Yi-Heng Li

Effects of oxidative stress on endothelial function after a high-fat meal

Postprandial lipaemia is known to cause endothelial dysfunction, but its underlying mechanism is still under debate. The present study was undertaken to investigate the effects of postprandial lipaemia on endothelial dysfunction and oxidative stress. We measured plasma glutathione peroxidase (GSH-Px), an antioxidant enzyme, and the urinary excretion of 8-epi-prostaglandin F2alpha (8-PGF2alpha), a free radical-catalysed product from the oxidative modification of arachidonic acid, in 16 healthy subjects (mean age, 30 +/- 5 years) without major coronary risk factors. Plasma high-sensitive C-reactive protein, soluble intercellular cell-adhesion molecule-1 and vascular cell-adhesion molecule-1 were also measured. High-resolution ultrasound was used to assess the flow-mediated vasodilatation (FMD) of the brachial artery. Blood and urine samples were collected before and 2, 4 and 6 h after a standard high-fat meal (3677 J, containing 50 g of fat). Serum triacylglycerol (triglyceride) increased and FMD decreased significantly after a high-fat meal. Plasma GSH-Px significantly decreased from 27.2 +/- 12.3 microg/ml to 25.7 +/- 11.8 microg/ml (P=0.022) 2 h after the meal, and urinary excretion of 8-PGF2alpha significantly increased from 1286 +/- 1401 pg/mg of creatinine to 2197 +/- 1343 pg/mg of creatinine (P=0.014) at 4 h after the meal. However, there were no significant changes in the levels of high-sensitive C-reactive protein and adhesion molecules after a high-fat meal. In conclusion, endothelial dysfunction was observed after consuming a high-fat meal and is associated with augmented oxidative stress manifested by the depletion of serum antioxidant enzymes and increased excretion of oxidative modification products.

G-33A Mutation in the Promoter Region of Thrombomodulin Gene and Its Association With Coronary Artery Disease and Plasma Soluble Thrombomodulin Levels

Thrombomodulin is an endothelial glycoprotein that decreases thrombin activity and activates protein C. A recent study has shown that G-33A promoter mutation of the thrombomodulin gene occurs particularly in Asians. In this study, we analyzed the distribution of G-33A mutation in the promoter region of the thrombomodulin gene in the Chinese population and determined whether the mutation might be a risk for coronary artery disease (CAD). In addition, the influence of this mutation on plasma soluble thrombomodulin levels in patients with CAD was also examined. We studied 320 consecutive patients (mean age 63 years; 73% men) with CAD and 200 age- and sex-matched control subjects. Screening for thrombomodulin G-33A promoter mutation was conducted using polymerase chain reaction, single-strand conformation polymorphism, and direct deoxyribonucleic acid sequencing. The frequency of the G-33A mutation (GA+AA genotypes) was significantly higher in the CAD group (23.8% vs 15.5%, odds ratio [OR] 1.70, p = 0.031). Multiple logistic regression analysis showed that the mutation was an independent risk factor (OR 1.81, p = 0.016) for CAD, as was hypertension (OR 1.44, p = 0.040), diabetes mellitus (OR 2.50, p <0.001), and smoking (OR 2.15, p <0.001). In CAD patients with GG genotype, the soluble thrombomodulin level increased with the extent of CAD (36 +/- 15 vs 47 +/- 18 vs 55 +/- 36 ng/ml in 1-, 2-, or 3-vessel CAD, p <0.001). However, in CAD patients with G-33A mutation, there was no difference between the levels of soluble thrombomodulin (39 +/- 17 vs 37 +/- 15 vs 42 +/- 18 ng/ml, p = NS) in 1-, 2-, or 3-vessel CAD. Our observations suggest that there is a significant association of the G-33A mutation in thrombomodulin gene with CAD, and this mutation may influence the soluble thrombomodulin levels in patients with CAD.

Functional mutation in the promoter region of thrombomodulin gene in relation to carotid atherosclerosis

Thrombomodulin is an important endothelial anticoagulant protein that decreases thrombin activity and activates protein C. Our recent study has shown that the G-33A promoter mutation of thrombomodulin gene is associated with coronary artery disease. This study was conducted to determine whether the G-33A mutation in the promoter region of thrombomodulin gene is a genetic risk factor for ischemic stroke or carotid atherosclerosis. The functional significance of this mutation was also evaluated. We recruited 333 patients (mean age 64 years, 59% male) with ischemic stroke and 257 age- and sex-matched controls. In all study participants, carotid atherosclerosis was assessed by Duplex scanning, and thrombomodulin G-33A promoter mutation was detected by single-strand conformation polymorphism. Luciferase reporter gene assay was used to assess the influence of this mutation on thrombomodulin promoter activity. There was no significant difference in the thrombomodulin G-33A mutation frequency (GA+AA genotypes) between the stroke and the control groups (18.3 vs. 24. 1%, P=0.105). The G-33A mutation frequency was also similar between the study participants with and without carotid atherosclerosis (22.2 vs. 19.8%, P=0.550). When only younger subjects (age </=60 years) were included in the analysis, however, we found the mutation occurred more frequently in participants with carotid atherosclerosis (33.3 vs. 17.3%, odds ratio [OR]=2.38, 95% confidence interval [CI]=1.16-4.90, P=0.027). Multiple logistic regression analyses showed that only diabetes mellitus (OR=3.11, 95% CI=1.33-7.30, P=0.009) and G-33A mutation (OR=2.46, 95% CI=1.14-5.29, P=0.021) were associated independently with carotid atherosclerosis in younger subjects. As assessed by luciferase reporter gene assays, the contructs bearing the G-33A mutation showed a significant decrease (36+/-12%) in transcriptional activity in comparison with the wild type constructs. Our findings suggest that G-33A mutation reduces the thrombomodulin promoter activity and is associated with carotid atherosclerosis in younger subjects.

Doppler evaluation of peripheral vascular adaptations to transverse aortic banding in mice

Abstract Transverse aortic banding in mice is commonly used to produce pressure overload, but the resulting cardiac hypertrophy is variable and the actual load produced is unknown. The purposes of the study were to characterize peripheral blood flow in banded mice using noninvasive Doppler methods, investigate whether changes in flow could predict the amount of cardiac hypertrophy induced and validate the simplified Bernoulli equation for estimating the pressure drop across the stenosis in very small vessels. Wild-type mice underwent aortic banding ( n = 15) or sham operation ( n = 6). Doppler velocity was measured in the right and left carotid arteries (RCA and LCA) 1 day later, and the heart weight/body weight ratio was measured at 7 days. The RCA/LCA peak velocity ratio at 1 day was significantly correlated with the heart weight/body weight ratio at 7 days after banding (r = 0.62, p p 2 ) can be used to estimate the pressure drop across the aortic band in mice noninvasively. (E-mail: chartley@bcm.tmc.edu)

Pulsed Doppler signal processing for use in mice: applications

We have developed a high-frequency, high-resolution Doppler spectrum analyzer (DSPW) and compared its performance against an adapted clinical Medasonics spectrum analyzer (MSA) and a zero-crossing interval histogram (ZCIH) used previously by us to evaluate cardiovascular physiology in mice. The aortic velocity (means /spl plusmn/ SE: 92.7 /spl plusmn/ 2.5 versus 82.2 /spl plusmn/ 1.8 cm/s) and aortic acceleration (8194 /spl plusmn/ 319 versus 5178 /spl plusmn/ 191 cm/s/sup 2/) determined by the DSPW were significantly higher compared to those by the MSA. Aortic ejection time was shorter (48.3/spl plusmn/ 0.9 versus 64.6 /spl plusmn/ 1.8 ms) and the isovolumic relaxation was longer (17.6 /spl plusmn/ 0.6 versus 13.5 /spl plusmn/0.6 ms) when determined by the DSPW because it generates shorter temporal widths in the velocity spectra when compared to the MSA. These data indicate that the performance of the DSPW in evaluating cardiovascular physiology was better than that of the MSA. There were no significant differences between the aortic pulse wave velocity determined by using the ZCIH (391 /spl plusmn/ 16 cm/s) and the DSPW (394 /spl plusmn/ 20 cm/s). Besides monitoring cardiac function, we have used the DSPW for studying peripheral vascular physiology in normal, transgenic, and surgical models of mice. Several applications such as the detection of high stenotic jet velocities (>4 m/s), vortex shedding frequencies (250 Hz), and subtle changes in wave shapes in peripheral vessels which could not obtained with clinical Doppler systems are now made possible with the DSPW.

Time domain heart rate variability as a predictor of long-term prognosis after acute myocardial infarction.

BACKGROUND AND PURPOSEnDecreased heart rate variability (HRV) has been shown to be a predictor of both sudden cardiac death and cardiovascular death among patients surviving acute myocardial infarction (MI). However, the prognostic significance of time domain HRV in patients with MI is still controversial. In addition to the mean of all normal-to-normal (NN) intervals, we analyzed the prognostic significance of the 5 most widely used time domain parameters of HRV during long-term follow-up in patients surviving their first MI.nnnMETHODSnFive time domain measures of HRV from 24-hour ECG were obtained after discharge in 260 consecutive patients (207 males; mean age, 60 years) surviving their first MI. These parameters included: standard deviation of all NN intervals, mean of standard deviations of all NN intervals in all 5-minute segments (SDNNi), standard deviation of the average of all NN intervals in all 5-minute segments, the square root of the mean of the sum of the squares of differences between adjacent NN intervals, and percentage of differences between adjacent NN intervals > 50 ms.nnnRESULTSnThe study endpoint was cardiovascular death. After follow-up for 67 months (range, 1 to 114 months), there were 55 cardiovascular deaths (21%) including 39 sudden deaths (15%). Multivariate Cox regression analysis showed that SDNNi < 30 ms was a significant predictor of cardiovascular death (hazard ratio, 4.98; 95% confidence interval [CI], 2.03 to 12.21; p < 0.001) as was number of ventricular premature complexes >/= 10 beats/hour (hazard ratio, 5.34; 95% CI, 2.26 to 12.62; p < 0.001), age >/= 70 years (hazard ratio, 3.65; 95% CI, 1.44 to 9.23; p = 0.006), and left ventricular ejection fraction < 45% (hazard ratio, 3.29; 95% CI, 1.13 to 9.57; p = 0.03). SDNNi < 30 ms was also an important predictor of sudden cardiac death (hazard ratio, 5.02; 95% CI, 1.49 to 16.85; p = 0.009).nnnCONCLUSIONSnThese data suggest that SDNNi is a significant time domain parameter of HRV for long-term prognosis in post-MI patients.

Association of elevation of anti-Helicobacter pylori antibody with myocardial ischemic events in coronary artery disease.

There is a growing body of evidence supporting the concept that inflammation plays an important role in the initiation and progression of atherosclerosis and its complications.1,2 Previous studies 1,3 have demonstrated that there are infectious and noninfectious factors that may drive the inflammatory activities in coronary artery disease (CAD). Helicobacter pylori (H. pylori) is a gram-negative, flagellate bacillus that is associated with peptic ulcer disease and gastric malignancy.4 The relation between H. pylori infection and CAD has been studied extensively.5‐ 8 Nevertheless, the effect of H. pylori infection on the long-term outcome of patients with CAD remains unknown. Because serum level of specific anti-H. pylori immunoglobulin G (anti-H. pylori IgG) antibody is a reliable indicator of chronic H. pylori infection,9,10 we evaluated the serum concentrations of anti-H. pylori IgG antibody among patients with CAD in this study to determine whether H. pylori infection was a predictor for subsequent ischemic events during followup. ••• Ninety consecutive patients admitted to our hospital with a diagnosis of CAD were included in this study. All patients underwent coronary angiography and had coronary stenosis .50% in diameter in

Indices of aortic stiffness in mice

1 major coronary artery. After admission, these patients received appropriate treatment, including percutaneous transluminal coronary angioplasty (n 5 30), coronary bypass surgery (n 5 30), or medication only (n 5 30). Of these patients, 4 were excluded because 1 patient died during bypass surgery and 3 patients were lost to follow-up. The remaining 86 patients (mean age 62 years; 64 men) formed the basis of this study. No patients had peptic ulcer disease, uremia, and any previous coronary intervention or bypass surgery. According to the World Health Organization diagnostic criteria, 48 patients had a previous myocardial infarction. The 86 patients were free of ischemic symptoms when discharged from our hospital and regularly followed in our cardiology clinic after discharge. The study end points were acute myocardial infarction, or hospital readmission due to newly developed class III or IV angina according to Canadian Cardiovascular Society classification. Blood samples were drawn after fasting overnight and before catheterization for anti-H. pylori IgG antibody study. The blood samples were centrifuged at 1,000 g for 10 minutes. The supernatant serum was collected and immediately frozen at 270°C until analyzed. Serum assay for specific anti-H. pylori IgG antibody was performed using a highly sensitive and specific enzyme-linked immunosorbent assay (HEL-p test, Amrad Corporation, Victoria, Australia). The IgG assay had both a sensitivity and specificity of .90%. 11,12 All patients were divided into 2 groups according to the occurrence or nonoccurrence of new ischemic events. Levels of anti-H. pylori IgG antibody, clinical characteristics, and management were compared between patients with or without ischemic events. Chisquare tests were used for categorical variables, and Student’s t tests were used for continuous variables. Pearson’s correlation analysis was used to assess the relation between levels of anti-H. pylori IgG antibody and patients’ age, concentrations of serum lipoproteins, C-reactive proteins, and left ventricular ejection fraction. A Cox proportional hazard model was used for analysis of the risk factors for ischemic events. The data for levels of anti-H. pylori IgG antibody

Prognostic value and the changes of plasma levels of secretory type ii phospholipase a2 in patients with coronary artery disease undergoing percutaneous coronary intervention

Ascending aortic input impedance spectra and pressure augmentation index was determined in young (8-month) and old (29-month) mice to see if arterial stiffening occurred with age in mice as it does in humans. Pressure and blood velocity signals measured simultaneously from the same location in the ascending aorta of a mouse were used to determine input impedance spectra (DC-10 harmonics). The first minimum of the impedance modulus shifted from the 2nd harmonic in young mice to the 4th harmonic in old mice. Characteristic impedance (estimated as average of 2nd to 10th harmonic) was significantly higher in old mice (mean/spl plusmn/SEM, 471/spl plusmn/62 vs. 299110 dynes-s/cm/sup 3/, p<0.05). Pulse pressure and augmentation index, determined from the aortic pressure signals were also higher in old mice: pulse pressure (42/spl plusmn/2.2 vs. 29/spl plusmn/4.9 mmHg, p<0.05) and augmentation index (37/spl plusmn/5 vs. 14/spl plusmn/2 %, p<0.005). These results are similar to the findings reported in humans and confirm that mice may be used as models of age-related vascular stiffening.