ACE2 and obesity due to melanocortin 4 receptor deficiency: The RAS classic arm (ACE1/AngII) and the RAS counter-regulatory arm (ACE2/Ang(1-7)) [14] seem to play important ‘YIN’ and ‘YANG’ counter-regulatory roles in maintaining healthy cardiovascular, blood pressure, insulin resistance, metabolism, and renal function, also in the development of cardiovascular, hypertensive, diabetes, obesity, and renal diseases [1,11,12,76,96,137–140].