ARG1 and obesity due to melanocortin 4 receptor deficiency: Lumeng’s group reported that after diet-induced obesity, murine ATMs had high gene expressions of cluster of differentiation (CD)11c+, TNF-α, and inducible nitric oxide synthase (iNOS), which are markers characteristic of M1 macrophages, whereas ATMs from lean mice expressed many genes characteristic of M2 macrophages, including arginase 1 (Arg1), Ym1, and IL-10 (8).