Investigating the Effect of Olive Leaf Extract on Antioxidant Activity, and its Regulatory Role on RBP4 Inflammatory Gene Expression in 3T3-L1 Cell Line

Background: The leaves of the olive plant (Olea europaea) contain significantly higher levels of phenolic compounds than the fruit and olive oil, acting as a natural supplement for antioxidant activities. Objectives: This research aimed to investigate the effect of this extract on certain inflammatory factors (TNF-α, IL-1, IL-6) and its regulatory role on tissue gene (RBP4) in fibroblast cell lines (3T3-L1). Methods: After culturing adipose tissue fibroblast cells (3T3-L1) under sterile and standard conditions, the cells were exposed to different logarithmic concentrations of the extract. The production of inflammatory cytokines TNF-α, IL-1, and IL-6 was measured using ELISA methods, and the expression level of the RBP4 gene was assessed using a real-time PCR technique. Results: The results showed dose-dependent effects of the extract on the 3T3-L1 cells. The MTT assay indicated that the hydroalcoholic extract of olive plant leaves has a concentration-dependent effect on cell proliferation (∗∗P ≤ 0.05). The DPPH test results showed a significant decrease in the level of active oxygen in the presence of Olive leaf extract (OLE). The catalase and MDA test results also indicated an increase in antioxidant activity in cells treated with the extract. Conversely, the expression levels of inflammatory cytokines IL-1 and IL-6 increased by 0.05 and 0.01 (pg/mL), respectively, while changes in TNF-α and RBP4 gene expression were insignificant (P 0.05). Conclusions: The results demonstrated that OLE can enhance the efficiency of antioxidant and inflammatory pathways in the cell and significantly reduce the level of active oxygen in the cell.