Estrogen Status Influences Whole-Body Vibration Training-Induced Improvements on Muscle Mass and Strength in Female Ovariectomized Mice.

Estradiol (E2) deficiency arising from menopause is closely related to changes in body composition and declines of muscle mass and strength in elderly women. Whole-body vibration training (WBV) is an emerging approach expected to improve muscle mass and strength of older person, but the underlying mechanisms remain unclear. The balance between protein synthesis and degradation is a determining factor for muscle mass and strength, which is regulated by Akt-mTOR and FoxO1 signal pathway, respectively. In the present study, we firstly determined whether the effects of WBV on muscle mass and strength in ovariectomized female mice was affected by estrogen level, then investigated whether this was associated with Akt-mTOR and FoxO1 signal pathways. We found that (1) WBV, E2 supplementation (E) and WBV combined with E2 supplementation (WBV+E) significantly increased serum estradiol content, quadriceps muscle mass and grip strength in ovariectomized mice, accompanied with alterations of body composition (reducing fat content, increasing lean body mass and lean percent), furthermore, the altered degrees of these indicators by WBV+E were greater than WBV alone; (2) WBV, E and WBV+E remarkably increased the activities of Akt and mTOR and decreased FoxO1 activity, and the changed degrees by WBV+E were greater than WBV alone; (3) Pearson correlation coefficient revealed that serum estradiol content was positively correlated with Akt and mTOR activities, while inversely associated with FoxO1 activity. We concluded that WBV could significantly increase muscle mass and strength in ovariectomized mice, which might achieve through activating Akt-mTOR and suppressing FoxO1 signal pathways, and the improving effect of WBV on muscle mass and strength was better when in the presence of estrogen.