Abstract
BACKGROUND AND PURPOSE: Adipocyte differentiation in vitro is coordinately activated by two transcription factors, peroxisome proliferator-activated receptor gamma (PPARgamma) and CCAAT enhancer binding protein alpha (C/EBPalpha), but it is inhibited by preadipocyte factor-1 (pref-1). Statins, inhibitors of HMG-CoA reductase and de novo cholesterol synthesis, can have pleiotropic effects which influence adipocyte phenotype by ill-defined mechanisms. We investigated the effects of pitavastatin (NK-104) on adipocyte differentiation and the transcriptional pathways involved. EXPERIMENTAL APPROACH: The effects of pitavastatin on adipocyte differentiation were evaluated by the formation of oil droplets, content of cellular triglyceride and expression of adipocyte-specific genes. Regulatory mechanisms were assessed by analysis of PPARgamma, C/EBPalpha and pref-1 expression. KEY RESULTS: Pitavastatin significantly inhibited adipocyte differentiation of 3T3-L1 preadipocytes in response to adipogenic inducers. Evidence for inhibition included fewer Oil Red O positive droplets, less cellular triglyceride and decreased expression of adipocyte-specific genes, including fatty acid binding protein (aP2), CD36, adipsin and glucose transporter 4 (GLUT4). The inhibitory effects of pitavastatin on adipocyte differentiation of 3T3-L1 preadipocytes were time and concentration dependent. Pitavastatin significantly blocked induction of PPARgamma expression, but not C/EBPalpha expression or DNA binding activity of PPARgamma. Also, pitavastatin induced pref-1 expression in preadipocytes and maintained expression of pref-1 at high levels in differentiated cells. CONCLUSIONS AND IMPLICATIONS: Our data suggest that pitavastatin inhibits adipocyte differentiation by blocking PPARgamma expression and activating pref-1 expression. These studies may have implications in the regulation of adipogenesis in response to statins.