CCL2 and obesity due to melanocortin 4 receptor deficiency: Obesity-related metabolic disorders elicit systemic low-grade inflammation by increasing the levels of proinflammatory factors, such as monocyte chemoattractant protein-1 (MCP-1), CD11c, tumor necrosis factor-α (TNF-α), leptin, lipopolysaccharide binding protein (LBP), and interleukin-6 (IL-6) [26,28,29].