For example, it has been recognized that, in obesity, hypertrophic adipocytes produce monocyte chemotactic protein-1 (MCP-1), a factor favoring the infiltration of macrophages into fat tissue, while these immune cells produce pro-inflammatory cytokines, including the tumor necrosis factor α (TNFα), which sustain, in turn, adipose cell dysfunction (6, 7). Here, CCL2 is linked to obesity due to melanocortin 4 receptor deficiency.