Malignant brain tumors are known to utilize acetate as an alternate carbon source in the citric acid cycle for their bioenergetics. 13C NMR-based isotopomer analysis has been used to measure turnover of 13C-acetate carbons into glutamate and glutamine pools in tumors. Plasma from the patients infused with [1,2-13C]acetate further revealed the presence of 13C isotopomers of glutamine, glucose, and lactate in the circulation that were generated due to metabolism of [1,2-13C]acetate by peripheral organs. In the tumor cells, [4-13C] and [3,4-13C]glutamate and glutamine isotopomers were generated from blood-borne 13C-labeled glucose and lactate which were formed due to [1,2-13C[acetate metabolism of peripheral tissues. [4,5-13C] and [3,4,5-13C]glutamate and glutamine isotopomers were produced from [1,2-13C]acetyl-CoA that was derived from direct oxidation of [1,2-13C] acetate in the tumor. Major portion of C4 13C fractional enrichment of glutamate (93.3 ± 0.02%) and glutamine (90.9 ± 0.03%) were derived from [1,2-13C]acetate-derived acetyl-CoA.
- C isotopomer
- glutamate and glutamine synthesis
- peripheral metabolism