Indeed, adipocytes secrete the primary ligand for C-C motif chemokine receptor 2 (CCR2; expressed on circulating monocytes), the monocyte chemoattractant CCL2 (MCP-1), and its expression increases in obesity (Sartipy & Loskutoff 2003). Here, CCR2 is linked to obesity due to melanocortin 4 receptor deficiency.