Malic acid

All reagents were Fisher Optima grade (Fisher Scientific, Hanover Park, IL). Authentic chemical standards were obtained from Sigma-Aldrich (St. Louis, MO) (citric acid, lactic acid, cis-aconitic acid, isocitric acid, malic acid, phenylacetic acid, hippuric acid, hexanedioic acid, threonine, palmitic acid, methylsuccinic acid, succinic acid, glycine, leucine, asparagine, isoleucine, serine, lysine, pyroglutamic acid, pipecolic acid, 3-hydroxybutyric acid, glyceric acid, alanine, and aspartic acid), Santa Cruz Biotechnology (Dallas, TX) (propionylglycine), or MP Biomedicals (Santa Ana, CA) (4-hydroxyproline). Internal standards were obtained from Sigma-Aldrich (4-nitrobenzoic acid) or Cambridge Isotope Laboratories (Andover, MA) (citric acid-d₄, D-sorbitol-¹³C₁, D,L-glutamic acid-d₅, and L-leucine-d₃). Chemicals for derivatization and analysis were obtained from Sigma-Aldrich (urease type III, anhydrous sodium sulfate, C4–C24 FAMEs, methyl nonanoate, and alkane standard mix [C₁₀-C₄₀]) or Thermo Scientific (Waltham, MA) (N-methyl -N- [trimethylsilyl] -trifluoroacetamide (MSTFA) with 1% [vol/vol] trimethyl-chlorosilane (TMCS)).

The pCMV5-Flag-XBP1s plasmid was purchased from Addgene. Human TNF siRNA, GOT2 siRNA and control siRNA were obtained from Thermo Fisher Scientific. The mitochondrial respiration inhibitors Antimycin A, Rotenone and Oligomycin were purchased from Agilent Technologies, Piericidin A was from Cayman Chemical. NAD⁺ was obtained from Cayman Chemical. α-ketoglutaric acid, succinic acid, L-aspartic acid, α-ketobutyric acid, L-asparagine were from Sigma-Aldrich. Malic acid was from Santa Cruz Biotechnology. MitoTracker Red and MitoTracker Green were purchased from Thermo Fisher Scientific. Assay kits for aspartate, oxaloacetate, NAD⁺/NADH and phosphatidylcholine were obtained from Sigma-Aldrich. Elisa kit for human TNF was from Thermo Fisher Scientific.