Circular RNA-mediated regulatory networks drive oxidative stress and metabolic dysregulation in broiler breast muscle under chronic heat stress.

Chronic heat stress (CHS) disrupts broiler breast muscle physiology homeostasis, yet the underlying molecular mechanisms remain unclear. In this study, 144 male Arbor Acres broilers (28 d old) were randomly allocated into 3 treatment groups: the normal control (NC) group (22 °C, ad libitum), the heat stress (HS) group (22 °C, ad libitum), the pair-fed (PF) group (22 °C, feed matched to HS). After two weeks of CHS, the HS group exhibited elevated ROS production, increased antioxidant enzyme activities (GSH-Px, CAT, SOD), and higher MDA and carbonyl levels, accompanied by pronounced ultrastructural damage in mitochondria and myofibrils. Metabolic analyses revealed enhanced glycolysis, suppressed lipolysis and oxidative phosphorylation, and reduced ATP and ADP levels, indicating impaired energy homeostasis. CircRNA sequencing identified 61 differentially expressed circRNAs independent of feed intake, which were associated with metabolic regulation, oxidative stress response, and cell growth and apoptosis. GO and KEGG enrichment analyses of parental and target genes implicated key pathways, including peroxisome, glycolysis/gluconeogenesis, HIF-1 signaling, and apoptosis. ceRNA network analysis revealed critical circRNA-miRNA-mRNA axes regulating ROS generation and metabolic adaptation under CHS, such as novel_circ_004536/gga-miR-10c-5p/CYP1C1 and novel_circ_003382/gga-miR-34a-5p/UQCRB. These findings highlight the regulatory role of circRNAs in CHS-induced oxidative stress and metabolic dysregulation in broiler breast muscle, providing potential molecular targets to mitigate heat-induced muscle damage and improve meat quality in poultry.