Age-related Macular Degeneration

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Wiecek E, Lashkari K, Dakin S, Bex PJ. Novel Quantitative Assessment of Metamorphopsia in Maculopathy. Invest Ophthalmol Vis Sci 2014;Abstract

Purpose: Patients with macular disease often report experiencing metamorphopsia (visual distortion). Although typically measured with Amsler charts, more objective and quantitative assessments of perceived distortion are desirable to effectively monitor the presence, progression and remediation of visual impairment. Methods: Participants with binocular (n = 33) and monocular (n= 50) maculopathy across seven disease groups, and control participants (n = 10) with no identifiable retinal disease completed a modified Amsler Grid assessment (presented on a computer screen with eye tracking to ensure fixation compliance) and two novel objective measures of metamorphopsia in the central five degrees of visual field. 81% (67/83) of participants completed a task requiring them to configure eight dots in the shape of a square, and 64% (32/50) of participants experiencing monocular distortion completed a spatial alignment task using dichoptic stimuli. 10 controls completed all tasks. Results: Horizontal and vertical distortion magnitudes were calculated for each of the three assessments. Distortion magnitudes were significantly higher in patients than controls in all assessments. There was no significant difference in magnitude of distortion across different macular diseases. Among patients, there were no significant correlations between overall magnitude of distortion among any of the three measures and no significant correlations in localized measures of distortion. Conclusions: Three alternative quantifications of monocular spatial distortion in the central visual field generated uncorrelated estimates of visual distortion. It is therefore unlikely that metamorphopsia is caused solely by displacement of photoreceptors in the retina, but instead involves additional top-down information, knowledge about the scene, and perhaps, cortical reorganization.

Winkler TW, Grassmann F, Brandl C, Kiel C, Günther F, Strunz T, Weidner L, Zimmermann ME, Korb CA, Poplawski A, Schuster AK, Müller-Nurasyid M, Peters A, Rauscher FG, Elze T, Horn K, Scholz M, Cañadas-Garre M, McKnight AJ, Quinn N, Hogg RE, Küchenhoff H, Heid IM, Stark KJ, Weber BHF. Genome-wide association meta-analysis for early age-related macular degeneration highlights novel loci and insights for advanced disease. BMC Med Genomics 2020;13(1):120.Abstract
BACKGROUND: Advanced age-related macular degeneration (AMD) is a leading cause of blindness. While around half of the genetic contribution to advanced AMD has been uncovered, little is known about the genetic architecture of early AMD. METHODS: To identify genetic factors for early AMD, we conducted a genome-wide association study (GWAS) meta-analysis (14,034 cases, 91,214 controls, 11 sources of data including the International AMD Genomics Consortium, IAMDGC, and UK Biobank, UKBB). We ascertained early AMD via color fundus photographs by manual grading for 10 sources and via an automated machine learning approach for > 170,000 photographs from UKBB. We searched for early AMD loci via GWAS and via a candidate approach based on 14 previously suggested early AMD variants. RESULTS: Altogether, we identified 10 independent loci with statistical significance for early AMD: (i) 8 from our GWAS with genome-wide significance (P < 5 × 10), (ii) one previously suggested locus with experiment-wise significance (P < 0.05/14) in our non-overlapping data and with genome-wide significance when combining the reported and our non-overlapping data (together 17,539 cases, 105,395 controls), and (iii) one further previously suggested locus with experiment-wise significance in our non-overlapping data. Of these 10 identified loci, 8 were novel and 2 known for early AMD. Most of the 10 loci overlapped with known advanced AMD loci (near ARMS2/HTRA1, CFH, C2, C3, CETP, TNFRSF10A, VEGFA, APOE), except two that have not yet been identified with statistical significance for any AMD. Among the 17 genes within these two loci, in-silico functional annotation suggested CD46 and TYR as the most likely responsible genes. Presence or absence of an early AMD effect distinguished the known pathways of advanced AMD genetics (complement/lipid pathways versus extracellular matrix metabolism). CONCLUSIONS: Our GWAS on early AMD identified novel loci, highlighted shared and distinct genetics between early and advanced AMD and provides insights into AMD etiology. Our data provide a resource comparable in size to the existing IAMDGC data on advanced AMD genetics enabling a joint view. The biological relevance of this joint view is underscored by the ability of early AMD effects to differentiate the major pathways for advanced AMD.
Wu J, Uchino M, Sastry SM, Schaumberg DA. Age-related macular degeneration and the incidence of cardiovascular disease: a systematic review and meta-analysis. PLoS One 2014;9(3):e89600.Abstract
IMPORTANCE: Research has indicated some shared pathogenic mechanisms between age-related macular degeneration (AMD) and cardiovascular disease (CVD). However, results from prior epidemiologic studies have been inconsistent as to whether AMD is predictive of future CVD risk. OBJECTIVE: To systematically review population-based cohort studies of the association between AMD and risk of total CVD and CVD subtypes, coronary heart disease (CHD) and stroke. DATA SOURCES: A systematic search of the PubMed and EMBASE databases and reference lists of key retrieved articles up to December 20, 2012 without language restriction. DATA EXTRACTION: Two reviewers independently extracted data on baseline AMD status, risk estimates of CVD and methods used to assess AMD and CVD. We pooled relative risks using random or fixed effects models as appropriate. RESULTS: Thirteen cohort studies (8 prospective and 5 retrospective studies) with a total of 1,593,390 participants with 155,500 CVD events (92,039 stroke and 62,737 CHD) were included in this meta-analysis. Among all studies, early AMD was associated with a 15% (95% CI, 1.08-1.22) increased risk of total CVD. The relative risk was similar but not significant for late AMD (RR, 1.17; 95% CI, 0.98-1.40). In analyses restricted to the subset of prospective studies, the risk associated with early AMD did not appreciably change; however, there was a marked 66% (95% CI, 1.31-2.10) increased risk of CVD among those with late AMD. CONCLUSION: Whereas the results from all cohort studies suggest that both early and late AMD are predictive of a small increase in risk of future CVD, subgroup analyses limited to prospective studies demonstrate a markedly increased risk of CVD among people with late AMD. Retrospective studies using healthcare databases may have inherent methodological limitations that obscure such association. Additional prospective studies are needed to further elucidate the associations between AMD and specific CVD outcomes.
Wu J, Cho E, Willett WC, Sastry SM, Schaumberg DA. Intakes of Lutein, Zeaxanthin, and Other Carotenoids and Age-Related Macular Degeneration During 2 Decades of Prospective Follow-up. JAMA Ophthalmol 2015;:1-10.Abstract

Importance: Despite strong biological plausibility, evidence from epidemiologic studies and clinical trials on the relations between intakes of lutein and zeaxanthin and age-related macular degeneration (AMD) has been inconsistent. The roles of other carotenoids are less thoroughly investigated. Objective: To investigate the associations between intakes of carotenoids and AMD. Design, Setting, and Participants: Prospective cohort study, with cohorts from the Nurses' Health Study and the Health Professionals Follow-up Study in the United States. A total of 63 443 women and 38 603 men were followed up, from 1984 until May 31, 2010, in the Nurses' Health Study and from 1986 until January 31, 2010, in the Health Professionals Follow-up Study. All participants were aged 50 years or older and were free of diagnosed AMD, diabetes mellitus, cardiovascular disease, and cancer at baseline. Main Outcomes and Measures: Predicted plasma carotenoid scores were computed directly from food intake, assessed by repeated food frequency questionnaires at baseline and follow-up, using validated regression models to account for bioavailability and reporting validity of different foods, and associations between predicted plasma carotenoid scores and AMD were determined. Results: We confirmed 1361 incident intermediate and 1118 advanced AMD cases (primarily neovascular AMD) with a visual acuity of 20/30 or worse by medical record review. Comparing extreme quintiles of predicted plasma lutein/zeaxanthin score, we found a risk reduction for advanced AMD of about 40% in both women and men (pooled relative risk comparing extreme quintiles = 0.59; 95% CI, 0.48-0.73; P for trend < .001). Predicted plasma carotenoid scores for other carotenoids, including β-cryptoxanthin, α-carotene, and β-carotene, were associated with a 25% to 35% lower risk of advanced AMD when comparing extreme quintiles. The relative risk comparing extreme quintiles for the predicted plasma total carotenoid index was 0.65 (95% CI, 0.53-0.80; P for trend < .001). We did not identify any associations of carotenoids, either as predicted plasma score or calculated intake, with intermediate AMD. Conclusions and Relevance: Higher intake of bioavailable lutein/zeaxanthin is associated with a long-term reduced risk of advanced AMD. Given that some other carotenoids are also associated with a lower risk, a public health strategy aimed at increasing dietary consumption of a wide variety of fruits and vegetables rich in carotenoids may reduce the incidence of advanced AMD.

Wu EW, Schaumberg DA, Park SK. Environmental cadmium and lead exposures and age-related macular degeneration in U.S. adults: the National Health and Nutrition Examination Survey 2005 to 2008. Environ Res 2014;133:178-84.Abstract
Age-related macular degeneration (AMD) is a complex disease resulting from the interplay of genetic predisposition and environmental exposures, and has been linked to oxidative stress and inflammatory mechanisms. Lead and cadmium can accumulate in human retinal tissues and may damage the retina through oxidative stress, and may thereby play a role in the development of AMD. We examined associations between blood lead, blood cadmium, and urinary cadmium concentrations and the presence of AMD in 5390 participants aged 40 years and older with blood lead and blood cadmium measures and a subsample of 1548 with urinary cadmium measures in the 2005-2008 National Health and Nutrition Examination Surveys. AMD was identified by grading retinal photographs with a modification of the Wisconsin Age-Related Maculopathy Grading System. The weighted prevalence of AMD was 6.6% (n=426). Controlling for age, gender, race/ethnicity, education and body mass index, adults in the highest blood cadmium quartile had higher odds of AMD compared to the lowest quartile (odds ratio [OR], 1.56; 95% CI, 1.02-2.40), with a significant trend across quartiles (p-trend=0.02). After further adjustment for pack-years of cigarette smoking, estimates were somewhat attenuated (OR, 1.43; 95% CI, 0.91-2.27; p-trend=0.08). Similar associations were found with urinary cadmium. The association between urinary cadmium and AMD was stronger in non-Hispanic whites (NHW) than in non-Hispanic blacks (NHB) (OR, 3.31; 95% CI, 1.37-8.01 for levels above versus below the median among NHW; OR,1.45; 95% CI, 0.40-5.32 for levels above versus below the median among NHB; p-interaction=0.03). We found no association between blood lead levels and AMD. Higher cadmium body burden may increase risk of AMD, particularly among non-Hispanic white individuals; however, additional studies are needed before firm conclusions can be drawn.
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Yanai R, Mulki L, Hasegawa E, Takeuchi K, Sweigard H, Suzuki J, Gaissert P, Vavvas DG, Sonoda K-H, Rothe M, Schunck W-H, Miller JW, Connor KM. Cytochrome P450-generated metabolites derived from ω-3 fatty acids attenuate neovascularization. Proc Natl Acad Sci U S A 2014;111(26):9603-8.Abstract
Ocular neovascularization, including age-related macular degeneration (AMD), is a primary cause of blindness in individuals of industrialized countries. With a projected increase in the prevalence of these blinding neovascular diseases, there is an urgent need for new pharmacological interventions for their treatment or prevention. Increasing evidence has implicated eicosanoid-like metabolites of long-chain polyunsaturated fatty acids (LCPUFAs) in the regulation of neovascular disease. In particular, metabolites generated by the cytochrome P450 (CYP)-epoxygenase pathway have been shown to be potent modulators of angiogenesis, making this pathway a reasonable previously unidentified target for intervention in neovascular ocular disease. Here we show that dietary supplementation with ω-3 LCPUFAs promotes regression of choroidal neovessels in a well-characterized mouse model of neovascular AMD. Leukocyte recruitment and adhesion molecule expression in choroidal neovascular lesions were down-regulated in mice fed ω-3 LCPUFAs. The serum of these mice showed increased levels of anti-inflammatory eicosanoids derived from eicosapentaenoic acid and docosahexaenoic acid. 17,18-epoxyeicosatetraenoic acid and 19,20-epoxydocosapentaenoic acid, the major CYP-generated metabolites of these primary ω-3 LCPUFAs, were identified as key lipid mediators of disease resolution. We conclude that CYP-derived bioactive lipid metabolites from ω-3 LCPUFAs are potent inhibitors of intraocular neovascular disease and show promising therapeutic potential for resolution of neovascular AMD.
Yonekawa Y, Kim IK. Clinical Characteristics and Current Treatment of Age-Related Macular Degeneration. Cold Spring Harb Perspect Med 2014;Abstract

Age-related macular degeneration (AMD) is a multifactorial degeneration of photoreceptors and retinal pigment epithelium. The societal impact is significant, with more than 2 million individuals in the United States alone affected by advanced stages of AMD. Recent progress in our understanding of this complex disease and parallel developments in therapeutics and imaging have translated into new management paradigms in recent years. However, there are many unanswered questions, and diagnostic and prognostic precision and treatment outcomes can still be improved. In this article, we discuss the clinical features of AMD, provide correlations with modern imaging and histopathology, and present an overview of treatment strategies.

Yonekawa Y, Andreoli C, Miller JB, Loewenstein JI, Sobrin L, Eliott D, Vavvas DG, Miller JW, Kim IK. Conversion to aflibercept for chronic refractory or recurrent neovascular age-related macular degeneration. Am J Ophthalmol 2013;156(1):29-35.e2.Abstract
PURPOSE: To explore the visual and anatomic outcomes of patients with refractory or recurrent neovascular age-related macular degeneration (AMD) who were converted from bevacizumab and/or ranibizumab to aflibercept. DESIGN: Two-center, retrospective chart review. METHODS: Treatment history, visual acuity (VA), and central macular thickness (CMT) on spectral-domain optical coherence tomography were collected. Patients were divided into "refractory" (persistent exudation despite monthly injections) or "recurrent" (exudation suppressed, but requiring frequent injections). RESULTS: One hundred and two eyes of 94 patients were included; 68 were refractory and 34 were recurrent. Eyes received a mean of 20.4 prior bevacizumab/ranibizumab injections and a mean of 3.8 aflibercept injections. Mean follow-up was 18 weeks. Mean VA was 20/50-1 before conversion, 20/50-2 after 1 aflibercept injection (P = .723), and 20/50+2 after the final injection (P = .253). Subgroup analysis of refractory and recurrent cases also showed stable VA. Of the refractory cases, mean CMT had improved after 1 injection (P < .001) and the final injection (P < .001). Intraretinal (P < .001) and subretinal (P < .001) fluid decreased after 1 injection, and the mean injection interval was extended from 5.2 to 6.2 weeks (P = .003). Of the recurrent cases, mean CMT improved after 1 injection (P < .001) and the final injection (P < .001). Intraretinal (P = .003) and subretinal (P = .046) fluid decreased after 1 injection, and the mean injection interval was extended from 7.2 to 9.5 weeks (P = .001). CONCLUSIONS: Converting patients with chronic neovascular AMD to aflibercept results in stabilized vision and improved anatomic outcomes, while allowing injection intervals to be extended.
Yu G, Duguay J, Marra KV, Gautam S, Le Guern G, Begum S, Sharifzadeh A, Arroyo JG. EFFICACY AND SAFETY OF TREATMENT OPTIONS FOR VITREOMACULAR TRACTION: A Case Series and Meta-Analysis. Retina 2016;36(7):1260-70.Abstract

PURPOSE: To evaluate treatment options for vitreomacular traction (VMT). METHODS: A retrospective, consecutive case series and a literature search with Boolean search logic. A random-effects meta-analysis was conducted to combine the rates of VMT resolution per treatment. Patients from studies analyzed were placed into cohorts based on the treatment received. RESULTS: CASE SERIES: Zero of 10 control, 3 of 7 intravitreal ocriplasmin (IVO, P = 0.10), 7 of 8 intravitreal expansile gas (pneumatic vitreolysis, PV, P < 0.01), and 10 of 10 pars plana vitrectomy (P < 0.01)-treated eyes experienced VMT release (VMTr) at Day 28. No patients developed retinal tears or detachment. One PV-treated (12.5%) eye developed a macular hole. Meta-analysis: Twenty-three of 131 prospective or retrospective and consecutive articles were included. Sixty-three eyes were treated with PV, 726 eyes were treated with intravitreal ocriplasmin, and 253 eyes were characterized as the control group (saline injection). The weighted rate of VMT resolution for the control group was 0.09 (95% confidence interval [CI]: 0.06-0.13), PV was 0.84 (95% CI: 0.76-0.92), and intravitreal ocriplasmin was 0.26 (95% CI: 0.23-0.29). CONCLUSION: Our analysis found that PV releases VMT in most patients and suggest that PV may be as effective or superior to nonsurgical options for VMTr at Day 28 with a similar risk profile.

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Zahr A, Alcaide P, Yang J, Jones A, Gregory M, Dela Paz NG, Patel-Hett S, Nevers T, Koirala A, Luscinskas FW, Saint-Geniez M, Ksander B, D'Amore PA, Argüeso P. Endomucin prevents leukocyte-endothelial cell adhesion and has a critical role under resting and inflammatory conditions. Nat Commun 2016;7:10363.Abstract

Endomucin is a membrane-bound glycoprotein expressed luminally by endothelial cells that line postcapillary venules, a primary site of leukocyte recruitment during inflammation. Here we show that endomucin abrogation on quiescent endothelial cells enables neutrophils to adhere firmly, via LFA-1-mediated binding to ICAM-1 constitutively expressed by endothelial cells. Moreover, TNF-α stimulation downregulates cell surface expression of endomucin concurrent with increased expression of adhesion molecules. Adenovirus-mediated expression of endomucin under inflammatory conditions prevents neutrophil adhesion in vitro and reduces the infiltration of CD45(+) and NIMP-R14(+) cells in vivo. These results indicate that endomucin prevents leukocyte contact with adhesion molecules in non-inflamed tissues and that downregulation of endomucin is critical to facilitate adhesion of leukocytes into inflamed tissues.

Zandi S, Nakao S, Chun K-H, Fiorina P, Sun D, Arita R, Zhao M, Kim E, Schueller O, Campbell S, Taher M, Melhorn MI, Schering A, Gatti F, Tezza S, Xie F, Vergani A, Yoshida S, Ishikawa K, Yamaguchi M, Sasaki F, Schmidt-Ullrich R, Hata Y, Enaida H, Yuzawa M, Yokomizo T, Kim Y-B, Sweetnam P, Ishibashi T, Hafezi-Moghadam A. ROCK-Isoform-Specific Polarization of Macrophages Associated with Age-Related Macular Degeneration. Cell Rep 2015;10(7):1173-86.Abstract

Age is a major risk factor in age-related macular degeneration (AMD), but the underlying cause is unknown. We find increased Rho-associated kinase (ROCK) signaling and M2 characteristics in eyes of aged mice, revealing immune changes in aging. ROCK isoforms determine macrophage polarization into M1 and M2 subtypes. M2-like macrophages accumulated in AMD, but not in normal eyes, suggesting that these macrophages may be linked to macular degeneration. M2 macrophages injected into the mouse eye exacerbated choroidal neovascular lesions, while M1 macrophages ameliorated them, supporting a causal role for macrophage subtypes in AMD. Selective ROCK2 inhibition with a small molecule decreased M2-like macrophages and choroidal neovascularization. ROCK2 inhibition upregulated M1 markers without affecting macrophage recruitment, underlining the plasticity of these macrophages. These results reveal age-induced innate immune imbalance as underlying AMD pathogenesis. Targeting macrophage plasticity opens up new possibilities for more effective AMD treatment.

Zekavat SM, Sekimitsu S, Ye Y, Raghu V, Zhao H, Elze T, Segrè AV, Wiggs JL, Natarajan P, Del Priore L, Zebardast N, Wang JC. Photoreceptor Layer Thinning Is an Early Biomarker for Age-Related Macular Degeneration: Epidemiologic and Genetic Evidence from UK Biobank OCT Data. Ophthalmology 2022;129(6):694-707.Abstract
PURPOSE: Despite widespread use of OCT, an early-stage imaging biomarker for age-related macular degeneration (AMD) has not been identified. Pathophysiologically, the timing of drusen accumulation in relationship to photoreceptor degeneration in AMD remains unclear, as are the inherited genetic variants contributing to these processes. Herein, we jointly analyzed OCT, electronic health record data, and genomic data to characterize the time sequence of changes in retinal layer thicknesses in AMD, as well as epidemiologic and genetic associations between retinal layer thicknesses and AMD. DESIGN: Cohort study. PARTICIPANTS: Forty-four thousand eight hundred twenty-three individuals from the UK Biobank (enrollment age range, 40-70 years; 54% women; median follow-up, 10 years). METHODS: The Topcon Advanced Boundary Segmentation algorithm was used for retinal layer segmentation. We associated 9 retinal layer thicknesses with prevalent AMD (present at enrollment) in a logistic regression model and with incident AMD (diagnosed after enrollment) in a Cox proportional hazards model. Next, we associated AMD-associated genetic alleles, individually and as a polygenic risk score (PRS), with retinal layer thicknesses. All analyses were adjusted for age, age-squared (age2), sex, smoking status, and principal components of ancestry. MAIN OUTCOME MEASURES: Prevalent and incident AMD. RESULTS: Photoreceptor segment (PS) thinning was observed throughout the lifespan of individuals analyzed, whereas retinal pigment epithelium (RPE) and Bruch's membrane (BM) complex thickening started after 57 years of age. Each standard deviation (SD) of PS thinning and RPE-BM complex thickening was associated with incident AMD (PS: hazard ratio [HR], 1.35; 95% confidence interval [CI], 1.23-1.47; P = 3.7 × 10-11; RPE-BM complex: HR, 1.14; 95% CI, 1.06-1.22; P = 0.00024). The AMD PRS was associated with PS thinning (β, -0.21 SD per twofold genetically increased risk of AMD; 95% CI, -0.23 to -0.19; P = 2.8 × 10-74), and its association with RPE-BM complex was U-shaped (thinning with AMD PRS less than the 92nd percentile and thickening with AMD PRS more than the 92nd percentile). The loci with strongest support for genetic correlation were AMD risk-raising variants Complement Factor H (CFH):rs570618-T, CFH:rs10922109-C, and Age-Related Maculopathy Susceptibility 2 (ARMS2)/High-Temperature Requirement Serine Protease 1 (HTRA1):rs3750846-C on PS thinning and SYN3/Tissue Inhibitor of Metalloprotease 3 (TIMP3):rs5754227-T on RPE-BM complex thickening. CONCLUSIONS: Epidemiologically, PS thinning precedes RPE-BM complex thickening by decades and is the retinal layer most strongly predictive of future AMD risk. Genetically, AMD risk variants are associated with decreased PS thickness. Overall, these findings support PS thinning as an early-stage biomarker for future AMD development.
Zeng R, Garg I, Miller JB. Complete Resolution of Central Soft Drusen without Geographic Atrophy or Choroidal Neovascularization. J Clin Med 2022;11(6)Abstract
The treatment and prevention of dry age-related macular degeneration (AMD) traditionally involve lifestyle modifications and antioxidant supplementation, including the AREDS2 formula. We present a case of a woman with dry AMD in her right eye with several large, confluent central drusen on her exam and optical coherence tomography B-scan. Over the course of a year, the drusen almost completely disappeared, but the retinal layers were preserved without the development of geographic atrophy or choroidal neovascularization. While the exact cause of this phenomenon is unclear, it was thought to be associated with this patient's strict daily use of numerous dietary supplements. This case highlights the potential in exploring alternative medicine supplements in the treatment of AMD.
Zhang C, Owen LA, Lillvis JH, Zhang SX, Kim IK, Deangelis MM. AMD Genomics: Non-Coding RNAs as Biomarkers and Therapeutic Targets. J Clin Med 2022;11(6)Abstract
Age-related macular degeneration (AMD) is a progressive neurodegenerative disease that is the world's leading cause of blindness in the aging population. Although the clinical stages and forms of AMD have been elucidated, more specific prognostic tools are required to determine when patients with early and intermediate AMD will progress into the advanced stages of AMD. Another challenge in the field has been the appropriate development of therapies for intermediate AMD and advanced atrophic AMD. After numerous negative clinical trials, an anti-C5 agent and anti-C3 agent have recently shown promising results in phase 3 clinical trials, in terms of slowing the growth of geographic atrophy, an advanced form of AMD. Interestingly, both drugs appear to be associated with an increased incidence of wet AMD, another advanced form of the disease, and will require frequent intravitreal injections. Certainly, there remains a need for other therapeutic agents with the potential to prevent progression to advanced stages of the disease. Investigation of the role and clinical utility of non-coding RNAs (ncRNAs) is a major advancement in biology that has only been minimally applied to AMD. In the following review, we discuss the clinical relevance of ncRNAs in AMD as both biomarkers and therapeutic targets.
Zhang P, Zhu M, Geng-Spyropoulos M, Shardell M, Gonzalez-Freire M, Gudnason V, Eiriksdottir G, Schaumberg D, Van Eyk JE, Ferrucci L, Semba RD. A novel, multiplexed targeted mass spectrometry assay for quantification of complement factor H (CFH) variants and CFH-related proteins 1-5 in human plasma. Proteomics 2017;17(6)Abstract

Age-related macular degeneration (AMD) is a leading cause of visual loss among older adults. Two variants in the complement factor H (CFH) gene, Y402H and I62V, are strongly associated with risk of AMD. CFH is encoded in regulator of complement activation gene cluster in chromosome 1q32, which includes complement factor related (CFHR) proteins, CFHR1 to CFHR5, with high amino acid sequence homology to CFH. Our goal was to build a SRM assay to measure plasma concentrations of CFH variants Y402, H402, I62, and V62, and CFHR1-5. The final assay consisted of 24 peptides and 72 interference-free SRM transition ion pairs. Most peptides showed good linearity over 0.3-200 fmol/μL concentration range. Plasma concentrations of CFH variants and CFHR1-5 were measured using the SRM assay in 344 adults. Plasma CFH concentrations (mean, SE in μg/mL) by inferred genotype were: YY402, II62 (170.1, 31.4), YY402, VV62 (188.8, 38.5), HH402, VV62 (144.0, 37.0), HY402, VV62 (164.2, 42.3), YY402, IV62 (194.8, 36.8), HY402, IV62 (181.3, 44.7). Mean (SE) plasma concentrations of CFHR1-5 were 1.63 (0.04), 3.64 (1.20), 0.020 (0.001), 2.42 (0.18), and 5.49 (1.55) μg/mL, respectively. This SRM assay should facilitate the study of the role of systemic complement and risk of AMD.

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