Adipose tissue expression of monocyte chemotactic protein-1 (MCP-1) and circulating MCP-1 levels are increased upon obesity in rodent, suggesting that MCP-1-mediated macrophage infiltration of adipose tissue may contribute to the metabolic disequilibrium associated with obesity and insulin resistance [5, 6]. This evidence concerns the gene CCL2 and obesity due to melanocortin 4 receptor deficiency.