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. 2021 Feb 22;22(4):2188. doi: 10.3390/ijms22042188

Table 1.

Important investigations into the roles of Zn in human reproduction and human male infertility and its implications conducted in the last 13 years.

Author and Year Zn Role in Human Reproduction and Infertility Study Conclusion
Qu et al., 2007 [138] Zn-α2-glycoprotein, termed ZAG, plays a major action in sperm motility. ZAG could be present in human semen, and it could help with proper motility as well as with the signaling pathway known as PKA (Protein Kinase A).
Saleh, 2008 [139] Semen contains higher concentrations of Zn and copper than any other body fluid. This helps to maintain sperm quality. For proper diagnosis of male infertility, Zn and Cu estimation is important.
Colagar et al., 2009 [140] The absence or moderate deficiency of Zn in the seminal plasma leads to increased reactive oxygen species (ROS) and increased oxidative damage, which could result in low sperm quality. The seminal Zn concentration was found to be significantly positively correlated with sperm count and the normal morphology of sperm. A low or absent Zn intake results in low semen quality and leads to idiopathic male infertility.
Dissanayake et al., 2010 [141] Zn plays major parameter in determining sperm count, normal sperm morphology, and other parameters. Both the Zn concentration and total amount of Zn per volume of ejaculate were calculated in this study. The total Zn content was termed Zn (T), and it was positively correlated with the sperm count and normal morphology.
Khan et al., 2011 [142] Zn deficiency plays a key act in human male infertility. Zn deficiency is associated with hypogonadism and deficient development of secondary sex characteristics. Having adequate Zn in the seminal plasma aids in proper sperm functioning. An increased amount of Zn results in decreased sperm motility, but a decreased amount of Zn in the seminal plasma was associated with an increased sperm count. It is very crucial to monitor the Zn content in seminal plasma.
Hadwan et al., 2012 [143] Human seminal Zn is classified into three types of ligands: high, intermediate, and low molecular weight ligands. An increase in the oral supplementation of Zn results in increased sperm motility for asthenospermic patients. This study concludes that the overall increase in motility in asthenospermic patients following Zn supplementation increases the overall high and low molecular Zn ligand levels.
Sundaram et al., 2013 [144] Zn acts as a cofactor for DNA binding proteins and Zn fingers. Zn could be the best biochemical marker for major semen anomalies, as well as for the proper diagnosis of human male infertility.
Foresta, 2014
[20]
Zn is involved in a number of sperm functions after the post-epididymal phase reaches a maximum. During the entire lifetime of sperm, Zn trafficking occurs.
Altaher and Abdrabo, 2015 [145] Zn and Cu play major actions in oligospermic and asthenospermic patients. Zn concentration was significantly lower in cases of azoospermia and oligospermia.
Zhao et al., 2016 [146] Systematic data analysis suggests that Zn concentration is significantly lower than in other fertile groups, which proves the significance of Zn in semen parameters. Zn supplementation increases the major semen parameters like semen volume, forwarded motility, and normal morphology.
Nenkova et al., 2017 [137] Zn plays a major action in protecting spermatozoa against oxidative stress. There is evidence that trace elements play an antioxidative role at the time of ejaculation.
Fallah et al., 2018 [1] Zn acts as an antibacterial agent in the female genital tract and even helps in protection from immunological shock. Zn could be considered as a nutrient marker for male reproductive potential.
Mirnamniha et al., 2019 [6] Zn plays a major function in the incitation of capacitation. The measurement of Zn in the seminal plasma of idiopathic male infertility is essential.
Vickram et al., 2020 [84] Zn plays a major function in mediating the binding of prostasomes on spermatozoa to transfer essential compounds, which paves the way for fertilization. Prostasomes are biomarkers for both male infertility and prostate cancer diagnosis.