Phosphatase and tensin homologue deleted from chromosome ten (PTEN) has recently been characterized as a regulator of insulin sensitivity in the insulin target tissue. However, whether PTEN gene expression is changed in insulin resistance remains unclear. We observed that both the mRNA and protein level of PTEN in soleus muscle isolated from the obese Zucker rats (Fa/Fa) were increased compared to the age-matched lean group. Similarly, both the mRNA and protein level of PTEN in soleus muscle of the fructose-fed lean Zucker rats (Fa/Fa) showing the higher glucose-insulin index were higher than that of the regular chow fed group. These results suggest that increase of PTEN gene expression seems to be related to the development of insulin resistance.