Expression Signatures of microRNAs and Their Targeted Pathways in the Adipose Tissue of Chickens during the Transition from Embryonic to Post-Hatch Development

Special Issue: Lipid Metabolism, Adipogenesis and Fat Tissue Metabolism: Gene Regulation

Lipid metabolism is pivotal in controlling energy homeostasis [...].

RNA-seq Based Transcriptome Analysis Reveals The Cross-Talk of Macrophage and Adipocyte of Chicken Subcutaneous Adipose Tissue during The Embryonic and Post-Hatch Period

With high fecundity and short production cycle, poultry is one of the important sources of meat. During the embryonic and post-hatch period, the higher death rate caused huge economic losses in poultry production. Our previous study showed that chick subcutaneous adipose tissue is an important energy supply tissue besides yolk. Therefore, the metabolic mechanism of subcutaneous adipose tissue in chicks could provide a new perspective of brooding. The objectives of the current study were to evaluate the differences between chick subcutaneous adipose tissue and abdominal adipose tissue before and after hatching and reveal the cross-talk of different cells within the chick subcutaneous adipose tissue. The results of RNA-seq and weighted gene co-expression network analysis (WGCNA) of chick subcutaneous and abdominal adipose tissues showed that the function of chick subcutaneous tissue was related to immunoreaction, and macrophage could be the major immune infiltration cell type in chicken subcutaneous adipose tissue, which were also verified by qPCR, HE stain, and IHC. The results of free fatty acids (FFAs)-induced the cross-talk between macrophages and adipocytes showed that FFAs-Ccl2 (chicken CCL26) axis could have an important role in lipid transportation in adipose tissue. The results of Oil Red O and Nile red stain demonstrated that macrophages have the ability to absorb FFAs quickly. Interestingly, according to the genomic organization of CCL family with representative vertebrate species, we found that chicken CCL26 could be the major chemokine in chicken adipocyte as the status of CCL2 in mammal adipocyte. In conclusion, we demonstrate that FFA-induced Ccl2 (chicken CCL26) secretion is crucial in determining fat depot-selective adipose tissue macrophage (ATM) infiltration, which could be an important medium of lipid transportation in chicken subcutaneous adipose tissue. These findings may have multiple important implications for understanding macrophage biology with chick subcutaneous adipose tissue and provide theoretical basis for lipid metabolism in poultry brooding.

Function of Chick Subcutaneous Adipose Tissue During the Embryonic and Posthatch Period

Since excess abdominal fat is one of the main problems in the broiler industry for the development of modern broiler and layer industry, the importance of subcutaneous adipose tissue has been neglected. However, chick subcutaneous adipose tissue appeared earlier than abdominal adipose tissue and more than abdominal adipose tissue. Despite a wealth of data, detailed information is lacking about the development and function of chick subcutaneous adipose tissue during the embryonic and posthatch period. Therefore, the objective of the current study was to determine the developmental changes of adipocyte differentiation, lipid synthesis, lipolysis, fatty acid β-oxidation, and lipid contents from E12 to D9.5. The results showed that subcutaneous adipose tissue was another important energy supply tissue during the posthatch period. In this stage, the mitochondrial copy number and fatty acid β-oxidation level significantly increased. It revealed that chick subcutaneous adipose tissue not only has the function of energy supply by lipidolysis but also performs the same function as brown adipose tissue to some extent, despite that the brown adipose tissue does not exist in birds. In addition, this finding improved the theory of energy supply in the embryonic and posthatch period and might provide theoretical basis on physiological characteristics of lipid metabolism in chicks.