CETP activity is not associated with carotid intima-media thickness in patients with poorly controlled type 2 diabetes.

AIM: The impact of cholesteryl ester transfer protein (CETP) on atherosclerotic development in humans remains unclear. Plasma cholesteryl ester transfer was shown to be associated with carotid intima-media thickness in type 2 diabetic (T2D) patients with adequate metabolic control. Since glycation of CETP may influence cholesteryl ester transfer processes, it is important to determine if plasma cholesteryl ester transfer is still a determinant of carotid intima-media thickness (IMT) in patients with poorly controlled diabetes. The aim of the present study was to determine whether CETP activity influences carotid IMT in T2D patients with poor metabolic control. METHODS: In 110 individuals with T2D, we measured CETP mass concentration with ELISA, CETP activity with a radioactivity method and carotid intima-media thickness with high-resolution real-time B-mode ultrasonography. RESULTS: The mean HbA1C was 8.8 ± 1.7%. Carotid IMT did not correlate with CETP activity in the total population. In T2D patients with HbA1C < 8% (n = 33), mean HbA1C was 6.9% and the correlation between carotid IMT and CETP activity was not significant (p = 0.09). In a multivariable analysis that included the total population, carotid intima-media thickness was positively associated with diabetes duration (p = 0.02) but not with CETP activity or HbA1C. CONCLUSIONS: We observed no correlation between carotid intima-media thickness, a marker of early atherosclerosis, and CETP activity in T2D patients with poor metabolic control. Disease duration, which reflects accumulated metabolic abnormalities, may have blunted the potential effect of CETP on atherosclerosis. Metabolic control appears essential to determine the pro- or anti-atherogenic influence of CETP in patients with T2D.

Effect of insulin treatment on plasma oxidized LDL/LDL-cholesterol ratio in type 2 diabetic patients.

OBJECTIVE: In type 2 diabetes mellitus, oxidized LDL/LDL-Cholesterol ratio, an accurate estimation of in vivo LDL oxidation, has been reported elevated and associated with macrovascular disease. Because insulin therapy induces significant modification of lipid metabolism, in type 2 diabetes, we evaluated the effect of insulin treatment on oxidized LDL/LDL-C ratio in type 2 diabetic patients and analyzed the results in comparison with the modifications induced by insulin on glycaemia, plasma lipids and LDL receptors. RESEARCH DESIGN AND METHODS: Plasma oxidized LDL concentrations were measured by sandwich ELISA in 21 type 2 diabetic patients before and 3 months after the introduction of insulin therapy, and in 27 age-matched controls. RESULTS: Type 2 diabetic patients had, compared to controls, significantly increased oxidized LDL/LDL-C ratio (P<0.0001). Three months after insulin treatment, oxidized LDL/LDL-C ratio was significantly reduced (21.1+/-4.7 vs. 24.0+/-5.8 U/mmol, P<0.01). This reduction was strongly associated, in multivariate analysis, with reduction of LDL(TG/cholesterol ratio) (P=0.008), and to a lesser extent with the decrease of LDL fructosamine (P=0.034), but not with the increase of the number of LDL receptors. CONCLUSIONS: In the present study we demonstrate for the first time a lowering effect of insulin therapy on oxidized LDL/LDL-C ratio in type 2 diabetic patients. This decrease is mainly associated with the reduction of LDL TG-enrichment, and to a lesser extent with the decrease of LDL glycation, but not with the insulin-induced increase in number of LDL receptors.

Plasma apolipoprotein C1 concentration is associated with plasma triglyceride concentration, but not visceral fat, in patients with type 2 diabetes.

INTRODUCTION: Apolipoprotein C1 (apoC1) is likely to play an important role in triglyceride (TG) metabolism. Mice overexpressing human apoC1 present decreased adipose tissue stores. This study aimed to determine whether apoC1 concentration influences fat mass and distribution and liver fat content (LFC) in patients with type 2 diabetes (T2D). METHODS: ApoC1 concentrations were measured by ELISA in 113 T2D patients and 56 normolipidaemic-normoglycaemic subjects. Visceral and subcutaneous fat areas were determined by single-slice axial T1-weighted magnetic resonance imaging (MRI), while LFC was measured by hydrogen-1 ((1)H) MR spectroscopy. RESULTS: ApoC1 concentrations were higher in T2D patients than in normolipidaemic-normoglycaemic subjects (P<0.0001), and did not correlate with visceral or subcutaneous fat areas, but significantly correlated with TG (P<0.0001) and LFC (P=0.02) in T2D patients. However, the correlation between apoC1 and LFC was lost after adjusting for TG. ApoC1 concentration was also significantly higher in T2D patients with TG<1.5mmol/L than in control subjects (P<0.0001), although both groups had similar TG levels. On multivariate analysis performed in T2D patients with TG<1.5mmol/L and control subjects, apoC1 concentration was independently and positively associated with type 2 diabetes (P<0.0001) and TG levels (P=0.03). CONCLUSION: This study reports, for the first time, that apoC1 is increased in T2D patients and is significantly correlated with TG, whereas no association was found between apoC1 and adipose tissue. This indicates that, in T2D, apoC1 may play a role in TG metabolism, but is unlikely to modulate fat mass and distribution. This increased apoC1 concentration in T2D patients is not only explained by the increased TG level in T2D patients.

Differential effects of cis and trans fatty acid isomers, oleic and elaidic acids, on the cholesteryl ester transfer protein activity.

In a previous publication (Lagrost, L. and Barter, P.J. (1991) Biochim. Biophys. Acta 1085, 209-216), saturated and cis unsaturated non-esterified fatty acids have been shown to modulate the rate at which cholesteryl esters are transferred from high-density lipoproteins (HDL) to low-density lipoproteins (LDL) in the presence of the human cholesteryl ester transfer protein (CETP). In the present report, the effects of cis (oleic acid) and trans (elaidic acid) monounsaturated isomers on the CETP-mediated transfer of cholesteryl esters between HDL and LDL were compared. Mixtures of human LDL and HDL3, containing or not radiolabelled cholesteryl esters, were incubated at 37 degrees C with CETP in the presence or in the absence of either stearic (18:0), oleic (18:1 cis) or elaidic (18:1 trans) acids. It was observed that oleic acid and elaidic acid had different effects on the CETP-mediated redistribution of radiolabelled cholesteryl esters as well as on the net mass transfer of cholesterol from HDL3 to LDL. In particular, at high non-esterified fatty acid/lipoprotein ratio, the transfer of cholesteryl esters was significantly inhibited by the cis isomer and increased by the trans isomer.

Effect of the human cholesteryl ester transfer protein on the particle size redistribution of specific subpopulations of high density lipoproteins-3.

The effect of the cholesteryl ester transfer protein (CETP) on the size redistribution of high density lipoprotein-3 (HDL3) particles containing either apolipoprotein A-I without apolipoprotein A-II, designated HDL3 (A-I w/o A-II), or apolipoprotein A-I with apolipoprotein A-II, designated HDL3 (A-I w A-II), was investigated by incubating HDL3 at 37 degrees C in the presence of a purified preparation of CETP. At the end of the incubation, the distribution of total HDL3 as well as HDL3 (A-I w/o A-II) particles, recovered after immunoprecipitation of HDL3 (A-I w A-II) particles with anti-apo A-II antibodies, was determined by non-denaturing polyacrylamide gradient gel electrophoresis. Total HDL3 ultracentrifugally isolated from plasma consisted of two distinct subpopulations of particles with apparent diameters of 8.5 and 7.8 nm. The distribution profile of HDL3 (A-I w/o A-II) particles, revealed that the HDL3 subpopulation with a mean diameter of 8.5 nm comprised two typs of particles, containing either only apo A-I or apo A-I with apo A-II, while the lipoprotein subpopulation with a mean diameter of 7.8 nm consisted exclusively of particles containing both apolipoproteins. During incubation at 37 degrees C, CETP induced the redistribution of HDL3 with a mean apparent diameter of 8.5 nm towards particle subpopulations of larger (9.4 nm diameter) and smaller (7.8 and 7.4 nm diameter) size. It was demonstrated that the CETP-mediated conversion of HDL3 concerned both type of particles. CETP preferentially induced the transformation of HDL3 (A-I w A-II) particles with a mean diameter of 8.5 nm into larger (9.4 nm diameter) and smaller (7.8 nm diameter) particles containing apo A-I and apo A-II. Secondly, CETP induced a shift of HDL3 (A-I w/o A-II) particles with a mean diameter of 8.5 nm towards particles of smaller size (7.4 nm diameter) containing only apo A-I, while HDL3 (A-I w A-II) particles with mean diameters of 7.8 and 9.4 nm remained stable. In addition, this study demonstrated that the redistribution of HDL3 particles was accompanied by a dissociation of apolipoprotein A-I from the lipoprotein surfaces. The effect of myristic acid on CETP-induced HDL3 redistribution was mainly due to a redistribution of HDL3 (AI w/o AII) particles.

Effects of various non-esterified fatty acids on the particle size redistribution of high density lipoproteins induced by the human cholesteryl ester transfer protein.

The effects of various non-esterified fatty acids on the CETP-mediated particle size redistribution of HDL were studied by incubating HDL3 and CETP for 24 h at 37 degrees C in the absence or in the presence of either saturated, monounsaturated or polyunsaturated non-esterified fatty acids. In the absence of non-esterified fatty acids, CETP induced a redistribution of the initial population of HDL3 (Stokes' radius 4.3 nm) by promoting the appearance of one larger (Stokes' radius 4.8 nm) and two smaller (Stokes' radii 3.9 and 3.7 nm) HDL subpopulations. Whereas the non-esterified fatty acids alone did not modify the HDL3 distribution profile, they were able to alter markedly the capacity of CETP to induce the particle size redistribution of HDL. All the saturated fatty acids with at least 10 carbons were able to increase the formation of the very small sized particles (Stokes' radius 3.7 nm) in a concentration dependent manner, the medium chain fatty acids (12 and 14 carbons) being the best activators. The potential effect of non-esterified fatty acids was also influenced by the presence of double bonds in their monomeric carbon chain. While at low concentrations of non-esterified fatty acids (0.1 mmol/l) the enhancement of the formation of very small HDL particles appeared to be greater with oleic and linoleic acids than with stearic acid, at higher concentrations (0.4 mmol/l), oleic, linoleic and arachidonic acids decreased the formation of the 3.7 nm radius particles. The inhibition of the process at high concentrations of unsaturated fatty acids was linked to the degree of unsaturation of their carbon chain, arachidonic acid being the strongest inhibitor. The present study has demonstrated that non-esterified fatty acids can modulate the particle size redistribution of HDL3 mediated by the cholesteryl ester transfer protein even in the absence of any other lipoprotein classes. The effect of non-esterified fatty acid is dependent on both the length and the degree of unsaturation of their monomeric carbon chain.

Effects of various non-esterified fatty acids on the transfer of cholesteryl esters from HDL to LDL induced by the cholesteryl ester transfer protein.

The effects of saturated, monounsaturated and polyunsaturated non-esterified fatty acids on the rate of transfer of radiolabeled cholesteryl esters from high density lipoproteins (HDL) to low density lipoproteins (LDL), induced by the cholesteryl ester transfer protein (CETP), have been studied. Human high-density lipoproteins-subfraction 3 (HDL3) containing radiolabeled cholesteryl esters were incubated with LDL at 37 degrees C with or without CETP and in the absence or in the presence of non-esterified fatty acids. Less than 6% of the total radioactivity was recovered in the LDL fraction after incubation of HDL3, and LDL for 3 h at 37 degrees C in the absence of CETP, regardless of whether or not non-esterified fatty acids were added. The addition of CETP to the incubation mixture induced a time-dependent redistribution of radiolabeled cholesteryl esters from HDL3 to LDL. Non-esterified fatty acids were found to alter the rate of transfer of cholesteryl esters induced by CETP. While short chain saturated non-esterified fatty acids (caprylic and capric acids) had no effect on the rate of transfer of cholesteryl esters, the medium and long chain ones (lauric, myristic, palmitic and stearic acids) significantly increased the CETP-mediated transfers from HDL3 to LDL. At low concentrations, unsaturated fatty acids also stimulated the CETP-mediated redistribution of radiolabeled cholesteryl esters from HDL3 to LDL. As the concentration of either oleic, linoleic or arachidonic acids increased to higher levels, a significant proportion of fatty acids remained unassociated with lipoprotein particles. Under these circumstances the transfer process was inhibited. These results show that non-esterified fatty acids can modulate the CETP-mediated transfer of cholesteryl esters from HDL to LDL and that this effect is dependent on both the length and the degree of unsaturation of their monomeric carbon chain.

Cholesteryl ester transfer protein promotes the association of HDL apolipoproteins A-I and A-II with LDL: potentiation by oleic acid.

The association of apolipoprotein (apo) A-I and apo A-II with apo-B-containing particles was measured after incubation at 37 degrees C of either total plasma or low-density lipoproteins (LDL) and high-density lipoproteins-3 (HDL3) in the presence of partially purified cholesteryl ester transfer protein (CETP). At the end of the incubation, apo-B-containing lipoproteins were separated by immunoprecipitation with an anti-apo B gamma-globulin fraction. In mixtures containing LDL and HDL3, either maintained at 4 degrees C or incubated at 37 degrees C, optimal concentrations of anti-apo B antibodies induced the precipitation of more than 95% of apo B without precipitation of apo A-I and apo A-II. When total plasma was incubated at 37 degrees C for 24 h, a significant proportion of apo A-I and apo A-II became associated with apo-B-containing lipoproteins. The fraction of HDL apoproteins associated with apo-B-containing lipoproteins was significantly reduced when plasma was supplemented with TP2 anti-CETP monoclonal antibodies, which are known to inhibit CETP activity. Incubation of LDL and HDL3 for 24 h at 37 degrees C in the presence of purified CETP also induced the association of a significant proportion of apo A-I and apo A-II with apo-B-containing particles. This effect was dependent on CETP concentration in the incubation mixtures and could be suppressed by the addition of anti-CETP monoclonal antibodies. While oleic acid alone, at a final concentration of 0.2 mmol/l, did not promote any association of HDL-apolipoproteins with LDL, it was able, at this concentration, to greatly enhance the CETP-mediated association of apo A-I and apo A-II with apo-B-containing particles. In the presence of both CETP and oleic acid, the association of apo A-I and apo A-II with apo-B-containing particles was apparent within 3 h of commencing the incubation. Approximately 3 mol of apo A-I and 1 mol of apo A-II co-precipitated with each mol of apo B after a 24 h incubation of LDL, HDL3 and CETP. When oleic acid was added to the incubation mixture in addition to CETP, up to 5.5 mol of apo A-I and 2.3 mol of apo A-II were associated with each mol of apo B.(ABSTRACT TRUNCATED AT 400 WORDS)

Impairment of endothelium-dependent arterial relaxation by high-fat feeding in ApoE-deficient mice: toward normalization by human ApoA-I expression.

BACKGROUND: Atherogenic lipoproteins can impair the endothelium-dependent arterial relaxation, and circumstantial evidence suggests a beneficial role of plasma high density lipoproteins and apolipoprotein (apo) A-I in counteracting the endothelium dysfunction. In the present study, vascular reactivity was determined in control, apoE-deficient mice (apoE-KO mice), and apoE-deficient mice expressing human apoA-I (apoE-KO/HuAITg mice). METHODS AND RESULTS: In the first part of the study, control and apoE-KO mice were fed a low-fat or a high-fat diet for 23 weeks, and the vasoactive responses of isolated thoracic aortic segments to norepinephrine, sodium nitroprusside, and acetylcholine (ACh) were determined. Whereas norepinephrine, sodium nitroprusside, and ACh evoked similar vascular responses in control and apoE-KO mice fed the low-fat diet, high-fat feeding in apoE-KO mice produced a significant 3-fold increase in the mean concentration required to produce a half-maximal relaxing effect (EC(50)) of ACh as compared with control mice. This reflects a weaker sensitivity to ACh of the aortic segments from the apoE-deficient animals. In the second part of the study, the mean EC(50) for ACh after high-fat feeding was found to be 4.4-fold lower in apoE-KO/HuAITg mice than in apoE-KO mice, indicating that the reduced sensitivity to ACh of the thoracic aorta from the apoE-KO mice fed the high-fat diet is improved by the expression of human apoA-I. CONCLUSIONS: The present study demonstrates that the endothelium-dependent arterial relaxation is impaired in apoE-KO mice fed the high-fat diet. The endothelium dysfunction tends to be normalized by human apoA-I expression.

Macrovascular disease is associated with increased plasma apolipoprotein A-IV levels in NIDDM.

Apolipoprotein A-IV (apoA-IV) might play an important role in lipoprotein metabolism, including modulation of triglyceride-rich lipoprotein catabolism, reverse cholesterol transport and cholesteryl ester transfer protein (CETP) activity. Increased apoA-IV levels have been reported in plasma from NIDDM patients. The aim of the present study was to look for a possible association between plasma apoA-IV level and prevalence of macrovascular disease in NIDDM. One hundred and thirty-six NIDDM patients were studied (71 men, 65 women). Macrovascular disease was assessed in each patient by a standardized questionnaire, physical examination, resting electrocardiogram (ECG), and laboratory evaluation (ankle/arm blood pressure ratio, continuous wave Doppler velocimetry). Moreover, patients without any history of coronary heart disease and showing a normal resting ECG underwent a bicycle exercise test or a dipyridamole thallium scintigraphy to detect possible silent myocardial ischemia. Among the 136 NIDDM patients, 56 had macrovascular disease. ApoA-IV levels were significantly higher in NIDDM patients with macrovascular disease than in NIDDM patients without macrovascular disease (20.9 +/- 8.6 vs. 13.3 +/- 5.3 mg/dl; P < 0.001). The influence of different factors, such as age, BMI, cigarette smoking, hypertension, total cholesterol, triglycerides, HDL cholesterol, apoA-IV level, apoA-IV phenotype, fasting glycemia, fasting C-peptide, and microalbuminuria, on the prevalence of macrovascular disease was analyzed using a logistic regression model. In the univariate analysis, apoA-IV level (P < 0.00001), age (P = 0.0087), hypertension (P = 0.012), microalbuminuria (P = 0.018), triglycerides (P = 0.02), and fasting C-peptide (P = 0.03) were positively associated with macrovascular disease. In the multivariate analysis, macrovascular disease was positively associated only with apoA-IV (P < 0.0001) and age (P = 0.003) and negatively associated with HDL cholesterol (P = 0.013). These results indicate that increased plasma apoA-IV level is associated with an increased prevalence of macrovascular disease in NIDDM. Moreover, apoA-IV, in NIDDM patients, appears to be a better marker for macrovascular disease than triglycerides.

The role of cholesteryl ester transfer protein and phospholipid transfer protein in the remodeling of plasma high-density lipoproteins.

Recent studies demonstrated that alterations in the size distribution of high-density lipoproteins (HDLs) constitute reliable markers for the risk of coronary artery disease. These observations suggested that the determination of the size distribution of HDL subpopulations by using polyacrylamide gradient gel electrophoresis might constitute an effective tool in clinical practice for the detection of patients with elevated risk. During the last decade, concordant observations revealed that all the HDL subpopulations are metabolically interrelated, and their relative abundances are dependent on the activity of several plasma factors, among them the cholesteryl ester transfer protein (CETP) and the phospholipid transfer protein (PLTP). As reviewed in the present article, although both CETP and PLTP can promote the size redistribution or conversion of HDL, the two plasma lipid transfer proteins can alter differently the plasma HDL distribution profile through distinct mechanisms. (Trends Cardiovasc Med 1997;7:218-224). © 1997, Elsevier Science Inc.

Apolipoprotein A-IV levels and phenotype distribution in NIDDM.

OBJECTIVE: To determine plasma apolipoprotein A-IV (apoA-IV) levels and phenotype distribution in non-insulin-dependent diabetes mellitus (NIDDM) patients and to analyze the influence of apoA-IV phenotype on lipid profiles in NIDDM. RESEARCH DESIGN AND METHODS: Total cholesterol, triglyceride, high-density lipoprotein (HDL) cholesterol, HDL2 cholesterol, HDL3 cholesterol, free fatty acid, and apoA-IV levels were measured in 83 NIDDM patients and 100 normal control subjects. The apoA-IV phenotype was determined in each individual. RESULTS: In both sexes, NIDDM patients had significantly higher levels of triglyceride and free fatty acid and significantly lower levels of HDL cholesterol and HDL2 cholesterol than control subjects. In men and women, apoA-IV levels were significantly higher in diabetic patients than in control subjects (men: 17.1 +/- 7.9 vs. 12.3 +/- 3.6 mg/dl, P < 0.001; women: 18.9 +/- 9.9 vs. 11.9 +/- 3.5 mg/dl, P < 0.001). The multiple regression analysis showed that the apoA-IV level in NIDDM patients was significantly and independently related to log triglyceride (P = 0.0001) and HDL cholesterol (P = 0.01) levels. The apoA-IV phenotype distribution was not significantly different between NIDDM patients and control subjects. In the control subjects, the apoA-IV-1-2 phenotype was associated with significantly higher levels of HDL cholesterol (69 +/- 12 vs. 56 +/- 11 mg/dl, P < 0.01) and of HDL2 cholesterol (36 +/- 15 vs. 25 +/- 12 mg/dl, P < 0.05) compared with the apoA-IV-1-1 phenotype; on the other hand, HDL cholesterol and HDL2 cholesterol levels were not different between the two apoA-IV phenotypes in NIDDM patients. CONCLUSIONS: Plasma apoA-IV levels are increased in NIDDM patients. This increase in apoA-IV is related mainly to hypertriglyceridemia and, to a lesser extent, to HDL cholesterol level. The apoA-IV phenotype distribution is not different between NIDDM patients and nondiabetic control subjects. The potential protective lipid profile (characterized by increased HDL and HDL2 cholesterol levels) linked with apoA-IV-1-2 phenotype in control subjects is no longer found in NIDDM patients. We suggest that the metabolic state of NIDDM has erased the potential protective lipid profile associated with the apoA-IV-1-2 phenotype.

Variation at the apo AI/CIII/AIV gene complex is associated with elevated plasma levels of apo CIII.

A number of studies have reported that a variant allele (S2) of the apo AI/CIII/AIV complex is associated with high plasma lipid levels in some populations and furthermore that the frequency of this allele is 2-5-fold higher in patient groups with premature coronary heart disease compared to control groups. This study shows in the healthy "English" population that the S2 allele is associated with elevated plasma apo CIII levels but not with low apo AI levels. In addition, it shows that the allele is associated with elevated plasma levels of apo B in men. Regression analysis shows in both men and women that apo CIII levels are positively correlated with plasma triglyceride levels and moreover that they are a stronger predictor of this parameter than apo AI, B or AIV. Apo CIII levels are also an independent predictor of total plasma cholesterol and HDL-cholesterol levels in males and females, respectively. Together these data suggest that a genetic predisposition to develop elevated plasma levels of apo CIII, alone or in combination with elevated plasma apo AIV levels, is the primary defect responsible for the association of the S2 allele with hyperlipidemia and/or premature CHD.

Plasma lipoprotein distribution and lipid transfer activities in patients with type IIb hyperlipidemia treated with simvastatin.

The aim of the present study was to search in type IIb hyperlipidemic patients for putative concomitant effects of simvastatin on the physicochemical characteristics of low density lipoproteins (LDL) and high density lipoproteins (HDL), as well as on the activities of the cholesteryl ester transfer protein (CETP) and the phospholipid transfer protein (PLTP) that were determined in both endogenous lipoprotein-dependent and endogenous lipoprotein-independent assays. In a double-blind, randomized trial, patients received either placebo (one tablet/day; n = 12) or simvastatin (20 mg/day; n = 12) for a period of 8 weeks after a 5-week run-in period. Simvastatin, unlike placebo, reduced the lipid and apolipoprotein B contents of the most abundant LDL-1, LDL-2, and LDL-3 subfractions without inducing significant changes in the overall size distribution of LDL and HDL. Whereas simvastatin significantly increased PLTP activity in an endogenous lipoprotein-dependent assay (P < 0.01), no variation was observed in a lipoprotein-independent assay. Simvastatin significantly decreased plasma CETP activity in an endogenous lipoprotein-dependent assay (P < 0.01), and the reduction in plasma cholesteryl ester transfer rates was explained by a 16% drop in CETP mass concentration (P < 0.01). In contrast, the specific activity of CETP was unaffected by the simvastatin treatment reflecting at least in part the lack of significant alteration in plasma triglyceride-rich lipoprotein acceptors. The simvastatin-induced changes in plasma CETP mass levels correlated positively with changes in plasma CETP activity (r = 0.483, P = 0.0561), in total cholesterol levels (r = 0.769; P < 0.01), and in LDL-cholesterol levels (r = 0.736; P < 0.01). Whereas the observations suggest that simvastatin might exert concomitant beneficial effects on plasma CETP and LDL levels, neither plasma cholesteryl ester transfer activity nor plasma phospholipid transfer activity appeared as the main determinants of the LDL and HDL distribution profiles in type IIb hyperlipidemic patients.

Variations in serum cholesteryl ester transfer and phospholipid transfer activities in healthy women and men consuming diets enriched in lauric, palmitic or oleic acids.

Cholesteryl ester transfer protein (CETP) and phospholipid transfer protein (PLTP) activities were measured in sera from 32 normolipidemic women and men consuming diets enriched in lauric, palmitic, or oleic acids. Serum CETP activity, measured as the rate of radiolabeled cholesteryl esters transferred from HDL toward serum apo B-containing lipoproteins, was higher with the palmitic acid diet (25.1+/-2.5%) than with the lauric acid (23.7+/-2.4%) and the oleic acid (24.0+/-2.7%) diets (P = 0.0028 and 0.0283, respectively). CETP mass concentrations, as measured with an enzyme-linked immunosorbent assay were increased after the lauric acid diet (2.57+/-0.63 mg/l) and the palmitic acid diet (2.49+/-0.64 mg/l) as compared with the oleic acid diet (2.34+/-0.45 mg/l) (P = 0.0035 and 0.0249, respectively). In contrast with CETP, serum PLTP activity, as measured as the rate of radiolabeled phosphatidylcholine transferred from liposomes toward serum HDL, was significantly higher with the lauric acid diet (23.5+/2.6%) than with the palmitic acid diet (22.5+/-2.5%) (P = 0.0013), while no significant differences were noted when comparing the saturated diets versus the oleic acid diet (23.0+/-2.3%). No significant alterations in the mean apparent diameter of LDL, and in the relative proportions of individual HDL subpopulations were observed from one dietary period to another. Nevertheless, lipid transfer activities correlated significantly with the relative abundance of HDL2b, HDL2a, HDL3b, and HDL3c, with opposite tendencies being observed for cholesteryl ester transfer and phospholipid transfer activities. In general, serum CETP activity correlated negatively with HDL cholesterol, but positively with triglyceride concentrations after the dietary interventions, and the relations with serum lipids were just the opposite for PLTP activity. In addition, CETP and PLTP activities correlated negatively when subjects consumed the standardized diets (P < 0.05 in all cases), but not when subjects consumed their habitual diet. It is concluded that serum lipid transfer activities in normolipidemic subjects can be significantly affected by the fatty acid content of the diet, with differential effects on CETP and PLTP activities.

Characterization of two HDL subfractions and LpA-I, LpA-I:A-II distribution profiles and clinical characteristics of hyperalphalipoproteinemic subjects without cholesterol ester transfer protein deficiency.

The aims of the present study were (i) to characterize the HDL2, HDL3 and the LpA-I, LpA-I:A-II distribution, (ii) to investigate the prevalence of atherosclerotic lesions and (iii) to assess the activity of cholesteryl ester transfer protein (CETP) in 29 hyperalphalipoproteinemic (HALP) patients (HDL-C=90+/-11 mg/dl) with combined hypercholesterolemia (LDL-C=180+/-16 mg/dl). According to the HDL2/HDL3 and LpA-I/LpA-I:A-II ratios, two HALP profiles (A and B) were defined: in 22 patients (HALP profile A) these ratios were increased compared to the normolipidemic control subjects (1.19+/-0.11 versus 0.53+/-0.19, P < 0.001 and 1.01+/-0.2 versus 0.51+/-0.25, P < 0.001, respectively) and in seven patients (HALP profile B) these ratios were within the normal range (0.64+/-0.20 and 0.69+/-0.2, respectively). The atherosclerotic lesions were assessed by ultrasonography of the carotid arteries. Amongst patients with HALP profile A, 17 were free from lesions, five had intimal wall thickening and none displayed plaques, whereas for patients within the HALP profile B, only one was free from lesions, two had intimal wall thickening and four displayed plaques. CETP activities (348+/-116 versus 371+/-75%/ml/h) and CETP concentrations (2.4+/-0.5 versus 2.5+/-0.6 microg/ml) were similar in HALP profiles A and B, however these values were both higher than in control subjects (190+/-40%/ml/h, P < 0.001 and 1.8+/-0.3 microg/ml, P < 0.001, respectively). Hence the hyperalphalipoproteinemic profiles (A and B) described here were not related to CETP deficiency. In conclusion, the HALP profile A was characterized by both increased HDL2/HDL3 and LpA-I/LpA-I:A-II ratios and was associated with a low prevalence of atherosclerosis, whereas the HALP profile B, characterized by HDL2/HDL3 and LpA-I/LpA-I:A-II ratios within the normal range, was less cardioprotective.

Hyperalphalipoproteinemia: characterization of a cardioprotective profile associating increased high-density lipoprotein2 levels and decreased hepatic lipase activity.

The aim of the present study was to investigate the high-density lipoprotein (HDL) structural characteristics and metabolism in hyperalphalipoproteinemic (HALP) patients (HDL-cholesterol [HDL-C], 92 +/- 14 mg/dL) with combined elevated low-density lipoprotein-cholesterol (LDL-C) levels (LDL-C, 181 +/- 33 mg/dL). Patients were subjected to a complete cardiovascular examination, including ultrasonographic investigation of carotid arteries. Two HALP profiles were identified according to the HDL2/HDL3 ratio. HALP profile A was characterized in 28 patients by increased HDL2/HDL3 ratio, HDL2b, and lipoprotein (Lp)A-I levels compared with normolipidemic subjects, and HALP profile B, including the 12 remaining patients, was characterized by a HDL2/HDL3 ratio within the normal range and by the increase of all HDL subclasses (HDL(2b,2a,3a,3b,3c)), LpA-I, and LpA-I:A-II levels. With regard to the exploration of carotid arteries, in HALP profile A, 20 patients were free from lesions and eight had only intimal wall thickening. In HALP profile B, only one patient was free from lesions, four had intimal wall thickening, and seven displayed plaques, but none had stenosis. Taking into account the number of patients with plaques within each group, HALP profile A was associated with a low prevalence of atherosclerotic lesions, whereas HALP profile B was less cardioprotective (odds ratio, 77.7 [95% confidence interval, 3.7 to 1,569.7]; P < .0001). For both HALP profiles, cholesteryl ester transfer protein (CETP) deficiency was discarded and activities of phospholipid transfer protein (PLTP) and lipoprotein lipase (LPL) were normal. However, hepatic lipase (HL) activity was significantly decreased in HALP profile A, but within the normal range for HALP profile B. In conclusion, an HALP profile A with a low prevalence of atherosclerosis was characterized by an increased HDL2/HDL3 ratio, HDL2b, and LpA-I levels associated with decreased HL activity.

Competitive enzyme-linked immunosorbent assay of the human cholesteryl ester transfer protein (CETP).

The present report describes the first competitive enzyme-linked immunosorbent assay (ELISA) for the cholesteryl ester transfer protein (CETP), an enzyme playing an important role in lipoprotein metabolism. This assay was developed with well-characterized TP1 anti-CETP monoclonal antibodies. The sensitivity of the ELISA assay was comparable with the sensitivity of the previously described radioimmunoassays since 1 ng of CETP per microwell of the immunoplate could be detected. Intra- and inter-assay coefficients of variation were 4% and 6%, respectively. This enzyme immunoassay provides a specific, sensitive and reproducible method for measuring CETP concentrations in various biological samples. Within normolipidemic subjects, the mean (+/- S.D.) of the plasma CETP concentration was 2.77 (+/- 0.59) micrograms/ml with a range of 1.87 to 4.23 micrograms/ml. When plasmas were supplemented with fatty acid-free albumin, the positive correlation observed between plasma CETP mass and CETP activity was improved, suggesting that plasma non-esterified fatty acids could play a role in modulating the activity of the cholesteryl ester transfer protein. When applied to the study of the binding of CETP to lipoprotein substrates, the enzyme immunoassay revealed that the experimental protocol used to separate lipoprotein fractions can have a great influence on the plasma distribution of CETP.

Phospholipid and cholesteryl ester transfer activities in plasma from 14 vertebrate species. Relation to atherogenesis susceptibility.

Cholesteryl ester and phospholipid transfer activities were determined in plasmas from 14 vertebrates, and lipid transfer values were analyzed in the light of the known atherogenesis susceptibility of studied species. Whereas cholesteryl ester transfer protein (CETP) and phospholipid transfer protein (PLTP) activities among vertebrate species were only measured in lipoprotein-deficient fractions in previous studies, both endogenous lipoprotein-dependent and endogenous lipoprotein-independent assays were used in the present work. In agreement with previous studies, a few species (chicken, man, rabbit and trout) displayed substantial CETP activity, whereas CETP activity was not detectable in other species (cow, dog, horse, mouse, pig, and rat). Additional species that were not studied before, i.e. cat, goat, and sheep, were shown to be deficient in plasma cholesteryl ester transfer activity, while duck was shown to constitute a new member of the high activity group. Unlike CETP activity, PLTP activity was detected in plasmas from all studied species, most of them being assayed here for the first time (cat, chicken, cow, duck, goat, horse, sheep, and trout). While dog, trout, mouse, and pig displayed the highest phospholipid transfer activity levels, the remarkable preservation of facilitated phospholipid transfers in plasma from all vertebrates might indicate an essential role of PLTP in vivo. Interestingly, animals with well-documented atherogenesis susceptibility (chicken, pig, rabbit, and man) displayed significantly higher mean CETP activity, but lower mean PLTP activity than known 'resistant' animals (cat, dog, mouse, and rat). In conclusion, the present study revealed marked differences in plasma lipid transfer activities between vertebrate species, and interspecies comparisons indicated that both CETP and PLTP may constitute two determinants of the atherogenicity of the plasma lipoprotein profile.