LEPR and obesity due to melanocortin 4 receptor deficiency: • 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.