TNF and obesity due to melanocortin 4 receptor deficiency: FFA activates the toll-like receptor 4 (TLR4)/the inhibitor kappa B kinase β (IKKβ)/nuclear factor-κB (NF-κB) proinflammatory signaling pathway and induces the expression of proinflammatory cytokines such as interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α) in a variety of cell types [3–5], thereby contributing to many obesity-related metabolic diseases, including type 2 diabetes, atherosclerotic cardiovascular disease and nonalcoholic fatty liver disease (NAFLD) [6].