Exendin-4, an analog of glucagon-like peptide (GLP)-1, has beneficial effects on cardiovascular disease induced by diabetes mellitus (DM). Recently, exendin-4 was reported to induce the proliferation of endothelial cells. However, its angiogenic effect on endothelial cells has not been clearly evaluated. Therefore, we investigated the effects of exendin-4 on the angiogenic process with respect to migration, sprouting, and neovascularization using in vitro and in vivo assays. Treatment with exendin-4 increased the migration of human umbilical vein endothelial cells (HUVECs) in in vitro scratch wound assays, as well as the number of lumenized vessels sprouting from HUVECs in in vitro 3D bead assays. These responses were abolished by co-treatment with exendin (9-39), a GLP-1 receptor antagonist, which suggests that exendin-4 regulates endothelial cell migration and tube formation in a GLP-1 receptor-dependent manner. In an ex vivo assay, treatment of aortic rings with exendin-4 increased the sprouting of endothelial cells. Exendin-4 also significantly increased the number of new vessels and induced blood flow in Matrigel plugs in in vivo assays. Our results provide clear evidence for the angiogenic effect of exendin-4 in in vitro and in vivo assays and provide a mechanism underlying the cardioprotective effects of exendin-4. (C) 2013 Elsevier Inc. All rights reserved.