TLR4 and obesity due to melanocortin 4 receptor deficiency: In addition to adipose tissue all nucleated human cells have the capacity to respond to endotoxin as part of their innate immune response where the myeloid differentiation factor 2/toll-like receptor 4 (MD2-TLR4) can sense circulating endotoxin and initiate a local or systemic inflammatory processes involved in pathologies as diverse as metabolic syndrome, atherosclerosis, obesity, and T2DM (Shimazu et al., 1999, Andreasen et al., 2008).