Figure 4. Exogenous pyruvate supports amino acid biosynthesis under GLS1 restriction.

(A) Pathway analysis using MetaboAnalyst 5.0 of metabolites with high [U-¹³C]-pyruvate enrichment in 1 μM CB-839–treated and TGF-β₁–stimulated (1 ng/mL) pHLFs following 48 hours. (B–J) Intracellular isotopolog levels, (F–I) fractional enrichment, and (J) total abundance of specified metabolites in pHLFs grown in DMEM^lo supplemented with [U-¹³C]-glucose (5 mM) or [U-¹³C]-pyruvate (1 mM) and preincubated with media control (0.1% DMSO) or 1 μM CB-839 for 1 hour before stimulation with TGF-β₁ (1 ng/mL) for 48 hours and quantification using LC-MS (n = 3).