Effect of stevioside on the expression of glucose tranport proteins, GLUT1, GLUT3 and GLUT4,, in diabetic rat placenta

Objective: One of important roles of the placenta is to provide maternal-fetal nutrient transport. The primary source of energy for embryo development is glucose and maternal-fetal glucose transport occurs through glucose transporters(GLUTs) which are present in placenta. Stevia plant has been used as natural sweetener and medicinal for a long time. The purpose of this study is to determine the effects of stevioside on blood glucose and insulin levels in normal and diabetic animals. Moreover, we aimed to determine the effects of stevioside on GLUT1, GLUT3 and GLUT4 proteins which have important roles for glucose transport. Method: After mating, the presence of the sperm in the vaginal smear the following morning was designated as day 0 of pregnancy. Control, stevioside, diabetes and diabetes + stevioside groups were formed. Amount of insülin was determined by Elisa method. Expressions of GLUT1, GLUT3 and GLUT4 proteins in the placenta were evaluated by western blot and immunohistochemistry. Results: GLUT1 protein significantly decreased in the diabetes + stevioside group compared to other groups on the 15th day of gestation according to the results of western blotting and immunohistochemistry (p<0,05). On the 20th day of gestation, GLUT1 protein increased (P <0.05) significantly in diabetic group compared to other groups. There was no difference between other groups while GLUT3 protein was increasing in stevioside group on the 15th day of gestation. At 20 days, there was no difference compared to control group while diabetic group was increasing compared to stevioside and diabetes + stevioside. On the 15th day of gestation, GLUT4 protein significantly increased in the diabetic group compared to the control and stevioside groups, but not in the diabetes + stevioside group. There was no difference between all groups for GLUT 4 protein at 20 days. According to the findings of Elisa, the amount of insulin decreased in the statistically significant range in other groups compared to control group on the 15th and 20th day of gestation, respectively (p <0,05, p <0,01, p <0,005). Conclusion: Changes in the expression of GLUT proteins in rat placenta may be a compensatory mechanism for embryonic protection and the effect of stevioside on placenta may be limited.