Can Galactose Be Converted To Glucose In HepG2 Cells? -Improving the in vitro Mitochondrial Toxicity Assay for the Assessment of Drug Induced Liver Injury

Human hepatocellular carcinoma cells, HepG2, are often used for drug mediated mitochondrial toxicity assessments. Glucose in HepG2 culture media is replaced by galactose to reveal drug-induced mitochondrial toxicity as a marked shift of drug IC50 values for the reduction of cellular ATP. It has been postulated that galactose sensitizes HepG2 mitochondria by the additional ATP consumption demand in the Leloir pathway, which describes the galactose→glucose conversion. However, our NMR metabolomics analysis of HepG2 cells and culture media showed very limited, if any, galactose metabolism. To clarify the role of galactose in HepG2 cellular metabolism, U-13C6-galactose or U-13C6-glucose was added to HepG2 culture media to help specifically track the metabolism of those two sugars. No conversion to U-13C3-lactate was detected when HepG2 cells were incubated with U-13C6-galactose, while an abundance of U-13C3-lactate was produced when HepG2 cells were incubated with U-13C6-glucose. In the absence of glucose, He...