Identification of Differentially Expressed Genes in the Hypothalamus of Broilers Under Heat Stress Using...

The hypothalamus is the advanced center that regulates visceral activities under the cerebral cortex. It plays some key roles, such as regulating body temperature, assessing feed intake, and balancing blood glucose and endocrine gland activities. Heat stress is known to trigger a series of detrimental consequences, prominently featuring a reduction in feed intake, an elevation in body temperature, and other related phenomena. To understand the mechanisms of how heat stress affects the function of the hypothalamus, broilers were allocated to three groups: the normal control (NC) group, the heat-stress (HS) group, and the pair-fed (PF) group. The PF group was established with the aim of eliminating the confounding effect of reduced feed intake. The trial lasted for two weeks, from the age of 28 to 42 d. A total of 280 differential expressed genes (DEGs) were identified (p_adj < 0.05, |log₂(FC)| ≥ 1) among three groups, including 3 up-regulated and 112 down-regulated genes in the HS group compared to the NC group, and 3 up-regulated and 13 down-regulated genes between the PF and NC groups. Compared with the HS group, a total of 149 genes were identified in the PF group, of which 125 genes were up-regulated and 24 genes were down-regulated. Gene Ontology enrichment indicated that a subset of DEGs was involved in brain development, the central nervous system (CNS), nerve signal transduction, and calcium homeostasis. The solute carrier family 1 member A6 and solute carrier family 6 member 13, identified as down-regulated genes (p_adj < 0.05) in the HS group, were considered as key genes in Gamma-aminobutyric acid (GABA) transportation, the normal expression of which ensures that extracellular GABA is maintained at a certain level and provides the amino acids needed for metabolism. Simultaneously, the solute carrier family 13 member 4 and solute carrier family 16 member 8 were also identified as down-regulated, which indicated that heat stress resulted in disorder and physiologic derangement in the hypothalamus. Meanwhile, the anorexigenic part of pro-opiomelanocortin genes was up-regulated significantly in the HS group. The transcriptome sequencing results can help us understand the regulatory mechanism of feed intake decline in broilers under heat stress at the genetic level.