Background-Cholesteryl ester transfer protein (CETP) mediates the transfer of neutral lipids between lipoproteins. High plasma levels of CETP are correlated with low HDL cholesterol levels, a strong risk factor for coronary artery disease. In earlier studies, JTT-705, a novel CETP inhibitor, was shown to increase plasma HDL cholesterol and to inhibit the progression of atherosclerosis in cholesterol-fed rabbits. This study describes the first results using this CETP inhibitor in humans. Methods and Results-In a randomized, double-blind, and placebo-controlled trial, we evaluated the efficacy and safety of daily treatment with 300, 600, and 900 mg JTT-705 in 198 healthy subjects with mild hyperlipidemia. Treatment with 900 mg JTT-705 for 4 weeks led to a 37% decrease in CETP activity (PϽ0.0001), a 34% increase in HDL cholesterol (PϽ0.0001), and a 7% decrease in LDL cholesterol (Pϭ0.017), whereas levels of triglycerides, phospholipid transfer protein, and lecithin-cholesterol acyltransferase were unaffected. In line with the increase of total HDL, a rise of HDL 2, HDL 3 , and apolipoprotein A-I was also noted. JTT-705 showed no toxicity with regard to physical examination and routine laboratory tests. Conclusions-We show that the use of the CETP inhibitor JTT-705 in humans is an effective means to raise HDL cholesterol levels with minor gastrointestinal side effects (Pϭ0.06). Although these results hold promise, further studies are needed to investigate whether the observed increase in HDL cholesterol translates into a concomitant reduction in coronary artery disease risk.

A delayed clearance of postprandial lipoproteins from the plasma may play a role in the etiology of premature coronary atherosclerosis. To address this hypothesis, we studied chylomicron (remnant) metabolism in two groups of 20 selected normolipidemic men aged 35-65 years, a group of coronary artery disease (CAD) patients, and a matched control group with documented minimal coronary atherosclerosis. Subjects received an oral fat load supplemented with cholesterol and retinyl palmitate. Plasma samples obtained during the next 24-hour period were analyzed for total as well as d less than 1.019 g/ml and d greater than 1.019 g/ml triacylglycerol, cholesterol, and retinyl ester concentrations. Although both groups of patients responded identically in terms of the appearance of gut-derived lipids in the plasma, CAD patients showed a marked delay in the clearance of retinyl esters as well as in the normalization of plasma triacylglycerol concentrations. Postheparin plasma hepatic lipase activity was significantly lower in the CAD group. Apolipoprotein E phenotype measurements did not reveal marked differences in frequency between both groups. The frequency distribution was not unusual in comparison with the normal Dutch population. The magnitude of the postprandial responses of triacylglycerol and retinyl esters was correlated positively with the fasting levels of plasma triacylglycerol and negatively with high density lipoprotein subfraction 2 cholesterol concentrations. These data indicate that the clearance of postprandial lipoproteins in normolipidemic CAD patients as selected in the present study is delayed as compared with that of controls without coronary atherosclerosis and suggest that postprandial lipoproteins may play a role in the etiology of their disease.

Abstract-Plasma phospholipid transfer protein (PLTP) transfers phospholipids between lipoprotein particles and alters high density lipoprotein (HDL) subfraction patterns in vitro, but its physiological function is poorly understood. Transgenic mice that overexpress human PLTP were generated. Compared with wild-type mice, these mice show a 2.5-to 4.5-fold increase in PLTP activity in plasma. This results in a 30% to 40% decrease of plasma levels of HDL cholesterol. Incubation of plasma from transgenic animals at 37°C reveals a 2-to 3-fold increase in the formation of pre-␤-HDL compared with plasma from wild-type mice. Although pre-␤-HDL is normally a minor subfraction of HDL, it is known to be a very efficient acceptor of peripheral cell cholesterol and a key mediator in reverse cholesterol transport. Further experiments show that plasma from transgenic animals is much more efficient in preventing the accumulation of intracellular cholesterol in macrophages than plasma from wild-type mice, despite lower total HDL concentrations. It is concluded that PLTP can act as an antiatherogenic factor preventing cellular cholesterol overload by generation of pre-␤-HDL.

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Abstract-Plasma cholesteryl ester transfer protein (CETP) facilitates intravascular lipoprotein remodeling by promoting the heteroexchange of neutral lipids. To determine whether the degree of triglyceridemia may influence the CETP-mediated redistribution of HDL CE between atherogenic plasma lipoprotein particles in type 2 diabetes, we evaluated CE mass transfer from HDL to apoB-containing lipoprotein acceptors in the plasma of type 2 diabetes subjects (nϭ38). In parallel, we investigated the potential relationship between CE transfer and the appearance of an atherogenic dense LDL profile. The diabetic population was divided into 3 subgroups according to fasting plasma triglyceride (TG) levels: group 1 (G1), TGϽ100 mg/dL; group 2 (G2), 100ϽTGϽ200 mg/dL; and group 3 (G3), TGϾ200 mg/dL. Type 2 diabetes patients displayed an asymmetrical LDL profile in which the dense LDL subfractions predominated. Plasma levels of dense LDL subfractions were strongly positively correlated with those of plasma triglyceride (TG) (rϭ0.471; Pϭ0.0003). The rate of CE mass transfer from HDL to apoB-containing lipoproteins was significantly enhanced in G3 compared with G2 or G1 (46.2Ϯ8.1, 33.6Ϯ5.3, and 28.2Ϯ2.7 g CE transferred ⅐ h Ϫ1 ⅐ mL Ϫ1 in G3, G2, and G1, respectively; PϽ0.0001 G3 versus G1, Pϭ0.0001 G2 versus G1, and Pϭ0.02 G2 versus G3). The relative capacities of VLDL and LDL to act as acceptors of CE from HDL were distinct between type 2 diabetes subgroups. LDL particles represented the preferential CE acceptor in G1 and accounted for 74% of total CE transferred from HDL. By contrast, in G2 and G3, TG-rich lipoprotein subfractions accounted for 47% and 72% of total CE transferred from HDL, respectively. Moreover, the relative proportion of CE transferred from HDL to VLDL 1 in type 2 diabetes patients increased progressively with increase in plasma TG levels. The VLDL 1 subfraction accounted for 34%, 43%, and 52% of total CE transferred from HDL to TG-rich lipoproteins in patients from G1, G2, and G3, respectively. Finally, dense LDL acquired an average of 45% of total CE transferred from HDL to LDL in type 2 diabetes patients. In conclusion, CETP contributes significantly to the formation of small dense LDL particles in type 2 diabetes by a preferential CE transfer from HDL to small dense LDL, as well as through an indirect mechanism involving an enhanced CE transfer from HDL to VLDL 1 , the specific precursors of small dense LDL particles in plasma. T he most common alterations in lipid and lipoprotein profile in type 2 diabetes involve an elevation in both postprandial and fasting plasma triglyceride (TG) and VLDL concentrations, a dense LDL phenotype, and low levels of HDL cholesterol. 1 Hypertriglyceridemia contributes significantly to the increased risk for premature cardiovascular disease in type 2 diabetes. 2 There is a strong positive correlation between plasma concentrations of TG and small dense LDL in nondiabetic subjects, suggesting that plasma TG concentrations influence LDL subclass distribution. 3 The particle si...

The mechanisms responsible for the decreased high density lipoprotein (HDL) cholesterol levels associated with obesity and insulin resistance are not well understood. Lecithin: cholesterol acyltransferase (LCAT) and cholesterol ester transfer protein (CETP) are key factors in the esterification of cholesterol in HDL and the subsequent transfer of cholesteryl ester towards apolipoprotein B-containing lipoproteins. Phospholipid transfer protein (PLTP) may be involved in the regulation of HDL particle size. We therefore measured the activities of LCAT, CETP and PLTP using exogenous substrate assays, as well as lipids, lipoproteins, insulin and C-peptide in fasting plasma from eight healthy obese men (body mass index > 27 kg m-2) and 24 non-obese subjects. The obese men had lower levels of HDL cholesterol (P < 0.05) and higher levels of plasma triglycerides (P < 0.05), insulin (P < 0.05) and C-peptide (P < 0.01), as compared to the quartile of subjects with the lowest body mass index (BMI < 22.4 kg m-2). CETP and PLTP activities were elevated in the obese men by 35% (P < 0.01) and by 15% (P < 0.05), respectively. LCAT activity was comparable among the quartiles. Linear regression analysis showed that CETP activity was positively correlated with body mass index (P < 0.02), fasting blood glucose (P < 0.05) and plasma C-peptide (P < 0.05). PLTP activity was positively related to body mass index (P < 0.01), waist to hip circumference ratio (P < 0.001), as well as to fasting blood glucose (P < 0.05) and plasma C-peptide (P < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

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Plasma phospholipid transfer protein (PLTP) is thought to be involved in the remodeling of high density lipoproteins (HDL), which are atheroprotective. It is also involved in the metabolism of very low density lipoproteins (VLDL). Hence, PLTP is thought to be an important factor in lipoprotein metabolism and the development of atherosclerosis. We have overexpressed PLTP in mice heterozygous for the low density lipoprotein (LDL) receptor, a model for atherosclerosis. We show that increased PLTP activity results in a dose-dependent decrease in HDL, and a moderate stimulation of VLDL secretion (<1.5-fold). The mice were given a high fat, high cholesterol diet, which resulted in hypercholesterolemia in all animals. HDL concentrations were dramatically reduced in PLTP-overexpressing animals when compared with LDL receptor controls, whereas VLDL ؉ LDL cholesterol levels were identical. Susceptibility to atherosclerosis was increased in a PLTP doseresponsive manner. We conclude that PLTP increases susceptibility to atherosclerosis by lowering HDL concentrations, and therefore we suggest that an increase in PLTP is a novel, long term risk factor for atherosclerosis in humans. High density lipoproteins (HDL)1 are believed to be protective against the development of atherosclerosis because they mediate reverse cholesterol transport, i.e. the transfer of cholesterol from peripheral tissues to the liver (1, 2). However, our understanding of the molecular details and key regulatory proteins involved is incomplete (3-5). One effector of this process is the ATP-binding cassette ABCA1, which is functionally deficient in Tangier disease (reviewed in Ref. 6). The high incidence of coronary artery disease in Tangier patients suggests an essential, protective role of HDL-mediated reverse cholesterol transport in the development of atherosclerosis (7).However, recent results suggest that the contribution of ABCA1 to overall reverse cholesterol transport and its role in atherogenesis are primarily related to its function in macrophages (8 -10). Therefore, other potential key proteins in reverse cholesterol transport are of interest, including PLTP (11-13).Previously, we generated transgenic mice overexpressing human PLTP and showed that plasma from these animals is more effective in preventing accumulation of cholesterol by cultured macrophages (14). We and others therefore suggested an antiatherogenic effect for PLTP (14 -16). On the other hand, overexpression of PLTP results in a decrease of plasma HDL levels (14, 17, 18), which could be an atherogenic effect. Thus, it is unclear whether the net effect of high PLTP activity levels would be atherogenic or anti-atherogenic. The complete absence of PLTP activity in PLTP knockout mice inhibits HDL maturation, which results in reduced levels of plasma HDL caused by accelerated decay (19,20). Still, PLTP knockout mice showed decreased atherosclerosis (21). This could be partly explained by the discovery of a novel, intracellular function of PLTP in hepatocytes; it was found that PLTP def...