Effects and mechanism of different levels of Fe₂O₃ nanoparticles on muscle development in juvenile yellow catfish (Pelteobagrus fulvidraco)

To investigate the effects of different levels of nano-iron oxide on the muscle development of young yellow catfish (Pelteobagrus fulvidraco), using Fe₂O₃ NPs as the Fe sources, the present study formulated three experimental diets with dietary Fe levels at 22.23 (control), 44.53 (low Fe₂O₃ NPs group), 61.85 mg Fe/kg diet (high Fe₂O₃ NPs group), respectively, and fed to P. fulvidraco for 10 weeks. Our aims were to investigate whether and how different levels of Fe₂O₃ NPs affected the muscle development of juvenile P. fulvidraco. Low dietary Fe₂O₃ NPs level significantly augmented muscle fiber diameter, stimulated protein deposition, decreased NEFA and MDA levels in muscle tissue, elevated GSH content, upregulated the mRNA expression of MRF family members and fsp1 and slc7a11 genes, downregulated the mRNA expression of mstn gene but inhibited both mRNA and protein expressions of inflammatory factor nf-κb1 gene. The high Fe₂O₃ NPs diets inhibited muscle fiber diameter, increased the contents of iron, NEFA and MDA, induced GSH depletion, stimulated the expression of ferroptosis related genes and inhibited the expression of fsp1 and slc7a11 genes, and increased mRNA and protein expression of inflammatory factor nf-κb1 gene. Moreover, we cloned the sequences of myog and slc7a11 promoters from yellow catfish, and predicted the potential binding sites for NF-κB1 transcription factor on these two promoters. The dual luciferase activity assay and EMSA indicated that the NF-κB1 transcription factor directly binds to the myog promoter (-6 bp/-16 bp) and slc7a11 promoter (-430 bp/-439 bp). Furthermore, NF-κB1 transcription factor plays a direct role in mediating the transcription and regulation of these promoters; Fe₂O₃ NPs incubation enhanced this binding. This study revealed the potential mechanism of the regulation of muscle development by Fe₂O₃ NPs, and provided good basis for dietary Fe₂O₃ NPs addition in the aquafeeds.