Increasing High-Density Lipoprotein Cholesterol in Dyslipidemia by Cholesteryl Ester Transfer Protein Inhibition

Abstract

Abstract-Reduced HDL cholesterol may be a risk factor comparable in importance to increased LDL cholesterol.Interventions that raise HDL are antiatherosclerotic, presumably through acceleration of reverse cholesterol transport and by antioxidant and antiinflammatory effects. In the hypercholesterolemic rabbit, HDL levels can be increased by Ͼ50% by inhibition of cholesteryl ester transfer protein (CETP), a molecule that plays a central role in HDL metabolism. This HDL-raising effect is antiatherosclerotic in moderately severe hyperlipidemia but appears to be ineffective in the presence of severe hypertriglyceridemia. In humans, mutations resulting in CETP inhibition have been associated with both reduced and increased risk of atherosclerosis. Proposed explanations for these apparently disparate observations are that the antiatherosclerotic effect of CETP inhibition varies with either the metabolic milieu or the degree of CETP inhibition. We now have pharmacological inhibitors of CETP that are capable of increasing HDL by as much as 50% to 100% in humans. The importance of this development is that reduced HDL is a risk factor independent of LDL and that these new agents alter HDL by a magnitude comparable to that of statins on LDL. Clinical trials, now beginning, will need to identify the patient subsets in which CETP inhibition may be more or less effective. Key Words: atherosclerosis Ⅲ cholesterol Ⅲ lipids Ⅲ metabolism Ⅲ statins A lthough lipid-lowering therapies now have the capability of reducing LDL cholesterol to levels recommended by the National Cholesterol Education Program (NCEP) guidelines in as many as 90% of treated patients, 1 the rate of cardiovascular events is reduced by only 20% to 35% in large, randomized trials. These data suggest that the LDL target set by NCEP guidelines may be too high. 1-5 Indeed, among patients with acute myocardial infarction, Ϸ15% have LDL levels Ͻ100 mg/dL on presentation.A complementary hypothesis is that there is a finite limit to the benefit of LDL lowering and that other non-LDL lipid risk factors must be managed for optimal outcomes. Indeed, epidemiological studies suggest that low HDL cholesterol may be a risk factor comparable in importance to high LDL and that the 2 risk factors are independent (Figure 1). 6,7 Although the mechanism by which HDL reduces the development of atherosclerosis has not been defined with certainty, acceleration of reverse cholesterol transport, antioxidant activity, and antiinflammatory action are likely to play central roles. 8 -10 In contrast to the ability of potent statins to reduce the level of LDL by Ͼ50%, however, no currently approved therapy increases HDL by a comparable magnitude. The most potent, currently available HDL-raising therapy is nicotinic acid. This therapy also has a multitude of other antiatherosclerotic effects on the levels of LDL and triglycerides, lipid oxidation, and endothelial function. 11 Combination therapy with a statin has been reported to increase HDL levels by Ϸ30% 12 and to decrease cardiac events...

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