Effect of Bacillus amyloliquefaciens LSG2-8 on the intestinal barrier function of Amur minnow (Rhynchocypris lagowskii).

Probiotics are widely used in aquaculture. This article aims to study the effect of Bacillus amyloliquefaciens LSG2-8 on the intestinal barrier function of Rhynchocypris lagowskii. B. amyloliquefaciens LSG2-8 were added to R. lagowskii basal diets (CK) as additives at four concentrations: 1.0 × 106 (D-6), 1.0 × 107 (D-7), 1.0 × 108 (D-8) and 1.0 × 109 (D-9) CFU g-1 by dry weight of basal diet. After a 56-day feeding experiment, the activities of intestinal digestive enzymes and immunity-related enzymes of R. lagowskii on group D-6, D-7, D-8 and D-9 diet were significantly higher than the control (P < 0.05). In molecular experiments, the authors found that the levels of TGF-ß mRNA, IL-10 mRNA, ZO-1 mRNA and claudin-3 mRNA in group D-8 R. lagowskii were significantly higher (P < 0.05) than those of the control and other groups. Furthermore, the levels of IL-1ß and IL-8 mRNA of R. lagowskii on group D-6, D-7, D-8 and D-9 diet were significantly lower than those of the control (P < 0.05). In addition, the authors found that B. amyloliquefaciens LSG2-8 can regulate the intestinal flora balance and improve the intestinal structure of R. lagowskii. In conclusion, B. amyloliquefaciens LSG2-8 can improve the intestinal barrier function of R. lagowskii and can be used as a feed additive in aquaculture.

The immuneoreaction and antioxidant status of Chinese mitten crab (Eriocheir sinensis) involve protein metabolism and the response of mTOR signaling pathway to dietary methionine levels.

To study the effects of dietary methionine on growth performance, immunity, antioxidant capacity, protein metabolism, inflammatory response and apoptosis factors in Chinese mitten crabs (Eriocheir sinensis). Five diets with different methionine levels (0.63%, 0.85%, 1.06%, 1.25% and 1.47%) were fed to E. sinensis for 8 weeks. Results showed that in the 1.25% Met group, both growth performance and feed utilization were significantly increased. The crude protein content of crab muscle in the 1.06% and 1.25% Met groups was significantly higher than that in the control group. The immune and antioxidant enzyme activities, as well as gene expression levels of anti-lipopolysaccharide factor 1 (ALF1), Crustin-1, prophenoloxidase (proPO), cap 'n' collar isoform C (CncC) in 1.25% Met group were significantly higher than other groups. The activities of adenosine deaminase (ADA) and glutamate transaminase (GPT) in serum decreased first and then increased with the increase of methionine content, while the changes of ADA and GPT in hepatopancreas increased first and then decreased. 1.25% Met group exhibited significantly increased levels of GOT, GPT, and ADA compared to the control group. 1.25% Met diet group significantly up-regulated protein synthesis and anti-apoptotic factors, and significantly down-regulated inflammatory and pro-apoptotic factors in hepatopancreas. At 1.25% in the diet, methionine was found to boost E. sinensis growth, muscle protein deposition and immunity, as well as its antioxidant capacity. Combined with the above results, based on the expression of factors involved in the mammalian target of rapamycin (mTOR) signaling pathway and the mitogen-activated protein kinase (MAPK) signaling pathway, it is proved that methionine can not only promote protein metabolism, improve feed utilization, but also alleviate the inflammatory response and apoptosis caused by oxidative stress in the body.

L-carnitine regulated Nrf2/Keap1 activation in vitro and in vivo and protected oxidized fish oil-induced inflammation response by inhibiting the NF-κB signaling pathway in Rhynchocypris lagowski Dybowski.

Nrf2/Keap1 pathway is associated with oxidative stress. l-carnitine is currently under preclinical evaluation as a antioxidant, but the use of l-carnitine in aquaculture has been poorly evaluated and so far no mechanism has been demonstrated. Here, we explored the effects of l-carnitine in vitro and in vivo and discussed the possible molecular mechanisms involved. Firstly, Nrf2-siRNA significantly knocked down the mRNA level of Nrf2 in FHM cells. Thus, the activities of antioxidant enzymes (T-SOD, CAT, GSH-PX) and the level of antioxidant substance (GSH) and the level of MDA showed that Nrf2-siRNA pretreatment weakened the protective effect of l-carnitine. Moreover, the mRNA levels of Keap1, Nrf2, Maf and HO-1 indicated that l-carnitine regulated Nrf2/Keap1 activation. Furthermore, oxidized fish oil remarkably suppressed growth in Rhynchocypris lagowski Dybowski, and the lower antioxidant capacity was also observed in liver. According to the results of immune related indexes (the levels of IL-1ß, TNF-α, LZM, AKP) in serum and the mRNA levels of immune related genes (NF-κB, IL-1ß, TNF-α, IL-8, IL-10 and TGF-ß) in liver, oxidized fish oil also induced inflammatory response in fish. Also, l-carnitine supplementation can relieve this bad condition. In conclusion, l-carnitine regulated Nrf2/Keap1 activation in vitro and in vivo and protected oxidized fish oil-induced inflammation response by inhibiting the NF-κB signaling pathway in Rhynchocypris lagowski Dybowski.

Effects of antimicrobial peptides (AMPs) on blood biochemical parameters, antioxidase activity, and immune function in the common carp (Cyprinus carpio).

Antibiotic use in livestock feed additives has resulted in harmful residue accumulation and spread of drug-resistance. We examined the use of antimicrobial peptides (AMPs) as a safer alternative to antibiotics in feeding the common carp. AMPs were added to common carp basal diets (Control) as additives at four concentrations: 100 mg kg(-1) (B1), 200 mg kg(-1) (B2), 400 mg kg(-1) (B3), 600 mg kg(-1) (B4) by dry weight of basal diet. After a 60-day feeding experiment, the final weight, DG and SGR of carps on B1, B2 and B3 diet were significantly higher than the control (p < 0.05). The FCR of carps on B1, B2 and B3 diet were significantly lower than the control (p < 0.05). Carps on B2, B3, and B4 diets showed significantly lower (p < 0.05) levels of triglyceride than the control. B4-fed carps showed significantly lower (p < 0.05) levels of total protein, albumin, and total cholesterol than the control. However there was no remarkable difference (p > 0.05) in levels of uric ammonia, globulin, glutamic-pyruvic transaminase, glutamic-oxalacetic transaminase, lactic dehydrogenase and blood glucose in all groups. The serum superoxide dismutase and catalase activity of B1-fed carps was significantly higher (p < 0.05) than the control and B4-fed carps. The serum alkaline phosphate activity of carps on B1 diets was significantly higher (p < 0.05) than B4-fed carps. The serum acid phosphatase activity of B1-fed carps was significantly higher (p < 0.05) than the control and other antimicrobial peptide-fed groups. The serum lysozyme activity of carps on B1, B2, and B3 diets was significantly higher (p < 0.05) than the control- and B4-fed carps. Regarding immune factors in serum, the levels of immunoglobulin (Ig) and interleukin (IL)-1ß in B1-fed carps were significantly higher (p < 0.05) than the control and other groups, while IL-1α levels in B1-fed carps was significantly higher (p < 0.05) than the control-, B2-, and B3-fed carps. Furthermore, there were no significant differences in the content of MHC among the five groups. In conclusion, antimicrobial peptide can reduce triglyceride levels in serum, enrich oxidation resistance, and improve immunity of the common carp. It showed that appropriate concentration of antibacterial peptide as supplements in diets for common carp increased the final weight, DG, SGR and decreased the FCR.