Differential protein expression profile in the liver of pikeperch (Sander lucioperca) larvae fed with increasing levels of phospholipids

DIGE Analysis of Fish Tissues

Two-dimensional difference gel electrophoresis (2D-DIGE) appears to be especially useful in quantitative approaches, allowing the co-separation of proteins of control samples and proteins of treated/disease samples on the same gel, eliminating gel-to-gel variability. The principle of 2D-DIGE is to label proteins prior to isoelectric focusing and use three spectrally resolvable fluorescent dyes, allowing the independent labeling of control and experimental samples. This procedure makes it possible to reduce the number of gels in an experiment, allowing the accurate and reproducible quantification of multiple samples. 2D-DIGE has been found to be an excellent methodical tool in several areas of fish research, including environmental pollution and toxicology, the mechanisms of development and disorders, reproduction, nutrition, evolution, and ecology.

Key nutritional factors and interactions during larval development of pikeperch (Sander lucioperca)

The effects of 8 nutritional variables (Ca/P, Eicosapentaenoic acid (20:5n-3) + Docosahexaenoic acid (22:6n − 3) (EPA + DHA), Arachidonic acid (20:4n − 6) (ARA), Se, vitamins E, C, D and A) were investigated to identify their respective importance and interactions in pikeperch larval development. In this respect, two modalities (low and high levels) of each variable were tested through a fractional factorial experimental design allowing a reduction from 256 (2⁸) to 16 (2^8 – 4) experimental units. Survival was significantly higher in larvae fed a high Ca/P diet while larval growth was significantly lower in larvae fed the same diet variant, associated with a higher incidence of kyphosis and pectoral anomalies in these larvae. Lordosis and scoliosis seemed to be mostly affected by dietary long chain polyunsaturated fatty acids (LC-PUFAs). A significant interaction was shown between n-3 LC-PUFA and vitamin C on jaw anomalies, while myocyte-specific enhancer factor 2C (mef2c) gene expression correlated positively with dietary vitamin C increment. Results also demonstrated an effect of the different nutrients and their interactions on the activity levels of digestive enzymatic activities. The results of the present study highlight the importance of the interactions between Ca/P, LC-PUFAs and vitamins C and E, suggesting their essential roles as key nutritional factors influencing pikeperch larval development.

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

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.

DIGE Analysis of Fish Tissues

Two-dimensional difference gel electrophoresis (2D-DIGE) appears to be especially useful in quantitative approaches, allowing the co-separation of proteins of control samples from proteins of treatment/disease samples on the same gel, eliminating gel-to-gel variability. The principle of 2D-DIGE is to label proteins prior to isoelectric focusing and use three spectrally resolvable fluorescent dyes, allowing the independent labeling of control and experimental samples. This procedure makes it possible to reduce the number of gels in an experiment, allowing the accurate and reproducible quantification of multiple samples. 2D-DIGE has been found to be an excellent methodical tool in several areas of fish research, including environmental pollution and toxicology, the mechanisms of development and disorders, reproduction, nutrition, evolution, and ecology.

Comparative proteomic analysis of liver antioxidant mechanisms in Megalobrama amblycephala stimulated with dietary emodin

Oxidative stress is a toxicological endpoint that correlates with the nutrition status of fish through cellular damage, inflammation, and apoptosis. In order to understand the antioxidant mechanism induced by dietary emodin in Megalobrama amblycephala liver, a comparative proteomic analysis was performed to investigate the proteome alteration under emodin administration. 27 altered protein spots were separated under 30 mg kg^-1 emodin stimulation based on 2-DE, and were all successfully identified using MALDI-TOF/TOF, representing 17 unique proteins. These proteins were functionally classified into antioxidant, metabolism, cytoskeleton, chaperone, signal transduction and cofactor groups. Network interaction and Gene Ontology annotation indicated 10 unique proteins were closely related to antioxidation and directly regulated by each other. Compared with the control group, administration of 30 mg kg^-1 emodin significantly increased the antioxidant-related mRNA expressions of GPx1, GSTm and HSP70, but decreased the mRNA expressions of GAPDH and Sord, which was consistent with the protein expression. Nevertheless, Pgk1 and Aldh8a1 were up- and down-regulated, and ALDOB was down- and up-regulated at the mRNA and protein levels, respectively. These results revealed that the altered proteins enhanced antioxidation via complex regulatory mechanisms, and 30 mg kg^-1 emodin was a suitable immunostimulant for M. amblycephala.

The impaired intestinal mucosal immune system by valine deficiency for young grass carp (Ctenopharyngodon idella) is associated with decreasing immune status and regulating tight junction proteins transcript abundance in the intestine

This study investigated the effects of dietary valine on the growth, intestinal immune response, tight junction proteins transcript abundance and gene expression of immune-related signaling molecules in the intestine of young grass carp (Ctenopharyngodon idella). Six iso-nitrogenous diets containing graded levels of valine (4.3-19.1 g kg(-)(1) diet) were fed to the fish for 8 weeks. The results showed that percentage weight gain (PWG), feed intake and feed efficiency of fish were the lowest in fish fed the valine-deficient diet (P < 0.05). In addition, valine deficiency decreased lysozyme, acid phosphatase activities and complement 3 content in the intestine (P < 0.05), down-regulated mRNA levels of interleukin 10, transforming growth factor β1, IκBα and target of rapamycin (TOR) (P < 0.05), and up-regulated tumor necrosis factor α, interleukin 8 and nuclear factor κB P65 (NF-κB P65) gene expression (P < 0.05). Additionally, valine deficiency significantly decreased transcript of Occludin, Claudin b, Claudin c, Claudin 3, and ZO-1 (P < 0.05), and improved Claudin 15 expression in the fish intestine (P < 0.05). However, valine did not have a significant effect on expression of Claudin 12 in the intestine of grass carp (P > 0.05). In conclusion, valine deficiency decreased fish growth and intestinal immune status, as well as regulated gene expression of tight junction proteins, NF-κB P65, IκBα and TOR in the fish intestine. Based on the quadratic regression analysis of lysozyme activity or PWG, the dietary valine requirement of young grass carp (268-679 g) were established to be 14.47 g kg(-1) diet (4.82 g 100 g(-1) CP) or 14.00 g kg(-1) diet (4.77 g 100 g(-1) CP), respectively.

PROTEOMICS in aquaculture: applications and trends

Over the last forty years global aquaculture presented a growth rate of 6.9% per annum with an amazing production of 52.5 million tonnes in 2008, and a contribution of 43% of aquatic animal food for human consumption. In order to meet the world's health requirements of fish protein, a continuous growth in production is still expected for decades to come. Aquaculture is, though, a very competitive market, and a global awareness regarding the use of scientific knowledge and emerging technologies to obtain a better farmed organism through a sustainable production has enhanced the importance of proteomics in seafood biology research. Proteomics, as a powerful comparative tool, has therefore been increasingly used over the last decade to address different questions in aquaculture, regarding welfare, nutrition, health, quality, and safety. In this paper we will give an overview of these biological questions and the role of proteomics in their investigation, outlining the advantages, disadvantages and future challenges. A brief description of the proteomics technical approaches will be presented. Special focus will be on the latest trends related to the aquaculture production of fish with defined nutritional, health or quality properties for functional foods and the integration of proteomics techniques in addressing this challenging issue.

Proteomic analysis of blood cells in fish exposed to chemotherapeutics: evidence for long term effects

Proteomics technology are increasingly used in ecotoxicological studies to characterize and monitor biomarkers of exposure. The present study aims at identifying long term effects of malachite green (MG) exposure on the proteome of peripheral blood mononuclear cells (PBMC) from the Asian catfish, Pangasianodon hypophthalmus. A common (0.1 ppm) concentration for therapeutic treatment was applied twice with a 72 h interval. PBMC were collected directly at the end of the second bath of MG (T1) and after 1 month of decontamination (T2). Analytical 2D-DIGE gels were run and a total of 2551±364 spots were matched. Among them, MG induced significant changes in abundance of 116 spots with no recovery after one month of decontamination. Using LC-MS/MS and considering single identification per spot, we could identify 25 different proteins. Additionally, MG residues were measured in muscle and in blood indicating that leuco-MG has almost totally disappeared after one month of decontamination. This work highlights long term effects of MG treatment on the PBMC proteome from fish intended for human consumption.