👤 Lionel Ginsberg

Familial chylomicronemia syndrome (FCS) is diagnosed by genetic or nongenetic criteria. To assess responses to treatment of apolipoprotein (apo)C-III, triglycerides, and pancreatitis events in patients with FCS-based diagnostic methods. APPROACH enrolled 66 patients with FCS randomized to volanesorsen or placebo for 12 months. In 50 participants, genetic confirmation of FCS was based on the presence of pathogenic bi-allelic variants in LPL, APOC2, APOA5, GPIHBP1, or LMF1 genes. In 16 participants without a genetic diagnosis, FCS was diagnosed using clinical criteria and postheparin lipoprotein lipase activity ≤20% of normal. Plasma levels of apoC-III, triglycerides and related variables were measured at 3, 6, and 12 months. No significant differences were present in mean apoC-III reductions with volanesorsen at 3, 6, or 12 months in patients with FCS diagnosed either genetically or nongenetically. In contrast, the triglyceride reductions were statistically less robust in patients with genetic diagnosis at each timepoint, with mean (95% CI) percent reduction in triglycerides of -68.7% (-78.7, -58.6) vs -84.0% (-99.4, -68.6), P = .014 at Month 3; -58.2% (-78.1, -38.2) vs -84.5% (-122.4, -46.7), P = .009 at Month 6; and -35.6% (-57.7, -13.4) vs. -69.0% (-105.0, -33.1), P = .005 at Month 12. Patients with a genetic diagnosis had significantly lower response rates for achieved triglycerides <500 mg/dL, <750 mg/dL, <880 mg/dL and <1000 mg/dL than patients with a nongenetic diagnosis. All 5 episodes of acute pancreatitis occurred in patients with a genetic diagnosis. For a similar reduction in apoC-III in response to volanesorsen, triglyceride reduction is attenuated in patients with genetically vs nongenetically diagnosed FCS. Show less

Apolipoprotein B-containing triglyceride-rich lipoproteins (TRLs) -chylomicrons, very low-density lipoproteins (VLDL), their remnants, and intermediate-density lipoproteins (IDL) - are recognised as key contributors to atherosclerotic cardiovascular disease (ASCVD). On a per particle basis, genetic and clinical evidence indicates that TRL/remnants exhibit a greater atherogenic potential than LDL and evidence points to this being mediated by enhanced arterial wall retention of TRLs, the pro-inflammatory actions of their constituent apolipoproteins and cargo of cholesterol and bioactive lipids, and their capacity to induce endothelial dysfunction. Despite the strong association between plasma triglyceride levels and ASCVD, TRL-lowering trials have produced inconsistent, often negative results. The answer to this conundrum, as explored here, likely lies in the complexity of TRL structure, composition and metabolism, and in the dynamic influence that TRLs have on the properties of LDL, the most abundant atherogenic lipoprotein. The substantial heterogeneity in the TRL/remnant/IDL spectrum means that these particles present a wide range of potentially pathogenic factors to the artery wall in the form of major and minor lipids and a variety of surface apolipoproteins. Significant gaps exist in our knowledge: how are TRL remodelled during their lifetime in the bloodstream to become cholesterol-enriched lipoproteins; which are the most relevant TRL subspecies or TRL constituents, that initiate and progress the formation of atherosclerotic lesions; and what are the prime targets for effective intervention. Critical to the design of future triglyceride-lowering prevention trials will be the development of superior biomarkers of TRL/remnant atherogenicity and the development of a precision medicine approach to ASCVD prevention. Show less

Familial chylomicronemia syndrome (FCS) is a rare, recessive monogenic disorder characterized by severely elevated plasma triglyceride (TG) levels due to absent or markedly impaired lipoprotein lipase activity, leading to a greatly increased risk of acute pancreatitis. Naturally occurring very low levels of apoC-III are associated with low TG levels; thus, apoC-III is a target for TG lowering, and therapies have been developed to reduce apoC-III. Strategies to inhibit hepatic apoC-III synthesis include antisense oligonucleotides (ASOs) and small interfering RNAs (siRNAs). In the last decade, technologies have been developed to enhance hepatic delivery of these potential therapeutic agents by conjugation of the ligand triantennary N-acetyl galactosamine to ASO and siRNA for receptor-mediated uptake by hepatocytes, where apoC-III is predominantly expressed. Enhanced delivery of these pharmacological agents to the target tissue has been found to support lower and/or less frequent dosing with consequent lower total systemic exposure. One antisense agent, the ASO olezarsen, is now approved by the US Food and Drug Administration (FDA) as an adjunct to diet to lower triglycerides in adults with FCS, and the other, the siRNA plozasiran, is in late-stage clinical development. Both agents have shown effectiveness in reducing both apoC-III and TG levels across several study populations. Reduced TG, lower rates of acute pancreatitis events, and similar proportions of adverse events in placebo and treated patients were recently demonstrated in placebo-controlled phase 3 trials of patients with FCS treated with olezarsen in Balance and with plozasiran in PALISADE. This review discusses causes and consequences of FCS and the rationale and progress made in developing APOC3 RNA-targeted therapeutics for the treatment of FCS. Show less

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. Show less

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. Show less

In this issue of the JCI, Kanter et al. make a strong case for implicating apolipoprotein C3 (APOC3) as a central player in atherosclerotic cardiovascular disease that is commonly seen in individuals with type 1 diabetes mellitus (T1DM). Kanter and colleagues suggest that insulin deficiency elevates plasma APOC3 as well as atherogenic triglyceride-rich (TG-rich) lipoproteins (TRLs). Using two mouse models of T1DM, the authors investigated APOC3-mediated inhibition of both TG hydrolysis by lipoprotein lipase and hepatic uptake of remnant lipoproteins. They suggest that poorly catabolized lipoproteins, enriched in both APOC3 and APOE content, are particularly atherogenic. Notably, treating both mouse models with an APOC3 antisense oligonucleotide lowered both plasma APOC3 and TRLs, and prevented atherosclerosis. These impactful mouse studies were supported by the initial finding that APOC3 predicted coronary artery disease events in participants of the prospective Coronary Artery Calcification in Type 1 Diabetes study with normal TG levels. Show less

Objective- Apo (apolipoprotein) CIII inhibits lipoprotein lipase (LpL)-mediated lipolysis of VLDL (very-low-density lipoprotein) triglyceride (TG) and decreases hepatic uptake of VLDL remnants. The discovery that 5% of Lancaster Old Order Amish are heterozygous for the APOC3 R19X null mutation provided the opportunity to determine the effects of a naturally occurring reduction in apo CIII levels on the metabolism of atherogenic containing lipoproteins. Approach and Results- We conducted stable isotope studies of VLDL-TG and apoB100 in 5 individuals heterozygous for the null mutation APOC3 R19X (CT) and their unaffected (CC) siblings. Fractional clearance rates and production rates of VLDL-TG and apoB100 in VLDL, IDL (intermediate-density lipoprotein), LDL, apo CIII, and apo CII were determined. Affected (CT) individuals had 49% reduction in plasma apo CIII levels compared with CCs ( P<0.01) and reduced plasma levels of TG (35%, P<0.02), VLDL-TG (45%, P<0.02), and VLDL-apoB100 (36%, P<0.05). These changes were because of higher fractional clearance rates of VLDL-TG and VLDL-apoB100 with no differences in production rates. CTs had higher rates of the conversion of VLDL remnants to LDL compared with CCs. In contrast, rates of direct removal of VLDL remnants did not differ between the groups. As a result, the flux of apoB100 from VLDL to LDL was not reduced, and the plasma levels of LDL-cholesterol and LDL-apoB100 were not lower in the CT group. Apo CIII production rate was lower in CTs compared with CCs, whereas apo CII production rate was not different between the 2 groups. The fractional clearance rates of both apo CIII and apo CII were higher in CTs than CCs. Conclusions- These studies demonstrate that 50% reductions in plasma apo CIII, in otherwise healthy subjects, results in a significantly higher rate of conversion of VLDL to LDL, with little effect on direct hepatic uptake of VLDL. When put in the context of studies demonstrating significant protection from cardiovascular events in individuals with loss of function variants in the APOC3 gene, our results provide strong evidence that therapies which increase the efficiency of conversion of VLDL to LDL, thereby reducing remnant concentrations, should reduce the risk of cardiovascular disease. Show less

Military personnel and athletes exposed to traumatic brain injury may develop chronic traumatic encephalopathy (CTE). Brain pathology in CTE includes intracellular accumulation of abnormally phosphorylated tau proteins (p-tau), the main constituent of neurofibrillary tangles (NFTs). Recently, we found that cholinergic basal forebrain (CBF) neurons within the nucleus basalis of Meynert (nbM), which provide the major cholinergic innervation to the cortex, display an increased number of NFTs across the pathological stages of CTE. However, molecular mechanisms underlying nbM neurodegeneration in the context of CTE pathology remain unknown. Here, we assessed the genetic signature of nbM neurons containing the p-tau pretangle maker pS422 from CTE subjects who came to autopsy and received a neuropathological CTE staging assessment (Stages II, III, and IV) using laser capture microdissection and custom-designed microarray analysis. Quantitative analysis revealed dysregulation of key genes in several gene ontology groups between CTE stages. Specifically, downregulation of the nicotinic cholinergic receptor subunit β-2 gene (CHRNB2), monoaminergic enzymes catechol-O-methyltransferase (COMT) and dopa decarboxylase (DDC), chloride channels CLCN4 and CLCN5, scaffolding protein caveolin 1 (CAV1), cortical development/cytoskeleton element lissencephaly 1 (LIS1), and intracellular signaling cascade member adenylate cyclase 3 (ADCY3) was observed in pS422-immunreactive nbM neurons in CTE patients. By contrast, upregulation of calpain 2 (CAPN2) and microtubule-associated protein 2 (MAP2) transcript levels was found in Stage IV CTE patients. These single-population data in vulnerable neurons indicate alterations in gene expression associated with neurotransmission, signal transduction, the cytoskeleton, cell survival/death signaling, and microtubule dynamics, suggesting novel molecular pathways to target for drug discovery in CTE. Show less

Some cholesteryl ester transfer protein (CETP) inhibitors lower low-density lipoprotein cholesterol (LDL-C) levels without reducing cardiovascular events, suggesting that the clinical benefit of lowering LDL-C may depend on how LDL-C is lowered. To estimate the association between changes in levels of LDL-C (and other lipoproteins) and the risk of cardiovascular events related to variants in the CETP gene, both alone and in combination with variants in the 3-hydroxy-3-methylglutaryl-CoA reductase (HMGCR) gene. Mendelian randomization analyses evaluating the association between CETP and HMGCR scores, changes in lipid and lipoprotein levels, and the risk of cardiovascular events involving 102 837 participants from 14 cohort or case-control studies conducted in North America or the United Kingdom between 1948 and 2012. The associations with cardiovascular events were externally validated in 189 539 participants from 48 studies conducted between 2011 and 2015. Differences in mean high-density lipoprotein cholesterol (HDL-C), LDL-C, and apolipoprotein B (apoB) levels in participants with CETP scores at or above vs below the median. Odds ratio (OR) for major cardiovascular events. The primary analysis included 102 837 participants (mean age, 59.9 years; 58% women) who experienced 13 821 major cardiovascular events. The validation analyses included 189 539 participants (mean age, 58.5 years; 39% women) with 62 240 cases of coronary heart disease (CHD). Considered alone, the CETP score was associated with higher levels of HDL-C, lower LDL-C, concordantly lower apoB, and a corresponding lower risk of major vascular events (OR, 0.946 [95% CI, 0.921-0.972]) that was similar in magnitude to the association between the HMGCR score and risk of major cardiovascular events per unit change in levels of LDL-C (and apoB). When combined with the HMGCR score, the CETP score was associated with the same reduction in LDL-C levels but an attenuated reduction in apoB levels and a corresponding attenuated nonsignificant risk of major cardiovascular events (OR, 0.985 [95% CI, 0.955-1.015]). In external validation analyses, a genetic score consisting of variants with naturally occurring discordance between levels of LDL-C and apoB was associated with a similar risk of CHD per unit change in apoB level (OR, 0.782 [95% CI, 0.720-0.845] vs 0.793 [95% CI, 0.774-0.812]; P = .79 for difference), but a significantly attenuated risk of CHD per unit change in LDL-C level (OR, 0.916 [95% CI, 0.890-0.943] vs 0.831 [95% CI, 0.816-0.847]; P < .001) compared with a genetic score associated with concordant changes in levels of LDL-C and apoB. Combined exposure to variants in the genes that encode the targets of CETP inhibitors and statins was associated with discordant reductions in LDL-C and apoB levels and a corresponding risk of cardiovascular events that was proportional to the attenuated reduction in apoB but significantly less than expected per unit change in LDL-C. The clinical benefit of lowering LDL-C levels may therefore depend on the corresponding reduction in apoB-containing lipoprotein particles. Show less

Lp(a) [lipoprotein (a)] is composed of apoB (apolipoprotein B) and apo(a) [apolipoprotein (a)] and is an independent risk factor for cardiovascular disease and aortic stenosis. In clinical trials, anacetrapib, a CETP (cholesteryl ester transfer protein) inhibitor, causes significant reductions in plasma Lp(a) levels. We conducted an exploratory study to examine the mechanism for Lp(a) lowering by anacetrapib. We enrolled 39 participants in a fixed-sequence, double-blind study of the effects of anacetrapib on the metabolism of apoB and high-density lipoproteins. Twenty-nine patients were randomized to atorvastatin 20 mg/d, plus placebo for 4 weeks, and then atorvastatin plus anacetrapib (100 mg/d) for 8 weeks. The other 10 subjects were randomized to double placebo for 4 weeks followed by placebo plus anacetrapib for 8 weeks. We examined the mechanisms of Lp(a) lowering in a subset of 12 subjects having both Lp(a) levels >20 nmol/L and more than a 15% reduction in Lp(a) by the end of anacetrapib treatment. We performed stable isotope kinetic studies using Anacetrapib reduces Lp(a) levels by decreasing its production. URL: http://www.clinicaltrials.gov. Unique identifier: NCT00990808. Show less

Cholesteryl ester transfer protein (CETP) mediates the transfer of HDL cholesteryl esters for triglyceride (TG) in VLDL/LDL. CETP inhibition, with anacetrapib, increases HDL-cholesterol, reduces LDL-cholesterol, and lowers TG levels. This study describes the mechanisms responsible for TG lowering by examining the kinetics of VLDL-TG, apoC-II, apoC-III, and apoE. Mildly hypercholesterolemic subjects were randomized to either placebo (N = 10) or atorvastatin 20 mg/qd (N = 29) for 4 weeks (period 1) followed by 8 weeks of anacetrapib, 100 mg/qd (period 2). Following each period, subjects underwent stable isotope metabolic studies to determine the fractional catabolic rates (FCRs) and production rates (PRs) of VLDL-TG and plasma apoC-II, apoC-III, and apoE. Anacetrapib reduced the VLDL-TG pool on a statin background due to an increased VLDL-TG FCR (29%; Show less

LC/MS quantification of multiple plasma proteins that differ by several orders of magnitude in concentration from a single sample is challenging. We present a strategy that allows the simultaneous determination of the concentration and turnover kinetics of higher and lower abundant proteins from a single digestion mixture. Our attention was directed at a cluster of proteins that interact to affect the absorption and interorgan lipid trafficking. We demonstrate that apos involved in TG metabolism such as apoC2, C3, E, and A4 (micromolar concentration), and apoB48 and apoA5 (single-digit nanomolar concentration) can be quantified from a single digestion mixture. A high degree of correlation between LC/MS and immunobased measurements for apoC2, C3, E, and B48 was observed. Moreover, apoA5 fractional synthesis rate was measured in humans for the first time. Finally, the method can be directly applied to studies involving nonhuman primates because peptide sequences used in the method are conserved between humans and nonhuman primates. Show less

Congenital myasthenic syndromes (CMS) are rare genetic disorders characterized by impaired neuromuscular transmission. They are caused by mutations in synaptic, presynaptic and post synaptic proteins. Rapsyn is a postsynaptic peripheral membrane protein that anchors the nicotinic acetylcholine receptor to the motor endplate. CMS patients of Iraqi and Persian Jewish origin, carry a common founder mutation in the E box of the RAPSN promoter region (-38A-G) that causes impaired transcriptional activities of the promoter region. We describe a Persian Jewish family with two siblings affected with typical CMS, harboring the common heterozygous (-38A-G) E-box mutation associated with a previously unreported heterozygous p.224 insT causing an insertion of Threonine in the TPR6 domain. To the best of our knowledge, this is the first mutation in the TPR6 domain and might give supportive evidence to the role of this domain in rapsyn self association and consequently co-clustering with AchR in the post synaptic membrane. Show less

To examine the genotype:phenotype association in children compared with their parents. Variations at 4 key gene loci, namely lipoprotein lipase (LPL S447X), hepatic lipase (HL -480C>T), cholesteryl ester transfer protein (CETP TaqIB), and apolipoprotein CIII (APOC3 -455T>C and -482C>T), were examined in children (n = 495) and their parents (n = 353) in the Columbia University BioMarkers Study, 1994 to 1998. The frequencies of the rare alleles of the HL -480C>T and APOC3 -455T>C and -482C>T (but not LPL S447X or CETP TaqIB) were significantly lower in non-Hispanic white participants compared with Hispanics. Overall, genotype effects seen in the adults were weaker in the children, although similar trends were seen. In an examination of the effect of body fat on the genotypic effects in the children, there was significant HL -480C>T:sum of skinfold interaction. All genotypes were associated with clear relationships to plasma lipid levels in adults, but the effects were weaker in their children, unless stressed by body fat. atherosclerosis, cardiovascular disease, child, lipids, genetics. Show less