A pro-atherogenic HDL profile in coronary heart disease patients: an iTRAQ labelling-based proteomic approach

Closing the gaps in patient management of dyslipidemia: stepping into cardiovascular precision diagnostics with apolipoprotein profiling

In persons with dyslipidemia, a high residual risk of cardiovascular disease remains despite lipid lowering therapy. Current cardiovascular risk prediction mainly focuses on low-density lipoprotein cholesterol (LDL-c) levels, neglecting other contributing risk factors. Moreover, the efficacy of LDL-c lowering by statins resulting in reduced cardiovascular risk is only partially effective. Secondly, from a metrological viewpoint LDL-c falls short as a reliable measurand. Both direct and calculated LDL-c tests produce inaccurate test results at the low end under aggressive lipid lowering therapy. As LDL-c tests underperform both clinically and metrologically, there is an urging need for molecularly defined biomarkers. Over the years, apolipoproteins have emerged as promising biomarkers in the context of cardiovascular disease as they are the functional workhorses in lipid metabolism. Among these, apolipoprotein B (ApoB), present on all atherogenic lipoprotein particles, has demonstrated to clinically outperform LDL-c. Other apolipoproteins, such as Apo(a) - the characteristic apolipoprotein of the emerging risk factor lipoprotein(a) -, and ApoC-III - an inhibitor of triglyceride-rich lipoprotein clearance -, have attracted attention as well. To support personalized medicine, we need to move to molecularly defined risk markers, like the apolipoproteins. Molecularly defined diagnosis and molecularly targeted therapy require molecularly measured biomarkers. This review provides a summary of the scientific validity and (patho)physiological role of nine serum apolipoproteins, Apo(a), ApoB, ApoC-I, ApoC-II, ApoC-III, ApoE and its phenotypes, ApoA-I, ApoA-II, and ApoA-IV, in lipid metabolism, their association with cardiovascular disease, and their potential as cardiovascular risk markers when measured in a multiplex apolipoprotein panel.

Searching for Atherosclerosis Biomarkers by Proteomics: A Focus on Lesion Pathogenesis and Vulnerability

Plaque rupture and thrombosis are the most important clinical complications in the pathogenesis of stroke, coronary arteries, and peripheral vascular diseases. The identification of early biomarkers of plaque presence and susceptibility to ulceration could be of primary importance in preventing such life-threatening events. With the improvement of proteomic tools, large-scale technologies have been proven valuable in attempting to unravel pathways of atherosclerotic degeneration and identifying new circulating markers to be utilized either as early diagnostic traits or as targets for new drug therapies. To address these issues, different matrices of human origin, such as vascular cells, arterial tissues, plasma, and urine, have been investigated. Besides, proteomics was also applied to experimental atherosclerosis in order to unveil significant insights into the mechanisms influencing atherogenesis. This narrative review provides an overview of the last twenty years of omics applications to the study of atherogenesis and lesion vulnerability, with particular emphasis on lipoproteomics and vascular tissue proteomics. Major issues of tissue analyses, such as plaque complexity, sampling, availability, choice of proper controls, and lipoproteins purification, will be raised, and future directions will be addressed.

SARS-CoV-2 induced HDL dysfunction may affect the host's response to and recovery from COVID-19

INTRODUCTION

Covid-19 is linked with the development of cardio-metabolic disorders, including dyslipidemia, dysregulation of high-density lipoprotein (HDL), and low-density lipoprotein (LDL). Furthermore, SARS-Co-2 infection is associated with noteworthy changes in lipid profile, which is suggested as a possible biomarker to support the diagnosis and management of Covid-19.

METHODS

This paper adopts the literature review method to obtain information about how Covid-19 affects high-risk group patients and may cause severe and critical effects due to the development of acute lung injury and acute respiratory distress syndrome. A narrative and comprehensive review is presented.

RESULTS

Reducing HDL in Covid-19 is connected to the disease severity and poor clinical outcomes, suggesting that high HDL serum levels could benefit Covid-19. SARS-CoV-2 binds HDL, and this complex is attached to the co-localized receptors, facilitating viral entry. Therefore, SARS-CoV-2 infection may induce the development of dysfunctional HDL through different mechanisms, including induction of inflammatory and oxidative stress with activation of inflammatory signaling pathways. In turn, the induction of dysfunctional HDL induces the activation of inflammatory signaling pathways and oxidative stress, increasing Covid-19 severity.

CONCLUSIONS

Covid-19 is linked with the development of cardio-metabolic disorders, including dyslipidemia in general and dysregulation of high-density lipoprotein and low-density lipoprotein. Therefore, the present study aimed to overview the causal relationship between dysfunctional high-density lipoprotein and Covid-19.

Differences in HDL-Bound Apolipoproteins in Patients With Advanced Liver Fibrosis Due to Nonalcoholic Fatty Liver Disease

CONTEXT

The mechanisms leading to increased cardiovascular disease in patients with nonalcoholic fatty liver disease (NAFLD) and advanced liver fibrosis remain incompletely understood.

OBJECTIVE

This study assessed HDL-bound proteins in patients with NAFLD with or without advanced fibrosis.

METHODS

This cross-sectional study at a university hospital included 185 patients with or without type 2 diabetes (T2D). Patients underwent liver proton magnetic resonance spectroscopy to measure intrahepatic triglyceride accumulation and those with NAFLD underwent a percutaneous liver biopsy. Advanced lipid testing with lipoprotein subfraction measurements and targeted proteomics of HDL-bound proteins was performed.

RESULTS

Patients with and without advanced fibrosis had similar clinical characteristics, except for lower HDL-C (34 ± 8 vs 38 ± 9 mg/dL, P = 0.024) and higher prevalence of T2D in advanced fibrosis. Patients with advanced fibrosis had lower HDL particle number. A panel of 28 HDL-bound proteins were targeted and quantified by multiple reaction monitoring liquid chromatography-tandem mass spectrometry. Five proteins were found to be decreased in patients with advanced fibrosis (ApoC-I [P < 0.001], ApoC-IV [P = 0.012], ApoM [P = 0.008], LCAT [P = 0.014], and SAA4 [P = 0.016]). No differences were observed in these proteins in patients with vs without NAFLD or steatohepatitis. The pCAD index, associated with coronary artery disease and cardiovascular mortality, was significantly higher in patients with advanced fibrosis (97 ± 5 vs 86 ± 25, P = 0.04).

CONCLUSION

Patients with NAFLD with advanced fibrosis showed significant differences in HDL-bound protein levels; this translated into increased cardiovascular risk based on pCAD index. Different lipoprotein composition and function may explain the link between liver disease and increased cardiovascular mortality in these patients.

Plasma high-density lipoprotein cargo is altered in Alzheimer's disease and is associated with regional brain volume

Cholesterol levels have been repeatedly linked to Alzheimer's Disease (AD), suggesting that high levels could be detrimental, but this effect is likely attributed to Low-Density Lipoprotein (LDL) cholesterol. On the other hand, High-Density Lipoproteins (HDL) cholesterol levels have been associated with reduced brain amyloidosis and improved cognitive function. However, recent findings have suggested that HDL-functionality, which depends upon the HDL-cargo proteins associated with HDL, rather than HDL levels, appears to be the key factor, suggesting a quality over quantity status. In this report, we have assessed the HDL-cargo (Cholesterol, ApoA-I, ApoA-II, ApoC-I, ApoC-III, ApoD, ApoE, ApoH, ApoJ, CRP, and SAA) in stable healthy control (HC), healthy controls who will convert to MCI/AD (HC-Conv) and AD patients (AD). Compared to HC we observed an increased cholesterol/ApoA-I ratio in AD and HC-Conv, as well as an increased ApoD/ApoA-I ratio and a decreased ApoA-II/ApoA-I ratio in AD. Higher cholesterol/ApoA-I ratio was also associated with lower cortical grey matter volume and higher ventricular volume, while higher ApoA-II/ApoA-I and ApoJ/ApoA-I ratios were associated with greater cortical grey matter volume (and for ApoA-II also with greater hippocampal volume) and smaller ventricular volume. Additionally, in a clinical status-independent manner, the ApoE/ApoA-I ratio was significantly lower in APOE ε4 carriers and lowest in APOE ε4 homozygous. Together, these data indicate that in AD patients the composition of HDL is altered, which may affect HDL functionality, and such changes are associated with altered regional brain volumetric data.

Arylesterase activity of paraoxonase 1 in patients with primary hypertension

Introduction

Paraoxonase 1 is an enzyme associated with high-density lipoprotein fraction and is considered to present antioxidant activity.

Objectives

The aim of the study was to assess the arylesterase activity of paraoxonase 1 (PON1) in the serum of patients with hypertension, due to effect of therapy and before treatment. Patients and Methods. The study was conducted in 76 patients with primary hypertension and 28 volunteers for the control group. Hypertensive subjects were assigned to one of three groups: well controlled (n=25), poorly controlled (n=26), and newly diagnosed before therapy (n=25) hypertension. We evaluated metabolic parameters in all participants using routine laboratory methods, as well as arylesterase activity of PON1.

Results

The four study groups differed with arylesterase activity of PON1 and the highest levels were found in patients with well controlled hypertension and the lowest in newly diagnosed. All patients diagnosed with hypertension presented negative correlations between PON1 and systolic and diastolic blood pressure.

Conclusions

Effective treatment of hypertension could result in increased PON1 activity, despite unfavorable homocysteine concentrations in blood. Untreated hypertension might decrease activity of PON.

Apolipoprotein Signature of HDL and LDL from Atherosclerotic Patients in Relation with Carotid Plaque Typology: A Preliminary Report

In the past years, it has become increasingly clear that the protein cargo of the different lipoprotein classes is largely responsible for carrying out their various functions, also in relation to pathological conditions, including atherosclerosis. Accordingly, detailed information about their apolipoprotein composition and structure may contribute to the revelation of their role in atherogenesis and the understanding of the mechanisms that lead to atherosclerotic degeneration and toward vulnerable plaque formation. With this aim, shotgun proteomics was applied to identify the apolipoprotein signatures of both high-density and low-density lipoproteins (HDL and LDL) plasma fractions purified from healthy volunteers and atherosclerotic patients with different plaque typologies who underwent carotid endarterectomy. By this approach, two proteins with potential implications in inflammatory, immune, and hemostatic pathways, namely, integrin beta-2 (P05107) and secretoglobin family 3A member 2 (Q96PL1), have been confirmed to belong to the HDL proteome. Similarly, the list of LDL-associated proteins has been enriched with 21 proteins involved in complement and coagulation cascades and the acute-phase response, which potentially double the protein species of LDL cargo. Moreover, differential expression analysis has shown protein signatures specific for patients with “hard” or “soft” plaques.

The Importance of Lipoprotein Lipase Regulation in Atherosclerosis

Lipoprotein lipase (LPL) plays a major role in the lipid homeostasis mainly by mediating the intravascular lipolysis of triglyceride rich lipoproteins. Impaired LPL activity leads to the accumulation of chylomicrons and very low-density lipoproteins (VLDL) in plasma, resulting in hypertriglyceridemia. While low-density lipoprotein cholesterol (LDL-C) is recognized as a primary risk factor for atherosclerosis, hypertriglyceridemia has been shown to be an independent risk factor for cardiovascular disease (CVD) and a residual risk factor in atherosclerosis development. In this review, we focus on the lipolysis machinery and discuss the potential role of triglycerides, remnant particles, and lipolysis mediators in the onset and progression of atherosclerotic cardiovascular disease (ASCVD). This review details a number of important factors involved in the maturation and transportation of LPL to the capillaries, where the triglycerides are hydrolyzed, generating remnant lipoproteins. Moreover, LPL and other factors involved in intravascular lipolysis are also reported to impact the clearance of remnant lipoproteins from plasma and promote lipoprotein retention in capillaries. Apolipoproteins (Apo) and angiopoietin-like proteins (ANGPTLs) play a crucial role in regulating LPL activity and recent insights into LPL regulation may elucidate new pharmacological means to address the challenge of hypertriglyceridemia in atherosclerosis development.

Proteomics applications in biomarker discovery and pathogenesis for abdominal aortic aneurysm

Introduction: Abdominal aortic aneurysm (AAA) is a common, complex, and life-threatening disease. Currently, the pathogenesis of AAA is not well understood. No biomarkers or specific drugs are available for AAA in clinical applications. Proteomics is a powerful tool in biomarker discovery, exploration of pathogenesis, and drug target identification.Areas covered: We review the application of mass spectrometry-based proteome analysis in AAA patients within the last ten years. Differentially expressed proteins associated with AAA were identified in multiple sample sources, including vascular tissue, intraluminal thrombus, tissue secretome, blood, and cells. Some potential disease biomarkers, pathogenic mechanisms, or therapeutic targets for AAA were discovered using proteome analysis. The challenges and prospects of proteomics applied to AAA are also discussed.Expert opinion: Since most of the previous proteomic studies used relatively small sample sizes, some promising biomarkers need to be validated in multicenter cohorts to accelerate their clinical application. With the rapid development of mass spectrometry technology, modification-specific proteomics and multi-omics research in the future will enhance our understanding of the pathogenesis of AAA and promote biomarker discovery and drug development for clinical translation.

Protein-Defined Subspecies of HDLs (High-Density Lipoproteins) and Differential Risk of Coronary Heart Disease in 4 Prospective Studies

OBJECTIVE

HDL (high-density lipoprotein) contains functional proteins that define single subspecies, each comprising 1% to 12% of the total HDL. We studied the differential association with coronary heart disease (CHD) of 15 such subspecies. Approach and Results: We measured plasma apoA1 (apolipoprotein A1) concentrations of 15 protein-defined HDL subspecies in 4 US-based prospective studies. Among participants without CVD at baseline, 932 developed CHD during 10 to 25 years. They were matched 1:1 to controls who did not experience CHD. In each cohort, hazard ratios for each subspecies were computed by conditional logistic regression and combined by meta-analysis. Higher levels of HDL subspecies containing alpha-2 macroglobulin, CoC3 (complement C3), HP (haptoglobin), or PLMG (plasminogen) were associated with higher relative risk compared with the HDL counterpart lacking the defining protein (hazard ratio range, 0.96-1.11 per 1 SD increase versus 0.73-0.81, respectively; P for heterogeneity <0.05). In contrast, HDL containing apoC1 or apoE were associated with lower relative risk compared with the counterpart (hazard ratio, 0.74; P=0.002 and 0.77, P=0.001, respectively).

CONCLUSIONS

Several subspecies of HDL defined by single proteins that are involved in thrombosis, inflammation, immunity, and lipid metabolism are found in small fractions of total HDL and are associated with higher relative risk of CHD compared with HDL that lacks the defining protein. In contrast, HDL containing apoC1 or apoE are robustly associated with lower risk. The balance between beneficial and harmful subspecies in a person's HDL sample may determine the risk of CHD pertaining to HDL and paths to treatment.

Association of an HDL Apolipoproteomic Score With Coronary Atherosclerosis and Cardiovascular Death

BACKGROUND

Concentrations of circulating apolipoproteins are strongly linked to risk for coronary artery disease (CAD). The relative importance of the additional knowledge of apolipoprotein concentrations within specific lipoprotein species for CAD risk prediction is limited.

OBJECTIVES

This study sought to evaluate the performance of a high-density lipoprotein (HDL) apolipoproteomic score, based on targeted mass spectrometry of HDL-associated apolipoproteins, for the detection of angiographic CAD and outcomes.

METHODS

HDL-associated apolipoprotein (apo) A-1, apoC-1, apoC-2, apoC-3, and apoC-4 were measured in 943 participants without prevalent myocardial infarction (MI) referred for coronary angiography in the CASABLANCA (Catheter Sampled Blood Archive in Cardiovascular Diseases) study. A composite HDL apolipoproteomic score (pCAD) was associated with likelihood of obstructive CAD (≥70% lesion in ≥1 vessel) and with incident cardiovascular outcomes over 4-year follow-up.

RESULTS

There were 587 (62.2%) patients with coronary stenosis. The pCAD score was associated with the presence of obstructive CAD (odds ratio: 1.39; 95% confidence interval [CI]: 1.14 to 1.69; p < 0.001), independently of conventional cardiovascular risk factors including circulating plasma apoA-1 and apoB. The C-index for pCAD was 0.63 (95% CI: 0.59 to 0.67) for the presence of obstructive CAD. Although pCAD was not associated with cardiovascular mortality among all individuals (hazard ratio: 1.24; 95% CI: 0.93 to 1.66; p = 0.15), there was evidence of association for individuals with obstructive CAD (hazard ratio: 1.48; 95% CI: 1.07 to 2.05; p = 0.019).

CONCLUSIONS

An HDL apolipoproteomic score is associated with the presence of CAD, independent of circulating apoA-1 and apoB concentrations and other conventional cardiovascular risk factors. Among individuals with CAD, this score may be independently associated cardiovascular death. (The CASABLANCA Study: Catheter Sampled Blood Archive in Cardiovascular Diseases [CASABLANCA]; NCT00842868).

The Active Compounds of Yixin Ningshen Tablet and Their Potential Action Mechanism in Treating Coronary Heart Disease- A Network Pharmacology and Proteomics Approach

Yixin Ningshen tablet is a CFDA-approved TCM formula for treating coronary heart disease (CHD) clinically. However, its active compounds and mechanism of action in treating CHD are unknown. In this study, a novel strategy with the combination of network pharmacology and proteomics was proposed to identify the active components of Yixin Ningshen tablet and the mechanism by which they treat CHD. With the application of network pharmacology, 62 active compounds in Yixin Ningshen tablet were screened out by text mining, and their 313 potential target proteins were identified by a tool in SwissTargetPrediction. These data were integrated with known CHD-related proteomics results to predict the most possible targets, which reduced the 313 potential target proteins to 218. The STRING database was retrieved to find the enriched pathways and related diseases of these target proteins, which indicated that the Calcium, MAPK, PI3K-Akt, cAMP, Rap1, AGE-RAGE, Relaxin, HIF-1, Prolactin, Sphingolipid, Estrogen, IL-17, Jak-STAT signaling pathway, necroptosis, arachidonic acid metabolism, insulin resistance, endocrine resistance, and steroid hormone biosynthesis might be the main pathways regulated by Yixin Ningshen tablet for the treatment of CHD. Through further enrichment analysis and literature study, EGFR, ERBB2, VGFR2, FGF1, ESR1, LOX15, PGH2, HMDH, ADRB1, and ADRB2 were selected and then validated to be the target proteins of Yixin Ningshen tablet by molecular docking, which indicated that Yixin Ningshen tablet might treat CHD mainly through promoting heart regeneration, new vessels' formation, and the blood supply of the myocardial region and reducing cardiac output, oxygen demand, and inflammation as well as arteriosclerosis (promoting vasodilation and intraplaque neoangiogenesis, lowering blood lipid). This study is expected to benefit the clinical application of Yixin Ningshen tablet for the treatment of CHD.

Apolipoprotein C1: Its Pleiotropic Effects in Lipid Metabolism and Beyond

Apolipoprotein C1 (apoC1), the smallest of all apolipoproteins, participates in lipid transport and metabolism. In humans, APOC1 gene is in linkage disequilibrium with APOE gene on chromosome 19, a proximity that spurred its investigation. Apolipoprotein C1 associates with triglyceride-rich lipoproteins and HDL and exchanges between lipoprotein classes. These interactions occur via amphipathic helix motifs, as demonstrated by biophysical studies on the wild-type polypeptide and representative mutants. Apolipoprotein C1 acts on lipoprotein receptors by inhibiting binding mediated by apolipoprotein E, and modulating the activities of several enzymes. Thus, apoC1 downregulates lipoprotein lipase, hepatic lipase, phospholipase A2, cholesterylester transfer protein, and activates lecithin-cholesterol acyl transferase. By controlling the plasma levels of lipids, apoC1 relates directly to cardiovascular physiology, but its activity extends beyond, to inflammation and immunity, sepsis, diabetes, cancer, viral infectivity, and-not last-to cognition. Such correlations were established based on studies using transgenic mice, associated in the recent years with GWAS, transcriptomic and proteomic analyses. The presence of a duplicate gene, pseudogene APOC1P, stimulated evolutionary studies and more recently, the regulatory properties of the corresponding non-coding RNA are steadily emerging. Nonetheless, this prototypical apolipoprotein is still underexplored and deserves further research for understanding its physiology and exploiting its therapeutic potential.

Deepening our understanding of HDL proteome

Introduction: High-density lipoprotein (HDL) particles are heterogeneous and their proteome is complex and distinct from HDL cholesterol. However, it is largely unknown whether HDL proteins are associated with cardiovascular protection. Areas covered: HDL isolation techniques and proteomic analyses are reviewed. A list of HDL proteins reported in 37 different studies was compiled and the effects of different isolation techniques on proteins attributed to HDL are discussed. Mass spectrometric techniques used for HDL analysis and the need for precise and robust methods for quantification of HDL proteins are discussed. Expert opinion: Proteins associated with HDL have the potential to be used as biomarkers and/or help to understand HDL functionality. To achieve this, large cohorts must be studied using precise quantification methods. Key factors in HDL proteome quantification are the isolation methodology and the mass spectrometry technique employed. Isolation methodology affects what proteins are identified in HDL and the specificity of association with HDL particles needs to be addressed. Shotgun proteomics yields imprecise quantification, but the majority of HDL studies relied on this approach. Few recent studies used targeted tandem mass spectrometry to quantify HDL proteins, and it is imperative that future studies focus on the application of these precise techniques.

Modified lipoproteins in periodontitis: a link to cardiovascular disease?

There is a strong association between periodontal disease and atherosclerotic cardiovascular disorders. A key event in the development of atherosclerosis is accumulation of modified lipoproteins within the arterial wall. We hypothesise that patients with periodontitis have an altered lipoprotein profile towards an atherogenic form. Therefore, the present study aims at identifying modifications of plasma lipoproteins in periodontitis. Lipoproteins from ten female patients with periodontitis and gender- and age-matched healthy controls were isolated by density-gradient ultracentrifugation. Proteins were separated by 2D gel-electrophoresis and identified by map-matching or by nano-LC followed by MS. Apolipoprotein (Apo) A-I (ApoA-I) methionine oxidation, Oxyblot, total antioxidant capacity and a multiplex of 71 inflammation-related plasma proteins were assessed. Reduced levels of apoJ, phospholipid transfer protein, apoF, complement C3, paraoxonase 3 and increased levels of α-1-antichymotrypsin, apoA-II, apoC-III were found in high-density lipoprotein (HDL) from the patients. In low-density lipoprotein (LDL)/very LDL (VLDL), the levels of apoL-1 and platelet-activating factor acetylhydrolase (PAF-AH) as well as apo-B fragments were increased. Methionine oxidation of apoA-I was increased in HDL and showed a relationship with periodontal parameters. α-1 antitrypsin and α-2-HS glycoprotein were oxidised in LDL/VLDL and antioxidant capacity was increased in the patient group. A total of 17 inflammation-related proteins were important for group separation with the highest discriminating proteins identified as IL-21, Fractalkine, IL-17F, IL-7, IL-1RA and IL-2. Patients with periodontitis have an altered plasma lipoprotein profile, defined by altered protein levels as well as post-translational and other structural modifications towards an atherogenic form, which supports a role of modified plasma lipoproteins as central in the link between periodontal and cardiovascular disease (CVD).

Analysis of the plasma proteome using iTRAQ and TMT-based Isobaric labeling

Over the past decade, chemical labeling with isobaric tandem mass tags, such as isobaric tags for relative and absolute quantification reagents (iTRAQ) and tandem mass tag (TMT) reagents, has been employed in a wide range of different clinically orientated serum and plasma proteomics studies. In this review the scope of these works is presented with attention to the areas of research, methods employed and performance limitations. These applications have covered a wide range of diseases, disorders and infections, and have implemented a variety of different preparative and mass spectrometric approaches. In contrast to earlier works, which struggled to quantify more than a few hundred proteins, increasingly these studies have provided deeper insight into the plasma proteome extending the numbers of quantified proteins to over a thousand.

Association of plasma apolipoprotein CIII, high sensitivity C-reactive protein and tumor necrosis factor-α contributes to the clinical features of coronary heart disease in Li and Han ethnic groups in China

Background

Apolipoprotein CIII (apoCIII) is an independent risk for coronary heart disease (CHD). In this study, we investigated the associations among plasma apoCIII, hs-CRP and TNF-α levels and their roles in the clinical features of CHD in the Li and Han ethnic groups in China.

Methods

A cohort of 474 participants was recruited (238 atherosclerotic patients and 236 healthy controls) from the Li and Han ethnic groups. Blood samples were obtained to evaluate apoCIII, TNF-α, hs-CRP and lipid profiles. Chi-squared, t-tests, and Kruskal–Wallis or Wilcoxon–Mann–Whitney tests, Pearson or Spearman correlation tests and multiple unconditional logistic regression were employed to analyze lipid profiles and variations in plasma apoCIII, TNF-α, hs-CRP in subgroups of CHD and their contributions to CHD using SPSS version 20.0 software.

Results

Compared to healthy participants, unfavorable lipid profiles were identified in CHD patients with enhanced systolic pressure, diastolic pressure, fasting blood sugar (FBS), TG, TC, LDL-C, apoB, Lp(a) (P < 0.05, TC and Lp(a); P < 0.01, FBS, TG, LDL-C, apoB); and lower HDL-C and apoAI (P < 0.05). Plasma apoCIII, TNF-α and hs-CRP levels were higher in CHD individuals (16.77 ± 5.98 mg/dL vs. 10.91 ± 4.97 mg/dL; 17.23 ± 6.34 pg/mL vs. 9.49 ± 3.88 pg/mL; 9.55 ± 7.32 mg/L vs. 2.14 ± 1.56 mg/L; P < 0.01 vs. healthy participants). Identical patterns were obtained in the Li and Han groups (16.46 ± 6.08 mg/dL vs. 11.72 ± 5.16 mg/dL; 15.71 ± 5.52 pg/mL vs. 9.74 ± 4.31 pg/mL; 8.21 ± 7.09 mg/L vs. 2.15 ± 1.51 mg/L in Li people; 17.05 ± 5.90 mg/dL vs. 10.07 ± 4.63 mg/dL; 18.59 ± 6.73 pg/mL vs. 9.23 ± 3.38 pg/mL; 10.75 ± 7.44 mg/L vs. 2.12 ± 1.63 mg/L in Han people; P < 0.01). Paired comparisons of subgroups with stable angina, unstable angina, and acute myocardial infarction (AMI) revealed significant variation in plasma levels of apoCIII, TNF-α and hs-CRP (P < 0.01), but not among subgroups with mild, moderate and severe stenosis (P > 0.05). Plasma apoCIII, TNF-α and hs-CRP contributed to the development of CHD (OR = 2.554, 7.252, 6.035, P < 0.01) with paired correlations in CHD patients (apoCIII vs. TNF-α, r = 0.425; apoCIII vs. hs-CRP, r = 0.319; TNF-α vs. hs-CRP, r = 0.400, P < 0.01).

Conclusions

Association among plasma apoCIII, hs-CRP and TNF-α interacts with unfavorable lipid profiles to contribute to the clinical features of CHD with stable angina, unstable angina, and AMI in the Li and Han ethnic groups in China.

Myeloperoxidase mediated HDL oxidation and HDL proteome changes do not contribute to dysfunctional HDL in Chinese subjects with coronary artery disease

High density lipoprotein (HDL) cholesterol levels and cholesterol efflux capacity (CEC) are inversely correlated with coronary artery disease (CAD) risk. Myeloperoxidase (MPO) derived oxidants and HDL proteome changes are implicated in HDL dysfunction in subjects with CAD in the United States; however, the effect of MPO on HDL function and HDL proteome in ethnic Chinese population is unknown. We recruited four matched ethnic Chinese groups (20 patients each): subjects with 1) low HDL levels (HDL levels in men <40mg/dL and women <50mg/dL) and non-CAD (identified by coronary angiography or cardiac CT angiography); 2) low HDL and CAD; 3) high HDL (men >50mg/dL; women >60mg/dL) with no CAD; and 4) high HDL with CAD. Serum cytokines, serum MPO levels, serum CEC, MPO-oxidized HDL tyrosine moieties, and HDL proteome were assessed by mass spectrometry individually in the four groups.

The cytokines, MPO levels, and HDL proteome profiles were not significantly different between the four groups. As expected, CEC was depressed in the entire CAD group but more specifically in the CAD low-HDL group. HDL of CAD subjects had significantly higher 3-nitrotyrosine than non-CAD subjects, but the MPO-specific 3-chlorotyrosine was unchanged; CEC in the CAD low-HDL group did not correlate with either HDL 3-chlorotyrosine or 3-nitrotyrosine levels. Neither 3-chlorotyrosine, which is MPO-specific, nor 3-nitrotyrosine generated from MPO or other reactive nitrogen species was associated with CEC. MPO mediated oxidative stress and HDL proteome composition changes are not the primary cause HDL dysfunction in Chinese subjects with CAD. These studies highlight ethnic differences in HDL dysfunction between United States and Chinese cohorts raising possibility of unique pathways of HDL dysfunction in this cohort.

Quantifying HDL proteins by mass spectrometry: how many proteins are there and what are their functions?

INTRODUCTION

Many lines of evidence indicate that low levels of HDL cholesterol increase the risk of cardiovascular disease (CVD). However, recent clinical studies of statin-treated subjects with established atherosclerosis cast doubt on the hypothesis that elevating HDL cholesterol levels reduces CVD risk. Areas covered: It is critical to identify new HDL metrics that capture HDL's proposed cardioprotective effects. One promising approach is quantitative MS/MS-based HDL proteomics. This article focuses on recent studies of the feasibility and challenges of using this strategy in translational studies. It also discusses how lipid-lowering therapy and renal disease alter HDL's functions and proteome, and how HDL might serve as a platform for binding proteins with specific functional properties. Expert commentary: It is clear that HDL has a diverse protein cargo and that its functions extend well beyond its classic role in lipid transport and reverse cholesterol transport. MS/MS analysis has demonstrated that HDL might contain >80 different proteins. Key challenges are demonstrating that these proteins truly associate with HDL, are functionally important, and that MS-based HDL proteomics can reproducibly detect biomarkers in translational studies of disease risk.

Apolipoprotein C-III in the high-density lipoprotein proteome of cerebral lacunar infarction patients impairs its anti-inflammatory function

High-density lipoprotein (HDL) proteomic study has identified substantial changes associated with various disease states. In the current study, the HDL proteomes in patients with cerebral lacunar infarction (LACI) and control subjects were investigated. A total of 12 LACI patients without evident large vessel occlusions and 12 controls were enrolled in the study. The HDL fraction from each sample was isolated from the plasma by ultracentrifugation. The protemics of the HDL were investigated using nano liquid chromatography coupled to tandem mass spectrometry. There were 55 proteins identified as differentially expressed in the LACI and control groups. Among the 55 proteins, 33 were upregulated and 22 were downregulated in the patients with LACI. The identified proteins were associated with numerous molecular functions, including lipid and cholesterol transport, lipid metabolism, inflammatory response, the complement and coagulation pathway, metal ion metabolism, hemostasis and endopeptidase inhibitory activity. Serum amyloid A, apolipoprotein C (apoC-III) and apolipoprotein A-II (apoA-II) were selected to confirm the proteomics results via western blotting. HDL from the LACI patients exhibited an impaired ability to inhibit the binding of THP-1 cells to endothelial cells compared with the controls (P<0.01). ApoC-III-rich HDL also had a significantly reduced ability to inhibit the binding of THP-1 cells to endothelial cells (P<0.01). The expression of vascular cell adhesion molecule-1 protein by the endothelial cells exhibited a similar pattern of response to the different HDL samples. In conclusion, the present study demonstrates major modifications of the HDL proteome in patients with LACI. The ApoC-III enrichment of the HDL of patients with LACI may cause a reduction in the anti-inflammatory ability of HDL, which may contribute to the progression of the disease.

Identification of CALM as the potential serum biomarker for predicting the recurrence of nasopharyngeal carcinoma using a mass spectrometry-based comparative proteomic approach

To date, there are no serum biomarkers available for the prediction of recurrent nasopharyngeal carcinoma (rNPC). The diagnosis of rNPC mostly depends on imaging and biopsy of diseased tissue; however, both of these methods work mostly if the target tumor is at an advanced stage. Therefore, the identificaqtion of recurrent biomarkers is urgently required. In the present study, we used tandem mass tag (TMT) labeling and high performance liquid chromatography (HPLC) fractionation followed by liquid chromatography-tandem mass spectrometry (LC-MS/MS) to identify differentially expressed proteins. Serum was collected from 40 patients with NPC [recurrence (n=20) and no recurrence (n=20)]. Compared to non-recurrent NPC (nrNPC), we found 59 proteins to be significantly dysregulated in rNPC; most of these have been previously reported to play a role in carcinogenesis. The dysregulation of calmodulin (CALM) was confirmed in 74 new patients [recurrence (n=32) and no recurrence (n=42)] by ELISA. Moreover, we performed a preliminary pathway analysis which revealed that oxidative phosphorylation was altered in the patients with rNPC compared to those with nrNPC. Taken together, these data identify a potential diagnostic biomarker for rNPC and elucidate the potential molecular mechanisms that are dysregulated and contribute to the pathogenesis of rNPC.

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.

Quantitative HDL Proteomics Identifies Peroxiredoxin-6 as a Biomarker of Human Abdominal Aortic Aneurysm

High-density lipoproteins (HDLs) are complex protein and lipid assemblies whose composition is known to change in diverse pathological situations. Analysis of the HDL proteome can thus provide insight into the main mechanisms underlying abdominal aortic aneurysm (AAA) and potentially detect novel systemic biomarkers. We performed a multiplexed quantitative proteomics analysis of HDLs isolated from plasma of AAA patients (N = 14) and control study participants (N = 7). Validation was performed by western-blot (HDL), immunohistochemistry (tissue), and ELISA (plasma). HDL from AAA patients showed elevated expression of peroxiredoxin-6 (PRDX6), HLA class I histocompatibility antigen (HLA-I), retinol-binding protein 4, and paraoxonase/arylesterase 1 (PON1), whereas α-2 macroglobulin and C4b-binding protein were decreased. The main pathways associated with HDL alterations in AAA were oxidative stress and immune-inflammatory responses. In AAA tissue, PRDX6 colocalized with neutrophils, vascular smooth muscle cells, and lipid oxidation. Moreover, plasma PRDX6 was higher in AAA (N = 47) than in controls (N = 27), reflecting increased systemic oxidative stress. Finally, a positive correlation was recorded between PRDX6 and AAA diameter. The analysis of the HDL proteome demonstrates that redox imbalance is a major mechanism in AAA, identifying the antioxidant PRDX6 as a novel systemic biomarker of AAA.

Proteome Dynamics Reveals Pro-Inflammatory Remodeling of Plasma Proteome in a Mouse Model of NAFLD

Nonalcoholic fatty liver disease (NAFLD) is associated with an increased risk of cardiovascular disease. Because the liver is the major source of circulatory proteins, it is not surprising that hepatic disease could lead to alterations in the plasma proteome, which are therein implicated in atherosclerosis. The current study used low-density lipoprotein receptor-deficient (LDLR(-/-)) mice to examine the impact of Western diet (WD)-induced NAFLD on plasma proteome homeostasis. Using a (2)H2O-metabolic labeling method, we found that a WD led to a proinflammatory distribution of circulatory proteins analyzed in apoB-depleted plasma, which was attributed to an increased production. The fractional turnover rates of short-lived proteins that are implicated in stress-response, lipid metabolism, and transport functions were significantly increased with WD (P < 0.05). Pathway analyses revealed that alterations in plasma proteome dynamics were related to the suppression of hepatic PPARα, which was confirmed based on reduced gene and protein expression of PPARα in mice fed a WD. These changes were associated with ∼4-fold increase (P < 0.0001) in the proinflammatory property of apoB-depleted plasma. In conclusion, the proteome dynamics method reveals proinflammatory remodeling of the plasma proteome relevant to liver disease. The approach used herein may provide a useful metric of in vivo liver function and better enable studies of novel therapies surrounding NAFLD and other diseases.

Proteomics and metabolomics in biomarker discovery for cardiovascular diseases: progress and potential

INTRODUCTION

The process of discovering novel biomarkers and potential therapeutic targets may be shortened using proteomic and metabolomic approaches.

AREAS COVERED

Several complementary strategies, each one presenting different advantages and limitations, may be used with these novel approaches. In vitro studies show how cells involved in cardiovascular disease react, although the phenotype of cultured cells differs to that occurring in vivo. Tissue analysis either in human specimens or animal models may show the proteins that are expressed in the pathological process, although the presence of structural proteins may be confounding. To identify circulating biomarkers, analyzing the secretome of cultured atherosclerotic tissue, analysis of blood cells and/or plasma may be more straightforward. However, in the latter approach, high-abundant proteins may mask small molecules that could be potential biomarkers. The study of sub-proteomes such as high-density lipoproteins may be useful to circumvent this limitation. Regarding metabolomics, most studies have been performed in small populations, and we need to perform studies in large populations in order to discover robust biomarkers. Expert commentary: It is necessary to involve the clinicians in these areas to improve the design of clinical studies, including larger populations, in order to obtain consistent novel biomarkers.

HDL as a prognostic biomarker for coronary atherosclerosis: the role of inflammation

INTRODUCTION

Emerging evidence suggests that the role of high density lipoprotein (HDL) in the atherosclerotic process is not as clear as previously thought, since atheroprotective HDL becomes atherogenic in states of increased inflammatory processes.

AREAS COVERED

In this review we aim to elucidate the role of HDL as a prognostic biomarker and we discuss therapeutic approaches that aim to increase HDL and their possible clinical benefit.

EXPERT OPINION

Given the structural variability and biological complexity of the HDL particle, its role in the atherosclerotic process is far from clear. According to current evidence, the atheroprotective role of HDL turns atherogenic in states of increased inflammatory processes, while even minor alterations in systemic inflammation are likely to hinder the endothelial protective effects of HDL. In accordance, significant data have revealed that HDL-related drugs may be effective in reducing cardiovascular mortality; however they are not as encouraging or unanimous as expected. Possible future goals could be to quantify either HDL subclasses or functions in an attempt to reach safer conclusions as to the prognostic importance of HDL in coronary atherosclerosis. Having achieved that, a more targeted therapy that would aim to raise either HDL functionality or to remodel HDL structure would be more easily designed.

Dysfunctional High-Density Lipoprotein: An Innovative Target for Proteomics and Lipidomics

High-Density Lipoprotein-Cholesterol (HDL-C) is regarded as an important protective factor against cardiovascular disease, with abundant evidence of an inverse relationship between its serum levels and risk of cardiovascular disease, as well as various antiatherogenic, antioxidant, and anti-inflammatory properties. Nevertheless, observations of hereditary syndromes featuring scant HDL-C concentration in absence of premature atherosclerotic disease suggest HDL-C levels may not be the best predictor of cardiovascular disease. Indeed, the beneficial effects of HDL may not depend solely on their concentration, but also on their quality. Distinct subfractions of this lipoprotein appear to be constituted by specific protein-lipid conglomerates necessary for different physiologic and pathophysiologic functions. However, in a chronic inflammatory microenvironment, diverse components of the HDL proteome and lipid core suffer alterations, which propel a shift towards a dysfunctional state, where HDL-C becomes proatherogenic, prooxidant, and proinflammatory. This heterogeneity highlights the need for further specialized molecular studies in this aspect, in order to achieve a better understanding of this dysfunctional state; with an emphasis on the potential role for proteomics and lipidomics as valuable methods in the search of novel therapeutic approaches for cardiovascular disease.

The association of HDL-apoCIII with coronary heart disease and the effect of statin treatment on it

Background

Apolipoprotein CIII (apoCIII) is considered to impair the anti-atherogenic effect of high density lipoprotein (HDL) in coronary heart disease (CHD) patients, and apoCIII content in HDL (HDL-apoCIII) predicts CHD more accurately. However, the relationship between HDL-apoCIII and CHD, and the effect of statin treatment on HDL-apoCIII are still unclear. The aims of the study are to establish the association of HDL-apoCIII with CHD, and investigate the effect of statin treatment on HDL-apoCIII in CHD patients.

Methods

We conducted a hospital-based observational study. Totally 80 non-CHD patients and 120 CHD patients without statin treatment were previously enrolled in this study. All the CHD patients received statin treatment, and 63 of them were followed after 3 months of regular statin treatment. HDL sample of each patient was isolated by density gradient ultracentrifugation from fasting venous plasma, and HDL-apoCIII of each patient was measured by ELISA method.

Results

HDL-apoCIII was significantly higher in CHD patients than non-CHD patients (p < 0.05), and it was still an independent predictor of CHD after adjusting for other factors. Total plasma apoCIII, especially HDL-apoCIII was significantly elevated after statin treatment in CHD patients, whereas total cholesterol (TC), low density lipoprotein cholesterol (LDL-c) and apolipoprotein B (apoB) were decreased significantly (p < 0.05). Compared with CHD patients without diabetes mellitus (DM), the effect of statin treatment on apoCIII markers was minor in CHD patients with DM. And HDL-apoCIII correlated with plasma TG significantly in non-CHD and CHD patients (p < 0.05), but the correlation in CHD patients did not exist after statin treatment (p > 0.05).

Conclusions

HDL-apoCIII has a significant and positive association with CHD. Although conventional atherogenic lipid markers have a significantly decrease in CHD patients after statin treatment, HDL-apoCIII has a further elevation at the same time.

Electronic supplementary material

The online version of this article (doi:10.1186/s12944-015-0129-8) contains supplementary material, which is available to authorized users.

iTRAQ-Based Quantitative Proteomic Analysis Identified HSC71 as a Novel Serum Biomarker for Renal Cell Carcinoma

Renal cell carcinoma (RCC) is one of the most lethal urologic cancers and about 80% of RCC are of the clear-cell type (ccRCC). However, there are no serum biomarkers for the accurate diagnosis of RCC. In this study, we performed a quantitative proteomic analysis on serum samples from ccRCC patients and control group by using isobaric tag for relative and absolute quantitation (iTRAQ) labeling and LC-MS/MS analysis to access differentially expressed proteins. Overall, 16 proteins were significantly upregulated (ratio > 1.5) and 14 proteins were significantly downregulated (ratio < 0.67) in early-stage ccRCC compared to control group. HSC71 was selected and subsequently validated by Western blot in six independent sets of patients. ELISA subsequently confirmed HSC71 as a potential serum biomarker for distinguishing RCC from benign urologic disease with an operating characteristic curve (ROC) area under the curve (AUC) of 0.86 (95% confidence interval (CI), 0.76~0.96), achieving sensitivity of 87% (95% CI 69%~96%) at a specificity of 80% (95% CI 61~92%) with a threshold of 15 ng/mL. iTRAQ-based quantitative proteomic analysis led to identification of serum HSC71 as a novel serum biomarker of RCC, particularly useful in early diagnosis of ccRCC.

The role of high-density lipoproteins in the regulation of angiogenesis

Angiogenesis is important for postnatal physiological processes including tissue neovascularization in response to an ischaemic injury. Conversely, uncontrolled inflammatory-driven angiogenesis can accelerate atherosclerotic plaque and tumour growth. Angiogenesis-associated diseases are highly prevalent globally, with cardiovascular-related disorders and cancer being the leading causes of mortality worldwide. A vast amount of research has been conducted on the vasculoprotective effects of high-density lipoproteins (HDLs) and while current HDL-raising therapies to date have not yielded the desired benefits clinically, its role in angiogenesis is yet to be fully elucidated. Epidemiological studies report positive correlations between elevated HDL levels and improved prognosis in both ischaemia- and inflammatory-driven pathologies, in which angiogenesis plays a key role. This review focuses on current evidence from epidemiological and prospective studies, coupled with animal models and mechanistic studies that highlight the ability of HDL to conditionally regulate angiogenesis.

Anticipatory role of high density lipoprotein and endothelial dysfunction: an overview

High Density Lipoprotein (HDL) has been witnessed to possess a range of different functions that contribute to its atheroprotective effects. These functions are: the promotion of macrophage cholesterol efflux, reverse cholesterol transport, anti-inflammatory, anti-thrombotic, anti-apoptotic, pro-fibrinolytic and anti-oxidative functions. Paraoxonase 1 (PON1) is an HDL associated enzyme esterase/homocysteinethiolactonase that contributes to the anti-oxidant and anti-atherosclerotic capabilities of HDL. PON1 is directly involved in the etiopathogenesis of atherosclerosis through the modulation of nitric oxide (NO) bioavailability. The aim of this review is to summarize the role of HDL on endothelial homeostasis, and also to describe the recently characterized molecular pathways involved.

HDL functionality and crystal-based sterile inflammation in atherosclerosis

Change is inevitable. In early evolution, due to the limited availability of resources, the sole purpose of living organisms was to survive long enough to transmit their genes to the next generation. During their short lifetime, organisms used pathogen-associated and damage-associated molecular pattern pathways as an inflammatory response against pathogens (exogenous factors) and tissue damage (endogenous factors), respectively. Despite advances in human lifespan, it appears that an increasing number of diseases such as atherosclerosis are associated with inflammation. Excessive glucose, lipid and protein intake leads to the formation of endogenous crystals, i.e., cholesterol, which can induce a sterile inflammatory immune response that manifests as a vicious cycle. In this review, we evaluate the possible relationship between crystal-based sterile inflammatory response and HDL functionality.