PPAR-mediated diverse responses in various tissues of mouse

Peroxisome proliferator-activated receptors (PPARs) play the essential role in transcriptional modulations of the genes involved in lipid metabolism. In vitro studies have shown that all the mechanisms of the modulations are similarly mediated by PPAR and the response elements through heterodimerization with retinoid X receptors (RXRs). However, PPARs mediate the diverse effects induced in various tissues of mouse by their activators. First, PPAR alpha also plays an obligatory role in the activator-induced transcriptional modulations of various genes, some of which are not related to lipid metabolism. Second, responsiveness of various genes to several activators varies considerably. Third, some of the activator-induced transcriptional activation of several genes is strictly tissue-specific. Fourth, the time courses of the activator-induced transcriptional modulations are diverse. Following brief review of these diverse responses, emphasis is laid on the need for studies of these diversely regulated genes to understand the species-general and coordinated interplay between PPARs and other factors to maintain lipid homeostasis at the body level.