Effect of olive leaf extract on glucose levels in diabetes-induced rats: A systematic review and meta-analysis

Abstract

Background: The present systematic review statistically analyzed randomized controlled trials on olive leaf extract (OLE) for effectiveness in managing glucose levels in diabetic rats. Methods: A literature search was performed using PubMed, the Cochrane Central Register of Controlled Trials, and EBSCO host databases. Selected articles, with no date restriction in the search process, were assessed independently by the authors using SYRCLE's risk of bias tool for animal studies. Data from eight trials on 162 rats were reviewed. Data were analyzed using Comprehensive Meta Analysis version 3.0. Results: Combined random effects analysis revealed that treatment of diabetic rats with OLE significantly increased insulin levels (standardized mean difference [SMD] 4.83 μIU/mL; 95% confidence interval [CI] 2.13, 7.54) and reduced blood glucose levels (SMD −4.21 mg/dL; 95% CI −5.75, −2.67). Secondary outcomes included significant reductions in total cholesterol and triglyceride levels, with a forest plot showing hypolipidemic effects among OLE-treated rats compared with placebo (SMD −6.32 mg/dL [95% CI −9.75, −2.88] and −4.22 mg/dL [95% CI −6.96, −1.48], respectively). There was no significant difference in body weight between OLE-treated rats and the placebo groups (SMD 0.46 g; 95% CI −0.05, 0.96; P = 0.98). Conclusion: Olive leaf extract is beneficial for both the lipid profile and glycemic control in diabetes-induced rats and may be as effective among humans.