CCL2 and obesity due to melanocortin 4 receptor deficiency: In contrast, in obesity, interferon (IFN)-gamma and lipopolysaccharide (LPS) drive the polarization of recruited monocytes toward inflammatory M1-type macrophages and produce a large amount of nitric oxide by expressing inducible nitric oxide synthase (Inos), TNF-α, IL-6, IL-1β, IL-12, and MCP-1[29].