Incretin effect of Urena lobata leaves extract on structure and function of rats islet β-cells

This study aims to determine the incretin effects of Urena lobata leaves extract on the structure and function of rats islet β-cells. This study utilizes male Sprague-Dawley rats divided into 2 control group and 3 test group (n = 5). Diabetic rats were induced with High Fructose Diet (HFD) and single dose intra-peritoneal streptozotocin 25 mg/kg bw. Aqueous leaves extract of U. lobata was prepared by decoction methods and administrated orally with doses of 250, 500, and 1000 mg/kg bw for 4 weeks then incretin effect was evaluated by measuring serum GLP-1, insulin, and blood glucose levels. Histology of islet β-cells was evaluated using photomicroscopy by analyzing size, shape, and number. Data were analyzed using ANOVA test followed by LSD test and p ≤ 0.05 is considered significant. Oral administration of aqueous extract U. lobata leaves at doses of 250, 500, and 1000 mg/kg body weight were able to prolong GLP-1 bioavailability by 3-fold, 5-fold, and 7-fold respectively when compared to the diabetic group whereas blood glucose level were decreased about 30%, 35%, and 40% respectively (p ＜ 0.05). Extract at doses of 500 and 1000 mg/kg bw also increased insulin level by 4-fold and 8-fold respectively compared to the diabetic group and the islet β-cells were repaired. The active compound in U. lobata leaves extract are suggested to prevent degradation of GLP-1 by inhibition of DPP-4 activity. Aqueous extract of U. lobata also improved the structure and function of islet b-cells by increasing of GLP-1 bioavailability.