title: Reduced efficiency, but increased fat oxidation, in mitochondria from human skeletal muscle after 24-h ultraendurance exercise.
abstract: The hypothesis that ultraendurance exercise influences muscle mitochondrial function has been investigated. Athletes in ultraendurance performance performed running, kayaking, and cycling at 60% of their peak O(2) consumption for 24 h. Muscle biopsies were taken preexercise (Pre-Ex), postexercise (Post-Ex), and after 28 h of recovery (Rec). Respiration was analyzed in isolated mitochondria during state 3 (coupled to ATP synthesis) and state 4 (noncoupled respiration), with fatty acids alone [palmitoyl carnitine (PC)] or together with pyruvate (Pyr). Electron transport chain activity was measured with NADH in permeabilized mitochondria. State 3 respiration with PC increased Post-Ex by 39 and 41% (P < 0.05) when related to mitochondrial protein and to electron transport chain activity, respectively. State 3 respiration with Pyr was not changed (P > 0.05). State 4 respiration with PC increased Post-Ex but was lower than Pre-Ex at Rec (P < 0.05 vs. Pre-Ex). Mitochondrial efficiency [amount of added ADP divided by oxygen consumed during state 3 (P/O ratio)] decreased Post-Ex by 9 and 6% (P < 0.05) with PC and PC + Pyr, respectively. P/O ratio remained reduced at Rec. Muscle uncoupling protein 3, measured with Western blotting, was not changed Post-Ex but tended to decrease at Rec (P = 0.07 vs. Pre-Ex). In conclusion, extreme endurance exercise decreases mitochondrial efficiency. This will increase oxygen demand and may partly explain the observed elevation in whole body oxygen consumption during standardized exercise (+13%). The increased mitochondrial capacity for PC oxidation indicates plasticity in substrate oxidation at the mitochondrial level, which may be of advantage during prolonged exercise.
authors.affiliation: Department of Physiology, Karolinska Institute, Stockholm, Sweden.
authors.forename: Maria
authors.initials: M
authors.lastname: Fernström
authors.forename: Linda
authors.initials: L
authors.lastname: Bakkman
authors.forename: Michail
authors.initials: M
authors.lastname: Tonkonogi
authors.forename: Irina G
authors.initials: IG
authors.lastname: Shabalina
authors.forename: Zinaida
authors.initials: Z
authors.lastname: Rozhdestvenskaya
authors.forename: C Mikael
authors.initials: CM
authors.lastname: Mattsson
authors.forename: Jonas K
authors.initials: JK
authors.lastname: Enqvist
authors.forename: Björn
authors.initials: B
authors.lastname: Ekblom
authors.forename: Kent
authors.initials: K
authors.lastname: Sahlin
mesh_terms: D000244:Adenosine Diphosphate / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000378:metabolism; D000328:Adult; D019069:Cell Respiration; D015444:Exercise / Q000502:physiology*; D005227:Fatty Acids / Q000097:blood / Q000378:metabolism*; D006801:Humans; D007473:Ion Channels / Q000378:metabolism; D008297:Male; D008931:Mitochondria, Muscle / Q000378:metabolism*; D024101:Mitochondrial Proteins / Q000378:metabolism; D009119:Muscle Contraction; D018482:Muscle, Skeletal / Q000378:metabolism*; D010084:Oxidation-Reduction; D010101:Oxygen Consumption; D010172:Palmitoylcarnitine / Q000378:metabolism; D010807:Physical Endurance / Q000502:physiology*; D019289:Pyruvic Acid / Q000378:metabolism; D020127:Recovery of Function; D013997:Time Factors; D000071247:Uncoupling Protein 3
chemical_list: D005227:Fatty Acids; D007473:Ion Channels; D024101:Mitochondrial Proteins; C000604392:UCP3 protein, human; D000071247:Uncoupling Protein 3; D010172:Palmitoylcarnitine; D000244:Adenosine Diphosphate; D019289:Pyruvic Acid; D000255:Adenosine Triphosphate