Journal Article

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

Xu, Houguo, Wei, Yuliang, Zhang, Yuanqin, Cao, Lin, Liang, Mengqing

2017

Overview

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.

• Publisher: Cambridge University Press
• Subject: 17-beta-hydroxysteroid dehydrogenase / 17-Hydroxysteroid Dehydrogenases - genetics / 17-Hydroxysteroid Dehydrogenases - metabolism / animal ovaries / Animal reproduction / Animal tissues / Animals / Aquaculture / Arachidonic acid / Arachidonic Acid - administration & dosage / Arachidonic Acid - analysis / Bass / Biosynthesis / Cholesterol / Cynoglossus semilaevis / Diet / Diet - veterinary / Docosahexaenoic Acids - administration & dosage / Docosahexaenoic Acids - analysis / Eicosapentaenoic Acid - administration & dosage / Eicosapentaenoic Acid - analysis / estradiol / Estradiol - biosynthesis / Estradiol - blood / experimental diets / fatty acid composition / Fatty acids / Feeding / Female / Females / Fish / Flatfishes - metabolism / Follicle-stimulating hormone / follicle-stimulating hormone receptors / Gene expression / Gonadal Steroid Hormones - biosynthesis / Gonadal Steroid Hormones - blood / Gonads - drug effects / Gonads - metabolism / Hormones / Hydroxylase / Laboratories / Lipids / Lipogenesis - drug effects / Liver / Male / Males / Nutrition research / Nutritional Endocrinology / Ovaries / Proteins / rearing / Receptors, FSH - genetics / Receptors, FSH - metabolism / Regulation / RNA, Messenger - genetics / RNA, Messenger - metabolism / Satiety / Seawater / Sex / Sex ratio / Sexual dimorphism / Spawning / Steroid 17-alpha-Hydroxylase - genetics / Steroid 17-alpha-Hydroxylase - metabolism / steroid hormones / Steroidogenesis / Steroidogenic acute regulatory protein / Steroids / tanks / Testes / Testosterone / Testosterone - biosynthesis / Testosterone - blood / tissues