👤 A T Remaley

Apolipoprotein AV (APOA5) regulates intravascular triglyceride metabolism by binding to the angiopoietin-like protein 3/8 complex (ANGPTL3/8) and suppressing its ability to unfold the native conformation of lipoprotein lipase (LPL). LPL unfolding results in loss of catalytic activity and the detachment of LPL from the surface of cells. An Show less

Familial hypobetalipoproteinemia is a rare autosomal codominant disorder, often caused by a defect in apolipoprotein B (apoB) production required for lipoprotein formation and secretion. Characterization of the lipid profiles of 3 family members exhibiting very low circulating cholesterol levels. Plasma samples from the control sibling and the affected patients were analyzed. Fast protein liquid chromatography and high-performance liquid chromatography were used to characterize the lipid profiles, size, and distribution of lipoprotein particles. Exome sequencing of family members revealed a single-nucleotide deletion in APOB in the 3 affected individuals. The effect of the single-nucleotide deletion on the secretion of apoB was analyzed in Immortalized Human Hepatocyte (IHH) cells. Plasma lipid profiles revealed that the affected individuals have low levels of total cholesterol and low-density lipoprotein cholesterol, with no difference in lipoprotein particle size. DNA sequencing of APOB revealed a single heterozygote deletion of an adenosine in exon 3 at the nucleotide position 1268 in all affected members. This deletion introduces a reading frame shift at glutamine 380, resulting in a stop codon at position 397. The C-terminally truncated apoB, called apoB9, is a variant spanning ∼9% of the full-length protein. Upon expression of apoB9 in IHH cells, the protein did not exit the endoplasmic reticulum/cis-Golgi and, hence, was not secreted into the media. Molecular modeling revealed that apoB9 lacks the βA- and βB-sheets that are required for lipid particle formation, which can explain the absence of apoB9 secretion. Our data suggested that the affected family members have ∼50% to 60% lower apoB levels and are likely protected against the development of atherosclerosis and cardiovascular diseases. Show less

Familial dysbetalipoproteinemia (FDB) is a genetic lipoprotein disorder that can develop in patients homozygous for the APOE2 genotype (ε2/ε2). It is associated with decreased clearance of remnant lipoproteins and increased atherosclerotic cardiovascular disease (ASCVD) risk disproportionate to their level of LDL-C. A goal of this study was to develop a screening test for the ε2/ε2 genotype based on routinely available lipid tests and to determine those at most risk for ASCVD. After assembly of a primary prevention cohort from the UK Biobank (n= 269,895), gene array and exome data was utilized to classify patients as being ε2/ε2 genotype positive or negative. Lipid profiles and APOB levels were extracted and the number of ASCVD events was tabulated during a 15-year follow-up period. Using a newly developed equation for estimating APOB (eAPOB) with lipid panel test results, the ratio of measured APOB to eAPOB was better than any other individual lipid test or ratio for identifying patients with the ε2/ε2 genotype (AUC: APOB/eAPOB: 0.990 (0.986-0.994), nonHDL-C/APOB: 0.961 (0.952-0.970), APOB: 0.955 (0.949-0.961), VLDL/TG: 0.788 (0.771-0.804)). The majority of ε2/ε2 patients could be identified with the APOB/eAPOB ratio even before they expressed the FDB phenotype with elevated TG and nonHDL-C. The PCE or PREVENT risk equations were the most accurate method for identifying higher risk patients (AUC: PREVENT: 0.690 (0.637-0.742), PCE: 0.697 (0.645-0.749)). The APOB/eAPOB ratio can be used to accurately identify the ε2/ε2 genotype and conventional risk equations are the best method for determining those at risk for ASCVD. Show less

Cardiovascular disease is a major cause of human morbidity and mortality. Drug strategies for the prevention of the disease are largely centered on the interaction of low-density lipoprotein receptor (LDLR) with the apolipoprotein B-100 (apoB-100) protein on low-density lipoprotein (LDL). Recently, the structure of apoB-100 on LDL was determined in the absence and presence of LDLR, using cryo-electron microscopy. A remarkable structural feature of apoB-100 is the lack of any significant tertiary structure within the C-terminal two-thirds of the protein (>3000 residues). Instead, apoB-100 forms amphipathic helices and β-sheets on the phospholipid surface of LDL, which envelops its neutral lipid core. The apoB-100 ligand binding domain for LDLR includes multiple points on a circumferential β-belt and on the N terminus. In the course of this study, we also observed several instances of structural heterogeneity in apoB-100. The various conformations may allow apoB-100 to accommodate different size lipoprotein particles and to permit recognition by other apolipoproteins or receptors. Show less

Lipoprotein lipase (LPL) carries out the lipolytic processing of triglyceride-rich lipoproteins (TRL) along the luminal surface of capillaries. LPL activity is regulated by the angiopoietin-like proteins (ANGPTL3, ANGPTL4, ANGPTL8), which control the delivery of TRL-derived lipid nutrients to tissues in a temporal and spatial fashion. This regulation of LPL mediates the partitioning of lipid delivery to adipose tissue and striated muscle according to nutritional status. A complex between ANGPTL3 and ANGPTL8 (ANGPTL3/8) inhibits LPL activity in oxidative tissues, but its mode of action has remained unknown. Here, we used biophysical techniques to define how ANGPTL3/8 and ANGPTL3 interact with LPL and how they drive LPL inactivation. We demonstrate, by mass photometry, that ANGPTL3/8 is a heterotrimer with a 2:1 ANGPTL3:ANGPTL8 stoichiometry and that ANGPTL3 is a homotrimer. Hydrogen-deuterium exchange mass spectrometry (HDX-MS) studies revealed that ANGPTL3/8 and ANGPTL3 use the proximal portion of their N-terminal α-helices to interact with sequences surrounding the catalytic pocket in LPL. That binding event triggers unfolding of LPL's Show less

Despite the growing burden of youth-onset type 2 diabetes (Y-T2D), the long-term risk for fatal/non-fatal cardiovascular disease (CVD) in Y-T2D compared to peers is unknown. The International Childhood Cardiovascular Cohort (i3C) combined-risk z-score is a novel tool for predicting 35-year risk of adult CVD events. In Y-T2D compared to peers (Lean and overweight/obesity [OW/OB]), we estimated predicted CVD events and evaluated the relationship of the i3C z-score with risk-enhancing factors. In a pooled cohort cross-sectional analysis of 1547 adolescents and young adults (AYA) aged 10-25 years [627 Lean, 803 OW/OB, 117 Y-T2D], i3C combined-risk z-scores and estimated hazard ratios (HR) were obtained from the published i3C equation using risk z-scores of systolic blood pressure, body mass index (BMI), smoking history, total cholesterol, and triglycerides. ANCOVA regression models were used: 1) to compare i3C z-scores and HR in AYA with Y-T2D, OW/OB and Lean peers, and 2) to measure associations between i3C estimated HR and risk-enhancing factors including apolipoprotein B (ApoB), total low density lipoprotein particle number (LDL-P), and high sensitivity C reactive protein (hsCRP). Models were adjusted for diagnosis group, race, study center and multiple comparisons with Bonferroni. Y-T2D had the highest i3C z-score (Y-T2D: 1.23 [1.10, 1.36] vs. OW/OB: 0.84 [0.80, 0.88] vs. Lean: -0.11 [-0.15, -0.06], mean[95%CI]) and estimated HR for predicted CVD events (Y-T2D: 4.25 [3.65-4.86] vs. OW/OB: 3.04 [2.85-3.22] vs. Lean: 0.95 [0.74-1.17], HR [95% CI]). Risk-enhancing factors increased the HR for predicted CVD risk by 0.3 for each 10 mg/dL increase in ApoB, 0.1 for each 100 nmol/L increase in LDL-P, and 0.16 for each 2 mg/L increase in hsCRP, all P < 0.001. Y-T2D had an estimated 4.5- and 1.4-times higher risk for predicted CVD events compared to Lean and OW/OB peers, respectively. Lipoprotein and inflammatory risk-enhancing factors may help stratify and guide primary prevention strategies in high-risk AYA. Show less

A key step in primary prevention is the assessment of atherosclerotic cardiovascular disease (ASCVD) risk. Risk enhancer tests are additional tools used to further improve ASCVD risk assessment over conventional risk markers. Our objective was to determine whether estimated small, dense low-density lipoprotein cholesterol (E-sdLDL-C) can improve risk assessment and serve as a new risk enhancer test. We used a prospective cohort analysis of participants in the UK Biobank study with a median (interquartile range) follow-up of 10 (6.7-12.3) years. We included 271 760 individuals who were not on lipid-lowering medication at baseline and did not have incident ASCVD. The primary study outcome was the incidence of all-cause ASCVD. E-sdLDL-C was strongly associated with ASCVD events with a hazard ratio (HR) of 1.23 (95% CI, 1.22-1.24). After multivariable adjustment for age, sex, systolic blood pressure, hypertension, type 2 diabetes, and blood pressure medications, E-sdLDL-C and ApoB (apolipoprotein B) remained the most significant lipid risk factors (HR, 1.18 [95% CI, 1.16-1.19] and 1.17 [95% CI, 1.16-1.18] per SD, respectively). After further adjustment for ApoB, the association between low-density lipoprotein cholesterol (LDL-C) with all-cause ASCVD was completely reversed with an HR of 0.84 (95% CI, 0.81-0.86), but E-sdLDL-C continued to have a significant positive association with an HR of 1.11 (95% CI, 1.08-1.13). When E-sdLDL-C was discordantly higher than either LDL-C or ApoB, the risk for ASCVD was higher (LDL-C, 31% higher; ApoB, 17% higher). When elevated E-sdLDL-C is coupled with other risk enhancer tests, there is a greater risk for developing ASCVD. In a UK Biobank cohort for primary prevention, the risk of all-cause ASCVD was better captured by E-sdLDL-C than LDL-C. It was also more predictive than LDL-C and ApoB when discordant with these 2 measures. E-sdLDL-C, which can be freely and automatically calculated from a standard lipid panel, can potentially improve ASCVD risk assessment without additional laboratory testing. Show less

Chronic hepatitis C virus (HCV) infection is associated with hypolipidemia. HCV eradication may, therefore, result in hyperlipidemia and increase cardiovascular disease (CVD) risk. We investigated the impact of HCV eradication on serum lipid and lipoprotein profiles and CVD risk during and following direct-acting antiviral (DAA) therapy. We retrospectively analysed stored sera and plasma from 60 DAA-naïve patients, genotypes 1-4, treated with 12 weeks of sofosbuvir-velpatasvir. Serum lipids, apolipoproteins (apo), and a systemic inflammatory marker, GlycA, were measured serially beginning early on treatment and off treatment. Additionally, NMR LipoProfile analysis was performed on plasma samples. Expression of genes regulating lipid metabolism was assessed from paired liver biopsies obtained before and on treatment. Linear mixed models were used to examine changes in lipid and inflammatory markers; Framingham and ASCVD CVD risk scores were assessed before and after treatment. Decline in HCV viremia was associated with a rapid, significant increase in TChol, HDL-C, LDL-C, ApoA-1 and ApoB, and GlycA, improvement in ALT, hepatic inflammation, and steatosis but no change in glycemic control (HOMA-IR and HbA1c). Increase in TChol, LDL-C, and ApoB was associated with an increased SREBP1expression. Both ASCVD and Framingham risk scores were significantly increased at week 24 post treatment after adjusting for age (p < 0.0001). Serum lipids and lipoproteins rapidly increase with inhibition of viral replication during DAA therapy, an effect that may be mediated by genes affecting hepatic de novo lipogenesis. Based on lipid changes, HCV eradication may increase CVD risk, but this needs to be investigated prospectively. Show less

The triglyceride (TG) content of low-density lipoprotein (LDL-TG) has been shown to be more predictive of atherosclerotic cardiovascular disease (ASCVD) events than the cholesterol content of LDL (LDL-C). The goal of our study was to develop an equation for estimating LDL-TG ( Using least-square regression analysis, the following Like LDL-C, LDL-TG can also be calculated from the results of the standard lipid panel. Compared to estimated LDL-C, Show less

This National Lipid Association (NLA) Expert Clinical Consensus provides an overview of the physiologic and clinical considerations regarding the role of apolipoprotein B (apoB) measurement to guide clinical care based on the available scientific evidence and expert opinion. ApoB represents the total concentration of atherogenic lipoprotein particles in the circulation and more accurately reflects the atherogenic burden of lipoproteins when compared to low-density lipoprotein cholesterol (LDL-C). ApoB is a validated clinical measurement that augments the information found in a standard lipoprotein lipid panel; therefore, there is clinical value in using apoB in conjunction with a standard lipoprotein lipid profile when assessing risk and managing lipid-lowering therapy (LLT). ApoB has been shown to be superior to LDL-C in risk assessment both before and during treatment with LLT. In individuals, there can be discordance between levels of LDL-C and apoB, as well as LDL-C and non-high-density lipoprotein cholesterol (non-HDL-C), despite high levels of population-wide correlation. When there is discordance between LDL-C and apoB, or LDL-C and non-HDL-C, atherosclerotic cardiovascular disease risk generally aligns better with apoB or non-HDL-C. Additionally, apoB can be used in tandem with standard lipoprotein lipid measurements to diagnose distinct lipoprotein phenotypes. ApoB testing can inform clinical prognosis and care, as well as enable family cascade screening, when an inherited lipoprotein syndrome is identified. The NLA and other organizations will continue to educate clinicians about the role of apoB measurement in improving clinical risk assessment and dyslipidemia management. An urgent need exists to improve access and reimbursement for apoB testing. Show less

The accurate measurement of blood lipids and lipoproteins is crucial for the clinical management of atherosclerotic disease risk. Despite progress in standardization, there are still significant variations in pre-analytical requirements, methods, nomenclature, and reporting work flows. The guidance document aims to improve standardization of clinical lipid testing work flows. It provides recommendations for the components of the lipid panel, fasting requirements, reporting of results, and specific recommendations for non-high-density lipoprotein cholesterol (non-HDL-C), low-density lipoprotein cholesterol (LDL-C), lipoprotein(a) [Lp(a)], apolipoprotein B (apo B), point-of-care lipid testing, and LDL subfraction testing. Lipid panels should always report non-HDL-C and LDL-C calculations if possible. Fasting is not routinely required except in specific cases. Modern equations should be utilized for LDL-C calculation. These equations allow for LDL-C reporting at elevated concentrations of triglycerides and obviate the need for direct measured LDL-C in most cases. Show less

Defects in lipolysis can lead to hypertriglyceridemia, which can trigger acute pancreatitis and is also associated with cardiovascular disease. Decreasing plasma triglycerides (TGs) by activating lipoprotein lipase (LPL) with ApoC2 mimetic peptides is a new treatment strategy for hypertriglyceridemia. We recently described a dual ApoC2 mimetic/ApoC3 antagonist peptide called D6PV that effectively lowered TG in several mouse models but has limitations in terms of drug development. The aim of this study was to create the next generation of ApoC2 mimetic peptides. We employed hydrocarbon staples, as well as select amino acid substitutions, to make short single helical mimetic peptides based on the last helix of ApoC2. Peptides were first tested for their ability to activate LPL and then in hypertriglyceridemia mouse models. All-atom simulations of peptides were performed in a lipid-trilayer model of TG-rich lipoproteins to discern their possible mechanism of action. We designed a single stapled peptide called SP1 (21 residues), and a double stapled (stitched) peptide called SP2 (21 residues) and its N-terminal acylated analogue, SP2a. The hydrocarbon staples increased the amphipathicity of the peptides and their ability to bind lipids without interfering with LPL activation. Indeed, from all-atom simulations, the conformations of SP1 and SP2a are restrained by the staples and maintains the proper orientation of the LPL activation motif, while still allowing their deeper insertion into the lipid-trilayer model. Intraperitoneal injection of stapled peptides (1-5 umoles/kg) into ApoC2-hypomorphic mice or human ApoC3-transgenic resulted in an 80%-90% reduction in plasma TG within 3 h, similar to the much longer D6PV peptide (41 residues). Other modifications (replacement L-Glu20, L-Glu21 with their D-isomers, N-methylation of Gly19, Met2NorLeu and Ala1alpha-methylAla substitutions, N-terminal octanoylation) were introduced into the SP2a peptide. These changes made SP2a highly resistant to proteolysis against trypsin, pepsin, and Proteinase K, while maintaining similar efficacy in lowering plasma TG in mice. We describe a new generation of ApoC2 mimetic peptides based on hydron carbon stapling that are at least equally potent to earlier peptides but are much shorter and resistant to proteolysis and could be further developed into a new therapy for hypertriglyceridemia. Show less

Elevated triglycerides (TGs) are an important risk factor for the development of coronary heart disease (CHD) and in acute pancreatitis. Angiopoietin-like proteins 3 (ANGPTL3) and 4 (ANGPTL4) are critical regulators of TG metabolism that function by inhibiting the activity of lipoprotein lipase (LPL), which is responsible for hydrolyzing triglycerides in lipoproteins into free fatty acids. Interestingly, individuals with loss-of-function mutations in ANGPTL3 and ANGPTL4 have low plasma TG levels, have a reduced risk of CHD, and are otherwise healthy. Consequently, interventions targeting ANGPTL3 and ANGPTL4 have emerged as promising new approaches for reducing elevated TGs. Here, we developed virus-like particle (VLP) based vaccines that target the LPL binding domains of ANGPTL3 and ANGPTL4. ANGPTL3 VLPs and ANGPTL4 VLPs are highly immunogenic in mice and vaccination with ANGPTL3 VLPs, but not ANGPTL4 VLPs, was associated with reduced steady state levels of TGs. Immunization with ANGPTL3 VLPs rapidly cleared circulating TG levels following an oil gavage challenge and enhanced plasma LPL activity. These data indicate that targeting ANGPTL3 by active vaccination is a potential alternative to other ANGPTL3-inhibiting therapies. Show less

Lipodystrophy syndromes cause hypertriglyceridemia that improves with leptin treatment using metreleptin. Mechanisms causing hypertriglyceridemia and improvements after metreleptin are incompletely understood. Determine relationship of circulating lipoprotein lipase (LPL) modulators with hypertriglyceridemia in healthy controls and in patients with lipodystrophy before and after metreleptin. Cross-sectional comparison of patients with lipodystrophy (generalized lipodystrophy n = 3; partial lipodystrophy n = 11) vs age/sex-matched healthy controls (n = 28), and longitudinal analyses in patients before and after 2 weeks and 6 months of metreleptin. The study was carried out at the National Institutes of Health, Bethesda, Maryland. Outcomes were LPL stimulators apolipoprotein (apo) C-II and apoA-V and inhibitors apoC-III and angiopoietin-like proteins (ANGPTLs) 3, 4, and 8; ex vivo activation of LPL by plasma. Patients with lipodystrophy were hypertriglyceridemic and had higher levels of all LPL stimulators and inhibitors vs controls except for ANGPTL4, with >300-fold higher ANGPTL8, 4-fold higher apoC-III, 3.5-fold higher apoC-II, 1.9-fold higher apoA-V, 1.6-fold higher ANGPTL3 ( Elevations in LPL inhibitors apoC-III and ANGPTL8 may contribute to hypertriglyceridemia in lipodystrophy, and may mediate reductions in circulating and hepatic triglycerides after metreleptin. These therefore are strong candidates for therapies to lower triglycerides in these patients. Show less

Among many causes of hypertriglyceridemia (HTG), familial chylomicronemia syndrome (FCS) is a rare monogenic disorder that manifests as severe HTG and acute pancreatitis. Among the known causal genes for FCS, mutations in We present the challenging care of a 43-year-old man with FCS with apoC-II deficiency and the results of two types of TPE and of investigational TG-lowering biologic therapies. The patient's lipid profile was consistent with FCS. A novel homozygous variant was identified in Our case demonstrates the importance of delineating and defining the underlying etiology of a rare disorder to optimize therapy and to minimize unfavorable outcomes. Show less

The high-speed supernatant (100,000 g, 1 h) obtained after centrifuging a suspension of Legionella micdadei that had been freeze-thawed and sonicated contained (i) considerable acid phosphatase activity when assayed using 4-methylumbelliferyl phosphate (MUP) as the substrate, and a factor that blocked superoxide anion production by human neutrophils stimulated with f-Met-Leu-Phe. Chromatography of the extract on a hydroxylapatite column resolved two acids phosphatases (designated ACP1 and ACP2). Subsequent chromatography of ACP2 on a Sephadex G-150 column revealed coincident elution of phosphatase activity and neutrophil blocking activity. When heated at 45 degrees C for various periods of time, the phosphatase activity of the acid phosphatase preparation was lost at the same rate as the ability of the preparation to block superoxide anion production by neutrophils. Furthermore, preincubation of neutrophils and acid phosphatase together in the presence of a heteropolymolybdate complex that inhibits the phosphatase eliminated the effect of the L. micdadei phosphatase on neutrophil superoxide anion production. ACP2 had the following properties: pH optimum, 6.0; Km for MUP, 3.8 mM; isoelectric point, 4.5; substrate specificity, MUP greater than ADP greater than phosphoenolpyruvate greater than phosphothreonine greater than phosphoserine greater than phosphotyrosine; molecular weight (estimated by sucrose density gradient centrifugation and gel filtration chromatography), 71,000-86,000. These results indicate that a cell-associated phosphatase may play a role in the virulence of L. micdadei. Show less