Large-scale gene-centric analysis identifies novel variants for coronary artery disease

Polygenic Risk Score Associates With Atherosclerotic Plaque Characteristics at Autopsy

BACKGROUND

Polygenic risk scores (PRSs) for coronary artery disease (CAD) potentially improve cardiovascular risk prediction. However, their relationship with histopathologic features of CAD has never been examined systematically.

METHODS

From 4327 subjects referred to CVPath by the State of Maryland Office Chief Medical Examiner for sudden death between 1994 and 2015, 2455 cases were randomly selected for genotyping. We generated PRS from 291 known CAD risk loci. Detailed histopathologic examination of the coronary arteries was performed in all subjects. The primary study outcome measurements were histopathologic plaque features determining severity of atherosclerosis, including %stenosis, calcification, thin-cap fibroatheromas, and thrombotic CAD.

RESULTS

After exclusion of cases with insufficient DNA sample quality or with missing data, 954 cases (mean age, 48.8±14.7 years; 75.7% men) remained in the final study cohort. Subjects in the highest PRS quintile exhibited more severe atherosclerosis compared with subjects in the lowest quintile, with greater %stenosis (80.3%±27.0% versus 50.4%±38.7%; adjusted P<0.001) and a higher frequency of calcification (69.6% versus 35.8%; adjusted P=0.004) and thin-cap fibroatheroma (26.7% versus 9.5%; adjusted P=0.007). Even after adjustment for traditional CAD risk factors, subjects within the highest PRS quintile had higher odds of severe atherosclerosis (ie, ≥75% stenosis; adjusted odds ratio, 3.77 [95% CI, 2.10-6.78]; P<0.001) and plaque rupture (adjusted odds ratio, 4.05 [95% CI, 2.26-7.24]; P<0.001). Moreover, subjects within the highest quintile had higher odds of CAD-associated cause of death, especially among those aged ≤50 years (adjusted odds ratio, 4.08 [95% CI, 2.01-8.30]; P<0.001). No statistically significant associations were observed with plaque erosion after adjusting for covariates.

CONCLUSIONS

This is the first autopsy study investigating associations between PRS and atherosclerosis severity at the histopathologic level in subjects with sudden death. Our pathological analysis suggests PRS correlates with plaque burden and features of advanced atherosclerosis and may be useful as a method for CAD risk stratification, especially in younger subjects.

Polygenic Risk Score Associates with Atherosclerotic Plaque Characteristics at Autopsy

Background

Polygenic risk scores (PRS) for coronary artery disease (CAD) potentially improve cardiovascular risk prediction. However, their relationship with histopathologic features of CAD has never been examined systematically.

Methods

From 4,327 subjects referred to CVPath by the State of Maryland Office Chief Medical Examiner (OCME) for sudden death between 1994 and 2015, 2,455 cases were randomly selected for genotyping. We generated PRS from 291 known CAD risk loci. Detailed histopathologic examination of the coronary arteries was performed in all subjects. The primary study outcome measurements were histopathologic plaque features determining severity of atherosclerosis, including %stenosis, calcification, thin-cap fibroatheromas (TCFA), and thrombotic CAD.

Results

After exclusion of cases with insufficient DNA sample quality or with missing data, 954 cases (mean age 48.8±14.7; 75.7% men) remained in the final study cohort. Subjects in the highest PRS quintile exhibited more severe atherosclerosis compared to subjects in the lowest quintile, with greater %stenosis (80.3%±27.0% vs. 50.4%±38.7%; adjusted p<0.001) and a higher frequency of calcification (69.6% vs. 35.8%; adjusted p=0.004) and TCFAs (26.7% vs. 9.5%; adjusted p=0.007). Even after adjustment for traditional CAD risk factors subjects within the highest PRS quintile had higher odds of severe atherosclerosis (i.e., ≥75% stenosis; adjusted OR 3.77; 95%CI 2.10-6.78; p<0.001) and plaque rupture (adjusted OR 4.05; 95%CI 2.26-7.24; p<0.001). Moreover, subjects within the highest quintile had higher odds of CAD-associated cause of death, especially among those aged 50 years and younger (adjusted OR 4.08; 95%CI 2.01-8.30; p<0.001). No associations were observed with plaque erosion.

Conclusions

This is the first autopsy study investigating associations between PRS and atherosclerosis severity at the histopathologic level in subjects with sudden death. Our pathological analysis suggests PRS correlates with plaque burden and features of advanced atherosclerosis and may be useful as a method for CAD risk stratification, especially in younger subjects.

Highlights

In this autopsy study including 954 subjects within the CVPath Sudden Death Registry, high PRS correlated with plaque burden and atherosclerosis severity.The PRS showed differential associations with plaque rupture and plaque erosion, suggesting different etiologies to these two causes of thrombotic CAD.PRS may be useful for risk stratification, particularly in the young. Further examination of individual risk loci and their association with plaque morphology may help understand molecular mechanisms of atherosclerosis, potentially revealing new therapy targets of CAD.

Graphic Abstract

A polygenic risk score, generated from 291 known CAD risk loci, was assessed in 954 subjects within the CVPath Sudden Death Registry. Histopathologic examination of the coronary arteries was performed in all subjects. Subjects in the highest PRS quintile exhibited more severe atherosclerosis as compared to subjects in the lowest quintile, with a greater plaque burden, more calcification, and a higher frequency of plaque rupture.

Plant Sterols and Plant Stanols in Cholesterol Management and Cardiovascular Prevention

Atherosclerotic cardiovascular disease (ASCVD) remains the major mortality cause in developed countries with hypercholesterolaemia being one of the primary modifiable causes. Lifestyle intervention constitutes the first step in cholesterol management and includes dietary modifications along with the use of functional foods and supplements. Functional foods enriched with plant sterols/stanols have become the most widely used nonprescription cholesterol-lowering approach, despite the lack of randomized trials investigating their long-term safety and cardiovascular efficacy. The cholesterol-lowering effect of plant-sterol supplementation is well-established and a potential beneficial impact on other lipoproteins and glucose homeostasis has been described. Nevertheless, experimental and human observational studies investigating the association of phytosterol supplementation or circulating plant sterols with various markers of atherosclerosis and ASCVD events have demonstrated controversial results. Compelling evidence from recent genetic studies have also linked elevated plasma concentrations of circulating plant sterols with ASCVD presence, thus raising concerns about the safety of phytosterol supplementation. Thus, the aim of this review is to provide up-to-date data on the effect of plant sterols/stanols on lipid-modification and cardiovascular outcomes, as well as to discuss any safety issues and practical concerns.

Genetic Analysis Reveals Different Mechanisms of IL-5 Involved in the Development of CAD in a Chinese Han Population

Background

Coronary artery disease (CAD) is a complex disease and the leading cause of death worldwide. It is caused by genetic and environmental factors or their interactions. Candidate gene association studies are an important genetic strategy for the study of complex diseases, and multiple variants of inflammatory cytokines have been found to be associated with CAD using this method. Interleukin-5 (IL-5) is an important inflammatory immune response factor that plays a role in a various inflammatory disease. Clinical tests and animal experiments indicated that IL-5 is involved in CAD development, but the exact mechanisms are unclear. This study investigated the genetic relationship between the single nucleotide polymorphisms (SNPs) in IL5 and CAD.

Materials and Methods

Based on the Chinese Han population, we collected 1,824 patients with CAD and 1,920 control subjects and performed a two-stage case-control association analysis for three SNPs in IL5 (rs2057687, rs78546665, and rs2069812) using the high resolution melt (HRM) technology. Logistic regression analyses were applied to adjust for traditional risk factors for CAD and to perform haplotype and gene interaction analyses. Multiple linear regression analyses were used to study relationships between the selected SNPs and serum lipid levels.

Results

In this study, two-stage case-control association analysis revealed that the allele and genotype frequency distributions of the three IL5 SNPs were not statistically significant between the case and control groups. In addition, none of the IL5 haplotypes were associated with CAD. Further stratified analyses were conducted by sex, age, hypertension, and disease status, respectively, and the results revealed that the rs2057687 and rs2069812 of IL5 were associated with CAD in the male group (p adj = 0.025, OR, 0.77 (95% CI, 0.62-0.97); p adj = 0.016, OR, 0.82 (95% CI, 0.70-0.97), respectively); the rs2057687 and rs78546665 of IL5 were associated with late-onset CAD (p adj = 0.039, OR, 0.78 (95% CI, 0.62-0.99); p adj = 0.036, OR, 1.46 (95% CI, 1.02-1.53), respectively); the rs2069812 of IL5 was associated with CAD in the hypertension group (p adj = 0.036, OR, 0.84 (95% CI, 0.71-0.99)); and none of the SNPs in IL5 were associated with different CAD states (anatomical CAD and clinical CAD). In addition, the association between SNPs and the serum lipid levels indicated that rs78546665 was positively correlated with triglyceride levels (p = 0.012). Finally, SNP-SNP interaction analyses revealed that interactions of rs2057687 and rs2069812 were associated with CAD (p adj = 0.046, OR, 0.77 (95% CI, 0.13-4.68)).

Conclusion

This study suggested that the common variants of IL5 might play a role in CAD by affecting the risk factors for CAD and through SNP-SNP interactions, which provides a new target for specific treatment of CAD patients and a theoretical basis for personalized medicine.

Effect of TRIB1 Variant on Lipid Profile and Coronary Artery Disease: A Systematic Review and Meta-Analysis

Background

Emerging evidence indicates tribbles homolog 1 (Trib1) protein may be involved in lipid metabolism regulation and coronary artery disease (CAD) pathogenesis. However, whether TRIB1 gene variants affect lipid levels and CAD remains elusive, this study is aimed at clarifying the effect of TRIB1 variants on lipid profile and CAD.

Methods

By searching PubMed and Cochrane databases for studies published before December 18, 2022, a total of 108,831 individuals were included for the analysis.

Results

The outcomes of the analysis on all individuals showed that the A allele carriers of rs17321515 and rs2954029 variants had higher low-density lipoprotein cholesterol (LDL-C) and total cholesterol (TC) levels than the noncarriers. Consistently, a higher CAD risk was observed in the A allele carriers. Subgroup analysis indicated that increased LDL-C, TC, and CAD risk were observed in Asian population.

Conclusions

Variants of TRIB1 (i.e., rs17321515 and rs2954029) may serve as causal genetic markers for dyslipidemia and CAD in Asian population.

The role of long non-coding RNA ANRIL in the development of atherosclerosis

Atherosclerosis is an important pathological basis of coronary heart disease, and the antisense non-coding RNA in the INK4 locus (ANRIL) is located in the genetically susceptible segment with the strongest correlation with it - the short arm 2 region 1 of chromosome 9 (Chr9p21). ANRIL can produce linear, circular and other transcripts through different transcriptional splicing methods, which can regulate the proliferation and apoptosis of related cells and closely related to the development of atherosclerotic plaques. Linear ANRIL can regulate proliferation of vascular smooth muscle cells (VSMCs) in plaques by chromatin modification, as well as affecting on proliferation and the apoptosis of macrophages at the transcriptional level; circular ANRIL can affect on proliferation and apoptosis of VSMCs by chromatin modification as well as interfering with rRNA maturation. In this review we describe the evolutionary characteristics of ANRIL, the formation and structure of transcripts, and the mechanism by which each transcript regulates the proliferation and apoptosis of vascular cells and then participates in atherosclerosis.

The Role of Certain Polymorphic Variants in Genes, Previously Associated with Blood Pressure Values, with Reference to the Risk of Development of Coronary Artery Disease

The aim of the study was to analyze the effect of polymorphic variants previously associated with arterial hypertension (AH) in Genome Wide Association Studies (GWASs) in/next to genes and locuses CYP7A1 and PLEKHA7 on the development of coronary artery disease (CAD) in Bulgarian patients. A hundred and nine consecutive patients with angiographically documented CAD were studied. The genotyping was done with 7900 HT Fast Real-Time PCR (Applied Biosystems) with TaqMan® method. The control group consisted of 192 healthy population controls, selected from the bio- bank of the Molecular Medicine Center. SPSS and PLINK were used for the statistical analysis with level of significance < 0.05 and confidence interval 95%. The mean age of the studied patients was 63.71 ± 9.35 years; 35 (35%) females. Previous myocardial infarction (MI) had 38(38%); one-vessel – 39 (39%); two-vessel – 28 (28%); three-vessel disease – 34 (34%); 43 (43%) were with diabetes mellitus; 92 (92%) – with arterial hypertension (AH); 77 (77%) – with dyslipidemia; 42 (42%) were smokers; 25 (25%) were obese. We did not find any significant association between CAD and poly- morphism rs11191548 near CYP17A1 and only a tendency for genotype of rs381815 in PLEKHA7 (p = 0.06; OR 0.64; CI 0.40-1.02 for CAD) under dominant model. This is of practical importance both for studying the genetic aspects of CAD in the future and for enlargement of the current database.

Validation of Polygenic Risk Scores for Coronary Heart Disease in a Middle Eastern Cohort Using Whole Genome Sequencing

BACKGROUND

Enthusiasm for using polygenic risk scores (PRSs) in clinical practice is tempered by concerns about their portability to diverse ancestry groups, thus motivating genome-wide association studies in non-European ancestry cohorts.

METHODS

We conducted a genome-wide association study for coronary heart disease in a Middle Eastern cohort using whole genome sequencing and assessed the performance of 6 PRSs developed with methods including LDpred (PGS000296), metaGRS (PGS000018), Pruning and Thresholding (PGS000337), and an EnsemblePRS we developed. Additionally, we evaluated the burden of rare variants in lipid genes in cases and controls. Whole genome sequencing at 30× coverage was performed in 1067 coronary heart disease cases (mean age=59 years; 70.3% males) and 6170 controls (mean age=40 years; 43.5% males).

RESULTS

The majority of PRSs performed well; odds ratio (OR) per 1 SD increase (OR1sd) was highest for PGS000337 (OR1sd=1.81, 95% CI [1.66-1.98], P=3.07×10-41). EnsemblePRS performed better than individual PRSs (OR1sd=1.8, 95% CI [1.66-1.96], P=5.89×10-44). The OR for the 10th decile versus the remaining deciles was >3.2 for PGS000337, PGS000296, PGS000018, and reached 4.58 for EnsemblePRS. Of 400 known genome-wide significant loci, 33 replicated at P<10-4. However, the 9p21 locus did not replicate. Six suggestive (P<10-5) new loci/genes with plausible biological function were identified (eg, CORO7, RBM47, PDE4D). The burden of rare functional variants in LDLR, APOB, PCSK9, and ANGPTL4 was greater in cases than controls.

CONCLUSIONS

Overall, we demonstrate that PRSs derived from European ancestry genome-wide association studies performed well in a Middle Eastern cohort, suggesting these could be used in the clinical setting while ancestry-specific PRSs are developed.

Lysosomal acid lipase deficiency: A rare inherited dyslipidemia but potential ubiquitous factor in the development of atherosclerosis and fatty liver disease

Lysosomal acid lipase (LAL), encoded by the gene LIPA, is the sole neutral lipid hydrolase in lysosomes, responsible for cleavage of cholesteryl esters and triglycerides into their component parts. Inherited forms of complete (Wolman Disease, WD) or partial LAL deficiency (cholesteryl ester storage disease, CESD) are fortunately rare. Recently, LAL has been identified as a cardiovascular risk gene in genome-wide association studies, though the directionality of risk conferred remains controversial. It has also been proposed that the low expression and activity of LAL in arterial smooth muscle cells (SMCs) that occurs inherently in nature is a likely determinant of the propensity of SMCs to form the majority of foam cells in atherosclerotic plaque. LAL also likely plays a potential role in fatty liver disease. This review highlights the nature of LAL gene mutations in WD and CESD, the association of LAL with prediction of cardiovascular risk from genome-wide association studies, the importance of relative LAL deficiency in SMC foam cells, and the need to further interrogate the pathophysiological impact and cell type-specific role of enhancing LAL activity as a novel treatment strategy to reduce the development and induce the regression of ischemic cardiovascular disease and fatty liver.

The genetic interactions between non-alcoholic fatty liver disease and cardiovascular diseases

The ongoing debate on whether non-alcoholic fatty liver disease (NAFLD) is an active contributor or an innocent bystander in the development of cardiovascular disease (CVD) has sparked interests in understanding the common mediators between the two biologically distinct entities. This comprehensive review identifies and curates genetic studies of NAFLD overlapping with CVD, and describes the colinear as well as opposing correlations between genetic associations for the two diseases. Here, CVD described in relation to NAFLD are coronary artery disease, cardiomyopathy and atrial fibrillation. Unique findings of this review included certain NAFLD susceptibility genes that possessed cardioprotective properties. Moreover, the complex interactions of genetic and environmental risk factors shed light on the disparity in genetic influence on NAFLD and its incident CVD. This serves to unravel NAFLD-mediated pathways in order to reduce CVD events, and helps identify targeted treatment strategies, develop polygenic risk scores to improve risk prediction and personalise disease prevention.

Etiologic Puzzle of Coronary Artery Disease: How Important Is Genetic Component?

In the modern era, coronary artery disease (CAD) has become the most common form of heart disease and, due to the severity of its clinical manifestations and its acute complications, is a major cause of morbidity and mortality worldwide. The phenotypic variability of CAD is correlated with the complex etiology, multifactorial (caused by the interaction of genetic and environmental factors) but also monogenic. The purpose of this review is to present the genetic factors involved in the etiology of CAD and their relationship to the pathogenic mechanisms of the disease. Method: we analyzed data from the literature, starting with candidate gene-based association studies, then continuing with extensive association studies such as Genome-Wide Association Studies (GWAS) and Whole Exome Sequencing (WES). The results of these studies revealed that the number of genetic factors involved in CAD etiology is impressive. The identification of new genetic factors through GWASs offers new perspectives on understanding the complex pathophysiological mechanisms that determine CAD. In conclusion, deciphering the genetic architecture of CAD by extended genomic analysis (GWAS/WES) will establish new therapeutic targets and lead to the development of new treatments. The identification of individuals at high risk for CAD using polygenic risk scores (PRS) will allow early prophylactic measures and personalized therapy to improve their prognosis.

Genetic Regulatory Networks of Apolipoproteins and Associated Medical Risks

Apolipoproteins (APO proteins) are the lipoprotein family proteins that play key roles in transporting lipoproteins all over the body. There are nearly more than twenty members reported in the APO protein family, among which the A, B, C, E, and L play major roles in contributing genetic risks to several disorders. Among these genetic risks, the single nucleotide polymorphisms (SNPs), involving the variation of single nucleotide base pairs, and their contributing polymorphisms play crucial roles in the apolipoprotein family and its concordant disease heterogeneity that have predominantly recurred through the years. In this review, we have contributed a handful of information on such genetic polymorphisms that include APOE, ApoA1/B ratio, and A1/C3/A4/A5 gene cluster-based population genetic studies carried throughout the world, to elaborately discuss the effects of various genetic polymorphisms in imparting various medical conditions, such as obesity, cardiovascular, stroke, Alzheimer's disease, diabetes, vascular complications, and other associated risks.

Association of rs2954029 and rs6982502 Variants with Coronary Artery Disease by HRM Technique: A GWAS Replication Study in an Iranian Population

BACKGROUND

Genome-wide association studies (GWAS) have been the primary tool for an unbiased study of the genetic background of coronary artery disease (CAD). They have identified a list of single-nucleotide polymorphisms (SNPs) associated with coronary artery disease (CAD). In this study, we aimed to replicate the association of rs2954029 and rs6982502, a GWAS identified SNP, to CAD in an Iranian population.

METHODS

A sample of 285 subjects undergoing coronary angiography, including 134 CAD patients and 151 healthy. The genotype determination of rs2954029 and rs6982502 SNPs performed using the high-resolution melting analysis (HRM) technique.

RESULTS

Our results revealed that the TT genotype of rs2954029 (p= 0.009) and rs6982502 (p< 0.001) were significantly higher in CAD patients compared with controls. Binary logistic regression showed that rs6982502 and rs2954029 increase the risk of CAD incidence (2.470 times, p= 0.011, 95% CI= [1.219-4.751], and 2.174 times, p= 0.033, 95% CI= [1.066-4.433] respectively). After adjusting for confounders, we found that rs6982502 and rs2954029 are significantly associated with CAD risk.

CONCLUSION

These data showed that the TT genotype of rs2954029 and rs6982502 is associated with the risk of CAD in a hospital-based sample of the Iranian population, which has replicated the result of recent GWAS studies.

Cohort profile: Copenhagen Hospital Biobank - Cardiovascular Disease Cohort (CHB-CVDC): Construction of a large-scale genetic cohort to facilitate a better understanding of heart diseases

PURPOSE

The aim of Copenhagen Hospital Biobank-Cardiovascular Disease Cohort (CHB-CVDC) is to establish a cohort that can accelerate our understanding of CVD initiation and progression by jointly studying genetics, diagnoses, treatments and risk factors.

PARTICIPANTS

The CHB-CVDC is a large genomic cohort of patients with CVD. CHB-CVDC currently includes 96 308 patients. The cohort is part of CHB initiated in 2009 in the Capital Region of Denmark. CHB is continuously growing with ~40 000 samples/year. Patients in CHB were included in CHB-CVDC if they were above 18 years of age and assigned at least one cardiovascular diagnosis. Additionally, up-to 110 000 blood donors can be analysed jointly with CHB-CVDC. Linkage with the Danish National Health Registries, Electronic Patient Records, and Clinical Quality Databases allow up-to 41 years of medical history. All individuals are genotyped using the Infinium Global Screening Array from Illumina and imputed using a reference panel consisting of whole-genome sequence data from 8429 Danes along with 7146 samples from North-Western Europe. Currently, 39 539 of the patients are deceased.

FINDINGS TO DATE

Here, we demonstrate the utility of the cohort by showing concordant effects between known variants and selected CVDs, that is, >93% concordance for coronary artery disease, atrial fibrillation, heart failure and cholesterol measurements and 85% concordance for hypertension. Furthermore, we evaluated multiple study designs and the validity of using Danish blood donors as part of CHB-CVDC. Lastly, CHB-CVDC has already made major contributions to studies of sick sinus syndrome and the role of phytosterols in development of atherosclerosis.

FUTURE PLANS

In addition to genetics, electronic patient records, national socioeconomic and health registries extensively characterise each patient in CHB-CVDC and provides a promising framework for improved understanding of risk and protective variants. We aim to include other measurable biomarkers for example, proteins in CHB-CVDC making it a platform for multiomics cardiovascular studies.

Phytosterol accumulation results in ventricular arrhythmia, impaired cardiac function and death in mice

Heart failure (HF) and cardiac arrhythmias share overlapping pathological mechanisms that act cooperatively to accelerate disease pathogenesis. Cardiac fibrosis is associated with both pathological conditions. Our previous work identified a link between phytosterol accumulation and cardiac injury in a mouse model of phytosterolemia, a rare disorder characterized by elevated circulating phytosterols and increased cardiovascular disease risk. Here, we uncover a previously unknown pathological link between phytosterols and cardiac arrhythmias in the same animal model. Phytosterolemia resulted in inflammatory pathway induction, premature ventricular contractions (PVC) and ventricular tachycardia (VT). Blockade of phytosterol absorption either by therapeutic inhibition or by genetic inactivation of NPC1L1 prevented the induction of inflammation and arrhythmogenesis. Inhibition of phytosterol absorption reduced inflammation and cardiac fibrosis, improved cardiac function, reduced the incidence of arrhythmias and increased survival in a mouse model of phytosterolemia. Collectively, this work identified a pathological mechanism whereby elevated phytosterols result in inflammation and cardiac fibrosis leading to impaired cardiac function, arrhythmias and sudden death. These comorbidities provide insight into the underlying pathophysiological mechanism for phytosterolemia-associated risk of sudden cardiac death.

Coronary Artery Disease Genetics Enlightened by Genome-Wide Association Studies

Many cardiovascular diseases are facilitated by strong inheritance. For example, large-scale genetic studies identified hundreds of genomic loci that affect the risk of coronary artery disease. At each of these loci, common variants are associated with disease risk with robust statistical evidence but individually small effect sizes. Only a minority of candidate genes found at these loci are involved in the pathophysiology of traditional risk factors, but experimental research is making progress in identifying novel, and, in part, unexpected mechanisms. Targets identified by genome-wide association studies have already led to the development of novel treatments, specifically in lipid metabolism. This review summarizes recent genetic and experimental findings in this field. In addition, the development and possible clinical usefulness of polygenic risk scores in risk prediction and individualization of treatment, particularly in lipid metabolism, are discussed.

Coronary Artery Disease: Association Study of 5 Loci with Angiographic Indices of Disease Severity

Background

Different common gene variants were related to coronary artery disease (CAD) in many studies. Yet, the relation of these loci to the severity of CAD is not completely elucidated.

Methods

We enrolled 520 subjects (315 CAD cases and 205 controls). CAD presence and extension were assessed by coronary angiography (CAG). Genotyping of five SNPs (namely, rs2230806 (1051G > A) in ABCA1 on chromosome 9, rs2075291 (553G > T) in ApoA5 on chromosome 11, rs320 in LPL on chromosome 8 intron (T → G at position 481), rs10757278 (c.22114477A > G), and rs2383206 (c.22115026 A > G) on chromosome 9p21 locus) was performed by allele-specific PCR. The degree and site of arterial lesions were used to classify patients, tested for association with CAD severity, and related to allele dosage.

Results

The polymorphisms rs2383206 and rs10757278 showed significant associations with 2- and 3-vessel coronary disease (p =0.003 and 0.006, respectively). The homozygous GG genotypes of rs10757278 was associated with higher frequency of left anterior descending (LAD), right coronary artery (RCA) and left circumflex (LCX) diseases (p =0.002, 0.016 and 0.002, respectively). The GG genotypes of rs2383206 were found in higher percentage in patients with left main (LM) trunk and left circumflex (LCX) diseases (p = 0.013 and 0.002, respectively).

Conclusion

SNPs rs10757278 and rs2383206 allele dosage could predict CAD severity in the Saudi Arab population.

Effect of Differences in the Microbiome of Cyp17a1-Deficient Mice on Atherosclerotic Background

CYP17A1 is a cytochrome P450 enzyme that has 17-alpha-hydroxylase and C17,20-lyase activities. Cyp17a11 deficiency is associated with high body mass and visceral fat deposition in atherosclerotic female ApoE knockout (KO, d/d or -/-) mice. In the present study, we aimed to investigate the effects of diet and Cyp17a1 genotype on the gut microbiome. Female Cyp17a1 (d/d) × ApoE (d/d) (DKO) and ApoE (d/d) (controls) were fed either standard chow or a Western-type diet (WTD), and we demonstrated the effects of genetics and diet on the body mass of the mice and composition of their gut microbiome. We found a significantly lower alpha diversity after accounting for the ecological network structure in DKO mice and WTD-fed mice compared with chow-fed ApoE(d/d). Furthermore, we found a strong significant positive association of the Firmicutes vs. Bacteroidota ratio with body mass and the circulating total cholesterol and triglyceride concentrations of the mice when feeding the WTD, independent of the Cyp17a1 genotype. Further pathway enrichment and network analyses revealed a substantial effect of Cyp17a1 genotype on associated cardiovascular and obesity-related pathways involving aspartate and L-arginine. Future studies are required to validate these findings and further investigate the role of aspartate/L-arginine pathways in the obesity and body fat distribution in our mouse model.

Inflammation-Related Risk Loci in Genome-Wide Association Studies of Coronary Artery Disease

Although the importance of inflammation in atherosclerosis is now well established, the exact molecular processes linking inflammation to the development and course of the disease are not sufficiently understood. In this context, modern genetics—as applied by genome-wide association studies (GWAS)—can serve as a comprehensive and unbiased tool for the screening of potentially involved pathways. Indeed, a considerable proportion of loci discovered by GWAS is assumed to affect inflammatory processes. Despite many well-replicated association findings, however, translating genomic hits to specific molecular mechanisms remains challenging. This review provides an overview of the currently most relevant inflammation-related GWAS findings in coronary artery disease and explores their potential clinical perspectives.

Dynamic effects of genetic variation on gene expression revealed following hypoxic stress in cardiomyocytes

One life-threatening outcome of cardiovascular disease is myocardial infarction, where cardiomyocytes are deprived of oxygen. To study inter-individual differences in response to hypoxia, we established an in vitro model of induced pluripotent stem cell-derived cardiomyocytes from 15 individuals. We measured gene expression levels, chromatin accessibility, and methylation levels in four culturing conditions that correspond to normoxia, hypoxia, and short- or long-term re-oxygenation. We characterized thousands of gene regulatory changes as the cells transition between conditions. Using available genotypes, we identified 1,573 genes with a cis expression quantitative locus (eQTL) in at least one condition, as well as 367 dynamic eQTLs, which are classified as eQTLs in at least one, but not in all conditions. A subset of genes with dynamic eQTLs is associated with complex traits and disease. Our data demonstrate how dynamic genetic effects on gene expression, which are likely relevant for disease, can be uncovered under stress.

A fast and efficient colocalization algorithm for identifying shared genetic risk factors across multiple traits

Genome-wide association studies (GWAS) have identified thousands of genomic regions affecting complex diseases. The next challenge is to elucidate the causal genes and mechanisms involved. One approach is to use statistical colocalization to assess shared genetic aetiology across multiple related traits (e.g. molecular traits, metabolic pathways and complex diseases) to identify causal pathways, prioritize causal variants and evaluate pleiotropy. We propose HyPrColoc (Hypothesis Prioritisation for multi-trait Colocalization), an efficient deterministic Bayesian algorithm using GWAS summary statistics that can detect colocalization across vast numbers of traits simultaneously (e.g. 100 traits can be jointly analysed in around 1 s). We perform a genome-wide multi-trait colocalization analysis of coronary heart disease (CHD) and fourteen related traits, identifying 43 regions in which CHD colocalized with ≥1 trait, including 5 previously unknown CHD loci. Across the 43 loci, we further integrate gene and protein expression quantitative trait loci to identify candidate causal genes.

Exploration of CYP21A2 and CYP17A1 polymorphisms and preeclampsia risk among Chinese Han population: a large-scale case-control study based on 5021 subjects

BACKGROUND

Several genome-wide association studies have identified single-nucleotide polymorphisms (SNPs), such as rs4409766, rs1004467, and rs3824755 in CYP17A1 and rs2021783 in CYP21A2, as new hypertension susceptibility genetic variants in the Chinese population. This study aimed to look into the relationship between preeclampsia (PE) and these SNPs in Chinese Han women.

METHODS

Overall, 5021 unrelated pregnant women were recruited, including 2002 patients with PE and 3019 normal healthy controls. The real-time PCR (TaqMan) method was applied to genotype these four polymorphisms.

RESULTS

A statistically obvious difference in the allelic frequencies was observed in CYP21A2 rs2021783 between cases and controls (χ2 = 7.201, Pc = 0.028 by allele), and the T allele was associated with the occurrence and development of PE (OR = 1.151, 95% CI 1.039-1.275). We also found a significant association between rs2021783 and the development of early-onset PE (Pc = 0.008 by genotype, Pc = 0.004 by allele). For rs1004467 and rs3824755, the distribution of allelic frequencies differed markedly between mild PE and control groups (χ2 = 6.843, Pc = 0.036; χ2 = 6.869, Pc = 0.036), and patients with the TT genotype of rs1004467 were less easy to develop mild PE than were those carrying the CT or CC genotype (χ2 = 7.002, Pc = 0.032, OR = 1.306, 95% CI 1.071-1.593). The GG genotype of rs3824755 appeared to a protective effect on the occurrence of mild PE (OR = 0.766, 95% CI 0.629-0.934).

CONCLUSIONS

CYP21A2 rs2021783 appears to be closely related to PE susceptibility, and CYP17A1 rs1004467 and rs3824755 seem to be closely associated with mild PE in Han women.

Application of Genome-Wide Association Studies in Coronary Artery Disease

Coronary artery disease (CAD) is a complex disease caused by the combination of environmental and genetic factors. It is one of the leading causes of death and disability in the world. Much research has been focussed on CAD genetic mechanism. In recent years, genome-wide association study (GWAS) has developed rapidly around the world. Medical researchers around the world have successfully discovered a series of CAD genetic susceptibility genes or susceptible loci using medical research strategies, leading CAD research toward a new stage. This paper briefly summarizes the important progress made by GWAS for CAD in the world in recent years, and then analyzes the challenges faced by GWAS at this stage and the development trend of future research, to promote the transformation of genetic research results into clinical practice and provide guidance for further exploration of the genetic mechanism of CAD.

CYP17A1 Polymorphisms Are Linked to the Risk of Coronary Heart Disease in a Case-Control Study

BACKGROUND

Cytochrome P450 17A1 (CYP17A1) catalyzes the formation and metabolism of steroid hormones and is required for cortisol and androgens. There is increasing evidence that CYP17A1 plays an important role in the development of coronary heart disease (CHD). However, the association of CYP17A1 polymorphisms and CHD susceptibility is still not clear.

METHODS

We conducted a case-control study with 396 CHD cases and 461 healthy controls from Hainan province, China. Using the Agena MassARRAY platform, we genotyped 4 genetic variants (rs3740397, rs1004467, rs4919687, and rs3781286) in CYP17A1. Logistic regression analysis was used to assess the association of CYP17A1 polymorphisms with CHD risk by odds ratios (ORs) and 95% confidence intervals (CIs).

RESULTS

It showed that A allele of CYP17A1 rs4919687 carried with a 1.59-fold increased risk of CHD (OR = 1.59; 95% CI = 1.26-1.99; P < 0.001). Also, rs4919687 was significantly associated with CHD risk under various models (homozygote: OR = 3.60; 95% CI = 1.64-7.83; P = 0.001; dominant: OR = 1.51; 95% CI = 1.06-2.13; P = 0.021; recessive: OR = 3.28; 95% CI = 1.51-7.14; P = 0.003; additive: OR = 1.56; 95% CI = 1.17-2.07; P = 0.002). Moreover, analysis showed that Ars1004467 Ars4919687 haplotype was a protective factor of CHD (OR = 0.64; 95% CI = 0.48-0.86; P = 0.002).

CONCLUSIONS

Our study suggests that CYP17A1 polymorphisms are associated with CHD susceptibility in the Hainan Han Chinese population.

CYP17A1 deficient XY mice display susceptibility to atherosclerosis, altered lipidomic profile and atypical sex development

CYP17A1 is a cytochrome P450 enzyme with 17-alpha-hydroxylase and C17,20-lyase activities. CYP17A1 genetic variants are associated with coronary artery disease, myocardial infarction and visceral and subcutaneous fat distribution; however, the underlying pathological mechanisms remain unknown. We aimed to investigate the function of CYP17A1 and its impact on atherosclerosis in mice. At 4–6 months, CYP17A1-deficient mice were viable, with a KO:Het:WT ratio approximating the expected Mendelian ratio of 1:2:1. All Cyp17a1 knockout (KO) mice were phenotypically female; however, 58% were Y chromosome-positive, resembling the phenotype of human CYP17A1 deficiency, leading to 46,XY differences/disorders of sex development (DSD). Both male and female homozygous KO mice were infertile, due to abnormal genital organs. Plasma steroid analyses revealed a complete lack of testosterone in XY-KO mice and marked accumulation of progesterone in XX-KO mice. Elevated corticosterone levels were observed in both XY and XX KO mice. In addition, Cyp17a1 heterozygous mice were also backcrossed onto an Apoe KO atherogenic background and fed a western-type diet (WTD) to study the effects of CYP17A1 on atherosclerosis. Cyp17a1 x Apoe double KO XY mice developed more atherosclerotic lesions than Apoe KO male controls, regardless of diet (standard or WTD). Increased atherosclerosis in CYP17A1 XY KO mice lacking testosterone was associated with altered lipid profiles. In mice, CYP17A1 deficiency interferes with sex differentiation. Our data also demonstrate its key role in lipidomic profile, and as a risk factor in the pathogenesis of atherosclerosis.

[Research advance of ANRIL on atherosclerosis by regulating cell proliferation and apoptosis]

Atherosclerosis is an important pathological basis for coronary artery disease. ANRIL is an antisense non-coding RNA located in Chr9p21 locus, which was identified as the most significant risk locus associated with atherosclerosis. ANRIL can produce multiple transcripts including linear and circular transcripts after various transcript splicing. It has been illustrated that ANRIL plays important roles in the pathology of atherosclerosis by regulating the proliferation and apoptosis of vascular cells. Linear ANRIL can regulate the proliferation of vascular smooth muscle cells (VSMCs) in plaques by chromatin modification, as well as influence the proliferation and the apoptosis of macrophages in post transcription; circular ANRIL can affect the proliferation and apoptosis of VSMCs by chromatin modification as well as interfering with rRNA maturation. In this review, we describe the ANRIL evolution, different transcripts characteristics, and their roles in the proliferation and apoptosis of vascular cells to participate in the process of atherosclerosis, for further understanding the pathogenesis of atherosclerosis and finding potential targets for diagnosis and treatment of atherosclerosis.

Lysosomal Acid Lipase in Lipid Metabolism and Beyond

Lysosomal acid lipase (LAL), encoded by the lipase A ( LIPA) gene, hydrolyzes cholesteryl esters and triglycerides to generate free fatty acids and cholesterol in the cell. The essential role of LAL in lipid metabolism has been confirmed in mice and human with LAL deficiency. In humans, loss-of-function mutations of LIPA cause rare lysosomal disorders, Wolman disease and cholesteryl ester storage disease, in which LAL enzyme-replacement therapy has shown significant benefits in a phase 3 clinical trial. Recent studies have revealed the regulatory role of lipolytic products of lysosomal lipid hydrolysis in catabolic, anabolic, and signaling pathways. In vivo studies in mice with knockout of Lipa highlight the systemic impact of Lipa deficiency on metabolic homeostasis and immune cell function. Genome-wide association studies and functional genomic studies have identified LIPA as a risk locus for coronary heart disease, but the causal variants and mechanisms remain to be determined. Future studies will continue to focus on the role of LAL in the crosstalk between lipid metabolism and cellular function in health and diseases including coronary heart disease.

Genomic Strategies Toward Identification of Novel Therapeutic Targets

Coronary artery disease, myocardial infarction, and secondary damages of the myocardium in the form of ischemic heart disease remain major causes of death in Western countries. Beyond traditional risk factors such as smoking, hypertension, dyslipidemia, or diabetes, a positive family history is known to increase risk. The genetic factors underlying this observation remained unknown for decades until genetic studies were able to identify multiple genomic loci contributing to the heritability of the trait. Knowledge of the affected genes and the resulting molecular and cellular mechanisms leads to improved understanding of the pathophysiology leading to coronary atherosclerosis. Major goals are also to improve prevention and therapy of coronary artery disease and its sequelae via improved risk prediction tools and pharmacological targets. In this chapter, we recapitulate recent major findings. We focus on established novel targets and discuss possible further targets which are currently explored in translational studies.

A decade of genome-wide association studies for coronary artery disease: the challenges ahead

In this review, we summarize current knowledge on the genetics of coronary artery disease, based on 10 years of genome-wide association studies. The discoveries began with individual studies using 200K single nucleotide polymorphism arrays and progressed to large-scale collaborative efforts, involving more than a 100 000 people and up to 40 Mio genetic variants. We discuss the challenges ahead, including those involved in identifying causal genes and deciphering the links between risk variants and disease pathology. We also describe novel insights into disease biology based on the findings of genome-wide association studies. Moreover, we discuss the potential for discovery of novel treatment targets through the integration of different layers of 'omics' data and the application of systems genetics approaches. Finally, we provide a brief outlook on the potential for precision medicine to be enhanced by genome-wide association study findings in the cardiovascular field.

Polygenetic risk for coronary artery disease increases hospitalization burden and mortality

Background

Coronary artery disease (CAD) is a leading cause of death worldwide and increasing cost for society. Genome wide association studies (GWAS) have identified common variants associated with CAD. Combining single nucleotide polymorphisms (SNPs) into a genetic risk score (GRS) can estimate an individual's genetic burden.

Objectives

To investigate whether GRS for CAD can predict hospitalization and mortality.

Methods

23,594 individuals without CAD at baseline and with full data for all covariates from the population based prospective study Malmö diet and cancer study were investigated. The association between hospitalizations was calculated by negative binomial regression and risk of mortality was calculated by Cox proportional hazards regression. The GRS was constructed from 50 SNPs.

Results

The study population was divided into quintiles according to the value of GRS. During the mean follow-up time of 17.8 years, 17,254 individuals were hospitalized at least once. Individuals in the highest quintile of GRS were hospitalized 10% more often than individuals in the lowest quintile (IRR: 1.10 [95% CI 1.04–1.16], p = 0.001), mainly for cardiovascular reasons (IRR: 1.31 [95% CI 1.20–1.43], p = 5.17 × 10⁻¹⁰). These individuals had highly increased risk of CVD mortality (HR: 1.44 [1.25–1.66], p = 6.56 × 10⁻⁷) but not the risk of mortality due to other causes.

Conclusion

Our results suggest that genetic predisposition for CAD can predict hospitalization burden and mortality, especially due to cardiovascular causes, independently of traditional risk factors. As the risk conferred by the GRS is partially modifiable, our results may help to reduce societal costs, individual suffering and prolong life.

Influence of ABO Locus on PFA-100 Collagen-ADP Closure Time Is Not Totally Dependent on the Von Willebrand Factor. Results of a GWAS on GAIT-2 Project Phenotypes

(1) Background: In a previous study, we found that two phenotypes related to platelet reactivity, measured with the PFA-100 system, were highly heritable. The aim of the present study was to identify genetic determinants that influence the variability of these phenotypes: closure time of collagen-ADP (Col-ADP) and of collagen-epinephrine (Col-Epi). (2) Methods: As part of the GAIT-2 (Genetic Analysis of Idiopathic Thrombophilia (2) Project, 935 individuals from 35 large Spanish families were studied. A genome-wide association study (GWAS) with ≈ 10 M single nucleotide polymorphisms (SNPs) was carried out with Col-ADP and Col-Epi phenotypes. (3) Results: The study yielded significant genetic signals that mapped to the ABO locus. After adjusting both phenotypes for the ABO genotype, these signals disappeared. After adjusting for von Willebrand factor (VWF) or for coagulation factor VIII (FVIII), the significant signals disappeared totally for Col-Epi phenotype but only partially for Col-ADP phenotype. (4) Conclusion: Our results suggest that the ABO locus exerts the main genetic influence on PFA-100 phenotypes. However, while the effect of the ABO locus on Col-Epi phenotype is mediated through VWF and/or FVIII, the effect of the ABO locus on Col-ADP phenotype is partly produced through VWF and/or FVIII, and partly through other mechanisms.

Impact of Apolipoprotein(a) Isoform Size on Lipoprotein(a) Lowering in the HPS2-THRIVE Study

Supplemental Digital Content is available in the text.

Background:

Genetic studies have shown lipoprotein(a) (Lp[a]) to be an important causal risk factor for coronary disease. Apolipoprotein(a) isoform size is the chief determinant of Lp(a) levels, but its impact on the benefits of therapies that lower Lp(a) remains unclear.

Methods:

HPS2-THRIVE (Heart Protection Study 2–Treatment of HDL to Reduce the Incidence of Vascular Events) is a randomized trial of niacin–laropiprant versus placebo on a background of simvastatin therapy. Plasma Lp(a) levels at baseline and 1 year post-randomization were measured in 3978 participants from the United Kingdom and China. Apolipoprotein(a) isoform size, estimated by the number of kringle IV domains, was measured by agarose gel electrophoresis and the predominantly expressed isoform identified.

Results:

Allocation to niacin–laropiprant reduced mean Lp(a) by 12 (SE, 1) nmol/L overall and 34 (6) nmol/L in the top quintile by baseline Lp(a) level (Lp[a] ≥128 nmol/L). The mean proportional reduction in Lp(a) with niacin–laropiprant was 31% but varied strongly with predominant apolipoprotein(a) isoform size (P_Trend=4×10⁻²⁹) and was only 18% in the quintile with the highest baseline Lp(a) level and low isoform size. Estimates from genetic studies suggest that these Lp(a) reductions during the short term of the trial might yield proportional reductions in coronary risk of ≈2% overall and 6% in the top quintile by Lp(a) levels.

Conclusions:

Proportional reductions in Lp(a) were dependent on apolipoprotein(a) isoform size. Taking this into account, the likely benefits of niacin–laropiprant on coronary risk through Lp(a) lowering are small. Novel therapies that reduce high Lp(a) levels by at least 80 nmol/L (≈40%) may be needed to produce worthwhile benefits in people at the highest risk because of Lp(a).

Clinical Trial Registration:

URL: https://clinicaltrials.gov. Unique identifier: NCT00461630.

Stigmasterol accumulation causes cardiac injury and promotes mortality

Cardiovascular disease is expected to remain the leading cause of death worldwide despite the introduction of proprotein convertase subtilisin/kexin type 9 inhibitors that effectively control cholesterol. Identifying residual risk factors for cardiovascular disease remains an important step for preventing and clinically managing the disease. Here we report cardiac injury and increased mortality occurring despite a 50% reduction in plasma cholesterol in a mouse model of phytosterolemia, a disease characterized by elevated levels of dietary plant sterols in the blood. Our studies show accumulation of stigmasterol, one of phytosterol species, leads to left ventricle dysfunction, cardiac interstitial fibrosis and macrophage infiltration without atherosclerosis, and increased mortality. A pharmacological inhibitor of sterol absorption prevents cardiac fibrogenesis. We propose that the pathological mechanism linking clinical sitosterolemia to the cardiovascular outcomes primarily involves phytosterols-induced cardiac fibrosis rather than cholesterol-driven atherosclerosis. Our studies suggest stigmasterol is a potent and independent risk factor for cardiovascular disease.

DNA methylation in blood as a mediator of the association of mid-childhood body mass index with cardio-metabolic risk score in early adolescence

Obesity is associated with higher cardio-metabolic risk even in childhood and adolescence; whether this association is mediated by epigenetic mechanisms remains unclear. We examined the extent to which mid-childhood body mass index (BMI) z-score (median age 7.7 years) was associated with cardio-metabolic risk score in early adolescence (median age 12.9 years) via mid-childhood DNA methylation among 265 children in the Project Viva. We measured DNA methylation in leukocytes using the Infinium Human Methylation450K BeadChip. We assessed mediation CpG-by-CpG using epigenome-wide association analyses, high-dimensional mediation analysis, and natural effect models. We observed mediation by mid-childhood DNA methylation at 6 CpGs for the association between mid-childhood BMI z-score and cardio-metabolic risk score in early adolescence in the high-dimensional mediation analysis (accounting for 10% of the total effect) and in the natural effect model (β = 0.04, P = 3.2e-2, accounting for 13% of the total effect). The natural direct effect of BMI z-score on cardio-metabolic risk score was still evident (β = 0.27, P = 1.1e-25). We also observed mediation by mid-childhood DNA methylation at 5 CpGs that was in the opposite direction from the total effect (natural effect model: β = -0.04, P = 2.0e-2). Mediation in different directions implies a complex role of DNA methylation in the association between BMI and cardio-metabolic risk and needs further investigation. Future studies with larger sample size and greater variability in cardio-metabolic risk will further help elucidate the role of DNA methylation for cardio-metabolic risk.

Long Noncoding RNA ANRIL: Lnc-ing Genetic Variation at the Chromosome 9p21 Locus to Molecular Mechanisms of Atherosclerosis

Ever since the first genome-wide association studies (GWAS) on coronary artery disease (CAD), the Chr9p21 risk locus has emerged as a top signal in GWAS of atherosclerotic cardiovascular disease, including stroke and peripheral artery disease. The CAD risk SNPs on Chr9p21 lie within a stretch of 58 kilobases of non-protein-coding DNA, containing the gene body of the long noncoding RNA (lncRNA) antisense non coding RNA in the INK4 locus (ANRIL). How risk is affected by the Chr9p21 locus in molecular detail is a matter of ongoing research. Here we will review recent advances in the understanding that ANRIL serves as a key risk effector molecule of atherogenesis at the locus. One focus of this review is the shift in understanding that genetic variation at Chr9p21 not only affects the abundance of ANRIL, and in some cases expression of the adjacent CDKN2A/B tumor suppressors, but also impacts ANRIL splicing, such that 3′-5′-linked circular noncoding ANRIL RNA species are produced. We describe how the balance of linear and circular ANRIL RNA, determined by the Chr9p21 genotype, regulates molecular pathways and cellular functions involved in atherogenesis. We end with an outlook on how manipulating circular ANRIL abundance may be exploited for therapeutic purposes.

Global genetic diversity of human apolipoproteins and effects on cardiovascular disease risk

Abnormal plasma apolipoprotein levels are consistently implicated in CVD risk. Although 30% to 60% of their interindividual variability is genetic, common genetic variants explain only 10% to 20% of these differences. Rare genetic variants may be major sources of the missing heritability, yet quantitative evaluations of their contribution to phenotypic variability are lacking. Here, we analyzed whole-genome and whole-exome sequencing data from 138,632 individuals across seven major human populations to present a systematic overview of genetic apolipoprotein variability. We provide population-specific frequencies of 38 clinically important apolipoprotein alleles and identify further 6,875 genetic variants, 33% of which are novel and 98.7% of which are rare with minor allele frequencies <1%. We predicted the functional impact of rare variants and found that their relative importance differed drastically between genes and among ethnicities. Importantly, we validated the clinical relevance of multiple variants with predicted effects by leveraging association data from the CARDIoGRAM (Coronary Artery Disease Genomewide Replication and Meta-analysis) and Global Lipids Genetics consortia. Overall, we provide a consolidated overview of population-specific apolipoprotein genetics as a valuable data resource for scientists and clinicians, estimate the importance of rare genetic variants for the missing heritability of apolipoprotein-associated disease traits, and pinpoint multiple novel apolipoprotein variants with putative population-specific impacts on serum lipid levels.

Lysosomal acid lipase and lipid metabolism: new mechanisms, new questions, and new therapies

PURPOSE OF REVIEW

Lysosomal acid lipase (LAL), encoded by the LIPA gene, is an essential lysosomal enzyme that hydrolyzes cholesteryl ester and triglyceride delivered to the lysosome. This review highlights the novel pathophysiological role of LAL, the functional genomic discoveries of LIPA as a risk locus for coronary heart diseases (CHD), and the clinical advance in therapies for LAL deficiency.

RECENT FINDINGS

The essential role of LAL in lipid metabolism has been confirmed in human and mice with LAL deficiency. In humans, loss-of-function mutations of LIPA cause rare lysosomal disorders, Wolman disease, and cholesteryl ester storage disease, in which LAL enzyme replacement therapy has shown significant benefits in a phase 3 clinical trial. Recent studies have revealed the role of LAL-mediated lysosomal lipolysis in regulating macrophage M2 polarization, lipid mediator production, VLDL secretion, lysosomal function and autophagy, extracellular degradation of aggregated-LDL, and adipose tissue lipolysis. Genome-wide association studies and functional genomic studies have identified LIPA as a risk locus for CHD, but the causal variants and mechanisms remain to be determined.

SUMMARY

Despite years of research, our understanding of LAL is incomplete. Future studies will continue to focus on the key pathophysiological functions of LAL in health and diseases including CHD.

Metformin and AMP Kinase Activation Increase Expression of the Sterol Transporters ABCG5/8 (ATP-Binding Cassette Transporter G5/G8) With Potential Antiatherogenic Consequences

OBJECTIVE

The mechanisms underlying the cardiovascular benefit of the anti-diabetic drug metformin are poorly understood. Recent studies have suggested metformin may upregulate macrophage reverse cholesterol transport. The final steps of reverse cholesterol transport are mediated by the sterol transporters, ABCG5 (ATP-binding cassette transporter G5) and ABCG8 (ATP-binding cassette transporter G8), which facilitate hepato-biliary transport of cholesterol. This study was undertaken to assess the possibility that metformin induces Abcg5 and Abcg8 expression in liver and to elucidate the underlying mechanisms.

APPROACH AND RESULTS

Metformin-treated mouse or human primary hepatocytes showed increased expression of Abcg5/8 and the bile salt export pump, Bsep. Administration of metformin to Western-type diet-fed mice showed significant upregulation of Abcg5/8 and Bsep. This resulted in increased initial clearance of ³H-cholesteryl ester HDL (high-density lipoprotein) from plasma. However, fecal ³H-cholesterol output was only marginally increased, possibly reflecting increased hepatic Ldlr (low-density lipoprotein receptor) expression, which would increase nonradiolabeled cholesterol uptake. Abcg5/8 undergo strong circadian variation. Available chromatin immunoprecipitation-Seq data suggested multiple binding sites for Period 2, a transcriptional repressor, within the Abcg5/8 locus. Addition of AMPK (5' adenosine monophosphate-activated protein kinase) agonists decreased Period 2 occupancy, suggesting derepression of Abcg5/8. Inhibition of ATP citrate lyase, which generates acetyl-CoA from citrate, also decreased Period 2 occupancy, with concomitant upregulation of Abcg5/8. This suggests a mechanistic link between feeding-induced acetyl-CoA production and decreased cholesterol excretion via Period 2, resulting in inhibition of Abcg5/8 expression.

CONCLUSIONS

Our findings provide partial support for the concept that metformin may provide cardiovascular benefit via increased reverse cholesterol transport but also indicate increased Ldlr expression as a potential additional mechanism. AMPK activation or ATP citrate lyase inhibition may mediate antiatherogenic effects through increased ABCG5/8 expression.

The Contribution of Autoantibodies to Inflammatory Cardiovascular Pathology

Chronic inflammation and resulting tissue damage underlie the vast majority of acquired cardiovascular disease (CVD), a general term encompassing a widely diverse array of conditions. Both innate and adaptive immune mechanisms contribute to chronic inflammation in CVD. Although maladies, such as atherosclerosis and cardiac fibrosis, are commonly conceptualized as disorders of inflammation, the cellular and molecular mechanisms that promote inflammation during the natural history of these diseases in human patients are not fully defined. Autoantibodies (AAbs) with specificity to self-derived epitopes accompany many forms of CVD in humans. Both adaptive/induced iAAbs (generated following cognate antigen encounter) and also autoantigen-reactive natural antibodies (produced independently of infection and in the absence of T cell help) have been demonstrated to modulate the natural history of multiple forms of CVD including atherosclerosis (atherosclerotic cardiovascular disease), dilated cardiomyopathy, and valvular heart disease. Despite the breadth of experimental evidence for the role of AAbs in CVD, there is a lack of consensus regarding their specific functions, primarily due to disparate conclusions reached, even when similar approaches and experimental models are used. In this review, we seek to summarize the current understanding of AAb function in CVD through critical assessment of the clinical and experimental evidence in this field. We additionally highlight the difficulty in translating observations made in animal models to human physiology and disease and provide a summary of unresolved questions that are critical to address in future studies.

Plasma cytokines and risk of coronary heart disease in the PROCARDIS study

Objective

The aims of the study were to examine the associations of plasma levels of five cytokines (interleukin (IL)-6, IL-5, interferon-gamma (IFN-γ), tumour necrosis factor-alpha (TNF-α) and IL-6 receptor (IL-6R)) and C reactive protein (CRP) with risk of coronary heart disease (CHD).

Methods

In a case–control study of 931 CHD cases and 974 controls, logistic regression was used to estimate the OR and 95% CI of CHD for extreme thirds of biomarkers after adjustment for established risk factors. Sensitivity analyses were conducted in non-statin and in non-aspirin users.

Results

Plasma levels of CRP were moderately correlated with IL-6 (r=0.45) in controls, but more weakly correlated with other cytokines. Likewise, all other cytokines were only weakly correlated with each other. After adjustment for established risk factors, the ORs (95% CI) for CHD comparing extreme thirds of cytokine levels (defined in controls) were 2.53 (1.86 to 3.43) for IL-6, 1.46 (1.11 to 1.93) for IL-5 and 1.46 (1.09 to 1.95) for IFN-γ, respectively. However, neither TNF-α, IL-6R nor CRP was significantly associated with CHD. After further adjustment for the associated cytokines, only IL-5 (1.34; 1.00 to 1.80) and IL-6 (2.39; 1.73 to 3.30) remained significantly associated with CHD. The risk associations of cytokines in non-users of statins or aspirin were comparable with the overall population.

Conclusions

This study confirmed the importance of IL-6 as the most strongly associated cytokine with CHD risk, but also demonstrated novel and independent associations of IL-5 with CHD that warrant further investigation using larger panels of cytokines.

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.

Integrative Bioinformatics Approaches for Identification of Drug Targets in Hypertension

High blood pressure or hypertension is an established risk factor for a myriad of cardiovascular diseases. Genome-wide association studies have successfully found over nine hundred loci that contribute to blood pressure. However, the mechanisms through which these loci contribute to disease are still relatively undetermined as less than 10% of hypertension-associated variants are located in coding regions. Phenotypic cell-type specificity analyses and expression quantitative trait loci show predominant vascular and cardiac tissue involvement for blood pressure-associated variants. Maps of chromosomal conformation and expression quantitative trait loci (eQTL) in critical tissues identified 2,424 genes interacting with blood pressure-associated loci, of which 517 are druggable. Integrating genome, regulome and transcriptome information in relevant cell-types could help to functionally annotate blood pressure associated loci and identify drug targets.

Genome-Wide Association and Functional Studies Identify SCML4 and THSD7A as Novel Susceptibility Genes for Coronary Artery Disease

OBJECTIVE

The genetic contribution to coronary artery disease (CAD) remains largely unclear. We combined genetic screening with functional characterizations to identify novel loci and candidate genes for CAD.

APPROACH AND RESULTS

We performed genome-wide screening followed by multicenter validation in 8 cohorts consisting of 21 828 participants of Han ethnicity and identified 3 novel intragenic SNPs (single nucleotide polymorphisms), rs9486729 (SCML4 [Scm polycomb group protein-like 4]; odds ratio, 1.25; 95% CI, 1.17-1.34; P=3.51×10^-11), rs17165136 (THSD7A [thrombospondin type 1 domain-containing 7A]; odds ratio 1.28; 95% CI, 1.21-1.35; P<1.00×10^-25), and rs852787 (DAB1 [disabled-1]; odds ratio, 1.29; 95% CI, 1.21-1.38; P=2.02×10^-14), associated with CAD with genome-wide significance. The risk allele of rs9486729 and protective allele of rs17165136 were associated with the decreased expression of their host genes, SCML4 and THSD7A, respectively, whereas rs852787 did not have transcriptional effects on any gene. Knockdown of SCML4 activated endothelial cells by increasing the expression of IL-6, E-selectin, and ICAM and weakened their antiapoptotic activity, whereas the knockdown of THSD7A had little effect on these endothelial cell functions but attenuated monocyte adhesion via decreasing the expression of ICAM, L-selectin, and ITGB2. We further showed that inhibiting the expression of SCML4 exacerbated endothelial dysfunction and vascular remodeling in a rat model with partial carotid ligation.

CONCLUSIONS

We identify 3 novel loci associated with CAD and show that 2 genes, SCML4 and THSD7A, make functional contributions to atherosclerosis. How rs852787 and its host gene DAB1 are linked to CAD needs further studies.

Atherosclerosis Is an Inflammatory Disease which Lacks a Common Anti-inflammatory Therapy: How Human Genetics Can Help to This Issue. A Narrative Review

Atherosclerosis is a multifactorial disease triggered and sustained by different risk factors such as dyslipidemia, arterial hypertension, diabetes mellitus, smoke, etc. Since a couple of decades, a pivotal role for inflammation in its pathogenesis has been recognized and proved at molecular levels, and already described in many animal models. Despite all this knowledge, due to the complexity of the specific inflammatory process subtending atherosclerosis and to the fact that inflammation is also a protective response against microorganisms, no anti-inflammatory therapy has been rendered available in the therapeutic armamentarium against atherosclerosis and vascular events till 2017 when canakinumab in the first ad-hoc randomized clinical trial (RCT) proved for the first time that targeting specifically inflammation lowers cardiovascular (CV) events. From the genetic side, in the 90's and early 2000, several genetic markers in inflammatory pathway have been explored searching for an association with athero-thrombosis which gave seldom consistent results. Then, in the genomic era, plenty of genetic markers covering most of the genome have been analyzed at once without a priori information. The results coming from genome wide association studies (GWAS) have pinpointed some loci closed to inflammatory molecules consistently associated with atherosclerosis and CV consequences revamping the strict link between inflammation and atherosclerosis and suggesting some tailored target therapy. Whole-exome and whole-genome sequencing will come soon showing new and old loci associated with atherosclerosis suggesting new molecular targets or underlying which inflammatory pathway could be most attractive to target for blocking atherosclerosis even in its early stages.

Polygenic Risk Score for Coronary Heart Disease Modifies the Elevated Risk by Cigarette Smoking for Disease Incidence

BACKGROUND

Coronary heart disease (CHD) is a multifactorial disease with both genetic and environmental components. Smoking is the most important modifiable risk factor for CHD. Our aim was to test whether the increased CHD incidence by smoking is modified by genetic predisposition to CHD.

METHODS AND RESULTS

Our study included 24 443 individuals from the MDCS (Malmö Diet and Cancer Study). A weighted polygenic risk score (PRS) was created by summing the number of risk alleles for 50 single-nucleotide polymorphisms associated with CHD. Individuals were classified as current, former, or never smokers. Interactions were primarily tested between smoking status and PRS and secondarily with individual single-nucleotide polymorphisms. Then, the predictive use of PRS for CHD incidence was tested among different smoking categories. During a median follow-up time of 19.4 years, 3217 incident CHD cases were recorded. The association between smoking and CHD was modified by the PRS (P_interaction=0.005). The magnitude of increased incidence of CHD by smoking was highest among individuals in the lowest tertile of PRS (odds ratio, 1.42; 95% confidence interval, 1.29-1.56 per smoking risk category) compared with the highest tertile (odds ratio, 1.20; 95% confidence interval, 1.11-1.30 per smoking risk category). This interaction was stronger among men (P_interaction=0.001) compared with women (P_interaction=0.44). The PRS provided a significantly better net reclassification and discrimination on top of traditional risk factors among never smokers compared with current smokers (P<0.001).

CONCLUSIONS

Genetic predisposition to CHD modifies the associated increased CHD risk by smoking. The PRS has a better predictive use among never smokers compared with smokers.

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.