Abstract
Hepatoma cell lines are widely used to model the hepatocyte for insulin signaling and fatty liver disease. However, a direct comparison of insulin action in primary hepatocytes and in hepatoma cell lines is needed to validate this model and to better understand liver cancer. Here we have investigated insulin signaling, gluconeogenic gene expression, glucose production, and fatty acid synthase abundance in primary hepatocytes and in HepG2, Hepa 1–6, and McARH7777 hepatoma cell lines. Differences in the electrophoretic profiles of protein extracts from human and mouse primary hepatocytes and the hepatoma cells lines are shown. Compared to primary hepatocytes, hepatoma cells showed high basal phosphorylation of AKT at Thr 308 and constitutively activated RAS-MAPK signaling, which were resistant to the dominant negative Ras mutant H-Ras17N. Hepatoma cell lines also showed defective expression of gluconeogenic enzymes, insulin unresponsive GSK phosphorylation, and marginal glucose production. Hepatoma cells also showed lower protein levels of fatty acid synthase and a largely distinct protein electrophoresis profile from hepatocytes but similar between different hepatoma lines. We conclude that hepatoma cell lines do not accurately model the hepatocyte for insulin action but may be valuable tools to investigate the proteomic changes conferring to hepatocellular carcinoma its peculiar metabolisms.
Highlights
Hepatoma cell lines are widely used to model the hepatocyte for insulin signaling and fatty liver disease
We have found that, compared to primary hepatocytes, hepatoma cell lines display aberrant insulin—receptor tyrosine kinase signaling consisting in elevated basal phosphorylation of AKT at Thr 308 and constitutively activated RAS-MAPK signaling, which were resistant to the effects of the dominant negative Ras mutant H-RAS17N
These results are relevant to the interpretation of a large bulk of scientific literature where these hepatoma cells have been used to model the hepatocyte to investigate insulin signaling, insulin resistance, glucose and lipid metabolism for the study of diabetes and fatty liver disease
Summary
Hepatoma cell lines are widely used to model the hepatocyte for insulin signaling and fatty liver disease. We have investigated insulin signaling, gluconeogenic gene expression, glucose production, and fatty acid synthase abundance in primary hepatocytes and in HepG2, Hepa 1–6, and McARH7777 hepatoma cell lines. Only one recent study has directly compared insulin action in HepG2 and other immortalized hepatocyte cell lines, to the one in primary mouse hepatocytes, and several metabolic differences between these cell types were found[11]. The authors could not measure insulin-induced phosphorylation of insulinreceptor and AKT in HepG2 cells, probably because of technical difficulties, and have not evaluated MAPK signaling, which complicates the interpretation of this study Another recent study compared HepG2 cells with two lines of immortalized hepatocytes for insulin action and hepatokine gene expression[12]. This study has not directly compared HepG2 and immortalized hepatocytes to primary cell cultures, or to the liver in in-vivo settings
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