P62/SQSTM1 is required for exercise training‐mediated regulation of antioxidant enzymes in skeletal muscle

Abstract

Oxidative stress has been implicated in the pathogenesis of skeletal muscle wasting. Regular exercise training prevents oxidative stress‐induced muscle wasting at least partially by improving the antioxidant defense system. It has been shown that p62/sequestosome1 (SQSTM1) competitively binds to Keap1 activating the nuclear factor erythroid 2‐related factor 2 (Nrf2), which stimulates transcription of antioxidant enzymes. However, it remains to be determined if this process is active in skeletal muscle. Therefore, this study aims to determine whether p62 is required for the exercise training‐mediated increase in antioxidant enzymes in skeletal muscle. To do so, we used 3 complementary studies: i) C2C12 myotubes were subjected to 110% cyclic uniaxial stretch for 1 and 6 hours at a frequency of 1 Hz to assess whether stretching regulates p62 mRNA expression; ii) C57BL/6 mice were assigned to either voluntary wheel running for 4 weeks or no exercise to examine whether exercise training regulates p62 protein expression and phosphorylation (Ser351), both of which increase p62 affinity for Keap1 binding; and iii) muscle‐specific p62 knockout (p62MKO) and wild‐type littermates (WT) mice were assigned to either exercise training or sedentary groups, and the muscle content of antioxidant enzymes was determined after 4 weeks of exercise training. Our results demonstrated that p62 mRNA levels were significantly increased at 6 hours of mechanical stretch in C2C12 myotubes. Voluntary running in C57BL/6 mice increased p62 protein and p62 phosphorylation in soleus muscle. Moreover, expression of the Nrf2 target antioxidant gene NQO1 in p62MKO skeletal muscle was abolished compared to WT mice. Loss of p62 in skeletal muscle also blunted the exercise training‐mediated increase in antioxidant enzymes (i.e. Cu/ZnSOD, EcSOD) in soleus muscle. These findings indicate that p62 is required for exercise training‐mediated increase of antioxidant enzymes in skeletal muscle likely via modulation of Nrf2 function.Support or Funding InformationThis study was funded by Grant‐in‐Aid for Challenging Exploratory Research (16K13019) and Grant‐in‐Aid for Scientific Research (B) (15H03080) to M. Okutsu.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.