Farnesoid X receptor and bile acids regulate vitamin A storage

Sci Rep. 2019 Dec 20;9(1):19493. doi: 10.1038/s41598-019-55988-w.

Abstract

The nuclear receptor Farnesoid X Receptor (FXR) is activated by bile acids and controls multiple metabolic processes, including bile acid, lipid, carbohydrate, amino acid and energy metabolism. Vitamin A is needed for proper metabolic and immune control and requires bile acids for efficient intestinal absorption and storage in the liver. Here, we analyzed whether FXR regulates vitamin A metabolism. Compared to control animals, FXR-null mice showed strongly reduced (>90%) hepatic levels of retinol and retinyl palmitate and a significant reduction in lecithin retinol acyltransferase (LRAT), the enzyme responsible for hepatic vitamin A storage. Hepatic reintroduction of FXR in FXR-null mice induced vitamin A storage in the liver. Hepatic vitamin A levels were normal in intestine-specific FXR-null mice. Obeticholic acid (OCA, 3 weeks) treatment rapidly reduced (>60%) hepatic retinyl palmitate levels in mice, concurrent with strongly increased retinol levels (>5-fold). Similar, but milder effects were observed in cholic acid (12 weeks)-treated mice. OCA did not change hepatic LRAT protein levels, but strongly reduced all enzymes involved in hepatic retinyl ester hydrolysis, involving mostly post-transcriptional mechanisms. In conclusion, vitamin A metabolism in the mouse liver heavily depends on the FXR and FXR-targeted therapies may be prone to cause vitamin A-related pathologies.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Acyltransferases / metabolism
  • Animals
  • Bile Acids and Salts / metabolism
  • Bile Acids and Salts / pharmacology*
  • Chenodeoxycholic Acid / analogs & derivatives
  • Chenodeoxycholic Acid / metabolism
  • Chenodeoxycholic Acid / pharmacology
  • Cholic Acid / metabolism
  • Cholic Acid / pharmacology
  • Hepatocytes / drug effects
  • Hepatocytes / metabolism
  • Liver / metabolism*
  • Mice
  • Mice, Knockout
  • Receptors, Cytoplasmic and Nuclear / metabolism*
  • Vitamin A / metabolism*

Substances

  • Bile Acids and Salts
  • Receptors, Cytoplasmic and Nuclear
  • obeticholic acid
  • farnesoid X-activated receptor
  • Chenodeoxycholic Acid
  • Vitamin A
  • Acyltransferases
  • lecithin-retinol acyltransferase
  • Cholic Acid