Effect of oral creatine supplementation on human muscle GLUT4 protein content after immobilization

The purpose of this study was to investigate the effect of oral creatine su pplementation on muscle GLUT4 protein content and total creatine and glycog en content during muscle disuse and subsequent training. A double-blind pla cebo-controlled trial was performed with 22 young healthy volunteers. The r ight leg of each subject was immobilized using a cast for 2 weeks, after wh ich subjects participated in a 10-week heavy resistance training program in volving the knee-extensor muscles (three sessions per week). Half of the su bjects received creatine monohydrate supplements (20 g daily during the imm obilization period and 15 and 5 g daily during the first 3 and the last 7 w eeks of rehabilitation training, respectively), whereas the other 11 subjec ts ingested placebo (maltodextrine). Muscle GLUT4 protein content and glyco gen and total creatine concentrations were assayed in needle biopsy samples from the vastus lateralis muscle before and after immobilization and after 3 and 10 weeks of training. Immobilization decreased GLUT4 in the placebo group (-20%, P < 0.05), but not in the creatine group (+9% NS). Glycogen an d total creatine were unchanged in both groups during the immobilization pe riod. In the placebo group, during training, GLUT4 was normalized, and glyc ogen and total creatine were stable. Conversely, in the creatine group, GLU T4 increased by <similar to>40% (P < 0.05) during rehabilitation. Muscle gl ycogen and total creatine levels were higher in the creatine group after 3 weeks of rehabilitation (P < 0.05), but not after 10 weeks of rehabilitatio n. We concluded that 1) oral creatine supplementation offsets the decline i n muscle GLUT4 protein content that occurs during immobilization, and 2) or al creatine supplementation increases GLUT4 protein content during subseque nt rehabilitation training in healthy subjects.