Regulation of retinal dehydrogenases and retinoic acid synthesis by cholesterol metabolites

EMBO J. 2006 Jul 12;25(13):3203-13. doi: 10.1038/sj.emboj.7601181. Epub 2006 Jun 8.

Abstract

Retinoic acid (RA) constitutes the major active ingredient of vitamin A and is required for various biological processes. The tissue RA level is maintained through a cascade of metabolic reactions where retinal dehydrogenases (RALDHs) catalyze the terminal reaction of RA biosynthesis from retinal, a rate-limiting step. We showed that dietary supplement of cholesterol enhanced the expression of RALDH1 and 2 genes and the cellular RA content in vital organs such as brain, kidney, liver and heart. Consistently, the cholesterol-lowering agent (pravastatin sodium) downregulated the expression of RALDH1 and 2 genes in several organs especially the liver and in cultured liver cells. Further, cholesterol metabolites, predominantly the oxysterols, the natural ligands for liver X receptor (LXR), induced these genes via upregulation of sterol regulatory element binding protein-1c (SREBP-1c) that bound to the regulatory regions of these genes. Knockdown of LXRalpha/beta or SREBP-1c downregulated the expression of RALDH genes, which could be rescued by re-expressing SREBP-1c, suggesting SREBP-1c as a direct positive regulator for these genes. This study uncovered a novel crosstalk between cholesterol and RA biosynthesis.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Aldehyde Oxidoreductases / biosynthesis
  • Aldehyde Oxidoreductases / physiology
  • Animals
  • Anticholesteremic Agents / pharmacology
  • Cells, Cultured
  • Cholesterol / metabolism*
  • Cholesterol, Dietary / metabolism
  • DNA-Binding Proteins / genetics
  • DNA-Binding Proteins / metabolism
  • Gene Expression Regulation
  • Liver X Receptors
  • Male
  • Mice
  • Mice, Inbred ICR
  • Organ Specificity
  • Orphan Nuclear Receptors
  • Pravastatin / pharmacology
  • Promoter Regions, Genetic
  • Receptors, Cytoplasmic and Nuclear / genetics
  • Receptors, Cytoplasmic and Nuclear / metabolism
  • Response Elements
  • Retinal Dehydrogenase / biosynthesis
  • Retinal Dehydrogenase / physiology*
  • Sterol Regulatory Element Binding Protein 1 / biosynthesis
  • Tretinoin / metabolism*

Substances

  • Anticholesteremic Agents
  • Cholesterol, Dietary
  • DNA-Binding Proteins
  • Liver X Receptors
  • Nr1h3 protein, mouse
  • Orphan Nuclear Receptors
  • Receptors, Cytoplasmic and Nuclear
  • Sterol Regulatory Element Binding Protein 1
  • Tretinoin
  • Cholesterol
  • Aldehyde Oxidoreductases
  • RALDH2 protein, mouse
  • Retinal Dehydrogenase
  • Pravastatin