Anacetrapib reduces progression of atherosclerosis, mainly by reducing non-HDL-cholesterol, improves lesion stability and adds to the beneficial effects of atorvastatin

The present study is the first intervention study in a well-established, translational mouse model for hyperlipidaemia and atherosclerosis showing that anacetrapib dose-dependently reduces atherosclerosis development and adds to the anti-atherogenic effects of atorvastatin. This effect is mainly ascribed to the reduction in non-HDL-C despite a remarkable increase in HDL-C and without affecting HDL functionality. In addition, anacetrapib improves lesion stabilit

Anacetrapib reduces progression of atherosclerosis, mainly by reducing non-HDL-cholesterol, improves lesion stability and adds to the beneficial effects of atorvastatin

BACKGROUND The residual risk that remains after statin treatment supports the addition of other LDL-C-lowering agents and has stimulated the search for secondary treatment targets. Epidemiological studies propose HDL-C as a possible candidate. Cholesteryl ester transfer protein (CETP) transfers cholesteryl esters from atheroprotective HDL to atherogenic (V)LDL. The CETP inhibitor anacetrapib decreases (V)LDL-C by ∼15-40% and increases HDL-C by ∼40-140% in clinical trials. We evaluated the effects of a broad dose range of anacetrapib on atherosclerosis and HDL function, and examined possible additive/synergistic effects of anacetrapib on top of atorvastatin in APOE*3Leiden.CETP mice. METHODS AND RESULTS Mice were fed a diet without or with ascending dosages of anacetrapib (0.03; 0.3; 3; 30 mg/kg/day), atorvastatin (2.4 mg/kg/day) alone or in combination with anacetrapib (0.3 mg/kg/day) for 21 weeks. Anacetrapib dose-dependently reduced CETP activity (-59 to -100%, P < 0.001), thereby decreasing non-HDL-C (-24 to -45%, P < 0.001) and increasing HDL-C (+30 to +86%, P < 0.001). Anacetrapib dose-dependently reduced the atherosclerotic lesion area (-41 to -92%, P < 0.01) and severity, increased plaque stability index and added to the effects of atorvastatin by further decreasing lesion size (-95%, P < 0.001) and severity. Analysis of covariance showed that both anacetrapib (P < 0.05) and non-HDL-C (P < 0.001), but not HDL-C (P = 0.76), independently determined lesion size. CONCLUSION Anacetrapib dose-dependently reduces atherosclerosis, and adds to the anti-atherogenic effects of atorvastatin, which is mainly ascribed to a reduction in non-HDL-C. In addition, anacetrapib improves lesion stability

Niacin Reduces Atherosclerosis Development in APOE*3Leiden.CETP Mice Mainly by Reducing NonHDL-Cholesterol

<div><p>Objective</p><p>Niacin potently lowers triglycerides, mildly decreases LDL-cholesterol, and largely increases HDL-cholesterol. Despite evidence for an atheroprotective effect of niacin from previous small clinical studies, the large outcome trials, AIM-HIGH and HPS2-THRIVE did not reveal additional beneficial effects of niacin (alone or in combination with laropiprant) on top of statin treatment. We aimed to address this apparent discrepancy by investigating the effects of niacin without and with simvastatin on atherosclerosis development and determine the underlying mechanisms, in APOE*3Leiden.CETP mice, a model for familial dysbetalipoproteinemia (FD).</p><p>Approach and Results</p><p>Mice were fed a western-type diet containing cholesterol without or with niacin (120 mg/kg/day), simvastatin (36 mg/kg/day) or their combination for 18 weeks. Similarly as in FD patients, niacin reduced total cholesterol by -39% and triglycerides by −50%, (both P<0.001). Simvastatin and the combination reduced total cholesterol (−30%; −55%, P<0.001) where the combination revealed a greater reduction compared to simvastatin (−36%, P<0.001). Niacin decreased total cholesterol and triglycerides primarily by increasing VLDL clearance. Niacin increased HDL-cholesterol (+28%, P<0.01) and mildly increased reverse cholesterol transport. All treatments reduced monocyte adhesion to the endothelium (−46%; −47%, P<0.01; −53%, P<0.001), atherosclerotic lesion area (−78%; −49%, P<0.01; −87%, P<0.001) and severity. Compared to simvastatin, the combination increased plaque stability index [(SMC+collagen)/macrophages] (3-fold, P<0.01). Niacin and the combination reduced T cells in the aortic root (−71%, P<0.01; −81%, P<0.001). Lesion area was strongly predicted by nonHDL-cholesterol (R² = 0.69, P<0.001) and to a much lesser extent by HDL-cholesterol (R² = 0.20, P<0.001).</p><p>Conclusion</p><p>Niacin decreases atherosclerosis development mainly by reducing nonHDL-cholesterol with modest HDL-cholesterol-raising and additional anti-inflammatory effects. The additive effect of niacin on top of simvastatin is mostly dependent on its nonHDL-cholesterol-lowering capacities. These data suggest that clinical beneficial effects of niacin are largely dependent on its ability to lower LDL-cholesterol on top of concomitant lipid-lowering therapy.</p></div

Effect of niacin on VLDL production and clearance.

<p>To determine VLDL production, mice were injected with Trans³⁵S label and tyloxapol and the accumulation of TG in plasma (A) and the production rate of VLDL-TG and apoB, as well as VLDL lipidation, defined as the ratio of VLDL-TG/apoB, were determined (B). To determine VLDL clearance, mice were injected with glycerol tri[³H]oleate- and [¹⁴C]cholesteryl oleate-labeled VLDL-like emulsion particles. Plasma ³H-activity was determined as percentage of the initial dose (C), and uptake of ³H-activity by various organs was determined as percentage of the injected dose per gram wet tissue (D). (BAT, brown adipose tissue; gonWAT, gonadal white adipose tissue; subWAT, subcutaneous white adipose tissue; visWAT, visceral white adipose tissue; values are means ± SD; n = 6 per group for VLDL production and n = 3–5 per group for VLDL clearance; *P<0.05 as compared to control).</p

The effect of niacin, simvastatin and their combination on plasma CETP activity after 4 and 18 weeks of treatment, as well as plasma CETP mass and hepatic CETP expression after 18 weeks of treatment.

<p>CETP, cholesteryl ester transfer protein; Simva, simvastatin. Values are means ± SD (n = 15 per group for plasma CETP activity and mass and n = 6–8 per group for hepatic CETP expression). **P<0.01 and ***P<0.001 as compared to control.</p

Effect of niacin, simvastatin and their combination on plasma lipid levels.

<p>Plasma total cholesterol (A), triglycerides (B) and HDL-cholesterol levels were measured at various time points throughout the study. The average HDL-cholesterol levels were calculated for all the treatment groups (C). Lipoproteins were separated by FPLC and cholesterol was measured in the fractions after 18 weeks of treatment (D). (Simva, simvastatin; values are means ± SD; n = 15 per group; **P<0.01 and ***P<0.001 as compared to control; ^#P<0.05 and ^###P<0.001 as compared to niacin+simvastatin).</p

Effect of niacin, simvastatin and their combination on lesion composition.

<p>Macrophage area (A) and SMC area (B) were determined for all lesions and calculated per cross section. To correct for lesion size, macrophage content (C), SMC content (D), as well as plaque stability index (ratio of collagen and SMC content to macrophage content) (E) were also calculated as a percentage of lesion area, specifically in severe lesions (Type IV–V). (Simva, simvastatin; SMC, smooth muscle cells; values are means ± SD; n = 15 per group; *P<0.05, **P<0.01 and ***P<0.001 as compared to control; ^#P<0.05, and ^###P<0.001 as compared to niacin+simvastatin).</p

Effect of niacin, simvastatin and their combination on monocyte adhesion and T cell number.

<p>The number of monocytes adhering to the endothelium (A) and the number of T cells in the aortic root area (B) were determined per cross section. (Simva, simvastatin; values are means ± SD; n = 15 per group; **P<0.01; ***P<0.001 as compared to control; ^###P<0.001 as compared to niacin+simvastatin).</p

Effect of niacin, simvastatin and their combination on plaque morphology.

<p>Representative images of hematoxylin-phloxine-saffron-stained atherosclerotic lesions in a cross section of the aortic root area for the control group (A), niacin group (B), simvastatin group (C) and the combination group (D) after 18 weeks of treatment.</p

Effect of niacin, simvastatin and their combination on atherosclerosis development in aortic root area.

<p>After 18 weeks of treatment, number of lesions (A), lesion severity (B), percentage undiseased segments (C) and total lesion area (D) were determined per cross section. Lesion severity was classified as mild (type I–III) and severe (type IV–V) lesions. (Simva, simvastatin; values are means ± SD; n = 15 per group; **P<0.01 and ***P<0.001 as compared to control; ^##P<0.01 as compared to niacin+simvastatin).</p