Hepatocyte growth factor levels are associated with the results of 123I-metaiodobenzylguanidine myocardial scintigraphy in patients with type 2 diabetes mellitus

Elevated hepatocyte growth factor (HGF) levels and cardiovascular autonomic dysfunction are associated with a high mortality rate in patients with type 2 diabetes mellitus. We tested the hypothesis that elevated HGF is associated with insulin resistance and cardiovascular autonomic dysfunction in patients with type 2 diabetes mellitus not receiving insulin treatment. The study group consisted of 21 type 2 diabetes mellitus patients with high HGF levels (>0.26 ng/mL, 58 +/- 5 years old, high-HGF group). The control group consisted of 25 type 2 diabetes mellitus patients with normal HGF levels (<or=0.26 ng/mL, 58 +/- 9 years old, normal-HGF group). Cardiovascular autonomic function was assessed by baroreflex sensitivity, heart rate variability, plasma norepinephrine concentrations, and cardiac (123)I-metaiodobenzylguanidine (MIBG) scintigraphy. Early and delayed (123)I-MIBG myocardial uptake values were lower (P < .005 and P < .01, respectively) and the percentage of washout rate of (123)I-MIBG was higher (P < .001) in the high-HGF group than in the normal-HGF group. The fasting plasma insulin concentrations (P < .0001) and the homeostasis model assessment index values (P < .0001) were higher in the high-HGF group than in the normal-HGF group. Multiple regression analysis revealed that the level of HGF was independently predicted by the homeostasis model assessment index values and the myocardial uptake of (123)I-MIBG at the delayed phase. Our results demonstrate that high levels of HGF are associated with depressed cardiovascular autonomic function and insulin resistance in patients with type 2 diabetes mellitus.

Correlations of visceral fat accumulation and atherosclerosis in Japanese patients with type 2 diabetes mellitus

We tested the hypothesis that increased abdominal visceral fat accumulation (VFA) is associated with insulin resistance and aortic stiffness in patients with type 2 diabetes mellitus not receiving insulin treatment. The study consisted of 22 Japanese patients with type 2 diabetes mellitus and high VFA (> or =100 cm(2); age, 61 +/- 7 years; high VFA group) and a control group of 18 age-matched patients with normal VFA (<100 cm(2); age, 60 +/- 8 years; normal VFA group). Brachial-ankle pulse wave velocity (BaPWV) was measured by automatic oscillometric method. The BaPWV was used as an index of atherosclerosis. The body mass index values (P < .05), waist circumferences (P < .0005), and waist-to-hip ratios (P < .05) were larger in the high VFA group than in the normal VFA group. The BaPWV was higher in the high VFA group than in the normal VFA group (P < .0001). Fasting plasma glucose (P < .05), insulin concentrations (P < .0001), and the homeostasis model assessment (HOMA) index (P < .001) were higher in the high VFA group than in the normal VFA group. Multiple regression analysis showed that the VFA level was independently predicted by BaPWV and the HOMA index. Our results indicate that the elevation of VFA in Japanese patients with type 2 diabetes mellitus is characterized by increased aortic stiffness and insulin resistance and that BaPWV and the HOMA index are independent predictors of VFA.

High-sensitivity C-reactive protein level is a significant risk factor for silent cerebral infarction in patients on hemodialysis

In patients with chronic renal failure on hemodialysis (HD), silent cerebral infarctions (SCIs) are associated with high mortality. The levels of high-sensitivity C-reactive protein (HSCRP), a marker of inflammation and atherosclerosis, elevate with increasing renal dysfunction. We tested the hypothesis that increased HSCRP levels correlate with the occurrence of SCI in HD patients. By brain magnetic resonance imaging findings, we divided 54 patients undergoing HD into a with-SCI group (61 +/- 8 years, n = 30) and a without-SCI group (60 +/- 7 years, n = 24). We compared sex, body mass index, metabolic profiles, HSCRP levels, and smoking habits in Japanese patients on HD with and without SCI. We made the following observations: (1) The number of patients with diabetes or hypertension did not differ between the 2 groups. (2) The levels of HSCRP were higher in the with-SCI group in comparison with the without-SCI group (P < .0001). (3) The proportion of smokers was higher in the with-SCI group than in the without-SCI group (P < .05). (4) Plasma levels of high-density lipoprotein cholesterol were lower, whereas uric acid was higher, in the with-SCI group than in the without-SCI group (P < .05 and P < .0001, respectively). (5) Multivariate logistic analysis identified HSCRP levels as being significantly associated with the presence of SCI (odds ratio, 1.61; 95% confidence interval, 1.17-2.85; P < .001). This study indicates that patients in chronic renal failure who are maintained on HD exhibit an increased prevalence of SCI and that HSCRP is significantly associated with the presence of SCI in HD patients.

Correlations between homocysteine levels and atherosclerosis in Japanese type 2 diabetic patients

Elevated total plasma homocysteine (tHcy) level and aortic stiffness are associated with high mortality in type 2 diabetic patients. We tested the hypothesis that tHcy correlates with aortic stiffness and insulin resistance in type 2 diabetic patients. The study consisted of 40 Japanese patients with type 2 diabetes mellitus and high tHcy levels (mean age +/- SD, 57 +/- 7 years) and a control group of 45 age-matched patients with normal tHcy levels (mean age +/- SD, 57 +/- 6 years). Brachial-ankle pulse wave velocity (BaPWV) was measured by an automatic oscillometric method. Brachial-ankle pulse wave velocity was used as an index of atherosclerosis. Body mass index values (P < .05), waist circumferences (P < .05), and the waist-to-hip ratios (P < .05) were larger in the high-tHcy group than in the normal-tHcy group. The BaPWV was higher in the high-tHcy group than in the normal-tHcy group (P < .0001). Fasting plasma glucose (P < .005) and insulin concentrations (P < .0001), and the homeostasis model assessment (HOMA) index (P < .0001) were higher in the high-tHcy group than in the normal-tHcy group. Multiple regression analysis showed that tHcy levels were independently predicted by BaPWV and the HOMA index. In conclusion, our results indicate that the elevated level of tHcy in Japanese patients with type 2 diabetes mellitus is characterized by increased aortic stiffness and insulin resistance, and that the BaPWV and the HOMA index are independent predictors of tHcy.

Correlations of high-sensitivity C-reactive protein and atherosclerosis in Japanese type 2 diabetic patients

BACKGROUND

The elevated level of high-sensitivity C-reactive protein (HSCRP) and aortic stiffness are associated with high mortality in type 2 diabetic patients. We tested the hypothesis that the HSCRP correlates with aortic stiffness and insulin resistance in type 2 diabetic patients.

MATERIAL AND METHODS

The study consisted of 46 Japanese patients with type 2 diabetes and high HSCRP group (0.3-1.0 mg/dl, age: 57+/-5 years, mean+/-s.d.) and a control group of 55 age-matched patients with low HSCRP group (<0.3 mg/dl, 57+/-6 years). Brachial-ankle pulse wave velocity (BaPWV) was measured by automatic oscillometric method and was used as an index of atherosclerosis.

RESULTS

The body mass index (BMI) values (P<0.05) and waist circumferences (P<0.0005) and the waist-to-hip ratios (P<0.05) were higher in the high HSCRP group than in the low HSCRP group. The BaPWV was higher in the high HSCRP group than in the low HSCRP group (P<0.0001). Fasting plasma glucose (FPG; P<0.005) and insulin concentrations (P<0.0001), and the homeostasis model assessment (HOMA) index (P<0.0001), were higher in the high HSCRP group than in the low HSCRP group. Multiple regression analysis showed that HSCRP levels were independently predicted by BaPWV and HOMA index.

CONCLUSIONS

Our results indicate that the elevated level of HSCRP in Japanese patients with type 2 diabetes is characterized by increased aortic stiffness and insulin resistance, and that the BaPWV and HOMA index are independent predictors of HSCRP.

Pioglitazone shift circadian rhythm of blood pressure from non-dipper to dipper type in type 2 diabetes mellitus

BACKGROUND

Insulin resistance significantly correlated with a non-dipper type of essential hypertension. Thiazolidinediones (TZD), oral hypoglycaemic agents that act as insulin sensitizers, have been demonstrated in multiple in vivo and in vitro studies to possess antihypertensive properties. This study examined the efficacy of TZD therapy with pioglitazone at transforming the circadian rhythms of blood pressure from a non-dipper to a dipper type.

MATERIALS

We examined 31 patients with type 2 diabetes mellitus during both a baseline period and a period of treatment with pioglitazone. Patients received 15 mg day(-1) pioglitazone for four weeks and 30 mg day(-1) for 12 weeks. Twenty-four hour ambulatory blood pressure monitoring (ABPM) and laboratory data (blood tests for cardiovascular risk factors) were obtained at the beginning and end of the study.

RESULTS

In non-dippers (n = 16), but not dippers (n = 15), we observed a significant interaction between pioglitazone therapy and nocturnal falls in systolic and diastolic blood pressure. This examination indicated that the magnitude of the nocturnal blood pressure fall was affected by pioglitazone therapy. In non-dippers, but not dippers, a significant correlation was observed between the percent decrease in nocturnal BP and the homeostasis model assessment (HOMA) index (r = 0.774, P = 0.0007).

CONCLUSIONS

The present study demonstrated that pioglitazone can restore the nocturnal BP declines in parallel to reductions in the HOMA index, suggesting that insulin resistance may play an important role in the genesis of circadian BP rhythms. TZD-based treatment may thus have the additional therapeutic advantage of reducing the risk of cardiovascular complications by transforming the circadian rhythm of BP.

Correlations of urinary albumin excretion and atherosclerosis in Japanese type 2 diabetic patients

Microalbuminuria and aortic stiffness are associated with high mortality in type 2 diabetic patients. We tested the hypothesis that the presence of microalbuminuria correlates with aortic stiffness and insulin resistance in type 2 diabetic patients. The study consisted of 36 Japanese patients with type 2 diabetes and microalbuminuria (age: 56+/-9 years, mean+/-S.D.) and a control group of 44 age-matched patients with normoalbuminuria (56+/-7 years). Brachial-ankle pulse wave velocity (BaPWV) was measured by automatic oscillometric method. BaPWV was used as an index of atherosclerosis. The BaPWV was higher in the microalbuminuria group than in the normoalbuminuria group (p<0.005). Fasting plasma glucose (p<0.05) and insulin concentrations (p<0.005), and the homeostasis model assessment (HOMA) index (p<0.0005), were higher in the microalbuminuria group than in the normoalbuminuria group. Multiple regression analysis showed that urinary albumin excretion was independently predicted by BaPWV and HOMA index. Our results indicate that the presence of microalbuminuria in Japanese patients with type 2 diabetes is characterized by increased aortic stiffness and insulin resistance, and that the BaPWV, HOMA index are independent predictors of urine albumin excretion.

Hyperthermia treatment prevents angiotensin II-mediated atrial fibrosis and fibrillation via induction of heat-shock protein 72

We tested the hypothesis that atrial fibrosis and atrial fibrillation (AF) evoked by angiotensin II (AII) could be prevented by the induction of heat-shock protein 72 (HSP72) by hyperthermia (HT). In cultured atrial fibroblasts isolated from male Sprague-Dawley rats, HT (42 degrees C) was applied for 30 min. AII (100 nmol/L) was added to the medium 8 h later. HT induced the expression of HSP72, which was associated with the attenuation of AII-induced extracellular signal-regulated kinase (ERK1/ERK2) phosphorylation, alpha-smooth muscle actin (alpha-SMA) expression, transforming growth factor-beta(1) secretion, collagen synthesis, and expression of collagen type I and tissue inhibitor of metalloproteinases-1. A small interfering RNA targeting HSP72 abolished these anti-fibrotic effects of HT. In male Sprague-Dawley rats in vivo, an osmotic mini-pump was subcutaneously implanted for continuous infusion of AII (400 ng/kg/min). Whole-body HT (43 degrees C, 20 min) was applied 24 h before and 7, 14, and 21 days after the start of the AII infusion. Repeated HT led to the induction of HSP72 expression, which resulted in an attenuation of AII-induced left atrial fibrosis. In an electrophysiological study using isolated perfused heart, continuous AII caused slowing of interatrial conduction without affecting atrial refractoriness. In AII-treated hearts, extrastimuli from the right atrial appendage resulted in a high incidence of repetitive atrial responses, which were suppressed by treatment with HT. Our results suggest that HT treatment is effective in suppressing AII-mediated atrial fibrosis and AF via induction of HSP72 at least in parts, and is thus expected to be a novel strategy for prevention of AF.

Receptor-mediated suppression of cardiac heat-shock protein 72 expression by testosterone in male rat heart

The impact of testosterone on cardiac expression of heat-shock protein 72 (HSP72) remains to be elucidated. Male Sprague Dawley rats 10 wk of age (adult) were castrated. Four weeks later, testosterone (10 mg/kg, ip) was administered as a single dose, followed by the application of hyperthermia (HT) (43 C) at 6 h after testosterone administration. Twenty-four hours later, each heart was isolated. Cardiomyocytes were prepared from 3- to 5-d-old Wistar rats and male Sprague Dawley rats 10 wk of age. Testosterone (0.1-10 microM) was added to the medium, followed by the application of HT (42 C). Twenty-four hours later, cells were collected. We observed the following: 1) Exogenous testosterone suppressed HT-induced HSP72 expression, but castration alone had no influence. 2) HT resulted in better reperfusion-induced cardiac performance in castrated rats comparable with sham-operated rats, which was inhibited by testosterone. The number of apoptotic cells after ischemia/reperfusion was also increased by testosterone. 3) HT-induced HSP72 expression in cultured cardiomyocytes was suppressed by testosterone. 4) HT resulted in less damage to cells, including apoptosis, in response to hypoxia/reoxygenation, which was inhibited by testosterone. 5) Flutamide, a testosterone receptor blocker, cancelled the suppressive effects of testosterone on HSP72 expression. 6) The HT-induced increase in heat-shock factor 1 activity to bind to heat-shock element DNA was suppressed by testosterone, and this was reversed by flutamide. Our results indicate that testosterone potentially has inhibitory effects on cardiac HSP72 expression by modulating transcription, through testosterone receptor-mediated genomic mechanisms.

High-density lipoprotein cholesterol and insulin resistance are independent and additive markers of left ventricular hypertrophy in essential hypertension

We examined whether plasma high-density lipoprotein-cholesterol (HDL-C) levels and glucose metabolism parameters are independent or additive predictors of left ventricular hypertrophy (LVH) in patients with untreated essential hypertension. The study group consisted of 41 Japanese patients with untreated essential hypertension and LVH (left ventricular mass index [LVMI] >125 g/m2; age 58+/-6 years, mean+/-SD), and the control group consisted of 39 age-matched patients with untreated essential hypertension without LVH (LVMI <or=125 g/m2; age 58+/-7 years). The following metabolic parameters were higher in the group with LVH: fasting plasma glucose (FPG) (p<0.01), fasting insulin concentration (F-IRI) (p<0.0001), and homeostasis model assessment (HOMA)-index (p<0.0001). Among the laboratory parameters investigated, plasma HDL-C levels were lower (p<0.0001), and triglyceride and uric acid levels were higher in the group with LVH (p<0.05 for both). The nighttime systolic and diastolic ambulatory blood pressure (ABP) (p<0.0001, p<0.01, respectively) and nighttime heart rate (p<0.01) were higher in patients with LVH. Multivariate logistic analysis identified HDL-C (odds ratio [OR]=0.92, 95% confidence interval [CI]=0.87-0.98, p<0.05), HOMA-index (OR=3.83, 95% CI=1.28-11.5, p<0.05) and nighttime systolic ambulatory blood pressure (ABP) (OR=1.06, 95% CI=1.00-1.13, p<0.05) as independent significant risk factors for LVH. Our findings suggest that HDL-C, HOMA-index and nighttime systolic ABP are independent predictors for the presence of LVH in Japanese patients with essential hypertension.

Predictors for silent cerebral infarction in patients with chronic renal failure undergoing hemodialysis

In patients with chronic renal failure undergoing hemodialysis (HD), silent cerebral infarctions (SCIs) are associated with high mortality. Levels of hepatocyte growth factor (HGF) increase with renal dysfunction and may be a novel predictor of cerebrovascular events. We examined if HGF is a predictor of SCI in HD patients. Brain magnetic resonance imaging findings were used to divide 50 patients undergoing HD into 2 groups, a group with SCI (age, 61 +/- 8 years, mean +/- SD; n = 27) and a group without SCI (age, 60 +/- 7 years; n = 23). These patients received 24-hour ambulatory blood pressure monitoring. The number of patients with diabetes or hypertension was not different between the 2 groups. We made the following observations: (1) The percentage of smokers was higher in the group with SCI than in the group without SCI (P < .05). (2) Plasma levels of high-density lipoprotein cholesterol were lower and HGF levels were higher in the group with SCI compared with the group without SCI (P < .05 and P < .005, respectively). (3) Systolic ambulatory blood pressure and mean heart rate at night were higher in the group with SCI than in the group without SCI (P < .05). Multiple logistic regression analysis identified HGF as a significant risk factor for SCI (odds ratio, 1.89; 95% confidence interval, 1.57-3.38; P < .005). Our findings indicate that HGF may be a novel useful predictor of SCI in patients with chronic renal failure undergoing HD.

Abdominal visceral fat accumulation is associated with the results of (123)I-metaiodobenzylguanidine myocardial scintigraphy in type 2 diabetic patients

PURPOSE

We tested the hypothesis that increased abdominal visceral accumulation (VFA) is associated with insulin resistance and cardiovascular autonomic dysfunction in type 2 diabetic patients not receiving insulin treatment.

METHODS

The fat distribution was evaluated by measuring the VFA by abdominal computed tomography at the umbilical level. The study group consisted of 24 type 2 diabetic patients with high VFA (> or =100 cm(2), age 60 +/- 8 years, high VFA group). The control group consisted of 19 age-matched type 2 diabetic patients with normal VFA (<100 cm(2), age 60 +/- 7 years, normal VFA group). Cardiovascular autonomic function was assessed by baroreflex sensitivity, heart rate variability, plasma norepinephrine concentrations, and cardiac (123)I-metaiodobenzylguanidine (MIBG) scintigraphy.

RESULTS

Early and delayed (123)I-MIBG myocardial uptake values were lower (p < 0.005 and p < 0.0001, respectively) and the percent washout rate of (123)I-MIBG was higher (p < 0.0005) in the high VFA group than in the normal VFA group. The fasting plasma insulin concentrations (p < 0.005) and the homeostasis model assessment (HOMA) index values (p < 0.0005) were higher in the high VFA group than in normal VFA group. Multiple regression analysis revealed that the level of VFA was independently predicted by the HOMA index values and the myocardial uptake of (123)I-MIBG during the delayed phase.

CONCLUSION

Our results demonstrate that the level of VFA is associated with depressed cardiovascular autonomic function and insulin resistance in patients with type 2 diabetes mellitus.

Smoking is associated with urinary albumin excretion: an evaluation of premenopausal patients with type 2 diabetes mellitus

Cigarette smoking and an increase in urinary albumin excretion are associated with high mortality in patients with type 2 diabetes mellitus. We tested the hypothesis that the presence of a smoking habit correlates with increased urinary albumin excretion in premenopausal Japanese women with type 2 diabetes mellitus. The study consisted of 20 premenopausal Japanese patients with type 2 diabetes mellitus in the current-smokers group (age, 45 +/- 4 years, mean +/- SD). The control group consisted of 35 age-matched never-smoker patients (age, 45 +/- 5 years). Serum triglyceride levels were higher and high-density lipoprotein cholesterol levels were lower in the current-smokers group than in the never-smokers group (P < .05 and P < .01, respectively). Furthermore, fasting plasma insulin concentrations and the homeostasis model assessment index were higher in the current-smokers group than in the never-smokers group (P < .005 and P < .001, respectively). Urinary albumin excretion also was higher in the current-smokers group than in the never-smokers group (P < .0001). Multivariate logistic analysis revealed that urinary albumin excretion is independently associated with current smoking in Japanese premenopausal with type 2 diabetes mellitus (odds ratio, 1.79; 95% confidence interval, 1.08-3.87; P < .01). The results of this study show that current smoking is associated with an increased level of urinary albumin excretion, suggesting that smoking was a risk factor in the development of increased urinary albumin excretion in these patients.

Diazoxide-induced cardioprotection via ΔΨm loss depending on timing of application

Although the role of mitochondrial ATP-sensitive potassium (mitoKATP) channels in cardioprotection is widely accepted, it remains unclear when their opening is critical for protection. We tested the hypothesis that the mitoKATP channel acts as a trigger or mediator of protection against apoptosis through loss of mitochondrial inner membrane potential (DeltaPsim). Exposure of neonatal rat cardiomyocytes to H2O2 (0.5 mmol/L) resulted in apoptosis associated with severe DeltaPsim loss. Pretreatment with diazoxide (20 to 100 micromol/L) prevented H2O2-induced apoptosis and DeltaPsim loss at 2 but not 18 h after exposure, while the latter was prevented by cotreatment with diazoxide. Lack of protection by pretreatment with diazoxide was observed in cardiomyocytes cultured in a medium containing H2O2 for 2 h and then not containing for 16 h. The slopes of the regression lines of the relationship between the proportion of apoptotic cells and DeltaPsim loss (y = -0.89 vs. -0.42) and the proportion of cells with high side scatter signal differed between cardiomyocytes exposed H2O2 for 2 and 18 h. Diazoxide per se caused a transient DeltaPsim loss (within 30 min) with a recovery followed by persistent DeltaPsim loss (after 6 h). Inhibition of the former by 5-hydroxydecanoate (5-HD, 0.5 mmol/L) abolished protection of pretreatment with diazoxide (trigger phase), while that of the latter prevented the protection of cotreatment with diazoxide (mediator phase). Our results suggest that mitoKATP channels act as a trigger and mediator of cardioprotection through a transient or persistent DeltaPsim loss depending on phenotypic consequence in response to oxidants.

Homocysteine levels are associated with the results of 123I-metaiodobenzylguanidine myocardial scintigraphy in type 2 diabetic patients

PURPOSE

Elevated total plasma homocysteine (tHcy) levels and cardiovascular autonomic dysfunction are associated with a high mortality in type 2 diabetic patients. We tested the hypothesis that hyperhomocysteinemia is associated with insulin resistance and cardiovascular autonomic dysfunction in type 2 diabetic patients not receiving insulin treatment.

METHODS

The study group consisted of 17 type 2 diabetic patients with high tHcy levels (>15 mmol/l, age 58+/-5 years, high tHcy group). The control group consisted of 23 age-matched type 2 diabetic patients with normal tHcy levels (<or=15 mmol/l, age 58+/-9 years, normal tHcy group). Cardiovascular autonomic function was assessed by baroreflex sensitivity, heart rate variability, plasma norepinephrine concentrations, and cardiac (123)I-metaiodobenzylguanidine (MIBG) scintigraphy.

RESULTS

Early and delayed (123)I-MIBG myocardial uptake values were lower (p<0.005 and p<0.01, respectively) and the percent washout rate of (123)I-MIBG was higher (p<0.001) in the high tHcy group than in the normal tHcy group. The fasting plasma insulin concentrations (p<0.0001) and the homeostasis model assessment (HOMA) index values (p<0.0001) were higher in the high tHcy group than in the normal tHcy group. Multiple regression analysis revealed that the level of tHcy was independently predicted by the HOMA index values and the myocardial uptake of (123)I-MIBG at the delayed phase.

CONCLUSION

Our results demonstrate that high levels of tHcy are associated with depressed cardiovascular autonomic function and insulin resistance in patients with type 2 diabetes mellitus.

Pioglitazone but not glibenclamide improves cardiac expression of heat shock protein 72 and tolerance against ischemia/reperfusion injury in the heredity insulin-resistant rat

We tested the hypothesis that pioglitazone could restore expression of heat shock protein (HSP)72 in insulin-resistant rat heart. At 12 weeks of age, male Otsuka Long-Evans Tokushima Fatty (OLETF) rats and control (LETO) rats were treated with pioglitazone (10 mg x kg(-1) x day(-1)) or glibenclamide (5 mg x kg(-1) x day(-1)) for 4 weeks. Thereafter, hyperthermia (43 degrees C for 20 min) was applied. In response to hyperthermia, the activation of serine/threonine kinase Akt depending on phosphatidylinositol 3 (PI3) kinase was necessary for cardiac expression of HSP72. Hyperthermia-induced activation of Akt and HSP72 expression were depressed in OLETF rat hearts. Pioglitazone but not glibenclamide improved insulin sensitivity in OLETF rats, which was associated with the restoration of Akt activation and HSP72 expression. In experiments with isolated perfused heart, reperfusion-induced cardiac functional recovery was suppressed in OLETF rat hearts, which was improved by pioglitazone but not glibenclamide. Our results suggest that PI3 kinase-dependent Akt activation, an essential signal for HSP72 expression, is depressed in the heart in insulin-resistant OLETF rats, and the results suggest also that the restoration of HSP72 expression and tolerance against ischemia/reperfusion injury by treatment with pioglitazone might be due to an improvement of insulin resistance, leading to restoration of impaired PI3 kinase-dependent Akt activation in response to hyperthermia.

[Evaluation of autonomic function using posture change]

There are several examinations to evaluate cardiac autonomic function. Autonomic neuropathy is a common complication of diabetes mellitus and is associated with increased mortality. Baroreflex sensitivity (BRS) is a marker for the ability to augment vagal activity. Several studies have shown that BRS is impaired in diabetes with autonomic neuropathy. The head-up tilt test is the most useful tool to diagnose the neurally mediated syncope. We have developed a new non-invasive method to evaluate the baroreflex using downward tilting (DT-BRS). In our previous study conducted in healthy volunteers and diabetic patients, we demonstrated a strong correlation between systolic blood pressure increase and corresponding RR interval lengthening during downward tilting, which yielded DT-BRS values that correlated well with the BRS value obtained by the phenylephrine method (Phe-BRS). Heart rate responses observed after both squatting and standing (squatting test) are assumed to be a simple and useful tool to assess autonomic activity. We reported that indices of the squatting test showed a significant correlation with BRS assessed by Phe-BRS in diabetes. DT-BRS and the squatting test may provide promising information for the assessment of reflex vagal activity in diabetes.

Smoking is associated with insulin resistance and cardiovascular autonomic dysfunction in type 2 diabetic patients

BACKGROUND

Smoking and cardiovascular autonomic dysfunction are associated with high mortality in type 2 diabetic patients. This study tested the hypothesis that smoking is associated with insulin resistance/hyperinsulinaemia and cardiovascular autonomic dysfunction in type 2 diabetic patients who are not treated with insulin.

MATERIALS AND METHODS

The study patients were 22 current smokers with type 2 diabetes mellitus (age: 57 +/- 5 years, mean +/- SD) and 30 age-matched never-smoked patients with type 2 diabetes mellitus (control group, 57 +/- 8 years). The quality of blood glucose was assessed by fasting plasma glucose (FPG), fasting immunoreactive insulin (F-IRI), homeostasis model assessment (HOMA) index and haemoglobin A1c (HbA1c). The severity of smoking status was expressed by the Brinkman index, which is calculated as number of cigarettes per day multiplied by years of smoking. Cardiovascular autonomic function was assessed by baroreflex sensitivity (BRS), heart-rate variability, plasma norepinephrine concentration and cardiac (123)I-metaiodobenzylguanidine (MIBG) scintigraphic findings.

RESULTS

Baroreflex sensitivity was lower in the current smokers group than in the never-smoked group (P < 0.05). Early and delayed (123)I-MIBG myocardial uptake values were lower (P < 0.05, and P < 0.01, respectively) and the percentage washout-rate of (123)I-MIBG was higher (P < 0.0001) in the current smokers group than in the never-smoked group. Fasting immunoreactive insulin (F-IRI) concentration (P < 0.0001) and the homeostasis model assessment (HOMA) index (P < 0.0001) were higher in the current smokers group than the never-smoked group. Multiple logistic regression analysis revealed that smoking was independently predicted by F-IRI and the percentage washout-rate of (123)I-MIBG.

CONCLUSIONS

The results of the study suggested that smoking was associated with cardiovascular autonomic dysfunction and hyperinsulinaemia and that F-IRI and the percentage washout-rate of (123)I-MIBG were independent predictors of smoking in these Japanese patients with type 2 diabetes mellitus.

Influence of Menstrual Cycle on QT Interval Dynamics

OBJECTIVES

The aim of this study was to investigate the effects of the menstrual cycle on QT interval dynamics and the autonomic tone in healthy women.

METHODS

Holter ECGs were recorded in 11 healthy women aged 18-32 years during the follicular and luteal phases of their regular menstrual cycle. The interval from QRS onset to the apex (QaT) and to the end of the T-wave (QeT), the interval between the apex and the end of the T-wave (Ta-e), and RR intervals were measured automatically in the course of 24 hours by Holter ECGs. The QeT/RR, QaT/RR, and Ta-e/RR relationships were evaluated in each subject. The autonomic tone was assessed by the serum catecholamine level at rest and heart rate variability was measured by Holter ECGs.

RESULTS

(1) The follicular and luteal phases did not differ significantly with respect to the slopes of the QeT/RR, QaT/RR, and Ta-e/RR relationships. However, QeT and QaT intervals were significantly shorter for all RR intervals in the luteal than in the follicular phase (P < 0.0001). (2) The serum progesterone concentration was significantly higher in the luteal than in the follicular phase (P < 0.001). (3) Noradrenaline was significantly higher in the luteal than in the follicular phase (P < 0.05). There was no significant difference in the follicular and luteal phases with respect to heart rate variability measurements.

CONCLUSIONS

Our results suggest that the menstrual cycle affects the QT intervals. The observed shorter QT interval during the luteal than the follicular phase may be attributable to the increase in serum progesterone and sympathetic tone.

Phosphatidylinositol 3-kinase-dependent activation of akt, an essential signal for hyperthermia-induced heat-shock protein 72, is attenuated in streptozotocin-induced diabetic heart

We tested the hypothesis that phosphatidylinositol 3-kinase (PI 3-kinase)-dependent activation of Akt is essential for the expression of cardiac heat-shock protein 72 (HSP72) and that this pathway is impaired in the streptozotocin (STZ)-induced diabetic heart. STZ-induced male diabetic rats were treated with insulin (STZ-insulin group, n = 26) or vehicle (STZ-vehicle group, n = 61) for 3 weeks. Whole-body hyperthermia (43 degrees C for 20 min) was applied, and the heart was isolated 24 h later. Compared with control heart, hyperthermia-induced HSP72 expression and phosphorylation of Akt were attenuated in the STZ-vehicle heart. Pretreatment with wortmannin attenuated hyperthermia-induced HSP72 expression and phosphorylation of Akt. In isolated perfused heart experiments, the hyperthermia-treated STZ-vehicle heart showed poor left ventricular functional recovery during reperfusion after no-flow global ischemia compared with hyperthermia-treated control heart. Insulin treatment restored HSP72 expression and reperfusion-induced functional recovery. In cultured neonatal rat cardiomyocytes, hyperthermia-induced HSP72 expression was enhanced by insulin, together with tolerance against hypoxia-reoxygenation injury. Wortmannin and LY294002 inhibited hyperthermia-induced HSP72 expression and phosphorylation of Akt. Our results indicate that activation of Akt, in a PI 3-kinase-dependent manner, is essential for hyperthermia-induced HSP72 expression in association with cardioprotection, suggesting impairment of this signaling pathway in the STZ-induced diabetic heart, probably due to insulin deficiency.

Hyperhomocysteinemia is a significant risk factor for silent cerebral infarction in patients with chronic renal failure undergoing hemodialysis

In patients with chronic renal failure undergoing hemodialysis (HD), the presence of silent cerebral infarction (SCI) is associated with high mortality. Plasma total homocysteine (tHcy), which increases with renal dysfunction, has been flagged as a novel predictor for cerebrovascular events. We tested the hypothesis that the presence of SCI correlates with tHcy in HD patients. Based on brain magnetic resonance imaging findings, 44 patients undergoing HD were divided into a with-SCI group (61+/-9 years [mean+/-SD]; n=24) and a without-SCI group (60+/-8 years, n=20), in whom 24-hour ambulatory blood pressure monitoring was performed. The number of patients with diabetes or hypertension was not different between the 2 groups. We made the following observations: (1) the percentage of smokers was higher in the with-SCI group than in the without-SCI group (P<.05); (2) plasma levels of high-density lipoprotein cholesterol were lower and tHcy was higher in the with-SCI group than in the without-SCI group (P<.05 and P<.0001, respectively); (3) and systolic ambulatory blood pressure and mean heart rate during nighttime were higher in the with-SCI group than in the without-SCI group (P<.05). Multivariate logistic analysis identified hyperhomocysteinemia as an independent and significant risk factor for SCI (odds ratio, 1.22; 95% CI, 1.10-1.36; P<.01). Our findings indicate that plasma tHcy may be a novel useful predictor for SCI in patients with chronic renal failure undergoing HD.

Gender differences in autonomic modulation of ventricular repolarization in humans

BACKGROUND

Gender differences in the incidence of ventricular arrhythmias have been reported and torsades de pointes associated with long QT syndrome are more common in women than men. Although increased sympathetic tone has an important role in vulnerability to arrhythmia, little is currently known regarding gender differences in the dynamic electrophysiological response to sympathetic stimulation. Therefore, we investigated whether there is a gender difference in humans with respect to the dynamic response of ventricular repolarization to beta-adrenergic stimulation and to autonomic blockade.

METHODS

Twelve-lead ECGs were continuously recorded during isoproterenol infusion (protocol 1) and autonomic blockade with propranolol and atropine infusion (protocol 2) in 24 healthy volunteers (12 men, 23 +/- 2 years; 12 women, 23 +/- 5 years). QT (QTc) intervals were measured at the baseline and at a heart rate of 75, 100, and 120 beats/min.

RESULTS

(1) The morphology of the T wave dynamically and transiently changed to bifid or biphasic during the acute phase of isoproterenol infusion. The incidence of these morphologic changes was higher in women than men (P < 0.05). (2) The QTc interval was initially prolonged and then shortened in both men and women during isoproterenol administration. However, QTc prolongation was significantly greater in women (0.44 +/- 0.02 to 0.55 +/- 0.03 sec) than men (0.42 +/- 0.03 to 0.51 +/- 0.04 sec; P < 0.05). (3) The QTc interval was significantly prolonged under autonomic blockade and the intrinsic QTc interval was longer in women than men (P < 0.05).

CONCLUSION

While sympathetic stimulation and autonomic blockade modulated the dynamics of ventricular repolarization in both sexes, it was more pronounced in women. This gender difference may partially account for the susceptibility of women to arrhythmogenesis.

Heterogeneous expression of connexin 43 in the myocardium of rabbit right ventricular outflow tract

The right ventricular outflow tract (RVOT) has been demonstrated as an important focus in idiopathic ventricular arrhythmias. However, the role of the gap junction in this region in arrhythmic events has not been fully investigated. The purpose of this study was to evaluate the expression and distribution of the gap junction protein connexin 43 (Cx43) in the myocardium of the RVOT area of normal adult rabbits. Tissue samples were obtained from 6 regions of normal rabbit heart, i.e. the left ventricle (LV) free wall, the LV papillary muscle, the RVOT free wall, and the RVOT septum which was subdivided into the RV side, the central layer, and the LV side. Immunohistochemical analysis was performed to investigate the characteristics of Cx43 distribution in the RVOT area. In the LV free wall and papillary muscle, Cx43 was abundantly, homogeneously, and approximately equally expressed in end-to-end- and side-to-side intercellular connections. In the free wall of the RVOT, Cx43 expression was poor compared to both these LV regions and side-to-side cell connections were predominant. Cx43 was as richly and homogeneously distributed in the central layer and LV side of the RVOT septum as in the two LV regions. However, in the RV side of the RVOT septum, its distribution was scant and an unstained area was noted. The heterogeneous expression of Cx43 in the RVOT area may serve as substrate for idiopathic ventricular arrhythmia.

Effects of valsartan and perindopril combination therapy on left ventricular hypertrophy and aortic arterial stiffness in patients with essential hypertension

OBJECTIVE

To compare the effects of combined therapy of an angiotensin II receptor blocker (ARB; valsartan) and an angiotensin converting enzyme inhibitor (ACEI; perindopril) on blood pressure (BP), metabolic profiles, plasma brain natriuretic peptide (BNP) levels, echocardiographic findings, and aortic pulse wave velocity (PWV) with those of respective monotherapy in never-treated patients with essential hypertension.

METHODS

This was a prospective randomized trial, in which there were 31 patients with essential hypertension and left ventricular hypertrophy (LVH) who visited the outpatient clinic of Oita Red Cross Hospital (14 women and 17 men; mean+/-SD age, 59+/-5 years). Each patient was randomly assigned to receive valsartan (160 mg/day, V group, n=10), perindopril (8 mg/day, P group, n=11), or a combination of valsartan (80 mg/day) and perindopril (4 mg/day, V+P group, n=10) for 40 weeks. Ambulatory BP monitoring (ABPM), echocardiographic findings, metabolic findings, plasma BNP levels, and brachial-ankle PWV (baPWV) were evaluated before and after the 40-week therapy.

RESULTS

The baseline and post-therapeutic BP levels were similar among the three groups. At baseline ABPM, non-dipping was observed in 80, 82, and 80% in the V, P, and V+P groups, respectively. Each 40-week therapy regimen comparably reduced ABP. The plasma BNP levels (P<0.0001 for each), left ventricular mass index (LVMI) (P<0.01 for each), and PWV values (P<0.0001 for each) were also reduced. However, when compared with either V or P group, the percentage reduction in LVMI (P<0.05 and P<0.005, respectively), BNP (P<0.05 for each), and baPWV values (P<0.005 and P<0.001, respectively) was greater in the V+P group.

CONCLUSIONS

Our findings suggest that, when compared with each monotherapy, perindopril and valsartan combination therapy exerts greater beneficial effects regarding the regression of LVH, reduction in BNP, and improvement of PWV in a selected group of essential hypertensive patients with LVH and high prevalence of non-dipping patterns.

Estrogen inhibits hyperthermia-induced expression of heat-shock protein 72 and cardioprotection against ischemia/reperfusion injury in female rat heart

There is still controversy as to whether estrogen inhibits or enhances heat-shock protein (HSP72) expression in the heart. To evaluate the gender difference, whole-body hyperthermia (HT, 43 degrees C for 20 min) or normothermia (NT, 37 degrees C for 20 min) was applied to both male and female rats. Twenty-four hours after each thermo-treatment, the heart was isolated for either Western blot analysis or isolated-perfused heart experiments. Induction of HSP72 expression and post-ischemic recovery of left ventricular (LV) function was pronounced in male than in female heart. To evaluate the effect of estrogen, female rats received ovariectomy. One week after the operation, ovariectomized rats were treated with 17beta-estradiol in a single administration of 4, 40, or 400 mug/kg or vehicle (placebo) intraperitoneally (IP), followed by HT or NT at 6 h after the administration. In the placebo-treated ovariectomized female, HT-induced cardiac HSP72 expression was more remarkable with better LV functional recovery than sham-operated gonadally intact female. Treatment with 17beta-estradiol reduced HT-induced cardiac HSP72 overexpression and abolished better LV functional recovery observed in placebo-treated ovariectomized female. Inhibition of HT-induced HSP72 expression was in association with the inhibition of activation of heat-shock factor 1 (HSF1). In cultured rat neonatal cardiomyocytes, prior exposure to H(2)O(2)-induced HSP72 expression and rendered protection against hypoxia/reoxygenation, which was attenuated by the treatment with 17beta-estradiol. The washout of 17beta-estradiol for 48 h recovered the H(2)O(2)-induced HSP72 expression and tolerance against hypoxia/reoxygenation. Our results suggest that the male heart is more sensitive than gonadally intact female heart in terms of response to HT to express HSP72 in association with protection against ischemic insult. This observation may be due to the inhibitory effects of estrogen on HSP72 expression at a transcriptional level.

Patients with mild hypertensive heart disease and left ventricular outflow tract obstruction: treatment with angiotensin II antagonists

Systolic anterior motion of the mitral leaflet (SAM) combined with obstruction at the left ventricular (LV) outflow tract is often observed on echocardiography in elderly hypertensive patients with severe concentric LV hypertrophy. We experienced, however, two patients with mild hypertension who had an ejection systolic murmur, SAM, and LV outflow tract obstruction with a pressure gradient of 46 and 45 mmHg, respectively, despite very mild symmetric hypertrophy of LV wall (12 mm) by echocardiography. Treatment with angiotensin II type 1 receptor blocker improved intraventricular obstruction and LV hypertrophy in both patients. Left ventricular outflow tract obstruction should be suspected in hypertensive patients with mild LV hypertrophy, particularly in those with an ejection systolic murmur. Angiotensin II antagonists could be considered as the treatment of choice for such patients.

Gender Differences in the Dynamics of Terminal T Wave Intervals

This study was designed to investigate gender differences in the dynamic changes of the terminal T wave (Ta-e interval) of healthy subjects. Holter ECGs were recorded in 24 healthy volunteers (12 men aged 23 +/- 2 years). The intervals from QRS onset to the apex (QaT) and to the end of the T wave (QeT), and the interval between the apex and the end of the T wave (Ta-e) were measured. Then, the QeT/RR, QaT/RR, and Ta-e/RR relationship was evaluated by linear regression analysis in each subject. The QeT and QaT intervals were significantly longer in women than men and the slope of the QeT/RR and QaT/RR relationship was steeper in women than men. The Ta-e intervals showed a significant but weaker positive correlation with the preceding RR intervals in 7 (58.3%) men and 9 (75.0%) women. The average values of the slope and the correlation coefficient of the Ta-e/RR relationship were significantly smaller compared to those of QeT and QaT in both men and women (P < 0.0001). The slope of the Ta-e/RR relationship was significantly greater in women than men (0.025 +/- 0.009 vs 0.011 +/- 0.012, P < 0.005). However, the Ta-e intervals were significantly longer over the entire range of RR intervals in men than women (P < 0.0001). The rate-correcting formulas of Bazett and Framingham overcorrected the Ta-e intervals. The observed gender difference in the measurement and dynamics of the Ta-e interval may help to understand the mechanisms underlying the gender difference in the incidence of ventricular arrhythmias.

Dynamics of T-U Wave in Patients with Idiopathic Ventricular Tachycardia Originating From the Right Ventricular Outflow Tract

Postextrasystolic U wave augmentation is observed in patients with long QT syndrome and those with organic heart disease. This phenomenon is considered a marker of increased risk of arrhythmia. However, the characteristics of the U wave have not been evaluated in patients with idiopathic VT originating from the right ventricular outflow tract (RVOT-VT). The present study evaluated the dynamic change in the T-U wave in patients with RVOT-VT. Holter ECGs obtained from 14 patients with RVOT-VT and 11 healthy control subjects were analyzed. The amplitude of T and U waves (Tamp and Uamp) and preceding RR intervals were measured during stable sinus rhythm (rate dependent change) and in the postextrasystolic sinus complex (pause dependent change). Uamp correlated negatively and significantly with the preceding RR interval in 13 (93%) RVOT-VT patients but in only 2 (18%) control subjects. The average value of the slope of the Uamp/RR relationship was negative (-0.22 +/- 0.10 mV/s) in the RVOT-VT group, but was positive (0.04 +/- 0.07 mV/s, P < 0.001) in the control group. Pause dependent U wave augmentation was observed in 12 (86%) of 14 patients. Increased frequency of consecutive preceding premature ventricular contractions (PVCs) was associated with a larger postextrasystolic Uamp. PVC or the first ventricular beat of VT arose from near the peak of augmented U waves. The dynamic changes in the T-U wave were observed in patients with RVOT-VT. Further investigations are required to elucidate the precise role of the U wave in arrhythmogenesis in those patients.

Characteristics of new-onset ventricular arrhythmias in pregnancy

The characteristics and underlying mechanisms of new-onset ventricular arrhythmia during pregnancy have not been adequately investigated. We studied 11 pregnant women aged 35.4 +/- 3.1 years who experienced new-onset ventricular arrhythmias during pregnancy. The onset of their first episode of ventricular arrhythmia was distributed equally over the 3 trimesters. Ventricular premature contractions (VPCs) and ventricular tachycardia (VT) exhibited a monomorphic configuration in all patients; in 8 (73%) they originated from the right ventricular outflow tract. The frequency of VPCs decreased by more than 95% in 83% of the patients; couplets and VTs disappeared completely in all patients during the postpartum period. All parameters of heart rate variability were significantly lower during pregnancy than postpartum (P < .05). QT and QTc intervals were normal during pregnancy in all patients. The slope and the intersect of the QT/RR relationship obtained from Holter ECGs were not significantly different during pregnancy and in the postpartum period. New-onset ventricular arrhythmias in pregnancy manifest characteristics similar to those of idiopathic VT. Our findings suggest that various hemodynamic and neurohormonal changes associated with pregnancy play an important role in ventricular arrhythmogenesis.

Diazoxide triggers cardioprotection against apoptosis induced by oxidative stress

Although mitochondrial ATP-sensitive potassium (mitoK(ATP)) channels have been reported to reduce the extent of apoptosis, the critical timing of mitoK(ATP) channel opening required to protect myocytes against apoptosis remains unclear. In the present study, we examined whether the mitoK(ATP) channel serves as a trigger of cardioprotection against apoptosis induced by oxidative stress. Apoptosis of cultured neonatal rat cardiomyocytes was determined by flow cytometry (light scatter and propidium iodide/annexin V-FITC fluorescence) and by nuclear staining with Hoechst 33342. Mitochondrial membrane potential (DeltaPsi) was measured by flow cytometry of cells stained with rhodamine-123 (Rh-123). Exposure to H(2)O(2) (500 microM) induced apoptosis, and the percentage of apoptotic cells increased progressively and peaked at 2 h. This H(2)O(2)-induced apoptosis was associated with the loss of DeltaPsi, and the time course of decrease in Rh-123 fluorescence paralleled that of apoptosis. Pretreatment of cardiomyocytes with diazoxide (100 microM), a putative mitoK(ATP) channel opener, for 30 min before exposure to H(2)O(2) elicited transient and mild depolarization of DeltaPsi and consequently suppressed both apoptosis and DeltaPsi loss after 2-h exposure to H(2)O(2). These protective effects of diazoxide were abrogated by the mitoK(ATP) channel blocker 5-hydroxydecanoate (500 microM) but not by the sarcolemmal K(ATP) channel blocker HMR-1098 (30 microM). Our results suggest for the first time that diazoxide-induced opening of mitoK(ATP) channels triggers cardioprotection against apoptosis induced by oxidative stress in rat cardiomyocytes.

Norepinephrine evoked by potassium depolarization increases interstitial adenosine concentration via activation of ecto-5'-nucleotidase in rat hearts

We examined whether the increase of the extracellular potassium ion concentration, [K(+)](o), can increase the production of interstitial adenosine in the ventricular myocardium, with the use of microdialysis techniques in in situ rat hearts. A microdialysis probe was implanted in the left ventricular myocardium of anesthetized rat hearts, and the tissue in the vicinity of the dialysis was perfused with Tyrode's solution containing AMP through the dialysis probe at a rate of 1.0 microl/min to assess the activity of ecto-5'-nucleotidase. When the K(+) concentration of the perfusate ([K(+)](o)) was increased stepwise from 5.4 mM (control) to up to 140.4 mM, the level of dialysate adenosine significantly increased, in a [K(+)](o)-dependent manner. The presence of CsCl or BaCl(2) (20 mM), which markedly depolarized the resting potential, significantly increased the level of adenosine in the dialysate. Equivalent increases in the osmotic concentration of the perfusate, made by adding sucrose (270 mM), did not change the dialysate adenosine concentration. Introduction of high [K(+)](o) (140.4 mM) significantly increased the level of norepinephrine (NE) in the dialysate, and this increase was abolished in the reserpinized rats hearts. In the presence of an antagonist of alpha(1)-adrenoceptor (prazosin, 50 microM) or protein kinase C (PKC) (chelerythrine, 10 microM) and in reserpinized rats, an introduction of high [K(+)](o) failed to increase the AMP-primed dialysate adenosine concentration. We conclude that high [K(+)](o)-induced NE release from sympathetic nerve terminals increases adenosine by stimulating the PKC-ecto-5'-nucleotidase cascade through alpha(1)-adrenoceptors.

Gender differences in ventricular repolarization: terminal T wave interval was shorter in women than in men

The incidence of sudden death is lower in women than in men, although women have a longer QT interval and are more prone to develop torsades de points than men. It has been recently proposed that the time interval between the apex and end of the T wave (Ta-e) represents the transmural dispersion of ventricular repolarization. Gender and age differences in Ta-e interval have not been fully assessed previously. Standard surface 12-lead ECGs recorded in 760 healthy subjects (382 women, 0-88 years of age) were studied. The intervals from j-point to the apex of the T wave (JaT) and to the end of the T wave (JeT) were measured in lead V5 in each ECG and corrected by preceding RR intervals using the formula of Bazett (JaTc and JeTc). The Ta-e and Ta-e/JeT ratio were also evaluated. Both JaTc and JeTc intervals were significantly longer in women aged > 20 years than in men of the same age (P < 0.0001). The difference was due to shortening of these intervals after puberty in men. However, the Ta-e interval was significantly shorter in women than in men (P < 0.05) and subsequently the Ta-e/JeT ratio was significantly smaller in women than in men (P < 0.0001). The results showed gender differences in the Ta-e interval and JaTc and JeTc intervals in healthy adults, and suggest that the small transmural dispersion of repolarization in women, in spite of the long JaTc and JeTc intervals, might be a beneficial antiarrhythmic property.

Gender differences in various types of idiopathic ventricular tachycardia

INTRODUCTION

The aim of this study was to evaluate gender differences in the incidence and age distribution of various types of idiopathic ventricular tachycardia (VT).

METHODS AND RESULTS

We conducted a search of the medical literature on idiopathic VT. According to their site of origin, we divided the VTs into three types: right ventricular outflow tract (RVOT-VT), left ventricular outflow tract (LVOT-VT), and left ventricular (LV) septum (LV-VT). We reviewed 68 articles and a total of 748 patients. Among RVOT-VT patients, there were more females than males (311 vs 153, male/female ratio 0.49). In LV-VT, males prevailed over females (175 vs 52, male/female ratio 3.37), whereas LVOT-VT was distributed almost equally between males (n = 33) and females (n = 24). To determine the age distribution, we assessed 419 patients from 51 studies. In both males and females, the highest incidence of RVOT-VT occurred in the third to fifth decade of life (males, mean 43.5 +/- 18.7; females, mean 40.9 +/- 13.8 years). LV-VT occurred at a younger age in both males and females than did RVOT-VT (mean 33.0 +/- 13.9 and 25.7 +/- 12.0 years, respectively, P < 0.0001 vs RVOT-VT). LV-VT occurred at a younger age in females than males (P < 0.005).

CONCLUSION

Gender-specific differences exist in the incidence and age distribution of the various types of idiopathic VT. Studies on gender-specific differences in arrhythmia will lead to a better understanding of its mechanism(s) and provide valuable information for the development of optimal treatment strategies.

Circadian variation of short-lasting asymptomatic paroxysmal supraventricular tachycardia

This study determines the circadian variation of transient asymptomatic paroxysmal supraventricular tachycardia (PSVT). A total of 416 asymptomatic PSVT episodes (> or = 10 consecutive supraventricular beats) recorded in 62 patients were obtained from Holter monitoring. The incidence of the onset of PSVT was counted at the 1-hour interval. The duration (beats) and rate (beats/min) of PSVT and the preceding heart rate were also evaluated. The circadian variations of the onset, duration, and rate of PSVT were analyzed by the single cosinor method. The incidence of the onset of PSVT showed a significant circadian variation (P = .001); with high incidence in the daytime and low at nighttime. The rate and duration of PSVT also showed significant circadian variation (P = .02), faster and longer in daytime and slower and shorter at night, respectively. The rate (r = .45, P < .001) and duration (r = .22, P < .001) of PSVT correlated significantly with the preceding heart rate. Our findings suggest that the onset and persistence of short-lasting asymptomatic PSVT exhibit a circadian pattern and that autonomic tone might play an important role in the genesis of this form of PSVT.

Development of a new method for assessing the cardiac baroreflex: response to downward tilting in patients with diabetes mellitus

OBJECTIVE

To investigate the clinical value of a new non-invasive method for assessing baroreflex sensitivity using downward tilting.

PATIENTS

34 patients with diabetes mellitus, mean (SD) age, 53.6 (11.8) years.

DESIGN

Arterial blood pressure and ECG were recorded simultaneously while the patients were on a tilt table. After 20 minutes at a 70 degrees upright tilt, the patients were returned to the supine position at a speed of 3.2 degrees /s (downward tilting baroreflex sensitivity test, DT-BRS). A beat to beat systolic blood pressure increase associated with a corresponding lengthening of the RR interval was noted during downward tilting. Baroreflex sensitivity was also assessed using the conventional method of an intravenous injection of phenylephrine (Phe-BRS). Heart rate variability was analysed during rest and tilting.

RESULTS

The slope of the regression line for systolic blood pressure v RR interval during downward tilting was highly correlated with Phe-BRS (r = 0.83, p < 0.0001). Both DT-BRS and Phe-BRS were correlated with the high frequency (HF) component of resting heart rate variability (p < 0.005) and with the ratio of the low frequency to the high frequency component (LF/HF) during upright tilting (p < 0.005). DT-BRS and Phe-BRS were also correlated with the difference between rest and tilting values of HF and LF/HF (p < 0.005).

CONCLUSIONS

DT-BRS provides a physiological, non-invasive method for determining baroreflex sensitivity and may be a useful index of reflex cardiac vagal and sympathetic function in patients with diabetes mellitus.

[Present and future of cardiac function tests: electrophysiologic tests]

Various electrocardiographic and physiologic tests have been developing for almost 100 years since Einthoven established the standard 12 lead electrocardiogram(ECG) system. Recently, interest has focused on the new developing parameters associated with cardiac ventricular repolarization, such as transmural dispersion of repolarization, T wave alternans and QT dispersion. QT dispersion, measured as interlead difference of QT interval, has been suggested to reflect regional variation of ventricular repolarization. However, still unsolved basic problems give difficulties for clinical acceptance of this parameter. On the other hand, it is generally accepted that heart rate variability obtained from Holter ECG is useful tool to assess the autonomic tone. Head-up tilt test is a valuable diagnostic tool to identify patients with neurally mediated syncope and also useful for assessment of reflex cardiac autonomic function, such as baroreflex sensitivity. The number of electrophysiologic study(EPS) dramatically increased together with increase of radiofrequency catheter ablation. A new three-dimensional nonfluoroscopic electroanatomical mapping system(CARTO) is an exciting development in catheter ablation treatment. Transtelephonic ECG and its computer-assisted answering system are also useful for diagnose and treatment in the patients of paroxysmal cardiac symptoms.

Determination of left ventricular mass by echocardiography in normotensive diabetic patients

Patients with Type 2 diabetes mellitus (DM) have excessive cardiovascular morbidity and mortality, even in the absence of hypertension. Left ventricular hypertrophy (LVH), which is an ominous prognostic sign and an independent risk factor for cardiac events, is often present in Type 2 DM patients. Forty-two Type 2 DM patients without hypertension, all of whom had been diagnosed more than 10 years ago, were examined in the present study. They had no evidence of renal dysfunction and had not received any anti-hypertensive drugs. Age-matched healthy normal subjects (n=47) were recruited as controls. All participants were classified according to the left ventricular mass index (LVMI) using M-mode echocardiography and their systolic function (fractional shortening) was examined. The systolic function was not significantly different between the Type 2 DM and control groups. LVH can be seen even in the normotensive Type 2 DM patients, with these patients still having a higher LVMI than the normal control subjects. Although the plasma insulin levels were not significantly increased in the Type 2 DM patients, the LVMI significantly correlated with plasma insulin levels. However, the LVMI did not significantly correlate with plasma fasting glucose and hemoglobin A1c in the Type 2 DM patients. These results suggest that LVH in Type 2 DM patients without hypertension may be associated with elevated plasma insulin levels.

Malignant neurocardiogenic vasovagal syncope associated with chronic exaggerated vagal tone

A head-up tilt test was performed in a 23-year-old woman with a history of two syncopal episodes. The patient developed abrupt syncope with 48 seconds of sinus arrest. Analysis of the high frequency (HF) power of heart rate variability over 24 hours before and after metoprolol therapy showed a significantly elevated HF power in this patient compared to age- and sex-matched healthy subjects. It is suggested that an exaggerated resting vagal tone might be associated with the pathogenesis of prolonged asystole in our patient.

Preceding stimulus frequency-dependent potentiation of the postrest shortening of the action potential duration in rabbits

Action potential duration (APD) in rabbit ventricular myocardium shortens after a rest period (postrest shortening). However, the effects of preceding stimulus frequency on the postrest shortening have not been elucidated. We recorded transmembrane action potentials (TAPs) and monophasic action potentials (MAPs) from the rabbit ventricle. In in vitro experiments. repetitive regular stimuli (S1) at cycle lengths ranging between 500 to 3000 ms were followed by a single extrastimulus (S2) at a coupling interval of 5000 ms. A decrease in S1S1 interval resulted in a progressive shortening of the duration of TAP (TAPD) elicited by S2 (S2-TAPD), which was potentiated by increasing extracellular calcium concentration ([Ca2+]o) or application of ouabain and was inhibited by lowering [Ca2+]o or verapamil. Application of ryanodine was most effective in lengthening S2-TAPD following a short S1S1 interval. 4-aminopyridine and E4031 caused marked lengthening of S2-TAPD when S1S1 was long. However, the lengthening effect was attenuated and disappeared with a shorter S1S1 interval. In in vivo experiments, regular ventricular pacing (S1) at cycle lengths ranging between 250 to 1000 ms was followed by a single extrastimulus (S2) with a coupling interval (S1S2) of 1500 ms. A decrease in the S1S1 interval also resulted in progressive shortening of the duration of MAP elicited by S2. Our results indicate that the postrest shortening is potentiated by an increase in the preceding stimulus frequency in the rabbit ventricle, in which the function of sarcoplasmic reticulum may play a significant role.

Rapid electrical stimulation of contraction reduces the density of beta-adrenergic receptors and responsiveness of cultured neonatal rat cardiomyocytes. Possible involvement of microtubule disassembly secondary to mechanical stress

BACKGROUND

Although tachycardia is commonly present in patients with congestive heart failure, its role in the development of congestive heart failure remains unclear. We studied the effect of rapid electrical stimulation of contraction on beta-adrenergic receptor (beta-AR) signal pathway in cultured cardiomyocytes of neonatal rats.

METHODS AND RESULTS

Contraction of cardiomyocytes was induced by electrical stimulation at 50 V with twice the threshold pulse width. beta-ARs were identified by [(3)H]CGP-12177 and [(3)H]dihydroalprenolol. Electrical stimulation reduced cell-surface but not total beta-AR density; the effect was dependent on pacing frequency (a reduction of 11%, 28%, and 18% in cells paced at 2.5, 3. 0, and 3.3 Hz, respectively). This reduction was apparent at 3 hours, in contrast to reduced beta-AR density after exposure to isoproterenol (ISP) for 1 hour. The fraction and inhibition constant of beta-AR binding agonist with high affinity were not affected by rapid electrical stimulation. In cardiomyocytes paced at 3.0 Hz for 24 hours, the response to ISP decreased compared with unpaced cells, 142% versus 204% of baseline with 1 micromol/L ISP, whereas the responses to forskolin or acetylcholine were not different. Treatment of cardiomyocytes with 2,3-butanedione monoxime (10 mmol/L) or taxol (10 micromol/L) inhibited the rapid pacing-induced reduction in beta-AR density.

CONCLUSIONS

Our results suggest that contractile activity is involved in regulation of cardiac function by modulating the beta-AR system independently of hemodynamic and neurohormonal factors. This may help to elucidate the role of mechanical stress in the development of heart failure.

Effect of constant and intermittent vagal stimulation on the heart rate and heart rate variability in rabbits

To examine whether the high-frequency (HF) component of heart rate variability (HRV) reflects fluctuation or tonic level of vagal outflow, we investigated the effects of vagal efferent nerve stimulation (VS) on the heart rate and HRV in anesthetized open-chest rabbit under artificial respiration at a rate of 52 breaths/min (0.86 Hz). A power spectral analysis was performed at baseline and during VS (stimuli at 2 ms, 1-10 V and 5-25 Hz). VS was applied using two different patterns. The first was constant VS; continuous stimulation at graded frequency or voltage to simulate changes in the level of vagal "tone." The second pattern was intermittent VS; stimulation at 0.5 Hz of on-off cycle to simulate fluctuations in vagal efferent activity. The power spectrum at baseline showed a single narrow component at 0.86 Hz, identical to respiration rate. Both the constant and intermittent VS prolonged RR interval. The amplitude of the component at 0.86 Hz remained unaffected by either the constant or intermittent VS, whereas the latter evoked a distinct narrow component at 0.5 Hz, reflecting the on-off cycle of intermittent VS. Our results suggest that the HF component of the power spectrum of HRV measures the magnitude of fluctuations of vagal input associated with respiratory modulation.

Influence of autonomic tone on the filtered QRS duration from signal averaged electrocardiograms in healthy volunteers

We recently reported that signal averaged electrocardiograms (SAECG) measurements possess a circadian rhythm and are closely related to heart rate or heart rate variability in healthy volunteers. This study determines the influence of autonomic tone on the filtered QRS (f-QRS) duration from SAECG by using pharmacologic autonomic blockade and exercise in healthy volunteers. Eleven healthy male volunteers were studied. Three protocols were designed to study the effects of exercise (Ex) under control conditions, beta adrenergic blockade or double blockade. SAECGs and heart rate variability (LF and HF: low and high frequency power, LF/HF ratio) were determined from Holter recordings. Ex significantly decreased the f-QRS duration and HF and significantly increased heart rate and LF/HF. Ex during beta adrenergic blockade significantly increased heart rate and decreased f-QRS duration and HF, but did not change LF/HF. Ex during double blockade did not affect the f-QRS duration, HF, or LF/HF. The changes in f-QRS duration induced during Ex, autonomic blockade, or both were inversely correlated with changes in heart rate and LF/HF and positively correlated with changes in HF. These data suggest that f-QRS duration in healthy subjects is shortened by Ex with increased sympathetic tone or decreased parasympathetic tone or the combination.

Bradykinin regulates captopril-induced upregulation of beta-adrenergic receptor in cultured neonatal rat cardiomyocytes

The aim of this study was to elucidate the role of bradykinin in mediating captopril-induced upregulation of beta-adrenergic receptor (beta-AR). The density of beta-AR on the surface of cardiac myocytes was measured by binding assay using [(3)H]CGP-12177. Treatment of cultured neonatal rat cardiomyocytes with captopril resulted in a time-dependent elevation of bradykinin concentration in the culture medium. The increased bradykinin concentration was significant at 2, 3 and 6 h, but not at 12 h after exposure to captopril. This time-dependent effect of captopril on enhancement of bradykinin levels paralleled that of beta-AR upregulation. Exogenously applied bradykinin increased beta-AR density by 22, 30 and 35% at 0.01, 0.1 and 1 microm concentrations, respectively. Myocytes treated with 1 microm bradykinin responded to isoproterenol (ISP) in a dose-dependent manner, as demonstrated by acceleration of spontaneous beating frequency. These beating acceleration effects of bradykinin were abolished by Hoe 140. Stimulation of bradykinin B2 receptor by exogenously added bradykinin for 6 h was sufficient to produce beta-AR up-regulation to a level similar to that seen after 24 h. Our results indicate that bradykinin potentiation by ACE inhibitors regulates, at least in part, captopril-induced beta-AR up-regulation.

Baroreflex sensitivity predicts the induction of ventricular arrhythmias by cesium chloride in rabbits

Previous studies have shown that the autonomic nervous system plays an important role in the genesis of ventricular tachycardia (VT) in patients with long QT syndrome, and in cesium chloride (Cs)-induced VT in animals. The present study investigated whether baroreflex sensitivity predicts the induction of VT by Cs in the rabbit in vivo. Monophasic action potentials (MAPs) of the left ventricular endocardium were recorded simultaneously with the surface ECG in 27 rabbits. Rabbits were divided into 4 groups based on the Cs-induced ventricular arrhythmias: (1) no ventricular premature contractions (No-VPC group), (2) single or paired VPC (VPC group), (3) monomorphic VT (MVT group), and (4) polymorphic VT (PVT group). Baroreflex sensitivity was significantly lower in the MVT and PVT groups than in the No-VPC and VPC groups. The plasma norepinephrine concentration before Cs injection was significantly higher in the MVT group than in the other 3 groups, and the norepinephrine concentration after Cs injection was significantly higher in the MVT and PVT groups than in the No-VPC and VPC groups. Baroreflex sensitivity was negatively correlated with the norepinephrine concentration before Cs injection. These results suggest that autonomic nervous system dysfunction, as defined by reduced baroreflex sensitivity, and elevated plasma norepinephrine concentrations predict increased susceptibility to Cs-induced VT.

Evaluation of autonomic influences on QT dispersion using the head-up tilt test in healthy subjects

Our objective was to examine the autonomic influence on QT interval dispersion using the head-up tilt test in healthy subjects. RR and QT intervals, heart rate variability, and plasma norepinephrine concentration were measured in the supine position and tilting to 70 degrees for 20 minutes using a footboard support in 15 healthy male volunteers (mean age +/- SD: 28.0 +/- 4.5 years). The rate-corrected QT interval (QTc) was calculated using Bazett's formula, and QT and QTc dispersions were defined as the maximum minus minimum values for the QT and QTc, respectively, from the 12-lead ECG. Spectral analysis of the heart rate variability generated values for the low- and high-frequency powers (LF and HF) and their ratio (LF/HF). Compared with values obtained in the supine position, tilting significantly increased QT (P < 0.05) and QTc dispersion (P < 0.01), the LF/HF ratio (P < 0.0001), and plasma norepinephrine concentration (P < 0.0001), and significantly decreased HF (P < 0.0001). QTc dispersion was positively correlated with the LF/HF ratio and plasma norepinephrine concentration, and negatively correlated with HF. These results suggest that head-up tilt testing increases QT dispersion by increasing sympathetic tone and/or decreasing vagal tone in healthy subjects.

Noninvasive assessment of the cardiac baroreflex: response to downward tilting and comparison with the phenylephrine method

OBJECTIVES

We studied the relation between changes in systolic blood pressure and RR interval during downward tilting in comparison with assessment of baroreflex sensitivity (BRS) measured by the phenylephrine method (Phe-BRS) and with measures of heart rate variability (HRV).

BACKGROUND

The method most extensively used for assessing BRS involves bolus injections of phenylephrine. Several noninvasive methods proposed to assess BRS have not been widely applied in the clinical setting.

METHODS

Sixteen healthy male volunteers were studied (mean age +/- SD 27.5+/-4.6 years). Arterial blood pressure using tonometry and electrocardiogram was simultaneously recorded. After 20 min of 70 degrees upright tilting, the table was returned to supine position at a speed of 3.2 degrees/s. Subsequently, BRS was assessed using an intravenous bolus injection of phenylephrine (2 to 3 microg/kg). Heart rate variability under resting conditions also was analyzed.

RESULTS

In all subjects, a beat to beat systolic blood pressure increase associated with corresponding RR interval lengthening was observed during downward tilting as well as during phenylephrine administration. During both testing procedures, these two variables showed linear correlation, and the slope of regression line during downward tilting (DT-BRS) correlated significantly with Phe-BRS (r = 0.79, p = 0.0003). The DT- and Phe-BRS also correlated significantly with the high frequency component of resting HRV (r = 0.70, p = 0.0023 for DT-BRS; r = 0.58, p = 0.0185 for Phe-BRS).

CONCLUSIONS

We conclude that in a small homogeneous group DT-BRS provided an assessment of reflex cardiac vagal function comparable to that obtained by the phenylephrine method.

Alteration of heart uncoupling protein-2 mRNA regulated by sympathetic nerve and triiodothyronine during postnatal period in rats

To provide tissue-specific and developmental characteristics of gene expression of rat heart uncoupling protein-2 (UCP2), we investigated developmental alterations of UCPs mRNA expression in the heart and brown adipose tissue (BAT), and examined possible up-regulators of heart UCP2 expression using in vitro studies. Heart UCP2 mRNA expression was low during the early postnatal days followed by a rapid and significant increase in the 2nd postnatal week. Heart UCP3 mRNA remained undetectable until the 2nd postnatal week when the expression reached a small but significant peak. BAT UCP1 mRNA was abundantly expressed in the neonate, but the expression rapidly decreased to the adult level. The studies using cultured cardiomyocytes demonstrated that both 10(-8) M triiodothyronine and 10(-7) M isoproterenol, but not phenylephrine, increased UCP2 mRNA expression. These results indicate that the sympathetic nervous system and/or thyroid hormones may be involved in the up-regulation of heart UCP2 gene expression during postnatal development. The increase in postnatal heart UCP2 may provide a key link between the postnatal energy shift and adaptation of rat pups to their novel environment.

Pericoronal hamartomatous lesions in the opercula of teeth delayed in eruption: an immunohistochemical study of the extracellular matrix

Opercula of teeth delayed in eruption were examined histopathologically and immunohistochemically to determine the possible causes for tooth eruption failure. Specimens were obtained from 58 patients with non-erupted teeth by surgical removal of their gingival opercula. Among the 61 specimens, 31 (50.8%) were diagnosed as pericoronal myxofibrous hyperplasia (PMH), 8 (13.1%) as infantile ameloblastic fibromatosis (IAF), and 19 (31.2%) as odontomas. Histopathologically, PMH is characterized by hyperplasia of odontogenic mesenchymal tissues with a myxoid appearance in which odontogenic epithelial islands and mesenchymal multinucleated giant cells are scattered randomly. Between the mucosal epithelium and the PMH, there is a layer of fibrosis, whose matrix is strongly immunopositive for tenascin. The PMH seems to induce its overlying gingival mucosa to remodel the connective tissue, which obstructs tooth eruption. IAF is usually located adjacent to the PMH and shows an ameloblastic fibroma-like histology with atrophic ameloblastic components and poor encapsulation. The findings suggest that IAF associated with PMH is not a true neoplasm and should be distinguished from ameloblastic fibromas by the name of IAF, and that both lesions are included in the range of hamartomas formed only in the pericoronal tissue of teeth in eruption. We propose to categorize these lesions into a new disease entity of pericoronal hamartomas of odontogenic origin.