The association between angiotensin-converting enzyme gene polymorphism and coronary calcification. The Rotterdam Coronary Calcification Study

Application of Genome-Wide Association Studies in Coronary Artery Disease

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

Association of systemic inflammation with epicardial fat and coronary artery calcification

BACKGROUND

Increased epicardial fat volume (EFV) has been shown to be associated with coronary atherosclerosis. While it is postulated to be an independent risk factor, a possible mechanism is local or systemic inflammation. We analyzed the relationship between coronary atherosclerosis, quantified by coronary calcium in CT, epicardial fat volume and systemic inflammation.

METHODS

Using non-enhanced dual-source CT, we quantified epicardial fat volume (EFV) and coronary artery calcium (CAC) in 391 patients who underwent coronary computed tomography for suspected coronary artery disease. In addition to traditional risk factors, serum markers of systemic inflammation were measured (IL-1α, IL-2, IL-4, IL-6, IL-7, IL-8, IL-10,IL-12, IL-13, IL-15, IL-17, IFN-γ, TNF-α, hs-CRP, GM-CS, G-CSF, MCP-1, MIP-1, Eotaxin and IP-10). In 94 patients follow-up data were obtained after 1.9 ± 0.5 years.

RESULTS

The 391 patients had a mean age of 60 ± 10 years, and 69 % were males. Mean EFV was 116 ± 50 mL. Median CAC was 12 (IQR 0; 152). CAC and EFV showed a significant correlation (ρ = 0.37; P < 0.001). EFV and CAC were significantly correlated with the traditional risk factors like age, male gender, diabetes, smoking and hypertension. With regard to biomarkers, CAC was significantly associated (negatively) to G-CSF and IL-13. EFV (median binned) was significantly associated (positively) with IP-10 (P = 0.002) and MCP-1 (ρ = 0.037). In follow-up, EFV showed a mean annualized progression of 6 mL (IQR 3; 9) (P < 0.001); CAC progressed by a mean of six Agatston Units (IQR 0; 30). The progression of CAC was significantly correlated with the extent of EFV (P < 0.001) while there was no significant correlation between progression of EFV or CAC with systemic inflammation markers.

CONCLUSION

Epicardial fat volume and the baseline extent as well as progression of coronary atherosclerosis-measured by the calcium score-are significantly correlated. While both baseline EFV and CAC displayed significant correlations with systemic inflammation markers, biomarkers were not predictive of the progression of CAC or EFV.

Can antihypertensive medication interfere with the vicious cycle between hypertension and vascular calcification?

Vascular calcification is a phenomenon of disturbed calcium deposition, as part of the calcium that is supposed to be deposited to our bones, is lodged to our vessels. There are two forms of vascular calcification, each with a distinct anatomical distribution and clinical relevance, namely the intimal and medial calcification. Studies have demonstrated that hypertension may cause vascular calcification but also that both types of calcification, especially medial, promote arterial rigidity and hence hypertension. Implications of this two-way road are largely unknown as there is no consensus yet on their exact clinical value. However, several antihypertensive medications seem to be able to interfere with the cycle of high blood pressure and vascular calcium deposits. The present review summarizes the up-to-date data regarding the effect of antihypertensive medication on vascular calcification.

Genetic polymorphisms associated with carotid artery intima-media thickness and coronary artery calcification in women of the Kronos Early Estrogen Prevention Study

Menopausal hormone treatment (MHT) may limit progression of cardiovascular disease (CVD) but poses a thrombosis risk. To test targeted candidate gene variation for association with subclinical CVD defined by carotid artery intima-media thickness (CIMT) and coronary artery calcification (CAC), 610 women participating in the Kronos Early Estrogen Prevention Study (KEEPS), a clinical trial of MHT to prevent progression of CVD, were genotyped for 13,229 single nucleotide polymorphisms (SNPs) within 764 genes from anticoagulant, procoagulant, fibrinolytic, or innate immunity pathways. According to linear regression, proportion of European ancestry correlated negatively, but age at enrollment and pulse pressure correlated positively with CIMT. Adjusting for these variables, two SNPs, one on chromosome 2 for MAP4K4 gene (rs2236935, β = 0.037, P value = 2.36 × 10(-06)) and one on chromosome 5 for IL5 gene (rs739318, β = 0.051, P value = 5.02 × 10(-05)), associated positively with CIMT; two SNPs on chromosome 17 for CCL5 (rs4796119, β = -0.043, P value = 3.59 × 10(-05); rs2291299, β = -0.032, P value = 5.59 × 10(-05)) correlated negatively with CIMT; only rs2236935 remained significant after correcting for multiple testing. Using logistic regression, when we adjusted for waist circumference, two SNPs (rs11465886, IRAK2, chromosome 3, OR = 3.91, P value = 1.10 × 10(-04); and rs17751769, SERPINA1, chromosome 14, OR = 1.96, P value = 2.42 × 10(-04)) associated positively with a CAC score of >0 Agatston unit; one SNP (rs630014, ABO, OR = 0.51, P value = 2.51 × 10(-04)) associated negatively; none remained significant after correcting for multiple testing. Whether these SNPs associate with CIMT and CAC in women randomized to MHT remains to be determined.

Understanding the genetics of coronary artery disease through the lens of noninvasive imaging

Coronary artery disease is a common condition with a known heritable component that has spurred interest in genetic research for decades, resulting in a handful of candidate genes and an appreciation for the complexity of its genetic contributions. Recent advances in sequencing technologies have resulted in large-scale association studies, possibly adding to our current understanding of the genetics of coronary artery disease. Sifting through the statistical noise, however, requires the selection of effective phenotypic markers. New imaging technologies have improved our ability to detect subclinical atherosclerosis in a safe and reproducible manner in large numbers of patients. In this article, we propose that advances in imaging technology have generated improved phenotypic markers for genetic association studies of coronary artery disease.

HDL-associated enzymes and proteins in hemodialysis patients

OBJECTIVES

To evaluate HDL-associated proteins and enzymes and their relation with lipoprotein profile and inflammatory markers in chronic renal patients on hemodialysis.

DESIGN AND METHODS

We studied 53 patients under hemodialysis and 32 healthy subjects as controls. We compared plasma lipids, Apoprotein-AI and hs-CRP, as a marker of chronic inflammation. We evaluated proteins and enzymes associated to HDL, involved in several points of lipoprotein metabolism: CETP, paraoxonase and LpPLA2 activities. Hepatic lipase was measured in postheparin plasma.

RESULTS

Patients showed higher triglycerides and lower LDL-, HDL- and total-cholesterol than controls (p<0.05). Also, in comparison with controls, Apoprotein-AI, paraoxonase and hepatic lipase were lower, while CETP was higher (p<0.03). LpPLA2 did not show changes between groups.

CONCLUSION

Beyond plasma lipid-lipoprotein profile, other factors could contribute to induce a pro-oxidative and pro-inflammatory status. The protective role of HDL does not only depend on its concentration, but also on its functionality.

Association of systemic inflammation markers with the presence and extent of coronary artery calcification

BACKGROUND

Coronary artery calcification (CAC) is a marker for the presence and extent of coronary atherosclerotic plaques and can be detected non-invasively by multi-detector row CT (MDCT). Well known predictors of CAC are age, gender, and the classical atherogenic risk factors. CAC is associated with atherosclerotic plaque burden, but it is still elusive if atherosclerosis-relevant cytokines and chemokines are also associated with CAC.

METHODS

We conducted a clinical study among 455 consecutive individuals who underwent coronary calcium assessment performed by MDCT. Before MDCT, blood was drawn and subsequently analyzed for 20 different atherosclerosis-relevant cytokines and chemokines using a Luminex-laser-based fluorescence analysis.

RESULTS

Using univariate analyses, CAC patients revealed significantly higher levels of the chemokines IP-10 (P=0.047) and eotaxin (P=0.031) as compared to non-CAC patients. In multivariate analyses using common thresholds for calcium burden, the three cytokines interleukin-6 (P=0.028), interleukin-8 (P=0.009), and interleukin-13 (P=0.024) were associated with high coronary calcium levels after adjustment for classical variables and risk factors.

CONCLUSIONS

In a large group of individuals with atypical chest pain and a low to intermediate likelihood for coronary artery disease elevated plasma levels of IL-6 and reduced levels of IL-8 and IL-13 were predictive for distinct coronary artery calcification. These findings support a specific role of these cytokines in coronary calcification.

Genetics in arterial calcification: pieces of a puzzle and cogs in a wheel

Artery calcification reflects an admixture of factors such as ectopic osteochondral differentiation with primary host pathological conditions. We review how genetic factors, as identified by human genome-wide association studies, and incomplete correlations with various mouse studies, including knockout and strain analyses, fit into "pieces of the puzzle" in intimal calcification in human atherosclerosis, and artery tunica media calcification in aging, diabetes mellitus, and chronic kidney disease. We also describe in sharp contrast how ENPP1, CD73, and ABCC6 serve as "cogs in a wheel" of arterial calcification. Specifically, each is a minor component in the function of a much larger network of factors that exert balanced effects to promote and suppress arterial calcification. For the network to normally suppress spontaneous arterial calcification, the "cogs" ENPP1, CD73, and ABCC6 must be present and in working order. Monogenic ENPP1, CD73, and ABCC6 deficiencies each drive a molecular pathophysiology of closely related but phenotypically different diseases (generalized arterial calcification of infancy (GACI), pseudoxanthoma elasticum (PXE) and arterial calcification caused by CD73 deficiency (ACDC)), in which premature onset arterial calcification is a prominent but not the sole feature.

Coronary Calcification and Hormones

The pathogenesis of coronary artery calcification and its role in atherogenesis has not been completely understood but is a new focus of interest in experimental and clinical research. Various bioactive substances, including hormones, have been implicated in the process of arterial calcification. This review considers the relationship between coronary artery calcification and hormones. These hormones may become therapeutic targets for the prevention of arterial calcification.

Renin-angiotensin-aldosterone system gene polymorphisms in coronary artery bypass graft surgery patients

INTRODUCTION

Candidates for coronary artery bypass grafting (CABG) represent a group of patients with well documented, severe coronary artery disease (CAD). Genetic polymorphisms of renin-angiotensin-aldosterone system (RAAS) components have been associated with CAD. We examined the association of polymorphisms of angiotensin-converting enzyme (ACE), angiotensinogen (AGT), and angiotensin II type 1 receptor (AT(1) receptor) with severe CAD in CABG patients.

MATERIALS AND METHODS

One hundred and fifty-four CABG patients and 155 non-CAD controls were included in the study. Established PCR methods were used for genotyping of AGT M235T, AGT T174M, AT(1) receptor A1166C, and ACE I/D polymorphisms. Cumulative effect of analysed polymorphisms was assessed by calculation of each individual's RAAS gene score (addition of 0.5 points for each variant allele and then calculating the sum for all four polymorphisms).

RESULTS

No association between AGT M235T, AGT T174M, ACE I/D and AT(1) receptor A1166C polymorphisms and CAD was observed. Within CABG patients, the frequency of homozygous AGT 235TT genotype was higher in hypertensive compared to normotensive CABG patients (21.7% vs. 6.3%, p=0.03). RAAS gene score did not differ between CABG patients and non-CAD controls.

CONCLUSIONS

There is no association of the analysed RAAS polymorphisms with severe CAD in CABG patients. However, within these patients, an association was found between AGT 235TT genotype and hypertension.

Relationship between angiotensin-converting enzyme gene polymorphism and severity of aortic valve calcification

OBJECTIVE

To investigate the role of angiotensin-converting enzyme (ACE) gene polymorphism in patients with degenerative aortic valve calcification (AVC).

PATIENTS AND METHODS

Our study consisted of 305 Turkish patients of European descent (139 male, 166 female; mean plus or minus age, 68 plus or minus 9 years) referred to our echocardiography laboratory for aortic valve evaluation between June 2, 2003, and April 29, 2005. The severity of AVC was graded from 1 to 6 by echocardiography. We used polymerase chain reaction to determine ACE gene polymorphism.

RESULTS

The ACE insertion/deletion genotype distributions for the study population were in Hardy-Weinberg equilibrium (chi square equals 3.5, P equals .18). The study population was divided into 3 groups based on the severity of AVC: those with grade 1 calcification were in group 1, those with grades 2 to 4 in group 2, and those with grades 5 to 6 in group 3. Group 1 patients were significantly younger, less likely to have hypertension and diabetes, and had higher high-density lipoprotein cholesterol levels. The genotype frequencies were significantly different among groups, with the insertion/insertion genotype being less prevalent in group 3 patients. In multivariate analysis, independent predictors of severe AVC were hypertension (odds ratio [OR], 5.6; 95% confidence interval [CI], 2.8 to 11.0; P less than .001), low high-density lipoprotein cholesterol (OR, 2.7; 95 percent CI, 1.5 to 4.9; P equals .001), and the deletion/deletion and insertion/deletion vs insertion/insertion genotype (OR, 3.2; 95 percent CI, 1.5 to 7.2; P equals .004).

CONCLUSION

These results suggest that ACE gene polymorphism may be associated with severe AVC.

Polymorphisms of the renin-angiotensin system genes predict progression of subclinical coronary atherosclerosis

Premature coronary artery disease (CAD) in subjects with type 1 diabetes dramatically affects quality of life and morbidity and leads to premature death, but there is still little known about the mechanisms and predictors of this complication. In the present study, we explored the role of genetic variants of angiotensinogen (AGT, M235T), ACE (I/D), and angiotensin type 1 receptor (ATR1, A1166C) as predictors of rapid progression of subclinical coronary atherosclerosis. Five-hundred eighty-five type 1 diabetic patients and 592 similar age and sex control subjects were evaluated for progression of coronary artery calcification (CAC), a marker of subclinical CAD, before and after a 2.5-year follow-up. In logistic regression analysis, CAC progression was dramatically more likely in type 1 diabetic subjects not treated with ACE inhibitor/angiotensin receptor blocker who had the TT-ID-AA/AC genotype combination than in those with other genotypes (odds ratio 11.6 [95%CI 4.5-29.6], P < 0.0001) and was even stronger when adjusted for cardiovascular disease risk factors and the mean A1C (37.5 [3.6-388], P = 0.002). In conclusion, a combination of genotype variants of the renin-angiotensin system genes is a powerful determinant of subclinical progression of coronary artery atherosclerosis in type 1 diabetic patients and may partially explain accelerated CAD in type 1 diabetes.

Thematic review series: Patient-Oriented Research. Imaging atherosclerosis: state of the art

The ability to image obstructive arterial disease brought about a revolution in clinical cardiovascular care; the development of newer technologies that image arterial wall thicknesses, areas, volumes, and composition allows valid imaging of atherosclerosis for the first time. Development of noninvasive imaging of atherosclerosis has further led to a quantum shift in research in the field by enabling the study of asymptomatic populations and thus allowing investigators to focus on preclinical disease without the many biases associated with the study of symptomatic patients. These noninvasive investigations have broad implications for clinical care as well. Coronary angiography, computed tomographic (CT) imaging of coronary calcium, intravascular ultrasound, multidetector CT angiography, B mode ultrasound of the carotid arteries, and MRI of the carotid arteries all have unique strengths and weaknesses for imaging atherosclerosis. Certain of these techniques are extremely useful as outcome variables for clinical trials, and others are uniquely useful as predictors of the risk of cardiovascular disease. All are informative in one way or another with regard to the role of plaque remodeling and composition in disease causation. CT and MRI technology are advancing very rapidly, and research and clinical uses of these imaging modalities promise to further advance our understanding of atherosclerosis and its prevention.

ACEPolymorphisms

Angiotensin converting enzyme (ACE) plays an essential role in two physiological systems, one leading to the production of angiotensin II and the other to the degradation of bradykinin. The wide distribution and multifunctional properties of these peptides suggest that ACE could be involved in various pathophysiological conditions. The discovery that ACE levels are under genetic control ushered in a new era of investigation; most studies focused on an insertion/deletion (I/D) polymorphism in intron 16 of the ACE gene as a marker for a functional polymorphism. Recently, many single nucleotide polymorphisms were detected in the gene and the search for the locations of functional polymorphisms became a topic of extensive investigation. Nevertheless, association studies on the I/D polymorphism and clinical outcomes continued, mostly with conflicting results. This article reviews the current state of knowledge regarding ACE polymorphisms and suggests that a functional polymorphism is most likely located between intron 18 and the 3' UTR. The potential existence of another functional polymorphism in the 5' UTR, however, cannot be excluded. This review also presents an overview of ACE function in different pathophysiological systems, and summarizes previous reports on ACE and clinical outcomes. Although findings on the I/D polymorphism and disorders like diabetic nephropathy and Alzheimer disease can be considered conclusive, reports on most of the cardiovascular phenotypes are still controversial. Genotypic and phenotypic misclassifications, insufficient power in some studies, and the presence of interaction with other genes or environmental factors are possible explanations for the contradictory findings.