Fig. 3.

Schematic of potential metabolic links among photoreceptors and support cells. RPE cells may uptake: 1) glucose from the choroid and transport it to photoreceptors where glucose is converted to lactate through glycolysis and then used by RPE as metabolic fuel; 2) palmitate from the choroid and convert it to ketone bodies, which are then used in photoreceptors as energy fuel. RPE may also transfer lipid droplets to photoreceptors for energy production. Photoreceptors may spare lactate to fuel Müller glial cells. Müller glial cells uptake glutamate released from photoreceptors and convert it to glutamine. Glutamine as well as lactate and lipoprotein from Müller glial cells may be transported to photoreceptors and used as energy substrates. The metabolic links need to be further validated. BM, Bruch’s membrane.