Whereas insulin resistance decreases NO release and synthesis and increases oxidative stress and inflammatory cytokines in endothelial cells, correlative experiments indicate that in insulin-resistant obese rats, IR leads to increased expression of vascular endothelin-b receptors, which play a role in increased reactive oxygen species production, endothelial dysfunction, and increased vasoconstriction in erectile tissue (18). This evidence concerns the gene INS and endothelial dysfunction.