Antidiabetic Effect of Asparagus adscendens Roxb. in RIN-5F Cells, HepG2 Cells, and Wistar Rats

Background: The antidiabetic effect of Asparagus adscendens root ethanolic extract (AAE) was evaluated in this study using both in vivo and in vitro models. The effect of AAE on carbohydrate metabolizing enzymes (α-amylase and α-glucosidase) was determined. The safety of AAE was tested on Wistar rats and two different cell lines. Some mechanisms of action were also investigated with AAE’s dose-response. Methods: Glucose-loaded (10 g/kg) and streptozotocin-induced (60 mg/kg) diabetic Wistar rats were used in the in vivo model, whereas RIN-5F pancreatic cells and HepG2 liver cells were used in the in vitro model. Nontoxic mass value of AAE was used in the in vitro (from 0.625 to 2.5 μg/100 µl) and in vivo (up to 400 mg/kg) studies. The inhibitory activity of AAE on α-amylase and α-glucosidase was examined by spectrophotometric and microplate reader techniques. Results: The AAE inhibited α-amylase and α-glucosidase, two key enzymes of the carbohydrate metabolism, and stimulated the release of insulin in RIN-5F cells line and glucose uptake in HepG2 cells in a concomitant way. Lower mass values of the extract caused no significant change in the viability of the cells, whereas 5 μg caused a significant reduction in the viability of RIN-5F (59.78%) and HepG2 (56.87%) when compared to the control. The 2.5 μg extract stimulated 91% insulin release in RIN-5F cells when compared with the control. Also, 2.5 μg extract induced 86% and 83% glucose uptake in HepG2 cells in the presence and absence of insulin, respectively, when compared with the control. The median lethal dose of AAE was ≥5000 mg/kg in Wistar rats. AAE caused a decrease in fasting blood glucose level from 30 min in glucose-loaded Wistar rats and from the 4th day in streptozotocin-induced diabetic rats when compared with the control. There was also an increase in serum insulin and serum α-amylase level in streptozotocin-induced diabetic rats, compared to the control, at the end of the study. Conclusion: A. adscendens root exerts its antidiabetic effect by inhibiting α-amylase and α-glucosidase enzymes, inducing insulin secretion in RIN-5F pancreatic cells, and enhancing glucose uptake in HepG2 liver cells.