Muscle Mass Assessed by the D3-Creatine Dilution Method and Incident Self-reported Disability and Mortality in a Prospective Observational Study of Community-Dwelling Older Men

Biomarkers of aging: from molecules and surrogates to physiology and function

Many countries face an unprecedented challenge in aging demographics. This has led to an exponential growth in research on aging, which, coupled to a massive financial influx of funding in the private and public sectors, has resulted in seminal insights into the underpinnings of this biological process. However, critical validation in humans has been hampered by the limited translatability of results obtained in model organisms, additionally confined by the need for extremely time-consuming clinical studies in the ostensible absence of robust biomarkers that would allow monitoring in shorter time frames. In the future, molecular parameters might hold great promise in this regard. In contrast, biomarkers centered on function, resilience, and frailty are available at the present time, with proven predictive value for morbidity and mortality. In this review, the current knowledge of molecular and physiological aspects of human aging, potential antiaging strategies, and the basis, evidence, and potential application of physiological biomarkers in human aging are discussed.

Novel multimodal intervention for surgical prehabilitation on functional recovery and muscle characteristics in patients with non-small cell lung cancer: study protocol for a randomised controlled trial (MMP-LUNG)

INTRODUCTION

Lung cancer is the leading cause of cancer-related deaths. Patients with stage I-III non-small cell lung cancer (NSCLC) are candidates for surgical resection; however, patients with low muscle mass, myosteatosis, malnutrition or reduced functional capacity preoperatively have a higher risk of postoperative morbidity. Prehabilitation is a care process aiming to enhance functional capacity before surgery to improve surgical outcomes. Study objectives are to test the effect of prehabilitation interventions of a mixed-nutrient supplement (NUT) alone or its combination with exercise (MM, multimodal prehabilitation), compared with placebo-control (CTL), in NSCLC patients on change in functional capacity pre-surgery and post-discharge, muscle mass and myosteatosis, postoperative health-related quality of life (HRQoL), complications and length of hospital stay. We hypothesise that a multi-nutrient supplement, with or without exercise, will be of benefit.

METHODS AND ANALYSIS

Randomised controlled trial of three parallel arms: 168 patients with operable NSCLC at nutritional risk are randomised 1:1:1 to CTL, NUT or MM. Patients in the NUT and MM groups receive a nutritional supplement consisting of whey protein, leucine, vitamin D and fish oil 4-6 weeks preoperatively and 6 weeks post-discharge. The exercise programme (MM) consists of daily moderate-intensity aerobic activity and resistance training 3 days/week. The following is assessed at baseline, preoperatively and week six post-discharge: functional capacity using the 6 min walk test, muscle mass and myosteatosis using D3-creatine dilution and peripheral quantitative CT, and HRQoL using the Functional Assessment of Cancer Therapy-Lung. Intention-to-treat analysis of covariance will compare between-group differences adjusted for baseline variables. Postoperative functional recovery will be tested by logistic regression. Between-group differences in clinical outcomes will be tested, applying Bonferroni correction.

ETHICS AND DISSEMINATION

This trial is approved by the McGill University Health Centre Research Ethics Board (2022-7782). Results will be published in open-access peer-reviewed journals and conference presentations.

TRIAL REGISTRATION DETAILS

NCT05955248.

Investigating the role of adipose tissue in mobility and aging: design and methods of the Adipose Tissue ancillary to the Study of Muscle, Mobility, and Aging (SOMMA-AT)

BACKGROUND

Age-related changes in adipose tissue affect chronic medical diseases and mobility disability but mechanism remains poorly understood. The goal of this study is to define methods for phenotyping unique characteristics of adipose tissue from older adults.

METHODS

Older adults enrolled in study of muscle, mobility, and aging selected for the adipose tissue ancillary (SOMMA-AT; N = 210, 52.38% women, 76.12 ± 4.37 years) were assessed for regional adiposity by whole-body magnetic resonance (AMRA) and underwent a needle-aspiration biopsy of abdominal subcutaneous adipose tissue (ASAT). ASAT biopsies were flash frozen, fixed, or processed for downstream applications and deposited at the biorepository. Biopsy yields, qualitative features, adipocyte sizes, and concentration of adipokines secreted in ASAT explant conditioned media were measured. Inter-measure Spearman correlations were determined.

RESULTS

Regional, but not total, adiposity differed by sex: women had greater ASAT mass (8.20 ± 2.73 kg, p < .001) and biopsy yield (3.44 ± 1.81 g, p < .001) than men (ASAT = 5.95 ± 2.30 kg, biopsy = 2.30 ± 1.40 g). ASAT mass correlated with leptin (r = 0.54, p < .001) and not resistin (p = .248) and adiponectin (p = .353). Adipocyte area correlated with ASAT mass (r = 0.34, p < .001), BMI (r = 0.33, p < .001), adiponectin (r = -0.22, p = .005) and leptin (r = 0.18, p = .024) but not with resistin (p = .490).

CONCLUSION

In addition to the detailed ASAT biopsy processing in this report, we found that adipocyte area correlated with ASAT mass, and both measures related to some key adipokines in the explant conditioned media. These results, methods, and biological repositories underscore the potential of this unique cohort to impact the understanding of aging adipose biology on disease, disability, and other aging tissues.

Bidirectional association between sarcopenia and depression: A systematic review and meta-analysis

PURPOSE

Recent research has reported a potential bidirectional association between sarcopenia and depression, yet systematic evidence supporting this relationship is still lacking. This study evaluated the bidirectional association of sarcopenia with depression to provide reliable evidence for the development of specific prevention and control strategies.

METHODS

Relevant articles were extracted from PubMed, Embase, Cochrane, and Web of Science from inception to July 4, 2024. Quality was assessed using the Newcastle-Ottawa Scale (NOS) for cohort and case-control studies, and the Joanna Briggs Institute (JBI) Critical Appraisal Checklist for cross-sectional studies. Changes in the association between sarcopenia and depression were compared across different study designs, sources of study subjects, and sarcopenia diagnostic criteria by subgroup analyses. Meta-analysis was conducted using R 4.4.1.

RESULTS

Thirty-three original studies involving 119,421 subjects were incorporated into this review. Pooled analysis revealed a significant reciprocal relationship between sarcopenia and depression in community populations. The risk of depression increased when sarcopenia was the exposure factor [OR = 2.40(95 % CI: 1.87, 3.08)]. Conversely, the risk of sarcopenia significantly increased when depression was the exposure factor [OR = 1.90(95 % CI: 1.44, 2.50)]. Additionally, there was a markedly increased risk of sarcopenia when depressive symptoms were the exposure factor [OR = 1.38(95 % CI: 1.25, 1.53)]. Similar conclusions were obtained in patients with other diseases.

CONCLUSIONS

The significant bidirectional association between sarcopenia and depression enhances the prevention, screening, diagnosis, and treatment of depression, thereby improving quality of life and outcomes.

Change in D3Cr muscle mass in oldest old men and its association with changes in grip strength and walking speed

BACKGROUND

The use of lean soft tissue (LST) mass as a surrogate measurement of skeletal muscle mass (SMM) has led to the conclusion that muscle loss is poorly related to functional decline. We hypothesized that when using a more accurate measure of SMM determined by D3-creatine dilution (D3Cr), longitudinal changes in SMM will be similar in magnitude to changes in strength and physical performance and that skeletal muscle mass will partially mediate the relationship of age with these outcomes.

METHODS

We measured change in D3Cr muscle mass (kg), handgrip strength (kg), and 6m walk speed (m/s) in 208 men from the Osteoporotic Fractures in Men Study (85.2 ± 4.3 years) over an average of 6.1 years follow-up. Mixed linear effects models adjusted for potential confounders were used to examine the relationship of changes in D3Cr muscle mass with changes in grip strength and walking speed.

RESULTS

Annual losses of D3Cr muscle mass, grip strength, and walking speed were 2.1%, 2.2%, and 2.6%, respectively (p < 0.001). Each additional kg loss in D3Cr muscle mass was associated with a 0.55 kg loss in grip strength and a 0.01 m/s loss in walking speed independent of changes in age (p < 0.001). 41.3% and 22.4% of the relationship between age and loss of grip strength and walking speed, respectively, was attributed to loss of D3Cr muscle mass (p < 0.001).

CONCLUSION

Skeletal muscle mass may have a more important role than previously considered and should not be overlooked as a potentially modifiable determinant in the loss of strength and performance in older age.

Association of body composition measures to muscle strength using DXA, D3Cr, and BIA in collegiate athletes

Muscle mass and strength are crucial for physiological function and performance in athletes, playing a significant role in maintaining health and optimal athletic performance. Skeletal muscle, which constitutes the majority of lean soft tissue (LST) and appendicular lean soft tissue (ALST) when measured by dual-energy X-ray absorptiometry (DXA), represents a commonly used surrogate for strength. Research has investigated alternative measures of body composition, such as the assessment of ALST through bioelectrical impedance analysis (BIA) and the determination of whole-body muscle mass from creatine pool size using the deuterated creatine (D3Cr) dilution method, for their associations to strength. While the relationship between body composition measures and strength has been studied in older adults, this relationship remains unexplored in athletic populations. This study examined muscle body composition measures using DXA, D3Cr, and BIA and their association with strength in a sample of collegiate athletes. The study enrolled 80 collegiate athletes (40 females) of differing sports disciplines who consumed a 60 mg dose of D3Cr and completed DXA and BIA measures in addition to trunk and leg strength tests. Analysis was sex-stratified using Pearson's correlations, linear regression, and quartile p trend significance. With an average participant age of 21.8 years, whole-body DXA correlations to muscle strength surpassed height- or mass-normalized values. This trend was especially pronounced in trunk strength's relationship with body composition over leg strength, across measurement methods. While DXA LST values were higher than BIA and D3Cr in predicting strength, the values did not differ significantly. Adjustments for age, BMI, and BIA variables didn't enhance this association. A significant trend between DXA LST and all strength measures underscored the equal relevance of DXA and D3Cr muscle mass to strength, favoring whole-body over regional assessments. This calls for future research on muscle mass's effects on LST and functional outcomes in broader groups, highlighting the importance of comprehensive body composition analysis in athletic performance studies.

Skeletal Muscle mRNA Splicing Variants Association With Four Different Fitness and Energetic Measures in the GESTALT Study

BACKGROUND

Physical activity is essential for maintaining muscle mitochondrial function and aerobic capacity. The molecular mechanisms underlying such protective effects are incompletely understood, in part because it is difficult to separate the effects of disease status and physical activity. We explored the association of human skeletal muscle transcriptomic with four measures of energetics and mitochondria oxidative capacity in healthy individuals.

METHODS

Using RNA sequencing of vastus lateralis muscle biopsies from 82 GESTALT participants (52 males, aged 22-89 years), we explored gene and splicing variant expression profiles associated with self-reported physical activity, peak oxygen consumption (VO2 peak), muscle oxidative capacity (kPCr) and mitochondrial respiration (Mit-O2 flux). The effect of aging on gene expression was examined in participants with low and high VO2 peak.

RESULTS

The four measures of energetics were negative correlated with age and generally intercorrelated. We identified protein-coding genes associated with four energetic measures adjusting for age, muscle fiber-ratio, sex and batch effect. Mitochondrial pathways were overrepresented across all energetic variables, albeit with little overlap at the gene level. Alternative spliced transcript isoforms associated with energetics were primarily enriched for cytoplasmic ribonucleoprotein granules. The splicing pathway was up-regulated with aging in low but not in high fitness participants, and transcript isoforms detected in the low fitness group pertain to processes such as cell cycle regulation, RNA/protein localization, nuclear transport and catabolism.

CONCLUSIONS

A consistent mitochondrial signature emerged across all energetic measures. Alternative splicing was enhanced in older, low fitness participants supporting the energy-splicing axis hypothesis. The identified splicing variants were enriched in pathways involving the accumulation of ribonucleoproteins in cytoplasmic granules, whose function remains unclear. Further research is needed to understand the function of these proteoforms in promoting adaptation to low energy availability.

Unravelling the transcriptomic symphony of muscle ageing: key pathways and hub genes altered by ageing and caloric restriction in rat muscle revealed by RNA sequencing

Age-related muscle wasting, sarcopenia is an extensive loss of muscle mass and strength with age and a major cause of disability and accidents in the elderly. Mechanisms purported to be involved in muscle ageing and sarcopenia are numerous but poorly understood, necessitating deeper study. Hence, we employed high-throughput RNA sequencing to survey the global changes in protein-coding gene expression occurring in skeletal muscle with age. Caloric restriction (CR) is a known prophylactic intervention against sarcopenia. Therefore, total RNA was isolated from the muscle tissue of both rats fed ad libitum and CR rats. RNA-seq data were subjected to Gene Ontology, pathway, co-expression, and interaction network analyses. This revealed the functional pathways most activated by both ageing and CR, as well as the key "hub" proteins involved in their activation.RNA-seq revealed 442 protein-coding genes to be upregulated and 377 to be downregulated in aged muscle, compared to young muscle. Upregulated genes were commonly involved in protein folding and immune responses; meanwhile, downregulated genes were often related to developmental biology. CR was found to suppress 69.7% and rescue 57.8% of the genes found to be upregulated and downregulated in aged muscle, respectively. In addition, CR uniquely upregulated 291 and downregulated 304 protein-coding genes. Hub genes implicated in both ageing and CR included Gc, Plg, Irf7, Ifit3, Usp18, Rsad2, Blm and RT1-A2, whilst those exclusively implicated in CR responses included Alb, Apoa1, Ambp, F2, Apoh, Orm1, Mx1, Oasl2 and Rtp4. Hub genes involved in ageing but unaffected by CR included Fgg, Fga, Fgb and Serpinc1. In conclusion, this comprehensive RNA sequencing study highlights gene expression patterns, hub genes and signalling pathways most affected by ageing in skeletal muscle. This data may provide the initial evidence for several targets for potential future therapeutic interventions against sarcopenia.

Exploring Opportunities to Better Characterize the Effects of Dietary Protein on Health across the Lifespan

Remarkable advances have been made over the last 30 y in understanding the role of dietary protein in optimizing muscle health across the lifespan. That is, acute (<24 h) stable isotope-derived measures of muscle protein synthesis have led to established recommendations for protein quantity, quality, source, and timing of protein ingestion to support muscle health at rest, post exercise, and to overcome age-related anabolic resistance in older adults. Although muscle health is undoubtedly important, moving from muscle to other associated or disease-specific outcomes is a critical next step for the field, given the mounting evidence documenting the effects of dietary protein on measures of chronic disease and age-related decline (for example, cardiovascular disease, type 2 diabetes mellitus, obesity, frailty, and osteoporosis). In this narrative review, we posit that future studies evaluating the potential role of dietary protein build off of the existing knowledge base generated from decades of past research and focus their efforts on closing unanswered knowledge gaps pertaining to dietary protein and health across the lifespan. Throughout this review, we highlight potential methodologies and novel outcome measures that researchers may consider as starting points to facilitate the next 30 y of advances in the field of dietary protein and health.

Reductions in functional muscle mass and ability to ambulate in Duchenne muscular dystrophy from ages 4 to 24 years

Duchenne muscular dystrophy (DMD) results in a progressive loss of functional skeletal muscle mass (MM) and replacement with fibrofatty tissue. Accurate evaluation of MM in DMD patients has not previously been available. Our objective was to measure MM using the D3creatine (D3Cr) dilution method and determine its relationship with strength and functional capacity in patients with DMD over a wide range of ages. Subjects were recruited for participation in a 12 month, longitudinal, observational study. Here, we report the baseline data. A 20 mg dose of D3Cr dissolved in water was ingested by 92 patients with DMD (ages 4-25 years) followed later with a fasting urine sample. Enrichment of D3creatinine was determined by liquid chromatography-mass spectrometry analysis. The North Star Ambulatory Assessment (NSAA) total score was determined for ambulatory participants, and the Performance of Upper Limb (PUL 2.0) total score and grip strength for all participants. We observed a significant age-associated increase in body weight along with a substantial decrease in MM/body weight (%MM). MM and %MM were associated with PUL score (r = 0.517, P < 0.0001 and r = 0.764, P < 0.0001 respectively). The age-associated decrease in MM and %MM was strongly associated with ambulatory status. We observed very little overlap in %MM between ambulant and non-ambulant subjects, suggesting a threshold of 18-22% associated with loss of ambulation. MM is substantially diminished with advancing age and is highly related to clinically meaningful functional status. The D3Cr dilution method may provide a biomarker of disease progression and therapeutic efficacy in patients with DMD or other neuromuscular disorders. KEY POINTS: The non-invasive D3creatine dilution method provides novel data on whole body functional muscle mass (MM) in a wide range of ages in patients with DMD and reveals profoundly low functional MM in older non-ambulant patients. The difference in %MM between ambulant and non-ambulant subjects suggests a threshold for loss of ambulatory ability between 18 and 22% MM. The data suggest that as functional MM declines with age, maintaining a lower body weight may help to conserve ambulatory ability.

Controversies and Conundrums in Cardiac Cachexia: Key Questions About Wasting in Patients With HFrEF

Cardiac cachexia is characterized by unintentional catabolic weight loss, decreased appetite, and inflammation and is common in patients with stage D (advanced) heart failure with reduced ejection fraction (HFrEF). Cardiac cachexia and related muscle-wasting syndromes are markers of, and a consequence of, the heart failure (HF) syndrome. Although many potential modalities for identifying cardiac cachexia exist, the optimal definition, diagnostic tools, and treatment options for cardiac cachexia remain unclear. Furthermore, it remains unclear whether attempts to reverse muscle wasting prior to advanced HF surgeries, such as left ventricular assist devices and heart transplantation, can improve outcomes. It is important that HF clinicians and dietitians are aware of the pathophysiology and mechanisms of muscle-wasting syndromes in patients with HF, to aid in the recognition and risk stratification of advanced HFrEF. Although the opportunities and rationale for attempting to address cardiac cachexia prior to advanced HF surgeries are uncertain, recent publications suggest that control of the neurohumoral syndrome of advanced HF may be important to permit the recovery of skeletal muscle mass.

Association between sarcopenic obesity and knee osteoarthritis: A narrative review

Sarcopenia and obesity have been studied independently as risk factors for knee osteoarthritis. However, there is now research interest in investigating whether the co-existence of sarcopenia and obesity (sarcopenic obesity) within the same individual significantly increases the risk of knee osteoarthritis, compared to sarcopenia or obesity alone. This review synthesises current literature to explore the association between sarcopenic obesity and knee osteoarthritis, emphasising both the clinical evidence and existing gaps. We highlight the challenges and progress in defining sarcopenic obesity and discuss the impact that the lack of a consensus definition of sarcopenic obesity has on comparing outcomes of studies investigating the relationship between sarcopenic obesity and knee OA. We offer methodological insights to guide future studies investigating whether sarcopenic obesity increases the risk of knee osteoarthritis above and beyond the risk associated with each condition on its own. The implications for clinical practice are discussed, including the need to incorporate effective resistance exercise into weight loss programs for individuals with sarcopenic obesity. This is critical as a general weight loss program alone among individuals with sarcopenic obesity can include substantial loss of muscle mass, potentially predisposing patients to further functional decline.

Changes in lean body mass with glucagon-like peptide-1-based therapies and mitigation strategies

Weight loss induced by glucagon-like peptide-1 receptor agonists (GLP-1RAs) and dual glucagon-like peptide-1 receptor (GLP-1R)/glucose-dependent insulinotropic polypeptide receptor agonists is coming closer to the magnitudes achieved with surgery. However, with greater weight loss there is concern about potential side effects on muscle quantity (mass), health and function. There is heterogeneity in the reported effects of GLP-1-based therapies on lean mass changes in clinical trials: in some studies, reductions in lean mass range between 40% and 60% as a proportion of total weight lost, while other studies show lean mass reductions of approximately 15% or less of total weight lost. There are several potential reasons underlying this heterogeneity, including population, drug-specific/molecular, and comorbidity effects. Furthermore, changes in lean mass may not always reflect changes in muscle mass as the former measure includes not only muscle but also organs, bone, fluids, and water in fat tissue. Based on contemporary evidence with the addition of magnetic resonance imaging-based studies, skeletal muscle changes with GLP-1RA treatments appear to be adaptive: reductions in muscle volume seem to be commensurate with what is expected given ageing, disease status, and weight loss achieved, and the improvement in insulin sensitivity and muscle fat infiltration likely contributes to an adaptive process with improved muscle quality, lowering the probability for loss in strength and function. Nevertheless, factors such as older age and severity of disease may influence the selection of appropriate candidates for these therapies due to risk of sarcopenia. To further improve muscle health during weight loss, several pharmacological treatments to maintain or improve muscle mass designed in combination with GLP-1-based therapies are under development. Future research on GLP-1-based and other therapies designed for weight loss should focus on more accurate and meaningful assessments of muscle mass, composition, as well as function, mobility or strength, to better define their impact on muscle health for the substantial number of patients who will likely be taking these medications well into the future.

Predictive value of sarcopenia components for all-cause mortality: findings from population-based cohorts

BACKGROUND

Low grip strength and gait speed are associated with mortality. However, investigation of the additional mortality risk explained by these measures, over and above other factors, is limited.

AIM

We examined whether grip strength and gait speed improve discriminative capacity for mortality over and above more readily obtainable clinical risk factors.

METHODS

Participants from the Health, Aging and Body Composition Study, Osteoporotic Fractures in Men Study, and the Hertfordshire Cohort Study were analysed. Appendicular lean mass (ALM) was ascertained using DXA; muscle strength by grip dynamometry; and usual gait speed over 2.4-6 m. Verified deaths were recorded. Associations between sarcopenia components and mortality were examined using Cox regression with cohort as a random effect; discriminative capacity was assessed using Harrell's Concordance Index (C-index).

RESULTS

Mean (SD) age of participants (n = 8362) was 73.8(5.1) years; 5231(62.6%) died during a median follow-up time of 13.3 years. Grip strength (hazard ratio (95% CI) per SD decrease: 1.14 (1.10,1.19)) and gait speed (1.21 (1.17,1.26)), but not ALM index (1.01 (0.95,1.06)), were associated with mortality in mutually-adjusted models after accounting for age, sex, BMI, smoking status, alcohol consumption, physical activity, ethnicity, education, history of fractures and falls, femoral neck bone mineral density (BMD), self-rated health, cognitive function and number of comorbidities. However, a model containing only age and sex as exposures gave a C-index (95% CI) of 0.65(0.64,0.66), which only increased to 0.67(0.67,0.68) after inclusion of grip strength and gait speed.

CONCLUSIONS

Grip strength and gait speed may generate only modest adjunctive risk information for mortality compared with other more readily obtainable risk factors.

Biomarkers of frailty

Several biomarkers have been proposed to identify frailty, a multisystemic age-related syndrome. However, the complex pathophysiology and the absence of a consensus on a comprehensive and universal definition make it challenging to pinpoint a singular biomarker or set of biomarkers that conclusively characterize frailty. This review delves into the main laboratory biomarkers, placing special emphasis on those associated with various pathways closely tied to the frailty condition, such as inflammation, oxidative stress, mitochondrial dysfunction, metabolic and endocrine alterations and microRNA. Additionally, we provide a summary of different clinical biomarkers encompassing different tools that have been proposed to assess frailty. We further address various imaging biomarkers such as Dual Energy X-ray Absorptiometry, Bioelectrical Impedance analysis, Computed Tomography and Magnetic Resonance Imaging, Ultrasound and D3 Creatine dilution. Intervention to treat frailty, including non-pharmacological ones, especially those involving physical exercise and nutrition, and pharmacological interventions, that include those targeting specific mechanisms such as myostatin inhibitors, insulin sensitizer metformin and with special relevance for hormonal treatments are mentioned. We further address the levels of different biomarkers in monitoring the potential positive effects of some of these interventions. Despite the availability of numerous biomarkers, their performance and usefulness in the clinical arena are far from being satisfactory. Considering the multicausality of frailty, there is an increasing need to assess the role of sets of biomarkers and the combination between laboratory, clinical and image biomarkers, in terms of sensitivity, specificity and predictive values for the diagnosis and prognosis of the different outcomes of frailty to improve detection and monitoring of older people with frailty or at risk of developing it, being this a need in the everyday clinical practice.

Sarcopenia definitions and their association with fracture risk in older Swedish women

The purpose of this study was to investigate the prevalence of three sarcopenia definitions and their associations with fracture risk in older Swedish women when adjusted for fracture risk assessment (FRAX)-based risk factors; 2,883 women with a mean age of 77.8 years were included. Sarcopenia was defined based on the Sarcopenia Definitions and Outcomes Consortium (SDOC; low handgrip strength [kg] and gait speed (m/s)), revised European Working Group on Sarcopenia in Older People (EWGSOP2; low appendicular lean mass index, appendicular lean mass [ALM]/height; kg/m2], and hand grip strength [kg]), and Asian Working Group for Sarcopenia (AWGS; low ALM (kg), and hand grip strength [kg]) definitions. Femoral neck T-score was obtained from dual-energy X-ray absorptiometry. All fractures, confirmed by X-ray or medical record review, were subsequently categorized as major osteoporotic fractures (MOFs) and hip fractures. Deaths were verified through regional registers. The total follow-up time was 6.4 ± 1.3 (mean ± SD) yr. Cox regression (hazard ratios [HR] and 95% CIs) analyses were performed with adjustment for age, FRAX variables, and femoral neck T-score. Sarcopenia prevalence was 4.5% (n = 129) according to SDOC, 12.5% (n = 360) for EWGSOP2, and 10.3% (n = 296) defined by AWGS. Individuals with sarcopenia defined by SDOC had a higher mortality risk than individuals without sarcopenia (HR: 3.41; 95% CI: 2.51, 4.62) after adjusting for age and FRAX variables. Sarcopenia according to EWGSOP2 and AWGS was not associated with an increased fracture risk after adjusting for age and FRAX variables. Individuals with sarcopenia defined by SDOC had a higher risk for any fractures (HR: 1.48; 95% CI: 1.10, 1.99) and MOF (HR: 1.42; 95% CI: 1.03, 1.98) compared with individuals without sarcopenia after adjusting for clinical risk factors used in FRAX. In conclusion, sarcopenia defined by SDOC, incorporating muscle function/strength, was the only sarcopenia definition associated with fracture risk in older women.

Retirement risk factors, exercise management and muscle mass in US senior horses

BACKGROUND

Information on the management and health of US senior horses (≥15 years of age) is currently limited.

OBJECTIVES

Provide information on (1) primary use of US senior horses, (2) reasons and risk factors for horse retirement, (3) exercise management, (4) prevalence of low muscle mass and (5) risk factors for, and owner-perceived consequences of, low muscle mass.

STUDY DESIGN

Online survey.

METHODS

Survey responses from 2717 owners of U.S.-resident senior horses (≥15 years of age) were analysed descriptively and inferentially, using ordered and binomial logistic regression, ANOVA and the Kruskal-Wallis test.

RESULTS

The most frequently reported primary uses were pleasure riding/driving (38.5%) and full retirement (39.8%). Most horses (61.5%) were retired between 15 and 24 years of age, with health problems being the main reason. Age, female sex, Thoroughbred breed and various medical conditions were identified as risk factors for retirement. In working horses (i.e., those not retired or semi-retired), exercise intensity was negatively associated with age. The owner-reported prevalence of low muscle mass in all horses was 17.2% (95%CI = 15.7-18.7). In those affected by low muscle mass, the ability to work and welfare-related aspects were commonly perceived to be impaired. Increasing age, sex (gelding), pituitary pars intermedia dysfunction, osteoarthritis, laminitis and primary use (retired and semi-retired vs. use for competition) were identified as risk factors for owner-reported low muscle mass.

MAIN LIMITATIONS

Potential response, recall and sampling bias. Causal relationships cannot be established.

CONCLUSIONS

Although structured exercise into old age may provide health benefits (as seen in elderly people), a large proportion of horses were fully retired in the current study. Senior horses were mainly retired for health problems and characterising these problems may aid in extending their work/active life. Low muscle mass was perceived to affect horses' welfare and ability to work, and identification of prevention and treatment strategies is therefore warranted.

Estimating Muscle Mass Using D3-Creatine Dilution: A Narrative Review of Clinical Implications and Comparison With Other Methods

BACKGROUND

The D3-creatine (D3-Cr) dilution method is of emerging interest for estimating total-body skeletal muscle mass. This review explores the association of muscle mass estimated via D3-Cr with various clinical outcomes and provides a summary of the literature comparing D3-Cr with other body composition techniques.

METHODS

A literature search was conducted on PubMed/MEDLINE and Web of Science for studies using D3-Cr to measure muscle in adult populations (ie, ≥18 years old) from inception until September 2023.

RESULTS

Out of the 23 included studies, 15 investigated the correlation between D3-Cr and clinical outcomes. More consistent associations were reported for mortality (100%, n = 2), mobility disability (100%; n = 5), falls and fractures (100%; n = 3), physical performance (63.3%; n = 11), muscle strength (44.4%; n = 9), and muscle composition (33.3%; n = 3). However, conflicting findings were also reported for such correlations. Among the 23 studies, 14 compared D3-Cr-estimated muscle with other body composition techniques, including magnetic resonance imaging (MRI) as a reference method. Strong and positive correlations were found between D3-Cr and MRI. Nonetheless, variations in muscle measurements were noted, with differences in D3-Cr values ranging from 0.62 kg lower to 13.47 kg higher compared to MRI.

CONCLUSIONS

D3-Cr-estimated muscle mass may be a valuable predictor of clinical outcomes showing consistent associations with falls and fractures, mobility disability, and mortality. However, less consistent associations were found with muscle strength and composition, and physical performance. Although a strong correlation exists between D3-Cr-estimated muscle mass and MRI measurements, under- or overestimation may occur.

The Conceptual Definition of Sarcopenia: Delphi Consensus from the Global Leadership Initiative in Sarcopenia (GLIS)

IMPORTANCE

Sarcopenia, the age-related loss of muscle mass and strength/function, is an important clinical condition. However, no international consensus on the definition exists.

OBJECTIVE

The Global Leadership Initiative in Sarcopenia (GLIS) aimed to address this by establishing the global conceptual definition of sarcopenia.

DESIGN

The GLIS steering committee was formed in 2019-21 with representatives from all relevant scientific societies worldwide. During this time, the steering committee developed a set of statements on the topic and invited members from these societies to participate in a two-phase International Delphi Study. Between 2022 and 2023, participants ranked their agreement with a set of statements using an online survey tool (SurveyMonkey). Statements were categorised based on predefined thresholds: strong agreement (>80%), moderate agreement (70-80%) and low agreement (<70%). Statements with strong agreement were accepted, statements with low agreement were rejected and those with moderate agreement were reintroduced until consensus was reached.

RESULTS

107 participants (mean age: 54 ± 12 years [1 missing age], 64% men) from 29 countries across 7 continents/regions completed the Delphi survey. Twenty statements were found to have a strong agreement. These included; 6 statements on 'general aspects of sarcopenia' (strongest agreement: the prevalence of sarcopenia increases with age (98.3%)), 3 statements on 'components of sarcopenia' (muscle mass (89.4%), muscle strength (93.1%) and muscle-specific strength (80.8%) should all be a part of the conceptual definition of sarcopenia)) and 11 statements on 'outcomes of sarcopenia' (strongest agreement: sarcopenia increases the risk of impaired physical performance (97.9%)). A key finding of the Delphi survey was that muscle mass, muscle strength and muscle-specific strength were all accepted as 'components of sarcopenia', whereas impaired physical performance was accepted as an 'outcome' rather than a 'component' of sarcopenia.

CONCLUSION AND RELEVANCE

The GLIS has created the first global conceptual definition of sarcopenia, which will now serve to develop an operational definition for clinical and research settings.

Sarcopenia: no consensus, no diagnostic criteria, and no approved indication-How did we get here?

In addition to the role of skeletal muscle in movement and locomotion, muscle plays a critical role in a broad array of metabolic processes that can contribute to improved health or risk of disease. The age-associated loss of muscle has been termed sarcopenia. The muscle is the primary site of insulin-stimulated glucose disposal and the largest component of basal metabolic rate, directly and indirectly affects bone density, produces myokines with pleiotropic effect on muscle and other tissues including the brain, and stores essential amino acids essential for the maintenance of protein synthesis during periods of reduced food intake and stress. As such, not surprisingly deterioration of skeletal muscle health, typically operationalized as decline of muscle mass and muscle strength is both a powerful risk factor and main consequence of chronic diseases, disability, and loss of independence, and it is one of the strongest risk factors for mortality. However, skeletal muscle remains one of the most plastic of all tissues, with rapid changes in rates of protein synthesis and degradation in response to physical activity and inactivity, inflammation, and nutritional and hormonal status. This has made the development of pharmacological therapies to increase muscle mass (or prevent loss), an important goal for decades. However, while remarkable advances in the understanding of molecular and cellular regulation of muscle protein metabolism have occurred recently, there are no approved drugs for the treatment of sarcopenia, the loss of skeletal muscle affecting millions of older people. The goal of this paper is to describe the possible reasons for the lack of new and effective pharmacotherapies to treat one of the most important risk factors for age-associated disease and loss of independence.

D3Creatine Dilution as a Direct, Non-invasive and Accurate Measurement of Muscle Mass for Aging Research

Initial definitions of sarcopenia included the age-associated loss of skeletal muscle mass that was presumed to be associated with late-life reduced functional capacity, disability and loss of independence. Because no method for determination of muscle mass was available for large cohort studies of aging men and women, lean body mass determined by dual X-ray absorptiometry or bioelectrical impedance was used as a surrogate measure of muscle mass. The data from these studies showed either no or a poor relationship between LBM and functional capacity and health related outcomes, leading to the conclusion of many that the amount of muscle may not be associated with these age-associated outcomes. It was assumed that some undefined index of muscle quality is the critical contributor. These studies also consistently showed that muscle strength is lost more quickly than lean mass. Total body muscle mass can now be measured directly, accurately and non-invasively using the D3creatine (D3Cr) dilution method. D3Cr muscle mass, but not DXA derived LBM, is strongly associated with functional capacity, falls and insulin resistance in older men and women. In addition, D3Cr muscle mass is associated with risk of disability, hip fracture and mortality. New and emerging data demonstrate that low muscle mass may serve as a diagnostic criterion for sarcopenia.

D3-creatine dilution, computed tomography and dual-energy X-ray absorptiometry for assessing myopenia and physical function in colon cancer: A cross-sectional study

BACKGROUND

Low skeletal muscle mass (myopenia) is common in cancer populations and is associated with functional decline and mortality, but prior oncology studies did not assess total body skeletal muscle mass. Instead, they measured surrogates such as cross-sectional area (CSA) of skeletal muscle at L3 from computed tomography (CT) or appendicular lean mass (ALM) from dual-energy X-ray absorptiometry (DXA). D3-creatine (D3Cr) dilution is a non-invasive method to assess total body skeletal muscle mass, which has been examined in a variety of populations but not in cancer. To compare the associations of D3Cr muscle mass, CT CSA, and DXA ALM with myopenia and physical function, we conducted a cross-sectional study among 119 patients with colon cancer (2018-2022).

METHODS

For each technique (D3Cr, CT and DXA), myopenia was defined as the lowest sex-specific quartile of its measurement. Physical function was measured by the short physical performance battery and grip strength. We calculated Pearson correlations (r) among three techniques, computed Cohen's kappa coefficients (κ) to assess the agreement of myopenia, and estimated Pearson correlations (r) of three techniques with physical function. All analyses were sex-specific.

RESULTS

Sixty-one (51.3%) participants were male, the mean (standard deviation) age was 56.6 (12.9) years, and most (68.9%) had high physical function (short physical performance battery: ≥11 points). Correlations and myopenia agreement among three techniques were greater in men than women; for example, regarding D3Cr muscle mass versus CT CSA, r was 0.73 (P < 0.001) for men versus 0.45 (P < 0.001) for women, and κ was 0.82 (95% CI: 0.65, 0.99) for men versus 0.24 (95% CI: -0.08, 0.52) for women. Among men, higher D3Cr muscle mass was significantly correlated with faster gait speed (r = 0.43, P < 0.01) and stronger grip strength (r = 0.32, P < 0.05); similar correlations were observed for CT CSA and DXA ALM. However, among women, no measure of muscle or lean mass was significantly associated with physical function.

CONCLUSIONS

This is the first study using D3-creatine dilution method to assess muscle mass in a cancer population. Regardless of the techniques used for muscle or lean mass assessment, we observed stronger correlations, greater myopenia agreement, and more significant associations with physical function in men with colon cancer than women. D3Cr, CT and DXA are not interchangeable methods for assessing myopenia and physical function, especially in women with colon cancer. Future studies should consider relative advantages of these techniques and examine the D3-creatine dilution method in other cancer types.

Associations between D3Cr muscle mass and MR thigh muscle volume with strength, power, physical performance, fitness, and limitations in older adults in the SOMMA study

Background

Different measures to assess muscle size - magnetic resonance (MR) derived thigh muscle volume and d3-creatine dilution derived muscle mass (D3Cr muscle mass) - may have similar associations with strength, power, physical performance, fitness, and functional limitations in older adults.

Methods

Men (N=345) and women (N=482) aged ≥70 years from the Study of Muscle, Mobility and Aging completed exams including leg extension strength (1-repetition max) and cardiopulmonary exercise testing to assess fitness (VO2peak). Correlations and adjusted regression models stratified by sex were used to assess the association between muscle size measures and study outcomes; we tested for sex interactions.

Results

D3Cr muscle mass and MR thigh muscle volume were correlated (men: r=0.62, women: r=0.51, p<.001). Lower D3Cr muscle mass and lower MR thigh muscle volume were associated with lower strength and lower VO2peak in both men and women; D3Cr muscle mass was more strongly associated with strength in men than in women (p-int<0.05). There were correlations, though less consistent, between muscle size or mass with physical performance and function. Associations between the muscle size measures and the study outcomes occasionally varied by sex, and associations of MR thigh muscle volume were, at times, slightly more strongly associated with the study outcomes than was D3Cr muscle mass.

Conclusions

Less muscle -measured by either D3Cr muscle mass or MR thigh muscle volume - was associated with lower strength and worse performance. Varied associations by sex and assessment method suggest consideration be given to which measurement to use in future studies.

Associations of Skeletal Muscle Mass, Muscle Fat Infiltration, Mitochondrial Energetics, and Cardiorespiratory Fitness with Liver Fat Among Older Adults

Background

Muscle mass loss may be associated with liver fat accumulation, yet scientific consensus is lacking and evidence in older adults is scant. It is unclear which muscle characteristics might contribute to this association in older adults.

Methods

We associated comprehensive muscle-related phenotypes including muscle mass normalized to body weight (D 3 -creatine dilution), muscle fat infiltration (MRI), carbohydrate-supported muscle mitochondrial maximal oxidative phosphorylation (respirometry), and cardiorespiratory fitness (VO 2 peak) with liver fat among older adults. Linear regression models adjusted for age, gender, technician (respirometry only), daily minutes of moderate to vigorous physical activity, and prediabetes/diabetes status tested main effects and interactions of each independent variable with waist circumference (high: women-≥88 cm, men-≥102 cm) and gender.

Results

Among older adults aged 75 (IQR 73, 79 years; 59.8% women), muscle mass and liver fat were not associated overall but were positively associated among participants with a high waist circumference (β: 25.2; 95%CI 11.7, 40.4; p =.0002; N=362). Muscle fat infiltration and liver fat were positively associated (β: 15.2; 95%CI 6.8, 24.3; p =.0003; N=378). Carbohydrate-supported maximum oxidative phosphorylation and VO 2 peak (adjusted β: -12.9; 95%CI -20.3, -4.8; p =0.003; N=361) were inversely associated with liver fat; adjustment attenuated the estimate for maximum oxidative phosphorylation although the point estimate remained negative (β: -4.0; 95%CI -11.6, 4.2; p =0.32; N=321).

Conclusions

Skeletal muscle-related characteristics are metabolically relevant factors linked to liver fat in older adults. Future research should confirm our results to determine whether trials targeting mechanisms common to liver and muscle fat accumulation are warranted.

Muscle Mass Assessment in Sarcopenia: A Narrative Review

Sarcopenia is a condition characterized by age-related muscle loss and dysfunction. Over the past decade, several working groups have developed diagnostic criteria for sarcopenia, including muscle mass, grip strength, and gait speed measurements. However, there is debate over which muscle mass indicator is the most appropriate. Some groups used appendicular lean mass divided by height squared, whereas others used appendicular lean mass divided by body mass index. In addition, the association between muscle mass and long-term health outcomes is inconsistent. As a result, some experts question the necessity of using muscle mass as a diagnostic criterion for sarcopenia. This review summarizes the measurement methods and muscle mass indicators of previous studies, highlighting issues with past muscle mass assessments.

Application of the D3 -creatine muscle mass assessment tool to a geriatric weight loss trial: A pilot study

BACKGROUND

Traditionally, weight loss (WL) trials utilize dual energy X-ray absorptiometry (DXA) to measure lean mass. This method assumes lean mass, as the sum of all non-bone and non-fat tissue, is a reasonable proxy for muscle mass. In contrast, the D3 -creatine (D3 Cr) dilution method directly measures whole body skeletal muscle mass, although this method has yet to be applied in the context of a geriatric WL trial. The purpose of this project was to (1) describe estimates of change and variability in D3 Cr muscle mass in older adults participating in an intentional WL intervention and (2) relate its change to other measures of body composition as well as muscle function and strength.

METHODS

The INVEST in Bone Health trial (NCT04076618), used as a scaffold for this ancillary pilot project, is a three-armed, 12-month randomized, controlled trial designed to determine the effects of resistance training or weighted vest use during intentional WL on a battery of musculoskeletal health outcomes among 150 older adults living with obesity. A convenience sample of 24 participants (n = 8/arm) are included in this analysis. At baseline and 6 months, participants were weighed, ingested a 30 mg D3 Cr tracer dose, provided a fasted urine sample 3-6 days post-dosage, underwent DXA (total body fat and lean masses, appendicular lean mass) and computed tomography (mid-thigh and trunk muscle/intermuscular fat areas) scans, and performed 400-m walk, stair climb, knee extensor strength, and grip strength tests.

RESULTS

Participants were older (68.0 ± 4.4 years), mostly White (75.0%), predominantly female (66.7%), and living with obesity (body mass index: 33.8 ± 2.7 kg/m2 ). Six month total body WL was -10.3 (95% confidence interval, CI: -12.7, -7.9) kg. All DXA and computed tomography-derived body composition measures were significantly decreased from baseline, yet D3 Cr muscle mass did not change [+0.5 (95% CI: -2.0, 3.0) kg]. Of muscle function and strength measures, only grip strength significantly changed [+2.5 (95% CI: 1.0, 4.0) kg] from baseline.

CONCLUSIONS

Among 24 older adults, significant WL with or without weighted vest use or resistance training over a 6-month period was associated with significant declines in all bioimaging metrics, while D3 Cr muscle mass and muscle function and strength were preserved. Treatment assignment for the trial remains blinded; therefore, full interpretation of these findings is limited. Future work in this area will assess change in D3 Cr muscle mass by parent trial treatment group assignment in all study participants.

Interactions Between HR-pQCT Bone Density and D3 Cr Muscle Mass (or HR-pQCT Bone Structure and HR-pQCT Muscle Density) in Predicting Fractures: The Osteoporotic Fractures in Men Study

We examined if an interaction exists between bone and muscle in predicting fractures in older men. Prospective data from the Osteoporotic Fractures in Men study was used to build Cox proportional hazards models. Predictors included HR-pQCT total volumetric BMD (Tt.BMD), trabecular BMD (Tb.BMD), cortical BMD (Ct.BMD) and cortical area (Ct.Ar) at distal radius/tibia, HR-pQCT muscle volume and density (diaphyseal tibia), D3 -creatine dilution (D3 Cr) muscle mass, and grip strength and leg force, analyzed as continuous variables and as quartiles. Incident fractures were self-reported every 4 months via questionnaires and centrally adjudicated by physician review of radiology reports. Potential confounders (demographics, comorbidities, lifestyle factors, etc.) were considered. A total of 1353 men (mean age 84.2 ± 4.0 years, 92.7% white) were followed for 6.03 ± 2.11 years. In the unadjusted (continuous) model, there were no interactions (p > 0.05) between any muscle variable (D3 Cr muscle mass, muscle volume, muscle density, grip strength or leg force) and Tt.BMD at distal radius/tibia for fractures (all: n = 182-302; nonvertebral: n = 149-254; vertebral: n = 27-45). No consistent interactions were observed when interchanging Tt.BMD for Tb.BMD/Ct.BMD or for Ct.Ar (bone structure) at the distal radius/tibia in the unadjusted (continuous) models. Compared with men in quartiles (Q) 2-4 of D3 Cr muscle mass and Q2-4 of distal tibia Tt.BMD, men in Q1 of both had increased risk for all fractures (hazard ratio (HR) = 2.00; 95% confidence interval [CI] 1.24-3.23, p = 0.005) and nonvertebral fractures (HR = 2.10; 95% CI 1.25-3.52, p < 0.001) in the multivariable-adjusted model. Confidence intervals overlapped (p > 0.05) when visually inspecting other quartile groups in the multivariable-adjusted model. In this prospective cohort study of older men, there was no consistent interactions between bone and muscle variables on fracture risk. Larger sample sizes and longer follow-up may be needed to clarify if there is an interaction between bone and muscle on fracture risk in men. © 2023 The Authors. Journal of Bone and Mineral Research published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research (ASBMR).

Estimation of skeletal muscle mass in 4-year-old children using the D3-creatine dilution method

BACKGROUND

Given limited experience in applying the creatine-(methyl-D3) (D3Cr) dilution method to measure skeletal muscle mass (SMM) in young children, the feasibility of deployment in a fielding setting and performance of the method was assessed in a cohort of 4-year-old children in Dhaka, Bangladesh.

METHODS

Following D3Cr oral dose (10 mg) administration, single fasting urine samples were collected at 2-4 days (n = 100). Twenty-four-hour post-dose collections and serial spot urine samples on days 2, 3 and 4 were obtained in a subset of participants (n = 10). Urinary creatine, creatinine, D3Cr and D3-creatinine enrichment were analyzed by liquid chromatography-tandem mass spectrometry. Appendicular lean mass (ALM) was measured by dual-energy x-ray absorptiometry and grip strength was measured by a hand-held dynamometer.

RESULTS

SMM was measured successfully in 91% of participants, and there were no adverse events. Mean ± SD SMM was greater than ALM (4.5 ± 0.4 and 3.2 ± 0.6 kg, respectively). Precision of SMM was low (intraclass correlation = 0.20; 95% CI: 0.02, 0.75; n = 10). Grip strength was not associated with SMM in multivariable analysis (0.004 kg per 100 g of SMM; 95% CI: -0.031, 0.038; n = 91).

CONCLUSIONS

The D3Cr dilution method was feasible in a community setting. However, high within-child variability in SMM estimates suggests the need for further optimization of this approach.

IMPACT

The D3-creatine (D3Cr) stable isotope dilution method was considered a feasible method for the estimation of skeletal muscle mass (SMM) in young children in a community setting and was well accepted among participants. SMM was weakly associated with both dual-energy x-ray absorptiometry-derived values of appendicular lean mass and grip strength. High within-child variability in estimated values of SMM suggests that further optimization of the D3Cr stable isotope dilution method is required prior to implementation in community research settings.

Comparing D3-Creatine Dilution and Dual-Energy X-ray Absorptiometry Muscle Mass Responses to Strength Training in Low-Functioning Older Adults

BACKGROUND

In contrast to dual-energy x-ray absorptiometry (DXA), the D3-creatine (D3Cr) dilution method provides a direct measure of skeletal muscle mass and in a cohort of older men has been strongly associated with health-related outcomes. However, sensitivity to detect changes in D3Cr-derived muscle mass due to an intervention is limited.

METHODS

Twenty-one older adults (≥70 years) with low-to-moderate physical function were randomized to a 15-week high-intensity strength training (ST) or a health education (HE) group. Full-body progressive intensity ST was performed 3 days per week.

RESULTS

The mean age was 82.1 years, with 64% females. After 15 weeks, both D3Cr muscle mass (MM; 2.29 kg; 95% CI: 0.22, 4.36) and DXA appendicular lean mass (ALM; 1.04 kg; 95% CI: 0.31, 1.77) were greater in ST group compared to HE. Baseline correlations between D3Cr MM and DXA ALM (r = 0.79; 95% CI: 0.53, 0.92) or total lean body mass (LBM; r = 0.79; 95% CI: 0.52, 0.91) were high. However, longitudinal changes in D3Cr MM were weakly correlated with changes in DXA ALM (r = 0.19; 95% CI: -0.35, 0.64) and LBM (r = 0.40; 95% CI: -0.13, 0.76). More participants showed positive response rates, defined as a >5% increase from baseline, with D3Cr MM (80%) than DXA measures (14%-43%).

CONCLUSIONS

A progressive ST intervention in low-functioning older adults increased D3Cr MM and DXA ALM. These data suggest that the D3Cr dilution is potentially sensitive to detect changes in muscle mass in response to resistance exercise training. These results are preliminary and could be used for planning larger trials to replicate these results.

The D3 -creatine dilution method non-invasively measures muscle mass in mice

Developing accurate methods to quantify age-related muscle loss (sarcopenia) could greatly accelerate development of therapies to treat muscle loss in the elderly, as current methods are inaccurate or expensive. The current gold standard method for quantifying sarcopenia is dual-energy X-ray absorptiometry (DXA) but does not measure muscle directly-it is a composite measure quantifying "lean mass" (muscle) excluding fat and bone. In humans, DXA overestimates muscle mass, which has led to erroneous conclusions about the importance of skeletal muscle in human health and disease. In animal models, DXA is a popular method for measuring lean mass. However, instrumentation is expensive and is potentially limited by anesthesia concerns. Recently, the D3 -creatine (D3 Cr) dilution method for quantifying muscle mass was developed in humans and rats. This method is faster, cheaper, and more accurate than DXA. Here, we demonstrate that the D3 Cr method is a specific assay for muscle mass in mice, and we test associations with DXA and body weight. We evaluated the D3 Cr method compared to DXA-determined lean body mass (LBM) in aged mice and reported that DXA consistently overestimates muscle mass with age. Overall, we provide evidence that the D3 Cr dilution method directly measures muscle mass in mice. Combined with its ease of use, accessibility, and non-invasive nature, the method may prove to more quickly advance development of preclinical therapies targeting sarcopenia.

Synergistic Strategies to Accelerate the Development of Function-Promoting Therapies: Lessons From Operation Warp Speed and Oncology Drug Development

BACKGROUND

Functional limitations and physical disabilities associated with aging and chronic disease are major concerns for human societies and expeditious development of function-promoting therapies is a public health priority.

METHODS

Expert panel discussion.

RESULTS

The remarkable success of Operation Warp Speed for the rapid development of COVID-19 vaccines, COVID-19 therapeutics, and of oncology drug development programs over the past decade have taught us that complex public health problems such as the development of function-promoting therapies will require collaboration among many stakeholders, including academic investigators, the National Institutes of Health, professional societies, patients and patient advocacy organizations, the pharmaceutical and biotechnology industry, and the U.S. Food and Drug Administration.

CONCLUSIONS

There was agreement that the success of well designed, adequately powered clinical trials will require careful definitions of indication/s, study population, and patient-important endpoints that can be reliably measured using validated instruments, commensurate resource allocation, and versatile organizational structures such as those used in Operation Warp Speed.

Optimizing the Design of Clinical Trials to Evaluate the Efficacy of Function-Promoting Therapies

BACKGROUND

Several candidate molecules that may have application in treating physical limitations associated with aging and chronic diseases are in development. Challenges in the framing of indications, eligibility criteria, and endpoints and the lack of regulatory guidance have hindered the development of function-promoting therapies.

METHODS

Experts from academia, pharmaceutical industry, National Institutes of Health (NIH), and Food and Drug Administration (FDA) discussed optimization of trial design including the framing of indications, eligibility criteria, and endpoints.

RESULTS

Mobility disability associated with aging and chronic diseases is an attractive indication because it is recognized by geriatricians as a common condition associated with adverse outcomes, and it can be ascertained reliably. Other conditions associated with functional limitation in older adults include hospitalization for acute illnesses, cancer cachexia, and fall injuries. Efforts are underway to harmonize definitions of sarcopenia and frailty. Eligibility criteria should reconcile the goals of selecting participants with the condition and ensuring generalizability and ease of recruitment. An accurate measure of muscle mass (eg, D3 creatine dilution) could be a good biomarker in early-phase trials. Performance-based and patient-reported measures of physical function are needed to demonstrate whether treatment improves how a person lives, functions, or feels. Multicomponent functional training that integrates training in balance, stability, strength, and functional tasks with cognitive and behavioral strategies may be needed to translate drug-induced muscle mass gains into functional improvements.

CONCLUSIONS

Collaborations among academic investigators, NIH, FDA, pharmaceutical industry, patients, and professional societies are needed to conduct well-designed trials of function-promoting pharmacological agents with and without multicomponent functional training.

Low skeletal muscle mass index and all-cause mortality risk in adults: A systematic review and meta-analysis of prospective cohort studies

OBJECTIVE

The relationship between low skeletal muscle mass index (SMI) and all-cause mortality risk in the general adults remains unclear. Our study was conducted to examine and quantify the associations between low SMI and all-cause mortality risks.

METHODS

PubMed, Web of Science, and Cochrane Library for primary data sources and references to relevant publications retrieved until 1 April 2023. A random-effect model, subgroup analyses, meta-regression, sensitivity analysis, and publication bias were conducted using STATA 16.0.

RESULTS

Sixteen prospective studies were included in the meta-analysis of low SMI and the risk of all-cause mortality. A total of 11696 deaths were ascertained among 81358 participants during the 3 to 14.4 years follow-up. The pooled RR of all-cause mortality risk was 1.57 (95% CI, 1.25 to 1.96, P < 0.001) across the lowest to the normal muscle mass category. The results of meta-regression showed that BMI (P = 0.086) might be sources of heterogeneity between studies. Subgroup analysis showed that low SMI was significantly associated with an increased risk of all-cause mortality in studies with a body mass index (BMI) between 18.5 to 25 (1.34, 95% CI, 1.24-1.45, P<0.001), 25 to 30 (1.91, 95% CI, 1.16-3.15, P = 0.011), and over 30 (2.58, 95% CI, 1.20-5.54 P = 0.015).

CONCLUSIONS

Low SMI was significantly associated with the increased risk of all-cause mortality, and the risk of all-cause mortality associated with low SMI was higher in adults with a higher BMI. Low SMI Prevention and treatment might be significant for reducing mortality risk and promoting healthy longevity.

Association of muscle wasting with mortality risk among adults: A systematic review and meta-analysis of prospective studies

The relationship between muscle wasting and mortality risk in the general population remains unclear. Our study was conducted to examine and quantify the associations between muscle wasting and all-cause and cause-specific mortality risks. PubMed, Web of Science and Cochrane Library were searched until 22 March 2023 for main data sources and references of retrieved relevant articles. Prospective studies investigating the associations of muscle wasting with risks of all-cause and cause-specific mortality in the general population were eligible. A random-effect model was used to calculate the pooled relative risk (RR) and 95% confidence intervals (CIs) for the lowest versus normal categories of muscle mass. Subgroup analyses and meta-regression were performed to investigate the potential sources of heterogeneities among studies. Dose-response analyses were conducted to evaluate the relationship between muscle mass and mortality risk. Forty-nine prospective studies were included in the meta-analysis. A total of 61 055 deaths were ascertained among 878 349 participants during the 2.5- to 32-year follow-up. Muscle wasting was associated with higher mortality risks of all causes (RR = 1.36, 95% CI, 1.28 to 1.44, I²  = 94.9%, 49 studies), cardiovascular disease (CVD) (RR = 1.29, 95% CI, 1.05 to 1.58, I²  = 88.1%, 8 studies), cancer (RR = 1.14, 95% CI, 1.02 to 1.27, I²  = 38.7%, 3 studies) and respiratory disease (RR = 1.36, 95% CI, 1.11 to 1.67, I²  = 62.8%, 3 studies). Subgroup analyses revealed that muscle wasting, regardless of muscle strength, was significantly associated with a higher all-cause mortality risk. Meta-regression showed that risks of muscle wasting-related all-cause mortality (P = 0.06) and CVD mortality (P = 0.09) were lower in studies with longer follow-ups. An approximately inverse linear dose-response relationship was observed between mid-arm muscle circumference and all-cause mortality risk (P < 0.01 for non-linearity). Muscle wasting was associated with higher mortality risks of all causes, CVD, cancer and respiratory disease in the general population. Early detection and treatment for muscle wasting might be crucial for reducing mortality risk and promoting healthy longevity.

Combinations of Sarcopenia Diagnostic Criteria by Asian Working Group of Sarcopenia (AWGS) 2019 Guideline and Incident Adverse Health Outcomes in Community-Dwelling Older Adults

OBJECTIVES

This study aimed to investigate the association between combinations of sarcopenia criteria by the Asian Working Group of Sarcopenia (AWGS) 2019 guideline and incident adverse health outcomes.

DESIGN

Longitudinal analyses of a cohort study.

SETTING AND PARTICIPANTS

We conducted prospective 2-year follow-up analyses (N = 1959) among community-dwelling older adults enrolled in the nationwide Korean Frailty and Aging Cohort Study (KFACS).

METHODS

From the KFACS, 1959 older adults (52.8% women; mean age = 75.9 ± 3.9 years) who underwent assessments for appendicular skeletal mass using dual-energy X-ray absorptiometry, handgrip strength, usual gait speed, 5-times sit-to-stand test, and Short Physical Performance Battery (SPPB) at baseline were included. Participants with each adverse health outcome [mobility disability, falls, and instrumental activities of daily living (IADL) disabilities] at baseline were excluded for each corresponding analysis. Multivariable logistic regression was performed to examine whether sarcopenia defined by different diagnostic criteria was associated with incident adverse health outcomes after 2 years.

RESULTS

A total of 444 participants (22.7%) were diagnosed with sarcopenia as defined by AWGS 2019. In the multivariable analysis, sarcopenia defined as both low muscle mass and low physical performance increased the risk of mobility disability (OR 2.14, 95% CI 1.35-3.38) and falls (1.74, 95% CI 1.21-2.49). Only the criterion defined as both low muscle mass and physical performance using the SPPB increased the risk of falls with fracture (2.53, 95% CI 1.01-6.35) and IADL disabilities (2.77, 95% CI 1.21-6.33). However, sarcopenia defined as both low muscle mass and low hand grip strength showed no associations with the incidence of any of the adverse health outcomes.

CONCLUSIONS AND IMPLICATIONS

Our study suggests that the predictive value of adverse health outcomes for community-dwelling older adults is better when diagnosed with sarcopenia based on low muscle mass and physical performance. Furthermore, using the SPPB as a diagnostic tool for low physical performance may improve the predictive validity for falls with fracture and IADL disability. Our findings may be helpful for the early detection of individuals with sarcopenia who have a higher risk of adverse health outcomes.

Sarcopenic obesity research perspectives outlined by the sarcopenic obesity global leadership initiative (SOGLI) - Proceedings from the SOGLI consortium meeting in rome November 2022

The European Society for Clinical Nutrition and Metabolism (ESPEN) and the European Association for the Study of Obesity (EASO) launched the Sarcopenic Obesity Global Leadership Initiative (SOGLI) to reach expert consensus on a definition and diagnostic criteria for Sarcopenic Obesity (SO). The present paper describes the proceeding of the Sarcopenic Obesity Global Leadership Initiative (SOGLI) meeting that was held on November 25th and 26th, 2022 in Rome, Italy. This consortium involved the participation of 50 researchers from different geographic regions and countries. The document outlines an agenda advocated by the SOGLI expert panel regarding the pathophysiology, screening, diagnosis, staging and treatment of SO that needs to be prioritized for future research in the field.

Single-leg disuse decreases skeletal muscle strength, size, and power in uninjured adults: A systematic review and meta-analysis

We aimed to quantify declines from baseline in lower limb skeletal muscle size and strength of uninjured adults following single-leg disuse. We searched EMBASE, Medline, CINAHL, and CCRCT up to 30 January 2022. Studies were included in the systematic review if they (1) recruited uninjured participants; (2) were an original experimental study; (3) employed a single-leg disuse model; and (4) reported muscle strength, size, or power data following a period of single-leg disuse for at least one group without a countermeasure. Studies were excluded if they (1) did not meet all inclusion criteria; (2) were not in English; (3) reported previously published muscle strength, size, or power data; or (4) could not be sourced from two different libraries, repeated online searches, and the authors. We used the Cochrane Risk of Bias Assessment Tool to assess risk of bias. We then performed random-effects meta-analyses on studies reporting measures of leg extension strength and extensor size. Our search revealed 6548 studies, and 86 were included in our systematic review. Data from 35 and 20 studies were then included in the meta-analyses for measures of leg extensor strength and size, respectively (40 different studies). No meta-analysis for muscle power was performed due to insufficient homogenous data. Effect sizes (Hedges' g_av ) with 95% confidence intervals for leg extensor strength were all durations = -0.80 [-0.92, -0.68] (n = 429 participants; n = 68 aged 40 years or older; n ≥ 78 females); ≤7 days of disuse = -0.57 [-0.75, -0.40] (n = 151); >7 days and ≤14 days = -0.93 [-1.12, -0.74] (n = 206); and >14 days = -0.95 [-1.20, -0.70] (n = 72). Effect sizes for measures of leg extensor size were all durations = -0.41 [-0.51, -0.31] (n = 233; n = 32 aged 40 years or older; n ≥ 42 females); ≤7 days = -0.26 [-0.36, -0.16] (n = 84); >7 days and ≤14 days = -0.49 [-0.67, -0.30] (n = 102); and >14 days = -0.52 [-0.74, -0.30] (n = 47). Decreases in leg extensor strength (cast: -0.94 [-1.30, -0.59] (n = 73); brace: -0.90 [-1.18, -0.63] (n = 106)) and size (cast: -0.61[-0.87, -0.35] (n = 41); brace: (-0.48 [-1.04, 0.07] (n = 41)) following 14 days of disuse did not differ for cast and brace disuse models. Single-leg disuse in adults resulted in a decline in leg extensor strength and size that reached a nadir beyond 14 days. Bracing and casting led to similar declines in leg extensor strength and size following 14 days of disuse. Studies including females and males and adults over 40 years of age are lacking.

C-reactive protein and muscle-related measures over 14 years in Chinese community-dwelling older adults

BACKGROUND

Inflammation has been proposed to initiate the development of cachexia and is a driver of skeletal muscle loss. It raised the question of whether inflammation may also predict the age-related decline in muscle-related measures. This study explored the longitudinal association between high-sensitivity C-reactive protein (hsCRP) and muscle-related measures over a 14-year follow-up period, among Chinese community-dwelling older adults ≥65 years.

METHODS

Data was derived from the Mr. and Ms. Osteoporosis (Hong Kong) study. hsCRP was measured at baseline as a marker of inflammation. Muscle-related measures including handgrip strength, gait speed, chair-stand test (CST) and appendicular skeletal muscle mass/height² (ASM/ht², using dual-energy x-ray absorptiometry) were measured at baseline, 2-, 4-, 7- (except CST and ASM/ht²) and 14-year follow up. Adjusted linear mixed models were used to examine associations between baseline sex-specific tertiles of hsCRP and changes in muscle-related measures.

RESULTS

2534 participants were included (mean age 72.3 ± 5.1 years, 49.4% female). There were significant time changes in all muscle-related measures (all p for time <0.001). Participants in the higher tertile of hsCRP had poorer handgrip strength and gait speed and a higher ASM/ht² compared with those in the lower tertile of hsCRP (all p < 0.05). A higher tertile of hsCRP did not predict the decline in muscle-related measures (all p for hsCRP tertile x time interaction >0.05).

CONCLUSIONS

This prospective study suggests that, among Chinese community-dwelling older adults, baseline inflammatory state as measured by hsCRP was not associated with the decline in muscle-related measures over a long period of time.

Comparing the Fracture Profile of Osteosarcopenic Older Adults with Osteopenia/Osteoporosis Alone

PURPOSE

To determine whether osteosarcopenia is associated with a greater likelihood of recurrent fractures, as well as type of fracture, than osteopenia/osteoporosis or sarcopenia alone.

METHODS

Anthropometry (height/weight; scales and stadiometer), body composition (bone mineral density [BMD] and appendicular lean mass; dual-energy x-ray absorptiometry), grip strength (hydraulic dynamometer), and gait speed (4 m) were measured in an outpatient clinic. WHO definition for osteopenia/osteoporosis (BMD T-score below -1 SDs) while sarcopenia was defined by SDOC or EWGSOP2. Number and location of fractures within the past 5 years were self-reported and verified by medical records (unverified fractures excluded). Univariable and multivariable regressions were used to examine the association between the exposure and outcome while adjusting for confounders.

RESULTS

481 community-dwelling older adults (median age: 78, IQR: 72, 83; 75.9% women) were included. Prevalence of osteosarcopenia depended on the definition (SDOC: 179 (37.2%); EWGSOP2: 123 (25.6%)). In multivariable analysis adjusting for age, sex, alcohol, smoking, BMI, lowest BMD T-score, physical activity, and comorbidities, the likelihood of recurrent fractures (≥ 2 vs 0-1) was significantly higher in those with osteosarcopenia versus osteopenia/osteoporosis irrespective of the definition (SDOC: odds ratio [OR]: 1.63, 95% CI: 1.03, 2.59, p = 0.037; EWGSOP2: OR: 1.83, 95% CI: 1.12, 3.01, p = 0.016]. Associations with sarcopenia alone (SDOC: 10; EWGSOP2: 7) were not possible due to the extremely low prevalence of this condition in those with normal BMD.

CONCLUSION

Our data suggest osteosarcopenia is associated with a greater likelihood of recurrent fractures versus osteopenia/osteoporosis alone. Further studies are needed to evaluate the relationship with sarcopenia alone.

Recent sarcopenia definitions-prevalence, agreement and mortality associations among men: Findings from population-based cohorts

BACKGROUND

The 2019 European Working Group on Sarcopenia in Older People (EWGSOP2) and the Sarcopenia Definitions and Outcomes Consortium (SDOC) have recently proposed sarcopenia definitions. However, comparisons of the performance of these approaches in terms of thresholds employed, concordance in individuals and prediction of important health-related outcomes such as death are limited. We addressed this in a large multinational assembly of cohort studies that included information on lean mass, muscle strength, physical performance and health outcomes.

METHODS

White men from the Health Aging and Body Composition (Health ABC) Study, Osteoporotic Fractures in Men (MrOS) Study cohorts (Sweden, USA), the Hertfordshire Cohort Study (HCS) and the Sarcopenia and Physical impairment with advancing Age (SarcoPhAge) Study were analysed. Appendicular lean mass (ALM) was ascertained using DXA; muscle strength by grip dynamometry; and usual gait speed over courses of 2.4-6 m. Deaths were recorded and verified. Definitions of sarcopenia were as follows: EWGSOP2 (grip strength <27 kg and ALM index <7.0 kg/m2 ), SDOC (grip strength <35.5 kg and gait speed <0.8 m/s) and Modified SDOC (grip strength <35.5 kg and gait speed <1.0 m/s). Cohen's kappa statistic was used to assess agreement between original definitions (EWGSOP2 and SDOC). Presence versus absence of sarcopenia according to each definition in relation to mortality risk was examined using Cox regression with adjustment for age and weight; estimates were combined across cohorts using random-effects meta-analysis.

RESULTS

Mean (SD) age of participants (n = 9170) was 74.3 (4.9) years; 5929 participants died during a mean (SD) follow-up of 12.1 (5.5) years. The proportion with sarcopenia according to each definition was EWGSOP2 (1.1%), SDOC (1.7%) and Modified SDOC (5.3%). Agreement was weak between EWGSOP2 and SDOC (κ = 0.17). Pooled hazard ratios (95% CI) for mortality for presence versus absence of each definition were EWGSOP2 [1.76 (1.42, 2.18), I2 : 0.0%]; SDOC [2.75 (2.28, 3.31), I2 : 0.0%]; and Modified SDOC [1.93 (1.54, 2.41), I2 : 58.3%].

CONCLUSIONS

There was low prevalence and poor agreement among recent sarcopenia definitions in community-dwelling cohorts of older white men. All indices of sarcopenia were associated with mortality. The strong relationship between sarcopenia and mortality, regardless of the definition, illustrates that identification of appropriate management and lifecourse intervention strategies for this condition is of paramount importance.

Biochemical Markers of Musculoskeletal Health and Aging to be Assessed in Clinical Trials of Drugs Aiming at the Treatment of Sarcopenia: Consensus Paper from an Expert Group Meeting Organized by the European Society for Clinical and Economic Aspects of Osteoporosis, Osteoarthritis and Musculoskeletal Diseases (ESCEO) and the Centre Académique de Recherche et d'Expérimentation en Santé (CARES SPRL), Under the Auspices of the World Health Organization Collaborating Center for the Epidemiology of Musculoskeletal Conditions and Aging

In clinical trials, biochemical markers provide useful information on the drug's mode of action, therapeutic response and side effect monitoring and can act as surrogate endpoints. In pharmacological intervention development for sarcopenia management, there is an urgent need to identify biomarkers to measure in clinical trials and that could be used in the future in clinical practice. The objective of the current consensus paper is to provide a clear list of biochemical markers of musculoskeletal health and aging that can be recommended to be measured in Phase II and Phase III clinical trials evaluating new chemical entities for sarcopenia treatment. A working group of the European Society for Clinical and Economic Aspects of Osteoporosis, Osteoarthritis and Musculoskeletal Diseases (ESCEO) proposed classifying biochemical markers into 2 series: biochemical markers evaluating musculoskeletal status and biochemical markers evaluating causal factors. For series 1, the group agreed on 4 biochemical markers that should be assessed in Phase II or Phase III trials (i.e., Myostatin-Follistatin, Brain Derived Neurotrophic Factor, N-terminal Type III Procollagen and Serum Creatinine to Serum Cystatin C Ratio - or the Sarcopenia Index). For series 2, the group agreed on 6 biochemical markers that should be assessed in Phase II trials (i.e., the hormones insulin-like growth factor-1 (IGF-I), dehydroepiandrosterone sulphate, and cortisol, and the inflammatory markers C-reactive protein (CRP), interleukin-6 and tumor necrosis factor-α), and 2 in Phase III trials (i.e., IGF-I and CRP). The group also proposed optional biochemical markers that may provide insights into the mode of action of pharmacological therapies. Further research and development of new methods for biochemical marker assays may lead to the evolution of these recommendations.

Nutrition Strategies Promoting Healthy Aging: From Improvement of Cardiovascular and Brain Health to Prevention of Age-Associated Diseases

BACKGROUND

An increasing number of studies suggest that diet plays an important role in regulating aging processes and modulates the development of the most important age-related diseases.

OBJECTIVE

The aim of this review is to provide an overview of the relationship between nutrition and critical age-associated diseases.

METHODS

A literature review was conducted to survey recent pre-clinical and clinical findings related to the role of nutritional factors in modulation of fundamental cellular and molecular mechanisms of aging and their role in prevention of the genesis of the diseases of aging.

RESULTS

Studies show that the development of cardiovascular and cerebrovascular diseases, neurodegenerative diseases, cognitive impairment and dementia can be slowed down or prevented by certain diets with anti-aging action. The protective effects of diets, at least in part, may be mediated by their beneficial macro- (protein, fat, carbohydrate) and micronutrient (vitamins, minerals) composition.

CONCLUSIONS

Certain diets, such as the Mediterranean diet, may play a significant role in healthy aging by preventing the onset of certain diseases and by improving the aging process itself. This latter can be strengthened by incorporating fasting elements into the diet. As dietary recommendations change with age, this should be taken into consideration as well, when developing a diet tailored to the needs of elderly individuals. Future and ongoing clinical studies on complex anti-aging dietary interventions translating the results of preclinical investigations are expected to lead to novel nutritional guidelines for older adults in the near future.

D3 -creatine dilution for skeletal muscle mass measurement: historical development and current status

The French chemist Michel Eugène Chevreul discovered creatine in meat two centuries ago. Extensive biochemical and physiological studies of this organic molecule followed with confirmation that creatine is found within the cytoplasm and mitochondria of human skeletal muscles. Two groups of investigators exploited these relationships five decades ago by first estimating the creatine pool size in vivo with 14 C and 15 N labelled isotopes. Skeletal muscle mass (kg) was then calculated by dividing the creatine pool size (g) by muscle creatine concentration (g/kg) measured on a single muscle biopsy or estimated from the literature. This approach for quantifying skeletal muscle mass is generating renewed interest with the recent introduction of a practical stable isotope (creatine-(methyl-d3 )) dilution method for estimating the creatine pool size across the full human lifespan. The need for a muscle biopsy has been eliminated by assuming a constant value for whole-body skeletal muscle creatine concentration of 4.3 g/kg wet weight. The current single compartment model of estimating creatine pool size and skeletal muscle mass rests on four main assumptions: tracer absorption is complete; tracer is all retained; tracer is distributed solely in skeletal muscle; and skeletal muscle creatine concentration is known and constant. Three of these assumptions are false to varying degrees. Not all tracer is retained with urinary isotope losses ranging from 0% to 9%; an empirical equation requiring further validation is used to correct for spillage. Not all tracer is distributed in skeletal muscle with non-muscle creatine sources ranging from 2% to 10% with a definitive value lacking. Lastly, skeletal muscle creatine concentration is not constant and varies between muscles (e.g. 3.89-4.62 g/kg), with diets (e.g. vegetarian and omnivore), across age groups (e.g. middle-age, ~4.5 g/kg; old-age, 4.0 g/kg), activity levels (e.g. athletes, ~5 g/kg) and in disease states (e.g. muscular dystrophies, <3 g/kg). Some of the variability in skeletal muscle creatine concentrations can be attributed to heterogeneity in the proportions of wet skeletal muscle as myofibres, connective tissues, and fat. These observations raise serious concerns regarding the accuracy of the deuterated-creatine dilution method for estimating total body skeletal muscle mass as now defined by cadaver analyses of whole wet tissues and in vivo approaches such as magnetic resonance imaging. A new framework is needed in thinking about how this potentially valuable method for measuring the creatine pool size in vivo can be used in the future to study skeletal muscle biology in health and disease.

Public Health Need, Molecular Targets, and Opportunities for the Accelerated Development of Function-Promoting Therapies: Proceedings of a National Institute on Aging Workshop

Background

People ≥ 65 years are expected to live a substantial portion of their remaining lives with a limiting physical condition and the numbers of affected individuals will increase substantially due to the growth of the population of older adults worldwide. The age-related loss of muscle mass, strength, and function is associated with an increased risk of physical disabilities, falls, loss of independence, metabolic disorders, and mortality. The development of function-promoting therapies to prevent and treat age-related skeletal muscle functional limitations is a pressing public health problem.

Methods

On March 20–22, 2022, the National Institute on Aging (NIA) held a workshop entitled “Development of Function-Promoting Therapies: Public Health Need, Molecular Targets, and Drug Development.”

Results

The workshop covered a variety of topics including advances in muscle biology, novel candidate molecules, findings from randomized trials, and challenges in the design of clinical trials and regulatory approval of function-promoting therapies. Leading academic investigators, representatives from the National Institutes of Health (NIH) and the U.S. Food and Drug Administration (FDA), professional societies, pharmaceutical industry, and patient advocacy organizations shared research findings and identified research gaps and strategies to advance the development of function-promoting therapies. A diverse audience of 397 national and international professionals attended the conference.

Conclusions

Function-promoting therapies to prevent and treat physical disabilities associated with aging and chronic diseases are a public health imperative. Appropriately powered, well-designed clinical trials and synergistic collaboration among academic experts, patients and stakeholders, the NIH and the FDA, and the pharmaceutical industry are needed to accelerate the development of function-promoting therapies.

An umbrella review of systematic reviews of β-hydroxy-β-methyl butyrate supplementation in ageing and clinical practice

The compound β-hydroxy-β-methyl butyrate (HMB) is proposed to increase or mitigate the loss of skeletal muscle and improve muscle function. We undertook a review of systematic reviews of HMB supplementation to promote gains or mitigate muscle loss in ageing and clinical populations. Following PRISMA guidelines, we searched for systematic reviews reporting the effect of HMB in our target populations. Dual-energy X-ray absorptiometry (DXA) measured lean soft-tissue mass (LSTM) was accepted as a proxy for muscle. We identified 15 systematic reviews that met our inclusion criteria, which were independently evaluated. The methodological quality of the reviews was assessed using A Measurement Tool to Assess Systematic Reviews (AMSTAR), and standardized effectiveness statements were generated. Five of 15 studies found some evidence that HMB augmented LSTM; the remaining 10 studies reported some evidence favouring no difference (6/10 studies) or insufficient evidence to determine an effect (4/10 studies). Of the 12 studies that evaluated strength, 4/12 found some evidence, 5/12 found some evidence of no effect with one article finding some evidence in favour of patients in peri-hospitalized and no evidence for those that are community-dwelling, 4/12 had insufficient evidence to determine an effect, and 1/12 had insufficient evidence. No]study reported a positive effect of HMB on physical function; however, 2/10 studies found some evidence favouring no effect, and 7/10 studies reported insufficient evidence to determine an effect. The effectiveness of HMB supplementation in augmenting LSTM was heterogeneous, with most reviews finding no effect or inconclusive evidence to determine an effect. Most reviews concluded that HMB supplementation did not affect strength outcome measures or studies were inconclusive. The current evidence is insufficient to assess the impact of HMB supplementation on functional outcome measures. Our analysis shows minor, inconsistent support for HMB as part of an oral nutritional supplement or as a stand-alone supplement (or combined with other amino acids) to increase or promote retention of LSTM, improve strength, and no evidence that it improves physical function in older persons or clinical populations.

Lean mass, grip strength, and hospital-associated disability among older adults in Health ABC

INTRODUCTION

Older adults with cognitive impairment, including those with Alzheimer's disease and related dementias, are particularly at risk for hospitalization and hospital-associated disability. Understanding of key risk factors for hospital-associated disability is limited. Sarcopenia, age-related declines in muscle mass and strength, is common in older adults with cognitive impairment and may be an important risk factor for hospital-associated disability.

METHODS

Using data from the Health ABC Study, we examined associations of pre-hospitalization appendicular lean mass (ALM) and grip strength with the development of a new activity of daily living (ADL) disability at the next annual assessment after hospitalization.

RESULTS

Grip strength, but not ALM, was negatively associated with increased risk of hospital-associated ADL disability, and this association was greater among those with cognitive impairment compared to those without.

DISCUSSION

Lower grip strength may be an important risk factor for hospital-associated ADL disability in older adults, particularly those with cognitive impairment.

Associations of components of sarcopenia with risk of fracture in the Osteoporotic Fractures in Men (MrOS) study

Our aim was to evaluate the associations between the individual components of sarcopenia and fracture types. In this cohort, the risk of experiencing any clinical, hip, or major osteoporotic fracture is greater in men with slow walking speed in comparison to normal walking speed.

INTRODUCTION

The association between the components of sarcopenia and fractures has not been clearly elucidated and has hindered the development of appropriate therapeutic interventions. Our aim was to evaluate the associations between the individual components of sarcopenia, specifically lean mass, strength, and physical performance and fracture (any fracture, hip fracture, major osteoporotic fracture) in the Osteoporotic Fractures in Men (MrOS) study.

METHODS

The Osteoporotic Fractures in Men study (MrOS) recruited 5995 men ≥ 65 years of age. We measured appendicular lean mass (ALM) by dual-energy X-ray absorptiometry (low as residual value < 20th percentile for the cohort), walking speed (fastest trial of usual pace, values < 0.8 m/s were low), and grip strength (max score of 2 trials, values < 30 kg were low). Information on fractures was assessed tri-annually over an average follow-up of 12 years and centrally adjudicated. Cox proportional hazard models estimated the hazard ratio (HR) (95% confidence intervals) for slow walking speed, low grip strength, and low lean mass.

RESULTS

Overall, 1413 men had a fracture during follow-up. Slow walking speed was associated with an increased risk for any HR = 1.39, 1.05-1.84; hip HR = 2.37, 1.54-3.63; and major osteoporotic, HR = 1.89, 1.34-2.67 in multi-variate-adjusted models. Low lean mass and low grip strength were not significantly associated with fracture.

CONCLUSIONS

In this cohort of older adult men, the risk of experiencing any, hip, or major osteoporotic fracture is greater in men with slow walking speed in comparison to men with normal walking speed, but low grip strength and low lean mass were not associated with fracture.