title: Effect of antioxidant supplementation on insulin sensitivity in response to endurance exercise training.
abstract: While production of reactive oxygen and nitrogen species (RONS) is associated with some of the beneficial adaptations to regular physical exercise, it is not established whether RONS play a role in the improved insulin-stimulated glucose uptake in skeletal muscle obtained by endurance training. To assess the effect of antioxidant supplementation during endurance training on insulin-stimulated glucose uptake, 21 young healthy (age 29 ± 1 y, BMI 25 ± 3 kg/m(2)) men were randomly assigned to either an antioxidant [AO; 500 mg vitamin C and 400 IU vitamin E (α-tocopherol) daily] or a placebo (PL) group that both underwent a supervised intense endurance-training program 5 times/wk for 12 wk. A 3-h euglycemic-hyperinsulinemic clamp, a maximal oxygen consumption (Vo(2max)) and maximal power output (P(max)) test, and body composition measurements (fat mass, fat-free mass) were performed before and after the training. Muscle biopsies were obtained for determination of the concentration and activity of proteins regulating glucose metabolism. Although plasma levels of vitamin C (P < 0.05) and α-tocopherol (P < 0.05) increased markedly in the AO group, insulin-stimulated glucose uptake increased similarly in both the AO (17.2%, P < 0.05) and the PL (18.9%, P < 0.05) group in response to training. Vo(2max) and P(max) also increased similarly in both groups (time effect, P < 0.0001 for both) as well as protein content of GLUT4, hexokinase II, and total Akt (time effect, P ≤ 0.05 for all). Our results indicate that administration of antioxidants during strenuous endurance training has no effect on the training-induced increase in insulin sensitivity in healthy individuals.
authors.affiliation: Rigshospitalet, Centre of Inflammation and Metabolism, 7641, Blegdamsvej 9, DK-2100 Copenhagen, Denmark. christinayfanti@inflammation-metabolism.dk
authors.forename: Christina
authors.initials: C
authors.lastname: Yfanti
authors.forename: Anders R
authors.initials: AR
authors.lastname: Nielsen
authors.forename: Thorbjörn
authors.initials: T
authors.lastname: Akerström
authors.forename: Søren
authors.initials: S
authors.lastname: Nielsen
authors.forename: Adam J
authors.initials: AJ
authors.lastname: Rose
authors.forename: Erik A
authors.initials: EA
authors.lastname: Richter
authors.forename: Jens
authors.initials: J
authors.lastname: Lykkesfeldt
authors.forename: Christian P
authors.initials: CP
authors.lastname: Fischer
authors.forename: Bente K
authors.initials: BK
authors.lastname: Pedersen
mesh_terms: D015502:Absorptiometry, Photon; D000328:Adult; D015308:Anaerobic Threshold / Q000187:drug effects; D000975:Antioxidants / Q000494:pharmacology*; D001205:Ascorbic Acid / Q000494:pharmacology; D015153:Blotting, Western; D001823:Body Composition; D019587:Dietary Supplements; D004311:Double-Blind Method; D005951:Glucose Tolerance Test; D006801:Humans; D007333:Insulin Resistance / Q000502:physiology; D049449:Luminescence; D008297:Male; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000378:metabolism; D010100:Oxygen / Q000097:blood; D010807:Physical Endurance / Q000502:physiology*; D010809:Physical Fitness / Q000502:physiology*; D012313:RNA / Q000096:biosynthesis / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014810:Vitamin E / Q000494:pharmacology; D055815:Young Adult
chemical_list: D000975:Antioxidants; D014810:Vitamin E; D012313:RNA; D001205:Ascorbic Acid; D010100:Oxygen