This article is, in part, a review of present knowledge regarding the lipid metabolism of the sperm cell and the lipid composition of the sperm plasma membrane. It is also a summary of our research on this topic, reporting published and unpublished data. The article tries to cover both basic and clinical research. Sperm cells use lipid metabolic pathways for the production of part of their energy. The double leaflets of the membrane are not simply a passive, bilayer, lipidic film in which the receptors receive their molecular specific signals, but are a very specialized structure. Complete maturation of the lipids of the sperm cell membrane is reached after passage of the spermatozoon through the epididymis. A specific composition of phospholipids and a significant concentration of polyunsaturated fatty acids (PUFA) have been shown to be present in sperm membranes. Plasmalogen is a special kind of phospholipid found exclusively in spermatozoa and other cells with the capacity to react promptly to stimuli. In addition, we have found a high concentration of the n-3 PUFA family in the sperm membrane. Seminal plasma has a highly specialized scavenger system that defends the sperm membrane against lipoperoxidation. Various pathologies and systemic predisposition can lead to an antioxidant/pro-oxidant disequilibrium. Clinical trials with natural scavengers could be a useful research area in which to seek a treatment for these pathologies. Of the natural scavengers, glutathione has been shown to restore the physiological constitution of PUFA in the cell membrane under certain conditions.

The aim of our work was to define and better understand apoptosis in the spermatozoa of normal subjects, infertile patients and patients affected by specific tumoral diseases employing the method of the terminal deoxynucleotidyl transferase-mediated dUTP nick-end labelling and confirming the results by electron microscopy. We studied 23 healthy, normozoospermic subjects (group A), 29 oligoasthenoteratozoospermic patients, affected by various andrological pathologies (group B), 28 patients with Hodgkin's disease (C1) and 30 patients with testicular cancer (C2). Our data demonstrate that the percentage of apoptosis in normozoospermic subjects (group A) is significantly lower than in all the other groups (B, C1, C2) (P < 0.001). This confirms that high DNA fragmentation is one of the characteristics of spermatogenetic failure. The induction of apoptosis, which can also be a basic response to neoplastic disease, can even act right up to the mature male gamete. Our results suggest that apoptosis could be the final result of various pathologies and of a deregulation of spermatogenesis control systems.

There is still controversy over whether analytical techniques currently in use are able to identify the level of damage to spermatozoa. Large-scale studies should be conducted in different clinical settings to determine the effects of sperm DNA damage on the outcome of ART.

No abstract

A great deal of attention has recently been given to the essential role of polyunsaturated fatty acids (PUFA) of sperm membranes. We studied the fatty acid composition of the immature germ cells (IGC) and of the sperm populations separated by Percoll gradient in the ejaculate of normozoospermic patients. Fatty acid pattern was analysed by combined gas chromatography-mass spectrometry on a capillary column. In IGC, differences were found compared with mature spermatozoa, with a higher percentage of saturated fatty acids and of essential fatty acids. On the contrary, the long-chain PUFA were significantly lower in IGC. The highest concentration of n3 PUFA docohexaenoic acid (DHA) was detected in the spermatozoa deriving from 70-100% Percoll layers and a direct linear correlation was found between the increase of DHA and increased percentage of Percoll gradient. An inverse relationship between the percentage of atypical sperm forms in each layer and the percentage of DHA was also observed. This study demonstrates that the human germ cell line can elongate and desaturate essential fatty acids and that the percentage of long-chain PUFA is correlated with the normal morphology of sperm cells.

Glutathione therapy was used for 2 months in a placebo-controlled double-blind cross-over trial of 20 infertile patients with dyspermia associated with unilateral varicocele (VAR) or germ-free genital tract inflammation (INF). The patients received either glutathione (group 1) or placebo (group 2) for 2 months, then they crossed over to the alternative treatment for a further 2 months. The patients were randomly and blindly assigned to treatment (one i.m. injection every other day of either 600 mg glutathione or an equal volume of a placebo preparation). The standard semen analysis and the computer-assisted sperm motility analyses were carried out before treatment and during the trial. Statistical cross-over analysis, case-control study and treatment efficacy test were carried out on groups 1 and 2 and differences in the effects of therapy between VAR and INF patients with varicocele or inflammation were tested. Glutathione therapy demonstrated a statistically significant positive effect on sperm motility, in particular on the percentage of forward motility, the kinetic parameters of the computerized analysis and on sperm morphology. The findings of this study indicate that glutathione therapy could represent a possible therapeutical tool for both of the selected andrological pathologies.

We recently introduced reduced glutathione into the therapeutic protocols in some selected cases of dyspermia. This therapy improved semen quality both in a pilot follow-up study and in a double-blind cross-over trial. This improvement was seen in patients with varicocele and germ-free genital tract inflammation, two pathologies in which production of reactive oxygen species or other toxic compounds could have a pathogenic role. Polyunsaturated fatty acids of phospholipids play a major role in membrane constitution and function and are one of the main targets of the lipoperoxidative process. Therefore, to understand the therapeutic action of reduced glutathione, we selected infertile patients and studied the modifications produced by the therapy in seminal parameters, biochemical sperm membrane parameters, and the pattern of fatty acids of phospholipids from blood serum and red blood cell membranes (a model widely accepted as representative of general cell membrane status). The results showed an improvement in both sperm parameters and cell membrane characteristics. This study suggests that biochemical modifications in membrane constitution could explain the seminal results of glutathione therapy. On the other hand, it seems likely that only subjects with systemic membrane disturbances associated with andrological pathologies express this membrane damage in spermatozoa, resulting in dyspermia. This sperm alteration can be partially reversed by glutathione therapy if the structural cell membrane damage is not too severe.

No abstract