Structural and functional characterization of turbot pparγ: Activation during high temperature and regulation of lipid metabolism.

Transcription factors of the peroxisome proliferator-activated receptor gamma (pparγ) is a ligand-activated receptor that plays key roles in lipid metabolism and inflammation. In this study, we cloned the pparγ cDNA of turbot (Scophthalmus maximus). It has a 1659 bp coding sequence (CDS) and encodes 552 amino acids. The deduced PPARγ protein of turbot contains two highly conserved domains, a C4-type zinc finger, a nuclear hormone receptor DNA-binding region signature, and a HOLI domain (ligand-binding domain of hormone receptors) identical to that of in other species. qPCR results showed that the expression level of pparγ and the expression of the fatty acid transporters fatp and cd36 were significantly increased under high-temperature stress. This indicates that high temperatures activate the transcriptional activity of pparγ, and lipid metabolism plays an important role in turbot under high-temperature stress. In addition, RNA interference was used to explore the regulation of pparγ on lipid metabolism of turbot at high temperatures. The results showed that the mRNA level of pparγ was significantly decreased. After the expression level of pparγ was inhibited, the expression levels of fatp and cd36 were significantly decreased. At the same time, GW9662 (a pparγ antagonist) was used to inhibit pparγ activity in turbot kidney cells, and fatp and cd36 gene expressions were detected. The mRNA expression levels of pparγ, fatp, and cd36 were significantly decreased. Our results suggest that high temperatures activate pparγ in turbot and that pparγ regulates lipid transport and maintains lipid metabolism homeostasis through positive regulation of the expression of downstream genes fatp and cd36. This study further elucidates that the pparγ-mediated signaling pathway may play an important role in regulating lipid metabolism during heat stress in teleost fish.