AMPK enhances insulin-stimulated GLUT4 regulation via lowering membrane cholesterol

Kirk M. Habegger, Nolan J. Hoffman, Colin M. Ridenour, Joseph T. Brozinick, Jeffrey Elmendorf

Research output: Contribution to journalArticle

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Abstract

AMP-activated protein kinase (AMPK) enhances glucose transporter GLUT4 regulation. AMPK also suppresses energy-consuming pathways such as cholesterol synthesis. Interestingly, recent in vitro and in vivo data suggest that excess membrane cholesterol impairs GLUT4 regulation. Therefore, this study tested whether a beneficial, GLUT4-regulatory aspect of AMPK stimulation involved cholesterol lowering. Using L6 myotubes stably expressing an exofacial myc-epitope-tagged-GLUT4, AMPK stimulation by 5-aminoimidazole-4-carboxamide-1- β-D-ribonucleoside (AICAR; 45 min, 1 mM) or 2,4-dinitrophenol (DNP; 30 min, 200 μM) increased cell surface GLUT4myc labeling by approximately ∼25% (P < 0.05). Insulin (20 min, 100 nM) also increased GLUT4myc labeling by about 50% (P < 0.05), which was further enhanced (∼25%, P < 0.05) by AICAR or DNP. Consistent with AMPK-mediated suppression of cholesterol synthesis, AICAR and DNP decreased membrane cholesterol by 20-25% (P< 0.05). Whereas AMPK knockdown prevented the enhanced basal and insulin-stimulated GLUT4myc labeling by AICAR and DNP, cholesterol replenishment only blocked the AMPK-associated enhancement in insulin action. Cells cultured in a hyperinsulinemic milieu, resembling conditions in vivo that promote the progression/worsening of insulin resistance, displayed an increase in membrane cholesterol. This occurred concomitantly with a loss of cortical filamentous actin (F-actin) and defects in GLUT4 regulation by insulin. These derangements were prevented by AMPK stimulation. Examination of skeletal muscle from insulin-resistant Zucker rats revealed a similar elevation in membrane cholesterol and loss of F-actin. Lowering cholesterol to control levels restored F-actin structure and insulin sensitivity. In conclusion, these data suggest a novel aspect of GLUT4 regulation by AMPK involves membrane cholesterol lowering. Moreover, this AMPK-mediated process protected against hyperinsulinemia-induced insulin resistance.

Original languageEnglish
Pages (from-to)2130-2141
Number of pages12
JournalEndocrinology
Volume153
Issue number5
DOIs
StatePublished - May 2012

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AMP-Activated Protein Kinases
Cholesterol
Insulin
Membranes
Insulin Resistance
2,4-Dinitrophenol
Actins
Aminoimidazole Carboxamide
Ribonucleosides
Zucker Rats
Facilitative Glucose Transport Proteins
Skeletal Muscle Fibers
Hyperinsulinism
Epitopes
Cultured Cells
Skeletal Muscle

ASJC Scopus subject areas

  • Endocrinology

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AMPK enhances insulin-stimulated GLUT4 regulation via lowering membrane cholesterol. / Habegger, Kirk M.; Hoffman, Nolan J.; Ridenour, Colin M.; Brozinick, Joseph T.; Elmendorf, Jeffrey.

In: Endocrinology, Vol. 153, No. 5, 05.2012, p. 2130-2141.

Research output: Contribution to journalArticle

Habegger, KM, Hoffman, NJ, Ridenour, CM, Brozinick, JT & Elmendorf, J 2012, 'AMPK enhances insulin-stimulated GLUT4 regulation via lowering membrane cholesterol', Endocrinology, vol. 153, no. 5, pp. 2130-2141. https://doi.org/10.1210/en.2011-2099
Habegger, Kirk M. ; Hoffman, Nolan J. ; Ridenour, Colin M. ; Brozinick, Joseph T. ; Elmendorf, Jeffrey. / AMPK enhances insulin-stimulated GLUT4 regulation via lowering membrane cholesterol. In: Endocrinology. 2012 ; Vol. 153, No. 5. pp. 2130-2141.
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