Abstract
In recent years, some metal ions and their complexes have been found to treat diabetes mellitus (DM) in not only experimental animals but also humans. Among them, vanadyl(IV) and zinc(II) ions as well as their complexes have been shown to be the most expectant agents. Then, the differences in the insulin-mimetic effects of vanadyl(IV) and zinc(II) ions as well as their complexes were investigated. In vitro insulin-mimetic activities of the compounds were estimated by both glucose uptake enhancing effect and inhibitory effect of free fatty acid (FFA) release in isolated rat adipocytes treated with epinephrine. Vanadyl(IV) compounds exhibited the higher glucose uptake enhancing activities than zinc(II) compounds, however, vanadyl(IV) compounds showed the lower inhibitory activities of FFA release than zinc(II) compounds. Next, we examined the blood glucose lowering effects of the compounds in both streptozotocin (STZ)-induced type 1 DM mice and type 2 DM KK-Ay mice by intraperitoneal injection of the compounds. Vanadyl(IV) compounds lowered the high blood glucose levels in both types of DM mice. In contrast, zinc(II) showed the blood glucose lowering effects in KK-Ay mice.
