Abstract
Muscle degradation occurs as a response to various physiological states that are regulated by specific molecular mechanisms. Previously, we characterized the metabolic changes of muscle deterioration of the female rainbow trout at full sexual maturity and spawning (Salem et al., Physiol. Genomics 2006;28:33–45; J. Proteomics 2010;73:778–789). Muscle deterioration in this model represents nutrient mobilization as a response to the energetic overdemands of the egg/ovarian growth phase. Our recent studies showed that most of the changes in muscle growth and quality start 2–3 months before spawning. Gravid fish exhibited reduced intramuscular fat that is lower in saturated and monounsaturated fatty acids and higher in polyunsaturated fatty acids compared to sterile fish. In this study, RNA-Seq was used to explain the mechanisms underlying changes during this phase of sexual maturity. Furthermore, to minimize changes due to nutrient deficits, fish were fed on a high-plane of nutrition. The RNA-Seq technique identified a gene expression signature that is consistent with metabolic changes of gravid fish. Gravid fish exhibited increased abundance of transcripts in metabolic pathways of fatty acid degradation and up-regulated expression of genes involved in biosynthesis of unsaturated fatty acids. In addition, increased expression of genes involved in the citric acid cycle and oxidative phosphorylation was observed for gravid fish. This muscle transcriptomic signature of fish fed on a high nutritional plane is quite distinct from that previously described for fish at terminal stages of maturity and suggest that female rainbow trout approaching spawning, on high nutritional planes, likely mobilize intramuscular fat rather than protein to support gonadal maturation.
Highlights
Skeletal muscle is the most abundant and edible tissue of fish and typically makes up more than 50% of the fish weight (Salem et al 2006a; Aussanasuwannakul et al 2011)
Using microarray-chip and proteomic technologies, we studied the problem of muscle quality deterioration in gravid female rainbow trout compared to sterile female fish (Salem et al 2006b, 2010a)
2–3 months prior to spawning, mobilized intramuscular fat rather than proteins to fuel gonadal maturation; whereas, protein, which is mobilized at terminal stages of sexual maturation when dietary nutrients are limiting and body stores of fat are low (Salem et al 2006a,b), was minimally changed
Summary
Skeletal muscle is the most abundant and edible tissue of fish and typically makes up more than 50% of the fish weight (Salem et al 2006a; Aussanasuwannakul et al 2011). Growth, and quality are complex and polygenic traits; regulated by synchronized expression of several genes that are organized in transcriptional networks (Gerrard 2003; Salem et al 2008). Microarray studies identified genes that control muscle development, growth and quality in model organisms including mice (Raffaello et al 2006), humans (Timmons and Sundberg 2006) cattle (Byrne et al 2005) and swine Physiological Reports published by Wiley Periodicals, Inc. on behalf of the American Physiological Society and The Physiological Society
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