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Received Oct 19, 2017; Accepted Dec 6, 2017
This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
1. Introduction
Sperm membrane is a key structure influencing sperm function; it is involved not only in sperm motility and vitality but also in acrosomal reaction and sperm-oocyte fusion. The characteristics and performance of the plasma membrane are strongly determined by its own fatty acid (FA) profile [1].
To this regard, mammalian spermatozoa are characterized by a high proportion of polyunsaturated fatty acids (PUFAs); in particular, testicular cells and spermatozoa contain large amounts of 20 and 22 carbon n-3 and n-6 PUFAs [2], which are considered as major constituents in human spermatozoa phospholipids [3–5]. Actually, the FA ratio appears to be critical to infertility in asthenozoospermic males [6], and FA composition has been suggested as a predictor of cryopreservation success of a seminal sample [7]. On this point, PUFAs were generally found higher in samples from normozoospermic men as compared to infertile patients [8–10] even if Khosrowbeygi and Zarghami [11] found higher levels of linoleic, arachidonic, and docosahexaenoic acids (DHA) in spermatozoa of patients with altered semen parameters compared to normozoospermic men. Moreover, Martinez-Soto et al. [7] demonstrated that spermatozoa the n-6/n-3 PUFA ratio was at a lower level in fertile men compared to the infertile ones, due to a significantly higher amount of total n-3 PUFA.
Oxidative stress (OS) results from a number of endogenous and exogenous stressors and is believed to play a central role in the pathogenesis of male infertility; when excessive amounts of reactive oxygen species (ROS) are produced or when antioxidant activity fails, the status of OS rises. It has been known that PUFAs represent the main target of the free radical insult, leading to the oxidative lipid deterioration causing alterations in sperm functional characteristics [12, 13].
To this regard, F2-isoprostanes (F2-IsoPs) are the most proximal products of the free radical-catalyzed arachidonic acid oxidation and are one of the most reliable approaches to evaluate a condition of endogenous lipid peroxidation in vivo [14–16]. Moreover, F2-IsoPs are not mere markers of OS, but they also elicit a...