Kazuhide Yamaoki

Genetic Polymorphism of 5,10-Methylenetetrahydrofolate Reductase (MTHFR) as a Risk Factor for Coronary Artery Disease

BACKGROUND Epidemiological studies have identified hyperhomocyst(e)inemia as an independent risk factor for coronary artery disease (CAD). Recently, the alanine/valine (A/V) polymorphism of the 5,10-methylenetetrahydrofolate reductase (MTHFR) gene, one of the key enzymes catalyzing remethylation of homocysteine, has been reported. The VV genotype correlates with increased plasma homocyst(e)ine levels as a result of the reduced activity and increased thermolability of this enzyme. In this study, we examined the distribution of the MTHFR genotypes in Japanese men and the association between the VV genotype and CAD. METHODS AND RESULTS The diagnoses of CAD of all the studied patients were confirmed by coronary angiography. The MTHFR genotype was analyzed by PCR followed by HinfI digestion. In 778 healthy male subjects, the frequency of the V allele was 0.33, comparable to that in a French Canadian population. In 362 patients with CAD, the VV genotype was significantly more frequent than in control subjects (16% versus 10%, P=.0067). The association of the VV genotype with CAD was further increased in patients with > or = 99% stenotic lesions (18%, P=.0010), whereas no significant association with the VV genotype was observed in patients without a > or = 99% stenosis. When the genotype frequency was compared among patients with different numbers of stenotic coronary arteries, the frequency of the VV genotype was significantly higher in patients with triple-vessel disease (26%) than in patients with single- or double-vessel disease (15% and 14%, respectively). CONCLUSIONS The VV genotype of MTHFR was also common in the Japanese population and was significantly associated with CAD. The frequency of this genotype in particular was correlated with the severity of disease. The VV genotype associated with a predisposition to increased plasma homocyst(e)ine levels may represent a genetic risk factor for CAD.

The possible role of endothelin-1 in the pathogenesis of coronary vasospasm

Summary We investigated the in vivo vasoconstrictor effects of endothelin-1 (ET-1) on canine coronary arteries and the regulation of ET-1 gene expression with special reference to the pathogenesis of coronary vasospasm. ET-1, administered into the coronary arteries of anesthetized dogs, produced a profound and long-lasting reduction in coronary blood flow with myocardial ischemia. Coronary angiography revealed delayed filling of the distal branches and, in some cases, total occlusion in the epicardial portions of coronary arteries. The coronary vasoconstriction induced by ET-1 subsided after intracoronary administration of nitroglycerin. Pretreatment with the Ca2+-channel antagonist, nitrendipine, suppressed ET-1-induced vasoconstriction. In cultured porcine aortic endothelial cells, ET-1 gene expression was induced by agents related to thrombus formation, such as thrombin and transforming growth factor β (TGFβ). These findings suggest that ET-1, produced by vascular endothelial cells, may contribute to the regulation of coronary circulation and the pathogenesis of coronary vasospasm with respect to intimal injury and subsequent thrombus formation.

Measurement of plasma brain natriuretic peptide level as a guide for cardiac overload.

OBJECTIVES We examined whether measurement of the plasma BNP concentrations might be useful for the early diagnosis of the existence and severity of disease in patients with heart disease in daily clinical practice. METHODS AND RESULTS The plasma BNP and ANP concentrations in 415 patients with heart disease and hypertension and 65 control subjects were measured. Patients with heart disease had higher plasma BNP and ANP concentrations than did those with hypertension or control subjects. Among the etiology of cardiac diseases, specifically dilated cardiomyopathy and hypertrophic cardiomyopathy, was associated with the highest plasma BNP concentrations, whereas dilated cardiomyopathy was associated with the highest plasma ANP concentrations. Plasma BNP concentrations showed an increase as the severity of the heart disease, as graded according to the NYHA classification of cardiac function, increased. In both patients with heart disease and hypertension, the plasma BNP values were higher in those who had abnormalities in their echocardiogram and electrocardiogram as compared to those without any abnormalities. The plasma BNP levels also showed a significant correlation with left ventricular wall thickness and left ventricular mass. On the other hand, the plasma ANP levels showed significant correlations with left ventricular dimension. Receiver operative characteristic analysis revealed that plasma BNP levels showed substantially high sensitivity and specificity to detect the existence of heart diseases. CONCLUSION Measurements of the plasma BNP concentrations is useful to detect the existence of the diseases, and abnormalities of left ventricular function and hypertrophy in patients with heart disease in daily clinical practice.

Endothelin: A potent vasoconstrictor associated with coronary vasospasm

Endothelin, administered into the coronary arteries of anesthetized dogs, produced a profound and long-lasting reduction in coronary blood flow with electrocardiographical evidence of myocardial ischemia. Coronary angiography revealed delayed filling of the distal branches and, in some cases, cessation of the blood flow distal to the epicardial portions of coronary arteries. The coronary vasoconstriction induced by endothelin subsided after intracoronary administration of nitroglycerin. Pretreatment with the Ca2+-channel antagonist, nitrendipine, suppressed endothelin-induced vasoconstriction. These findings suggest that endothelin, produced by vascular endothelial cells, may contribute to the pathogenesis of coronary vasospasm.

Effect of long-term treatment with beta-blocker on cardiac hypertrophy in SHR.

Recent studies suggest that beta-blocker treatment may attenuate cardiac hypertrophy induced by pressure overload in the spontaneously hypertensive rat (SHR), but the effect of this therapy on the reconstitution of the intracellular constituents in the heart that occurs during the development of cardiac hypertrophy has not been examined. In this study, we investigated the effect of chronic administration of carteolol (4 mg/kg/day p.o.) or propranolol (20 mg/kg/day p.o.), beta-blockers with distinct modes of action, on the composition of cardiac myosin isozymes and histological findings as well as heart weight. Therapeutic periods were 4, 12 or 30 weeks. Though blood pressure was not significantly reduced, the development of cardiac hypertrophy was suppressed as evidenced by left ventricular weight in both groups of carteolol- and propranolol-treated SHR for all therapeutic periods. Again, beta-blocker treatment for 12 weeks alleviated myocardial degeneration and reactive fibrosis which were observed in all cases of age-matched untreated SHR. However the extent of the transition of cardiac myosin isozymes from V1 to V2 or V3 were essentially the same among all groups including untreated SHR. These results indicate that chronic administration of beta-blockers attenuates the development of cardiac hypertrophy and degeneration without affecting the transition of myosin isozymes which is thought to be a kind of biochemical adaptation of the myocardium to overload.

Angiotensin converting enzyme polymorphism is associated with severity of coronary heart disease and serum lipids (total cholesterol and triglycerides levels) in Japanese patients.

BACKGROUND Much past research has concerned the relationship between coronary heart disease and the angiotensin converting enzyme (ACE) genotype, with many lines of evidence demonstrating polymorphism to be an independent risk factor for myocardial infarction. Interestingly, however, association of ACE polymorphism and severity of coronary artery stenosis according to racial background has recently been proposed. OBJECTIVE To clarify the relationship between the ACE genotype and severity of coronary artery stenosis in Japanese patients. METHODS In 36 consecutive patients undergoing coronary catheterization, comparative examination of coronary angiography findings with the ACE genotype was conducted. RESULTS The severity of coronary artery stenosis indeed showed a relationship with the ACE genotype, with more severe coronary artery stenosis associated with the deletion (D) allele (P < 0.05). The serum lipids, total cholesterol and triglycerides levels, were also elevated in patients with the D allele (P < 0.05). CONCLUSION We have provided further evidence that ACE polymorphism is associated with severity of coronary heart disease in a Japanese population. A possible relationship between serum lipids and the ACE genotype is also suggested.

Quantification of myocardial infarct size after coronary reperfusion by serum cardiac myosin light chain II in conscious dogs.

The effects of early coronary artery reperfusion on the relation between the extent of myocardial infarction and serum levels of cardiac myosin light chain II or plasma creatine kinase levels were evaluated in the conscious dog. Hydraulic occluders were placed on the left anterior descending arteries of 38 dogs. Seven to 10 days later, myocardial infarction was produced. Coronary reperfusion was performed 3 hours (group Al, n=13) and 6 hours (group A2, n = l2) after the occlusion. In the other 13 dogs, coronary occlusion was sustained throughout the course of the experiment (group B). Seven days after the occlusion, the heart was cut from the apex to the base into 4-mm slices, and infarct size was determined macroscopically. Rapid appearance and early peaking of creatine kinase were observed in group A. Cumulative release of creatine kinase significantly correlated with infarct size in group A (infarct size ranged from 0.1 to 20.1 g, r=0.90) and group B (from 0.6 to 26.8 g, r=0.91). However, since creatine kinase release in group A was greater in comparison with that from infarcts of the same size in group B, the slope of the regression line for group A was significantly steeper (p<0.05). Cardiac myosin light chain II appeared as early as creatine kinase did and continued to be elevated for 7 days. A very close relation was observed between infarct size and total cardiac myosin light chain II release (r=0.87 for group A, and r=0.88 for group B) or peak level of light chain II (r=0.85 for group A, and r=0.81 for group B). In addition, the slopes of the regression lines for infarct size and both peak and total release of light chain II did not differ between group A and group B. On histological examination, viable myocardium was frequently observed in the epicardium of the ischemic area in group Al; therefore, infarct size was greater in group B than in group Al (p<0.05). Also, myocardial creatine kinase content in the epicardium of the center of the ischemic area in group Al was greater than that in group B. Cardiac myosin light chain II release in group Al was less than that in group B, whereas no difference was found in plasma creatine kinase release among groups Al, A2, and B. These results suggest that serum levels of cardiac myosin light chain II better quantitate the extent of infarction than plasma creatine kinase levels do. The relations stand regardless of the presence of coronary reperfusion, probably because of the gradual degradation of the myosin molecule.

Serial Changes in Cytosolic, Mitochondrial, and Lysosomal Enzymes and Cardiac Myosin Light Chain II in Plasma following Coronary Ligation in Conscious Closed-Chest Dogs

We studied serial changes in various myocardial enzymes and cardiac myosin light chain II (LCII) in plasma following coronary ligation in 14 conscious closed-chest dogs. Cytoplasmic enzymes [creatine phosphokinase (CPK) and supernatant glutamic oxaloacetic transaminase (sGOT)] reached maximum at 12-24 hr and returned to normal at 72-96 hr. The mitochondrial isozyme of GOT (mGOT) began to rise at 6-9 hr, peaked at 12-30 hr (4.8-42.2 IU/liter), and stayed higher at 96 hr than before infarction. Glutamate dehydrogenase (GLDH), another mitochondrial enzyme, began to elevate at 6-16 hr and reached maximum at 24-60 hr (6.2-20.5 U/liter); GLDH also showed higher levels at 96 hr than before infarction. N-Acetyl-beta-glucosaminidase (NAG), a lysosomal enzyme, showed a biphasic pattern in every case. The first peak appeared at 3-12 hr, and the second one at 36-72 hr. Myosin LCII began to rise at 3-9 hr, peaked at 30-120 hr (34-136 ng/ml), and remained elevated for 7 to 10 days. Determination of these myocardial enzymes or LCII in plasma is useful for the diagnosis of acute myocardial infarction.

Transmitral reversed blood flow during mid- and end diastole in constrictive pericarditis

block in the AP. A development of this type would suggest the possibility of an AP with relatively long refractory periods. This response would delineate a group of patients who most probably would have slow ventricular rates during atria1 fibrillation. In the case presented, exercise testing uncovered a second AP. The possibility that the two QRS morphologies observed do not represent two different APs but instead represent artifactual, positional, or respiratory changes is highly unlikely. This can be seen in the center strip of Fig. 3, where alternating patterns of QRS morphology are clearly delineated. To our knowledge, the demonstration of multiple AP by exercise testing has not yet been reported in the medical literature. The identification of multiple AP is, however, likely to be of clinical significance. Klein et a1.3 discuss patients with WPW syndrome in whom ventricular fibrillation (VF) occurred as a consequence of atria1 fibrillation, with rapid conduction over the AP. These patients were compared to cases with no history of VF. A higher prevalence of reentrant tachycardia, as well as atrial fibrillation, was found in the patients who developed VF. Moreover, the mean R-R interval during atria1 fibrillation was shorter than in patients without VF, and the incidence of multiple AI% was also higher in this group. Five of 25 patients with VF were found to have multiple APs, compared to 4 of 73 patients without VF (p = 0.012). In summation, it is reasonable to state that the diagnostic modality of exercise testing may help to expose multiple APs.

Myocardial Infarct Size from Serum Cardiac Myosin Light Chain

The relationship between myocardial infarct size and serum cardiac light chain (LC) levels was studied in experimental and clinical myocardial infarction. In dogs with left anterior descending coronary artery occlusion, regression analysis showed good correlation between infarct size and LC II release, but CPK-MB release failed to correlate with infarct size because of a decreasing value of cumulative CPK with larger sized infarctions. In patients with acute myocardial infarction, Peak LC I levels correlated well with CPK release, since the phenomenon of the decreased CPK release in larger sized infarction was not so distinctive in human cases. Thus, LC determination may better quantitate the extent of myocardial damage as well as provide a specific and sensitive method for diagnosis of acute myocardial infarction.