| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
|
|
|
|||||||
|
|||||||||
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
1 Department of Physiology and Pharmacology, Karolinska Institutet, 2 Department of Sports and Health Science, Stockholm University College of Physical Education and Sports, Stockholm, Sweden 3 Institute of Sports Science and Clinical Biomechanics, University of Southern Denmark, Odense, Denmark
 |
Abstract |
|---|
 Top Abstract IntroductionMethodsResultsDiscussionReferences |
|---|
) or 6 weeks endurance training. Mitochondria were isolated and respiration measured in the absence (UCR or state 4) and presence of ADP (coupled respiration or state 3). Protein expression of UCP3 and ANT was measured with Western blotting. After endurance training 
, citrate synthase activity (CS), state 3 respiration and ANT increased by 24, 47, 40 and 95%, respectively (all P < 0.05), whereas UCP3 remained unchanged. When expressed per unit of CS (a marker of mitochondrial volume) UCP3 and UCR decreased by 54% and 18%(P < 0.05). CS increased by 43% after acute exercise and remained elevated after 3 h of recovery (P < 0.05), whereas the other muscle parameters remained unchanged. An intriguing finding was that acute exercise reversibly enhanced the capacity of mitochondria to accumulate Ca2+(P < 0.05) before opening of permeability transition pores. In conclusion, UCP3 protein and UCR decrease after endurance training when related to mitochondrial volume. These changes may prevent excessive basal thermogenesis. Acute exercise enhances mitochondrial resistance to Ca2+ overload but does not influence UCR or protein expression of UCP3 and ANT. The increased Ca2+ resistance may prevent mitochondrial degradation and the mechanism needs to be further explored.
(Received 17 September 2003;
accepted after revision 18 November 2003;
first published online 21 November 2003)
Corresponding author K. Sahlin: Institute of Sports Science and Clinical Biomechanics, University of Southern Denmark, Campusvej 55, 5230 Odense, Denmark. Email: ksahlin{at}health.sdu.dk
|
Introduction |
|---|
|
TopAbstractIntroductionMethodsResultsDiscussionReferences |
|---|
The mechanism behind UCR and its physiological role is not fully understood but is currently an intensive research field. One hypothesis is that specific mitochondrial proteins mediate back-leakage of protons over the inner mitochondrial membrane and therefore have the capacity to uncouple respiration from ATP synthesis (Hagen & Vidal-Puig, 2002). The presence of such proteins is well documented in brown adipose tissue where uncoupling protein 1 (UCP1) mediates non-shivering thermogenesis (Klaus et al. 1991). Homologous proteins have been identified in other tissues and the major forms found in skeletal muscle have been named uncoupling protein 2 (UCP2) and 3 (UCP3) (Gong et al. 1997; Giacobino, 2001). The functional role of UCP2 and UCP3 (Garvey, 2003) is under debate.
Previous studies in humans have shown that UCP3 mRNA expression is increased after acute exercise (Pilegaard et al. 2000) but unchanged after endurance training (Tonkonogi et al. 2000a). Cross-sectional studies have shown reduced expression of UCP3 mRNA (Boss et al. 2000) and UCP3 protein (Schrauwen et al. 1999; Russell et al. 2003) in skeletal muscle from trained subjects. In contrast, recent data from Holloszy's group show that during short-term training in rats UCP3 protein increases in parallel with other mitochondrial proteins and thus in accordance with mitochondrial biogenesis (Jones et al. 2003). It was considered unlikely that the relative composition of mitochondrial proteins could change considerable (Jones et al. 2003). A longitudinal training study in human subjects would solve the controversy but remains to be done. Furthermore, the effect of acute exercise on UCP3 protein expression has not been studied in humans.
Proton leakage through the phospholipid bilayer accounts for only a small proportion of total UCR (Brookes et al. 1997) and is more likely to be mediated by mitochondrial proteins such as UCP3, adenine nucleotide translocase (ANT) and ATP synthase. ANT mediates ADP influx into mitochondrial matrix and efflux of ATP and is considered to contribute to uncoupled respiration (Tikhonova et al. 1994; Skarka et al. 2003). The effect of acute exercise and endurance training on ANT protein expression in humans is not known.
Leakage of protons may also occur by intermittent opening of mitochondrial permeability transition (MPT) pores. MPT pores are large mitochondrial membrane channels formed as a complex between mitochondrial proteins (porin, ANT and cyclophilin-D). Oxidative stress, elevation of plasma Ca2+ and low ATP favour the opening of MPT pores (Bowser et al. 2002), which leads to release of mitochondrial substances from the matrix, decreased membrane potential and increased UCR. The effect of acute exercise on MPT pore opening in human skeletal muscle mitochondria has previously not been studied.
During prolonged exercise above the lactate threshold, oxygen uptake 
increases slowly despite maintained power output. This phenomenon has been named the slow component of 
kinetics or the 
drift. 
drift may in part be explained by increased body temperature, elevated levels of adrenaline (epinephrine), increased recruitment of fast-twitch fibres and an increased reliance on fat oxidation. However, the reasons for oxygen drift remain elusive (Zoladz & Korzeniewski, 2001). After strenuous exercise, oxygen consumption remains elevated for several hours and is referred to as the slow component of excess post-exercise oxygen consumption (EPOC) (Gaesser & Brooks, 1984). The mechanism for the slow component of EPOC is not fully understood. We hypothesize that increased UCR can contribute to EPOC and oxygen drift.
The purpose of this study was (i) to investigate the effects of acute exercise and training on the protein expression of UCP3 and ANT, (ii) to investigate the effect of acute exercise and training on UCR in isolated mitochondria and relate these findings to 
drift, EPOC and putative mediators of proton leakage (i.e. UCP3 and ANT), and (iii) to investigate the effect of exercise on the vulnerability of mitochondria to Ca2+ overload.
|
Methods |
|---|
|
TopAbstractIntroductionMethodsResultsDiscussionReferences |
|---|
Acute exercise.
Nine healthy subjects (5 male and 4 female) performed one single bout of cycle exercise. The age, height, weight and 
of the subjects in this group were (mean ±S.E.M.) 25 ± 1 years, 176 ± 3 cm, 72 ± 3.9 kg and 50 ± 2.1 ml min-1 kg -1.
Endurance training.
Eight healthy subjects (4 male and 4 female) participated in the endurance-training program. The age, height, weight and 
of the subjects were 26 ± 2 years, 173 ± 3 cm, 70 ± 4.7 kg and 38 ± 2.5 ml min-1 kg -1. Results on oxidative capacities have been reported previously (Tonkonogi et al. 2000a).
The subjects were fully informed of the possible risks and discomforts involved in the experiment before giving their written voluntary consent. The study was carried out in accordance with the Declaration of Helsinki of the World Medical Association. The experimental design of the study was approved by the Ethics Committee of the Karolinska Institutet, Stockholm, Sweden.
Determination of 
test was conducted on an ergometer cycle (Monark 829e, Varberg, Sweden). An incremental submaximal exercise test was performed to estimate 
. After a brief period of rest, the workrate was raised rapidly above that estimated to elicit 
and thereafter raised in small steps until exhaustion. Expired air was analysed for O2 and CO2 online using the AMIS cardiopulmonary function test system (Innovision A/S DK-5260 Odense S, Denmark).
Experimental protocol
Acute exercise.
At least 2 days after the 
test the subjects reported to the laboratory to perform the experiment. They were instructed to abstain from heavy physical exercise and from alcohol on the day before the experiment. They were also instructed to avoid breakfast on the day for the experiment and were not allowed to eat until the experiment was completed as it is known that UCP3 is influenced by food intake (Schrauwen et al. 2002). Cardiorespiratory parameters were measured pre- and 3 h post-exercise (after the subjects had rested in the supine position for 30 min). The expired air was collected using the Douglas bags technique and analysed for O2 and CO2 using a Beckman S-3 A and LB-2 analyser (Beckman Instruments, Fullerton, CA, USA). Subjects cycled on a Monark ergometer cycle for 75 min at an intensity of approximately 70% of their 
. Expired air was collected online every 15 min and analysed for O2, CO2 and RER (respiratory exchange ratio) on the AMIS cardiopulmonary function test system. Heart rate was registered continuously with a Polar sport tester (Polar Electro, Kemple, Finland). Muscle biopsies were taken from m. vastus lateralis pre-exercise, immediately post-exercise (within 5 min) and 3 h post-exercise. The biopsies taken pre-exercise and 3 h post-exercise were taken after measurements of cardiorespiratory parameters. The first two biopsies were taken from the same leg. Blood samples were taken from an antecubital vein prior to the muscle biopsies (pre- and 3 h post-exercise) and during the last minutes of exercise.
Endurance training.
Eight untrained subjects completed a six-week training program consisting of four sessions per week. Prior to the first training session measurements of 
were conducted. Each training session was performed on a Monark cycle ergometer and lasted one hour. The subjects cycled at 70% of 
for the first 30 min and performed interval training for the remaining 30 min. After 2 and 4 weeks, the workrate was increased by 5% to account for the estimated increase in 
. Two to three days following the last training session, the test of 
was repeated. Muscle biopsies were taken from m. vastus lateralis pre- and post-training (2 days after the 
test).
Muscle biopsies and isolation of mitochondria
Muscle biopsies were taken from the lateral aspect of the quadriceps femoris muscle, at a depth of 2–3 cm. After local anaesthesia (1–2 ml Carbocain; 20 mg ml-1, AstraZeneca), an incision was made through the skin and fascia and the biopsy was taken using a Bergström needle with suction. The biopsy was divided into portions. One portion was frozen in liquid nitrogen and stored at -80°C until determination of CS and protein expression of UCP3 and ANT. Another portion was used for preparation of isolated mitochondria according to the method of Tonkonogi & Sahlin (1997). Briefly, a muscle specimen was minced with scissors and muscle mitochondria were isolated by protease treatment (Nagarse, 0.4 mg ml-1, Sigma P4789), followed by homogenization and differential centrifugation. The final mitochondria pellet was resuspended in a medium consisting of (mM) 225 mannitol, 75 sucrose, and 10 Tris, 0.1 EDTA (pH 7.40), and kept on ice until analysis of respiratory activity. An aliquot of the suspension (10 µl) was taken for measurements of mitochondrial citrate synthase activity (CS) as previously described (Tonkonogi et al. 1997).
Analytical methods
Measurements of mitochondrial respiratory activity. Oxygen consumption was measured using a Clark-type electrode (Hansatech DW1; Hansatech, King's Lynn, Norfolk, UK), at 25°C. Respiration was analysed in medium containing (mM): mannitol 225, sucrose 75, Tris 10, KCL 10, K2HPO4 10, EDTA 0.1, pyruvate 5, malate 2 (pH 7.35). The mitochondrial suspension was added to the reaction medium and coupled respiration (state 3) was initiated by the addition of 200 µM ADP. The respiratory rate returned to that prior to the addition of ADP when all ADP was phosphorylated to ATP and corresponds to UCR or state 4.
The effect of free fatty acids on UCR was determined by addition of oleate in increasing concentrations to the mitochondrial suspension in the respiration medium as above but including oligomycin (0.5 mg ml-1), fatty acid-free BSA (0.2%), 0.05 mM hypoxanthine and 0.003 U ml-1 xanthine oxidase. Oligomycin was added to block proton leakage through ATP synthase. Hypoxanthine and xanthine oxidase were added to generate superoxide, since this has been reported to activate proton leakage through UCP3. Oleate was added to final concentrations of 40, 80 and 100 µM corresponding to calculated free concentrations of 0.02, 0.24 and 8.36 µM (Richieri et al. 1993).
Muscle citrate synthase activity. CS was measured by spectrophotometry in isolated mitochondria and in freeze-dried muscle dissected free from non-muscle constituents using a technique previously described (Tonkonogi et al. 1997).
UCP3. Portions of freeze-dried muscle were homogenized in ice-cold lysis buffer and the protein concentration was determined (BCA protein assay 23223 Pierc Cat. 1610737, Bio Rad Laboratories, Hercules, CA, USA). Homogenates were solubilized in Laemmli sample buffer and denaturated by boiling. A constant amount of protein was added per lane (75 µg) on 12% polyacrylamide gels and separated by SDS-PAGE for 60 min at 135 V. The separated polypeptides were transferred to a PVDF membrane at 10 V for 60 min, and blocked in tris-buffered saline (TBS) with 5% non-fat milk. Membranes were incubated overnight with polyclonal antibody against UCP3 (Chemicon AB3046), diluted 1: 1000, washed and incubated with secondary antibody goat antirabbit (IgG-HRP, NO.sc-2030 Santa Cruz). The membrane was again washed and incubated with the chemiluminescence detection reagent ECL, No RPN 2106 (Amersham). Finally, an X-ray film was exposed to the membrane for 50 min. The optical density of the bands was quantified by using Molecular Analyst 1.5 (Bio-Rad). The analytical procedure for analysis of UCP3 has previously been described in detail (Tonkonogi et al. 2003).
ANT. Homogenization, measurement of protein concentration and denaturation was performed as for UCP3. A constant amount of protein was added per lane (75 µg) on 12% polyacrylamide gels and separated by SDS-PAGE for 60 min at 135 V. Polypeptides were transferred to a PVDF membrane at 100 V for 120 min, and blocked in TBS with 5% non-fat milk. Membranes were incubated 2 h with polyclonal antibody against ANT (ANT-1, Q-18, No,sc-9300, Santa Cruz) diluted 1: 200, washed and incubated with secondary antibody bovine antigoat (IgG-HRP, No. sc-2350 Santa Cruz). After washing the membrane was incubated with chemiluminescence detection reagent ECL (No RPN 2106, Amersham), and exposed to a film for 50 min. The optical density of the bands was quantified by using Molecular Analyst 1.5 (Bio-Rad). The Western blot procedure for ANT has previously been described in detail (Tonkonogi et al. 2003).
Mitochondrial permeability transition pores. Mitochondrial swelling was monitored continuously as the change in absorbance at 540 nm. An aliquot of mitochondrial suspension equivalent to 5 x 10-2 U CS corresponding to 19.1 µg protein (3.15–7.47 µl mitochondrial suspension) was diluted to a final volume of 7.5 µl and resuspended in 100 µl of buffer (pH 7.4) containing (mM) 150 KCl, 5 Tris, 5 K2HPO4, 5 malate, 5 pyruvate. Equivalent pulses of CaCl2 (2 µmol of Ca2+ (U CS)-1= 10 nmol) were added to the mitochondria every 3 min until a rapid decrease in absorbance occurred. This condition indicates progressive swelling of mitochondria due to opening of MPT pores. The time point for massive MPT pore opening was defined as the point when the rate of decrease in absorbance exceeded 0.0175 absorbance units per minute. Results from preliminary experiments on human muscle mitochondria using Ca2+-sensitive electrodes showed that 3 min was sufficient for complete uptake of Ca2+ from the medium during initial calcium pulses.
NEFA and blood glucose. Glucose concentration was measured in whole blood with Accu-Chek (Roche Diagnostics AB). Blood for analysis of nonesterified fatty acids (NEFA) was centrifuged and the supernatant was immediately frozen. NEFA was measured in plasma using the Wako NEFA C-test kit. Nr: 994–75409 D (Waco Chemicals Inc, Richmond, USA).
Data analysis
Data are presented as means ±S.E.M. Statistical significance of the difference between means was tested with either Student's paired t test or repeated measures analysis of variance (ANOVA). ANOVA was followed by a post hoc test with Greenhouse-Geisser and Huynh-Feldt adjustments. Significance of differences was set as P < 0.05.
|
Results |
|---|
|
TopAbstractIntroductionMethodsResultsDiscussionReferences |
|---|
The subjects cycled for 75 min at a constant workrate corresponding to about 70% of their individual 
. Despite the constant power output there was a slow increase (Fig. 1) in 
(from 2.47 ± 0.20 l min-1 at 15 min to 2.72 ± 0.23 l min-1 at 75 min, P < 0.05) and heart rate (156 ± 3 versus 170 ± 3 beats min-1, P < 0.05). 
drift between 15 and 75 min averaged 10% (range 3–16%) of 
at 15 min. 
drift was neither correlated to the increase in heart rate nor to the increase in ventilation. The respiratory exchange ratio decreased from 0.95 ± 0.01 after 15 min exercise to 0.92 ± 0.01 after 75 min of exercise (P < 0.05), and corresponds to an increased relative fat oxidation from 17% (15 min) to 27% (75 min). The observed shift in substrate oxidation would increase 
by 1% (assuming 10% higher P/O ratio for fat oxidation). 
, measured while the subjects rested in the supine position was 17% higher 3 h post-exercise than pre-exercise (0.28 ± 0.02 versus 0.24 ± 0.01 l min-1, P < 0.05) and corresponds to the slow phase of EPOC.
|
|
3 h post-exercise (r = 0.15). Furthermore, measurements in isolated mitochondria demonstrated that the sensitivity of mitochondrial respiration to oleate was similar pre- and post-exercise (Fig. 2).
|
|
As previously reported (Tonkonogi et al. 2000b), endurance training for 6 weeks increased oxidative power at the whole body level (24% increase in 
, P < 0.05) and at the muscle level as demonstrated by increases in CS (47% increase in CS, P < 0.05) and ADP-stimulated mitochondrial respiration (40% increase in state 3 respiration, P < 0.05). When mitochondrial respiration was expressed in relation to a marker of mitochondrial volume (CS), state 3 respiration remained unchanged, whereas state 4 respiration (UCR) decreased by 18% (P < 0.05, Table 2).
|
|
|
Discussion |
|---|
|
TopAbstractIntroductionMethodsResultsDiscussionReferences |
|---|
The physiological role of UCP3 is under debate and suggested roles include mitochondrial uncoupling, reduced formation of reactive oxygen species (ROS) (Vidal-Puig et al. 2000), transport of ionized fatty acids out of the mitochondrial matrix (Schrauwen et al. 2001) and control of oxidative phosphorylation (Toukouogi et al. 2000a). These suggested functional roles are independent but could all be correct. Evidence for a role of UCP3 in uncoupling comes from studies on UCP3 knock-out mice, which have lower state 4 respiration (Harper & Himms-Hagen, 2001). It has also been reported that obese diet-resistant women have decreased mitochondrial proton leak and reduced expression of UCP3 in skeletal muscle (Harper et al. 2002). Evidence against UCP3 being an uncoupler includes the finding that fasting increases mRNA for UCP3 in skeletal muscle, despite a reduced metabolic rate (Millet et al. 1997). Furthermore, elevation of UCP3 by a high-fat diet did not change the efficiency of mitochondrial energy conversion (measured as the rate of PCr resynthesis after exercise) and it was concluded that the primary role of UCP3 was not uncoupling (Hesselink et al. 2003). However, actively phosphorylating mitochondria have a lower membrane potential than mitochondria in state 4 and it seems likely that this would reduce or abolish proton leak. Therefore a maintained level of mitochondrial efficiency during exercise does not exclude the possibility that UCP3 functions as a mild uncoupler during basal conditions.
Mitochondrial density was increased by about 40% after 6 weeks of training and maintenance of the intrinsic proton leakage per mitochondrion would correspond to a large increase in basal metabolic rate. Providing that UCP3 has a role in uncoupling, the observed reduction in UCP3 in response to training could be an important compensatory mechanism to avoid excessive heat production and energy expenditure during basal conditions. Given the role of UCP3 in reducing mitochondrial ROS formation one could argue that training should increase vulnerability to oxidative damage. However, the system is complex and compensatory mechanisms are likely to be involved.
Acute exercise had no effect on UCP3 and ANT protein expression or on UCR, measured in isolated mitochondria. The hypothesis that increased UCR could explain oxygen drift or the slow component of EPOC cannot therefore be supported. However, metabolic conditions and the control of UCR are different in vivo than during the experimental conditions used in vitro. Previous studies on isolated mitochondria have shown that state 4 respiration increases (Brooks et al. 1971) and that the efficiency in energy transfer decreases (Brooks et al. 1971; Willis & Jackman, 1994) during hyperthermia. Furthermore, fatty acids are known to increase UCR and both fatty acids and superoxide are potent stimulators of proton leakage through UCP3 (Echtay et al. 2002). Plasma levels of NEFA increased 3–4 times during exercise and continued to increase during the post-exercise period. Furthermore, since mitochondrial formation of superoxide is elevated during exercise it is possible that mitochondrial uncoupling will be augmented.
An interesting finding in this study was that the resistance of isolated mitochondria to Ca2+ overload was increased in samples taken immediately post-exercise. The results are surprising since mitochondrial Ca2+ content is known to increase after prolonged exercise (Madsen et al. 1996). The present data do not provide any clue as to the mechanism behind the protective effect of exercise on MPT. Opening of MPT is associated with dysfunction and eventually degradation of mitochondria. Mitochondrial degradation can in its turn lead to destruction of the nucleus in the vicinity and thereby to muscle hypotrophy (Primeau et al. 2002). The increased Ca2+ tolerance of mitochondria post-exercise could serve as a protective mechanism, resulting in a decrease in the rate of mitochondrial degradation and instead favouring an increased rate of mitochondrial biogenesis. Ischaemic injury is known to be associated with opening of MPT (Xu et al. 2001). The association between ischaemic preconditioning and mitochondrial resistance to Ca2+ overload should be further investigated.
Acute exercise resulted in a large increase in muscle CS (+43%) and is consistent with that observed in previous studies (Tonkonogi et al. 1997; Leek et al. 2001). However, the high CS maintained after 3 h of recovery is a new intriguing finding which opens up new perspectives in training and athletic performance. De novo enzyme synthesis seems unlikely due to the short time period and an increased specific activity of CS appears to be more plausible. The mechanism for this is however, unknown (see Tonkonogi et al. 1997 for a full discussion).
In summary, the present study demonstrated that the density and oxidative power of mitochondria increases after endurance training but that UCP3 protein and UCR are reduced in relation to mitochondrial volume. The reduction in UCR may relate to the reduction in UCP3 and serve as prevention against excessive basal thermogenesis due to increased mitochondrial density. An intriguing finding was the increase in mitochondrial Ca2+ tolerance immediately post-exercise, which may serve as a protective mechanism against exercise-induced mitochondrial degradation. The mechanism behind this needs to be further explored.
|
References |
|---|
|
TopAbstractIntroductionMethodsResultsDiscussionReferences |
|---|
Bowser DN, Petrou S, Panchal RG, Smart ML & Williams DA (2002). Release of mitochondrial Ca2+ via the permeability transition activates endoplasmic reticulum Ca2+ uptake. Faseb J 16, 1105–1107.
Brookes PS, Rolfe DF & Brand MD (1997). The proton permeability of liposomes made from mitochondrial inner membrane phospholipids: comparison with isolated mitochondria. J Membr Biol 155, 167–174.[CrossRef][Medline]
Brooks GA, Hittelman KJ, Faulkner JA & Beyer RE (1971). Temperature, skeletal muscle mitochondrial functions, and oxygen debt. Am J Physiol 220, 1053–1059.
Echtay KS, Roussel D, St-Pierre J, Jekabsons MB, Cadenas S, Stuart JA, Harper JA, Roebuck SJ, Morrison A, Pickering S, Clapham JC & Brand MD (2002). Superoxide activates mitochondrial uncoupling proteins. Nature 415, 96–99.[CrossRef][Medline]
Gaesser GA & Brooks GA (1984). Metabolic bases of excess post-exercise oxygen consumption: a review. Med Sci Sports Exerc 16, 29–43.[Medline]
Garvey WT (2003). The role of uncoupling protein 3 in human physiology. J Clin Invest 111, 438–441.[CrossRef][Medline]
Giacobino JP (2001). Uncoupling protein 3 biological activity. Biochem Soc Trans 29, 774–777.[CrossRef][Medline]
Gong DW, He Y, Karas M & Reitman M (1997). Uncoupling protein-3 is a mediator of thermogenesis regulated by thyroid hormone, beta3-adrenergic agonists, and leptin. J Biol Chem 272, 24129–24132.
Hagen T & Vidal-Puig A (2002). Mitochondrial uncoupling proteins in human physiology and disease. Minerva Med 93, 41–57.[Medline]
Harper ME, Dent R, Monemdjou S, Bezaire V, Van Wyck L, Wells G, Kavaslar GN, Gauthier A, Tesson F & McPherson R (2002). Decreased mitochondrial proton leak and reduced expression of uncoupling protein 3 in skeletal muscle of obese diet-resistant women. Diabetes 51, 2459–2466.
Harper ME & Himms-Hagen J (2001). Mitochondrial efficiency: lessons learned from transgenic mice. Biochim Biophys Acta 1504, 159–172.[Medline]
Hesselink MK, Greenhaff PL, Constantin-Teodosiu D, Hultman E, Saris WH, Nieuwlaat R, Schaart G, Kornips E & Schrauwen P (2003). Increased uncoupling protein 3 content does not affect mitochondrial function in human skeletal muscle in vivo. J Clin Invest 111, 479–486.[CrossRef][Medline]
Hesselink MK, Keizer HA, Borghouts LB, Schaart G, Kornips CF, Slieker LJ, Sloop KW, Saris WH & Schrauwen P (2001). Protein expression of UCP3 differs between human type 1, type 2a, and type 2b fibers. Faseb J 15, 1071–1073.
Jones TE, Baar K, Ojuka E, Chen M & Holloszy JO (2003). Exercise induces an increase in muscle UCP3 as a component of the increase in mitochondrial biogenesis. Am J Physiol Endocrinol Metab 284, E96–E101.
Klaus S, Casteilla L, Bouillaud F & Ricquier D (1991). The uncoupling protein UCP: a membraneous mitochondrial ion carrier exclusively expressed in brown adipose tissue. Int J Biochem 23, 791–801.[CrossRef][Medline]
Leek BT, Mudaliar SR, Henry R, Mathieu-Costello O & Richardson RS (2001). Effect of acute exercise on citrate synthase activity in untrained and trained human skeletal muscle. Am J Physiol Regul Integr Comp Physiol 280, R441–R447.
Madsen K, Ertbjerg P, Djurhuus MS & Pedersen PK (1996). Calcium content and respiratory control index of skeletal muscle mitochondria during exercise and recovery. Am J Physiol 271, E1044–E1050.[Medline]
Millet L, Vidal H, Andreelli F, Larrouy D, Riou JP, Ricquier D, Laville M & Langin D (1997). Increased uncoupling protein-2 and – 3 mRNA expression during fasting in obese and lean humans. J Clin Invest 100, 2665–2670.[Medline]
Pilegaard H, Ordway GA, Saltin B & Neufer PD (2000). Transcriptional regulation of gene expression in human skeletal muscle during recovery from exercise. Am J Physiol Endocrinol Metab 279, E806–E814.
Primeau AJ, Adhihetty PJ & Hood DA (2002). Apoptosis in heart and skeletal muscle. Can J Appl Physiol 27, 349–395.[Medline]
Richieri GV, Anel A & Kleinfeld AM (1993). Interactions of long-chain fatty acids and albumin: determination of free fatty acid levels using the fluorescent probe ADIFAB. Biochemistry 32, 7574–7580.[CrossRef][Medline]
Rolfe DF & Brand MD (1996). Contribution of mitochondrial proton leak to skeletal muscle respiration and to standard metabolic rate. Am J Physiol 271, C1380–C1389.[Medline]
Russell P, Wadley G, Hesselink C, Schaart G, Lo S, Leger B, Garnham A, Kornips E, Cameron-Smith D, Giacobino JP, Muzzin P, Snow R & Schrauwen P (2003). UCP3 protein expression is lower in type I, IIa and IIx muscle fiber types of endurance-trained compared to untrained subjects. Pflugers Arch 445, 563–569.[Medline]
Schrauwen P, Hesselink MK, Vaartjes I, Kornips E, Saris WH, Giacobino JP & Russell A (2002). Effect of acute exercise on uncoupling protein 3 is a fat metabolism-mediated effect. Am J Physiol Endocrinol Metab 282, E11–E17.
Schrauwen P, Saris WH & Hesselink MK (2001). An alternative function for human uncoupling protein 3: protection of mitochondria against accumulation of nonesterified fatty acids inside the mitochondrial matrix. Faseb J 15, 2497–2502.
Schrauwen P, Troost FJ, Xia J, Ravussin E & Saris WH (1999). Skeletal muscle UCP2 and UCP3 expression in trained and untrained male subjects. Int J Obes Relat Metab Disord 23, 966–972.[CrossRef][Medline]
Skarka L, Bardova K, Brauner P, Flachs P, Jarkovska D, Kopecky J & Ostadal B (2003). Expression of mitochondrial uncoupling protein 3 and adenine nucleotide translocase 1 genes in developing rat heart: putative involvement in control of mitochondrial membrane potential. J Mol Cell Cardiol 35, 321–330.[CrossRef][Medline]
Thayer R, Collins J, Noble EG & Taylor AW (2000). A decade of aerobic endurance training: histological evidence for fibre type transformation. J Sports Med Phys Fitness 40, 284–289.[Medline]
Tikhonova IM, Andreyev A, Antonenko YuN, Kaulen AD, Komrakov A & Skulachev VP (1994). Ion permeability induced in artificial membranes by the ATP/ADP antiporter. FEBS Lett 337, 231–234.[CrossRef][Medline]
Tonkonogi M, Fernstrom M, Walsh B, Ji LL, Rooyackers O, Hammarqvist F, Wernerman J & Sahlin K (2003). Reduced oxidative power but unchanged antioxidative capacity in skeletal muscle from aged humans. Pflugers Arch 446, 261–269.[Medline]
Tonkonogi M, Harris B & Sahlin K (1997). Increased activity of citrate synthase in human skeletal muscle after a single bout of prolonged exercise. Acta Physiol Scand 161, 435–436.[CrossRef][Medline]
Tonkonogi M, Krook A, Walsh B & Sahlin K (2000a). Endurance training increases stimulation of uncoupling of skeletal muscle mitochondria in humans by non-esterified fatty acids: an uncoupling-protein-mediated effect?Biochem J 351, 805–810.[CrossRef][Medline]
Tonkonogi M & Sahlin K (1997). Rate of oxidative phosphorylation in isolated mitochondria from human skeletal muscle: effect of training status. Acta Physiol Scand 161, 345–353.[CrossRef][Medline]
Tonkonogi M, Walsh B, Svensson M & Sahlin K (2000b). Mitochondrial function and antioxidative defence in human muscle: effects of endurance training and oxidative stress. J Physiol 528, 379–388.
Vidal-Puig AJ, Grujic D, Zhang CY, Hagen T, Boss O, Ido Y, Szczepanik A, Wade J, Mootha V, Cortright R, Muoio DM & Lowell BB (2000). Energy metabolism in uncoupling protein 3 gene knockout mice. J Biol Chem 275, 16258–16266.
Willis WT & Jackman MR (1994). Mitochondrial function during heavy exercise. Med Sci Sports Exerc 26, 1347–1353.[Medline]
Xu M, Wang Y, Hirai K, Ayub A & Ashraf M (2001). Calcium preconditioning inhibits mitochondrial permeability transition and apoptosis. Am J Physiol Heart Circ Physiol 280, H899–H908.
Zoladz JA & Korzeniewski B (2001). Physiological background of the change point in VO2 and the slow component of oxygen uptake kinetics. J Physiol Pharmacol 52, 167–184.[Medline]
|
Acknowledgements |
|---|
This article has been cited by other articles:
|
|
 |
|
  M. Mogensen, K. Sahlin, M. Fernstrom, D. Glintborg, B. F. Vind, H. Beck-Nielsen, and K. Hojlund Mitochondrial Respiration Is Decreased in Skeletal Muscle of Patients With Type 2 Diabetes Diabetes, June 1, 2007; 56(6): 1592 - 1599. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 M. Fernstrom, L. Bakkman, M. Tonkonogi, I. G. Shabalina, Z. Rozhdestvenskaya, C. M. Mattsson, J. K. Enqvist, B. Ekblom, and K. Sahlin Reduced efficiency, but increased fat oxidation, in mitochondria from human skeletal muscle after 24-h ultraendurance exercise J Appl Physiol, May 1, 2007; 102(5): 1844 - 1849. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 K. E. Conley, C. E. Amara, S. A. Jubrias, and D. J. Marcinek Muscle-energetic and cardio-pulmonary determinants of exercise tolerance in humans: Mitochondrial function, fibre types and ageing: new insights from human muscle in vivo Exp Physiol, March 1, 2007; 92(2): 333 - 339. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 C. E. Amara, E. G. Shankland, S. A. Jubrias, D. J. Marcinek, M. J. Kushmerick, and K. E. Conley Mild mitochondrial uncoupling impacts cellular aging in human muscles in vivo PNAS, January 16, 2007; 104(3): 1057 - 1062. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
K. Sahlin, J. S. Nielsen, M. Mogensen, and M. Tonkonogi Repeated static contractions increase mitochondrial vulnerability toward oxidative stress in human skeletal muscle J Appl Physiol, September 1, 2006; 101(3): 833 - 839. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 G. S. Supinski and L. A. Callahan Polyethylene Glycol-Superoxide Dismutase Prevents Endotoxin-induced Cardiac Dysfunction Am. J. Respir. Crit. Care Med., June 1, 2006; 173(11): 1240 - 1247. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 M. Mogensen, M. Bagger, P. K. Pedersen, M. Fernstrom, and K. Sahlin Cycling efficiency in humans is related to low UCP3 content and to type I fibres but not to mitochondrial efficiency J. Physiol., March 15, 2006; 571(3): 669 - 681. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
E. F. Coyle Understanding efficiency of human muscular movement exemplifies integrative and translational physiology J. Physiol., March 15, 2006; 571(3): 501 - 501. [Full Text] [PDF]
|
|
|
|
 |
|
 S. Schenk, J. N. Cook, A. E. Kaufman, and J. F. Horowitz Postexercise insulin sensitivity is not impaired after an overnight lipid infusion Am J Physiol Endocrinol Metab, March 1, 2005; 288(3): E519 - E525. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
M. J. Watt, G. J. F. Heigenhauser, P. J. LeBlanc, J. G. Inglis, L. L. Spriet, and S. J. Peters Rapid upregulation of pyruvate dehydrogenase kinase activity in human skeletal muscle during prolonged exercise J Appl Physiol, October 1, 2004; 97(4): 1261 - 1267. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 D. M. Bailey, I. S. Young, J. McEneny, L. Lawrenson, J. Kim, J. Barden, and R. S. Richardson Regulation of free radical outflow from an isolated muscle bed in exercising humans Am J Physiol Heart Circ Physiol, October 1, 2004; 287(4): H1689 - H1699. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
V. Ljubicic, P. J. Adhihetty, and D. A. Hood Role of UCP3 in state 4 respiration during contractile activity-induced mitochondrial biogenesis J Appl Physiol, September 1, 2004; 97(3): 976 - 983. [Abstract] [Full Text] [PDF]
|
|
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
. *Significant difference from value at 15 min.
for 75 min. Values are mean ±S.E.M., n= 7, *P < 0.05.