Genetic factors in cardiovascular disease. 10 questions

Genomic insights into heart health: Exploring the genetic basis of cardiovascular disease

Cardiovascular diseases (CVDs) are considered as the leading cause of death worldwide. CVD continues to be a major cause of death and morbidity despite significant improvements in its detection and treatment. Therefore, it is strategically important to be able to precisely characterize an individual's sensitivity to certain illnesses. The discovery of genes linked to cardiovascular illnesses has benefited from linkage analysis and genome-wide association research. The last 20 years have seen significant advancements in the field of molecular genetics, particularly with the development of new tools like genome-wide association studies. In this article we explore the profound impact of genetic variations on disease development, prognosis, and therapeutic responses. And the significance of genetics in cardiovascular risk assessment and the ever-evolving realm of genetic testing, offering insights into the potential for personalized medicine in this domain. Embracing the future of cardiovascular care, the article explores the implications of pharmacogenomics for tailored treatments, the promise of emerging technologies in cardiovascular genetics and therapies, including the transformative influence of nanotechnology. Furthermore, it delves into the exciting frontiers of gene editing, such as CRISPR/Cas9, as a novel approach to combat cardiovascular diseases. And also explore the potential of stem cell therapy and regenerative medicine, providing a holistic view of the dynamic landscape of cardiovascular genomics and its transformative potential for the field of cardiovascular medicine.

The role of genetic predisposition in cardiovascular risk after cancer diagnosis: a matched cohort study of the UK Biobank

BACKGROUND

Evidence is scarce regarding the potential modifying role of disease susceptibility on the association between a prior cancer diagnosis and cardiovascular disease (CVD).

METHODS

We conducted a matched cohort study of UK Biobank including 78,860 individuals with a cancer diagnosis between January 1997 and January 2020, and 394,300 birth year and sex individually matched unexposed individuals. We used Cox model to assess the subsequent relative risk of CVD, which was further stratified by individual genetic predisposition.

RESULTS

During nearly 23 years of follow-up, an elevated risk of CVD was constantly observed among cancer patients, compared to their matched unexposed individuals. Such excess risk was most pronounced (hazard ratio [HR] = 5.28, 95% confidence interval [CI] 4.90-5.69) within 3 months after a cancer diagnosis, which then decreased rapidly and stabilised for >6 months (HR = 1.22, 95% CI 1.19-1.24). For all the studied time periods, stratification analyses by both levels of polygenic risk score for CVD and by family history of CVD revealed higher estimates among individuals with lower genetic risk predisposition.

CONCLUSIONS

Our findings suggest that patients with a recent cancer diagnosis were at an increased risk of multiple types of CVD and the excess CVD risk was higher among individuals with lower genetic susceptibility to CVD, highlighting a general need for enhanced psychological assistance and clinical surveillance of CVD among newly diagnosed cancer patients.

Risk of cardiovascular disease is driven by different combinations of environmental, medical and behavioral factors: Building a conceptual model for cumulative risk assessment

The U.S. Environmental Protection Agency (EPA) and National Institute of Environmental Health (NIEHS) held a workshop in 2012 to discuss principles and applications of cumulative risk assessment (CRA). The workshop organizers chose cardiovascular disease (CVD) as an example health outcome for which cumulative risk considerations could illuminate environmental and health management strategies. To guide discussions, we developed a series of conceptual models illustrating factors influencing CVD. The CVD conceptual model represents complex processes across varying space and time scales, different causal pathways, and multiple chemical and non-chemical stressors and factors. It includes causal influences of environmental exposures and lifestyle choices, in the context of genetics and medical factors. The representation of cumulative risk as a network of interrelated nodes and arrows helps define and organize the problem and available information, determine the scope and scale, and creates a platform for analysis. It provides an interface for discussing how different entities (e.g., environmental versus health-driven organizations) can work together on different parts of the problem, and facilitates relative risk ranking and management triage. Color coding is used to distinguish categories of stressors and possible oversight responsibility. This work informs guidelines for CRA planning and assessment of factor combinations affecting real-world risk.

High-Throughput Screening to Identify Chemical Cardiotoxic Potential

Cardiovascular (CV) disease is one of the most prevalent public health concerns, and mounting evidence supports the contribution of environmental chemicals to CV disease burden. In this study, we performed cardiotoxicity profiling for the Tox21 chemical library by focusing on high-throughput screening (HTS) assays whose targets are associated with adverse events related to CV failure modes. Our objective was to develop new hypotheses around environmental chemicals of potential interest for adverse CV outcomes using Tox21/ToxCast HTS data. Molecular and cellular events linked to six failure modes of CV toxicity were cross-referenced with 1399 Tox21/ToxCast assays to identify cardio-relevant bioactivity signatures. The resulting 40 targets, measured in 314 assays, were integrated via a ToxPi visualization tool and ranking system to prioritize 1138 chemicals based upon formal integration across multiple domains of information. Filtering was performed based on cytotoxicity and generalized cell stress endpoints to try and isolate chemicals with effects specific to CV biology, and bioactivity- and structure-based clustering identified subgroups of chemicals preferentially affecting targets such as ion channels and vascular tissue biology. Our approach identified drugs with known cardiotoxic effects, such as estrogenic modulators like clomiphene and raloxifene, anti-arrhythmic drugs like amiodarone and haloperidol, and antipsychotic drugs like chlorpromazine. Several classes of environmental chemicals such as organotins, bisphenol-like chemicals, pesticides, and quaternary ammonium compounds demonstrated strong bioactivity against CV targets; these were compared to existing data in the literature (e.g., from cardiomyocytes, animal data, or human epidemiological studies) and prioritized for further testing.

CD36 expression in peripheral blood mononuclear cells reflects the onset of atherosclerosis

Together with complex genetic and environmental factors, increased serum cholesterol and ox-LDL levels are considered as major triggering factors of atherosclerosis. Mononuclear cell infiltration to the arterial wall and uptake of ox-LDL, which is facilitated by CD36 receptor through an uncontrolled manner, play a key role in foam cell formation followed by atherogenesis development. The aim of this study was to analyze if CD36 expression in peripheral blood mononuclear cells reflect its aortic tissue level in hypercholesterolemia. In this study, CD36 protein expression was evaluated in aortic specimens of cholesterol or cholesterol plus Vitamin E treated animals in relation to the immunohistochemical analyses for the HNE-protein adducts, as well as for smooth muscle actin and vimentin. The CD36 mRNA expression was determined by RT-PCR in PBMC of hypercholesterolemic rabbits and hypercholesterolemic versus normocholesterolemic individuals. Immunohistochemistry findings revealed that smooth muscle actin, smooth muscle vimentin, HNE-protein conjugates, and CD36 protein expressions were significantly increased in aorta of hypercholesterolemic group where foam cells were present. High cholesterol diet significantly induced CD36 mRNA expression in both rabbit aorta and PBMCs, while positive correlation between aortic and PBMC CD36 expression has been found. In addition, consistent with the rabbit model, CD36 mRNA expression levels in human PBMCs were significantly higher in hypercholesterolemic patients than in normocholesterolemic individuals. Taken together, these results demonstrate that the CD36 mRNA levels of PBMCs could reflect the CD36 mRNA levels in aorta and could be used as a biomarker for diagnosis of atherosclerotic burden. © 2018 BioFactors, 44(6):588-596, 2018.

Establishment of a quantitative in vivo method for estimating adipose tissue volumes and the effects of dietary soy sauce oil on adipogenesis in medaka, Oryzias latipes

Adipose tissue, which is conserved in higher eukaryotes, plays central roles in controlling the body’s energy balance, including excess energy storage and energy expenditure during starvation. In adipogenesis, intranuclear receptor, peroxisome proliferator–activated receptor gamma (PPARγ) is a key molecule, and PPARγ agonists can promote adipogenesis. Many studies on the in vitro screening of PPARγ agonists with compounds derived from various materials have been reported; however, in vivo assays for quick examination of these feeding effects have not been established. In this study, we developed a technique using a lipophilic fluorescent reagent, Nile red to quantitatively estimate the adipose tissue volumes by using Japanese rice fish, medaka (Oryzias latipes) and studied effects of dietary soy sauce oil (SSO), which is a discarded by-product from Japanese traditional food and is known to have PPARγ-agonistic activity, on adipogenesis. We found that SSO feeding increased the adipose tissue volumes, and the expression levels of adipogenesis-related genes increased in these medaka larvae. These results suggest that SSO feeding increases the adipose tissue volumes through adipogenesis promotion by PPARγ-agonistic activity in medaka, and medaka is a powerful model for studying adipogenesis. Furthermore, our study also demonstrates the availability of SSO as a dietary additive for farmed fish.

Matrix metalloproteinases in coronary artery disease

Matrix metalloproteinases (MMP) are a family of zinc-containing endoproteinases that degrade extracellular matrix (ECM) components. MMP have important roles in the development, physiology and pathology of cardiovascular system. Metalloproteases also play key roles in adverse cardiovascular remodeling, atherosclerotic plaque formation and plaque instability, vascular smooth muscle cell (SMC) migration and restenosis that lead to coronary artery disease (CAD), and progressive heart failure. The study of MMP in developing animal model cardiovascular systems has been helpful in deciphering numerous pathologic conditions in humans. Increased peripheral blood MMP-2 and MMP-9 in acute coronary syndrome (ACS) may be useful as noninvasive tests for detection of plaque vulnerability. MMP function can be modulated by certain pharmacological drugs that can be exploited for treatment of ACS. CAD is a polygenic disease and hundreds of genes contribute toward its predisposition. A large number of sequence variations in MMP genes have been identified. Case-control association studies have highlighted their potential association with CAD and its clinical manifestations. Although results thus far are inconsistent, meta-analysis has demonstrated that MMP-3 Glu45Lys and MMP-9 1562C/T gene polymorphisms were associated with CAD risk.

Variants in exon 11 of MEF2A gene and coronary artery disease: evidence from a case-control study, systematic review, and meta-analysis

Background

Coronary artery disease (CAD) is the most common heart disease worldwide. Association of CAD with variants in the myocyte enhancer factor 2A (MEF2A) gene, the first identified CAD-causing gene, has attracted special attention but the results are controversial. We aimed to evaluate this genetic association via a case-control study and meta-analysis.

Methodology/Principal Findings

We performed a case-control association study to investigate the relationship between variations in exon 11 of MEF2A gene and CAD in 1045 sporadic patients and 1008 controls enrolled angiographically among southern Chinese population, and then the data from this study were compared and discussed in a systematic review and meta-analysis with all available published studies on MEF2A gene and CAD. In total, eight variants were identified (21-bp deletion, CAG repeats, CCG repeats, a CCA deletion and four SNPs). No significant link was observed between the common (CAG)_n polymorphism and CAD, whereas the rare 21-bp deletion was detected only in five affected individuals. The meta-analysis of (CAG)_n polymorphism and CAD risk, including nine studies with 3801 CAD patients and 4020 controls, also provided no convincing evidence for the genetic association, even upon stratification by race (mainly Whites and Chinese). However, the 21-bp deletion was regarded as a potentially logical, albeit undetermined, candidate for CAD in the following systematic review.

Conclusions/Significance

Our findings failed to demonstrate a correlation between (CAG)_n polymorphism with CAD, however, we concluded that the rare 21-bp deletion might have a more compelling effect on CAD than the common (CAG)_n polymorphism, and MEF2A genetic variant might be a rare but specific cause of CAD/MI.

The genetics of congestive heart failure

The heart failure syndrome is known to represent a final common pathway for a broad range of etiologies, but there is tremendous variation in the propensity to develop congestive heart failure after a given insult. This variation is thought to result in part from inherited differences in myocardial, vascular or systemic responses, but the nature of the underlying traits responsible ultimately for the development of heart failure has remained elusive. There has been limited progress in the genetic exploration of the key clinical phenotype itself: heart failure. In this article, the author attempts to place the results of genetic studies of cardiomyopathy in the broader context of the clinical syndrome of heart failure, highlighting some of the key questions for future study.

CCR2 and coronary artery disease: a woscops substudy

Background

Several lines of evidence support a role for CCL2 (monocyte chemotactic protein-1) and its receptor CCR2 in the development of atherosclerosis. The aim of the present study was to determine the association of the CCR2 Val64Ile polymorphism with the development of coronary artery disease in the WOSCOPS study sample set.

Findings

A total of 443 cases and 1003 controls from the West of Scotland Coronary Prevention Study (WOSCOPS) were genotyped for the Val64Ile polymorphism in the CCR2 gene. Genotype frequencies were compared between cases and controls. The CCR2 Val64Ile polymorphism was found not to be associated with coronary events in this study population (odds ratio 1.15, 95% CI 0.82-1.61, p = 0.41).

Conclusions

This case-control study does not support an association of the CCR2 Val64Ile polymorphism with coronary artery disease in the WOSCOPS sample set and does not confirm a possible protective role for CCR2 Val64Ile in the development of coronary artery disease.

Using new tools to define the genetic underpinnings of risky traits associated with coronary artery disease: the SardiNIA study

Genomewide association studies are increasingly being applied to search for novel genes that might underlie cardiovascular diseases. In this article, we briefly review the principles that underlie modern genetic analyses and provide several illustrations from the SardiNIA study of genomewide association studies for cardiovascular risk factor traits.

Cholesteryl ester transfer protein gene haplotypes, plasma high-density lipoprotein levels and the risk of coronary heart disease

High-density lipoprotein cholesterol (HDL-C) is a known inverse predictor of coronary heart disease (CHD) and is thus a potential therapeutic target. Cholesteryl ester transfer protein (CETP) is a key protein in HDL-C metabolism such that elevated CETP activity is associated with lower HDL-C. Currently available HDL-C raising drugs are relatively ineffective and evidence suggesting the role of CETP in HDL-C levels has promoted the development of CETP inhibitors as potential therapeutic agents for CHD. We investigated three SNPs in the CETP gene in two cross-sectional community-based populations (n = 1,574 and 1,109) and a population of 556 CHD patients to determine if reduced CETP activity due to genetic variations in the CETP gene would increase HDL-C levels and reduce the risk of CHD. CETP genotypes and haplotypes were tested for association with lipid levels, CETP activity and risk of CHD. Multivariate analysis showed the common AAB2 haplotype defined by the G-2708A, C-629A and TaqIB polymorphisms, was consistently associated with reduced CETP activity and increased HDL-C levels. A mean increase in HDL-C levels of 0.16-0.24 mmol/l was observed in individuals with two copies of the AAB2 haplotype relative to non AAB2 carriers across all three populations (P < 0.001). A case-control study of males indicated no association between single SNPs or haplotypes and the risk of CHD. These results suggest that raising HDL-C via CETP inhibition may not alter risk of CHD. Randomized control trials are needed to determine whether CETP inhibition will in reality reduce risk of CHD by raising HDL-C.

Environmental cardiology: studying mechanistic links between pollution and heart disease

Environmental factors are considered key determinants of cardiovascular disease. Although lifestyle choices such as smoking, diet, and exercise are viewed as major environmental influences, the contribution of pollutants and environmental chemicals is less clear. Accumulating evidence suggests that exposure to pollutants and chemicals could elevate the risk of cardiovascular disease. Many epidemiological studies report that exposure to fine particles present in ambient air is associated with an increase in cardiovascular mortality. Statistically significant relationships between particulate air pollution and ischemic heart disease, arrhythmias, and heart failure have been reported. Animal studies show that exposure to ambient air particles increases peripheral thrombosis and atherosclerotic lesion formation. Exposures to arsenic, lead, cadmium, pollutant gases, solvents, and pesticides have also been linked to increased incidence of cardiovascular disease. Mechanistically, these effects have been attributed to changes in the synthesis or reactivity of nitric oxide that may be caused by environmental oxidants or increased endogenous production of reactive oxygen species. Additional studies are urgently needed to: identify the contribution of individual pollutants to specific aspects of cardiovascular disease; establish causality; elucidate the underlying physiological and molecular mechanisms; estimate the relative susceptibility of diseased and healthy individuals and that of specific population groups; and determine whether pollutant exposure are risk correlates, that is, whether they influence major risk factors, such as hypertension, cholesterol, or diabetes, or whether they contribute to the absolute risk of heart disease. Collectively, these investigations could contribute to the emergent field of environmental cardiology.

The C-480T hepatic lipase polymorphism is associated with HDL-C but not with risk of coronary heart disease

High-density lipoprotein cholesterol (HDL-C) is a known predictor of coronary heart disease (CHD). Studies have shown that the C-480T polymorphism of the hepatic lipase (HL) gene is predictive of HDL-C; however, its observed relationship with the risk of CHD has been inconsistent. We analysed four biallelic polymorphisms in the HL gene in participants from three independent Western Australian populations. Samples were collected from two cross-sectional studies of 1111 and 4822 community-based subjects assessed for cardiovascular risk factors, and a third sample of 556 subjects with physician-diagnosed CHD. Genotypes were tested for association with plasma lipids and the risk of CHD. All polymorphisms were highly correlated (D' > 0.97, r(2) > 0.90); therefore, only C-480T was analysed. The -480T allele was significantly associated with an increase in HDL-C of between 0.08 and 0.16 mmol/l in all three populations (p < 0.001). No associations with other lipids were observed, nor was an association with CHD in a case-control study of males. The TT genotype was however associated with decreased risk of myocardial infarction among cases (odds ratio = 0.39, 95% confidence interval = 0.19-0.78, p = 0.008). These findings replicate those of previous studies in three independent populations and suggest that the genetic determinants of CHD are complex and cannot be entirely explained through intermediate phenotypes.

Genetic competencies essential for health care professionals in primary care

The completion of the sequencing of the human genome in 2003 signaled the onset of the genomic era in health care. The knowledge gleaned from the Human Genome Project has led to the understanding that every health problem has a genetic component and that clinicians should include the application of genetic information in all aspects of health care. This article describes the genetic competencies essential for all health care professionals in primary care. Health care professionals should augment their current practice by obtaining a multigenerational genetic family history for each patient, assessing all patients for potentially heritable conditions, providing referrals to genetic health professionals as needed, offering genetic testing when indicated, and considering an individual's genetic makeup in the selection of medications and treatments for that person. Finally, all health care professionals ought to be prepared to address the complex personal, cultural, theological, ethical, legal, and social issues associated with genetic testing and other genetic issues commonly encountered in clinical practice.

Genetic and genomic analysis of a fat mass trait with complex inheritance reveals marked sex specificity

The integration of expression profiling with linkage analysis has increasingly been used to identify genes underlying complex phenotypes. The effects of gender on the regulation of many physiological traits are well documented; however, “genetical genomic” analyses have not yet addressed the degree to which their conclusions are affected by sex. We constructed and densely genotyped a large F2 intercross derived from the inbred mouse strains C57BL/6J and C3H/HeJ on an apolipoprotein E null (ApoE^−/−) background. This BXH.ApoE^−/− population recapitulates several “metabolic syndrome” phenotypes. The cross consists of 334 animals of both sexes, allowing us to specifically test for the dependence of linkage on sex. We detected several thousand liver gene expression quantitative trait loci, a significant proportion of which are sex-biased. We used these analyses to dissect the genetics of gonadal fat mass, a complex trait with sex-specific regulation. We present evidence for a remarkably high degree of sex-dependence on both the cis and trans regulation of gene expression. We demonstrate how these analyses can be applied to the study of the genetics underlying gonadal fat mass, a complex trait showing significantly female-biased heritability. These data have implications on the potential effects of sex on the genetic regulation of other complex traits.

Although their genomes are nearly identical, the males and females of a species exhibit striking differences in many traits, including complex traits such as obesity. This study combines genetic and genomic tools to identify in parallel quantitative trait loci (QTLs) for a measure of gonadal fat mass and for expression of transcripts in the liver. The results are used to explore the relationship between genetic variation, sexual differentiation, and obesity in the mouse model. Using over 300 intercross progeny of two inbred mouse strains, five loci in the genome were found to be highly correlated with abdominal fat mass. Four of the five loci exhibited opposite effects on obesity in the two sexes, a phenomenon known as sexual antagonism. To identify candidate genes that may be involved in obesity through their expression in the liver, global gene expression analysis was employed using microarrays. Many of these expression QTLs also show sex-specific effects on transcription. A hotspot for trans-acting QTLs regulating the expression of transcripts whose abundance is correlated with gonadal fat mass was identified on Chromosome 19. This region of the genome colocalizes with a clinical QTL for gonadal fat mass, suggesting that it harbors a good candidate gene for obesity.

Lack of MEF2A mutations in coronary artery disease

Mutations in MEF2A have been implicated in an autosomal dominant form of coronary artery disease (adCAD1). In this study we sought to determine whether severe mutations in MEF2A might also explain sporadic cases of coronary artery disease (CAD). To do this, we resequenced the coding sequence and splice sites of MEF2A in approximately 300 patients with premature CAD and failed to find causative mutations in the CAD cohort. However, we did identify the 21-bp MEF2A coding sequence deletion originally implicated in adCAD1 in 1 of 300 elderly control subjects without CAD. Further screening of approximately 1,500 additional individuals without CAD revealed 2 more subjects with the MEF2A 21-bp deletion. Genotyping of 19 family members of the 3 probands with the 21-bp deletion in MEF2A revealed that the mutation did not cosegregate with early CAD. These studies support that MEF2A mutations are not a common cause of CAD in white people and argue strongly against a role for the MEF2A 21-bp deletion in autosomal dominant CAD.

Genetics of atherosclerosis

Atherosclerosis, the primary cause of coronary artery disease (CAD) and stroke, is a disorder with multiple genetic and environmental contributions. Genetic-epidemiologic studies have identified a surprisingly long list of genetic and nongenetic risk factors for CAD. However, such studies indicate that family history is the most significant independent risk factor (15, 52, 77). Many Mendelian disorders associated with atherosclerosis, such as familial hypercholesterolemia (FH), have been characterized, but they explain only a small percentage of disease susceptibility (although a substantial fraction of early CAD). Most cases of myocardial infarction (MI) and stroke result from the interactions of multiple genetic and environmental factors, none of which can cause disease by itself. Successful discovery of these genetic factors will require using complementary approaches with animal models, large-scale human genetic studies, and functional experiments. This review emphasizes the common, complex forms of CAD.