Michael J. Zhang

BACKGROUND: Ischemic stroke preventive therapies have been slow to emerge due to a limited understanding of the underlying molecular mechanisms. We aimed to discover new protein risk factors that are potential etiologic factors and may be candidates for therapeutic intervention. METHODS: We included ARIC study (Atherosclerosis Risk in Communities) and CHS (Cardiovascular Health Study) participants without prevalent stroke at the time of proteomic profiling (1990–1992 in ARIC and 1992–1993 in CHS). Relative concentrations of proteins in blood were assessed with aptamers (n=4954). Ischemic stroke events were adjudicated through 2019 in ARIC and 2015 in CHS. Study-specific Cox regression adjusting for ischemic stroke risk factors was used to estimate associations between proteins and incident ischemic stroke. Study-specific estimates were combined using fixed-effects meta-analysis. Replication was conducted in 2 independent cohorts (AGES-Reykjavik, UK Biobank). Proteins with a false discovery rate q value P −5 ), of which 26 are novel. In 2 independent cohorts, 37 (84%) associations were directionally concordant, and 26 (59%) met criteria for replication. Mendelian randomization analyses suggested MMP12 (matrix metallopeptidase-12) and CNTN1 (contactin-1) may be causally related to ischemic stroke risk. In multivariable Mendelian randomization analyses, higher MMP12 levels had a direct protective effect on ischemic stroke risk, while CNTN1 had a direct harmful effect. CONCLUSIONS: This proteomic and genomic investigation of ischemic stroke identified novel risk biomarkers and 2 potential etiologic CNTN1 factors that are regulated in response to atherosclerosis and obesity. If future studies confirm our findings, these results may have implications for the development of new preventive therapies.

Aging is a primary driver of atrial remodeling and dysfunction, and contributes to the increasing prevalence of atrial myopathy in the aging population. Atrial myopathy, characterized by structural, functional, and electrophysiological abnormalities of the atria, is a key pathological process underlying adverse cardiovascular outcomes such as atrial fibrillation (AF), heart failure with preserved ejection fraction (HFpEF), and ischemic stroke. Although these outcomes are often treated as distinct clinical entities, emerging evidence suggests that they may represent symptomatic manifestations of an underlying atrial disease process. Aging promotes atrial myopathy through multiple mechanisms, including inflammation, extracellular matrix remodeling, electrophysiological alterations, cellular senescence, epigenetic modifications, and non-coding RNA regulation. These changes collectively lead to atrial fibrosis, impaired mechanical function, conduction abnormalities, and a prothrombotic state. Despite its clinical significance, atrial myopathy remains an underrecognized entity, with current management strategies primarily focusing on treating its downstream complications rather than the underlying disease. Advances in imaging techniques, biomarker discovery, and molecular research have the potential to improve the early detection and risk stratification of atrial myopathy, paving the way for novel therapeutic strategies. In this review, we discuss the structural, mechanical, electrophysiological, and metabolic changes that occur in the aging atrium, explore the cellular and molecular mechanisms that drive these changes, and highlight recent advances in diagnostic and therapeutic approaches. By shifting the focus from managing AF and HFpEF to targeting the underlying atrial myopathy, we can unlock new avenues for prevention and treatment, ultimately improving cardiovascular health in the aging population.

BACKGROUND: Coagulation factor XI (FXI) inhibitors are a promising and novel class of anticoagulants, but a recent animal study found that FXI inhibition exacerbated diastolic dysfunction and heart failure (HF). In the ARIC study (Atherosclerosis Risk in Communities), we investigated whether plasma FXI level was associated with cardiovascular events and cardiac function. METHODS: ARIC was our primary analytic cohort. We included 4471 participants (median age, 75 years; 57% female; 17% Black) who attended visit 5 (2011–2013) with Somalogic-quantified plasma FXI levels and echocardiographic cardiac function. Prevalent HF and atrial fibrillation (AF) cases were defined as having HF or AF diagnosed at or before each participant’s visit 5 exam date. Incident HF and AF events were ascertained through 2021. Associations were assessed using Cox, logistic, and linear regression models. Primary prospective associations were also validated in the CHS (Cardiovascular Health Study) using an orthogonal FXI assay (enzyme-linked immunosorbent assay). RESULTS: At ARIC visit 5, there were 665 and 419 participants with prevalent HF and AF, respectively. During a median follow-up of 9 years, there were 580 and 788 incident HF and AF events, respectively. Lower FXI level was associated prospectively with higher incidence of HF (hazard ratio [HR], 1.36 [for each 1-unit decrement of log ₂ -transformed FXI level] [95% CI, 1.01–1.83]) but not incident AF, and cross-sectionally with increased odds of AF (odds ratio [OR], 1.96 [95% CI, 1.23–3.07]) but not HF. In age-stratified analyses, decreased FXI was associated with higher incidence of HF in participants ≥75 years of age (HR, 1.57 [95% CI, 1.08–2.28]) but not <75 years of age (HR, 1.11 [95% CI, 0.68–1.79]). The inverse FXI–HF association was validated in CHS (HR, 1.18 [95% CI, 1.02–1.36]). At ARIC visit 5, lower FXI level was also associated with higher prevalence of diastolic dysfunction and worse E/A ratio, left atrial (LA) volume index, LA function, and left ventricular mass index, but not left ventricular ejection fraction or global longitudinal strain. CONCLUSIONS: Decreased FXI level is associated with greater incidence of HF, especially in older adults. It is also associated with prevalent AF, worse diastolic function, worse LA function, and greater LA size. More research is needed to assess potential unwanted effects of FXI inhibition on the risk of cardiovascular events and cardiac function.

Aims: Many studies have utilized data sources such as clinical variables, polygenic risk scores, electrocardiogram (ECG), and plasma proteins to predict the risk of atrial fibrillation (AF). However, few studies have integrated all four sources from a single study to comprehensively assess AF prediction. Methods and results: We included 8374 (Visit 3, 1993–95) and 3730 (Visit 5, 2011–13) participants from the Atherosclerosis Risk in Communities Study to predict incident AF and prevalent (but covert) AF. We constructed a (i) clinical risk score using CHARGE-AF clinical variables, (ii) polygenic risk score using pre-determined weights, (iii) protein risk score using regularized logistic regression, and (iv) ECG risk score from a convolutional neural network. Risk prediction performance was measured using regularized logistic regression. After a median follow-up of 15.1 years, 1910 AF events occurred since Visit 3 and 229 participants had prevalent AF at Visit 5. The area under curve (AUC) improved from 0.660 to 0.752 (95% CI, 0.741–0.763) and from 0.737 to 0.854 (95% CI, 0.828–0.880) after addition of the polygenic risk score to the CHARGE-AF clinical variables for predicting incident and prevalent AF, respectively. Further addition of ECG and protein risk scores improved the AUC to 0.763 (95% CI, 0.753–0.772) and 0.875 (95% CI, 0.851–0.899) for predicting incident and prevalent AF, respectively. Conclusion: A combination of clinical and polygenic risk scores was the most effective and parsimonious approach to predicting AF. Further addition of an ECG risk score or protein risk score provided only modest incremental improvement for predicting AF.

Atrial myopathy—defined as abnormal left atrial (LA) size and function—is associated with an increased risk of atrial fibrillation, heart failure, and dementia. Central arterial stiffness is associated with increased atrial afterload and fibrosis and may be a risk factor for atrial myopathy. We examined the association of carotid-femoral pulse wave velocity (cfPWV) with LA function and assessed potential causal relationships. We included 2825 Atherosclerosis Risk in Communities (ARIC) study participants from Visit 5 (2011–2013). cfPWV was related to echocardiographic LA function continuously per 1-SD and categorically in quartiles. Mendelian randomization (MR) analysis was performed using U.K. Biobank-derived genetic variants associated with arterial stiffness index and cardiac magnetic resonance measures of LA function. When analyzed per SD increment (297.6 cm/s), higher cfPWV was significantly associated with lower LA reservoir and conduit strain (β = −0.53%, 95% CI [−0.81, −0.25] and β = −0.46%, 95% CI [−0.68, −0.25], respectively) after adjusting for demographics, clinical characteristics, systolic blood pressure, and left ventricular (LV) morphology and function. In MR analyses there was a non-significant inverse association of arterial stiffness index with LA total, passive, and active emptying fractions. Higher cfPWV is associated with lower LA reservoir and conduit strain, independent of systolic blood pressure and LV morphology and function. No evidence for a causal relationship between arterial stiffness index and alterations in LA function was found. Future studies should examine the prospective association of central arterial stiffness with LA function alterations.

Yuekai Ji, MBBS, MS, Lin Yee Chen, MD, MS, Michael J Zhang, MD, PhD; Association of Genetically Predicted Problem Alcohol Use with Risk of Atrial Fibrillat

Aims Free fatty acid receptor 4 (Ffar4) is a receptor for long-chain fatty acids that attenuates heart failure driven by increased afterload. Recent findings suggest that Ffar4 prevents ischemic injury in brain, liver, and kidney, and therefore, we hypothesized that Ffar4 would also attenuate cardiac ischemic injury. Methods and Results Using a mouse model of ischemia-reperfusion (I/R), we found that mice with systemic deletion of Ffar4 (Ffar4KO) demonstrated impaired recovery of left ventricular systolic function post-I/R with no effect on initial infarct size. To identify potential mechanistic explanations for the cardioprotective effects of Ffar4, we performed bulk RNAseq to compare the transcriptomes from wild-type (WT) and Ffar4KO infarcted myocardium 3-days post-I/R. In the Ffar4KO infarcted myocardium, gene ontology (GO) analyses revealed augmentation of glycosaminoglycan synthesis, neutrophil activation, cadherin binding, extracellular matrix, rho signaling, and oxylipin synthesis, but impaired glycolytic and fatty acid metabolism, cardiac repolarization, and phosphodiesterase activity. Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis indicated impaired AMPK signaling and augmented cellular senescence in the Ffar4KO infarcted myocardium. Interestingly, phosphodiesterase 6c (PDE6c), which degrades cGMP, was the most upregulated gene in the Ffar4KO heart. Further, the soluble guanylyl cyclase stimulator, vericiguat, failed to increase cGMP in Ffar4KO cardiac myocytes, suggesting increased phosphodiesterase activity. Finally, cardiac myocyte-specific overexpression of Ffar4 prevented systolic dysfunction post-I/R, defining a cardioprotective role of Ffa4 in cardiac myocytes. Conclusions Our results demonstrate that Ffar4 in cardiac myocytes attenuates systolic dysfunction post-I/R, potentially by attenuating oxidative stress, preserving mitochondrial function, and modulation of cGMP signaling.

BACKGROUND: Rheumatic heart disease is the major cause of valvular heart disease in developing nations. Endothelial cells (ECs) are considered crucial contributors to rheumatic heart disease, but greater insight into their roles in disease progression is needed. METHODS: We used a Cdh5 -driven EC lineage-tracing approach to identify and track ECs in the K/B.g7 model of autoimmune valvular carditis. Single-cell RNA sequencing was used to characterize the EC populations in control and inflamed mitral valves. Immunostaining and conventional histology were used to evaluate lineage tracing and validate single-cell RNA-sequencing findings. The effects of VEGFR3 (vascular endothelial growth factor receptor 3) and VEGF-C (vascular endothelial growth factor C) inhibitors were tested in vivo. The functional impact of mitral valve disease in the K/B.g7 mouse was evaluated using echocardiography. Finally, to translate our findings, we analyzed valves from human patients with rheumatic heart disease undergoing mitral valve replacements. RESULTS: Lineage tracing in K/B.g7 mice revealed new capillary lymphatic vessels arising from valve surface ECs during the progression of disease in K/B.g7 mice. Unsupervised clustering of mitral valve single-cell RNA-sequencing data revealed novel lymphatic valve ECs that express a transcriptional profile distinct from other valve EC populations including the recently identified PROX1 (Prospero homeobox protein 1)+ lymphatic valve ECs. During disease progression, these newly identified lymphatic valve ECs expand and upregulate a profibrotic transcriptional profile. Inhibiting VEGFR3 through multiple approaches prevented expansion of this mitral valve lymphatic network. Echocardiography demonstrated that K/B.g7 mice have left ventricular dysfunction and mitral valve stenosis. Valve lymphatic density increased with age in K/B.g7 mice and correlated with worsened ventricular dysfunction. Importantly, human rheumatic valves contained similar lymphatics in greater numbers than nonrheumatic controls. CONCLUSIONS: These studies reveal a novel mode of inflammation-associated, VEGFR3-dependent postnatal lymphangiogenesis in murine autoimmune valvular carditis, with similarities to human rheumatic heart disease.