Comparative studies of antidiabetic activity of bilberry leaf extract in Wistar rats with STZ-induced diabetes and Zucker diabetic fatty rats

The use of biologically active substances (BAS) in the composition of the antidiabetic specialized food requires the in vivo pre-testing using experimental models of diabetes in laboratory animals. The aim of this work was the comparative research of antidiabetic activity of Vaccinium myrtillus L. bilberry leaf extract (VLE) in Wistar rats with diabetes induced by STZ injection and a high-carbohydrate diet and in Zucker Diabetic Fatty (ZDF) male rats (Zucker Rat Crl: ZUC-Leprfa rats). The prospects of using the extract for the dietary management of diabetes are discussed. In the1st experiment male Wistar rats with streptozotocin (STZ) and high-fructose diet-induced diabetes were fed with a 2% solution of bilberry leaf extract ad libitum for the 50 days. In the 2nd experiment, ZDF rats were treated once daily with 2 g/kg day of bilberry leaf extract orally via a gastric tube for the following 28 days. During daily inspection were observed the general conditions of all animals in appearance, quality of coat, and behavior. At different intervals, blood glucose and body weight were recorded. Blood samples were collected to determine glycated hemoglobin. Oral glucose tolerance test and insulin tolerance test before and after treatment were performed. Food and water consumption was measured. Results of the glycated hemoglobin and blood glucose level analysis showed the ameliorative effect of VLE on carbohydrate metabolism in diabetic rats. A significant decrease of the fluid intake and increase of the weight gain in animals are the beneficial effects of VLE treatment that speaks in favor to the normalization of metabolic processes in animals. After 2 weeks of VLE consumption, the body weight of ZDF rats was significantly decreased and the growth’s slowdown was not due to the different food intake. VLE to a certain extent also reduced hyperglycemia and improved insulin sensitivity in diabetic animals.