Diminished overload-induced hypertrophy in aged fast-twitch skeletal muscle is associated with AMPK hyperphosphorylation

Thomson, David M.; Gordon, Scott E.

doi:10.1152/japplphysiol.00811.2004

Cited by 102 publications

(117 citation statements)

References 51 publications

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“…Thomson et al (93) also reported that AICAR treatment inhibited mTOR activation, which is induced by high-frequency electrical stimulation of rat EDL muscle. Finally Thomason and Gordon (94) found a correlation between increased phosphorylation of AMPK and reduced muscle hypertrophy in aging rats.…”

Section: Cellular Energy Status and Mtor Activitymentioning

confidence: 95%

Cellular mechanisms regulating protein synthesis and skeletal muscle hypertrophy in animals

Miyazaki

Esser²

2009

Journal of Applied Physiology

163

142

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Miyazaki M, Esser KA. Cellular mechanisms regulating protein synthesis and skeletal muscle hypertrophy in animals. J Appl Physiol 106: 1367-1373, 2009; doi:10.1152/japplphysiol.91355.2008.-Growth and maintenance of skeletal muscle mass is critical for long-term health and quality of life. Skeletal muscle is a highly adaptable tissue with well-known sensitivities to environmental cues such as growth factors, cytokines, nutrients, and mechanical loading. All of these factors act at the level of the cell and signal through pathways that lead to changes in phenotype through multiple mechanisms. In this review, we discuss the animal and cell culture models used and the signaling mechanisms identified in understanding regulation of protein synthesis in response to mechanical loading/resistance exercise. Particular emphasis has been placed on 1) alterations in mechanical loading and regulation of protein synthesis in both in vivo animal studies and in vitro cell culture studies and 2) upstream mediators regulating mammalian target of rapamycin signaling and protein synthesis during skeletal muscle hypertrophy. mechanical stretch; REDD2; overload; IGF-1; amino acids IT IS WIDELY ACCEPTED that repeated bouts of resistance exercise/ high-force contractions produce compensatory growth of skeletal muscle (35,42,47,95). The increase in skeletal muscle mass results from rates of protein synthesis increased more than changes in protein degradation with the net result being an accumulation of protein and increased fiber area (66,96). While the effect of resistance exercise/contraction on muscle mass has long been recognized, the mechanisms underlying the link between high resistance contractions and muscle growth are, to date, not fully understood.One of the important variables contributing to the growth response in skeletal muscle is the application of mechanical loading. For this review we use mechanical loading very generally as the application of force on the muscle or muscle cell. This force on the muscle can occur via active cross-bridge interactions (such as during concentric, isometric, or eccentric contractions) in a gravity-based environment or via external application of force such as passive stretching. The most established animal model for studying skeletal muscle hypertrophy in response to mechanical loading was described by Dr. A. L. Goldberg (38) and was referred to as work-induced muscle growth. This model is now commonly known as the synergist ablation/mechanical overload model and is a surgical model that involves cutting of the tendon and removal of the gastrocnemius muscle, resulting in loading and compensatory growth of the remaining plantar flexors, the plantaris, and soleus muscles. These muscles are involved in maintenance of posture and walking so are loaded by the body weight of the animal. Muscle mass changes are fairly rapid and the growth is robust, ranging from 40 to 200% depending on the muscle and species studied (7,37,38,53,56). Many labs use this model in their research programs to study mole...

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Section: Cellular Energy Status and Mtor Activitymentioning

confidence: 95%

Cellular mechanisms regulating protein synthesis and skeletal muscle hypertrophy in animals

Miyazaki

Esser²

2009

Journal of Applied Physiology

163

142

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“…In higher organisms, the role of AMPK in the regulation of aging is not clear, with some reports demonstrating a significant reduction in AMPK signaling in muscle (399,408) while others report no change (169,379) or even increased AMPK activity (494,495). The effects of metabolic stress such as hypoxia, caloric restriction, or muscle contraction on AMPK signaling in aging are equally equivocal with some studies reporting increased activation (169,379), while others have reported a reduction (349,408).…”

Section: A Aging and Longevitymentioning

confidence: 99%

AMPK in Health and Disease

Steinberg¹,

Kemp²

2009

Physiological Reviews

1,420

1,419

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The function and survival of all organisms is dependent on the dynamic control of energy metabolism, when energy demand is matched to energy supply. The AMP-activated protein kinase (AMPK) αβγ heterotrimer has emerged as an important integrator of signals that control energy balance through the regulation of multiple biochemical pathways in all eukaryotes. In this review, we begin with the discovery of the AMPK family and discuss the recent structural studies that have revealed the molecular basis for AMP binding to the enzyme's γ subunit. AMPK's regulation involves autoinhibitory features and phosphorylation of both the catalytic α subunit and the β-targeting subunit. We review the role of AMPK at the cellular level through examination of its many substrates and discuss how it controls cellular energy balance. We look at how AMPK integrates stress responses such as exercise as well as nutrient and hormonal signals to control food intake, energy expenditure, and substrate utilization at the whole body level. Lastly, we review the possible role of AMPK in multiple common diseases and the role of the new age of drugs targeting AMPK signaling.

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“…In particular, these studies consistently reported increased Type I myosin heavy chain (Type I MHC) content in chronically overloaded rat plantaris muscles. Previous studies have also demonstrated that a sham-operated contralateral control limb does not demonstrate hy-pertrophy or alter its protein expression following synergistic ablation (Thomson andGordon 2005, Sun et al 2006), indicating that the control limb is not favored and experiences normal loading following the surgical procedure. Furthermore, the effect of overload on hypertrophy is similar when either a unilateral or a bilateral synergistic ablation model is employed (Soltow et al 2006).…”

Section: Introductionmentioning

confidence: 99%

Heat stress inhibits skeletal muscle hypertrophy

Frier

Locke

2007

Cell Stress Chaper

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Heat shock proteins (Hsps) are molecular chaperones that aid in protein synthesis and trafficking and have been shown to protect cells/tissues from various protein damaging stressors. To determine the extent to which a single heat stress and the concurrent accumulation of Hsps influences the early events of skeletal muscle hypertrophy, Sprague-Dawley rats were heat stressed (42ЊC, 15 minutes) 24 hours prior to overloading 1 plantaris muscle by surgical removal of the gastrocnemius muscle. The contralateral plantaris muscles served as controls. Heat-stressed and/or overloaded plantaris muscles were assessed for muscle mass, total muscle protein, muscle protein concentration, Type I myosin heavy chain (Type I MHC) content, as well as Hsp72 and Hsp25 content over the course of 7 days following removal of the gastrocnemius muscle. As expected, in non-heat-stressed animals, muscle mass, total muscle protein and MHC I content were significantly increased (P Ͻ 0.05) following overload. In addition, Hsp25 and Hsp72 increased significantly after 2 and 3 days of overload, respectively. A prior heat stress-elevated Hsp25 content to levels similar to those measured following overload alone, but heat stress-induced Hsp72 content was increased significantly greater than was elicited by overload alone. Moreover, overloaded muscles from animals that experienced a prior heat stress showed a lower muscle mass increase at 5 and 7 days; a reduced total muscle protein elevation at 3, 5, and 7 days; reduced protein concentration; and a diminished Type I MHC content accumulation at 3, 5, and 7 days relative to nonheat-stressed animals. These data suggest that a prior heat stress and/or the consequent accumulation of Hsps may inhibit increases in muscle mass, total muscle protein content, and Type I MHC in muscles undergoing hypertrophy.

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Diminished overload-induced hypertrophy in aged fast-twitch skeletal muscle is associated with AMPK hyperphosphorylation

Cited by 102 publications

References 51 publications

Cellular mechanisms regulating protein synthesis and skeletal muscle hypertrophy in animals

Cellular mechanisms regulating protein synthesis and skeletal muscle hypertrophy in animals

AMPK in Health and Disease

Heat stress inhibits skeletal muscle hypertrophy

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