Amplification And Expression Of PRDM16，BMP7，PPARα，COXⅡ And PGC-1α Genes Of Adipose Tissue In Tupaia Belangeri

Brown adipose tissue (BAT) was an specialized thermogenic tissue, which wasthe main site of nonshivering thermogenesis (NST) in small mammals.PRdomain-containing16(PRDM16) was a brown adipose determination factor. Itwas selectively expressed in BAT and induced the expression of α subunit ofperoxisome proliferators-activated receptor-γcoactivator-1(PGC-1α) and uncouplingprotein1(UCP1). BMP7could stimulate brown adipocyte differentiation andenhance thermogenesis by activating the expression PRDM16and PGC-1α genes.COX Ⅱ, PPARαand PGC-1α were the key regulatory factors of differentiation andmetabolism in brown adipocyte. COX Ⅱwas a effector molecule of adrenergicpathway in WAT. It was necessary for the formation of brown adipocytes. PPARαexpression levels in BAT was higher than WAT. It could induce the expression ofthermogenesis related genes and promote the generation of primary brown adipocyte.PGC-1α also could induce the formation of brown adipocytes in WAT. In the processof brown adipocytes differentiation, PGC-1α expression level increased. In this paper,Tupaia belangeri, which was the unique tropic and subtropic small mammal, wasstudied on the role of PRDM16, BMP7, COXⅡ, PPARα and PGC-1α in theregulation of energy balance in individual levels to explore the theoretical basis forthe ecophysiological adaptive model in the small mammals.This thesis consists of three parts:1. Amplification and sequence analysis of partial cDNA sequence of PRDM16,BMP7, PPARα, COX Ⅱa nd PGC-1α genes in Tupaia belangeri. The obtained partialsequences of PRDM16, BMP7, PPARα, COXⅡ and PGC-1α in T. belangeri were184bp,84bp,358bp,212bp and271bp respectively. The coding protein of thesesequences include of61amino acids in PRDM16;27amino acids in BMP7;119amino acids in PPARα,70amino acids in COXⅡ,87amino acids in PGC-1α.Comparison of the amino acids of T. belangeri PRDM16, BMP7, PPARα,COX Ⅱa nd PGC-1α with the corresponding amino acid sequence in a variety of mammals found that the homology of amino acid is higher. The PRDM16, BMP7,PPARα, COX Ⅱ and PGC-1α genes were used to reconstruct phylogenetic trees andshowed that T. belangeri had the closest relationship relative to primates.2. Seasonal changes of thermogenesis, energy metabolism and expression ofPRDM16and BMP7genes in T. belangeri. Body weight, energy intake,nonshivering thermogenesis,“classical” BAT content, omental WAT content and theexperession of PRDM16mRNA and BMP7mRNA were seasonally varied andsignificantly higher in winter than that in summer,.The data suggestd that theincrease of the experession of PRDM16mRNA and BMP7mRNA in winter promotesthe formation of brown adipocytes to adapt to the cold environment in winter in T.belangeri.3. Effects of cold acclimation on thermogenesis, energy metabolism, adiposetissue microstructure, PRDM16, BMP7, PPARα, COX Ⅱa nd PGC-1α genesexpression levels in T. belangeri. Body weight, energy intake, nonshiveringthermogenesis,“classical” BAT content, omental WAT content and the mRNAexperession of PRDM16, BMP7, PPARα,COX Ⅱ and PGC-1α gene were increasedsignificantly under cold exposure. The result of electron microscopic section showedthat the number of mitochondria and mitochondrial cristae increased in “classical”BAT. All of the results indicated that the increase of the experession of PRDM16andBMP7may promotes the formation of brown adipocytes; COX Ⅱ, PPARαandPGC-1α genes expression increased may induce the formation of brown adipocytesin the WAT and improved the expression of thermogenesis related genes. Under theaction of a variety of regulatory factors, the differentiation and metabolism of brownadipocytes were promoted in T. belangeri, in order to increase nonshiveringthermogenesis to adapt to extreme conditions of cold exposure.In summary, brown adipocytes may exist the PRDM16and BMP7myogenicorigin in T. belangeri. Under the condition of cold acclimation, differentiation ofbrown adipocytes was induced in WAT. The previous researches of our lab showedthe T. belangeri had the ability to adapt to a certain cold stress was likely to spreadfrom the tropics to the present distribution area, as spread from south to north.However, tha share of “classical” BAT NST of T. belangeri in cold adaptive thermogenesis significantly lower than that in northern small mammals. It wassuggested that the T. belangeri in the course of the spread from south to north, whichwas likely to be through PRDM16and BMP7pathways and induce differentiation ofbrown adipocytes in WAT to increase thermogenesis to compensate for the lack ofnonshivering thermogenesis in “classical” BAT, so as to cope with the lowtemperature environment.