Heritability of death from coronary heart disease: a 36-year follow-up of 20 966 Swedish twins

Mendelian Randomization Studies Promise to Shorten the Journey to FDA Approval

There has been a dearth of new drugs approved for cardiovascular disorders. The cost is prohibitive, averaging to $2.5 billion, and requiring 12.5 years. This is in large part due to the high failure rate, with only 5% approval by the Food and Drug Administration. Despite preclinical studies showing potential safety and efficacy, most fail when they go to clinical trials phase I to III. One cause for failure is the drug target, often discovered to be a biomarker rather than causative for the disease. Mendelian randomization (MR) studies would determine whether the drug target is causative and could save millions of dollars and time, and prevent unnecessary exposure to adverse drug effects. This was demonstrated in 3 clinical trials that were negative with 2 drugs, veraspladib and darapladib. MR studies during the trials showed the targets of secretory and lipoprotein-associated phospholipids A2 are not causative for coronary artery disease and predicted negative results. The requirement for MR studies is a genetic risk variant with altered function, randomized at conception that remains fixed throughout one’s lifetime. It is not confounded by dietary, lifestyle, or socioeconomic factors. It is more sensitive than randomized controlled trials because exposure to the risk factor is fixed for a lifetime. MR studies showed plasma high-density lipoprotein cholesterol is not a causative target of coronary artery disease, and neither is uric acid, C-reactive protein, and others. MR studies are highly sensitive in determining whether drug targets are causative, and are relatively easy, inexpensive, and not time consuming. It is recommended that drug targets undergo MR studies before proceeding to randomized controlled trials.

Genomic Risk Stratification Predicts All-Cause Mortality After Cardiac Catheterization

BACKGROUND

Coronary artery disease (CAD) is influenced by genetic variation and traditional risk factors. Polygenic risk scores (PRS), which can be ascertained before the development of traditional risk factors, have been shown to identify individuals at elevated risk of CAD. Here, we demonstrate that a genome-wide PRS for CAD predicts all-cause mortality after accounting for not only traditional cardiovascular risk factors but also angiographic CAD itself.

METHODS

Individuals who underwent coronary angiography and were enrolled in an institutional biobank were included; those with prior myocardial infarction or heart transplant were excluded. Using a pruning-and-thresholding approach, a genome-wide PRS comprised of 139 239 variants was calculated for 1503 participants who underwent coronary angiography and genotyping. Individuals were categorized into high PRS (hiPRS) and low-PRS control groups using the maximally selected rank statistic. Stratified analysis based on angiographic findings was also performed. The primary outcome was all-cause mortality following the index coronary angiogram.

RESULTS

Individuals with hiPRS were younger than controls (66 years versus 69 years; P=2.1×10-5) but did not differ by sex, body mass index, or traditional risk-factor profiles. Individuals with hiPRS were at significantly increased risk of all-cause mortality after cardiac catheterization, adjusting for traditional risk factors and angiographic extent of CAD (hazard ratio, 1.6; 95% CI, 1.2-2.2; P=0.004). The strongest increase in risk of all-cause mortality conferred by hiPRS was seen among individuals without angiographic CAD (hazard ratio, 2.4; 95% CI, 1.1-5.5; P=0.04). In the overall cohort, adding hiPRS to traditional risk assessment improved prediction of 5-year all-cause mortality (area under the receiver-operating curve 0.70; 95% CI, 0.66-0.75 versus 0.66; 95% CI, 0.61-0.70; P=0.001).

CONCLUSIONS

A genome-wide PRS improves risk stratification when added to traditional risk factors and coronary angiography. Individuals without angiographic CAD but with hiPRS remain at significantly elevated risk of mortality.

Capitalizing on Insights from Human Genetics to Identify Novel Therapeutic Targets for Coronary Artery Disease

Coronary artery disease (CAD) is a major cause of morbidity and mortality. Unfortunately, despite decades of research focused on disease pathogenesis, we still lack a sufficient pharmacopeia for preventing CAD. The failure of many novel cardiovascular drugs to improve clinical outcomes reflects the major substantial challenge of drug development: identifying causal mechanisms that can be therapeutically manipulated to lower disease risk. Identifying genetic variants that are associated with risk of CAD has emerged as a clear path toward improving our understanding of the underlying mechanisms that lead to disease and to the development of new therapies. Here, we review the potential utility and limitations of using human genetics to guide the identification of therapeutic targets for CAD.

Free Will, Determinism, and Intuitive Judgments About the Heritability of Behavior

The fact that genes and environment contribute differentially to variation in human behaviors, traits and attitudes is central to the field of behavior genetics. Perceptions about these differential contributions may affect ideas about human agency. We surveyed two independent samples (N = 301 and N = 740) to assess beliefs about free will, determinism, political orientation, and the relative contribution of genes and environment to 21 human traits. We find that lay estimates of genetic influence on these traits cluster into four distinct groups, which differentially predict beliefs about human agency, political orientation, and religiosity. Despite apparent ideological associations with these beliefs, the correspondence between mean lay estimates and published heritability estimates for the surveyed traits is large (r = .77). Belief in genetic determinism emerges as a modest predictor of accuracy in these lay estimates. Additionally, educated mothers with multiple children emerge as particularly accurate in their estimates of the genetic contribution to these traits.

Identification of 26 novel loci that confer susceptibility to early-onset coronary artery disease in a Japanese population

Early-onset coronary artery disease (CAD) has a strong genetic component. Although genome-wide association studies have identified various genes and loci significantly associated with CAD mainly in European populations, genetic variants that contribute toward susceptibility to this condition in Japanese patients remain to be definitively identified. In the present study, exome-wide association studies (EWASs) were performed to identify genetic variants that confer susceptibility to early-onset CAD in Japanese. A total of 7,256 individuals aged ≤65 years were enrolled in the present study. EWAS were conducted on 1,482 patients with CAD and 5,774 healthy controls. Genotyping of single nucleotide polymorphisms (SNPs) was performed using Illumina Human Exome-12 DNA Analysis BeadChip or Infinium Exome-24 BeadChip arrays. The association between allele frequencies for 31,465 SNPs that passed quality control and CAD was examined using Fisher's exact test. To compensate for multiple comparisons of allele frequencies with CAD, a false discovery rate (FDR) of <0.05 was applied for statistically significant associations. The association between allele frequencies for 31,465 SNPs and CAD, as determined by Fisher's exact test, demonstrated that 170 SNPs were significantly (FDR <0.05) associated with CAD. Multivariable logistic regression analysis with adjustment for age, sex, and the prevalence of hypertension, diabetes mellitus and dyslipidemia revealed that 162 SNPs were significantly (P<0.05) associated with CAD. A stepwise forward selection procedure was performed to examine the effects of genotypes for the 162 SNPs on CAD. The 54 SNPs were significant (P<0.05) and independent [coefficient of determination (R²), 0.0008 to 0.0297] determinants of CAD. These SNPs together accounted for 15.5% of the cause of CAD. Following examination of results from previous genome-wide association studies and linkage disequilibrium of the identified SNPs, 21 genes (RNF2, YEATS2, USP45, ITGB8, TNS3, FAM170B-AS1, PRKG1, BTRC, MKI67, STIM1, OR52E4, KIAA1551, MON2, PLUT, LINC00354, TRPM1, ADAT1, KRT27, LIPE, GFY and EIF3L) and five chromosomal regions (2p13, 4q31.2, 5q12, 13q34 and 20q13.2) that were significantly associated with CAD were newly identified in the present study. Gene ontology analysis demonstrated that various biological functions were predicted in the 18 genes identified in the present study. The network analysis revealed that the 18 genes had potential direct or indirect interactions with the 30 genes previously revealed to be associated with CAD or with the 228 genes identified in previous genome-wide association studies. The present study newly identified 26 loci that confer susceptibility to CAD. Determination of genotypes for the SNPs at these loci may prove informative for assessment of the genetic risk for CAD in Japanese patients.

Genetic Regulatory Mechanisms of Smooth Muscle Cells Map to Coronary Artery Disease Risk Loci

Coronary artery disease (CAD) is the leading cause of death globally. Genome-wide association studies (GWASs) have identified more than 95 independent loci that influence CAD risk, most of which reside in non-coding regions of the genome. To interpret these loci, we generated transcriptome and whole-genome datasets using human coronary artery smooth muscle cells (HCASMCs) from 52 unrelated donors, as well as epigenomic datasets using ATAC-seq on a subset of 8 donors. Through systematic comparison with publicly available datasets from GTEx and ENCODE projects, we identified transcriptomic, epigenetic, and genetic regulatory mechanisms specific to HCASMCs. We assessed the relevance of HCASMCs to CAD risk using transcriptomic and epigenomic level analyses. By jointly modeling eQTL and GWAS datasets, we identified five genes (SIPA1, TCF21, SMAD3, FES, and PDGFRA) that may modulate CAD risk through HCASMCs, all of which have relevant functional roles in vascular remodeling. Comparison with GTEx data suggests that SIPA1 and PDGFRA influence CAD risk predominantly through HCASMCs, while other annotated genes may have multiple cell and tissue targets. Together, these results provide tissue-specific and mechanistic insights into the regulation of a critical vascular cell type associated with CAD in human populations.

The rs3850641 polymorphism of the TNFSF4 gene increases the risk of myocardial infarction in a Chinese Han population

Tumor necrosis factor superfamily member 4 (TNFSF4), also known as Ox40 ligand (Ox40l), plays an important role in atherosclerosis development. Several studies reported the association between the rs3850641 polymorphism of the TNFSF4 gene and the risk of myocardial infarction (MI). However, the results are inconsistent. In order to explore the relationship between the rs3850641 polymorphism of the TNFSF4 gene and MI, we conducted a case–control study including 454 cases and 512 controls in a Chinese Han population. Genotyping was performed using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. The present study found that AA genotype (AA vs. GG: odds ratio (OR) & 95% confidence interval (CI), 2.00(1.04,3.86), P=0.039; AA vs. AG+GG: OR & 95% CI, 1.93(1.00,3.70), P=0.049) or A allele carriers (A vs. G: OR & 95% CI, 1.27(1.00,1.60), P=0.047) of the rs3850641 polymorphism of the TNFSF4 gene increased the risk of MI. In conclusion, this case–control study confirms that the rs3850641 polymorphism of the TNFSF4 gene increases the risk of MI.

Poor oral health and risk of incident myocardial infarction: A prospective cohort study of Swedish adults, 1973-2012

Previous studies provide conflicting evidence as to whether there is an association between poor oral health and an increased risk of myocardial infarction. The aim of the study was to deepen knowledge of the association between oral health and myocardial infarction risk using a large (n = 20,133), prospective, and population-based cohort in Uppsala, Sweden. Oral health was determined during a clinical dental examination at entry into the cohort in 1973/74. Individuals were followed through linkage with the Swedish National Patient Register, Cause of Death Register and Emigration Register. Cox proportional hazards regression models were used to estimate hazard ratios (HRs) for total, non-fatal and fatal myocardial infarction events. Increased risks of total, non-fatal and fatal myocardial infarction events among individuals with fewer reference teeth at examination, more dental plaque and a borderline significant increased risk among individuals with oral lesions were observed. Adjustment for multiple potential confounding factors did not change the results appreciably. However, the observed HRs generally decreased towards one when the analysis was confined to non-tobacco users only. The results from this study indicate that poor oral health is associated with a slightly increased risk of myocardial infarction; however, these results may be partly explained by residual confounding.

APOA1 and APOB polymorphisms and apolipoprotein concentrations as biomarkers of risk in acute coronary syndrome: Relationship with lipid-lowering therapy effectiveness

BACKGROUND AND OBJECTIVE

Lipid metabolism alterations contribute to acute coronary syndrome (ACS). rs670, rs5070 and rs693 polymorphisms have shown to modify the risk of cardiovascular disease. Apolipoprotein A-I (ApoA-I) plays a major role in reverse cholesterol transport; apolipoprotein B (ApoB) contributes to accumulation of cholesterol in the plaque. The aim of this study was to investigate the association of rs670 and rs5070 polymorphisms of APOA1 and rs693 polymorphism of APOB with ACS and circulating levels of its proteins and find if ApoB/ApoA-I could be implemented as an independent parameter of risk for cardiovascular disease and as a biomarker of lipid-lowering therapy effectiveness in Mexican population.

METHODS

Three hundred patients with ACS and 300 control subjects (CS) were included.

RESULTS

Neither genotype nor allele frequencies of rs670, rs5070 and rs693 polymorphisms showed statistical differences between groups. Serum levels of ApoA-I (195 vs. 161.4mg/dL; P<.001) and ApoB (167 vs. 136.9mg/dL; P<.001) were significantly higher in CS compared with ACS; however, there was no genetic association. Unstable angina patients showed the highest ApoA-I levels (males: 176.3mg/dL; females: 209.1mg/dL).

CONCLUSION

The rs670, rs5070 and rs693 polymorphisms are not genetic susceptibility factors for ACS in Mexican population and had no effect on their apolipoprotein concentrations. In our population, ApoA-I, ApoB and HDL-C could be better biomarkers of cardiovascular risk and could indicate if statins doses reduce atherogenic particles properly.

GWAS Reveal Targets in Vessel Wall Pathways to Treat Coronary Artery Disease

Coronary artery disease (CAD) is the leading cause of mortality worldwide and poses a considerable public health burden. Recent genome-wide association studies (GWAS) have revealed >100 genetic loci associated with CAD susceptibility in humans. While a number of these loci harbor gene targets of currently approved therapies, such as statins and PCSK9 inhibitors, the majority of the annotated genes at these loci encode for proteins involved in vessel wall function with no known drugs available. Importantly many of the associated genes linked to vascular (smooth muscle, endothelial, and macrophage) cell processes are now organized into distinct functional pathways, e.g., vasodilation, growth factor responses, extracellular matrix and plaque remodeling, and inflammation. In this mini-review, we highlight the most recently identified loci that have predicted roles in the vessel wall and provide genetic context for pre-existing therapies as well as new drug targets informed from GWAS. With the development of new modalities to target these pathways, (e.g., antisense oligonucleotides, CRISPR/Cas9, and RNA interference) as well as the computational frameworks to prioritize or reposition therapeutics, there is great opportunity to close the gap from initial genetic discovery to clinical translation for many patients affected by this common disease.

The design and rationale of SAVE BC: The Study to Avoid CardioVascular Events in British Columbia

Atherosclerotic cardiovascular disease (ASCVD) is highly heritable, particularly when it occurs at a young age. The screening of individuals with premature ASCVD, although often recommended, is not routinely performed. Strategies to address this gap in care are essential. We designed the Study to Avoid CardioVascular Events in British Columbia (SAVE BC) as a prospective, observational study of individuals with a new diagnosis of very premature ASCVD (defined as age ≤ 50 years in males and age ≤ 55 years in females) and their first-degree relatives (FDRs) and spouses. FDRs and spouses will undergo screening for cardiovascular (CV) risk factors and subclinical ASCVD using a structured screening algorithm. All subjects will be followed longitudinally for ≥10 years. The overall goal of SAVE BC is to evaluate the yield of a structured screening program for identifying individuals at risk of premature ASCVD. The primary objectives of SAVE BC are to identify and follow index cases with very premature ASCVD and their FDRs and to determine the diagnostic yield of a structured screening program for these individuals. We will collect data on CV risk factors, medication use, CV events, and healthcare costs in these individuals. SAVE BC will provide insight regarding approaches to identify individuals at risk for premature ASCVD with implications for prevention and treatment in this population.

Genetic Markers for Coronary Artery Disease

Coronary artery disease (CAD) and myocardial infarction (MI) are recognized as leading causes of mortality in developed countries. Although typically associated with behavioral risk factors, such as smoking, sedentary lifestyle, and poor dietary habits, such vascular phenotypes have also long been recognized as being related to genetic background. We review the currently available data concerning genetic markers for CAD in English and non-English articles with English abstracts published between 2003 and 2018. As genetic testing is increasingly available, it may be possible to identify adequate genetic markers representing the risk profile and to use them in a clinical setting.

Lack of genetic support for shared aetiology of Coronary Artery Disease and Late-onset Alzheimer's disease

Epidemiological studies suggest a positive association between coronary artery disease (CAD) and late-onset Alzheimer's disease (LOAD). This large-scale genetic study brings together 'big data' resources to examine the causal impact of genetic determinants of CAD on risk of LOAD. A two-sample Mendelian randomization approach was adopted to estimate the causal effect of CAD on risk of LOAD using summary data from 60,801 CAD cases from CARDIoGRAMplusC4D and 17,008 LOAD cases from the IGAP Consortium. Additional analyses assessed the independent relevance of genetic associations at the APOE locus for both CAD and LOAD. Higher genetically determined risk of CAD was associated with a slightly higher risk of LOAD (Odds Ratio (OR) per log-odds unit of CAD [95% CI]: 1.07 [1.01-1.15]; p = 0.027). However, after exclusion of the APOE locus, the estimate of the causal effect of CAD for LOAD was attenuated and no longer significant (OR 0.94 [0.88-1.01]; p = 0.072). This Mendelian randomization study indicates that the APOE locus is the chief determinant of shared genetic architecture between CAD and LOAD, and suggests a lack of causal relevance of CAD for risk of LOAD after exclusion of APOE.

A role for collagen type IV in cardiovascular disease?

Over the past decade, studies have repeatedly found single-nucleotide polymorphisms located in the collagen ( COL) 4A1 and COL4A2 genes to be associated with cardiovascular disease (CVD), and the 13q34 locus harboring these genes is one of ~160 genome-wide significant risk loci for coronary artery disease. COL4A1 and COL4A2 encode the α₁- and α₂-chains of collagen type IV, a major component of basement membranes in various tissues including arteries. Despite the growing body of evidence indicating a role for collagen type IV in CVD, remarkably few studies have aimed to directly investigate such a role. The purpose of this review is to summarize the clinical reports linking 13q34 to coronary artery disease, atherosclerosis, and artery stiffening and to assemble the scattered pieces of evidence from experimental studies based on vascular cells and tissue collectively supporting a role for collagen type IV in atherosclerosis and other macrovascular disease conditions.

Genetic Risk Prediction for Primary and Secondary Prevention of Atherosclerotic Cardiovascular Disease: an Update

PURPOSE OF REVIEW

This review aims to summarize the research on genetic risk scores and their ability to improve risk prediction in both a primary and a secondary prevention population.

RECENT FINDINGS

Several groups have examined the role of genetic scores in different patient populations. Recent studies have capitalized on the growing number of identified genetic variants to construct polygenic risk scores that include hundreds and sometimes thousands of SNPs. Also, recent studies have demonstrated that individuals with high genetic risk scores can attenuate their risk with lifestyle modifications and with statins, for which the benefit of treatment may be greater in those at highest genetic risk. Genetic risk scores when added to existing clinical models appear to improve risk prediction, particularly in the setting of incident cardiovascular disease and may provide actionable information to optimize prevention early in life. Future research will need to establish how to best use this genetic risk information either as a means to further individualize treatment decisions or to better identify high-risk populations.

Evaluation of 71 Coronary Artery Disease Risk Variants in a Multiethnic Cohort

Background

Coronary heart disease (CHD) is the most common cause of death worldwide. Previous studies have identified numerous common CHD susceptibility loci, with the vast majority identified in populations of European ancestry. How well these findings transfer to other racial/ethnic populations remains unclear.

Methods and Results

We examined the generalizability of the associations with 71 known CHD loci in African American, Latino and Japanese men and women in the Multiethnic Cohort (6,035 cases and 11,251 controls). In the combined multiethnic sample, 78% of the loci demonstrated odds ratios that were directionally consistent with those previously reported (p = 2 × 10⁻⁶), with this fraction ranging from 59% in Japanese to 70% in Latinos. The number of nominally significant associations across all susceptibility regions ranged from only 1 in Japanese to 11 in African Americans with the most statistically significant association observed through locus fine-mapping noted for rs3832016 (OR = 1.16, p = 2.5×10⁻⁵) in the SORT1 region on chromosome 1p13. Lastly, we examined the cumulative predictive effect of CHD SNPs across populations with improved power by creating genetic risk scores (GRSs) that summarize an individual’s aggregated exposure to risk variants. We found the GRSs to be significantly associated with risk in African Americans (OR = 1.03 per allele; p = 4.1×10⁻⁵) and Latinos (OR = 1.03; p = 2.2 × 10⁻⁸), but not in Japanese (OR = 1.01; p = 0.11).

Conclusions

While a sizable fraction of the known CHD loci appear to generalize in these populations, larger fine-mapping studies will be needed to localize the functional alleles and better define their contribution to CHD risk in these populations.

Twins Lead to the Prevention of Atherosclerosis: Preliminary Findings of International Twin Study 2009

Introduction

Atherosclerosis is an inflammatory process in which the artery wall thickens as a result of plaque deposition, but this process may be preceded by increased arterial stiffness. We sought to evaluate the influence of genetics and shared and unshared environmental components on the onset of atherosclerosis.

Methods

A total of 135 monozygotic (MZ) and 70 dizygotic (DZ) twin pairs (mean age 49 ± 16 years) underwent carotid intima media thickness (IMT; carotid analyzer) and arterial stiffness (augmentation index on brachial artery [ Aixbra], pulse wave velocity on aorta [ PWVao]; TensioMed Arteriograph) measurements.

Results

Age-adjusted intraclass correlations were greater in MZ than in DZ pairs for proximal right common carotid artery (CCA; MZ = 0.19, DZ = 0.06), proximal and distal left CCA (MZ = 0.27, DZ = 0.06; MZ = 0.27, DZ = 0.13, respectively), and proximal left internal carotid artery (ICA; MZ = 0.39, DZ = −0.54), suggesting a moderate genetic effect. Heritability was estimated to be 18% (95% confidence interval [CI] = 3–33) for proximal right CCA, 26% and 27% for proximal and distal left CCA, respectively, and 38% (95% CI = 26–49) for proximal left ICA. Regarding distal right CCA and proximal right ICA, no genetic effects were detected. Age-adjusted intraclass correlation of Aixbra and PWVao were 0.65 (95% CI = 0.55–0.72) and 0.46 (95% CI = 0.33–0.57) in MZ, 0.42 (95% CI = 0.24–0.57) and 0.28 (95% CI = 0.08–0.47) in DZ pairs; heritability 45% (95% CI = 12–71%) and 42% (95% CI = 2–57%) adjusted by age, respectively.

Conclusions

The investigated parameters appeared to be only moderately influenced by genetic factors. Environmental factors of relevance for these measures appeared not to be shared within family but related to individual experience (e.g., smoking habits, diet, and physical activity). Atherosclerosis detection at an early stage is necessary for treatment to prevent serious complications such as stroke and heart attack.

Genetics in the prevention and management of coronary artery disease

PURPOSE OF REVIEW

The current review is to describe the genetic risk variants that have been discovered predisposing to coronary artery disease (CAD) and how they are utilized to stratify for risk of CAD.

RECENT FINDINGS

Over 90 genetic risk variants have been discovered that predispose to risk for CAD.

SUMMARY

The total genetic risk burden for CAD is proportional to the number of risk variants inherited and can be combined into a single number referred to as the genetic risk score (GRS). GRS has been utilized in multiple studies and shown to be more effective in risk stratification for CAD than conventional risk factors. There is a major advantage to risk stratification based on the GRS since the risk can be determined at birth or anytime throughout one's lifetime since the individual's DNA does not change. Widespread application of the GRS is likely to enable a paradigm shift in the primary prevention of CAD.

Polygenic Contribution in Individuals With Early-Onset Coronary Artery Disease

BACKGROUND

Despite evidence of high heritability, monogenic disorders are identified in a minor fraction of individuals with early-onset coronary artery disease (EOCAD). We hypothesized that some individuals with EOCAD carry a high number of common genetic risk variants, with a combined effect similar to Mendelian forms of coronary artery disease, such as familial hypercholesterolemia.

METHODS AND RESULTS

To confirm the polygenic contribution to EOCAD (age of ≤40 years for men and ≤45 years for women), we calculated in 111 418 British participants from the UK Biobank cohort a genetic risk score (GRS) based on the presence of 182 independent variants associated with coronary artery disease (GRS182). Participants with a diagnosis of EOCAD who underwent a revascularization procedure (n=96) had a significantly higher GRS182 (P=3.21×10^-9) than those without EOCAD. An increase of 1 SD in GRS182 corresponded to an odds ratio of 1.84 (1.52-2.24) for EOCAD. The prevalence of a polygenic contribution that increased EOCAD risk similar to what is observed in heterozygous familial hypercholesterolemia was estimated at 1 in 53. In a local cohort of individuals with EOCAD (n=30), GRS182 was significantly increased compared with UK Biobank controls (P=0.001). Seven participants (23%) had a GRS182 corresponding to an estimated 2-fold increase in EOCAD risk; none had a rare mutation involved in monogenic dyslipidemia or EOCAD.

CONCLUSIONS

These results suggest a significant polygenic contribution in individuals presenting with EOCAD, which could be more prevalent than familial hypercholesterolemia. Determination of the polygenic risk component could be included in the diagnostic workup of patients with EOCAD.

Genome-Wide Association Studies and Risk Scores for Coronary Artery Disease: Sex Biases

Phenotypic sex differences in coronary artery disease (CAD) and its risk factors have been apparent for many decades in basic and clinical research; however, whether these are also present at the gene level and thus influence genome-wide association and genetic risk prediction studies has often been ignored. From fundamental and medical standpoints, this is critically important to assess in order to fully understand the underlying genetic architecture that predisposes to CAD and better predict disease outcomes based on the interaction between genes, sex effects, and environment. In this chapter we aimed to (1) integrate the history and latest research from genome-wide association studies for CAD and clinical and genetic risk scores for prediction of CAD, (2) highlight sex-specific differences in these areas of research, and (3) discuss reasons why sex differences have often not been considered and, where present, why sex differences exist at genetic and phenotypic levels and how important they are for consideration in future research. While we find interesting examples of sex differences in effects of genetic variants on CAD, genome-wide association and genetic risk studies have typically not tested for sex-specific effects despite mounting evidence from diverse fields that these are likely very important to consider at both the genetic and phenotypic levels. In-depth testing for sex effects in large-scale genome-wide association studies that include autosomal and often excluded sex chromosomes alongside parallel improvements in resolution of sex-specific differences for risk factors and disease outcomes for CAD has the potential to substantially improve clinical and genetic risk prediction studies. Developing sex-tailored genetic risk scores as has been done recently for other disorders might be also warranted for CAD. In the era of precision medicine, this level of accuracy is essential for such a common and costly disease.

Genome-wide association study identifies a missense variant at APOA5 for coronary artery disease in Multi-Ethnic Cohorts from Southeast Asia

Recent genome-wide association studies (GWAS) have identified multiple loci associated with coronary artery disease (CAD) among predominantly Europeans. However, their relevance to multi-ethnic populations from Southeast Asia is largely unknown. We performed a meta-analysis of four GWAS comprising three Chinese studies and one Malay study (Total N = 2,169 CAD cases and 7,376 controls). Top hits (P < 5 × 10-8) were further evaluated in 291 CAD cases and 1,848 controls of Asian Indians. Using all datasets, we validated recently identified loci associated with CAD. The involvement of known canonical pathways in CAD was tested by Ingenuity Pathway Analysis. We identified a missense SNP (rs2075291, G > T, G185C) in APOA5 for CAD that reached robust genome-wide significance (Meta P = 7.09 × 10-10, OR = 1.636). Conditional probability analysis indicated that the association at rs2075291 was independent of previously reported index SNP rs964184 in APOA5. We further replicated 10 loci previously identified among predominantly Europeans (P: 1.33 × 10-7-0.047). Seven pathways (P: 1.10 × 10-5-0.019) were identified. We identified a missense SNP, rs2075291, in APOA5 associated with CAD at a genome-wide significance level and provided new insights into pathways contributing to the susceptibility to CAD in the multi-ethnic populations from Southeast Asia.

Novel common variants associated with body mass index and coronary artery disease detected using a pleiotropic cFDR method

Genome-wide association studies (GWAS) have been successfully applied in identifying single nucleotide polymorphisms (SNPs) associated with body mass index (BMI) and coronary heart disease (CAD). However, the SNPs to date can only explain a small percentage of the genetic variances of traits. Here, we applied a genetic pleiotropic conditional false discovery rate (cFDR) method that combines summary statistic p values from different multi-center GWAS datasets, to detect common genetic variants associated with these two traits. The enrichment of SNPs associated with BMI and CAD was assessed by conditional Q-Q plots and the common variants were identified by the cFDR method. By applying the cFDR level of 0.05, 7 variants were identified to be associated with CAD (2 variants being novel), 34 variants associated with BMI (11 variants being novel), and 3 variants associated with both BMI and CAD (2 variants being novel). The SNP rs653178 (ATXN2) is noteworthy as this variant was replicated in an independent analysis. SNP rs12411886 (CNNM2) and rs794356 (HIP1) were of note as the annotated genes may be associated with processes that are functionally important in lipid metabolism. In conclusion, the cFDR method identified novel variants associated with BMI and/or CAD by effectively incorporating different GWAS datasets.

Genetics-Current and Future Role in the Prevention and Management of Coronary Artery Disease

PURPOSE OF REVIEW

The purpose of this study is to review genetic risk variants for coronary artery disease (CAD) and how they will change the management and prevention of CAD currently and in the future.

RECENT FINDINGS

Through the efforts of international consortia, 58 genetic risk variants for CAD of genome-wide significance have been replicated in appropriate independent populations. Only one third of these variants mediate their risk through known conventional risk factors for CAD. Thus, unknown mechanisms contribute to CAD. Secondly, the genetic risk is proportional to the total number of risk variants rather than the intensity of any risk factor. Thirdly, the availability of the genetic risk variants enables one to perform Mendelian randomization (MR) studies since they are randomized at conception, not confounded, fixed for life, and can be used to determine if a risk factor is causative or just a marker. MR can also be used to determine the safety and efficacy of a gene product targeted for drug therapy. Genetic risk variants have been shown to successfully risk stratify for CAD in both primary and secondary preventions. Contrary to dogma, MR documents that plasma HDL-C is not protective of CAD. The use of genetic risk score (GRS) for CAD is shown to be more effective in risk stratifying for CAD than the Framingham risk score and independent of the conventional risk factors including family history. Furthermore, the GRS predicts the response to statin therapy in primary and secondary preventions. The use of GRS could represent a paradigm shift in the prevention of CAD.

Family-specific aggregation of lipid GWAS variants confers the susceptibility to familial hypercholesterolemia in a large Austrian family

BACKGROUND AND AIMS

Hypercholesterolemia confers susceptibility to cardiovascular disease (CVD). Both serum total cholesterol (TC) and LDL-cholesterol (LDL-C) exhibit a strong genetic component (heritability estimates 0.41-0.50). However, a large part of this heritability cannot be explained by the variants identified in recent extensive genome-wide association studies (GWAS) on lipids. Our aim was to find genetic causes leading to high LDL-C levels and ultimately CVD in a large Austrian family presenting with what appears to be autosomal dominant inheritance for familial hypercholesterolemia (FH).

METHODS

We utilized linkage analysis followed by whole-exome sequencing and genetic risk score analysis using an Austrian multi-generational family with various dyslipidemias, including elevated TC and LDL-C, and one family branch with elevated lipoprotein (a) (Lp(a)).

RESULTS

We did not find evidence for genome-wide significant linkage for LDL-C or apparent causative variants in the known FH genes rather, we discovered a particular family-specific combination of nine GWAS LDL-C SNPs (p = 0.02 by permutation), and putative less severe familial hypercholesterolemia mutations in the LDLR and APOB genes in a subset of the affected family members. Separately, high Lp(a) levels observed in one branch of the family were explained primarily by the LPA locus, including short (<23) Kringle IV repeats and rs3798220.

CONCLUSIONS

Taken together, some forms of FH may be explained by family-specific combinations of LDL-C GWAS SNPs.

Environmental Determinants of Cardiovascular Disease

Many features of the environment have been found to exert an important influence on cardiovascular disease (CVD) risk, progression, and severity. Changes in the environment because of migration to different geographic locations, modifications in lifestyle choices, and shifts in social policies and cultural practices alter CVD risk, even in the absence of genetic changes. Nevertheless, the cumulative impact of the environment on CVD risk has been difficult to assess and the mechanisms by which some environment factors influence CVD remain obscure. Human environments are complex, and their natural, social, and personal domains are highly variable because of diversity in human ecosystems, evolutionary histories, social structures, and individual choices. Accumulating evidence supports the notion that ecological features such as the diurnal cycles of light and day, sunlight exposure, seasons, and geographic characteristics of the natural environment such as altitude, latitude, and greenspaces are important determinants of cardiovascular health and CVD risk. In highly developed societies, the influence of the natural environment is moderated by the physical characteristics of the social environments such as the built environment and pollution, as well as by socioeconomic status and social networks. These attributes of the social environment shape lifestyle choices that significantly modify CVD risk. An understanding of how different domains of the environment, individually and collectively, affect CVD risk could lead to a better appraisal of CVD and aid in the development of new preventive and therapeutic strategies to limit the increasingly high global burden of heart disease and stroke.

Genetic risk factors for myocardial infarction more clearly manifest for early age of first onset

Epidemiological genetics established that heritability in determining the risk of myocardial infarction (MI) is substantially greater when MI occurs early in life. However, the genetic architecture of early-onset and late-onset MI was not compared. We analyzed genotype frequencies of SNPs in/near 20 genes whose protein products are involved in the pathogenesis of atherosclerosis in two groups of Russian patients with MI: the first group included patients with age of first MI onset <60 years (N = 230) and the second group with onset ≥60 years (N = 174). The control group of corresponding ethnicity consisted of 193 unrelated volunteers without cardiovascular diseases (93 individuals were over 60 years). We found that in the group of patients with age of onset <60 years, SNPs FGB rs1800788*T, TGFB1 rs1982073*T/T, ENOS rs2070744*C and CRP rs1130864*T/T were associated with risk of MI, whereas in patients with age of onset ≥60 years, only TGFB1 rs1982073*T/T was associated with risk of MI. Using APSampler software, we found composite markers associated with MI only in patients with early onset: FGB rs1800788*T + TGFB1 rs1982073*T; FGB rs1800788*T + LPL rs328*C + IL4 rs2243250*C; FGB rs1800788*T + ENOS rs2070744*C (Fisher p values of 1.4 × 10^-6 to 2.2 × 10^-5; the permutation p values of 1.1 × 10^-5 to 3.0 × 10^-4; ORs = 2.67-2.54). Alleles included in the combinations were associated with MI less significantly and with lower ORs than the combinations themselves. The result showed a substantially greater contribution of the genetic component in the development of MI if it occurs early in life, and demonstrated the usefulness of genetic testing for young people.

Genetics: Implications for Prevention and Management of Coronary Artery Disease

An exciting new era has dawned for the prevention and management of coronary artery disease (CAD) utilizing genetic risk variants. The recent identification of over 60 susceptibility loci for CAD confirms not only the importance of established risk factors, but also the existence of many novel causal pathways that are expected to improve our understanding of the genetic basis of CAD and facilitate the development of new therapeutic agents over time. Concurrently, Mendelian randomization studies have provided intriguing insights on the causal relationship between CAD-related traits, and highlight the potential benefits of long-term modifications of risk factors. Last, genetic risk scores of CAD may serve not only as prognostic, but also as predictive markers, and carry the potential to considerably improve the delivery of established prevention strategies. This review will summarize the evolution and discovery of genetic risk variants for CAD and their current and future clinical applications.

The Genetics of Ischemic Heart Disease: From Current Knowledge to Clinical Implications

Ischemic heart disease continues to cause high morbidity and mortality. Its prevalence is expected to increase due to population aging, and its prevention is a major goal of health policies. The risk of developing ischemic heart disease is related to a complex interplay between genetic, environmental, and lifestyle factors. In the last decade, considerable progress has been made in knowledge of the genetic architecture of this disease. This narrative review provides an overview of current knowledge of the genetics of ischemic heart disease and of its translation to clinical practice: identification of new therapeutic targets, assessment of the causal relationship between biomarkers and disease, improved risk prediction, and identification of responders and nonresponders to specific drugs (pharmacogenomics).

Genetics of coronary artery disease: discovery, biology and clinical translation

Coronary artery disease is the leading global cause of mortality. Long recognized to be heritable, recent advances have started to unravel the genetic architecture of the disease. Common variant association studies have linked approximately 60 genetic loci to coronary risk. Large-scale gene sequencing efforts and functional studies have facilitated a better understanding of causal risk factors, elucidated underlying biology and informed the development of new therapeutics. Moving forwards, genetic testing could enable precision medicine approaches by identifying subgroups of patients at increased risk of coronary artery disease or those with a specific driving pathophysiology in whom a therapeutic or preventive approach would be most useful.

Cardiovascular mortality - Comparing risk factor associations within couples and in the total population - The HUNT Study

BACKGROUND

To compare associations of conventional risk factors with cardiovascular death within couples and in the population as a whole.

METHODS

We analysed baseline data (1995-97) from the HUNT2 Study in Norway linked to the national Causes of Death Registry. We compared risk within couples using stratified Cox regression.

RESULTS

During 914776 person-years, 3964 cardiovascular deaths occurred, and 1658 of the deaths occurred among 1494 couples. There were consistently stronger associations of serum lipids and blood pressure with cardiovascular mortality within couples compared to the population as a whole. For instance, for systolic blood pressure (per 20mmHg), the hazard ratio (HR) within couples was 1.28 (95% confidence interval: 1.17, 1.40) compared to 1.16 (1.12, 1.20) in the total population, and for diastolic pressure (per 10mmHg), the corresponding HRs were 1.16 (1.07, 1.26) and 1.11 (1.08, 1.13). Anthropometric factors (BMI, waist circumference, waist-hip ratio) as well as diabetes, smoking, physical activity, and education, showed nearly identical positive associations within couples and in the total population.

CONCLUSIONS

Prospective population studies may tend to slightly underestimate associations of these factors with cardiovascular mortality.

Genomic Variant in IL-37 Confers A Significant Risk of Coronary Artery Disease

The interleukin 1 family plays an important role in the immune and inflammatory responses. Coronary artery disease (CAD) is a chronic inflammatory disease. However, the genetic association between IL-37, the seventh member of the IL-1 family, and CAD is unknown. Here we show that a single nucleotide polymorphism in the IL-37 gene (rs3811047) confers a significant risk of CAD. We have performed an association analysis between rs3811047 and CAD in two independent populations with 2,501 patients and 3,116 controls from China. Quantitative RT-PCR analysis has been performed to determine if the IL-37 expression level is influenced by rs3811047. We show that the minor allele A of rs3811047 is significantly associated with CAD in two independent populations under a recessive model (P_adj = 5.51 × 10^-3/OR = 1.56 in the GeneID Northernern population and P_adj = 1.23 × 10^-3/OR = 1.45 in the GeneID Central population). The association became more significant in the combined population (P_adj = 9.70 × 10^-6/OR = 1.47). Moreover, the association remains significant in a CAD case control population matched for age and sex. Allele A of rs3811047 shows significant association with a decreased mRNA expression level of IL-37 (n = 168, P = 3.78 × 10^-4). These data suggest that IL37 is a new susceptibility gene for CAD, which provides a potential target for the prevention and treatment of CAD.

Association of the FADS gene cluster with coronary artery disease and plasma lipid concentrations in the northern Chinese Han population

We investigated the association of single nucleotide polymorphisms (SNPs) in the fatty acid desaturase (FADS) gene cluster with coronary artery disease (CAD) in a case-control study and evaluated the possible influence of genetic variation on total cholesterol (TC) and triglyceride concentrations in the controls. In total, 497 CAD patients and 495 unrelated controls were genotyped for eight SNPs in the FADS gene cluster, and the blood lipid levels of subjects were measured. Three genetic models, including codominant, dominant and recessive, were used to analyze the genotypic relationship with CAD and plasma lipid levels. Single locus genotypic analysis revealed that rs1000778 in FADS3 under a recessive model (AA vs. GG-GA) was significantly associated with CAD adjusted for risk factors. The rs1000778 minor allele AA was associated with a lower risk of CAD (OR =0.37, 95% CI: 0.15-0.89, P=0.025). In the control group, there were significant differences in TC concentrations under a recessive genetic model for rs174575 (C/G) in FADS2 and for rs174450 (A/C) and rs7115739 (G/T) in FADS3 (P=0.053, 0.016 and 0.018, respectively). The rs1000778-G variant in FADS3 may contribute to the susceptibility of CAD, but the result needs to be further confirmed because of small sample size in our study. Genetic variations in FADS2 and FADS3 influence TC concentration in the northern Chinese Han population.

MicroRNAs in Coronary Heart Disease: Ready to Enter the Clinical Arena?

Coronary artery disease (CAD) and its complication remain the leading cause of mortality in industrialized countries despite great advances in terms of diagnosis, prognosis, and treatment options. MicroRNAs (miRNAs), small noncoding RNAs, act as posttranscriptional gene expression modulators and have been implicated as key regulators in several physiological and pathological processes linked to CAD. Circulating miRNAs have been evaluated as promising novel biomarkers of CAD, acute coronary syndromes, and acute myocardial infarction, with prognostic implications. Several challenges related to technical aspects, miRNAs normalization, drugs interaction, and quality reporting of statistical multivariable analysis of the miRNAs observational studies remain unresolved. MicroRNA-based therapies in cardiovascular diseases are not ready yet for human trials but definitely appealing. Through this review we will provide clinicians with a concise overview of the pros and cons of microRNAs.

Utility of genetic and non-genetic risk factors in predicting coronary heart disease in Singaporean Chinese

Background Although numerous phenotype based equations for predicting risk of 'hard' coronary heart disease are available, data on the utility of genetic information for such risk prediction is lacking in Chinese populations. Design Case-control study nested within the Singapore Chinese Health Study. Methods A total of 1306 subjects comprising 836 men (267 incident cases and 569 controls) and 470 women (128 incident cases and 342 controls) were included. A Genetic Risk Score comprising 156 single nucleotide polymorphisms that have been robustly associated with coronary heart disease or its risk factors ( p < 5 × 10^-8) in at least two independent cohorts of genome-wide association studies was built. For each gender, three base models were used: recalibrated Adult Treatment Panel III (ATPIII) Model (M₁); ATP III model fitted using Singapore Chinese Health Study data (M₂) and M₃: M₂ + C-reactive protein + creatinine. Results The Genetic Risk Score was significantly associated with incident 'hard' coronary heart disease ( p for men: 1.70 × 10^-10-1.73 × 10^-9; p for women: 0.001). The inclusion of the Genetic Risk Score in the prediction models improved discrimination in both genders (c-statistics: 0.706-0.722 vs. 0.663-0.695 from base models for men; 0.788-0.790 vs. 0.765-0.773 for women). In addition, the inclusion of the Genetic Risk Score also improved risk classification with a net gain of cases being reclassified to higher risk categories (men: 12.4%-16.5%; women: 10.2% (M₃)), while not significantly reducing the classification accuracy in controls. Conclusions The Genetic Risk Score is an independent predictor for incident 'hard' coronary heart disease in our ethnic Chinese population. Inclusion of genetic factors into coronary heart disease prediction models could significantly improve risk prediction performance.

c.*84G>A Mutation in CETP Is Associated with Coronary Artery Disease in South Indians

BACKGROUND

Coronary artery disease (CAD) is one of the leading causes of mortality worldwide. It is a multi-factorial disease and several studies have demonstrated that the genetic factors play a major role in CAD. Although variations in cholesteryl ester transfer protein (CETP) gene are reported to be associated with CAD, this gene has not been studied in South Indian populations. Hence we evaluated the CETP gene variations in CAD patients of South Indian origin.

METHODS

We sequenced all the exons, exon-intron boundaries and UTRs of CETP in 323 CAD patients along with 300 ethnically and age matched controls. Variations observed in CETP were subjected to various statistical analyses.

RESULTS AND DISCUSSION

Our analysis revealed a total of 13 variations. Of these, one3'UTRvariant rs1801706 (c.*84G>A) was significantly associated with CAD (genotype association test: OR = 2.16, 95% CI: 1.50-3.10, p = 1.88x10-5 and allelic association test: OR = 1.92, 95% CI: 1.40-2.63, p = 2.57x10-5). Mutant allele "A" was observed to influence the higher concentration of mRNA (p = 7.09×10-3, R2 = 0.029 and β = 0.2163). Since expression of CETP has been shown to be positively correlated with the risk of CAD, higher frequency of "A" allele (patients: 22.69% vs.controls: 13%) reveals that c.*84G>A is a risk factor for CAD in South Indians.

CONCLUSIONS

This is the first report of the CETP gene among South Indians CAD patients. Our results suggest that rs1801706 (c.*84G>A) is a risk factor for CAD in South Indian population.

Association between intelligence and coronary heart disease mortality: a population-based cohort study of 682 361 Swedish men

Background

Socio-economic position and intelligence predict coronary heart disease but their mutual associations are not yet well understood. We investigated associations between intelligence and coronary heart disease mortality and explored if they are confounded or modified by socio-economic position.

Design

This was a cohort-based follow-up study.

Methods

Data on intelligence, systolic and diastolic blood pressures and body mass index were measured at conscription examination at age 18 years in 682 361 Swedish men born 1951-1965. Data on parental and own education and social position were derived from censuses in 1960, 1970, 1980 and 1990. Follow-up data up to end of 2001 were derived from the Swedish Cause of Death Register and 737 coronary heart disease deaths were observed. Data were analyzed by Cox regression and conditional logistic regression models.

Results

An inverse association was found between intelligence and coronary heart disease mortality after adjustment for parental and own education and social position, body mass index and blood pressure (hazard ratio 0.92; 95% confidence interval 0.88-0.96). These associations were of similar strengths within all socio-economic categories and also found within 215 brother pairs discordant for coronary heart disease mortality and intelligence (odds ratio 0.76; 95% confidence interval 0.58-1.00).

Conclusions

Intelligence is associated with coronary heart disease mortality independently of socio-economic position. Health education messages should be tailored according to intellectual performance of the recipients, but also other factors are important for socio-economic coronary heart disease inequalities.

Relationship of classical and non-classical risk factors with genetic variants relevant to coronary heart disease

BACKGROUND

In addition to the well established cardiovascular risk factors, evidence suggests a possible role of genetic and non-classical risk factors in the development and progression of atherothrombosis. We aimed to determine the relationship of classical and non-classical cardiovascular risk factors with candidate gene polymorphisms potentially involved in cardiovascular risk in the general Mediterranean population.

DESIGN

Cross-sectional study.

METHODS

We have determined the prevalence of classical (lipid profile, blood pressure, glycaemia, diabetes, smoking, body mass index, menopause and family history of coronary heart disease) and non-classical cardiovascular risk factors (infectious processes, homocysteinaemia, oxidative status, C-reactive protein, lipoprotein (a) and fibrinogen) in a population-based study. We analysed the relationship of these risk factors with the following five gene polymorphisms potentially involved in cardiovascular risk: ATP-binding cassette transporter A1-R219K, Peroxisome proliferator-activated receptor (PPAR)-alpha-L162V, Lipoprotein lipase (LPL)-HindIII, Paraoxonase (PON)1-Q192R, and Tumour necrosis factor (TNF)-alpha-G-308A.

RESULTS

We found PPAR-alpha-V and LPL-H alleles to be associated with decreased high-density lipoprotein-cholesterol (HDL-c) concentration and with increased total cholesterol : HDL-c and triglyceride : HDL-c ratios. Regarding the non-classical risk factors, C-reactive protein concentration was higher for the PPAR-alpha-V allele. A higher oxidative status was shown in homozygotes for LPL-H and TNF-alpha-G alleles, although the latter also had lower homocysteinaemia.

CONCLUSIONS

Three of the genetic variants analysed, PPAR-alpha-L162V, LPL-HindIII, and TNF-alpha-G-308A, were associated with non-classical risk factors, specifically lipid profile, inflammation, and oxidative status.

Cholesteryl ester transfer protein (CETP) I405V polymorphism and cardiovascular disease in eastern European Caucasians - a cross-sectional study

Background

The cholesteryl ester transfer protein (CETP) polymorphism I405V has been suggested to be involved in longevity and susceptibility to cardiovascular diseases. An enhanced reverse cholesterol transport due to enhanced HDL levels has been hypothesized to be the underlying mechanism. However, clinical trials with HDL-enhancing drugs failed to show beneficial effects. Consequently, it has been postulated that genetic variations enhancing HDL levels are cardioprotective only if they also decrease LDL levels.

Methods

A cross-sectional study was conducted to genotype 1028 healthy blood donors and 1517 clinically well characterized elderly for CETP I405V.

Results

We could not find any association of this polymorphism with age for both, males or females, in any of these cohorts (P = 0.71 and P = 0.57, respectively, for males and P = 0.55 and P = 0.88, respectively, for females). In addition, no association with cardiovascular diseases could be observed in the elderly cohort (males OR = 1.12 and females OR = 0.88). In the same cohort, the CETP V405V genotype was associated with significantly enhanced HDL levels (P = 0.03), mostly owing to the female sex (P = 0.46 for males, P = 0.02 for females), whereas LDL and triglyceride levels were unchanged (P = 0.62 and P = 0.18, respectively).

Conclusion

Our data support the recent hypothesis that variations enhancing HDL levels without affecting LDL levels are not associated with the risk for cardiovascular diseases.

Genetics of Coronary Artery Disease

Genetic factors contribute importantly to the risk of coronary artery disease (CAD), and in the past decade, there has been major progress in this area. The tools applied include genome-wide association studies encompassing >200,000 individuals complemented by bioinformatic approaches, including 1000 Genomes imputation, expression quantitative trait locus analyses, and interrogation of Encyclopedia of DNA Elements, Roadmap, and other data sets. close to 60 common SNPs (minor allele frequency>0.05) associated with CAD risk and reaching genome-wide significance (P<5 × 10(-8)) have been identified. Furthermore, a total of 202 independent signals in 109 loci have achieved a false discovery rate (q<0.05) and together explain 28% of the estimated heritability of CAD. These data have been used successfully to create genetic risk scores that can improve risk prediction beyond conventional risk factors and identify those individuals who will benefit most from statin therapy. Such information also has important applications in clinical medicine and drug discovery by using a Mendelian randomization approach to interrogate the causal nature of many factors found to associate with CAD risk in epidemiological studies. In contrast to genome-wide association studies, whole-exome sequencing has provided valuable information directly relevant to genes with known roles in plasma lipoprotein metabolism but has, thus far, failed to identify other rare coding variants linked to CAD. Overall, recent studies have led to a broader understanding of the genetic architecture of CAD and demonstrate that it largely derives from the cumulative effect of multiple common risk alleles individually of small effect size rather than rare variants with large effects on CAD risk. Despite this success, there has been limited progress in understanding the function of the novel loci; the majority of which are in noncoding regions of the genome.

Is Chronic Low Back Pain Associated with the Prevalence of Coronary Heart Disease when Genetic Susceptibility Is Considered? A Co-Twin Control Study of Spanish Twins

Objective

To investigate the chronic low back pain and coronary heart disease relationship, after adjusting for relevant confounders, including genetics.

Methods

In a cross-sectional design, 2148 twins were recruited from the Murcia Twin Registry, Spain. The exposure was chronic LBP and the outcomes were myocardial infarction and other coronary heart diseases—lifetime and in the last 2 years–based on standardized health-related questionnaires. First, logistic regression analysis investigated associations of the total sample followed by a matched co-twin control analyses, with all complete twin pairs discordant for chronic LBP utilised, separated for zygosity—dizygotic (DZ) and monozygotic (MZ) pairs, which adjusted for shared familial factors, including genetics.

Results

Chronic LBP pain is associated with lifetime myocardial infarction [odds ratio (OR) = 2.69, 95% confidence interval (CI) = 1.35–5.36], other coronary heart diseases over a lifetime (OR = 2.58, 95% CI: 1.69–3.93) and in the last two years (OR = 2.19, 95% CI: 1.33–3.60), while there was a borderline association with myocardial infarction in the last 2 years (OR = 2.64, 95% CI: 0.98–7.12). Although the magnitude of the association remained or increased in the co-twin control analyses, none reached statistical significance.

Conclusion

Chronic LBP is associated with a higher prevalence of myocardial infarction and coronary heart disease. It is possible that this association remains even when controlling for genetics and early shared environment, although this should be investigated with larger samples of twins discordant for LBP.