Differentially Expressed Genes Analysis Of Brown Adipose Tissue During Cold Acclimation In Tree Shrews (Tupaia Belangeri) Based On RNA-Seq

The survival of animals were inseparable from their living environment.The adaptive heat production and regulation mechanism of mammals in different environments was one of the current hotspots in physiological ecology research.In a cold environment,animals can increase nonshivering thermogenesis(NST)by activating gene expression related to cold resistance,and help keep the animal's body temperature constant to protect it from cold.Brown adipose tissue(BAT)was the main organ of adaptive heat production and the main part of NST in mammals in cold environments.The Tupaia belangeri was closely related to living primates and can be used as an animal model of human metabolic diseases.It was distributed in the northern limit of my country and belonged to the typical tropical and subtropical small mammals,the low temperature may limit its spread,the changing trend of NST's contribution to adaptive thermogenesis of T.belangeri under cold conditions was different from the trend of northern small mammals,showing a decreasing trend..In order to investigate the regulation mechanism of thermogenesis in T.belangeri under cold acclimation,in the present study,transcriptome sequencing of BAT in T.belangeri between control group,cold acclimation group and rewarming group were carried out by Illumina novaseq 6000 platform,respectively.Then metabolic pathways and key genes related to thermogenesis were screened out by bioinformatics analysis,which was conducive to the analysis of the function of thermogenic genes.The specific results of this research were as follows:(1)The results showed that there were significant difference in the expression of2879 genes in cold acclimation group compared with that of control group,1181 were increased expression and 1698 were repressed in cold acclimation group,there were no significant difference in genes in rewarming group compared with that of control group.It showed that the BAT genes expression pattern of T.belangeri under cold acclimation has changed significantly,and it basically recovered to the control level after rewarming.(2)The GO analysis results between the control group and the cold acclimation group showed that there were 24,28 and 55 terms were significantly enriched in cellular components,molecular functions and biological processes,respectively,and differentially expressed genes were mainly enriched in biological processes.Among the first 10 items,there were 5 terms related to metabolic processes in "biological processes",2 terms were related to prominence and neurons in "cell components",and 3 terms were related to catalysis Activity in "molecular function".It indicated that the cold adaptation mechanism of T.belangeri was mainly related to the metabolic process,and was also regulated by enzyme activity and neuromodulation.(3)The KEGG analysis results between the control group and the cold acclimation group showed that the differentially expressed genes were significantly enriched in 20 pathways,and the differentially expressed genes were significantly enriched in oxidative phosphorylation,steroid biosynthesis,glycerophospholipidand and fatty acid metabolism pathways related to energy metabolism and lipid metabolism.It indicated that T.belangeri can adapt to the cold environment by regulating genes expression in energy metabolism and lipid metabolismi pathways in BAT.The key genes screened were ND3,ND4,ND5,ND6,ND4 L,CYTB,ATP8 and ATP6,which were in the oxidative phosphorylation pathway significantly upregulated,Thereby boosting energy consumption.The expression of most genes related to lipid metabolism was repressed,including SQLE,LSS,DHCR7,DHCR24,CYP51A1,ACACA,SCD,SCSL4,ELOVL6,ACACA,HSD17B12,GPD2,LPGAT1 and SELENOI,etc.These genes responded to the cold environment by affecting energy production,heat production,and membrane fluidity.T.belangeri also regulated the down-regulation of PDPK1,AKT2,ACACA,SLC2A4,and THRB genes in the insulin and thyroid hormone signaling pathways in BAT,thereby responding to glycolipid synthesis and cell proliferation and differentiation to adapt the cold environment.All of the above results revealed that the cold adaptation mechanism of the T.belangeri at the transcriptome level,and a number of pathways and key genes related to energy metabolism were screened to provide references for in-depth study of the cold adaptation mechanism of small mammals in the Oriental world and human metabolic diseases.