The Relationship between Seminal Fluid Hyperviscosity and Oxidative Stress: A Systematic Review

Abstract

Introduction: Seminal fluid viscosity is a key parameter to achieve fertilization. Viscosity is more frequently increased in patients with infertility. However, the mechanism by which hyperviscosity causes infertility is still poorly understood. As an increased blood viscosity is associated with diseases caused by oxidative stress, it can be supposed that there is a relationship between seminal fluid viscosity and oxidative stress in male infertility. Therefore, this systematic review aims to investigate the relationship between hyperviscous seminal fluid and oxidative stress.

Materials and methods: We performed a systematic search on the following databases Pubmed, MEDLINE, Cochrane, and Scopus from the earliest available date to 10 January 2021, using Medical Subjects Headings (MeSH) indexes and keywords searches. The study included all the articles that evaluated the relationship between increased seminal fluid viscosity and oxidative stress. Article reviews even though dealing with seminal fluid hyperviscosity were excluded.

Results: 5 articles were included in this systematic review. The results demonstrated an important impairment of antioxidant systems and increased oxidative stress in patients with high seminal fluid viscosity.

Conclusions: These findings suggest that a careful assessment of oxidative stress in patients with hyperviscosity may be very useful in clinical practice. Infertile patients with seminal fluid hyperviscosity could benefit from the treatment with antioxidants to protect sperm cells from oxidative damage and to improve their functional properties.

Keywords: antioxidants; idiopathic male infertility; male infertility; oxidative stress; seminal fluid viscosity.

Figure 1

Flowchart of the studies included in systematic review.

Figure 2

Seminal fluid hyperviscosity and oxidative stress. The mechanism by which hyperviscosity causes infertility is still poorly understood. Increased seminal fluid viscosity worsens sperm parameters, especially motility, and decrease chromatin integrity [35]. Interestingly, previous studies have shown an imbalance between oxidant production and antioxidant capacity in patients with high seminal fluid viscosity. A decreased activity of catalase (CAT) and total antioxidant capacity (TAC) have been reported in patients with hyperviscous ejaculates [8,62]. On the contrary, seminal fluid hyperviscosity correlated to increased levels of malondialdehyde (MDA) and protein carbonyls [63], high levels of pro-inflammatory interleukins, and leukocytes [19]. The increased oxidative stress damages DNA, proteins, and lipids and in turn, impairs male fertility. Thus, a careful assessment of oxidative stress in patients with hyperviscosity may be very useful in clinical practice. Infertile patients with seminal fluid hyperviscosity could benefit from the treatment with antioxidants to protect sperm cells from oxidative damage and to improve their functional properties.