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: 294/3/E582    most recent 00312.2007v1 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 Google Scholar Articles by Mukwevho, E. Articles by Ojuka, E. O. PubMed PubMed Citation Articles by Mukwevho, E. Articles by Ojuka, E. O.

Caffeine induces hyperacetylation of histones at the MEF2 site on the Glut4 promoter and increases MEF2A binding to the site via a CaMK-dependent mechanism

¹University of Cape Town/Medical Research Council Research Unit for Exercise Science and Sports Medicine, Department of Human Biology; and ²Division of Neuroscience, Department of Human Biology, University of Cape Town, Cape Town, South Africa

Submitted 19 May 2007 ; accepted in final form 10 January 2008

This study was conducted to explore the mechanism by which caffeine increases GLUT4 expression in C₂C₁₂ myotubes. Myoblasts were differentiated in DMEM containing 2% horse serum for 13 days and the resultant myotubes exposed to 10 mM caffeine in the presence or absence of 25 µM KN93 or 10 mM dantrolene for 2 h. After the treatment, cells were kept in serum-free medium and harvested between 0 and 6 h later, depending on the assay. Chromatin immunoprecipitation (ChIP) assays revealed that caffeine treatment caused hyperacetylation of histone H3 at the myocyte enhancer factor 2 (MEF2) site on the Glut4 promoter (P < 0.05) and increased the amount of MEF2A that was bound to this site 2.2-fold (P < 0.05) 4 h posttreatment compared with controls. These increases were accompanied by an 1.8-fold rise (P < 0.05 vs. control) in GLUT4 mRNA content at 6 h post-caffeine treatment. Both immunoblot and immunocytochemical analyses showed reduced nuclear content of histone deacetylase-5 in caffeine-treated myotubes compared with controls at 0–2 h posttreatment. Inclusion of 10 mM dantrolene in the medium to prevent the increase in cytosolic Ca²⁺, or 25 µM KN93 to inhibit Ca²⁺/calmodulin-dependent protein kinase (CaMK II), attenuated all the above caffeine-induced changes. These data indicate that caffeine increases GLUT4 expression by acetylating the MEF2 site to increase MEF2A binding via a mechanism that involves CaMK II.

myocyte enhancer factor 2; glucose transporter 4; histone deacetylase; chromatin immunoprecipitation assay; Ca²⁺/calmodulin-dependent protein kinase II; histone H3