title: Postexercise repletion of muscle energy stores with fructose or glucose in mixed meals.
abstract: Background:Postexercise nutrition is paramount to the restoration of muscle energy stores by providing carbohydrate and fat as precursors of glycogen and intramyocellular lipid (IMCL) synthesis. Compared with glucose, fructose ingestion results in lower postprandial glucose and higher lactate and triglyceride concentrations. We hypothesized that these differences in substrate concentration would be associated with a different partition of energy stored as IMCLs or glycogen postexercise.Objective:The purpose of this study was to compare the effect of isocaloric liquid mixed meals containing fat, protein, and either fructose or glucose on the repletion of muscle energy stores over 24 h after a strenuous exercise session.Design:Eight male endurance athletes (mean ± SEM age: 29 ± 2 y; peak oxygen consumption: 66.8 ± 1.3 mL · kg-1· min-1) were studied twice. On each occasion, muscle energy stores were first lowered by a combination of a 3-d controlled diet and prolonged exercise. After assessment of glycogen and IMCL concentrations in vastus muscles, subjects rested for 24 h and ingested mixed meals providing fat and protein together with 4.4 g/kg fructose (the fructose condition; FRU) or glucose (the glucose condition; GLU). Postprandial metabolism was assessed over 6 h, and glycogen and IMCL concentrations were measured again after 24 h. Finally, energy metabolism was evaluated during a subsequent exercise session.Results:FRU and GLU resulted in similar IMCL [+2.4 ± 0.4 compared with +2.0 ± 0.6 mmol · kg-1wet weight · d-1; time × condition (mixed-model analysis):P= 0.45] and muscle glycogen (+10.9 ± 0.9 compared with +12.3 ± 1.9 mmol · kg-1wet weight · d-1; time × condition:P= 0.45) repletion. Fructose consumption in FRU increased postprandial net carbohydrate oxidation and decreased net carbohydrate storage (estimating total, muscle, and liver glycogen synthesis) compared with GLU (+117 ± 9 compared with +135 ± 9 g/6 h, respectively;P< 0.01). Compared with GLU, FRU also resulted in lower plasma glucose concentrations and decreased exercise performance the next day.Conclusions:Mixed meals containing fat, protein, and either fructose or glucose elicit similar repletion of IMCLs and muscle glycogen. Under such conditions, fructose lowers whole-body glycogen synthesis and impairs subsequent exercise performance, presumably because of lower hepatic glycogen stores. This trial was registered at clinicaltrials.gov as NCT01866215.
authors.affiliation: Department of Physiology, University of Lausanne, Lausanne, Switzerland; and.
authors.forename: Robin
authors.identifier: 0000-0003-4708-2771
authors.initials: R
authors.lastname: Rosset
authors.affiliation: Department of Physiology, University of Lausanne, Lausanne, Switzerland; and.
authors.forename: Virgile
authors.initials: V
authors.lastname: Lecoultre
authors.affiliation: Department of Physiology, University of Lausanne, Lausanne, Switzerland; and.
authors.forename: Léonie
authors.initials: L
authors.lastname: Egli
authors.affiliation: Department of Physiology, University of Lausanne, Lausanne, Switzerland; and.
authors.forename: Jérémy
authors.initials: J
authors.lastname: Cros
authors.affiliation: Department of Clinical Research and Radiology, University of Bern, Bern, Switzerland.
authors.forename: Ayse Sila
authors.initials: AS
authors.lastname: Dokumaci
authors.affiliation: Department of Clinical Research and Radiology, University of Bern, Bern, Switzerland.
authors.forename: Karin
authors.initials: K
authors.lastname: Zwygart
authors.affiliation: Department of Clinical Research and Radiology, University of Bern, Bern, Switzerland.
authors.forename: Chris
authors.identifier: 0000-0001-8498-8543
authors.initials: C
authors.lastname: Boesch
authors.affiliation: Department of Clinical Research and Radiology, University of Bern, Bern, Switzerland.
authors.forename: Roland
authors.identifier: 0000-0002-8618-6875
authors.initials: R
authors.lastname: Kreis
authors.affiliation: Department of Physiology, University of Lausanne, Lausanne, Switzerland; and.
authors.forename: Philippe
authors.initials: P
authors.lastname: Schneiter
authors.affiliation: Department of Physiology, University of Lausanne, Lausanne, Switzerland; and luc.tappy@unil.ch.
authors.forename: Luc
authors.identifier: 0000-0001-8469-4692
authors.initials: L
authors.lastname: Tappy
mesh_terms: D000328:Adult; D050260:Carbohydrate Metabolism; D004032:Diet; D004040:Dietary Carbohydrates / Q000378:metabolism / Q000494:pharmacology; D004041:Dietary Fats / Q000378:metabolism; D004044:Dietary Proteins / Q000378:metabolism; D004734:Energy Metabolism; D015444:Exercise / Q000502:physiology*; D005632:Fructose / Q000378:metabolism / Q000494:pharmacology*; D005947:Glucose / Q000378:metabolism / Q000494:pharmacology*; D006003:Glycogen / Q000378:metabolism*; D006801:Humans; D050356:Lipid Metabolism / Q000187:drug effects; D008099:Liver / Q000187:drug effects / Q000378:metabolism; D008297:Male; D062407:Meals; D018482:Muscle, Skeletal / Q000187:drug effects* / Q000378:metabolism; D010084:Oxidation-Reduction; D010807:Physical Endurance / Q000502:physiology; D064133:Sports Nutritional Physiological Phenomena
chemical_list: D004040:Dietary Carbohydrates; D004041:Dietary Fats; D004044:Dietary Proteins; D005632:Fructose; D006003:Glycogen; D005947:Glucose
keywords: athletes; hypertriglyceridemia; intramyocellular lipids; lactate shuttle; muscle glycogen; recovery