TLR4 and metabolic dysfunction-associated steatotic liver disease: The interaction between metabolic dysfunction-associated seatotic liver disease (MASLD) and gut microbiota regulates hepatic metabolic homeostasis through the gut-liver axis, and its mechanisms involve intestinal dysbiosis (decreased bacteroidetes, increased ratio of firmicutes/proteobacteria), bile acid metabolism reprogramming (secondary bile acids inhibit FXR signaling), short-chain fatty acid (SCFAs) deficiency, and endotoxin-mediated inflammatory activation (TLR4/NF-κB pathway).