Circular RNA circINSR regulates bovine intramuscular adipocyte development and lipid accumulation through insulin...

Intramuscular fat, deposited as marbling in beef, is a key economic indicator of meat quality in cattle production. A series of circular RNAs (circRNAs) have emerged as critical regulators of lipogenesis. In this study, we identified 373 differentially expressed circRNAs between calves and adult cattle, among which circINSR was markedly upregulated in adults. Single-nucleus RNA sequencing (snRNA-seq) analysis revealed the developmental trajectory of intramuscular adipocytes, demonstrating the differentiation of preadipocytes into both white and beige adipocytes. Along the preadipocyte-to-white adipocyte differentiation axis, 133 genes were significantly upregulated in white adipocytes, with notable enrichment in the INSR-mediated PI3K-Akt signaling pathway. Functional studies in vitro and in vivo confirmed that circINSR promotes adipocyte differentiation, facilitates fatty acid transport and synthesis, enhances triglyceride accumulation, and drives lipid droplet maturation through PI3K-Akt signaling. Mechanistically, circINSR functions as a competitive endogenous RNA (ceRNA) by sequestering miR-712-5p, thereby upregulating INSR expression and potentiating lipogenesis. The results delineates the cellular heterogeneity and differentiation program of intramuscular adipocytes in bovine longissimus dorsi muscle and establishes circINSR as a miR-712-5p sponge that orchestrates lipogenesis. The findings advance our understanding of the molecular mechanisms governing IMF deposition in high-quality beef cattle.