Dietary synbiotic application modulates Atlantic salmon (Salmo salar) intestinal microbial communities and intestinal immunity.

A feeding trial was conducted to determine the effect of dietary administration of Pediococcus acidilactici MA18/5M and short chain fructooligosaccharides (scFOS) on Atlantic salmon (Salmo salar L.) intestinal health. Salmon (initial average weight 250 g) were allocated into triplicate sea pens and were fed either a control diet (commercial diet: 45% protein, 20% lipid) or a synbiotic treatment diet (control diet + P. acidilactici at 3.5 g kg(-1) and 7 g kg(-1) scFOS) for 63 days. At the end of this period, fish were sampled for intestinal microbiology, intestinal histology and the expression of selected immune-related genes (IL1ß, TNFα, IL8, TLR3 and MX-1) in the intestine. Compared to the control fish, the total bacterial levels were significantly lower in the anterior mucosa, posterior mucosa and posterior digesta of the synbiotic fed fish. qPCR revealed good recovery (log 6 bacteria g(-1)) of the probiotic in the intestinal digesta of the synbiotic fed fish and PCR-DGGE revealed that the number of OTUs, as well as the microbial community diversity and richness were significantly higher in the anterior digesta of the synbiotic fed fish than the control. Compared to the control fed fish, the mucosal fold (villi) length and the infiltration of epithelial leucocytes were significantly higher in the anterior and posterior intestine, respectively, in the synbiotic group. Real-time PCR demonstrated that all of the genes investigated were significantly up-regulated in the anterior and posterior intestine of the synbiotic fed salmon, compared to the control group. At the systemic level, serum lysozyme activity was significantly higher in the synbiotic fed fish and growth performance, feed utilisation and biometric measurements (condition factor, gutted weight and gut loss) were not affected. Together these results suggest that the synbiotic modulation of the gut microbiota has a protective action on the intestinal mucosal cells, improving morphology and stimulating the innate immune response without negatively affecting growth performance or feed utilization of farmed Atlantic salmon.

Effects of probiotic administration on zebrafish development and reproduction.

As the consumption of probiotics increases worldwide, scientists focus on identifying bacterial strains able to improve human life quality and evidence the biological pathways affected by probiotic treatment. In this review, some recent observations on the effects of changes of microbiota on zebrafish metabolism were discussed. In addition, the effects of Lactobacillus rhamnosus - a component of the human gut microflora - as a diet supplement on Danio rerio were presented. When administered chronically, L. rhamnosus may affect larval development and the physiology of reproductive system in the zebrafish model. It was hypothesized exogenous L. rhamnosus accelerates larval growth and backbone development by acting on insulin-like growth factors-I (igfI) and -II (igfII), peroxisome proliferator activated receptors-α and -ß, (pparα,ß) vitamin D receptor-α (vdrα) and retinoic acid receptor-γ (rarγ). Gonadal differentiation was anticipated at 6weeks together with a higher expression of gnrh3 at the larval stage when L. rhamnosus was administered throughout development. Moreover, brood stock alimented with a L. rhamnosus-supplemented diet showed better reproductive performances as per follicles development, ovulated oocytes quantification and embryos quality. A plausible involvement of factors such as leptin, and kiss1 and 2 in the improvements was concluded. The observations made on the physiology of female reproduction were correlated with the gene expression of a gigantic number of factors as the aromatase cytochrome p 19 (cyp19a), the vitellogenin (vtg) and the α isoform of the E2 receptor (erα), luteinizing hormone receptor (lhr), 20-ß hydroxysteroid dehydrogenase (20ß-hsd), membrane progesterone receptors α and ß, cyclin B, activinßA1, smad2, transforming growth factor ß1 (tgfß1), growth differentiation factor9 (gdf9) and bone morphogenetic protein15 (bmp15.) A model in which the exogenous L. rhamnosus in the digestive tract of zebrafish from the first days of life through sexual maturation positively influences the physiological performances of zebrafish was evidenced and a number of pathways that might be influenced by the presence of this human probiotic strain were proposed.

Perspectives on endocrine disruptor effects on metabolic sensors.

Endocrine disrupting (EDs) chemicals can increase or block the metabolism of endogenous peptidergic or steroid hormones by activating or antagonizing nuclear receptors in the hypothalamus, besides adipose tissue, liver and gonads. Toxicological and epidemiological studies have suggested the involvement of different EDs in an increasing number of metabolic disorders such as obesity and diabetes. The aim of this review is to summarize the literature from experimental animal studies demonstrating the impairment of body weight raised by the deregulation of peptidergic signals as well as by the activation of key metabolic molecular targets. Regarding the modification of gene transcription levels induced by EDs, new data on DEHP effect on food intake and lipid metabolism in the experimental model zebrafish (Danio rerio) have also been included in this review providing evidences about the dangerousness of DEHP low doses.

Environmental estrogens and reproductive biology in amphibians.

In this paper, the effects of an estrogenic compound, 4-nonyl-phenol (NP), on the amphibians Rana esculenta and Triturus carnifex are described together with those on sexual differentiation in Xenopus laevis. NP increased plasma vitellogenin in male frogs and newts in a dose-related manner; moreover, inhibitory effects on gonadotropin and prolactin (PRL) secretion by pituitary were found together with an elevation of plasma androgens. NP treatment also caused a remarkable increase in number of prolactin-immunolabeled cells, suggesting that xenoestrogen might induce, at least in the newt pituitary, a PRL accumulation possibly due to a reduction of the hormone release. In addition, both NP and bisphenol A caused feminization by increasing the percentage of female phenotypes in X. laevis, and the in vivo effects were more pronounced than those of estradiol-17beta.

Ovarian opioids and the reproductive cycle of the frog Rana esculenta.

In mammals, proopiomelanocortin-related peptides are involved in reproductive processes both at the hypothalamo-pituitary and ovarian levels. Using immunocytochemical, biochemical and physiological "in vitro" studies, we provide here evidence for a diffuse POMC-related opioid system in the frog Rana esculenta. Ovarian beta-endorphin (beta-EP) is expressed in thecal cells and changes during the reproductive cycle in an inverse relationship with follicular development. Seasonal changes in the ovary are different to those in the brain or in the pituitary. The ratio of acetylated vs native beta-EP in the ovary also changes over the reproductive period, affecting the biological activity of the peptide. During both the reproductive spring period and the summer post-reproductive phase pMol amounts of beta-EP stimulate follicular androgen secretion in vitro, in a naloxone-reversible way. In either period, an inhibition of estradiol, possibly mediated via other factors, is the result of opioid action. In conclusion, these data demonstrate for the first time the widespread presence of beta-EP-related peptides in the frog Rana esculenta. Both immunocytochemical and biochemical evidence, as well as in vitro responses, support a physiological role for beta-EP in ovarian seasonality during the reproductive cycle of this amphibian.