FIGURE 3.

DDN activates insulin signaling pathways in vivo and possesses hypoglycemic activity. A, DDN reduces blood glucose in C57BL/6J mice. C57BL/6J mice were starved for 12 h and then orally administrated with vehicle (0.5% methylcellulose), DDN (20 mg/kg), or the inactive analog 2NH₂-NQ (20 mg/kg). Human insulin (1 unit/kg) was injected intraperitoneally as a positive control. Blood glucose was monitored before and after dosing at various time points as indicated (*, p < 0.05; **, p < 0.01; ***, p < 0.001, n = 10–13, Two-way analysis of variance versus vehicle). B, DDN provokes IR phosphorylation and its downstream signaling in C57BL/6J mice. Three-month-old C57BL/6J mice were starved for 12 h and then orally administrated with vehicle (0.5% methylcellulose), DDN (20 mg/kg), or 2NH₂-NQ (20 mg/kg). Cell lysates were prepared from liver and muscle tissues, which were collected at 3, 4, and 5 h after drug administration and analyzed by immunoprecipitation and immunoblotting. C, DDN quickly activates IR phosphorylation and its downstream signaling. Three-month-old C57BL/6J mice were starved for 12 h and then injected with vehicle, 5 mg/kg DDN, or 5 mg/kg 2NH₂-NQ through the vena cava. After 5 min, the liver was collected and analyzed by immunoblotting using specific antibodies.