Metformin and liver glycogen synthase activity in obese Zucker rats.

The effect of chronic treatment with metformin (320 mg/kg/day) on plasma glucose and insulin as well as liver glycogen synthase activity and hepatic glycogen content was studied in obese hyperinsulinemic Zucker rats. Metformin significantly reduced both plasma glucose (by 10%) and insulin levels (by 39%) at fasting but had no effect on hepatic glycogen content or on the basal activity of liver glycogen synthase.