Abstract 4708: Mammalian glutamine metabolism controls circadian rhythm through regulation of reactive oxygen species

Abstract Circadian rhythms are twenty-four hour physiologic cycles present in all eukaryotes that control a variety of organismal processes, including metabolism, but the role of metabolism in control of circadian rhythms is still not well understood. Peripheral clocks such as those present in the liver control metabolic pathways such as glucose metabolism and respiration as well as amino acid metabolism. It has been recently demonstrated that the availability of the metabolite NAD (nicotinamide adenine dinucleotide) can feed back to control circadian rhythm. There is much interest in targeting glutamine metabolism in cancer, but it is still not fully understood how inhibition of glutamine metabolism affects normal cell physiology, including circadian rhythm. Here we show using the commonly-used circadian model U2OS osteosarcoma cells and other cell lines that glutamine withdrawal blocked proper circadian oscillation of gene expression. Glutamine withdrawal led to distinct and dramatic changes in circadian gene expression in several cell lines with highly different tissue origins, which could be rescued by addition of the cell permeable TCA-intermediate α-ketoglutarate. However, cells withdrawn from glutamine did not show signs of metabolic stress or impairment of the mTOR pathway. While alterations to histone modifications possibly stemming from impairment of αKG-dependent enzymes were observed, these did not explain the observed alterations in circadian rhythm. Rather, RNA-seq analysis of genetic changes after glutamine withdrawal and α-ketoglutarate rescue revealed strong induction of several genetic pathways associated with reactive-oxygen species (ROS) induction, particularly those resulting from chemotherapy or photodynamic therapy of cancer. Further supporting the importance of ROS in regulation of circadian rhythm, addition of cell permeable antioxidants rescued the disruption of circadian oscillation in the absence of glutamine. Finally, inhibiting expression of the key ROS-defense catalase phenocopied circadian rhythm disruption observed after glutamine withdrawal. Together, these data suggest that glutamine availability and metabolism are critical to support circadian rhythm and gene expression through modulation of intracellular ROS, and furthermore that cancer treatments that lead to induction of ROS could affect normal cellular circadian rhythm. We thank the following funding: NIH F32CA180370, NIH F32CA174148, NIH R01CA051497, LLS 610614 Citation Format: Brian J. Altman, Zachary E, Stine, Annie L. Hsieh, Ralph J. Deberardinis, Chi V. Dang. Mammalian glutamine metabolism controls circadian rhythm through regulation of reactive oxygen species. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 4708. doi:10.1158/1538-7445.AM2015-4708