Power and instrument strength requirements for Mendelian randomization studies using multiple genetic variants

The causal relationship between gut microbiota and preterm birth: a two-sample Mendelian randomization study

BACKGROUND

Preterm birth, a significant global health concern, has been associated with alterations in the gut microbiota. However, the causal nature of this relationship remains uncertain due to the limitations inherent in observational studies.

PURPOSE

To investigate the potential causal relationship between gut microbiota imbalances and preterm birth.

METHODS

We conducted a two-sample Mendelian randomization (MR) study using genome-wide association study (GWAS) data from the MiBioGen consortium focusing on microbiota and preterm birth. Single nucleotide polymorphisms (SNPs) associated with the microbiota were selected as instrumental variables. The inverse variance weighting (IVW) method was used to estimate causality. We confirmed pleiotropy and identified and excluded outlier SNPs using MR-PRESSO and MR-Egger regression. Cochran's Q test was applied to assess heterogeneity among SNPs, and a leave-one-out analysis was performed to evaluate the influence of individual SNPs on overall estimates.

RESULTS

Our findings provide evidence for a causal link between specific components of the gut microbiota and preterm birth, with the identification of relevant metabolites.

CONCLUSION

This study highlights the causal role of gut microbiota imbalances in preterm birth, offering novel insights into the development of preterm birth and potential targets for prevention strategies.

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.

Relationships between emotional states, bipolar disorder, and gastrointestinal disorders: A two-sample Mendelian randomization study

BACKGROUND

Functional gastrointestinal symptoms are frequently observed in patients with bipolar affective disorder, but the causal relationship between these conditions remains unclear. To establish causality, this study utilized Mendelian randomization (MR) with data from large-scale genomic research. The investigation aimed to elucidate the relationship between emotional states, bipolar disorder, and functional gastrointestinal disorders (FGIDs).

METHODS

Summary statistics from GWAS were utilized for mood swings (UK biobank, N = 451,619), irritable mood (UK biobank, N = 373,733), bipolar disorder (UK biobank, N = 352,006),functional dyspepsia (FinnGen biobank, N = 194,071), and irritable bowel syndrome (UK biobank, N = 486,601). All GWAS summary statistics were derived from individuals of European ancestry. The primary analysis employed the inverse variance-weighted method for Mendelian randomization (MR). Additionally, we conducted tests for heterogeneity and pleiotropy to ensure the robustness of our results.

RESULTS

A suggestive positive causal relationship was identified between mood swings-related conditions and IBS using the inverse variance-weighted (IVW) method [mood swings-IBS: OR/95%CI: 3.221(2.417,4.294), P(1.42E-15); irritable mood-IBS: OR/95%CI: 1.881(1.615,2.191), P(4.56E-16); bipolar disorder-IBS: OR/95%CI: 1.003(1.001,1.006), P(0.009)]. For functional dyspepsia, a suggestive positive causal relationship was observed with mood swings [mood swings-FD: OR/95%CI: 2.827(1.124,7.109), P(0.027)]. In the reverse analysis, causal relationship was observed between IBS and emotional states [IBS and mood swings: OR/95%CI: 1.030(1.021,1.040), P(1.10E-10); IBS and irritable mood: OR/95%CI: 1.064(1.041,1.087), P(2.58E-08)].

CONCLUSIONS

Mood swings, irritable mood, and bipolar disorder were associated with an increased risk of functional gastrointestinal disorders (FGIDs). Additionally, reverse analysis revealed a causal relationship between irritable bowel syndrome (IBS) and both mood swings and irritable mood. These findings suggest that targeted emotional interventions may be beneficial for patients with FGIDs. Further research is warranted to explore the relationship between mood instability-related disorders and FGIDs, particularly IBS.

Associations between Type 2 Diabetes Mellitus, Metabolic Traits, and Abdominal Aortic Aneurysm: A Cross-Ethnic Mendelian Randomization Analysis

BACKGROUND

Evidence suggests that type 2 diabetes mellitus (T2DM) may protect from abdominal aortic aneurysm (AAA). However, it is unclear whether a causal relationship exists between these 2 conditions and, if so, whether it remains consistent among racial groups.

METHODS

Cross-ethnic Mendelian randomization (MR) was used to examine the causal relationships between T2DM, metabolic traits, and AAA. Inverse variance weighted (IVW) was the primary analysis tool, supplemented by MR-Egger, weighted median, and MR Pleiotropy RESidual Sum and Outlier. Heterogeneity and horizontal pleiotropy were assessed using the Cochran's Q test and MR-Egger intercept, respectively.

RESULTS

According to IVW, an inverse correlation between T2DM and AAA was detected in Europeans (odds ratio [OR] 0.91, 95% confidence interval [CI] 0.84-0.99; P = 0.034) and East Asians (OR 0.87, 95% CI 0.77-0.99; P = 0.038). Fasting glucose was inversely associated with AAA in Europeans (OR 0.56, 95% CI 0.33-0.96; P = 0.034) but not in East Asians. In Europeans, fasting insulin was a risk factor for AAA (OR 3.03, 95% CI 1.53-6.01; P = 0.001), while 2-hour glucose was protective (OR 0.67, 95% CI 0.49-0.91; P = 0.011). Glycated hemoglobin (HbA1c) had no effect. Insufficient instrumental variables prevented the evaluation of the relationships of fasting insulin, HbA1c, and 2-hour glucose with AAA in East Asians.

CONCLUSIONS

T2DM protects against AAA in Europeans and East Asians. The effects of different glucose metabolism characteristics on AAA may inform AAA treatment.

Unraveling the causal associations between systemic cytokines and six inflammatory skin diseases

BACKGROUND

Previous observational studies have reported that systemic cytokines are associated with the risk of inflammatory skin diseases, but their conclusions remain controversial.

METHOD

We conducted a two-sample Mendelian randomization analysis to assess the relationship between systemic cytokines and six inflammatory skin disorders (including alopecia areata (AA), acne, atopic dermatitis (AD), hidradenitis suppurativa (HS), psoriasis (PS) and vitiligo), based on datasets from EArly Genetics and Lifecourse Epidemiology (EAGLE) eczema consortium, acne GWAS conducted by Maris Teder Laving et al., IEU Open GWAS, and FinnGen database. Inverse-variance weighted (IVW) method was conducted in primary MR analysis, and supplemented by MR-Egger, weighted median, weighted mode, and MR-PRESSO.

RESULTS

By integrating the findings from both primary and sensitivity analyses, we identified ten systemic cytokines linked to the risk of six skin diseases using the IVW method. Briefly, four cytokines increased the risk of corresponding skin diseases: β-nerve growth factor (β-NGF) to AA (p = 0.005) and HS (p = 0.001), interleukin-8 (p = 0.014) to acne; interleukin-5 (p = 0.042) to AD; interleukin-13 (p = 0.049) to PS. In the meantime, seven cytokines could have protective effect on specific skin diseases: interleukin-9 (p = 0.040) and interleukin-2 receptor subunit alpha (IL-2ra) (p = 0.020) on AA; macrophage inflammatory protein (MIP)-1β (p = 0.020) on acne; monokine induced by IFN-γ (p = 0.006) on AD; interleukin-16 (p = 0.038), MIP-1β (p = 0.017) and IL-2ra (p = 0.020) on PS.

CONCLUSIONS

This study reveals 13 causal associations between systemic cytokines and 6 skin diseases, offering new perspectives on the prevention and management of widespread inflammatory skin disorders.

Association of anxiety disorder, depression, and bipolar disorder with autoimmune thyroiditis: A bidirectional two-sample mendelian randomized study

BACKGROUND

Anxiety disorder, depression, and bipolar disorder are common psychiatric disorders, and their association with autoimmune thyroiditis (AIT) has been of great interest. This study aimed to investigate the potential causal relationship between these psychiatric disorders and AIT.

METHODS

We used publicly available summary statistics from large-scale genome-wide association studies to select, quality control and cluster genetic variant loci associated with anxiety disorder, depression, bipolar disorder and AIT as instrumental variables (IVs). The Mendelian randomization (MR) study mainly used inverse variance weighting (IVW) combined with MR-egger regression and weighted median estimation (WME) to estimate bidirectional causality between mental disorders and AIT. In addition, we conducted heterogeneity and multivariate tests to verify the validity of IVW.

RESULTS

Two-sample bidirectional MR analysis revealed a positive causal link between depression and AIT. The forward MR analysis of IVW (OR 1.614, 95 % CI 1.104-2.358, P = 0.013) and WME (OR 2.314, 95 % CI 1.315-4.074, P = 0.004) demonstrated thatdepression potentially elevate the risk of AIT development, while, our investigation did not uncover a causal relationship between anxiety disorder, bipolar disorder and AIT. The results of reverse MR analysis showed that there was no significant causal relationship between AIT and anxiety disorder, depression, and bipolar disorder (P > 0.05).

CONCLUSIONS

The results of the forward MR analysis suggest a positive association between depression, and AIT risk, while indicating no support for a causal link between anxiety disorder or bipolar disorder and AIT risk based on the current data. Subsequent studies will be essential for elucidating the biological mechanisms and potential confounders underlying these associations.

Vitamin C and suicidal ideation: A cross-sectional and Mendelian randomization study

BACKGROUND

Studies have shown that a history of suicide attempts is associated with low levels of antioxidant vitamins. However, the specific relationship between vitamin C and suicidal ideation remains poorly understood. The purpose of this study is to investigate the effect of vitamin C on the development of suicidal ideation and to explore further the causal relationship using Mendelian randomization (MR).

METHODS

Using the 2005-2018 National Health and Nutrition Examination Survey (NHANES) dataset, a comprehensive, cross-sectional, stratified survey of 28,623 participants aged 20 years and older was conducted. Suicidal ideation was assessed using item 9 of the Patient Health Questionnaire-9 (PHQ-9) item. The relationship between vitamin C and suicidal ideation was revealed by weighted multiple linear regression, smooth curve fitting, hierarchical analysis, and interaction test. To determine causality, MR was performed on vitamin C and suicidal ideation.

RESULTS

In cross-sectional studies, all models showed a negative association between vitamin C and suicidal ideation, with a 37 % reduction in the risk of suicidal ideation for each unit increase in vitamin C in the highest quartile in the fully adjusted model. The results of the subgroup analysis showed that the association between vitamin C and suicidal ideation was stable across gender, age, education, smoking status, and marital status. In the MR study, our bivariate model showed no significant causal relationship between vitamin C and the development of suicidal ideation.

CONCLUSIONS

Dietary vitamin C intake was negatively associated with the development of suicidal ideation. However, genetic evidence does not support causation of these associations.

Effect of iron status on myocardial infarction: A two-sample Mendelian randomization study

Background

In observational studies, connections have been identified between iron status and myocardial infarction (MI). The significance of changes in iron status as either a risk factor or a result of MI remains unclear.

Methods

We obtained our instrumental variables from a meta-analysis of three GWASs in Iceland, the UK, and Denmark, which discovered 62 independent sequence variants across 56 loci linked to blood iron levels, ferritin, total iron binding capacity (TIBC), transferrin saturation (TSAT), and the Genetics of Iron Status (GIS) database for transferrin. To evaluate the connection between iron status markers and myocardial infarction (MI), we used three GWAS datasets focused on MI outcomes. The chosen datasets included one representing the European population (ebi-a-GCST011364: n case = 14,825, n control = 380,970; finn-b-I9_MI: n case = 12,801, n control = 187,840) and another with a mixed population (ieu-a-798: n case = 43,676, n control = 128,199). The primary method used in our study was inverse variance-weighting, while we also assessed heterogeneity and horizontal pleiotropy to enhance the robustness of our findings.

Results

The main analysis with the inverse variance-weighted method showed no significant impact of iron marker levels on MI risk in the ebi-a-GCST011364 and finn-b-I9-MI cohorts. In contrast, the ieu-a-798 cohort indicated that higher ferritin levels had a protective effect against MI (OR = 0.87, 95 % CI 0.78-0.98, P = 0.03). Additionally, TSAT showed an association with decreased MI risk (OR = 0.91, 95 % CI 0.84-0.98, P = 0.01). No significant correlations were observed for other iron status traits examined in this study. Evaluations of horizontal pleiotropy and heterogeneity showed no abnormalities, further strengthening the reliability of our results.

Conclusions

Our multi-cohort MR analysis suggests a potential protective effect of higher ferritin levels and TSAT against MI risk. These findings contribute to our understanding of the relationship between iron status markers and cardiovascular health, offering insights for future research and potential therapeutic interventions.

The causal association between asthma and the risk of frailty: A two-sample Mendelian randomization study

BACKGROUND

The correlation between asthma and frailty is increasingly garnering attention. The association between asthma and frailty remains inconclusive in observational studies, and the causality of this relationship still needs to be established.

AIMS

Therefore, we employed two-sample Mendelian randomization analyses using genetic instruments to determine the causal association of asthma on frailty.

METHODS

Two-sample Mendelian randomization (MR) analyses were performed to assess the causal effect of asthma on frailty. The genetic variants strongly associated with asthma (P < 5E-08) during the discovery and replication stages were derived from a recent meta-analysis of genome-wide association studies (GWAS) (N = 408,442) in the UK Biobank and a GWAS in the FinnGen Consortium (N = 217,421), respectively. Summary statistics of the frailty index (N = 175,226) are derived from the latest released GWAS dataset on frailty index. The inverse variance weighted (IVW) method was employed as the primary approach for calculating estimated values, with additional sensitivity analyses and heterogeneity analyses utilized to further validate the results.

RESULTS

Using the IVW method, genetic susceptibility to asthma was associated with an increased risk of frailty in the discovery stage (odds ratio [OR] = 1.092, 95% confidence interval [CI] = 1.075-1.109, P = 5.00E-28), which was also validated in the replication stage (OR = 1.073, 95% CI = 1.052-1.096, P = 1.41E-11). Sensitivity analyses yielded consistent causal estimate, and no significant pleiotropy was found throughout the MR study.

CONCLUSION

The present study demonstrated that asthma is causally associated with an elevated risk of frailty. Further studies are needed to elucidate the potential pathophysiological mechanisms between asthma and frailty.

Exploring the associations of plasma proteins with frailty based on Mendelian randomization

BACKGROUND

Frailty is an emerging global burden of disease, characterized as an age-related clinical syndrome. Recent studies have suggested a potential link of circulating protein levels with the onset of frailty. This study aims to analyze the potential causal relationships of plasma proteins with frailty using a Mendelian Randomization (MR) study design.

METHODS

Associations of plasma proteins with frailty were assessed using inverse variance weighted (IVW), MR-Egger regression, weighted median, maximum-likelihood method, and MR-PRESSO test. Protein-protein interaction network construction and gene ontology functional enrichment analysis were conducted based on MR-identified target proteins.

RESULTS

After false discovery rate (FDR) correction, MR analysis identified five plasma proteins, including BIRC2 [OR = 0.978, 95%CI (0.967-0.990)] and PSME1 [OR = 0.936, 95%CI (0.909-0.965)], as protective factors against frailty, and 49 proteins, including APOB [OR = 1.053, 95%CI (1.037-1.069)] and CYP3A4 [OR = 1.098, 95%CI (1.068-1.128)], as risk factors. Network analysis suggested BIRC2, PSME1, APOE, and CTNNB1 as key intervention targets.

CONCLUSION

This study employed MR design to investigate the association of circulating plasma proteins with frailty, identified five proteins negatively associated with frailty risk and 49 proteins positively associated with frailty.

Dietary salt intake is not associated with risk of stroke: A Mendelian randomization study

Previous studies have demonstrated a correlation between dietary salt intake and stroke; however, there was a lack of conclusive evidence regarding a causal connection between them. We undertook a two-sample Mendelian randomization (MR) study to examine their potential association. The genome-wide data for dietary salt intake was sourced from genome-wide association study that involved 462,630 samples. Genetic instruments for stroke were also obtained from genome-wide association study, which included 446,696 samples. Both samples were from European. The inverse variance weighting was used as the main method in MR analysis. We also performed several complementary MR methods, including MR-Egger, position weighted median, simple model, and weighted model. Our results showed that there was no causal relationship between dietary salt intake and stroke, which was genetically determined (fixed-effects inverse variance weighted: odds ratio, 0.95; 95% confidence interval, 0.74-1.21; P  = .67). Neither Cochran Q test (P = .52) nor MR-Egger method (P = .48) found obvious heterogeneity; in addition, the MR pleiotropy residual sum and outliers global test (P = .52) and MR-Egger regression intercept (P = .74) also showed no pleiotropy. The result of our MR study showed that there was no direct causal relationship between dietary salt intake and stroke risk. More studies were required to further confirm the stability of this relationship and to trying applied the findings to the clinic.

The adverse effect of mood swings on the risk of cardiovascular diseases: Evidence from Mendelian randomization analysis

Recent studies have explored the impact of personality traits, including mood swings, on physical health. However, it remains unclear whether there is a direct cause-and-effect link between mood swings and cardiovascular diseases (CVDs). A STROBE-compliant cross-sectional observational study was conducted and analyzed using a two-sample Mendelian randomization (MR) approach to examine the potential causal relationship between mood swings and a range of CVDs, such as arrhythmia, artery aneurysm, coronary heart disease (CHD), heart failure, hypertension, stroke, ischemic stroke, and peripheral artery disease. We sourced genome-wide association studies (GWAS) summary data for mood swings from the UK Biobank, and for CVDs from the GWAS Catalog and FinnGen databases. We excluded single-nucleotide polymorphisms (SNPs) linked to potential confounders such as obesity, smoking, sex, diabetes, as well as SNPs suspected of horizontal pleiotropy, as identified by MR-PRESSO and the MR-pleiotropy method, prior to the final analysis. Sensitivity analyses were conducted using the MR-Egger, inverse variance weighted, and leave-one-out methods. After screening, 57 SNPs were identified as instrumental variables for mood swings, and 9 SNPs related to confounding factors were excluded. An increase in mood swing frequency is correlated with a significant increase in the likelihood of various conditions. Notably, arrhythmia in the FinnGen dataset showed an odds ratio (OR: 2.28, 95% confidence interval [CI]: 1.44-3.61, P < .001), and atrial fibrillation had an OR (OR: 2.25, 95% CI: 1.23-4.11, P = .01). CHD risk was elevated in both the IEU OpenGWAS project (OR: 2.05, 95% CI: 1.30-3.21, P < .001) and GWAS Catalog (OR: 4.45, 95% CI: 1.75-11.33, P < .001). Increased risks were also noted for heart failure (GWAS Catalog: OR: 1.75, 95% CI: 1.09-2.83, P = .02) and hypertension (FinnGen: OR, 2.17; 95% CI: 1.47-3.19, P < .001). However, no significant associations were found for conditions such as arterial aneurysms or ischemic stroke. In combined analyses, mood swings were associated with a higher risk of CHD (OR: 2.21, 95% CI: 1.64-2.97, P < .01), heart failure (OR: 1.74, 95% CI: 1.21-2.50, P < .01), and other CVDs. This study revealed a causal link between mood swings and various CVDs, highlighting intriguing findings. This suggests that implementing proper psychological interventions to stabilize mood may be beneficial for preventing negative cardiovascular events.

Association between thyroid dysfunction and diabetic retinopathy: a two-sample bidirectional Mendelian randomization study

OBJECTIVES

To assess the association between thyroid dysfunction and diabetic retinopathy (DR), a two-sample bidirectional Mendelian randomization (MR) study utilizing the Genome-wide Association Study (GWAS) database was conducted to investigate the causal relationship between these two variables.

METHODS

In this study, GWAS of 48,328,151 single nucleotide polymorphisms(SNP) in the European population from the IEU open GWAS database were utilized as genetic tools for investigating thyroid dysfunction. The total sample size for the study on hyperthyroidism was 460,499 (case group: 3557; control group: 456,942). The total sample size for hypothyroidism was 410,141 (case group: 30,155; control group: 37,986). In addition, the data on DR were extracted from the FinnGen Biobank, comprising a total sample size of 319,046 individuals (10,413 cases and 308,633 controls). For the forward MR analysis, hyperthyroidism and hypothyroidism were considered as exposures with DR as the outcome. Reverse MR analysis was conducted using DR as exposure and hyperthyroidism and hypothyroidism as outcomes.

METHODS

The main analytical approach employed inverse variance weighting(IVW), supplemented by MR-Egger, Weighted mode method, weighted median, and Simple mode. Cochran's Q test, MR-PRESSO, MR-Egger and leave-one-out analysis were used to evaluate the sensitivity and pleiotropy.

RESULTS

Two-sample bidirectional MR analysis revealed a significant association between the presence of hyperthyroidism and hypothyroidism and an increased risk of DR in the forward MR analysis (IVW: OR = 1.29, 95% [CI] = 1.12-1.49, P < 0.001; OR = 1.17, 95% CI = 1.10-1.25, P < 0.001). In the reverse MR analysis, DR was found to be associated with an elevated risk of developing hyperthyroidism and hypothyroidism (IVW: OR = 1.56, 95% CI 1.38-1.76, P < 0.001; OR = 1.41, 95% CI 1.25-1.59, P < 0.001). Furthermore, most supplementary MR methods also demonstrated statistically significant differences and exhibited effect sizes consistent with those obtained from IVW. The sensitivity analysis confirmed the relative reliability of our causal findings.

CONCLUSIONS

Our findings provide genetic evidence supporting a bidirectional causal relationship between thyroid function and DR.

Causal relationships between depression, emotional changes, and hiatal hernia: A Mendelian randomization analysis

Hiatal hernia (HH) is a common gastrointestinal disorder characterized by the displacement of abdominal contents, particularly the stomach, into the thoracic cavity. This condition is frequently associated with gastroesophageal reflux disease (GERD) and can lead to various symptoms, including chronic cough and respiratory issues. Despite its prevalence, the mechanisms linking psychological factors to HH are not well understood. Observational studies have suggested correlations between mental health issues - such as stress, anxiety, and depression - and gastrointestinal disorders, indicating that emotional states may influence the development of HH. This study aims to clarify the causal relationships between mood swings, depression, and the risk of developing HH using Mendelian randomization (MR), a robust method that utilizes genetic variants as instrumental variables (IVs) to infer causality. Data for this MR analysis were obtained from publicly available genome-wide association studies (GWAS). We employed a bidirectional, 2-sample MR approach, using IVs associated with mood swings, depression, feelings of tension, and feelings of misery as exposures, with HH as the outcome. A reverse MR analysis was also conducted, treating HH as the exposure and the aforementioned emotional states as outcomes. The primary analytical method used was inverse variance weighting (IVW), supplemented by sensitivity analyses, including MR-Egger and weighted median methods. Our analysis revealed significant associations: mood swings (OR = 1.014; 95% CI = 1.001-1.027; P = .032), depression (OR = 1.019; 95% CI = 1.006-1.033; P = .003), feelings of tension (OR = 1.012; 95% CI = 1.004-1.020; P = .001), and feelings of misery (OR = 1.007; 95% CI = 1.003-1.010; P = .0001) significantly increased the risk of HH. Importantly, reverse MR analysis indicated no causal influence of HH on these emotional states. This study provides evidence that mood swings, depression, feelings of tension, and feelings of misery are significant risk factors for developing HH. These findings highlight the need to address psychological factors in the clinical management and prevention strategies for HH, potentially improving patient outcomes.

Picolinate-mediated immunomodulation: insights from Mendelian randomization on the role of NK cell percentage in the pathogenesis of lichen planus

Background

Lichen planus (LP), an autoimmune disorder, remains incompletely understood in terms of its etiological mechanisms. This study aims to elucidate causal relationships among immune cell populations, plasma metabolites, and lichen planus using Mendelian randomization (MR) techniques.

Methods

Employing a two-sample, two-step MR approach, with single nucleotide polymorphisms (SNP) serving as genetic instruments for both exposures and mediators, this study minimizes biases from confounding and reverse causality. Leveraging summary statistics from genome-wide association studies (GWAS) involving 731 immune cell traits (N = 3757), 1091 plasma metabolite traits (N = 8299), and lichen planus (N = 367668), inverse variance weighting (IVW) is adopted as the primary MR analytical method. The total effect of immune cells traits on LP is decomposed into direct and indirect effects mediated by plasma metabolites.

Results

MR analysis reveals causal associations for 28 immune cell traits and 38 plasma metabolites with LP (PIVW < 0.05). Specifically, NK % lymphocyte shows a negatively correlated causal effect with LP (ORIVW = 0.952; 95% CI: [0.910, 0.995], PIVW = 0.030). Among mediators, Picolinate significantly contributes, explaining 16.4% (95% CI: [28.3%, 4.54%]) of the association between NK % lymphocyte and LP.

Conclusion

These findings support a potential protective causal effect of NK % lymphocyte on LP, partially mediated by Picolinate levels. Thus, interventions targeting Picolinate levels may mitigate LP burden attributed to low NK % lymphocyte counts. This study provides new evidence and insights into the pathogenesis of lichen planus, advancing our understanding of its underlying mechanisms.

Causal association between sarcopenia and cognitive impairment contributes to the muscle-brain axis: A bidirectional Mendelian randomization study

AIM

There is a growing body of evidence suggesting a correlation between sarcopenia (SP) and cognitive impairment (CI), but with conflict. This study employed a bidirectional Mendelian randomization (MR) approach to ascertain the causality between SP and CI.

METHOD

This study looked at whether there might be causality between SP and CI by using a bidirectional MR analysis on the GWAS summary datasets, which anyone can publicly access. The primary analysis employed inverse variance weighting (IVW), with MR-Egger, weighted median, and mendelian randomization pleiotropy residual sum and outlier (MR-PRESSO) serving as supplements. Multiple sensitivity analyses were performed to enhance the stability of the results, which encompassed heterogeneity tests and pleiotropy tests.

RESULTS

Appendicular lean mass (ALM), walking pace (WP), and grip strength (GS) were found to be causally connected to cognitive performance in forward MR analysis. In the reverse MR study, cognitive performance also had a causal impact on ALM and WP. Additionally, we discovered comparable outcomes in the replication samples, which strengthens the validity of our findings.

CONCLUSIONS

The results of our MR investigation revealed a definitive cause-and-effect association between SP and CI. Our findings provide additional supporting evidence for the muscle-brain axis, which may suggest that muscle strengthening has a significant impact on the management and avoidance of CI. Geriatr Gerontol Int 2024; ••: ••-••.

Association between hypothyroidism and obstructive sleep apnea: a bidirectional Mendelian randomization study combined with the geo database

Background

The causal relationship between hypothyroidism and obstructive sleep apnea (OSA) remains controversial. Therefore, our research used a bidirectional Mendelian randomization (MR) method in an attempt to determine the causal relationship between hypothyroidism and OSA.

Methods

From the publicly accessible genome-wide association analysis (GWAS) summary database, we obtained single nucleotide polymorphism (SNPs) data pertaining to hypothyroidism and OSA. Inverse variance weighting (IVW) was the principal method of analysis utilized, with validation also conducted via weighted median, MR-Egger, simple model, and weighted model approaches. To further evaluate the robustness of the results, heterogeneity testing, pleiotropy testing, and the "leave-one-out" sensitivity analysis were performed. Differentially expressed genes (DEGs) from the OSA dataset (GSE135917) and hypothyroidism dataset (GSE176153) derived from the Gene Expression Omnibus (GEO) database were screened using the "limma" package. The "clusterProfiler" and "GO plot" packages were used for further enrichment analysis in order to validate the findings of the MR study. The Cytoscape software was utilized to build a protein-protein interaction (PPI) network of DEGs and to screen for hub genes.

Results

The MR analysis showed that genetically predicted hypothyroidism was associated with an increased risk of OSA [IVW odds ratio (OR) = 1.734; 95% confidence interval (CI) = 1.073-2.801; p = 0.025]. The trend of the outcomes of the other approaches is consistent with the trend of the IVW outcome. However, the reverse MR analysis suggested no evidence for the causal effect of OSA on hypothyroidism (IVW OR = 1.002, 95% CI: 0.996-1.009, p = 0.454). The robustness of the results was confirmed by the sensitivity analysis. Bioinformatics analysis revealed that there were DEGs that hypothyroidism and OSA have in common.

Conclusion

Our findings suggested that hypothyroidism may increase the risk of OSA, while the effect of OSA on hypothyroidism was not found in this MR study. Thus, patients with hypothyroidism should be enhanced with screening for OSA for early diagnosis and appropriate treatment.

Genetic determinants of telomere length and risk of aneurysmal subarachnoid hemorrhage: a bidirectional two-sample mendelian randomization study

BACKGROUND

Our objective is to investigate the potential causal relationship between telomere length (TL) and aneurysmal subarachnoid hemorrhage (aSAH) and intracranial aneurysms (IAs) by conducting a bidirectional two-sample Mendelian Randomization (MR) study.

METHODS

We utilized publicly available summary data from genome-wide association studies (GWAS) for comprehensive analysis. Telomere length-associated data were sourced from the Epidemiology Unit (IEU) GWAS database (n = 472,174), while data pertaining to intracranial aneurysms were derived from a GWAS meta-analysis conducted by Bakker et al. encompassing aneurysmal subtypes including aSAH (n = 77,074), IAs (n = 79,429), and unruptured intracranial aneurysms (uIA) (n = 74,004), all sampled from European populations. The primary method for MR analysis employed was the Inverse Variance Weighted (IVW) method. Additionally, we conducted various sensitivity analyses to assess the heterogeneity and pleiotropy of study findings. Reverse MR analysis was employed to explore potential reverse causality.

RESULTS

In the forward MR analysis, the IVW method indicated a negative association between TL and aSAH (OR = 0.636, 95% CI: 0.459-0.883, p = 0.006) as well as IAs (OR = 0.670, 95% CI: 0.499-0.900, p = 0.0079). There was no evidence of heterogeneity or horizontal pleiotropy in the forward MR analysis. Reverse MR analysis did not reveal any causal relationship between aSAH, IAs, uIA and TL.

CONCLUSIONS

In European populations, there exists a causal relationship between longer TL and reduced risks of aSAH and IAs Further research is warranted to elucidate the underlying mechanisms and the potential of TL as an intervention target for lowering the incidence of aSAH and IAs.

Effect of different types of milk consumption on Crohn's disease and the mediating effect of amino acids: a Mendelian randomization study

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

Mendelian randomization study of causal link from Cerebrospinal fluid metabolomics to neurodegenerative diseases

To investigate the causal relationships between cerebrospinal fluid (CSF) metabolites and various neurodegenerative diseases (NDDs), we conducted a two-sample Mendelian randomization (MR) analysis. This study utilized summary statistics from genome-wide association studies (GWAS) of CSF metabolites and four common neurodegenerative diseases: Alzheimer's disease (AD), Parkinson's disease (PD), multiple sclerosis (MS), and amyotrophic lateral sclerosis (ALS). MR methods were employed to determine causal associations, with the inverse variance weighted method as the primary approach. Additionally, different GWAS summary data for NDDs were used to validate the initial results and perform sensitivity analyses to enhance the robustness of the findings. Finally, reverse MR analyses were conducted to assess the possibility of reverse causation. Combining results from the initial and replication phases of MR analysis, we identified potential causal relationships between various CSF metabolites and different NDDs. Specifically, we found potential causal relationships between five CSF metabolites and AD, six CSF metabolites and MS, and thirteen CSF metabolites and ALS. Further sensitivity analyses confirmed the robustness of these associations. Reverse MR analysis indicated causal effects of AD on glucuronate and ALS on acetylcarnitine (C2). Our study, through genetic means, demonstrates close causal associations between the specific types of CSF metabolites and the risk of NDDS (AD, PD, MS, and ALS), providing useful guidance for future clinical researches.

Exploring the relationship between gut microbiota, immune characteristics, and female genital tract polyps using genetic evidence

The study investigates the causal relationship between gut microbes and female genital tract polyps, exploring the potential mediating role of immune cells via Mendelian randomization (MR) analysis. Our MR study was designed following the STROBE-MR guidelines. We combined data from a large-scale GWAS meta-analysis, including 731 immune profiles and female genital tract polyps, with gut microbiology data sourced from the MiBioGen consortium. Univariate Mendelian randomization was employed to identify gut microbes and immune profiles significantly associated with female genital tract polyps causally. A 2-step MR analysis was utilized to investigate the potential mediating role of immune cells. Furthermore, we utilized the multivariable MR approach based on Bayesian model averaging (MR-BMA) to further assess the prioritization of gut microbiota vs immune characteristics in the development of female genital tract polyps. Through univariate MR analysis, we identified a significant causal link between 12 gut microbiota, 31 immune features, and female genital tract polyps. Four causal pathways involving gut microbiota, immune cells, and polyps were identified among them. MR-BMA analysis indicated marginal inclusion probability (MIP) values exceeding 0.1 for 5 gut microbiota groups: Victivallaceae (model-averaged causal estimate [MACE] = 0.060, MIP = 0.581, P = .0089), Ruminococcus gautreuii (MACE = 0.052, MIP = 0.346, P = .0640), Lachnoclostrium (MACE = 0.0380, MIP = 0.225, P = .1875), Alphaprobacter (MACE = 0.0186, MIP = 0.140, P = .3934), and Fusicatenibacter (MACE = 0.013, MIP = 0.110, P = .5818). Six immune features exhibit high priority, with MIP values exceeding 0.5, including HLA DR on CD33+ HLA DR+ CD14dim (MACE = -0.015, MIP = 0.753, P = .0853), HVEM on naive CD4+ T cell (MACE = 0.024, MIP = 0.737, P = .0053), CD80 on CD62L+ plastic cytoplasmic dendritic cell (MACE = 0.024, MIP = 0.721, P = .0228), CD28 on activated and secret CD4 regulatory T cell (MACE = 0.0054, MIP = 0.706, P = .3245), HLA DR on CD14+ CD16 monocyte (MACE = -0.0003, MIP = 0.520, P = .7927), HLA DR on CD14+ monocyte (MACE = -0.0029, MIP = 0.509, P = .5576). Our research indicates that gut microbiota exerts an independent causal influence on female genital tract polyps, potentially impacting them via various immune cells.

Exploring the causal link between serum amino acids and Parkinson's disease: a Mendelian randomization approach

This study aimed to explore the causal relationships between multiple blood amino acids (BAAs) and the Parkinson's disease (PD). We downloaded genome-wide association study (GWAS) data for BAAs and PD from the OpenGWAS database, screened single nucleotide polymorphisms (SNPs) from the data, and evaluated the causal relationship between BAA levels and PD using the inverse variance weighted (IVW) method. The sensitivity analysis was also conducted. After SNP screening, three amino acid indicators were identified: met-a-308 (phenylalanine), met-a-584 (X-12100 hydroxytryptophan), and met-a-337 (5-hydroxyproline), which showed significant causal relationship with the occurrence of PD. There was no significant heterogeneity or horizontal pleiotropy, and the results were stable. The multivariate MR analysis showed that the mediating effects generated by the introduction of multiple variables were not significant. In conclusion, phenylalanine, X-12,100 hydroxytryptophan, and 5-hydroxyproline have a causal relationship with the occurrence of PD and may be potential early screening biomarkers and blocking targets.

Role of metabolites in mediating the effect of triacylglycerol on aplastic anemia

BACKGROUND

Observational studies have found a link between lipid metabolism disorders and aplastic anemia (AA). However, due to confounding variables and reverse causation, it is difficult to conclude such a causal link. The precise mechanism and potential implications of lipid metabolism disorder in AA remain unclear, necessitating further studies in this area.

METHOD

This study aimed to examine the causal relationship between 38 different subtypes of triacylglycerols and AA using two-sample Mendelian randomization (MR). Additionally, two-step MR analyses were conducted to investigate the mediating effects of vitamin A to oleoyl-linoleoyl-glycerol (18:1-18:2) ratio.

RESULTS

MR analysis showed that triacylglycerol (53:3) levels were positively associated with the risk of AA [inverse variance weighting (IVW): odds ratio (OR) = 1.131,95% confidence interval (CI):1.029-1.243, P = 0.011; Bayesian weighted MR (BWMR): OR = 1.137,95% CI:1.031-1.254, P = 0.010]. Triacylglycerol (53:3) level showed no inverse causality with AA (IVW:P = 0.834; BWMR:P = 0.349). Mediation analyses showed that increasing the vitamin A to oleoyl-linoleoyl-glycerol (18:1-18:2) ratio can decrease the risk of AA.

CONCLUSION

This study revealed the association between vitamin A to oleoyl-linoleoyl-glycerol (18:1-18:2) ratio, triacylglycerol (53:3) levels and AA, and indicated that lowering triacylglycerol (53:3) levels can reduce the risk of AA.

Inflammatory cytokines and carpal tunnel syndrome: A causal relationship revealed

OBJECTIVES

Carpal tunnel syndrome (CTS) and certain inflammatory cytokines have been linked in observational studies; however, the exact causative linkages remain unknown. The purpose of this study is to investigate any possible link between the onset of CTS and 91 inflammatory cytokines.

METHODS

A two-sample bidirectional Mendelian randomization (MR) approach was used in this investigation. 91 circulating inflammatory cytokines' genetic variants were retrieved from the European ancestry genome-wide association study (GWAS) database. From germline GWAS, summary data for 24,766 CTS patients and 360,538 controls were gathered. The instrumental variables were single nucleotide polymorphisms (SNPs) that were highly correlated with the 91 inflammatory cytokines. The random-effects inverse-variance weighted (IVW) approach was employed in the primary analysis, and multiple comparisons were subjected to the Bonferroni correction. Sensitivity analysis was performed to evaluate the validity of the causal relationship.

RESULTS

Our findings showed a negative correlation between CCL19, FGF-19, IL-5, TGF-alpha, TRAIL, and the risk of CTS. Specifically, CCL19 (odds ratio [OR]: 0.944, 95 % confidence interval [CI]: 0.894-0.996, p = 0.0349), FGF-19 (OR: 0.940, 95 % CI: 0.894-0.987, p = 0.0133), IL-5 (OR: 0.936, 95 % CI: 0.885-0.990, p = 0.0212), TGF-alpha (OR: 0.902, 95 % CI: 0.838-0.970, p = 0.0057), and TRAIL (OR: 0.926, 95 % CI: 0.881-0.974, p = 0.0026) were inversely related to CTS risk. Conversely, CCL20, IL-2RB, and IL-6 were positively associated with an increased risk of CTS. Specifically, CCL20 (OR: 1.072, 95 % CI: 1.005-1.142, p = 0.0334), IL-2RB (OR: 1.067, 95 % CI: 1.001-1.137, p = 0.0463), and IL-6 (OR: 1.088, 95 % CI: 1.005-1.177, p = 0.0365) were positively correlated with CTS risk. Reverse Mendelian randomization analyses indicated no evidence of a reverse causal relationship between CTS and inflammatory cytokines.

CONCLUSION

According to this study, there is a causal link between CTS and certain inflammatory cytokines, which suggests that these cytokines may be important in the pathophysiology of CTS. To confirm these results and investigate the specific function of these cytokines in the beginning and development of CTS, more investigation is necessary.

Absence of Causal Relationship Between Levels of Unsaturated Fatty Acids and ADHD: Evidence From Mendelian Randomization Study

OBJECTIVE

Previous research suggests a potential link between unsaturated fatty acids (UFAs) and ADHD, but the causal relationship remains uncertain. This study aims to investigate the causal association between ADHD and UFAs using Mendelian randomization (MR) analysis.

METHODS

Summary data from genome-wide association studies were used to estimate the concentration of circulating UFAs, including Monounsaturated Fatty Acids (MUFAs), Polyunsaturated Fatty Acids (PUFAs), Omega-3 PUFAs, Omega-6 PUFAs, Linoleic Acid (LA), and Docosahexaenoic Acid (DHA). Data from the Psychiatric Genomics Consortium, including both childhood and adult ADHD, were respectively used to examine the relationship between genetically predicted UFAs levels and ADHD. Various MR methods, including Inverse-variance weighted (IVW), MR Pleiotropy RESidual Sum and Outlier, MR-Egger, weighted median, and weighted mode, were employed to assess heterogeneity and pleiotropy.

RESULTS

The IVW revealed only nominal evidence suggesting a potential causal relationship between genetically predicted PUFAs (OR = 0.92, 95% CI [0.85, 0.99], p = .031), Omega-6 PUFAs (OR = 0.90, 95% CI [0.83, 0.98], p = .020), and LA levels (OR = 0.90, 95% CI [0.82, 0.98], p = .021) with childhood ADHD risk. However, after false discovery rate correction, the p-values for PUFAs, Omega-6 PUFAs, and LA levels all exceeded the threshold for significance. For adult ADHD, we did not find any significant associations between the six circulating UFA levels and adult ADHD.

CONCLUSION

Our findings do not support a causal relationship between UFAs levels and ADHD. This suggests that UFAs supplements may not be effective in improving ADHD symptoms and importantly, it appears that UFAs levels may not have a long-term effect on ADHD.

Exploring Genetic Association of Tea Intake With Allergic Diseases Among European Population: A Bidirectional Mendelian Randomization Study

Previous observational studies focused on the association of tea intake and allergic diseases. However, it is not known whether these associations are causal. We used a bidirectional Mendelian randomization (MR) study to assess the causal relationship of tea intake with the risk of allergic diseases, such as atopic dermatitis (AD), allergic rhinitis (AR), and allergic asthma (AA). Single-nucleotide polymorphisms (SNPs) which had genetic statistical significance with tea intake were used as instrumental variables (IVs). We employed heritable IVs of tea intake from the UK Biobank, which included 447,485 samples. Sensitivity analyses were further performed using MR Egger and MR-PRESSO. Inverse variance weighted (IVW) method was used as the main approach. In this MR study, 40 independent SNPs were selected for tea intake. The MR analysis revealed that an increase in genetically predicted tea intake was associated with a lower risk of AD (OR = 0.709, 95% CI = 0.546-0.919, p = 0.009). Furthermore, we observed a causal effect of genetically predicted tea intake on the risk of AA (OR = 0.498, 95% CI = 0.320-0.776, p = 0.002). However, no significant causal relationship was found between genetically predicted tea intake and AR (OR = 1.008, 95% CI = 0.998-1.017, p = 0.115). Our MR analysis suggested that increased tea intake may reduce the risk of AD and AA in European population. This suggests that tea intake is likely a trigger or a prevention strategy for AD and AA.

Causal relationship between imaging-derived phenotypes and neurodegenerative diseases: a Mendelian randomization study

Neurodegenerative diseases are incurable conditions that lead to gradual and progressive deterioration of brain function in patients. With the aging population, the prevalence of these diseases is expected to increase, posing a significant economic burden on society. Imaging techniques play a crucial role in the diagnosis and monitoring of neurodegenerative diseases. This study utilized a two-sample Mendelian randomization (MR) analysis to assess the causal relationship between different imaging-derived phenotypes (IDP) in the brain and neurodegenerative diseases. Multiple MR methods were employed to minimize bias and obtain reliable estimates of the potential causal relationship between the variable exposures of interest and the outcomes. The study found potential causal relationships between different IDPs and Alzheimer's disease (AD), Parkinson's disease (PD), amyotrophic lateral sclerosis (ALS), multiple sclerosis (MS), and frontotemporal dementia (FTD). Specifically, the study identified potential causal relationships between 2 different types of IDPs and AD, 8 different types of IDPs and PD, 11 different types of imaging-derived phenotypes and ALS, 1 type of IDP and MS, and 1 type of IDP and FTD. This study provides new insights for the prevention, diagnosis, and treatment of neurodegenerative diseases, offering important clues for understanding the pathogenesis of these diseases and developing relevant intervention strategies.

Causal association and shared genetics between telomere length and COVID-19 outcomes: New evidence from the latest large-scale summary statistics

Background

Observational studies suggested that leukocyte telomere length (LTL) is shortened in COVID-19 patients. However, the genetic association and causality remained unknown.

Methods

Based on the genome-wide association of LTL (N = 472,174) and COVID-19 phenotypes (N = 1086,211-2597,856), LDSC and SUPERGNOVA were used to estimate the genetic correlation. Cross-trait GWAS meta-analysis, colocalization, fine-mapping analysis, and transcriptome-wide association study were conducted to explore the shared genetic etiology. Mendelian randomization (MR) was utilized to infer the causality. Upstream and downstream two-step MR was performed to investigate the potential mediating effects.

Results

LDSC identified a significant genetic association between LTL and all COVID-19 phenotypes (rG < 0, p < 0.05). Six significant regions were observed for LTL and COVID-19 susceptibility and hospitalization, respectively. Colocalization analysis found rs144204502, rs34517439, and rs56255908 were shared causal variants between LTL and COVID-19 phenotypes. Numerous biological pathways associated with LTL and COVID-19 outcomes were identified, mainly involved in -immune-related pathways. MR showed that longer LTL was significantly associated with a lower risk of COVID-19 severity (OR [95% CI] = 0.81 [0.71-0.92], p = 1.24 ×10-3) and suggestively associated with lower risks of COVID-19 susceptibility (OR [95% CI] = 0.96 [0.92-1.00], p = 3.44 ×10-2) and COVID-19 hospitalization (OR [95% CI] = 0.89 [0.80-0.98], p = 1.89 ×10-2). LTL partially mediated the effects of BMI, smoking, and education on COVID-19 outcomes. Furthermore, six proteins partially mediated the causality of LTL on COVID-19 outcomes, including BNDF, QPCT, FAS, MPO, SFTPB, and APOF.

Conclusions

Our findings suggested that shorter LTL was genetically associated with a higher risk of COVID-19 phenotypes, with shared genetic etiology and potential causality.

The metabolome-wide signature of major depressive disorder

Major Depressive Disorder (MDD) is a common, frequently chronic condition characterized by substantial molecular alterations and pathway dysregulations. Single metabolite and targeted metabolomics platforms have revealed several metabolic alterations in depression, including energy metabolism, neurotransmission, and lipid metabolism. More comprehensive coverage of the metabolome is needed to further specify metabolic dysregulations in depression and reveal previously untargeted mechanisms. Here, we measured 820 metabolites using the metabolome-wide Metabolon platform in 2770 subjects from a large Dutch clinical cohort with extensive clinical phenotyping (1101 current MDD, 868 remitted MDD, 801 healthy controls) at baseline, which were repeated in 1805 subjects at 6-year follow up (327 current MDD, 1045 remitted MDD, 433 healthy controls). MDD diagnosis was based on DSM-IV psychiatric interviews. Depression severity was measured with the Inventory of Depressive Symptomatology Self-report. Associations between metabolites and MDD status and depression severity were assessed at baseline and at 6-year follow-up. At baseline, 139 and 126 metabolites were associated with current MDD status and depression severity, respectively, with 79 overlapping metabolites. Adding body mass index and lipid-lowering medication to the models changed results only marginally. Among the overlapping metabolites, 34 were confirmed in internal replication analyses using 6-year follow-up data. Downregulated metabolites were enriched with long-chain monounsaturated (P = 6.7e-07) and saturated (P = 3.2e-05) fatty acids; upregulated metabolites were enriched with lysophospholipids (P = 3.4e-4). Mendelian randomization analyses using genetic instruments for metabolites (N = 14,000) and MDD (N = 800,000) showed that genetically predicted higher levels of the lysophospholipid 1-linoleoyl-GPE (18:2) were associated with greater risk of depression. The identified metabolome-wide profile of depression indicated altered lipid metabolism with downregulation of long-chain fatty acids and upregulation of lysophospholipids, for which causal involvement was suggested using genetic tools. This metabolomics signature offers a window on depression pathophysiology and a potential access point for the development of novel therapeutic approaches.

The genetic causal association between arthritis and low back pain

Background

Arthritis and low back pain (LBP) are prevalent musculoskeletal conditions with a perceived association. Previous observational studies have suggested a possible link between arthritis and LBP, but causality has not been firmly established.

Methods

The analysis involved data from a meta-analysis of genome-wide association studies sourced from the UK Biobank Genetics resources on rheumatoid arthritis (RA), osteoarthritis (OA) at any site, knee osteoarthritis (KOA), hip osteoarthritis (HOA), and LBP. Two-sample Mendelian randomization analysis was utilized to evaluate the causal link between arthritis and LBP. The primary method employed was inverse-variance weighting (IVW), with additional techniques such as MR-Egger, weighted median, Cochran Q statistic, and leave-one-out analysis used to identify heterogeneity and pleiotropy.

Results

Genetically determined RA exhibited a causal impact on LBP (Weighted median: odds ratio [OR] = 1.094, 95% confidence interval [CI] 1.002-1.195, p = 0.043). Furthermore, OA at any site and KOA showed causal associations with LBP (Inverse variance weighted: OR = 1.089, 95% CI 1.011-1.173, p = 0.026) and (OR = 1.0004, 95% CI 1.000-1.008, p = 0.019), respectively. Additionally, HOA was also linked causally with an elevated risk of developing LBP (Weighted median: OR = 1.002, 95% CI 1.000-1.004, p = 0.049; Inverse variance weighted: OR = 1.002, 95% CI 1.001-1.004, p = 0.003).

Conclusions

This study offers genetic evidence supporting the causal relationship between RA, OA at any site, KOA, HOA and the increased risk of LBP, especially highlighting the significant impact of HOA.

Mendelian Randomization Study Investigating the Causal Relationship Between Thyroid Dysfunction and Cerebral Infarction

BACKGROUND

There is an association between thyroid dysfunction and cerebral infarction (CI), but the causality cannot be determined. A two-sample two-way Mendelian randomization (MR) study was conducted to assess the causal relationship between thyroid function and CI.

METHODS

We selected single-nucleotide polymorphisms (SNPs) associated with five phenotypes, including CI from the UK Biobank (n = 361,194), hyperthyroidism from the IEU Open GWAS database (n = 484,598), hypothyroidism from the IEU Open GWAS database (n = 473,703), normal thyroid-stimulating hormone (TSH) (n = 271,040), and normal free thyroxine (FT4) (n = 119,120) from the Thyroidomics Consortium database. For the forward MR analysis, the exposures were hyperthyroidism, hypothyroidism, TSH, and FT4. The inverse variance weighted (IVW) method, weighted median (WM), and MR-Egger revealed the causality with CI. For the reverse MR analysis, CI was regarded as the exposure, and four thyroid function phenotypes were the outcomes. The sensitivity and heterogeneity test was assessed using Cochran's Q test, MR-Egger regression, and leave-one-out analysis.

RESULTS

The MR analysis indicated that genetic susceptibility to hyperthyroidism increased the risk of CI (IVW-OR = 1.070; 95% CI: 1.015-1.128; p = 0.003). In reverse MR, genetic susceptibility to RA is not associated with hyperthyroidism (IVW-OR = 1.001; 95% CI: 1.000-1.001; p = 0.144). Any positive or reverse causal relationship between hypothyroidism, FT4, and TSH with CI could not be established. Sensitivity and heterogeneity test consolidated our findings.

CONCLUSION

The causality between CI and hyperthyroidism demonstrated patients with hyperthyroidism have a risk of genetic variants for CI. In the future, further studies are needed to fully explore their mechanisms of action.

Causal relationship between branched-chain amino acids and leukemia risk: insights from a two-sample Mendelian randomization study

BACKGROUND

Branched-chain amino acids (BCAAs), including leucine, isoleucine, and valine, are essential amino acids involved in protein synthesis, energy metabolism, and immune regulation. While BCAAs are known to influence cancer biology, their role in leukemia remains unclear. This study employs Mendelian randomization (MR) analysis to explore the causal relationship between BCAA levels and four leukemia subtypes: acute myeloid leukemia (AML), acute lymphoblastic leukemia (ALL), chronic lymphocytic leukemia (CLL), and chronic myeloid leukemia (CML).

METHODS

Data from genome-wide association studies (GWAS) were used to select single nucleotide polymorphisms (SNPs) as instrumental variables (IVs) for BCAA levels. The inverse-variance weighted (IVW) method served as the primary analytical approach, with heterogeneity assessed via Cochran's Q test and pleiotropy through MR-Egger intercept. Sensitivity analysis was performed using leave-one-out analysis.

RESULTS

A significant inverse association was observed between total BCAA levels, leucine, valine, and ALL risk. Total BCAA levels showed an odds ratio (OR) of 0.16 (95% CI: 0.05-0.54, p=0.003), leucine 0.17 (95% CI: 0.04-0.61, p=0.007), and valine 0.21 (95% CI: 0.07-0.61, p=0.004). No significant associations were found for AML, CLL, or CML.

CONCLUSION

This study suggests that BCAAs, particularly leucine and valine, may protect against ALL, offering insights into leukemia metabolic regulation and potential targets for prevention and therapy.

Mendelian randomization analysis revealed that albuminuria is the key factor affecting socioeconomic status in CKD patients

Previous studies indicate a strong correlation between the incidence of chronic kidney disease (CKD) and lower economic status. However, these studies often struggle to delineate a clear cause-effect relationship, leaving healthcare providers uncertain about how to manage kidney disease in a way that improves patients' financial outcomes. Our study aimed to explore and establish a causal relationship between CKD and socioeconomic status, identifying critical influencing factors. We utilized summary meta-analysis data from the CKDGen Consortium and UK Biobank. Genetic variants identified from these sources served as instrumental variables (IVs) to estimate the association between CKD and socioeconomic status. The presence or absence of CKD, estimated glomerular filtration rate (eGFR), and albuminuria were used as exposures, while income and regional deprivation were analyzed as outcomes. We employed the R packages 'TwoSampleMR' and 'Mendelianrandomization' to conduct both univariable and multivariable Mendelian randomization (MR) analyses, assessing for potential pleiotropy and heterogeneity. Our univariable MR analysis revealed a significant causal relationship between high levels of albuminuria and lower income (OR = 0.84, 95% CI: 0.73-0.96, p = 0.013), with no significant pleiotropy detected. In the multivariable MR analysis, both CKD (OR = 0.867, 95% CI: 0.786-0.957, p = 0.0045) and eGFR (OR = 0.065, 95% CI: 0.010-0.437, p = 0.0049) exhibited significant effects on income. This study underscores that higher albuminuria levels in CKD patients are associated with decreased income and emphasizes the importance of effective management and treatment of albuminuria in CKD patients to mitigate both social and personal economic burdens.

The effect of histo-blood group ABO system transferase (BGAT) on pregnancy related outcomes：A Mendelian randomization study

Protein level of Histo-Blood Group ABO System Transferase (BGAT) has been reported to be associated with cardiometabolic diseases. But its effect on pregnancy related outcomes still remains unclear. Here we conducted a two-sample Mendelian randomization (MR) study to ascertain the putative causal roles of protein levels of BGAT in pregnancy related outcomes. Cis-acting protein quantitative trait loci (pQTLs) robustly associated with protein level of BGAT (P < 5 ×10-8) were used as instruments to proxy the BGAT protein level (N = 35,559, data from deCODE), with two additional pQTL datasets from Fenland (N = 10,708) and INTERVAL (N = 3301) used as validation exposures. Ten pregnancy related diseases and complications were selected as outcomes. We observed that a higher protein level of BGAT showed a putative causal effect on venous complications and haemorrhoids in pregnancy (VH) (odds ratio [OR]=1.19, 95% confidence interval [95% CI]=1.12-1.27, colocalization probability=91%), which was validated by using pQTLs from Fenland and INTERVAL. The Mendelian randomization results further showed effects of the BGAT protein on gestational hypertension (GH) (OR=0.97, 95% CI=0.96-0.99), despite little colocalization evidence to support it. Sensitivity analyses, including proteome-wide Mendelian randomization of the cis-acting BGAT pQTLs, showed little evidence of horizontal pleiotropy. Correctively, our study prioritised BGAT as a putative causal protein for venous complications and haemorrhoids in pregnancy. Future epidemiology and clinical studies are needed to investigate whether BGAT can be considered as a drug target to prevent adverse pregnancy outcomes.

Causal effects of genetically determined blood metabolites on asthma: a bidirectional Mendelian randomization study

OBJECTIVE

The observational association between blood metabolites and asthma has been extensively studied. However, it is still unclear whether this association is causal. In this study, we aimed to investigate the causal relationship between blood metabolites and asthma using a bidirectional Mendelian randomization (MR) analysis. Additionally, we aimed to explore the potential mechanisms underlying this relationship.

METHODS

The study design involved the use of genetic instruments as instrumental variables (IVs) to fulfill the assumptions of MR analysis. The data on 1,091 metabolites and 309 metabolite ratios were obtained from the Canadian Longitudinal Study on Aging (CLSA), while the data on asthma were obtained from the Integrative Epidemiology Unit (IEU) Open GWAS Project. Utilizing the inverse variance-weighted (IVW) method as the primary MR analysis approach, sensitivity tests were conducted to assess the reliability of the findings, which involved employing Cochran's Q and the MR-Egger intercept. Furthermore, Bayesian weighted MR was used to further test the robustness of the results. Additionally, pathway analysis was conducted to explore the metabolic explanations underlying asthma.

RESULT

In our study, a comprehensive MR Analysis identified 10 metabolites and 6 metabolite ratios significantly associated with the development of asthma (FDR < 0.05). The metabolites included glycerophosphocholines(GPCs), glycerophosphoethanolamines(GPEs), and an unknown metabolite. Of these, 1-arachidonoyl-GPC, 1-myristoyl-2-arachidonoyl-GPC, 1-palmitoyl-2-arachidonoyl-GPC, and 1-(1-enyl-palmitoyl)-2-arachidonoyl-GPC were associated with an increased risk of asthma, whereas 1,2-dilinoleoyl-GPC, 1-palmitoyl-2-linoleoyl-GPC, 1,2-dilinoleoyl-GPE, 1 - oleoyl - 2 - linoleoyl - GPE, 1-palmitoyl-2-linoleoyl-GPE, and X-21470 were found to have a protective effect. No heterogeneity and pleiotropy were observed in the significant metabolites (p > 0.05), and each metabolite exhibited a consistent effect direction across all five methods. BWMR analysis results confirmed the significance and direction of effects across exposures, except for Cholesterol to linoleoyl-arachidonoyl-glycerol ratio(p = 0.673). Pathway analysis suggests that glycerophospholipid metabolism may potentially be a mechanism underlying the development of asthma.

CONCLUSION

Our MR findings suggest that the identified metabolites and pathways can serve as biomarkers for clinical asthma screening and prevention, while also providing new insights for future mechanistic exploration and drug target selection.

The association between overweight and varying degrees of obesity with subjective well-being and depressive symptoms: A two sample Mendelian randomization study

OBJECTIVE

This study utilized the Mendelian randomization (MR) method to elucidate the causal relationship between genetically predicted overweight and various degrees of obesity with depressive symptoms and subjective well-being (SWB).

METHODS

Pooled genome-wide association studies (GWAS) data for overweight (BMI ≥ 25 kg/m2), class 1 obesity (BMI ≥ 30 kg/m2), and class 2 obesity (BMI ≥ 35 kg/m2) were used as exposures. Summary GWAS data for depressive symptoms and SWB were used as outcomes. Multiple MR methods, primarily inverse-variance weighted (IVW), were applied, and sensitivity analyses were conducted to assess heterogeneity and pleiotropy.

RESULTS

The MR analysis provided evidence that genetically predicted overweight(IVW β = 0.033; 95 %CI 0.008-0.057; P = 0.010) and class 1 obesity(IVW β = -0.033; 95 %CI -0.047 - -0.020; P < 0.001) were causally associated with increased depressive symptoms. Genetically predicted class 2 obesity(IVW β = 1.428; 95 %CI 1.193-1.710; P < 0.001) were associated with reduced SWB. There was no strong evidence of a causal association between genetically predicted overweight and class 1 obesity with SWB. Similarly, genetically predicted class 2 and class 3 obesity did not show strong evidence of a causal association with depressive symptoms. Sensitivity analysis revealed relationships of a similar magnitude.

CONCLUSION

This genetically informed MR study suggests that Overweight and class 1 obesity may causally increased depressive symptoms but not decrease SWB. In contrast, class 2 obesity may causally decrease SWB but not increase depressive symptoms.

Exposure to air pollution might decrease bone mineral density and increase the prevalence of osteoporosis: a Mendelian randomization study

This study, using Mendelian randomization, reveals a causal link between nitrogen oxides and PM2.5 exposure and reduced total-body bone mineral density, highlighting a potential risk factor for osteoporosis. The findings emphasize the importance of targeted interventions in populations exposed to higher air pollution.

INTRODUCTION

With the aging of the population, the prevalence of osteoporosis is escalating. Observational studies suggest that air pollution might diminish bone mineral density (BMD), contributing to elevating the likelihood of developing osteoporosis.

METHODS

Employing a two-sample Mendelian randomization (MR) analysis, our study aimed to explore the potential causal effect of air pollution on total-body BMD. We utilized extensive publicly available data from genome-wide association studies (GWAS) in this research. Inverse variance weighting was selected for the primary effect estimation, complemented by additional approaches such as the weighted median, MR-Egger, simple mode, and weighted mode. Sensitivity analyses were then conducted to evaluate heterogeneity, pleiotropy, and the presence of outliers.

RESULTS

In the MR analysis, our findings revealed causal associations between nitrogen oxides (β =  - 0.55, 95% CI - 0.90 to - 0.21, P = 0.002) and particulate matter (PM) 2.5 (β =  - 0.33, 95% CI - 0.59 to - 0.08, P = 0.010) and a reduction in total-body BMD. No significant associations were detected between PM2.5-10, PM10, nitrogen dioxide, and total-body BMD (P > 0.05). Rigorous sensitivity analyses verified the stability of these significant results.

CONCLUSIONS

Our study illustrates that exposure to nitrogen oxides and PM2.5 may lead to a decrease in total-body BMD, increasing the risk of osteoporosis. This evidence holds crucial implications for policymakers and healthcare providers, as it can provide targeted interventions for the prevention of osteoporosis.

The association between serum 25-hydroxyvitamin D levels and erectile dysfunction: a two-sample Mendelian randomization analysis

Considering that vascular endothelial cell dysfunction is the pathological basis of erectile dysfunction (ED), and recognizing the beneficial effects of 25-hydroxyvitamin D (25(OH)D) on vascular endothelial cell protection, the researchers diligently investigated the causal relationship between serum 25(OH)D levels and ED. However, inconsistent clinical evidence has left the association between serum 25(OH)D levels and ED unclear. The objective of this work was to employ Mendelian randomization (MR) analysis to ascertain the potential causal relationship between serum 25(OH)D levels and ED. We conducted a two-sample MR analysis utilizing data from publicly available genome-wide association studies (GWASs). The primary analysis method for the MR analysis was the inverse-variance weighted (IVW) method, supplemented by the MR-Egger and weighted median methods. In addition, we evaluated heterogeneity with Cochran's Q test, assessed pleiotropy using the MR-Egger intercept test, and performed a leave-one-out analysis to identify single-nucleotide polymorphisms (SNPs) with potential effects. Outliers were detected using MR-pleiotropy residual sum and outlier (MR-PRESSO). Genetically predicted serum 25(OH)D levels were not found to be causally associated with ED in IVW method (OR = 1.028, 95% CI = 0.845-1.250, P = 0.785), MR-Egger method (OR = 1.057, 95% CI = 0.782-1.430, P = 0.720), and weighted median method (OR = 1.225, 95% CI = 0.920-1.633, P = 0.165). The results of sensitivity analyses reinforced our conclusion, indicating no evidence of heterogeneity or directional pleiotropy. In summary, our findings do not substantiate a genetic-level causal link between serum 25(OH)D levels and the prevalence of ED. Nonetheless, future research, including larger MR studies, clinical trials, and additional observational studies, is essential to validate and reinforce the outcomes of our present study.

Mendelian randomization and multi-omics approach analyses reveal impaired glucose metabolism and oxidative phosphorylation in visceral adipose tissue of women with polycystic ovary syndrome

STUDY QUESTION

What is the significance of visceral adipose tissue (VAT) in the pathogenesis of polycystic ovary syndrome (PCOS) and its impact on the regulation of metabolic disorders in women with PCOS?

SUMMARY ANSWER

We revealed a potentially causal relationship between increased genetically predicted VAT and PCOS-related traits, and found that VAT exhibited impaired glucose metabolism and mitochondrial oxidative phosphorylation (OXPHOS) in women with PCOS.

WHAT IS KNOWN ALREADY

PCOS is a common reproductive endocrine disorder accompanied by many metabolic abnormalities. Adipose tissue is a metabolically active endocrine organ that regulates multiple physiological processes, and VAT has a much stronger association with metabolism than subcutaneous adipose tissue does.

STUDY DESIGN, SIZE, DURATION

Mendelian randomization (MR) analysis was used to investigate the potential causal association between genetically predicted VAT and the risk of PCOS. Data for MR analysis were extracted from European population cohorts. VAT samples from sixteen PCOS patients and eight control women who underwent laparoscopic surgery were collected for proteomics and targeted metabolomics analyses.

PARTICIPANTS/MATERIALS, SETTING, METHODS

PCOS was diagnosed according to the 2003 Rotterdam Criteria. The control subjects were women who underwent laparoscopic investigation for infertility or benign indications. Proteomics was performed by TMT labeling and liquid chromatography-tandem mass spectrometry analysis, and targeted metabolomics was performed by ultra-performance liquid chromatography-tandem mass spectrometry analysis. The key differentially expressed proteins (DEPs) were validated by immunoblotting.

MAIN RESULTS AND THE ROLE OF CHANCE

MR analysis revealed a potentially causal relationship between increased genetically predicted VAT and PCOS, as well as related traits, such as polycystic ovaries, total testosterone, bioavailable testosterone, and anti-Müllerian hormone, while a negative relationship was found with sex hormone-binding globulin. Enrichment pathway analysis of DEPs indicated the inhibition of glycolysis and activation of mitochondrial OXPHOS in the VAT of PCOS patients. MR analysis revealed that key DEPs involved in glycolysis and OXPHOS were significantly linked to PCOS and its related traits. Dot blot assay confirmed a significant decrease in glycolysis enzymes PKM2 and HK1, and an increase in mitochondrial Complex I and III subunits, NDUFS3 and UQCR10. Moreover, metabolomics analysis confirmed down-regulated metabolites of energy metabolic pathways, in particular glycolysis. Further analysis of PCOS and control subjects of normal weight revealed that dysregulation of glucose metabolism and OXPHOS in VAT of women with PCOS was independent of obesity.

LARGE SCALE DATA

The mass spectrometry proteomics data have been deposited to the iProX database (http://www.iprox.org) with the iProX accession: IPX0005774001.

LIMITATIONS, REASONS FOR CAUTION

There may be an overlap in some exposure and outcome data, which might affect the results in the MR analysis.

WIDER IMPLICATIONS OF THE FINDINGS

The changes in protein expression of key enzymes affect their activities and disrupt the energy metabolic homeostasis in VAT, providing valuable insight for identifying potential intervention targets of PCOS.

STUDY FUNDING/COMPETING INTEREST(S)

This work was supported by the National Key Research and Development Project of China (2021YFC2700402), the National Natural Science Foundation of China (82071608, 82271665), the Key Clinical Projects of Peking University Third Hospital (BYSY2022043), and the CAMS Innovation Fund for Medical Sciences (2019-I2M-5-001). All authors report no conflict of interest.

TRIAL REGISTRATION NUMBER

N/A.

Assessment of bidirectional relationships between frailty and acute respiratory distress syndrome: a bidirectional Mendelian Randomization study

BACKGROUND

While previous observational studies have suggested a link between frailty and acute respiratory distress syndrome (ARDS), the causality of this connection remains unclear. The objective of this study was to explore the potential bidirectional causal links between frailty and ARDS.

METHODS

A two-sample univariable Mendelian randomization (MR) was performed to assess the causal relationship between frailty, as defined by frailty index (FI, n = 175,226) and fried frailty score (FFS, n = 386,565), and ARDS. The genome-wide association study (GWAS) data of frailty was from the UK Biobank and the ARDS data was from the FinnGen Database. Univariable MR analyses were conducted using inverse-variance weighted (IVW), weighted median, MR-Egger regression, and robust adjusted profile score (MR. RAPS). We also performed multivariable Mendelian randomization (MVMR) analysis including smoking initiation, alcohol consumption, body mass index (BMI), and cognitive performance.

RESULTS

This bidirectional MR analysis demonstrated no causal effect of FI (OR = 0.96, 95% CI 0.14-6.88) and FFS (OR = 1.95, 95%CI 0.14-28.16) on increased susceptibility of ARDS. Also, no evidence was found for an effect of ARDS on the risk of frailty. The MVMR analysis indicated higher BMI and poorer cognitive performance were associated with increased risk of ARDS.

CONCLUSIONS

The outcomes of our analysis imply a probable absence of a direct causal relationship between frailty and susceptibility to ARDS. To reinforce and expand upon these preliminary findings, it is imperative to conduct larger-scale genome-wide association studies.

Obesity and risk for liver disease: a two-sample Mendelian randomisation study

The associations between obesity and liver diseases are complex and diverse. To explore the causal relationships between obesity and liver diseases, we applied two-sample Mendelian randomisation (MR) and multivariable MR analysis. The data of exposures (BMI and WHRadjBMI) and outcomes (liver diseases and liver function biomarker) were obtained from the open genome-wide association study database. A two-sample MR study revealed that the genetically predicted BMI and WHRadjBMI were associated with non-alcoholic fatty liver disease, liver fibrosis and autoimmune hepatitis. Obesity was not associated with primary biliary cholangitis, liver failure, liver cell carcinoma, viral hepatitis and secondary malignant neoplasm of liver. A higher WHRadjBMI was associated with higher levels of biomarkers of lipid accumulation and metabolic disorders. These findings indicated independent causal roles of obesity in non-alcoholic fatty liver disease, liver fibrosis and impaired liver metabolic function rather than in viral or autoimmune liver disease.

Causal relationship between major depressive disorder, anxiety disorder and constipation: a two-sample Mendelian randomization study

BACKGROUND

Epidemiological and other studies have shown correlations among major depressive disorder (MDD), anxiety disorder (AXD) and constipation. However, no consensus has been reached regarding their interdependence and pathogenesis. Herein, we sought to further explore the causal associations between them.

METHODS

Bidirectional two-sample Mendelian randomization (MR) analysis was performed to confirm the causal link between MDD, AXD and constipation. Genetic instrumental variables for MDD, AXD, and constipation were obtained from publicly available genome-wide association studies (GWASs). In this MR analysis, inverse variance weighting (IVW) was used as the primary analysis method to evaluate the causal effect. Additionally, we employed Cochran's Q test, MR‒Egger intercept and MR-PRESSO analysis to examine heterogeneity and pleiotropy. Moreover, leave-one-out analysis was employed to investigate the stability of the associations. Finally, a reverse analysis of Mendelian randomization was conducted.

RESULTS

The results revealed a causal relationship between MDD and an increased risk of constipation (p = 0.0001), whereas AXD (p = 8.52 × 10-1) did not increase the risk of constipation. In the inverse MR analysis, no causal associations were found (constipation to MDD: p = 9.37 × 10-1; constipation to AXD: p = 8.51 × 10-1).

CONCLUSION

This MR study revealed genetic evidence supporting a causal relationship between MDD and constipation.

The causal effects of dietary component intake and blood metabolites on risk of delirium: a Mendelian randomization study

Backgrounds

Growing evidence has indicated that the nutritional quality of dietary intake and alterations in blood metabolites were related to human brain activity. This study aims to investigate the causal relationship between dietary component intake, blood metabolites, and delirium risks.

Methods

We performed Mendelian randomization (MR) analysis using genetic variants as instrumental variables for dietary component intake, blood metabolites, and delirium. Inverse variance weighting, maximum likelihood, weighted median, weighted mode, and MR-Egger methods were used for statistical analyses.

Results

We found that genetic prediction of salt added to food (odds ratio [OR] 1.715, 95% confidence interval [CI] 1.239-2.374, p = 0.001) significantly increased the risks of delirium, while low-fat polyunsaturated margarine used in cooking (OR 0.044, 95%CI 0.004-0.432, p = 0.007), cheese intake (OR 0.691, 95%CI 0.500-0.955, p = 0.025) and coffee intake (OR 0.595, 95%CI 0.370-0.956, p = 0.032) was suggestively associated with decreased risks of delirium. Moreover, increased blood 1-stearoylglycerol levels (OR 0.187, 95%CI 0.080-0.435, p = 9.97E-05) significantly contributed to reducing the risks of delirium. 3-methoxytyrosine (OR 0.359, 95%CI 0.154-0.841, p = 0.018) also has the potential to decrease the risk of delirium.

Conclusion

Our study highlights the potential causal effect relationships of dietary component intake and blood metabolites on the risk of delirium, which potentially provides novel insights into targeted dietary prevention strategies or biomarkers for delirium.

Genetic insights into blood protein correlations with colorectal cancer: a Mendelian randomization study

BACKGROUND

Several blood proteins might be associated with the development of colorectal cancer (CRC), but many studies on this topic are often biased. By using genetic variation data, which is less influenced by environmental factors, we can better determine the causal relationship between specific blood proteins and the occurrence of colorectal cancer.

METHODS

Data from a genome-wide association study (GWAS) on blood proteins, encompassing 1,478 proteins, and colorectal cancer (CRC) GWAS data, covering 637,693 subjects, were collected and organized. Additionally, GWAS data for obesity, diabetes mellitus (DM), and smoking were obtained for further analysis. Single nucleotide polymorphisms (SNPs) significantly associated with the exposure factors (blood proteins) were selected to ensure their independence from other confounding factors and outcomes (CRC onset), and that they only affected outcomes through blood proteins. The causal effects of Mendelian Randomization (MR) were primarily estimated using the inverse variance weighted (IVW) method, with other methods serving as supplementary approaches. The Cochran's Q-test assessed heterogeneity among SNP estimates; the MR Egger method evaluated pleiotropy; and the leave-one-out test examined the sensitivity of individual SNPs. Obesity, DM, and smoking were included in the multivariate MR analysis.

RESULT

A total of 31 SNPs and 8 blood protein exposure factors were identified, specifically TNFRSF16 (4 SNPs), RNF8 (4 SNPs), MRM3 (4 SNPs), ST6GALNAC1 (4 SNPs), TIE1 (4 SNPs), CBP (4 SNPs), DNAJB9 (4 SNPs), and EDN2 (3 SNPs). The IVW results showed a significant causal relationship between all 8 exposure factors and colorectal cancer (P < 0.05). Among these, TNFRSF16, TIE1, and EDN2 were identified as risk factors, while the remaining five served as protective factors. The causal inference in this study was not influenced by pleiotropy or environmental factors such as obesity, diabetes, and smoking. Therefore, the results were both stable and reliable.

CONCLUSION

Eight blood proteins (or genes) have been identified as having a causal relationship with the onset of colorectal cancer, suggesting their potential use as screening biomarkers and treatment targets.

Impact of gut microbiota on metabolic syndrome and its comprising traits: a two-sample mendelian randomization study

BACKGROUND

The prevalence of metabolic syndrome is on the rise globally. Understanding the etiology and discovering potential treatment target have become a priority. Observational data have linked gut microbiota with metabolic syndrome and its comprising traits. However, whether these relations underlie causal effects remains unclear.

METHODS

Using Inver Variance Weighted (IVW) as primary analysis method, we performed two-sample Mendelian Randomization (MR) analyses to explore the causal relationship between gut microbiota and metabolic syndrome with its comprising traits. Methods including MR-Egger regression, MR Pleiotropy RESidual Sum and Outlier (MR-PRESSO), Weighted Mode, and Weighted Median were chosen for additional MR analysis to test the robustness of MR results. Cochran's IVW Q test and leave-one-out IVW analysis tested the heterogeneity among instrumental variables (IVs). Steiger filtering was utilized to exclude all IVs with reverse causality. Genome-wide association study (GWAS) data used in this study were all from the largest respective GWAS studies available.

RESULTS

Out of 1172 tests, a total of 16 associations with evidence of causality were identified after sensitivity analyses, but only 3 remained after multiple testing correction. Class Melainabacteria (β = 0.02, adjusted P = 0.01) with affiliated order Gastranaerophilales (β = 0.02, adjusted P = 1.20*10- 3) and genus Eubacterium hallii (β = 0.03, adjusted P = 0.03) showed a positive effect on abdominal obesity. All effect sizes were small (abs(β) < 0.1). All causal relationships identified were unidirectional.

CONCLUSIONS

Given the study's limitations, we found little evidence supporting a large causal effect, i.e. absolute effect size > 0.1, of gut microbial taxa abundance on metabolic syndrome and its comprising traits. This study also suggests that previously reported associations between gut microbiota and metabolic syndrome with its comprising traits may not necessarily lead to causal relations.

CLINICAL TRIAL NUMBER

Not applicable.

The harmful effect of ankylosing spondylitis on diabetes mellitus: new evidence from the Mendelian randomization analysis

Background

While observational research has highlighted a possible link between ankylosing spondylitis (AS) and type 2 diabetes (T2DM), the quality of evidence remains limited, and the causal relationship is yet to be established. This study aims to explore the causal link between AS and T2DM, as well as its impact on traits related to glucose metabolism.

Method

To infer a causal relationship between AS and various diabetes-related traits, including type 1 diabetes (T1DM), T2DM, blood glucose levels, fasting glucose, glycated hemoglobin, and fasting insulin, we employed Mendelian randomization (MR) analysis. We sourced GWAS summary data for both exposure and outcome variables from the IEU OpenGWAS database, GWAS Catalog, and FinnGen database. To synthesize the results of the MR analyses, we applied meta-analysis techniques using either a fixed or random effects model. For identifying and excluding instrumental variants (IVs) that exhibit horizontal pleiotropy with the outcomes, we utilized the MR-PRESSO method. Sensitivity analyses were conducted using the MR-Egger method, along with Q and I^2 tests, to ensure the robustness of our findings.

Results

Our analysis revealed a significant association between AS and an increased risk of T1DM with an odds ratio (OR) of 1.5754 (95% CI: 1.2935 to 1.9187) and T2DM with an OR of 1.0519 (95% CI: 1.0059 to 1.1001). Additionally, AS was associated with elevated levels of fasting glucose (beta coefficient = 0.0165, 95% CI: 0.0029 to 0.0301) and blood glucose (beta coefficient = 0.0280, 95% CI: 0.0086 to 0.0474), alongside a decrease in fasting insulin levels (beta coefficient = -0.0190, 95% CI: -0.0330 to -0.0050).

Conclusion

Our findings collectively underscore the detrimental impact of AS on the development of diabetes, highlighting the critical influence of autoimmune disorders in diabetes onset. This provides profound insights into the pathogenesis of diabetes from an immunological standpoint.

Genetic insight into the relationship between inflammatory bowel disease and Clostridioides difficile infection

Patients with inflammatory bowel disease (IBD) are at increased risk of Clostridioides difficile infection (CDI). Herein, we aimed to determine if genetic risk contributes to this observed association. We carried out a genome-wide association study (GWAS) analysis in the Michigan Genomics Initiative and the United Kingdom Biobank for CDI based on ICD codes and meta-analyzed these results with similar publicly accessible GWAS summary statistics from Finngen. Conditional and joint multi-SNP analyses were used to identify independent associations. Imputation of the human leukocyte antigen (HLA) region with fine mapping was used to try to identify causal HLA allele groups. Two-sample bidirectional Mendelian randomization (MR) was implemented to determine causal relationships between IBD and CDI. A total of 3,500 cases of CDI and 674,323 controls were meta-analyzed, revealing one genome-wide significant variant for CDI, HLA-C;LINC02571-rs3134745-C (P = 4.27E-08), which annotated to the major histocompatibility complex on chromosome 6. While fine mapping did not identify a statistically significant HLA allele group, there was a suggestive signal for HLA-B*35:01 (P = 4.74e-04). Using two-sample MR, genetically predicted IBD was associated with increased risk of CDI (MR Egger [odds ratio {OR} 1.16, 95% confidence interval {CI} 1.02-1.31]). Subset analysis revealed that risk was primarily driven by genetically predicted ulcerative colitis (MR Egger [OR 1.22, 95% CI 1.05-1.41]). These results highlight the importance of the host immune response in CDI pathogenesis, help explain the observed relationship between IBD and CDI, and open new avenues for targeted treatment of CDI in IBD.IMPORTANCEData from this paper (i) provide reproducible evidence that susceptibility CDI is genetically mediated, (ii) highlight genetic risk as a mechanism for the increased risk of CDI in patients with inflammatory bowel disease, and (iii) point toward anti-interleukin-23 therapy as a common therapeutic strategy.

Genetic Evidence for the Causal Link Between Coagulation Factors and the Risk of Ovarian Cancer: A Two-Sample Mendelian Randomization Study

Background

Prior investigations have suggested a significant association between coagulation factors and ovarian cancer; however, the precise nature of the causal relationship remains elusive. Our objective is to thoroughly investigate this causal link and delineate the influence of coagulation factors on the risk of ovarian cancer through a rigorous two-sample Mendelian randomization (MR) analysis.

Methods

Genetic instrumental variables representing coagulation factors were sourced from four distinct data repositories. Summary statistics pertaining to ovarian cancer were obtained from two extensive Genome-Wide Association Studies (GWAS) for primary and replication analyses, respectively. The primary Mendelian randomization (MR) analysis utilized the inverse-variance weighted (IVW) method. To fortify the reliability of our findings, additional analyses were conducted, including the weighted-median method, MR-Egger regression, MR pleiotropy residual sum and outlier test, Cochran's Q statistic test, MR-Egger intercept analysis, and leave-one-out method, among others.

Results

We identified four coagulation factors that were associated with the risk of ovarian cancer in the primary analysis, [odds ratio (OR): 1.365, 95% confidence interval (CI): 1.209-1.542, P <0.001 for von Willebrand factor measurement(vWF); OR: 1.060, 95% CI: 1.018-1.104, P = 0.005 for A disintegrin and metalloproteinase with thrombospondin motifs 13 (ADATMS13); OR: 1.317, 95% CI: 1.002-1.730, P = 0.048 for activated partial thromboplastin time (aPTT); OR: 1.139, 95% CI: 1.063-1.221, P <0.001 for coagulation Factor VIII (FVIII)]. In the meta-analysis, we found that higher levels of coagulation factor VII measurement(FVII) (OR=1.0007, 95% CI: 1.0001-1.0013, P=1.0007) was associated with increased ovarian cancer risk. The results of sensitivity analyses for these coagulation factors were consistent (P<0.05).

Conclusion

Our systematic analyses have furnished evidence suggesting a plausible causal association between FVII and the susceptibility to ovarian cancer. Further investigations are warranted to delineate the mechanistic pathways through which coagulation factors influence the progression of ovarian cancer.

Relationship between immune cell traits, circulating inflammatory cytokines, and the risk of incisional hernia after gastric surgery

PURPOSE

The systemic and local inflammatory response in patients after surgical operation is closely related to the quality of the wound healing. Low-quality wound healing and defects in the suture technique lead to the occurrence of incisional hernia (IH). However, the causal relationship between human circulating inflammatory cytokines, immune cell traits, and the risk of IH remains unclear.

METHODS

We used summary data from genome-wide association studies to assess the causal relationship between 91 types of circulating inflammatory factors, 731 types of circulating immune cell traits, and the risk of IH. The outcome dataset was obtained from FinnGen, including 6,336 patients with IH and 232,612 controls. We performed Mendelian Randomization (MR) analysis to identify their causal relationship and immune cell phenotypes upstream of inflammatory factors. Inverse variance weighting is considered to be the main analysis method.

RESULTS

Among the identified cytokines, TNF-related activation-induced cytokine levels were associated with a lower risk of IH (OR: 0.89; 95% CI: 0.82-0.96; P = 0.003). In contrast, interleukin-5 levels were associated with an increased risk of IH (OR: 1.18; 95% CI: 1.06-1.31; P = 0.003). Additionally, a significant causal relationship was found between four immune cell traits and the risk of IH (P < 0.01). Through two-step MR analysis, we determined that interleukin-5 levels mediate the causal relationship between the relative count of CD25hi % CD4 + in Treg cells and the higher risk of IH.

CONCLUSION

This study found a causal relationship between specific inflammatory cytokines, immune cell traits, and risk of IH. These results can help surgeons predict the risk of IH and take preventive measures.

Systematic review of Mendelian randomization studies on antihypertensive drugs

BACKGROUND

We systematically reviewed Mendelian randomization (MR) studies and summarized evidence on the potential effects of different antihypertensive drugs on health.

METHODS

We searched PubMed and Embase for MR studies evaluating the effects of antihypertensive drug classes on health outcomes until 22 May 2024. We extracted data on study characteristics and findings, assessed study quality, and compared the evidence with that from randomized controlled trials (RCTs).

RESULTS

We identified 2643 studies in the search, of which 37 studies were included. These studies explored a wide range of health outcomes including cardiovascular diseases and their risk factors, psychiatric and neurodegenerative diseases, cancer, immune function and infection, and other outcomes. There is strong evidence supporting the protective effects of genetically proxied antihypertensive drugs on cardiovascular diseases. We found strong protective effects of angiotensin-converting enzyme (ACE) inhibitors on diabetes whereas beta-blockers showed adverse effects. ACE inhibitors might increase the risk of psoriasis, schizophrenia, and Alzheimer's disease but did not affect COVID-19. There is strong evidence that ACE inhibitors and calcium channel blockers (CCBs) are beneficial for kidney and immune function, and CCBs showed a safe profile for disorders of pregnancy. Most studies have high quality. RCT evidence supports the beneficial effects of ACE inhibitors and CCBs on stroke, diabetes, and kidney function. However, there is a lack of reliable RCTs to confirm the associations with other diseases.

CONCLUSIONS

Evidence of the benefits and off-target effects of antihypertensive drugs contribute to clinical decision-making, pharmacovigilance, and the identification of drug repurposing opportunities.