Enhanced insulin sensitivity in MCK PTP1B−/− mice. (a and b) IR phosphorylation in muscles from mice fed with chow (a) or HFD (b) and injected with saline or insulin (10 mU/g i.p.). Lysates were immunoprecipitated with IR antibodies, immunoblotted with antiphosphotyrosine antibody, and then stripped and reprobed with IR antibodies to control for loading. Immunoblots were then quantified using an Odyssey infrared imaging system. Bar graphs represent pooled, normalized data (arbitrary units) for MCK PTP1B−/− (n = 4 and 6 [for saline and insulin groups, respectively]) and PTP1Bflox/flox (n = 4 and 6) mice (males; 18 weeks on each diet). (c) IRS1 tyrosine phosphorylation in muscles from HFD-fed MCK PTP1B−/− mice (n = 4 and 6) and PTP1Bflox/flox controls (n = 4 and 6). Lysates were immunoprecipitated with IRS1 antibodies, immunoblotted with antiphosphotyrosine antibody, and then stripped and reprobed with IRS1 antibodies to control for loading. Immunoblots were then quantified using an Odyssey infrared imaging system. (d) IRS1-associated PI3K activity, expressed as x-fold increases from basal activity, in muscles from HFD-fed MCK PTP1B−/− (n = 3 and 6) and PTP1Bflox/flox (n = 3 and 6) mice. There was no difference in basal PI3K activity between MCK PTP1B−/− and PTP1Bflox/flox mice. (e) Akt phosphorylation, as assessed by immunoblots, in muscle lysates from HFD-fed MCK PTP1B−/− (n = 4 and 4) and PTP1Bflox/flox (n = 4 and 4) mice. A representative blot is shown, wherein each lane represents the muscle lysate from a different mouse. The blot was reprobed with anti-PTP1B antibodies to show the absence of PTP1B in muscles of MCK PTP1B−/− mice. Proteins were visualized by enhanced chemiluminescence, and the data were pooled, normalized, and represented in a bar graph. (f) Representative blots of IR phosphorylation in muscle lysates from mice on chow and HFD, as well as IRS1 phosphorylation. Statistical analysis was performed using one-way ANOVA followed by Tukey's multiple comparison test (**, P < 0.01; *, P < 0.05).