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Troglitazone-binding to LDL and its glycated modifications: its role in cell-catalysed and Cu-mediated LDL-oxidation

G Sobal1, H Sinzinger, E J Menzel

  • 1Department of Nuclear Medicine, Radiopharmacology Unit, University of Vienna, Währinger Guertel 18-20, A-1090 Vienna, Austria.

Life Sciences
|March 28, 2003
PubMed

Insights

Troglitazone inhibits copper-induced oxidation of native and glycated low-density lipoprotein (LDL). However, its efficacy is reduced for glycoxidated LDL and diminishes over longer oxidation times.

Area of Science:

  • Biochemistry
  • Pharmacology
  • Cardiovascular Research

Background:

  • Low-density lipoprotein (LDL) oxidation is a key factor in atherosclerosis.
  • Modified LDL, such as glycated and glycoxidated forms, may have different susceptibility to oxidation.
  • Troglitazone (T) is an anti-diabetic drug known to improve insulin resistance.

Purpose of the Study:

  • To investigate the inhibitory effects of Troglitazone on copper ion-catalyzed oxidation of native, glycated, and glycoxidated LDL.
  • To explore the binding affinity of Troglitazone to different LDL modifications.
  • To assess Troglitazone's impact on endothelial cell-mediated LDL oxidation.

Main Methods:

  • Copper ion-catalyzed oxidation of native, glycated, and glycoxidated LDL was monitored.
  • Formation of thiobarbituric acid-reactive substances (TBARS) was measured.
  • Binding of Troglitazone to LDL was assessed.
  • Human umbilical vein endothelial cell-mediated LDL oxidation was evaluated.

Main Results:

  • Troglitazone exhibited dose-dependent inhibition of LDL oxidation (40-160 microg/ml).
  • Near-complete inhibition of native and glycated LDL oxidation was observed at 160 microg/ml T within 2-8 hours.
  • Maximal inhibition for glycoxidated LDL was 60%, with different binding characteristics.
  • In endothelial cell-mediated oxidation, Troglitazone reduced fluorescent chromophores and 8-epi-PGF2alpha, but not TBARS.

Conclusions:

  • Troglitazone effectively inhibits copper-mediated oxidation of native and glycated LDL, with varying efficacy depending on LDL modification and oxidation time.
  • Binding affinity of Troglitazone differs between LDL modifications, influencing its inhibitory action in copper-catalyzed oxidation.
  • Troglitazone demonstrates protective effects in endothelial cell-mediated LDL oxidation, though the mechanism differs from copper-catalyzed pathways.

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