Evaluation of the Japanese Metabolic Syndrome Risk Score (JAMRISC): a newly developed questionnaire used as a screening tool for diagnosing metabolic syndrome and insulin resistance in Japan

Objectives

To prevent the onset of lifestyle-related diseases associated with metabolic syndrome (MetS) in Japan, research into the development of a useful screening method is strongly desired. We developed a new screening questionnaire (JAMRISC) utilizing a logistic regression model and evaluated its ability to predict the development of MetS, type 2 diabetes and other lifestyle-related diseases in Japanese populace.

Methods

JAMRISC questionnaire was sent to 1,850 individuals in Rumoi, a small city in Hokkaido. We received a total of 1,054 valid responses. To maximize the target individuals accurately diagnosed with MetS, logistic regression analysis was used to generate a unique metabolic syndrome score calculation formula as taking into consideration the clinical relevance of each question item as individual coefficients.

Results

The results of our comparative research utilizing both JAMRISC and Finnish Diabetes Risk Score (FINDRISC) questionnaires revealed the usefulness of JAMRISC for its ability to detect risks for MetS, pre-MetS, diabetes, and pre-diabetes. Study of disease risk detection via JAMRISC questionnaire targeting the 4283 residents of Rumoi indicated a high detection rate for pre-MetS (98.8 %), MetS (94.2 %), pre-diabetes (85.1 %) and type 2 diabetes (94.9 %). In addition, JAMRISC was useful not only as a MetS risk score test, but also as a screening tool for diagnosing insulin resistance.

Conclusions

JAMRISC questionnaire is a useful instrument for the detection of early risk of not only MetS and type 2 diabetes but also insulin resistance.

Gastric Invasive Micropapillary Carcinoma with Intestinal Phenotypes Harboring a TP53 R175H Mutation

We report a case of gastric invasive micropapillary carcinoma (IMPC) in an 86-year-old female patient. She was admitted to our hospital with a chief complaint of bloody emesis. Upper gastrointestinal endoscopy found a gastric adenocarcinoma at the antrum. The biopsy specimens showed moderately differentiated adenocarcinoma with invasive small tumor nests. Distal gastrectomy with systematic lymph node dissection demonstrated that the tumor had IMPC through a pathological examination. Despite the depth of tumor invasion (the submucosa), extensive lymph node metastases were observed. Anti-D2-40 immunostaining revealed numerous infiltrating tumor cell nests in the lymphatic vessels, which could explain subsequent multiple lymph node metastases. The adenocarcinoma showed intestinal phenotypes by several immunohistochemical studies. One of these antibodies (CD10) clearly demonstrated the inverted apical-basal (inside-out) pattern of IMPC, whereas it showed an ordinary pattern in intestinal metaplasia adjacent to the tumor. Furthermore, genetic analysis by direct sequencing revealed a point mutation in the exon 5 of TP53 in the tumor. The mutation presumably harbors a missense mutation from Arg to His at the codon 175 (R175H). R175H has been previously described as a ‘gain-of-function’ mutation with a high invasive or metastatic potential in several types of cancers. In summary, this is one of the first reported cases of gastric IMPC with intestinal phenotypes harboring a TP53 R175H mutation in the literature.

Monocyte chemoattractant protein-1 is associated with silent cerebral infarction in patients on haemodialysis

BACKGROUND

In patients with chronic renal failure undergoing haemodialysis (HD), silent cerebral infarctions (SCI) are associated with high mortality. Levels of monocyte chemoattractant protein-1 (MCP-1) increase with renal dysfunction and may be a novel predictor for cerebrovascular events. We tested the hypothesis that increased MCP-1 concentration correlate with the occurrence of SCI in HD patients.

METHODS

Using cranial magnetic resonance imaging (MRI) findings, 52 Japanese patients undergoing HD were divided into two groups: with SCI (61 ± 7 years, mean ± SD, n= 28) and without SCI (60 ± 6 years, n= 24). The gender, metabolic profiles and MCP-1 concentration were compared between the two groups.

RESULTS

The level of MCP-1 was higher in the with-SCI group than in the without-SCI group (P < 0.0001). The proportion of smokers was higher in the with-SCI group (P < 0.05) than in the without-SCI group. Plasma level of high-density lipoprotein cholesterol was lower, while uric acid level was higher, in the with-SCI group (P < 0.05 and P < 0.05 respectively) compared to the without-SCI group. Multiple logistic regression analysis identified MCP-1 level as being significantly associated with the presence of SCI (odds ratio 1.48, 95% confidence interval = 1.10-5.75, P < 0.0001).

CONCLUSIONS

This study indicates that patients with chronic renal failure who are maintained on HD exhibit an increased prevalence of SCI, and that MCP-1 is significantly associated with the presence of SCI in HD patients.

Interleukin-6 and silent cerebral infarction in hemodialysis patients: a cross-sectional study

BACKGROUND

In patients with chronic renal failure undergoing hemodialysis (HD), silent cerebral infarctions (SCI) are associated with high mortality. Levels of interleukin-6 (IL-6) increase with renal dysfunction and may be a novel predictor for cerebrovascular events. We tested the hypothesis that increased IL-6 levels correlate with the occurrence of SCI in HD patients.

METHODS

Using cranial magnetic resonance imaging findings, we divided 50 Japanese patients undergoing HD into two groups: with SCI (60 ± 7 years, mean ± SD, n = 27) and without SCI (60 ± 6 years, n = 23). We compared the gender, body mass index, metabolic profiles, IL-6 levels, and smoking habits between the two groups.

RESULTS

We made the following observations: (i) The prevalence of diabetes or hypertension did not differ between the two groups, (ii) the level of IL-6 was higher in the with-SCI group than in the without-SCI group (P < 0.0001), (iii) the proportion of smokers was higher in the with-SCI group (P < 0.05), (iv) plasma level of high-density lipoprotein cholesterol was lower, whilst uric acid level was higher, in the with-SCI group (P < 0.05 and P < 0.05, respectively), and (v) multiple logistic regression analysis identified IL-6 levels as being significantly associated with the presence of SCI (odds ratio 3.13, 95% CI = 1.42-7.89, P < 0.0001).

CONCLUSIONS

This study indicates that patients with chronic renal failure who are maintained on HD exhibit an increased prevalence of SCI and that IL-6 is significantly associated with the presence of SCI in HD patients.

Induction of heat shock proteins prevents the arrhythmogenic substrate for atrial fibrillation

Atrial fibrillation (AF) is the commonest arrhythmia. Studies have shown that atrial tachypacing (artificial persistent AF) causes electrical remodelling. This is characterised by the shortening of the atrial effective refractory period (ERP), in which reduction in L-type Ca(2+) channel current plays an essential part. Atrial fibrosis, a feature of structural remodelling, is induced by continuous infusion of angiotensin II, and has been associated with conduction delay in atria, which promotes AF. Acute atrial ischaemia, frequently observed during development of acute coronary syndrome, has been associated with atrial conduction heterogeneity, which also promotes AF. Induction of heat shock proteins (Hsp72 and Hsp27) by hyperthermia and/or geranylgeranylacetone has demonstrated to protect the heart against such atrial remodelling. The potent protective role of Hsp72 and Hsp27 against clinical AF in patients who underwent open heart surgery has been shown. Taken together, interventions that induce heat shock responses (including induction of Hsp72 and Hsp27) may prevent newly developed AF and delay the progression of paroxysmal AF to persistent AF.

Visceral fat accumulation is a significant risk factor for white matter lesions in Japanese type 2 diabetic patients

BACKGROUND

The presence of white matter lesions (WML) is an important prognostic factor for the development of stroke. The elevated visceral fat accumulation (VFA) has been reported to be closely related to the development of atherosclerosis. This preliminary study was therefore designed to test the hypothesis that the presence of WML correlates with VFA and insulin resistance in type 2 diabetic patients not receiving insulin treatment.

MATERIAL AND METHODS

Based on brain magnetic resonance imaging (MRI), 95 type 2 diabetic patients were divided into two groups: WML-positive group (aged 59 +/- 7 years, mean +/- SD n = 37) and WML-negative group (aged 58 +/- 5, years, n = 58). The level of blood glucose was assessed by fasting plasma glucose (FPG), fasting immunoreactive insulin, homeostasis model assessment (HOMA) index, and haemoglobin A1c. The fat distribution was evaluated by measuring the visceral fat accumulation by abdominal computerized tomography at the umbilical level.

RESULTS

The body mass index was higher in the WML-positive group than in the WML-negative group (P < 0.005). Plasma levels of triglycerides were higher while high-density lipoprotein cholesterol was lower in the WML-positive group than in the WML-negative group (P < 0.05 and P < 0.01, respectively). FPG (P < 0.01), insulin concentrations (P < 0.0001), HOMA index (P < 0.0001) and VFA (<0.0001) levels were higher in the WML-positive group than in the WML-negative group. Multivariate logistic analysis revealed that WML was independently predicted by the high VFA and insulin resistance (P < 0.001, P < 0.0001, respectively).

CONCLUSIONS

The results of this preliminary study indicate that the presence of WML was associated with the high VFA and insulin resistance in Japanese patients with type 2 diabetes mellitus. Further larger cohort studies are warranted to confirm these findings.

New squatting test indices are useful for assessing baroreflex sensitivity in diabetes mellitus

AIMS

The heart rate (HR) responses after performance of the squatting and standing manoeuvre are thought to be a useful tool to assess autonomic neuropathy in diabetics. Our aim was to develop new simple squatting test indices and to analyse their applicability to the assessment of baroreflex sensitivity (BRS) in patients with diabetes.

METHODS

Twenty healthy volunteers (mean age 23.2 +/- 3.8 years) and 51 patients with diabetes (mean age 55.9 +/- 10.6 years) were enrolled in study 1 and study 2, respectively. Each subject stood for 3 min (basal period), then squatted down for 1 min (Sq) and stood up again for 1 min (St). In study 1, the squatting test was performed before and after pharmacological autonomic blockade. In study 2, we measured HR in each period and calculated the difference between basal HR and HRSq (DeltaHRSq) and between HRSt and HRSq (DeltaHRSt). BRS was also measured using the phenylephrine method in diabetic patients.

RESULTS

In healthy individuals during autonomic blockade, HR changes were mainly controlled by the vagal tone during squatting and by the sympathetic tone during standing. In diabetic patients, DeltaHRSq and DeltaHRSt positively correlated (r = 0.86, P < 0.0001) and both DeltaHRSq and DeltaHRSt significantly correlated with BRS (r = 0.66, P < 0.0001 and r = 0.61, P < 0.0001, respectively).

CONCLUSIONS

The new squatting test indices provide useful information for assessing autonomic neuropathy and for identifying diabetic patients at high risk of cardiovascular events.

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.

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.

Potential Candidates for Cardiac Resynchronization Therapy in Japanese Patients With Idiopathic Dilated Cardiomyopathy-A Niigata Multicenter Study of DCM-

BACKGROUND

The purpose of this study was to assess the candidates suitable for cardiac resynchronization therapy (CRT) and to examine the significance of the QRS duration in Japanese patients with idiopathic dilated cardiomyopathy (DCM).

METHODS AND RESULTS

The study population consisted of 357 patients. The selection criteria for candidates suitable for CRT were QRS duration =130 ms, left ventricular ejection fraction (LVEF) =35% and New York Heart Association (NYHA) functional class III or IV by ACC/AHA/NASPE 2002 guidelines. We divided the study population into 2 groups: group A with a QRS duration <130 ms, and group B with a QRS duration =130 ms. In 25 of the 375 patients (7.0%), all the criteria were fulfilled. Group B had a significantly larger left ventricular diameter end-diastole and end-systole than group A (P<0.0001). Group B had a lower LVEF (P<0.0001). There was a fair inverse correlation (r=-0.58, P<0.0001) between the length of the QRS duration and LVEF.

CONCLUSION

Approximately 7% of the Japanese patients with DCM are CRT candidates. In the present study, we found that prolonged QRS duration was associated with poor systolic function.

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.

[Respiratory function tests--current and future perspective]

The apparatus for the respiratory function test have recently made a great progress and become very easy to handle owing to the development of computer technology and medical ordering system. However, the respiratory function tests depend its result on the cooperation of patients. Thus, it is important for the medical technician to obtain the maximum efforts and cooperation of the patients in the testing. In the sense, the standardization of the testing should be done urgently regarding procedures, softwares, hardwares and maintenance of apparatus. In the future perspectives, we would like to emphasize following 3 points. First, more noninvasive and sophisticated testing methods and instruments should be developed, since the patients' age will become more and more old and vigorous active cooperation may not be possible for the assessment of respiratory function. The testing for the transplantation of lung should also be developed. Second, the development of screening test and its performance for the routine medical check for the local inhabitants have been important for the early detection, treatment, and follow up of respiratory diseases. Finally, the medical technician should be prepared so that the testing is available when it is needed.

[Clinical characterization of blaIMP positive gram-negative rods isolated cases]

We detected the metallo-beta-lactamase gene blaIMP positive strains of the gram-negative rods (GNR) isolated in Oita Medical University Hospital between 1993 and 1999 and studied the clinical characteristics of patients infected or colonized with blaIMP positive GNR. 25 strains (20 Pseudomonas aeruginosa and 5 Serratia marcescens) were detected and most of them were isolated from urinary samples after 1997. In the studies of antimicrobial susceptibility, some strains had sensitivity to aztreonum or imipenem although most of the strains showed multidrug resistance. When blaIMP positive GNR were isolated from patients, these strains were thought to have caused infection in 88% of the patients. About half of the patients were over 65 years old and had malignant diseases. Most of the patients had inserted urinary tract catheters, intratracheal tube or intravernous catheters. It was suggested that the insertion of the catheters were related to infection of blaIMP positive GNRs. Two patients were not treated with any antibiotics before the isolation of blaIMP positive GNRs although more than half of the patients were administered carbapenems and cephems. Most of strains were isolated in the same department and showed the same genotype by pulsed field gel electrophoresis.

The effect of propafenone on premature ventricular contractions (PVC): an analysis based on heart rate dependency of PVCs

The effect of 450 mg/day propafenone for two weeks on premature ventricular contractions (PVCs) was studied in combination with an assessment of heart rate (HR) dependency of PVCs using Holter ECG monitoring in patients with more than 720 PVCs per day. The PVC-HR correlation was classified into positive (P), bidirectional (B), and flat and negative (FN) correlation groups. The positive group included only patients in whom PVC frequency increased with a heart rate increase, while the bidirectional group included patients with PVCs whose frequency increased at low heart rates and decreased at high heart rates. The FN group contained both flat (PVC frequency was almost fixed regardless of heart rate changes) and negative (PVC frequency decreased as heart rate increased) correlations. The effectiveness of propafenone was 70% in the positive group and 50% in the nonpositive group which included both bidirectional (67%) and FN (0%) groups, using a > 70% PVC reduction as a criterion of efficacy. From this, we concluded that propafenone is effective in patients showing either positive or bidirectional PVC-HR correlation. The coupling interval (CI) of PVCs was also prolonged by propafenone as a whole. The present study suggests that there are differences in the mechanism of PVC development in patients with flat or negative correlation and those with a positive or bidirectional correlation. Thus, this type of analysis contributes to an understanding of the action of antiarrhythmic agents, and may allow the prediction of their efficacy on PVCs.

[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.

Single oral dose of geranylgeranylacetone induces heat-shock protein 72 and renders protection against ischemia/reperfusion injury in rat heart

BACKGROUND

Induction of heat-shock proteins (HSPs) results in cardioprotection against ischemic insult. Geranylgeranylacetone (GGA), known as an antiulcer agent, reportedly induces HSP72 in the gastric mucosa and small intestine of rats. The present study tested the hypothesis that oral GGA would induce HSP72 in the heart and thus render cardioprotection against ischemia/reperfusion injury in rats.

METHODS AND RESULTS

Cardiac expression of HSPs was quantitatively evaluated in rats by Western blot analysis. Ten minutes of whole-body hyperthermia induced HSP72 expression in the rat hearts. A single oral dose of GGA (200 mg/kg) also induced expression of HSP72, which peaked at 24 hours after administration. Therefore, isolated perfused heart experiments using a Langendorff apparatus were performed 24 hours after administration of 200 mg/kg GGA (GGA group) or vehicle (control group). After a 5-minute stabilization period, no-flow global ischemia was given for 20, 40, or 60 minutes, followed by 30 minutes of reperfusion. During reperfusion, the functional recovery was greater and the released creatine kinase was less in the GGA group than in the control group. Electron microscopy findings revealed that the ischemia/reperfusion-induced damage of myocardial cells was prevented in GGA-treated myocytes.

CONCLUSIONS

The results suggest that oral GGA is cardioprotective against ischemic insult through its induction of HSP72.

Effect of essential hypertension on cardiac autonomic function in type 2 diabetic patients

OBJECTIVES

The aim of this study was to examine the effects of essential hypertension on cardiac autonomic function in type 2 diabetic patients.

BACKGROUND

Hypertension is common in type 2 diabetic patients and is associated with a high mortality. However, the combined effects of type 2 diabetes and essential hypertension on cardiac autonomic function have not been fully elucidated.

METHODS

Thirty-three patients with type 2 diabetes were assigned to a hypertensive diabetic group (n = 15; age: 56 +/- 8 years, mean +/- SD) or an age-matched normotensive diabetic group (n = 18, 56 +/- 6 years). Cardiac autonomic function was assessed by baroreflex sensitivity (BRS), heart rate variability (HRV), plasma norepinephrine concentration and cardiac 123I-metaiodobenzylguanidine (MIBG) scintigraphic findings.

RESULTS

Baroreflex sensitivity was lower in the hypertensive diabetic group than it was in the normotensive diabetic group (p < 0.05). The early and delayed myocardial uptake of 123I-MIBG was lower (p < 0.01 and p < 0.05, respectively), and the percent washout rate of 123I-MIBG was higher (p < 0.05) in the hypertensive diabetic group. However, the high frequency (HF) power and the ratio of low frequency (LF) power to HF power (LF/HF) of HRV and plasma norepinephrine concentration were not significantly different. The homeostasis model assessment index was higher in the hypertensive diabetic group than it was in the normotensive diabetic group (p < 0.01).

CONCLUSIONS

Our results indicate that essential hypertension acts synergistically with type 2 diabetes to depress cardiac reflex vagal and sympathetic function, and the results also suggest that insulin resistance may play a pathogenic role in these processes.

[Electrophysiological tests in clinical laboratory]

We briefly described recently developed methods for testing cardiac electrophysiological phenomena such as 24-hour Ambulatory ECG, high resolution ECG, body surface mapping ECG, heart rate variability, QT and QT dispersion, and T wave alternans. Of these methods ambulatory ECG monitoring is important and useful for detecting malignant arrhythmias and ischemia attacks, especially in cases of vasospastic angina. Using this method, it is possible to quantitatively analyze arrhythmia and elucidate the pathophysiology of vasospastic angina. The monitoring system is useful not only for diagnosis, but also for assessing treatment efficacy. Heart rate variability is currently used for analyzing the autonomic nervous system; however, the exact meaning of each index still remains to be confirmed. The concept of QT dispersion was recently introduced as an index for detecting dispersion of ventricular repolarization and QT dispersion is still controversial. T wave alternans monitoring has been recently introduced as a new method of assessing the microvolt level of T wave alternans, which has been hypothesized to correlate with the occurrence of arrhythmic events in myocardial infarction. The possible roles of these methods and their applications for clinical practice are discussed.

[An approach for the quality control in clinical microbiology laboratory by antibiotic susceptibility]

It is important to develop a system for the prevention of various errors and the maintenance of the high quality level in the department of laboratory medicine. We developed a computer program to infer the species of microorganisms by assessing the minimal inhibitory concentration of respective microorganisms to various antibiotics, antibiotic susceptibility patterns(ASP). Retrospective analysis of 3,405 strains from 39 species using this program resulted in a sensitivity of 91.4% and specificity of 98.9%. Furthermore, in 1,660 strains isolated from September 1999 to August 2000, the efficacy of this program was evaluated using both this program and conventional identifying method such as VITEK, api and ATB. The discrepancy between this inferring method and conventional method was noted in 179 strains, revealing errors in 12 strains. We conclude that this ASP inferring program is useful for preventing errors and the maintenance of high quality examination by combining with conventional methods in the laboratory.

Hypoglycemic effect of cibenzoline in patients with abnormal glucose tolerance and frequent ventricular arrhythmias

While some antiarrhythmic agents have potential hypoglycemic effects and indeed some reports of hypoglycemic adverse effect of those drugs, no systematic reports have been issued. We studied the hypoglycemic effects of cibenzoline, a class I antiarrhythmic agent. Cibenzoline succinate (150-300 mg/day) was given orally for 12 weeks to 10 patients who had ventricular premature complexes (VPCs) of >1000 per 24 hours and abnormal glucose tolerance before treatment with cibenzoline. Abnormal glucose tolerance, judged by a 75-g oral glucose tolerance test (OGTT), was defined as the response designated as "diabetic" or "borderline" type according to the criteria specified by the Japan Diabetes Society. In OGTT, the insulinogenic index (defined as the ratio of the increment of IRI [immunoreactive insulin] to that of plasma glucose at 30 minutes after a glucose load) and the sum of IRI (sigma IRI) were also determined. Holter ECG recordings, OGTT, and measurements of fasting plasma glucose IRI, and HbA(1c) were performed before and during cibenzoline treatment. Cibenzoline caused VPC reduction of >70% in 6 of the 10 patients. The drug significantly decreased fasting plasma glucose and HbA(1c) (mean +/- SD) 12 weeks after treatment, from 6.18 +/-0.92 mM/L to 5.54 +/- 1.08 mM/L and from 6.17 +/- 1.03% to 5.83 +/- 0.96%, respectively (P < 0.05). While it significantly increased fasting IRI from 4.99 +/- 1.50 to 6.51 +/- 1.47 microU/mL (P < 0.01), the insulinogenic index from 0.33 +/- 0.26 to 0.65 +/- 0.38 (P < 0.05), and sigma IRI from 168 +/- 67 microU/mL to 199 +/-46 (P < 0.05). Cibenzoline exerted a hypoglycemic effect, facilitating insulin secretion in patients with abnormal glucose tolerance and ventricular arrhythmias.

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.

Suppression of cesium-induced ventricular tachyarrhythmias by atrial natriuretic peptide in rabbits

BACKGROUND

Intravenous injection of cesium chloride (Cs) causes ventricular tachyarrhythmias in rabbits. We investigated whether these tachyarrhythmias were caused by increased pressure load and whether they could be suppressed by atrial natriuretic peptide (ANP).

METHODS AND RESULTS

Cs was injected in a bolus dose (1.5 mmol/kg), which was repeated 20 minutes later. Rabbits were then divided into 3 groups: control, ANP-treated, and hydralazine-treated groups. ANP or hydralazine was administered between the first and second Cs injections. The experiments were performed during intrinsic sinus rhythm (protocol A) or during ventricular pacing (protocol B). In protocol A, the second injection of Cs in the control group induced early afterdepolarizations and ventricular tachycardia, which were preceded by a marked increase in left ventricular end-diastolic pressure (LVEDP). Both ANP and hydralazine significantly suppressed Cs-induced increase in LVEDP. The arrhythmia score after the second injection of Cs was significantly lower in the ANP-treated and hydralazine-treated group compared with the control group (P < .005 and P < .05, respectively). In protocol B, the duration of left ventricular monophasic action potential and early afterdepolarization amplitude before and/or after the injections of Cs did not differ significantly between control and ANP-treated groups.

CONCLUSIONS

Our results suggest that increased pressure load may play a role in the arrhythmogenic effect of Cs. The protective effect of ANP against Cs-induced ventricular tachycardia may be explained in part by a reduction in pressure overload. However, this effect might also be explained by the diverse action of ANP on the cardiovascular system.

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.

Radiofrequency catheter ablation from the left sinus of Valsalva in a patient with idiopathic ventricular tachycardia

We report the case of a 54-year-old woman with idiopathic VT originating in the left ventricular outflow tract. She initially presented with palpitations and light-headedness. The morphology of the PVCs exhibited an inferior axis and tall R waves were noted in all the precordial leads. Spontaneous PVCs were transiently terminated by an intravenous injection of adenosine triphosphate. Radiofrequency catheter ablation from the left sinus of Valsalva successfully abolished the PVCs and the VT.

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.

H2-blocker modulates heart rate variability

The use of H2-blockers in the treatment of patients with peptic ulcer has become popular. However, this treatment has adverse cardiovascular effects. The aim of this study was to investigate proarrhythmic rhythm and autonomic nervous activity by analyzing heart rate variability in patients treated with omeprazole, ranitidine, and plaunotol. Nineteen patients (mean age 67.5 +/- 2.7 years) with active gastric ulcer were treated with omeprazole (20 mg/day) for 8 weeks, then ranitidine (300 mg/day) for the next 4 months, and finally plaunotol (240 mg/day). At each stage of the treatment, Holter electrocardiography was performed, and heart rate variability and arrhythmias analyzed. Heart rate variability yielded power in the low- (0.04-0.15 Hz) and high-frequency components (0.15-0.4 Hz). Although both ranitidine and omeprazole induced little change in cardiac rhythm, the high-frequency power was higher (10.3 +/- 0.8 vs 8.6 +/- 0.6 ms, P < 0.05) and the ratio of low-to-high frequency power was lower (1.41 +/-0.10 vs 1.59 +/- 0.09. P < 0.05) during ranitidine than during plaunotol treatment. Cosinor analysis of heart rate variability revealed a decreased amplitude of low-frequency power during omeprazole compared with during ranitidine and plaunotol treatment. Ranitidine modulated high-frequency power which may be related to the adverse cardiovascular effects of H2-blocker.

Diminished expression of sarcoplasmic reticulum Ca(2+)-ATPase and ryanodine sensitive Ca(2+)Channel mRNA in streptozotocin-induced diabetic rat heart

The diabetic heart has an abnormal intracellular calcium ([Ca(2+)]i) metabolism. However, the responsible molecular mechanisms are unclear. The present study aimed to investigate mRNAs expressed in the proteins which regulate heart [Ca(2+)]i metabolism in streptozotocin (STZ)-induced diabetic rats. Expression of sarcoplasmic reticulum Ca(2+)-adenosine triphosphatase (SR Ca(2+)-ATPase) mRNA was significantly less in the heart 3 weeks after STZ injection than that in the age-matched controls. Together with the down-regulation of SR Ca(2+)-ATPase, expression of ryanodine sensitive Ca(2+)channel (RYR) mRNA was also decreased 12 weeks after STZ injection. Insulin supplementation fully restored the decreased mRNAs expression of SR Ca(2+)-ATPase and RYR. The diminished expression and restoration with insulin supplementation of SR Ca(2+)-ATPase was further confirmed at the protein level. In contrast, expression of mRNAs coding the L-type Ca(2+)channel, Na(+)-Ca(2+)exchanger, or phospholamban were not affected 3 or 12 weeks after STZ injection. These results can be taken to indicate that the down-regulation of SR Ca(2+)-ATPase and RYR mRNAs is a possible underlying cause of cardiac dysfunction in STZ-induced diabetic rats.

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.

Beneficial effects of long-term treatment with enalapril on cardiac function and heart rate variability in patients with old myocardial infarction

BACKGROUND

The beneficial effects of the early use of angiotensin-converting enzyme inhibitors (ACEis) in patients with acute myocardial infarction (MI) are well documented. However, the effects of ACEis in patients with an old MI and preserved cardiac function have not yet been studied. We examined the effects of 12 months of enalapril treatment in patients with previous MI.

METHODS AND RESULTS

Thirteen patients with an old MI and no overt congestive heart failure (CHF), aged 70 +/- 2 years, were treated with enalapril for 12 months. We also included 13 age- and sex-matched control patients who had a similar clinical background but were not treated with enalapril. Holter electrocardiography and echocardiography were performed at entry and after 12 months of treatment. Heart rate variability, low- and high-frequency powers (LF and HF), and the ratio between LF and HF (LF/HF) were analyzed. Changes from baseline to 12 months in HF, LF/HF, left ventricular end-diastolic dimension (LVEDD), and end-systolic dimension (LVESD) were significantly different in the enalapril group (HF, 8.1 +/- 0.9 to 9.3 +/- 0.9 milliseconds: LF/HF, 1.65 +/- 0.11 to 1.53 +/- 0.16; LVEDD, 57.2 +/- 1.6 to 54.7 +/- 1.6 mm; LVESD, 40.0 +/- 2.4 to 36.3 +/- 1.9 mm) compared with the control group (HF, 8.9 +/- 0.9 to 8.5 +/- 0.7 milliseconds; LF/HF, 1.78 +/- 0.18 to 1.88 +/- 0.15; LVEDD, 52.3 +/- 2.5 to 55.9 +/- 2.2 mm; LVESD, 32.5 +/- 2.6 to 36.1 +/- 2.6 mm; P < .05). The delta change (delta) in LVESD between the end and the start of study correlated inversely with deltaHF (r = -0.56; P < .05) and positively with deltaLF/HF (r = 0.65; P < .01).

CONCLUSION

Our results suggest possible ongoing structural changes in patients with old MI even in the absence of overt CHF. Enalapril seemed to prevent such changes and to restore cardiac autonomic tone toward normal. Further prospective studies using a larger sample size are warranted to confirm potential beneficial effects of ACEis in patients with previous MI and preserved left ventricular function.

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.

QT interval and QT dispersion before and after diet therapy in patients with simple obesity

To evaluate whether a disordered QT interval and its dispersion in obese patients, if any, may be improved by therapeutic weight reduction, 36 obese patients admitted to our university hospital were examined over a 5-year period from April 1, 1992 to March 31, 1997. Participants included 18 males and 18 females whose mean age +/- SD was 28 +/- 9 and 33 +/- 14 years, respectively, and whose mean body mass index +/- SD was 35 +/- 5 and 38 +/- 6 kg/m2, respectively. Thirty-six control patients were matched in age and gender with the obese patients. All the obese patients were treated with behavioral therapy together with very-low-calorie conventional Japanese diet (VLCD: 370 kcal/day). A standard 12-lead electrocardiogram (ECG) revealed longer maximum (445 +/- 32 msec, mean +/- SD) and minimum (388 +/- 29 msec) heart rate corrected QT intervals (QTc intervals) in the obese group than in the control group (P < 0.0001 for each). QTc dispersion, defined as the difference between maximum and minimum QTc intervals derived from 12-lead ECG, was greater in the obese group (57 +/- 19 msec) than in the control group (32 +/- 13 msec) (P < 0.0001). Both the maximum and minimum QTc intervals in the obese patients were shortened, respectively, to 434 +/- 28 msec and 377 +/- 29 msec (P < 0.05 for each) with no significant change in either QTc dispersion, QRS voltage, or QRS duration following weight reduction. The coefficient value from the linear regression line between QT interval and RR interval in the obese group was less than in the control group. Together, the results show that obesity per se causes both a prolongation of QTc interval and an increase in QTc dispersion, and that weight reduction improves the prolonged QTc interval observed in obese patients.

QT interval and QT dispersion before and after diet therapy in patients with simple obesity

To evaluate whether a disordered QT interval and its dispersion in obese patients, if any, may be improved by therapeutic weight reduction, 36 obese patients admitted to our university hospital were examined over a 5-year period from April 1, 1992 to March 31, 1997. Participants included 18 males and 18 females whose mean age +/- SD was 28 +/- 9 and 33 +/- 14 years, respectively, and whose mean body mass index +/- SD was 35 +/- 5 and 38 +/- 6 kg/m2, respectively. Thirty-six control patients were matched in age and gender with the obese patients. All the obese patients were treated with behavioral therapy together with very-low-calorie conventional Japanese diet (VLCD: 370 kcal/day). A standard 12-lead electrocardiogram (ECG) revealed longer maximum (445 +/- 32 msec, mean +/- SD) and minimum (388 +/- 29 msec) heart rate corrected QT intervals (QTc intervals) in the obese group than in the control group (P < 0.0001 for each). QTc dispersion, defined as the difference between maximum and minimum QTc intervals derived from 12-lead ECG, was greater in the obese group (57 +/- 19 msec) than in the control group (32 +/- 13 msec) (P < 0.0001). Both the maximum and minimum QTc intervals in the obese patients were shortened, respectively, to 434 +/- 28 msec and 377 +/- 29 msec (P < 0.05 for each) with no significant change in either QTc dispersion, QRS voltage, or QRS duration following weight reduction. The coefficient value from the linear regression line between QT interval and RR interval in the obese group was less than in the control group. Together, the results show that obesity per se causes both a prolongation of QTc interval and an increase in QTc dispersion, and that weight reduction improves the prolonged QTc interval observed in obese patients.

Inhibition of Na(+)-K+ pump alleviates the shortening of action potential duration caused by metabolic inhibition via blockade of KATP channels in coronary perfused ventricular muscles of guinea-pigs

The Na(+)-K+ pump is a consumer of intracellular ATP. We therefore examined whether blockade of the Na(+)-K+ pump by cardiac glycosides could inhibit ATP-sensitive K+ (KATP) channels and prolong the action potential duration (APD) of the guinea-pig ventricular muscles perfused with Tyrode's solution via the coronary artery and stimulated at 3 Hz. The metabolic inhibition (MI) achieved by application of 0.1 microM carbonyl cyanide p-(trifluoromethoxy) phenylhydrazone (a mitochondrial uncoupler) shortened the APD in a time-dependent manner. When dihydroouabain (DHO, 5 microM) was introduced 5 min but not 10 min after introduction of MI, the APD shortening was significantly attenuated. Application of glibenclamide (1 microM), a blocker of KATP channels, introduced both 5 and 10 min after MI also alleviated the APD shortening: DHO did not alleviate the APD shortening effect produced by cromakalim (5 microM), a KATP-channel opener. In separate experiments using whole-cell patch-clamp techniques, we found that this concentration of DHO (5 microM) depressed the Na(+)-K+ pump current of the guinea-pig ventricular myocytes from 210 to 100 pA (at 0 mV) or by 49.5%. We conclude that, during early phase (approximately 5 min) of MI, the APD shortening mostly results from the activation of KATP channels, and that even a approximately 50% inhibition of the Na(+)-K+ pump by DHO leads to the blockade of KATP channels and eventual lengthening of the APD.

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.

The I/D polymorphism of angiotensin-converting enzyme gene but not the angiotensinogen gene is associated with insulin response to oral glucose in Japanese

Polymorphisms of angiotensin-converting enzyme (ACE) and angiotensinogen (AGT) genes have been reported to be associated with myocardial infarction and coronary artery disease, both of which are closely related to atherosclerosis and insulin resistance. In this study, we investigated the association between ACE and AGT genotypes and insulin sensitivity in a sample of 142 nondiabetic and 64 noninsulin-dependent diabetes mellitus (NIDDM) Japanese subjects, aged 62.7 +/- 9.5 years. The insulin response to the 75-g oral glucose tolerance test (OGTT) was significantly lower in subjects with the ACE D/D genotype compared to those with the I allele (I/D and I/I genotypes) in both nondiabetic (P < 0.05) and NIDDM subjects (P < 0.005). These homozygous D/D subjects also had lower insulin area under the curve of plasma insulin concentrations during OGTT compared to those with the I allele in nondiabetic (P < 0.05) and NIDDM subjects (P < 0.01). However, there was no significant association between AGT genotypes and either insulin response or insulin area under the curve during OGTT, in either nondiabetic or NIDDM subjects. From a viewpoint that insulin response to oral glucose is significantly correlated with insulin sensitivity, these results suggest that polymorphic variations at the ACE gene, but not the AGT gene, may be involved in the genetic regulation of insulin sensitivity in both nondiabetic and NIDDM Japanese subjects.