Abstract 19834: MicroRNA-148a Inhibits Expression of Plasminogen Activator Inhibitor-1: Mechanistic Implications for Obesity-associated Thrombosis

Abstract

Obesity is an epidemic in developed countries and is associated with an increased incidence of arterial and venous thrombosis. The mechanisms of obesity-induced thrombosis, however, are not well defined. In the current study, we tested the hypothesis that diet-induced obesity causes alterations in microRNA expression that may predispose to thrombosis. To induce obesity, C57Bl/6J mice were fed a 60% high fat diet. Compared with lean mice, obese mice had elevated fasting levels of glucose and insulin resistance, and exhibited acceleration of carotid artery thrombosis after photochemical injury (P<0.01) and increased susceptibility to venous thrombosis induced by inferior vena cava ligation (P<0.05). Plasma levels of plasminogen activator inhibitor-1 (PAI-1), an inhibitor of fibrinolysis secreted by adipocytes and endothelial cells, were elevated 3-fold in obese mice, suggesting a potential mechanism of thrombosis in diet-induced obesity. TaqMan low-density microRNA arrays detected downregulation of 41 microRNAs in plasma exosomes from obese mice (P<0.05). Bioinformatic analysis of the downregulated microRNAs in relation to the PAI-1 3’-UTR identified microRNA-148a as a potential inhibitor of PAI-1 expression in obesity. We found that levels of PAI-1 mRNA were increased 4.5-fold (P<0.05) and levels of microRNA-148a decreased 4-fold (P<0.05) in white adipose tissue from obese mice compared with lean mice. Transfection of primary adipocytes or a murine endothelial cell line (MS-1) with a microRNA-148a mimetic resulted in 50-70% downregulation of PAI-1 expression (P<0.05), demonstrating a causal inverse relationship between microRNA-148a and PAI-1 mRNA. Our findings suggest that downregulation of microRNA-148a in diet-induced obesity may promote thrombosis through loss of repression of PAI-1 expression at the mRNA level.