Impaired High-density Lipoprotein Function Research Articles

ANGPTL3 as a target for treating lipid disorders in type 2 diabetes patients

Type 2 diabetes mellitus (T2DM) is a globally prevalent metabolic disorder, and cardiovascular disease (CVD) is a significant cause of mortality and morbidity in diabetic individuals. In addition to hyperglycemia, lipid abnormalities associated with T2DM play a crucial role in the development of CVD complications. Diabetic dyslipidemia is characterized by elevated levels of triglyceride (TG)-rich lipoproteins and small dense low-density lipoprotein (LDL) particles, reduced high-density lipoprotein (HDL) cholesterol, and impaired HDL function. Angiopoietin protein-like 3 (ANGPTL3) is a liver-derived protein that plays a crucial role in regulating plasma lipoprotein metabolism by inhibiting lipoprotein lipase and influencing lipid levels. Inhibiting ANGPTL3 has shown promising effects in promoting HDL-mediated cholesterol reverse transport and reducing the levels of TG-rich lipoproteins and LDL cholesterol. Here, we explore the potential of ANGPTL3 as a therapeutic target for lipid management in T2DM patients.

Impaired HDL antioxidant and anti-inflammatory functions are linked to increased mortality in acute heart failure patients

AimsAcute heart failure (AHF) is typified by inflammatory and oxidative stress responses, which are associated with unfavorable patient outcomes. Given the anti-inflammatory and antioxidant properties of high-density lipoprotein (HDL), this study sought to examine the relationship between impaired HDL function and mortality in AHF patients. The complex interplay between various HDL-related biomarkers and clinical outcomes remains poorly understood. MethodsHDL subclass distribution was quantified by nuclear magnetic resonance spectroscopy. Lecithin–cholesterol acyltransferase (LCAT) activity, cholesterol ester transfer protein (CETP) activity, and paraoxonase (PON-1) activity were assessed using fluorometric assays. HDL-cholesterol efflux capacity (CEC) was assessed in a validated assay using [3H]-cholesterol-labeled J774 macrophages. ResultsAmong the study participants, 74 (23.5 %) out of 315 died within three months after hospitalization due to AHF. These patients exhibited lower activities of the anti-oxidant enzymes PON1 and LCAT, impaired CEC, and lower concentration of small HDL subclasses, which remained significant after accounting for potential confounding factors. Smaller HDL particles, particularly HDL3 and HDL4, exhibited a strong association with CEC, PON1 activity, and LCAT activity. ConclusionsIn patients with AHF, impaired HDL CEC, HDL antioxidant and anti-inflammatory function, and impaired HDL metabolism are associated with increased mortality. Assessment of HDL function and subclass distribution could provide valuable clinical information and help identify patients at high risk.

Impaired high-density lipoprotein function and endothelial barrier stability in severe anaphylaxis

Growing evidence demonstrates the importance of high- and low-density lipoprotein cholesterol in certain immune and allergy-mediated diseases. This study aimed to evaluate levels of high- and low-density lipoprotein cholesterol and apolipoproteins A1 and B in sera from a cohort of patients presenting with hypersensitivity reactions. We further assessed the function of high-density lipoprotein particles as well as their involvement in the molecular mechanisms of anaphylaxis. Lipid profile determination was performed in paired (acute and baseline) serum samples from 153 patients. Thirty-eight experienced a non-anaphylactic reaction and 115 had an anaphylactic reaction (88 moderate and 27 severe). Lecithin cholesterol acyl transferase activity was assessed in patient sera, and we also evaluated macrophage cholesterol efflux in response to the serum samples. Last, the effect of anaphylactic-derived high-density lipoprotein (HDL) particles on the endothelial barrier was studied. Detailed methods are provided in the Methods section in this article's Online Repository available at www.jacionline.org. Serum samples from severe anaphylactic reactions show statistically significant low levels of HDL cholesterol, low-density lipoprotein cholesterol, and apolipoproteins A1 and B, which points to their possible role as biomarkers. Specifically, HDL particles play a protective role in cardiovascular diseases. Using functional human serum cell assays, we observed impaired capacity of apolipoprotein B-depleted serum to induce macrophage cholesterol efflux in severe anaphylactic reactions. In addition, purified HDL particles from human anaphylactic sera failed to stabilize and maintain the endothelial barrier. These results encourage further research on HDL functions in severe anaphylaxis, which may lead to new diagnostic and therapeutic strategies.

High-density lipoprotein cholesterol efflux capacity in patients with obstructive sleep apnea and its relation with disease severity

BackgroundObstructive sleep apnea (OSA) is linked to an accelerated risk of cardiovascular disease (CVD). Some key CVD risk factors are present in patients suffering from OSA such as hypertension, inflammation, oxidative stress, and dyslipidemia. High-density lipoprotein (HDL) cholesterol efflux capacity (CEC) is proposed as a reliable biomarker of HDL function and the present study aimed to quantify this biomarker in patients with OSA.MethodsATP binding cassette subfamily A member 1 (ABCA1), non-ABCA1, and total CEC were determined in 69 polysomnographic-confirmed OSA patients and 23 controls. Moreover, paraoxonase (PON) activities, high-sensitivity C-reactive protein (hsCRP), apolipoprotein B (apo B), and apolipoprotein A-I (apo A-I) circulating levels were quantified in the studied population.Results: All CEC measures were reduced in the OSA group compared to the control group. Strikingly, ABCA1 CEC was diminished in severe OSA in comparison with mild OSA. Furthermore, PON activities and apo A-I showed lower levels, while hsCRP and apo B were elevated in OSA patients compared to controls. Moreover, ABCA1 CEC showed an inverse association with hsCRP and a positive association with apo A-I, while non-ABCA1 CEC presented an association with HDL-C.ConclusionThese results suggest the presence of an impaired HDL function in OSA. In particular, ABCA1 CEC was associated with disease severity and inflammation which could be a factor increasing the risk of CVD.

Association between high oxidized high-density lipoprotein levels and increased pericoronary inflammation determined by coronary computed tomography angiography

BackgroundImpaired high-density lipoprotein (HDL) function is a risk factor for cardiac mortality. We aimed to investigate the association between oxidized HDL (oxHDL) and pericoronary adipose tissue (PCAT) attenuation, a novel imaging biomarker of pericoronary inflammation, by using coronary computed tomography angiography (CTA). MethodsA total of 287 outpatients with suspected coronary artery disease who had undergone both oxHDL measurement and coronary CTA were examined. PCAT attenuation values were assessed at the proximal 10–50 mm segments of the right coronary artery on coronary CTA. The presence of significant stenosis (luminal narrowing of >50 %) and high-risk plaque characteristics were also evaluated. Patients were then classified into tertiles according to their oxHDL level: low (n = 95), moderate (n = 96), and high (n = 96) groups. ResultsPCAT attenuation in the high oxHDL group was significantly higher than that in other groups after adjusting for age and apolipoprotein-A-I. Multivariate linear regression analysis revealed that oxHDL was significantly associated with PCAT attenuation in the right coronary artery (β = 3.832, p < 0.001), whereas HDL cholesterol was not. Furthermore, subgroup analyses demonstrated that the association between oxHDL and PCAT attenuation remained significant in older patients (β = 6.367, p < 0.001) and in those with hypertension (β = 4.922, p < 0.011), dyslipidemia (β = 3.264, p = 0.010), diabetes mellitus (β = 4.284, p = 0.015), and significant stenosis (β = 3.075, p = 0.021). ConclusionsHigh oxHDL levels were significantly associated with increased pericoronary inflammation, as assessed using coronary CTA. Our results may explain the association between impaired HDL function and the development of coronary atherosclerosis.

High-density lipoprotein lipid peroxidation in association with presence of coronary artery disease and atrial fibrillation in a large cross-sectional study

Abstract Background The function of high-density lipoprotein (HDL) cholesterol may play a more important role in the prevention of cardiovascular disease compared to the concentration of the HDL. Cardiovascular diseases such as coronary artery disease (CAD) and atrial fibrillation (AF) have been linked to impaired HDL function. Purpose The aim of the present study is to assess a biochemical measure of the antioxidant function of HDL and its association with presence of CAD and AF. Methods Patients admitted for elective cardiac catheterization were recruited in this cross-sectional study. Out of 1231 participants that were included in the analyses, 727 patients had confirmed CAD (CAD group), 369 patients had no CAD (no CAD group) and 129 persons were included as a control group. HDL function was measured in sera by determination of HDL-lipid peroxidation content (HDLox) assessed by a validated fluorometric cell-free biochemical assay and was normalized for the levels of HDL cholesterol (normalized HDLox/HDL-C ratio or nHDLox; no units). Results are expressed as median with interquartile range. Associations of nHDLox with presence of CAD and AF were assessed by univariate and multivariate analyses. Results Participants in the CAD group had higher levels of nHDLox (0.80, 0.61–1.03) compared to the no CAD (0.70, 0.55–0.93) and control (0.66, 0.55–1.03, no units, p&amp;lt;0.001) group. Out of 1206 participants, 233 (19%) had AF and 973 (81%) had no AF. Patients with AF have also higher nHDLox (0.82, 0.60–10.03) compared to persons without AF (0.73, 0.58–0.98, p=0.03). In univariate analysis nHDLox was associated with CAD (p&amp;lt;0.001). In multivariate analysis adjusted for age, gender, CAD, BMI and hypertension, nHDLox was a strong independent predictor of atrial fibrillation (p=0.015) but was not an independent predictor of CAD (p&amp;gt;0.05) Conclusions Reduced antioxidant function of HDL (increased HDLox measured by a biochemical assay), a metric of HDL function, is increased in patients with atherosclerosis and manifested CAD and is also associated with the presence of atrial fibrillation independent of the presence of CAD. Funding Acknowledgement Type of funding sources: Public hospital(s). Main funding source(s): Medical School of Brandenburg-MHB Fontane

Impaired high-density lipoprotein function in patients with heart failure

Abstract Background We recently showed that a lower high-density lipoprotein cholesterol (HDL-C) concentration was one of the strongest predictors of death or heart failure (HF) hospitalisation in patients with HF. In a follow-up study, we suggested that this association could be partly explained by HDL proteome composition. However, whether the emerging concept of HDL function contributes to prognosis of HF patients has not been addressed. Methods We measured three key HDL function metrics, namely cholesterol efflux, antioxidative capacity, and anti-inflammatory capacity, at baseline and after 9 months in 446 randomly selected HF patients from BIOSTAT-CHF. Additionally, the relationship between HDL functionality and HDL proteome composition was determined in 86 patients. Results From baseline to 9 months, HDL-C concentrations did not substantially change, but HDL-mediated cholesterol efflux and anti-inflammatory capacity had decreased (both P&amp;lt;0.001). In contrast, antioxidative capacity improved during the 9 months follow-up (P&amp;lt;0.001). Higher HDL-mediated cholesterol efflux was independently associated with lower risk of mortality after adjustment for BIOSTAT risk models and log HDL-C (HR=0.81 [95% CI: 0.71–0.92], P=0.001). Other functionality parameters were not associated with outcome. Several HDL proteins correlated with HDL functionality, mainly with cholesterol efflux, and apolipoprotein A1 emerged as the main protein associated with all three functionality parameters. Conclusions HDL-mediated cholesterol efflux and anti-inflammatory capacity significantly decreased over time in patients with HF. Better baseline cholesterol efflux was prospectively associated with reduced mortality during follow-up independent of HDL-C. Combined these data indicate that HDL function measurements have the potential to provide clinical information beyond static HDL-C concentrations in HF patients. Changes in HDL functionality over time Funding Acknowledgement Type of funding source: Public grant(s) – EU funding. Main funding source(s): European Commission

HDL and Reverse Cholesterol Transport.

Cardiovascular disease, with atherosclerosis as the major underlying factor, remains the leading cause of death worldwide. It is well established that cholesterol ester-enriched foam cells are the hallmark of atherosclerotic plaques. Multiple lines of evidence support that enhancing foam cell cholesterol efflux by HDL (high-density lipoprotein) particles, the first step of reverse cholesterol transport (RCT), is a promising antiatherogenic strategy. Yet, excitement towards the therapeutic potential of manipulating RCT for the treatment of cardiovascular disease has faded because of the lack of the association between cardiovascular disease risk and what was typically measured in intervention trials, namely HDL cholesterol, which has an inconsistent relationship to HDL function and RCT. In this review, we will summarize some of the potential reasons for this inconsistency, update the mechanisms of RCT, and highlight conditions in which impaired HDL function or RCT contributes to vascular disease. On balance, the evidence still argues for further research to better understand how HDL functionality contributes to RCT to develop prevention and treatment strategies to reduce the risk of cardiovascular disease.

Soluble levels of receptor for advanced glycation endproducts and dysfunctional high-density lipoprotein in persons infected with human immunodeficiency virus: ACTG NWCS332.

The role of high-density lipoprotein (HDL) function and advanced glycation end products (AGEs) in HIV-related atherosclerotic cardiovascular disease (CVD) is unclear. Both glycation and oxidation (HDLox) are major modifications of HDL that can alter its composition and function. Therefore, we explored the longitudinal association of HDLox with progression of glycation, as evaluated by measurement of circulating forms of receptor for AGE that predict morbidity (soluble Receptors for Advanced Glycation Endproducts [sRAGE], endogenous secretory Receptors for Advanced Glycation Endproducts [esRAGE]), in people with HIV-1 (PWH; HIV-1+) and uninfected (HIV-1−) individuals.We retrospectively assessed if levels of plasma sRAGE and esRAGE and HDL function (reduced antioxidant function is associated with increased HDL lipid hydroperoxide content; HDLox) in a subset of participants (n = 80) from a prospective 3-year study (AIDS Clinical Trials Group A5078). Primary outcomes were baseline and yearly rates of change over 96 of 144 weeks (Δ) in HDLox in HIV-1+ versus uninfected HIV-1 controls (noted as HIV-1−).Higher baseline levels of sRAGE in PWH on effective anti-retroviral therapy and with low CVD risk, but not in HIV-1− persons, were independently associated with higher HDLox. EsRAGE, but not sRAGE, had consistent inverse relationships with ΔHDLox in both HIV-1+ and HIV-1− persons at baseline. In HIV-1− but not in HIV-1+ persons, ΔHDLox had positive and inverse relationships with ΔRAGE and ΔesRAGE, respectively.Glycation and oxidation of HDL may contribute to impaired HDL function present in PWH.

Dysfunctional high-density lipoprotein from HIV+ individuals promotes monocyte-derived foam cell formation in vitro.

The role of high-density lipoprotein (HDL) function in HIV-related atherosclerotic cardiovascular disease (CVD) is unclear. HDLs isolated from HIV [HIV(+)HDL] and HIV-uninfected individuals [HIV(-)HDL] were assessed for HDL function and ability to promote monocyte-derived foam cell formation (MDFCF; a key event in HIV-related CVD) ex vivo. Using an established in-vitro model of atherogenesis and plasma samples from an established cross-sectional study of virologically suppressed HIV men on stable effective antiretroviral therapy and with low CVD risk (median age: 42 years; n = 10), we explored the impact of native HDL [HIV(+)HDL] on MDFCF. In this exploratory study, we selected HIV(+)HDL known to be dysfunctional based on two independent measures of impaired HDL function: antioxidant (high HDLox) ability of HDL to release apolipoprotein A-I (ApoA-I) (low HDL-ApoA-I exchange). Five healthy men matched by age and race to the HIV group were included. Given that oxidation of HDL leads to abnormal HDL function, we also compared proatherogenic effects of HIV(+)HDL vs. chemically derived HDLox. The ex-vivo atherogenesis assay was performed using lipoproteins (purchased or isolated from plasma using ultracentrifugation) and monocytes purified via negative selection from healthy donors. HIV(+)HDL known to have reduced antioxidant function and rate of HDL/ApoAI exchange promoted MDFCF to a greater extent than HDL (33.0 vs. 26.2% foam cells; P = 0.015). HDL oxidized in vitro also enhanced foam cell formation as compared with nonoxidized HDL (P < 0.01). Dysfunctional HDL in virologically suppressed HIV individuals may potentiate atherosclerosis in HIV infection by promoting MDFCF.The role of HDL function in HIV-related atherosclerotic CVD is unclear. HDL isolated from HIV [HIV(+)HDL] and HIV-uninfected individuals [HIV(-)HDL] were assessed for HDL function and ability to promote foam cell formation ex vivo. HIV(+)HDL known to have reduced antioxidant function and rate of HDL/ApoA1 exchange promoted MDFCF to a greater extent than HDL(-)HDL (33.0 vs. 26.2% foam cells.Subject codes: Inflammation, Lipids and Cholesterol, Vascular Biology, Oxidant Stress, Atherosclerosis.

Predictors of Impaired HDL Function in HIV-1 Infected Compared to Uninfected Individuals.

High-density lipoprotein (HDL) function rather than absolute level may be a more accurate indicator for cardiovascular disease (CVD). Novel methods can measure HDL function using patient samples. The objective of this study is to identify factors that may contribute to HDL dysfunction in chronic treated HIV-1 infection. Retrospective study of HDL function measured in 2 ways in HIV-1-infected men with low overall CVD risk and healthy men with no known CVD risk matched by race to the HIV-1-infected participants. We examined patient-level factors associated with 2 different measures of HDL dysfunction: reduced antioxidant function (oxidized HDL, HDLox) and reduced HDL-apoA-I exchange (HAE), a measure of HDL remodeling, in the HIV infected and control men. Multivariable-adjusted linear regression analyses were used adjusting for false discovery rate, age, race, body mass index (BMI), CD4 count, viremia, CVD risk, smoking, lipids, apoA-I, and albumin. In multivariate analysis among HIV-1-infected men (n = 166) (median age 45 years, CD4 T-cell count 505 cells/mm, 30.1% were viremic), higher BMI, lower apoA-I, and lower albumin were among the most notable correlates of higher HDLox and lower HAE (P < 0.05). In HIV-1 uninfected participants, lower albumin and higher BMI were associated with lower HAE and higher HDLox, respectively (P ≤ 0.05). HDLox was inversely related to HAE in HIV-1-infected individuals (P < 0.001). Increased HDLox correlates with reduced HAE in chronic HIV-1 infection. Higher BMI, lower apoA-I, and albumin were identified as factors associated with HDL dysfunction in chronic HIV-1 infection using 2 independent methods.

Impaired High-Density Lipoprotein Anti-Oxidant Function Predicts Poor Outcome in Critically Ill Patients.

IntroductionOxidative stress affects clinical outcome in critically ill patients. Although high-density lipoprotein (HDL) particles generally possess anti-oxidant capacities, deleterious properties of HDL have been described in acutely ill patients. The impact of anti-oxidant HDL capacities on clinical outcome in critically ill patients is unknown. We therefore analyzed the predictive value of anti-oxidant HDL function on mortality in an unselected cohort of critically ill patients.MethodWe prospectively enrolled 270 consecutive patients admitted to a university-affiliated intensive care unit (ICU) and determined anti-oxidant HDL function using the HDL oxidant index (HOI). Based on their HOI, the study population was stratified into patients with impaired anti-oxidant HDL function and the residual study population.ResultsDuring a median follow-up time of 9.8 years (IQR: 9.2 to 10.0), 69% of patients died. Cox regression analysis revealed a significant and independent association between impaired anti-oxidant HDL function and short-term mortality with an adjusted HR of 1.65 (95% CI 1.22–2.24; p = 0.001) as well as 10-year mortality with an adj. HR of 1.19 (95% CI 1.02–1.40; p = 0.032) when compared to the residual study population. Anti-oxidant HDL function correlated with the amount of oxidative stress as determined by Cu/Zn superoxide dismutase (r = 0.38; p<0.001).ConclusionImpaired anti-oxidant HDL function represents a strong and independent predictor of 30-day mortality as well as long-term mortality in critically ill patients.

Abstract 15426: CSL112 Enhances Cholesterol Efflux Equally in Patients with High and Low High Density Lipoprotein Functionality

Introduction: The ability of high-density lipoprotein (HDL) to remove cholesterol from macrophages in atherosclerotic plaque is thought to underlie its inverse correlation with cardiovascular risk. CSL112 is a novel formulation of apoA-I purified from human plasma and reconstituted to form HDL particles suitable for infusion. Two phase 1 studies in healthy subjects and one phase 2a study in coronary heart disease (CHD) patients have demonstrated favorable safety, pharmacokinetics and biomarker responses to single or multiple infusions of CSL112. The aim of the current study was to assess the influence of subject-specific HDL functionality, sometimes described as HDL dysfunction, on the pharmacodynamic effects of CSL112. Methods and Results: To assess HDL functionality, we measured the specific cholesterol efflux activity of apoA-I (cholesterol efflux divided by apoA-I) in subjects at baseline. CHD patients (mean ± SD = 7.3 ± 0.3 %efflux per g/L apoA-I (n=43)) had lower activity (p&lt;0.001) than healthy subjects (mean ± SD = 8.8 ± 0.2 % efflux per g/L apoA-I (n=93)), consistent with prior work showing impaired HDL function in CHD patients. Every subject infused with CSL112 responded, showing increased apoA-I plasma levels and serum cholesterol efflux. To assess changes in HDL functionality upon infusion of CSL112, we plotted changes in cholesterol efflux vs changes in apoA-I. To account for variations of these analytes over time and dose, we plotted area under curve (AUC) for 0 to 24 h after infusion of various doses of CSL112. In all three studies, AUC for apoA-I correlated with the AUC for cholesterol efflux, with coincident lines, indicating equal elevation in efflux among healthy and CHD patients. To further examine this relationship, subjects were stratified into tertiles based on specific activity. Infusion of CSL112 elevated efflux similarly in subjects in the highest HDL functionality and lowest HDL functionality tertiles. Conclusion: ApoA-I from CHD patients compared to healthy subjects had lower specific activity in regards to cholesterol efflux. CSL112 causes strong elevation in cholesterol efflux regardless of HDL function and represents a promising candidate to rapidly remove plaque cholesterol and reduce recurrent atherothrombotic events.

Molecular Composition and Function of High-Density Lipoprotein Is Uniquely Altered After Kidney Transplantation.

Background: Renal transplant recipients experience increased cardiovascular morbidity and mortality, largely unaffected by therapeutic measures such as statins: here we studied molecular composition and functionality of High-Density Lipoprotein (HDL) to explore a potential mechanism of this excessive cardiovascular risk. Methods: HDL from fresh human plasma of stable renal transplant (CKD I-IV) and end-stage renal disease (ESRD) patients as well as matched healthy controls was isolated by one-step density gradient ultracentrifugation. Protein composition was analyzed by shotgun proteomics and confirmed by immunoblot. Functional HDL modifications were determined by measurement of cholesterol-efflux, the membrane cholesterol concentration in peripheral blood mononuclear cells and paraoxonase-1 activity. Results: We found that distinct proteins like surfactant protein B, serum amyloid A, pigment epithelium-derived factor and alpha-1 microglobulin/bikunin precursor were enriched in HDL of renal transplant patients similar to ESRD patients indicating a characteristic disease-specific HDL proteome. Of note, alterations of HDL were virtually identical between patients with CKD I-II and III-IV and independent of transplant vintage. Furthermore, transplant HDL displayed decreased cholesterol acceptor capacity, but substantially increased free cholesterol within patient leukocytes. Finally, impaired anti-oxidative HDL function was demonstrated by decreased paraoxonase-1 activity in all transplant groups. Conclusion: We demonstrate unique alterations of HDL from renal transplant recipients at the molecular and functional level. Importantly, remodeling of HDL including enrichment of distinct proteins previously identified from uremic HDL was also observed in patients with excellent graft function independent of the transplant vintage. These data may therefore not only help to unravel the causes of the excessive cardiovascular risk in renal transplant patients, but may also pave the way for novel diagnostic and innovative therapeutic directions.

Decreased cholesterol efflux capacity in patients with low cholesteryl ester transfer protein plasma levels

Cholesteryl ester transfer protein (CETP) has been considered as a possible target for treatment of cardiovascular disease. However, first clinical studies employing CETP inhibitors have failed to demonstrate clinical benefit. Additionally, we have previously shown that low endogenous plasma levels of CETP are associated with increased mortality in coronary artery disease (CAD) patients. We hypothesized that low CETP plasma levels are associated with decreased high-density lipoprotein (HDL) function. Serum HDL efflux capacity was measured in 154 patients of the Ludwigshafen Risk and Cardiovascular Health (LURIC) study displaying extremely low (< 0·68 μg/mL, n = 77) or high (> 2·13 μg/mL, n = 77) CETP concentrations in their plasma, respectively. The LURIC study is a prospective observational study of patients referred to coronary angiography at baseline with a median follow-up time of 7·75 years. Primary and secondary endpoints were cardiovascular and all-cause mortality, respectively. High CETP patients showed a significant increase in the capacity of their plasma to mediate cholesterol efflux from cholesterol laden macrophages when compared to the efflux capacity observed in low CETP patients (+ 5·4%, P = 0·015). As shown by multiregression analysis, the impact of CETP on cholesterol efflux capacity was independent from classical risk and lifestyle factors, as well as from lipid parameters including HDL cholesterol, LDL cholesterol and triglycerides. Our findings indicate that low plasma concentrations of CETP might indeed lead to impaired HDL function within the reverse cholesterol transport pointing towards an atheroprotective role of CETP at least in patients with high risk of CAD.

Phospholipid Transfer Protein Deficiency Decreases the Content of S1P in HDL via the Loss of its Transfer Capability

Sphingosine-1-phosphate (S1P) is an amphiphilic signaling molecule, which is enriched in functional high density lipoprotein (HDL) and shows arterial protection. The distribution of S1P is changed with increased plasma phospholipid transfer protein (PLTP) activity and impaired HDL function in patients with coronary heart diseases. Therefore, we hypothesized that PLTP might transfer S1P among cells or lipoproteins. We found that plasma S1P contents were decreased by 60.1% in PLTP knockout mice (PLTP-/-, N=5) compared with their wild type littermates (WT, N=5) (151.70±38.59 vs. 379.32±59.90nmol/l, P<0.01). S1P content in HDL fraction (HDL-S1P) from PLTP-/- was decreased by 64.7% compared with WT (49.36±1.49 vs. 139.76±2.94nmol/l, P<0.01). The results of the S1P transfer assay indicated that PLTP could facilitate S1P transport from erythrocytes to HDL at 37°C in D-Hanks buffer. Plasma content of apolipoprotein M, a specific adaptor of S1P, was not changed in PLTP-/- compared with WT. Therefore, we concluded that PLTP was a key factor to maintain plasma HDL-S1P, and PLTP deficiency could decrease the S1P content in plasma lipoproteins, which involves its capability of transferring S1P from erythrocyte to HDL.