(A) de novo serine/glycine synthesis pathway. 3PG: 3-phosphoglycerate, PHGDH: 3-phosphoglycerate dehydrogenase, PSAT1: phosphoserine aminotransferase 1, PSPH: phosphoserine phosphatase, SHMT: serine hydroxymethyltransferase. (B) Simplified schematic of steps in de novo serine/glycine synthesis, showing 13C labeling patterns resulting from 13C6 glucose substrate. Red fills indicate 13C atoms. (C–D) 13C-serine/glycine levels in M-huPMCs and P-huPMCs after treatment with 13C-glucose (C) or 13C-serine (D). (E–H) Seahorse XF analysis of M-huPMCs and P-huPMCs. Glycolytic (E–F) and mitochondrial functions (G–H) were evaluated in human Müller cells in primary culture isolated from macula and peripheral regions (n = 4).