Abstract: Provided are a sirtuin inducer, a tissue repairing agent, a hepatocyte growth factor inducer, a tissue homeostasis maintenance agent, and a TLR4 agonist, which utilize a hyaluronic acid fragment as an active ingredient. A hyaluronic acid fragment selected from sizes of 2 to 20 sugar units, a pharmaceutically acceptable salt thereof, or pharmaceutically acceptable solvates thereof, is employed as the active ingredient for the sirtuin inducer, tissue repairing agent, hepatocyte growth factor inducer, tissue homeostasis maintenance agent, or TLR4 agonist. The hyaluronic acid fragment is preferably selected from sizes of 3 to 10 sugar units, and more preferably selected from a size of 3 or 4 sugar unite.