Gilthead Seabream Liver Integrative Proteomics and Metabolomics Analysis Reveals Regulation by Different Prosurvival Pathways in the Metabolic Adaptation to Stress.

The study of the molecular mechanisms of stress appraisal on farmed fish is paramount to ensuring a sustainable aquaculture. Stress exposure can either culminate in the organism's adaptation or aggravate into a metabolic shutdown, characterized by irreversible cellular damage and deleterious effects on fish performance, welfare, and survival. Multiomics can improve our understanding of the complex stressed phenotype in fish and the molecular mediators that regulate the underlying processes of the molecular stress response. We profiled the stress proteome and metabolome of Sparus aurata responding to different challenges common to aquaculture production, characterizing the disturbed pathways in the fish liver, i.e., the central organ in mounting the stress response. Label-free shotgun proteomics and untargeted metabolomics analyses identified 1738 proteins and 120 metabolites, separately. Mass spectrometry data have been made fully accessible via ProteomeXchange, with the identifier PXD036392, and via MetaboLights, with the identifier MTBLS5940. Integrative multivariate statistical analysis, performed with data integration analysis for biomarker discovery using latent components (DIABLO), depicted the 10 most-relevant features. Functional analysis of these selected features revealed an intricate network of regulatory components, modulating different signaling pathways related to cellular stress, e.g., the mTORC1 pathway, the unfolded protein response, endocytosis, and autophagy to different extents according to the stress nature. These results shed light on the dynamics and extent of this species' metabolic reprogramming under chronic stress, supporting future studies on stress markers' discovery and fish welfare research.

Protein changes as robust signatures of fish chronic stress: a proteomics approach to fish welfare research.

BACKGROUND: Aquaculture is a fast-growing industry and therefore welfare and environmental impact have become of utmost importance. Preventing stress associated to common aquaculture practices and optimizing the fish stress response by quantification of the stress level, are important steps towards the improvement of welfare standards. Stress is characterized by a cascade of physiological responses that, in-turn, induce further changes at the whole-animal level. These can either increase fitness or impair welfare. Nevertheless, monitorization of this dynamic process has, up until now, relied on indicators that are only a snapshot of the stress level experienced. Promising technological tools, such as proteomics, allow an unbiased approach for the discovery of potential biomarkers for stress monitoring. Within this scope, using Gilthead seabream (Sparus aurata) as a model, three chronic stress conditions, namely overcrowding, handling and hypoxia, were employed to evaluate the potential of the fish protein-based adaptations as reliable signatures of chronic stress, in contrast with the commonly used hormonal and metabolic indicators. RESULTS: A broad spectrum of biological variation regarding cortisol and glucose levels was observed, the values of which rose higher in net-handled fish. In this sense, a potential pattern of stressor-specificity was clear, as the level of response varied markedly between a persistent (crowding) and a repetitive stressor (handling). Gel-based proteomics analysis of the plasma proteome also revealed that net-handled fish had the highest number of differential proteins, compared to the other trials. Mass spectrometric analysis, followed by gene ontology enrichment and protein-protein interaction analyses, characterized those as humoral components of the innate immune system and key elements of the response to stimulus. CONCLUSIONS: Overall, this study represents the first screening of more reliable signatures of physiological adaptation to chronic stress in fish, allowing the future development of novel biomarker models to monitor fish welfare.

Enhanced dietary formulation to mitigate winter thermal stress in gilthead sea bream (Sparus aurata): a 2D-DIGE plasma proteome study.

Low water temperatures during winter are common in farming of gilthead sea bream in the Mediterranean. This causes metabolic disorders that in extreme cases can lead to a syndrome called "winter disease." An improved immunostimulatory nutritional status might mitigate the effects of this thermal metabolic stress. A trial was set up to assess the effects of two different diets on gilthead sea bream physiology and nutritional state through plasma proteome and metabolites. Four groups of 25 adult gilthead sea bream were reared during winter months, being fed either with a control diet (CTRL) or with a diet called "winter feed" (WF). Proteome results show a slightly higher number of proteins upregulated in plasma of fish fed the WF. These proteins are mostly involved in the immune system and cell protection mechanisms. Lipid metabolism was also affected, as shown both by plasma proteome and by the cholesterol plasma levels. Overall, the winter feed diet tested seems to have positive effects in terms of fish condition and nutritional status, reducing the metabolic effects of thermal stress.

Transcriptomic changes behind Sparus aurata hepatic response to different aquaculture challenges: An RNA-seq study and multiomics integration.

Gilthead seabream (Sparus aurata) is an important species in Mediterranean aquaculture. Rapid intensification of its production and sub-optimal husbandry practices can cause stress, impairing overall fish performance and raising issues related to sustainability, animal welfare, and food safety. The advent of next-generation sequencing technologies has greatly revolutionized the study of fish stress biology, allowing a deeper understanding of the molecular stress responses. Here, we characterized for the first time, using RNA-seq, the different hepatic transcriptome responses of gilthead seabream to common aquaculture challenges, namely overcrowding, net handling, and hypoxia, further integrating them with the liver proteome and metabolome responses. After reference-guided transcriptome assembly, annotation, and differential gene expression analysis, 7, 343, and 654 genes were differentially expressed (adjusted p-value < 0.01, log2|fold-change| >1) in the fish from the overcrowding, net handling, and hypoxia challenged groups, respectively. Gene set enrichment analysis (FDR < 0.05) suggested a scenario of challenge-specific responses, that is, net handling induced ribosomal assembly stress, whereas hypoxia induced DNA replication stress in gilthead seabream hepatocytes, consistent with proteomics and metabolomics' results. However, both responses converged upon the downregulation of insulin growth factor signalling and induction of endoplasmic reticulum stress. These results demonstrate the high phenotypic plasticity of this species and its differential responses to distinct challenging environments at the transcriptomic level. Furthermore, it provides significant resources for characterizing and identifying potentially novel genes that are important for gilthead seabream resilience and aquaculture production efficiency with regard to fish welfare.

Proteomic analysis shows that individual Listeria monocytogenes strains use different strategies in response to gastric stress.

Ingestion of contaminated dairy products, in particular soft cheese, is one of the major routes of infection by the human pathogen Listeria monocytogenes. During cheese processing, this foodborne pathogen is exposed to sublethal acid and osmotic stress conditions, which may induce tolerance responses and influence subsequent survival in the gastric tract. The aim of the current study was to evaluate the impact on a L. monocytogenes cheese isolate (serotype 4b) and two cheese dairy isolates (T8, serotype 4b, isolated from vat; and A9, serotype 1/2b or 3b, isolated from shelf stand) of exposure to sublethal conditions of pH and salt (5.5 and 3.5% [w/v] NaCl) in a cheese-simulated medium and further challenge with gastric stress. The bacterial cells exposed to pH 7.0 and no added salt were considered non-adapted. Via two-dimensional gel electrophoresis (2-DE), the proteomes of cheese-simulated medium and gastric challenged Listeria cells were compared. All L. monocytogenes isolates were able to survive the high acidity of gastric fluid (pH 2.5), and no significant differences were observed between adapted and non-adapted cells. However, the analysis of the intracellular proteome profiles revealed a significant intra-strain variation in the protein arsenal used to respond to the adaptation in the cheese-based medium and to the gastric stress. In cheese-based medium, the three strains produced different stress proteins. All three strains showed a higher abundance of carbohydrate proteins, but there was no overlap between them. Exposure to the gastric fluid induced the production of a group of proteins in T8 adapted and non-adapted cells that had not been detected previously in the cheese-based proteome. No such response was shown by A9 and C882 strains. Taken together, this study evidences the proteome tools used by adapted and non-adapted cells to cope with the hostile microenvironment of the stomach.

A new window into fish welfare: A proteomic discovery study of stress biomarkers in the skin mucus of gilthead seabream (Sparus aurata).

Fish skin mucus is a dynamic external mucosal layer that acts as the first line of defense in the innate immune system. Skin mucus' exudation and composition change severely under stress, making it a valuable biofluid to search for minimally invasive stress markers. This study focused on the skin mucus proteome response to repetitive handling, overcrowding, and hypoxia, using Sparus aurata, an important species in the Mediterranean aquaculture, as a model. Biomarker discovery analysis was performed using label-free shotgun proteomics coupled with bioinformatics to unveil the most predictive proteins for the stressed phenotype. A mean of 2166 proteins were identified at a < 0.2% false discovery rate, from which the differentially abundant proteins (DAPs) were mainly involved in the immune system and protein metabolism. A sparse partial least squares regression analysis revealed a high correlation between DAPs and plasma physiological stress indicators. Feature selection, performed by recursive feature elimination followed by logistic regression analysis of the selected proteins, disclosed 28 candidate biomarkers with values of area under the curve >0.75. These minimally invasive biomarkers could be used in forthcoming species-specific stress management protocols to improve fish welfare and promote farmed fish safety, positive societal outcomes, and business sustainability. SIGNIFICANCE: The fish skin mucus holds a great promise into fish welfare, as a valuable source of minimally invasive biomarkers for stress assessment. In this shotgun proteomics discovery study, we have identified 28 candidate biomarkers by combining a comprehensive functional analysis of the stress regulated proteome with predictive modeling, supported by a significant correlation (p < 0.01) with physiological stress indicators (cortisol, lactate and glucose). The candidate biomarkers showed a good predictive value in the testing set (AUC > 0.75), paving the way for the next step in their validation by targeted proteomics. An early and timely assessment of fish stressful events, by using minimally invasive biomarkers, as those that can be found in the fish skin mucus, can contribute to promote fish health/welfare in the aquaculture sector and its sustainability. The adoption of preventive and surveillance measures based on proteomics approaches can therefore help to avoid unnecessary adverse outcomes with a negative impact on this primordial food sector.

Fish Allergenicity Modulation Using Tailored Enriched Diets-Where Are We?

Food allergy is an abnormal immune response to specific proteins in a certain food. The chronicity, prevalence, and the potential fatality of food allergy, make it a serious socio-economic problem. Fish is considered the third most allergenic food in the world, affecting part of the world population with a higher incidence in children and adolescents. The main allergen in fish, responsible for the large majority of fish-allergic reactions in sensitized patients, is a small and stable calcium-binding muscle protein named beta-parvalbumin. Targeting the expression or/and the 3D conformation of this protein by adding specific molecules to fish diets has been the innovative strategy of some researchers in the fields of fish allergies and nutrition. This has shown promising results, namely when the apo-form of ß-parvalbumin is induced, leading in the case of gilthead seabream to a 50% reduction of IgE-reactivity in fish allergic patients.

Fish Processing and Digestion Affect Parvalbumins Detectability in Gilthead Seabream and European Seabass.

Consumption of aquatic food, including fish, accounts for 17% of animal protein intake. However, fish consumption might also result in several side-effects such as sneezing, swelling and anaphylaxis in sensitized consumers. Fish allergy is an immune reaction to allergenic proteins in the fish muscle, for instance parvalbumin (PV), considered the major fish allergen. In this study, we characterize PV in two economically important fish species for southern European aquaculture, namely gilthead seabream and European seabass, to understand its stability during in vitro digestion and fish processing. This information is crucial for future studies on the allergenicity of processed fish products. PVs were extracted from fish muscles, identified by mass spectrometry (MS), and detected by sandwich enzyme-linked immunosorbent assay (ELISA) after simulated digestion and various food processing treatments. Secondary structures were determined by circular dichroism (CD) after purification by anion exchange and gel filtration chromatography. In both species, PVs presented as α-helical and ß-sheet structures, at room temperature, were shown to unfold at boiling temperatures. In European seabass, PV detectability decreased during the simulated digestion and after 240 min (intestinal phase) no detection was observed, while steaming showed a decrease (p < 0.05) in PVs detectability in comparison to raw muscle samples, for both species. Additionally, freezing (−20 °C) for up to 12 months continued to reduce the detectability of PV in tested processing techniques. We concluded that PVs from both species are susceptible to digestion and processing techniques such as steaming and freezing. Our study obtained preliminary results for further research on the allergenic potential of PV after digestion and processing.

Effect of creatine and EDTA supplemented diets on European seabass (Dicentrarchus labrax) allergenicity, fish muscle quality and omics fingerprint.

The relatively easy access to fish worldwide, alongside the increase of aquaculture production contributes to increased fish consumption which result in higher prevalence of respective allergies. Allergies to fish constitute a significant concern worldwide. ß-parvalbumin is the main elicitor for IgE-mediated reactions. Creatine, involved in the muscle energy metabolism, and ethylenediamine tetraacetic acid (EDTA), a calcium chelator, are potential molecules to modulate parvalbumin. The purpose of this study was to test creatine (2, 5 and 8%) and EDTA (1.5, 3 and 4.5%) supplementation in fish diets to modulate ß-parvalbumin expression and structure and its allergenicity in farmed European seabass (Dicentrarchus labrax) while assessing its effects on the end-product quality. Fish welfare and muscle quality parameters were evaluated by plasma metabolites, rigor mortis, muscle pH and sensory and texture analysis. Proteomics was used to assess alterations in muscle proteome profile and metabolic fingerprinting by Fourier transform infrared spectroscopy was used to assess the liver metabolic profile. In addition, IgE-reactivity to parvalbumin was analysed using fish allergic patient sera. Metabolic fingerprinting of liver tissue revealed no major alterations in infrared spectra with creatine supplementation, while with EDTA, only absorption bands characteristic of lipids were altered. Comparative proteomics showed up regulation of (tropo) myosin and phosphoglycerate mutase 2 with Creatine supplementation. In the case of EDTA proteomics showed up regulation of proteins involved in cellular and ion homeostasis. Allergenicity seems not to be modulated with creatine or EDTA supplementation as no decreased expression levels were found and IgE-binding reactivity showed no quantitative differences.

Are Physicochemical Properties Shaping the Allergenic Potency of Plant Allergens?

This review searched for published evidence that could explain how different physicochemical properties impact on the allergenicity of food proteins and if their effects would follow specific patterns among distinct protein families. Owing to the amount and complexity of the collected information, this literature overview was divided in two articles, the current one dedicated to protein families of plant allergens and a second one focused on animal allergens. Our extensive analysis of the available literature revealed that physicochemical characteristics had consistent effects on protein allergenicity for allergens belonging to the same protein family. For example, protein aggregation contributes to increased allergenicity of 2S albumins, while for legumins and cereal prolamins, the same phenomenon leads to a reduction. Molecular stability, related to structural resistance to heat and proteolysis, was identified as the most common feature promoting plant protein allergenicity, although it fails to explain the potency of some unstable allergens (e.g. pollen-related food allergens). Furthermore, data on physicochemical characteristics translating into clinical effects are limited, mainly because most studies are focused on in vitro IgE binding. Clinical data assessing how these parameters affect the development and clinical manifestation of allergies is minimal, with only few reports evaluating the sensitising capacity of modified proteins (addressing different physicochemical properties) in murine allergy models. In vivo testing of modified pure proteins by SPT or DBPCFC is scarce. At this stage, a systematic approach to link the physicochemical properties with clinical plant allergenicity in real-life scenarios is still missing.

Are Physicochemical Properties Shaping the Allergenic Potency of Animal Allergens?

Key determinants for the development of an allergic response to an otherwise 'harmless' food protein involve different factors like the predisposition of the individual, the timing, the dose, the route of exposure, the intrinsic properties of the allergen, the food matrix (e.g. lipids) and the allergen modification by food processing. Various physicochemical parameters can have an impact on the allergenicity of animal proteins. Following our previous review on how physicochemical parameters shape plant protein allergenicity, the same analysis was proceeded here for animal allergens. We found that each parameter can have variable effects, ranging on an axis from allergenicity enhancement to resolution, depending on its nature and the allergen. While glycosylation and phosphorylation are common, both are not universal traits of animal allergens. High molecular structures can favour allergenicity, but structural loss and uncovering hidden epitopes can also have a similar impact. We discovered that there are important knowledge gaps in regard to physicochemical parameters shaping protein allergenicity both from animal and plant origin, mainly because the comparability of the data is poor. Future biomolecular studies of exhaustive, standardised design together with strong validation part in the clinical context, together with data integration model systems will be needed to unravel causal relationships between physicochemical properties and the basis of protein allergenicity.

Fish Pathology Research and Diagnosis in Aquaculture of Farmed Fish; a Proteomics Perspective.

One of the main constraints in aquaculture production is farmed fish vulnerability to diseases due to husbandry practices or external factors like pollution, climate changes, or even the alterations in the dynamic of product transactions in this industry. It is though important to better understand and characterize the intervenients in the process of a disease outbreak as these lead to huge economical losses in aquaculture industries. High-throughput technologies like proteomics can be an important characterization tool especially in pathogen identification and the virulence mechanisms related to host-pathogen interactions on disease research and diagnostics that will help to control, prevent, and treat diseases in farmed fish. Proteomics important role is also maximized by its holistic approach to understanding pathogenesis processes and fish responses to external factors like stress or temperature making it one of the most promising tools for fish pathology research.

Data on European seabass fed with methionine-enriched diets obtained through label free shotgun proteomics.

This data article is associated with the research article "Evaluating the impact of methionine-enriched diets in the liver of European seabass through label-free shotgun proteomics". Here it is described the data obtained from proteomic analysis of 36 European seabass juveniles (3 fish x 3 replicate tanks) after 18 days of feeding with experimental diets containing four inclusion levels of methionine (Met): 0.77%, 1%, 1.36% and 1.66% Met (w/w). We analysed this dataset and compared it with that obtained during the long-term feeding period i.e., 85 days. Fish liver proteins were digested with trypsin and purified peptides were analysed by LC-MS/MS. Proteins were identified with at least two peptides at 0.1% Decoy false discovery rate (FDR). In this dataset, we present the analysis of the differential abundant proteins (DAP) with significant differences across treatments after 18 days of feeding (One-Way ANOVA, p < 0.05). Treatment's comparisons were also performed between the 18- and 85-days feeding trials through Two-Way ANOVA (p < 0.05). MS/MS raw data are available via ProteomeXChange with identifiers PXD019610 and 10.6019/PXD019610 (18-days dataset); and PXD019622 and 10.6019/PXD019622 (85-days dataset). This dataset corresponds to fish sampled after 18-days of experimental trial and is made available to support the study conducted in the afore-mentioned article, by performing the analysis during a short-term period of feeding. The data presented may be further used in other nutritional studies e.g., addressing hepatic changes mediated by Met.

Evaluating the impact of methionine-enriched diets in the liver of European seabass through label-free shotgun proteomics.

Plant protein sources play an essential role in aquaculture by reducing the use of fish meal to sustainable levels, although further supplementation is needed to fulfill fish nutritional requirements. This work addressed fish growth performance and proteome changes to dietary methionine in European seabass juveniles. A dose-dependent response to methionine (Met) was observed on fish growth consistent with proteomic analyses, suggesting Met requirement ≥0.9% (w/w). Fish fed at 0.77% (w/w) exhibited reduced growth and an enrichment in proteins involved in cellular homeostasis. Proteomics data suggest an optimal nutritional status at 1.36% Met (w/w), together with putative beneficial effects on the immune system up to 1.66% Met (w/w). The response to dietary Met involved the convergence of different metabolic and signalling pathways implicated in cell growth and immune response e.g., mTOR, Hedgehog or the T Cell receptor signalling, coupled with a fine-tuning regulation of amino acid metabolism and translation.

Effects of Different Dietary Vegetable Lipid Sources on Health Status in Nile Tilapia (Oreochromis niloticus): Haematological Indices, Immune Response Parameters and Plasma Proteome.

This study aimed to investigate the effects of DLs, including palm oil (PO; an SFAs), linseed oil (LO; n-3 PUFAs) and soybean oil (SBO; n-6 PUFAs) on the health status of Nile tilapia (Oreochromis niloticus) during adulthood. Three experimental diets incorporating PO, LO or SBO were fed to adult Nile tilapia for a period of 90 days, and haematological and innate immune parameters were evaluated. Proteome analysis was also conducted to evaluate the effects of DLs on plasma proteins. The tested DLs had no significant effects on red blood cell (RBC) count, haematocrit, haemoglobin, and total immunoglobulin and lysozyme activity. Dietary LO led to increased alternative complement 50 activity (ACH50), and proteome analysis revealed that PO and SBO enhanced A2ML, suggesting that different DLs promote immune system via different processes. Dietary LO or SBO increased the expression of several proteins involved in coagulation activity such as KNG1, HRG and FGG. Increased HPX in fish fed with PO suggests that SFAs are utilised in heme lipid-oxidation. Overall, DLs with distinct fatty acids (FAs) affect several parameters corresponding to health status in Nile tilapia, and dietary LO and SBO seemed to strengthen health in this species.

Effect of EDTA enriched diets on farmed fish allergenicity and muscle quality; a proteomics approach.

Fish is one of the most common elicitors of food-allergic reactions worldwide. These reactions are triggered by the calcium-binding muscle protein ß-parvalbumin, which was shown to have reduced immunoglobulin E (IgE)-binding capacity upon calcium depletion. This work aimed to reduce gilthead seabream allergenicity using diets supplemented with a calcium chelator. Three experimental feeds were tested, differing in ethylenediaminetetraacetic acid (EDTA) supplementation, and its effects on muscle and parvalbumin's IgE-reactivity were analyzed. Chromatographic determination of EDTA showed no accumulation in the muscle and sensory results demonstrated that the lowest concentration did not affect fish quality as edible fish. Proteomics revealed one protein related to muscle contraction with significantly different relative abundance. Immunoblot assays performed with fish-allergic patients sera indicated a 50% reduction in IgE-reactivity upon EDTA presence. These preliminary results provide the basis for the further development of a non-GMO approach to modulate fish allergenicity and improve safety of aquaculture fish.

Mid-infrared spectroscopic screening of metabolic alterations in stress-exposed gilthead seabream (Sparus aurata).

Stress triggers a battery of physiological responses in fish, including the activation of metabolic pathways involved in energy production, which helps the animal to cope with the adverse situation. Prolonged exposure to stressful farming conditions may induce adverse effects at the whole-animal level, impairing welfare. Fourier transform infrared (FTIR) spectroscopy is a rapid biochemical fingerprinting technique, that, combined with chemometrics, was applied to disclose the metabolic alterations in the fish liver as a result of exposure to standard stressful practices in aquaculture. Gilthead seabream (Sparus aurata) adults exposed to different stressors were used as model species. Spectra were preprocessed before multivariate statistical analysis. Principal components analysis (PCA) was used for pattern recognition and identification of the most discriminatory wavenumbers. Key spectral features were selected and used for classification using the k-nearest neighbour (KNN) algorithm to evaluate whether the spectral changes allowed for the reliable discrimination between experimental groups. PCA loadings suggested that major variations in the hepatic infrared spectra responsible for the discrimination between the experimental groups were due to differences in the intensity of absorption bands associated with proteins, lipids and carbohydrates. This broad-range technique can thus be useful in an exploratory approach before any targeted analysis.

How tryptophan levels in plant-based aquafeeds affect fish physiology, metabolism and proteome.

Fish meal replacement by plant-protein sources is a priority in aquaculture feeds. Within this framework, dietary supplementation with essential amino acids (EAA), as tryptophan (TRP), is strategic to ensure that the individual nutritional needs are met, besides promoting enhanced immunological status. The purpose of this study was to examine the beneficial effects of TRP incorporation in plant-protein source diets on fish growth performance and nutritional status. We tested diets with 20% lower (LTRP) and 27% higher (HTRP) of the putative requirements of TRP for seabream (Sparus aurata) and assessed its impact on fish physiology and liver metabolism and proteome. After 12 weeks, growth performance, body proximate, hepatic composition and liver metabolic profiling were similar between diets. Nevertheless, liver proteome analysis indicated a higher accumulation of proteins involved in acute-phase responses, typically triggered by infection, inflammation or trauma, in fish fed with HTRP diet as compared with those fed with LTRP. The overall results obtained suggest a potential beneficial effect of TRP supplementation in terms of immune stimulation, without compromising growth or feed intake. Moreover, proteomics and metabolic profiling demonstrate to be valuable tools in this endeavour. SIGNIFICANCE: Nutritional needs are hard to assess in aquaculture fisheries, and many times controversial depending on the methodology employed. The estimated amino acid requirements depend on both fish species and stage development, making it extremely hard to standardise. On the other hand, the substitution of fish-based to plant-based protein sources diets towards a sustainable aquaculture, may imbalance these requirements, being necessary further studies to assess the impact on fish growth and development. Finally, the incorporation of crystalized amino acids such as TRP into diets aims global better performance both at fish health/immune condition and growth development. This work focused on the potential beneficial effects of TRP supplementation into diets with a plant-based protein source, addressing the effects on the liver metabolism and proteome, and on growth performance of Gilthead seabream juveniles, a species with special relevance and economical importance in the Mediterranean region. The present study by employing proteomics together with metabolic profiling shows that TRP supplementation at the tested doses, does not compromise growth performance, and seems to stimulate the immune system. Our findings can contribute to the development of new feed formulations for Gilthead seabream species, therefore, reinforcing the resilience and competitiveness of the on-growing aquaculture industry and impact directly the sustainability of living resources with the decrease of the fisheries needs to fulfil the human search for quality proteins consume.

Use of Two-Dimensional Electrophoresis to Explore Foodborne Bacterial Pathogen Responses to Gastrointestinal Stress.

Proteomics was applied here to study Listeria monocytogenes response to gastrointestinal stress. It separated extracted proteins by their isoelectric point (pI) in the first dimension followed by separation by molecular weight in the second dimension on a polyacrylamide gel. L. monocytogenes was grown in an appropriate culture medium after which it was transferred to a simulated cheese medium for 2 h. Bacteria were exposed to gastric stress using artificial saliva and gastric fluid for 5 min and 2 h, respectively. After each step samples were taken for protein extraction and a two-dimensional electrophoresis approach. Proteins were separated on 18 cm Immobiline DryStrip gels with a pH range of 4-7 and the protein pattern analyzed.

Effects of dietary lipid sources on hepatic nutritive contents, fatty acid composition and proteome of Nile tilapia (Oreochromis niloticus).

Dietary oils of varying fatty acid composition have been used in tilapia feeds; nevertheless, investigation of their effects on metabolism and physiological processes has been limited. Therefore, in this study, using proteomic technology, the effects of different dietary lipids (DLs) on hepatic lipid metabolism and physiological processes were investigaed in Nile tilapia (Oreochromis niloticus). Fish were fed with different DL, which included palm oil (PO), linseed oil (LO) and soybean oil (SBO) for 90 days. Growth performance appeared to be similar among the dietary group. Hepatic FA contents were reflected by DL. Dietary PO (source of saturated fatty acids; SFA) led to an increase in the hepatosomatic index as well as lipid and protein contents in liver. Dietary SBO (source of n-6 polyunsaturated fatty acids; n-6 PUFAs) increased hepatic carbohydrate contents, but decreased the hepatic protein. The proteomic analysis showed that these nutritive changes in the liver were mediated by several proteins involved in lipid, carbohydrate, and amino acid metabolism. Dietary SBO showed an increased accumulation in proteins related to oxidative stress, immune and inflammatory processes. Dietary LO (source of n-3 PUFAs) increased abundance of cytoskeleton-related proteins. qRT-PCR was performed to provide supportive information for the result of proteomic study. Similar effects of DLs on mRNA levels were observed for atp5b, krt18, and selenbp1. Combined together, dietary SFA could supply as energy reservoir for regular activites. Dietary n-3 and n-6 PUFAs led to induce vital metabolic and physiologic processes which would contribute to maintaining normal health and/or providing health-related benefits. SIGNIFICANCE: Dietary SBO increased hepatic carbohydrate contents, but decreased the hepatic protein. Different dietary lipid led to alter the abundance of several proteins (i.e., DHRS1, ATP5B, PLA2G12B, APO, AMY2A, GRP78, PRSS1, FAH, and PRSS36) involved in lipid, carbohydrate, and amino acid metabolism. Dietary SBO showed an increased accumulation in proteins (i.e., QDPR, CABC1, and PRDX6) that respond to oxidative stress, suggesting that n-6 PUFAs induce oxidative conditions. Dietary SBO led to increase the accumulation of proteins (i.e., NITR26, NCCRP1, and LCN) involved in immune and inflammatory processes. Dietary LO increased the abundant levels of cytoskeleton-related proteins (i.e., ACTB, AHNAK, ERC2, KRT18, and RILP1). Other proteins (i.e., SELENBP1, FAM46C, and ANC1) involved in other physiological processes were also modulated by DL. qRT-PCR was performed to provide supportive information of proteomic study. Similar effects of DLs on mRNA levels were observed for atp5b, krt18, and selenbp1.