TLR4 and obesity due to melanocortin 4 receptor deficiency: Macrophage activation via innate pattern recognition receptors such as Toll-like receptor 4 (TLR4) and nuclear factor “kappa-light-chain-enhancer” of activated B cells (NF-κB) and the production of cytokines such as tumor necrosis factor-alpha (TNF-α), interleukin-1β (IL-1β), and interleukin-6 (IL-6) is proposed to mediate insulin resistance and other complications of obesity (Arkan et al., 2005, Biswas and Mantovani, 2012, Jin and Flavell, 2013, Moore and Tabas, 2011, Olefsky, 2009, Reilly et al., 2013).