Gymnema’s antidiabetic activity appears to be due to a combination of mechanisms. Two animal studies on beryllium nitrate- and streptozotocin-diabetic rats found Gymnema extracts doubled the number of insulin-secreting beta cells in the pancreas and returned blood sugars to almost normal. Gymnema increases the activity of enzymes responsible for glucose uptake and utilization, and inhibits peripheral utilization of glucose by somatotrophin and corticotrophin. Plant extracts have also been found to inhibit epinephrine-induced hyperglycemia.
Gymnema sylvestre. Alternative Medicine Review 1999 February