KCNJ2 and obesity due to melanocortin 4 receptor deficiency: In the present study, we used an in vitro model whereby human adipose microvascular endothelial cells in culture were incubated with AT from lean or obese mice to determine the effects of AT on endothelial Kir2.1 channel function, a critical component of endothelium-dependent NO production and vasodilation well-known to be disrupted in obesity (17, 28), which we recently showed to be impaired in endothelium of VAT arteries isolated from obese mice and humans (5, 11).