Search

This article aims to study the effect of rapeseed meal and cottonseed meal on the muscle quality and the expression of genes related to muscle fiber development after replacing part of the fish meal in the diets of yellow catfish (Pelteobagrus fulvidraco). Five groups of equal nitrogen and equal energy diets were designed in the experiment. The group containing 25% fish meal was used as the control diet (FM), and rapeseed meal and cotton meal were mixed 3: 2 to replace 10%, 20%, 30% and 40% fish meal, and then set up four test groups as RM10, RM20, RM30 and RM40, respectively. The juvenile yellow catfish with an initial body weight of (2.38±0.02) g were fed with the above five diets for 8 weeks. The experiment showed that, compared with the fishmeal group, as the replacement level exceeded 10%, the crude protein and crude fat in the muscle of yellow catfish decreased significantly when the replacement level increased, but there was no significant difference in moisture and ash. In addition, the content of hydroxyproline in muscle also showed a downward trend. Among the muscle fibers of yellow catfish, the number with a diameter of ≥50 µm decreased when the replacement level reached 10%, while the number of fibers with a diameter of ≤20 µm showed an upward trend. At the same time, the replacement of plant protein sources will also have a certain impact on the muscle texture of yellow catfish. In addition, the mRNA levels of muscle fiber development-related genes myod, myog, and mrf4 gradually increased as the replacement level reached 10%, while the gene expression of myf5 and mstn did not show significance between the groups. The expression of TOR and S6K1 decreased as the replacement level increased, and the expression of 4E-BP1 increased as the replacement level increased. Therefore, this study show that use of the rapeseed meal and cottonseed meal to replace more than 10% of the fish meal in the diet of yellow catfish juveniles will damage the muscle growth and muscle quality. [ABSTRACT FROM AUTHOR]

Nowadays, fatty liver and visceral excessive lipid accumulation are common in cultured fish, which reduces survival rate, growth performance and disease resistance. Yellow catfish Pelteobagrus fulvidraco is widely distributed in rivers, lakes and other fresh waters in China, and cultured in China and several Asian countries. The fish has relatively high economic value because of delicious taste and abundant nutrition. However, due to intensive culture and improper feeding, excessive fat accumulation in abdominal cavity and liver commonly occurs, which seriously affects the taste and health of yellow catfish. Therefore, the research on fat metabolism of yellow catfish has always been the focus. Lysosomal acid lipase (LAL), encoded by LIPA, hydrolyzes cholesterylesters (CEs) and triglycerides (TGs) to cholesterol and free fatty acids (FFAs), which are then used for metabolic purposes in the cells. The studies have been conducted to explore lal structure in mammals, but were scarce in fish. For this reason, it is important to study the molecular characteristics of lal in the regulation of lipid metabolism of yellow catfish. In this study, we analyzed molecular structure, tissue expression, promoter structure and function, and transcriptional regulation of lal. The lal gene was amplified from yellow catfish by RT-PCR and RACE approaches. The cDNAs of lal was 1802 bp, encoding a peptide of 398 amino acid residues, and 5' upstream promoter was 2052 bp in length. The molecular weight of the theoretical protein was 45.42 kDa, the isoelectric point was 7.70, and it had a signal peptide with 23 residues, five glycosylation sites, three cysteines, a catalytic ternary and a "cap" domain and a "lid" region. The amino acid alignment and phylogenetic analysis revealed that lal of P. fulvidraco was closely related to that of Ictalurus punctatus. The lal mRNA was expressed in all tested tissues (heart, liver, brain, spleen, kidney, muscle, fat, intestine, testis and ovary), with the highest expression levels in spleen, intestine and testis. Promoter sequence analysis revealed several transcription factor binding sites in lal promoter, such as Sp1, STAT3, PPARα, FOXO1, PPARγ, and HNF4α. Studies on promoter activity showed that -1507/-1016 region negatively regulated promoter activity, while -1016/+51 region positively regulated promoter activity. The present study indicated that lal mRNA was expressed in multiple high metabolism tissues. The transcription of lal was regulated by multiple transcription factors. This study help us to understand the structure and function of lal, and lay a foundation for further research on the regulatory mechanism of lipid metabolism in fish. [ABSTRACT FROM AUTHOR]