Stress-Induced Immunosuppression Inhibits Regional Immune Responses in Chicken Adipose Tissue Partially through Suppressing T Cells by Up-Regulating Steroid Metabolism

Simple Summary Adipose tissue (AT) plays an important role in maintaining lipid homeostasis and regulating immune function in mammals. However, the regulatory functions and mechanisms of avian AT in immune response have not been reported. In this study, we found that chicken AT actively responded to stress-induced immunosuppression (SIIS), and adipose triglyceride lipase (ATGL), carnitine palmitoyltransferase 1A (CPT1A), and 3-hydroxy-3-methylglutaryl-CoA reductase (HMGCR) all constitute the key genes involved in the processes of SIIS inhibiting the immune response to the Newcastle disease virus vaccine. Moreover, SIIS significantly inhibited the different phases of the primary and secondary immune response in AT through the upregulation of steroid anabolism. Interestingly, AT could inhibit or promote immune responses through the upregulation or downregulation of steroid metabolism, respectively. The miR-29a/c-3p-HMGCR network is a potential regulation mechanism of AT participating in immune response and circulating miR-29a/c-3p is a potential molecular marker. This study can provide references for further investigating the immune functions of AT.Abstract Lipid metabolism plays an important role in maintaining lipid homeostasis and regulating immune functions. However, the regulations and mechanisms of lipid metabolism on the regional immune function of avian adipose tissue (AT) have not been reported. In this study, qRT-PCR was used to investigate the changes and relationships of different lipid metabolism pathways in chicken AT during stress-induced immunosuppression (SIIS) inhibiting immune response to Newcastle disease virus vaccine, then the miRNA regulation patterns of 3-hydroxy-3-methylglutaryl-CoA reductase (HMGCR) gene and its potential applications were further identified. The results showed that AT actively responded to SIIS, and ATGL, CPT1A and HMGCR were all the key genes involved in the processes of SIIS inhibiting the immune responses. SIIS significantly inhibited the natural and specific immune phases of the primary immune response and the initiation phase of the secondary immune response in AT by suppressing T cells by up-regulating steroid anabolism. Moreover, steroid metabolism could play dual roles in regulating the regional immune functions of AT. The miR-29a/c-3p-HMGCR network was a potential regulation mechanism of steroid metabolism in AT, and serum circulating miR-29a/c-3p had the potential as molecular markers. The study can provide valuable references for an in-depth investigation of the regional immune functions regulated by lipid metabolism in AT.