Researchers at the University of Vermont Cardiovascular Research Institute, Colchester, Vermont have found that increased expression in the heart of plasminogen activator inhibitor type-1 (PAI-1) is profibrotic. The results, which appear in the March 2009 issue of Experimental Biology and Medicine, implicate PAI-1 overexpression, known to accompany insulin resistance and type 2 diabetes, as a factor contributing to the high incidence of heart failure after myocardial infarction in people with diabetes. The research team, Dr. A.K.M. Tarikuz Zaman, a research associate, Mr. Christopher J. French, medical and graduate student, Dr. David J. Schneider, Professor of Medicine and Director of the Cardiology and Vascular Biology Units, and Dr. Burton E. Sobel, Professor of Medicine and Director of the Cardiovascular Research Institute, performed studies in 10 week old mice subjected to coronary occlusion. Controls and PAI-1 overexpressing mice congenic on a C57BL6 background had comparable PAI-1 content in left ventricular myocardium despite a marked elevation of PAI-1 in plasma in the latter. 6 weeks after coronary occlusion the PAI-1 overexpressing mice exhibited a 2-fold increase in left ventricular (LV) PAI-1 content. Histochemical analysis demonstrated 33% more LV fibrosis as well. The increased fibrosis associated with increased PAI-1 was accompanied by functional derangements including diminished LV wall thickness in both diastole and systole, increased end systolic LV dimensions, depressed fractional shortening, a greater impairment of LV segmental function, and greater transmitral E-wave amplitude.
In summary, overexpression of PAI-1 in the heart altered the response of the left ventricle to myocardial infarction. It led to increased expression of PAI-1 late after coronary occlusion accompanied by increased fibrosis and functional derangements indicative of both systolic and diastolic dysfunction. Dr. Sobel said that "in concert with o
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