Gentaro Watanabe

A 192Arg Variant of the Human Paraoxonase (HUMPONA) Gene Polymorphism Is Associated With an Increased Risk for Coronary Artery Disease in the Japanese

Recent reports have suggested that polymorphisms in the human paraoxonase (HUMPONA) gene may be a genetic risk factor for coronary artery disease (CAD) in white populations. However, this association has not yet been confirmed in other ethnic populations. We studied 75 Japanese patients with CAD, whose coronary lesions were confirmed by angiography, and 115 Japanese control subjects with no history of CAD and a normal resting electrocardiogram. The assays for genotyping the two polymorphisms in the HUMPONA gene (192Arg/Gln and 55Leu/Met) were based on changes in restriction enzyme digestion patterns. For codon 192, the frequencies of the Arg-coding allele (B allele) in both patients and control subjects were much higher than those from published results of whites (.26 to .31), and the difference between patients (.74) and control subjects (.59) was statistically significant (P = .002). The patient group had a higher proportion of Arg/Arg (B/B) homozygotes (52.0% vs 32.2%, P = .006). For codon 55, the frequencies of the Leu-coding allele in control subjects and patients were much higher (.91 and .93, respectively) than those published results for whites, but there was no difference between Japanese control subjects and Japanese patients. When subjects with the 55Leu/Leu genotype only were analyzed, 192Arg/Arg homozygotes were still significantly more frequent in the patients than in the control subjects (55.4% vs 37.2%, P = .024), and the frequency of the 192Arg allele was also higher in patients than control subjects (P = .013). Logistic regression analysis including conventional coronary risk factors revealed that 192Arg is an independent risk factor for CAD. Thus, in the Japanese, the association of CAD with the 192Arg variant of HUMPONA (B-type enzyme) is similar to that reported for whites, although the allele frequencies for 192Arg and 55Leu are much higher in the former than the latter population.

Coronary Artery Disease and Polymorphisms in a Receptor Mediating Shear Stress–Dependent Platelet Activation

BACKGROUND Platelets play pivotal roles in coronary thrombosis, and antiplatelet therapies are widely used for coronary artery disease (CAD). However, the effects of genetic variation in platelets on CAD are poorly understood. We have assessed the association between CAD and polymorphisms in a platelet receptor for von Willebrand factor, the glycoprotein (GP) Ib/IX complex, which mediates shear stress-dependent platelet activation. METHODS AND RESULTS Genotypes of the alpha-chain of the receptor (GP Ib alpha, 145Thr/Met) were determined in 91 patients with myocardial infarction (MI) or angina pectoris whose lesions were confirmed by coronary angiography as well as in 105 individuals from the general population with no history of angina or other heart diseases and normal resting ECGs. There was no homozygote for Met/Met in either the control or patient groups. The prevalence of the Thr/Met genotype (T/M) in all patients was not significantly different from that in the control group. However, the frequency of T/M was significantly higher in patients aged < or = 60 years (31.8%) than in control subjects aged < or = 60 years (16.0%; P<.05, odds ratio=2.5). An association was also demonstrated between CAD and the other polymorphism of GP Ib alpha, a variable number of tandem repeats of a 13-amino acid sequence, which is known to be linked to the 145Thr/Met polymorphism. There was an association between the frequency of the T/M genotype and the angiographic severity of CAD: 11.1% for Gensini score < 40 versus 50.0% for Gensini score > or = 40 (P=.0015). There was no difference in the distribution of GP Ib alpha genotypes between patients with MI and those with angina pectoris. CONCLUSIONS This study suggests that the presence of the Met allele in GP Ib alpha is a risk factor for the prevalence and severity of CAD in individuals aged < or = 60 years. The results need to be confirmed in a large-scale study of incident case subjects and matching control subjects.

Genotype distribution of estrogen receptor polymorphisms in men and postmenopausal women from healthy and coronary populations and its relation to serum lipid levels

The cardiovascular protective effects of estrogen are known to be mediated by its beneficial effects on lipid metabolism and its direct actions on the vessel wall. The latter can be mediated by a specific receptor for estrogen present on smooth muscle cells and endothelial cells. The gene for the receptor (the classic estrogen receptor [ER]) has three known polymorphisms, Pvu II, Xba I, and B-variant polymorphisms, which are reportedly associated with receptor expression and altered receptor function and with some disorders including breast cancer, hypertension, and spontaneous abortion. However, the significance of genetic variations of the ER in vascular diseases has not been reported. We have examined the association between coronary artery disease (CAD) and the three polymorphisms in ER. Genotypes (P1/P2, X1/X2, and B-wild type/B-variant type) were determined in 87 men and postmenopausal women with myocardial infarction or angina pectoris whose lesions were confirmed by coronary angiography, as well as from 94 control individuals from the general population with no coronary heart disease and normal resting ECG. For B-variant polymorphism, all individuals examined had B-wild type, which contrasts with the reported allele frequency for B-variant type (0.1) in the white population. Genotype distributions and allele frequencies of Pvu II or Xba I polymorphisms were not significantly different between control subjects and patients (P > .05 for Pvu II or Xba I genotypes; P > .05 for Pvu II or Xba I allele frequencies). When the allele frequencies were analyzed separately by sex, there was still no statistically significant difference for both polymorphisms (P > .05 for men; P > .05 for women). No association was found between the polymorphisms and the angiographic severity of CAD. Total cholesterol, triglyceride, or HDL-cholesterol levels were not significantly different among ER genotypes. These findings suggest that the three polymorphisms in ER are not associated with the prevalence and severity of CAD and that the polymorphisms are unrelated to the serum lipid levels in control subjects and patients.

Angiotensin converting enzyme insertion/deletion polymorphism is associated with plasma antigen levels of plasminogen activator inhibitor-1 in healthy Japanese population

Plasminogen activator inhibitor-1 (PAI-1) has a central role in the regulation of the fibrinolytic enzyme system. An elevated plasma PAI-1 level is associated with thrombotic disorders. In vitro and in vivo studies indicate that the renin-angiotensin system is involved in the regulation of PAI-1. A 287-bp insertion/deletion (I/D) polymorphism in the gene-encoding angiotensin converting enzyme (ACE) is associated with cardiovascular disorders. We evaluated the association between the ACE I/D polymorphism and plasma PAI-1 antigen levels in 110 healthy Japanese male subjects. Subjects with the D-allele of the gene-encoding ACE had higher levels of PAI-1 (26.3 +/- 14.7 ng/ml, mean +/- standard deviation) compared with those without (21.0 +/- 12.0; P = 0.0491). A multiple linear regression model with independent variables (age, body-mass index, total cholesterol level, triglyceride level, ACE I/D genotype, and PAI-1 genotype due to a single guanine I/D polymorphism in the PAI-1 gene) demonstrated that the triglyceride level (P = 0.0059) and ACE I/D genotype (P = 0.0372) were independent predictors of plasma PAI-1 antigen levels in a subset of the subjects without diabetes mellitus that were not taking lipid-lowering drugs. These findings suggest that the ACE I/D polymorphism is a genetic factor for the regulation of plasma PAI-1 antigen levels in the healthy Japanese population.

Enhancing effect of the 145Met-allele of GPIb alpha on platelet sensitivity to aspirin under high-shear conditions

Aspirin (ASA) is widely used as an antiplatelet drug, and a large number of clinical trials with ASA have demonstrated significant efficacies for the prevention and treatment of atherothrombosis [1,2]. Recent accumulating evidence, however, indicates that there are individuals with unexpected platelet reactivity to ASA [3]. This subpopulation, called ASA resistant, has lower sensitivity to ASA in ex vivo and in vitro platelet function tests and has poor clinical outcomes. The mechanism underlying the variability in ASA sensitivity is largely unknown. The glycoprotein (GP) Ib/IX/V complex is a receptor for von Willebrand factor (VWF) that mediates sheardependent platelet function. GPIbα, the largest subunit of this complex, contains the VWF binding site [4]. Binding of VWF to GPIbα has critical roles in thrombus formation at the site of vascular injury, especially under high shear conditions. The GPIbα/

Alpha 2A adrenergic receptor polymorphism is associated with plasma von Willebrand factor levels in a general population

High levels of plasma von Willebrand factor are a proposed risk factor for atherothrombotic disorders. Previously, ABO blood type and the von Willebrand factor −1793C/G polymorphism were shown to affect interindividual variations in plasma von Willebrand factor levels. We previously reported that polymorphisms of the alpha 2A adrenergic receptor, an epinephrine receptor, were associated with platelet function as assessed by platelet function analyzer-100. The measurement value of platelet function analyzer-100 has been reportedly associated with plasma von Willebrand factor levels. Also, it was demonstrated that epinephrine administration increases plasma von Willebrand factor levels in vivo. Thus, the present study investigated the association between plasma von Willebrand factor levels and genetic polymorphisms as follows: ABO blood type, von Willebrand factor −1051G/A (linked with −1793C/G), alpha 2A adrenergic receptor 1780A/G, and alpha 2A adrenergic receptor 2372A/G. Study subjects were genetically unrelated Japanese men (n = 277) recruited at their regular medical examinations. Genotyping of the polymorphisms was performed using the single nucleotide primer extension-based method. Plasma von Willebrand factor levels were measured as ristocetin-cofactor activities. The O blood type and alpha 2A adrenergic receptor 2372AA genotype were significantly associated with lower von Willebrand factor levels, though von Willebrand factor −1051G/A polymorphism did not affect them. In stratification analysis of the group according to blood type O and non-O, the significant association between the 2372AA genotype and lower plasma von Willebrand factor levels was observed in non-O subjects, but not O subjects. In conclusion, the alpha 2A adrenergic receptor 2372A/G polymorphism is associated with plasma von Willebrand factor levels in a general population.