Sex-Related Adaptation to Disuse-Induced Skeletal Muscle Wasting

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Sex-Related Adaptation to Disuse-Induced Skeletal Muscle Wasting

Journal Title: Biomedical Journal of Scientific & Technical Research (BJSTR) - Year 2019, Vol 14, Issue 3

Abstract

Males and females have some key different physiologies and hormonal profiles. These differences sometimes impact on muscle adaptation to various extracellular stimuli, including muscle disuse. For example, some investigators reported that muscles in women had a greater response to disuse than men. This suggests that disuse-induced skeletal muscle loss may be sex-specific; however, current evidence is limited and the underlying mechanisms responsible for this difference remain unclear. Nonetheless, growing evidences from human and animal studies are showing that there are sex-related differences in adaptation to muscle disuse, and the FoxO3a signaling pathway may be associated with this phenomenon. Moreover, sex may affect unloading-induced functional neuromuscular adaptations during disuse. This review summarizes sex-specific differential responses to muscle disuse in humans and provides potential mechanisms for such differences in the response to disuse-induced skeletal muscle wasting.Sex-related differences are well known in body composition [1], hormone concentrations [2], muscle fiber type composition [3], and substrate utilization [4]. These differences could affect muscle responses and adaptations to various extracellular stimuli such as exercise [5]. Importantly, some investigators reported that muscles in women have a greater response to disuse [6,7]. The goals of this review are: a) to summarize sex-specific differences in responses to muscle disuse in humans, and b) to discuss the underlying mechanisms responsible for sex-related differences in skeletal muscular wasting.Information on sex-specific differences in muscle adaptation to disuse is still limited. However, some investigators report that women have a greater response to muscle disuse than men. For example, Shackelford et al. [7] demonstrated that 17 weeks of horizontal bed rest induced a greater reduction in whole muscle volume in women (-17.3%) as compared to men (-10.7%) subjects. Moreover, in a side-by-side comparison, women showed a greater decline in thigh muscle size than men, even after shorter periods of bed rest (-21% in 60 days in women vs. -17% in 84 days in men) [8- 11]. In contrast, Yasuda et al. [12] demonstrated that immobilizationinduced loss of knee extensor muscle strength was greater after 14 days of unilateral leg immobilization in women than in men despite a similar extent of atrophy at the myofiber and whole muscle levels. Moreover, after seven days of unloading by unilateral lower limb suspension, women experienced a greater strength decline during maximal isometric contractions, but not muscle mass, than men [13]. In addition, another study showed that the recovery of muscle strength from unloading was slower for women than for men [14]. These data indicate that the reduction in muscle strength and recovery period after disuse are greater in women regardless of the unloading period. However, sex differences are minimal in terms of a reduction in muscle size (2–4%) in the first two weeks of unloading. Collectively, unloading (disuse)-induced skeletal muscle loss and weakness may be sex-specific. However, there is limited evidence supporting this possibility and it depends on the duration of disuse and the method of unloading in human skeletal muscle.

Authors and Affiliations

Toshinori Yoshihara, Hisashi Naito

Keywords

Sex Specific Differences; Muscle Atrophy; Neuromuscular Adaptation; Forkhead Box O Signaling; Toshinori Yoshihara Journal on Medical Science List of Open Access Medical Journal Journals on Medical Case Reports Journals on Medical Drug and Therapeutics Biopsychological Medicine Biomedical Journal Articles Biomedical Open Access Journals

EP ID EP587641
DOI 10.26717/BJSTR.2019.14.002546
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