Fat-specific protein 27b is regulated by hepatic peroxisome proliferator-activated receptor γ in hepatic steatosis.

The fat-specific protein 27 gene (Fsp27) belongs to the cell death-inducing DNA fragmentation factor 45-like effector family. Fsp27 is highly expressed in adipose tissue and fatty liver. In adipocytes, FSP27 localizes to the membrane of lipid droplets and promotes lipid droplet hypertrophy. Recently, FSP27 was shown to consist of two isoforms, FSP27 alpha and FSP27 beta. Previously, we demonstrated that Fsp27a is directly regulated by peroxisome proliferator-activated receptor gamma (PPAR(gamma)) in fatty livers of genetically obese leptin deficient ob/ob mice and that Fsp27b may potentially be regulated by different factors transcriptionally as they both have a different promoter region. Thus, the aim of the present study was to elucidate whether Fsp27b is regulated by PPAR gamma in fatty liver. Fsp27a and Fsp27b were markedly induced in fatty liver of ob/ob mice compared with those in the normal liver. However, both Frp27a/b were expressed at markedly lower levels in liver-specific PPAR(gamma) knockout mice with an ob/ob background. Further, the PPAR response element (PPRE) for the PPAR(gamma)-dependent promotion of Fsp27b promotor activity was revealed at position -1,163/-1,151 from the transcriptional start site (+1). Interestingly, the cis-element responsible for the PPAR(gamma)-dependent induction of Fsp27b was the same as that responsible for PPAR(gamma)-dependent induction of Fsp27a. These results suggest that PPAR(gamma) regulates not only Fsp27a but also Fsp27b in fatty liver of ob/ob mice through a common PPRE.