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High temperatures induce autophagy in skeletal muscle of Rainbow Trout

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By Milthon Lujan

Rainbow trout. Source: Hero
Rainbow trout. Source: Hero

Transcriptomic analysis revealed that 293 genes were upregulated in the high-temperature group, mainly associated with autophagosome assembly, amino acid transport, and glutamine metabolic process.

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Global warming has a significant impact on animal populations worldwide, primarily through chronic temperature increases and an increased incidence of heatwaves.

Rising atmospheric temperatures are reflected in higher temperatures in marine and freshwater habitats, home to a great diversity of living organisms. By the end of this century, it is predicted that the average ocean temperature will have increased between 1 and 4 °C, negatively affecting the physiology of aquatic organisms.

In this regard, ectothermic animals, such as teleosts, are increasingly exposed to high-temperature stress events due to global warming. The effects of thermal stress on skeletal muscle, a key tissue for fish growth, remain unknown.

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Recently, a group of researchers from the Universidad Andrés Bello, Universidad de Concepción, Pontificia Universidad Católica de Chile, and the Interdisciplinary Center for Aquaculture Research (INCAR) examined the impact of high-temperature stress on the transcriptome of Rainbow Trout (Oncorhynchus mykiss) skeletal muscle under control conditions (15 °C) and high-temperature conditions (20 °C). They demonstrated that increased stress induced significant increases in plasma cortisol and glucose levels.

“We investigated the effects of high-temperature stress on gene expression response in Rainbow Trout (O. mykiss) skeletal muscle,” the study reports.

Increase in cortisol and glucose levels

According to the study results, the stress protocol led to a significant increase in cortisol and glucose levels in plasma, reaching concentrations of approximately 110 ng/mL and 59 mg/dL, respectively.

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Transcriptomic analysis revealed that 293 genes were upregulated in the high-temperature group, mainly associated with autophagosome assembly, amino acid transport, and glutamine metabolic process. On the other hand, 119 genes were downregulated in the high-temperature group, primarily associated with digestion, proteolysis, and muscle contraction processes.

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Furthermore, RT-qPCR of differentially expressed representative genes and Western blot analysis of LC3-II/LC3-I levels confirmed autophagy of skeletal muscle induced by high temperature.

The study “High-Temperature Stress Induces Autophagy in Rainbow Trout Skeletal Muscle,” authored by Alfredo Molina, Phillip Dettleff, Valentina Valenzuela-Muñoz, Cristian Gallardo-Escárate, and Juan Antonio Valdés, sheds light on intriguing aspects of the adaptive response of Rainbow Trout skeletal muscle to high-temperature stress and provides important information about the physiology of autophagy in teleosts.

“Considering the absence of protein carbonylation and DNA oxidation in skeletal muscle and the absence of skeletal muscle atrophy markers in plasma, we propose that autophagy acts as a negative regulator of damage in this tissue, inducing the process of mitophagy and inhibiting cellular apoptosis,” the study authors concluded.

Conclusion

“In this study, we demonstrated that temperature stress induces autophagy in the skeletal muscle of O. mykiss. Considering the absence of protein carbonylation and DNA oxidation in skeletal muscle and the absence of skeletal muscle atrophy markers in plasma, we propose that autophagy acts as a negative regulator of damage in this tissue, inducing the process of mitophagy and inhibiting cellular apoptosis,” they concluded.

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The study was funded by the National Fund for Scientific and Technological Development (FONDECYT), the Funding Fund for Research Centers in Priority Areas (FONDAP) INCAR, and the Contest for Support to Centers of Excellence in Research FONDAP 2022.

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Reference (open access)
Molina, Alfredo, Phillip Dettleff, Valentina Valenzuela-Muñoz, Cristian Gallardo-Escarate, and Juan Antonio Valdés. 2023. “High-Temperature Stress Induces Autophagy in Rainbow Trout Skeletal Muscle” Fishes 8, no. 6: 303. https://doi.org/10.3390/fishes8060303

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