Η επίδραση της χορήγησης με την τροφή ωμέγα-3 λιπαρών οξέων και φυσικών αντιοξειδωτικών ουσιών σε παραμέτρους του σπέρματος κονίκλων

Abstract

Spermatozoa have cell membranes that differ structurally from those of somatic cells, because of their high content of polyunsaturated fatty acids (PUFA). PUFA are responsible for membrane fluidity and therefore, their levels affect the fusing events that are associated with fertilization. However, PUFA are also vulnerable to be attacked by reactive oxygen species (ROS), which leads to lipid peroxidation and thus can seriously affect the integrity of the spermatozoon and its fertilizing ability. Despite the disadvantages of high concentrations of PUFA in the cell membrane, a continuously increasing research interest is focused on the exploration of the possibility to increase the fertilizing ability of spermatozoa with diet-provided PUFA, in both humans and domestic animals. The aim of this study was to investigate the effect of PUFA-supplementation in the diet, in the presence or absence of green tea catechin extract, on the lipid profile of the spermatozoa membranes, as well as, on various sperm evaluation parameters. The antioxidant potential of catechins was evaluated in comparison to that of vitamin E, a customly-used standard antioxidant supplement. For this purpose, 35 male New Zealand rabbits were assigned to five different diets: a) 1st group: standard diet (control), b) 2nd group: n-3-supplemented diet (standard diet were 2% ROPUFA® “30” was substituted for the soybean oil that is contained in the standard diet, c) 3rd group: n-3-supplemented diet enriched with 200ppm catechin extract (CE), d) 4th group: n-3-supplemented diet enriched with 400ppm CE and e) 5th group: n-3-supplemented diet enriched with 200ppm vitamin E. Sperm samples were collected from all bucks following 20, 40, 60, 80, 100 and 120 days of continuous feeding on the respective diet, with the use of an artificial vagina. Conclusively, dietary supplementation of n-3 fatty acids altered the lipid profile of the spermatozoa. In particular, n-3 lipids were incorporated in the membranes of the spermatozoa from the 40th day of experimentation. The enrichment of membranes in n-3 fatty acids was manifested by an elevation of the 22:5 n-3 (DPA) levels and resulted in the induction of lipid peroxidation in ejaculated spermatozoa, as determined on the basis of the malondialdehyde content. However, there was no detection of any changes in the quantitative and qualitative characteristics of the spermatozoa, such as motility, and concentration and viability, abnormal forms and acrosome integrity, respectively. Nevertheless, lipid peroxidation increased the percentage of apoptosis in the PUFA-enriched spermatozoa. The induction of apoptosis was also accompanied by an increase in plasminogen activator activity. All these effects of PUFA on sperm cells were detected after 40 days on the corresponding diet and remained more or less stable during the entire experimental period of 120 days. Supplementation of diet with 200ppm CE sufficiently alleviated the effects mediated by the enrichment of spermatozoa with PUFA by preventing lipid peroxidation, as demonstrated by the decreased MDA levels in the spermatozoa of this group. Specifically, CE inhibited the induction of apoptosis and the activation of plasminogen activators in the spermatozoa. The protective role of CE was comparable to that of vitamin E, which was used as a standard antioxidant-supplement, but equal or more effective than that of CE at higher concentration (400ppm). In conclusion, the results of this study indicate that the role of PUFA in sperm physiology is not thoroughly clear and suggest that further research is required in order to further clarify the mechanisms by which PUFA affect the oxidative status and the fertilizing potential of the spermatozoa. In addition, this study provides further data that indicate the necessity for simultaneous supplementation of antioxidant substances along with the PUFA, in order to maintain the oxidative balance in the spermatozoa. The contribution of green tea catechin extracts in the restoration of the oxidative balance is comparable to that of vitamin E.

[…] Ο σκοπός της διατριβής αυτής ήταν να μελετηθεί η επίδραση της χορήγησης σιτηρεσίου εμπλουτισμού σε πολυακόρεστα λιπαρά οξέα, παρουσία ή απουσία εκχυλίσματος κατεχινών πράσινου τσαγιού στη λιπιδική σύσταση του σπέρματος, καθώς και σε διάφορες παραμέτρους εκτίμησής του. Η αντιοξειδωτική δράση των κατεχινών σε διαφορετικές συγκεντρώσεις, εκτιμήθηκε σε σύγκριση με τη δράση της βιταμίνης Ε., ουσίας με γνωστή αντιοξειδωτική δράση. […]