Dietary Oil Source and Selenium Supplementation Modulate Fads2 and Elovl5 Transcriptional Levels in Liver and Brain of Meagre (Argyrosomus regius)

Effects of Dietary Bio-Fermented Selenium Supplementation on Growth, Immune Performance, and Intestinal Microflora of Chinese Mitten Crabs, Eriocheir sinensis

Selenium is a vital trace mineral that is crucial for maintaining regular biological processes in aquatic animals. In this study, a four-week dietary trial was carried out to assess the impact of bio-fermented selenium (Bio-Se) on the growth and immune response of Chinese mitten crabs, Eriocheir sinensis. The crabs were randomly allocated to five dietary treatment groups, each receiving a different dose of Bio-Se. The doses included 0, 0.3, 0.6, 1.5, and 3.0 mg/kg and were accurately measured in basal diet formulations. The results showed the weight gain rate (WGR), specific growth rate (SGR), and survival rate (SR) in the 1.5 mg/kg Bio-Se group were the highest, and 3.0 mg/kg of Bio-Se has an inhibitory effect on the WGR, SGR, and SR. The activities of the immune enzymes, including glutathione peroxidase (GPX), superoxide dismutase (SOD), and acid phosphatase (ACP), of the hepatopancreas were significantly (p < 0.05) increased in the 1.5 mg/kg Bio-Se group, while they decreased (p < 0.05) in the 3.0 mg/kg feeding group compared to the 0 mg/kg feeding group. The concentration of maleic dialdehyde (MDA) exhibited the opposite pattern. Similarly, the mRNA expression levels of antimicrobial peptides (ALF-1, Crus-1, and LYS), ERK, and Relish genes were also observed to be the highest in the 1.5 mg/kg Bio-Se group compared with the other groups. Furthermore, the administration of 1.5 mg/kg of Bio-Se resulted in an increase in the thickness of the intestinal plica and mucosal layer, as well as in alterations in the intestinal microbial profile and bacterial diversity compared to the dose of 0 mg/kg of Bio-Se. Notably, the population of the beneficial bacterial phylum Fusobacteria was increased after crabs were fed the 1.5 mg/kg Bio-Se diet. In conclusion, the oral administration of 1.5 mg/kg of Bio-Se improved the growth efficiency, antioxidant capabilities, immunity, and intestinal health of E. sinensis. Through a broken-line analysis of the WGR against dietary Bio-Se levels, optimal dietary Bio-Se levels were determined to be 1.1 mg/kg. These findings contribute valuable insights to the understanding of crab cultivation and nutrition.

Valorization of Side Stream Products from Sea Cage Fattened Bluefin Tuna (Thunnus thynnus): Production and In Vitro Bioactivity Evaluation of Enriched ω-3 Polyunsaturated Fatty Acids

The valorization of side streams from fishery and aquaculture value-chains is a valuable solution to address one of the challenges of the circular economy: turning wastes into profit. Side streams produced after filleting of sea cage fattened bluefin tuna (Thunnus thynnus) were analyzed for proximate composition and fatty acid profile to evaluate the possibility of producing tuna oil (TO) as a valuable source of ω-3 polyunsaturated fatty acids (PUFA) and testing its bioactivity in vitro. Ethyl esters of total fatty acids (TFA), obtained from TO, were pre-enriched by urea complexation (PUFA-Ue) and then enriched by short path distillation (SPD) up to almost 85% of the PUFA fraction (PUFA-SPe). The bioactivity of TFA, PUFA-SPe, and ethyl esters of depleted PUFA (PUFA-SPd) were tested in vitro, through analysis of lipid metabolism genes, in gilthead sea bream (Sparus aurata) fibroblast cell line (SAF-1) exposed to oils. TFA and PUFA-SPd upregulated transcription factors (pparβ and pparγ) and lipid metabolism-related genes (D6D, fas, fabp, fatp1, and cd36), indicating the promotion of adipogenesis. PUFA-SPe treated cells were similar to control. PUFA-SPe extracted from farmed bluefin tuna side streams could be utilized in fish feed formulations to prevent excessive fat deposition, contributing to improving both the sustainability of aquaculture and the quality of its products.

Tilapia can be a Beneficial n-3 LC-PUFA Source due to Its High Biosynthetic Capacity in the Liver and Intestine

To assess whether farmed tilapia can be a beneficial n-3 long-chain polyunsaturated fatty acid (LC-PUFA) source for human health, four diets with linoleic acid (LA) to α-linolenic acid (ALA) ratios at 9, 6, 3, and 1 were prepared to feed juveniles for 10 weeks, and the LC-PUFA biosynthetic characteristics in the liver, intestine, and brain and the muscular quality were analyzed. It was shown that the n-3 LC-PUFA levels of the intestine and liver increased in a parallel pattern with the dietary ALA levels. Correspondingly, in the fish fed diet with high ALA levels, the mRNA levels of genes related to LC-PUFA biosynthesis including fads2, elovl5, and pparα in the intestine and elovl5 in the liver were increased, and the muscular n-3 LC-PUFA levels and textures were improved. The results demonstrated that tilapia intestine and liver possess high n-3 LC-PUFA biosynthetic capacity, which suggests that farmed tilapia can be a beneficial n-3 LC-PUFA source.

Optimum dietary sources and levels of selenium improve growth, antioxidant status, and disease resistance: re-evaluation in a farmed fish species, Nile tilapia (Oreochromis niloticus)

The objective of this study was to investigate the effects of sources and levels of selenium (Se) on juvenile Nile tilapia (Oreochromis niloticus). A completely randomized design involving a 2 × 3 factorial arrangement of treatments was used in this study. Organic Se (L-selenomethionine; SeMet) and inorganic Se (sodium selenite; Na₂SeO₃) were each added to the basal diet at 1, 3 and 5 mg Se/kg. The basal diet, without Se supplementation, was used as a control. There was a total of 7 experimental diets, and each was fed in triplicate to groups of fish with an initial average body weight of 13.5 g for 8 weeks. The results showed that growth performance was significantly affected by dietary sources and levels of Se (P < 0.05). Fish fed diets supplemented with SeMet of 1.0 mg Se/kg resulted in higher growth performance compared to basal diet (P < 0.05), but Na₂SeO₃ supplementation did not affect growth. The feed conversion ratio was significantly decreased as dietary sources of SeMet (P < 0.05). Interestingly, fish fed diets supplemented with both forms of Se had lower cholesterol levels than those fed the basal diet (P < 0.05). Moreover, dietary sources and levels of Se significantly increased (P < 0.05) the antioxidant enzyme activities such as lysozyme, catalase, myeloperoxidase, superoxide dismutase and glutathione peroxidase. Dietary sources and levels of Se significantly could enhance the Nile tilapia resistance against Streptococcusagalactiae infection (P < 0.05). Overall, it can be concluded that the inclusion level of 1.0 mg Se/kg of organic Se in the diet is suggested to be the optimal level for the growth performance and immune response of Nile tilapia. Therefore, dietary supplementation with Se is useful for improving growth, antioxidant status, immune response, and disease resistance.

Dietary selenium enhances the growth and anti-oxidant capacity of juvenile blunt snout bream (Megalobrama amblycephala)

Sodium selenite was added to basal diet at five levels (0.10, 0.42, 0.67, 1.06 and 1.46 mg Se/kg) and fed fish for 8 weeks. The dietary selenium requirement of juvenile blunt snout bream (Megalobrama amblycephala) was quantified. Dietaryseleniums at 0.67-1.06 mg Se/kg improved weight gain rate, specific growth rate and feed efficiency. The optimal amount was 0.96 mg/kg, for which the specific growth rate was 1.798%/day and the weight gain rate was 173.852% (p < 0.05). Se deposition in muscle was increased (p < 0.05) at ≥0.67 mg/kg, but moisture, protein, lipid and ash content were not affected. Physiological status and lipid metabolism were improved by 1.06-1.46 mg/kg dietary selenium based on total protein and albumin in plasma, and total cholesterol and triglycerides (p < 0.05). Activities of hepatic anti-oxidant enzymes catalase, total superoxide dismutase, glutathione peroxidase and reduced glutathione were enhanced at Se1.06 (p < 0.05). However, malondialdehyde content was lowered at Se1.06 (p < 0.05). Expression of anti-inflammatory cytokines, nuclear factor erythroid 2-related factor 2 (Nrf2) and kelch-like ECH-associated protein 1 (Keap-1) in liver were elevated at Se1.06 (p < 0.05), as were mRNA levels of glutathione peroxidase, copper zinc superoxide dismutase and catalase. Expression of pro-inflammatory cytokines, interleukin 8, tumour necrosis factor-α and transforming growth factor-β were inhibited at 0.67-1.46 mg/kg (p < 0.05). In general, 0.96 mg/kg was optimal, and optimal selenium enhanced antioxidant stress tolerance and anti-inflammatory ability.

Dietary Fish Oil Alters DNA Methylation of Genes Involved in Polyunsaturated Fatty Acid Biosynthesis in Muscle and Liver of Atlantic Salmon (Salmo salar)

Adequate dietary supply of eicosapentaenoic acid (20:5n-3) and docosahexaenoic acid (22:6n-3) is required to maintain health and growth of Atlantic salmon (Salmo salar). However, salmon can also convert α-linolenic acid (18:3n-3) into eicosapentaenoic acid (20:5n-3) and docosahexaenoic acid (22:6n-3) by sequential desaturation and elongation reactions, which can be modified by 20:5n-3 and 22:6n-3 intake. In mammals, dietary 20:5n-3 + 22:6n-3 intake can modify Fads2 expression (Δ6 desaturase) via altered DNA methylation of its promoter. Decreasing dietary fish oil (FO) has been shown to increase Δ5fad expression in salmon liver. However, it is not known whether this is associated with changes in the DNA methylation of genes involved in polyunsaturated fatty acid synthesis. To address this, we investigated whether changing the proportions of dietary FO and vegetable oil altered the DNA methylation of Δ6fad_b, Δ5fad, Elovl2, and Elovl5_b promoters in liver and muscle from Atlantic salmon and whether any changes were associated with mRNA expression. Higher dietary FO content increased the proportions of 20:5n-3 and 22:6n-3 and decreased Δ6fad_b mRNA expression in liver, but there was no effect on Δ5fad, Elovl2, and Elovl5_b expression. There were significant differences between liver and skeletal muscle in the methylation of individual CpG loci in all four genes studied. Methylation of individual Δ6fad_b CpG loci was negatively related to its expression and to proportions of 20:5n-3 and 22:6n-3 in the liver. These findings suggest variations in dietary FO can induce gene-, CpG locus-, and tissue-related changes in DNA methylation in salmon.

Dietary cosupplementation with curcumin and different selenium sources (nanoparticulate, organic, and inorganic selenium): influence on growth performance, body composition, immune responses, and glutathione peroxidase activity of rainbow trout (Oncorhynchus mykiss)

The aim of this study was to investigate the effects of dietary selenium (nanoparticles, organic, and inorganic forms), curcumin (CUR), and their combination on survival, growth performance, body composition, innate immune responses, and glutathione peroxidase activity of rainbow trout (Oncorhynchus mykiss). CUR at level of 400 mg/kg dry diet and each of selenium nanoparticles (Se-NPs), organic selenium (Sel-Plax®), and sodium selenite at level of 1 mg/kg Se dry diet were added to basal diet. A total of 240 rainbow trout with mean initial weight of 14.65 ± 0.86 g were fed eight diets including control (basal diet), CUR, Se-NPs, Se-NPs + CUR, organic Se, organic Se + CUR, sodium Se, and sodium Se + CUR for 8 weeks. No significant increase in survival rate, growth performance, feed utilization, and body composition was observed in fish-fed CUR and Se included diets compared to control (P > 0.05). The highest lysozyme and alternative hemolytic complement activity was observed in fish-fed CUR and organic Se + CUR-supplemented diets (P < 0.05). Fish-fed Se-NPs and Se-NPs + CUR-supplemented diets had the highest glutathione peroxidase activity (P < 0.05). The results of the present study indicated that the combination of CUR and Se in nanoparticles and organic forms was more effective in promoting innate immune responses of rainbow trout compared to the other combined or separated Se and CUR forms.

Dietary supplementation of organic selenium improves growth, survival, antioxidant and immune status of meagre, Argyrosomus regius, juveniles

Oxidative stress is considered one of the main obstacles to immune competence and high mortality rate of marine fish larvae due to the high dietary polyunsaturated fatty acids and accelerated metabolic rate. This study was carried out to assess the effect of different dietary selenium (Se) yeast on growth, antioxidant status, hematological changes, and cellular and humoral immune parameters in meagre (Argyrosomus regius). Juvenile specimens (3.20 ± 0.17 g) were randomly assigned to four experimental groups, a control group fed a basal diet and another three groups fed Se-supplemented diets at doses of 1, 2 and 3 mg Se-yeast kg^-1 diet for 63 days and the final analyzed selenium concentrations were 0.77, 1.51, 2.97 and 3.98 mg Se kg^-1 diet, respectively. The results indicated that growth performance, feed conversion ratio and survival were significantly improved with 2.97 and 3.98 mg Se-yeast kg^-1 compared to the control group. The catalase, superoxide dismutase activities and total antioxidant status were significantly increased, and thiobarbituric reactive substances in liver homogenate were significantly decreased with increasing Se supplementation respect to the control fish in a dose-dependent manner. Furthermore, hematological and innate immune parameters (immunoglobulin, lysozyme, myeloperoxidase, ACH₅₀ and respiratory burst activity) were also significantly higher in fish fed the Se-yeast supplemented diets compared to the control group. The results demonstrated that the supplementation of 3.98 mg Se-yeast kg^-1 diet improves growth performance, antioxidant balance and innate immune status of meagre juveniles.