Mas deficiency was shown to lead to metabolic abnormalities, e.g., dyslipidemia and type 2 diabetes in FVB/N mice16, but in another studies, diet-induced obesity was less pronounced in Mas-knockout FVB/N than in wild type mice17, and Mas deficiency in C57BL/6 mice have no effect on lipid metabolism18. Here, MAS1 is linked to obesity due to melanocortin 4 receptor deficiency.