Comparative study of enzymatic antioxidants in muscle of elasmobranch and teleost fishes

Induced swimming in European seabass (Dicentrarchus labrax): effects on the stress response, immune, and antioxidant status

Suitable swimming conditions can improve the growth and welfare of farmed fish. This study investigated how swimming affects immune and oxidative responses in European seabass (Dicentrarchus labrax), an important farmed fish species in Southern Europe. Thirty-two specimens were assigned into four experimental groups with the following conditions for 6 h: steady low (L, 0.8 body lengths (BL)⋅s-1); steady high (H, 2.2 BL⋅s-1); oscillating (O, 0.8-2.2 BL⋅s-1) swimming speeds; and control non-induced to swim (C, < 0.1 BL⋅s-1). The H group exhibited higher white blood cell counts and plasma cortisol levels compared to the C and L groups. However, innate immune parameters in plasma and skin mucus showed no differences between groups. Gene expression revealed an up-regulation of inflammatory cytokines (tnfα and il1β) and igf1 in the gills of fish from H and L groups, respectively, whilst no variations were observed in the head-kidney. In the skin, tnfα was up-regulated in the L group. Moreover, the H group showed increased superoxide dismutase and catalase activities and higher lipid peroxidation levels in red muscle. The L group had a higher ratio of reduced/oxidized glutathione (GSH: GSSG) in red muscle, suggesting enhanced antioxidant status. Under all swimming conditions, the GSH: GSSG ratio was increased in the white muscle. Conversely, hepatic markers of oxidative stress were similar among groups. Results suggest that steady swimming at 0.8 BL⋅s-1 enhanced the antioxidant status in red muscle which may be of relevance to improve the welfare of this cultured species.

Influence of water chemistry and contaminant occurrence on the oxidative stress ecology of Cottus gobio in a high-mountain lake (Carnic Alps)

Understanding oxidative stress in high-mountain lake fish offers crucial insights into their health, resilience, and adaptation to extreme environmental changes. This study investigates the oxidative stress response of Cottus gobio in a high-mountain lake (Dimon Lake) located in the northeast Italy during the ice-free season, focusing on the relationship between oxidative stress biomarkers and physicochemical water parameters, as well as persistent and emerging contaminants. Significant seasonal variations were observed in water parameters, with lower oxygen, pH, conductivity, and phosphate levels in summer compared to autumn, while temperature, ammonium, and nitrate were higher in summer. Metal concentrations in C. gobio muscle were higher in autumn, with Zn showing the most significant increase. PAHs, NDL-PCBs, and pesticides were all below the limit of quantification in the fish muscle samples. No microplastics items were found in the gastrointestinal tracts of fish. Oxidative stress biomarkers revealed organ-specific and seasonal variations. The liver exhibited the highest activities of catalase (CAT), glutathione peroxidase (GPx), glutathione S-tranferase (GST), and glutathione reductase (GR), highlighting its central role in detoxification and metabolic processes. Superoxide dismutase (SOD) activity was notably higher in muscle tissue during summer, suggesting increased metabolic activity. A strong correlation was found between pH and the activities of SOD, CAT, GPx, GR, and metallothioneins (MTs), emphasizing the importance of water chemistry in influencing oxidative stress responses. This approach not only aids in understanding the local adaptations of these fish but also highlights the impacts of environmental stressors on high-mountain ecosystems. Continuous monitoring of water chemistry, particularly pH, is crucial for understanding and managing oxidative stress in aquatic organisms, especially in the context of global environmental changes.

Inter- and intraspecific blood-related biomarkers and chemical exposure in confined and free-living sea turtles

The relevance of recovery centers and head-starting programs for rescue, rehabilitation, rearing, and conservation of sea turtles is recognized worldwide. In addition, these centers contribute to generating biochemical and physiological data needed to identify health markers and provide baseline values. Because of the marine ecosystems' deterioration, biomarker identification is a global priority for sea turtle conservation; nevertheless, information on specific endpoints, such as neurotoxicity and mutagenesis, is still limited in sea turtles. This study aimed to contrast a set of non-invasive blood biomarkers with ecotoxicological and clinical applications in confined green sea turtles (Chelonia mydas) compared with free-living ones from the Mexican Caribbean. Additionally, interspecific (green, hawksbill (Eretmochelys imbricata), loggerhead (Caretta caretta) turtles) differences were also evaluated. Plasmatic organochlorine pesticides (OCs) and polychlorinated biphenyl (PCBs) were also determined. The concentration ranges of uric acid, total proteins, lipids (cholesterol and triglycerides), and thyroxine of both confined and free-living green turtles fell outside the reference intervals for the species. Additionally, confined green turtles had the highest number of erythrocytic nuclear abnormalities (ENA) and elevated levels of hemoglobin, lipid peroxidation, and activity of glutathione S-transferase, glutathione peroxidase, and carboxylesterase (CE). Contrasts among confined species identified hawksbill turtles with the lowest glutathione reductase activity, green turtles with the lowest ENA frequency and CE activity, and loggerhead turtles with the highest plasmatic concentrations of PCBs and OCs. The information here provided can be used as information in health monitoring programs and for conservation and management policies at regional, national, and international level.

Inclusion of Sorghum in Cyprinus carpio L. Diet: Effects on Growth, Flesh Quality, Microbiota, and Oxidative Status

This study investigates the impact of including sorghum in the diet of the common carp (Cyprinus carpio) on its growth, blood parameters, meat composition, intestinal microbiota, and oxidative stress. Experimental diets with varying sorghum content (0%-V0 or control, 10%-V1, 20%-V2, and 30%-V3) were administered to carp weighing 43 g initially. Notably, in the 30% variant, sorghum entirely replaced corn and barley in the diet. Chemical analysis of sorghum unveiled a protein content of 14% and a fat content of 3.9%. Sorghum inclusion led to a decline in final body weight and weight gain, particularly notable in the V3 group with 30% sorghum. However, other physiological parameters, such as feed conversion ratio, specific growth rate, and organ indices, remained unaffected. Protein and salt content in carp flesh increased with higher sorghum inclusion levels, while hematological parameters showed minimal variations. Analysis of the intestinal microbiota revealed increases in both aerobic and anaerobic bacterial populations with sorghum inclusion. Furthermore, sorghum concentration inversely correlated with glutathione levels and positively correlated with malondialdehyde content, indicating a disruption of antioxidant defense mechanisms and elevated oxidative stress.

Effects of dietary nanoliposome-coated astaxanthin on haematological parameters, immune responses and the antioxidant status of rainbow trout (Oncorhynchus mykiss)

BACKGROUND

Astaxanthin is the most prevalent carotenoid in the marine environment and is widely used as an additive in formulated aquafeeds.

OBJECTIVES

A 60-day feeding trial was conducted to consider the effect of dietary nanoliposome-coated astaxanthin (NA) on haematological parameters, serum antioxidant activities and immune responses of rainbow trout, Oncorhynchus mykiss.

METHODS

A total of 450 healthy fish weighing 31.00 ± 2.09 g were randomly assigned in triplicate (30 fish per replicate) to 5 dietary treatments: 0 (control), 25.00, 50.00, 75.00, and 100.00 mg kg-1 NA.

RESULTS

Fish fed the diet supplemented with 50.00 mg kg-1 NA exhibited the highest values of red blood cells, white blood cells, haemoglobin and haematocrit of 1.64 ± 0.01 × 106 mm-3, 5.54 ± 0.21 × 103 mm-3, 8.73 ± 0.24 g dL-1 and 46.67% ± 0.88%, respectively, which were significantly higher than those fed the basal diet (p < 0.05). The lowest and highest percentages of lymphocytes (67.67% ± 0.33%) and neutrophils (27.33% ± 1.20%) were also obtained in fish fed 50.00 mg kg-1 NA compared to those fed the basal diet (p < 0.05). Fish receiving diet supplemented with 50.00 mg kg-1 NA revealed the highest serum activity in superoxide dismutase, catalase, glutathione peroxidase, lysozyme and alternative complement and the lowest level of total cholesterol, cortisol, aspartate aminotransferase and alanine aminotransferase than fish receiving the basal diet (p < 0.05). Serum immunoglobulin (Ig) and ACH50 contents significantly increased with increasing dietary NA supplementation to the highest values of 43.17 ± 1.46 and 293.33 ± 2.03 U mL-1, respectively, in fish fed diet supplemented with 50 mg kg-1 NA (p < 0.05).

CONCLUSIONS

Supplementation of NA in rainbow trout diet at 50 mg kg-1 exhibited a positive effect on haematological parameters, antioxidant capacity and immune responses. Administration of such dosage can enhance rainbow trout immune responses against unfavourable or stressful conditions, for example disease outbreaks, hypoxic condition, thermal stress and sudden osmotic fluctuations, which usually happen in an intensive culture system.

Induced swimming modified the antioxidant status of gilthead seabream (Sparus aurata)

Swimming has relevant physiological changes in farmed fish, although the potential link between swimming and oxidative stress remains poorly studied. We investigated the effects of different medium-term moderate swimming conditions for 6 h on the antioxidant status of gilthead seabream (Sparus aurata), analyzing the activity of enzymes related to oxidative stress in the liver and skeletal red and white muscle. Forty fish were induced to swim individually with the following conditions: steady low (SL, 0.8 body length (BL)·s-1), steady high (SH, 2.3 BL·s-1), oscillating low (OL, 0.2-0.8 BL·s-1) and oscillating high (OH, 0.8-2.3 BL·s-1) velocities, and a non-exercised group with minimal water flow (MF, < 0.1 BL·s-1). All swimming conditions resulted in lower activities of superoxide dismutase (SOD), glutathione reductase (GR), and glutathione-S-transferase (GST) in the liver compared to the MF group, while steady swimming (SL and SH) led to higher reduced glutathione/oxidized glutathione ratio (GSH/GSSG) compared to the MF condition. Swimming also differently modulated the antioxidant enzyme activities in red and white muscles. The OH condition increased lipid peroxidation (LPO), catalase (CAT) and glutathione peroxidase (GPx) activities in the red muscle, decreasing the GSH/GSSG ratio, whereas the SL condition led to increased GSH. Oscillating swimming conditions (OL and OH) led to lower CAT activity in the white muscle, although GPx activity was increased. The GSH/GSSG ratio in white muscle was increased in all swimming conditions. Liver and skeletal muscle antioxidant status was modulated by exercise, highlighting the importance of adequate swimming conditions to minimize oxidative stress in gilthead seabream.

A higher mitochondrial content is associated with greater oxidative damage, oxidative defenses, protein synthesis and ATP turnover in resting skeletal muscle

An unavoidable consequence of aerobic metabolism is the production of reactive oxygen species (ROS). Mitochondria have historically been considered the primary source of ROS; however, recent literature has highlighted the uncertainty in primary ROS production sites and it is unclear how variation in mitochondrial density influences ROS-induced damage and protein turnover. Fish skeletal muscle is composed of distinct, highly aerobic red muscle and anaerobic white muscle, offering an excellent model system in which to evaluate the relationship of tissue aerobic capacity and ROS-induced damage under baseline conditions. The present study used a suite of indices to better understand potential consequences of aerobic tissue capacity in red and white muscle of the pinfish, Lagodon rhomboides. Red muscle had a 7-fold greater mitochondrial volume density than white muscle, and more oxidative damage despite also having higher activity of the antioxidant enzymes superoxide dismutase and catalase. The dominant protein degradation system appears to be tissue dependent. Lysosomal degradation markers and autophagosome volume density were greater in white muscle, while ubiquitin expression and 20S proteasome activity were significantly greater in red muscle. However, ubiquitin ligase expression was significantly higher in white muscle. Red muscle had a more than 2-fold greater rate of translation and total ATP turnover than white muscle, results that may be due in part to the higher mitochondrial density and the associated increase in oxidative damage. Together, these results support the concept that an elevated aerobic capacity is associated with greater oxidative damage and higher costs of protein turnover.

Efficacy of nano zinc oxide dietary supplements on growth performance, immunomodulation and disease resistance of African catfish Clarias gariepinus

Zinc (Zn) is an important trace element in fish diets that is required for growth, immunity and antioxidant defense mechanisms. The current study assessed the effects of both organic and nanoparticle zinc oxide (ZnO and ZnO-NPs, respectively) on growth performance, immune response and the antimicrobial effect against Pseudomonas aeruginosa in African catfish Clarias gariepinus. Fish were fed either a control diet or diets supplemented with organic ZnO at concentrations of 20 and 30 mg kg-1 or ZnO-NPs at concentrations of 20 and 30 mg kg-1. After 60 d, a subset of the fish was injected intraperitoneally with 3 × 107 CFU ml-1 of P. aeruginosa. Results showed that body weight gain, feed conversion ratio and specific growth rates were significantly increased in ZnO-NPs20 compared to all other groups. The dietary supplementation with 20 mg kg-1 of ZnO-NPs improved the antioxidant status of fish. Moreover, IgM, lysozyme and nitric oxide showed a significant increase in the fish which received the ZnO-NPs20-supplemented diet. A significant upregulation of growth and stress-related genes was seen in the ZnO-NPs20-supplemented group compared to other groups. However, there was no significant difference in the expression of immune-related genes among ZnO-NPs20, ZnO-NPs30 and ZnO30 groups. These findings highlight the potential use of nano-ZnO for improving growth performance, antioxidant status, immunological status and antibacterial activity against P. aeruginosa in African catfish.

Acute effects of intense exercise on the antioxidant system in birds: does exercise training help?

The acute effects of an energy-intensive activity such as exercise may alter an animal's redox homeostasis, although these short-term effects may be ameliorated by chronic exposure to that activity, or training, over time. Although well documented in mammals, how energy-intensive training affects the antioxidant system and damage by reactive species has not been investigated fully in flight-trained birds. We examined changes to redox homeostasis in zebra finches exposed to energy-intensive activity (60 min of perch-to-perch flights twice a day), and how exercise training over many weeks affected this response. We measured multiple components of the antioxidant system: an enzymatic antioxidant (glutathione peroxidase, GPx) and non-enzymatic antioxidants (measured by the OXY-adsorbent test) as well as a measure of oxidative damage (d-ROMs). At no point during the experiment did oxidative damage change. We discovered that exposure to energy-intensive exercise training did not alter baseline levels of GPx, but induced exercise-trained birds to maintain a higher non-enzymatic antioxidant status as compared with untrained birds. GPx activity was elevated above baseline in trained birds immediately after completion of the second 1 h flight on each of the three sampling days, and non-enzymatic antioxidants were acutely depleted during flight after 13 and 44 days of training. The primary effect of exercise training on the acute response of the antioxidant system to 2 h flights was increased coordination between the enzymatic (GPx) and non-enzymatic components of the antioxidant system of birds that reduced oxidative damage associated with exercise.

Protective Effect of Dietary Taurine from ROS Production in European Seabass under Conditions of Forced Swimming

Simple Summary

A number of recent studies have demonstrated the essentiality of dietary taurine in many commercially relevant cultured fish species. Taurine is involved in many physiological functions in fish and represents an essential nutrient, which exert powerful antioxidant properties and is required as a supplement in the feed when a relevant percentage of vegetable protein sources are utilized. Our results show that dietary taurine can reduce the oxidative status of marine fish under swim stamina stress conditions. These data could be essential for the development of diets with fishmeal/soybean meal substitutions in the effort to improve the sustainability of the aquaculture.

Abstract

Taurine (Tau) is an amino sulfonic acid, which is widely distributed in animal tissues, whereas it is almost lacking in plants with the exception of certain algae, seaweeds, and few others. In the aquafeed industry, Tau is mainly used as a feed additive to promote growth in marine fish species with limited cysteine sulfinate decarboxylase activity. In particular, Tau supplementation is required in feeds in which fishmeal (FM) is substituted with high percentages of plant-derived protein sources such as soybean meals (SBM) that have much lower levels of Tau than FM. In addition to being a growth promoter, Tau exert powerful antioxidant properties being a scavenger of the reactive oxygen species (ROS). Under sustained swimming conditions, an intracellular increase in ROS production can occur in fish red muscle where the abundance of mitochondria (the main site of ROS formation) is high. Accordingly, this study aimed at investigating the effects of dietary Tau on European seabass (Dicentrarchus labrax) growth and oxidative stress response induced by swimming exercise. Individually tagged fish of 92.57 ± 20.33 g mean initial weight were fed two experimental diets containing the same low percentage of FM and high percentage of SBM. One diet was supplemented with 1.5% of Tau. Tau supplemented in the diet had a positive effect on fish growth, and enhanced swimming performance and antioxidant status. Two swim endurance tests were performed during the feeding trial. Metabolic oxygen consumption (MO₂) was measured during exercise at incremental swimming speeds (0.7, 1.4, 2.1, 2.8, 3.5, and then 4.2 BL (body length) s⁻¹, until fatigue). Fish maximal sustainable swimming speed (Ucrit) was determined too. To investigate the antioxidant effect of dietary Tau, we also measured ROS production in fish blood by RBA (respiratory burst activity) assay and quantified the expression of genes coding for antioxidant enzymes by qPCR (quantitative polymerase chain reaction) , such as SOD (superoxide dismutase), GPX (glutathione peroxidase), and CAT (catalase) in red muscle and liver. There was a significant effect of Tau upon Ucrit during exercise. Additionally, ROS production was significantly lower in fish fed with Tau supplemented diet, supporting the role of Tau as ROS scavenger. The protective effect of Tau against oxidative stress induced by forced swimming was denoted also by a significant decrease in antioxidant enzymes gene expression in fish liver and muscle. Taken together these results demonstrate that Tau is beneficial in low FM-based diets for seabass.