Plasma Protein Pentosidine and Carboxymethyllysine, Biomarkers for Age-related Macular Degeneration

Abstract

Age-related macular degeneration (AMD) causes severe vision loss in the elderly; early identification of AMD risk could help slow or prevent disease progression. Toward the discovery of AMD biomarkers, we quantified plasma protein Nε-carboxymethyllysine (CML) and pentosidine from 58 AMD and 32 control donors. CML and pentosidine are advanced glycation end products that are abundant in Bruch membrane, the extracellular matrix separating the retinal pigment epithelium from the blood-bearing choriocapillaris. We measured CML and pentosidine by LC-MS/MS and LC-fluorometry, respectively, and found higher mean levels of CML (∼54%) and pentosidine (∼64%) in AMD (p < 0.0001) relative to normal controls. Plasma protein fructosyl-lysine, a marker of early glycation, was found by amino acid analysis to be in equal amounts in control and non-diabetic AMD donors, supporting an association between AMD and increased levels of CML and pentosidine independent of other diseases like diabetes. Carboxyethylpyrrole (CEP), an oxidative modification from docosahexaenoate-containing lipids and also abundant in AMD Bruch membrane, was elevated ∼86% in the AMD cohort, but autoantibody titers to CEP, CML, and pentosidine were not significantly increased. Compellingly higher mean levels of CML and pentosidine were present in AMD plasma protein over a broad age range. Receiver operating curves indicate that CML, CEP adducts, and pentosidine alone discriminated between AMD and control subjects with 78, 79, and 88% accuracy, respectively, whereas CML in combination with pentosidine provided ∼89% accuracy, and CEP plus pentosidine provided ∼92% accuracy. Pentosidine levels appeared slightly altered in AMD patients with hypertension and cardiovascular disease, indicating further studies are warranted. Overall this study supports the potential utility of plasma protein CML and pentosidine as biomarkers for assessing AMD risk and susceptibility, particularly in combination with CEP adducts and with concurrent analyses of fructosyl-lysine to detect confounding factors.

Long-chain and very long-chain polyunsaturated fatty acids in ocular aging and age-related macular degeneration

“…Crabb et al demonstrated that carboxyethyl pyrrole (CEP) protein adducts, the oxidative protein modifi cations generated uniquely from the docosahexaenoate-containing lipids such as DHA and adrenic acid ( 51 ), are more abundant in ocular tissues from AMD retina than from normal retina ( 52 ). CEP biomarkers have been shown to enhance the AMD predictive accuracy of genomic AMD biomarkers ( 53,54 ). The increase of CEP protein adducts in AMD retinas indicates that increased oxidation of DHA and adrenic acid that likely occurs in AMD eyes may lead to a reduction in DHA and adrenic acid, which is consistent with our study results.…”

Involvement of a gut–retina axis in protection against dietary glycemia-induced age-related macular degeneration

“…Accumulation of AGEs is diagnostic of many age-related diseases, including AMD, and is a reporter of chronic hyperglycemia and its downstream glycoxidative and other cytotoxic stresses (13,(30)(31)(32). Plasma levels of the AGEs, including glucosepane, Ne(1-carboxyethyl)-lysine (CEL), and 3-deoxyglucosone-derived hydroimidazolone (3DG-H), were all higher in these HG nondiabetic mice ( Fig.…”

The Role of Vascular Endothelial Growth Factor-Induced Activation of NADPH Oxidase in Choroidal Endothelial Cells and Choroidal Neovascularization

“…Proteomic analysis of Bruch's membrane from human eyes with AMD revealed the presence of oxidized compounds. 17 The Eye Disease Case Control Study found an association between reduced prevalence of AMD and high dietary intake of antioxidants. 18 The placebo-controlled, double-masked multicenter clinical Age-Related Eye Disease Study provided strong support for the relationship between AMD and oxidants by finding reduced progression to advanced AMD and vision loss in subjects who took certain antioxidants and zinc supplements.…”