PTPN1 and Insulin resistance: Likewise, abnormal expression and activity of PTP-1B have been reported in skeletal muscle of insulin-resistant obese people (Ahmad et al., 1997), as well as in non-obese Goto-Kakizaki rats with spontaneously generated insulin resistance (Dadke et al., 2000), and in STZ-hyperglycemic rats fed with high-fat diet (Wu et al., 2005).