Protein Composition Of High-density Lipoprotein Research Articles

Abstract 3040: Quantitative Proteomic Analysis Of HDL Shows Apolipoprotein M (ApoM) As A Possible Marker For COVID-19 Mortality

Introduction: High-density lipoprotein (HDL) comprises a heterogeneous group of particles that differ in many aspects, such as density, size, composition and function. The use of mass spectrometry-based proteomics to investigate HDL protein composition has brought some new insights into the field. The qualitative and quantitative HDL proteome is remodeled in different disease states, such as diabetes mellitus, hypercholesterolemia and kidney dysfunction. Beyond its established role in inflammatory and cardiovascular diseases, HDL's involvement in infectious diseases, such as COVID-19, has recently come to light. Here, we investigate the remodeling of HDL proteome in hospitalized and non-hospitalized COVID-19 patients. Hypothesis: We hypothesize HDL proteome is remodeled in infectious diseases and may be a marker and perhaps a predictor of a poor prognosis. Methods: We implemented a robust, global label-free quantification proteomic approach to unravel relative changes in HDL protein composition. We analyzed the proteome of COVID-19 subjects from Brazil categorized in two groups, hospitalized (n=30) and non-hospitalized (n=11). Results: Comparative analysis between hospitalized and non-hospitalized patients revealed a more than 50% increase in relative levels of certain proteins in hospitalized patients, including the inflammatory proteins serum amyloid A1 and A2, as well as pulmonary surfactant-associated protein B. We also observed reductions in the lipid-metabolism related apolipoprotein A2 and phospholipid transfer protein. These findings, independent of sex, triglyceride and HDL-cholesterol, suggest an inflammatory remodeling of the HDL particles. Further analysis of surviving (n=35) and deceased patients (n=6) indicated a negative association between ApoM levels and odds of death due to COVID-19 complications (odds ratio per 1-SD increase in ApoM was 0.27 [0.07 to 0.72], P=0.007). Conclusions: Our results point out HDL remodeling is a marker of COVID-19 severity and ApoM-carried sphingosine-1-phosphate signaling pathway may play a pivotal role in the disease outcome.

THE PROTEOME OF HIGH DENSITY LIPOPROTEIN CHANGES THROUGHOUT GESTATION IN HEALTHY PREGNANCY AND DIFFERS BETWEEN HEALTHY PREGNANCY AND PREECLAMPSIA IN THE THIRD TRIMESTER

Objective: High-density lipoprotein (HDL) has well-established anti-atherosclerotic properties in the non-pregnant population. HDL may have a potential role in protecting maternal vascular function during pregnancy that fails to occur in preeclampsia. HDL function is determined by its protein and lipid composition. This study aimed to examine protein composition of HDL at different gestations throughout healthy pregnancy and to compare HDL proteome in the third trimester of healthy pregnancy and preeclampsia. Design and method: HDL was isolated from two cohorts of n = 10 healthy pregnant women at 8 different timepoints throughout pregnancy; pre-pregnancy, week 4.6, week 6.1, week 8.4, (cohort 1) and week 15, week 25, week 35 and 3 months post-natal (cohort 2), and from healthy pregnant (n = 10) and preeclampsia (n = 6) women at the third trimester. The proteome of HDL was measured by nano liquid chromatography coupled to tandem mass spectrometry (nLC-MS/MS). Results: There were 16 proteins in HDL that showed significant differences throughout healthy pregnancy which were apolipoprotein A-IV, apolipoprotein C-II, apolipoprotein C-III, apolipoprotein C-IV, apolipoprotein F, apolipoprotein L-I, angiotensinogen, alpha-1-acid glycoprotein 2, alpha-1-antitrypsin, cathelicidin antimicrobial peptide, fibrinogen alpha chain, fibrinogen beta chain, prenylcysteine oxidase 1, serum amyloid a-I, serum paraoxonase/lactonase 3 and vitronectin. In preeclampsia, HDL apolipoprotein A-I was lower than healthy pregnancy, while HDL alpha-1-antitrypsin, pigment epithelium-derived factor and vitamin D-binding protein were higher. Conclusions: There were significant differences in the protein composition of HDL during pregnancy and between healthy pregnancy and preeclampsia in the third trimester. These compositional differences may be involved in HDL function and may indicate HDL's role in vascular protection in pregnancy.

Connection between the Altered HDL Antioxidant and Anti-Inflammatory Properties and the Risk to Develop Alzheimer's Disease: A Narrative Review.

The protein composition of high-density lipoprotein (HDL) is extremely fluid. The quantity and quality of protein constituents drive the multiple biological functions of these lipoproteins, which include the ability to contrast atherogenesis, sustained inflammation, and toxic effects of reactive species. Several diseases where inflammation and oxidative stress participate in the pathogenetic process are characterized by perturbation in the HDL proteome. This change inevitably affects the functionality of the lipoprotein. An enlightening example in this frame comes from the literature on Alzheimer's disease (AD). Growing lines of epidemiological evidence suggest that loss of HDL-associated proteins, such as lipoprotein phospholipase A2 (Lp-PLA2), glutathione peroxidase-3 (GPx-3), and paraoxonase-1 and paraoxonase-3 (PON1, PON3), may be a feature of AD, even at the early stage. Moreover, the decrease in these enzymes with antioxidant/defensive action appears to be accompanied by a parallel increase of prooxidant and proinflammatory mediators, in particular myeloperoxidase (MPO) and serum amyloid A (SAA). This type of derangement of balance between two opposite forces makes HDL dysfunctional, i.e., unable to exert its “natural” vasculoprotective property. In this review, we summarized and critically analyzed the most significant findings linking HDL accessory proteins and AD. We also discuss the most convincing hypothesis explaining the mechanism by which an observed systemic occurrence may have repercussions in the brain.

Hydrogen influences HDL-associated enzymes and reduces oxidized phospholipids levels in rats fed with a high-fat diet

AimsOxidized phospholipids (OxPLs) are formed as a result of oxidative stress, which potentially mediate multiple pathological effects. We aimed to evaluate the effects of hydrogen (H2) on OxPLs in vivo and the underlying mechanism. Main methodsRats were randomly assigned to three groups: control group fed with a chow diet, model group fed with a high-fat diet, and H2-treated group fed with a high-fat diet and treated by 4% H2 inhalation for ten weeks. OxPLs in liver and plasma were analyzed by liquid chromatography–mass spectrometry. High-density lipoprotein (HDL) was separated by ultracentrifugation. A proteomic analysis was performed to reveal the alternation of HDL protein composition and he antioxidant capacity of HDL was tested by low-density lipoprotein oxidation experiment. Furthermore, the activity or expression of HDL-associated enzymes were evaluated. Key findingsInhalation of 4% H2 decreased the accumulation of OxPLs in rats. In vitro tests revealed that the different concentrations of H2 did not inhibit the formation of OxPLs mediated by non-enzymatic oxidation. H2 inhalation altered the components and enhanced the anti-oxidative capacity of HDL in rats fed with a high-fat diet. Further experiments showed that H2 significantly regulated the activity of lipoprotein-associated phospholipase A2, paraoxonase-1, and the expression of lecithin:cholesterol acyltransferase. SignificanceOur findings revealed that H2 may reduce the OxPLs levels through its influence on HDL-associated enzymes that can act on OxPLs, suggesting that H2 can be used in alleviating diseases related to lipid peroxidation due to oxidative stress.

Proteomic alterations of HDL in youth with type 1 diabetes and their associations with glycemic control: a case\u2013control study

BackgroundPatients with type 1 diabetes (T1DM) typically have normal or even elevated plasma high density lipoprotein (HDL) cholesterol concentrations; however, HDL protein composition can be altered without a change in cholesterol content. Alteration of the HDL proteome can result in dysfunctional HDL particles with reduced ability to protect against cardiovascular disease (CVD). The objective of this study was to compare the HDL proteomes of youth with T1DM and healthy controls (HC) and to evaluate the influence of glycemic control on HDL protein composition.MethodsThis was a cross-sectional case–control study. Blood samples were obtained from patients with T1DM and HC. HDL was isolated from plasma by size-exclusion chromatography and further purified using a lipid binding resin. The HDL proteome was analyzed by mass spectrometry using label-free SWATH peptide quantification.ResultsSamples from 26 patients with T1DM and 13 HC were analyzed and 78 HDL-bound proteins were measured. Youth with T1DM had significantly increased amounts of complement factor H related protein 2 (FHR2; adjusted P < 0.05), compared to HC. When patients were analyzed based on glucose control, several trends emerged. Some proteins were altered in T1DM and not influenced by glycemic control (e.g. FHR2) while others were partially or completely corrected with optimal glucose control (e.g. alpha-1-beta glycoprotein, A1BG). In a subgroup of poorly controlled T1DM patients, inter alpha trypsin inhibitor 4 (ITIH4) was dramatically elevated (P < 0.0001) and this was partially reversed in patients with optimal glucose control. Some proteins including complement component C3 (CO3) and albumin (ALB) were significantly different only in T1DM patients with optimal glucose control, suggesting a possible effect of exogenous insulin.ConclusionsYouth with T1DM have proteomic alterations of their HDL compared to HC, despite similar concentration of HDL cholesterol. The influence of these compositional changes on HDL function are not yet known. Future efforts should focus on investigating the role of these HDL associated proteins in regard to HDL function and their role in CVD risk in patients with T1DM.Trial registration NCT02275091

Serum amyloid A levels are associated with polymorphic variants in the serum amyloid A 1 and 2 genes

BackgroundSerum amyloid A (SAA) is secreted by liver hepatocytes in response to increased inflammation whereupon it associates with high-density lipoprotein (HDL) and alters the protein and lipid composition of HDL negating some of its anti-atherogenic properties.AimsTo identify variants within the SAA gene that may be associated with SAA levels and/or cardiovascular disease (CVD).MethodsWe identified exonic variants within the SAA genes by deoxyribonucleic acid (DNA) Sanger sequencing. We tested the association between SAA variants and serum SAA levels in 246 individuals with and without CVD.ResultsIncreased SAA was associated with rs2468844 (beta [β] = 1.73; confidence intervals [CI], 1.14–1.75; p = 0.01), rs1136747 (β = 1.53 (CI, 1.11–1.73); p = 0.01) and rs149926073 (β = 3.37 (CI, 1.70–4.00); p = 0.02), while rs1136745 was significantly associated with decreased SAA levels (β = 0.70 (CI, 0.53–0.94); p = 0.02). Homozygous individuals with the SAA1.3 haplotype had significantly lower levels of SAA compared with those with SAA1.1 or SAA1.5 (β = 0.43 (CI, 0.22–0.85); p = 0.02) while SAA1.3/1.5 heterozygotes had significantly higher SAA levels compared with those homozygous for SAA1.1 (β = 2.58 (CI, 1.19–5.57); p = 0.02).ConclusionsWe have identified novel genetic variants in the SAA genes associated with SAA levels, a biomarker of inflammation and chronic disease. The utility of SAA as a biomarker for inflammation and chronic disease may be influenced by underlying genetic variation in baseline levels.

Association of Perfluoroalkyl substances with Hyperuricemia and Gout

There is a growing body of evidence that persistent organic pollutants (POPs) may increase the risk for cardiovascular disease (CVD), but the mechanisms remain unclear. High-density lipoprotein (HDL) acts protective against CVD by different processes, and we have earlier found that HDL from subjects with CVD contains higher levels of POPs than healthy controls. In the present study, we have expanded analyses on the same individuals living in a contaminated community and investigated the relationship between the HDL POP levels and protein composition/function.HDL from 17 subjects was isolated by ultracentrifugation. HDL protein composition, using nanoliquid chromatography tandem mass spectrometry, and antioxidant activity were analyzed. The associations of 16 POPs, including polychlorinated biphenyls (PCBs) and organochlorine pesticides, with HDL proteins/functions were investigated by partial least square and multiple linear regression analysis.Proteomic analyses identified 118 HDL proteins, of which ten were significantly (p < 0.05) and positively associated with the combined level of POPs or with highly chlorinated PCB congeners. Among these, cholesteryl ester transfer protein and phospholipid transfer protein, as well as the inflammatory marker serum amyloid A, were found. The serum paraoxonase/arylesterase 1 activity was inversely associated with POPs. Pathway analysis demonstrated that up-regulated proteins were associated with biological processes involving lipoprotein metabolism, while down-regulated proteins were associated with processes such as negative regulation of proteinases, acute phase response, platelet degranulation, and complement activation.These results indicate an association between POP levels, especially highly chlorinated PCBs, and HDL protein alterations that may result in a less functional particle. Further studies are needed to determine causality and the importance of other environmental factors. Nevertheless, this study provides a first insight into a possible link between exposure to POPs and risk of CVD.

Kidney function is associated with an altered protein composition of high-density lipoprotein

Patients with chronic kidney disease (CKD) exhibit a myriad of metabolic derangements, including dyslipidemia characterized by low plasma concentrations of high-density lipoprotein (HDL)-associated cholesterol. However, the effects of kidney disease on HDL composition have not been comprehensively determined. Here we used a targeted mass spectrometric approach to quantify 38 proteins contained in the HDL particles within a CKD cohort of 509 participants with a broad range of estimated glomerular filtration rates (eGFRs) (CKD stages I-V, and amean eGFR of 45.5 mL/min/1.73m2). After adjusting formultiple testing, demographics, comorbidities, medications, and other characteristics, eGFR was significantly associated with differences in four HDL proteins. Compared to participants with an eGFR of 60mL/min/1.73m2 or more, those with an eGFR under 15mL/min/1.73m2 exhibited 1.89-fold higher retinol-binding protein 4 (95% confidence interval 1.34-2.67), 1.52-fold higher apolipoprotein C-III (1.25-1.84), 0.70-fold lower apolipoprotein L1 (0.55-0.92), and 0.64-fold lower vitronectin (0.48-0.85). Although the HDL apolipoprotein L1was slightly lower among African Americans than among Caucasian individuals, the relationship to eGFR didnot differ by race. After adjustment, no HDL-associated proteins associated with albuminuria. Thus, modest changes in the HDL proteome provide preliminary evidence for an association between HDL proteins and declining kidney function, but this needs to be replicated. Future analyses will determine if HDL proteomics is indeed a clinical predictor of declining kidney function or cardiovascular outcomes.

Alterations in high-density lipoprotein proteome and function associated with persistent organic pollutants

There is a growing body of evidence that persistent organic pollutants (POPs) may increase the risk for cardiovascular disease (CVD), but the mechanisms remain unclear. High-density lipoprotein (HDL) acts protective against CVD by different processes, and we have earlier found that HDL from subjects with CVD contains higher levels of POPs than healthy controls. In the present study, we have expanded analyses on the same individuals living in a contaminated community and investigated the relationship between the HDL POP levels and protein composition/function.HDL from 17 subjects was isolated by ultracentrifugation. HDL protein composition, using nanoliquid chromatography tandem mass spectrometry, and antioxidant activity were analyzed. The associations of 16 POPs, including polychlorinated biphenyls (PCBs) and organochlorine pesticides, with HDL proteins/functions were investigated by partial least square and multiple linear regression analysis.Proteomic analyses identified 118 HDL proteins, of which ten were significantly (p<0.05) and positively associated with the combined level of POPs or with highly chlorinated PCB congeners. Among these, cholesteryl ester transfer protein and phospholipid transfer protein, as well as the inflammatory marker serum amyloid A, were found. The serum paraoxonase/arylesterase 1 activity was inversely associated with POPs. Pathway analysis demonstrated that up-regulated proteins were associated with biological processes involving lipoprotein metabolism, while down-regulated proteins were associated with processes such as negative regulation of proteinases, acute phase response, platelet degranulation, and complement activation.These results indicate an association between POP levels, especially highly chlorinated PCBs, and HDL protein alterations that may result in a less functional particle. Further studies are needed to determine causality and the importance of other environmental factors. Nevertheless, this study provides a first insight into a possible link between exposure to POPs and risk of CVD.

Abstract 530: A Cluster of Proteins Implicated in Kidney Disease Are Increased in HDL of Hemodialysis Subjects

Objectives: Cardiovascular disease (CVD) is the leading cause of death in uremic subjects on dialysis. However, this large increase cannot be completely explained by the conventional risk factors frequently seen in this population. One important factor could be alterations of high-density lipoprotein (HDL) protein composition that impair its cardioprotective functions. We therefore investigated alterations in the HDL proteome of end-stage renal disease (ESRD) patients undergoing hemodialysis. Methods and Results: We first used shotgun proteomics to investigate the protein composition of HDL isolated by ultracentrifugation in 20 control and 40 ESRD subjects. This analysis identified 63 proteins in HDL, which were linked to lipid and lipoprotein metabolism, immune response, acute phase response, complement regulation, inhibitors of proteolysis, vitamin binding and transport, and platelet activation/coagulation. We then used targeted proteomics by isotope-dilution MS/MS with selected reaction monitoring (SRM) to provide precise and accurate relative quantification of 37 proteins in HDL. This quantitative approach revealed that 22 proteins (including SAA1, apoA-IV, apoC-II, apoC-III) were significantly enriched and six proteins (including apoA-I, apoA-II, PON1) were significantly decreased in ESRD patients. Moreover, several of these proteins (SAA1, apoC-III, PON1, etc.) have been associated with atherosclerosis. Strikingly, six proteins implicated in renal disease–AMBP, B2M, CFD, CST3, PTGDS and RBP4–were markedly increased in HDL of uremic subjects. Conclusions: Our observations indicate that ESRD markedly remodels the HDL proteome. Moreover, our quantitative analysis of the HDL proteome identified a cluster of six proteins that are dramatically enriched in HDL from patients with ESRD. Our observations support the proposal that the protein cargo of HDL can serve as a marker - and perhaps mediator - of renal disease and serve as novel biomarkers for ESRD status. Therefore, quantifying proteins in HDL might help diagnose and perhaps treat human cardiovascular disease in kidney disease.

Fatty acid manipulation of obesity – consequences for high-density lipoprotein protein composition and macrophage-to-feces reverse cholesterol transport (rct)

Fatty acid manipulation of obesity – consequences for high-density lipoprotein protein composition and macrophage-to-feces reverse cholesterol transport (rct)

ApoA‐I mutations, L202P and K131del, in HDL from heterozygotes with low HDL‐C

Mutations in apolipoprotein A-I (apoA-I) may affect plasma high-density lipoprotein (HDL) cholesterol levels and the risk for cardiovascular disease but little is known about the presence and effects of circulating apoA-I variants. This study investigates whether the apoA-I mutations, apoA-I(L202P) and apoA-I(K131del) , are present on plasma HDL particles derived from heterozygote carriers and whether this is associated to changes in HDL protein composition. Plasma HDL of heterozygotes for either apoA-I(L202P) or apoA-I(K131del) and family controls was isolated using ultracentrifugation. HDL proteins were separated by 2DE and analyzed by MS. ApoA-I peptides containing apoA-I(L202P) or apoA-I(K131del) were identified in HDL from heterozygotes. The apoA-I(L202P) mutant peptide was less abundant than wild-type peptide while the apoA-I(K131del) mutant peptide was more abundant than wild-type peptide in the heterozygotes. Two-dimensional gel electrophoresis analyses indicated that, compared to controls, HDL in apoA-I(L202P) carriers contained less apoE and more zinc-α-2-glycoprotein while HDL from the apoA-I(K131del) heterozygotes contained more alpha-1-antitrypsin and transthyretin. Both apoA-I(L202P) and apoA-I(K131del) were identified in HDL. In heterozygotes, these mutations have markedly differential effects on the concentration of wild-type apoA-I in the circulation, as well as the HDL proteome, both of which might affect the clinical phenotype encountered in the heterozygous carriers.

The relationship between serum amyloid A and apolipoprotein A-I in high-density lipoprotein isolated from patients with coronary heart disease

Background Alteration in the protein composition of high-density lipoprotein (HDL) has been proposed as a mechanism for the development of coronary heart disease (CHD). In HDL, an increase in serum amyloid A protein (SAA) accompanying the decrease in apolipoprotein A-I (apoA-I) has been found during the acute inflammation period. However, whether this phenomenon persists in CHD patients, a disease related to inflammation, is unknown. The purpose of the present study was to explore the relationship between SAA and apoA-I in HDL isolated from CHD patients. Methods Overall, 98 patients with confirmed stable CHD and 90 control subjects matched for age and gender were enrolled in this case-control study. Potassium bromide (KBr) density gradient ultracentrifugation was used to isolate HDL from plasma. The levels of SAA and apoA-I in the HDL samples were detected by enzyme-linked immunosorbent assay kits. Pearson's correlation and general linear models were used in the analysis. Results Compared with controls, patients with CHD had a significant decrease in the amount of apoA-I ((14.21±8.44) μg/ml vs. (10.95±5.95) μg/ml, P =0.003) in HDL and a significant increase in the amount of log SAA (1.21±0.46 vs. 1.51±0.55, P &lt;0.00001). Differences were independent of age, body mass index (BMI), HDL cholesterol (HDL-C), and other factors. An independently and statistically significant positive correlation between log SAA and apoA-I in HDL was observed only in the CHD group (β =2.0, P =0.026). In the general linear model, changes in log(SAA), age, age2, gender, BMI and HDL-C could explain a statistically significant 43% of the variance in apoA-I. Conclusions This study provides direct evidence for the first time that there was an independent positive correlation between log SAA and apoA-I in the HDL of CHD patients, indicating the alteration of protein composition in HDL. However, the question of whether this alteration in HDL is associated with impairment of HDL functions requires further research.

HDL’s Protein Cargo

Low levels of high-density lipoprotein (HDL) particles were first linked to increased risk of cardiovascular disease (CVD) >40 years ago.1 Because analytic ultracentrifugation, the method used for those pioneering studies, is complex and time consuming, clinical investigators began to use HDL cholesterol (HDL-C) as a surrogate measure for HDL concentration. Clinical, epidemiological, and genetic studies provide robust evidence that low HDL-C levels associate with clinically significant CVD.2 Moreover, atherosclerosis increases markedly in hypercholesterolemic mice deficient in apolipoprotein (apoA)-I,3 the major HDL protein, whereas overexpression of human apoA-I dramatically retards atherosclerosis in hypercholesterolemic mice.4 Many lines of evidence indicate that apoA-I and HDL promote cholesterol efflux from macrophages, a key step in atherogenesis.5 Taken together, these findings provide strong evidence that apoA-I plays a key role in HDL’s cardioprotective activities. Article see p 891 These observations have triggered intense interest in targeting HDL-C for therapeutic intervention, because lowering low-density lipoprotein (LDL) levels with statins leaves a large residual risk in CVD subjects. However, several lines of evidence suggest that the association between HDL-C levels and CVD status is not a causal relationship and that elevating HDL-C is not necessarily therapeutic.6,7 For example, genetic variations that only affect HDL-C levels do not markedly alter CVD risk. Also, trials of several drugs that elevate …

HDL protein composition alters from proatherogenic into less atherogenic and proinflammatory in rheumatoid arthritis patients responding to rituximab

ObjectiveAn atherogenic lipid profile is an established risk factor for cardiovascular (CV) diseases. Interestingly, high inflammatory states as present in rheumatoid arthritis (RA) are associated with unfavourable lipid profile. Data...

High-density lipoprotein proteome dynamics in human endotoxemia

BackgroundA large variety of proteins involved in inflammation, coagulation, lipid-oxidation and lipid metabolism have been associated with high-density lipoprotein (HDL) and it is anticipated that changes in the HDL proteome have implications for the multiple functions of HDL. Here, SELDI-TOF mass spectrometry (MS) was used to study the dynamic changes of HDL protein composition in a human experimental low-dose endotoxemia model. Ten healthy men with low HDL cholesterol (0.7+/-0.1 mmol/L) and 10 men with high HDL cholesterol levels (1.9+/-0.4 mmol/L) were challenged with endotoxin (LPS) intravenously (1 ng/kg bodyweight). We previously showed that subjects with low HDL cholesterol are more susceptible to an inflammatory challenge. The current study tested the hypothesis that this discrepancy may be related to differences in the HDL proteome.ResultsPlasma drawn at 7 time-points over a 24 hour time period after LPS challenge was used for direct capture of HDL using antibodies against apolipoprotein A-I followed by subsequent SELDI-TOF MS profiling. Upon LPS administration, profound changes in 21 markers (adjusted p-value < 0.05) were observed in the proteome in both study groups. These changes were observed 1 hour after LPS infusion and sustained up to 24 hours, but unexpectedly were not different between the 2 study groups. Hierarchical clustering of the protein spectra at all time points of all individuals revealed 3 distinct clusters, which were largely independent of baseline HDL cholesterol levels but correlated with paraoxonase 1 activity. The acute phase protein serum amyloid A-1/2 (SAA-1/2) was clearly upregulated after LPS infusion in both groups and comprised both native and N-terminal truncated variants that were identified by two-dimensional gel electrophoresis and mass spectrometry. Individuals of one of the clusters were distinguished by a lower SAA-1/2 response after LPS challenge and a delayed time-response of the truncated variants.ConclusionsThis study shows that the semi-quantitative differences in the HDL proteome as assessed by SELDI-TOF MS cannot explain why subjects with low HDL cholesterol are more susceptible to a challenge with LPS than those with high HDL cholesterol. Instead the results indicate that hierarchical clustering could be useful to predict HDL functionality in acute phase responses towards LPS.

The role of high-density lipoproteins in reducing the risk of vascular diseases, neurogenerative disorders, and cancer.

High-density lipoprotein (HDL) is one of the major carriers of cholesterol in the blood. It attracts particular attention because, in contrast with other lipoproteins, as many physiological functions of HDL influence the cardiovascular system in favourable ways unless HDL is modified pathologically. The functions of HDL that have recently attracted attention include anti-inflammatory and anti-oxidant activities. High anti-oxidant and anti-inflammatory activities of HDL are associated with protection from cardiovascular disease. Atheroprotective activities, as well as a functional deficiency of HDL, ultimately depend on the protein and lipid composition of HDL. Further, numerous epidemiological studies have shown a protective association between HDL-cholesterol and cognitive impairment. Oxidative stress, including lipid peroxidation, has been shown to be the mediator of the pathologic effects of numerous risk factors of Alzheimer's disease. Lifestyle interventions proven to increase HDL- cholesterol levels including “healthy” diet, regular exercise, weight control, and smoking cessation have also been shown to provide neuro-protective effects. This review will focus on current knowledge of the beneficial effects of HDL-cholesterol as it relates to cardiovascular diseases, breast and lung cancers, non-Hodgkin's lymphoma, as well as its neuroprotective potential in reducing the risk of Alzheimer's disease and dementia.

Anti‐oxidant properties of high‐density lipoprotein and atherosclerosis

1. High-density lipoprotein (HDL) is one of the major carriers of cholesterol in the blood. It attracts particular attention because, in contrast with other lipoproteins, many physiological functions of HDL influence the cardiovascular system in favourable ways unless HDL is modified pathologically. 2. The best known function of HDL is the capacity to promote cellular cholesterol efflux from peripheral cells and deliver cholesterol to the liver for excretion, thereby playing a key role in reverse cholesterol transport. The functions of HDL that have recently attracted attention include anti-inflammatory and anti-oxidant activities. High anti-oxidant and anti-inflammatory activities of HDL are associated with protection from cardiovascular disease. 3. Atheroprotective activities, as well as a functional deficiency of HDL, ultimately depend on the protein and lipid composition of HDL. Conversely, these activities are compromised in many pathological states associated with inflammation. 4. The focus of the present review is on the anti-oxidant and anti-inflammatory functions of HDL and its individual components in relation to protection from atherosclerosis.

SELDI-TOF mass spectrometry of High-Density Lipoprotein

BackgroundHigh-Density Lipoprotein (HDL), one of the main plasma lipoproteins, serves as a docking station for proteins involved in inflammation, coagulation, and lipid metabolism.MethodsTo elucidate the protein composition of HDL, we employed SELDI-TOF mass spectrometry as a potential high-throughput proteomic candidate for protein profiling of HDL. HDL derived from normolipemic individuals was captured on PS20 protein-chips using covalently bound antibodies against apo A-I or A-II.ResultsAfter optimisation, on-chip capture of HDL particles directly from plasma or from pre-purified HDL resulted in comparable fingerprints confirming specific capture of HDL. Depending on the capture antibody some differences in the fingerprint were observed. The most detailed fingerprint was observed up to 50 kDa; approximately 95 peaks were detected in the 3–50 kDa molecular mass range. Between 50 and 160 kDa, 27 more peaks were detected.ConclusionBased on these results, SELDI-TOF MS may be a suitable high-throughput candidate for HDL protein profiling and marker search. This approach may be used to i) investigate the underlying mechanisms that lead to increased atherothrombotic risk and ii) to investigate the atherothrombotic state of an individual.

Characterization of lipoproteins during human cholestasis

We have characterized changes in lipoproteins from cholestatic individuals and reproduced them by incubating lipoproteins from healthy individuals with cholic acid. The cholestatic patients showed an increase in low density lipoprotein (LDL) (> 85%), with a smaller proportion of esterified cholesterol, and a fall in high density lipoprotein (HDL) (< 10%), with a larger proportion of phospholipids. The protein composition of cholestatic HDL 1 was characterized by a smaller proportion of apo A (I, II) and a prominent apo E fraction (39% vs. 9%). These changes involved an increase in degree of molecular packing (order) of HDL 1. The addition of cholic acid to serum from healthy individuals altered the lipoprotein distribution, with an increase in LDL, the disappearance of HDL 2 and HDL 3 and the appearance of HDL 1. These HDL 1 were characterized by increased phospholipid and reduced apo AI fractions. They also showed a lower density and appeared as spherical particles in contrast to cholestatic HDL. Incubation of healthy HDL with cholic acid in vitro reproduces some of the alteration observed in cholestatic HDL.