LPS binds to the TLR4 receptor and triggers a strong immune response, and this activation leads to an enhanced production of cytokines and chemokines via mediators such as nuclear factor-κB (NF-κB), activator protein-1 (AP-1), and interferon regulatory factors (IRFs), which contribute to the development of the chronic low-grade inflammation seen in obesity [14]. The gene discussed is JUN; the disease is obesity due to melanocortin 4 receptor deficiency.