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Sylvers-Davie KL, Bierstedt KC, Schnieders MJ, Davies BSJ. Endothelial lipase variant T111I does not alter inhibition by angiopoietin-like proteins. Sci Rep 2024; 14:4246. [PMID: 38379026 PMCID: PMC10879187 DOI: 10.1038/s41598-024-54705-6] [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: 09/28/2023] [Accepted: 02/15/2024] [Indexed: 02/22/2024] Open
Abstract
High levels of HDL-C are correlated with a decreased risk of cardiovascular disease. HDL-C levels are modulated in part by the secreted phospholipase, endothelial lipase (EL), which hydrolyzes the phospholipids of HDL and decreases circulating HDL-C concentrations. A 584C/T polymorphism in LIPG, the gene which encodes EL, was first identified in individuals with increased HDL levels. This polymorphism results in a T111I point mutation the EL protein. The association between this variant, HDL levels, and the risk of coronary artery disease (CAD) in humans has been extensively studied, but the findings have been inconsistent. In this study, we took a biochemical approach, investigating how the T111I variant affected EL activity, structure, and stability. Moreover, we tested whether the T111I variant altered the inhibition of phospholipase activity by angiopoietin-like 3 (ANGPTL3) and angiopoietin-like 4 (ANGPTL4), two known EL inhibitors. We found that neither the stability nor enzymatic activity of EL was altered by the T111I variant. Moreover, we found no difference between wild-type and T111I EL in their ability to be inhibited by ANGPTL proteins. These data suggest that any effect this variant may have on HDL-C levels or cardiovascular disease are not mediated through alterations in these functions.
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Affiliation(s)
- Kelli L Sylvers-Davie
- Department of Biochemistry and Molecular Biology, University of Iowa, 169 Newton Rd., PBDB 3326, Iowa, IA, 52242, USA
- Fraternal Order of Eagles Diabetes Research Center, University of Iowa, Iowa, IA, 52242, USA
| | - Kaleb C Bierstedt
- Department of Biochemistry and Molecular Biology, University of Iowa, 169 Newton Rd., PBDB 3326, Iowa, IA, 52242, USA
- Department of Biomedical Engineering, University of Iowa, Iowa, IA, 52242, USA
| | - Michael J Schnieders
- Department of Biochemistry and Molecular Biology, University of Iowa, 169 Newton Rd., PBDB 3326, Iowa, IA, 52242, USA
- Department of Biomedical Engineering, University of Iowa, Iowa, IA, 52242, USA
| | - Brandon S J Davies
- Department of Biochemistry and Molecular Biology, University of Iowa, 169 Newton Rd., PBDB 3326, Iowa, IA, 52242, USA.
- Fraternal Order of Eagles Diabetes Research Center, University of Iowa, Iowa, IA, 52242, USA.
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Cole J, Blackhurst DM, Solomon GAE, Ratanjee BD, Benjamin R, Marais AD. Atherosclerotic cardiovascular disease in hyperalphalipoproteinemia due to LIPG variants. J Clin Lipidol 2020; 15:142-150.e2. [PMID: 33414088 DOI: 10.1016/j.jacl.2020.12.007] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2020] [Revised: 11/30/2020] [Accepted: 12/08/2020] [Indexed: 01/28/2023]
Abstract
BACKGROUND High density lipoprotein cholesterol (HDL-C) concentration correlates inversely with atherosclerotic cardiovascular disease (ASCVD) risk and is included in risk calculations. Endothelial lipase (EL) is a phospholipase that remodels HDL. Deficiency of EL due to mutations in its gene, LIPG, is associated with hyperalphalipoproteinemia. The effects of EL on HDL function and ASCVD risk remain poorly understood. OBJECTIVES To determine whether hyperalphalipoproteinemia due to EL deficiency is protective against ASCVD. METHODS We identified LIPG variants amongst patients with severe hyperalphalipoproteinemia (HDL-C >2.5 mmol/L) attending a referral lipid clinic in the Western Cape Province of South Africa. We analysed the clinical and biochemical phenotypes amongst primary hyperalphalipoproteinemia cases (males HDL-C >1.6 mmol/L; females HDL-C >1.8 mmol/L) due to LIPG variants, and the distribution of variants in normal and hyperalphalipoproteinemia ranges of HDL-C. RESULTS 1007 patients with HDL-C concentration ranging from 1.2 to 4.5 mmol/L were included. Seventeen females had primary hyperalphalipoproteinemia. Vascular disease was prominent, but not associated with HDL-C concentration, LDL-C concentration or carotid artery intima media thickness. Two novel and three known LIPG variants were identified in severe hyperalphalipoproteinemia. Four additional variants were identified in the extended cohort. Two common variants appeared normally distributed across the HDL-C concentration range, while six less-common variants were found only at higher HDL-C concentrations. One rare variant had a moderate effect. CONCLUSION Hyperalphalipoproteinemia due to LIPG variants is commoner in females and may not protect against ASCVD. Use of current risk calculations may be inappropriate in patients with hyperalphalipoproteinemia due to EL deficiency. Our study cautions targeting EL to reduce risk.
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Affiliation(s)
- Justine Cole
- Division of Chemical Pathology, University of Cape Town Faculty of Health Sciences, Anzio Road, Observatory, 7925, Cape Town, South Africa; Chemical Pathology, National Health Laboratory Service, C17 Groote Schuur Hospital, Main Road, Observatory, 7925, Cape Town, South Africa.
| | - Diane Mary Blackhurst
- Division of Chemical Pathology, University of Cape Town Faculty of Health Sciences, Anzio Road, Observatory, 7925, Cape Town, South Africa
| | - Gabriele Anna Eva Solomon
- Division of Chemical Pathology, University of Cape Town Faculty of Health Sciences, Anzio Road, Observatory, 7925, Cape Town, South Africa
| | - Bharati Dhanluxmi Ratanjee
- Division of Chemical Pathology, University of Cape Town Faculty of Health Sciences, Anzio Road, Observatory, 7925, Cape Town, South Africa
| | - Ryan Benjamin
- Division of Chemical Pathology, University of Cape Town Faculty of Health Sciences, Anzio Road, Observatory, 7925, Cape Town, South Africa; Chemical Pathology, National Health Laboratory Service, C17 Groote Schuur Hospital, Main Road, Observatory, 7925, Cape Town, South Africa
| | - Adrian David Marais
- Division of Chemical Pathology, University of Cape Town Faculty of Health Sciences, Anzio Road, Observatory, 7925, Cape Town, South Africa.
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Vitali C, Khetarpal SA, Rader DJ. HDL Cholesterol Metabolism and the Risk of CHD: New Insights from Human Genetics. Curr Cardiol Rep 2017; 19:132. [PMID: 29103089 DOI: 10.1007/s11886-017-0940-0] [Citation(s) in RCA: 76] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
PURPOSE OF REVIEW Elevated high-density lipoprotein cholesterol levels in the blood (HDL-C) represent one of the strongest epidemiological surrogates for protection against coronary heart disease (CHD), but recent human genetic and pharmacological intervention studies have raised controversy about the causality of this relationship. Here, we review recent discoveries from human genome studies using new analytic tools as well as relevant animal studies that have both addressed, and in some cases, fueled this controversy. RECENT FINDINGS Methodologic developments in genotyping and sequencing, such as genome-wide association studies (GWAS), exome sequencing, and exome array genotyping, have been applied to the study of HDL-C and risk of CHD in large, multi-ethnic populations. Some of these efforts focused on population-wide variation in common variants have uncovered new polymorphisms at novel loci associated with HDL-C and, in some cases, CHD risk. Other efforts have discovered loss-of-function variants for the first time in genes previously implicated in HDL metabolism through common variant studies or animal models. These studies have allowed the genetic relationship between these pathways, HDL-C and CHD to be explored in humans for the first time through analysis tools such as Mendelian randomization. We explore these discoveries for selected key HDL-C genes CETP, LCAT, LIPG, SCARB1, and novel loci implicated from GWAS including GALNT2, KLF14, and TTC39B. Recent human genetics findings have identified new nodes regulating HDL metabolism while reshaping our current understanding of known candidate genes to HDL and CHD risk through the study of critical variants across model systems. Despite their effect on HDL-C, variants in many of the reviewed genes were found to lack any association with CHD. These data collectively indicate that HDL-C concentration, which represents a static picture of a very dynamic and heterogeneous metabolic milieu, is unlikely to be itself causally protective against CHD. In this context, human genetics represent an extremely valuable tool to further explore the biological mechanisms regulating HDL metabolism and investigate what role, if any, HDL plays in the pathogenesis of CHD.
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Affiliation(s)
- Cecilia Vitali
- Perelman School of Medicine at the University of Pennsylvania, 11-162 TRC, 3400 Civic Center Blvd, Philadelphia, PA, 19104, USA
| | - Sumeet A Khetarpal
- Perelman School of Medicine at the University of Pennsylvania, 11-162 TRC, 3400 Civic Center Blvd, Philadelphia, PA, 19104, USA
| | - Daniel J Rader
- Perelman School of Medicine at the University of Pennsylvania, 11-162 TRC, 3400 Civic Center Blvd, Philadelphia, PA, 19104, USA. .,Departments of Genetics and Medicine, Cardiovascular Institute, and Institute for Translational Medicine and Therapeutics, Perelman School of Medicine at the University of Pennsylvania, 11-125 TRC, 3400 Civic Center Blvd, Philadelphia, PA, 19104, USA.
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Larach DB, Cuchel M, Rader DJ. Monogenic causes of elevated HDL cholesterol and implications for development of new therapeutics. CLINICAL LIPIDOLOGY 2013; 8:635-648. [PMID: 25374625 PMCID: PMC4217288 DOI: 10.2217/clp.13.73] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Identification of the CETP, LIPG (encoding endothelial lipase) and APOC3 genes, and ana lysis of rare genetic variants in them, have allowed researchers to increase understanding of HDL metabolism significantly. However, development of cardiovascular risk-reducing therapeutics targeting the proteins encoded by these genes has been less straightforward. The failure of two CETP inhibitors is complex but illustrates a possible over-reliance on HDL cholesterol as a marker of therapeutic efficacy. The case of endothelial lipase exemplifies the importance of utilizing population-wide genetic studies of rare variants in potential therapeutic targets to gain information on cardiovascular disease end points. Similar population-wide studies of cardiovascular end points make apoC-III a potentially attractive target for lipid-related drug discovery. These three cases illustrate the positives and negatives of single-gene studies relating to HDL-related cardiovascular drug discovery; such studies should focus not only on HDL cholesterol and other components of the lipid profile, but also on the effect genetic variants have on cardiovascular end points.
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Affiliation(s)
- Daniel B Larach
- Division of Translational Medicine & Human Genetics, Department of Medicine, Perelman School of Medicine at the University of Pennsylvania, PA, USA
| | - Marina Cuchel
- Division of Translational Medicine & Human Genetics, Department of Medicine, Perelman School of Medicine at the University of Pennsylvania, PA, USA
| | - Daniel J Rader
- Division of Translational Medicine & Human Genetics, Department of Medicine, Perelman School of Medicine at the University of Pennsylvania, PA, USA
- 11–125 Smilow Center for Translational Research, 3400 Civic Center Boulevard, Building 421, PA 19104–5158, USA
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Razzaghi H, Tempczyk-Russell A, Haubold K, Santorico SA, Shokati T, Christians U, Churchill MEA. Genetic and structure-function studies of missense mutations in human endothelial lipase. PLoS One 2013; 8:e55716. [PMID: 23536757 PMCID: PMC3607615 DOI: 10.1371/journal.pone.0055716] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2012] [Accepted: 12/29/2012] [Indexed: 11/18/2022] Open
Abstract
Endothelial lipase (EL) plays a pivotal role in HDL metabolism. We sought to characterize EL and its interaction with HDL as well as its natural variants genetically, functionally and structurally. We screened our biethnic population sample (n = 802) for selected missense mutations (n = 5) and identified T111I as the only common variant. Multiple linear regression analyses in Hispanic subjects revealed an unexpected association between T111I and elevated LDL-C (p-value = 0.012) and total cholesterol (p-value = 0.004). We examined lipase activity of selected missense mutants (n = 10) and found different impacts on EL function, ranging from normal to complete loss of activity. EL-HDL lipidomic analyses indicated that EL has a defined remodeling of HDL without exhaustion of the substrate and a distinct and preference for several fatty acids that are lipid mediators and known for their potent pro- and anti-inflammatory properties. Structural studies using homology modeling revealed a novel α/β motif in the C-domain, unique to EL. The EL dimer was found to have the flexibility to expand and to bind various sizes of HDL particles. The likely impact of the all known missense mutations (n = 18) on the structure of EL was examined using molecular modeling and the impact they may have on EL lipase activity using a novel structure-function slope based on their structural free energy differences. The results of this multidisciplinary approach delineated the impact of EL and its variants on HDL. Moreover, the results suggested EL to have the capacity to modulate vascular health through its role in fatty acid-based signaling pathways.
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Affiliation(s)
- Hamid Razzaghi
- Division of Cardiology, Department of Medicine, University of Colorado Denver, Aurora, Colorado, United States of America.
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