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

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.

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)-α 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.

Ghrelin reduced the triglyceride content in high fat diet (HFD) group in vivo and free fatty acid (FFA) group in vitro. TNF-α 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.

The results indicate that ghrelin attenuates lipotoxicity by autophagy stimulation and NF-κB inhibition.