The role of hormones, cytokines and heat shock proteins during age-related muscle loss

doi:10.1016/j.clnu.2007.05.005

Clinical Nutrition

Volume 26, Issue 5, October 2007, Pages 524-534

https://doi.org/10.1016/j.clnu.2007.05.005 Get rights and content

Summary

Ageing is associated with a progressive decline of muscle mass, strength, and quality, a condition known as sarcopenia. Due to the progressive ageing of western populations, age-related sarcopenia is a major public health problem. Several possible mechanisms for age-related muscle atrophy have been described; however the precise contribution of each is unknown. Age-related muscle loss is thought to be a multi-factoral process composed of events such as physical activity, nutritional intake, oxidative stress, inflammatory insults and hormonal changes. There is a need for a greater understanding of the loss of muscle mass with age as this could have a dramatic impact on the elderly and critically ill if this research leads to maintenance or improvement in functional ability. This review aims to outline the process of skeletal muscle degeneration with ageing, normal and aberrant skeletal muscle regeneration, and to address recent research on the effects of gender and sex steroid hormones during the process of age-related muscle loss.

Introduction

Ageing is associated with a progressive decline of muscle mass, strength, and quality, a condition known as the sarcopenia of ageing.¹ Sarcopenia is associated with a decrease in functional performance, a greater risk of falls in the aged,1, 2 increased mobility disability³ and reduced energy needs.⁴ In addition, reduced muscle mass in aged individuals has been associated with decreased survival rates following critical illness.⁵ Estimates of the prevalence of sarcopenia range from 13% to 24% in adults over 60 years of age to more than 50% in persons aged 80 and older.2, 3, 4 Furthermore, the prevalence of age-related muscle loss is expected to dramatically increase, due to the progressive ageing of western populations.

Several possible mechanisms for age-related muscle atrophy have been described; however the precise contribution of each is unknown. Age-related muscle loss is thought to be a multi-factoral process composed of events such as physical activity, nutritional intake, oxidative stress, inflammatory insults and hormonal changes.6, 7, 8 In addition mitochondrial dysfunction may contribute to the development of sarcopenia, however this has been a subject of contentious debate and will not be discussed here, for a recent review on this subject see Dirks et al.⁹ The specific contribution of each of these factors is unknown but there is emerging evidence that the loss of gonadal hormones with age may be an important feature in the progression of sarcopenia. Gallagher et al. found that gender influenced muscle mass and determined that, with age, there was almost twice the reduction in muscle mass in males than in women.¹⁰ Factors such as testosterone levels, physical activity, cardiovascular disease and insulin-like growth factor-1 (IGF-1) have been shown to be significant predictors of muscle mass in men, and total fat mass and physical activity were significantly associated with muscle mass in women.⁶

There is a need for a greater understanding of the loss of muscle mass with age as this could have a dramatic impact on the elderly if this research leads to maintenance or improvement in functional ability. The majority of the literature presented here is mouse based, however the mechanisms of mouse muscle loss are similar to those in humans.¹¹ The benefit of using animal studies eliminates secondary effects of disease caused by old age. This review aims to outline the process of skeletal muscle degeneration with ageing, normal and aberrant skeletal muscle regeneration, and to address recent research on the effects of gender and sex steroid hormones during the process of age-related muscle loss.

Section snippets

Skeletal muscle ageing

Muscle wasting and loss of skeletal muscle strength are inevitable concomitants of ageing and result from the loss of muscle fibres and atrophy of the remaining fibres as described in Fig. 1. By the age of 70 years, the cross-sectional area of skeletal muscle is reduced by up to 25–30%. Strength is reduced by 30–40%,¹² and this continues to fall by 1–2% per year.¹³ Muscles of older individuals are also more susceptible to damage and recover poorly following damage.12, 14, 15, 16

One mechanism of

Does gender protect against age-related muscle loss?

In the developed world, most women live one-third of their lives in a state of profound estrogenic deprivation.⁹⁴ In addition, with advancing age of women there is a decrease in the serum levels of testosterone and androgens.⁹⁵ Moreover, elderly males have altered local levels of bioactive estrogens, secondary to reduced secretion of adrenal sex-steriod precursors to estrogen by aromatisation.⁹⁶ Concentrations of other sex steroids in serum from men decline progressively with age, due to

Conclusions

Age-related sarcopenia is a major public health problem in the rapidly expanding elderly population. There is a need for a better understanding of the biological mechanisms and pathophysiology of sarcopenia as this may result in the development of therapeutic or preventative measures to address this problem. Ageing is associated with reduced levels of steroid hormones and this review has highlighted several differences between males and females with regard to age-related muscle loss and

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The primary aim of this investigation was to explore the impact of different temporal stress conditions on the regulators associated with skeletal muscle hypertrophy in bovine myocytes. Bovine satellite cells (BSCs) were extracted from three-month-old Holstein bull calves and subjected to myogenic differentiation under three thermal treatments: 38 °C (control; CON), 39.5 °C (moderate heat stress; MHS), and 41 °C (extreme heat stress; EHS) for a duration of 3 or 48 h. Exposure to EHS resulted in elevated (P < 0.01) expression levels of heat shock protein (HSP)20, HSP27, HSP70, and HSP90, along with increased (P < 0.01) protein levels. Moreover, cells exposed to MHS and EHS exhibited enhanced (P < 0.01) gene expression of myoblast determination protein 1 (MyoD), while myogenin (MyoG) was overexpressed (P < 0.01) in cells exposed to EHS. These findings suggest that heat exposure can potentially induce myogenic differentiation through the modulation of myogenic regulatory factors. Furthermore, our investigations revealed that exposure to EHS upregulated (P < 0.01) myosin heavy chain (MHC) I expression, whereas MHC IIA (P < 0.01) and IIX (P < 0.01) expression were increased; P < 0.01) under MHS conditions. These observations suggest that the temperature of the muscle may alter the proportion of muscle fiber types. Additionally, our data indicated that EHS activated (P < 0.01) the expression of insulin-like growth factor 1 (IGF-1) and triggered the activation of the Akt/mTOR/S6KB1 pathway, a known anabolic pathway associated with cellular protein synthesis. Consequently, these altered signaling pathways contributed to enhanced protein synthesis and increased myotube size. Overall, the results obtained from our current study revealed that extreme heat exposure (41 °C) may promote skeletal muscle hypertrophy by regulating myogenic regulatory factors and IGF-1-mediated mTOR pathway in bovine myocytes.
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It seems that E2 deficiency results in some, yet not all apoptosis-related changes similar to the ageing process. Previous studies have found a link between estrogen and HSP expression in skeletal muscle (Lee et al., 2007; Vasconsuelo et al., 2010). These studies indicate that estrogen may protect skeletal muscle tissue against apoptosis through HSPs.
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ReviewThe role of hormones, cytokines and heat shock proteins during age-related muscle loss

Summary

Introduction

Section snippets

Skeletal muscle ageing

Does gender protect against age-related muscle loss?

Conclusions

J Nutr

Nutrition

Mech Ageing Dev

Ageing Res Rev

J Neurol Sci

Cell

Cell

Int J Biochem Cell Biol

Exp Gerontol

Exp Gerontol

Ageing Res Rev

Mech Ageing Dev

Exp Gerontol

Biochem Biophys Res Commun

Mech Ageing Dev

Exp Gerontol

Neuromuscul Disord

Endocrinol Metab Clin North Am

Epidemiology of sarcopenia among the elderly in New Mexico

Am J Epidemiol

Epidemiology of sarcopenia

J Am Geriatr Soc

Exercise, substrate utilization and energy requirements in the elderly

Int J Obesity Relat Metab Disord

Association of dehydroepiandrosterone sulfate, body composition, and physical fitness in independent community-dwelling older men and women

J Am Geriatr Soc

Sarcopenia: current concepts

J Gerontol A Biol Sci Med Sci

Appendicular skeletal muscle mass: effects of age, gender, and ethnicity

J Appl Physiol

Age-associated changes in the innervation of muscle fibers and changes in the mechanical properties of motor units

Ann N Y Acad Sci

Aging of human muscle: structure, function and adaptability

Scand J Med Sci Sports

Strength, power and related functional ability of healthy people aged 65–89 years

Age Ageing

Contractile properties of skeletal muscles from young, adult and aged mice

J Physiol

Contraction-induced injury: recovery of skeletal muscles in young and old mice

Am J Physiol

Free radical injury to skeletal muscles of young, adult, and old mice

Am J Physiol

Human aging, muscle mass, and fiber type composition

J Gerontol A Biol Sci Med Sci

Isometric and dynamic endurance as a function of age and skeletal muscle characteristics

Acta Physiol Scand

Skeletal muscle weakness and fatigue in old age: underlying mechanisms

Annu Rev Gerontol Geriatr

Effects of age and training on skeletal muscle physiology and performance

Phys Ther

The effects of aging and training on skeletal muscle

Am J Sports Med

Inflammatory cell response to acute muscle injury

Med Sci Sports Exerc

Macrophages enhance muscle satellite cell proliferation and delay their differentiation

Muscle Nerve

Skeletal muscle damage with exercise and aging

Sports Med

Satellite cell of skeletal muscle fibers

J Biophys Biochem Cytol

Cellular and molecular regulation of muscle regeneration

Physiol Rev

The distribution of satellite cells and their relationship to specific fiber types in soleus and extensor digitorum longus muscles

Anat Rec

Perisynaptic satellite cells in human external intercostal muscle: a quantitative and qualitative study

Anat Rec

The number of nuclei in adult rat muscles with special reference to satellite cells

Anat Rec

Response of satellite cells to focal skeletal muscle injury

Muscle Nerve

Skeletal muscle satellite cells

Rev Physiol Biochem Pharmacol

Myogenic satellite cells: physiology to molecular biology

Review
The role of hormones, cytokines and heat shock proteins during age-related muscle loss