CCL2 and obesity due to melanocortin 4 receptor deficiency: Intriguingly, obesity is also associated with a state of chronic low-grade inflammation characterized by elevated plasma concentrations of pro-inflammatory cytokines (IL-6, IL-1, and TNF-α), chemokines (MCP-1) and adipokines (haptoglobin, PAI-1, leptin, visfatin, resistin, and VEGF; Hotamisligil, 2006).