Investigation of 95 variants identified in a genome-wide study for association with mortality after acute coronary syndrome

Mitochondrial-cell cycle cross-talk drives endoreplication in heart disease

[Figure: see text].

Importance of Thyroid Hormone level and Genetic Variations in Deiodinases for Patients after Acute Myocardial Infarction: A Longitudinal Observational Study

This study aimed to examine the influence of thyroid hormone (TH) levels and genetic polymorphisms of deiodinases on long-term outcomes after acute myocardial infarction (AMI). In total, 290 patients who have experienced AMI were evaluated for demographic, clinical characteristics, risk factors, TH and NT-pro-BNP. Polymorphisms of TH related genes were included deiodinase 1 (DIO1) (rs11206244-C/T, rs12095080-A/G, rs2235544-A/C), deiodinase 2 (DIO2) (rs225015-G/A, rs225014-T/C) and deiodinase 3 (DIO3) (rs945006-T/G). Both all-cause and cardiac mortality was considered key outcomes. Cox regression model showed that NT-pro-BNP (HR = 2.11; 95% CI = 1.18– 3.78; p = 0.012), the first quartile of fT3, and DIO1 gene rs12095080 were independent predictors of cardiac-related mortality (HR = 1.74; 95% CI = 1.04–2.91; p = 0.034). The DIO1 gene rs12095080 AG genotype (OR = 3.97; 95% CI = 1.45–10.89; p = 0.005) increased the risk for cardiac mortality. Lower fT3 levels and the DIO1 gene rs12095080 are both associated with cardiac-related mortality after AMI.

A novel genetic marker of decreased inflammation and improved survival after acute myocardial infarction

The CHRNA5 gene encodes a neurotransmitter receptor subunit involved in multiple processes, including cholinergic autonomic nerve activity and inflammation. Common variants in CHRNA5 have been linked with atherosclerotic cardiovascular disease. Association of variation in CHRNA5 and specific haplotypes with cardiovascular outcomes has not been described. The aim of this study was to examine the association of CHRNA5 haplotypes with gene expression and mortality among patients with acute myocardial infarction (AMI) and explore potential mechanisms of this association. Patients (N = 2054) hospitalized with AMI were genotyped for two common variants in CHRNA5. Proportional hazard models were used to estimate independent association of CHRNA5 haplotype with 1-year mortality. Both individual variants were associated with mortality (p = 0.0096 and 0.0004, respectively) and were in tight LD (D' = 0.99). One haplotype, HAP3, was associated with decreased mortality one year after AMI (adjusted HR = 0.42, 95% CI 0.26, 0.68; p = 0.0004). This association was validated in an independent cohort (N = 637) of post-MI patients (adjusted HR = 0.23, 95% CI 0.07, 0.79; p = 0.019). Differences in CHRNA5 expression by haplotype were investigated in human heart samples (n = 28). Compared with non-carriers, HAP3 carriers had threefold lower cardiac CHRNA5 mRNA expression (p = 0.023). Circulating levels of the inflammatory marker hsCRP were significantly lower in HAP3 carriers versus non-carriers (3.43 ± 4.2 versus 3.91 ± 5.1; p = 0.0379). Activation of the inflammasome, an important inflammatory complex involved in cardiovascular disease that is necessary for release of the pro-inflammatory cytokine IL-1 β, was assessed in bone marrow-derived macrophages (BMDM) from CHRNA5 knockout mice and wild-type controls. In BMDM from CHRNA5 knockout mice, IL-1β secretion was reduced by 50% compared to wild-type controls (p = 0.004). Therefore, a common haplotype of CHRNA5 that results in reduced cardiac expression of CHRNA5 and attenuated macrophage inflammasome activation is associated with lower mortality after AMI. These results implicate CHRNA5 and the cholinergic anti-inflammatory pathway in survival following AMI.

Cohort profile: the Emory Cardiovascular Biobank (EmCAB)

PURPOSE

The Emory Cardiovascular Biobank (EmCAB) is an ongoing prospective registry of patients undergoing cardiac catheterisation, which was established to identify novel factors associated with the pathobiological process and treatment of cardiovascular disease.

PARTICIPANTS

Individuals aged 18 years and older undergoing cardiac catheterisation at three Emory Healthcare sites in Atlanta are asked to participate in this prospective registry. Around 95% agree to participate. Around 7000 unique patients have been enrolled. The current data set contains detailed phenotyping, patient outcomes, genomics, protein biomarkers, regenerative markers, transcriptomic analysis, metabolomics profiling and longitudinal follow-up for adverse cardiovascular outcomes.

FINDINGS TO DATE

Thus far, the EmCAB has approximately 3000 major cardiovascular events. About 48% of the EmCAB participants have more than 5 years of follow-up. It is a great resource for discovery of novel predictive factors for cardiovascular disease outcomes, including genomics, transcriptomics, protein biomarkers, oxidative stress markers and circulating progenitor cells. Several circulating inflammatory markers have shown to improve risk prediction metrics beyond standard risk factors.

FUTURE PLANS

Future integrative -omics analyses will provide the cardiovascular research community opportunities for subsequent mechanistic confirmation studies, which will promote the development of effective personalised therapy that leads to clinical care tailored to the individual patient.

Case-Only Survival Analysis Reveals Unique Effects of Genotype, Sex, and Coronary Disease Severity on Survivorship

Survival bias may unduly impact genetic association with complex diseases; gene-specific survival effects may further complicate such investigations. Coronary artery disease (CAD) is a complex phenotype for which little is understood about gene-specific survival effects; yet, such information can offer insight into refining genetic associations, improving replications, and can provide candidate genes for both mortality risk and improved survivorship in CAD. Building on our previous work, the purpose of this current study was to: evaluate LSAMP SNP-specific hazards for all-cause mortality post-catheterization in a larger cohort of our CAD cases; and, perform additional replication in an independent dataset. We examined two LSAMP SNPs—rs1462845 and rs6788787—using CAD case-only Cox proportional hazards regression for additive genetic effects, censored on time-to-all-cause mortality or last follow-up among Caucasian subjects from the Catheterization Genetics Study (CATHGEN; n = 2,224) and the Intermountain Heart Collaborative Study (IMHC; n = 3,008). Only after controlling for age, sex, body mass index, histories of smoking, type 2 diabetes, hyperlipidemia and hypertension (HR = 1.11, 95%CI = 1.01–1.22, p = 0.032), rs1462845 conferred significantly increased hazards of all-cause mortality among CAD cases. Even after controlling for multiple covariates, but in only the primary cohort, rs6788787 conferred significantly improved survival (HR = 0.80, 95% CI = 0.69–0.92, p = 0.002). Post-hoc analyses further stratifying by sex and disease severity revealed replicated effects for rs1462845: even after adjusting for aforementioned covariates and coronary interventional procedures, males with severe burden of CAD had significantly amplified hazards of death with the minor variant of rs1462845 in both cohorts (HR = 1.29, 95% CI = 1.08–1.55, p = 0.00456; replication HR = 1.25, 95% CI = 1.05–1.49, p = 0.013). Kaplan-Meier curves revealed unique cohort-specific genotype effects on survival. Additional analyses demonstrated that the homozygous risk genotype (‘A/A’) fully explained the increased hazard in both cohorts. None of the post-hoc analyses in control subjects were significant for any model. This suggests that genetic effects of rs1462845 on survival are unique to CAD presence. This represents formal, replicated evidence of genetic contribution of rs1462845 to increased risk for all-cause mortality; the contribution is unique to CAD case status and specific to males with severe burden of CAD.

Rs6922269 marker at the MTHFD1L gene predict cardiovascular mortality in males after acute coronary syndrome

Myocardial infarction (MI) is the leading cause of death in industrialized countries. All the traditional risk factors for MI are responsible for approximately 50% of cases of MI cases. Attention therefore has recently focused on genetic variants that are not associated with conventional risk factors. One of them is the marker rs6922269, which has been suggested as a risk factor for development of MI in Western populations. We analyzed the relationship between rs6922269 variant on MTHFD1L gene and (i) risk of the acute coronary syndrome (ACS) in the Czech population and (ii) mortality in 7 years follow up. Rs6922269 (G>A) variant was analyzed (CR 99.3% for patients and 98.0% for controls) by PCR-RFLP in consecutively examined 1614 men and 503 women with ACS (age below 65 years) and in population-based controls--1191 men and 1368 women (aged up to 65 years). ANOVA and Chi square were used for statistical analysis. The genotype frequencies were almost identical (P=0.87) in the ACS patients and in controls and no differences were observed, if males (P=0.73) and females (P=0.93) were analysed separately. In addition, rs6922269 polymorphism was not associated with the classical risk factors (dyslipidemia, hypertension, obesity, smoking, diabetes) in control population. Cardiovascular mortality was significantly higher in males, carriers of the AA genotype (P<0.001, OR 2.52, 95% CI 1.40-4.55, for AA vs. +G). We conclude, that rs6922269 variant at MTHFD1L gene could be an important prognostic factor for cardiovascular mortality in patients after ACS.

Genetic polymorphism rs6922269 in the MTHFD1L gene is associated with survival and baseline active vitamin B12 levels in post-acute coronary syndromes patients

Background and Aims

The methylene-tetrahydrofolate dehydrogenase (NADP+ dependent) 1-like (MTHFD1L) gene is involved in mitochondrial tetrahydrofolate metabolism. Polymorphisms in MTHFD1L, including rs6922269, have been implicated in risk for coronary artery disease (CAD). We investigated the association between rs6922269 and known metabolic risk factors and survival in two independent cohorts of coronary heart disease patients.

Methods and Results

DNA and plasma from 1940 patients with acute coronary syndromes were collected a median of 32 days after index hospital admission (Coronary Disease Cohort Study, CDCS). Samples from a validation cohort of 842 patients post-myocardial infarction (PMI) were taken 24–96 hours after hospitalization. DNA samples were genotyped for rs6922269, using a TaqMan assay. Homocysteine and active vitamin B12 were measured by immunoassay in baseline CDCS plasma samples, but not PMI plasma. All cause mortality was documented over follow-up of 4.1 (CDCS) and 8.8 (PMI) years, respectively. rs6922269 genotype frequencies were AA n = 135, 7.0%; GA n = 785, 40.5% and GG n = 1020, 52.5% in the CDCS and similar in the PMI cohort. CDCS patients with AA genotype for rs6922269 had lower levels of co-variate adjusted baseline plasma active vitamin B12 (p = 0.017) and poorer survival than patients with GG or GA genotype (mortality: AA 19.6%, GA 12.0%, GG 11.6%; p = 0.007). In multivariate analysis, rs6922269 genotype predicted survival, independent of established covariate predictors (p = 0.03). However the association between genotype and survival was not validated in the PMI cohort.

Conclusion

MTHFD1L rs6922269 genotype is associated with active vitamin B12 levels at baseline and may be a marker of prognostic risk in patients with established coronary heart disease.

The genetic basis for survivorship in coronary artery disease

Survivorship is a trait characterized by endurance and virility in the face of hardship. It is largely considered a psychosocial attribute developed during fatal conditions, rather than a biological trait for robustness in the context of complex, age-dependent diseases like coronary artery disease (CAD). The purpose of this paper is to present the novel phenotype, survivorship in CAD as an observed survival advantage concurrent with clinically significant CAD. We present a model for characterizing survivorship in CAD and its relationships with overlapping time- and clinically-related phenotypes. We offer an optimal measurement interval for investigating survivorship in CAD. We hypothesize genetic contributions to this construct and review the literature for evidence of genetic contribution to overlapping phenotypes in support of our hypothesis. We also present preliminary evidence of genetic effects on survival in people with clinically significant CAD from a primary case-control study of symptomatic coronary disease. Identifying gene variants that confer improved survival in the context of clinically appreciable CAD may improve our understanding of cardioprotective mechanisms acting at the gene level and potentially impact patients clinically in the future. Further, characterizing other survival-variant genetic effects may improve signal-to-noise ratio in detecting gene associations for CAD.

Genetic association analysis and meta-analysis of imputed SNPs in longitudinal studies

In this paper we propose a new method to analyze time-to-event data in longitudinal genetic studies. This method address the fundamental problem of incorporating uncertainty when analyzing survival data and imputed single-nucleotide polymorphisms (SNPs) from genome-wide association studies (GWAS). Our method incorporates uncertainty in the likelihood function, the opposite of existing methods that incorporate the uncertainty in the design matrix. Through simulation studies and real data analyses, we show that our proposed method is unbiased and provides powerful results. We also show how combining results from different GWAS (meta-analysis) may lead to wrong results when effects are not estimated using our approach. The model is implemented in an R package that is designed to analyze uncertainty not only arising from imputed SNPs, but also from copy number variants.