Ursodeoxycholic acid is a GPBAR1 agonist and resets liver/intestinal FXR signaling in a model of diet-induced dysbiosis and NASH

Biochim Biophys Acta Mol Cell Biol Lipids. 2019 Oct;1864(10):1422-1437. doi: 10.1016/j.bbalip.2019.07.006. Epub 2019 Jul 17.

Abstract

Obeticholic acid (OCA) is a farnesoid-X-receptor (FXR) ligand, shown effective in reducing steatosis and fibrosis in NASH patients. However, OCA causes major side effects including pruritus, while increases the risk for liver decompensation in cirrhotic patients. Ursodeoxycholic acid (UDCA), is a safe and unexpensive bile acid used in the treatment of liver disorders whose mechanism of action is poorly defined. Here we have compared the effects of OCA and UDCA in a mouse model of NASH. In mice exposed to a diet rich in fat/cholesterol and fructose (HFD-F), treatment with OCA or UDCA effectively prevented body weight gain, insulin resistance, as demonstrated by OGTT, and AST plasma levels. After 12 weeks HFD-F mice developed liver microvesicular steatosis, inflammation and mild fibrosis, increased expression of inflammatory (TNFα, IL6, F4/80) and fibrosis (αSma, Col1α1, Tgfβ) markers, reduced liver expression of FXR, dysregulated liver FXR signaling and elevated levels of Tauro-α and β-muricholic acid (T-α and βMCA), two FXR antagonists in mice. Both compounds prevented these changes and improved liver histopathology. OCA reduced primary bile acid synthesis worsening the T-CA/T-βMCA ratio. UDCA effectively transactivated GPBAR1 in vitro. By RNAseq analysis we found that among over 2400 genes modulated by the HFD-F, only 32 and 60 genes were modulated by OCA and UDCA, with only 3 genes (Dbp, Adh7, Osgin1) being modulated by both agents. Both agents partially prevented the intestinal dysbiosis. CONCLUSIONS: UDCA is a GPBAR1 ligand and exerts beneficial effects in a rodent model of NASH by activating non-overlapping pathway with OCA.

Keywords: Bile acids; FXR; GPBAR1; NASH; Obeticholic acid; Ursodeoxycholic acid.

MeSH terms

  • Animals
  • Chenodeoxycholic Acid / analogs & derivatives*
  • Chenodeoxycholic Acid / therapeutic use
  • Diet / adverse effects
  • Dysbiosis / drug therapy*
  • Dysbiosis / etiology
  • Dysbiosis / metabolism
  • Humans
  • Male
  • Mice, Inbred C57BL
  • Non-alcoholic Fatty Liver Disease / drug therapy*
  • Non-alcoholic Fatty Liver Disease / etiology
  • Non-alcoholic Fatty Liver Disease / metabolism
  • Receptors, Cytoplasmic and Nuclear / metabolism*
  • Receptors, G-Protein-Coupled / agonists*
  • Receptors, G-Protein-Coupled / metabolism
  • Signal Transduction / drug effects
  • Ursodeoxycholic Acid / therapeutic use*

Substances

  • GPBAR1 protein, human
  • Receptors, Cytoplasmic and Nuclear
  • Receptors, G-Protein-Coupled
  • obeticholic acid
  • farnesoid X-activated receptor
  • Chenodeoxycholic Acid
  • Ursodeoxycholic Acid