Figure 5.

Stable isotope tracing using [U–¹³C₅] glutamine in SFD iRPE cells compared with controls. Steady state isotopic tracing with [U–¹³C₅] Glutamine was conducted for 24 h, and fractional enrichment was calculated and is displayed on the Y axis. M5 glutamine is metabolized to M5 glutamate (A) which converted to either M5 proline (B) or M5 αkg (C). M4 fumarate or M5 citrate (D) or M4 fumarate (E) are produced from reductive carboxylation or oxidation of αKG respectively. Forward flow of the TCA cycle results in M4 Malate (F), M4 Aspartate (G), and M4 Citrate (D). Carbons can exit the TCA cycle to generate M2 pyruvate (H) and M2 lactate (I) via Acetyl CoA or M3 pyruvate and M3 lactate via malic enzyme (ME). (J) M5 glutamine represents glutamine taken up from the media. Individual data points represent biological replicates(n = 7). A two-tailed unpaired Mann–Whitney test was used to evaluate statistical significance. ∗p < 0.05, ∗∗p < 0.01, ∗∗∗p < 0.001, ∗∗∗∗p < 0.0001. Experimental schematic was generated using BioRender. Graphs were made with GraphPad Prism.