1
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Wang X, Guo M, Wang Q, Wang Q, Zuo S, Zhang X, Tong H, Chen J, Wang H, Chen X, Guo J, Su X, Liang H, Zhou H, Li JZ. The Patatin-Like Phospholipase Domain Containing Protein 7 Facilitates VLDL Secretion by Modulating ApoE Stability. Hepatology 2020; 72:1569-1585. [PMID: 32103509 DOI: 10.1002/hep.31161] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/19/2019] [Accepted: 01/21/2020] [Indexed: 12/16/2022]
Abstract
BACKGROUND AND AIMS The regulation of hepatic very-low-density lipoprotein (VLDL) secretion is vital for lipid metabolism whose pathogenetic status is involved in fatty liver disease and dyslipidemia seen in hepatic steatosis. Accumulated evidence suggest that apolipoprotein E (ApoE) is closely related to hepatic VLDL secretion. Here, we report that the expression of patatin-like phospholipase domain containing protein 7 (PNPLA7) is strongly induced by hepatic steatosis and positively correlates with plasma triacylglycerol (TAG) levels in the human subjects, whereas the role of PNPLA7 in hepatic VLDL secretion is unknown. APPROACH AND RESULTS Herein, with genetic manipulation in the mice, the deficiency of hepatic PNPLA7 expression resulted in reduced VLDL secretion accompanied by enhanced hepatic lipid accumulation and decreased hepatic ApoE expression. Furthermore, knockdown of PNPLA7 in the livers of the db/db mice also resulted in significant reduction in plasma TAG level but aggravated hepatic steatosis. Importantly, we observed that PNPLA7 interacted with ApoE and presumably at the site of endoplasmic reticulum. Mechanistically, we have shown that PNPLA7 could modulate polyubiquitination and proteasomal-mediated degradation of ApoE. Overexpressed ApoE restored the impaired VLDL-TAG metabolism in PNPLA7-knockdown primary hepatocytes. CONCLUSION PNPLA7 plays a critical role in regulating hepatic VLDL secretion by modulating ApoE stability through its interaction with ApoE.
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Affiliation(s)
- Xiuyun Wang
- The Key Laboratory of Rare Metabolic Disease, Nanjing Medical University, Nanjing, China.,Department of Biochemistry and Molecular Biology, Nanjing Medical University, Nanjing, China.,The Key Laboratory of Human Functional Genomics of Jiangsu Province, Nanjing Medical University, Nanjing, China
| | - Min Guo
- The State Key Laboratory of Natural Medicines, School of Life Science and Technology, China Pharmaceutical University, Nanjing, China
| | - Qian Wang
- The Key Laboratory of Rare Metabolic Disease, Nanjing Medical University, Nanjing, China.,Department of Biochemistry and Molecular Biology, Nanjing Medical University, Nanjing, China.,The Key Laboratory of Human Functional Genomics of Jiangsu Province, Nanjing Medical University, Nanjing, China
| | - Qingjie Wang
- The Key Laboratory of Rare Metabolic Disease, Nanjing Medical University, Nanjing, China.,Department of Biochemistry and Molecular Biology, Nanjing Medical University, Nanjing, China.,The Key Laboratory of Human Functional Genomics of Jiangsu Province, Nanjing Medical University, Nanjing, China
| | - Shasha Zuo
- The Key Laboratory of Rare Metabolic Disease, Nanjing Medical University, Nanjing, China.,Department of Biochemistry and Molecular Biology, Nanjing Medical University, Nanjing, China.,The Key Laboratory of Human Functional Genomics of Jiangsu Province, Nanjing Medical University, Nanjing, China
| | - Xu Zhang
- The Key Laboratory of Rare Metabolic Disease, Nanjing Medical University, Nanjing, China.,Department of Biochemistry and Molecular Biology, Nanjing Medical University, Nanjing, China.,The Key Laboratory of Human Functional Genomics of Jiangsu Province, Nanjing Medical University, Nanjing, China
| | - Hui Tong
- The Key Laboratory of Rare Metabolic Disease, Nanjing Medical University, Nanjing, China.,Department of Biochemistry and Molecular Biology, Nanjing Medical University, Nanjing, China.,The Key Laboratory of Human Functional Genomics of Jiangsu Province, Nanjing Medical University, Nanjing, China
| | - Jizheng Chen
- The State Key Laboratory of Virology, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan, China
| | - Huimin Wang
- The Sate Key laboratory of Membrane Biology, Center for Life Science and Institute of Molecular Medicine, Peking University, Beijing, China
| | - Xiaowei Chen
- The Sate Key laboratory of Membrane Biology, Center for Life Science and Institute of Molecular Medicine, Peking University, Beijing, China
| | - Junyuan Guo
- Department of Biochemistry and Molecular Biology, Soochow University Medical College, Suzhou, China
| | - Xiong Su
- Department of Biochemistry and Molecular Biology, Soochow University Medical College, Suzhou, China
| | - Hui Liang
- Department of General Surgery, The First affiliated Hospital of Nanjing Medical University, Nanjing, China
| | - Hongwen Zhou
- The Key Laboratory of Rare Metabolic Disease, Nanjing Medical University, Nanjing, China.,Department of Endocrinology, The First affiliated Hospital of Nanjing Medical University, Nanjing, China
| | - John Zhong Li
- The Key Laboratory of Rare Metabolic Disease, Nanjing Medical University, Nanjing, China.,Department of Biochemistry and Molecular Biology, Nanjing Medical University, Nanjing, China.,The Key Laboratory of Human Functional Genomics of Jiangsu Province, Nanjing Medical University, Nanjing, China
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2
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Croyal M, Blanchard V, Ouguerram K, Chétiveaux M, Cabioch L, Moyon T, Billon-Crossouard S, Aguesse A, Bernardeau K, Le May C, Flet L, Lambert G, Hadjadj S, Cariou B, Krempf M, Nobécourt-Dupuy E. VLDL (Very-Low-Density Lipoprotein)-Apo E (Apolipoprotein E) May Influence Lp(a) (Lipoprotein [a]) Synthesis or Assembly. Arterioscler Thromb Vasc Biol 2020; 40:819-829. [DOI: 10.1161/atvbaha.119.313877] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Objective:
To clarify the association between PCSK9 (proprotein convertase subtilisin/kexin type 9) and Lp(a) (lipoprotein [a]), we studied Lp(a) kinetics in patients with loss-of-function and gain-of-function
PCSK9
mutations and in patients in whom extended-release niacin reduced Lp(a) and PCSK9 concentrations.
Approach and Results:
Six healthy controls, 9 heterozygous patients with familial hypercholesterolemia (5 with low-density lipoprotein receptor [
LDLR
] mutations and 4 with
PCSK9
gain-of-function mutations) and 3 patients with heterozygous dominant-negative
PCSK9
loss-of-function mutations were included in the preliminary study. Eight patients were enrolled in a second study assessing the effects of 2 g/day extended-release niacin. Apolipoprotein kinetics in VLDL (very-low-density lipoprotein), LDL (low-density lipoprotein), and Lp(a) were studied using stable isotope techniques. Plasma Lp(a) concentrations were increased in
PCSK9
-gain-of-function and familial hypercholesterolemia-
LDLR
groups compared with controls and
PCSK9
-loss-of-function groups (14±12 versus 5±4 mg/dL;
P
=0.04), but no change was observed in Lp(a) fractional catabolic rate. Subjects with
PCSK9
-loss-of-function mutations displayed reduced apoE (apolipoprotein E) concentrations associated with a VLDL-apoE absolute production rate reduction. Lp(a) and VLDL-apoE absolute production rates were correlated (
r
=0.50;
P
<0.05). ApoE-to-apolipoprotein (a) molar ratios in Lp(a) increased with plasma Lp(a) (
r
=0.96;
P
<0.001) but not with PCSK9 levels. Extended-release niacin-induced reductions in Lp(a) and VLDL-apoE absolute production rate were correlated (
r
=0.83;
P
=0.015). In contrast, PCSK9 reduction (−35%;
P
=0.008) was only correlated with that of VLDL-apoE absolute production rate (
r
=0.79;
P
=0.028).
Conclusions:
VLDL-apoE production could determine Lp(a) production and/or assembly. As PCSK9 inhibitors reduce plasma apoE and Lp(a) concentrations, apoE could be the link between PCSK9 and Lp(a).
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Affiliation(s)
- Mikaël Croyal
- From the NUN, INRA, CHU Nantes, UMR 1280, PhAN, IMAD, CRNH-O, France (M. Croyal, K.O., S.B.-C., A.A., M.K.)
- CRNH-O Mass Spectrometry Core Facility, F-44000 Nantes, France (M. Croyal, K.O., T.M., S.B.-C., A.A., M.K.)
| | - Valentin Blanchard
- Université de La Réunion, INSERM, UMR 1188 Diabète athérothrombose Réunion Océan Indien (DéTROI), Plateforme CYROI, Saint-Denis de La Réunion, France (V.B., G.L.)
| | - Khadija Ouguerram
- From the NUN, INRA, CHU Nantes, UMR 1280, PhAN, IMAD, CRNH-O, France (M. Croyal, K.O., S.B.-C., A.A., M.K.)
- CRNH-O Mass Spectrometry Core Facility, F-44000 Nantes, France (M. Croyal, K.O., T.M., S.B.-C., A.A., M.K.)
| | - Maud Chétiveaux
- L’institut du thorax, INSERM, CNRS, University of Nantes, France (M. Chétiveaux, C.L.M.)
| | - Léa Cabioch
- Biogenouest-Corsaire platform, Saint Gilles, France (L.C.)
| | - Thomas Moyon
- CRNH-O Mass Spectrometry Core Facility, F-44000 Nantes, France (M. Croyal, K.O., T.M., S.B.-C., A.A., M.K.)
| | - Stéphanie Billon-Crossouard
- From the NUN, INRA, CHU Nantes, UMR 1280, PhAN, IMAD, CRNH-O, France (M. Croyal, K.O., S.B.-C., A.A., M.K.)
- CRNH-O Mass Spectrometry Core Facility, F-44000 Nantes, France (M. Croyal, K.O., T.M., S.B.-C., A.A., M.K.)
| | - Audrey Aguesse
- From the NUN, INRA, CHU Nantes, UMR 1280, PhAN, IMAD, CRNH-O, France (M. Croyal, K.O., S.B.-C., A.A., M.K.)
- CRNH-O Mass Spectrometry Core Facility, F-44000 Nantes, France (M. Croyal, K.O., T.M., S.B.-C., A.A., M.K.)
| | - Karine Bernardeau
- P2R «Production de protéines recombinantes», CRCINA, SFR-Santé, INSERM, CNRS, UNIV Nantes, CHU Nantes, France (K.B.)
| | - Cédric Le May
- L’institut du thorax, INSERM, CNRS, University of Nantes, France (M. Chétiveaux, C.L.M.)
| | - Laurent Flet
- Pharmacy Department, Nantes University Hospital, France (L.F.)
| | - Gilles Lambert
- Université de La Réunion, INSERM, UMR 1188 Diabète athérothrombose Réunion Océan Indien (DéTROI), Plateforme CYROI, Saint-Denis de La Réunion, France (V.B., G.L.)
| | - Samy Hadjadj
- L’institut du thorax, INSERM, CNRS, University of Nantes, CHU Nantes, France (S.H., B.C.)
| | - Bertrand Cariou
- L’institut du thorax, INSERM, CNRS, University of Nantes, CHU Nantes, France (S.H., B.C.)
| | - Michel Krempf
- From the NUN, INRA, CHU Nantes, UMR 1280, PhAN, IMAD, CRNH-O, France (M. Croyal, K.O., S.B.-C., A.A., M.K.)
- CRNH-O Mass Spectrometry Core Facility, F-44000 Nantes, France (M. Croyal, K.O., T.M., S.B.-C., A.A., M.K.)
- ELSAN, clinique Bretéché, Nantes, France (M.K.)
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3
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Update on the molecular biology of dyslipidemias. Clin Chim Acta 2016; 454:143-85. [DOI: 10.1016/j.cca.2015.10.033] [Citation(s) in RCA: 82] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2015] [Revised: 10/24/2015] [Accepted: 10/30/2015] [Indexed: 12/20/2022]
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4
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Xiao C, Lewis GF. Regulation of chylomicron production in humans. Biochim Biophys Acta Mol Cell Biol Lipids 2012; 1821:736-46. [DOI: 10.1016/j.bbalip.2011.09.019] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2011] [Revised: 09/20/2011] [Accepted: 09/21/2011] [Indexed: 12/18/2022]
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5
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Versmissen J, Oosterveer DM, Hoekstra M, Out R, Berbée JFP, Blommesteijn-Touw AC, van Vark-van der Zee L, Vongpromek R, Vanmierlo T, Defesche JC, Mulder M, Kastelein JJP, Sijbrands EJG. Apolipoprotein isoform E4 does not increase coronary heart disease risk in carriers of low-density lipoprotein receptor mutations. ACTA ACUST UNITED AC 2011; 4:655-60. [PMID: 22010136 DOI: 10.1161/circgenetics.111.959858] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
BACKGROUND In humans, the E4 allele of the apolipoprotein E gene is associated with increased coronary heart disease risk. Surprisingly, in rodents, apolipoprotein E4 only accelerates the atherosclerotic process when transgenic for the human low-density lipoprotein receptor (LDLR) protein. We therefore investigated whether the LDLR locus interacted with the apolipoprotein E gene genotype on coronary heart disease risk in patients clinically diagnosed with familial hypercholesterolemia with and without LDLR mutation. We investigated whether the presence of an LDLR mutation diminishing LDLR function was protective in E4/E4 carriers. METHODS AND RESULTS In a cohort of 2400 patients clinically diagnosed with familial hypercholesterolemia, we found an LDLR gene mutation in 1383 patients, whereas in 1013 patients, such mutation was not present. In 92 patients homozygous for the apolipoprotein E4, the presence of an LDLR mutation conferred lower coronary heart disease risk (hazard ratio, 0.16; 95% CI, 0.05-0.58; P=0.005). Mirroring these results, the apolipoprotein E4/E4 genotype was also associated with lower coronary heart disease risk in patients with familial hypercholesterolemia with an LDLR mutation (hazard ratio, 0.26; hazard ratio, 0.08-0.80; P=0.02). CONCLUSIONS LDLR function is key to the detrimental effects of apolipoprotein E4 in humans. Kinetic studies in humans are now required to study the consequences of our observation for prevention of both coronary heart disease and Alzheimer disease.
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Affiliation(s)
- Jorie Versmissen
- Department of Internal Medicine, Erasmus University Medical Center, Rotterdam, The Netherlands
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6
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Calandra S, Tarugi P, Speedy HE, Dean AF, Bertolini S, Shoulders CC. Mechanisms and genetic determinants regulating sterol absorption, circulating LDL levels, and sterol elimination: implications for classification and disease risk. J Lipid Res 2011; 52:1885-926. [PMID: 21862702 DOI: 10.1194/jlr.r017855] [Citation(s) in RCA: 62] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
This review integrates historical biochemical and modern genetic findings that underpin our understanding of the low-density lipoprotein (LDL) dyslipidemias that bear on human disease. These range from life-threatening conditions of infancy through severe coronary heart disease of young adulthood, to indolent disorders of middle- and old-age. We particularly focus on the biological aspects of those gene mutations and variants that impact on sterol absorption and hepatobiliary excretion via specific membrane transporter systems (NPC1L1, ABCG5/8); the incorporation of dietary sterols (MTP) and of de novo synthesized lipids (HMGCR, TRIB1) into apoB-containing lipoproteins (APOB) and their release into the circulation (ANGPTL3, SARA2, SORT1); and receptor-mediated uptake of LDL and of intestinal and hepatic-derived lipoprotein remnants (LDLR, APOB, APOE, LDLRAP1, PCSK9, IDOL). The insights gained from integrating the wealth of genetic data with biological processes have important implications for the classification of clinical and presymptomatic diagnoses of traditional LDL dyslipidemias, sitosterolemia, and newly emerging phenotypes, as well as their management through both nutritional and pharmaceutical means.
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Affiliation(s)
- Sebastiano Calandra
- Department of Biomedical Sciences, University of Modena and Reggio Emilia, Modena, Italy.
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7
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Zheng C, Khoo C, Ikewaki K, Sacks FM. Rapid turnover of apolipoprotein C-III-containing triglyceride-rich lipoproteins contributing to the formation of LDL subfractions. J Lipid Res 2007; 48:1190-203. [PMID: 17314277 DOI: 10.1194/jlr.p600011-jlr200] [Citation(s) in RCA: 81] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The atherogenicity theory for triglyceride-rich lipoproteins (TRLs; VLDL + intermediate density lipoprotein) generally cites the action of apolipoprotein C-III (apoC-III), a component of some TRLs, to retard their metabolism in plasma. We studied the kinetics of multiple TRL and LDL subfractions according to the content of apoC-III and apoE in 11 hypertriglyceridemic and normolipidemic persons. The liver secretes mainly two types of apoB lipoproteins: TRL with apoC-III and LDL without apoC-III. Approximately 45% of TRLs with apoC-III are secreted together with apoE. Contrary to expectation, TRLs with apoC-III but not apoE have fast catabolism, losing some or all of their apoC-III and becoming LDL. In contrast, apoE directs TRL flux toward rapid clearance, limiting LDL formation. Direct clearance of TRL with apoC-III is suppressed among particles also containing apoE. TRLs without apoC-III or apoE are a minor, slow-metabolizing precursor of LDL with little direct removal. Increased VLDL apoC-III levels are correlated with increased VLDL production rather than with slow particle turnover. Finally, hypertriglyceridemic subjects have significantly greater production of apoC-III-containing VLDL and global prolongation in residence time of all particle types. ApoE may be the key determinant of the metabolic fate of atherogenic apoC-III-containing TRLs in plasma, channeling them toward removal from the circulation and reducing the formation of LDLs, both those with apoC-III and the main type without apoC-III.
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Affiliation(s)
- Chunyu Zheng
- Department of Nutrition, Harvard School of Public Health, Boston, MA 02115, USA
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8
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Nishiwaki M, Ikewaki K, Bader G, Nazih H, Hannuksela M, Remaley AT, Shamburek RD, Brewer HB. Human Lecithin:Cholesterol Acyltransferase Deficiency. Arterioscler Thromb Vasc Biol 2006; 26:1370-5. [PMID: 16543491 DOI: 10.1161/01.atv.0000217910.90210.99] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Objectives—
Lecithin:cholesterol acyltransferase deficiency (LCAT-def) is characterized by low levels of high-density lipoprotein (HDL) and low-density lipoprotein (LDL) and the accumulation of lipoprotein-X (LpX). Despite the low HDL, atherosclerosis is uncommon in LCAT-def. The decreased LDL would be a possible explanation but the underlying mechanism is not clear. In addition, the mechanism(s) for LpX accumulation is not known. The aim of the present study is to elucidate the mechanism(s) responsible for the low LDL and determine the plasma kinetics of LpX in LCAT-def.
Methods and Results—
We conducted a radiotracer study in LCAT-def (n=2) and normal controls (n=10) and a stable isotope study in one patient and other controls (n=7). LCAT-def LDL was catabolized faster than control LDL in the control subjects as well as in LCAT-def patients. Control LDL was catabolized faster in LCAT-def patients than the controls. The production rate of LDL apolipoprotein B-100 was normal in LCAT-def. The increased LDL apoB-100 catabolism was confirmed by a stable isotope study. LpX was catabolized more slowly in LCAT-def.
Conclusions—
The decreased LDL in LCAT-def is attributable to an increased catabolism caused by a rapid catabolism of abnormal LDL and an upregulation of LDL receptor pathway. The decreased catabolism of LpX contributes to its accumulation in LCAT-def.
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Affiliation(s)
- Masato Nishiwaki
- Molecular Disease Branch, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD, USA.
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9
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Devlin CM, Lee SJ, Kuriakose G, Spencer C, Becker L, Grosskopf I, Ko C, Huang LS, Koschinsky ML, Cooper AD, Tabas I. An Apolipoprotein(a) Peptide Delays Chylomicron Remnant Clearance and Increases Plasma Remnant Lipoproteins and Atherosclerosis In Vivo. Arterioscler Thromb Vasc Biol 2005; 25:1704-10. [PMID: 15905467 DOI: 10.1161/01.atv.0000170819.57945.03] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Objective—
Humans with high expression of apolipoprotein(a) [apo(a)] and high plasma levels of lipoprotein(a) [Lp(a)] are at increased risk for atherosclerosis, but the mechanism is not known. We have previously shown that the KIV
5–8
domain of apo(a) has unique cell-surface binding properties, and naturally occurring fragments of apo(a) encompassing this domain are thought to be atherogenic in humans. To investigate the effect of KIV
5–8
on lipoprotein metabolism and atherosclerosis in vivo, we created several independent lines of liver-targeted KIV
5–8
transgenic mice.
Methods and Results—
The transgenic mice have plasma apo(a) peptide concentrations that are similar to Lp(a) concentrations in humans at risk for coronary artery disease. Remarkably, the transgenic mice had a 2- to 4-fold increase in cholesterol-rich remnant lipoproteins (RLPs) when fed a cholesterol-rich diet, and a 5- to 20-fold increase in atherosclerosis lesion area in the aortic root. Using an in vivo clearance study, we found only slight differences in the triglyceride and apolipoprotein B secretion rates between the 2 groups of mice, suggesting an RLP clearance defect. Using an isolated perfused mouse liver system, we showed that transgenic livers had a slower rate of RLP removal, which was retarded further when KIV
5–8
, full-length apo(a), or Lp(a) were added to the perfusate. An apo(a) peptide that does not interact with cells, K(IV
2
)
3
, did not retard RLP removal, and low-density lipoprotein (LDL) had a much smaller effect than Lp(a).
Conclusions—
We propose that high levels of apo(a)/Lp(a), perhaps acting via a specific cell-surface binding domain, inhibit hepatic clearance of remnants, leading to high plasma levels of RLPs and markedly enhanced atherosclerosis. We speculate that the KIV
5–8
region of apo(a) competes with one or more receptors for remnant clearance in the liver and that this process may represent one mechanism accounting for increased atherosclerosis in humans with high secretion levels of apo(a).
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Affiliation(s)
- Cecilia M Devlin
- Department of Medicine, Columbia University, 630 W 168th St, New York, NY 10032, USA
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10
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Yue P, Isley WL, Harris WS, Rosipal S, Akin CD, Schonfeld G. Genetic variants of ApoE account for variability of plasma low-density lipoprotein and apolipoprotein B levels in FHBL. Atherosclerosis 2005; 178:107-13. [PMID: 15585207 DOI: 10.1016/j.atherosclerosis.2004.06.020] [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] [Received: 12/09/2003] [Revised: 06/16/2004] [Accepted: 06/28/2004] [Indexed: 10/26/2022]
Abstract
We report two novel APOB mutations causing short apolipoprotein B (apoB) truncations undetectable in plasma and familial hypobetalipoproteinemia (FHBL). In Family 56, a 5 bp deletion in APOB exon 7 (870_874del5) causes a frame shift, converting tyrosine to a stop codon (Y220X) and producing an apoB-5 truncation. In Family 59, a point mutation (1941G>T) in APOB exon 13 converts glutamic acid to stop codon (E578X), specifying apoB-13. A recurrent mutation in exon 26 (4432delT) produces apoB-30.9 in Family 58. In some members of these families, we observed that plasma low-density lipoprotein (LDL) cholesterol and apoB levels were unusually low even for subjects heterozygous for FHBL. To ascertain whether genetic variations in apolipoprotein E (apoE) would explain some of the variations of apoB and LDL cholesterol levels, apoE genotypes were assessed in affected subjects from a total of eight FHBL families with short apoB truncations. Heterozygous FHBL with the epsilon3/epsilon4 genotype had 10-1 5mg/dL higher plasma LDL cholesterol and apoB levels compared to subjects with the epsilon2/epsilon3 and epsilon3/epsilon3 genotypes. The apoE genotype has been reported to account for approximately 10% of the variation of LDL cholesterol in the general population. It accounted for 15-60% of the variability of plasma LDL cholesterol or apoB levels in our FHBL subjects. The physiologic bases for the greater effects of apoE in FHBL remain to be determined.
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Affiliation(s)
- Pin Yue
- Division of Endocrinology, Metabolism, and Lipid Research, Washington University, School of Medicine, St. Louis, MO 63110, USA
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