APOC3 Loss-of-Function Mutations, Remnant Cholesterol, Low-Density Lipoprotein Cholesterol, and Cardiovascular Risk

Emerging therapies for refractory hypercholesterolemia: a narrative review

Refractory hypercholesterolemia (RH) is characterized by the failure of patients to achieve therapeutic targets for low-density lipoprotein-cholesterol (LDL-C) despite receiving maximal tolerable doses of standard lipid-lowering treatments. It predominantly impacts individuals with familial hypercholesterolemia (FH), thereby elevating the risk of cardiovascular complications. The prevalence of RH is now recognized to be substantially greater than previously thought. This review provides a comprehensive insight into current and emerging therapies for RH patients, including groundbreaking genetic-based therapeutic approaches. The review places emphasis on the dependency of therapies on low-density lipoprotein receptors (LDLRs) and highlights the critical role of considering LDLR activity in RH patients for individualization of the treatment.

Triglyceride-rich lipoprotein, remnant cholesterol, and apolipoproteins CII, CIII, and E in patients with schizophrenia

Patients with schizophrenia show a disproportionally increased risk of cardiovascular disease. Hypertriglyceridemia is prevalent in this population; however, how this relates to levels of remnant cholesterol, triglyceride (TG)-rich lipoprotein (TRL) particle size and composition, TG turnover, and apolipoprotein (apo) and angiopoietin-like protein (ANGPTL) concentrations is unknown. Fasting levels of cholesterol (total [TC], LDL-C, HDL-C, non-HDL-C and remnant cholesterol) and TG were determined in 110 patients diagnosed with schizophrenia, and 46 healthy controls. TRL particle size, concentration and composition, and β-hydroxybutyrate (TG turnover marker) were assessed by NMR. Levels of apoCII, apoCIII, apoE, ANGPTL3, ANGPTL4, and ANGPTL8 were measured by ELISA, and apoCII, apoCIII and apoE were further evaluated in HDL and non-HDL fractions. Patients with schizophrenia had significantly elevated TG, TG:apoB ratio, non-HDL-C, remnant cholesterol, non-HDL-apoCII and non-HDL-apoCIII, and HDL-apoE (all P < 0.05), lower HDL-C and apoA-I (all P < 0.001), and comparable apoB, TC, TC:apoB ratio, LDL-C, β-hydroxybutyrate, ANGPTL3, ANGPTL4 and ANGPTL8 to healthy controls. Patients had a 12.0- and 2.5-fold increase in the concentration of large and medium TRL particles respectively, but similar cholesterol:TG ratio within each particle. Plasma TG, remnant cholesterol, and large and medium TRL particle concentrations correlated strongly with apoCII, apoCIII, and apoE in the non-HDL fraction, and with apoCIII and apoE in the HDL fraction in patients with schizophrenia. Differences in TG, HDL-C, TRL particle concentrations, apoCIII, and apoE persisted after adjustment for conventional risk factors. These results are consistent with impaired TRL lipolysis and clearance in patients with schizophrenia which may be responsive to targeting apoCIII.

Plozasiran, an RNA Interference Agent Targeting APOC3, for Mixed Hyperlipidemia

BACKGROUND

Persons with mixed hyperlipidemia are at risk for atherosclerotic cardiovascular disease due to an elevated non-high-density lipoprotein (HDL) cholesterol level, which is driven by remnant cholesterol in triglyceride-rich lipoproteins. The metabolism and clearance of triglyceride-rich lipoproteins are down-regulated through apolipoprotein C3 (APOC3)-mediated inhibition of lipoprotein lipase.

METHODS

We carried out a 48-week, phase 2b, double-blind, randomized, placebo-controlled trial evaluating the safety and efficacy of plozasiran, a hepatocyte-targeted APOC3 small interfering RNA, in patients with mixed hyperlipidemia (i.e., a triglyceride level of 150 to 499 mg per deciliter and either a low-density lipoprotein [LDL] cholesterol level of ≥70 mg per deciliter or a non-HDL cholesterol level of ≥100 mg per deciliter). The participants were assigned in a 3:1 ratio to receive plozasiran or placebo within each of four cohorts. In the first three cohorts, the participants received a subcutaneous injection of plozasiran (10 mg, 25 mg, or 50 mg) or placebo on day 1 and at week 12 (quarterly doses). In the fourth cohort, participants received 50 mg of plozasiran or placebo on day 1 and at week 24 (half-yearly dose). The data from the participants who received placebo were pooled. The primary end point was the percent change in fasting triglyceride level at week 24.

RESULTS

A total of 353 participants underwent randomization. At week 24, significant reductions in the fasting triglyceride level were observed with plozasiran, with differences, as compared with placebo, in the least-squares mean percent change from baseline of -49.8 percentage points (95% confidence interval [CI], -59.0 to -40.6) with the 10-mg-quarterly dose, -56.0 percentage points (95% CI, -65.1 to -46.8) with the 25-mg-quarterly dose, -62.4 percentage points (95% CI, -71.5 to -53.2) with the 50-mg-quarterly dose, and -44.2 percentage points (95% CI, -53.4 to -35.0) with the 50-mg-half-yearly dose (P<0.001 for all comparisons). Worsening glycemic control was observed in 10% of the participants receiving placebo, 12% of those receiving the 10-mg-quarterly dose, 7% of those receiving the 25-mg-quarterly dose, 20% of those receiving the 50-mg-quarterly dose, and 21% of those receiving the 50-mg-half-yearly dose.

CONCLUSIONS

In this randomized, controlled trial involving participants with mixed hyperlipidemia, plozasiran, as compared with placebo, significantly reduced triglyceride levels at 24 weeks. A clinical outcomes trial is warranted. (Funded by Arrowhead Pharmaceuticals; MUIR ClinicalTrials.gov number NCT04998201.).

Apolipoprotein B - An ideal biomarker for atherosclerosis?

This review article describes the pathophysiological mechanisms linking Apolipoprotein B (Apo-B) and atherosclerosis, summarizes the existing evidence on Apo B as a predictor of atherosclerotic cardiovascular disease and recommendations of (inter)national treatment guidelines regarding Apo B in dyslipidemia management. A single Apo B molecule is present in every particle of very low-density lipoprotein, intermediate density lipoprotein, low density lipoprotein, and lipoprotein(a). This unique single Apo B per particle ratio makes plasma Apo B concentration a direct measure of the number of circulating atherogenic lipoproteins. This review of global evidence on Apo B as a biomarker for atherosclerosis confirms that Apo B is a single atherogenic lipid marker present in all lipids sub-fractions except HDL-C, and thus, Apo B integrates and extends the information from triglycerides and cholesterol, which could simplify and improve care for atherosclerotic cardiovascular disease.

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.

Apolipoprotein C3: form begets function

Increased circulating levels of apolipoprotein C3 (APOC3) predict cardiovascular disease (CVD) risk in humans, and APOC3 promotes atherosclerosis in mouse models. APOC3's mechanism of action is due in large part to its ability to slow the clearance of triglyceride-rich lipoproteins (TRLs) and their remnants when APOC3 is carried by these lipoproteins. However, different pools and forms of APOC3 exert distinct biological effects or associations with atherogenic processes. Thus, lipid-free APOC3 induces inflammasome activation in monocytes whereas lipid particle-bound APOC3 does not. APOC3-enriched LDL binds better to the vascular glycosaminoglycan biglycan than does LDL depleted of APOC3. Patterns of APOC3 glycoforms predict CVD risk differently. The function of APOC3 bound to HDL is largely unknown. There is still much to learn about the mechanisms of action of different forms and pools of APOC3 in atherosclerosis and CVD, and whether APOC3 inhibition would prevent CVD risk in patients on LDL-cholesterol lowering medications.

Advances in Dyslipidaemia Treatments: Focusing on ApoC3 and ANGPTL3 Inhibitors

Apolipoprotein C3 (apoC3) and angiopoietin-like protein 3 (ANGPTL3) inhibit lipolysis by lipoprotein lipase and may influence the secretion and uptake of various lipoproteins. Genetic studies show that depletion of these proteins is associated with improved lipid profiles and reduced cardiovascular events so it was anticipated that drugs which mimic the effects of loss-of-function mutations would be useful lipid treatments. ANGPTL3 inhibitors were initially developed as a treatment for severe hypertriglyceridaemia including familial chylomicronaemia syndrome (FCS), which is usually not adequately controlled with currently available drugs. However, it was found ANGPTL3 inhibitors were also effective in reducing low-density lipoprotein cholesterol (LDL-C) and they were studied in patients with homozygous familial hypercholesterolaemia (FH). Evinacumab targets ANGPTL3 and reduced LDL-C by about 50% in patients with homozygous FH and it has been approved for that indication. The antisense oligonucleotide (ASO) vupanorsen targeting ANGPTL3 was less effective in reducing LDL-C in patients with moderate hypertriglyceridaemia and its development has been discontinued but the small interfering RNA (siRNA) ARO-ANG3 is being investigated in Phase 2 studies. ApoC3 can be inhibited by the ASO volanesorsen, which reduced triglycerides by >70% in patients with FCS and it was approved for FCS in Europe but not in the United States because of concerns about thrombocytopaenia. Olezarsen is an N-acetylgalactosamine-conjugated ASO targeting apoC3 which appears as effective as volanesorsen without the risk of thrombocytopaenia and is undergoing Phase 3 trials. ARO-APOC3 is an siRNA targeting apoC3 that is currently being investigated in Phase 3 studies.

Association between remnant cholesterol and progression of bioprosthetic valve degeneration

AIMS

Remnant cholesterol (RC) seems associated with native aortic stenosis. Bioprosthetic valve degeneration may share similar lipid-mediated pathways with aortic stenosis. We aimed to investigate the association of RC with the progression of bioprosthetic aortic valve degeneration and ensuing clinical outcomes.

METHODS AND RESULTS

We enrolled 203 patients with a median of 7.0 years (interquartile range: 5.1-9.2) after surgical aortic valve replacement. RC concentration was dichotomized by the top RC tertile (23.7 mg/dL). At 3-year follow-up, 121 patients underwent follow-up visit for the assessment of annualized change in aortic valve calcium density (AVCd). RC levels showed a curvilinear relationship with an annualized progression rate of AVCd, with increased progression rates when RC >23.7 mg/dL (P = 0.008). There were 99 deaths and 46 aortic valve re-interventions in 133 patients during a median clinical follow-up of 8.8 (8.7-9.6) years. RC >23.7 mg/dL was independently associated with mortality or re-intervention (hazard ratio: 1.98; 95% confidence interval: 1.31-2.99; P = 0.001).

CONCLUSION

Elevated RC is independently associated with faster progression of bioprosthetic valve degeneration and increased risk of all-cause mortality or aortic valve re-intervention.

Severe hypertriglyceridemia: Existing and emerging therapies

Severe hypertriglyceridemia (sHTG), defined as a triglyceride (TG) concentration ≥ 500 mg/dL (≥ 5.7 mmol/L) is an important risk factor for acute pancreatitis. Although lifestyle, some medications, and certain conditions such as diabetes may lead to HTG, sHTG results from a combination of major and minor genetic defects in proteins that regulate TG lipolysis. Familial chylomicronemia syndrome (FCS) is a rare disorder caused by complete loss of function in lipoprotein lipase (LPL) or LPL activating proteins due to two homozygous recessive traits or compound heterozygous traits. Multifactorial chylomicronemia syndrome (MCS) and sHTG are due to the accumulation of rare heterozygous variants and polygenic defects that predispose individuals to sHTG phenotypes. Until recently, treatment of sHTG focused on lifestyle interventions, control of secondary factors, and nonselective pharmacotherapies that had modest TG-lowering efficacy and no corresponding reductions in atherosclerotic cardiovascular disease events. Genetic discoveries have allowed for the development of novel pathway-specific therapeutics targeting LPL modulating proteins. New targets directed towards inhibition of apolipoprotein C-III (apoC-III), angiopoietin-like protein 3 (ANGPTL3), angiopoietin-like protein 4 (ANGPTL4), and fibroblast growth factor-21 (FGF21) offer far more efficacy in treating the various phenotypes of sHTG and opportunities to reduce the risk of acute pancreatitis and atherosclerotic cardiovascular disease events.

The Role of Triglyceride-rich Lipoproteins and Their Remnants in Atherosclerotic Cardiovascular Disease

Atherosclerotic cardiovascular disease (ASCVD) is the world's leading cause of death. ASCVD has multiple mediators that therapeutic interventions target, such as dyslipidaemia, hypertension, diabetes and heightened systemic inflammatory tone, among others. LDL cholesterol is one of the most well-studied and established mediators targeted for primary and secondary prevention of ASCVD. However, despite the strength of evidence supporting LDL cholesterol reduction by multiple management strategies, ASCVD events can still recur, even in patients whose LDL cholesterol has been very aggressively reduced. Hypertriglyceridaemia and elevated levels of triglyceride-rich lipoproteins (TRLs) may be key contributors to ASCVD residual risk. Several observational and genetic epidemiological studies have highlighted the causal role of triglycerides within the TRLs and/or their remnant cholesterol in the development and progression of ASCVD. TRLs consist of intestinally derived chylomicrons and hepatically synthesised very LDL. Lifestyle modification has been considered the first line intervention for managing hypertriglyceridaemia. Multiple novel targeted therapies are in development, and have shown efficacy in the preclinical and clinical phases of study in managing hypertriglyceridaemia and elevated TRLs. This comprehensive review provides an overview of the biology, pathogenicity, epidemiology, and genetics of triglycerides and TRLs, and how they impact the risk for ASCVD. In addition, we provide a summary of currently available and novel emerging triglyceride-lowering therapies in development.

Novel and future lipid-modulating therapies for the prevention of cardiovascular disease

Lowering the levels of LDL cholesterol in the plasma has been shown to reduce the risk of atherosclerotic cardiovascular disease (ASCVD). Several other lipoproteins, such as triglyceride-rich lipoproteins, HDL and lipoprotein(a) are associated with atherosclerosis and ASCVD, with strong evidence supporting causality for some. In this Review, we discuss novel and upcoming therapeutic strategies targeting different pathways in lipid metabolism to potentially attenuate the risk of cardiovascular events. Key proteins involved in lipoprotein metabolism, such as PCSK9, angiopoietin-related protein 3, cholesteryl ester transfer protein and apolipoprotein(a), have been identified as viable targets for therapeutic intervention through observational and genetic studies. These proteins can be targeted using a variety of approaches, such as protein inhibition or interference, inhibition of translation at the mRNA level (with the use of antisense oligonucleotides or small interfering RNA), and the introduction of loss-of-function mutations through base editing. These novel and upcoming strategies are complementary to and could work synergistically with existing therapies, or in some cases could potentially replace therapies, offering unprecedented opportunities to prevent ASCVD. Moreover, a major challenge in the prevention and treatment of non-communicable diseases is how to achieve safe, long-lasting reductions in causal exposures. This challenge might be overcome with approaches such as small interfering RNAs or genome editing, which shows how far the field has advanced from when the burden of achieving this goal was placed upon patients through rigorous adherence to daily small-molecule drug regimens.

Causal associations of remnant cholesterol with cardiometabolic diseases and risk factors: a mendelian randomization analysis

BACKGROUND

Emerging evidence suggests that remnant cholesterol (RC) is strongly associated with an increased incidence of cardiometabolic diseases (CMD). However, the causality have not been confirmed. We aimed to evaluate the causal associations of RC with CMD and the relative risk factors using two-sample Mendelian randomization (MR) methods.

METHODS

Summary-level statistics of RC, CMD, and cardiometabolic risk factors were obtained from the published data from individuals with a predominantly European ancestry mainly from the UK Biobank and the FinnGen biobank. Univariable and multivariable MR analyses were used to evaluate the causal relationships between RC and CMD. A bidirectional MR analysis was performed to estimate the causality between RC and cardiometabolic risk factors. The main MR method was conducted using the inverse-variance weighted method.

RESULTS

Univariable MR analyses showed that genetically predicted RC was causally associated with higher risk of ischemic heart disease, myocardial infarction, atrial fibrillation and flutter, peripheral artery disease, and non-rheumatic valve diseases (all P < 0.05). Multivariable MR analyses provided compelling evidence of the harmful effects of RC on the risk of ischemic heart disease (P < 0.05). Bidirectional MR analysis demonstrated that RC was bidirectionally causally linked to total cholesterol, triglycerides, low-density lipoprotein cholesterol, hypercholesterolemia (all P < 0.05). However, no genetic association was found between RC and metabolic disorders or the other cardiometabolic risk factors.

CONCLUSIONS

This MR study demonstrates that genetically driven RC increases the risk of several CMD and cardiometabolic risk factors, suggesting that targeted RC-lowering therapies may be effective for the primary prevention of CMD.

A Review of Progress on Targeting LDL Receptor-Dependent and -Independent Pathways for the Treatment of Hypercholesterolemia, a Major Risk Factor of ASCVD

Since the discovery of the LDL receptor in 1973 by Brown and Goldstein as a causative protein in hypercholesterolemia, tremendous amounts of effort have gone into finding ways to manage high LDL cholesterol in familial hypercholesterolemic (HoFH and HeFH) individuals with loss-of-function mutations in the LDL receptor (LDLR) gene. Statins proved to be the first blockbuster drug, helping both HoFH and HeFH individuals by inhibiting the cholesterol synthesis pathway rate-limiting enzyme HMG-CoA reductase and inducing the LDL receptor. However, statins could not achieve the therapeutic goal of LDL. Other therapies targeting LDLR include PCSK9, which lowers LDLR by promoting LDLR degradation. Inducible degrader of LDLR (IDOL) also controls the LDLR protein, but an IDOL-based therapy is yet to be developed. Among the LDLR-independent pathways, such as angiopoietin-like 3 (ANGPTL3), apolipoprotein (apo) B, apoC-III and CETP, only ANGPTL3 offers the advantage of treating both HoFH and HeFH patients and showing relatively better preclinical and clinical efficacy in animal models and hypercholesterolemic individuals, respectively. While loss-of-LDLR-function mutations have been known for decades, gain-of-LDLR-function mutations have recently been identified in some individuals. The new information on gain of LDLR function, together with CRISPR-Cas9 genome/base editing technology to target LDLR and ANGPTL3, offers promise to HoFH and HeFH individuals who are at a higher risk of developing atherosclerotic cardiovascular disease (ASCVD).

Clinical Trial Design for Triglyceride-Rich Lipoprotein-Lowering Therapies: JACC Focus Seminar 3/3

Triglyceride-rich lipoproteins (TRLs) are a source of residual risk in patients with atherosclerotic cardiovascular disease, and are indirectly correlated with triglyceride (TG) levels. Previous clinical trials studying TG-lowering therapies have either failed to reduce major adverse cardiovascular events or shown no linkage of TG reduction with event reduction, particularly when these agents were tested on a background of statin therapy. Limitations in trial design may explain this lack of efficacy. With the advent of new RNA-silencing therapies in the TG metabolism pathway, there is renewed focus on reducing TRLs for major adverse cardiovascular event reduction. In this context, the pathophysiology of TRLs, pharmacological effects of TRL-lowering therapies, and optimal design of cardiovascular outcomes trials are major considerations.

Current and Emerging Therapies for Atherosclerotic Cardiovascular Disease Risk Reduction in Hypertriglyceridemia

Hypertriglyceridemia (HTG) is a prevalent medical condition in patients with cardiometabolic risk factors and is associated with an increased risk of atherosclerotic cardiovascular disease (ASCVD), if left undiagnosed and undertreated. Current guidelines identify HTG as a risk-enhancing factor and, as a result, recommend clinical evaluation and lifestyle-based interventions to address potential secondary causes of elevated triglyceride (TG) levels. For individuals with mild to moderate HTG at risk of ASCVD, statin therapy alone or in combination with other lipid-lowering medications known to decrease ASCVD risk are guideline-endorsed. In addition to lifestyle modifications, patients with severe HTG at risk of acute pancreatitis may benefit from fibrates, mixed formulation omega-3 fatty acids, and niacin; however, evidence does not support their use for ASCVD risk reduction in the contemporary statin era. Novel therapeutics including those that target apoC-III and ANGPTL3 have shown to be safe, well-tolerated, and effective for lowering TG levels. Given the growing burden of cardiometabolic disease and risk factors, public health and health policy strategies are urgently needed to enhance access to effective pharmacotherapies, affordable and nutritious food options, and timely health care services.

Acupoint Catgut Embedding Improves Lipid Metabolism in Exercise-Induced Fatigue Rats via the PPAR Signaling Pathway

To improve the phenomenon of exercise-induced fatigue that often occurs during horse racing, we previously studied the improvement in exercise tolerance by acupoint catgut embedding preconditioning in an exercise-induced fatigue rat model. We found that acupoint catgut embedding pretreatment effectively improved animal exercise tolerance. Here, by combining transcriptomics and metabolomics, we aimed to explore the underlying mechanisms of this improvement. We used blood biochemical detection combined with ELISA to detect triglyceride (TG), total cholesterol (TC), lactate dehydrogenase (LDH), high-density lipoprotein (HDL), alanine transaminase (ALT), aspartate aminotransferase (AST), and glucose (GLU), arachidonic acid (AA), and free fatty acid (FFA) content and found that acupoint embedding can correct FFA, AA, TG, LDH, and AST in the blood. We used RT-qPCR to measure the expression of genes in tissue from the quadriceps femoris muscle. We found that solute carrier family 27 member 2 (Slc27a2), fatty acid binding protein 1 (Fabp1), apolipoprotein C3 (Apoc3), and lipoprotein lipase (Lpl) genes in the peroxisome proliferator-activated receptor (PPAR) signaling pathway were important. The regulation of lipid metabolism through the PPAR signaling pathway was important for improving the exercise endurance of rats in our exercise-induced fatigue model. Therefore, we conclude that acupoint catgut embedding can not only promote body fat decomposition and reduce lactic acid accumulation but also promote the repair of tissue damage and liver damage caused by exercise fatigue. Acupoint catgut embedding regulates the PPAR signaling pathway by upregulating Lpl expression and downregulating Slc27a2, Fabp1, and Apoc3 expression to further improve body fat metabolism.

Prognostic value of remnant cholesterol in patients with coronary heart disease: A systematic review and meta-analysis of cohort studies

Background

The relationship between abnormal lipid levels and atherosclerotic cardiovascular diseases is well established, but the association between remnant cholesterol (RC) and coronary heart disease (CHD) remains uncertain. The aim of this meta-analysis is to systematically evaluate the prognostic value of RC concentration in patients with CHD.

Methods

PubMed, EMBASE, Cochrane, and Web of Science databases were reviewed to identify relevant observational cohort studies published in English up to December 2021. Random-effects meta-analysis compared the highest and lowest RC concentration. The primary outcome was a composite of major adverse cardiovascular events (MACEs) and all-cause mortality in patients with CHD.

Results

A total of 10 studies recruiting 30,605 patients with CHD were selected to be included in this meta-analysis. Patients with CHD with elevated RC concentration had an increased risk of the composite endpoint events (RR = 1.54, 95% CI: 1.26-1.87) and MACEs (RR = 1.70, 95% CI: 1.54-1.88), but the risk of all-cause mortality was not statistically significant (RR = 1.16, 95% CI: 0.79-1.69, P = 0.44). Subgroup analysis showed consistent results.

Conclusion

Our results suggest that elevated concentration RC may independently predict MACEs in patients with CHD. Determination of RC concentration may improve risk stratification of prognosis in patients with CHD. However, more high-quality studies are necessary to confirm this association.

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.

Translating atherosclerosis research from bench to bedside: navigating the barriers for effective preclinical drug discovery

Cardiovascular disease (CVD) remains the leading cause of death worldwide. An ongoing challenge remains the development of novel pharmacotherapies to treat CVD, particularly atherosclerosis. Effective mechanism-informed development and translation of new drugs requires a deep understanding of the known and currently unknown biological mechanisms underpinning atherosclerosis, accompanied by optimization of traditional drug discovery approaches. Current animal models do not precisely recapitulate the pathobiology underpinning human CVD. Accordingly, a fundamental limitation in early-stage drug discovery has been the lack of consensus regarding an appropriate experimental in vivo model that can mimic human atherosclerosis. However, when coupled with a clear understanding of the specific advantages and limitations of the model employed, preclinical animal models remain a crucial component for evaluating pharmacological interventions. Within this perspective, we will provide an overview of the mechanisms and modalities of atherosclerotic drugs, including those in the preclinical and early clinical development stage. Additionally, we highlight recent preclinical models that have improved our understanding of atherosclerosis and associated clinical consequences and propose model adaptations to facilitate the development of new and effective treatments.

Spotlight on very-low-density lipoprotein as a driver of cardiometabolic disorders: Implications for disease progression and mechanistic insights

Very-low-density lipoprotein (VLDL) is the only lipoprotein containing apolipoprotein B that is secreted from the liver, where VLDL is assembled from apolipoproteins, cholesterol, and triglycerides. The primary function of VLDL is to transport cholesterol and other lipids to organs and cells for utilization. Apart from its role in normal biologic processes, VLDL is also known to contribute to the development of atherosclerotic cardiovascular disease. Large VLDL particles, which are subclassified according to their size by nuclear magnetic resonance spectrometry, are significantly correlated not only with atherosclerosis, but also with insulin resistance and diabetes incidence. VLDL can also be subclassified according to surface electrical charge by using anion-exchange chromatography. The most electronegative VLDL subclass is highly cytotoxic to endothelial cells and may contribute to coronary heart disease. In addition, electronegative VLDL contributes to the development of atrial remodeling, especially in patients with metabolic syndrome, which is an established risk factor for atrial fibrillation. In this review, we focus on the VLDL subclasses that are associated with apolipoprotein alterations and are involved in cardiometabolic disease. The postprandial enhancement of VLDL’s pathogenicity is a critical medical issue, especially in patients with metabolic syndrome. Therefore, the significance of the postprandial modification of VLDL’s chemical and functional properties is extensively discussed.

The Regulation of Triacylglycerol Metabolism and Lipoprotein Lipase Activity

Triacylglycerol (TG) metabolism is tightly regulated to maintain a pool of TG within circulating lipoproteins that can be hydrolyzed in a tissue-specific manner by lipoprotein lipase (LPL) to enable the delivery of fatty acids to adipose or oxidative tissues as needed. Elevated serum TG concentrations, which result from a deficiency of LPL activity or, more commonly, an imbalance in the regulation of tissue-specific LPL activities, have been associated with an increased risk of atherosclerotic cardiovascular disease through multiple studies. Among the most critical LPL regulators are the angiopoietin-like (ANGPTL) proteins ANGPTL3, ANGPTL4, and ANGPTL8, and a number of different apolipoproteins including apolipoprotein A5 (ApoA5), apolipoprotein C2 (ApoC2), and apolipoprotein C3 (ApoC3). These ANGPTLs and apolipoproteins work together to orchestrate LPL activity and therefore play pivotal roles in TG partitioning, hydrolysis, and utilization. This review summarizes the mechanisms of action, epidemiological findings, and genetic data most relevant to these ANGPTLs and apolipoproteins. The interplay between these important regulators of TG metabolism in both fasted and fed states is highlighted with a holistic view toward understanding key concepts and interactions. Strategies for developing safe and effective therapeutics to reduce circulating TG by selectively targeting these ANGPTLs and apolipoproteins are also discussed.

[Lipid lowering: new agents and new concepts]

Low-density lipoprotein (LDL) cholesterol (LDL-C) is a causal risk factor for cardiovascular complications. A target value is set according to risk, guideline-based and individual basis. We now have the means to lower LDL‑C levels to ranges that are even associated with plaque volume regression. Moreover, lipid treatment is an example of how pharmacotherapy has evolved from classical selective inhibition of enzymes by drugs (e.g. statins) to targeted neutralization of proteins by antibodies. The reduction of atherogenic lipoproteins by specific inhibition or reduction of mRNA of target proteins, e.g. PCSK‑9, ANGPLT3, ApoC-III or Apo (a), and possibly one day by vaccination or even CRISP-based gene therapy will in the long term lead to new concepts in the treatment and prevention of dyslipidemia and cardiovascular complications. The cumulative exposure of atherogenic lipoproteins to the vessel wall is determined by the time-averaged LDL‑C level. This essentially depends on patient adherence and prescribed treatment intensity by physicians. Therefore, it is likely that treatment adherence influences the cumulative benefit of treatment. Accordingly, the new therapeutic strategies mentioned above with presumably higher adherence rates could help to optimize cardiovascular prevention. Early and effective LDL‑C lowering could drastically reduce the incidence of cardiovascular complications in the long term and help to maintain the health of our patients.

Remnant lipoprotein particles and cardiovascular disease risk

Intravascular catabolism of chylomicrons and very low-density lipoproteins (VLDLs) gives rise to a spectrum of partially lipolyzed remnant particles. Their plasma levels and properties are influenced by lipases, lipid transfer proteins, and content of exchangeable lipoproteins. Particularly important among the latter are apoE, which mediates hepatic binding and uptake of remnants, and apoCIII, which can retard this process. In the course of their plasma transit, remnants can acquire pathologic properties that promote the development of atherosclerotic cardiovascular disease (ASCVD) including increased cholesterol content and transport of thrombogenic and inflammatory mediators. Levels of cholesterol-enriched remnant particles determined by various analytic techniques have been significantly linked to the incidence of ASCVD, most dramatically in dyslipidemic patients homozygous for the apoE2 genetic isoform. Further research is warranted for development of clinical assays that can better capture the pathologic impact of remnant lipoprotein subspecies, and for testing the impact on ASCVD of therapies that reduce their levels.

Emerging Evidence of Pathological Roles of Very-Low-Density Lipoprotein (VLDL)

Embraced with apolipoproteins (Apo) B and Apo E, triglyceride-enriched very-low-density lipoprotein (VLDL) is secreted by the liver into circulation, mainly during post-meal hours. Here, we present a brief review of the physiological role of VLDL and a systemic review of the emerging evidence supporting its pathological roles. VLDL promotes atherosclerosis in metabolic syndrome (MetS). VLDL isolated from subjects with MetS exhibits cytotoxicity to atrial myocytes, induces atrial myopathy, and promotes vulnerability to atrial fibrillation. VLDL levels are affected by a number of endocrinological disorders and can be increased by therapeutic supplementation with cortisol, growth hormone, progesterone, and estrogen. VLDL promotes aldosterone secretion, which contributes to hypertension. VLDL induces neuroinflammation, leading to cognitive dysfunction. VLDL levels are also correlated with chronic kidney disease, autoimmune disorders, and some dermatological diseases. The extra-hepatic secretion of VLDL derived from intestinal dysbiosis is suggested to be harmful. Emerging evidence suggests disturbed VLDL metabolism in sleep disorders and in cancer development and progression. In addition to VLDL, the VLDL receptor (VLDLR) may affect both VLDL metabolism and carcinogenesis. Overall, emerging evidence supports the pathological roles of VLDL in multi-organ diseases. To better understand the fundamental mechanisms of how VLDL promotes disease development, elucidation of the quality control of VLDL and of the regulation and signaling of VLDLR should be indispensable. With this, successful VLDL-targeted therapies can be discovered in the future.

An Amish founder population reveals rare-population genetic determinants of the human lipidome

Identifying the genetic determinants of inter-individual variation in lipid species (lipidome) may provide deeper understanding and additional insight into the mechanistic effect of complex lipidomic pathways in CVD risk and progression beyond simple traditional lipids. Previous studies have been largely population based and thus only powered to discover associations with common genetic variants. Founder populations represent a powerful resource to accelerate discovery of previously unknown biology associated with rare population alleles that have risen to higher frequency due to genetic drift. We performed a genome-wide association scan of 355 lipid species in 650 individuals from the Amish founder population including 127 lipid species not previously tested. To the best of our knowledge, we report for the first time the lipid species associated with two rare-population but Amish-enriched lipid variants: APOB_rs5742904 and APOC3_rs76353203. We also identified novel associations for 3 rare-population Amish-enriched loci with several sphingolipids and with proposed potential functional/causal variant in each locus including GLTPD2_rs536055318, CERS5_rs771033566, and AKNA_rs531892793. We replicated 7 previously known common loci including novel associations with two sterols: androstenediol with UGT locus and estriol with SLC22A8/A24 locus. Our results show the double power of founder populations and detailed lipidome to discover novel trait-associated variants.

A GWAS of 355 lipid species in the Old Order Amish founder population reveals associations between Amish-enriched loci and several sphingolipids.

Is Apo-CIII the new cardiovascular target? An analysis of its current clinical and dietetic therapies

AIMS

Recently, Apolipoprotein CIII (Apo-CIII) has gained remarkable attention since its overexpression has been strongly correlated to cardiovascular disease (CVD) occurrence. The aim of this review was to summarize the latest findings of Apo-CIII as a CVDs and diabetes risk factor, as well as the plausible mechanisms involved in the development of these pathologies, with particular emphasis on current clinical and dietetic therapies.

DATA SYNTHESIS

Apo-CIII is a small protein (∼8.8 kDa) that, among other functions, inhibits lipoprotein lipase, a key enzyme in lipid metabolism. Apo-CIII plays a fundamental role in the physiopathology of atherosclerosis, type-1, and type-2 diabetes. Apo-CIII has become a potential clinical target to tackle these multifactorial diseases. Dietetic (omega-3 fatty acids, stanols, polyphenols, lycopene) and non-dietetic (fibrates, statins, and antisense oligonucleotides) therapies have shown promising results to regulate Apo-CIII and triglyceride levels. However, more information from clinical trials is required to validate it as a new target for atherosclerosis and diabetes types 1 and 2.

CONCLUSIONS

There are still several pathways involving Apo-CIII regulation that might be affected by bioactive compounds that need further research. The mechanisms that trigger metabolic responses following bioactive compounds consumption are mainly related to higher LPL expression and PPARα activation, although the complete pathways are yet to be elucidated.

Characterising metabolomic signatures of lipid-modifying therapies through drug target mendelian randomisation

Large-scale molecular profiling and genotyping provide a unique opportunity to systematically compare the genetically predicted effects of therapeutic targets on the human metabolome. We firstly constructed genetic risk scores for 8 drug targets on the basis that they primarily modify low-density lipoprotein (LDL) cholesterol (HMGCR, PCKS9, and NPC1L1), high-density lipoprotein (HDL) cholesterol (CETP), or triglycerides (APOC3, ANGPTL3, ANGPTL4, and LPL). Conducting mendelian randomisation (MR) provided strong evidence of an effect of drug-based genetic scores on coronary artery disease (CAD) risk with the exception of ANGPTL3. We then systematically estimated the effects of each score on 249 metabolic traits derived using blood samples from an unprecedented sample size of up to 115,082 UK Biobank participants. Genetically predicted effects were generally consistent among drug targets, which were intended to modify the same lipoprotein lipid trait. For example, the linear fit for the MR estimates on all 249 metabolic traits for genetically predicted inhibition of LDL cholesterol lowering targets HMGCR and PCSK9 was r² = 0.91. In contrast, comparisons between drug classes that were designed to modify discrete lipoprotein traits typically had very different effects on metabolic signatures (for instance, HMGCR versus each of the 4 triglyceride targets all had r² < 0.02). Furthermore, we highlight this discrepancy for specific metabolic traits, for example, finding that LDL cholesterol lowering therapies typically had a weak effect on glycoprotein acetyls, a marker of inflammation, whereas triglyceride modifying therapies assessed provided evidence of a strong effect on lowering levels of this inflammatory biomarker. Our findings indicate that genetically predicted perturbations of these drug targets on the blood metabolome can drastically differ, despite largely consistent effects on risk of CAD, with potential implications for biomarkers in clinical development and measuring treatment response.

Early Investigational and Experimental Therapeutics for the Treatment of Hypertriglyceridemia

Hypertriglyceridemia has been identified as a risk factor for cardiovascular disease and acute pancreatitis. To date, there are only few drug classes targeting triglyceride levels such as fibrates and ω-3 fatty acids. These agents are at times insufficient to address very high triglycerides and the residual cardiovascular risk in patients with mixed dyslipidemia. To address this unmet clinical need, novel triglyceride-lowering agents have been in different phases of early clinical development. In this review, the latest and experimental therapies for the management of hypertriglyceridemia are presented. Specifically, ongoing trials evaluating novel apolipoprotein C-III inhibitors, ω-3 fatty acids, as well as fibroblast growth 21 analogues are discussed.

Apolipoprotein C-III reduction in subjects with moderate hypertriglyceridaemia and at high cardiovascular risk

Aims

Hypertriglyceridaemia is associated with increased risk of cardiovascular events. This clinical trial evaluated olezarsen, an N-acetyl-galactosamine-conjugated antisense oligonucleotide targeted to hepatic APOC3 mRNA to inhibit apolipoprotein C-III (apoC-III) production, in lowering triglyceride levels in patients at high risk for or with established cardiovascular disease.

Methods and results

A randomized, double-blind, placebo-controlled, dose-ranging study was conducted in 114 patients with fasting serum triglycerides 200–500 mg/dL (2.26–5.65 mmol/L). Patients received olezarsen (10 or 50 mg every 4 weeks, 15 mg every 2 weeks, or 10 mg every week) or saline placebo subcutaneously for 6–12 months. The primary endpoint was the percent change in fasting triglyceride levels from baseline to Month 6 of exposure. Baseline median (interquartile range) fasting triglyceride levels were 262 (222–329) mg/dL [2.96 (2.51–3.71) mmol/L]. Treatment with olezarsen resulted in mean percent triglyceride reductions of 23% with 10 mg every 4 weeks, 56% with 15 mg every 2 weeks, 60% with 10 mg every week, and 60% with 50 mg every 4 weeks, compared with increase by 6% for the pooled placebo group (P-values ranged from 0.0042 to <0.0001 compared with placebo). Significant decreases in apoC-III, very low-density lipoprotein cholesterol, non-high-density lipoprotein cholesterol, and apolipoprotein B were also observed. There were no platelet count, liver, or renal function changes in any of the olezarsen groups. The most common adverse event was mild erythema at the injection site.

Conclusion

Olezarsen significantly reduced apoC-III, triglycerides, and atherogenic lipoproteins in patients with moderate hypertriglyceridaemia and at high risk for or with established cardiovascular disease.

Trial registration number

NCT03385239.

Addressing dyslipidemic risk beyond LDL-cholesterol

Despite the success of LDL-lowering drugs in reducing cardiovascular disease (CVD), there remains a large burden of residual disease due in part to persistent dyslipidemia characterized by elevated levels of triglyceride-rich lipoproteins (TRLs) and reduced levels of HDL. This form of dyslipidemia is increasing globally as a result of the rising prevalence of obesity and metabolic syndrome. Accumulating evidence suggests that impaired hepatic clearance of cholesterol-rich TRL remnants leads to their accumulation in arteries, promoting foam cell formation and inflammation. Low levels of HDL may associate with reduced cholesterol efflux from foam cells, aggravating atherosclerosis. While fibrates and fish oils reduce TRL, they have not been uniformly successful in reducing CVD, and there is a large unmet need for new approaches to reduce remnants and CVD. Rare genetic variants that lower triglyceride levels via activation of lipolysis and associate with reduced CVD suggest new approaches to treating dyslipidemia. Apolipoprotein C3 (APOC3) and angiopoietin-like 3 (ANGPTL3) have emerged as targets for inhibition by antibody, antisense, or RNAi approaches. Inhibition of either molecule lowers TRL but respectively raises or lowers HDL levels. Large clinical trials of such agents in patients with high CVD risk and elevated levels of TRL will be required to demonstrate efficacy of these approaches.

Genetically Engineered Hamster Models of Dyslipidemia and Atherosclerosis

Animal models of human diseases play an extremely important role in biomedical research. Among them, mice are widely used animal models for translational research, especially because of ease of generation of genetically engineered mice. However, because of the great differences in biology between mice and humans, translation of findings to humans remains a major issue. Therefore, the exploration of models with biological and metabolic characteristics closer to those of humans has never stopped.Although pig and nonhuman primates are biologically similar to humans, their genetic engineering is technically difficult, the cost of breeding is high, and the experimental time is long. As a result, the application of these species as model animals, especially genetically engineered model animals, in biomedical research is greatly limited.In terms of lipid metabolism and cardiovascular diseases, hamsters have several characteristics different from rats and mice, but similar to those in humans. The hamster is therefore an ideal animal model for studying lipid metabolism and cardiovascular disease because of its small size and short reproduction period. However, the phenomenon of zygote division, which was unexpectedly blocked during the manipulation of hamster embryos for some unknown reasons, had plagued researchers for decades and no genetically engineered hamsters have therefore been generated as animal models of human diseases for a long time. After solving the problem of in vitro development of hamster zygotes, we successfully prepared enhanced green fluorescent protein (eGFP) transgenic hamsters by microinjection of lentiviral vectors into the zona pellucida space of zygotes. On this basis, we started the development of cardiovascular disease models using the hamster embryo culture system combined with the novel genome editing technique of clustered regularly interspaced short palindromic repeats (CRISPR )/CRISPR associated protein 9 (Cas9). In this chapter, we will introduce some of the genetically engineered hamster models with dyslipidemia and the corresponding characteristics of these models. We hope that the genetically engineered hamster models can be further recognized and complement other genetically engineered animal models such as mice, rats, and rabbits. This will lead to new avenues and pathways for the study of lipid metabolism and its related diseases.

Genetic Determinants of Plasma Low-Density Lipoprotein Cholesterol Levels: Monogenicity, Polygenicity, and "Missing" Heritability

Changes in plasma low-density lipoprotein cholesterol (LDL-c) levels relate to a high risk of developing some common and complex diseases. LDL-c, as a quantitative trait, is multifactorial and depends on both genetic and environmental factors. In the pregenomic age, targeted genes were used to detect genetic factors in both hyper- and hypolipidemias, but this approach only explained extreme cases in the population distribution. Subsequently, the genetic basis of the less severe and most common dyslipidemias remained unknown. In the genomic age, performing whole-exome sequencing in families with extreme plasma LDL-c values identified some new candidate genes, but it is unlikely that such genes can explain the majority of inexplicable cases. Genome-wide association studies (GWASs) have identified several single-nucleotide variants (SNVs) associated with plasma LDL-c, introducing the idea of a polygenic origin. Polygenic risk scores (PRSs), including LDL-c-raising alleles, were developed to measure the contribution of the accumulation of small-effect variants to plasma LDL-c. This paper discusses other possibilities for unexplained dyslipidemias associated with LDL-c, such as mosaicism, maternal effect, and induced epigenetic changes. Future studies should consider gene-gene and gene-environment interactions and the development of integrated information about disease-driving networks, including phenotypes, genotypes, transcription, proteins, metabolites, and epigenetics.

Lipids and Lipoproteins in Health and Disease: Focus on Targeting Atherosclerosis

Despite advances in pharmacotherapy, intervention devices and techniques, residual cardiovascular risks still cause a large burden on public health. Whilst most guidelines encourage achieving target levels of specific lipids and lipoproteins to reduce these risks, increasing evidence has shown that molecular modification of these lipoproteins also has a critical impact on their atherogenicity. Modification of low-density lipoprotein (LDL) by oxidation, glycation, peroxidation, apolipoprotein C-III adhesion, and the small dense subtype largely augment its atherogenicity. Post-translational modification by oxidation, carbamylation, glycation, and imbalance of molecular components can reduce the capacity of high-density lipoprotein (HDL) for reverse cholesterol transport. Elevated levels of triglycerides (TGs), apolipoprotein C-III and lipoprotein(a), and a decreased level of apolipoprotein A-I are closely associated with atherosclerotic cardiovascular disease. Pharmacotherapies aimed at reducing TGs, lipoprotein(a), and apolipoprotein C-III, and enhancing apolipoprotein A-1 are undergoing trials, and promising preliminary results have been reported. In this review, we aim to update the evidence on modifications of major lipid and lipoprotein components, including LDL, HDL, TG, apolipoprotein, and lipoprotein(a). We also discuss examples of translating findings from basic research to potential therapeutic targets for drug development.

Metabolic-associated fatty liver disease and lipoprotein metabolism

BACKGROUND

Non-alcoholic fatty liver disease, or as recently proposed 'metabolic-associated fatty liver disease' (MAFLD), is characterized by pathological accumulation of triglycerides and other lipids in hepatocytes. This common disease can progress from simple steatosis to steatohepatitis, and eventually end-stage liver diseases. MAFLD is closely related to disturbances in systemic energy metabolism, including insulin resistance and atherogenic dyslipidemia.

SCOPE OF REVIEW

The liver is the central organ in lipid metabolism by secreting very low density lipoproteins (VLDL) and, on the other hand, by internalizing fatty acids and lipoproteins. This review article discusses recent research addressing hepatic lipid synthesis, VLDL production, and lipoprotein internalization as well as the lipid exchange between adipose tissue and the liver in the context of MAFLD.

MAJOR CONCLUSIONS

Liver steatosis in MAFLD is triggered by excessive hepatic triglyceride synthesis utilizing fatty acids derived from white adipose tissue (WAT), de novo lipogenesis (DNL) and endocytosed remnants of triglyceride-rich lipoproteins. In consequence of high hepatic lipid content, VLDL secretion is enhanced, which is the primary cause of complex dyslipidemia typical for subjects with MAFLD. Interventions reducing VLDL secretory capacity attenuate dyslipidemia while they exacerbate MAFLD, indicating that the balance of lipid storage versus secretion in hepatocytes is a critical parameter determining disease outcome. Proof of concept studies have shown that promoting lipid storage and energy combustion in adipose tissues reduces hepatic lipid load and thus ameliorates MAFLD. Moreover, hepatocellular triglyceride synthesis from DNL and WAT-derived fatty acids can be targeted to treat MAFLD. However, more research is needed to understand how individual transporters, enzymes, and their isoforms affect steatosis and dyslipidemia in vivo, and whether these two aspects of MAFLD can be selectively treated. Processing of cholesterol-enriched lipoproteins appears less important for steatosis. It may, however, modulate inflammation and consequently MAFLD progression.

HDL in the 21st Century: A Multifunctional Roadmap for Future HDL Research

Low high-density lipoprotein cholesterol (HDL-C) characterizes an atherogenic dyslipidemia that reflects adverse lifestyle choices, impaired metabolism, and increased cardiovascular risk. Low HDL-C is also associated with increased risk of inflammatory disorders, malignancy, diabetes, and other diseases. This epidemiologic evidence has not translated to raising HDL-C as a viable therapeutic target, partly because HDL-C does not reflect high-density lipoprotein (HDL) function. Mendelian randomization analyses that have found no evidence of a causal relationship between HDL-C levels and cardiovascular risk have decreased interest in increasing HDL-C levels as a therapeutic target. HDLs comprise distinct subpopulations of particles of varying size, charge, and composition that have several dynamic and context-dependent functions, especially with respect to acute and chronic inflammatory states. These functions include reverse cholesterol transport, inhibition of inflammation and oxidation, and antidiabetic properties. HDLs can be anti-inflammatory (which may protect against atherosclerosis and diabetes) and proinflammatory (which may help clear pathogens in sepsis). The molecular regulation of HDLs is complex, as evidenced by their association with multiple proteins, as well as bioactive lipids and noncoding RNAs. Clinical investigations of HDL biomarkers (HDL-C, HDL particle number, and apolipoprotein A through I) have revealed nonlinear relationships with cardiovascular outcomes, differential relationships by sex and ethnicity, and differential patterns with coronary versus noncoronary events. Novel HDL markers may also have relevance for heart failure, cancer, and diabetes. HDL function markers (namely, cholesterol efflux capacity) are associated with coronary disease, but they remain research tools. Therapeutics that manipulate aspects of HDL metabolism remain the holy grail. None has proven to be successful, but most have targeted HDL-C, not metrics of HDL function. Future therapeutic strategies should focus on optimizing HDL function in the right patients at the optimal time in their disease course. We provide a framework to help the research and clinical communities, as well as funding agencies and stakeholders, obtain insights into current thinking on these topics, and what we predict will be an exciting future for research and development on HDLs.

Genetics of hypertriglyceridemia and atherosclerosis

PURPOSE OF REVIEW

The relationship between elevated triglyceride levels (i.e. hypertriglyceridemia) and risk of atherosclerotic cardiovascular disease (ASCVD) has been investigated for decades. Recent genetic studies have sought to resolve the decades-old question of a causal relationship.

RECENT FINDINGS

Genetic studies seem to demonstrate associations between elevated triglyceride levels and ASCVD risk. Mendelian randomization studies suggest this association may be causal. However, simultaneous pleiotropic effects of metabolically linked lipid variables - such as non-HDL cholesterol, apolipoprotein B and HDL cholesterol -- often go unaccounted for in these studies. Complex underlying pleiotropic interactions of triglycerides with these lipid fractions together with unmeasured intercalated nonlipid-related mechanisms, such as inflammation and coagulation, impair the ability of genetic studies to implicate a direct role for triglycerides on ASCVD risk. One potential mechanism seems largely driven by the cholesterol carried within triglyceride-rich lipoproteins and their remnants, rather than their triglyceride content.

SUMMARY

Although the exact mechanisms linking elevated triglyceride levels to ASCVD remain to be determined, new therapeutics that reduce triglyceride levels might be advantageous in certain patients. Newer investigational triglyceride-lowering therapies derived from human genetics target key proteins, such as apo C-III and ANGPTL3. Although these treatments clearly lower triglyceride levels, their efficacy in atherosclerotic risk reduction remains unproven.

Triglyceride-rich lipoproteins and atherosclerotic cardiovascular disease risk: current status and treatments

PURPOSE OF REVIEW

The role of triglyceride-rich lipoproteins (TRLs) in the development of atherosclerotic cardiovascular disease (ASCVD) is at the forefront of current research and treatment development programs. Despite extreme lowering of LDL-cholesterol there remains a high risk of cardiovascular disease and mortality. Recent large epidemiological, genomic wide association studies and Mendelian randomization studies have identified novel mechanisms and targets regulating TRL. This review will focus on recent and ongoing clinical trials that aim to reduce cardiovascular risk by decreasing plasma levels of TRL.

RECENT FINDINGS

Ongoing efforts of basic and clinical scientist have described novel TRL regulating mechanism. The concentration on lifestyle changes is key to prevention and treatment guidelines. There is continue evidence that supports previous guidelines using fibrates alone and in combination with niacin to reduce TRLs, in special cases. The recent results from the REDUCE-IT study support the use of eicosapentaenoic acid (EPA) for risk reduction and ASCVD, but recently presented data from the Long-Term Outcome Study to Assess Statin Residual Risk Reduction With Epanova in High Cardiovascular Risk Patients with Hypertriglyceridemia and Omega-3 Fatty Acids in Elderly Patients With Acute Myocardial Infarction studies do not support the use of combination EPA/docosahexaenoic acid. The latter highlights the need for further studies into the pathways regulating ASCVD risk reduction after EPA administration. The identification of novel targets, such as apolipoprotein C3 and angiopoietin-like protein-3, are driving the development of novel treatments, and is the focus of this review.

SUMMARY

The current management of elevated triglyceride levels and the effect on cardiovascular outcomes is an emerging area of research. New data from fish oil studies suggest differences in EPA vs. EPA/docosahexaenoic acid cardio protection outcomes. The preliminary data from ongoing clinical trials of novel triglyceride-lowering therapeutics are promising. These programs will ultimately provide foundations for future triglyceride-lowering guidelines.

Triglycerides and risk of atherosclerotic cardiovascular disease: An update

Low-density lipoprotein cholesterol is a well-known causal factor for atherosclerotic cardiovascular disease, and is the primary target of lipid-lowering therapy. There is, however, still a substantial risk of atherosclerotic cardiovascular disease events despite intensive statin therapy, and data from clinical trials suggest that an elevated concentration of triglycerides is a marker of residual cardiovascular risk on low-density lipoprotein-lowering therapy. Serum triglycerides are a biomarker for triglyceride-rich lipoproteins, and several lines of evidence indicate that triglyceride-rich lipoproteins and their cholesterol-enriched remnant particles are associated with atherogenesis. Moreover, genetic data in humans strongly suggest that the remnants of triglyceride-rich lipoproteins are a causal cardiovascular risk factor. Although lifestyle changes remain the cornerstone of management of hypertriglyceridaemia, a recent trial with high doses of the omega-3 fatty acid icosapent ethyl showed a significant reduction in cardiovascular events that was not explained by the reduction in triglycerides alone. In patients with elevated triglycerides, several novel drugs are in development to reduce the residual risk on statin therapy linked to an excess of atherogenic triglyceride-rich lipoproteins. In this review, we provide an update on the biology, epidemiology and genetics of triglycerides, and the risk of atherosclerotic cardiovascular disease.

ApoCIII: A multifaceted protein in cardiometabolic disease

ApoCIII has a well-recognized role in triglyceride-rich lipoproteins metabolism. A considerable amount of data has clearly highlighted that high levels of ApoCIII lead to hypertriglyceridemia and, thereby, may influence the risk of cardiovascular disease. However, recent findings indicate that ApoCIII might also act beyond lipid metabolism. Indeed, ApoCIII has been implicated in other physiological processes such as glucose homeostasis, monocyte adhesion, activation of inflammatory pathways, and modulation of the coagulation cascade. As the inhibition of ApoCIII is emerging as a new promising therapeutic strategy, the complete understanding of multifaceted pathophysiological role of this apoprotein may be relevant. Therefore, the purpose of this work is to review available evidences not only related to genetics and biochemistry of ApoCIII, but also highlighting the role of this apoprotein in triglyceride and glucose metabolism, in the inflammatory process and coagulation cascade as well as in cardiovascular disease.

The relation between VLDL-cholesterol and risk of cardiovascular events in patients with manifest cardiovascular disease

INTRODUCTION

Apolipoprotein B containing lipoproteins are atherogenic. There is evidence that with low plasma low density lipoprotein cholesterol (LDL-C) levels residual vascular risk might be caused by triglyceride rich lipoproteins such as very-low density lipoproteins (VLDL), chylomicrons and their remnants. We investigated the relationship between VLDL-cholesterol (VLDL-C) and recurrent major adverse cardiovascular events (MACE), major adverse limb events (MALE) and all-cause mortality in a cohort of patients with cardiovascular disease.

METHODS

Prospective cohort study in 8057 patients with cardiovascular disease from the UCC-SMART study. The relation between calculated VLDL-C levels and the occurrence of MACE, MALE and all-cause mortality was analyzed with Cox regression models.

RESULTS

Patients mean age was 60 ± 10 years, 74% were male, 4894 (61%) had coronary artery disease, 2445 (30%) stroke, 1425 (18%) peripheral arterial disease and 684 (8%) patients had an abdominal aorta aneurysm at baseline. A total of 1535 MACE, 571 MALE and 1792 deaths were observed during a median follow up of 8.2 years (interquartile range 4.512.2). VLDL-C was not associated with risk of MACE or all-cause mortality. In the highest quartile of VLDL-C the risk was higher for major adverse limb events (MALE) (HR 1.49; 95%CI 1.16-1.93) compared to the lowest quartile, after adjustment for confounders including LDL-C and lipid lowering medication.

CONCLUSION

In patients with clinically manifest cardiovascular disease plasma VLDL-C confers an increased risk for MALE, but not for MACE and all-cause mortality, independent of established risk factors including LDL-C and lipid-lowering medication.

Consensus document of an expert group from the Spanish Society of Arteriosclerosis (SEA) on the clinical use of nuclear magnetic resonance to assess lipoprotein metabolism (Liposcale®)

The assessment and prevention of cardiovascular risk (CVR) that persists in patients with dyslipidaemia despite treatment and achievement of goals specific to the plasma concentration of cholesterol linked to low density (c-LDL) is a clinical challenge today, and suggests that conventional lipid biomarkers are insufficient for an accurate assessment of CVR. Apart from their lipid content, there are other lipid particle characteristics. The results of this study show that there are a number of lipoprotein compounds that determine atherogenic potential and its influence on the CVR. However, such additional characteristics cannot be analysed by the techniques commonly used in clinical laboratories. Nuclear Magnetic Resonance (NMR) is a technique that allows a detailed analysis to be made of the amount, composition, and size of lipoproteins, as well as providing more information about the detailed status of lipid metabolism and CVR in dyslipidaemia patients. In this article a group of lipidologists from the Spanish Society of Arteriosclerosis review the existing evidence on the atherogenic mechanisms of particles and describe the technical basis and interpretation of the profiles lipoproteins obtained by MRI, with special reference to the test available in Spain (Liposcale®). Likewise, the main patient profiles are defined as such that an analysis would provide information of greater clinical interest. These include: a) Suspected mismatch between lipid concentrations and particles, a common situation in diabetes, obesity, metabolic syndrome; b) Early atherothrombotic cardiovascular disease (ECVA) or recurrent without CVR factors to justify it; c) Lipid disorders, rare or complex, such as extreme concentrations of c-HDL, and d) Clinical situations where classical analytical techniques cannot be applied, such as very low c-LDL values.

Emerging Targets for Cardiovascular Disease Prevention in Diabetes

Type 1 and type 2 diabetes mellitus (T1DM and T2DM) increase the risk of atherosclerotic cardiovascular disease (CVD), resulting in acute cardiovascular events, such as heart attack and stroke. Recent clinical trials point toward new treatment and prevention strategies for cardiovascular complications of T2DM. New antidiabetic agents show unexpected cardioprotective benefits. Moreover, genetic and reverse translational strategies have revealed potential novel targets for CVD prevention in diabetes, including inhibition of apolipoprotein C3 (APOC3). Modeling and pharmacology-based approaches to improve insulin action provide additional potential strategies to combat CVD. The development of new strategies for improved diabetes and lipid control fuels hope for future prevention of CVD associated with diabetes.

The next generation of triglyceride-lowering drugs: will reducing apolipoprotein C-III or angiopoietin like protein 3 reduce cardiovascular disease?

PURPOSE OF REVIEW

Apolipoprotein C-III (ApoC-III) and angiopoietin like protein 3 (angptl3) have emerged as key regulators of triglyceride metabolism. Based on Mendelian randomisation studies, novel therapeutic strategies inhibiting these proteins using monoclonal antibodies or gene silencing techniques might reduce residual cardiovascular disease (CVD) risk in dyslipidemic patients. This article aims to review the role of apoC-III and angptl3 in triglyceride metabolism and combine early clinical evidence of CVD reducing potential of these new therapeutic targets.

RECENT FINDINGS

Angptl3 inhibition by mAb or antisense therapy has recently completed phase I and II studies, respectively and demonstrate robust apolipoprotein B (apoB) lowering up to 46%. Volanesorsen is an antisense therapy approved for patients with extremely elevated plasma triglyceride levels in which it showed no consistent apoB reduction. However, the GalNAc-conjugated oligonucleotide showed moderate (up to ∼30%) apoB reduction in a phase 1/2a dose-finding study.

SUMMARY

Angptl3 and apoC-III are novel targets in lipoprotein metabolism that reduce triglycerides when inhibited. The expected CVD risk reduction may be mediated through reduced triglyceride-rich lipoprotein particle number, reflected by apoB, rather than triglyceride reduction per se. Limited human evidence shows that apoC-III and angptl3 inhibition both potently lower triglycerides, but since angptl3 inhibition reduces apoB more robustly it may be expected to confer more favorable CVD risk reduction.

Apolipoprotein CIII predicts cardiovascular events in patients with coronary artery disease: a prospective observational study

Background

Apolipoprotein CIII (apoCIII) is associated with triglyceride-rich lipoprotein metabolism and has emerged as independent marker for risk of cardiovascular disease. The objective was to test whether apoCIII is regulated postprandially and whether apoCIII concentrations in native and chylomicron-free serum predict future cardiovascular events in patients with stable coronary artery disease (CAD).

Methods

ApoCIII concentrations were measured in native and chylomicron-free serum in the fasting state and after a standardized oral fat load test in 195 patients with stable CAD. Clinical follow-up was 48 months. Chylomicron-free serum was prepared by ultracentrifugation (18,000 rpm, 3 h). The log-rank test and Cox regression analyses were used to investigate the association of apoCIII with recurrent cardiovascular events.

Results

Of the 195 patients included, 92 had a cardiovascular event, and 103 did not. 97% were treated with a statin. No significant changes in apoCIII concentration were observed after the oral fat load test. The apoCIII concentration was associated with event-free survival independent of conventional risk factors. This association reached statistical significance only for apoCIII concentration measured in chylomicron-free serum (hazard ratio [95% confidence interval] for apoCIII above the mean: postprandial: 1.67 (1.06–2.29), P = 0.028, fasting: 2.09 (1.32–3.32), P = 0.002), but not for apoCIII concentration measured in native serum (postprandial: 1.47 [0.89–2.43], P = 0.133, fasting: 1.56 [0.95–2.58], P = 0.081). The effects were independent of other risk factors.

Conclusions

ApoCIII concentrations in chylomicron-free serum are independently associated with event-free survival in patients with CAD both in fasting and postprandial state. This findings support considering apoCIII for risk assessment and attempting to test the hypothesis that lowering apoCIII reduces residual cardiovascular risk.

Take home message

Apolipoprotein CIII concentration measured in chylomicron-free serum predicts recurrent cardiovascular events in patients with stable coronary artery disease.

Trial registration

The trial which included the participants of this study was registered at https://clinicaltrials.gov (NCT00628524) on March 5, 2008.

Gene-based therapy in lipid management: the winding road from promise to practice

INTRODUCTION

Cardiovascular disease (CVD) is a leading cause of morbidity and mortality. High plasma low-density lipoprotein cholesterol (LDL-C) levels are a key CVD-risk factor. Triglyceride-rich remnant particles and lipoprotein(a) (Lp[a]) are also causally related to CVD. Consequently, therapeutic strategies for lowering LDL-C and triglyceride levels are widely used in routine clinical practice; however, specific Lp(a) lowering agents are not available. Many patients do not achieve guideline-recommended lipid levels with currently available therapies; hence, novel targets and treatment modalities are eagerly sought.

AREAS COVERED

We discuss the milestones on the trajectory toward the full application of gene-based therapies in daily clinical practice. We describe the different methods, ranging from antisense oligonucleotides to liver-directed gene therapy and Crispr-cas9 modification to target the pivotal players in lipid metabolism: PCSK9, APOB, ANGPTL3, Lp(a), LDLR, and apoC-III.

EXPERT OPINION

While acknowledging their different stages of development, gene-based therapies are likely to invoke a paradigm shift in lipid management because they allow us to target previously undruggable targets. Moreover, their low dosing frequency, high target selectivity, and relatively predictable adverse event profile are considered major advantages over current lipid-lowering therapies.

Triglycerides and remnant cholesterol associated with risk of aortic valve stenosis: Mendelian randomization in the Copenhagen General Population Study

Aims

We tested the hypothesis that higher levels of plasma triglycerides and remnant cholesterol are observationally and genetically associated with increased risk of aortic valve stenosis.

Methods and results

We included 108 559 individuals from the Copenhagen General Population Study. Plasma triglycerides, remnant cholesterol (total cholesterol minus low-density lipoprotein and high-density lipoprotein cholesterol), and 16 genetic variants causing such increased or decreased levels were determined. Incident aortic valve stenosis occurred in 1593 individuals. Observationally compared to individuals with triglycerides &lt;1 mmol/L (&lt;89 mg/dL), the multifactorially adjusted hazard ratio for aortic valve stenosis was 1.02 [95% confidence interval (CI) 0.87–1.19] for individuals with triglycerides of 1.0–1.9 mmol/L (89–176 mg/dL), 1.22 (1.02–1.46) for 2.0–2.9 mmol/L (177–265 mg/dL), 1.40 (1.11–1.77) for 3.0–3.9 mmol/L (266–353 mg/dL), 1.29 (0.88–1.90) for 4.0–4.9 mmol/L (354–442 mg/dL), and 1.52 (1.02–2.27) for individuals with triglycerides ≥5 mmol/L (≥443 mg/dL). By age 85, the cumulative incidence of aortic valve stenosis was 5.1% for individuals with plasma triglycerides &lt;2.0 mmol/L (77 mg/dL), 6.5% at 2.0–4.9 mmol/L (177–442 mg/dL), and 8.2% for individuals with plasma triglycerides ≥5.0 mmol/L (443 mg/dL). The corresponding values for remnant cholesterol categories were 4.8% for &lt;0.5 mmol/L (19 mg/dL), 5.6% for 0.5–1.4 mmol/L (19–57 mg/dL), and 7.4% for ≥1.5 mmol/L (58 mg/dL). Genetically, compared to individuals with allele score 13–16, odds ratios for aortic valve stenosis were 1.30 (95% CI 1.20–1.42; Δtriglycerides +12%; Δremnant cholesterol +11%) for allele score 17–18, 1.41 (1.31–1.52; +25%; +22%) for allele score 19–20, and 1.51 (1.22–1.86; +51%; +44%) for individuals with allele score 21–23.

Conclusion

Higher triglycerides and remnant cholesterol were observationally and genetically associated with increased risk of aortic valve stenosis.