We and other previous research found that elevated vascular arginase activity, especially arginase 1, can impair normal vascular endothelial function in various cardiovascular disease models, for example, diabetes (Elms et al., 2013), atherosclerosis (Rabelo et al., 2015), hypertension (Toque et al., 2013), aging (Santhanam et al., 2007), coronary artery disease (Shemyakin et al., 2012), and ischemia-reperfusion (Jung et al., 2010). The gene discussed is ARG1; the disease is diabetes mellitus.