Genetic polymorphisms, lipoproteins and coronary artery disease risk

Association studies between gene variants (polymorphisms) and measured intermediate phenotypes, such as lipid/lipoprotein levels, or disease endpoints such as coronary artery disease, are commonplace in the literature. But have we learnt anything from the shortcomings in study design and analytical strategies that have resulted in much controversy in this field over the last few years? This review highlights some of these problems. Using the lipoprotein lipase gene as an example, we evaluate new approaches to identifying polymorphisms that will stand up to linkage disequilibrium/association studies with complex disorders in this post Human Genome Project age, and emphasize the importance of gene-environment interaction in assessing the impact of gene variants.     

The ethnicity-specific association of biomarkers with the angiographic severity of coronary artery disease

Background

Risk factor burden and clinical characteristics of patients with coronary artery disease (CAD) differ among ethnic groups. We related biomarkers to CAD severity in Caucasians, Chinese, Indians and Malays.

Methods

In the Dutch-Singaporean UNICORN coronary angiography cohort (n = 2033) we compared levels of five cardiovascular biomarkers: N-terminal pro-brain natriuretic peptide (NTproBNP), high-sensitivity C-reactive protein (hsCRP), cystatin C (CysC), myeloperoxidase (MPO) and high-sensitivity troponin I (hsTnI). We assessed ethnicity-specific associations of biomarkers with CAD severity, quantified by the SYNTAX score.

Results

Adjusted for baseline differences, NTproBNP levels were significantly higher in Malays than in Chinese and Caucasians (72.1 vs. 34.4 and 41.1 pmol/l, p < 0.001 and p = 0.005, respectively). MPO levels were higher in Caucasians than in Indians (32.8 vs. 27.2 ng/ml, p = 0.026), hsTnI levels were higher in Malays than in Caucasians and Indians (33.3 vs. 16.4 and 17.8 ng/l, p < 0.001 and p = 0.029) and hsTnI levels were higher in Chinese than in Caucasians (23.3 vs. 16.4, p = 0.031). We found modifying effects of ethnicity on the association of biomarkers with SYNTAX score. NTproBNP associated more strongly with the SYNTAX score in Malays than Caucasians (β 0.132 vs. β 0.020 per 100 pmol/l increase in NTproBNP, p = 0.032). For MPO levels the association was stronger in Malays than Caucasians (β 1.146 vs. β 0.016 per 10 ng/ml increase, p = 0.017). Differing biomarker cut-off levels were found for the ethnic groups.

Conclusion

When corrected for possible confounders we observe ethnicity-specific differences in biomarker levels. Moreover, biomarkers associated differently with CAD severity, suggesting that ethnicity-specific cut-off values should be considered.     

Association of male pattern baldness with angiographic coronary artery disease severity and collateral development

Objective

We aimed to investigate whether there is an association between male pattern baldness and angiographic coronary artery disease (CAD) severity and collateral development, which has not been reported previously.

Methods

Coronary arteriograms, CAD risk factors, lipid parameters and presence and severity of baldness in 511 male patients were prospectively evaluated. Baldness was classified into five groups. Severity of CAD was evaluated with the Gensini scoring system and collateral development with Rentrop scores.

Results

Although subjects with a higher Gensini score had more frequent and severe baldness, they were older than the group with lower Gensini scores. Bald patients had a higher Gensini score when compared with their non-bald counterparts. In univariate analysis, age more than 60, body mass index more than 30, smoking and baldness were predictors of high Gensini scores. In multivariate analysis, only age more than 60, body mass index more than 30 and smoking were independent predictors of a high Gensini score. There were no differences in terms of presence and severity of baldness in subjects with and without adequate collateral development.

Conclusions

There was no relation between presence, severity and age of occurrence of male pattern baldness and Gensini and Rentrop scores, which are important measures of presence and severity of CAD.     

Association between the severity of angiographic coronary artery disease and paraoxonase gene polymorphisms in the National Heart,Lung, and Blood Institute-sponsored Women's Ischemia Syndrome Evaluation (WISE) study

Paraoxonase (PON), a high-density lipoprotein-associated enzyme, is believed to protect against low-density lipoprotein oxidation and thus affects the risk of coronary artery disease (CAD). Three polymorphisms in the PON1 (Leu55Met and Gln192Arg) and PON2 (Ser311Cys) genes have been shown to be associated with the risk of CAD in several European or European-derived populations. In the present study, we examined the associations between these three markers and the severity of CAD as determined by the number of diseased coronary artery vessels in 711 subjects (589 whites and 122 blacks) from the Women's Ischemia Syndrome Evaluation (WISE) study. WISE is a National Heart, Lung, and Blood Institute-sponsored multicenter study designed to address issues related to ischemic-heart-disease recognition and diagnosis in women. Subjects were classified as having normal/minimal CAD (<20% stenosis), mild CAD (20%-49% stenosis), and significant CAD (>/=50% stenosis). The women who had >/=50% stenosis were further classified into groups with one-, two-, or three-vessel disease if any of the three coronary arteries had diameter stenosis >/=50%. No significant association was found between the PON polymorphisms and stenosis severity in either white or black women. However, among white women, when data were stratified by the number of diseased vessels, the frequency of the PON1 codon 192 Arg/Arg genotype was significantly higher in the group with three-vessel disease than in the other groups (those with one-vessel and two-vessel disease) combined (17.02% vs. 4.58%; P=.0066). Similarly, the frequency of the PON2 codon 311 Cys/Cys genotype was significantly higher in the group with three-vessel disease than in the other groups combined (15.22% vs. 4.61%; P=.018). The adjusted odds ratios for the development of three-vessel disease were 2.80 (95% confidence interval 1.06-7.37; P=.038) for PON1 codon 192 Arg/Arg and 3.68 (95% confidence interval 1.26-10.68; P=.017) for PON2 codon 311 Cys/Cys. Our data indicate that the severity of CAD, in terms of the number of diseased vessels, may be affected by common genetic variation in the PON gene cluster, on chromosome 7.     

Low-density lipoprotein-associated variables and the severity of coronary artery disease: an untreated Chinese cohort study

Abstract

Background and aims: Elevated low-density lipoprotein cholesterol (LDL-C) is causal risk for coronary artery disease (CAD) and LDL-associated variables including LDL-C, apolipoprotein B (apoB), non-high-density lipoprotein cholesterol (non-HDL-C), lipoprotein a [Lp(a)], small dense LDL (sd-LDL), and oxidized LDL (ox-LDL) have been widely used for predicting the risk of CAD. This study was aimed to compare the values of six LDL-related variables for predicting the severity of CAD using untreated patients undergoing coronary angiography (CAG).

Methods: A group of 1977 individuals were consecutively enrolled and divided into CAD (n?=?1151) and non-CAD groups (n?=?826) according to the results of CAG. LDL-C, apoB, non-HDL-C, Lp(a), sd-LDL and ox-LDL were measured, respectively. The numbers of stenotic arteries and Gensini Scores (GS) were used to calculate the severity of CAD and the associations of six variables with the severity of CAD and predicting value of these parameters were simultaneously examined.

Results: CAD patients had significantly higher concentrations of LDL-related variables than non-CAD ones (all p?<?0.05). Importantly, all variables rose with the increase in the severity of CAD. The predicting value of CAD manifested as sd-LDL?>?ox-LDL?>?apoB?>?non-HDL-C?>?LDL-C?>?Lp(a) [area under curve (AUC): sd-LDL 0.641; ox-LDL 0.640; apoB 0.611; non-HDL-C 0.587; LDL-C 0.583; Lp(a) 0.554; respectively]. In multivariate logistic analysis, all variables showed as independent risk factors for the severity of CAD [odds ratio (OR): ox-LDL?>?sd-LDL?>?apoB?>?non-HDL-C?>?LDL-C?>?Lp(a)].

Conclusions: All of LDL-related variables could be useful marker for predicting the severity of CAD but sd-LDL and ox-LDL appeared to litter better. Further study may be needed to validate our results.     

Association of NT-proBNP and multiple biomarkers with severity of angiographic coronary artery disease in diabetic and pre-diabetic Chinese patients

Background

Little is known about the plasma levels of N-terminal pro-brain natriuretic peptide (NT-proBNP), and the relationship between the severity of coronary heart disease (CHD) with NT-proBNP and multiple biomarkers in diabetic and pre-diabetic patients, compared to individuals with normal glucose levels.

Methods

Four hundred and fifteen consecutive Chinese patients of both sexes were assigned to three groups on the basis of the new hemoglobin (Hb) A1c (HbA1c) cut-off points for diagnosis of diabetes and pre-diabetes. The three groups were divided into tertiles according to NT-proBNP, hs-CRP, cystatin C, and troponin T levels. Gensini scores were compared among the three groups and biomarker tertiles. Receiver operating characteristic (ROC) curves were used to obtain the angiographic CHD cut-off points for each biomarker. Stepwise multivariate linear correlation analysis was applied to examine the association between the severity of CHD and biomarker levels.

Results

Gensini scores increased with increasing biomarker tertile levels and HbA1c. Gensini scores were significantly different in the middle and upper NT-proBNP tertiles of the diabetic, pre-diabetic and control groups. NT-proBNP had the highest positive and negative predictive values and area under the curve for CHD. Only NT-proBNP was identified as an independent variable for Gensini score.

Conclusions

Plasma NT-proBNP may be an important biomarker to evaluate the severity of CHD and screen for CHD in diabetic or pre-diabetic patients.     

Modification of coronary artery disease progression by cholesterol-lowering therapy: the angiographic studies

Large randomized placebo-controlled trials have demonstrated that cholesterol lowering with statin therapy reduces the incidence of adverse cardiac events. Smaller angiographic studies have shown that coronary artery disease progression can be slowed and, in some cases, reversed by cholesterol-lowering interventions. These anatomical changes, however, are small and occur too slowly to account for the early clinical benefit. Current evidence suggests that plaque stabilization is the most important mechanism, by which cholesterol-lowering therapy reduces both the incidence of adverse cardiac events and coronary artery disease progression.     

Relationship between serum high sensitivity C-reactive protein with angiographic severity of coronary artery disease and traditional cardiovascular risk factors

Serum high-sensitivity C-reactive protein (hs-CRP) is predictive of coronary artery disease (CAD). The aim of this study was to examine the possible association of hs-CRP with presence and severity of CAD and traditional CAD risk factors. This case-control study was carried out on 2,346 individuals from September 2011 to May 2013. Of these 1,187 had evidence of coronary disease, and were subject to coronary angiography, and the remainder were healthy controls (n = 1,159). Characteristics were determined using standard laboratory techniques and serum Hs-CRP levels were estimated using enzyme-linked immunosorbent assay (ELISA) kits, and severity of CAD was assessed according to the score of obstruction in coronary artery. Serum hs-CRP levels were higher in those with severe coronary disease, who had stenosis ≥ 50% stenosis of at least one coronary artery (all p < 0.001 vs. individuals in healthy control), and correlated significantly with the score for coronary artery disease (all p < 0.01). After adjustment for conventional risk factors, regression analysis revealed that smoking habits, fasting blood glucose, total cholesterol, high-density lipoprotein, hs-CRP, blood pressure, anxiety, dietary intake of vitamin E, and cholesterol remained as independent determinants for angiographic severity of CAD. The area under the receiving operating characteristic (ROC) curve for serum hs-CRP was 0.869 (CI 95% 0.721–0.872, p < 0.001). The optimal values for the cut-off point was a serum hs-CRP of 2.78 mg/l (sensitivity 80.20%, specificity 85%) to predict severity of CAD. Increased serum hs-CRP levels are significantly associated with angiographic severity of CAD, suggesting its value as a biomarkers for predicting CAD.     

ApoC-III gene polymorphisms and risk of coronary artery disease

Several polymorphisms in the apolipoprotein C-III (apoC-III) gene have been associated with hypertriglyceridemia, but the link with coronary artery disease risk is still controversial. In particular, apoC-III promoter sequence variants in the insulin responsive element (IRE), constitutively resistant to downregulation by insulin, have never been investigated in this connection. We studied a total of 800 patients, 549 of whom had angiographically documented coronary atherosclerosis, whereas 251 had normal coronary arteriograms. We measured plasma lipids, insulin, apoA-I, apoB, and apoC-III and assessed three polymorphisms in the apoC-III gene, namely, T-455C in the IRE promoter region, C1100T in exon 3, and Sst1 polymorphic site (S1/S2) in the 3' untranslated region. Each variant influenced triglyceride levels, but only the T-455C (in homozygosity) and S2 alleles influenced apoC-III levels. In coronary artery disease (CAD) patients, 18.6% were homozygous for the -455C variant compared with only 9.2% in CAD-free group (P < 0.001). In logistic regression models, homozygosity for -455C variant was associated with a significantly increased risk of CAD (OR = 2.5 and 2.18 for unadjusted and adjusted models, respectively) suggesting that it represents an independent genetic susceptibility factor for CAD.     

Fibroblast growth factor receptor 4 polymorphisms and coronary artery disease: a case control study

Fibroblast growth factors (FGFs) and their receptors (FGFRs) play important roles in vascular system. FGFR4 rs351855 (Gly388Arg) polymorphism has shown to be a risk factor for many diseases. The aim of this study was to investigate the association between FGFR4 polymorphisms and the susceptibility to coronary artery disease (CAD) in the Chinese population. We identified three polymorphisms in the FGFR4 gene, rs351855G/A (Gly388Arg), rs145302848C/G and rs147603016G/A, by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) in 658 CAD cases and 692 healthy controls. Results showed that frequencies of GA genotype, AA genotype and A allele in rs351855 (Gly388Arg) polymorphism were significantly lower in CAD patients than in controls [odds ratio (OR) = 0.79, 95 % confidence intervals (CI) 0.62-0.99, P = 0.042; OR = 0.58, 95 % CI 0.41-0.81, P = 0.002; and OR = 0.77, 95 % CI 0.66-0.90, P = 0.001, respectively]. The rs147603016GA genotype and A allele also showed lower numbers in CAD cases (OR = 0.58, 95 % CI 0.36-0.93, P = 0.025; and OR = 0.59, 95 % CI 0.40-0.95, P = 0.028). The rs145302848C/G polymorphism did not show any correlation with CAD. Haplotype analysis revealed that the prevalence of ACG haplotype (rs351855, rs145302848 and rs147603016) was significantly decreased in CAD patients (P = 0.002). Our data suggested that the FGFR4 rs351855G/A (Gly388Arg) and rs147603016G/A polymorphisms could act as protective factors against CAD in the Chinese population and indicated that a single gene polymorphism could have diverse functions in different diseases.     

Relation between extent of coronary artery disease and blood viscosity.

Blood viscosity (shear rate 100/s) and its major determinants (packed cell volume, plasma fibrinogen concentration, and plasma viscosity) were measured before coronary angiography in 50 men aged 30-55 and related to the extent of coronary artery disease. Twenty-six men had extensive disease (stenosis of two or three major coronary vessels), and 24 had either stenosis of one vessel or no stenosis. The 26 men with extensive disease had significantly higher mean blood viscosity than those with mild or no disease and 25 healthy controls (p less than 0.001). The increased viscosity was due partly to a higher packed cell volume and partly to a higher fibrinogen concentration; plasma viscosity was not significantly increased. These differences could not be explained by smoking history. These results suggest an association between increased blood viscosity and extensive coronary artery disease in men, which merits further investigation.     

Genetic effects on obesity assessed by bivariate genome scan: the Mexican-American coronary artery disease study

Objective: To identify the genetic determinants of obesity using univariate and bivariate models in a genome scan. Research Methods and Procedures: We evaluated the genetic and environmental effects and performed a genome‐wide linkage analysis of obesity‐related traits in 478 subjects from 105 Mexican‐American nuclear families ascertained through a proband with documented coronary artery disease. The available obesity traits include BMI, body surface area (BSA), waist‐to‐hip ratio (WHR), and trunk fat mass as percentage of body weight. Heritability estimates and multipoint linkage analysis were performed using a variance components procedure implemented in SOLAR software. Results: The heritability estimates were 0.62 for BMI, 0.73 for BSA, 0.40 for WHR, and 0.38 for trunk fat mass as percentage of body weight. Using a bivariate genetic model, we observed significant genetic correlations between BMI and other obesity‐related traits (all p < 0.01). Evidence for univariate linkage was observed at 252 to approximately 267 cM on chromosome 2 for three obesity‐related traits (except for WHR) and at 163 to approximately 167 cM on chromosome 5 for BMI and BSA, with the maximum logarithm of the odds ratio score of 3.12 (empirical p value, 0.002) for BSA on chromosome 2. Use of the bivariate linkage model yielded an additional peak (logarithm of the odds ratio = 3.25, empirical p value, 0.002) at 25 cM on chromosome 7 for the pair of BMI and BSA. Discussion: The evidence for linkage on chromosomes 2q36‐37 and 5q36 is supported both by univariate and bivariate analysis, and an additional linkage peak at 7p15 was identified by the bivariate model. This suggests that use of the bivariate model provides additional information to identify linkage of genes responsible for obesity‐related traits.     

Association between interleukin-16 polymorphisms and risk of coronary artery disease

Growing evidence has shown that inflammation plays crucial roles in the development of coronary artery disease (CAD). Interleukin-16 (IL-16), a multifunctional cytokine, is involved in a series of inflammatory disorders. The aim of this study was to investigate the association between IL-16 polymorphisms and risk of CAD. We analyzed two polymorphisms of IL-16 (rs4778889 T/C and rs11556218 T/G) in 157 patients with CAD and 202 healthy controls by using polymerase chain reaction-restriction fragment length polymorphism and DNA sequencing methods. The TG/GG genotypes of rs11556218 T/G were associated with a significantly increased risk of CAD as compared with the TT genotype (odds ratio?=?1.77; 95% confidence intervals, 1.16-2.71). This finding indicates that IL-16 may be used as a genetic marker for CAD susceptibility.     

Serum Metrnl is associated with the presence and severity of coronary artery disease

Meteorin‐like (Metrnl) is a novel adipokine that is highly expressed in white adipose tissue. Metrnl stimulates energy expenditure and improves glucose tolerance in rodents. However, whether Metrnl plays a role in coronary artery disease (CAD) remains to be elucidated. The present study aimed to investigate the association of serum Metrnl with CAD in Chinese patients. A total of 193 patients with CAD and 156 control subjects were enrolled in this study. Serum Metrnl concentration was measured by enzyme‐linked immunosorbent assay. Anthropometric phenotypes, fasting glucose, serum lipids, and inflammatory cytokines were measured. Serum Metrnl was lower in CAD patients when compared to those controls (132.41 vs 173.17 pg/mL, P < 0.001). Serum Metrnl was negatively correlated with metabolic parameters, including body mass index, total cholesterol, and low‐density lipoprotein cholesterol as well as inflammatory markers including high‐sensitivity C‐reactive protein, IL‐1β, and IL‐11 even after adjustment for potential confounding variables (P < 0.05). In multivariable logistic regression analyses, compared to those in the highest tertile of serum Metrnl levels, subjects in the lowest tertile had the highest risks for CAD (adjusted OR = 2.63, 95% CI = 1.46‐4.27, P = 0.001). After adjustment for potential confounding variables, serum Metrnl was also decreased as the number of stenosed vessels increased (P < 0.001). Furthermore, decreased Metrnl level was negatively correlated with the severity of CAD quantified by the Gensini score. This first case‐control study shows significant associations of serum Metrnl with the presence and severity of CAD, suggesting Metrnl might be a new promising therapeutic target for CAD.     

Genetic contribution of the leukotriene pathway to coronary artery disease

We evaluated the genetic contribution of the leukotriene (LT) pathway to risk of coronary artery disease (CAD) in 4,512 Caucasian and African American subjects ascertained through elective cardiac evaluation. Of the three previously associated variants, the shorter "3" and "4" alleles of a promoter repeat polymorphism in ALOX5 increased risk of CAD in African Americans (OR?=?1.4, 95% CI 1.0-1.9; p?=?0.04), whereas a haplotype of LTA4H (HapK) was associated with CAD in Caucasians (OR?=?1.2, 95% CI 1.01-1.4; p?=?0.03). In Caucasians, first-stage analysis of 254 haplotype-tagging SNPs in 15 LT pathway genes with follow-up of 19 variants in stage 2 revealed an LTA4H SNP (rs2540477) that increased risk of CAD (OR?=?1.2, 95% CI 1.1-1.5; p?=?0.003) and a PLA2G4A SNP (rs12746200) that decreased risk of CAD (OR?=?0.7, 95% CI 0.6-0.9; p?=?0.0007). The PLA2G4A rs12746200 variant also decreased risk of experiencing a major adverse cardiac event (MACE?=?myocardial infarction, stroke, or death) over 3?years of follow-up (HR?=?0.7, 95% CI 0.5-0.9; p?=?0.01), consistent with its cardioprotective effect. Functional experiments demonstrated that stimulated monocytes from carriers of LTA4H variants HapK or rs2540477 had 50% (p?=?0.002) and 33% (p?=?0.03) higher LTB(4) production, respectively, compared to non-carriers. These ex vivo results are consistent with LTB(4) being the direct product of the reaction catalyzed by LTA4H and its role in promoting monocyte chemotaxis to sites of inflammation, including the artery wall of atherosclerotic lesions. Taken together, this study provides additional evidence that functional genetic variation of the LT pathway can mediate atherogenic processes and the risk of CAD in humans.     

Genetic epidemiology of coronary artery disease: an Asian Indian perspective

Journal of Genetics - Coronary artery disease (CAD) has emerged as a major cause of morbidity and mortality worldwide. Recent findings on the role of genetic factors in the aetiopathology of CAD...