The Effects Of Treadmill Training And Detraing On Serum Sex Hormones, Bone Mineral Density, And Bone Structure In Ovariectomized Rats

Objective:Postmenopausal osteoporosis is a commen disease occurred in postmenopausal women. Using ovariectomized-induced osteoporosis model, this paper explored the prevention mechanism of treadmill exercise on the bone loss of ovariectomized rats.Methods:Sixty female Sprague-Dawley rats were randomly divided into following three groups: sham-operation (Sham), ovariectomized (OVX), ovariectomized exercised (EX). After one week of adapatation exercise, the EX rat were regular trained for 45 min at a speed of 18 m.min-1 with 5°slope five times a week. At the end of the exercise training all the three groups were also divided into two subgroups according to the body weight. At week16 or week32, the rats were necrosy by abdimibnal blooding. The abdominal fat, uterus, subcutaneous fat, and bone tissues were isolated and weighted. Then the bone mineral density (BMD) and bone mineral content (BMC) in isolated femur, tibiae, and the fifth lumbar vertebrae were detected by dual-energy X-ray. The serum level of FSH, LH, E2, and T were measured by immuno RIA. After the BMD measurement, the fourth lumbar vertebrae, the distal femur and the proximal tibiae were scanned with Micro-CT. Then the biomechanical properties of femur and lumbar vertebrae were detected by compression tests or three-bending test.Result:After 16 weeks of OVX, (1) the body weight, wet weight of abdominal fat and the wet weight of subcutaneous femur fat in OVX were significantly higher than the other two groups. The uterus wet weight was significantly lower than that of in Sham group while no difference was seen compared with the OVX group. (2) Compared with OVX group, the level of serum E2 in EX group was significantly higher while the serum level of T was significantly lower. No difference was seen in serum level of FSH and LH between EX group and OVX group. (3) The BMD in fifth lumbar vertebrae, the proximal and distal femur, and the proximal tibiae as well as maximum load, failure load, elastic modulus, maximum stress, failure stress, failure strain in the fourth lumbar vertebrae were significantly lower than that of sham group. All these changes could be reversed by EX treatment. (4) Compared with the other two groups, the number of trabecular bone in ovariectomized rats was fewer than the other two groups and the trabecular sparse was great.After 32 weeks of OVX, Compared with OVX group:(1)the body weight ,wet weight of abdominal fat and the wet weight of subcutaneous femur fat in EX group were significantly higher, the number of trabecular bone in EX group rats was more,(2)The failure load, elastic modulus, failure stress in the fourth lumbar vertebrae in EX group were significantly lower than the OVX group,the trabecular sparse was smaller. (3) There were no significant changes in other indicators.Conclusions:(1)Treadmill exercise with moderate intensity could inhibit the increase of body fat, increase serum E₂ levels, improve the bone histology and biomechanical properties of lumbar vertebra in OVX rats.(2) Apart from the effect of exercise training on BMD, elastic modulus, and failure stress, all the effects produced by exercise training in OVX rats had disappeared after detraining.