Abstract 792: Acetate production from glucose and coupling to mitochondrial metabolism in mammals
Authors: Liu Xiaojing , Cooper Daniel E. , Cluntun Ahmad A. , Warmoes Marc O. , Zhao Steven , Reid Michael A. , Liu Juan , Lund Peder J. , Lopes Mariana , Garcia Benjamin A. , Wellen Kathryn E. , Kirsch David G. , Locasale Jason W. 
Published: August 2019

Background: In conditions of hyperactive cellular metabolism, excessive cellular nutrient uptake results in incomplete metabolism and excretion of intermediates. These intermediates may serve as unconventional fuel sources satisfy metabolic demands during nutrient scarcity. Interestingly, acetate metabolism provides a parallel pathway for acetyl-CoA production and allows for protein acetylation and lipogenesis independent of citrate conversion to acetyl-CoA. This pathway is important in tumorigenesis, immune alertness, neural plasticity, and other diverse contexts but the origin of acetate has been unclear. Thus, we have conducted a re-evaluation of endogenous acetate generation and the biological relevance.

Method: Cancer cells were cultured in RPMI medium with 13C labelled nutrients in the presence of 18O2. Mouse models of soft tissue sarcoma were generated in a mixed 129/SVJae and C57BL/6 background. A jugular vein catheter was surgically implanted and exteriorized via a vascular access port, which allows infusion of [13C6]-glucose via the venous catheter. Acetate in medium and blood is quantified using [2H3] labelled acetate as the standard after 2-hydrazinoquinoline (HQ) derivatization, and other polar metabolites were directly analyzed after cold methanol extraction. All metabolites were measured using liquid chromatography coupled with high resolution mass spectrometer.

Results: By employing multiple-isotope tracing technology, quantitative proteomics, and mouse genetics tools, we demonstrated that acetate is quantitatively generated from pyruvate, the end product of glycolysis and key node in central carbon metabolism in cancer cells and tumor. One reaction mechanism found to generate acetate occur through altered enzyme activity of thiamine-dependent keto acid dehydrogenases, which transforms their activity to keto acid decarboxylases. The other reaction mechanism to generate acetate occur by reaction with reactive oxygen species (ROS), a finding which potentially links this pathway to numerous physiological and pathophysiological processes. Thiamine starvation and the addition of exogeneous ROS greatly stimulated the ROS contribution to acetate production, which can be used to replenish intracellular acetyl groups. Thus, increased acetate production and release could potentially favor the neighboring cells deficient in cytosolic acetyl-CoA, as demonstrated by co-culturing ACLY KO cells with HCT116 cells.

Conclusion: We have not only provided direct evidence that acetate arises from endogenous metabolism of glucose in mammalian cells, but also identified the regulatory mechanisms, which involve ROS and mitochondrial functions.

Note: This abstract was not presented at the meeting.

Citation Format: Xiaojing Liu, Daniel E. Cooper, Ahmad A. Cluntun, Marc O. Warmoes, Steven Zhao, Michael A. Reid, Juan Liu, Peder J. Lund, Mariana Lopes, Benjamin A. Garcia, Kathryn E. Wellen, David G. Kirsch, Jason W. Locasale. Acetate production from glucose and coupling to mitochondrial metabolism in mammals [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 792.