Consistent Estimation in Mendelian Randomization with Some Invalid Instruments Using a Weighted Median Estimator

Exploring the genetic correlation and causal relationships between breast cancer and meningioma using bidirectional Mendelian randomization

Previous studies have indicated a significantly higher prevalence of breast cancer (BC) among female patients with meningioma compared to the general female population. Therefore, this study aimed to assess the causal relationship between BC and meningioma at the genetic level. Genetic instrumental variables (IVs) for BC were identified from the Breast Cancer Association Consortium (BCAC), the Discovery Biology and Risk of Inherited Variants in Breast Cancer Consortium (DRIVE), the Collaborative Oncological Gene-environment Study (iCOGS), and 11 other BC genome-wide association studies (GWAS). Meningioma GWAS data were obtained from the FinnGen consortium and were further divided into intracranial and spinal meningioma groups for analysis. The primary analysis employed the inverse-variance weighted (IVW) method, supported by sensitivity analysis to address pleiotropy and enhance robustness. Next, linkage disequilibrium score regression (LDSC) was used to assess the genetic correlation between BC and meningioma. Finally, we applied the Functional Mapping and Annotation (FUMA) platform to conduct an in-depth analysis of the GWAS data. After rigorous screening and Mendelian randomization (MR) tests, genetically predicted overall BC (OR: 1.17, P = 0.0045) and ER(estrogen receptors) + BC (OR: 1.21, P = 0.0006) showed a potential causal association with intracranial meningioma. No causal relationships were found between intracranial meningioma and three BC subtypes. No bidirectional causal relationships were found between spinal meningioma and any BC subtype. The LDSC results suggested a modest positive genetic correlation between overall BC (rg: 0.152, SE: 0.077, P = 0.048), ER + BC (rg: 0.181, SE: 0.086, P = 0.035), and intracranial meningioma. FUMA analysis identified PITPNB, TTC28, and CHEK2 as shared risk genes between overall BC, ER + BC, and intracranial meningioma. These findings suggest that BC, especially ER + BC, may be a risk factor for intracranial meningioma. ER-related signaling pathways and the regulation of DNA damage may play a critical role in the pathogenesis of both diseases.

Integrative bioinformatic approach reveals novel melatonin-related biomarkers for Alzheimer's disease

BACKGROUND

Melatonin (MLT) can improve mitophagy, thereby ameliorating cognitive deficits in Alzheimer's disease (AD) patients. Hence, our research focused on the potential value of MLT-related genes (MRGs) in AD through bioinformatic analysis.

METHODS

First, the key cells in the single-cell dataset GSE138852 were screened out based on the proportion of annotated cells and Fisher's test between the AD and control groups. The differentially expressed genes (DEGs) in the key cell and GSE5281 datasets were identified, and the MRGs in GSE5281 were selected via weighted gene coexpression network analysis. After intersecting two sets of DEGs and MRGs, we performed Mendelian randomization analysis to identify the MRGs causally related to AD. Biomarkers were further ascertained through receiver operating characteristic curve (ROC) and expression analysis in GSE5281 and GSE48350. Furthermore, gene set enrichment analysis, immune infiltration analysis and correlation analysis with metabolic pathways were conducted, as well as construction of a regulator network and molecular docking.

RESULTS

According to the Fisher test, oligodendrocytes were regarded as key cells due to their excellent abundance in the GSE138852 dataset, in which there were 281 DEGs between the AD and control groups. After overlapping with 3,490 DEGs and 550 MRGs in GSE5281, four genes were found to be causally related to AD, namely, G protein-coupled receptor, family C, group 5, member B (GPRC5B), Methyltransferase-like protein 7 A (METTL7A), NF-κB inhibitor alpha (NFKBIA) and RAS association domain family 4(RASSF4). Moreover, GPRC5B, NFKBIA and RASSF4 were deemed biomarkers, except for METTL7A, because of their indistinctive expression between the AD and control groups. Biomarkers might be involved in oxidative phosphorylation, adipogenesis and heme metabolism. Moreover, T helper type 17 cells, natural killer cells and CD56dim natural killer cells were significantly correlated with biomarkers. Transcription factors (GATA2, POU2F2, NFKB1, etc.) can regulate the expression of biomarkers. Finally, we discovered that all biomarkers could bind to MLT with a strong binding energy.

CONCLUSION

Our study identified three novel biomarkers related to MLT for AD, namely, GPRC5B, NFKBIA and RASSF4, providing a novel approach for the investigation and treatment of AD patients.

Proteome-Wide Mendelian Randomization Identifies Therapeutic Targets for Abdominal Aortic Aneurysm

BACKGROUND

The proteome is a key source of therapeutic targets. We conducted a comprehensive Mendelian randomization analysis across the proteome to identify potential protein markers and therapeutic targets for abdominal aortic aneurysm (AAA).

METHODS AND RESULTS

Our study used plasma proteomics data from the UK Biobank, comprising 2923 proteins from 54 219 individuals, and from deCODE Genetics, which measured 4907 proteins across 35 559 individuals. Significant proteomic quantitative trait loci were used as instruments for Mendelian randomization. Genetic associations with AAA were sourced from the AAAgen consortium, a large-scale genome-wide association study meta-analysis involving 37 214 cases and 1 086 107 controls, and the FinnGen study, which included 3869 cases and 381 977 controls. Sequential analyses of colocalization and summary-data-based Mendelian randomization were performed to verify the causal roles of candidate proteins. Additionally, single-cell expression analysis, protein-protein interaction network analysis, pathway enrichment analysis, and druggability assessments were conducted to identify cell types with enriched expression and prioritize potential therapeutic targets. The proteome-wide Mendelian randomization analysis identified 34 proteins associated with AAA risk. Among them, 2 proteins, COL6A3 and PRKD2, were highlighted by colocalization analysis, summary-data-based Mendelian randomization, and the heterogeneity in an independent instrument test, providing the most convincing evidence. These protein-coding genes are primarily expressed in macrophages, smooth muscle cells, and mast cells within abdominal aortic aneurysm tissue. Several causal proteins are involved in pathways regulating lipid metabolism, immune responses, and extracellular matrix organization. Nine proteins have already been targeted for drug development in diabetes and other cardiovascular diseases, presenting opportunities for repurposing as AAA therapeutic targets.

CONCLUSIONS

This study identifies causal proteins for AAA, enhancing our understanding of its molecular cause and advancing the development of therapeutics.

Air Pollution and Oral Health: An Overall Insight From Genetic Causality

BACKGROUND

A growing body of epidemiological data consistently links air pollution to various adverse health outcomes. However, the potential connection between air pollution and the risk of oral diseases remains underexplored.

METHODS

This study utilized a two-sample Mendelian randomization approach to assess the causal relationship between air pollution and oral diseases. Six categories of air pollution were considered as exposures: nitrogen oxides (NOx), nitrogen dioxide (NO2), particulate matter (PM2.5, PM2.5-10, PM10), and PM2.5 absorbance. The outcomes included 18 oral health-related diseases drawn from the Finngen R10 dataset, the Gene-Lifestyle Interactions in Dental Endpoints consortium, and the Oncoarray oral cavity and oropharyngeal cancer consortium. Sensitivity analyses were performed to validate the primary inverse-variance weighted estimates using methods such as weighted median, weighted mode, and MR Egger.

RESULTS

The inverse-variance weighted analysis demonstrated a detrimental effect of air pollution on multiple oral health conditions, yielding 5 positive associations including PM2.5 with oral leukoplakia, gingivitis and periodontitis; PM2.5-10 with pulp and periapical diseases, and NO2 with gingivitis and periodontitis, and oral cavity, salivary glands and jaws diseases. Sensitivity tests showed no evidence of heterogeneity or pleiotropy, affirming the robustness of the findings.

CONCLUSION

This study highlights the detrimental impact of air pollution on oral health, emphasizing the need for further research into the underlying mechanisms and interactions. These findings reinforce the importance of implementing environmental interventions to mitigate the associated risks for oral health.

Lung Function as a Biomarker for Glaucoma: The UK Biobank Study

Purpose

To investigate the associations of lung function with glaucoma and related traits, explore the interactions between glaucoma genetic risk and lung function, and assess the causal relationships using Mendelian randomization (MR).

Methods

This cross-sectional study involved 85,369 participants with lung function measurements at baseline from the UK Biobank. Associations between lung function parameters and glaucoma and related traits were tested by multivariable logistic and linear regression. Two-sample MR analyses were conducted using summary statistics from large genetic datasets.

Results

Forced vital capacity (FVC), forced expiratory volume in 1 second (FEV1), and FEV1/FVC ratio were inversely associated with glaucoma, with the lowest quartiles conferring odds ratios (ORs) of 1.51 (95% confidence interval [CI], 1.31-1.74; P = 7.6 × 10-8), 1.58 (95% CI, 1.37-1.81; P = 4.7 × 10-10) and 1.20 (95% CI, 1.08-1.34; P = 0.002), respectively, compared with the highest quartiles (P trends < 0.001 observed for each). Similar associations were found for impaired lung function (FEV1 <80% Global Lung Initiative predicted FEV1: OR, 1.22, 95% CI, 1.11-1.33; P = 1.2 × 10-5; FEV1/FVC <0.7: OR, 1.13, 95% CI, 1.03-1.24; P = 0.01). Lower lung function was associated with lower intraocular pressure (IOP), thinner macular retinal nerve fiber layer thickness, and thinner ganglion cell-inner plexiform layer thickness. No interactions were observed between glaucoma genetic risk and lung function. MR analyses did not suggest causal relationships.

Conclusions

Lower FVC, FEV1, FEV1/FVC, and impaired lung function are potential biomarkers for glaucoma risk. These findings may facilitate clinical strategies for glaucoma management, particularly for individuals with impaired lung function.

Genetics of Circulating Inflammatory Proteins and Iridocyclitis: An Exploratory Mendelian Randomization Study

Purpose

This study aimed to explore the potential causal relationship between genetically determined elevated levels of pro-inflammatory cytokines and iridocyclitis, including its subtypes: acute and subacute iridocyclitis (ASIR) and chronic iridocyclitis (CIR).

Methods

A two-sample Mendelian randomization (MR) analysis was conducted using genome-wide association study (GWAS) summary data for inflammatory cytokines (cases, n = 14,824), iridocyclitis (IR; cases, n = 7306 and controls, n = 357,814), and its subtypes (ASIR: cases, n = 6166 and controls, n = 357,814; and CIR: cases, n = 1401 and controls, n = 357,814). The inverse variance-weighted (IVW) method served as the primary analysis method. Supplementary analytic methods included MR Egger, Weighted median, Weighted mode, and Simple mode methods. Pleiotropy and heterogeneity were evaluated using the Cochran's Q test, MR Egger intercept test, MR Pleiotropy RESidual Sum and Outlier test (MR-PRESSO), Bayesian colocalization analysis, and Linkage disequilibrium score regression (LDSC) analysis.

Results

Genetically predicted high levels of eotaxin, fibroblast growth factor 23 (FGF23), TNF-related apoptosis-inducing ligand (TRAIL), and Neurotrophin-3 were associated with an increased risk of IR. On the contrary, a high level of interleukin (IL)-2 was associated with a decreased risk of IR. Meanwhile, the IR subgroup analysis demonstrated that high levels of eotaxin and TRAIL were also associated with an increased risk of ASIR. High levels of cystatin D, tumor necrosis factor receptor superfamily member 9 (TNFRSF9), and caspase 8 were associated with an increased risk of CIR. CCL20 and CDCP1 were associated with a decreased risk of CIR. Heterogeneity and pleiotropy tests demonstrated that our findings were stable and reliable.

Conclusions

Inflammatory cytokines are involved in the occurrence of IR and its subtypes. Further studies are warranted to elucidate the precise mechanisms of inflammatory cytokines in IR and its subtypes.

Translational Relevance

The present study highlighted the role of inflammatory cytokines in the development of IR.

The mediating role of thyroid-related hormones between thyroid dysfunction diseases and osteoporosis: a mediation mendelian randomization study

The links between Thyroid dysfunction diseases (TDFDs) and osteoporosis (OP) has received widespread attention, but the causal relationships and mediating factors have not been systematically studied. We used two-sample Mendelian randomization (MR) analysis to elucidate the causal relationship between TDFDs and OP. Moreover, we performed mediation MR analyses to explore the role of thyroid-related hormones and OP risk factors in the association between TDFDs and OP. Two sample MR analyses showed that hyperthyroidism increased OP (OR = 1.080, 95% CI 1.026 to 1.137; P = 0.0032) risk. Hypothyroidism increases OP (OR = 1.183, 95% CI 1.125 to 1.244; P < 0.0001) risk. Furthermore, mediation analysis revealed that TSH mediated 5.314% of the relationship between hypothyroidism and OP. In contrast, FT4 mediated 9.670% of the relationship between hyperthyroidism and OP. In European populations, TDFDs may increase OP risk. TSH mediates in the causal association between hypothyroidism and OP, and similarly, FT4 mediates in the causal link between hyperthyroidism and OP. Our findings underscore the significance of improving integrative care for individuals with TDFDs to mitigate the risk of OP. It is essential to maintain stable levels of thyroid hormones and closely monitor bone health to effectively mitigate and prevent OP.

Mendelian randomization and multiomics comprehensively reveal the causal relationship and potential mechanism between atrial fibrillation and gastric cancer

Objective

Gastric cancer is a harmful disease, the comorbidity mechanism and causality relationship between this disease and other diseases are worth studying.

Methods

Using a two-sample Mendelian Randomization method, this study revealed the potential causal effect of atrial fibrillation (AF) on gastric cancer (GC) risk by constructing a genetic instrument containing 136 AF associated SNPs. Subsequently, analysis identifies 62 AF-GC co-associated genes and constructs a protein-protein interaction network of key genes. High-throughput sequencing data were further used to analyze the association between the two and their impact on the survival outcome of gastric cancer.

Results

The results showed that AF was negatively associated with gastric cancer, and further analysis revealed that this relationship was independent of GC risk factors such as chronic gastritis, Helicobacter pylori infection, and alcohol consumption. Enrichment analysis reveals associations of key genes with pathways related to cardiovascular disease, inflammatory gastrointestinal diseases, and tumorigenesis. Through single-cell sequencing data analysis, fibroblast subpopulations associated with the key gene set are identified in GC, showing significant correlations with cancer progression and inflammation regulation pathways. Transcription factor analysis and developmental trajectory analysis reveal the potential role of fibroblasts in GC development. Finally, prognosis analysis and gene mutation analysis using TCGA-STAD data indicate an adverse prognosis associated with the key gene set in GC.

Conclusion

This study provides new insights into the association between AF and GC and offers novel clues for understanding its impact on the pathogenesis and therapeutic strategies of GC.

Exploring the causal relationship between inflammatory cytokines and myasthenia gravis: A two-way Mendelian randomization study

BACKGROUND

Based on previous research, it is well-established that myasthenia gravis (MG) is linked to chronic inflammation. However, the exact nature of the relationship between inflammatory factors and the development of MG remains unclear. Consequently, the objective of this study is to explore whether alterations in the levels of inflammatory factors, as influenced by genetic factors, are associated with the occurrence of MG. This will be achieved through a two-sample Mendelian randomization (MR) analysis.

METHODS

We conducted a bidirectional Mendelian randomization (MR) study utilizing genetic data from genome-wide association studies (GWAS), encompassing 1873 MG cases and 36,370 individuals of European ancestry as controls. Data on inflammatory cytokines were obtained from GWAS data of 8293, healthy participants. The inverse variance-weighted (IVW) method was primarily employed to investigate the causal relationship between exposure and outcome. Additionally, various sensitivity analysis methods such as MR-Egger, weighted median, simple mode, weighted mode, and MR-PRESSO were applied to strengthen the reliability of the results. Through these rigorous approaches, we extensively examined the relationship between inflammatory factors and MG; however, further research is required to establish the specific causal relationship.

RESULTS

After applying Bonferroni correction, the genetic predictions revealed a significant correlation between Monokine induced by gamma interferon (MIG) and MG (OR: 1.09, 95 % CI: 1.04-1.14; P = 0.0006). Furthermore, there were preliminary findings indicating a positive genetic association between Eotaxin and interleukin-2 receptor antagonist (IL-2ra) with MG (OR: 0.81, 95 % CI: 0.66-0.99, P = 0.044; OR: 0.80, 95 % CI: 0.68-0.94, P = 0.008). Reverse MR analysis provided initial evidence of associations between MIP1α, GROa, IL-13, TRAIL, IL-2ra, and IL-1ra with the development of MG. No indications of pleiotropy or heterogeneity among genetic variants were observed (P > 0.05).

CONCLUSION

This study uncovers a new connection between inflammatory cytokines and MG, shedding light on potential factors contributing to the development of the disease. Elevated levels of Eotaxin and IL-2ra are associated with a higher risk of MG, while indicating that MIG, MIP1α, GROa, IL-13, TRAIL, IL-2ra, and IL-1ra may be elevated as a result of MG, Especially MIG. These findings suggest that targeting and regulating specific inflammatory factors could offer promising avenues for the treatment and prevention of MG.

Dietary, metabolic and gut microbiota influences on primary ovarian failure: a two-sample Mendelian randomization study

BACKGROUND AND OBJECTIVES

Previous studies have reported there were associations between ovarian function and dietary factors, metabolic factors and gut microbiota. However, it is unclear whether causal associations exist. We aimed to explore the causal relationship of these factors with risk of primary ovarian failure (POF).

METHODS AND STUDY DESIGN

Two-sample Mendelian randomization (MR) analysis was performed to genetically predict the causal effects of dietary and metabolic factors and gut microbiota on POF. The inverse variance weighted (IVW) method was used as the primary statistical method. A series of sensitivity analyses, including weighted median, MR-Egger, simple mode, weighted mode methods, and leave-one-out analysis, were conducted to assess the robustness of the MR analysis results.

RESULTS

IVW analysis revealed that cigarettes smoked per day, coffee intake and cooked vegetable intake were not causally correlated with POF at the genetic level. However, POF were associated with fresh fruit intake, BMI, Eubacterium (hallii group), Eubacterium (ventriosum group), Adlercreutzia, Intestinibacter, Lachnospiraceae (UCG008), and Terrisporobacter. These findings were robust according to extensive sensitivity analyses.

CONCLUSIONS

This study identified several dietary factors, metabolic factors and gut microbiota taxa that may be causally implicated in POF, potentially offering new therapeutic targets.

Is the occurrence of deep vein thrombosis related to the fracture site? A two-sample Mendelian randomization study

OBJECTIVE

Deep vein thrombosis (DVT) is a known complication of fractures. This study aimed to explore the genetic causal relationship between DVT and fracture sites.

RESEARCH DESIGN AND METHODS

The exposures analyzed in this study included fracture of femur (FFE), fracture of lower leg, including ankle (FLLA), fracture of shoulder and upper arm (FSUA), fracture of forearm (FFO), fracture of rib, sternum and thoracic spine (FRSTS) and fracture of lumbar spine and pelvis (FLSP). DVT as the outcome. A two-sample Mendelian randomization (MR) approach was employed to investigate the genetic causal relationship, and a series of sensitivity analyses were conducted.

RESULTS

The findings indicated no genetic causal relationship between FFE (p = 0.569, OR 95% CI = 1.001 [0.998-1.003]), FLLA (p = 0.371, OR 95% CI = 0.999 [0.995-1.002]), FSUA (p = 0.871, OR 95% CI = 1.000 [0.998-1.002]), FFO (p = 0.281, OR 95% CI = 1.001 [0.999-1.002]), FRSTS (p = 0.346, OR 95% CI = 0.999 [0.996-1.001]) or FLSP (p = 0.759, OR 95% CI = 1.000 [0.999-1.002]) and DVT. Sensitivity analyses reinforced the robustness.

CONCLUSIONS

This study indicate that no genetic causal relationship exists between DVT and fracture site, the observed association may be attributable to non-genetic factors.

White-Matter Structural Connectivity and Alzheimer's Disease: A Mendelian Randomization Study

BACKGROUND

Alzheimer's disease (AD) and white-matter structural connectivity have been linked in some observational studies, although it is unknown if this is a causal relationship. The purpose of this study was to examine the impact of various white-matter structural connectivity on AD via a two-sample multivariate Mendelian randomization (MR) approach.

METHODS

The genome-wide association study (GWAS) of Wainberg et al. provided the summary data on white-matter structural connectivity, and Bellenguez et al.'s study provided the GWAS aggregated data for AD. MR methods included inverse variance weighted, Mendelian randomization Egger, simple mode, weighted median, and weighted mode. Heterogeneity, horizontal pleiotropy, and "leave-one-out" analysis guaranteed the robustness of causation. Finally, reverse MR analysis was conducted on the white-matter structural connectivity that showed positive results in the forward MR analysis.

RESULTS

Among 206 white-matter structural connections, we identified 10 connections were strongly correlated with genetic susceptibility to AD. Right-hemisphere limbic network to thalamus white-matter structural connectivity and Right-hemisphere salience_ventral attention network to accumbens white-matter structural connectivity were positively correlated with the likelihood of AD, while the remaining 8 white-matter structural connections were negatively related with AD. None of the above 10 white-matter structural connections have a reverse causal relationship with AD.

CONCLUSION

Our MR study reveals a certain degree of association between white-matter structural connectivity and AD, which may provide support for future diagnosis and treatment of AD.

Causal Association Between Multidimensional Plasma Lipid Composition and Pediatric Asthma: A Mendelian Randomization Study

BACKGROUND

Asthma is the most common chronic disease among children and poses a major threat to their health. Observational studies have shown lipid disorders in children with asthma. However, it was not possible to determine whether there is a causal link between the two. Therefore, the aim of this study was to assess the causal relationship between serum liposomes and asthma in children.

METHODS

We used large-scale publicly available genome-wide association study summary statistics to elucidate causal associations between plasma liposomes and children using a two-sample Mendelian randomization (MR) approach. The IVW method was used as the primary analysis method, and tests such as the Cochran Q test, MR-Egger intercept, and leave-one-out method were utilized to explore whether there was heterogeneity and pleiotropy in the MR results. In addition, Steiger's test and reverse MR analysis were performed to test the directionality of the MR results.

RESULTS

Our MR results identified a causal link between six plasma liposomes and childhood asthma. Among them, negative association between Diacylglycerol (16:0_18:2) (OR = 0.952, 95%CI = 0.913-0.992, p = 0.018), Triacylglycerol (52:4) (OR = 0.949, 95%CI = 0.905-0.994, p = 0.028), Phosphatidylcholine (18:2_20:3) (OR = 0.915, 95%CI = 0.843-0.993, p = 0.034), sterol ester (27:1/22:6) (OR = 0.929, 95% CI = 0.869-0.994, p = 0.031) and childhood asthma. There is a positive association between Phosphatidylcholine (16:0_22:5) (OR = 1.061, 95%CI = 1.006-1.120, p = 0.030), sterol ester (27:1/20:4) (OR = 1.046, 95% CI = 1.021-1.072, p = 0.0003) and pediatric asthma. A series of sensitivity tests also demonstrate the robustness of the results.

CONCLUSION

This MR study identified a causal link between some plasma liposomes and childhood asthma. This will provide new perspectives on the prevention and treatment of childhood asthma in the future.

Unraveling the Link: Mendelian Randomization Reveals Causal Relationship Between Selenium and Metabolic Syndrome

Observational studies have linked selenium and metabolic syndrome (MetS), but the causality remains unclear. Therefore, this study intends to determine the causal relationship between selenium and the risk of MetS and its component features [body mass index (BMI), waist circumference adjusted for BMI (WCadjBMI), triglycerides (TC), HDL-cholesterol (HDL-C), fasting blood glucose (FBG), fasting blood insulin (FBI), systolic blood pressure (SBP), and diastolic blood pressure (DBP)]. This study was designed as the two-sample Mendelian randomization (MR), and genetic variants were obtained from the genome-wide association studies. The inverse variance weighted (IVW) was applied as the primary method, and the MR-Egger, weighted median, and MR-PRESSO were supplemented to assess its robustness. The Bonferroni method was used to correct p-values for multiple tests. Genetically incremented selenium level was related to higher odds ratios of developing the MetS (OR = 1.054, 95% CI = 1.016-1.094, p = 0.0049). As for components, significant causal links were identified between selenium and BMI (β = 0.015, p = 1.321 × 10-5), WCadjBMI (β = 0.033, p = 2.352 × 10-4), HDL-C (β = -0.036, p = 1.352 × 10-8), FBG (β = 0.028, p = 0.001), and FBI (β = 0.028, p = 0.002). No significant association was discovered for SBP (β = -0.076, p = 0.218) and DBP (β = 0.054, p = 0.227). These results were generally supported by the weighted median and MR-PRESSO methods. Our study provided evidence of the causal effect of selenium on MetS risk from the genetic perspective in the European population, and further investigation across diverse populations was warranted.

Identification of Circulating Proteins Associated With Blood Pressure

BACKGROUND

Circulating proteins in blood are involved in various physiological processes, but their contributions to blood pressure regulation remain partially understood. In traditional observational studies, identifying circulating proteins causally associated with blood pressure is challenging because of potentially unmeasured confounding and possible reverse causality.

METHODS

Two-sample Mendelian randomization analyses were conducted to estimate the causal effects of 2270 circulating proteins (data sourced from 8 genome-wide association studies) on diastolic blood pressure, systolic blood pressure, and pulse pressure. Colocalization analyses were then used to investigate whether the circulating proteins and blood pressure traits shared causal genetic variants. To further verify the findings, we subsequently performed Steiger filtering analyses, annotation of protein-altering variants, assessment of overlap between protein quantitative trait loci and expression quantitative trait loci, protein-protein interaction and functional enrichment analyses, and drug target evaluation. To provide more potential biomarkers, we further evaluated the epidemiological associations of 2923 circulating proteins with blood pressure and hypertension by cross-sectional and longitudinal analyses using individual data in the UK Biobank.

RESULTS

Mendelian randomization and colocalization analyses identified 121 circulating proteins with putative causal effects on at least 1 blood pressure trait. Many of the identified proteins are enriched in the pathways relevant to blood pressure regulation, and a majority of these proteins are either known drug targets or druggable candidates.

CONCLUSIONS

This study has uncovered numerous circulating proteins potentially causally associated with blood pressure, providing insights into the regulatory mechanisms of blood pressure and potential therapeutic targets to facilitate blood pressure management.

Smoking may increase the usage of antidepressant: evidence from genomic perspective analysis

This study uses the two-sample Mendelian randomization (TSMR) method to explore the causal relationships between smoking initiation (SMKI), never smoking (NSMK), past tobacco smoking (PTSMK), and the usage of antidepressants (ATD). Single-nucleotide polymorphisms (SNPs) with genome-wide significance (P < 5E-08) related to SMKI, NSMK, and PTSMK were selected from the genome-wide association study (GWAS) database as instrumental variables (IVs). The main method, inverse variance weighted (IVW), was utilized to investigate the causal relationship. The results demonstrated a positive causal relationship between SMKI and ATD use, where SMKI leads to an increase in ATD use. Conversely, NSMK and PTSMK showed a negative causal relationship with ATD use, meaning that NSMK and PTSMK lead to a reduction in ATD use. Additionally, sensitivity analysis showed that the results of this study were robust and reliable. Using the TSMR method and from a genetic perspective, this study found that SMKI leads to an increase in ATD use, while NSMK and PTSMK reduce ATD use.

The association between ambient air pollution and colorectal cancer: a Mendelian randomization study

Mounting epidemiology studies have reported the potential associations between ambient air pollution exposure and colorectal cancer (CRC). However, the genetic association between ambient air pollution and CRC remains unclear. Using the Genome-wide association study (GWAS) data from UK biobank, we explored the genetic association of CRC (5,657 cases and 372,016 controls) with four ambient air pollutants (PM2.5, PM10, NO2, NOx; n = 423,796 to 456,380) under the framework of Mendelian randomization (MR). Our results revealed a significant association between long-term NO2 exposure (per 10 µg/m3) and increased CRC risk, with an odds ratio (OR) of 1.02 (95% confidence interval [CI]: 1.00-1.03), while no statistical association was found between CRC risk and the other air pollutants. Sensitivity analysis confirmed the robustness of the results. It is imperative to consider the impact of air pollution, particularly NO2, in mitigating the risk of CRC.

Genetically determined physical activity levels, sedentary behaviours, and their association with the risk of age-related macular degeneration

OBJECTIVE

To investigate the causal effects of physical activity and sedentary traits on risk of Age-related macular degeneration (AMD).

METHODS

A two-sample Mendelian randomization (MR) analysis was used to investigate the causal relationship between physical activity and risk of AMD. We used genome-wide association studies (GWAS) summary statistics from two publicly available biobank-scale cohorts: UK Biobank and FinnGen. Physical activity data were self-reported by 703,901 UK Biobank participants and sedentary behaviour data were gathered from 159,606 FinnGen participants. Our analysis primarily used the inverse variance weighted (IVW) method.

RESULT

Engaging in moderate-to-vigorous physical activity significantly reduced the risk of AMD with an odds ratio of 0.77 (95% CI: 0.66-0.89). However, leisure screen time showed a slight but non-statistically significant upward trend. Sedentary behaviour at work, sedentary commuting showed no causal effects on AMD risk.

CONCLUSIONS

This study used MR analysis to examine the causal relationship between physical activity, sedentary behaviour, and AMD. It offers genetic evidence suggesting that physical activity may protect against AMD, emphasizing the significance of lifestyle factors in maintaining ocular health.

Association Analysis of the Circulating Proteome With Sarcopenia-Related Traits Reveals Potential Drug Targets for Sarcopenia

BACKGROUND

Sarcopenia severely affects the physical health of the elderly. Currently, there is no specific drug available for sarcopenia. This study aims to identify pathogenic proteins and druggable targets for sarcopenia through Mendelian randomization (MR)-based analytical framework.

METHODS

A sequential stepwise screening method that includes two-sample MR, Steiger filtering test and colocalization (MRSC) was applied to identify causal proteins associated with sarcopenia-related traits. In the MR analyses, 4372 circulating proteins with valid instrumental variables (IVs) from eight proteomic genome-wide association studies were utilized as exposures, and nine sarcopenia-related traits were utilized as outcomes. IVs were classified into cis-protein quantitative trait loci (pQTLs) and trans-pQTLs based on their positions. We conducted cis-only MRSC analyses and cis + trans MRSC analyses using cis-pQTLs and cis + trans pQTLs as IVs, respectively. Post-MRSC analyses were conducted on the prioritized findings of MRSC, including annotation of protein-altering variants (PAVs), assessment of overlap between pQTLs and expression quantitative trait loci (eQTLs), protein-protein interaction (PPI) analysis, pathway enrichment analysis and annotation of drug targets. Utilizing data from the UK Biobank, we performed an observational study to explore the associations between baseline circulating protein levels and the longitudinal changes in nine sarcopenia-related traits.

RESULTS

A total of 181 causal associations for 65 proteins were prioritized by the cis-only MRSC analyses and 227 associations for 91 proteins were prioritized by the cis + trans MRSC analyses. Among the prioritized proteins, the majority of them employed non-PAVs as IVs and most of their cis-pQTLs overlapped with corresponding eQTLs and exhibited consistent directionality, with only one trans-pQTL overlapping with an eQTL. The PPI network of cis-only MRSC-prioritized proteins (p = 4.04 × 10-4) and cis + trans MRSC-prioritized proteins (p = 8.76 × 10-5) showed significantly more interactions than expected. Reactome, KEGG and GO pathway enrichment analyses for cis-only MRSC-prioritized proteins identified 52, 12 and 79 enriched pathways, respectively (adjusted p < 0.05). For proteins identified by cis + trans MRSC analyses, only 15 pathways were enriched through the GO pathway enrichment analyses. In the observational study, 197 circulating proteins were identified to be associated with one or more sarcopenia-related traits (p < 0.05/2923). Among them, the significant associations of CTSB (negative association) and ASGR1 (positive association) with sarcopenia-related traits were observed to have consistent directional associations in both MR-based studies and observational studies. Drug target annotations suggested that 52 MRSC-prioritized proteins and 145 biomarkers are drug targets or druggable.

CONCLUSIONS

This study identified 89 potential pathogenic proteins and 197 candidate biomarkers for sarcopenia, providing valuable clues for the development of therapeutic drugs for sarcopenia.

Causal role of 731 immune cells in diabetic nephropathy: a bi-directional two-sample Mendelian randomization study

BACKGROUND

The primary cause of end-stage renal disease (ESRD) is diabetic nephropathy (DN), and a growing body of research indicates that immunology plays a part in how DN develops into ESRD. Our objective is to identify causal relationships between various immune invading cells and DN to identify possible targets for immunotherapy.

METHODS

This study used a complete Mendelian randomization (MR) analysis with two samples to identify the underlying mechanism linking immune cell characteristics with DN. Using publicly available genetic data, we investigated the causal link between 731 immune cell profiles and DN risk. Included were four different types of immune systems: morphological parameters (MP), absolute cell (AC), relative cell (RC), and median fluorescence intensities (MFI). The results' robustness, heterogeneity, and horizontal pleiotropy were confirmed through extensive sensitivity analysis.

RESULTS

Following FDR (False Discovery Rate correction method) correction, no statistically significant differences were observed; however, six immunophenotypes were shown to be significantly associated with DN risk at the 0.25 level. Only CD28+ CD4- CD8- T cells were identified as the protective immunophenotype (OR = 0.588, 95% CI 0.437-0.792, P = 4.71 × 10-4). Moreover, DN had no discernible impact on immunophenotyping after FDR correction. Surprisingly, three unadjusted phenotypes with low P values were discovered to be positively correlated with the risk of DN: CD20 on IgD- CD27- B cells (OR = 1.263, 95% CI 1.076-1.482, P = 4.22 × 10-3), CD8 on naive CD8 + T cells with Effector Memory (OR = 1.107, 95% CI 1.013-1.209, P = 2.40 × 10-2), and CD8 on Effector Memory CD8 + T cells (OR = 1.126, 95% CI 1.024-1.239, P = 1.46 × 10-2).

CONCLUSIONS

Our findings provide a genetic basis for the association between immune cells and DN and should inform future clinical research.

Causal links between immune cells and asthma: Insights from a Mendelian Randomization analysis

OBJECTIVES

Recent studies suggest immunophenotypes may play a role in asthma, but their causal relationship has not been thoroughly examined.

METHODS

We used single nucleotide polymorphism (SNP)-derived instrumental variables. Summary data from 731 immune cell profiles and asthma cases were analyzed from genome-wide association studies (GWAS) of European populations. Mendelian Randomization (MR) analyses included inverse variance weighted (IVW), weighted median, and MR-Egger methods. Pleiotropy was assessed using the MR-Egger intercept and MR pleiotropy residual sum and outlier (MR-PRESSO) tests. Reverse MR analysis explored bidirectional causation between asthma and immunophenotypes. All statistical analyses were conducted using R software.

RESULTS

MR analysis identified 108 immune signatures potentially contributing to asthma. Two immunophenotypes were significantly associated with asthma risk: CD4+ secreting Treg cells in allergic asthma (ORIVW = 1.078; 95% CI: 1.036-1.122; PIVW = 0.0002) and IgD + CD38- %lymphocyte cells in non-allergic asthma (ORIVW = 1.123; 95% CI: 1.057-1.194; PIVW = 0.0002).

CONCLUSIONS

This study highlights the causal associations between specific immunophenotypes and asthma risk, providing new insights into asthma pathogenesis.

Effect of smoking behaviour and related blood DNA methylation on visceral adipose tissues

BACKGROUND

Recent studies have found that tobacco smoking is associated with fat distribution, yet limited research has focused on its relationship with visceral adipose tissues (VATs). Furthermore, the cellular and molecular mechanisms underlying the interactions among smoking, epigenetic modifications, and VATs remain unknown.

METHOD

We performed univariable Mendelian randomization (MR) analysis to elucidate the causal relationship between smoking behaviours and VATs, including epicardial and pericardial adipose tissue (EPAT), liver fat (LF), and pancreas fat (PF). This approach could minimize the impact of confounders and reverse causality through utilizing genetic variants to proxy the smoking behaviours. Mediation MR analysis were conducted to detect potential mediators. Additionally, summary-data-based MR (SMR) and colocalization analysis were performed to explore the association between smoking-related DNA methylation and VATs.

RESULTS

We identified a convincing association between smoking initiation and increased EPAT (beta: 0.15, 95% CI: 0.06, 0.23, p = 7.01 × 10-4) and LF area (beta: 0.15, 95% CI = 0.05, 0.24, p = 2.85 × 10-3), respectively. Further mediation analysis suggested type 2 diabetes mellitus (T2DM) as a potential mediator within these co-relationships. When further exploring the associations between the smoking related DNA methylation and VATs, we identified that WT1 methylation at cg05222924 was significantly linked to a lower EPAT area (beta: -0.12, 95% CI: -0.16, -0.06, PFDR = 2.24 × 10-3), while GPX1 methylation at cg18642234 facilitated the deposition of EPAT (beta: 0.15, 95% CI: 0.10, 0.20, PFDR = 1.66 × 10-4).

CONCLUSION

Our study uncovered a significant causal effect between smoking and VATs, with T2DM identified as a potential mediator. Further investigation into DNA methylation yielded novel insights into the pathogenic role of smoking on EPAT.

Appendectomy, acute appendicitis, and gastrointestinal diseases: A Mendelian randomization study

BACKGROUND

Appendectomy is the standard treatment for acute appendicitis. However, the effects of appendectomy and acute appendicitis on gastrointestinal diseases are not fully understood.

METHODS

Genetic variants associated with appendectomy and acute appendicitis at a genome-wide significance level (P ​< ​5.0E-08) were selected as instrumental variables. Two-sample univariate and multivariate Mendelian randomization (MR) analyses were performed to examine the independent effects of appendectomy and acute appendicitis on related gastrointestinal diseases.

RESULTS

Appendectomy was linked to an increased risk of colon cancer (odds ratio [OR], 1.54; 95 ​% confidence interval [CI], 1.15-2.07; P ​= ​0.004; FDR-corrected P ​= ​0.016) and a decreased risk of primary sclerosing cholangitis (OR, 0.57; 95 ​% CI, 0.38-0.84; P ​= ​0.004; FDR-corrected P ​= ​0.016). Acute appendicitis was associated with a higher risk of cholelithiasis (OR, 1.16; 95 ​% CI, 1.06-1.27; P ​= ​0.002; FDR-corrected P ​= ​0.016).

CONCLUSION

This study suggested that appendectomy and acute appendicitis might affect the risk of several gastrointestinal diseases in European populations.

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.

Associations between post-traumatic stress disorder and neurological disorders: A genetic correlation and Mendelian randomization study

BACKGROUND

Observational studies have reported a close relationship between post-traumatic stress disorder (PTSD) and neurological disorders, but the existence of a causal link remains uncertain. The aim of this study is to investigate these relationships and potential mediators via Mendelian randomization (MR) analysis.

METHODS

We sourced pooled data for genome-wide association study (GWAS) of PTSD (n = 1,222,882) from the psychiatric genomics consortium. Summary-level data for eight neurological traits were derived from large-scale GWASs. Genetic correlations were computed using linkage disequilibrium (LD) score regression. The inverse variance weighted (IVW) method served as the primary analysis method for MR. We employed a range of sensitivity analysis methods to ensure result robustness. A two-step approach was utilized to ascertain the effects and proportions of mediations.

RESULTS

We identified significant genetic associations between PTSD and any dementia, cognitive performance, multiple sclerosis, and migraine. MR analysis revealed a significant association between PTSD and an increased risk of migraine (P = 0.02). This was substantiated by the results of several sensitivity analyses. Notably, the robust association between PTSD and migraine persisted even after adjustment for major depressive disorder and anxiety. Mediation analysis revealed that both alcohol intake frequency and insomnia partially mediated the association between PTSD and migraine.

LIMITATIONS

Participants in the MR analysis were of European descent, and verification in other ethnicities was not possible due to data limitations.

CONCLUSION

Our findings indicate a close association between PTSD and migraine. Alcohol intake frequency and insomnia serve as intermediate factors, partially explaining the relationship between PTSD and migraine.

Physical Activities and Parkinson's Disease Progression: A Two-Sample Mendelian Randomization Study

AIMS

To explore the causal relationship between physical activity (PA) and the progression of Parkinson's disease (PD), we conducted a two-sample Mendelian randomization (MR) analysis.

METHODS

Genetic variants were obtained from publicly available genome-wide association study (GWAS) summary statistics for PA (N = 377,000), age at onset (N = 28,568), and PD progression (N = 4093). Causal estimates were calculated using the inverse variance weighted (IVW) method, with MR-Egger and weighted median analyses performed to assess the robustness of the results.

RESULTS

Genetically predicted accelerometer-based overall acceleration average (OAA) was associated with a reduced risk of constipation in PD progression (OR: 0.60, 95% CI: 0.42-0.86, p = 5.50 × 10-3). Moderate-to-vigorous physical activity (MVPA) demonstrated a similar but stronger effect on constipation risk (OR: 0.03, 95% CI: 9.38 × 10-4-0.90, p = 0.043). Additionally, OAA showed a protective effect on motor experiences of daily living (OR: 0.84, 95% CI: 0.71-1.00, p = 0.046). No causal effects were identified for vigorous physical activity (VPA) or the fraction of accelerations exceeding 425 milligravities (FAA) on PD progression.

CONCLUSION

Our findings suggest a negative causal relationship between PA and PD progression, highlighting the potential role of physical activity in guiding therapeutic strategies for PD management.

Antibody Responses to EBV and Toxoplasma and Their Genetic Links to Guillain-Barré Syndrome: A Mendelian Randomization Study

BACKGROUND

This study aims to investigate the potential causal relationship between antibody-mediated immune responses to infectious agents and Guillain-Barré syndrome (GBS) using a two-sample Mendelian randomization (MR) approach.

METHODS

Publicly available summary data from genome-wide association studies (GWAS) were utilized for comprehensive analysis. A genome-wide and human leukocyte antigen association study conducted by Guillaume Butler-Laporte et al. (n = 9724) examined 46 types of antibody-mediated immune responses. GWAS summary statistics for GBS were obtained from the FinnGen consortium (n = 215,931) comprising European populations. The primary method for MR analysis was the inverse-variance weighted (IVW) method. Various sensitivity analyses were conducted to assess the heterogeneity and pleiotropy of the findings.

RESULTS

The IVW method indicates a negative correlation between elevated levels of Epstein-Barr virus (EBV) viral capsid antigen (VCA) p18 antibody and the risk of GBS (OR = 0.79, 95% confidence interval [CI]: 0.65-1.85, p = 0.012). Elevated levels of Toxoplasma gondii surface antigen 1 (sag1) antibody also show a negative correlation with the risk of GBS (OR = 0.79, 95% CI: 0.67-0.92, p = 0.003). No evidence of heterogeneity or horizontal pleiotropy was found in the MR analysis.

CONCLUSIONS

Elevated levels of EBV VCA p18 and T. gondii sag1 antibodies appear to be negatively correlated with the risk of GBS, suggesting that immune responses to these pathogens may play a protective role. However, the CI for the EBV VCA p18 association includes 1, indicating the need for caution in interpreting this result. Further research, including mechanistic studies and broader immune profiling, is needed to confirm these findings and explore the underlying pathways.

The association between precuneus cortex thickness and mild behavioral impairment in patients with mild stroke

The objective of this research was to examine the association between precuneus cortex thickness and mild behavioral impairment (MBI) in patients with mild stroke. Seventy-two patients were evaluated by high-resolution 3 T magnetic resonance and the mild behavioral impairment checklist (MBI-C). To determine the association between precuneus cortex thickness and MBI, we adjusted for demographics, vascular risk factors, and laboratory examination indicators in logistic regression analysis. In addition, we used mendelian randomization to further study the association through genetic databases. Of the 72 mild stroke patients in this study, 26 had MBI. We found a strong negative connection between precuneus cortex thickness and MBI after adjusting for any confounding variables. In patients with an initial mild stroke, the thinner the precuneus cortex, the higher the risk of MBI (OR: 0.02; 95% CI: 0.00-0.39; P < 0.05). Our study has uncovered a significant negative association between the thickness of the precuneus cortex and MBI. This finding provides a novel viewpoint for the radiological diagnosis of MBI, thereby augmenting the contribution of imaging to the diagnostic process of MBI and advancing the prediction of dementia. Specifically, in patients who have suffered mild stroke, a reduction in the cortical thickness of the precuneus has been pinpointed as crucial radiographic evidence of preclinical cognitive impairment. This insight could potentially facilitate earlier detection and intervention strategies for cognitive decline.

A Bidirectional Mendelian Randomization Study of Tea-Drinking Habits and Risk of Elevated Serum Uric Acid Levels

BACKGROUND

Although recent animal experiments have revealed that tea intake improves elevated serum uric acid (SUA) levels, a causal link between the consumption of different types of tea and SUA levels remains undetermined.

METHODS

Bidirectional Mendelian randomization (MR) analysis based on genome-wide association studies was used to assess the causal relationship between consumption of different types of tea and the risk of elevated SUA levels in European and Asian populations.

RESULTS

Forward MR analysis showed that tea intake was significantly associated with lower SUA levels (p = 0.0013). The estimated effect value (β $$ \beta $$  = $$ = $$  -0.0440) suggests that for every 1-unit increase in tea intake, there is a 0.044-unit decrease in SUA levels. However, there is no reverse causality between SUA and tea intake (p = 0.2824). No causal relationship was found between the consumption of different types of tea and risk of elevated SUA levels (p > 0.05).

CONCLUSION

Although this bidirectional MR study provided evidence of a causal relationship between tea intake and SUA levels, however, due to limitations associated with the sample size and strength of instrumental variables, a definite conclusion was not possible.

Elucidating the role of genetically determined metabolites in Diabetic Retinopathy: insights from a mendelian randomization analysis

AIMS

Diabetic retinopathy (DR) results from complex genetic and metabolic interactions. Unraveling the links between blood metabolites and DR can advance risk prediction and therapy.

METHODS

Leveraging Mendelian Randomization (MR) and Linkage Disequilibrium Score Regression (LDSC), we analyzed 10,413 DR cases and 308,633 controls. Data was sourced from the Metabolomics GWAS server and the FinnGen project.

RESULTS

Our research conducted a comprehensive MR analysis across 486 serum metabolites to investigate their causal role in DR. After stringent selection and validation of instrumental variables, we focused on 480 metabolites for analysis. Our findings revealed 38 metabolites potentially causally associated with DR. Specifically, 4-androsten-3beta,17beta-diol disulfate 2 was identified as significantly associated with a reduced risk of DR (OR = 0.471, 95% CI = 0.324-0.684, p = 7.87 × 10- 5), even after rigorous adjustments for multiple testing. Sensitivity analyses further validated the robustness of this association, and linkage disequilibrium score regression analyses showed no significant genetic correlation between this metabolite and DR, suggesting a specific protective effect against DR.

CONCLUSIONS

Our study identifies 4-androsten-3beta,17beta-diol disulfate 2, a metabolite of androgens, as a significant protective factor against diabetic retinopathy, suggesting androgens as potential therapeutic targets.

Relationship of urate-lowering drugs with cognition and dementia: A Mendelian randomization and observational study

Prior studies have presented paradoxical results regarding the association of uric acid-lowering drugs (ULDs) therapy with cognition and dementia. We aimed to explore this correlation. In this observational study, we extracted and analyzed the data from the National Health and Nutrition Examination Survey (NHANES) database and the FDA Adverse Event Reporting System (FAERS) database to investigate the association of ULDs with cognitive function and dementia. Two-simple Mendelian randomization (MR) and multivariable MR (MVMR) analyses were conducted to evaluate the causal associations of ULDs for all common types of dementia, including Alzheimer's disease (AD), vascular dementia (VD), frontotemporal dementia (FTD), and dementia with Lewy bodies (DLB). In the NHANES database, regardless of whether ULDs were included only or adjusted for covariates, the linear regression models did not find a correlation between ULDs and three cognitive tests (all p > 0.05). In the FAERS database, the dementia signal in ULDs lost significance after stepwise constraints (the lower limit of proportional reporting ratio lower than 1). In the two-sample MR analysis, allopurinol was associated with an increased risk of VD (OR = 123.747, p = 0.002), and a positive causal relationship was found between uricosuric drugs and AD (OR = 1.003, p = 0.003). However, the significance disappeared after adjusting for risk factors of dementia (p > 0.05). This study indicates that ULDs may not be related to an increase or decrease risk of cognition function and dementia, including all common types of dementia (AD, VD, FTD, and DLB).

Skin Microbiota and Pathological Scars: A Bidirectional Two-Sample Mendelian Randomization Study

BACKGROUND

Pathological scars (PSs), resulting from abnormal skin repair, chronic inflammation, and fibrosis, affect millions of people. Previous studies have demonstrated that skin microbiota (SM) plays a role in cutaneous inflammation and healing, but the interplay between PSs and SM remains unclear yet.

OBJECTIVE

To investigate the causal associations between SM and two specific PSs: hypertrophic scars (HSs) and keloids.

METHODS

A bidirectional two-sample mendelian randomization (MR) analysis using genetic data for SM, HS, and keloids was conducted. The random-effects inverse variance weighted (IVW) method was used as the primary approach, along with multiple MR methods. False discovery rate (FDR) correction was employed to address multiple testing.

RESULTS

In forward analysis, the family Moraxellaceae and order Pseudomonadales exhibited the same significant protective effects on keloids (odds ratio [OR]: 0.849, 95% confidence interval [CI]: 0.770-0.935, q2 = 0.03626). The class Betaproteobacteria (OR: 0.938, 95% CI: 0.894-0.985, q1 = 0.01965) and genus Bacteroides (OR: 0.928, 95% CI: 0.884-0.973, q1 = 0.00889) each demonstrated a suggestive protective effect on HSs and keloids, respectively. Some limited evidence suggested that order Actinomycetales contributes to an increased risk of keloids. In reverse analysis, keloids were found to have negative effects on the class Gammaproteobacteria with limited evidence. There was no detectable evidence of horizontal pleiotropy or heterogeneity.

CONCLUSION

This study provided evidence for the causalities between SM and PSs, which laid foundation for furthering clinical practice and research of microorganism-skin interaction.

Causal association between insulin sensitivity index and Alzheimer's disease

Evidence from observational and Mendelian randomization (MR) studies suggested that insulin resistance (IR) was associated with Alzheimer's disease (AD). However, the causal effects of different indicators of IR on AD remain inconsistent. Here, we aim to assess the causal association between the insulin sensitivity index (ISI), a measure of post-prandial IR, and the risk of AD. We first conducted primary and secondary univariable MR analyses. We selected 8 independent genome-wide significant (p < 5E-08, primary analyses) and 61 suggestive (p < 1E-05, secondary analyses) ISI genetic variants from large-scale genome-wide association studies (GWAS; N = 53 657), respectively, and extracted their corresponding GWAS summary statistics from AD GWAS, including IGAP2019 (N = 63 926) and FinnGen_G6_AD_WIDE (N = 412 181). We selected five univariable MR methods and used heterogeneity, horizontal pleiotropy test, and leave-one-out sensitivity analysis to confirm the stability of MR estimates. Finally, we conducted a meta-analysis to combine MR estimates from two non-overlapping AD GWAS datasets. We further performed multivariable MR (MVMR) to assess the potential mediating role of type 2 diabetes (T2D) on the association between ISI and AD using two MVMR methods. In univariable MR, utilizing 8 genetic variants in primary analyses, we found a significant causal association of genetically increased ISI with decreased risk of AD (OR = 0.79, 95% CI: 0.68-0.92, p = 0.003). Utilizing 61 genetic variants in secondary analyses, we found consistent findings of a causal effect of genetically increased ISI on the decreased risk of AD (OR = 0.89, 95% CI: 0.82-0.96, p = 0.003). Heterogeneity, horizontal pleiotropy test, and leave-one-out sensitivity analysis ensured the reliability of the MR estimates. In MVMR, we found no causal relationship between ISI and AD after adjusting for T2D (p > 0.05). We provide genetic evidence that increased ISI is significantly and causally associated with reduced risk of AD, which is mediated by T2D. These findings may inform prevention strategies directed toward IR-associated T2D and AD.

SGLT2 inhibition, circulating biomarkers, and Alzheimer's disease: A Mendelian randomization study

BACKGROUND

Sodium-glucose cotransporter 2 (SGLT2) inhibitors is a novel category of medications for diabetes, exhibiting neuroprotective potential. However, evidence regarding whether the use of SGLT2 inhibitors effectively reduces the risk of Alzheimer's disease (AD) remains unclear.

OBJECTIVE

Our study employed Mendelian randomization (MR) analysis to investigate potential causal relationships between SGLT2 inhibition, metabolites, and AD.

METHODS

In our research, we used a two-sample MR method to explore the link between SGLT2 inhibitor use and AD, addressing both its late-onset and early-onset forms. Furthermore, we executed a two-step MR analysis to explore how circulating metabolites, primarily endogenous in nature due to SGLT2 inhibition, mediate the relationship between SGLT2 inhibition and AD. The genetic instruments for SGLT2 inhibition were pinpointed through their association with SLC5A2 gene expression and the decreased glycated hemoglobin (HbA1c) levels.

RESULTS

Genetic analysis indicated that SGLT2 inhibition, which effectively reduces HbA1c by enhancing renal glucose excretion and improving glycemic control, was associated with a lower likelihood of developing AD for every 1 SD decrease in HbA1c (OR = 0.48, [0.36, 0.63], p < 0.001). Our MR analysis revealed that SGLT2 inhibition significantly affected 27 of the 123 metabolites examined, adhering to a Bonferroni correction threshold (p < 4.06 × 10-4). Among these 27 significant metabolites, citrate was also associated with AD, showing a significant association (0.81 [0.79, 0.83], p < 0.001).

CONCLUSIONS

The study provides strong evidence linking SGLT2 inhibition with a lower AD risk, highlighting citrate's potential mediating role for subsequent clinical research.

Deciphering the genetic underpinnings of neuroticism: A Mendelian randomization study of druggable gene targets

BACKGROUND

Neuroticism, known for its association with a greater risk of psychiatric conditions such as depression and anxiety, is a critical focus of research.

METHODS

Cis-expression quantitative trait loci (eQTLs) from 31,684 whole blood samples provided by the eQTLGen Consortium, alongside data from a large neuroticism cohort, were analyzed to identify genes causally linked to neuroticism. To further explore the influence of gene expression changes on neuroticism, colocalization analysis was conducted. Identified drug targets were assessed for potential side effects using a phenome-wide association study (PheWAS). Additionally, we utilized multiple databases to explore the interactions between drugs and genes for drug prediction and assess the current medications for drug repurposing.

RESULTS

The analysis involved a total of 4473 druggable genes, with two-sample Mendelian randomization (MR) identifying 186 genes that are causally linked to neuroticism. Colocalization analysis highlighted 11 genes (TLR4, MMRN1, EP300, BRAF, ORM1, ACVR1B, LRRC17, NOS2, ADAMTS6, GPX1, and VCL) with a posterior probability of colocalization (PPH4) >0.8. PheWAS revealed that drugs targeting BRAF, LRRC17, ADAMTS6, and GPX1 were also associated with other traits. Notably, six of these genes (TLR4, MMRN1, BRAF, ACVR1B, NOS2, and GPX1) are already being explored for drug development in psychiatric and other diseases.

CONCLUSION

This study pinpointed six genes as promising therapeutic targets for neuroticism. The repurposing and development of drugs targeting these genes hold potential for managing neuroticism and associated psychiatric disorders.

Plasma Proteomes and Genome-Wide Association Data for Causal Protein Identification in Stroke

Plasma proteins are promising biomarkers and potential drug targets for stroke. This study aimed to explore whether there is a causal relationship between plasma proteins and subtypes of stroke using a Mendelian randomization (MR) approach. A two-sample bidirectional Mendelian randomization approach was employed to investigate the causal link between plasma proteins and stroke. Data on plasma proteins were obtained from three studies, including INTERVAL, and pooled stroke information was sourced from the MEGASTROKE consortium and the UK Biobank dataset, covering four subtypes of stroke. MR analyses were primarily conducted using inverse variance weighting, and sensitivity analyses were also performed. Finally, potential reverse causality was assessed using bidirectional MR. We identified two proteins causally associated with stroke: one as a potential therapeutic target and another as a protective factor. CXCL8 was found to be positively associated with the risk of developing large-artery atherosclerotic (LAA) stroke (OR, 1.005; 95% CI 1.001 to 1.010; p = 0.022), whereas TNFRSF11b was negatively correlated with the risk of developing LAA stroke (OR, 0.937; 95% CI 0.892 to 0.984; p = 0.010), independently of other stroke subtypes. Reverse bivariate analysis did not indicate that ischemic stroke was causally associated with CXCL8 and TNFRSF11b. There is a causal relationship between CXCL8 and TNFRSF11b with LAA stroke, independent of other subtypes. This study offers a new perspective on the genetics of stroke.

Exploring estrogen-related mechanisms in ovarian carcinogenesis: association between bone mineral density and ovarian cancer risk in a multivariable Mendelian randomization study

BACKGROUND

Estrogen may play a role in epithelial ovarian cancer (EOC) carcinogenesis, with effects varying by EOC histotype. Measuring women's long-term exposure to estrogen is difficult, but bone mineral density (BMD) may be a reasonable proxy of longer-term exposure. We examined this relationship by assessing the association between genetic predisposition for higher BMD and risk of EOC by histotype.

METHODS

We used Mendelian randomization (MR) to assess associations between genetic markers for femoral neck and lumbar spine BMD and each EOC histotype. We used multivariable MR (MVMR) to adjust for probable pleiotropic traits, including body mass index, height, menarcheal age, menopausal age, smoking, alcohol intake, and vitamin D.

RESULTS

Univariable analyses suggested greater BMD was associated with increased risk of endometrioid EOC (per standard deviation increase; lumbar spine OR = 1.21; 95% CI 0.93,1.57, femoral neck: OR = 1.25; 0.99,1.57), but sensitivity analyses indicated that pleiotropy was likely. Adjustment using MVMR reduced the magnitude of estimates slightly (lumbar spine: OR = 1.13; 95% CI 1.00,1.28, femoral neck: OR = 1.18; 1.03,1.36). Results for lumbar spine BMD and high-grade serous EOC were also suggestive of an association (univariable MR: OR = 1.16; 95% CI 1.03,1.30; MVMR: OR = 1.06; 0.99,1.14).

CONCLUSION

Our study found associations between genetic predisposition to higher BMD, a proxy for long-term estrogen exposure, and risk of developing endometroid and high-grade serous EOC cancers. These findings add to existing evidence of the relationship between estrogen and increased risk of EOC for certain histotypes.

Discovery and exploration of adaptive immune response-related drug targets in diabetic retinopathy by Mendelian randomization

BACKGROUND

Persistent diabetes raises diabetic retinopathy (DR) risk, and management is challenging. Integrating transcriptomics and MR, this study provides a current reference for the clinical treatment of DR by identifying potential drug targets in adaptive immune response-associated genes (AIR-RGs).

METHODS

The GSE102485 dataset about AIR-RGs and DR was downloaded from a public database. Initially, the MR and Steiger test identified AIR-related candidate genes with causal associations to DR. Bayesian co-localization analysis pinpointed DR drug targets, followed by phenotype scanning for side effects. Functional enrichment and immune infiltration analyses elucidated target mechanisms in DR.

RESULTS

Identified 27 AIR-RGs associated with DR, with TRAV23DV6 (OR = 1.367, 95 % CI = 1.005-1.859, p = 0.0046) as a risk factor. Co-localization analysis confirmed TRAV23DV6's potential as a DR drug target. Phenotype scanning linked TRAV23DV6 to hepatocellular carcinoma, thromboembolism, and pyelonephritis, indicating potential side effects. TRAV23DV6 engages in adaptive immunity, autophagy, and antigen binding. DR involves infiltration of 22 immune cell types and activation of 16 immune functions related to TCR, BCR pathways, and TNF family. Correlation analysis shows high TRAV23DV6 expression, immune cell infiltration, and function activation may exacerbate DR.

CONCLUSION

TRAV23DV6 has been identified as a potential drug target for DR, offering a new perspective for the treatment of this condition.

Copper and iron as unique trace elements linked to fibromyalgia risk

Fibromyalgia (FM) is a prevalent chronic pain condition with a complex and not fully understood etiology. Abnormal metabolism of trace elements is suspected to play a role in the pathogenesis of FM, though the exact relationships have yet to be clarified. This study employed Mendelian randomization (MR) to assess potential causal relationships between 15 major trace elements and the risk of FM, focusing on the specific roles of elements that show significant associations. Genetic instrumental variables (single nucleotide polymorphisms, SNPs), related to these trace elements and FM were extracted from genome-wide association studies (GWAS). Analyses were performed using various methods including inverse-variance weighting (IVW), MR Egger, weighted median, weighted mode, and simple mode. Furthermore, multivariable analysis controlled for selenium as a potential confounder to evaluate the independent associations of copper (Cu) and iron (Fe) with FM risk. Two-sample MR analysis indicated a positive association between Cu and increased risk of FM (IVW: OR = 1.095, 95% CI: 1.015 to 1.181, P = 0.018), and a negative association between Fe and FM risk (IVW: OR = 0.440, 95% CI: 0.233 to 0.834, P = 0.011). These associations remained significant in the multivariable analysis, highlighting the independent effects of Cu and Fe. No significant correlations were observed with other trace elements such as selenium and zinc. This study provides new evidence of the roles of Cu and Fe in the pathophysiology of FM and underscores the importance of considering trace elements in the prevention and treatment strategies for FM. Future research should further validate these findings and explore the specific biological mechanisms through which Cu and Fe influence FM risk.

Causal association of physical activity with lymphoma risk: a Mendelian randomization analysis

Controversial relationship of physical activity with lower lymphoma risk has been reported in observational studies. The purpose of this study was to explore the causal correlation of physical activity with lymphoma risk using two-sample Mendelian randomization (MR). Genetic variants associated with physical activity (moderate-to-vigorous physical activity (MVPA), average acceleration physical activity, number of days/week of moderate physical activity 10+ min, and number of days/week of vigorous physical activity 10+ min) and lymphoma [overall lymphoma, Hodgkin lymphoma, mature T/NK-cell lymphomas, diffuse large B-cell lymphoma (DLBCL), and follicular lymphoma] were obtained from published genome-wide association studies (GWAS) and the FinnGen database and used as instrumental variables. Primary results were based on inverse variance-weighted (IVW) analysis and were described as odds ratio (OR) and 95% confidence interval (CI). Higher levels of genetically predicted MVPA (OR = 0.079, 95% CI: 0.021-0.300, P = 0.0002) and number of days/week of vigorous physical activity 10+ min (OR = 0.237, 95% CI: 0.098-0.573, P = 0.0014) were negatively associated with Hodgkin lymphoma risk. There was a weak negative association between high levels of genetically predicted MVPA (OR = 0.114, 95% CI: 0.015-0.856, P = 0.0348) and average acceleration physical activity (OR = 0.830, 95% CI: 0.705-0.976, P = 0.0243) and risk of DLBCL. No causal relationship was observed between physical activity and the risk of overall lymphoma, mature T/NK-cell lymphomas, and follicular lymphoma (P > 0.05). This study supported the causal relationship between higher physical activity levels and lower risks of Hodgkin lymphoma and DLBCL.

Biological pathways underlying the relationship between childhood maltreatment and Multimorbidity: A two-step, multivariable Mendelian randomisation study

Childhood maltreatment has been associated with multimorbidity of depression, coronary artery disease and type 2 diabetes. However, the biological mechanisms underlying this association remain unclear. We employed two-step and multivariable Mendelian randomisation (MR) to understand the role of three potential biological mediating mechanisms - inflammation (92 proteins), metabolic processes (54 markers), and cortisol - in the link between childhood maltreatment liability and multimorbidity. Using summary statistics from large-scale genome-wide association studies of European ancestry for childhood maltreatment (N = 185,414) and multimorbidity (Neffective = 156,717), we tested for the presence of an indirect effect via each mediator individually. We found a potential role of metabolic pathways. Up to 11% of the effect of childhood maltreatment on multimorbidity was mediated by triglycerides (indirect effect [95% CI]: 0.018 [0.009-0.027]), 8% by glycated haemoglobin (indirect effect: 0.013 [0.003-0.023]), and up to 7% by high-density lipoprotein cholesterol (indirect effect: 0.011 [0.005-0.017]). We did not find evidence for mediation via any inflammatory protein or cortisol. Our findings shed light on the biological mechanisms linking childhood maltreatment liability to multimorbidity, highlighting the role of metabolic pathways. Future studies may explore underlying pathways via non-biological mediators (e.g., lifestyle factors) or via multiple mediators simultaneously.

LASSO-type instrumental variable selection methods with an application to Mendelian randomization

Valid instrumental variables (IVs) must not directly impact the outcome variable and must also be uncorrelated with nonmeasured variables. However, in practice, IVs are likely to be invalid. The existing methods can lead to large bias relative to standard errors in situations with many weak and invalid instruments. In this paper, we derive a LASSO procedure for the k-class IV estimation methods in the linear IV model. In addition, we propose the jackknife IV method by using LASSO to address the problem of many weak invalid instruments in the case of heteroscedastic data. The proposed methods are robust for estimating causal effects in the presence of many invalid and valid instruments, with theoretical assurances of their execution. In addition, two-step numerical algorithms are developed for the estimation of causal effects. The performance of the proposed estimators is demonstrated via Monte Carlo simulations as well as an empirical application. We use Mendelian randomization as an application, wherein we estimate the causal effect of body mass index on the health-related quality of life index using single nucleotide polymorphisms as instruments for body mass index.

Investigating the Link between Psychological Well-Being and Early-Stage Age-Related Macular Degeneration: A Mendelian Randomization Analysis

PURPOSE

While some studies have started to focus on the link between psychological well-being and age-related macular degeneration (AMD), the relationship remains uncertain. Our research aims to provide new insights into this association, laying a foundation for future interventions and addressing existing knowledge gaps.

METHODS

We utilized the "TwoSampleMR" package in R for a bidirectional Mendelian randomization analysis of psychological well-being (subjective well-being, depression, neuroticism, and Sensitivity to Environmental Stress and Adversity) and early-stage AMD. Causal effects were estimated using the inverse-variance weighted method, and additional methods included weighted median and MR-Egger regression. Sensitivity analyses included Cochran's Q test, MR-Egger intercept analysis, MR-PRESSO, and leave-one-out analysis.

RESULTS

The study found that the population with genetic predisposition to neuroticism had a 39.7% lower risk of early-stage AMD (OR = 0.603, 95% CI = 0.385-0.945, p = 0.027). Conversely, the population with genetic predisposition to subjective well-being had a 3.2% increased risk of early-stage AMD (OR = 1.032, 95% CI = 1.003-1.063, p = 0.029). No significant causal relationships were found from depression or Sensitivity to Environmental Stress and Adversity to early-stage AMD, nor from early-stage AMD to psychological well-being.

CONCLUSION

This study provides preliminary evidence that the relationship between psychological well-being and early-stage AMD may be complex and multifaceted. It suggests that moderate neuroticism levels might reduce early-stage AMD risk through health behaviors, pathophysiological mechanisms, and other factors, while high subjective well-being levels might increase this risk similarly. However, these findings are insufficient for preventive strategies due to a lack of substantial evidence and still require extensive experimental research for further validation.

Association between myopia and diabetic retinopathy: A two-sample mendelian randomization study

Objective

The association between myopia and diabetic retinopathy (DR) is unclear, with inconsistent results reported, and whether the association represents causality remains unknown. This study aimed to investigate the causal associations of genetically determined myopia with DR, and further explore specific mechanisms.

Methods

We conducted two-sample mendelian randomization (MR) analyses of any myopia and high myopia on six DR phenotypes, including any DR, background DR, severe background DR, proliferative DR (PDR), diabetic maculopathy and unspecific DR in the primary study. Mechanism exploration of spherical equivalent refraction (SER), corneal curvature (CC) and axial length (AL) on any DR was carried out subsequently. Single-nucleotide polymorphisms (SNPs), used as genetic instruments, were derived from UK Biobank, Genetic Epidemiology Research on Adult Health and Aging cohort (GERA) and FinnGen. The inverse variance weighted (IVW) method was mainly used to assess the causality, and was complemented with sensitivity analyses and causality direction analyses.

Results

Using SNPs that have excluded possible confounders, we discovered suggestive and positive causal associations of any myopia with any DR (IVW: odds ratio [OR] ​= ​1.133, 95% confidence interval [95%CI]: 1.070-1.201, P ​= ​1.91×10-5) and PDR (IVW: OR ​= ​1.182, 95% CI: 1.088-1.285, P ​= ​8.31×10-5). Similar but more significant associations were found of high myopia with any DR and PDR (IVW: OR ​= ​1.107, 95%CI: 1.051-1.166, P ​= ​1.39×10-4; OR ​= ​1.163, 95%CI: 1.088-1.244, P ​= ​8.76×10-6, respectively). Further mechanism analyses found only AL, rather than SER or CC, was strongly and significantly associated with any DR. These associations were robust in sensitivity analyses and causality direction analyses.

Conclusions

We found significant and positive causal associations of any myopia and high myopia with the risk of DR and PDR, which might be related with AL, indicating the significance of myopia control for preventing DR development and progression.

Causality between diabetes and membranous nephropathy: Mendelian randomization

BACKGROUND

Membranous nephropathy (MN) has not yet been fully elucidated regarding its relationship with Type I and II Diabetes. This study aims to evaluate the causal effect of multiple types of diabetes and MN by summarizing the evidence from the Mendelian randomization (MR) study.

METHODS

The statistical data for MN was obtained from a GWAS study encompassing 7979 individuals. Regarding diabetes, fasting glucose, fasting insulin, and HbA1C data, we accessed the UK-Biobank, within family GWAS consortium, MAGIC, FinnGen database, MRC-IEU, and Neale Lab, which provided sample sizes ranging from 17,724 to 298,957. As a primary method in this MR analysis, we employed the Inverse Variance Weighted (IVW), Weighted Median, Weighted mode, MR-Egger, Mendelian randomization pleiotropy residual sum, and outlier (MR-PRESSO) and Leave-one-out sensitivity test. Reverse MR analysis was utilized to investigate whether MN affects Diabetes. Meta-analysis was applied to combine study-specific estimates.

RESULTS

It has been determined that type 2 diabetes, gestational diabetes, type 1 diabetes with or without complications, maternal diabetes, and insulin use pose a risk to MN. Based on the genetic prediction, fasting insulin, fasting blood glucose, and HbA1c levels were not associated with the risk of MN. No heterogeneity, horizontal pleiotropy, or reverse causal relationships were found. The meta-analysis results further validated the accuracy.

CONCLUSIONS

The MR analysis revealed the association between MN and various subtypes of diabetes. This study has provided a deeper understanding of the pathogenic mechanisms connecting MN and diabetes.

Immune cells: Mediators in the metabolites and Alzheimer's disease

BACKGROUND

Alzheimer's disease (AD) is a progressive neurodegenerative disorder that predominantly affects elderly individuals across the globe. While genetic, environmental, and lifestyle factors are known to influence the onset of AD, the underlying mechanisms remain unclear.

OBJECTIVE

To elucidate the intricate interplay between metabolites and immune cell activation in the ethology of AD, and to determine their collective impact on AD risk.

METHODS

We conducted a comprehensive analysis of genome-wide association studies data to examine the relationships between metabolites, immune cell phenotypes, and the risk of AD. Our study encompassed a comprehensive examination involving 731 distinct immune cell types, 1400 metabolites, and a large cohort comprising10,520 AD cases with 401,661 controls. We employed univariate Mendelian randomization to assess bidirectional relationships between metabolites and AD, metabolites and immune cells, as well as immune cells and AD. Subsequently, multivariate Mendelian randomization was then applied to evaluate the potential mediating role of immune cells on the relationship between metabolites and AD.

RESULTS

Specific metabolites, the histidine/pyruvate ratio and homoarginine, were positively associated with the risk of AD, mediated by immune cells. Conversely, 4-hydroxycoumarin and glycolithocholate sulfate showed protective associations against AD. Immune cell markers, CD64 on monocytes and HLA DR on CD14+ CD16- monocytes were linked to higher AD risk, while CD33dim HLA DR+ CD11b- myeloid cells and HLA DR on CD8+ T cells were protective.

CONCLUSIONS

This study highlights the critical role of immune cells in the pathogenesis of AD, demonstrating how their interaction with specific metabolites influences disease risk.

Causal association between non-thyroidal autoimmune diseases and Graves' ophthalmopathy: A mendelian randomization study

Purpose

This Mendelian randomization (MR) analysis study aimed to investigate the genetic causal relationship between non-thyroidal autoimmune diseases (ADs) and Graves' ophthalmopathy (GO).

Materials

Single nucleotide polymorphisms (SNPs) associated with inflammatory bowel disease (IBD), multiple sclerosis (MS), psoriasis vulgaris (PV), type 1 diabetes (T1D), systemic lupus erythematosus (SLE), and rheumatoid arthritis (RA) were obtained from the IEU Open genome-wide association studies (GWAS) database, GWAS data for GO were obtained from the FinnGen database. Bidirectional MR analysis was conducted using inverse variance weighted (IVW) method, weighted median (WM) method and MR-Egger test. Cochran's Q statistic was used to assess the heterogeneity between SNP estimates. MR-Egger regression was used to evaluate horizontal pleiotropy and MR pleiotropy residual sum and outlier (MR-PRESSO) test was used to detect the outliers.

Results

For non-thyroidal ADs, the forward MR results using the IVM method showed that T1D (OR ​= ​1.259, 95%CI 1.026-1.5465; P ​= ​0.028) and SLE (OR ​= ​1.807, 95%CI 1.229-2.655; P ​= ​0.003) were correlated with the risk of GO at the genetic level, while there was no evidence showing that IBD, MS, PV and RA were correlated with GO. In the reverse MR study, there was a significant increase in the risk of developing T1D in GO (OR ​= ​1.135, 95%CI 1.018-1.265; P ​= ​0.022), but pleiotropy and heterogeneity existed.

Conclusions

In the European population, there is strong genetic evidence that patients with T1D and SLE have a higher risk of developing GO, whereas the effect of GO on ADs is unclear.

Genetic evidence of the causal relationships between psychiatric disorders and cardiovascular diseases

OBJECTIVE

Our primary objective is to investigate the causal relationships between 12 psychiatric disorders (PDs) and atrial fibrillation (AF), coronary artery disease (CAD), myocardial infarction (MI), and heart failure (HF).

METHODS

Firstly, we used linkage disequilibrium score regression to calculate the genetic correlations between 12 PDs and 4 cardiovascular diseases (CVDs). Subsequently, we performed two-sample and bidirectional Mendelian randomization (MR) analyses of phenotypes with significant genetic correlations to explore the causal relationships between PDs and CVDs. Inverse variance weighted with modified weights (MW-IVW), Robust Adjusted Profile Score, Inverse Variance Weighted, weighted median and weighted mode were used to evaluate causal effects, with MW-IVW being the main analysis method. And to validate the MR results, we conducted the replicate analyses using data from the FinnGen database.

RESULTS

Conducting MR analyses in phenotypes with significant genetic correlations, we identified bidirectional causal relationships between depression (DEP) and MI (DEP as exposure: OR = 1.1324, 95 % confidence interval (CI): 1.0984-1.1663, P < 0.0001; MI as exposure: OR = 1.0268, 95 % CI: 1.0160-1.0375, P < 0.0001). Similar relationships were observed in Attention Deficit/Hyperactivity Disorder (ADHD) and HF (ADHD as exposure: OR = 1.0270, 95 % CI: 1.0144-1.0395, P < 0.0001; HF as exposure: OR = 1.0980, 95 % CI: 1.0502-1.1458, P < 0.0001).

CONCLUSIONS

In our study, we conducted the comprehensive analyses between 12 PDs and CVDs. By bidirectional MR analysis, we observed significant causal relationships between MI and DEP, HF and ADHD. These findings suggest possible complex causal relationships between PDs and CVDs.

Child maltreatment as a transdiagnostic risk factor for the externalizing dimension: a Mendelian randomization study

Observational studies suggest that child maltreatment increases the risk of externalizing spectrum disorders such as attention deficit hyperactivity disorder (ADHD), conduct disorder (CD), antisocial personality disorder (ASPD), and substance use disorder (SUD). Yet, only few of such associations have been investigated by approaches that provide strong evidence for causation, such as Mendelian Randomization (MR). Establishing causal inference is essential given the growing recognition of gene-environment correlations, which can confound observational research in the context of childhood maltreatment. Evaluating causality between child maltreatment and the externalizing phenotypes, we used genome-wide association study (GWAS) summary data for child maltreatment (143,473 participants), ADHD (20,183 cases; 35,191 controls), CD (451 cases; 256,859 controls), ASPD (381 cases; 252,877 controls), alcohol use disorder (AUD; 13,422 cases; 244,533 controls), opioid use disorder (OUD; 775 cases; 255,921 controls), and cannabinoid use disorder (CUD; 14,080 cases; 343,726 controls). We also generated a latent variable 'common externalizing factor' (EXT) using genomic structural equation modeling. Genetically predicted childhood maltreatment was consistently associated with ADHD (odds ratio [OR], 10.09; 95%-CI, 4.76-21.40; P = 1.63 × 10-09), AUD (OR, 3.72; 95%-CI, 1.85-7.52; P = 2.42 × 10-04), and the EXT (OR, 2.64; 95%-CI, 1.52-4.60; P = 5.80 × 10-04) across the different analyses and pleiotropy-robust methods. A subsequent GWAS on childhood maltreatment and the externalizing dimension from Externalizing Consortium (EXT-CON) confirmed these results. Two of the top five genes with the strongest associations in EXT GWAS, CADM2 and SEMA6D, are also ranked among the top 10 in the EXT-CON. The present results confirm the existence of a common externalizing factor and an increasing vulnerability caused by child maltreatment, with crucial implications for prevention. However, the partly diverging results also indicate that specific influences impact individual phenotypes separately.

Association of serum lipidomic profiles with risk of intracranial aneurysm: A Mendelian randomization study

A two-sample Mendelian randomization (MR) analysis was utilized to assess the causal relationship between lipidomic profiles and the risk of intracranial aneurysms (IAs). Genetic variants related to lipidomic profiles (227 components) and IA [IA, aneurysmal subarachnoid hemorrhage (aSAH) only, unruptured IA (uIA) only] were obtained from published genome-wide association studies (GWASs) or the IEU Open GWAS project and used as instrumental variables for MR analysis. The inverse-variance weighted method was used in the primary analyses to derive causality estimates and was expressed as odds ratio (OR) with 95% confidence interval (CI). Of these 227 lipidomic profiles, only genetically predicted high levels of cholesterol to total lipids ratio in very small very-low-density lipoproteins (VLDL) [OR = 0.629 (95% CI, 0.504-0.786)], cholesteryl esters to total lipids ratio in very small VLDL [OR = 0.637 (95% CI, 0.509-0.797)], ratio of docosahexaenoic acid to total fatty acids [OR = 0.691 (95% CI, 0.582-0.820)], and ratio of polyunsaturated fatty acids to monounsaturated fatty acids [OR = 0.630 (95% CI, 0.522-0.760)] reduced the risk of aSAH, whereas genetically predicted high ratio of monounsaturated fatty acids to total fatty acids [OR = 1.471 (95% CI, 1.215-1.781)] increased the risk of aSAH. Moreover, genetically predicted high levels of cholesterol to total lipids ratio in very small VLDL [OR = 0.657 (95% CI, 0.542-0.798)], cholesteryl esters to total lipids ratio in very small VLDL [OR = 0.663 (95% CI, 0.548-0.803)], free cholesterol to total lipids ratio in small VLDL [OR = 0.682 (95% CI, 0.560-0.832)], phospholipids to total lipids ratio in small VLDL [OR = 0.674 (95% CI, 0.548-0.830)], and ratio of polyunsaturated fatty acids to monounsaturated fatty acids [OR = 0.678 (95% CI, 0.569-0.808)] reduced the risk of IA. The results of multivariable MR demonstrated that these causal associations persisted after adjusting for systolic blood pressure and cigarettes smoked per day. The effect of serum lipids on IA and aSAH may be mainly caused by subclasses of lipids such as VLDL.