HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Full Text (PDF) All Versions of this Article: 292/3/E884    most recent 00569.2006v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in ISI Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via ISI Web of Science (3) Citing Articles via Google Scholar Google Scholar Articles by Robinson, K. A. Articles by Buse, M. G. Search for Related Content PubMed PubMed Citation Articles by Robinson, K. A. Articles by Buse, M. G.

Reduction of O-GlcNAc protein modification does not prevent insulin resistance in 3T3-L1 adipocytes

Department of Medicine, Division of Endocrinology, Diabetes, and Medical Genetics, Medical University of South Carolina, Charleston, South Carolina

Submitted 20 October 2006 ; accepted in final form 16 November 2006

3T3-L1 adipocytes develop insulin-resistant glucose transport upon preincubation with high (25 mM) glucose, provided that insulin (0.6 nM) is included, Akt activation is impaired, and high glucose and insulin act synergistically. Considerable evidence suggests that increased glucose flux via the hexosamine biosynthesis pathway enhances the O-GlcNAc modification (O-GlcNAcylation) of some critical protein(s) that may contribute to insulin resistance. However, whether enhanced protein O-GlcNAcylation is necessary for the development of insulin resistance is unknown. We used two strategies to test this hypothesis. The first strategy was the overexpression of O-GlcNAcase, which removes O-GlcNAc from Ser/Thr of proteins. Cells were infected with O-GlcNAcase-expressing adenovirus (or empty virus) 5 days before they were submitted to protocols that elicit (or not) insulin resistance. O-GlcNAcase was highly expressed and functional as assessed by Western blot, O-GlcNAcase assay, and marked reduction of O-GlcNAcylated proteins. The activity was mainly cytosolic. The second strategy was the expression of O-GlcNAc transferase (OGT) being markedly reduced by transfection of OGT siRNA, resulting in an approximately 90% decrease of nuclear and cytosolic OGT protein expression and similar reduction in O-GlcNAcylated proteins. Nontargeting siRNA had no effect. Preincubation in high glucose with low-dose insulin decreased the acute insulin response of glucose transport by at least 50% and impaired Akt activation. None of these parameters were affected by overexpression of O-GlcNAcase or by OGT knockout. Excess O-GlcNAcylation is one of many factors that can cause insulin resistance. It does not seem to be required for the development of glucose/insulin-induced insulin resistance of glucose transport and Akt activation in 3T3-L1 adipocytes.

glucose transport; Akt activation; O-linked N-acetylglucosamine

This article has been cited by other articles:

				R. J. Copeland, J. W. Bullen, and G. W. Hart Cross-talk between GlcNAcylation and phosphorylation: roles in insulin resistance and glucose toxicity Am J Physiol Endocrinol Metab, July 1, 2008; 295(1): E17 - E28. [Abstract] [Full Text] [PDF]

				K. A. Robinson and M. G. Buse Mechanisms of high-glucose/insulin-mediated desensitization of acute insulin-stimulated glucose transport and Akt activation Am J Physiol Endocrinol Metab, May 1, 2008; 294(5): E870 - E881. [Abstract] [Full Text] [PDF]