RETN 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 proinflammatory cytokines (IL-6, IL-1 and TNFα), chemokines (monocyte chemotactic protein 1, MCP-1), and adipokines (haptoglobin, PAI-1, leptin, visfatin, resistin and VEGF) [63].