Deakin University
Browse

File(s) under permanent embargo

Creatine supplementation increases glycogen storage but not GLUT-4 expression in human skeletal muscle

journal contribution
posted on 2004-01-01, 00:00 authored by L van Loon, R Murphy, A Oosterlaar, David Cameron-Smith, Mark Hargreaves, A Wagenmakers, Rod SnowRod Snow
It has been speculated that creatine supplementation affects muscle glucose metabolism in humans by increasing muscle glycogen storage and up-regulating GLUT-4 protein expression. In the present study, we assessed the effects of creatine loading and prolonged supplementation on muscle glycogen storage and GLUT-4 mRNA and protein content in humans. A total of 20 subjects participated in a 6-week supplementation period during which creatine or a placebo was ingested. Muscle biopsies were taken before and after 5 days of creatine loading (20 g.day(-1)) and after 6 weeks of continued supplementation (2 g.day(-1)). Fasting plasma insulin concentrations, muscle creatine, glycogen and GLUT-4 protein content as well as GLUT-4, glycogen synthase-1 (GS-1) and glycogenin-1 (Gln-1) mRNA expression were determined. Creatine loading significantly increased total creatine, free creatine and creatine phosphate content with a concomitant 18 +/- 5% increase in muscle glycogen content (P<0.05). The subsequent use of a 2 g.day(-1) maintenance dose for 37 days did not maintain total creatine, creatine phosphate and glycogen content at the elevated levels. The initial increase in muscle glycogen accumulation could not be explained by an increase in fasting plasma insulin concentration, muscle GLUT-4 mRNA and/or protein content. In addition, neither muscle GS-1 nor Gln-1 mRNA expression was affected. We conclude that creatine ingestion itself stimulates muscle glycogen storage, but does not affect muscle GLUT-4 expression.

History

Journal

Clinical science

Volume

106

Pagination

99 - 106

Publisher

Portland Press Ltd

Location

London, England

ISSN

0143-5221

eISSN

1470-8736

Language

eng

Publication classification

C1 Refereed article in a scholarly journal

Copyright notice

2004, Biochemical Society