Identification and organ expression of peroxisome proliferator activated receptors in brown trout (Salmo trutta f. fario)

Although widely studied in mammals, little information about fish peroxisome proliferator activated receptors (PPARs) is yet available. As a baseline for future studies, the three PPAR isotypes were identified in brown trout (Salmo trutta f. fario) and their organ distribution pattern was established. The cDNA fragments encoding PPARs α, β and γ were amplified by PCR, and the deduced sequences of the correspondent peptides were compared with other species sequences. Both the 183 amino acid sequence from PPARα and the 103 amino acid sequence from PPARβ shared high levels of homology with the correspondent peptides of other fishes and terrestrial vertebrates, whereas PPARγ 108 amino acid sequence showed much less similarity with non-fish PPARγ. According to both semi-quantitative RT-PCR and real-time RT-PCR, PPARα mRNA predominates in white muscle, heart and liver and PPARβ is more expressed in testis, heart, liver, white muscle and trunk kidney. PPARγ was only detected in trunk kidney and liver by real-time RT-PCR and also in spleen by semi-quantitative RT-PCR. PPARβ seems to be the most strongly expressed isotype, whereas PPARγ shows a much weaker global expression.