GR-mediated transcriptional regulation of m6A metabolic genes contributes to diet-induced fatty liver in hens

PXR Activation Relieves Deoxynivalenol-Induced Liver Oxidative Stress Via Malat1 LncRNA m6A Demethylation

Deoxynivalenol (DON) is a prevalent toxin causing severe liver damage through hepatocellular oxidative stress. However, the underlying mechanisms and effective therapeutic approaches remain unknown. Here, the unique role of the xenobiotic metabolism factor pregnane X receptor (PXR) in mediating DON-induced hepatocellular oxidative stress is investigated. Treatment with the PXR agonist 3-indole-propionic acid (IPA) alleviates DON-induced oxidative stress and liver injury both in vitro and in vivo. Mechanistically, it is discovered for the first time that PXR agonist IPA directly transactivates the m6A demethylase FTO expression, leading to site-specific demethylation and decreased abundance of YTHDC1-bound Malat1 lncRNA at single-nucleotide resolution. The diminished m6A modification of Malat1 lncRNA reduces its stability and augments antioxidant pathways governed by NRF2, consequently mitigating DON-induced liver injury. Furthermore, Malat1 knockout mice exhibit decreased DON-induced liver injury, emphasizing the role of Malat1 lncRNA in oxidative stress. Collectively, the findings establish that PXR-mediated m6A-dependent Malat1 lncRNA expression determines hepatocyte oxidative stress via m6A demethylase FTO, providing valuable insights into the potential mechanisms underlying DON-induced liver injury and offers potential therapeutic strategies for its treatment.

Reorganization of 3D genome architecture provides insights into pathogenesis of early fatty liver disease in laying hens

BACKGROUND

Fatty liver disease causes huge economic losses in the poultry industry due to its high occurrence and lethality rate. Three-dimensional (3D) chromatin architecture takes part in disease processing by regulating transcriptional reprogramming. The study is carried out to investigate the alterations of hepatic 3D genome and H3K27ac profiling in early fatty liver (FLS) and reveal their effect on hepatic transcriptional reprogramming in laying hens.

RESULTS

Results show that FLS model is constructed with obvious phenotypes including hepatic visible lipid deposition as well as higher total triglyceride and cholesterol in serum. A/B compartment switching, topologically associating domain (TAD) and chromatin loop changes are identified by high-throughput/resolution chromosome conformation capture (HiC) technology. Targeted genes of these alternations in hepatic 3D genome organization significantly enrich pathways related to lipid metabolism and hepatic damage. H3K27ac differential peaks and differential expression genes (DEGs) identified through RNA-seq analysis are also enriched in these pathways. Notably, certain DEGs are found to correspond with changes in 3D chromatin structure and H3K27ac binding in their promoters. DNA motif analysis reveals that candidate transcription factors are implicated in regulating transcriptional reprogramming. Furthermore, disturbed folate metabolism is observed, as evidenced by lower folate levels and altered enzyme expression.

CONCLUSION

Our findings establish a link between transcriptional reprogramming changes and 3D chromatin structure variations during early FLS formation, which provides candidate transcription factors and folate as targets for FLS prevention or treatment.

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.

Dietary bile acids improve breast muscle growth in chickens through FXR/IGF2 pathway

It is a common practice to provide fast-growing broilers with high-fat diets in the context of integrated farms in Northeast China. Therefore, fat digestion, absorption, and utilization efficiency are critical for broiler meat production. Bile acids (BA) promote fat digestion and absorption, but whether and how BA affects muscle growth in broilers remains unclear. In this study, 1-day-old broilers were fed diets containing varying levels of crude fat (low, medium, and high) with or without BA supplementation for 42 d. Chickens fed a high-fat diet supplemented with BA exhibited significantly (P < 0.05) higher body weight (BW) at 21 d and average daily gain (ADG) during the first 21 d compared to the other groups. Throughout the entire experiment, feed conversion rate (FCR) was significantly (P < 0.05) lower in the high-fat group without the addition of BA, which was further decreased (P < 0.05) with BA supplementation. The improved growth performance in the BA-supplemented high-fat group was associated with significantly (P < 0.05) higher lipase activity in the small intestine chyme, a decreased trend (P = 0.06) in abdominal fat ratio, and significantly (P < 0.05) higher breast muscle mass. Histological analysis revealed significant (P < 0.05) increases in myofiber diameter, cross-sectional area, and RNA and DNA concentrations in the breast muscle of BA-supplemented broilers on the high-fat diet. Additional histological analysis further revealed significant (P < 0.05) enhancements in myofiber diameter, cross-sectional area, and RNA and DNA concentrations within the breast muscles of broilers supplemented with BA and a high-fat diet. The increased insulin-like growth factor 2 (IGF2) in the breast muscle of broilers fed a BA-supplemented high-fat diet correlated with significantly (P < 0.05) increased farnesoid X factor (FXR) protein expression and binding to the IGF2 promoter. These results suggest that dietary BA supplementation improves FCR and breast muscle growth in broilers fed a high-fat diet, potentially through the FXR-mediated IGF2 pathway.

Stress-Related Gene Expression in Liver Tissues from Laying Hens Housed in Conventional Cage and Cage-Free Systems in the Tropics

Global egg production is mainly based on cage systems, which have been associated with negative effects on the welfare of birds. Stress factors in restrictive production systems can lead to changes in gene transcription and protein synthesis, ultimately impacting the quality of poultry products. The liver serves various metabolic functions, such as glycogen storage, and plays a crucial role in animals' adaptation to environmental changes. Consequently, both internal and external conditions can influence liver functions. The aim of this study was to evaluate the gene expression of AGP, CRP, NOX4, SOD1, CAT, GPX1, SREBF1, and FXR in the liver of laying hens under two different production systems. Liver tissues from Hy-Line Brown hens housed in conventional cage and cage-free egg production systems at 60 and 80 weeks of production were used. mRNA transcript levels were determined by qPCR using the relative quantification method and ACTB as the reference gene. AGP, SOD1, and SREBF1 gene expressions were significantly higher in the conventional cage group at the 60 weeks of production. Furthermore, the mRNA levels of transcripts related to oxidative stress and lipid metabolism were higher in the group of laying hens housed in conventional cages compared to those in cage-free systems. These results suggest differential gene expression of genes related to oxidative stress in liver tissues from hens housed in conventional cages compared to cage-free systems. The conditions of the egg production system can impact the gene expression of oxidative stress and lipid synthesis genes, potentially leading to changes in the metabolism and performance of hens, including egg quality.

Genomic Insights into Molecular Regulation Mechanisms of Intramuscular Fat Deposition in Chicken

Intramuscular fat (IMF) plays an important role in the tenderness, water-holding capacity, and flavor of chicken meat, which directly affect meat quality. In recent years, regulatory mechanisms underlying IMF deposition and the development of effective molecular markers have been hot topics in poultry genetic breeding. Therefore, this review focuses on the current understanding of regulatory mechanisms underlying IMF deposition in chickens, which were identified by multiple genomic approaches, including genome-wide association studies, whole transcriptome sequencing, proteome sequencing, single-cell RNA sequencing (scRNA-seq), high-throughput chromosome conformation capture (HiC), DNA methylation sequencing, and m6A methylation sequencing. This review comprehensively and systematically describes genetic and epigenetic factors associated with IMF deposition, which provides a fundamental resource for biomarkers of IMF deposition and provides promising applications for genetic improvement of meat quality in chicken.

Chronic Heat Stress Affects Bile Acid Profile and Gut Microbiota in Broilers

Heat stress (HS) can inhibit the growth performance of broilers and cause substantial economic losses. Alterations in bile acid (BA) pools have been reported to be correlated with chronic HS, yet the specific mechanism and whether it is related to gut microbiota remains unclear. In this study, 40 Rugao Yellow chickens were randomly selected and distributed into two groups (20 broilers in each group) when reaching 56-day age: a chronic heat stress group (HS, 36 ± 1 °C for 8 h per day in the first 7 days and 36 ± 1 °C for 24 h in the last 7 days) and a control group (CN, 24 ± 1 °C for 24 h within 14 days). Compared with the CN group, total BAs' serum content decreased, while cholic acid (CA), chenodeoxycholic acid (CDCA), and taurolithocholic acid (TLCA) increased significantly in HS broilers. Moreover, 12α-hydroxylase (CYP8B1) and bile salt export protein (BSEP) were upregulated in the liver, and the expression of fibroblast growth factor 19 (FGF19) decreased in the ileum of HS broilers. There were also significant changes in gut microbial composition, and the enrichment of Peptoniphilus was positively correlated with the increased serum level of TLCA. These results indicate that chronic HS disrupts the homeostasis of BA metabolism in broilers, which is associated with alterations in gut microbiota.

DNA 5mC and RNA m6A modification successively facilitates the initiation and perpetuation stages of HSC activation in liver fibrosis progression

Hepatic stellate cells (HSC) are key effector cells in liver fibrosis. Upon stimulation, the quiescent HSC undergoes complex morphological and functional changes to transdifferentiate into activated collagen-producing myofibroblasts. DNA/RNA methylations (5mC/m6A) are both implicated to participate in hepatic fibrosis, yet their respective roles and specific targets in HSC activation remain elusive. Here, we demonstrate that 5mC is indispensable for the initiation stage of HSC activation (myofibroblast transdifferentiation), whereas m6A is essential for the perpetuation stage of HSC activation (excessive ECM production). Mechanistically, DNA 5mC hypermethylation on the promoter of SOCS3 and PPARγ genes leads to STAT3-mediated metabolic reprogramming and lipid loss in the initiation stage. RNA m6A hypermethylation on the transcripts of major collagen genes enhances the mRNA stability in a YTHDF1-dependent manner, which contributes to massive ECM production. Vitamin A-coupled YTHDF1 siRNA alleviates CCl4-induced liver fibrosis in mice through HSC-specific inhibition of collagen production. HIF-1α, which is transactivated by STAT3, serves as a bridge linking the initiation and the perpetuation stages through transactivating YTHDF1. These findings indicate successive roles of DNA 5mC and RNA m6A modification in the progression of HSC activation, which provides new drug targets for epigenetic therapy of liver fibrosis.

Alleviation effect of conjugated linoleic acid on estradiol benzoate induced fatty liver hemorrhage syndrome in Hy-line male chickens

The purpose of this study was to explore whether conjugated linoleic acid (CLA) could alleviate fatty liver hemorrhagic syndrome (FLHS) induced by estradiol benzoate intramuscular injection in laying hens. One hundred male Hy-Line white chickens were randomly divided into two groups, namely, the control (CON) and estradiol benzoate (E) groups, and both groups were fed the same basal diet. After injections of estradiol benzoate at 2 mg/kg every two days for a total of 7 times, chickens in the E group showed FLHS symptoms, including liver enlargement, hemorrhage, and steatosis. Then half of the chickens in the E group received an additional diet containing 5000 mg/kg CLA for 8 weeks. The results of morphological observations, hematoxylin and eosin staining, and Oil Red O staining showed that CLA alleviated liver enlargement, hemorrhage, and lipid accumulation in FLHS chickens. In addition, we measured liver function and lipid metabolism indicators, including ALT, AST, TG, TCH, HDL-C, and LDL-C, which further suggested that CLA mitigated the disturbance of serum and liver metabolism in FLHS chickens. Mechanistically, CLA inhibited hepatic de novo lipogenesis, cholesterol synthesis, and TG accumulation and increased TG hydrolysis in FLHS chickens by regulating the gene expression of CD36, ACC, FAS, SCD 1, DGAT2, LIPE, ATGL, CPT1A, SREBP-1c, SREBP-2, PPARγ, and PPARα. Furthermore, CLA ameliorated hepatic oxidative stress and inhibited NF-κB signaling pathway-mediated inflammation in FLHS chickens. In conclusion, CLA regulated lipid metabolism, thus further alleviating oxidative stress and inflammation to alleviate FLHS induced by estrogen in chickens.

Glucocorticoid Regulates the Synthesis of Porcine Muscle Protein through m6A Modified Amino Acid Transporter SLC7A7

The occurrence of stress is unavoidable in the process of livestock production, and prolonged stress will cause the decrease of livestock productivity. The stress response is mainly regulated by the hypothalamic-pituitary-adrenal axis (HPA axis), which produces a large amount of stress hormones, namely glucocorticoids (GCs), and generates a severe impact on the energy metabolism of the animal body. It is reported that m⁶A modification plays an important role in the regulation of stress response and also participates in the process of muscle growth and development. In this study, we explored the effect of GCs on the protein synthesis procession of porcine skeletal muscle cells (PSCs). We prove that dexamethasone affects the expression of SLC7A7, a main amino acid transporter for protein synthesis by affecting the level of m⁶A modification in PSCs. In addition, we find that SLC7A7 affects the level of PSC protein synthesis by regulating the conduction of the mTOR signaling pathway, which indicates that the reduction of SLC7A7 expression may alleviate the level of protein synthesis under stress conditions.