Effects of hypervitaminosis C and D on spermatogenesis through CDKN1B modulation in adult male mice: biochemical and immunohistochemical studies

Abstract

Background The complex biological process of spermatogenesis produces mature spermatozoa within the testicular environment by terminally differentiating male germ precursor cells. Vitamin C (VC) is a potent water-soluble antioxidant. It has a vital antioxidant role, crucial for maintaining tissue formation and functionality by protecting vital macromolecules from oxidative damage. The essential role of vitamin D (VD) in the male reproductive system has been suggested due to the expression of vitamin D receptor (VDR) and Vitamin D-metabolizing enzymes in the testis and spermatozoa. Aim This study examines the effects of high-dose VC and VD on sperm quality, testosterone levels, and hepatorenal function, focusing on CDKN1B expression during spermatogenesis. Methods Twenty-seven male mice were divided into three groups (n=9/group): (1) saline vehicle control, (2) VC treatment (40 mg/kg, or 800 IU/kg), and (3) VD treatment (25 µg/kg, or 1000 IU/kg). For 15 days, intraperitoneal injections were given every day. Histological and immunohistochemical expression of CDKN1B, as well as biochemical investigations, including liver and kidney biomarkers, testosterone, and sperm parameters, were performed on day 16." Results High-dose vitamin D (VD) treatment significantly reduced sperm count and motility (p<0.01), alongside a marked decline in testosterone levels (p<0.01). Hepatorenal toxicity was evident, with significantly elevated liver enzymes (ALT & AST) and kidney biomarkers (Creatinine & Urea) (p<0.05), with a significant reduction in testis length and weight (p<0.05). In contrast, vitamin C (VC) treatment showed non-significant improvements in sperm motility and testosterone levels, with no adverse hepatorenal effects. Immunohistochemical analysis revealed elevated CDKN1B expression in VDtreated spermatocytes, indicative of cell cycle arrest during spermatogenesis. In contrast, VC downregulated CDKN1B, with no significant reduction in testis weight or length. Conclusion Through hepatorenal toxicity, hormonal suppression, and spermatogenesis disruption mediated by CDKN1B, hypervitaminosis D reduces male fertility. VC, on the other hand, has beneficial antioxidant properties without any adverse effects. These results support cautious VD monitoring and draw attention to the dangers of excessive VD supplementation, especially in clinical settings that employ CYP-inducing drugs. VC might be a safe supplemental treatment for infertility brought on by oxidative stress.