Potential effects of standardized Olea europaea L. (olive) leaf extract in an experimental animal model of metabolic syndrome induced by a high-fat diet

Introduction Metabolic syndrome (MS) is commonly developed in the context of sustained hypercaloric dietary intake and presents, over time, an increased risk of cardiovascular disease (2 × ) and type 2 diabetes mellitus (5 × ). To control mild-moderate forms, along with a healthy lifestyle, vegetal products rich in active principles with hypoglycemic, hypolipidemic, antihypertensive and antioxidant properties can also be considered. Objective Our study aimed to evaluate cardiometabolic parameters and oxidative stress markers in the presence of standardized olive leaf extract, in an experimental animal model of MS induced by a high-fat diet. Method Forty male Wistar rats were fed a standard diet ( n = 20) or a high-fat or hypercaloric diet (HD, n = 20). In each diet category, one group ( n = 10) of rats was treated daily orally with Olea europaea leaf extract (OE and HD + OE groups) for 10 weeks (W). Body weight, food and water intake, systolic blood pressure (SBP) and glycemia (OGTT) were monitored over a period of initial 2 W and during 10 W of treatment. At the end of the study (12 W), in addition to plasma lipoprotein level, HOMA-IR and plasma oxidative stress markers (malondialdehyde [MDA] level and total antioxidant capacity [TAC]) were also assessed. Results Compared to control group, the HD (58.8% energy from lipids) induced a significant weight gain (+15%) since 3 W, a significant increase in SBP (+20 mmHg, since 6 W) and glycemia values (> 140 mg/dl, OGTT). Also, in MS group the plasma triglyceride and MDA levels were significantly higher, while TAC was lower. Chronic treatment with a standardized O. europaea leaf extract (rich in luteolin-7-O-glucoside) did not influence the evolution of body weight but prevented ( P < 0.05) the increase in SBP and glycemia values, in HD - fed rats. Furthermore, the values of plasma lipoproteins, HOMA-IR and oxidative stress markers were significantly ( P < 0.05) reduced in the HD + OE group as compared to the MS group. Conclusion Chronic oral administration of a standardized O. europaea (olive) leaf extract prevented the onset of MS and reduced overall plasma oxidative stress in a high-fat diet experimental model, without influencing body weight.