The Effects and Mechanism of Saponins of Panax notoginseng on Glucose Metabolism in 3T3-L1 Cells

This study was carried out to determine the effect of saponins of Panax notoginseng (SPN), a naturally occurring cardiovascular agent, on: (1) glucose uptake, (2) GLUT4 translocation and (3) glycogen synthesis in 3T3-L1 adipocytes. Electrospray ionization-Mass spectrometry (ESI-MS) was used to determine the structural characterization of the major active components of SPN. 3T3-L1 adipocytes were cultured and treated with 100 nM insulin alone or with 10, 50 and 100 μg/ml of SPN. [³H]2-deoxyglucose glucose uptake, GLUT4 immunofluorescence imaging and glycogen synthesis assay were carried out to determine the effects of SPN on glucose metabolism. Under insulin stimulation, SPN significantly increased glucose uptake in a dose-dependent manner; 50 μg/ml of SPN increased glucose uptake by 64% (p < 0.001). Immunofluorescence imaging and analysis have revealed that 50 and 100 μg/ml of SPN increased GLUT4 in the plasma membrane by 3-fold and 6-fold respectively (p < 0.001). Furthermore, the incorporation of D-[U-¹⁴C] glucose into glycogen was enhanced by 53% in 3T3-L1 cells treated with 100 μg/ml of SPN (p < 0.01 vs. insulin stimulation alone). SPN, a naturally occurring agent used to treat ischemic cardio-cerebral vascular disease in China, enhanced insulin-stimulated glucose uptake and glycogen synthesis in adipocytes. The results of this study indicate that SPN may have a therapeutic potential for hyperglycaemia in type 2 diabetes.