Identification and structural characterization of two peroxisome proliferator activated receptors and their transcriptional changes at different developmental stages and after feeding with different fatty acids.

Peroxisome proliferator activated receptors beta1 (PPARβ1) and beta2 (PPARβ2) were investigated in loach (Misgurnus anguillicaudatus). The PPARβ1 and PPARβ2 were widely distributed in loach tissues. Multiple alignments of deduced amino acid sequences revealed homologous characteristics of the two subtypes of PPARβ with 88% identity. PPARβ1 was markedly expressed in the liver, about 100-fold higher than liver PPARβ2. The two subtypes in unfertilized ovum (UO) showed the highest transcriptions in early life stages, and there were great divergences in expression between unfertilized and fertilized stages. The regulation of PPARβ1 and PPARβ2 in response to dietary fatty acids was studied in liver of loach fed with diets containing fish oil (FO, rich in n-3 highly unsaturated fatty acid) or soybean oil (SO, rich in 18:2n-6) for 75days. Results showed that hepatic transcription of PPARβ1 in the SO group was higher than in the FO group. However, PPARβ2 expression was similar. The differences of molecular characterization, tissue expressions in early life stages, and transcriptional regulation by lipid resources indicated that PPARβ1 and PPARβ2 were functionally different. This is the first report of differential expression of PPARβ1 and PPARβ2 in various tissues and early life stages of loach are regulated by lipid resources. These results will stimulate further studies to better understand the functional characterization of PPARβ1 and PPARβ2.