Obeticholic acid orchestrates the crosstalk between ileal autophagy and tight junctions in non-alcoholic steatohepatitis: Role of TLR4/TGF-β1 axis

Document Type

Article

Publication Date

2022

Abstract

An interplay exists between non-alcoholic steatohepatitis (NASH) and intestinal barrier dysfunction. A plethora of mechanisms are implicated in the regulation of intestinal integrity, among which is autophagy. Farnesoid X receptor (FXR) is a key metabolic regulator in the liver, however, its impact on ileal autophagy and barrier integrity in the context of NASH has not yet been unraveled. Accordingly, the present study aimed at investigating the impact of the FXR agonist, obeticholic acid (OCA), on modulating the aberrant ileal autophagy and barrier dysfunction in NASH, exploring the possible implication of the TLR4/TGF-β1 axis. High-fat diet (HFD) and dextran sulfate sodium (DSS, MW ∼40 kDa) were used for 13 weeks to induce NASH with distorted intestinal integrity in Swiss albino male mice. Post-treatment with OCA (5 mg/kg/day; p.o; 4 weeks), histopathological evaluation revealed a restoration of normal hepatic and ileal architectures. OCA partially restored intestinal permeability, as evidenced by the FITC-dextran leakage assay, with no change in serum LPS or LBP levels. Meanwhile, ileal expression of the tight junctions; claudin-1, zonulin-1, and occludin, was upregulated. Hepatic and ileal TLR-4 and TGF-β1 immunoreactivities were also decreased with no change observed in ileal phosphorylated Akt. In addition, ATG5 gene expression and LC3II/I protein ratio were upregulated in the ileum. Overall, the present study suggests a protective role of OCA on intestinal integrity in NASH, possibly through autophagy induction via interfering with the TLR4/TGF-β1 pathway.

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