CircITGB5 regulates the proliferation and adipogenic differentiation of chicken intramuscular preadipocytes through the miR-181b-5p/CPT1A axis.

Non-coding RNA is known to play a crucial role in the generation and deposition of intramuscular fat (IMF) in vertebrates by regulating the expression of genes involved in the synthesis, degradation and transportation of IMF. With the introduction of the competing endogenous RNA (ceRNA) hypothesis, circular RNA (circRNA) and long non-coding RNA (lncRNA) have been identified as natural "sponges" for microRNA (miRNA), yet their precise mechanisms and biological functions in chicken IMF are still not fully understood. In earlier research, we observed a significant association between Carnitine O-palmitoyltransferase 1, liver isoform (CPT1A) and fatty acid metabolism in chicken breast muscle. In this study, we utilized bioinformatics and previous sequencing data to construct a ceRNA regulatory network linked to intramuscular adipogenesis and deposition in chickens. This investigation aimed to unravel the post-transcriptional regulatory mechanism of CPT1A. The results showed that, functionally, CPT1A inhibited the proliferation and differentiation of intramuscular preadipocytes and affected the fatty acid composition of intramuscular adipocytes, and serving as a direct target of miR-181b-5p. In terms of mechanism, through a combination of bioinformatics analysis, dual luciferase reporter assays, quantitative real-time PCR (qRT-PCR), and Western blotting (WB), it was confirmed the interaction of a novel circRNA named circITGB5 with miR-181b-5p. CircITGB5 increased the expression of CPT1A mRNA and protein through post-transcriptional regulation. Acting as a ceRNA, circITGB5 competed with miR-181b-5p for binding to CPT1A, thereby shielding CPT1A from miR-181b-5p-mediated degradation. Subsequent rescue experiments confirmed the above conclusions. In conclusion, circITGB5 regulates the expression of the downstream target gene CPT1A by adsorption of miR-181b-5p, thereby regulating the proliferation and adipogenic differentiation of intramuscular preadipocytes. This discovery may have implications for achieving balanced breeding strategies aimed at enhancing the quality of chicken.