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Articles by S Yokoyama
Total Records ( 3 ) for S Yokoyama
  R Sofat , A. D Hingorani , L Smeeth , S. E Humphries , P. J Talmud , J Cooper , T Shah , M. S Sandhu , S. L Ricketts , S. M Boekholdt , N Wareham , K. T Khaw , M Kumari , M Kivimaki , M Marmot , F. W Asselbergs , P van der Harst , R. P.F Dullaart , G Navis , D. J van Veldhuisen , W. H Van Gilst , J. F Thompson , P McCaskie , L. J Palmer , M Arca , F Quagliarini , C Gaudio , F Cambien , V Nicaud , O Poirer , V Gudnason , A Isaacs , J. C.M Witteman , C. M van Duijn , M Pencina , R. S Vasan , R. B D'Agostino , J Ordovas , T. Y Li , S Kakko , H Kauma , M. J Savolainen , Y. A Kesaniemi , A Sandhofer , B Paulweber , J. V Sorli , A Goto , S Yokoyama , K Okumura , B. D Horne , C Packard , D Freeman , I Ford , N Sattar , V McCormack , D. A Lawlor , S Ebrahim , G. D Smith , J. J.P Kastelein , J Deanfield and J. P. Casas

Background— Cholesteryl ester transfer protein (CETP) inhibitors raise high-density lipoprotein (HDL) cholesterol, but torcetrapib, the first-in-class inhibitor tested in a large outcome trial, caused an unexpected blood pressure elevation and increased cardiovascular events. Whether the hypertensive effect resulted from CETP inhibition or an off-target action of torcetrapib has been debated. We hypothesized that common single-nucleotide polymorphisms in the CETP gene could help distinguish mechanism-based from off-target actions of CETP inhibitors to inform on the validity of CETP as a therapeutic target.

Methods and Results— We compared the effect of CETP single-nucleotide polymorphisms and torcetrapib treatment on lipid fractions, blood pressure, and electrolytes in up to 67 687 individuals from genetic studies and 17 911 from randomized trials. CETP single-nucleotide polymorphisms and torcetrapib treatment reduced CETP activity and had a directionally concordant effect on 8 lipid and lipoprotein traits (total, low-density lipoprotein, and HDL cholesterol; HDL2; HDL3; apolipoproteins A-I and B; and triglycerides), with the genetic effect on HDL cholesterol (0.13 mmol/L, 95% confidence interval [CI] 0.11 to 0.14 mmol/L) being consistent with that expected of a 10-mg dose of torcetrapib (0.13 mmol/L, 95% CI 0.10 to 0.15). In trials, 60 mg of torcetrapib elevated systolic and diastolic blood pressure by 4.47 mm Hg (95% CI 4.10 to 4.84 mm Hg) and 2.08 mm Hg (95% CI 1.84 to 2.31 mm Hg), respectively. However, the effect of CETP single-nucleotide polymorphisms on systolic blood pressure (0.16 mm Hg, 95% CI –0.28 to 0.60 mm Hg) and diastolic blood pressure (–0.04 mm Hg, 95% CI –0.36 to 0.28 mm Hg) was null and significantly different from that expected of 10 mg of torcetrapib.

Conclusions— Discordance in the effects of CETP single-nucleotide polymorphisms and torcetrapib treatment on blood pressure despite the concordant effects on lipids indicates the hypertensive action of torcetrapib is unlikely to be due to CETP inhibition or shared by chemically dissimilar CETP inhibitors. Genetic studies could find a place in drug-development programs as a new source of randomized evidence for drug-target validation in humans.

  S Yokoyama , M Takano , M Yamamoto , S Inami , S Sakai , K Okamatsu , S Okuni , K Seimiya , D Murakami , T Ohba , R Uemura , Y Seino , N Hata and K. Mizuno

Background— Although coronary angiograms after bare-metal stent (BMS) implantation show late luminal narrowing beyond 4 years, the detailed changes inside the BMS have not yet been fully elucidated.

Methods and Results— Serial angiographic and angioscopic examinations were performed immediately (baseline), 6 to 12 months (first follow-up), and ≥4 years (second follow-up) after stenting without target lesion revascularization in 26 segments of 26 patients who received BMS deployment for their native coronary arteries. Angioscopic observation showed atherosclerotic yellow plaque crushed out by stent struts in 22 patients (85%) and mural thrombus in 21 patients (81%) at baseline. At first follow-up, white neointimal hyperplasia was almost completely buried inside the struts, and both yellow plaque and thrombus had decreased in comparison with baseline (12% and 4%, respectively; P<0.001). The frequencies of yellow plaque and thrombus increased from the first to second follow-ups (58% and 31%, respectively; P<0.05). All of the yellow plaques in the second follow-up were located not exterior to the struts but protruding from the vessel wall into the lumen. Late luminal narrowing, defined as an increasing of percent diameter stenosis between the first and second follow-ups, was greater in segments with yellow plaque than in those without yellow plaque (18.4±17.3% versus 3.6±4.2%, respectively; P=0.011).

Conclusions— This angiographic and angioscopic study suggests that white neointima of the BMS may often change into yellow plaque over an extended period of time, and atherosclerotic progression inside the BMS may contribute to late luminal narrowing.

  F Han , K Takeda , M Ono , F Date , K Ishikawa , S Yokoyama , Y Shinozawa , K Furuyama and S. Shibahara

Heme oxygenase (HO) catalyzes oxidative breakdown of heme, and constitutes two isozymes, HO-1 and HO-2. Here, we explored the tissue-specific regulation of expression of HO-1 and HO-2 under hypoxemia. There was no significant change in the overall expression levels of HO-1 and HO-2 mRNAs and proteins in the lung during adaptation of C57BL/6 mice to normobaric hypoxia (10% O2). However, immunohistochemical analysis revealed the increased expression of HO-1 and HO-2 proteins after 28 days of normobaric hypoxia in the pulmonary venous myocardium that is the extension of the left atrial myocardium into pulmonary venous walls. Moreover, the expression of HO-2 protein was increased in the sub-endocardial myocardium of ventricles under hypoxia, while HO-1 protein level was increased in the full-thickness walls. Thus, hypoxemia induces expression of both HO-1 and HO-2 proteins in the myocardium. Using C57BL/6 mice lacking HO-2 (HO-2–/–), which manifest chronic hypoxemia, we also showed that the HO-1 protein level in the lung was similar between HO-2–/– mice and wild-type mice. Unexpectedly, HO-1 protein level was lower by 35% in the HO-2–/– mouse liver than the wild-type liver. These results indicate that the expression of HO-1 protein is regulated in a tissue-specific manner under hypoxemia.

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