Prevention of type I diabetes by low-dose gamma irradiation in NOD mice.

Pretreatment with nonlethal, low-dose irradiation has been shown to have a protective effect against oxidative injury in animal tissues. Since oxidative injury of tissues is known to be a major cause of many human diseases, we examined the effect of low-dose irradiation on the progression of type I diabetes in mice. Nonobese diabetic (NOD) mice were treated with gamma irradiation and the progression of the disease was monitored. An elevated level of glucose in urine was first detected at 15 weeks of age in the control NOD mice, whereas the detection was delayed as long as 7 weeks when the mice received a single dose of 0.5 Gy total-body irradiation between 12 and 14 weeks of age. The greatest effect was observed in the mice irradiated at 13 weeks of age. The increase in blood glucose and decrease in blood insulin were effectively suppressed by irradiation at 13 weeks of age. Both suppression of cell death by apoptosis and an increase in superoxide dismutase (SOD) activity were observed in the pancreas 1 week after irradiation. The results indicate that treatment with 0.5 Gy gamma rays suppresses progression of type I diabetes in NOD mice. This is the first report on the preventive effect of low-dose irradiation on disease progression.