Ghrelin Attenuated Lipotoxicity via Autophagy Induction and Nuclear Factor-κB Inhibition

Abstract

Background/Aims: Nonalcoholic fatty liver disease (NAFLD) is the most common chronic liver disease worldwide. Autophagy is associated with NAFLD. Ghrelin is a gut hormone with various functions including energy metabolism and inflammation inhibition. We investigated the therapeutic effect of ghrelin on NAFLD and its association with autophagy. Methods: C57bl/6 mice were fed a high-fat diet for 8 weeks to induce a model of chronic NAFLD, with ghrelin (10 µg/kg) administrated subcutaneously twice weekly from weeks 6 to 8. LO2 cells were pretreated with ghrelin (10-8 M) before stimulation with free fatty acid (palmitic and oleic acids; 1 mM). Lipid droplets were identified by hematoxylin and eosin and Red O staining and quantified by triglyceride test kits. LC3I/II, an important biomarker protein of autophagy was detected by western blotting, real-time polymerase chain reaction, immunohistochemistry and immunofluorescence. Tumor necrosis factor (TNF)-a and interleukin (IL)-6 were detected by ELISA and immunohistochemistry. Nuclear factor (NF)-κB p65 was detected by western blotting and immunofluorescence. AMP-activated protein kinase (AMPK) and mammalian target of rapamycin (mTOR) were detected by western blotting. Results: Ghrelin reduced the triglyceride content in high fat diet (HFD) group in vivo and free fatty acid (FFA) group in vitro. TNF-a and IL-6 were significantly reduced in the ghrelin-treated mice compared with the control group. Autophagy induction was accompanied with intracellular lipid reduction in ghrelin-treated mice. Ghrelin upregulated autophagy via AMPK/mTOR restoration and inhibited translocation of NF-κB into the nucleus. Conclusions: The results indicate that ghrelin attenuates lipotoxicity by autophagy stimulation and NF-κB inhibition.