TLR2 and irritable bowel syndrome: These compounds prevent IBD by activating/inhibiting multiple signaling pathways, including TGF-β/Smad, TRL-4/NF-κB/MAPK, TLR2-NF-κB, autophagy, pyroptosis, glycolysis/gluconeogenesis and amino acid metabolism, Nrf-2/HO-1, microbiota-macrophage-arginine metabolism, and bile acid metabolism.