Lactococcus G423 Improves Lipid Metabolism in Broilers Through the Gut Microbiota and AMPK Signaling Pathway

This study aimed to elucidate the role of Lactococcus G423 in regulating the AMPK (AMP-activated protein kinase) signaling pathway and gut microbiota, and to investigate the mechanisms underlying its potential to improve lipid metabolism in broilers. In this trial, 960 one-day-old Arbor Acres (AA) broilers were randomly assigned to one of three groups: a control group (CON), a low-dose Lactococcus G423 group (Lac-L), and a high-dose Lactococcus G423 group (Lac-H). Each group consisted of eight replicates, with 40 individuals per replicate. Compared with the CON group, the Lac-L and Lac-H groups showed no significant differences in ADFI (Average Daily Feed Intake), ADG (Average Daily Gain), FCR (Feed Conversion Ratio), breast muscle yield, leg muscle yield, or abdominal fat yield (p > 0.05). Compared with the control group, neither Lac-L nor Lac-H affected serum TG (Triglyceride) or LDL (Low-Density Lipoprotein) levels (p > 0.05). However, both Lac-L and Lac-H significantly decreased serum CHO (Cholesterol) and increased serum HDL (High-Density Lipoprotein) (p < 0.05). Regarding the AMPK signaling pathway, both the Lac-L and Lac-H groups significantly downregulated the hepatic mRNA expression of Acetyl-CoA carboxylase (ACC) (p < 0.05). The Lac-L groups significantly increased the mRNA expression of AMP-activated protein kinase (AMPK) and Sterol Regulatory Element-Binding Protein 1 (SREBP1) (p < 0.05), and the Lac-H groups significantly increased the mRNA expression of Apolipoprotein A1 (APOA1) and Protein kinase B (PKB) (p < 0.05) and significantly reduced the mRNA expression of Fatty acid-binding protein 1 (FABP1) (p < 0.05), compared to the CON group. Gut microbiota analysis indicated that both treatment groups exhibited significantly increased α-diversity indices (p < 0.05) and altered microbial composition at an order level comparable with that of the CON group. Specifically, the abundances of beneficial families such as Lachnospirales and Lactobacillales were elevated, while significant changes were observed in other taxa including Ruminococcaceae and Akkermansiaceae (p < 0.05). These changes corresponded with significant differences in the MDI and GMHI (p < 0.05). In conclusion, Lactococcus G423 may regulate lipid metabolism in broilers through the combined modulation of the AMPK signaling pathway and the gut microbiota. Specifically, Lactococcus G423 appears to regulate broiler lipid metabolism by modulating the gut microbiota–hepatic lipid metabolism axis.