Inhibition of the anti-adipogenic Hedgehog signaling pathway by cyclopamine does not trigger adipocyte differentiation

Biochem Biophys Res Commun. 2006 Oct 20;349(2):799-803. doi: 10.1016/j.bbrc.2006.08.112. Epub 2006 Aug 28.

Abstract

Dysregulation of Hedgehog signaling can lead to several pathologies such as congenital defects and cancer. Here, we show that Hedgehog signaling is active in undifferentiated 3T3-L1 cells and decreases during adipocyte differentiation. Interestingly, this is paralleled by a decrease in Indian Hedgehog expression. We then tested if this down-regulation was sufficient to induce adipocyte differentiation. To this end, we demonstrate that the well-characterized Hedgehog inhibitor cyclopamine induced a decrease in Hedgehog signaling, similar to the one observed during adipocyte differentiation. However, cyclopamine did not induce nor potentiate adipocyte differentiation, as monitored by triglyceride staining and by the expression of several adipocyte markers: aP2, adipsin, C/EBPalpha, and Pref-1. Moreover, cyclopamine cannot substitute for other components of the differentiation medium: insulin, dexamethasone or IBMX. These results indicate that although Hedgehog signaling decreases during adipocyte differentiation, this down-regulation is not sufficient to trigger adipocyte differentiation. This suggests that Hedgehog signaling is an inadequate pharmacological target for patient suffering from syndromes associated with a decrease in fat mass, such as the ones observed in lipodystrophies.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • 1-Methyl-3-isobutylxanthine / pharmacology
  • 3T3-L1 Cells
  • Adipocytes / cytology*
  • Adipocytes / metabolism
  • Animals
  • Cell Differentiation
  • Dexamethasone / pharmacology
  • Hedgehog Proteins
  • Insulin / metabolism
  • Lipodystrophy / metabolism
  • Mice
  • Oncogene Proteins / metabolism
  • Signal Transduction
  • Time Factors
  • Trans-Activators / antagonists & inhibitors
  • Trans-Activators / metabolism*
  • Veratrum Alkaloids / metabolism
  • Veratrum Alkaloids / pharmacology*
  • Zinc Finger Protein GLI1

Substances

  • Hedgehog Proteins
  • Insulin
  • Oncogene Proteins
  • Trans-Activators
  • Veratrum Alkaloids
  • Zinc Finger Protein GLI1
  • Dexamethasone
  • 1-Methyl-3-isobutylxanthine
  • cyclopamine