TLR4 and obesity due to melanocortin 4 receptor deficiency: Animal studies have shown that dysregulation of the gut microbiota caused by obesity impairs the integrity of the gut barrier, causing the release of LPS from intestinal gram-negative bacteria and subsequent LPS into mesenteric veins, triggering obesity-associated chronic inflammation by activating the TLR4/NF-κB signaling pathway (Wu et al., 2019; Guo et al., 2021; Xia et al., 2022).