The flavonoid Silibinin decreases glucose-6-phosphate hydrolysis in perifused rat Hepatocytes by an inhibitory effect on glucose-6-phosphatase

Background/Aims: The flavonoid silibinin has been reported to be beneficial in several hepatic disorders. Recent evidence also suggests that silibinin could be beneficial in the treatment of type 2 diabetes, owing to its anti-Hyperglycemic properties. However, the mechanism(s) underlying these metabolic effects remains unknown. Methods: The effects of silibinin on liver gluconeogenesis were studied by titrating hepatocytes from starved rats with sub-saturating concentrations of various exogenous substrates in a perifusion system. Hepatocytes from fed rats were also used to investigate glycogenolysis from endogenous glycogen. The effect of silibinin on glucose-6-phosphatase kinetics was determined in intact and permeabilized rat liver microsomes. Results: Silibinin induced a dose-dependent inhibition of gluconeogenesis associated with a potent decrease in glucose-6-phosphate hydrolysis. This effect was demonstrated whatever the gluconeogenic substrates used, i.e. dihydroxyacetone, lactate/pyruvate, glycerol and fructose. In addition, silibinin decreased the glucagoninduced stimulation of both gluconeogenesis and glycogenolysis, this being associated with a reduction of glucose-6-phosphate hydrolysis. Silibinin inhibits glucose-6-phosphatase in rat liver microsomes in a concentration-dependent manner that could explain the decrease in glucose-6-phosphate hydrolysis seen in intact cells. Conclusion: The inhibitory effect of silibinin on both hepatic glucose-6-phosphatase and gluconeogenesis suggests that its use may be interesting in treatment of type 2 diabetes. Copyright (c) 2007 S. Karger AG, Basel.