[Studies of WBN/Kob rat, 18th report: effect of 1 alpha-OH-D3 on diabetic osteopenia]

We examined the effect of 1 alpha-OH-D3 on diabetic osteopenia in spontaneously-developed diabetic WBN/Kob rats. Diabetic male WBN/Kob rats aged 12 to 15 months were randomly divided into 1 alpha-OH-D3-treated group (n = 6) and control group (n = 5). 1 alpha-OH-D3 was administered 3 times a week at an oral dose of 0.1 microgram/kg and triglyceride was administered in the control group during the observation period of 12 weeks. Although plasma Ca level decreased significantly in the vehicle-treated group, there was no significant change in plasma Ca level in the 1 alpha-OH-D3-treated group. Urinary Ca excretion significantly increased in the 1 alpha-OH-D3-treated group compared with that in the vehicle-treated group. As for plasma vitamin D metabolites levels after the 12 week-treatment, although there was no significant difference in plasma 25-OH-D and 24,25(OH)2D levels, plasma 1,25(OH)2D level was significantly increased in the 1 alpha-OH-D3-treated group compared with that in the vehicle-treated group. There was no significant difference in plasma bone-Gla protein level between 1 alpha-OH-D3-treated and vehicle-treated groups. As for bone mineral content (BMC) in the femur measured by a dual energy absorptiometer, BMC was significantly increased in the 1 alpha-OH-D3-treated group compared with than in the vehicle-treated group. In conclusion, 1 alpha-OH-D3 ameliorated diabetic osteopenia in WBN/Kob rats through the normalization of vitamin D metabolism.