Cystathionine Enzymes in Transsulfuration and HO-1 Production: Impact on Spermatogenic Disorders in Folate and B12...

The 1-carbon metabolic cycle is essential for cellular growth, biomolecule synthesis, and epigenetic regulation. This cycle depends on B-complex vitamins, particularly folate (B9) and cobalamin (B12), which act as cofactors. Deficiencies in these vitamins can disrupt homocysteine metabolism, impair spermatogenesis, and increase oxidative stress, thereby compromising male fertility. To investigate the impact of dietary deficiencies in vitamins B12 and B9 on trans-sulfuration enzymes [cystathionine-β-synthase (CBS) and cystathionine-γ-lyase (CSE)], sperm function, oxidative stress, and DNA methylation in a mouse model.

In this experimental study, male mice were fed either a standard chow diet or a diet deficient in vitamins B12 and B9. Sperm parameters, chromatin integrity [via acridine orange (AO) and aniline blue (AB)], lipid peroxidation, and intracellular reactive oxygen species (ROS; assessed using DCFH-DA and BODIPY C11) were evaluated. Sperm DNA methylation was measured using immunofluorescence. Serum levels of folate, vitamin B12, and testosterone were quantified. Expression of CBS, CSE, and HO-1 were analyzed by quantitative reverse transcriptase polymerase chain reaction (qRTPCR) and Western blot.

Mice on the vitamin B deficient (VBD) exhibited significantly decreased sperm concentration and motility, along with increased morphological abnormalities, DNA damage, histone retention, and lipid peroxidation. Intracellular ROS levels did not differ significantly from controls. The VBD group also showed lower serum folate and B12, elevated homocysteine, and reduced testosterone levels. DNA methylation intensity in sperm was significantly decreased. Histological analysis revealed impaired testicular architecture and reduced spermatogenic indices. CSE gene expression was significantly downregulated, whereas CBS and Heme oxygenase 1 (HO-1) expression remained unchanged. Protein levels of CBS, CSE, and HO-1 showed no significant differences.

Deficiencies in folate and vitamin B12 negatively affect sperm quality and testicular function in male mice, likely through disrupted homocysteine metabolism and altered gene expression in the trans-sulfuration pathway. These findings underscore the importance of adequate B-vitamin intake for male reproductive health.