Investigation of Fructose Metabolism in Hypoxic Liver Cancer Using 13C Nuclear Magnetic Resonance Spectroscopy

Fructolysis is the simple pathway which converts fructose, an isomer of glucose, into 2, 3-carbon molecules, dihydroxyacetone-P and glyceraldehyde which are used as part of glycolysis which is the main energy pathway for cellular metabolism. The enzyme which initiates fructolysis, fructokinase, is primarily found in the liver and is highly specific to fructose. Therefore, a large portion of the fructose in liver cancer is used for glycolysis and is converted into lactate due to the Warburg Effect. In fact, liver cancer cells can often survive on fructose alone for their main carbon source. Under hypoxic conditions, the canonical response of the cell is to increase glycolytic enzymes and anaerobic production of lactate for its energy needs. Therefore, we expected to see an increase in fructose metabolism in 2% O2 hypoxia when fructose and glucose were available to the cell at the same time. However, for HUH7 and HEPG2 we instead see a distinct fructose metabolism and response to hypoxia. HUH7 seems to significantly decrease fructose metabolism under hypoxia while HEPG2 seems to increase the metabolism alongside glucose. For our NMR experiments we grew both HuH7 and HEPG2 liver cancer cells under both normoxic (20% O2) and hypoxic (2% O2) incubation conditions with different combinations of 10mM [1-¹³C] glucose and 10mM [1-¹³C] fructose available to the cell. The cell and media extracts were analyzed with 13C Nuclear Magnetic Resonance. These results will be discussed together with other supporting data.