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- Larsen, Filip J, 1977-, et al.
(author)
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Mitochondrial oxygen affinity increases after sprint interval training and is related to the improvement in peak oxygen uptake.
- 2020
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In: Acta Physiologica. - : John Wiley & Sons. - 1748-1708 .- 1748-1716. ; 229:3
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Journal article (peer-reviewed)abstract
- AIMS: The body responds to exercise training by profound adaptations throughout the cardiorespiratory and muscular systems, which may result in improvements in maximal oxygen consumption (VO2 peak) and mitochondrial capacity. By convenience, mitochondrial respiration is often measured at supra-physiological oxygen levels, an approach that ignores any potential regulatory role of mitochondrial affinity for oxygen (p50mito ) at physiological oxygen levels.METHODS: In this study, we examined the p50mito of mitochondria isolated from the Vastus lateralis and Triceps brachii in 12 healthy volunteers before and after a training intervention with 7 sessions of sprint interval training using both leg cycling and arm cranking. The changes in p50mito were compared to changes in whole-body VO2 peak.RESULTS: We here show that p50mito is similar in isolated mitochondria from the Vastus (40 ± 3.8 Pa) compared to Triceps (39 ± 3.3) but decreases (mitochondrial oxygen affinity increases) after 7 sessions of sprint interval training (to 26 ± 2.2 Pa in Vastus and 22 ± 2.7 Pa in Triceps, both p<0.01). The change in VO2 peak modeled from changes in p50mito was correlated to actual measured changes in VO2 peak (R2 =0.41, p=0.002).CONCLUSION: Together with mitochondrial respiratory capacity, p50mito is a critical factor when measuring mitochondrial function, it can decrease with sprint interval training and should be considered in the integrative analysis of the oxygen cascade from lung to mitochondria.
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| 2. |
- Perez-Valera, Mario, et al.
(author)
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Angiotensin-Converting Enzyme 2 (SARS-CoV-2 receptor) expression in human skeletal muscle
- 2021
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In: Scandinavian Journal of Medicine and Science in Sports. - : John Wiley & Sons. - 0905-7188 .- 1600-0838. ; 31:12, s. 2249-2258
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Journal article (peer-reviewed)abstract
- The study aimed to determine the levels of skeletal muscle Angiotensin-Converting Enzyme 2 (ACE2, the SARS-CoV-2 receptor) protein expression in men and women and assess whether ACE2 expression in skeletal muscle is associated with cardiorespiratory fitness and adiposity. The level of ACE2 in vastus lateralis muscle biopsies collected in previous studies from 170 men (age:19-65 yrs, weight:56-137 kg, BMI:23-44) and 69 women (age:18-55 yrs, weight:41-126 kg, BMI:22-39) was analysed in duplicate by western blot. VO2max was determined by ergospirometry and body composition by DXA. ACE2 protein expression was 1.8-fold higher in women than men (p=0.001, n=239). This sex difference disappeared after accounting for the percentage of body fat (fat %), VO2max per kg of legs lean mass (VO2max-LLM) and age (p=0.47). Multiple regression analysis showed that the fat % (β=0.47) is the main predictor of the variability in ACE2 protein expression in skeletal muscle, explaining 5.2 % of the variance. VO2max-LLM had also predictive value (β=0.09). There was a significant fat % by VO2max-LLM interaction, such that for subjects with low fat %, VO2max-LLM was positively associated with ACE2 expression while as fat % increased the slope of the positive association between VO2max-LLM and ACE2 was reduced. In conclusion, women express higher amounts of ACE2 in their skeletal muscles than men. This sexual dimorphism is mainly explained by sex differences in fat % and cardiorespiratory fitness. The percentage of body fat is the main predictor of the variability in ACE2 protein expression in human skeletal muscle.
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| 4. |
- Galvan-Alvarez, Victor, et al.
(author)
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Antioxidant enzymes and Nrf2/Keap1 in human skeletal muscle: Influence of age, sex, adiposity and aerobic fitness
- 2023
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In: Free Radical Biology & Medicine. - : Elsevier Inc.. - 0891-5849 .- 1873-4596. ; 209:Part 2, s. 282-291
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Journal article (peer-reviewed)abstract
- Whether a higher aerobic fitness is associated with increased expression of antioxidant enzymes and their regulatory factors in skeletal muscle remains unknown. Although oestrogens could promote a higher antioxidant capacity in females, it remains unknown whether a sex dimorphism exists in humans regarding the antioxidant capacity of skeletal muscle. Thus, the aim was to determine the protein expression levels of the antioxidant enzymes SOD1, SOD2, catalase and glutathione reductase (GR) and their regulatory factors Nrf2 and Keap1 in 189 volunteers (120 males and 69 females) to establish whether sex differences exist and how age, VO2max and adiposity influence these. For this purpose, vastus lateralis muscle biopsies were obtained in all participants under resting and unstressed conditions. No significant sex differences in Nrf2, Keap1, SOD1, SOD2, catalase and GR protein expression levels were observed after accounting for VO2max, age and adiposity differences. Multiple regression analysis indicates that the VO2max in mL.kg LLM−1.min−1can be predicted from the levels of SOD2, Total Nrf2 and Keap1 (R = 0.58, P < 0.001), with SOD2 being the main predictor explaining 28 % of variance in VO2max, while Nrf2 and Keap1 explained each around 3 % of the variance. SOD1 protein expression increased with ageing in the whole group after accounting for differences in VO2max and body fat percentage. Overweight and obesity were associated with increased pSer40-Nrf2, pSer40-Nrf2/Total Nrf2 ratio and SOD1 protein expression levels after accounting for differences in age and VO2max. Overall, at the population level, higher aerobic fitness is associated with increased basal expression of muscle antioxidant enzymes, which may explain some of the benefits of regular exercise.
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| 5. |
- Galvan-Alvarez, Victor, et al.
(author)
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Determinants of the maximal functional reserve during repeated supramaximal exercise by humans: The roles of Nrf2/Keap1, antioxidant proteins, muscle phenotype and oxygenation
- 2023
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In: Redox Biology. - : Elsevier B.V.. - 2213-2317. ; 66
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Journal article (peer-reviewed)abstract
- When high-intensity exercise is performed until exhaustion a “functional reserve” (FR) or capacity to produce power at the same level or higher than reached at exhaustion exists at task failure, which could be related to reactive oxygen and nitrogen species (RONS)-sensing and counteracting mechanisms. Nonetheless, the magnitude of this FR remains unknown. Repeated bouts of supramaximal exercise at 120% of VO2max interspaced with 20s recovery periods with full ischaemia were used to determine the maximal FR. Then, we determined which muscle phenotypic features could account for the variability in functional reserve in humans. Exercise performance, cardiorespiratory variables, oxygen deficit, and brain and muscle oxygenation (near-infrared spectroscopy) were measured, and resting muscle biopsies were obtained from 43 young healthy adults (30 males). Males and females had similar aerobic (VO2max per kg of lower extremities lean mass (LLM): 166.7 ± 17.1 and 166.1 ± 15.6 ml kg LLM−1.min−1, P = 0.84) and anaerobic fitness (similar performance in the Wingate test and maximal accumulated oxygen deficit when normalized to LLM). The maximal FR was similar in males and females when normalized to LLM (1.84 ± 0.50 and 2.05 ± 0.59 kJ kg LLM−1, in males and females, respectively, P = 0.218). This FR depends on an obligatory component relying on a reserve in glycolytic capacity and a putative component generated by oxidative phosphorylation. The aerobic component depends on brain oxygenation and phenotypic features of the skeletal muscles implicated in calcium handling (SERCA1 and 2 protein expression), oxygen transport and diffusion (myoglobin) and redox regulation (Keap1). The glycolytic component can be predicted by the protein expression levels of pSer40-Nrf2, the maximal accumulated oxygen deficit and the protein expression levels of SOD1. Thus, an increased capacity to modulate the expression of antioxidant proteins involved in RONS handling and calcium homeostasis may be critical for performance during high-intensity exercise in humans.
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| 6. |
- Morales-Alamo, David, et al.
(author)
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Sarcolipin expression in human skeletal muscle : Influence of energy balance and exercise
- 2020
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In: Scandinavian Journal of Medicine and Science in Sports. - : Wiley. - 0905-7188 .- 1600-0838. ; 30:3, s. 408-420
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Journal article (peer-reviewed)abstract
- Sarcolipin (SLN) is a SERCA uncoupling protein associated with exercise performance and lower adiposity in mice. To determine SLN protein expression in human skeletal muscle and its relationship with adiposity, resting energy expenditure (REE), and performance, SLN was assessed by Western blot in 199 biopsies from two previous studies. In one study, 15 overweight volunteers underwent a pretest followed by 4 days of caloric restriction and exercise (45-minute one-arm cranking + 8-hour walking), and 3 days on a control diet. Muscle biopsies were obtained from the trained and non-exercised deltoid, and vastus lateralis (VL). In another study, 16 men performed seven sessions of 4-6 x 30-sec all-out sprints on the cycle ergometer with both limbs, and their VL and triceps brachii biopsied pre- and post-training. SLN expression was twofold and 44% higher in the VL than in the deltoids and triceps brachii, respectively. SLN was associated with neither adiposity nor REE, and was not altered by a severe energy deficit (5500 kcal/day). SLN and cortisol changes after the energy deficit were correlated (r = .38, P = .039). SLN was not altered by low-intensity exercise in the overweight subjects, whereas it was reduced after sprint training in the other group. The changes in SLN with sprint training were inversely associated with the changes in gross efficiency (r = -.59, P = .016). No association was observed between aerobic or anaerobic performance and SLN expression. In conclusion, sarcolipin appears to play no role in regulating the fat mass of men. Sprint training reduces sarcolipin expression, which may improve muscle efficiency.
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