Molecular mechanisms of photoperiod regulation of bile acid metabolism in Taihe silky fowls based on the gut-liver axis.

Photoperiod, a pivotal environmental clue, orchestrates animal growth, reproduction, and metabolism through circadian rhythm regulation. However, the regulatory mechanisms of photoperiod on bile acid metabolism in poultry remain unclear. In this study, eighty 132-day-old Taihe silky fowls were allocated to either a control photoperiod group (CP, 13 h of light [L]: 11 h of dark [D]) or long photoperiod group (LP, 17L: 7D) for 240 days, and multi-omics approaches were applied to decipher the molecular mechanisms of bile acid metabolism regulation by photoperiod. Biochemical assays showed that LP treatment significantly increased serum total bile acids (TBA), hepatic triglycerides (TG), and hepatic TBA levels (P < 0.05). Targeted metabolomic analysis revealed significantly elevated serum levels of TCA, Tα-MCA, Tω-MCA, TCDCA, CDCA and TLCA-3S in LP group (P < 0.05). 16S rDNA sequencing indicated that LP group dramatically reduced gut microbial alpha diversity (Chao1, ACE, Shannon; P < 0.05) and altered microbiota composition, with enriched Fusobacteriota and depleted Actinobacteriota and Spirochaetota at the phylum level (P < 0.05), and significantly increased Fournierella, Megamonas, Bacteroides and decreased Ruminococcus, Parabacteroides at the genus level (P < 0.05). Transcriptome analysis identified 395 differentially expressed genes (DEGs) enriched in primary bile acid biosynthesis, ABC transporters, bile secretion, peroxisome, and cholesterol metabolism pathways. Notably, genes involved in bile acid synthesis genes (CYP7A1, CYP7B1), secretion gene (AQP9), and transport gene (ABCG5) showed significant upregulation under LP conditions (P < 0.05). In vitro validation confirmed TCA dose-dependently enhanced ABCG5 expression in hepatocytes (P < 0.05). Collectively, our findings demonstrate that photoperiod modulates bile acid metabolism through gut microbiota remodeling and hepatic gene reprogramming, offering novel targets for metabolic intervention in poultry.