IL1B and metabolic dysfunction-associated steatohepatitis: For example, a tryptophan-derived metabolite indole-3-propionic acid (IPA) by gut microbiota showed anti-NASH ability in rats by reducing gut LPS leakage, which can activate hepatic macrophages to produce proinflammatory cytokines (e.g., tumor necrosis factor (TNF)-α and interleukin (IL)-1β) to cause liver inflammation and fibrosis [21,22].