Soymilk Improves Muscle Weakness in Young Ovariectomized Female Mice

Yuriko Kitajima,Yusuke Ono,Shizuka Ogawa,Shintaro Egusa

doi:10.3390/nu9080834

Abstract

Estrogens play a key role in an extensive range of physiological functions in various types of tissues throughout the body in females. We previously showed that estrogen insufficiency caused muscle weakness that could be rescued by estrogen administration in a young female ovariectomized (OVX) mouse model. However, long-term estrogen replacement therapy increases risks of breast cancer and cardiovascular diseases. Soymilk contains plant-based protein and isoflavones that exert estrogen-like activity. Here we examined the effects of prolonged soymilk intake on muscle and its resident stem cells, called satellite cells, in the estrogen-insufficient model. Six-week-old C57BL/6 OVX female mice were fed with a dried soymilk-containing diet. We found that prolonged soymilk intake upregulated grip strength in OVX mice. Correspondingly, cross-sectional area of tibialis anterior muscle was significantly increased in OVX mice fed with soymilk. Furthermore, soymilk diet mitigated dysfunction of satellite cells isolated from OVX mice. Thus, these results indicated that prolonged soymilk intake is beneficial for improving muscle weakness in an estrogen-insufficient state in females.

Highlights

Skeletal muscle is a highly plastic tissue that adapts muscle mass and strength in response to exercise stimuli such as resistance training
One week following the surgery, mice were randomly divided into two groups: one was given the conventional food, while the other was given the conventional food replaced by dried soymilk composed of 5% total protein (11.05% of total calorie was replaced by soymilk, termed low-soymilk (Low-SM)) (Table S1), for 24 weeks
We showed that estrogen insufficiency resulted in a decrease in muscle the previous we showed estrogen resulted in a decrease muscle force forceIn generation andstudy, induced muscle that atrophy in a insufficiency time‐dependent manner

Summary

Introduction

Skeletal muscle is a highly plastic tissue that adapts muscle mass and strength in response to exercise stimuli such as resistance training. Muscle mass and strength are decreased with denervation, disuse and aging [1,2]. Skeletal muscle characteristics are influenced by steroid hormones including glucocorticoids, androgens and estrogens [3,4]. Estrogens have crucial roles in an extensive range of physiological functions in various types of tissues throughout the body including bone, skeletal muscle, and white-adipose tissues [5]. Studies showed that estrogens maintain muscle strength and promote activation of muscle stem cells, called satellite cells [6,7]. Our previous study reported that reduced level of estrogens resulted in a decrease in myofiber-sizes and grip strength in ovariectomized (OVX) young female mice [8]

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Discussion

Conclusion