Fibroblast growth factor 21 alleviates acetaminophen induced acute liver injury by activating Sirt1 mediated autophagy

Acetaminophen (APAP) is the main cause of acute liver injury (ALI) in the Western. Our previous study has shown that fenofibrate activated hepatic expression of fibroblast growth factor 21 (FGF21) can protect the liver form APAP injuries by promoting autophagy. However, the underlying mechanism involved in FGF21-mediated autophagy remains unsolved. The ALI mice model was established by intraperitoneal injection of APAP. To investigate the influence of FGF21 on autophagy and Sirt1 expression in APAP-induced ALI, FGF21 knockout (FGF21KO) mice and exogenously supplemented mouse recombinant FGF21 protein were used. In addition, primary isolated hepatocytes and the Sirt1 inhibitor EX527 were used to observe whether FGF21 activated autophagy in APAP injury is regulated by Sirt1 at the cellular level. FGF21, Sirt1, and autophagy levels increased in mice with acute liver injury (ALI) and in primary cultured hepatocytes. Deletion of the FGF21 gene exacerbated APAP-induced liver necrosis and oxidative stress, and decreased mitochondrial potential. It also reduced the mRNA and protein levels of autophagy-related proteins such as Sirt1, LC3-II, and p62, as well as the number of autophagosomes. Replenishment of FGF21 reversed these processes. In addition, EX527 partially counteracted the protective effect of FGF21 by worsening oxidative damage, mitochondrial damage, and reducing autophagy in primary liver cells treated with APAP. FGF21 increases autophagy by upregulating Sirt1 to alleviate APAP-induced injuries.