Plasma Phospholipid Transfer Protein Research Articles

Impact of site-specific N-glycosylation on cellular secretion, activity and specific activity of the plasma phospholipid transfer protein

The plasma phospholipid transfer protein (PLTP) plays a key role in lipid and lipoprotein metabolism. It has six potential N-glycosylation sites. To study the impact of these sites on PLTP secretion and activity, six variants containing serine to alanine point mutations were prepared by site-directed mutagenesis and expressed in Chinese hamster ovary Flp-In cells. The apparent size of each of the six PLTP mutants was slightly less than that of wild type by Western blot, indicating that all six sites are glycosylated or utilized. The size of the carbohydrate at each N-glycosylation site ranged from 3.14 to 4.2 kDa. The effect of site-specific N-glycosylation removal on PLTP secretion varied from a modest enhancement (15% and 60%), or essentially no effect, to a reduction in secretion (8%, 14% and 32%). Removal of N-glycosylation at any one of the six glycosylation sites resulted in a significant 35-78% decrease in PLTP activity, and a significant 29-80% decrease in PLTP specific activity compared to wild type. These data indicate that although no single N-linked carbohydrate chain is a requirement for secretion or activity, the removal of the carbohydrate chains had a quantitative impact on cellular secretion of PLTP and its phospholipid transfer activity.

Plasma phospholipid transfer protein activity is independently determined by obesity and insulin resistance in non-diabetic subjects

BackgroundPhospholipid transfer protein (PLTP) is an emerging cardio-metabolic risk factor which is intricately involved in lipoprotein metabolism. Elevated plasma PLTP activity levels are reported in obesity and diabetes mellitus, but the relative contributions of obesity and insulin resistance to plasma PLTP activity remain unclear. We tested whether plasma PLTP activity is independently related to (central) obesity and insulin resistance in non-diabetic subjects. MethodsThe relationships of plasma PLTP activity levels (phospholipid vesicles–HDL system) with waist circumference, waist/hip ratio, body mass index (BMI) and insulin resistance (homeostasis model assessment (HOMAir)) were determined in 313 non-diabetic subjects (273 men). ResultsPLTP activity was higher in 67 subjects with enlarged waist circumference (NCEP-ATP-III criteria; 102±11AU) compared to 246 subjects with normal waist (98±11AU, P=0.027). In univariate analysis PLTP activity correlated positively with waist (r=0.188), waist/hip ratio (r=0.143), BMI (r=0.125) and HOMAir (r=0.192) (P<0.05 to P<0.001). The relationship of PLTP with HOMAir was confined to subjects with the highest waist circumference and waist/hip ratio. In age- and sex-adjusted multiple linear regression models, waist circumference (β=0.158, P=0.025), but not BMI, predicted PLTP activity independently of HOMAir (β=0.126, P=0.047). Furthermore, both waist and waist/hip ratio interacted positively with HOMAir on PLTP activity (β=0.109, P=0.056 and β=0.156, P=0.034, respectively). ConclusionsIn non-diabetic subjects, both obesity and insulin resistance influence plasma PLTP activity, resulting in elevated plasma PLTP activity particularly with combined increases in obesity and insulin resistance. Higher PLTP activity could contribute to elevated cardiovascular risk in the presence of obesity and insulin resistance.

Different phospholipid transfer protein complexes contribute to the variation in plasma PLTP specific activity

Phospholipid transfer protein (PLTP) facilitates the transfer of phospholipids among lipoproteins. Over half of the PLTP in human plasma has been found to have little phospholipid transfer activity (inactive PLTP). We recently observed that plasma PLTP specific activity is inversely correlated with high-density lipoprotein (HDL) level and particle size in healthy adults. The purpose of this study was to evaluate the factors that contribute to the variation in plasma PLTP specific activity. Analysis of the specific activity of PLTP complexes in nine plasma samples from healthy adults revealed two clusters of inactive PLTP complexes with mean molecular weights (MW) of 342 kDa and 146 kDa. The large and small inactive PLTP complexes represented 52 ± 8% (range 39–63%) and 8 ± 8% (range 1–28%) of the plasma PLTP, respectively. Active PLTP complexes had a mean MW of 207 kDa and constituted 40 ± 6% (range 33–50%) of the plasma PLTP. The specific activity of active PLTP varied from 16 to 32 μmol/μg/h. These data demonstrate for the first time the existence of small inactive plasma PLTP complexes. Variation in the amount of the two clusters of inactive PLTP complexes and the specific activity of the active PLTP contribute to the variation in plasma PLTP specific activity.

Worsening of Diet-Induced Atherosclerosis in a New Model of Transgenic Rabbit Expressing the Human Plasma Phospholipid Transfer Protein

Plasma phospholipid transfer protein (PLTP) is involved in intravascular lipoprotein metabolism. PLTP is known to act through 2 main mechanisms: by remodeling high-density lipoproteins (HDL) and by increasing apolipoprotein (apo) B-containing lipoproteins. The aim of this study was to generate a new model of human PLTP transgenic (HuPLTPTg) rabbit and to determine whether PLTP expression modulates atherosclerosis in this species that, unlike humans and mice, displays naturally very low PLTP activity. In HuPLTPTg rabbits, the human PLTP cDNA was placed under the control of the human eF1-α gene promoter, resulting in a widespread tissue expression pattern and in increased plasma PLTP. The HuPLTPTg rabbits showed a significant increase in the cholesterol content of the plasma apoB-containing lipoprotein fractions, with a more severe trait when animals were fed a cholesterol-rich diet. In contrast, HDL cholesterol level was not modified in HuPLTPTg rabbits. Formation of aortic fatty streaks was increased in hypercholesterolemic HuPLTPTg animals as compared with nontransgenic littermates. Human PLTP expression in HuPLTPTg rabbit worsens atherosclerosis as a result of increased levels of atherogenic apoB-containing lipoproteins but not of alterations in their antioxidative protection or in cholesterol content of plasma HDL.

ChemInform Abstract: Synthesis of a Series of Novel 2,4,5‐Trisubstituted Selenazole Compounds as Potential PLTP Inhibitors.

AbstractThe title compounds are evaluated for their plasma phospholipid transfer protein (PLTP) inhibiting activities.

Differential effects of gemfibrozil and fenofibrate on reverse cholesterol transport from macrophages to feces in vivo

Gemfibrozil and fenofibrate, two of the fibrates most used in clinical practice, raise HDL cholesterol (HDLc) and are thought to reduce the risk of atherosclerotic cardiovascular disease. These drugs act as PPARα agonists and upregulate the expression of genes crucial in reverse cholesterol transport (RCT). In the present study, we determined the effects of these two fibrates on RCT from macrophages to feces in vivo in human apoA-I transgenic (hApoA-ITg) mice. [3H]cholesterol-labeled mouse macrophages were injected intraperitoneally into hApoA-ITg mice treated with intragastric doses of fenofibrate, gemfibrozil or a vehicle solution for 17days, and radioactivity was determined in plasma, liver and feces. Fenofibrate, but not gemfibrozil, enhanced [3H]cholesterol flux to plasma and feces of female hApoA-ITg mice. Fenofibrate significantly increased plasma HDLc, HDL phospholipids, hApoA-I levels and phospholipid transfer protein activity, whereas these parameters were not altered by gemfibrozil treatment. Unlike gemfibrozil, fenofibrate also induced the generation of larger HDL particles, which were more enriched in cholesteryl esters, together with higher potential to generate preβ-HDL formation and caused a significant increase in [3H]cholesterol efflux to plasma. Our findings demonstrate that fenofibrate promotes RCT from macrophages to feces in vivo and, thus, highlight a differential action of this fibrate on HDL.

Plasma Phospholipid Transfer Protein Deficiency in Mice Is Associated With a Reduced Thrombotic Response to Acute Intravascular Oxidative Stress

Earlier in vitro studies suggested a putative role for the plasma phospholipid transfer protein (PLTP) in the modulation of blood coagulation. The effect of PLTP expression on blood coagulation under both basal and oxidative stress conditions was compared here in wild-type and PLTP-deficient (PLTP-/-) mice. Under basal conditions, PLTP deficiency was associated with an extended tail bleeding time despite a significant depletion of vascular α-tocopherol content and an impairment of endothelial function. When acute oxidative stress was generated in vivo in the brain vasculature, the steady state levels of oxidized lipid derivatives, the extent of blood vessel occlusion, and the volume of ischemic lesions were more severe in wild-type than in PLTP-/- mice. In addition to its recognized hyperlipidemic, proinflammatory, and proatherogenic properties, PLTP increases blood coagulation and worsens the extent of ischemic lesions in response to acute oxidative stress. Thus, PLTP arises here as a cardiovascular risk factor for the late thrombotic events occurring in the acute phase of atherosclerosis.

Phospholipid Transfer Protein and Atherosclerosis

Phospholipid transfer protein (PLTP) is a member of the lipid transfer/lipopolysaccharide-binding protein family that first attracted attention by virtue of its functions in intravascular lipoprotein metabolism. These include its key role in mediating transfer of phospholipids from very-low-density lipoprotein to high-density lipoprotein (HDL) in conjunction with very-low-density lipoprotein lipolysis and its capacity to remodel HDL by promoting the production of larger HDL through fusion of 2 smaller particles with generation of lipid-poor apolipoprotein (apo) AI.1 The latter has properties consistent with pre-β1 HDL, a species that can contribute to cellular cholesterol efflux2 and plays a role in reverse cholesterol transport. Together with evidence that PLTP levels are correlated with plasma concentrations of HDL cholesterol and apoAI,3 these properties of PLTP led to the suggestion that it may have an atheroprotective role; however, an increasing body of evidence from animal and human studies has pointed to its proatherogenic effects. In apoB-transgenic and apoE-deficient mice, PLTP deficiency resulted in markedly decreased atherosclerosis,4 whereas in PLTP-transgenic mice, atherosclerosis was increased5 and macrophage cholesterol efflux and reverse cholesterol transport were impaired.6 Moreover, macrophages were shown to be a source of plasma PLTP,7 and bone marrow transplantation of cells overexpressing PLTP into low-density lipoprotein-receptor–null mice resulted in proatherogenic lipid changes and increased atherosclerosis.8 On the other hand, atherosclerosis was decreased by bone marrow transplantation of macrophages expressing PLTP in double low-density lipoprotein-receptor– and PLTP-deficient mice, in conjunction with reduced plasma total cholesterol and increased HDL.9 Thus, it appears that systemic PLTP has proatherogenic effects, although in some circumstances, macrophage-derived PLTP may be atheroprotective. Article see p 470 Notably, 2 forms of immunoreactive plasma PLTP have been identified with high versus low phospholipid transfer activity,10 and it has been reported that only the form with high …

Genetic Variation at the Phospholipid Transfer Protein Locus Affects Its Activity and High-Density Lipoprotein Size and Is a Novel Marker of Cardiovascular Disease Susceptibility

In contrast to clear associations between variants in genes participating in low-density lipoprotein metabolism and cardiovascular disease risk, such associations for high-density lipoprotein (HDL)-related genes are not well supported by recent large studies. We aimed to determine whether genetic variants at the locus encoding phospholipid transfer protein (PLTP), a protein involved in HDL remodeling, underlie altered PLTP activity, HDL particle concentration and size, and cardiovascular disease risk. We assessed associations between 6 PLTP tagging single nucleotide polymorphisms and PLTP activity in 2 studies (combined n=384) and identified 2 variants that show reproducible associations with altered plasma PLTP activity. A gene score based on these variants is associated with lower hepatic PLTP transcription (P=3.2x10(-18)) in a third study (n=957) and with an increased number of HDL particles of smaller size (P=3.4x10(-17)) in a fourth study (n=3375). In a combination of 5 cardiovascular disease case-control studies (n=4658 cases and 11 459 controls), a higher gene score was associated with a lower cardiovascular disease risk (per-allele odds ratio, 0.94; 95% confidence interval, 0.90 to 0.98; P=1.2x10(-3); odds ratio for highest versus lowest gene score, 0.69; 95% confidence interval, 0.55 to 0.86; P=1.0x10(-3)). A gene score based on 2 PLTP single nucleotide polymorphisms is associated with lower PLTP transcription and activity, an increased number of HDL particles, smaller HDL size, and decreased risk of cardiovascular disease. These findings indicate that PLTP is a proatherogenic entity and suggest that modulation of specific elements of HDL metabolism may offer cardiovascular benefit.

Innate immune response triggered by triacyl lipid A is dependent on phospholipid transfer protein (PLTP) gene expression

Hexaacyl lipopolysaccharide (LPS) aggregates in aqueous media, but its partially deacylated lipid A moiety forms monomers with weaker toxicity. Because plasma phospholipid transfer protein (PLTP) transfers hexaacyl LPS, its impact on metabolism and biological activity of triacyl lipid A in mice was addressed. Triacyl lipid A bound readily to plasma high-density lipoproteins (HDLs) when active PLTP was expressed [HDL-associated lipid A after 4.5 h: 59.1+/-16.0% of total in wild-type (WT) vs. 32.5+/-10.3% in PLTP-deficient mice, P<0.05]. In the opposite to hexaacyl LPS, plasma residence time of lipid A was extended by PLTP, and proinflammatory cytokines were produced in higher amounts in WT than PLTP(-/-) mice (remaining lipid A after 8 h: 53+/-12 vs. 35+/-7%, and IL6 concentration after 4.5 h: 45.5+/-5.9 vs. 14.6+/-7.8 ng/ml, respectively; P<0.05 in all cases). After 1 wk, onset of B16-induced melanoma was observed in only 30% of lipid A-treated WT mice, whereas >80% of the untreated WT, untreated PLTP-deficient, or lipid A-treated PLTP-deficient animals bore tumors (P<0.05 in all cases). It is concluded that PLTP is essential in mediating the association of triacyl lipid A with lipoproteins, leading to extension of its residence time and to magnification of its proinflammatory and anticancer properties.

Serum Phospholipid Transfer Protein Activity After a High Fat Meal in Patients with Insulin‐Treated Type 2 Diabetes

Plasma phospholipid transfer protein (PLTP) mediates both net transfer and exchange of phospholipids between different lipoproteins. Animal studies have shown that it is closely related to the development of atherosclerosis. Although many studies have indicated that PLTP activity is increased in diabetes mellitus, the role of PLTP in diabetes is still unclear. To evaluate the influence of a high-fat meal on PLTP activity, 50 nondiabetic patients with coronary heart disease (CHD), 50 insulin-treated Type 2 diabetics, and 50 healthy controls were included. We determined PLTP activity before and 4 and 8 h after a high-fat meal. As expected, serum PLTP activity was significantly higher in CHD patients than in healthy controls (71.0 +/- 46.2 vs. 54.0 +/- 33.8 pmol/microl/h, P = 0.032) at baseline. More importantly, we found that serum PLTP activity increased to its maximum 4 h after fat loading and then decreased to nearly basal levels after 8 h both in controls and CHD patients. In contrast, PLTP activity continuously increased during this time period in the diabetic patients. With regards to the data from this study we hypothesize that serum PLTP is involved in the clearance of postprandial lipoproteins and this process is attenuated in diabetes. Since postprandial lipoproteins are atherogenic, the delay in clearance of these particles could play an important role in the development of atherosclerosis in patients with diabetes mellitus.

Low cholesteryl ester transfer protein and phospholipid transfer protein activities are the factors making tree shrew and beijing duck resistant to atherosclerosis

BackgroundTree shrew and beijing duck are regarded as animal models resistant to atherosclerosis (AS). This study was carried out to discover the potential mechanism.MethodsBlood samples were collected from healthy men and male animals. Plasma lipid profile and activities of cholesteryl ester transfer protein (CETP) and phospholipid transfer protein (PLTP) were measured, compared and analyzed in human, tree shrew, and Beijing duck.ResultsThe results showed that there were species differences on plasma lipid profile and activities of CETP and PLTP in the three species. Compared with human, tree shrew and beijing duck had higher high density lipoprotein cholesterol (HDL-C)/total cholesterol (TC) and HDL-C/low density lipoprotein cholesterol (LDL-C) ratios, but lower CETP and PLTP activities. In the three species, CETP and PLTP activities were negatively related with the ratio of HDL-C/LDL-C.ConclusionsThe present study suggested that low plasma CETP and PLTP activities may lead to a high HDL-C/LDL-C ratio and a high resistance to AS finally in tree shrew and beijing duck. Moreover, low PLTP activity may also make the animals resistant to AS by the relative high vitamin E content of apoB-containing lipoproteins and high anti-inflammatory and antioxidative properties of HDL particles. A detailed study in the future is recommended.

Plasma phospholipid transfer protein (PLTP): review of an emerging cardiometabolic risk factor

Plasma phospholipid transfer protein (PLTP) is a lipid transfer glycoprotein that binds to and transfers a number of amphipathic compounds. In earlier studies, the attention of the scientific community focused on the positive role of PLTP in high-density lipoprotein (HDL) metabolism. However, this potentially anti-atherogenic role of PLTP has been challenged recently by another picture: PLTP arose as a pro-atherogenic factor through its ability to increase the production of apolipoprotein B-containing lipoproteins, to decrease their antioxidative protection and to trigger inflammation. In humans, PLTP has mostly been studied in patients with cardiometabolic disorders. Both PLTP and related cholesteryl ester transfer protein (CETP) are secreted proteins, and adipose tissue is an important contributor to the systemic pools of these two proteins. Coincidently, high levels of PLTP and CETP have been found in the plasma of obese patients. PLTP activity and mass have been reported to be abnormally elevated in type 2 diabetes mellitus (T2DM) and insulin-resistant states, and this elevation is frequently associated with hypertriglyceridemia and obesity. This review article presents the state of knowledge on the implication of PLTP in lipoprotein metabolism, on its atherogenic potential, and the complexity of its implication in obesity, insulin resistance and T2DM.

Novel roles of hepatic lipase and phospholipid transfer protein in VLDL as well as HDL metabolism

Objective Elevated plasma phospholipid transfer protein (PLTP) expression may increase atherosclerosis in mice by reducing plasma HDL and increasing hepatic VLDL secretion. Hepatic lipase (HL) is a lipolytic enzyme involved in several aspects of the same pathways of lipoprotein metabolism. We investigated whether the effects of elevated PLTP activity are compromised by HL deficiency. Methods and results HL deficient mice were crossbred with PLTP transgenic (PLTPtg) mice and studied in the fasted state. Plasma triglycerides were decreased in HL deficiency, explained by reduced hepatic triglyceride secretion. In PLTPtg mice, a redistribution of HL activity between plasma and tissue was evident and plasma triglycerides were also decreased. HL deficiency mitigated or even abolished the stimulatory effect of elevated PLTP activity on hepatic triglyceride secretion. HL deficiency had a modest incremental effect on plasma HDL, which remained present in PLTP transgenic/HL −/− mice, thereby partially compensating the decrease in HDL caused by elevation of PLTP activity. HDL decay experiments showed that the fractional turnover rate of HDL cholesteryl esters was delayed in HL deficient mice, increased in PLTPtg mice and intermediate in PLTPtg mice in an HL −/− background. Conclusions HL affects hepatic VLDL. Elevated PLTP activity lowers plasma HDL-cholesterol by stimulating the plasma turnover and hepatic uptake of HDL cholesteryl esters. HL is not required for the increase in hepatic triglyceride secretion or for the lowering of HDL-cholesterol induced by PLTP overexpression.

Reduction of HDL levels lowers plasma PLTP and affects its distribution among lipoproteins in mice

Phospholipid transfer protein (PLTP) is associated with HDL particles in plasma, where it transfers phospholipids between lipoproteins and remodels HDL particles. Tangier disease patients, with a mutated ABCA1 transporter, have extremely low plasma HDL concentration and reduced PLTP activity levels, a phenotype that is also observed in mice lacking ABCA1. We investigated whether low HDL levels and low PLTP activity are mechanistically related. Firstly, we studied PLTP expression and distribution among lipoproteins in mice lacking ABCA1 (ABCA1 −/−). Parallel to the strong reduction in PLTP activity in plasma of ABCA1 −/− mice, decreased PLTP protein levels were observed. Neither PLTP synthesis in liver or macrophages nor the ability of the macrophages to secrete PLTP were impaired in ABCA1 −/− mice. However, the PLTP activity level in the medium of cultured macrophages was determined by HDL levels in the medium. PLTP was associated with HDL particles in wild type mice, whereas in ABCA1 −/− mice, PLTP was associated with VLDL and LDL particles. Secondly, we treated different mouse models with varying plasma HDL and PLTP levels (wild type, ABCA1 −/−, apoE −/− and PLTPtg mice, overexpressing human PLTP) with a synthetic LXR ligand, and investigated the relationship between LXR-mediated PLTP induction and HDL levels in plasma. Plasma PLTP activity in wild type mice was induced 5.6-fold after LXR activation, whereas in ABCA1 −/−, apoE −/− and PLTPtg mice, all having reduced HDL levels, induction of PLTP activity was 2.4- , 3.2- and 2.0-fold, respectively. The less pronounced PLTP induction in these mice compared to wild type mice was not caused by a decreased PLTP gene expression in the liver or macrophages. Our findings indicate that the extent of LXR-mediated PLTP induction depends on plasma HDL levels. In conclusion, we demonstrate that ABCA1 deficiency in mice affects plasma PLTP level and distribution through an indirect effect on HDL metabolism. In addition, we show that the extent of LXR-mediated PLTP induction is HDL-dependent. These findings indicate that plasma HDL level is an important regulator of plasma PLTP and might play a role in the stabilization of PLTP in plasma.

Relation of baseline plasma phospholipid transfer protein (PLTP) activity to left ventricular systolic dysfunction in patients referred for coronary angiography

Phospholipid transfer protein (PLTP) is an important modulator of phospholipid transfer and exchange among proteins. It also plays a role in inflammation and oxidative stress. Accordingly, PLTP has been implicated in the development of atherosclerosis. Left ventricular (LV) systolic dysfunction is common in patients with atherosclerosis, and both inflammation and oxidative stress have also been implicated in its development and progression. The goal of the present study was to examine the relation between plasma PLTP activity and LV systolic function. Baseline plasma PLTP activity was measured in 389 male patients referred for coronary angiography for a variety of indications. Detailed clinical, angiographic and laboratory characteristics were available for the patients. Compared to those patients with normal LV function (defined as an ejection fraction of ≥55% on ventriculography), patients with any degree of LV dysfunction had elevated PLTP activity (median PLTP 17.8 pmol/μl/h versus 15.9 pmol/μl/h, p = 0.0038). Using multivariate analysis, and adjusting for a variety of confounding variables known to affect both LV function and PLTP activity, PLTP activity was an independent predictor of the presence of any left ventricular systolic dysfunction in the entire population (OR 1.47, 95% CI 1.12–1.93, p = 0.0052). Furthermore, PLTP activity was an independent predictor of the presence of LV dysfunction in both patients with and without myocardial infarction on presentation (OR 2.39, 95% CI 1.18–4.86, p = 0.0161 and OR 1.41, 95% CI 1.05–1.89, p = 0.0206, respectively). In conclusion, PLTP activity may represent a novel marker of LV systolic dysfunction in patients with known or suspected coronary artery disease.

PLTP activity is a risk factor for subsequent cardiovascular events in CAD patients under statin therapy: the AtheroGene Study

Phospholipid transferprotein (PLTP) mediates both net transfer and exchange of phospholipids between different lipoproteins. Although many studies have investigated the role of PLTP in atherogenesis, the role of PLTP in atherosclerotic diseases is unclear. We investigated the association of serum PLTP activity with the incidence of a combined endpoint (myocardial infarction and cardiovascular death) and its relation to other markers of atherosclerosis in 1,085 patients with angiographically documented coronary artery disease (CAD). In the median follow-up of 5.1 years, 156 patients had suffered from the combined endpoint of myocardial infarction or cardiovascular death including 47 of 395 patients who were on statins at baseline. In Kaplan-Meyer analyses serum PLTP activity was not associated with the combined endpoint in all patients. However, in the subgroup of patients receiving statins at baseline, PLTP was shown to be a significant predictor of cardiovascular outcome (P = 0.019), and this also remained stable in univariate (P = 0.027) and multivariate cox regression analyses (P = 0.041) including potential confounders (classical risk factors, HDL cholesterol (HDL-C), and others). We showed in our study that, under statin treatment, high plasma PLTP activity was related to fatal and nonfatal cardiovascular events in CAD patients.

Plasma pre β-HDL formation is decreased by atorvastatin treatment in type 2 diabetes mellitus: Role of phospholipid transfer protein

Atorvastatin lowers plasma phospholipid transfer protein (PLTP) activity, which stimulates pre-β-HDL generation in vitro. We determined the effect of atorvastatin on pre-β-HDL formation and its relation with PLTP activity in type 2 diabetes. Methods: Plasma pre-β-HDL formation as well as plasma apo A-I, LpA, LpAI:AII, cholesteryl ester transfer protein (CETP) and PLTP activity were measured before and after 30 weeks treatment in 40 patients randomized to atorvastatin 80 mg daily and 41 placebo receiving patients. Pre-β HDL formation was measured by crossed immunoelectrophoresis under conditions of lecithin:cholesterol acyltransferase (LCAT) inhibition. Results: Plasma pre-β-HDL formation, triglycerides, LDL cholesterol, PLTP activity, and CETP decreased after statin treatment (all P < 0.001 vs placebo), whereas HDL cholesterol increased ( P < 0.005). Plasma apo A-I, LpAI and LpAI:AII remained unchanged compared to placebo. In all patients combined, the changes in pre-β-HDL formation were independently related to the decrease in plasma triglycerides ( β = 0.31; P = 0.006) and PLTP activity ( β = 0.23; P = 0.038), without a contribution of CETP. In the atorvastatin treated patients, the decrease in pre-β-HDL formation tended to be related to the decrease in PLTP activity ( β = 0.30, P = 0.061) after controlling for decreases in triglycerides ( β = 0.22, P = 0.22). Conclusion: High dose atorvastatin decreases the capacity of plasma to generate pre-β-HDL particles in type 2 diabetic patients, probably via lowering of plasma PLTP activity and triglycerides. This could contribute to an improvement in the atherogenic lipoprotein profile.

Ataxia with vitamin E deficiency with a mutation in a phospholipid transfer protein gene

Sirs, Ataxia with isolated vitamin E deficiency (AVED) is an autosomal-recessive spinocerebellar degeneration caused by a mutation of the a-tocopherol transfer protein gene (aTTP) [3, 8]. This report presents a case of juvenile spinocerebellar ataxia caused by mutations in the phospholipid transfer protein (PLTP) gene as well as the aTTP gene. This is the first report to indentify a mutation in the PLTP gene associated with vitamin E-mediated spinocerebellar ataxia. The proband was a 54-year-old female who had developed resting tremors in her right hand and ataxia at 14 years of age. At around 30 years of age, her bilateral visual acuity was decreased by retinitis pigmentosa. Her parents were second-degree cousins. On neurological examination she exhibited ataxia, dysarthria, hyporeflexia, decreased proprioceptive and vibratory sensations, and resting tremors of the extremities. The serum vitamin E concentration was observed to be about half normal level, 4.2 mg/l (normal: 10.8 ± 3.3 mg/l). The results of the following laboratory tests were normal: other fat-soluble vitamins, liverand pancreas-function tests, serum lipids, lipoproteins and apoproteins. The gene analysis revealed a homozygous H101Q mutation in the aTTP gene (Fig. 1a). In AVED, the genotype–phenotype correlation is confirmed, thus indicating that the H101Q mutation is associated with retinitis pigmentosa, late onset during the 3rd decade of life and very low serum vitamin E levels (Table 1) [3, 10, 11]. The clinical findings of the current patient characteristic of juvenile onset and a mild decrease in the serum vitamin E level suggested that other genes associated with vitamin E metabolism might affect the phenotype. Genomic analyses in the PLTP gene revealed the patient and her mother were heterozygous for a H154R mutation (Fig. 1b, c). This mutation was not found in 96 healthy subjects and was different from any previously reported polymorphisms. Following intestinal absorption of vitamin E, aTTP incorporates vitamin E into VLDL resulting in secretion from the liver to the circulation. The plasma PLTP transfers vitamin E from VLDL to HDL. HDL is the predominant source of vitamin E for the brain capillary endothelial cells which facilitates uptake of vitamin E to deliver it to the central nervous system [2, 9]. The PLTP is expressed in the brain, and PLTP knock-out studies showed that PLTP deficiency caused a decrease of vitamin E content in the brain and elevated plasma concentration of vitamin E [1, 6]. The proband and mother heterozygous for the H154R mutation showed a normal plasma PLTP concentration measured by ELISA [7]; however, the plasma PLTP activity was decreased to half the normal level measured by a PLTP assay kit (BioVision, Mountain View, CA) (Table 2). His154 is located in the N-terminal domain with conserved lipid-binding pockets associated with biochemical activity [4], and therefore this H154R mutation may induce the biological dysfunction of the PLTP without causing any impairment of intracellular trafficking. PLTP is an important factor regulating the size and composition of HDL and controlling plasma HDL levels [5]. The identification of the PLTP mutation may thus make it S. Kono (&) A. Otsuji K. Shirakawa H. Suzuki H. Miyajima First Department of Medicine, Hamamatsu University School of Medicine, 1-20-1 Handayama, Hamamatsu 431-3192, Japan e-mail: satokono@hama-med.ac.jp

Human plasma phospholipid transfer protein specific activity is correlated with HDL size: Implications for lipoprotein physiology

To gain further insights into the relationship between plasma phospholipid transfer protein (PLTP) and lipoprotein particles, PLTP mass and phospholipid transfer activity were measured, and their associations with the level and size of lipoprotein particles examined in 39 healthy adult subjects. No bivariate correlation was observed between PLTP activity and mass. PLTP activity was positively associated with cholesterol, triglyceride, apo B and VLDL particle level ( r s = 0.40–0.56, p ≤ 0.01) while PLTP mass was positively associated with HDL-C, large HDL particles, and mean LDL and HDL particle sizes ( r s = 0.44–0.52, p < 0.01). Importantly, plasma PLTP specific activity (SA) was significantly associated with specific lipoprotein classes, positively with VLDL, IDL, and small LDL particles ( r s = 0.42–0.62, p ≤ 0.01) and inversely with large LDL, large HDL, and mean LDL and HDL particle size ( r s = − 0.42 to − 0.70, p ≤ 0.01). After controlling for triglyceride levels, the correlation between PLTP mass or SA and HDL size remained significant. In linear models, HDL size explained 45% of the variability of plasma PLTP SA while triglyceride explained 34% of the PLTP activity. Thus, in healthy adults a significant relationship exists between HDL size and plasma PLTP SA ( r s = − 0.70), implying that HDL particle size may modulate PLTP SA in the vascular compartment.