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ABSTRACT: BACKGROUND: Atrial fibrillation (AF) increases the risks of stroke and death, and the prevalence of AF is increasing significantly. Until recently, warfarin was the only oral anticoagulant for stroke prevention, but novel anticoagulants are now under development. METHODS AND RESULTS: The Fushimi AF Registry is a community-based survey of AF patients. We aimed to enroll all of the AF patients in Fushimi-ku, which is located at the southern end of the city of Kyoto. Fushimi-ku is densely populated with a total population of 283,000, and is assumed to represent a typical urban community in Japan. On the basis of the general prevalence of AF in the Japanese (0.6%), we estimated the total number of AF patients as 1700. A total of 76 institutions, a large proportion of which were private clinics, participated in the study. At present, we have enrolled 3183 patients from March 2011 to June 2012 (approximately 1.12% of total population). The mean age was 74.2±11.0 years, and 59.3% of subjects were male. The mean body weight was 58.5±13.2kg, and the proportions with a body weight of less than 50kg and 60kg were 25.7% and 55.0%, respectively. The type of AF was paroxysmal in 46.0%, persistent in 7.3%, and permanent in 46.7%. Major co-existing diseases were hypertension (60.6%), heart failure (27.9%), diabetes (23.2%), stroke (19.4%), coronary artery disease (15.0%), myocardial infarction (6.4%), dyslipidemia (42.4%), and chronic kidney disease (26.4%). The mean CHADS2 score was 2.09±1.35: 0 in 11.8% of patients, 1 in 27.1%, and 2 in 29.1%. Warfarin was prescribed in only 48.5% of patients, whereas anti-platelet drugs, mainly aspirin, were prescribed for more than 30% of the patients. CONCLUSIONS: The Fushimi AF Registry provides a unique snapshot of current AF management in an urban community in Japan.
Journal of Cardiology 02/2013; · 1.28 Impact Factor
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Hiromichi Wada,
Shuichi Ura,
Noriko Satoh-Asahara,
Shuji Kitaoka,
Shinichi Mashiba, Masaharu Akao,
Mitsuru Abe,
Koh Ono,
Tatsuya Morimoto,
Masatoshi Fujita,
Akira Shimatsu,
Yuko Takahashi,
Koji Hasegawa
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ABSTRACT: While smoking cessation (SC) leads to a reduction of cardiovascular events, atherogenic biomarkers specifically connected with cigarette smoking and SC are unknown. Circulating levels of oxidatively modified low-density-lipoprotein (LDL) are associated with a high risk of cardiovascular diseases. Recently, two novel, oxidatively modified LDL markers, serum amyloid A-LDL (SAA-LDL) and α1-antitrypsin-LDL (AT-LDL), were identified; however, the significance of SAA-LDL and AT-LDL as cardiovascular risk markers is unknown.
We carried out a cross-sectional study involving 243 patients, and determined serum levels of SAA-LDL and AT-LDL.
Both serum levels of SAA-LDL and AT-LDL were significantly increased in current compared to non-current smokers. Stepwise regression analysis revealed that the current smoking status and duration of smoking were strong independent determinants of the AT-LDL level. In contrast, high-sensitivity C-reactive protein was the strongest determinant of the SAA-LDL level. In multiple logistic regression analysis, the current smoking status was most closely associated with the AT-LDL level. Successful SC employing a 12-week program significantly increased the body mass index and serum levels of obesity-related markers. Notably, successful SC significantly decreased levels of AT-LDL, but not those of SAA-LDL.
The present study provides the first evidence for the distinct characteristics of two novel, oxidatively modified LDL markers, SAA-LDL and AT-LDL. In contrast to SAA-LDL, an inflammatory marker, AT-LDL serves as a marker of smoking-specific oxidative stress. These findings warrant further investigations to clarify if AT-LDL provides a key link between smoking and cardiovascular diseases.
Journal of atherosclerosis and thrombosis 01/2012; 19(1):47-58. · 2.69 Impact Factor
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Tetsuhisa Hattori,
Takeru Makiyama, Masaharu Akao,
Eiji Ehara,
Seiko Ohno,
Moritake Iguchi,
Yukiko Nishio,
Kenichi Sasaki,
Hideki Itoh,
Masayuki Yokode,
Toru Kita,
Minoru Horie,
Takeshi Kimura
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ABSTRACT: Short-QT syndrome (SQTS) is a recently recognized disorder associated with atrial fibrillation (AF) and sudden death due to ventricular arrhythmias. Mutations in several ion channel genes have been linked to SQTS; however, the mechanism remains unclear. This study describes a novel heterozygous gain-of-function mutation in the inward rectifier potassium channel gene, KCNJ2, identified in SQTS.
We studied an 8-year-old girl with a markedly short-QT interval (QT = 172 ms, QTc = 194 ms) who suffered from paroxysmal AF. Mutational analysis identified a novel heterozygous KCNJ2 mutation, M301K. Functional assays displayed no Kir2.1 currents when M301K channels were expressed alone. However, co-expression of wild-type (WT) with M301K resulted in larger outward currents than the WT at more than -30 mV. These results suggest a gain-of-function type modulation due to decreased inward rectification. Furthermore, we analysed the functional significance of the amino acid charge at M301 (neutral) by changing the residue. As with M301K, in M301R (positive), the homozygous channels were non-functional, whereas the heterozygous channels demonstrated decreased inward rectification. Meanwhile, the currents recorded in M301A (neutral) showed normal inward rectification under both homo- and heterozygous conditions. Heterozygous overexpression of WT and M301K in neonatal rat ventricular myocytes exhibited markedly shorter action potential durations than the WT alone.
In this study, we identified a novel KCNJ2 gain-of-function mutation, M301K, associated with SQTS. Functional assays revealed no functional currents in the homozygous channels, whereas impaired inward rectification demonstrated under the heterozygous condition resulted in larger outward currents, which is a novel mechanism predisposing SQTS.
Cardiovascular research 12/2011; 93(4):666-73. · 5.80 Impact Factor
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ABSTRACT: KCNQ1 gene encodes the delayed rectifier K(+) channel in cardiac muscle, and its mutations cause long QT syndrome type 1 (LQT1). Especially exercise-related cardiac events predominate in LQT1. We previously reported that a KCNQ1 splicing mutation displays LQT1 phenotypes.
We identified novel mutation at the third base of intron 7 (IVS7 +3A>G) in exercise-induced LQT1 patients. Minigene assay in COS7 cells and RT-PCR analysis of patients' lymphocytes demonstrated the presence of exon 7-deficient mRNA in IVS7 +3A>G, as well as c.1032G>A, but not in c.1022C>T. Real-time RT-PCR demonstrated that both IVS7 +3A>G and c.1032G>A carrier expressed significant amounts of exon-skipping mRNAs (18.8% and 44.8% of total KCNQ1 mRNA). Current recordings from Xenopus oocytes injected cRNA by simulating its ratios of exon skipping displayed a significant reduction in currents to 64.8 ± 4.5% for IVS7 +3A>G and to 41.4 ± 9.5% for c.1032G>A carrier, respectively, compared to the condition without splicing error. Computer simulation incorporating these quantitative results revealed the pronounced QT prolongation under beta-adrenergic stimulation in IVS7 +3A>G carrier model.
Here we report a novel splicing mutation IVS7 +3A>G, identified in a family with mild form LQT1 phenotypes, and examined functional outcome in comparison with three other variants around the exon 7-intron 7 junction. In addition to c.1032G>A mutation, IVS7 +3A>G generates exon-skipping mRNAs, and thereby causing LQT1 phenotype. The severity of clinical phenotypes appeared to differ between the two splicing-related mutations and to result from the amount of resultant mRNAs and their functional consequences.
Biochimica et Biophysica Acta 07/2011; 1812(11):1452-9. · 4.66 Impact Factor
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Masahiro Natsuaki,
Yutaka Furukawa,
Takeshi Morimoto,
Yoshihisa Nakagawa, Masaharu Akao,
Koh Ono,
Tetsuo Shioi,
Satoshi Shizuta,
Ryuzo Sakata,
Hitoshi Okabayashi,
Noboru Nishiwaki,
Tatsuhiko Komiya,
Satoru Suwa,
Takeshi Kimura
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ABSTRACT: Among hemodialysis (HD) patients, those who have diabetes have poorer cardiovascular outcomes than non-diabetic patients, but the impact of diabetes on cardiovascular outcomes has not been fully elucidated in HD patients undergoing coronary revascularization.
We identified 375 HD patients (203 diabetes, 172 non-diabetes) and 9,006 patients without HD (3,455 diabetes, 5,551 non-diabetes) in the database of the CREDO-Kyoto registry of patients undergoing their first coronary revascularization. In non-HD patients, significantly higher risks of death (10.8% vs. 7.7%, P < 0.0001; adjusted hazard ratio (HR) 1.29, P < 0.0001) and major adverse cardiovascular events (MACE), a composite of death, myocardial infarction and stroke (18.8% vs. 13.3%, P < 0.0001; HR 1.36, P < 0.0001) were seen in diabetic patients than in non-diabetic patients through 4-year follow-up. Analysis in HD patients showed that the duration of HD before first coronary revascularization was significantly shorter in diabetic patients than in non-diabetic patients (median interval: 858 vs. 2,216 days, P < 0.0001). In contrast to the results in non-HD patients, the risks of death (41.9% vs. 39.1%, P=0.75; HR 0.98, P=0.93) and MACE (45.6% vs. 45.8%, P=0.83; HR 0.87, P=0.50) after first revascularization were comparable between diabetic and non-diabetic HD patients. There were significant interactions between HD and diabetes for death and for MACE.
HD patients who require coronary revascularization have extremely poor outcomes irrespective of concomitant diabetes.
Circulation Journal 06/2011; 75(7):1616-25. · 3.77 Impact Factor
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ABSTRACT: Mutations in KCNJ2, a gene encoding the inward rectifier K(+) channel Kir2.1, are associated with Andersen-Tawil syndrome (ATS), which is characterized by (1) ventricular tachyarrhythmias associated with QT (QU)-interval prolongation, (2) periodic paralysis, and (3) dysmorphic features.
We identified a novel KCNJ2 mutation, S369X, in a 13-year-old boy with prominent QU-interval prolongation and mild periodic paralysis. The mutation results in the truncation at the middle of the cytoplasmic C-terminal domain that eliminates the endoplasmic reticulum (ER)-to-Golgi export signal. Current recordings from Chinese hamster ovary cells transfected with KCNJ2-S369X exhibited significantly smaller K(+) currents compared with KCNJ2 wild type (WT) (1 μg each) (-84 ± 14 versus -542 ± 46 picoamperes per picofarad [pA/pF]; -140 mV; P<0.0001). Coexpression of the WT and S369X subunits did not show a dominant-negative suppression effect but yielded larger currents than those of WT+S369X (-724 ± 98 pA/pF>-[84+542] pA/pF; 1 μg each; -140 mV). Confocal microscopy analysis showed that the fluorescent protein-tagged S369X subunits were predominantly retained in the ER when expressed alone; however, the expression of S369X subunits to the plasma membrane was partially restored when coexpressed with WT. Fluorescence resonance energy transfer analysis demonstrated direct protein-protein interactions between WT and S369X subunits in the intracellular compartment.
The S369X mutation causes a loss of the ER export motif. However, the trafficking deficiency can be partially rescued by directly assembling with the WT protein, resulting in a limited restoration of plasma membrane localization and channel function. This alleviation may explain why our patient presented with a relatively mild ATS phenotype.
Circulation Cardiovascular Genetics 06/2011; 4(3):253-60. · 6.11 Impact Factor
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Hiroki Shiomi,
Toshihiro Tamura,
Shunichiro Niki,
Tomohisa Tada,
Junichi Tazaki,
Masanao Toma,
Koh Ono,
Tetsuo Shioi,
Takeshi Morimoto, Masaharu Akao,
Yutaka Furukawa,
Yoshihisa Nakagawa,
Takeshi Kimura
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ABSTRACT: The Synergy Between Percutaneous Coronary Intervention With TAXUS and Cardiac Surgery (SYNTAX) score was proposed as a method to evaluate the complexity of coronary anatomy. However, the reproducibility of assessment for the SYNTAX score in unprotected left main coronary artery (ULMCA) disease has not yet been adequately evaluated. The purpose of this study is to assess inter- and intra-observer variability for the assessment of the SYNTAX score in patients undergoing ULMCA stenting in daily clinical practice.
The SYNTAX score of 101 consecutive patients who underwent ULMCA stenting with sirolimus-eluting stent was independently assessed by 2 experienced interventional cardiologists. One of the 2 cardiologists evaluated all the cases again 6 months after the initial assessment. The κ value for inter-observer variability in estimating the SYNTAX score was 0.62 according to the dichotomized analysis (≥ 33, < 33) and 0.58 according to the tertile analysis (< 23, 23 ≤ - < 33, ≥ 33), while the intra-observer variability was 0.78 and 0.69, respectively. Patients with a high SYNTAX score (≥ 33, n = 55) compared with those with low or intermediate score (< 33, n = 46) had a significantly higher rate of target-lesion revascularization (TLR) of the ULMCA lesion at 2 years (24% vs. 4.4%, P = 0.01).
Both inter- and intra-observer variability for estimating the SYNTAX score were within an acceptable range and a high SYNTAX score showed a higher rate of TLR in patients undergoing ULMCA stenting in daily clinical practice.
Circulation Journal 03/2011; 75(5):1130-7. · 3.77 Impact Factor
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ABSTRACT: An opening of the mitochondrial permeability transition pore (MPTP), which leads to loss of mitochondrial membrane potential (ΔΨ(m)), is the earliest event that commits a cell to death. Mitochondrial matrix calcium ([Ca(2+)](m)) is considered to be a critical regulator of MPTP, but direct monitoring of [Ca(2+)](m) is difficult with previously-reported sensors. We developed a novel fluorescent indicator for [Ca(2+)](m), GCaMP2-mt, by adding a mitochondrial targeting sequence to a high signal-to-noise Ca(2+) sensor protein GCaMP2, and monitored dynamic changes in oxidant-induced cardiac myocyte death.
GCaMP2-mt was transduced into neonatal rat cardiac myocytes using a recombinant adenovirus. We confirmed that GCaMP2-mt colocalized with tetramethylrhodamine ethyl-ester, a fluorescent indicator of ΔΨ(m). We monitored oxidant-induced responses of [Ca(2+)](m) and ΔΨ(m) using time-lapse confocal microscopy. The response of [Ca(2+)](m) was synchronous with that of cytosolic calcium and was divided into three kinetically-distinct phases; the first phase, during which [Ca(2+)](m) maintained its baseline level; the second phase, during which [Ca(2+)](m) showed a rapid and sudden increase; and the third phase, during which [Ca(2+)](m) continued to increase at a slower rate until the collapse of ΔΨ(m). The third phase was likely to be mediated through a mitochondrial Ca(2+) uniporter, because it was modulated by uniporter-acting drugs. Importantly, there was a remarkable cellular heterogeneity in the third phase, and ΔΨ(m) loss occurred in an all-or-none manner depending on the cellular [Ca(2+)](m) level with a clear cut-off value.
Direct monitoring of [Ca(2+)](m) using GCaMP2-mt provides deeper insight into the mechanism of cardiac myocyte death.
International journal of cardiology 02/2011; 158(2):225-34. · 7.08 Impact Factor
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Hiromichi Wada,
Shuichi Ura,
Shuji Kitaoka,
Noriko Satoh-Asahara,
Takahiro Horie,
Koh Ono,
Tomohide Takaya,
Rieko Takanabe-Mori, Masaharu Akao,
Mitsuru Abe,
Tatsuya Morimoto,
Toshinori Murayama,
Masayuki Yokode,
Masatoshi Fujita,
Akira Shimatsu,
Koji Hasegawa
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ABSTRACT: The mechanisms that lead from obesity to atherosclerotic disease are not fully understood. Obesity involves angiogenesis in which vascular endothelial growth factor-A (VEGF-A) plays a key role. On the other hand, vascular endothelial growth factor-C (VEGF-C) plays a pivotal role in lymphangiogenesis. Circulating levels of VEGF-A and VEGF-C are elevated in sera from obese subjects. However, relationships of VEGF-C with atherosclerotic risk factors and atherosclerosis are unknown. We determined circulating levels of VEGF-A and VEGF-C in 423 consecutive subjects not receiving any drugs at the Health Evaluation Center. After adjusting for age and gender, VEGF-A levels were significantly and more strongly correlated with the body mass index (BMI) and waist circumference than VEGF-C. Conversely, VEGF-C levels were significantly and more closely correlated with metabolic (e.g., fasting plasma glucose, hemoglobin A1c, immunoreactive insulin, and the homeostasis model assessment of insulin resistance) and lipid parameters (e.g., triglycerides, total cholesterol (TC), low-density-lipoprotein cholesterol (LDL-C), and non-high-density-lipoprotein cholesterol (non-HDL-C)) than VEGF-A. Stepwise regression analyses revealed that independent determinants of VEGF-A were the BMI and age, whereas strong independent determinants of VEGF-C were age, triglycerides, and non-HDL-C. In apolipoprotein E-deficient mice fed a high-fat-diet (HFD) or normal chow (NC) for 16 weeks, levels of VEGF-A were not significantly different between the two groups. However, levels of VEGF-C were significantly higher in HFD mice with advanced atherosclerosis and marked hypercholesterolemia than NC mice. Furthermore, immunohistochemistry revealed that the expression of VEGF-C in atheromatous plaque of the aortic sinus was significantly intensified by feeding HFD compared to NC, while that of VEGF-A was not. In conclusion, these findings demonstrate that VEGF-C, rather than VEGF-A, is closely related to dyslipidemia and atherosclerosis.
PLoS ONE 01/2011; 6(12):e29351. · 4.09 Impact Factor
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ABSTRACT: The rat demyelination (dmy) mutation serves as a unique model system to investigate the maintenance of myelin, because it provokes severe myelin breakdown in the central nervous system (CNS) after normal postnatal completion of myelination. Here, we report the molecular characterization of this mutation and discuss the possible pathomechanisms underlying demyelination. By positional cloning, we found that a G-to-A transition, 177 bp downstream of exon 3 of the Mrs2 (MRS2 magnesium homeostasis factor (Saccharomyces cerevisiae)) gene, generated a novel splice acceptor site which resulted in functional inactivation of the mutant allele. Transgenic rescue with wild-type Mrs2-cDNA validated our findings. Mrs2 encodes an essential component of the major Mg²+ influx system in mitochondria of yeast as well as human cells. We showed that the dmy/dmy rats have major mitochondrial deficits with a markedly elevated lactic acid concentration in the cerebrospinal fluid, a 60% reduction in ATP, and increased numbers of mitochondria in the swollen cytoplasm of oligodendrocytes. MRS2-GFP recombinant BAC transgenic rats showed that MRS2 was dominantly expressed in neurons rather than oligodendrocytes and was ultrastructurally observed in the inner membrane of mitochondria. Our observations led to the conclusion that dmy/dmy rats suffer from a mitochondrial disease and that the maintenance of myelin has a different mechanism from its initial production. They also established that Mg²+ homeostasis in CNS mitochondria is essential for the maintenance of myelin.
PLoS Genetics 01/2011; 7(1):e1001262. · 8.69 Impact Factor
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ABSTRACT: Cigarette smoking is an independent risk factor for cardiovascular events such as myocardial infarction and stroke. To date, a useful and convenient method of predicting such events in smokers has not been established. The rheological properties of blood assessed by the microchannel method reflect the blood's viscosity and the state of microthrombus formation, which may predict cardiovascular thrombotic events.
Blood fluidity was assessed in 74 smoking patients (54 men, 20 women, mean age 57.9 years) by measuring the blood passage time (BPT) in an aliquot (100 µl) of blood using the Micro Channel Array Flow Analyzer. BPT was significantly related with smoking variables such as daily consumption of tobacco (r = 0.236, P = 0.044), Brinkman's index (r = 0.252, P = 0.033), the Fagerstrom Test for Nicotine Dependence (r = 0.257, P = 0.029), and the score of a self-rating depression scale (r = 0.236, P < 0.05). Multivariate regression analysis revealed that an independent BPT determinant was daily consumption of tobacco (r = 0.326, P = 0.045). Furthermore, smoking cessation markedly decreased BPT from 63.0 s to 49.7 s (P = 0.002) at 3 months after the start of therapy.
Unfavorable blood rheology is closely associated with cigarette smoking and may reflect increased cardiovascular risk in smokers. The study results also suggest that such risk can be reduced after only 3 months of smoking cessation.
Circulation Journal 11/2010; 75(1):185-9. · 3.77 Impact Factor
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Hideki Itoh,
Wataru Shimizu,
Kenshi Hayashi,
Kenichiro Yamagata,
Tomoko Sakaguchi,
Seiko Ohno,
Takeru Makiyama, Masaharu Akao,
Tomohiko Ai,
Takashi Noda,
Aya Miyazaki,
Yoshihiro Miyamoto,
Masakazu Yamagishi,
Shiro Kamakura,
Minoru Horie
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ABSTRACT: Long QT syndrome (LQTS) can be caused by mutations in the cardiac ion channels. Compound mutations occur at a frequency of 4% to 11% among genotyped LQTS cases.
The purpose of this study was to determine the clinical characteristics and manner of onset of cardiac events in Japanese patients with LQTS and compound mutations.
Six hundred three genotyped LQTS patients (310 probands and 293 family members) were divided into two groups: those with a single mutation (n = 568) and those with two mutations (n = 35). Clinical phenotypes were compared between the two groups.
Of 310 genotyped probands, 26 (8.4%) had two mutations in the same or different LQTS-related genes (compound mutations). Among the 603 LQTS patients, compound mutation carriers had significantly longer QTc interval (510 ± 56 ms vs 478± 53 ms, P = .001) and younger age at onset of cardiac events (10 ± 8 years vs 18 ± 16 years, P = .043) than did single mutation carriers. The incidence rate of cardiac events before age 40 years and use of beta-blocker therapy among compound mutation carriers also were different than in single mutation carriers. Subgroup analysis showed more cardiac events in LQTS type 1 (LQT1) and type 2 (LQT2) compound mutations compared to single LQT1 and LQT2 mutations.
Compound mutation carriers are associated with a more severe phenotype than single mutation carriers.
Heart rhythm: the official journal of the Heart Rhythm Society 10/2010; 7(10):1411-8. · 4.56 Impact Factor
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Hideki Itoh,
Tomoko Sakaguchi,
Wei-Guang Ding,
Eiichi Watanabe,
Ichiro Watanabe,
Yukiko Nishio,
Takeru Makiyama,
Seiko Ohno, Masaharu Akao,
Yukei Higashi, [......],
Yuko Nakazawa,
Takenori Yao,
Hikari Jo,
Yoshihisa Sugimoto,
Takashi Ashihara,
Hideki Hayashi,
Makoto Ito,
Keiji Imoto,
Hiroshi Matsuura,
Minoru Horie
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ABSTRACT: Drugs with I(Kr)-blocking action cause secondary long-QT syndrome. Several cases have been associated with mutations of genes coding cardiac ion channels, but their frequency among patients affected by drug-induced long-QT syndrome (dLQTS) and the resultant molecular effects remain unknown.
Genetic testing was carried out for long-QT syndrome-related genes in 20 subjects with dLQTS and 176 subjects with congenital long-QT syndrome (cLQTS); electrophysiological characteristics of dLQTS-associated mutations were analyzed using a heterologous expression system with Chinese hamster ovary cells together with a computer simulation model. The positive mutation rate in dLQTS was similar to cLQTS (dLQTS versus cLQTS, 8 of 20 [40%] versus 91 of 176 [52%] subjects, P=0.32). The incidence of mutations was higher in patients with torsades de pointes induced by nonantiarrhythmic drugs than by antiarrhythmic drugs (antiarrhythmic versus others, 3 of 14 [21%] versus 5 of 6 [83%] subjects, P<0.05). When reconstituted in Chinese hamster ovary cells, KCNQ1 and KCNH2 mutant channels showed complex gating defects without dominant negative effects or a relatively mild decreased current density. Drug sensitivity for mutant channels was similar to that of the wild-type channel. With the Luo-Rudy simulation model of action potentials, action potential durations of most mutant channels were between those of wild-type and cLQTS.
dLQTS had a similar positive mutation rate compared with cLQTS, whereas the functional changes of these mutations identified in dLQTS were mild. When I(Kr)-blocking agents produce excessive QT prolongation (dLQTS), the underlying genetic background of the dLQTS subject should also be taken into consideration, as would be the case with cLQTS; dLQTS can be regarded as a latent form of long-QT syndrome.
Circulation Arrhythmia and Electrophysiology 10/2009; 2(5):511-23. · 6.46 Impact Factor
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Yasuaki Nakagawa,
Koichiro Kuwahara,
Genzo Takemura, Masaharu Akao,
Masashi Kato,
Yuji Arai,
Makoto Takano,
Masaki Harada,
Masao Murakami,
Michio Nakanishi,
Satoru Usami,
Shinji Yasuno,
Hideyuki Kinoshita,
Masataka Fujiwara,
Kenji Ueshima,
Kazuwa Nakao
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ABSTRACT: It is known that the transcriptional coactivator p300 is crucially involved in the differentiation and growth of cardiac myocytes during development. However, the physiological function of p300 in the postnatal hearts remains to be characterized.
We have now investigated the physiological function of p300 in adult hearts.
We analyzed transgenic mice exhibiting cardiac-specific overexpression of a dominant-negative p300 mutant lacking the C/H3 domain (p300DeltaC/H3 transgenic [TG] mice). p300DeltaC/H3 significantly inhibited p300-induced activation of GATA- and myocyte enhancer factor 2-dependent promoters in cultured ventricular myocytes, and p300DeltaC/H3-TG mice showed cardiac dysfunction that was lethal by 20 weeks of age. The numbers of mitochondria in p300DeltaC/H3-TG myocytes were markedly increased, but the mitochondria were diminished in size. Moreover, cardiac mitochondrial gene expression, mitochondrial membrane potential and ATP contents were all significantly disrupted in p300DeltaC/H3-TG hearts, suggesting that mitochondrial dysfunction contributes to the progression of the observed cardiomyopathy. Transcription of peroxisome proliferator-activated receptor gamma coactivator (PGC)-1alpha, a master regulator of mitochondrial gene expression, and its target genes was significantly downregulated in p300DeltaC/H3-TG mice, and p300DeltaC/H3 directly repressed myocyte enhancer factor 2C-dependent PGC-1alpha promoter activity and disrupted the transcriptional activity of PGC-1alpha in cultured ventricular myocytes. In addition, myocytes showing features of autophagy were observed in p300DeltaC/H3-TG hearts.
Collectively, our findings suggest that p300 is essential for the maintenance of mitochondrial integrity and for myocyte survival in the postnatal left ventricular myocardium.
Circulation Research 10/2009; 105(8):746-54. · 9.49 Impact Factor
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Yukiko Nishio,
Takeru Makiyama,
Hideki Itoh,
Tomoko Sakaguchi,
Seiko Ohno,
Yin-Zhi Gong,
Satoshi Yamamoto,
Tomoya Ozawa,
Wei-Guang Ding,
Futoshi Toyoda,
Mihoko Kawamura, Masaharu Akao,
Hiroshi Matsuura,
Takeshi Kimura,
Toru Kita,
Minoru Horie
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ABSTRACT: This study aims to address whether D85N, a KCNE1 polymorphism, is a gene variant that causes long QT syndrome (LQTS) phenotype.
KCNE1 encodes the beta-subunit of cardiac voltage-gated K(+) channels and causes LQTS, which is characterized by the prolongation of the QT interval and torsades de pointes, a lethal arrhythmia. D85N, a KCNE1 polymorphism, is known to be a functional variant associated with drug-induced LQTS.
In order to elucidate the prevalence and clinical significance of this polymorphism, we performed genetic screening in 317 LQTS probands. For comparison, we examined its presence in 496 healthy control subjects. We also conducted biophysical assays for the D85N variant in mammalian cells.
The allele frequency for D85N carriers was 0.81% in healthy people. In contrast, among LQTS probands, there were 1 homozygous and 23 heterozygous carriers (allele frequency 3.9%). Seven of 23 heterozygous carriers had additional mutations in LQTS-related genes, and 3 female subjects had documented factors predisposing to the symptom. After excluding these probands, the D85N prevalence was significantly higher compared with control subjects (allele frequency 2.1%, p < 0.05). In a heterologous expression study with Chinese hamster ovarian cells, KCNE1-D85N was found to exert significant loss-of-function effects on both KCNQ1- and KCNH2-encoded channel currents.
The KCNE1-D85N polymorphism was significantly more frequent in our LQTS probands. The functional variant is a disease-causing gene variant of LQTS phenotype that functions by interacting with KCNH2 and KCNQ1. Since its allele frequency was approximately 1% among control individuals, KCNE1-D85N may be a clinically important genetic variant.
Journal of the American College of Cardiology 08/2009; 54(9):812-9. · 14.16 Impact Factor
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Toshikazu Jinnai,
Hisanori Horiuchi,
Takeru Makiyama,
Junichi Tazaki,
Tomohisa Tada, Masaharu Akao,
Koh Ono,
Kozo Hoshino,
Yumiko Naruse,
Kanako Takahashi,
Haruyo Watanabe,
Toru Kita,
Takeshi Kimura
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ABSTRACT: The P2Y(12) adenosine diphosphate (ADP) receptor blocker, clopidogrel, an essential drug for the prevention of stent thrombosis after percutaneous coronary intervention (PCI), is a prodrug that requires CYP2C19- and CYP3A4-mediating activation. CYP2C19*2 and *3 polymorphisms are known to lack enzymatic activity. CYP2C19 polymorphisms have been reported to exhibit weaker antiplatelet response to clopidogrel in healthy subjects. The effect of polymorphisms of CYP2C19, CYP3A4 and P2Y(12) on the antiplatelet effect of clopidogrel in clinical patients was examined in the present study.
Single nucleotide polymorphisms of CYP2C19*2, *3, CYP3A4 (IVS10 +12G>A) and P2Y(12) (T744C) were determined in 25 PCI-scheduled patients who had been systematically analyzed for the antiplatelet effect of clopidogrel in a previous study. On the basis of CYP2C19 genotype, 11 patients (44%) were classified as extensive metabolizers (EMs), 8 (32%) as intermediate metabolizers (IMs) and 6 (24%) as poor metabolizers (PMs). The rates of inhibition of 5 micromol/L ADP-induced platelet aggregation by clopidogrel intake at 48 h were 31.6 +/-14.3% in EMs, 18.4 +/-10.0% in IMs (P=0.04 vs EMs) and 16.0 +/-13.0% in PMs (P=0.02 vs EMs).
CYP2C19 polymorphisms are frequent in Japanese, and the antiplatelet effect of clopidogrel is strongly affected by them in the real-world clinical setting.
Circulation Journal 07/2009; 73(8):1498-503. · 3.77 Impact Factor
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ABSTRACT: An opening of the mitochondrial permeability transition pore (MPTP), which leads to the loss of mitochondrial membrane potential (DeltaPsi(m)), is the earliest event that commits cells to death, and this process is potentially a prime target for therapeutic intervention against myocardial ischaemia/reperfusion. We aimed to investigate the protective effects of RNA interference (RNAi)-mediated gene silencing of cyclophilin D (CypD), one of the putative components of the MPTP, against myocardial ischaemia/reperfusion using two-photon laser scanning microscopy.
We created an adenovirus carrying short-interfering RNA (siRNA) that inactivates CypD. Transduction of CypD-siRNA in rat cardiomyocytes achieved a 61% reduction in CypD mRNA and a 63% reduction in protein levels as well as protection against oxidant-induced DeltaPsi(m) loss and cytotoxicity. To further investigate the effects in vivo, we monitored the spatio-temporal changes of DeltaPsi(m) in perfused rat hearts subjected to ischaemia/reperfusion using two-photon imaging. Adult rats received direct intramyocardial injections of the adenovirus. Two to three days after injection, rat hearts were perfused by the Langendorff method and DeltaPsi(m) levels of individual cells were monitored. The progressive loss of DeltaPsi(m) during ischaemia/reperfusion was significantly suppressed in CypD-siRNA-transduced cells compared with non-transduced cells. Furthermore, the protective effect of CypD-siRNA was dose-dependent.
Therapeutic interventions designed to inactivate CypD may be a promising strategy for reducing cardiac injury against myocardial ischaemia/reperfusion. The two-photon imaging technique provides deeper insight into cardioprotective therapy that targets mitochondria.
Cardiovascular research 04/2009; 83(2):335-44. · 5.80 Impact Factor
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Kozo Hoshino,
Hisanori Horiuchi,
Tomohisa Tada,
Junichi Tazaki,
Eiichiro Nishi,
Mitsunori Kawato,
Tomoyuki Ikeda,
Hiromi Yamamoto, Masaharu Akao,
Yutaka Furukawa, [......],
Neiko Ozasa,
Toshikazu Jinnai,
Kanako Takahashi,
Haruyo Watanabe,
Yuka Yoshikawa,
Naoko Nishimoto,
Chiho Ouchi,
Takeshi Morimoto,
Toru Kita,
Takeshi Kimura
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ABSTRACT: Dual antiplatelet therapy with acetylsalicylic acid (ASA) and a P2Y(12) ADP-receptor blocker is standard for prevention of coronary stent thrombosis. Clopidogrel, a 2(nd)-generation P2Y(12) blocker, has recently become available in Japan and this study aimed to evaluate its antiplatelet effects in Japanese patients.
Thirty Japanese patients scheduled for elective coronary stent implantation were enrolled. Under low-dose ASA therapy, 300 mg clopidogrel was loaded on the 1(st) day and a daily 75-mg dose was administered on the following days. Assessed by optical aggregometer, rapid inhibition occurred at 4 h, when the inhibition of platelet aggregation rate (IPA) was 16.4+/-12.8% using 5 mumol/L ADP as the stimulus. The antiplatelet efficacy of clopidogrel was reasonably constant in each patient throughout the study period, although there was a broad inter-individual variation. At 48 h after clopidogrel loading, the ratios of responders (IPA > or =30%), hypo-responders (10%< or =IPA<30%), and non-responders (IPA <10%) were 36%, 50%, and 14%, respectively.
The antiplatelet effectiveness of clopidogrel appeared individual-specific with wide inter-individual variation. The rate of clopidogrel non-responders was 14% among the examined Japanese patients.
Circulation Journal 12/2008; 73(2):336-42. · 3.77 Impact Factor
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Takeru Makiyama, Masaharu Akao,
Satoshi Shizuta,
Takahiro Doi,
Kei Nishiyama,
Yuko Oka,
Seiko Ohno,
Yukiko Nishio,
Keiko Tsuji,
Hideki Itoh,
Takeshi Kimura,
Toru Kita,
Minoru Horie
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ABSTRACT: This study describes a novel heterozygous gain-of-function mutation in the cardiac sodium (Na+) channel gene, SCN5A, identified in a Japanese family with lone atrial fibrillation (AF).
SCN5A mutations have been associated with a variety of inherited arrhythmias, but the gain-of-function type modulation in SCN5A is associated with only 1 phenotype, long-QT syndrome type 3 (LQTS3).
We studied a Japanese family with autosomal dominant hereditary AF, multiple members of which showed an onset of AF or frequent premature atrial contractions at a young age.
The 31-year-old proband received radiofrequency catheter ablation, during which time numerous ectopic firings and increased excitability throughout the right atrium were documented. Mutational analysis identified a novel missense mutation, M1875T, in SCN5A. Further investigations revealed the familial aggregation of this mutation in all of the affected individuals. Functional assays of the M1875T Na(+) channels using a whole-cell patch-clamp demonstrated a distinct gain-of-function type modulation; a pronounced depolarized shift (+16.4 mV) in V(1/2) of the voltage dependence of steady-state inactivation; and no persistent Na+ current, which is a defining mechanism of LQTS3. These biophysical features of the mutant channels are potentially associated with increased atrial excitability and normal QT interval in all of the affected individuals.
We identified a novel SCN5A mutation associated with familial AF. The mutant channels displayed a gain-of-function type modulation of cardiac Na+ channels, which is a novel mechanism predisposing to increased atrial excitability and familial AF. This is a new phenotype resulting from the SCN5A gain-of-function mutations and is distinct from LQTS3.
Journal of the American College of Cardiology 11/2008; 52(16):1326-34. · 14.16 Impact Factor
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ABSTRACT: Brugada syndrome is an inherited arrhythmic disorder, and mutations in the SCN5A gene, encoding cardiac sodium channels, are identified in approximately 15% of cases. A novel causative gene (glycerol-3 phosphate dehydrogenase-1 like; GPD1L) has been reported, and in the present study, 80 unrelated Japanese patients were screened for GPD1L mutations: 1 synonymous mutation was identified, as well as 1 intronic variant, both of which were absent in 220 control alleles. Additionally, a single-nucleotide polymorphism was detected in 4 patients. No non-synonymous mutations were found. GPD1L does not appear to be a major cause of Brugada syndrome in the Japanese population.
Circulation Journal 10/2008; 72(10):1705-6. · 3.77 Impact Factor
