Hip Bone Marrow Adiposity as a Risk Factor for Alzheimer's Disease: Insights From Mendelian Randomization Analysis.

Objective. To examine whether bone mineral density (BMD) is causally associated with osteoarthritis (OA). Methods. We performed a two-sample Mendelian randomization (MR) analysis using the inverse-variance weighting (IVW), weighted median, and MR-Egger regression methods. We used publicly available summary statistics datasets of a genome-wide association study (GWAS) on femur neck (FN) BMD of individuals of European ancestry as the exposure and a GWAS for non-cancer illness code self-reported: OA from the individuals included in the UK Biobank as the outcome. Results. We selected 21 independent single- nucleotide polymorphisms with genome-wide significance (p＜5.00E-08) from GWAS on FN BMD as the instrumental variables. The IVW method (beta=0.010, standard error [SE]=0.003, p=0.002) and the weighted median approach (beta=0.011, SE=0.004, p=0.006) yielded evidence of a causal association between FN BMD and OA. However, the MR-Egger analysis showed no causal association between FN BMD and OA (beta=0.005, SE=0.017, p=0.753). Since MR-Egger regression suffers from a lack of power and a susceptibility to weak instrument bias, the MR analysis results may support a causal association between FN BMD and OA. Conclusion. The results of MR analysis by IVW and weighted median, but not MR-Egger regression indicate that FN BMD is likely to be causally associated with an increased risk of OA incidence The current findings may provide an opportunity to elucidate the underlying mechanisms of the effects of BMD on the OA incidence. (J Rheum Dis 2019;26:104-110)

Until recently, it remains unclear whether schizophrenia, bipolar disorder (BD), and Alzheimer’s disease (AD) is associated with bone mineral density (BMD). We aimed to investigate the causal effects of schizophrenia, BD and AD on BMD with Mendelian randomization (MR) analysis. Single-nucleotide polymorphisms (SNPs) strongly associated with these three neuropsychiatric diseases as instrumental variables were selected from genome-wide association studies in the MR Base database. We analyzed the effects of these SNPs on the femoral neck BMD (FN-BMD), lumbar spine BMD (LS-BMD) and forearm BMD (FA-BMD), and evaluated the heterogeneities and pleiotropy of these genetic variants. We also evaluated the potential confounding factors in the association between these three neuropsychiatric diseases and the BMD level. It was found that none of these genetic variants were significantly associated with BMD or confounding factors. Using these genetic variants, we did not find statistically significant causal effects of per unit increase in the log-odds of having schizophrenia, BD or AD with FN-BMD, LS-BMD and FA-BMD changes (e.g. schizophrenia and FN-BMD, MR-Egger OR 0.9673, 95% CI 0.8382 to 1.1163, p = 0.6519). The MR results also revealed that directional pleiotropy was unlikely to bias the causality (e.g., schizophrenia and FN-BMD, intercept = 0.0023, p = 0.6887), and no evidence of heterogeneity was found between the genetic variants (e.g., schizophrenia and FN-BMD, MR-Egger Q = 46.1502, I2 = 0.0899, p = 0.3047). Our MR study did not support causal effects of increased risk of schizophrenia, BD and AD status with BMD level.

Assessing causal relationship between non-alcoholic fatty liver disease and risk of atrial fibrillation

Epidemiological studies showed that COVID-19 increases risk of Alzheimer's disease (AD). However, it remains unknown if there is a potential genetic predispositional effect. To examine potential effects of genetic susceptibility of COVID-19 on the risk and progression of AD, we performed a non-overlapping 2-sample Mendelian randomization (MR) study using summary statistics from genome-wide association studies (GWAS). Two-sample Mendelian randomization (MR) analysis of over 2.6 million subjects was used to examine whether genetic susceptibility of COVID-19 is not associated with the risk of AD, cortical amyloid burden, hippocampal volume, or AD progression score. Additionally, a validation analysis was performed on a combined sample size of 536,190 participants. We show that the AD risk was not associated with genetic susceptibility of COVID-19 risk (OR = 0.98, 95% CI 0.81-1.19) and COVID-19 severity (COVID-19 hospitalization: OR = 0.98, 95% CI 0.9-1.07, and critical COVID-19: OR = 0.98, 95% CI 0.92-1.03). Genetic predisposition to COVID-19 is not associated with AD progression as measured by hippocampal volume, cortical amyloid beta load, and AD progression score. These findings were replicated in a set of 536,190 participants. Consistent results were obtained across models based on different GWAS summary statistics, MR estimators and COVID-19 definitions. Our findings indicated that the genetic susceptibility of COVID-19 is not associated with the risk and progression of AD.

A novel Mendelian randomisation framework unravels one gene expression component, correlated with proliferation and genome stability-related features, associated with telomere length in lung adenocarcinoma tumours, which provides insights into how telomere length influences the genetic basis of lung cancer aetiology.

A novel Mendelian randomisation framework unravels one gene expression component, correlated with proliferation and genome stability-related features, associated with telomere length in lung adenocarcinoma tumours, which provides insights into how telomere length influences the genetic basis of lung cancer aetiology.

Emerging evidence from observational studies and clinical trials suggests a connection between the gut microbiota and variations in bone mineral density (BMD). Nonetheless, the specific association between gut microbiota and BMD alterations at different skeletal sites has not been comprehensively explored. To address this, we employed Genome-Wide Association Study (GWAS) summary statistics from a publicly accessible database, conducting a two-sample Mendelian Randomization analysis to elucidate the potential causal relationship between gut microbiota composition and BMD. This study utilized two distinct thresholds for screening instrumental variables (IVs), followed by an extensive series of quality control procedures to identify IVs that were significantly related to exposure. Gut microbiota were classified into two sets based on hierarchical levels: phylum, class, order, family, and genus. Bone mineral density (BMD) data were systematically collected from four skeletal sites: femoral neck, lumbar spine, forearm, and heel. For Mendelian Randomization (MR) analysis, robust methods including Inverse-Variance Weighting (IVW) and the Wald Ratio Test were employed. Additional analytical tests such as the Outlier Test, Heterogeneity Test, 'Leave-One-Out' Test, and Pleiotropy Test were conducted to assess the impact of horizontal pleiotropy, heterogeneities, and the genetic variation stability of gut microbiota on BMD causal associations. The MR Steiger Directionality Test was applied to exclude studies with potential directional biases. In this two-sample Mendelian randomization analysis, we utilized five sets of exposure GWAS (Genome-Wide Association Studies) summary statistics and four sets of outcome GWAS summary statistics. The initial analysis, applying a threshold of p < 5 × 10-6, identified 48 significant causal relationships between genetic liability in the gut microbiome and bone mineral density (BMD). A subsequent analysis with a more stringent threshold of p < 5 × 10-8 uncovered 14 additional causal relationships. Upon applying the Bonferroni correction, 9 results from the first analysis and 10 from the second remained statistically significant. Our MR analysis revealed a causal relationship between gut microbiota and bone mineral density at all sites, which could lead to discoveries in future mechanistic and clinical studies of microbiota-associated osteoporosis.

Increased levels of sex hormones have been hypothesized to decrease Alzheimer's disease (AD) risk. We assessed the association between sex steroid hormones with AD using a Mendelian randomization (MR) approach. An inverse-variance weighting (IVW) MR analysis was performed using effect estimates from external genome-wide association study (GWAS) summary statistics. We included independent variants (linkage disequilibrium R2 <0.001) and a p-value threshold of 5×10-8 . An increase in androgens was associated with a decreased AD risk among men: testosterone (odds ratio [OR]: 0.53; 95% confidence interval [CI]: 0.32-0.88; p-value: 0.01; false discovery rate [FDR] p-value: 0.03); dehydroepiandrosterone sulfate (DHEAS; OR: 0.56; 95% CI: 0.38-0.85; p-value: 0.01; FDR p-value: 0.03); and androsterone sulfate (OR: 0.69; 95% CI: 0.46-1.02; p-value: 0.06; FDR p-value: 0.10). There was no association between sex steroid hormones and AD among women, although analysis for estradiol had limited statistical power. A higher concentration of androgens was associated with a decreased risk of AD among men of European ancestry, suggesting that androgens among men might be neuroprotective and could potentially prevent or delay an AD diagnosis. Sex hormones are hypothesized to play a role in developing Alzheimer's disease (AD). The effect of sex hormones on AD was assessed using Mendelian randomization (MR) analysis. Among women, genetically determined effects of sex hormones were limited or null. Among men, a higher concentration of androgens decreased AD risk. This study suggests a causal relationship between androgens and AD among men.

Vitamin D deficiency is a candidate risk factor for osteoporosis, characterized by decreased bone mineral density (BMD). We performed this two-sample Mendelian randomization (MR) analysis to investigate the causal effect of vitamin D on BMD. We extracted 143 single-nucleotide polymorphisms from a recent GWAS on 417,580 participants of European ancestry as instrumental variables, and used summary statistics for BMD at forearm (n = 10,805), femoral neck (n = 49,988), lumbar spine (n = 44,731) and total-body of different age-stages (< 15, 15–30, 30–45, 45–60, > 60) (n = 67,358). We explored the direct effect of vitamin D on BMD with an adjusted body mass index (BMI) in a multivariable MR analysis. We found no support for causality of 25-hydroxyvitamin D on BMD at forearm, femoral neck, lumbar spine, and total-body BMD across the lifespan. There was no obvious difference between the total and direct effect of vitamin D on BMD after adjusting for BMI. Our MR analysis provided evidence that genetically determined vitamin D was not causally associated with BMD in the general population. Large-scale randomized controlled trials are warranted to investigate the role of vitamin D supplementation in preventing osteoporosis in the high-risk population.

Objectives : Observational studies have suggested associations between retinal layer thinning and increased susceptibility to Alzheimer’s disease (AD), but causal inference remains inconclusive. This study aimed to investigate potential genetic causality between inner retinal layer (IRL) thickness, specifically the retinal nerve fiber layer (RNFL) and the ganglion cell inner plexiform layer (GCIPL), and AD risk. Methods : We conducted a bidirectional two-sample Mendelian randomization (MR) analysis using genome-wide association study (GWAS) summary statistics for RNFL/GCIPL thickness (n = 31,434; UK Biobank) and AD status (39,106 cases vs. 401,577 controls; European Alzheimer and Dementia Biobank). Replication was performed in an independent AD cohort (35,274 cases vs. 59,163 controls). The inverse-variance weighted (IVW) method was used as the primary analytical approach. Results : No significant associations were found between retinal thickness and AD risk (RNFL: odds ratio [OR]IVW = 1.001, 95% confidence interval [CI] = 0.986-1.017, P = 0.883; GCIPL: ORIVW = 1.008, 95% CI = 0.997-1.019, P = 0.172). Reverse MR analyses also showed no causal effect of genetic liability to AD on retinal thickness (RNFL: ORIVW = 0.907, 95% CI = 0.786-1.046, P = 0.179; GCIPL: ORIVW = 1.014, 95% CI = 0.828-1.242, P = 0.890). These findings were consistent in replication analyses (RNFL: ORIVW = 1.015, 95% CI = 0.987-1.043, P = 0.305; GCIPL: ORIVW = 1.014, 95% CI = 0.991-1.037, P = 0.237). Conclusion : This MR analysis found no evidence of a causal genetic relationship between IRL thickness variations and AD. Future investigations should focus on trans-ethnic populations, longitudinal studies, and multimodal retinal phenotyping within GWAS cohorts to further clarify this relationship.

Bone mineral density (BMD) is a key indicator of osteoporosis, which may influence the development of intervertebral disc degeneration (IDD). However, the causal relationship and underlying signaling pathways between BMD and IDD remain unclear. Therefore, this study aimed to investigate the potential causal relationship and underlying signaling pathways between BMD and IDD. A two-sample Mendelian randomization (MR) analysis was employed to analyze the causal effects of BMD levels across 3 anatomical sites [total body BMD (TB-BMD), lumbar spine BMD (LS-BMD), and femoral neck BMD (FN-BMD)] on risks of IDD. In this study, IDD was divided into 2 groups, namely cervical IDD (C-IDD) and thoracic/thoracolumbar/lumbosacral IDD (TTL-IDD). Additionally, multivariable MR (MVMR) was applied to explore whether type 2 diabetes (T2D) and body mass index (BMI) would mediate the identification of causal pathways. Moreover, gene ontology (GO) enrichment analysis and expression quantitative trait locus (eQTL) colocalization analyses were utilized to examine the potential mechanisms and shared genes involved in osteoporosis and IDD. The results showed that genetic predispositions to TB-BMD, LS-BMD, and FN-BMD were associated with increased risk of C-IDD. Furthermore, TB-BMD, LS-BMD, and FN-BMD were identified as significant risk factors causally associated with TTL-IDD. The MVMR analysis revealed that even after adjusting for T2D and BMI, lower TB-BMD could significantly increase the odds of C-IDD and TTL-IDD. In the subgroup analysis, a significant causal effect of TB-BMD on TTL-IDD was observed in individuals aged 30 to 45, 45 to 60, and > 60 years. Polypeptide N-acetylgalactosaminyltransferase 3 (GALNT3) and homeobox C4 (HOXC4) were the most prominent co-located genes illustrated by GO enrichment analysis and eQTL analysis. In conclusion, we found that lower BMD exerts significant causal effects on elevated IDD risk (both C-IDD and TTL-IDD).

African Americans (AAs) and European Americans (EAs) differ in Alzheimer's disease (AD) prevalence, risk factors, and symptomatic presentation and AAs are less likely to enroll in AD clinical trials. We conducted race-conscious pharmacoepidemiologic studies of 5.62 million older individuals (age ≥60) to investigate the association of telmisartan exposure and AD outcome using Cox analysis, Kaplan-Meier analysis, and log-rank test. We performed Mendelian randomization (MR) analysis of large ethnically diverse genetic data to test likely causal relationships between telmisartan's target and AD. We identified that moderate/high telmisartan exposure was significantly associated with a reduced incidence of AD in the AAs compared to low/no telmisartan exposure (hazard ratio [HR] = 0.77, 95% CI: 0.65-0.91, p-value = 0.0022), but not in the non-Hispanic EAs (HR = 0.97, 95% CI: 0.89-1.05, p-value = 0.4110). Sensitivity and sex-/age-stratified patient subgroup analyses identified that telmisartan's medication possession ratio (MPR) and average hypertension daily dosage were significantly associated with a stronger reduction in the incidence of both AD and dementia in AAs. Using MR analysis from large genome-wide association studies (GWAS) (over 2 million individuals) across AD, hypertension, and diabetes, we further identified AA-specific beneficial effects of telmisartan for AD. Randomized controlled trials with ethnically diverse patient cohorts are warranted to establish causality and therapeutic outcomes of telmisartan and AD. Telmisartan is associated with lower risk of Alzheimer's disease (AD) in African Americans (AAs). Telmisartan is the only angiotensin II receptor blockers having PPAR-γ agonistic properties with beneficial anti-diabetic and renal function effects, which mitigate AD risk in AAs. Mendelian randomization (MR) analysis demonstrates the specificity of telmisartan's protective mechanism to AAs.

BackgroundExamining sex differences on the impact of modifiable risk factors in Alzheimer’s disease (AD) risk can help us better understand the mechanisms underlying sex differences in the prevalence and incidence of AD. Here, we used polygenic risk scores (PRS) and Mendelian randomization (MR) to investigate sex‐specific effects of sleep duration, insomnia, blood pressure, diabetes, alcohol intake, smoking, body mass index, high cholesterol, and education on AD risk.MethodWe obtained combined and sex‐stratified genome‐wide association study (GWAS) summary statistics for each risk factor from the UK Biobank and used them as the base dataset for constructing PRS and exposure datasets in the MR analysis. Linkage disequilibrium clumping was performed to identify independent genome‐wide significant single nucleotide polymorphisms (SNPs) across the sex‐combined, male‐specific, and female‐specific GWAS. The combined lead SNPs were then weighted by their strata‐specific effect sizes in the stratified PRS and MR analyses. PRS were constructed for each risk factor in participants from the Alzheimer’s Disease Genetics Consortium. Linear regression was used to investigate the association of each PRS with AD risk, adjusting for age, principal components, and cohort. MR was used to estimate sex‐stratified causal effects of each risk factor on AD. Sex differences in PRS associations and MR causal estimates were determined using Fisher’s Z score method.ResultsAssociation testing of the PRS with AD risk in sex stratified cohorts revealed that the BMI PRS was associated with differential effects in men and women (OR [95%CI]: males: 1.05 [1.00, 1.10] vs females: 0.96 [0.93, 0.99], p = 0.003). Furthermore, the university completion PRS was non‐significant in men but was associated with reduced risk in women (OR [95%CI]: males: 0.96 [0.92, 1.01] vs females: 0.92 [0.89, 0.96], p = 0.12). In the follow‐up MR analysis, university completion was also causally associated with reduced risk in women only (OR [95%CI]: males: 1.09 [0.77, 1.53] vs females: 0.55 [0.42, 0.72], p = 0.002) (Figure 1). No other risk factors showed evidence of sex‐differences.ConclusionOur study found sex‐specific effects of genetically predicted BMI and educational attainment on AD risk. These findings suggest the need for sex‐specific approaches to AD prevention and management.

BackgroundAlthough previous studies have suggested a possible association between bone mineral density (BMD) and intervertebral disc degeneration (IDD), the causal relationship between them remains unclear. Evidence from accumulating studies indicates that they might mutually influence one another. However, observational studies may be affected by potential confounders. Meanwhile, Mendelian randomization (MR) study can overcome these confounders to assess causality.ObjectivesThis Mendelian randomization (MR) study aimed to explore the causal effect of bone mineral density (BMD) on intervertebral disc degeneration (IDD).MethodsSummary data from genome-wide association studies of bone mineral density (BMD) and IDD (the FinnGen biobank) have been acquired. The inverse variance weighted (IVW) method was utilized as the primary MR analysis approach. Weighted median, MR-Egger regression, weighted mode, and simple mode were used as supplements. The Mendelian randomization pleiotropy residual sum and outlier (MR-PRESSO) and MR-Egger regression were performed to assess horizontal pleiotropy. Cochran’s Q test evaluated heterogeneity. Leave-one-out sensitivity analysis was further conducted to determine the reliability of the causal relationship. Multivariate MR (MVMR) analyses used multivariable inverse variance-weighted methods to individually and jointly adjust for four potential confounders, body mass index (BMI), Type2 diabetes, hyperthyroidism and smoking. A reverse MR analysis was conducted to assess potential reverse causation.ResultsIn the univariate MR analysis, femoral neck bone mineral density (FNBMD), heel bone mineral density (eBMD), lumbar spine bone mineral density (LSBMD), and total body bone mineral density (TB BMD) had a direct causal effect on intervertebral disc degeneration (IDD) [FNBMD-related analysis: OR(95%CI) = 1.17 (1.04 to 1.31), p = 0.008, eBMD-related analysis: OR(95%CI) = 1.06 (1.01 to 1.12), p = 0.028, LSBMD-related analysis: OR(95%CI) = 1.20 (1.10 to 1.31), p = 3.38E-7,TB BMD-related analysis: OR(95%CI) = 1.20 (1.12 to 1.29), p = 1.0E-8]. In the MVMR analysis, it was revealed that, even after controlling for confounding factors, heel bone mineral density (eBMD), lumbar spine bone mineral density (LSBMD), and total body bone mineral density (TB BMD) still maintained an independent and significant causal association with IDD(Adjusting for heel bone mineral density: beta = 0.073, OR95% CI = 1.08(1.02 to 1.14), P = 0.013; Adjusting for lumbar spine bone mineral density: beta = 0.11, OR(95%CI) = 1.12(1.02 to 1.23), P = 0.03; Adjusting for total body bone mineral density: beta = 0.139, OR95% CI = 1.15(1.06 to 1.24), P = 5.53E − 5). In the reverse analysis, no evidence was found to suggest that IDD has an impact on BMD.ConclusionsThe findings from our univariate and multivariable Mendelian randomization analysis establish a substantial positive causal association between BMD and IDD, indicating that higher bone mineral density may be a significant risk factor for intervertebral disc degeneration. Notably, no causal effect of IDD on these four measures of bone mineral density was observed. Further research is required to elucidate the underlying mechanisms governing this causal relationship.

Observational and genetic studies have reported the relationship between dyslexia and Alzheimer’s disease (AD). Until now, the causal effect of dyslexia on AD risk has remained unclear. We conducted a two-sample univariable Mendelian randomization (MR) analysis to determine the causal association between dyslexia and the risk of AD, vascular dementia (VD), Lewy body dementia (LBD), and frontotemporal dementia (FTD) and its four subtypes. First, we selected 42 dyslexia genetic variants from a large-scale genome-wide association studies (GWAS) dataset and extracted their corresponding GWAS summary statistics from AD, VD, LBD, and FTD. Second, we selected four MR methods, including inverse-variance weighted (IVW), weighted median, MR-Egger, and MR-PRESSO. Heterogeneity, horizontal pleiotropy, and leave-one-out sensitivity analysis were then used to evaluate the reliability of all causal estimates. We also conducted multivariable MR (MVMR) and mediation analysis to assess the potential mediating role of cognitive performance (CP) or educational achievement (EA) on the causal association between dyslexia and AD. Two MVMR methods, including MV IVW and MV-Egger, and two-step MR were used to perform the analysis. Using IVW, we found a significant causal association between increased dyslexia and increased risk of AD (OR = 1.15, 95% CI: 1.04–1.28, P = 0.006), but not VD, LBD, FTD, or its four subtypes. MR-PRESSO further supported the statistically significant association between dyslexia and AD (OR = 1.15, 95% CI: 1.05–1.27, P = 0.006). All sensitivity analyses confirmed the reliability of causal estimates. Using MV IVW and mediation analysis, we found no causal relationship between dyslexia and AD after adjusting for CP but not EA, CP mediated the total effect of dyslexia on AD with a proportion of 46.32%. We provide genetic evidence to support a causal effect of increased dyslexia on increased risk of AD, which was largely mediated by CP. Reading activity may be a potential intervention strategy for AD by improving cognitive function.