Single-fiber expression and fiber-specific adaptability to short-term intense exercise training of Na+-K+-ATPase α- and β-isoforms in human skeletal muscle

2015 ◽  
Vol 118 (6) ◽  
pp. 699-706 ◽  
Author(s):  
V. L. Wyckelsma ◽  
M. J. McKenna ◽  
F. R. Serpiello ◽  
C. R. Lamboley ◽  
R. J. Aughey ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Western Blotting ◽  
Human Skeletal Muscle ◽  
Fiber Type ◽  
Vastus Lateralis ◽  
Single Fiber ◽  
Vastus Lateralis Muscle ◽  
Type I ◽  
Fiber Types ◽  
Functional Roles

The Na+-K+-ATPase (NKA) plays a key role in muscle excitability, but little is known in human skeletal muscle about fiber-type-specific differences in NKA isoform expression or adaptability. A vastus lateralis muscle biopsy was taken in 17 healthy young adults to contrast NKA isoform protein relative abundance between type I and IIa fibers. We further investigated muscle fiber-type-specific NKA adaptability in eight of these adults following 4-wk repeated-sprint exercise (RSE) training, comprising three sets of 5 × 4-s sprints, 3 days/wk. Single fibers were separated, and myosin heavy chain (I and IIa) and NKA (α1–3 and β1–3) isoform abundance were determined via Western blotting. All six NKA isoforms were expressed in both type I and IIa fibers. No differences between fiber types were found for α1-, α2-, α3-, β1-, or β3-isoform abundances. The NKA β2-isoform was 27% more abundant in type IIa than type I fibers ( P < 0.05), with no other fiber-type-specific trends evident. RSE training increased β1 in type IIa fibers (pretraining 0.70 ± 0.25, posttraining 0.84 ± 0.24 arbitrary units, 42%, P < 0.05). No training effects were found for other NKA isoforms. Thus human skeletal muscle expresses all six NKA isoforms and not in a fiber-type-specific manner; this points to their different functional roles in skeletal muscle cells. Detection of elevated NKA β1 after RSE training demonstrates the sensitivity of the single-fiber Western blotting technique for fiber-type-specific intervention effects.

Gene Polymorphisms and Fiber-Type Composition of Human Skeletal Muscle

2012 ◽  
Vol 22 (4) ◽  
pp. 292-303 ◽  
Author(s):  
Ildus I. Ahmetov ◽  
Olga L. Vinogradova ◽  
Alun G. Williams
Keyword(s):  
Skeletal Muscle ◽  
Muscle Fiber ◽  
Human Skeletal Muscle ◽  
Fiber Type ◽  
Vastus Lateralis Muscle ◽  
Type I ◽  
Fiber Types ◽  
Fiber Type Composition ◽  
Type Composition ◽  
Type I Fibers

The ability to perform aerobic or anaerobic exercise varies widely among individuals, partially depending on their muscle-fiber composition. Variability in the proportion of skeletal-muscle fiber types may also explain marked differences in aspects of certain chronic disease states including obesity, insulin resistance, and hypertension. In untrained individuals, the proportion of slow-twitch (Type I) fibers in the vastus lateralis muscle is typically around 50% (range 5–90%), and it is unusual for them to undergo conversion to fast-twitch fibers. It has been suggested that the genetic component for the observed variability in the proportion of Type I fibers in human muscles is on the order of 40–50%, indicating that muscle fiber-type composition is determined by both genotype and environment. This article briefly reviews current progress in the understanding of genetic determinism of fiber-type proportion in human skeletal muscle. Several polymorphisms of genes involved in the calcineurin–NFAT pathway, mitochondrial biogenesis, glucose and lipid metabolism, cytoskeletal function, hypoxia and angiogenesis, and circulatory homeostasis have been associated with fiber-type composition. As muscle is a major contributor to metabolism and physical strength and can readily adapt, it is not surprising that many of these gene variants have been associated with physical performance and athlete status, as well as metabolic and cardiovascular diseases. Genetic variants associated with fiber-type proportions have important implications for our understanding of muscle function in both health and disease.

scholarly journals Skeletal muscle fiber type-selective effects of acute exercise on insulin-stimulated glucose uptake in insulin-resistant, high-fat-fed rats

2019 ◽  
Vol 316 (5) ◽  
pp. E695-E706 ◽  
Author(s):  
Mark W. Pataky ◽  
Carmen S. Yu ◽  
Yilin Nie ◽  
Edward B. Arias ◽  
Manak Singh ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Glucose Uptake ◽  
Acute Exercise ◽  
Fiber Type ◽  
Single Fiber ◽  
Male Rats ◽  
Type I ◽  
Fiber Types ◽  
High Fat ◽  
Insulin Resistant

Insulin-stimulated glucose uptake (GU) by skeletal muscle is enhanced several hours after acute exercise in rats with normal or reduced insulin sensitivity. Skeletal muscle is composed of multiple fiber types, but exercise’s effect on fiber type-specific insulin-stimulated GU in insulin-resistant muscle was previously unknown. Male rats were fed a high-fat diet (HFD; 2 wk) and were either sedentary (SED) or exercised (2-h exercise). Other, low-fat diet-fed (LFD) rats remained SED. Rats were studied immediately postexercise (IPEX) or 3 h postexercise (3hPEX). Epitrochlearis muscles from IPEX rats were incubated in 2-deoxy-[3H]glucose (2-[3H]DG) without insulin. Epitrochlearis muscles from 3hPEX rats were incubated with 2-[3H]DG ± 100 µU/ml insulin. After single fiber isolation, GU and fiber type were determined. Glycogen and lipid droplets (LDs) were assessed histochemically. GLUT4 abundance was determined by immunoblotting. In HFD-SED vs. LFD-SED rats, insulin-stimulated GU was decreased in type IIB, IIX, IIAX, and IIBX fibers. Insulin-independent GU IPEX was increased and glycogen content was decreased in all fiber types (types I, IIA, IIB, IIX, IIAX, and IIBX). Exercise by HFD-fed rats enhanced insulin-stimulated GU in all fiber types except type I. Single fiber analyses enabled discovery of striking fiber type-specific differences in HFD and exercise effects on insulin-stimulated GU. The fiber type-specific differences in insulin-stimulated GU postexercise in insulin-resistant muscle were not attributable to a lack of fiber recruitment, as indirectly evidenced by insulin-independent GU and glycogen IPEX, differences in multiple LD indexes, or altered GLUT4 abundance, implicating fiber type-selective differences in the cellular processes responsible for postexercise enhancement of insulin-mediated GLUT4 translocation.

Do skeletal muscle phenotypic characteristics of Xhosa and Caucasian endurance runners differ when matched for training and racing distances?

2007 ◽  
Vol 103 (3) ◽  
pp. 932-940 ◽  
Author(s):  
Tertius A. Kohn ◽  
Birgitta Essén-Gustavsson ◽  
Kathryn H. Myburgh
Keyword(s):  
Skeletal Muscle ◽  
Fiber Type ◽  
Vastus Lateralis ◽  
Dry Weight ◽  
Vastus Lateralis Muscle ◽  
Type I ◽  
Endurance Running ◽  
Exercise Tests ◽  
Black And White ◽  
Endurance Runners

Although East African black athletes dominate endurance running events, it is unknown whether black and white endurance runners with similar racing ability, matched for training, may differ in their skeletal muscle biochemical phenotype. Thirteen Xhosa (XR) and 13 Caucasian (CR) endurance runners were recruited and matched for 10-km performance, average preferred racing distance (PRDA), and training volume. Submaximal and maximal exercise tests were done, and vastus lateralis muscle biopsies were taken. XR were significantly lighter and shorter than CR athletes but had similar maximum oxygen consumption corrected for body weight and peak treadmill speed (PTS). XR had lower plasma lactate concentrations at 80% PTS ( P < 0.05) compared with CR. Also, XR had more type IIA (42.4 ± 9.2 vs. 31.3 ± 11.5%, P < 0.05) and less type I fibers (47.8 ± 10.9 vs. 63.1 ± 13.2%, P < 0.05), although oxidative enzyme activities did not differ. Furthermore, XR compared with CR had higher lactate dehydrogenase (LDH) activity in homogenate muscle samples (383 ± 99 vs. 229 ± 85 μmol·min−1·g dry weight−1, P < 0.05) and in both type IIa ( P < 0.05) and type I ( P = 0.05) single-fiber pools. A marked difference ( P < 0.05) in the composition of LDH isoform content was found between the two groups with XR having higher levels of LDH5-4 isoforms (skeletal muscle isozymes; LDH-M) than CR, which was not accounted for by fiber-type differences alone. These results confirm differences in muscle phenotype and physiological characteristics, particularly associated with high-intensity running.

Muscle fiber type-specific response of Hsp70 expression in human quadriceps following acute isometric exercise

2007 ◽  
Vol 103 (6) ◽  
pp. 2105-2111 ◽  
Author(s):  
A. R. Tupling ◽  
E. Bombardier ◽  
R. D. Stewart ◽  
C. Vigna ◽  
A. E. Aqui
Keyword(s):  
Skeletal Muscle ◽  
Time Course ◽  
Human Skeletal Muscle ◽  
Fiber Type ◽  
Hsp70 Expression ◽  
Type I ◽  
Fiber Types ◽  
Type Ii ◽  
Exercise Induced ◽  
Type I Fibers

To investigate the time course of fiber type-specific heat shock protein 70 (Hsp70) expression in human skeletal muscle after acute exercise, 10 untrained male volunteers performed single-legged isometric knee extensor exercise at 60% of their maximal voluntary contraction (MVC) with a 50% duty cycle (5-s contraction and 5-s relaxation) for 30 min. Muscle biopsies were collected from the vastus lateralis before (Pre) exercise in the rested control leg (C) and immediately after exercise (Post) in the exercised leg (E) only and on recovery days 1 (R1), 2 (R2), 3 (R3), and 6 (R6) from both legs. As demonstrated by Western blot analysis, whole muscle Hsp70 content was unchanged ( P > 0.05) immediately after exercise (Pre vs. Post), was increased ( P < 0.05) by ∼43% at R1, and remained elevated throughout the entire recovery period in E only. Hsp70 expression was also assessed in individual muscle fiber types I, IIA, and IIAX/IIX by immunohistochemistry. There were no fiber type differences ( P > 0.05) in basal Hsp70 expression. Immediately after exercise, Hsp70 expression was increased ( P < 0.05) in type I fibers by ∼87% but was unchanged ( P > 0.05) in type II fibers (Pre vs. Post). At R1 and throughout recovery, Hsp70 content in E was increased above basal levels ( P < 0.05) in all fiber types, but Hsp70 expression was always highest ( P < 0.05) in type I fibers. Hsp70 content in C was not different from Pre at any time throughout recovery. Glycogen depletion was observed at Post in all type II, but not type I, fibers, suggesting that the fiber type differences in exercise-induced Hsp70 expression were not related to glycogen availability. These results demonstrate that the time course of exercise-induced Hsp70 expression in human skeletal muscle is fiber type specific.

Enhanced technique to measure proteins in single segments of human skeletal muscle fibers: fiber-type dependence of AMPK-α1 and -β1

2011 ◽  
Vol 110 (3) ◽  
pp. 820-825 ◽  
Author(s):  
Robyn M. Murphy
Keyword(s):  
Skeletal Muscle ◽  
Human Skeletal Muscle ◽  
Fiber Type ◽  
Significant Advance ◽  
Vastus Lateralis Muscle ◽  
Fiber Types ◽  
Freeze Dried ◽  
Slow Twitch ◽  
Fast Twitch ◽  
Muscle Biopsies

Human physiological studies typically use skeletal muscle biopsies from the heterogeneous vastus lateralis muscle comprised of both fast-twitch and slow-twitch fiber types. It is likely that potential changes of physiological importance are overlooked because fiber-type specific responses may not be apparent in the whole muscle preparation. A technological advance in Western blotting is presented where proteins are analyzed in just one small segment (<2 mm) of individual fibers dissected from freeze-dried muscle samples using standard laboratory equipment. A significant advance is being able to classify every fiber at the level of both contractile (myosin heavy chain and tropomyosin) and sarcoplasmic reticulum [sarco(endo)plasmic reticulum Ca2+-ATPase type 1] properties and then being able to measure specific proteins in the very same segments. This removes the need to fiber type segments before further analyses and, as such, dramatically reduces the time required for sample collection. Compared with slow-twitch fibers, there was less AMP-activated protein kinase (AMPK)-α1 (∼25%) and AMPK-β1 (∼60%) in fast-twitch fibers from human skeletal muscle biopsies.

scholarly journals Histochemical, biochemical, and ultrastructural analyses of single human muscle fibers, with special reference to the C-fiber population.

1992 ◽  
Vol 40 (4) ◽  
pp. 563-568 ◽  
Author(s):  
R S Staron ◽  
R S Hikida
Keyword(s):  
Fiber Type ◽  
Vastus Lateralis ◽  
Oxidative Capacity ◽  
Vastus Lateralis Muscle ◽  
Type I ◽  
Fiber Types ◽  
Heavy Chains ◽  
C Fibers ◽  
C Fiber ◽  
Ph Range

A muscle biopsy from the vastus lateralis muscle of a strength-trained woman was found to contain an unusual fiber type composition and was analyzed by histochemical, biochemical, and ultrastructural techniques. Special attention was given to the C-fibers, which comprised over 15% of the total fiber number in the biopsy. The mATPase activity of the C-fibers remained stable to varying degrees over the pH range normally used for routine mATPase histochemistry. Although a continuum existed, the C-fibers were histochemically subdivided into three main fiber types: IC, IIC, and IIAC. The IC fibers were histochemically more similar to the Type I, the IIAC were more similar to the Type IIA, and the IIC were darkly stained throughout the pH range. Biochemical analysis revealed that all C-fibers coexpressed myosin heavy chains (MHC) I and IIa in variable ratios. The histochemical staining intensity correlated with the myosin heavy chain composition such that the Type IC fibers contained a greater ratio of MHCI/MHCIIa, the IIAC contained a greater ratio of MHCIIa/MHCI, and the Type IIC contained equal amounts of these two heavy chains. Ultrastructural data of the C-fiber population revealed an oxidative capacity between fiber Types I and IIA and suggested a range of mitochondrial volume percent from highest to lowest such that I greater than IC greater than IIC greater than IIA-C greater than IIA. Under physiological conditions, it appears that the IC fibers represent Type I fibers that additionally express some fast characteristics, whereas the Type IIAC are Type IIA fibers that additionally express some slow characteristics. Fibers expressing a 50:50 mixture of MHCI and MHCIIa (IIC fibers) were rarely found. It is not known whether C-fibers represent a distinct population between the fast- and slow-twitch fibers that is specifically adapted to a particular usage or whether they are transforming fibers in the process of going from fast to slow or slow to fast.

scholarly journals Super-relaxed state of myosin in human skeletal muscle is fiber-type dependent

2020 ◽  
Author(s):  
Lien A. Phung ◽  
Aurora D. Foster ◽  
Mark S. Miller ◽  
Dawn A. Lowe ◽  
David D. Thomas
Keyword(s):  
Skeletal Muscle ◽  
Human Skeletal Muscle ◽  
Fiber Type ◽  
Vastus Lateralis ◽  
Epifluorescence Microscopy ◽  
Model Organisms ◽  
Muscle Physiology ◽  
Fiber Types ◽  
Mhc I

AbstractThe myosin super-relaxed state (SRX) in skeletal muscle is hypothesized to play an important role in regulating muscle contractility and thermogenesis in humans, but has only been examined in model organisms. Here we report the first human skeletal muscle SRX measurements, using quantitative epifluorescence microscopy of fluorescent 2’/3’-O-(N-methylanthraniloyl) ATP (mantATP) single-nucleotide turnover. Myosin heavy chain (MHC) isoform expression was determined using gel electrophoresis for each permeabilized vastus lateralis fiber, to allow for novel comparisons of SRX between fiber-types. We find that the fraction of myosin in SRX is less in MHC IIA fibers than in MHC I and IIAX fibers (p = 0.008). ATP turnover of SRX is faster in MHC IIAX fibers compared to MHC I and IIA fibers (p = 0.001). We conclude that SRX biochemistry is measurable in human skeletal muscle, and our data indicate that SRX depends on fiber type as classified by MHC isoform. Extension from this preliminary work would provide further understanding regarding the role of SRX in human muscle physiology.

Variablity in vastus lateralis fiber type distribution, fiber size and myonuclear content along and the between legs

2021 ◽  
Author(s):  
Oscar Horwath ◽  
Helena Envall ◽  
Julia Röja ◽  
Eric Bengt Emanuelsson ◽  
Gema Sanz ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Human Skeletal Muscle ◽  
Fiber Type ◽  
Vastus Lateralis ◽  
Domain Size ◽  
Type I ◽  
Longitudinal Orientation ◽  
Type Composition ◽  
Fiber Size ◽  
Myonuclear Domain

Human skeletal muscle characteristics such as fiber type composition, fiber size and myonuclear content are widely studied in clinical and sports related contexts. Being aware of the methodological and biological variability of the characteristics is a critical aspect in study design and outcome interpretation, but comprehensive data on the variability of morphological features in human skeletal muscle is currently limited. Accordingly, in the present study, m. vastus lateralis biopsies (10 per subject) from young and healthy individuals, collected in a systematic manner, were analyzed for various characteristics using immunohistochemistry (n=7) and SDS-PAGE (n=25). None of the analyzed parameters; fiber type % (FT%), type I and II CSA (fCSA), percentage fiber type area (fCSA%), myosin heavy chain composition (MyHC%), type IIX content, myonuclear content or myonuclear domain varied in a systematic manner longitudinally along the muscle or between the two legs. The average within subject coefficient of variation for FT%, fCSA, fCSA%, and MyHC% ranged between 13-18%, but was only 5% for fiber specific myonuclear content, which reduced the variability for myonuclear domain size to 11-12%. Pure type IIX fibers and type IIX MyHC were randomly distributed and present in <24% of the analyzed samples, with the average content being 0.1 and 1.1%, respectively. In conclusion, leg or longitudinal orientation does not seem to be an important aspect to consider when investigating human vastus lateralis characteristics. However, single muscle biopsies should preferably not be used when studying fiber type and fiber size related aspects given the notable sample to sample variability.

scholarly journals Cytoskeletal structure of skeletal muscle: identification of an intricate exosarcomeric microtubule lattice in slow- and fast-twitch muscle fibers.

1993 ◽  
Vol 41 (7) ◽  
pp. 1013-1021 ◽  
Author(s):  
S Boudriau ◽  
M Vincent ◽  
C H Côté ◽  
P A Rogers
Keyword(s):  
Skeletal Muscle ◽  
Muscle Fiber ◽  
Vastus Lateralis ◽  
Muscle Fiber Types ◽  
Vastus Lateralis Muscle ◽  
Type I ◽  
Fiber Types ◽  
Mammalian Skeletal Muscle ◽  
Microtubule Network ◽  
Fast Twitch

We used immunochemical quantification and indirect immunofluorescence to investigate the cell content, distribution, and organization of microtubules in adult rat slow-twitch soleus and fast-twitch vastus lateralis muscles. An immunoblotting assay demonstrated that the soleus muscle (primarily Type I fibers) was found to have a 1.7-fold higher relative content of alpha-tubulin compared with the superficial portion of the vastus lateralis muscle (primarily Type IIb fibers). Both physiological muscle types revealed a complex arrangement of microtubules which displayed oblique, longitudinal, and transverse orientations within the sarcoplasmic space. The predominance of any one particular orientation varied significantly from one muscle tissue section to another. Nuclei were completely surrounded by a dense net-like structure of microtubules. Both muscle fiber types were found to possess a higher density of microtubules in the subsarcolemmal region. These microtubules followed the contour of the sarcolemma in slightly contracted fibers and showed a fine punctate appearance indicative of a restricted distribution. The immunofluorescence results indicate that microtubules are associated with the sarcolemma and therefore may form a part of the membrane cytoskeletal domain of the muscle fiber. We conclude that the microtubule network of the adult mammalian skeletal muscle fiber constitutes a bone fide component of the exosarcomeric cytoskeletal lattice domain along with the intermediate filaments, and as such could therefore participate in the mechanical integration of the various organelles of the myofibers during the contraction-relaxation cycle.

Subcellular fractionation reveals HSP72 does not associate with SERCA in human skeletal muscle following damaging eccentric and concentric exercise

2014 ◽  
Vol 116 (11) ◽  
pp. 1503-1511 ◽  
Author(s):  
Noni T. Frankenberg ◽  
Graham D. Lamb ◽  
Kristian Vissing ◽  
Robyn M. Murphy
Keyword(s):  
Skeletal Muscle ◽  
Protein Content ◽  
Human Skeletal Muscle ◽  
Physiological Stress ◽  
Vastus Lateralis ◽  
Tight Binding ◽  
Fold Increase ◽  
Subcellular Fractionation ◽  
Vastus Lateralis Muscle ◽  
Type I

Through its upregulation and/or translocation, heat shock protein 72 (HSP72) is involved in protection and repair of key proteins after physiological stress. In human skeletal muscle we investigated HSP72 protein after eccentric (ECC1) and concentric (CONC) exercise and repeated eccentric exercise (ECC2; 8 wk later) and whether it translocated from its normal cytosolic location to membranes/myofibrils. HSP72 protein increased ∼2-fold 24 h after ECC1, with no apparent change after CONC or ECC2. In resting (nonstressed) human skeletal muscle the total pool of HSP72 protein was present almost exclusively in the cytosolic fraction, and after each exercise protocol the distribution of HSP72 protein remained unaltered. Overall, the amount of HSP72 protein in the cytosol increased 24 h after ECC1, matching the fold increase that was measured in total HSP72 protein. To better ascertain the capabilities and limitations of HSP72, using quantitative Western blotting we determined the HSP72 protein content to be 11.4 μmol/kg wet weight in resting human vastus lateralis muscle, which is comprised of Type I (slow-twitch) and Type II (fast-twitch) fibers. HSP72 protein content was similar in individual Type I or II fiber segments. After physiological stress, HSP72 content can increase and, although the functional consequences of increased amounts of HSP72 protein are poorly understood, it has been shown to bind to and protect protein pumps like SERCA and Na+-K+-ATPase. Given no translocation of cytosolic HSP72, these findings suggest eccentric contractions, unlike other forms of stress such as heat, do not trigger tight binding of HSP72 to its primary membrane-bound target proteins, in particular SERCA.

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