ABSTRACT
ObjectiveTo investigate the effect and mechanism of total saponins from Panax japonicus （TSPJ） on white adipose tissue （WAT） browning/brown adipose tissue （BAT） activation in C57BL6/J male mice fed on a high-fat diet （HFD）. MethodThirty-two C57BL6/J male mice （8-week-old） were randomly divided into a normal group， a model group， a low-dose TSPJ group， and a high-dose TSPJ group. The mice in the low-dose and high-dose TSPJ groups were given TSPJ for four months by gavage at 25， 75 mg·kg-1·d-1， respectively， and those in the other groups were given 0.5% sodium carboxymethyl cellulose （CMC-Na） accordingly. After four months of feeding， all mice were placed at 4 ℃ for acute cold exposure， and the core body temperature was monitored. Subsequently， all mice were sacrificed， and BAT and inguinal WAT （iWAT） were separated rapidly to detect the corresponding indexes. Hematoxylin-eosin （HE） staining was used to observe the morphological changes in each group. The effect of TSPJ on the mRNA expression of uncoupling protein 1 （UCP1）， fatty acid-binding protein 4 （FABP4）， cytochrome C （CytC）， PR domain-containing protein 16 （PRDM16）， elongation of very long chain fatty acids protein 3 （ELOVL3）， peroxisome proliferator-activated receptor γ （PPARγ）， and peroxisome proliferator-activated receptor-γ coactivator-1α （PGC-1α） in iWAT and BAT was detected by Real-time polymerase chain reaction （Real-time PCR）. Western blot was also used to detect the protein expression of UCP1， PRDM16， PPARγ， and PGC-1α in BAT and iWAT of each group. The effect of TSPJ on UCP1 expression in BAT and iWAT was detected by immunohistochemistry. Result① Compared with the model group， TSPJ could decrease the body weight and proportions of iWAT and BAT in the HFD-induced mice （P<0.05， P<0.01）. ② The body temperature of mice in the model group decreased compared with that in the normal group in the acute cold exposure tolerance test （P<0.05）. The body temperature in the high-dose TSPJ group increased compared with that in the model group （P<0.01）. ③ Compared with the normal group， the model group showed increased adipocyte diameter in iWAT and BAT and decreased number of adipocytes per unit area. Compared with the model group， the TSPJ groups showed significantly reduced cell diameter and increased number of cells per unit area， especially in the high-dose TSPJ group. ④ Compared with the normal group， the model group showed decreased mRNA expression of FABP4， UCP1， CytC， PRDM16， ELOVL3， PGC-1α， and PPARγ in adipose tissues of mice （P<0.05， P<0.01）. Compared with the model group， after intervention with TSPJ， the mRNA expression was significantly up-regulated （P<0.05， P<0.01）. ⑤ Compared with the normal group， the model group showed decreased protein expression of UCP1， PRDM16， PPARγ， and PGC-1α in adipose tissues of mice （P<0.05， P<0.01）. Compared with the model group， after intervention with TSPJ， the protein expression increased significantly （P<0.05， P<0.01）. ConclusionTSPJ could induce the browning of iWAT/BAT activation and enhance adaptive thermogenesis in obese mice induced by HFD. The underlying mechanism may be attributed to the activation of the PPARγ/PGC-1α signaling pathway.