Emma Hawe

Apolipoprotein E4 and coronary heart disease in middle-aged men who smoke: a prospective study

BACKGROUND The common isoforms of apolipoprotein E (apoE), E2, E3, and E4, are important determinants of plasma lipid concentrations, and the epsilon4 allele is associated with raised risk of coronary heart disease. We investigated whether the effect of smoking on coronary heart disease risk is affected by APOE genotype. METHODS We enrolled 3052 middle-aged men who were free of coronary heart disease for prospective cardiovascular surveillance in the second Northwick Park Heart Study (NPHSII). Smoking habit was ascertained at baseline and yearly by questionnaire. APOE genotype was identified by PCR and restriction enzyme digestion. Endpoints were fatal coronary heart disease, non-fatal myocardial infarction, and coronary artery surgery and silent myocardial infarction at follow-up. FINDINGS During 18836 person years of surveillance, 96 men had an acute myocardial infarction, 26 needed coronary artery surgery, and 14 had silent myocardial infarctions. Compared with never-smokers, risk of coronary heart disease in ex-smokers was 1.34 (95% CI 0.86-2.08) and in smokers it was 1.94 (1.25-3.01). This risk was independent of other classic risk factors. In never-smokers, risk was closely similar in men with different genotypes. Risk in men homozygous for the epsilon3 allele was 1.74 (1.10-2.77) in ex-smokers and 1.68 (1.01-2.83) in smokers, whereas in men carrying the epsilon4 allele risk was 0.84 (0.40-1.75) and 3.17 (1.82-5.50), respectively, with no significant differences in risk in the epsilon2 carriers. For the epsilon3 group, the genotype effect on risk was no longer significant after adjustment for classic risk factors (including plasma lipids). However, even after adjustment, smokers who were carriers of the epsilon4 allele, showed significantly raised risk of coronary heart disease compared with the non-smoking group (2.79, 1.59-4.91, epsilon4-smoking interaction p=0.007). INTERPRETATION Smoking increases the risk of coronary heart disease in men of all genotypes but particularly in men carrying the epsilon4 allele.

Plasma Thrombin-Activatable Fibrinolysis Inhibitor Antigen Concentration and Genotype in Relation to Myocardial Infarction in the North and South of Europe

The thrombin-activatable fibrinolysis inhibitor (TAFI) is a recently described inhibitor of fibrinolysis that decreases plasminogen binding to the fibrin surface. The plasma TAFI concentration is almost entirely genetically determined. We investigated whether plasma TAFI levels and polymorphisms located in the TAFI gene could constitute risk markers of myocardial infarction (MI). Plasma TAFI antigen (Ag) levels were assayed by ELISA and 2 TAFI gene polymorphisms (Ala147Thr and C+1542G in the 3′ untranslated region) were determined in a large European case-control study. This study compared 598 men recruited 3 to 6 months after MI with 653 age-matched controls from North Europe (Stockholm, Sweden, and London, England) and South Europe (Marseilles, France, and San Giovanni Rotondo, Italy). A TAFI Ag value above the 90th percentile was associated with a significantly lower risk of MI (odds ratio 0.55, P <0.02), indicating that elevated TAFI may be protective against MI. As previously shown, the 2 TAFI gene polymorphisms were in strong linkage disequilibrium and were associated with the TAFI Ag concentration, with carriers of the Thr147 and 1542C alleles having higher levels (P <0.0005). These effects were similar in controls and cases and in each center. There was a difference in allele frequency between cases and controls for the Ala147Thr polymorphism, with Thr147 allele carriers being more frequent in controls than in cases in 2 centers, Stockholm (P =0.03) and San Giovanni Rotondo (P =0.03); the odds ratio for the entire cohort was 0.78 (P <0.05). In conclusion, patients with a recent MI presented lower values of TAFI Ag and higher frequencies of the “TAFI-decreasing” alleles. The geographical differences observed do not contribute to explaining the North-South gradient in MI risk in Europe.

Peroxisome Proliferator-Activated Receptor α Gene Variants Influence Progression of Coronary Atherosclerosis and Risk of Coronary Artery Disease

BACKGROUND Peroxisome proliferator-activated receptor alpha (PPARalpha) regulates the expression of genes involved in lipid metabolism and inflammation, making it a candidate gene for atherosclerosis and ischemic heart disease (IHD). METHODS AND RESULTS We investigated the association between the leucine 162 to valine (L162V) polymorphism and a G to C transversion in intron 7 of the PPARalpha gene and progression of atherosclerosis in the Lopid Coronary Angiography Trial (LOCAT), a trial examining the effect of gemfibrozil treatment on progression of atherosclerosis after bypass surgery and on risk of IHD in the second Northwick Park Heart Study (NPHS2), a prospective study of healthy middle-aged men in the United Kingdom. There was no association with plasma lipid concentrations in either study. Both polymorphisms influenced progression of atherosclerosis and risk of IHD. V162 allele carriers had less progression of diffuse atherosclerosis than did L162 allele homozygotes with a similar trend for focal atherosclerosis. Intron 7 C allele carriers had greater progression of atherosclerosis than did G allele homozygotes. The V162 allele attenuated the proatherosclerotic effect of the intron 7 C allele. Homozygotes for the intron 7 C allele had increased risk of IHD, an effect modulated by the L162V polymorphism CONCLUSIONS The PPARalpha gene affects progression of atherosclerosis and risk of IHD. Absence of association with plasma lipid concentrations suggests that PPARalpha affects atherosclerotic progression directly in the vessel wall.

Endothelial NO Synthase Genotype and Risk of Preeclampsia: A Multicenter Case-Control Study

Polymorphisms in the endothelial NO synthase (eNOS) gene have been evaluated as risk factors for preeclampsia. However, data from small studies are conflicting. We assessed whether eNOS genotypes alter the risk of preeclampsia in a population in which the incidence of this disorder is high. A total of 844 young pregnant women (322 preeclamptic and 522 controls) were recruited from 5 cities. Genotyping for the Glu298Asp, intron-4 and –786T→C polymorphisms in the eNOS gene was conducted. Multivariate odds ratios (ORs) were obtained to estimate the association of individual polymorphisms and haplotypes with preeclampsia risk. No increase in the risk of preeclampsia for the intron-4 or –786T→C polymorphisms was observed under any model of inheritance. In contrast, in women homozygous for the Asp298 allele, the adjusted OR for preeclampsia was 4.60 (95% confidence interval [CI], 1.73 to 12.22) compared with carriers of the Glu298 allele. After a multivariate analysis, carriage of the “Asp298–786C-4b” haplotype was also associated with increased risk of preeclampsia (OR, 2.11 [95% CI, 1.33 to 3.34]) compared with carriers of the “Glu298–786T-4b” haplotype. The eNOS Glu298Asp polymorphism and the Asp298–786C-4b haplotype are risk factors for preeclampsia.

Genetic Variants of Angiotensin II Receptors and Cardiovascular Risk in Hypertension

Abstract—Renin-angiotensin systems may mediate cardiovascular disease pathogenesis through a balance of actions of angiotensin II on (potentially proatherogenic) constitutive type 1 (AT1R) and (potentially antiatherogenic) inducible type 2 (AT2R) receptors. We explored such potential roles in a prospective candidate gene association study. Cardiovascular end points (fatal, nonfatal, and silent myocardial infarction and coronary artery bypass surgery/angioplasty) were documented among 2579 healthy UK men (mean age, 56.1±3.5 years; median follow-up, 10.1 years) genotyped for the AT1R1166A>C and the X chromosome located AT2R1675A>G and 3123C>A polymorphisms. Baseline characteristics, including blood pressure, were independent of genotype. The AT1R1166CC genotype was associated with relative cardiovascular risk (hazard ratio, 1.65 [1.05 to 2.59]; P =0.03) independent of blood pressure. Systolic blood pressure was associated with risk (P =0.0005), but this association was restricted to AT2R1675A allele carriers (P <0.00001), with G allele carriers protected from the risk associated with blood pressure (P =0.18). Hypertensive carriers with the AT2R1675A/3123A haplotype were at most risk, with 37.5% having an event. This is the first study to demonstrate an association of AT2R genotype with coronary risk, an effect that was confined to hypertensive subjects and supports the concept that the inducible AT2R is protective. Conversely, the AT1R1166CC genotype was associated with cardiovascular risk irrespective of blood pressure. These data are important to our understanding of the divergent role of angiotensin II acting at its receptor subtypes and coronary disease pathogenesis and for the development of future cardiovascular therapies.

Family History is a Coronary Heart Disease Risk Factor in the Second Northwick Park Heart Study

We have estimated the risk of coronary heart disease (CHD) from family history of CHD (FHCHD) in 2827 healthy European middle‐aged men, and explored the extent to which this can be explained by classical and genetic risk factors. Men with FHCHD (obtained by questionnaire) had a hazard ratio of CHD of 1.73 (95% confidence interval: 1.30, 2.31) compared to those without FHCHD; after adjusting for classical risk factors this did not change substantially. Those with FHCHD had 2.3% lower Factor VIIc (p = 0.03) and 1.14% higher systolic and 1.21% higher diastolic blood pressure (p = 0.04 and p = 0.02), with evidence of interaction between blood pressure and FHCHD status on risk (p = 0.01). The risk for those with a positive family history who were also current smokers was 3.01 compared to non‐smokers without FHCHD, which is greater than the risk posed by smoking or FHCHD alone (1.96 and 2.05 respectively compared to non‐smokers without FHCHD), but not significantly different from a multiplicative model (p‐value for interaction 0.33). Allele frequencies for 13 candidate gene variants were not significantly different between those with and without FHCHD. In those with FHCHD, current smokers who carried the APOE4 allele (e4+) had a hazard ratio of 5.66 compared to non‐smokers who had no FHCHD and were not APOE4+, with a significant interaction between smoking and APOE4 in those with FHCHD p = 0.001. These data demonstrate the complex interaction between genetic and environmental factors in determining CHD risk, and suggest that the causes of the familial clustering of CHD remain largely unexplained.

The Significant Increase in Cardiovascular Disease Risk in APOEɛ4 Carriers is Evident Only in Men Who Smoke: Potential Relationship Between Reduced Antioxidant Status and ApoE4

Data from 1668 men (316 cardiovascular disease events) from the Framingham Offspring Study was reanalysed, specifically examining APOE:smoking interactions. Overall hazard ratio (HR) for smoking was 1.95 (1.52, 2.50) compared to non‐smokers. Using ɛ3/3 as a referent group, in non‐smokers HRs for ɛ2 carriers (ɛ2+; 1.04 (0.61, 1.76) and ɛ4 carriers (ɛ4+; 1.04 (0.70, 1.54) showed no major risk increase. In smokers, HRs were 1.96 (1.26, 2.78) in ɛ3ɛ3 men, 3.46 (2.14, 5.60; p = 0.09 for interaction) in ɛ2+ and 3.81 (2.49, 5.84; p = 0.01 for interaction), with a significant interaction between daily cigarette consumption and APOE genotype on risk (p = 0.03). The potential mechanism for this APOEɛ4:smoking interaction was examined in a second study of 728 Caucasian patients with diabetes, where markers of reactive oxygen species were available. APOE genotype was not associated with plasma OX‐LDL or total antioxidant status (TAOS) in non‐smokers. However, in smokers ɛ4+ had 26.7% higher plasma OX‐LDL than other genotypes (APOE:smoking interaction p = 0.04), while ɛ2+ had 28.4% higher plasma TAOS than ɛ3ɛ3 and ɛ4+ combined (APOE:smoking interaction p = 0.026). Although direct extrapolation needs to be considered with caution, these results identify that the cardiovascular disease risk‐raising effect of ɛ4+ is confined to smokers, and a feasible mechanism is presented by the reduced antioxidant capacity/increased OX‐LDL of apoE4.

Apolipoprotein AIV Gene Variant S347 Is Associated With Increased Risk of Coronary Heart Disease and Lower Plasma Apolipoprotein AIV Levels

Abstract— The impact of common variants in the apolipoprotein gene cluster (APOC3-A4-A5) on prospective coronary heart disease (CHD) risk was examined in healthy UK men. Of the 2808 men followed over 9 years, 187 had a clinically defined CHD event. Examination of 9 single nucleotide polymorphisms (SNPs) in this group revealed that homozygotes for APOA4 S347 had significantly increased risk of CHD [hazard ratio (HR) of 2.07 (95%CI 1.04 to 4.12)], whereas men homozygous for APOC3 1100T were protected [HR 0.28 (95%CI 0.09 to 0.87)]. In stepwise multiple regression analysis, after entering all the variants and adjusting for established risk factors APOA4 T347S alone remained in the model. Using all nine SNPs, the highest risk-estimate haplotypes carried APOA4 S347 and rare alleles of the two flanking intergenic markers. The protective effect of APOC3 1100T could be explained by negative linkage disequilibrium with these alleles. To determine the association of APOA4 T347S with apoAIV levels, the relationship was examined in 1600 healthy young European men and women. S347 homozygotes had significantly lower apoAIV plasma levels (13.64±0.59 mg/dL) compared with carriers of the T347 allele (14.90±0.12 mg/dL) (P =0.035). These results demonstrate that genetic variation in and around APOA4, independent of the effects of triglyceride, is associated with risk of CHD and apoAIV levels, supporting an antiatherogenic role for apoAIV.

The plasminogen activator inhibitor-1 -675 4G/5G genotype influences the risk of myocardial infarction associated with elevated plasma proinsulin and insulin concentrations in men from Europe: The HIFMECH Study

Summary.  Although the potential role of plasminogen activator inhibitor‐1 (PAI‐1) in the development of coronary artery disease is strongly supported by its biological characteristics, results of clinical studies remain controversial. Objectives: To investigate whether plasma PAI‐1 concentrations and the −675 4G/5G polymorphism located in the PAI‐1 gene could constitute risk markers for myocardial infarction (MI). Patients and methods: We used a European case–control study, the HIFMECH study, comparing 598 men with MI and 653 age‐matched controls. Results: Insulin resistance explained a major part of the variation in PAI‐1 (24%) whereas inflammation had only a minor contribution (0.01%). For both cases and controls plasma PAI‐1 concentrations were significantly higher in the North than the South, and in both regions were higher in individuals with MI compared with control subjects [overall odds ratio (OR) for a 1 SD increase = 1.54, 95% confidence interval (CI) 1.34, 1.77]. This difference was observed in all the centers studied. Overall, the difference between cases and control subjects remained significant after controlling for inflammation variables (OR = 1.30, 95% CI 1.08, 1.57), but lost significance after controlling for insulin resistance variables (OR = 1.17, 95% CI 0.98, 1.40). The 4G allele was associated with significantly higher PAI‐1 levels in cases but not controls and, taken independently, did not modify the risk of MI (P = 0.9). However, a significant interaction was observed with both insulin or proinsulin and the risk of MI (P = 0.05 and 0.02, respectively), but not with triglycerides or body mass index (BMI). The insulin or proinsulin effect on risk was observed only in the carriers of the 4G/4G genotype. This interaction appeared not to be mediated by plasma PAI‐1 antigen concentrations (P = 0.01 and 0.02 after adjustment for PAI‐1 plasma levels). The interaction with proinsulin but not insulin remained statistically significant after further adjustment for other factors associated with insulin resistance (triglycerides and BMI) and C‐reactive protein (P = 0.01). Conclusion: This study suggests that PAI‐1 has a role in risk of MI in the presence of underlying insulin resistance. A significant interaction between insulin or proinsulin and the −675 4G/5G polymorphism was observed in risk for MI. The mechanisms for these interactions remain to be determined.

Variation in bradykinin receptor genes increases the cardiovascular risk associated with hypertension

AIMS The contribution of kinins to the beneficial effects of angiotensin I converting enzyme (ACE) inhibition in cardiovascular risk reduction remains unclear. The genes for the kinin inducible B1 receptor (B(1)R) and constitutive B2 receptor (B(2)R) contain functional variants: the B(1)R-699C (rather than G) and the B(2)R(-9) (rather than +9) alleles are associated with greater mRNA expression and the B(2)R(-9) allele with reduced left ventricular hypertrophic responses. We tested whether these gene variants influenced hypertensive coronary risk in a large prospective study. METHODS AND RESULTS Two thousand, seven hundred and six previously healthy UK men (mean age at recruitment 56 years; median follow-up 10.8 years) were genotyped for the kinin receptor variants. The coronary risk attributable to systolic hypertension (SBP>/=160 mmHg) was significantly higher only in B(1)R-699GG homozygotes (HR 2.14 [1.42-3.22]; P<0.0001) and B(2)R(+9,+9) individuals (HR 3.51 [1.69-7.28]; P=0.001) but not in B(1)R-699C allele carriers (HR 0.82 [0.28-2.42]; P=0.76) or in B(2)R(-9,-9) homozygotes (HR 1.25 [0.51-3.04]; P=0.63). CONCLUSIONS Common variation in the genes for the kinin B(1)and B(2)receptors influences prospective hypertensive coronary risk. These are the first reported human data to suggest a role for the B(1)R in human coronary vascular disease, and the first prospective study to demonstrate a similar role for the B(2)R.