CCL2 and obesity due to melanocortin 4 receptor deficiency: In obesity, pro-inflammatory M1 macrophages infiltrate adipose tissue, and in conjunction with hypertrophic adipocytes, they secrete cytokines such as tumour necrosis factor-alpha (TNF-α), interleukin-6 (IL-6), and monocyte chemoattractant protein-1 (MCP-1) [10].