Fatty liver hemorrhagic syndrome (FLHS) in laying hens is a nutritional and metabolic disease involving liver enlargement, hepatic steatosis, and hepatic hemorrhage as the primary symptoms. The syndrome is prone to occur during the peak laying period of laying hens, which has resulted in significant economic losses in the laying hen breeding industry; however, the specific pathogenesis of FLHS remains unclear. Our group and previous studies have shown that bile acid levels are significantly decreased during the development of fatty liver and that targeted activation of bile acid–related signaling pathways is beneficial for preventing and treating fatty liver. In this study, we generated a FLHS laying hen model by feeding hens a high-energy, low-protein diet, with goose deoxycholic acid (CDCA) given as an intervention. HE staining, fluorescence quantitative PCR, and ELISA were used to evaluate the effects of CDCA on pathological changes and inflammatory responses in the liver. The results showed that hepatic hemorrhage in FLHS laying hens was reduced after CDCA treatment. Furthermore, fat vacuoles and transaminase levels decreased significantly. In addition, expression levels of M1-type macrophage markers and polarization products were significantly reduced, and the expression of pro-inflammatory regulatory factors related to the JAK-STAT signaling pathway, LPS-TLR4-Myd88–NF-kB signaling pathway, and NLRP3 inflammasomes decreased significantly as well. Expression levels of M2-type macrophage markers and polarization products increased significantly, as did the expression of anti-inflammatory regulators related to the JAK-STAT signaling pathway. These results suggest that CDCA ameliorates liver injury in laying hens with FLHS by inhibiting macrophage M1-type polarization and the resulting pro-inflammatory response, thereby promoting M2-type macrophage polarization and an anti-inflammatory response.

Background: Metabolic dysfunction-associated steatotic liver disease (MASLD) is now the most prevalent chronic liver disease worldwide, imposing a severe public health burden. Its core pathological hallmark is excessive hepatic lipid accumulation driven by systemic metabolic dysregulation. Concomitant hepatocellular injury impairs hepatic lactate clearance, leading to aberrant lactate buildup in the liver microenvironment. However, the causal role of lactate in exacerbating liver lipid metabolism dysfunction and driving the progression of MASLD remains unclear. Methods: First, we performed a comprehensive bioinformatic analysis of publicly available transcriptomic datasets. Mining of the Gene Expression Omnibus (GEO) database showed that lactate dehydrogenase (LDH) expression was significantly upregulated in liver tissues from both metabolic dysfunction-associated fatty liver disease (MASLD) patients and MASLD mouse models. Next, network pharmacology approaches were employed to predict putative molecular targets that could mediate lactate’s biological effects. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses indicated that these candidate targets were predominantly enriched in pathways governing fatty acid metabolism and long-chain fatty acid transport. Molecular docking and molecular dynamics simulations further suggested possible interactions and supported the prioritization of cluster of differentiation 36 (CD36) as candidate lipid metabolism regulators potentially involved in lactate-mediated effects. Finally, liver-specific Ldha knockdown mice (AAV8-TBG-shRNA) and free fatty acid-induced steatotic AML12 hepatocytes were used to investigate the functional relevance of these findings in vivo and in vitro. Results: Network pharmacology analyses preliminarily identified the PPAR signaling pathway as a candidate pathway potentially linking lactate to MASLD. Experimental results showed that exogenous lactate administration was associated with significantly increased lipid accumulation in steatotic AML12 hepatocytes and the livers of MASLD mice, manifested as elevated triglyceride levels and enhanced lipid droplet formation, accompanied by upregulated expression of PPARγ and CD36. Conversely, inhibiting endogenous lactate production or silencing PPARγ or CD36 attenuated this lipid-accumulation phenotype and significantly reduced intracellular triglyceride levels. Conclusions: In conclusion, these findings indicate that lactate exposure is associated with hepatic lipid accumulation and upregulation of the PPARγ/CD36 axis. Pharmacological inhibition or silencing of PPARγ or CD36 attenuates this phenotype, suggesting that this pathway may contribute to lactate-associated hepatic steatosis and potentially accelerate MASLD progression.