APOE and obesity due to melanocortin 4 receptor deficiency: Its popularity owes in large part to the suitability of ApoE−/− mice as an experimental animal model to study the pathogenesis of numerous diseases, as well as the association between APOE polymorphism and a wide spectrum of diseases in humans, including coronary and peripheral vascular disease [2,3,4,5,6,7,8,9,10,11,12,13], obesity/diabetes [10,14,15], and Alzheimer’s disease [16].