CCL2 and obesity due to melanocortin 4 receptor deficiency: Several chemotactic factors, including monocytic chemotactic protein-1 (MCP-1), osteopontin, CXC motif chemokine ligand-14, and angiopoietin-like protein 2, are upregulated in adipose tissue during the early phase of obesity and mediate the recruitment of monocytes to adipose tissue, and genetic ablation of these genes ameliorates obesity-induced adipose inflammation and insulin resistance in animals [5], [6], [7], [8].