Autophagy flux is decreased in response to endurance exercise training in aged mouse skeletal muscle.

Hong, Yong-Sik; Oh, Sung-Hee; Lee, Dong-Won; Ju, Jeong-Sun; Hong, Yong-Sik; Oh, Sung-Hee; Lee, Dong-Won; Ju, Jeong-Sun

Yong-Sik Hong¹, Sung-Hee Oh¹, Dong-Won Lee¹, Jeong-Sun Ju¹

¹The University of Suwon, Hwaseong, Gyeonggi-do, Korea
²The University of Suwon, Hwaseong, Korea
³The University of Suwon, Hwaseong, Korea

Correspondence

Jeong-Sun Ju , Tel: 031-220-2368, Fax: 031-220-2563, Email: jju625@hotmail.com

Received: January 16, 2016; Accepted: February 1, 2016. Published online: February 1, 2016.

ABSTRACT

PURPOSE:
The aims of this study were to investigate if autophagy was up-regulated in skeletal muscle from old mice, and to determine if endurance exercise training can intervene the autophagy process in old mouse muscle tissue.
METHODS:
Two age groups (10-wk and 18-mo old) of mice were assigned either swimming exercise training or sedentary control group. Male wild-type ICR mice performed five daily bouts of one hour swimming per week for 8 weeks. To determine autophagic flux in mouse skeletal muscle, mice were treated with or without 2 days of 0.4 mg/kg/day colchicine (blocking the degradation of autophagosome) administration intraperitoneally following swimming exercise training. Triceps muscles were harvested, and autophagic marker proteins and autophagy-related proteins were analyzed by Western blot analysis.
RESULTS:
The autophagic flux assay demonstrated that swimming training increased the autophagic flux (~3-fold increase in LC3-II, P<.05) in young mice, yet exhibited ~2-fold increase in the autophagic flux in muscle of aged mice. The basal autophagy was also decreased in aged mice (LC3, p62, P<.05). Despite no changes in Beclin-1 proteins, other autophagy marker proteins (Bnip3, Lamp1 and HDAC6) were significantly decreased in aged mice compared with young mice (P<.05).
CONCLUSIONS:
It is concluded that both basal and induced autophagy activated by exercise training was decreased in aged mouse skeletal muscle. The inhibited autophagy in skeletal muscle of aged mice was not reversed by endurance exercise training which activates autophagy in skeletal muscle.

Key words: Autophagy; Autophagic Flux; Endurance Exercise; Aging ; Skeletal Muscle