Cho-Kai Wu

Increased Expression of Mineralocorticoid Receptor in Human Atrial Fibrillation and a Cellular Model of Atrial Fibrillation

OBJECTIVES This study was designed to evaluate the status of steroidogenesis proteins and de novo synthesis of aldosterone in the atrium, and relationships of these factors to atrial fibrillation (AF). BACKGROUND The role of mineralocorticoid in the pathogenesis of AF is unknown. METHODS We studied atrial expression of steroidogenesis proteins and aldosterone level in patients with and without AF, and in HL-1 atrial myocytes. We also investigated the electrophysiologic effects and signal transduction of aldosterone on atrial myocytes. RESULTS We found basal expressions of mineralocorticoid receptors (MRs), glucocorticoid receptors, and 11-beta-hydroxysteroid dehydrogenase type 2 (11bHSD2) but not 11-beta-hydroxylase (CYP11B1) or aldosterone synthase (CYP11B2) in human atria and HL-1 myocytes. There was no significant difference of mean atrial aldosterone level between patients with AF and those with normal sinus rhythm. However, patients with AF had a significantly higher atrial MR expression compared with those with normal sinus rhythm (1.73 +/- 0.24-fold, p < 0.001). Using mouse HL-1 atrial myocytes as a cellular AF model, we found that rapid depolarization increased MR expression (1.97 +/- 0.72-fold, p = 0.008) through a calcium-dependent mechanism, thus augmenting the genomic effect of aldosterone signaling as evaluated by MR reporter. Aldosterone increased intracellular oxidative stress through a nongenomic pathway, which was attenuated by nicotinamide adenine dinucleotide phosphate oxidase inhibitor diphenyleneiodonium, but not by MR-blockade spironolactone. Aldosterone increased expression of the alpha-1G and -1H subunits of the T-type calcium channel and thus increased the T-type calcium current (-13.6 +/- 2.9 pA/pF vs. -4.5 +/- 1.6 pA/pF, p < 0.01) and the intracellular calcium load through a genomic pathway, which were attenuated by spironolactone, but not by diphenyleneiodonium. CONCLUSIONS Expression of MR increased in AF, thus augmenting the genomic effects of aldosterone. Aldosterone induced atrial ionic remodeling and calcium overload through a genomic pathway, which was attenuated by spironolactone. These results suggest that aldosterone may play a role in AF electrical remodeling and provide insight into the treatment of AF with MR blockade.

CMR-Verified Diffuse Myocardial Fibrosis Is Associated With Diastolic Dysfunction in HFpEF

OBJECTIVES The purpose of this study was to investigate diffuse myocardial fibrosis in patients with systolic heart failure (SHF) and in patients with heart failure with preserved ejection fraction (HFpEF) and the association with diastolic dysfunction of the left ventricle (LV). BACKGROUND Increased diffuse myocardial fibrosis may impair LV diastolic function. However, no study has verified the association between the degree of diffuse myocardial fibrosis and the severity of impaired diastolic function in SHF and HFpEF. METHODS Forty patients with SHF, 62 patients with HFpEF, and 22 patients without HF underwent cardiac magnetic resonance (CMR), including T1 mapping and cine CMR on a 3-T system. Extracellular volume fraction (ECV), a measure of diffuse myocardial fibrosis, was quantified from T1 mapping. Systolic and diastolic functions of the LV were assessed by cine CMR. The ECV values and LV functional indexes were compared among the 3 groups. Associations between ECV and LV diastolic function were also investigated. RESULTS Compared with patients without HF, significantly higher ECV was found in patients with SHF (31.2% [interquartile range (IQR): 29.0% to 34.1%] vs. 27.9% [IQR: 26.2% to 29.4%], p < 0.001) and HFpEF (28.9% [IQR: 27.8% to 31.3%] vs. 27.9% [IQR: 26.2% to 29.4%], p = 0.006). Peak filling rate, a diastolic functional index assessed by cine CMR, was significantly decreased in patients with SHF (1.00 s(-1) [IQR: 0.79 to 1.49 s(-1)] vs. 3.86 s(-1) [IQR: 3.34 to 4.48 s(-1)], p < 0.001) and HFpEF (2.89 s(-1) [IQR: 2.13 to 3.50 s(-1)] vs. 3.86 s(-1) [IQR: 3.34 to 4.48 s(-1)], p < 0.001). Myocardial ECV was significantly correlated with peak filling rate in the HFpEF group (r = -0.385, p = 0.002), but no correlation was found in the SHF and non-HF groups (r = 0.030, p = 0.856 and r = -0.238, p = 0.285, respectively). CONCLUSIONS In patients with HF, only those with HFpEF show a significant correlation between increased diffuse myocardial fibrosis and impaired diastolic function. Diffuse myocardial fibrosis plays a unique role in the pathogenesis of HFpEF.

Plasma levels of tumor necrosis factor-α and interleukin-6 are associated with diastolic heart failure through downregulation of sarcoplasmic reticulum Ca2+ ATPase.

Objective:The inflammatory process is associated with cardiac diastolic dysfunction, which has been demonstrated to be an independent prognostic marker for the mortality of critically ill patients. We investigated the association among inflammatory cytokines (tumor necrosis factor-&agr; and interleukin-6), diastolic heart failure, and the possible molecular mechanism. Design:Prospective case-controlled cohort and molecular studies. Setting:University hospital and research laboratory. Subjects:Patients with a diagnosis of diastolic heart failure by echocardiography and matched control subjects from the general population (study group 1) and also subjects from the intensive care unit (study group 2). Sarcoplasmic reticulum Ca2+-ATPase (SERCA2) gene expression and diastolic calcium decay in HL-1 cardiomyocytes were used as molecular phenotypes of diastolic heart failure. Interventions:Soluble plasma levels of tumor necrosis factor-&agr; and interleukin-6 were measured in all subjects. An approximate 1.75-kb promoter of the SERCA2 gene was cloned to the pGL3 luciferase reporter. The effect of tumor necrosis factor-&agr; and interleukin-6 on SERCA2 gene expression and diastolic calcium decay of HL-1 cardiomyocytes were investigated. Measurements and Main Results:Patients with diastolic heart failure had significantly higher plasma levels of tumor necrosis factor-&agr; and interleukin-6 than the control subjects. Significant correlations (p < .01 for each) were found for tumor necrosis factor-&agr; and E/Em (r = .87) and E/A (r = −0.69), and for interleukin-6 and E/Em (r = .80) and E/A (r = −0.65). Cytokine levels were also correlated with diastolic function in critically ill patients (study group 2), and diastolic function improved significantly in association with decrease of cytokines. Tumor necrosis factor-&agr;, interleukin-6, and sera from critically ill patients downregulated the expression of the SERCA2 gene. Tumor necrosis factor-&agr; and interleukin-6 also delayed the diastolic calcium reuptake and decay in cardiomyocytes. Conclusions:Through downregulation of SERCA2 gene expression, inflammatory cytokines may cause cardiac diastolic dysfunction by decreasing diastolic calcium reuptake. Our study may suggest novel therapeutic strategies for diastolic heart failure and critically ill patients by modulating inflammatory reactions.

Cystatin C and Long-Term Mortality Among Subjects With Normal Creatinine-Based Estimated Glomerular Filtration Rates : NHANES III (Third National Health and Nutrition Examination Survey)

OBJECTIVES The objective was to test the association of cystatin C (Cys-C) with long-term mortality risk in the subjects with normal creatinine-based estimated glomerular filtration rates (eGFR). BACKGROUND Cys-C has been proposed as a sensitive indicator of renal dysfunction that is associated with cardiovascular events. The predictive value of Cys-C for mortality risk (both cardiovascular and noncardiovascular) and its utility among persons with normal kidney function remains unclear. METHODS The analysis included 2,990 subjects over 40 years of age with normal eGFR who participated in NHANES III (Third National Health and Nutrition Examination Survey). Normal eGFR was defined by Modification of Diet in Renal Disease (MDRD) equation ≥60 ml/min/1.73 m(2). Serum Cys-C was categorized as high, medium, or low. In 1 analysis, the high and low groups were the top and bottom 10%, and in the second analysis, they were the upper and lower thirds. All-cause and cause-specific mortality were obtained from the NHANES III-linked follow-up file through December 31, 2006. Multivariate Cox regression models were applied to assess the association of interest. RESULTS Within an average of 13.7 years follow-up, 488 cardiovascular and 719 noncardiovascular deaths occurred. When the first and last deciles were compared, the relative risks were all increased statistically as follows: all-cause, 4.36 (95% confidence interval [CI]: 2.52 to 7.82); cardiovascular, 7.44 (95% CI: 3.06 to 18.1); cancer, 2.45 (95% CI: 0.85 to 7.04); and noncardiovascular 3.15 (95% CI: 1.53 to 6.49) mortalities. Relative risks all moderated to lower values when the comparisons were expanded to include the upper and lower thirds. Similar associations were still present when Cys-C was modeled on a continuous scale, suggesting a linear relationship between Cys-C and mortality outcomes. CONCLUSIONS Serum Cys-C is prognostic of long-term mortality in the subjects with relatively normal renal function, independent of MDRD eGFR and albuminuria.

Association of low glomerular filtration rate and albuminuria with peripheral arterial disease: The National Health and Nutrition Examination Survey, 1999–2004

Microalbuminuria may be an early sign of intra-renal vascular dysfunction and a marker of vascular risk in the general population as well as in high-risk individuals. However, the association between albuminuria and PAD has been demonstrated only in few small studies. The aim of current study is to evaluate the relative impact of albuminuria and glomerular filtration rate on the risk of peripheral artery disease (PAD) in a nationally representative sample population. Data (ankle brachial index [ABI], urine albumin, fasting glucose, and glomerular filtration rate [GFR] estimated using the Modification of Diet in Renal Disease [MDRD] Study equation) were collected on 7068 adults from the National Health and Nutrition Examination Survey (NHANES 1999-2004). PAD was defined as ABI <0.9 or >1.4. There was a trend towards an association between the presence of abnormal renal function (GFR<60mL/min/1.73m(2)) and PAD in the non-diabetic patients (OR of 1.43, 95% CI: 0.98-2.09; P=0.07) where as the presence of abnormal renal function was strongly associated PAD in the diabetic patients (OR of 2.3, 95% CI: 1.34-3.95; P=0.046). On the contrary, albuminuria was independently associated with PAD in the non-diabetic (OR, 1.87; 95% CI, 1.38-2.52; P=0.0003) but not in the diabetic patients (OR: 1.08, 95% CI: 0.68-1.73, P=0.7411). We concluded that albuminuria, independent of renal function, is strongly associated with PAD in non-diabetic subjects. As diabetes develops and HbA1c level increases, the predictive value of albuminuria gradually diminishes after adjustment for renal function.

Demonstrating the pharmacogenetic effects of angiotensin-converting enzyme inhibitors on long-term prognosis of diastolic heart failure

The objective of this study was to evaluate the effects of angiotensin-converting enzyme (ACE) inhibitors and pharmacogenetic interaction on the survival of the patients with diastolic heart failure (DHF). A total of 285 subjects with DHF confirmed by echocardiography were recruited in the period between 1995 and 2003. Baseline characteristics (age, sex, prior history, medication, and echocardiographic findings) and genetic polymorphisms (ACE gene insertion/deletion (I/D) polymorphism; T174M, M235T, G-6A, A-20C, G-152A, and G-217A polymorphisms of the angiotensinogen (AGT) gene; and A1166C polymorphisms of the angiotensin II type I receptor (AT1R)) were collected and matched (by propensity score) in those who received and those who did not receive ACE inhibitors. The patients were followed up to 10 years. Kaplan–Meier curves and Cox regression models were used to demonstrate the survival trend. The 85 patients who received ACE inhibitors and the other 85 patients who did not were found to have comparable baseline characteristics and polymorphism distribution. Prescription of ACE inhibitors was associated with a significant decrease in overall mortality (hazard ratio (HR), 0.45; 95% confidence interval (CI), 0.24–0.83; P=0.01), and a lower rate of cardiovascular events at 4000 days (HR, 0.53; 95% CI, 0.32–0.90; P=0.02). In addition, ACE I/D gene D allele was associated with higher overall mortality as compared with the I allele (HR, 2.04; P=0.003). This effect was diminished in those who received ACE inhibitors. The use of ACE inhibitor was associated with a significant decrease in long-term mortality and cardiovascular events in the patients with DHF. Genetic variants in the renin-angiotensin system genes were also associated, but their effects could be modified by the use of ACE inhibitors.

In-vitro recording of adult zebrafish heart electrocardiogram — A platform for pharmacological testing

BACKGROUND Recently zebrafish has become a powerful vertebrate model system for cardiac arrhythmia and another advantage is that the heart could be rapidly excised for in-vitro electrophysiological recording. METHODS We made direct in-vitro recordings of adult zebrafish heart ECG using the microelectrode and tested the effects of various drugs on zebrafish heart ECG. RESULTS The QT interval change in the ECG was verified by optically mapped action potential duration (APD). The mean in-vitro heart rate (HR) of the adult zebrafish was 118 ± 22 beats/min. The mean QT interval was 312 ± 36 ms and mean HR corrected QT interval (QTc) 439 ± 39 ms. The mean optically mapped APD was 308 ± 30 ms, which was close to the QT interval in ECG (p=0.815). We found that sympathomimetic drug isoproterenol increased HR, whereas L-type calcium channel blocker verapamil decreased HR. Sodium channel blocker quinidine and L-type calcium channel activator BayK8644 prolonged QTc interval in a dose-dependent manner (515 ± 24 ms and 519 ± 27 ms, respectively, both p<0.01). The APD was also prolonged accordingly. Both rapidly and slowly activating delayed rectifier potassium channel (IKr and IKs) blockers E4031 and chromanol 293B, respectively, also prolonged QTc interval in a dose-dependent manner (523 ± 25 ms and 529 ± 27 ms, respectively, both p<0.01). Quinidine, E4031 and chromanol 293B also decreased HR. CONCLUSIONS Direct in-vitro recording of adult zebrafish heart is an efficient platform for test of drugs which exert electrophysiological effects on cardiomyocytes, and perturbation of ionic channels that are responsible for human long QT syndrome also modulates QT interval in adult zebrafish heart.

A propensity score-based case-control study of renin-angiotensin system gene polymorphisms and diastolic heart failure

Angiotensin II plays an important role in diastolic heart failure (DHF). However, genetic studies of DHF are scarce in the literature. We hypothesized that RAS genes might be the susceptible genes for DHF and conducted a propensity score-based case-control study to prove this hypothesis. A total of 666 subjects (285 diagnosed with DHF confirmed by echocardiography and 381 without diastolic dysfunction) were recruited. Genotyped were: the angiotensin-converting enzyme (ACE) gene insertion/deletion polymorphism; the T174M, M235T, G-6A, A-20C, G-152A and G-217A polymorphisms of the angiotensinogen (AGT) gene; and the A1166C polymorphisms of the angiotensin II type I receptor (AT1R) gene. Propensity scores (PS) were used to find patients with and without DHF with equalized characteristics. We also assembled another set of PS matched groups for all characteristics except left ventricular mass (LVM) to detect the genetic association with DHF through the effect of left ventricular hypertrophy. PS matched 210 patients with DHF to 210 without. In a single-locus analysis, the odds ratios (ORs) for DHF were significant with the ACE DD genotype (OR=1.30, 95% CI=1.13-1.49, permuted P=0.003) and the AT1R 1166 CC genotype (OR=2.61, 95% CI=1.52-4.45, permuted P<0.001). Significant gene-gene interaction between the two genes was also detected. However, the ACE gene effect was diminished if LVM was not controlled in the propensity scores. We concluded that genetic variants in the RAS genes may determine individual risk to develop DHF through different pathways. Concomitant presence of ACE DD and AT1R 1166 CC genotypes synergistically increased the predisposition to DHF.

The Relationship Among Central Obesity, Systemic Inflammation, and Left Ventricular Diastolic Dysfunction as Determined by Structural Equation Modeling

The purpose of this study was to investigate the associations among central obesity, inflammation, and left ventricular (LV) diastolic dysfunction by structural equation modeling. Echocardiographic parameters were assessed in 102 otherwise‐healthy adults over age 30. The participants were classified as having LV diastolic dysfunction by echocardiographic findings including mitral inflow E/A ratio <1, deceleration time >220 cm/s, or decreased peak annular early diastolic velocity in tissue Doppler imaging or otherwise the control group. Serum C‐reactive protein (CRP) and lipid profile were also measured. The homeostasis model of insulin resistance (HOMA) was calculated. Central obesity was assessed by computerized tomography (CT) at the L4 level. In a multivariate regression analysis, the relationship between visceral adipose tissue (VAT) and LV diastolic dysfunction became insignificant when CRP was introduced into the model, although CRP itself was significantly associated with LV diastolic dysfunction (odds ratio (OR): 1.32, 95% confidence interval (CI): 1.01–1.72, P = 0.04). A significant correlation was also found between VAT and CRP (r = 0.70; P < 0.001). We then performed path analysis as illustrated by the structural equation model. This proved our hypotheses that VAT might affect LV diastolic dysfunction through the effect of CRP (total fat load with inflammation (B = 1.133, P < 0.001) and that inflammation might affect LV diastolic dysfunction (B = 0.373. P < 0.001)). Using structural equation modeling, we concluded that higher amounts of VAT were associated with low‐grade inflammation and this may lead to subclinical LV diastolic dysfunction in otherwise‐healthy subjects.

Renin-angiotensin system gene polymorphisms and diastolic heart failure

Background  Diastolic heart failure (DHF) refers to an abnormality of diastolic distensibility, filling or relaxation of the left ventricle. The genetic study of DHF is scarce in the literature. The association of renin‐angiotensin system (RAS) and DHF are well known. We hypothesized that RAS genes might be the susceptible genes for DHF and conducted a case‐control study to prove the hypothesis.