Increased P85α is a potent negative regulator of skeletal muscle insulin signaling and induces in vivo insulin resistance associated with growth hormone excess Academic Article uri icon

Overview

MeSH Major

  • Growth Hormone
  • Insulin
  • Insulin Resistance
  • Muscle, Skeletal
  • Phosphatidylinositol 3-Kinases
  • Signal Transduction

abstract

  • Insulin resistance is a cardinal feature of normal pregnancy and excess growth hormone (GH) states, but its underlying mechanism remains enigmatic. We previously found a significant increase in the p85 regulatory subunit of phosphatidylinositol kinase (PI 3-kinase) and striking decrease in IRS-1-associated PI 3-kinase activity in the skeletal muscle of transgenic animals overexpressing human placental growth hormone. Herein, using transgenic mice bearing deletions in p85alpha, p85beta, or insulin-like growth factor-1, we provide novel evidence suggesting that overexpression of p85alpha is a primary mechanism for skeletal muscle insulin resistance in response to GH. We found that the excess in total p85 was entirely accounted for by an increase in the free p85alpha-specific isoform. In mice with a liver-specific deletion in insulin-like growth factor-1, excess GH caused insulin resistance and an increase in skeletal muscle p85alpha, which was completely reversible using a GH-releasing hormone antagonist. To understand the role of p85alpha in GH-induced insulin resistance, we used mice bearing deletions of the genes coding for p85alpha or p85beta, respectively (p85alpha (+/-) and p85beta(-/-)). Wild type and p85beta(-/-) mice developed in vivo insulin resistance and demonstrated overexpression of p85alpha and reduced insulin-stimulated PI 3-kinase activity in skeletal muscle in response to GH. In contrast, p85alpha(+/-)mice retained global insulin sensitivity and PI 3-kinase activity associated with reduced p85alpha expression. These findings demonstrated the importance of increased p85alpha in mediating skeletal muscle insulin resistance in response to GH and suggested a potential role for reducing p85alpha as a therapeutic strategy for enhancing insulin sensitivity in skeletal muscle.

publication date

  • November 11, 2005

Research

keywords

  • Academic Article

Identity

Language

  • eng

Digital Object Identifier (DOI)

  • 10.1074/jbc.M506967200

PubMed ID

  • 16166093

Additional Document Info

start page

  • 37489

end page

  • 94

volume

  • 280

number

  • 45