Anti-inflammatory, anti-oxidant and anti-apoptotic effects of olive leaf extract in cardiac tissue of diabetic rats

Objectives Inflammatory process and apoptosis are involved in the pathogenesis of cardiac injury and oxidative damage caused by diabetes mellitus. The cardioprotective effects of standardized aqueous ethanolic olive leaf extract (OLE), metformin (as a cardiovascular protective agent) and valsartan (as an angiotensin receptor blocker) in the streptozotocin-induced diabetic rats were evaluated. Methods Wistar rats divided into control, diabetic, OLE-treated (100, 200 and 400 mg/kg), metformin (300 mg/kg)-treated, valsartan (30 mg/kg)-treated and metformin/valsartan-treated diabetic groups. Biochemical parameters, including malondialdehyde (MDA) levels, superoxide dismutase (SOD) and catalase (CAT) activates, and the total contents of thiol were measured, and histopathological and gene expression studies were done on cardiac tissues. Fasting blood sugar (FBS) and cardiac injury markers were examined in serum. Key findings FBS; the serum levels of lactate dehydrogenase (LDH), creatine kinase-muscle/brain (CK-MB), aspartate aminotransferase (AST); and heart tissue MDA levels due to diabetes were significantly alleviated by OLE treatment (effect size; eta(2)(p) = 0.934, 0.888, 0.848, 0.888 and 0.879, respectively), and SOD and CAT activity and the thiol content in heart tissue were significantly increased (effect size; eta(2)(p) = 0.770, 0.749 and 0.753, respectively). Interleukin-1 beta (IL-1 beta), tumour necrosis factor-alpha (TNF-alpha) and the number of infiltrating inflammatory cells were reduced in cardiac tissues of OLE-treated groups compared with the diabetic rats (effect size; eta(2)(p) = 0.969 and 0.949, respectively). OLE up-regulated BCL2 gene expression and down-regulated BAX gene expression in cardiac tissue (effect size; eta(2)(p)= 0.490 and 0.522, respectively). Conclusion OLE in a dose-dependent manner ameliorates cardiac damage in diabetic cardiomyopathy, perhaps through attenuating inflammation, oxidative stress and apoptosis.