Abstract

When confined in pairs, juvenile rainbow trout (Oncorhynchus mykiss) form dominance hierarchies in which subordinate fish exhibit characteristic physiological changes including reduced growth rates and chronically elevated plasma cortisol concentrations. We hypothesized that alterations in protein metabolism contribute to the reduced growth rate of socially stressed trout, and predicted that subordinate trout would exhibit reduced rates of protein synthesis coupled with increases in protein degradation. Protein metabolism was assessed in dominant and subordinate fish after 4 days of social interaction, and in fish that were separated after 4 days of interaction for a 4 days recovery period, to determine whether effects on protein metabolism recovered when social stress was alleviated. Protein metabolism was assessed in liver and white muscle by measuring the fractional rate of protein synthesis and markers of protein degradation. In the white muscle of subordinate fish, protein synthesis was inhibited and activities of the ubiquitin-proteasome pathway (UPP) and the autophagy lysosomal system (ALS) were elevated. By contrast, the liver of subordinate fish exhibited increased rates of protein synthesis and activation of the ALS. When allowed to recover from chronic social stress for 4 days, differences in protein metabolism observed in white muscle of subordinate fish during the interaction period disappeared. In liver, protein synthesis returned to baseline levels during recovery from social stress, but markers of protein degradation did not. Collectively, these data support the hypothesis that inhibition of muscle protein synthesis coupled with increases in muscle protein breakdown contribute to the reduced growth rates of subordinate rainbow trout.

Highlights

  • In fishes as in mammals, growth suppression is a widely observed feature of chronic stress (Sadoul and Vijayan 2016)

  • The flooding dose technique is based on four assumptions (24) that must be met for this method of measuring the fractional rate of protein synthesis to be valid: (1) the isotope enrichment must be detectable within a short period of time; (2) the free-pool enrichment must remain stable over time; (3) the protein-pool enrichment must increase in a linear fashion over time; and (4) the isotope tracer used must not alter overall protein metabolism (Fraser and Rogers 2007; Garlick et al 1980; Lamarre et al 2015)

  • A similar but stronger recovery was apparent after 4 days of separation in the present study, because plasma cortisol levels, growth rates, and feeding scores for recovering subordinates did not differ statistically from those of recovering dominant or sham-treated fish

Read more

Summary

Introduction

In fishes as in mammals, growth suppression is a widely observed feature of chronic stress (Sadoul and Vijayan 2016). Growth in fishes is determined by a variety of factors, including food intake, nutrient assimilation, and energy allocation to maintenance versus structural growth, all of which may be impacted by chronic stress (Sadoul and Vijayan 2016) Both appetite suppression and exclusion from food resources by dominant individuals reduce food intake in subordinate fish (DiBattista et al 2006; Adams et al 1998; Metcalfe et al 1989). Indices of protein degradation, such as plasma amino acid or ammonia concentrations (Haller and Wittenberger 1988; Vijayan et al 1997; DiBattista et al 2006), or molecular markers of proteolysis (Valenzuela et al 2018), have been measured in some studies of chronic stress, but data are sparse. To our knowledge, the impact of chronic social stress on rates of protein synthesis has not yet been assessed

Objectives
Methods
Results
Conclusion
Full Text
Published version (Free)

Talk to us

Join us for a 30 min session where you can share your feedback and ask us any queries you have

Schedule a call