Abstract
In the last two decades, the human sperm count linearly decreased in Western countries. Health problems, lifestyle, pollutants, and dietary behaviours are considered as the main risk factors, and the unbalance of dietary n‐6/n‐3 fatty acids is one of the most relevant. The aim of the present research is to study the effect of different dietary sources of n‐3 polyunsaturated fatty acids (PUFA) on reproductive traits using rabbit buck as the animal model. Fifteen rabbit bucks were assigned to three experimental groups: the control group, the FLAX group fed 10% extruded flaxseed, and the FISH group fed 3.5% fish oil for 110 days (50-day adaptation and 60-day experimental periods). Semen samples were collected weekly, whereas blood was collected every two weeks for the analytical determination of semen traits, oxidative status, fatty acid profiles, isoprostanes, neuroprostanes, and the immunocytochemistry of docosahexaenoic acid (DHA) and eicosapentaenoic (EPA) acid. At the end of the trial, the rabbits were killed and the testes were removed and stored for the analysis of fatty acid profile and immunocytochemistry. Results showed that dietary administration of n‐3 PUFA improved the track speed of the sperm and increased the n‐3 long-chain PUFA mainly confined in the sperm tail. Seminal plasma increased the thiobarbituric reactive substances (TBARs) by three times in the groups fed supplemental n‐3, whereas the F2-isoprotanes (F2-IsoPs) and F4-neuroprostanes (F4-NeuroPs) were lower and higher, respectively, in both supplemented groups than in the control. The testes and sperm showed a higher DHA and EPA distribution in rabbits from the n‐3 supplemented groups compared with the control. In conclusion, supplemental dietary n‐3 PUFA improved sperm motion traits and resulted in an enrichment of membrane fatty acid in the sperm and testes of the rabbits. However, such an increased amount of PUFA negatively affected the sperm oxidative status, which was mainly correlated with the generation of F4-NeuroPs with respect to F2-IsoPs. Accordingly, the latter cannot be considered a good marker of oxidation when diets rich in n‐3 PUFA are provided.
Highlights
In the last two decades, the sperm count has been progressively and linearly decreasing [1]; in the 30 years, a dramatic decrease in the fertility rate is expected
In agreement with our previous research [33], we demonstrated the ability of the reproductive tissues to efficiently synthesize and accumulate n‐3 LC polyunsaturated fatty acids (PUFA)
The dietary administration of n‐3 PUFA resulted in an enrichment of docosahexaenoic acid (DHA) and EPA in rabbit sperm and testes and indicated that the rabbit is a suitable model for the study of the spermatogenic process
Summary
In the last two decades, the sperm count has been progressively and linearly decreasing [1]; in the 30 years, a dramatic decrease in the fertility rate is expected. Long-chain (LC, ≥20C) PUFA result from elongations and desaturations of essential FA: linoleic acid (LA, 18 : 2n‐6) and α-linolenic acid (ALA, 18 : 3n‐3). These FA are known to affect membrane behaviour and flexibility [3] and are eicosanoid precursors [4]. PUFA accumulate in mammalian testes during puberty and are essential for sperm maturation, motility, and acrosome reaction [6]. They are incorporated into maturing germ cells by lysophosphatidic acid acyltransferase 3 [7]. During epididymal maturation, the lipid composition of the sperm membrane is remodelled and the saturation of FA increases from caput to the cauda epididymis, while the proportion of PUFA remains similar [9]
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