CCL2 and obesity due to melanocortin 4 receptor deficiency: In some cases, inflammatory factors such as TNF-α in the peripheral circulation of individuals with obesity stimulate microglia to produce MCP-1/C-C motif chemokine 2 (CCL2) and brain monocytes (Kerfoot et al., 2006; D'Mello et al., 2009) and activate vagal afferent neurons to induce central inflammation (Valdearcos et al., 2017).