1
|
Helgadottir A, Sulem P, Thorgeirsson G, Gretarsdottir S, Thorleifsson G, Jensson BÖ, Arnadottir GA, Olafsson I, Eyjolfsson GI, Sigurdardottir O, Thorsteinsdottir U, Gudbjartsson DF, Holm H, Stefansson K. Rare SCARB1 mutations associate with high-density lipoprotein cholesterol but not with coronary artery disease. Eur Heart J 2019; 39:2172-2178. [PMID: 29596577 PMCID: PMC6001888 DOI: 10.1093/eurheartj/ehy169] [Citation(s) in RCA: 49] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/18/2017] [Accepted: 03/14/2018] [Indexed: 12/16/2022] Open
Abstract
Aims Scavenger receptor Class B Type 1 (SR-BI) is a major receptor for high-density lipoprotein (HDL) that promotes hepatic uptake of cholesterol from HDL. A rare mutation p.P376L, in the gene encoding SR-BI, SCARB1, was recently reported to associate with elevated HDL cholesterol (HDL-C) and increased risk of coronary artery disease (CAD), suggesting that increased HDL-C caused by SR-BI impairment might be an independent marker of cardiovascular risk. We tested the hypothesis that alleles in or close to SCARB1 that associate with elevated levels of HDL-C also associate with increased risk of CAD in the relatively homogeneous population of Iceland. Methods and results Using a large resource of whole-genome sequenced Icelanders, we identified thirteen SCARB1 coding mutations that we examined for association with HDL-C (n = 136 672). Three rare SCARB1 mutations, encoding p.G319V, p.V111M, and p.V32M (combined allelic frequency = 0.2%) associate with elevated levels of HDL-C (p.G319V: β = 11.1 mg/dL, P = 8.0 × 10−7; p.V111M: β = 8.3 mg/dL, P = 1.1 × 10−6; p.V32M: β = 10.2 mg/dL, P = 8.1 × 10−4). These mutations do not associate with CAD (36 886 cases/306 268 controls) (odds ratio = 0.90, 95% confidence interval 0.67–1.22, P = 0.49), despite effects on HDL-C comparable to that reported for p.P376L, both in terms of direction and magnitude. Furthermore, HDL-C raising alleles of three common SCARB1 non-coding variants, including one previously unreported (rs61941676-C: β = 1.25 mg/dL, P = 1.7 × 10−18), and of one low frequency coding variant (p.V135I) that independently associate with higher HDL-C, do not confer increased risk of CAD. Conclusion Elevated HDL-C due to genetically compromised SR-BI function is not a marker of CAD risk. ![]()
Collapse
Affiliation(s)
- Anna Helgadottir
- deCODE Genetics/Amgen, Inc., Sturlugata 8, 101 Reykjavik, Iceland
| | - Patrick Sulem
- deCODE Genetics/Amgen, Inc., Sturlugata 8, 101 Reykjavik, Iceland
| | - Gudmundur Thorgeirsson
- deCODE Genetics/Amgen, Inc., Sturlugata 8, 101 Reykjavik, Iceland.,Faculty of Medicine, Department of Medicine, University of Iceland, Saemundargata 2, 101 Reykjavik, Iceland.,Division of Cardiology, Department of Internal Medicine, Landspitali, National University Hospital of Iceland, Hringbraut, 101 Reykjavik, Iceland
| | | | | | | | | | - Isleifur Olafsson
- Department of Clinical Biochemistry, Landspitali, National University Hospital, Hringbraut, 101 Reykjavik, Iceland
| | | | - Olof Sigurdardottir
- Department of Clinical Biochemistry, Akureyri Hospital, 600 Akureyri, Iceland
| | - Unnur Thorsteinsdottir
- deCODE Genetics/Amgen, Inc., Sturlugata 8, 101 Reykjavik, Iceland.,Faculty of Medicine, Department of Medicine, University of Iceland, Saemundargata 2, 101 Reykjavik, Iceland
| | - Daniel F Gudbjartsson
- deCODE Genetics/Amgen, Inc., Sturlugata 8, 101 Reykjavik, Iceland.,School of Engineering and Natural Sciences, University of Iceland, 101 Reykjavik, Iceland
| | - Hilma Holm
- deCODE Genetics/Amgen, Inc., Sturlugata 8, 101 Reykjavik, Iceland
| | - Kari Stefansson
- deCODE Genetics/Amgen, Inc., Sturlugata 8, 101 Reykjavik, Iceland.,Faculty of Medicine, Department of Medicine, University of Iceland, Saemundargata 2, 101 Reykjavik, Iceland
| |
Collapse
|
2
|
Lee P, Ulatowski LM. Vitamin E: Mechanism of transport and regulation in the CNS. IUBMB Life 2018; 71:424-429. [PMID: 30556640 DOI: 10.1002/iub.1993] [Citation(s) in RCA: 41] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2018] [Revised: 11/17/2018] [Accepted: 11/26/2018] [Indexed: 12/11/2022]
Abstract
Although vitamin E has been recognized as a critical micronutrient to neuronal health for more than half a century, vitamin E transport and regulation in the brain remain a mystery. Currently, the majority of what is known about vitamin E transport has been delineated in the liver. However, clues from the pathogenesis of neurological-related vitamin E deficient diseases point to compromised neuronal integrity and function, underlining the critical need to understand vitamin E regulation in the CNS. Additionally, most of the same molecular players involved in vitamin E transport in the liver are also found in CNS, including sterol SRB1, TTP, and ABCA/ABCG, suggesting similar intracellular pathways between these organ systems. Finally, based on chemical similarities, intracellular CNS shuttling of vitamin E likely resembles cholesterol's use of ApoE particles. Utilizing this information, this review will address what is currently known about trafficking vitamin E across the blood brain barrier in order to ensure an adequate supply of the essential nutrient to the brain. Although debatable, the health of the brain in relation to vitamin E levels has been demonstrated, most notably in oxidative stress-related conditions such as ataxias, Alzheimer's disease, and Parkinson's disease. Future vitamin E research is vital in understanding how the regulation of the vitamin can aid in the prevention, treatment, and curing of neurological diseases. © 2018 IUBMB Life, 71(4):424-429, 2019.
Collapse
Affiliation(s)
- Paris Lee
- Ursuline College, Department of Biology, 2550 Lander Rd Pepper Pike, Ohio 44124
| | - Lynn M Ulatowski
- Ursuline College, Department of Biology, 2550 Lander Rd Pepper Pike, Ohio 44124
| |
Collapse
|
3
|
Reboul E. Vitamin E intestinal absorption: Regulation of membrane transport across the enterocyte. IUBMB Life 2018; 71:416-423. [PMID: 30308094 DOI: 10.1002/iub.1955] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2018] [Revised: 08/28/2018] [Accepted: 08/31/2018] [Indexed: 12/29/2022]
Abstract
Vitamin E is an essential molecule for our development and health. It has long been thought that it was absorbed and transported through cellular membranes by a passive diffusion process. However, data obtained during the past 15 years showed that its absorption is actually mediated, at least in part, by cholesterol membrane transporters including the scavenger receptor class B type I (SR-BI), CD36 molecule (CD36), NPC1-like transporter 1 (NPC1L1), and ATP-binding cassettes A1 and G1 (ABCA1 and ABCG1). This review focuses on the absorption process of vitamin E across the enterocyte. A special attention is given to the regulation of this process, including the possible competition with other fat-soluble micronutrients, and the modulation of transporter expressions. Overall, recent results noticeably increased the comprehension of vitamin E intestinal transport, but additional investigations are still required to fully appreciate the mechanisms governing vitamin E bioavailability. © 2018 IUBMB Life, 71(4):416-423, 2019.
Collapse
|
4
|
Effect of anti-hyperlipidemia drugs on the alpha-tocopherol concentration and their potential for murine malaria infection. Parasitol Res 2015; 115:69-75. [PMID: 26358099 DOI: 10.1007/s00436-015-4722-6] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2015] [Accepted: 09/02/2015] [Indexed: 10/23/2022]
Abstract
The current preventions of malaria are protection against mosquito bites and taking chemoprophylactic anti-malarial drugs. However, drug therapies are usually associated with adverse events and emergency of drug-resistant malaria parasites. Previous study showed that host plasma alpha-tocopherol deficiency enhanced resistance against malaria infection in mice. Here, we report a new prevention strategy against malaria by using anti-hyperlipidemia drugs, ezetimibe, berberine, cholestyramine, and probucol to modify the host plasma alpha-tocopherol concentration. The drugs were mixed with diet and fed to C57BL/6J mice for 2 weeks. Although all drugs reduced plasma alpha-tocopherol concentration after 2 weeks of feeding, probucol-treated mice showed 90 % reduction and it was the lowest alpha-tocopherol concentration among the four drugs. Ezetimibe, berberine, and combination of ezetimibe and berberine pretreatment for 2 weeks were not effective against infection of Plasmodium yoelii XL17, a lethal strain, for survival and parasitemia in mice. Two-week pretreatment and 1-week treatment after infection of cholestyramine had also no effect on malaria infection. Survival rates of cholestyramine, ezetimibe, and/or berberine treated mice were 0-22 %. However, probucol caused significant decrease in parasitemia and increased in mice survival following 2-week pretreatment and 1-week treatment after infection. All control mice died while all probucol treated mice survived during the course of infection. Thus, probucol which reduced plasma alpha-tocopherol concentration was effective in enhancing the host to resist malaria infection in mice. Our finding indicates that plasma alpha-tocopherol reducing drugs like probucol might be a candidate for beneficial prevention strategy for travelers from malaria-free area.
Collapse
|
5
|
Major JM, Yu K, Wheeler W, Zhang H, Cornelis MC, Wright ME, Yeager M, Snyder K, Weinstein SJ, Mondul A, Eliassen H, Purdue M, Hazra A, McCarty CA, Hendrickson S, Virtamo J, Hunter D, Chanock S, Kraft P, Albanes D. Genome-wide association study identifies common variants associated with circulating vitamin E levels. Hum Mol Genet 2011; 20:3876-83. [PMID: 21729881 PMCID: PMC3168288 DOI: 10.1093/hmg/ddr296] [Citation(s) in RCA: 89] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2011] [Revised: 06/17/2011] [Accepted: 06/27/2011] [Indexed: 02/07/2023] Open
Abstract
In genome-wide association studies (GWAS) of common genetic variants associated with circulating alpha- and gamma-tocopherol concentrations in two adult cohorts comprising 5006 men of European descent, we observed three loci associated with alpha-tocopherol levels, two novel single-nucleotide polymorphisms (SNPs), rs2108622 on 19pter-p13.11 (P= 1.7 × 10(-8)) and rs11057830 on 12q24.31 (P= 2.0 × 10(-8)) and confirmed a previously reported locus marked by rs964184 on 11q23.3 (P= 2.7 × 10(-10)). The three SNPs have been reported to be associated with lipid metabolism and/or regulation. We replicated these findings in a combined meta-analysis with two independent samples, P= 7.8 × 10(-12) (rs964184 on 11q23.3 near BUD13, ZNF259 and APOA1/C3/A4/A5), P= 1.4 × 10(-10) (rs2108622 on 19pter-p13.11 near CYP4F2) and P= 8.2 × 10(-9) (rs11057830 on 12q24.31 near SCARB1). Combined, these SNPs explain 1.7% of the residual variance in log alpha-tocopherol levels. In one of the two male GWAS cohorts (n= 992), no SNPs were significantly associated with gamma-tocopherol concentrations after including data from the replication sample for 71 independent SNPs with P< 1 × 10(-4) identified.
Collapse
Affiliation(s)
| | - Kai Yu
- Division of Cancer Epidemiology and Genetics and
| | - William Wheeler
- Information Management Services, Inc., Silver Spring, MD, USA
| | - Hong Zhang
- Division of Cancer Epidemiology and Genetics and
- Institute of Biostatistics, School of Life Science, Fudan University, Shanghai, People's Republic of China
| | | | | | - Meredith Yeager
- Core Genotyping Facility, National Cancer Institute, NIH, Bethesda, MD, USA
| | - Kirk Snyder
- Information Management Services, Inc., Silver Spring, MD, USA
| | | | | | - Heather Eliassen
- Channing Laboratory, Brigham and Women's Hospital, Harvard Medical School, Boston, MA, USA
| | - Mark Purdue
- Division of Cancer Epidemiology and Genetics and
| | - Aditi Hazra
- Program in Molecular and Genetic Epidemiology and
| | | | - Sara Hendrickson
- Department of Nutrition
- Department of Epidemiology, Harvard School of Public Health, Boston, MA, USA,
| | - Jarmo Virtamo
- Department of Chronic Disease Prevention, National Institute for Health and Welfare, Helsinki, Finland
| | - David Hunter
- Department of Nutrition
- Program in Molecular and Genetic Epidemiology and
- Department of Epidemiology, Harvard School of Public Health, Boston, MA, USA,
| | | | - Peter Kraft
- Program in Molecular and Genetic Epidemiology and
- Department of Epidemiology, Harvard School of Public Health, Boston, MA, USA,
| | | |
Collapse
|
6
|
Li B, Vachali P, Bernstein PS. Human ocular carotenoid-binding proteins. Photochem Photobiol Sci 2010; 9:1418-25. [PMID: 20820671 PMCID: PMC3938892 DOI: 10.1039/c0pp00126k] [Citation(s) in RCA: 74] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2010] [Accepted: 07/29/2010] [Indexed: 02/06/2023]
Abstract
Two dietary carotenoids, lutein and zeaxanthin, are specifically delivered to the human macula at the highest concentration anywhere in the body. Whenever a tissue exhibits highly selective uptake of a compound, it is likely that one or more specific binding proteins are involved in the process. Over the past decade, our laboratory has identified and characterized several carotenoid-binding proteins from human retina including a pi isoform of glutathione S-transferase (GSTP1) as a zeaxanthin-binding protein, a member of the steroidogenic acute regulatory domain (StARD) family as a lutein-binding protein, and tubulin as a less specific, but higher capacity site for carotenoid deposition. In this article, we review the purification and characterization of these carotenoid-binding proteins, and we relate these ocular carotenoid-binding proteins to the transport and uptake role of serum lipoproteins and scavenger receptor proteins in a proposed pathway for macular pigment carotenoid delivery to the human retina.
Collapse
Affiliation(s)
- Binxing Li
- Department of Ophthalmology and Visual Sciences, 65 Mario Capecchi Drive, Moran Eye Center, University of Utah School of Medicine, Salt Lake City, UT, 84132, U. S. A.; Fax: +1 801-581-3357; Tel: +1 801-581-6078
| | - Preejith Vachali
- Department of Ophthalmology and Visual Sciences, 65 Mario Capecchi Drive, Moran Eye Center, University of Utah School of Medicine, Salt Lake City, UT, 84132, U. S. A.; Fax: +1 801-581-3357; Tel: +1 801-581-6078
| | - Paul S. Bernstein
- Department of Ophthalmology and Visual Sciences, 65 Mario Capecchi Drive, Moran Eye Center, University of Utah School of Medicine, Salt Lake City, UT, 84132, U. S. A.; Fax: +1 801-581-3357; Tel: +1 801-581-6078
| |
Collapse
|
7
|
Lemaire-Ewing S, Desrumaux C, Néel D, Lagrost L. Vitamin E transport, membrane incorporation and cell metabolism: Is alpha-tocopherol in lipid rafts an oar in the lifeboat? Mol Nutr Food Res 2010; 54:631-40. [PMID: 20166147 DOI: 10.1002/mnfr.200900445] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Vitamin E is composed of closely related compounds, including tocopherols and tocotrienols. Studies of the last decade provide strong support for a specific role of alpha-tocopherol in cell signalling and the regulation of gene expression. It produces significant effects on inflammation, cell proliferation and apoptosis that are not shared by other vitamin E isomers with similar antioxidant properties. The different behaviours of vitamin E isomers might relate, at least in part, to the specific effects they exert at the plasma membrane. alpha-Tocopherol is not randomly distributed throughout the phospholipid bilayer of biological membranes, and as compared with other isomers, it shows a propensity to associate with lipid rafts. Distinct aspects of vitamin E transport and metabolism is discussed with emphasis on the interaction between alpha-tocopherol and lipid rafts and the consequences of these interactions on cell metabolism.
Collapse
|
8
|
|
9
|
Nell S, Bahtz R, Bossecker A, Kipp A, Landes N, Bumke-Vogt C, Halligan E, Lunec J, Brigelius-Flohé R. PCR-verified microarray analysis and functionalin vitrostudies indicate a role of α-tocopherol in vesicular transport. Free Radic Res 2009; 41:930-42. [PMID: 17654050 DOI: 10.1080/10715760701416988] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Global gene expression profiles of livers from mice, fed diets differing in alpha-tocopherol content, were compared using DNA microarray technology. Three hundred and eighty nine genes were found to significantly differ in their expression level by a factor of 2 or higher between the high and the low alpha-tocopherol group. Functional clustering using the EASE software identified 121 genes involved in transport processes. Twenty-one thereof were involved in (synaptic) vesicular trafficking. Up-regulation of syntaxin 1C (Stx1c), vesicle-associated membrane protein 1 (Vamp1), N-ethylmaleimide-sensitive factor (Nsf) and syntaxin binding protein 1 (Stxbp1, Munc18-1) was verified by real time PCR. At a functional level, alpha-tocopherol increased the secretory response in RBL and PC12 cells. Although here detected in liver, the alpha-tocopherol-responsive pathways are also relevant to neurotransmission. A role of alpha-tocopherol in the vesicular transport might not only affect its own absorption and transport but also explain the neural dysfunctions observed in severe alpha-tocopherol deficiency.
Collapse
Affiliation(s)
- Sandra Nell
- German Institute of Human Nutrition Potsdam-Rehbrücke, Nuthetal, Germany
| | | | | | | | | | | | | | | | | |
Collapse
|
10
|
Brigelius-Flohé R. Vitamin E: the shrew waiting to be tamed. Free Radic Biol Med 2009; 46:543-54. [PMID: 19133328 DOI: 10.1016/j.freeradbiomed.2008.12.007] [Citation(s) in RCA: 159] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/22/2008] [Revised: 11/28/2008] [Accepted: 12/03/2008] [Indexed: 12/16/2022]
Abstract
Vitamin E is the last of all vitamins whose essentiality is not yet understood. Its widely accepted role as a lipophilic antioxidant has been questioned, since proof of its in vivo relevance remained scarce. The influence of vitamin E on biomarkers of oxidative stress in vivo is inconsistent and metabolites of vitamin E having reacted as an antioxidant are hardly detectable. Novel functions of vitamin E include the regulation of enzymes, most of which are membrane bound or activated by membrane recruitment. Also, expression of genes responds to vitamin E. The search for a transcription factor common to all regulated genes failed so far and a receptor that specifically binds vitamin E has not yet been identified. According to microarray data, pathways preferentially affected by the vitamin E status are the inflammatory response and cellular traffic. A role of vitamin E in cellular trafficking could best explain the neurological symptoms seen in vitamin E deficiency. Emerging knowledge on vitamin E is compiled here with the perspective to unravel the molecular mechanisms that could more likely explain the essentiality of the vitamin than its ability to scavenge free radicals.
Collapse
Affiliation(s)
- Regina Brigelius-Flohé
- German Institute of Human Nutrition Potsdam-Rehbruecke, Department of Biochemistry of Micronutrients, Nuthetal, Germany.
| |
Collapse
|
11
|
B M, V A, C C, I S, E O, C B. So many options but one choice: the human body prefers alpha-tocopherol. A matter of stereochemistry. J Med Life 2008; 1:376-82. [PMID: 20108516 PMCID: PMC5654212] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
alpha-Tocopherol belongs to the group of vitamin E vitamers. Recent years findings indicate that alpha-tocopherol is more than just a simple fat-soluble anti-oxidant as it was found that it can also regulate gene expression. From all vitamin E vitamers human body preferentially retains alpha-tocopherol, but the reasons for this preference are still elusive. Different studies indicated that human body, through the action of two hepatic proteins, alpha-tocopherol transfer protein (alpha-TTP) and cytochrome P450 4F2 (CYP4F2), is able to make subtle structural differences between different vitamin E forms. This is an example of stereochemistry used as a discrimination factor between molecules with different biological activities.
Collapse
Affiliation(s)
- Manolescu B
- Department of Biochemistry, Faculty of Medicine, University of Medicine and Pharmacy “Carol Davila”
| | - Atanasiu V
- Department of Biochemistry, Faculty of Medicine, University of Medicine and Pharmacy “Carol Davila”
| | - Cercasov C
- Department of Organic Chemistry, Faculty of Chemistry, University of Bucharest
| | - Stoian I
- Department of Biochemistry, Faculty of Medicine, University of Medicine and Pharmacy “Carol Davila”
| | - Oprea E
- Department of Organic Chemistry, Faculty of Chemistry, University of Bucharest
| | - Buşu C
- Department of Biochemistry, Faculty of Medicine, University of Medicine and Pharmacy “Carol Davila”
| |
Collapse
|
12
|
Human fasting plasma concentrations of vitamin E and carotenoids, and their association with genetic variants in apo C-III, cholesteryl ester transfer protein, hepatic lipase, intestinal fatty acid binding protein and microsomal triacylglycerol transfer protein. Br J Nutr 2008; 101:680-7. [DOI: 10.1017/s0007114508030754] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Plasma concentrations of vitamin E and carotenoids are governed by several factors, including genetic factors. Single nucleotide polymorphisms (SNP) in some genes involved in lipid metabolism have recently been associated with fasting plasma concentrations of these fat-soluble micronutrients. To further investigate the role of genetic factors that modulate the plasma concentrations of these micronutrients, we assessed whether SNP in five candidate genes (apo C-III,CETP,hepatic lipase,I-FABPandMTP) were associated with the plasma concentrations of these micronutrients. Fasting plasma vitamin E and carotenoid concentrations were measured in 129 French Caucasian subjects (forty-eight males and eighty-one females). Candidate SNP were genotyped by PCR amplification followed by restriction fragment length polymorphisms. Plasma γ-tocopherol, α-carotene and β-carotene concentrations were significantly different (P < 0·05) in subjects who carried different SNP variants in hepatic lipase. Plasma α-tocopherol concentrations were significantly different in subjects who had different SNP variants in apo C-III and cholesteryl ester transfer protein (CETP). Plasma lycopene concentrations were significantly different (P < 0·05) in women who had different SNP variants in intestinal fatty acid binding protein (I-FABP). Finally, there was no effect of SNP variants in microsomal TAG transfer protein upon the plasma concentrations of these micronutrients. Most of the observed differences remained significant after the plasma micronutrients were adjusted for plasma TAG and cholesterol. These results suggest that apo C-III, CETP and hepatic lipase play a role in determining the plasma concentrations of tocopherols while hepatic lipase and I-FABP may modulate plasma concentrations of carotenoids.
Collapse
|
13
|
Borel P, Moussa M, Reboul E, Lyan B, Defoort C, Vincent-Baudry S, Maillot M, Gastaldi M, Darmon M, Portugal H, Planells R, Lairon D. Human plasma levels of vitamin E and carotenoids are associated with genetic polymorphisms in genes involved in lipid metabolism. J Nutr 2007; 137:2653-9. [PMID: 18029479 DOI: 10.1093/jn/137.12.2653] [Citation(s) in RCA: 117] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Vitamin E and carotenoids are fat-soluble micronutrients carried by plasma lipoproteins. Their plasma concentrations are governed by several factors, some of which are genetic, but data on these genetic factors remain scarce. We hypothesized that genes involved in lipid metabolism, i.e. the genes implicated in intestinal uptake, intracellular trafficking, and the lipoprotein distribution of lipids, play a role in the plasma concentrations of these micronutrients. To verify this hypothesis, we assessed whether the plasma status of vitamin E and carotenoids is related to genes involved in lipid metabolism. Fasting plasma vitamin E (alpha- and gamma-tocopherol) and carotenoid (alpha- and beta-carotene, lutein, lycopene, beta-cryptoxanthin, and zeaxanthin) concentrations were measured in 48 males and 80 females. The following genes were genotyped [single nucleotide polymorphisms (SNP)]: apolipoprotein (apo) A-IV, apo B, apo E, lipoprotein lipase, and scavenger-receptor class B type I (SR-BI). Plasma alpha-tocopherol concentrations were different (P < 0.05) in subjects bearing different SNP in apo A-IV, apo E, and SR-BI. Plasma gamma-tocopherol concentrations were different (P < 0.05) in subjects bearing different SNP in apo A-IV and SR-BI. Alpha-carotene concentrations were different (P < 0.05) in subjects bearing different SNP in SR-BI. Beta-carotene concentrations were different (P < 0.05) in subjects bearing different SNP in apo B and SR-BI. Lycopene concentrations were different (P < 0.05) in subjects bearing different SNP in apo A-IV and apo B. Beta-cryptoxanthin concentrations were different (P < 0.05) in subjects bearing different SNP in SR-BI. Plasma lutein and zeaxanthin concentrations did not differ in subjects bearing different SNP. Most of the differences remained significant after the plasma micronutrients were adjusted for plasma triglycerides and cholesterol. These results suggest that genes involved in lipid metabolism influence the plasma concentrations of these fat-soluble micronutrients.
Collapse
Affiliation(s)
- Patrick Borel
- INSERM, U476 Nutrition Humaine et Lipides, INRA, UMR1260, and Univ Méditerranée Aix-Marseille 2, Faculté de Médecine, IPHM-IFR 125, Marseille, F-13385 France.
| | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
14
|
Rigotti A. Absorption, transport, and tissue delivery of vitamin E. Mol Aspects Med 2007; 28:423-36. [PMID: 17320165 DOI: 10.1016/j.mam.2007.01.002] [Citation(s) in RCA: 162] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2006] [Accepted: 01/02/2007] [Indexed: 02/07/2023]
Abstract
Vitamin E is one of the most abundant lipid-soluble antioxidant agents found in plasma and cells of higher mammals. The uptake, transport and tissue delivery of alpha-tocopherol, a key vitamin E form, involves molecular, biochemical, and cellular processes closely related to overall lipid and lipoprotein homeostasis. This review highlights recent findings that have led to a better understanding of vitamin E transport, including intestinal absorption, hepatic transport, and cellular uptake of alpha-tocopherol in vivo. This new information may be critical for manipulation of vitamin E homeostasis in a variety of oxidative stress-related disease conditions in humans.
Collapse
Affiliation(s)
- Attilio Rigotti
- Departamento de Gastroenterología, Facultad de Medicina, Pontificia Universidad Católica, Hospital UC, Marcoleta 367, Santiago, Chile.
| |
Collapse
|
15
|
Abstract
Almost a century ago, plant extracts were documented to be critical for the fertility of rodents. This activity was later ascribed to vitamin E, a term comprising a number of structurally related plant lipids that function as fat soluble antioxidants. The alpha-tocopherol transfer protein (TTP) is a critical regulator of vitamin E status that stimulates the movement of vitamin E between membrane vesicles in vitro and facilitates the secretion of tocopherol from hepatocytes. Heritable mutations in the ttpA gene cause ataxia with vitamin E deficiency (AVED), an autosomal recessive disorder characterized by low plasma vitamin E levels and progressive neurodegeneration. This chapter summarizes recent advances in our understanding of the molecular and physiological aspects of TTP activity.
Collapse
Affiliation(s)
- D Manor
- Division of Nutritional Sciences, Cornell University, Ithaca, New York 14853, USA
| | | |
Collapse
|
16
|
Sun B, Eckhardt ERM, Shetty S, van der Westhuyzen DR, Webb NR. Quantitative analysis of SR-BI-dependent HDL retroendocytosis in hepatocytes and fibroblasts. J Lipid Res 2006; 47:1700-13. [PMID: 16705213 DOI: 10.1194/jlr.m500450-jlr200] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
Previous studies have suggested that HDL retroendocytosis may play a role in scavenger receptor class B type I (SR-BI)-dependent selective lipid uptake in a cell-specific manner. To investigate this possibility, we developed methods to quantitatively measure HDL uptake and resecretion in fibroblast (COS-7) and hepatocyte (HepG2) cells expressing exogenous SR-BI. Approximately 17% and 24% of HDL associated in an SR-BI-dependent manner with COS-7 and HepG2 cells, respectively, accumulates intracellularly after a 10 min incubation. To determine whether this intracellular HDL undergoes retroendocytosis, we developed a pulse-chase assay whereby internalized biotinylated (125)I-HDL(3) secreted from cells is quantitatively precipitated from cell supernatants using immobilized streptavidin. Our results show a rapid secretion of a portion of intracellular HDL from both cell types (representing 4-7% of the total cell-associated HDL) that is almost complete within 30 min (half-life approximately 10 min). In COS-7 cells, the calculated rate of HDL secretion ( approximately 0.5 ng HDL/mg/min) was >30-fold slower than the rate of SR-BI-dependent selective cholesteryl ester (CE) uptake ( approximately 17 ng HDL/mg/min), whereas the rate of release of HDL from the cell surface ( approximately 19 ng HDL/mg/min) was similar to the rate of selective CE uptake. Notably, the rate of SR-BI-dependent HDL resecretion in COS-7 and HepG2 cells was similar. BLT1, a compound that inhibits selective CE uptake, does not alter the amount of SR-BI-mediated HDL retroendocytosis in COS-7 cells. From these data, we conclude that HDL retroendocytosis in COS-7 and HepG2 cells is similar and that the vast majority of SR-BI-dependent selective uptake occurs at the cell surface in both cell types.
Collapse
Affiliation(s)
- Bing Sun
- Department of Internal Medicine, Graduate Center for Nutritional Sciences, University of Kentucky Medical Center, Lexington, 40536, USA
| | | | | | | | | |
Collapse
|
17
|
Jerkovic L, Voegele AF, Chwatal S, Kronenberg F, Radcliffe CM, Wormald MR, Lobentanz EM, Ezeh B, Eller P, Dejori N, Dieplinger B, Lottspeich F, Sattler W, Uhr M, Mechtler K, Dwek RA, Rudd PM, Baier G, Dieplinger H. Afamin is a novel human vitamin E-binding glycoprotein characterization and in vitro expression. J Proteome Res 2005; 4:889-99. [PMID: 15952736 DOI: 10.1021/pr0500105] [Citation(s) in RCA: 85] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Hydrophobic vitamins are transported in human plasma and extravascular fluids by carrier proteins. No specific protein has been described so far for vitamin E, which plays a crucial role in protecting against oxidative damage and disease. We report here the purification of a 75-kDa glycoprotein with vitamin E-binding properties by stepwise chromatography of lipoprotein-depleted human plasma and monitoring of vitamin E (alpha-tocopherol)-binding activity. Partial sequencing identified this protein as afamin, a previously described member of the albumin gene family with four or five potential N-glycosylation sites. Glycosylation analysis indicated that >90% of the glycans were sialylated biantennary complex structures. The vitamin E-binding properties were confirmed using recombinantly expressed afamin. Qualitative and quantitative analysis of plasma and extravascular fluids revealed an abundant presence of this protein not only in plasma (59.8+/-13.3 microg/mL) but also in extravascular fluids such as follicular (34.4+/-12.7 microg/mL) and cerebrospinal (0.28+/-0.16 microg/mL) fluids, suggesting potential roles for afamin in fertility and neuroprotection. Afamin is partly (13%) bound to plasma lipoproteins. Afamin and vitamin E concentrations significantly correlate in follicular and cerebrospinal fluids but not in plasma. The vitamin E association of afamin in follicular fluid was directly demonstrated by gel filtration chromatography and immunoprecipitation which complements the in vitro findings for purified native and recombinant afamin.
Collapse
Affiliation(s)
- Lidija Jerkovic
- Division of Genetic Epidemiology, Department of Medical Genetics, Clinical and Molecular Pharmacology, Innsbruck Medical University, Schoepfstrasse 41, A-6020 Innsbruck, Austria
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
18
|
Wu JHY, Hodgson JM, Ward NC, Clarke MW, Puddey IB, Croft KD. Nitration of gamma-tocopherol prevents its oxidative metabolism by HepG2 cells. Free Radic Biol Med 2005; 39:483-94. [PMID: 16043020 DOI: 10.1016/j.freeradbiomed.2005.04.001] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/01/2005] [Revised: 03/29/2005] [Accepted: 04/02/2005] [Indexed: 10/25/2022]
Abstract
Gamma-tocopherol (gammaT) is one of the major forms of vitamin E consumed in the diet. Previous reports have suggested increased levels of nitrated gamma-tocopherol (5-NO2-gammaT) in smokers and individuals with conditions associated with elevated nitrative stress. The monitoring of 5-NO2-gammaT and its possible metabolite(s) may be a useful marker of reactive nitrogen species generation in vivo. The major pathway for the metabolism of gammaT is the cytochrome P450 dependent oxidation to its water-soluble metabolite gamma-CEHC, which is excreted in urine. In order to determine if 5-NO2-gammaT could be metabolised via the same route and detected in urine we developed a sensitive gas chromatography-mass spectrometry assay for 5-NO2-gamma-CEHC. 5-NO2-gamma-CEHC was synthesised and its structure confirmed by proton nuclear magnetic resonance and mass spectrometry. While gamma-CEHC was abundant in urine from healthy volunteers, as well as patients with coronary heart disease and type 2 diabetes, 5-NO2-gamma-CEHC was undetectable (limit of detection of 5 nM). To understand this observation we examined the uptake and metabolism of gammaT and 5-NO2-gammaT by HepG2 cells. gammaT was readily incorporated into cells and metabolised to gamma-CEHC over a period of 48 hours. In contrast, 5-NO2-gammaT was poorly incorporated into HepG2 cells and not metabolised to 5-NO2-gamma-CEHC over the same time period. We conclude that nitration of gammaT prevents its incorporation into liver cells and therefore its metabolism to the water-soluble metabolite. Whether 5-NO2-gammaT could be metabolised via other pathways in vivo requires further investigation.
Collapse
Affiliation(s)
- Jason H Y Wu
- School of Medicine and Pharmacology, University of Western Australia, PO Box X2213, GPO Perth 6847, West Australia
| | | | | | | | | | | |
Collapse
|
19
|
Qian J, Morley S, Wilson K, Nava P, Atkinson J, Manor D. Intracellular trafficking of vitamin E in hepatocytes: the role of tocopherol transfer protein. J Lipid Res 2005; 46:2072-82. [PMID: 16024914 DOI: 10.1194/jlr.m500143-jlr200] [Citation(s) in RCA: 105] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
The term vitamin E denotes a family of tocopherols and tocotrienols, plant lipids that are essential for vertebrate fertility and health. The principal form of vitamin E found in humans, RRR-alpha-tocopherol (TOH), is thought to protect cells by virtue of its ability to quench free radicals, and functions as the main lipid-soluble antioxidant. Regulation of vitamin E homeostasis occurs in the liver, where TOH is selectively retained while other forms of vitamin E are degraded. Through the action of tocopherol transfer protein (TTP), TOH is then secreted from the liver into circulating lipoproteins that deliver the vitamin to target tissues. Presently, very little is known regarding the intracellular transport of vitamin E. We utilized biochemical, pharmacological, and microscopic approaches to study this process in cultured hepatocytes. We observe that tocopherol-HDL complexes are efficiently internalized through scavenger receptor class B type I. Once internalized, tocopherol arrives within approximately 30 min at intracellular vesicular organelles, where it co-localizes with TTP, and with a marker of the lysosomal compartment (LAMP1), before being transported to the plasma membrane in a TTP-dependent manner. We further show that intracellular processing of tocopherol involves a functional interaction between TTP and an ABC-type transporter.
Collapse
Affiliation(s)
- Jinghui Qian
- Division of Nutritional Sciences, Cornell University, Ithaca, NY, 14853, USA
| | | | | | | | | | | |
Collapse
|
20
|
Abstract
Atherosclerosis and its complications such as coronary heart disease, myocardial infarction and stroke are the leading causes of death in the developed world. High blood pressure, diabetes, smoking and a diet high in cholesterol and lipids clearly increase the likelihood of premature atherosclerosis, albeit other factors, such as the individual genetic makeup, may play an additional role. Several epidemiological studies and intervention trials have been performed with vitamin E, and some of them showed that it prevents atherosclerosis. For a long time, vitamin E was assumed to act by decreasing the oxidation of LDL, a key step in atherosclerosis initiation. However, at the cellular level, vitamin E acts by inhibition of smooth muscle cell proliferation, platelet aggregation, monocyte adhesion, oxLDL uptake and cytokine production, all reactions implied in the progression of atherosclerosis. Recent research revealed that these effects are not the result of the antioxidant activity of vitamin E, but rather of precise molecular actions of this compound. It is assumed that specific interactions of vitamin E with enzymes and proteins are at the basis of its non-antioxidant effects. Vitamin E influences the activity of several enzymes (e.g. PKC, PP2A, COX-2, 5-lipooxygenase, nitric oxide synthase, NADPH-oxidase, superoxide dismutase, phopholipase A2) and modulates the expression of genes that are involved in atherosclerosis (e.g. scavenger receptors, integrins, selectins, cytokines, cyclins). These interactions promise to reveal the biological properties of vitamin E and allow designing better strategies for the protection against atherosclerosis progression.
Collapse
Affiliation(s)
- Adelina Munteanu
- Institute of Biochemistry and Molecular Biology, University of Bern, Bern, Switzerland
| | | | | |
Collapse
|
21
|
Mardones P, Rigotti A. Cellular mechanisms of vitamin E uptake: relevance in α-tocopherol metabolism and potential implications for disease. J Nutr Biochem 2004; 15:252-60. [PMID: 15135148 DOI: 10.1016/j.jnutbio.2004.02.006] [Citation(s) in RCA: 74] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2003] [Indexed: 01/24/2023]
Abstract
alpha-Tocopherol is an essential micronutrient involved in various oxidative stress-related processes. Because of its hydrophobic nature, alpha-tocopherol is transported in plasma lipoproteins, and the pathways involved in its cellular uptake are closely related to the lipoprotein metabolism. alpha-Tocopherol transfer from plasma to cells can occur by different mechanisms such as uptake facilitated by lipid transfer proteins and lipases, receptor-mediated lipoprotein endocytosis, and selective lipid uptake. Here we discuss recent progress in understanding the physiological and pathophysiological relevance of these different pathways for cellular uptake of vitamin E in vivo. This review is mainly focused on the role of the scavenger receptor class B type I (SR-BI) on alpha-tocopherol metabolism and its potential implications for disease conditions.
Collapse
Affiliation(s)
- Pablo Mardones
- Departamento de Gastroenterología, Facultad de Medicina, Pontificia Universidad Católica, Marcoleta 367, Santiago, Chile
| | | |
Collapse
|
22
|
Balazs Z, Panzenboeck U, Hammer A, Sovic A, Quehenberger O, Malle E, Sattler W. Uptake and transport of high-density lipoprotein (HDL) and HDL-associated alpha-tocopherol by an in vitro blood-brain barrier model. J Neurochem 2004; 89:939-50. [PMID: 15140193 DOI: 10.1111/j.1471-4159.2004.02373.x] [Citation(s) in RCA: 160] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
The present study aimed to investigate pathways that contribute to uptake and transcytosis of high-density lipoproteins (HDLs) and HDL-associated alpha-tocopherol (alpha TocH) across an in vitro model of the blood-brain barrier (BBB). In primary porcine brain capillary endothelial cells HDL-associated alpha TocH was taken up in 10-fold excess of HDL holoparticles, indicating efficient selective uptake, a pathway mediated by scavenger receptor class B, type I (SR-BI). SR-BI was present in caveolae of brain capillary endothelial cells and expressed almost exclusively at the apical membrane. Disruption of caveolae with methyl-beta-cyclodextrin (CDX) resulted in (mis)sorting of SR-BI to the basolateral membrane. Immunohistochemistry of porcine brain cryosections revealed SR-BI expression on brain capillary endothelial cells and presumably astrocytic endfeet. HDL-associated [(14)C]alpha TocH taken up by brain capillary endothelial cells was recovered in sucrose gradient fractions containing the majority of cellular caveolin-1, the major caveolae-associated protein. During mass transfer studies using alpha TocH-enriched HDL, approximately 50% of cellular alpha TocH was recovered with the bulk of cellular caveolin-1 and SR-BI. Efflux experiments revealed that a substantial amount of cell-associated [(14)C]alpha TocH could be mobilized into the culture medium. In addition, apical-to-basolateral transport of HDL holoparticles and HDL-associated alpha TocH was saturable. Results from the present study suggest that part of cerebral apolipoprotein A-I and alpha TocH originates from plasma HDL transcytosed across the BBB and that caveolae-located SR-BI facilitates selective uptake of HDL-associated alpha TocH at the BBB.
Collapse
Affiliation(s)
- Zoltan Balazs
- Institute of Molecular Biology and Biochemistry, Medical University Graz, Graz, Austria
| | | | | | | | | | | | | |
Collapse
|
23
|
Oettl K, Höfler G, Ness GC, Sattler W, Malle E. An apparent decrease in cholesterol biosynthesis in peroxisomal-defective Chinese hamster ovary cells is related to impaired mitochondrial oxidation. Biochem Biophys Res Commun 2003; 305:957-63. [PMID: 12767923 DOI: 10.1016/s0006-291x(03)00855-6] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
Recent data suggest that impaired mitochondrial activities in Zellweger fibroblasts are related to defective peroxisome biogenesis and vice versa. To investigate the contribution of functional mitochondria to cholesterol biosynthesis, radioactive precursor molecules that form acetyl-CoA via beta-oxidation-independent (pyruvate) or -dependent (palmitate and octanoate) pathways were used. Production of both 14C-labeled cholesterol and 14C-labeled CO(2) from these radioactive tracers was significantly impaired in peroxisomal-defective ZR-82 Chinese hamster ovary cells in comparison to controls. In contrast, cholesterol synthesis from acetate--a tracer directly converted to acetyl-CoA without the involvement of mitochondrial activities--was threefold higher in ZR-82 cells than in controls. Pathways further contributing to cellular cholesterol homeostasis, i.e., receptor-mediated binding of exogenous lipoprotein-associated cholesterol as well as intracellular mobilization of cholesteryl ester deposits were similar in ZR-82 and controls. From these findings, we propose that peroxisomal dysfunction in ZR-82 cells is tightly coupled to impaired mitochondrial activities, e.g., defective mitochondrial beta-oxidation and formation of acetyl-CoA from short chain fatty acids resulting in a decreased rate of CO(2) production, and an apparent decrease in cholesterol biosynthesis. Actually, cholesterol biosynthesis from acetate is increased in the peroxisomal-defective cells. This explains previous conflicting conclusions.
Collapse
Affiliation(s)
- Karl Oettl
- Institute of Medical Biochemistry and Molecular Biology, Karl-Franzens University Graz, Harrachgasse 21, Graz A-8010, Austria
| | | | | | | | | |
Collapse
|
24
|
Rigotti A, Miettinen HE, Krieger M. The role of the high-density lipoprotein receptor SR-BI in the lipid metabolism of endocrine and other tissues. Endocr Rev 2003; 24:357-87. [PMID: 12788804 DOI: 10.1210/er.2001-0037] [Citation(s) in RCA: 312] [Impact Index Per Article: 14.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Because cholesterol is a precursor for the synthesis of steroid hormones, steroidogenic tissues have evolved multiple pathways to ensure adequate supplies of cholesterol. These include synthesis, storage as cholesteryl esters, and import from lipoproteins. In addition to endocytosis via members of the low-density lipoprotein receptor superfamily, steroidogenic cells acquire cholesterol from lipoproteins by selective lipid uptake. This pathway, which does not involve lysosomal degradation of the lipoprotein, is mediated by the scavenger receptor class B type I (SR-BI). SR-BI is highly expressed in steroidogenic cells, where its expression is regulated by various trophic hormones, as well as in the liver. Studies of genetically manipulated strains of mice have established that SR-BI plays a key role in regulating lipoprotein metabolism and cholesterol transport to steroidogenic tissues and to the liver for biliary secretion. In addition, analysis of SR-BI-deficient mice has shown that SR-BI expression is important for alpha-tocopherol and nitric oxide metabolism, as well as normal red blood cell maturation and female fertility. These mouse models have also revealed that SR-BI can protect against atherosclerosis. If SR-BI plays similar physiological and pathophysiological roles in humans, it may be an attractive target for therapeutic intervention in cardiovascular and reproductive diseases.
Collapse
Affiliation(s)
- Attilio Rigotti
- Departamento de Gastroenterología, Facultad de Medicina, Pontificia Universidad Católica, Santiago, Chile
| | | | | |
Collapse
|
25
|
Yokogawa K, Shima Y, Hashimoto T, Hiyajyo M, Kadoyama K, Ishizki J, Nomura M, Miyamoto KI. Disposition kinetics of alpha-tocopherol in apolipoprotein B knockout mice. Pharm Res 2003; 20:368-72. [PMID: 12669955 DOI: 10.1023/a:1022691718226] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
PURPOSE We examined the effects of apolipoprotein B (apoB) on the disposition kinetics of alpha-tocopherol by using apoB knockout mice. METHODS The concentrations of alpha-tocopherol in plasma and tissues were measured by gas chromatography-mass spectrometry. RESULTS In apob (-/-) mice, the endogenous levels of alpha-tocopherol in plasma and tissues (except liver) were significantly lower, and the liver concentration was significantly higher than those in wild-type mice. After single i.v. administration of alpha-tocopherol (25 mg/kg), the area under the plasma concentration-time curve (AUC) and the distribution volume at steady state were significantly decreased, whereas the total clearance of alpha-tocopherol was significantly increased in apob (-/-) vs. wild-type mice. Alpha-Tocopherol was highly distributed to the liver, compared with other tissues. After an oral administration of alpha-tocopherol (100 mg/kg), the intestinal absorption of alpha-tocopherol was very low in apoB knockout mice, as the value of AUC0-32h for apob (-/-) mice (17.7 +/- 8.3 (microg h/mL) was significantly less than that for apob (+/+) wild-type mice (96.5 +/- 15.8 microg h/mL, mean +/- SD of five experiments, p < 0.01). The biliary excretion of alpha-tocopherol was significantly greater in apob (+/-) mice than in apob (+/+) mice. CONCLUSIONS These results show that apoB plays a role in hepatic secretion and intestinal absorption of alpha-tocopherol.
Collapse
Affiliation(s)
- Koichi Yokogawa
- Department of Hospital Pharmacy, School of Medicine, Kanazawa University, 13-1 Takara-machi, Kanazawa 920-8641, Japan
| | | | | | | | | | | | | | | |
Collapse
|
26
|
Ricciarelli R, Zingg JM, Azzi A. The 80th anniversary of vitamin E: beyond its antioxidant properties. Biol Chem 2002; 383:457-65. [PMID: 12033435 DOI: 10.1515/bc.2002.048] [Citation(s) in RCA: 79] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
Molecules provided with an antioxidant function may have additional properties, the latter being sometimes of greater importance than the former. In the last ten years, alpha-tocopherol has revealed precise cellular functions, some of which are independent of its antioxidant/radical scavenging ability. At the posttranslational level, alpha-tocopherol inhibits protein kinase C and 5-lipoxygenase and activates protein phosphatase 2A and diacylglycerol kinase. Some genes (CD36, alpha-TTP, alpha-tropomyosin, and collagenase) are affected by alpha-tocopherol at the transcriptional level. alpha-Tocopherol also induces inhibition of cell proliferation, platelet aggregation and monocyte adhesion. These effects are unrelated to the antioxidant activity of vitamin E, but rather are believed to be a result of specific interactions of vitamin E with components of the cell, e. g. proteins, enzymes and membranes. This review focuses on novel non-antioxidant functions of alpha-tocopherol and discusses the possibility that many of the effects previously attributed to the antioxidant functions can also be explained by non-antioxidant mechanisms.
Collapse
Affiliation(s)
- Roberta Ricciarelli
- Institute of Biochemistry and Molecular Biology, University of Berne, Switzerland
| | | | | |
Collapse
|
27
|
Mardones P, Strobel P, Miranda S, Leighton F, Quiñones V, Amigo L, Rozowski J, Krieger M, Rigotti A. Alpha-tocopherol metabolism is abnormal in scavenger receptor class B type I (SR-BI)-deficient mice. J Nutr 2002; 132:443-9. [PMID: 11880569 DOI: 10.1093/jn/132.3.443] [Citation(s) in RCA: 147] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Despite the physiologic importance of vitamin E, in particular its alpha-tocopherol (alpha-T) isoform, the molecular mechanisms involved in the cellular uptake of this antioxidant from plasma lipoproteins have not been well-defined. Recent studies have suggested that selective lipid uptake, rather than endocytosis, is important for alpha-T delivery to cells. Here we show that the scavenger receptor class B type I (SR-BI), which mediates cellular selective cholesteryl ester uptake from lipoproteins, facilitates efficient transfer of alpha-T from HDL to cultured cells. In SR-BI-deficient mutant mice, relative to wild-type control animals, there was a significant increase in plasma alpha-T levels (1.1- to 1.4-fold higher) that was mostly due to the elevated alpha-T content of their abnormally large plasma HDL-like particles. This increase in plasma alpha-T in SR-BI knockout mice was accompanied by a significant decrease (65-80%) in the alpha-T concentrations in bile and several tissues including ovary, testis, lung and brain. SR-BI deficiency did not alter the alpha-T concentrations of the liver, spleen, kidney or white fat. These data show that SR-BI plays an important role in transferring alpha-T from plasma lipoproteins to specific tissues. Also, in the case of the liver as was previously shown for SR-BI-dependent hepatic cholesterol transport, SR-BI-mediated uptake of alpha-T was primarily coupled to biliary excretion rather than to tissue accumulation. Defective tissue uptake of lipoprotein alpha-T in SR-BI-deficient mice may contribute to the reproductive and cardiovascular pathologies exhibited by these animals.
Collapse
MESH Headings
- Animals
- Bile/chemistry
- Bile/metabolism
- Brain Chemistry
- CD36 Antigens
- Female
- Lipoproteins/blood
- Lipoproteins, HDL/blood
- Liver/chemistry
- Lung/chemistry
- Male
- Membrane Proteins
- Mice
- Mice, Inbred C57BL
- Mice, Knockout
- Mutagenesis
- Ovary/chemistry
- Receptors, Immunologic/deficiency
- Receptors, Immunologic/genetics
- Receptors, Immunologic/physiology
- Receptors, LDL/deficiency
- Receptors, Lipoprotein
- Receptors, Scavenger
- Scavenger Receptors, Class B
- Testis/chemistry
- Transfection
- alpha-Tocopherol/analysis
- alpha-Tocopherol/blood
- alpha-Tocopherol/metabolism
Collapse
Affiliation(s)
- Pablo Mardones
- Departamento de Gastroenterología, Facultad de Medicina, Pontificia Universidad Católica, Santiago, Chile
| | | | | | | | | | | | | | | | | |
Collapse
|
28
|
Abstract
Since the discovery of vitamin E in 1922, its deficiency has been associated with various disorders, particularly atherosclerosis, ischemic heart disease, and the development of different types of cancer. A neurological syndrome associated with vitamin E deficiency resembling Friedreich ataxia has also been described. Whereas epidemiological studies have indicated the role of vitamin E in preventing the progression of atherosclerosis and cancer, intervention trials have produced contradictory results, indicating strong protection in some cases and no significant effect in others. Although it is commonly believed that phenolic compounds like vitamin E exert only a protective role against free radical damage, antioxidant molecules can exert other biological functions. For instance, the antioxidant activity of 17-beta-estradiol is not related to its role in determining secondary sexual characters, and the antioxidant capacity of all-trans-retinal is distinguished from its role in rhodopsin and vision. Thus, it is not unusual that alpha-tocopherol (the most active form of vitamin E) has properties independent of its antioxidant/radical scavenging ability. The Roman god Janus, shown in ancient coins as having two faces in one body, inspired the designation of 'Janus molecules' for these substances. The new biochemical face of vitamin E was first described in 1991, with an inhibitory effect on cell proliferation and protein kinase C activity. After a decade, this nonantioxidant role of vitamin E is well established, as confirmed by authoritative studies of signal transduction and gene regulation. More recently, a tocopherol binding protein with possible receptor function has been discovered. Despite such important developments in understanding the molecular mechanism and the targets of vitamin E, its new Janus face is not fully elucidated. Greater knowledge of the molecular events related to vitamin E will help in selecting the parameters for clinical intervention studies such as population type, dose response effects, and possible synergism with other compounds.
Collapse
Affiliation(s)
- R Ricciarelli
- Institute of Biochemistry and Molecular Biology, University of Bern, 3012 Bern, Switzerland
| | | | | |
Collapse
|
29
|
Oram JF, Vaughan AM, Stocker R. ATP-binding cassette transporter A1 mediates cellular secretion of alpha-tocopherol. J Biol Chem 2001; 276:39898-902. [PMID: 11546785 DOI: 10.1074/jbc.m106984200] [Citation(s) in RCA: 149] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
Alpha-tocopherol (alpha-TOH) is associated with plasma lipoproteins and accumulates in cell membranes throughout the body, suggesting that lipoproteins play a role in transporting alpha-TOH between tissues. Here we show that secretion of alpha-TOH from cultured cells is mediated in part by ABCA1, an ATP-binding cassette protein that transports cellular cholesterol and phospholipids to lipid-poor high density lipoprotein (HDL) apolipoproteins such as apoA-I. Treatment of human fibroblasts and murine RAW264 macrophages with cholesterol and/or 8-bromo-cyclic AMP, which induces ABCA1 expression, enhanced apoA-I-mediated alpha-TOH efflux. ApoA-I lacked the ability to remove alpha-TOH from Tangier disease fibroblasts that have a nonfunctional ABCA1. BHK cells that lack an active ABCA1 pathway markedly increased secretion of alpha-TOH to apoA-I when forced to express ABCA1. ABCA1 also mediated a fraction of the alpha-TOH efflux promoted by lipid-containing HDL particles, indicating that HDL promotes alpha-TOH efflux by both ABCA1-dependent and -independent processes. Exposing apoA-I to ABCA1-expressing cells did not enhance its ability to remove alpha-TOH from cells lacking ABCA1, consistent with this transporter participating directly in the translocation of alpha-TOH to apolipoproteins. These studies provide evidence that ABCA1 mediates secretion of cellular alpha-TOH into the HDL metabolic pathway, a process that may facilitate vitamin transport between tissues and influence lipid oxidation.
Collapse
Affiliation(s)
- J F Oram
- Department of Medicine, University of Washington, Seattle, WA 98195, USA.
| | | | | |
Collapse
|
30
|
Abstract
Plasma and tissue alpha-tocopherol concentrations are remarkably stable, which suggests that they are regulated. alpha-Tocopherol transfer protein, tocopherol-associated protein, and tocopherol-binding protein bind alpha-tocopherol. These proteins might function as tocopherol regulatory proteins, although only tocopherol transfer protein has been shown to influence plasma and tissue alpha-tocopherol concentrations. Tissue alpha-tocopherol concentrations likely depend on tocopherol regulatory protein function and tissue lipid content, vitamin E uptake and efflux, oxidative stress, and interactions between vitamin E and other antioxidants. Pharmacokinetic models often divide tissues into rapidly perfused, slowly perfused, and very slowly perfused compartments. Tissue vitamin E concentrations might equilibrate more rapidly in tissues with greater perfusion, greater vitamin E uptake, increased amounts or activities of tocopherol regulatory protein, and lower lipid contents. The rate at which tissue concentrations approach equilibrium, however, does not predict the final equilibrium concentrations because of redistribution among tissues. Redistribution of vitamin E to adipose tissue from other tissues may be significant. Intracellular trafficking of vitamin E might occur in conjunction with membrane recycling because membrane constituents rapidly recycle between the plasma membrane and intracellular endocytic compartments. Thus, tocopherol regulatory proteins may modulate rather than directly regulate vitamin E tissue distribution and intracellular trafficking.
Collapse
Affiliation(s)
- D H Blatt
- Linus Pauling Institute, Oregon State University, Corvallis, OR 97331-6512, USA
| | | | | |
Collapse
|
31
|
Bergt C, Marsche G, Panzenboeck U, Heinecke JW, Malle E, Sattler W. Human neutrophils employ the myeloperoxidase/hydrogen peroxide/chloride system to oxidatively damage apolipoprotein A-I. EUROPEAN JOURNAL OF BIOCHEMISTRY 2001; 268:3523-31. [PMID: 11422382 DOI: 10.1046/j.1432-1327.2001.02253.x] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
The structural integrity of apolipoprotein A-I (apo A-I) is critical to the physiological function of high-density lipoprotein (HDL). Oxidized lipoproteins are thought to be of central importance in atherogenesis, and oxidation products characteristic of myeloperoxidase, a heme protein secreted by activated phagocytes, have been detected in human atherosclerotic tissue. At plasma concentrations of halide ion, hypochlorous acid is a major product of the myeloperoxidase-hydrogen peroxide-chloride system. We therefore investigated the effects of activated human neutrophils, a potent source of myeloperoxidase and hydrogen peroxide, on the protein and lipid components of HDL. Both free and HDL-associated apo A-I exposed to activated human neutrophils underwent extensive degradation as monitored by RP-HPLC and Western blotting with a polyclonal antibody to apo A-I. Replacement of the neutrophils with reagent HOCl resulted in comparable damage (at molar oxidant : HDL subclass 3 ratio = 100) as observed in the presence of activated phagocytes. Apo A-I degradation by activated neutrophils was partially inhibited by the HOCl scavenger methionine, by the heme inhibitor azide, by chloride-free conditions, by the peroxide scavenger catalase, and by a combination of superoxide dismutase (SOD)/catalase, implicating HOCl in the cell-mediated reaction. The addition of a protease inhibitor (3,4-dichloroisocoumarin) further reduced the extent of apo A-I damage. In contrast to the protein moiety, there was little evidence for oxidation of unsaturated fatty acids or cholesterol in HDL3 exposed to activated neutrophils, suggesting that HOCl was selectively damaging apo A-I. Our observations indicate that HOCl generated by myeloperoxidase represents one pathway for protein degradation in HDL3 exposed to activated phagocytes.
Collapse
Affiliation(s)
- C Bergt
- Institute of Medical Biochemistry and Molecular Biology, University Graz, Austria
| | | | | | | | | | | |
Collapse
|
32
|
Goti D, Hrzenjak A, Levak-Frank S, Frank S, van der Westhuyzen DR, Malle E, Sattler W. Scavenger receptor class B, type I is expressed in porcine brain capillary endothelial cells and contributes to selective uptake of HDL-associated vitamin E. J Neurochem 2001; 76:498-508. [PMID: 11208913 DOI: 10.1046/j.1471-4159.2001.00100.x] [Citation(s) in RCA: 127] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
It is clearly established that an efficient supply to the brain of alpha-tocopherol (alphaTocH), the most biologically active member of the vitamin E family, is of the utmost importance for proper neurological functioning. Although the mechanism of uptake of alphaTocH into cells constituting the blood-brain barrier (BBB) is obscure, we previously demonstrated that high-density lipoprotein (HDL) plays a major role in the supply of alphaTocH to porcine brain capillary endothelial cells (pBCECs). Here we studied whether a porcine analogue of human and rodent scavenger receptor class B, type I mediates selective (without concomitant lipoprotein particle internalization) uptake of HDL-associated alphaTocH in a similar manner to that described for HDL-associated cholesteryl esters (CEs). In agreement with this hypothesis we observed that a major proportion of alphaTocH uptake by pBCECs occurred by selective uptake, exceeding HDL3 holoparticle uptake by up to 13-fold. The observation that selective uptake of HDL-associated CE exceeded HDL3 holoparticle up to fourfold suggested that a porcine analogue of SR-BI (pSR-BI) may be involved in lipid uptake at the BBB. In line with the observation of selective lipid uptake, RT-PCR and northern and western blot analyses revealed the presence of pSR-BI in cells constituting the BBB. Adenovirus-mediated overexpression of the human analogue of SR-BI (hSR-BI) in pBCECs resulted in a fourfold increase in selective HDL-associated alphaTocH uptake. In accordance with the proposed function of SR-BI, selective HDL-CE uptake was increased sixfold in Chinese hamster ovary cells stably transfected with murine SR-BI (mSR-BI). Most importantly stable mSR-BI overexpression mediated a twofold increase in HDL-associated [14C]alphaTocH selective uptake in comparison with control cells. In line with tracer experiments, mass transfer studies with unlabelled lipoproteins revealed that mSR-BI overexpression resulted in a twofold increase in endogenous HDL3-associated alphaTocH uptake. The results of this study indicate that SR-BI promotes the uptake of HDL-associated alphaTocH into cells constituting the BBB and plays an important role during the supply of the CNS with this indispensable micronutrient.
Collapse
Affiliation(s)
- D Goti
- Institute of Medical Biochemistry and Molecular Biology, Karl Franzens University Graz, Austria
| | | | | | | | | | | | | |
Collapse
|
33
|
Witt W, Kolleck I, Fechner H, Sinha P, Rüstow B. Regulation by vitamin E of the scavenger receptor BI in rat liver and HepG2 cells. J Lipid Res 2000. [DOI: 10.1016/s0022-2275(20)32362-2] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
|
34
|
Pussinen PJ, Lindner H, Glatter O, Reicher H, Kostner GM, Wintersperger A, Malle E, Sattler W. Lipoprotein-associated alpha-tocopheryl-succinate inhibits cell growth and induces apoptosis in human MCF-7 and HBL-100 breast cancer cells. BIOCHIMICA ET BIOPHYSICA ACTA 2000; 1485:129-44. [PMID: 10832094 DOI: 10.1016/s1388-1981(00)00035-4] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
alpha-Tocopheryl succinate (alpha-TS) is a potent inhibitor of tumor cell proliferation. The goal of the present study was to investigate whether and to what extent alpha-TS associates with plasma lipoproteins and if alpha-TS-enriched lipoproteins inhibit breast cancer cell growth in a manner comparable to the free drug. In vitro enrichment of human plasma revealed that alpha-TS readily associated with the main lipoprotein classes, findings confirmed in vivo in mice. At the highest alpha-TS concentrations, lipoproteins carrying 50000 (VLDL), 5000 (LDL) and 700 (HDL) alpha-TS molecules per lipoprotein particle were generated. alpha-TS enrichment generated lipoprotein particles with slightly decreased density and increased particle radius. To study whether the level of LDL-receptor (LDL-R) expression affects alpha-TS uptake from apoB/E containing lipoprotein particles human breast cancer cells with low (MCF-7) and normal (HBL-100) LDL-R expression were used. The uptake of free, VLDL- and (apoE-free) HDL(3)-associated alpha-TS was nearly identical for both cell lines. In contrast, uptake of LDL-associated alpha-TS by HBL-100 cells (normal LDL-R expression) was about twice as high as compared to MCF-7 cells (low LDL-R expression). VLDL and LDL-associated alpha-TS inhibited proliferation most effectively at the highest concentration of alpha-TS used (100% inhibition of MCF-7 growth with 20 microg/ml of lipoprotein-associated alpha-TS). However, also alpha-TS-free VLDL and LDL inhibited HBL-100 cell proliferation up to 55%. In both cell lines, alpha-TS-enriched HDL(3) inhibited cell growth by 40-60%. Incubation of both cell lines in the presence of free or lipoprotein-associated alpha-TS resulted in DNA fragmentation indicative of apoptosis. Collectively, the present findings demonstrate that: (1) alpha-TS readily associates with lipoproteins in vitro and in vivo; (2) the lipoprotein-enrichment efficacy was dependent on the particle size and/or the triglyceride content of the lipoprotein; (3) uptake of LDL-associated alpha-TS was apparently dependent on the level of LDL-R expression; and (4) lipoproteins were efficient alpha-TS carriers inducing reduced cell proliferation rates and apoptosis in human breast cancer cells as observed for the free drug.
Collapse
Affiliation(s)
- P J Pussinen
- Institute of Medical Biochemistry, Graz, Austria
| | | | | | | | | | | | | | | |
Collapse
|
35
|
Goti D, Hammer A, Galla HJ, Malle E, Sattler W. Uptake of lipoprotein-associated alpha-tocopherol by primary porcine brain capillary endothelial cells. J Neurochem 2000; 74:1374-83. [PMID: 10737592 DOI: 10.1046/j.1471-4159.2000.0741374.x] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
From the severe neurological syndromes resulting from vitamin E deficiency, it is evident that an adequate supply of the brain with alpha-tocopherol (alphaTocH), the biologically most active member of the vitamin E family, is of utmost importance. However, uptake mechanisms of alphaTocH in cells constituting the blood-brain barrier are obscure. Therefore, we studied the interaction of low (LDL) and high (HDL) density lipoproteins (the major carriers of alphaTocH in the circulation) with monolayers of primary porcine brain capillary endothelial cells (pBCECs) and compared the ability of these two lipoprotein classes to transfer lipoprotein-associated alphaTocH to pBCECs. With regard to potential binding proteins, we could identify the presence of the LDL receptor and a putative HDL3 binding protein with an apparent molecular mass of 100 kDa. At 4 degrees C, pBCECs bound LDL with high affinity (K(D) = 6 nM) and apolipoprotein E-free HDL3 with low affinity (98 nM). The binding capacity was 20,000 (LDL) and 200,000 (HDL3) lipoprotein particles per cell. alphaTocH uptake was approximately threefold higher from HDL3 than from LDL when [14C]alphaTocH-labeled lipoprotein preparations were used. The majority of HDL3-associated alphaTocH was taken up in a lipoprotein particle-independent manner, exceeding HDL3 holoparticle uptake 8- to 20-fold. This uptake route is less important for LDL-associated alphaTocH (alphaTocH uptake approximately 1.5-fold higher than holoparticle uptake). In line with tracer experiments, mass transfer studies with unlabeled lipoproteins revealed that alphaTocH uptake from HDL3 was almost fivefold more efficient than from LDL. Biodiscrimination studies indicated that uptake efficacy for the eight different stereoisomers of synthetic alphaTocH is nearly identical. Our findings indicate that HDL could play a major role in supplying the central nervous system with alphaTocH in vivo.
Collapse
Affiliation(s)
- D Goti
- Institute of Medical Biochemistry, University of Graza, Austria
| | | | | | | | | |
Collapse
|
36
|
Simon E, Paul JL, Atger V, Simon A, Moatti N. Study of vitamin E net mass transfer between alpha-tocopherol-enriched HDL and erythrocytes: application to asymptomatic hypercholesterolemic men. Free Radic Biol Med 2000; 28:815-23. [PMID: 10754278 DOI: 10.1016/s0891-5849(00)00166-0] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Abstract
We previously showed that hypercholesterolemic asymptomatic men had lower erythrocyte vitamin E content, despite normal plasma concentrations compared to normocholesterolemic men. We hypothesized that the reduced erythrocyte vitamin E concentration could be due to an impairment of transfer of vitamin E from plasma lipoproteins. We first developed a model for testing the ability of erythrocytes to accept vitamin E from high-density lipoproteins (HDL) pre-enriched in vitamin E, which allows to measure a net mass transfer of vitamin E from HDL to erythrocytes. Vitamin E-enriched HDL were obtained in controlled conditions of concentration and incubation time with a good reproducibility (CV </= 10%). The kinetic study of the net mass transfer of vitamin E to erythrocytes of healthy volunteers shows small inter- and intraindividual variations. The application of this model to erythrocytes of hyper- and normocholesterolemic men demonstrates that the reduced erythrocyte vitamin E content observed in hypercholesterolemic men was not due to a reduced ability of these cells to accept vitamin E from HDL. It might rather be due to an impairment of lipoproteins in the delivery of vitamin E to tissues, or to an oxidative stress which consumes antioxidants.
Collapse
Affiliation(s)
- E Simon
- Laboratoire de Biochimie Appliquée, Faculté des Sciences pharmaceutigques et biologiques, Châtenay-Malabry, France
| | | | | | | | | |
Collapse
|
37
|
Desrumaux C, Deckert V, Athias A, Masson D, Lizard G, Palleau V, Gambert P, Lagrost L. Plasma phospholipid transfer protein prevents vascular endothelium dysfunction by delivering alpha-tocopherol to endothelial cells. FASEB J 1999; 13:883-92. [PMID: 10224231 DOI: 10.1096/fasebj.13.8.883] [Citation(s) in RCA: 74] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
alpha-tocopherol, the most potent antioxidant form of vitamin E, is mainly bound to lipoproteins in plasma and its incorporation into the vascular wall can prevent the endothelium dysfunction at an early stage of atherogenesis. In the present study, the plasma phospholipid transfer protein (PLTP) was shown to promote the net mass transfer of alpha-tocopherol from high density lipoproteins (HDL) and alpha-tocopherol-albumin complexes toward alpha-tocopherol-depleted, oxidized low density lipoproteins (LDL). The facilitated transfer reaction of alpha-tocopherol could be blocked by specific anti-PLTP antibodies. These observations indicate that PLTP may restore the antioxidant potential of plasma LDL at an early stage of the oxidation cascade that subsequently leads to cellular damages. In addition, the present study demonstrated that the PLTP-mediated net mass transfer of alpha-tocopherol can constitute a new mechanism for the incorporation of alpha-tocopherol into the vascular wall in addition to the previously recognized LDL receptor and lipoprotein lipase pathways. In ex vivo studies on rabbit aortic segments, the impairment of the endothelium-dependent arterial relaxation induced by oxidized LDL was found to be counteracted by a pretreatment with purified PLTP and alpha-tocopherol-albumin complexes, and both the maximal response and the sensitivity to acetylcholine were significantly improved. We conclude that PLTP, by supplying oxidized LDL and endothelial cells with alpha-tocopherol through a net mass transfer reaction may play at least two distinct beneficial roles in preventing endothelium damage, i.e., the antioxidant protection of LDL and the preservation of a normal relaxing function of vascular endothelial cells.
Collapse
Affiliation(s)
- C Desrumaux
- Laboratoire de Biochimie des Lipoprotéines-INSERM U498, Hôpital du Bocage, BP 1542,21034 Dijon Cedex, France
| | | | | | | | | | | | | | | |
Collapse
|
38
|
Nakamura T, Reicher H, Sattler W. Comparison of RRR-alpha- and all-rac-alpha-tocopherol uptake by permanent rat skeletal muscle myoblasts (L6 cells): effects of exogenous lipoprotein lipase. Lipids 1998; 33:1001-8. [PMID: 9832080 DOI: 10.1007/s11745-998-0298-3] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
The purpose of the present investigation was to test whether permanent skeletal muscle cells (rat L6 cells) could serve as an in vitro model for alpha-tocopherol (alphaTocH) biodiscrimination studies. L6 cells were incubated in the presence of high density lipoprotein (HDL), low density lipoprotein (LDL), and very low density lipoprotein (VLDL) labeled in the lipid moiety with either all-rac- or RRR-[14C]alphaTocH. These incubations were performed either in the absence or in the presence of exogenously added bovine lipoprotein lipase (LPL) since skeletal muscle is one of the major expression sites of LPL in vivo. Time-dependent uptake studies (up to 24 h) in the absence of LPL have shown that equipotent doses of all-rac- and RRR-[14C]alphaTocH (1.36:1) led to almost identical accumulation of the tracer, independent of the lipoprotein class used as alphaTocH carrier. With regard to alphaTocH donor capacity, it appeared that HDL is the most potent alphaTocH donor, followed by LDL and VLDL. In the presence of LPL, all-rac- and RRR-[14C]alphaTocH uptake was significantly enhanced (between two- and tenfold). Biodiscrimination studies using chiral high-performance liquid chromatographic analysis with radiometric detection of the corresponding methyl ether derivatives on a Chiralcel OD column have demonstrated that the 2S-and 2R-isomers of alphaTocH were taken up in a 1:1 ratio by L6 cells independent of the absence or presence of LPL. In addition, we have not observed biodiscrimination between the four 2R-isomers, i.e., there was no preferential accumulation of the RRR-isomer. These data suggest that L6 cells do not discriminate between different alphaTocH isomers and that the addition of endogenous LPL significantly enhances the uptake of RRR- and all-rac-alphaTocH.
Collapse
MESH Headings
- Animals
- Carbon Radioisotopes
- Cattle
- Chromatography, High Pressure Liquid/methods
- Humans
- Isomerism
- Lipoprotein Lipase/pharmacology
- Lipoproteins, HDL/metabolism
- Lipoproteins, HDL/pharmacology
- Lipoproteins, LDL/metabolism
- Lipoproteins, LDL/pharmacology
- Lipoproteins, VLDL/metabolism
- Lipoproteins, VLDL/pharmacology
- Muscle, Skeletal/cytology
- Muscle, Skeletal/drug effects
- Muscle, Skeletal/metabolism
- Radiometry
- Rats
- Tocopherols
- Vitamin E/analogs & derivatives
- Vitamin E/chemistry
- Vitamin E/pharmacokinetics
- alpha-Tocopherol/analogs & derivatives
Collapse
Affiliation(s)
- T Nakamura
- Eisai Co., Ltd., Vitamin E Technology Section, Tokyo, Japan
| | | | | |
Collapse
|