the T cell maturation stage on GBS were -0.0398, -0.0452, -0.0414, -0.0425, accounting for 5.00%, 5.67%, 5.19% and 5.34% of the total effect. 11 types of intestinal bacteria might be involved in the pyrimidine deoxyriboside degradation superpathway, including Staphylococcus A fleurettii, AR31,CAG-274 sp000432155, Photobacterium, Acetobacteraceae, Dysgonomonadaceae, NK4A144,Leptospirae, CAG-81 sp000435795, Leptospirales and CAG-873 sp001701165. This study suggests that there is a causal relationship between pyrimidine deoxyribonucleoside degradation superpathway and GBS, which may be mediated by HVEM on CD4 + and CD8 + T cells. As a bidirectional molecular switch, HVEM plays an important role in T cell regulation. 11 intestinal flora were found to be involved in pyrimidine deoxyribonucleoside degradation superpathway, and their changes may be related to the occurrence of GBS. However, extensive research is still warranted before microbiome sequencing can be used for prevention and targeted treatment of GBS.

Associations of human blood metabolome with optic neurodegenerative diseases: a bi-directionally systematic mendelian randomization study

BACKGROUND

Metabolic disruptions were observed in patients with optic neurodegenerative diseases (OND). However, evidence for the causal association between metabolites and OND is limited.

METHODS

Two-sample Mendelian randomization (MR). Summary data for 128 blood metabolites was selected from three genome-wide association study (GWASs) involving 147,827 participants of European descent. GWASs Data for glaucoma (20906 cases and 391275 controls) and age-related macular degeneration (AMD, 9721 cases and 381339 controls) came from FinnGen consortium. A bi-directional MR was conducted to assess causality, and a Mediation MR was further applied to explore the indirect effect, a phenome-wide MR analysis was then performed to identify possible side-effects of the therapies.

RESULTS

All the results underwent correction for multiple testing and rigorous sensitivity analyses. We identified N-acetyl glycine, serine, uridine were linked to an elevated risk of glaucoma. 1-arachidonic-glycerol-phosphate-ethanolamine, 4-acetamido butanoate, o-methylascorbate, saturated fatty acids, monounsaturated fatty acids, VLDL cholesterol, serum total cholesterol, X-11,529 were linked to reduced risk of glaucoma. There were 4 metabolites linked to a reduced risk of AMD, including tryptophan betaine, 4-androsten-3beta-17beta-diol disulfate, apolipoprotein B, VLDL cholesterol. We discovered IOP, AS, T2D as glaucoma risk factors, while BMI, AS, GCIPL as AMD factors. And 6 metabolites showed associations with risk factors in the same direction as their associations with glaucoma/AMD. Phenome-wide MR indicated that selected metabolites had protective/adverse effects on other diseases.

CONCLUSIONS

By integrating genomics and metabolomics, this study supports new insights into the intricate mechanisms, and helps prevent and screen glaucoma and AMD.

Causal effect of immune cells on idiopathic pulmonary fibrosis: A mendelian randomization study

BACKGROUND

A key component of idiopathic pulmonary fibrosis (IPF) is the involvement of immune cells. However, the causal interaction between different immune cell signatures and IPF remain inconclusive.

OBJECTIVES

Based on publicly accessible data, our study utilized the Mendelian randomization (MR) approach to determine the causative relevance of complex immune cell phenotypes in IPF.

METHODS

We deployed a two-sample Mendelian randomization approach to evaluate the causal interaction between immune cell markers and IPF. All data regarding 731 immune signatures and IPF were acquired from two genome-wide association studies (GWAS) that are accessible to the public. The original study adopted the inverse variance weighted (IVW) method, followed by sensitivity analyses aimed at eliminating heterogeneity and pleiotropy. Additionally, Multivariate Mendelian randomization (MVMR) was utilized to identify the independent risk factors in our study.

RESULTS

The summary dataset for IPF was accessed from the Finnish Genetic Consortium R9, comprising 2018 patients and 373,064 controls. And the dataset for immune signatures was conducted in 3,757 Sardinian individuals. By conducting IVW and extensive sensitivity analyses, univariate Mendelian randomization (UVMR) identified one immunophenotype that remained causally associated with IPF after false discovery rate (FDR) correction: CD39 on CD39+ CD8+T cells (odd ratio [OR] = 0.850, 95 % confidence interval [CI] = 0.787-0.918, P = 3.68 × 10-5). The causal association with IPF was further validated using MVMR.

CONCLUSIONS

Based on rigorous MR analysis methods and FDR correction, our study demonstrated that CD39 on CD39+ CD8+T cells showed a protective effect against IPF, providing effective insights for preventing and diagnosing pulmonary fibrosis.

Effect of smoking on melanoma incidence: a systematic review with meta-analysis

BACKGROUND

There is a strong correlation between cigarette smoking and the development of many cancer types. It is therefore paradoxical that multiple reports have suggested a reduced incidence of melanoma in smokers. This study aimed to analyze all existing studies of melanoma incidence in smokers relative to nonsmokers.

METHODS

Searches of MEDLINE and Embase were conducted for studies reporting data on melanoma in smokers and never-smokers. No study design limitations or language restrictions were applied. The outcome examined was the association between smoking status and melanoma. Analyses focused on risk of melanoma in smokers and never-smokers generated from multivariable analyses, and these analyses were pooled using a fixed-effects model. Risk of bias was assessed using the Newcastle-Ottawa tool.

RESULTS

Forty-nine studies that included 59 429 patients with melanoma were identified. Pooled analyses showed statistically significant reduced risks of melanoma in male smokers (risk ratio [RR] = 0.60, 95% confidence interval [CI] = 0.56 to 0.65, P < .001) and female smokers (RR = 0.79, 95% CI = 0.73 to 0.86, P < .001). Male former smokers had a 16% reduction in melanoma risk compared with male never-smokers (RR = 0.84, 95% CI = 0.77 to 0.93, P < .001), but no risk reduction was observed in female former smokers (RR = 1.0, 95% CI = 0.92 to 1.08).

CONCLUSIONS

Current smokers have a statistically significant reduced risk of developing melanoma compared with never-smokers, with a reduction in melanoma risk of 40% in men and 21% in women.

Exploring potential therapeutic targets for asthma: a proteome-wide Mendelian randomization analysis

BACKGROUND

Asthma poses a significant global health challenge, characterized by high rates of morbidity and mortality. Despite available treatments, many severe asthma patients remain poorly managed, highlighting the need for novel therapeutic strategies. This study aims to identify potential drug targets for asthma by examining the influence of circulating plasma proteins on asthma risk.

METHODS

This study employs summary-data-based Mendelian randomization (MR) and two-sample MR methods to investigate the association between 2940 plasma proteins from the UK Biobank study and asthma. The analysis includes discovery (FinnGen cohort) and replication (GERA cohort) phases, with Bayesian colocalization used to validate the relationships between proteins and asthma. Furthermore, protein-protein interaction and druggability assessments were conducted on high-evidence strength protein biomarkers, and candidate drug prediction and molecular docking were performed for proteins without targeted drugs. Given the complexity of asthma pathogenesis, the study also explores the relationships between plasma proteins and asthma-related endpoints (e.g., obesity-related asthma, infection-related asthma, childhood asthma) to identify potential therapeutic targets for different subtypes.

RESULTS

In the discovery cohort, 75 plasma proteins were associated with asthma, including IL1RAP, IL1RL1, IL6, CXCL5, and CXCL8. Additionally, 6 proteins (IL4R, LTB, CASP8, MAX, PCDH12, and SCLY) were validated through co-localization analysis and validation cohort. The assessment of drug targetability revealed potential drug targets for IL4R, CASP8, and SCLY, while candidate drugs were predicted for LTB and MAX proteins. MAX exhibited strong binding affinity with multiple small molecules indicating a highly stable interaction and significant druggability potential. Analysis of the 75 proteins with 9 asthma-related endpoints highlighted promising targets such as DOK2, ITGAM, CA1, BTN2A1, and GZMB.

CONCLUSION

These findings elucidate the link between asthma, its related endpoints, and plasma proteins, advancing our understanding of molecular pathogenesis and treatment strategies. The discovery of potential therapeutic targets offers new insights into asthma drug target research.

Genetic evidence of bidirectional mendelian randomization study on the causality between gut microbiome and respiratory diseases contributes to gut-lung axis

Observational studies and clinical trials have suggested the relationship between the gut microbiome and respiratory diseases, but the causality between them remains unclear. Firstly, we selected eight respiratory diseases Genome-wide association study (GWAS) datasets mainly from the FinnGen collaboration as outcomes. The exposure was based on GWAS statistics about the gut microbiome, sourced from the MiBioGen consortium, including gut microbial taxa. The causal link between the gut microbiome and respiratory illnesses was then estimated using a Two-sample Mendelian randomization (MR) analysis, including the inverse-variance weighted (IVW), weighted median, MR-Egger, simple mode, and weighted mode. To ensure reliability, F-statistics and sensitivity tests were conducted. Furthermore, we performed a reverse MR analysis of the pre-Mendelian positive findings to possible reverse causality. For the 196 gut microbe taxa, the IVW analysis suggested 88 potential associations with eight clinically prevalent respiratory diseases. Among them, 30 causal associations were found in more than one MR method. Multiple statistical corrections have confirmed three causal associations: genus Holdemanella was a risk factor for chronic obstructive pulmonary disease (COPD) (P = 1.3 × 10-4, OR = 1.18), family FamilyXIII was a protective factor for COPD (P = 1.3 × 10-3, OR = 0.75), and genus Oxalobacter was a risk factor for asthma (P = 2.1 × 10-4, OR = 1.09). Our MR analysis results indicate that there would be a causal relationship between the gut microbiome and respiratory diseases, contributing to the gut-lung axis. This finding offers new insights into the gut microbiome's roles in respiratory diseases' clinical prevention, pathogenesis, and improvement of clinical symptoms. Further randomized controlled trials are necessary to clarify the protective effect of probiotics and fecal microbial transplantation on respiratory health.

Validation of TYK2 and exploration of PRSS36 as drug targets for psoriasis using Mendelian randomization

Psoriasis is a chronic inflammatory skin disorder with multiple causes, including genetic and environmental factors. Despite advances in treatment, there remains a need to identify novel therapeutic targets. A Mendelian randomization (MR) analysis was conducted to identify therapeutic targets for psoriasis. Data on cis-expression quantitative trait loci were obtained from the eQTLGen Consortium (n = 31,684). Summary statistics for psoriasis (outcome) were sourced from the GWAS Catalog with a sample size of 484,598, including 5,427 cases and 479,171 controls. Colocalization analysis was used to assess whether psoriasis risk and gene expression were driven by shared single nucleotide polymorphisms. Drug prediction and molecular docking were utilized to validate the pharmacological value of the drug targets. The MR analysis found that 81 drug targets were significantly associated, and two (TYK2 and PRSS36) were supported by colocalization analysis (PP.H4 > 0.80). Phenome-wide association studies did not show any associations with other traits at the gene level. Biologically, these genes were closely related to immune function. Molecular docking revealed strong binding with drugs and proteins, as supported by available structural data. This study validated TYK2 as a drug target for psoriasis, in line with its existing clinical use, including the development of decucravacitinib. PRSS36 is a potential novel target requiring further investigation.

A Mendelian randomization study of the association between serum uric acid and osteoporosis risk

Background

The relationship between serum uric acid (SUA) and osteoporosis (OP) has yielded conflicting results in observational studies. This Mendelian randomization (MR) study aims to elucidate the causal association between SUA and OP.

Methods

A two-sample MR analysis was conducted using summary-level data from genome-wide association studies (GWAS). Two sets of polygenic instruments strongly associated (p < 5 × 10-8) with SUA were extracted from the CKDGen consortium and UK biobank. Polygenic instruments associated with OP (p < 5 × 10-8) were derived from FinnGen biobank and UK biobank. Inverse variance weighting (IVW) was employed as the primary analysis method. Additionally, we utilized MR-Egger, weighted median, the simple mode method, and the weighted mode as complementary analyses. Cochran's Q statistics were used to assess heterogeneity, with MR-Egger intercept testing and MR pleiotropy residual sum and outlier (MR-PRESSO) to examine horizontal pleiotropy. Sensitivity analysis was performed using the leave-one-out method.

Results

The IVW analysis conducted across four groups confirms no significant causal relationship between SUA concentration and OP: UKB-UKB (OR: 1.001, 95% CI: 0.999-1.003, p=0.464), CKD-UKB (OR: 1.001, 95% CI: 0.999-1.003, p=0.349), UKB-Fin (OR: 0.934, 95% CI: 0.747-1.168, p=0.549), CKD-Fin (OR: 1.041, 95%CI: 0.934-1.161, p=0.470). Furthermore, additional four MR analyses corroborated these findings. Upon excluding all outliers identified by the MR-PRESSO test, no significant directional pleiotropy was observed, except for some data heterogeneity noted in the UKB-UKB group (Q=50.65, P=0.002). Additionally, a leave-one-out analysis indicated that no single SNP exerted undue influence on the results.

Conclusion

This MR analysis provides convincing genetic evidence that there is no causal association between SUA and OP, SUA is unlikely to increase or reduce the risk of OP.

Genetic insights into dietary patterns, liposome mediation, and osteoporosis risk: a Mendelian randomization study

Background

This study examines the indirect causal relationships between dietary habits and osteoporosis, mediated through liposomes, utilizing a two-sample Mendelian randomization (MR) approach. The research leverages genetic variations as instrumental variables to explore the genetic influences on dietary habits, liposomes, and osteoporosis, aiming to unravel the complex interplay between diet, lipid metabolism, and bone health.

Methods

The study utilized genome-wide association studies (GWAS) data for liposomes from Finnish individuals and osteoporosis-related data, alongside dietary factors from the OpenGWAS database. Instrumental variables were selected based on genetic variants associated with these factors, using a strict significance level and linkage disequilibrium threshold. Statistical analysis employed the Inverse Variance Weighted method, weighted median, and mode-based methods within the R environment, complemented by sensitivity analyses to ensure the robustness of the causal inferences.

Results

Findings revealed significant causal relationships between specific dietary components (white rice, cereal, and non-oily fish) and osteoporosis risk, both directly and mediated through changes in liposome levels. Notably, white rice consumption was associated with an increased risk of osteoporosis, while cereal and non-oily fish intake showed protective effects. Further, certain liposomes were identified as mediators in these relationships, suggesting a link between diet, lipid profiles, and bone health.

Conclusion

The study highlights the significant impact of dietary habits on osteoporosis risk, mediated through liposomes. These findings underscore the importance of considering lipidomic profiles in dietary guidance and suggest potential targets for preventing osteoporosis through nutritional interventions.

Neuroticism and posttraumatic stress disorder: A Mendelian randomization analysis

OBJECTIVE

Epidemiological studies revealed an unestablished association between neuroticism and posttraumatic stress disorder (PTSD) and we conducted mendelian randomization (MR) analyses to examine whether neuroticism clusters of worry, depressed affect, and sensitivity to environmental stress and adversity (SESA) were involved in the development of PTSD.

METHOD

We obtained data on three neuroticism clusters, PTSD, and nine other psychiatric disorders from genome-wide association studies summary statistics and employed univariable, multivariable, and mediation MR analyses to explore causal associations among them.

RESULTS

Neuroticism clusters were linked with PTSD (depressed affect (odds ratio [OR]: 2.94 [95% confidence interval: 2.21-3.92]); SESA (2.69 [1.95-3.71]; worry (1.81 [1.37-2.99])). Neuroticism clusters were also associated with psychiatric disorders, with the depressed effect on panic disorder (PD) (2.60 [1.14-5.91]), SESA on anorexia nervosa (AN) (2.77 [1.95-3.94]) and schizophrenia (2.55 [1.99-3.25]), worry on major depressive disorder (MDD) (2.58 [2.19-3.05]). In multivariable MR, only the SESA-PTSD association remained (2.60 [2.096, 3.107]) while worry-PTSD and depressed affect-PTSD associations attenuated to nonsignificance. Mediation MR analyses suggested that PD mediated 3.76% of the effect of depressed effect on PTSD and AN mediated 10.33% of the effect of SESA on PTSD.

CONCLUSION

Delving deeper into neuroticism clusters, we comprehensively understand the role of neuroticism in PTSD.

Investigating Causal Associations between the Gut Microbiota and Dementia: A Mendelian Randomization Study

Background: The causal association of specific gut microbiota with dementia remains incompletely understood. We aimed to access the causal relationships in which one or more gut microbiota account for dementia. Method: Using data from the MiBioGen and FinnGen consortia, we employed multiple Mendelian randomization (MR) approaches including two-sample MR (TSMR), multivariable MR (MVMR), and Bayesian model averaging MR to comprehensively evaluate the causal associations between 119 genera and dementia, and to prioritize the predominant bacterium. Result: We identified 21 genera that had causal effects on dementia and suggested Barnesiella (OR = 0.827, 95%CI = 0.722-0.948, marginal inclusion probability [MIP] = 0.464; model-averaged causal estimate [MACE] = -0.068) and Allisonella (OR = 0.770, 95%CI = 0.693-0.855, MIP = 0.898, MACE = -0.204) as the predominant genera for AD and all-cause dementia. Conclusions: These findings confirm the causal relationships between specific gut microbiota and dementia, highlighting the necessity of multiple MR approaches in gut microbiota analysis, and provides promising genera as potential novel biomarkers for dementia risk.

Metabolite, immunocyte phenotype, and lymphoma: a Mendelian randomization study

Background

Recent studies have confirmed that metabolites and immunocyte phenotype may be associated with the risk of lymphoma. However, the bidirectional causality between metabolites, immunocyte phenotype, disease risk, and whether immunity is an intermediate mediator between metabolism and lymphoma causality is still unclear.

Objective

To elucidate the causal relationship between metabolites, immune cell phenotypes, and lymphomas, we used two-sample Mendelian randomization (MR) and two-step MR analysis.

Methods

Applying large-scale genome-wide association studies (GWAS) pooled data, we selected 1400 metabolites and 731 immunocyte phenotypes with eight lymphoma subtypes for two-sample bi-directional MR analysis. In addition, we used two-step MR to quantify the proportion of metabolite effects on lymphomas mediated by immunocyte phenotype.

Results

This study yielded a bidirectional causal relationship between 17 metabolites and lymphoma and a bidirectional causal relationship between 12 immunocyte phenotypes and lymphoma. In addition, we found causal associations between metabolites and lymphomas, three groups of which were mediated by immunocyte phenotypes. Among them, CD27 on plasmablast/plasma cell (PB/PC) was a mediator of the positive association of arginine to glutamate ratio with chronic lymphocytic leukemia, with a mediator ratio of 14.60% (95% CI=1.29-28.00%, P=3.17 × 10-2). Natural killer (NK) cells as a percentage of all lymphocytes(NK %lymphocyte) was a mediator of the negative association of X-18922(unknown metabolite) levels with diffuse large B-cell lymphoma, with a mediation proportion of -8.940% (95% CI=-0.063-(-17.800) %, P=4.84 × 10-2). CD25 on IgD- CD24- B cell was the mediator of the positive association between X-24531(unknown metabolite) levels and diffuse large B-cell lymphoma, with a mediation proportion of 13.200% (95% CI=-0.156-26.200%, P=4.73 × 10-2).

Conclusion

In the present study, we identified a causal relationship between metabolites and lymphoma, in which immunocyte phenotypes as mediators are involved in only a minor part. The mediators by which most metabolites affect the risk of lymphoma development remain unclear and require further exploration in the future.

Genetic correlation between chronic sinusitis and autoimmune diseases

Objective

The association between autoimmune diseases and chronic rhinosinusitis in observational studies remains unclear. This study aimed to explore the genetic correlation between chronic rhinosinusitis and autoimmune diseases.

Methods

We employed Mendelian randomization (MR) analysis and linkage disequilibrium score regression (LDSC) to investigate causal relationships and genetic correlations between autoimmune phenotypes and chronic rhinosinusitis. Additionally, transcriptome-wide association (TWAS) analysis was conducted to identify the shared genes between the two conditions to demonstrate their relationship. The CRS GWAS (genome-wide association study) data and other autoimmune diseases were retrieved from ieuOpenGWAS (https://gwas.mrcieu.ac.uk/), the FinnGen alliance (https://r8.finngen.fi/), the UK Biobank (https://www.ukbiobank.ac.uk/), and the EBI database (https://www.ebi.ac.uk/).

Results

Utilizing a bivariate two-sample Mendelian randomization approach, our findings suggest a significant association of chronic rhinosinusitis with various autoimmune diseases, including allergic rhinitis (p = 9.55E-10, Odds Ratio [OR] = 2,711.019, 95% confidence interval [CI] = 261.83391-28,069.8), asthma (p = 1.81E-23, OR = 33.99643, 95%CI = 17.52439-65.95137), rheumatoid arthritis (p = 9.55E-10, OR = 1.115526, 95%CI = 1.0799484-1.1522758), hypothyroidism (p = 2.08828E-2, OR = 4.849254, 95%CI = 1.7154455-13.707962), and type 1 diabetes (p = 2.08828E-2, OR = 01.04849, 95%CI = 1.0162932-1.0817062). LDSC analysis revealed a genetic correlation between the positive autoimmune phenotypes mentioned above and chronic rhinosinusitis: AR (rg = 0.344724754, p = 3.94E-8), asthma (rg = 0.43703672, p = 1.86E-10), rheumatoid arthritis (rg = 0.27834931, p = 3.5376E-2), and hypothyroidism (rg = -0.213201473, p = 3.83093E-4). Utilizing the Transcriptome-Wide Association Studies (TWAS) approach, we identified several genes commonly associated with both chronic rhinosinusitis and autoimmune diseases. Genes such as TSLP/WDR36 (Chromosome 5, top SNP: rs1837253), ORMDL3 (Chromosome 13, top SNP: rs11557467), and IL1RL1/IL18R1 (Chromosome 2, top SNP: rs12905) exhibited a higher degree of consistency in their shared involvement across atopic dermatitis (AT), allergic rhinitis (AR), and chronic rhinosinusitis (CRS).

Conclusion

Current evidence suggests a genetic correlation between chronic rhinosinusitis and autoimmune diseases like allergic rhinitis, asthma, rheumatoid arthritis, hypothyroidism, and type 1 diabetes. Further research is required to elucidate the mechanisms underlying these associations.

Association between air pollutants and four major mental disorders: Evidence from a Mendelian randomization study

BACKGROUND

Existing epidemiological studies have indicated a correlation between air pollutants and the occurrence of mental disorders. However, it is difficult to estimate the causal relationship between the two because of the limitations of traditional epidemiological research. In our study, we aimed to extensively explore the causal relationship between five types of air pollutants and four types of mental disorders.

METHODS

Based on the IEU OPEN GWAS database, we performed a two-sample MR analysis. The primary analysis method utilized was the inverse variance weighted (IVW) method, supplemented by the MR-Egger method and the weighted median method. Additionally, we conducted sensitivity analyses with the Cochran's Q statistic method, the leave-one-out method, and the MR-Egger intercept. We chose at least 4 GWAS datasets for each of the four psychiatric diseases and conducted a meta-analysis of our results of the MR analysis.

RESULTS

The meta-analysis's findings demonstrated a causal link between depression and PM2.5 (OR=1.020, 95 %CI: (1.010,1.030), P=0.001). PM10 and schizophrenia are also causally related (OR=1.136, 95 %CI: (1.034,1.248), P=0.008). Nitrogen oxides and bipolar disorder have a causal relationship (OR=1.002, 95 %CI: (1.000,1.003), P=0.022). Nitrogen oxides and schizophrenia have a high causal association (OR=1.439, 95 %CI: (1.183,1.752), P<0.001).

CONCLUSION

This study observed a causal association between increased concentrations of PM2.5, PM10, and nitrogen oxides and the occurrence of depression, schizophrenia, and bipolar disorder. Our research findings have certain guiding implications for treating and preventing mental disorders.

Rosacea and autoimmune liver diseases: a two-sample Mendelian randomization study

Rosacea and autoimmune liver diseases (AILDs) are diseases closely associated with immune system abnormalities. AILDs primarily includes autoimmune hepatitis (AIH), primary biliary cholangitis (PBC), and primary sclerosing cholangitis (PSC). Currently, research on the association between these two conditions is limited. Therefore, this study employed the bidirectional Mendelian randomization (MR) method to investigate potential causal relationships between rosacea and AILDs based on genetic predictions. Summary data related to Rosacea, AIH, PSC, and PBC were obtained from public genome-wide association studies (GWAS). The inverse variance weighted (IVW) method was used as the primary analytical approach, supplemented by the MR-Egger, weighted mode method, weighted median, and simple mode. A series of sensitivity analyses were also conducted to identify heterogeneity and pleiotropy effects. The MR analysis results indicated a significant increase in the risk of rosacea being associated with PBC (OR = 1.09, 95% CI = 1.02-1.18, P = 0.014), but no such association was found with AIH or PSC. Furthermore, this study did not find a significant impact of rosacea on the risk of AILDs. This study represents the first in-depth exploration of the potential causal relationship between rosacea and AILDs using MR analysis. Thes findings suggest an increased risk of rosacea among PBC patients.

The relationship between metabolite mediated immune regulatory imbalance and the occurrence of malignant tumors of bone and articular cartilage: a Mendelian randomization study

Background

This study aims to assess the causal relationship between immune cell characteristics and malignant tumors of bone and articular cartilage, focusing on the mediating role of metabolites. Using Mendelian randomization, we evaluated these relationships based on genetic variations to identify potential biomarkers and therapeutic targets.

Methods

A two-sample Mendelian randomization analysis was conducted using GWAS data for immune cell features and 1,400 metabolites to investigate direct and mediating effects. Effective instrumental variables (IVs) were selected, and statistical analyses-including inverse variance weighting (IVW), weighted median, and mode-based methods-were performed using R software. This approach enabled the assessment of direct causal relationships as well as the potential mediating role of metabolites in the association between immune cell features and malignancies.

Results

Significant causal relationships were identified between 26 immune phenotypes and the risk of malignant tumors of bone and articular cartilage. Notably, the HLA DR+ NK cell phenotype SSC-A showed a positive correlation with the risk of these malignancies. Further analysis revealed causal relationships with 67 metabolites, 38 of which were positively correlated and 29 negatively correlated. Mediation analysis highlighted the role of immune surveillance and metabolic dysregulation in tumor development, as evidenced by the association between the immune phenotype SSC-A on HLA DR+ NK cells and the metabolite 5-hydroxyhexanoate.

Conclusion

The findings suggest significant causal relationships between immune phenotypes and malignant tumors of bone and articular cartilage, with metabolites potentially mediating these relationships. These insights lay the groundwork for further research and could contribute to the development of new biomarkers and treatment strategies.

Gut microbiota, circulating inflammatory proteins and sepsis: a bi-directional Mendelian randomization study

Background

Gut microbiota is closely related to the occurrence and development of sepsis. However, the causal effects between the gut microbiota and sepsis, and whether circulating inflammatory proteins act as mediators, remain unclear.

Methods

Gut microbiota, circulating inflammatory proteins, and four sepsis-related outcomes were identified from large-scale genome wide association studies (GWAS) summary data. Inverse Variance Weighted (IVW) was the primary statistical method. Additionally, we investigated whether circulating inflammatory proteins play a mediating role in the pathway from gut microbiota to the four sepsis-related outcomes.

Results

There were 14 positive and 15 negative causal effects between genetic liability in the gut microbiota and four sepsis-related outcomes. Additionally, eight positive and four negative causal effects were observed between circulating inflammatory proteins and the four sepsis-related outcomes. Circulating inflammatory proteins do not act as mediators.

Conclusions

Gut microbiota and circulating inflammatory proteins were causally associated with the four sepsis-related outcomes. However, circulating inflammatory proteins did not appear to mediate the pathway from gut microbiota to the four sepsis-related outcomes.

The relationship between accelerometer-based physical activity, sedentary behavior, and seven common geriatric syndromes: a two-sample Mendelian randomization study

Introduction

To investigate the causal associations between accelerometer-based physical activity (PA), sedentary behavior (SB), and seven common geriatric syndromes (GSs) (frailty, falls, delirium, urinary incontinence, dysphagia, hearing loss, and visual impairment) by Mendelian randomization (MR) analysis.

Methods

Instrumental variables from a genome-wide association study were used for MR analysis. The exposure factors were three PA phenotypes (average acceleration, overall activity, and moderate-intensity activity) and one SB phenotype (SB). The outcome variables were seven common GSs. The inverse variance weighted (IVW) method was utilized for the primary MR analysis. Additionally, sensitivity, pleiotropy, and heterogeneity analyses were subsequently conducted to assess the robustness of the present study's findings.

Results

According to the primary MR results obtained using the IVW method, genetically predicted PA (average acceleration) decreased the risk of two GSs (frailty, p = 0.01; dysphagia, p = 0.03). Similarly, overall activity decreased the risk of two GSs (frailty, p = 0.01; delirium, p = 0.03), and moderate-intensity activity reduced the risk of three GSs (urinary incontinence, p = 0.04; hearing loss, p = 0.02; visual impairment, p = 0.01). Furthermore, SB was causally correlated with a greater risk for three GSs (frailty, p = 0.03; fall, p = 0.01; dysphagia, p = 0.04).

Conclusion

This study provided evidence that accelerometer-based PA may be causally associated with a lower risk of GSs, while SB may increase the risk of GSs.

Exploring correlations between immune cell phenotypes and the risk of epilepsy: A bidirectional Mendelian randomization study

BACKGROUND

Neuroinflammation plays an important pathophysiological role in epilepsy; however, the precise connection between immune cells and epilepsy remains unclear. This study used Mendelian randomization (MR) to analyze the causal relationship between 731 immune cell traits and epilepsy.

METHODS

Based on data from a genome-wide association study (GWAS), a bidirectional two-sample MR analysis was conducted to investigate the potential influence of immune cell phenotypes on epilepsy. Five MR methods were used to analyze the results, with the inverse variance weighted (IVW) method as the primary method, and the results were corrected using the false discovery rate (FDR) method. Sensitivity analyses were performed to test for heterogeneity and horizontal pleiotropy.

RESULTS

After correction for FDR, four immune traits remained significantly associated with epilepsy risk: CD25 expression on memory (OR = 1.04, 95 % CI = 1.02 ∼ 1.06,P = 2.55 × 10-4), IgD+CD38dim (OR = 1.05, 95 % CI = 1.02 ∼ 1.08, P = 4.73 × 10-4), CD24+CD27+ (OR = 1.04, 95 % CI = 1.02 ∼ 1.06, P = 4.82 × 10-4), and IgD-CD38dim (OR = 1.04, 95 % CI = 1.02 ∼ 1.06, P = 1.04 × 10-3) B cells. The risk of generalized epilepsy was significantly associated with two immune cell traits, whereas that of focal epilepsy was significantly associated with seven immune cell traits. Furthermore, immune cell phenotypes are not affected by genetically predicted epilepsy.

CONCLUSION

This MR study affirms the causal connection between circulating immune cells and epilepsy, offering guidance for further understanding of the immune mechanisms that underlie epilepsy and the discovery of novel targets for therapy.

Systematic investigation of genetically determined plasma and urinary metabolites to discover potential interventional targets for colorectal cancer

BACKGROUND

We aimed to identify plasma and urinary metabolites related to colorectal cancer (CRC) risk and elucidate their mediator role in the associations between modifiable risk factors and CRC.

METHODS

Metabolite quantitative trait loci were derived from 2 published metabolomics genome-wide association studies, and summary-level data were extracted for 651 plasma metabolites and 208 urinary metabolites. Genetic associations with CRC were obtained from a large-scale genome-wide association study meta-analysis (100 204 cases, 154 587 controls) and the FinnGen cohort (4957 cases, 304 197 controls). Mendelian randomization and colocalization analyses were performed to evaluate the causal roles of metabolites in CRC. Druggability evaluation was employed to prioritize potential therapeutic targets. Multivariable Mendelian randomization and mediation estimation were conducted to elucidate the mediating effects of metabolites on the associations between modifiable risk factors and CRC.

RESULTS

The study identified 30 plasma metabolites and 4 urinary metabolites for CRC. Plasma sphingomyelin and urinary lactose, which were positively associated with CRC risk, could be modulated by drug interventions (ie, olipudase alfa, tilactase). Thirteen modifiable risk factors were associated with 9 metabolites, and 8 of these modifiable risk factors were associated with CRC risk. These 9 metabolites mediated the effect of modifiable risk factors (Actinobacteria, body mass index, waist to hip ratio, fasting insulin, smoking initiation) on CRC.

CONCLUSION

This study identified key metabolite biomarkers associated with CRC and elucidated their mediator roles in the associations between modifiable risk factors and CRC. These findings provide new insights into the etiology and potential therapeutic targets for CRC and the etiological pathways of modifiable environmental factors with CRC.

Assessing the impact of circulating inflammatory cytokines and proteins as drivers and therapeutic targets in epilepsy: A Mendelian randomization study

BACKGROUND

Previous research has demonstrated that neuroinflammation is a key element in the progress of epilepsy. Nevertheless, it is currently unidentified which inflammatory factors and proteins increase or decrease the risk of epilepsy.

METHODS

We adopted Mendelian randomization techniques to explore the causal relationship between circulating inflammatory factors and proteins and various epilepsy. Our principal approach was inverse variance weighting, supplemented by several sensitivity analyses to guarantee the robustness of our findings.

RESULTS

Studies have identified associations between epilepsy and specific inflammatory factors and proteins: three inflammatory factors and six proteins are linked to epilepsy in general; one inflammatory factor and four proteins are associated with focal epilepsy with no documented lesions; two inflammatory factors and three proteins are related to focal epilepsy, excluding cases with hippocampal sclerosis; two inflammatory factors and two proteins are connected to juvenile myoclonic epilepsy; two inflammatory factors and five proteins are linked to juvenile absence epilepsy; four inflammatory proteins are associated with childhood absence epilepsy; two inflammatory factors are related to focal epilepsy overall; two inflammatory factors and two proteins are connected to generalized epilepsy; and two inflammatory proteins are linked to generalized epilepsy with tonic-clonic seizures. Additionally, six inflammatory factors may play a downstream role in focal epilepsy.

CONCLUSION

Our study uncovers various inflammatory factors and proteins that influence the risk of epilepsy, offering instructive insights to the diagnosis and therapy of the condition.

Causal associations of fatigue and functional outcome after ischemic stroke: a mediation Mendelian randomization study

Background and objectives

Fatigue has been associated with adverse effects on recovery from ischemic stroke based on previous observational research. The purpose of our study was to explore the potential causal association of fatigue with poor functional outcome after ischemic stroke by employing Mendelian randomization (MR).

Methods

A set of instrumental variables, comprising 36 single-nucleotide polymorphisms (SNPs) that are only related to fatigue, were derived from a genome-wide association study (GWAS) that included 449,019 general individuals. The functional outcomes after ischemic stroke were derived from a GWAS (Genetics of Ischemic Stroke Functional Outcome Network) involving 6,021 survivors. Two-sample MR methods were used to assess the causal effect, including inverse variance weighted, MR-Egger, weighted median, simple mode, and weighted mode. In bidirectional MR analysis, the reverse causal association was analyzed using the Wald ratio method. The mediation effects of lipid metabolites were analyzed using two-step MR analysis.

Results

Genetic liability to fatigue was causally associated with the poor functional outcome (modified Rankin Scale ≥3 at 3 months) after ischemic stroke (OR = 4.20, 95%CI [1.11-15.99], p < 0.05). However, genetic predicted poor functional outcome after ischemic stroke was not associated with fatigue (OR = 1.00, 95%CI [0.99-1.02], p > 0.05). The results of the two-step MR showed that cholesteryl esters to total lipids ratio in large very low-density lipoprotein (VLDL) (ME = -0.13, p < 0.05); concentration of very large VLDL particles (ME = -0.13, p < 0.05); free cholesterol in large VLDL (ME = -0.13, p < 0.05); free cholesterol to total lipids ratio in very large VLDL (ME = -0.22, p < 0.05); phospholipids in large VLDL (ME = -0.15, p < 0.05); phospholipids in very large VLDL (ME = -0.13, p < 0.05); phospholipids to total lipids ratio in large high-density lipoprotein (HDL) (ME = -0.17, p < 0.05); total lipids in very large VLDL (ME = -0.14, p < 0.05); triglycerides in small VLDL (ME = -0.11, p < 0.05); and triglycerides to total lipids ratio in large HDL (ME = -0.10, p < 0.05) assumed a pivotal role in mediating the association between fatigue and poor functional outcome after ischemic stroke.

Conclusion

Our study provides evidence supporting the causal association between fatigue and the poor functional outcome after ischemic stroke, which emphasizes the importance of implementing interventions aimed at addressing fatigue. This could offer a therapeutic target to improve recovery after ischemic stroke and warrant exploration in a clinical context. One potential mechanism by which fatigue affects functional outcomes after ischemic stroke is through the action of lipid metabolites.

Seven psychiatric traits and the risk of increased carotid intima-media thickness: a Mendelian randomization study

Background

Numerous observational studies have suggested an association between psychiatric traits and carotid intima-media thickness (cIMT). However, whether these associations have a causal relationship remains unknown, largely due to issues of reverse causality and potential confounders. This study aims to elucidate the potential causal role of psychiatric traits in the risk of arterial injury as measured by cIMT.

Methods

We utilized instrumental variables for attention deficit/hyperactivity disorder (ADHD, n = 226,534), bipolar disorder (n = 353,899), major depressive disorder (n = 142,646), post-traumatic stress disorder (n = 174,494), obsessive-compulsive disorder (n = 9,725), autism spectrum disorder (n = 173,773), and anxiety disease (n = 17,310), derived from the largest corresponding genome-wide association studies (GWAS). Summary statistics for cIMT associations were obtained from a meta-analysis combining GWAS data from the Cohorts for Heart and Aging Research in Genomic Epidemiology consortia (n = 71,128) and the UK Biobank study (n = 45,185). The inverse-variance weighted method served as the primary analytical tool, supplemented by additional statistical methods in the secondary analyses to corroborate the findings. Adjustments were made according to the Bonferroni correction threshold.

Results

The Mendelian randomization analyses indicated a suggestive causal link between genetically predicted ADHD and cIMT (beta = 0.05; 95% confidence interval, 0.01-0.09; p = 0.018). Sensitivity analyses largely concurred with this finding. However, no significant associations were found between other psychiatric traits and cIMT.

Conclusions

This study provides insights into the risk effect of ADHD on cIMT, suggesting that arteriopathy and potential associated complications should be considered during the treatment and monitoring of patients with ADHD.

Exploring genetic association of systemic iron status and risk with incidence of diabetic neuropathy

BACKGROUND

Diabetic neuropathy (DN), a frequent complication in individuals with diabetes mellitus (DM), is hypothesized to have a correlation with systemic iron status, though the nature of this relationship remains unclear. This study employs two-sample Mendelian randomization (MR) analysis to explore this potential genetic association.

METHODS

We used genetic instruments significant associated with iron status including serum iron, ferritin, transferrin, and transferrin saturation, derived from an extensive Genome-Wide Association Study (GWAS) undertaken by the Genetics of Iron Status Consortium, involving a cohort of 48,972 European ancestry individuals. Summary statistics for DN were collected from a public GWAS, including 1,415 patients and 162,201 controls of European descent. Our MR analysis used the inverse-variance-weighted (IVW) method, supplemented by MR-Egger, weighted-median (WM) methods, Cochran's Q test, MR-Egger intercept analysis, MR-Pleiotropy Residual Sum and Outlier (MR-PRESSO) method, and leave-one-out analysis to ensure robustness and consistency of the findings.

RESULTS

No genetic causal relationship was found between iron status markers and DN (all IVW p value > 0.05). Interestingly, a causative effect of DN on ferritin (IVW: OR = 0.943, 95% CI = 0.892-0.996, p = 0.035) and transferrin saturation (IVW: OR = 0.941, 95% CI = 0.888-0.998, p = 0.044) emerged. Sensitivity analyses confirmed the absence of significant heterogeneity and horizontal pleiotropy.

CONCLUSION

While systemic iron status was not found to be causally related to DN, our findings suggest that DN may increase the risk of iron deficiency. These results provide further evidence supporting iron supplementation in patients with DN.

Appendectomy and appendicitis do not increase colorectal cancer risk: evidence from Mendelian randomization

Background

Acute appendicitis (AA) is one of the most prevalent acute abdominal diseases and appendectomy is the definitive treatment of appendicitis. However, whether appendicitis and appendectomy cause colorectal cancer (CRC) is controversial. The results of observational studies are contradictory, but randomized controlled trials (RCT) cannot be conducted.

Methods

Data of appendectomy, AA, and CRC were obtained from the IEU Open GWAS project. We selected several Genome-wide association studies (GWAS) summary statistics for CRC: statistics for colon cancer (CC) were obtained from MRC-IEU and Neale lab, respectively; statistics for rectum cancer (RC) were obtained from MRC-IEU and FinnGen, respectively; statistics for CRC were provided by Sakaue S et al. Mendelian randomization (MR) was used to evaluate the causal relationships between exposure and outcomes. Inverse variance weighting (IVW) was the most important analysis method. Meta-analysis was used to summarize the results of IVW to increase the reliability and sensitivity analysis was used to evaluate the robustness of the results.

Results

According to the results of IVW, appendectomy did not increase risk of CC: MRC-IEU (OR:1.009, 95%CI:0.984-1.035, P=0.494), Neale lab (OR:1.016, 95%CI:0.993-1.040, P=0.174); Appendectomy also did not increase risk of RC: MRC-IEU(OR:0.994, 95%CI:0.974-1.014, P=0.538), FinnGen(OR:2.791, 95%CI:0.013-580.763, P=0.706); Appendectomy also did not increase risk of CRC: Sakaue S(OR:1.382, 95%CI:0.301-6.352, P=0.678). Appendicitis did not increase risk of CC: MRC-IEU(OR:1.000, 95%CI:0.999-1.001, P=0.641), Neale lab(OR:1.000, 95%CI:1.000-1.001, P=0.319); Appendicitis also did not increase risk of RC: MRC-IEU(OR:1.000, 95%CI:0.999-1.000, P=0.361), FinnGen(OR:0.903, 95%CI:0.737-1.105, P=0.321); Appendicitis also did not increase risk of CRC: Sakaue S (OR:1.018, 95%CI:0.950-1.091, P=0.609). The results of Meta-analysis also showed appendectomy (P=0.459) and appendicitis (P=0.999) did not increase the risk of CRC.

Conclusions

Appendectomy and appendicitis do not increase the risk of colorectal cancer. More clinical trials are needed in the future to verify the causal relationships.

Causality between major depressive disorder and functional dyspepsia: a two-sample Mendelian randomization study

Background

To investigate the causal relationship between major depression and functional dyspepsia using two-sample Mendelian randomization.

Methods

Data for major depression and functional dyspepsia were obtained from genome-wide association studies. We selected Single Nucleotide Polymorphisms (SNPs) strongly associated with severe depression. Mendelian randomization analysis was conducted using methods such as Inverse-Variance Weighted (IVW), MR-Egger, and Weighted Median Estimator (WME). Sensitivity analysis was performed to assess the robustness of the results.

Results

A total of 31 eligible SNPs were identified as instrumental variables for major depression. IVW analysis indicated a positive causal relationship between the two conditions (β = 0.328; SE = 0.137; p = 0.017), suggesting that severe depression increases the risk of functional dyspepsia (OR = 1.389; 95% CI: 1.062-1.816). Sensitivity tests showed no evidence of heterogeneity or horizontal pleiotropy (p > 0.05).

Conclusion

MR analysis had shown that major depressive disorder is associated with an increased risk of functional dyspepsia.

The causal role between circulating immune cells and diabetic nephropathy: a bidirectional Mendelian randomization with mediating insights

Diabetic nephropathy (DN) is a critical inflammatory condition linked to diabetes, affecting millions worldwide. This study employs Mendelian randomization (MR) to explore the causal relationship between immune cell signatures and DN, analyzing over 731 immune signatures and incorporating data from 1400 metabolites to investigate potential mediators. Despite no statistically significant influence of DN on immunophenotypes after FDR correction, some phenotypes with unadjusted low P-values warranted mention, including CD34 on Hematopoietic Stem Cell (Myeloid cell Panel), CD45 on CD33- HLA DR- (Myeloid cell Panel). Furthermore, three immunophenotypes were identified to have a significant impact on DN risk: CD16-CD56 on HLA DR+ NK (TBNK Panel), CD45 on HLA DR+ T cell (TBNK Panel), and CD33dim HLA DR+ CD11b+ AC (Myeloid cell Panel). Our findings underscore the critical role of immune cells in DN, highlighting potential mediators and offering new insights into its underlying mechanisms.

Causal associations between vitamin D and postpartum depression: A bidirectional mendelian randomization study

Background

Previous epidemiological studies have reported associations between vitamin D and postpartum depression (PPD); however, the findings are inconsistent. This study employs bidirectional Mendelian Randomization (MR) to investigate the causal link between serum 25-hydroxyvitamin D [25(OH)D] levels and PPD. By utilizing genetic data from cohorts, this research aims to provide a more robust understanding of the potential relationship between vitamin D and PPD, addressing a critical gap in the current literature.

Methods

A bidirectional MR analysis was conducted to investigate the genetic association between serum 25(OH)D and PPD using summary statistics extracted from GWAS datasets. The study included data from 15,668 patients with PPD and 376,755 healthy controls of European ancestry. The GWAS data for 25(OH)D were obtained from two studies within the UK Biobank, encompassing 496,946 and 79,366 participants. The primary analysis employed the inverse-variance weighted (IVW) method, while supplementary MR estimates were derived through the MR-Egger and weighted median (WME) methods. Furthermore, sensitivity analyses were implemented to ensure robustness and reliability, including Cochran's Q test, MR-PRESSO, MR-Egger intercept test, and the leave-one-out test.

Results

The MR study revealed no substantial genetic correlation between serum 25(OH)D levels and PPD (OR = 1.065, 95%CI = 0.878-1.293, P = 0.522 for set A; OR = 0.978, 95 % CI = 0.669-1.430, P = 0.910 for set B). Additionally, in the reverse analysis, we did not observe a significant causal impact of PPD on serum 25(OH)D (OR = 1.001, 95%CI = 0.974-1.028, P = 0.951 for set A; OR = 1.011, 95%CI = 0.992-1.031, P = 0.261 for set B). The results obtained from MR-Egger and WME analyses concord with those derived from the IVW method. Conducting leave-one-out tests did not identify any single nucleotide polymorphism that might have influenced the MR results, confirming the robustness and reliability of the findings.

Conclusions

The results suggest the absence of a causal link between vitamin D concentrations and PPD. Inconsistent observations in previous observational studies may be attributed to residual confounding.

Screen time in the development of type 2 diabetes mellitus (T2DM) : a two-sample Mendelian randomization study

OBJECTIVE

This study aimed to investigate the potential causal relationship between screen time and the risk of developing type 2 diabetes mellitus (T2DM) using Mendelian randomization.

METHODS

Two-sample Mendelian randomization was conducted, utilizing genetic variants associated with different types of screen time as instrumental variables. Single nucleotide polymorphisms (SNPs) were used to assess the primary outcome, which was the risk of developing T2DM.

RESULTS

The analysis revealed a significant positive causal association between television viewing time and the risk of T2DM. Specifically, excessive television viewing time was found to increase the risk of developing T2DM (OR: 2.39, 95% CI: 1.90 to 3.00, P < 0.01). However, no significant causal relationship was observed between computer usage time and the risk of T2DM. Additionally, mobile phone use time showed a positive correlation with the risk of T2DM (OR: 1.31, 95% CI: 1.04 to 1.64, P = 0.02), albeit to a lesser extent than television viewing time.

CONCLUSION

The findings of this study indicate a significant causal association between certain types of screen time, specifically television viewing and mobile phone use, and an increased risk of T2DM.

Association of obstructive sleep apnea syndrome with polycystic ovary syndrome through bidirectional Mendelian randomization

Background

Observational studies have established a link between polycystic ovary syndrome (PCOS) and obstructive sleep apnea syndrome (OSAS), with obesity being a significant confounding factor that complicates the understanding of causality. This study seeks to clarify the causal relationship by utilizing bidirectional two-sample Mendelian randomization (MR) analysis.

Methods

A bidirectional MR strategy was implemented to investigate the potential causal relationship between PCOS and OSAS. Instrumental variables (IVs) for PCOS were sourced from a dataset comprising 3,609 cases and 229,788 controls. For OSAS, statistical data were obtained from a genome-wide association study (GWAS) involving 38,998 subjects, alongside a control group of 336,659 individuals. Our MR analysis utilized several methods, including inverse variance weighted (IVW), weighted mode, weighted median, simple mode, and MR-Egger, primarily focusing on the IVW technique. Sensitivity tests were conducted to ensure the robustness of our findings.

Results

Utilizing the IVW method, we identified a notable causal association from OSAS to PCOS, with an odds ratio (OR) of 1.463 and a 95% confidence interval (CI) of 1.086-1.971 (p = 0.012). In the opposite direction, PCOS also appeared to significantly affect OSAS development, indicated by an OR of 1.041 and a 95% CI of 1.012-1.072 (p = 0.006). The MR-Egger intercept test showed no evidence of directional pleiotropy, affirming the credibility of our causal findings (p > 0.05).

Conclusion

This study suggests a bidirectional causal relationship between PCOS and an increased risk of OSAS. These insights could guide future screening and prevention strategies for both conditions.

Mendelian randomization analysis elucidates the causal relationship between celiac disease and the risk of thyroid dysfunction

The link between celiac disease (CeD) and thyroid dysfunction has been investigated. However, it is uncertain if CeD is causally linked to thyroid dysfunction. A 2-sample Mendelian randomization study was conducted to ascertain the causal connection between CeD and thyroid dysfunction. Using data from the FinnGen Consortium, a 2-sample Mendelian randomization study was conducted to look at the connection between thyroid dysfunction and CeD. Another replication of the data from the UK Biobank was subsequently performed to confirm our findings. Furthermore, a sequence of sensitivity analyses was performed. The inverse variance weighting technique demonstrates that genetically determined CeD is substantially linked with hypothyroidism, thyrotoxicosis, Graves' disease, and free thyroxine. However, no significant associations were found between CeD and thyroid-stimulating hormone or thyroiditis. Moreover, we achieve the same results in duplicate datasets, which increases the reliability of our findings. This study suggests that CeD and thyroid dysfunction are linked, and it gives theoretical support and new ways of thinking about how to diagnose and treat both conditions.

Refining the relationship between gut microbiota and common hematologic malignancies: insights from a bidirectional Mendelian randomization study

Background

The relationship between gut microbiota and hematologic malignancies has attracted considerable attention. As research progresses, it has become increasingly clear that the composition of gut microbiota may influence the onset and progression of hematologic malignancies. However, our understanding of this association remains limited.

Methods

In our study, we classified gut microbiota into five groups based on information at the phylum, class, order, family, and genus levels. Subsequently, we obtained data related to common hematologic malignancies from the IEU Open GWAS project. We then employed a bidirectional Mendelian Randomization (MR) approach to determine whether there is a causal relationship between gut microbiota and hematologic malignancies. Additionally, we conducted bidirectional MR analyses to ascertain the directionality of this causal relationship.

Results

Through forward and reverse MR analyses, we found the risk of lymphoid leukemia was significantly associated with the abundance of phylum Cyanobacteria, order Methanobacteriales, class Methanobacteria, family Peptococcaceae, family Methanobacteriaceae, and genera Lachnospiraceae UCG010, Methanobrevibacter, Eubacterium brachy group, and Butyrivibrio. The risk of myeloid leukemia was significantly associated with the abundance of phylum Actinobacteria, phylum Firmicutes, order Bifidobacteriales, order Clostridiales, class Actinobacteria, class Gammaproteobacteria, class Clostridia, family Bifidobacteriaceae, and genera Fusicatenibacter, Eubacterium hallii group, Blautia, Collinsella, Ruminococcus gauvreauii group, and Bifidobacterium. The risk of Hodgkin lymphoma was significantly associated with the abundance of family Clostridiales vadinBB60 group, genus Peptococcus, and genus Ruminococcaceae UCG010. The risk of malignant plasma cell tumor was significantly associated with the abundance of genera Romboutsia and Eubacterium rectale group. The risk of diffuse large B-cell lymphoma was significantly associated with the abundance of genera Erysipelatoclostridium and Eubacterium coprostanoligenes group. The risk of mature T/NK cell lymphomas was significantly associated with the abundance of phylum Verrucomicrobia, genus Ruminococcaceae UCG013, genus Lachnoclostridium, and genus Eubacterium rectale group. Lastly, the risk of myeloproliferative neoplasms was significantly associated with the abundance of genus Coprococcus 3 and Eubacterium hallii group.

Conclusion

Our study provided new evidence for the causal relationship between gut microbiota and hematologic malignancies, offering novel insights and approaches for the prevention and treatment of these tumors.

Exploring the relationship between life course adiposity and sepsis: insights from a two-sample Mendelian randomization analysis

Objectives

The relationship between adiposity and sepsis has received increasing attention. This study aims to explore the causal relationship between life course adiposity and the sepsis incidence.

Methods

Mendelian randomization (MR) method was employed in this study. Instrumental variants were obtained from genome-wide association studies for life course adiposity, including birth weight, childhood body mass index (BMI), childhood obesity, adult BMI, waist circumference, visceral adiposity, and body fat percentage. A meta-analysis of genome-wide association studies for sepsis including 10,154 cases and 454,764 controls was used in this study. MR analyses were performed using inverse variance weighted, MR Egger regression, weighted median, weighted mode, and simple mode. Instrumental variables were identified as significant single nucleotide polymorphisms at the genome-wide significance level (P < 5×10-8). The sensitivity analysis was conducted to assess the reliability of the MR estimates.

Results

Analysis using the MR analysis of inverse variance weighted method revealed that genetic predisposition to increased childhood BMI (OR = 1.29, P = 0.003), childhood obesity (OR = 1.07, P = 0.034), adult BMI (OR = 1.38, P < 0.001), adult waist circumference (OR = 1.01, P = 0.028), and adult visceral adiposity (OR = 1.53, P < 0.001) predicted a higher risk of sepsis. Sensitivity analysis did not identify any bias in the MR results.

Conclusion

The results demonstrated that adiposity in childhood and adults had causal effects on sepsis incidence. However, more well-designed studies are still needed to validate their association.

Metabolomic insights into pulmonary fibrosis: a mendelian randomization study

BACKGROUND

This study leverages a two-sample Mendelian Randomization (MR) approach to explore the causal relationships between 1,400 metabolites and pulmonary fibrosis, using genetic variation as instrumental variables. By adhering to stringent criteria for instrumental variable selection, the research aims to uncover metabolic pathways that may influence the risk and progression of pulmonary fibrosis, providing insights into potential therapeutic targets.

METHODS

Utilizing data from the OpenGWAS project, which includes a significant European cohort, and metabolite GWAS data from the Canadian Longitudinal Aging Study (CLSA), the study employs advanced statistical methods. These include inverse variance weighting (IVW), weighted median estimations, and comprehensive sensitivity analyses conducted using the R software environment to ensure the robustness of the causal inferences.

RESULTS

The study identified 62 metabolites with significant causal relationships with pulmonary fibrosis, highlighting both risk-enhancing and protective metabolic factors. This extensive list of metabolites presents a broad spectrum of potential therapeutic targets and biomarkers for early detection, underscoring the metabolic complexity underlying pulmonary fibrosis.

CONCLUSIONS

The findings from this MR study significantly advance our understanding of the metabolic underpinnings of pulmonary fibrosis, suggesting that alterations in specific metabolites could influence the risk and progression of the disease. These insights pave the way for the development of novel diagnostic and therapeutic strategies, emphasizing the potential of metabolic modulation in managing pulmonary fibrosis.