TLR4 and obesity due to melanocortin 4 receptor deficiency: In obesity and conditions related to intestinal permeability, TLR4 is known to be involved in the inflammatory response that culminates in insulin resistance and metabolic derangement, as those responses are attenuated by the inhibition of this protein activity [27, 34, 47–49], such as in TLR4 loss-of-function C3H/HeJ mice [50], in CD14−/− mice [51], and in TLR4−/− mice [52] (Figure 1).