Effects of a hypoglycemic component of ginseng radix on insulin biosynthesis in normal and diabetic animals

DPG-3-2, a component of ginseng radix, which lowers the blood glucose level and stimulates insulin release in diabetic animals, was studied for its effects on insulin biosynthesis in different preparations of pancreas from animals with normoglycemia and with hyperglycemia (alloxan diabetic rats and genetically diabetic mice, KK-CAy). We measured incorporation of radioactive leucine into insulin and other protein fractions during a 2-h perfusion of rat pancreas, and into insulin during a 3-h incubation of mouse islets. Biosynthesis of insulin during a long-term culture of islets from KK-CAy mice was also measured. DPG-3-2 was found practically not to increase the incorporation into insulin in the pancreatic preparations from animals with normoglycemia, but in such preparations from animals with hyperglycemia DPG-3-2 (0.2-1.0 mg/ml) caused 1.5-1.8-fold incorporation into insulin. In addition, a long-term treatment of DPG-3-2 (0.5 mg/ml) was shown to stimulate insulin biosynthesis in islets from KK-CAy mice. Ginsenoside-Rb1 and -Rg1 decreased the insulin content of islet to the undetectable level. Thus, DPG-3-2 was shown to stimulate insulin biosynthesis in different preparations of pancreas from animals with hyperglycemia.