biostudies-literatureCai FNIDDK NIH HHSHoward Hughes Medical InstituteNCI NIH HHSNIGMS NIH HHSNIH HHS1830-1843.e5https://www.ebi.ac.uk/biostudies/studies/S-EPMC10732579biostudies-literatureUnknown35(10)Stable isotopes are powerful tools to assess metabolism. ¹³C labeling is detected using nuclear magnetic resonance (NMR) spectroscopy or mass spectrometry (MS). MS has excellent sensitivity but generally cannot discriminate among different ¹³C positions (isotopomers), whereas NMR is less sensitive but reports some isotopomers. Here, we develop an MS method that reports all 16 aspartate and 32 glutamate isotopomers while requiring less than 1% of the sample used for NMR. This method discriminates between pathways that result in the same number of ¹³C labels in aspartate and glutamate, providing enhanced specificity over conventional MS. We demonstrate regional metabolic heterogeneity within human tumors, document the impact of fumarate hydratase (FH) deficieCell metabolismComprehensive isotopomer analysis of glutamate and aspartate in small tissue samples.PMC10732579P41 GM122698P50 CA196516P50 CA070907R35 CA220449RM1 GM148766U2C DK119889S10 OD028753F31 CA239330R01 DK132254Merritt MEDeBerardinis RJKo BPachnis PGu WBezwada DMartin-Sandoval MCai LCai FYang CDo DWu ZKelekar SMathews TPBrooks BMalloy CRMargulis VMahar RChang MCVu HSZacharias LGOaxaca KCJin ESfalseComprehensive isotopomer analysis of glutamate and aspartate in small tissue samples.Stable isotopes are powerful tools to assess metabolism. ¹³C labeling is detected using nuclear magnetic resonance (NMR) spectroscopy or mass spectrometry (MS). MS has excellent sensitivity but generally cannot discriminate among different ¹³C positions (isotopomers), whereas NMR is less sensitive but reports some isotopomers. Here, we develop an MS method that reports all 16 aspartate and 32 glutamate isotopomers while requiring less than 1% of the sample used for NMR. This method discriminates between pathways that result in the same number of ¹³C labels in aspartate and glutamate, providing enhanced specificity over conventional MS. We demonstrate regional metabolic heterogeneity within human tumors, document the impact of fumarate hydratase (FH) deficie2023-01-01T00:00:00Z2023 Oct2026-04-12T23:18:22.75Z2025-02-19T01:18:31.517ZS-EPMC107325793761158310.1016/j.cmet.2023.07.013