Objectives Musclin is a novel skeletal muscle-derived secretory factor discovered in 2004. In this study we aimed to investigate the endogenous changes of musclin in insulin resistance (IR) of rats.
Methods Male Sprague–Dawley rats were randomly divided into two groups (n = 8 each): normal diet groups (ND) and high fat diet groups (HFD). After 20 weeks, rats were executed and the soleus muscle and white gastrocnemius muscle were harvested. Radioimmunoassay was used to determine musclin levels in plasma and skeletal muscle. Western blot and real-time PCR were used to detect musclin protein levels of rats muscle.
Results Compared to the ND group, HFD increased musclin mRNA expression by 220% (p < 0.01), increased musclin protein level by 52.8% (p < 0.05) and 67.70% (p < 0.05), as determined by western blot and radioimmunoassay, respectively. HFD rats also exhibited increased musclin immunore activity in plasma (p < 0.01). Musclin-ir in plasma was positively correlated with fasting blood glucose (FBG) (r = 0.79, p < 0.05), serum insulin (r = 0.810, p < 0.05) and glucose uptake (r = 0.875, p < 0.05) in skeletal muscle of HFD rats. The musclin-ir level in skeletal muscle was also positively correlated with FBG (r = 0.901, p < 0.01), serum insulin (r = 0.879, p < 0.01) and glucose uptake (r = 0.777, p < 0.05) in skeletal muscle of HFD rats.
Conclusions We conclude that a HFD in IR rats causes the upregulation of endogenous musclin level in skeletal muscle and plasma. Musclin, is an important myokine that participates in the development of skeletal muscle IR in HFD rats and the regulation of peripheral glucose homeostasis.