Effect of zinc-alpha2-glycoprotein (ZAG) on expression of uncoupling proteins in skeletal muscle and adipose tissue

Cancer Lett. 2004 Aug 20;212(1):71-81. doi: 10.1016/j.canlet.2004.03.021.

Abstract

The plasma protein zinc-alpha2-glycoprotein (ZAG) has been shown to be identical with a lipid mobilizing factor capable of inducing loss of adipose tissue in cancer cachexia through an increased lipid mobilization and utilization. The ability of ZAG to induce uncoupling protein (UCP) expression has been determined using in vitro models of adipose tissue and skeletal muscle. ZAG induced a concentration-dependent increase in the expression of UCP-1 in primary cultures of brown, but not white, adipose tissue, and this effect was attenuated by the beta3-adrenergic receptor (beta3-AR) antagonist SR59230A. A 6.5-fold increase in UCP-1 expression was found in brown adipose tissue after incubation with 0.58 microM ZAG. ZAG also increased UCP-2 expression 3.5-fold in C2C12 murine myotubes, and this effect was also attenuated by SR59230A and potentiated by isobutylmethylxanthine, suggesting a cyclic AMP-mediated process through interaction with a beta3-AR. ZAG also produced a dose-dependent increase in UCP-3 in murine myotubes with a 2.5-fold increase at 0.58 microM ZAG. This effect was not mediated through the beta3-AR, but instead appeared to require mitogen activated protein kinase. These results confirm the ability of ZAG to directly influence UCP expression, which may play an important role in lipid utilization during cancer cachexia.

MeSH terms

  • Adipocytes / physiology
  • Adipose Tissue / physiology*
  • Adipose Tissue, Brown / cytology
  • Adipose Tissue, Brown / metabolism
  • Animals
  • Cachexia / physiopathology*
  • Carrier Proteins / biosynthesis*
  • Carrier Proteins / pharmacology*
  • Cell Culture Techniques
  • Humans
  • Ion Channels
  • Lipid Metabolism
  • Membrane Proteins / biosynthesis*
  • Membrane Proteins / pharmacology*
  • Mice
  • Mitochondria
  • Mitochondrial Proteins
  • Muscle Fibers, Skeletal
  • Muscle, Skeletal / physiology*
  • Neoplasms / complications
  • Seminal Plasma Proteins / pharmacology*
  • Uncoupling Agents / pharmacology
  • Uncoupling Protein 1

Substances

  • Carrier Proteins
  • Ion Channels
  • Membrane Proteins
  • Mitochondrial Proteins
  • Seminal Plasma Proteins
  • UCP1 protein, human
  • Ucp1 protein, mouse
  • Uncoupling Agents
  • Uncoupling Protein 1
  • Zn-alpha-2-glycoprotein