TLR4 and obesity due to melanocortin 4 receptor deficiency: In the state of obesity, massive expansion of adipose tissue, hypertrophy of white adipocytes, and macrophage infiltration in adipose tissue activates the complex of Toll-like Receptor 4 (TLR4) with LPS, which induces the production of pro-inflammatory adipocytokines, ultimately leading to IR (9).