The metabolism and anti-atherogenic properties of HDL

OBJECTIVE - The role of cholesteryl ester transfer protein (CETP) in the development of atherosclerosis is still undergoing debate. Therefore, we evaluated the effect of human CETP expression on atherosclerosis in APOE*3-Leiden (E3L) mice with a humanized lipoprotein profile. METHODS AND RESULTS - E3L mice were crossbred with human CETP transgenic mice. On a chow diet, CETP expression increased plasma total cholesterol (TC) (+43%; P<0.05). To evaluate the effects of CETP on the development of atherosclerosis, mice were fed a Western-type diet containing 0.25% cholesterol, leading to 4.3-fold elevated TC levels in both E3L and CETP.E3L mice (P<0.01). On both diets, CETP expression shifted the distribution of cholesterol from high-density lipoprotein (HDL) toward very-low-density lipoprotein (VLDL)/low-density lipoprotein (LDL). Moreover, plasma of CETP.E3L mice had reduced capacity (-39%; P<0.05) to induce SR-BI-mediated cholesterol efflux from Fu5AH cells than plasma of E3L mice. After 19 weeks on the Western-type diet, CETP.E3L mice showed a 7.0-fold increased atherosclerotic lesion area in the aortic root compared with E3L mice (P<0.0001). CONCLUSIONS - CETP expression in E3L mice shifts the distribution of cholesterol from HDL to VLDL/LDL, reduces plasma-mediated SR-BI-dependent cholesterol efflux, and represents a clear pro-atherogenic factor in E3L mice. We anticipate that the CETP.E3L mouse will be a valuable model for the preclinical evaluation of HDL-raising interventions on atherosclerosis development. © 2006 American Heart Association, Inc. Chemicals / CAS: cholesterol, 57-88-5; Antigens, CD36; apolipoprotein E3 (Leidein); Apolipoprotein E3; Apolipoproteins E; Carrier Proteins; CETP protein, human; Cholesterol Ester Transfer Proteins; Cholesterol, 57-88-5; Glycoproteins; Lipids; Lipoproteins; Lipoproteins, HDL

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Cholesteryl Ester Transfer Protein Decreases High-Density Lipoprotein and Severely Aggravates Atherosclerosis in APOE*3-Leiden Mice

Background—Despite favorable effects on high-density lipoprotein cholesterol (HDL-C) and low-density lipoprotein cholesterol, the cholesteryl ester transfer protein inhibitor torcetrapib failed to slow atherosclerosis progression and increased mortality. We investigated the relationship between lipid changes and progression of coronary atherosclerosis. Methods and Results—Intravascular ultrasound was performed at baseline and follow-up in 910 participants randomized to torcetrapib/atorvastatin or atorvastatin monotherapy. The relationship between changes in lipoprotein levels and the primary intravascular ultrasound end point, change in percent atheroma volume, was investigated. Compared with atorvastatin monotherapy, torcetrapib raised HDL-C by 61%, lowered low-density lipoprotein cholesterol by 20%, raised serum sodium (0.44±0.14 mmol/L, P=0.02), and lowered serum potassium (0.11±0.02 mmol/L, P<0.0001). Despite substantial increases in HDL-C, no effect was found of torcetrapib on percent atheroma volume...

Cholesteryl ester transfer protein inhibition, high-density lipoprotein raising, and progression of coronary atherosclerosis: insights from ILLUSTRATE (Investigation of Lipid Level Management Using Coronary Ultrasound to Assess Reduction of Atherosclerosis by CETP Inhibition and HDL Elevation).

Protein glycosylation affects nearly all molecular interactions at the cell surface and in the intercellular space. Many of the physiological variations which are part of homeostatic mechanisms influence glycosylation. However, a comprehensive overview of changes in glycosylation caused by aging and common lifestyle parameters is still lacking. After analyzing N-glycans in the plasma of 1914 individuals from the Croatian islands of Vis and Korcula, we performed a comprehensive analysis of the dependence of different glycosylation features (position of fucose, level of galactosylation, sialylation and branching) on aging, smoking, body fat and plasma lipid status. A number of statistically significant associations were observed. Glycosylation changes with aging were especially evident in females, mostly in association with the transition from pre-menopausal to post-menopausal age. Levels of core-fucosylated, non-galactosylated, digalactosylated and disialylated biantennary glycans were shown to be mainly age dependent, but the level of branching and higher levels of galactosylation were found to correlate with lipid status. For the majority of glycans which we analyzed, all examined parameters explained up to 5% of the variance. The only notable exception were non-galactosylated glycans where 20% of the variance was explained mostly by age and blood pressure. In general, only a small fraction of the variability in glycan levels observed in a population was explained by age and other measured parameters, indicating that even in the absence of a genetic template, glycan levels are mostly determined by genetic background and/or specific pathophysiological processes.

Effects of aging, body mass index, plasma lipid profiles, and smoking on human plasma N-glycans.

The effect of individual N-glycans on enzyme activity.

Objective— Inhibitors of cholesteryl ester transfer protein (CETP) have been developed as potential anti-atherogenic agents. Theoretically, however, they may be pro-atherogenic by blocking one of the pathways for removing high-density lipoprotein (HDL) cholesteryl esters (CE) from plasma in the final step of reverse cholesterol transport. Here we describe how CETP inhibition in rabbits impacts on the kinetics of HDL CE transport in plasma. Methods and Results— Administration of a CETP inhibitor reduced CETP activity by 80% to 90% and doubled the HDL cholesteryl ester concentration. Multi-compartmental analysis was used to determine HDL CE kinetics in CETP-inhibited and control rabbits after injection of tracer amounts of both native and reconstituted HDL labeled with 3H in the CE moiety. In control rabbits, HDL CE was removed from plasma by both a direct pathway and an indirect pathway after transfer of HDL CE to the very-low-density lipoprotein/low-density lipoprotein fraction. In CETP-inhibited rabbits ...

Effect of inhibiting cholesteryl ester transfer protein on the kinetics of high-density lipoprotein cholesteryl ester transport in plasma: in vivo studies in rabbits.

N-Glycosylation regulates endothelial lipase-mediated phospholipid hydrolysis in apoE- and apoA-I-containing high density lipoproteins.

Endothelial lipase (EL) is a newly identified member of the triglyceride lipase gene family that hydrolyzes high-density lipoprotein (HDL) phospholipids. This study investigates the ability of the major apolipoproteins ofrHDL to regulate the kinetics of EL-mediated phospholipid hydrolysis in well-characterized, homogeneous preparations of spherical rHDL. The rHDL contained either apoA-I as the only apolipoprotein, (A-I)rHDL, apoA-II as the only apolipoprotein, (A-II)rHDL, or apoA-I as well as apoA-II, (A-I/A-II)rHDL. The rHDL were comparable in terms of size and lipid composition and contained cholesteryl esters (CE) as their sole core lipid. Phospholipid hydrolysis was quantitated as the mass of nonesterified fatty acids (NEFA) released from the rHDL during incubation with EL. The V m a x of phospholipid hydrolysis for (A-I/A-II)rHDL [391.9 ′ 12.9 nmol of NEFA formed (mL of EL) - 1 h - 1 ] was greater than (A-I)rHDL [152.8 ′ 4.7 nmol of NEFA formed (mL of EL) - 1 h - 1 ]. The energy of activation (E a ) for the hydrolysis reactions was calculated to be 52.1 and 34.8 kJ mol - 1 for (A-I)rHDL and (A-I/A-II)rHDL, respectively. Minimal phospholipid hydrolysis was observed for the (A-II)rHDL. Kinetic analysis showed that EL has a higher affinity for the phospholipids in (A-I)rHDL [K m (app) = 0.10 ′ 0.01 mM] than in (A-I/A-II)rHDL [K m (app) = 0.27 ′ 0.03 mM]. Furthermore, (A-I)rHDL is a competitive inhibitor of the EL-mediated phospholipid hydrolysis of (A-I/A-II)rHDL. These results establish that apolipoproteins are major determinants of the kinetics of EL-mediated phospholipid hydrolysis in rHDL.

Daniela Caiazza

Papers

Effect of inhibiting cholesteryl ester transfer protein on the kinetics of high-density lipoprotein cholesteryl ester transport in plasma: in vivo studies in rabbits.

N-Glycosylation regulates endothelial lipase-mediated phospholipid hydrolysis in apoE- and apoA-I-containing high density lipoproteins.

Apolipoproteins regulate the kinetics of endothelial lipase-mediated hydrolysis of phospholipids in reconstituted high-density lipoproteins.