Zinc is an essential trace mineral for the normal functioning of the male reproductive system. Current studies have investigated the relationship between seminal plasma zinc and male infertility but have shown inconsistent results. Hence, we systematically searched PubMed, EMBASE, Science Direct/Elsevier, CNKI and the Cochrane Library for studies that examined the relationship between seminal plasma zinc and male infertility, as well as the effects of zinc supplementation on sperm parameters. Twenty studies were identified, including 2,600 cases and 867 controls. Our meta-analysis results indicated that the seminal plasma zinc concentrations from infertile males were significantly lower than those from normal controls (SMD (standard mean differences) [95% CI] −0.64 [−1.01, −0.28]). Zinc supplementation was found to significantly increase the semen volume, sperm motility and the percentage of normal sperm morphology (SMD [95% CI]: −0.99 [−1.60, −0.38], −1.82 [−2.63, −1.01], and −0.75 [−1.37, −0.14], respectively). The present study showed that the zinc level in the seminal plasma of infertile males was significantly lower than that of normal males. Zinc supplementation could significantly increase the sperm quality of infertile males. However, further studies are needed to better elucidate the correlation between seminal plasma zinc and male infertility.
Infertility is defined as the lack of ability to conceive within one year of unprotected intercourse with the same partner1. It is estimated that nearly 8–12% of couples are infertile2, and approximately 30–40% of infertility cases are caused by male factors3. Several risk factors are involved in the pathogenesis of infertility, some of which include alterations in spermatogenesis due to testicular cancer, aplasia of the germinal cells, varicocele, defects in the transport of sperm, or environmental factors as well as congenital anomalies, infectious diseases, bilateral spermaducts, pregnancy-related infections, alterations in the characteristics of semen such as a decrease in sperm motility and sperm count, the presence of antisperm antibodies (ASAs), and nutritional deficiency of trace elements such as selenium and zinc (Zn).
Trace elements play an important role in the male reproductive process because of their high activity at the molecular level, although they are known to exist in the body at very low levels. Zn is second only to iron as the most abundant element in human tissues. Although Zn is found in most types of foods such as red meat, white meat, fish, and milk, the World Health Organization (WHO) estimates that one-third of the world’s population is deficient in zinc. Zinc and citrate are excreted from the prostate gland as a low-molecular-weight complex; thus, it is estimated that the zinc levels in seminal plasma typically represent prostatic secretory function. After ejaculation, half of the quantity of this complex is redistributed and linked to medium- and high-molecular-weight compounds generated from the seminal vesicles9. The decrease in the seminal plasma zinc concentration may result in inadequate intake, reduced absorption, increased losses, or increased demand. Additionally, the commonest worldwide cause is inadequate intake as a result of a diet low in Zn or rich in phytate. Additionally, increased urinary losses can occur under conditions associated with muscle catabolism, such as sepsis, or iatrogenically from the prolonged use of drugs. Furthermore, some studies have reported that a sharp decrease in zinc in the prostatic fluid must result in a decreased zinc concentration in seminal plasma.
During reproduction, zinc has numerous important functions, and it is essential for conception, implantation, and a favorable pregnancy outcome Zinc is present in high concentrations in the seminal fluid, and it could play a multifaceted role in sperm functional properties. It influences the fluidity of lipids and, thus, the stability of biological membranes. It affects the stability of sperm chromatin16. It is involved in the formation of free oxygen radicals, and it could play a regulatory role in the process of capacitation and the acrosome reaction18. However, little is known concerning the role of zinc in seminal plasma or serum regarding the global functional competence of human spermatozoa, such as the sperm’s ability to penetrate cervical mucus (CM) or its fertilizing capacity. The relationship of zinc to the routinely determined variables of semen quality has been controversial.
Current studies have investigated the correlations between seminal plasma zinc concentrations and male infertility but have shown contradictory results, with some studies showing that the seminal plasma zinc concentrations of infertile men were significantly lower than those of normal controls; however, other studies did not report this outcome. Moreover, some studies have reported that zinc supplementation in the treatment of infertility could significantly increase the sperm quality of infertile males, while other studies have shown opposing results. Therefore, we systematically reviewed the available literature and performed a meta-analysis to evaluate the correlations between seminal plasma zinc concentrations and male infertility and the effects of zinc supplementation on sperm parameters to possibly provide valuable insights into the diagnosis and treatment of male infertility.
%20(2).jpeg)
0 Comments