TGFB1 and Hepatic fibrosis: Liu et al. found that indole-3-propionic acid (IPA) could reduce the gap in gut microbiota diversity between CCl4-induced mice and healthy counterparts, activated HSCs and the TGF-β1/Smads signaling pathway, leading to hepatocyte apoptosis, increased expression of extracellular matrix components such as collagen I and α-SMA, ultimately promoting liver fibrosis (Liu et al., 2021).