The Genetics of Age-Related Macular Degeneration: A Review of Progress to Date

Computational quantification of complex fundus phenotypes in age-related macular degeneration and Stargardt disease

PURPOSE

To describe an automated method of quantification of specific fundus phenotypes and evaluate its performance in differentiating drusen, the hallmark lesions of age-related macular degeneration (AMD), from similar-looking bright lesions, the pisciform deposits or flecks typical of Stargardt disease (SD).

METHODS

Fundus macular images of 30 eyes of 30 subjects were studied. Fifteen subjects had a clinical diagnosis of AMD with at least 10 intermediate and/or 1 large drusen, and the other 15 had SD. As a test of bright-lesion separation, AMD and SD subjects were chosen from the heterogeneous phenotypes of each disorder, to be as visually similar as possible. Drusen and fleck properties were quantified from the color images by using an automated method, and a shape classifier was used to divide the images as characteristic of either AMD or SD. Image identification performance was quantified by using the area under the receiver operating characteristic curve (AUC).

RESULTS

All SD subjects demonstrated at least one disease-associated variant of the ABCA4 gene. The method achieved an AUC of 0.936 for differentiating AMD from SD.

CONCLUSIONS

Automated quantification of fundus phenotypes was achieved, and the results show that the method can differentiate AMD from SD, two distinctly different genetically associated disorders, by quantifying the properties of the bright lesions (drusen and flecks) in their fundus images, even when the images were visually selected to be similar. Quantification of fundus phenotypes may allow recognition of new phenotypes, correlation with new genotypes and may measure disease-specific biomarkers to improve management of patients with AMD or SD.

Polyethylene glycol (PEG)-induced mouse model of choroidal neovascularization

In this study, we describe a new method for inducing choroidal neovascularization (CNV) in C57BL/6 mice, an animal model of wet age-related macular degeneration (AMD). AMD is a disease that causes central blindness in humans. We injected PEG-8 subretinally in different doses (0.125-2 mg) to induce CNV. After PEG-8 injection, we examined CNV at several time points (days 3-42). We also used Western blotting, immunohistochemistry, and ELISA to examine the complement component C3 split products, C9, VEGF, TGF-β2, and basic FGF. As early as day 1 after treatment, we found that a single subretinal injection of 1 mg of PEG-8 increased the C3 split products and the C9, TGF-β2, and basic FGF levels in the retinal pigment epithelium-choroid tissue. By day 3 after PEG-8 injection, the intraocular activation of the complement system caused induction and progression of CNV, including new vessels penetrating the Bruch's membrane. At day 5 after PEG-8 injection, we observed a fully developed CNV and retinal degeneration. Thus, in this study, we present a new, inexpensive, and accelerated mouse model of CNV that may be useful to study AMD.

Choriocapillaris vascular dropout related to density of drusen in human eyes with early age-related macular degeneration

PURPOSE

Age-related macular degeneration (AMD) is a common, potentially blinding disease characterized by the presence of extracellular deposits beneath the retinal pigment epithelium (RPE). Choroidal vascular changes have also been noted in AMD. This study examined the relationship between the choroidal vasculature and extent of drusen and other sub-RPE deposits, the key pathologic landmarks of AMD.

METHODS

Sections of the maculas of 45 human eyes (21 early AMD and 24 age-matched control) were evaluated morphometrically. The cross-sectional area of sub-RPE deposits, vascular density, number of CD45+ leukocytes, and number of "ghost vessels" were determined in a masked fashion and evaluated by regression analysis. In addition, the extramacular vascular density either directly beneath drusen or adjacent to drusen was evaluated in a separate set of donor eyes.

RESULTS

The vascular density of the choriocapillaris showed a trend toward decreasing in association with AMD status. By linear regression analysis, vascular density was inversely associated with sub-RPE deposit density (r(2) = 0.22, P < 0.01). The number of ghost vessels was negatively correlated with vascular density (r(2) = 0.55, P < 0.001) and positively correlated with sub-RPE deposit density (r(2) = 0.57, P < 0.001). In morphologic studies of extramacular solitary drusen, vascular density beneath drusen was found to be 45% lower than adjacent to drusen (P < 0.01).

CONCLUSIONS

These findings support the concept that microvascular changes are related to the pathogenesis of AMD and suggest that vascular endothelial cell loss occurs in association with sub-RPE deposit formation. Whether microvascular events are a cause or consequence of drusen or other deposit formation remains to be determined.

Age-related macular degeneration: genetic and environmental factors of disease

Age-related macular degeneration (AMD) is the most common cause of visual impairment among the elderly in developed countries, and its prevalence is thus increasing as the population ages; however, treatment options remain limited because the etiology and pathogenesis of AMD are incompletely defined. Recently, much progress has been made in gene discovery and mechanistic studies, which clearly indicate that AMD involves the interaction of multiple genetic and environmental factors. The identification of genes that have a substantial impact on the risk for AMD is not only facilitating the diagnosis and screening of populations at risk but is also elucidating key molecular pathways of pathogenesis. Pharmacogenetic studies of treatment responsiveness among patients with the "wet" form of AMD are increasingly proving to be clinically relevant; pharmacogenetic approaches hold great promise for both identifying patients with the best chance for vision recovery as well as tailoring individualized therapies.

The significance of the complement system for the pathogenesis of age-related macular degeneration - current evidence and translation into clinical application

BACKGROUND

Dysregulation of the complement system has been shown to play a major role in the pathogenesis of age-related macular degeneration (AMD).

METHODS

The current evidence from human studies derives from immunohistochemical and proteomic studies in donor eyes, genetic association studies, and studies of blood complement protein levels. These lines of evidence are corroborated by in vitro and animal studies.

RESULTS

In AMD donor eyes, detection of complement proteins in drusen suggested local inflammatory processes involving the complement system. Moreover, higher levels of complement proteins in the Bruch's membrane/choroid complex could be detected in AMD donor eyes compared to controls. A large number of independent genetic studies have consistently confirmed the association of AMD with risk or protective variants in genes coding for complement proteins, including complement factor H (CFH), CFH-related proteins 1 and 3, factor B/C2, C3 and factor I. Another set of independent studies detected increased levels of complement activation products in plasma of AMD patients, suggesting that AMD may be a systemic disease and the macula a vulnerable anatomic site of minimal resistance to complement activation. Genotype-phenotype correlations, including the impact of genetic variants on disease progression, gene-environment and pharmacogenetic interactions, have been investigated. There is evidence that complement gene variants may be associated with the progression from early to late forms of AMD, whereas they do not appear to play a significant role when late atrophic AMD has already developed. There are indications for an interaction between genetic variants and supplementation and dietary factors. Also, there is some evidence that variants in the CFH gene influence treatment effects in patients with neovascular AMD.

CONCLUSIONS

Such data suggest that the complement system may have a significant role for developing new prophylactic and therapeutic interventions in AMD. In fact, several compounds acting on the complement pathway are currently in clinical trials. Therapeutics that modulate the complement system need to balance inhibition with preservation of sufficient functional activity in order to maintain adequate immune responses and tissue homeostasis. Specifically, targeting the dysfunction appears more adequate than a global suppression of complement activation in chronic diseases such as AMD.

Correlation of complement factor H gene polymorphisms with exudative age-related macular degeneration in a Chinese cohort

To evaluate the association between complement factor H (CFH) gene polymorphism and the risk of exudative age-related macular degeneration (AMD) in a case-control study in a Chinese cohort. One hundred and thirty-six exudative AMD patients and 140 age- and sex-matched control subjects were recruited. We genotyped 3 common single nucleotide polymorphisms (SNPs), namely, -257C>T (rs3753394), Y402H (rs1061170) and IVS15 (rs1329428), genetic analyses were performed on all available genotype data. All the possible haplotypes of these 3 SNPs were detected. Polymerase chain reaction (PCR) and allele-specific restriction endonuclease digestion were performed, some PCR products of these 3 SNPs were sequenced. The risk alleles (T, C or G) of the 3 SNPs conferred 1.72-fold, 3.14-fold, and 1.79-fold of increased likelihood of the disease, respectively (P<0.05). The heterozygous genotype in rs1061170 (TC) revealed significant association, meanwhile rs3753394 and rs1329428 had a slight association with the disease, respectively. Significant differences were shown in the risk alleles in the 3 SNPs among different Chinese cohort. Low linkage disequilibrium was found among the 3 SNPs. The haplotypes TCG and CTG revealed as risk factors, whereas the protective haplotype CTA was over-represented in controls. We found significant association between risk alleles (T, C or G) of the 3 SNPs and the disease. The genetic divergence across multiple populations within Chinese existed. Risk haplotypes and protective haplotype were found in this study.

Association study of complement factor H, C2, CFB, and C3 and age-related macular degeneration in a Han Chinese population

PURPOSE

Genes in the complement pathway, including complement factor H (CFH), C2/BF, and C3, have been reported to be associated with age-related macular degeneration (AMD). Genetic variants, single-nucleotide polymorphisms (SNPs), in these genes were geno-typed for a case-control association study in a mainland Han Chinese population.

METHODS

One hundred and fifty-eight patients with wet AMD, 80 patients with soft drusen, and 220 matched control subjects were recruited among Han Chinese in mainland China. Seven SNPs in CFH and two SNPs in C2, CFB', and C3 were genotyped using the ABI SNaPshot method. A deletion of 84,682 base pairs covering the CFHR1 and CFHR3 genes was detected by direct polymerase chain reaction and gel electrophoresis.

RESULTS

Four SNPs, including rs3753394 (P = 0.0276), rs800292 (P = 0.0266), rs1061170 (P = 0.00514), and rs1329428 (P = 0.0089), in CFH showed a significant association with wet AMD in the cohort of this study. A haplotype containing these four SNPs (CATA) significantly increased protection of wet AMD with a P value of 0.0005 and an odds ratio of 0.29 (95% confidence interval: 0.15-0.60). Unlike in other populations, rs2274700 and rs1410996 did not show a significant association with AMD in the Chinese population of this study. None of the SNPs in CFH showed a significant association with drusen, and none of the SNPs in CFH, C2, CFB, and C3 showed a significant association with either wet AMD or drusen in the cohort of this study. The CFHR1 and CFHR3 deletion was not polymorphic in the Chinese population and was not associated with wet AMD or drusen.

CONCLUSION

This study showed that SNPs rs3753394 (P = 0.0276), rs800292 (P = 0.0266), rs1061170 (P = 0.00514), and rs1329428 (P = 0.0089), but not rs7535263, rs1410996, or rs2274700, in CFH were significantly associated with wet AMD in a mainland Han Chinese population. This study showed that CFH was more likely to be AMD susceptibility gene at Chr.1q31 based on the finding that the CFHR1 and CFHR3 deletion was not polymorphic in the cohort of this study, and none of the SNPs that were significantly associated with AMD in a white population in C2, CFB, and C3 genes showed a significant association with AMD.

Mutation screen of beta-crystallin genes in 274 patients with age-related macular degeneration

PURPOSE

The crystallin family of proteins comprise the main structural proteins of the vertebrate lens and have been classified into alpha-, beta-, and gamma- families. Several of the beta-crystallin proteins have been detected in the retina where they are each localized to different compartments of rod and cone photoreceptors. Functionally, beta-crystallins have been implicated in the protection of the retina from intense light exposure. Two members of the beta-crystallins, CRYBB1 and CRYBB2, have been identified in drusen preparations isolated from the retina of donor eyes of patients with age-related macular degeneration (AMD), the leading cause of blindness in the elderly population of developed countries. We therefore investigated CRYBB1 and CRYBB2 as candidate genes for AMD in 274 unrelated patients.

RESULTS

A mutation screen of the entire coding region of the CRYBB1gene uncovered eight sequence variations, including three missense changes, two intronic changes and three isocoding changes. A mutation screen of the entire coding region of the CRYBB2 gene uncovered three sequence variations, one isocoding change and two intronic changes.

CONCLUSIONS

Although variant alleles of the CRYBB1 and CRYBB2 genes were found, none are considered pathogenic.

LOC387715/HTRA1 polymorphisms, smoking and combined effects on exudative age-related macular degeneration in a Korean population

BACKGROUND

This study was to investigate the association of two single nucleotide polymorphisms (SNPs) in LOC387715 and HTRA1 with exudative age-related macular degeneration (AMD) in a Korean population and the gene-gene and gene-environment interactions in the development of AMD.

METHODS

We genotyped two SNPs that are located in the LOC387715 locus (rs10490924) and HTRA1 (rs11200638) in 137 cases of exudative AMD and 187 controls.

RESULTS

Both two SNPs were significantly associated with AMD (P = 0.0001). Homozygotes for the risk allele at LOC387715 and HTRA1 had a 3.80-fold and a 4.03-fold increased risk of exudative AMD, respectively, compared with homozygotes for the wild-type allele (P = 0.0001). The joint effects for complement factor H (CFH) Y402H and 10q26 variants indicated an increased risk of exudative AMD. The odds ratios (ORs) of AMD for individuals carrying one-, two- and three-copy risk alleles of CFH Y402H and LOC387715 were 1.08, 3.49 and 3.64, respectively. Also, the combination effect of the CFH Y402H risk alleles with HTRA1 risk alleles was dose-dependent. The interaction analysis between gene and environmental factors showed that among several factors, smoking synergistically increased the susceptibility of AMD for variants of LOC387715 and HTRA1, with OR 8.33 (3.05-22.74) and OR 8.50 (3.07-23.51), respectively.

CONCLUSION

This study demonstrated the significant association of the 10q26 SNPs (HTRA1 and LOC387715) in an AMD cohort from Korea and was consistent with previous studies from other populations. Also, a statistically significant interaction between genetic and environmental factors was found.

Role of ocular complement factor H in a murine model of choroidal neovascularization

The objective of this study was to explore the relationship between local (ie, ocular) complement factor H (CFH) and choroidal neovascularization (CNV) associated with wet age-related macular degeneration (AMD), a leading cause of irreversible blindness, in laser-treated C57BL/6 mice. Immunohistochemical and RT-PCR analysis of retinal pigmented epithelium (RPE)-choroid sclera revealed that the expression of CFH was down-regulated on day 1 with a dramatic increase on days 5 and 7 postlaser injury. Flat mount and Western blot analysis further revealed that membrane attack complex (MAC) expression was up-regulated on days 1 and 3 postlaser injury; however, MAC was down-regulated on days 5 and 7 postinjury but was still higher than in non-injured mice. Similar patterns for CFH and MAC were observed for RPE cells when serial paraffin sections of the laser spots were analyzed. Subretinal injection of siRNA directed against CFH resulted in a threefold suppression of CFH in the RPE and choroid without affecting either CFH levels in the liver or the functional activity of the alternative pathway in the peripheral blood. Ocular knock-down of CFH resulted in increased MAC deposition, which leads to the early onset as well as exacerbation of laser-induced CNV. In conclusion, our findings provide evidence that CFH present on RPE and choroid regulates local MAC formation that is critical for the development of laser-induced CNV.

C-reactive protein and CFH, ARMS2/HTRA1 gene variants are independently associated with risk of macular degeneration

PURPOSE

Genetic variants CFH and ARMS2/HTRA1 gene regions as well as high-sensitivity C-reactive protein (CRP) levels are related to age-related macular degeneration (AMD). We evaluated their independent and combined effects on risk of AMD, as well as their interactions.

DESIGN

Case-control study.

PARTICIPANTS

Subjects with AMD (n = 244) or no or minimal maculopathy (n = 209) in the Age Related Eye Disease Ancillary Study.

METHODS

Risk factors, genotypes, and biomarkers were assessed by questionnaire, direct measurement, and analyses of blood specimens. The independent and joint effects of serum CRP and CFH (rs1061170) and ARMS2/HTRA1 (rs10490924) genotypes were assessed using logistic regression analyses, adjusting for age, gender, education, smoking, body mass index, and vitamin/mineral supplementation.

MAIN OUTCOME MEASURES

We defined AMD as large drusen, geographic atrophy, or neovascular disease.

RESULTS

Higher CRP levels were associated with a higher risk of AMD, controlling for genotype and demographic and behavioral risk factors, with odds ratio 2.6 for levels of 3.0 mg/L and above versus below 1.0 mg/L (95% confidence interval, 1.01-6.7). Single nucleotide polymorphisms (SNPs) in both genes were also independently associated with risk of AMD, controlling for the level of CRP and other factors. Presence of both highest level of CRP together with risk genotypes for both SNPs, conferred the highest risk of AMD (OR 5.4, 95% CI 1.4-21.1).

CONCLUSIONS

High-sensitivity CRP and polymorphisms in the CFH and ARMS2/HTRA1 genes are independently associated with risk of AMD. Higher CRP level tends to confer a higher risk of AMD within most genotype groups.

ARMS2/HTRA1 and CFH polymorphisms are not associated with choroidal neovascularization in highly myopic eyes of the elderly Japanese population

PURPOSE

The purpose of this study was to investigate whether the genetic risk factors of age-related macular degeneration (AMD) are associated with the development of choroidal neovascularization (CNV) in highly myopic eyes of elderly Japanese.

METHODS

Highly myopic elderly Japanese patients with and without CNV were genotyped for three AMD-associated single nucleotide polymorphisms (SNPs), namely rs10490924 (A69S) of ARMS2, rs11200638 of HTRA1, and rs1061170 (Y402H) of complement factor H (CFH), with the TaqMan SNP assay. One hundred and eighty-three unrelated highly myopic (axial lengths>26.00 mm or refractive errors>-6.0 diopters) Japanese patients with CNV who were >or=50 years of age (mean age+/-standard deviation of 62.7+/-6.3 years) and 170 highly myopic patients without CNV who were >or=50 years old (62.3+/-7.1 years) were studied. The differences in the genotypic distributions for the three SNPs between the two groups were tested with the Trend chi2 test, and logistic regression analyses were performed for age and gender adjustment.

RESULTS

No significant difference was detected in the distribution of the three SNPs, rs10490924 (P>0.1), rs11200638 (P>0.1), and rs1061170 (P>0.5), between the two groups even after adjustments for age and gender differences.

CONCLUSION

The genetic risk factors of AMD related to these SNPs do not contribute significantly to the development of CNV in a highly myopic elderly Japanese population.

Recent statin use and 1-year incidence of exudative age-related macular degeneration

PURPOSE

To determine whether the statin class of drug is protective against exudative age-related macular degeneration (AMD).

DESIGN

Case-control study.

METHODS

The study was conducted at Kaiser Permanente Southern California. Cases was defined as incident cases, identified using outpatient diagnosis data. Controls were patients who had seen an ophthalmologist during the same year without the diagnosis of AMD. Drug use information was obtained using computerized databases.

RESULTS

In 2007, 86 635 patients older than 60 years underwent an eye examination. Cases comprised 719 patients newly diagnosed with exudative AMD. Controls (78 650) comprised everyone else who did not have any form of AMD. Use of statins was not associated with newly diagnosed exudative AMD.

CONCLUSIONS

Recent statin use is not associated with newly diagnosed exudative AMD. The current study had 80% statistical power to detect a protective effect of 0.70, but it cannot exclude a smaller effect.

The role of complement Factor H in age-related macular degeneration: a review

Factor H is a 155kDa sialic acid containing glycoprotein that plays an integral role in the regulation of the complement-mediated immune system that is involved in microbial defense, immune complex processing, and programmed cell death. These events take place primarily in fluid phase and on the cell surface and are particularly important in the context of distinguishing self from non-self. Activation of the complement system occurs within seconds and results in a proteolytic cascade eventually forming the membrane attack complex leading to cell lysis. Factor H protects host cells from injury resulting from unrestrained complement activation. Mutations and SNPs (single nucleotide polymorphisms) in Factor H have been implicated in a variety of human conditions including age-related macular degeneration (AMD), atypical hemolytic uremic syndrome, and membranoproliferative glomuleronephritis type II or dense deposit disease. It should not be surprising that these seemingly unrelated diseases involving mutations in Factor H may share common features. Because the immune process involves, in part, an inflammatory response and common or similar surface antigens, it is also not unexpected to observe features of inflammation, including deposition of bioactive complement fragments such as C3a and C5a, a cellular influx of immune related cells such as lymphocytes, and the potential for multiple organ involvement. We review recent developments in molecular genetics; SNPs, including Y402H; the three-dimensional structure; and mass spectroscopy of Factor H as it relates to the pathogenesis of eye disease. In addition, we discuss the concepts of molecular mimicry, sequestered or hidden antigens, and antigenic cross reactivity, and propose that AMD should not simply be considered to be an eye disease, but rather a systemic vascular disease where the eye has the ability to self regulate a local immune response. Identification of the initial event or inciting antigen has yet to be determined and will significantly advance the understanding of the pathogenesis of AMD.

The molecular genetic basis of age-related macular degeneration: an overview

Age-related macular degeneration (AMD) is a complex disorder of the eye and the third leading cause of blindness worldwide. With a multifactorial etiology, AMD results in progressive loss of central vision affecting the macular region of the eye in elderly. While the prevalence is relatively higher in the Caucasian populations, it has gradually become a major public health issue among the non-Caucasian populations (including Indians) as well due to senescence, rapidly changing demographics and life-style factors. Recent genome-wide association studies (GWAS) on large case-control cohorts have helped in mapping genes in the complement cascade that are involved in the regulation of innate immunity with AMD susceptibility. Genes involved with mitochondrial oxidative stress and extracellular matrix regulation also play a role in AMD pathogenesis. Majority of the associations observed in complement (CFH, CFB, C2 and C3) and other (ARMS2 and HTRA1) genes have been replicated in diverse populations worldwide. Gene-gene (CFH with ARMS2 and HTRA1) interactions and correlations with environmental traits (smoking and body mass index) have been established as significant covariates in AMD pathology. In this review, we have provided an overview on the underlying molecular genetic mechanisms in AMD worldwide and highlight the AMD-associated-candidate genes and their potential role in disease pathogenesis.

Retinal sphingolipids and their very-long-chain fatty acid-containing species

PURPOSE

Recent evidence suggests that ceramide metabolism plays an important role in retinal photoreceptor cell survival and apoptosis. The purpose of this study was to characterize sphingolipids in the retina with special emphasis on the very-long-chain-containing saturated (VLC-FA) and polyunsaturated (VLC-PUFA) fatty acid-containing species. The VLC-FAs and VLC-PUFAs are synthesized by the ELOVL4 protein, which is involved in human Stargardt's macular dystrophy type 3 (STGD3).

METHODS

Total lipids were extracted from retina and other tissues, and different sphingolipid classes were isolated and purified using various combinations of liquid- and solid-phase separation. Purified sphingolipids were analyzed by high-performance thin layer chromatography (HPTLC), gas chromatography (GC), and GC-MS (GC-mass spectrometry).

RESULTS

Nonsialylated sphingolipids (NSLs) comprised approximately 3.5% of total retinal lipids of which 70% was sphingomyelin. Ceramide and glycosylceramides (GCs) constituted<or=1% of total retinal lipids. Gangliosides (GGs), on the other hand, comprised approximately 3.0% of total retinal lipids. Fatty acid analysis of retinal NSLs indicated an abundance of saturated fatty acids, with the presence of VLC-FAs but not of VLC-PUFAs beyond 24 carbons. However, GG had significant levels of unsaturated, polyunsaturated, and VLC-PUFAs. Retinal rod outer segments (ROS) contained approximately 1% each of NSL and GG, and their fatty acid profile was not very different from whole retinal NSL and GG, respectively.

CONCLUSIONS

Retina has a total of 6% to 7% fatty acids that are N-linked to a sphingosine, which would be 11 to 13 mole % in comparison to phospholipids. The presence of VLC-FAs and VLC-PUFAs in retinal sphingolipids indicates that they may play role in ELOVL4-mediated Stargardt 3.

Genome-wide association study of advanced age-related macular degeneration identifies a role of the hepatic lipase gene (LIPC)

Advanced age-related macular degeneration (AMD) is the leading cause of late onset blindness. We present results of a genome-wide association study of 979 advanced AMD cases and 1,709 controls using the Affymetrix 6.0 platform with replication in seven additional cohorts (totaling 5,789 unrelated cases and 4,234 unrelated controls). We also present a comprehensive analysis of copy-number variations and polymorphisms for AMD. Our discovery data implicated the association between AMD and a variant in the hepatic lipase gene (LIPC) in the high-density lipoprotein cholesterol (HDL) pathway (discovery P = 4.53e-05 for rs493258). Our LIPC association was strongest for a functional promoter variant, rs10468017, (P = 1.34e-08), that influences LIPC expression and serum HDL levels with a protective effect of the minor T allele (HDL increasing) for advanced wet and dry AMD. The association we found with LIPC was corroborated by the Michigan/Penn/Mayo genome-wide association study; the locus near the tissue inhibitor of metalloproteinase 3 was corroborated by our replication cohort for rs9621532 with P = 3.71e-09. We observed weaker associations with other HDL loci (ABCA1, P = 9.73e-04; cholesterylester transfer protein, P = 1.41e-03; FADS1-3, P = 2.69e-02). Based on a lack of consistent association between HDL increasing alleles and AMD risk, the LIPC association may not be the result of an effect on HDL levels, but it could represent a pleiotropic effect of the same functional component. Results implicate different biologic pathways than previously reported and provide new avenues for prevention and treatment of AMD.

Complement, age-related macular degeneration and a vision of the future

Age-related macular degeneration (AMD) is one of the most well-characterized late-onset, complex trait diseases. Remarkable advances in our understanding of the genetic and biological foundations of this disease were derived from a recent convergence of scientific and clinical data. Importantly, the more recent identification of AMD-associated variations in a number of complement pathway genes has provided strong support for earlier, paradigm-shifting studies that suggested that aberrant function of the complement system plays a key role in disease etiology. Collectively, this wealth of information has provided an impetus for the development of powerful tools to accurately diagnose disease risk and progression and complement-based therapeutics that will ultimately delay or prevent AMD. Indeed, we are poised to witness a new era of a personalized approach toward the assessment, management, and treatment of this debilitating, chronic disease.

The molecular basis of human retinal and vitreoretinal diseases

During the last two to three decades, a large body of work has revealed the molecular basis of many human disorders, including retinal and vitreoretinal degenerations and dysfunctions. Although belonging to the group of orphan diseases, they affect probably more than two million people worldwide. Most excitingly, treatment of a particular form of congenital retinal degeneration is now possible. A major advantage for treatment is the unique structure and accessibility of the eye and its different components, including the vitreous and retina. Knowledge of the many different eye diseases affecting retinal structure and function (night and colour blindness, retinitis pigmentosa, cone and cone rod dystrophies, photoreceptor dysfunctions, as well as vitreoretinal traits) is critical for future therapeutic development. We have attempted to present a comprehensive picture of these disorders, including biological, clinical, genetic and molecular information. The structural organization of the review leads the reader through non-syndromic and syndromic forms of (i) rod dominated diseases, (ii) cone dominated diseases, (iii) generalized retinal degenerations and (iv) vitreoretinal disorders, caused by mutations in more than 165 genes. Clinical variability and genetic heterogeneity have an important impact on genetic testing and counselling of affected families. As phenotypes do not always correlate with the respective genotypes, it is of utmost importance that clinicians, geneticists, counsellors, diagnostic laboratories and basic researchers understand the relationships between phenotypic manifestations and specific genes, as well as mutations and pathophysiologic mechanisms. We discuss future perspectives.

Protective effect of paraoxonase 1 gene variant Gln192Arg in age-related macular degeneration

PURPOSE

Age-related macular degeneration (AMD) is the leading cause of blindness among older adults, in which oxidative damage may play a pivotal role. Paraoxonase 1 (PON1) protects against oxidative damage and has been evaluated for its involvement in aging diseases including AMD. This study investigated whether PON1 gene polymorphisms associate with AMD.

DESIGN

Case-control association study.

METHODS

We studied 1037 individuals with AMD subcategorized using AREDS criteria and 370 control subjects without retinal disease. Participants were primarily Caucasian of European descent. All exons of PON1 were evaluated by single-strand conformation polymorphism and direct sequence analysis.

RESULTS

Six missense changes (Leu55Met, Met127Arg, His155Arg, Gln192Arg, Gln192Glu, Ala252Gly) were identified in PON1. We observed a weak association of Leu55Met with an increased risk of wet AMD (P = .02), but not with dry AMD or when combining all patient categories. A significantly higher allele frequency for Gln192Arg was detected in controls than in the combined AMD patient population (P < .0001), and when category 2, 3, and 4 patients were separately considered (P = .004, P = .002, and P < .0001, respectively). For category 4 AMD, the Arg192 allele was significantly less prevalent in the wet form (P < .0001), but not in the dry form (P = .377).

CONCLUSION

We report a weak association of PON1 Leu55Met with an increased risk of wet AMD, replicating previous reports. Our findings indicate a protective role for Gln192Arg, particularly for patients with the wet form. Gln192Glu warrants consideration, as this variant alters the same amino acid as Gln192Arg and was identified only in category 4 AMD patients. We believe that Met127Arg, His155Arg, and Ala252Gly play minor roles in AMD susceptibility because of their limited frequency and/or location within the PON1 gene. The functional and biological mechanism by which Gln192Arg is acting to decrease AMD susceptibility remains to be determined.

Incorporating prior knowledge to facilitate discoveries in a genome-wide association study on age-related macular degeneration

Background

Substantial genotyping data produced by current high-throughput technologies have brought opportunities and difficulties. With the number of single-nucleotide polymorphisms (SNPs) going into millions comes the harsh challenge of multiple-testing adjustment. However, even with the false discovery rate (FDR) control approach, a genome-wide association study (GWAS) may still fall short of discovering any true positive gene, particularly when it has a relatively small sample size.

Findings

To counteract such a harsh multiple-testing penalty, in this report, we incorporate findings from previous linkage and association studies to re-analyze a GWAS on age-related macular degeneration. While previous Bonferroni correction and the traditional FDR approach detected only one significant SNP (rs380390), here we have been able to detect seven significant SNPs with an easy-to-implement prioritized subset analysis (PSA) with the overall FDR controlled at 0.05. These include SNPs within three genes: CFH, CFHR4, and SGCD.

Conclusions

Based on the success of this example, we advocate using the simple method of PSA to facilitate discoveries in future GWASs.

New era for personalized medicine: the diagnosis and management of age-related macular degeneration

It can be argued that age-related macular degeneration is one of the best characterized complex trait diseases. Extensive information related to genetic and environmental risk factors exists, and a number of different biological pathways are strongly implicated in its aetiology. Along with recent improvements in high throughput and relatively inexpensive genetic technologies, we are now in a position to consider developing a presymptomatic, personalized approach towards the assessment, management and treatment of this disease. We explore the applicability and challenges of this approach if it is to become commonplace for guiding treatment decisions for individuals with pre-existing disease or for those at high risk of developing it.

Genetics and molecular pathology of Stargardt-like macular degeneration

Stargardt-like macular degeneration (STGD3) is an early onset, autosomal dominant macular degeneration. STGD3 is characterized by a progressive pathology, the loss of central vision, atrophy of the retinal pigment epithelium, and accumulation of lipofuscin, clinical features that are also characteristic of age-related macular degeneration. The onset of clinical symptoms in STGD3, however, is typically observed within the second or third decade of life (i.e., starting in the teenage years). The clinical profile at any given age among STGD3 patients can be variable suggesting that, although STGD3 is a single gene defect, other genetic or environmental factors may play a role in moderating the final disease phenotype. Genetic studies localized the STGD3 disease locus to a small region on the short arm of human chromosome 6, and application of a positional candidate gene approach identified protein truncating mutations in the elongation of very long chain fatty acids-4 gene (ELOVL4) in patients with this disease. The ELOVL4 gene encodes a protein homologous to the ELO group of proteins that participate in fatty acid elongation in yeast. Pathogenic mutations found in the ELOVL4 gene result in altered trafficking of the protein and behave with a dominant negative effect. Mice carrying an Elovl4 mutation developed photoreceptor degeneration and depletion of very long chain fatty acids (VLCFA). ELOVL4 protein participates in the synthesis of fatty acids with chain length longer than 26 carbons. Studies on ELOVL4 indicate that VLCFA may be necessary for normal function of the retina, and the defective protein trafficking and/or altered VLCFA elongation underlies the pathology associated with STGD3. Determining the role of VLCFA in the retina and discerning the implications of abnormal trafficking of mutant ELOVL4 and depleted VLCFA content in the pathology of STGD3 will provide valuable insight in understanding the retinal structure, function, and pathology underlying STGD3 and may lead to a better understanding of the process of macular disease in general.

Integration of ER stress, oxidative stress and the inflammatory response in health and disease

There has been much effort to define the molecular basis by which pathophysiological stimuli initiate and/or propagate the inflammatory response. Recent research endeavors on stress response from a cellular organelle called the endoplasmic reticulum (ER) shed new light on the understating of the molecular basis of the inflammatory response and its interaction with other intracellular stress signaling pathways. As a protein folding compartment and dynamic calcium store, the ER plays major roles in sensing cellular stress and mediating highly-specific signaling pathways termed Unfolded Protein Response (UPR). The UPR signaling emanating from the ER has been identified as one of the avenues leading to the inflammatory response. The integration of ER stress, oxidative stress, and the inflammatory response is critical to the pathogenesis of a variety of diseases. In this brief review, we discuss some representative evidence for the integration of ER stress, oxidative stress, and inflammation in health and disease.

An ecological correlation study of late age-related macular degeneration and the complement factor H Y402H polymorphism

PURPOSE

To investigate whether variation in the distribution of the risk allele frequency of the Y402H single-nucleotide polymorphism (SNP) across various ethnicities and geographic regions reflects differences in the prevalence of late age-related macular degeneration (AMD) in those ethnicities.

METHODS

Published data were obtained via a systematic search. Study samples were grouped into clusters by ethnicity and geographic location and the Spearman correlation coefficient of the prevalence of late AMD and risk allele frequencies was calculated across clusters.

RESULTS

Across all ethnicities, AMD prevalence was seen to increase with age. Populations of European descent had both higher risk allele frequencies and prevalence of late AMD than did Japanese, Chinese, and Hispanic descendants. Results for African descendants were anomalous: although allele frequency was similar to that in European populations, the age-specific prevalence of late AMD was considerably lower. The correlation coefficient for the association between allele frequency and AMD prevalence was 0.40 (95% confidence interval [CI] = -0.36 to 0.84, P = 0.28) in all populations combined and 0.71 (95% CI = 0.02-0.94, P = 0.04) when people of African descent were excluded.

CONCLUSIONS

Evidence was found at the population level to support a positive association between the Y204H risk allele and the prevalence of AMD after exclusion of studies undertaken on persons of African ancestry. Data in African, Middle Eastern, and South American populations are needed to provide a better understanding of the association of late AMD genetic risk across ethnicities.

Association of c3 gene polymorphisms with neovascular age-related macular degeneration in a chinese population

PURPOSE

The purpose of this study was to determine whether the genetic polymorphisms of complement factor 3 (C3) are associated with neovascular age-related macular degeneration (AMD) in the Chinese population.

METHODS

A total of 123 unrelated Chinese Han patients with neovascular AMD and 130 control subjects were recruited. Their six single-nucleotide polymorphisms (SNPs) in the C3 gene, one in the complement factor H (CFH) gene and two in the complement factor B (CFB) gene were characterized. Their genotypes, allele frequencies, and odds ratios were analyzed.

RESULTS

The G allele of the C3 IVS2 rs2250656, but not other tested C3 SNPs of rs2230205, rs10411506, rs2230199, rs339392, and rs163913, was significantly associated with a reduced risk for AMD in the Chinese population (OR 0.605, 95% CI 0.39-0.93, p = 0.023), even after adjusting for age, gender, smoking status, CFH rs1061170, CFB rs4151667, and CFB rs641153 allele status (OR 0.58, 95% CI 0.35-0.96, p = 0.033). However, the C3 haplotype of A-A-C-A-T-T was identified as a statistically significant risk factor for neovascular AMD (OR 1.41, 95% CI 1.02-1.94). Furthermore, the C allele of the CFH rs1061170, but not the CFB rs4151667 and rs641153, was significnatly associated with increased risk for AMD (OR 3.09, 95% CI 1.55-6.15, p < 0.001).

CONCLUSION

The G allele of C3 IVS2 rs2250656 may be a significantly protective factor for neovascular AMD in the Chinese population. This, together with low MAF of C3 R102G, may be partially responsible for the low prevalence of AMD in the Chinese population.

Long-term safety and function of RPE from human embryonic stem cells in preclinical models of macular degeneration

Assessments of safety and efficacy are crucial before human ESC (hESC) therapies can move into the clinic. Two important early potential hESC applications are the use of retinal pigment epithelium (RPE) for the treatment of age-related macular degeneration and Stargardt disease, an untreatable form of macular dystrophy that leads to early-onset blindness. Here we show long-term functional rescue using hESC-derived RPE in both the RCS rat and Elov14 mouse, which are animal models of retinal degeneration and Stargardt, respectively. Good Manufacturing Practice-compliant hESC-RPE survived subretinal transplantation in RCS rats for prolonged periods (>220 days). The cells sustained visual function and photoreceptor integrity in a dose-dependent fashion without teratoma formation or untoward pathological reactions. Near-normal functional measurements were recorded at >60 days survival in RCS rats. To further address safety concerns, a Good Laboratory Practice-compliant study was carried out in the NIH III immune-deficient mouse model. Long-term data (spanning the life of the animals) showed no gross or microscopic evidence of teratoma/tumor formation after subretinal hESC-RPE transplantation. These results suggest that hESCs could serve as a potentially safe and inexhaustible source of RPE for the efficacious treatment of a range of retinal degenerative diseases.

Detecting Genes and Gene-gene Interactions for Age-related Macular Degeneration with a Forest-based Approach

Age-related macular degeneration (AMD) is a leading cause of vision loss in the elderly. Genetic mechanisms underlying AMD are complex. Understanding the etiology of AMD is important because of the significant health and social concerns. In this paper, we describe a forest-based approach to systematically identifying multiple genes, gene-gene interactions and gene-environment interactions underlying complex diseases in genomewide case-control studies and the application of this approach to a published data set on AMD. Our analysis not only confirmed two known haplotypes, ACTCCG (on chromosome 1 with a p-value of 1.98e-6) and TCTGGACGACA (on chromosome 7 with a p-value of 9.81e-3), but also revealed two novel haplotypes, GATAGT (on chromosome 5 with a p-value of 3.46e-3) and TCTTACGTAGA (on chromosome 12 with a p-value of 3.16e-2). Thus, the significance of this work is twofold. First, we propose a powerful and robust method to identify high-risk haplotypes and their interactions; second, we reveal potential genetic variants associated with AMD.

Genetic profile for five common variants associated with age-related macular degeneration in densely affected families: a novel analytic approach

About 40% of the genetic variance of age-related macular degeneration (AMD) can be explained by a common variation at five common single-nucleotide polymorphisms (SNPs). We evaluated the degree to which these known variants explain the clustering of AMD in a group of densely affected families. We sought to determine whether the actual number of risk alleles at the five variants in densely affected families matched the expected number. Using data from 322 families with AMD, we used a simulation strategy to generate comparison groups of families and determined whether their genetic profile at the known AMD risk loci differed from the observed genetic profile, given the density of disease observed. Overall, the genotypic loads for the five SNPs in the families did not deviate significantly from the genotypic loads predicted by the simulation. However, for a subset of densely affected families, the mean genotypic load in the families was significantly lower than the expected load determined from the simulation. Given that these densely affected families may harbor rare, more penetrant variants for AMD, linkage analyses and resequencing targeting these families may be an effective approach to finding additional implicated genes.

CFH, C3 and ARMS2 are significant risk loci for susceptibility but not for disease progression of geographic atrophy due to AMD

Background

Age-related macular degeneration (AMD) is a prevalent cause of blindness in Western societies. Variants in the genes encoding complement factor H (CFH), complement component 3 (C3) and age-related maculopathy susceptibility 2 (ARMS2) have repeatedly been shown to confer significant risks for AMD; however, their role in disease progression and thus their potential relevance for interventional therapeutic approaches remains unknown.

Methodology/Principal Findings

Here, we analyzed association between variants in CFH, C3 and ARMS2 and disease progression of geographic atrophy (GA) due to AMD. A quantitative phenotype of disease progression was computed based on longitudinal observations by fundus autofluorescence imaging. In a subset of 99 cases with pure bilateral GA, variants in CFH (Y402H), C3 (R102G), and ARMS2 (A69S) are associated with disease (P = 1.6×10⁻⁹, 3.2×10⁻³, and P = 2.6×10⁻¹², respectively) when compared to 612 unrelated healthy control individuals. In cases, median progression rate of GA over a mean follow-up period of 3.0 years was 1.61 mm²/year with high concordance between fellow eyes. No association between the progression rate and any of the genetic risk variants at the three loci was observed (P>0.13).

Conclusions/Significance

This study confirms that variants at CFH, C3, and ARMS2 confer significant risks for GA due to AMD. In contrast, our data indicate no association of these variants with disease progression which may have important implications for future treatment strategies. Other, as yet unknown susceptibilities may influence disease progression.

rs5888 variant of SCARB1 gene is a possible susceptibility factor for age-related macular degeneration

Major genetic factors for age-related macular degeneration (AMD) have recently been identified as susceptibility risk factors, including variants in the CFH gene and the ARMS2 LOC387715/HTRA1locus. Our purpose was to perform a case-control study in two populations among individuals who did not carry risk variants for CFHY402H and LOC387715 A69S (ARMS2), called “study” individuals, in order to identify new genetic risk factors. Based on a candidate gene approach, we analyzed SNP rs5888 of the SCARB1 gene, coding for SRBI, which is involved in the lipid and lutein pathways. This study was conducted in a French series of 1241 AMD patients and 297 controls, and in a North American series of 1257 patients with advanced AMD and 1732 controls. Among these individuals, we identified 61 French patients, 77 French controls, 85 North American patients and 338 North American controls who did not carry the CFH nor ARMS2 polymorphisms. An association between AMD and the SCARB1 gene was seen among the study subjects. The genotypic distribution of the rs5888 polymorphism was significantly different between cases and controls in the French population (p<0.006). Heterozygosity at the rs5888 SNP increased risk of AMD compared to the CC genotypes in the French study population (odds ratio (OR) = 3.5, CI95%: 1.4–8.9, p<0.01) and after pooling the 2 populations (OR = 2.9, 95% CI: 1.6–5.3, p<0.002). Subgroup analysis in exudative forms of AMD revealed a pooled OR of 3.6 for individuals heterozygous for rs5888 (95% CI: 1.7–7.6, p<0.0015). These results suggest the possible contribution of SCARB1, a new genetic factor in AMD, and implicate a role for cholesterol and antioxidant micronutrient (lutein and vitamin E) metabolism in AMD.

Convergence of linkage, gene expression and association data demonstrates the influence of the RAR-related orphan receptor alpha (RORA) gene on neovascular AMD: a systems biology based approach

To identify novel genes and pathways associated with AMD, we performed microarray gene expression and linkage analysis which implicated the candidate gene, retinoic acid receptor-related orphan receptor alpha (RORA, 15q). Subsequent genotyping of 159 RORA single nucleotide polymorphisms (SNPs) in a family-based cohort, followed by replication in an unrelated case-control cohort, demonstrated that SNPs and haplotypes located in intron 1 were significantly associated with neovascular AMD risk in both cohorts. This is the first report demonstrating a possible role for RORA, a receptor for cholesterol, in the pathophysiology of AMD. Moreover, we found a significant interaction between RORA and the ARMS2/HTRA1 locus suggesting a novel pathway underlying AMD pathophysiology.

Risk factors for age-related maculopathy

Age-related maculopathy (ARM) is the leading cause of blindness in the elderly. Although beneficial therapeutic strategies have recently begun to emerge, much remains unclear regarding the etiopathogenesis of this disorder. Epidemiologic studies have enhanced our understanding of ARM, but the data, often conflicting, has led to difficulties with drawing firm conclusions with respect to risk for this condition. As a consequence, we saw a need to assimilate the published findings with respect to risk factors for ARM, through a review of the literature appraising results from published cross-sectional studies, prospective cohort studies, case series, and case control studies investigating risk for this condition. Our review shows that, to date, and across a spectrum of epidemiologic study designs, only age, cigarette smoking, and family history of ARM have been consistently demonstrated to represent risk for this condition. In addition, genetic studies have recently implicated many genes in the pathogenesis of age-related maculopathy, including Complement Factor H, PLEKHA 1, and LOC387715/HTRA1, demonstrating that environmental and genetic factors are important for the development of ARM suggesting that gene-environment interaction plays an important role in the pathogenesis of this condition.

Choroideremia: new findings from ocular pathology and review of recent literature

Histopathology of young individuals affected by choroideremia is rarely available to allow correlation with the clinical presentation. A 30-year-old man with choroideremia died in a motor vehicle accident and one eye was subjected to histopathological examination. Immunoblot analysis of protein derived from white blood cells of a living brother, also affected with choroideremia, confirmed the absence of Rab escort protein-1, the normal CHM gene product. Direct sequencing of the coding region and adjacent splice sites of the CHM gene was undertaken on genomic DNA from the living brother and revealed a transition mutation, C to T, in exon 6 (R253X) which resulted in a stop codon and was predicted to truncate the protein product. Histopathological examination of the eye of the deceased brother showed relative independent degeneration of choriocapillaris, retinal pigment epithelium, and retina, similar to observations in the mouse model of choroideremia. In addition, mild T-lymphocytic infiltration was found within the choroid. The ophthalmic features and the pathology of choroideremia are discussed in light of new findings in the current case.

Analyses of single nucleotide polymorphisms and haplotype linkage of LOC387715 and the HTRA1 gene in exudative age-related macular degeneration in a Chinese cohort

PURPOSE

To investigate the effect of single nucleotide polymorphisms (SNPs) and haplotypes in the genes encoding age-related maculopathy susceptibility 2 (LOC387715/ARMS2) and high-temperature requirement A-1 (HTRA1) in a case-control study in a Chinese cohort of individuals with exudative age-related macular degeneration (AMD).

METHODS

We genotyped 2 SNPs, namely, LOC387715 rs10490924 and HTRA1 rs11200638, in 159 exudative AMD patients and 140 age- and sex-matched control subjects. All the four possible haplotypes of these two SNPs were detected. Comparisons of the risk genotypes and risk or protective haplotypes across multiple populations were performed.

RESULTS

Allelic or genotype association tests yielded significant results at P < 0.001. We observed that homozygous risk genotypes (TT in rs10490924 and AA in rs11200638) were more strongly associated with AMD than the heterozygous genotypes (GT in rs10490924 and geographic atrophy in rs11200638) for both SNPs. Comparisons of the odds ratios for genotypes revealed that there is ethnic disparity in AMD prevalence, even within the Chinese population. The haplotype TA, comprising both the SNPs, was identified as an at-risk factor and was significantly associated with AMD, whereas the protective haplotype GG was significantly overrepresented in the controls (P < 0.001). The frequency of the TA haplotype was relatively higher in the Chinese population than in the white population in both groups, whereas the frequency of the GG haplotype was relatively lower in the Chinese controls than in the white and Japanese controls.

CONCLUSION

Both SNPs are significantly associated with exudative AMD in the Chinese cohort and seem to contribute equally to the disease status. A higher frequency of homozygous risk genotypes and risk haplotype and a lower frequency of protective haplotype in the Chinese may be the cause of higher prevalence of exudative AMD in the Chinese than in the whites.

Vitreomacular adhesion in active and end-stage age-related macular degeneration

PURPOSE

To evaluate vitreomacular relations in different stages of age-related macular degeneration (AMD) without the influence of genetics and environmental factors.

DESIGN

Retrospective, observational case series.

METHODS

This was a multicenter study consisting of 29 previously untreated subjects with active exudative (wet) AMD in one eye and active nonexudative (dry) AMD in the fellow eye who were compared with 10 previously untreated subjects with end-stage geographic atrophy in one eye and an end-stage fibrotic (disciform) scar in the fellow eye. All subjects were studied with ultrasonography to identify the presence of posterior vitreous detachment (PVD) and by optical coherence tomography to detect vitreomacular adhesion (VMA).

RESULTS

The incidence of PVD in eyes with nonexudative AMD was 20 (69%) of 29, compared with 6 (21%) of 29 with active exudative AMD (P = .002). VMA was present in 11 (38%) of 29 of eyes with exudative AMD and in only 3 (10%) of 29 eyes with nonexudative AMD (P = .008). The incidence of PVD in geographic atrophy was 7 (70%) of 10, compared with 4 (40%) of 10 with disciform scar (P = .44). VMA was present in 2 (20%) of 10 eyes with disciform scars and in 0 (0%) of 10 eyes with geographic atrophy (P = .48).

CONCLUSIONS

PVD may protect against exudative AMD, whereas VMA may promote exudative AMD. This phenomenon is not evident in end-stage disease because of an increased incidence of PVD and a decreased incidence of VMA in eyes with disciform scars. Genetic and environmental factors do not seem to influence these observations.

Nutritional AMD treatment phase I (NAT-1): feasibility of oral DHA supplementation in age-related macular degeneration

PURPOSE

To create a pilot study in order to evaluate the feasibility of a prospective case-control study of oral supplementation with fish oil (docosahexaenoic acid [DHA]; eicosapentaenoic acid [EPA]) in a population with age-related macular degeneration (AMD).

METHODS

A homogeneous group of 38 patients with drusenoid pigment epithelial detachment in one eye (PED) without choroidal new vessels (CNV) was selected. A complete ophthalmologic examination, and a complete profile of fatty acids in serum (S) and in red blood cell membranes (RBCM), were recorded at day 0 and month 6. In group 1, 22 patients were orally supplemented with EPA (720 mg/day) and DHA (480 mg/day) during 6 months. In group 2, 16 patients were followed as controls. Nutritional recommendations on fish consumption were given to both groups.

RESULTS

In group 1, after 6 months supplementation we observed a significant blood enrichment in EPA (EPA-S: 2.20 vs 0.79, p<0.0001 and EPA-RBCM: 2.24 vs 0.85, p<0.0001) and in DHA (DHA-S: 2.47 vs 1.56, p<0.0001 and DHA-RBCM: 6.47 vs 4.67, p<0.0001). No change was observed in group 2 despite nutritional recommendations. In this short followup, no evolution to CNV was noted in either of the two groups. Neither side effects nor dropouts were observed in either of the groups.

DISCUSSION

This study supports the feasibility of a long-term double-masked prospective case-control study in an AMD population in order to evaluate a potential benefit from oral supplementation with DHA.

Dietary compound score and risk of age-related macular degeneration in the age-related eye disease study

PURPOSE

Because foods provide many nutrients that may interact to modify risk for multifactorial diseases such as age-related macular degeneration (AMD), we sought to develop a composite scoring system to summarize the combined effect of multiple dietary nutrients on AMD risk. This has not been done previously.

DESIGN

Cross-sectional study.

PARTICIPANTS

From the 4003 participants in the Age-Related Eye Disease Study (AREDS), there were 7,934 eyes included in this study.

METHODS

Considering dietary intakes of vitamins C and E, zinc, lutein/zeaxanthin, docosahexaenoic acid, eicosapentaenoic acid, and low-dietary glycemic index (dGI) from AREDS baseline information, we assigned each nutrient a percentile rank score then summed them into a compound score for each participant. Using eye as the unit of analysis, we evaluated the association between the compound score and risk of prevalent AMD. Validation, fitness, and performance of the model were evaluated using bootstrapping techniques, adjusted quasi-likelihood under the independence model criterion, and the c-index, respectively.

MAIN OUTCOME MEASURES

Stereoscopic fundus photographs of the macula were taken and graded at baseline using the AREDS protocol and AMD Classification System.

RESULTS

Our results showed that higher compound scores were associated with lower risk for early AMD, indicated by drusen, and advanced AMD. Validation analyses indicated that these relationships are robust (the average 50-time bootstrapping per quartile odds ratios = 0.727, 0.827, and 0.753, respectively, for drusen, and 0.616, 0.536, and 0.572, respectively, for advanced AMD). Model selection analyses suggested that the compound score should be included, but that measures of dietary beta-carotene should not be included.

CONCLUSIONS

We found that consuming diets that provide low dGI and higher intakes of these nutrients were associated with the greatest reduction in risk for prevalent drusen and advanced AMD, whereas dietary beta-carotene did not affect these relationships. These findings warrant further prospective studies.

FINANCIAL DISCLOSURE(S)

Proprietary or commercial disclosure may be found after the references.

Prediction model for prevalence and incidence of advanced age-related macular degeneration based on genetic, demographic, and environmental variables

PURPOSE

The joint effects of genetic, ocular, and environmental variables were evaluated and predictive models for prevalence and incidence of AMD were assessed.

METHODS

Participants in the multicenter Age-Related Eye Disease Study (AREDS) were included in a prospective evaluation of 1446 individuals, of which 279 progressed to advanced AMD (geographic atrophy or neovascular disease) and 1167 did not progress during 6.3 years of follow-up. For prevalent AMD, 509 advanced cases were compared with 222 controls. Covariates for the incidence analysis included age, sex, education, smoking, body mass index (BMI), baseline AMD grade, and the AREDS vitamin-mineral treatment assignment. DNA specimens were evaluated for six variants in five genes related to AMD. Unconditional logistic regression analyses were performed for prevalent and incident advanced AMD. An algorithm was developed and receiver operating characteristic curves and C statistics were calculated to assess the predictive ability of risk scores to discriminate progressors from nonprogressors.

RESULTS

All genetic polymorphisms were independently related to prevalence of advanced AMD, controlling for genetic factors, smoking, BMI, and AREDS treatment. Multivariate odds ratios (ORs) were 3.5 (95% confidence interval [CI], 1.7-7.1) for CFH Y402H; 3.7 (95% CI, 1.6-8.4) for CFH rs1410996; 25.4 (95% CI, 8.6-75.1) for LOC387715 A69S (ARMS2); 0.3 (95% CI, 0.1-0.7) for C2 E318D; 0.3 (95% CI, 0.1-0.5) for CFB; and 3.6 (95% CI, 1.4-9.4) for C3 R102G, comparing the homozygous risk/protective genotypes to the referent genotypes. For incident AMD, all these variants except CFB were significantly related to progression to advanced AMD, after controlling for baseline AMD grade and other factors, with ORs from 1.8 to 4.0 for presence of two risk alleles and 0.4 for the protective allele. An interaction was seen between CFH402H and treatment, after controlling for all genotypes. Smoking was independently related to AMD, with a multiplicative joint effect with genotype on AMD risk. The C statistic for the full model with all variables was 0.831 for progression to advanced AMD.

CONCLUSIONS

Factors reflective of nature and nurture are independently related to prevalence and incidence of advanced AMD, with excellent predictive power.

Hypoxia/reoxygenation induces CTGF and PAI-1 in cultured human retinal pigment epithelium cells

Early age-related macular degeneration (AMD) is characterized by thickening of Bruch's membrane due to the accumulation of extracellular matrix (ECM). This finding could be related to hypoxia of the retinal pigment epithelium (RPE). In the present study, we investigated the effects of hypoxia and reoxygenation on the expression of connective tissue growth factor (CTGF), plasminogen activator inhibitor-1 (PAI-1), collagen type IV (Col IV) and fibronectin (Fn) in cultured human RPE cells. Cultured human RPE cells were kept for 12-36h under hypoxic conditions (1% O(2)). Reoxygenation was conducted for 24h. Hypoxia-mediated CTGF and PAI-1 expression were analyzed by using immunohistochemistry, Northern and Western blot analysis. Actinomycin D was added to examine whether hypoxia induces the transcription of CTGF and PAI-1 mRNA. Furthermore, cells were transfected with siRNA against hypoxia-inducible factor-1alpha (HIF-1alpha) and kept under hypoxic conditions. The effects of antioxidants on hypoxia/reoxygenation-mediated CTGF and PAI-1 expression were tested by real-time PCR analysis. Production of Col IV and Fn were investigated by real-time PCR and Western blot analysis. Both hypoxia and hypoxia/reoxygenation increased the expression of CTGF, PAI-1, Col IV and Fn. Actinomycin D prevented the new transcription of CTGF and PAI-1 mRNA by hypoxia. Using siRNA against HIF-1alpha, the hypoxia-mediated increase of CTGF and PAI-1 was inhibited. Antioxidants attenuated the reoxygenation-mediated increase of CTGF and PAI-1. The process of hypoxia/reoxygenation in the RPE may lead to an increase of ECM in the RPE and thus may contribute to the accumulation of ECM in Bruch's membrane.

Retinal vascular caliber and age-related macular degeneration: the Singapore Malay Eye Study

PURPOSE

To investigate the relationship between retinal vascular caliber and age-related macular degeneration (AMD).

DESIGN

Population-based cross-sectional study.

METHODS

Three thousand two hundred and eighty (78.7% response rate) Malay Singaporeans aged 40 to 80 years residing in 15 districts of Singapore underwent retinal photography. Retinal vessel caliber was measured from retinal photographs using a validated computer-based technique. AMD was assessed following a modified Wisconsin Age-Related Maculopathy Grading System.

RESULTS

Retinal data were available from 3,265 subjects (99.5% of 3,280) for this study. Early and late AMD prevalence were 4.9% (n = 160) and 0.7% (n = 23) of the population, respectively, or in 205 (3.1%) and 30 (0.5%) eyes examined, respectively. After controlling for age and arteriolar caliber, wider venular caliber was associated with higher prevalence of early AMD (odds ratio [OR] per one standard deviation [SD] increment in venular caliber, 1.53; 95% confidence interval [CI], 1.13 to 2.09). This association remained significant after further adjustment for gender, smoking, hypertension, diabetes, and body mass index (OR per one SD, 1.52; 95% CI, 1.11 to 2.09). There was no significant association between retinal arteriolar caliber and early AMD, or between arteriolar or venular caliber and late AMD.

CONCLUSIONS

Wider venular caliber was associated independently with early AMD. This finding may suggest that pathogenic processes linking to wider venular caliber be shared by early AMD and common cardiovascular risk factors such as inflammation, dyslipidemia, and endothelial dysfunction.

Genotype-phenotype associations: modulation by diet and obesity

Changes in diet are likely to reduce chronic disorders, but after decades of active research and heated discussion, the question still remains: what is the optimal diet to achieve this elusive goal? Is it a low-fat diet, as traditionally recommended by multiple medical societies? Or a high monounsaturated fat (MUFA) diet as predicated by the Mediterranean diet? Perhaps a high polyunsaturated fat (PUFA) diet based on the cholesterol-lowering effects? The right answer may be all of the above but not for everybody. A well-known phenomenon in nutrition research and practice is the dramatic variability in interindividual response to any type of dietary intervention. There are many other factors influencing response, and they include, among many others, age, sex, physical activity, alcohol, and smoking as well as genetic factors that will help to identify vulnerable populations/individuals that will benefit from a variety of more personalized and mechanistic-based dietary recommendations. This potential could and needs to be developed within the context of nutritional genomics that in conjunction with systems biology may provide the tools to achieve the holy grail of dietary prevention and therapy of chronic diseases and cancer. This approach will break with the traditional public health approach of "one size fits all." The current evidence based on nutrigenetics has begun to identify subgroups of individuals who benefit more from a low-fat diet, whereas others appear to benefit more from high MUFA or PUFA diets. The continuous progress in nutrigenomics will allow some time in the future to provide targeted gene-based dietary advice.