Endogenous CSE/Hydrogen Sulfide System Regulates the Effects of Glucocorticoids and Insulin on Muscle Protein Synthesis

Abstract

Aims. Insulin and glucocorticoids play crucial roles in skeletal muscle protein turnover. Fast-twitch glycolytic fibres are more susceptible to atrophy than slow-twitch oxidative fibres. Based on accumulating evidence, hydrogen sulfide (H2S) is a physiological mediator of this process. The regulatory effect of H2S on protein synthesis in fast-twitch fibres was evaluated. Results. A NaHS (sodium hydrosulfide) injection simultaneously increased the diameter of M. pectoralis major (i.e., fast-twitch glycolytic fibres) and activated the mammalian target of the rapamycin (mTOR)/p70S6 kinase (p70S6K) pathway. Dexamethasone (DEX) inhibited protein synthesis, downregulated mTOR and p70S6K phosphorylation, and suppressed the expression of the cystathionine γ-lyase (CSE) protein in myoblasts. The precursor of H2S, L-cysteine, completely abolished the inhibitory effects of DEX. The CSE inhibitor DL-propargylglycine (PAG) completely abrogated the effects of RU486 on blocking the suppressive effects of DEX. The H2S donor NaHS increased the H2S concentrations and abrogated the inhibitory effects of DEX on protein synthesis. Insulin increased protein synthesis and upregulated CSE expression. However, PAG abrogated the stimulatory effects of insulin on protein synthesis and the activity of the mTOR/p70S6K pathway. Innovation. These results demonstrated that CSE/H2S regulated protein synthesis in fast-twitch muscle fibres, and glucocorticoids and insulin regulated protein synthesis in an endogenous CSE/H2S system-dependent manner. Conclusions. The results from the present study suggest that the endogenous CSE/H2S system regulates fast-twitch glycolytic muscle degeneration and regeneration.