NFKB1 and obesity due to melanocortin 4 receptor deficiency: Moreover, the recognition of both endogenous and exogenous ligands by pattern recognition receptors, such as Toll-like receptors, has been shown to initiate or promote chronic inflammation in obesity by activating downstream NF-kB signalling, which in turn upregulates the synthesis of chemokines like CCL2 [31,238,239].