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Enhanced Glycogen Storage of a Subcellular Hot Spot in Human Skeletal Muscle during Early Recovery from Eccentric Contractions.

Nielsen J, Farup J, Rahbek SK, de Paoli FV, Vissing K - PLoS ONE (2015)

Bottom Line: Quantitative imaging by transmission electron microscopy revealed an early (post 3 and 24 h) enhanced storage of intramyofibrillar glycogen (defined as glycogen particles located within the myofibrils) of type I fibers, which was associated with an increase in the number of particles.In contrast, late in recovery (post 48 h), intermyofibrillar, intramyofibrillar and subsarcolemmal glycogen in both type I and II fibers were lower in the exercise leg compared with the control leg, and this was associated with a smaller size of the glycogen particles.We conclude that in the carbohydrate-supplemented state, the effect of eccentric contractions on glycogen metabolism depends on the subcellular localization, muscle fiber's oxidative capacity, and the time course of recovery.

View Article: PubMed Central - PubMed

Affiliation: Department of Sports Science and Clinical Biomechanics, SDU Muscle Research Cluster (SMRC), University of Southern Denmark, Odense M, Denmark; Department of Pathology, SDU Muscle Research Cluster (SMRC), Odense University Hospital, Odense C, Denmark.

ABSTRACT
Unaccustomed eccentric exercise is accompanied by muscle damage and impaired glucose uptake and glycogen synthesis during subsequent recovery. Recently, it was shown that the role and regulation of glycogen in skeletal muscle are dependent on its subcellular localization, and that glycogen synthesis, as described by the product of glycogen particle size and number, is dependent on the time course of recovery after exercise and carbohydrate availability. In the present study, we investigated the subcellular distribution of glycogen in fibers with high (type I) and low (type II) mitochondrial content during post-exercise recovery from eccentric contractions. Analysis was completed on five male subjects performing an exercise bout consisting of 15 x 10 maximal eccentric contractions. Carbohydrate-rich drinks were subsequently ingested throughout a 48 h recovery period and muscle biopsies for analysis included time points 3, 24 and 48 h post exercise from the exercising leg, whereas biopsies corresponding to prior to and at 48 h after the exercise bout were collected from the non-exercising, control leg. Quantitative imaging by transmission electron microscopy revealed an early (post 3 and 24 h) enhanced storage of intramyofibrillar glycogen (defined as glycogen particles located within the myofibrils) of type I fibers, which was associated with an increase in the number of particles. In contrast, late in recovery (post 48 h), intermyofibrillar, intramyofibrillar and subsarcolemmal glycogen in both type I and II fibers were lower in the exercise leg compared with the control leg, and this was associated with a smaller size of the glycogen particles. We conclude that in the carbohydrate-supplemented state, the effect of eccentric contractions on glycogen metabolism depends on the subcellular localization, muscle fiber's oxidative capacity, and the time course of recovery. The early enhanced storage of intramyofibrillar glycogen after the eccentric contractions may entail important implications for muscle function and fatigue resistance.

No MeSH data available.


Related in: MedlinePlus

Changes in glycogen particle volume during recovery from eccentric contractions depend on fiber type and time course of recovery.The size of intermyofibrillar (light grey), intramyofibrillar (dark grey) and subsarcolemmal (black) glycogen particles are shown for type I fibers (A) and type II fibers (B). *: different from Pre (P = 0.02). (*): tendency to be different from Pre (P = 0.06). **: different from Pre (P < 0.001). †: different from Post 48h (P < 0.0001). Values are geometric means and horizontal bars represent 95% confidence interval.
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pone.0127808.g004: Changes in glycogen particle volume during recovery from eccentric contractions depend on fiber type and time course of recovery.The size of intermyofibrillar (light grey), intramyofibrillar (dark grey) and subsarcolemmal (black) glycogen particles are shown for type I fibers (A) and type II fibers (B). *: different from Pre (P = 0.02). (*): tendency to be different from Pre (P = 0.06). **: different from Pre (P < 0.001). †: different from Post 48h (P < 0.0001). Values are geometric means and horizontal bars represent 95% confidence interval.

Mentions: The average glycogen particle volume for each subcellular location of type I and II fibers during recovery from the eccentric exercise is presented in Fig 4. While, in type I fibers, the average glycogen particle volume did not change during early (3–24 h) recovery in any of the three subfractions of glycogen particles (Fig 4A), it was lowered by -21% (-26:-15) at post 48 h compared with the pre exercise value (Fig 4A). In type II fibers, on the other hand, the average glycogen particle volume was reduced by -16% (-27:-6), -10% (-18:01), and -20% (-27:-12) compared with pre exercise at post 3 h, 24 h and 28 h, respectively, and also lowered by -28% (-34:-21) compared with the control leg at 48 h. These changes in glycogen particle size during recovery from the eccentric contractions were not dependent on location in the type I fibers (P = 0.34) or the type II fibers (P = 0.99). Representative images are shown in Fig 5.


Enhanced Glycogen Storage of a Subcellular Hot Spot in Human Skeletal Muscle during Early Recovery from Eccentric Contractions.

Nielsen J, Farup J, Rahbek SK, de Paoli FV, Vissing K - PLoS ONE (2015)

Changes in glycogen particle volume during recovery from eccentric contractions depend on fiber type and time course of recovery.The size of intermyofibrillar (light grey), intramyofibrillar (dark grey) and subsarcolemmal (black) glycogen particles are shown for type I fibers (A) and type II fibers (B). *: different from Pre (P = 0.02). (*): tendency to be different from Pre (P = 0.06). **: different from Pre (P < 0.001). †: different from Post 48h (P < 0.0001). Values are geometric means and horizontal bars represent 95% confidence interval.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4440641&req=5

pone.0127808.g004: Changes in glycogen particle volume during recovery from eccentric contractions depend on fiber type and time course of recovery.The size of intermyofibrillar (light grey), intramyofibrillar (dark grey) and subsarcolemmal (black) glycogen particles are shown for type I fibers (A) and type II fibers (B). *: different from Pre (P = 0.02). (*): tendency to be different from Pre (P = 0.06). **: different from Pre (P < 0.001). †: different from Post 48h (P < 0.0001). Values are geometric means and horizontal bars represent 95% confidence interval.
Mentions: The average glycogen particle volume for each subcellular location of type I and II fibers during recovery from the eccentric exercise is presented in Fig 4. While, in type I fibers, the average glycogen particle volume did not change during early (3–24 h) recovery in any of the three subfractions of glycogen particles (Fig 4A), it was lowered by -21% (-26:-15) at post 48 h compared with the pre exercise value (Fig 4A). In type II fibers, on the other hand, the average glycogen particle volume was reduced by -16% (-27:-6), -10% (-18:01), and -20% (-27:-12) compared with pre exercise at post 3 h, 24 h and 28 h, respectively, and also lowered by -28% (-34:-21) compared with the control leg at 48 h. These changes in glycogen particle size during recovery from the eccentric contractions were not dependent on location in the type I fibers (P = 0.34) or the type II fibers (P = 0.99). Representative images are shown in Fig 5.

Bottom Line: Quantitative imaging by transmission electron microscopy revealed an early (post 3 and 24 h) enhanced storage of intramyofibrillar glycogen (defined as glycogen particles located within the myofibrils) of type I fibers, which was associated with an increase in the number of particles.In contrast, late in recovery (post 48 h), intermyofibrillar, intramyofibrillar and subsarcolemmal glycogen in both type I and II fibers were lower in the exercise leg compared with the control leg, and this was associated with a smaller size of the glycogen particles.We conclude that in the carbohydrate-supplemented state, the effect of eccentric contractions on glycogen metabolism depends on the subcellular localization, muscle fiber's oxidative capacity, and the time course of recovery.

View Article: PubMed Central - PubMed

Affiliation: Department of Sports Science and Clinical Biomechanics, SDU Muscle Research Cluster (SMRC), University of Southern Denmark, Odense M, Denmark; Department of Pathology, SDU Muscle Research Cluster (SMRC), Odense University Hospital, Odense C, Denmark.

ABSTRACT
Unaccustomed eccentric exercise is accompanied by muscle damage and impaired glucose uptake and glycogen synthesis during subsequent recovery. Recently, it was shown that the role and regulation of glycogen in skeletal muscle are dependent on its subcellular localization, and that glycogen synthesis, as described by the product of glycogen particle size and number, is dependent on the time course of recovery after exercise and carbohydrate availability. In the present study, we investigated the subcellular distribution of glycogen in fibers with high (type I) and low (type II) mitochondrial content during post-exercise recovery from eccentric contractions. Analysis was completed on five male subjects performing an exercise bout consisting of 15 x 10 maximal eccentric contractions. Carbohydrate-rich drinks were subsequently ingested throughout a 48 h recovery period and muscle biopsies for analysis included time points 3, 24 and 48 h post exercise from the exercising leg, whereas biopsies corresponding to prior to and at 48 h after the exercise bout were collected from the non-exercising, control leg. Quantitative imaging by transmission electron microscopy revealed an early (post 3 and 24 h) enhanced storage of intramyofibrillar glycogen (defined as glycogen particles located within the myofibrils) of type I fibers, which was associated with an increase in the number of particles. In contrast, late in recovery (post 48 h), intermyofibrillar, intramyofibrillar and subsarcolemmal glycogen in both type I and II fibers were lower in the exercise leg compared with the control leg, and this was associated with a smaller size of the glycogen particles. We conclude that in the carbohydrate-supplemented state, the effect of eccentric contractions on glycogen metabolism depends on the subcellular localization, muscle fiber's oxidative capacity, and the time course of recovery. The early enhanced storage of intramyofibrillar glycogen after the eccentric contractions may entail important implications for muscle function and fatigue resistance.

No MeSH data available.


Related in: MedlinePlus