Research objectives: To study the changes in the expression of antioxidant enzymes SOD1, SOD2 and GPX1 in the brain of healthy, diabetic and diabetic rats treated with olive leaf polyphenols. Material and methods: In the experimental model of SZT-induced diabetes (diabetes mellitus type 1, DMT1) and HFD-induced diabetes (diabetes mellitus type 2, DMT2), the cerebrum of male Wistar rats was used, which were divided into 4 groups: C (control) - control group without treatment; DMT1 group with developed diabetes after 8 days of single administration of streptozotocin (i.p., 60 mg/kg); DMT1+ OLE - group with developed diabetes and post-treatment i.p. by administration of olive leaf polyphenol extract (OLE); DMT2 group was fed a high fat diet (standard laboratory diet enriched with 50% palm oil) for 30 days. The groups consisted of 3-5 animals aged 2-3 months. Statistica (data analysis software), version 14 (TIBCO Software Inc., 2020, Palo Alto, CA, USA) was used for data analysis. Differences between groups were assessed using one-way analysis of variance (ANOVA one-way) followed by post-hoc Scheffé test and Kruskal-Wallis test (multiple comparison of pvalues). Linear regression analysis was used to compare the interdependence of variables in the groups. Statistical significance is determined with a p-value of less than 0.05 (p < 0.05) for the correlation factor R. Results: Under the experimental conditions conducted, the Kruskal-Wallis test showed a statistically significant difference in MDA values between groups DMT1 and DMT2 (p=0.0140). A statistically significant difference in SOD2 expression was found between the DMT1 and DMT1+ PF groups (p=0.011), indicating that the therapy has an effect on mitochondrial SOD2 expression. Statistical significance of the change in SOD2 expression in all groups studied was determined by analysis of variance (p=0.009). SOD2 showed a statistically significant positive correlation with SOD1 (r=0.67) and a negative correlation with GPX1 (r=- 0.74). Conclusions: When the expression of the antioxidant enzymes SOD1, SOD2 and GPX and the MDA level in the brain of diabetic rats after SZT-induced diabetes (DMT1) and treatment with olive leaf polyphenol extract were examined, differences were found between the tested groups. SOD2 was significantly expressed in the olive leaf polyphenol extract treated group. In the group fed a high-fat diet (DMT2), we found no significant differences compared to the control group and no differences between DMT1 and DMT2 in rat brain. The balance of the antioxidant status of the brain of diabetic animals is probably influenced by the presence of fat-soluble non-enzymatic antioxidants.