Figure 6.

A Proposed Model of Metabolic Communications between Human Retina and RPE/Choroid

Glucose transports through RPE from the choroid to the retina (bold green line). RPE strongly expresses genes in PPP, serine de novo synthesis, and one-carbon metabolism, which can use glucose to generate NADPH. The retina strongly expresses glycolic genes to produce lactate and NADH. The retina imports aspartate and glutamate through upregulated transporters (bold red line). Aspartate can be converted into OAA and malate to recycle NADH into NAD⁺ and bring electrons into mitochondria to produce ATP. Aspartate can also be used for the synthesis of glutamate, asparagine (ASN), N-acetylaspartate (Asp). The retina needs a large amount of glutamate for neurotransmission, the mitochondrial TCA cycle, and biosynthesis of GABA, glutathione (GSH), and glutamine (Gln) (bold blue line). RPE mitochondria use different substrates such as proline (yellow line), BCAAs, and lipids to synthesize NADPH and other metabolites that can be released to be used by the retina. Cone-rich retinas or human macula consumes more pyruvate (bold black line) for mitochondrial metabolism. Brown colored genes are upregulated genes in the retinas or RPE.

See also Figure S11.