Effect of vitamin K2 on trabecular bone mass in senescence‐accelerated mice P6 with water‐immersion restraint stress (1033.1)

Vitamin K2 (VK2) has been used as a therapeutic agent for osteoporosis, and might reduce the frequency of fractures by improving bone quality. In the present study, effect of VK2 on bone turnover was investigated using the P6 strain of senescence‐accelerated mice (SAMP6). We used water‐immersion restraint stress (WRS) as bone resorption model to SAMP6. Six week old male SAMP6 were divided into three groups, control, WRS, and WRS + VK2. WRS was performed 6 h/day, and VK2 (30mg/kg) was injected subcutaneously after WRS. These stresses were performed 3 times/week for 4 week.No growth retardation was observed in WRS groups compared to control. Bone histomorphometrical study showed that trabecular bone in second cancellous area at the distal femur showed significant decrease in WRS, and this reduction was recovered by VK2. Reduction of trabecular bone was caused by the activation of osteoclasts, and activity of osteoclasts was suppressed by VK2. Moreover, number of osteoblasts were significantly increased in WRS, and WRS + VK2. Mineral apposition rate was significantly higher in WRS, and WRS + VK2 than control. WRS reduced the BMD by high bone turnover, indicating that both bone formation and bone resorption were increased. Moreover, VK2 was effective to recover from bone mineral loss by WRS. This study was supported by Kakenhi (22500684).Grant Funding Source: Supported by Kakenhi