Hypoxia inhibits Cavin-1 and Cavin-2 expression and down-regulates caveolae in adipocytes

Endocrinology. 2015 Mar;156(3):789-801. doi: 10.1210/en.2014-1656. Epub 2014 Dec 18.

Abstract

During obesity, a hypoxic state develops within the adipose tissue, resulting in insulin resistance. To understand the underlying mechanism, we analyzed the involvement of caveolae because they play a crucial role in the activation of insulin receptors. In the present study, we demonstrate that in 3T3-L1 adipocytes, hypoxia induces the disappearance of caveolae and inhibits the expression of Cavin-1 and Cavin-2, two proteins necessary for the formation of caveolae. In mice, hypoxia induced by the ligature of the spermatic artery results in the decrease of cavin-1 and cavin-2 expression in the epididymal adipose tissue. Down-regulation of the expression of cavins in response to hypoxia is dependent on hypoxia-inducible factor-1. Indeed, the inhibition of hypoxia-inducible factor-1 restores the expression of cavins and caveolae formation. Expression of cavins regulates insulin signaling because the silencing of cavin-1 and cavin-2 impairs insulin signaling pathway. In human, cavin-1 and cavin-2 are decreased in the sc adipose tissue of obese diabetic patients compared with lean subjects. Moreover, the expression of cavin-2 correlates negatively with the homeostatic model assessment index of insulin resistance and glycated hemoglobin level. In conclusion, we propose a new mechanism in which hypoxia inhibits cavin-1 and cavin-2 expression, resulting in the disappearance of caveolae. This leads to the inhibition of insulin signaling and the establishment of insulin resistance.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • 3T3-L1 Cells
  • Adipocytes / drug effects*
  • Adipocytes / metabolism
  • Animals
  • Carrier Proteins / genetics
  • Carrier Proteins / metabolism
  • Caveolae / physiology*
  • Down-Regulation
  • Female
  • Humans
  • Hypoxia-Inducible Factor 1, alpha Subunit / genetics
  • Hypoxia-Inducible Factor 1, alpha Subunit / metabolism
  • Male
  • Membrane Proteins / genetics
  • Membrane Proteins / metabolism*
  • Mice
  • Mice, Inbred C57BL
  • Obesity
  • Oxygen / pharmacology*
  • Phosphate-Binding Proteins
  • RNA Interference
  • RNA, Small Interfering
  • RNA-Binding Proteins / genetics
  • RNA-Binding Proteins / metabolism*
  • Signal Transduction

Substances

  • CAVIN1 protein, human
  • CAVIN2 protein, human
  • Carrier Proteins
  • Cavin1 protein, mouse
  • Hif1a protein, mouse
  • Hypoxia-Inducible Factor 1, alpha Subunit
  • Membrane Proteins
  • Phosphate-Binding Proteins
  • RNA, Small Interfering
  • RNA-Binding Proteins
  • cavin-2 protein, mouse
  • Oxygen