Short-term studies in subjects with diabetes receiving glucagon-like peptide 1 (GLP-1)-targeted therapies have suggested a reduced number of cardiovascular events. The mechanisms underlying this unexpectedly rapid effect are not known. We cloned full-length GLP-1 receptor (GLP-1R) mRNA from a human megakaryocyte cell line (MEG-01), and found expression levels of GLP-1Rs in MEG-01 cells to be higher than those in the human lung but lower than in the human pancreas. Incubation with GLP-1 and the GLP-1R agonist exenatide elicited a cAMP response in MEG-01 cells, and exenatide significantly inhibited thrombin-, ADP-, and collagen-induced platelet aggregation. Incubation with exenatide also inhibited thrombus formation under flow conditions in ex vivo perfusion chambers using human and mouse whole blood. In a mouse cremaster artery laser injury model, a single intravenous injection of exenatide inhibited thrombus formation in normoglycemic and hyperglycemic mice in vivo. Thrombus formation was greater in mice transplanted with bone marrow lacking a functional GLP-1R (Glp1r 2/2 ), compared with those receiving wild-type bone marrow. Although antithrombotic effects of exenatide were partly lost in mice transplanted with bone marrow from Glp1r 2/2 mice, they were undetectable in mice with a genetic deficiency of endothelial nitric oxide synthase. The inhibition of platelet function and the prevention of thrombus formation by GLP-1R agonists represent potential mechanisms for reduced atherothrombotic events.Type 2 diabetes (T2D) is associated with a number of risk factors that contribute to an increased risk of atherothrombotic events, including hypertension, dyslipidemia, obesity, and chronic inflammation, as well as endothelial and platelet dysfunction (1). Platelets are small, versatile, anucleate cells in the circulation that play critical roles in both early and late stages of atherothrombosis, contributing also to cell-based thrombin generation and blood coagulation (2). Subjects with T2D exhibit a prothrombotic state, including increased production of coagulation factors; decreased production of fibrinolytic factors; and a propensity to platelet activation, aggregation, and adhesion (1,3,4). Compounding the latter, subjects with T2D show reduced sensitivity to antiplatelet drugs, such as aspirin and clopidogrel (5,6), and manifest a higher incidence of cardiovascular events (1,6,7). Although the currently available antidiabetic agents have been effective at lowering blood glucose levels and preventing microvascular disease, until the recent EMPA-REG study (8), it had been exceedingly difficult to demonstrate the beneficial effects of normalizing blood glucose

Objective-Regulatory complexes comprising myocardin and serum response factor (SRF) are critical for the transcriptional regulation of many smooth muscle-specific genes. However, little is known about the epigenetic mechanisms that regulate the activity of these complexes. In the current study, we investigated the role of SWI/SNF ATP-dependent chromatin remodeling enzymes in regulating the myogenic activity of myocardin. Methods and Results-We found that both Brg1 and Brm are required for maintaining expression of several smooth muscle-specific genes in primary cultures of aortic smooth muscle cells. Furthermore, the ability of myocardin to induce expression of smooth muscle-specific genes is abrogated in cells expressing dominant negative Brg1. In SW13 cells, which lack endogenous Brg1 and Brm1, myocardin is unable to induce expression of smooth muscle-specific genes. Whereas, reconstitution of wild-type, or bromodomain mutant forms Brg1 or Brm1, into SW13 cells restored their responsiveness to myocardin. SWI/SNF complexes were found to be required for myocardin to increase SRF binding to the promoters of smooth muscle-specific genes. Brg1 and Brm directly bind to the N terminus of myocardin, in vitro, through their ATPase domains and Brg1 forms a complex with SRF and myocardin in vivo in smooth muscle cells. Conclusion-These data demonstrate that the ability of myocardin to induce smooth muscle-specific gene expression is dependent on its interaction with SWI/SNF ATP-dependent chromatin remodeling complexes. Key Words: Brg1 Ⅲ Brm Ⅲ telokin Ⅲ calponin Ⅲ SRF S mooth muscle cells are important contractile components of the cardiovascular system that regulate blood pressure and flow. Vascular smooth muscle cells modulate their phenotype in response to extracellular cues during the development and progression of a variety of diseases including atherosclerosis and hypertension. These diseases are associated with decreased expression of proteins required for the normal contractile function of smooth muscle cells. 1 Understanding the mechanisms that control expression of contractile and regulatory proteins in smooth muscle cells is, therefore, an essential step toward determining how these processes are altered in pathological conditions. The interaction of serum response factor (SRF) with the coactivator myocardin is a critical determinant of vascular smooth muscle development. 2,3 Myocardin null mice lack differentiated smooth muscle cells in the dosal aorta and placental vasculature and die around E10. 2 Myocardin is thus critically required for the differentiation of these populations of vascular smooth muscle cells. Myocardin does not bind directly to DNA, but interacts with genes via its binding to SRF through a basic domain and polyglutamine-rich (poly Q) domain in myocardin. Myocardin-bound SRF binds to CArG elements within the promoters of many smooth musclespecific genes 4 and myocardin activates transcription of these genes through a strong transcriptional activation domain at its C terminus. 5 However, a...