22-Oxacalcitriol attenuates bone loss in nonobese type 2 diabetes

Active vitamin D is a major therapeutic agent for bone disease. Although some studies have reported that vitamin D ameliorates bone disease related to diabetes, the mechanism remains unclear. Our study investigated the effect of the vitamin D receptor activator 22-oxacalcitriol (OCT) on bone disease in a rat model of diabetes. OCT was administered at a dose of 0.2μg/kg three times per week for 10weeks. We performed blood and urine analyses, single energy X-ray absorptiometry, micro-computed tomography, bone histomorphometry, and oxidative stress assessment in rats at 30weeks of age. OCT did not affect hemoglobin A1c or serum calcium levels. Bone mineral density (BMD), bone volume in the cortical and trabecular bones, and bone turnover were decreased in rats with diabetes. OCT treatment increased BMD and bone formation and tended to increase bone volume in the trabecular bone, but did not change bone volume in the cortical bone or bone resorption. The urinary oxidative stress marker 8-hydroxydeoxyguanosine (8-OHdG) excretion and the number of 8-OHdG-positive cells in bone were increased in rats with diabetes, and OCT treatment suppressed these increases. Our data suggest that OCT attenuated bone loss in a rat model of diabetes. This attenuation may be partially mediated by improved bone formation resulting from the antioxidative effect of OCT.