Abstract
Obese patients are at risk for development of cardiovascular disease, which can in part be explained by disturbances in the haemostatic and fibrinolytic systems. Recently, it has been demonstrated that the adipocyte itself is able to produce a primary fibrinolytic inhibitor, PAI-1, possibly explaining the high levels found in obesity. To gain insight into molecular mechanism of up-regulation of PAI-1 gene expression in fat tissues, we investigated the role of an adipocyte-enriched transcription factor, PPARγ. To identify cis-acting genetic elements required for induction of PAI-1 gene transcription, we constructed the plasmids containing a 5' deletion series of the PAI-1 promoter. When sequences between -762 and -723 were deleted, the level of induction significantly fell. Gel mobility shift assay indicated that atypical PPRE overlapping C/EBP binding site (-752 to -733) is important for PPARγ binding. Chromatin immunoprecipitation assay demonstrated that PPARγ is physically associated with PAI-1 promoters in vivo. Furthermore, mutation of the atypical PPRE abrogated the increase in transcriptional activities of PAI-1 promoter. Functional assay revealed that besides PPARγ/RXRα expression vectors, transfection of CBP expression vectors increased the luciferase activity to 7.5 fold and 11 fold of control value in COS-1 cells and 3T3-L1 preadipocyte, respectively. These data indicate that up-regulation of PAI-1 gene expression during adipogenesis is due to the functional cooperation between CBP and PPARγ/RXRα through atypical PPRE. [Jpn J Physiol 54 Suppl:S220 (2004)]
