Aging and the acute phase response to exercise: implications for the role of systemic factors on skeletal muscle protein turnover

Effects of aging and exercise training on apoptosis in the heart

Aging is characterized by a progressive decline in cardiac function. A critical contributor to the age-related impairment in cardiac function is the loss of cardiac myocytes through “apoptosis”, or programmed cell death. Structural remodeling in the heart with advancing age includes (a) loss of cardiomyocytes, (b) reactive hypertrophy of the remaining cardiomyocytes, and (c) increased connective tissue and altered geometry. The loss of cardiomyocytes with aging occurs through apoptosis. Particularly, mitochondrial-mediated apoptotic pathway is the best characterized and believed critical in regulating apoptosis with aging, suggesting that mitochondria are very important sites of programmed cell death. It has been also reported that mitochondrial dysfunction, oxidative stress, and impaired stress response contribute to age-induced mechanical remodeling as well as apoptosis. In contrast, exercise training not only improves cardiac function, but also reduces the risk of heart disease. We recently found that aging increased mitochondrial-mediated apoptotic signaling and apoptosis in the left ventricle, while chronic exercise training was effective in diminishing mitochondrial-mediated apoptotic signaling pathways in the aging heart, as indicated by lower DNA fragmentation, terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL)-positive staining, and caspase-3 cleavage, when compared with left ventricles from the age-matched sedentary group. In this review, we will provide a comprehensive update regarding the effects of aging and exercise training on apoptosis in the heart.

Immune Alterations, Lipid Peroxidation, and Muscle Damage Following a Hill Race

Hill races usually include large downhill running sections, which can induce significant degrees of muscle damage in a field setting. This study examined the link between muscle damage, oxidative stress, and immune perturbations following a 7-km mountainous hill race with 457 m of ascent and 457 m of descent. Venous blood samples were taken from 7 club level runners before, immediately after, and 48 hrs postrace. Samples were analysed for total and differential leukocyte counts, markers of muscle damage (CK), lipid peroxidation (MDA), and acute phase proteins (CRP; fibrinogen; α-1-ACT). The total antioxidant status (TEAC) and plasma levels of the proinflammatory cytokines IL-6, IL-8, and TNF-α were also determined. Subjective pain reports, and plasma activities of CK, MDA, and circulatory monocytes reached peak values at 48 hrs postrace (p <  0.05). TEAC and the cytokine IL-8 increased immediately after the race (p <  0.05). Plasma TNF-α remained unchanged (p > 0.05). Despite the reports of muscle damage and soreness, no evidence of an acute phase response was observed (p > 0.05), which may be explained by the failure of the race to induce a plasma TNF-α response. Future studies should examine the link between muscle damage, oxidative stress, and the acute phase response following hill races of longer duration with larger eccentric components. Key words: acute phase response, cytokines, antioxidant capacity, creatine kinase, field study

Exercise immunology: the current state of man and mouse

The mechanisms governing the body's response to physical exercise have been investigated from various perspectives including metabolism, nutrition, age and sex. Increased attention to the immune system during recent decades is reflected by a rapidly growing number of publications in the field. This article highlights the most recent findings and only briefly summarises more basic concepts already reviewed by others. Topics include Th1/Th2 cytokine balance, inoculation time, age and immune compensation. Some less investigated areas are discussed including studies in children, the environment and dendritic cells. Because physical exercise enhances some aspects and suppresses other aspects of immunity, the biological significance of alterations in the immune system are unknown. So far, no link between immunological alterations and infection rate has been established and infection after strenuous physical exercise is equally likely to be the result of exercising with an already established rather than a new infection. If there is an increased risk for infections with increased exercise duration and intensity, why do overtrained athletes not display the greatest risk for upper respiratory tract infections? Increased knowledge on immune system modulations with physical exercise is relevant both from a public health and elite athlete's point of view.

Interleukin-1 polymorphisms are associated with the inflammatory response in human muscle to acute resistance exercise

Inflammation appears to play an important role in the repair and regeneration of skeletal muscle after damage. We tested the hypothesis that the severity of the inflammatory response in muscle after an acute bout of resistance exercise is associated with single nucleotide polymorphisms (SNPs) previously shown to alter interleukin-1 (IL-1) activity. Using a double-blind prospective design, sedentary young men were screened (n = 100) for enrolment (n = 24) based upon having 1 of 4 haplotype patterns composed of five polymorphic sites in the IL-1 gene cluster: IL-1A (+4845), IL-1B (+3954), IL-1B (-511), IL-1B (-3737) and IL-1RN (+2018). Subjects performed a standard bout of resistance leg exercise and vastus lateralis biopsies were obtained pre-, and at 24, and 72 h post-exercise. Inflammatory marker mRNAs (IL-1beta, IL-6 and tumor necrosis factor-alpha (TNF-alpha)) and the number of CD68(+) macrophages were quantified. Considerable variation was observed in the expression of these gene products between subjects. At 72 h post-exercise, IL-1beta had increased in a number of subjects (n = 10) and decreased (n = 4) or did not change (n = 10) in others. Inflammatory responses were significantly associated with specific haplotype patterns and were also influenced by individual SNPs. Subjects with genotypes 1.1 at IL-1B (+3954) or 2.2 at IL-1B (-3737) had approximately a 2-fold higher median induction of several markers, but no increase in macrophages, suggesting that cytokine gene expression is elevated per macrophage. The IL-1RN (+2018) SNP maximized the response specifically within these groups and was associated with increased macrophage recruitment. This is the first report that IL-1 genotype is associated with the inflammation of skeletal muscle following acute resistance exercise that may potentially affect the adaptations to chronic resistance exercise.

Contraction-induced injury run amok: an introduction

Skeletal muscle has an amazing capacity to adapt to increased levels of physical activity. Adaptation is often preceded by contraction-induced injury. In most cases, the damage is repaired quickly, the muscle adapts, and becomes stronger and less fatigable. Diseased or deconditioned muscle is an exception; the response to increased functional demand, and the associated injury can be incomplete or even maladaptive. When and why is an adaptive response limited? This question will be addressed in the symposium papers following this brief introduction. The papers will discuss cellular, molecular, and immunological mechanisms that may be involved in impaired muscle adaptation.

Regular moderate exercise training prevents decrease of CD4+ T-lymphocytes induced by a single bout of strenuous exercise in mice

The biphasic effects of exercise training on the immune system have been studied extensively and represented by the well-known J-shaped curve with respect to training intensity. However, the relationship and interactions between "beneficial" exercise training and "harmful" strenuous exercise have not been researched. This study was designed to determine whether regular moderate exercise training could affect the changes of percentage of T-lymphocytes induced by a single bout of strenuous exercise. A protocol to run uphill on a 10 degrees tilted treadmill for 4 weeks was employed as moderate exercise training in mice, while a sedentary control group of mice was exposed to the same handling stress without training. The trained and untrained mice were then exposed to a single bout of strenuous exercise until exhaustion. Total leukocytes were collected from spleen and peripheral blood at 0 hr, 3 hrs, and 24 hrs postexhaustion, as well as from the control groups. Flow cytometric analyses were conducted to determine the percentages of selected leukocyte populations. It was demonstrated that moderate exercise training prevented the decrease of CD4+ but stimulated the increase of CD25+ CD8+ T-lymphocytes induced by a single bout of strenuous exercise, indicating an adaptive response that can affect changes of leukocyte subpopulations.

Space flight and oxidative stress

Space flight is associated with an increase in oxidative stress after return to 1g. The effect is more pronounced after long-duration space flight. The effects lasts for several weeks after landing. In humans there is increased lipid peroxidation in erythrocyte membranes, reduction in some blood antioxidants, and increased urinary excretion of 8-iso-prostaglandin F(2alpha) and 8-oxo-7,8 dihydro-2 deoxyguanosine. Isoprostane 8-iso-prostaglandin F(2alpha) and 8-oxo-7,8 dihydro-2 deoxyguanosine are markers for oxidative damage to lipids and DNA, respectively. The changes have been attributed to a combination of the energy deficiency that occurs during flight and substrate competition for amino acids occurring between repleting muscle and other tissues during the recovery phase. The observations in humans have been complemented by rodent studies. Most rodent studies showed increased production of lipid peroxidation products postflight and decreased antioxidant enzyme activity postflight. The rodent observations were attributed to the stress associated with reentry into Earth's gravity. Decreasing the imbalance between the production of endogenous oxidant defenses and oxidant production by increasing the supply of dietary antioxidants may lessen the severity of the postflight increase in oxidative stress.

Surgical manipulation, but not moderate exercise, is associated with increased cytokine mRNA expression in the rat soleus muscle

Interleukin (IL)-6 production in contracting skeletal muscle and IL-6 concentration in plasma are increased after prolonged and strenuous exercise. However, as tissue stress or damage are unspecific triggers of increased cytokine levels, we examined whether moderate muscle activity is an independent stimulus for cytokine expression, and to which extent invasive procedures might affect the results. Soleus muscles were isolated from sedentary rats or from rats that had been running on a treadmill at moderate intensity (70% of maximal oxygen uptake) for 1 h. In another group the soleus muscle was prepared in situ and stimulated intermittently at 5 Hz for 1 h, so that maximal developed force declined by 30%. In situ prepared soleus muscles not subjected to electrical stimulation were used as controls. Messenger RNA (mRNA) expression of 11 cytokines was analysed in the soleus muscles using multiprobe RNAse protection assay, and IL-6 plasma concentration was measured by enzyme-linked immunosorbent assay. Treadmill exercise did not affect the mRNA expression of any of the measured cytokines in the soleus muscle. Irrespective of electrical stimulation, mRNA expression of IL-6 and IL-1beta were significantly increased in the surgically manipulated soleus muscles. Interleukin-6 plasma concentration was not affected by treadmill running or electrical stimulation. Conclusion, gentle surgical manipulation is a strong stimulus for IL-6 and IL-1beta mRNA synthesis in skeletal muscle, whereas exercise or electrical muscle stimulation at moderate intensity does not independently affect cytokine mRNA levels in the contracting soleus.

Exercise for patients with fibromyalgia: risks versus benefits

Although exercise in the form of stretching, strength maintenance, and aerobic conditioning is generally considered beneficial to patients with fibromyalgia (FM), there is no reliable evidence to explain why exercise should help alleviate the primary symptom of FM, namely pain. Study results are varied and do not provide a uniform consensus that exercise is beneficial or what type, intensity, or duration of exercise is best. Patients who suffer from exercise-induced pain often do not follow through with recommendations. Evidence-based prescriptions are usually inadequate because most are based on methods designed for persons without FM and, therefore, lack individualization. A mismatch between exercise intensity and level of conditioning may trigger a classic neuroendocrine stress reaction. This review considers the adverse and beneficial effects of exercise. It also provides a patient guide to exercise that takes into account the risks and benefits of exercise for persons with FM.

Immunological changes in human skeletal muscle and blood after eccentric exercise and multiple biopsies

1. A role of the immune system in muscular adaptation to physical exercise has been suggested but data from controlled human studies are scarce. The present study investigated immunological events in human blood and skeletal muscle by immunohistochemistry and flow cytometry after eccentric cycling exercise and multiple biopsies. 2. Immunohistochemical detection of neutrophil- (CD11b, CD15), macrophage- (CD163), satellite cell- (CD56) and IL-1beta-specific antigens increased similarly in human skeletal muscle after eccentric cycling exercise together with multiple muscle biopsies, or multiple biopsies only. 3. Changes in immunological variables in blood and muscle were related, and monocytes and natural killer (NK) cells appeared to have governing functions over immunological events in human skeletal muscle. 4. Delayed onset muscle soreness, serum creatine kinase activity and C-reactive protein concentration were not related to leukocyte infiltration in human skeletal muscle. 5. Eccentric cycling and/or muscle biopsies did not result in T cell infiltration in human skeletal muscle. Modes of stress other than eccentric cycling should therefore be evaluated as a myositis model in human. 6. Based on results from the present study, and in the light of previously published data, it appears plausible that muscular adaptation to physical exercise occurs without preceding muscle inflammation. Nevertheless, leukocytes seem important for repair, regeneration and adaptation of human skeletal muscle.

Beta-hydroxy-beta-methylbutyrate (HMB) supplementation and the promotion of muscle growth and strength

Beta-hydroxy beta-methylbutyrate (HMB), a metabolite of the essential amino acid leucine, is one of the latest dietary supplements promoted to enhance gains in strength and lean body mass associated with resistance training. Unlike anabolic hormones that induce muscle hypertrophy by increasing muscle protein synthesis, HMB is claimed to influence strength and lean body mass by acting as an anticatabolic agent, minimising protein breakdown and damage to cells that may occur with intense exercise. Research on HMB has recently tested this hypothesis, under the assumption that it may be the active compound associated with the anticatabolic effects of leucine and its metabolites. While much of the available literature is preliminary in nature and not without methodological concern, there is support for the claims made regarding HMB supplementation, at least in young, previously untrained individuals. A mechanism by which this may occur is unknown, but research undertaken to date suggests there may be a reduction in skeletal muscle damage, although this has not been assessed directly. The response of resistance trained and older individuals to HMB administration is less clear. While the results of research conducted to date appear encouraging, caution must be taken when interpreting outcomes as most manuscripts are presented in abstract form only, not having to withstand the rigors of peer review. Of the literature reviewed relating to HMB administration during resistance training, only 2 papers are full manuscripts appearing in peer reviewed journals. The remaining 8 papers are published as abstracts only, making it difficult to critically review the research. There is clearly a need for more tightly controlled, longer duration studies to verify if HMB enhances strength and muscular hypertrophy development associated with resistance training across a range of groups, including resistance trained individuals.