Power output of fast and slow skeletal muscles of mdx (dystrophic) and control mice after clenbuterol treatment

Lynch, Gordon S.; Hinkle, Richard T.

doi:10.1017/s0958067000020182

Cited by 15 publications

(16 citation statements)

References 7 publications

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“…Over the past 20 years there have been a multitude of studies demonstrating the growth-promoting actions of ␤-adrenoceptor stimulation in skeletal muscle (5,6,31,74,90,129,161,187,228,268,270,271,274,278,279,281,298,386,387,389,480,484). However, very little work has focused on the role of this pathway in normal muscle growth and development, muscle fiber regeneration after injury, or its involvement in pathological conditions where muscle wasting and weakness are indicated.…”

Section: Adrenoceptors and The Sympathetic Nervous Systemmentioning

confidence: 99%

“…As such, ␤ 2 -agonists such as clenbuterol (and cimaterol) became known as a "repartitioning agents" (223,304). These studies in a number of animal species have demonstrated that when administered in high doses (i.e., higher than what could be tolerated by humans), extended use of ␤-agonists can elicit significant increases in muscle mass (6,22,26,30,74,78,90,113,129,164,225,270,281,297,344,372,377,383,386,408,440,456,474,478,479), in the order of 10 -25% after 10 -20 days of administration. The increase in muscle protein is considered "true" muscle hypertrophy (474) since hyperplasia (increased cell number) and satellite cell division are not associated with the protein increases (278).…”

Section: Growth-promoting Effects Of ␤-Agonistsmentioning

confidence: 99%

“…However, it should be noted that ␤-agonist administration to dystrophic mdx mice has not led to improvements in diaphragm muscle function such as normalized force (or power output), either with clenbuterol or formoterol (174,270). The diaphragm is the most severely affected muscle in mdx mice, so demonstrating improvements in diaphragm function has important clinical implications since respiratory insufficiency is a major hallmark of DMD (234,289).…”

Section: B Muscular Dystrophymentioning

confidence: 99%

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Role of β-Adrenoceptor Signaling in Skeletal Muscle: Implications for Muscle Wasting and Disease

Lynch¹,

Ryall²

2008

Physiological Reviews

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366

356

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The importance of beta-adrenergic signaling in the heart has been well documented, but it is only more recently that we have begun to understand the importance of this signaling pathway in skeletal muscle. There is considerable evidence regarding the stimulation of the beta-adrenergic system with beta-adrenoceptor agonists (beta-agonists). Although traditionally used for treating bronchospasm, it became apparent that some beta-agonists could increase skeletal muscle mass and decrease body fat. These so-called "repartitioning effects" proved desirable for the livestock industry trying to improve feed efficiency and meat quality. Studying beta-agonist effects on skeletal muscle has identified potential therapeutic applications for muscle wasting conditions such as sarcopenia, cancer cachexia, denervation, and neuromuscular diseases, aiming to attenuate (or potentially reverse) the muscle wasting and associated muscle weakness, and to enhance muscle growth and repair after injury. Some undesirable cardiovascular side effects of beta-agonists have so far limited their therapeutic potential. This review describes the physiological significance of beta-adrenergic signaling in skeletal muscle and examines the effects of beta-agonists on skeletal muscle structure and function. In addition, we examine the proposed beneficial effects of beta-agonist administration on skeletal muscle along with some of the less desirable cardiovascular effects. Understanding beta-adrenergic signaling in skeletal muscle is important for identifying new therapeutic targets and identifying novel approaches to attenuate the muscle wasting concomitant with many diseases.

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Section: Adrenoceptors and The Sympathetic Nervous Systemmentioning

confidence: 99%

Section: Growth-promoting Effects Of ␤-Agonistsmentioning

confidence: 99%

Section: B Muscular Dystrophymentioning

confidence: 99%

See 1 more Smart Citation

Role of β-Adrenoceptor Signaling in Skeletal Muscle: Implications for Muscle Wasting and Disease

Lynch¹,

Ryall²

2008

Physiological Reviews

Self Cite

366

356

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“…1 The cell harvesting and cell culture of engineered muscles, as well as the determination of R 50 and C 50 , were carried out as described earlier, 1,2,25 except in the case of explanted adult whole muscles (the control, denervated, and stimulateddenervated groups), where a different LabVIEW-based in vitro muscle contractility experimental setup was used, due to the much larger specimens and contractile forces involved. 37 Briefly, muscle specimens were maintained in a saline solution between parallel platinum electrodes. Single unipolar square electrical pulses were applied, with variable pulse amplitude (voltage) and duration (microseconds).…”

Section: Methodsmentioning

confidence: 99%

Excitability of Skeletal Muscle during Development, Denervation, and Tissue Culture

Dennis

Dow

2007

Tissue Engineering

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A quantitative understanding of the bulk excitability of skeletal muscle tissues is important for the design of muscle tissue bioreactor systems, implantable muscle stimulators, and other systems where electrical pulses are employed to elicit contractions in muscle tissue both in vitro and in vivo. The purpose of the present study is to systematically compare the excitability of mammalian (rat) skeletal muscle under a range of conditions (including neonatal development, denervation, and chronic in vivo stimulation of denervated muscle) and of self-organized muscle tissue constructs engineered in vitro from both primary cells and cell lines. Excitability is represented by rheobase (R(50), units = V/mm) and chronaxie (C(50), units = microseconds) values, with lower values for each indicating greater excitability. Adult skeletal muscle is the most excitable (R(50) ~ 0.29, C(50) ~ 100); chronically denervated whole muscles (R(50) ~ 2.54, C(50) ~ 690) and muscle engineered in vitro from cell lines (C2C12 + 10T1/2) (R(50) ~ 1.93, C(50) ~ 416) have exceptionally low excitability; muscle engineered in vitro from primary myocytes (R(50) ~ 0.99, C(50) ~ 496) has excitability similar to that of day 14 neonatal rat muscle (R(50) ~ 0.65, C(50) ~ 435); stimulated-denervated muscles retain excellent excitability when chronically electrically stimulated (R(50) ~ 0.40, C(50) ~ 100); and neonatal rat muscle excitability improves during the first 6 weeks of development, steadily approaching that of adult muscle.

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“…In turn, CB has been abused as a sports doping agent because of its harmful side effects (Douillard 2011). In various mammalian models, especially rodents, CB has been shown to induce skeletal muscle hypertrophy under normal and catabolic conditions (e.g., age, disease, unweight, disuse, and training) (Maltin et al 1987;McElligott et al 1987;Agbenyega and Wareham 1990;Suzuki et al 1997;Lynch et al 2000;Stevens et al 2000;Sneddon et al 2001;von Deutsch et al 2002;Cavalie et al 2004;Mounier et al 2007). For example, Choo et al (1992) demonstrated that after rats consumed a CB-containing diet for a few days, gastrocnemius muscle mass increased significantly.…”

Section: Introductionmentioning

confidence: 99%

Temporal changes in ERK phosphorylation are harmonious with 4E-BP1, but not p70S6K, during clenbuterol-induced hypertrophy in the rat gastrocnemius

Sumi¹,

Higashi²,

Natsume³

et al. 2014

Appl. Physiol. Nutr. Metab.

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Extracellular signal-regulated kinase (ERK) is required for clenbuterol (CB)-dependent fast-type myofibril enlargement; however, its contribution to translation control is unclear. ERK mediates translational regulation through mammalian target of rapamycin complex 1 (mTORC1) activation and (or) mTORC1-independent pathways. In this study, we aimed to investigate the role of ERK in translational control during CB-induced muscular hypertrophy by measuring time-dependent changes in the phosphorylation statuses of ERK, p70 ribosomal S6 kinase (p70S6K; an indicator of mTORC1 activity), 4E-binding protein 1 (4E-BP1), eukaryotic elongation factor 2 (eEF2), and other related signaling molecules in rat gastrocnemius muscles. Five-day administration of CB induced phenotypes associated with muscular hypertrophy (significant increases in wet weight and isometric ankle flexion torque in the gastrocnemius muscle), but was not accompanied by elevated ERK or p70S6K phosphorylation. One-day administration of CB caused significant increases in the phosphorylation of ERK, p70S6K, and 4E-BP1. In contrast, 3-day administration of CB caused significant increases in the phosphorylation of ERK and 4E-BP1, but not p70S6K. In addition, positive correlations were observed between ERK and 4E-BP1 on days 1 and 3, whereas a correlation between ERK and p70S6K was only observed on day 1. eEF2 phosphorylation was unchanged on both days 1 and 3. These findings suggest that ERK accelerates the initiation of translation, but does not support the involvement of ERK in translational elongation. Furthermore, ERK may play a major role in promoting translational initiation by mediating the phosphorylation of 4E-BP1, and may contribute to the initial activation of mTORC1 during CB administration.

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Power output of fast and slow skeletal muscles of mdx (dystrophic) and control mice after clenbuterol treatment

Cited by 15 publications

References 7 publications

Role of β-Adrenoceptor Signaling in Skeletal Muscle: Implications for Muscle Wasting and Disease

Role of β-Adrenoceptor Signaling in Skeletal Muscle: Implications for Muscle Wasting and Disease

Excitability of Skeletal Muscle during Development, Denervation, and Tissue Culture

Temporal changes in ERK phosphorylation are harmonious with 4E-BP1, but not p70S6K, during clenbuterol-induced hypertrophy in the rat gastrocnemius

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