Activation by Vanadate of Glycolysis in Hepatocytes From Diabetic Rats

In hepatocytes from starved streptozocin-induced diabetic rats, vanadate increases the glycolytic flux because it raises the levels of fructose-2,6-bisphosphate (Fru-2,6-P₂), the main regulatory metabolite of this pathway. This effect of vanadate on Fru-2,6-P₂ levels is time and dose dependent, and it remains in cells incubated in a calcium-depleted medium. Vanadate is also able to counteract the decrease on Fru-2,6-P₂ levels produced by glucagon, colforsin, or exogenous cAMP. However, vanadate does not modify 6-phosphofructo-2-kinase and pyruvate kinase activities, but it does counteract the inactivation of these enzymes induced by glucagon. Likewise, Fru-2,6-P₂ase activity is also not affected by vanadate. In addition, vanadate is able to increase the production of both lactate and CO₂ in hepatocytes from streptozocin-induced diabetic rats incubated in the presence of glucose in the medium. Vanadate behaves as a glycolytic effector in these cells, and this effect may be related to its ability to normalize blood glucose levels in diabetic animals.