Bacterial translocation and in vivo assessment of intestinal barrier permeability in rainbow trout (Oncorhynchus mykiss) with and without soyabean meal-induced inflammation.
ABSTRACT: The primary aim of this experiment was to evaluate the intestinal barrier permeability in vivo in rainbow trout (Oncorhynchus mykiss) fed increasing levels of soyabean meal (SBM). The relationship between SBM-induced enteritis (SBMIE) and the permeability markers was also investigated. Our results showed that the mean score of morphological parameters was significantly higher as a result of 37·5 % SBM inclusion in the diet, while the scores of fish fed 25 % SBM or lower were not different from those of the fish meal-fed controls (P < 0·05). SBMIE was found in the distal intestine (DI) in 18 % of the fish (eleven of sixty): ten in the 37·5 % SBM-fed group and one in the 25 % SBM-fed group. Sugar markers in plasma showed large variation among individuals probably due to variation in feed intake. We found, however, a significant linear increase in the level of plasma d-lactate with increasing SBM inclusion level (P < 0·0001). Plasma concentration of endotoxin was not significantly different in groups with or without SBMIE. Some individual fish showed high values of endotoxin in blood, but the same individuals did not show any bacterial translocation. Plasma bacterial DNA was detected in 28 % of the fish with SBMIE, and 8 % of non-SBMIE fish (P = 0·07). Plasma concentration of d-lactate was significantly higher in fish with SBMIE (P < 0·0001). To conclude, SBMIE in the DI of rainbow trout was associated with an increase in bacterial translocation and plasma d-lactate concentration, suggesting that these permeability markers can be used to evaluate intestinal permeability in vivo.
Project description:Glutamate (Glu) plays various roles directly or through conversions to other amino acids in intracellular metabolisms such as energy source for enterocytes and precursor for nucleic acids. In this study, we examined the effect of single and chronic oral administration of Glu on cell proliferation in intestine and growth in rainbow trout fed soybean meal (SBM) based diet. In the single dose study, 30, 120 and 360 min after oral administration of 50 and 500 mg/kg Glu, the blood and intestine tissues were collected for amino acid concentration and gene expression analysis. Cell-proliferation was detected 24 h after administration using bromo-deoxy uridine (BrdU) in intestine. In the chronic experiment, fish were fed SBM-based diet added 1 and 2 % of Glu for 8 weeks. Final body weight, plasma amino acid concentrations, gene expression and cell-proliferation in the intestine were analyzed. The expressions of some nucleic acid-synthesis related genes were significantly increased 30 min after administration of 50 mg/kg of Glu. After 8 weeks of feeding, the fish fed SBM-based diet showed significantly lower body weight and microvillus thickness in proximal intestine. Supplementation of 2 % of Glu in the SBM-based feed improved both of them. Though it was not significant difference, Glu tended to increase cell-proliferation in the proximal intestine dose-dependently in both single and chronic administration. Our experiment indicates that Glu has positive effect on rainbow trout fed SBM-based feed by reforming proximal intestine through altering cell-proliferation.
Project description:The objective of this study was to identify and evaluate conserved biomarkers that could be used in most species of teleost fish at most life-stages. We investigated the effects of sublethal methylmercury (MeHg) exposure on developing rainbow trout and zebrafish. Juvenile rainbow trout and young adult zebrafish were fed food with MeHg added at 0, 0.5, 5, and 50 ppm. Atomic absorption spectrometry was applied to measure whole body total Hg levels, and pathologic analysis was performed to identify MeHg-induced toxicity. Fish at 6 weeks were sampled from each group for microarray analysis using RNA from whole fish. MeHg-exposed trout and zebrafish did not show overt signs of toxicity or pathology, nor were significant differences seen in mortality, length, mass, or condition factor. The accumulation of MeHg in trout and zebrafish exhibited dose- and time-dependent patterns during 6 weeks, and zebrafish exhibited greater assimilation of total Hg than rainbow trout. The dysregulated genes in MeHg-treated fish have multiple functional annotations, such as iron ion homeostasis, glutathione transferase activity, regulation of muscle contraction, troponin I binding and calcium-dependent protein binding. Genes were selected as biomarker candidates based on their microarray data and their expression was evaluated by QPCR. Unfortunately, these genes are not good consistent biomarkers for both rainbow trout and zebrafish from QPCR evaluation using individual fish. Our conclusion is that biomarker analysis for aquatic toxicant assessment using fish needs to be based on tissue-, sex- and species-specific consideration.
Project description:Microalgal docosahexaenoic acid (DHA) and astaxanthin (AST) may substitute for fish oil and synthetic AST in aquafeeds. This study explored the effects and mechanisms of those substitutions on AST metabolism and redox status of rainbow trout fed plant protein meal (PM)- or fishmeal (FM)-based diets. Two parallel experiments (PM vs. FM) were performed with 612 juvenile rainbow trout for 16 weeks as a 2 × 3 factorial arrangement of treatments with two AST sources (synthetic (SA) vs. microalgal (AA), at 80 mg/kg) and three levels (0, 50, and 100%) of fish oil substitutions with DHA-rich microalgae. The fish oil substitutions exhibit main effects (<i>p</i> < 0.05) and/or interactive effects (<i>p</i> < 0.05) with the source of AST on AST deposition, malondialdehyde and glutathione concentrations, and mRNA levels and activities of major redox enzymes (glutathione reductase (GR), glutathione peroxidase (GPX), glutathione S-transferase (GST), and superoxide dismutase (SOD)) in the muscle and liver of trout fed both diet series. The AST source produced only differences in tissue AST deposition (<i>p</i> < 0.05) and number of metabolites. In conclusion, the substitutions of fish oil by the DHA-rich microalgae exerted more impacts than those of SA by AA on redox status and functional expression of antioxidant enzymes in the tissues of rainbow trout.
Project description:In aquaculture, fish may be exposed to sub-optimal rearing conditions, which generate a stress response if full adaptation is not displayed. However, our current knowledge of several coexisting factors that may give rise to a stress response is limited, in particular when both chronic and acute stressors are involved. This study investigated changes in metabolic parameters, oxidative stress and innate immune markers in a rainbow trout (Oncorhynchus mykiss) isogenic line exposed to a combination of dietary (electrolyte-imbalanced diet, DEB 700 mEq Kg-1) and environmental (hypoxia, 4.5 mg O2 L-1) challenges and their respective controls (electrolyte-balanced diet, DEB 200 mEq Kg-1 and normoxia, 7.9 or mg O2 L-1) for 49 days. At the end of this period, fish were sampled or subjected to an acute stressor (2 min of handling/confinement) and then sampled. Feeding trout an electrolyte-imbalanced diet produced a reduction in blood pH, as well as increases in cortisol levels, hepato-somatic index (HSI) and total energy content in the liver. The ratio between the lactate dehydrogenase (LDH) and isocitrate dehydrogenase (IDH) activities decreased in the liver of trout fed the DEB 700 diet, but increased in the heart, suggesting a different modulation of metabolic capacity by the dietary challenge. Several markers of oxidative stress in the liver of trout, mainly related to the glutathione antioxidant system, were altered when fed the electrolyte-imbalanced diet. The dietary challenge was also associated with a decrease in the alternative complement pathway activity (ACH50) in plasma, suggesting an impaired innate immune status in that group. Trout subjected to the acute stressor displayed reduced blood pH values, higher plasma cortisol levels as well as increased levels of metabolic markers associated with oxidative stress in the liver. An interaction between diet and acute stressor was detected for oxidative stress markers in the liver of trout, showing that the chronic electrolyte-imbalance impairs the response of rainbow trout to handling/confinement. However, trout reared under chronic hypoxia only displayed changes in parameters related to energy use in both liver and heart. Taken together, these results suggest that trout displays an adaptative response to chronic hypoxia. Conversely, the dietary challenge profoundly affected fish homeostasis, resulting in an impaired physiological response leading to stress, which then placed constraints on a subsequent acute challenge.
Project description:The goal of this project was to use functional genomic methods to identify molecular biomarkers as indicators of the impact of TCDD exposure in rainbow trout. Specifically, we investigated the effects of chronic dietary TCDD exposure on whole juvenile rainbow trout global gene expression associated with histopathological analysis. Juvenile rainbow trout were fed Biodiet starter with TCDD added at 0, 0.1, 1, 10 and 100 ppb (ngTCDD/g food), and fish were sampled from each group at 7, 14, 28 and 42 days after initiation of feeding. 100 ppb TCDD caused 100% mortality at 39 days. Fish fed with 100 ppb TCDD food had TCDD accumulation of 47.37 ppb (ngTCDD/g fish) in whole fish at 28 days. Histological analysis from TCDD-treated trout sampled from 28 and 42 days revealed that obvious lesions were found in skin, oropharynx, liver, gas bladder, intestine, pancreas, nose and kidney. In addition, TCDD caused anemia in peripheral blood, decreases in abdominal fat, increases of remodeling of fin rays, edema in pericardium and retrobulbar hemorrhage in the 100 ppb TCDD-treated rainbow trout compared to the control group at 28 days. Dose- and time-dependent global gene expression analyses were performed using the cGRASP 16,000 (16K) cDNA microarray. TCDD-responsive whole body transcripts identified in the microarray experiments have putative functions involved in various biological processes including growth, cell proliferation, metabolic process, and immune system processes. Nine microarray-identified genes were selected for QPCR validation. CYP1A3 and CYP1A1 were common up-regulated genes and HBB1 was a common down-regulated gene among each group based on microarray data, and their QPCR validations are consistent with microarray data for the 10 and 100 ppb TCDD treatment groups after 28 days exposure (p<0.05). In addition, in the 100 ppb group at 28 days, expression of complement component C3-1 and trypsin-1 precursor have a more than 10-fold induction from the microarray experiments, and their QPCR validations are consistent and showed significant induction in the 100 ppb group at 28 days (p<0.05). Overall, lesion in nasal epithelium is a novel and significant result in this study, and TCDD-responsive rainbow trout transcripts identified in the present study may lead to the development of new molecular biomarkers for assessing the potential impacts of environmental TCDD on rainbow trout populations.
Project description:The metabolic peptide hormone nesfatin-1 has been linked to the reproductive axis in fishes. The purpose of this study was to determine how energy availability after spawning affects plasma levels of nesfatin-1, the metabolic peptide hormone ghrelin, and sex steroid hormones in rematuring female rainbow trout (Oncorhynchus mykiss). To limit reproductive maturation, a group of female trout was food-restricted after spawning and compared with a control group that was fed a standard broodstock ration. The experiment was conducted twice, once using two-year-old trout (second-time spawners) and once using three-year-old trout (third-time spawners). During monthly sampling, blood was collected from all fish, and a subset of fish from each treatment was sacrificed for pituitaries. Pituitary follicle-stimulating hormone-beta (fsh-?) mRNA expression was analyzed with q-RT-PCR; plasma hormone levels were quantified by radioimmunoassay (17?-estradiol and ghrelin) and enzyme-linked immunosorbent assay (11-keto-testosterone and nesfatin-1). Although plasma nesfatin-1 levels increased significantly in the months immediately after spawning within both feeding treatments, plasma nesfatin-1 did not differ significantly between the two treatments at any point. Similarly, plasma ghrelin levels did not differ significantly between the two treatments at any point. Food restriction arrested ovarian development by 15-20 weeks after spawning, shown by significantly lower plasma E2 levels among restricted-ration fish. Pituitary fsh-? mRNA levels were higher among control-ration fish than restricted-ration fish starting at 20 weeks, but did not differ significantly between treatment groups until 30 weeks after spawning. Within both treatment groups, plasma 11-KT was elevated immediately after spawning and rapidly decreased to and persisted at low levels; starting between 20 and 25 weeks after spawning, plasma 11-KT was higher among control-ration fish than restricted-ration fish. The results from these experiments do not provide support for plasma nesfatin-1 as a signal for the initiation of reproductive development in rematuring female rainbow trout.
Project description:Carnivorous rainbow trout exhibit prolonged postprandial hyperglycemia when fed a diet exceeding 20% carbohydrate content. This poor capacity to utilize carbohydrates has led to rainbow trout being classified as "glucose-intolerant" (GI). The metabolic phenotype has spurred research to identify the underlying cellular and molecular mechanisms of glucose intolerance, largely because carbohydrate-rich diets provide economic and ecological advantages over traditionally used fish meal, considered unsustainable for rainbow trout aquaculture operations. Evidence points to a contribution of hepatic intermediary carbohydrate and lipid metabolism, as well as upstream insulin signaling. Recently, microRNAs (miRNAs), small noncoding RNAs acting as negative posttranscriptional regulators affecting target mRNA stability and translation, have emerged as critical regulators of hepatic control of glucose-homeostasis in mammals, revealing that dysregulated hepatic miRNAs might play a role in organismal hyperglycemia in metabolic disease. To determine whether hepatic regulatory miRNA networks may contribute to GI in rainbow trout, we induced prolonged postprandial hyperglycemia in rainbow trout by using a carbohydrate-rich diet and profiled genome-wide hepatic miRNAs in hyperglycemic rainbow trout compared with fasted trout and trout fed a diet devoid of carbohydrates. Using small RNA next-generation sequencing and real-time RT-PCR validation, we identified differentially regulated hepatic miRNAs between these groups and used an in silico approach to predict bona fide mRNA targets and enriched pathways. Diet-induced hyperglycemia resulted in differential regulation of hepatic miRNAs compared with fasted fish. Some of the identified miRNAs, such as miRNA-27b-3p and miRNA-200a-3p, are known to be responsive to hyperglycemia in the liver of hyperglycemic glucose-tolerant fish and mammals, suggesting an evolutionary conserved regulation. Using Gene Ontology term-based enrichment analysis, we identify intermediate carbohydrate and lipid metabolism and insulin signaling as potential targets of posttranscriptional regulation by hyperglycemia-regulated miRNAs and provide correlative expression analysis of specific predicted miRNA-target pairs. This study identifies hepatic miRNAs in rainbow trout that exhibit differential postprandial expression in response to diets with different carbohydrate content and predicts posttranscriptionally regulated target mRNAs enriched for pathways involved in glucoregulation. Together, these results provide a framework for testable hypotheses of functional involvement of specific hepatic miRNAs in GI in rainbow trout.
Project description:The sustainable growth of fish aquaculture will require the procurement of non-marine feed sources. Glycerol is a potential feed supplement whose metabolism may spare the catabolism of dietary amino acids, thereby extending the use of the feed protein to other physiological functions such as growth. In the present study, the effects of dietary glycerol supplementation on the muscle and liver metabolomes of rainbow trout (Oncorhynchus mykiss) and European seabass (Dicentrarchus labrax) were evaluated. Fish juveniles were fed diets with 0%, 2.5%, and 5% glycerol. Muscle and liver aqueous fractions were extracted and 1H NMR spectra were acquired. Metabolite profiles derived from the 1H NMR signals were assessed using univariate and multivariate statistical analyses. The adenylate energy charge was determined in the muscle. For both species, the muscle metabolite profile showed more variability compared to that of the liver and was most perturbed by the 5.0% glycerol diet. For the liver metabolite profile, rainbow trout showed fewer differences compared to European seabass. No differences were observed in energy charge between experimental groups for either species. Thus, rainbow trout appeared to be less susceptible to tissue metabolite perturbations, compared to seabass, when the diet was supplemented with up to 5% glycerol.
Project description:An 8-week feeding trial was conducted to evaluate the effect of replacing soybean meal (SBM) with cottonseed meal (CSM) on growth and health of grass carp. Four isonitrogenous diets containing 0, 16.64, 32.73 and 48.94% of CSM, respectively, as replacements of 0, 35, 68 and 100% of SBM were fed to fish (initial body weight 7.14 ± 0.75 g/fish) in triplicate aquaria twice daily. The results indicated that fish fed diet containing 16.64% CSM as a replacement of 35% of SBM was not affected in weight gain (WG), feed efficiency ratio (FER) and feed conversion ratio (FCR) (P>0.05), while fish fed diets containing higher level of dietary CSM (32.73 and 48.94%) significantly decreased WGand PER and significantly increased FCR (P<0.05). Fish fed diets containing 16.64% of CSM had significantly increased hematocrit (Ht) and hemoglobin (Hb) values compared with fish fed with other diets (P<0.05). The activity of catalase (CAT), glutathione peroxidase (GSH-Px) and superoxide dismutase (SOD), gene expression levels of GSH-Px and CAT, and content of malondialdehyde (MDA) were significantly lower for fish fed diets containing 16.64% CSM compared with fish fed other diets (P<0.05). These results showed 16.64% CSM could be used to replace 35% SBM in the diets of juvenile grass carp and without health impact.
Project description:The use of natural dietary supplements in aquaculture has received a great deal of attention in recent years. This article provides data describing body weight and length of rainbow trout juveniles fed with natural dietary supplements dihydroquercetin, arabinogalactan or a mixture of both in an aquaria experiment. Before feeding trial, rainbow trout were tagged to identify individuals. Fish grown in tanks were fed one of four diets in duplicate: a basal diet without any supplements (control diet) or a basal diet supplemented with dihydroquercetin (experimental diet 1), arabinogalactan (experimental diet 2) or a mixture of both (experimental diet 3). Our dataset could be used to evaluate the effect of dihydroquercetin, arabinogalactan or a mixture of both on the growth performance of cultivated rainbow trout.