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Complementary roles of IRS-1 and IRS-2 in the hepatic regulation of metabolism
Cullen M. Taniguchi, … , Kohjiro Ueki, C. Ronald Kahn
Cullen M. Taniguchi, … , Kohjiro Ueki, C. Ronald Kahn
Published March 1, 2005
Citation Information: J Clin Invest. 2005;115(3):718-727. https://doi.org/10.1172/JCI23187.
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Article Metabolism

Complementary roles of IRS-1 and IRS-2 in the hepatic regulation of metabolism

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Abstract

Hepatic insulin resistance is a critical component in the development of type 2 diabetes mellitus. In many cases, insulin resistance in liver is associated with reduced expression of both major insulin receptor substrate (IRS) proteins, IRS-1 and IRS-2. To investigate the specific functions of IRS-1 and IRS-2 in regulating liver function in vivo, we developed an adenovirus-mediated RNA interference technique in which short hairpin RNAs (shRNAs) are used to knock down IRS-1, IRS-2, or both, by 70–80% in livers of WT mice. The knockdown of IRS-1 resulted in an upregulation of the gluconeogenic enzymes glucose-6 phosphatase and phosphoenolpyruvate carboxykinase, as well as a marked increase in hepatic nuclear factor–4 α. Decreased IRS-1 was also associated with a decrease in glucokinase expression and a trend toward increased blood glucose, whereas knockdown of IRS-2 resulted in the upregulation of lipogenic enzymes SREBP-1c and fatty acid synthase, as well as increased hepatic lipid accumulation. The concomitant injection of IRS-1 and IRS-2 adenoviral shRNAs resulted in systemic insulin resistance, glucose intolerance, and hepatic steatosis. The alterations in the dual-knockdown mice were associated with defective Akt activation and Foxo1 phosphorylation. Taken together, our results demonstrate that hepatic IRS-1 and IRS-2 have complementary roles in the control of hepatic metabolism, with IRS-1 more closely linked to glucose homeostasis and IRS-2 more closely linked to lipid metabolism.

Authors

Cullen M. Taniguchi, Kohjiro Ueki, C. Ronald Kahn

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