Human Plasma Metabolomics Study across All Stages of Age-Related Macular Degeneration Identifies Potential Lipid Biomarkers

Abstract

Purpose: To characterize the plasma metabolomic profile of patients with age-related macular degeneration (AMD) using mass spectrometry (MS).

Design: Cross-sectional observational study.

Participants: We prospectively recruited participants with a diagnosis of AMD and a control group (>50 years of age) without any vitreoretinal disease.

Methods: All participants underwent color fundus photography, used for AMD diagnosis and staging, according to the Age-Related Eye Disease Study classification scheme. Fasting blood samples were collected and plasma was analyzed by Metabolon, Inc. (Durham, NC), using ultrahigh-performance liquid chromatography (UPLC) and high-resolution MS. Metabolon's hardware and software were used to identify peaks and control quality. Principal component analysis and multivariate regression were performed to assess differences in the metabolomic profiles of AMD patients versus controls, while controlling for potential confounders. For biological interpretation, pathway enrichment analysis of significant metabolites was performed using MetaboAnalyst.

Main outcome measures: The primary outcome measures were levels of plasma metabolites in participants with AMD compared with controls and among different AMD severity stages.

Results: We included 90 participants with AMD (30 with early AMD, 30 with intermediate AMD, and 30 with late AMD) and 30 controls. Using UPLC and MS, 878 biochemicals were identified. Multivariate logistic regression identified 87 metabolites with levels that differed significantly between AMD patients and controls. Most of these metabolites (82.8%; n = 72), including the most significant metabolites, belonged to the lipid pathways. Analysis of variance revealed that of the 87 metabolites, 48 (55.2%) also were significantly different across the different stages of AMD. A significant enrichment of the glycerophospholipids pathway was identified (P = 4.7 × 10^-9) among these metabolites.

Conclusions: Participants with AMD have altered plasma metabolomic profiles compared with controls. Our data suggest that the most significant metabolites map to the glycerophospholipid pathway. These findings have the potential to improve our understanding of AMD pathogenesis, to support the development of plasma-based metabolomics biomarkers of AMD, and to identify novel targets for treatment of this blinding disease.

Figure 1.

Scatterplot showing principal component 1 (PC1) and principal component 2 (PC2) with controls and age-related macular degeneration (AMD) groups. The x-axis corresponds to PC1 and the y-axis to PC2.

Figure 2.

Graph showing pathway analysis based on the 87 metabolites associated significantly with age-related macular degeneration. −log(p) = minus logarithm of the P value.

Figure 3.

Receiver operating characteristic (ROC) curve analysis of model including the 87 significant metabolites compared with the baseline model. The results of the ROC analysis, including metabolite data, which outperformed (area under the ROC curve [AUC], 0.80; 95% confidence interval [CI], 0.71–0.90) a baseline model including only age, gender, body mass index, and smoking status (AUC, 0.71; 95% CI, 0.59–0.85), appear in red.

Figure 4.

Boxplots of the 13 most significant metabolites (P < 0.01) in analysis of variance results comparing severity stages of age-related macular degeneration (AMD). E = early; I = intermediate; L = late.