Polymorphisms in the angiotensinogen gene are associated with carotid intimal-medial thickening in females from a community-based population

Association Between M235T-AGT and I/D-ACE Polymorphisms and Carotid Atheromatosis in Hypertensive Patients: A Cross-Sectional Study

BACKGROUND/AIM

The renin-angiotensin-aldosterone system (RAAS) may be implicated in carotid atheromatosis (CA) development. We aimed to assess the relationship of M235T-angiotensinogen (AGT) and insertion/deletion of angiotensin conversion enzyme (I/D-ACE) genotypes with CA in patients with essential hypertension (EHT).

PATIENTS AND METHODS

We determined the M235T-AGT and I/D-ACE genotypes, using PCR-RFLP methods, in 162 hypertensive subjects from three tertiary regional medical centers. The relationship between the studied RAAS gene polymorphisms and CA was assessed by multiple logistic regressions.

RESULTS

Hypertensive patients carrying the MT/TT235-AGT and MT235-AGT genotypes had a 2.17-fold (p=0.033) and 2.24-fold (p=0.036) increased risk to develop CA, respectively. These genotypes, MT/TT 235-AGT (OR=2.17, p=0.033) and MT235-AGT (OR=2.24, p=0.036), remain independent risk factors for CA in hypertensive patients according to the multivariate model.

CONCLUSION

There is a statistically significant association between M235T-AGT and CA, when adjusting for several confounders and controlling for hypertension.

Association between angiotensin II type-1 receptor A1166C polymorphism and the presence of angiographically-defined coronary artery disease in an Iranian population

Background: There are reported associations between a polymorphism of the angiotensin II type 1 receptor (AT1R/A1166C) gene and coronary artery disease (CAD), hypertension, and myocardial infarction in some populations. Objective: Investigate the association between A1166C polymorphism and CAD in an Iranian population. Methods: Four hundred and thirteen patients with suspected CAD were recruited. Based on coronary angiography, the patients were classified into CAD+ (n=315) and CAD- (n=98) groups defined as >50% and <50% stenosis of any major coronary artery, respectively. One hundred and thirty-five healthy subjects were also recruited as the control group. The AT1R polymorphism was assessed using a polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) based method. Results: A higher frequency of the AC and CC genotypes and lower frequency of the AA genotype was observed in both CAD+ and CAD- groups, compared with the control group (p <0.05). CAD+ and CAD- groups also had a higher frequency of the C allele than controls (p <0.01). There was no significant difference in genotype and allele frequencies between hypertensive and non-hypertensive patients (p > 0.05). In addition, the AT1R genotype frequencies did not differ significantly among different subgroups of CAD+ patients, based on the number of affected coronary vessels (p >0.05). Conclusion: The frequency AT1R/A1166C polymorphism was higher among patients with some degrees of coronary stenosis who are candidates of coronary angiography.

Role of angiotensin II type I (AT1 A1166C) receptor polymorphism in susceptibility of left ventricular dysfunction

BACKGROUND

Left ventricular dysfunction (LVD) with subsequent congestive heart failure (CHF) constitutes the final common pathway for a host of cardiac disorders. The impaired LV function develops in response to an ischemic insult followed by a fall in cardiac output that leads to activation of renin-angiotensin-system (RAS). Angiotensin II type I receptor (AT1), which mediate the vasoconstrictive and salt-conserving actions of the RAS, represent interesting candidate genes for cardiovascular diseases. Therefore, we conducted an association study between single nucleotide polymorphism (SNP) in AT1 gene and LVD in CAD patients.

METHODS AND RESULTS

The present study recruited a total of 950 subjects including 720 angiography confirmed CAD patients and 230 healthy controls. Among 720 CAD patients, 229 with reduced left ventricle ejection fraction (LVEF≤45%) were categorized as LVD. The AT1 (A1166C, rs5186) polymorphism was determined by ARMS-PCR. Our results showed that the frequency of AT1 1166AC and CC genotypes were significantly higher in LVD patients in comparison to non-LVD (LVEF >45%) patients (p value = 0.003; OR = 1.81 and p value <0.001; OR = 4.33). Further analysis showed that AT1 A1166C polymorphism was significantly associated with LV end diastole (p-value = 0.031), end systole (p-value = 0.038) dimensions, and mean LVEF (p-value = 0.035). Moreover, on comparing the AT1 A1166C polymorphism in CAD patients with healthy controls, we did not find any association both at genotypic and allelic level (p value = 0.927; OR = 1.04 and p value = 0.219; OR = 0.83) respectively.

CONCLUSIONS

Our study suggests that AT1 A1166C polymorphism may play significant role in conferring genetic susceptibility of LVD.

The angiotensinogen gene polymorphism is associated with heart failure among Asians

The angiotensinogen (AGT) gene M235T polymorphism has been suggested to be linked to risk of heart failure (HF). However, association studies on the M235T polymorphism and HF risk have shown conflicting results. PubMed and China Biology Medicine (CBM) databases were systematically searched to identify relevant studies. Odds ratios (ORs) and 95% confidence intervals (CIs) were used to assess the strength of the association. A total of 1,281 HF cases and 1,376 controls were included in the analysis. The pooled data showed that there was no significant associations between the AGT M235T polymorphism and HF risk for TT vs. MM (OR = 1.17, 95%CI = 0.62–2.19, P = 0.635), MT vs. MM (OR = 0.97, 95%CI = 0.77–1.22, P = 0.776), MT/TT vs. MM (OR = 1.07, 95%CI = 0.67–1.69, P = 0.781), and TT vs. MM/MT (OR = 1.23, 95%CI = 0.86–1.76, P = 0.259). In contrast, in the HF subgroup analysis by ethnicity, the AGT M235T polymorphism had a decreased risk of HF among Asians (MT vs. MM, OR = 0.39, 95%CI = 0.17–0.92, P = 0.032). Our results suggest that the AGT M235T polymorphism is a low-penetrant risk factor for the development of HF among Asians.

Effect of the +781C/T polymorphism in the interleukin-8 gene on atherosclerotic cerebral infarction, and its interaction with smoking and drinking

OBJECTIVE

The aims of this study were to investigate the association between the +781C/T polymorphism of interleukin-8 (IL-8) and atherosclerotic cerebral infarction and the interaction between the +781C/T polymorphism and smoking or drinking in cerebral infarction in the Han Chinese population.

METHODS

We investigated the +781C/T polymorphism of IL-8 in 308 consecutive Han Chinese patients who were diagnosed with atherosclerotic cerebral infarction and in 294 age- and gender-matched healthy control subjects. The patients were classified using the Oxfordshire Community Stroke Project (OCSP) classification. The patients and subjects' histories of smoking and drinking were recorded, and atherosclerosis (AS) of the internal carotid artery (ICA) was evaluated in the patients. The +781C/T polymorphism was determined by polymerase chain reaction and restriction fragment length polymorphism (PCR-RFLP) analysis.

RESULTS

The +781C/T polymorphism and allele frequencies were not significantly different between the patients and controls and were not significantly associated with the OCSP classifications. We found that the 781C allele was significantly associated with AS of the ICA in the patients (p = 0.017), and the CT genotype was more prevalent in patients without AS of the ICA (p = 0.035). No interactions were observed between the +781C/T polymorphism and smoking or drinking.

CONCLUSION

Our results demonstrated that the +781C/T polymorphism of IL-8 did not play a role and had no interaction with smoking or drinking in the occurrence of cerebral infarction in the Han Chinese population. However, the C allele and the CT genotype might be associated with AS of the ICA in patients with ischemic stroke.

Angiotensinogen promoter polymorphisms predict low diffusing capacity in U.S. and Spanish IPF cohorts

BACKGROUND

Single nucleotide polymorphisms (SNPs) in angiotensinogen (AGT) at positions -20 and -6 are associated with increased severity and progression of various fibrotic diseases. Our earlier work demonstrated that the progression of idiopathic pulmonary fibrosis (IPF) was associated with the A-6 allele. This study examined the hypothesis that the homozygous CC genotype at -20 and the AA genotype at -6 would confer worse measures of pulmonary function (measured by pulmonary function tests) in IPF.

METHODS

Multiple logistic regression analysis was applied to a NIH Lung Tissue Research Consortium cohort and a Spanish cohort, while also adjusting for covariates to determine the effects of these SNPs on measures of pulmonary function.

RESULTS

Analysis demonstrated that the CC genotype at -20 was strongly associated with reduced diffusing capacity in males in both cohorts (p = 0.0028 for LTRC and p = 0.017 for the Spanish cohort). In females, the AA genotype was significantly associated with lower FVC (p = 0.0082) and V alv (p = 0.022). In males, the haplotype CA at -20 and -6 in AGT was also strongly associated with reduced diffusing capacity in both cohorts.

CONCLUSIONS

This study is the first to demonstrate an association of AGT polymorphisms (-20A > C and -6G > A) with lower measures of pulmonary function in IPF. It is also the first to relate the effect of gender in lung fibrosis with polymorphisms in AGT.

Angiotensinogen gene transcription in pulmonary fibrosis

An established body of literature supports the hypothesis that activation of a local tissue angiotensin (ANG) system in the extravascular tissue compartment of the lungs is required for lung fibrogenesis. Transcriptional activation of the angiotensinogen (AGT) gene is believed to be a critical and necessary step in this activation. This paper summarizes the data in support of this theory and discusses transcriptional regulation of AGT, with an emphasis on lung AGT synthesis as a determinant of fibrosis severity. Genetic data linking AGT polymorphisms to the severity of disease in Idiopathic Pulmonary Fibrosis are also discussed.

Recurrence and long-term maternal health risks of hypertensive disorders of pregnancy: a population-based study

OBJECTIVE

The purpose of this study was to investigate the recurrence risk of hypertensive disorders in subsequent pregnancies and to explore the associations among hypertensive disorders of pregnancy and maternal cardiovascular risk factor profile and the development of cardiovascular diseases later in life.

STUDY DESIGN

We used population-based, cross-sectional data from the fourth survey of the Tromsø Study.

RESULTS

Preeclampsia in the first pregnancy increased the risk of recurrence in later pregnancies (relative risk, 6.6; 95% confidence interval, 5.5-7.9) compared with a normotensive first pregnancy. Women with a history of preeclampsia or nonproteinuric hypertension had an unfavorable cardiovascular risk profile. Hypertension was prevalent in 25% and 28% of the women, respectively. The carotid artery intima-media thickness and total carotid plaque area were significantly larger in women with previous preeclampsia.

CONCLUSION

A strong association between hypertensive disorders of pregnancy and an increased risk of atherosclerosis and cardiovascular diseases was demonstrated by the assessment of risk factors that can be potentially modified.

Association of angiotensin II type 1 receptor gene A1166C polymorphism with the presence of diabetes mellitus and metabolic syndrome in patients with documented coronary artery disease

BACKGROUND

There are relatively limited data available on the genetic susceptibility to diabetes mellitus and metabolic syndrome in the Iranian population. We have therefore investigated the association between the angiotensin II type I receptor gene polymorphism (AT(1)R/A1166C) and the presence of diabetes mellitus and metabolic syndrome in a well defined group of patients.

METHODS

Patients with angiographically defined coronary artery disease (CAD) (n=309) were evaluated for the presence of AT(1)R/A1166C polymorphism. These patients were classified into subgroups with (n=164, M/F: 109/55) and without (n=145, M/F: 84/61) diabetes mellitus. The AT(1)R polymorphism was assessed using a polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) based method.

RESULTS

There was a higher frequency of polymorphic genotypes (AC+CC) in the diabetic compared with the non-diabetic group (p=0.01). When determined for each gender separately, this difference remained significant in the males (p=0.04) but not in females (p=0.09). With regard to the allele frequencies, the C allele was significantly higher and the A allele frequency was lower in the diabetic group (p=0.01). This remained significant after gender segregation for males (p=0.01) but not females. In the binary logistic regression analysis, only serum fasting glucose was found as the independent predictor for the presence of diabetes in the CAD patients (β=1.16, p<0.001 for total population and β=1.29, p<0.001 for male subjects). There was no significant difference in genotype or allele frequencies between subgroups with and without metabolic syndrome, this being unaffected by gender or the definition of metabolic syndrome used apart from a significantly lower frequency of C allele in male subjects with metabolic syndrome defined by the NCEP ATP III criteria (p=0.04).

CONCLUSION

The AT(1)R/A1166C polymorphism may be associated with the presence of diabetes mellitus in male subjects with documented CAD.

A polymorphism in transforming growth factor-β1 is associated with carotid plaques and increased carotid intima-media thickness in older Chinese men: the Guangzhou Biobank Cohort Study-Cardiovascular Disease Subcohort

OBJECTIVE

Polymorphisms of the transforming growth factor-β1 (TGFB1) gene have not been associated with asymptomatic atherosclerosis previously. We investigated the relationship between a single nucleotide polymorphism (SNP) rs4803455 in TGFB1 and atherosclerosis identified by the presence of carotid plaque and increased intima-media thickness (IMT) in an older Chinese population.

METHODS

1996 subjects (992 (49.7%) men aged 50-85 years) from the Guangzhou Biobank Cohort Study-Cardiovascular Subcohort (GBCS-CVD) were genotyped. Carotid plaque and IMT were assessed by B-mode ultrasonography.

RESULTS

In male subjects, the C allele of TGFB1 rs4803455 was significantly associated with prevalence of carotid plaque (adjusted OR: 2.49, 95% CI: 1.16-5.36, P = 0.03). The C allele was related to increased number of common carotid artery (CCA) plaques (P=0.03) and larger carotid plaque area (P = 0.02) in men. The homozygous carriers of allele C in male subjects also had a higher risk of having carotid IMT ≥ 1 mm (adjusted OR: 1.75, 95% CI: 1.05-2.93, P = 0.03). These associations were independent of age, smoking, physical activity, body mass index, blood pressure, lipid profile, fasting glucose and high sensitivity C-reactive protein.

CONCLUSION

This is the first study to show that the C allele in TGFB1 was associated with increased risk of atherosclerosis in older Chinese men. Further investigations on the linkage between the TGFB1 gene and progression of atherosclerosis in asymptomatic populations are warranted.

Difference in angiotensinogen haplotype frequencies between chronic heart failure and advanced atherosclerosis patients - new prognostic factor?

Numerous association studies have been involved in studying the angiotensinogen (AGT) variants, AGT plasma levels and relations to cardiovascular diseases, such as hypertension, myocardial infarction, coronary heart disease. To investigate a role of AGT G(-6)A and M235T genetic variants for chronic heart failure (CHF) and advanced atherosclerosis (AA), a total of 240 patients with CHF and 200 patients with AA of the Czech origin were evaluated for the study. The study shows the role of polymorphism AGT G(-6)A in genetic background among advanced atherosclerosis patients and chronic heart failure patients (Pg=0.001). This difference was also observed in comparison of AA patients with subgroup of CHF with dilated cardiomyopathy (Pg=0.02; Pa=0.009), and ischemic heart disease (Pg=0.007). The greatest difference between triple-vessel disease and chronic heart failure groups was observed in frequency of GT haplotype (P<0.001) and GGMT associated genotype (P<0.001). Retrospectively, we found the same trend when the subgroups of CHF were compared to AA group (AA vs. IHD with CHF P<0.001; AA vs. DCM P<0.001). These results suggest AGT genetic variants as a risk factor for chronic heart failure compared to advanced atherosclerosis disease without heart failure, with a strong difference between IHD patients and chronic heart failure patients with ischemic heart disease, especially in haplotypes and associated genotypes.

The longitudinal association of common susceptibility variants for type 2 diabetes and obesity with fasting glucose level and BMI

Background

Variation in the effects of genetic variants on physiological traits over time or with age may alter the trajectories of these traits. However, few studies have investigated this possibility for variants associated with type 2 diabetes or obesity, and these show little consensus. We aimed to characterise the possible longitudinal associations of common diabetes-susceptibility variants in the KCNJ11, PPARG, TCF7L2, IGF2BP2, CDKAL1, SLC30A8 and HHEX gene loci, with fasting glucose level; and of an obesity-associated variant in the FTO gene, with body mass index (BMI).

Methods

The study analysed data from the Busselton Health Study (n = 4,554). Cross-sectional association analyses included family data and used the total association test. Longitudinal association analyses of unrelated participant data (n = 2,864) used linear mixed-effects models.

Results

In cross-sectional analyses, we observed associations of the T allele at the IGF2BP2 single nucleotide polymorphism (SNP) rs4402960 with raised fasting glucose (p = 0.045), and the A allele at the FTO SNP rs9939609 with raised BMI (p = 0.003). Longitudinal analyses showed no significant associations between SNPs and changes in fasting glucose or BMI in the same individuals, either over mean follow-up times of 18.7 and 21.8 years respectively, or with age during adulthood.

Conclusions

There was no indication that the effects of common type 2 diabetes variants on fasting glucose varied with age during adulthood or over time.

The C609T variant of NQO1 is associated with carotid artery plaques in patients with type 2 diabetes

OBJECTIVE

Atherosclerosis in patients with type 2 diabetes has been linked to oxidative stress. NADP[1]:quinone oxidoreductase 1 (NQO1) plays a key role in cellular antioxidant defense. Recent reports suggest that highly expressed and inducible endogenous NQO1 from cardiovascular cells may act as a potential superoxide scavenger. We examined the relationship between the risk of NQO1 C609T polymorphism and carotid artery atherosclerosis in patients with type 2 diabetes.

METHODS

We recruited 601 (Seoul set) and 233 (Koyang set) unrelated patients with type 2 diabetes from independent groups. The C609T variant of NQO1 was genotyped by Taqman RT-PCR. Mean and maximum carotid intima-media thickness (IMT) and carotid artery plaques were measured by high-resolution ultrasonography.

RESULTS

Patients with the T allele exhibited a higher prevalence of atherosclerotic plaques than non-T allele carriers in both sets (Seoul set vs. Koyang set, p=0.021, p=0.023, respectively). After adjusting for age, sex, duration of diabetes, systolic blood pressure, body mass index, current smoking, HDL-cholesterol, LDL-cholesterol and HbA1c, subjects with the T allele had a significantly higher risk of carotid artery plaques (Seoul set vs. Koyang set, OR=1.65, p=0.015; OR=2.00, p=0.037, respectively) than subjects with the CC genotype.

CONCLUSION

These results suggest that the C609T polymorphism of NQO1 is associated with carotid artery plaques in type 2 diabetic patients.

Carotid plaque compared with intima-media thickness as a predictor of coronary and cerebrovascular disease

Atherosclerosis is the underlying cause of most myocardial infarction (MI) and ischemic strokes. B-mode ultrasound of carotid arteries provides measures of intima-media thickness (IMT) and plaques, both widely used as surrogate measures of cardiovascular disease. Although IMT and plaques are highly intercorrelated, IMT's role as a marker of atherosclerosis has been questioned, especially when measurements include the common carotid artery (CCA) only. Plaque and intima-media thickening may reflect different biological aspects of atherogenesis with distinctive relations to clinical vascular disease. Plaque measured in the carotid bulb or internal carotid artery is stronger related to hyperlipidemia and smoking and is a stronger predictor for MI, whereas CCA-IMT is stronger related to hypertension and ischemic stroke. Echolucent plaque morphology (ie, lipid-rich plaques) seems to increase the risk for MI and stroke. New evidence suggests that total plaque area is the most strongly predictive of cardiovascular risk of the ultrasound phenotypes.

The association of common genetic variants in the APOA5, LPL and GCK genes with longitudinal changes in metabolic and cardiovascular traits

AIMS/HYPOTHESIS

Common genetic variants influence plasma triacylglycerol, HDL-cholesterol (HDL-C) and glucose levels in cross-sectional studies. However, the longitudinal effects of these established variants have not been studied. Our aim was to examine the longitudinal associations of four such variants in the apolipoprotein A-V (APOA5), lipoprotein lipase (LPL), and glucokinase (GCK) genes with fasting glucose or lipid levels.

METHODS

The individuals analysed were participants in the Busselton Health Survey (n = 4,554). Cross-sectional analyses of family data used the total association test. Longitudinal association analyses of unrelated participant data (n = 2,864) used linear mixed-effects models.

RESULTS

The findings of cross-sectional association analyses replicated those of previous studies. We observed associations of the G and C alleles at the APOA5 single nucleotide polymorphisms (SNPs) rs662799 and rs3135506 with raised triacylglycerol levels (p = 0.0003 and p < 0.0001, respectively), the 447X allele at the LPL SNP rs328 with reduced triacylglycerol levels (p = 0.0004) and raised HDL-C levels (p = 0.0004), and the A allele of the GCK SNP rs1799884 with raised fasting glucose level (p = 0.015). Longitudinal association analyses showed that most of these associations did not change in the same individuals over an average follow-up time of 17.4 years, though there was some evidence that the association of the 447X allele of rs328 with raised HDL-C level significantly increased with age (p = 0.01), and that the association of the C allele of rs3135506 with raised triacylglycerol level significantly increased over time (p = 0.0007).

CONCLUSIONS/INTERPRETATION

The current study suggests that the effects of established gene variants on lipid and glucose traits do not tend to alter with age during adulthood or over time.

Association of PARL rs3732581 genetic variant with insulin levels, metabolic syndrome and coronary artery disease

PARL (presenilin-associated rhomboid-like) is a mitochondrial protein involved in mitochondrial membrane remodelling, and maps to a quantitative trait locus (3q27) associated with metabolic traits. Recently the rs3732581 (Leu262Val) variant was found to be associated with increased levels of plasma insulin, a finding not replicated in a larger cohort. The aim of the current study was to investigate the associations between rs3732581 and levels of plasma insulin, metabolic syndrome (MetS) and its components, and cardiovascular disease. The CUPID population consisted of 556 subjects with angiographically proven CAD and the CUDAS cohort consisted of 1,109 randomly selected individuals from Perth, Western Australia. Samples were genotyped using mutation-specific PCR. No significant associations were observed between rs3732581 and levels of plasma insulin, glucose, BMI or MetS in either population. However, carriers of the minor allele had significantly lower mean intima-media thickness (IMT) [0.69 mm, 95% CI (0.69, 0.70 mm); P = 0.004], compared with major allele homozygotes [mean IMT = 0.71 mm, 95% CI (0.70, 0.72 mm)] in the CUDAS population. Further analysis using a recessive model showed homozygous carriers of the minor allele were predisposed to CAD [OR 1.55, 95% CI (1.11, 2.16); P = 0.01]. Despite the functional evidence for a role of PARL in regulating insulin levels, no association with rs3732581 was found in the current study. Additionally, there were no associations with glucose levels, BMI or MetS. There were significant effects of the variant on mean IMT and risk of CAD. A role for PARL in metabolic conditions cannot be excluded and more comprehensive genetic studies are warranted.

15-Lipoxygenase gene variants are associated with carotid plaque but not carotid intima-media thickness

The major underlying cause of CHD is atherosclerosis, and oxidised LDL is known to play an important role in its development. We examined the role of three single nucleotide polymorphisms (SNPs) in the 15-lipoxygenase gene (ALOX15), in atherosclerosis. We genotyped three SNPs in the ALOX15 promoter in two Western Australian samples-1,111 community-based individuals and 556 with CHD. SNPs and haplotypes were tested for an association with carotid plaque, intima-media thickness and risk of CHD. The -611GG genotype was associated with increased likelihood of carotid plaque in CHD patients (OR = 4.01, 95%CI = 1.39-11.53, P = 0.005) and the C alleles of the G-220C and G-189C SNPs were associated with decreased likelihood of plaque among cases (OR = 0.66, 95%CI = 0.43-0.99, P = 0.05 and OR = 0.51, 95%CI = 0.34-0.78, P = 0.002 respectively). The GGG haplotype was associated with increased risk of carotid plaque in CHD patients (OR = 5.77, 95%CI = 1.82-18.29, P = 0.0007) and in community-based individuals under 53 years (OR = 4.15, 95%CI = 1.23-14.08, P = 0.02). No association was observed between ALOX15 SNPs or haplotypes and intima-media thickness. This study is novel as it is the first to examine the association between 15-lipoxygenase polymorphisms and atherosclerotic indicators. These findings suggest a possible role of ALOX15 polymorphisms in focal plaque formation.

Cholesteryl ester transfer protein gene haplotypes, plasma high-density lipoprotein levels and the risk of coronary heart disease

High-density lipoprotein cholesterol (HDL-C) is a known inverse predictor of coronary heart disease (CHD) and is thus a potential therapeutic target. Cholesteryl ester transfer protein (CETP) is a key protein in HDL-C metabolism such that elevated CETP activity is associated with lower HDL-C. Currently available HDL-C raising drugs are relatively ineffective and evidence suggesting the role of CETP in HDL-C levels has promoted the development of CETP inhibitors as potential therapeutic agents for CHD. We investigated three SNPs in the CETP gene in two cross-sectional community-based populations (n = 1,574 and 1,109) and a population of 556 CHD patients to determine if reduced CETP activity due to genetic variations in the CETP gene would increase HDL-C levels and reduce the risk of CHD. CETP genotypes and haplotypes were tested for association with lipid levels, CETP activity and risk of CHD. Multivariate analysis showed the common AAB2 haplotype defined by the G-2708A, C-629A and TaqIB polymorphisms, was consistently associated with reduced CETP activity and increased HDL-C levels. A mean increase in HDL-C levels of 0.16-0.24 mmol/l was observed in individuals with two copies of the AAB2 haplotype relative to non AAB2 carriers across all three populations (P < 0.001). A case-control study of males indicated no association between single SNPs or haplotypes and the risk of CHD. These results suggest that raising HDL-C via CETP inhibition may not alter risk of CHD. Randomized control trials are needed to determine whether CETP inhibition will in reality reduce risk of CHD by raising HDL-C.

Technology Insight: ultrasound measurement of carotid plaque--patient management, genetic research, and therapy evaluation

Various methods have been used to quantify atherosclerosis, beginning in the mid-1980s with ultrasound measurement of carotid intima-media thickness (IMT), and going on to coronary calcification assessed by electron-beam CT, measurement of carotid plaque by ultrasound, and measurement of carotid wall thickness by MRI. In recent years, it has become clear that carotid IMT, coronary calcification and carotid plaque reflect biologically and genetically different aspects of the atherosclerotic process, and will respond differentially to therapy. IMT represents mainly hypertensive medial hypertrophy; this measure is more predictive of stroke than of myocardial infarction, and is only weakly associated with traditional coronary risk factors. Carotid plaque area, on the other hand, is more strongly associated with traditional risk factors, and is more predictive of myocardial infarction than of stroke. A quantitative trait, called 'unexplained atherosclerosis', expresses the extent to which an individual has excess carotid plaque not explained by traditional risk factors, or the extent to which an individual is protected from traditional risk factors. Unexplained progression of plaque is an even more powerful tool for genetic research, because age, which accounts for the greatest proportion of baseline plaque, has much less influence on the rate of progression. Compared with IMT, measurement of carotid plaque volume by three-dimensional ultrasound reduces by two orders of magnitude the sample size and duration of treatment needed to evaluate new therapies. Measurement of carotid plaque is, therefore, an important tool for patient management, genetic research and evaluation of new therapies for stroke prevention.

The C-480T hepatic lipase polymorphism is associated with HDL-C but not with risk of coronary heart disease

High-density lipoprotein cholesterol (HDL-C) is a known predictor of coronary heart disease (CHD). Studies have shown that the C-480T polymorphism of the hepatic lipase (HL) gene is predictive of HDL-C; however, its observed relationship with the risk of CHD has been inconsistent. We analysed four biallelic polymorphisms in the HL gene in participants from three independent Western Australian populations. Samples were collected from two cross-sectional studies of 1111 and 4822 community-based subjects assessed for cardiovascular risk factors, and a third sample of 556 subjects with physician-diagnosed CHD. Genotypes were tested for association with plasma lipids and the risk of CHD. All polymorphisms were highly correlated (D' > 0.97, r(2) > 0.90); therefore, only C-480T was analysed. The -480T allele was significantly associated with an increase in HDL-C of between 0.08 and 0.16 mmol/l in all three populations (p < 0.001). No associations with other lipids were observed, nor was an association with CHD in a case-control study of males. The TT genotype was however associated with decreased risk of myocardial infarction among cases (odds ratio = 0.39, 95% confidence interval = 0.19-0.78, p = 0.008). These findings replicate those of previous studies in three independent populations and suggest that the genetic determinants of CHD are complex and cannot be entirely explained through intermediate phenotypes.

Genetic variants predisposing to cardiovascular disease

PURPOSE OF REVIEW

The goal of this review is to provide an update on the most recent and relevant findings in the area of genotype-phenotype associations as well as the relationships between genetic factors and cardiovascular disease risk markers and events. In addition, emphasis will be placed on the methodological problems associated with studying the genetics of complex disorders, specifically cardiovascular diseases.

RECENT FINDINGS

Genes associated with cardiovascular disease predisposition have been examined, including traditional cardiovascular disease candidate genes, such as ACE, AGT, eNOS, PON and MTHFR, new loci that have recently been added to the growing list of cardiovascular disease candidate genes (i.e. MEF2A, ALOX5, LTA, APOM, PDE4D), and genes that have been shown to be at the intersection of several age-related disorders through interaction with one another or with environmental factors (i.e. APOA5, APOE, PPARgamma, LPL and LIPC).

SUMMARY

During the last year, tremendous effort has been made in elucidating new genes associated with cardiovascular disease predisposition. For the most part, however, major breakthroughs have not been made, primarily due to the poor replication of results among studies, as a consequence of poor experimental design. Nevertheless, we have increased our understanding of the complexity of cardiovascular disease and the relevance of gene-environment interactions as the ultimate drivers of the individual predisposition to the disease. It is essential, therefore, that present and future genetic studies in this area take into consideration the inclusion of high-quality environmental data in the analytical process to test the clinical usefulness of a genetic marker as a risk predictor.

Association analysis of genes in the renin-angiotensin system with subclinical cardiovascular disease in families with Type 2 diabetes mellitus: the Diabetes Heart Study

AIMS

Cardiovascular disease (CVD) is a major complication of Type 2 diabetes mellitus. The renin-angiotensin system (RAS) and nitric oxide production are both important regulators of vascular function and blood pressure. Genes encoding proteins involved in these pathways are candidates for a contribution to CVD in diabetic patients. We have investigated variants of the angiotensinogen (AGT), angiotensin converting enzyme (ACE), angiotensin type 1 receptor (AT1R) and endothelial nitric oxide synthase (NOS3) genes for association with subclinical measures of CVD in families with Type 2 diabetes mellitus (T2DM).

METHODS

Atherosclerosis was measured by carotid intima-media thickness and calcification of the carotid and coronary arteries in 620 European Americans and 117 African Americans in the Diabetes Heart Study. Because of the role of these systems in blood pressure regulation, blood pressure was also investigated.

RESULTS

Compelling evidence of association was not detected with any of the SNPs with any outcome measures after adjustments for covariates despite sufficient power to detect relatively small differences in traits for specific genotype combinations.

CONCLUSIONS

Genetic variation of the RAS and NOS3 genes do not appear to strongly influence subclinical cardiovascular disease or blood pressure in this diabetic population.

The genetics of stroke

PURPOSE OF REVIEW

Ischaemic stroke is a heterogeneous disease caused by different pathogenic mechanisms, of which small artery and large artery stroke are the most common. The identification of the genes involved is unclear. The likely candidate genes associated with stroke are those that are associated with matrix deposition (stromelysin-1, MMP3), inflammation (IL-6), and lipid metabolism (hepatic lipase, APOE, PON1) and clotting (factor V Leiden, fibrinogen).

RECENT FINDINGS

In this review we will only discuss those genes in which there has been a significant contribution to the understanding of stroke since October 2003.

SUMMARY

The published data were reviewed to determine the robustness of these associations and to examine whether there is any evidence of risk modification by factors such as smoking habit, known to be associated with stroke.

A1166C polymorphism of angiotensin II type 1 receptor, blood pressure and arterial stiffness in hypertension

OBJECTIVE

To study the association of the AC polymorphism of angiotensin II type 1 receptor gene (AGTR1) with blood pressure and central arterial stiffness in a population of hypertensive patients referred to hospital for further work-up.

METHODS

One hundred and eighty-five patients, referred to our department from April 1998 to February 2002, were included. Blood pressure was measured by conventional and 24-h ambulatory methods, and arterial stiffness by carotid-femoral pulse wave velocity (PWV) determination. Genotyping for the AGTR1 AC polymorphism was performed by polymerase chain reaction.

RESULTS

AGTR1 AC polymorphism was not associated with systolic or diastolic blood pressure, measured either by conventional (P=0.89 and P=0.67, respectively) or by 24-h ambulatory (P=0.57 and P=0.56, respectively) methods. Conversely, this polymorphism was significantly associated with PWV (P=0.006) and had a dose-allele effect, PWV increasing with the number of A alleles (10.6 +/- 2.4 m/s in CC, 11.9 +/- 2.5 m/s in AC and 12.7 +/- 2.7 m/s in AA patients, P=0.002). Multiple regression analysis showed that AC polymorphism was still independently associated with PWV (P=0.01) and was the third most important determinant of PWV after age (P <0.0001) and 24-h mean blood pressure (P <0.0001).

CONCLUSION

In our study population, central arterial stiffness assessed by PWV was significantly and independently associated with the AC polymorphism, increased PWV being associated with the presence of the A allele. Further investigations are required for identification of the underlying mechanisms.

Gene polymorphisms of the renin???angiotensin???aldosterone system and the risk of ischemic stroke

OBJECTIVE

The role of the renin-angiotensin-aldosterone system (RAAS) genes on predisposition to develop stroke, a multifactorial and polygenic cardiovascular trait, is still under investigation. In the present study we characterized the contributory role of RAAS genes in the susceptibility to develop ischemic stroke in humans.

METHODS

Allele and genotype frequencies of RAAS genes were characterized in a population of 215 cases (including only atherothrombotic and lacunar forms) and 236 controls selected in Sardinia, a large Mediterranean island with a well-known segregated population. Statistical analysis was performed in the whole population and, based on a significant interaction between angiotensin II receptor (AT1) genotype and hypertension, was also repeated in the hypertensive subgroup.

RESULTS

A significant association of the C1166/AT1 gene allelic variant with stroke was found when assuming a dominant model of transmission [unadjusted odds ratio (OR)=1.5, 95% confidence interval (CI) 1.1-2.2, P=0.024]. The strength of the association became more evident in the subgroup of hypertensive individuals (135 cases and 110 controls). In fact, in this cohort the independent OR for the AT1 gene was 2.1, 95% CI 1.2-3.7, P=0.006 in the dominant model and 2.0, 95% CI 1.3-3.2, P=0.002 in the additive model. No other RAAS gene was identified as a contributor to stroke.

CONCLUSIONS

Our findings support a predisposing role of an AT1 gene variant in the development of ischemic stroke. In particular, the AT1 gene variant exerted a major impact on ischemic stroke occurrence in the presence of hypertension.

Genetics of Ultrasonographic Carotid Atherosclerosis

The search for genes related to the cause of common complex disorders such as cardiovascular disease has been frustrating, partly because of the many factors known to contribute to cardiovascular disease and the potential "distance" of cardiovascular disease as a phenotype from genes and gene products. Linkage and association studies for phenotypes more proximal in the pathway from DNA sequence variation to overt clinical disease, such as ultrasound-defined carotid atherosclerosis, may potentially be more enlightening. Only one genetic variant previously reported to be associated with atherosclerosis or clinically evident cardiovascular disease, matrix metalloproteinase (MMP) 3, has shown consistently positive associations with carotid disease, although it has not been studied widely. Another, PON1 L55M, is weakly associated in subgroups only, and 2, ApoE and MTHFR, are equivocal. Genetic variants reported to be associated with clinical cardiovascular disease show weak or no relationship to carotid atherosclerosis. This may reflect the known inconsistency in associations of genetic variants with clinical cardiovascular disease itself. Alternatively, genetic determinants of ultrasound-defined carotid atherosclerosis may differ from those of clinically manifest cardiovascular disease and may require pursuit through large-scale genomic studies of carotid atherosclerosis as a distinct phenotype. Only 1 genetic variant, MMP 3, has shown consistently positive associations with ultrasonographic carotid disease, although it has not been studied widely. Another, PON1 L55 mol/L, is weakly associated in subgroups only. Genetic variants reported to be associated with clinical cardiovascular disease show weak or no relationship to carotid atherosclerosis.

Genetic risk factors for stroke and carotid atherosclerosis: insights into pathophysiology from candidate gene approaches

Ischaemic stroke is the most common form of stroke and is caused by atherosclerosis in most patients. Several genetic determinants contribute to stroke risk. Of these, carotid intimal-medial wall thickness (IMT) is particularly relevant, because it is a surrogate measure of subclinical atherosclerosis and a strong predictor of future ischaemic stroke. Studies of twins, siblings, and families have provided significant evidence for heritability, but the genes involved have not been identified. Some researchers have reported that IMT is high in people with functional variants of genes related to matrix deposition (MMP3), inflammation (interleukin 6), and lipid metabolism (hepatic lipase, APOE, CETP, and PON1). In this review, we assess the robustness of these associations and examine whether there is any evidence of risk modification by factors, such as smoking.

Genetic influences on blood pressure within the Stanislas Cohort

OBJECTIVE

To investigate the association of 21 polymorphisms within 13 genes, APOE, APOB, APOC3, CETP, LPL, PON1, MTHFR, FGB, F5, GPIIIa, SELE, ACE and AGT, with inter-individual blood pressure (BP) variation.

PARTICIPANTS

Seven hundred and seventy-six men and 836 women, free of antihypertensive and lipid-lowering medications, were selected from the Stanislas Cohort.

RESULTS

ANOVA on blood pressure values after adjustment for covariates [age, body mass index (BMI), contraceptive pill, tobacco and alcohol] showed that lipoprotein lipase (LPL) Ser447Ter and glycoprotein IIIA (GpIIIa) Pl polymorphisms were significantly associated with BP in women (0.01 < or = P < or = 0.05), whereas BP levels in men were significantly different according to apolipoprotein CIII (APOC3) 3206T/G and -482C/T polymorphisms (P < or = 0.05). In women, compared to the most common allele, the GpIIIa Pl allele was associated with increased mean arterial pressure (MAP) (P < 0.05) and pulse pressure (PP) (P < 0.001), and the LPL 447Ter allele was associated with decreased systolic blood pressure (SBP) and PP levels (0.001 < or = P < or = 0.05). These two polymorphisms appeared to act independently. In men, the APOC3 3206GG genotype was related to decreased diastolic blood pressure (DBP) and MAP levels (P < or = 0.01), and the APOC3 -482T allele with decreased PP levels (P < or = 0.05). The presence of both the -482C allele and the 3206GG genotype was related to decreased DBP, suggesting that specific haplotypes might be involved.

CONCLUSION

The APOC3, LPL and GpIIIa genes were found to be associated with BP levels. The contributions of these genes, although modest, are consistent with the polygenic nature of BP levels.

Gln-Arg192 polymorphism of paraoxonase 1 is associated with carotid intima-media thickness in patients of type 2 diabetes mellitus of Chinese

Serum paraoxonase (PON) is a high-density lipoprotein-bound enzyme that can prevent oxidation of low-density lipoprotein by hydrolyzing lipid peroxides and thus exert an anti-atherogenic effect. Recent studies have suggested that glutamine(Q isoform)/arginine(R isoform) polymorphism at position 192 of PON(1) gene is associated with macrovascular disease of type 2 diabetes mellitus (T2DM). We re-investigated this relationship using carotid intima-media thickness (IMT) as a surrogate continuous variable for macroangiopathy. The genotype and allele frequency of PON(1) 192 Q/R polymorphism was assayed by polymerase chain reaction-restriction fragment length polymorphism in 152 type 2 diabetic patients and 128 healthy subjects from a population of Chinese Han nationality in ChengDu area. The carotid IMT was measured by B-mode ultrasonography in type 2 diabetic patients. No differences were found in PON(1) gene Q/R polymorphism in the type 2 diabetic patients when compared with the control group. The mean carotid IMT in type 2 diabetic subjects with the QQ, QR and RR genotype was 0.65+/-0.27, 0.83+/-0.27 and 1.05+/-0.32 mm, respectively. One-way ANOVA showed that IMT was significantly greater in the RR subgroup than in both QR and QQ subgroups (P<0.01). Multivariate logistic regression analysis showed R allele to be the main determinant of IMT variability (OR 4.0 95% CI 2.10-7.40 P=0.005). Our data support the view that 192 R allele of PON(1) gene is a risk factor for macrovascular disease of T2DM in Chinese.

Association of two angiotensinogen gene polymorphisms, M235T and G(-6)A, with chronic heart failure

The aim of the study was to focus on the relationship between the angiotensinogen (AGT) gene polymorphisms, M235T and promoter G(-6)A, and chronic heart failure in the Czech population. A total of 158 patients with chronic heart failure (functional class NYHA II-IV, ejection fraction <40%, cardiothoracic index >50%) were compared with a control group of 200 subjects of similar age and sex distribution, without any personal history of cardiovascular diseases. The AGT gene polymorphisms were detected by polymerase chain reaction (PCR) and restriction fragment length polymorphism (RFLP) methods. No significant differences in distributions of AGT genotypes between patients with chronic heart failure (CHF) and controls were found. The differences in distributions of alleles in AGT M235T (P(a)=0.02) and genotypes in AGT G(-6)A (P(g)=0.017) were found within women groups. Within CHF patients the distribution of AGT G(-6)A genotypes was not consistent with Hardy-Weinberg equilibrium (P=0.0001). We found significant relative risk of CHF in the GGMT genotype, OR=2.63 with 95% CI 1.39-4.95, P(corr)=0.01 (in the male group OR=1.83, 95% CI 0.92-3.66, P(corr)=0.3; in the female group OR=15.5, 95% CI 1.86-129.42, P(corr)=0.008). We provide evidence of increased risk in subjects with the GGMT variant of associated genotype of AGT gene for CHF, especially of fifteen-fold risk of this variant in women.

Apolipoprotein E gene polymorphisms are associated with carotid plaque formation but not with intima-media wall thickening: results from the Perth Carotid Ultrasound Disease Assessment Study (CUDAS)

BACKGROUND AND PURPOSE

Several studies have investigated the role of apolipoprotein E (apoE) polymorphisms on carotid intima-media thickness (IMT) with conflicting results. The objective of this study was to use a large, community-based population to investigate associations between apoE gene polymorphisms and cardiovascular disease-associated phenotypes: IMT, carotid artery plaque, and low- (LDL-C) and high-density lipoprotein cholesterol (HDL-C).

METHODS

ApoE genotypes were determined in 1109 randomly selected community subjects with an equal man-to-woman ratio and equal numbers in each age decile who were 27 to 77 years of age and had bilateral carotid B-mode ultrasound and cardiovascular risk factor measurements.

RESULTS

Multivariate analyses, stratified by sex, demonstrated an association between apoE genotypes and LDL-C levels in men (P=0.03) and women (P<0.001). A significant linear trend in increasing LDL-C (beta=0.33 per unit change in genotype; SE=0.07; P<0.001) levels with increasing number of epsilon4 alleles across the epsilon3/epsilon3, epsilon3/epsilon4, or epsilon4/epsilon4 genotypes was observed in women but not in men. The associations were independent of age, diastolic blood pressure, and history of diabetes mellitus. Multivariate analyses found a log-additive trend in risk of developing carotid plaque with increasing numbers of epsilon4 alleles across the epsilon3/epsilon3, epsilon3/epsilon4, and epsilon4/epsilon4 genotypes (odds ratio [OR], 1.72 per unit change in genotype; 95% CI, 1.05 to 2.80; P=0.03) in men. There was no association between plaque frequency and the epsilon4 allele in women. However, the epsilon2/epsilon3 genotype was shown to be associated with a lower OR (OR, 0.40; 95% CI, 0.17 to 0.91; P=0.03) for carotid plaques relative to the epsilon3/epsilon3 genotype in women. The associations were independent of age and standard vascular risk factors. There were no significant independent associations between apoE genotypes and IMT in either men or women.

CONCLUSIONS

Our data suggest that polymorphisms in the apoE gene are significantly associated with LDL-C levels and increased risk of carotid plaque formation in men but not IMT in either men or women.

Genetics of intima-media thickness

PURPOSE OF REVIEW

Increased carotid artery intima-media thickness is associated with an increased risk of coronary heart disease or cerebrovascular disease and is a powerful predictor of cardiovascular and cerebrovascular outcomes. Consequently, the measurement is now used in a number of case control, cohort and familial and linkage studies as an intermediate phenotype for the investigation of the genetic and environmental determinants of atherosclerosis. The aim of this paper is to review the most recent available data on the genetic determinants of carotid intima-media thickness.

RECENT FINDINGS

Genes could account for a significant amount of variation in carotid intima-media thickness: up to 30-66%. Carotid intima-media thickness progressed more rapidly with age in familial hypercholesterolemia patients than in patients without his condition. Familial hypercholesterolemia patients with a null LDL receptor allele tended to have higher carotid intima-media thickness than patients carrying the LDL receptor defective allele. Small association studies showing positive or negative results with the angiotensinogen gene variants as well as with the angiotensin converting enzyme I/D polymorphism add to the confusion in this largely controversial area. Differing results may depend on the vascular territory and genetic background. New associations have been described in small studies.

SUMMARY

Studies on the association of polymorphisms and intima-media thickness are frequently disappointing and lead occasionally to conflicting results. Among study limitations is the fact that mostly single gene effects are considered; longitudinal cohort studies may be more appropriate than case control studies. Ongoing large prospective population studies and clinical trials have integrated the measurements of intima-media thickness and genotype determination with a genomic approach. As a result, in the near future we may see more important and robust results with significant consequences on our understanding of genetic determinants of atherosclerotic cardiovascular disease.