Long-term effect of parental selenium supplementation on the one-carbon metabolism in rainbow trout (Oncorhynchus mykiss) fry exposed to hypoxic stress

Effect of organic selenium on performance and gill transcriptome of whiteleg shrimp Penaeus vannamei

BACKGROUND

Shrimp gill health is an indicator of their overall health and environmental stress, as gills are in direct contact with the external environment. Organic selenium (OS), known for its high bioavailability and antioxidant properties, potentially enhances shrimp growth, survival, and immune responses. This study investigated the physiological features through comprehensive gill gene expression profiling and growth parameters by incorporating OS into Penaeus vannamei diets.

METHODS AND RESULTS

Two OS-containing products, AlkoSel (AS) and SelPlex (SL), were supplied to the diet of P. vannamei (0.90 ± 0.05 g body weight, 4.54 ± 0.5 cm length) at a dose of 0.4 mg Se kg- 1 ration in the final feed. Three groups were organized: an AS-fed group, an SL-fed group, and a control (C) group without additives. After a one-month feeding trial, performance indices (PI) were assessed and RNA-Seq analysis was conducted. The PI revealed that both OS products had similar growth-stimulating effects, with no significant differences between the two groups. However, both groups showed significant improvement compared to the C-group. The P. vannamei gill transcriptome was strongly impacted by the two OS products, with several KEGG pathways implicated in their metabolic mechanisms. Pathways related to energy metabolism, carbohydrate metabolism, lipid metabolism, non-specific immunity, and antioxidative responses were significant in regulating the addition of AS and SL to P. vannamei diets.

CONCLUSIONS

While SL had some higher additive effects on the gene expression profile than AS, OS from either product is an essential micronutrient that promotes growth, normal metabolic activities, and good gill health in P. vannamei during the early feeding period.

Effects of dietary and/or parental supplementation with selenium and mercury on their localisation in rainbow trout fry tissues (Oncorhynchus mykiss) by quantitative LA-ICP MS imaging

The increasing use of alternative feeds for sustainable aquaculture leads to a reduced selenium content requiring the use of supplements to maintain the antioxidant status of farmed fish. The introduction of tuna by-products in fish feed is attractive for their selenium content, but the presence of mercury limits their use as it may negatively impact fish health. Indeed, selenium and mercury metabolism, in relation to their interaction and biological effects in fish, is far from being fully understood. This study aims to assess the impact of parental and dietary supplementation with selenomethionine and methylmercury on selenium and mercury localisation and concentrations in tissues of 3-week rainbow trout fry. Six diets were used. Broodstock were fed a plant-based diet Bpc (with 0.2 μg g-1 selenium and 0 μg g-1 mercury) or a tuna by-product-based diet Bt (with 4 μg g-1 selenium and basal mercury at 0.2 μg g-1) during 6 months, supplemented or not with 4 μg g-1 of selenomethionine for the plant-based diet Bpo and/or with 2 μg g-1 of methylmercury for diets Bph, Bpho and Bth. Their offspring were fed the plant-based diet Fpc, supplemented or not with the same levels of selenomethionine and methylmercury, until their third week. Mercury and selenium concentrations were determined in fry whole-body by ICP MS and quantitative images of selenium and mercury were produced by LA-ICP MS from fry whole-body thin sections. Dietary supplementation of fry with selenium and/or mercury increased their concentration in all tissues, especially in liver, kidney, muscle and intestine. Parental selenomethionine supplementation had a more pronounced effect on fry selenium levels than tuna by-products diet. Mercury transfer from broodstock to their offspring was weak. Mercury concentrations decreased in the kidney of fry supplemented with both selenium and mercury, which could be related to the presence of selenium.

Are the Main Methionine Sources Equivalent? A Focus on DL-Methionine and DL-Methionine Hydroxy Analog Reveals Differences on Rainbow Trout Hepatic Cell Lines Functions

The replacement of fishmeal by plant proteins in aquafeeds imposes the use of synthetic methionine (MET) sources to balance the amino acid composition of alternative diets and so to meet the metabolic needs of fish of agronomic interest such as rainbow trout (RT-Oncorhynchus mykiss). Nonetheless, debates still exist to determine if one MET source is more efficiently used than another by fish. To address this question, the use of fish cell lines appeared a convenient strategy, since it allowed to perfectly control cell growing conditions notably by fully depleting MET from the media and studying which MET source is capable to restore cell growth/proliferation and metabolism when supplemented back. Thus, results of cell proliferation assays, Western blots, RT-qPCR and liquid chromatography analyses from two RT liver-derived cell lines revealed a better absorption and metabolization of DL-MET than DL-Methionine Hydroxy Analog (MHA) with the activation of the mechanistic Target Of Rapamycin (mTOR) pathway for DL-MET and the activation of integrated stress response (ISR) pathway for MHA. Altogether, the results clearly allow to conclude that both synthetic MET sources are not biologically equivalent, suggesting similar in vivo effects in RT liver and, therefore, questioning the MHA efficiencies in other RT tissues.