As noted by excellent systematic reviews, interactions between these cells occur through the secretion of obesity-associated hormones (e.g., leptin, adiponectin, and IGF1), cytokines (including chemokines) (e.g., TNF-α, IL-6, IL-8, IL-10, and CCL2/MCP-1), VEGF and other activated CAA mediators. Here, CCL2 is linked to obesity due to melanocortin 4 receptor deficiency.