Peroxisome proliferator-activated receptor gamma (PPARγ) in yellow catfish Pelteobagrus fulvidraco: Molecular characterization, mRNA expression and transcriptional regulation by insulin in vivo and in vitro

Peroxisome proliferator-activated receptor gamma (PPAR gamma) is ligand-inducible transcription factor and has important roles in lipid metabolism, cell proliferation and inflammation. In the present study, yellow catfish Pelteobagrus fulvidraco PPAR gamma cDNA was isolated from liver by RT-PCR and RACE, and its molecular characterization and transcriptional regulation by insulin in vivo and in vitro were determined. The generation of PPAR gamma 1 and PPAR gamma 2 was due to alternative promoter of PPAR gamma gene. PPAR gamma 1 and PPAR gamma 2 mRNA covered 2426 bp and 2537 bp, respectively, with an open reading frame (ORF) of 1584 bp encoding 527 amino acid residues. Yellow catfish PPAR gamma gene was organized in a manner similar to that of their mammalian homologs, implying a modular organization of the protein's domains. A comparison between the yellow catfish PPAR gamma amino acid sequence and the correspondent sequences of several other species revealed the identity of 55-76.2%. Two PPAR gamma transcripts (PPAR gamma 1 and PPAR gamma 2) mRNAs were expressed in a wide range of tissues, but the abundance of each PPAR gamma mRNA showed the tissue- and developmental stage-dependent expression patterns. Intraperitoneal injection of insulin in vivo significantly stimulated the mRNA expression of total PPAR gamma and PPAR gamma 1, but not PPAR gamma 2 in the liver of yellow catfish. In contrast, incubation of hepatocytes with insulin in vitro increased the mRNA levels of PPAR gamma 1, PPAR gamma 2 and total PPAR gamma. To our knowledge, for the first time, the present study provides evidence that PPAR gamma 1 and PPAR gamma 2 are differentially expressed with and among tissues during different developmental stages and also regulated by insulin both in vivo and in vitro, which serves to increase our understanding on PPAR gamma physiological function in fish. (C) 2015 Elsevier Inc. All rights reserved.