Regulation of skeletal muscle glucose transporter 4 expression in fructose-fed exercised rats

Several studies have found that the expression of skeletal muscle glucose transporter 4 (GLUT4) is decreased by high fructose consumption but increased by exercise. However, the amounts of fructose used in these studies were extremely high and the effects of moderate feeding protocols are not known. While it is known that exercise enhances GLUT4 expression via increased histone H3 acetylation and binding of the myocyte enhancer factor- 2A (MEF2A) transcription factor to its binding domain on the Glut4 gene promoter, the impact of fructose consumption on this interaction has not been studied. Moreover, there is no direct evidence that an increase in MEF2 binding is due to increased accessibility of the MEF2 binding domain to transcription factors. This study tested the hypothesis that both exercise and high fructose consumption affect GLUT4 expression by altering the accessibility of the MEF2 binding domain on the Glut4 gene promoter via remodelling of chromatin in that region. Male Wistar rats (n=30) were randomly assigned to three dietary groups: a) standard Chow, b) Chow + 10% fructose drink and c) Chow + 10% maltodextrin drink. All rats had access to drinking water and chow ad libitum for a period of 13 days. In the last 6 days of the experiment 5 animals in each group performed 3 x 17 min daily bouts of intermittent swimming, with a load equivalent to 5% bodyweight attached to their tails. The remaining 5 rats from each group were untrained. Animals were fasted overnight on the last day of the experiment, anaesthetized and sacrificed on the morning of day 14. Triceps muscle were harvested and used: (a) for measurement of total GLUT4 content by western blot, (b) to obtain nuclei for assessment of accessibility of a 350bp region encompassing the MEF2 element on the Glut4 gene using nuclease digestion assay, and (c) to measure the acetylation of histones H3 and bound MEF2A in the region above using chromatin immunoprecipitation (ChIP) assay. Blood was also collected and assayed for fasting serum glucose, insulin and free fatty acids.

Grantor dc:publisher.institution

MRC/UCT RU for Exercise and Sport Medicine

Year dc:date.issued

2013

Author dc:creator

• Goyaram, Veeraj

Advisor dc:contributor.advisor

• Ojuka, Edward O

Language dc:language.iso

eng

Handle dc:identifier.uri

http://hdl.handle.net/11427/2751

OAI identifier oai:identifier

oai:open.uct.ac.za:11427/2751