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UCP3 Protein Regulation in Human Skeletal Muscle Fibre Types I, IIa and IIx is Dependent on Exercise Intensity
Author(s) -
Russell Aaron P.,
Somm Emmanuel,
Praz Manu,
Crettenand Antoinette,
Hartley Oliver,
Melotti Astrid,
Giacobino JeanPaul,
Muzzin Patrick,
Gobelet Charles,
Dériaz Olivier
Publication year - 2003
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1113/jphysiol.2003.040162
Subject(s) - ucp3 , uncoupling protein , oxidative phosphorylation , medicine , endocrinology , chemistry , skeletal muscle , biology , biochemistry , brown adipose tissue , obesity
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 β oxidation and oxidative phosphorylation, the more it responds to ETr by a decrease in its UCP3 content.