The effects of hydroxytyrosol on Prdx6 and insulin expression in diabetic rat pancreases

Diabetes mellitus is a widespread endocrine disease worldwide, accompanying chronic hyperglycemia. In this study, we investigated the effect of hydroxytyrosol, which exerts an antioxidant effect, on the expressions of insulin and peroxiredoxin-6 (Prdx6), which protect cells against oxidative injury in diabetic rat pancreas. This experimental study had four groups with ten animals in each group: control (nondiabetic) group, hydroxytyrosol group [10 mg/kg/day intraperitoneal injection (ip) hydroxytyrosol for 30 days], streptozotocin group (single ip injection of 55 mg/kg streptozotocin), and streptozotocin + hydroxytyrosol group (single ip injection of streptozotocin and ip injection of 10 mg/kg/day hydroxytyrosol for 30 days). During the experiment, blood glucose levels were measured at regular intervals. Insulin expression was determined by immunohistochemistry and Prdx6 expression was determined by immunohistochemistry and western blot. Immunohistochemistry and western blot results were analyzed by one-way ANOVA with applied Holm-Sidak multiple comparison test, and blood glucose results were analyzed by two-way repeated measures ANOVA with applied Tukey's multiple comparison test. Blood glucose levels on days 21 and 28 were significantly lower in the streptozotocin + hydroxytyrosol group compared with the streptozotocin group (day 21, p = 0.049 and day 28, p = 0.003). Expression of both insulin and Prdx6 were lower in the streptozotocin and the streptozotocin + hydroxytyrosol groups compared with the control and hydroxytyrosol groups (p < 0.001). Insulin and Prdx6 expression in the streptozotocin + hydroxytyrosol group were higher compared with the streptozotocin group (p < 0.001). The immunohistochemical findings of Prdx6 and western blot were the same. In conclusion, hydroxytyrosol, which is an antioxidant compound, increased Prdx6 and insulin expression in diabetic rats. Insulin increased by hydroxytyrosol may have been effective in reducing blood glucose levels. Furthermore, hydroxytyrosol may exert its effect on insulin by increasing Prdx6 expression. Thus, hydroxytyrosol may decrease or prevent several hyperglycemia-dependent complications by increasing the expression of these proteins.