Vitamin D receptors and vitamin D₃-metabolizing enzymes have been found to be highly expressed in the ovaries and spermatophores of fish. However, the role of vitamin D₃ on fish gonadal development has rarely been reported. In this study, 2-month-old female zebrafish were fed with different concentrations of vitamin D₃ diets (0, 700, 1400, and 11 200 IU/kg) to investigate the effects of vitamin D₃ on ovarian development. The diet with 0 IU/kg vitamin D₃ resulted in elevated interstitial spaces, follicular atresia, and reproductive toxicity in zebrafish ovaries. Supplementation with 700 and 1400 IU/kg of vitamin D₃ significantly increased the oocyte maturation rate; upregulated ovarian gonadal steroid hormone synthesis capacity; and elevated plasma estradiol, testosterone, and ovarian vitellogenin levels. Furthermore, the current study identified a vitamin D response element in the cyp19a1a promoter and demonstrated that 1.25(OH)₂D₃-vitamin D response directly activated cyp19a1a production through activating the vitamin D response element. In conclusion, this study shows that an appropriate concentration of vitamin D₃ can promote zebrafish ovarian development and affect vitellogenin synthesis through the vdr/cyp19a1a/er/vtg gene axis.

Summary Sentence

Vitamin D₃ can promote the maturation of fish oocytes and improve the quality of embryos.

Graphical Abstract