Author
MEISSEN, JOHN - University Of California | |
HIRAHATAKE, KRISTIN - University Of California | |
Adams, Sean | |
FIEHN, OLIVER - University Of California |
Submitted to: Metabolomics
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 8/29/2014 Publication Date: 9/19/2014 Citation: Meissen, J.K., Hirahatake, K.M., Adams, S.H., Fiehn, O. 2014. Temporal metabolomic responses of cultured HepG2 liver cells to high fructose and high glucose exposures . Metabolomics. 11(3):707-721, DOI:10.1007/S11306-014-0729-8. Interpretive Summary: High fructose consumption has been implicated with deleterious effects on human health, including hyperlipidemia elicited through de novo lipogenesis. However, more global effects of fructose on cellular metabolism have not been elucidated. In order to explore the metabolic impact of fructose-containing nutrients, we applied a new comprehensive metabolite profiling strategy using extracts from a human liver cell model, cultured HepG2 cells, exposed to fructose, glucose, or fructose + glucose. A total of 156 unique known metabolites and a large number of unknown compounds were detected in these cells, and examining their concentrations over time following sugar exposure revealed metabolite changes due to both utilization of fructose specifically and due to high carbohydrate loads independent of sugar type. Fructose was shown to be partially converted to sorbitol, and generated higher levels of fructose-1-phosphate as a precursor for glycolytic intermediates. Differentially regulated ratios of 3-phosphoglycerate to serine pathway intermediates in high fructose media indicated a diversion of carbon backbones away from energy metabolism and toward anabolic pathways yielding newly-made metabolites. Additionally, high fructose conditions changed levels of complex lipids toward phosphatidylethanolamines and increased levels of fatty acylcarnitines, suggesting a reduced mitochondrial capacity for beta-oxidation. These studies highlight, for the first time, global metabolic shifts that occur dynamically in human liver-type cells in response to glucose, fructose specifically or those pathways that are shared in these cells regardless of sugar type. This provides insights that may shed light on events that occur in human liver following high intakes of sucrose (table sugar) or the metabolically-equivalent high fructose corn syrup (HFCS). Technical Abstract: High fructose consumption has been implicated with deleterious effects on human health, including hyperlipidemia elicited through de novo lipogenesis. However, more global effects of fructose on cellular metabolism have not been elucidated. In order to explore the metabolic impact of fructose-containing nutrients, we applied both GC-TOF and HILIC-QTOF mass spectrometry metabolomic strategies using extracts from cultured HepG2 cells exposed to fructose, glucose, or fructose + glucose. Cellular responses were analyzed in a time-dependent manner, incubated in media containing 5.5 mM glucose + 5.0 mM fructose in comparison to controls incubated in media containing either 5.5 mM glucose or 10.5 mM glucose. Mass spectrometry identified 156 unique known metabolites and a large number of unknown compounds, which revealed metabolite changes due to both utilization of fructose and highcarbohydrate loads independent of hexose structure. Fructose was shown to be partially converted to sorbitol, and generated higher levels of fructose-1-phosphate as a precursor for glycolytic intermediates. Differentially regulated ratios of 3-phosphoglycerate to serine pathway intermediates in high fructose media indicated a diversion of carbon backbones away from energy metabolism. Additionally, high fructose conditions changed levels of complex lipids toward phosphatidylethanolamines and increased levels of fatty acylcarnitines, suggesting a reduced mitochondrial capacity for beta-oxidation. |