Chinese yam peel enhances the immunity of the common carp (Cyprinus carpio L.) by improving the gut defence barrier and modulating the intestinal microflora.

The Chinese yam peel (CYP) is a by-product of yam processing that is rich in various nutrients and a good source for feed additives. This study investigated the effects of CYP on the intestinal microbiota and gut defence barrier of the common carp (Cyprinus carpio L.). Different groups of experimental fish were fed a normal control diet (NC), a low CYP diet (LYP) and a high CYP diet (HYP) for 8 weeks. After the feeding trial, the fish were assessed for intestinal enzyme activity, intestinal histology, immune-related gene expression, intestinal SCFAs and intestinal microbiota. Our results indicated that the intestinal integrity and antioxidant enzyme (CAT and SOD) activity in the common carp were enhanced following CYP supplementation. The mRNA levels of anti-inflammatory (TGF-ß), tight binding protein (occludin and ZO-1) and pathway factor genes (TLR4 and NF-κB) were significantly upregulated in the HYP group (P＜0.05), which was accompanied by an increase in the level of pro-inflammatory IL-1ß in the gut (P＜0.05). High-throughput sequencing revealed that Fusobacteria, Proteobacteria, and Bacteroidetes bacteria were most abundant in the microbial community in the gut of the common carp. The relative abundances of Bacteroides, Flavobacterium and Lactobacillus were increased, while the abundances of pathogenic microorganisms such as Enterobacteriaceae, Shewanella, Pseudomonas and Vibrio were reduced after treatment with CYP. Furthermore, the concentrations of acetic acid, propionic acid, butyric acid and total short-chain fatty acids (SCFAs) in the gut were also increased (P＜0.05). Finally, our results revealed correlations between gut microbiota, SCFAs, non-specific immunity and antioxidant enzymes in CYP-fed carp. These results suggest that CYP-supplemented feed could improve the immunity of the common carp by modulating the intestinal microflora and enhancing the gut defence barrier and has the potential to be used as an immunostimulating feed additive in aquaculture.

Regulation of growth performance and lipid metabolism in juvenile grass carp (Ctenopharyngodon idella) with honeysuckle (Lonicera japonica) extract.

This study investigated the effects of honeysuckle extract (Lonicera japonica, HE) on the growth performance and lipid metabolism of juvenile grass carp (Ctenopharyngodon idella). HE at doses of 10 g kg-1 (LHE), 20 g kg-1 (MHE), and 40 g kg-1 (HHE) were individually mixed with the basal diet and fed to grass carp for 10 weeks, and ginseng extract (20 g kg-1, GSE) was used as a positive control. The results showed that HE administration exerted no effect on growth performance, but the hepatosomatic index (HSI) and muscle and liver lipid contents were significantly decreased in the LHE and MHE groups. The serum levels of LDL-c, total triglyceride (TG) and total cholesterol (TC) also declined in the HE-treated groups. Moreover, the disordered vacuolization and nucleus migration in the liver were alleviated in the MHE and HHE groups, and mRNA expressions of lipogenesis-related genes, such as acc1, fas, srebp1, and pparγ decreased. Similarly, the expression of genes related to lipolysis, such as cpt1, atgl, lpl, and pparα, was found to be significantly increased in the MHE and HHE groups compared with the control. Taken together, HE can effectively improve the lipid metabolism and ameliorate the lipid deposition of grass carp and thus may be a promising feed additive in aquaculture.

Intestinal microbiota and lipid metabolism responses in the common carp (Cyprinus carpio L.) following copper exposure.

The present study was conducted to determine the effects of waterborne copper exposure on the lipid metabolism and intestinal microbiota of juvenile common carp (Cyprinus carpio L.). Common carp were exposed to four waterborne copper (Cu) concentrations (0 (control), 0.07 (low), 0.14 (medium), and 0.28 (high) mg Cu/L) for 8 weeks. Exposure to a high concentration of Cu had a negative effect on growth indices (weight gain rate (WGR) and specific growth rate (SGR)). The biochemical indices measured in serum (low-density lipoprotein (LDL) and triglycerides (TGs)) were significantly affected by exposure to medium concentration levels of Cu. The mRNA levels of lipogenic enzymes (acetyl-CoA carboxylase 1 (ACC-1) and fatty acid synthase (FAS)) and sterol-regulator element-binding protein-1 (SREBP-1) in liver tissue and tight binding protein genes (ZO-1 and occludin) in intestinal epithelial tissue were significantly downregulated in the 0.14 and 0.28 mg/L Cu treatment groups, accompanied by upregulated mRNA levels of lipolysis enzymes (lipoprotein lipase (LPL) and carnitine palmitoyl transferase 1 (CPT-1)) in the liver. The data also showed that the composition of intestinal microbiota was changed following Cu exposure and could alter the α-diversity and ß-diversity. The abundances of few putative short-chain fatty acid (SCFA)-producing bacteria, including Allobaculum, Blautia, Coprococcus, Faecalibacterium, Roseburia, and Ruminococcus, decreased significantly. More specifically, Roseburia sequences were positively associated with lipogenic enzymes, total protein (TP), and TGs and negatively associated with lipolysis enzymes. Other sequences related to probiotics (Lactobacillus, Bacillus and Akkermansia) were also found to decrease, accompanied by an increase in sequences related to pathogens (Pseudomonas and Acinetobacter). To the best of our knowledge, the present study provides the first evidence that waterborne, chronic Cu exposure can disturb the composition of intestinal microbiota related to lipid metabolism and immunity in freshwater fish, thereby increasing the risk of pathogen invasion.

Feeding tea polysaccharides affects lipid metabolism, antioxidant capacity and immunity of common carp (Cyprinus carpio L.).

Tea polysaccharides plays a role in lipid metabolism, antioxidant capacity and immunity of mammals. To investigate the functions of tea polysaccharides on fish, the common carp (Cyprinus carpio L.) was selected as the animal model in this study. In our study, the common carp (45±0.71g) were randomly divided into four groups and were fed fodder with 50% carbohydrate. The common carp were orally administrated with 0 mg/kg BW (control group), 200 mg/kg BW (low-dose group), 400 mg/kg BW (medium-dose group) and 800 mg/kg BW (high-dose group) tea polysaccharide for two week. At the end of experiment, the serum glucose, TG, MDA contents and antioxidase activities were measured by commercial kits. The serum immune factors levels were tested by ELISA. The genes expression levels related to antioxidant capacity, metabolism and immunity were measured by real-time PCR. The results showed that the glucose, TG and MDA contents in serum were significantly decreased by tea polysaccharides treatment. The serum activities of SOD were significantly increased by low-dose tea polysaccharides treatment. The serum activities of GPX were significantly increased by medium-dose tea polysaccharides treatment. The serum levels of IL-1ß and TNFα were significantly decreased in the tea polysaccharides treatment group. In the high-dose treatment group, the serum level of TGFß was significantly increased, and the serum level of IL-12 was markedly decreased. In the hepatopancreas, the expression of acc1, fas, srebp1c, lpl, gys and pparγ were significantly reduced, and the expression of pygl, cat, mnsod, ho-1 and gr were significantly up-regulated in the tea polysaccharides group. In the intestine, the expression of zo-1, occ and gip was significantly up-regulated in the high-dose treatment group. Moreover, the expression of glut2 and sglt1 were significantly down regulated. In the spleen, the expression of il-12, tnfα and il-6 were significantly decreased, and the expression of il-10 and tgfß was significantly increased by the tea polysaccharides. In the spleen cells, the tea polysaccharides could relieve the LPS-induced immune damage. In conclusion, tea polysaccharides can improve antioxidant capacity, lipid metabolism and immunity of common carp.