Project Summary/Abstract Metabolic relationships between retina and RPE are essential for retina function and survival. Biochemical comparisons of explanted retina to RPE/choroid have revealed striking metabolic differences. Retinas consume glucose rapidly and convert most of it to lactate. Cultured RPE cells and RPE/choroid consume glucose more slowly than retinas. RPE/choroid tissue can oxidize many types of fuels as an alternative to glucose. We proposed that retina and RPE/choroid function synergistically as a “metabolic ecosystem”. RPE/choroid minimizes its own consumption of glucose so more glucose can be delivered to the retina. The simple model we proposed was based on measurements of energy metabolism in cultured cells or in retinal or RPE/choroid explants. Those types of experiments do not prove that these types of metabolic interactions occur in the eye of a living animal. The experiments in this proposal test this idea more directly and more rigorously. We will measure metabolic flux in tissue explants and we will measure it in living mice in which 13C labeled fuels are delivered via a jugular vein catheter. We will use retinas and RPE/choroid from mice in which genes encoding specific enzymes required for metabolism have been disrupted. Our 1st aim is to Identify biochemical changes in degenerated retinas that cause glycolytic intermediates upstream of pyruvate kinase to accumulate. For our 2nd aim we collaborate with other labs that have generated mice with mutations that disrupt specific metabolic activities in retinas. Our 3rd aim is to analyze changes in metabolic interactions caused by disrupted RPE metabolism. Aim 4 will complete metabolic analyses of mouse models with metabolic changes designed to slow degeneration of photoreceptors by enhancing glycolysis in rods and by suppressing it in RPE. Our findings will help the vision community recognize therapeutic strategies that may succesfully treat multiple types of retinal degenerations.