Dietary bile acid supplementation reveals beneficial effects on intestinal healthy status of tongue sole (Cynoglossus semiliaevis).

The aim of this study was to investigate the effects of dietary bile acids (BAs) on intestinal healthy status of tongue sole in terms of immunity, antioxidant status, digestive ability, mucosal barrier-related genes expression and microbiota. Three experimental diets were prepared with BA levels at 0 mg/kg (CT), 300 mg/kg (BA1) and 900 mg/kg (BA2) in a commercial basal diet. Each diet was fed to three replicates with 120 fish (10.87 ± 0.32 g) in each tank. After an 8-week feeding trial, growth parameters were significantly enhanced in both BAs supplementary groups (P < 0.05), and compared with CT group, survival rate in BA2 group was significantly improved (P < 0.05). Intestinal lysozyme activity and contents of immunoglobulin M and complement 3 were significantly increased in both BAs supplementary groups (P < 0.05), suggesting an enhancement effect on the non-specific immune response. BAs inclusion also significantly improved intestinal antioxidant capabilities by increasing antioxidase activities and decreasing malondialdehyde levels. In addition, compared with CT group, intestinal digestive ability was substantially enhanced as indicated by the significantly increased lipase activity in BA2 group (P < 0.05) and significantly increased amylase activity in BA1 and BA2 groups (P < 0.05). Coincidentally, BAs inclusion significantly upregulated the relative expression of intestinal mucosal barrier-related genes (P < 0.05). Further, dietary BAs distinctly remodeled intestinal microbiota by decreased the abundance of some potential pathogenic bacteria. In conclusion, dietary BAs supplementation is an effective way to improve the intestinal healthy status of tongue sole.

Identification of Potential Blind-Side Hypermelanosis-Related lncRNA-miRNA-mRNA Regulatory Network in a Flatfish Species, Chinese Tongue Sole (Cynoglossus semilaevis).

Blind-side hypermelanosis has emerged as a major concern in commercial rearing environments of the flatfish aquaculture industry. To date, the underlying molecular mechanisms are not well understood. To fill this gap, in this study, whole transcriptomic sequencing and analyses were performed using normal skins and hypermelanic skins of the blind side of Chinese tongue sole (Cynoglossus semilaevis). Differentially expressed long non-coding RNAs (DElncRNAs), miRNAs (DEmiRNAs), and differentially expressed genes as well as their competing endogenous RNA (ceRNA) networks were identified. A total of 34 DElncRNAs, 226 DEmiRNAs, and 610 DEGs were identified. Finally, lncRNA-miRNA-mRNA regulatory networks (involving 29 DElncRNAs, 106 DEmiRNAs, and 162 DEGs) associated with blind-side hypermelanosis were constructed. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses of 162 DEGs in ceRNA networks identified DEGs (e.g., oca2, mc1r, and ihhb) in pigmentation-related biological processes and DEGs (e.g., ca4, glul, and fut9) in nitrogen metabolism, glycosphingolipid biosynthesis, and folate biosynthesis pathways, as well as their corresponding DElncRNAs and DEmiRNAs to potentially play key regulatory roles in blind-side hypermelanosis. In conclusion, this is the first study on the ceRNA regulatory network associated with blind-side hypermelanosis in flatfish. These new findings expand the spectrum of non-coding regulatory mechanisms underpinning blind-side hypermelanosis, which facilitates the further exploration of molecular regulatory mechanisms of malpigmentation in flatfish.