Author(s): YASUNAGA, S., FUJIE, S.1, HORII, N.2, INOUE, K.1, IEMITSU, M.1, Institution: RITSUMIKAN UNIVERSITY, Country: JAPAN, Abstract-ID: 1052

INTRODUCTION:
Muscle mass and muscle function decline with advance of age, and muscle fibrosis is involved in this muscle loss. Our studies showed that high-intensity resistance training improves muscle fibrosis via down-regulation of muscle component 1q (C1q)-Wnt signaling pathway in older adults and senescent mice. Low-intensity resistance training is effective in improving muscle mass and muscle function in older adults, but it is not clear whether low-intensity resistance training improves muscle fibrosis with advance of age. This study aimed to clarify the effects of resistance training at low- and high-intensity on muscle fibrosis in senescent mice.
METHODS:
In this study, 38-week-old male senescence-accelerated mouse prone 1 (SAMP1) mice were divided into three groups: sedentary control (CON, N=7), low-intensity resistance training (LRT, N=8) and high-intensity resistance training (HRT, N=8) groups. LRT was performed 3 days a week, 6 to 8 sets per day with rest between sets for 1 minute for 12 weeks using a climbing ladder with attachment 40% lead weight of body weight to the mouses tail. HRT was performed using the same protocol with 70~100% loads of body weight. The frozen tibialis muscle (TA) samples were sliced, subjected to Masson trichrome staining, and then measured the cross-sectional area (CSA) of muscle fibers and fibrotic area. Serum C1q levels were detected using a sandwich ELISA kit. The one-way ANOVA was used to compare among the three groups. A p<0.05 was considered statistically significant.
RESULTS:
After 12 weeks of each intervention, the TA muscle mass in the HRT group was significantly higher than the CON and LRT groups (each p<0.05). Maximal carrying capacity of lead weight and CSA of TA muscle in the HRT group were significantly higher than those in the CON and LRT groups, and the LRT group was significantly higher to compared with the CON group (each p<0.05). In addition, muscle fibrosis and circulating C1q levels in the HRT and LRT groups were significantly lower than those in the CON group (each p<0.05). No significant differences in muscle fibrosis and circulating C1q levels between the HRT and LRT groups were observed.
CONCLUSION:
These findings suggest that low-intensity resistance training in senescent mice may suppress muscle fibrosis and promote muscle hypertrophy with a decrease in C1q secretion, similar to high-intensity resistance training.