UCP3 protein regulation in human skeletal muscle fibre types I, IIa and IIx is dependent on exercise intensity.
It has been proposed that mitochondrial uncoupling protein 3 (UCP3) behaves as an uncoupler of oxidative phosphorylation. In a cross-sectional study, UCP3 protein levels were found to be lower in all fibre types of endurance-trained cyclists as compared to healthy controls. This decrease was greatest in the type I oxidative fibres, and it was hypothesised that this may be due to the preferential recruitment of these fibres during endurance training. To test this hypothesis, we compared the effects of 6 weeks of endurance (ETr) and sprint (STr) running training on UCP3 mRNA expression and fibre-type protein content using real-time PCR and immunofluorescence techniques, respectively. UCP3 mRNA and protein levels were downregulated similarly in ETr and STr (UCP3 mRNA: by 65 and 50%, respectively; protein: by 30 and 27%, respectively). ETr significantly reduced UCP3 protein content in type I, IIa and IIx muscle fibres by 54, 29 and 16%, respectively. STr significantly reduced UCP3 protein content in type I, IIa and IIx muscle fibres by 24, 31 and 26%, respectively. The fibre-type reductions in UCP3 due to ETr, but not STr, were significantly different from each other, with the effect being greater in type I than in type IIa, and in type IIa than in type IIx fibres. As a result, compared to STr, ETr reduced UCP3 expression significantly more in fibre type I and significantly less in fibre types IIx. This suggests that the more a fibre is recruited, the more it adapts to training by a decrease in its UCP3 expression. In addition, the more a fibre type depends on fatty acid beta oxidation and oxidative phosphorylation, the more it responds to ETr by a decrease in its UCP3 content.
Russell
Aaron P
AP
Clinique Romande de Réadaptation SUVA Care, Sion, Switzerland. aaron.russell@ccr-suva.ch
Somm
Emmanuel
E
Praz
Manu
M
Crettenand
Antoinette
A
Hartley
Oliver
O
Melotti
Astrid
A
Giacobino
Jean-Paul
JP
Muzzin
Patrick
P
Gobelet
Charles
C
Dériaz
Olivier
O
D000328:Adult; D015308:Anaerobic Threshold / Q000502:physiology; D001823:Body Composition / Q000502:physiology; D002352:Carrier Proteins / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*; D015444:Exercise / Q000502:physiology*; D005455:Fluorescent Antibody Technique; D006801:Humans; D007473:Ion Channels; D007527:Isoenzymes / Q000096:biosynthesis / Q000235:genetics; D008297:Male; D024101:Mitochondrial Proteins; D018656:Muscle Fibers, Fast-Twitch / Q000378:metabolism / Q000502:physiology*; D018657:Muscle Fibers, Slow-Twitch / Q000378:metabolism / Q000502:physiology*; D018482:Muscle, Skeletal / Q000166:cytology / Q000378:metabolism*; D018995:Myosin Heavy Chains / Q000378:metabolism; D010101:Oxygen Consumption / Q000502:physiology; D010807:Physical Endurance / Q000502:physiology; D010809:Physical Fitness / Q000502:physiology; D012333:RNA, Messenger / Q000096:biosynthesis; D020133:Reverse Transcriptase Polymerase Chain Reaction; D000071247:Uncoupling Protein 3
D002352:Carrier Proteins; D007473:Ion Channels; D007527:Isoenzymes; D024101:Mitochondrial Proteins; D012333:RNA, Messenger; C000604392:UCP3 protein, human; D000071247:Uncoupling Protein 3; D018995:Myosin Heavy Chains