Metabolic dysfunction from ECM remodeling in diseases of human RPE

PROJECT SUMMARY/ABSTRACT
The presence of lipid-rich deposits underneath the retinal pigment epithelium (RPE) is a pathologic feature of
early age-related macular degeneration (AMD). Drusen development has been associated with RPE lipid
metabolism, redox biology and extracellular matrix (ECM) degradation. Mutations in a gene affecting ECM
degradation, tissue inhibitor of metalloproteinase 3 (TIMP3), results in a rare inherited retinal degeneration with
similar clinical features to AMD, called Sorsby Fundus Dystrophy (SFD). The mechanism by which abnormal
ECM turnover influences lipid metabolism and RPE redox resulting in the formation of sub-RPE deposits
remains unknown.
The goal of this proposal is to test the hypothesis that ECM degradation overloads the RPE with ECM-derived
metabolites, resulting in the reprogramming of RPE towards lipid synthesis and mitochondrial oxidative
metabolism. This in turn results in the deposition of excess lipids and reduced antioxidative capacity of the
RPE. The proposed specific aims are:
Aim 1. Determine the influence of ECM degradation on lipid metabolism. Our preliminary results show
that increased ECM degradation in SFD RPE activates lipid synthesis and oxidation of branch-chain amino
acids (BCAAs). BCAAs are ketogenic and abundant in the ECM. The goal of Aim 1 is to test the hypothesis
that ECM degradation of protein-rich components reprograms RPE metabolism towards enhanced BCAA
oxidation for lipid synthesis and lipid deposition. We will use quantitative proteomics, quantitative
metabolomics, metabolic flux analysis, perifusion assays, CRISPR/Cas9 gene-editing, and single cell nuclear
RNA-Seq of patient-derived iPSC RPE to comprehensively investigate the metabolic pathways in ECM
remodeling and lipid deposition.
Aim 2. Determine the influence of ECM degradation on redox metabolism. Our preliminary data show that
both NADPH and glutathione are depleted in SFD RPE, and ECM-derived metabolites interfere with NADPH
and glutathione metabolism. The goal of Aim 2 is to test the hypothesis that increased ECM turnover results in
impaired NADPH and glutathione metabolism. We will quantify the metabolic flux of ECM degradation,
determine the roles of ECM-related metabolites in NADPH production and glutathione synthesis, and restore
cellular redox with different approaches to enhance antioxidative capacity.
The proposed research will define the biochemical impacts of ECM turnover on RPE metabolism, including
changes in lipid metabolism and oxidative stress, and identify the relationship between nutrient metabolism,
protein synthesis and degradation, and redox biology in normal and disease-relevant RPE.

Grant Number: 5R01EY034364-04
NIH Institute/Center: NIH
Principal Investigator: Jennifer Chao