title: Combined creatine and protein supplementation in conjunction with resistance training promotes muscle GLUT-4 content and glucose tolerance in humans.
abstract: The present study was undertaken to explore the effects of creatine and creatine plus protein supplementation on GLUT-4 and glycogen content of human skeletal muscle. This was investigated in muscles undergoing a decrease (immobilization) and subsequent increase (resistance training) in activity level, compared with muscles with unaltered activity pattern. A double-blind, placebo-controlled trial was performed by 33 young healthy subjects. The subjects' right legs were immobilized with a cast for 2 wk, followed by a 6-wk resistance training program for the right knee extensor muscles. The participants were supplemented throughout the study with either placebo (Pl group) or creatine (Cr group) or with creatine during immobilization and creatine plus protein during retraining (Cr+P group). Needle biopsies were bilaterally taken from the vastus lateralis. GLUT-4 protein expression was reduced by the immobilization in all groups (P < 0.05). During retraining, GLUT-4 content increased (P < 0.05) in both Cr (+24%) and Cr+P (+33%), which resulted in higher posttraining GLUT-4 expression compared with Pl (P < 0.05). Compared with Pl, muscle glycogen content was higher (P < 0.05) in the trained leg in both Cr and Cr+P. Supplements had no effect on GLUT-4 expression or glycogen content in contralateral control legs. Area under the glucose curve during the oral glucose tolerance test was decreased from 232 +/- 23 mmol. l(-1). min(-1) at baseline to 170 +/- 23 mmol. l(-1). min(-1) at the end of the retraining period in Cr+P (P < 0.05), but it did not change in Cr or Pl. We conclude that creatine intake stimulates GLUT-4 and glycogen content in human muscle only when combined with changes in habitual activity level. Furthermore, combined protein and creatine supplementation improved oral glucose tolerance, which is supposedly unrelated to the changes in muscle GLUT-4 expression.
authors.affiliation: Exercise Physiology and Biomechanics Laboratory, Department of Kinesiology, Katholieke Universiteit Leuven, 3001, Belgium. wim.derave@flok.kuleuven.ac.be
authors.forename: Wim
authors.initials: W
authors.lastname: Derave
authors.forename: Bert O
authors.initials: BO
authors.lastname: Eijnde
authors.forename: Patricia
authors.initials: P
authors.lastname: Verbessem
authors.forename: Monique
authors.initials: M
authors.lastname: Ramaekers
authors.forename: Mark
authors.initials: M
authors.lastname: Van Leemputte
authors.forename: Erik A
authors.initials: EA
authors.lastname: Richter
authors.forename: Peter
authors.initials: P
authors.lastname: Hespel
mesh_terms: D000293:Adolescent; D000328:Adult; D001786:Blood Glucose / Q000378:metabolism; D001835:Body Weight / Q000187:drug effects; D002452:Cell Count; D003401:Creatine / Q000378:metabolism / Q000494:pharmacology*; D004044:Dietary Proteins / Q000494:pharmacology*; D004311:Double-Blind Method; D005260:Female; D007839:Functional Laterality / Q000502:physiology; D005947:Glucose / Q000378:metabolism*; D005951:Glucose Tolerance Test; D051275:Glucose Transporter Type 4; D006003:Glycogen / Q000378:metabolism; D006801:Humans; D007103:Immobilization; D008297:Male; D009004:Monosaccharide Transport Proteins / Q000378:metabolism*; D009119:Muscle Contraction / Q000502:physiology; D018656:Muscle Fibers, Fast-Twitch / Q000187:drug effects / Q000502:physiology; D018657:Muscle Fibers, Slow-Twitch / Q000187:drug effects / Q000502:physiology; D009124:Muscle Proteins; D018482:Muscle, Skeletal / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D010809:Physical Fitness / Q000502:physiology*
chemical_list: D001786:Blood Glucose; D004044:Dietary Proteins; D051275:Glucose Transporter Type 4; D009004:Monosaccharide Transport Proteins; D009124:Muscle Proteins; C495692:SLC2A4 protein, human; D006003:Glycogen; D005947:Glucose; D003401:Creatine