Patients with non-insulin-dependent diabetes mellitus (NIDDM) have increased risk of cardiovascular disease. Coronary artery thrombosis resulting from impaired fibrinolysis plays an important role in coronary artery disease (CAD) and eventual myocardial infarction. Fibrinolysis involves the regulated interaction of fibrinolytic proteins, tissue-type plasminogen activator, urokinase, the major fibrinolysis regulator, plasminogen activator inhibitor type I (PAI-1) and plasminogen. Risk factors for coronary artery disease (CAD), including hyperinsulinemia, are often associated with impaired fibrinolysis and can be correlated with increased PAI-1 levels. Elevated blood levels of PA-1 seen in NIDDM patients with high insulin levels may explain, in part, the increased thrombotic risk and CAD prevalence, unexplained by conventional risk factors in these subjects. Since endothelial cells (ECs) are a major site of synthesis of the fibrinolysis regulator, PAI-1, risk factor-induced (via insulin) expression of EC PAI-1 may be expected to promote early initiation of fibrin deposition, atherogenesis and atherothrombotic events associated with CAD. Variations in plasma PAI-1 levels have been attributed to variations in the PAI-1 gene, and associations between PAI-1 levels, PAI-1 genotypes (HindIII RFLPs, designated 1/1, 1/2 and 2/2) and insulin suggest that PAI-1 expression may be regulated by insulin in a genotype specific manner. The Principal Investigator has now demonstrated that insulin does, in fact, transcriptionally regulate primarily the 1/1 PAI-1 genotype in cultured human ECs. The overall long-term goal of these studies is to define the molecular regulatory mechanisms by which insulin affect PAI-1 expression at the level of gene transcription.
Specific aims i nclude: Identification of the regulatory elements(s) in the 1/1PAI-1 genotype promoter and 5' flanking region associated transcriptional factor(s) responsive to insulin (mobility shift assay, site-directed mutagenesis, EC cultures, liposome-mediated transfection). These studies will provide new insights into how genetic predisposition in combination with certain risk factors may predetermine the mechanism(s) that underlie the pathology of increased thrombosis and CAD in certain individuals with hyperinsulinemia and non-insulin-dependent diabetes mellitus.
| Grenett, H E; Benza, R L; Li, X N et al. (1999) Expression of plasminogen activator inhibitor type I in genotyped human endothelial cell cultures: genotype-specific regulation by insulin. Thromb Haemost 82:1504-9 |
| Grenett, H E; Benza, R L; Fless, G M et al. (1998) Genotype-specific transcriptional regulation of PAI-1 gene by insulin, hypertriglyceridemic VLDL, and Lp(a) in transfected, cultured human endothelial cells. Arterioscler Thromb Vasc Biol 18:1803-9 |
