Activation of the constitutive androstane receptor inhibits gluconeogenesis without affecting lipogenesis or fatty acid synthesis in human hepatocytes

Toxicol Appl Pharmacol. 2014 Aug 15;279(1):33-42. doi: 10.1016/j.taap.2014.05.009. Epub 2014 May 27.

Abstract

Objective: Accumulating evidence suggests that activation of mouse constitutive androstane receptor (mCAR) alleviates type 2 diabetes and obesity by inhibiting hepatic gluconeogenesis, lipogenesis, and fatty acid synthesis. However, the role of human (h) CAR in energy metabolism is largely unknown. The present study aims to investigate the effects of selective hCAR activators on hepatic energy metabolism in human primary hepatocytes (HPH).

Methods: Ligand-based structure-activity models were used for virtual screening of the Specs database (www.specs.net) followed by biological validation in cell-based luciferase assays. The effects of two novel hCAR activators (UM104 and UM145) on hepatic energy metabolism were evaluated in HPH.

Results: Real-time PCR and Western blotting analyses reveal that activation of hCAR by UM104 and UM145 significantly repressed the expression of glucose-6-phosphatase and phosphoenolpyruvate carboxykinase, two pivotal gluconeogenic enzymes, while exerting negligible effects on the expression of genes associated with lipogenesis and fatty acid synthesis. Functional experiments show that UM104 and UM145 markedly inhibit hepatic synthesis of glucose but not triglycerides in HPH. In contrast, activation of mCAR by 1,4-bis[2-(3,5-dichloropyridyloxy)]benzene, a selective mCAR activator, repressed the expression of genes associated with gluconeogenesis, lipogenesis, and fatty acid synthesis in mouse primary hepatocytes, which were consistent with previous observations in mouse model in vivo.

Conclusion: Our findings uncover an important species difference between hCAR and mCAR in hepatic energy metabolism, where hCAR selectively inhibits gluconeogenesis without suppressing fatty acid synthesis.

Implications: Such species selectivity should be considered when exploring CAR as a potential therapeutic target for metabolic disorders.

Keywords: Constitutive androstane receptor; Energy metabolism; Human primary hepatocytes; Species difference.

Publication types

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

MeSH terms

  • Animals
  • Blotting, Western
  • Cell Line
  • Computer Simulation
  • Energy Metabolism / drug effects
  • Fatty Acids / biosynthesis*
  • Gluconeogenesis / drug effects*
  • Glucose / metabolism
  • Glucose-6-Phosphatase / metabolism
  • Hepatocytes / drug effects
  • Hepatocytes / metabolism
  • Humans
  • Lipogenesis / drug effects*
  • Male
  • Mice
  • Mice, Inbred C57BL
  • Models, Molecular
  • Phosphoenolpyruvate Carboxykinase (ATP) / metabolism
  • Primary Cell Culture
  • Protein Transport / drug effects
  • Real-Time Polymerase Chain Reaction
  • Receptors, Cytoplasmic and Nuclear / agonists*
  • Triglycerides / metabolism

Substances

  • Fatty Acids
  • Receptors, Cytoplasmic and Nuclear
  • Triglycerides
  • constitutive androstane receptor
  • Glucose-6-Phosphatase
  • Phosphoenolpyruvate Carboxykinase (ATP)
  • Glucose