CCL2 and obesity due to melanocortin 4 receptor deficiency: Furthermore, several studies have demonstrated that lipid species elevated by diet or obesity, including free fatty acids, stimulate inflammation by activating Toll-like receptors and thereby strengthen the downstream Nuclear Factor kappa-light-chain-enhancer of activated B cells (NF-kB) signalling cascade, which further upregulates the synthesis and secretion of chemokines, such as Ligand chemokine CC Motif 2 (CCL2) by adipocytes, thus increasing macrophage infiltration [31].