# Comparative Analysis of Muscle Metabolome and Amino Acid Profiles in All-Female Rainbow Trout (Oncorhynchus mykiss) from Different Germplasm Sources

## TL;DR

This study compares muscle metabolites and amino acids in all-female rainbow trout from China, Spain, and Denmark to assess nutritional differences and support breeding efforts.

## Contribution

The study identifies key amino acids and metabolic pathways that differ between rainbow trout strains, offering insights for improving fish nutritional quality through breeding.

## Key findings

- 228 differential metabolites were identified, mainly organic acids, benzene derivatives, and amino acids.
- The phenylalanine, tyrosine, and tryptophan biosynthesis pathway was most significantly affected.
- L-tyrosine, tryptamine, and L-phenylalanine were key metabolites influencing muscle composition differences.

## Abstract

This metabolomics study compared muscle composition in three all-female rainbow trout strains: Chinese “All-Female No. 1,” and Spanish and Danish strains. Analysis of 2198 metabolites identified 228 differential compounds, primarily organic acids, benzene derivatives, and amino acids. Enrichment revealed the phenylalanine, tyrosine, and tryptophan biosynthesis pathway as most significantly affected. Targeted quantification identified 11 key differential amino acids, with L-tyrosine, tryptamine, and L-phenylalanine being crucial for this pathway. The research provides essential data for evaluating nutritional value and supports future breeding for muscle quality in rainbow trout.

Rainbow trout (Oncorhynchus mykiss) is an economically important fish species, in which the muscle nutritional composition of market-size fish can vary significantly due to differences in genetic background and breeding environments. This study employed a metabolomics approach to conduct an in-depth comparative analysis of muscle samples from our independently bred new variety “All-Female No. 1”, as well as Spanish and Danish all-female strains. A total of 2198 metabolites were identified. Following screening with PCA and PLS-DA, 228 differential metabolites were obtained. These were most abundantly enriched in the categories of organic acids and derivatives, benzene and substituted derivatives, and amino acids and metabolites. KEGG pathway enrichment analysis revealed that the differential metabolites had the most significant impact on the phenylalanine, tyrosine, and tryptophan biosynthesis pathway. Further targeted quantification of amino acid metabolites identified 11 differentially expressed amino acids, which also exerted the strongest influence on this key pathway. Consequently, L-tyrosine, tryptamine, and L-phenylalanine were determined to be the key metabolites affecting the phenylalanine, tyrosine, and tryptophan biosynthesis pathway in the muscle of rainbow trout from different germplasms. This study provides a comprehensive evaluation of the nutritional value, particularly regarding amino acid profiles, of rainbow trout from different genetic sources, offering critical data and a scientific basis for subsequent related research.