Exploring correlations between sex steroids and fatty acids and their potential roles in the induced maturation of the male European eel

Abstract

ElsevierBaeza Ariño, R.; Peñaranda, D.; Vilchez Olivencia, MC.; Tveiten, H.; Pérez Igualada, LM.; Asturiano Nemesio, JF. (2015). Exploring correlations between sex steroids and fatty acids and their potential roles in the induced maturation of the male European eel. Aquaculture. 435:328-335. doi:10.1016Aquaculture. 435:328-335. doi:10. /j.aquaculture.2014 . 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 AbstractThe present study was undertaken to evaluate the correlations between the fatty acids in the liver and testis and the plasma levels of the hormonal steroids used during eel spermatogenesis, in order to clarify the physiological roles fatty acids play in the spermatogenetic process. The stages of testis development (S1-S5) were assessed by histological observations in order to classify the different phases of hormonally-induced spermatogenesis and evaluate the possible relationships between the hormones and fatty acids in each stage.The highest plasma levels of 17β-Estradiol (E2), testosterone (T) and 11-ketotestosterone (11KT) were found in S1, when spermatogonial proliferation occurs. A correlation was found between 17α-20β-dihydroxy-4-pregnen-3-one (DHP) levels and some fatty acids during the proliferation and growing phases (S1-2), suggesting that DHP might modulate lipid metabolism in the liver during early spermatogenesis. The DHP levels increased significantly during the growing phase (S2) and remained at high levels throughout the subsequent development stages (S3-S5).Similar to results found in mammals, our results show that in the eel there are regulatory mechanisms, including eicosapentaenoic acid (20:5-n3, EPA) and docosahexaenoic acid (22:6-n3, DHA), which act as modulators in the synthesis of androgens, particularly during the final phase of sperm maturation. Our results suggest that the fact that EPA, ARA and DHA concentrations in the eel testis remain constant/stable during spermiation could be related to the subsequent union of the spermatozoa and the egg.The findings from this research provide new insights for further studies about the possible effect of steroids on desaturase activity and highlight the importance of the effect of lipid metabolism during male eel spermatogenesis.

Roles of lipids and fatty acids through the spermatogenesis of European eel (Anguilla anguilla)

“…Baeza et al (2014b) found a negative correlation between EPA from the liver and sperm volume, suggesting its synthesis in the liver and its subsequent mobilization to the testis to be used to produce sperm cell membranes. Finally, correlations between EPA and androgens during the final phase of sperm maturation, exemplifies the modulatory effect of EPA on the synthesis of androgens (Baeza et al, 2015). Together, these studies highlight the importance of EPA in male eel reproduction and compliment our findings; our study shows that PRO-EEL2, PRO-EEL3 and DAN-EX diet, having the highest percentage of EPA in sperm, showed the highest sperm motility.…”

“…All of this information, together with the conclusions made by Baeza et al (2014Baeza et al ( , 2015; Chapters I-II), could prove useful in the development of enriched diets that may improve sperm quality, which in turn, could have an impact on the reproductive abilities of European eel males, thus improving fertilization success and embryo development. With the importance of PUFA in mind we propose further research aimed at improving the reproductive performance of eels by manipulating dietary requirements.…”

“…In the present study, negative and positive correlations were found (but lower than in the case of ARA) between EPA in the testis and the highest registered velocities. Recently, EPA seems to have a modulatory effect on the synthesis of androgens in eels with mature sperm (Baeza et al, 2015; Chapter II) so, both fatty acids (ARA and EPA) play important roles in male reproduction. ARA has been shown to be the main precursor for the production of series-2 prostaglandins, whereas it has been reported that EPA functions as an inhibitory regulator , Sargent et al, 2002 and in our study, both ARA and EPA appear to have an important function with regard to spermatozoal velocity.…”

Molecular approaches related to the European eel (Anguilla anguilla) reproductive process

“…The testis samples were processed and analysed as described by Baeza et al (2015). The maturation stages ( Figure 1) were determined using the following criteria: dominance of germ cell types, degree of development of the seminal tubules, GSI and sperm production by the male sampled in the same week of the sacrifice.…”

“…In the case of the European eel, the temperature of the hypothetical spawning area is around 20 ºC (Boëtius and Boëtius, 1967), and that is the reason why the maturation of males and females of this species has traditionally been performed in water of that temperature (Peñaranda et al, 2010;Pérez et al, 2009). However, the influence of temperature on the maturation process of the European eel has recently been noted both in females Pérez et al, 2011) and in males (Baeza et al, 2015;Tanaka et al, 2001). …”