Plasma lipoprotein subfraction concentrations are associated with lipid metabolism and age-related macular degeneration
2017; Elsevier BV; Volume: 58; Issue: 9 Linguagem: Inglês
10.1194/jlr.m073684
ISSN1539-7262
AutoresChui Ming Gemmy Cheung, Alfred Tau Liang Gan, Qiao Fan, Miao Ling Chee, Rajendra S. Apte, Chiea Chuen Khor, Ian Yeo, Ranjana Mathur, Ching‐Yu Cheng, Tien Yin Wong, E. Shyong Tai,
Tópico(s)Antioxidant Activity and Oxidative Stress
ResumoDisturbance in lipid metabolism has been suggested as a major pathogenic factor for age-related macular degeneration (AMD). Conventional lipid measures have been inconsistently associated with AMD. Other factors that can alter lipid metabolism include lipoprotein phenotype and genetic mutations. We performed a case-control study to examine the association between lipoprotein profile and neovascular AMD (nAMD) and whether the cholesterylester transfer protein (CETP) D442G mutation modulates these associations. Patients with nAMD had significantly higher concentrations of HDL and IDL compared with controls. The increase in HDL particles in nAMD patients was driven by an excess of medium-sized particles. Concurrently, patients with nAMD also had lower Apo A-1, lower VLDL and chylomicron lipoprotein. Many of these associations showed a dose-dependent association between controls, early AMD cases, and nAMD cases. Adjustment for the presence of the D442G mutation at the CETP locus did not significantly alter the increased AMD risk associated with HDL particle concentration. AMD is associated with variation in many lipoprotein subclasses, including increased HDL and IDL particles and decreased Apo A-1, VLDL, and chylomicron particles. These data suggest widespread systemic disturbance in lipid metabolism in the pathogenesis of AMD, including possible alterations in lipoprotein carrier capacity. Disturbance in lipid metabolism has been suggested as a major pathogenic factor for age-related macular degeneration (AMD). Conventional lipid measures have been inconsistently associated with AMD. Other factors that can alter lipid metabolism include lipoprotein phenotype and genetic mutations. We performed a case-control study to examine the association between lipoprotein profile and neovascular AMD (nAMD) and whether the cholesterylester transfer protein (CETP) D442G mutation modulates these associations. Patients with nAMD had significantly higher concentrations of HDL and IDL compared with controls. The increase in HDL particles in nAMD patients was driven by an excess of medium-sized particles. Concurrently, patients with nAMD also had lower Apo A-1, lower VLDL and chylomicron lipoprotein. Many of these associations showed a dose-dependent association between controls, early AMD cases, and nAMD cases. Adjustment for the presence of the D442G mutation at the CETP locus did not significantly alter the increased AMD risk associated with HDL particle concentration. AMD is associated with variation in many lipoprotein subclasses, including increased HDL and IDL particles and decreased Apo A-1, VLDL, and chylomicron particles. These data suggest widespread systemic disturbance in lipid metabolism in the pathogenesis of AMD, including possible alterations in lipoprotein carrier capacity. Age-related macular degeneration (AMD) is one of the major causes of blindness worldwide (1.Lim L.S. Mitchell P. Seddon J.M. Holz F.G. Wong T.Y. Age-related macular degeneration.Lancet. 2012; 379: 1728-1738Abstract Full Text Full Text PDF PubMed Scopus (1233) Google Scholar, 2.Wong W.L. Su X. Li X. Cheung C.M. Klein R. Cheng C.Y. Wong T.Y. Global prevalence of age-related macular degeneration and disease burden projection for 2020 and 2040: a systematic review and meta-analysis.Lancet Glob. Health. 2014; 2: e106-e116Abstract Full Text Full Text PDF PubMed Scopus (2413) Google Scholar). Despite extensive research, the pathogenesis of AMD remains elusive and is likely multifactorial, involving genetic, lifestyle, and systemic factors (3.Zarbin M.A. Current concepts in the pathogenesis of age-related macular degeneration.Arch. 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In further support of this hypothesis are recent studies that show variants in genes involved in lipid metabolism, including hepatic lipase (LIPC), cholesterylester transfer protein (CETP), and ATP-binding cassette transporter A1 (ABCA1), confer increased risk of AMD (29.Neale B.M. Fagerness J. Reynolds R. Sobrin L. Parker M. Raychaudhuri S. Tan P.L. Oh E.C. Merriam J.E. Souied E. et al.Genome-wide association study of advanced age-related macular degeneration identifies a role of the hepatic lipase gene (LIPC).Proc. Natl. Acad. Sci. USA. 2010; 107: 7395-7400Crossref PubMed Scopus (352) Google Scholar, 30.Reynolds R. Rosner B. Seddon J.M. Serum lipid biomarkers and hepatic lipase gene associations with age-related macular degeneration.Ophthalmology. 2010; 117: 1989-1995Abstract Full Text Full Text PDF PubMed Scopus (119) Google Scholar, 31.Chen W. Stambolian D. Edwards A.O. Branham K.E. Othman M. Jakobsdottir J. Tosakulwong N. Pericak-Vance M.A. Campochiaro P.A. Klein M.L. 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Hagbi-Levi S. et al.Impaired cholesterol efflux in senescent macrophages promotes age-related macular degeneration.Cell Metab. 2013; 17: 549-561Abstract Full Text Full Text PDF PubMed Scopus (173) Google Scholar). The proteins encoded by most of these cholesterol-related genes have also been immunolocalized to the retina (21.Tserentsoodol N. Gordiyenko N.V. Pascual I. Lee J.W. Fliesler S.J. Rodriguez I.R. Intraretinal lipid transport is dependent on high density lipoprotein-like particles and class B scavenger receptors.Mol. Vis. 2006; 12: 1319-1333PubMed Google Scholar). We recently completed a genome-wide association study in East Asian AMD and have identified a missense mutation (D442G) in the CETP gene that is associated with elevated HDL-C and an increased risk of nAMD. CETP mediates the transfer of cholesteryl ester from HDL to LDL (33.Cheng C.Y. Yamashiro K. Chen L.J. Ahn J. Huang L. Huang L. Cheung C.M. Miyake M. Cackett P.D. Yeo I.Y. et al.New loci and coding variants confer risk for age-related macular degeneration in East Asians.Nat. Commun. 2015; 6: 6063Crossref PubMed Scopus (99) Google Scholar). CETP deficiency generates enlarged HDL particles containing an excess of cholesteryl esters, which are thought to be dysfunctional and incapable of reverse cholesterol transport (34.Inazu A. Jiang X.C. Haraki T. Yagi K. Kamon N. Koizumi J. Mabuchi H. Takeda R. Takata K. Moriyama Y. Genetic cholesteryl ester transfer protein deficiency caused by two prevalent mutations as a major determinant of increased levels of high density lipoprotein cholesterol.J. Clin. Invest. 1994; 94: 1872-1882Crossref PubMed Scopus (218) Google Scholar, 35.Takahashi K. Jiang X.C. Sakai N. Yamashita S. Hirano K. Bujo H. Yamazaki H. Kusunoki J. Miura T. Kussie P. A missense mutation in the cholesteryl ester transfer protein gene with possible dominant effects on plasma high density lipoproteins.J. Clin. Invest. 1993; 92: 2060-2064Crossref PubMed Scopus (118) Google Scholar). How genetic variants at the CETP locus influence or modulate the relationship between plasma lipids, lipoproteins, and AMD is unknown. To address these major gaps, we examined the association between lipoprotein phenotype (size and distribution) and AMD. We also explored the possibility that the CETP D442G mutation may mediate or modulate these associations. Our hypothesis is that patients with AMD have abnormal lipid metabolism, which may give rise to abnormal lipoprotein profile characterized by an increase in large HDL particles, which are inefficient carriers of cholesterol. We performed a case-control study utilizing serum from 193 participants of Chinese ethnicity with nAMD enrolled in a prospective clinical cohort study, the Asian AMD Phenotyping Study; and 184 subjects with early AMD and 289 age and gender-matched controls free of AMD enrolled in the Singapore Chinese Eye Study. Both studies were approved by the Singhealth Institutional Review Board and were conducted in accordance with the Declaration of Helsinki (protocol nos. R697/47/2009 and R498/47/2006). Detailed methodology of both studies has been published previously (36.Cheung C.M. Bhargava M. Laude A. Koh A. Xiang L. Wong D. Niang T. Lim T.H. Gopal L. Wong T.Y. Asian age-related macular degeneration phenotyping study: rationale, design and protocol of a prospective cohort study.Clin. Experiment. Ophthalmol. 2012; 40: 727-735Crossref PubMed Scopus (36) Google Scholar, 37.Cheung C.M. Li X. Mathur R. Lee S.Y. Chan C.M. Yeo I. Loh B.K. Williams R. Wong E.Y. Wong D. et al.A prospective study of treatment patterns and 1-year outcome of Asian age-related macular degeneration and polypoidal choroidal vasculopathy.PLoS One. 2014; 9: e101057Crossref PubMed Scopus (40) Google Scholar, 38.Cheung C.M. Bhargava M. Xiang L. Mathur R. Mun C.C. Wong D. Wong T.Y. 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The impact of typical neovascular age-related macular degeneration and polypoidal choroidal vasculopathy on vision-related quality of life in Asian patients.Br. J. Ophthalmol. 2017; 101: 591-596Crossref PubMed Scopus (17) Google Scholar, 42.Lavanya R. Jeganathan V.S. Zheng Y. Raju P. Cheung N. Tai E.S. Wang J.J. Lamoureux E. Mitchell P. Young T.L. et al.Methodology of the Singapore Indian Chinese Cohort (SICC) eye study: quantifying ethnic variations in the epidemiology of eye diseases in Asians.Ophthalmic Epidemiol. 2009; 16: 325-336Crossref PubMed Scopus (273) Google Scholar), and all participants provided written informed consent (additional information is available in supplemental data). The Asian AMD Phenotyping Study prospectively recruited a consecutive series of treatment-naıve Asian patients with exudative maculopathy secondary to nAMD from the retinal clinic of the Singapore National Eye Centre since March 1, 2010, and is still ongoing (32.Klaver C.C. Kliffen M. van Duijn C.M. Hofman A. Cruts M. Grobbee D.E. van Broeckhoven C. de Jong P.T. Genetic association of apolipoprotein E with age-related macular degeneration.Am. J. Hum. Genet. 1998; 63: 200-206Abstract Full Text Full Text PDF PubMed Scopus (381) Google Scholar, 33.Cheng C.Y. Yamashiro K. Chen L.J. Ahn J. Huang L. Huang L. Cheung C.M. Miyake M. Cackett P.D. Yeo I.Y. et al.New loci and coding variants confer risk for age-related macular degeneration in East Asians.Nat. Commun. 2015; 6: 6063Crossref PubMed Scopus (99) Google Scholar, 34.Inazu A. Jiang X.C. Haraki T. Yagi K. Kamon N. Koizumi J. Mabuchi H. Takeda R. Takata K. Moriyama Y. Genetic cholesteryl ester transfer protein deficiency caused by two prevalent mutations as a major determinant of increased levels of high density lipoprotein cholesterol.J. Clin. Invest. 1994; 94: 1872-1882Crossref PubMed Scopus (218) Google Scholar, 35.Takahashi K. Jiang X.C. Sakai N. Yamashita S. Hirano K. Bujo H. Yamazaki H. Kusunoki J. Miura T. Kussie P. A missense mutation in the cholesteryl ester transfer protein gene with possible dominant effects on plasma high density lipoproteins.J. Clin. Invest. 1993; 92: 2060-2064Crossref PubMed Scopus (118) Google Scholar, 36.Cheung C.M. Bhargava M. Laude A. Koh A. Xiang L. Wong D. Niang T. Lim T.H. Gopal L. Wong T.Y. Asian age-related macular degeneration phenotyping study: rationale, design and protocol of a prospective cohort study.Clin. Experiment. Ophthalmol. 2012; 40: 727-735Crossref PubMed Scopus (36) Google Scholar, 37.Cheung C.M. Li X. Mathur R. Lee S.Y. Chan C.M. Yeo I. Loh B.K. Williams R. Wong E.Y. Wong D. et al.A prospective study of treatment patterns and 1-year outcome of Asian age-related macular degeneration and polypoidal choroidal vasculopathy.PLoS One. 2014; 9: e101057Crossref PubMed Scopus (40) Google Scholar). To facilitate comparison of potential risk factors, the Asian AMD Phenotyping study adopted methods modeled after the Singapore Epidemiology of Eye Disease program, which enrolled more than 10,000 participants by using standardized methodology and photographic grading of AMD and risk factor assessment. The Singapore Chinese Eye Study is part of the Singapore Epidemiology of Eye Disease program and is a population-based cohort study of major eye diseases in urban Chinese adults ranging from 40 to 80 years of age residing in Singapore (42.Lavanya R. Jeganathan V.S. Zheng Y. Raju P. Cheung N. Tai E.S. Wang J.J. Lamoureux E. Mitchell P. Young T.L. et al.Methodology of the Singapore Indian Chinese Cohort (SICC) eye study: quantifying ethnic variations in the epidemiology of eye diseases in Asians.Ophthalmic Epidemiol. 2009; 16: 325-336Crossref PubMed Scopus (273) Google Scholar). Subjects were selected from a computer-generated list provided by the Singapore Ministry of Home Affairs, using an age-stratified (by 10 year age groups) random sampling method. The study took place between 2009 and 2011. A total of 3,353 Chinese persons were eligible, and 72.8% participated in the study. Subjects with early AMD and age- and gender-matched controls without AMD were selected from this cohort. Each patient was examined at baseline according to a standardized protocol derived in part from the Singapore Chinese Eye Study (42.Lavanya R. Jeganathan V.S. Zheng Y. Raju P. Cheung N. Tai E.S. Wang J.J. Lamoureux E. Mitchell P. Young T.L. et al.Methodology of the Singapore Indian Chinese Cohort (SICC) eye study: quantifying ethnic variations in the epidemiology of eye diseases in Asians.Ophthalmic Epidemiol. 2009; 16: 325-336Crossref PubMed Scopus (273) Google Scholar, 43.Klein R. Davis M.D. Magli Y.L. Segal P. Klein B.E. Hubbard L. The Wisconsin age-related maculopathy grading system.Ophthalmology. 1991; 98: 1128-1134Abstract Full Text PDF PubMed Scopus (961) Google Scholar). The examination procedures included measurements of height, weight, blood pressure, and pulse rate, followed by a comprehensive ocular examination (visual acuity, dilated fundus examination, color fundus photography, fluorescein angiography, indocyanine green angiography, and spectral domain optical coherence tomography). nAMD was diagnosed clinically and confirmed by ocular imaging results, which were graded by retinal specialists. All participants had an interview, systemic examination and laboratory investigations to determine socioeconomic, ocular, and systemic risk factors. We used a digital fundus camera to capture color photographs of each eye after pupil dilation. Photograph of at least one eye of sufficient quality for assessment of AMD status was available in 3,312 participants (98.8%). The Centre for Vision Research, University of Sydney, performed AMD grading using a modification of the Wisconsin Age-Related Maculopathy Grading System (43.Klein R. Davis M.D. Magli Y.L. Segal P. Klein B.E. Hubbard L. The Wisconsin age-related maculopathy grading system.Ophthalmology. 1991; 98: 1128-1134Abstract Full Text PDF PubMed Scopus (961) Google Scholar), which defines early AMD as either soft indistinct or reticular drusen or both soft, distinct drusen plus retinal pigment epithelium (RPE) abnormalities. Early AMD cases and age- and gender-matched subjects free of any stage of AMD were selected as controls for this study (Fig. 1). A detailed interviewer-administered questionnaire was used to collect information about medical history (including hypertension, diabetes, angina, myocardial infarction, and stroke), medication including lipid-altering drugs, and cigarette smoking (defined as current, past, and never) in participants of both studies. The questionnaire was administered in English or translated into Chinese (Mandarin) and back-translated into English. In both cohorts, a nonfasting venous blood sample was collected at baseline. Lipid biochemistry was performed by standard automated methods at the Biochemistry Department at the Singapore General Hospital, which utilized a Beckman Coulter ExC800 automated chemistry analyzer. Total cholesterol, HDL-cholesterol, TGs, and LDL-cholesterol were analyzed based on homogenous enzymatic colorimetry assay using 500 μl of serum. Serum and plasma were extracted and stored at −80°C prior to DNA extraction. Lipoprotein subclass levels and mean particle sizes were determined for all participants by NMR spectroscopy at LipoScience Inc. (Raleigh, NC) as previously described (26.Thompson A. Di Angelantonio E. Sarwar N. Erqou S. Saleheen D. Dullaart R.P. Keavney B. Ye Z. Danesh J. Association of cholesteryl ester transfer protein genotypes with CETP mass and activity, lipid levels, and coronary risk.JAMA. 2008; 299: 2777-2788Crossref PubMed Scopus (424) Google Scholar, 28.Freedman D.S. Otvos J.D. Jeyarajah E.J. Shalaurova I. Cupples L.A. Parise H. D'Agostino R.B. Wilson P.W. Schaefer E.J. Sex and age differences in lipoprotein subclasses measured by nuclear magnetic resonance spectroscopy: the Framingham Study.Clin. Chem. 2004; 50: 1189-1200Crossref PubMed Scopus (228) Google Scholar), by using stored serum. Each NMR measurement produces the concentrations of three subclasses of VLDL, LDL, and HDL particles each. From the subclass levels, the weighted-mean VLDL, LDL, and HDL particle sizes (nanometers in diameter) and particle concentrations were calculated. Lipoprotein subclasses were grouped as large LDL (21.3–23.0 nm), intermediate LDL (19.8–21.2 nm), small LDL (18.3–19.7 nm), large HDL (8.8–13.0 nm), medium HDL (8.2–8.8 nm), and small HDL (7.3–8.2 nm). CETP D442G (rs2303790) genotype was determined from the existing Illumina Human OmniExpress genotyping or by using Taqman allelic discrimination probes (Applied Biosystems). The genotyped SNP rs2303790 was within Hardy-Weinberg Equilibrium in health controls (P = 0.190). CETP concentration was determined by using a commercially available human cholesteryl ester transfer protein ELISA Kit (CSB-E08567h, Cusabio), which offers a detection range of 0.195–50 ng/ml. Serum samples (100 µl) were used for the assay following dilution and preparation instructions supplied by the vendor. All baseline and lipoprotein profile characteristics (LPCs) of study participants were summarized and compared between the three groups of study participants, namely, nAMD cases, early AMD cases, and age- and gender-matched controls. ANOVA using an F-test was conducted to compare the means of continuous variables, whereas a chi-squared or Fisher'ns exact test was used to compare the proportional distribution of categorical variables between the three groups. Pairwise comparisons of the mean of each LPC were also performed by using Tukey'ns honest significant difference test for multiple comparisons. For assessing crudely the presence of a linear trend relating the mean of each LPC with increasing AMD severity (from no AMD to early AMD to nAMD), an F-test of the linear orthogonal polynomial contrast was conducted, treating AMD severity as an equally spaced ordinal variable in a regression model. D442G mutation carrier status was dichotomized, with individuals carrying at least one mutant allele classified as mutation carriers. The mean of each LPC between D442G mutation carriers and noncarriers was compared in nAMD cases and controls separately with a linear regression of the LPC against mutation status, adjusting for potential confounders of th
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