Effect of skeletal muscle phenotype and gender on fasting-induced myokine expression in mice.

Skeletal muscle secretes myokines, which are involved in metabolism and muscle function regulation. The role of fasting on myokine expression in skeletal muscle is largely unknown. In this study, we used gastrocnemius skeletal muscle RNA sequencing data from fasting male mice in the Gene Expression Omnibus (GEO) database. Adopted male and female C57BL/6J mice that fasted for 24 h were included to examine the effect of fasting on myokine expression in slow-twitch soleus and fast-twitch tiabialis anterior (TA) skeletal muscle. We found that fasting significantly affected many myokines in muscle. Fasting reduced Fndc5 and Igf1 gene expression in soleus and TA muscles in both male and female mice without muscle phenotype or gender differences, but Il6, Mstn and Erfe expression was influenced by fasting with fibre type- and gender-dependent effects. Fasting also induced muscle atrophy marker genes Murf1 and Fbxo32 and reduced myogenesis factor Mef2 expression without muscle fibre or gender differences. We further found that the expression of transcription factors Pgc1α, Pparα, Pparγ and Pparδ had muscle fibre type-dependent effects, and the expression of Pgc1α and Pparα had gender-dependent effects. The sophisticated expression pattern of myokines would partially explain the complicated cross-talk between skeletal muscle and other organs in different genders and muscles phenotypes, and it is worth further investigation.