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Metabolic effects of rexinoids: tissue-specific regulation of lipoprotein lipase activity

P J Davies1, S A Berry, G L Shipley

  • 1Department of Integrative Biology and Pharmacology, University of Texas School of Medicine, Houston, Texas 77225, USA. peter.j.davies@uth.tmc.edu

Molecular Pharmacology
|February 13, 2001
PubMed

Insights

RXR-selective retinoids, or rexinoids, increase triglyceride levels by reducing lipoprotein lipase activity in muscle tissue. This suggests rexinoids impact post-translational processing, distinct from other retinoid receptors.

Area of Science:

  • Biochemistry
  • Molecular Biology
  • Endocrinology

Background:

  • Hypertriglyceridemia is a common side effect of retinoid and rexinoid therapies.
  • Retinoid X receptor (RXR)-selective retinoids (rexinoids) are used in patient treatment.

Purpose of the Study:

  • To investigate the cellular and molecular mechanisms behind rexinoid-induced hypertriglyceridemia.
  • To examine the effects of rexinoids on triglyceride metabolism in normal and diabetic rodents.

Main Methods:

  • Administration of rexinoid LG100268 (LG268) to normal and diabetic rats.
  • Measurement of serum triglyceride levels, hepatic triglyceride production, and post-heparin plasma lipoprotein lipase (LPL) activity.
  • Analysis of LPL activity and mRNA in C2C12 myocytes and rodent tissues (skeletal muscle, cardiac muscle, adipose tissue).

Main Results:

  • LG268 administration rapidly increased serum triglyceride levels in rats.
  • LG268 suppressed peripheral LPL activity, particularly in skeletal and cardiac muscle, but not adipose tissue.
  • In C2C12 myocytes, LG268 rapidly decreased cell surface LPL activity without affecting LPL mRNA levels, indicating post-translational regulation.
  • This effect was blocked by actinomycin D, suggesting a requirement for ongoing transcription.

Conclusions:

  • RXR ligands significantly impact the post-translational processing of lipoprotein lipase.
  • Skeletal muscle may be a key target tissue for rexinoid action regarding LPL regulation.
  • The metabolic effects of RXR activation are distinct from those of retinoic acid receptor or peroxisome proliferator-activated receptor activation.

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