PTPN1 and Insulin resistance: Another experiment on sex-dependent insulin resistance was carried out on hepatic AR knockout mice, where overweight male H-AR−/y, but not female H-AR−/− mice, fed a high-fat diet (HFD) were characterized by reduced sensitivity to insulin as a result of increased expression of protein-tyrosine phosphatase 1B (PTP1B, negative regulator of the insulin signaling pathway).