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Abbi Engel, Kaitlen Knight, Megan Manson, Bela Anand-Apte, James Hurley, Jianhai Du, Jennifer R Chao; Impaired Reductive Carboxylation of the Retinal Pigment Epithelium in Sorsby Fundus Dystrophy. Invest. Ophthalmol. Vis. Sci. 2017;58(8):3593.
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© ARVO (1962-2015); The Authors (2016-present)
Previous studies have demonstrated the importance of retinal pigment epithelium (RPE) metabolism in countering oxidative stress. Sorsby Fundus Dystrophy (SFD) is a rare disease that affects the RPE and Bruch’s membrane, resulting in central vision loss. Our aim is to determine whether SFD RPE have altered metabolism compared to normal controls.
RPE cell lines were differentiated from three distinct induced pluripotent stem cell (iPSC) clones from each of three normal control individuals and three iPSC clones from an individual with SFD (S181C TIMP3 mutation). After the RPE cells were cultured to maturity, they were incubated with 13C tracers and metabolites were prepared for analysis and quantified by GC-MS and LC-MS. Transmission electron microscopy (TEM) was performed on RPE cells cultured on transwell filter membranes.
Unlike control RPE cells, SFD RPE cultured on transwell filter membranes did not elaborate an ECM, as detected by transmission electron microscopy. Metabolite analysis revealed a 30-fold increase in 4-hydroxyproline, a metabolite produced by collagen degradation, suggesting that metalloproteinases may be more active in the SFD RPE. Further analysis demonstrated that there was a 25% decrease in reductive flux of alpha-ketoglutarate to citrate and an overall decrease in 13C glutamine-derived M3 metabolites such as malate, fumarate, and aspartate compared to controls, indicating impaired reductive carboxylation in SFD RPE. In addition, SFD RPE appeared to be more energy depleted as noted by a decrease in the NAD+/NADH ratio and an increase in the AMP/ATP ratio. Finally, we determined that SFD RPE have increased susceptibility to oxidative stress that can be rescued by supplementation with nicotinamide mononucleotide.
Collagen degradation, reductive carboxylation, and mitochondrial bioenergetics are altered in SFD RPE. These changes may contribute to their susceptibility to oxidative stress.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.
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