ANGPTL3 decreases very low density lipoprotein triglyceride clearance by inhibition of lipoprotein lipase

METFORMIN: FROM DIABETES TO CANCER TO PROLONGATION OF LIFE

The metformin molecule dates back to over a century, but its clinical use started in the '50s. Since then, its use in diabetics has grown constantly, with over 150 million users today. The therapeutic profile also expanded, with improved understanding of novel mechanisms. Metformin has a major activity on insulin resistance, by acting on the insulin receptors and mitochondria, most likely by activation of the adenosine monophosphate-activated kinase. These and associated mechanisms lead to significant lipid lowering and body weight loss. An anti-cancer action has come up in recent years, with mechanisms partly dependent on the mitochondrial activity and also on phosphatidylinositol 3-kinase resistance occurring in some malignant tumors. The potential of metformin to raise life-length is the object of large ongoing studies and of several basic and clinical investigations. The present review article will attempt to investigate the basic mechanisms behind these diverse activities and the potential clinical benefits. Metformin may act on transcriptional activity by histone modification, DNA methylation and miRNAs. An activity on age-associated inflammation (inflammaging) may occur via activation of the nuclear factor erythroid 2 related factor and changes in gut microbiota. A senolytic activity, leading to reduction of cells with the senescent associated secretory phenotype, may be crucial in lifespan prolongation as well as in ancillary properties in age-associated diseases, such as Parkinson's disease. Telomere prolongation may be related to the activity on mitochondrial respiratory factor 1 and on peroxisome gamma proliferator coactivator 1-alpha. Very recent observations on the potential to act on the most severe neurological disorders, such as amyotrophic lateral sclerosis and frontotemporal dementia, have raised considerable hope.

Hepatokines: unveiling the molecular and cellular mechanisms connecting hepatic tissue to insulin resistance and inflammation

Insulin resistance arising from Non-Alcoholic Fatty Liver Disease (NAFLD) stands as a prevalent global ailment, a manifestation within societies stemming from individuals' suboptimal dietary habits and lifestyles. This form of insulin resistance emerges as a pivotal factor in the development of type 2 diabetes mellitus (T2DM). Emerging evidence underscores the significant role of hepatokines, as hepatic-secreted hormone-like entities, in the genesis of insulin resistance and eventual onset of type 2 diabetes. Hepatokines exert influence over extrahepatic metabolism regulation. Their principal functions encompass impacting adipocytes, pancreatic cells, muscles, and the brain, thereby playing a crucial role in shaping body metabolism through signaling to target tissues. This review explores the most important hepatokines, each with distinct influences. Our review shows that Fetuin-A promotes lipid-induced insulin resistance by acting as an endogenous ligand for Toll-like receptor 4 (TLR-4). FGF21 reduces inflammation in diabetes by blocking the nuclear translocation of nuclear factor-κB (NF-κB) in adipocytes and adipose tissue, while also improving glucose metabolism. ANGPTL6 enhances AMPK and insulin signaling in muscle, and suppresses gluconeogenesis. Follistatin can influence insulin resistance and inflammation by interacting with members of the TGF-β family. Adropin show a positive correlation with phosphoenolpyruvate carboxykinase 1 (PCK1), a key regulator of gluconeogenesis. This article delves into hepatokines' impact on NAFLD, inflammation, and T2DM, with a specific focus on insulin resistance. The aim is to comprehend the influence of these recently identified hormones on disease development and their underlying physiological and pathological mechanisms.

APOA5 deficiency causes hypertriglyceridemia by reducing amounts of lipoprotein lipase in capillaries

Apolipoprotein AV (APOA5) deficiency causes hypertriglyceridemia in mice and humans. For years, the cause remained a mystery, but the mechanisms have now come into focus. Here, we review progress in defining APOA5's function in plasma triglyceride metabolism. Biochemical studies revealed that APOA5 binds to the angiopoietin-like protein 3/8 complex (ANGPTL3/8) and suppresses its ability to inhibit the activity of lipoprotein lipase (LPL). Thus, APOA5 deficiency is accompanied by increased ANGPTL3/8 activity and lower levels of LPL activity. APOA5 deficiency also reduces amounts of LPL in capillaries of oxidative tissues (e.g., heart, brown adipose tissue). Cell culture experiments revealed the likely explanation: ANGPTL3/8 detaches LPL from its binding sites on the surface of cells, and that effect is blocked by APOA5. Both the low intracapillary LPL levels and the high plasma triglyceride levels in Apoa5-/- mice are normalized by recombinant APOA5. Carboxyl-terminal sequences in APOA5 are crucial for its function; a mutant APOA5 lacking 40-carboxyl-terminal residues cannot bind to ANGPTL3/8 and lacks the ability to change intracapillary LPL levels or plasma triglyceride levels in Apoa5-/- mice. Also, an antibody against the last 26 amino acids of APOA5 reduces intracapillary LPL levels and increases plasma triglyceride levels in wild-type mice. An inhibitory ANGPTL3/8-specific antibody functions as an APOA5-mimetic reagent, increasing intracapillary LPL levels and lowering plasma triglyceride levels in both Apoa5-/- and wild-type mice. That antibody is a potentially attractive strategy for treating elevated plasma lipid levels in human patients.

Evinacumab: Mechanism of action, clinical, and translational science

Homozygous familial hypercholesterolemia (HoFH) is a rare and serious genetic condition characterized by premature cardiovascular disease due to severely elevated low-density lipoprotein cholesterol (LDL-C). HoFH primarily results from loss-of-function (LOF) mutations in the LDL receptor (LDLR), reducing LDL-C clearance such that patients experience severe hypercholesterolemia, exacerbating the risk of developing cardiovascular events. Treatment options such as statins, lomitapide, ezetimibe, proprotein convertase subtilisin/kexin type 9 inhibitors, and apheresis help lower LDL-C; however, many patients with HoFH still fail to reach their target LDL-C levels and many of these lipid-lowering therapies are not indicated for pediatric use. Angiopoietin-like protein 3 (ANGPTL3) has been identified as a target to treat elevated LDL-C by acting as a natural inhibitor of lipoprotein lipase (LPL) and endothelial lipase (EL), enzymes involved in the hydrolysis of the triglyceride and phospholipid content of very low-density lipoproteins. Persons heterozygous for LOF mutations in ANGPTL3 were reported to have lower LDL-C than non-carriers and lower risk of coronary artery disease. Evinacumab is a first-in-class human monoclonal antibody that specifically binds to ANGPTL3 to prevent its inhibition of LPL and EL. In clinical trials, a 15 mg/kg intravenous dose every 4 weeks has shown a mean percent change from baseline in LDL-C of ~50% in adult, adolescent, and pediatric patients with HoFH. This mini review article describes the mechanism of action of evinacumab, evinacumab population PK and PD modeling, and clinical development history of evinacumab for the treatment of HoFH.

Triglyceride-rich lipoproteins and cardiovascular diseases

The global prevalence of cardiovascular diseases (CVD) continues to rise steadily, making it a leading cause of mortality worldwide. Atherosclerosis (AS) serves as a primary driver of these conditions, commencing silently at an early age and culminating in adverse cardiovascular events that severely impact patients' quality of life or lead to fatality. Dyslipidemia, particularly elevated levels of low-density lipoprotein cholesterol (LDL-C), plays a pivotal role in AS pathogenesis as an independent risk factor. Research indicates that abnormal LDL-C accumulation within arterial walls acts as a crucial trigger for atherosclerotic plaque formation. As the disease progresses, plaque accumulation may rupture or dislodge, resulting in thrombus formation and complete blood supply obstruction, ultimately causing myocardial infarction, cerebral infarction, and other common adverse cardiovascular events. Despite adequate pharmacologic therapy targeting LDL-C reduction, patients with cardiometabolic abnormalities remain at high risk for disease recurrence, highlighting the importance of addressing lipid risk factors beyond LDL-C. Recent attention has focused on the causal relationship between triglycerides, triglyceride-rich lipoproteins (TRLs), and their remnants in AS risk. Genetic, epidemiologic, and clinical studies suggest a causal relationship between TRLs and their remnants and the increased risk of AS, and this dyslipidemia may be an independent risk factor for adverse cardiovascular events. Particularly in patients with obesity, metabolic syndrome, diabetes, and chronic kidney disease, disordered TRLs and its remnants levels significantly increase the risk of atherosclerosis and cardiovascular disease development. Accumulation of over-synthesized TRLs in plasma, impaired function of enzymes involved in TRLs lipolysis, and impaired hepatic clearance of cholesterol-rich TRLs remnants can lead to arterial deposition of TRLs and its remnants, promoting foam cell formation and arterial wall inflammation. Therefore, understanding the pathogenesis of TRLs-induced AS and targeting it therapeutically could slow or impede AS progression, thereby reducing cardiovascular disease morbidity and mortality, particularly coronary atherosclerotic heart disease.

SharePro: an accurate and efficient genetic colocalization method accounting for multiple causal signals

MOTIVATION

Colocalization analysis is commonly used to assess whether two or more traits share the same genetic signals identified in genome-wide association studies (GWAS), and is important for prioritizing targets for functional follow-up of GWAS results. Existing colocalization methods can have suboptimal performance when there are multiple causal variants in one genomic locus.

RESULTS

We propose SharePro to extend the COLOC framework for colocalization analysis. SharePro integrates linkage disequilibrium (LD) modeling and colocalization assessment by grouping correlated variants into effect groups. With an efficient variational inference algorithm, posterior colocalization probabilities can be accurately estimated. In simulation studies, SharePro demonstrated increased power with a well-controlled false positive rate at a low computational cost. Compared to existing methods, SharePro provided stronger and more consistent colocalization evidence for known lipid-lowering drug target proteins and their corresponding lipid traits. Through an additional challenging case of the colocalization analysis of the circulating abundance of R-spondin 3 GWAS and estimated bone mineral density GWAS, we demonstrated the utility of SharePro in identifying biologically plausible colocalized signals.

AVAILABILITY AND IMPLEMENTATION

SharePro for colocalization analysis is written in Python and openly available at https://github.com/zhwm/SharePro_coloc.

ANGPTL3 Downregulation Increases Intracellular Lipids by Reducing Energy Utilization

BACKGROUND

ANGPTL3 (angiopoietin-like protein 3) is a circulating protein with a key role in maintaining lipoprotein homeostasis. A monoclonal antibody against ANGPTL3 is an approved and well-tolerated treatment to reduce lipoproteins in familial hypercholesterolemia homozygotes. However, the reduction of hepatic ANGPTL3 synthesis using an antisense oligonucleotide unexpectedly resulted in a dose-dependent increase in liver lipid content and circulating transaminases, resulting in the termination of the clinical trial. Meanwhile, the use of silencing RNAs remains an area of active investigation. Our study sought to investigate whether intracellular downregulation of ANGPTL3 may lead to a primary increase in neutral lipids within the hepatocyte.

METHODS

We downregulated ANGPTL3 by silencing RNA in primary human hepatocytes 3-dimensional spheroids, HepG2/LX-2 3-dimensional spheroids, and in HepG2, Hep3B2, and Huh7 cultured in 2 dimensions.

RESULTS

ANGPTL3 downregulation increased neutral lipids in all models investigated. Interestingly, ANGPTL3 induced lower intracellular deiodinase type 1 protein levels resulting in a reduction in beta-oxidation and causing an increase in triglycerides stored in lipid droplets.

CONCLUSIONS

In conclusion, intracellular ANGPTL3 downregulation by silencing RNA led to an increase in triglycerides content due to a reduction in energy substrate utilization resembling a primary intracellular hepatocyte hypothyroidism.

ANGPTL3 inhibition, dyslipidemia, and cardiovascular diseases

Optimal management of low-density lipoprotein cholesterol (LDL-C) is a central tenet in the primary and secondary prevention of atherosclerotic cardiovascular disease (ASCVD). However, significant residual cardiovascular risk remains despite achieving guideline-directed LDL-C levels, in part due to mixed hyperlipidemia with elevated fasting and non-fasting triglyceride-rich lipoprotein levels. Advances in human genetics have identified angiopoietin-like 3 (ANGPTL3) as a promising therapeutic target to lower cardiovascular risk. Evidence accrued from genetic epidemiological studies demonstrate that ANGPTL3 loss of function is strongly associated with lowering of circulating LDL-C, triglyceride-rich lipoproteins and concurrent risk reduction in development of coronary artery disease. Pharmacological inhibition of ANGPTL3 with monoclonal antibodies, antisense oligonucleotides and gene editing are in development with early studies showing their safety and efficacy in lowering in both, LDL-C and TGs, circumventing a key limitation of previous therapies. Monoclonal antibodies targeting ANGPTL3 are approved for clinical use in homozygous familial hypercholesteremia in USA and Europe. Although promising, future studies focusing on long-term beneficial effect in reducing cardiovascular events with inhibition of ANGPTL3 are warranted.

Zebrafish ApoB-Containing Lipoprotein Metabolism: A Closer Look

Zebrafish have become a powerful model of mammalian lipoprotein metabolism and lipid cell biology. Most key proteins involved in lipid metabolism, including cholesteryl ester transfer protein, are conserved in zebrafish. Consequently, zebrafish exhibit a human-like lipoprotein profile. Zebrafish with mutations in genes linked to human metabolic diseases often mimic the human phenotype. Zebrafish larvae develop rapidly and externally around the maternally deposited yolk. Recent work revealed that any disturbance of lipoprotein formation leads to the accumulation of cytoplasmic lipid droplets and an opaque yolk, providing a visible phenotype to investigate disturbances of the lipoprotein pathway, already leading to discoveries in MTTP (microsomal triglyceride transfer protein) and ApoB (apolipoprotein B). By 5 days of development, the digestive system is functional, making it possible to study fluorescently labeled lipid uptake in the transparent larvae. These and other approaches enabled the first in vivo description of the STAB (stabilin) receptors, showing lipoprotein uptake in endothelial cells. Various zebrafish models have been developed to mimic human diseases by mutating genes known to influence lipoproteins (eg, ldlra, apoC2). This review aims to discuss the most recent research in the zebrafish ApoB-containing lipoprotein and lipid metabolism field. We also summarize new insights into lipid processing within the yolk cell and how changes in lipid flux alter yolk opacity. This curious new finding, coupled with the development of several techniques, can be deployed to identify new players in lipoprotein research directly relevant to human disease.

Gene Silencing of Angiopoietin-like 3 (ANGPTL3) Induced De Novo Lipogenesis and Lipid Accumulation in Huh7 Cell Line

Angiopoietin-like 3 (ANGPTL3) is a hepatokine acting as a negative regulator of lipoprotein lipase (LPL). Vupanorsen, an ANGPTL3 directed antisense oligonucleotide, showed an unexpected increase in liver fat content in humans. Here, we investigated the molecular mechanism linking ANGPTL3 silencing to hepatocyte fat accumulation. Human hepatocarcinoma Huh7 cells were treated with small interfering RNA (siRNA) directed to ANGPTL3, human recombinant ANGPTL3 (recANGPTL3), or their combination. Using Western blot, Oil Red-O, biochemical assays, and ELISA, we analyzed the expression of genes and proteins involved in lipid metabolism. Oil Red-O staining demonstrated that lipid content increased after 48 h of ANGPTL3 silencing (5.89 ± 0.33 fold), incubation with recANGPTL3 (4.08 ± 0.35 fold), or their combination (8.56 ± 0.18 fold), compared to untreated cells. This effect was also confirmed in Huh7-LX2 spheroids. A total of 48 h of ANGPTL3 silencing induced the expression of genes involved in the de novo lipogenesis, such as fatty acid synthase, stearoyl-CoA desaturase, ATP citrate lyase, and Acetyl-Coenzyme A Carboxylase 1 together with the proprotein convertase subtilisin/kexin 9 (PCSK9). Time-course experiments revealed that 6 h post transfection with ANGPTL3-siRNA, the cholesterol esterification by Acyl-coenzyme A cholesterol acyltransferase (ACAT) was reduced, as well as total cholesterol content, while an opposite effect was observed at 48 h. Under the same experimental conditions, no differences in secreted apoB and PCSK9 were observed. Since PCSK9 was altered by the treatment, we tested a possible co-regulation between the two genes. The effect of ANGPTL3-siRNA on the expression of genes involved in the de novo lipogenesis was not counteracted by gene silencing of PCSK9. In conclusion, our in vitro study suggests that ANGPTL3 silencing determines lipid accumulation in Huh7 cells by inducing the de novo lipogenesis independently from PCSK9.

Endothelial lipase variant T111I does not alter inhibition by angiopoietin-like proteins

High levels of HDL-C are correlated with a decreased risk of cardiovascular disease. HDL-C levels are modulated in part by the secreted phospholipase, endothelial lipase (EL), which hydrolyzes the phospholipids of HDL and decreases circulating HDL-C concentrations. A 584C/T polymorphism in LIPG, the gene which encodes EL, was first identified in individuals with increased HDL levels. This polymorphism results in a T111I point mutation the EL protein. The association between this variant, HDL levels, and the risk of coronary artery disease (CAD) in humans has been extensively studied, but the findings have been inconsistent. In this study, we took a biochemical approach, investigating how the T111I variant affected EL activity, structure, and stability. Moreover, we tested whether the T111I variant altered the inhibition of phospholipase activity by angiopoietin-like 3 (ANGPTL3) and angiopoietin-like 4 (ANGPTL4), two known EL inhibitors. We found that neither the stability nor enzymatic activity of EL was altered by the T111I variant. Moreover, we found no difference between wild-type and T111I EL in their ability to be inhibited by ANGPTL proteins. These data suggest that any effect this variant may have on HDL-C levels or cardiovascular disease are not mediated through alterations in these functions.

Effects of exercise training on ANGPTL3/8 and ANGPTL4/8 and their associations with cardiometabolic traits

Angiopoietin-like protein (ANGPTL) complexes 3/8 and 4/8 are established inhibitors of LPL and novel therapeutic targets for dyslipidemia. However, the effects of regular exercise on ANGPTL3/8 and ANGPTL4/8 are unknown. We characterized ANGPTL3/8 and ANGPTL4/8 and their relationship with in vivo measurements of lipase activities and cardiometabolic traits before and after a 5-month endurance exercise training intervention in 642 adults from the HERITAGE (HEalth, RIsk factors, exercise Training And GEnetics) Family Study. At baseline, higher levels of both ANGPTL3/8 and ANGPTL4/8 were associated with a worse lipid, lipoprotein, and cardiometabolic profile, with only ANGPTL3/8 associated with postheparin LPL and HL activities. ANGPTL3/8 significantly decreased with exercise training, which corresponded with increases in LPL activity and decreases in HL activity, plasma triglycerides, apoB, visceral fat, and fasting insulin (all P < 5.1 × 10-4). Exercise-induced changes in ANGPTL4/8 were directly correlated to concomitant changes in total cholesterol, LDL-C, apoB, and HDL-triglycerides and inversely related to change in insulin sensitivity index (all P < 7.0 × 10-4). In conclusion, exercise-induced decreases in ANGPTL3/8 and ANGPTL4/8 were related to concomitant improvements in lipase activity, lipid profile, and cardiometabolic risk factors. These findings reveal the ANGPTL3-4-8 model as a potential molecular mechanism contributing to adaptations in lipid metabolism in response to exercise training.

ANGPTL3 deficiency impairs lipoprotein production and produces adaptive changes in hepatic lipid metabolism

Angiopoietin-like protein 3 (ANGPTL3) is a hepatically secreted protein and therapeutic target for reducing plasma triglyceride-rich lipoproteins and low-density lipoprotein (LDL) cholesterol. Although ANGPTL3 modulates the metabolism of circulating lipoproteins, its role in triglyceride-rich lipoprotein assembly and secretion remains unknown. CRISPR-associated protein 9 (CRISPR/Cas9) was used to target ANGPTL3 in HepG2 cells (ANGPTL3-/-) whereupon we observed ∼50% reduction of apolipoprotein B100 (ApoB100) secretion, accompanied by an increase in ApoB100 early presecretory degradation via a predominantly lysosomal mechanism. Despite defective particle secretion in ANGPTL3-/- cells, targeted lipidomic analysis did not reveal neutral lipid accumulation in ANGPTL3-/- cells; rather ANGPTL3-/- cells demonstrated decreased secretion of newly synthesized triglycerides and increased fatty acid oxidation. Furthermore, RNA sequencing demonstrated significantly altered expression of key lipid metabolism genes, including targets of peroxisome proliferator-activated receptor α, consistent with decreased lipid anabolism and increased lipid catabolism. In contrast, CRISPR/Cas9 LDL receptor (LDLR) deletion in ANGPTL3-/- cells did not result in a secretion defect at baseline, but proteasomal inhibition strongly induced compensatory late presecretory degradation of ApoB100 and impaired its secretion. Additionally, these ANGPTL3-/-;LDLR-/- cells rescued the deficient LDL clearance of LDLR-/- cells. In summary, ANGPTL3 deficiency in the presence of functional LDLR leads to the production of fewer lipoprotein particles due to early presecretory defects in particle assembly that are associated with adaptive changes in intrahepatic lipid metabolism. In contrast, when LDLR is absent, ANGPTL3 deficiency is associated with late presecretory regulation of ApoB100 degradation without impaired secretion. Our findings therefore suggest an unanticipated intrahepatic role for ANGPTL3, whose function varies with LDLR status.

Macromolecular Interactions of Lipoprotein Lipase (LPL)

Lipoprotein lipase (LPL) is a critical enzyme in humans that provides fuel to peripheral tissues. LPL hydrolyzes triglycerides from the cores of lipoproteins that are circulating in plasma and interacts with receptors to mediate lipoprotein uptake, thus directing lipid distribution via catalytic and non-catalytic functions. Functional losses in LPL or any of its myriad of regulators alter lipid homeostasis and potentially affect the risk of developing cardiovascular disease-either increasing or decreasing the risk depending on the mutated protein. The extensive LPL regulatory network tunes LPL activity to allocate fatty acids according to the energetic needs of the organism and thus is nutritionally responsive and tissue dependent. Multiple pharmaceuticals in development manipulate or mimic these regulators, demonstrating their translational importance. Another facet of LPL biology is that the oligomeric state of the enzyme is also central to its regulation. Recent structural studies have solidified the idea that LPL is regulated not only by interactions with other binding partners but also by self-associations. Here, we review the complexities of the protein-protein and protein-lipid interactions that govern LPL structure and function.

A novel fully human anti-NT-ANGPTL3 antibody from phage display library exhibits potent ApoB, TG, and LDL-C lowering activities in hyperlipidemia mice

Dyslipidemia is characterized by elevated plasma levels of low-density lipoprotein cholesterol (LDL-C), triglycerides (TG), and TG-rich lipoprotein (TGRLs) in circulation, and is closely associated with the incidence and development of cardiovascular disease. Angiopoietin-like protein 3 (ANGPTL3) deficiency has been identified as a cause of familial combined hypolipidemia in humans, which allows it to be an important therapeutic target for reducing plasma lipids. Here, we report the discovery and characterization of a novel fully human antibody F1519-D95aA against N-terminal ANGPTL3 (NT-ANGPTL3), which potently inhibits NT-ANGPTL3 with a KD as low as 9.21 nM. In hyperlipidemic mice, F1519-D95aA shows higher apolipoprotein B (ApoB) and TG-lowering, and similar LDL-C reducing activity as compared to positive control Evinacumab (56.50% vs 26.01% decrease in serum ApoB levels, 30.84% vs 25.28% decrease in serum TG levels, 23.32% vs 22.52% decrease in serum LDLC levels, relative to vehicle group). Molecular docking and binding energy calculations reveal that the F1519-D95aA-ANGPTL3 complex (10 hydrogen bonds, -65.51 kcal/mol) is more stable than the Evinacumab-ANGPTL3 complex (4 hydrogen bonds, -63.76 kcal/mol). Importantly, F1519-D95aA binds to ANGPTL3 with different residues in ANGPTL3 from Evinacumab, suggesting that F1519-D95aA may be useful for the treatment of patients resistant to Evinacumab. In conclusion, F1519-D95aA is a novel fully human anti-NT-ANGPTL3 antibody with potent plasma ApoB, TG, and LDL-C lowering activities, which can potentially serve as a therapeutic agent for hyperlipidemia and relevant cardiovascular diseases.

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.

New opportunities in the management and treatment of refractory hypercholesterolemia using in vivo CRISPR-mediated genome/base editing

AIMS

Refractory hypercholesterolemia (RH), caused primarily by the loss-of-function mutation of LDL receptor (LDLR) gene seen in HoFH and HeFH patients, remains a major risk factor for atherosclerotic cardiovascular disease (ASCVD). Statin and ezetimibe combination therapy lower circulating LDL by 30% in HoFH patients. PCSK9 mAB, being an LDLR-dependent therapy, is not effective in HoFH, but lowers LDL by 25% in HeFH patients. A maximum reduction of 50% was noted in HoFH patients treated with ANGPTL3 mAB, which was not enough to achieve therapeutic goal of LDL. Therefore, new approaches are warranted to offer hopes to individuals intolerant to higher dose statins and not able to achieve recommended LDL level.

DATA SYNTHESIS

New approaches to lower LDL include gene therapy and gene editing. AAV-based gene therapy has shown encouraging results in animal models. Using CRISPR/Cas9-mediated genome/base editing, gain of function and loss of function have been successfully done in animal models. Recent progress in the refinement of genome/base editing has overcome the issues of off-target mutagenesis with ∼1% mutagenesis in case of PCSK9 and almost no off-target mutagenesis in inactivating ANGPTL3 in animal models showing 50% reduction in cholesterol. Current approaches using CRISPR-Cas9 genome/base editing targeting LDLR-dependent and LDLR-independent pathways are underway.

CONCLUSIONS

The new information on gain of LDLR function and inactivation of ANGPTL3 together with developments in genome/base editing technology to overcome off-target insertion and deletion mutagenesis offer hope to refractory hypercholesterolemic individuals who are at a higher risk of developing ASCVD.

ANGPTL3 (Angiopoietin-Like 3) Preferentially Resides on High-Density Lipoprotein in the Human Circulation, Affecting Its Activity

Background ANGPTL3 (angiopoietin-like protein 3) is an acknowledged crucial regulator of lipid metabolism by virtue of its inhibitory effect on lipoprotein lipase and endothelial lipase. It is currently unknown whether and to which lipoproteins ANGPTL3 is bound and whether the ability of ANGPTL3 to inhibit lipase activity is affected by binding to lipoproteins. Methods and Results Incubation of ultracentrifugation-isolated low-density lipoprotein (LDL) and high-density lipoprotein (HDL) fractions from healthy volunteers with recombinant ANGPTL3 revealed that ANGPTL3 associates with both HDL and LDL particles ex vivo. Plasma from healthy volunteers and a patient deficient in HDL was fractionated by fast protein liquid chromatography, and ANGPTL3 distribution among lipoprotein fractions was measured. In healthy volunteers, ≈75% of lipoprotein-associated ANGPTL3 resides in HDL fractions, whereas ANGPTL3 was largely bound to LDL in the patient deficient in HDL. ANGPTL3 activity was studied by measuring lipolysis and uptake of 3H-trioleate by brown adipocyte T37i cells. Unbound ANGPTL3 did not suppress lipase activity, but when given with HDL or LDL, ANGPTL3 suppressed lipase activity by 21.4±16.4% (P=0.03) and 25.4±8.2% (P=0.006), respectively. Finally, in a subset of the EPIC (European Prospective Investigation into Cancer) Norfolk study, plasma HDL cholesterol and amount of large HDL particles were both positively associated with plasma ANGPTL3 concentrations. Moreover, plasma ANGPTL3 concentrations showed a positive association with incident coronary artery disease (odds ratio, 1.25 [95% CI, 1.01-1.55], P=0.04). Conclusions Although ANGPTL3 preferentially resides on HDL, its activity was highest once bound to LDL particles.

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.

Applications of Genome Editing Technologies in CAD Research and Therapy with a Focus on Atherosclerosis

Cardiovascular diseases, particularly coronary artery disease (CAD), remain the leading cause of death worldwide in recent years, with myocardial infarction (MI) being the most common form of CAD. Atherosclerosis has been highlighted as one of the drivers of CAD, and much research has been carried out to understand and treat this disease. However, there remains much to be better understood and developed in treating this disease. Genome editing technologies have been widely used to establish models of disease as well as to treat various genetic disorders at their root. In this review, we aim to highlight the various ways genome editing technologies can be applied to establish models of atherosclerosis, as well as their therapeutic roles in both atherosclerosis and the clinical implications of CAD.

Endothelial Lipase Variant, T111I, Does Not Alter Inhibition by Angiopoietin-like Proteins

High levels of HDL-C are correlated with a decreased risk of cardiovascular disease. HDL-C levels are modulated in part by the secreted phospholipase, endothelial lipase (EL), which hydrolyzes the phospholipids of HDL and decreases circulating HDL-C concentrations. A 584C/T polymorphism in LIPG, the gene which encodes EL, was first identified in individuals with increased HDL levels. This polymorphism results in a T111I point mutation the EL protein. The association between this variant, HDL levels, and the risk of coronary artery disease (CAD) in humans has been extensively studied, but the findings have been inconsistent. In this study, we took a biochemical approach, investigating how the T111I variant affected EL activity, structure, and stability. Moreover, we tested whether the T111I variant altered the inhibition of phospholipase activity by angiopoietin-like 3 (ANGPTL3) and angiopoietin-like 4 (ANGPTL4), two known EL inhibitors. We found that neither the stability nor enzymatic activity of EL was altered by the T111I variant. Moreover, we found no difference between wild-type and T111I EL in their ability to be inhibited by ANGPTL proteins. These data suggest that any effect this variant may have on HDL-C levels or cardiovascular disease are not mediated through alterations in these functions.

A population pharmacokinetic and pharmacokinetic-pharmacodynamic analysis of vupanorsen from phase I and phase II studies

Vupanorsen (PF-07285557) is a second-generation ligand-conjugated 2'O-methoxyethyl modified antisense oligonucleotide designed to target angiopoietin-like 3 (ANGPTL3) mRNA expressed by the liver, shown to reduce lipids and apolipoproteins in subjects with dyslipidemia. Using pooled data from two phase I studies of participants with elevated triglycerides (Western: n = 48 and Japanese: n = 12), and two phase II studies of patients with hypertriglyceridemia, diabetes, and nonalcoholic fatty liver disease (n = 105), and statin-treated patients with dyslipidemia (n = 286), we developed population pharmacokinetic (PK) and PK/pharmacodynamic (PK/PD) models. Efficacy target values were set a priori to -75%, -60%, and -35% for ANGPTL3, triglyceride (TG), and non-high-density lipoprotein-cholesterol (non-HDL-C), respectively. Covariates evaluated via a full model approach included baseline body weight, age, estimated glomerular filtration rate (eGFR), anti-drug antibody (ADA) status, sex, and race. Vupanorsen population PK was well-characterized by a two-compartment model with first-order absorption and elimination. Apparent clearance (CL/F) for ADA-positive, female, and Asian participants was estimated to be about 62% (relative standard error 12%), 18% (9%), and 30% (20%) lower than ADA-negative, male, and non-Asian participants, respectively. The associations between CL/F and Black race, age, and eGFR were negligible. The developed population PK/PD model was robust to predict the dose-response relationships. The model predicted that ANGPTL3 target reduction of 75% can be sufficiently achieved with a 320-mg monthly dose of vupanorsen, but target values for TG and non-HDL-C were not expected to be achieved at doses up to 320 mg monthly in patients with dyslipidemia.

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).

Elevated angiopoietin-like protein 3 serum levels in diabetic nephropathy patients and its association with renal function and lipid profile

BACKGROUND

Type 2 diabetes mellitus (T2DM) is a highly prevalent disease that has life-threatening consequences like micro and macrovascular complication. Diabetic nephropathy (DN) is one of the common consequences of T2DM which is related to secretory factors like hepatokines. Angiopoietin-Like Protein 3 (ANGPTL3) is a hepatokine that is perturbated in cardiometabolic diseases and experimental studies showed its effect on renal functions and lipid metabolism. For the first time, ANGPTL3 was measured in patients with T2DM and DN in the present study.

METHODS

Serum levels of ANGPTL3, IL-6, and TNF-α were measured in 60 healthy control, 60 T2DM patients, and 61 DN patients.

RESULTS

Serum levels of ANGPTL3 increased in T2DM (252.39 ± 66.01) and DN (284.59 ± 69.27) patients compared to controls (160.22 ± 48.96), and DN patients compared with T2DM patients. Urinary albumin excretion (UAE) was higher in the DN group compared to T2DM and control groups. Moreover, serum levels of IL-6 and TNF-α were elevated in both patient groups compared to controls. Moreover, ANGPTL3 represented a positive correlation with triglycerides, creatinine, and UAE in patients with both T2DM and DN groups and showed an inverse correlation with eGFR in patients with DN. Moreover, this hepatokine had a good potential to differentiate patients from controls, especially, DN patients.

CONCLUSIONS

these findings provide invivo evidence for the relation of ANGPTL3 with renal dysfunction and hypertriglyceridemia in patients with DN which is in line with experimental findings and suggested a potential role for this hepatokine in DN pathogenesis.

Hepatokines, bile acids and ketone bodies are novel Hormones regulating energy homeostasis

Current views show that an impaired balance partly explains the fat accumulation leading to obesity. Fetal malnutrition and early exposure to endocrine-disrupting compounds also contribute to obesity and impaired insulin secretion and/or sensitivity. The liver plays a major role in systemic glucose homeostasis through hepatokines secreted by hepatocytes. Hepatokines influence metabolism through autocrine, paracrine, and endocrine signaling and mediate the crosstalk between the liver, non-hepatic target tissues, and the brain. The liver also synthetizes bile acids (BAs) from cholesterol and secretes them into the bile. After food consumption, BAs mediate the digestion and absorption of fat-soluble vitamins and lipids in the duodenum. In recent studies, BAs act not simply as fat emulsifiers but represent endocrine molecules regulating key metabolic pathways. The liver is also the main site of the production of ketone bodies (KBs). In prolonged fasting, the brain utilizes KBs as an alternative to CHO. In the last few years, the ketogenic diet (KD) became a promising dietary intervention. Studies on subjects undergoing KD show that KBs are important mediators of inflammation and oxidative stress. The present review will focus on the role played by hepatokines, BAs, and KBs in obesity, and diabetes prevention and management and analyze the positive effects of BAs, KD, and hepatokine receptor analogs, which might justify their use as new therapeutic approaches for metabolic and aging-related diseases.

Angiopoietin-like 3: An important protein in regulating lipoprotein levels

ANGPTL3 has emerged as a therapeutic target whose inhibition results in profound reductions of plasma lipids, including atherogenic triglyceride-rich lipoproteins and low-density lipoprotein cholesterol. The identification of ANGPTL3 deficiency as a cause of familial combined hypolipidemia in humans hastened the development of anti-ANGPTL3 therapeutic agents, including evinacumab (a monoclonal antibody inhibiting circulating ANGPTL3), vupanorsen (an antisense oligonucleotide [ASO] targeting hepatic ANGPTL3 mRNA for degradation), and others. Advances have also been made in ANGPTL3 vaccination and gene editing strategies, with the former still in preclinical phases and the latter in preparation for Phase 1 trials. Here, we review the discovery of ANGPTL3 as an important regulator of lipoprotein metabolism, molecular characteristics of the protein, mechanisms by which it regulates plasma lipids, and the clinical development of anti-ANGPTL3 agents. The clinical success of therapies inhibiting ANGPTL3 highlights the importance of this target as a novel approach in treating refractory hypertriglyceridemia and hypercholesterolemia.

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.

Gene transfer and genome editing for familial hypercholesterolemia

Familial hypercholesterolemia (FH) is an autosomal dominant inherited disease characterized by high circulating low-density lipoprotein (LDL) cholesterol. High circulating LDL cholesterol in FH is due to dysfunctional LDL receptors, and is mainly expressed by hepatocytes. Affected patients rapidly develop atherosclerosis, potentially leading to myocardial infarction and death within the third decade of life if left untreated. Here, we introduce the disease pathogenesis and available treatment options. We highlight different possible targets of therapeutic intervention. We then review different gene therapy strategies currently under development, which may become novel therapeutic options in the future, and discuss their advantages and disadvantages. Finally, we briefly outline the potential applications of some of these strategies for the more common acquired hypercholesterolemia disease.

Broadening the Scope of Dyslipidemia Therapy by Targeting APOC3 (Apolipoprotein C3) and ANGPTL3 (Angiopoietin-Like Protein 3)

The positive relationship between increased levels of circulating triglycerides and cardiovascular events has been observed for decades. Driven by genetic cohort studies, inhibitors of APOC3 (apolipoprotein C3) and ANGPTL (angiopoietin-like protein) 3 that reduce circulating triglycerides are poised to enter clinical practice. We will review the biology of how inhibition of these 2 proteins affects circulating lipoproteins as well as the current state of clinical development of monoclonal antibodies, antisense oligonucleotides, and silencing RNAs targeting APOC3 and ANGPTL3.

ANGPTL4 stabilizes atherosclerotic plaques and modulates the phenotypic transition of vascular smooth muscle cells through KLF4 downregulation

Atherosclerosis, the leading cause of death, is a vascular disease of chronic inflammation. We recently showed that angiopoietin-like 4 (ANGPTL4) promotes cardiac repair by suppressing pathological inflammation. Given the fundamental contribution of inflammation to atherosclerosis, we assessed the role of ANGPTL4 in the development of atherosclerosis and determined whether ANGPTL4 regulates atherosclerotic plaque stability. We injected ANGPTL4 protein twice a week into atherosclerotic Apoe-/- mice and analyzed the atherosclerotic lesion size, inflammation, and plaque stability. In atherosclerotic mice, ANGPTL4 reduced atherosclerotic plaque size and vascular inflammation. In the atherosclerotic lesions and fibrous caps, the number of α-SMA(+), SM22α(+), and SM-MHC(+) cells was higher, while the number of CD68(+) and Mac2(+) cells was lower in the ANGPTL4 group. Most importantly, the fibrous cap was significantly thicker in the ANGPTL4 group than in the control group. Smooth muscle cells (SMCs) isolated from atherosclerotic aortas showed significantly increased expression of CD68 and Krüppel-like factor 4 (KLF4), a modulator of the vascular SMC phenotype, along with downregulation of α-SMA, and these changes were attenuated by ANGPTL4 treatment. Furthermore, ANGPTL4 reduced TNFα-induced NADPH oxidase 1 (NOX1), a major source of reactive oxygen species, resulting in the attenuation of KLF4-mediated SMC phenotypic changes. We showed that acute myocardial infarction (AMI) patients with higher levels of ANGPTL4 had fewer vascular events than AMI patients with lower levels of ANGPTL4 (p < 0.05). Our results reveal that ANGPTL4 treatment inhibits atherogenesis and suggest that targeting vascular stability and inflammation may serve as a novel therapeutic strategy to prevent and treat atherosclerosis. Even more importantly, ANGPTL4 treatment inhibited the phenotypic changes of SMCs into macrophage-like cells by downregulating NOX1 activation of KLF4, leading to the formation of more stable plaques.

Physiological roles and regulation of hepatic angiopoietin-like protein 3 in Japanese Black cattle (Bos taurus) during the fattening period

Angiopoietin-like protein 3 (ANGPTL3) is expressed predominantly in the liver and plays a major role in regulating the circulating triglyceride and lipoprotein fraction concentrations by inhibiting lipoprotein lipase (LPL) activity. Given these physiological roles, ANGPTL3 may play an important role in metabolic changes related to fat accumulation during the fattening period in Japanese Black. This study aimed to reveal the physiological roles of hepatic ANGPTL3 in Japanese Black steers (Bos taurus) during the fattening period and investigate the regulatory effects of hepatic ANGPTL3. To investigate the gene expression and protein localization of ANGPTL3, 18 tissue samples were collected from tree male Holstein bull calves aged 7 wk. Biopsied liver tissues and blood samples were collected from 21 Japanese Black steers during the early (T1; 13 mo of age), middle (T2; 20 mo), and late fattening phases (T3; 28 mo). Relative mRNA expression, blood metabolite concentrations, hormone concentrations, growth, and carcass traits were analyzed. To identify the regulatory factors of hepatic ANGPTL3, primary bovine hepatocytes collected by two Holstein calves aged 7 wk were incubated with insulin, palmitate, oleate, propionate, acetate, or beta-hydroxybutyric acid (BHBA). The ANGPTL3 gene was most highly expressed in the liver, with minor expression in the renal cortex, lungs, reticulum, and jejunum in Holstein bull calves. In Japanese Black steers, relative ANGPTL3 mRNA expressions were less as fattening progressed, and blood triglyceride, total cholesterol, and nonesterified fatty acid (NEFA) concentrations increased. Relative ANGPTL8 and Liver X receptor alpha (LXRα) mRNA expressions decreased in late and middle fattening phases, respectively. Furthermore, relative ANGTPL3 mRNA expression was positively correlated with ANGPTL8 (r = 0.650; P < 0.01) and ANGPTL4 (r = 0.540; P < 0.05) in T3 and T1, respectively, and LXRα showed no correlation with ANGPTL3. Relative ANGTPL3 mRNA expression was negatively correlated with total cholesterol (r = -0.434; P < 0.05) and triglyceride (r = -0.645; P < 0.01) concentrations in T3 and T1, respectively; There was no significant correlation between ANGTPL3 and carcass traits. Relative ANGTPL3 mRNA expression in cultured bovine hepatocytes was downregulated in oleate treatment. Together, these findings suggest that ANGPTL3 downregulation in late fattening phases is associated with the changes in lipid metabolism.

The interplay between nonalcoholic fatty liver disease and atherosclerotic cardiovascular disease

Therapeutic approaches that lower circulating low-density lipoprotein (LDL)-cholesterol significantly reduced the burden of cardiovascular disease over the last decades. However, the persistent rise in the obesity epidemic is beginning to reverse this decline. Alongside obesity, the incidence of nonalcoholic fatty liver disease (NAFLD) has substantially increased in the last three decades. Currently, approximately one third of world population is affected by NAFLD. Notably, the presence of NAFLD and particularly its more severe form, nonalcoholic steatohepatitis (NASH), serves as an independent risk factor for atherosclerotic cardiovascular disease (ASCVD), thus, raising interest in the relationship between these two diseases. Importantly, ASCVD is the major cause of death in patients with NASH independent of traditional risk factors. Nevertheless, the pathophysiology linking NAFLD/NASH with ASCVD remains poorly understood. While dyslipidemia is a common risk factor underlying both diseases, therapies that lower circulating LDL-cholesterol are largely ineffective against NASH. While there are no approved pharmacological therapies for NASH, some of the most advanced drug candidates exacerbate atherogenic dyslipidemia, raising concerns regarding their adverse cardiovascular consequences. In this review, we address current gaps in our understanding of the mechanisms linking NAFLD/NASH and ASCVD, explore strategies to simultaneously model these diseases, evaluate emerging biomarkers that may be useful to diagnose the presence of both diseases, and discuss investigational approaches and ongoing clinical trials that potentially target both diseases.

New Therapeutic Approaches to the Treatment of Dyslipidemia 1: ApoC-III and ANGPTL3

Low-density lipoprotein cholesterol (LDL-C)-lowering therapy that increases LDL receptor expression in several ways robustly reduces the risk of atherosclerotic cardiovascular disease (CVD). However, a substantial risk of CVD still remains after intensive LDL-C reduction, which requires new treatment modalities for dyslipidemia and cardiovascular risk management. Triglycerides (TGs) and triglyceride-rich lipoproteins (TRLs) have received attention as indicators of residual cardiovascular risk and as direct causal factors for atherosclerosis and CVDs. Advances in understanding TG and TRL metabolism and their association with clinically evident CVDs have led to the development of novel therapeutic targets, including apolipoprotein C-III (apoC-III) and angiopoietin-like protein 3 (ANGPTL3). Genetic association studies have indicated that both apoC-III and ANGPTL3 play a causal role in the development of atherosclerotic CVD. Both molecules contribute to lipid dysregulation and atherosclerosis primarily by inhibiting lipoprotein lipase; however, recent evidence has shown that novel pathways exist in relation to their lipid-modifying activities. Notably, recent progress in therapeutic approaches, such as monoclonal antibodies or antisense oligonucleotides, has led to several novel therapeutics targeting apoC-III and ANGPTL3. This review summarized the recent updates and discussions related to apoC-III and ANGPTL3 expression.

Genetic Mimicry Analysis Reveals the Specific Lipases Targeted by the ANGPTL3-ANGPTL8 Complex and ANGPTL4

Angiopoietin-like proteins, ANGPTL3, ANGPTL4, and ANGPTL8, are involved in regulating plasma lipids. In vitro and animal-based studies point to LPL and endothelial lipase (EL, LIPG) as key targets of ANGPTLs. To examine the ANGPTL mechanisms for plasma lipid modulation in humans, we pursued a genetic mimicry analysis of enhancing or suppressing variants in the LPL, LIPG, lipase C hepatic type (LIPC), ANGPTL3, ANGPTL4, and ANGPTL8 genes using data on 248 metabolic parameters derived from over 110,000 nonfasted individuals in the UK Biobank and validated in over 13,000 overnight fasted individuals from 11 other European populations. ANGPTL4 suppression was highly concordant with LPL enhancement but not HL or EL, suggesting ANGPTL4 impacts plasma metabolic parameters exclusively via LPL. The LPL-independent effects of ANGPTL3 suppression on plasma metabolic parameters showed a striking inverse resemblance with EL suppression, suggesting ANGPTL3 not only targets LPL but also targets EL. Investigation of the impact of the ANGPTL3-ANGPTL8 complex on plasma metabolite traits via the ANGPTL8 R59W substitution as an instrumental variable showed a much higher concordance between R59W and EL activity than between R59W and LPL activity, suggesting the R59W substitution more strongly affects EL inhibition than LPL inhibition. Meanwhile, when using a rare and deleterious protein-truncating ANGPTL8 variant as an instrumental variable, the ANGPTL3-ANGPTL8 complex was very LPL specific. In conclusion, our analysis provides strong human genetic evidence that the ANGPTL3-ANGPTL8 complex regulates plasma metabolic parameters, which is achieved by impacting LPL and EL. By contrast, ANGPTL4 influences plasma metabolic parameters exclusively via LPL.

Genetic Testing for Hypertriglyceridemia in Academic Lipid Clinics: Implications for Precision Medicine-Brief Report

BACKGROUND

Severe hypertriglyceridemia is often caused by variants in genes of triglyceride metabolism. These variants include rare, heterozygous pathogenic variants (PVs), or multiple common, small-effect single nucleotide polymorphisms that can be quantified using a polygenic risk score (PRS). The role of genetic testing to examine PVs and PRS in predicting risk for pancreatitis and severity of hypertriglyceridemia is unknown.

METHODS

We examined the relationship of PVs and PRSs associated with hypertriglyceridemia with the highest recorded plasma triglyceride level and risk for acute pancreatitis in 363 patients from 3 academic lipid clinics who underwent genetic testing (GBinsight's Dyslipidemia Comprehensive Panel). Categories of hypertriglyceridemia included: normal triglyceride (<200 mg/dL), moderate (200-499 mg/dL), severe (500-999 mg/dL), or very severe (≥1000 mg/dL).

RESULTS

PVs and high PRSs were identified in 37 (10%) and 59 (16%) individuals, respectively. Patients with both had increased risk for very severe hypertriglyceridemia compared with those with neither genetic risk factor. Risk for acute pancreatitis was also increased in individuals with both genetic risk factors (odds ratio, 5.1 [P=0.02] after controlling for age, race, sex, body mass index, and highest triglyceride level), but not in individuals with PV or high PRS alone.

CONCLUSIONS

The presence of both PV and high PRS significantly increased risk for very severe hypertriglyceridemia and acute pancreatitis, whereas PV or PRS alone only modestly increased risk. Genetic testing may help identify patients with hypertriglyceridemia who have the greatest risk for developing pancreatitis and may derive the greatest benefit from novel triglyceride-lowering therapies.

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.

New, Novel Lipid-Lowering Agents for Reducing Cardiovascular Risk: Beyond Statins

Statins are the cornerstone of the prevention and treatment of atherosclerotic cardiovascular disease (ASCVD). However, even under optimal statin therapy, a significant residual ASCVD risk remains. Therefore, there has been an unmet clinical need for novel lipid-lowering agents that can target low-density lipoprotein cholesterol (LDL-C) and other atherogenic particles. During the past decade, several drugs have been developed for the treatment of dyslipidemia. Inclisiran, a small interfering RNA that targets proprotein convertase subtilisin/kexin type 9 (PCSK9), shows comparable effects to that of PCSK9 monoclonal antibodies. Bempedoic acid, an ATP citrate lyase inhibitor, is a valuable treatment option for the patients with statin intolerance. Pemafibrate, the first selective peroxisome proliferator-activated receptor alpha modulator, showed a favorable benefit-risk balance in phase 2 trial, but the large clinical phase 3 trial (PROMINENT) was recently stopped for futility based on a late interim analysis. High dose icosapent ethyl, a modified eicosapentaenoic acid preparation, shows cardiovascular benefits. Evinacumab, an angiopoietin-like 3 (ANGPTL3) monoclonal antibody, reduces plasma LDL-C levels in patients with refractory hypercholesterolemia. Novel antisense oligonucleotides targeting apolipoprotein C3 (apoC3), ANGPTL3, and lipoprotein(a) have significantly attenuated the levels of their target molecules with beneficial effects on associated dyslipidemias. Apolipoprotein A1 (apoA1) is considered as a potential treatment to exploit the athero-protective effects of high-density lipoprotein cholesterol (HDL-C), but solid clinical evidence is necessary. In this review, we discuss the mode of action and clinical outcomes of these novel lipid-lowering agents beyond statins.

Identification and evaluation of a lipid-lowering small compound in preclinical models and in a Phase I trial

Developing non-statin-based small compounds to battle the global epidemic of hyperlipidemia remains challenging. Here, we report the discovery of DC371739, an indole-containing tetrahydroisoquinoline compound with promising lipid-lowering effects, both in vitro and in vivo, and with good tolerability in a Phase I clinical trial (NCT04927221). DC371739 significantly reduced the plasma levels of total cholesterol, low-density lipoprotein cholesterol, and triglycerides simultaneously in several animal models and showed preliminary positive results in the Phase I trial. Mechanistically, DC371739 acts in a distinct manner from other known lipid-lowering reagents. We show that it physically binds HNF-1α, impeding the transcription of both PCSK9 and ANGPTL3, two genes that are known to contribute to hypercholesterolemia and dyslipidemia. Moreover, the distinct mechanism of action of DC371739 allows its combination with atorvastatin treatment to additively improve dyslipidemia, while providing a potential alternative therapeutic strategy for individuals with statin intolerance.

Lessons learned from the evinacumab trials in the treatment of homozygous familial hypercholesterolemia

Homozygous familial hypercholesterolemia (HoFH) is a life-threatening disease characterized by extremely elevated LDL cholesterol (LDL-C) levels which result in premature atherosclerotic cardiovascular disease. As conventional lipid-lowering therapies, which mainly depend on LDL receptors for LDL particle clearance, remain insufficient for reaching the recommended LDL-C levels in HoFH, agents acting independently of LDL receptors, such as ANGPTL3 inhibitors, constitute a promising target. Evinacumab, a monoclonal antibody directed against ANGPTL3, was approved in the USA in 2021 for treating patients with HoFH. Evinacumab has shown an adequate safety profile with strong LDL-lowering efficacy. This review highlights the development path of evinacumab and provides insight on the lessons learned from trials as well as the hurdles facing accessibility.

Effect of Vupanorsen on Non-High-Density Lipoprotein Cholesterol Levels in Statin-Treated Patients With Elevated Cholesterol: TRANSLATE-TIMI 70

Genetic loss-of-function variants in ANGPTL3 are associated with lower levels of plasma lipids. Vupanorsen is a hepatically targeted antisense oligonucleotide that inhibits Angiopoietin-like 3 (ANGPTL3) protein synthesis.

Targeting the vasculature in cardiometabolic disease

Obesity has reached epidemic proportions and is a major contributor to insulin resistance (IR) and type 2 diabetes (T2D). Importantly, IR and T2D substantially increase the risk of cardiovascular (CV) disease. Although there are successful approaches to maintain glycemic control, there continue to be increased CV morbidity and mortality associated with metabolic disease. Therefore, there is an urgent need to understand the cellular and molecular processes that underlie cardiometabolic changes that occur during obesity so that optimal medical therapies can be designed to attenuate or prevent the sequelae of this disease. The vascular endothelium is in constant contact with the circulating milieu; thus, it is not surprising that obesity-driven elevations in lipids, glucose, and proinflammatory mediators induce endothelial dysfunction, vascular inflammation, and vascular remodeling in all segments of the vasculature. As cardiometabolic disease progresses, so do pathological changes in the entire vascular network, which can feed forward to exacerbate disease progression. Recent cellular and molecular data have implicated the vasculature as an initiating and instigating factor in the development of several cardiometabolic diseases. This Review discusses these findings in the context of atherosclerosis, IR and T2D, and heart failure with preserved ejection fraction. In addition, novel strategies to therapeutically target the vasculature to lessen cardiometabolic disease burden are introduced.

Therapeutic RNA-silencing oligonucleotides in metabolic diseases

Recent years have seen unprecedented activity in the development of RNA-silencing oligonucleotide therapeutics for metabolic diseases. Improved oligonucleotide design and optimization of synthetic nucleic acid chemistry, in combination with the development of highly selective and efficient conjugate delivery technology platforms, have established and validated oligonucleotides as a new class of drugs. To date, there are five marketed oligonucleotide therapies, with many more in clinical studies, for both rare and common liver-driven metabolic diseases. Here, we provide an overview of recent developments in the field of oligonucleotide therapeutics in metabolism, review past and current clinical trials, and discuss ongoing challenges and possible future developments.

Causes, clinical findings and therapeutic options in chylomicronemia syndrome, a special form of hypertriglyceridemia

The prevalence of hypertriglyceridemia has been increasing worldwide. Attention is drawn to the fact that the frequency of a special hypertriglyceridemia entity, named chylomicronemia syndrome, is variable among its different forms. The monogenic form, termed familial chylomicronemia syndrome, is rare, occuring in 1 in every 1 million persons. On the other hand, the prevalence of the polygenic form of chylomicronemia syndrome is around 1:600. On the basis of the genetical alterations, other factors, such as obesity, alcohol consumption, uncontrolled diabetes mellitus and certain drugs may significantly contribute to the development of the multifactorial form. In this review, we aimed to highlight the recent findings about the clinical and laboratory features, differential diagnosis, as well as the epidemiology of the monogenic and polygenic forms of chylomicronemias. Regarding the therapy, differentiation between the two types of the chylomicronemia syndrome is essential, as well. Thus, proper treatment options of chylomicronemia and hypertriglyceridemia will be also summarized, emphasizing the newest therapeutic approaches, as novel agents may offer solution for the effective treatment of these conditions.

A New Modality in Dyslipidemia Treatment: Antisense Oligonucleotide Therapy

There are unmet needs for pharmacologic agents beyond current medications, such as statins, to effectively lower low-density lipoprotein cholesterol levels to target goals, especially in patients with very high or extremely high risk. Pharmacological targeting of mRNA represents an emerging, innovative approach with the potential to expand upon current therapies. In RNA-targeted therapeutics, a novel approach is the use of chemically modified oligonucleotides to inhibit the production of target proteins at their sites of gene coding. There are two main classes of RNA-targeted therapeutics: single-stranded antisense oligonucleotides (ASOs) and double-stranded small inhibiting RNAs. ASOs are synthetic molecules with a length of 15–30 nucleotides that are designed specifically to bind to a target mRNA in a sequence-specific manner. Using these agents to inhibit the translation of key regulatory proteins, such as apolipoprotein CIII, apolipoprotein(a), and angiopoietin-like protein 3, has demonstrated treatment efficacy for dyslipidemia. Many cardiovascular outcome trials with ASOs are ongoing. As clinicians, we must carefully monitor the long-term safety and efficacy of this new modality through large clinical trials in the future.

An updated ANGPTL3-4-8 model as a mechanism of triglyceride partitioning between fat and oxidative tissues

In mammals, triglyceride (TG), the main form of lipids for storing and providing energy, is stored in white adipose tissue (WAT) after food intake, while during fasting it is routed to oxidative tissues (heart and skeletal muscle) for energy production, a process referred to as TG partitioning. Lipoprotein lipase (LPL), a rate-limiting enzyme in this fundamental physiological process, hydrolyzes circulating TG to generate free fatty acids that are taken up by peripheral tissues. The postprandial activity of LPL declines in oxidative tissues but rises in WAT, directing TG to WAT; the reverse is true during fasting. However, the molecular mechanism in regulating tissue-specific LPL activity during the fed-fast cycle has not been completely understood. Research on angiopoietin-like (ANGPTL) proteins (A3, A4, and A8) has resulted in an ANGPTL3-4-8 model to explain the TG partitioning between WAT and oxidative tissues. Food intake induces A8 expression in the liver and WAT. Liver A8 activates A3 by forming the A3-8 complex, which is then secreted into the circulation. The A3-8 complex acts in an endocrine manner to inhibit LPL in oxidative tissues. WAT A8 forms the A4-8 complex, which acts locally to block A4's LPL-inhibiting activity. Therefore, the postprandial activity of LPL is low in oxidative tissues but high in WAT, directing circulating TG to WAT. Conversely, during fasting, reduced A8 expression in the liver and WAT disables A3 from inhibiting oxidative-tissue LPL and restores WAT A4's LPL-inhibiting activity, respectively. Thus, the fasting LPL activity is high in oxidative tissues but low in WAT, directing TG to the former. According to the model, we hypothesize that A8 antagonism has the potential to simultaneously reduce TG and increase HDL-cholesterol plasma levels. Future research on A3, A4, and A8 can hopefully provide more insights into human health, disease, and therapeutics.

Positive correlation of serum angiopoietin-like protein 3 levels with metabolic syndrome in patients with coronary artery disease

Objectives:

Angiopoietin-like protein 3 (ANGPTL3) regulates triglyceride metabolism by reversibly inhibiting the lipoprotein lipase activity. Metabolic syndrome (MetS) is an independent risk factor for further cardiovascular disease. This study evaluated the relationship between the fasting serum ANGPTL3 levels and MetS in patients with coronary artery disease (CAD).

Materials and Methods:

Fasting blood samples were obtained from 90 patients with CAD. Serum ANGPTL3 levels were measured using a commercial enzyme-linked immunosorbent assay kit. MetS and its components were defined using the diagnostic criteria of the International Diabetes Federation.

Results:

Fifty-three patients (58.9%) had MetS. The hypertension (P = 0.001), diabetes (P < 0.001), body weight (P = 0.027), body mass index (P = 0.001), waist circumference (P < 0.001), systolic blood pressure (P = 0.001), fasting glucose (P < 0.001), triglycerides (P < 0.001), blood urea nitrogen (P = 0.044), C-reactive protein (P = 0.010), insulin (P = 0.040), homeostasis model assessment of insulin resistance (P = 0.002), and ANGPTL3 level (P = 0.001) of CAD patients who had MetS were higher, and the high-density lipoprotein cholesterol (P = 0.001) and estimated glomerular filtration rate (P = 0.016) were lower. A binary logistic regression analysis of the significant variables also revealed that the ANGPTL3 level (odds ratio: 1.023, 95% confidence interval: 1.008–1.038, P = 0.002) was an independent predictor of MetS in patients with CAD.

Conclusion:

The results of our study indicated that the fasting ANGPTL3 level was positively associated with MetS among patients with CAD.

ANGPTL3 as a Drug Target in Hyperlipidemia and Atherosclerosis

PURPOSE OF REVIEW

Elevated low-density lipoprotein cholesterol (LDL-C) and triglyceride-rich lipoproteins (TRLs) or remnants are important risk factors for the development of atherosclerotic cardiovascular disease (ASCVD). The ongoing challenge of not being able to achieve recommended LDL-C targets despite maximally tolerated lipid-lowering therapy (LLT) has led to the development of novel therapeutic agents including angiopoietin-like 3 (ANGPTL3) inhibitors.

RECENT FINDINGS

ANGPTL3 is a glycoprotein produced by the liver that inhibits lipoprotein lipase and endothelial lipase. Data from genetic and clinical studies have shown that a lower ANGPTL3 level is associated with lower plasma LDL-C, triglyceride (TG), and other lipoproteins. Pharmacological inactivation of ANGPTL3 with the monoclonal antibody, evinacumab, results in a 50% reduction in LDL-C, even in patients with homozygous familial hypercholesterolemia (HoFH). The safe and effective targeted delivery of nucleic acid-based therapies will shape the future of the lipid arena. ANGPTL3 is a novel target in lipoprotein metabolism, targeting not only LDL-C via an LDL-receptor (LDLR) independent mechanism but also TRLs and carries a significant promise for further ASCVD risk reduction.