Down-Regulated Expression of Cystathionine β-Synthase and Cystathionine γ-Lyase in Varicocele, and Infertile Men: A Case-Control Study

Cystathionine β-synthase (CBS) and cystathionine γ-lyase (CSE) are two important enzymes involved in One-Carbon metabolism. These enzymes play important roles in modulating oxidative stress and inflammation in male factor infertility through participating in the synthesis of glutathione (GSH) antioxidants in the trans-sulfuration pathway. Besides, the direct release of hydrogen sulfide (H2S) has anti-inflammatory and antioxidant effects. Therefore, the expression of CBS and CSE genes at mRNA levels in infertile and varicocele men was evaluated and compared to the healthy counterparts to clarify their possible role in the pathology of male infertility.

In this case-control study, semen parameter assessment (concentration, morphology, and motility of sperms) was performed on 28 men with varicocele, 43 infertile men with abnormal sperm parameters, and 19 fertile men. RNA was extracted from sperm samples followed by cDNA synthesis and real-time polymerase chain reaction (PCR) using CBS, CSE, and GAPDH primers.

Sperm concentration and motility in infertile and varicocele groups were significantly lower (P=0.001), while spermatoza normal morphology was higher than fertile group (P=0.05). The expression levels of both CBS and CSE genes in infertile (P=0.04 and P=0.037 respectively) and varicocele (P=0.01 and P=0.046 respectively) groups were significantly lower than fertile group. Additionally, CBS gene expression indicated a positive correlation with expression of CSE gene (r=0.296, P=0.025) and sperm parameters.

In light of our findings, there is a valid rationale to consider the primary role of CBS and CSE enzymes impairment in male factor infertility which specifically may point to a deficit in the release of essential antioxidants including the H2S as a molecular basis of infertility and warrants further investigation.