Apolipoproteins E and CIII interact to regulate HDL metabolism and coronary heart disease risk

Investigating the molecular mechanisms and clinical potential of APO+ endothelial cells associated with PANoptosis in the tumor microenvironment of hepatocellular carcinoma using single-cell sequencing data

INTRODUCTION

PANoptosis is a newly identified form of programmed cell death that integrates elements of pyroptosis, apoptosis, and necroptosis. It plays a pivotal role in shaping the tumor immune microenvironment. Despite its significance, the specific functions and mechanisms of PANoptosis within the tumor microenvironment (TME) of hepatocellular carcinoma (HCC) remain unclear. This study aims to investigate these mechanisms using single-cell RNA sequencing data.

METHODS

Single-cell RNA sequencing data from HCC patients were obtained from the GEO database. The AUCell algorithm was used to quantify PANoptosis activity across various cell types in the TME. Cell populations with high PANoptosis scores were further analyzed using CytoTRACE and scMetabolism to assess their differentiation states and metabolic profiles. Associations between these high-score cell subsets and patient prognosis, tumor stage, and response to immunotherapy were examined. Cell-cell communication analysis was performed to explore how PANoptosis-related APO+ endothelial cells (ECs) may influence HCC progression. Immunofluorescence staining was used to assess the spatial distribution of APO+ ECs in tumor and adjacent tissues. Finally, a CCK8 assay was conducted to evaluate the effect of APOH+ HUVECs on HCC cell proliferation.

RESULTS

A total of 16 HCC patient samples with single-cell RNA sequencing data were included in the study. By calculating the PANoptosis scores of different cell types, we found that ECs, macrophages, hepatocytes, and fibroblasts exhibited higher PANoptosis scores. The PANoptosis scores, differentiation trajectories, intercellular communication, and metabolic characteristics of these four cell subpopulations with high PANoptosis scores were visualized. Among all subpopulations, APO+ ECs demonstrated the most significant clinical relevance, showing a positive correlation with better clinical staging, prognosis, and response to immunotherapy in HCC patients. Cellular communication analysis further revealed that APO+ ECs might regulate the expression of HLA molecules, thereby influencing T cell proliferation and differentiation, potentially contributing to improved prognosis in HCC patients. Immunofluorescence staining results indicated that APO+ ECs were primarily located in the adjacent tissues of HCC patients, with lower expression in tumor tissues. The results of cellular experiments showed that APOH+ HUVECs significantly inhibited the proliferation of HCC cells.

CONCLUSIONS

This study systematically mapped the cellular landscape of the TME in HCC patients and explored the differences in differentiation trajectories, metabolic pathways, and other aspects of subpopulations with high PANoptosis scores. Additionally, the study elucidated the potential molecular mechanisms through which APO+ ECs inhibit HCC cell proliferation and improve prognosis and immunotherapeutic efficacy in HCC patients. This research provides new insights for clinical prognosis evaluation and immunotherapy strategies in HCC.

Relevance of Lipoprotein Composition in Endothelial Dysfunction and the Development of Hypertension

Endothelial dysfunction and chronic inflammation are determining factors in the development and progression of chronic degenerative diseases, such as hypertension and atherosclerosis. Among the shared pathophysiological characteristics of these two diseases is a metabolic disorder of lipids and lipoproteins. Therefore, the contents and quality of the lipids and proteins of lipoproteins become the targets of therapeutic objective. One of the stages of lipoprotein formation occurs through the incorporation of dietary lipids by enterocytes into the chylomicrons. Consequently, the composition, structure, and especially the properties of lipoproteins could be modified through the intake of bioactive compounds. The objective of this review is to describe the roles of the different lipid and protein components of lipoproteins and their receptors in endothelial dysfunction and the development of hypertension. In addition, we review the use of some non-pharmacological treatments that could improve endothelial function and/or prevent endothelial damage. The reviewed information contributes to the understanding of lipoproteins as vehicles of regulatory factors involved in the modulation of inflammatory and hemostatic processes, the attenuation of oxidative stress, and the neutralization of toxins, rather than only cholesterol and phospholipid transporters. For this review, a bibliographic search was carried out in different online metabases.

Recent advances in MASLD genetics: Insights into disease mechanisms and the next frontiers in clinical application

Metabolic dysfunction-associated steatotic liver disease (MASLD) is the most common chronic liver disease in the world and a growing cause of liver-related morbidity and mortality. Yet, at the same time, our understanding of the pathophysiology and genetic underpinnings of this increasingly common yet heterogeneous disease has increased dramatically over the last 2 decades, with the potential to lead to meaningful clinical interventions for patients. We have now seen the first pharmacologic therapy approved for the treatment of MASLD, and multiple other potential treatments are currently under investigation-including gene-targeted RNA therapies that directly extend from advances in MASLD genetics. Here we review recent advances in MASLD genetics, some of the key pathophysiologic insights that human genetics has provided, and the ways in which human genetics may inform our clinical practice in the field of MASLD in the near future.

Reduced Oxidative Susceptibility of Lp(a) and LDL Fractions as a Pleiotropic Effect of Lipoprotein Apheresis in Patients with Elevated Lp(a) and ASCVDs

Oxidative modifications of lipoproteins play a crucial role in the initiation of atherosclerotic cardiovascular diseases (ASCVDs). Nowadays, the one effective strategy for the treatment of patients with hyperlipoproteinemia(a) is lipoprotein apheresis (LA), which has a pleiotropic effect on reducing the risk of ASCVDs. The significance of oxidative susceptibility of the LDL fraction in ASCVDs has been extensively studied. Whether LA alters the susceptibility of lipoprotein(a) to oxidative modifications remains an unresolved issue. In this study, we isolated lipoprotein fractions by ultracentrifugation in patients with hyperlipoproteinemia(a) undergoing apheresis (LA group) at three time points and patients who were qualified for LA but did not consent to the procedure (non-LA group). We performed copper-mediated oxidation of Lp(a) and LDL fractions and determined autotaxin activity. After apheresis, we observed a lower susceptibility to oxidation of the Lp(a) and LDL fractions as expressed by the extended value of oxidation lag time, decreased slope of the oxidation curve, and decreased final concentration of conjugated dienes. No significant differences were found between these parameters before and 7 days after LA. Additionally, both patients undergoing and not undergoing LA had a significant correlation between autotaxin activity and all parameters characterizing susceptibility to oxidation in the Lp(a) fraction. Our results demonstrate that the pleiotropic effect of apheresis may be related to the reduced oxidative susceptibility of Lp(a) and LDL particles, which may influence the reduction in ASCVD risk in patients undergoing apheresis. The results of the rebound effect 7 days after LA will contribute to a better definition of apheresis frequency guidelines.

Per- and polyfluoroalkyl substances, apolipoproteins and the risk of coronary heart disease in US men and women

BACKGROUND

Existing evidence for associations of per- and polyfluoroalkyl substances (PFASs) with blood lipids, lipoproteins and apolipoproteins (apo), and coronary heart disease (CHD) risk is limited and inconsistent. This study aims to explore associations between plasma PFASs, blood lipoprotein subspecies defined by apolipoproteins, and CHD risk.

METHODS

A case-control study of CHD was conducted in the Health Professionals Follow-Up Study (HPFS) and Nurses' Health Study (NHS). Among participants initially free of cardiovascular disease at blood collection in 1994 (HPFS) or 1990 (NHS), 101 participants who developed non-fatal myocardial infarction or fatal CHD were identified and confirmed. A healthy control was matched to each case for age, smoking status, and date of blood draw. Plasma levels of perfluorohexane sulfonic acid (PFHxS), perfluorooctanoic acid (PFOA), total perfluorooctane sulfonic acid (PFOS), branched PFOS (brPFOS), linear PFOS (nPFOS), perfluorononanoic acid (PFNA), and perfluorodecanoic acid (PFDA) were measured. Conditional logistic regression and cubic spline regression models were used to examine associations between baseline PFASs and CHD risk. Linear regression models were applied to study PFAS associations with lipids and their subfractions.

RESULTS

After multivariate adjustments, total PFOS, brPFOS and nPFOS were significantly associated with increased risk of developing CHD, and HRs (95% CIs) per log(ng/mL) increment of PFASs were 3.66 (1.36-9.89), 3.68 (1.55-8.76), and 3.01 (1.16-7.86), respectively. Significant positive dose-response relationships were identified for these PFASs (Plinearity = 0.01, 0.002, 0.02, respectively). Other PFASs were not associated with CHD risk. PFNA and PFDA were positively associated with total apoE levels among HDL particles with or without apoC-III. No associations were observed for other PFASs with blood lipid subspecies. Blood lipid subfractions did not explain the association between PFOS and CHD risk.

CONCLUSIONS

Plasma PFOS and its isomers were positively associated with CHD risk. These findings suggest that PFOS exposure causes public health risks that are greater than hitherto believed.

Multifaceted Role of Apolipoprotein C3 in Cardiovascular Disease Risk and Metabolic Disorder in Diabetes

Apolipoprotein C3 (APOC3) plays a critical role in regulating triglyceride levels and serves as a key predictor of cardiovascular disease (CVD) risk, particularly in patients with diabetes. While APOC3 is known to inhibit lipoprotein lipase, recent findings reveal its broader influence across lipoprotein metabolism, where it modulates the structure and function of various lipoproteins. Therefore, this review examines the complex metabolic cycle of APOC3, emphasizing the impact of APOC3-containing lipoproteins on human metabolism, particularly in patients with diabetes. Notably, APOC3 affects triglyceride-rich lipoproteins and causes structural changes in high-, very low-, intermediate-, and low-density lipoproteins, thereby increasing CVD risk. Evidence suggests that elevated APOC3 levels-above the proposed safe range of 10-15 mg/dL-correlate with clinically significant CVD outcomes. Recognizing APOC3 as a promising biomarker for CVD, this review underscores the urgent need for high-throughput, clinically feasible methods to further investigate its role in lipoprotein physiology in both animal models and human studies. Additionally, we analyze the relationship between APOC3-related genes and lipoproteins, reinforcing the value of large-population studies to understand the impact of APOC3 on metabolic diseases. Ultimately, this review supports the development of therapeutic strategies targeting APOC3 reduction as a preventive approach for diabetes-related CVD.

The functional subclasses of AT1 receptor autoantibody in patients with coronary heart disease

Recently, the identification of autoantibodies (AT1-AA) targeting the second extracellular loop of angiotensin II type 1 receptor (AT1R-ECII) in patients with coronary heart disease (CHD) offers a novel perspective on the interplay between immunity and cardiovascular disease. However, much remains unknown regarding the functional diversity of AT1-AA. In this study, we measured the levels of AT1-AA in the sera of 306 CHD patients and purified AT1-AA from patient's sera (n = 127). The subclasses of AT1-AA were categorized based on their impact on intracellular calcium ([Ca2+]i) levels in mouse arterial smooth muscle cells (MASMCs). Our findings revealed 4 distinct [Ca2+]i response patterns indicating the existence of 4 functional subclasses named H1-, H2-, H3-, and H4-AT1-AA. The correlation analysis demonstrated a positive association between H1-AT1-AA and endogenous coagulation, as well as between H2-AT1-AA and exogenous coagulation; no significant correlation was observed between H3-AT1-AA and the indicators we analyzed. Conversely, H4-AT1-AA exhibited a negative correlation with both leukocyte number and bile acid levels. Logistic regression analysis showed that H2-AT1-AA possessed predictive value for severe CHD. Furthermore, in vitro experiments indicated that both H1- and H2-AT1-AA exerted cytotoxic effects on MASMCs, while H4-AT1-AA increased cell viability. Additionally, an AT1-AA-positive rat model was established by subcutaneously injecting with AT1R-ECII peptide, which produced four similar functional subclasses of rat AT1-AA upon active immunization. This study suggested that classifying different functional subclasses of AT1-AAs can facilitate more accurate evaluation of the condition and prognosis in patients with CHD, thereby providing a novel basis for clinical diagnosis and treatment.

Alzheimer's disease risk gene CD2AP is a dose-sensitive determinant of synaptic structure and plasticity

CD2-Associated protein (CD2AP) is a candidate susceptibility gene for Alzheimer's disease, but its role in the mammalian central nervous system remains largely unknown. We show that CD2AP protein is broadly expressed in the adult mouse brain, including within cortical and hippocampal neurons, where it is detected at pre-synaptic terminals. Deletion of Cd2ap altered dendritic branching and spine density, and impaired ubiquitin-proteasome system activity. Moreover, in mice harboring either one or two copies of a germline Cd2ap null allele, we noted increased paired-pulse facilitation at hippocampal Schaffer-collateral synapses, consistent with a haploinsufficient requirement for pre-synaptic release. Whereas conditional Cd2ap knockout in the brain revealed no gross behavioral deficits in either 3.5- or 12-month-old mice, Cd2ap heterozygous mice demonstrated subtle impairments in discrimination learning using a touchscreen task. Based on unbiased proteomics, partial or complete loss of Cd2ap triggered perturbation of proteins with roles in protein folding, lipid metabolism, proteostasis, and synaptic function. Overall, our results reveal conserved, dose-sensitive requirements for CD2AP in the maintenance of neuronal structure and function, including synaptic homeostasis and plasticity, and inform our understanding of possible cell-type specific mechanisms in Alzheimer's Disease.

Relationships between HDL subpopulation proteome and HDL function in overweight/obese people with and without coronary heart disease

BACKGROUND AND AIMS

The structure-function relationships of high-density lipoprotein (HDL) subpopulations are not well understood. Our aim was to examine the interrelationships between HDL particle proteome and HDL functionality in subjects with and without coronary heart disease (CHD).

METHODS

We isolated 5 different HDL subpopulations based on charge, size, and apolipoprotein A1 (APOA1) content from the plasma of 33 overweight/obese CHD patients and 33 age-and body mass index (BMI)-matched CHD-free subjects. We measured the relative molar concentration of HDL-associated proteins by liquid chromatography tandem mass spectrometry (LC-MS/MS) and assessed particle functionality.

RESULTS

We quantified 110 proteins associated with the 5 APOA1-containing HDL subpopulations. The relative molar concentration of these proteins spanned five orders of magnitude. Only 10 proteins were present in >1% while 73 were present in <0.1% concentration. Only 6 of the 10 most abundant proteins were apolipoproteins. Interestingly, the largest (α-1) and the smallest (preβ-1) HDL particles contained the most diverse proteomes. The protein composition of each HDL subpopulation was altered in CHD cases as compared to controls with the most prominent differences in preβ-1 and α-1 particles. APOA2 concentration was positively correlated with preβ-1 particle functionality (ABCA1-CEC/mg APOA1 in preβ-1) (R2 = 0.42, p = 0.005), while APOE concentration was inversely correlated with large-HDL particle functionality (SRBI-CEC/mg APOA1 in α-1+α-2) (R2 = 0.18, p = 0.01).

CONCLUSIONS

The protein composition of the different HDL subpopulations was altered differentially in CHD patients. The functionality of the small and large HDL particles correlated with the protein content of APOA2 and APOE, respectively. Our data indicate that distinct particle subspecies and specific particle associated proteins provide new information about the role of HDL in CHD.

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

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

Exploring apolipoprotein C-III: pathophysiological and pharmacological relevance

The availability of pharmacological approaches able to effectively reduce circulating LDL cholesterol (LDL-C) has led to a substantial reduction in the risk of atherosclerosis-related cardiovascular disease (CVD). However, a residual cardiovascular (CV) risk persists in treated individuals with optimal levels of LDL-C. Additional risk factors beyond LDL-C are involved, and among these, elevated levels of triglycerides (TGs) and TG-rich lipoproteins are causally associated with an increased CV risk. Apolipoprotein C-III (apoC-III) is a key regulator of TG metabolism and hence circulating levels through several mechanisms including the inhibition of lipoprotein lipase activity and alterations in the affinity of apoC-III-containing lipoproteins for both the hepatic receptors involved in their removal and extracellular matrix in the arterial wall. Genetic studies have clarified the role of apoC-III in humans, establishing a causal link with CVD and showing that loss-of-function mutations in the APOC3 gene are associated with reduced TG levels and reduced risk of coronary heart disease. Currently available hypolipidaemic drugs can reduce TG levels, although to a limited extent. Substantial reductions in TG levels can be obtained with new drugs that target specifically apoC-III; these include two antisense oligonucleotides, one small interfering RNA and an antibody.

High-density lipoprotein functionality, cardiovascular health, and patterns of alcohol consumption: new insights and future perspectives

PURPOSE OF REVIEW

Cardiovascular diseases (CVD) pose a significant public health challenge, contributing to 422 million disability-adjusted life years in 2021. The role of high-density lipoproteins (HDL) and alcohol consumption, one of their major modifiable determinants, remains controversial. The objective of this review is to provide a comprehensive narrative overview of HDL functionality and its predictive value for CVD in relation to patterns of alcohol consumption.

RECENT FINDINGS

HDL phenotypes beyond HDL-cholesterol (HDL-c) such as distribution of HDL subspecies, HDL particle abundance, and reverse cholesterol transport capacity are promising indicators of atherosclerotic CVD risk. Low-to-moderate alcohol consumption seems to improve HDL functionality and reduce the incidence of CVD among primarily middle-aged men and postmenopausal women. Advancements in our understanding of HDL biogenesis, structure, and function hold promise for improving HDL-related measures and their predictive value for cardiovascular health.

SUMMARY

Low-to-moderate alcohol consumption appears to not only increase HDL-c concentration found in the HDL fraction of plasma but also enhance HDL functionality, providing insights into the underlying mechanisms linking alcohol exposure and cardiovascular health benefits. However, rigorous, well designed intervention trials of alcohol consumption on hard cardiovascular outcomes are needed to identify robust causal associations of HDL phenotypes and alcohol consumption with cardiovascular risk.

Understanding HDL Metabolism and Biology Through In Vivo Tracer Kinetics

HDL (high-density lipoprotein), owing to its high protein content and small size, is the densest circulating lipoprotein. In contrast to lipid-laden VLDL (very-low-density lipoprotein) and LDL (low-density lipoprotein) that promote atherosclerosis, HDL is hypothesized to mitigate atherosclerosis via reverse cholesterol transport, a process that entails the uptake and clearance of excess cholesterol from peripheral tissues. This process is mediated by APOA1 (apolipoprotein A-I), the primary structural protein of HDL, as well as by the activities of additional HDL proteins. Tracer-dependent kinetic studies are an invaluable tool to study HDL-mediated reverse cholesterol transport and overall HDL metabolism in humans when a cardiovascular disease therapy is investigated. Unfortunately, HDL cholesterol-raising therapies have not been successful at reducing cardiovascular events suggesting an incomplete picture of HDL biology. However, as HDL tracer studies have evolved from radioactive isotope- to stable isotope-based strategies that in turn are reliant on mass spectrometry technologies, the complexity of the HDL proteome and its metabolism can be more readily addressed. In this review, we outline the motivations, timelines, advantages, and disadvantages of the various tracer kinetics strategies. We also feature the metabolic properties of select HDL proteins known to regulate reverse cholesterol transport, which in turn underscore that HDL lipoproteins comprise a heterogeneous particle population whose distinct protein constituents and kinetics likely determine its function and potential contribution to cholesterol clearance.

Roles of peripheral lipoproteins and cholesteryl ester transfer protein in the vascular contributions to cognitive impairment and dementia

This narrative review focuses on the role of cholesteryl ester transfer protein (CETP) and peripheral lipoproteins in the vascular contributions to cognitive impairment and dementia (VCID). Humans have a peripheral lipoprotein profile where low-density lipoproteins (LDL) represent the dominant lipoprotein fraction and high-density lipoproteins (HDL) represent a minor lipoprotein fraction. Elevated LDL-cholesterol (LDL-C) levels are well-established to cause cardiovascular disease and several LDL-C-lowering therapies are clinically available to manage this vascular risk factor. The efficacy of LDL-C-lowering therapies to reduce risk of all-cause dementia and AD is now important to address as recent studies demonstrate a role for LDL in Alzheimer's Disease (AD) as well as in all-cause dementia. The LDL:HDL ratio in humans is set mainly by CETP activity, which exchanges cholesteryl esters for triglycerides across lipoprotein fractions to raise LDL and lower HDL as CETP activity increases. Genetic and pharmacological studies support the hypothesis that CETP inhibition reduces cardiovascular risk by lowering LDL, which, by extension, may also lower VCID. Unlike humans, wild-type mice do not express catalytically active CETP and have HDL as their major lipoprotein fraction. As HDL has potent beneficial effects on endothelial cells, the naturally high HDL levels in mice protect them from vascular disorders, likely including VCID. Genetic restoration of CETP expression in mice to generate a more human-like lipid profile may increase the relevance of murine models for VCID studies. The therapeutic potential of existing and emerging LDL-lowering therapies for VCID will be discussed. Figure Legend. Cholesteryl Ester Transfer Protein in Alzheimer's Disease. CETP is mainly produced by the liver, and exchanges cholesteryl esters for triglycerides across lipoprotein fractions to raise circulating LDL and lower HDL as CETP activity increases. Low CETP activity is associated with better cardiovascular health, due to decreased LDL and increased HDL, which may also improve brain health. Although most peripheral lipoproteins cannot enter the brain parenchyma due to the BBB, it is increasingly appreciated that direct access to the vascular endothelium may enable peripheral lipoproteins to have indirect effects on brain health. Thus, lipoproteins may affect the cerebrovasculature from both sides of the BBB. Recent studies show an association between elevated plasma LDL, a well-known cardiovascular risk factor, and a higher risk of AD, and considerable evidence suggests that high HDL levels are associated with reduced CAA and lower neuroinflammation. Considering the potential detrimental role of LDL in AD and the importance of HDL's beneficial effects on endothelial cells, high CETP activity may lead to compromised BBB integrity, increased CAA deposits and greater neuroinflammation. Abbreviations: CETP - cholesteryl transfer ester protein; LDL - low-density lipoproteins; HDL - high-density lipoproteins; BBB - blood-brain barrier; CAA - cerebral amyloid angiopathy, SMC - smooth muscle cells, PVM - perivascular macrophages, RBC - red blood cells.

Genome-wide association meta-analysis identifies 17 loci associated with nonalcoholic fatty liver disease

Nonalcoholic fatty liver disease (NAFLD) is common and partially heritable and has no effective treatments. We carried out a genome-wide association study (GWAS) meta-analysis of imaging (n = 66,814) and diagnostic code (3,584 cases versus 621,081 controls) measured NAFLD across diverse ancestries. We identified NAFLD-associated variants at torsin family 1 member B (TOR1B), fat mass and obesity associated (FTO), cordon-bleu WH2 repeat protein like 1 (COBLL1)/growth factor receptor-bound protein 14 (GRB14), insulin receptor (INSR), sterol regulatory element-binding transcription factor 1 (SREBF1) and patatin-like phospholipase domain-containing protein 2 (PNPLA2), as well as validated NAFLD-associated variants at patatin-like phospholipase domain-containing protein 3 (PNPLA3), transmembrane 6 superfamily 2 (TM6SF2), apolipoprotein E (APOE), glucokinase regulator (GCKR), tribbles homolog 1 (TRIB1), glycerol-3-phosphate acyltransferase (GPAM), mitochondrial amidoxime-reducing component 1 (MARC1), microsomal triglyceride transfer protein large subunit (MTTP), alcohol dehydrogenase 1B (ADH1B), transmembrane channel like 4 (TMC4)/membrane-bound O-acyltransferase domain containing 7 (MBOAT7) and receptor-type tyrosine-protein phosphatase δ (PTPRD). Implicated genes highlight mitochondrial, cholesterol and de novo lipogenesis as causally contributing to NAFLD predisposition. Phenome-wide association study (PheWAS) analyses suggest at least seven subtypes of NAFLD. Individuals in the top 10% and 1% of genetic risk have a 2.5-fold to 6-fold increased risk of NAFLD, cirrhosis and hepatocellular carcinoma. These genetic variants identify subtypes of NAFLD, improve estimates of disease risk and can guide the development of targeted therapeutics.

Genome-wide analysis identifies novel loci influencing plasma apolipoprotein E concentration and Alzheimer's disease risk

The APOE 2/3/4 polymorphism is the greatest genetic risk factor for Alzheimer's disease (AD). This polymorphism is also associated with variation in plasma ApoE level; while APOE*4 lowers, APOE*2 increases ApoE level. Lower plasma ApoE level has also been suggested to be a risk factor for incident dementia. To our knowledge, no large genome-wide association study (GWAS) has been reported on plasma ApoE level. This study aimed to identify new genetic variants affecting plasma ApoE level as well as to test if baseline ApoE level is associated with cognitive function and incident dementia in a longitudinally followed cohort of the Ginkgo Evaluation of Memory (GEM) study. Baseline plasma ApoE concentration was measured in 3031 participants (95.4% European Americans (EAs)). GWAS analysis was performed on 2580 self-identified EAs where both genotype and plasma ApoE data were available. Lower ApoE concentration was associated with worse cognitive function, but not with incident dementia. As expected, the risk for AD increased from E2/2 through to E4/4 genotypes (P for trend = 4.8E-75). In addition to confirming the expected and opposite associations of APOE*2 (P = 4.73E-79) and APOE*4 (P = 8.73E-12) with ApoE level, GWAS analysis revealed nine additional independent signals in the APOE region, and together they explained about 22% of the variance in plasma ApoE level. We also identified seven new loci on chromosomes 1, 4, 5, 7, 11, 12 and 20 (P range = 5.49E-08 to 5.36E-10) that explained about 9% of the variance in ApoE level. Plasma ApoE level-associated independent variants, especially in the APOE region, were also associated with AD risk and amyloid deposition in the brain, indicating that genetically determined ApoE level variation may be a risk factor for developing AD. These results improve our understanding of the genetic determinants of plasma ApoE level and their potential value in affecting AD risk.

Apolipoprotein E-containing HDL decreases caspase-dependent apoptosis of memory regulatory T lymphocytes

Plasma levels of HDL cholesterol are inversely associated with CVD progression. It is becoming increasingly clear that HDL plays important roles in immunity that go beyond its traditionally understood roles in lipid transport. We previously reported that HDL interaction with regulatory T cells (Treg) protected them from apoptosis, which could be a mechanism underlying the broad anti-inflammatory effect of HDL. Herein, we extend our work to show that HDL interacts mainly with memory Treg, particularly with the highly suppressive effector memory Treg, by limiting caspase-dependent apoptosis in an Akt-dependent manner. Reconstitution experiments identified the protein component of HDL as the primary driver of the effect, though the most abundant HDL protein, apolipoprotein A-I (APOA1), was inactive. In contrast, APOE-depleted HDL failed to rescue effector memory Treg, suggesting the critical role of APOE proteins. HDL particles reconstituted with APOE, and synthetic phospholipids blunted Treg apoptosis at physiological concentrations. The APOE3 and APOE4 isoforms were the most efficient. Similar results were obtained when lipid-free recombinant APOEs were tested. Binding experiments showed that lipid-free APOE3 bound to memory Treg but not to naive Treg. Overall, our results show that APOE interaction with Treg results in blunted caspase-dependent apoptosis and increased survival. As dysregulation of HDL-APOE levels has been reported in CVD and obesity, our data bring new insight on how this defect may contribute to these diseases.

Apolipoproteins as potential communicators play an essential role in the pathogenesis and treatment of early atherosclerosis

Atherosclerosis as the leading cause of the cardiovascular disease is closely related to cholesterol deposition within subendothelial areas of the arteries. Significantly, early atherosclerosis intervention is the critical phase for its reversal. As atherosclerosis progresses, early foam cells formation may evolve into fibrous plaques and atheromatous plaque, ulteriorly rupture of atheromatous plaque increases risks of myocardial infarction and ischemic stroke, resulting in high morbidity and mortality worldwide. Notably, amphiphilic apolipoproteins (Apos) can concomitantly combine with lipids to form soluble lipoproteins that have been demonstrated to associate with atherosclerosis. Apos act as crucial communicators of lipoproteins, which not only can mediate lipids metabolism, but also can involve in pro-atherogenic and anti-atherogenic processes of atherosclerosis via affecting subendothelial retention and aggregation of low-density lipoprotein (LDL), oxidative modification of LDL, foam cells formation and reverse cholesterol transport (RCT) in macrophage cells. Correspondingly, Apos can be used as endogenous and/or exogenous targeting agents to effectively attenuate the development of atherosclerosis. The article reviews the classification, structure, and relationship between Apos and lipids, how Apos serve as communicators of lipoproteins to participate in the pathogenesis progression of early atherosclerosis, as well as how Apos as the meaningful targeting mass is used in early atherosclerosis treatment.

A Current Update on the Role of HDL-Based Nanomedicine in Targeting Macrophages in Cardiovascular Disease

High-density lipoproteins (HDL) are complex endogenous nanoparticles involved in important functions such as reverse cholesterol transport and immunomodulatory activities, ensuring metabolic homeostasis and vascular health. The ability of HDL to interact with a plethora of immune cells and structural cells places it in the center of numerous disease pathophysiologies. However, inflammatory dysregulation can lead to pathogenic remodeling and post-translational modification of HDL, rendering HDL dysfunctional or even pro-inflammatory. Monocytes and macrophages play a critical role in mediating vascular inflammation, such as in coronary artery disease (CAD). The fact that HDL nanoparticles have potent anti-inflammatory effects on mononuclear phagocytes has opened new avenues for the development of nanotherapeutics to restore vascular integrity. HDL infusion therapies are being developed to improve the physiological functions of HDL and to quantitatively restore or increase the native HDL pool. The components and design of HDL-based nanoparticles have evolved significantly since their initial introduction with highly anticipated results in an ongoing phase III clinical trial in subjects with acute coronary syndrome. The understanding of mechanisms involved in HDL-based synthetic nanotherapeutics is critical to their design, therapeutic potential and effectiveness. In this review, we provide a current update on HDL-ApoA-I mimetic nanotherapeutics, highlighting the scope of treating vascular diseases by targeting monocytes and macrophages.

The distinct metabolism between large and small HDL indicates unique origins of human apolipoprotein A4

Apolipoprotein A4's (APOA4's) functions on HDL in humans are not well understood. A unique feature of APOA4 is that it is an intestinal apolipoprotein secreted on HDL and chylomicrons. The goal of this study was to gain a better understanding of the origin and function of APOA4 on HDL by studying its metabolism across 6 HDL sizes. Twelve participants completed a metabolic tracer study. HDL was isolated by APOA1 immunopurification and separated by size. Tracer enrichments for APOA4 and APOA1 were determined by targeted mass spectrometry, and metabolic rates were derived by compartmental modeling. APOA4 metabolism on small HDL (alpha3, prebeta, and very small prebeta) was distinct from that of APOA4 on large HDL (alpha0, 1, 2). APOA4 on small HDL appeared in circulation by 30 minutes and was relatively rapidly catabolized. In contrast, APOA4 on large HDL appeared in circulation later (1-2 hours) and had a much slower catabolism. The unique metabolic profiles of APOA4 on small and large HDL likely indicate that each has a distinct origin and function in humans. This evidence supports the notion that APOA4 on small HDL originates directly from the small intestine while APOA4 on large HDL originates from chylomicron transfer.

Proteomic analysis of postprandial high-density lipoproteins in healthy subjects

The relationship between the functionality and composition of high-density lipoproteins (HDL) is yet not fully studied, and little is known about the influence of the diet in HDL proteome. Therefore, the aim of this research was to elucidate the HDL proteome associated to postprandial hyperlipidemia. Male volunteers were recruited for an interventional study with high fatty acid-based meals. Blood samples were collected before the intake (baseline), and 2-3 (postprandial peak) and 5-6 (postprandial post peak) hours later. HDL were purified and the protein composition was quantified by LC-MS/MS. Statistical analysis was performed by lineal models (amica) and by ANOVA and multi-t-test of the different conditions (MetaboAnalyst). Additionally, a clustering of the expression profiles of each protein was done with coseq R package (RStudio). Initially, 320 proteins were identified but only 119 remained after the filtering. APOM, APOE, APOB, and APOA2, proteins previously identified in the HDL proteome, were the only proteins with a statistically significant altered expression in postprandial hyperlipidemia when compared to baseline (p values <0.05 and logFC >1). In conclusion, we have been able to describe several behaviors of the whole HDL proteome during the postprandial hyperlipidemic metabolism.

Associations between Alcohol Consumption and HDL Subspecies Defined by ApoC3, ApoE and ApoJ: the Cardiovascular Health Study

Alcohol consumption increases circulating high-density lipoprotein cholesterol (HDL-C), but HDL protein cargo may better reflect HDL function. This study examined the associations between alcohol intake and HDL subspecies containing or lacking apoC3, apoE, and apoJ in a well-phenotyped cohort. We performed a cross-sectional analysis of 2092 Cardiovascular Health Study participants aged 70 or older with HDL subspecies measured in stored specimens from 1998 to 1999. Associations between alcohol intake and apoA1 defined HDL subspecies lacking or containing apoC3, apoE, and apoJ, and circulating levels of total apoA1, apoC3, apoE, and apoJ were examined. HDL subspecies lacking and containing apoC3, apoE, and apoJ were all positively associated with alcohol intake, with ∼1% per additional drink per week or ∼7% per additional drink per day (subspecies without the apolipoproteins, P ≤ 2 × 10^-9, subspecies with the apolipoproteins, P ≤ 3 × 10^-5). Total apoA1 was also directly associated with alcohol consumption, with a 1% increase per additional drink per week (P = 1 × 10^-14). Total apoC3 blood levels were 0.5% higher per additional drink per week (P = 0.01), but the association was driven by a few heavily drinking men. Alcohol intake was positively associated with HDL subspecies lacking and containing apoC3, apoE, or apoJ, and with total plasma apoA1. ApoC3 was directly, albeit not as robustly associated with alcohol intake. HDL protein cargo is crucial for its anti-atherosclerotic functions, but it remains to be determined whether HDL subspecies play a role in the putative association between limited alcohol intake and lower risk of coronary heart disease.

Circadian Rhythm of Subspecies of Low-Density Lipoprotein-Cholesterol and High-Density Lipoprotein-Cholesterol in Healthy Subjects and Patients with Type 2 Diabetes

AIMS

We established automated assay kits for quantifying small dense low-density lipoprotein (sdLDL)-cholesterol (C), LDL-triglyceride (TG), and high-density lipoprotein (HDL)3-C, and apolipoprotein (apo)E-rich HDL-C, and these have been recognized as sensitive biomarkers for predicting coronary artery disease. We investigated the circadian rhythms of these novel lipids to determine if fasting is required to determine basal levels.

METHODS

Forty-eight inpatients with type 2 diabetes and 19 healthy volunteers were studied. Blood samples were collected at seven time points, which were obtained after an overnight fast, before and 2 h after each meal, and before the next breakfast. sdLDL-C, LDL-TG, remnant-like particle (RLP)-C, TG-rich lipoprotein (TRL-C), HDL3-C, and apoE-rich HDL-C were measured by the homogeneous methods. NonHDL-C, large buoyant (lb)LDL-C and HDL2-C were calculated by subtracting sdLDL-C from LDL-C or HDL3-C from HDL-C, respectively.

RESULTS

Serum TG levels were significantly increased after meals in both healthy participants and patients with diabetes. RLP-C and TRL-C were also increased postprandially. LDL-TG, LDL-C, nonHDL-C, HDL2,3-C, and apoE-rich HDL-C did not exhibit significant fluctuation during the day in healthy participants and patients with diabetes. sdLDL-C was slightly increased postprandially in subjects with diabetes (1-2 mg/dl, 3%-9%), though its increase was not significant compared to the baseline (fasting) level. Significant postprandial reduction was observed with LDL-C and lbLDL-C. There was no influence of statin therapy or oral anti-diabetes drugs on the circadian rhythm of LDL-C subspecies.

CONCLUSIONS

Subtle postprandial increase in sdLDL-C is considered a negligible level in general clinical practice. Fasting is not mandatory to measure basal concentrations of LDL and HDL subspecies.

APOC-III: a Gatekeeper in Controlling Triglyceride Metabolism

PURPOSE OF REVIEW

Apolipoprotein C-III (ApoC-III) is a widely known player in triglyceride metabolism, and it has been recently recognized as a polyhedric factor which may regulate several pathways beyond lipid metabolism by influencing cardiovascular, metabolic, and neurological disease risk. This review summarizes the different functions of ApoC-III and underlines the recent findings related to its multifaceted pathophysiological role.

RECENT FINDINGS

The role of ApoC-III has been implicated in HDL metabolism and in the development of atherosclerosis, inflammation, and ER stress in endothelial cells. ApoC-III has been recently considered an important player in insulin resistance mechanisms, lipodystrophy, diabetic dyslipidemia, and postprandial hypertriglyceridemia (PPT). The emerging evidence of the involvement of ApoC-III in the in the pathogenesis of Alzheimer's disease open the way to further study if modification of ApoC-III level slows disease progression. Furthermore, ApoC-III is clearly linked to cardiovascular disease (CVD) risk, and progression of coronary artery disease (CAD) as well as the calcification of aortic valve and recent clinical trials has pointed out the inhibition of ApoC-III as a promising approach to manage hypertriglyceridemia and prevent CVD. Several evidences highlight the role of ApoC-III not only in triglyceride metabolism but also in several cardio-metabolic pathways. Results from recent clinical trials underline that the inhibition of ApoC-III is a promising therapeutical strategy for the management of severe hypertriglyceridemia and in CVD prevention.

Alterations of HDL's to piHDL's Proteome in Patients with Chronic Inflammatory Diseases, and HDL-Targeted Therapies

Chronic inflammatory diseases, such as rheumatoid arthritis, steatohepatitis, periodontitis, chronic kidney disease, and others are associated with an increased risk of atherosclerotic cardiovascular disease, which persists even after accounting for traditional cardiac risk factors. The common factor linking these diseases to accelerated atherosclerosis is chronic systemic low-grade inflammation triggering changes in lipoprotein structure and metabolism. HDL, an independent marker of cardiovascular risk, is a lipoprotein particle with numerous important anti-atherogenic properties. Besides the essential role in reverse cholesterol transport, HDL possesses antioxidative, anti-inflammatory, antiapoptotic, and antithrombotic properties. Inflammation and inflammation-associated pathologies can cause modifications in HDL's proteome and lipidome, transforming HDL from atheroprotective into a pro-atherosclerotic lipoprotein. Therefore, a simple increase in HDL concentration in patients with inflammatory diseases has not led to the desired anti-atherogenic outcome. In this review, the functions of individual protein components of HDL, rendering them either anti-inflammatory or pro-inflammatory are described in detail. Alterations of HDL proteome (such as replacing atheroprotective proteins by pro-inflammatory proteins, or posttranslational modifications) in patients with chronic inflammatory diseases and their impact on cardiovascular health are discussed. Finally, molecular, and clinical aspects of HDL-targeted therapies, including those used in therapeutical practice, drugs in clinical trials, and experimental drugs are comprehensively summarised.

Complex association of apolipoprotein E-containing HDL with coronary artery disease burden in cardiovascular disease

Background

Although traditional lipid parameters and coronary imaging techniques are valuable for cardiovascular disease (CVD) risk prediction, better diagnostic tests are still needed.

Methods

In a prospective, observational study, 795 individuals had extensive cardiometabolic profiling, including emerging biomarkers, such as apolipoprotein E–containing HDL-cholesterol (ApoE-HDL-C). Coronary artery calcium (CAC) score was assessed in the entire cohort, and quantitative coronary computed tomography angiography (CCTA) characterization of total burden, noncalcified burden (NCB), and fibrous plaque burden (FB) was performed in a subcohort (n = 300) of patients stratified by concentration of ApoE-HDL-C. Total and HDL-containing apolipoprotein C-III (ApoC-III) were also measured.

Results

Most patients had a clinical diagnosis of coronary artery disease (CAD) (n = 80.4% of 795), with mean age of 59 years, a majority being male (57%), and about half on statin treatment. The low ApoE-HDL-C group had more severe stenosis (11% vs. 2%, overall P < 0.001), with higher CAC as compared with high ApoE-HDL-C. On quantitative CCTA, the high ApoE-HDL-C group had lower NCB (β = –0.24, P = 0.0001), which tended to be significant in a fully adjusted model (β = –0.32, P = 0.001) and altered by ApoC-III in HDL levels. Low ApoE-HDL-C was significantly associated with LDL particle number (β = 0.31; P = 0.0001). Finally, when stratified by FB, ApoC-III in HDL showed a more robust predictive value of CAD over ApoE-HDL-C (AUC: 0.705, P = 0.0001) in a fully adjusted model.

Conclusion

ApoE-containing HDL-C showed a significant association with early coronary plaque characteristics and is affected by the presence of ApoC-III, indicating that low ApoE-HDL-C and high ApoC-III may be important markers of CVD severity.

Trial Registration

ClinicalTrials.gov: NCT01621594.

Funding

This work was supported by the NHLBI at the NIH Intramural Research Program.

Evaluation of the apolipoprotein E (apoE)-HDL-associated risk factors for coronary heart disease using duo-functional electrochemical aptasensor

Apolipoprotein E containing high-density lipoprotein (apoE-HDL) and apoE-HDL cholesterol (apoE-HDL-C) are recently recognized as potential biomarkers for coronary heart disease (CHD). We herein developed a two-stage, enzyme-assisted, dual-signal aptasensor that enables a useful electrochemical sensing platform for simultaneous determination of apoE-HDL, apoE-HDL-C, and total HDL-C presented in the sample. The detection scheme consists of two subsystems. In subsystem (I), the level of apoE-HDL is evaluated upon the binding of apoE-specific aptamer and subsequently methylene blue (MB)-labeled DNA displacement occurs on the electrode surface, resulting in electrochemical reduction of methylene blue. In subsystem (II), two kinds of cholesterol levels (apoE-HDL-C and total HDL-C) can be measured. For apoE-HDL-C, the amount of cholesterol in apoE-HDL captured by the aptamer in the first step can be further determined with the aid of surfactant, cholesterol esterase, cholesterol oxidase, and p-aminophenol-mediated electrochemical signal amplification. As for total HDL-C, the amount of cholesterol is determined by the same approach as that used for apoE-HDL-C determination, but without washing (separation). The linear dynamic range for apoE-HDL determination is from 1 to 100 mg/dL (R² = 1.00). For cholesterol standards, the linear dynamic range is determined to be 0-250 mg/dL (R² = 0.98). Finally, serial dilutions of purified human HDL preparations were examined using the newly developed aptasensor; the percentage of apoE-HDL-C to HDL-C was found to be ~10%, which correlated well with previously reported values. In conclusion, we successfully developed an electrochemical aptasensor that allows concurrent quantification of apoE-HDL, apoE-HDL-C, and HDL-C on the same platform, offering an efficient, convenient, and purification-free sensing strategy for predictive CHD biomarkers.

The Functional Role of Lipoproteins in Atherosclerosis: Novel Directions for Diagnosis and Targeting Therapy

Dyslipidemia, characterized by a high level of lipids (cholesterol, triglycerides, or both), can increase the risk of developing and progressing atherosclerosis. As atherosclerosis progresses, the number and severity of aterial plagues increases with greater risk of myocardial infarction, a major contributor to cardiovascular mortality. Atherosclerosis progresses in four phases, namely endothelial dysfunction, fatty streak formation, lesion progression and plaque rupture, and eventually thrombosis and arterial obstruction. With greater understanding of the pathological processes underlying atherosclerosis, researchers have identified that lipoproteins play a significant role in the development of atherosclerosis. In particular, apolipoprotein B (apoB)-containing lipoproteins have been shown to associate with atherosclerosis. Oxidized low-density lipoproteins (ox-LDLs) also contribute to the progression of atherosclerosis whereas high-density lipoproteins (HDL) contribute to the removal of cholesterol from macrophages thereby inhibiting the formation of foam cells. Given these known associations, lipoproteins may have potential as biomarkers for predicting risk associated with atherosclerotic plaques or may be targets as novel therapeutic agents. As such, the rapid development of drugs targeting lipoprotein metabolism may lead to novel treatments for atherosclerosis. A comprehensive review of lipoprotein function and their role in atherosclerosis, along with the latest development of lipoprotein targeted treatment, is timely. This review focuses on the functions of different lipoproteins and their involvement in atherosclerosis. Further, diagnostic and therapeutic potential are highlighted giving insight into novel lipoprotein-targetted approaches to treat atherosclerosis.

Alzheimer Disease: Recent Updates on Apolipoprotein E and Gut Microbiome Mediation of Oxidative Stress, and Prospective Interventional Agents

Alzheimer's disease (AD) is a current public health challenge and will remain until the development of an effective intervention. However, developing an effective treatment for the disease requires a thorough understanding of its etiology, which is currently lacking. Although several studies have shown the association between oxidative damage and AD, only a few have clarified the specific mechanisms involved. Herein, we reviewed recent preclinical and clinical studies that indicated the significance of oxidative damage in AD, as well as potential antioxidants. Although several factors regulate oxidative stress in AD, we centered our investigation on apolipoprotein E and the gut microbiome. Apolipoprotein E, particularly apolipoprotein E-ε4, can impair the structural facets of the mitochondria. This, in turn, can minimize the mitochondrial functionality and result in the progressive build-up of free radicals, eventually leading to oxidative stress. Similarly, the gut microbiome can influence oxidative stress to a significant degree via its metabolite, trimethylamine N-oxide. Given the various roles of these two factors in modulating oxidative stress, we also discuss the possible relationship between them and provide future research directions.

Dietary fat and carbohydrate affect the metabolism of protein-based high-density lipoprotein subspecies

PURPOSE OF REVIEW

Dietary fat compared to carbohydrate increases the plasma concentration of high-density lipoprotein (HDL)-cholesterol. However, neither the mechanism nor its connection to cardiovascular disease is known.

RECENT FINDINGS

Protein-based subspecies of HDL, especially those containing apolipoprotein E (apoE) or apolipoprotein C3 (apoC3), offer a glimpse of a vast metabolic system related to atherogenicity, coronary heart disease (CHD) and other diseases. ApoE stimulates several processes that define reverse cholesterol transport through HDL, specifically secretion of active HDL subspecies, cholesterol efflux to HDL from macrophages involved in atherogenesis, size enlargement of HDL with cholesterol ester, and rapid clearance from the circulation. Dietary unsaturated fat stimulates the flux of HDL that contains apoE through these protective pathways. Effective reverse cholesterol transport may lessen atherogenesis and prevent disease. In contrast, apoC3 abrogates the benefit of apoE on reverse cholesterol transport, which may account for the association of HDL that contains apoC3 with dyslipidemia, obesity and CHD.

SUMMARY

Dietary unsaturated fat and carbohydrate affect the metabolism of protein-defined HDL subspecies containing apoE or apoC3 accelerating or retarding reverse cholesterol transport, thus demonstrating new mechanisms that may link diet to HDL and to CHD.

High levels of oxidized fatty acids in HDL impair the antioxidant function of HDL in patients with diabetes

AIMS

Previous studies demonstrate that the antioxidant functions of high-density lipoprotein (HDL) are impaired in diabetic patients. The composition of HDL plays an important role in maintaining the normal functionality of HDL. In this study, we compared the levels of oxidized fatty acids in HDL from diabetic subjects and non-diabetic healthy controls, aiming to investigate the role of oxidized fatty acids in the antioxidant property of HDL.

METHODS

HDL was isolated from healthy subjects (n=6) and patients with diabetes (n=6, hemoglobin A1c ≥ 9%, fasting glucose ≥ 7 mmol/L) using a dextran sulfate precipitation method. Cholesterol efflux capacity mediated by HDL was measured on THP-1 derived macrophages. The antioxidant capacity of HDL was evaluated with dichlorofluorescein-based cellular assay in human aortic endothelial cells. Oxidized fatty acids in HDL were determined by liquid chromatography-tandem mass spectrometry. The correlations between the levels of oxidized fatty acids in HDL and the endothelial oxidant index in cells treated with HDLs were analyzed through Pearson's correlation analyses, and the effects of oxidized fatty acids on the antioxidant function of HDL were verified in vitro.

RESULTS

The cholesterol efflux capacity of HDL and the circulating HDL-cholesterol were similar in diabetic patients and healthy controls, whereas the antioxidant capacity of HDL was significantly decreased in diabetic patients. There were higher levels of oxidized fatty acids in HDL isolated from diabetic patients, which were strongly positively correlated with the oxidant index of cells treated with HDLs. The addition of a mixture of oxidized fatty acids significantly disturbed the antioxidant activity of HDL from healthy controls, while the apolipoprotein A-I mimetic peptide D-4F could restore the antioxidant function of HDL from diabetic patients.

CONCLUSION

HDL from diabetic patients displayed substantially impaired antioxidant activity compared to HDL from healthy subjects, which is highly correlated with the increased oxidized fatty acids levels in HDL.

Pharmacological Inhibition of CETP (Cholesteryl Ester Transfer Protein) Increases HDL (High-Density Lipoprotein) That Contains ApoC3 and Other HDL Subspecies Associated With Higher Risk of Coronary Heart Disease

Supplemental Digital Content is available in the text.

Plasma total HDL (high-density lipoprotein) is a heterogeneous mix of many protein-based subspecies whose functions and associations with coronary heart disease vary. We hypothesize that increasing HDL by CETP (cholesteryl ester transfer protein) inhibition failed to reduce cardiovascular disease risk, in part, because it increased dysfunctional subspecies associated with higher risk such as HDL that contains apoC3.

Guanidinylated Apolipoprotein C3 (ApoC3) Associates with Kidney and Vascular Injury

BACKGROUND

Coexistent CKD and cardiovascular diseases are highly prevalent in Western populations and account for substantial mortality. We recently found that apolipoprotein C-3 (ApoC3), a major constituent of triglyceride-rich lipoproteins, induces sterile systemic inflammation by activating the NOD-like receptor protein-3 (NLRP3) inflammasome in human monocytes via an alternative pathway.

METHODS

To identify posttranslational modifications of ApoC3 in patients with CKD, we used mass spectrometry to analyze ApoC3 from such patients and from healthy individuals. We determined the effects of posttranslationally modified ApoC3 on monocyte inflammatory response in vitro, as well as in humanized mice subjected to unilateral ureter ligation (a kidney fibrosis model) and in a humanized mouse model for vascular injury and regeneration. Finally, we conducted a prospective observational trial of 543 patients with CKD to explore the association of posttranslationally modified ApoC3 with renal and cardiovascular events in such patients.

RESULTS

We identified significant posttranslational guanidinylation of ApoC3 (gApoC3) in patients with CKD. We also found that mechanistically, guanidine and urea induce guanidinylation of ApoC3. A 2D-proteomic analysis revealed that gApoC3 accumulated in kidneys and plasma in a CKD mouse model (mice fed an adenine-rich diet). In addition, gApoC3 augmented the proinflammatory effects of ApoC3 in monocytes in vitro . In humanized mice, gApoC3 promoted kidney tissue fibrosis and impeded vascular regeneration. In CKD patients, higher gApoC3 plasma levels (as determined by mass spectrometry) were associated with increased mortality as well as with renal and cardiovascular events.

CONCLUSIONS

Guanidinylation of ApoC3 represents a novel pathogenic mechanism in CKD and CKD-associated vascular injury, pointing to gApoC3 as a potential therapeutic target.

Assessing HDL Metabolism in Subjects with Elevated Levels of HDL Cholesterol and Coronary Artery Disease

High-density lipoprotein cholesterol (HDL-C) is thought to be atheroprotective yet some patients with elevated HDL-C levels develop cardiovascular disease, possibly due to the presence of dysfunctional HDL. We aimed to assess the metabolic fate of circulating HDL particles in patients with high HDL-C with and without coronary artery disease (CAD) using in vivo dual labeling of its cholesterol and protein moieties. We measured HDL apolipoprotein (apo) A-I, apoA-II, free cholesterol (FC), and cholesteryl ester (CE) kinetics using stable isotope-labeled tracers (D3-leucine and 13C2-acetate) as well as ex vivo cholesterol efflux to HDL in subjects with (n = 6) and without (n = 6) CAD that had HDL-C levels >90th percentile. Healthy controls with HDL-C within the normal range (n = 6) who underwent the same procedures were used as the reference. Subjects with high HDL-C with and without CAD had similar plasma lipid levels and similar apoA-I, apoA-II, HDL FC, and CE pool sizes with no significant differences in fractional clearance rates (FCRs) or production rates (PRs) of these components between groups. Subjects with high HDL-C with and without CAD also had similar basal and cAMP-stimulated ex vivo cholesterol efflux to HDL. When all subjects were considered (n = 18), unstimulated non-ABCA1-mediated efflux (but not ABCA1-specific efflux) was correlated positively with apoA-I production (r = 0.552, p = 0.017) and HDL FC and CE pool sizes, and negatively with the fractional clearance rate of FC (r = -0.759, p = 4.1 × 10-4) and CE (r = -0.652, p = 4.57 × 10-3). Our data are consistent with the concept that ex vivo non-ABCA1 efflux capacity may correlate with slower in vivo turnover of HDL cholesterol moieties. The use of a dual labeling protocol provided for the first time the opportunity to assess the association of ex vivo cholesterol efflux capacity with in vivo HDL cholesterol metabolic parameters.

HDL (High-Density Lipoprotein) Subspecies, Prevalent Covert Brain Infarcts, and Incident Overt Ischemic Stroke: Cardiovascular Health Study

BACKGROUND AND PURPOSE

Whether HDL (high-density lipoprotein) is associated with risk of vascular brain injury is unclear. HDL is comprised of many apo (apolipoprotein) species, creating distinct subtypes of HDL.

METHODS

We utilized sandwich ELISA to determine HDL subspecies from plasma collected in 1998/1999 from 2001 CHS (Cardiovascular Health Study) participants (mean age, 80 years).

RESULTS

In cross-sectional analyses, participants with higher apoA1 in plasma and lower apoE in HDL were less likely to have prevalent covert magnetic resonance imaging-defined infarcts: odds ratio for apoA1 Q4 versus Q1, 0.68 (95% CI, 0.50-0.93), and odds ratio for apoE Q4 versus Q1, 1.36 (95% CI, 1.01-1.84). Similarly, apoA1 in the subspecies of HDL that lacked apoC3, apoJ, or apoE was inversely related to covert infarcts, and apoE in the subspecies of HDL that lacked apoC3 or apoJ was directly related to covert infarcts in prospective analyses. In contrast, the concentrations of apoA1 and apoE in the complementary subspecies of HDL that contained these apos were unrelated to covert infarcts. Patterns of associations between incident overt ischemic stroke and apoA1, apoE, and apoA1 and apoE in subspecies of HDL were similar to those observed for covert infarcts but less pronounced.

CONCLUSIONS

This study highlights HDL subspecies defined by apo content as relevant biomarkers of covert and overt vascular brain injury.

HDL and reverse cholesterol transport in humans and animals: Lessons from pre-clinical models and clinical studies

The ability to accept cholesterol from cells and to promote reverse cholesterol transport (RCT) represents the best characterized antiatherogenic function of HDL. Studies carried out in animal models have unraveled the multiple mechanisms by which these lipoproteins drive cholesterol efflux from macrophages and cholesterol uptake to the liver. Moreover, the influence of HDL composition and the role of lipid transporters have been clarified by using suitable transgenic models or through experimental design employing pharmacological or nutritional interventions. Cholesterol efflux capacity (CEC), an in vitro assay developed to offer a measure of the first step of RCT, has been shown to associate with cardiovascular risk in several human cohorts, supporting the atheroprotective role of RCT in humans as well. However, negative data in other cohorts have raised concerns on the validity of this biomarker. In this review we will present the most relevant data documenting the role of HDL in RCT, as assessed in classical or innovative methodological approaches.

HDL cholesterol concentrations and risk of atherosclerotic cardiovascular disease - Insights from randomized clinical trials and human genetics

Through seven decades the inverse association between HDL cholesterol concentrations and risk of atherosclerotic cardiovascular disease (ASCVD) has been observed in case-control and prospective cohort studies. This robust inverse association fuelled the enthusiasm towards development of HDL cholesterol increasing drugs, exemplified by the cholesteryl ester transfer protein (CETP) inhibitor trials and the extended-release niacin HPS2-THRIVE trial. These HDL cholesterol increasing trials were launched without conclusive evidence from human genetics, and despite discrepant species dependent evidence from animal studies. Evidence from human genetics and from randomized clinical trials over the last 13 years now point in the direction that concentrations of HDL cholesterol, do not appear to be a viable future path to target therapeutically for prevention of ASCVD. A likely explanation for the strong observational association between low HDL cholesterol and high ASCVD risk is the concomitant inverse association between HDL cholesterol and atherogenic triglyceride-rich lipoproteins. The purpose of the present review is to bring HDL cholesterol increasing trials into a human genetics context exemplified by candidate gene studies of key players in HDL biogenesis as well as by HDL cholesterol related genome-wide association studies.

HDL Containing Apolipoprotein C-III is Associated with Insulin Sensitivity: A Multicenter Cohort Study

CONTEXT

High density lipoprotein (HDL) in humans is composed of a heterogeneous group of particles varying in protein composition as well as biological effects.

OBJECTIVE

We investigated the prospective associations between HDL subspecies containing and lacking apolipoprotein (apo) C-III at baseline and insulin sensitivity at year 3.

DESIGN, SETTING, AND PARTICIPANTS

A prospective cohort study of 864 healthy volunteers drawn from the relationship between insulin sensitivity and cardiovascular disease (RISC) study, a multicenter European clinical investigation, whose recruitment initiated in 2002, with a follow-up of 3 years.

MAIN MEASURES

Insulin sensitivity was estimated from an oral glucose tolerance test at baseline and year 3, and by euglycemic-hyperinsulinemic clamp at baseline only. The apolipoprotein concentrations were measured at baseline by a sandwich enzyme-linked immunosorbent assay (ELISA)-based method.

RESULTS

The 2 HDL subspecies demonstrated significantly opposite associations with insulin sensitivity at year 3 (P-heterogeneity = 0.004). The highest quintile of HDL containing apoC-III was associated with a 1.2% reduction in insulin sensitivity (P-trend = 0.02), while the highest quintile of HDL lacking apoC-III was associated with a 1.3% increase (P-trend = 0.01), compared to the lowest quintile. No significant association was observed for total HDL, and very low density lipoprotein (VLDL) and low density lipoprotein (LDL) containing apoC-III. ApoC-III contained in HDL was associated with a decrease in insulin sensitivity even more strongly than plasma total apoC-III.

CONCLUSION

Both HDL containing apoC-III and apoC-III in HDL adversely affect the beneficial properties of HDL on insulin response to glucose. Our results support the potential of HDL-associated apoC-III as a promising target for diabetes prevention and treatment.

Apolipoprotein C-II and C-III preferably transfer to both high-density lipoprotein (HDL)2 and the larger HDL3 from very low-density lipoprotein (VLDL)

Triglyceride hydrolysis by lipoprotein lipase (LPL), regulated by apolipoproteins C-II (apoC-II) and C-III (apoC-III), is essential for maintaining normal lipid homeostasis. During triglyceride lipolysis, the apoCs are known to be transferred from very low-density lipoprotein (VLDL) to high-density lipoprotein (HDL), but the detailed mechanisms of this transfer remain unclear. In this study, we investigated the extent of the apoC transfers and their distribution in HDL subfractions, HDL2 and HDL3. Each HDL subfraction was incubated with VLDL or biotin-labeled VLDL, and apolipoproteins and lipids in the re-isolated HDL were quantified using western blotting and high-performance liquid chromatography (HPLC). In consequence, incubation with VLDL showed the increase of net amount of apoC-II and apoC-III in the HDL. HPLC analysis revealed that the biotin-labeled apolipoproteins, including apoCs and apolipoprotein E, were preferably transferred to the larger HDL3. No effect of cholesteryl ester transfer protein inhibitor on the apoC transfers was observed. Quantification of apoCs levels in HDL2 and HDL3 from healthy subjects (n = 8) showed large individual differences between apoC-II and apoC-III levels. These results suggest that both apoC-II and apoC-III transfer disproportionately from VLDL to HDL2 and the larger HDL3, and these transfers might be involved in individual triglyceride metabolism.

High Density Lipoproteins and Diabetes

Epidemiological studies have established that a high plasma high density lipoprotein cholesterol (HDL-C) level is associated with reduced cardiovascular risk. However, recent randomised clinical trials of interventions that increase HDL-C levels have failed to establish a causal basis for this relationship. This has led to a shift in HDL research efforts towards developing strategies that improve the cardioprotective functions of HDLs, rather than simply increasing HDL-C levels. These efforts are also leading to the discovery of novel HDL functions that are unrelated to cardiovascular disease. One of the most recently identified functions of HDLs is their potent antidiabetic properties. The antidiabetic functions of HDLs, and recent key advances in this area are the subject of this review. Given that all forms of diabetes are increasing at an alarming rate globally, there is a clear unmet need to identify and develop new approaches that will complement existing therapies and reduce disease progression as well as reverse established disease. Exploration of a potential role for HDLs and their constituent lipids and apolipoproteins in this area is clearly warranted. This review highlights focus areas that have yet to be investigated and potential strategies for exploiting the antidiabetic functions of HDLs.

Comparison of Plasma Lipoprotein Composition and Function in Cerebral Amyloid Angiopathy and Alzheimer's Disease

Cerebral amyloid angiopathy (CAA) refers to beta-amyloid (Aβ) deposition in brain vessels and is clinically the main cause of lobar intracerebral hemorrhage (ICH). Aβ can also accumulate in brain parenchyma forming neuritic plaques in Alzheimer’s disease (AD). Our study aimed to determine whether the peripheral lipid profile and lipoprotein composition are associated with cerebral beta-amyloidosis pathology and may reflect biological differences in AD and CAA. For this purpose, lipid and apolipoproteins levels were analyzed in plasma from 51 ICH-CAA patients (collected during the chronic phase of the disease), 60 AD patients, and 60 control subjects. Lipoproteins (VLDL, LDL, and HDL) were isolated and their composition and pro/antioxidant ability were determined. We observed that alterations in the lipid profile and lipoprotein composition were remarkable in the ICH-CAA group compared to control subjects, whereas the AD group presented no specific alterations compared with controls. ICH-CAA patients presented an atheroprotective profile, which consisted of lower total and LDL cholesterol levels. Plasma from chronic ICH-CAA patients also showed a redistribution of ApoC-III from HDL to VLDL and a higher ApoE/ApoC-III ratio in HDL. Whether these alterations reflect a protective response or have a causative effect on the pathology requires further investigation.

Atherosclerotic cardiovascular disease in hyperalphalipoproteinemia due to LIPG variants

BACKGROUND

High density lipoprotein cholesterol (HDL-C) concentration correlates inversely with atherosclerotic cardiovascular disease (ASCVD) risk and is included in risk calculations. Endothelial lipase (EL) is a phospholipase that remodels HDL. Deficiency of EL due to mutations in its gene, LIPG, is associated with hyperalphalipoproteinemia. The effects of EL on HDL function and ASCVD risk remain poorly understood.

OBJECTIVES

To determine whether hyperalphalipoproteinemia due to EL deficiency is protective against ASCVD.

METHODS

We identified LIPG variants amongst patients with severe hyperalphalipoproteinemia (HDL-C >2.5 mmol/L) attending a referral lipid clinic in the Western Cape Province of South Africa. We analysed the clinical and biochemical phenotypes amongst primary hyperalphalipoproteinemia cases (males HDL-C >1.6 mmol/L; females HDL-C >1.8 mmol/L) due to LIPG variants, and the distribution of variants in normal and hyperalphalipoproteinemia ranges of HDL-C.

RESULTS

1007 patients with HDL-C concentration ranging from 1.2 to 4.5 mmol/L were included. Seventeen females had primary hyperalphalipoproteinemia. Vascular disease was prominent, but not associated with HDL-C concentration, LDL-C concentration or carotid artery intima media thickness. Two novel and three known LIPG variants were identified in severe hyperalphalipoproteinemia. Four additional variants were identified in the extended cohort. Two common variants appeared normally distributed across the HDL-C concentration range, while six less-common variants were found only at higher HDL-C concentrations. One rare variant had a moderate effect.

CONCLUSION

Hyperalphalipoproteinemia due to LIPG variants is commoner in females and may not protect against ASCVD. Use of current risk calculations may be inappropriate in patients with hyperalphalipoproteinemia due to EL deficiency. Our study cautions targeting EL to reduce risk.

An Increased Plasma Level of ApoCIII-Rich Electronegative High-Density Lipoprotein May Contribute to Cognitive Impairment in Alzheimer's Disease

High-density lipoprotein (HDL) plays a vital role in lipid metabolism and anti-inflammatory activities; a dysfunctional HDL impairs cholesterol efflux pathways. To understand HDL's role in patients with Alzheimer's disease (AD), we analyzed the chemical properties and function. HDL from AD patients (AD-HDL) was separated into five subfractions, H1-H5, using fast-protein liquid chromatography equipped with an anion-exchange column. Subfraction H5, defined as the most electronegative HDL, was increased 5.5-fold in AD-HDL (23.48 ± 17.83%) in comparison with the control HDL (4.24 ± 3.22%). By liquid chromatography mass spectrometry (LC/MS^E), AD-HDL showed that the level of apolipoprotein (apo)CIII was elevated but sphingosine-1-phosphate (S1P)-associated apoM and anti-oxidative paraoxonase 1 (PON1) were reduced. AD-HDL showed a lower cholesterol efflux capacity that was associated with the post-translational oxidation of apoAI. Exposure of murine macrophage cell line, RAW 264.7, to AD-HDL induced a vibrant expression of ganglioside GM1 in colocalization with apoCIII on lipid rafts alongside a concomitant increase of tumor necrosis factor-α (TNF-α) detectable in the cultured medium. In conclusion, AD-HDL had a higher proportion of H5, an apoCIII-rich electronegative HDL subfraction. The associated increase in pro-inflammatory (apoCIII, TNF-α) components might favor Amyloid β assembly and neural inflammation. A compromised cholesterol efflux capacity of AD-HDL may also contribute to cognitive impairment.

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

OBJECTIVE

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

CONCLUSIONS

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

Association of Apolipoprotein E in Lipoprotein Subspecies With Risk of Dementia

Importance

The ε4 allele of the apolipoprotein E (APOE) gene and lower apolipoprotein E (apoE) protein levels in plasma are risk factors for Alzheimer disease, but the underlying biological mechanisms are not fully understood. Half of plasma apoE circulates on high-density lipoproteins (HDLs). Higher apoE levels in plasma HDL were previously found to be associated with lower coronary heart disease risk, but the coexistence of another apolipoprotein, apoC3, modified this lower risk.

Objective

To investigate associations between the presence of apoE in different lipoproteins with cognitive function, particularly the risk of dementia.

Design, Setting, and Participants

This prospective case-cohort study embedded in the Ginkgo Evaluation of Memory Study (2000-2008) analyzed data from 1351 community-dwelling participants 74 years and older. Of this group, 995 participants were free of dementia at baseline (recruited from September 2000 to June 2002) and 521 participants were diagnosed with incident dementia during follow-up until 2008. Data analysis was performed from January 2018 to December 2019.

Exposures

Enzyme-linked immunosorbent assay-measured concentration of apoE in whole plasma, HDL-depleted plasma (non-HDL), HDL, and HDL subspecies that contain or lack apoC3 or apoJ.

Main Outcomes and Measures

Adjusted hazard ratios for risk of dementia and Alzheimer disease during follow-up and adjusted differences (β coefficients) in Alzheimer Disease Assessment-Cognitive Subscale (ADAS-cog) and Modified Mini-Mental State Examination scores at baseline.

Results

Among 1351 participants, the median (interquartile range) age was 78 (76-81) years; 639 (47.3%) were women. The median (interquartile range) follow-up time was 5.9 (3.7-6.5) years. Higher whole plasma apoE levels and higher apoE levels in HDL were associated with better cognitive function assessed by ADAS-cog (whole plasma, β coefficient, -0.15; 95% CI, -0.24 to -0.06; HDL, β coefficient, -0.20; 95% CI, -0.30 to -0.10) but were unassociated with dementia or Alzheimer disease risk. When separated by apoC3, a higher apoE level in HDL that lacks apoC3 was associated with better cognitive function (ADAS-cog per SD: β coefficient, 0.17; 95% CI, -0.27 to -0.07; Modified Mini-Mental State Examination score per SD: β coefficient, 0.25; 95% CI, 0.07 to 0.42) and lower risk of dementia (hazard ratio per SD, 0.86; 95% CI, 0.76 to 0.99). In contrast, apoE levels in HDL that contains apoC3 were unassociated with any of these outcomes.

Conclusions and Relevance

In a prospective cohort of older adults with rigorous follow-up of dementia, the apoE level in HDL that lacked apoC3 was associated with better cognitive function and lower dementia risk. This finding suggests that the cardioprotective associations of this novel lipoprotein extend to dementia.

COVID-19-Associated dyslipidemia: Implications for mechanism of impaired resolution and novel therapeutic approaches

The current coronavirus disease 2019 (COVID‐19) pandemic presents a global challenge for managing acutely ill patients and complications from viral infection. Systemic inflammation accompanied by a “cytokine storm,” hemostasis alterations and severe vasculitis have all been reported to occur with COVID‐19, and emerging evidence suggests that dysregulation of lipid transport may contribute to some of these complications. Here, we aim to summarize the current understanding of the potential mechanisms related to COVID‐19 dyslipidemia and propose possible adjunctive type therapeutic approaches that modulate lipids and lipoproteins. Specifically, we hypothesize that changes in the quantity and composition of high‐density lipoprotein (HDL) that occurs with COVID‐19 can significantly decrease the anti‐inflammatory and anti‐oxidative functions of HDL and could contribute to pulmonary inflammation. Furthermore, we propose that lipoproteins with oxidized phospholipids and fatty acids could lead to virus‐associated organ damage via overactivation of innate immune scavenger receptors. Restoring lipoprotein function with ApoA‐I raising agents or blocking relevant scavenger receptors with neutralizing antibodies could, therefore, be of value in the treatment of COVID‐19. Finally, we discuss the role of omega‐3 fatty acids transported by lipoproteins in generating specialized proresolving mediators and how together with anti‐inflammatory drugs, they could decrease inflammation and thrombotic complications associated with COVID‐19.

Targeting apoC-III and ANGPTL3 in the treatment of hypertriglyceridemia

INTRODUCTION

The prevalence of hypertriglyceridemia (HTG) is increasing. Elevated triglyceride (TG) levels are associated with an increased cardiovascular disease (CVD) risk. Moreover, severe HTG results in an elevated risk of pancreatitis, especially in severe HTG with an up to 350-fold increased risk. Both problems emphasize the clinical need for effective TG lowering.

AREAS COVERED

The purpose of this review is to discuss the currently available therapies and to elaborate the most promising novel therapeutics for TG lowering.

EXPERT OPINION

Conventional lipid lowering strategies do not efficiently lower plasma TG levels, leaving a residual CVD and pancreatitis risk. Both apolipoprotein C-III (apoC-III) and angiopoietin-like 3 (ANGPTL3) are important regulators in TG-rich lipoprotein (TRL) metabolism. Several novel agents targeting these linchpins have ended phase II/III trials. Volanesorsen targeting apoC-III has shown reductions in plasma TG levels up to 90%. Multiple ANGPLT3 inhibitors (evinacumab, IONIS-ANGPTL3-L_Rx, ARO-ANG3) effectuate TG reductions up to 70% with concomitant potent reduction in all other apoB containing lipoprotein fractions. We expect these therapeutics to become players in the treatment for (especially) severe HTG in the near future.