Quantitative lipidomics reveals lipid perturbation in the liver of fatty liver hemorrhagic syndrome in laying hens

Development of fatty liver disease model using high cholesterol and low choline diet in white leghorn chickens

Nonalcoholic fatty liver disease (NAFLD), which shows similar symptoms as fatty liver hemorrhage syndrome (FLHS) in chickens, is the most common cause of chronic liver disease and cancer in humans. NAFLD patients and FLHS in chickens have demonstrated severe liver disorders when infected by emerging strains of human hepatitis E virus (HEV) and avian HEV, respectively. We sought to develop a fatty liver disease chicken model by altering the diet of 3-week-old white leghorn chickens. The high cholesterol, and low choline (HCLC) diet included 7.6% fat with additional 2% cholesterol and 800 mg/kg choline in comparison to 5.3% fat, and 1,300 mg/kg choline in the regular diet. Our diet induced fatty liver avian model successfully recapitulates the clinical features seen during NAFLD in humans and FLHS in chickens, including hyperlipidemia and hepatic steatosis, as indicated by significantly higher serum triglycerides, serum cholesterol, liver triglycerides, cholesterol, and fatty acids. By developing this chicken model, we expect to provide a platform to explore the role of lipids in the liver pathology linked with viral infections and contribute to the development of prophylactic interventions.

Quantitative lipidomics reveals the changes of lipids and antioxidant capacity in egg yolk from laying hens with fatty liver hemorrhagic syndrome

In laying hens, fatty liver hemorrhagic syndrome (FLHS) is a common metabolic disorder, which can affect egg production and nutritional value. However, the impact of FLHS on the lipid content in egg yolks was not clear. In this study, FLHS model was induced by using high-energy low-protein diet, and the egg quality was evaluated. Egg yolk lipids were quantitatively analyzed by using ultra-performance liquid chromatography-mass spectrometry combined with multivariate statistical analysis. Gene expressions of the lipoprotein were determined by qRT-PCR and antioxidant capacity of the egg yolk were determined by kits. The elevated blood lipids and extensive lipid droplets observed indicated successful establishment of the FLHS model in laying hens. Measurements of egg quality showed that egg yolk weight was increased in the FLHS group. Lipidomics revealed that 1,401 lipids, comprising 27 lipid subclasses in the egg yolk. According to score plots of principal component analysis and orthogonal partial least squares discriminant analysis, different lipid profile was observed between the control and FLHS groups. A total of 97 different lipid species were screen out. Sphingolipid and glycerophospholipid metabolism were identified as key pathways. Free polyunsaturated fatty acids (PUFA) exhibited an increase in the FLHS group (P < 0.05). Notably, the form of PUFAs was changed that the FLHS group showed an increase in triacylglycerol-docosahexenoic acid and triacylglycerol-arachidonic acid in the egg yolk, while triacylglycerol-α-linolenic acid was decreased (P < 0.05). Total superoxide dismutase was decreased in the egg yolks affected by FLHS. Gene expressions of vitellogenin 2 (VTG2), VTG3, very low-density apolipoprotein II and apolipoprotein B were increased in the liver of laying hens with FLHS (P < 0.05). In conclusion, FLHS promoted the lipid transport from the liver to the yolk by upregulating lipoprotein expression, which altered lipid profile, and reduced antioxidant capacity in the yolk. This study provided a foundation for understanding the changes in lipids, lipid transport and lipid antioxidation capacity in egg yolk from laying hens with FLHS.

Lactiplantibacillus plantarum FRT4 attenuates high-energy low-protein diet-induced fatty liver hemorrhage syndrome in laying hens through regulating gut-liver axis

BACKGROUND

Fatty liver hemorrhage syndrome (FLHS) becomes one of the most major factors resulting in the laying hen death for caged egg production. This study aimed to investigate the therapeutic effects of Lactiplantibacillus plantarum (Lp. plantarum) FRT4 on FLHS model in laying hen with a focus on liver lipid metabolism, and gut microbiota.

RESULTS

The FLHS model of laying hens was established by feeding a high-energy low-protein (HELP) diet, and the treatment groups were fed a HELP diet supplemented with differential proportions of Lp. plantarum FRT4. The results indicated that Lp. plantarum FRT4 increased laying rate, and reduced the liver lipid accumulation by regulating lipid metabolism (lipid synthesis and transport) and improving the gut microbiota composition. Moreover, Lp. plantarum FRT4 regulated the liver glycerophospholipid metabolism. Meanwhile, "gut-liver" axis analysis showed that there was a correlation between gut microbiota and lipid metabolites.

CONCLUSIONS

The results indicated that Lp. plantarum FRT4 improved the laying performance and alleviated FLHS in HELP diet-induced laying hens through regulating "gut-liver" axis. Our findings reveal that glycerophospholipid metabolism could be the underlying mechanism for the anti-FLHS effect of Lp. plantarum FRT4 and for future use of Lp. plantarum FRT4 as an excellent additive for the prevention and mitigation of FLHS in laying hens.

Osteocalcin activates lipophagy via the ADPN-AMPK/PPARα-mTOR signaling pathway in chicken embryonic hepatocyte

Fatty liver hemorrhage syndrome (FLHS) is the leading cause of noninfectious mortality in caged layers worldwide. Osteocalcin (OCN) is a protein secreted by osteoblasts, and its undercarboxylated form (ucOCN) acts as a multifunctional hormone that protects laying hens from FLHS. Lipophagy is a form of selective autophagy that breaks down lipid droplets (LDs) through lysosomes, and defective lipophagy is associated with FLHS. The aim of this study was to investigate the effects of ucOCN on the lipophagy of chicken embryonic hepatocytes and associated the function of the adiponectin (ADPN) signaling pathway. In this study, chicken embryonic hepatocytes were divided into 5 groups: control (CONT), fat emulsion (FE, 10% FE, v/v), FE with ucOCN at 1 ng/mL (FE-LOCN), 3 ng/mL (FE-MOCN), and 9 ng/mL (FE-HOCN). In addition, 4 μM AdipoRon, an adiponectin receptor agonist, was used to investigate the function of ADPN. The results showed that compared with CONT group, FE promoted the levels of phosphorylation of mammalian target of rapamycin (p-mTOR) (P < 0.05) and decreased the mRNA expression of ADNP receptors (AdipoR1 and AdipoR2). Compared with FE group, 3 and 9 ng/mL ucOCN inhibited the levels of autophagy adaptor p62 and p-mTOR (P < 0.05), increased the ratios of LC3-II/LC3-I (P < 0.05) and phosphorylated adenosine 5'-monophosphate-activated protein kinase (p-AMPK)/AMPK (P < 0.05), as well as the levels of peroxisome proliferator-activated receptor α (PPAR-α) and ADPN (P < 0.05). In addition, ucOCN at the tested concentrations increased the colocalization of LC3 and LDs in fatty hepatocytes. Administrated 4 μM AdipoRon activated AdipoR1 and AidpoR2 mRNA expression (P < 0.05), decreased the concentrations of triglyceride (P < 0.05), without effects on cell viability (P > 0.05). AdipoRon also increased the LC3-II/LC3-I ratio (P < 0.05) and the levels of p-AMPK/AMPK and PPAR-α (P < 0.05). In conclusion, the results reveal that ucOCN regulates lipid metabolism by activating lipophagy via the ADPN-AMPK/PPARα-mTOR signaling pathway in chicken embryonic hepatocytes. The results may provide new insights for controlling FLHS in laying hens.

MiRNA-21-5p induces chicken hepatic lipogenesis by targeting NFIB and KLF3 to suppress the PI3K/AKT signaling pathway

The liver plays a critical role in metabolic activity and is the body's first immune barrier, and maintaining liver health is particularly important for poultry production. MicroRNAs (miRNAs) are involved in a wide range of biological activities due to their capacity as posttranscriptional regulatory elements. A growing body of research indicates that miR-21-5p plays a vital role as a modulator of liver metabolism in various species. However, the effect of miR-21-5p on the chicken liver is unclear. In the current study, we discovered that the fatty liver had high levels of miR-21-5p. Then the qPCR, Western blot, flow cytometry, enzyme-linked immunosorbent assay, dual-luciferase, and immunofluorescence assays were, respectively, used to determine the impact of miR-21-5p in the chicken liver, and it turned out that miR-21-5p enhanced lipogenesis, oxidative stress, and inflammatory responses, which ultimately induced hepatocyte apoptosis. Mechanically, we verified that miR-21-5p can directly target nuclear factor I B (NFIB) and kruppel-like factor 3 (KLF3). Furthermore, our experiments revealed that the suppression of NFIB promoted apoptosis and inflammation, and the KLF3 inhibitor accelerated lipogenesis and enhanced oxidative stress. Furthermore, the cotransfection results suggest that the PI3K/AKT pathway is also involved in the process of miRNA-21-5p-mediate liver metabolism regulation. In summary, our study demonstrated that miRNA-21-5p plays a role in hepatocyte lipogenesis, oxidative stress, inflammation, and apoptosis, via targeting NFIB and KLF3 to suppress the PI3K/AKT signal pathway in chicken.

Osteocalcin and Its Potential Functions for Preventing Fatty Liver Hemorrhagic Syndrome in Poultry

Osteocalcin (OCN) is synthesized and secreted by differentiating osteoblasts. In addition to its role in bone, OCN acts as a hormone in the pancreas, liver, muscle, fat, and other organs to regulate multiple pathophysiological processes including glucose homeostasis and adipic acid metabolism. Fat metabolic disorder, such as excessive fat buildup, is related to non-alcoholic fatty liver disease (NAFLD) in humans. Similarly, fatty liver hemorrhage syndrome (FLHS) is a metabolic disease in laying hens, resulting from lipid accumulation in hepatocytes. FLHS affects hen health with significant impact on poultry egg production. Many studies have proposed that OCN has protective function in mammalian NAFLD, but its function in chicken FLHS and related mechanism have not been completely clarified. Recently, we have revealed that OCN prevents laying hens from FLHS through regulating the JNK pathway, and some pathways related to the disease progression have been identified through both in vivo and vitro investigations. In this view, we discussed the current findings for predicting the strategy for using OCN to prevent or reduce FLHS impact on poultry production.

Protective effects of genistein on the production performance and lipid metabolism disorders in laying hens with fatty liver hemorrhagic syndrome by activation of the GPER-AMPK signaling pathways

The aim of this study was to evaluate the beneficial effects and potential mechanisms of genistein (GEN) on production performance impairments and lipid metabolism disorders in laying hens fed a high-energy and low-protein (HELP) diet. A total of 120 Hy-line Brown laying hens were fed with the standard diet and HELP diet supplemented with 0, 50, 100, and 200 mg/kg GEN for 80 d. The results showed that the declines in laying rate (P < 0.01), average egg weight (P < 0.01), and egg yield (P < 0.01), and the increase of the ratio of feed to egg (P < 0.01) induced by HELP diet were markedly improved by 100 and 200 mg/kg of GEN treatment in laying hens (P < 0.05). Moreover, the hepatic steatosis and increases of lipid contents (P < 0.01) in serum and liver caused by HELP diet were significantly alleviated by treatment with 100 and 200 mg/kg of GEN in laying hens (P < 0.05). The liver index and abdominal fat index of laying hens in the HELP group were higher than subjects in the control group (P < 0.01), which were evidently attenuated by dietary 50 to 200 mg/kg of GEN supplementation (P < 0.05). Dietary 100 and 200 mg/kg of GEN supplementation significantly reduced the upregulations of genes related to fatty acid transport and synthesis (P < 0.01) but enhanced the downregulations of genes associated with fatty acid oxidation (P < 0.01) caused by HELP in the liver of laying hens (P < 0.05). Importantly, 100 and 200 mg/kg of GEN supplementation markedly increased G protein-coupled estrogen receptor (GPER) mRNA and protein expression levels and activated the AMP-activated protein kinase (AMPK) signaling pathway in the liver of laying hens fed a HELP diet (P < 0.05). These data indicated that the protective effects of GEN against the decline of production performance and lipid metabolism disorders caused by HELP diet in laying hens may be related to the activation of the GPER-AMPK signaling pathways. These data not only provide compelling evidence for the protective effect of GEN against fatty liver hemorrhagic syndrome in laying hens but also provide the theoretical basis for GEN as an additive to alleviate metabolic disorders in poultry.