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- Aflatoxicosis Dysregulates the Physiological Responses to Crowding Densities in the Marine Teleost Gilthead Seabream (Sparus aurata)Publication . Barany, Andre; Fuentes, Juan; Martínez-Rodríguez, Gonzalo; Mancera, Juan MiguelSeveral studies in fish have shown that aflatoxin B1 (AFB1) causes a disparity of speciesdependent physiological disorders without compromising survival. We studied the effect of dietary administration of AFB1 (2 mg AFB1 kg−1 diet) in gilthead seabream (Sparus aurata) juveniles in combination with a challenge by stocking density (4 vs. 40 g L−1 ). The experimental period duration was ten days, and the diet with AFB1 was administered to the fish for 85 days prior to the stocking density challenge. Our results indicated an alteration in the carbohydrate and lipid metabolites mobilization in the AFB1 fed group, which was intensified at high stocking density (HSD). The CT group at HSD increased plasma cortisol levels, as expected, whereas the AFB1-HSD group did not. The star mRNA expression, an enzyme involved in cortisol synthesis in the head kidney, presented a ninefold increase in the AFB1 group at low stocking density (LSD) compared to the CT-LSD group. Adenohypophyseal gh mRNA expression increased in the AFB1-HSD but not in the CT-HSD group. Overall, these results confirmed that chronic AFB1 dietary exposure alters the adequate endocrinological physiological cascade response in S. aurata, compromising the expected stress response to an additional stressor, such as overcrowding.
- Intestinal response to ocean acidification in the European sea bass (Dicentrarchus labrax)Publication . Alves, Alexandra; Gregorio, Silvia F.; Ruiz-Jarabo, Ignacio; Fuentes, Juanthe intestine of marine fishes contributes to the ocean carbon cycle producing carbonate aggregates as part of the osmoregulatory process. Therefore, this study aimed to evaluate physiological adjustments of European sea bass (Dicentrarchus labrax) intestine to a higher pCO(2) environment likely in the near future (similar to 1700 mu atm). At the whole-body level, hypercapnia for 5 weeks resulted in fish having a significantly diminished specific growth rate, condition factor and hepatosomatic index. An increase in plasma osmolality and HCO3- concentration was detected, paralleled by decreased metabolites concentrations. In the intestine, high seawater pCO(2) was without effect on ouabain-sensitive ATPase activities, while Bafilomycin A1-sensitive ATPase activity significantly decreased in the anterior intestine. Anterior and mid intestine were mounted in Ussing chambers in order to measure bioelectrical parameters and bicarbonate secretion by pH-Stat ex-vivo. Hypercapnia induced a 2.3 and 2.8-fold increase in bicarbonate secretion rates in the anterior and mid intestine, respectively. In the intestinal fluid, HCO3- concentration increased 2.2-fold, and carbonate precipitates showed a 4.4-fold increase in response to hypercapnia, paralleled by a > 3-fold increase of drinking and a > 2-fold increase of intestinal volume at any given time. At the molecular level, hypercapnia elicited higher intestinal mRNA expression levels for atp6v1b (V-ATPase B subunit), slc4a4, slc26a3, and slc26a6, both in the anterior and mid intestine. As a whole, our results show that the intestine of sea bass responds to high seawater pCO(2), a response that comes at a cost at the whole-body level with an impact in the fish specific growth rate, condition factor, and hepatosomatic index.
- Editorial: microbiome dynamics as biomarkers of welfare status in aquatic speciesPublication . Fonseca, Filomena; Fuentes, JuanThe importance of the microbiome in aquaculture species is widely acknowledged. The fish gut microbiota is essential for host fitness, modulated by diet and environment, and affects animal physiology. The gut microbiome optimizes nutrient uptake and immunomodulation and enhances host resilience against infectious diseases. Understanding microbiome dynamics in aquaculture species is vital in promoting animal health and industry sustainability. In this Research Topic of Frontiers four original papers and one review paper were accepted. This editorial provides an integrated summary of those papers’ main discoveries and clues.
- Oral cortisol and dexamethasone intake: Differential physiology and transcriptional responses in the marine juvenile Sparus aurataPublication . Barany, A.; Fuentes, Juan; Valderrama, V.; Broz-Ruiz, A.; Martínez-Rodríguez, G.; Mancera, J. M.This study approached the long-term oral administration of cortisol (F) and dexamethasone (DEX), two synthetic glucocorticoids, compared to a control group (CT) in the juveniles of a marine teleost, the gilthead seabream (Sparus aurata). Physiologically, DEX treatment impaired growth, which appears to be linked to carbohydrate allocation in muscle and liver, hepatic triglycerides depletion, and reduced hematocrit. Hypophyseal gh mRNA expression was 2-fold higher in DEX than in CT or F groups. Similarly, hypothalamic trh and hypophyseal pomcb followed this pattern. Plasma cortisol levels were significantly lower in DEX than in CT, while F presented intermediate levels. In the posterior intestine, measured short circuit-current (Isc) was more anion absorptive in CT and F compared to the DEX group, whereas Isc remained unaffected in the anterior intestine. The derived transepithelial electric resistance (TEER) significantly differed between intestinal regions in the DEX group. These results provide new insights to understand better potential targeted biomarkers indicative of the differential glucocorticoid or mineralocorticoid-receptors activation in fish.
- Dysregulation of intestinal physiology by Aflatoxicosis in the Gilthead Seabream (Sparus aurata)Publication . Barany, Andre; Oliva, Milagrosa; Gregorio, Silvia; Martínez-Rodríguez, Gonzalo; Mancera, Juan Miguel; Fuentes, JuanAflatoxin B1 (AFB1) is a mycotoxin often present in food. This study aimed to understand the physiological effects of AFB1 on the seabream (Sparus aurata) gastrointestinal system. In a first in vitro approach, we investigated ion transport using the short-circuit current (Isc) technique in Ussing chambers in the anterior intestine (AI). Application of apical/ luminal AFB1 concentrations of 8 and 16μM to healthy tissues was without effect on tissue transepithelial electrical resistance (TER), and apparent tissue permeability (Papp) was measured using fluorescein FITC (4 kD). However, it resulted in dose-related effects on Isc. In a second approach, seabream juveniles fed with different AFB1 concentrations (1 and 2mg AFB1 kg−1 fish feed) for 85days showed significantly reduced gill Na+ /K+-ATPase (NKA) and H+-ATPase (HA) activities in the posterior intestine (PI). Moreover, dietary AFB1 modified Isc in the AI and PI, significantly affecting TER in the AI. To understand this effect on TER, we analyzed the expression of nine claudins and three occludins as markers of intestinal architecture and permeability using qPCR. Around 80% of the genes presented significantly different relative mRNA expression between AI and PI and had concomitant sensitivity to dietary AFB1. Based on the results of our in vitro, in vivo, and molecular approaches, we conclude that the effects of dietary AFB1 in the gastrointestinal system are at the base of the previously reported growth impairment caused by AFB1 in fish.
- Low dietary inclusion of nutraceuticals from microalgae improves feed efficiency and modifies intermediary metabolisms in gilthead sea bream (Sparus aurata)Publication . Perera, Erick; Sánchez-Ruiz, David; Sáez, María Isabel; Galafat, Alba; Barany, A.; Fernández-Castro, Miriam; Vizcaíno, Antonio Jesús; Fuentes, Juan; Martínez, Tomás Francisco; Mancera, Juan Miguel; Alarcón, Francisco Javier; Martos-Sitcha, Juan AntonioThe aim of this work was to evaluate two functional feeds for the gilthead seabream, Sparus aurata, containing low inclusion of two microalgae-based products (LB-GREENboost, LBGb; and LB-GUThealth, LBGh). Fish (12-13 g) were fed for 13 weeks a control diet or one of the four diets supplemented with both products at 0.5% or 1%. LBGb and LBGh did not affect specific growth rate or survival, but increased feed efficiency by decreasing feed intake and enlarging the intestines. LBGb increased hepatosomatic index and reduced cortisol levels in plasma, while both products lowered plasma lactate. Extensive metabolite and metabolic enzyme profiling revealed that microalgae supplementations, especially 1% LBGh: (i) decrease plasma lactate and increase hepatic glycogen, (ii) reduce hepatic gluconeogenesis, (iii) enhance hepatic lipogenic activity and lipid secretion, (iv) led fish to double triglyceride content in muscle and to stimulate its lipid oxidative capacity, and (v) increase the content of monounsaturated fatty acids and the omega-3 alpha-linolenic acid in muscle. This study demonstrates that both microalgae-based products are suited to improve feed efficiency and orchestrate significant changes in the intermediary metabolism in gilthead seabream juveniles.
- Ocean acidification compromises energy management in Sparus aurata (Pisces: Teleostei)Publication . Ruiz-Jarabo, I.; Gregorio, SF; Alves, Alexandra; Mancera, J. M.; Fuentes, JuanThe effects of ocean acidification mediated by an increase in water pCO(2) levels on marine organisms are currently under debate. Elevated CO2 concentrations in the seawater induce several physiological responses in teleost fish, including acid-base imbalances and osmoregulatory changes. However, the consequences of CO2 levels enhancement on energy metabolism are mostly unknown. Here we show that 5 weeks of exposure to hypercapnia (950 and 1800 mu atm CO2) altered intermediary metabolism of gilthead seabream (Sparus aurata) compared to fish acclimated to current ocean values (440 mu atm CO2). We found that seabream compromises its physiological acid-base balance with increasing water CO2 levels and the subsequent acidification. Intestinal regions (anterior, mid, and rectum) engaged in maintaining this balance are thus altered, as seen for Na+/K+ ATPase and the vacuolar-type H+-ATPase activities. Moreover, liver and muscle counteracted these effects by increasing catabolic routes e.g., glycogenolysis, glycolysis, amino acid turnover, and lipid catabolism, and plasma energy metabolites were altered. Our results demonstrate how a relatively short period of 5 weeks of water hypercapnia is likely to disrupt the acid-base balance, osmoregulatory capacity and intermediary metabolism in S. aurata. However, long-term studies are necessary to fully understand the consequences of ocean acidification on growth and other energy-demanding activities, such as reproduction.
- Agouti overexpression in a transgenic model regulates integrity, permeability and electrogenic amino acid transport in zebrafish intestinePublication . Leal, Esther; Angotzi, Anna Rita; Godino-Gimeno, Alejandra; Gregorio, Silvia F.; Rotllant, Josep; Saera-Vila, Alfonso; Fuentes, Juan; Cerdá-Reverter, José MiguelOverexpression of asip1 in transgenic zebrafish disrupts dorsoventral pigment pattern in addition to increasing food intake levels and linear growth. A higher feed intake is unnecessary in transgenic fish to enable larger and heavier growth. A plausible explanation may rely on the enhanced feeding efficiency mediated by improved nutrient absorption in transgenic animals. To test this hypothesis, wide scope transcriptomic techniques were used to elucidate the potential pathways involved in the enhanced nutrient absorption and intestinal epithelium permeability/integrity. In addition, the electrogenic capacity for amino acid transport was analysed. Transcriptomic analysis reveal that amino acid, monocarboxylates, ionic and vitamin transmembrane transporters were substantially modified. Enrichment analysis also revealed an inhibition of intestinal lipid metabolism and down-regulation of KEGG pathways related to membrane integrity suggesting augmented intestinal laxity that may enhance paracellular transport. Electrophysiological experiments carried out in Ussing chambers show that asip1 overexpression decrease membraned tissue resistance (Rt), indicating a modification of the intestinal barrier function in ASIP1 transgenic animals. Similarly, paracellular permeability was higher in transgenic zebrafish. Both the decrease in Rt and the increase in permeability point to an ASIP1-dependent decrease in the tissue barrier function. Electrogenic amino acid transport was also enhanced in transgenic animals providing strong indication that ASIP1 fish can extract more amino acids from their diet at similar feeding levels. Both transcriptomic and electrophysiological results suggest that asip1-overexpressing zebrafish display improved nutrient absorption and by extension a higher feed efficiency which explains enhanced growth in the absence of augmented food intake. The enhanced growth of ASIP1 zebrafish potentially mediated by improved nutrient uptake and feed efficiency suggests that the melanocortin system, specifically asip1 overexpression, is a potential target for the development of genetically engineered fish displaying improved performance and no differential lipid accumulation.
- From invasion to fish fodder: inclusion of the brown algae rugulopteryx okamurae in aquafeeds for european sea bass dicentrarchus labrax (L., 1758)Publication . Fonseca, Filomena; Fuentes, Juan; Vizcaíno, Antonio Jesús; Alarcón, Francisco Javier; Mancera, Juan Miguel; Martínez-Rodríguez, Gonzalo; Martos-Sitcha, Juan AntonioIn keeping with the premises of Blue Circular Economy in the European Union, the present study explored the possibility of using the invasive brown alga Rugulopteryx okamurae in aquafeeds for European sea bass (Dicen-trarchus labrax). Assuming the raw algae biomass could negatively impact animal performance, four experi-mental formulations were prepared, by including macroalgae material at 5%, using crude (CR), enzymatically hydrolysed and fermented (EF), enzymatically hydrolysed (E), or fermented (F) R. okamurae biomass, which we tested against a control feed (CT). To evaluate the effects of the experimental diets, besides animal growth performance and biometric parameters, we devised a toolbox focused on the intestine and intestinal function: i) ex-vivo epithelial resistance and permeability in Ussing chambers; ii) microbiota composition through NGS; iii) expression profiles of selected markers for epithelial integrity, transport, metabolism, and immune response, by qPCR. Our results show differentiated allometric growth among diets, coupled with intestinal epithelium al-terations in permeability, integrity, and amino acid transport. Additionally, evidence of microbiota dysbiosis and contrasting immune responses between experimental diets, i.e. pro-inflammatory vs. anti-inflammatory, are also described. In conclusion, we believe that R. okamurae could be a suitable resource for aquafeeds for the European sea bass, although its use requires a pre-treatment before inclusion. Otherwise, while the fish still have a positive growth performance, the gastrointestinal tract pays a toll on the integrity, transport, and inflammatory processes.
- Biotechnological treatment of microalgae enhances growth performance, hepatic carbohydrate metabolism and intestinal physiology in gilthead seabream (Sparus aurata) juveniles close to commercial sizePublication . Molina-Roque, Luis; Bárany, André; Sáez, María Isabel; Alarcón, Francisco Javier; Tapia, Silvana Teresa; Fuentes, Juan; Mancera, Juan Miguel; Perera, Erick; Martos-Sitcha, Juan AntonioThe aim of this work was to evaluate the effects on growth performance, intermediary metabolism and welfare of the inclusion of two commercial microalgae-based ingredients called LB-ChromaBream (LB-CB) and LB-ChromaBream-plus (LB-CBplus) in the diet of gilthead seabream (Sparus aurata) close to commercial size. For this purpose, fish of similar to 182 g of initial body mass were fed to satiety (ad libitum) for 41 days with three different diets: (i) CONTROL diet (CTRL), with a commercial-like formulation; (ii) LB-CB diet, with a 10 % inclusion of microalgal product; (iii) LB-CBplus diet, with a 10 % inclusion of the same product but enzymatically hydrolysed to increase the bioavailability of the nutrients. The results obtained show that the use of these microalgal products leads an overall improvement in productive parameters in terms of growth (15 % in SGR) and feed efficiency (11 %), as well as a significant reduction in circulating cortisol with the LB-CBplus diet. Observations on plasma and liver metabolites, and particularly on hepatic metabolic enzymes, collectively indicate that microalgae supplementation of feed lead to a better use of carbohydrates as a source of energy in the liver and other tissues, potentially sparing triglycerides within this tissue, and a channelling hepatic triglycerides to fuels growth. Finally, the specimens fed the supplemented diets experienced a substantial improvement in intestinal health, achieved by longer intestines, a higher transepithelial resistance and better apparent permeability measured by electrophysiological methods, especially those fed LB-CBplus, which could explain the increase in productive performance by improving nutrient assimilation. In conclusion, this study shows that the experi-mental feeds, especially the one containing biotechnologically treated microalgae, are suitable for improving some important indicators of growth performance and physiological condition of gilthead seabream, thus revealing the potential for their inclusion in new functional feeds for this species at an advanced stage of the production cycle.