Mendelian Randomization Pleiotropy Residual Sum Research Articles

Inflammatory bowel disease and prostate cancer risk: a two-sample Mendelian randomization analysis.

Previous epidemiological observational studies have reported an association between inflammatory bowel disease (IBD) and prostate cancer (PCa), but the causality is inconclusive. The purpose of this study was to evaluate the causality of IBD on PCa using the mendelian randomization (MR) analysis. We performed a two-sample MR analysis with public genome-wide association studies (GWAS) data. Eligible instrumental variables (IVs) were selected according to the three assumptions of MR analysis. The inverse-variance weighted (IVW) method was the main method. Complementary methods included the MR-Egger regression, the Weighted Median, the Simple Mode, the Weighted Mode and MR pleiotropy residual sum and outlier (MR-PRESSO) methods. Genetically determined IBD did not have a causal effect on PCa (IVW P > 0.05). Additionally, there was no causal effect of Crohn's disease (CD) and ulcerative colitis (UC) on PCa in the MR analysis (IVW P > 0.05). Results of complementary methods were consistent with those of the IVW method. This study does not support a causal association of IBD on PCa, which is in contrast to most observational studies.

Association Between Rheumatoid Arthritis and Osteoporosis in Japanese Populations: A Mendelian Randomization Study.

The positive association between rheumatoid arthritis (RA) and osteoporosis has been reported in previous observational studies, but the causal relationship remains unclear. This study was undertaken to investigate whether RA was causally associated with osteoporosis in Japanese populations using Mendelian randomization (MR) analyses. Publicly available summarized data from genome-wide association studies (GWAS) on RA (4,199 cases and 208,254 controls) and osteoporosis (7,788 cases and 204,665 controls) were obtained from BioBank Japan. Eleven RA-related single-nucleotide polymorphisms (P < 5×10-8 ) were selected as instrumental variables. We used the inverse variance-weighted method as the primary method to calculate the odds ratios (ORs) and 95% confidence intervals (95% CIs). We also used the MR-Egger's method, weighted median, and weighted mode to determine the robustness of the main results. To partially test the horizontal pleiotropy, we used the MR-Egger's intercept test and the Mendelian randomization pleiotropy residual sum and outlier (MRPRESSO) test. Using the inverse variance-weighted method, we showed that genetically predicted RA was positively associated with osteoporosis (OR 1.10, 95% CI 1.06-1.14, P < 0.001). The positive association was robust when we tested the results using the MR-Egger's method (OR 1.09, 95% CI 1.03-1.16, P = 0.023), weighted median (OR 1.09, 95% CI 1.04-1.15, P < 0.001), and weighted mode (OR 1.08, 95% CI 1.03-1.13, P = 0.012). Horizontal pleiotropy was not detected (P = 0.737) by the MR-Egger's intercept test or the MRPRESSO test. Our results show a potential causal association between genetically predicted RA and osteoporosis. The finding was consistent when we used different MR methods and the sensitivity analysis. Further MR studies are needed when GWAS with more details of RA and osteoporosis performed in other East Asian/Japanese populations are available.

A bidirectional Mendelian randomization study about the role of morning plasma cortisol in attention deficit hyperactivity disorder.

Cortisol, a hormone regulated by the hypothalamic-pituitary-adrenal (HPA) axis, has been linked to attention deficit hyperactivity disorder (ADHD). The nature of the relationship between cortisol and ADHD, and whether it is causal or explained by reverse causality, remains a matter of debate. This study aims to evaluate the bidirectional causal relationship between morning plasma cortisol levels and ADHD. This study used a bidirectional 2-sample Mendelian randomization (MR) design to analyze the association between morning plasma cortisol levels and ADHD using genetic information from the authoritative Psychiatric Genomics Collaboration (PGC) database (n = 55,347) and the ADHD Working Group of the CORtisol NETwork (CORNET) Consortium (n = 12,597). MR analyses were employed: inverse variance weighting (IVW), MR-Egger regression, and weighted medians. OR values and 95% CI were used to evaluate whether there was a causal association between morning plasma cortisol levels on ADHD and ADHD on morning plasma cortisol levels. The Egger-intercept method was employed to test for level pleiotropy. Sensitivity analysis was performed using the "leave-one-out" method, MR pleiotropy residual sum, and MR pleiotropy residual sum and outlier (MR-PRESSO). Findings from bidirectional MR demonstrated that lower morning plasma cortisol levels were associated with ADHD (ADHD-cortisol OR = 0.857; 95% CI, 0.755-0.974; P = 0.018), suggesting there is a reverse causal relationship between cortisol and ADHD. However, morning plasma cortisol levels were not found to have a causal effect on the risk of ADHD (OR = 1.006; 95% CI, 0.909-1.113; P = 0.907), despite the lack of genetic evidence. The MR-Egger method revealed intercepts close to zero, indicating that the selected instrumental variables had no horizontal multiplicity. The "leave-one-out" sensitivity analysis revealed stable results, with no instrumental variables significantly affecting the results. Heterogeneity tests were insignificant, and MR-PRESSO did not detect any significant outliers. The selected single-nucleotide polymorphisms (SNPs) F were all >10, indicating no weak instrumental variables. Thus, the overall MR analysis results were reliable. The study findings suggest a reverse causal relationship between morning plasma cortisol levels and ADHD, with low cortisol levels associated with ADHD. No genetic evidence was found to support a causal relationship between morning plasma cortisol levels and the risk of ADHD. These results suggest that ADHD may lead to a significant reduction in morning plasma cortisol secretion.

#6774 CAUSAL ASSOCIATION OF COVID-19 AND KIDNEY FUNCTION: A MENDELIAN RANDOMIZATION ANALYSIS

Abstract Background and Aims Previous observational studies suggest that there are potential relationships between COVID-19 and kidney functions. However, whether COVID-19 had causal effects on different kidney traits is currently unclear. We aimed to investigate the causal link between genetically determined COVID-19 and following kidney traits. Method We performed univariate Mendelian randomization (MR) studies using summary genome-wide association studies (GWAS) statistics of COVID-19 severity (n case/n control: 13,769/1,072,442 for European, n case/n control: 794/4862 for Asian), COVID-19 hospitalization (n case/n control: 32,519/2,062,805 for European, n case/n control:2882/31,200 for Asian) and COVID-19 susceptibility (n case/n control: 122,616/2,475,240 for European, n case/n control: 4459/36,121 for Asian) derived from THE COVID-19 Host Genetics Initiative (r7) as exposure. Phenotypic outcomes analyzed for Europeans included chronic kidney disease (CKD), creatinine-based estimated glomerular filtration rate, Cystatin C-based estimated glomerular filtration rate, Urine albumin-to-creatinine ratio, acute and chronic glomerulonephritis, membranous nephropathy, diabetic nephropathy, acute and chronic nephritic syndrome, acute renal failure, glomerular diseases and IgA nephropathy. While for Asians, outcomes including CKD, estimated glomerular filtration rate, serum creatinine, acute and chronic renal failure, diabetic nephropathy, IgA nephropathy, nephrotic syndrome, acute and chronic glomerulonephritis as well as membranous nephropathy were analyzed. The inverse variance weighted (IVW) MR with multiplicative random effects model was performed as primary analysis to evaluate the causal effects of COVID-19 on different kidney traits, and potential pleiotropy as well as heterogeneity was evaluated by using MR Egger and heterogeneity test, respectively. A series of sensitivity analyses, including weighted median MR, weighted mode MR, MR Pleiotropy Residual Sum and Outlier (MR PRESSO) were performed. In addition, the causal effects of COVID-19 on different kidney traits were validated by using additional GWAS summary data of critical COVID-19 (n case/n control: 5989/42891 for European, n case/n control: 274/366 for Asian) from GenOMICC database (r6) as exposure. After multiple corrections, a P value &amp;lt; 0.0036 for Europeans and P value &amp;lt; 0.0045 for Asians were considered as significant. Results IVW MR indicated that none of the COVID-19 phenotypes were associated with CKD (OR, 0.99: P = 0.16 for COVID-19 severity; OR, 0.99: P = 0.41 for COVID-19 hospitalization; OR, 0.95: P = 0.26 for COVID-19 susceptibility), nor other kidney traits for Europeans. As for Asian ancestry, consistent with the findings in Europeans, none of the COVID-19 phenotypes were associated with CKD (OR, 0.89: P = 0.16 for COVID-19 severity; OR, 0.93: P = 0.42 for COVID-19 hospitalization; OR, 0.95: P = 0.61 for COVID-19 susceptibility), nor other kidney traits as mentioned above. All sensitivity analyses also consistently indicated the absence of causal effects of COVID-19 severity, hospitalization and susceptibility on different kidney traits, neither in the European nor in the Asian population. Conclusion There is no significant evidence supporting the causal effects of genetically predicted COVID-19 phenotype on the following different kidney traits. More deeply explorations focused on the association between COVID-19 and kidney traits should be performed with more data would be available in the future.

Depression and sarcopenia: a Mendelian randomization analysis.

The association between depression and sarcopenia has been reported in observational studies but the causality of depression on sarcopenia remained unknown. We aimed to assess the causal effect between major depressive disorder (MDD) and sarcopenia using the two-sample Mendelian randomization (MR) method. A set of genetics instruments were used for analysis, derived from publicly available genetic summary data. Clinically, appendicular lean mass (ALM) and low hand grip strength (LHGS) have been widely used for the diagnosis of sarcopenia. Inverse-variance weighted method, weighted median method, MR-Egger, MR Pleiotropy RESidual Sum and Outlier test were used for the bidirectional MR analyses. No evidence for an effect of MDD on sarcopenia risk was found. MDD was not associated with ALM [effect = -0.17 (-0.60 to 0.27), P = 0.449] and LHGS [effect = 0.24 (-0.46 to 0.93), P = 0.506]. Sarcopenia was not associated with MDD [ALM: odds ratio (OR) = 0.999 (0.996-1.001), P = 0.374; LHGS: OR = 0.999 (0.996-1.002), P = 0.556]. MDD and Sarcopenia might mutually have no causal effect on each other.

Correlation between obstructive sleep apnea and cerebral small vessel disease: a mendelian randomization study.

Whether obstructive sleep apnea (OSA) is causally associated with an increased risk of cerebral small vessel disease (CSVD) remains controversial. We conducted a two-sample Mendelian randomization (MR) study to clarify the causal relationship between OSA and CSVD risk. Single-nucleotide polymorphisms associated with OSA at the genome-wide significance level (P < 5 × 10- 8) in the FinnGen consortium were selected as instrumental variables. Summary-level data for white matter hyperintensities (WMHs), lacunar infarctions (LIs), cerebral microbleeds (CMBs), fractional anisotropy (FA), and mean diffusivity (MD) were obtained from three meta-analyses of genome-wide association studies (GWASs). The random-effects inverse-variance weighted (IVW) method was selected for the major analysis. Weighted-median, MR-Egger, MR pleiotropy residual sum and outlier (MR-PRESSO), and leave-one-out analysis methods were implemented for the sensitivity analyses. Genetically predicted OSA was not associated with LIs (odds ratio [OR] = 1.10, 95% confidence interval [CI] = 0.86-1.40), WMHs (OR = 0.94, 95% CI = 0.83-1.07), FA (OR = 1.33, 95% CI = 0.75-2.33), MD (OR = 0.93, 95% CI = 0.58-1.47), CMBs (OR = 1.29, 95% CI = 0.86-1.94), mixed CMBs (OR = 1.17, 95% CI = 0.63-2.17), and lobar CMBs (OR = 1.15, 95% CI = 0.75-1.76) in IVW method. The results of the sensitivity analyses were generally consistent with the major analyses. This MR study does not support causal associations between OSA and the risk of CSVD in individuals of European ancestry. These findings need to be further validated in randomized controlled trials, larger cohort studies, and MR studies based on larger GWASs.

Causal Association Between Anemia and Cardiovascular Disease: A 2-Sample Bidirectional Mendelian Randomization Study.

Background Although previous observational studies have shown an association between anemia and cardiovascular disease (CVD), the underlying causal relationship between anemia and CVD remains uncertain. Methods and Results We conducted a 2-sample bidirectional Mendelian randomization (MR) study to assess the causal association between anemia and CVD. We extracted summary statistics data for anemia, heart failure (HF), coronary artery disease (CAD), atrial fibrillation, any stroke, and any ischemic stroke (AIS) from relevant published genome-wide association studies. After rigorous quality control steps, independent single-nucleotide polymorphisms for each disease were selected as instrumental variables. Inverse-variance weighting was used as the primary method to estimate the causal association between anemia and CVD in the 2-sample MR analysis. Simultaneously, we performed a series of multiple methods analyses (median weighting, maximum likelihood [MR robust adjusted profile score]), sensitivity analyses (Cochran's Q test and MR-Egger intercept, leave-one-out test [MR pleiotropy residual sum and outlier]), instrumental variable strength evaluations (F statistic), and statistic power estimates to verify the robustness and reliability of our results. Furthermore, the associations between anemia and CVD from different studies, including the UK Biobank and FinnGen studies, were combined by meta-analysis. The MR analysis showed that genetically predicted anemia was significantly associated with HF risk at the Bonferroni-corrected significance level (odds ratio [OR], 1.11 [95% CI, 1.04-1.18]; P=0.002) and was suggestively associated with CAD risk (OR, 1.11 [95% CI, 1.02-1.22]; P=0.020). However, the associations between anemia and atrial fibrillation, any stroke, or AIS were not statistically significant. In the reverse MR analysis, we found that genetic susceptibility to HF, CAD, and AIS was significantly associated with anemia risk. The ORs of HF, CAD, and AIS were 1.64 (95% CI, 1.39-1.94; P=7.60E-09), 1.16 (95% CI, 1.08-1.24; P=2.32E-05), and 1.30 (95% CI, 1.11-1.52; P=0.001), respectively. Genetically predicted atrial fibrillation was suggestively associated with anemia (OR, 1.06 [95% CI, 1.01-1.12]; P=0.015). Sensitivity analyses found weak evidence of horizontal pleiotropy and heterogeneity, which ensured the robustness and reliability of the results. Meta-analysis also showed the statistically significant association between anemia and HF risk. Conclusions Our study supports bidirectional causality between anemia and HF and significant associations between genetic predisposition to CAD and AIS with anemia, which contributes to the clinical management of both diseases.

Lifestyle factors, metabolic factors and socioeconomic status for pelvic organ prolapse: a Mendelian randomization study

BackgroundPrevious observational studies have reported that lifestyle factors, metabolic factors and socioeconomic status are associated with the development of female pelvic organ prolapse (POP); however, whether these associations are causal remains unclear. The current study aimed to assess the causal effect of lifestyle factors, metabolic factors and socioeconomic status on POP risk.MethodsWe conducted a two-sample Mendelian randomization (MR) study based on summary-level data from the largest available genome-wide association studies (GWAS) to evaluate whether lifestyle factors, metabolic factors and socioeconomic status are causally related to POP. We used single nucleotide polymorphisms that are strongly associated with exposure at the genome-wide significance level (P < 5 × 10–8) as instrumental variables from genome-wide association studies. The method of random-effect inverse-variance weighting (IVW) was used as the primary analysis method, supplemented with the weighted median, MR-Egger and the MR pleiotropy residual sum and outlier applied to verify the MR assumptions. Two-step MR was conducted to investigate potential intermediate factors that are on the causal pathway from exposure to POP.ResultsThere were associations with POP for genetically predicted waist-to-hip ratio (WHR) (odds ratio (OR) 1.02, 95% confidence interval (CI) 1.01–1.03 per SD-increase, P < 0.001), WHR adjusted for body mass index (WHRadjBMI) (OR 1.017, 95% CI 1.01–1.025 per SD-increase, P < 0.001) and education attainment (OR 0.986, 95% CI 0.98–0.991 per SD-increase) in the meta-analysis. Additionally, genetically predicted coffee consumption (OR per 50% increase 0.67, 95% CI 0.47–0.96, P = 0.03), vigorous physical activity (OR 0.83, 95% CI 0.69–0.98, P = 0.043) and high-density lipoprotein cholesterol (HDL-C) (OR 0.91, 95% CI 0.84–0.98 per SD-increase, P = 0.049) were inversely associated with POP in the FinnGen Consortium. The mediation analysis showed that the indirect effects of education attainment on POP were partly mediated by WHR and WHRadjBMI, with a mediated proportion of 27% and 13% in the UK Biobank study, respectively.ConclusionsOur study provides MR evidence of a robust causal association of WHR, WHRadjBMI and education attainment with POP.

The Causal Effect of Dietary Composition on the Risk of Breast Cancer: A Mendelian Randomization Study.

Breast cancer has become the most common malignancy among women, posing a severe health risk to women worldwide and creating a heavy social burden. Based on current observational studies, the dietary factor may have a causal relationship with breast cancer. Therefore, exploring how dietary composition affects breast cancer incidence will provide nutrition strategies for clinicians and women. We performed a two-sample Mendelian randomization (MR) analysis to find the causal effect of four kinds of relative macronutrient intake (protein, carbohydrate, sugar, and fat) on the risk of breast cancer and its subtypes [Luminal A, Luminal B, Luminal B HER2-negative, HER2-positive, Triple-negative, Estrogen receptor (ER) positive, and ER-negative breast cancer]. The Mendelian randomization pleiotropy residual sum and outlier (MR-PRESSO) test, MR-Egger intercept test, Cochran's Q statistic, funnel plot, and leave-one-out (Loo) analysis were all used in a sensitivity analysis to test the robustness of MR. Genetically, a higher relative protein intake was found as a protective factor for Luminal A and overall breast cancer, which was inconsistent with recent findings. A higher relative sugar intake could genetically promote the risk of Luminal B and HER2-positive breast cancer. Conclusions: A higher protein proportion in diet genetically reduces the risk of breast cancer, while higher relative sugar intake does the opposite.

The relationship between major depression and delirium: A two-sample Mendelian randomization analysis

BackgroundMajor depression (MD) is a well-recognized risk factor for delirium. However, observational studies cannot provide direct evidence of causality between MD and delirium. MethodsThis study explored the genetic causal association between MD and delirium using two-sample Mendelian randomization (MR). Genome-wide association study (GWAS) summary data for MD were obtained from the UK Biobank. GWAS summary data for delirium were obtained from the FinnGen Consortium. Inverse-variance weighted (IVW), MR Egger, weighted median, simple mode, and weighted mode were used to perform the MR analysis. In addition, the Cochrane's Q test was used to detect heterogeneity in the MR results. Horizontal pleiotropy was detected using the MR-Egger intercept test and MR pleiotropy residual sum and outliers (MR-PRESSO) test. Leave-one-out analysis was used to investigate the sensitivity of this association. ResultsThe IVW method showed that MD was an independent risk factor for delirium (P = 0.013). Horizontal pleiotropy was unlikely to bias causality (P > 0.05), and no evidence of heterogeneity was found between the genetic variants (P > 0.05). Finally, a leave-one-out test showed that this association was stable and robust. LimitationsAll participants included in the GWAS were of European ancestry. Due to database limitations, the MR analysis did not conduct stratified analyses for different countries, ethnicities, or age groups. ConclusionWe conducted a two-sample MR analysis and found the evidence of genetic causal association between MD and delirium.

Causal relationships between COVID-19 and osteoporosis: a two-sample Mendelian randomization study in European population.

The causal relationship between Coronavirus disease 2019 (COVID-19) and osteoporosis (OP) remains uncertain. We aimed to assess the effect of COVID-19 severity (severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection, COVID-19 hospitalization, and severe COVID-19) on OP by a two-sample Mendelian randomization (MR) study. We conducted a two-sample MR analysis using publicly available genome-wide association study (GWAS) data. Inverse variance weighting (IVW) was used as the main analysis method. Four complementary methods were used for our MR analysis, which included the MR-Egger regression method, the weighted median method, the simple mode method, and the weighted mode method. We utilized the MR-Egger intercept test and MR pleiotropy residual sum and outlier (MR-PRESSO) global test to identify the presence of horizontal pleiotropy. Cochran's Q statistics were employed to assess the existence of instrument heterogeneity. We conducted a sensitivity analysis using the leave-one-out method. The primary results of IVW showed that COVID-19 severity was not statistically related to OP (SARS-CoV-2 infection: OR (95% CI) = 0.998 (0.995 ~ 1.001), p = 0.201403; COVID-19 hospitalization: OR (95% CI) =1.001 (0.999 ~ 1.003), p = 0.504735; severe COVID-19: OR (95% CI) = 1.000 (0.998 ~ 1.001), p = 0.965383). In addition, the MR-Egger regression, weighted median, simple mode and weighted mode methods showed consistent results. The results were robust under all sensitivity analyses. The results of the MR analysis provide preliminary evidence that a genetic causal link between the severity of COVID-19 and OP may be absent.

Investigating association between gut microbiota and sarcopenia-related traits: a Mendelian randomization study.

Observational studies have indicated a potential link between gut microbiota and sarcopenia. However, the underlying mechanisms and a causal relationship have not been established. Thus, the objective of this study is to examine the possible causal association between gut microbiota and sarcopenia-related traits, including low hand-grip strength and appendicular lean mass (ALM), to shed light on the gut-muscle axis. To investigate the potential impact of gut microbiota on low hand-grip strength and ALM, we utilized a two-sample Mendelian randomization (MR) approach. Summary statistics were obtained from genome-wide association studies of gut microbiota, low hand-grip strength, and ALM. The primary MR analysis employed the random-effects inverse-variance weighted (IVW) method. To assess the robustness, we conducted sensitivity analyses using the MR pleiotropy residual sum and outlier (MR-PRESSO) test to detect and correct for horizontal pleiotropy, as well as the MR-Egger intercept test and leave-one-out analysis. Alcaligenaceae, Family XIII, and Paraprevotella were positively associated with the risk of low hand-grip strength (P-values<0.05). Streptococcaceae were negatively associated with low hand-grip strength (P-values<0.05). Eight bacterial taxa (Actinomycetales, Actinomycetaceae, Bacteroidaceae, Porphyromonadaceae, Prevotellaceae, Bacteroides, Marvinbryantia, and Phascolarctobacterium) were associated with a higher risk of ALM (P-values<0.05). Eubacterium fissicatena group was negatively associated with ALM (P-values<0.05). We found several gut microbiota components causally associated with sarcopenia-related traits. Our findings provided insights into novel strategies for the prevention and treatment of sarcopenia through the regulation of the gut microbiota, contributing to a better understanding of the gut-muscle axis.

Alzheimer Disease and Epilepsy: A Mendelian Randomization Study.

Observational studies suggested a bidirectional relationship between Alzheimer disease (AD) and epilepsies. However, it remains debated whether and in which direction a causal association exists. This study aims to explore the relationship between genetic predisposition to AD, CSF biomarkers of AD (β-amyloid [Aβ] 42 and phosphorylated tau [pTau]), and epilepsies with 2-sample, bidirectional Mendelian randomization (MR) method. Genetic instruments were obtained from large-scale genome-wide meta-analysis of AD (Ncase/proxy = 111,326, Ncontrol = 677,663), CSF biomarkers of AD (Aβ42 and pTau, N = 13,116), and epilepsy (Ncase = 15,212, Ncontrol = 29,677) of European ancestry. Epilepsy phenotypes included all epilepsy, generalized epilepsy, focal epilepsy, childhood absence epilepsy, juvenile absence epilepsy, juvenile myoclonic epilepsy, generalized epilepsy with tonic-clonic seizures, focal epilepsy with hippocampal sclerosis (focal HS), and lesion-negative focal epilepsy. Main analyses were performed using generalized summary data-based MR. Sensitivity analyses included inverse variance weighted, MR pleiotropy residual sum and outlier, MR-Egger, weighted mode, and weighted median. For forward analysis, genetic predisposition to AD was associated with an increased risk of generalized epilepsy (odds ratio [OR] 1.053, 95% CI 1.002-1.105, p = 0.038) and focal HS (OR 1.013, 95% CI 1.004-1.022, p = 0.004). These associations were consistent across sensitivity analyses and replicated using a separate set of genetic instruments from another AD genome-wide association study. For reverse analysis, there was a suggestive effect of focal HS on AD (OR 3.994, 95% CI 1.172-13.613, p = 0.027). In addition, genetically predicted lower CSF Aβ42 was associated with an increased risk of generalized epilepsy (β = 0.090, 95% CI 0.022-0.158, p = 0.010). This MR study supports a causal link between AD, amyloid pathology, and generalized epilepsy. This study also indicates a close association between AD and focal HS. More effort should be made to screen seizure in AD, unravel its clinical implications, and explore its role as a putative modifiable risk factor.

Assessing the relationship between gut microbiota and irritable bowel syndrome: a two-sample Mendelian randomization analysis

BackgroundGrowing evidence has suggested that gut microbiota is closely related to the risk of irritable bowel syndrome (IBS), but whether there is a causal effect remains unknown. We adopted a Mendelian randomization (MR) approach to evaluate the potential causal relationships between gut microbiota and the risk of IBS.MethodsGenetic instrumental variables for gut microbiota were identified from a genome-wide association study (GWAS) of 18,340 participants. Summary statistics of IBS were drawn from a GWAS including 53,400 cases and 433,201 controls. We used the inverse-variance weighted (IVW) method as the primary analysis. To test the robustness of our results, we further performed the weighted-median method, MR-Egger regression, and MR pleiotropy residual sum and outlier test. Finally, reverse MR analysis was performed to evaluate the possibility of reverse causation.ResultsWe identified suggestive associations between three bacterial traits and the risk of IBS (odds ratio (OR): 1.08; 95% confidence interval (CI): 1.02, 1.15; p = 0.011 for phylum Actinobacteria; OR: 0.95; 95% CI: 0.91, 1.00; p = 0.030 for genus Eisenbergiella and OR: 1.10; 95% CI: 1.03, 1.18; p = 0.005 for genus Flavonifractor). The results of sensitivity analyses for these bacterial traits were consistent. We did not find statistically significant associations between IBS and these three bacterial traits in the reverse MR analysis.ConclusionsOur systematic analyses provide evidence to support a potential causal relationship between several gut microbiota taxa and the risk of IBS. More studies are required to show how the gut microbiota affects the development of IBS.

Age at menarche and polycystic ovary syndrome: A Mendelian randomization study.

The authors aimed to use a large two-sample Mendelian randomization (MR) study to reveal the causality between age at menarche (AAM) and polycystic ovary syndrome (PCOS) incidence. The authors collected summary statistics from the hitherto largest genome-wide association studies conducted in AAM and PCOS in the same ancestry. MR with inverse variance weighting was conducted as the main analysis method, while weighted median and MR-Egger regression were used for comprehensive analysis. As for pleiotropy detection, inverse variance weighting, MR-Egger regression, Mendelian Randomization Pleiotropy Residual Sum and Outlier, as well as leave-one-out analysis were used to detect pleiotropy. Risk factor analysis was conducted to investigate the underlying mechanisms linking AAM to PCOS. Each standard deviation increment in AAM was associated with a significantly lower incidence of PCOS (odds ratio, 0.86 [95% confidence interval, 0.75-0.98]). After adjustment in horizontal pleiotropy by eliminating four outliers, this pathogenic association was still statistically detected. All pleiotropy indexes were without statistical differences, which suggested the conclusions were robust. It showed the causal association between later AAM and lower body mass index, lower fasting insulin level and insulin resistance. Our MR analysis verified that a slightly later onset age (15 to 18 years) at menarche could reduce the risk of PCOS. A more comprehensive investigation in a prospective setting is strongly advised.

Illuminating the potential causality of serum level of matrix metalloproteinases and the occurrence of cardiovascular and cerebrovascular diseases: a Mendelian randomization study.

It is still not clear that whether the expression levels of matrix metalloproteinases (MMPs) family are associated with cardiovascular and cerebrovascular diseases (CCDs) in genetic level. We explored the causal role of 12 members of MMPs in CCDs with mendelian randomization (MR) method to facilitate further exploring the underlying mechanisms. The relationship between MMPs and CCDs including intracerebral hemorrhage (ICH), hypertension, coronary heart disease (CHD), atrial fibrillation (AF), and outstanding risk factors of type II diabetes were determined with the inverse variance-weighted (IVW) method. The sensitivity analyses including MR-Egger regression, weighted median estimation, and MR pleiotropy residual sum and outlier were utilized to test the robustness of the results generated from the MR method. We found that a higher serum level of MMP-12 was related to a lower risk of ICH (OR = 0.8287, 95% CI: 0.7526-0.9125, p = 0.00013), but not hypertension, CHD, type II diabetes or AF. And our study also revealed that a higher serum level of MMP-8 could result in a lower risk of hypertension (OR = 0.9976, 95% CI: 0.9964-0.9988, p = 0.00012) and AF (OR = 0.9851, 95% CI: 0.9741-0.9963, p = 0.0092), but not ICH, CHD or type II diabetes. All other members of MMPs other than MMP-8 and MMP-12 showed no statistical association with CCDs according to this study. Sensitivity analyses confirmed the reliability of our results. We provided statistical evidences for a potential causal relationship between MMP-12 and ICH, as well as MMP-8 and hypertension, while other MMPs showed weaker association with CCDs. The underlying mechanisms need to be established in the future.

Genetic proxies for calcium channel blockers and cancer: a Mendelian randomization study.

Calcium channel blockers (CCBs) are commonly prescribed antihypertensives. However, concerns exist about potential off-target effects on cancer. This Mendelian randomization (MR) study examined the associations of genetic proxies for CCBs with the risk of cancer. We used published genetic proxies in the target genes of CCBs as instruments, and obtained MR estimates by applying them to large studies of 17 site-specific cancers (non-Hodgkin lymphoma, melanoma, leukemia, thyroid, rectal, pancreatic, oral cavity/pharyngeal, kidney, esophagus/stomach, colon, bladder, endometrial, cervical and breast, prostate, lung and ovarian cancer) from the Pan-Cancer study, with replication for breast cancer (133,384 cases, 113,789 controls from the Breast Cancer Association Consortium), prostate cancer (79,148 cases, 61,106 controls from the Prostate Cancer Association Group to Investigate Cancer Associated Alterations in the Genome consortium), lung cancer (11,348 cases, 15,861 controls from the International Lung Cancer Consortium), and ovarian cancer (25,509 cases, 40,941 controls from the Ovarian Cancer Association Consortium). We used inverse variance weighting for the main analysis and the weighted median, MR-Egger and Mendelian Randomization Pleiotropy Residual Sum and Outlier as sensitivity analyses. Genetic proxies for CCBs were not associated with any cancer after Bonferroni-correction (at the threshold of p < 0.003). Associations were robust to different MR methods. In conclusion, our study suggests no association of genetic proxies forCCBs with 17 different cancers. While the findings add some support to the safety profile of CCBs in long-term use, future replication is necessary to provide definitive evidence.

Causal relationship between cannabis use and cancer: a genetically informed perspective.

Cannabis use is increasing legally worldwide, while its impact on cancer risk is unclear. This study was performed to investigate the relationship between cannabis use and the risk of several types of cancer. We conducted a two-sample Mendelian randomization (MR) study to explore the causality of cannabis use on 9 site-specific types of cancer including breast cancer, cervical cancer, melanoma, colorectal cancer, laryngeal cancer, oral cancer, oropharyngeal cancer, esophageal cancer, and glioma. Genome-wide significant genetic instruments (P < 5E-06) for cannabis use were extracted from a large-scale genome-wide association meta-analysis of European ancestry, whereas cancer genetic instruments were extracted from the UK Biobank (UKB) cohort and GliomaScan consortium in the OpenGWAS database. The inverse-variance weighted (IVW) was considered the main method for MR analysis, and sensitivity analyses including MR-Egger, weighted median, MR pleiotropy residual sum, and outlier test (MR-PRESSO) were conducted to evaluate the robustness of the results. Cannabis use was a significant promoting factor for cervical cancer (OR = 1.001265, 95% CI 1.000375-1.002155, P = 0.0053). And we also detected suggestive evidence of the causality of cannabis use on laryngeal cancer (OR = 1.000350, 95% CI 1.000027-1.000672, P = 0.0336) and breast cancer (OR = 1.003741, 95% CI 1.000052-1.007442, P = 0.0467). No evidence of a causal association of cannabis use with other site-specific types of cancer was detected. Additionally, no pleiotropy or heterogeneity was found in the sensitivity analysis. This study indicates a causative association of cannabis use on cervical cancer, while cannabis use may increase the odds of breast cancer and laryngeal cancer, which require further evaluation in large-scale population-based studies.

Circulating metabolites and depression: a bidirectional Mendelian randomization.

Studies have shown an association between depression and circulating metabolites, but the causal relationship between them has not been elucidated. The purpose of this study was to elucidate the causal relationship between circulating metabolites and depression and to explore the role of circulating metabolites in depression. In this study, the top single-nucleotide polymorphisms (SNPs) associated with circulating metabolites (n = 24,925) and depression (n = 322,580) were obtained based on the publicly available genome-wide association study using two-sample Mendelian randomization (MR). SNP estimates were summarized through inverse variance weighted, MR Egger, weighted median, MR pleiotropy residual sum and outlier, and "leave-one-out" methods. Apolipoprotein A-I (OR 0.990, 95% CI 981-0.999) and glutamine (OR 0.985, 95% CI 0.972-0.997) had protective causal effects on depression, whereas acetoacetate (OR 1.021, 95% CI 1.009-1.034), glycoproteins (OR 1.005, 95% CI 1.000-1.009), isoleucine (OR 1.013, 95% CI 1.002-1.024), and urea (OR 1.020, 95% CI 1.000-1.039) had an anti-protective effect on depression. Reversed MR showed no effect of depression on the seven circulating metabolites. In this study, MR analysis showed that apolipoprotein A-I and glutamine had a protective effect on depression, and acetoacetate, glycoprotein, isoleucine, glucose, and urea may be risk factors for depression. Therefore, further research must be conducted to translate the findings into practice.

Inflammatory bowel disease is causally related to irritable bowel syndrome: a bidirectional two-sample Mendelian randomization study.

Inflammatory bowel disease (IBD) and irritable bowel syndrome (IBS) are lifelong digestive diseases that severely impact patients' quality of life. The existence of a causal association between IBS and IBD remains unclear. This study aimed to determine the direction of causality between IBD and IBS by quantifying their genome-wide genetic associations and performing bidirectional two-sample Mendelian randomization (MR) analyses. Genome-wide association studies (GWAS) among a predominantly European patient cohort identified independent genetic variants associated with IBS and IBD. Two separate databases (a large GWAS meta-analysis and the FinnGen cohort) for both IBS and IBD were consulted to retrieve statistics on instrument-outcome associations. MR analyses included inverse-variance-weighted, weighted-median, MR-Egger regression, MR Pleiotropy RESidual Sum and Outlier (MR-PRESSO) methods, and sensitivity analyses were performed. The MR analyses were carried out for each outcome data, followed by a fixed-effect meta-analysis. Genetically predicted IBD was associated with an increased risk of IBS. Odds ratios (95% confidence intervals) for samples of 211,551 (17,302 individuals with IBD), 192,789 (7,476 Crohn's disease cases), and 201,143 (10,293 ulcerative colitis cases) individuals were 1.20 (1.00, 1.04), 1.02 (1.01, 1.03), and 1.01 (0.99, 1.03), respectively. After outlier correction using MR-PRESSO, the odds ratio for ulcerative colitis was 1.03 (1.02, 1.05) (p = 0.001). However, an association between genetically influenced IBS and IBD was not identified. This study confirms that IBD is causally related to IBS, which may interfere with the diagnosis and treatment of both diseases.