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Articles by Y Higashi
Total Records ( 2 ) for Y Higashi
  Y Higashi , H Matsuoka , H Umei , R Sugano , Y Fujii , J Soga , Y Kihara , K Chayama and T. Imaizumi

Epidemiologic studies have shown that a low level of high-density lipoprotein (HDL) cholesterol is a risk factor for cardiovascular diseases. The purpose of this study was to determine the contribution of isolated low HDL cholesterol to endothelial function. Thirty-nine subjects with low HDL cholesterol who had no other cardiovascular risk factors were selected from the 5,417 participants from our population. We evaluated flow-mediated vasodilation (FMD) before and after 4 wk of treatment with the HMG-CoA reductase inhibitor pravastatin in 29 of the 39 subjects with isolated low HDL cholesterol. FMD was lower in the low-HDL-cholesterol group (n = 29) than in the control group (n = 29), whereas NTG-induced vasodilation was similar in the two groups. Pravastatin increased HDL cholesterol, urinary excretion of nitrite/nitrate, circulating levels of progenitor cells, and cell migration response to vascular endothelial growth factor in 15 subjects with low HDL cholesterol but not in 14 placebo control subjects. FMD increased in the pravastatin treatment group but not in the control group. NTG-induced vasodilation was similar before and after 4 wk of treatment in the two groups. Multiple regression analysis revealed that changes in HDL cholesterol, the number of progenitor cells, and migration of progenitor cells were independent predictors of augmentation of FMD with pravastatin. These findings suggest that low HDL cholesterol is an independent risk factor for endothelial dysfunction and that pravastatin improves endothelial function in individuals with isolated low HDL cholesterol through, at least in part, an increase in circulating progenitor cells.

  H Itoh , T Sakaguchi , W. G Ding , E Watanabe , I Watanabe , Y Nishio , T Makiyama , S Ohno , M Akao , Y Higashi , N Zenda , T Kubota , C Mori , K Okajima , T Haruna , A Miyamoto , M Kawamura , K Ishida , I Nagaoka , Y Oka , Y Nakazawa , T Yao , H Jo , Y Sugimoto , T Ashihara , H Hayashi , M Ito , K Imoto , H Matsuura and M. Horie

Background— Drugs with IKr-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.

Methods and Results— 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.

Conclusions— dLQTS had a similar positive mutation rate compared with cLQTS, whereas the functional changes of these mutations identified in dLQTS were mild. When IKr-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.

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