Increase of fecundity by probiotic administration in zebrafish (Danio rerio)

Abstract

It is well known established that reproduction is sensitive to the state of energy reserves, and that there is a balance between energy homeostasis and fertility. In this view, this study examined the effects of the probioticLactobacillus rhamnosus, as a feed additive, on zebrafish (Danio rerio) fecundity. Ten days of probiotic treatment modulate the gene expression of neuropeptide hormones and metabolic signals, such askiss1,kiss2andleptinboth at the CNS level and at the peripheral level. The increase in fecundity brought about by the probiotic was demonstrated by the higher number of ovulated eggsin vivoand by the higher germinal vesicle breakdown rate obtained with thein vitromaturation assay. The increase in oocyte maturation was associated with increased transcription of genes coding for signals which induce the maturation phase, such aslhcgr,cbr1l, andpaqr8genes, concomitant with a decreased transcription of genes coding for local factors which prevent oocyte maturation, such astgfb1,gdf9, andbmp15. In conclusion, all these findings highlight the action ofL. rhamnosusboth on the endocrine system and at the local level by inducing oocyte maturation. The significance of the results herein obtained underlined the importance of diet in the reproductive process, supporting the hypothesis that feed additives can improve fecundity. Considering that the zebrafish has been clearly established as a vertebrate model for biomedical research, these results support the potentiality of feed additives such as probiotics, frequently used in the human diet, as a new technology to improve reproduction in all vertebrates, including humans.