TLR4 and obesity due to melanocortin 4 receptor deficiency: For example, in the cases of obesity, LPSs present in the cell membrane of Gram-negative bacteria (Figure 2—3) bind to receptor proteins (e.g., Toll-like receptor 4—TLR4) that upregulate pro-inflammatory cytokines and signaling pathways that regulate the nature, magnitude, and duration of the inflammatory response [97,102].