Fibronectin Type III Domain-Containing 5 Attenuates Liver Fibrosis Via Inhibition of Hepatic Stellate Cell Activation

Background/aims: Fibronectin type III domain-containing 5 (FNDC5) protein is involved in the beneficial effects of exercise on metabolism. FNDC5 attenuates hepatic steatosis induced by high fat diet (HFD). Here, we examined the effects of FNDC5 on liver fibrosis and underline mechanisms.

Methods: Experiments were carried out on wild-type and FNDC5-/- mice, primary mouse hepatic stellate cells (HSCs) and human hepatic stellate cell line (LX-2). The mice were fed with HFD for 6 months to induce liver fibrosis. Oxidized low density lipoprotein (oxLDL) were used to induce the activation of hepatic stellate cells and fibrosis in mouse HSCs and human LX-2 cells. H&E, Masson's trichrome staining and Sirius red staining were used for liver sections. Protein and mRNA expressions were evaluated with Western blot and RT-PCR, respectively.

Results: FNDC5 deficiency aggravated the HFD-induced liver fibrosis and HSCs activation in mice. It exacerbated the HFD-induced inhibition of AMPK phosphorylation, upregulation of connective tissue growth factor (CTGF) and Transforming Growth Factor-β (TGF-β), and deposition of extracellular matrix (ECM) in liver of mice. Administration of FNDC5 attenuated oxLDL-induced AMPK deactivation, HSCs activation, CTGF and TGF-β upregulation and ECM deposition in mouse HSCs. The beneficial effects of FNDC5 on oxLDL-induced AMPK dephosphorylation, HSCs activation and ECM deposition were prevented by the inhibition of AMPK with compound C in human LX-2 cells. However, the effects of FNDC5 on hepatic fibrosis in vivo in this study cannot be distinguished from its effects on adiposity and hepatic steatosis.

Conclusions: FNDC5 deficiency aggravates HFD-induced liver fibrosis in mice. FNDC5 plays beneficial roles in attenuating liver fibrosis via AMPK phosphorylation-mediated inhibition of HSCs activation.