Activation of MOR located on the soleus muscle, resulting in reversal of the impairment of insulin-stimulated glucose disposal in obese Zucker rats, has been documented; this improvement in insulin resistance was associated with the amelioration of the post-receptor insulin-signaling cascade, including downstream effectors of the PI3-kinase signaling pathway involved in glucose-transporter translocation [11]. This evidence concerns the gene OPRM1 and Insulin resistance.