Prolonged Incubation in PUGNAc Results in Increased Protein O-Linked Glycosylation and Insulin Resistance in Rat Skeletal Muscle

  1. Edward B. Arias,
  2. Junghoon Kim and
  3. Gregory D. Cartee
  1. From the Department of Kinesiology, University of Wisconsin-Madison, Madison, Wisconsin
  1. Address correspondence and reprint requests to Edward B. Arias, PhD, Division of Kinesiology, University of Michigan, 401 Washtenaw Ave., Ann Arbor, MI 48109. E-mail: edarias{at}umich.edu

Abstract

Increased flux through the hexosamine biosynthetic pathway and increased O-linked glycosylation (N-acetylglucosamine [O-GlcNAc]) of proteins have been implicated in insulin resistance. Previous research in 3T3-L1 adipocytes indicated that insulin-stimulated glucose uptake and phosphorylation of Akt were reduced after incubation with O-(2-acetamido-2-deoxy-d-glucopyranosylidene)amino-N-phenylcarbamate (PUGNAc; 100 μmol/l), an inhibitor of the O-GlcNAcase that catalyzes removal of O-GlcNAc from proteins. Therefore, in this study, we tested the effects of PUGNAc on skeletal muscle. Incubation of rat epitrochlearis muscles for 19 h with 100 μmol/l PUGNAc resulted in a marked increase in O-GlcNAcylation of multiple proteins. Incubation with PUGNAc reduced glucose transport with a physiologic insulin concentration without affecting glucose transport without insulin or with supraphysiologic insulin. PUGNAc did not significantly alter insulin-stimulated phosphorylation of Akt (serine and threonine) or its substrates glycogen synthase kinase (GSK)3α and GSK3β. Insulin stimulated a dose-dependent (12.0 > 0.6 > 0 nmol/l) increase in the phosphorylation of a 160-kDa protein detected using an antibody against an Akt substrate phosphomotif. PUGNAc treatment did not alter phosphorylation of this protein. These results indicate that PUGNAc is an effective inhibitor of O-GlcNAcase in skeletal muscle and suggest that O-GlcNAc modification of proteins can induce insulin resistance in skeletal muscle independent of attenuated phosphorylation of Akt, GSK3α, GSK3β, and a 160-kDa protein with an Akt phosphomotif.

Footnotes

    • Accepted January 20, 2004.
    • Received July 1, 2003.
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