GP.01 Childhood obesity and multiple sclerosis susceptibility: a Mendelian randomization study

Background: Observational studies have reported an association between childhood obesity and a higher risk of multiple sclerosis (MS). However, the difficulties to fully account for confounding and long recall periods make causal inference from these studies challenging. The objective of this study was to assess the contribution of childhood obesity to the development of MS through Mendelian randomization, which uses genetic associations to minimize the risk of confounding. Methods: We selected 23 independent genetic variants strongly associated with childhood body mass index (BMI) in a genome-wide association study (GWAS) which included 47,541 children. The corresponding effects of these variants on risk of MS were obtained from a GWAS of 14,802 MS cases and 26,703 controls. Standard two-sample Mendelian randomization methods were performed, with additional sensitivity analyses to assess the likelihood of bias from genetic pleiotropy. Results: The inverse-variance weighted MR analysis revealed that one standard deviation increase in childhood BMI increased odds of MS by 26% (odds ratio=1.26, 95% confidence interval 1.10-1.45, p=0.001). There was no significant heterogeneity across the individual estimates. Sensitivity analyses were consistent with the main findings and provided no evidence of pleiotropy. Conclusions: This study provides genetic support of a role for increased childhood BMI in the development of MS.

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Genetically Determined Levels of Serum Metabolites and Risk of Neuroticism: A Mendelian Randomization Study

The International Journal of Neuropsychopharmacology ◽

10.1093/ijnp/pyaa062 ◽

2020 ◽

Author(s):

Li Qian ◽

Yajuan Fan ◽

Fengjie Gao ◽

Binbin Zhao ◽

Bin Yan ◽

...

Keyword(s):

Uric Acid ◽

Lower Risk ◽

Genome Wide Association Study ◽

Mendelian Randomization ◽

Strong Predictor ◽

Causal Effects ◽

Sensitivity Analyses ◽

Nucleotide Polymorphisms ◽

Genetic Associations ◽

Inverse Variance

Abstract Background Neuroticism is a strong predictor for a variety of social and behavioral outcomes, but the etiology is still unknown. Our study aims to provide a comprehensive investigation of causal effects of serum metabolome phenotypes on risk of neuroticism using Mendelian randomization (MR) approaches. Methods Genetic associations with 486 metabolic traits were utilized as exposures, and data from a large genome-wide association study of neuroticism were selected as outcome. For MR analysis, we used the standard inverse-variance weighted (IVW) method for primary MR analysis and 3 additional MR methods (MR-Egger, weighted median, and MR pleiotropy residual sum and outlier) for sensitivity analyses. Results Our study identified 31 metabolites that might have causal effects on neuroticism. Of the 31 metabolites, uric acid and paraxanthine showed robustly significant association with neuroticism in all MR methods. Using single nucleotide polymorphisms as instrumental variables, a 1-SD increase in uric acid was associated with approximately 30% lower risk of neuroticism (OR: 0.77; 95% CI: 0.62–0.95; PIVW = 0.0145), whereas a 1-SD increase in paraxanthine was associated with a 7% higher risk of neuroticism (OR: 1.07; 95% CI: 1.01–1.12; PIVW = .0145). Discussion Our study suggested an increased level of uric acid was associated with lower risk of neuroticism, whereas paraxanthine showed the contrary effect. Our study provided novel insight by combining metabolomics with genomics to help understand the pathogenesis of neuroticism.

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Iron Status May Not Affect Amyotrophic Lateral Sclerosis: A Mendelian Randomization Study

Frontiers in Genetics ◽

10.3389/fgene.2021.617245 ◽

2021 ◽

Vol 12 ◽

Author(s):

Jiahao Cai ◽

Xiong Chen ◽

Hongxuan Wang ◽

Zixin Wei ◽

Mei Li ◽

...

Keyword(s):

Amyotrophic Lateral Sclerosis ◽

Genome Wide Association Study ◽

Mendelian Randomization ◽

Causal Effect ◽

Iron Status ◽

Transferrin Saturation ◽

Outcome Data ◽

Sensitivity Analyses ◽

A Genome ◽

Lateral Sclerosis

BackgroundObservational studies have shown an association of increased iron status with a higher risk of amyotrophic lateral sclerosis (ALS). Iron status might be a novel target for ALS prevention if a causal relationship exists. We aimed to reveal the causality between iron status and ALS incidence using a large two-sample Mendelian randomization (MR).MethodsSingle nucleotide polymorphisms (SNPs) for iron status were identified from a genome-wide association study (GWAS) on 48,972 individuals. The outcome data came from the largest ALS GWAS to date (20,806 cases; 59,804 controls). We conducted conservative analyses (using SNPs with concordant change of biomarkers of iron status) and liberal analyses (using SNPs associated with at least one of the biomarkers of iron status), with inverse variance weighted (IVW) method as the main analysis. We then performed sensitivity analyses including weighted median, MR-Egger and MR-pleiotropy residual sum and outlier, as well as leave-one-out analysis to detect pleiotropy.ResultsIn the conservative analyses, we found no evidence of association between four biomarkers of iron status and ALS using IVW method with odds ratio (OR) 1.00 [95% confidence interval (CI): 0.90–1.11] per standard deviation (SD) increase in iron, 0.96 (95% CI: 0.77–1.21) in ferritin, 0.99 (95% CI: 0.92–1.07) in transferrin saturation, and 1.04 (95% CI: 0.93–1.16) in transferrin. Findings from liberal analyses were similar, and sensitivity analyses suggested no pleiotropy detected (all p > 0.05).ConclusionOur findings suggest no causal effect between iron status and risk of ALS. Efforts to change the iron status to decrease ALS incidence might be impractical.

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Large differences in adiponectin levels have no clear effect on multiple sclerosis risk: A Mendelian randomization study

Multiple Sclerosis Journal ◽

10.1177/1352458516681196 ◽

2016 ◽

Vol 23 (11) ◽

pp. 1461-1468 ◽

Cited By ~ 6

Author(s):

Julia Devorak ◽

Lauren E Mokry ◽

John A Morris ◽

Vincenzo Forgetta ◽

George Davey Smith ◽

...

Keyword(s):

Multiple Sclerosis ◽

Body Mass ◽

Mendelian Randomization ◽

Strong Support ◽

Sensitivity Analyses ◽

Nucleotide Polymorphisms ◽

Standard Deviation Increase ◽

Clear Effect ◽

Genome Wide ◽

Unit Increase

Background: Mendelian randomization (MR) studies have demonstrated strong support for an association between genetically increased body mass index and risk of multiple sclerosis (MS). The adipokine adiponectin may be a potential mechanism linking body mass to risk of MS. Objective: To evaluate whether genetically increased adiponectin levels influence risk of MS. Methods: Using genome-wide significant single nucleotide polymorphisms (SNPs) for adiponectin, we undertook an MR study to estimate the effect of adiponectin on MS. This method prevents bias due to reverse causation and minimizes bias due to confounding. Sensitivity analyses were performed to evaluate the assumptions of MR. Results: MR analyses did not support a role for genetically elevated adiponectin in risk of MS (odds ratio (OR) = 0.93 per unit increase in natural-log-transformed adiponectin, equivalent to a two-standard deviation increase in adiponectin on the absolute scale; 95% confidence interval (CI) = 0.66–1.33; p = 0.61). Further MR analysis suggested that genetic variation at the adiponectin gene, which influences adiponectin level, does not impact MS risk. Sensitivity analyses, including MR-Egger regression, suggested no bias due to pleiotropy. Conclusion: Lifelong genetically increased adiponectin levels in humans have no clear effect on risk of MS. Other biological factors driving the association between body mass and MS should be investigated.

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Childhood obesity and multiple sclerosis: A Mendelian randomization study

Multiple Sclerosis Journal ◽

10.1177/13524585211001781 ◽

2021 ◽

pp. 135245852110017

Author(s):

Adil Harroud ◽

Ruth E Mitchell ◽

Tom G Richardson ◽

John A Morris ◽

Vincenzo Forgetta ◽

...

Keyword(s):

Multiple Sclerosis ◽

Childhood Obesity ◽

Mendelian Randomization ◽

Pubertal Timing ◽

Association Studies ◽

Sensitivity Analyses ◽

Genome Wide Association Studies ◽

Uk Biobank ◽

Increased Risk ◽

Age At Puberty

Background: Higher childhood body mass index (BMI) has been associated with an increased risk of multiple sclerosis (MS). Objective: To evaluate whether childhood BMI has a causal influence on MS, and whether this putative effect is independent from early adult obesity and pubertal timing. Methods: We performed Mendelian randomization (MR) using summary genetic data on 14,802 MS cases and 26,703 controls. Large-scale genome-wide association studies provided estimates for BMI in childhood ( n = 47,541) and adulthood ( n = 322,154). In multivariable MR, we examined the direct effects of each timepoint and further adjusted for age at puberty. Findings were replicated using the UK Biobank ( n = 453,169). Results: Higher genetically predicted childhood BMI was associated with increased odds of MS (odds ratio (OR) = 1.26/SD BMI increase, 95% confidence interval (CI): 1.07–1.50). However, there was little evidence of a direct effect after adjusting for adult BMI (OR = 1.03, 95% CI: 0.70–1.53). Conversely, the effect of adult BMI persisted independent of childhood BMI (OR = 1.43; 95% CI: 1.01–2.03). The addition of age at puberty did not alter the findings. UK Biobank analyses showed consistent results. Sensitivity analyses provided no evidence of pleiotropy. Conclusion: Genetic evidence supports an association between childhood obesity and MS susceptibility, mediated by persistence of obesity into early adulthood but independent of pubertal timing.

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Inflammatory Cytokines and Risk of Ischemic Stroke: A Mendelian Randomization Study

Frontiers in Pharmacology ◽

10.3389/fphar.2021.779899 ◽

2022 ◽

Vol 12 ◽

Author(s):

Yalan Li ◽

Jun Lu ◽

Jie Wang ◽

Peizhi Deng ◽

Changjiang Meng ◽

...

Keyword(s):

Ischemic Stroke ◽

Inflammatory Cytokines ◽

Large Scale ◽

Genome Wide Association Study ◽

Mendelian Randomization ◽

Causal Effect ◽

Meta Analysis ◽

Outcome Data ◽

Sensitivity Analyses ◽

A Genome

Background: Observational studies have revealed the association between some inflammatory cytokines and the occurrence of ischemic stroke, but the causal relationships remain unclear.Methods: We conducted a two-sample Mendelian randomization (MR) analysis to assess the causal effects of thirty inflammatory cytokines and the risk of ischemic stroke. For exposure data, we collected genetic variants associated with inflammatory cytokines as instrumental variables (IVs) from a genome-wide association study (GWAS) meta-analysis from Finland (sample size up to 8,293). For the outcome data, we collected summary data of ischemic stroke from a large-scale GWAS meta-analysis involved 17 studies (34,217 cases and 406,111 controls). We further performed a series of sensitivity analyses as validation of primary MR results.Results: According to the primary MR estimations and further sensitivity analyses, we established one robust association after Bonferroni correction: the odds ratio (95% CI) per unit change in genetically increased IL-4 was 0.84 (0.89–0.95) for ischemic stroke. The chemokine MCP3 showed a nominally significant association with ischemic stroke risk (OR: 0.93, 95% CI: 0.88–0.99, unadjusted p < 0.05). There was no evidence of a causal effect of other inflammatory cytokines and the risk of ischemic stroke.Conclusions: Our study suggested that genetically increased IL-4 levels showed a protective effect on the risk of ischemic stroke, which provides important new insights into the potential therapeutic target for preventing ischemic stroke.

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Carnitine and COVID-19 Susceptibility and Severity: A Mendelian Randomization Study

Frontiers in Nutrition ◽

10.3389/fnut.2021.780205 ◽

2021 ◽

Vol 8 ◽

Author(s):

Chunyu Li ◽

Ruwei Ou ◽

Qianqian Wei ◽

Huifang Shang

Keyword(s):

Causal Relationship ◽

Genome Wide Association Study ◽

Mendelian Randomization ◽

Sensitivity Analyses ◽

Nucleotide Polymorphisms ◽

Carnitine Level ◽

Standard Deviation Increase ◽

Inverse Variance ◽

Weighted Median ◽

Genetically Determined

Background: Carnitine, a potential substitute or supplementation for dexamethasone, might protect against COVID-19 based on its molecular functions. However, the correlation between carnitine and COVID-19 has not been explored yet, and whether there exists causation is unknown.Methods: A two-sample Mendelian randomization (MR) analysis was conducted to explore the causal relationship between carnitine level and COVID-19. Significant single nucleotide polymorphisms from genome-wide association study on carnitine (N = 7,824) were utilized as exposure instruments, and summary statistics of the susceptibility (N = 1,467,264), severity (N = 714,592) and hospitalization (N = 1,887,658) of COVID-19 were utilized as the outcome. The causal relationship was evaluated by multiplicative random effects inverse variance weighted (IVW) method, and further verified by another three MR methods including MR Egger, weighted median, and weighted mode, as well as extensive sensitivity analyses.Results: Genetically determined one standard deviation increase in carnitine amount was associated with lower susceptibility (OR: 0.38, 95% CI: 0.19–0.74, P: 4.77E−03) of COVID-19. Carnitine amount was also associated with lower severity and hospitalization of COVID-19 using another three MR methods, though the association was not significant using the IVW method but showed the same direction of effect. The results were robust under all sensitivity analyses.Conclusions: A genetic predisposition to high carnitine levels might reduce the susceptibility and severity of COVID-19. These results provide better understandings on the role of carnitine in the COVID-19 pathogenesis, and facilitate novel therapeutic targets for COVID-19 in future clinical trials.

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Effect of age at puberty on risk of multiple sclerosis

Neurology ◽

10.1212/wnl.0000000000007325 ◽

2019 ◽

Vol 92 (16) ◽

pp. e1803-e1810 ◽

Cited By ~ 7

Author(s):

Adil Harroud ◽

John A. Morris ◽

Vincenzo Forgetta ◽

Ruth Mitchell ◽

George Davey Smith ◽

...

Keyword(s):

Multiple Sclerosis ◽

Weight Status ◽

Genome Wide Association Study ◽

Causal Effect ◽

Pubertal Timing ◽

Sensitivity Analyses ◽

Age At Menarche ◽

A Genome ◽

Age At Puberty ◽

Effect Of Age

ObjectiveTo investigate the potential for a causal effect of age at puberty on multiple sclerosis (MS) susceptibility using a mendelian randomization (MR) approach.MethodsWe used 372 genetic variants strongly associated with age at menarche in a genome-wide association study (GWAS) involving 329,245 women. The genetic architecture of pubertal timing across both sexes is highly correlated (genetic correlation [rg] = 0.75, p = 1.2 × 10−79), allowing these variants to provide reliable insight into pubertal timing in males as well. The effect of pubertal timing on risk of MS was measured with summary statistics from a GWAS of 14,802 cases with MS and 26,703 controls from the International Multiple Sclerosis Genetics Consortium. Multivariable MR controlling for effects of body mass index (BMI) using genetic data from additional consortia investigated whether pubertal effects on MS were dependent on weight status.ResultsA 1-year increase in genetically predicted age at puberty decreased odds of MS by 8% (odds ratio [OR] 0.92, 95% confidence interval [CI] 0.86–0.99, p = 0.03). However, multivariable MR analysis showed that after accounting for effects on adult BMI, the association of age at puberty with MS susceptibility attenuated (OR 0.96, 95% CI 0.88–1.04, p = 0.36). Similar results were obtained when childhood BMI was incorporated. Sensitivity analyses provided no evidence of major bias from genetic pleiotropy.ConclusionsWe found support for an association between higher age at puberty and decreased risk of MS with a magnitude comparable to that reported in observational studies. This effect appears to be largely mediated by the strong association between age at puberty and obesity. A large causal effect of pubertal timing independent of BMI is unlikely.

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Periodontitis and pulmonary function: a Mendelian randomization study

Clinical Oral Investigations ◽

10.1007/s00784-021-04000-9 ◽

2021 ◽

Author(s):

Sebastian-Edgar Baumeister ◽

Michael Nolde ◽

Birte Holtfreter ◽

Hansjörg Baurecht ◽

Sven Gläser ◽

...

Keyword(s):

Pulmonary Function ◽

Genome Wide Association Study ◽

Mendelian Randomization ◽

Forced Expiratory Volume ◽

Sensitivity Analyses ◽

Observational Research ◽

Nucleotide Polymorphisms ◽

Genetic Liability ◽

A Genome ◽

The Uk

Abstract Objectives Observational research suggests that periodontitis affects pulmonary function; however, observational studies are subject to confounding and reverse causation, making causal inference and the direction of these associations difficult. We used Mendelian randomization (MR) to assess the potential causal association between genetic liability to periodontitis and pulmonary function. Materials and methods We used six single-nucleotide polymorphisms (SNPs) associated with periodontitis (P < 5 × 10−6) from a genome-wide association study (GWAS) of 17,353 European descent periodontitis cases and 28,210 controls from the GeneLifestyle Interactions in Dental Endpoints consortium and the UK Biobank, and related these to SNPs from a lung function GWAS including 79,055 study participants of the SpiroMeta Consortium. Results MR analysis suggested no effect of periodontitis on the ratio of forced expiratory volume in one second to lower forced vital capacity (standard deviation increment in outcome per doubling of the odds of the exposure (95% confidence interval) = − 0.004 (− 0.028; 0.020)). Replication analysis using genetic instruments from two different GWAS and sensitivity analyses to address potential pleiotropy led to no substantial changes in estimates. Conclusions Collectively, these findings do not support a relationship between genetic liability for periodontitis and pulmonary function. Clinical relevance Periodontitis does not seem to be a risk factor for worsening of pulmonary function.

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Association of telomere length with risk of rheumatoid arthritis: a meta-analysis and Mendelian randomization

Rheumatology ◽

10.1093/rheumatology/kez524 ◽

2019 ◽

Vol 59 (5) ◽

pp. 940-947 ◽

Cited By ~ 1

Author(s):

Zhen Zeng ◽

Wanting Zhang ◽

Yu Qian ◽

Huijun Huang ◽

David J H Wu ◽

...

Keyword(s):

Genome Wide Association Study ◽

Mendelian Randomization ◽

Meta Analysis ◽

Genome Wide Association ◽

Sensitivity Analyses ◽

Causal Association ◽

Genome Wide ◽

Inverse Variance ◽

A Genome ◽

Mean Differences

Abstract Objective To evaluate the telomere length (TL) in patients with RA relative to that in controls and to test whether TL is causally associated with risk of RA. Methods Systematic review and meta-analysis of relevant literature was conducted to evaluate the association between TL and RA. Standardized mean differences with 95% CIs of TL in RA patients relative to controls were pooled using fixed or random-effects models. TL-related single-nucleotide polymorphisms were selected from a genome-wide association study of 37 684 individuals, and summary statistics of RA were obtained from a genome-wide association study meta-analysis including 14 361 RA patients and 43 923 controls. Mendelian randomization was performed using the inverse-variance weighted, weighted-median and likelihood-based methods. Sensitivity analyses were performed to test the robustness of the association. Results In the meta-analysis of 911 RA patients and 2498 controls, we found that patients with RA had a significantly shorter TL compared with controls (standardized mean differences = −0.50; 95% CI −0.88, −0.11; P = 0.012). In the Mendelian randomization analysis, we found that genetically predicted longer TL was associated with a reduced risk of RA [odds ratio = 0.68; 95% CI 0.54, 0.86; P = 0.002 using the inverse-variance weighted method]. Sensitivity analyses using alternative Mendelian randomization approaches yielded similar findings, suggesting the robustness of the causal association. Conclusion Our study provides evidence for a negative causal association of TL with risk of RA. Further studies are warranted to elucidate the underlying mechanism for the role of telomeres in the development of RA.

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Mendelian randomization study shows no causal effects of serum urate levels on the risk of MS

Neurology Neuroimmunology & Neuroinflammation ◽

10.1212/nxi.0000000000000920 ◽

2020 ◽

Vol 8 (1) ◽

pp. e920

Author(s):

Adil Harroud ◽

J. Brent Richards ◽

Sergio E. Baranzini

Keyword(s):

Large Scale ◽

Genome Wide Association Study ◽

Mendelian Randomization ◽

Causal Effect ◽

Meta Analysis ◽

Serum Urate ◽

Sensitivity Analyses ◽

Data Sets ◽

A Genome ◽

Mr Study

ObjectiveTo examine whether lifelong genetically increased serum urate levels, a potent antioxidant, contribute to MS susceptibility using Mendelian randomization (MR).MethodsThis 2-sample MR study included 25 independent genetic variants strongly associated with serum urate levels in a genome-wide association study meta-analysis of 140,949 individuals. Effects on the risk of MS were assessed with summary statistics from 3 large-scale MS genetic data sets totaling 61,667 MS cases and 86,806 controls from the International MS Genetic Consortium. Multiple sensitivity analyses were performed to evaluate the assumptions of MR and remove potentially pleiotropic variants.ResultsUsing inverse-variance weighted MR, we found no evidence for a causal effect of serum urate level on the risk of MS in any of the cohorts (MS1: OR 0.99 per each mg/dL unit increase in urate, 95% CI 0.89–1.08, p = 0.76; MS2: OR = 0.99, 95% CI 0.89–1.11, p = 0.90; MS3: OR = 1.00, 95% CI 0.98–1.2, p = 0.91). Pleiotropy robust MR methods yielded consistent estimates.ConclusionThis MR study does not support a clinically relevant causal effect of serum urate levels on the risk of MS.

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