Vanadium treatment normalizes plasma
glucose levels in
streptozotocin-diabetic rats in vivo, but the mechanism(s) involved are still unclear. Here, we tested the hypothesis that the in vivo effects of
vanadium are mediated by changes in gluconeogenesis. Diabetic rats were treated with
bis(maltolato)oxovanadium(IV) (BMOV) in the
drinking water (0.75-1 mg/ml, 4 wk) or, for comparison, with
insulin implants (4 U/d) for the final week of study. As with
insulin, BMOV lowered plasma
glucose and normalized
phosphoenolpyruvate carboxykinase (PEPCK) and
glucose-6-phosphatase (G-6-Pase)
mRNA in the liver and kidney of diabetic rats. To determine the importance of reducing
hyperglycemia per se, diabetic rats were treated either with a single ED(50) dose of BMOV (0.1 mmol/kg, ip) or with
phlorizin (900 mg/kg.d, 5 d). BMOV rapidly restored PEPCK and G-6-Pase
mRNA and normalized plasma
glucose in responsive (50%) diabetic rats but had no effect on the nonresponsive hyperglycemic rats.
Phlorizin corrected plasma
glucose but had no effect on PEPCK
mRNA and only partially normalized G-6-Pase
mRNA. In conclusion, 1) BMOV inhibits PEPCK
mRNA expression and activity by rapid mechanisms that are not reproduced simply by correction of
hyperglycemia; and 2) BMOV inhibits G-6-Pase expression by complex mechanisms that depend, in part, on correction of
hyperglycemia.