Whole-exome sequencing identifies rare, functional CFH variants in families with macular degeneration.

We sequenced the whole exome of 35 cases and 7 controls from 9 age-related macular degeneration (AMD) families in whom known common genetic risk alleles could not explain their high disease burden and/or their early-onset advanced disease. Two families harbored novel rare mutations in CFH (R53C and D90G). R53C segregates perfectly with AMD in 11 cases (heterozygous) and 1 elderly control (reference allele) (LOD = 5.07, P = 6.7 × 10(-7)). In an independent cohort, 4 out of 1676 cases but none of the 745 examined controls or 4300 NHBLI Exome Sequencing Project (ESP) samples carried the R53C mutation (P = 0.0039). In another family of six siblings, D90G similarly segregated with AMD in five cases and one control (LOD = 1.22, P = 0.009). No other sample in our large cohort or the ESP had this mutation. Functional studies demonstrated that R53C decreased the ability of FH to perform decay accelerating activity. D90G exhibited a decrease in cofactor-mediated inactivation. Both of these changes would lead to a loss of regulatory activity, resulting in excessive alternative pathway activation. This study represents an initial application of the whole-exome strategy to families with early-onset AMD. It successfully identified high impact alleles leading to clearer functional insight into AMD etiopathogenesis.

(Epi)Genetic analyses of age-related macular degeneration: case-control and discordant twin studies.

BACKGROUND/AIMS: Phenotypic discordance in monozygotic (MZ) twin pairs can have an epigenetic or genetic basis. Although age-related macular degeneration (AMD) has a strong genetic component, few studies have addressed its epigenetic basis. METHODS: Using SNP arrays, we evaluated differences in copy number variation (CNV) and allele-specific methylation (ASM) patterns (via methyl-sensitive restriction enzyme digestion of DNA) in MZ twin pairs from the US Twin Study of AMD. Further analyses examined the relationship between ASM and CNVs with AMD by both case/control analysis of ASM at candidate regions and by analysis of ASM and CNVs in twins discordant for AMD. RESULTS: The frequency of ASM sites differs between cases and controls in regions surrounding the AMD candidate genes CFH, C2 and CFB. While ASM patterns show a substantial dependence on local sequence polymorphisms, we observed dissimilar patterns of ASM between MZ twins. The genes closest to the sites where discordant MZ twins have dissimilar patterns of ASM are enriched for genes implicated in gliosis, a process associated with neovascular AMD. Similar twin-based analyses revealed no AMD-associated CNVs. CONCLUSIONS: Our results provide evidence of epigenetic influences beyond the known genetic susceptibility and implicate inflammatory responses and gliosis in the etiology of AMD.

Common variants near FRK/COL10A1 and VEGFA are associated with advanced age-related macular degeneration.

Despite significant progress in the identification of genetic loci for age-related macular degeneration (AMD), not all of the heritability has been explained. To identify variants which contribute to the remaining genetic susceptibility, we performed the largest meta-analysis of genome-wide association studies to date for advanced AMD. We imputed 6 036 699 single-nucleotide polymorphisms with the 1000 Genomes Project reference genotypes on 2594 cases and 4134 controls with follow-up replication of top signals in 5640 cases and 52 174 controls. We identified two new common susceptibility alleles, rs1999930 on 6q21-q22.3 near FRK/COL10A1 [odds ratio (OR) 0.87; P = 1.1 × 10(-8)] and rs4711751 on 6p12 near VEGFA (OR 1.15; P = 8.7 × 10(-9)). In addition to the two novel loci, 10 previously reported loci in ARMS2/HTRA1 (rs10490924), CFH (rs1061170, and rs1410996), CFB (rs641153), C3 (rs2230199), C2 (rs9332739), CFI (rs10033900), LIPC (rs10468017), TIMP3 (rs9621532) and CETP (rs3764261) were confirmed with genome-wide significant signals in this large study. Loci in the recently reported genes ABCA1 and COL8A1 were also detected with suggestive evidence of association with advanced AMD. The novel variants identified in this study suggest that angiogenesis (VEGFA) and extracellular collagen matrix (FRK/COL10A1) pathways contribute to the development of advanced AMD.

Dietary omega-3 fatty acids, other fat intake, genetic susceptibility, and progression to incident geographic atrophy.

OBJECTIVE: To investigate associations between dietary omega-3 fatty acids and other fat intake, genes related to age-related macular degeneration (AMD), and progression to geographic atrophy (GA). DESIGN: Observational analysis of a prospective cohort. PARTICIPANTS: A total of 2531 individuals from the Age-Related Eye Disease Study, among which 525 eyes progressed to GA and 4165 eyes did not. METHODS: Eyes without advanced AMD at baseline were evaluated for progression to GA. Behavioral data, including smoking and body mass index measurements, were collected at baseline using questionnaires. Dietary data were collected from food frequency questionnaires (FFQs) at baseline. Omega-3 fatty acids (docosahexaenoic acid [DHA] and eicosapentaenoic acid [EPA]), omega-6 fatty acids, monounsaturated, saturated, polyunsaturated, and total fat were adjusted for sex and calories and divided into quintiles (Q). Eight single nucleotide polymorphisms in 7 genes (CFH, ARMS2/HTRA1, CFB, C2, C3, CFI, and LIPC) were genotyped. Cox proportional hazards models were used to test for associations between incident GA and intake of dietary lipids and interaction effects between dietary fat intake and genetic variation on risk of GA. MAIN OUTCOME MEASURES: Associations between dietary fat intake reported from FFQs, genetic variants, and incident GA. RESULTS: Increased intake of DHA was significantly associated with reduced risk of progression to GA in models with behavioral factors (model A) plus genetic variants (model B) (P trend = 0.01 and 0.03, respectively). Total omega-3 long chain polyunsaturated (DHA + EPA) fatty acid intake was significantly associated with reduced risk of progression in model B (P trend = 0.02). Monounsaturated fat was associated with increased risk in model A (P trend = 0.05). DHA intake was significantly associated with reduced risk of incident GA among those with the ARMS2/HTRA1 homozygous risk genotype (hazard ratio [HR] Q5 vs Q1, 0.4; P = 0.002; P for interaction between gene and fat intake = 0.05). DHA was not associated with reduced risk of GA among those with the homozygous ARMS2/HTRA1 nonrisk genotype (HR, 1.0; P = 0.90). CONCLUSIONS: Increased self-reported dietary intake of omega-3 fatty acids is associated with reduced risk of GA and may modify genetic susceptibility for progression to GA. FINANCIAL DISCLOSURE(S): The author(s) have no proprietary or commercial interest in any materials discussed in this article.

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.

Genetic variants near TIMP3 and high-density lipoprotein-associated loci influence susceptibility to age-related macular degeneration.

We executed a genome-wide association scan for age-related macular degeneration (AMD) in 2,157 cases and 1,150 controls. Our results validate AMD susceptibility loci near CFH (P < 10(-75)), ARMS2 (P < 10(-59)), C2/CFB (P < 10(-20)), C3 (P < 10(-9)), and CFI (P < 10(-6)). We compared our top findings with the Tufts/Massachusetts General Hospital genome-wide association study of advanced AMD (821 cases, 1,709 controls) and genotyped 30 promising markers in additional individuals (up to 7,749 cases and 4,625 controls). With these data, we identified a susceptibility locus near TIMP3 (overall P = 1.1 x 10(-11)), a metalloproteinase involved in degradation of the extracellular matrix and previously implicated in early-onset maculopathy. In addition, our data revealed strong association signals with alleles at two loci (LIPC, P = 1.3 x 10(-7); CETP, P = 7.4 x 10(-7)) that were previously associated with high-density lipoprotein cholesterol (HDL-c) levels in blood. Consistent with the hypothesis that HDL metabolism is associated with AMD pathogenesis, we also observed association with AMD of HDL-c-associated alleles near LPL (P = 3.0 x 10(-3)) and ABCA1 (P = 5.6 x 10(-4)). Multilocus analysis including all susceptibility loci showed that 329 of 331 individuals (99%) with the highest-risk genotypes were cases, and 85% of these had advanced AMD. Our studies extend the catalog of AMD associated loci, help identify individuals at high risk of disease, and provide clues about underlying cellular pathways that should eventually lead to new therapies.

Heritability and genome-wide association study to assess genetic differences between advanced age-related macular degeneration subtypes.

PURPOSE: To investigate whether the 2 subtypes of advanced age-related macular degeneration (AMD), choroidal neovascularization (CNV), and geographic atrophy (GA) segregate separately in families and to identify which genetic variants are associated with these 2 subtypes. DESIGN: Sibling correlation study and genome-wide association study (GWAS). PARTICIPANTS: For the sibling correlation study, 209 sibling pairs with advanced AMD were included. For the GWAS, 2594 participants with advanced AMD subtypes and 4134 controls were included. Replication cohorts included 5383 advanced AMD participants and 15 240 controls. METHODS: Participants had the AMD grade assigned based on fundus photography, examination, or both. To determine heritability of advanced AMD subtypes, a sibling correlation study was performed. For the GWAS, genome-wide genotyping was conducted and 6 036 699 single nucleotide polymorphisms (SNPs) were imputed. Then, the SNPs were analyzed with a generalized linear model controlling for genotyping platform and genetic ancestry. The most significant associations were evaluated in independent cohorts. MAIN OUTCOME MEASURES: Concordance of advanced AMD subtypes in sibling pairs and associations between SNPs with GA and CNV advanced AMD subtypes. RESULTS: The difference between the observed and expected proportion of siblings concordant for the same subtype of advanced AMD was different to a statistically significant degree (P = 4.2 × 10(-5)), meaning that in siblings of probands with CNV or GA, the same advanced subtype is more likely to develop. In the analysis comparing participants with CNV to those with GA, a statistically significant association was observed at the ARMS2/HTRA1 locus (rs10490924; odds ratio [OR], 1.47; P = 4.3 × 10(-9)), which was confirmed in the replication samples (OR, 1.38; P = 7.4 × 10(-14) for combined discovery and replication analysis). CONCLUSIONS: Whether CNV versus GA develops in a patient with AMD is determined in part by genetic variation. In this large GWAS meta-analysis and replication analysis, the ARMS2/HTRA1 locus confers increased risk for both advanced AMD subtypes, but imparts greater risk for CNV than for GA. This locus explains a small proportion of the excess sibling correlation for advanced AMD subtype. Other loci were detected with suggestive associations that differ for advanced AMD subtypes and deserve follow-up in additional studies.

Smoking, dietary betaine, methionine, and vitamin D in monozygotic twins with discordant macular degeneration: epigenetic implications.

OBJECTIVE: We evaluated monozygotic twin pairs with discordant age-related macular degeneration (AMD) phenotypes to assess differences in behavioral and nutritional factors. DESIGN: Case series. PARTICIPANTS: Caucasian male twin pairs from the United States Twin Study of Macular Degeneration. METHODS: Twin pairs were genotyped to confirm monozygosity. Ocular characteristics were evaluated based on fundus photographs using the Wisconsin Grading System and a 5-grade Clinical Age-Related Maculopathy Staging System. We selected twin pairs discordant in each of the following phenotypic categories: Stage of AMD (n = 28), drusen area (n = 60), drusen size (n = 40), and increased pigment area (n = 56). The Wilcoxon signed-rank test and linear regression were used to assess associations between behavioral and nutritional characteristics and each phenotype within discordant twin pairs. MAIN OUTCOME MEASURES: Differences in smoking and dietary factors within twin pairs discordant for stage of AMD, drusen area, drusen size, and pigment area. RESULTS: Representative fundus photographs depict the discordant phenotypes. Pack-years of smoking were higher for the twin with the more advanced stage of AMD (P = 0.05). Higher dietary intake of vitamin D was present in the twins with less severe AMD (P = 0.01) and smaller drusen size (P = 0.05) compared with co-twins, adjusted for smoking and age. Dietary intakes of betaine and methionine were significantly higher in the twin with lower stage of AMD (P = 0.009) and smaller drusen area (P = 0.03), respectively. CONCLUSIONS: The twin with the more advanced stage of AMD, larger drusen area, drusen size, and pigment area tended to be the heavier smoker. The twin with the earlier stage of AMD, smaller drusen size and area, and less pigment tended to have higher dietary vitamin D, betaine, or methionine intake. Results suggest that behavioral and nutritional factors associated with epigenetic mechanisms are involved in the etiology of AMD, in addition to genetic susceptibility.

Risk models for progression to advanced age-related macular degeneration using demographic, environmental, genetic, and ocular factors.

PURPOSE: To expand our predictive models for progression to advanced stages of age-related macular degeneration (AMD) based on demographic, environmental, genetic, and ocular factors, using longer follow-up, time varying analyses, calculation of absolute risks, adjustment for competing risks, and detailed baseline AMD and drusen status. DESIGN: Prospective, longitudinal study. PARTICIPANTS: We included 2937 individuals in the Age-Related Eye Disease Study, of which 819 subjects progressed to advanced AMD during 12 years of follow-up. METHODS: Cox proportional hazards regression analyses were performed to calculate hazard ratios for progression. Covariates included demographic and environmental factors, 6 variants in 5 genes, baseline macular drusen size, and presence and type of advanced AMD in 1 eye at baseline. To assess the ability of risk scores based on all covariates to discriminate between progressors and nonprogressors, an algorithm was developed and the area under the receiver operating characteristic curve (AUC) was calculated. To validate the overall model, the total sample was randomly subdivided into derivation and test samples. Another model was built based on the derivation sample and assessed for calibration and discrimination in the test sample. Sample sizes needed for testing new treatments in clinical trials were estimated based on models with and without genetic variables. MAIN OUTCOME MEASURES: Progression to advanced AMD, including geographic atrophy and neovascular disease. RESULTS: In multivariate models, age, smoking, body mass index, single nucleotide polymorphisms in the CFH, ARMS2/HTRA1, C3, C2, and CFB genes, as well as presence of advanced AMD in 1 eye and drusen size in both eyes were all independently associated with progression. The AUC for progression at 10 years in the model with genetic factors, drusen size, and environmental covariates was 0.915 in the total sample. In the test sample, based on a model estimated from the derivation sample, the AUC was 0.908. The sample sizes needed for clinical trials were estimated to be lower when genetic susceptibility was considered. CONCLUSIONS: Factors reflective of nature and nurture were incorporated into an expanded algorithm for risk prediction, which performed very well in both derivation and test samples. Risk scores and predicted progression rates will be useful for AMD surveillance and for designing clinical trials. FINANCIAL DISCLOSURE(S): Proprietary or commercial disclosure may be found after the references.

Kidney function, albuminuria and age-related macular degeneration in NHANES III.

BACKGROUND: Age-related macular degeneration (AMD) and kidney disease may have shared risk factors, including cardiovascular disease risk factors; additionally AMD and dense deposit disease share a common causal link, with both associated with polymorphisms in the complement pathway. Accordingly, we explored a population-based cohort of US adults to examine if markers of kidney disease identify a higher risk population for prevalent AMD. METHODS: A cross-sectional nested case-control study matching on age, sex and race was performed using data on adult participants in the Third National Health and Nutrition Examination Survey. Predictor variables included urine albumin-to-creatinine ratio and estimated glomerular filtration rate (eGFR). Study outcomes included late AMD, defined as neovascular disease or geographic atrophy (5:1 matching), and a composite of both early AMD, defined as soft drusen or pigment irregularities with or without any drusen, and late AMD (1:1 matching). RESULTS: There were 51 participants with late AMD and 865 with any AMD. In conditional logistic regression adjusting for diabetes, hypertension and total cholesterol, lower eGFR was independently associated with late AMD [odds ratio (OR) = 3.05, 95% confidence interval (CI): 1.51-6.13], while albuminuria was not significant. For any AMD, neither albuminuria nor eGFR were significant in adjusted models. In sensitivity analyses excluding diabetics, albuminuria was associated with any AMD (OR = 1.56, 95% CI: 1.11-1.29 and 1.57, 95% CI: 0.61-3.69 for micro- and macroalbuminuria, respectively, P = 0.03). CONCLUSIONS: Late AMD is more common among individuals with reduced kidney function. Whether this association reflects a common causal pathway or shared risk factors such as hypertension requires additional investigation.

Associations of smoking, body mass index, dietary lutein, and the LIPC gene variant rs10468017 with advanced age-related macular degeneration.

OBJECTIVE: A novel locus in the hepatic lipase (LIPC) gene was found to be significantly related to advanced age-related macular degeneration (AMD) in our genome-wide association study. We evaluated its association and interaction with previously identified genetic variants and modifiable factors. METHODS: Participants in the Age-Related Eye Disease Study with advanced AMD (n=545 cases) or no AMD (n=275 controls) were evaluated. AMD status was determined using fundus photography. Covariates included cigarette smoking, body mass index (BMI), and dietary lutein. Individuals were genotyped for the rs10468017 polymorphism in LIPC as well as seven previously identified AMD genetic loci. Unconditional logistic regression analyses were then performed. RESULTS: The TT genotype of the LIPC variant was associated with a reduced risk of AMD, with odds ratios (OR) of 0.50 (95% confidence interval (CI) 0.20-0.90) and p=0.014 for the TT genotype versus the CC genotype, controlling for age, gender, smoking, body mass index (BMI), and nutritional factors. Controlling for seven other AMD genetic variants, the OR was 0.50, 95% (CI 0.20-1.1, p=0.077). The magnitude of the effect was similar for both atrophic and neovascular forms of AMD. Cigarette smoking and higher BMI increased the risk, while higher dietary lutein reduced the risk of advanced AMD, adjusting for genetic variants. There were no significant interactions between LIPC and smoking, BMI, or lutein. There was a possible association between LIPC and complement factor H (CFH) rs1410996, and a possible interaction effect between LIPC and both CFH rs10033900 and the complement factor I (CFI) variants in terms of risk of AMD. CONCLUSIONS: LIPC is associated with reduced risk of advanced AMD, independent of demographic and environmental variables. Both genetic susceptibility and behavioral and lifestyle factors modify the risk of developing AMD.

Serum lipid biomarkers and hepatic lipase gene associations with age-related macular degeneration.

OBJECTIVE: A genetic variant in the high-density lipoprotein (HDL) cholesterol pathway, hepatic lipase (LIPC), was discovered to be associated with advanced age-related macular degeneration (AMD) in a genome-wide association study. In this study, we evaluated whether LIPC is associated with serum lipids, and whether this gene and serum lipids are independently associated with AMD. DESIGN: Case-control study. PARTICIPANTS: A total of 458 participants from the Progression Study of Macular Degeneration and the Age-Related Eye Disease Ancillary Biomarker Study, including 318 advanced AMD cases with either geographic atrophy (n = 123) or neovascular disease (n = 195) and 140 controls. METHODS: Participants were genotyped for 8 variants associated with AMD: 2 CFH variants, C2, CFB, C3, CFI, the ARMS2/HTRA1 gene region, and LIPC. Fasting blood specimens were obtained at study onset, and serum levels of total cholesterol, low-density lipoprotein (LDL), HDL, and triglycerides were determined. Logistic and linear regression were used to evaluate associations between serum lipids, LIPC genotype, and AMD. MAIN OUTCOME MEASURES: LIPC and serum lipid associations with AMD. RESULTS: The minor T allele of the LIPC gene was associated with a reduced risk of AMD (odds ratio, 0.4; 95% confidence interval, 0.2-0.9; P = 0.01, trend for number of T alleles, controlling for age and gender). Mean level of HDL was lower (P = 0.05) and mean level of LDL (P = 0.03) was higher in cases of advanced AMD compared with controls. Higher total cholesterol and LDL levels were associated with increased risk of AMD, with P for trend = 0.01 for both, in models controlling for environmental and genetic covariates. The T allele of LIPC was associated with higher levels of HDL, although LIPC was associated with advanced AMD independent of HDL level. CONCLUSIONS: The HDL-raising allele of the LIPC gene (T) was associated with a reduced risk of AMD. Higher total cholesterol and LDL levels were associated with increased risk, whereas higher HDL levels tended to reduce the risk of AMD. The specific mechanisms underlying the association between AMD and LIPC require further investigation.

CFH and LOC387715/ARMS2 genotypes and treatment with antioxidants and zinc for age-related macular degeneration.

OBJECTIVE: To determine if CFH and LOC387715/ARMS2 genotypes influence treatment response to AREDS-type nutritional supplementation with antioxidants and zinc. DESIGN: Retrospective analysis of participants in a randomized, controlled clinical trial, the Age-Related Eye Disease Study (AREDS). PARTICIPANTS AND/OR CONTROLS: Eight hundred seventy-six AREDS study participants who were considered at high risk for developing advanced age-related macular degeneration (AMD). METHODS: Using DNA extracted from venous blood of 876 white participants in AREDS categories 3 and 4, that is, those considered to be at high risk for progression to advanced AMD, the authors genotyped for the single nucleotide polymorphisms in the CFH (Y402H, rs1061170) and LOC387715/ARMS2 (A69S, rs10490924) genes. The authors performed adjusted unconditional logistic regression analysis and assessed interactions of these genotypes to determine the relationship between CFH and LOC387715/ARMS2 genotype and treatment with antioxidants plus zinc. MAIN OUTCOME MEASURES: Interaction between genetic variants and treatment response as determined by progression from high-risk to advanced AMD. RESULTS: Progression occurred in 264 of 876 patients from AREDS category 3 (intermediate AMD) to category 4 or 5 (unilateral or bilateral advanced AMD, respectively), or from category 4 to category 5. A treatment interaction was observed between the CFH Y402H genotype and supplementation with antioxidants plus zinc (CC; P = 0.03). An interaction (P = 0.004) was observed in the AREDS treatment groups taking zinc when compared with the groups taking no zinc, but not in groups taking antioxidants compared with those taking no antioxidants (P = 0.59). There were no significant treatment interactions observed with LOC387715/ARMS2. CONCLUSIONS: The findings of this study indicate that an individual's response to AREDS supplements may be related to CFH genotype. This could have clinical relevance by predicting treatment outcome and potentially preventing unwanted side effects in those who may not benefit. Corroboration of these analyses is needed before considering modification of current management. This is among the first pharmacogenetic studies to suggest interaction between genotype and treatment.

Effect of extended exposure to grapefruit juice on cytochrome P450 3A activity in humans: comparison with ritonavir.

BACKGROUND AND OBJECTIVES: Acute ingestion of usual quantities of grapefruit juice produces inhibition of enteric cytochrome P450 (CYP) 3A enzymes, causing pharmacokinetic interactions with a number of drugs. However, the effect of extended exposure to grapefruit juice on CYP3A activity is not established. METHODS: Triazolam, a CYP3A index compound, was administered to 3 cohorts of volunteers (n = 6-7 per group) on 4 occasions (trials 1-4), as follows: 1 day prior to cotreatment initiation, at the beginning and end of cotreatment, and 3 days after cotreatment discontinuation. The 3 cotreatments (daily administration for 10 consecutive days) were: 300 mL grapefruit juice, 400 mg ritonavir, or 300 mL water. RESULTS: Grapefruit juice cotreatment (trial 2) increased the triazolam area under the plasma concentration curve by 50% compared to the trial 1 control (15.1 +/- 7.6 ng/mL.h versus 10.0 +/- 3.5 ng/mL.h, P < .05), but the half-life was not changed. Effects of acute and extended exposure to grapefruit juice (trials 2 and 3) were similar, and produced augmentation in benzodiazepine agonist effects measured by the Digit Symbol Substitution Test and electroencephalographic beta amplitude. Kinetic and dynamic effects reverted to baseline (trial 1) values at 3 days after grapefruit juice discontinuation (trial 4). Ritonavir caused a more than 20-fold increase in the triazolam area under the plasma concentration curve during trial 2 (553 +/- 422 ng/mL.h) and trial 3 (287 +/- 299 ng/mL.h) compared to the trial 1 control (13.3 +/- 16.3 ng/mL.h) (P < .05 for both comparisons); Digit Symbol Substitution Test and electroencephalographic pharmacodynamics increased in parallel. During trial 4, triazolam kinetics reverted close to trial 1 values, with no evidence of induction. Triazolam kinetics were not altered by water cotreatment. CONCLUSION: Acute and extended exposure to grapefruit juice produces quantitatively similar inhibition of enteric, but not hepatic, CYP3A. Recovery is complete within 3 days after grapefruit juice discontinuation. Ritonavir greatly inhibits both enteric and hepatic CYP3A. With extended exposure to ritonavir, inhibition is the predominant effect, and recovery to baseline is nearly complete 3 days after ritonavir discontinuation.

Ginkgo biloba does not alter clearance of flurbiprofen, a cytochrome P450-2C9 substrate.

The effect of Ginkgo biloba on the activity of CYP2C9, the isoform responsible for S-warfarin clearance, was assessed in 11 healthy volunteers who received single 100-mg doses of flurbiprofen, a probe substrate for CYP2C9. Subjects also received either a standardized G biloba leaf preparation (Ginkgold, 3 doses of 120 mg) or matching placebo in a randomized, double-blind, 2-way crossover study. Mean kinetic variables for flurbiprofen with either placebo or G biloba were elimination half-life, 3.9 versus 3.5 hours; total AUC, 57 versus 55 microg/mL h; and oral clearance, 32.9 versus 31.6 mL/min. None of these differences was significant. Based on highperformance liquid chromatography analysis, each 60-mg Ginkgold tablet contained 6.6 mug of amentoflavone and 61.2 microg of quercetin, both previously identified as CYP2C9 inhibitors. These amounts were apparently too low to inhibit CYP2C9 function in vivo. The results confirm previous controlled clinical studies showing no effect of ginkgo on the kinetics or dynamics of warfarin.

Three new genetic loci (R1210C in CFH, variants in COL8A1 and RAD51B) are independently related to progression to advanced macular degeneration.

OBJECTIVES: To assess the independent impact of new genetic variants on conversion to advanced stages of AMD, controlling for established risk factors, and to determine the contribution of genes in predictive models. METHODS: In this prospective longitudinal study of 2765 individuals, 777 subjects progressed to neovascular disease (NV) or geographic atrophy (GA) in either eye over 12 years. Recently reported genetic loci were assessed for their independent effects on incident advanced AMD after controlling for 6 established loci in 5 genes, and demographic, behavioral, and macular characteristics. New variants which remained significantly related to progression were then added to a final multivariate model to assess their independent effects. The contribution of genes to risk models was assessed using reclassification tables by determining risk within cross-classified quintiles for alternative models. RESULTS: THREE NEW GENETIC VARIANTS WERE SIGNIFICANTLY RELATED TO PROGRESSION: rare variant R1210C in CFH (hazard ratio (HR) 2.5, 95% confidence interval [CI] 1.2-5.3, P = 0.01), and common variants in genes COL8A1 (HR 2.0, 95% CI 1.1-3.5, P = 0.02) and RAD51B (HR 0.8, 95% CI 0.60-0.97, P = 0.03). The area under the curve statistic (AUC) was significantly higher for the 9 gene model (.884) vs the 0 gene model (.873), P = .01. AUC's for the 9 vs 6 gene models were not significantly different, but reclassification analyses indicated significant added information for more genes, with adjusted odds ratios (OR) for progression within 5 years per one quintile increase in risk score of 2.7, P<0.001 for the 9 vs 6 loci model, and OR 3.5, P<0.001 for the 9 vs. 0 gene model. Similar results were seen for NV and GA. CONCLUSIONS: Rare variant CFH R1210C and common variants in COL8A1 and RAD51B plus six genes in previous models contribute additional predictive information for advanced AMD beyond macular and behavioral phenotypes.

Validation of a prediction algorithm for progression to advanced macular degeneration subtypes.

IMPORTANCE: Risk score models predicting the progression of age-related macular degeneration (AMD) to its advanced forms may be useful for targeting high-risk individuals for lifestyle changes that reduce risk for AMD progression, helping with differential diagnosis of AMD and its subtypes, identifying high-risk subjects for participation in clinical trials, and selecting appropriate therapies. OBJECTIVE: To develop and validate a predictive model for progression to advanced stages of AMD in 2 independent cohorts. DESIGN Participants in a validation cohort and an independent derivation population were classified into 5 stages of AMD based on ocular examination and fundus photographs at baseline. Progression was defined as either eye progressing from stage 1, 2, or 3 to either stage 4 or stage 5 at any follow-up visit to the end of the study. Cox proportional hazards models were used for progression analyses. Covariates included demographic and environmental factors, 6 variants in 5 genes, and baseline AMD grades in both eyes. The algorithm developed with the derivation sample was assessed for calibration and discrimination in the validation data set. SETTING: Clinic populations and referrals. PARTICIPANTS: The derivation population comprised 2914 subjects with 809 progressors. The independent validation cohort comprised 980 individuals with no, early, or intermediate AMD in at least one eye at baseline, of whom 294 progressed to advanced stages of geographic atrophy or neovascular disease. MAIN OUTCOME MEASURE: Progression to advanced AMD. RESULTS For the model with all nongenetic and genetic factors, the respective C statistics for progression to advanced AMD in the derivation and validation samples were 0.858 and 0.750 at 5 years and 0.884 and 0.809 at 10 years, and models also discriminated risk for progression to geographic atrophy and neovascular disease separately. For unilateral or bilateral intermediate AMD, 5-year cumulative incidence rates of progression to advanced AMD were 10% with the low-risk score and 50% with the high-risk score; for unilateral advanced disease, the progression rates were 22% and 80% for the fellow eye. CONCLUSIONS AND RELEVANCE: The risk prediction model was validated in an independent study of progression from no, early, or intermediate stages to advanced subtypes of AMD and will be useful for research, clinical trials, and personalized medicine.

Rare variants in CFI, C3 and C9 are associated with high risk of advanced age-related macular degeneration.

To define the role of rare variants in advanced age-related macular degeneration (AMD) risk, we sequenced the exons of 681 genes within all reported AMD loci and related pathways in 2,493 cases and controls. We first tested each gene for increased or decreased burden of rare variants in cases compared to controls. We found that 7.8% of AMD cases compared to 2.3% of controls are carriers of rare missense CFI variants (odds ratio (OR) = 3.6; P = 2 × 10(-8)). There was a predominance of dysfunctional variants in cases compared to controls. We then tested individual variants for association with disease. We observed significant association with rare missense alleles in genes other than CFI. Genotyping in 5,115 independent samples confirmed associations with AMD of an allele in C3 encoding p.Lys155Gln (replication P = 3.5 × 10(-5), OR = 2.8; joint P = 5.2 × 10(-9), OR = 3.8) and an allele in C9 encoding p.Pro167Ser (replication P = 2.4 × 10(-5), OR = 2.2; joint P = 6.5 × 10(-7), OR = 2.2). Finally, we show that the allele of C3 encoding Gln155 results in resistance to proteolytic inactivation by CFH and CFI. These results implicate loss of C3 protein regulation and excessive alternative complement activation in AMD pathogenesis, thus informing both the direction of effect and mechanistic underpinnings of this disorder.

Prospective assessment of genetic effects on progression to different stages of age-related macular degeneration using multistate Markov models.

PURPOSE: Understanding the effect of genes on progression to different stages of age-related macular degeneration (AMD) may suggest stage-specific therapeutic targets and more precise prediction of the development of this disease. METHODS: Progression events and time to each stage of AMD were derived from the longitudinal data of 2560 subjects without advanced AMD. SNPs in 12 AMD risk loci were genotyped. A multistate Markov model for progression from normal to intermediate drusen, then to large drusen, and eventually to neovascular disease (NV) or geographic atrophy (GA) was applied to estimate stage-specific hazard ratios for each SNP. The effects of these genetic factors were also estimated by a multivariate multistate Markov model adjusted for baseline age, sex, smoking, body mass index (BMI), education, antioxidant treatment, and the status of AMD in the fellow eye. RESULTS: Controlling for demographic and behavioral factors and other SNPs, the TT genotype of rs10468017 in LIPC was associated with decreased risk of progression from large drusen to NV (HR = 0.57, P = 0.04) and tended to reduce the risk of progression from normal to intermediate drusen (HR = 0.72, P = 0.07). The SNP rs1883025 (T allele) in ABCA1 was associated with decreased risk of progression from normal to intermediate drusen (HR per allele = 0.82 per allele, P = 9.7 × 10(-3)) and from intermediate drusen to large drusen (HR per allele = 0.77, P = 5.2 × 10(-3)). The genes CFH, C3, CFB, and ARMS2/HTRA1 were associated with progression from intermediate drusen to large drusen and from large drusen to GA or NV. CONCLUSIONS: Genes in different pathways influence progression to different stages of AMD.

Genetic factors for choroidal neovascularization associated with high myopia.

PURPOSE: Nonsyndromic high myopia, defined by a refractive error greater than -6 diopters (D), is associated with an increased risk of macular choroidal neovascularization (CNV), a vision-threatening complication. The aim of this study was to investigate whether genetic factors associated with age-related macular degeneration (AMD) are related to myopic CNV. METHODS: We conducted a case-control study, including 71 cases with myopic CNV and 196 myopic controls without CNV, from Creteil and Toulouse, France, and Boston, MA. Single nucleotide polymorphisms (SNPs) from 15 genes reported to be related to AMD were selected for association testing in this study. RESULTS: In univariate analysis, the rs10033900 SNP located in CFI was associated with myopic CNV (P = 0.0011), and a SNP in APOE was also related (P = 0.041). After adjustment for age, sex, and degree of myopia, SNPs in three genes were significantly associated, including CFI (odds ratio [OR] 2.1, 95% confidence interval [CI] 1.3-3.37, P = 0.0023), COL8A1 (OR 1.88, 95% CI 1.18-2.98, P = 0.0076), and CFH (OR 1.65, 95% CI 1.02-2.66, P = 0.04). After correction for multiple testing, only CFI remained significantly related to high myopic CNV (P = 0.045). CONCLUSIONS: We report the first genetic associations with choroidal neovascularization (CNV) in a high myopic Caucasian population. One SNP (rs10033900) in the CFI gene, which encodes a protein involved in the inflammatory pathway, was significantly associated with myopic CNV in multivariate analysis after correction for multiple testing. This SNP is a plausible biological marker associated with CNV outgrowth among high myopic patients. Results generate hypotheses about potential loci related to CNV in high myopia, and larger studies are needed to expand on these findings.