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Troglitazone induces expression of PPARgamma in liver

G F Davies1, R L Khandelwal, W J Roesler

  • 1Department of Biochemistry, University of Saskatchewan, Saskatoon, Canada.

Molecular Cell Biology Research Communications : MCBRC
|February 9, 2000
PubMed

Insights

Troglitazone increases peroxisome proliferator-activated receptor gamma (PPARγ) in liver cells. This induction may explain how troglitazone sensitizes the liver to insulin and improves hyperglycemia.

Area of Science:

  • Pharmacology
  • Molecular Biology
  • Hepatology

Background:

  • Troglitazone is an insulin sensitizer acting via peroxisome proliferator-activated receptor gamma (PPARγ).
  • PPARγ levels are often low in target organs like the liver, where other PPAR isoforms predominate.
  • The mechanism by which troglitazone sensitizes liver to insulin requires further elucidation.

Purpose of the Study:

  • To investigate whether troglitazone induces PPARγ expression in liver cells.
  • To determine if troglitazone alters the expression of other PPAR isoforms (α and β).
  • To explore the potential role of PPARγ induction in troglitazone's mechanism of action.

Main Methods:

  • Treatment of isolated rat hepatocytes with troglitazone and 15-deoxy-delta12,14-prostaglandin J2.
  • Analysis of PPARγ mRNA and protein levels via dose-dependent assays.
  • Administration of troglitazone-containing diet to rats and subsequent liver analysis.
  • Assessment of PPARα and PPARβ expression levels.

Main Results:

  • Troglitazone significantly increased PPARγ mRNA and protein levels in rat hepatocytes (3-4 fold induction).
  • 15-deoxy-delta12,14-prostaglandin J2, a PPARγ ligand, also induced PPARγ expression, while PPARα ligands had no effect.
  • Troglitazone administration to rats increased hepatic PPARγ expression.
  • Troglitazone did not affect the expression of PPARα or PPARβ isoforms in the liver.

Conclusions:

  • Troglitazone induces PPARγ expression in liver cells and in vivo.
  • This induction represents a reprogramming of hepatic PPAR isoform content.
  • PPARγ induction by troglitazone may contribute to its insulin-sensitizing effects and hyperglycemia amelioration in the liver.

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