Investigation of the effects of zingerone on Testikular Apoptozis, SIRT1/Nrf2/HO-1 signaling pathway and spermatological parameters in diabetic rats

Diabetes mellitus, a prevalent condition worldwide that affects multiple body systems, plays a significant role in male infertility. The use of herbal antioxidants to ameliorate the effects of diabetes on the male reproductive system has attracted much interest in recent years. The aim of this study was to investigate the dose-dependent effect of zingerone on the reproductive system in diabetic male rats. For this purpose, 75 male Sprague Dawley rats weighing 250-300 g and 10-12 weeks old were used. They were divided into 6 groups as 15 rats in diabetic groups and 10 rats in non-diabetic groups. Groups; 1st Group: Control Group (saline), 2nd Group: Zingeron 50 Group (Zingeron 50 mg/kg), 3rd Group: Zingeron 100 Group (Zingeron 100 mg/kg), 4th Group: Diabetes Group (STZ 55 mg/kg), 5. Group: Diabetes+Zingeron 50 Group (STZ 55 mg/kg + Zingeron 50 mg/kg), 6th Group: Diabetes+Zingeron 100 Group (STZ 55 mg/kg + Zingeron 100 mg/kg). The diabetes model was induced by the intraperitoneal administration of a single dose of streptozotocin at a dose of 55 mg/kg. Zingerone was prepared as a solution in saline and administered by gavage on a daily basis for a period of eight weeks. At the conclusion of the eighth week, serum glucose and testosterone levels were quantified from blood samples obtained from rats via decapitation under anaesthesia. The levels of malondialdehyde (MDA) and glutathione (GSH) were determined, as well as the activity of glutathione peroxidase (GSH. Px) and Catalase (CAT) enzyme activities, Sirt1, Nrf2, HO-1, Bax, Bcl-2 protein expression levels, spermatological parameters (spermatozoon motility, abnormal spermatozoon ratio, spermatozoon density) and reproductive organ weights (testis, epididymis, vesicula seminalis, ventral prostate) were determined. Additionally, testicular tissue histopathology and the Johnsen score were evaluated. The findings of the study indicate that, despite a reduction in body weight and testosterone levels in the DM group compared to the control group (p<0.001), there was an increase in glucose levels (p<0.001). In the testicular tissue of the DM group, there was a significant decrease in GSH (p<0.001), GSH.Px (p<0.001), and CAT levels (p<0.001). Additionally, there was a notable decline in Sirt1, Nrf2, and HO-1 protein expression levels (p<0.001), as well as a reduction in Bcl-2 protein expression (p<0.01). The level of malondialdehyde (MDA) was found to be significantly increased (p<0.001), as was the expression of the pro-apoptotic protein Bax (p<0.05) and the Bax/Bcl-2 ratio (p<0.01). There was a significant decrease in sperm motility, epididymal sperm density and reproductive organ weights (p<0.001). In addition, there was a significant increase in the proportion of abnormal spermatozoa (head, tail, total) (p<0.001). In comparison to the DM group, the live weight values and testosterone levels exhibited an increase in the DM+Zin50 and DM+Zin100 groups (p<0.001). Although there was no difference in glucose levels between the DM+Zin50 and DM+Zin100 groups (p>0.05), there was a decrease in glucose levels in the DM+Zin100 group (p<0.001). While malondialdehyde (MDA) levels decreased in the DM+Zin50 and DM+Zin100 groups (p<0.001), a significant increase in glutathione (GSH), glutathione peroxidase (GSH.Px) and catalase (CAT) activities was observed (p<0.001). While no difference was observed in Sirt1, Nrf2, and HO-1 protein expression levels in the DM+Zin50 group (p>0.05), a significant increase was observed in the DM+Zin100 group (p<0.001). There was no difference in Bax and Bcl-2 protein expression levels between the DM+Zin50 and DM+Zin100 groups (p>0.05). However, the Bax/Bcl-2 ratio was found to be significantly lower in the DM+Zin50 group (p<0.01). In the DM+Zin50 group, although no difference was observed in spermatozoon motility, density, and vesicular seminalis weight (p>0.05), the total abnormal spermatozoon ratio decreased (p<0.001), testis, epididymis, and ventral prostate weights increased (p<0.001). Although there was no difference in spermatozoon density in the DM+Zin100 group (p>0.05), the total abnormal spermatozoon ratio decreased (p<0.001), and motility and reproductive organ weights increased (p<0.001). Furthermore, although there was no difference in germinal cell thickness between the DM+Zin50 and DM groups in the histopathological evaluation (p>0.05), the tubulus seminiferus contortus diameter and Johnsen testicular score value increased (p<0.001). In the DM+Zin100 group, there was a significant increase in the values of the tubulus seminiferus contortus diameter, germinal cell thickness and Johnsen testicular score (p<0.001). Although histopathological lesions were observed in diabetic rats, the severity and frequency of lesions decreased in a dose-dependent manner in zingerone-treated diabetic rats. Consequently, the findings of this study, which were obtained from both healthy rats and diabetics, are consistent with one another. This evidence suggests that zingerone may be a suitable candidate for inclusion in preventive medicine. This study demonstrated for the first time that zingerone plays a dose-dependent ameliorative role on reproductive disorders that may occur in male rats with experimental diabetes. This study provides compelling evidence for the use of zingerone in the treatment of diabetes-induced male infertility. The results confirm that zingerone dose-dependently attenuates diabetes-related reproductive dysfunctions. It may therefore be recommended that the use of zingerone be included both in the prevention of reproductive disorders in healthy rats and in the therapeutic procedure. Furthermore, the combination of zingerone with other drugs may prove to be an effective strategy for reducing the toxicity of the drugs used and combating diabetes-related infertility.