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Biomedical subjects

Hiroshi Mabuchi

Publications and source records attributed to Hiroshi Mabuchi.

At least 37 records · Page 2Linked to original sources
PubMed2005

Long-term course of lipoprotein lipase (LPL) deficiency due to homozygous LPL(Arita) in a patient with recurrent pancreatitis, retained glucose tolerance, and atherosclerosis.

CONTEXT: Lipoprotein lipase (LPL) deficiency is a rare autosomal recessive disorder caused by LPL gene mutation and is characterized by severe hyperchylomicronemia. Patients with LPL deficiency suffer from the frequent recurrence of acute pancreatitis, but the underlying mechanisms are not fully understood. CASE REPORT: A 22-yr-old male Japanese patient with severe hyperchylomicronemia was admitted to our hospital in 1973. He had no consanguinity and no family history of hyperlipidemia. He was genetically diagnosed as LPL deficiency (homozygous for LPL(Arita)) with no LPL mass or activity in postheparin plasma. He has experienced recurrent acute pancreatitis 22 times during our 31-yr clinical follow-up, but no pancreatic pseudocyst, irregularity of the pancreatic duct, or abnormal pancreatic calcification was observed in computed tomography. Moreover, his pancreatic endocrine function, as assessed by the oral glucose tolerance test, has preserved more than 30 yr. Although he was a current smoker, no clinically significant atherosclerotic lesion had been observed. CONCLUSIONS: From the long-term observation of this patient, we propose that LPL deficiency is not invariably associated with high mortality and that even with repeated episodes of acute pancreatitis, pancreatic function may be slow to decline.

Acute Disease↗
PubMed2005

Differences in diagnostic value of four electrocardiographic voltage criteria for hypertrophic cardiomyopathy in a genotyped population.

The diagnostic value of various classic electrocardiographic (ECG) voltage criteria for hypertrophic cardiomyopathy (HC) has not been established in a genotyped population. This study aimed to determine the most accurate diagnostic definition of classic ECG voltage criteria for detecting carriers of HC. ECG and echocardiographic findings were analyzed in 161 genotyped subjects (97 genetically affected, 64 unaffected) from 20 families with disease-causing mutations in 4 genes. The diagnostic value of 4 voltage criteria (Cornell, Sokolow-Lyon, Romhilt-Estes, and 12-lead QRS voltage) for detecting carriers of HC was investigated. In all subjects, the Romhilt-Estes (point score > or =4) criterion and 12-lead QRS voltage (> or =240 mm) were most sensitive (37% and 36%, respectively), with high specificity (95% each), resulting in the greatest accuracy (60% and 59%, respectively). Using these criteria, in subjects without echocardiographic evidence of left ventricular hypertrophy, voltage abnormalities were found in 22.6% of carriers and 4.7% of noncarriers (p <0.01). In conclusion, these findings suggest that the Romhilt-Estes and the 12-lead QRS voltage criteria may be the most accurate diagnostic definitions for HC on the basis of molecular genetic diagnoses. Furthermore, this study demonstrated that voltage abnormalities may be found in prehypertrophic carriers. Even when genetic testing becomes widely available, it will be difficult to make genetic diagnoses in all patients with HC because of its genetic heterogeneity. Therefore, understanding the diagnostic value of classic ECG voltage criteria may be important in detecting carriers, including those without left ventricular hypertrophy.

Adult↗
PubMed2005

High incidence of sudden cardiac death with conduction disturbances and atrial cardiomyopathy caused by a nonsense mutation in the STA gene.

BACKGROUND: The STA gene encodes emerin and is one of the genes that is affected in Emery-Dreifuss muscular dystrophy (EDMD). Although it has been reported that EDMD caused by the STA gene mutation is associated with X-linked recessive inheritance, the genotype-phenotype correlations, with special reference to cardiac manifestations, are not well defined. METHODS AND RESULTS: We identified 16 carriers (7 male and 9 female) with a nonsense mutation in exon 6 of the STA gene in 2 EDMD families. Pacemakers were required for treatment of bradyarrhythmias in all 7 male carriers and in 2 of the 9 female carriers. In addition, 2 of the 9 female carriers displayed atrial fibrillation. In these 2 families, 3 males without pacemaker implantation, who were not tested genetically, had died suddenly. In these family members, the majority of carriers with the mutation had not been clinically diagnosed as having EDMD before genetic testing because of extremely mild or nonexistent skeletal myopathy. CONCLUSIONS: EDMD caused by this mutation is characterized by atypical clinical features and incomplete penetrance of the clinical phenotype and may result in serious cardiac complications, including sudden death. Approaches to preventing possible sudden death in carriers with the STA gene mutation require further study.

Adolescent↗
PubMed2005

Electrocardiographic events and cholesterol reduction with pravastatin in patients with hypercholesterolemia: the Hokuriku Lipid Coronary Heart Disease Study-Pravastatin Atherosclerosis Trial.

BACKGROUND: Cholesterol lowering therapy may offset the development of coronary atherosclerosis, and the resulting reduction in coronary ischemia may be observed in the electrocardiogram (ECG). METHODS: A total of 2039 Japanese adults with hypercholesterolemia were divided into two groups (receiving 10-20 mg pravastatin daily or a normal diet) and were followed up for 5 years. ECG studies were performed at entry and every year during the follow-up period. The occurrence of myocardial infarction and the appearance or worsening of ischemic ST changes were assessed in terms of effects on the ECG. RESULTS: Of the 2039 patients registered, 827 were excluded from the study for various reasons. Consequently, a total of 1212 patients were analyzed. There was a lower degree of worsening in the pravastatin group (n=757) than in the normal diet group (n=455) in the primary prevention cohort [11 (1.8%) vs. 16 (4.3%), respectively, P=0.031]. On the other hand, there was no difference in the frequency of worsening between the two groups in the secondary prevention cohort [7 (4.4%) in the pravastatin group vs. 4 (4.9%) in the diet group, P=0.25]. Event-free survival was better in the pravastatin group than in the normal diet group in the primary prevention cohort (P=0.011), but there was no difference between the two groups in the secondary prevention cohort. CONCLUSIONS: These results suggest that pravastatin may reduce the incidence of coronary heart disease and that this effect may be predominantly observed in patients with early atheromatous lesions.

Aged↗
PubMed2005

Inhibition of Rac activation as a mechanism for negative regulation of actin cytoskeletal reorganization and cell motility by cAMP.

cAMP has been found to play a role in mediating the negative regulation of cell motility, although its underlying molecular mechanism remains poorly understood. By using CHO (Chinese-hamster ovary) cells that express the EP2 subtype of PGE2 (prostaglandin E2) receptors, we provide evidence that an increase in cellular cAMP content leads to inhibition of cellular Rac activity, which serves as a mechanism for this negative regulation. In CHO cells expressing EP2, but not in vector control cells, PGE2 dose-dependently inhibited chemotaxis towards IGF-I (insulin-like growth factor-I), which is a Rac-dependent process, with the maximal 75% inhibition observed at 10(-8) M PGE2. EP2 stimulation failed to inhibit tyrosine phosphorylation either of IGF-I receptor or IRS-1 (insulin receptor substrate-1), or activation of phosphoinositide 3-kinase or Akt in response to IGF-I, but potently and dose-dependently inhibited IGF-I-induced activation of cellular Rac activity and membrane ruffling. However, PGE2 failed to inhibit Val12-Rac-induced membrane ruffling. Similar to the case of CHO cells, PGE2 inhibited PDGF (platelet-derived growth factor)-induced Rac activation and chemotaxis in vascular smooth muscle cells endogenously expressing EP2. The inhibitory effects of PGE2 on IGF-I-induced chemotaxis, membrane ruffling and Rac activation were faithfully reproduced by a low concentration of forskolin, which induced a comparable extent of cAMP elevation as with 10(-8) M PGE2, and were potentiated by isobutylmethylxanthine. The protein kinase A inhibitor Rp isomer of adenosine 3',5'-cyclic monophosphorothioate reduced PGE2 inhibition of Rac activation and chemotaxis. These results indicate that EP2 mediates Rac inhibition through a mechanism involving cAMP and protein kinase A, thereby inhibiting membrane ruffling and chemotaxis.

Actins↗
PubMed2005

Association of coronary artery ectasia with plasma insulin levels in Japanese men of heterozygous familial hypercholesterolemia with the low-density lipoprotein receptor gene mutation K790X.

BACKGROUND: Hyperinsulinemia is widely believed to be an important coronary risk factor. We investigated the effect of plasma insulin levels on the development of coronary ectasia in Japanese men with heterozygous familial hypercholesterolemia (FH). METHODS: A cross-sectional study was conducted in 20 FH men with the LDL receptor mutation (K790X) [age 42.3+/-2.8 years old, body mass index (BMI) 24.6+/-0.7 kg/m2, total cholesterol (TC) 8.68+/-0.36 mmol/l, triglycerides (TG) 1.76+/-0.23 mmol/l, high-density lipoprotein cholesterol (HDL-C) 0.977+/-0.065 mmol/l]. Subjects with diabetes mellitus were excluded. Plasma insulin levels, either fasting or during oral glucose tolerance test, were compared between subjects with and without coronary artery ectasia. RESULTS: FH subjects with coronary ectasia had significantly higher fasting plasma insulin levels than those without (12.6+/-1.4 vs. 7.7+/-0.5 mU/l; p<0.05). Also, plasma insulin levels during oral glucose tolerance test tended to be higher in the former than in the latter. CONCLUSIONS: Plasma insulin level could be an important determinant of the development of coronary artery ectasia in Japanese heterozygous FH men.

Adult↗
PubMed2005

Scintigraphic evaluation of regression of abnormal Q waves in myocardial infarction.

We report regression of the abnormal Q waves of an inferior old myocardial infarction after an additional anterior acute myocardial infarction, and demonstrate the scintigraphic correlation and chronological course of this phenomenon. Scintigraphic findings in the present case here may contribute to an interpretation of regression of abnormal Q waves in myocardial infarction.

Aged↗
PubMed2005

Abnormal sympathetic innervation of the heart in a patient with Emery-Dreifuss muscular dystrophy.

A 33-year-old man was admitted for general malaise and vomiting. An electrocardiogram showed a complete atrioventricular block and an echocardiogram showed right atrial dilatation and normal wall motion of left ventricle (LV). Gene analysis showed nonsense mutation in the STA gene, which codes for emerin, and Emery-Dreifuss muscular dystrophy was diagnosed. An endomyocardial biopsy of right ventricle showed mild hypertrophy of myocytes. Myocardial scintigraphic studies with Tc-99m methoxyisobutylisonitrile (MIBI) and I-123-betamethyl-p-iodophenylpentadecanoic acid (BMIPP) scintigrams showed no abnormalities. In contrast, I-123 metaiodobenzylguanidine (MIBG) scintigrams showed a diffuse and severe decrease in accumulation of MIBG in the heart. Six months later, his LV wall motion on echocardiograms developed diffuse hypokinesis. These results suggest that the abnormality on I-123 MIBG myocardial scintigrams may predict LV dysfunction in Emery-Dreifuss muscular dystrophy.

3-Iodobenzylguanidine↗
PubMed2005

Severely elevated serum triglycerides in a case of heterozygous familial hypercholesterolemia with the 317 cysteine to serine mutation in the LDL receptor gene.

We present a case of a 43-year-old Japanese man with heterozygous familial hypercholesterolemia (FH) with severely elevated serum triglycerides (TG). He drank large quantities of alcohol but had no endocrinological disorder or diabetes mellitus. He had a recurrent, acute pancreatitis. His fasting serum total cholesterol (TC), TG, and HDL-C levels and an apolipoprotein E genotype of E3/E3 suggested a diagnosis of type V hyperlipidemia. Yet, the patient had bilateral Achilles tendinous xanthomata, which prompted us to conduct a gene analysis for the LDL receptor, and this revealed the heterozygous form of the 317 cysteine to serine mutation, demonstrating that this was a case of FH. We recommend that physicians consider the existence of FH, even in hyperlipidemic subjects with lipid profiles far from those typical of FH, whenever a patient has tendinous xanthomata.

Journal Article↗
PubMed2005

Compound heterozygosity for mutations Asp611-->Tyr in KCNQ1 and Asp609-->Gly in KCNH2 associated with severe long QT syndrome.

LQTS (long QT syndrome) is an inherited cardiac disorder characterized by prolongation of QT interval, torsades de pointes and sudden death. We have identified two heterozygous missense mutations in the KCNQ1 and KCNH2 (also known as HERG) genes [Asp611-->Tyr (D611Y) in KCNQ1 and Asp609-->Gly (D609G) in KCNH2] in a 2-year-old boy with LQTS. The aim of the present study was to characterize the contributions of the mutations in the KCNQ1 and KCNH2 genes relative to the clinical manifestations and electrophysiological properties of LQTS. Six of 11 carriers of D611Y in KCNQ1 had long QT intervals. D609G in KCNH2 was detected only in the proband. Studies on the electrophysiological alterations due to the two missense mutations revealed that the D611Y mutation in KCNQ1 did not show a significant suppression of the currents compared with wild-type, but the time constants of current activation in the mutants were increased compared with that in the wild-type. In contrast, the D609G mutation in KCNH2 showed a dominant-negative suppression. Our results suggest that the mild phenotype produced by the D611Y mutation in KCNQ1 became more serious by addition of the D609G mutation in KCNH2 in the proband.

Adolescent↗
PubMed2005

ATP-binding cassette transporter G8 M429V polymorphism as a novel genetic marker of higher cholesterol absorption in hypercholesterolaemic Japanese subjects.

The ratio of serum plant sterols to cholesterol is positively correlated with the fractional cholesterol absorption, whereas serum precursors of cholesterol synthesis are positively correlated with cholesterol synthesis. Recently, two ABC (ATP-binding cassette) transporters, ABCG5 and ABCG8, have been described as playing an important role in the absorption and excretion of sterols. In the present study, we tested the hypothesis that genetic variation in ABCG5/ABCG8 influences the levels of serum plant sterol (sitosterol) and cholesterol precursor (lathosterol) in Japanese primary hypercholesterolaemic patients (n = 100). We identified a novel mutation [859T/C (C287R)] and a novel polymorphism [1285A/G (M429V)] at the ABCG5/ABCG8 loci, as well as four polymorphisms reported previously [1810C/G (Q604E), 161G/A (C54Y), 1199C/A (T400K) and 1895C/T (A632V)]. In carriers of the novel M429V variant, the serum level of sitosterol and the sitosterol/cholesterol ratio were significantly higher than those in non-carriers (3.64 compared with 2.56 microg/ml, and 1.45 microg/mg compared with 1.00 microg/mg respectively; P < 0.01 for both), and serum lathosterol tended to be lower (1.95 microg/ml compared with 3.03 microg/ml; P = 0.08), whereas no significant difference was observed in other lipid profiles. These four polymorphisms (1810C/G, 161G/A, 1199C/A and 1285A/G) generated six haplotypes, and the C/G/C/G haplotype was significantly associated with a higher sitosterol level and sitosterol/cholesterol ratio compared with the other five haplotypes (P < 0.05 for both). We conclude that, in 8% of patients with hypercholesterolaemia, the novel ABCG8 M429V variant was associated with higher cholesterol absorption efficiency. Future studies should investigate whether these findings have implications for the optimal cholesterol-lowering drug treatment in hypercholesterolaemic patients.

ATP-Binding Cassette Transporters↗
PubMed2005

Clinical and electrophysiological characteristics of Brugada syndrome caused by a missense mutation in the S5-pore site of SCN5A.

Brugada syndrome is an inherited cardiac disorder caused by mutations in the SCN5A gene encoding the cardiac sodium channel alpha-subunit, and potentially leads to ventricular fibrillation and sudden death. We report a case of a novel SCN5A mutation associated with Brugada syndrome. A 51-year-old man suffered from recurrent nocturnal syncopal attacks due to polymorphic ventricular tachycardia. His electrocardiogram showed ST-segment elevation in V1-V3 leads, but there was no evidence of structural heart disease. DNA sequence analysis of SCN5A in this patient revealed a missense mutation (R282H) in the S5-pore region of domain I. This mutational change was not present in 100 healthy Japanese controls. In the patient's family, a 36-year-old brother had died suddenly. Genetic analysis identified two other carriers of the R282H mutation, who had ST-segment elevation and slightly increased QRS widths, but they experienced no syncopal episodes or ventricular fibrillation. Electrophysiological investigation of the R282H mutant channel expressed in cultured cells showed a severe reduction in sodium current density and a mild positive shift of activation curve. R282H did not enhance intermediate inactivation. Single-channel conductance of R282H was slightly decreased compared with WT. The electrophysiological characteristics of the R282H channel are suggested to be closely related to the clinical phenotype of Brugada syndrome.

DNA Mutational Analysis↗
PubMed2005

The expression of messenger RNA for ADP-ribosyl cyclase in aldosterone-producing adenomas.

OBJECTIVE: Cyclic ADP-ribose (cADPR) has been reported to be as potent and powerful at releasing intracellular Ca(2+) as inositol triphosphate (IP(3)). To determine whether the cADPR system plays a signalling role in angiotensin II (Ang II)-induced aldosterone synthesis in the human adrenal gland, we investigated the effects of Ang II on ADP-ribosyl cyclase activity in human adrenal cortical tissue. In addition, the expression of ADP-ribosyl cyclase messenger RNA was evaluated in aldosterone-producing adenomas (APAs) and compared with normal adrenal tissue and nonfunctioning adenomas. DESIGN: ADP-ribosyl cyclase activity was measured in crude membrane fractions of human adrenocortical tissues with Ang II or with Ang II plus the Ang II receptor (AT(1)R) antagonist losartan or plus the AT(2)R antagonist PD123319. The effect of 8-bromo-cADPR on Ang II-induced aldosterone production from adrenal tissue was estimated. The expression of ADP-ribosyl cyclase, CYP11B2 and AT(1)R mRNA was measured in APAs, nonfunctioning adenomas, adjacent adrenal tissue and normal adrenal tissue. MEASUREMENTS: ADP-ribosyl cyclase activity was measured by using high-performance liquid chromatography (HPLC) and [(3)H] NAD(+). mRNA expression was measured by competitive reverse-transcription polymerase chain reaction (RT-PCR). Results Ang II (10(-7) and 10(-8) mol/l) significantly increased ADP-ribosyl cyclase activity in a dose-dependent manner. This increase was inhibited by pretreatment with losartan but not with PD123319. Treatment with 8-bromo-cADPR (50 micromol/l) reduced Ang II-induced aldosterone secretion. ACTH did not significantly increase the enzyme activity. The expression of ADP-ribosyl cyclase, CYP11B2 and AT(1)R mRNA was increased in APAs compared with that of nonfunctioning adenomas, adjacent adrenal tissue or normal adrenal tissue. CONCLUSIONS: These results demonstrated the existence of a signalling pathway from the Ang II receptor to ADP-ribosyl cyclase in the human adrenal gland and suggest that the cADP-ribose signalling system might play an important role in the pathogenesis of APAs.

ADP-ribosyl Cyclase↗
PubMed2005

Association of LMNA 1908C/T polymorphism with cerebral vascular disease and diabetic nephropathy in Japanese men with type 2 diabetes.

OBJECTIVE: The LMNA 1908C/T polymorphism has been reported to be associated with dyslipidaemia, metabolic syndrome, adipose tissue metabolism and obesity phenotypes, suggesting that this polymorphism presents an increased risk of atherosclerosis and vascular diseases. However, there have been no previous reports on the relationship between the LMNA 1908C/T polymorphism and vascular diseases. The aim of this study therefore was to investigate the association between the LMNA 1908C/T polymorphism and the prevalence of vascular disease in Japanese patients with type 2 diabetes. DESIGN: A cross-sectional, hospital-based study of diabetic complications with an LMNA gene background. PATIENTS: One hundred and sixty-six Japanese men with type 2 diabetes. Measurements LMNA 1908C/T polymorphism (by polymerase chain reaction restriction fragment length polymorphism, PCR-RFLP); diabetic retinopathy (by standard fundus photography); diabetic nephropathy (by urinary albumin excretion rate); diabetic neuropathy (by signs, symptoms and/or nerve conduction velocity); coronary heart disease (by symptoms of typical chest pain and/or history of myocardial infarction, and ischaemic electrocardiographic alteration and/or coronary artery bypass graft surgery); cerebral vascular disease (by ultrasonography, computed tomography and/or magnetic resonance imaging). RESULTS: Carriers of the LMNA 1908T allele manifested a significantly higher prevalence of diabetic nephropathy and cerebral vascular disease than carriers of the C allele. Multiple regression analysis showed that the LMNA 1908T allele tended to be associated with cerebral vascular disease, but was independent of age, hypertension, total cholesterol or triglyceride [odds ratio (OR) 7.03, P=0.0611]. Similarly, the LMNA 1908T allele showed a significant association with diabetic nephropathy, not independent of total cholesterol or triglyceride. CONCLUSIONS: The LMNA 1908C/T polymorphism plays an important role in the development of cerebral vascular disease and diabetic nephropathy in Japanese men with type 2 diabetes.

Aged↗
PubMed2005

A novel missense mutation in the SCN5A gene associated with Brugada syndrome bidirectionally affecting blocking actions of antiarrhythmic drugs.

Brugada syndrome is an inherited cardiac disorder caused by mutations in the SCN5A gene encoding the cardiac sodium channel alpha subunit, which can lead ventricular fibrillation and sudden death. Inattentive use of antiarrhythmic drugs potentially triggers fatal cardiac arrhythmias through further reduction of sodium current (I(Na)). We studied the molecular mechanism underlying a case of Brugada syndrome that showed no response to a class Ic antiarrhythmic drug. Molecular genetic studies of a patient with Brugada syndrome identified a novel mutation in SCN5A, which causes substitution of serine for asparagine (N406S) in S6 of domain I (IS6). The provocation test with pilsicainide, a class Ic antiarrhythmic drug, failed to exacerbate ST-segment elevation in this case. Electrophysiological analyses of the N406S-mutant channel expressed together with the beta1 subunit in HEK293 cells showed that the voltage dependence of activation was positively shifted by 16 mV and that intermediate inactivation was enhanced. Whereas tonic block by pilsicainide was not changed in the N406S channel, use-dependent block by pilsicainide was almost completely abolished, consistent with the clinical findings of the negative provocation test. In contrast, the N406S channel showed stronger use-dependent block by quinidine than the wild-type channel. We demonstrate a novel Brugada mutation N406S, which is associated with the discordant effects on blocking actions of antiarrhythmic drugs as well as the multiple channel gating defects. We emphasis that an antiarrhythmic drug may exert unpredicted effects in patients with channel mutations.

Adult↗