| Objective: As the incidence rising continuously, the osteoporosis has become of increasing health concern throughout the world. Studies have shown that 60% of senile osteoporosis was caused by the too little bone mass in adolescent. This study was designed to investigate the effect of exercise and Vitamin D supplementation on bone density of mice in growing stage and bone Biomechanics, provide theoretical basis for the function of exercise and vitamin D on improving the peak bone mass.Materials and Methods: Material and grouping: Male mouse C57BL/6,after raised to 7 week old, were divided into 8 groups randomly. No significant differences in weight gain among every group, control group, low-intensity group, mid-intensity group, high-intensity group, Vitamin D group, Vitamin D low –intensity group, Vitamin D mid-intensity group, Vitamin D high –intensity group respectively. Treadmill training protocol: Treadmill training lasted for 5 weeks. The low-intensity group, mid-intensity group and high-intensity group took adaptation training at a speed of 8m/min、12m/min and 18m/min respectively for 20 minutes on a 0°slope in the first week. Medium and high intensity group increased 3m/min the next day and the low-intensity group remained, the slope is 0 °. From the 2nd week to 4th week, The low-intensity group, mid-intensity group and high-intensity group took a training at a speed of 8m/min、18m/min and 24m/min respectively for 50 minutes on a 5°slope. Maintain the respective intensity for 6 days a week, and Sundays off. Irrigation protocol: The mice in Vitamin D group were executed by intragastric administration since the 2nd week. The intragastric administration was executed on Tuesday, Thursday and Saturday in the 2nd week and 3rd week, and executed every day in the 4th and 5th week. Mouse gavage is dose of 5 μg l/g weight. The control group and others were executed by intragastric administration with same dose of propylene glycol as placebo. Testing index and method:Following all the intervention program, bladder massage for all mice and took urine and enucleation of eye ball in the ether anesthesia for blood. If the mouse did not die, dislocate the cervical vertebrae for death at once. Take the left femur and tibia. The left femoral dual energy x-ray bone density,Electronic universal testing machine was used to detect the tibia bonebiomechanical properties, including the maximum load, tensile strengthand elastic modulus. Urine deoxypyridinoline(DPD) using the ELISA method for detecting urine Creatinine(Ucr), serum calcium and phosphorus detection bychemiluminescence detection. Statistical method Analysis and processing of all data using SPSS13.0 software(SPSS,Chicago,IL,USA). Two-factor analysis of variance first, make sure exercise training and activated vitamin D supplement produce independent effects or interactions, the contributed factors were to be compared or do independent sample testing.Results: 1 Weight: Exercise and Vitamin D supplement have no effect on body weight in mice. 2 bone mineral density: Exercise could improve the bone density of mice, of which the mid-intensity group has significant effect and has statistical significance. 3 bone biomechanical properties 3.1 bend(rupture) strength Exercise can improve the fracture strength of growing mice, with low,medium, high breaking strength is hither than in the control group of mice and the high-intensity group, the difference has statistical significance. 3.2 Maximum loading Exercise has no effect on maximum loading, while Vitamin D can increase the maximum loading of mice in growing stage. After further comparison, it was found that Vitamin D high-intensity group is higher than high-intensity group.(P<0.05)3.3 elasticity modulus Separate exercise and vitamin d supplements didn’t effect on elastic modulus(P>0.05)But exercise and vitamin d supplements have synergy(P<0.05)the elasticity modulus of vitamin D Low-intensity and vitamin d high-intensity group is higher than control group. 3.4 Cross-sectional Area : Two factor analysis of variance showed that there was statistical significance,movement of mouse femur cross-sectional area, and took active vitamin D had no statistical significance in cross sectional area; further through two two comparison showed: in control group, there was no significant difference between low intensity exercise group, moderate intensity exercise group and high intensity exercise group; vitamin D+ the strength of high strength and vitamin D+ group was significantly higher than that in vitamin D group and vitamin D+ of low intensity exercise group(p<0.05), vitamin D+ and vitamin D+ in intensity and high intensity exercise group, no difference between the groups; 4 Blood and urine biochemical indexes Exercise and active vitamin d supplementation can reduce mouse urine DPD/Ucr,of which mid and high intensity exercise group are lower than control group(P<0.05)High-intensity group is lower than mid-intensity group( P<0.05); Vitamin D high-intensity group is lower than high-intensity exercise group and vitamin d low-intensity group(P<0.01). Exercise and active vitamin D supplementation had no effect on mice serumcalcium and serum phosphorus.Conclusion: 1 treadmill training can improve bone density of mice in growing stage, mid-intensity group is notable, but low-intensity and high-intensity group has no significant effect. 2 To some extent, mid-intensity and low intensity exercise training can improve the biomechanical properties of the mice in growing stage and high-intensity exercise has no significant effect. 3 Active vitamin D supplements can improve bone strength of mice in growing stage and had a significant effect with mid-intensity and high-intensity exercise. 4 treadmill training and Active vitamin D supplements can reduce the growth of mice DPD/Ucr in urine, buthad no effect on the serum calcium and phosphorus. |
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