Value of High-Density Lipoprotein (HDL) Subpopulations in Predicting Recurrent Cardiovascular Events in the Veterans Affairs HDL Intervention Trial

HDL abnormalities in type 2 diabetes: Clinical implications

Atherosclerotic cardiovascular disease (ASCVD) represents the primary cause of mortality among patients with Type 2 Diabetes Mellitus (T2DM). In this population, High-Density Lipoprotein (HDL) particles exhibit abnormalities in number, composition, and function, culminating in diminished anti-atherosclerotic capabilities despite normal HDL cholesterol (HDL-C) concentrations. Hyperglycemic conditions contribute to these alterations in HDL kinetics, composition, and function, causing T2DM patients' HDL particles to exhibit decreased concentrations of diverse lipid species and proteins. Treatment of hyperglycemia has the potential to correct abnormal HDL particle attributes in T2DM; however, pharmacological interventions, including metformin and thiazolidinediones, yield inconsistent outcomes with respect to HDL-C concentrations and functionality. Despite numerous attempts with diverse drugs, pharmacologically augmenting HDL-C levels has not resulted in clinical benefits in mitigating ASCVD risk. In contrast, reducing Low Density Lipoprotein cholesterol (LDL-C) via statins and ezetimibe has demonstrated significant efficacy in curtailing CVD risk among T2DM individuals. Promising results have been observed in animal models and early-phase trials utilizing recombinant HDL and Lecitin Cholesterol Acyl Transferase (LCAT) -enhancing agents, but the evaluation of their efficacy and safety in large-scale clinical trials is ongoing. While aberrant HDL metabolism constitutes a prevalent aspect of dyslipidemia in T2DM, HDL cholesterol concentrations and composition no longer offer valuable insights for informing therapeutic decisions. Nevertheless, HDL metabolism remains a critical research area in T2DM, necessitating further investigation to elucidate the role of HDL particles in the development of diabetes-associated complications.

Cystic fibrosis and fat malabsorption: Pathophysiology of the cystic fibrosis gastrointestinal tract and the impact of highly effective CFTR modulator therapy

Cystic fibrosis (CF) is a progressive, genetic, multi-organ disease affecting the respiratory, digestive, endocrine, and reproductive systems. CF can affect any aspect of the gastrointestinal (GI) tract, including the esophagus, stomach, small intestine, colon, pancreas, liver, and gall bladder. GI pathophysiology associated with CF results from CF membrane conductance regulator (CFTR) dysfunction. The majority of people with CF (pwCF) experience exocrine pancreatic insufficiency resulting in malabsorption of nutrients and malnutrition. Additionally, other factors can cause or worsen fat malabsorption, including the potential for short gut syndrome with a history of meconium ileus, hepatobiliary diseases, and disrupted intraluminal factors, such as inadequate bile salts, abnormal pH, intestinal microbiome changes, and small intestinal bacterial overgrowth. Signs and symptoms associated with fat malabsorption, such as abdominal pain, bloating, malodorous flatus, gastroesophageal reflux, nausea, anorexia, steatorrhea, constipation, and distal intestinal obstruction syndrome, are seen in pwCF despite the use of pancreatic enzyme replacement therapy. Given the association of poor nutrition status with lung function decline and increased mortality, aggressive nutrition support is essential in CF care to optimize growth in children and to achieve and maintain a healthy body mass index in adults. The introduction of highly effective CFTR modulator therapy and other advances in CF care have profoundly changed the course of CF management. However, GI symptoms in some pwCF may persist. The use of current knowledge of the pathophysiology of the CF GI tract as well as appropriate, individualized management of GI symptoms continue to be integral components of care for pwCF.

High-Density Lipoprotein Metabolism and Function in Cardiovascular Diseases: What about Aging and Diet Effects?

Cardiovascular diseases (CVDs) have become the leading global cause of mortality, prompting a heightened focus on identifying precise indicators for their assessment and treatment. In this perspective, the plasma levels of HDL have emerged as a pivotal focus, given the demonstrable correlation between plasma levels and cardiovascular events, rendering them a noteworthy biomarker. However, it is crucial to acknowledge that HDLs, while intricate, are not presently a direct therapeutic target, necessitating a more nuanced understanding of their dynamic remodeling throughout their life cycle. HDLs exhibit several anti-atherosclerotic properties that define their functionality. This functionality of HDLs, which is independent of their concentration, may be impaired in certain risk factors for CVD. Moreover, because HDLs are dynamic parameters, in which HDL particles present different atheroprotective properties, it remains difficult to interpret the association between HDL level and CVD risk. Besides the antioxidant and anti-inflammatory activities of HDLs, their capacity to mediate cholesterol efflux, a key metric of HDL functionality, represents the main anti-atherosclerotic property of HDL. In this review, we will discuss the HDL components and HDL structure that may affect their functionality and we will review the mechanism by which HDL mediates cholesterol efflux. We will give a brief examination of the effects of aging and diet on HDL structure and function.

A new risk factor for coronary artery disease can be detected by an ApoA1 mAb-based assay

BACKGROUND

This study aimed to find coronary artery disease (CAD) related apolipoprotein A1 (ApoA1) monoclonal antibody (mAb) and to evaluate the diagnostic value of the assay based on it.

METHODS

Patients with CAD diagnosed by coronary angiography (disease group, n = 180) and healthy subjects (control group, n = 199) were recruited. The correlation between methods and CAD were evaluated by Spearman's rank correlation coefficients. Receiver operating characteristic (ROC) curve analysis was used to evaluate the auxiliary diagnostic value of methods for CAD. Odds ratios (ORs) of the test results in CAD were estimated using logistic regression analysis.

RESULTS

Measurements from an ApoA1 mAb were found significantly positively correlated with CAD (r = 0.243, P < 0.01), unlike the measurements from the ApoA1 pAb were negatively correlated with CAD (r = -0.341, P < 0.001). The areas under the ROC curve of the ApoA1 mAb and pAb measurements were 0.704 and 0.563, respectively, in patients with normal HDL-C levels. ApoA1 values from the mAb assay had a significant positive impact on CAD risk.

CONCLUSION

An ApoA1 mAb-based assay can distinguish a high-density lipoprotein (HDL) subclass positively related to CAD, which can be used to improve and reappraise CAD risk assessment.

Values of Donor Serum Lipids and Calcium in Predicting Graft Function after Kidney Transplantation: A Retrospective Study

OBJECTIVE

Delayed graft function (DGF) and early graft loss of renal grafts are determined by the quality of the kidneys from the deceased donor. As "non-traditional" risk factors, serum biomarkers of donors, such as lipids and electrolytes, have drawn increasing attention due to their effects on the postoperative outcomes of renal grafts. This study aimed to examine the value of these serum biomarkers for prediction of renal graft function.

METHODS

The present study consecutively collected 306 patients who underwent their first single kidney transplantation (KT) from adult deceased donors in our center from January 1, 2018 to December 31, 2019. The correlation between postoperative outcomes [DGF and abnormal serum creatinine (SCr) after 6 and 12 months] and risk factors of donors, including gender, age, body mass index (BMI), past histories, serum lipid biomarkers [cholesterol, triglyceride, high-density lipoprotein (HDL) and low-density lipoprotein (DL)], and serum electrolytes (calcium and sodium) were analyzed and evaluated.

RESULTS

(1) Donor age and pre-existing hypertension were significantly correlated with the incidence rate of DGF and high SCr level (≥2 mg/dL) at 6 and 12 months after KT (P<0.05); (2) The donor's BMI was significantly correlated with the incidence rate of DGF after KT (P<0.05); (3) For serum lipids, merely the low level of serum HDL of the donor was correlated with the reduced incidence rate of high SCr level at 12 months after KT [P<0.05, OR (95% CI): 0.425 (0.202-0.97)]; (4) The serum calcium of the donor was associated with the reduced incidence rate of high SCr level at 6 and 12 months after KT [P<0.05, OR (95% CI): 0.184 (0.045-0.747) and P<0.05, OR (95% CI): 0.114 (0.014-0.948), respectively].

CONCLUSION

The serum HDL and calcium of the donor may serve as predictive factors for the postoperative outcomes of renal grafts after KT, in addition to the donor's age, BMI and pre-existing hypertension.

Genetically determined deficiency of ANGPTL3 does not alter HDL ability to preserve endothelial homeostasis

Individuals with loss-of-function mutations in the ANGPTL3 gene express a rare lipid phenotype called Familial Combined Hypolipidemia (FHBL2). FHBL2 individuals show reduced plasma concentrations of total cholesterol and triglycerides as well as of lipoprotein particles, including HDL. This feature is particularly remarkable in homozygotes in whom ANGPTL3 in blood is completely absent. ANGPTL3 acts as a circulating inhibitor of LPL and EL and it is thought that EL hyperactivity is the cause of plasma HDL reduction in FHBL2. Nevertheless, the consequences of ANGTPL3 deficiency on HDL functionality have been poorly explored. In this report, HDL isolated from homozygous and heterozygous FHBL2 individuals were evaluated for their ability to preserve endothelial homeostasis as compared to control HDL. It was found that only the complete absence of ANGPTL3 alters HDL subclass distribution, as homozygous, but not heterozygous, carriers have reduced content of large and increased content of small HDL with no alterations in HDL2 and HDL3 size. The plasma content of preβ-HDL was reduced in carriers and showed a positive correlation with plasma ANGPTL3 levels. Changes in composition did not however alter the functionality of FHBL2 HDL, as particles isolated from carriers retained their capacity to promote NO production and to inhibit VCAM-1 expression in endothelial cells. Furthermore, no significant changes in circulating levels of soluble ICAM-1 and E-selectin were detected in carriers. These results indicate that changes in HDL composition associated with the partial or complete absence of ANGPTL3 did not alter some of the potentially anti-atherogenic functions of these lipoproteins.

PCSK9 is minimally associated with HDL but impairs the anti-atherosclerotic HDL effects on endothelial cell activation

Proprotein Convertase Subtilisin/Kexin type 9 (PCSK9) regulates the cell-surface localization of LDL receptors in hepatocytes and is associated with LDL and lipoprotein(a) [Lp(a)] uptake, reducing blood concentrations. However, the connection between PCSK9 and HDL is unclear. Here, we investigated the association of plasma PCSK9 with HDL subpopulations and examined the effects of PCSK9 on the atheroprotective function of HDL. We examined the association of PCSK9 with HDL in apoB-depleted plasma by ELISA, native PAGE, and immunoblotting. Our analyses showed that upon apoB-depletion, total circulating PCSK9 levels were 32% of those observed in normolipidemic plasma, and only 6% of PCSK9 in the apoB-depleted plasma, including both the mature and furin-cleaved forms, was associated with HDL. We also show human recombinant PCSK9 abolished the capacity of reconstituted HDL to reduce the formation of ROS in endothelial cells, while a PCSK9-blocking antibody enhanced the capacity of human HDL (in apoB-depleted plasma) to reduce ROS formation in endothelial cells and promote endothelial cell migration. Overall, our findings suggest that PCSK9 is only minimally associated with HDL particles, but PCSK9 in apoB-depleted plasma can affect the atheroprotective properties of HDL related to preservation of endothelial function. This study contributes to the elucidation of the pathophysiological role of plasma PCSK9 and highlights further the anti-atherosclerotic effect of PCSK9 inhibition.

ABCA1, ABCG1, and Cholesterol Homeostasis

Cholesterol is a major component of mammalian cell membranes and plays important structural and functional roles. However, excessive cholesterol accumulation is toxic to cells and constitutes the molecular basis for many diseases, especially atherosclerotic cardiovascular disease. Thus, cellular cholesterol is tightly regulated to maintain a homeostasis. Reverse cholesterol transport (RCT) is thought to be one primary pathway to eliminate excessive cholesterol from the body. The first and rate-limiting step of RCT is ATP-binding cassette (ABC) transports A1 (ABCA1)- and ABCG1-dependent cholesterol efflux. In the process, ABCA1 mediates initial transport of cellular cholesterol to apolipoprotein A-I (apoA-I) for forming nascent high-density lipoprotein (HDL) particles, and ABCG1 facilitates subsequent continued cholesterol efflux to HDL for further maturation. In this chapter, we summarize the roles of ABCA1 and ABCG1 in maintaining cellular cholesterol homoeostasis and discuss the underlying mechanisms by which they mediate cholesterol export.

The Role of High-Density Lipoprotein Cholesterol in 2022

PURPOSE OF THE REVIEW

High-density lipoproteins (HDL) are responsible for the transport in plasma of a large fraction of circulating lipids, in part from tissue mobilization. The evaluation of HDL-associated cholesterol (HDL-C) has provided a standard method for assessing cardiovascular (CV) risk, as supported by many contributions on the mechanism of this arterial benefit. The present review article will attempt to investigate novel findings on the role and mechanism of HDL in CV risk determination.

RECENT FINDINGS

The most recent research has been aimed to the understanding of how a raised functional capacity of HDL, rather than elevated levels per se, may be responsible for the postulated CV protection. Markedly elevated HDL-C levels appear instead to be associated to a raised coronary risk, indicative of a U-shaped relationship. While HDL-C reduction is definitely related to a raised CV risk, HDL-C elevations may be linked to non-vascular diseases, such as age-related macular disease. The description of anti-inflammatory, anti-oxidative and anti-infectious properties has indicated potential newer areas for diagnostic and therapeutic approaches. In the last two decades inconclusive data have arisen from clinical trials attempting to increase HDL-C pharmacologically or by way of recombinant protein infusions (most frequently with the mutant A-I _Milano); prevention of stent occlusion or heart failure treatment have shown instead significant promise. Targeted clinical studies are still ongoing.

HDL Is Not Dead Yet

High-density lipoprotein cholesterol (HDL-C) levels are inversely correlated with coronary heart disease (CHD) in multiple epidemiological studies, but whether HDL is causal or merely associated with CHD is unclear. Recent trials for HDL-raising drugs were either not effective in reducing CHD events or, if beneficial in reducing CHD events, were not conclusive as the findings could be attributed to the drugs’ LDL-reducing activity. Furthermore, the first large Mendelian randomization study did not causally relate HDL-C levels to decreased CHD. Thus, the hypothesis that HDL is protective against CHD has been rightfully challenged. However, subsequent Mendelian randomization studies found HDL characteristics that are causally related to decreased CHD. Many aspects of HDL structure and function, especially in reverse cholesterol transport, may be better indicators of HDL’s protective activity than simply measuring HDL-C. Cholesterol efflux capacity is associated with lower levels of prevalent and incident CHD, even after adjustment for HDL-C and apolipoprotein A-1 levels. Also, subjects with very high levels of HDL-C, including those with rare mutations that disrupt hepatic HDL uptake and reverse cholesterol transport, may be at higher risk for CHD than those with moderate levels. We describe here several cell-based and cell-free in vitro assays of HDL structure and function that may be used in clinical studies to determine which of HDL’s functions are best associated with protection against CHD. We conclude that the HDL hypothesis may need revision based on studies of HDL structure and function, but that the HDL hypothesis is not dead yet.

High-Density Lipoprotein Subfractions: Much Ado about Nothing or Clinically Important?

High-density lipoproteins (HDL) are a heterogenous group of plasma molecules with a large variety in composition. There is a wide specter in lipid content and the number of different proteins that has been associated with HDL is approaching 100. Given this heterogeneity and the fact that the total amount of HDL is inversely related to the risk of coronary heart disease (CHD), there has been increasing interest in the function of specific HDL subgroups and in what way measuring and quantifying these subgroups could be of clinical importance in determining individual CHD risk. If certain subgroups appear to be more protective than others, it may also in the future be possible to pharmacologically increase beneficial and decrease harmful subgroups in order to reduce CHD risk. In this review we give a short historical perspective, summarize some of the recent clinical findings regarding HDL subclassifications and discuss why such classification may or may not be of clinical relevance.

Arylesterase activity of paraoxonase 1 (PON1) on HDL3 and HDL2: Relationship with Q192R, C-108T, and L55M polymorphisms

Background

Controversy exists regarding the role of the subfractions of high-density lipoproteins (HDL₂ and HDL₃) in cardiovascular disease. The functionality of these particles, and their protective role, is due in part to the paraoxonase 1 (PON1) presence in them. The polymorphisms rs662 (Q192R, A/G), rs854560 (L55 M, T/A), and rs705379 (C-108T) of the PON1 gene have been related to enzyme activity and, with the anti-oxidative capacity of the HDL. The objective was to determine the arylesterase PON1 activity in HDL₃ and HDL₂ and its relationship with the polymorphisms mentioned, in a young population.

Methods

The polymorphisms were determined through mini-sequencing (SnaPshot). The HDL subpopulations were separated via ionic precipitation, cholesterol was measured with enzymatic methods, and PON1 activity was measured through spectrophotometry.

Results

The results show that the PON1 polymorphisms do not influence the cholesterol in the HDL. A variation between 40.02 and 43.9 mg/dL was in all the polymorphisms without significant differences. Additionally, PON1 activity in the HDL₃ subfractions was greater (62.83 ± 20 kU/L) than with HDL₂ (35.8 ± 20.8 kU/L) in the whole population and in all the polymorphisms (p < 0.001), and it was independent of the polymorphism and differential arylesterase activity in the Q192R polymorphism (QQ > QR > RR). Thus, 115.90 ± 30.7, 88.78 ± 21.3, 65.29 ± 10.2, respectively, for total HDL, with identical behavior for HDL₃ and HDL₂.

Conclusions

PON1 polymorphisms do not influence the HDL_-c, and the PON activity is greater in the HDL₃ than in the HDL₂, independent of the polymorphism, but it is necessary to delve into the functionality of these findings in different populations.

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PON1 polymorphisms do not influence the cholesterol in the HDL subfractions.

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PON1 arylesterase activity in the HDL₃ subfractions was greater than with HDL₂.

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In Q192R, L55 M and C-108T polymorphisms, PON1 activity is always higher in HDL3.

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This study shows that healthy young people in Colombia have very low HDL cholesterol.

Levels of Prebeta-1 High-Density Lipoprotein Are a Strong Independent Positive Risk Factor for Coronary Heart Disease and Myocardial Infarction: A Meta-Analysis

Background We previously showed that levels of prebeta-1 high-density lipoprotein (HDL), the principal acceptor of cholesterol effluxed from cells, including artery wall macrophages, are positively associated with coronary heart disease (CHD) and myocardial infarction (MI) risk. Methods and Results In a multiethnic follow-up cohort of 1249 individuals from University of California-San Francisco clinics, we determined the degree to which prebeta-1 HDL levels, both absolute and percentage of apolipoprotein AI, are associated with CHD and history of MI. Independent, strong, positive associations were found. Meta-analysis revealed for the absolute prebeta-1 HDL for the top tertile versus the lowest, unadjusted odds ratios of 1.90 (95% CI, 1.40-2.58) for CHD and 1.79 (95% CI, 1.35-2.36) for MI. For CHD, adjusting for established risk factors, the top versus bottom tertiles, quintiles, and deciles yielded sizable odds ratios of 2.37 (95% CI, 1.74-3.25, P<0.001), 3.20 (95% CI, 2.07-4.94, P<0.001), and 4.00 (95% CI, 2.11-7.58, P<0.001), respectively. Men and women were analyzed separately in a combined data set of 2507 individuals. The odds ratios for CHD and MI risk were similar. Higher levels of prebeta-1 HDL were associated with all 5 metabolic syndrome features. Addition of prebeta-1 HDL to these 5 features resulted in significant improvements in risk-prediction models. Conclusions Analysis of 2507 subjects showed conclusively that levels of prebeta-1 HDL are strongly associated with a history of CHD or MI, independently of traditional risk factors. Addition of prebeta-1 HDL can significantly improve clinical assessment of risk of CHD and MI.

[The Current Significance of Measuring HDL-Cholesterol in Cardiovascular Risk Assessment]

The Current Significance of Measuring HDL-Cholesterol in Cardiovascular Risk Assessment Abstract. In clinical practice, high-density lipoprotein cholesterol (HDL-C) levels are frequently used for cardiovascular risk prediction. HDL particles perform numerous functions that theoretically protect against atherosclerosis. Accordingly, extensive studies have clearly demonstrated that low HDL-C is an important independent risk factor for cardiovascular diseases. However, it is now considered questionable whether very high HDL-C levels are always cardioprotective. This may be explained by the structural heterogeneity of HDL particles and the loss of HDL protective functions in the context of disease, which cannot be detected by the simple measurement of HDL-C. In the future new markers of the functional capacity of HDL particles may replace HDL-C as a traditional parameter for cardiovascular risk assessment.

Effects of fatty liver on the size and composition of high-density lipoprotein cholesterol subpopulations in adolescents with type 2 diabetes mellitus

BACKGROUND

Type 2 diabetes mellitus (T2DM) is an emerging disease in the pediatric population. The association between T2DM and non-alcoholic fatty liver disease (NAFLD) has been described. Recent evidence suggests that sizes and composition of high-density lipoprotein (HDL) may be more important that HDL-C levels in predicting coronary heart disease. There is not data regarding the HDL subclasses distribution and composition in T2DM youths with NAFLD.

METHODS

This cross-sectional study included 47 adolescents with T2DM and 23 non-diabetic controls of both sexes aged 10 to 18 years. The presence of NAFLD was determined estimated proton density fat fraction (PDFF) by magnetic resonance by spectroscopy. We compared the HDL subclasses distribution (HDL2b, HDL2a, HDL3a HDL3b and HDL3c) and the HDL chemical composition (total protein, triglyceride, phospholipid, cholesteryl esters, and free cholesterol) between the groups of adolescents with T2DM and the control group.

RESULTS

Patients with T2DM and NAFLD had a significantly lower proportion HDL2b (P = .040) and a higher proportion of HDL3c (P = .035); higher proportion of TG (P = .032) and a lower CE (P = .002) and FC (P < .001). A negative association was observed between PDFF and the percentages of HDL2b (r² = -0.341, P = .004) and the average particle size (r² = -0.327, P = .05), and a positive association with HDL3c subpopulations (r² = 0.327, P = .015); about composition inside HDL particle, a positive association with PDFF and the TG (r² = 0.299, P = .013) and negative with CE (r² = -0.265, P = .030).

CONCLUSIONS

In adolescents diagnosed with T2DM, the presence of NAFLD is associated with abnormalities in the distribution of HDL subpopulations and the lipid composition of HDL particles.

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.

Lipid efflux mechanisms, relation to disease and potential therapeutic aspects

Lipids are hydrophobic and amphiphilic molecules involved in diverse functions such as membrane structure, energy metabolism, immunity, and signaling. However, altered intra-cellular lipid levels or composition can lead to metabolic and inflammatory dysfunction, as well as lipotoxicity. Thus, intra-cellular lipid homeostasis is tightly regulated by multiple mechanisms. Since most peripheral cells do not catabolize cholesterol, efflux (extra-cellular transport) of cholesterol is vital for lipid homeostasis. Defective efflux contributes to atherosclerotic plaque development, impaired β-cell insulin secretion, and neuropathology. Of these, defective lipid efflux in macrophages in the arterial walls leading to foam cell and atherosclerotic plaque formation has been the most well studied, likely because a leading global cause of death is cardiovascular disease. Circulating high density lipoprotein particles play critical roles as acceptors of effluxed cellular lipids, suggesting their importance in disease etiology. We review here mechanisms and pathways that modulate lipid efflux, the role of lipid efflux in disease etiology, and therapeutic options aimed at modulating this critical process.

The PPAR pan-agonist tetradecylthioacetic acid promotes redistribution of plasma cholesterol towards large HDL

Tetradecylthioacetic acid (TTA) is a synthetic fatty acid with a sulfur substitution in the β-position. This modification renders TTA unable to undergo complete β-oxidation and increases its biological activity, including activation of peroxisome proliferator activated receptors (PPARs) with preference for PPARα. This study investigated the effects of TTA on lipid and lipoprotein metabolism in the intestine and liver of mice fed a high fat diet (HFD). Mice receiving HFD supplemented with 0.75% (w/w) TTA had significantly lower body weights compared to mice fed the diet without TTA. Plasma triacylglycerol (TAG) was reduced 3-fold with TTA treatment, concurrent with increase in liver TAG. Total cholesterol was unchanged in plasma and liver. However, TTA promoted a shift in the plasma lipoprotein fractions with an increase in larger HDL particles. Histological analysis of the small intestine revealed a reduced size of lipid droplets in enterocytes of TTA treated mice, accompanied by increased mRNA expression of fatty acid transporter genes. Expression of the cholesterol efflux pump Abca1 was induced in the small intestine, but not in the liver. Scd1 displayed markedly increased mRNA and protein expression in the intestine of the TTA group. It is concluded that TTA treatment of HFD fed mice leads to increased expression of genes involved in uptake and transport of fatty acids and HDL cholesterol in the small intestine with concomitant changes in the plasma profile of smaller lipoproteins.

Composition-function analysis of HDL subpopulations: influence of lipid composition on particle functionality

The composition-function relationship of HDL particles and its effects on the mechanisms driving coronary heart disease (CHD) is poorly understood. We tested the hypothesis that the functionality of HDL particles is significantly influenced by their lipid composition. Using a novel 3D-separation method, we isolated five different-sized HDL subpopulations from CHD patients who had low preβ-1 functionality (low-F) (ABCA1-dependent cholesterol-efflux normalized for preβ-1 concentration) and controls who had either low-F or high preβ-1 functionality (high-F). Molecular numbers of apoA-I, apoA-II, and eight major lipid classes were determined in each subpopulation by LC-MS. The average number of lipid molecules decreased from 422 in the large spherical α-1 particles to 57 in the small discoid preβ-1 particles. With decreasing particle size, the relative concentration of free cholesterol (FC) decreased in α-mobility but not in preβ-1 particles. Preβ-1 particles contained more lipids than predicted; 30% of which were neutral lipids (cholesteryl ester and triglyceride), indicating that these particles were mainly remodeled from larger particles not newly synthesized. There were significant correlations between HDL-particle functionality and the concentrations of several lipids. Unexpectedly, the phospholipid:FC ratio was significantly correlated with large-HDL-particle functionality but not with preβ-1 functionality. There was significant positive correlation between particle functionality and total lipids in high-F controls, indicating that the lipid-binding capacity of apoA-I plays a major role in the cholesterol efflux capacity of HDL particles. Functionality and lipid composition of HDL particles are significantly correlated and probably both are influenced by the lipid-binding capacity of apoA-I.

The Role and Function of HDL in Patients with Chronic Kidney Disease and the Risk of Cardiovascular Disease

Chronic kidney disease (CKD) is a worldwide health problem with steadily increasing occurrence. Significantly elevated cardiovascular morbidity and mortality have been observed in CKD. Cardiovascular diseases are the most important and frequent cause of death of CKD patients globally. The presence of CKD is related to disturbances in lipoprotein metabolism whose consequences are dyslipidemia and the accumulation of atherogenic particles. CKD not only fuels the reduction of high-density lipoprotein (HDL) cholesterol concentration, but also it modifies the composition of this lipoprotein. The key role of HDL is the participation in reverse cholesterol transport from peripheral tissues to the liver. Moreover, HDL prevents the oxidation of low-density lipoprotein (LDL) cholesterol by reactive oxygen species (ROS) and protects against the adverse effects of oxidized LDL (ox-LDL) on the endothelium. Numerous studies have demonstrated the ability of HDL to promote the production of nitric oxide (NO) by endothelial cells (ECs) and to exert antiapoptotic and anti-inflammatory effects. Increasing evidence suggests that in patients with chronic inflammatory disorders, HDLs may lose important antiatherosclerotic properties and become dysfunctional. So far, no therapeutic strategy to raise HDL, or alter the ratio of HDL subfractions, has been successful in slowing the progression of CKD or reducing cardiovascular disease in patients either with or without CKD.

Is high-density lipoprotein a modifiable treatment target or just a biomarker for cardiovascular disease?

Epidemiological data strongly support the inverse association between high-density lipoprotein cholesterol concentration and cardiovascular risk. Over the last three decades, pharmaceutical strategies have been partially successful in raising high-density lipoprotein cholesterol concentration, but clinical outcomes have been disappointing. A recent therapeutic class is the cholesteryl ester transfer protein inhibitor. These drugs can increase circulating high-density lipoprotein cholesterol levels by inhibiting the exchange of cholesteryl ester from high-density lipoprotein for triacylglycerol in larger lipoproteins, such as very low-density lipoprotein and low-density lipoprotein. Recent trials of these agents have not shown clinical benefit. This article will review the evidence for cardiovascular risk associated with high-density lipoprotein cholesterol and discuss the implications of the trial data for cholesteryl ester transfer protein inhibitors.

High-density lipoprotein: our elusive friend

PURPOSE OF REVIEW

Despite advances in the research on HDL composition (lipidomics and proteomics) and functions (cholesterol efflux and antioxidative capacities), the relationship between HDL compositional and functional properties is not fully understood. We have reviewed the recent literature on this topic and pointed out the difficulties which limit our understanding of HDL's role in cardiovascular disease (CVD).

RECENT FINDINGS

Though current findings strongly support that HDL has a significant role in CVD, the underlying mechanisms by which HDL mitigates CVD risk are not clear. This review focuses on studies that investigate the cell-cholesterol efflux capacity and the proteomic and lipidomic characterization of HDL and its subfractions especially those that analyzed the relationship between HDL composition and functions.

SUMMARY

Recent studies on HDL composition and HDL functions have greatly contributed to our understanding of HDL's role in CVD. A major problem in HDL research is the lack of standardization of both the HDL isolation and HDL functionality methods. Data generated by different methods often produce discordant results on the particle number, size, lipid and protein composition, and the various functions of HDL.

High-Density Lipoprotein Particles, Cell-Cholesterol Efflux, and Coronary Heart Disease Risk

Objective- The cell-cholesterol efflux capacity of HDL (high-density lipoprotein) is inversely associated with coronary heart disease risk. ABCA1 (ATP-binding cassette transporter A1) plays a crucial role in cholesterol efflux from macrophages to preβ-1-HDL. We tested the hypothesis that coronary heart disease patients have functionally abnormal preβ-1-HDL. Approach and Results- HDL cell-cholesterol efflux capacity via the ABCA1 and the SR-BI (scavenger receptor class B type I) pathways, HDL antioxidative capacity, apo (apolipoprotein) A-I-containing HDL particles, and inflammatory- and oxidative-stress markers were measured in a case-control study of 100 coronary heart disease cases and 100 sex-matched controls. There were significant positive correlations between ABCA1-dependent cholesterol efflux and the levels of small lipid-poor preβ-1 particles ( R²=0.535) and between SR-BI-dependent cholesterol efflux and the levels of large lipid-rich (α-1+α-2) HDL particles ( R²=0.712). Cases had significantly higher (87%) preβ-1 concentrations than controls, but the functionality of their preβ-1 particles (preβ-1 concentration normalized ABCA1-dependent efflux capacity) was significantly lower (-31%). Cases had significantly lower (-12%) mean concentration of large HDL particles, but the functionality of their particles (α-1+α-2 concentration normalized SR-BI-dependent efflux capacity) was significantly higher (22%) compared with that of controls. HDL antioxidative capacity was significantly lower (-16%) in cases than in controls. There were no significant correlations between either preβ-1 functionality or large HDL particle functionality with HDL antioxidative capacity or the concentrations of inflammatory- and oxidative-stress markers. Conclusions- HDL cell-cholesterol efflux capacity is significantly influenced by both the concentration and the functionality of specific HDL particles participating in cell-cholesterol efflux. Coronary heart disease patients have higher than normal preβ-1 concentrations with decreased functionality and lower than normal large HDL particle concentrations with enhanced functionality.

An in-depth analysis shows a hidden atherogenic lipoprotein profile in non-diabetic chronic kidney disease patients

Background: Chronic kidney disease (CKD) is an independent risk factor for atherosclerotic disease. We hypothesized that CKD promotes a proatherogenic lipid profile modifying lipoprotein composition and particle number. Methods: Cross-sectional study in 395 non-diabetic individuals (209 CKD patients and 186 controls) without statin therapy. Conventional lipid determinations were combined with advanced lipoprotein profiling by nuclear magnetic resonance, and their discrimination ability was assessed by machine learning. Results: CKD patients showed an increase of very-low-density (VLDL) particles and a reduction of LDL particle size. Cholesterol and triglyceride content of VLDLs and intermediate-density (IDL) particles increased. However, low-density (LDL) and high-density (HDL) lipoproteins gained triglycerides and lost cholesterol. Total-Cholesterol, HDL-Cholesterol, LDL-Cholesterol, non-HDL-Cholesterol and Proprotein convertase subtilisin-kexin type (PCSK9) were negatively associated with CKD stages, whereas triglycerides, lipoprotein(a), remnant cholesterol, and the PCSK9/LDL-Cholesterol ratio were positively associated. PCSK9 was positively associated with total-Cholesterol, LDL-Cholesterol, LDL-triglycerides, LDL particle number, IDL-Cholesterol, and remnant cholesterol. Machine learning analysis by random forest revealed that new parameters have a higher discrimination ability to classify patients into the CKD group, compared to traditional parameters alone: area under the ROC curve (95% CI), .789 (.711, .853) vs .687 (.611, .755). Conclusions: non-diabetic CKD patients have a hidden proatherogenic lipoprotein profile.

Evacetrapib reduces preβ-1 HDL in patients with atherosclerotic cardiovascular disease or diabetes

BACKGROUND AND AIMS

Cholesteryl ester transfer protein (CETP) inhibitor-mediated induction of HDL-cholesterol has no effect on the protection from cardiovascular disease (CVD). However, the mechanism is still unknown. Data on the effects of this class of drugs on subclasses of HDL are either limited or insufficient. In this study, we investigated the effect of evacetrapib, a CETP inhibitor, on subclasses of HDL in patients with atherosclerotic cardiovascular disease or diabetes.

METHODS

Baseline and 3-month post-treatment samples from atorvastatin 40 mg plus evacetrapib 130 mg (n = 70) and atorvastatin 40 mg plus placebo (n = 30) arms were used for this purpose. Four subclasses of HDL (large HDL, medium HDL, small HDL, and preβ-1 HDL) were separated according to their size and quantified by densitometry using a recently developed native polyacrylamide gel electrophoresis (PAGE) system.

RESULTS

Relative to placebo, while evacetrapib treatment dramatically increased large HDL and medium HDL subclasses, it significantly reduced small HDL (27%) as well as preβ-1 HDL (36%) particles. Evacetrapib treatment reduced total LDL, but also resulted in polydisperse LDL with LDL particles larger and smaller than the LDL subclasses of the placebo group.

CONCLUSION

Evacetrapib reduced preβ-1 HDL and small HDL in patients with ASCVD or diabetes on statin. Preβ-1 HDL and medium HDL are negatively interrelated. The results could give a clue to understand the effect of CETP inhibitors on cardiovascular outcomes.

Effects of weight change on HDL-cholesterol and its subfractions in over 28,000 men and women

BACKGROUND

Changes in body mass index (ΔBMI) have well-established relationships to changes in high-density lipoprotein (ΔHDL)-cholesterol concentrations; however, their relationships to ΔHDL subfractions are less well understood.

OBJECTIVE

Assess the associations between ΔHDL and ΔBMI in a very large cohort.

METHOD

Age and sex-adjusted Δapo A1 concentrations were measured within 10 HDL subfractions in 14,121 women and 13,969 men using two-dimensional HDL-mapping. Significance was identified at .01 < P ≤ .05 (*), .001 < P ≤ .01 (†), .0001 < P ≤ .001 (‡), and P ≤ .0001 (§).

RESULTS

ΔBMI was significantly associated with Δα-1 (very large HDL, slope ± SE, females: -0.39 ± 0.07^§; males: -0.51 ± 0.05^§), Δα-3 (medium HDL, females: 0.18 ± 0.04^§; males: 0.19 ± 0.04^§), and Δα-4 (small HDL, females: 0.14 ± 0.03^§; males: 0.15 ± 0.04^§ mg/dL per kg/m²). As a percent of baseline, the changes in α-1 per ΔBMI were nearly twice as great as the changes in HDL-cholesterol per ΔBMI in both males (-1.53% vs -0.77%) and females (-0.79% vs -0.42%). HDL-cholesterol decreased significantly in healthy-weight patients who became overweight, overweight patients who became class I or class II obese, class I obese patients who became class II obese, and class II obese patients who became class III. In contrast, HDL-cholesterol increased in class III obese patients who became class II or class I, class II obese patients who became class I or overweight, class I patients who became overweight or healthy weight, overweight patients who became healthy weight, and healthy weight patients who became underweight.

CONCLUSIONS

Weight change significantly affects HDL-cholesterol concentrations throughout the obesity spectrum. ΔBMI's effect on Δα-1 was nearly twice as great as its effect on HDL-cholesterol.

Cholesterol transport system: An integrated cholesterol transport model involved in atherosclerosis

Atherosclerosis, the pathological basis of most cardiovascular disease (CVD), is closely associated with cholesterol accumulation in the arterial intima. Excessive cholesterol is removed by the reverse cholesterol transport (RCT) pathway, representing a major antiatherogenic mechanism. In addition to the RCT, other pathways are required for maintaining the whole-body cholesterol homeostasis. Thus, we propose a working model of integrated cholesterol transport, termed the cholesterol transport system (CTS), to describe body cholesterol metabolism. The novel model not only involves the classical view of RCT but also contains other steps, such as cholesterol absorption in the small intestine, low-density lipoprotein uptake by the liver, and transintestinal cholesterol excretion. Extensive studies have shown that dysfunctional CTS is one of the major causes for hypercholesterolemia and atherosclerosis. Currently, several drugs are available to improve the CTS efficiently. There are also several therapeutic approaches that have entered into clinical trials and shown considerable promise for decreasing the risk of CVD. In recent years, a variety of novel findings reveal the molecular mechanisms for the CTS and its role in the development of atherosclerosis, thereby providing novel insights into the understanding of whole-body cholesterol transport and metabolism. In this review, we summarize the latest advances in this area with an emphasis on the therapeutic potential of targeting the CTS in CVD patients.

Genetic and secondary causes of severe HDL deficiency and cardiovascular disease

We assessed secondary and genetic causes of severe HDL deficiency in 258,252 subjects, of whom 370 men (0.33%) and 144 women (0.099%) had HDL cholesterol levels <20 mg/dl. We excluded 206 subjects (40.1%) with significant elevations of triglycerides, C-reactive protein, glycosylated hemoglobin, myeloperoxidase, or liver enzymes and men receiving testosterone. We sequenced 23 lipid-related genes in 201 (65.3%) of 308 eligible subjects. Mutations (23 novel) and selected variants were found at the following gene loci: 1) ABCA1 (26.9%): 2 homozygotes, 7 compound or double heterozygotes, 30 heterozygotes, and 2 homozygotes and 13 heterozygotes with variants rs9282541/p.R230C or rs111292742/c.-279C>G; 2) LCAT (12.4%): 1 homozygote, 3 compound heterozygotes, 13 heterozygotes, and 8 heterozygotes with variant rs4986970/p.S232T; 3) APOA1 (5.0%): 1 homozygote and 9 heterozygotes; and 4) LPL (4.5%): 1 heterozygote and 8 heterozygotes with variant rs268/p.N318S. In addition, 4.5% had other mutations, and 46.8% had no mutations. Atherosclerotic cardiovascular disease (ASCVD) prevalence rates in the ABCA1, LCAT, APOA1, LPL, and mutation-negative groups were 37.0%, 4.0%, 40.0%, 11.1%, and 6.4%, respectively. Severe HDL deficiency is uncommon, with 40.1% having secondary causes and 48.8% of the subjects sequenced having ABCA1, LCAT, APOA1, or LPL mutations or variants, with the highest ASCVD prevalence rates being observed in the ABCA1 and APOA1 groups.

N-terminal mutation of apoA-I and interaction with ABCA1 reveal mechanisms of nascent HDL biogenesis

ApoA-I and ABCA1 play important roles in nascent HDL (nHDL) biogenesis, the first step in the pathway of reverse cholesterol transport that protects against cardiovascular disease. On the basis of the crystal structure of a C-terminally truncated form of apoA-I[Δ(185-243)] determined in our laboratory, we hypothesized that opening the N-terminal helix bundle would facilitate lipid binding. To that end, we structurally designed a mutant (L38G/K40G) to destabilize the N-terminal helical bundle at the first hinge region. Conformational characterization of this mutant in solution revealed minimally reduced α-helical content, a less-compact overall structure, and increased lipid-binding ability. In solution-binding studies, apoA-I and purified ABCA1 also showed direct binding between them. In ABCA1-transfected HEK293 cells, L38G/K40G had a significantly enhanced ability to form nHDL, which suggests that a destabilized N-terminal bundle facilitates nHDL formation. The total cholesterol efflux from ABCA1-transfected HEK293 cells was unchanged in mutant versus WT apoA-I, though, which suggests that cholesterol efflux and nHDL particle formation might be uncoupled events. Analysis of the particles in the efflux media revealed a population of apoA-I-free lipid particles along with nHDL. This model improves knowledge of nHDL formation for future research.

Where next with HDL assays?

PURPOSE OF REVIEW

The inverse association between HDL cholesterol (HDL-C) and cardiovascular disease (CVD) has been unequivocally proven in the past several decades. However, some interventions aiming to increase HDL-C failed to reduce CVD risk. HDL is structurally and functionally complex and HDL-associated metrics other than HDL-C, such as the concentration, composition, and functionality of HDL particles, have been considered as better determinants of CVD risk. A large body of recent research has addressed changes in HDL functions and HDL subpopulations in CVD with the goal of discovering novel and reliable biomarkers and targets for the treatment or prevention of CVD.

RECENT FINDINGS

We have reviewed recent findings on HDL composition, HDL particle concentrations, and cell-cholesterol efflux capacity that have lately contributed to our understanding of HDL's role in CVD.

SUMMARY

We point out that a major problem in HDL research is the lack of standardization of HDL assays that has led to discrepancies among studies. Therefore, there is a need for new standardized assays that capture the complexities of key HDL parameters.

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.

HDL Particle Measurement: Comparison of 5 Methods

BACKGROUND

HDL cell cholesterol efflux capacity has been documented as superior to HDL cholesterol (HDL-C) in predicting cardiovascular disease risk. HDL functions relate to its composition. Compositional assays are easier to perform and standardize than functional tests and are more practical for routine testing. Our goal was to compare measurements of HDL particles by 5 different separation methods.

METHODS

HDL subfractions were measured in 98 samples using vertical auto profiling (VAP), ion mobility (IM), nuclear magnetic resonance (NMR), native 2-dimensional gel electrophoresis (2D-PAGE), and pre-β1-ELISA. VAP measured cholesterol in large HDL₂ and small HDL₃; IM measured particle number directly in large, intermediate, and small HDL particles; NMR measured lipid signals in large, medium, and small HDL; 2D-PAGE measured apolipoprotein (apo) A-I in large (α1), medium (α2), small (α3-4), and pre-β1 HDL particles; and ELISA measured apoA-I in pre-β1-HDL. The data were normalized and compared using Passing-Bablok, Lin concordance, and Bland-Altman plot analyses.

RESULTS

With decreasing HDL-C concentration, NMR measured a gradually lower percentage of large HDL, compared with IM, VAP, and 2D-PAGE. In the lowest HDL-C tertile, NMR measured 8% of large HDL, compared with IM, 22%; VAP, 20%; and 2D-PAGE, 18%. There was strong discordance between 2D-PAGE and NMR in measuring medium HDL (R² = 0.356; r_c = 0.042) and small HDL (R² = 0.376; r_c = 0.040). The 2D-PAGE assay measured a significantly higher apoA-I concentration in pre-β1-HDL than the pre-β1-ELISA (9.8 vs 1.6 mg/dL; R² = 0.246; r_c = 0.130).

CONCLUSIONS

NMR agreed poorly with the other methods in measuring large HDL, particularly in low HDL-C individuals. Similarly, there was strong discordance in pre-β1-HDL measurements between the ELISA and 2D-PAGE assays.

Levels of prebeta-1 high-density lipoprotein are elevated in 3 phenotypes of dyslipidemia

BACKGROUND

Prebeta-1 high-density lipoprotein (HDL) is a small subspecies of HDL that functions as the HDL quantum particle and is the principal acceptor of cholesterol effluxed from macrophages through the ATP-binding cassette transporter, ABCA1. High levels of prebeta-1 HDL are associated with increased risk of structural coronary artery disease and myocardial infarction.

OBJECTIVE

We aimed to compare prebeta-1 HDL levels in normal subjects and in 3 phenotypes of dyslipidemia.

METHODS

We studied 2435 individuals (1388 women; 1047 men). Of these, 2018 were not taking lipid-lowering medication when enrolled: 392 were normolipidemic controls; 713 had elevated levels of low-density lipoprotein cholesterol; 623 had combined hyperlipidemia; and 290 had hypertriglyceridemia.

RESULTS

Relative to controls, prebeta-1 HDL levels were increased in all 3 dyslipidemic phenotypes, particularly the combined and hypertriglyceridemia groups. This increase possibly reflects increased acceptor capacity of apolipoprotein B-100 containing lipoproteins for entropically driven transfer of cholesteryl esters from HDL via cholesteryl ester transfer protein. Multiple regression analysis revealed that the main predictor variables significantly associated with prebeta-1 HDL levels were apolipoprotein A-I (apoA-1) (β = 0.500), triglyceride (β = 0.285), HDL-C (β = -0.237), and age (β = -0.169). There was an interaction between apoA-1 and sex (female vs male; β = -0.110). Among postmenopausal women, estrogenized subjects had a similar level of prebeta-1 HDL compared to those not receiving estrogens.

CONCLUSIONS

Prebeta-1 HDL levels are elevated in the 3 most common types of hyperlipidemia and are most strongly influenced by the levels of apoA-1, triglyceride, and HDL-C.

High density lipoprotein modulates osteocalcin expression in circulating monocytes: a potential protective mechanism for cardiovascular disease in type 1 diabetes

Background

Cardiovascular disease (CVD) is a major cause of mortality in type 1 diabetes (T1D). A pro-calcific drift of circulating monocytes has been linked to vascular calcification and is marked by the surface expression of osteocalcin (OCN). We studied OCN+ monocytes in a unique population with ≥50 years of T1D, the 50-Year Joslin Medalists (J50M).

Methods

CD45 bright/CD14+/OCN+ cells in the circulating mononuclear blood cell fraction were quantified by flow cytometry and reported as percentage of CD45 bright cells. Mechanisms were studied by inducing OCN expression in human monocytes in vitro.

Results

Subjects without history of CVD (n = 16) showed lower levels of OCN+ monocytes than subjects with CVD (n = 14) (13.1 ± 8.4% vs 19.9 ± 6.4%, p = 0.02). OCN+ monocytes level was inversely related to total high density lipoprotein (HDL) cholesterol levels (r = −0.424, p = 0.02), large (r = −0.413, p = 0.02) and intermediate (r = −0.445, p = 0.01) HDL sub-fractions, but not to small HDL. In vitro, incubation with OxLDL significantly increased the number of OCN+ monocytes (p < 0.01). This action of OxLDL was significantly reduced by the addition of HDL in a concentration dependent manner (p < 0.001). Inhibition of the scavenger receptor B1 reduced the effects of both OxLDL and HDL (p < 0.05).

Conclusions

Low OCN+ monocytes levels are associated with lack of CVD in people with long duration T1D. A possible mechanism for the increased OCN+ monocytes could be the elevated levels of oxidized lipids due to diabetes which may be inhibited by HDL. These findings suggest that circulating OCN+ monocytes could be a marker for vascular disease in diabetic patients and possibly modified by HDL elevation.

Electronic supplementary material

The online version of this article (doi:10.1186/s12933-017-0599-2) contains supplementary material, which is available to authorized users.

New perspectives on CKD-induced dyslipidemia

INTRODUCTION

Chronic kidney disease (CKD) is a world-wide health concern associated with a significantly higher cardiovascular morbidity and mortality. One of the principal cardiovascular risk factors is the lipid profile. CKD patients have a more frequent and progressive atheromatous disease that cannot be explained by the classical lipid parameters used in the daily clinical practice. Areas covered: The current review summarizes prevailing knowledge on the role of lipids in atheromathosis in CKD patients, including an overview of lipoprotein metabolism highlighting the CKD-induced alterations. Moreover, to obtain information beyond traditional lipid parameters, new state-of-the-art technologies such as lipoprotein subfraction profiling and lipidomics are also reviewed. Finally, we analyse the potential of new lipoprotein subclasses as therapeutic targets in CKD. Expert opinion: The CKD-induced lipid profile has specific features distinct from the general population. Besides quantitative alterations, renal patients have a plethora of qualitative lipid alterations that cannot be detected by routine determinations and are responsible for the excess of cardiovascular risk. New parameters, such as lipoprotein particle number and size, together with new biomarkers obtained by lipidomics will personalize the management of these patients. Therefore, nephrologists need to be aware of new insights into lipoprotein metabolism to improve cardiovascular risk assessment.

Influence of HDL particles on cell-cholesterol efflux under various pathological conditions

It has been reported that low cell-cholesterol efflux capacity (CEC) of HDL is an independent risk factor for CVD. To better understand CEC regulation, we measured ABCA1- and scavenger receptor class B type I (SR-BI)-dependent cell-cholesterol efflux, HDL anti-oxidative capacity, HDL particles, lipids, and inflammatory- and oxidative-stress markers in 122 subjects with elevated plasma levels of triglyceride (TG), serum amyloid A (SAA), fibrinogen, myeloperoxidase (MPO), or β-sitosterol and in 146 controls. In controls, there were strong positive correlations between ABCA1-dependent cholesterol efflux and small preβ-1 concentrations (R2 = 0.317) and SR-BI-dependent cholesterol efflux and large (α-1 + α-2) HDL particle concentrations (R2 = 0.774). In high-TG patients, both the concentration and the functionality (preβ-1 concentration-normalized ABCA1 efflux) of preβ-1 particles were significantly elevated compared with controls; however, though the concentration of large particles was significantly decreased, their functionality (large HDL concentration-normalized SR-BI efflux) was significantly elevated. High levels of SAA or MPO were not associated with decreased functionality of either the small (preβ-1) or the large (α-1 + α-2) HDL particles. HDL anti-oxidative capacity was negatively influenced by high plasma β-sitosterol levels, but not by the concentrations of HDL particles, TG, SAA, fibrinogen, or MPO. Our data demonstrate that under certain conditions CEC is influenced not only by quantitative (concentration), but also by qualitative (functional) properties of HDL particles.

The effect of weight loss on HDL subfractions and LCAT activity in two genotypes of APOA-II -265T>C polymorphism

Background

People may have different responses to the same environmental changes. It has been reported that genome variations may be responsible for these differences. Also, HDL subfractions may be influenced by different genetic variations. The aim of the present study was to determine gene-diet interactions and to evaluate the influence of weight loss on HDL subfractions between two genotypes of -265 T>C APOA-II polymorphism.

Methods

In the present study, 56 overweight and obese patients with type 2 diabetes mellitus were selected from 697 genotype-specified subjects. After matching for gender, age and BMI at the beginning of the study, an equal number of patients remained on each genotype of APOA-II (TT/TC and CC group). After a 6-week calorie restriction program, 44 patients completed the study. Serum HDL subfractions, including HDL2 and HDL3 and LCAT activity, were compared between the two genotypes and, before and after the intervention, were separated in each genotype.

Results

Serum concentration of HDL and its subfractions decreased significantly due to the weight loss. A comparison of the mean changes between the genotypes showed that HDL3 significantly decreased in the CC genotype while, in the TT/TC group, the serum concentration of HDL2 was significantly reduced. However, the increase of LCAT activity was not significant among the two genotypes.

Conclusion

A comparison of mean changes of variables within two genotype groups showed that C homozygote carriers lead to a general shift toward larger size HDL subfractions and T allele carriers shift toward smaller size HDL subfractions after weight loss.

Moderate statin treatment reduces prebeta-1 high-density lipoprotein levels in dyslipidemic patients

BACKGROUND

Elevated plasma levels of prebeta-1 high-density lipoprotein (HDL), the principal acceptor of cholesterol effluxed from macrophages, are associated with increased risk of atherosclerotic coronary heart disease and myocardial infarction.

OBJECTIVE

The objective of the study was to assess the effects on prebeta-1 HDL levels of 6-week moderate-dose statin treatment.

METHODS

We studied 101 patients (mean age 52.7 years; 53.5% female; 63 with primary hypercholesterolemia; 38 with combined hyperlipidemia) before and after treatment with statins. Mean atorvastatin potency equivalence was 23.6 mg/d. Prebeta-1 HDL plasma levels were measured by immunofixation of agarose gels using anti-apolipoprotein A-1 antibody.

RESULTS

We observed a 42.0% reduction of low-density lipoprotein cholesterol (181 ± 56 vs 105 mg/dL, P < .001). Triglyceride (TG) levels decreased by 22.3% (157 vs 122 mg/dL, P < .001), HDL cholesterol levels remained similar (56.0 vs 57.1, P = NS). Levels of prebeta-1 HDL were significantly reduced by 17.9% after statin treatment (mean 11.4 vs 9.4 mg apoA-1/dL, P < .001). The magnitude of this decrease was similar with each of 3 statins (atorvastatin, simvastatin, and rosuvastatin). The decrease in prebeta-1 HDL was strongly associated with the decline in TG, but not with the decline in low-density lipoprotein cholesterol.

CONCLUSIONS

The association of high prebeta-1 HDL with coronary heart disease identifies it as an inferential measure of the rate of cholesterol efflux from the artery wall. Our observations demonstrate a reduction of prebeta-1 HDL with statin therapy, partially reflecting the reduced TGs, and probably reflecting a direct beneficial impact on cholesterol efflux.

Elevated levels of preβ1-high-density lipoprotein are associated with cholesterol ester transfer protein, the presence and severity of coronary artery disease

Background

Preβ1-high-density lipoprotein (preβ1-HDL), plays an important role in reverse cholesterol transport and exhibits potent risk for coronary artery disease (CAD). However, the association of plasma preβ1-HDL and cholesterol ester transfer protein (CETP) levels in CAD patients and the relationship of preβ1-HDL with extent of CAD are debatable.

Methods

Preβ1-HDL and CETP levels were measured by enzymed-linked immunosorbent assay (ELISAs) in 88 acute coronary syndromes (ACS), 79 stable coronary artery disease (SCAD) patients and 85 control subjects. The correlation analyses, multiple linear regression analyses and logistic regression analyses were performed, respectively.

Results

The preβ1-HDL and CETP levels in ACS patients were significantly higher than those in SCAD patients and both of them were higher than controls’. Preβ1-HDL levels were positively associated with CETP (R = 0.348, P = 0.000), the diameter of stenosis (R = 0.253, P = 0.005), the number of vessel disease (R = 0.274, P = 0.002) and Gensini score (R = 0.227, P = 0.009) in CAD patients. Stepwise multiple linear regression analyses showed that CETP was one of the determinants of preβ1-HDL levels. Logistic regression analysis revealed that elevated preβ1-HDL and CETP were potential risk factors for both ACS and SCAD.

Conclusion

The elevated preβ1-HDL levels may change with CETP concentrations in CAD patients and were related to the presence and severity of CAD.

Total HDL cholesterol efflux capacity in healthy children - Associations with adiposity and dietary intakes of mother and child

BACKGROUND AND AIMS

High-density lipoprotein (HDL) cholesterol efflux capacity in adults may be a measure of the atheroprotective property of HDL. Little however, is known about HDL cholesterol efflux capacity in childhood. We aimed to investigate the relationship between HDL cholesterol efflux capacity and childhood anthropometrics in a longitudinal study.

METHODS AND RESULTS

Seventy-five children (mean age = 9.4 ± 0.4 years) were followed from birth until the age of 9 years. HDL cholesterol efflux capacity was determined at age 9 by incubating serum-derived HDL-supernatants with ³H-cholesterol labeled J774 macrophages and percentage efflux determined. Mothers provided dietary information by completing food frequency questionnaires in early pregnancy and then 5 years later on behalf of themselves and their children. Pearson's correlations and multiple regression analyses were conducted to confirm independent associations with HDL efflux. There was a negative correlation between HDL cholesterol efflux capacity and waist circumference at age 5 (r = -0.3, p = 0.01) and age 9 (r = -0.24, p = 0.04) and BMI at age 5 (r = -0.45, p = 0.01) and age 9 (r = -0.19, p = 0.1). Multiple regression analysis showed that BMI at age 5 remained significantly associated with reduced HDL cholesterol efflux capacity (r = -0.45, p < 0.001). HDL-C was negatively correlated with energy-adjusted fat intake (r = -0.24, p = 0.04) and positively correlated with energy-adjusted protein (r = 0.24, p = 0.04) and starch (r = 0.29, p = 0.01) intakes during pregnancy. HDL-C was not significantly correlated with children dietary intake at age 5. There were no significant correlations between maternal or children dietary intake and HDL cholesterol efflux capacity.

CONCLUSIONS

This novel analysis shows that efflux capacity is negatively associated with adiposity in early childhood independent of HDL-C.

High-density lipoprotein subpopulation profiles in lipoprotein lipase and hepatic lipase deficiency

BACKGROUND AND AIMS

Our aim was to gain insight into the role that lipoprotein lipase (LPL) and hepatic lipase (HL) plays in HDL metabolism and to better understand LPL- and HL-deficiency states.

METHODS

We examined the apolipoprotein (apo) A-I-, A-II-, A-IV-, C-I-, C-III-, and E-containing HDL subpopulation profiles, assessed by native 2-dimensional gel-electrophoresis and immunoblotting, in 6 homozygous and 11 heterozygous LPL-deficient, 6 homozygous and 4 heterozygous HL-deficient, and 50 control subjects.

RESULTS

LPL-deficient homozygotes had marked hypertriglyceridemia and significant decreases in LDL-C, HDL-C, and apoA-I. Their apoA-I-containing HDL subpopulation profile was shifted toward small HDL particles compared to controls. HL-deficient homozygotes had moderate hypertriglyceridemia, modest increases in LDL-C and HDL-C level, but normal apoA-I concentration. HL-deficient homozygotes had a unique distribution of apoA-I-containing HDL particles. The normally apoA-I:A-II, intermediate-size (α-2 and α-3) particles were significantly decreased, while the normally apoA-I only (very large α-1, small α-4, and very small preβ-1) particles were significantly elevated. In contrast to control subjects, the very large α-1 particles of HL-deficient homozygotes were enriched in apoA-II. Homozygous LPL- and HL-deficient subjects also had abnormal distributions of apo C-I, C-III, and E in HDL particles. Values for all measured parameters in LPL- and HL-deficient heterozygotes were closer to values measured in controls than in homozygotes.

CONCLUSIONS

Our data are consistent with the concept that LPL is important for the maturation of small discoidal HDL particles into large spherical HDL particles, while HL is important for HDL remodeling of very large HDL particles into intermediate-size HDL particles.

Subfractions of high-density lipoprotein (HDL) and dysfunctional HDL in chronic kidney disease patients

A number of studies have shown that chronic kidney disease (CKD) is associated with increased risk for cardiovascular disease (CVD). Chronic kidney disease is characterized by significant disturbances in lipoprotein metabolism, including differences in quantitative and qualitative content of high-density lipoprotein (HDL) particles. Recent studies have revealed that serum HDL cholesterol levels do not predict CVD in CKD patients; thus CKD-induced modifications in high-density lipoprotein (HDL) may be responsible for the increase in CV risk in CKD patients. Various methods are available to separate several subclasses of HDL and confirm their atheroprotective properties. However, under pathological conditions associated with inflammation and oxidation, HDL can progressively lose normal biological activities and be converted into dysfunctional HDL. In this review, we highlight the current state of knowledge on subfractions of HDL and HDL dysfunction in CKD.

Human serum preβ1-high density lipoprotein levels are independently and negatively associated with coronary artery diseases

BACKGROUND

Serum preβ1-high density lipoprotein (preβ1-HDL) was defined by two-dimensional non-denaturing linear gel electrophoresis and apolipoprotein A-I immuno-blotting. Serum preβ1-HDL seems to play an important role in reverse cholesterol transport, a well-known anti-atherosclerosis process. However, there are still debatable questions for its quantification and coronary artery disease (CAD) relevance.

METHODS

We isolated the preβ1-HDL using a new native polyacrylamide gel electrophoresis (PAGE) system and lipid pre-staining serum. We established a two-demensional gel electrophoresis system.

RESULTS

We measured the preβ1-HDL in Tangier disease patients and subjects with cholesterol ester transfer protein (CETP) mutation. The preβ1-HDL is clearly separated from lipid-free apoA-I monomer and cannot be converted into other HDL particles under lecithin-cholesterol acyltransferase (LCAT) inhibition. This preβ1-HDL is a spheroidal particle with the highest apoA-1/cholesterol ratio and highest density (≥1.21 g/ml), as compared with all other HDLs. Importantly, we found that serum from subjects with Tangier disease or with cholesterol ester transfer protein (CETP) mutation have no detectible preβ1-HDL particles. We recruited a total of 102 subjects underwent diagnostic coronary angiography and measured their preβ1-HDL levels. Among them, 56 had no stenosis of coronary artery and 46 were diagnosed as CAD, which was predefined as the presence of a luminal diameter stenosis ≥50 % in at least 1 major coronary artery territory. We found that preβ1-HDL is independently and negatively associated with the severity of the coronary artery stenosis (Gensini score).

CONCLUSION

We established a novel and simple method for human serum preβ1-HDL quantification. We found that human lower preβ1-HDL is an independent predictor for severer coronary artery stenosis.

An evaluation of RVX-208 for the treatment of atherosclerosis

INTRODUCTION

RVX-208 is a first-in-class, orally active, novel small molecule in development by Resverlogix Corporation (Calgary, AB, Canada). It acts through an epigenetic mechanism by inhibiting the bromodomain and extraterminal (BET) family of proteins, increasing apolipoprotein A-I (apoA-I) and targeting high-density lipoprotein (HDL) metabolism, including generating of nascent HDL and increased larger HDL particles, resulting in the stimulation of reverse cholesterol transport. RVX-208 also has a beneficial effect on inflammatory factors known to be involved in atherosclerosis and plaque stability. New therapeutic strategies are needed for patients with atherosclerosis.

AREAS COVERED

In this review, the authors evaluate the use of RVX-208 as an agent for the treatment of atherosclerosis. The article is based on a literature search considering both animal and human studies available on PubMed as well as Media Releases from the Resverlogix Corporation.

EXPERT OPINION

The current evidence suggests promising beneficial effects of this novel drug in the prevention and treatment of atherosclerosis and other metabolic disorders. Its unique mechanism of action is encouraging; it affects several pathways and has a modest effect on HDL levels. There is also a shift in particle size to larger HDL particles, which may have potent atheroprotective effects. Future clinical development is needed, including safety assessment.