Can Probiotics Affect Reproductive Processes of Aquatic Animals? - Aquaculture Nutrition: Gut Health, Probiotics and Prebiotics - page 335

A

PV PV

V V

B

PV PV

V V

Fig. 12.3 Representative micrographs of ovaries from (A) zebrafish females fed on a Lb. rhamnosus
supplemented diet and (B) control fed females, revealing an increase in vitellogenic follicles in ovary
sections from fish treated with the probiotic. PV = pre-vitellogenic follicles; V = vitellogenic follicles. Scale
bars = 100 μ m. (Source: Gioacchini et al . 2011.) For colour detail see Plate 14.

microbial communities, causing a clear shift in microbial populations, specifically enhancing
the presence of another LAB, Streptococcusthermophilus (refer to Figure 8.2 Gioacchini etal.
2012).
Regarding the effects of Lb. rhamnosus administration on ovary development, the results
indicate a positive effect on both growth and maturation phases. The effect of the probiotic
on follicle enhancing growth phase was supported by the increase in GSI (Gioacchini et al.
2011) along with histological studies evidencing, in ovary sections from fish treated with the
probiotic, an increase in vitellogenic follicles (Gioacchini et al. 2010a; 2011) (Figure 12.3).
Concomitantly, increases were observed in gene expression of cytochrome p 19 (cyp19a),
codifying the enzyme responsible for the final conversion of testosterone into E 2 , in the ovary,
and of vitellogenin (vtg) and the α isoform of the E 2 receptor (erα) in the liver (Gioacchini
et al. 2011).
Evidence is also available to demonstrate the stimulating role of Lb. rhamnosus on follicle
maturation phase. First, in vitro maturation assays showed that oocytes isolated from probi-
otic fed females displayed higher GVBD rates (Gioacchini et al. 2010a; 2010b; 2010c). At
the molecular level, in the ovary an increase in the transcription of genes codifying for sig-
nals which induce the maturation phase (such as lhr, 20β-hsd, mprβ, cyclin B, activinβA1
and smad2 genes) concomitantly with a reduction in the transcription of genes codifying
for local factors which prevent oocyte maturation (tgfβ1, gdf9 and bmp15) were observed.
An SDS-PAGE conducted on zebrafish follicles at different stages of development revealed
changes in cytoplasmic proteins induced by probiotic treatment. In particular, major modifica-
tions of the electrophoretic pattern were evidenced during maturation, which were also evident