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Inhibition of AMPK activity in response to insulin in adipocytes : involvement of AMPK pS485, PDEs, and cellular energy levels

Kopietz, Franziska LU orcid ; Rupar, Kaja LU ; Berggreen, Christine LU ; Säll, Johanna LU orcid ; Vertommen, Didier ; Degerman, Eva LU orcid ; Rider, Mark H. and Göransson, Olga LU orcid (2020) In American Journal of Physiology - Endocrinology and Metabolism 319(3). p.459-471
Abstract

Insulin resistance in obesity and type 2 diabetes has been shown to be associated with decreased de novo fatty acid (FA) synthesis in adipose tissue. It is known that insulin can acutely stimulate FA synthesis in adipocytes; however, the mechanisms underlying this effect are unclear. The rate-limiting step in FA synthesis is catalyzed by acetyl-CoA carboxylase (ACC), known to be regulated through inhibitory phosphorylation at S79 by the AMP-activated protein kinase (AMPK). Previous results from our laboratory showed an inhibition of AMPK activity by insulin, which was accompanied by PKB-dependent phosphorylation of AMPK at S485. However, whether the S485 phosphorylation is required for insulin-induced inhibition of AMPK or other... (More)

Insulin resistance in obesity and type 2 diabetes has been shown to be associated with decreased de novo fatty acid (FA) synthesis in adipose tissue. It is known that insulin can acutely stimulate FA synthesis in adipocytes; however, the mechanisms underlying this effect are unclear. The rate-limiting step in FA synthesis is catalyzed by acetyl-CoA carboxylase (ACC), known to be regulated through inhibitory phosphorylation at S79 by the AMP-activated protein kinase (AMPK). Previous results from our laboratory showed an inhibition of AMPK activity by insulin, which was accompanied by PKB-dependent phosphorylation of AMPK at S485. However, whether the S485 phosphorylation is required for insulin-induced inhibition of AMPK or other mechanisms underlie the reduced kinase activity is not known. To investigate this, primary rat adipocytes were transduced with a recombinant adenovirus encoding AMPK-WT or a nonphosphorylatable AMPK S485A mutant. AMPK activity measurements by Western blot analysis and in vitro kinase assay revealed that WT and S485A AMPK were inhibited to a similar degree by insulin, indicating that AMPK S485 phosphorylation is not required for insulin-induced AMPK inhibition. Further analysis suggested an involvement of decreased AMP-to-ATP ratios in the insulin-induced inhibition of AMPK activity, whereas a possible contribution of phosphodiesterases was excluded. Furthermore, we show that insulin-induced AMPK S485 phosphorylation also occurs in human adipocytes, suggesting it to be of an importance yet to be revealed. Altogether, this study increases our understanding of how insulin regulates AMPK activity, and with that, FA synthesis, in adipose tissue.

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author
; ; ; ; ; ; and
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
adipocytes, AMP-activated protein kinase, fatty acid synthesis, insulin, pS485
in
American Journal of Physiology - Endocrinology and Metabolism
volume
319
issue
3
pages
459 - 471
publisher
American Physiological Society
external identifiers
  • pmid:32663099
  • scopus:85089801017
ISSN
1522-1555
DOI
10.1152/ajpendo.00065.2020
language
English
LU publication?
yes
id
a9dc70fc-0d39-45d1-be08-44237b5a7056
date added to LUP
2020-09-07 11:40:50
date last changed
2024-03-20 15:51:15
@article{a9dc70fc-0d39-45d1-be08-44237b5a7056,
  abstract     = {{<p>Insulin resistance in obesity and type 2 diabetes has been shown to be associated with decreased de novo fatty acid (FA) synthesis in adipose tissue. It is known that insulin can acutely stimulate FA synthesis in adipocytes; however, the mechanisms underlying this effect are unclear. The rate-limiting step in FA synthesis is catalyzed by acetyl-CoA carboxylase (ACC), known to be regulated through inhibitory phosphorylation at S79 by the AMP-activated protein kinase (AMPK). Previous results from our laboratory showed an inhibition of AMPK activity by insulin, which was accompanied by PKB-dependent phosphorylation of AMPK at S485. However, whether the S485 phosphorylation is required for insulin-induced inhibition of AMPK or other mechanisms underlie the reduced kinase activity is not known. To investigate this, primary rat adipocytes were transduced with a recombinant adenovirus encoding AMPK-WT or a nonphosphorylatable AMPK S485A mutant. AMPK activity measurements by Western blot analysis and in vitro kinase assay revealed that WT and S485A AMPK were inhibited to a similar degree by insulin, indicating that AMPK S485 phosphorylation is not required for insulin-induced AMPK inhibition. Further analysis suggested an involvement of decreased AMP-to-ATP ratios in the insulin-induced inhibition of AMPK activity, whereas a possible contribution of phosphodiesterases was excluded. Furthermore, we show that insulin-induced AMPK S485 phosphorylation also occurs in human adipocytes, suggesting it to be of an importance yet to be revealed. Altogether, this study increases our understanding of how insulin regulates AMPK activity, and with that, FA synthesis, in adipose tissue.</p>}},
  author       = {{Kopietz, Franziska and Rupar, Kaja and Berggreen, Christine and Säll, Johanna and Vertommen, Didier and Degerman, Eva and Rider, Mark H. and Göransson, Olga}},
  issn         = {{1522-1555}},
  keywords     = {{adipocytes; AMP-activated protein kinase; fatty acid synthesis; insulin; pS485}},
  language     = {{eng}},
  number       = {{3}},
  pages        = {{459--471}},
  publisher    = {{American Physiological Society}},
  series       = {{American Journal of Physiology - Endocrinology and Metabolism}},
  title        = {{Inhibition of AMPK activity in response to insulin in adipocytes : involvement of AMPK pS485, PDEs, and cellular energy levels}},
  url          = {{http://dx.doi.org/10.1152/ajpendo.00065.2020}},
  doi          = {{10.1152/ajpendo.00065.2020}},
  volume       = {{319}},
  year         = {{2020}},
}