Identification, organ expression and ligand-dependent expression levels of peroxisome proliferator activated receptors in grass carp (Ctenopharyngodon idella)

Abstract

The peroxisome proliferator-activated receptors (PPARs) are ligand-dependent transcription factors belonging to the nuclear receptor family, and can regulate various genes involved in lipid metabolism. The aim of the present study was to investigate the tissue distribution patterns of PPARs and their ligand specificities in grass carp. We cloned three PPAR isotypes of the species and evaluated their organ distribution patterns using real-time PCR. Through analyzing the deduced amino acid sequences identities between the products cloned in grass carp and those described in other species, we concluded that the same type of PPAR amino acid sequences in different species were with high homology, and different subtypes of PPAR in the same species were with low homology. The mRNA constitutive expression level of PPARα predominated in the liver, but was weak in other tested tissues. PPARβ was present in all tested organs, and particularly abundant in heart, liver and muscle. PPARγ was only detected in the liver, and to a lesser extent in brain, muscle and visceral adipose tissue. Grass carp were intraperitoneally injected with 50 mg kg(-1) body mass (bw) dose of clofibrate, 42 mg kg(-1) bw dose of 2-bromo palmitate and 1 mg kg(-1) bw dose of 15-deoxy-Δ(12,14) prostaglandin J2 (15d-PGJ2), respectively, and the relative changes of the mRNA abundance of PPARs in liver were analyzed by real-time PCR. Clofibrate was able to increase the expressions of both PPARα and β, but was not able to for PPARγ. 2-bromo palmitate could affect the expressions of both PPARβ and γ, but was not able to for PPARα. 15d-PGJ2 was able to induce PPARβ expression, but PPARα and γ were not enhanced. Consequently, these results indicate that clofibrate, 2-bromo palmitate and 15d-PGJ2 could be applied as the activators of grass carp PPARs.