Considerations in the Development of Drugs to Treat Sarcopenia

Human umbilical cord-derived mesenchymal stromal cells ameliorate aging-associated skeletal muscle atrophy and dysfunction by modulating apoptosis and mitochondrial damage in SAMP10 mice

Background

Skeletal muscle mass and function losses in aging individuals are associated with quality of life deterioration and disability. Mesenchymal stromal cells exert immunomodulatory and anti-inflammatory effects and could yield beneficial effects in aging-related degenerative disease.

Methods and results

We investigated the efficacy of umbilical cord-derived mesenchymal stromal cells (UC-MSCs) on sarcopenia-related skeletal muscle atrophy and dysfunction in senescence-accelerated mouse prone 10 (SAMP10) mice. We randomly assigned 24-week-old male SAMP10 mice to a UC-MSC treatment group and control group. At 12 weeks post-injection, the UC-MSC treatment had ameliorated sarcopenia-related muscle changes in performance, morphological structures, and mitochondria biogenesis, and it enhanced the amounts of proteins or mRNAs for myosin heavy chain, phospho-AMP-activated protein kinase, phospho-mammalian target of rapamycin, phospho-extracellular signal-regulated kinase1/2, peroxisome proliferator-activated receptor-γ coactivator, GLUT-4, COX-IV, and hepatocyte growth factor in both gastrocnemius and soleus muscles, and it reduced the levels of proteins or mRNAs for cathepsin K, cleaved caspase-3/-8, tumor necrosis factor-α, monocyte chemoattractant protein-1, and gp91^phox mRNAs. The UC-MSC treatment retarded mitochondria damage, cell apoptosis, and macrophage infiltrations, and it enhanced desmin/laminin expression and proliferating and CD34⁺/Integrin α₇⁺ cells in both types of skeletal muscle of the SAMP10 mice. In vitro, we observed increased levels of HGF, PAX-7, and MoyD mRNAs at the 4th passage of UC-MSCs.

Conclusions

Our results suggest that UC-MSCs can improve sarcopenia-related skeletal muscle atrophy and dysfunction via anti-apoptosis, anti-inflammatory, and mitochondrial biogenesis mechanisms that might be mediated by an AMPK-PGC1-α axis, indicating that UC-MSCs may provide a promising treatment for sarcopenia/muscle diseases.

Proliferin-1 Ameliorates Cardiotoxin-Related Skeletal Muscle Repair in Mice

Background

We recently demonstrated that proliferin-1 (PLF-1) functions as an apoptotic cell-derived growth factor and plays an important role in vascular pathobiology. We therefore investigated its role in muscle regeneration in response to cardiotoxin injury.

Methods and Results

To determine the effects of PLF-1 on muscle regeneration, we used a CTX-induced skeletal muscle injury model in 9-week-old male mice that were administered with the recombinant PLF-1 (rPLF-1) or neutralizing PLF-1 antibody. The injured muscles exhibited increased levels of PLF-1 gene expression in a time-dependent manner. On day 14 after injury, rPLF-1 supplementation ameliorated CTX-induced alterations in muscle fiber size, interstitial fibrosis, muscle regeneration capacity, and muscle performance. On day 3 postinjury, rPLF-1 increased the levels of proteins or genes for p-Akt, p-mTOR, p-GSK3α/β, p-Erk1/2, p-p38MAPK, interleukin-10, Pax7, MyoD, and Cyclin B1, and it increased the numbers of CD34⁺/integrin-α7⁺ muscle stem cells and proliferating cells in the muscles and/or bone marrow of CTX mice. An enzyme-linked immunosorbent assay revealed that rPLF-1 suppressed the levels of plasma tumor necrosis factor-α and interleukin-1β in CTX mice. PLF-1 blocking accelerated CTX-related muscle damage and dysfunction. In C2C12 myoblasts, rPLF-1 increased the levels of proteins for p-Akt, p-mTOR, p-GSK3α/β, p-Erk1/2, and p-p38MAPK as well as cellular functions; and these effects were diminished by the depletion of PLF-1 or silencing of its mannose-6-phosphate receptor.

Conclusions

These findings demonstrated that PLF-1 can improve skeletal muscle repair in response to injury, possibly via the modulation of inflammation and proliferation and regeneration, suggesting a novel therapeutic strategy for the management of skeletal muscle diseases.

[Sarcopenia: a geriatric syndrome that impacts urology]

With increasing age, people lose muscle strength and muscle mass. Acute illnesses, surgical interventions or chronic illnesses can quickly lead to immobility and even more muscle loss. For the elderly, there is a risk of reduced functionality and everyday skills. This syndrome, referred to sarcopenia, is characterized by a progressive and generalized loss of muscle mass and strength with negative consequences such as functional impairment and frailty. In the case of serious illnesses or surgical interventions, this is particularly noticeable in prolonged convalescence. Sarcopenia is associated with reduced quality of life and increased mortality. It is important to diagnose sarcopenia with the help of specific anamnesis questions and clinical functional examinations and to initiate adequate interventions, if possible preoperatively, for example. In addition to treating the underlying disease, it is crucial to always pay attention to the combination of a balanced protein-rich diet and appropriate physical training. Use of only one of the components or even the drug therapy approach is not effective.

Computerised cognitive remediation to enhance mobility in older adults: a single-blind, single-centre, randomised trial

Background

Decline in executive functions and related cognitive processes is associated with mobility decline, and these functions might be amenable to cognitive remediation. This study aimed to examine whether a computerised cognitive remediation programme would improve walking in adults aged 70 years and older.

Methods

This single-blind, randomised trial at one academic centre in the USA evaluated the efficacy of an 8-week computerised programme (also known as brain games) of progressive intensity and complexity to improve walking in older adults at high-risk for mobility disability. Inclusion criteria included being 70 years or older; ambulatory; and at high-risk for mobility disability, defined using a cutscore of nine or less (frail range) on the Short Physical Performance Battery and a walking speed of 100 cm/s or less. Individuals with dementia, acute or terminal medical illnesses, recent or planned surgery affecting mobility, mobility limitations solely due to musculoskeletal limitation or pain that prevented them from completing mobility tests, and those who were nursing home residents were excluded. Participants were block randomised (1:1; block size 12 and no stratification) to the intervention group or the control group (low complexity computer games and health education classes). Primary outcomes were change in walking speed at normal pace and walking while talking conditions assessed from baseline to 8 weeks post-intervention by investigators who were masked to group assignment. Groups were compared using the intention-to-treat principle with linear mixed models adjusted for confounders. This trial was registered with ClinicalTrails.gov, NCT02567227.

Findings

Between March 1, 2016, and March 12, 2020, 383 patients were enrolled and randomly assigned to the intervention or control group. After randomisation, 11 (3%) patients were diagnosed with dementia. 372 (97%; 271 [73%] women) were included in the intention-to-treat analysis. The mean age of participants was 77·0 years [SD 5·6]). 183 (49·2%) participants were Black and 62 (16·7%) were Hispanic. 314 (93%) of the target 338 completers had finished the intervention when the trial was terminated due to the COVID-19 pandemic. Although there were significant within-group improvements in both groups after the 8-week intervention, there was no significant difference in normal walking speed (-1·03 cm/s [SD 1·30]; 95% CI -3·60 to 1·54) and walking while talking conditions (0·59 cm/s [SD 1·61]; 95% CI -2·59 to 3·76) between the intervention and control groups. Similarly, within-group, but no between-group, differences were seen on executive function tests and physical function. There were no severe adverse events related to interventions.

Interpretation

Computerised cognitive remediation improved walking in adults aged 70 years and older at high-risk for mobility disability, but improvements were not significantly greater compared with an active control. Although our findings corroborate the within-group improvements on cognition and mobility reported in previous pilot clinical trials, future studies are required to determine the optimal dose, frequency, intensity, and content of computerised cognitive remediation programmes.

Funding

National Institute on Aging.

Ferroptosis in a sarcopenia model of senescence accelerated mouse prone 8 (SAMP8)

As a systemic syndrome characterized by age-associated degenerative skeletal muscle atrophy, sarcopenia leads to a risk of adverse outcomes in the elderly. Age-related iron accumulation is found in the muscles of sarcopenia animal models and patients, but the role of iron in sarcopenia remains poorly understood. It has been recently found that iron overload in several diseases is involved in ferroptosis, an iron- dependent form of programmed cell death. However, whether this excess iron can result in ferroptosis in muscles is still unclear. In our present study, we found that ferric citrate induced ferroptosis in C2C12 cells, as well as impaired their differentiation from myoblasts to myotubes. Due to the decreased muscle mass and fiber size, 40-week-old senescence accelerated mouse prone 8 (SAMP8) mice were used as a sarcopenia model, in whose muscles the iron content and markers of ferroptosis were found to increase, compared to 8-week- old SAMP8 controls. Moreover, our results showed that iron overload upregulated the expression of P53, which subsequently repressed the protein level of Slc7a11 (solute carrier family 7, member 11), a known ferroptosis-related gene. The downregulation of Slc7a11 then induced the ferroptosis of muscle cells through the accumulation of lipid peroxidation products, which may be one of the causes of sarcopenia. The findings in this study indicate that iron plays a key role in triggering P53- Slc7a11-mediated ferroptosis in muscles, and suggest that targeting iron accumulation and ferroptosis might be a therapeutic strategy for treating sarcopenia.

Impact of drugs with anti-inflammatory effects on skeletal muscle and inflammation: A systematic literature review

BACKGROUND

Ageing-related low-grade inflammation is suggested to aggravate sarcopenia and frailty. This systematic review investigates the influence that drugs with anti-inflammatory effects (AIDs) have on inflammation and skeletal muscle.

METHODS

PubMed and Web of Science were systematically screened for articles reporting the effects of AIDs on inflammation on one hand and on muscle mass and/or performance on the other.

RESULTS

Twenty-eight articles were included. These articles were heterogeneous in terms of the subjects studied, intervention components, setting, and outcome measures. Articles on older humans with acute inflammation showed evidence that celecoxib and piroxicam could reduce inflammation and improve performance and that ibuprofen improves exercise-induced muscle hypertrophy and gains in strength. In younger humans, only the effects of AIDs combined with exercise were investigated; no significant benefits of non-selective COX-inhibitors were reported, but improved strength gains with etanercept and reduced muscle soreness with celecoxib were noted. Indomethacin increased acute exercise-induced inflammation and reduced satellite cell differentiation in exercising muscle. Most articles did not systematically report occurrences of side effects.

CONCLUSIONS

Although AIDs showed significant reduction in inflammation-induced muscle weakness in older hospitalised patients with acute inflammation, robust evidence is still lacking. When combined with exercise, AIDs presented a protective effect against age-related loss of muscle mass, thus enhancing muscle mass and performance. The mechanism regulating muscle strength and its mass seems to differ between individuals of old and young age. However, the effects seem drug-specific and dose-dependent and appear to be influenced by subjects' trainability and the clinical context. In addition, the balance between benefits and harm remains unclear.

Exercise restores muscle stem cell mobilization, regenerative capacity and muscle metabolic alterations via adiponectin/AdipoR1 activation in SAMP10 mice

BACKGROUND

Exercise train (ET) stimulates muscle response in pathological conditions, including aging. The molecular mechanisms by which exercise improves impaired adiponectin/adiponectin receptor 1 (AdipoR1)-related muscle actions associated with aging are poorly understood. Here we observed that in a senescence-accelerated mouse prone 10 (SAMP10) model, long-term ET modulated muscle-regenerative actions.

METHODS

25-week-old male SAMP10 mice were randomly assigned to the control and the ET (45 min/time, 3/week) groups for 4 months. Mice that were maintained in a sedentary condition served controls.

RESULTS

ET ameliorated aging-related muscle changes in microstructure, mitochondria, and performance. The amounts of proteins or mRNAs for p-AMPKα, p-Akt, p-ERK1/2, p-mTOR, Bcl-XL, p-FoxO3, peroxisome proliferators-activated receptor-γ coactivator, adiponectin receptor1 (adpoR1), and cytochrome c oxidase-IV, and the numbers of CD34⁺ /integrin-α₇⁺ muscle stem cells (MuSCs) and proliferating cells in the muscles and bone-marrow were enhanced by ET, whereas the levels of p-GSK-3α and gp91phox proteins and apoptotic cells were reduced by ET. The ET also resulted in increased levels of plasma adiponectin and the numbers of bone-marrow (BM)-derived circulating CD34⁺ /integrin-α₇⁺ MuSCs and their functions. Integrin-α₇⁺ MuSCs of exercised mice had improved changes of those beneficial molecules. These ET-mediated aged muscle benefits were diminished by adiponectin and AdipoR1 blocking as well as AMPK inhibition. Finally, recombinant mouse adiponectin enhanced AMPK and mTOR phosphorylations in BM-derived integrin-α₇⁺ cells.

CONCLUSIONS

These findings suggest that ET can improve aging-related impairments of BM-derived MuSC regenerative capacity and muscle metabolic alterations via an AMPK-dependent mechanism that is mediated by an adiponectin/AdipoR1 axis in SAMP10 mice.

Low Lean Mass Predicts Incident Fractures Independently From FRAX: a Prospective Cohort Study of Recent Retirees

Whether low muscle mass predisposes to fracture is still poorly understood. In the diagnosis of sarcopenia, different thresholds for low lean mass have been proposed but comparative data for these criteria against hard outcomes such as fractures are lacking. This study aimed to investigate the prevalence of low lean mass according to different thresholds used in operational definitions of sarcopenia and their association with 3-year fracture incidence in a cohort of healthy 63- to 67-year-old community dwellers. In a longitudinal analysis of 913 participants (mean age 65.0 ± 1.4 years) enrolled in the Geneva Retirees Cohort (GERICO) study, lean mass was assessed by dual-energy X-ray absorptiometry (DXA), and low trauma clinical fracture incidence was recorded over a 3-year period. Prevalence of low lean mass ranged from 3.5% to 20.2% according to the threshold applied. During a follow-up of 3.4 ± 0.9 years, 40 (4.4%) participants sustained at least one low trauma fracture. After multivariate adjustment including Fracture Risk Assessment Tool (FRAX) probability with femoral neck bone mineral density (BMD), low lean mass, as defined by Baumgartner thresholds, was associated with higher fracture risk (odds ratio [OR], 2.32; 95% CI, 1.04 to 5.18; p = 0.040). It also added significant predictive value beyond FRAX (likelihood ratio test for nested models, 4.28; p < 0.039). No significant association was found for other definition thresholds. The coexistence of sarcopenia and a T-score <-2.5 at spine or hip was associated with a 3.39-fold (95% CI, 1.54 to 7.46; p = 0.002) increase in low trauma fracture risk. In conclusion, low lean mass, as defined by the Baumgartner thresholds, is a predictor of incident fractures in a large cohort of healthy 65-year-old community dwellers, independently of FRAX probability. The increased risk is related to the threshold for low lean mass selected. These findings suggest that identification of sarcopenia should be considered in fracture risk assessment beyond usual risk factors. © 2016 American Society for Bone and Mineral Research.

Melatonin as a Potential Agent in the Treatment of Sarcopenia

Considering the increased speed at which the world population is aging, sarcopenia could become an epidemic in this century. This condition currently has no means of prevention or treatment. Melatonin is a highly effective and ubiquitously acting antioxidant and free radical scavenger that is normally produced in all organisms. This molecule has been implicated in a huge number of biological processes, from anticonvulsant properties in children to protective effects on the lung in chronic obstructive pulmonary disease. In this review, we summarize the data which suggest that melatonin may be beneficial in attenuating, reducing or preventing each of the symptoms that characterize sarcopenia. The findings are not limited to sarcopenia, but also apply to osteoporosis-related sarcopenia and to age-related neuromuscular junction dysfunction. Since melatonin has a high safety profile and is drastically reduced in advanced age, its potential utility in the treatment of sarcopenic patients and related dysfunctions should be considered.

Sarcopenia and frailty: new challenges for clinical practice

Sarcopenia and frailty are important conditions that become increasingly prevalent with age. Sarcopenia is the loss of muscle mass and function, and frailty can be defined as multi-system impairment associated with increased vulnerability to stressors. There is overlap between the two conditions, especially in terms of the physical aspects of the frailty phenotype: low grip strength, gait speed and muscle mass. These measures have been associated with a wide range of ageing outcomes and can be assessed in the clinical setting. In terms of intervention, there is evidence for the benefit of resistance exercise programmes, although these may not always be feasible. Considerable research into the use of medicines, both existing and new, as well as dietary supplements is ongoing. Finally in order to prevent or delay the development of these conditions, an additional approach is to consider aetiological factors operating across the life course.

Sarcopenia and frailty: new challenges for clinical practice

Sarcopenia and frailty are important conditions that become increasingly prevalent with age. Sarcopenia is the loss of muscle mass and function, and frailty can be defined as multi-system impairment associated with increased vulnerability to stressors. There is overlap between the two conditions, especially in terms of the physical aspects of the frailty phenotype: low grip strength, gait speed and muscle mass. These measures have been associated with a wide range of ageing outcomes and can be assessed in the clinical setting. In terms of intervention, there is evidence for the benefit of resistance exercise programmes, although these may not always be feasible. Considerable research into the use of medicines, both existing and new, as well as dietary supplements is ongoing. Finally in order to prevent or delay the development of these conditions, an additional approach is to consider aetiological factors operating across the life course.

Design considerations for an integrated microphysiological muscle tissue for drug and tissue toxicity testing

Microphysiological systems provide a tool to simulate normal and pathological function of organs for prolonged periods. These systems must incorporate the key functions of the individual organs and enable interactions among the corresponding microphysiological units. The relative size of different microphysiological organs and their flow rates are scaled in proportion to in vivo values. We have developed a microphysiological three-dimensional engineered human skeletal muscle system connected to a circulatory system that consists of a tissue-engineered blood vessel as part of a high-pressure arterial system. The engineered human skeletal muscle tissue reproduces key mechanical behaviors of skeletal muscle in vivo. Pulsatile flow is produced using a novel computer-controlled magnetically activated ferrogel. The system is versatile and the muscle unit can be integrated with other organ systems. Periodic monitoring of biomechanical function provides a non-invasive assessment of the health of the tissue and a way to measure the response to drugs and toxins.

Myostatin--the holy grail for muscle, bone, and fat?

Myostatin, a member of the transforming growth factor beta (TGF-β) superfamily, was first described in 1997. Since then, myostatin has gained growing attention because of the discovery that myostatin inhibition leads to muscle mass accrual. Myostatin not only plays a key role in muscle homeostasis, but also affects fat and bone. This review will focus on the impact of myostatin and its inhibition on muscle mass/function, adipose tissue and bone density/geometry in humans. Although existing data are sparse, myostatin inhibition leads to increased lean mass and 1 study found a decrease in fat mass and increase in bone formation. In addition, myostatin levels are increased in sarcopenia, cachexia and bed rest whereas they are increased after resistance training, suggesting physiological regulatory of myostatin. Increased myostatin levels have also been found in obesity and levels decrease after weight loss from caloric restriction. Knowledge on the relationship of myostatin with bone is largely based on animal data where elevated myostatin levels lead to decreased BMD and myostatin inhibition improved BMD. In summary, myostatin appears to be a key factor in the integrated physiology of muscle, fat, and bone. It is unclear whether myostatin directly affects fat and bone, or indirectly via muscle. Whether via direct or indirect effects, myostatin inhibition appears to increase muscle and bone mass and decrease fat tissue-a combination that truly appears to be a holy grail. However, at this time, human data for both efficacy and safety are extremely limited. Moreover, whether increased muscle mass also leads to improved function remains to be determined. Ultimately potential beneficial effects of myostatin inhibition will need to be determined based on hard outcomes such as falls and fractures.

Sarcopenia: a clinical review

Although sarcopenia has been used to define muscle mass loss in older subjects, muscle mass is not directly linked to muscle function. Recent definitions consider sarcopenia as a syndrome characterized by progressive and generalized loss of skeletal muscle mass and strength with a risk of adverse outcomes, such as physical disability, poor quality of life, and death. It is closely linked with physical frailty, and also with other muscle wasting disorders, including cachexia and malnutrition. This review focuses on the incorporation of sarcopenia into clinical practice, reviews case finding and diagnosis of sarcopenia, proposes a syndromic approach for the diagnostic work-up of sarcopenic patients, and looks at intervention trials with physical exercise and nutrition, as drugs to treat this condition are not expected to be available in the near future.

Mitochondrial dysfunction and sarcopenia of aging: from signaling pathways to clinical trials

Sarcopenia, the age-related loss of muscle mass and function, imposes a dramatic burden on individuals and society. The development of preventive and therapeutic strategies against sarcopenia is therefore perceived as an urgent need by health professionals and has instigated intensive research on the pathophysiology of this syndrome. The pathogenesis of sarcopenia is multifaceted and encompasses lifestyle habits, systemic factors (e.g., chronic inflammation and hormonal alterations), local environment perturbations (e.g., vascular dysfunction), and intramuscular specific processes. In this scenario, derangements in skeletal myocyte mitochondrial function are recognized as major factors contributing to the age-dependent muscle degeneration. In this review, we summarize prominent findings and controversial issues on the contribution of specific mitochondrial processes - including oxidative stress, quality control mechanisms and apoptotic signaling - on the development of sarcopenia. Extramuscular alterations accompanying the aging process with a potential impact on myocyte mitochondrial function are also discussed. We conclude with presenting methodological and safety considerations for the design of clinical trials targeting mitochondrial dysfunction to treat sarcopenia. Special emphasis is placed on the importance of monitoring the effects of an intervention on muscle mitochondrial function and identifying the optimal target population for the trial. This article is part of a Directed Issue entitled: Molecular basis of muscle wasting.

Prevalence of sarcopenia and associated factors among Thai population

The purpose of this study was to determine the prevalence of sarcopenia using the skeletal muscle index (SMI) criteria in the Thai population. The secondary objective was to demonstrate factors influencing low SMI in this population. Femoral neck bone mass density (BMD) was measured by dual-energy X-ray absorptiometry (GE Lunar, Madison, WI, USA) in 435 urban and 397 rural subjects (334 men and 498 women) between 20 and 84 years of age. Body mass index (BMI) was calculated from weight and height. The respective prevalence of sarcopenia among men and women was 35.33 % (95 % CI, 29.91, 40.41) and 34.74 % (95 % CI, 30.56, 39.10). Factors associated with sarcopenia using multiple logistic regression analyses in both sexes were (a) living in the city, (b) higher BMI, and (c) older age. Living in an urban area was the strongest factor, with an odds ratio (OR) of 17.26 ± 7.12 (95 % CI, 7.68, 38.76) in men and 8.62 ± 2.74 (95 % CI, 4.62, 16.05) in women (p < 0.05). The prevalence rate ratio for persons living in urban compared to rural areas was 2.01 (95 % CI, 1.14, 3.53) in men and 1.69 (95 % CI, 1.31, 2.17) in women (p < 0.05). Sarcopenia, as based on SMI, occurs frequently in the Thai population and increases with age. The prevalence of sarcopenia is particularly high among pre-retirement women (50-59 years of age) whereas the number of men with sarcopenia gradually rises with age. An urban environment is the most predictive factor for sarcopenia, followed by high BMI and age. Given the aging population, early recognition of this condition can be beneficial for prevention of an epidemic of sarcopenia-related disability.

New horizons in the pathogenesis, diagnosis and management of sarcopenia

Sarcopenia is the age-related loss of skeletal muscle mass and function. It is now recognised as a major clinical problem for older people and research in the area is expanding exponentially. One of the most important recent developments has been convergence in the operational definition of sarcopenia combining measures of muscle mass and strength or physical performance. This has been accompanied by considerable progress in understanding of pathogenesis from animal models of sarcopenia. Well-described risk factors include age, gender and levels of physical activity and this knowledge is now being translated into effective management strategies including resistance exercise with recent interest in the additional role of nutritional intervention. Sarcopenia is currently a major focus for drug discovery and development although there remains debate about the best primary outcome measure for trials, and various promising avenues to date have proved unsatisfactory. The concept of 'new tricks for old drugs' is, however, promising, for example, there is some evidence that the angiotensin-converting enzyme inhibitors may improve physical performance. Future directions will include a deeper understanding of the molecular and cellular mechanisms of sarcopenia and the application of a lifecourse approach to understanding aetiology as well as to informing the optimal timing of interventions.

Chronic low-grade inflammation and age-related sarcopenia

PURPOSE OF REVIEW

Age-related chronic low-grade inflammatory profile (CLIP) has been recognized as an important causative factor for sarcopenia. Here, we report the recent evidence concerning CLIP and sarcopenia.

RECENT FINDINGS

Twenty-one studies were included (12 observational, five interventional studies and four randomized controlled trials). Observational studies strengthen the association between CLIP and sarcopenia in cross-sectional and longitudinal designs. Interleukin (IL)-6 and tumour necrosis factor-α are the most reported inflammatory parameters. Biopsy studies confirm the role of oxidative mechanisms, protein kinase B and nuclear factor kappa-light-chain-enhancer of activated B cells pathways and implicate stress response mechanisms and heat shock protein. Adipose tissue as source of inflammatory cytokines remains unclear and correction for fat mass is advisable in new research. Exercise interventions (both aerobic and resistance training) demonstrate beneficial effects on CLIP even in the absence of decreases in weight, BMI or fat mass. IL-6 is also released during exercise, in hormone-like fashion unrelated to inflammation, and exercise-induced IL-6 changes require careful interpretation. Soy supplementation in one study showed no influence on CLIP and no recent pharmacological trials were retrieved.

SUMMARY

Associations between CLIP and sarcopenia are observed quite consistently and underlying mechanisms become apparent. Exercise remains the mainstay intervention to lower CLIP and counter sarcopenia. More research is warranted to unravel the exact dose-response relationship.

Sarcopenia in the elderly: diagnosis, physiopathology and treatment

Sarcopenia, defined as a syndrome rather than as a pathology, is the loss of muscle mass and function associated with age. Sarcopenia is an enigma for medicine, and despite the numerous publications available in the literature and the number of papers currently being published, there is no agreement about its definition, and even less about its root causes. One salient aspect that proves the lack of consensus is the fact that different working groups are still debating about the right name for this syndrome (which is associated with the loss of muscle mass and strength in the elderly). In hospitalized patients, sarcopenia has been shown to raise the risk of complications such as infections, pressure ulcers, loss of autonomy, institutionalization and poor quality of life, as well as to increase mortality. The factors that contribute to the development of sarcopenia in the elderly are: the state of chronic inflammation, atrophy of motoneurons, reduced protein intake (secondary among others to the condition defined as geriatric anorexia), and immobility. There is ongoing debate about the causes of sarcopenia, but the aspect that generates most interest today is the quest to achieve repeatable and clinically useful diagnostic criteria for its diagnosis, prevention and treatment. The aim of this narrative review is to summarise the abundant information available in the literature and to draw useful conclusions.