FIGURE 1.

The cAMP-PKA pathway negatively regulates AMPK activation. a, primary hepatocytes were treated with the indicated amount of metformin (Pre-T) or vehicle (Same-T) for 3 h during serum starvation, then washed with PBS, followed by incubation of primary hepatocytes from both groups with 0.2 mm Bt-cAMP and indicated amounts of metformin for 4 h before harvest. b, inhibition of PKA by H89 attenuated phosphorylation of AMPKα at Ser-485 and CREB at Ser-133, while the phosphorylation of AMPKα at Thr-172 was elevated in primary hepatocytes. Hepatocytes were pretreated with H89 for 6 h before the addition of Bt-cAMP. c, Hepa1–6 cells were treated with 0.5 mm metformin or vehicle for 2 h, then 20 μm H89 was added. After 1-h incubation, 0.2 mm Bt-cAMP was added. d, the PKA competitive inhibitor Rp-cAMP (100 μm) was administrated 1 h before the addition of 0.2 mm Bt-cAMP in Hepa1–6 cells.