Sarcopenia and cachexia: the adaptations of negative regulators of skeletal muscle mass

Sarcopenia is associated with significant liver fibrosis independently of obesity and insulin resistance in nonalcoholic fatty liver disease: Nationwide surveys (KNHANES 2008-2011)

Sarcopenia is associated with nonalcoholic fatty liver disease (NAFLD). This study investigated whether sarcopenia is associated with significant liver fibrosis in subjects with NAFLD. Data from the Korean National Health and Nutrition Examination Surveys 2008-2011 database were analyzed. NALFD was defined by NAFLD liver fat score, comprehensive NAFLD score, or hepatic steatosis index. Degree of liver fibrosis was assessed by NAFLD fibrosis score (NFS), FIB-4, and Forns index. Significant liver fibrosis was defined as FIB-4 ≥2.67 and the highest quartile values of NFS and Forns index. Sarcopenia index (= total appendicular skeletal muscle mass [kg]/body mass index (kg/m(2) ]) was calculated using dual-energy X-ray absorptiometry. Using the NAFLD liver fat score, NAFLD was identified in 2761 (28.5%) of 9676 subjects. Of subjects with NAFLD, sarcopenia was identified in 337 (12.2%). Sarcopenia was significantly associated with significant liver fibrosis assessed in fibrosis prediction models (all P < 0.05). In subgroups stratified according to body mass index and homeostasis model assessment of insulin resistance, a significant association between sarcopenia and significant liver fibrosis by NFS was consistently present (odds ratio = 1.76-2.68 depending on the subgroup, all P < 0.05). Multivariate logistic regression analysis demonstrated an independent association between SI and significant liver fibrosis by NFS after adjusting for other confounders (odds ratio = 0.52-0.67, all P < 0.01). Other NAFLD (comprehensive NAFLD score, hepatic steatosis index) and fibrosis prediction models (FIB-4 and Forns index) produced similar results.

CONCLUSION

Sarcopenia is associated with significant liver fibrosis in subjects with NAFLD, and the association is independent of obesity and insulin resistance.

Molecular pathways leading to loss of skeletal muscle mass in cancer cachexia--can findings from animal models be translated to humans?

Background

Cachexia is a multi-factorial, systemic syndrome that especially affects patients with cancer of the gastrointestinal tract, and leads to reduced treatment response, survival and quality of life. The most important clinical feature of cachexia is the excessive wasting of skeletal muscle mass. Currently, an effective treatment is still lacking and the search for therapeutic targets continues. Even though a substantial number of animal studies have contributed to a better understanding of the underlying mechanisms of the loss of skeletal muscle mass, subsequent clinical trials of potential new drugs have not yet yielded any effective treatment for cancer cachexia. Therefore, we questioned to which degree findings from animal studies can be translated to humans in clinical practice and research.

Discussion

A substantial amount of animal studies on the molecular mechanisms of muscle wasting in cancer cachexia has been conducted in recent years. This extensive review of the literature showed that most of their observations could not be consistently reproduced in studies on human skeletal muscle samples. However, studies on human material are scarce and limited in patient numbers and homogeneity. Therefore, their results have to be interpreted critically.

Summary

More research is needed on human tissue samples to clarify the signaling pathways that lead to skeletal muscle loss, and to confirm pre-selected drug targets from animal models in clinical trials. In addition, improved diagnostic tools and standardized clinical criteria for cancer cachexia are needed to conduct standardized, randomized controlled trials of potential drug candidates in the future.

Fetuin-A as a predicator of sarcopenic left ventricular dysfunction

Sarcopenia is an aging condition involving low muscle mass and function. Fetuin-A (FetA) appears to be a factor for body composition remodeling. We hypothesized that age increases FetA levels and deteriorates the myocardial function by affecting diastolic function, especially in people with sarcopenia. We enrolled 541 asymptomatic elderly (≥65 years) patients. Compared with non-sarcopenic population, FetA levels were significantly elevated in the ninety-two (17%) patients (79 ± 6 years; male: 34.7%) diagnosed with sarcopenia (621.1 ± 140.7 vs. 697.3 ± 179.6 μg/ml, < 0.001). Sarcopenic left ventricular dysfunction (S-LVD) was defined by the coexistence of sarcopenia and systolic impairment (LVEF < 50%) and 23 (4.3%) of them met the criteria. Patients with S-LVD showed relatively reduced systolic heart function, higher end-diastolic pressure and a higher FetA level (all p < 0.001) than did those with sarcopenia but without LV dysfunction (S-NLVD). Conversely, in the group without sarcopenia, FetA levels were similar regardless of systolic function. Multivariable logistic regression showed that older age, impaired diastolic function, and higher FetA levels were significantly associated with S-LVD. In conclusion, we found that FetA was significantly higher in elderly patients with sarcopenia, which was associated with impaired diastolic and systolic functions.

Febuxostat improves outcome in a rat model of cancer cachexia

BACKGROUND

Activity of xanthine oxidase is induced in cancer cachexia, and its inhibition by allopurinol or oxypurinol improves survival and reduces wasting in the Yoshida hepatoma cancer cachexia model. Here, we tested the effects of the second-generation xanthine oxidase inhibitor febuxostat compared with placebo in the same model as used previously by our group.

METHODS

Wistar rats (~200 g) were treated daily with febuxostat at 5 mg/kg/day or placebo via gavage for a maximum of 17 days. Weight change, quality of life, and body composition were analysed. After sacrifice, proteasome activity in the gastrocnemius muscle was measured. Muscle-specific proteins involved in metabolism were analysed by western blotting.

RESULTS

Treatment of the tumour-bearing rats with febuxostat led to a significantly improved survival compared with placebo (hazard ratio: 0.45, 95% confidence interval: 0.22-0.93, P = 0.03). Loss of body weight was reduced (-26.3 ± 12.4 g) compared with placebo (-50.2 ± 2.1 g, P < 0.01). Wasting of lean mass was attenuated (-12.7 ± 10.8 g) vs. placebo (-31.9 ± 2.1 g, P < 0.05). While we did not see an effect of febuxostat on proteasome activity at the end of the study, the pAkt/Akt ratio was improved by febuxostat (0.94 ± 0.09) vs. placebo (0.41 ± 0.05, P < 0.01), suggesting an increase in protein synthesis.

CONCLUSIONS

Febuxostat attenuated cachexia progression and improved survival of tumour-bearing rats.

Is TP53INP2 a critical regulator of muscle mass?

PURPOSE OF REVIEW

The main aim of this review is to summarize current knowledge of tumor protein p53-inducible nuclear protein 2 (TP53INP2) function and its role in skeletal muscle proteostasis.

RECENT FINDINGS

Autophagy is directly involved in the regulation of skeletal muscle mass. Thus, excessive autophagy is associated with several diseases that cause muscle wasting, and it promotes the loss of muscle protein. Furthermore, compromised autophagy also leads to muscle atrophy. In this regard, TP53INP2 activates autophagy in skeletal muscle, thus causing a reduction in muscle mass. Moreover, TP53INP2 gain of function enhances muscle wasting in a highly catabolic context such as in streptozotocin-induced diabetes. However, TP53INP2 is naturally repressed in human insulin resistance and in murine models of diabetes. These observations suggest that TP53INP2 repression would reduce muscle atrophy under conditions that favor protein loss in skeletal muscle.

SUMMARY

To date, there is no effective treatment for muscle wasting. Thus, the identification of new putative pharmacological targets to effectively treat this devastating condition is crucial. Given current knowledge about the role of TP53INP2 in skeletal muscle, this protein may be an optimal candidate to target for the prevention of muscle wasting.

Distinct muscle apoptotic pathways are activated in muscles with different fiber types in a rat model of critical illness myopathy

Critical illness myopathy (CIM) is associated with severe muscle atrophy and fatigue in affected patients. Apoptotic signaling is involved in atrophy and is elevated in muscles from patients with CIM. In this study we investigated underlying mechanisms of apoptosis-related pathways in muscles with different fiber type composition in a rat model of CIM using denervation and glucocorticoid administration (denervation and steroid-induced myopathy, DSIM). Soleus and tibialis anterior (TA) muscles showed severe muscle atrophy (40-60% of control muscle weight) and significant apoptosis in interstitial as well as myofiber nuclei that was similar between the two muscles with DSIM. Caspase-3 and -8 activities, but not caspase-9 and -12, were elevated in TA and not in soleus muscle, while the caspase-independent proteins endonuclease G (EndoG) and apoptosis inducing factor (AIF) were not changed in abundance nor differentially localized in either muscle. Anti-apoptotic proteins HSP70, -27, and apoptosis repressor with a caspase recruitment domain (ARC) were elevated in soleus compared to TA muscle and ARC was significantly decreased with induction of DSIM in soleus. Results indicate that apoptosis is a significant process associated with DSIM in both soleus and TA muscles, and that apoptosis-associated processes are differentially regulated in muscles of different function and fiber type undergoing atrophy due to DSIM. We conclude that interventions combating apoptosis with CIM may need to be directed towards inhibiting caspase-dependent as well as -independent mechanisms to be able to affect muscles of all fiber types.

Cachexia & debility diagnoses in hospitalized children and adolescents with complex chronic conditions: evidence from the Kids' Inpatient Database

Objective:

To characterize the frequency, cost, and hospital-reported outcomes of cachexia and debility in children and adolescents with complex chronic conditions (CCCs).

Methods:

We identified children and adolescents (aged ≤20 years) with CCCs, cachexia, and debility in the Kids’ Inpatient Database [Healthcare Cost and Utilization Project, Agency for Healthcare Research & Quality]. We then compared the characteristics of patients and hospitalizations, including cost and duration of stay, for CCCs with and without cachexia and/or debility. We examined factors that predict risk of inpatient mortality in children and adolescents with CCCs using a logistic regression model. We examined factors that impact duration of stay and cost in children and adolescents with CCCs using negative binomial regression models. All costs are reported in US dollars in 2014 using Consumer Price Index inflation adjustment.

Results:

We estimated the incidence of hospitalization of cachexia in children and adolescents with CCCs at 1,395 discharges during the sample period, which ranged from 277 discharges in 2003 to 473 discharges in 2012. We estimated the incidence of hospitalization due to debility in children and adolescents with CCCs at 421 discharges during the sample period, which ranged from 39 discharges in 2003 to 217 discharges in 2012. Cachexia was associated with a 60% increase in the risk of inpatient mortality, whereas debility was associated with a 40% decrease in the risk of mortality. Cachexia and debility increased duration of stay in hospital (17% and 39% longer stays, respectively). Median cost of hospitalization was $15,441.59 and $23,796.16 for children and adolescents with cachexia and debility, respectively.

Conclusions:

Incidence of hospitalization for cachexia in children and adolescents with CCCs is less than that for adults but the frequency of cachexia diagnoses increased over time. Estimates of the incidence of hospitalization with debility in children and adolescents with CCCs have not been reported, but our study demonstrates that the frequency of these discharges is also increasing.

Rehabilitation nutrition for sarcopenia with disability: a combination of both rehabilitation and nutrition care management

Malnutrition and sarcopenia often occur in rehabilitation settings. The prevalence of malnutrition and sarcopenia in older patients undergoing rehabilitation is 49-67 % and 40-46.5 %, respectively. Malnutrition and sarcopenia are associated with poorer rehabilitation outcome and physical function. Therefore, a combination of both rehabilitation and nutrition care management may improve outcome in disabled elderly with malnutrition and sarcopenia. The concept of rehabilitation nutrition as a combination of both rehabilitation and nutrition care management and the International Classification of Functioning, Disability and Health guidelines are used to evaluate nutrition status and to maximize functionality in the elderly and other people with disability. Assessment of the multifactorial causes of primary and secondary sarcopenia is important because rehabilitation nutrition for sarcopenia differs depending on its etiology. Treatment of age-related sarcopenia should include resistance training and dietary supplements of amino acids. Therapy for activity-related sarcopenia includes reduced bed rest time and early mobilization and physical activity. Treatment for disease-related sarcopenia requires therapies for advanced organ failure, inflammatory disease, malignancy, or endocrine disease, while therapy for nutrition-related sarcopenia involves appropriate nutrition management to increase muscle mass. Because primary and secondary sarcopenia often coexist in people with disability, the concept of rehabilitation nutrition is useful for their treatment. Stroke, hip fracture, and hospital-associated deconditioning are major causes of disability, and inpatients of rehabilitation facilities often have malnutrition and sarcopenia. We review the concept of rehabilitation nutrition, the rehabilitation nutrition options for stroke, hip fracture, hospital-associated deconditioning, sarcopenic dysphagia, and then evaluate the amount of research interest in rehabilitation nutrition.

Treatment of cachexia: an overview of recent developments

Body wasting in the context of chronic illness is associated with reduced quality of life and impaired survival. Recent clinical trials have investigated different approaches to improve patients' skeletal muscle mass and strength, exercise capacity, and survival in the context of cachexia and body wasting, many of them in patients with cancer. The aim of this article was to summarize clinical trials published over the past 2 years. Therapeutic approaches discussed include appetite stimulants, such as megestrol acetate, L-carnitine, or melatonin, anti-inflammatory drugs, such as thalidomide, pentoxyphylline, or a monoclonal antibody against interleukin-1α as well as ghrelin and the ghrelin agonist anamorelin; nutritional support, and anabolics, such as enobosarm and testosterone.

Muscle wasting: an overview of recent developments in basic research

The syndrome of cachexia, i.e., involuntary weight loss in patients with underlying diseases, sarcopenia, i.e., loss of muscle mass due to aging, and general muscle atrophy from disuse and/or prolonged bed rest have received more attention over the last decades. All lead to a higher morbidity and mortality in patients, and therefore, they represent a major socio-economic burden for the society today. This mini-review looks at recent developments in basic research that are relevant to the loss of skeletal muscle. It aims to cover the most significant publication of last 3 years on the causes and effects of muscle wasting, new targets for therapy development, and potential biomarkers for assessing skeletal muscle mass. The targets include the following: (1) E-3 ligases TRIM32, SOCS1, and SOCS3 by involving the elongin BC ubiquitin-ligase, Cbl-b, culling 7, Fbxo40, MG53 (TRIM72), and the mitochondrial Mul1; (2) the kinase MST1; and (3) the G-protein Gαi2. D(3)-creatine has the potential to be used as a novel biomarker that allows to monitor actual change in skeletal muscle mass over time. In conclusion, significant development efforts are being made by academic groups as well as numerous pharmaceutical companies to identify new target and biomarker muscles, as muscle wasting represents a great medical need, but no therapies have been approved in the last decades.

The intriguing regulators of muscle mass in sarcopenia and muscular dystrophy

Recent advances in our understanding of the biology of muscle have led to new interest in the pharmacological treatment of muscle wasting. Loss of muscle mass and increased intramuscular fibrosis occur in both sarcopenia and muscular dystrophy. Several regulators (mammalian target of rapamycin, serum response factor, atrogin-1, myostatin, etc.) seem to modulate protein synthesis and degradation or transcription of muscle-specific genes during both sarcopenia and muscular dystrophy. This review provides an overview of the adaptive changes in several regulators of muscle mass in both sarcopenia and muscular dystrophy.

Muscle wasting: an overview of recent developments in basic research

The syndrome of cachexia, i.e. involuntary weight loss in patients with underlying diseases, sarcopenia, i.e. loss of muscle mass due to ageing, and general muscle atrophy from disuse and/or prolonged bed rest have received more attention over the last decades. All lead to a higher morbidity and mortality in patients and therefore, they represent a major socio-economic burden for the society today. This mini-review looks at recent developments in basic research that are relevant to the loss of skeletal muscle. It aims to cover the most significant publication of last three years on the causes and effects of muscle wasting, new targets for therapy development and potential biomarkers for assessing skeletal muscle mass. The targets include 1) E-3 ligases: TRIM32, SOCS1 and SOCS3 by involving the elongin BC ubiquitin-ligase, Cbl-b, culling 7, Fbxo40, MG53 (TRIM72) and the mitochondrial Mul1, 2) the kinase MST1 and 3) the G-protein Gαi2. D(3)-creatine has the potential to be used as a novel biomarker that allows to monitor actual change in skeletal muscle mass over time. In conclusion, significant development efforts are being made by academic groups as well as numerous pharmaceutical companies to identify new targets and biomarkers muscle, as muscle wasting represents a great medical need, but no therapies have been approved in the last decades.

Current understanding of sarcopenia: possible candidates modulating muscle mass

The world's elderly population is expanding rapidly, and we are now faced with the significant challenge of maintaining or improving physical activity, independence, and quality of life in the elderly. Sarcopenia, the age-related loss of skeletal muscle mass, is characterized by a deterioration of muscle quantity and quality leading to a gradual slowing of movement, a decline in strength and power, increased risk of fall-related injury, and often, frailty. Since sarcopenia is largely attributed to various molecular mediators affecting fiber size, mitochondrial homeostasis, and apoptosis, the mechanisms responsible for these deleterious changes present numerous therapeutic targets for drug discovery. Muscle loss has been linked with several proteolytic systems, including the ubuiquitin-proteasome, lysosome-autophagy, and tumor necrosis factor (TNF)-α/nuclear factor-kappaB (NF-κB) systems. Although many factors are considered to regulate age-dependent muscle loss, this gentle atrophy is not affected by factors known to enhance rapid atrophy (denervation, hindlimb suspension, etc.). In addition, defects in Akt-mammalian target of rapamycin (mTOR) and serum response factor (SRF)-dependent signaling have been found in sarcopenic muscle. Intriguingly, more recent studies indicated an apparent functional defect in autophagy- and myostatin-dependent signaling in sarcopenic muscle. In this review, we summarize the current understanding of the adaptation of many regulators in sarcopenia.

Animal models of chronic obstructive pulmonary disease

INTRODUCTION

Chronic obstructive pulmonary disease (COPD) is a leading global cause of mortality and chronic morbidity. Inhalation of cigarette smoke is the principal risk factor for development of this disease. COPD is a progressive disease that is typically characterised by chronic pulmonary inflammation, mucus hypersecretion, airway remodelling and emphysema that collectively reduce lung function. There are currently no therapies that effectively halt or reverse disease progression. It is hoped that the development of animal models that develop the hallmark features of COPD, in a short time frame, will aid in the identifying and testing of new therapeutic approaches.

AREAS COVERED

The authors review the recent developments in mouse models of chronic cigarette smoke-induced COPD as well as the principal findings. Furthermore, the authors discuss the use of mouse models to understand the pathogenesis and the contribution of infectious exacerbations. They also discuss the investigations of the systemic co-morbidities of COPD (pulmonary hypertension, cachexia and osteoporosis).

EXPERT OPINION

Recent advances in the field mark a point where animal models recapitulate the pathologies of COPD patients in a short time frame. They also reveal novel insights into the pathogenesis and potential treatment of this debilitating disease.

The role of micronutrients and macronutrients in patients hospitalized for heart failure

The detrimental pathophysiology of heart failure (HF) leaves room for physiologic and metabolomic concepts that include supplementation of micronutrients and macronutrients in these patients. Hence myocardial energetics and nutrient metabolism may represent relevant treatment targets in HF. This review focuses on the role of nutritive compounds such as lipids, amino acids, antioxidants, and other trace elements in the setting of HF. Supplementation of ferric carboxymaltose improves iron status, functional capacity, and quality of life in HF patients. To close the current gap in evidence further interventional studies investigating the role of micro- and macronutrients are needed in this setting.

Physiologic frailty as a sign of accelerated aging among adult survivors of childhood cancer: a report from the St Jude Lifetime cohort study

PURPOSE

Frailty, a phenotype reported among 9.9% of individuals 65 years old and older (9.6% of women; 5.2% of men), has not been assessed among adult childhood cancer survivors (CCS). We estimated the prevalence of frailty and examined associations with morbidity and mortality.

METHODS

Participants included 1,922 CCS at least 10 years from original cancer diagnosis (men, 50.3%; mean age, 33.6 ± 8.1 years) and a comparison population of 341 participants without cancer histories. Prefrailty and frailty were defined as two and ≥ three of the following conditions: low muscle mass, self-reported exhaustion, low energy expenditure, slow walking speed, and weakness. Morbidity was defined as grade 3 to 4 chronic conditions (Common Terminology Criteria for Adverse Events version 4.0). Fisher's exact tests were used to compare, by frailty status, percentages of those with morbidity. In a subset of 162 CCS who returned for a second visit, Poisson regression was used to evaluate associations between frailty and new onset morbidity. Cox proportional hazards regression was used to evaluate associations between frailty and death.

RESULTS

The prevalence of prefrailty and frailty were 31.5% and 13.1% among women and 12.9% and 2.7% among men, respectively, with prevalence increasing with age. Frail CCS were more likely than nonfrail survivors to have a chronic condition (82.1% v 73.8%). In models adjusted for existing chronic conditions, baseline frailty was associated with risk of death (hazard ratio, 2.6; 95% CI, 1.2 to 6.2) and chronic condition onset (relative risk, 2.2; 95% CI, 1.2 to 4.2).

CONCLUSION

The prevalence of frailty among young adult CCS is similar to that among adults 65 years old and older, suggesting accelerated aging.

TNF- α and IFN-s-dependent muscle decay is linked to NF-κB- and STAT-1α-stimulated Atrogin1 and MuRF1 genes in C2C12 myotubes

TNF-α was shown to stimulate mitogenicity in C2C12 myoblasts. Selected cytokines TNF-α, IFNα, or IFNγ reduced the expression of myosin heavy chain (MyHC IIa) when given together. Molecular mechanisms of cytokine activities were controlled by NF-κB and JAK/STAT signaling pathways, as metabolic inhibitors, curcumin and AG490, inhibited some of TNF-α and IFNα/IFNγ effects. Insulin was hardly antagonistic to TNF-α- and IFNα/IFNγ-dependent decrease in MyHC IIa protein expression. Cytokines used individually or together also repressed myogenesis of C2C12 cells. Moreover, TNF-α- and IFNα/IFNγ-dependent effects on C2C12 myotubes were associated with increased activity of Atrogin1 and MuRF1 genes, which code ubiquitin ligases. MyHC IIa gene activity was unaltered by cytokines. Inhibition of NF-κB or JAK/STAT with specific metabolic inhibitors decreased activity of Atrogin1 and MuRF1 but not MyHC IIa gene. Overall, these results suggest cooperation between cytokines in the reduction of MyHC IIa protein expression level via NF-κB/JAK/STAT signaling pathways and activation of Atrogin1 and MuRF1 genes as their molecular targets. Insulin cotreatment or pretreatment does not protect against muscle decay induced by examined proinflammatory cytokines.

Myostatin inhibitors as therapies for muscle wasting associated with cancer and other disorders

PURPOSE OF REVIEW

This review summarizes recent progress in the development of myostatin inhibitors for the treatment of muscle wasting disorders. It also focuses on findings in myostatin biology that may have implications for the development of antimyostatin therapies.

RECENT FINDINGS

There has been progress in evaluating antimyostatin therapies in animal models of muscle wasting disorders. Some programs have progressed into clinical development with initial results showing positive impact on muscle volume.In normal mice myostatin deficiency results in enlarged muscles with increased total force but decreased specific force (total force/total mass). An increase in myofibrillar protein synthesis without concomitant satellite cell proliferation and fusion leads to muscle hypertrophy with unchanged myonuclear number. A specific force reduction is not observed when atrophied muscle, the predominant therapeutic target of myostatin inhibitor therapy, is made myostatindeficient.Myostatin has been shown to be expressed by a number of tumor cell lines in mice and man.

SUMMARY

Myostatin inhibition remains a promising therapeutic strategy for a range of muscle wasting disorders.

Nutritional influences on age-related skeletal muscle loss

Age-related muscle loss impacts on whole-body metabolism and leads to frailty and sarcopenia, which are risk factors for fractures and mortality. Although nutrients are integral to muscle metabolism the relationship between nutrition and muscle loss has only been extensively investigated for protein and amino acids. The objective of the present paper is to describe other aspects of nutrition and their association with skeletal muscle mass. Mechanisms for muscle loss relate to imbalance in protein turnover with a number of anabolic pathways of which the mechanistic TOR pathway and the IGF-1–Akt–FoxO pathways are the most characterised. In terms of catabolism the ubiquitin proteasome system, apoptosis, autophagy, inflammation, oxidation and insulin resistance are among the major mechanisms proposed. The limited research associating vitamin D, alcohol, dietary acid–base load, dietary fat and anti-oxidant nutrients with age-related muscle loss is described. Vitamin D may be protective for muscle loss; a more alkalinogenic diet and diets higher in the anti-oxidant nutrients vitamin C and vitamin E may also prevent muscle loss. Although present recommendations for prevention of sarcopenia focus on protein, and to some extent on vitamin D, other aspects of the diet including fruits and vegetables should be considered. Clearly, more research into other aspects of nutrition and their role in prevention of muscle loss is required.

Muscle wasting in collagen-induced arthritis and disuse atrophy

The mechanisms of muscle wasting and decreased mobility have a major functional effect in rheumatoid arthritis, but they have been poorly studied. The objective of our study is to describe muscular involvement and the pathways in an experimental model of arthritis compared to the pathways in disuse atrophy. Female Wistar rats were separated into three groups: control (CO), collagen-induced arthritis (CIA), and immobilized (IM). Spontaneous locomotion and weight were evaluated weekly. The gastrocnemius muscle was evaluated by histology and immunoblotting to measure the expression of myostatin (a negative regulator), LC3 (autophagy), MuRF-1 (proteasome-mediated proteolysis), MyoD, and myogenin (satellite-cell activation). The significance level was set at P < 0.05, and histological analysis of joints confirmed the severity of the arthropathy. There was a significant difference in spontaneous locomotion in the CIA group. Animal body weight, gastrocnemius muscle weight, and relative muscle weight decreased 20%, 30%, and 20%, respectively, in the CIA rats. Inflammatory infiltration and swelling were present in the gastrocnemius muscles of the CIA rats. The mean cross-sectional area was reduced by 30% in the CIA group and by 60% in the IM group. The expressions of myostatin and LC3 between the groups were similar. There was increased expression of MuRF-1 in the IM (1.9-fold) and CIA (3.1-fold) groups and of myogenin in the muscles of the CIA animals (1.7-fold), while MyoD expression was decreased in the IM (20%) rats. This study demonstrated that the development of experimental arthritis is associated with decreased mobility, body weight, and muscle loss. Both IM and CIA animal models presented muscle atrophy, but while proteolysis and the regeneration pathways were activated in the CIA model, there was no activation of regeneration in the IM model. We can assume that muscle atrophy in experimental arthritis is associated with the disease itself and not simply with decreased mobility.

Restoration versus reconstruction: cellular mechanisms of skin, nerve and muscle regeneration compared

In tissues characterized by a high turnover or following acute injury, regeneration replaces damaged cells and is involved in adaptation to external cues, leading to homeostasis of many tissues during adult life. An understanding of the mechanics underlying tissue regeneration is highly relevant to regenerative medicine-based interventions. In order to investigate the existence a leitmotif of tissue regeneration, we compared the cellular aspects of regeneration of skin, nerve and skeletal muscle, three organs characterized by different types of anatomical and functional organization. Epidermis is a stratified squamous epithelium that migrates from the edge of the wound on the underlying dermis to rebuild lost tissue. Peripheral neurons are elongated cells whose neurites are organized in bundles, within an endoneurium of connective tissue; they either die upon injury or undergo remodeling and axon regrowth. Skeletal muscle is characterized by elongated syncytial cells, i.e. muscle fibers, that can temporarily survive in broken pieces; satellite cells residing along the fibers form new fibers, which ultimately fuse with the old ones as well as with each other to restore the previous organization. Satellite cell asymmetrical division grants a reservoir of undifferentiated cells, while other stem cell populations of muscle and non-muscle origin participate in muscle renewal. Following damage, all the tissues analyzed here go through three phases: inflammation, regeneration and maturation. Another common feature is the occurrence of cellular de-differentiation and/or differentiation events, including gene transcription, which are typical of embryonic development. Nonetheless, various strategies are used by different tissues to replace their lost parts. The epidermis regenerates ex novo, whereas neurons restore their missing parts; muscle fibers use a mixed strategy, based on the regrowth of missing parts through reconstruction by means of newborn fibers. The choice of either strategy is influenced by the anatomical, physical and chemical features of the cells as well as by the extracellular matrix typical of a given tissue, which points to the existence of differential, evolutionary-based mechanisms for specific tissue regeneration. The shared, ordered sequence of steps that characterize the regeneration processes examined suggests it may be possible to model this extremely important phenomenon to reproduce multicellular organisms.

Quality of life in sarcopenia and frailty

The reduced muscle mass and impaired muscle performance that define sarcopenia in older individuals are associated with increased risk of physical limitation and a variety of chronic diseases. They may also contribute to clinical frailty. A gradual erosion of quality of life (QoL) has been evidenced in these individuals, although much of this research has been done using generic QoL instruments, particularly the SF-36, which may not be ideal in older populations with significant comorbidities. This review and report of an expert meeting presents the current definitions of these geriatric syndromes (sarcopenia and frailty). It then briefly summarizes QoL concepts and specificities in older populations and examines the relevant domains of QoL and what is known concerning QoL decline with these conditions. It calls for a clearer definition of the construct of disability, argues that a disease-specific QoL instrument for sarcopenia/frailty would be an asset for future research, and discusses whether there are available and validated components that could be used to this end and whether the psychometric properties of these instruments are sufficiently tested. It calls also for an approach using utility weighting to provide some cost estimates and suggests that a time trade-off study could be appropriate.

Recent developments in the treatment of heart failure: highlights from the American Heart Association's Scientific Sessions, Los Angeles, California, 3 - 7 December 2012

Over the last decade, the treatment of heart failure has seen the introduction of several novel therapeutic avenues into the guidelines; however, these were mostly devoted to device therapies. Not much has changed with regards to the pharmacological treatment of this syndrome. Serelaxin, a recombinant form of the human peptide hormone relaxin-2, is a promising treatment candidate for patients presenting with acute heart failure. The Relaxin in Acute Heart Failure (RELAX-AHF) trial has shown beneficial effects in terms of relief of dyspnea and congestion in these patients. Even beneficial effects on short-term survival were reported. Another treatment approach to acute heart failure was pursued in the Cardiorenal Rescue Study in Acute Decompensated Heart Failure (CARRESS-HF) trial but the ultrafiltration used here lead to significantly worsened renal function as compared to standard pharmacologic care. Multicenter Automatic Defibrillator Implantation Trial - Reduce Inappropriate Therapy (MADIT-RIT) randomized patients with heart failure with a primary preventive indication for the implantation of an implantable cardioverter defibrillator to one of three algorithms for anti-tachycardia pacing (ATP) and shock. The authors found that initiation of such therapies only at higher heart rates than commonly used as threshold and longer time delays before the initiation of therapy may have two big advantages: the more conservative algorithms lead to a significant reduction in the cumulative probability of first inappropriate therapy and, even more striking, a reduced probability of death during follow-up. Biventricular versus Right Ventricular Pacing in Patients with Left Ventricular Dysfunction and Atrioventricular Block (BLOCK-HF) showed beneficial outcomes for cardiac resynchronization therapy in heart failure patients with a mere pacemaker indication. Other studies discussed here embraced the course of body wasting, particularly cachexia, and muscle wasting in patients with heart failure and the influence of eating behavior.

Novel aspects of health promoting compounds in meat

Meat is an integral part of the human diet. Besides essential amino acids and nutritive factors of high quality and availability, meat provides often overlooked components of importance for human health. These are amino acids and bioactive compounds that may be very important in i) preventing muscle wasting diseases, such as in sarcopenia, ii) reducing food and caloric intake to prevent metabolic syndrome, iii) blood pressure homeostasis via ACE-inhibitory components from connective tissue, and iv) maintaining functional gut environment through meat-derived nucleotides and nucleosides. In addition, meat could be an important source of phytanic acid, conjugated linoleic acids and antioxidants. Further, it becomes increasingly apparent that design of in vitro meat will be possible, and that this development may lead to improved health benefits from commercially viable and sustainable meat products.

Murine models of atrophy, cachexia, and sarcopenia in skeletal muscle

With the extension of life span over the past several decades, the age-related loss of muscle mass and strength that characterizes sarcopenia is becoming more evident and thus, has a more significant impact on society. To determine ways to intervene and delay, or even arrest the physical frailty and dependence that accompany sarcopenia, it is necessary to identify those biochemical pathways that define this process. Animal models that mimic one or more of the physiological pathways involved with this phenomenon are very beneficial in providing an understanding of the cellular processes at work in sarcopenia. The ability to influence pathways through genetic manipulation gives insight into cellular responses and their impact on the physical expression of sarcopenia. This review evaluates several murine models that have the potential to elucidate biochemical processes integral to sarcopenia. Identifying animal models that reflect sarcopenia or its component pathways will enable researchers to better understand those pathways that contribute to age-related skeletal muscle mass loss, and in turn, develop interventions that will prevent, retard, arrest, or reverse this phenomenon. This article is part of a Special Issue entitled: Animal Models of Disease.

Automated methods for the analysis of skeletal muscle fiber size and metabolic type

It is of interest to quantify the size, shape, and metabolic subtype of skeletal muscle fibers in many areas of biomedical research. To do so, skeletal muscle samples are sectioned transversely to the length of the muscle and labeled for extracellular or membrane proteins to delineate the fiber boundaries and additionally for biomarkers related to function or metabolism. The samples are digitally photographed and the fibers "outlined" for quantification of fiber cross-sectional area (CSA) using pointing devices interfaced to a computer, which is tedious, prone to error, and can be nonobjective. Here, we review methods for characterizing skeletal muscle fibers and describe new automated techniques, which rapidly quantify CSA and biomarkers. We discuss the applications of these methods to the characterization of mitochondrial dysfunctions, which underlie a variety of human afflictions, and we present a novel approach, utilizing images from the online Human Protein Atlas to predict relationships between fiber-specific protein expression, function, and metabolism.

Sarcopenic obesity and endocrinal adaptation with age

In normal aging, changes in the body composition occur that result in a shift toward decreased muscle mass and increased fat mass. The loss of muscle mass that occurs with aging is termed sarcopenia and is an important cause of frailty, disability, and loss of independence in older adults. Age-related changes in the body composition as well as the increased prevalence of obesity determine a combination of excess weight and reduced muscle mass or strength, recently defined as sarcopenic obesity. Weight gain increases total/abdominal fat, which, in turn, elicits inflammation and fatty infiltration in muscle. Sarcopenic obesity appears to be linked with the upregulation of TNF-α, interleukin (IL)-6, leptin, and myostatin and the downregulation of adiponectin and IL-15. Multiple combined exercise and mild caloric restriction markedly attenuate the symptoms of sarcopenic obesity. Intriguingly, the inhibition of myostatin induced by gene manipulation or neutralizing antibody ameliorates sarcopenic obesity via increased skeletal muscle mass and improved glucose homeostasis. In this review, we describe the possible influence of endocrinal changes with age on sarcopenic obesity.

Intensive care unit-acquired weakness: clinical phenotypes and molecular mechanisms

Intensive care unit-acquired weakness (ICUAW) begins within hours of mechanical ventilation and may not be completely reversible over time. It represents a major functional morbidity of critical illness and is an important patient-centered outcome with clear implications for quality of life and resumption of prior work and lifestyle. There is heterogeneity in functional outcome related to ICUAW across various patient populations after an episode of critical illness. This state-of-the art review argues that this observed heterogeneity may represent a clinical spectrum of disability in which there are recognizable clinical phenotypes for outcome according to age, burden of comorbid illness, and ICU length of stay. It further argues that these functional outcomes are modified by mood, cognition, and caregiver physical and mental health. This proposed construct of clinical phenotypes will be used as a framework for a review of the current literature on the molecular biology of muscle and nerve injury. This translational approach for the development of models pairing clinical phenotypes for different functional outcomes after critical illness with molecular mechanism of injury may offer unique insights into the diagnosis and treatment of muscle and nerve lesions.

Sarcopenia and age-related endocrine function

Sarcopenia, the age-related loss of skeletal muscle, is characterized by a deterioration of muscle quantity and quality leading to a gradual slowing of movement, a decline in strength and power, and an increased risk of fall-related injuries. Since sarcopenia is largely attributed to various molecular mediators affecting fiber size, mitochondrial homeostasis, and apoptosis, numerous targets exist for drug discovery. In this paper, we summarize the current understanding of the endocrine contribution to sarcopenia and provide an update on hormonal intervention to try to improve endocrine defects. Myostatin inhibition seems to be the most interesting strategy for attenuating sarcopenia other than resistance training with amino acid supplementation. Testosterone supplementation in large amounts and at low frequency improves muscle defects with aging but has several side effects. Although IGF-I is a potent regulator of muscle mass, its therapeutic use has not had a positive effect probably due to local IGF-I resistance. Treatment with ghrelin may ameliorate the muscle atrophy elicited by age-dependent decreases in growth hormone. Ghrelin is an interesting candidate because it is orally active, avoiding the need for injections. A more comprehensive knowledge of vitamin-D-related mechanisms is needed to utilize this nutrient to prevent sarcopenia.