| 1. |
- Mascher, Henrik, et al.
(författare)
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Changes in signalling pathways regulating protein synthesis in human muscle in the recovery period after endurance exercise
- 2007
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Ingår i: Acta Physiologica. - : Blackwel. - 1748-1708 .- 1748-1716. ; 191:1, s. 67-75
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Tidskriftsartikel (refereegranskat)abstract
- AIM: Exercise induced alterations in the rate of muscle protein synthesis may be related to activity changes in signalling pathways involved in protein synthesis. The aim of the present study was to investigate whether such changes in enzyme phosphorylation occur after endurance exercise. METHODS: Six male subjects performed ergometer cycling exercise for 1 h at 75% of the maximal oxygen uptake. Muscle biopsy samples from the vastus lateralis were taken before, immediately after, 30 min, 1 h, 2 h and 3 h after exercise for the determination of protein kinase B (PKB/Akt), mammalian target of rapamycin (mTOR), glycogen synthase 3 kinase (GSK-3), p70S6 kinase (p70(S6k)) and eukaryotic elongation factor 2 (eEF2) phosphorylation. RESULTS: The phosphorylation of Akt was unchanged directly after exercise, but two- to fourfold increased 1 and 2 h after the exercise, whereas GSK-3alpha and beta phosphorylation were two- to fourfold elevated throughout most of the 3-h recovery period. Phosphorylation of mTOR was elevated threefold directly after, 30 min and 2 h after exercise and eEF2 phosphorylation was decreased by 35-75% from 30 min to 3 h-recovery. Exercise led to a five- to eightfold increase in Ser(424)/Thr(421) phosphorylation of p70(S6k) up to 30 min after exercise, but no change in Thr(389) phosphorylation. CONCLUSIONS: The marked decrease in eEF2 phosphorylation suggests an activation of translation elongation and possibly protein synthesis in the recovery period after sustained endurance exercise. The lack of p70(S6k) activation suggests that translation initiation is activated via alternative pathways, possibly via the activation of eukaryotic initiating factor 2B.
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| 2. |
- Borgenvik, Marcus, et al.
(författare)
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Alterations in amino acid concentrations in the plasma and muscle in human subjects during 24 h of simulated adventure racing
- 2012
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Ingår i: European Journal of Applied Physiology. - : Springer Science and Business Media LLC. - 1439-6319 .- 1439-6327. ; 112, s. 3679-3688
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Tidskriftsartikel (refereegranskat)abstract
- This investigation was designed to evaluate changes in plasma and muscle levels of free amino acids during an ultra-endurance exercise and following recovery. Nine male ultra-endurance trained athletes participated in a 24-h standardized endurance trial with controlled energy intake. The participants performed 12 sessions of running, kayaking and cycling (4 x each discipline). Blood samples were collected before, during and after exercise, as well as after 28 h of recovery. Muscle biopsies were taken 1 week before the test and after exercise, as well as after 28 h of recovery. During the 24-h exercise, plasma levels of branched-chain (BCAA), essential amino acids (EAA) and glutamine fell 13%, 14% and 19% (P<0.05) respectively, whereas their concentrations in muscle were unaltered. Simultaneously, tyrosine and phenylalanine levels rose 38% and 50% (P<0.05) in the plasma and 66% and 46% (P<0.05) in muscle, respectively. After the 24-h exercise, plasma levels of BCAA were positively correlated with muscle levels of glycogen (r2=0.73, P<0.05), as was the combined concentrations of muscle tyrosine and phenylalanine with plasma creatine kinase (r2=0.55, P<0.05). Following 28-h of recovery, plasma and muscle levels of amino acids had either returned to their initial levels or were elevated. In conclusion, ultra-endurance exercise caused significant changes elevations in plasma and muscle levels of tyrosine and phenylalanine, which suggest an increase in net muscle protein breakdown during exercise. There was a reduction in plasma concentrations of EAA and glutamine during exercise, whereas no changes were detected in their muscle concentration after exercise.
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| 3. |
- Flockhart, Mikael, 1980-
(författare)
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Exercising on the edge: mitochondrial and metabolic responses to intense training
- 2022
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Exercise and exercise training induces several physiological adaptations that increase the oxidative capacity of the muscles and improve glucose regulation. While the positive metabolic adaptations and effects on glucose regulation after exercise and exercise training have been extensively studied, negative outcomes have not. This thesis aims to address these questions and investigate possible negative effects of intensified training on mitochondrial parameters and glucose regulation.In two separate interventions, we studied these outcomes after progressive exercise training, and after different intensities of exercise. Mitochondrial respiration was assessed in muscle biopsies taken from m. vastus lateralis 14 hours after exercise and oral glucose tolerance tests were performed at the same time point.In paper I, we demonstrate that there is an upper limit of training load that can be tolerated without the manifestation of negative outcomes. After administrating almost daily sessions of high-intensity interval training, mitochondrial function and glucose control were impaired. In paper II, we used mitochondrial function as a novel biomarker of maladaptive training loads and constructed a diagnostic model that can be used for the early detection of maladaptations to exercise training. In paper III, we further demonstrated that endurance-trained athletes can have decreased glucose tolerance and increased insulin resistance the day after three hours of continuous cycling whereas these responses were not accentuated in healthy controls. Our results indicate that a metabolic switch in favor of lipid metabolism is the probable cause of this phenomenon. In paper IV, we briefly commented on a publication that described changes in whole-body VO2 responses to work rates in the athlete with the highest recorded VO2max. We provided arguments that the observed changes in VO2 and gross efficiency can in part have their origin in the mitochondria.We here combine measurements in muscle tissue with physiological measurements in an applied context. Using this integrated approach, we investigated the effects of intensified training on health-related and performance outcomes, thereby presenting insights into what maladaptations to exercise can constitute. We hope that our results and conclusions can help to further understand the complex relationship between exercise and health and to guide athletes and coaches to optimize training outcomes.
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| 4. |
- Blomstrand, Eva, et al.
(författare)
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Changes in amino acid concentration in plasma and type I and type II fibres during resistance exercise and recovery in human subjects.
- 2009
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Ingår i: Amino Acids. - : Springer Science and Business Media LLC. - 0939-4451 .- 1438-2199. ; 37:4, s. 629-36
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Tidskriftsartikel (refereegranskat)abstract
- Eight male subjects performed leg press exercise, 4 x 10 repetitions at 80% of their maximum. Venous blood samples were taken before, during exercise and repeatedly during 2 h of recovery. From four subjects, biopsies were taken from the vastus lateralis muscle prior to, immediately after and following one and 2 h of recovery. Samples were freeze-dried, individual muscle fibres were dissected out and identified as type I or type II. Resistance exercise led to pronounced reductions in the glutamate concentration in both type I (32%) and type II fibres (70%). Alanine concentration was elevated 60-75% in both fibre types and 29% in plasma. Glutamine concentration remained unchanged after exercise; although 2 h later the concentrations in both types of fibres were reduced 30-35%. Two hours after exercise, the plasma levels of glutamate and six of the essential amino acids, including the branched-chain amino acids were reduced 5-30%. The data suggest that glutamate acts as an important intermediate in muscle energy metabolism during resistance exercise, especially in type II fibres.
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| 5. |
- Apró, William, et al.
(författare)
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Influence of supplementation with branched-chain amino acids in combination with resistance exercise on p70S6 kinase phosphorylation in resting and exercising human skeletal muscle.
- 2010
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Ingår i: Acta Physiologica. - : Wiley. - 1748-1708 .- 1748-1716. ; 200:3, s. 237-48
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Tidskriftsartikel (refereegranskat)abstract
- AIM: Skeletal muscle growth is thought to be regulated by the mammalian target of rapamycin (mTOR) pathway, which can be activated by resistance exercise and branched-chain amino acids (BCAA). The major aim of the present study was to distinguish between the influence of resistance exercise and BCAA on key enzymes considered to be involved in the regulation of protein synthesis, including p70(S6) kinase (p70(S6k)). METHODS: Nine healthy subjects (four men and five women) performed unilateral resistance exercise on two occasions separated by 1 month. Subjects were randomly supplied either a mixture of BCAA or flavoured water. Muscle biopsies were taken from both resting and exercising muscle before, after and 1 h after exercise. RESULTS: Phosphorylation of Akt was unaltered by either resistance exercise and/or BCAA supplementation whereas mTOR phosphorylation was enhanced (P<0.05) to a similar extent in both exercising and resting muscle following exercise in the absence (70-90%) and presence of BCAA supplementation (80-130%). Phosphorylation of p70(S6k) was unaffected by resistance exercise alone; however, BCAA intake increased (P<0.05) this phosphorylation in both legs following exercise. In resting muscle, a 5- and 16-fold increase in p70(S6k) was observed immediately after and 1 h after exercise, respectively, as compared to 11- and 30-fold increases in the exercising muscle. Phosphorylation of eukaryotic elongation factor 2 was attenuated 1 h after exercise (P<0.05) in both resting (10-40%) and exercising muscle (30-50%) under both conditions. CONCLUSION: The present findings indicate that resistance exercise and BCAA exert both separate and combined effects on the p70(S6k) phosphorylation in an Akt-independent manner.
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| 6. |
- Apró, William, et al.
(författare)
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Is leucine induced p70S6 kinase phosphorylation following resistance exercise dependent on elevated phenylalanine levels in human skeletal muscle?
- 2010
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Ingår i: The FASEB Journal. - 0892-6638 .- 1530-6860. ; 24, s. lb273-
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Tidskriftsartikel (refereegranskat)abstract
- The purpose of this study was to investigate the specific role ofleucine in the stimulation of the mammalian target of rapamycinsignalling pathway. Six male subjects performed four heavyresistance exercise sessions, each separated by approximately oneweek. Subjects were randomly supplemented with one of fourdrinks: placebo (flavored water), leucine or essential amino acids(EAA) with and without leucine. Immediately following eachexercise session, four subjects were infused with a flooding dose ofL-[2H5] phenylalanine (Inf) while two subjects served as controls(Ctrl). Muscle biopsies were taken before and one hour afterexercise. In the Ctrl group, resistance exercise resulted in asubstantial increase (45-fold) in p70 kinase phosphorylationwhen all EAA were ingested, whereas ingestion of leucine alonehad no greater effect than that of placebo. In the Inf group,however, ingestion of leucine alone and EAA increased p70phosphorylation to a similar extent (35-fold). The divergentsignalling response in the two groups suggests that leucine alone isinsufficient to increase p70phosphorylation. Indeed, in the Infgroup, there was a strong correlation (r=0.91) betweenp70 phosphorylation and the product of muscle leucine andphenylalanine levels. These results suggest that the stimulatoryeffect of leucine on p70 phosphorylation is dependent onelevated muscle phenylalanine levels. Supported by the SwedishNational Centre for Research in Sports
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| 7. |
- Moberg, Marcus, 1986-, et al.
(författare)
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High-intensity leg cycling alters the molecular response to resistance exercise in the arm muscles.
- 2021
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Ingår i: Scientific Reports. - : Nature Publishing Group. - 2045-2322. ; 11:1
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Tidskriftsartikel (refereegranskat)abstract
- This study examined acute molecular responses to concurrent exercise involving different muscles. Eight men participated in a randomized crossover-trial with two sessions, one where they performed interval cycling followed by upper body resistance exercise (ER-Arm), and one with upper body resistance exercise only (R-Arm). Biopsies were taken from the triceps prior to and immediately, 90- and 180-min following exercise. Immediately after resistance exercise, the elevation in S6K1 activity was smaller and the 4E-BP1:eIF4E interaction greater in ER-Arm, but this acute attenuation disappeared during recovery. The protein synthetic rate in triceps was greater following exercise than at rest, with no difference between trials. The level of PGC-1α1 mRNA increased to greater extent in ER-Arm than R-Arm after 90 min of recovery, as was PGC-1α4 mRNA after both 90 and 180 min. Levels of MuRF-1 mRNA was unchanged in R-Arm, but elevated during recovery in ER-Arm, whereas MAFbx mRNA levels increased slightly in both trials. RNA sequencing in a subgroup of subjects revealed 862 differently expressed genes with ER-Arm versus R-Arm during recovery. These findings suggest that leg cycling prior to arm resistance exercise causes systemic changes that potentiate induction of specific genes in the triceps, without compromising the anabolic response.
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| 8. |
- Rundqvist, Håkan Claes, et al.
(författare)
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Influence of nutrient ingestion on amino acid transporters and protein synthesis in human skeletal muscle after sprint exercise
- 2017
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Ingår i: Journal of applied physiology. - : American Physiological Society. - 8750-7587 .- 1522-1601. ; 123:6, s. 1501-1515
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Tidskriftsartikel (refereegranskat)abstract
- Nutrient ingestion is known to increase the exercise-induced stimulation of muscle protein synthesis following resistance exercise. Less is known about the effect of nutrients on muscle protein synthesis following sprint exercise. At two occasions separated by one month, twelve healthy subjects performed three 30-s sprints with 20-min rest between bouts. In randomized order, they consumed a drink with essential amino acids and maltodextrin (nutrient) or flavored water (placebo). Muscle biopsies were obtained 80 and 200 min after the last sprint and blood samples were taken repeatedly during the experiment. Fractional synthetic rate (FSR) was measured by continuous infusion of L-[(2)H5]-phenylalanine up to 200 min postexercise. The mRNA and protein expression of SNAT2 were both 1.4-fold higher (P < 0.05) after nutrient intake compared to placebo at 200 min postexercise. Phosphorylated Akt, mTOR and p70S6k was 1.7- to 3.6-fold higher (P<0.01) 80 min after the last sprint with nutrient ingestion as compared to placebo. In addition, FSR was higher (P<0.05) with nutrients when plasma phenylalanine (FSRplasma) was used as a precursor, but not when intracellular phenylalanine (FSRmuscle) was used. Significant correlations were also found between FSRplasma on the one hand and plasma leucine and serum insulin on the other hand in the nutrient condition. The results show that nutrient ingestion induces the expression of the amino acid transporter SNAT2, stimulates Akt/mTOR signaling and most likely the rate of muscle protein synthesis following sprint exercise.
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| 9. |
- Terzis, Gerasimos, et al.
(författare)
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The degree of p70(S6k) and S6 phosphorylation in human skeletal muscle in response to resistance exercise depends on the training volume.
- 2010
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Ingår i: European Journal of Applied Physiology. - : Springer Science and Business Media LLC. - 1439-6319 .- 1439-6327. ; 110:4, s. 835-43
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Tidskriftsartikel (refereegranskat)abstract
- Regular performance of resistance exercise induces an increase in skeletal muscle mass, however, the molecular mechanisms underlying this effect are not yet fully understood. The purpose of the present investigation was to examine acute changes in molecular signalling in response to resistance exercise involving different training volumes. Eight untrained male subjects carried out one, three and five sets of 6 repetition maximum (RM) in leg press exercise in a random order. Muscle biopsies were taken from the vastus lateralis both prior to and 30 min after each training session and the effect on protein signalling was studied. Phosphorylation of Akt was not altered significantly after any of the training protocols, whereas that of the mammalian target of rapamycin was enhanced to a similar extent by training at all three volumes. The phosphorylation of p70S6 kinase (p70(S6k)) was elevated threefold after 3 × 6 RM and sixfold after 5 × 6 RM, while the phosphorylation of S6 was increased 30- and 55-fold following the 3 × 6 RM and 5 × 6 RM exercises, respectively. Moreover, the level of the phosphorylated form of the gamma isoform of p38 MAPK was enhanced three to fourfold following each of the three protocols, whereas phosphorylation of ERK1/2 was unchanged 30 min following exercise. These findings indicate that when exercise is performed in a fasted state, the increase in phosphorylation of signalling molecules such as p70(S6k) and the S6 ribosomal protein in human muscle depends on the exercise volume.
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| 10. |
- Apró, William, et al.
(författare)
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Leucine does not affect mechanistic target of rapamycin complex 1 assembly but is required for maximal ribosomal protein s6 kinase 1 activity in human skeletal muscle following resistance exercise
- 2015
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Ingår i: The FASEB Journal. - : Wiley. - 0892-6638 .- 1530-6860. ; 29:10, s. 4358-4373
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Tidskriftsartikel (refereegranskat)abstract
- We examined how the stimulatory effect of leucine on the mechanistic target of rapamycin complex 1 (mTORC1) pathway is affected by the presence of the remaining essential amino acids (EAAs). Nine male subjects performed resistance exercise on 4 occasions and were randomly supplied EAAs with leucine, EAAs without leucine (EAA-Leu), leucine alone, or flavored water (placebo; control). Muscle biopsies were taken from the vastus lateralis before and 60 and 90 min after exercise. Biopsies were analyzed for protein phosphorylation, kinase activity, protein-protein interactions, amino acid concentrations, and tracer incorporation. Leucine alone stimulated ribosomal protein s6 kinase 1 (S6K1) phosphorylation similar to 280% more than placebo and EAA-Leu after exercise. Moreover, this response was enhanced by 60-75% after intake of EAAs compared with that of leucine alone (P < 0.05). Kinase activity of S6K1 reflected that of S6K1 phosphorylation; 60 min after exercise, the activity was elevated 3.3- and 4.2-fold with intake of leucine alone and with EAAs, respectively (P < 0.05). The interaction between mammalian target of rapamycin and regulatory-associated protein of mammalian target of rapamycin was unaltered in response to both resistance exercise and amino acid provision. Leucine alone stimulates mTORC1 signaling, although this response is enhanced by other EAAs and does not appear to be caused by alterations inmTORC1 assembly.
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