Molecular Mechanisms of Insulin Resistance in Humans and Their Potential Links With Mitochondrial Dysfunction

  1. Katsutaro Morino,
  2. Kitt Falk Petersen and
  3. Gerald I. Shulman
  1. From the Howard Hughes Medical Institute, Departments of Internal Medicine and Cellular and Molecular Physiology, Yale University School of Medicine, New Haven, Connecticut
  1. Address correspondence and reprint requests to Gerald I. Shulman, MD, PhD, Howard Hughes Medical Institute, Yale University School of Medicine, P.O. Box 9812, New Haven, CT 06536-8012. E-mail: gerald.shulman{at}yale.edu

Abstract

Recent studies using magnetic resonance spectroscopy have shown that decreased insulin-stimulated muscle glycogen synthesis due to a defect in insulin-stimulated glucose transport activity is a major factor in the pathogenesis of type 2 diabetes. The molecular mechanism underlying defective insulin-stimulated glucose transport activity can be attributed to increases in intramyocellular lipid metabolites such as fatty acyl CoAs and diacylglycerol, which in turn activate a serine/threonine kinase cascade, thus leading to defects in insulin signaling through Ser/Thr phosphorylation of insulin receptor substrate (IRS)-1. A similar mechanism is also observed in hepatic insulin resistance associated with nonalcoholic fatty liver, which is a common feature of type 2 diabetes, where increases in hepatocellular diacylglycerol content activate protein kinase C-ε, leading to reduced insulin-stimulated tyrosine phosphorylation of IRS-2. More recently, magnetic resonance spectroscopy studies in healthy lean elderly subjects and healthy lean insulin-resistant offspring of parents with type 2 diabetes have demonstrated that reduced mitochondrial function may predispose these individuals to intramyocellular lipid accumulation and insulin resistance. Further analysis has found that the reduction in mitochondrial function in the insulin-resistant offspring can be mostly attributed to reductions in mitochondrial density. By elucidating the cellular and molecular mechanisms responsible for insulin resistance, these studies provide potential new targets for the treatment and prevention of type 2 diabetes.

Footnotes

  • This article is based on a presentation at a symposium. The symposium and the publication of this article were made possible by an unrestricted educational grant from Servier.

    The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.

    • Accepted May 27, 2006.
    • Received April 27, 2006.
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