Stereological and immunohistochemical investigation of the liver protective effect of thymoquinone and vitamin c in rats with experimental diabetes

Diabetes mellitus (DM) is a metabolic disease characterised by impaired carbohydrate, fat, and protein metabolism due to insulin deficiency or decreased tissue sensitivity to insulin. The aim of this study was to investigate the effects of thymoquinone and vitamin C on the liver in a streptozotocin (STZ)-induced experimental diabetes model in rats using stereological and immunohistochemical (IHC) methods. A total of 30 adult male Wistar albino rats were used in the study. The rats were divided into 6 groups (n=6) as control, thymoquinone (TQ), diabetes (STZ), diabetes+tymoquinone (STZ+TQ), diabetes+vitamin C (STZ+Vit C), diabetes+tymoquinone+vitamin C (STZ+TQ+Vit C). STZ (45 mg i.p.) was administered to the other 4 groups except the control and TQ groups before the experiment. On day 3 of the study, blood glucose levels were measured in all groups and diabetes was confirmed in rats in the diabetes groups. TQ (50 mg/kg/day) and vitamin C (500 mg/kg/day) were then administered orally to the treatment groups for 21 days. At the end of the study, the liver was evaluated by stereology and HRC. The Cavalieri method was used for stereological volume measurements. Caspase-3, Bcl-2, TNF-α, and IL-10 expression were evaluated by IHC. According to our findings; in stereological measurements of both mean total volume and vessel volume densities of the liver, it was found that the mean measurement value in the STZ group was statistically significantly higher than the other groups (P<0.05). No significant difference was observed between the STZ+VITC+TQ group and the control and TQ groups (P>0.05). Immunohistochemically, caspase-3 expression was intense in the STZ group, weak in the STZ+VITC, STZ+TQ and STZ+VITC+TQ groups and negative in the control and TQ groups. While Bcl-2 activation was not observed in the STZ group, moderate Bcl-2 expression was detected in all other groups. TNF-alpha expression was strong in the STZ group, moderate in the STZ+TQ group, weak in the STZ+VITC group and negative in the control, TQ and STZ+VITC+TQ groups. IL-10 activity was strong in the control group, moderate in the TQ, STZ+VITC, STZ+TQ, STZ+VITC+TQ groups and weak in the STZ group. The results of the study show that STZ-induced liver injury is ameliorated when both TQ and vitamin C are administered separately, but more effective results are obtained when they are used together.