Background & aims: Previous observational studies have reported associations between plasma vitamin C levels, and cardiovascular diseases (CVDs) and Alzheimer's disease (AD); however, no conclusive results have been obtained. We conducted a Mendelian randomization (MR) study to investigate the causality of vitamin C on the risk of nine CVDs [including coronary artery disease (CAD), myocardial infarction (MI), atrial fibrillation (AF), heart failure (HF), stroke, ischemic stroke (IS), and IS subtypes] and Alzheimer's disease. Methods: Eleven single-nucleotide polymorphisms (SNPs) identified in a recent genome-wide metaanalysis (N ¼ 52,018) were used as the instrumental variables for plasma vitamin C levels. The summarylevel data for CVDs and AD were extracted from consortia and genome-wide association studies (GWAS). We performed MR analyses using the fixed-effects inverse-variance-weighted (IVW) method, weighted median, and MR-Egger approaches.Results: This MR study found suggestive evidence that genetic liability to higher vitamin C levels was associated with a lower risk of cardioembolic stroke [odds ratio (OR, presented per 1 standard deviation increase in plasma vitamin C levels) ¼ 0.773; 95% confidence interval (CI), 0.623e0.959; P ¼ 0.020] and AD (OR ¼ 0.968; 95% CI, 0.946e0.991; P ¼ 0.007) using the fixed-effects IVW method. Sensitivity analysis yielded directionally similar results. A null-association was observed between vitamin C and the other CVDs. Conclusion: Our MR study provided suggestive evidence that higher vitamin C levels were casually associated with a decreased risk of cardioembolic stroke and AD. No evidence was observed to suggest that vitamin C affected the risk of CAD, MI, AF, HF, stroke, IS, large artery stroke, or small vessel stroke. However, well-designed studies are warranted to confirm these results and determine the underlying mechanisms of the causal links.

Background: Previous observational studies have reported an association between psychiatric traits and cardiovascular diseases (CVDs). In this two-sample Mendelian randomization (MR) study, we aimed to investigate the causality between psychiatric traits and CVDs.Methods: Single-nucleotide polymorphisms (SNPs) associated with autism spectrum disorder (ASD), neuroticism, and subjective well-being at genome-wide significance (P < 1 × 10−8) were identified from genome-wide association studies. Summary-level data of the outcomes, including coronary artery disease (CAD), myocardial infarction (MI), atrial fibrillation (AF), and heart failure (HF), were obtained from several largest datasets. The inverse-variance weighted (IVW) method was used as our main analyses to conduct this MR study. Sensitivity analyses included the weighted median, the MR-robust adjusted profile score (MR-RAPS), and the MR pleiotropy residual sum and outlier (MR-PRESSO) method. Repeated MR analyses using a more relaxed threshold (P < 1 × 10−6) for instruments selection and multivariable MR analyses were also applied to evaluate the robustness of results.Results: The MR analyses showed that genetic predisposition to ASD was associated with a higher risk of AF [odds ratio (OR), 1.109; 95% confidence interval (CI), 1.023–1.201; P = 0.011] and HF (OR, 1.138; 95% CI, 1.036–1.251; P = 0.007). Neuroticism was casually associated with an increased risk of AF (OR, 1.201; 95% CI, 1.037–1.392; P = 0.015), whereas subjective well-being had a protective effect on HF (OR, 0.732; 95% CI, 0.574–0.933; P = 0.012). No other causal association between psychiatric traits and CVDs was observed. Consistent results were obtained in sensitivity analyses.Conclusion: This study provided evidence of causal associations of ASD with a higher risk of AF and HF. Besides, neuroticism was casually associated with an increased risk of AF, and subjective well-being was associated with a decreased risk of HF.

Background Observational studies have suggested that obstructive sleep apnea (OSA) is in relation to atrial fibrillation (AF); however, these studies might be confounded and whether the relationship is causal remains unclear. We conducted a bidirectional Mendelian randomization (MR) study to clarify the causal inference between OSA and AF. Methods Genetic instruments for OSA and AF were obtained from genome-wide association studies. The fixed-effects inverse-variance weighted (IVW) method was used as the main method, supplemented by several sensitivity analyses. For replication, another AF dataset was used to validate the causal effect of OSA on AF. Furthermore, multivariable MR analyses were performed to obtain direct estimates adjusting for potential confounders. Results Genetic liability to OSA was found to be significantly associated with a higher AF risk in the fixed-effects IVW method [odds ratio (OR) 1.210; 95% CI 1.119–1.307; P = 1.51 × 10–6]. The results were consistent in MR sensitivity analyses as well as in replication analyses, and the significance remained after adjusting for potential confounders. In the reverse MR analyses, there was no causal effect of AF on OSA. Conclusions Our study strengthened the causal evidence of genetically predicted OSA with a higher AF risk. Early screening and appropriate management of OSA might show anti-arrhythmic benefits.

Observational studies have reported that gastroesophageal reflux disease (GERD) is a risk factor for cardiovascular diseases (CVD); however, the causal inferences between them remain unknown. We conducted a Mendelian randomization (MR) study to estimate the causal associations between GERD and 10 CVD outcomes, as well as 14 cardiovascular risk factors. We used summary statistics from genome-wide association studies for GERD and the FinnGen consortium for CVD. We further investigated whether GERD correlated with cardiovascular risk factors and performed multivariable MR and mediation analyses to estimate the mediating effects of these risk factors on GERD-CVD progression. Sensitivity analyses and replication analyses were also performed. Our results indicated that GERD was positively associated with seven CVD outcomes with odds ratios of 1.26 [95% confidence interval (CI), 1.15, 1.37] for coronary artery disease, 1.41 (95% CI, 1.28,1.57) for myocardial infarction, 1.34 (95% CI, 1.19, 1.51) for atrial fibrillation, 1.34 (95% CI, 1.21, 1.50) for heart failure, 1.30 (95% CI, 1.18, 1.43) for any stroke, 1.19 (95% CI, 1.06,1.34) for ischemic stroke, and 1.29 (95% CI, 1.16,1.44) for venous thromboembolism. Furthermore, GERD was associated with nine cardiovascular risk factors and major depressive disorder demonstrated significant mediation effects on the causal pathway linking GERD and any stroke. This study demonstrates that GERD is associated with seven CVD outcomes and nine cardiovascular risk factors. Importantly, GERD treatment may help prevent common CVD events.

Aim: The structural and electrical changes in the atrium, also known as atrial remodeling, are the main characteristics of atrial fibrillation (AF). Fibroblast growth factor 21 (Fgf21) is an important endocrine factor, which has been shown to play an important role in cardiovascular diseases. However, the effects of Fgf21 on atrial remodeling have not been addressed yet. The purpose of the present study is to evaluate the effects of Fgf21 on atrial remodeling.Methods and Results: Adult mice were treated with Ang II, and randomly administrated with or without Fgf21 for 2 weeks. The susceptibility to AF was assessed by electrical stimulation and optical mapping techniques. Here, we found that Fgf21 administration attenuated the inducibility of atrial fibrillation/atrial tachycardia (AF/AT), improved epicardial conduction velocity in the mice atria. Mechanistically, Fgf21 protected against atrial fibrosis and reduced oxidative stress of the atria. Consistently, in vitro study also demonstrated that Fgf21 blocked the upregulation of collagen by Tgf-β in fibroblasts and attenuated tachypacing-induced oxidative stress including reactive oxygen species (ROS), Tgf-β, and ox-CaMKII in atrial myocytes. We further found that Fgf21 attenuated oxidative stress by inducing antioxidant genes, such as SOD2 and UCP3. Fgf21 also improved tachypacing-induced myofibril degradation, downregulation of L-type calcium channel, and upregulation of p-RyR2, which implicated protective effects of Fgf21 on structural and electrical remodeling in the atria. Moreover, Nrf2 was identified as a downstream of Fgf21 and partly mediated Fgf21-induced antioxidant gene expression in atrial myocytes.Conclusion: Fgf21 administration effectively suppressed atrial remodeling by reducing oxidative stress, which provides a novel therapeutic insight for AF.