Skeletal Muscle: A Brief Review of Structure and Function

Frontera, Walter R.; Ochala, Julien

doi:10.1007/s00223-014-9915-y

Cited by 940 publications

(747 citation statements)

References 74 publications

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“…Skeletal muscle accounts for almost 40% of the total body mass, and the maintenance of healthy skeletal muscles is vital for providing energy for locomotion, preventing metabolic disorders and promoting healthy aging [1][2][3]. Many pathological conditions characterized by muscle atrophy, including cachexia, diabetes, sepsis, starvation, metabolic acidosis and chronic kidney disease, are associated with elevated circulating glucocorticoid (GC) levels [4].…”

Section: Introductionmentioning

confidence: 99%

Dihydromyricetin Attenuates Dexamethasone-Induced Muscle Atrophy by Improving Mitochondrial Function via the PGC-1α Pathway

Huang¹,

Chen²,

Ren³

et al. 2018

Cell Physiol Biochem

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Background/Aims: Skeletal muscle atrophy is an important health issue and can impose tremendous economic burdens on healthcare systems. Glucocorticoids (GCs) are well-known factors that result in muscle atrophy observed in numerous pathological conditions. Therefore, the development of effective and safe therapeutic strategies for GC-induced muscle atrophy has significant clinical implications. Some natural compounds have been shown to effectively prevent muscle atrophy under several wasting conditions. Dihydromyricetin (DM), the most abundant flavonoid in Ampelopsis grossedentata, has a broad range of health benefits, but its effects on muscle atrophy are unclear. The purpose of this study was to evaluate the effects and underlying mechanisms of DM on muscle atrophy induced by the synthetic GC dexamethasone (Dex). Methods: The effects of DM on Dex-induced muscle atrophy were assessed in Sprague-Dawley rats and L6 myotubes. Muscle mass and myofiber cross-sectional areas were analyzed in gastrocnemius muscles. Muscle function was evaluated by a grip strength test. Myosin heavy chain (MHC) content and myotube diameter were measured in myotubes. Mitochondrial morphology was observed by transmission electron microscopy and confocal laser scanning microscopy. Mitochondrial DNA (mtDNA) was quantified by real-time PCR. Mitochondrial respiratory chain complex activities were examined using the MitoProfile Rapid Microplate Assay Kit, and mitochondrial membrane potential was assessed by JC-1 staining. Protein levels of mitochondrial biogenesis and dynamics markers were detected by western blotting. Myotubes were transfected with siRNAs targeting peroxisome proliferator-activated receptor γ coactivator 1α (PGC-1α), mitochondrial transcription factor A (TFAM) and mitofusin-2 (mfn2) to determine the underlying mechanisms. Results: In vivo, DM preserved muscles from weight and average fiber cross-sectional area losses and improved grip strength. In vitro, DM prevented the decrease in MHC content and myotube diameter. Moreover, DM stimulated mitochondrial biogenesis and promoted mitochondrial fusion, rescued the reduced mtDNA content, improved mitochondrial morphology, prevented the collapse in mitochondrial membrane potential and enhanced mitochondrial respiratory chain complex activities; these changes restored mitochondrial function and improved protein metabolism, contributing to the prevention of Dex-induced muscle atrophy. Furthermore, the protective effects of DM on mitochondrial function and muscle atrophy were alleviated by PGC-1α siRNA, TFAM siRNA and mfn2 siRNA transfection in vitro. Conclusion: DM attenuated Dex-induced muscle atrophy by reversing mitochondrial dysfunction, which was partially mediated by the PGC-1α/TFAM and PGC-1α/mfn2 signaling pathways. Our findings may open new avenues for identifying natural compounds that improve mitochondrial function as promising candidates for the management of muscle atrophy.

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Section: Introductionmentioning

confidence: 99%

Dihydromyricetin Attenuates Dexamethasone-Induced Muscle Atrophy by Improving Mitochondrial Function via the PGC-1α Pathway

Huang¹,

Chen²,

Ren³

et al. 2018

Cell Physiol Biochem

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“…Maintenance of muscle protein content depends on the balance between protein synthesis and degradation. 5 Under normal conditions, muscle protein mass gains during the fed state balance losses during the fasted state. 4 However, under severe metabolic stress generated by serious illness or injury, muscle protein can become Glucose metabolism in fed, fasted and malnourished states.…”

Section: Muscle Metabolism and Interorgan Crosstalkmentioning

confidence: 99%

“…Different muscle types have been classified according to histochemical features, structural protein composition, and major metabolic properties. 5,6 Most commonly, skeletal muscles are referred to as either "slow" or "fast" to reflect speeds of contraction, or the shortening of myosin heavy chain (MHC) protein. 6 The velocity of this shortening is dependent on the MHC isoform present; "fast" fiber isoforms MHCIIa and IIb demonstrate a higher shortening velocity than their "slow" fiber MHCI counterparts.…”

Section: Muscle Structure and Classificationmentioning

confidence: 99%

Skeletal Muscle Regulates Metabolism via Interorgan Crosstalk: Roles in Health and Disease

Argilés

Campos

López-Pedrosa

et al. 2016

Journal of the American Medical Directors Association

335

255

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Skeletal muscle is recognized as vital to physical movement, posture, and breathing. In a less known but critically important role, muscle influences energy and protein metabolism throughout the body. Muscle is a primary site for glucose uptake and storage, and it is also a reservoir of amino acids stored as protein. Amino acids are released when supplies are needed elsewhere in the body. These conditions occur with acute and chronic diseases, which decrease dietary intake while increasing metabolic needs. Such metabolic shifts lead to the muscle loss associated with sarcopenia and cachexia, resulting in a variety of adverse health and economic consequences. With loss of skeletal muscle, protein and energy availability is lowered throughout the body. Muscle loss is associated with delayed recovery from illness, slowed wound healing, reduced resting metabolic rate, physical disability, poorer quality of life, and higher health care costs. These adverse effects can be combatted with exercise and nutrition. Studies suggest dietary protein and leucine or its metabolite β-hydroxy β-methylbutyrate (HMB) can improve muscle function, in turn improving functional performance. Considerable evidence shows that use of high-protein oral nutritional supplements (ONS) can help maintain and rebuild muscle mass and strength. We review muscle structure, function, and role in energy and protein balance. We discuss how disease- and age-related malnutrition hamper muscle accretion, ultimately causing whole-body deterioration. Finally, we describe how specialized nutrition and exercise can restore muscle mass, strength, and function, and ultimately reverse the negative health and economic outcomes associated with muscle loss.

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“…The activation of DHPRs, in turn opens RYR1, which releases calcium stores from the sarcoplasmic reticulum (SR) [4, 5]. Calcium ions stimulate muscle contraction by binding troponin c, which displaces tropomyosin from the actin active site, and allows myosin to bind to actin to generate a contraction [6]. Muscle contraction ends when the sarcolemma repolarizes, RYR1 channels close, and calcium ATPases known as SERCAs pump calcium ions back into the SR [5, 7].…”

Section: The Role Of Ryr1 In Skeletal Musclementioning

confidence: 99%