Effects of crowding on the three main proteolytic mechanisms of skeletal muscle in rainbow trout (Oncorhynchus mykiss)

Abstract

Background: Skeletal muscle is one of the tissues most affected by stress conditions. The protein degradation in this tissue is vital for the supply of energy mediated by different proteolytic pathways such as the ubiquitinproteasome (UPS), autophagy-lysosome (ALS) and the calpain/calpastatin system (CCS). Nevertheless, the regulation of this proteolytic axis under stress conditions is not yet completely clear. Chile is the main producer of rainbow trout (Oncorhynchus mykiss) in the world. This intensive fish farming has resulted in growing problems as crowding and stress are one of the major problems in the freshwater stage. In this context, we evaluated the crowding effect in juvenile rainbow trout kept in high stocking density (30 kg/m 3) for 15, 45 and 60 days, using a control group of fish (10 kg/m 3). Results: Plasmatic cortisol and glucose were evaluated by enzyme immunoassay. The mRNA levels of stress-related genes (gr1, gr2, mr, hsp70, klf15 and redd1), markers of the UPS (atrogin1 and murf1) and CCS (capn1, capn1, cast-l and casts) were evaluated using qPCR. ALS (LC3-I/II and P62/SQSTM1) and growth markers (4E-BP1 and ERK) were measured by Western blot analysis. The cortisol levels increased concomitantly with weight loss at 45 days of crowding. The UPS alone was upregulated at 15 days of high stocking density, while ALS activation was observed at 60 days. However, the CCS was inactivated during the entire trial. Conclusion: All these data suggest that stress conditions, such as crowding, promote muscle degradation in a time-dependent manner through the upregulation of the UPS at early stages of chronic stress and activation of the ALS in long-term stress, while the CCS is strongly inhibited by stress conditions in the rainbow trout muscle farmed during freshwater stage. Our descriptive study will allow perform functional analysis to determine, in a more detailed way, the effect of stress on skeletal muscle physiology as well as in the animal welfare in rainbow trout. Moreover, it is the first step to elucidate the optimal crop density in the freshwater stage and improve the standards of Chilean aquaculture.

Differential Metabolic and Transcriptional Responses of Gilthead Seabream (Sparus aurata) Administered with Cortisol or Cortisol-BSA

“…However, after prolonged cortisol treatment, atrophy-related processes are mediated by genomic cortisol signaling. This agrees with the reported muscular proteolytic action of cortisol as well as with its negative influence on growth during chronic stress situations [ 49 , 50 ].…”

Gilthead Seabream Liver Integrative Proteomics and Metabolomics Analysis Reveals Regulation by Different Prosurvival Pathways in the Metabolic Adaptation to Stress

“…The upregulation of different aminoacyl-tRNA synthetases and several translation-related proteins ( Table S3 ) corroborated this hypothesis. Furthermore, previous studies have reported an upregulation of ER stress in seawater-transferred rainbow trout livers [ 36 ], common carp exposed to hydrogen peroxide [ 37 ], rainbow trout following overcrowding stress [ 38 ], and gilthead seabream exposed to low temperatures [ 39 ]. On the other hand, PDIP5 was found to be downregulated in hypoxia-exposed fish, exposing again the divergent responses of NET and HYP fish according to the challenge severity.…”

Effect of rearing density on nervous necrosis virus infection in Senegalese sole (Solea senegalensis)

“…Expression of gr1 gene could be down-or up-regulated in adults and juveniles of different species subjected to increasing stocking densities (Kim et al, 2013;Terova et al, 2005;Valenzuela et al, 2020), while up-regulation of pepck has been observed in river pufferfish (Takifugu obscurus) adults reared at high density (Kim et al, 2013).…”