Anti-inflammatory and direct antifibrotic effect of the oral hepatotropic DPP4 inhibitor Linagliptin in model of bilary fibrosis and NASH

Background and aims: Non-alcoholic steatohepatitis (NASH) ischaracterized by steatosis, lobular inflammation and progressive pericellular fibrosis. Anti-inflammatory and especially antifibrotic therapies for NASH are urgently needed. The incretin glucagon like peptide 1 (GLP-1) is rapidly inactivated by dipeptidyl peptidase-4 (DPP-4), an enzyme produced by various cells, including intestinal epithelia and hepatocytes. Therefore we studied the effect of the indirect GLP-1 agonist Linagliptin, a DPP4-inhibitor, on hepatic inflammation and fibrosis in models of biliary fibrosis and NASH.

Methods: Linagliptin was administered daily by gavage at 0.5, 5, 10 and 50 mg daily per kg BW to Mdr2KO mice from week 7 – 11 of age, and to 8 weeks old C57BL/6mice fed a methionine and choline deficient diet (MCD) for 8 weeks. Hepatic fibrosis was assessed by hepatic hydroxyproline content. Serum biochemistries were determined by an autoanalyzer. Fibrosis and inflammation related transcript levels were quantified by quantitative real-time polymerase chain reaction (qPCR). Liver histology was assessed by connective tissue staining and histochemistry for inflammation and alpha-smooth muscle actin (alpha-SMA).

Results: In Mdr2KO mice, 10 and 50 mg/kg/day of Linagliptin decreased procollagenα1 (I) and TGFβ1, TIMP-1, MMP-8 transcript levels, and increased MMP-9 and -13. Mice fed the MCD diet showed a rapid induction of hepatic steatosis, inflammation and a 2-fold increase in relative collagen content compared to controls, with an up to 10-fold upregulation of procollagen α1(I), TGFβ1,aSMA, MMP-3 and- 9, TIMP-1, CCL3 and TNFa mRNA expression. In the MCD model, Linagliptin lowered serum ALT, AST, ALP and triglycerides, and at 50 mg/kg/day Linagliptin induced a yet insignificant decrease of aSMA, procollagen α1 (I), TIMP-1 and MMP-3 transcripts compared to the vehicle group.

Conclusion: In experimental biliary fibrosis (Mdr2KO mice) and in a surrogate NASH model (MCD) oral Linagliptin was well tolerated and lowered parameters of (hepatocyte) inflammation. Linagliptin demonstrated only a modest direct antifibrotic effect at a higher dose, possibly due to an inhibitory effect on fibroblast activation protein (FAP) rather than via induction of GLP-1.