Protective effects of metallothionein on streptozotocin-induced diabetes in rats

The protective roles of metallothionein (MT) in streptozotocin (STZ)-induced pancreatic damage were investigated using zinc (Zn) as the inducer of MT synthesis in rats. Diabetes was produced in a group of Sprague Dawley rats by a single injection of STZ. In another group of rats, to induce the synthesis of MT, Zn was injected subcutaneously about 12 h before injection of STZ. Rats were sacrificed at about 30 h, 3 and 6 weeks after administration of STZ. The plasma glucose levels in STZ and Zn+STZ group increased significantly in 30 h, 3 and 6 weeks compared with the control group, but the level of glucose in Zn+STZ group was lower than that in the STZ group. Both Zn and MT levels increased in pancreas, liver, and kidney of rats injected with Zn or Zn+STZ. The induction of MT synthesis in pancreas of Zn-injected rats was also demonstrated by Western Blot analysis. Lipid peroxidation induced by STZ was inhibited significantly by pretreatment with Zn. Injection of STZ decreased the activities of superoxide dismutase (SOD) in plasma, liver and pancreas, but injection of Zn had no effect on the activities of SOD. The results support that pretreatment with Zn can partially prevent the development of diabetes induced by STZ injection and it may be related to the effects of MT as a scavenger for the oxygen free radicals.