Hypoglycemic Activity and the Mechanisms of Lycium Bark Extract in db/db Mice

The extract of Lycium bark (LBE), which is the root bark of Lycium chinense, has long been used in China for hypertension, inflammation, and diabetes. LBE has been reported to ameliorate hyperglycemia in mice with alloxan-induced type 1 diabetes, but evidence on the effect of LBE in diabetes had not been enough. Therefore, we investigated the effects of LBE on type 2 diabetes using db/db mice. Nine-week-old male db/db mice were orally administered LBE (425 mg/kg) for 10 weeks. Blood samples were collected under anesthesia for the determination of blood glucose and insulin levels. The blood glucose level was increased in the control group and was unchanged in the LBE group. The blood insulin level was increased in both groups within 4 weeks, but it decreased in the control group and was maintained at a relatively high level in the LBE group thereafter. Furthermore, LBE increased the glucose uptake, which was measured using C2C12 myotubes, in a concentration-dependent manner, independent of the addition of a phosphatidylinositol 3-kinase inhibitor (i.e., LY294002) and an AMP-activated kinase inhibitor (i.e., dorsomorphin). And LBE increased the mRNA expression of glucose transporter (GLUT) 1. These results suggested that LBE decreased the blood glucose level by additive effect such as improvement of the insulin secretion, promoting activity of glucose uptake. These findings suggested that LBE administration can be a novel therapeutic approach for type 2 diabetes.