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Brosolo G, Da Porto A, Marcante S, Picci A, Capilupi F, Capilupi P, Bulfone L, Vacca A, Bertin N, Vivarelli C, Comand J, Catena C, Sechi LA. Lipoprotein(a): Just an Innocent Bystander in Arterial Hypertension? Int J Mol Sci 2023; 24:13363. [PMID: 37686169 PMCID: PMC10487946 DOI: 10.3390/ijms241713363] [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: 08/07/2023] [Revised: 08/25/2023] [Accepted: 08/25/2023] [Indexed: 09/10/2023] Open
Abstract
Elevated plasma lipoprotein(a) [Lp(a)] is a relatively common and highly heritable trait conferring individuals time-dependent risk of developing atherosclerotic cardiovascular disease (CVD). Following its first description, Lp(a) triggered enormous scientific interest in the late 1980s, subsequently dampened in the mid-1990s by controversial findings of some prospective studies. It was only in the last decade that a large body of evidence has provided strong arguments for a causal and independent association between elevated Lp(a) levels and CVD, causing renewed interest in this lipoprotein as an emerging risk factor with a likely contribution to cardiovascular residual risk. Accordingly, the 2022 consensus statement of the European Atherosclerosis Society has suggested inclusion of Lp(a) measurement in global risk estimation. The development of highly effective Lp(a)-lowering drugs (e.g., antisense oligonucleotides and small interfering RNA, both blocking LPA gene expression) which are still under assessment in phase 3 trials, will provide a unique opportunity to reduce "residual cardiovascular risk" in high-risk populations, including patients with arterial hypertension. The current evidence in support of a specific role of Lp(a) in hypertension is somehow controversial and this narrative review aims to overview the general mechanisms relating Lp(a) to blood pressure regulation and hypertension-related cardiovascular and renal damage.
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Affiliation(s)
- Gabriele Brosolo
- Department of Medicine, University of Udine, 33100 Udine, Italy; (A.D.P.); (S.M.); (A.P.); (F.C.); (P.C.); (L.B.); (A.V.); (N.B.); (C.V.); (J.C.); (C.C.)
- European Hypertension Excellence Center, Clinica Medica, University of Udine, 33100 Udine, Italy
| | - Andrea Da Porto
- Department of Medicine, University of Udine, 33100 Udine, Italy; (A.D.P.); (S.M.); (A.P.); (F.C.); (P.C.); (L.B.); (A.V.); (N.B.); (C.V.); (J.C.); (C.C.)
- Diabetes and Metabolism Unit, Clinica Medica, University of Udine, 33100 Udine, Italy
| | - Stefano Marcante
- Department of Medicine, University of Udine, 33100 Udine, Italy; (A.D.P.); (S.M.); (A.P.); (F.C.); (P.C.); (L.B.); (A.V.); (N.B.); (C.V.); (J.C.); (C.C.)
- European Hypertension Excellence Center, Clinica Medica, University of Udine, 33100 Udine, Italy
| | - Alessandro Picci
- Department of Medicine, University of Udine, 33100 Udine, Italy; (A.D.P.); (S.M.); (A.P.); (F.C.); (P.C.); (L.B.); (A.V.); (N.B.); (C.V.); (J.C.); (C.C.)
- European Hypertension Excellence Center, Clinica Medica, University of Udine, 33100 Udine, Italy
| | - Filippo Capilupi
- Department of Medicine, University of Udine, 33100 Udine, Italy; (A.D.P.); (S.M.); (A.P.); (F.C.); (P.C.); (L.B.); (A.V.); (N.B.); (C.V.); (J.C.); (C.C.)
- European Hypertension Excellence Center, Clinica Medica, University of Udine, 33100 Udine, Italy
| | - Patrizio Capilupi
- Department of Medicine, University of Udine, 33100 Udine, Italy; (A.D.P.); (S.M.); (A.P.); (F.C.); (P.C.); (L.B.); (A.V.); (N.B.); (C.V.); (J.C.); (C.C.)
- European Hypertension Excellence Center, Clinica Medica, University of Udine, 33100 Udine, Italy
| | - Luca Bulfone
- Department of Medicine, University of Udine, 33100 Udine, Italy; (A.D.P.); (S.M.); (A.P.); (F.C.); (P.C.); (L.B.); (A.V.); (N.B.); (C.V.); (J.C.); (C.C.)
- European Hypertension Excellence Center, Clinica Medica, University of Udine, 33100 Udine, Italy
| | - Antonio Vacca
- Department of Medicine, University of Udine, 33100 Udine, Italy; (A.D.P.); (S.M.); (A.P.); (F.C.); (P.C.); (L.B.); (A.V.); (N.B.); (C.V.); (J.C.); (C.C.)
- European Hypertension Excellence Center, Clinica Medica, University of Udine, 33100 Udine, Italy
| | - Nicole Bertin
- Department of Medicine, University of Udine, 33100 Udine, Italy; (A.D.P.); (S.M.); (A.P.); (F.C.); (P.C.); (L.B.); (A.V.); (N.B.); (C.V.); (J.C.); (C.C.)
- Thrombosis and Hemostasis Unit, Clinica Medica, University of Udine, 33100 Udine, Italy
| | - Cinzia Vivarelli
- Department of Medicine, University of Udine, 33100 Udine, Italy; (A.D.P.); (S.M.); (A.P.); (F.C.); (P.C.); (L.B.); (A.V.); (N.B.); (C.V.); (J.C.); (C.C.)
| | - Jacopo Comand
- Department of Medicine, University of Udine, 33100 Udine, Italy; (A.D.P.); (S.M.); (A.P.); (F.C.); (P.C.); (L.B.); (A.V.); (N.B.); (C.V.); (J.C.); (C.C.)
- European Hypertension Excellence Center, Clinica Medica, University of Udine, 33100 Udine, Italy
| | - Cristiana Catena
- Department of Medicine, University of Udine, 33100 Udine, Italy; (A.D.P.); (S.M.); (A.P.); (F.C.); (P.C.); (L.B.); (A.V.); (N.B.); (C.V.); (J.C.); (C.C.)
- European Hypertension Excellence Center, Clinica Medica, University of Udine, 33100 Udine, Italy
| | - Leonardo A. Sechi
- Department of Medicine, University of Udine, 33100 Udine, Italy; (A.D.P.); (S.M.); (A.P.); (F.C.); (P.C.); (L.B.); (A.V.); (N.B.); (C.V.); (J.C.); (C.C.)
- European Hypertension Excellence Center, Clinica Medica, University of Udine, 33100 Udine, Italy
- Diabetes and Metabolism Unit, Clinica Medica, University of Udine, 33100 Udine, Italy
- Thrombosis and Hemostasis Unit, Clinica Medica, University of Udine, 33100 Udine, Italy
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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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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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Lipoprotein(a) beyond the kringle IV repeat polymorphism: The complexity of genetic variation in the LPA gene. Atherosclerosis 2022; 349:17-35. [PMID: 35606073 PMCID: PMC7613587 DOI: 10.1016/j.atherosclerosis.2022.04.003] [Citation(s) in RCA: 59] [Impact Index Per Article: 29.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/04/2021] [Revised: 02/23/2022] [Accepted: 04/01/2022] [Indexed: 12/24/2022]
Abstract
High lipoprotein(a) [Lp(a)] concentrations are one of the most important genetically determined risk factors for cardiovascular disease. Lp(a) concentrations are an enigmatic trait largely controlled by one single gene (LPA) that contains a complex interplay of several genetic elements with many surprising effects discussed in this review. A hypervariable coding copy number variation (the kringle IV type-2 repeat, KIV-2) generates >40 apolipoprotein(a) protein isoforms and determines the median Lp(a) concentrations. Carriers of small isoforms with up to 22 kringle IV domains have median Lp(a) concentrations up to 5 times higher than those with large isoforms (>22 kringle IV domains). The effect of the apo(a) isoforms are, however, modified by many functional single nucleotide polymorphisms (SNPs) distributed over the complete range of allele frequencies (<0.1% to >20%) with very pronounced effects on Lp(a) concentrations. A complex interaction is present between the apo (a) isoforms and LPA SNPs, with isoforms partially masking the effect of functional SNPs and, vice versa, SNPs lowering the Lp(a) concentrations of affected isoforms. This picture is further complicated by SNP-SNP interactions, a poorly understood role of other polymorphisms such as short tandem repeats and linkage structures that are poorly captured by common R2 values. A further layer of complexity derives from recent findings that several functional SNPs are located in the KIV-2 repeat and are thus not accessible to conventional sequencing and genotyping technologies. A critical impact of the ancestry on correlation structures and baseline Lp(a) values becomes increasingly evident. This review provides a comprehensive overview on the complex genetic architecture of the Lp(a) concentrations in plasma, a field that has made tremendous progress with the introduction of new technologies. Understanding the genetics of Lp(a) might be a key to many mysteries of Lp(a) and booster new ideas on the metabolism of Lp(a) and possible interventional targets.
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Korneva VA, Kuznetsova TY, Julius U. Modern Approaches to Lower Lipoprotein(a) Concentrations and Consequences for Cardiovascular Diseases. Biomedicines 2021; 9:biomedicines9091271. [PMID: 34572458 PMCID: PMC8469722 DOI: 10.3390/biomedicines9091271] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2021] [Revised: 09/09/2021] [Accepted: 09/15/2021] [Indexed: 12/11/2022] Open
Abstract
Lipoprotein(a) (Lp(a)) is a low density lipoprotein particle that is associated with poor cardiovascular prognosis due to pro-atherogenic, pro-thrombotic, pro-inflammatory and pro-oxidative properties. Traditional lipid-lowering therapy does not provide a sufficient Lp(a) reduction. For PCSK9 inhibitors a small reduction of Lp(a) levels could be shown, which was associated with a reduction in cardiovascular events, independently of the effect on LDL cholesterol. Another option is inclisiran, for which no outcome data are available yet. Lipoprotein apheresis acutely and in the long run decreases Lp(a) levels and effectively improves cardiovascular prognosis in high-risk patients who cannot be satisfactorily treated with drugs. New drugs inhibiting the synthesis of apolipoprotein(a) (an antisense oligonucleotide (Pelacarsen) and two siRNA drugs) are studied. Unlike LDL-cholesterol, for Lp(a) no target value has been defined up to now. This overview presents data of modern capabilities of cardiovascular risk reduction by lowering Lp(a) level.
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Affiliation(s)
- Victoria A. Korneva
- Department of Faculty Therapy, Petrozavodsk State University, Lenin Ave. 33, 185000 Petrozavodsk, Russia;
- Correspondence:
| | | | - Ulrich Julius
- Lipidology and Lipoprotein Apheresis Center, Department of Internal Medicine III, University Hospital Carl Gustav Carus, Technische Universität Dresden, Fetscherstr. 74, 01307 Dresden, Germany;
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Blanchard V, Chemello K, Hollstein T, Hong-Fong CC, Schumann F, Grenkowitz T, Nativel B, Coassin S, Croyal M, Kassner U, Lamina C, Steinhagen-Thiessen E, Lambert G. The size of apolipoprotein (a) is an independent determinant of the reduction in lipoprotein (a) induced by PCSK9 inhibitors. Cardiovasc Res 2021; 118:2103-2111. [PMID: 34314498 DOI: 10.1093/cvr/cvab247] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/28/2021] [Accepted: 07/24/2021] [Indexed: 12/14/2022] Open
Abstract
AIMS Lipoprotein (a) [Lp(a)] is a lipoprotein species causatively associated with atherosclerosis. Unlike statins, PCSK9 inhibitors (PCSK9i) reduce Lp(a), but this reduction is highly variable. Levels of Lp(a) are chiefly governed by the size of its signature protein, apolipoprotein (a) [apo(a)]. Whether this parameter determines some of the reduction in Lp(a) induced by PCSK9i remains unknown. We aimed to investigate if the Lp(a) lowering efficacy of PCSK9i is modulated by the size of apo(a), which is genetically determined by the variable number of KIV domains present on that protein. METHODS AND RESULTS The levels of Lp(a) and the size of apo(a) were assessed in plasma samples from 268 patients before and after treatment with PCSK9i. Patients were recruited at the Outpatient Lipid Clinic of the Charité Hospital (Berlin) between 2015 and 2020. They were hypercholesterolemic at very high CVD risk with LDL-cholesterol levels above therapeutic targets despite maximally tolerated lipid-lowering therapy. Patients received either Alirocumab (75 or 150 mg) or Evolocumab (140 mg) every 2 weeks. Apo(a), apoB100, and apoE concentrations as well as apoE major isoforms were determined by liquid chromatography high-resolution mass spectrometry. Apo(a) isoforms sizes were determined by Western Blot. PCSK9i sharply reduced LDL-cholesterol (-57%), apoB100 (-47%) and Lp(a) (-36%). There was a positive correlation between the size of apo(a) and the relative reduction in Lp(a) induced by PCSK9i (r = 0.363, p = 0.0001). The strength of this association remained unaltered after adjustment for baseline Lp(a) levels and all other potential confounding factors. In patients with two detectable apo(a) isoforms, there was also a positive correlation between the size of apo(a) and the reduction in Lp(a), separately for the smaller (r = 0.350, p = 0.0001) and larger (r = 0.324, p = 0.0003) isoforms. The relative contribution of the larger isoform to the total concentration of apo(a) was reduced from 29% to 15% (p < 0.0001). CONCLUSIONS The size of apo(a) is an independent determinant of the response to PCSK9i. Each additional kringle domain is associated with a 3% additional reduction in Lp(a). This explains in part the variable efficacy of PCSK9i and allows to identify patients who will benefit most from these therapies in terms of Lp(a) lowering. TRANSLATIONAL PERSPECTIVE Unlike statins, PCSK9 inhibitors reduce the circulating levels of the highly atherogenic Lipoprotein (a). The underlying mechanism remains a matter of considerable debate. The size of apo(a), the signature protein of Lp(a), is extremely variable (300 to more than 800 kDa) and depends on its number of kringle domains. We now show that each increase in apo(a) size by one kringle domain is associated with a 3% additional reduction in Lp(a) following PCSK9i treatment and that apo(a) size polymorphism is an independent predictor of the reduction in Lp(a) induced by these drugs. In an era of personalized medicine, this allows to identify patients who will benefit most from PCSK9i in terms of Lp(a) lowering.
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Affiliation(s)
- Valentin Blanchard
- Université de La Réunion, INSERM UMR 1188 DéTROI, Sainte-Clotilde, France.,Centre for Heart & Lung Innovation, St. Paul's Hospital, Vancouver, Canada; Department of Medicine, UBC, Vancouver, Canada
| | - Kévin Chemello
- Université de La Réunion, INSERM UMR 1188 DéTROI, Sainte-Clotilde, France
| | - Tim Hollstein
- Department of Endocrinology, Campus Virchow-Klinikum, Charité Universitätsmedizin, Berlin, Germany.,Division of Endocrinology, Diabetology and Clinical Nutrition, Department of Internal Medicine 1, University of Kiel, Kiel, Germany
| | | | - Friederike Schumann
- Department of Endocrinology, Campus Virchow-Klinikum, Charité Universitätsmedizin, Berlin, Germany
| | - Thomas Grenkowitz
- Department of Endocrinology, Campus Virchow-Klinikum, Charité Universitätsmedizin, Berlin, Germany
| | - Brice Nativel
- Université de La Réunion, INSERM UMR 1188 DéTROI, Sainte-Clotilde, France
| | - Stefan Coassin
- Institute of Genetic Epidemiology, Department of Genetics and Pharmacology, Medical University of Innsbrück, Innsbrück, Austria
| | - Mikaël Croyal
- NUN, INRA, CHU Nantes, UMR 1280, PhAN, IMAD, CRNH-O, Nantes, France
| | - Ursula Kassner
- Department of Endocrinology, Campus Virchow-Klinikum, Charité Universitätsmedizin, Berlin, Germany
| | - Claudia Lamina
- Institute of Genetic Epidemiology, Department of Genetics and Pharmacology, Medical University of Innsbrück, Innsbrück, Austria
| | | | - Gilles Lambert
- Université de La Réunion, INSERM UMR 1188 DéTROI, Sainte-Clotilde, France
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Rhainds D, Brodeur MR, Tardif JC. Lipoprotein (a): When to Measure and How to Treat? Curr Atheroscler Rep 2021; 23:51. [PMID: 34235598 DOI: 10.1007/s11883-021-00951-2] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/03/2021] [Indexed: 12/11/2022]
Abstract
PURPOSE OF REVIEW The purpose of this article is to review current evidence for lipoprotein (a) (Lp(a)) as a risk factor for multiple cardiovascular (CV) disease phenotypes, provide a rationale for Lp(a) lowering to reduce CV risk, identify therapies that lower Lp(a) levels that are available clinically and under investigation, and discuss future directions. RECENT FINDINGS Mendelian randomization and epidemiological studies have shown that elevated Lp(a) is an independent and causal risk factor for atherosclerosis and major CV events. Lp(a) is also associated with non-atherosclerotic endpoints such as venous thromboembolism and calcific aortic valve disease. It contributes to residual CV risk in patients receiving standard-of-care LDL-lowering therapy. Plasma Lp(a) levels present a skewed distribution towards higher values and vary widely between individuals and according to ethnic background due to genetic variants in the LPA gene, but remain relatively constant throughout a person's life. Thus, elevated Lp(a) (≥50 mg/dL) is a prevalent condition affecting >20% of the population but is still underdiagnosed. Treatment guidelines have begun to advocate measurement of Lp(a) to identify patients with very high levels that have a family history of premature CVD or elevated Lp(a). Lipoprotein apheresis (LA) efficiently lowers Lp(a) and was recently associated with a reduction of incident CV events. Statins have neutral or detrimental effects on Lp(a), while PCSK9 inhibitors significantly reduce its level by up to 30%. Specific lowering of Lp(a) with antisense oligonucleotides (ASO) shows good safety and strong efficacy with up to 90% reductions. The ongoing CV outcomes study Lp(a)HORIZON will provide a first answer as to whether selective Lp(a) lowering with ASO reduces the risk of major CV events. Given the recently established association between Lp(a) level and CV risk, guidelines now recommend Lp(a) measurement in specific clinical conditions. Accordingly, Lp(a) is a current target for drug development to reduce CV risk in patients with elevated levels, and lowering Lp(a) with ASO represents a promising avenue.
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Affiliation(s)
- David Rhainds
- Montreal Heart Institute Research Center, 5000 Belanger Street, Montréal, Canada
| | - Mathieu R Brodeur
- Montreal Heart Institute Research Center, 5000 Belanger Street, Montréal, Canada
| | - Jean-Claude Tardif
- Montreal Heart Institute Research Center, 5000 Belanger Street, Montréal, Canada. .,Faculty of Medicine, Université de Montréal, Montréal, Canada.
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Vavuranakis MA, Jones SR, Cardoso R, Gerstenblith G, Leucker TM. The role of Lipoprotein(a) in cardiovascular disease: Current concepts and future perspectives. Hellenic J Cardiol 2020; 61:398-403. [PMID: 33039574 DOI: 10.1016/j.hjc.2020.09.016] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2020] [Revised: 09/15/2020] [Accepted: 09/24/2020] [Indexed: 12/24/2022] Open
Abstract
High lipoprotein(a) [Lp(a)] levels are associated with the development of atherosclerotic cardiovascular disease (ASCVD) and with calcific aortic valve stenosis (CAVS) both observationally and causally from human genetic studies. The mechanisms are not well characterized but likely involve its role as a carrier of oxidized phospholipids (OxPLs), which are known to be increased in pro-inflammatory states, to induce pro-inflammatory changes in monocytes leading to plaque instability, and to impair vascular endothelial cell function, a driver of acute and recurrent ischemic events. In addition, Lp(a) itself has prothrombotic activity. Current lipid-lowering strategies do not sufficiently lower Lp(a) serum levels. Lp(a)-specific-lowering drugs, targeting apolipoprotein(a) synthesis, lower Lp(a) by up to 90% and are being evaluated in ongoing clinical outcome trials. This review summarizes the current knowledge on the associations of Lp(a) with ASCVD and CAVS, the current role of Lp(a) assessment in the clinical setting, and emerging Lp(a)-specific-lowering therapies.
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Affiliation(s)
- Michael A Vavuranakis
- Division of Cardiology, Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, MD, USA.
| | - Steven R Jones
- Division of Cardiology, Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Rhanderson Cardoso
- Division of Cardiology, Brigham and Women's Hospital, Harvard Medical School, Boston, MA, USA
| | - Gary Gerstenblith
- Division of Cardiology, Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Thorsten M Leucker
- Division of Cardiology, Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, MD, USA
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Tomova VD, Alexandrova ML, Atanasova MA, Tzekova ML, Rashev TR, Ahmad S. Plasma lipoprotein(a) concentration as an independent predictor of hemodynamic progression of aortic valve stenosis. Mol Cell Biochem 2020; 472:199-207. [PMID: 32577944 DOI: 10.1007/s11010-020-03797-5] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2019] [Accepted: 06/14/2020] [Indexed: 10/24/2022]
Abstract
Calcific aortic valve disease (CAVD) is a common cardiovascular disorder of high social significance. This study aimed to identify independent predictors of hemodynamic progression of CAVD. The relationship between some risk factors, including the rs10455872 polymorphism in the intron 25 of the lipoprotein(a) [Lp(a)] coding region and the plasma Lp(a) concentration, and CAVD severity were prospectively examined in 114 patients. Age (p = 0.023), smoking (p = 0.038), lack of obesity (p = 0.005), triglyceride levels (p = 0.039), and plasma Lp(a) (p < 0.0001) levels were found to be significant determinants of stenosis progression. The rs10455872 polymorphism; however, was not found to be a significant factor for neither the stenosis severity (p = 0.773) nor for plasma Lp(a) levels (p = 0.617). We established a highly significant Lp(a) cut-off concentration (21.2 mg/dL) distinguishing the aortic valve calcification without stenosis from the significant stenosis. Plasma Lp(a) concentration was the only independent predictor of disease progression (p < 0.0001). Moreover, patients with plasma levels of Lp(a) ≥ 21.2 mg/dL were 55 times more likely to develop aortic valve stenosis. We conclude that Lp(a) concentration may prove valuable for more reliable identification of patients at risk of accelerated CAVD development. Future studies are desirable to determine whether plasma Lp(a) levels could be used as a potential biomarker for aortic stenosis progression.
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Affiliation(s)
- Vesela D Tomova
- Department of Internal Diseases, University Hospital "St. Marina" - Pleven, Medical University - Pleven, 5800, Pleven, Bulgaria.
| | | | | | - Maria L Tzekova
- Second Clinic of Cardiology, University Hospital, "Dr. G. Stranski" - Pleven, Medical University - Pleven, Pleven, Bulgaria
| | - Tihomir R Rashev
- Department of Anatomy, Histology, Cytology and Biology, Medical University - Pleven, Pleven, Bulgaria
| | - Sarfraz Ahmad
- AdventHealth Medical Center, 2501 N. Orange Ave., Suite 786, Orlando, FL, 32804, USA.
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Morgan BM, Brown AN, Deo N, Harrop TWR, Taiaroa G, Mace PD, Wilbanks SM, Merriman TR, Williams MJA, McCormick SPA. Nonsynonymous SNPs in LPA homologous to plasminogen deficiency mutants represent novel null apo(a) alleles. J Lipid Res 2019; 61:432-444. [PMID: 31806727 DOI: 10.1194/jlr.m094540] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2019] [Revised: 11/18/2019] [Indexed: 12/20/2022] Open
Abstract
Plasma lipoprotein (a) [Lp(a)] levels are largely determined by variation in the LPA gene, which codes for apo(a). Genome-wide association studies (GWASs) have identified nonsynonymous variants in LPA that associate with low Lp(a) levels, although their effect on apo(a) function is unknown. We investigated two such variants, R990Q and R1771C, which were present in four null Lp(a) individuals, for structural and functional effects. Sequence alignments showed the R990 and R1771 residues to be highly conserved and homologous to each other and to residues associated with plasminogen deficiency. Structural modeling showed both residues to make several polar contacts with neighboring residues that would be ablated on substitution. Recombinant expression of the WT and R1771C apo(a) in liver and kidney cells showed an abundance of an immature form for both apo(a) proteins. A mature form of apo(a) was only seen with the WT protein. Imaging of the recombinant apo(a) proteins in conjunction with markers of the secretory pathway indicated a poor transit of R1771C into the Golgi. Furthermore, the R1771C mutant displayed a glycosylation pattern consistent with ER, but not Golgi, glycosylation. We conclude that R1771 and the equivalent R990 residue facilitate correct folding of the apo(a) kringle structure and mutations at these positions prevent the proper folding required for full maturation and secretion. To our knowledge, this is the first example of nonsynonymous variants in LPA being causative of a null Lp(a) phenotype.
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Affiliation(s)
- Benjamin M Morgan
- Department of Biochemistry, School of Biomedical Sciences University of Otago, Dunedin, New Zealand
| | - Aimee N Brown
- Department of Biochemistry, School of Biomedical Sciences University of Otago, Dunedin, New Zealand
| | - Nikita Deo
- Department of Biochemistry, School of Biomedical Sciences University of Otago, Dunedin, New Zealand.,Maurice Wilkins Centre for Molecular Biodiscovery, Auckland, New Zealand
| | - Tom W R Harrop
- Department of Biochemistry, School of Biomedical Sciences University of Otago, Dunedin, New Zealand
| | - George Taiaroa
- Department of Biochemistry, School of Biomedical Sciences University of Otago, Dunedin, New Zealand
| | - Peter D Mace
- Department of Biochemistry, School of Biomedical Sciences University of Otago, Dunedin, New Zealand.,Maurice Wilkins Centre for Molecular Biodiscovery, Auckland, New Zealand
| | - Sigurd M Wilbanks
- Department of Biochemistry, School of Biomedical Sciences University of Otago, Dunedin, New Zealand
| | - Tony R Merriman
- Department of Biochemistry, School of Biomedical Sciences University of Otago, Dunedin, New Zealand.,Maurice Wilkins Centre for Molecular Biodiscovery, Auckland, New Zealand
| | - Michael J A Williams
- Department of Medicine, Dunedin School of Medicine, University of Otago, Dunedin, New Zealand
| | - Sally P A McCormick
- Department of Biochemistry, School of Biomedical Sciences University of Otago, Dunedin, New Zealand .,Maurice Wilkins Centre for Molecular Biodiscovery, Auckland, New Zealand
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11
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Ma L, Chan DC, Ooi EMM, Marcovina SM, Barrett PHR, Watts GF. Apolipoprotein(a) Kinetics in Statin-Treated Patients With Elevated Plasma Lipoprotein(a) Concentration. J Clin Endocrinol Metab 2019; 104:6247-6255. [PMID: 31393573 DOI: 10.1210/jc.2019-01382] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/19/2019] [Accepted: 08/02/2019] [Indexed: 02/08/2023]
Abstract
BACKGROUND Lipoprotein(a) [Lp(a)] is a low-density lipoprotein‒like particle containing apolipoprotein(a) [apo(a)]. Patients with elevated Lp(a), even when treated with statins, are at increased risk of cardiovascular disease. We investigated the kinetic basis for elevated Lp(a) in these patients. OBJECTIVES Apo(a) production rate (PR) and fractional catabolic rate (FCR) were compared between statin-treated patients with and without elevated Lp(a). METHODS The kinetics of apo(a) were investigated in 14 patients with elevated Lp(a) and 15 patients with normal Lp(a) levels matched for age, sex, and body mass index using stable isotope techniques and compartmental modeling. All 29 patients were on background statin treatment. Plasma apo(a) concentration was measured using liquid chromatography-mass spectrometry. RESULTS The plasma concentration and PR of apo(a) were significantly higher in patients with elevated Lp(a) than in patients with normal Lp(a) concentration (all P < 0.01). The FCR of apo(a) was not significantly different between the groups. In univariate analysis, plasma concentration of apo(a) was significantly associated with apo(a) PR in both patient groups (r = 0.699 and r = 0.949, respectively; all P < 0.01). There was no significant association between plasma apo(a) concentration and FCR in either of the groups (r = 0.160 and r = -0.137, respectively). CONCLUSION Elevated plasma Lp(a) concentration is a consequence of increased hepatic production of Lp(a) particles in these patients. Our findings provide a kinetic rationale for the use of therapies that target the synthesis of apo(a) and production of Lp(a) particles in patients with elevated Lp(a).
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Affiliation(s)
- Louis Ma
- School of Biomedical Sciences, Faculty of Health and Medicine, University of Western Australia, Perth, Western Australia, Australia
- School of Medicine, Faculty of Health and Medicine, University of Western Australia, Perth, Western Australia, Australia
| | - Dick C Chan
- School of Biomedical Sciences, Faculty of Health and Medicine, University of Western Australia, Perth, Western Australia, Australia
- School of Medicine, Faculty of Health and Medicine, University of Western Australia, Perth, Western Australia, Australia
| | - Esther M M Ooi
- School of Biomedical Sciences, Faculty of Health and Medicine, University of Western Australia, Perth, Western Australia, Australia
| | - Santica M Marcovina
- Northwest Lipid Metabolism and Diabetes Research Laboratories, Division of Metabolism, Endocrinology, and Nutrition, Department of Medicine, University of Washington, Seattle, Washington
| | - P Hugh R Barrett
- Faculty of Medicine and Health, University of New England, Armidale, New South Wales, Australia
| | - Gerald F Watts
- School of Medicine, Faculty of Health and Medicine, University of Western Australia, Perth, Western Australia, Australia
- Lipid Disorders Clinic, Department of Cardiology, Royal Perth Hospital, Perth, Western Australia, Australia
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12
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Yahya R, Berk K, Verhoeven A, Bos S, van der Zee L, Touw J, Erhart G, Kronenberg F, Timman R, Sijbrands E, Roeters van Lennep J, Mulder M. Statin treatment increases lipoprotein(a) levels in subjects with low molecular weight apolipoprotein(a) phenotype. Atherosclerosis 2019; 289:201-205. [PMID: 31327478 DOI: 10.1016/j.atherosclerosis.2019.07.001] [Citation(s) in RCA: 36] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/26/2018] [Revised: 05/20/2019] [Accepted: 07/02/2019] [Indexed: 10/26/2022]
Abstract
BACKGROUND AND AIMS We aimed to evaluate the effect of statin treatment initiation on lipoprotein(a) [Lp(a)] levels in patients with dyslipidemia, and the interactions with the apolipoprotein(a) [apo(a)] phenotype, LPA single nucleotide polymorphisms (SNPs) and change in LDL cholesterol. METHODS The study population consisted of patients with dyslipidemia, predominantly familial hypercholesterolemia, who first initiated statin treatment (initiation group; n = 39) or were already on stable statin treatment for at least 4 months (control group; n = 42). Plasma Lp(a) levels were determined with a particle-enhanced immunoturbidimetric assay before and at least 2 months after start of statin treatment in individuals of the initiation group, and at two time points with an interval of at least 2 months in the control group. High and low molecular weight (HMW and LMW, respectively) apo(a) phenotype was determined by immunoblotting, and the common LPA SNPs rs10455872, rs3798220 and rs41272110 by Taqman assay. RESULTS Plasma Lp(a) levels did not increase significantly in the initiation group (median 20.5 (IQR 10.9-80.7) to 23.3 (10.8-71.8) mg/dL; p = 0.09) nor in the control group (30.9 (IQR 9.2-147.0) to 31.7 (IQR 10.9-164.0) mg/dL; p = 0.61). In patients with the LMW apo(a) phenotype, Lp(a) levels increased significantly from 66.4 (IQR 23.5-148.3) to 97.4 (IQR 24.9-160.4) mg/dL (p = 0.026) in the initiation group, but not in the control group and not in patients characterized by the HMW apo(a) phenotype. Interactions with common LPA SNPs and change in LDL cholesterol were not significant. CONCLUSIONS Statins affect Lp(a) levels differently in patients with dyslipidemia depending on the apo(a) phenotype. Statins increase Lp(a) levels exclusively in patients with the LMW apo(a) phenotype.
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Affiliation(s)
- Reyhana Yahya
- Department of Internal Medicine, division of Vascular Medicine and Pharmacology, Division of Medical Psychology and Psychotherapy, Erasmus MC, Erasmus University Medical Center, Rotterdam, Netherlands
| | - Kirsten Berk
- Department of Internal Medicine, division of Vascular Medicine and Pharmacology, Division of Medical Psychology and Psychotherapy, Erasmus MC, Erasmus University Medical Center, Rotterdam, Netherlands; Department of Dietetics and Division of Medical Psychology and Psychotherapy, Erasmus MC, Erasmus University Medical Center, Rotterdam, Netherlands
| | - Adrie Verhoeven
- Department of Internal Medicine, division of Vascular Medicine and Pharmacology, Division of Medical Psychology and Psychotherapy, Erasmus MC, Erasmus University Medical Center, Rotterdam, Netherlands
| | - Sven Bos
- Department of Internal Medicine, division of Vascular Medicine and Pharmacology, Division of Medical Psychology and Psychotherapy, Erasmus MC, Erasmus University Medical Center, Rotterdam, Netherlands
| | - Leonie van der Zee
- Department of Internal Medicine, division of Vascular Medicine and Pharmacology, Division of Medical Psychology and Psychotherapy, Erasmus MC, Erasmus University Medical Center, Rotterdam, Netherlands
| | - Jeanette Touw
- Department of Internal Medicine, division of Vascular Medicine and Pharmacology, Division of Medical Psychology and Psychotherapy, Erasmus MC, Erasmus University Medical Center, Rotterdam, Netherlands
| | - Gertraud Erhart
- Division of Genetic Epidemiology, Department of Medical Genetics, Molecular and Clinical Pharmacology, Medical University of Innsbruck, Innsbruck, Austria
| | - Florian Kronenberg
- Division of Genetic Epidemiology, Department of Medical Genetics, Molecular and Clinical Pharmacology, Medical University of Innsbruck, Innsbruck, Austria
| | - Reinier Timman
- Department of Psychiatry, Division of Medical Psychology and Psychotherapy, Erasmus MC, Erasmus University Medical Center, Rotterdam, Netherlands
| | - Eric Sijbrands
- Department of Internal Medicine, division of Vascular Medicine and Pharmacology, Division of Medical Psychology and Psychotherapy, Erasmus MC, Erasmus University Medical Center, Rotterdam, Netherlands
| | - Jeanine Roeters van Lennep
- Department of Internal Medicine, division of Vascular Medicine and Pharmacology, Division of Medical Psychology and Psychotherapy, Erasmus MC, Erasmus University Medical Center, Rotterdam, Netherlands
| | - Monique Mulder
- Department of Internal Medicine, division of Vascular Medicine and Pharmacology, Division of Medical Psychology and Psychotherapy, Erasmus MC, Erasmus University Medical Center, Rotterdam, Netherlands.
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13
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Ma L, Chan DC, Ooi EMM, Barrett PHR, Watts GF. Fractional turnover of apolipoprotein(a) and apolipoprotein B-100 within plasma lipoprotein(a) particles in statin-treated patients with elevated and normal Lp(a) concentration. Metabolism 2019; 96:8-11. [PMID: 30995439 DOI: 10.1016/j.metabol.2019.04.010] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/15/2019] [Revised: 04/08/2019] [Accepted: 04/10/2019] [Indexed: 12/31/2022]
Abstract
CONTEXT Lipoprotein(a) [Lp(a)] is a highly atherogenic lipoprotein characterized by apolipoprotein(a) [apo(a)] covalently bounded to apoB-100 (apoB). However, the metabolism of apo(a) and apoB within plasma Lp(a) particles in patients on statins remains unclear. METHODS The kinetics of Lp(a)-apo(a) and Lp(a)-apoB were determined in 20 patients with elevated Lp(a) (≥0.8 g/L; n = 10) and normal Lp(a) (≤0.3 g/L; n = 10) using stable isotope techniques and compartmental modeling. Plasma apo(a) concentration was measured using liquid chromatography-mass spectrometry. All patients were on statin therapy and were studied in the fasting state. RESULTS The fractional catabolic rate (FCR) of Lp(a)-apo(a) was not significantly different from that of Lp(a)-apoB in statin-treated patients with elevated or normal Lp(a) (P > 0.05 in both). Lp(a)-apo(a) FCR was significantly correlated with Lp(a)-apoB in patients with elevated and normal Lp(a) concentrations (r = 0.970 and r = 0.979, respectively; all P < 0.001) with Lin's concordance test showing substantial agreement between the FCRs of Lp(a)-apo(a) and Lp(a)-apoB in patients with elevated and normal Lp(a) concentrations (rc = 0.978 and rc = 0.966, respectively). CONCLUSION Our data indicate that the apo(a) and apoB proteins within Lp(a) particles have similar FCR and are therefore tightly coupled as an Lp(a) holoparticle in statin-treated patients with elevated and normal Lp(a) concentrations.
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Affiliation(s)
- Louis Ma
- School of Biomedical Sciences, University of Western Australia, Perth, Australia; School of Medicine, University of Western Australia, Perth, Australia
| | - Dick C Chan
- School of Biomedical Sciences, University of Western Australia, Perth, Australia; School of Medicine, University of Western Australia, Perth, Australia
| | - Esther M M Ooi
- School of Biomedical Sciences, University of Western Australia, Perth, Australia
| | - P Hugh R Barrett
- Faculty of Medicine and Health, University of New England, Armidale, Australia
| | - Gerald F Watts
- School of Medicine, University of Western Australia, Perth, Australia; Lipid Disorders Clinic, Department of Cardiology, Royal Perth Hospital, Australia.
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14
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McCormick SPA, Schneider WJ. Lipoprotein(a) catabolism: a case of multiple receptors. Pathology 2018; 51:155-164. [PMID: 30595508 DOI: 10.1016/j.pathol.2018.11.003] [Citation(s) in RCA: 64] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2018] [Revised: 10/31/2018] [Accepted: 11/01/2018] [Indexed: 01/09/2023]
Abstract
Lipoprotein(a) [Lp(a)] is an apolipoprotein B (apoB)-containing plasma lipoprotein similar in structure to low-density lipoprotein (LDL). Lp(a) is more complex than LDL due to the presence of apolipoprotein(a) [apo(a)], a large glycoprotein sharing extensive homology with plasminogen, which confers some unique properties onto Lp(a) particles. ApoB and apo(a) are essential for the assembly and catabolism of Lp(a); however, other proteins associated with the particle may modify its metabolism. Lp(a) specifically carries a cargo of oxidised phospholipids (OxPL) bound to apo(a) which stimulates many proinflammatory pathways in cells of the arterial wall, a key property underlying its pathogenicity and association with cardiovascular disease (CVD). While the liver and kidney are the major tissues implicated in Lp(a) clearance, the pathways for Lp(a) uptake appear to be complex and are still under investigation. Biochemical studies have revealed an exceptional array of receptors that associate with Lp(a) either via its apoB, apo(a), or OxPL components. These receptors fall into five main categories, namely 'classical' lipoprotein receptors, toll-like and scavenger receptors, lectins, and plasminogen receptors. The roles of these receptors have largely been dissected by genetic manipulation in cells or mice, although their relative physiological importance for removal of Lp(a) from the circulation remains unclear. The LPA gene encoding apo(a) has an overwhelming effect on Lp(a) levels which precludes any clear associations between potential Lp(a) receptor genes and Lp(a) levels in population studies. Targeted approaches and the selection of unique Lp(a) phenotypes within populations has nevertheless allowed for some associations to be made. Few of the proposed Lp(a) receptors can specifically be manipulated with current drugs and, as such, it is not currently clear whether any of these receptors could provide relevant targets for therapeutic manipulation of Lp(a) levels. This review summarises the current status of knowledge about receptor-mediated pathways for Lp(a) catabolism.
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Affiliation(s)
- Sally P A McCormick
- Department of Biochemistry, School of Biomedical Sciences, University of Otago, Dunedin, New Zealand.
| | - Wolfgang J Schneider
- Department of Medical Biochemistry, Max F. Perutz Laboratories, Medical University of Vienna, Vienna, Austria
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15
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Mathieu P, Arsenault BJ, Boulanger MC, Bossé Y, Koschinsky ML. Pathobiology of Lp(a) in calcific aortic valve disease. Expert Rev Cardiovasc Ther 2017; 15:797-807. [DOI: 10.1080/14779072.2017.1367286] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Affiliation(s)
- Patrick Mathieu
- Laboratory of Cardiovascular Pathobiology, Quebec Heart and Lung Institute/Research Center, Department of Surgery, Laval University, Quebec, QC, Canada
| | - Benoit J. Arsenault
- Quebec Heart and Lung Institute/Department of Medicine, Laval University, Quebec, QC, Canada
| | - Marie-Chloé Boulanger
- Laboratory of Cardiovascular Pathobiology, Quebec Heart and Lung Institute/Research Center, Department of Surgery, Laval University, Quebec, QC, Canada
| | - Yohan Bossé
- Quebec Heart and Lung Institute/Department of Molecular Medicine, Laval University, Quebec, QC, Canada
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16
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Reyes-Soffer G, Ginsberg HN, Ramakrishnan R. The metabolism of lipoprotein (a): an ever-evolving story. J Lipid Res 2017; 58:1756-1764. [PMID: 28720561 DOI: 10.1194/jlr.r077693] [Citation(s) in RCA: 52] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2017] [Revised: 07/18/2017] [Indexed: 02/06/2023] Open
Abstract
Lipoprotein (a) [Lp(a)] is characterized by apolipoprotein (a) [apo(a)] covalently bound to apolipoprotein B 100. It was described in human plasma by Berg et al. in 1963 and the gene encoding apo(a) (LPA) was cloned in 1987 by Lawn and colleagues. Epidemiologic and genetic studies demonstrate that increases in Lp(a) plasma levels increase the risk of atherosclerotic cardiovascular disease. Novel Lp(a) lowering treatments highlight the need to understand the regulation of plasma levels of this atherogenic lipoprotein. Despite years of research, significant uncertainty remains about the assembly, secretion, and clearance of Lp(a). Specifically, there is ongoing controversy about where apo(a) and apoB-100 bind to form Lp(a); which apoB-100 lipoproteins bind to apo(a) to create Lp(a); whether binding of apo(a) is reversible, allowing apo(a) to bind to more than one apoB-100 lipoprotein during its lifespan in the circulation; and how Lp(a) or apo(a) leave the circulation. In this review, we highlight past and recent data from stable isotope studies of Lp(a) metabolism, highlighting the critical metabolic uncertainties that exist. We present kinetic models to describe results of published studies using stable isotopes and suggest what future studies are required to improve our understanding of Lp(a) metabolism.
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Affiliation(s)
- Gissette Reyes-Soffer
- Departments of Medicine Columbia University College of Physicians and Surgeons, New York, NY 10032
| | - Henry N Ginsberg
- Departments of Medicine Columbia University College of Physicians and Surgeons, New York, NY 10032
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17
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Kostner KM, Kostner GM. Lipoprotein (a): a historical appraisal. J Lipid Res 2016; 58:1-14. [PMID: 27821413 DOI: 10.1194/jlr.r071571] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2016] [Revised: 11/01/2016] [Indexed: 11/20/2022] Open
Abstract
Initially, lipoprotein (a) [Lp(a)] was believed to be a genetic variant of lipoprotein (Lp)-B. Because its lipid moiety is almost identical to LDL, Lp(a) has been deliberately considered to be highly atherogenic. Lp(a) was detected in 1963 by Kare Berg, and individuals who were positive for this factor were called Lpa+ Lpa+ individuals were found more frequently in patients with coronary heart disease than in controls. After the introduction of quantitative methods for monitoring of Lp(a), it became apparent that Lp(a), in fact, is present in all individuals, yet to a greatly variable extent. The genetics of Lp(a) had been a mystery for a long time until Gerd Utermann discovered that apo(a) is expressed by a variety of alleles, giving rise to a unique size heterogeneity. This size heterogeneity, as well as countless mutations, is responsible for the great variability in plasma Lp(a) concentrations. Initially, we proposed to evaluate the risk of myocardial infarction at a cut-off for Lp(a) of 30-50 mg/dl, a value that still is adopted in numerous epidemiological studies. Due to new therapies that lower Lp(a) levels, there is renewed interest and still rising research activity in Lp(a). Despite all these activities, numerous gaps exist in our knowledge, especially as far as the function and metabolism of this fascinating Lp are concerned.
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Affiliation(s)
- Karam M Kostner
- Department of Cardiology, Mater Hospital and University of Queensland, Brisbane, 4101 Queensland, Australia
| | - Gert M Kostner
- Institute of Molecular Biology and Biochemistry, Medical University of Graz, A-8010 Graz, Austria
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18
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Schmidt K, Noureen A, Kronenberg F, Utermann G. Structure, function, and genetics of lipoprotein (a). J Lipid Res 2016; 57:1339-59. [PMID: 27074913 DOI: 10.1194/jlr.r067314] [Citation(s) in RCA: 319] [Impact Index Per Article: 39.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2016] [Indexed: 12/29/2022] Open
Abstract
Lipoprotein (a) [Lp(a)] has attracted the interest of researchers and physicians due to its intriguing properties, including an intragenic multiallelic copy number variation in the LPA gene and the strong association with coronary heart disease (CHD). This review summarizes present knowledge of the structure, function, and genetics of Lp(a) with emphasis on the molecular and population genetics of the Lp(a)/LPA trait, as well as aspects of genetic epidemiology. It highlights the role of genetics in establishing Lp(a) as a risk factor for CHD, but also discusses uncertainties, controversies, and lack of knowledge on several aspects of the genetic Lp(a) trait, not least its function.
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Affiliation(s)
- Konrad Schmidt
- Divisions of Human Genetics Medical University of Innsbruck, Innsbruck, Austria Genetic Epidemiology, Medical University of Innsbruck, Innsbruck, Austria
| | - Asma Noureen
- Genetic Epidemiology, Medical University of Innsbruck, Innsbruck, Austria
| | - Florian Kronenberg
- Genetic Epidemiology, Medical University of Innsbruck, Innsbruck, Austria
| | - Gerd Utermann
- Divisions of Human Genetics Medical University of Innsbruck, Innsbruck, Austria
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19
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Damluji AA, El-Maouche D, Alsulaimi A, Martin P, Shamburek RD, Goldberg RB, Baum SJ, de Marchena EJ. Accelerated atherosclerosis and elevated lipoprotein (a) after liver transplantation. J Clin Lipidol 2015; 10:434-7. [PMID: 27055975 DOI: 10.1016/j.jacl.2015.12.022] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2015] [Revised: 11/29/2015] [Accepted: 12/17/2015] [Indexed: 11/29/2022]
Abstract
Cumulative evidence suggests that lipoprotein(a) [Lp(a)] exerts an independent effect on the initiation and progression of atherosclerotic cardiovascular disease. The genetically mediated expression of apolipoprotein(a), which is the key structural and functional component of Lp(a), occurs in hepatocytes with subsequent extracellular Lp(a) assembly at the hepatic cell surface. Here, we describe a case of elevated Lp(a) concentrations identified after (and likely acquired by) orthotopic liver transplantation that contributed to accelerated atherosclerotic cardiovascular disease despite intensive therapeutic interventions. This case study represents an important example to include Lp(a) screening in routine lipid panel testing for all liver transplant donors and recipients; to reduce unanticipated and debilitating cardiovascular morbidity and mortality.
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Affiliation(s)
- Abdulla A Damluji
- Cardiovascular Division and Elaine and Sydney Sussman Cardiac Catheterization Laboratories, University of Miami, Miller School of Medicine, Miami, FL, USA
| | - Diala El-Maouche
- Division of Endocrinology, Diabetes, and Metabolism, University of Miami, Miller School of Medicine, Miami, FL, USA; National Institutes of Health, Bethesda, MD, USA
| | - Ali Alsulaimi
- Cardiovascular Division and Elaine and Sydney Sussman Cardiac Catheterization Laboratories, University of Miami, Miller School of Medicine, Miami, FL, USA
| | - Paul Martin
- Division of Hepatology, University of Miami, Miller School of Medicine, Miami, FL, USA
| | | | - Ronald B Goldberg
- Division of Endocrinology, Diabetes, and Metabolism, University of Miami, Miller School of Medicine, Miami, FL, USA
| | - Seth J Baum
- Cardiovascular Division and Elaine and Sydney Sussman Cardiac Catheterization Laboratories, University of Miami, Miller School of Medicine, Miami, FL, USA
| | - Eduardo J de Marchena
- Cardiovascular Division and Elaine and Sydney Sussman Cardiac Catheterization Laboratories, University of Miami, Miller School of Medicine, Miami, FL, USA.
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Abstract
PURPOSE OF REVIEW Lipoprotein(a) [Lp(a)] is an atherogenic lipoprotein. The metabolism of this lipoprotein is still not well understood. RECENT FINDINGS It has long been known that the plasma concentration of Lp(a) is highly heritable, with its genetic determinants located in the apo(a) locus and regulating the rate of hepatic apo(a) production. Recent human intervention trials have convincingly established that, in addition to apo(a) production, hepatic apoB100 production plays an important role in Lp(a) levels. Although the major site and mode of Lp(a) clearance remain unidentified, a recent cell and animal study points to the involvement of the hepatic scavenger receptor class B type I in the uptake of both the lipid and protein constituents of Lp(a) from plasma. SUMMARY Progress in the understanding of Lp(a) metabolism has the potential to lead to the development of novel and specific treatments for the reduction of Lp(a) levels and the associated risk of cardiovascular disease.
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Affiliation(s)
- Stefania Lamon-Fava
- aCardiovascular Nutrition Laboratory, Jean Mayer USDA Human Nutrition Research Center on Aging, Tufts University bGerald J. and Dorothy R. Friedman School of Nutrition Science and Policy, Tufts University, Boston, Massachusetts, USA cNorthwest Lipid Metabolism and Diabetes Research Laboratories, University of Washington, Seattle, Washington, USA
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22
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Lipoprotein(a): a promising marker for residual cardiovascular risk assessment. DISEASE MARKERS 2013; 35:551-9. [PMID: 24249942 PMCID: PMC3819768 DOI: 10.1155/2013/563717] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/31/2013] [Revised: 09/03/2013] [Accepted: 09/04/2013] [Indexed: 01/14/2023]
Abstract
Atherosclerotic cardiovascular diseases (CVD) are still the leading cause of morbidity and mortality worldwide, although optimal medical therapy has been prescribed for primary and secondary preventions. Residual cardiovascular risk for some population groups is still considerably high although target low density lipoprotein-cholesterol (LDL-C) level has been achieved. During the past few decades, compelling pieces of evidence from clinical trials and meta-analyses consistently illustrate that lipoprotein(a) (Lp(a)) is a significant risk factor for atherosclerosis and CVD due to its proatherogenic and prothrombotic features. However, the lack of effective medication for Lp(a) reduction significantly hampers randomized, prospective, and controlled trials conducting. Based on previous findings, for patients with LDL-C in normal range, Lp(a) may be a useful marker for identifying and evaluating the residual cardiovascular risk, and aggressively lowering LDL-C level than current guidelines' recommendation may be reasonable for patients with particularly high Lp(a) level.
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Hoover-Plow J, Huang M. Lipoprotein(a) metabolism: potential sites for therapeutic targets. Metabolism 2013; 62:479-91. [PMID: 23040268 PMCID: PMC3547132 DOI: 10.1016/j.metabol.2012.07.024] [Citation(s) in RCA: 112] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/04/2012] [Revised: 07/03/2012] [Accepted: 07/11/2012] [Indexed: 11/20/2022]
Abstract
Lipoprotein(a) [Lp(a)] resembles low-density lipoprotein (LDL), with an LDL lipid core and apolipoprotein B (apoB), but contains a unique apolipoprotein, apo(a). Elevated Lp(a) is an independent risk factor for coronary and peripheral vascular diseases. The size and concentration of plasma Lp(a) are related to the synthetic rate, not the catabolic rate, and are highly variable with small isoforms associated with high concentrations and pathogenic risk. Apo(a) is synthesized in the liver, although assembly of apo(a) and LDL may occur in the hepatocytes or plasma. While the uptake and clearance site of Lp(a) is poorly delineated, the kidney is the site of apo(a) fragment excretion. The structure of apo(a) has high homology to plasminogen, the zymogen for plasmin and the primary clot lysis enzyme. Apo(a) interferes with plasminogen binding to C-terminal lysines of cell surface and extracellular matrix proteins. Lp(a) and apo(a) inhibit fibrinolysis and accumulate in the vascular wall in atherosclerotic lesions. The pathogenic role of Lp(a) is not known. Small isoforms and high concentrations of Lp(a) are found in healthy octogenarians that suggest Lp(a) may also have a physiological role. Studies of Lp(a) function have been limited since it is not found in commonly studied small mammals. An important aspect of Lp(a) metabolism is the modification of circulating Lp(a), which has the potential to alter the functions of Lp(a). There are no therapeutic drugs that selectively target elevated Lp(a), but a number of possible agents are being considered. Recently, new modifiers of apo(a) synthesis have been identified. This review reports the regulation of Lp(a) metabolism and potential sites for therapeutic targets.
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Affiliation(s)
- Jane Hoover-Plow
- J. J. Jacobs Center for Thrombosis and Vascular Biology, Department of Cardiovascular Medicine, Lerner Research Institute, Cleveland Clinic, Cleveland, OH 44139, USA.
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Frischmann ME, Ikewaki K, Trenkwalder E, Lamina C, Dieplinger B, Soufi M, Schweer H, Schaefer JR, König P, Kronenberg F, Dieplinger H. In vivo stable-isotope kinetic study suggests intracellular assembly of lipoprotein(a). Atherosclerosis 2012; 225:322-7. [PMID: 23099120 DOI: 10.1016/j.atherosclerosis.2012.09.031] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/21/2012] [Revised: 08/17/2012] [Accepted: 09/26/2012] [Indexed: 11/29/2022]
Abstract
OBJECTIVE Lipoprotein(a) [Lp(a)] consists of apolipoprotein B-100 (apoB-100) as part of an LDL-like particle and the covalently linked glycoprotein apolipoprotein(a) [apo(a)]. Detailed mechanisms of its biosynthesis, assembly, secretion and catabolism are still poorly understood. To address the Lp(a) assembly mechanism, we studied the in vivo kinetics of apo(a) and apoB-100 from Lp(a) and LDL apoB-100 in nine healthy probands using stable-isotope methodology. METHODS The level of isotope enrichment was used to calculate the fractional synthesis rate (FSR), production rate (PR) and retention time (RT) using SAAMII software and multicompartmental modeling. RESULTS We observed a similar mean PR for apo(a) (1.15 nmol/kg/d) and apoB-100 (1.31 nmol/kg/d) from Lp(a), which differed significantly from the PR for apoB-100 from LDL (32.6 nmol/kg/d). Accordingly, mean FSR and RT values for Lp(a)-apo(a) were similar to those of Lp(a)-apoB and different from those for LDL-apoB. CONCLUSION Two different kinetic apoB pools within Lp(a) and LDL suggest intracellular Lp(a) assembly from apo(a) and newly synthesized LDL.
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Affiliation(s)
- Michael E Frischmann
- Division of Genetic Epidemiology, Department of Medical Genetics, Molecular and Clinical Pharmacology, Innsbruck Medical University, Austria
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Nassir F, Xie Y, Davidson NO. Apolipoprotein[a] secretion from hepatoma cells is regulated in a size-dependent manner by alterations in disulfide bond formation. J Lipid Res 2003; 44:816-27. [PMID: 12562843 DOI: 10.1194/jlr.m200451-jlr200] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Apolipoprotein[a] (apo[a]) is a large disulfide linked glycoprotein synthesized by hepatocytes. We have examined the role of disulfide bond formation in the processing of apo[a] using human and rat hepatoma cells expressing apo[a] isoforms containing varying numbers of kringle 4 (K4) domains, following treatment with DTT. Hepatoma cells expressing 6- or 9-K4 isoforms revealed approximately 90% inhibition of apo[a] secretion following DTT treatment, although larger isoforms containing 13- or 17-K4 domains demonstrated continued secretion (up to 30% of control values), suggesting that a fraction of the larger isoforms is at least partially DTT resistant. Wash-out experiments demonstrated that these effects were completely reversible for all isoforms studied, with no enhanced degradation associated with prolonged intracellular retention. DTT treatment was associated with enhanced binding of apo[a] with the endoplasmic reticulum-associated chaperone proteins calnexin, calreticulin, and BiP, which was reversible upon DTT removal. The chemical chaperone 6-aminohexanoic acid, previously demonstrated by others to rescue defective apo[a] secretion associated with alterations in glycosylation, failed to alter the secretion of apo[a] following DTT treatment. The demonstration that DTT modulates apo[a] secretion in a manner influenced by both the type and number of K4 repeats extends understanding of the mechanisms that regulate its exit from the endoplasmic reticulum.
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Affiliation(s)
- Fatiha Nassir
- Department of Internal Medicine, Washington University School of Medicine, St. Louis, MO 63110, USA
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26
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Abstract
Lipoprotein(a) is a cholesterol-enriched lipoprotein, consisting of a covalent linkage joining the unique and highly polymorphic apolipoprotein(a) to apolipoprotein B100, the main protein moiety of low-density lipoproteins. Although the concentration of lipoprotein(a) in humans is mostly genetically determined, acquired disorders might influence synthesis and catabolism of the particle. Raised concentration of lipoprotein(a) has been acknowledged as a leading inherited risk factor for both premature and advanced atherosclerosis at different vascular sites. The strong structural homologies with plasminogen and low-density lipoproteins suggest that lipoprotein(a) might represent the ideal bridge between the fields of atherosclerosis and thrombosis in the pathogenesis of vascular occlusive disorders. Unfortunately, the exact mechanisms by which lipoprotein(a) promotes, accelerates, and complicates atherosclerosis are only partially understood. In some clinical settings, such as in patients at exceptionally low risk for cardiovascular disease, the potential regenerative and antineoplastic properties of lipoprotein(a) might paradoxically counterbalance its athero-thrombogenicity, as attested by the compatibility between raised plasma lipoprotein(a) levels and longevity.
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Affiliation(s)
- Giuseppe Lippi
- Istituto di Chimica e Microscopia Clinica, Dipartimento di Scienze Morfologiche e Biomediche, Università degli Studi di Verona, Verona, Italy
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27
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Puckey LH, Knight BL. Sequence and functional changes in a putative enhancer region upstream of the apolipoprotein(a) gene. Atherosclerosis 2003; 166:119-27. [PMID: 12482558 DOI: 10.1016/s0021-9150(02)00315-5] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Two enhancer regions upstream of the apolipoprotein(a) (apo(a)) gene were amplified and sequenced from subjects who were known to express abnormally high or low amounts of lipoprotein(a) (Lp(a)). No base changes were found in the DHII region situated 28 kb from the apo(a) gene. Three common base substitutions were found in the DHIII region about 20 kb from the gene. One, an A to G change at position -1230, increased the activity of reporter-gene constructs approximately 2.5-fold. The other two, a C to A change at -1617 and a G to T change at -1712, decreased reporter activity by 30 and 40%, respectively. The sites at -1230 and -1617 were in linkage disequilibrium with each other and also with a polymorphic site near the DHII enhancer and sites in the apo(a) promoter and gene. The rarer G variant at -1230 was associated with smaller alleles. After correcting for the effect of allele size, values of Lp(a) concentration for alleles associated with the G variant at -1230 were 70% higher than those associated with the more common A variant. In contrast, the corrected values for alleles associated with the rare T variant at -1712 were 40% lower than those associated with the common G variant. Thus, overall the changes observed in this enhancer could influence apo(a) gene transcription up to 4-fold and could provide a significant contribution to the variation in Lp(a) concentrations in plasma.
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Affiliation(s)
- Loretto H Puckey
- Lipoprotein Group, MRC Clinical Sciences Centre, Faculty of Medicine, Imperial College of Science, Technology and Medicine, Hammersmith Hospital, London W12 ONN, UK
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28
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Puckey LH, Knight BL. Interaction of oestrogen and peroxisome proliferator-activated receptors with apolipoprotein(a) gene enhancers. Biochem J 2002; 366:157-63. [PMID: 12023905 PMCID: PMC1222770 DOI: 10.1042/bj20020293] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2002] [Revised: 05/09/2002] [Accepted: 05/22/2002] [Indexed: 11/17/2022]
Abstract
A high plasma concentration of lipoprotein(a) [Lp(a)] confers an increased risk for the development of coronary heart disease. Hormones, such as oestrogen, are some of the few compounds known to reduce plasma Lp(a) levels. A putative enhancer region, located at the DHII DNase I hypersensitive site approx. 28 kb upstream of the apolipoprotein(a) [apo(a)] gene, contains a number of sequences similar to the binding half-sites for nuclear hormone receptors, such as the oestrogen receptor and the peroxisome proliferator-activated receptor (PPAR). The 180 bp core DHII enhancer increased the activity of the apo(a) promoter by over 7-fold in reporter-gene assays in HepG2 cells in vitro. Almost 60% of this increase was lost in the presence of co-transfected oestrogen receptor and oestrogen. In contrast, co-transfection with PPARalpha increased the effect of the DHII enhancer on apo(a) transcriptional activity by approx. 70% and could overcome the inhibitory effect of the oestrogen receptor on apo(a) transcription. Gel mobility-shift assays showed that oestrogen receptor protein bound to one half of a sequence corresponding to a predicted oestrogen receptor response element. PPARalpha also bound to this site and competed with oestrogen receptors for binding. In addition, PPARalpha bound to a separate site that comprised part of a direct repeat of nuclear hormone receptor half-sites. The results suggest that nuclear hormones affect plasma Lp(a) concentrations by binding to the sequences within the DHII enhancer, thereby altering the amount by which the enhancer increases the transcription of the apo(a) gene.
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Affiliation(s)
- Loretto H Puckey
- Lipoprotein Group, MRC Clinical Sciences Centre, Faculty of Medicine, Imperial College, Hammersmith Hospital, DuCane Road, London W12 ONN, U.K
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Rubin J, Paultre F, Tuck CH, Holleran S, Reed RG, Pearson TA, Thomas CM, Ramakrishnan R, Berglund L. Apolipoprotein [a] genotype influences isoform dominance pattern differently in African Americans and Caucasians. J Lipid Res 2002. [DOI: 10.1016/s0022-2275(20)30165-6] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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Huby T, Dachet C, Lawn RM, Wickings J, Chapman MJ, Thillet J. Functional analysis of the chimpanzee and human apo(a) promoter sequences: identification of sequence variations responsible for elevated transcriptional activity in chimpanzee. J Biol Chem 2001; 276:22209-14. [PMID: 11301336 DOI: 10.1074/jbc.m102204200] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Lp(a) concentrations vary considerably among individuals and are primarily determined by the apo(a) gene locus. We have previously shown that mean plasma Lp(a) levels in the chimpanzee are significantly higher than those observed in humans (Doucet, C., Huby, T., Chapman, J., and Thillet, J. (1994) J. Lipid Res 35, 263-270). To evaluate the possibility that this difference may result from a high level of expression of chimpanzee apo(a), we cloned and sequenced 1.4 kilobase (kb) of the 5'-flanking region of the gene and compared promoter activity to that of its human counterpart. Sequence analysis revealed 98% homology between chimpanzee and human apo(a) 5' sequences; among the differences observed, two involved polymorphic sites associated with Lp(a) levels in humans. The TTTTA repeat located 1.3 kb 5' of the apo(a) gene, present in a variable number of copies (n = 5-12) in humans, is uniquely present as four copies in the chimpanzee sequence. The second position concerns the +93 C>T polymorphism that creates an additional ATG start codon in the human apo(a) gene, thereby impairing translation efficiency. In chimpanzee, this position did not appear polymorphic, and a base difference at position +94 precluded the presence of an additional ATG. In transient transfection assays, the chimpanzee apo(a) promoter exhibited a 5-fold elevation in transcriptional activity as compared with its human counterpart. This marked difference in activity was maintained with either 1.4 kb of 5' sequence or the minimal promoter region -98 to +141 of the human and chimpanzee apo(a) genes. Using point mutational analyses, nucleotides present at positions -3, -2, and +8 (relative to the start site of transcription) were found to be essential for the high transcription efficiency of the chimpanzee apo(a) promoter. High transcriptional activity of the chimpanzee apo(a) gene may therefore represent a key factor in the elevated plasma Lp(a) levels characteristic of this non-human primate.
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Affiliation(s)
- T Huby
- INSERM, Unité 551, Dyslipoprotéinémies, Athérosclérose: Génétique, Métabolisme et Thérapeutique, Hôpital de la Pitié, 83 Boulevard de l'Hôpital, Paris 75651 Cedex 13, France
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Wang J, Boedeker J, Hobbs HH, White AL. Determinants of human apolipoprotein [a] secretion from mouse hepatocyte cultures. J Lipid Res 2001. [DOI: 10.1016/s0022-2275(20)32336-1] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
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Abstract
Our understanding of the genetics, metabolism and pathophysiology of the atherogenic plasma lipoprotein Lp(a) has considerably increased over past years. Nevertheless, the precise mechanisms regulating the biosynthesis and assembly of Lp(a) are poorly understood and controversially discussed. Lp(a) plasma concentrations are determined by synthesis and not by degradation. Transcriptional and post-translational mechanisms have been identified as regulating Lp(a) production in primary hepatocytes and transfected cell lines. Assembly of Lp(a) occurs extracellularly from newly synthesized apolipoprotein(a) and circulating LDL. This view has recently been challenged by in-vivo kinetic studies in humans which are compatible with an intracellular assembly event. Lp(a) assembly is a complex two-step process of multiple non-covalent interactions between apolipoprotein(a) and apolipoprotein B-100 of LDL followed by covalent disulfide linkage of two free cysteine residues on both proteins.
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Affiliation(s)
- H Dieplinger
- Institute of Medical Biology and Human Genetics, University of Innsbruck, Austria
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33
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Abstract
Apolipoprotein(a) is coded by one of the most polymorphic genes known in humans. In white and Asian populations variation in this gene is the major determinant of the plasma concentrations of the atherogenic lipoprotein(a) which varies enormously between individuals and considerably across populations. Recent studies have shown that the genetic architecture of the quantitative Lp(a) trait differs among major human groups. In Africans there is evidence for a transacting factor. Three types of variation have been identified in the apo(a) gene: a size polymorphism in the coding region (K IV type 2 repeats), a pentanucleotide repeat polymorphism in the promoter (5'PNRP) and sequence variation in coding and non-coding regions of the gene including a C/T polymorphism at +93 which creates an additional ATG start codon but also affects transcription. The causal +93 C/T effect is masked by linkage disequilibrium in white populations. Analysis of apo(a) K IV 6-10 exons revealed the existence of population-specific spectra of polymorphism in this domain. However further sequence variation which may provide clues for the understanding of the regulation of apo(a) concentrations still needs to be identified. DNA sequencing and phylogenetic analysis have demonstrated that two types of apo(a) exist, in phylogenetically distant mammalian lineages a K IV derived primate form and a K III-derived hedgehog form which are products of convergent evolution.
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Affiliation(s)
- G Utermann
- Institute for Medical Biology and Human Genetics, Innsbruck, Austria.
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Abstract
Lipoprotein(a) is a plasma particle which is considered to be a risk factor for the development of coronary heart disease. Plasma levels of lipoprotein(a) are affected by different types of dietary fat and steroid hormones. Two regions upstream of the apolipoprotein(a) promoter have been isolated which could be the site of regulation of apolipoprotein(a) gene transcription.
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Affiliation(s)
- L Puckey
- Clinical Sciences Centre, Imperial College School of Medicine, Hammersmith Hospital, London, UK
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