Mechanism of Quercetin alleviated E. coli K88-induced Liver Injury in Broilers

The present study aimed to explore the mechanism by which quercetin alleviates E. coli K88-induced liver injury in broilers. A total of 240 one-day-old broilers were chosen and randomly divided into four groups: control, E. coli K88, aureomycin and quercetin groups with six replicates per group and 10 broilers per replicate. Broilers in control and E. coli K88 groups were fed a basal diet, broilers in aureomycin and quercetin groups were fed a basal diet supplemented with 75 mg/kg aureomycin and 750 mg/kg quercetin until 20 days of age, respectively. At the 21st day of age, broilers in E. coli K88, aureomycin and quercetin groups were treated by 2×10⁹ CFU chicken E. coli K88 gavage, while those in control group were treated by sterile saline (equal volume with E. coli K88) gavage, feeding continued for three weeks. The mechanism of quercetin in alleviating E. coli K88-induced liver injury was explored by 16S rDNA sequencing, non-targeted metabolomics and transcriptomics. The present result showed that compared with E. coli K88 group, 1) Dietary quercetin and aureomycin alleviated E. coli K88-induced liver injury to varying degrees in broilers, and quercetin worked better than aureomycin; aureomycin and quercetin significantly decreased content of GGT, ALB, ALP, TBIL, ALT and ALB/GLB (P < 0.05). 2) Quercetin significantly decreased the abundance of Proteobacteria, and significantly increased the abundance of Actinobacteria and Fusobacteriota at phylum level (P < 0.05). 3)The transcriptomic and metabolomic results showed that quercetin significantly increased expression of PISD and MBOAT1 (P < 0.05), and significantly decreased expression of GPAT4, GPAT3, PCYT2, SELENOI, PLPP5, ADPRM, LCAT, LYPLA2 and CDS2 (P < 0.05); quercetin significantly increased the relative mabundance of Glycerol 3-phosphate, Glycerophosphate(2), Phosphorylcholine, Glycerol-phosphocholine, Sn-glycerol-3-phosphoethanolamine(P < 0.05); aureomycin significantly increased the relative abundance of phenylacetaldehyde. The KEGG results showed that quercetin and aureomycin alleviated E. coli K88-induced liver injury in broilers by significantly regulating glycerophospholipid metabolic and phenylalanine metabolism, respectively (P < 0.05). In conclusion, dietary quercetin alleviated E. coli K88-induced liver injury by regulating flora and glycerophospholipid metabolism in liver of broilers.