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Rainbow trout (Oncorhynchus mykiss) is a cold-water fish widely cultivated in the world. Heat stress has a great impact on its growth and reproduction. At present, global warming and extreme high temperature in summer have seriously affected its growth and survival. To characterise their metabolic changes under heat stress, this study explored the metabolic physiological responses of rainbow trout gill target organs under high temperature exposure (20°C and 24°C) and subsequent return to initial temperature (14°C) based on UPLC-Q-TOF/MS metabolomics techniques. The results showed that compared to the control group, 128, 130 and 108 differentially significant metabolites were identified in the high temperature groups (20°C and 24°C) and the recovery group(14°C), respectively. Metabolites related to lipid metabolism such as linoleic acid and arachidonic acid, as well as metabolites related to cellular redox status such as reduced coenzyme II (NADPH), glutathione (GSH) and glutathione disulfide (GSSG) were significantly altered by high temperature exposure. Enrichment analysis showed that these metabolites were mainly involved in metabolic pathways such as glycerophospholipid metabolism, sphingolipid metabolism, linoleic acid metabolism, arachidonic acid metabolism, pentose phosphate pathway and glutathione metabolism in rainbow trout gills. Notably, none of the metabolic pathways, except sphingolipid metabolism, returned to normal after the temperature returned to initial. The above results suggested that heat stress led to disruption of lipid metabolism in rainbow trout gill target organs, which may lead to structural and functional damage to gill cell membranes, induced an inflammatory response in gill cells and generated an immune response. At the same time, rainbow trout gill cells regulated the GSH/GSSG ratio in glutathione metabolism through NADPH production by the pentose phosphate pathway to increase the antioxidant capacity of cells to counter oxidative stress and prevent apoptosis. The results of this study provided a scientific basis for understanding the physiological responses of rainbow trout under heat stress. [ABSTRACT FROM AUTHOR]

It is critical to investigate the adaptive development and the physiological mechanism of fish in external stimulation. In this study, the response of Barbus capito to salinity–alkalinity exposure was explored by high‐throughput nontargeted and liquid chromatography–mass spectrometry‐based metabolomics to investigate metabolic biomarker and pathway changes. Meanwhile, the biochemical indexes of Barbus capito were measured to discover the chronic impairment response to salinity–alkalinity exposures. A total of 29 tissue metabolites were determined to deciphering the endogenous metabolic changes of fishes during the different concentration salinity–alkalinity exposures environment, which were mainly involved in the key metabolism including the phenylalanine, tyrosine, and tryptophan biosynthesis, arachidonic acid metabolism, pyruvate metabolism, citrate cycle, and glycerophospholipid metabolism. Finally, we found the amino acid metabolism as key target was associated with the endogenous metabolites and metabolic pathways of Barbus capito to salinity–alkalinity exposures. In conclusion, metabolomics is a potentially powerful tool to reveal the mechanism information of fish in various exposure environments. [ABSTRACT FROM AUTHOR]

To determine dietary selenium (Se) status regulates the transcriptions of selenoproteome and activities of selenoenzymes in chicken kidney, 1-day-old chickens received low Se (0.028 mg Se per kg of diet) or super-nutritional Se (3.0 or 5.0 mg Se per kg of diet) in their diets for 8 weeks. It was observed that dietary low or super-nutritional Se did not make renal appearance pathological changes in chicken. Low Se significantly reduced total antioxidant capability (T-AOC), glutathione (GSH) content, but malondialdehyde (MDA) content in the kidney increased and decreased glutathione peroxidase (Gpx) and thioredoxin reductase (TrxR) activity with changes in their mRNA levels. Super-nutritional Se (3.0 mg/kg) increased T-AOC and GSH contents then made them reduce, but it reduced MDA content significantly, elevated then reduced Gpx activity, and decreased TrxR activity with changes in their mRNA levels. Dietary low Se downregulated the mRNA expressions of Gpx1-4, Txnrd3, Sepn1, Selw, Sepx1, Selh, and SEPSECS. At super-nutritional Se, most selenoproteins were upregulated in chicken kidney, but Sepp2 and Sep15 was only upregulated in Se excess (5.0 mg/kg) bird. These results indicated that dietary Se status stabilizes normal renal physiology function via regulation of the selenoprotemic transcriptions and selenoenzyme activities in avian. [ABSTRACT FROM AUTHOR]