Inflammation is a critical event in the development of insulin resistance. Macrophage migration inhibitory factor (MIF) is now known as a proinflammatory cytokine that was recently associated with insulin resistance and exhibited previously to be induced by angiotensin (Ang) II. Our aim was to investigate whether Ang II, its fragment Ang IV and related enzyme angiotensin-converting enzyme 2 (ACE2) could modulate the expression of MIF and insulin signaling in cultured human endothelial cells. A recombinant plasmid encompassing human ACE2 gene was constructed and transfected into these cells. The mRNA, phosphorylation and protein levels of p22phox, MIF and Akt in cells were determined by real-time polymerase chain reaction and Western blotting, respectively. ACE2 gene transfer strikingly suppresses the expressions of p22phox and MIF induced by Ang II and IV in endothelial cells. In addition, Ang II diminished insulin-stimulated Akt activation on serine 473, whereas no effect was observed with Ang IV. This inhibitory effect of Ang II was reversed by ACE2 gene transfer and anti-MIF treatment in endothelial cells. Our findings reveal that ACE2 overexpression counteracts the prooxidative and proinflammatory effects of Ang II and Ang IV and ameliorates the Ang II-induced impairments of insulin signaling involving Akt phosphorylation pathway. These beneficial effects of ACE2 are thought to result mainly from blocking MIF expression in endothelial cells.