Prospective study of coronary heart disease vs. HDL2, HDL3, and other lipoproteins in Gofman's Livermore Cohort

Associations between lipid abnormalities and diabetic retinopathy across a large United States national database

BACKGROUND/OBJECTIVES

While dyslipidaemia has been suggested as a potential risk factor for diabetic retinopathy (DR), previous studies have reported conflicting findings. This study aimed to better characterize the relationship between abnormal serum levels of various lipid markers and the risk of the development and progression of DR.

SUBJECTS/METHODS

This retrospective cohort study utilized a United States national database of electronic medical records. Adults with a history of type 2 diabetes mellitus without type 1 diabetes mellitus were divided into cohorts based on the presence of abnormal serum levels of various lipid markers. Propensity score matching was performed to match cohorts with abnormal lipid levels to those with normal lipid levels on covariates. The cohorts were then compared to evaluate the hazard ratios (HR) of receiving a new DR diagnosis, pars plana vitrectomy, panretinal photocoagulation, vitreous haemorrhage, proliferative diabetic retinopathy, diabetic macular oedema (DMO), and traction retinal detachment.

RESULTS

The database contained 1,126,231 eligible patients (mean age: 60.8 [14.2] years; 46.0% female). Among patients without prior DR, low HDL (HR = 0.94, CI = 0.90-0.98), total cholesterol (HR = 0.88, CI = 0.85-0.91), and high triglyceride (HR = 0.91, CI = 0.86-0.97) levels were associated with a decreased risk of receiving a DR diagnosis. Among patients with preexisting DR, high LDL levels was associated with an increased risk of DMO (HR = 1.42, CI = 1.15-1.75), whereas low HDL levels was associated with a marginally decreased risk (HR = 0.92, CI = 0.85-0.99).

CONCLUSIONS

Elevated levels of markers of dyslipidaemia are inversely associated with the risk of receiving a DR diagnosis, but this relationship is blunted after the onset of DR.

Association Between HDL2-C and HDL3-C with Cardiovascular Disease: A Nested Case-Control Study in an Iranian Population

Background

The contribution of high-density lipoprotein cholesterol (HDL-C) subclasses to incident cardiovascular disease (CVD) and coronary heart disease (CHD) remains a subject of debate.

Objectives

The objective of this study was to investigate these associations in a population with a high prevalence of dyslipidemia and CVD.

Methods

In a nested case-control study, HDL-C and its subclasses (HDL2-C and HDL3-C) in 370 age and gender-matched case and control subjects were determined. This study employed multivariable-adjusted conditional logistic regression to calculate the odds ratios (ORs) for the associations between HDL-C, HDL2-C, HDL3-C, and HDL2-C/HDL3-C (both as continuous and categorical variables) with incident CVD and CHD. The present study models were adjusted for a comprehensive set of confounders, including body mass index, current smoking, hypertension, type 2 diabetes mellitus, use of lipid-lowering drugs, family history of premature CVD, non-HDL-C, and triglycerides.

Results

In multivariate analysis, when considering lipoprotein parameters as continuous variables, a 1-unit increase in HDL-C and HDL3-C was associated with a reduced risk of incident CVD and CHD. For CVD, the ORs (95% confidence intervals [CI]) were 0.95 (0.92 - 0.98) and 0.95 (0.93 - 0.98) for HDL-C and HDL3-C, respectively. The corresponding values for CHD were 0.94 (0.91 - 0.97) and 0.94 (0.91 - 0.97). In the categorical approach to lipoprotein parameters, higher quartiles of HDL-C and HDL3-C, compared to the first quartile, were significantly associated with a lower risk of incident CVD and CHD. The ORs (95% CI) for the fourth quartiles were 0.43 (0.25 - 0.74, P for trend = 0.003) and 0.46 (0.27 - 0.78, P for trend = 0.005) for HDL-C and HDL3-C regarding CVD and 0.32 (0.17 - 0.59) and 0.32 (0.18 - 0.59) (all P for trend = 0.001) regarding CHD, respectively. Paradoxically, across quartiles of HDL2-C/HDL3-C, this lipid ratio was associated with a higher risk of CHD (92% higher risk in the fourth quartile).

Conclusions

The results showed that HDL3-C, but not HDL2-C, was primarily responsible for the protective effect of HDL-C against CVD, particularly CHD, in Iranian adults.

Novel Size-Based High-Density Lipoprotein Subspecies and Incident Vascular Events

Background High-density lipoprotein (HDL) particle concentration likely outperforms HDL cholesterol in predicting atherosclerotic cardiovascular events. Whether size-based HDL subspecies explain the atheroprotective associations of HDL particle concentration remains unknown. Our objective was to assess whether levels of specific size-based HDL subspecies associate with atherosclerotic cardiovascular disease in a multiethnic pooled cohort and improve risk prediction beyond traditional atherosclerotic cardiovascular disease risk factors. Methods and Results Seven HDL size-based subspecies were quantified by nuclear magnetic resonance (LP4 algorithm; H1=smallest; H7=largest) among participants without prior atherosclerotic cardiovascular disease in ARIC (Atherosclerosis Risk in Communities), MESA (Multi-Ethnic Study of Atherosclerosis), PREVEND (Prevention of Renal and Vascular Endstage Disease), and DHS (Dallas Heart Study) cohorts (n=15 371 people). Multivariable Cox proportional hazards models were used to evaluate the association between HDL subspecies and incident myocardial infarction (MI) or ischemic stroke at follow-up (average 8-10 years) adjusting for HDL cholesterol and risk factors. Improvement in risk prediction was assessed via discrimination and reclassification analysis. Within the pooled cohort (median age 57 years; female 54%; Black 22%) higher H1 (small) and H4 (medium) concentrations were inversely associated with incident MI (hazard ratio [HR]/SD, H1 0.88 [95% CI, 0.81-0.94]; H4 0.89 [95% CI, 0.82-0.97]). H4 but not H1 improved risk prediction indices for incident MI. Increasing H2 and H4 were inversely associated with improved risk prediction indices for composite end point of stroke, MI, and cardiovascular death (HR/SD, H2 0.94 [95% CI, 0.88-0.99]; H4 0.91 [95% CI, 0.85-0.98]). Levels of the large subspecies (H6 and H7) were not associated with any vascular end point. Conclusions Two of 7 HDL size-based subspecies modestly improved risk prediction for MI and composite vascular end points in a large multiethnic pooled cohort. These findings support assessment of precise HDL subspecies for future studies regarding clinical utility.

Dyslipidemia in rheumatoid arthritis: the possible mechanisms

Rheumatoid arthritis (RA) is an autoimmune inflammatory disease, of which the leading cause of death is cardiovascular disease (CVD). The levels of total cholesterol (TC), low-density lipoprotein cholesterol (LDL-c), and high-density lipoprotein cholesterol (HDL-c) in RA decrease especially under hyperinflammatory conditions. It is conflictive with the increased risk of CVD in RA, which is called "lipid paradox". The systemic inflammation may explain this apparent contradiction. The increased systemic proinflammatory cytokines in RA mainly include interleukin-6(IL-6)、interleukin-1(IL-1)and tumor necrosis factor alpha(TNF-α). The inflammation of RA cause changes in the subcomponents and structure of HDL particles, leading to a weakened anti-atherosclerosis function and promoting LDL oxidation and plaque formation. Dysfunctional HDL can further worsen the abnormalities of LDL metabolism, increasing the risk of cardiovascular disease. However, the specific mechanisms underlying lipid changes in RA and increased CVD risk remain unclear. Therefore, this article comprehensively integrates the latest existing literature to describe the unique lipid profile of RA, explore the mechanisms of lipid changes, and investigate the impact of lipid changes on cardiovascular disease.

Adsorption of Acylhydroperoxy-Derivatives of Phospholipids from Biomembranes by Blood Plasma Lipoproteins

It has been established that acylhydroperoxy derivatives of phospholipids from oxidized rat liver mitochondria are captured predominantly by LDL particles but not by HDL during co-incubation with blood plasma lipoproteins, which refutes the previously suggested hypothesis about the involvement of HDL in the reverse transport of oxidized phospholipids and confirms the possibility of different mechanisms of lipohydroperoxide accumulation in LDL during oxidative stress.

Association between Lipoprotein Subfractions, Hemostatic Potentials, and Coronary Atherosclerosis

Background. Dyslipidemias are associated with atherosclerotic plaque formation and a prothrombotic state, thus increasing the risk of both atherosclerotic vascular disease and atherothrombotic adverse events. We sought to explore the association between lipoprotein subfractions, overall hemostasis, and coronary calcifications in individuals at intermediate cardiovascular risk. Methods. Consecutive statin-naive individuals at intermediate cardiovascular risk referred for coronary artery calcium score (CACS) scanning were included. CACS was assessed using a 128-slice dual-source CT scanner. Traditional lipid profile, high-density lipoprotein (HDL) subfractions 2 and 3, and small dense low-density lipoproteins (sdLDL) were measured with commercially available assays. Overall hemostatic (OHP) and coagulation potentials (OCP) were measured spectrophotometrically, using fibrin aggregation curves after exposure to thrombin and recombinant tissue-type plasminogen activator, respectively. Overall fibrinolytic potential (OFP) was calculated as a difference between the two areas under curves. Results. We included 160 patients (median age 63 (interquartile range (IQR), 56-71 years, 52% women, and median CACS 8, IQR 0-173 Agatston units). HDL3 levels—but not sdLDL or hemostatic potentials—were significantly associated with CACS zero, even after adjusting for age, sex, arterial hypertension, dyslipidemia, diabetes, and smoking history (OR 0.980 (0.962-0.999), $p=0.034$ ). HDL3 was also significantly associated with OCP ( $r=-0.232$ , $p$ adjusted for age and sex 0.037). Conclusions. In patients at intermediate cardiovascular risk, HDL3 is associated with both subclinical atherosclerosis and overall coagulation. Our findings are in line with studies reporting on an inverse relationship between HDL3 and atherosclerosis and provide one possible mechanistic explanation for the association between novel lipid biomarkers and coagulation derangements.

HDL and Cholesterol Ester Transfer Protein (CETP)

Cholesterol ester transfer protein (CETP) is important clinically and is one of the major targets in cardiovascular disease studies. With high conformational flexibility, its tunnel structure allows unforced movement of high-density lipoproteins (HDLs), VLDLs, and LDLs. Research in reverse cholesterol transports (RCT) reveals that the regulation of CETP activity can change the concentration of cholesteryl esters (CE) in HDLs, VLDLs, and LDLs. These molecular insights demonstrate the mechanisms of CETP activities and manifest the correlation between CETP and HDL. However, animal and cell experiments focused on CETP give controversial results. Inhibiting CETP is found to be beneficial to anti-atherosclerosis in terms of increasing plasma HDL-C, while it is also claimed that CETP weakens atherosclerosis formation by promoting RCT. Currently, the CETP-related drugs are still immature. Research on CETP inhibitors is targeted at improving efficacy and minimizing adverse reactions. As for CETP agonists, research has proved that they also can be used to resist atherosclerosis.

Small Dense LDL: Scientific Background, Clinical Relevance, and Recent Evidence Still a Risk Even with 'Normal' LDL-C Levels

Residual cardiovascular disease event risk, following statin use and low-density lipoprotein cholesterol (LDL-C) reduction, remains an important and common medical conundrum. Identifying patients with significant residual risk, despite statin drug use, is an unmet clinical need. One pathophysiologic disorder that contributes to residual risk is abnormal distribution in lipoprotein size and density, which is referred to as lipoprotein heterogeneity. Differences in low density lipoprotein (LDL) composition and size have been linked to coronary heart disease (CHD) risk and arteriographic disease progression. The clinical relevance has been investigated in numerous trials since the 1950s. Despite this long history, controversy remains regarding the clinical utility of LDL heterogeneity measurement. Recent clinical trial evidence reinforces the relevance of LDL heterogeneity measurement and the impact on CHD risk prediction and outcomes. The determination of LDL subclass distribution improves CHD risk prediction and guides appropriate treatment.

Cholesterol Transport Dysfunction and Its Involvement in Atherogenesis

Atherosclerosis is the cause of the development of serious cardiovascular disorders, leading to disability and death. Numerous processes are involved in the pathogenesis of atherosclerosis, including inflammation, endothelial dysfunction, oxidative stress, and lipid metabolism disorders. Reverse transport of cholesterol is a mechanism presumably underlying the atheroprotective effect of high-density lipoprotein. In this review, we examined disorders of cholesterol metabolism and their possible effect on atherogenesis. We paid special attention to the reverse transport of cholesterol. Transformed cholesterol metabolism results in dyslipidemia and early atherosclerosis. Reverse cholesterol transport is an endogenous mechanism by which cells export cholesterol and maintain homeostasis. It is known that one of the main factors leading to the formation of atherosclerotic plaques on the walls of blood vessels are multiple modifications of low-density lipoprotein, and the formation of foam cells following them.

CSL112 (Apolipoprotein A-I [Human]) Strongly Enhances Plasma Apoa-I and Cholesterol Efflux Capacity in Post-Acute Myocardial Infarction Patients: A PK/PD Substudy of the AEGIS-I Trial

Introduction:

Cholesterol efflux capacity (CEC) is impaired following acute myocardial infarction (AMI). CSL112 is an intravenous preparation of human plasma-derived apoA-I formulated with phosphatidylcholine (PC). CSL112 is intended to improve CEC and thereby prevent early recurrent cardiovascular events following AMI. AEGIS-I (ApoA-I Event Reducing in Ischemic Syndromes I) was a multicenter, randomized, double-blind, placebo-controlled, dose-ranging phase 2b study, designed to evaluate the hepatic and renal safety of CSL112. Here, we report an analysis of a pharmacokinetic (PK) and pharmacodynamic (PD) substudy of AEGIS-I.

Methods:

AMI patients were stratified by renal function and randomized 3:3:2 to 4, weekly, 2-hour infusions of low- and high-dose (2 g and 6 g) CSL112, or placebo. PK/PD assessments included plasma concentrations of apoA-I and PC, and measures of total and ABCA1-dependent CEC, as well as lipids/lipoproteins including high density lipoprotein cholesterol (HDL-C), non-HDL-C, low density lipoprotein cholesterol (LDL-C), ApoB, and triglycerides. Inflammatory and cardio-metabolic biomarkers were also evaluated.

Results:

The substudy included 63 subjects from AEGIS-I. CSL112 infusions resulted in rapid, dose-dependent increases in baseline corrected apoA-I and PC, which peaked at the end of the infusion (Tmax ≈ 2 hours). Similarly, there was a dose-dependent elevation in both total CEC and ABCA1-mediated CEC. Mild renal impairment did not affect the PK or PD of CSL112. CSL112 administration was also associated with an increase in plasma levels of HDL-C but not non-HDL-C, LDL-C, apoB, or triglycerides. No dose-effects on inflammatory or cardio-metabolic biomarkers were observed.

Conclusion:

Among patients with AMI, impaired CEC was rapidly elevated by CSL112 infusions in a dose-dependent fashion, along with an increase in apoA-I plasma concentrations. Findings from the current sub-study of the AEGIS-I support a potential atheroprotective benefit of CSL112 for AMI patients.

The Association of Passive Smoking and Dyslipidemia Among Adolescence in Japan: Results From A-CHILD Study

CONTEXT

Passive smoking in childhood has been reported to be associated with dyslipidemia in Western countries. However, this association in Asian countries remains unclear. Further, no study has investigated the sex difference of the association.

OBJECTIVE

This study aimed to elucidate the association between passive smoking and dyslipidemia in adolescent boys and girls in Japan.

METHODS

We used a cross-sectional data of junior high school students in the Adachi Child Health Impact of Living Difficulty (A-CHILD) study in Adachi City, Tokyo, Japan in 2016 and 2018. Of the 1431 available students, 1166 students and their parents responded to the survey, including frequency of passive smoking (response rate 81.5%). We assessed dyslipidemia using total cholesterol (TC) levels, low-density lipoprotein cholesterol (LDL-C) levels and high-density lipoprotein cholesterol (HDL-C) levels. The association between passive smoking and dyslipidemia was evaluated by using multivariate regression analyses adjusted for socioeconomic status and lifestyle factors stratified by boys (N = 564) and girls (N = 602).

RESULTS

Among boys, HDL-C levels were significantly lower if exposed to passive smoking frequently, compared with those not exposed (β = -3.19; 95% CI, -5.84 to -0.55). However, this trend does not hold true among girls. Passive smoking was not associated with TC levels and LDL-C levels in either boys or girls.

CONCLUSION

We found that exposure to passive smoking was associated with HDL-C level among boys in Japan, but not in girls. Further longitudinal study is needed to confirm the association between passive smoking and dyslipidemia among boys in Japan.

HDL Subclass Analysis in Predicting Metabolic Syndrome in Koreans With High HDL Cholesterol Levels

Background

High-density lipoprotein cholesterol (HDL-C) is a complex mixture of subclasses with heterogeneous atheroprotective activities. We analyzed HDL-C subclass in relation to cardiovascular risk and metabolic syndrome (MetS) in a population with high HDL-C levels.

Methods

A total of 300 Korean individuals with high HDL-C levels (≥2.331 mmol/L) were enrolled following a comprehensive general medical examination including body composition analysis. HDL3-C levels were measured using the HDL3-EX SEIKEN kit (Randox Ltd., Crumlin, UK) and non-HDL3-C levels were calculated by subtracting HDL3-C levels from total HDL-C levels.

Results

HDL3-C levels and HDL3-C proportion had a weak positive correlation with low-density lipoprotein cholesterol (LDL-C) and triglycerides (r=0.21, r=0.25; r=0.26, r=0.34, respectively, all P<0.001); in contrast, non-HDL3-C levels had a weak negative correlation with these parameters (r=−0.17 and r=−0.25, respectively, both P<0.005). HDL3-C levels and HDL3-C proportion were significantly higher in the MetS group (N=8) than in the non-MetS group (0.71 vs 0.63 mmol/L, P=0.001; 29.7 vs 25.8%, P=0.001, respectively); these were the only predictors of MetS among the lipid variables (areas under the curves [AUC]=0.84 and 0.83, respectively, both P=0.001).

Conclusions

In populations with high HDL-C levels, HDL-C subclass may provide a greater amount of information on cardiovascular risk and MetS than HDL-C levels alone.

Untying the correlation between apolipoproteins and rheumatoid arthritis

AIM AND OBJECTIVE

The concentration of lipoproteins and apolipoprotein are extremely low in the synovial fluid of any healthy person as compared to the concentrations in plasma. However, in the synovial fluid of any diseased patient the amount of cholesterol and lipids is sharply increased. The current review defines the role of various apolipoproteins and lipoproteins and their constituent subfractions in the synovial fluid embarking its principal role in rheumatoid arthritis. It also explains the need to define synovial fluid lipids, lipoprotein particle subfractions and their constituent apolipoproteins in synovial fluid.

MATERIALS AND METHODS

Various research and review articles highlighting the role of apolipoproteins and lipoproteins were procured from medical websites mainly Pubmed, Medline, Science Direct, etc., and studied for the writing of the review paper.

CONCLUSION

Mainly apolipoproteins A-1, B and E are prominently increased in chronic inflammatory joint disorders. Several theories have been proposed to understand the source of increase of lipids and apolipoproteins in synovial fluid of the diseased patients compared to healthy individuals, yet the precise mechanism is still not lucid. Lipoproteins are believed to play both functional role and pathological role in the synovial fluid. The activated T-lymphocytes in patients of RA lead to activation of inflammatory cytokines such as tumor necrosis factor and interleukins which embark to be the principal mechanism for induction of the disease. It can be thus concluded that the apolipoproteins prevent the activation of monocytes by blocking their contact of activation and thus play critical role in management of RA by inhibiting the production of proinflammatory cytokines.

Cardiovascular Risk Factor Reduction in First Responders Resulting From an Individualized Lifestyle and Blood Test Program: A Randomized Controlled Trial

OBJECTIVE

We tested the hypothesis that a lifestyle program would improve risk factors linked to cardiovascular disease (CVD) in first responders.

METHODS

A 1-year cluster-randomized controlled clinical trial in 10 cities. Participants were 175 first responders, with increased waist circumference and/or low levels of large (α1) high-density lipoprotein (HDL) particles. The intervention group received personalized online tools and access to telephonic coaching sessions.

RESULTS

At 1 year the intervention significantly reduced body weight (P = 0.004) and waist circumference (P = 0.002), increased α1 HDL (P = 0.01), and decreased triglyceride (P = 0.005) and insulin concentrations (P = 0.03). Program adherence was associated with weight loss (P = 0.0005) and increases in α1 HDL (P = 0.03).

CONCLUSIONS

In first responders, a personalized lifestyle intervention significantly improved CVD risk factors in proportion to program adherence. Changes in large HDL particles were more sensitive indicators of lifestyle changes than HDL-cholesterol measurement.

CLINICAL TRIAL REGISTRATION NUMBER

ClinicalTrials.gov: NCT03322046.

The Alcohol-High-Density Lipoprotein Athero-Protective Axis

Ingestion of alcohol is associated with numerous changes in human energy metabolism, especially that of plasma lipids and lipoproteins. Regular moderate alcohol consumption is associated with reduced atherosclerotic cardiovascular disease (ASCVD), an effect that has been attributed to the concurrent elevations of plasma high-density lipoprotein-cholesterol (HDL-C) concentrations. More recent evidence has accrued against the hypothesis that raising plasma HDL concentrations prevents ASCVD so that other metabolic processes associated with alcohol consumption have been considered. This review explored the roles of other metabolites induced by alcohol consumption-triglyceride-rich lipoproteins, non-esterified free fatty acids, and acetate, the terminal alcohol metabolite in athero-protection: Current evidence suggests that acetate has a key role in athero-protection but additional studies are needed.

Impact of obeticholic acid on the lipoprotein profile in patients with non-alcoholic steatohepatitis

BACKGROUND & AIMS

Obeticholic acid (OCA), a farnesoid X receptor agonist, increases total and low-density lipoprotein cholesterol (LDL-C) in patients with non-alcoholic steatohepatitis. In the present study, we aimed to evaluate the impact of OCA therapy on lipoprotein sub-particles.

METHOD

This study included 196 patients (99 OCA group and 97 placebo group) who were enrolled in the FLINT trial and had samples available for lipid analysis and liver biopsies at enrollment and end-of-treatment (EOT) at 72 weeks. Very low-density lipoprotein (VLDL), low-density lipoprotein (LDL), and high-density lipoprotein (HDL) particles were evaluated at baseline, 12 and 72 weeks after randomization, and 24 weeks following EOT.

RESULTS

Baseline lipoprotein profiles were similar among OCA and placebo groups. OCA did not affect total VLDL particle concentrations, but OCA vs. placebo treatment was associated with decreased large VLDL particle concentration at 12 weeks (baseline-adjusted mean: 6.8 vs. 8.9 nmol/L; p = 0.002), mirrored by an increase in less atherogenic, small VLDL particle concentration (33.9 vs. 28.0 nmol/L; p = 0.02). After 12 weeks, total LDL particle concentration was higher in the OCA group than the placebo group (1,667 vs. 1,329 nmol/L; p <0.0001), characterized by corresponding increases in both less atherogenic, large-buoyant LDL (475 vs. 308 nmol/L; p ≤0.001) and more atherogenic small-dense LDL particles (1,015 vs. 872 nmol/L; p = 0.002). The changes in LDL particle concentrations were similar between treatment groups (OCA and placebo) 24 weeks following EOT due to improvement in the OCA cohort. Compared to placebo, a reduction in total HDL particle concentration, particularly large and medium HDL particles, was noted in the OCA-treated patients, but this resolved after drug discontinuation.

CONCLUSION

OCA therapy is associated with increases in small VLDL particles, large and small LDL particles, and a reduction in HDL particles at 12 weeks. These lipoprotein concentrations reverted to baseline values 24 weeks after drug discontinuation.

LAY SUMMARY

Non-alcoholic steatohepatitis is a chronic liver disease that is associated with an increased risk of developing cirrhosis and cardiovascular disease. Recently, obeticholic acid (OCA), a farnesoid X receptor agonist, improved liver disease but led to an increase in cholesterol. However, the impact of OCA on cholesterol is not well understood. In the present study, we show that OCA therapy is associated with a detrimental increase in lipoprotein levels, which improves after drug discontinuation. ClinicalTrials.gov numbers: NCT01265498.

High-density lipoprotein or cyclodextrin extraction of cholesterol from aggregated LDL reduces foam cell formation

Low-density lipoprotein (LDL) deposition, aggregation and retention in the endothelial sub-intima are critical initiating events during atherosclerosis. Macrophages digest aggregated LDL (agLDL) through a process called exophagy. High-density lipoprotein (HDL) plays an atheroprotective role, but studies attempting to exploit it therapeutically have been unsuccessful, highlighting gaps in our current understanding of HDL function. Here, we characterized the role of HDL during exophagy of agLDL. We find that atherosclerotic plaque macrophages contact agLDL and form an extracellular digestive compartment similar to that observed in vitro During macrophage catabolism of agLDL in vitro, levels of free cholesterol in the agLDL are increased. HDL can extract free cholesterol directly from this agLDL and inhibit macrophage foam cell formation. Cholesterol-balanced hydroxypropyl-β-cyclodextrin similarly reduced macrophage cholesterol uptake and foam cell formation. Finally, we show that HDL can directly extract free cholesterol, but not cholesterol esters, from agLDL in the absence of cells. Together, these results suggest that the actions of HDL can directly extract free cholesterol from agLDL during catabolism, and provide a new context in which to view the complex relationship between HDL and atherosclerosis.

Comparing Data-Independent Acquisition and Parallel Reaction Monitoring in Their Abilities To Differentiate High-Density Lipoprotein Subclasses

High-density lipoprotein (HDL) is a diverse group of particles with multiple cardioprotective functions. HDL proteome follows HDL particle complexity. Many proteins were described in HDL, but consistent quantification of HDL protein cargo is still a challenge. To address this issue, the aim of this work was to compare data-independent acquisition (DIA) and parallel reaction monitoring (PRM) methodologies in their abilities to differentiate HDL subclasses through their proteomes. To this end, we first evaluated the analytical performances of DIA and PRM using labeled peptides in pooled digested HDL as a biological matrix. Next, we compared the quantification capabilities of the two methodologies for 24 proteins found in HDL₂ and HDL₃ from 19 apparently healthy subjects. DIA and PRM exhibited comparable linearity, accuracy, and precision. Moreover, both methodologies worked equally well, differentiating HDL subclasses' proteomes with high precision. Our findings may help to understand HDL functional diversity.

Small Dense Low-Density Lipoprotein Cholesterol Predicts Cardiovascular Events in Liver Transplant Recipients

Cardiovascular disease (CVD) is an important cause of morbidity and mortality after liver transplantation (LT). Although LT is associated with dyslipidemia, particularly atherogenic lipoprotein subparticles, the impact of these subparticles on CVD-related events is unknown. Therefore, the aim of the current study was to evaluate the impact of small dense (sdLDL-C) low-density lipoprotein (LDL) cholesterol (LDL-C) on CVD events. Prospectively enrolled patients (N = 130) had detailed lipid profile consisting of traditional lipid parameters and sdLDL-C and were followed for CVD events. The primary endpoint was a CVD composite consisting of myocardial infarction (MI), angina, need for coronary revascularization, and cardiac death. Mean age of the cohort was 58 ± 11 years, and the most common etiology of liver disease (LD) was hepatitis C virus (N = 48) and nonalcoholic steatohepatitis (N = 23). A total of 20 CVD events were noted after median follow-up of 45 months. The baseline traditional profile was similar in patients with and without CVD events. A serum LDL-C cutoff of 100 mg/dL was unable to identify individuals at risk of a CVD event (P = 0.86). In contrast, serum concentration of atherogenic sdLDL-C >25 mg/dL was predictive of CVD events with a hazard ratio of 6.376 (95% confidence interval, 2.65, 15.34; P < 0.001). This relationship was independent of diabetes, hypertension, sex, ethnicity, LD, obesity, and statin use. Conclusion: sdLDL-C independently predicted CVD events whereas LDL-C did not. Thus, sdLDL-C may provide a useful clinical tool in risk stratifying and managing patients after LT.

Ten years in: APOL1 reaches beyond the kidney

PURPOSE OF REVIEW

APOL1 nephropathy risk variants drive most of the excess risk of chronic kidney disease (CKD) seen in African Americans, but whether the same risk variants account for excess cardiovascular risk remains unclear. This mini-review highlights the controversies in the APOL1 cardiovascular field.

RECENT FINDINGS

In the past 10 years, our understanding of how APOL1 risk variants contribute to renal cytotoxicity has increased. Some of the proposed mechanisms for kidney disease are biologically plausible for cells and tissues relevant to cardiovascular disease (CVD), but cardiovascular studies published since 2014 have reported conflicting results regarding APOL1 risk variant association with cardiovascular outcomes. In the past year, several studies have also contributed conflicting results from different types of study populations.

SUMMARY

Heterogeneity in study population and study design has led to differing reports on the role of APOL1 nephropathy risk variants in CVD. Without consistently validated associations between these risk variants and CVD, mechanistic studies for APOL1's role in cardiovascular biology lag behind.

Serum amyloid A does not affect high-density lipoprotein cholesterol measurement by a homogeneous assay

BACKGROUND

Serum amyloid A (SAA), which is one of the acute phase proteins, alters the structure of HDL by associating with it during circulation. We focused on whether SAA influences the values of HDL-cholesterol (HDL-C) measurements when using a homogeneous assay.

METHODS

HDLs were isolated by ultracentrifugation from serum samples of 248 patients that were stratified into three groups based on their serum SAA concentrations (low: SAA ≤ 8 μg/mL; middle: 8 < SAA ≤ 100 μg/mL; and high: SAA > 100 μg/mL). HDL-C concentrations of the serum samples measured by the homogeneous assay were compared with the total cholesterol concentrations of HDL fractions isolated by ultracentrifugation.

RESULTS

HDLs obtained from patients with low SAA concentrations were separated into their general particle sizes and classified as HDL₂ and HDL₃ by native-gel electrophoresis. On the other hand, HDLs obtained from patients with high SAA concentrations occasionally showed distributions different from the typical sizes of HDL₂ and HDL₃, such as extremely small or large particles. Nevertheless, HDL-C concentrations measured using the homogeneous assay were strongly correlated with those measured using the ultracentrifugation method, regardless of the SAA concentrations. However, the ratios of HDL-C concentrations obtained by the homogeneous assay to those obtained by the ultracentrifugation method for patients with high SAA concentrations were significantly lower than those of patients with low SAA concentrations.

CONCLUSIONS

A large amount of SAA attached to HDL altered the HDL particle size but did not essentially affect HDL-C measurement by homogeneous assay.

Consumption of a defined, plant-based diet reduces lipoprotein(a), inflammation, and other atherogenic lipoproteins and particles within 4 weeks

BACKGROUND

Lipoprotein(a) [Lp(a)] is a highly atherogenic lipoprotein and is minimally effected by lifestyle changes. While some drugs can reduce Lp(a), diet has not consistently shown definitive reduction of this biomarker. The effect of consuming a plant-based diet on serum Lp(a) concentrations have not been previously evaluated.

HYPOTHESIS

Consumption of a defined, plant-based for 4 weeks reduces Lp(a).

METHODS

Secondary analysis of a previous trial was conducted, in which overweight and obese individuals (n = 31) with low-density lipoprotein cholesterol concentrations >100 mg/dL consumed a defined, plant-based diet for 4 weeks. Baseline and 4-week labs were collected. Data were analyzed using a paired samples t-test.

RESULTS

Significant reductions were observed for serum Lp(a) (-32.0 ± 52.3 nmol/L, P = 0.003), apolipoprotein B (-13.2 ± 18.3 mg/dL, P < 0.0005), low-density lipoprotein (LDL) particles (-304.8 ± 363.0 nmol/L, P < 0.0005) and small-dense LDL cholesterol (-10.0 ± 9.2 mg/dL, P < 0.0005). Additionally, serum interleukin-6 (IL-6), total white blood cells, lipoprotein-associated phospholipase A2 (Lp-PLA2), high-sensitivity c-reactive protein (hs-CRP), and fibrinogen were significantly reduced (P ≤ 0.004).

CONCLUSIONS

A defined, plant-based diet has a favorable impact on Lp(a), inflammatory indicators, and other atherogenic lipoproteins and particles. Lp(a) concentration was previously thought to be only minimally altered by dietary interventions. In this protocol however, a defined plant-based diet was shown to substantially reduce this biomarker. Further investigation is required to elucidate the specific mechanisms that contribute to the reductions in Lp(a) concentrations, which may include alterations in gene expression.

From High-Density Lipoprotein Cholesterol to Measurements of Function: Prospects for the Development of Tests for High-Density Lipoprotein Functionality in Cardiovascular Disease

The evidence is strong that biological functions contained in high-density lipoproteins (HDL) are antiatherogenic. These functions may track with HDL cholesterol or apolipoprotein A1 concentration to explain the strongly inverse risk curve for cardiovascular disease. Moreover, there are harmful as well as protective HDL subspecies in regard to cardiovascular disease, which could be responsible for paradoxical responses to HDL-directed treatments. Recent metabolic studies show that apolipoprotein A1-containing HDL is secreted into the circulation as mostly spherical cholesterol ester-rich lipoproteins that span the HDL size range. Most of the flux of apolipoprotein A1 HDL into and out of the circulation occurs in these spherical cholesterol-replete particles. Discoidal cholesterol-poor HDL comprises a minority of HDL secretion. We propose that much cholesterol in reverse cholesterol transport enters and exits medium and large size HDL without changing a size category, and its flux may be estimated provisionally from holoparticle clearance of cholesterol ester-rich HDL. An accurate framework for metabolism of HDL is essential to finding steady-state biomarkers that reflect HDL function in vivo. Whereas cholesterol efflux from cells to mainly discoidal HDL, mediated by ABCA1 (ATP-binding cassette transporter ABCA1), predicts cardiovascular disease, cholesterol transfers to spherical HDL also can be measured and may be relevant to protection against atherosclerosis. We propose several investigative paths on which human HDL biology may be investigated leading to convenient biomarkers of HDL quality and function having potential not only to improve risk prediction but also to more accurately target drug treatments.

Update on the laboratory investigation of dyslipidemias

The role of the clinical laboratory is evolving to provide more information to clinicians to assess cardiovascular disease (CVD) risk and target therapy more effectively. Current routine methods to measure LDL-cholesterol (LDL-C), the Friedewald calculation, ultracentrifugation, electrophoresis and homogeneous direct methods have established limitations. Studies suggest that LDL and HDL size or particle concentration are alternative methods to predict future CVD risk. At this time there is no consensus role for lipoprotein particle or subclasses in CVD risk assessment. LDL and HDL particle concentration are measured by several methods, namely gradient gel electrophoresis, ultracentrifugation-vertical auto profile, nuclear magnetic resonance and ion mobility. It has been suggested that HDL functional assays may be better predictors of CVD risk. To assess the issue of lipoprotein subclasses/particles and HDL function as potential CVD risk markers robust, simple, validated analytical methods are required. In patients with small dense LDL particles, even a perfect measure of LDL-C will not reflect LDL particle concentration. Non-HDL-C is an alternative measurement and includes VLDL and CM remnant cholesterol and LDL-C. However, apolipoprotein B measurement may more accurately reflect LDL particle numbers. Non-fasting lipid measurements have many practical advantages. Defining thresholds for treatment with new measurements of CVD risk remain a challenge. In families with genetic variants, ApoCIII and lipoprotein (a) may be additional risk factors. Recognition of familial causes of dyslipidemias and diagnosis in childhood will result in early treatment. This review discusses the limitations in current laboratory technologies to predict CVD risk and reviews the evidence for emergent approaches using newer biomarkers in clinical practice.

Fractional esterification rate of cholesterol in high-density lipoprotein associates with risk of coronary heart disease

Background

Fractional esterification rate of cholesterol in high-density lipoprotein (FER_HDL) has been found to be closely correlated with atherosclerotic dyslipidemia, especially lipoprotein distributions, and is a potentially useful predictor for coronary heart disease (CHD). The associations of FER_HDL, measured by the simple and precise HPLC method, with angiographically defined CHD and its related risk factors in Chinese patients were evaluated.

Methods

Two hundred and fifty eight Chinese patients who had indications for angiography were enrolled in this study. Coronary angiograms were obtained by the standard techniques. FER_HDL was determined by the HPLC method. Cholesterol levels in serum HDL, LDL and subfractions were measured by ultracentrifugation/HPLC method. Associations between FER_HDL and CHD and CHD risk factors were analyzed.

Results

FER_HDL was correlated with almost all the CHD risk factors. Compared with the non-CHD group, the CHD patients had higher values of FER_HDL (20.9 ± 7.9%/h vs 17.7 ± 7.1%/h, p = 0.001). FER_HDL was found to be independently and positively correlated with log TG (β = 0.386, P < 0.001) and log (LDLb-C) (β = 0.165, P = 0.020), respectively, and negatively correlated with log (HDL2-C)(β = −0.351, P < 0.001). Logistic regression analysis demonstrated that age, diabetes mellitus, smoking and FER_HDL (OR = 1.056–1.080, p < 0.05) were independent risk factors for CHD.

Conclusion

FER_HDL significantly correlated with both HDL2-C and LDLb-C, and therefore, is the predictor of lipoprotein distributions. In addition, after correcting for the presence of classic risk factors, FER_HDL was independently associated with the presence of angiographically defined CHD.

Impact of menopause and diabetes on atherogenic lipid profile: is it worth to analyse lipoprotein subfractions to assess cardiovascular risk in women?

Cardiovascular disease is the leading cause of death in women at advanced age, who are affected a decade later compared to men. Cardiovascular risk factors in women are not properly investigated nor treated and events are frequently lethal. Both menopause and type 2 diabetes substantially increase cardiovascular risk in the female sex, promoting modifications on lipid metabolism and circulating lipoproteins. Lipoprotein subfractions suffer a shift after menopause towards a more atherogenic lipid profile, consisted of hypertriglyceridemia, lower levels of both total high density lipoprotein (HDL) and its subfraction HDL2, but also higher levels of HDL3 and small low-density lipoprotein particles. This review discusses the impact of diabetes and menopause to the lipid profile, challenges in lipoprotein subfractions determination and their potential contribution to the cardiovascular risk assessment in women. It is still unclear whether lipoprotein subfraction changes are a major driver of cardiometabolic risk and which modifications are predominant. Prospective trials with larger samples, methodological standardizations and pharmacological approaches are needed to clarify the role of lipoprotein subfractions determination on cardiovascular risk prediction and intervention planning in postmenopausal women, with or without DM.

High-Density Lipoprotein Processing and Premature Cardiovascular Disease

High plasma concentrations of low-density lipoprotein-cholesterol (LDL-C) are a well-accepted risk factor for cardiovascular disease (CVD), and the statin class of hypolipidemic drugs has emerged as an effective means of lowering LDL-C and reducing CVD risk. In contrast, the role of plasma high-density lipoproteins (HDL) in protection against atherosclerotic vascular disease is the subject of considerable controversy. Although the inverse correlation between plasma HDL-C and CVD is widely acknowledged, reduction of CVD risk by interventions that increase HDL-C have not been uniformly successful. Several studies of large populations have shown that the first step in reverse cholesterol transport (RCT), the transfer of cholesterol from the subendothelial space of the arterial wall via the plasma compartment to the liver for disposal, is impaired in patients with CVD. Here we review HDL function, the mechanisms by which HDL supports RCT, and the role of RCT in preventing CVD.

Prompt impact of first prospective statin mega-trials on postoperative lipid management of CABG patients: a 20-year follow-up in a single hospital

BACKGROUND

The long-term success of coronary artery bypass grafting (CABG) depends on secondary prevention. Vast evidence provided by the results of cholesterol mega-trials over two decades has shown that effective reduction of LDL cholesterol improves the prognosis of patients with coronary heart disease. However, the implementation of these results into the clinical practice has turned out to be challenging. We analysed how the information derived from clinical statin trials and international recommendations affected the local treatment practices of dyslipidaemia of CABG patients during a 20-year time period.

METHODS

The cohort includes all CABG patients (n = 953) treated in Kanta-Häme Central Hospital during the time period 1990-2009. At the postoperative visits in the cardiology outpatient clinic, each patient's statin prescription was recorded, and blood lipids were determined.

RESULTS

During 1990-1994, 12.0 % of patients were on statins and during the following 5-year time periods the proportion was 57.2, 82.2 and 96.8 %, respectively. During the 20-year observation period (1990-2009), the effective statin dose increased progressively during these 5-year periods up to 36-fold, while the mean concentration of LDL cholesterol decreased from 3.7 to 2.1 mmol/l and that of apolipoprotein B from 1.3 to 0.8 g/l. In the very last year of follow-up, the mean concentrations of LDL-C and apoB were 1.83 mmol/l and 0.78 g/l, respectively. The most prominent increase in statin use and dosage took place during 1994-1996 and 2003-2005, respectively.

CONCLUSIONS

Among CABG patients the lipid-lowering efficacy of statin therapy improved dramatically since 1994. This progress was accompanied by significant and favourable changes of lipid and apolipoprotein-B values. This study shows that it is possible to effectively improve lipid treatment policy once the results of relevant trials are available, and that this may happen even before international or national guidelines have been updated.

Large high-density lipoprotein particle number is independently associated with microvascular function in patients with well-controlled low-density lipoprotein concentration: A vasodilator stress magnetic resonance perfusion study

BACKGROUND

Abnormalities in total cholesterol, high-density lipoprotein, low-density lipoprotein, and triglycerides are associated with microvascular dysfunction. Recent studies suggest that lipid subfractions better predict atherogenic burden than a routine lipid panel. We sought to determine, whether lipid subfractions are more strongly associated with microvascular function and subclinical atherosclerosis, than conventional lipid measurements using vasodilator stress cardiovascular magnetic resonance (CMR).

METHODS

Twenty-four adults referred for risk stratification from a lipid clinic with low-density lipoprotein cholesterol (LDL-C) <100 mg/dL underwent vasodilator CMR. Time-intensity curves generated from stress and rest perfusion images were used to determine the area under the curve (AUC) for the mid-ventricular slice myocardium and the left ventricular (LV) cavity. Myocardial perfusion reserve index (MPRi) was defined as stress to rest ratio of mid-ventricular myocardium AUC, normalized to LV cavity AUC. Lipid panels that included subfractions of LDL and high-density lipoprotein (HDL) were measured using nuclear magnetic resonance testing. The association between MPRi and lipid parameters was examined using univariate linear regression; lipid components statistically correlated with MPRi (P < .05) were then subjected to multivariate analysis.

RESULTS

Univariate regression analysis showed MPRi was associated with HDL-C, triglycerides, large HDL-P, and small LDL-P; no association was found between MPRi and total cholesterol, LDL-C, total LDL-P, or total HDL-P. Using multivariate analysis, large HDL-P was independently associated with MPRi.

CONCLUSIONS

In patients with LDL-C <100 mg/dL, large HDL-P is independently associated with CMR-derived myocardial perfusion reserve, a surrogate for microvascular function and subclinical atherosclerosis. Further studies using lipid subfractions to better understand cardiovascular risks are warranted.

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.

Causal Role of Alcohol Consumption in an Improved Lipid Profile: The Atherosclerosis Risk in Communities (ARIC) Study

INTRODUCTION

Health benefits of low-to-moderate alcohol consumption may operate through an improved lipid profile. A Mendelian randomization (MR) approach was used to examine whether alcohol consumption causally affects lipid levels.

METHODS

This analysis involved 10,893 European Americans (EA) from the Atherosclerosis Risk in Communities (ARIC) study. Common and rare variants in alcohol dehydrogenase and acetaldehyde dehydrogenase genes were evaluated for MR assumptions. Five variants, residing in the ADH1B, ADH1C, and ADH4 genes, were selected as genetic instruments and were combined into an unweighted genetic score. Triglycerides (TG), total cholesterol, high-density lipoprotein cholesterol (HDL-c) and its subfractions (HDL2-c and HDL3-c), low-density lipoprotein cholesterol (LDL-c), small dense LDL-c (sdLDL-c), apolipoprotein B (apoB), and lipoprotein (a) (Lp(a)) levels were analyzed.

RESULTS

Alcohol consumption significantly increased HDL2-c and reduced TG, total cholesterol, LDL-c, sdLDL-c, and apoB levels. For each of these lipids a non-linear trend was observed. Compared to the first quartile of alcohol consumption, the third quartile had a 12.3% lower level of TG (p < 0.001), a 7.71 mg/dL lower level of total cholesterol (p = 0.007), a 10.3% higher level of HDL2-c (p = 0.007), a 6.87 mg/dL lower level of LDL-c (p = 0.012), a 7.4% lower level of sdLDL-c (p = 0.037), and a 3.5% lower level of apoB (p = 0.058, poverall = 0.022).

CONCLUSIONS

This study supports the causal role of regular low-to-moderate alcohol consumption in increasing HDL2-c, reducing TG, total cholesterol, and LDL-c, and provides evidence for the novel finding that low-to-moderate consumption of alcohol reduces apoB and sdLDL-c levels among EA. However, given the nonlinearity of the effect of alcohol consumption, even within the range of low-to-moderate drinking, increased consumption does not always result in a larger benefit.

New Insights into the High-Density Lipoprotein Dilemma

Although high-density lipoprotein-cholesterol (HDL-C) concentration is a negative risk factor for atherosclerotic cardiovascular disease (CVD), efforts to reduce CVD risk by raising HDL-C have not been uniformly successful. Many studies have shown that alcohol consumption, that increases plasma HDL-C concentration, reduces CVD incidence. However, recent genetic studies in large populations have not only removed HDL-C from the causal link between plasma HDL-C concentration and reduced CVD risk, but also suggest that the association is weak. We propose here that the cardioprotective effects of alcohol are mediated by the interaction of its terminal metabolite, acetate, with the adipocyte free fatty acid receptor 2 (FFAR2), which elicits a profound antilipolytic effect that may increase insulin sensitivity without necessarily raising plasma HDL-C concentration.

A Novel Anti-Inflammatory Effect for High Density Lipoprotein

High density lipoprotein has anti-inflammatory effects in addition to mediating reverse cholesterol transport. While many of the chronic anti-inflammatory effects of high density lipoprotein (HDL) are attributed to changes in cell adhesion molecules, little is known about acute signal transduction events elicited by HDL in endothelial cells. We now show that high density lipoprotein decreases endothelial cell exocytosis, the first step in leukocyte trafficking. ApoA-I, a major apolipoprotein of HDL, mediates inhibition of endothelial cell exocytosis by interacting with endothelial scavenger receptor-BI which triggers an intracellular protective signaling cascade involving protein kinase C (PKC). Other apolipoproteins within the HDL particle have only modest effects upon endothelial exocytosis. Using a human primary culture of endothelial cells and murine apo-AI knockout mice, we show that apo-AI prevents endothelial cell exocytosis which limits leukocyte recruitment. These data suggest that high density lipoprotein may inhibit diseases associated with vascular inflammation in part by blocking endothelial exocytosis.

Role of serum high density lipoprotein levels and functions in calcific aortic valve stenosis progression

BACKGROUND

Clinical and epidemiological data well defines the role of atherosclerotic risk factors in pathogenesis of aortic stenosis. Especially dyslipidemia with elevated total and LDL cholesterol levels exerts certain histopathological changes on calcified valve tissue. Exact role of HDL in this process is not known.

OBJECTIVE

To evaluate the lipid profiles of patients with mild aortic valve stenosis with special focus on HDL; HDL subspecies, serum apoA1 levels, HDL related PON1 and PAF-AH enzyme activities and to correlate this with disease progression rates.

METHOD

42 patients (26 female; 16 male), with calcific aortic valve stenosis were enrolled in the study. Serum fasting lipid parameters, HDL subspecies (HDL2, HDL3), serum apoA1 levels and HDL related PON1 and PAF-AH enzyme activities were determined. All participants underwent detailed follow-up transthoracic echocardiography examination.

RESULTS

Among 42 study participants mean serum total cholesterol level was 195 ± 27.3 mg/dl, LDL-c level was 123 ± 19.1 mg/dl, HDL-c level was 44 ± 10.3 mg/dl and total cholesterol/HDL-c ratio was 4.64 ± 1.13. Basal peak aortic jet velocity (Vmax2) was 2.67 ± 0.39 m/sec, mean pressure gradient (Pmean2) was 15.6 ± 5.5 mmhg. Annual progression rate in peak aortic jet velocity (Vmax) was 0.23 ± 0.17 m/sec, in mean pressure gradient (Pmean) was 3 ± 2.1 mmhg. Annual progression rate in Pmean was most strongly correlated with serum HDL-c level and total/HDL-c ratio (r=-0.528 and 0.505; <0.001 and 0.001 respectively). Progression in Vmax values was positively correlated with serum LDL-c level and total/HDL-c ratio while negatively correlated with serum HDL-c levels (r=0.328, 0.499 and -0.464; P=0.034, 0.001 and 0.002 respectively). Among HDL subspecies HDL2 was the predominant type. HDL2 levels were found to be positively correlated with progression rates. There was no significant correlation between apolipoprotein A1 level and annual progression rate. Serum PON1 activity level was determined to be negatively correlated to doppler echocardiographic progression parameters while HDL related PAF-AH activity was independent of disease progression.

CONCLUSION

Present study demonstrated a positive correlation between disease progression and serum total cholesterol/HDL-c ratio. Serum HDL-c level was inversely correlated with hemodynamic progression. The majority of HDL was HDL2 subtype. Among HDL related enzymes PON1 enzyme activity exhibited an inverse correlation with disease progression.

Variation in the Phosphoinositide 3-Kinase Gamma Gene Affects Plasma HDL-Cholesterol without Modification of Metabolic or Inflammatory Markers

Objective

Phosphoinositide 3-kinase γ (PI3Kγ) is a G-protein-coupled receptor-activated lipid kinase mainly expressed in leukocytes and cells of the cardiovascular system. PI3Kγ plays an important signaling role in inflammatory processes. Since subclinical inflammation is a hallmark of atherosclerosis, obesity-related insulin resistance, and pancreatic β-cell failure, we asked whether common genetic variation in the PI3Kγ gene (PIK3CG) contributes to body fat content/distribution, serum adipokine/cytokine concentrations, alterations in plasma lipid profiles, insulin sensitivity, insulin release, and glucose homeostasis.

Study Design

Using a tagging single nucleotide polymorphism (SNP) approach, we analyzed genotype-phenotype associations in 2,068 German subjects genotyped for 10 PIK3CG SNPs and characterized by oral glucose tolerance tests. In subgroups, data from hyperinsulinaemic-euglycaemic clamps, magnetic resonance spectroscopy of the liver, whole-body magnetic resonance imaging, and intravenous glucose tolerance tests were available, and peripheral blood mononuclear cells (PBMCs) were used for gene expression analysis.

Results

After appropriate adjustment, none of the PIK3CG tagging SNPs was significantly associated with body fat content/distribution, adipokine/cytokine concentrations, insulin sensitivity, insulin secretion, or blood glucose concentrations (p>0.0127, all; Bonferroni-corrected α-level: 0.0051). However, six non-linked SNPs displayed at least nominal associations with plasma HDL-cholesterol concentrations, two of them (rs4288294 and rs116697954) reaching the level of study-wide significance (p = 0.0003 and p = 0.0004, respectively). More precisely, rs4288294 and rs116697954 influenced HDL2-, but not HDL3-, cholesterol. With respect to the SNPs’ in vivo functionality, rs4288294 was significantly associated with PIK3CG mRNA expression in PBMCs.

Conclusions

We could demonstrate that common genetic variation in the PIK3CG locus, possibly via altered PIK3CG gene expression, determines plasma HDL-cholesterol concentrations. Since HDL2-, but not HDL3-, cholesterol is influenced by PIK3CG variants, PI3Kγ may play a role in HDL clearance rather than in HDL biogenesis. Even though the molecular pathways connecting PI3Kγ and HDL metabolism remain to be further elucidated, this finding could add a novel aspect to the pathophysiological role of PI3Kγ in atherogenesis.

New and emerging biomarkers in cardiovascular disease

Cardiovascular disease (CVD) is the most common cause of death and disability worldwide. Therefore, great importance has been placed on the discovery of novel risk factors and metabolic pathways relevant in the prevention and management of CVD. Such research is ongoing and may continue to lead to better risk stratification of individuals and/or the development of new intervention targets and treatment options. This review highlights emerging biomarkers related to lipid metabolism, glycemia, inflammation, and cardiac damage, some of which show promising associations with CVD risk and provide further understanding of the underlying pathophysiology. However, their measurement methodology and assays will require validation and standardization, and it will take time to accumulate evidence of their role in CVD in various population settings in order to fully assess their clinical utility. Several of the novel biomarkers represent intriguing, potentially game-changing targets for therapy.

High-Density Lipoprotein Subfractions and Their Oxidized Subfraction Particles in Patients with Chronic Kidney Disease

AIM

Chronic kidney disease (CKD) may lead to reduced concentrations of high-density lipoprotein (HDL) and its subfractions (HDL2 and HDL3), and damage them via inflammation and oxidative stress. The present study aimed to determine the contribution of such changes to cardiovascular disease (CVD) in patients with CKD.

METHODS

The levels of total cholesterol, low-density lipoprotein cholesterol, HDL-C, HDL2, HDL3, apolipoproteins, malondialdehyde-modified LDL (MDA-LDL), oxidized (ox) HDL, oxHDL2, and oxHDL3 were measured in blood samples from patients with CKD (stages 2-5, n=86) who were not on dialysis and from patients undergoing hemodialysis (CKD stage 5D, n=25). The patients were followed up for 28±9 months after baseline examinations and CVD events were recorded.

RESULT

The levels of HDL3 and ApoA1 in HDL3 fraction decreased according to CKD severity, whereas those of HDL2 and ApoA1 in HDL2 fraction did not differ. The levels of oxHDL were similar across CKD stages. The levels of oxHDL3 and MDA-LDL were decreased, whereas those of oxHDL2 increased according to CKD severity. Multivariate analyses using the Cox proportional hazards model selected high levels of oxHDL and its subfractions, and those adjusted with HDL-C and HDL subfractions or ApoA1 in HDL fractions respectively, compared with HDL-C and HDL subfractions or ApoA1 in HDL fractions alone as independent risk factors for CVD events.

CONCLUSION

The levels of HDL subfractions and their oxidized subfraction particles differed among patients with CKD. The increasing levels of oxHDL subfractions might cause a high frequency of CVD events in such patients.

Severity of nonalcoholic fatty liver disease and progression to cirrhosis are associated with atherogenic lipoprotein profile

BACKGROUND & AIMS

Nonalcoholic fatty liver disease (NAFLD) is associated independently with increased cardiovascular mortality. Although NAFLD is associated with dyslipidemia, it is not clear whether recently identified markers of cardiovascular risk indicate liver disease progression in patients with histologically confirmed NAFLD. We evaluated an extensive panel of serum markers of cardiovascular risk in nondiabetic patients with histologically proven NAFLD.

METHODS

We performed a case-control study in which we compared serum levels of laboratory markers of cardiovascular risk among 81 nondiabetic subjects with histologically confirmed NAFLD vs lean (N = 81) and obese (N = 81) individuals without NAFLD (based on liver fat score, controls). For ex vivo studies, liver tissues were obtained from subjects undergoing elective cholecystectomy or from a tissue repository.

RESULTS

Subjects with NAFLD had increased serum levels of insulin, triglycerides, and apolipoprotein B; increased size and concentration of very large density lipoprotein particles; increased concentrations of low-density lipoprotein (LDL) particles and small dense LDL (sdLDL) cholesterol, and an increased percentage of sdLDL, compared with controls. Although nonalcoholic steatohepatitis was associated with a worse profile of serum atherogenic markers than NAFLD, these differences did not reach statistical significance. Despite hyperinsulinemia, triglyceride and apolipoprotein B levels, concentrations of LDL particles and LDL cholesterol, and sdLDL-related parameters decreased significantly in patients with cirrhosis. Ex vivo studies showed that patients with NAFLD had increased sensitivity of hepatic triglyceride levels and cholesterol synthesis to insulin, and that sensitivity increased the development of cirrhosis.

CONCLUSIONS

Atherogenic dyslipidemia is related to increased insulin-induced hepatic lipid synthesis in patients with NAFLD. Reduced dyslipidemia in patients with cirrhosis is associated with increased insulin resistance and possibly failed lipid synthesis.

Evolution of serum atherogenic risk in liver transplant recipients: Role of lipoproteins and metabolic and inflammatory markers

Although cardiovascular disease (CVD) is the leading cause of long-term mortality in liver transplant recipients (LTRs), the role of recently identified biomarkers of CVD risk in liver transplantation is unknown. We aimed to evaluate an extensive CVD risk profile in LTRs. Markers of CVD risk in 65 LTRs with no known history of diabetes mellitus (DM), dyslipidemia, or ischemic heart disease were compared to age-, sex-, and body mass index (BMI)-matched controls with no chronic medical disease. LTRs on corticosteroids or those with graft cirrhosis (GC) were excluded. The effect of calcineurin inhibitors on the CVD risk profile was separately analyzed in LTRs receiving either tacrolimus (Tac) or cyclosporine A (CsA). To evaluate the impact of GC, a comparison was made between LTRs with and without GC. Non-DM LTRs were matched to controls with respect to age, sex, and BMI. LTRs had similar serum high-density lipoprotein-cholesterol (HDL-C), low-density lipoprotein-cholesterol (LDL-C), and total cholesterol in comparison with BMI-matched controls. Proatherogenic small-dense (sd) LDL-C (33.6 ± 14 versus 25.9 ± 9.9 mg/dL; P < 0.001) and %sdLDL-C (30% ± 10% versus 26.4% ± 9%; P = 0.02) were significantly higher in LTRs. In comparison with controls, LTRs had higher apolipoprotein B (apoB; 98 ± 37 versus 88 ± 24 mg/dL; P < 0.01), very low density lipoprotein-particle concentration (VLDL-P; 7.7 ± 6.7 nmol/L versus 3.2 ± 9.1 nmol/L; P < 0.001), and VLDL size (51.1 ± 6.6 versus 46.5 ± 6.9 nm; P < 0.001). In LTRs, VLDL size and VLDL-P were directly related to serum CsA levels (r = 0.53, P = 0.09, and r = 0.63, P < 0.01, respectively) but not to Tac levels. In comparison with controls, LTRs had significantly lower total serum high-density lipoprotein-particle concentration. In comparison with those with preserved graft function, LTRs with GC had lower levels of serum atherogenic markers characterized by low sdLDL-C, apoB, triglycerides, LDL-C, and total cholesterol. In conclusion, LTRs have a proatherogenic lipoprotein profile that is not captured with a traditional lipid panel, and this suggests that a detailed serum atherogenic profile is needed to truly assess CVD risk in LTRs.

Apolipoprotein AI deficiency inhibits serum opacity factor activity against plasma high density lipoprotein via a stabilization mechanism

The reaction of Streptococcal serum opacity factor (SOF) against plasma high-density lipoproteins (HDL) produces a large cholesteryl ester-rich microemulsion (CERM), a smaller neo HDL that is apolipoprotein (apo) AI-poor, and lipid-free apo AI. SOF is active versus both human and mouse plasma HDL. In vivo injection of SOF into mice reduces plasma cholesterol ∼40% in 3 h while forming the same products observed in vitro, but at different ratios. Previous studies supported the hypothesis that labile apo AI is required for the SOF reaction vs HDL. Here we further tested that hypothesis by studies of SOF against HDL from apo AI-null mice. When injected into apo AI-null mice, SOF reduced plasma cholesterol ∼35% in 3 h. The reaction of SOF vs apo AI-null HDL in vitro produced a CERM and neo HDL, but no lipid-free apo. Moreover, according to the rate of CERM formation, the extent and rate of the SOF reaction versus apo AI-null mouse HDL were less than that against wild-type (WT) mouse HDL. Chaotropic perturbation studies using guanidine hydrochloride showed that apo AI-null HDL was more stable than WT HDL. Human apo AI added to apo AI-null HDL was quantitatively incorporated, giving reconstituted HDL. Both SOF and guanidine hydrochloride displaced apo AI from the reconstituted HDL. These results support the conclusion that apo AI-null HDL is more stable than WT HDL because it lacks apo AI, a labile protein that is readily displaced by physicochemical and biochemical perturbations. Thus, apo AI-null HDL is less SOF-reactive than WT HDL. The properties of apo AI-null HDL can be partially restored to those of WT HDL by the spontaneous incorporation of human apo AI. It remains to be determined what other HDL functions are affected by apo AI deletion.

Effects of menopause, gender and age on lipids and high-density lipoprotein cholesterol subfractions

OBJECTIVE

To distinguish the effects of menopause, gender and age on serum lipid risk markers for vascular disease, including high-density lipoprotein cholesterol (HDL-C) subfractions 2 and 3 (HDL2-C and HDL3-C).

METHODS

We undertook a cross-sectional database analysis of apparently healthy Caucasian pre- and postmenopausal women and men (n=515, 518 and 800, respectively) not taking drugs affecting lipid metabolism (including contraceptive or post-menopausal steroids). Measurements of serum total cholesterol (TC), low-density lipoprotein (LDL-C), triglycerides (TG), HDL-C, HDL2-C, HDL3-C and non-HDL-C concentrations and the TC/HDL-C concentration ratio were considered.

RESULTS

Men had lower TC than postmenopausal women (p<0.001) and similar LDL-C. Compared with premenopausal women, postmenopausal women had a more atherogenic lipid profile with lower HDL2-C (median 0.67 vs 0.60 mmol/L, p<0.001) but no difference in HDL3-C (0.96 vs 0.96 mmol/L, p=0.8). Compared with either pre or postmenopausal women, men had a more atherogenic profile with lower HDL2-C (0.36 mmol/L) and HDL3-C (0.91 mmol/L, all p<0.001). With standardization for confounding variables, including standardization to age of menopause (50 years), differences apparent in the non-standardized comparisons were generally sustained, although HDL3-C levels were lower at menopause, HDL2-C ceased to differ and LDL-C was lower in postmenopausal women than men.

CONCLUSIONS

Male gender is associated with a more atherogenic profile than female gender, with appreciably lower levels of the HDL2-C subfraction. Among women, menopause is associated with a more atherogenic lipid profile, but has less effect than male gender.

Metabolic alterations, HFE gene mutations and atherogenic lipoprotein modifications in patients with primary iron overload

HFE gene mutations contributed to a decrease of insulin secretion, an atherogenic LDL subfraction distribution and altered LDL and HDL particles in patients with iron overload. It remains to be determined whether these alterations contribute to cardiovascular risk.

High density lipoproteins: Measurement techniques and potential biomarkers of cardiovascular risk

Plasma high density lipoprotein cholesterol (HDL) comprises a heterogeneous family of lipoprotein species, differing in surface charge, size and lipid and protein compositions. While HDL cholesterol (C) mass is a strong, graded and coherent biomarker of cardiovascular risk, genetic and clinical trial data suggest that the simple measurement of HDL-C may not be causal in preventing atherosclerosis nor reflect HDL functionality. Indeed, the measurement of HDL-C may be a biomarker of cardiovascular health. To assess the issue of HDL function as a potential therapeutic target, robust and simple analytical methods are required. The complex pleiotropic effects of HDL make the development of a single measurement challenging. Development of laboratory assays that accurately HDL function must be developed validated and brought to high-throughput for clinical purposes. This review discusses the limitations of current laboratory technologies for methods that separate and quantify HDL and potential application to predict CVD, with an emphasis on emergent approaches as potential biomarkers in clinical practice.

Epidemiology: disease associations and modulators of HDL-related biomarkers

Epidemiological studies have shown an inverse association between high-density lipoprotein cholesterol (HDL-C) levels and risk of ischemic heart disease. In addition, a low level of HDL-C has been shown to be a risk factor for other diseases not related to atherosclerosis. However, recent studies have not supported a causal effect of HDL-C in the development of atherosclerosis. Furthermore, new drugs markedly elevating HDL-C levels have been disappointing with respect to clinical endpoints. Earlier, most studies have focused almost exclusively on the total HDL-C without regard to the chemical composition or multiple subclasses of HDL particles. Recently, there have been efforts to dissect the HDL fraction into as many well-defined subfractions and individual molecules of HDL particles as possible. On the other hand, the focus is shifting from the structure and composition to the function of HDL particles. Biomarkers and mechanisms that could potentially explain the beneficial characteristics of HDL particles unrelated to their cholesterol content have been sought with sophisticated methods such as proteomics, lipidomics, metabonomics, and function studies including efflux capacity. These new approaches have been used in order to resolve the complex effects of diseases, conditions, environmental factors, and genes in relation to the protective role of HDL but high-throughput methods are still needed for large-scale epidemiological studies.

Novel metabolic biomarkers of cardiovascular disease

Coronary heart disease (CHD) accounts for one in every six deaths in US individuals. Great advances have been made in identifying important risk factors for CHD, such as hypertension, diabetes mellitus, smoking and hypercholesterolaemia, which have led to major developments in therapy. In particular, statins represent one of the greatest successes in the prevention of CHD. While these standard risk factors are important, an obvious opportunity exists to take advantage of ongoing scientific research to better risk-stratify individuals and to identify new treatment targets. In this Review, we summarize ongoing scientific research in a number of metabolic molecules or features, including lipoproteins, homocysteine, calcium metabolism and glycaemic markers. We evaluate the current state of the research and the strength of evidence supporting each emerging biomarker. We also discuss whether the associations with CHD are strong and consistent enough to improve current risk stratification metrics, and whether these markers enhance our understanding of the underlying biology of CHD and thus point towards new treatment options.