Sarcopenia: describing rather than defining a condition

Development of HRP-assisted rGO-FET biosensors for high-precision measurement of serological steroid hormones

BACKGROUND

Sarcopenia, which is associated with many pathways and molecular mechanisms, not only deteriorates the quality of life in old age but is also linked to various diseases. The ratio between cortisol and dehydroepiandrosterone sulfate (DHEAS) was utilized as a candidate method to diagnose sarcopenia. The hormones can fluctuate in concentration throughout the day, so monitoring the ratio between the two hormones is necessary. Therefore, accurate sensors are essential to measure each cortisol and DHEAS in human-derived biofluids such as blood and plasma.

RESULTS

An electric-based biosensor that does not require a complicated manufacturing process was utilized using reduced graphene oxide (rGO) and improves sensitivity and selectivity by using HRP to monitor hormone changes in the human body, especially in human plasma. To prove the performance of the proposed hormone-monitoring sensor, we performed quantitative detection of cortisol and DHEAS in the buffer solution and human plasma with pre/absence HRP binding. Additionally, the selectivity of the sensor was verified by the detection of cortisol and DHEAS constitutional isomers, such as estradiol, dexamethasone, and cortisone. Furthermore, the quantitative detection results of cortisol and DHEAS in buffer solution were used to calculate the concentrations of cortisol and DHEAS from human plasma results.

SIGNIFICANCE

This analysis defined the detection accuracy compared with the normal human range of certain hormones. The accuracy of the analyzed data was up to 99 %, thus suggesting that the presented HRP replacement detection method utilizing the rGO-FET biosensor could be used for quantitative hormone measurement as well as sarcopenia monitoring.

Does the Number of Turns during Sleep Have Utility in the Early Detection of Parkinson's Disease and Its Related Disorders?

Introduction

Patients with Parkinson's disease (PD) and its related disorders exhibit decreased sleep activity. However, the factors associated with this decreased sleep activity remain unknown. Thus, we aimed to explore the factors associated with sleep activity in patients with PD and its related disorders.

Methods

This study included 33 patients with PD and its related disorders and 57 healthy participants who visited our outpatient clinics between November 2018 and March 2020. We evaluated the patients' muscle masses and measured the number of times they turned during sleep. The limb skeletal muscle index was utilized to evaluate the loss of muscle mass. This study was registered in the UMIN Clinical Trials Registry (Clinical Trials Registry number: UMIN000052436).

Results

Age, maximal grip strength, presarcopenia, phase angle (legs), history of hypertension, diabetes mellitus, dyslipidemia, orthopedic diseases, and the number of turns during sleep were associated with PD and its related disorders. The number of turns was independently associated with PD and its related disorders. Receiver operating characteristic curve analysis revealed that the cutoff value for the number of turns was 6 (area under the curve, 0.986; sensitivity, 93.9%; specificity, 96.5%). The cutoff numbers of turns for men and women were 9 and 6, respectively (area under the curve, 1.0 and 0.981; sensitivity, 100% and 94.7%; specificity, 100% and 95.2%; respectively).

Conclusions

The number of turns during sleep is significantly associated with PD and its related disorders and may decrease before patients present with sarcopenia. In addition, PD and its related disorders may coexist in men who turn less than nine times during sleep.

Acetylcholine receptor-β inhibition by interleukin-6 in skeletal muscles contributes to modulating neuromuscular junction during aging

BACKGROUND

Aging-related strength decline contributes to physiological deterioration and is a good predictor of poor prognosis. However, the mechanisms underlying neuromuscular junction disorders affecting contraction in aging are not well described. We hypothesized that the autocrine effect of interleukin (IL)-6 secreted by skeletal muscle inhibits acetylcholine receptor (AChR) expression, potentially causing aging-related strength decline. Therefore, we investigated IL-6 and AChR β-subunit (AChR-β) expression in the muscles and sera of aging C57BL/6J mice and verified the effect of IL-6 on AChR-β expression.

METHODS

Animal experiments, in vitro studies, bioinformatics, gene manipulation, dual luciferase reporter gene assays, and chromatin immunoprecipitation experiments were used to explore the role of the transcription cofactor peroxisome proliferator-activated receptor gamma coactivator 1-α (PGC1α) and its interacting transcription factors in the IL-6-mediated regulation of AChR-β expression.

RESULTS

IL-6 expression gradually increased during aging, inhibiting AChR-β expression, which was reversed by tocilizumab. Both tocilizumab and the PGC1α agonist reversed the inhibiting effect of IL-6 expression on AChR-β. Compared to inhibition of signal transducer and activator of transcription 3, extracellular signal-regulated kinases 1/2 (ERK1/2) inhibition suppressed the effects of IL-6 on AChR-β and PGC1α. In aging mouse muscles and myotubes, myocyte enhancer factor 2 C (MEF2C) was recruited by PGC1α, which directly binds to the AChR-β promoter to regulate its expression.

CONCLUSIONS

This study verifies AChR-β regulation by the IL-6/IL-6R-ERK1/2-PGC1α/MEF2C pathway. Hence, evaluating muscle secretion, myokines, and AChRs at an earlier stage to determine pathological progression is important. Moreover, developing intervention strategies for monitoring, maintaining, and improving muscle structure and function is necessary.

Unraveling the causes of sarcopenia: Roles of neuromuscular junction impairment and mitochondrial dysfunction

Sarcopenia is a systemic skeletal muscle disease characterized by a decline in skeletal muscle mass and function. Originally defined as an age-associated condition, sarcopenia presently also encompasses muscular atrophy due to various pathological factors, such as intensive care unit-acquired weakness, inactivity, and malnutrition. The exact pathogenesis of sarcopenia is still unknown; herein, we review the pathological roles of the neuromuscular junction and mitochondria in this condition. Sarcopenia is caused by complex and interdependent pathophysiological mechanisms, including aging, neuromuscular junction impairment, mitochondrial dysfunction, insulin resistance, lipotoxicity, endocrine factors, oxidative stress, and inflammation. Among these, neuromuscular junction instability and mitochondrial dysfunction are particularly significant. Dysfunction in neuromuscular junction can lead to muscle weakness or paralysis. Mitochondria, which are plentiful in neurons and muscle fibers, play an important role in neuromuscular junction transmission. Therefore, impairments in both mitochondria and neuromuscular junction may be one of the key pathophysiological mechanisms leading to sarcopenia. Moreover, this article explores the structural and functional alterations in the neuromuscular junction and mitochondria in sarcopenia, suggesting that a deeper understanding of these changes could provide valuable insights for the prevention or treatment of sarcopenia.

The Neuromuscular Junction: Roles in Aging and Neuromuscular Disease

The neuromuscular junction (NMJ) is a specialized synapse that bridges the motor neuron and the skeletal muscle fiber and is crucial for conversion of electrical impulses originating in the motor neuron to action potentials in the muscle fiber. The consideration of contributing factors to skeletal muscle injury, muscular dystrophy and sarcopenia cannot be restricted only to processes intrinsic to the muscle, as data show that these conditions incur denervation-like findings, such as fragmented NMJ morphology and corresponding functional changes in neuromuscular transmission. Primary defects in the NMJ also influence functional loss in motor neuron disease, congenital myasthenic syndromes and myasthenia gravis, resulting in skeletal muscle weakness and heightened fatigue. Such findings underscore the role that the NMJ plays in neuromuscular performance. Regardless of cause or effect, functional denervation is now an accepted consequence of sarcopenia and muscle disease. In this short review, we provide an overview of the pathologic etiology, symptoms, and therapeutic strategies related to the NMJ. In particular, we examine the role of the NMJ as a disease modifier and a potential therapeutic target in neuromuscular injury and disease.

Improper Remodeling of Organelles Deputed to Ca2+ Handling and Aerobic ATP Production Underlies Muscle Dysfunction in Ageing

Proper skeletal muscle function is controlled by intracellular Ca2+ concentration and by efficient production of energy (ATP), which, in turn, depend on: (a) the release and re-uptake of Ca2+ from sarcoplasmic-reticulum (SR) during excitation-contraction (EC) coupling, which controls the contraction and relaxation of sarcomeres; (b) the uptake of Ca2+ into the mitochondrial matrix, which stimulates aerobic ATP production; and finally (c) the entry of Ca2+ from the extracellular space via store-operated Ca2+ entry (SOCE), a mechanism that is important to limit/delay muscle fatigue. Abnormalities in Ca2+ handling underlie many physio-pathological conditions, including dysfunction in ageing. The specific focus of this review is to discuss the importance of the proper architecture of organelles and membrane systems involved in the mechanisms introduced above for the correct skeletal muscle function. We reviewed the existing literature about EC coupling, mitochondrial Ca2+ uptake, SOCE and about the structural membranes and organelles deputed to those functions and finally, we summarized the data collected in different, but complementary, projects studying changes caused by denervation and ageing to the structure and positioning of those organelles: a. denervation of muscle fibers-an event that contributes, to some degree, to muscle loss in ageing (known as sarcopenia)-causes misplacement and damage: (i) of membrane structures involved in EC coupling (calcium release units, CRUs) and (ii) of the mitochondrial network; b. sedentary ageing causes partial disarray/damage of CRUs and of calcium entry units (CEUs, structures involved in SOCE) and loss/misplacement of mitochondria; c. functional electrical stimulation (FES) and regular exercise promote the rescue/maintenance of the proper architecture of CRUs, CEUs, and of mitochondria in both denervation and ageing. All these structural changes were accompanied by related functional changes, i.e., loss/decay in function caused by denervation and ageing, and improved function following FES or exercise. These data suggest that the integrity and proper disposition of intracellular organelles deputed to Ca2+ handling and aerobic generation of ATP is challenged by inactivity (or reduced activity); modifications in the architecture of these intracellular membrane systems may contribute to muscle dysfunction in ageing and sarcopenia.

Terminal Schwann Cell Aging: Implications for Age-Associated Neuromuscular Dysfunction

Action potential is transmitted to muscle fibers through specialized synaptic interfaces called neuromuscular junctions (NMJs). These structures are capped by terminal Schwann cells (tSCs), which play essential roles during formation and maintenance of the NMJ. tSCs are implicated in the correct communication between nerves and muscles, and in reinnervation upon injury. During aging, loss of muscle mass and strength (sarcopenia and dynapenia) are due, at least in part, to the progressive loss of contacts between muscle fibers and nerves. Despite the important role of tSCs in NMJ function, very little is known on their implication in the NMJ-aging process and in age-associated denervation. This review summarizes the current knowledge about the implication of tSCs in the age-associated degeneration of NMJs. We also speculate on the possible mechanisms underlying the observed phenotypes.

Factors related with sarcopenia and sarcopenic obesity among low- and middle-income settings: the 10/66 DRG study

Sarcopenia and sarcopenic obesity research in low- and middle- income countries (LMICs) is limited. We investigated sarcopenia and sarcopenic obesity prevalence and sociodemographic, bio-clinical and lifestyle factors in LMICs settings. For the purposes of this study, the 10/66 Dementia Research Group follow-up wave information from individuals aged 65 and over in Cuba, Dominican Republic, Peru, Mexico, Puerto Rico, China, was employed and analysed (n = 8.694). Based on indirect population formulas, we calculated body fat percentage (%BF) and skeletal muscle mass index (SMI). Sarcopenia prevalence ranged from 12.4% (Dominican Republic) to 24.6% (rural Peru); sarcopenic obesity prevalence ranged from 3.0% (rural China) to 10.2% (rural Peru). Odds ratios (OR) with 95% confidence intervals (CI) for sarcopenia were higher for men 2.82 (2.22-3.57) and those with higher %BF 1.08 (1.07-1.09), whereas higher number of assets was associated with a decreased likelihood 0.93 (0.87-1.00). OR of sarcopenic obesity were higher for men 2.17 (1.70-2.76), those reporting moderate alcohol drinking 1.76 (1.21-2.57), and those with increased number of limiting impairments 1.54 (1.11-2.14). We observed heterogeneity in the prevalence of sarcopenia and sarcopenic obesity in the 10/66 settings. We also found a variety of factors to be associated with those. Our results reveal the need for more research among the older population of LMICs.

Sarcopenia is a poor prognostic factor of castration-resistant prostate cancer treated with docetaxel therapy

Background

Sarcopenia is a geriatric syndrome that is characterized by the gradual muscle loss and frailty in the elderly. Meanwhile, the prevalence of prostate cancer is on the rise worldwide. Mainstay treatments for metastatic prostate cancer are androgen-deprivation therapy and taxane-based chemotherapy. Owing to the indolent nature of prostate cancer, these treatments tend to be long-lasting, giving rise to the problem of tolerance to the treatments. Especially given the fact that long-term chemotherapy is closely associated with muscle loss, we aimed to elucidate the correlation between chemotherapy and sarcopenia in the clinical setting.

Materials and methods

This study was a retrospective study. Participants with castration-resistant prostate cancer were recruited from November 2009 to September 2015.Participants were recruited at two hospitals, Juntendo and Teikyo University Hospital, Tokyo, Japan.Participants were 77 Japanese males with castration-resistant prostate cancer who underwent docetaxel chemotherapy.Sarcopenia was defined as L3-psoas muscle index < 5.7 cm²/m². We statistically investigated whether the existence of sarcopenia has an impact on the survival time, and identified potential covariates that affect it.

Results

Out of 77 patients, 26 patients (34%) were diagnosed as sarcopenia. Analysis showed that sarcopenia is independently associated with mortality risk (hazards ratio = 2.74, P = 0.0055). Sarcopenic patients showed significant decrease in body mass index, pretreatment hemoglobin, C-related protein, and L3-psoas muscle index as compared with nonsarcopenic patients. The median observation period was 499 days (330-790). Thirty-five patients (45%) died of prostate cancer during that period. Sarcopenic patients showed significantly shorter survival time after the initiation of docetaxel treatments (P = 0.0055).

Conclusion

Sarcopenia is an independent predictive factor for a poor tolerance to docetaxel treatment. Given that cessation of the treatment leads to death from the disease, our study identified sarcopenia as an independent factor that raises mortality risk.

Molecular mechanisms and therapeutic interventions in sarcopenia

Sarcopenia is the degenerative loss of muscle mass and function with aging. Recently sarcopenia was recognized as a clinical disease by the International Classification of Disease, 10th revision, Clinical Modification. An imbalance between protein synthesis and degradation causes a gradual loss of muscle mass, resulting in a decline of muscle function as a progress of sarcopenia. Many mechanisms involved in the onset of sarcopenia include age-related factors as well as activity-, disease-, and nutrition-related factors. The stage of sarcopenia reflecting the severity of conditions assists clinical management of sarcopenia. It is important that systemic descriptions of the disease conditions include age, sex, and other environmental risk factors as well as levels of physical function. To develop a new therapeutic intervention needed is the detailed understanding of molecular and cellular mechanisms by which apoptosis, autophagy, atrophy, and hypertrophy occur in the muscle stem cells, myotubes, and/or neuromuscular junction. The new strategy to managing sarcopenia will be signal-modulating small molecules, natural compounds, repurposing of old drugs, and muscle-specific microRNAs.

Neuromuscular adaptability of male and female rats to muscle unloading

Previously, it has been shown that following muscle unloading, males and females experience different maladaptations in neuromuscular function. As a follow-up, the present investigation sought to determine if male and female neuromuscular systems demonstrated similar, or disparate morphological adaptations to muscle unloading. Twenty young adult male, and 20 young adult female rats were randomly assigned to one of two treatment protocols: muscle unloading, or control conditions. Following the 2-week intervention period, immunofluorescent procedures were used to quantify pre- and post-synaptic features of neuromuscular junctions (NMJs), and to assess myofiber profiles (size and fiber type composition) of the soleus, plantaris, and EDL muscles. A 2-way ANOVA with main effects for sex and treatment was then used to identify statistically significant (p ≤ .05) differences among structural parameters. Analysis of NMJs showed a consistent lack of differences between males and females. Overall, NMJs were also found to be resistant to the effects of unloading. When examining myofiber profiles, however, male myofibers were revealed to be significantly larger than female ones in each of the muscles examined. Unloading resulted in significant myofiber atrophy only in the primarily weight-bearing soleus muscle. Only the EDL showed unloading-induced differences in myofiber type distribution (Type II → I). These data indicate that different components of the neuromuscular system (NMJs, myofibers) respond uniquely to unloading, and that sex affects myofiber type profiles, but not NMJs. Moreover, it appears that only muscles that have their habitual activity patterns disturbed by unloading (i.e., the soleus, adapt to that intervention).

Muscle wasting in heart failure : The role of nutrition

Muscle wasting and malnutrition are common complications in patients with advanced heart failure (HF); however, both remain underdiagnosed and undertreated although they both play relevant roles in the progression of HF. The risk of muscle wasting in patients with HF increases in those patients with malnutrition or at risk of malnutrition. Muscle wasting and malnutrition are thought to be positively influenced by adequate therapeutic interventions such as physical activity and nutritional support. Consequently, early detection of malnutrition in patients with HF is recommended. This review discusses muscle wasting and nutritional status, describing the effects of malnutrition on muscle wasting in patients with HF. We review specific issues related to muscle wasting and nutritional status in patients with HF; however, no established strategies currently exist to focus on patients suffering from muscle wasting with malnutrition.

The Current Understanding of Sarcopenia: Emerging Tools and Interventional Possibilities

The purpose of this review is to provide health practitioners and physicians the most current state of the research on sarcopenia, its consequences, and to offer a summary of consensus guidelines for identification based on the most recent and compelling investigations and analyses. To accomplish this, the causes and consequences of sarcopenia will be described, and definitions and screening methods are updated. Importantly, interventional recommendations for sarcopenia will be discussed with a special emphasis on the effects of resistance training on sarcopenia-related outcomes. Furthermore, due to the increasing usage of hormone treatment as a strategy to combat sarcopenia, special consideration on the effects of hormone changes with aging and as interventions will be briefly reviewed.

Factors associated with skeletal muscle mass, sarcopenia, and sarcopenic obesity in older adults: a multi-continent study

BACKGROUND

The aim of this study was to evaluate the factors associated with low skeletal muscle mass (SMM), sarcopenia, and sarcopenic obesity using nationally representative samples of people aged ≥65 years from diverse geographical regions of the world.

METHODS

Data were available for 18 363 people aged ≥65 years who participated in the Collaborative Research on Ageing in Europe survey conducted in Finland, Poland, and Spain, and the World Health Organization Study on global AGEing and adult health survey conducted in China, Ghana, India, Mexico, Russia, and South Africa, between 2007 and 2012. A skeletal muscle mass index (SMI) was created to reflect SMM. SMM, SMI, and percent body fat (%BF) were calculated with specific indirect population formulas. These estimates were based on age, sex, weight, height, and race. Sarcopenia and sarcopenic obesity were defined with specific cut-offs.

RESULTS

The prevalence of sarcopenia ranged from 12.6% (Poland) to 17.5% (India), and that of sarcopenic obesity ranged from 1.3% (India) to 11.0% (Spain). Higher %BF was associated with lower SMM in all countries, and with sarcopenia in five countries (p < 0.001). Compared to high levels of physical activity, low levels were related with higher odds for sarcopenia [OR 1.36 (95%CI 1.11-1.67)] and sarcopenic obesity [OR 1.80 (95%CI 1.23-2.64)] in the overall sample. Also, a dose-dependent association between higher numbers of chronic diseases and sarcopenic obesity was observed.

CONCLUSIONS

Physical activity and body composition changes such as high %BF are key factors for the prevention of sarcopenia syndrome.

Evaluation of C-terminal Agrin Fragment as a marker of muscle wasting in patients after acute stroke during early rehabilitation

BACKGROUND

C-terminal Agrin Fragment (CAF) has been proposed as a novel biomarker for sarcopenia originating from the degeneration of the neuromuscular junctions. In patients with stroke muscle wasting is a common observation that predicts functional outcome. We aimed to evaluate agrin sub-fragment CAF22 as a marker of decreased muscle mass and physical performance in the early phase after acute stroke.

METHODS

Patients with acute ischaemic or haemorrhagic stroke (n = 123, mean age 70 ± 11 y, body mass index BMI 27.0 ± 4.9 kg/m(2)) admitted to inpatient rehabilitation were studied in comparison to 26 healthy controls of similar age and BMI. Functional assessments were performed at begin (23 ± 17 days post stroke) and at the end of the structured rehabilitation programme (49 ± 18 days post stroke) that included physical assessment, maximum hand grip strength, Rivermead motor assessment, and Barthel index. Body composition was assessed by bioelectrical impedance analysis (BIA). Serum levels of CAF22 were measured by ELISA.

RESULTS

CAF22 levels were elevated in stroke patients at admission (134.3 ± 52.3 pM) and showed incomplete recovery until discharge (118.2 ± 42.7 pM) compared to healthy controls (95.7 ± 31.8 pM, p < 0.001). Simple regression analyses revealed an association between CAF22 levels and parameters of physical performance, hand grip strength, and phase angle, a BIA derived measure of the muscle cellular integrity. Improvement of the handgrip strength of the paretic arm during rehabilitation was independently related to the recovery of CAF22 serum levels only in those patients who showed increased lean mass during the rehabilitation.

CONCLUSIONS

CAF22 serum profiles showed a dynamic elevation and recovery in the subacute phase after acute stroke. Further studies are needed to explore the potential of CAF22 as a serum marker to monitor the muscle status in patients after stroke.

Reversible sarcopenia in patients with gastrointestinal stromal tumor treated with imatinib

BACKGROUND

Imatinib is a long-term, oral, targeted therapy for high-risk resected and advanced gastrointestinal stromal tumours (GIST). It is known that sarcopenia affects prognosis and treatment tolerance in patients with various solid cancers. We analysed lumbar skeletal muscle index changes in imatinib-treated GIST patients. Imatinib tolerance was also assessed to evaluate the influence of pre-treatment sarcopenia.

METHODS

Thirty-one patients with advanced (n = 16) or high-risk resected (n = 15) GIST treated with imatinib (400 mg/day) were analysed retrospectively. Lumbar skeletal muscle indexes were evaluated on computed tomography images obtained before starting imatinib for all patients and at 6 months for those initially sarcopenic. Sarcopenia was defined using consensual cutoffs. Imatinib-induced toxicities were assessed after 3 months of administration.

RESULTS

Twelve (38.7%) of the 31 patients were sarcopenic, including one unassessable at 6 months. Seven (63.6%) of the 11 assessable sarcopenic patients became non-sarcopenic after 6 months of imatinib. Pre-treatment sarcopenia was not associated with grades 3-4 toxicities, but the mean number of all-grade toxicities per sarcopenic patient was significantly higher for those non-sarcopenic (4.1 vs. 1.7, respectively, p < 0.01) after 3 months of treatment. Grades 1-2 anaemia and grades 1-2 fatigue were more frequent for sarcopenic than non-sarcopenic patients (83% vs. 26%, P < 0.01 and 42% vs. 5%, P = 0.02, respectively).

CONCLUSIONS

Sarcopenia is reversible in some GIST patients treated with imatinib. Pre-imatinib sarcopenia is predictive of non-severe toxicities, particularly anaemia and fatigue.

microRNAs: Modulators of the underlying pathophysiology of sarcopenia?

Skeletal muscle homeostasis depends on an intricate balance between muscle hypertrophy, atrophy and regeneration. As we age, maintenance of muscle homeostasis is perturbed, resulting in a loss of muscle mass and function, termed sarcopenia. Individuals with sarcopenia exhibit impaired balance, increased falls (leading to subsequent injury) and an overall decline in quality of life. The mechanisms mediating sarcopenia are still not fully understood but clarity in our understanding of the precise pathophysiological changes occurring during skeletal muscle ageing has improved dramatically. Advances in transcriptomics has highlighted significant deregulation in skeletal muscle gene expression with ageing, suggesting epigenetic alterations may play a crucial and potentially causative role in the skeletal muscle ageing process. microRNAs (miRNAs, miRs), novel regulators of gene expression, can modulate many processes in skeletal muscle, including myogenesis, tissue regeneration and cellular programming. Expression of numerous evolutionary conserved miRNAs is disrupted in skeletal muscle with age. Given that a single miRNA can simultaneously affect the functionality of multiple signaling pathways, miRNAs are potent modulators of pathophysiological changes. miRNA-based interventions provide a promising new therapeutic strategy against alterations in muscle homeostasis. The aim of this review is two-fold; firstly to outline the latest understanding of the pathophysiological alterations impacting the deregulation of skeletal muscle mass and function with ageing, and secondly, to highlight the mounting evidence for a role of miRNAs in modulating muscle mass, and the need to explore their specific role in sarcopenia.

The wasting continuum in heart failure: from sarcopenia to cachexia

Sarcopenia (muscle wasting) and cachexia share some pathophysiological aspects. Sarcopenia affects approximately 20 %, cachexia <10 % of ambulatory patients with heart failure (HF). Whilst sarcopenia means loss of skeletal muscle mass and strength that predominantly affects postural rather than non-postural muscles, cachexia means loss of muscle and fat tissue that leads to weight loss. The wasting continuum in HF implies that skeletal muscle is lost earlier than fat tissue and may lead from sarcopenia to cachexia. Both tissues require conservation, and therapies that stop the wasting process have tremendous therapeutic appeal. The present paper reviews the pathophysiology of muscle and fat wasting in HF and discusses potential treatments, including exercise training, appetite stimulants, essential amino acids, growth hormone, testosterone, electrical muscle stimulation, ghrelin and its analogues, ghrelin receptor agonists and myostatin antibodies.

Sarcopenia--The search for emerging biomarkers

Sarcopenia, an age-related decline in skeletal muscle mass and function, dramatically affects the life quality of elder people. In view of increasing life expectancy, sarcopenia renders a heavy burden on the health care system. However, although there is a consensus that sarcopenia is a multifactorial syndrome, its etiology, underlying mechanisms, and even definition remain poorly delineated, thus, preventing development of a precise treatment strategy. The main aim of our review is to critically analyze potential sarcopenia biomarkers in light of the molecular mechanisms of their involvement in sarcopenia pathogenesis. Normal muscle mass and function maintenance are proposed to be dependent on the dynamic balance between the positive regulators of muscle growth such as bone morphogenetic proteins (BMPs), brain-derived neurotrophic factor (BDNF), follistatin (FST) and irisin, and negative regulators including TGFβ, myostatin, activins A and B, and growth and differentiation factor-15 (GDF-15). We hypothesize that the shift in this balance to muscle growth inhibitors, along with increased expression of the C- terminal agrin fragment (CAF) associated with age-dependent neuromuscular junction (NMJ) dysfunction, as well as skeletal muscle-specific troponin T (sTnT), a key component of contractile machinery, is a main mechanism underlying sarcopenia pathogenesis. Thus, this review proposes and emphasizes that these molecules are the emerging sarcopenia biomarkers.

The role of muscle mass and body fat on disability among older adults: A cross-national analysis

BACKGROUND

The aim of this study was to evaluate the association of sarcopenia and sarcopenic obesity with disability among older adults (≥65years old) in nine high-, middle- and low-income countries from Asia, Africa, Europe, and Latin America.

METHODS

Data were available for 53,289 people aged ≥18years who participated in the Collaborative Research on Ageing in Europe (COURAGE) survey conducted in Finland, Poland, and Spain, and the WHO Study on global AGEing and adult health (SAGE) survey conducted in China, Ghana, India, Mexico, Russia, and South Africa, between 2007 and 2012. Skeletal muscle mass, skeletal muscle mass index, and percent body fat were calculated with specific population formulas. Sarcopenia and sarcopenic obesity were defined by specific cut-offs used in previous studies. Disability was assessed with the WHODAS 2.0 score (range 0-100) with higher scores corresponding to higher levels of disability. Multivariable linear regression analysis was conducted with disability as the outcome.

RESULTS

The analytical sample consisted of 18,363 people (males; n=8116, females; n=10247) aged ≥65years with mean (SD) age 72.9 (11.1) years. In the fully-adjusted overall analysis, sarcopenic obesity was associated with greater levels of disability [b-coefficient 3.01 (95% CI 1.14-4.88)]. In terms of country-wise analyses, sarcopenia was associated with higher WHODAS 2.0 scores in China [b-coefficient 4.56 (95% CI: 3.25-5.87)], Poland [b-coefficient 6.66 (95% CI: 2.17-11.14)], Russia [b-coefficient 5.60 (95% CI: 2.03-9.16)], and South Africa [b-coefficient 7.75 (95% CI: 1.56-13.94)].

CONCLUSIONS

Prevention of muscle mass decline may contribute to reducing the global burden of disability.

Muscle wasting in ageing and chronic illness

PURPOSE

As life expectancy increases, muscle wasting is becoming a more and more important public health problem. This review summarizes the current knowledge of pathophysiological mechanisms underlying muscle loss in ageing and chronic diseases such as heart failure and discusses evolving interventional strategies.

RECENT FINDINGS

Loss of skeletal muscle mass and strength is a common phenomenon in a wide variety of disorders associated with ageing and morbidity-associated catabolic conditions such as chronic heart failure. Muscle wasting in ageing but otherwise healthy human beings is referred to as sarcopenia. Unlike cachexia in advanced stages of chronic heart failure, muscle wasting per se is not necessarily associated with weight loss. In this review, we discuss pathophysiological mechanisms underlying muscle loss in sarcopenia and cachexia, highlight similarities and differences of both conditions, and discuss therapeutic targets and possible treatments, such as exercise training, nutritional support, and drugs. Candidate drugs to treat muscle wasting disease include myostatin antagonists, ghrelin agonists, selective androgen receptor molecules, megestrol acetate, activin receptor antagonists, espindolol, and fast skeletal muscle troponin inhibitors.

SUMMARY

Present approaches to muscle wasting disease include exercise training, nutritional support, and drugs, although particularly the latter remain currently restricted to clinical studies. Optimizing skeletal muscle mass and function in ageing and chronic illness including heart failure is one of the chapters that are far from finished and gains future potential for new therapeutic interventions to come.

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.