Genetic analysis of 103 candidate genes for coronary artery disease and associated phenotypes in a founder population reveals a new association between endothelin-1 and high-density lipoprotein cholesterol

Endothelin-1 RS5370 gene polymorphism in primary nephrotic syndrome: A case-control study

INTRODUCTION

Primary nephrotic syndrome (NS) is a common glomerular disease in children. We assessed the genotypes and frequency of the rs5370 allelic variant of the EDN1 gene in children with primary NS.

PATIENTS AND METHODS

We conducted a case-control study in Mansoura University Children's Hospital, Egypt between December 2015 and January 2018. We recruited 50 patients with steroid-sensitive NS (SSNS) and 50 patients with steroid-resistant NS (SRNS) in addition to 100 healthy controls. The patients underwent clinical evaluations and tests including measurement of serum albumin, cholesterol, creatinine and urea levels and a 24-h urinary protein test. We used polymerase chain reaction methods to assess the genotypes of rs5370 variants of the EDN1 gene (GG, GT and TT) and alleles (T and G) in the groups under study.

RESULTS

The most frequent genotype of the EDN1 gene at the locus of interest in the control group was the GT genotype (88%; P=.001) while the GG genotype was more frequent in the NS group compared to the control group (P=.02). We did not find statistically significant differences between the NS and control groups in regard to the EDN1 rs5370 alleles (P=.69). The GG genotype was more frequent in the SSNS group compared to the SRNS and control groups (P=.03). When we compared allele frequencies between the control, SSNS and SRNS groups, we did not find significant differences (P=.89). The GT genotype was associated with normal blood pressure in children with NS (P=.007), while the GG genotype was associated with hypertension (P<.001). We did not find statistically significant differences in renal histopathology or serum cholesterol levels based on the genotype.

CONCLUSIONS

The GG genotype at the rs5370 locus of the EDN1 gene may be associated with an increased risk of primary NS and a better response to steroid therapy.

The genetics of human performance

Human physiology is likely to have been selected for endurance physical activity. However, modern humans have become largely sedentary, with physical activity becoming a leisure-time pursuit for most. Whereas inactivity is a strong risk factor for disease, regular physical activity reduces the risk of chronic disease and mortality. Although substantial epidemiological evidence supports the beneficial effects of exercise, comparatively little is known about the molecular mechanisms through which these effects operate. Genetic and genomic analyses have identified genetic variation associated with human performance and, together with recent proteomic, metabolomic and multi-omic analyses, are beginning to elucidate the molecular genetic mechanisms underlying the beneficial effects of physical activity on human health.

[Endothelin-1 rs5370 gene polymorphism in primary nephrotic syndrome: A case-control study]

INTRODUCTION

Primary nephrotic syndrome (NS) is a common glomerular disease in children. We assessed the genotypes and frequency of the rs5370 allelic variant of the EDN1 gene in children with primary NS.

PATIENTS AND METHODS

We conducted a case-control study in Mansoura University Children's Hospital, Egypt, between December 2015 and January 2018. We recruited 50 patients with steroid-sensitive NS (SSNS) and 50 patients with steroid-resistant NS (SRNS) in addition to 100 healthy controls. The patients underwent clinical evaluations and tests including measurement of serum albumin, cholesterol, creatinine and urea levels and a 24-hour urinary protein test. We used polymerase chain reaction methods to assess the genotypes of rs5370 variants of the EDN1 gene (GG, GT and TT) and alleles (T and G) in the groups under study.

RESULTS

The most frequent genotype of the EDN1 gene at the locus of interest in the control group was the GT genotype (88%; P=.001) while the GG genotype was more frequent in the NS group compared to the control group (P=.02). We did not find statistically significant differences between the NS and control groups in regard to the EDN1 rs5370 alleles (P=.69). The GG genotype was more frequent in the SSNS group compared to the SRNS and control groups (P=.03). When we compared allele frequencies between the control, SSNS and SRNS groups, we did not find significant differences (P=.89). The GT genotype was associated with normal blood pressure in children with NS (P=.007), while the GG genotype was associated with hypertension (P<.001). We did not find statistically significant differences in renal histopathology or serum cholesterol levels based on the genotype.

CONCLUSIONS

The GG genotype at the rs5370 locus of the EDN1 gene may be associated with an increased risk of primary NS and a better response to steroid therapy.

Detection of ADTRP in circulation and its role as a novel biomarker for coronary artery disease

Androgen dependent tissue factor pathway inhibitor regulating protein (ADTRP) is a novel protein associated with coronary artery disease (CAD) susceptibility, and reduced mRNA expression of ADTRP was shown to be associated with increased CAD risk. This study aimed to determine and compare circulating ADTRP levels between CAD patients and controls, and to test the performance of plasma ADTRP as a biomarker for CAD. We measured plasma ADTRP, tumor necrosis factor-alpha (TNF-α), interleukin-6 (IL-6) and high sensitivity-C reactive protein (hs-CRP) levels in 362 CAD patients, 150 angiographically negative CAD controls, and 83 healthy adults with no known clinical or medical conditions using commercial ELISA. Statistical analyses were performed using receiver operator characteristic (ROC) curves, quantile regression and logistic regression, with adjustments for age, gender, ethnicity and BMI. CAD patients had significantly lower plasma ADTRP levels 1,545 (1,087–2,408) pg/ml as compared to CAD controls 2,259 (1,533–3,778) pg/ml and healthy adults 3,904 (2,732–5,463) pg/ml. Plasma ADTRP outperformed the other three inflammatory biomarkers (TNF-α, IL-6 and hs-CRP) for CAD (Area under ROC curve: 0.67, Odds ratio (OR): 0.907). Our study has shown for the first time that ADTRP is present in circulation, and that plasma ADTRP may be a novel independent biomarker for CAD.

Association of +138I/D and Lys198Asn Polymorphisms in the Endothelin-1 Gene with Early Onset of Coronary Artery Disease among the Chinese Han Population

Background

Human endothelin-1 (ET-1) gene polymorphism is closely associated with coronary artery disease (CAD). This study aimed to investigate the association of 2 single-nucleotide polymorphisms (SNPs), +138 I/D and Lys198Asn) of the ET-1 gene,with early onset of CAD in Han Chinese patients. We investigated the effects of Lys198Asn polymorphism on ET-1 protein expression upon stimulation with pro-inflammatory factors.

Material/Methods

Genotyping of the 2 SNPs +138 I/D and Lys198Asn was performed in 88 early-onset CAD patients (≤55 years for males; ≤60 years for females) and 52 healthy control participants using a polymerase chain reaction direct sequencing method. The association of the 2 SNPs was analyzed with SPSS 17.0 software. Western blotting was performed to assess the effects of ET-1 polymorphisms on ET-1 protein expression upon tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), and lipopolysaccharide (LPS) stimulation in HEK-293T cells.

Results

Fisher’s exact test showed that the T allele (odds ratio [OR]=3.38, P=0.02) and GT/TT genotype (OR=3.76, P=0.02) of the ET-1 gene Lys198Asn were associated with increased early-onset CAD risk. Multivariate logistic regression analysis showed smoking was the single independent variable related to early-onset CAD (P<0.05). An increase of ET-1 protein levels in cells transfected with Asn198 plasmid was seen upon TNF-α or IL-6 stimulation.

Conclusions

T allele frequency in Lys198Asn loci might be associated with the pathogenesis of early-onset CAD. T-variant might contribute to early-onset CAD by upregulating ET-1 expression upon inflammatory cytokines stimulation, and smokers who have the T allele might be vulnerable to CAD in the Chinese population.

Analysis of causal effect of APOA5 variants on premature coronary artery disease

Apolipoprotein A5 (APOA5) regulates the metabolisms of triglyceride and HDL. APOA5 variants have been linked to coronary artery disease (CAD), but their causal roles are not well studied yet. This study aims to identify the causal effects of APOA5 variants on premature CAD. Sequencing analysis of APOA5 in 128 premature, familiar CAD patients from GeneQuest identified 11 genomic variants, including p.S19W (rs3135506). SKAT analysis showed that all sequenced variants, in aggregate, significantly increased the risk of premature CAD (P-skat = 0.037). Individually, the p.S19W variant was significantly associated with risk of premature CAD (OR = 2.30, P = 0.008) in an independent set of 342 premature CAD patients and 537 controls after adjusting for covariates of sex, age, hypertension, body mass index, triglycerides (TGs), and total, LDL-, and HDL-cholesterol levels. Meanwhile, p.S19W significantly correlated with HDL-C levels (P = 0.048) and TG levels (P = 0.025). Mediation analysis yielded a mediation effect of p.S19W on risk of premature CAD through HDL-C (OR = 0.98, P = 0.040) and TG (OR = 0.98, P = 0.042), suggesting a causal relationship between p.S19W and premature CAD partially through its effects on HDL-C and TG levels. These results suggest that APOA5 variation regulates TG and HDL levels, thus displaying a causal role in the development of CAD.

Interactions among genes involved in reverse cholesterol transport and in the response to environmental factors in dyslipidemia in subjects from the Xinjiang rural area

Gene-gene and gene-environment interactions may be partially responsible for dyslipidemia, but studies investigating interactions in the reverse cholesterol transport system (RCT) are limited. We explored these interactions in a Xinjiang rural population by genotyping five SNPs using SNPShot technique in APOA1, ABCA1, and LCAT, which are involved in the RCT (690 patients, 743 controls). We conducted unconditional logistical regression analysis to evaluate associations and generalized multifactor dimensionality reduction to evaluate interactions. Results revealed significant differences in rs670 and rs2292318 allele frequencies between cases and controls (P<0.025). rs670 G allele carriers were more likely to develop dyslipidemia than A allele carriers (OR = 1.315, OR 95% CI: 1.067–2.620; P = 0.010). rs2292318 T allele carriers were more likely to develop dyslipidemia than A allele carriers (OR = 1.264, OR 95% CI: 1.037–1.541; P = 0.020). Gene-gene interaction model APOA1rs670-ABCA1rs1800976-ABCA1rs4149313-LCATrs1109166 (P = 0.0107) and gene-environment interaction model ABCA1rs1800976-ABCA1rs4149313-LCATrs1109166-obesity-smoking were optimal dyslipidemia predictors (P = 0.0107) and can interact (4). Differences in A-C-A-C-A and G-G-G-T-G haplotype frequencies were observed (P<0.05). Serum lipid profiles could be partly attributed to RCT gene polymorphisms. Thus, dyslipidemia is influenced by APOA1, ABCA1, LCAT, environmental factors, and their interactions.

CETP and LCAT Gene Polymorphisms Are Associated with High-Density Lipoprotein Subclasses and Acute Coronary Syndrome

We evaluated whether CETP and LCAT gene polymorphisms are statistically associated with the high-density lipoprotein (HDL) size distribution, the cholesterol level of HDL subclasses, and the acute coronary syndrome (ACS) susceptibility. Two CETP gene polymorphisms (rs4783961 and rs708272) and one LCAT polymorphism (rs2292318) were genotyped by 5' exonuclease TaqMan assays in 619 patients with ACS and 607 control individuals. For HDL analysis, a subgroup of 100 healthy individuals was recruited; the HDL subclasses were separated via ultracentrifugation and polyacrylamide gradient gel electrophoresis under native conditions. Under a dominant model, the G allele of the rs708272 polymorphism was associated with an increased risk of ACS (odds ratios [OR] = 1.45, corrected p-value [pC_Dom ] = 0.036). The linkage disequilibrium analysis showed that one of the eight possible combinations was associated with the risk of developing ACS (OR = 1.52, pC = 0.02), which suggests that it may contribute to coronary atherosclerosis. The rs708272 G allele carriers had a lower concentration of cholesterol associated with the HDL2a and HDL3a subclasses when compared with subjects carrying the A allele. Carriers of LCAT rs2292318 A allele showed a lower concentration of high-density lipoprotein-cholesterol (HDL-C) in comparison to the GG genotype; the cholesterol associated with the each one of the five HDL subclasses was significantly lower in rs2292318 A than in GG subjects. In summary, this study demonstrates that the rs708272 polymorphism is associated with a heightened risk of developing ACS. In addition, we report the association of the rs708272 and rs2292318 polymorphisms with HDL-C levels and HDL subclasses.

Lack of Evidence of the Role of APOA5 3'UTR Polymorphisms in Iranian Children and Adolescents with Metabolic Syndrome

BACKGROUND

Metabolic syndrome (MetS) is a complex and multifactorial disorder characterized by insulin resistance, dyslipidaemia, hyperglycemia, abdominal obesity, and elevated blood pressure. The apolipoprotein A5 (APOA5) gene variants have been reported to correlate with two major components of MetS, including low levels of high density lipoprotein cholesterol (HDL-C) and high levels of triglyceride. In the present study, we explored the associations between five single nucleotide polymorphisms (SNPs) of APOA5 gene and the MetS risk.

METHODS

In a case-control design, 120 Iranian children and adolescents with/without MetS were genotyped by polymerase chain reaction-sequencing for these SNPs. Then, we investigated the association of SNPs, individually or in haplotype constructs, with MetS risk.

RESULTS

The rs34089864 variant and H1 haplotype (harboring the two major alleles of rs619054 and rs34089864) were associated with HDL-C levels. However, there was no significant association between different haplotypes/individual SNPs and MetS risk.

CONCLUSION

These results presented no association of APOA5 3'UTR SNPs with MetS. Further studies, including other polymorphisms, are required to investigate the involvement of APOA5 gene in the genetic susceptibility to MetS in the pediatric age group.

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.

Population-based Study of Risk Polymorphisms Associated with Vascular Disorders and Dementia

Introduction:

Cardiovascular and neurodegenerative disorders are among the major causes of mortality in the developed countries. Population studies evaluate the genetic risk, i.e. the probability of an individual carrying a specific disease-associated polymorphism. Identification of risk polymorphisms is essential for an accurate diagnosis or prognosis of a number of pathologies.

Aims:

The aim of this study was to characterize the influence of risk polymorphisms associated with lipid metabolism, hypertension, thrombosis, and dementia, in a large population of Spanish individuals affected by a variety of brain and vascular disorders as well as metabolic syndrome.

Material & Method:

We performed a cross-sectional study on 4415 individuals from a widespread regional distribution in Spain (48.15% males and 51.85% females), with mental, neurodegenerative, cerebrovascular, and metabolic disorders. We evaluated polymorphisms in 20 genes involved in obesity, vascular and cardiovascular risk, and dementia in our population and compared it with representative Spanish and European populations. Risk polymorphisms in ACE, AGT(235), IL6(573), PSEN1, and APOE (specially the APOE-ε4 allele) are representative of our population as compared to the reference data of Spanish and European individuals.

Conclusion:

The significantly higher distribution of risk polymorphisms in PSEN1 and APOE-ε4 is characteristic of a representative number of patients with Alzheimer’s disease; whereas polymorphisms in ACE, AGT(235), and IL6(573), are most probably related with the high number of patients with metabolic syndrome or cerebrovascular damage.

Genetic Risk Factors in Cerebrovascular Disorders and Cognitive Deterioration

INTRODUCTION

The study of variations in genes involved in the different events that trigger the atherogenic process, such as lipid metabolism (modification of LDL-cholesterol), endothelial function and hypertension, immune response (recruitment of macrophages and foam cell formation) and stability of atherosclerotic plaques (thrombosis), established the risk for suffering a vascular disorder. A total of 2455 cases over 50 years of age were genotyped for a panel of 19 SNPs in 15 genes encoding for proteins involved in the atherogenic process. This study shows the relevance of polymorphisms in APOB (odds ratio (OR), 1.17; 95% confidence interval (95% CI), 0.74-1.85), APOC3 (OR, 1.33; 95% CI, 0.82-2.17) and APOE (OR, 1.75; 95% CI, 1.09-2.80), as genetic risk markers for hypercholesterolemia; polymorphisms in ACE (OR, 1.68; 95% CI, 0.32-8.77) and AGT (OR, 1.74; 95% CI, 0.97-3.14) for hypertension; and in APOE*3/*4 (OR, 2.06; 95% CI, 1.70-2.51) and APOE*4/*4 (OR, 3.08; 95% CI, 1.85-5.12) as unambiguous markers of dementia.

RESULT

Our results also showed the transversal importance of proinflammatory cytokines in different stages of atherogenesis, with special relevance of IL6 (OR, 1.39; 95% CI, 0.56-3.49) and TNF (OR, 1.40; 95% CI, 0.92-2.15) related to hypercholesterolemia and hypertension. The set of markers involved in this genetic risk panel makes it a powerful tool in the management of patients with different vascular disorders.

A Breakthrough in Genetics and its Relevance to Prevention of Coronary Artery Disease in LMIC

More than 60 genetic risk variants predisposing to coronary artery disease (CAD) have been confirmed. The genetic risk for CAD is related to the number of genetic risk variants present and can be expressed as a genetic risk score (GRS), by summing the product of the number of high-risk variants inherited by each individual times the log of the odds ratio. Studies show risk stratification for CAD, based on the GRS, is more discriminatory than conventional risk factors and predicts the response to statin therapy. A prospective trial showed individuals with high GRS had 91% greater risk of cardiac events, and individuals with a healthy lifestyle had 46% fewer cardiac events than an unfavorable lifestyle. GRS remains the same throughout one's lifetime because your deoxyribonucleic acid does not change. GRS, determined as early as birth from saliva, is inexpensive and could transform the prevention of CAD in low- and middle-income countries.

Association between the MVK and MMAB polymorphisms and serum lipid levels

Maonan ethnic group is a relatively conservative and isolated minority in China. Little is known about the association of the mevalonate kinase (MVK), methylmalonic aciduria (cobalamin deficiency) cblB type (MMAB) single nucleotide polymorphisms (SNPs) and serum lipid levels. This study aimed to determine the association between four SNPs in the MVK/MMAB and serum lipid levels. Genotyping of the rs3759387, rs877710, rs7134594 and rs9593 SNPs was performed in 1264 Maonan subjects and 1251 Han participants. Allele and genotype frequencies of the selected SNPs were different between the two populations (P < 0.05-0.001). Four SNPs were associated with high-density lipoprotein cholesterol (HDL-C) in the both ethnic groups (P < 0.0125-0.001); and one SNP with apolipoprotein (Apo) A1 (rs7134594) in Han Chinese (P <0.0125). Strong linkage disequilibria were noted among the SNPs (D'=0.63-0.96; r² =0.13-0.88). The commonest haplotype was C-C-C-T (> 50%). The frequencies of C-C-C-T, C-G-T-A, A-G-T-A, C-G-C-T, and A-C-T-A were different between the two populations (P <0.001). The associations between haplotypes and dyslipidemia were different in the Han and/or Maonan population (P < 0.05-0.001), haplotypes could explain much more serum lipid variation than any single SNP alone especially for HDL-C. Differences in lipid profiles between the two populations might partially attribute to these SNPs and their haplotypes.

Polymorphisms of lipid metabolism enzyme-coding genes in patients with diabetic dyslipidemia

Objective:

The polymorphisms/mutations of genes encoding proteins and enzymes involved in lipoprotein metabolism play important roles in the development of diabetic dyslipidemia. The aim of our study was to investigate the effects of LPL (rs320), LIPC (rs2070895), SCARB1 (rs5888), LCAT (rs2292318), CETP (rs708272), ADIPOQ (rs1501299), RETN (rs3745367), PON1 (rs662), and MNSOD (rs4880) gene polymorphisms on lipid metabolism and diabetic dyslipidemia.

Methods:

This case-control study included 217 patients with diabetic dyslipidemia and 212 healthy age- and gender-matched individuals. Genomic DNA isolation was performed from blood samples, and genotype analysis was performed using melting curve analysis on a LightCycler^® 480 Instrument. The chi-square test was used to compare genotype distribution and allele frequencies between the groups.

Results:

Significant associations were observed between LPL (rs320) (p<0.001), LIPC (rs2070895) (p<0.001), SCARB1 (rs5888) (p<0.001), LCAT (rs2292318) (p<0.001), CETP (rs708272) (p<0.001), ADIPOQ (rs1501299) (p=0.01), RETN (rs3745367) (p<0.001), and MNSOD (rs4880) (p<0.001) polymorphisms and diabetic dyslipidemia. However, no association was observed between PON1 (rs662) polymorphisms and diabetic dyslipidemia (p=0.611).

Conclusion:

LPL (rs320), LIPC (rs2070895), SCARB1 (rs5888), LCAT (rs2292318), CETP (rs708272), ADIPOQ (rs1501299), RETN (rs3745367), and MNSOD (rs4880) polymorphisms play an important role in basic molecular metabolism in diabetic dyslipidemia. Therefore, these polymorphisms may be used as a predictive marker for diabetic dyslipidemia in high-risk patients. (Anatol J Cardiol 2017; 17: 313-21)

Effect of SNP polymorphisms of EDN1, EDNRA, and EDNRB gene on ischemic stroke

The objective of this study is to investigate the association between SNP polymorphisms of endothelin-1 (EDN1) and endothelin receptor (EDNRA and EDNRB) gene and ischemic stroke (IS) in the Chinese Han population in northern. A case-control study was introduced. We genotyped eight SNPs (rs1800541, rs2070699, and rs5370 in EDN1 gene; rs1801708, rs5333, and rs5335 in EDNRA gene; and rs3818416 and rs5351 in EDNRB gene) and calculated their polymorphic distribution in control group, IS group, and the IS subgroups. In male population, EDN1 gene rs2070699 G allele increased the incidence risk to 1.78 times (P = 0.009; OR 1.78; 95 % CI 1.15-2.75) and the risk of morbidity of rs5370 T allele carrying increased to 1.49 times (P = 0.048; OR 1.49; 95 % CI 1.00-2.21). EDNRA gene mutation rs5335 homozygous CC morbidity risk was significantly lower (P = 0.016; OR 0.52; 95 % CI 0.31-0.88). In the female population, the mutant homozygous AA cancer risk was significantly higher than G allele carriers (P = 0.019; OR 2.65; 95 % CI 1.18-6.00) on EDNRA gene rs1801708. In EDN1 gene, T allele of rs5370 and G allele of rs2070699 may be IS incidence risk factors in Northern Han male population. A allele of rs1801708 in EDNRA gene can increase the risk of IS in Northern Han women population.

Endothelin-1 gene polymorphisms and diabetic kidney disease in patients with type 2 diabetes mellitus

BACKGROUND AND AIMS

Diabetic kidney disease (DKD) is the leading cause of end stage renal disease worldwide and is associated with increased cardiovascular mortality. The endothelin system has been implicated in the pathogenesis of arterial hypertension and renal dysfunction. In the present study, the association of DKD with polymorphisms in ET-1 (EDN1) and ETRA (EDNRA) genes was analyzed in patients with type 2 diabetes mellitus (T2DM).

METHODS

A case-control study was conducted in 548 white T2DM patients. Patients with proteinuria or on dialysis were considered cases and patients with normoalbuminuria were considered controls. Two polymorphisms in the EDN1 gene (rs1800541 and rs57072783) and five in EDNRA gene (rs6842241; rs4835083; rs4639051; rs5333 and rs5343) were genotyped and haplotype analyses were performed.

RESULTS

The presence of rs57072783 T allele (TT/TG vs. GG) or rs1800541 G allele (GG/GT vs. TT) protected against DKD (OR = 0.69, 95 % CI 0.48-0.99, P = 0.049; and OR = 0.60, 95 % CI 0.41-0.88, P = 0.009, respectively). However in multivariate analyses, only the rs1800541 G allele remained independently associated with DKD (P = 0.046).

CONCLUSIONS

The present study shows that ET-1 could be involved in the pathogenesis of DKD in patients with T2DM.

The role of genetic risk factors in coronary artery disease

Genome-wide association studies for coronary artery disease utilizing the case control association study approach has identified 50 genetic risk variants associated with coronary artery disease or myocardial infarction. All of these genetic variants are of genome wide significance and replicated in an independent population. It is of note that 35 of these 50 genetic risk variants act through mechanisms as yet unknown. These findings have great implications for the pathogenesis of atherosclerosis, as well as new targets for the development of novel therapies for the prevention and treatment of CAD. The genetic variant PCSK9 has already led to the development of a monoclonal anti-body which is undergoing assessment in phases I, II, and III clinical trials. This therapy shows very promising results and since it increases removal of LDL-C, it is complementary to current statin therapy. Assessing the beneficial or deleterious effects of a lifelong exposure to a genetic risk variant (Mendelian randomization) will be an important adjunct to clinical trials.

Endothelin-1 gene polymorphisms influence cerebrospinal fluid endothelin-1 levels following aneurysmal subarachnoid hemorrhage

Aneurysmal subarachnoid hemorrhage is a type of stroke with high morbidity and mortality. Increased endothelin-1 (ET-1) levels have been associated with increased risk of cerebral vasospasm, which is associated with increased morbidity. The purpose of this study was to investigate the relationships between ET-1 genotypes and ET-1 protein levels in cerebrospinal fluid (CSF) measured 72 hr before angiographic vasospasm measurement in subjects at high risk of cerebral vasospasm. Specifically, this study evaluated the differences between variant positive and variant negative groups of nine different ET-1 single-nucleotide polymorphisms (SNPs) in relationship with the ET-1 protein exposure rate. The CSF ET-1 protein levels were quantified using enzyme-linked immunosorbent assay. One functional SNP and eight ET-1 tagging SNPs were selected because they represent genetic variability in the entire ET-1 gene. The variant negative group of SNP rs2070699 was associated with a significantly higher ET-1 exposure rate than the variant positive group (p = 0.004), while the variant positive group of the rs5370 group showed a trend toward association with a higher ET-1 exposure rate (p = 0.051). Other SNPs were not informative. This is the first study to show differences in ET-1 exposure rate 72 hr before angiography in relation to ET-1 genotypes. These exploratory findings need to be replicated in a larger study; if replicated, these differences in genotypes may be a way to inform clinicians of those patients at a higher risk of increased ET-1 protein levels, which may lead to a higher risk of angiographic vasospasm.

Gene-based sequencing identifies lipid-influencing variants with ethnicity-specific effects in African Americans

Although a considerable proportion of serum lipids loci identified in European ancestry individuals (EA) replicate in African Americans (AA), interethnic differences in the distribution of serum lipids suggest that some genetic determinants differ by ethnicity. We conducted a comprehensive evaluation of five lipid candidate genes to identify variants with ethnicity-specific effects. We sequenced ABCA1, LCAT, LPL, PON1, and SERPINE1 in 48 AA individuals with extreme serum lipid concentrations (high HDLC/low TG or low HDLC/high TG). Identified variants were genotyped in the full population-based sample of AA (n = 1694) and tested for an association with serum lipids. rs328 (LPL) and correlated variants were associated with higher HDLC and lower TG. Interestingly, a stronger effect was observed on a "European" vs. "African" genetic background at this locus. To investigate this effect, we evaluated the region among West Africans (WA). For TG, the effect size among WA was the same in AA with only African local ancestry (2-3% lower TG), while the larger association among AA with local European ancestry matched previous reports in EA (10%). For HDLC, there was no association with rs328 in AA with only African local ancestry or in WA, while the association among AA with European local ancestry was much greater than what has been observed for EA (15 vs. ∼ 5 mg/dl), suggesting an interaction with an environmental or genetic factor that differs by ethnicity. Beyond this ancestry effect, the importance of African ancestry-focused, sequence-based work was also highlighted by serum lipid associations of variants that were in higher frequency (or present only) among those of African ancestry. By beginning our study with the sequence variation present in AA individuals, investigating local ancestry effects, and seeking replication in WA, we were able to comprehensively evaluate the role of a set of candidate genes in serum lipids in AA.

The protective effect of the obesity-associated rs9939609 A variant in fat mass- and obesity-associated gene on depression

Candidate gene and genome-wide association studies have not identified common variants, which are reliably associated with depression. The recent identification of obesity predisposing genes that are highly expressed in the brain raises the possibility of their genetic contribution to depression. As variation in the intron 1 of the fat mass- and obesity-associated (FTO) gene contributes to polygenic obesity, we assessed the possibility that FTO gene may contribute to depression in a cross-sectional multi-ethnic sample of 6561 depression cases and 21,932 controls selected from the EpiDREAM, INTERHEART, DeCC (depression case-control study) and Cohorte Lausannoise (CoLaus) studies. Major depression was defined according to DSM IV diagnostic criteria. Association analyses were performed under the additive genetic model. A meta-analysis of the four studies showed a significant inverse association between the obesity risk FTO rs9939609 A variant and depression (odds ratio=0.92 (0.89, 0.97), P=3 × 10(-4)) adjusted for age, sex, ethnicity/population structure and body-mass index (BMI) with no significant between-study heterogeneity (I(2)=0%, P=0.63). The FTO rs9939609 A variant was also associated with increased BMI in the four studies (β 0.30 (0.08, 0.51), P=0.0064) adjusted for age, sex and ethnicity/population structure. In conclusion, we provide the first evidence that the FTO rs9939609 A variant may be associated with a lower risk of depression independently of its effect on BMI. This study highlights the potential importance of obesity predisposing genes on depression.

Genetic variance in nitric oxide synthase and endothelin genes among children with and without endothelial dysfunction

Background

The presence of endothelial dysfunction (ED) constitutes an early risk factor for cardiovascular disease (CVD) in children. Nitric oxide (NO) and endothelin (EDN) are generated in endothelial cells and are critical regulators of vascular function, with ED resulting from an imbalance between these two molecules. We hypothesized that genetic variants in NO synthase and EDN isoforms and its receptors (EDNRA and EDNRB) may account for a proportion of the risk for ED in developing children.

Methods

Consecutive children (ages 5–10 years) were prospectively recruited from the community. Time to peak post-occlusive reperfusion (Tmax) was considered as the indicator of either normal endothelial function (NEF; Tmax < 45 sec) or ED (Tmax ≥ 45 sec). Lipid profiles, high sensitivity C-reactive protein (hsCRP), fasting glucose and insulin were assayed using ELISA. Genomic DNA from peripheral blood was extracted and genotyped for NOS1 (209 SNPs), NOS2 (122 SNPs), NOS3 (50 SNPs), EDN1 (43 SNPs), EDN2 (48 SNPs), EDN3 (14 SNPs), EDNRA (27 SNPs), and EDNRB (23 SNPs) using a custom SNPs array. Linkage disequilibrium was analyzed using Haploview version 4.2 software.

Results

The relative frequencies of SNPs were evaluated in 122 children, 84 with NEF and 38 with ED. The frequencies of NOS1 (11 SNPs), and EDN1 (2 SNPs) were differentially distributed between NEF vs. ED, and no significant differences emerged for all other genes. Significant SNPs for NOS1 and EDN1 SNPs were further validated with RT-PCR.

Conclusions

Genetic variants in the NOS1 and EDN1 genes appear to account for important components of the variance in endothelial function, particularly when concurrent risk factors such as obesity exist. Thus, analysis of genotype-phenotype interactions in children at risk for ED will be critical for more accurate formulation of categorical CVD risk estimates.

Lecithin:cholesterol acyltransferase: old friend or foe in atherosclerosis?

Lecithin:cholesterol acyltransferase (LCAT) is a key enzyme that catalyzes the esterification of free cholesterol in plasma lipoproteins and plays a critical role in high-density lipoprotein (HDL) metabolism. Deficiency leads to accumulation of nascent preβ-HDL due to impaired maturation of HDL particles, whereas enhanced expression is associated with the formation of large, apoE-rich HDL(1) particles. In addition to its function in HDL metabolism, LCAT was believed to be an important driving force behind macrophage reverse cholesterol transport (RCT) and, therefore, has been a subject of great interest in cardiovascular research since its discovery in 1962. Although half a century has passed, the importance of LCAT for atheroprotection is still under intense debate. This review provides a comprehensive overview of the insights that have been gained in the past 50 years on the biochemistry of LCAT, the role of LCAT in lipoprotein metabolism and the pathogenesis of atherosclerosis in animal models, and its impact on cardiovascular disease in humans.

Association between adiponectin gene polymorphisms and coronary artery disease across different populations

OBJECTIVE

Many studies have suggested that adiponectin gene might be involved in the development of coronary artery disease (CAD). However, the results have been inconsistent. In this study, the authors performed a meta-analysis to assess the associations of +45T/G, +276G/T and -11377C/G polymorphisms in adiponectin gene with CAD susceptibility.

METHODS

Published literature from PubMed and EMBASE databases were searched. Pooled odds ratio (OR) and corresponding 95% confidence interval (CI) were calculated using fixed- or random-effects model.

RESULTS

Sixteen studies (4394 cases / 8187 controls) for +45T/G polymorphism, fifteen studies (3569 cases / 7463 controls) for +276G/T polymorphism, and thirteen studies (3531 cases / 7072 controls) for -11377C/G polymorphism were included in the meta-analysis. The overall results showed that there was a statistically significant association between -11377C/G polymorphism and CAD (G vs. C: OR=1.15, 95%CI 1.07-1.24).Similar results were observed among European (G vs. C: OR=1.11, 95%CI 1.02-1.20) and East Asian populations (G vs. C: OR=1.27, 95%CI 1.11-1.45). However, no significant association was found for +45T/G or +276G/T polymorphism with CAD susceptibility.

CONCLUSIONS

The meta-analysis indicated the significant association of -11377C/G polymorphism, but not +45T/G or +276G/T polymorphism, with CAD susceptibility. However, large-scale studies with the consideration of gene-gene and gene-environment interactions should be conducted to investigate the associations in future.

9p21 and the Genetic Revolution for Coronary Artery Disease

BACKGROUND

It has long been recognized that 50% of the susceptibility for coronary artery disease (CAD) is due to predisposing genetic factors. Comprehensive prevention is likely to require knowledge of these genetic factors.

CONTENT

Using a genomewide association study (GWAS), the Ottawa Heart Genomic Study and the deCODE group simultaneously identified the first genetic risk variant, at chromosome 9p21. The 9p21 variant became the first risk factor to be identified since 1964. 9p21 occurs in 75% of the population except for African Americans and is associated with a 25% increased risk for CAD with 1 copy and a 50% increased risk with 2 copies. Perhaps the most remarkable finding is that 9p21 is independent of all known risk factors, indicating there are factors contributing to the pathogenesis of CAD that are yet unknown. 9p21 in individuals with premature CAD is associated with a 2-fold increase in risk, similar to that of smoking and cholesterol. Routine genetic testing will probably remain controversial until a specific treatment is developed. Over a period of 5 years, however, GWASs have identified 30 genetic variants for CAD risk, of which only 6 act through the known risk factors.

SUMMARY

The 9p21 variant has now been established as an independent risk factor for CAD and, along with the additional 29 risk genetic variants recently identified, is likely to provide the thrust for genetic testing and personalized medicine in the near future.

Recent success in the discovery of coronary artery disease genes

For more than 50 years, epidemiological studies have indicated that genetic predisposition accounts for approximately 50% of the susceptibility to coronary artery disease (CAD) and its sequelae, including myocardial infarction. Since common diseases such as CAD are caused by multiple genes, the age-old method of linkage analysis used to map monogenic Mendelian disorders in families unfortunately lacks the required sensitivity. The technology to identify genes predisposing individuals to CAD and other common diseases did not become available until 2005. This technology provided computerized arrays containing hundreds of thousands of DNA markers in the form of single-nucleotide polymorphisms (SNPs). This made it possible to pursue an unbiased approach referred to as genome-wide association studies. The first gene for CAD was simultaneously identified by 2 independent groups in 2007. In a very short interval, a total of 23 loci were mapped that were linked to increased risk for CAD. The results of these studies confirm that CAD is caused by multiple genes, each contributing minimal risk. The most exciting and novel findings are that these loci do not act through known risk factors for CAD and that the loci are more likely to be in DNA regions that regulate transcription rather than being in coding regions for protein.

Arterial thrombus formation in cardiovascular disease

The pathogenesis of arterial thrombosis is complex and dynamic. Unlike venous thrombi, arterial thrombi typically form under conditions of high blood flow and are mainly composed of platelet aggregates, giving them the appearance of 'white clots'. Strong evidence suggests that arterial thrombi originate as a consequence of an injured atherosclerotic plaque, and that their formation involves the release of prothrombotic material (such as tissue factor), platelet aggregation, and platelet adhesion to the vascular wall. The initially labile platelet plaque is then stabilized by insoluble fibrin produced upon activation of the coagulation cascade. Inherited genetic factors (gene polymorphisms) and acquired predisposing conditions (such as the concentration and activity of clotting factors) can influence both the composition and the size of an arterial thrombus. Further research is needed to elucidate the functions of blood coagulation proteins and cellular elements that are critical to the pathogenesis of arterial thrombosis. This Review explains mechanisms of pathological arterial thrombus formation and discusses genetic and acquired risk factors of atherothrombosis.

Using evidence for population stratification bias in combined individual- and family-level genetic association analyses of quantitative traits

Genetic association studies are generally performed either by examining differences in the genotype distribution between individuals or by testing for preferential allele transmission within families. In the absence of population stratification bias (PSB), integrated analyses of individual and family data can increase power to identify susceptibility loci [Abecasis et al., 2000. Am. J. Hum. Genet. 66:279-292; Chen and Lin, 2008. Genet. Epidemiol. 32:520-527; Epstein et al., 2005. Am. J. Hum. Genet. 76:592-608]. In existing methods, the presence of PSB is initially assessed by comparing results from between-individual and within-family analyses, and then combined analyses are performed only if no significant PSB is detected. However, this strategy requires specification of an arbitrary testing level alpha(PSB), typically 5%, to declare PSB significance. As a novel alternative, we propose to directly use the PSB evidence in weights that combine results from between-individual and within-family analyses. The weighted approach generalizes previous methods by using a continuous weighting function that depends only on the observed P-value instead of a binary weight that depends on alpha(PSB). Using simulations, we demonstrate that for quantitative trait analysis, the weighted approach provides a good compromise between type I error control and power to detect association in studies with few genotyped markers and limited information regarding population structure.

Fine Mapping of the Insulin-Induced Gene 2 Identifies a Variant Associated With LDL Cholesterol and Total Apolipoprotein B Levels

Background—

In a whole-genome scan, a single nucleotide polymorphism (SNP) (rs7566605) upstream of the insulin-induced gene 2 ( INSIG2 ) was shown to influence body mass index and obesity in the Framingham Heart Study, with replication of these results in an additional 4 of 5 studies. However, other studies could not replicate the association. Because INSIG2 plays an important role in cholesterol biosynthesis, we hypothesized that human INSIG2 variants might play a role in the regulation of plasma lipid and lipoprotein levels.

Methods and Results—

We selected tagging SNPs spanning >100 kb of INSIG2 locus and sequenced 18 434 base pairs to discover novel SNPs. Thirty-two SNPs were genotyped in 645 individuals from the Quebec Family Study. Two SNPs (rs10490626 and rs12464355) were associated with plasma low-density lipoprotein cholesterol (LDL-C) ( P <0.0015) and total apolipoprotein B (apoB) levels ( P <0.014), whereas no association was found between any SNP and body mass index. We replicated the finding of rs10490626 for both LDL-C and total apoB in additional study samples, including 758 individuals from Saguenay–Lac St. Jean, Quebec ( P =0.040 for LDL-C, P =0.044 for apoB), 3247 Europeans ( P =0.028 for LDL-C, P =0.030 for apoB), and 1695 South Asians ( P =0.0036 for LDL-C, P =0.034 for apoB) from the INTERHEART study (for LDL-C, the combined 2-sided P =6.2×10 −5 and for total apoB, P =0.0011). Furthermore, we identified a variant in the human sorbin and SH 3 -domain–containing-1 gene that was associated with INSIG2 mRNA levels, and this SNP was shown to act in combination with rs10490626 to affect LDL-C ( P =0.022) in the Quebec Family Study and in INTERHEART South Asians ( P =0.019) and Europeans ( P =0.052).

Conclusion—

These results suggest that INSIG2 genetic variants may have a more direct role in lipid and lipoprotein metabolism than in obesity.

Genetic causes of high and low serum HDL-cholesterol

Plasma levels of HDL cholesterol (HDL-C) have a strong inherited basis with heritability estimates of 40-60%. The well-established inverse relationship between plasma HDL-C levels and the risk of coronary artery disease (CAD) has led to an extensive search for genetic factors influencing HDL-C concentrations. Over the past 30 years, candidate gene, genome-wide linkage, and most recently genome-wide association (GWA) studies have identified several genetic variations for plasma HDL-C levels. However, the functional role of several of these variants remains unknown, and they do not always correlate with CAD. In this review, we will first summarize what is known about HDL metabolism, monogenic disorders associated with both low and high HDL-C levels, and candidate gene studies. Then we will focus this review on recent genetic findings from the GWA studies and future strategies to elucidate the remaining substantial proportion of HDL-C heritability. Comprehensive investigation of the genetic factors conferring to low and high HDL-C levels using integrative approaches is important to unravel novel pathways and their relations to CAD, so that more effective means of diagnosis, treatment, and prevention will be identified.

Patterns of linkage disequilibrium in different populations: implications and opportunities for lipid-associated loci identified from genome-wide association studies

PURPOSE OF REVIEW

Genome-wide association studies across numerous populations have uncovered a remarkable number of loci implicated with lipid-related traits. The association signals at a number of these loci have been successfully replicated across multiple populations, but a fraction failed to be reproduced when tested in other populations. The present review examines the patterns of linkage disequilibrium at these lipid-associated loci and the implications to replication studies, meta-analyses and fine-mapping efforts across multiple populations.

RECENT FINDINGS

The extent of linkage disequilibrium has been well established to differ across populations, particularly between African and non-African groups. A novel strategy has been developed for assessing interpopulation variations in regional patterns of linkage disequilibrium. This approach has been applied to the genomes of populations in public databases, identifying regions where linkage disequilibrium is considerably different, some of which exist in regions associated with phenotypic variation. It has been shown that such diversity in linkage disequilibrium can challenge replication studies and meta-analyses while benefiting the pursuit for the functional variants in fine-mapping studies.

SUMMARY

The next phases in genome-wide studies aim to reproduce the emerging association signals across different populations and to identify the functional variants directly responsible for these signals. Recent publications are beginning to yield valuable insights into the unique challenges and opportunities presented by both consistent and varying patterns of linkage disequilibrium in these follow-up phases.

Genome-wide association studies of hypertension: have they been fruitful?

Over the last two decades candidate gene association studies and genome-wide linkage scans have met with little success in characterizing risk variants for hypertension. Several factors could be responsible for the relative lack of success, although our understanding of the genetics has evolved to support the belief that there are multiple common risk variants, which are associated with hypertension with modest effect sizes. Genome-wide association studies (GWAS) have successfully identified risk loci for several complex polygenic disease states. Until recently, the productivity of GWAS with respect to identifying risk loci for hypertension was limited. In this paper we describe the recent success of GWAS of hypertension in identifying over a dozen loci associated with essential hypertension. We will review these findings, and place these results in the context of the future potential of pharmocogenetics of hypertension.

Plasma levels of lecithin:cholesterol acyltransferase and risk of future coronary artery disease in apparently healthy men and women: a prospective case-control analysis nested in the EPIC-Norfolk population study

LCAT plays a key role in the maturation of HDL, as evidenced by low HDL-cholesterol levels in carriers of deleterious mutations in LCAT. However, the role of LCAT in atherosclerosis is unclear. We set out to study this in a prospective study. Plasma LCAT levels, which strongly correlate with LCAT activity, were measured in baseline nonfasting samples of 933 apparently healthy men and women who developed coronary artery disease (CAD) and 1,852 matched controls who remained free of CAD during 6 year follow-up. LCAT levels did not differ between cases and controls but were higher in women than men. Stratification into LCAT quartiles revealed a positive association with plasma LDL-cholesterol and triglyceride levels in the unexpected absence of an association with HDL-cholesterol. In mixed-gender analyses, the odds ratio (OR) for future CAD in the highest LCAT quartile versus the lowest was 1.00 [confidence interval (CI): 0.76-1.29, P for linearity = 0.902], although opposite trends were observed in men and women. In fact, high LCAT levels were associated with an increased CAD risk in women (unadjusted OR 1.45, CI: 0.94-2.22, P for linearity = 0.036). In contrast to our studies in carriers of LCAT mutations, the current data show that low LCAT plasma levels are not associated with increased atherosclerosis in the general population.

No evidence of an association between two genes, EDN1 and ACE, and childhood-onset mood disorders

Recent evidence supports a pathological link between heart disease and depressive symptoms, suggesting that depression is both etiologic and prognostic to heart disease. Thus, biological molecules which are at the interface between heart and mind are plausible candidate genes for depressive disorders. To investigate this line of enquiry we have investigated two genes, Endothelin 1 (EDN1) and Angiotensin-converting enzyme (ACE) in a family-based sample with childhood-onset mood disorders (COMDs). EDN1 is highly expressed in endothelium where it acts as a potent vasoconstrictor, and is also expressed in the brain where it exhibits neurotransmitter characteristics. ACE acts as a potent vasopressor, and interacts with the hypothalamic-pituitary-adrenocortical (HPA) system, which is often dysregulated in mood disorders. Furthermore, ACE has recently been found to be associated with major depression. Polymorphisms were selected to best capture the genetic variation at the two loci, and to replicate previous associations. The markers were genotyped across EDN1 and ACE in a sample comprised of 382 Hungarian nuclear families ascertained through affected probands diagnosed with a mood disorders before the age of 15. We found no evidence of association between either of these genes and COMD. Consequently, we were unable to support our hypothesis that these two genes, which are involved in both vascular and brain functions are contributing to the susceptibility to mood disorders of children/adolescents.

Genome scan for loci regulating HDL cholesterol levels in Finnish extended pedigrees with early coronary heart disease

Coronary heart disease (CHD) is the leading cause of mortality in Western societies. Its risk is inversely correlated with plasma high-density lipoprotein cholesterol (HDL-C) levels, and approximately 50% of the variability in these levels is genetically determined. In this study, the aim was to carry out a whole-genome scan for the loci regulating plasma HDL-C levels in 35 well-defined Finnish extended pedigrees (375 members genotyped) with probands having low HDL-C levels and premature CHD. The additive genetic heritability of HDL-C was 43%. A variance component analysis revealed four suggestive quantitative trait loci (QTLs) for HDL-C levels, with the highest LOD score, 3.1, at the chromosomal locus 4p12. Other suggestive LOD scores were 2.1 at 2q33, 2.1 at 6p24 and 2.0 at 17q25. Three suggestive loci for the qualitative low HDL-C trait were found, with a nonparametric multipoint score of 2.6 at the chromosomal locus 10p15.3, 2.5 at 22q11 and 2.1 at 6p12. After correction for statin use, the strongest evidence of linkage was shown on chromosomes 4p12, 6p24, 6p12, 15q22 and 22q11. To search for the underlying gene on chromosome 6, we analyzed two functional and positional candidate genes (peroxisome proliferator-activated receptor-delta (PPARD), and retinoid X receptor beta, (RXRB)), but found no significant evidence of association. In conclusion, we identified seven chromosomal regions for HDL-C regulation exceeding the level for suggestive evidence of linkage.

Genomic view of factors leading to plaque instability

The manifestations of coronary artery disease are varied. They all arise as a consequence of the deposition of atherosclerotic plaque within the vessel wall. The most feared sequela of coronary artery disease is sudden and unexpected death in the ostensibly healthy patient. Plaque rupture of hemodynamically insignificant atherosclerotic plaques and ensuing thrombosis is likely responsible for a large proportion of such deaths. Identifying populations at increased risk for sudden death would represent a major advance. Such screening is contingent upon identification of DNA sequence variants that predispose individuals to plaque rupture. Phenotyping is not sufficiently nuanced to detect such variants on a large scale, so we are limited to end points that are crude surrogates for plaque rupture. As imaging modalities are refined and our ability to recruit large numbers of appropriate patients is facilitated by the formation of alliances, our ability to probe this conundrum via a genome-wide approach will improve.

Lack of association between endothelin-1 gene variants and myocardial infarction

AIM

Endothelin-1 (ET-1) promotes vasoconstriction and cell proliferation, and has been implicated in hypertension and coronary artery disease. Our aim was to analyse the role of the ET-1 gene (EDN1) in the risk for atherosclerosis/myocardial infarction (MI) in a population with smoking as the prevalent risk factor.

METHODS

The study included 316 patients with early onset MI (<55 years old). All were male with at least one diseased coronary vessel. Denaturing high performance liquid chromatography (DHPLC), single-strand conformation analysis (SSCA), and direct sequencing were used to search for DNA variants in the five EDN1 exons and the promoter region. To determine the association of EDN1 polymorphisms with MI, we genotyped the patients and controls (n=350) and compared the allele and genotype frequencies between groups.

RESULTS

We found six common nucleotide changes: -1394 (T/G) and -974 C/A (promoter), +120 ins/del A (exon 1, 5' UTR), 568 A/G (exon 3, E106E), 844 G/T (exon 5, K198N), and 1617 T/C (exon 5, 3' UTR). No rare EDN1-variants specific to the MIpatients were found. None of the EDN1 polymorphisms were significantly associated with early-onset MI in our population. The two promoter polymorphisms were in linkage disequilibrium with K198N, but no haplotype was associated with MI risk.

CONCLUSIONS

In our population, the EDN1 variation did not contribute to early-onset MI.

Genetic Loci associated with C-reactive protein levels and risk of coronary heart disease

CONTEXT

Plasma levels of C-reactive protein (CRP) are independently associated with risk of coronary heart disease, but whether CRP is causally associated with coronary heart disease or merely a marker of underlying atherosclerosis is uncertain.

OBJECTIVE

To investigate association of genetic loci with CRP levels and risk of coronary heart disease.

DESIGN, SETTING, AND PARTICIPANTS

We first carried out a genome-wide association (n = 17,967) and replication study (n = 13,615) to identify genetic loci associated with plasma CRP concentrations. Data collection took place between 1989 and 2008 and genotyping between 2003 and 2008. We carried out a mendelian randomization study of the most closely associated single-nucleotide polymorphism (SNP) in the CRP locus and published data on other CRP variants involving a total of 28,112 cases and 100,823 controls, to investigate the association of CRP variants with coronary heart disease. We compared our finding with that predicted from meta-analysis of observational studies of CRP levels and risk of coronary heart disease. For the other loci associated with CRP levels, we selected the most closely associated SNP for testing against coronary heart disease among 14,365 cases and 32,069 controls.

MAIN OUTCOME MEASURE

Risk of coronary heart disease.

RESULTS

Polymorphisms in 5 genetic loci were strongly associated with CRP levels (% difference per minor allele): SNP rs6700896 in LEPR (-14.8%; 95% confidence interval [CI], -17.6% to -12.0%; P = 6.2 x 10(-22)), rs4537545 in IL6R (-11.5%; 95% CI, -14.4% to -8.5%; P = 1.3 x 10(-12)), rs7553007 in the CRP locus (-20.7%; 95% CI, -23.4% to -17.9%; P = 1.3 x 10(-38)), rs1183910 in HNF1A (-13.8%; 95% CI, -16.6% to -10.9%; P = 1.9 x 10(-18)), and rs4420638 in APOE-CI-CII (-21.8%; 95% CI, -25.3% to -18.1%; P = 8.1 x 10(-26)). Association of SNP rs7553007 in the CRP locus with coronary heart disease gave an odds ratio (OR) of 0.98 (95% CI, 0.94 to 1.01) per 20% lower CRP level. Our mendelian randomization study of variants in the CRP locus showed no association with coronary heart disease: OR, 1.00; 95% CI, 0.97 to 1.02; per 20% lower CRP level, compared with OR, 0.94; 95% CI, 0.94 to 0.95; predicted from meta-analysis of the observational studies of CRP levels and coronary heart disease (z score, -3.45; P < .001). SNPs rs6700896 in LEPR (OR, 1.06; 95% CI, 1.02 to 1.09; per minor allele), rs4537545 in IL6R (OR, 0.94; 95% CI, 0.91 to 0.97), and rs4420638 in the APOE-CI-CII cluster (OR, 1.16; 95% CI, 1.12 to 1.21) were all associated with risk of coronary heart disease.

CONCLUSION

The lack of concordance between the effect on coronary heart disease risk of CRP genotypes and CRP levels argues against a causal association of CRP with coronary heart disease.

Lecithin: cholesterol acyltransferase--from biochemistry to role in cardiovascular disease

PURPOSE OF REVIEW

We discuss the latest findings on the biochemistry of lecithin : cholesterol acyltransferase (LCAT), the effect of LCAT on atherosclerosis, clinical features of LCAT deficiency, and the impact of LCAT on cardiovascular disease from human studies.

RECENT FINDINGS

Although there has been much recent progress in the biochemistry of LCAT and its effect on high-density lipoprotein metabolism, its role in the pathogenesis of atherosclerosis is still not fully understood. Studies from various animal models have revealed a complex interaction between LCAT and atherosclerosis that may be modified by diet and by other proteins that modify lipoproteins. Furthermore, the ability of LCAT to lower apoB appears to be the best way to predict its effect on atherosclerosis in animal models. Recent studies on patients with LCAT deficiency have shown a modest but significant increase in incidence of cardiovascular disease consistent with a beneficial effect of LCAT on atherosclerosis. The role of LCAT in the general population, however, has not revealed a consistent association with cardiovascular disease.

SUMMARY

Recent research findings from animal and human studies have revealed a potential beneficial role of LCAT in reducing atherosclerosis but additional studies are necessary to better establish the linkage between LCAT and cardiovascular disease.

Genetic Variants Associated With Myocardial Infarction Risk Factors in Over 8000 Individuals From Five Ethnic Groups

Background— Myocardial infarction (MI) is a leading cause of death globally, but specific genetic variants that influence MI and MI risk factors have not been assessed on a global basis.

Methods and Results— We included 8795 individuals of European, South Asian, Arab, Iranian, and Nepalese origin from the INTERHEART case-control study that genotyped 1536 single-nucleotide polymorphisms (SNPs) from 103 genes. One hundred and two SNPs were nominally associated with MI, but the statistical significance did not remain after adjustment for multiple testing. A subset of 940 SNPs from 69 genes were tested against MI risk factors. One hundred and sixty-three SNPs were nominally associated with a MI risk factor and 13 remained significant after adjusting for multiple testing. Of these 13, 11 were associated with apolipoprotein (Apo) B/A1 levels: 8 SNPs from 3 genes were associated with Apo B, and 3 cholesteryl ester transfer protein SNPs were associated with Apo A1. Seven of 8 of the SNPs associated with Apo B levels were nominally associated with MI ( P <0.05), whereas none of the 3 cholesteryl ester transfer protein SNPs were associated with MI ( P ≥0.17). Of the 3 SNPs most significantly associated with MI, rs7412, which defines the Apo E2 isoform, was associated with both a lower Apo B/A1 ratio ( P =1.0�10 −7 ) and lower MI risk ( P =0.0004). Two low-density lipoprotein receptor variants, 1 intronic (rs6511720) and 1 in the 3′ untranslated region (rs1433099) were both associated with a lower Apo B/A1 ratio ( P <1.0�10 −5 ) and a lower risk of MI ( P =0.004 and P =0.003, respectively).

Conclusions— Thirteen common SNPs were associated with MI risk factors. Importantly, SNPs associated with Apo B levels were associated with MI, whereas SNPs associated with Apo A1 levels were not. The Apo E isoform, and 2 common low-density lipoprotein receptor variants (rs1433099 and rs6511720) influence MI risk in this multiethnic sample.

CANDID: a flexible method for prioritizing candidate genes for complex human traits

Genomewide studies and localized candidate gene approaches have become everyday study designs for identifying polymorphisms in genes that influence complex human traits. Yet, in general, the number of significant findings and the need to focus on smaller regions require a prioritization of genes for further study. Some candidate gene identification algorithms have been proposed in recent years to attempt to streamline this prioritization, but many suffer from limitations imposed by the source data or are difficult to use and understand. CANDID is a prioritization algorithm designed to produce impartial, accurate rankings of candidate genes that influence complex human traits. CANDID can use information from publications, protein domain descriptions, cross-species conservation measures, gene expression profiles and protein-protein interactions in its analysis. Additionally, users may supplement these data sources with results from linkage, association and other studies. CANDID was tested on well-known complex trait genes using data from the Online Mendelian Inheritance in Man database. Additionally, CANDID was evaluated in a modeled gene discovery environment, where it ranked genes whose trait associations were published after CANDID's databases were compiled. In all settings, CANDID exhibited high sensitivity and specificity, indicating an improvement upon previously published algorithms. Its accuracy and ease of use make CANDID a highly useful tool in study design and analysis for complex human traits.

Common variants at 30 loci contribute to polygenic dyslipidemia

Blood low-density lipoprotein (LDL) cholesterol, high-density lipoprotein (HDL) cholesterol and triglyceride levels are risk factors for cardiovascular disease. To dissect the polygenic basis of these traits, we conducted genome-wide association screens in 19,840 individuals and replication in up to 20,623 individuals. We identified 30 distinct loci associated with lipoprotein concentrations (each with P < 5 x 10(-8)), including 11 loci that reached genome-wide significance for the first time. The 11 newly defined loci include common variants associated with LDL cholesterol near ABCG8, MAFB, HNF1A and TIMD4; with HDL cholesterol near ANGPTL4, FADS1-FADS2-FADS3, HNF4A, LCAT, PLTP and TTC39B; and with triglycerides near AMAC1L2, FADS1-FADS2-FADS3 and PLTP. The proportion of individuals exceeding clinical cut points for high LDL cholesterol, low HDL cholesterol and high triglycerides varied according to an allelic dosage score (P < 10(-15) for each trend). These results suggest that the cumulative effect of multiple common variants contributes to polygenic dyslipidemia.

Genetic-epidemiological evidence on genes associated with HDL cholesterol levels: a systematic in-depth review

High-density lipoprotein (HDL) particles exhibit multiple antiatherogenic effects. They are key players in the reverse cholesterol transport which shuttles cholesterol from peripheral cells (e.g. macrophages) to the liver or other tissues. This complex process is thought to represent the basis for the antiatherogenic properties of HDL particles. The amount of cholesterol transported in HDL particles is measured as HDL cholesterol (HDLC) and is inversely correlated with the risk for coronary artery disease: an increase of 1mg/dL of HDLC levels is associated with a 2% and 3% decrease of the risk for coronary artery disease in men and women, respectively. Genetically determined conditions with high HDLC levels (e.g. familial hyperalphalipoproteinemia) often coexist with longevity, and higher HDLC levels were found among healthy elderly individuals. HDLC levels are under considerable genetic control with heritability estimates of up to 80%. The identification and characterization of genetic variants associated with HDLC concentrations can provide new insights into the background of longevity. This review provides an extended overview on the current genetic-epidemiological evidence from association studies on genes involved in HDLC metabolism. It provides a path through the jungle of association studies which are sometimes confusing due to the varying and sometimes erroneous names of genetic variants, positions and directions of associations. Furthermore, it reviews the recent findings from genome-wide association studies which have identified new genes influencing HDLC levels. The yet identified genes together explain only a small amount of less than 10% of the HDLC variance, which leaves an enormous room for further yet to be identified genetic variants. This might be accomplished by large population-based genome-wide meta-analyses and by deep-sequencing approaches on the identified genes. The resulting findings will probably result in a re-drawing and extension of the involved metabolic pathways of HDLC metabolism.

Gender differences in genetic risk profiles for cardiovascular disease

BACKGROUND

Cardiovascular disease (CVD) incidence, complications and burden differ markedly between women and men. Although there is variation in the distribution of lifestyle factors between the genders, they do not fully explain the differences in CVD incidence and suggest the existence of gender-specific genetic risk factors. We aimed to estimate whether the genetic risk profiles of coronary heart disease (CHD), ischemic stroke and the composite end-point of CVD differ between the genders.

METHODOLOGY/PRINCIPAL FINDINGS

We studied in two Finnish population cohorts, using the case-cohort design the association between common variation in 46 candidate genes and CHD, ischemic stroke, CVD, and CVD-related quantitative risk factors. We analyzed men and women jointly and also conducted genotype-gender interaction analysis. Several allelic variants conferred disease risk for men and women jointly, including rs1801020 in coagulation factor XII (HR = 1.31 (1.08-1.60) for CVD, uncorrected p = 0.006 multiplicative model). Variant rs11673407 in the fucosyltransferase 3 gene was strongly associated with waist/hip ratio (uncorrected p = 0.00005) in joint analysis. In interaction analysis we found statistical evidence of variant-gender interaction conferring risk of CHD and CVD: rs3742264 in the carboxypeptidase B2 gene, p(interaction) = 0.009 for CHD, and rs2774279 in the upstream stimulatory factor 1 gene, p(interaction) = 0.007 for CHD and CVD, showed strong association in women but not in men, while rs2069840 in interleukin 6 gene, p(interaction) = 0.004 for CVD, showed strong association in men but not in women (uncorrected p-values). Also, two variants in the selenoprotein S gene conferred risk for ischemic stroke in women, p(interaction) = 0.003 and 0.007. Importantly, we identified a larger number of gender-specific effects for women than for men.

CONCLUSIONS/SIGNIFICANCE

A false discovery rate analysis suggests that we may expect half of the reported findings for combined gender analysis to be true positives, while at least third of the reported genotype-gender interaction results are true positives. The asymmetry in positive findings between the genders could imply that genetic risk loci for CVD are more readily detectable in women, while for men they are more confounded by environmental/lifestyle risk factors. The possible differences in genetic risk profiles between the genders should be addressed in more detail in genetic studies of CVD, and more focus on female CVD risk is also warranted in genome-wide association studies.

Genetics of premature myocardial infarction

Common multigene disorders account for 80% of deaths in the world and all have significant genetic predisposition. Coronary artery disease and myocardial infarction (MI) account for more than 40% of these deaths. The genetic component is due to multiple genes, each contributing only minimally to the phenotype. Linkage analysis, which has been successful in identifying rare disorders that cause MI, is not sensitive for multigene disorders. The recent candidate case-control approach has been equally unsuccessful. Multigene disorders require genome-wide association studies involving genotyping hundreds of thousands of DNA markers in thousands of individuals with replication in independent populations. Platforms with 500,000 and 1 million single nucleotide polymorphisms provide the necessary high-throughput genotyping for genome-wide association. The first confirmed common locus, 9p21, is independent of conventional risk factors. Identifying the 9p21 gene will elucidate novel mechanisms responsible for MI. Comprehensive prevention of MI based on individual genetic variants (personalized medicine) is expected in the next decade.