Long-term correction of STZ-diabetic rats after short-term i.p. VOSO4 treatment: Persistence of insulin secreting capacities assessed by isolated pancreas studies

We have previously shown that 3 week oral VOSO₄ treatment of streptozotocin (STZ, 60 mg/kg)-induced diabetic rats was able to correct diabetes for 13 weeks after treatment withdrawal. In the present study, we investigated whether a short-term (8 days) i.p. VOSO₄ treatment was similarly able to reverse the diabetic state. Insulin secretory capacities were assessed at distance of treatment using the isolated pancreas preparation. Seven treatment-groups were performed: high dose VOSO₄-treated diabetics (HVD, 1.3 mM/kg/8 days), food-restricted diabetics (FRD, food adjusted to HVD levels), low dose VOSO₄-treated diabetes (LVD, 0.06 mM/kg/day), insulin-treated diabetics (ID, dose adjusted to normalize glycaemia) and VOSO₄ (0.06 mM/kg/day) + insulin (dose adjusted to normalize glycaemia in the presence of vanadium)-treated diabetics (IVD), in addition to the corresponding untreated non-diabetic controls (C) and diabetics (D). Our results indicate that long-term correction of diabetes (a) can be obtained after an 8 day treatment using i.p. VOSO₄ in diabetic animals retaining some degree of pancreatic function, (b) is not obtained with insulin treatment or food restriction although the association of VOSO₄ and insulin was found beneficial, (c) can be prolonged in some individuals for at least 4 months, i.e. in conditions such that tissue vanadium concentrations had returned to values close to pre-treatment levels, (d) is associated with improved and in some cases normalized insulin secretion from isolated pancreas. The protective or corrective role of VOSO₄ on diabetes-related pancreatic alterations, as well as the potential of the VOSO₄-insulin association should be further studied in view of the possible use of vanadium derivatives in the treatment of diabetes.