Evidence for dissociation of gluconeogenesis stimulated by non-esterified fatty acids and changes in fructose 2,6-bisphosphate in cultured rat hepatocytes.

In order to examine the role of fructose 2,6-bisphosphate (Fru-2,6-P2) in non-esterified-fatty-acid-stimulated gluconeogenesis, Fru-2,6-P2 levels were measured in cultured rat hepatocytes under conditions mimicking the fasted state. After addition of either 1.5 mM-palmitate or 10 nM-glucagon, [U-14C]lactate incorporation into glucose increased 2-fold, but only glucagon suppressed Fru-2,6-P2. Prevention of palmitate oxidation with a carnitine palmitoyltransferase-I inhibitor (2-bromopalmitate) diminished glucose production and Fru-2,6-P2 levels. Addition of exogenous glucose to the media increased Fru-2,6-P2 in a dose-related manner, which was further augmented by addition of palmitate. When Fru-2,6-P2 levels were examined in cells cultured under conditions mimicking the fed state (significantly higher basal Fru-2,6-P2 levels and lower glucose production), palmitate oxidation was associated with a significant fall in Fru-2,6-P2. In conclusion, the present studies have demonstrated a dissociation between fatty-acid-stimulated gluconeogenesis and changes in Fru-2,6-P2 in cultured rat hepatocytes. Further experiments suggest that the accumulation of intracellular hexose 6-phosphate as a result of fatty-acid-stimulated gluconeogenesis masks a putative inhibitory effect of fatty acids on Fru-2,6-P2 concentrations.