Propionate induces mRNA expression of gluconeogenic genes in bovine calf hepatocytes

Hepatocytes monolayers from neonatal calves were used to determine the responses of the cytosolic phosphoenolpyruvate carboxykinase (PCK1) mRNA expression to propionate and direct hormonal cues including cyclic AMP (cAMP), dexamethasone, and insulin. The responses of other key gluconeogenic genes, including mitochondrial phosphoenolpyruvate carboxykinase (PCK2), pyruvate carboxylase (PC), and glucose-6-phosphotase,(G6PC), were also measured. Expression of PCK1 was linearly induced with increasing propionate concentrations in media and 2.5 mM propionate increased PCK1 mRNA at 3 and 6 h of incubation; however, the induction disappeared at 12 and 24 h. The induction of PCK1 mRNA by propionate was mimicked by 1 mM cAMP, or in combination with 5 mu M dexamethasone, but not by dexamethasone alone. The induction of PCK1 mRNA by propionate or cAMP was eliminated by addition of 100 nM insulin. Additionally, expression of PCK2 and PC mRNA was also induced by propionate in a concentration-dependent manner. Consistent with PCK1, propionate-stimulated PCK2 and PC mRNA expression was inhibited by insulin. Expression of G6PC mRNA was neither affected by propionate nor cAMP, dexamethasone, insulin, or their combinations. These findings demonstrate that propionate can directly regulate its own metabolism in bovine calf hepatocytes through upregulation of PCK1, PCK2, and PC mRNA expression.