Shingo Seki

RETRACTED: Valsartan in a Japanese population with hypertension and other cardiovascular disease (Jikei Heart Study): a randomised, open-label, blinded endpoint morbidity-mortality study

BACKGROUND Drugs that inhibit the renin-angiotensin-aldosterone system benefit patients at risk for or with existing cardiovascular disease. However, evidence for this effect in Asian populations is scarce. We aimed to investigate whether addition of an angiotensin receptor blocker, valsartan, to conventional cardiovascular treatment was effective in Japanese patients with cardiovascular disease. METHODS We initiated a multicentre, prospective, randomised controlled trial of 3081 Japanese patients, aged 20-79 years, (mean 65 [SD 10] years) who were undergoing conventional treatment for hypertension, coronary heart disease, heart failure, or a combination of these disorders. In addition to conventional treatment, patients were assigned either to valsartan (40-160 mg per day) or to other treatment without angiotensin receptor blockers. Our primary endpoint was a composite of cardiovascular morbidity and mortality. Analysis was by intention to treat. The study was registered at clintrials.gov with the identifier NCT00133328. FINDINGS After a median follow-up of 3.1 years (range 1-3.9) the primary endpoint was recorded in fewer individuals given valsartan than in controls (92 vs 149; absolute risk 21.3 vs 34.5 per 1000 patient years; hazard ratio 0.61, 95% CI 0.47-0.79, p=0.0002). This difference was mainly attributable to fewer incidences of stroke and transient ischaemic attack (29 vs 48; 0.60, 0.38-0.95, p=0.028), angina pectoris (19 vs 53; 0.35, 0.20-0.58, p<0.0001), and heart failure (19 vs 36; 0.53, 0.31-0.94, p=0.029) in those given valsartan than in the control group. Mortality or tolerability did not differ between groups. INTERPRETATION The addition of valsartan to conventional treatment prevented more cardiovascular events than supplementary conventional treatment. These benefits cannot be entirely explained by a difference in blood pressure control.

Thyroid hormones and cardiac arrhythmias.

Thyroid hormone plays an important role in cardiac electrophysiology and Ca2+ handling through both genomic and nongenomic mechanisms of action, while both actions can interfere. Chronic changes in the amount of circulating thyroid hormone due to thyroid dysfunction or systemic disease result in structural, electrophysiological and Ca2+ handling remodeling, while acute changes may affect basal activity of cardiac cells membrane systems. Consequently, long-term or rapid modulation of sarcolemmal ion channels, Ca2+ cycling proteins and intercellular communicating channels by thyroid hormone may affect heart function as well as susceptibility of the heart to arrhythmias. This aspect including pro- and anti-arrhythmic potential of thyroid hormone is highlighted in this review.

Effects of sustained low-flow ischemia and reperfusion on Ca2+ transients and contractility in perfused rat hearts.

We investigated changes in cytoplasmic Ca2+ concentration ([Ca2+]i) and in left ventricular contractility during sustained ischemia and reperfusion in isolated beating rat hearts. Hearts from male Sprague-Dawley rats were perfused retrogradely and were loaded with 4 μM fura-2. Low-flow global ischemia was induced by reducing perfusion flow to 10% and by electric pacing. The hearts were exposed to ischemia for 10 min or 30 min and then reperfused. [Ca2+]i was measured by monitoring the ratio of 500 nm fluorescence excited at 340 and 380 nm while simultaneously measuring left ventricular pressure (LVP). To determine diastolic [Ca2+]i, background autofluorescence was subtracted. LVP rapidly decreased from 82.3 ± 8.2 to 17.1 ± 2.9 mmHg , whereas the amplitude of the Ca2+ transient did not change significantly during the first 1 min of ischemia. After 10 min of ischemia, the amplitude decreased to 60.8 ± 10.6% (p < 0.05) and diastolic [Ca2+]i increased by 26.3 ± 2.9% (p < 0.001) compared with the pre-ischemic value (n = 8). When the hearts were reperfused after 10 min of ischemia, the amplitude of the Ca2+ transient and LVP recovered to 79.0 ± 7.2% and 73.2 ± 7.5 mmHg, respectively. Whereas diastolic [Ca2+]i decreased to the pre-ischemic value. In the hearts exposed to 30 min of ischemia (n = 10), diastolic [Ca2+]i increased even further by 32.7 ± 5.3% at the end of ischemia and continued increasing during the 10 min of reperfusion by 42.6 ± 15.6%. Six of 10 hearts developed ventricular fibrillation (VF) and intracellular Ca2+ overload after reperfusion. Recovery of LVP after reperfusion was significantly smaller in the hearts exposed to 30 min of ischemia than in the hearts exposed to 10 min of ischemia (58.9 ± 11.7 vs. 97.2 ± 3.0% of pre-ischemic value, p < 0.05). Diastolic [Ca2+]i also increased under hypoxic conditions (N2 bubbling) in this model. These results suggest that increases in diastolic [Ca2+]i might play an important role in myocardial contractile dysfunction and viability in ischemia-reperfusion injury.

Cardioprotective action of perindopril versus candesartan in renovascular hypertensive rats.

We investigated the effects of an angiotensin-converting enzyme inhibitor and an angiotensin II type 1 receptor blocker on cardiac hypertrophy in rats with renovascular hypertension. Renovascular hypertensive (Goldblatt) rats were surgically prepared from Wistar rats. Four weeks later, the rats showed a significant increase in blood pressure. At high doses, both the perindopril (1 mg/kg/day) and the candesartan (2 mg/kg/day) decreased the systolic pressure in these rats to the level of control Wistar rats. At low doses (perindopril 0.1 mg/kg/day and candesartan 0.1 mg/kg/day), these drugs lowered blood pressure to 85% of that in hypertensive rats.Echocardiographic and morphological studies revealed severe cardiac hypertrophy and fibrosis in untreated Goldblatt rats. High-dose treatment with both drugs suppressed the progression of hypertrophy and fibrosis. Also, low-dose perindopril prevented cardiac hypertrophy and fibrosis. In contrast, at the same levels of blood-pressure reduction, low-dose candesartan did not prevent cardiac fibrosis nor the upregulation of cardiac collagen types I and III mRNA observed in untreated Goldblatt rats. Atrial natriuretic peptide mRNA was up-regulated in untreated Goldblatt rats. These changes were significantly decreased by both doses of perindopril or the high dose of candesartan. Serum levels of angiotensin II and aldosterone were significantly higher in untreated Goldblatt rats. Both doses of perindopril inhibited activation of the renin-angiotensin system, whereas candesartan had weaker effects. In particular, serum aldosterone was 347 ± 20 pg/ml in low-dose perindopril versus 1796 ± 324 pg/ml in low-dose candesartan. These results suggest that there were no differences between the cardioprotective actions of perindopril and candesartan at high dosages. On the other hand, low-dose treatment with perindopril was more effective in preventing cardiac fibrosis than was low-dose treatment with candesartan, despite similar changes in blood pressure. It is possible that changes in aldosterone secretion are related to this difference.

Association of Uric Acid with Risk Factors for Chronic Kidney Disease and Metabolic Syndrome in Patients with Essential Hypertension

Hyperuricemia has recently been recognized to not only be a predictor of cardiovascular disease but also a marker of metabolic syndrome. We examined the association between uric acid levels and various clinical parameters, including the components of metabolic syndrome, in essential hypertension. One hundred forty-six untreated Japanese hypertensive patients (mean 58.3 years) without overt cardiovascular disease were divided into low and high uric acid groups by the median uric acid value (cut-off: 6.3 for men and 4.4 mg/dL for women). The high uric acid group had higher serum creatinine (0.74 vs. 0.67 mg/dL, p = 0.019) and a larger body mass index (BMI) (25.2 vs. 23.6 kg/m2, p = 0.018) compared to the low group. Men from the high uric acid group were younger and had higher blood pressure (BP) than men from the low group. Uric acid levels were correlated with creatinine in both genders, with blood pressure, triglycerides in men only, and with BMI, fasting glucose in women only. Multiple regression analysis also indicated a significant correlation of uric acid with creatinine in both genders, with triglycerides in men, and with glucose in women. Metabolic syndrome (modified NCEP-ATPIII definition) was found in 37.0% of the high uric acid group (men 45.0, women 27.3%) and 20.8% of the low group. Results suggest that an increase of uric acid is associated with impaired renal function and constitutes a risk factor for metabolic syndrome. Uric acid may also be a useful index for initial risk stratification of untreated patients with essential hypertension.

The role of Na+/H+ exchanger in Ca2+ overload and ischemic myocardial damage in hearts from type 2 diabetic db/db mice

BackgroundA higher increase in intracellular Na+ via Na+/H+ exchanger (NHE) during ischemia has been reported in type 2 diabetic mouse hearts. We investigated the role of NHE in inducing changes in cytoplasmic Ca2+ concentration ([Ca2+]i) and alterations in ventricular function during ischemia-reperfusion in type 2 diabetic mouse hearts.MethodsHearts from male type 2 diabetic db/db (12-15 weeks old) and age-matched control db/+ mice were subjected to Langendorff perfusion and loaded with 4μM of the Ca2+ indicator fura-2. The hearts were exposed to no-flow ischemia for 15 minutes and then reperfused. [Ca2+]i was measured by monitoring fura-2 fluorescence at 500 nm (excitation wavelengths of 340 and 380 nm), while left ventricular (LV) pressure was simultaneously measured.Resultsdb/db hearts exhibited a lower recovery of LV developed pressure than db/+ hearts during reperfusion following ischemia. Diastolic [Ca2+]i was increased to a greater level in diabetic hearts than in the control hearts during ischemia and reperfusion. Such an increase in cytoplasmic Ca2+ overload during ischemia-reperfusion in diabetic hearts was markedly reduced in the presence of the NHE inhibitor cariporide. This was accompanied by a significantly improved recovery of ventricular function on reperfusion, as shown by a lower increase in diastolic pressure and increased recovery of developed pressure.ConclusionNHE plays a key role in enhancing cytoplasmic Ca2+ overload during ischemia-reperfusion and severely impairing post-ischemic cardiac function in hearts from type 2 diabetic db/db mice.

Telmisartan predominantly suppresses cardiac fibrosis, rather than hypertrophy, in renovascular hypertensive rats

Angiotensin II receptor blockers have beneficial effects in patients with cardiac diseases. We examined the effects of an angiotensin II receptor blocker, telmisartan, on cardiac remodeling in renovascular hypertensive rats. Telmisartan was administered to renovascular hypertensive rats at either a high dose (5 mg per kg per day; high-T group) or a low dose (0.5 mg per kg per day; low-T group). After 4 weeks, histomorphological studies, including an evaluation of cardiac fibrosis, hypertrophy, vascular changes and measurement of the serum aldosterone concentration, were performed. A significant reduction in systolic blood pressure was obtained in the high-T group, and the heart weight to body weight ratio in the high-T and low-T groups was significantly lower than that in the control renovascular hypertensive group. Cardiac and perivascular fibrosis and the accumulation of collagen were significantly suppressed in the high-T and low-T groups. An increase in the cross-sectional area of the myocytes and vessel hypertrophy were significantly prevented in the high-T group, but not in the low-T group. The dependence of myocyte lengthening on the blood pressure was also prevented in the high-T group, but not to a significant degree. The elevation of the serum aldosterone level observed in the renovascular hypertensive group was prevented in both the high-T and low-T groups.Treatment with telmisartan strongly suppresses the progression of cardiac fibrosis, rather than cardiac hypertrophy, in a manner that is independent of the blood pressure.

Modulation of intracellular Ca2+ concentration by tedisamil, a class III antiarrhythmic agent, in isolated heart preparation

New class III antiarrhythmic/defibrillating compound tedisamil was shown to facilitate termination of atrial and ventricular fibrillation in experimental as well as clinical conditions. However, class III-related inhibition of K(+) current associated with prolongation of repolarization can not solely explain its defibrillating ability. Following recent findings it was hypothesized that defibrillating effect of tedisamil is likely due to its sympathomimetic feature linked with modulation of intracellular calcium. Results of this study obtained in isolated heart preparation showed that elevated intracellular Ca(2+) free concentration was decreased by administration of tedisamil in concentration that did not induce Q-T interval prolongation. Due to species differences the effective concentration was in rat 10(-7) M, while in guinea pig 10(-5) M. On the contrary, further dramatic increase of elevated Ca(2+) was detected upon administration of tedisamil in concentration that markedly prolonged Q-T interval (10(-5) M in rat). It is concluded that defibrillating ability of tedisamil is most likely associated with attenuation of abnormal and harmful intracellular Ca(2+) elevation (that is highly arrhythmogenic) than with prolongation of APD or Q-T interval.

Exacerbation of acidosis during ischemia and reperfusion arrhythmia in hearts from type 2 Diabetic Otsuka Long-Evans Tokushima Fatty rats

BackgroundSensitivity to ischemia and its underlying mechanisms in type 2 diabetic hearts are still largely unknown. Especially, correlation between reperfusion induced ventricular arrhythmia and changes in intracellular pH has not been elucidated.Methods and resultsMale Otsuka Long-Evans Tokushima Fatty (OLETF) rats at 16 and 32 weeks of age were used along with age-matched nondiabetic Long-Evans Tokushima Otsuka (LETO) rats. Hearts from rats in these 4 groups were perfused in the working heart mode, thus inducing whole heart ischemia. At 16 weeks of age, no differences in blood glucose levels or incidence and duration of reperfusion arrhythmia were found between the strains. At 32 weeks of age, both impaired glucose tolerance and obesity were observed in the OLETF rats. Further, the duration of reperfusion-induced ventricular fibrillation (VF) was significantly longer in the OLETF rats, while the pH level was significantly lower and proton contents were significantly higher in coronary effluent during ischemia in those rats. Following treatment with troglitazone, improvements in pH and proton level in coronary effluent during ischemia were observed, as was the duration of reperfusion-induced VF in OLETF rats at 32 weeks of age.ConclusionThe hearts of spontaneously diabetic OLETF rats were found to be more susceptible to ischemic insult. Troglitazone treatment improved ischemic tolerance by improving glucose metabolism in the myocardium of those rats.

Impact of alcohol intake on the relationships of uric acid with blood pressure and cardiac hypertrophy in essential hypertension

BACKGROUND Hyperuricemia, which is frequently associated with hypertension, can be caused by alcohol intake. To date, limited data have shown the link between alcohol intake and hyperuricemic hypertension. METHODS We retrospectively examined the influence of alcohol intake on the relationship between the uric acid level and blood pressure or cardio-metabolic parameters in 171 untreated non-failing hypertensive patients (mean 59.3±10.7 years). Cross-sectional analysis was separately performed in regular alcohol drinkers (more than 25g/day ethanol, n=74, 82.4% men) and non-drinkers (n=97, 33.0% men). RESULTS Diastolic blood pressure was significantly higher in drinkers than in non-drinkers (101.6±11.5mmHg vs. 96.8±8.2mmHg, p<0.01). Estimated glomerular filtration rate (80.4±14.7mL/min/1.73m2 vs. 80.0±17.8mL/min/1.73m2) and body mass index (BMI, 24.7±4.4kg/m2 vs. 24.8±4.2kg/m2) were similar in the two groups. In the drinker group, the uric acid level (mean 6.3±1.7mg/dL) was positively correlated with both systolic and diastolic blood pressures (r=0.270/p=0.020 and r=0.354/p=0.0020, respectively), and with the markers of cardiac hypertrophy, including electrocardiographic voltage (V1S+V5R, r=0.244/p=0.042) and echocardiographic left ventricular mass index (r=0.270/p=0.026). These correlations were also observed in the male drinker sub-group. In the non-drinkers, the uric acid level (mean 5.0±1.4mg/dL) was positively correlated with BMI (r=0.369/p=0.0002) but not with blood pressure or the markers of cardiac hypertrophy. CONCLUSIONS The results suggest that the role of uric acid in blood pressure might differ between hypertensive drinkers and non-drinkers. In regular alcohol drinkers, there was a positive association of uric acid level with blood pressure and the severity of cardiac hypertrophy. In non-regular drinkers, an increased uric acid level is likely to be closely associated with increased BMI.