Protective effects of a squalene synthase inhibitor, lapaquistat acetate (TAK-475), on statin-induced myotoxicity in guinea pigs
Introduction
According to many epidemiological studies, including the Framingham Heart Study, an elevated plasma level of low-density lipoprotein (LDL) cholesterol is a significant risk factor for coronary heart disease (Gordon et al., 1981, Anderson et al., 1987). Various cholesterol-lowering drugs with different action mechanisms have been developed and used for the treatment of patients with hypercholesterolemia. Among them, 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase inhibitors, known as statins, are the most common cholesterol-lowering drugs. Many clinical studies have revealed that cholesterol-lowering therapy with statins significantly reduces coronary heart disease risk (Scandinavian Simvastatin Survival Study Group, 1994, Sacks et al., 1996, Downs et al., 1998). Recently, clinical studies have suggested that aggressive cholesterol-lowering therapy produces more benefits than mild therapy (Heart Protection Study Collaborative Group, 2002, Cannon et al., 2004, Nissen et al., 2004). More effective cholesterol-lowering therapy is required in the clinical setting; however, high-dose statins, albeit rarely, increase the risk of toxicity such as myotoxicity (Illingworth et al., 2001, Brewer, 2003). This toxicity is thought to result from the reduction of isoprenylated metabolites such as ubiquinones, dolichols or isoprenylated proteins in tissues (Thibault et al., 1996, Flint et al., 1997b, Bliznakov, 2002), but the precise mechanism of statin-induced myotoxicity remains unclear. Recently, we discovered a novel squalene synthase inhibitor, lapaquistat acetate (hereafter abbreviated to lapaquistat) called as TAK-475(1-[[(3R,5S)-1-(3-acetoxy-2,2-dimethylpropyl)-7-chloro-5-(2,3-dimethoxyphenyl)-2-oxo-1,2,3,5-tetrahydro-4,1-benzoxazepin-3-yl]acetyl]piperidin-4-yl)acetic acid) previously, which lowered plasma cholesterol levels in various animals (Amano et al., 2003, Nishimoto et al., 2003b) and humans (Perez et al., 2006, Piper et al., 2006). Squalene synthase catalyzes the conversion of farnesyl diphosphate to squalene in the cholesterol biosynthetic pathway. Since farnesyl diphosphate is a precursor of isoprenylated metabolites (Fig. 1), they may be increased by lapaquistat. Thus, the combination of lapaquistat with statins is expected to prevent the decrease in isoprenylated metabolites by statins, which may reduce the frequency of statin-induced myopathy. In our previous work, T-91485, a pharmacologically active metabolite of lapaquistat exhibited very little cytotoxicity in human skeletal myocytes. In addition, treatment with this compound attenuated statin-induced cytotoxicity (Nishimoto et al., 2003a). In the present study, we examined the effects of squalene synthase inhibition on statin-induced myotoxicity in in vivo models. Guinea pigs are a particularly useful model for studying the lipid-lowering drugs because of their similarities to humans in terms of hepatic cholesterol and lipoprotein metabolism (Fernandez, 2001, West and Fernandez, 2004). We report that lapaquistat offered near complete protection from cerivastatin-induced myotoxicity in guinea pigs.
Section snippets
Materials
Lapaquistat was synthesized by Takeda Pharmaceutical Company Limited (Osaka, Japan). dl-Mevalonolactone was purchased from Sigma Chemical Co. (St. Louis, MO, U.S.A.). Cerivastatin was purchased from Sequoia Research Products (Oxford, U.K.). Other chemicals were purchased from Wako Pure Chemical Industries (Osaka, Japan).
Animals
Male guinea pigs (Hartley strain, std grade) were purchased from Japan SLC Inc. (Shizuoka, Japan). They were fed a chow diet (Labo G diet; Nippon Nosan, Kanagawa, Japan) and
Protective effects of lapaquistat on cerivastatin-induced myotoxicity
In our preliminary studies, CEV (0.5 and 2 mg/kg) lowered plasma cholesterol levels by 40% and 61% and increased plasma CK levels to 10- and 32-fold, respectively, while lapaquistat (30 and 100 mg/kg) lowered plasma cholesterol level by 31% and 53%, respectively, without increasing plasma CK levels (− 29% and − 25% compared to control, respectively). In the current study, cerivastatin (1 mg/kg) alone decreased plasma cholesterol level by 45% and increased plasma CK level, a marker of myotoxicity,
Discussion
Many clinical studies have supported that aggressive cholesterol-lowering therapy produces more benefits than mild therapy; however, high-dose statins increase the risk of toxicity such as myotoxicity (Illingworth et al., 2001, Brewer, 2003). Indeed, one statin, cerivastatin, was withdrawn from the world market due to the high frequency of myotoxicity. In the present study, we showed that high dose cerivastatin-induced myotoxicity in guinea pigs. Interestingly, lapaquistat remarkably prevented
Acknowledgments
We thank Drs. Yoshimi Imura, Hideaki Nagaya and Takeo Wada in our laboratories for their continuous advice on completing this manuscript. We thank Dr. Masanori Yoshida from Takeda Analytical Research Laboratories, Ltd. for the determination of the plasma concentration of cerivastatin. We also thank Dr. William R. Lagor in the University of Pennsylvania School of Medicine for his valuable advice on revising this manuscript.
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The authors contributed equally to this work.