Effects of different dietary DHA:EPA ratios on gonadal steroidogenesis in the marine teleost, tongue sole (Cynoglossus semilaevis)

Abstract

The present study was conducted to investigate the effects of dietary DHA and EPA on gonadal steroidogenesis in mature females and males, with a feeding trial on tongue sole, a typical marine teleost with sexual dimorphism. Three experimental diets differing basically in DHA:EPA ratio, that is, 0·68 (diet D:E-0·68), 1·09 (D:E-1·09) and 2·05 (D:E-2·05), were randomly assigned to nine tanks of 3-year-old tongue sole (ten females and fifteen males in each tank). The feeding trail lasted for 90 d before and during the spawning season. Fish were reared in a flowing seawater system and fed to apparent satiation twice daily. Compared with diet D:E-0·68, diet D:E-1·09 significantly enhanced the oestradiol production in females, whereas diet D:E-2·05 significantly enhanced the testosterone production in males. In ovaries, diet D:E-1·09 induced highest mRNA expression of follicle-stimulating hormone receptor (FSHR), steroidogenic acute regulatory protein, 17α-hydroxylase (P450c17) and 3β-hydroxysteroid dehydrogenase (3β-HSD). In testes, diet 2·05 resulted in highest mRNA expression of FSHR, cholesterol side-chain cleavage enzyme, P450c17 and 3β-HSD. Fatty acid profiles in fish tissues reflected closely those of diets. Female fish had more gonadal EPA content but less DHA content than male fish, whereas there was a reverse observation in liver. In conclusion, the dietary DHA:EPA ratio, possibly combined with the dietary EPA:arachidonic acid ratio, differentially regulated sex steroid hormone synthesis in mature female and male tongue soles. Females seemed to require more EPA but less DHA for the gonadal steroidogenesis than males. The results are beneficial to sex-specific nutritive strategies in domestic teleost.

Transcriptomic Analysis of Potential “lncRNA–mRNA” Interactions in Liver of the Marine Teleost Cynoglossus semilaevis Fed Diets With Different DHA/EPA Ratios

“…Moreover, compared to total DHA+EPA contents, the effects of DHA/EPA ratio were interesting as well but relatively less studied (Sargent et al, 1999; Kim et al, 2002; Lee et al, 2003; Wu et al, 2003; Skalli and Robin, 2004; Hamre and Harboe, 2008; Wilson, 2009; Lund and Steenfeldt, 2011; ØStbye et al, 2011; Tocher, 2015). Our previous studies with marine species such as large yellow croaker Larmichthys crocea (Zuo et al, 2012a), Japanese seabass Lateolabrax japonicus (Xu et al, 2016) and tongue sole (Xu et al, 2017) have shown the significantly different roles of DHA and EPA in some physiological processes such as non-specific immune response and gonadal steroidogenesis. In the present study, taking advantage of completely sequenced genome data on tongue sole C. semilaevis , a genome-wide hepatic transcriptome analysis was conducted with tongue sole following an 80-day feeding trial with diets containing different DHA/EPA ratios.…”

“…Limited studies on lncRNAs in fish have been restricted to model fish species, and most of the studies focused on developmental biology (Kaushik et al, 2013; Liu et al, 2013; Haque et al, 2014; Dhiman et al, 2015; Al-Tobasei et al, 2016; Wang et al, 2016, 2017; Sarangdhar et al, 2017; Hu et al, 2018). Therefore, following our previous studies on lipid/fatty acid nutrition of marine fish (Zuo et al, 2012a,b; Xu et al, 2016, 2017), the present study was aimed at investigating the potential involvement of lncRNAs in effects of dietary fatty acids on a non-model marine teleost tongue sole Cynoglossus semilaevis , which is also an important aquaculture species. A feeding trial was conducted in this study, followed by hepatic transcriptome analysis.…”

“…Docosahexaenoic acid (DHA, 22:6n-3) and eicosapentaenoic acid (EPA, 20:5n-3) are the most important essential fatty acids for marine fish. Previous studies have widely demonstrated the critical roles of DHA and EPA in a series of physiological functions of marine fish such as functions of visual and neural systems (Bell et al, 1995; Furuita and Takeuchi, 1998; Ishizaki et al, 2000, 2001; Benítez-Santana et al, 2007; Noffs et al, 2009), bone development (Gapasin and Duray, 2001; Roo et al, 2009), pigmentation (Villalta et al, 2008; Vizcaíno-Ochoa et al, 2010), stress resistance (Kanazawa, 1997; Liu et al, 2002), immune response (Zuo et al, 2012b; Xu et al, 2016), and reproduction (Wilson, 2009; Xu et al, 2017). However, more fundamental mechanisms involved are still elusive.…”

Integrated lncRNA and mRNA Transcriptome Analyses in the Ovary of Cynoglossus semilaevis Reveal Genes and Pathways Potentially Involved in Reproduction

“…In tongue sole, fatty acids have been proven to be required for gonadal steroidogenesis. An appropriate DHA:EPA ratio can induce high expression of the follicle-stimulating hormone receptor (FSHR), steroidogenic acute regulatory protein (STAR), 17α-hydroxylase (P450c17) and 3β-hydroxysteroid dehydrogenase (3β-HSD), which are involved in steroidogenesis ( Xu et al, 2017 ). Thus, the retinol metabolism and fatty acid metabolism pathways may be involved in oocyte maturation, including steroidogenesis and oocyte meiosis, in tongue sole.…”

Testicular development and spermatogenesis in fish: insights into molecular aspects and regulation of gene expression by different exogenous factors

“…2). Different dietary DHA:EPA ratio increased the star mRNA expression in tongue sole (Cynoglossus semilaevis) (Xu et al 2017). Cabas et al (2013), treated gilthead seabream with 17aethynylestradiol which decreased the mRNA expression of the star.…”