A. Metformin prevents insulin-induced Cyclin D1 protein levels in hepatocytes. Overnight serum starved AML12 murine hepatocytes were treated with control, metformin (10 mM), insulin (200 nM) or both for 4 h, followed by immunoblotting to detect Cyclin D1 expression. B. Design and metabolic phenotypes of the metformin treatment experiment. Metformin was given at 50 mg/kg for 27 weeks. Endpoint blood insulin level and liver histology of the db/db mice were shown. Scale bar represents 500 μm. C. Metformin treatment prevents the induction of Cyclin D1 in type 2 diabetic liver as detected by immunoblotting. D. Metformin treatment protects mice from DEN-induced liver cancer in diabetic mice (water, n=5; metformin, n=4).