Effects of probiotics on zebrafish reproduction

Recent studies have demonstrated that probiotics can infuence reproductive performance, however, the mechanisms infuencing oogenesis remain poorly explored. In this study, the effects of dietary probiotic Lactobacillus rhamnosus IMC 501® administration was investigated on female zebrafish (D. rerio) reproductive performance and ovarian development (both growth and maturation phases). After feeding the zebrafish experimental diets for 10 days, real-time PCR and culture based methods revealed alterations on gut microbiota, characterised by high levels of L. rhamnosus IMC 501® in the gut of probiotic treated zebrafish, which were absent in the control. The microbial modulation in the gut was related with a signifcant increase of the gonadosomatic-index (GSI) associated, at the molecular level, to a signifcant increase of ovarian expression of cytochrome p 19 (cyp19a), hepatic vitellogenin (vtg) and the α isoform of the estradiol receptor (erα) genes evidencing a positive role of probiotic administration on the ovarian growth phase. Concomitantly, a signifcant increase of signals which positively control the maturation phase such as, cyclin B, activinβA1 and small mother against decapentaplegic 2 (smad2) genes in the ovary led us to confirm the beneficial role of the probiotic on maturation processes. Next to the enhancement of oocyte development processes by probiotic administration, an improvement of fecundity was evidenced which was associated with the increase of cyclooxygenase 2a (co×2a) gene expression in the ovary. The significance of the results obtained herein underlines the importance of diet and gut microbes in the reproductive processes, supporting the hypothesis that feed additives could improve fecundity.