Jun Xie

Effect of nitrite exposure on the antioxidant enzymes and glutathione system in the liver of bighead carp, Aristichthys nobilis.

&NA; Nitrite (NO2−) can cause oxidative stress in aquatic animal when it accumulates in the organism, resulting in different toxic effects on fish. In the present study, we investigated the effects of nitrite exposure on the antioxidant enzymes and glutathione system in the liver of Bighead carp (Aristichthys nobilis). Fish [Initial average weight: (180.05 ± 0.092) g] were exposed to 48.634 mg/L nitrite for 96 h, and a subsequent 96 h for the recovery test. Fish livers were collected to assay antioxidant enzymes activity, hepatic structure and expression of genes after 0 h, 6 h, 12 h, 24 h, 48 h, 72 h, 96 h of exposure and 12 h, 24 h, 48 h, 72 h, 96 h of recovery. The results showed that the activity of glutathione peroxidase (GSH‐Px), glutathione S‐transferase (GST), and glutathione reductase (GR) increased significantly in the early stages of nitrite exposure. The study also showed that nitrite significantly up‐regulated the mRNA levels of glutathione peroxidase (GSH‐Px), glutathione S‐transferase (GST), and glutathione reductase (GR) after 6, 48, and 72 h of exposure respectively. Nitrite also increased the formation of malondialdehyde (MDA), oxidized glutathione (GSSG), and the activity of catalase (CAT). Nitrite was observed to reduce the activity of superoxide dismutase (SOD) and the level of glutathione (GSH). In the recovery test, GSH and the GSSG recovered but did not return to pre‐stress levels. The results suggested that the glutathione system played important roles in nitrite‐induced oxidative stress in fish. The bighead carp responds to oxidative stress by enhancing the activity of GSH‐Px, GST, GR and up‐regulating the expression level of GSH‐Px, GST, GR, a whilst simultaneously maintaining the dynamic balance of GSH/GSSG. CAT was also indispensable. They could reduce the degree of lipid peroxidation, and ultimately protect the body from oxidative damage. Graphical abstract Figure. No caption available. HighlightsNitrite exposure induced oxidative stress and tissue damaged on the liver of Aristichthys nobilis.Upregulation of GSH‐Px, GST, GR mRNA expressions and enzyme activities maintained the dynamic balance of GSH/GSSG system.The GSH/GSSG system fighted against oxidative injury caused by nitrite stress.

Bactericidal activity of grass carp Ctenopharyngodon idella C9-deficient serum against Aeromonas hydrophila

Neutralizing complement C9 in grass carp Ctenopharyngodon idella sera with rabbit anti-C9 sera against fish complement C9, demonstrated that bactericidal activity against Aeromonas hydrophila of the C9-deficient fish sera was greatly impaired. These results indicated that the fish complement C9 plays a key role in pathogen killing through the lytic pathway.

Publisher Correction: Dietary arginine affects the insulin signaling pathway, glucose metabolism and lipogenesis in juvenile blunt snout bream Megalobrama amblycephala

A correction to this article has been published and is linked from the HTML version of this paper. The error has been fixed in the paper.

Comparative proteomic analysis of hepatic mechanisms of Megalobrama amblycephala infected by Aeromonas hydrophila

Abstract Hemorrhage syndrome is one of the most prevalent and epidemic diseases that is mainly caused by Aeromonas hydrophila invasion in Megalobrama amblycephala. Recent studies have uncovered a number of immune enzymes and transcripts that are differently expressed in this disease, but the molecular mechanism elicited still remain largely unknown. Here, we constructed an in vivo A. hydrophila infection to investigate the immune mechanism in M. amblycephala using comparative proteomic approach at the one day after infection. 30 altered protein spots were found to undergo differential expression against A. hydrophila infection in the hepatopancreas of M. amblycephala based on 2‐DE and were all successfully identified using MALDI‐TOF/TOF, representing 18 unique proteins. These proteins were functionally classified into metabolism, antioxidant, cofactors and vitamins, chaperone and signal transduction. Network interaction and Gene Ontology annotation indicated 13 unique proteins were closely related to immune response and directly regulated by each other. Compared with the control group, A. hydrophila infection significantly decreased the metabolism‐related mRNA expressions of ENO3, APOA1, CAT and FASN, but increased the mRNA expressions of MDH, ALDOB and RSP12, which was consistent with the protein expression. Nevertheless, FAH was down‐regulated at both levels but had no significant difference in mRNA level, ALDH8a1 was down‐regulated at protein level but non‐significantly up‐regulated at the mRNA level. GSTm was up‐regulated at protein level but down‐regulated at the mRNA level. Consequently, these results revealed that A. hydrophila infection altered the related antioxidative proteins via complex regulatory mechanisms and reduced the immune ability of M. amblycephala at the one day after infection. Highlights30 significantly altered protein spots were identified after A. hydrophila infection.The significantly altered proteins were classified into 9 categories.13 unique proteins are involved in the interaction network.Elucidating the mechanism of altered proteins of M. amblycephala caused by A. hydrophila infection.

Dietary Chromium Picolinate Supplementation Affects Growth, Whole-Body Composition, and Gene Expression Related to Glucose Metabolism and Lipogenesis in Juvenile Blunt Snout Bream, Megalobrama amblycephala

An 11-week feeding trial was carried out to investigate the effects of supplemented chromium picolinate (Cr-Pic) on the growth, whole-body composition, and relative mRNA expression related to lipogenesis and glucose metabolism in juvenile blunt snout bream. Seven isonitrogenous and isoenergetic diets with graded Cr supplementation levels were fed to triplicate groups. The final weight (FW), feed conversion ratio (FCR), and specific growth rate (SGR) were improved with increasing dietary Cr supplementation levels up to 0.4xa0mg/kg, and thereafter showed relatively constant. However, 12.0xa0mg/kg dietary Cr supplementation decreased growth and feed utilization. Based on SGR and FCR, the optimal dietary Cr supplementation level for the juvenile was estimated to be 0.28xa0mg/kg. Significantly higher plasma insulin levels were found in juvenile fed diets with 0.4 and 0.8xa0mg/kg Cr supplementation compared to those fed diet sans supplemented Cr. Plasma glucose levels decreased with increasing dietary Cr supplementation, and the lowest value was remarked in the group added 3.2xa0mg/kg of Cr. Adding 0.4–0.8xa0mg/kg Cr enhanced insulin receptor substrate 1 (IRS-1), phosphoinositide-3-kinase (PI3K), and pyruvate kinase (PK) and inhibited expression of phosphoenolpyruvate carboxykinase (PEPCK), glucose-6-phosphatase (G6Pase), and glycogen synthase (GS) mRNA levels. High dietary Cr (12.0xa0mg/kg) supplementation resulted in high G6Pase and PEPCK expression. The highest content of whole-body lipid was remarked in fish fed with 0.4xa0mg/kg dietary Cr, which related to the enhanced gene expression related to lipogenesis; thereafter, mRNA levels showed a diminishing trend. These findings indicate that optimum dietary Cr-Pic supplementation has a positive effect on growth and blood glucose homeostasis by modifying the mRNA levels related to glucose metabolism and lipogenesis in juvenile blunt snout bream.