Age-related impairment of HDL-mediated cholesterol efflux
2006; Elsevier BV; Volume: 48; Issue: 2 Linguagem: Inglês
10.1194/jlr.m600167-jlr200
ISSN1539-7262
AutoresHicham Berrougui, Maxim Isabelle, Martin Cloutier, Guillaume Grenier, Abdelouahed Khalil,
Tópico(s)Lipid metabolism and disorders
ResumoOur aim in this study was to investigate the effect of aging on the capacity of HDLs to promote reverse cholesterol transport. HDLs were isolated from plasma of young (Y-HDL) and elderly (E-HDL) subjects. HDL-mediated cholesterol efflux was studied using THP-1 and J774 macrophages. Our results show that E-HDLs present a lower capacity to promote cholesterol efflux than Y-HDLs (41.7 ± 1.4% vs. 49.0 ± 2.2%, respectively; P = 0.013). Reduction in the HDL-mediated cholesterol efflux capacity with aging was more significant with HDL3 than HDL2 (Y-HDL3, 57.3 ± 1% vs. E-HDL3, 50.9 ± 2%; P = 0.012). Moreover, our results show that ABCA1-mediated cholesterol efflux is the more affected pathway in terms of cholesterol-removing capacity. Interestingly, the composition and structure of HDL revealed a reduction in the phosphatidylcholine-sphingomyelin ratio (E-HDL, 32.7 ± 2.7 vs. Y-HDL, 40.0 ± 1.9; P = 0.029) and in the phospholipidic layer membrane fluidity in E-HDL compared with Y-HDL as well as an alteration in the apolipoprotein A-I structure and charge. In conclusion, our results shown that E-HDLs present a reduced capacity to promote cholesterol efflux, principally through the ABCA1 pathway, and this may explain the increase of the incidence of cardiovascular diseases observed during aging. Our aim in this study was to investigate the effect of aging on the capacity of HDLs to promote reverse cholesterol transport. HDLs were isolated from plasma of young (Y-HDL) and elderly (E-HDL) subjects. HDL-mediated cholesterol efflux was studied using THP-1 and J774 macrophages. Our results show that E-HDLs present a lower capacity to promote cholesterol efflux than Y-HDLs (41.7 ± 1.4% vs. 49.0 ± 2.2%, respectively; P = 0.013). Reduction in the HDL-mediated cholesterol efflux capacity with aging was more significant with HDL3 than HDL2 (Y-HDL3, 57.3 ± 1% vs. E-HDL3, 50.9 ± 2%; P = 0.012). Moreover, our results show that ABCA1-mediated cholesterol efflux is the more affected pathway in terms of cholesterol-removing capacity. Interestingly, the composition and structure of HDL revealed a reduction in the phosphatidylcholine-sphingomyelin ratio (E-HDL, 32.7 ± 2.7 vs. Y-HDL, 40.0 ± 1.9; P = 0.029) and in the phospholipidic layer membrane fluidity in E-HDL compared with Y-HDL as well as an alteration in the apolipoprotein A-I structure and charge. In conclusion, our results shown that E-HDLs present a reduced capacity to promote cholesterol efflux, principally through the ABCA1 pathway, and this may explain the increase of the incidence of cardiovascular diseases observed during aging. The inverse relationship between plasma levels of HDLs and cardiovascular disease has been demonstrated in several epidemiological and interventional studies (1Wilson P.W. Abbott R.D. Castelli W.P. High density lipoprotein cholesterol and mortality. The Framingham Heart Study. Arteriosclerosis. 1988; 8: 737-741Google Scholar, 2Thom T. Haase N. Rosamond W. Howard V.J. Heart disease and stroke statistics—2006 update. A report from the American Heart Association Statistics Committee and Stroke Statistics Subcommittee. Circulation. and the American Heart Association Statistics Committee and Stroke Statistics Subcommittee. 2006; 113: 85-151Google Scholar). The antiatherogenic properties of HDL have been ascribed to their abilities to inhibit LDL oxidation (3Parthasarathy S. Barnett J. Fong L.G. High-density lipoprotein inhibits the oxidative modification of low-density lipoprotein. Biochim. Biophys. Acta. 1990; 1044: 275-283Google Scholar) and to prevent oxidized LDL-induced cytotoxicity and monocyte transmigration (4Suc I. Escargueil-Blanc I. Troly M. Salvayre R. Nègre-Salvayre A. HDL and apoA-I prevent cell death of endothelial cells induced by oxidized LDL. Arterioscler. Thromb. Vasc. Biol. 1997; 17: 2158-2166Google Scholar, 5Wang N. Lan D. Chen W. Mastuura F. Tall A.R. ATP-binding cassette transporters G1 and G4 mediate cellular cholesterol efflux to high-density lipoproteins. Proc. Natl. Acad. Sci. USA. 2004; 101: 9774-9779Google Scholar). One of the long-standing mechanisms to explain the protective effect of HDLs against cardiovascular disease is their capacity to promote reverse cholesterol transport (RCT) (6Kennedy M.A. Barrera G.C. Nakamura K. Baldan A. Tarr P. Fishbein M.C. Frank J. Francone O.L. Edwards P.A. ABCG1 has a critical role in mediating cholesterol efflux to HDL and preventing cellular lipid accumulation. Cell Metab. 2005; 2: 121-131Google Scholar). The concept of RCT, as suggested by Glomset (7Glomset J.A. The plasma lecithins cholesterol acyltransferase reaction. J. Lipid Res. 1968; 9: 155-167Google Scholar), consists of the movement of cholesterol from the peripheral tissues to the liver, which starts by the efflux of free cholesterol (FC) and phospholipids from cells of peripheral tissues to preβ-migrating lipid-poor or lipid-free apolipoprotein A-I (apoA-I) and to HDL3 (7Glomset J.A. The plasma lecithins cholesterol acyltransferase reaction. J. Lipid Res. 1968; 9: 155-167Google Scholar, 8Castro G.R. Fielding C.J. Early incorporation of cell-derived cholesterol into pre-beta-migrating high-density lipoprotein. Biochemistry. 1988; 27: 25-29Google Scholar, 9Bortnick A.E. Rothblat G.H. Stoudt G. Hoppe K.L. Royer L.J. McNeish J. Francone O.L. The correlation of ATP-binding cassette 1 mRNA levels with cholesterol efflux from various cell lines. J. Biol. Chem. 2000; 275: 28634-28640Google Scholar). The process of FC efflux occurs by three known pathways. 1) Aqueous diffusion. This process involves the desorption of FC molecules from the donor lipid-water interface and diffusion of these molecules through the intervening aqueous phase until they collide with and are absorbed by an acceptor. 2) Scavenger receptor class B type I (SR-BI)-mediated FC flux. The movement of FC via SR-BI is bidirectional, and like the aqueous diffusion mechanism, the net movement of FC via SR-BI depends on the direction of the cholesterol gradient (10de la Llera-Moya M. Connelly M.A. Drazul D. Klein S.M. Favari E. Yancey P.G. Williams D.L. Rothblat G.H. Scavenger receptor class B type I affects cholesterol homeostasis by magnifying cholesterol flux between cells and HDL. J. Lipid Res. 2001; 42: 1969-1978Google Scholar). 3) ATP binding cassette-mediated cholesterol efflux. ABCA1 and ABCG1/4 are members of a large family of ATP-dependent transporters that share common structural motifs for the active transport of a variety of substrates (11Dean M. Hamon Y. Chimini G. The human ATP-binding cassette (ABC) transporter superfamily. J. Lipid Res. 2001; 42: 1007-1017Google Scholar). In contrast to aqueous diffusion and SR-BI-mediated FC flux, the movement of FC by ABCA1 and ABCG1/4 is unidirectional, and net efflux of cellular FCs would always occur via this mechanism (12Yancey P.G. de la Llera-Moya M. Swarnakar S. Monzo P. Klein M.S. Connelly A. Johnson W.J. Williams D.L. Rothblat G.H. High density lipoprotein phospholipid composition is a major determinant of the bi-directional flux and net movement of cellular free cholesterol mediated by scavenger receptor BI. J. Biol. Chem. 2000; 275: 36596-36604Google Scholar). The preferred cholesterol acceptors for ABCA1 are lipid-poor apolipoproteins and all of the exchangeable apolipoproteins, such as apoA-I, apoA-II, apoA-IV, apoE, and apoC (13Remaley A.T. Stonik J.A. Demosky S.J. Neufeld E.B. Bocharov A.V. Vishnyakova T.G. Eggerman T.L. Patterson A.P. Duverger N.J. Santamarina-Fojo S. Apolipoprotein specificity for lipid efflux by the human ABCAI transporter. Biochem. Biophys. Res. Commun. 2001; 280 (et al.): 818-823Crossref PubMed Scopus (278) Google Scholar). ABCA1 has been shown to bind with apoA-I, indicating a very close association between the two proteins in mediating the cholesterol efflux process (14Oram J.F. Lawn R.M. Garvin M.R. Wade D.P. ABCA1 is the cAMP-inducible apolipoprotein receptor that mediates cholesterol secretion from macrophages. J. Biol. Chem. 2000; 275: 34508-34511Google Scholar). Recently, it was shown that another transporter, ABCG1, promotes mass cholesterol efflux from cells to mature HDL particles (HDL2 and HDL3) but not to lipid-poor apoA-I (5,6). Both ABCA1 and ABCG1 are abundant in macrophages, especially after cholesterol loading, suggesting their importance for the cholesterol efflux process. Cholesterol efflux was also correlated to HDL lipid composition and structure (12Yancey P.G. de la Llera-Moya M. Swarnakar S. Monzo P. Klein M.S. Connelly A. Johnson W.J. Williams D.L. Rothblat G.H. High density lipoprotein phospholipid composition is a major determinant of the bi-directional flux and net movement of cellular free cholesterol mediated by scavenger receptor BI. J. Biol. Chem. 2000; 275: 36596-36604Google Scholar). As an example, phosphatidylcholine (PC)-enriched HDL increases cholesterol efflux, whereas sphingomyelin (SPM)-enriched HDL decreases cholesterol influx to macrophages (12Yancey P.G. de la Llera-Moya M. Swarnakar S. Monzo P. Klein M.S. Connelly A. Johnson W.J. Williams D.L. Rothblat G.H. High density lipoprotein phospholipid composition is a major determinant of the bi-directional flux and net movement of cellular free cholesterol mediated by scavenger receptor BI. J. Biol. Chem. 2000; 275: 36596-36604Google Scholar). Moreover, several lipids that are common constituents of HDL are known to significantly affect the fluidity of lipid surfaces (e.g., PC and SPM) (15Johnson W.J. Mahlberg F.H. Rothblat G.H. Phillips M.C. Cholesterol transport between cells and high-density lipoproteins. Biochim. Biophys. Acta. 1991; 1085: 273-298Google Scholar). Indeed, the phospholipid fatty acyl composition of lipoproteins is known to have subtle but measurable effects on the fluidity of the lipoprotein phospholipidic layer (15Johnson W.J. Mahlberg F.H. Rothblat G.H. Phillips M.C. Cholesterol transport between cells and high-density lipoproteins. Biochim. Biophys. Acta. 1991; 1085: 273-298Google Scholar, 16Sola R. Baudete M.F. Motta C. Maille M. Boisnier C. Jacotot B. Effects of dietary fats on the fluidity of human high-density lipoprotein: influence of the overall composition and phospholipid fatty acids. Biochim. Biophys. Acta. 1990; 1043: 43-51Google Scholar). These changes may affect the ability of HDL particles to accommodate FC molecules that have desorbed from peripheral cells. Additionally, oxidative modifications of HDL affect its capacity to promote cholesterol efflux (17Bennefont-Rousselot D. Motta C. Khalil A. Sola R. La Ville A.K. Delattre J. Gardés-Albert M. Physiochemical changes in human high density lipoproteins (HDL) oxidized by gamma-radiolysis generated oxyradicals. Biochim. Biophys. Acta. 1995; 1255: 23-30Google Scholar). Indeed, the formation of peroxidation-derived lipid products is associated with changes of the physicochemical properties of HDL and especially a decrease in the fluidity of the HDL phospholipid layer (17Bennefont-Rousselot D. Motta C. Khalil A. Sola R. La Ville A.K. Delattre J. Gardés-Albert M. Physiochemical changes in human high density lipoproteins (HDL) oxidized by gamma-radiolysis generated oxyradicals. Biochim. Biophys. Acta. 1995; 1255: 23-30Google Scholar). In previous studies, we have demonstrated that HDLs from elderly subjects are more prone to lipid peroxidation (18Khalil A. Jay-Gerin J.P. Fülöp Jr., T. Age-related increased susceptibility of high-density lipoproteins (HDL) to in vitro oxidation induced by gamma-radiolysis of water. FEBS Lett. 1998; 435: 153-158Google Scholar) and present a significant reduction of their antioxidant property, along with a decrease in paraoxonase 1 activity (19Jaouad L. de Guise C. Berrougui H. Cloutier M. Isabelle M. Fulop T. Payette H. Khalil A. Age-related decrease in high-density lipoproteins antioxidant activity is due to an alteration in the PON1's free sulfhydyl groups. Atherosclerosis. 2006; 185: 191-200Google Scholar). In this study, we investigated the capacity of HDL to promote cholesterol efflux during aging with the aim of elucidating the biophysical and biochemical changes that influence this process. Hence, our results will contribute to a better understanding of the age-related increase in the incidence of cardiovascular disease. Acetic acid, sulfuric acid, sodium phosphate, thiobarbituric acid, n-butanol, methanol, ethanol, n-isopropanol, hexane, ammonium hydroxide, chloroform, and methanol were purchased from Fisher (Montréal, Québec, Canada). 1,1,3,3,-Tetraethoxypropane, d-α-tocopherol, γ-tocopherol, butylated hydroxytoluene, CuSO4, EDTA, lithium perchlorate, 1,6-diphenyl-1,3,5-hexatriene, PC, SPM, 8-(4-chlorophenylthio)adenosine 3′,5′-cyclic monophosphate (cAMP), and [3H]cholesterol were obtained from Sigma (St. Louis, MO). THP-1 and J774 cells were purchased from the American Type Culture Collection (Manassas, VA). Plasma was obtained from healthy volunteers (eight young, aged 20–30 years, and nine elderly, aged 65–70 years). Their demographic data are shown in Table 1 . All subjects were considered healthy because they were normolipidemic and had normal blood pressure. No subjects showed clinical signs of inflammation or diabetes. They were free of any medication, including lipid-lowering medications, and no oral antioxidant supplementation was used. They were all nonsmokers, and none of the women was currently taking estrogen replacement therapy for menopause. The elderly subjects were living at home, functionally independent, and cognitively intact (Mini Mental State Examination > 28). The Ethics Committee of the Sherbrooke Geriatric University Institute approved the study, and all subjects gave written informed consent.TABLE 1Demographic and biochemical parameters of the study subjectsParametersYoungElderlySubjects, n (male/female)8 (4/4)9 (4/5)Average age, years25.7 ± 0.8967.9 ± 1.63Body mass index, kg/m222.7 ± 3.5723.7 ± 4.61Total cholesterol, mmol/l4.56 ± 0.225.11 ± 0.23HDL, mmol/l1.33 ± 0.141.42 ± 0.11HDL cholesterol, mmol/l3.57 ± 0.323.47 ± 0.32LDL, mmol/l2.85 ± 0.232.83 ± 0.2Triglycerides, mmol/l1.11 ± 0.131.42 ± 0.13Apolipoprotein A-I, g/l1.23 ± 0.291.20 ± 0.25C-reactive protein, mg/l<3.0 1 indicate an increase of the negative charge compared with native Y-HDL. HDL electrophoresis was carried out in barbital buffer at pH 8.6 on 0.6% agarose gels (Helena Laboratories, Montreal, Québec, Canada). The gels were stained with 0.1% (w/v) Fat Red 7B in 95% methanol. ApoA-I-bound carbonyl content was assayed as described by Levine et al. (27Levine R.L. Garland D. Oliver C.N. Amici A. Climent I. Lenz A.G. Ahn B.W. Shaltiel S. Stadtman E.R. Determination of carbonyl content in oxidatively modified proteins. Methods Enzymol. 1990; 186: 464-478Google Scholar). Briefly, apoA-I was purified from HDL as described previously (27Levine R.L. Garland D. Oliver C.N. Amici A. Climent I. Lenz A.G. Ahn B.W. Shaltiel S. Stadtman E.R. Determination of carbonyl content in oxidatively modified proteins. Methods Enzymol. 1990; 186: 464-478Google Scholar). The carbonyl content were determined by dinitrophenylhydrazine derivatization. ApoA-I-bound carbonyls were detected in TCA-precipitable materials by absorbance at 370 nm (ϵ = 22,000 M−1 cm−1). Lipoprotein fluidity was determined by steady-state anisotropy of 1,6-diphenyl-1,3,5-hexatriene as described previously (28Beck R. Bertolino S. Abott S.E. Aaronson P.I. Smimou S.V. Modulation of arachidonic acid release and membrane fluidity by albumin in vascular smooth and endothelial cells. Circ. Res. 1998; 83: 923-931Google Scholar). Fluidity represents the inverse values of anisotropy and is expressed as 1/r (for steady-state fluorescence anisotropy). r was calculated as [(Iv − GIp)/(Iv − 2GIp)], where Iv and Ip are the parallel and perpendicular polarized fluorescence intensities and G is the monochromator grating correction factor. Total lipids were extracted using a modified method of Folch, Lees, and Sloane-Stanley (29Folch J. Lees M Sloane-Stanley A. Simple method for isolation and purification of total lipids from animal tissues. J. Biol. Chem. 1957; 22: 6497-6509Google Scholar). One hundred microliters of lipid extract was then injected into an HPLC system coupled to an evaporative light-scattering detector according to the method of Becart, Chevalier, and Biesse (30Becart J. Chevalier C. Biesse J.P. Quantitative analysis of phospholipids by HPLC with a light scattering evaporating detector—application to raw materials for cosmetic use. J. High Res. Chromatogr. 1999; 13: 126-129Google Scholar). Solvent eluents were prepared according to a binary gradient (A, chloroform-methanol-ammonium hydroxide at 30%: 80/19.5/0.5; B, chloroform-methanol-water-ammonium hydroxide at 30%: 60/34/5.5/0.5). Values are expressed as means ± SEM. One-way ANOVA was used for multiple comparisons. Linear regression analysis was used to assess the association between two continuous variables, and the t-test was used to assess the comparison between two groups. Statistical analyses were performed using Prism version 4.0. The biochemical characteristics of participating subjects are reported in Table 1. The two age groups had no significant differences in their body mass index, total cholesterol, or LDL and HDL cholesterol. ApoA-I concentrations were in the same range for young and elderly subjects, and the acute inflammation phase protein C-reactive protein was below detection levels for both age groups (<3 mg/l). To examine the effect of aging on the antiatherogenic activities of HDL and particularly their ability to promote RCT, we assessed the capacity of HDL obtained from young (Y-HDL) and elderly (E-HDL) healthy subjects to enable cholesterol efflux. A time course (0–48 h) on cholesterol efflux revealed differences between Y-HDL and E-HDL that were manifested with 50 μg/ml HDL after 24 h of incubation (Fig. 1 ). In fact, when Y-HDL and E-HDL were incubated for 24 h with THP-1 macrophages preloaded with radiolabled [3H]cholesterol, cholesterol efflux promoted by Y-HDL was significantly higher by 14.9% (P < 0.05) than that promoted by E-HDL. The amounts of cholesterol efflux promoted by Y-HDL and E-HDL were dependent on the incubation time with macrophages and reached a maximum after 24 h of incubation, this is in agreement with previous results published by Nagano, Arai, and Kita (31Nagano Y. Arai H. Kita T. High density lipoprotein loses its effect to stimulate efflux of cholesterol from foam cells after oxidative modification. Proc. Natl. Acad. Sci. USA. 1991; 88: 6457-6461Google Scholar). The measure of cholesterol mass in the media and in cells also demonstrated a higher significant capacity of Y-HDL to mediate net cholesterol efflux than E-HDL (P = 0.023). To gain more insight into the effect of aging on HDL-mediated cholesterol efflux, we assessed the capacity of different HDL subfractions to promote cholesterol efflux, in particular HDL2 and HDL3. Under our conditions, HDL2 and HDL3 were isolated by ultracentrifugation, which excluded the presence of preβ1-HDL in our preparations, thus eliminating its possible role in the difference of the RCT capacity between young and elderly (32Chétiveaux M. Nazih H. Ferchaud-Roucher V. Lambert G. Zaïr Y. Masson M. Ouguerram K. Bouhours D. Krempf M. The differential apoA-I enrichment of preβ1 and HDL is detectable by gel filtration separation. J. Lipid Res. 2002; 43: 1986-1993Google Scholar, 33Sviridov D. Miyazaki O. Theodore K. Hoang A. Fukamachi I. Nestel P. Delineation of the role of pre-β1-HDL in cholesterol efflux using isolated pre-β1 HDL. Arterioscler. Thromb. Vasc. Biol. 2002; 22: 1482-1488Google Scholar). We subsequently sought to determine, first, which HDL subfraction (HDL2 or HDL3) was more implicated in the HDL-mediated cholesterol efflux from macrophages, and second, the effect of aging in this process. Whole HDL, HDL2, and HDL3 isolated from both young and elderly subjects were incubated separately for 24 h with [3H]cholesterol-loaded THP-1 macrophages. Y-HDL3 induced significantly a higher [3H]FC efflux (9.7% higher; P < 0.05) than that induced by Y-HDL2, whereas no differences were apparent between E-HDL3 and E-HDL2 (Fig. 1). When regarded as a function of aging, Y-HDL3 showed a higher capacity to promote cholesterol efflux than E-HDL3 (11.1% higher; P < 0.05), with no observed variations between Y-HDL2 and E-HDL2. To clarify which of the cholesterol efflux pathways was more affected by aging, we investigated the mechanism based on the ABCA1 protein using a second macrophage cell line, J774. J774 cells express less ABCA1 compared with THP-1 macrophages (9Bortnick A.E. Rothblat G.H. Stoudt G. Hoppe K.L. Royer L.J. McNeish J. Francone O.L. The correlation of ATP-binding cassette 1 mRNA levels with cholesterol efflux from various cell lines. J. Biol. Chem. 2000; 275: 28634-28640Google Scholar), as confirmed by our results (Fig. 2A ). Interestingly, when Y-HDL and E-HDL (50 μg/ml) were incubated separately with [3H]cholesterol-loaded J774 cells during 24 h, there was no effect of aging on the capacity of either HDL to promote cholesterol efflux compared with the THP-1 cells (Fig. 2B). Furthermore, we chemically induced overexpression of ABCA1 by J774 to analyze the effect of aging on the ABCA1 cholesterol efflux-related pathway. Our results indicate that J774 cells stimulated with cAMP have a robust expression of ABCA1 (>9-fold) compared with nonstimulated cells (Fig. 3A ). Interestingly, the modulation of expression of ABCG1 by cAMP was <1.8-fold. The chemically induced expression of ABCA1 in J774 cells by cAMP (21Haidar B. Denis M. Krimbou L. Marcil M. Genest J. cAMP induces ABCA1 phosphorylation activity and promotes cholesterol efflux from fibroblasts. J. Lipid Res. 2002; 43: 2087-2094Google Scholar, 34Rosenblat M. Karry R. Aviram M. Paraoxonase 1 (PON1) is a more potent antioxidant and stimulant of macrophage cholesterol efflux, when present in HDL than in lipoprotein-deficient serum: relevance to diabetes. Atherosclerosis. 2006; 187: 74-81Google Scholar, 35Yancey P.G. Bortnick A.E. Kellner-Weibel G. de la Llera-Moya M. Phillips M.C. Rothblat G.H. Importance of different pathways of cellular cholesterol efflux. Arterioscler. Thromb. Vasc. Biol. 2003; 23: 712-719Crossref PubMed Scopus (439) Google Scholar) significantly increased whole HDL- and HDL3-mediated cholesterol efflux in both young and elderly subjects (Fig. 3B), whereas no differences were observed in HDL2-related cholesterol efflux as a function of aging (results not shown). Moreover, in ABCA1-enriched J774 cells, Y-HDL increased cholesterol efflux by 21.7% (P < 0.05) compared with E-HDL, whereas Y-HDL3 enhanced cholesterol efflux by 26.1% (P < 0.001) compared with E-HDL3 (Fig. 3B). ApoA-I purified from young subjects (Y-apoA-I) and elderly subjects (E-apoA-I) was also evaluated for its capacity to promote cholesterol efflux (Fig. 3C). Our results do not shown an effect of aging on the apoA-I-dependent cholesterol efflux from control J774 cells. However, in ABCA1-enriched J774 cells, E-apoA-I was significantly less efficient at mediating cholesterol efflux than Y-apoA-I (P = 0.0048) (Fig. 3C). The ABCA1-mediated cholesterol efflux pathway is dependent on the interaction of apoA-I with the ABCA1 receptor. Thus, alteration or modification of apoA-I protein could modulate the HDL cholesterol efflux capacity. For this purpose, we used SDS-P
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