Sarcopenia and physical independence in older adults: the independent and synergic role of muscle mass and muscle function

Association between dynapenic obesity and risk of cardiovascular disease: The Hisayama study

BACKGROUND

Dynapenic obesity is a condition characterized by high adiposity levels combined with muscle dysfunction. Although high adiposity and muscle loss/dysfunction are thought to synergistically increase the risk of cardiovascular disease (CVD), few studies have addressed the association between dynapenic and sarcopenic obesity and CVD. We aimed to investigate the association of dynapenic obesity with incident CVD events using the data from a population-based prospective longitudinal study in Japan.

METHODS

A total of 2490 community-dwelling Japanese aged 40-79 years (42.5% males, mean age 57.7 ± 10.6 years) without a history of CVD were followed up for a median of 24 years. Handgrip strength was classified as low, medium, or high by age- and sex-specific tertiles. Body mass index (BMI) levels were categorized as lean (<18.5 kg/m2), normal (18.5-24.9 kg/m2), or obese (≥25.0 kg/m2). Dynapenic obesity was defined as having both low handgrip strength and obesity. The outcomes were defined as the first-ever development of CVD (defined as stroke or coronary heart disease). The hazard ratios (HRs) and their 95% confidence intervals (CIs) for the development of CVD were estimated using a Cox proportional hazards model, in which participants with high handgrip strength and normal BMI were used as a reference group. Mediation analyses used serum high-sensitivity C-reactive protein (hs-CRP) and homeostatic model assessment for insulin resistance (HOMA-IR) as mediators.

RESULTS

During the follow-up period, 482 participants developed CVD events (324 cases of stroke and 209 of coronary heart disease). The multivariable-adjusted risk of CVD increased significantly among participants with dynapenic obesity compared with the reference group (HR 1.49, 95% CI 1.03-2.17). An analysis by age groups showed a further increase in the risk of CVD among participants with dynapenic obesity aged less than 65 years (HR 1.66, 95% CI 1.04-2.65). In mediation analyses for participants aged less than 65 years, serum hs-CRP was shown to be a significant mediator explaining 13.8% of the association between dynapenic obesity and the development of CVD, while HOMA-IR explained 12.2% of this relationship.

CONCLUSIONS

Dynapenic obesity was a significant risk factor for the development of CVD in a general Japanese population. This association was more pronounced among those aged <65 years. Inflammation, and possibly glucose metabolism, might partly mediate this association. Our findings suggest that preventing muscle dysfunction as well as appropriate weight control, especially in middle-age, are important for preventing the development of CVD.

Muscle quality and major adverse cardiovascular events in post-acute myocardial infarction: A prospective cohort study

BACKGROUND & AIMS

Functional muscle quality, as assessed through the muscle quality index (MQI), represents a contemporary method to measure the capacity to generate force. Despite its potential, the prognostic significance of MQI remains uncertain in various clinical conditions, particularly among patients following acute myocardial infarction (AMI). In light of this, our study sought to evaluate the prognostic relevance of MQI concerning major adverse cardiovascular events (MACE) in patients following AMI.

METHODS AND RESULTS

This is a secondary analysis of a prospective cohort study that included subjects aged ≥20 years from a Cardiovascular Unit Hospital. Functional muscle quality was estimated using MQI, defined as the ratio of handgrip strength (HGS) to muscle mass (MM) derived from bioelectrical impedance analysis. The outcomes included prolonged length of hospital stay, new adverse cardiovascular events (AMI, stroke and hospital readmission for unstable angina), and cardiovascular mortality. A composite score comprising all adverse events over the 1-year follow-up was calculated and defined as MACE. This study included 163 patients, with a median age of 61 years (IQ: 54-69 years), and the majority consisted of males (76.1%). Individual components of the functional muscle quality (HGS and MM) were not associated with any of the adverse outcomes. Only MQI was associated mortality over the 1-year follow-up. For each increase in MQI, the hazard of mortality decreases: adjusted HR: 0.08 (95% CI 0.01-0.84).

CONCLUSION

Functional muscle quality assessed by the MQI may be a valuable clinical predictor of 1-year cardiovascular mortality in patients hospitalized post-AMI.

The relation between preoperative radiological sarcopenia and postoperative recovery of physical activity in older surgical cancer patients; an explorative study

To identify older surgical cancer patients at risk of decreased postoperative recovery of physical activity (PA), this study assesses whether preoperative radiological sarcopenia (RS) is associated with a decreased ability to return to baseline PA. RS was defined as decreased psoas muscle mass or -density by gender-specific cut-offs on CT-scans at level of vertebra L3. PA was assessed as steps/day measured with PA tracker and recovery of PA was defined as >90% of preoperative steps/day at 3 months postoperatively. Of 44 included patients aged 65 and over undergoing oncologic surgery, 18 patients (41%) showed RS. Seventeen patients (39%) returned to baseline PA, of which eight patients had RS (47%). RS was not associated with a return to baseline PA (OR: 1.38, 95%CI 0.39-4.92, p = 0.61). In this exploratory study, no association was found between preoperative RS and recovery of PA postoperatively.

Myokines: A central point in managing redox homeostasis and quality of life

Redox homeostasis is a crucial phenomenon that is obligatory for maintaining the healthy status of cells. However, the loss of redox homeostasis may lead to numerous diseases that ultimately result in a compromised quality of life. Skeletal muscle is an endocrine organ that secretes hundreds of myokines. Myokines are peptides and cytokines produced and released by muscle fibers. Skeletal muscle secreted myokines act as a robust modulator for regulating cellular metabolism and redox homeostasis which play a prime role in managing and improving metabolic function in multiple organs. Further, the secretory myokines maintain redox homeostasis not only in muscles but also in other organs of the body via stabilizing oxidants and antioxidant levels. Myokines are also engaged in maintaining mitochondrial dynamics as mitochondria is a central point for the generation of reactive oxygen species (ROS). Ergo, myokines also act as a central player in communicating signals to other organs, including the pancreas, gut, liver, bone, adipose tissue, brain, and skin via their autocrine, paracrine, or endocrine effects. The present review provides a comprehensive overview of skeletal muscle-secreted myokines in managing redox homeostasis and quality of life. Additionally, probable strategies will be discussed that provide a solution for a better quality of life.

Skeletal muscle mass recovery after oesophagectomy and neoadjuvant chemotherapy in oesophageal cancer: retrospective cohort study

OBJECTIVE

Skeletal muscle mass (SMM) is an important biomarker for prognosis and health in older patients with cancer. Limited information is available on the recovery course of SMM after oesophagectomy following neoadjuvant chemotherapy (NAC) in older patients. This study was performed to investigate the recovery course of SMM after oesophagectomy following NAC and the preoperative predictors of delayed recovery in older patients with locally advanced oesophageal cancer (LAEC).

METHODS

This single-centre retrospective cohort study involved older (≥65 years) and non-older (<65 years) patients with LAEC who underwent oesophagectomy following NAC. The SMM index (SMI) was calculated using CT images. One-way analysis of variance and multivariate logistic regression analysis were performed.

RESULTS

In total, 110 older patients and 57 non-older patients were analysed. Loss of the SMI after NAC to 12 months postoperatively was significantly greater in older patients than in non-older patients (p<0.01). The significant preoperative predictor of delayed recovery of the SMI 12 months after surgery was loss of the SMI during NAC in older patients (per 1%: adjusted OR 1.249; 95% CI 1.131 to 1.403; p<0.001), but not in non-older patients (per 1%: OR 1.074; 95% CI 0.988 to 1.179; p=0.108).

CONCLUSIONS

There is an especially large unmet need for preventing the long-term sequelae of SMM loss in older patients with LAEC after oesophagectomy following NAC. In older patients, loss of SMM during NAC is an especially useful biomarker for prescribing postoperative rehabilitation to prevent postoperative loss of SMM.

Plasma C-terminal agrin fragment concentrations across adulthood: Reference values and associations with skeletal muscle health

BACKGROUND

Increasing interest surrounds the utility of blood-based biomarkers for diagnosing sarcopenia. C-terminal agrin fragment (CAF), a marker of neuromuscular junction stability, is amongst the most promising candidates; however, a dearth of reference data impedes the incorporation of its use in public health settings. This study aimed to establish reference values for plasma CAF concentrations across adulthood in a large, well-characterized cohort of healthy adults; and comprehensively examine the association between plasma CAF levels and skeletal muscle health.

METHODS

One thousand people aged between 18 and 87 years took part in this study (mean age = 50.4 years; 51% females). Body composition and muscle strength were examined using DXA and hand dynamometry. Plasma CAF concentrations were measured, in duplicate, using commercially available ELISA kits. Sarcopenia and individual sarcopenia signatures [low skeletal muscle index (SMI) only/low grip strength only] were classified using the EWGSOP2 algorithm.

RESULTS

Detailed reference CAF values, according to sex and age, are presented. A significant but modest age-related increase in plasma CAF concentration was observed (P = 0.018). Across adulthood, CAF concentrations were negatively associated with grip strength and SMI (both P < 0.001). In people ≥50 years old, CAF concentrations were 22.6% higher in those with sarcopenia (P < 0.001), 11.3% higher in those with low SMI (P = 0.006) and 9.6% higher in those with low grip strength (P = 0.0034), compared with controls. People in the highest CAF concentration quartile, had 3.25 greater odds for sarcopenia (95% CI = 1.41-7.49, P = 0.005), 2.76 greater odds for low SMI (95% CI = 1.24-5.22, P = 0.012), and 2.56 greater odds for low grip strength (95% CI = 1.07-5.57, P = 0.037), compared with those in the lowest quartile. People with a CAF Z-score ≥2 had 9.52 greater odds for sarcopenia (95% CI = 3.01-30.05, P < 0.001) compared with a Z-score <1. Plasma CAF concentration had an acceptable level of diagnostic accuracy for sarcopenia (AUC = 0.772, 95% CI = 0.733-0.807, P < 0.001).

CONCLUSIONS

The reference values presented herein may guide the clinical interpretation of circulating CAF and help identify people at risk of poor skeletal muscle outcomes for inclusion in therapeutic interventions. Our findings add clarity to existing data, demonstrating a robust relationship between circulating CAF and skeletal muscle integrity in the largest adult cohort to date, and support the use of CAF as an accessible, cost-effective screening tool for sarcopenia. However, further research into the prognostic utility of plasma CAF, and the establishment of normative data from other populations, are urgently needed if routine CAF screening is to be embedded into public healthcare settings.

Development of a community intervention combining social media-based health education plus exercise programme (SHEEP) to improve muscle function among young-old adults with possible sarcopenia: Co-design approach

OBJECTIVES

There is no precedent for the use of social media in preventing sarcopenia. The aim of this study is to develop a social media-based intervention programme for the young-old population in the community in China to improve their awareness and behaviours regarding sarcopenia prevention.

STUDY DESIGN

Using guidelines for developing complex interventions, this study was divided into two main phases: a co-development phase and a preliminary test phase. Both were carried out in Changsha, China. The development phase employed co-design methodology with relevant stakeholders, including two rounds of consultation with patient and public involvement (12 members) and two rounds of focus groups (30 participants); this was followed by the three-week preliminary test phase (22 participants).

MAIN OUTCOME MEASURES

This study evaluated the consultation with patient and public involvement, and mainly collected qualitative data from the two rounds of focus group interviews and a final semi-structured interview following the preliminary test, so as to explore the participants' experiences, comments, and suggestions for revising the social media-based intervention. Handgrip strength was also evaluated.

RESULTS

The health education included seven videos of 4-6 min each related to sarcopenia, including information on the concept, influencing factors, adverse effects, manifestations, screening methods, and preventions. The exercise video consisted of four types of training (warm-up, aerobic, resistance, and flexibility training) and lasted 30 min, with a suggested engagement of at least 3 days/week. The specific contents and "dosage" of the final intervention were unanimously favourable to the diverse stakeholders involved (older adults with possible sarcopenia, experts, researchers). After the preliminary test, an improvement in handgrip strength was observed, from M15.92±SD5.22 kg to M19.13±SD5.44 kg (T = -5.44, P < 0.001). Subgroup analysis revealed that this improvement was evident in both men and women.

CONCLUSIONS

The social media-based intervention was universally endorsed by the participants and showed indications of a positive influence on sarcopenia. A feasibility study is now needed.

Associations between meeting 24-h movement guidelines and sarcopenia risk among adults aged ≥ 55 years in five low- and middle-income countries

OBJECTIVE

To diminish the negative influence of sarcopenia on senior adults, the study aimed to investigate the association between adherence to 24-h movement behavior guidelines (physical activity, sedentary behavior, sleep duration) and the risk of sarcopenia among individuals aged ≥55 years in five low- and middle-income countries (LMICs).

METHODS

A total of 16,503 adults aged ≥55 years were included in this cross-sectional study. The study utilized data from Global Aging and Adult Health Survey (SAGE). Participants reported their information about physical activity, sedentary behavior, and sleep duration using the questionnaire. Sarcopenia was identified as low skeletal muscle mass with a diminished gait speed or weakened handgrip strength. Multiple logistic regression models were used to investigate the association between adherence to 24-h movement behavior guidelines and the risk of sarcopenia.

RESULTS

Merely 32.73 % of participants met all three 24-h movement behavior guidelines (physical activity, less sedentary behavior, sleep). Meeting all three guidelines (p < 0.01) was significantly associated with a lower risk of sarcopenia. Meeting physical activity only (p < 0.05), or meeting both physical activity and sedentary behaivor (p < 0.05), or meeting both physical activity and sleep duration (p < 0.01) guidelines were also associated with a reduced risk of sarcopenia. Moreover, adults aged 65+ years who adhered to 24-h movement behavior guidelines exhibited a significantly reduced risk of developing sarcopenia.

CONCLUSION

The findings suggest that the adherence to 24-h movement behavior guidelines for regular physical activity, limited sedentary behavior, and sufficient sleep duration was associated with a reduced risk of sarcopenia in adults aged ≥55 years in five LMICs.

Dietary characteristics of urban community-dwelling older adults with low muscle mass: the bunkyo health study: a cross-sectional study

BACKGROUND

With the aging of the population worldwide, extending healthy life expectancy is an urgent issue. Muscle mass has been reported to be associated with physical independence and longevity. This study aimed to investigate the characteristics of food intake in urban community-dwelling older adults with low muscle mass.

METHODS

This cross-sectional study used baseline data from the Bunkyo Health Study, which included 1618 urban community-dwelling older adults aged 65-84 years. All participants underwent measurement of body composition using bioelectrical impedance analysis and evaluation of nutrient and food intake using the brief-type self-administered diet history questionnaire. Participants were stratified by sex and divided into robust or low skeletal muscle mass index (SMI) groups according to the Asian Working Group for Sarcopenia criteria to compare differences in nutrient and food intake.

RESULTS

The mean age and body mass index were 73.1 ± 5.4 years and 22.6 ± 3.1 kg/m2, respectively. The prevalence of low SMI was 31.1% in men and 43.3% in women. In men, all food intake, including total energy intake, was similar between the low SMI group and the robust group. In women, the low SMI group had less total energy intake, and consumed lower amounts of energy-producing nutrients (protein, fat, and carbohydrates), but there were only small differences in the intake of specific foods.

CONCLUSIONS

There were sex differences in food intake characteristics between urban community-dwelling older adults with low SMI and those who were robust. Advising women to increase their energy intake may be important in preventing muscle loss, and further research is needed in men.

Skeletal muscle dysfunction with advancing age

As a result of advances in medical treatments and associated policy over the last century, life expectancy has risen substantially and continues to increase globally. However, the disconnect between lifespan and 'health span' (the length of time spent in a healthy, disease-free state) has also increased, with skeletal muscle being a substantial contributor to this. Biological ageing is accompanied by declines in both skeletal muscle mass and function, termed sarcopenia. The mechanisms underpinning sarcopenia are multifactorial and are known to include marked alterations in muscle protein turnover and adaptations to the neural input to muscle. However, to date, the relative contribution of each factor remains largely unexplored. Specifically, muscle protein synthetic responses to key anabolic stimuli are blunted with advancing age, whilst alterations to neural components, spanning from the motor cortex and motoneuron excitability to the neuromuscular junction, may explain the greater magnitude of function losses when compared with mass. The consequences of these losses can be devastating for individuals, their support networks, and healthcare services; with clear detrimental impacts on both clinical (e.g., mortality, frailty, and post-treatment complications) and societal (e.g., independence maintenance) outcomes. Whether declines in muscle quantity and quality are an inevitable component of ageing remains to be completely understood. Nevertheless, strategies to mitigate these declines are of vital importance to improve the health span of older adults. This review aims to provide an overview of the declines in skeletal muscle mass and function with advancing age, describes the wide-ranging implications of these declines, and finally suggests strategies to mitigate them, including the merits of emerging pharmaceutical agents.

Bidirectional Relationships between Sarcopenia and Pelvic Floor Disorders

Sarcopenia and pelvic floor disorders (PFDs) are prevalent and often cooccurring conditions in the aging population. However, their bidirectional relationship and underlying mechanisms remain underexplored. This narrative review aims to elucidate this relationship by exploring potential causative interplays, shared pathophysiological mechanisms, and common risk factors. A comprehensive literature search was conducted to identify relevant studies focusing on epidemiological associations, interaction mechanisms, and implications for patient care. While epidemiological studies demonstrate associations between sarcopenia and PFDs, our findings reveal a cyclical relationship where sarcopenia may exacerbate PFDs through mechanisms such as decreased muscle strength and mobility. Conversely, the presence of PFDs often leads to reduced physical activity due to discomfort and mobility issues, which in turn exacerbate the muscle atrophy associated with sarcopenia. Additionally, shared risk factors such as physical inactivity, nutritional deficiencies, metabolic syndrome, and menopausal hormonal changes likely contribute to the onset and progression of both conditions. These interactions underscore the importance of concurrently integrated care approaches that address both conditions. Effective management requires comprehensive screening, the recognition of contributing factors, and tailored exercise regimens supported by a multidisciplinary approach. Future research should focus on longitudinal studies tracking disease progression and evaluating the efficacy of multidisciplinary care models in optimizing patient outcomes.

Nicotinamide N-methyltransferase inhibition mimics and boosts exercise-mediated improvements in muscle function in aged mice

Human hallmarks of sarcopenia include muscle weakness and a blunted response to exercise. Nicotinamide N-methyltransferase inhibitors (NNMTis) increase strength and promote the regenerative capacity of aged muscle, thus offering a promising treatment for sarcopenia. Since human hallmarks of sarcopenia are recapitulated in aged (24-month-old) mice, we treated mice from 22 to 24 months of age with NNMTi, intensive exercise, or a combination of both, and compared skeletal muscle adaptations, including grip strength, longitudinal running capacity, plantarflexor peak torque, fatigue, and muscle mass, fiber type, cross-sectional area, and intramyocellular lipid (IMCL) content. Exhaustive proteome and metabolome analyses were completed to identify the molecular mechanisms underlying the measured changes in skeletal muscle pathophysiology. Remarkably, NNMTi-treated aged sedentary mice showed ~ 40% greater grip strength than sedentary controls, while aged exercised mice only showed a 20% increase relative to controls. Importantly, the grip strength improvements resulting from NNMTi treatment and exercise were additive, with NNMTi-treated exercised mice developing a 60% increase in grip strength relative to sedentary controls. NNMTi treatment also promoted quantifiable improvements in IMCL content and, in combination with exercise, significantly increased gastrocnemius fiber CSA. Detailed skeletal muscle proteome and metabolome analyses revealed unique molecular mechanisms associated with NNMTi treatment and distinct molecular mechanisms and cellular processes arising from a combination of NNMTi and exercise relative to those given a single intervention. These studies suggest that NNMTi-based drugs, either alone or combined with exercise, will be beneficial in treating sarcopenia and a wide range of age-related myopathies.

Association of ultra-processed food consumption with muscle mass among young and middle-aged US adults

INTRODUCTION

Muscle mass is vital for physical activity and fundamental physiological processes supporting long-term health. While aging is inevitable, certain modifiable factors positively influence muscle preservation and overall well-being. However, the relationship between the consumption of ultra-processed foods (UPF) and muscle mass is not yet clear.

METHODS

This study included 7,173 men and nonpregnant women aged 20-59 years with valid 24-hour dietary recalls and accessible whole-body dual-energy x-ray absorptiometry (DXA) scans from NHANES 2011-2018. UPFs were identified through the NOVA classification system, and the percentage of energy derived from UPF consumption was evaluated in quintiles. Muscle mass measures were derived from DXA scans and quantified by the total and regional muscle mass index (MMI, kg/m²) and appendicular muscle mass index (AMMI, kg/m²). Multivariable-adjusted generalized linear regression models were applied to investigate the association between consumption of UPFs and muscle mass measures overall and by sociodemographic subgroups.

RESULTS

The multivariable-adjusted differences of total MMI from the lowest to highest quintile of UPF consumption were 0 (reference), -0.03 (95% CI, -0.13, 0.07), -0.13 (95%CI, -0.24, -0.04), -0.12 (95% CI, -0.23, -0.01), and - 0.17 (95% CI, -0.27, -0.08) (P for trend < 0.001). Subtotal MMI followed a similar magnitude of associational pattern as total MMI. For trunk MMI, corresponding values from the lowest to highest quintiles of UPF consumption were 0 (reference), -0.02 (95% CI, -0.07, 0.02), -0.05 (95%CI, -0.11, 0.00), -0.07 (95% CI, -0.13, -0.01), and - 0.07 (95% CI, -0.12, -0.01). For AMMI, corresponding values from the lowest to highest quintiles of UPF consumption were 0 (reference), -0.004 (95% CI, -0.07, 0.06), -0.08 (95%CI, -0.14, -0.02), -0.05 (95% CI, -0.11, 0.02), and - 0.10 (95% CI, -0.16, -0.04) (All P for trend < 0.001). While most subgroups maintained similar overall patterns, heterogeneous findings were also observed. For example, the multivariable-adjusted differences in total MMI between the lowest and highest quantile of UPF consumption were - 0.19 (95% CI, -0.32, -0.06) for non-Hispanic Whites, 0.18 (95% CI, 0.01, 0.36) for non-Hispanic Blacks, -0.25 (95%CI, -0.45, -0.04) for Hispanics, -0.25 (95% CI, -0.51, 0.05) for non-Hispanic Asians and - 0.32 (95% CI, -0.75, 0.12) for others (P for interaction < 0.001).

CONCLUSION

Higher consumption of UPFs was significantly associated with lower values of total and regional muscle mass. Specifically, comparing the highest quantile of UPF consumption to the lowest, total MMI decreased by 0.93%, trunk MMI decreased by 0.76%, and AMMI decreased by 1.25%. The differences in associational patterns between UPF consumption and muscle mass across sociodemographic subgroups require further investigation.

Prediction of Subsequent Vertebral Fracture After Acute Osteoporotic Fractures from Clinical and Paraspinal Muscle Features

To construct a nomogram based on clinical factors and paraspinal muscle features to predict vertebral fractures occurring after acute osteoporotic vertebral compression fracture (OVCF). We retrospectively enrolled 307 patients with acute OVCF between January 2013 and August 2022, and performed magnetic resonance imaging of the L3/4 and L4/5 intervertebral discs (IVDs) to estimate the cross-sectional area (CSA) and degree of fatty infiltration (FI) of the paraspinal muscles. We also collected clinical and radiographic data. We used univariable and multivariable Cox proportional hazards models to identify factors that should be included in the predictive nomogram. Post-OVCF vertebral fracture occurred within 3, 12, and 24 months in 33, 69, and 98 out of the 307 patients (10.8%, 22.5%, and 31.9%, respectively). Multivariate analysis revealed that this event was associated with percutaneous vertebroplasty treatment, higher FI at the L3/4 IVD levels of the psoas muscle, and lower relative CSA of functional muscle at the L4/5 IVD levels of the multifidus muscle. Area under the curve values for subsequent vertebral fracture at 3, 12, and 24 months were 0.711, 0.724, and 0.737, respectively, indicating remarkable accuracy of the nomogram. We developed a model for predicting post-OVCF vertebral fracture from diagnostic information about prescribed treatment, FI at the L3/4 IVD levels of the psoas muscle, and relative CSA of functional muscle at the L4/5 IVD levels of the multifidus muscle. This model could facilitate personalized predictions and preventive strategies.

Usefulness of the serum creatinine/cystatin C ratio as a blood biomarker for sarcopenia components among age groups in community-dwelling older people: The SONIC study

AIM

The serum creatinine/cystatin C ratio (CCR) or sarcopenia index is considered a useful marker of muscle mass. However, its usefulness in late-stage older adults remains unclear. We aimed to determine the usefulness of CCR as an indicator of sarcopenia in community-dwelling Japanese adults aged >75 years.

METHODS

Our study recruited participants aged 70, 80, and 90 ± 1 years during the baseline years, and included a 3-year follow-up in the Septuagenarians, Octogenarians, Nonagenarians, Investigation with Centenarians study. From 2015 to 2018, 955 participants were eligible: 367 in their 70s, 304 in their 80s, and 284 in their 90s. The diagnostic components of sarcopenia, including "low muscle mass, plus low muscle strength, and/or low physical performance," were evaluated using the bioelectrical impedance analysis-measured skeletal muscle mass index (SMI), handgrip strength, and short physical performance battery (SPPB) score, respectively, in accordance with the Asia Working Group for Sarcopenia 2019 criteria. Separate analyses were performed between each component and CCR, adjusting for sex, body mass index, and other blood biomarkers in each group.

RESULTS

The relationship between CCR and sarcopenia components was significant for handgrip strength (β = 0.21, 0.13, 0.19, and P < 0.0001, =0.0088, <0.0001, for the 70s, 80s, and 90s age groups, respectively); however, it was limited for SMI (β = 0.14; P = 0.0022, only for the 90s) and not significant for the SPPB score.

CONCLUSION

CCR is a limited indicator of sarcopenia in late-stage older adults. Although its association with muscle strength was significant, its relationship with muscle mass and physical performance was less pronounced. Geriatr Gerontol Int 2024; 24: 529-536.

Breast arterial calcification is associated with sarcopenia in peri- and post-menopausal women

PURPOSE

Breast arterial calcification (BAC) refers to medial calcium deposition in breast arteries and is detectable via mammography. Sarcopenia, which is characterised by low skeletal muscle mass and quality, is associated with several serious clinical conditions, increased morbidity, and mortality. Both BAC and sarcopenia share common pathologic pathways, including ageing, diabetes, and chronic kidney disease. Therefore, this study evaluated the relationship between BAC and sarcopenia as a potential indicator of sarcopenia.

METHODS

This study involved women aged >40. BAC was evaluated using digital mammography and was defined as vascular calcification. Sarcopenia was assessed using abdominal computed tomography. The cross-sectional skeletal mass area was measured at the third lumbar vertebra level. The skeletal mass index was obtained by dividing the skeletal mass area by height in square meters(m2). Sarcopenia was defined as a skeletal mass index of ≤38.5 cm2/m2. A multivariable model was used to evaluate the relationship between BAC and sarcopenia.

RESULTS

The study involved 240 participants. Of these, 36 (15 %) were patients with BAC and 204 (85 %) were without BAC. Sarcopenia was significantly higher among the patients with BAC than in those without BAC (72.2 % vs 17.2 %, P < 0.001). The multivariable model revealed that BAC and age were independently associated with sarcopenia (odds ratio[OR]: 7.719, 95 % confidence interval[CI]: 3.201-18.614, and P < 0.001 for BAC and OR: 1.039, 95 % CI: 1.007-1.073, P = 0.01 for age).

CONCLUSION

BAC is independently associated with sarcopenia. BAC might be used as an indicator of sarcopenia on screening mammography.

Physical independence and related factors among older adults: a systematic review and meta-analysis

Background

Adopting a physically active lifestyle is advocated as a strategy to prevent loss of physical independence and support healthy aging. This study aimed to evaluate the physical independence and related factors among older adults.

Materials and methods

This systematic review and meta-analysis was conducted through electronic databases such as Scopus, PubMed, Web of Science, Iranmedex, and Scientific Information Database from the earliest to 1 April 2022. Two researchers independently extracted information from the studies and evaluated the quality of the studies. The analysis was conducted using CMA program version 3, and each study's importance was determined based on its inverse variance.

Results

Five thousand seven hundred thirty-three older adults participated in this review in six studies. All evaluated studies had high quality. The mean score of physical independence in older adults was 20.07 (SE=0.76) out of 24 (95% CI: 18.58-21.56; I2 =98.573%; P<0.001). Physical activity is very important for physical independence and reduces the risk of physical dependence in older adults. Other factors, such as sex, BMI, age, abnormal performance, timed performance, sufficiently active, muscle function, handgrip strength, lower extremity function, lower body strength, maximal isometric knee extension power, lung function, aerobic endurance, sedentary time, agility, and the prevalence of arthritis, had a significant relationship with physical independence in older adults.

Conclusion

Older adults demonstrate favourable levels of physical independence. Notably, physical activity emerges as a significant determinant positively associated with such independence. Thus, policymakers and administrators are encouraged to strategize the creation of conducive environments for walking and exercise among older adults.

The effect of protein or amino acid provision on immobilization-induced muscle atrophy in healthy adults: A systematic review and meta-analysis

Bed rest and limb immobilization are models of muscle disuse associated with skeletal muscle atrophy and reduced strength. The purpose of this systematic review was to examine the impact of protein or amino acid provision before and/or during a period of muscle disuse on muscle atrophy (primary outcome), strength and muscle protein synthesis (secondary outcomes) following a disuse period. We performed a systematic review of Embase, MEDLINE, Web of Science, PubMed and Clinical Trials in December 2022. Eligible studies were randomized controlled trials that combined a dietary protein or amino acid intervention versus control during an experimental model of disuse (bed rest or unilateral limb immobilization) in healthy individuals aged ≥18 years. Nine articles from eight independent trials were identified and rated for risk of bias by two authors. A meta-analysis of muscle mass data revealed no effect (standardized mean difference: 0.2; 95% confidence interval: -0.18 to 0.57, P = 0.31) of protein/amino acid intervention in preventing disuse-induced muscle atrophy. Although the meta-analysis was not conducted on strength or muscle protein synthesis data, there was insufficient evidence in the reviewed articles to support the use of protein/amino acid provision in mitigating the disuse-induced decline in either outcome measurement. Additional high-quality studies, including the reporting of randomization procedures and blinding procedures and the provision of statistical analysis plans, might be required to determine whether protein or amino acid provision serves as an effective strategy to attenuate muscle atrophy during periods of disuse.

Exploring the Association between Elevated Anxiety Symptoms and Low Skeletal Muscle Mass among Asymptomatic Adults: A Population-Based Study in Republic of Korea

Individuals with mental health problems are at higher risk of musculoskeletal diseases. However, the association between low muscle mass (LMM) and anxiety symptoms remains uninvestigated. This cross-sectional study enrolled 174,262 adults (73,833 women, 100,429 men), aged 18 to 89, who completed the anxiety scale and body composition analyses. Using bio-electrical impedance analysis, skeletal muscle mass index (SMI) was calculated based on appendicular skeletal muscle mass (ASM) (kg)/height (m2). LMM was defined as SMI < 7.0 kg/m2 in men and <5.4 kg/m2 in women. Anxiety symptoms were screened using the Clinical Useful Anxiety Outcome Scale (CUXOS) with cut-off scores of 20, 30, and 40. Multivariable logistic regression analyses were performed. LMM prevalence was 20.17% in women, 3.86% in men (p < 0.001). The prevalence of anxiety symptoms in LMM group decreased from mild (CUXOS > 20: women, 32.74%, men, 21.17%) to moderate (CUXOS > 30: 13.34%, 7.32%), to severe anxiety symptoms (CUXOS > 40: 4.00%, 1.73%). In multivariable-adjusted models, LMM was associated with mild (aOR (95% confidence interval)), women, 1.13 (1.08-1.17); men, 1.17 (1.08-1.27)), moderate (1.17 (1.11-1.24); 1.35 (1.19-1.53) and severe anxiety symptoms (1.18 (1.07-1.3), 1.36 (1.06-1.74)), demonstrating an increased risk of ORs with escalating anxiety severity. LMM was independently associated with a higher prevalence of anxiety symptoms.

Comorbidity of patients with noncommunicable diseases in general practice. Eurasian guidelines

Создание руководства поддержано Советом по терапевтическим наукам отделения клинической медицины Российской академии наук.

Prevalence and impact of sarcopenia in individuals with heart failure with reduced ejection fraction (the SARC-HF study): A prospective observational study protocol

Sarcopenia, a clinical syndrome primarily associated with reduced muscle mass in the elderly, has a negative impact on quality of life and survival. It can occur secondarily to other diseases such as heart failure (HF), a complex clinical syndrome with high morbidity and mortality. The simultaneous occurrence of these two conditions can worsen the prognosis of their carriers, especially in the most severe cases of HF, as in patients with reduced left ventricular ejection fraction (LVEF). However, due to the heterogeneous diagnostic criteria for sarcopenia, estimates of its prevalence present a wide variation, leading to new criteria having been recently proposed for its diagnosis, emphasizing muscle strength and function rather than skeletal muscle mass. The primary objective of this study is to evaluate the prevalence of sarcopenia and/or dynapenia in individuals with HF with reduced LVEF according to the most recent criteria, and compare the gene and protein expression of those patients with and without sarcopenia. The secondary objectives are to evaluate the association of sarcopenia and/or dynapenia with the risk of clinical events and death, quality of life, cardiorespiratory capacity, ventilatory efficiency, and respiratory muscle strength. The participants will answer questionnaires to evaluate sarcopenia and quality of life, and will undergo the following tests: handgrip strength, gait speed, dual-energy X-ray absorptiometry, respiratory muscle strength, cardiopulmonary exercise, as well as genomic and proteomic analysis, and dosage of N-terminal pro-B-type natriuretic peptide and growth differentiation factor-15. An association between sarcopenia and/or dynapenia with unfavorable clinical evolution is expected to be found, in addition to reduced quality of life, cardiorespiratory capacity, ventilatory efficiency, and respiratory muscle strength.

Associations of resistance training levels with low muscle mass: a nationwide cross-sectional study in Korea

BACKGROUND

Low muscle mass is associated with adverse health outcomes such as functional decline and all-cause mortality. This study investigated the relationship between the risk of low muscle mass and the training period and/or frequency of resistance training (RT).

METHODS

We included 126,339 participants (81,263 women) from nationwide cohorts in Korea. Low muscle mass was defined based on the fat-free mass index. To investigate the presence of an inverse dose-response relationship between RT levels and the risk of low muscle mass, the training period (months) and frequency (per week) of RT were used. Multiple logistic regression models were used to assess the risk of low muscle mass according to the RT levels.

RESULTS

Prevalence rates for low muscle mass in our study population were 21.27% and 6.92% in men and women, respectively. When compared with not performing RT, performing RT for 3-4 days/week and ≥5 days/week decreased the risk of low muscle mass by 22% and 27%, respectively, and performing RT for 12-23 months and ≥24 months decreased the risk by 19% and 41%, respectively. When simultaneously considering both training period and frequency, performing RT for either 3-4 days/week or ≥5 days/week was significantly related to risk reduction, provided that the training period was at least 1 year. Importantly, performing RT for more than 2 years resulted in an additional risk reduction. However, there was no additional effect of performing RT for ≥5 days/week compared to 3-4 days/week, regardless of whether the RT duration was 1-2 years or more than 2 years.

CONCLUSIONS

Since performing RT for 5 days/week or more did not yield any additional effects on the risk of low muscle mass, performing RT for 3-4 days/week was sufficient to prevent low muscle mass. The effectiveness of this preventive measure can be further enhanced by engaging in long-term RT, specifically for more than 2 years.

Musculoskeletal health and life-space mobility in older adults: Findings from the Hertfordshire Cohort Study

This study explores the relationship between musculoskeletal conditions of ageing and life-space mobility (LSM) in 1110 community-dwelling older adults from the Hertfordshire Cohort Study. LSM is a novel measure which captures ability to mobilise within the home, locally and more widely. Among men, older age, care receipt, not driving a car, lower wellbeing, and reduced physical function were associated with lower LSM, while in women only driving status and physical function were associated with LSM. Osteoporosis, arthritis, and fractures had no significant associations with LSM in either gender. These findings provide support for sex-specificity in the determinants of LSM and inform novel approaches to improving mobility and health in older age.

Diabetes Mellitus Should Be Considered While Analysing Sarcopenia-Related Biomarkers

Sarcopenia is a chronic, progressive skeletal muscle disease characterised by low muscle strength and quantity or quality, leading to low physical performance. Patients with type 2 diabetes mellitus (T2DM) are more at risk of sarcopenia than euglycemic individuals. Because of several shared pathways between the two diseases, sarcopenia is also a risk factor for developing T2DM in older patients. Various biomarkers are under investigation as potentially valuable for sarcopenia diagnosis and treatment monitoring. Biomarkers related to sarcopenia can be divided into markers evaluating musculoskeletal status (biomarkers specific to muscle mass, markers of the neuromuscular junction, or myokines) and markers assuming causal factors (adipokines, hormones, and inflammatory markers). This paper reviews the current knowledge about how diabetes and T2DM complications affect potential sarcopenia biomarker concentrations. This review includes markers recently proposed by the expert group of the European Society for the Clinical and Economic Aspects of Osteoporosis, Osteoarthritis and Musculoskeletal Diseases (ESCEO) as those that may currently be useful in phase II and III clinical trials of sarcopenia: myostatin (MSTN); follistatin (FST); irisin; brain-derived neurotrophic factor (BDNF); procollagen type III N-terminal peptide (PIIINP; P3NP); sarcopenia index (serum creatinine to serum cystatin C ratio); adiponectin; leptin; insulin-like growth factor-1 (IGF-1); dehydroepiandrosterone sulphate (DHEAS); C-reactive protein (CRP); interleukin-6 (IL-6), and tumor necrosis factor α (TNF-α). A better understanding of factors influencing these biomarkers' levels, including diabetes and diabetic complications, may lead to designing future studies and implementing results in clinical practice.

A Mixture of Morus alba and Angelica keiskei Leaf Extracts Improves Muscle Atrophy by Activating the PI3K/Akt/mTOR Signaling Pathway and Inhibiting FoxO3a In Vitro and In Vivo

Muscle atrophy, which is defined as a decrease in muscle mass and strength, is caused by an imbalance between the anabolism and catabolism of muscle proteins. Thus, modulating the homeostasis between muscle protein synthesis and degradation represents an efficient treatment approach for this condition. In the present study, the protective effects against muscle atrophy of ethanol extracts of Morus alba L. (MA) and Angelica keiskei Koidz. (AK) leaves and their mixtures (MIX) were evaluated in vitro and in vivo. Our results showed that MIX increased 5-aminoimidazole-4-carboxamide ribonucleotide-induced C2C12 myotube thinning, and enhanced soleus and gastrocnemius muscle thickness compared to each extract alone in dexamethasone-induced muscle atrophy Sprague Dawley rats. In addition, although MA and AK substantially improved grip strength and histological changes for dexamethasone-induced muscle atrophy in vivo, the efficacy was superior in the MIX-treated group. Moreover, MIX further increased the expression levels of myogenic factors (MyoD and myogenin) and decreased the expression levels of E3 ubiquitin ligases (atrogin-1 and muscle-specific RING finger protein-1) in vitro and in vivo compared to the MA- and AK-alone treatment groups. Furthermore, MIX increased the levels of phosphorylated phosphoinositide 3-kinase (PI3K), protein kinase B (Akt), and mammalian target of rapamycin (mTOR) that were reduced by dexamethasone, and downregulated the expression of forkhead box O3 (FoxO3a) induced by dexamethasone. These results suggest that MIX has a protective effect against muscle atrophy by enhancing muscle protein anabolism through the activation of the PI3K/Akt/mTOR signaling pathway and attenuating catabolism through the inhibition of FoxO3a.

The reliability and suitability of strength assessments in frail and pre-frail older adults: recommendations for strength testing in older populations

BACKGROUND

Lifelong strength is fundamental to physical function, health, and quality of life. Reliable appropriate strength assessment measures for older adults play an important role in effective evaluation of baseline ability and exercise prescription to counter disease and disuse. This study aimed to investigate the within-session reliability of maximal isometric knee extension and flexion, hip abduction and adduction, and handgrip strength measures in frail and pre-frail older adults.

METHOD

The study was conducted at a residential care home in Birmingham, UK. All care home residents aged ≥ 65 years; pre-frail or frail according to the Fried Frailty phenotype criteria; able to speak and read English; not currently involved in any other clinical trial; without severe sensory impairments; and with a predicted life expectancy greater than the trial length were eligible. Maximal isometric lower limb testing was performed using specialised resistance training equipment and a portable measurement device, and grip strength was assessed using a portable dynamometer. All eligible participants attended a single testing session and performed three trials per measure. Peak force measures were obtained for analysis. Within-session reliability for each measure was calculated from repeated-measures analysis of variance, intraclass correlation coefficients (ICC), and coefficients of variation (CV) with 95% confidence intervals.

RESULTS

Eleven frail and eleven pre-frail older adults participated in the study. Within-session absolute and relative measures were found to be reliable with the highest overall repeatability indicated between trial 2 and trial 3 for knee extension, hip abduction, and handgrip (CV ≤ 4.65%, ICC ≥ 0.96) with variation evident across all measures, except knee extension, from trial 1 to 2.

CONCLUSIONS

Overall, maximal isometric strength in frail and pre-frail older adults with no previous testing experience can be measured with good to high reliability within their first testing session. An initial two familiarisation trials followed by two measurement trials is recommended to achieve the highest level of overall repeatability.

TRIAL REGISTRATION

The trial was registered with ClinicalTrials.gov: NCT03141879 on 05/05/2017.

Healthy Aging and its Determinants Among Community-dwelling Older Persons in East Coast, Malaysia: A Multidimensional Assessment

Objectives

Exploring the possibility of healthy aging among older persons is crucial for achieving optimal health in the growing older population. This study aimed to determine the prevalence, pattern, and determinants of healthy aging among older persons in Terengganu, Malaysia.

Methods

We conducted a community-based cross-sectional study involving older persons aged % 60 years. An interviewer-guided questionnaire, anthropometric measurements, and physical assessments were administered to operationalize healthy aging based on a multidimensional concept.

Results

Among the 765 older persons surveyed, only 14.1% (95% CI: 11.64?"16.59) were classified as healthy agers. Multiple logistic regression analysis revealed that superior intrinsic religiosity (odds ratio (OR) = 3.42; 95% CI: 1.34?"8.73), higher social interaction (OR = 2.82; 95% CI: 1.32?"6.04), larger calf circumference (OR = 2.05; 95% CI: 1.24?"3.38), taking water intake % 5 cups per day (OR = 2.01; 95% CI: 1.23?"3.30), better gait speed (OR = 1.71; 95% CI: 1.04?"2.80), having savings (OR = 1.71; 95% CI: 1.10?"2.66), and normal waist circumference (OR = 1.63; 95% CI: 1.04?"2.55) were found positively associated with healthy aging.

Conclusions

Only one in 10 older persons in the state met all the criteria for healthy aging. Specific aspects of religious status, social interaction, socioeconomic, behavioral, physical, and nutritional factors were found to predict healthy ageing in this population. These important determinants should be considered in developing a well-defined and comprehensive public health policy to promote healthy aging in the nation.

Skeletal muscle and heart failure - What is the relationship between central versus peripheral affections?

BACKGROUND AND AIM

Heart failure is considered as a systemic disease as beside the heart, skeletal muscle is affected.

METHODS AND RESULTS

In this retrospective case-control study 64 men and 15 women with heart failure as well as an individually pairwise matched sample by sex, age and body mass index of healthy individuals from the COmPLETE cohort study performed an exhaustive cardiopulmonary exercise test, strength tests and anthropometric measurements. V̇O2peak was 28.6% lower in male and 24.6% lower in female patients with heart failure as compared to healthy controls. Strength parameters are significantly higher for counter movement jump in male subjects. In females, significant differences were detected for mid-thigh pull in healthy versus patients with heart failure. Skeletal muscle mass of patients was in male as well as female 3.7% lower than in controls. Furthermore, the function of skeletal muscle seems impaired as the ability to accelerate is significantly lower in affected male with a heart pathology.

CONCLUSION

It seems that severe affections (approx. 25 to 30%) on cardiocirculatory level are associated with moderate to low affections on functional and structural capacity on skeletal muscle level. Further, as in the male cohort with a heart pathology acceleration meaning 'fast' contracting is impaired, it is suggested, that the central limitations respectively the low perfusion of skeletal muscle over years yield to adaptions on muscle cell level ingoing with a decreased ability of fast contracting. It is therefore suggested, that the central circulatory limitations in patients with heart failure, respectively the low perfusion of skeletal muscle over years, promote maladaptation's in the periphery.

A Bidirectional Mendelian Randomization Study of Sarcopenia-Related Traits and Knee Osteoarthritis

Background

With the development of population aging worldwide, sarcopenia and knee osteoarthritis (KOA), two age-related diseases, will continue to impose increasing medical and economic burdens on the society. Previous studies have discovered an association between the two, but the causality remains controversial, and it is difficult to eliminate confounding factors. Therefore, a Mendelian randomization (MR) study was conducted to overcome these confounding factors and investigate the causal relationship between sarcopenia and KOA.

Objective

The present work focused on assessing the causality between KOA and sarcopenia, so as to provide new strategies to prevent and treat these two conditions in clinic.

Methods

We registered the title with PROSPERO (ID: CRD42023421096). The two-sample bidirectional MR analysis was conducted in two steps, with sarcopenia being the exposure whereas KOA being the outcome in the first step, and vice versa in the second step. Genome-wide association studies (GWAS) data on low hand-grip strength (n=256,523), walking pace (n=459,915), appendicular lean mass (ALM, n=450,243), and KOA (n=403,124) were obtained from the UK Biobank. Methods such as the inverse variance weighted (IVW) and weighted median were utilized for assessing the causality of KOA with sarcopenia, and sensitivity analyses were also conducted.

Results

In the main MR analysis using the IVW method, evidence suggested that low hand-grip strength, walking pace, and ALM had adverse effects on KOA (p-value 0.0001, odds ratio (OR) 1.4569, 95% confidence interval (CI) 1.2007-1.7677 for low hand-grip strength; p-value 0.0003, OR 1.1500, 95% CI 1.050-1.183 for ALM; p-value 5.29E-19, OR 0.0932, 95% CI 0.0553-0.1572 for walking pace). However, there was no causality of KOA with sarcopenia in the opposite direction.

Conclusion

Our study suggests an obvious unidirectional causality of KOA with sarcopenia, and supports the notion that patients with sarcopenia are more susceptible to the development of KOA.

Non-pharmacological interventions for community-dwelling older adults with possible sarcopenia or sarcopenia: a scoping review

BACKGROUND

Sarcopenia is a progressive, age-related muscle disease that, if left untreated, imposes significant personal, social, and economic burdens.

OBJECTIVE

To compile and document the nature and extent of existing studies exploring non-pharmacological interventions as a strategy to prevent or treat possible sarcopenia or sarcopenia in community-dwelling older adults.

METHOD

Thirteen databases were searched up from January 2010 to March 2023 and filters were limited to English and Chinese language. Studies with older adults (≥60 y) in the community were included. The review was conducted and reported according to the PRISMA-ScR guidance and seven stages of methodology framework. A descriptive synthesis of trial characteristics and effectiveness was conducted.

RESULTS

A total of 59 studies were included in the analysis. Most studies were RCTs. Few studies enrolled older adults with possible sarcopenia. The 70-79 age group has been studied more than any other age group. Six intervention types were identified, including exercise-only, nutrition-only, health education-only, traditional Chinese medicine-only, multicomponent intervention and control type. Majority of exercise-only interventions received resistance-based exercise. In nutrition-only category, overall food intervention or nutrients intervention was more than dietary pattern. Moreover, exercise plus nutrition was the main sub-type in multicomponent interventions. Health education-only and traditional Chinese medicine-only interventions were less frequently identified. Most studies had high and moderate compliance.

CONCLUSION

There is evidence for the effectiveness of exercise and exercise plus nutrition interventions in improving muscle strength and physical performance, whereas the effectiveness of other intervention types or their combinations requires additional research.

SCOPING REVIEW REGISTRATION

Open Science Framework (OSF) Registration DOI 10.17605/OSF.IO/RK3TE.

Neuromuscular junction transmission failure in aging and sarcopenia: The nexus of the neurological and muscular systems

Sarcopenia, or age-related decline in muscle form and function, exerts high personal, societal, and economic burdens when untreated. Integrity and function of the neuromuscular junction (NMJ), as the nexus between the nervous and muscular systems, is critical for input and dependable neural control of muscle force generation. As such, the NMJ has long been a site of keen interest in the context of skeletal muscle function deficits during aging and in the context of sarcopenia. Historically, changes of NMJ morphology during aging have been investigated extensively but primarily in aged rodent models. Aged rodents have consistently shown features of NMJ endplate fragmentation and denervation. Yet, the presence of NMJ changes in older humans remains controversial, and conflicting findings have been reported. This review article describes the physiological processes involved in NMJ transmission, discusses the evidence that supports NMJ transmission failure as a possible contributor to sarcopenia, and speculates on the potential of targeting these defects for therapeutic development. The technical approaches that are available for assessment of NMJ transmission, whether each approach has been applied in the context of aging and sarcopenia, and the associated findings are summarized. Like morphological studies, age-related NMJ transmission deficits have primarily been studied in rodents. In preclinical studies, isolated synaptic electrophysiology recordings of endplate currents or potentials have been mostly used, and paradoxically, have shown enhancement, rather than failure, with aging. Yet, in vivo assessment of single muscle fiber action potential generation using single fiber electromyography and nerve-stimulated muscle force measurements show evidence of NMJ failure in aged mice and rats. Together these findings suggest that endplate response enhancement may be a compensatory response to post-synaptic mechanisms of NMJ transmission failure in aged rodents. Possible, but underexplored, mechanisms of this failure are discussed including the simplification of post-synaptic folding and altered voltage-gated sodium channel clustering or function. In humans, there is limited clinical data that has selectively investigated single synaptic function in the context of aging. If sarcopenic older adults turn out to exhibit notable impairments in NMJ transmission (this has yet to be examined but based on available evidence appears to be plausible) then these NMJ transmission defects present a well-defined biological mechanism and offer a well-defined pathway for clinical implementation. Investigation of small molecules that are currently available clinically or being testing clinically in other disorders may provide a rapid route for development of interventions for older adults impacted by sarcopenia.

Prevalence and determinants of sarcopenia in community-dwelling older adults in Ireland

BACKGROUND

Data on the prevalence of sarcopenia among older adults in Ireland are lacking.

AIMS

To assess the prevalence and determinants of sarcopenia among community-dwelling older adults in Ireland.

METHODS

This cross-sectional analysis involved n = 308 community-dwelling adults aged ≥ 65 y living in Ireland. Participants were recruited via recreational clubs and primary healthcare services. Sarcopenia was defined according to the 2019 European Working Group on Sarcopenia in Older People (EWGSOP2) criteria. Skeletal muscle mass was estimated using bioelectrical impedance analysis, strength was measured via handgrip dynamometry, and physical performance was assessed using the Short Physical Performance Battery. Detailed information was collected on demographics, health, and lifestyle. Dietary macronutrient intake was measured via a single 24 h recall. Binary logistic regression was used to examine potential demographic, health, lifestyle, and dietary determinants of sarcopenia (where both probable and confirmed sarcopenia were combined).

RESULTS

The prevalence of EWGSOP2-defined probable sarcopenia was 20.8% and confirmed sarcopenia was 8.1% (5.8% had severe sarcopenia). Polypharmacy (OR 2.60, 95% confidence interval [CI] 1.3, 5.23), height (OR 0.95, 95% CI 0.91, 0.98), and Instrumental Activities Of Daily Living (IADL) score (OR 0.71, 95% CI 0.59, 0.86) were independently associated with sarcopenia (probable and confirmed combined). There were no independent associations between energy-adjusted macronutrient intakes, as determined by 24 h recall, and sarcopenia.

CONCLUSION

Sarcopenia prevalence within this sample of community-dwelling older adults in Ireland is broadly similar to other European cohorts. Polypharmacy, lower height, and lower IADL score were independently associated with EWGSOP2-defined sarcopenia.

Effectiveness of Home-Based Exercise and Nutrition Programs for Senior Adults on Muscle Outcomes: A Scoping Review

This scoping review investigates the volume of evidence for home-based exercise and nutrition programs and their effect on muscle quality among senior adults to inform implementation and future research. It aims to answer the research question: What are the evidence, challenges, and needs for research regarding a home-based exercise and nutrition intervention program to improve muscle outcomes in senior adults? This scoping review was conducted following the PRISMA extension for Scoping Review. The following databases were searched: PubMed, Scopus, MEDLINE, CINAHL, EMBASE, and the Cochrane Library. Applied filters were used to help condense the research articles. A total of 13 studies met the inclusion criteria for this scoping review. Most exercise interventions were either resistance or multi-component exercise programs. The nature of the nutrition intervention varied between different supplements, foods, education, or counseling. Muscle outcomes included muscle mass in nine studies, muscle function in all the studies, muscle strength in ten studies, and biochemical analyses in two studies. Two studies found improvements in muscle mass; two studies revealed improvements in all their muscle function tests; and three studies revealed improvements in muscle strength. Muscle biopsy in a study revealed enhanced muscle fibers, but both studies did not reveal any biomarker improvements. The scoping review findings revealed mixed results on the effectiveness of a home-based exercise and nutrition program. However, the current evidence does have many gaps to address before recommending this form of intervention for senior adults as an effective way to prevent and manage sarcopenia. Since this review identified multiple knowledge gaps, strengths, and limitations in this growing field, it can be a starting point to help build future study designs and interventions in this population.

High-velocity power training has similar effects to traditional resistance training for functional performance in older adults: a systematic review

QUESTIONS

What is the effect of high-velocity power training (HVPT) compared with traditional resistance training (TRT) on functional performance in older adults? What is the quality of intervention reporting for the relevant literature?

DESIGN

Systematic review and meta-analysis of randomised controlled trials.

PARTICIPANTS

Older adults (aged > 60 years), regardless of health status, baseline functional capacity or residential status.

INTERVENTIONS

High-velocity power training with the intent to perform the concentric phase as quickly as possible compared with traditional moderate-velocity resistance training performed with a concentric phase of ≥ 2 seconds.

OUTCOME MEASURES

Short Physical Performance Battery (SPPB), Timed Up and Go test (TUG), five times sit-to-stand test (5-STS), 30-second sit-to-stand test (30-STS), gait speed tests, static or dynamic balance tests, stair climb tests and walking tests for distance. The quality of intervention reporting was assessed with the Consensus on Exercise Reporting Template (CERT) score.

RESULTS

Nineteen trials with 1,055 participants were included in the meta-analysis. Compared with TRT, HVPT had a weak-to-moderate effect on change from baseline scores for the SPPB (SMD 0.27, 95% CI 0.02 to 0.53; low-quality evidence) and TUG (SMD 0.35, 95% CI 0.06 to 0.63; low-quality evidence). The effect of HVPT relative to TRT for other outcomes remained very uncertain. The average CERT score across all trials was 53%, with two trials rated high quality and four rated moderate quality.

CONCLUSION

HVPT had similar effects to TRT for functional performance in older adults, but there is considerable uncertainty in most estimates. HVPT had better effects on the SPPB and TUG, but it is unclear whether the benefit is large enough to be clinically worthwhile.

The association of dietary inflammatory potential with skeletal muscle strength, mass, and sarcopenia: a meta-analysis

Aims

Evidence suggested that dietary inflammatory potential may be associated with age-related skeletal muscle decline, but the results remained controversial. To summarize the evidence for the relationships between dietary inflammatory potential and skeletal muscle strength, mass, and sarcopenia in adults we conducted this meta-analysis.

Methods

Embase, Pubmed, and Web of Science were searched from inception up to 12 March 2023 for studies that evaluated the associations of dietary inflammatory potential [estimated by the Dietary inflammatory index (DII)] with skeletal muscle strength, mass, and sarcopenia. A meta-analysis was then performed to calculate the pooled regression coefficient (β) and odds ratio (OR). The non-linear dose-response relation between DII and sarcopenia was assessed using random-effects dose-response meta-analysis.

Results

This meta-analysis included 24 studies involving 56,536 participants. It was found that high DII was associated with low skeletal muscle strength [OR 1.435, 95% confidence interval (CI) 1.247-1.651, P < 0.001, I² = 4.97%]. There was a negative association of DII with skeletal muscle strength (β-0.031, 95% CI -0.056 to -0.006, P = 0.017, I² = 72.69%). High DII was also associated with low skeletal muscle mass (OR 1.106, 95% CI 1.058-1.157, P < 0.001, I² = 0%). DII had a negative relationship with skeletal muscle mass with high heterogeneity (β-0.099, 95% CI -0.145 to -0.053, P < 0.001, I² = 88.67%); we downgraded the inconsistency in the subgroup analysis of overweight/obese participants (β-0.042, 95% CI -0.065 to -0.019, I² = 12.54%). Finally, the pooled results suggested that high DII was significantly associated with sarcopenia with significant heterogeneity (OR 1.530, 95% CI 1.245-1.880, P < 0.001, I² = 69.46%); age and BMI may contribute partially to the heterogeneity since heterogeneity was decreased in the subgroup of older age (OR 1.939, 95% CI 1.232-3.051, I² = 0%) and the group of overweight/obesity (OR 1.853, 95% CI 1.398-2.456, I² = 0%). There was a non-linear dose-response association between DII and sarcopenia (P = 0.012 for non-linearity).

Conclusion

This meta-analysis suggested that higher dietary inflammatory potential was significantly associated with lower skeletal muscle strength, mass, and risk of sarcopenia. Future studies with consistent assessment and standardized methodology are needed for further analysis.

Development and validation of knowledge assessment scales on sarcopenia and fall for Chinese community-dwelling older adults

AIM

This study aimed to develop and validate sarcopenia and fall knowledge assessment scales for community-dwelling older adults.

METHODS

A five-phase, systematic and standardized process was used. Phase 1: item pools were constructed based on the Symptom Interpretation Model. Phase 2: the Delphi expert consultation was carried out for items selection and revision. Phase 3: a pilot survey was carried out to further select and revise the items. Phase 4: older adults were surveyed to finalize the items. Phase 5: older adults were surveyed to test the psychometric properties of the two developed scales, including construct validity, reliability and acceptability.

RESULTS

Both scales comprise three dimensions (symptom, risk factor and management strategy), with 10 items for the sarcopenia knowledge assessment scale and 14 items for the fall knowledge assessment scale. They had acceptable construct validity, with all indicators meeting their specific criteria. Their reliability was acceptable, with the Cronbach's α coefficients being 0.82 for both scales, the value of spilt-half reliability being 0.86 for the sarcopenia knowledge assessment scale and 0.85 for the fall knowledge assessment scale. Their acceptability was good, with both scales having a completion rate of 94.35% and an average completion time of 5 min.

DISCUSSION

Two Chinese knowledge assessment scales with acceptable validity, reliability and acceptability have been developed, which will facilitate the assessment of the knowledge on sarcopenia and fall among community-dwelling older adults, especially for large-scale surveys. Geriatr Gerontol Int 2023; ••: ••-••.

The contribution of motor efficiency to drawing performance of older people with and without signs of cognitive decline

In clinical practice, different drawing tests are used for the assessment of cognitive efficiency in the geriatric population. However, so far, the contribution of motor skills to drawing performance has not been sufficiently examined in the late adult life span. This study was aimed at disentangling the role played by motor functioning in three well-known drawing tests that in the clinical field are commonly used to detect some signs of cognitive impairment of older individuals. One hundred and forty-nine community dwellers (M_age = 77.4 years, SD = 5.9 years) completed a battery of tests assessing global cognitive efficiency, drawing skills (i.e., Clock Drawing, Visuo-spatial Drawing ACE-R, Copy Figures Tests), handgrip muscular strength (HGS), and functional mobility (assessed through the Timed-Up-and-Go test). Significant relationships were found among those measures. Moreover, handgrip strength and functional mobility explained 12-19% of the variance in each drawing condition. Finally, participants exhibiting poorer HGS performed worse the drawing tasks and were successively recognized as cognitively deteriorated. In conclusion, these findings highlight that motor skills can significantly impact the assessment of cognitive efficiency in late adulthood. Therefore, in clinical practice, the concurrent assessment of basic motor functions (in terms of muscular strength and functional mobility) and cognitive efficiency of the geriatric population at risk for cognitive decline should be encouraged.

Endogenous testosterone concentrations and muscle mass, strength and performance in women, a systematic review of observational studies

OBJECTIVE

To explore the associations between endogenous testosterone blood concentrations and muscle mass, strength and performance in community dwelling women. DESIGN, PATIENTS AND MEASUREMENTS: Online databases, including Ovid MEDLINE, EMBASE and Web of Science, were searched for observational studies, with at least 100 female participants, reporting associations between endogenous testosterone blood concentrations and muscle mass, strength and performance. The findings were synthesized in a narrative review. Heterogeneity in study design and analysis precluded a meta-analysis.

RESULTS

Of the 36 articles retrieved for full-text review, 10 met the inclusion criteria. Eight studies were cross-sectional, 1 longitudinal and 1 provided both cross-sectional and longitudinal data. Testosterone was measured by liquid chromatography-tandem mass spectrometry in two studies and by immunoassay in 8. An association between total testosterone and muscle mass, strength or performance in women was not found. The studies of calculated free or bioavailable testosterone and lean muscle mass reported a positive association, but no association was reported for muscle strength or performance. Each included study was limited by a high risk of bias in at least one assessed domain.

CONCLUSIONS

This review does not support an association between testosterone and muscle mass, strength or performance in women. This, together with the reported associations between free or bioavailable testosterone and muscle mass should be interpreted cautiously due to the predominant use of immunoassay and the inaccuracy of calculated variables. Additionally, biological significance of nonprotein bound testosterone has not been established. Further studies examining the relationship between precisely measured testosterone and muscle mass and function in women are required.

Increasing Muscle Mass in Elders through Diet and Exercise: A Literature Review of Recent RCTs

This study aimed to review the current evidence on the independent and combined effects of diet and exercise and their impact on skeletal muscle mass in the elderly population. Skeletal muscle makes up approximately 40% of total body weight and is essential for performing daily activities. The combination of exercise and diet is known to be a potent anabolic stimulus through stimulation of muscle protein synthesis from amino acids. Aging is strongly associated with a generalized deterioration of physiological function, including a progressive reduction in skeletal muscle mass and strength, which in turn leads to a gradual functional impairment and an increased rate of disability resulting in falls, frailty, or even death. The term sarcopenia, which is an age-related syndrome, is primarily used to describe the gradual and generalized loss of skeletal muscle mass (mainly in type II muscle fibers) and function. Multimodal training is emerging as a popular training method that combines a wide range of physical dimensions. On the other hand, nutrition and especially protein intake provide amino acids, which are essential for muscle protein synthesis. According to ESPEN, protein intake in older people should be at least 1 g/kgbw/day. Essential amino acids, such as leucine, arginine, cysteine, and glutamine, are of particular importance for the regulation of muscle protein synthesis. For instance, a leucine intake of 3 g administered alongside each main meal has been suggested to prevent muscle loss in the elderly. In addition, studies have shown that vitamin D and other micronutrients can have a protective role and may modulate muscle growth; nevertheless, further research is needed to validate these claims. Resistance-based exercise combined with a higher intake of dietary protein, amino acids, and/or vitamin D are currently recognized as the most effective interventions to promote skeletal muscle growth. However, the results are quite controversial and contradictory, which could be explained by the high heterogeneity among studies. It is therefore necessary to further assess the impact of each individual exercise and nutritional approach, particularly protein and amino acids, on human muscle turnover so that more efficient strategies can be implemented for the augmentation of muscle mass in the elderly.

Handgrip Measurement Method Affects Asymmetry but Not Weakness Identification in Community-Dwelling Older Adults

OBJECTIVES

The Asian Working Group for Sarcopenia (AWGS) 2019 recommends different measurement protocols for handgrip strength (HGS). We aimed to explore (1) whether these protocols induce a significant difference in HGS; (2) whether these differences be clinically meaningful; and (3) whether these protocols affect the identification of HGS weakness or asymmetry.

DESIGN

Cross-sectional study.

SETTING AND PARTICIPANTS

A total of 356 community-dwelling older adults (mean age 67.9 years; 146 women).

METHODS

Maximal HGS was measured according to protocols from the National Health and Nutrition Examination Survey (Method A, standing with full elbow extended) and the American Society of Hand Therapists (Method B, sitting with elbow flexed at 90°). HGS was analyzed using the maximal value of 2 or 3 repetitions of the dominant hand or 4 or 6 repetitions of both hands.

RESULTS

The difference in maximal HGS between Method A and Method B might have clinical meaning in approximately half of the participants. When measured using Method A, respective proportions of individuals with differences in HGS between the 6 repetitions group and the other repetition groups beyond the noninferiority threshold were 42%, 20%, and 25% in men and 39%, 21%, and 17% in women. Using Method B, the corresponding percentages were 25%, 18%, and 6% in men, and 27%, 20%, and 5% in women, respectively. Different protocols did not significantly affect the identification of HGS weakness, as different protocols reached diagnostic accuracies of 0.910 to 0.967 in men and 0.911 to 0.986 in women when using Method A (6 repetitions) as the reference standard. However, different protocols significantly affected the identification of HGS asymmetry, as different protocols had diagnostic accuracies of 0.667 to 0.886 in men and 0.658 to 0.863 in women.

CONCLUSIONS AND IMPLICATIONS

The different protocols recommended by the AWGS 2019 update significantly affect maximal HGS values and the identification of HGS asymmetry but not HGS weakness.

'I eat to not die': Diet and exercise experiences of older adults living alone

INTRODUCTION

Living alone is a critical health risk factor among older adults. Regular exercise and a balanced diet are important for maintaining an independent and healthy life. However, it can be more difficult for older adults living alone to maintain healthy exercise and dietary habits due to their lack of social support. This study aimed to explore the life changes that accompany living alone and their needs, focussing on exercise and diet.

METHODS

This was a qualitative descriptive study. Purposeful sampling was conducted to recruit community-dwelling older adults living alone. Thematic analyses were applied to analyse the qualitative data collected from semistructured interviews.

RESULTS

Fifteen subjects, including 5 men and 10 women, participated in the interviews. The median age was 77 years, ranging from 66 to 88, and the median duration of living alone was 16 years, ranging from 3 to 35. Six main themes were developed, namely unavoidable difficulties of living alone: lack of someone to depend on and loneliness, just eating 'to not die', exercise that is good for health but hard to do consistently, conflict between maintaining independence and dependence on others, coping with available resources, and resources needed for regular exercise and a balanced diet.

CONCLUSION

Living alone leads to poor dietary habits, such as skipping meals or insufficient food intake. Food security should be ensured through the reinforcement of social support, financial assistance and the operation of public cafeterias. In addition, an individually tailored group exercise programme that can meet the need for social interaction and improve self-efficacy would help older adults living alone maintain regular exercise habits.

Non-pharmacological interventions for possible sarcopenia or sarcopenia in community-dwelling older adults: a scoping review protocol

INTRODUCTION

Early prevention of sarcopenia is a recommendation to reduce morbidity, mortality and improve quality of life. Several non-pharmacological interventions to reduce the risk of sarcopenia in community-dwelling older people have been proposed. Therefore, there is a need to identify the scope and differences of these interventions. This scoping review will summarise the nature and extent of the existing literature that describes and examines non-pharmacological interventions for community-dwelling older adults with possible sarcopenia or sarcopenia.

METHODS AND ANALYSIS

The seven-stage review methodology framework will be used. Searches will be conducted in the following databases: Embase, Medline, PsycINFO, CINAHL, All EBM Reviews, Web of Science, Scopus, CBM, CNKI, WANFANG and VIP. Grey literature will also be identified from Google scholar. Search dates will be restricted to January 2010 to December 2022, in English and Chinese language only. Screening will be focused on published research, including both quantitative and qualitative study designs, and prospectively registered trials. Preferred Reporting Items for Systematic Reviews and Meta-Analyses extension for Scoping Reviews will be followed when delineating the search decision process. Findings will be synthesised quantitatively and qualitatively as appropriate and classified using key conceptual categories. We will identify whether studies identified have been included in systematic reviews or meta-analyses, and research gaps and opportunities will be identified and summarised.

ETHICS AND DISSEMINATION

As this is a review, ethical approval will not be sought. The results will be published in peer-reviewed scientific journals and also disseminated in relevant disease support groups and conferences. The planned scoping review will help us identify the current status of research and gaps in the literature, so as to develop a future research agenda.

Prevalence of Sarcopenia in Knee Osteoarthritis: A Systematic Review and Meta-Analysis

An association between knee osteoarthritis (OA) and sarcopenia has been proposed, but the evidence is controversial, with the recent literature showing disparate results. Therefore, we aimed to perform a systematic review and meta-analysis to evaluate the prevalence of sarcopenia in knee OA patients compared to people not affected by this condition. We searched several databases until 22 February 2022. The data regarding prevalence were summarized using odds ratios (ORs) with their 95% confidence intervals (CIs). Among the 504 papers initially screened, 4 were included for a total of 7495 participants with a mean age of 68.4 years, who were mainly females (72.4%). The prevalence of sarcopenia in people with knee OA was 45.2%, whilst, in the controls, it was 31.2%. Pooling the data of the studies included that the prevalence of sarcopenia in knee OA was more than two times higher than in the control group (OR = 2.07; 95%CI: 1.43-3.00; I2 = 85%). This outcome did not suffer any publication bias. However, after removing an outlier study, the recalculated OR was 1.88. In conclusion, the presence of sarcopenia in knee OA patients was high, affecting one person in every two persons and was higher than in the control groups included.

Considerations for designing trials targeting muscle dysfunction in exercise oncology

Individuals diagnosed with cancer commonly experience a significant decline in muscle mass and physical function collectively referred to as cancer related muscle dysfunction. This is concerning because impairments in functional capacity are associated with an increased risk for the development of disability and subsequent mortality. Notably, exercise offers a potential intervention to combat cancer related muscle dysfunction. Despite this, research is limited on the efficacy of exercise when implemented in such a population. Thus, the purpose of this mini review is to offer critical considerations for researchers seeking to design studies pertaining to cancer related muscle dysfunction. Namely, 1) defining the condition of interest, 2) determining the most appropriate outcome and methods of assessment, 3) establishing the best timepoint (along the cancer continuum) to intervene, and 4) understanding how exercise prescription can be configured to optimize outcomes.

Association of phase angle with sarcopenia in chronic musculoskeletal pain patients: a retrospective study

BACKGROUND

In chronic musculoskeletal pain patients, detection of sarcopenia is of significant clinical interest. Phase angle, which can be measured through bioelectrical impedance analysis (BIA), can detect sarcopenia; however, the evidence in chronic musculoskeletal pain patients is limited. This study aimed to assess the relationship between phase angle and sarcopenia in patients with chronic musculoskeletal pain. Our hypothesis was that phase angle would be a useful indicator to identify sarcopenia in patients with chronic musculoskeletal pain.

METHODS

A total of 190 patients (51 men and 139 women) with chronic musculoskeletal pain were included in this retrospective cross-sectional study. Patient data of backgrounds, numeric rating scale score for pain, skeletal muscle index, and phase angle assessed using BIA were retrospectively reviewed. Sarcopenia was diagnosed using the Asian Working Group for Sarcopenia criteria 2019.

RESULTS

A total of 51 patients (26.7%), including 10 men (19.6%) and 41 women (29.5%), were diagnosed with sarcopenia. Phase angle, sarcopenia-related factors, age, and body mass index (BMI) differed significantly in patients with and without sarcopenia. On multiple logistic regression analysis, the prevalence of sarcopenia was significantly correlated with phase angle and BMI. The areas under the curve exhibited high accuracy in discriminating sarcopenia in men and moderate accuracy in both sexes and in women.

CONCLUSIONS

Phase angle may be a valid discriminator of sarcopenia in patients with chronic musculoskeletal pain.

Impact of early postoperative factors on changes in skeletal muscle mass after esophagectomy in older patients with esophageal cancer

BACKGROUND

Loss of skeletal muscle mass, measured by the skeletal muscle mass index (SMI), after esophagectomy negatively impacts prognosis. However, the information to develop novel supportive care options for preventing loss of skeletal muscle mass is limited. The purpose of this retrospective cohort study was to investigate the impact of early postoperative factors on change in SMI 4 months after curative esophagectomy in older patients with esophageal cancer.

METHODS

This study included 113 subjects who underwent esophagectomy between 2015 and 2020. Preoperative and postoperative SMI (cm²/m²) were calculated from computed tomography images. The percentage change in SMI 4 months after surgery (SMI%) was calculated as follows: ([postoperative SMI - preoperative SMI] ÷ preoperative SMI) × 100. Potential factors affecting percentage change of SMI after surgery were analyzed by multiple regression.

RESULTS

The mean SMI% was - 5.6%. The percentage change (per 1%) in quadriceps muscle strength in the first month after surgery (standardized β = 0.190, p = 0.048) impacted the SMI%, which was independent of age, sex, preoperative SMI, comorbidity, pathological stage, and neoadjuvant chemotherapy.

CONCLUSION

Quadriceps muscle weakness in the first month after esophagectomy impacted the SMI% in a dose-dependent relationship.

Fiber-Type Shifting in Sarcopenia of Old Age: Proteomic Profiling of the Contractile Apparatus of Skeletal Muscles

The progressive loss of skeletal muscle mass and concomitant reduction in contractile strength plays a central role in frailty syndrome. Age-related neuronal impairments are closely associated with sarcopenia in the elderly, which is characterized by severe muscular atrophy that can considerably lessen the overall quality of life at old age. Mass-spectrometry-based proteomic surveys of senescent human skeletal muscles, as well as animal models of sarcopenia, have decisively improved our understanding of the molecular and cellular consequences of muscular atrophy and associated fiber-type shifting during aging. This review outlines the mass spectrometric identification of proteome-wide changes in atrophying skeletal muscles, with a focus on contractile proteins as potential markers of changes in fiber-type distribution patterns. The observed trend of fast-to-slow transitions in individual human skeletal muscles during the aging process is most likely linked to a preferential susceptibility of fast-twitching muscle fibers to muscular atrophy. Studies with senescent animal models, including mostly aged rodent skeletal muscles, have confirmed fiber-type shifting. The proteomic analysis of fast versus slow isoforms of key contractile proteins, such as myosin heavy chains, myosin light chains, actins, troponins and tropomyosins, suggests them as suitable bioanalytical tools of fiber-type transitions during aging.

Genes encoding agrin (AGRN) and neurotrypsin (PRSS12) are associated with muscle mass, strength and plasma C-terminal agrin fragment concentration

Although physiological data suggest that neuromuscular junction (NMJ) dysfunction is a principal mechanism underpinning sarcopenia, genetic studies have implicated few genes involved in NMJ function. Accordingly, we explored whether genes encoding agrin (AGRN) and neurotrypsin (PRSS12) were associated with sarcopenia phenotypes: muscle mass, strength and plasma C-terminal agrin fragment (CAF). PhenoScanner was used to determine if AGRN and/or PRSS12 variants had previously been implicated with sarcopenia phenotypes. For replication, we combined genotype from whole genome sequencing with phenotypic data from 6715 GenoFit participants aged 18-83 years. Dual energy X-ray absorptiometry assessed whole body lean mass (WBLM) and appendicular lean mass (ALM), hand dynamometry determined grip strength and ELISA measured plasma CAF in a subgroup (n = 260). Follow-up analyses included eQTL analyses, carrier analyses, single-variant and gene-burden tests. rs2710873 (AGRN) and rs71608359 (PRSS12) associate with muscle mass and strength phenotypes, respectively, in the UKBB (p = 8.9 × 10^-6 and p = 8.4 × 10^-6) and GenoFit cohort (p = 0.019 and p = 0.014). rs2710873 and rs71608359 are eQTLs for AGRN and PRSS12, respectively, in ≥ three tissues. Compared to non-carriers, carriers of rs2710873 had 4.0% higher WBLM and ALM (both p < 0.001), and 9.5% lower CAF concentrations (p < 0.001), while carriers of rs71608359 had 2.3% lower grip strength (p = 0.034). AGRN and PRSS12 are associated with muscle strength and mass in single-variant analyses, while PRSS12 has further associations with muscle strength in gene-burden tests. Our findings provide novel evidence of the relevance of AGRN and PRSS12 to sarcopenia phenotypes and support existing physiological data illustrating the importance of the NMJ in maintaining muscle health during ageing.

Age-Related Dysfunction in Proteostasis and Cellular Quality Control in the Development of Sarcopenia

Sarcopenia is a debilitating skeletal muscle disease that accelerates in the last decades of life and is characterized by marked deficits in muscle strength, mass, quality, and metabolic health. The multifactorial causes of sarcopenia have proven difficult to treat and involve a complex interplay between environmental factors and intrinsic age-associated changes. It is generally accepted that sarcopenia results in a progressive loss of skeletal muscle function that exceeds the loss of mass, indicating that while loss of muscle mass is important, loss of muscle quality is the primary defect with advanced age. Furthermore, preclinical models have suggested that aged skeletal muscle exhibits defects in cellular quality control such as the degradation of damaged mitochondria. Recent evidence suggests that a dysregulation of proteostasis, an important regulator of cellular quality control, is a significant contributor to the aging-associated declines in muscle quality, function, and mass. Although skeletal muscle mammalian target of rapamycin complex 1 (mTORC1) plays a critical role in cellular control, including skeletal muscle hypertrophy, paradoxically, sustained activation of mTORC1 recapitulates several characteristics of sarcopenia. Pharmaceutical inhibition of mTORC1 as well as caloric restriction significantly improves muscle quality in aged animals, however, the mechanisms controlling cellular proteostasis are not fully known. This information is important for developing effective therapeutic strategies that mitigate or prevent sarcopenia and associated disability. This review identifies recent and historical understanding of the molecular mechanisms of proteostasis driving age-associated muscle loss and suggests potential therapeutic interventions to slow or prevent sarcopenia.

Two-CyDye-Based 2D-DIGE Analysis of Aged Human Muscle Biopsy Specimens

The gradual loss of skeletal muscle mass during aging and associated decline in contractile strength can result in reduced fitness, frailty, and loss of independence. In order to better understand the molecular and cellular mechanisms that underlie sarcopenia of old age and the frailty syndrome, as well as identify novel therapeutic targets to treat age-related fiber wasting, it is crucial to develop a comprehensive biomarker signature of muscle aging. Fluorescence two-dimensional gel electrophoresis (2D-DIGE) in combination with sensitive mass spectrometry presents an ideal bioanalytical tool for biomarker discovery in biogerontology. This chapter outlines the application of the 2D-DIGE method for the comparative analysis of human biopsy specimens from middle-aged versus senescent individuals using a two-CyDye-based method.