TRX-Tg are C57BL/6 mice that carry the human TRX transgene under the control of β-actin promoter. Eight-week-old male TRX-Tg mice and wild type (WT) littermates were intraperitoneally injected with either streptozotocin or vehicle. Mice were grouped as 1) non-diabetic WT, 2) non-diabetic TRX-Tg, 3) diabetic WT, and 4) diabetic TRX-Tg. After 12 weeks of streptozotocin treatment, oxidative stress on the whole body and bone was evaluated, and the physical properties of the femora, and histomorphometry parameters of the tibiae were assessed.
TRX overexpression did not affect either body weight or hemoglobin A1c levels. There were no significant differences in renal function and in serum levels of calcium, phosphate, and intact parathyroid hormone among the four groups. On the other hand, urinary excretion of 8-hydroxydeoxyguanosine (8-OHdG), a marker of oxidative DNA damage, was significantly elevated in diabetic WT and attenuated in diabetic TRX-Tg. Immunohistochemical staining for 8-OHdG revealed marked intensity in the bone tissue of diabetic WT compared with non-diabetic WT, while staining was attenuated in diabetic TRX-Tg. TRX overexpression partially restored reduced bone mineral density and prevented the suppression of bone formation observed in diabetic WT. Increased oxidative stress in diabetic condition contributes to the development of diabetic osteopenia. Suppression of increased oxidative stress by TRX induction could be a potential therapeutic approach for diabetic osteopenia.