• b. Effects of 50 μM metformin on endothelium-dependent vasorelaxation (EDV) in aortae from mouse model, db/db (leptin receptor mutant) of T2DM and obesity.• Effects of metformin on eNOS phosphorylation in MMECs exposed to normal versus high glucose cell culture conditions. Here, NOS3 is linked to obesity due to melanocortin 4 receptor deficiency.