Immobilization induces skeletal muscle fibrosis characterized by increasing collagen synthesis in the perimysium and endomysium. Transforming growth factor-β1 (TGF-β1) is associated with this lesion via promoting differentiation of fibroblasts into myofibroblasts. In addition, reactive oxygen species (ROS) are shown to mediate TGF-β1-induced fibrosis in tissues. These reports suggest the importance of ROS reduction for attenuating skeletal muscle fibrosis. Astaxanthin, a powerful antioxidant, has been shown to reduce ROS production in disused muscle. Therefore, we investigated the effects of astaxanthin supplementation on muscle fibrosis under immobilization. In the present study, immobilization increased the collagen fiber area, the expression levels of TGF-β1, α-smooth muscle actin, and superoxide dismutase-1 protein and ROS production. However, these changes induced by immobilization were attenuated by astaxanthin supplementation. These results indicate the effectiveness of astaxanthin supplementation on skeletal muscle fibrosis induced by ankle joint immobilization.
Reduced ovarian hormone levels associated with menopause or ovariectomy (OVX) not only result in vascular dysfunction but also lead to structural abnormalities in capillaries. Therefore, the effect of OVX on the three-dimensional (3-D) architecture of capillary networks and the underlying molecular mechanisms were investigated in rat soleus muscle. Seven-week-old female Wistar rats were divided into the OVX and sham-treated (Sham) groups. The OVX group exhibited lower endurance exercise capacity compared to the sham group and resulted in decreased capillary diameter, number of anastomoses and capillary/anastomosis volume in soleus muscle, indicating 3-D structural abnormalities of capillary networks. Furthermore, OVX led to increased concentrations of thrombospondin-1 (TSP-1) protein and a decreased VEGF-A/TSP-1 ratio, an indicator of angio-adaptations, in soleus muscle compared with the Sham group. These results indicate OVX may induce 3-D capillary regression in soleus muscle through an imbalance between VEGF-A and TSP-1 expression, possibly associated with decreased exercise tolerance in ovariectomized rats.
New concept as wearable heart rate and gravity sensing system requires the development of bio‐signal acquisition device to be easily integrated into the health management in space, microgravity and hypergravity. The purpose of this study is to examine the acute effects of microgravity and hypergravity on the frequency domain analysis of heart rate variability (HRV) with the new wearable sensing system for electrocardiogram and gravity acquisition during parabolic flight. Six healthy volunteers underwent a series of experiments in sitting position involving parabolic flight. In this study, a new wearable sensing system “Mybeat” (Union Tool, Co., Tokyo) for Electrocardiogram and gravity acquisition was used. The ratio of low frequency to high frequency (LF/HF) components of HRV in the hypergravity phase before microgravity during parabolic flight was higher than that in horizontal before parabolic flight. In microgravity, the LF/HF components of HRV decreased. In contrast, there were no differences in the HF components of HRV between different gravity phases during parabolic flight. These results suggest that the acute effect of the different gravity phases on autonomic nervous activity might be affected by the modulating the dominance between sympathetic and parasympathetic nervous activity. In addition, the system could simultaneously provide information about the gravity and HRV in different gravity phases during parabolic flight. Supported by Grants‐in‐Aid for Science Research from the Japanese Ministry of Education, Culture, Sports, Science and Technology.
Reactive oxygen species (ROS) impairs mitochondrial respiratory chain and capillary structure in atrophied muscle. Impaired mitochondria and capillary are also associated with a decrease of exercise tolerance. Reloading promotes recovery from atrophy, whereas reloading induces the overexpression of ROS. Therefore, we investigated the effects of reloading and anti‐oxidant supplementation for the mitochondria enzyme activity, capillary number and oxidative stress marker during recovery from disuse‐induced muscle atrophy. Hindlimb unloading resulted in a reduction of citrate synthase (CS) activity, capillary‐to‐fiber (C/F) ratio and expression of PGC‐1α protein, and an increase of superoxide dismutase (SOD)‐2. Reloading after unloading improved the decreased CS activity and PGC‐1α expression level, but C/F ratio could not be recovered. Astaxanthin, anti‐oxidant, supplementation maintained all of them to control level through the unloading and reloading conditions. In addition, astaxanthin supplementation attenuated the overexpression of SOD‐2. These results suggest that astaxanthin supplementation approach may be effective as a therapeutic strategy under recovery conditions involving muscular debilitation.Supported by Grants‐in‐Aid for Science Research from the Japanese Ministry Education, Culture, Sports, Science and Technology, and the internal funds of Fuji Chemical Industry Co. Ltd.
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