Feeding faba beans to grass carp could crisp its muscle texture to avoid softening, the relationship between texture formation throughout the crisping process and the critical lipids regulating the fish quality has not yet been clarified. Herein, an 60-day nutritional trial and untargeted lipidomic analysis was used to study the changes of lipids in crisp grass carp dorsal muscle. A total of 1036 lipids were remarkably different between ordinary and crisp grass carp. The concentrations of the LPC, LPE, PG, Cer, Hex2Cer, SM, MG and MGMG were positively correlated with hardness and springiness, and the CL, TG, PMe, WE, dMePE and AcCa were negative correlation. High content of lipids involved in storage in ordinary grass carp, such as glycerophospholipids, polyunsaturated and saturated fatty acid content. In contrast, high content of membrane components in crisp grass carp, such as monounsaturated fatty acid, sphingolipid and glycerolipids content, and the distribution of PUFA in lipid molecules was related to lipid biosynthesis. This study might provide some insights into improved knowledge of the association between meat texture and lipid molecules in fish fed with faba bean.

While tissue amino acid compositions reflect that of the dietary protein source, and the liver orchestrates amino acid metabolism. In this study, we investigated the muscle amino acid profiles in ordinary and crisp grass carp. The 22 amino acids were measured, and seventeen showed significant concentration differences. To understand the molecular mechanisms behind changes, we analyzed the liver transcriptome, and the 2519 differentially expressed genes (DEGs) were identified, with 1156 up-regulated and 1363 down-regulated genes. DEGs were enriched in ribosome-related biological processes. KEGG pathway analysis showed enrichment in tryptophan metabolism, lysine degradation, valine, leucine and isoleucine degradation, galactose metabolism, and glutathione metabolism with up-regulated genes, arginine and proline metabolism, arginine biosynthesis and alanine, aspartate, amino sugar and nucleotide sugar metabolism, N-Glycan biosynthesis and glutamate metabolism with down-regulated genes. A protein-protein interaction network with 260 nodes and 249 edges was constructed, and 3 modules were extracted. The top 10 hub genes with close connections to other nodes were ITM1, STT3B, SEL1L, UGGT1, MLEC, IL1B, ALG5, KRTCAP2, NFKB2, and IRAK3. In summary, this study identified candidate genes and focused on amino acid and glycan metabolism pathways, providing a reference for further investigation into liver amino acid metabolism in grass carp fed with broad beans.

The meat of grass carp (Ctenopharyngodon idellus) fed broad beans is crispy, called crisp grass carp. In order to better understand the changes mechanistic in liver tissue of crisp grass carp, gene expression profiles and pathways of liver tissues were performed by using RNA-seq. As a result of the transcriptome analysis, the total number of reads produced for each liver sample ranged from 35,914,404 to 42,460,834. A total of 2519 differentially expressed genes (DEGs) were identified. Among them, 1156 genes were up-regulated and 1363 genes were down-regulated. Gene Ontology (GO) annotations indicated that DEGs were mainly enriched in biological processes of ribosome and structural constituent of ribosome. Kyoto encyclopedia of genes and genomes (KEGG) pathway analysis revealed that DEGs were mainly enriched in metabolism of energy, amino acid, carbohydrate, and lipid acid, and the genes in these pathways were up-regulated. The protein-protein interaction (PPI) network with 260 nodes and 249 edges was constructed and 3 modules were extracted from the entire network. ITML, STT3B, SEL1L, UGGT1, MLEC, IL1B, ALG5, KRTCAP2, NFKB2, IRAK3 genes were the top 10 hub genes with the closest connections to other nodes. In summary, this study identified several candidate genes and focused on glycan biosynthesis and metabolism pathways, providing a reference for further investigation into the mechanism of liver metabolism in grass carp fed with broad beans.