Long-term treatment with pitavastatin (NK-104), a new HMG-CoA reductase inhibitor, of patients with heterozygous familial hypercholesterolemia

Pitavastatin Downregulates Expression of the Macrophage Type B Scavenger Receptor, CD36

Background— Pitavastatin (NK-104) is a novel inhibitor of 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase, the rate-limiting enzyme for cholesterol biosynthesis. In clinical trials, pitavastatin has been shown to significantly decrease serum LDL cholesterol and triglyceride levels and increase HDL cholesterol. Scavenger receptor-mediated accumulation of oxidized LDL (OxLDL)-derived cholesteryl ester is considered to be a critical step in the development of atherosclerotic foam cell formation. We studied the effect of pitavastatin on CD36 (a class B scavenger receptor) expression by murine macrophages.

Methods and Results— Treatment of J774 cells and murine peritoneal macrophages with pitavastatin decreased CD36 mRNA expression in a dose-dependent manner. Decreased CD36 mRNA was associated with decreased CD36 cell surface protein expression in human THP-1 cells and human monocyte-derived macrophages. Pitavastatin also reduced the increase in CD36 mRNA, cell surface protein, and binding/uptake of OxLDL induced by peroxisome proliferator-activated receptor-γ (PPARγ) ligands and/or OxLDL. Pitavastatin did not alter the half-life of CD36 mRNA, which suggests pitavastatin downregulates CD36 expression by reducing CD36 transcription. In addition, pitavastatin significantly decreased PPARγ mRNA and protein expression. Finally, pitavastatin increased p44/42 mitogen-activated protein kinase activity and PPARγ phosphorylation and increased the ratio of phosphorylated PPARγ to nonphosphorylated PPARγ.

Conclusions— The present data demonstrate that pitavastatin prevents OxLDL uptake by macrophages through PPARγ-dependent inhibition of CD36 expression and suggest that pitavastatin could modulate CD36-mediated atherosclerotic foam cell formation.

Pitavastatin, a Potent Hydroxymethylglutaryl Coenzyme a Reductase Inhibitor, Increases Cholesterol 7 .ALPHA.-Hydroxylase Gene Expression in HepG2 Cells

BACKGROUND

The effect of pitavastatin on the mRNA levels of apolipoprotein (apo) A-I, peroxisome proliferator-activated receptor alpha (PPARalpha), cholesterol 7alpha-hydroxylase (CYP7A1), and farnesoid X receptor (FXR) in HepG2 cells was examined to establish whether pitavastatin affects bile acid synthesis and if so, to determine a possible molecular mechanism.

METHODS AND RESULTS

HepG2 cells were cultured in serum-free Dulbecco's modified Eagle medium for 18 h before drug treatment. Total RNA was extracted at set times and mRNA levels were quantified by reverse transcription-real time polymerase chain reaction. Pitavastatin at 0.1, 1, 5, and 10 micromol/L increased the mRNA levels of apo A-I, PPARalpha, CYP7A1, and FXR in a dose-dependent manner. The mRNA levels of apo A-I, PPAR alpha, CYP7A1, and FXR similarly increased with increasing doses of pitavastatin. Coincubation of mevalonate (4 mmol/L) with pitavastatin (5 micromol/L) reversed the inductive effects of pitavastatin on the mRNA levels of these genes, indicating that the inductive effects of pitavastatin were related to its inhibition of HMG-CoA reductase.

CONCLUSIONS

Pitavastatin increased the mRNA levels of CYP7A1 in HepG2 cells, suggesting that increased conversion of cholesterol to bile acids may be the mechanism for its potent low-density lipoprotein cholesterol-lowering effects.

Pitavastatin ameliorates severe hepatic steatosis in aromatase-deficient (Ar-/-) mice

Tamoxifen is a potent antagonist of estrogen, and hepatic steatosis is a frequent complication in adjuvant tamoxifen for breast cancer. Impaired hepatic FA beta-oxidation in peroxisomes, microsomes, and mitochondria results in progression of massive hepatic steatosis in estrogen deficiency. This impairment, although latent, is potentially serious: About 3% of the general population in the United States is now suffering from nonalcoholic steatohepatitis associated with obesity and hyperlipidemia. Therefore, in the present study we tried to restore impaired hepatic FA beta-oxidation by administering a novel statin, pitavastatin, to aromatase-deficient (Ar-/-) mice defective in intrinsic estrogen synthesis. Northern blot analysis of Ar-/- mice liver revealed a significant restoration of mRNA expression of essential enzymes involved in FA beta-oxidation such as very long fatty acyl-CoA synthetase in peroxisome, peroxisomal fatty acyl-CoA oxidase, and medium-chain acyl-CoA dehydrogenase. Severe hepatic steatosis observed in Ar-/- mice substantially regressed. Consistent findings were obtained in the in vitro assays of FA beta-oxidation activity. These findings demonstrate that pitavastatin is capable of restoring impaired FA beta-oxidation in vivo via the peroxisome proliferator-activated receptor-alpha-mediated signaling pathway and is potent enough to ameliorate severe hepatic steatosis in mice deficient in intrinsic estrogen.

The power of statins: aggressive lipid lowering

A large body of evidence has demonstrated that reductions in low-density lipoprotein cholesterol (LDL-C) decrease the risk of coronary heart disease (CHD) and related adverse events. The greatest reductions in morbidity and mortality are attained in higher-risk patients, suggesting that targeting this group can maximize the cost-effectiveness of statins, since fewer patients need to be treated to prevent one event. High-risk individuals (those with preexisting CHD or CHD risk equivalents) require aggressive lipid lowering to achieve the stringent LDL-C goal levels established by the third report of the National Cholesterol Education Program Adult Treatment Panel (NCEP ATP III). The hydroxymethylglutaryl coenzyme A (HMG-CoA) reductase inhibitors, or statins, have assumed the central role in this setting because of their superior ability to reduce LDL-C across the spectrum of CHD risk. Rosuvastatin, a new agent in this class, reduces LDL-C to a significantly greater degree than atorvastatin, pravastatin, or simvastatin. The more aggressive goals put forward since ATP I (1987) have heightened interest in more efficacious statins. As a result, simvastatin, atorvastatin, and now rosuvastatin have been developed, adding sequentially greater LDL-C-reducing capacity for the physician. Substantially more patients, particularly high-risk patients, are thereby able to achieve NCEP ATP III target LDL-C levels with rosuvastatin. Other cholesterol-lowering drugs (bile acid sequestrants, niacin, plant stanols, and fibrates) are much less effective at lowering LDL-C and are much less well tolerated but may be useful when combined with statins. A novel class of agents, cholesterol transport inhibitors, have recently become available. These and other new agents hold promise to help achieve ATP III goals when used in combination regimens initiated with a statin.

Treating hypercholesterolemia: looking forward

Despite important advances in the management of hypercholesterolemia in recent decades, many patients with lipid disorders remain unidentified or undertreated and so continue to have unfavorable levels of low-density lipoprotein (LDL) cholesterol and an increased risk for coronary events. The statins--which inhibit 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase, the rate-limiting enzyme in cholesterol biosynthesis--have proved to be the most powerful pharmacologic agents for lowering serum lipids, and newer statins offer even greater efficacy than the agents introduced 10 to 15 years ago. Studies have shown that rosuvastatin, in late-stage development, is a very potent agent for the treatment of primary hypercholesterolemia, and that relatively low doses decrease LDL cholesterol levels to a greater extent than do similar doses of pravastatin, simvastatin, or atorvastatin as evaluated in separate clinical trials. Pitavastatin, in phase II trials, also has promise as a more potent drug than currently available statins. Because neither of these drugs has been approved for use in the United States, clinical trial results should be considered preliminary. In the future, agents that combine the actions of statins and nicotinic acid may achieve still greater LDL cholesterol reductions. Drugs that lower lipids via mechanisms other than inhibition of HMG-CoA reductase also offer promise. The newest addition to the roster of lipid-regulating agents is ezetimibe, a cholesterol absorption inhibitor that has been approved for use either alone or in combination with a statin. Agents in development include bile acid transport inhibitors and inhibitors of acyl CoA:cholesterol acyltransferase. More research will be needed to determine the full clinical potential of such approaches to the management of hypercholesterolemia.

Management of dyslipidemia in the high-risk patient

Lipid-lowering agents have been shown to reduce morbidity and mortality associated with coronary heart disease (CHD), particularly in high-risk patients. The identification and treatment of these patients should therefore be a high priority for clinicians. Guidelines from medical organizations, such as the National Cholesterol Education Program Adult Treatment Panel (NCEP ATP) and the American Diabetes Association (ADA), suggest that patients with low-density lipoprotein cholesterol (LDL-C) levels > or =130 mg/dL, and perhaps even those with levels > or =100 mg/dL, should receive drug therapy. Optimal LDL-C levels have been set at <100 mg/dL and <115 mg/dL for high-risk patients by US and European guidelines, respectively. However, a recent survey shows that only about 20% of high-risk patients currently meet these goals. In order to achieve therapeutic targets for LDL-C, the statins are the foundation of treatment, as they are the most effective and best-tolerated form of lipid-lowering therapy. Other therapeutic options include bile acid sequestrants, niacin, and plant stanols, although seldom as monotherapy. Combination therapy with a statin and one of these other lipid-lowering agents can be useful in patients who are unable to achieve target lipid levels through monotherapy. There remains, however, a need for additional agents. Some of the new options for reducing LDL-C levels that may be available in the near future include 2 new statins, pitavastatin and rosuvastatin. In patients with heterozygous familial hypercholesterolemia, rosuvastatin, which is currently under review by the Food and Drug Administration (FDA), has been shown to produce significantly greater reductions in LDL-C than atorvastatin over its full dose range. In comparative clinical trials, it has also enabled more patients with primary hypercholesterolemia to meet lipid goals than atorvastatin, simvastatin, and pravastatin. Inhibitors of bile acid transport or cholesterol absorption may also have therapeutic value. The first cholesterol absorption inhibitor, ezetimibe, which has just been approved by the FDA, appears to be most effective when combined with a statin. It is anticipated that such new options will allow clinicians to optimize the management of dyslipidemia in high-risk patients, thereby reducing the morbidity and mortality of CHD.