Kazushi Murakami

Pioglitazone improves left ventricular diastolic function and decreases collagen accumulation in prediabetic stage of a type II diabetic rat.

This study investigated the effect of pioglitazone, an insulin sensitizer, on metabolic abnormalities and oxidative stress as a cause of myocardial collagen accumulation in prediabetic rat hearts. Twenty male diabetic rats and 9 male nondiabetic age-matched rats were used. The diabetic rats were divided into two groups: diabetic treated and untreated. Pioglitazone was mixed in rat chow fed to the diabetic treated group (0.01%). Treatment duration was 5 weeks. At baseline (15 weeks) and 20 weeks of age, blood glucose, lipid, insulin, and plasma malondialdehyde-thiobarbituric acid (MDA) levels were measured and Doppler echocardiography was tracked. At 20 weeks of age, left ventricular collagen content was studied. Blood glucose, plasma insulin, and triglyceride levels in the diabetic treated group were significantly lower than those in the untreated diabetic group. Deceleration time (ms) of early diastolic inflow in the treated diabetic group decreased significantly compared with the untreated diabetic group (65 ± 8 vs. 77 ± 8, p < 0.01). Ratio of left ventricular weight to body weight (mg/g) and ratio of left ventricular collagen content to dry weight (mg/100 mg) were decreased in the treated diabetic group (1.5 ± 0.1, 1.3 ± 0.3) compared with the untreated diabetic group (1.7 ± 0.2, p < 0.01; 1.7 ± 0.3, p < 0.05). Plasma MDA concentration (nmol/ml) significantly decreased (2.9 ± 0.3 at baseline to 2.3 ± 0.3 at 20 weeks, p = 0.001) in the treated diabetic group, and was lower than that in the untreated diabetic group (3.2 ± 0.7 at 20 weeks, p < 0.05). Pioglitazone improved glucose and lipid metabolism and reduced oxidative stress in the left ventricle, which decreased left ventricular collagen accumulation and improved left ventricular diastolic function of prediabetic rat hearts.

Contribution of reactive oxygen species to the pathogenesis of left ventricular failure in Dahl salt-sensitive hypertensive rats: effects of angiotensin II blockade.

Objective We investigated the contribution of reduced nicotinamide-adenine dinucleotide phosphate (NADPH) oxidase-dependent reactive oxygen species (ROS) generation to the pathogenesis of diastolic heart failure (DHF) in Dahl salt-sensitive (DS) hypertensive rats, with the aim of testing our hypothesis that the cardioprotective effects of angiotensin II (Ang II) blockade are provided by the suppression of this pathway. Methods DS rats were maintained on high (H: 8.0% NaCl) or low (L: 0.3% NaCl) salt diets from age 7 to 17 weeks. DS/H rats were also treated with candesartan cilexetil (10 mg/kg per day, orally) or a superoxide dismutase mimetic, tempol (3 mmol/l in drinking water) from age 7 to 17 weeks. Results DS/H rats represented hypertension, left ventricular (LV) relaxation abnormality and myocardial stiffening with preserved systolic heart function. As compared with DS/L rats, DS/H rats showed higher levels of transforming growth factor-β (TGF-β), connective tissue growth factor (CTGF), p22phox and gp91phox mRNA expression, NADPH oxidase activity and thiobarbituric acid-reactive substance (TBARS) contents in LV tissues. Gene expression of uncoupling protein-2 (UCP-2), an inner mitochondrial membrane proton transporter, was also 2.8 ± 0.5-fold higher. In DS/H rats, treatment with candesartan did not alter blood pressure, but resulted in a marked improvement of the hemodynamic deterioration; these therapeutic effects were accompanied by decreases in myocardial NADPH oxidase activity, TBARS contents and the expression of TGF-β, CTGF, p22phox, gp91phox and UCP-2. Similar therapeutic effects were provided by treatment with tempol in DS/H rats. Conclusions Our data suggest that NADPH oxidase-mediated ROS production contributes to the pathogenesis of DHF in DS hypertensive rats, and that the cardioprotective effects of AngII blockade are, at least partially, mediated through the suppression of this pathway.

Prevention of doxorubicin (adriamycin)-induced cardiomyopathy by simultaneous administration of angiotensin-converting enzyme inhibitor assessed by acoustic densitometry.

The purpose of our study has to determine the myocardial protective effects of the angiotensin-converting enzyme (ACE) inhibitor temocapril (TEM, 7 mg/kg/day) simultaneously administered with doxorubicin (Adriamycin). Twenty male Sprague-Dawley rats were intraperitoneally administered a cumulative dose of 15 mg/kg of doxorubicin (each dose of 1.0 mg/kg x 15) for 3 weeks, and divided into TEM-untreated and -treated rats. Seven control rats were injected with saline intraperitoneally. Body weight, hemodynamics, and echocardiographic measurements including quantitative analysis of ultrasonic integrated backscatter (IB) were obtained for 12 weeks after treatment. Finally, rats were killed for histopathologic study. At 6 weeks, end-diastolic left ventricular diameter (LVD) and percentage fractional shortening (%FS) were similar in TEM-treated and TEM-untreated rats, but cyclic variation of IB (dB) significantly decreased in TEM-untreated rats (7.3 +/- 1.2; control rats, 9.7 +/- 0.9; p < 0.01). At 12 weeks, %FS decreased in TEM-untreated rats (26.1 +/- 6.1%: TEM-treated rats, 34.2 +/- 6.2; p < 0.05), and calibrated IB (dB) in TEM-untreated rats (15.5 +/- 0.5) increased as compared with that in TEM-treated rats (12.1 +/- 0.7; p < 0.01). Interstitial collagen accumulation increased in TEM-untreated rats and was inhibited in treated rats. Simultaneous administration of TEM with doxorubicin was beneficial in preventing doxorubicin-induced myocardial damage, and myocardial tissue characterization was useful for the early detection of myocardial damage and the assessment of therapy.

Perindopril Effect on Uncoupling Protein and Energy Metabolism in Failing Rat Hearts

Uncoupling proteins, inner mitochondrial membrane proton transporters, are important for regulating myocardial energy efficiency. We investigated the effects of the ACE inhibitor perindopril on cardiac performance, myocardial energy efficiency, and uncoupling protein expression in an aortic regurgitation rat model. Twenty male Sprague-Dawley rats, in which aortic regurgitation was produced, were divided into untreated and perindopril-treated (5 mg · kg−1 · d−1) rats. The treatments were initiated 3 days after operation. Ten control rats were sham-operated. Measurements of blood pressure and echocardiography were repeated before and 100 days after operation (endpoint). Left ventricular uncoupling protein-2 expression, creatine phosphate, and adenosine triphosphate were measured at endpoint. In perindopril-treated rats, systolic and diastolic blood pressure decreased after treatment (92±4/65±2 mm Hg). At endpoint, left ventricular end-diastolic dimension in untreated (10.7±0.2 mm) and treated rats (9.2±0.2 mm) was increased, and fractional shortening was reduced in untreated rats (28±1%) but did not change in treated rats (36±2%). Uncoupling protein-2 mRNA expression increased in untreated rats (3.7-fold) and was suppressed by perindopril (1.5-fold). The creatine phosphate was reduced in untreated rats (10.6±0.7 &mgr;mol/g) but not in treated rats (15.9±2.0 &mgr;mol/g). In the chronic stage of aortic regurgitation, perindopril improved cardiac performance and myocardial energy efficiency, in which the suppression of uncoupling protein-2 may play an important role.

Possible role of uncoupling protein in regulation of myocardial energy metabolism in aortic regurgitation model rats

SPECIFIC AIMSMyocardial mitochondrial energy metabolism in heart failure is still controversial. We focused on serial changes in the cardiac performance and adenosine triphosphate (ATP) biosynthesi...

Improvement of left ventricular diastolic dynamics in prediabetic stage of a Type II diabetic rat model after troglitazone treatment

Troglitazone, an oral antidiabetic agent, has hypoglycemic effects in insulin-resistant animal models and humans. This study was conducted to evaluate its effect on left ventricular diastolic dynamics of a spontaneous diabetic (DM) rat model. Twenty DM rats and 20 age-matched nonDM rats were used, and 10 of each group were treated with troglitazone as a 0.2% food admixture for 10 weeks. At 5 and 15 weeks of age, Doppler echocardiography and M-mode echocardiography were performed. Troglitazone treatment significantly improved the left ventricular diastolic dynamics of DM rats: deceleration time (msec) of early diastolic inflow decreased significantly (treated 52 ±3 vs untreated 64 ±5, p = 0.0002), and peak velocity of early transmitral inflow (cm/sec) increased significantly (treated 96 ±7 vs untreated 86 ±8, p = 0.0216). The data suggest that troglitazone improves left ventricular diastolic dynamics of a DM rat model at prediabetic stage.

Improvement of aortic wall distensibility and reduction of oxidative stress by pioglitazone in pre-diabetic stage of otsuka long-evans Tokushima Fatty rats

We tested the hypothesis that pioglitazone (insulin sensitizer) reduces oxidative stress and improves aortic wall distensibility in the pre-diabetic stage of Otsuka Long-Evans Tokushima Fatty rats, type 2 diabetes mellitus (DM) model. 20 DM and 9 nonDM male rats were divided into 3 groups: treated-DM, untreated-DM, and untreated-nonDM. Pioglitazone (0.01%) was mixed in chow in the treated group from 15 to 20 weeks of age. At baseline and 20 weeks, plasma malondialdehyde (MDA) was measured. At 20 weeks, intravascular ultrasound images and aortic pressure were simultaneously recorded. Stiffness parameter β was calculated from the cyclic variations of aortic diameter and pressure. From an excised thoracic aorta, aortic wall collagen was measured, and the morphology was histopathologically evaluated by hematoxylin-eosin staining. At 20 weeks, MDA (nmol/ml) in treated-DM (2.3 ± 0.3) was lower than in untreated-DM (3.2 ± 0.6, p < 0.0001). β in treated-DM (0.53 ± 0.21) was smaller than that in untreated-DM (0.88 ± 0.26, p = 0.0067). Aortic wall collagen (mg/100 mg dry weight) did not decrease in treated-DM (22.3 ± 3.2 vs untreated-DM : 19.6 ± 4.7). Lumen/medial area ratio (L/M) increased in treated-DM (2.79 ± 0.40 vs untreated-DM : 2.22 ± 0.20, p = 0.0041, untreated-nonDM : 2.25 ± 0.55, p = 0.0075). MDA was significantly correlated with β (r = 0.65, p = 0.0005) or L/M (r = −0.60, p = 0.0008). Pioglitazone may reduce oxidative stress and contribute to improvement of aortic wall stiffness without decrease in collagen content at an early prediabetic stage of type 2 DM.

Association between arterial stiffness and pulmonary function in hypertensive patients

Arterial stiffness, assessed by cardio-ankle vascular index (CAVI), is clinically used to assess arteriosclerosis. Recently, pulmonary age, as determined by pulmonary function test, has been proposed by the Japanese Respiratory Society as a diagnostic measure for chronic obstructive pulmonary disease (COPD). This study aims to examine the association between CAVI and pulmonary function and to elucidate the correlation between vascular stiffness and pulmonary age in hypertensive patients. We enrolled a total of 45 hypertensive patients (70±9 years) who had been taking antihypertensive medications for at least 1 year. Pulmonary function was measured by the percentage of predicted forced vital capacity (FVC) and the ratio of forced expiratory volume in 1 s (FEV1) to FVC (FEV1/FVC ratio). Pulmonary age was determined by the equation proposed by the Japanese Respiratory Society. CAVI was measured at the same clinic visit. In the simple correlation analysis CAVI correlated with the FEV1/FVC ratio (r=−0.399, P=0.007) and pulmonary age (r=0.559, P<0.001). Multiple linear regression analysis revealed that CAVI was independently associated with FEV1/FVC ratio (β=−0.418, P=0.014) and pulmonary age (β=0.514, P=0.002). In addition, CAVI was significantly higher in patients with increased pulmonary age (9.4±1.4) than in those with normal pulmonary age (8.4±0.9) (P=0.011). The present study indicates that an increased CAVI is independently associated with reduced pulmonary function and increased pulmonary age. Hypertensive patients with high CAVI may need to be monitored for the progression of COPD.

Association of uncoupling protein-2 expression with increased reactive oxygen species in residual myocardium of the enlarged left ventricle after myocardial infarction.

Left ventricular (LV) dilatation following myocardial infarction (MI) is a major determinant of the patient’s prognosis, and myocardial energy metabolism may play a key role in LV remodeling. We aimed to investigate the relative timing of LV dilatation to LV function, myocardial energy regulation by uncoupling protein (UCP)-2, and cellular damage in the noninfarct zone. Myocardial infarction was produced in Sprague-Dawley rats by ligation of the coronary artery. The LV end-diastolic dimension (mm) increased (8.9 ± 0.3 vs 6.8 ± 0.8 in sham-operated rats, P < 0.01) in association with elevation of the LV end-diastolic pressure (mmHg) (18 ± 5 vs 6 ± 2 in sham-operated rats) at 1 week following the ligation. At 4 weeks, the UCP-2 expression (180% of that in sham-operated rats) and LV end-diastolic dimension increased further (11.1 ± 0.5, P < 0.01) but there was no change in the LV end-diastolic pressure. The mechanisms for LV dilatation were quite different between the early and late stages after MI. In the late stage, augmentation of UCP-2 expression in the noninfarct zone may be related to the LV dilatation. Further examinations regarding the possibility of the protective role of UCP-2 are needed.

Effects of perindopril on left ventricular remodeling and aortic regurgitation in rats assessed by echocardiography.

This study investigated the effect of the angiotensin-converting enzyme (ACE) inhibitor perindopril on left ventricular (LV) remodeling and cardiac function in rats with aortic regurgitation (AR). Twenty male Sprague-Dawley rats in which AR was produced by closed-chest aortic valve puncture were divided into untreated and perindopril-treated (5 mg/kg/day) rats. Ten control rats were sham-operated. Blood pressure, body weight, and echocardiographic recordings were followed every 2 weeks for a period of 12 weeks. LV dimension (LVD) and fractional shortening (FS) were calculated. The heart was finally excised for weight, hydroxyproline measurements, and histopathology. At 12 weeks, end- diastolic LVD increased in untreated rats (10.8 ±0.2 mm) but did not dilate in treated rats (9.6 ± 0.3 mm, p < 0.01 vs untreated rats). FS decreased from 6 weeks in untreated rats (27.3 ±0.9% at 12 weeks), but did not change in treated rats (33.8 ±0.5%, p < 0.001). The ratio of LV weight to body weight in untreated rats (2.62 ±0.11 mg/g, p < 0.05) was higher than in sham-operated rats (1.52 ±0.02 mg/g) and than in treated rats (1.95 ±0.07 mg/g). Interstitial collagen accumulation histopathologically increased in untreated rats and was inhibited in treated rats. LV collagen of untreated rats (1.46 ±0.08 mg/100 mg, p = 0.03) was higher than those of treated (1.08 ±0.09 mg/100 mg) and sham-operated rats (1.06 ±0.14 mg/100 mg). Perindopril inhibited LV remodeling induced by volume overload and preserved LV function in AR rats.