Very little is known about the effect of ethanol on PPARβ/δ. In rat hepatoma cells, acetaldehyde inhibited PPARβ/δ DNA binding activity but at a much higher concentration than that required for PPARα inhibition [28]. PPARβ/δ is also expressed in hepatic stellate cells, and its expression increases with cell activation in vitro and in vivo [78, 79]. However, the role of this PPAR isoform in stellate cells is of difficult interpretation, since if on one hand it promotes hepatic stellate cells proliferation [79], on the other it induces genes involved in the esterification of Vitamin A such as CRBP-1 and LRAT, possibly reflecting a compensatory mechanism aimed to counterbalance the loss of retinol storage during activation [78]. Very recently, the mRNA levels of PPARβ/δ have been shown to increase in livers of ethanol fed-rats [80]; however in this model activation of PPARβ/δ by the specific agonist L165,041 resulted in an attenuation of the ethanol-induced hepatic injury and in an improvement of liver regeneration [80].
