Effect of testosterone on insulin stimulated IRS1 ser phosphorylation in primary rat myotubes - A potential model for PCOS-related insulin resistance

Michael C. Allemand, Brian A. Irving, Yan W. Asmann, Katherine A. Klaus, Laura Tatpati, Charles C. Coddington, Sreekumaran Nair

Research output: Contribution to journalArticlepeer-review

45 Scopus citations

Abstract

Background: Polycystic ovary syndrome (PCOS) is characterized by a hyperandrogenic state and frequently develops skeletal muscle insulin resistance. We determined whether testosterone adversely affects insulin action by increasing serine phosphorylation of IRS-1636/639 in differentiated rat skeletal muscle myotubes. The phosphorylation of Akt, mTOR, and S6K, downstream targets of the PI3-kinase-IRS-1 complex were also studied. Methods: Primary differentiated rat skeletal muscle myotubes were subjected to insulin for 30 min after 16-hour pre-exposure to either low (20 ng/ml) or high (200 ng/ml) doses of testosterone. Protein phosphorylation of IRS-1 Ser636/639, Akt Ser473, mTOR-Ser2448, and S6K-Thr389 were measured by Western blot with signal intensity measured by immunofluorescence. Results: Cells exposed to 100 nM of insulin had increased IRS-1 Ser636/639 and Akt Ser473 phosphorylation. Cells pre-exposed to low-dose testosterone had significantly increased insulin-induced mTOR-Ser2448 and S6K-Thr389 phosphorylation (p,0.05), and further increased insulin-induced IRS-1 Ser636/639 phosphorylation (p = 0.042) compared to control cells. High-dose testosterone pre-exposure attenuated the insulin-induced mTOR-Ser2448 and S6K-Thr389 phosphorylation. Conclusions: The data demonstrated an interaction between testosterone and insulin on phosphorylation of intracellular signaling proteins, and suggests a link between a hyperandrogenic, hyperinsulinemic environment and the development of insulin resistance involving serine phosphorylation of IRS-1 Ser636/639. These results may guide further investigations of potential mechanisms of PCOS-related insulin resistance.

Original languageEnglish (US)
Article numbere4274
JournalPloS one
Volume4
Issue number1
DOIs
StatePublished - Jan 26 2009

ASJC Scopus subject areas

  • Biochemistry, Genetics and Molecular Biology(all)
  • Agricultural and Biological Sciences(all)
  • General

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