Dietary Chlorogenic Acid Attenuates Hepatic Lipid Accumulation and Reprograms Lipid Metabolism in Heat-Stressed Laying Hens: Integrated Transcriptomic and Metabolomic Analyses

Heat stress leads to excessive hepatic lipid deposition and oxidative imbalance in laying hens, especially during peak laying period. Chlorogenic acid (CGA), a dietary polyphenol with antioxidant and lipid-modulating properties, may improve hepatic lipid homeostasis, yet its effects under heat-stress conditions remain unclear. In this study, 240 Hy-Line Brown laying hens at 36 weeks of age were randomly assigned to one of two treatments (120 hens per treatment, with six replicates of 20 hens each): a basal diet or a basal diet supplemented with 300 mg/kg CGA and subjected to heat-stress conditions for 8 weeks. CGA supplementation significantly reduced liver weight (25.3%), liver index (14.4%), hepatic triglyceride content (29.1%), and serum triglyceride level (61.7%) (p < 0.05). Histological assessment revealed lower steatosis and inflammation scores, alongside increased hepatic SOD activity (13.6%) and decreased MDA content (58.7%) (p < 0.05). RNA-seq analysis identified 420 differentially expressed genes that were significantly enriched in PPAR signaling and fatty acid β-oxidation pathways. CGA upregulated fatty acid oxidation-related genes (ACSL1, CPT1A, ACOX1, ACAA1) and downregulated lipogenic markers (FASN, ACACA). Serum metabolomics revealed coordinated changes in lipid and carbon metabolism. These results indicate that dietary CGA alleviates hepatic lipid accumulation and oxidative stress in heat-stressed peak-laying hens, potentially via PPARα-mediated enhancement of fatty acid oxidation and inhibition of de novo lipogenesis.