Cloning of peroxisome proliferators activated receptors in the cobia (Rachycentron canadum) and their expression at different life-cycle stages under cage aquaculture

We present the cDNA sequences and tissue mRNA expression of peroxisome proliferator-activated receptor (PPAR) α, β and γ isotypes in the cobia (Rachycentron canadum), a warm water pelagic fish that is becoming a fish of choice for offshore cage farming. RT-PCR and real-time PCR showed that PPARα mRNA predominated in red muscle, heart and liver whereas PPARβ was expressed mainly in liver and pyloric caeca. In contrast, PPARγ transcripts were detected in all of the tissues examined, with the highest level occurring in visceral fat depot. Our 52-wk time-series investigation showed that while the mRNA expression of PPARγ in the cobia was positively (P < 0.05) related to its body lipid deposition, a negative (P < 0.05) relationship was found between PPARα expression in the liver and body lipid deposition. There was a significant increase in body lipid deposition and hepatic PPARγ expression as the fish grew. The hepatic PPARγ expression could be a sufficient parameter describing the bodily expression of PPARγ because of its positive correlation with PPARγ expressions in all other tissues. These results showed that PPARγ and α played a pivotal role in the control of lipid metabolic and storage functions in the liver, muscle and visceral fat depot of the cobia.