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Abstract
PURPOSE OF REVIEW Lp(a) is one of the most atherogenic lipoproteins, and significant progress has been made to understand its pathophysiology over the last 20 years. There are now selective therapies in late-stage clinical trials to lower Lp(a). Yet there are many outstanding questions about Lp(a). This review outlines 10 of the most burning questions and tries to answer some of them. RECENT FINDINGS Antisense oligonucleotide (ASO) treatment is currently the most advanced therapy to lower plasma Lp(a) by 60-80%. There are, however, also two small molecule medications in early stage of development with similar efficacy. SUMMARY This review aims to answer important preclinical and clinical questions about the metabolism and physiological role of Lp(a) and also outlines possible therapeutic approaches with nutraceuticals, currently available lipid-lowering therapies and new medications. In addition, ways are illustrated to use Lp(a) as a marker to better predict cardiovascular risk.
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Affiliation(s)
- Karam M Kostner
- Department of Cardiology Mater Hospital and University of Queensland, Brisbane, Australia
| | - Gerhard M Kostner
- Institute of Molecular Biology and Biochemistry, Medical University of Graz, Graz, Austria
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Siddiqui H, Deo N, Rutledge MT, Williams MJ, Redpath GM, McCormick SP. Plasminogen Receptors Promote Lipoprotein(a) Uptake by Enhancing Surface Binding and Facilitating Macropinocytosis. Arterioscler Thromb Vasc Biol 2023; 43:1851-1866. [PMID: 37589135 PMCID: PMC10521804 DOI: 10.1161/atvbaha.123.319344] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2023] [Accepted: 08/02/2023] [Indexed: 08/18/2023]
Abstract
BACKGROUND High levels of Lp(a) (lipoprotein(a)) are associated with multiple forms of cardiovascular disease. Lp(a) consists of an apoB100-containing particle attached to the plasminogen homologue apo(a). The pathways for Lp(a) clearance are not well understood. We previously discovered that the plasminogen receptor PlgRKT (plasminogen receptor with a C-terminal lysine) promoted Lp(a) uptake in liver cells. Here, we aimed to further define the role of PlgRKT and to investigate the role of 2 other plasminogen receptors, annexin A2 and S100A10 (S100 calcium-binding protein A10) in the endocytosis of Lp(a). METHODS Human hepatocellular carcinoma (HepG2) cells and haploid human fibroblast-like (HAP1) cells were used for overexpression and knockout of plasminogen receptors. The uptake of Lp(a), LDL (low-density lipoprotein), apo(a), and endocytic cargos was visualized and quantified by confocal microscopy and Western blotting. RESULTS The uptake of both Lp(a) and apo(a), but not LDL, was significantly increased in HepG2 and HAP1 cells overexpressing PlgRKT, annexin A2, or S100A10. Conversely, Lp(a) and apo(a), but not LDL, uptake was significantly reduced in HAP1 cells in which PlgRKT and S100A10 were knocked out. Surface binding studies in HepG2 cells showed that overexpression of PlgRKT, but not annexin A2 or S100A10, increased Lp(a) and apo(a) plasma membrane binding. Annexin A2 and S100A10, on the other hand, appeared to regulate macropinocytosis with both proteins significantly increasing the uptake of the macropinocytosis marker dextran when overexpressed in HepG2 and HAP1 cells and knockout of S100A10 significantly reducing dextran uptake. Bringing these observations together, we tested the effect of a PI3K (phosphoinositide-3-kinase) inhibitor, known to inhibit macropinocytosis, on Lp(a) uptake. Results showed a concentration-dependent reduction confirming that Lp(a) uptake was indeed mediated by macropinocytosis. CONCLUSIONS These findings uncover a novel pathway for Lp(a) endocytosis involving multiple plasminogen receptors that enhance surface binding and stimulate macropinocytosis of Lp(a). Although the findings were produced in cell culture models that have limitations, they could have clinical relevance since drugs that inhibit macropinocytosis are in clinical use, that is, the PI3K inhibitors for cancer therapy and some antidepressant compounds.
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Affiliation(s)
- Halima Siddiqui
- Department of Biochemistry (H.S., N.D., M.T.R., G.M.I.R., S.P.A.M.), Dunedin School of Medicine, University of Otago, New Zealand
- School of Biomedical Sciences, HeartOtago (H.S., N.D., M.T.R., M.J.A.W., G.M.I.R., S.P.A.M.), Dunedin School of Medicine, University of Otago, New Zealand
| | - Nikita Deo
- Department of Biochemistry (H.S., N.D., M.T.R., G.M.I.R., S.P.A.M.), Dunedin School of Medicine, University of Otago, New Zealand
- School of Biomedical Sciences, HeartOtago (H.S., N.D., M.T.R., M.J.A.W., G.M.I.R., S.P.A.M.), Dunedin School of Medicine, University of Otago, New Zealand
| | - Malcolm T. Rutledge
- Department of Biochemistry (H.S., N.D., M.T.R., G.M.I.R., S.P.A.M.), Dunedin School of Medicine, University of Otago, New Zealand
- School of Biomedical Sciences, HeartOtago (H.S., N.D., M.T.R., M.J.A.W., G.M.I.R., S.P.A.M.), Dunedin School of Medicine, University of Otago, New Zealand
| | - Michael J.A. Williams
- School of Biomedical Sciences, HeartOtago (H.S., N.D., M.T.R., M.J.A.W., G.M.I.R., S.P.A.M.), Dunedin School of Medicine, University of Otago, New Zealand
- Department of Medicine (M.J.A.W.), Dunedin School of Medicine, University of Otago, New Zealand
| | - Gregory M.I. Redpath
- Department of Biochemistry (H.S., N.D., M.T.R., G.M.I.R., S.P.A.M.), Dunedin School of Medicine, University of Otago, New Zealand
- School of Biomedical Sciences, HeartOtago (H.S., N.D., M.T.R., M.J.A.W., G.M.I.R., S.P.A.M.), Dunedin School of Medicine, University of Otago, New Zealand
| | - Sally P.A. McCormick
- Department of Biochemistry (H.S., N.D., M.T.R., G.M.I.R., S.P.A.M.), Dunedin School of Medicine, University of Otago, New Zealand
- School of Biomedical Sciences, HeartOtago (H.S., N.D., M.T.R., M.J.A.W., G.M.I.R., S.P.A.M.), Dunedin School of Medicine, University of Otago, New Zealand
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Koschinsky ML, Stroes ESG, Kronenberg F. Daring to dream: Targeting lipoprotein(a) as a causal and risk-enhancing factor. Pharmacol Res 2023; 194:106843. [PMID: 37406784 DOI: 10.1016/j.phrs.2023.106843] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/07/2023] [Revised: 06/15/2023] [Accepted: 06/27/2023] [Indexed: 07/07/2023]
Abstract
Lipoprotein(a) [Lp(a)], a distinct lipoprotein class, has become a major focus for cardiovascular research. This review is written in light of the recent guideline and consensus statements on Lp(a) and focuses on 1) the causal association between Lp(a) and cardiovascular outcomes, 2) the potential mechanisms by which elevated Lp(a) contributes to cardiovascular diseases, 3) the metabolic insights on the production and clearance of Lp(a) and 4) the current and future therapeutic approaches to lower Lp(a) concentrations. The concentrations of Lp(a) are under strict genetic control. There exists a continuous relationship between the Lp(a) concentrations and risk for various endpoints of atherosclerotic cardiovascular disease (ASCVD). One in five people in the Caucasian population is considered to have increased Lp(a) concentrations; the prevalence of elevated Lp(a) is even higher in black populations. This makes Lp(a) a cardiovascular risk factor of major public health relevance. Besides the association between Lp(a) and myocardial infarction, the relationship with aortic valve stenosis has become a major focus of research during the last decade. Genetic studies provided strong support for a causal association between Lp(a) and cardiovascular outcomes: carriers of genetic variants associated with lifelong increased Lp(a) concentration are significantly more frequent in patients with ASCVD. This has triggered the development of drugs that can specifically lower Lp(a) concentrations: mRNA-targeting therapies such as anti-sense oligonucleotide (ASO) therapies and short interfering RNA (siRNA) therapies have opened new avenues to lower Lp(a) concentrations more than 95%. Ongoing Phase II and III clinical trials of these compounds are discussed in this review.
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Affiliation(s)
- Marlys L Koschinsky
- Robarts Research Institute, Schulich School of Medicine & Dentistry, The University of Western Ontario, London, Ontario, Canada; Department of Physiology & Pharmacology, Schulich School of Medicine & Dentistry, The University of Western Ontario, London, Ontario, Canada
| | - Erik S G Stroes
- Department of Vascular Medicine, Amsterdam Cardiovascular Sciences, Amsterdam UMC, University of Amsterdam, Amsterdam, the Netherlands
| | - Florian Kronenberg
- Institute of Genetic Epidemiology, Medical University of Innsbruck, Innsbruck, Austria.
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Lorey MB, Youssef A, Äikäs L, Borrelli M, Hermansson M, Assini JM, Kemppainen A, Ruhanen H, Ruuth M, Matikainen S, Kovanen PT, Käkelä R, Boffa MB, Koschinsky ML, Öörni K. Lipoprotein(a) induces caspase-1 activation and IL-1 signaling in human macrophages. Front Cardiovasc Med 2023; 10:1130162. [PMID: 37293282 PMCID: PMC10244518 DOI: 10.3389/fcvm.2023.1130162] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2022] [Accepted: 05/02/2023] [Indexed: 06/10/2023] Open
Abstract
Introduction Lipoprotein(a) (Lp(a)) is an LDL-like particle with an additional apolipoprotein (apo)(a) covalently attached. Elevated levels of circulating Lp(a) are a risk factor for atherosclerosis. A proinflammatory role for Lp(a) has been proposed, but its molecular details are incompletely defined. Methods and results To explore the effect of Lp(a) on human macrophages we performed RNA sequencing on THP-1 macrophages treated with Lp(a) or recombinant apo(a), which showed that especially Lp(a) induces potent inflammatory responses. Thus, we stimulated THP-1 macrophages with serum containing various Lp(a) levels to investigate their correlations with cytokines highlighted by the RNAseq, showing significant correlations with caspase-1 activity and secretion of IL-1β and IL-18. We further isolated both Lp(a) and LDL particles from three donors and then compared their atheroinflammatory potentials together with recombinant apo(a) in primary and THP-1 derived macrophages. Compared with LDL, Lp(a) induced a robust and dose-dependent caspase-1 activation and release of IL-1β and IL-18 in both macrophage types. Recombinant apo(a) strongly induced caspase-1 activation and IL-1β release in THP-1 macrophages but yielded weak responses in primary macrophages. Structural analysis of these particles revealed that the Lp(a) proteome was enriched in proteins associated with complement activation and coagulation, and its lipidome was relatively deficient in polyunsaturated fatty acids and had a high n-6/n-3 ratio promoting inflammation. Discussion Our data show that Lp(a) particles induce the expression of inflammatory genes, and Lp(a) and to a lesser extent apo(a) induce caspase-1 activation and IL-1 signaling. Major differences in the molecular profiles between Lp(a) and LDL contribute to Lp(a) being more atheroinflammatory.
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Affiliation(s)
- Martina B. Lorey
- Atherosclerosis Research Laboratory, Wihuri Research Institute, Helsinki, Finland
- Molecular and Integrative Biosciences, Faculty of Biological and Environmental Sciences, University of Helsinki, Helsinki, Finland
| | - Amer Youssef
- Robarts Research Institute, Schulich School of Medicine & Dentistry, The University of Western Ontario, London, ON, Canada
| | - Lauri Äikäs
- Atherosclerosis Research Laboratory, Wihuri Research Institute, Helsinki, Finland
| | - Matthew Borrelli
- Department of Physiology & Pharmacology, Schulich School of Medicine & Dentistry, The University of Western Ontario, London, ON, Canada
| | - Martin Hermansson
- Atherosclerosis Research Laboratory, Wihuri Research Institute, Helsinki, Finland
| | - Julia M. Assini
- Robarts Research Institute, Schulich School of Medicine & Dentistry, The University of Western Ontario, London, ON, Canada
- Department of Biochemistry, Schulich School of Medicine & Dentistry, The University of Western Ontario, London, ON, Canada
| | - Aapeli Kemppainen
- Atherosclerosis Research Laboratory, Wihuri Research Institute, Helsinki, Finland
| | - Hanna Ruhanen
- Molecular and Integrative Biosciences, Faculty of Biological and Environmental Sciences, University of Helsinki, Helsinki, Finland
- Helsinki University Lipidomics Unit (HiLIPID), Helsinki Institute of Life Science (HiLIFE) and Biocenter Finland, Helsinki, Finland
| | - Maija Ruuth
- Atherosclerosis Research Laboratory, Wihuri Research Institute, Helsinki, Finland
| | - Sampsa Matikainen
- Helsinki Rheumatic Disease and Inflammation Research Group, University of Helsinki and Helsinki University Hospital, Helsinki, Finland
| | - Petri T. Kovanen
- Atherosclerosis Research Laboratory, Wihuri Research Institute, Helsinki, Finland
| | - Reijo Käkelä
- Molecular and Integrative Biosciences, Faculty of Biological and Environmental Sciences, University of Helsinki, Helsinki, Finland
- Helsinki University Lipidomics Unit (HiLIPID), Helsinki Institute of Life Science (HiLIFE) and Biocenter Finland, Helsinki, Finland
| | - Michael B. Boffa
- Robarts Research Institute, Schulich School of Medicine & Dentistry, The University of Western Ontario, London, ON, Canada
- Department of Biochemistry, Schulich School of Medicine & Dentistry, The University of Western Ontario, London, ON, Canada
| | - Marlys L. Koschinsky
- Robarts Research Institute, Schulich School of Medicine & Dentistry, The University of Western Ontario, London, ON, Canada
- Department of Physiology & Pharmacology, Schulich School of Medicine & Dentistry, The University of Western Ontario, London, ON, Canada
| | - Katariina Öörni
- Atherosclerosis Research Laboratory, Wihuri Research Institute, Helsinki, Finland
- Molecular and Integrative Biosciences, Faculty of Biological and Environmental Sciences, University of Helsinki, Helsinki, Finland
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Matveyenko A, Pavlyha M, Reyes-Soffer G. Supporting evidence for lipoprotein(a) measurements in clinical practice. Best Pract Res Clin Endocrinol Metab 2023; 37:101746. [PMID: 36828715 PMCID: PMC11014458 DOI: 10.1016/j.beem.2023.101746] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/13/2023]
Abstract
High levels of lipoprotein(a) [Lp(a)] are causal for development of atherosclerotic cardiovascular disease and highly regulated by genetics. Levels are higher in Blacks compared to Whites, and in women compared to men. Lp(a)'s main protein components are apolipoprotein (apo) (a) and apoB100, the latter being the main component of Low-Density Lipoprotein (LDL) particles. Studies have identified Lp(a) to be associated with inflammatory, coagulation and wound healing pathways. Lack of validated and accepted assays to measure Lp(a), risk cutoff values, guidelines for diagnosis, and targeted therapies have added challenges to the field. Scientific efforts are ongoing to address these, including studies evaluating the cardiovascular benefits of decreasing Lp(a) levels with targeted apo(a) lowering treatments. This review will provide a synopsis of evidence-based effects of high Lp(a) on disease presentation, highlight available guidelines and discuss promising therapies in development. We will conclude with current clinical information and future research needs in the field.
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Affiliation(s)
- Anastasiya Matveyenko
- Columbia University College of Physicians and Surgeons, Columbia University Irving Medical Center, 622 West 168th Street, P&S 10-501, New York, NY 10032, USA.
| | - Marianna Pavlyha
- Columbia University College of Physicians and Surgeons, Columbia University Irving Medical Center, 622 West 168th Street, P&S 10-501, New York, NY 10032, USA.
| | - Gissette Reyes-Soffer
- Columbia University College of Physicians and Surgeons, Columbia University Irving Medical Center, 622 West 168th Street, P&S 10-501, New York, NY 10032, USA.
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Matveyenko A, Matienzo N, Ginsberg H, Nandakumar R, Seid H, Ramakrishnan R, Holleran S, Thomas T, Reyes-Soffer G. Relationship of apolipoprotein(a) isoform size with clearance and production of lipoprotein(a) in a diverse cohort. J Lipid Res 2023; 64:100336. [PMID: 36706955 PMCID: PMC10006688 DOI: 10.1016/j.jlr.2023.100336] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2021] [Revised: 01/16/2023] [Accepted: 01/22/2023] [Indexed: 01/26/2023] Open
Abstract
Lipoprotein(a) [Lp(a)] has two main proteins, apoB100 and apo(a). High levels of Lp(a) confer an increased risk for atherosclerotic cardiovascular disease. Most people have two circulating isoforms of apo(a) differing in their molecular mass, determined by the number of Kringle IV Type 2 repeats. Previous studies report a strong inverse relationship between Lp(a) levels and apo(a) isoform sizes. The roles of Lp(a) production and fractional clearance and how ancestry affects this relationship remain incompletely defined. We therefore examined the relationships of apo(a) size with Lp(a) levels and both apo(a) fractional clearance rates (FCR) and production rates (PR) in 32 individuals not on lipid-lowering treatment. We determined plasma Lp(a) levels and apo(a) isoform sizes, and used the relative expression of the two isoforms to calculate a "weighted isoform size" (wIS). Stable isotope studies were performed, using D3-leucine, to determine the apo(a) FCR and PR. As expected, plasma Lp(a) concentrations were inversely correlated with wIS (R2 = 0.27; P = 0.002). The wIS had a modest positive correlation with apo(a) FCR (R2 = 0.10, P = 0.08), and a negative correlation with apo(a) PR (R2 = 0.11; P = 0.06). The relationship between wIS and PR became significant when we controlled for self-reported race and ethnicity (SRRE) (R2 = 0.24, P = 0.03); controlling for SRRE did not affect the relationship between wIS and FCR. Apo(a) wIS plays a role in both FCR and PR; however, adjusting for SRRE strengthens the correlation between wIS and PR, suggesting an effect of ancestry.
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Affiliation(s)
- Anastasiya Matveyenko
- Department of Medicine, Columbia University Vagelos College of Physicians and Surgeons, New York, NY, USA
| | - Nelsa Matienzo
- Department of Medicine, Columbia University Vagelos College of Physicians and Surgeons, New York, NY, USA
| | - Henry Ginsberg
- Department of Medicine, Columbia University Vagelos College of Physicians and Surgeons, New York, NY, USA
| | - Renu Nandakumar
- Irving Institute for Clinical and Translational Research, Columbia University, New York, NY, USA
| | - Heather Seid
- Irving Institute for Clinical and Translational Research, Columbia University, New York, NY, USA
| | - Rajasekhar Ramakrishnan
- Center for Biomathematics, Department of Pediatrics, Columbia University Vagelos College of Physicians and Surgeons, New York, NY, USA
| | - Steve Holleran
- Center for Biomathematics, Department of Pediatrics, Columbia University Vagelos College of Physicians and Surgeons, New York, NY, USA
| | - Tiffany Thomas
- Department of Pathology and Cell Biology, Columbia University Vagelos College of Physicians and Surgeons, New York, NY, USA
| | - Gissette Reyes-Soffer
- Department of Medicine, Columbia University Vagelos College of Physicians and Surgeons, New York, NY, USA.
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Ying Q, Croyal M, Chan DC, Blanchard V, Pang J, Krempf M, Watts GF. Effect of Omega-3 Fatty Acid Supplementation on the Postprandial Metabolism of Apolipoprotein(a) in Familial Hypercholesterolemia. J Atheroscler Thromb 2023; 30:274-286. [PMID: 35676030 PMCID: PMC9981347 DOI: 10.5551/jat.63587] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
AIM Lipoprotein(a) (Lp(a)) is a low-density lipoprotein-like particle containing apolipoprotein(a) (apo(a)) that increases the risk of atherosclerotic cardiovascular disease (ASCVD) in familial hypercholesterolemia (FH). Postprandial redistribution of apo(a) protein from Lp(a) to triglyceride-rich lipoproteins (TRLs) may also increase the atherogenicity of TRL particles. Omega-3 fatty acid (ω3FA) supplementation improves postprandial TRL metabolism in FH subjects. However, its effect on postprandial apo(a) metabolism has yet to be investigated. METHODS We carried out an 8-week open-label, randomized, crossover trial to test the effect of ω3FA supplementation (4 g/day) on postprandial apo(a) responses in FH patients following ingestion of an oral fat load. Postprandial plasma total and TRL-apo(a) concentrations were measured by liquid chromatography with tandem mass spectrometry, and the corresponding areas under the curve (AUCs) (0-10h) were determined using the trapezium rule. RESULTS Compared with no ω3FA treatment, ω3FA supplementation significantly lowered the concentrations of postprandial TRL-apo(a) at 0.5 (-17.9%), 1 (-18.7%), 2 (-32.6%), and 3 h (-19.2%) (P<0.05 for all). Postprandial TRL-apo(a) AUC was significantly reduced with ω3FA by 14.8% (P<0.05). By contrast, ω3FA had no significant effect on the total AUCs of apo(a), apoC-III, and apoE (P>0.05 for all). The decrease in postprandial TRL-apo(a) AUC was significantly associated with changes in the AUC of triglycerides (r=0.600; P<0.01) and apoB-48 (r=0.616; P<0.01). CONCLUSIONS Supplementation with ω3FA reduces postprandial TRL-apo(a) response to a fat meal in FH patients; this novel metabolic effect of ω3FA may have implications on decreasing the risk of ASCVD in patients with FH, especially in those with elevated plasma triglyceride and Lp(a) concentrations. However, the clinical implications of these metabolic findings require further evaluation in outcome or surrogate endpoint trials.
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Affiliation(s)
- Qidi Ying
- Medical School, University of Western Australia, Perth, Western Australia, Australia
| | - Mikaël Croyal
- Nantes Universite, CNRS, INSERM, l’institut du thorax, F-44000 Nantes, France,Nantes Universite, CHU Nantes, INSERM, CNRS, SFR Sante, INSERM UMS 016, CNRS UMS 3556, F-44000 Nantes, France,CRNH-Ouest Mass Spectrometry Core Facility, F-44000 Nantes, France
| | - Dick C Chan
- Medical School, University of Western Australia, Perth, Western Australia, Australia
| | - Valentin Blanchard
- Department of Medicine, Centre for Heart Lung Innovation, Providence Healthcare Research Institute, St. Paul’s Hospital, University of British Columbia, Vancouver, Canada
| | - Jing Pang
- Medical School, University of Western Australia, Perth, Western Australia, Australia
| | | | - Gerald F Watts
- Medical School, University of Western Australia, Perth, Western Australia, Australia,Lipid Disorders Clinic, Department of Cardiology and Internal Medicine, Royal Perth Hospital, Perth, Western Australia, Australia
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Abstract
PURPOSE OF REVIEW This review summarizes our current understanding of the processes of apolipoprotein(a) secretion, assembly of the Lp(a) particle and removal of Lp(a) from the circulation. We also identify existing knowledge gaps that need to be addressed in future studies. RECENT FINDINGS The Lp(a) particle is assembled in two steps: a noncovalent, lysine-dependent interaction of apo(a) with apoB-100 inside hepatocytes, followed by extracellular covalent association between these two molecules to form circulating apo(a).The production rate of Lp(a) is primarily responsible for the observed inverse correlation between apo(a) isoform size and Lp(a) levels, with a contribution of catabolism restricted to larger Lp(a) isoforms.Factors that affect apoB-100 secretion from hepatocytes also affect apo(a) secretion.The identification of key hepatic receptors involved in Lp(a) clearance in vivo remains unclear, with a role for the LDL receptor seemingly restricted to conditions wherein LDL concentrations are low, Lp(a) is highly elevated and LDL receptor number is maximally upregulated. SUMMARY The key role for production rate of Lp(a) [including secretion and assembly of the Lp(a) particle] rather than its catabolic rate suggests that the most fruitful therapies for Lp(a) reduction should focus on approaches that inhibit production of the particle rather than its removal from circulation.
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Affiliation(s)
| | - Marlys L Koschinsky
- Robarts Research Institute
- Department of Physiology & Pharmacology, Schulich School of Medicine & Dentistry, The University of Western Ontario, London, Ontario, Canada
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9
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Chemello K, Chan DC, Lambert G, Watts GF. Recent advances in demystifying the metabolism of lipoprotein(a). Atherosclerosis 2022; 349:82-91. [DOI: 10.1016/j.atherosclerosis.2022.04.002] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/08/2021] [Revised: 03/29/2022] [Accepted: 04/01/2022] [Indexed: 12/24/2022]
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Clark JR, Gemin M, Youssef A, Marcovina SM, Prat A, Seidah NG, Hegele RA, Boffa MB, Koschinsky ML. Sortilin enhances secretion of apolipoprotein(a) through effects on apolipoprotein B secretion and promotes uptake of lipoprotein(a). J Lipid Res 2022; 63:100216. [PMID: 35469919 PMCID: PMC9131257 DOI: 10.1016/j.jlr.2022.100216] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2021] [Revised: 04/06/2022] [Accepted: 04/08/2022] [Indexed: 12/30/2022] Open
Abstract
Elevated plasma lipoprotein(a) (Lp(a)) is an independent, causal risk factor for atherosclerotic cardiovascular disease and calcific aortic valve stenosis. Lp(a) is formed in or on hepatocytes from successive noncovalent and covalent interactions between apo(a) and apoB, although the subcellular location of these interactions and the nature of the apoB-containing particle involved remain unclear. Sortilin, encoded by the SORT1 gene, modulates apoB secretion and LDL clearance. We used a HepG2 cell model to study the secretion kinetics of apo(a) and apoB. Overexpression of sortilin increased apo(a) secretion, while siRNA-mediated knockdown of sortilin expression correspondingly decreased apo(a) secretion. Sortilin binds LDL but not apo(a) or Lp(a), indicating that its effect on apo(a) secretion is likely indirect. Indeed, the effect was dependent on the ability of apo(a) to interact noncovalently with apoB. Overexpression of sortilin enhanced internalization of Lp(a), but not apo(a), by HepG2 cells, although neither sortilin knockdown in these cells or Sort1 deficiency in mice impacted Lp(a) uptake. We found several missense mutations in SORT1 in patients with extremely high Lp(a) levels; sortilin containing some of these mutations was more effective at promoting apo(a) secretion than WT sortilin, though no differences were found with respect to Lp(a) internalization. Our observations suggest that sortilin could play a role in determining plasma Lp(a) levels and corroborate in vivo human kinetic studies which imply that secretion of apo(a) and apoB are coupled, likely within the hepatocyte.
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Affiliation(s)
- Justin R Clark
- Department of Physiology & Pharmacology, Schulich School of Medicine & Dentistry, The University of Western Ontario, London, ON, Canada
| | - Matthew Gemin
- Department of Chemistry & Biochemistry, University of Windsor, Windsor, ON, Canada
| | - Amer Youssef
- Robarts Research Institute, Schulich School of Medicine & Dentistry, The University of Western Ontario, London, ON, Canada
| | | | - Annik Prat
- Institut de Recherches Cliniques de Montreal, Montréal, QC, Canada
| | - Nabil G Seidah
- Institut de Recherches Cliniques de Montreal, Montréal, QC, Canada
| | - Robert A Hegele
- Robarts Research Institute, Schulich School of Medicine & Dentistry, The University of Western Ontario, London, ON, Canada; Department of Biochemistry, Schulich School of Medicine & Dentistry, The University of Western Ontario, London, ON, Canada; Department of Medicine, Schulich School of Medicine & Dentistry, The University of Western Ontario, London, ON, Canada
| | - Michael B Boffa
- Robarts Research Institute, Schulich School of Medicine & Dentistry, The University of Western Ontario, London, ON, Canada; Department of Biochemistry, Schulich School of Medicine & Dentistry, The University of Western Ontario, London, ON, Canada
| | - Marlys L Koschinsky
- Department of Physiology & Pharmacology, Schulich School of Medicine & Dentistry, The University of Western Ontario, London, ON, Canada; Robarts Research Institute, Schulich School of Medicine & Dentistry, The University of Western Ontario, London, ON, Canada.
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