To elucidate which PPAR subtype contributed to the chitosan-affected gene expression profile, we performed Pscan to analyze the PPRE in the promoter regions of chitosan-regulated genes. Pscan is a software that scans promoter sequences of genes with motifs describing the binding specificity of known transcription factors [29]. Over the half of genes contained PPAR-α and/or PPAR-γ responsive elements in their promoter regions, suggesting that the majority of genes were regulated by chitosan via PPAR-α and/or PPAR-γ signaling pathways (data not shown). PPAR-α and PPAR-γ-regulated genes were further validated by qPCR. The expression levels of PPAR-γ-regulated genes, xpo4 and penk1, and PPAR-α-regulated genes, pin1 and prdx2, were upregulated by chitosan in the stomach and brain, which were in agreement with microarray data (Table 3). These data suggested that chitosan regulated gene expression via PPAR-α and/or PPAR-γ signaling pathways.
