Weightlessness or simulated weightlessness leads atrophy in anti-gravity skeletal muscles.However, whether or not the atrophic skeletal muscle induces insulin resistance and its mechanisms are not resolved now.Insulin resistance in skeletal muscles is an important etiology of type 2 diabetes.The anti-gravity soleus muscle (SOL) showed a progressive atrophy in 1-week, 2-week, and 4-week tail-suspended rats, but not extensor digitorum longus (EDL).Hyperinsulinemic-euglycemic clamp showed that the steady-state glucose infusion rate was lower in 4-week tail-suspended rats than that in the control rats.The glucose uptake rates under insulin-or contraction-stimulation were significantly decreased in 4-week unloaded soleus muscle as compared with the control group.There was no difference in the glucose uptake rates of EDL between two groups.The key protein expression of IRS1, PI3K, and Akt on the insulin-dependent pathway and of AMPK, ERK, and p38 on the insulin-independent pathway were unchanged in unloaded soleus muscle.The unchanged phosphorylation of Akt and p38 suggested that the activity of two signal pathways was not altered in unloaded soleus muscle.The AS160 and GLUT4 expression on the common downstream pathway also was not changed in unloaded soleus muscle.But the GLUT4 translocation to sarcolemma was inhibited during insulin stimulation.The above results suggest that hindlimb unloading in tail-suspended rat induces atrophy in anti-gravity soleus muscle.The impaired GLUT4 translocation to sarcolemma under insulin stimulation may mediate insulin resistance in unloaded soleus muscle and further affect the insulin sensitivity of whole body in tail-suspended rats.