Insulin regulates adipocyte lipolysis via an Akt-independent signaling pathway

Mol Cell Biol. 2010 Nov;30(21):5009-20. doi: 10.1128/MCB.00797-10. Epub 2010 Aug 23.

Abstract

After a meal, insulin suppresses lipolysis through the activation of its downstream kinase, Akt, resulting in the inhibition of protein kinase A (PKA), the main positive effector of lipolysis. During insulin resistance, this process is ineffective, leading to a characteristic dyslipidemia and the worsening of impaired insulin action and obesity. Here, we describe a noncanonical Akt-independent, phosphoinositide-3 kinase (PI3K)-dependent pathway that regulates adipocyte lipolysis using restricted subcellular signaling. This pathway selectively alters the PKA phosphorylation of its major lipid droplet-associated substrate, perilipin. In contrast, the phosphorylation of another PKA substrate, hormone-sensitive lipase (HSL), remains Akt dependent. Furthermore, insulin regulates total PKA activity in an Akt-dependent manner. These findings indicate that localized changes in insulin action are responsible for the differential phosphorylation of PKA substrates. Thus, we identify a pathway by which insulin regulates lipolysis through the spatially compartmentalized modulation of PKA.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • 3T3-L1 Cells
  • Adipocytes / drug effects*
  • Adipocytes / metabolism*
  • Animals
  • Base Sequence
  • Cells, Cultured
  • Cyclic AMP-Dependent Protein Kinases / metabolism
  • Gene Knockdown Techniques
  • Insulin / metabolism*
  • Insulin / pharmacology*
  • Insulin Resistance
  • Lipolysis / drug effects*
  • Lipolysis / physiology
  • Mice
  • Phosphatidylinositol 3-Kinases / metabolism
  • Proto-Oncogene Proteins c-akt / antagonists & inhibitors
  • Proto-Oncogene Proteins c-akt / genetics
  • Proto-Oncogene Proteins c-akt / metabolism
  • RNA, Small Interfering / genetics
  • Signal Transduction

Substances

  • Insulin
  • RNA, Small Interfering
  • Phosphatidylinositol 3-Kinases
  • Akt2 protein, mouse
  • Proto-Oncogene Proteins c-akt
  • Cyclic AMP-Dependent Protein Kinases