Antidiabetic effects of Olea europaea L. leaves in diabetic rats induced by high-fat diet and low-dose streptozotocin

Ethnopharmacological relevance: Diabetes mellitus (DM) is a metabolic disorder characterized by hyperglycemia, insulin resistance, and dyslipidemia. It has broad occurrence worldwide, affecting millions of people, and can cause serious complications. The olive (Olea europaea L.) has important pharmacological functions, including anti-inflammatory, antioxidant, and hypoglycemic activities. Olive leaves are used in traditional medicine for diabetes and hypertension. Aim of the study: To evaluate the effect of the ethanolic extract of olive leaves (EEOL) on the metabolism of rats with diabetes induced by a high-fat diet and low dose of streptozotocin (STZ). Materials and methods: Male Wistar rats were either given normal feed or a high-fat diet (70% standard laboratory feed, 15% sucrose, 10% lard and 5% yolk powder) for four weeks, followed by administration of STZ (35 mg/kg, via ip). Animals with fasting glucose levels above 200 mg/dL were considered diabetic. Animals were divided into 5 groups, which received ethanol (10 mL/kg), metformin (250 mg/kg), or EEOL at doses of 200 and 400 mg/kg during 10 weeks by oral gavage. Blood samples were used to measure hematological and biochemical parameters, and kidneys were removed for posterior analysis. Body weight was recorded weekly. Results: A significant decrease in body weight was observed among diabetic animals treated with ethanol and EEOL compared to the control group. Moreover, animals treated with EEOL showed an improvement in glucose levels and in levels of inflammatory and metabolic markers when compared to diabetic animals. Conclusions: The results indicate a potential anti-diabetic activity of olive leaves, however more studies are needed to validate clinical effects.