Hertfordshire sarcopenia study: design and methods

The effect of low birth weight as an intrauterine exposure on the early onset of sarcopenia through possible molecular pathways

Sarcopenia, a musculoskeletal disease characterized by the progressive loss of skeletal muscle mass, strength, and physical performance, presents significant challenges to global public health due to its adverse effects on mobility, morbidity, mortality, and healthcare costs. This comprehensive review explores the intricate connections between sarcopenia and low birth weight (LBW), emphasizing the developmental origins of health and disease (DOHaD) hypothesis, inflammatory processes (inflammaging), mitochondrial dysfunction, circadian rhythm disruptions, epigenetic mechanisms, and genetic variations revealed through genome-wide studies (GWAS). A systematic search strategy was developed using PubMed to identify relevant English-language publications on sarcopenia, LBW, DOHaD, inflammaging, mitochondrial dysfunction, circadian disruption, epigenetic mechanisms, and GWAS. The publications consist of 46.2% reviews, 21.2% cohort studies, 4.8% systematic reviews, 1.9% cross-sectional studies, 13.4% animal studies, 4.8% genome-wide studies, 5.8% epigenome-wide studies, and 1.9% book chapters. The review identified key factors contributing to sarcopenia development, including the DOHaD hypothesis, LBW impact on muscle mass, inflammaging, mitochondrial dysfunction, the influence of clock genes, the role of epigenetic mechanisms, and genetic variations revealed through GWAS. The DOHaD theory suggests that LBW induces epigenetic alterations during foetal development, impacting long-term health outcomes, including the early onset of sarcopenia. LBW correlates with reduced muscle mass, grip strength, and lean body mass in adulthood, increasing the risk of sarcopenia. Chronic inflammation (inflammaging) and mitochondrial dysfunction contribute to sarcopenia, with LBW linked to increased oxidative stress and dysfunction. Disrupted circadian rhythms, regulated by genes such as BMAL1 and CLOCK, are associated with both LBW and sarcopenia, impacting lipid metabolism, muscle mass, and the ageing process. Early-life exposures, including LBW, induce epigenetic modifications like DNA methylation (DNAm) and histone changes, playing a pivotal role in sarcopenia development. Genome-wide studies have identified candidate genes and variants associated with lean body mass, muscle weakness, and sarcopenia, providing insights into genetic factors contributing to the disorder. LBW emerges as a potential early predictor of sarcopenia development, reflecting the impact of intrauterine exposures on long-term health outcomes. Understanding the complex interplay between LBW with inflammaging, mitochondrial dysfunction, circadian disruption, and epigenetic factors is essential for elucidating the pathogenesis of sarcopenia and developing targeted interventions. Future research on GWAS and the underlying mechanisms of LBW-associated sarcopenia is warranted to inform preventive strategies and improve public health outcomes.

A perspective on muscle phenotyping in musculoskeletal research

Musculoskeletal research should synergistically investigate bone and muscle to inform approaches for maintaining mobility and to avoid bone fractures. The relationship between sarcopenia and osteoporosis, integrated in the term 'osteosarcopenia', is underscored by the close association shown between these two conditions in many studies, whereby one entity emerges as a predictor of the other. In a recent workshop of Working Group (WG) 2 of the EU Cooperation in Science and Technology (COST) Action 'Genomics of MusculoSkeletal traits Translational Network' (GEMSTONE) consortium (CA18139), muscle characterization was highlighted as being important, but currently under-recognized in the musculoskeletal field. Here, we summarize the opinions of the Consortium and research questions around translational and clinical musculoskeletal research, discussing muscle phenotyping in human experimental research and in two animal models: zebrafish and mouse.

Trigonelline is an NAD+ precursor that improves muscle function during ageing and is reduced in human sarcopenia

Mitochondrial dysfunction and low nicotinamide adenine dinucleotide (NAD+) levels are hallmarks of skeletal muscle ageing and sarcopenia1-3, but it is unclear whether these defects result from local changes or can be mediated by systemic or dietary cues. Here we report a functional link between circulating levels of the natural alkaloid trigonelline, which is structurally related to nicotinic acid4, NAD+ levels and muscle health in multiple species. In humans, serum trigonelline levels are reduced with sarcopenia and correlate positively with muscle strength and mitochondrial oxidative phosphorylation in skeletal muscle. Using naturally occurring and isotopically labelled trigonelline, we demonstrate that trigonelline incorporates into the NAD+ pool and increases NAD+ levels in Caenorhabditis elegans, mice and primary myotubes from healthy individuals and individuals with sarcopenia. Mechanistically, trigonelline does not activate GPR109A but is metabolized via the nicotinate phosphoribosyltransferase/Preiss-Handler pathway5,6 across models. In C. elegans, trigonelline improves mitochondrial respiration and biogenesis, reduces age-related muscle wasting and increases lifespan and mobility through an NAD+-dependent mechanism requiring sirtuin. Dietary trigonelline supplementation in male mice enhances muscle strength and prevents fatigue during ageing. Collectively, we identify nutritional supplementation of trigonelline as an NAD+-boosting strategy with therapeutic potential for age-associated muscle decline.

The serum small non-coding RNA (SncRNA) landscape as a molecular biomarker of age associated muscle dysregulation and insulin resistance in older adults

Small noncoding RNAs (sncRNAs) are implicated in age-associated pathologies, including sarcopenia and insulin resistance (IR). As potential circulating biomarkers, most studies have focussed on microRNAs (miRNAs), one class of sncRNA. This study characterized the wider circulating sncRNA transcriptome of older individuals and associations with sarcopenia and IR. sncRNA expression including miRNAs, transfer RNAs (tRNAs), tRNA-associated fragments (tRFs), and piwi-interacting RNAs (piRNAs) was measured in serum from 21 healthy and 21 sarcopenic Hertfordshire Sarcopenia Study extension women matched for age (mean 78.9 years) and HOMA2-IR. Associations with age, sarcopenia and HOMA2-IR were examined and predicted gene targets and biological pathways characterized. Of the total sncRNA among healthy controls, piRNAs were most abundant (85.3%), followed by tRNAs (4.1%), miRNAs (2.7%), and tRFs (0.5%). Age was associated (FDR < 0.05) with 2 miRNAs, 58 tRNAs, and 14 tRFs, with chromatin organization, WNT signaling, and response to stress enriched among gene targets. Sarcopenia was nominally associated (p < .05) with 12 tRNAs, 3 tRFs, and 6 piRNAs, with target genes linked to cell proliferation and differentiation such as Notch Receptor 1 (NOTCH1), DISC1 scaffold protein (DISC1), and GLI family zinc finger-2 (GLI2). HOMA2-IR was nominally associated (p<0.05) with 6 miRNAs, 9 tRNAs, 1 tRF, and 19 piRNAs, linked with lysine degradation, circadian rhythm, and fatty acid biosynthesis pathways. These findings identify changes in circulating sncRNA expression in human serum associated with chronological age, sarcopenia, and IR. These may have clinical utility as circulating biomarkers of ageing and age-associated pathologies and provide novel targets for therapeutic intervention.

Prevalence and factors associated with sarcopenia among older adults in a post-acute hospital in Singapore

BACKGROUND

Sarcopenia is common in older adults worldwide, but its prevalence varies widely owing to differences in diagnostic criteria, population sampled, and care setting. We aimed to determine the prevalence and factors associated with sarcopenia in patients aged 65 and above admitted to a post-acute hospital in Singapore.

METHODS

This was a cross-sectional study of 400 patients recruited from a community hospital in Singapore. Data including socio-demographics, physical activity, nutritional status, cognition, clinical and functional status, as well as anthropometric measurements were collected. Sarcopenia was defined using the Asian Working Group for Sarcopenia 2019 criteria [AWGS2019].

RESULTS

Of the 383 patients with complete datasets, overall prevalence of sarcopenia was 54% while prevalence of severe sarcopenia was 38.9%. Participants with increased age, male gender and a low physical activity level were more likely to be sarcopenic, while those with higher hip circumference and higher BMI of ≥27.5m/kg2 were less likely to be sarcopenic. Other than the above-mentioned variables, cognitive impairment was also associated with severe sarcopenia.

CONCLUSIONS

More than 1 in 2 older adults admitted to a post-acute hospital in Singapore are sarcopenic. There is an urgent need to address this important clinical syndrome burden and to identify patients at risk of sarcopenia in post-acute settings in Singapore for early intervention.

Adiposity is associated with widespread transcriptional changes and downregulation of longevity pathways in aged skeletal muscle

BACKGROUND

Amongst healthy older people, a number of correlates of impaired skeletal muscle mass and function have been defined. Although the prevalence of obesity is increasing markedly in this age group, information is sparse about the particular impacts of obesity on ageing skeletal muscle or the molecular mechanisms that underlie this and associated disease risk.

METHODS

Here, we examined genome-wide transcriptional changes using RNA sequencing in muscle biopsies from 40 older community-dwelling men from the Hertfordshire Sarcopenia Study with regard to obesity (body mass index [BMI] >30 kg/m2 , n = 7), overweight (BMI 25-30, n = 19), normal weight (BMI < 25, n = 14), and per cent and total fat mass. In addition, we used EPIC DNA methylation array data to investigate correlations between DNA methylation and gene expression in aged skeletal muscle tissue and investigated the relationship between genes within altered regulatory pathways and muscle histological parameters.

RESULTS

Individuals with obesity demonstrated a prominent modified transcriptional signature in muscle tissue, with a total of 542 differentially expressed genes associated with obesity (false discovery rate ≤0.05), of which 425 genes were upregulated when compared with normal weight. Upregulated genes were enriched in immune response (P = 3.18 × 10-41 ) and inflammation (leucocyte activation, P = 1.47 × 10-41 ; tumour necrosis factor, P = 2.75 × 10-15 ) signalling pathways and downregulated genes enriched in longevity (P = 1.5 × 10-3 ) and AMP-activated protein kinase (AMPK) (P = 4.5 × 10-3 ) signalling pathways. Furthermore, differentially expressed genes in both longevity and AMPK signalling pathways were associated with a change in DNA methylation, with a total of 256 and 360 significant cytosine-phosphate-guanine-gene correlations identified, respectively. Similar changes in the muscle transcriptome were observed with respect to per cent fat mass and total fat mass. Obesity was further associated with a significant increase in type II fast-fibre area (P = 0.026), of which key regulatory genes within both longevity and AMPK pathways were significantly associated.

CONCLUSIONS

We provide for the first time a global transcriptomic profile of skeletal muscle in older people with and without obesity, demonstrating modulation of key genes and pathways implicated in the regulation of muscle function, changes in DNA methylation associated with such pathways and associations between genes within the modified pathways implicated in muscle regulation and changes in muscle fibre type.

Human non-CpG methylation patterns display both tissue-specific and inter-individual differences suggestive of underlying function

DNA methylation (DNAm) in mammals is mostly examined within the context of CpG dinucleotides. Non-CpG DNAm is also widespread across the human genome, but the functional relevance, tissue-specific disposition, and inter-individual variability has not been widely studied. Our aim was to examine non-CpG DNAm in the wider methylome across multiple tissues from the same individuals to better understand non-CpG DNAm distribution within different tissues and individuals and in relation to known genomic regulatory features.DNA methylation in umbilical cord and cord blood at birth, and peripheral venous blood at age 12-13 y from 20 individuals from the Southampton Women's Survey cohort was assessed by Agilent SureSelect methyl-seq. Hierarchical cluster analysis (HCA) was performed on CpG and non-CpG sites and stratified by specific cytosine environment. Analysis of tissue and inter-individual variation was then conducted in a second dataset of 12 samples: eight muscle tissues, and four aliquots of cord blood pooled from two individuals.HCA using methylated non-CpG sites showed different clustering patterns specific to the three base-pair triplicate (CNN) sequence. Analysis of CAC sites with non-zero methylation showed that samples clustered first by tissue type, then by individual (as observed for CpG methylation), while analysis using non-zero methylation at CAT sites showed samples grouped predominantly by individual. These clustering patterns were validated in an independent dataset using cord blood and muscle tissue.This research suggests that CAC methylation can have tissue-specific patterns, and that individual effects, either genetic or unmeasured environmental factors, can influence CAT methylation.

Epigenome-wide association study of sarcopenia: findings from the Hertfordshire Sarcopenia Study (HSS)

BACKGROUND

Sarcopenia is the age-related loss of muscle mass, strength, and function. Epigenetic processes such as DNA methylation, which integrate both genetic and environmental exposures, have been suggested to contribute to the development of sarcopenia. This study aimed to determine whether differences in the muscle methylome are associated with sarcopenia and its component measures: grip strength, appendicular lean mass index (ALMi), and gait speed.

METHODS

Using the Infinium Human MethylationEPIC BeadChip, we measured DNA methylation in vastus lateralis muscle biopsies of 83 male participants (12 with sarcopenia) with a mean (standard deviation) age of 75.7 (3.6) years from the Hertfordshire Sarcopenia Study (HSS) and Hertfordshire Sarcopenia Study extension (HSSe) and examined associations with sarcopenia and its components. Pathway, histone mark, and transcription factor enrichment of the differentially methylated CpGs (dmCpGs) were determined, and sodium bisulfite pyrosequencing was used to validate the sarcopenia-associated dmCpGs. Human primary myoblasts (n = 6) isolated from vastus lateralis muscle biopsies from male individuals from HSSe were treated with the EZH2 inhibitor GSK343 to assess how perturbations in epigenetic processes may impact myoblast differentiation and fusion, measured by PAX7 and MYHC immunocytochemistry, and mitochondrial bioenergetics determined using the Seahorse XF96.

RESULTS

Sarcopenia was associated with differential methylation at 176 dmCpGs (false discovery rate ≤ 0.05) and 141 differentially methylated regions (Stouffer ≤ 0.05). The sarcopenia-associated dmCpGs were enriched in genes associated with myotube fusion (P = 1.40E-03), oxidative phosphorylation (P = 2.78E-02), and voltage-gated calcium channels (P = 1.59E-04). ALMi was associated with 71 dmCpGs, grip strength with 49 dmCpGs, and gait speed with 23 dmCpGs (false discovery rate ≤ 0.05). There was significant overlap between the dmCpGs associated with sarcopenia and ALMi (P = 3.4E-35), sarcopenia and gait speed (P = 4.78E-03), and sarcopenia and grip strength (P = 7.55E-06). There was also an over-representation of the sarcopenia, ALMi, grip strength, and gait speed-associated dmCpGs with sites of H3K27 trimethylation (all P ≤ 0.05) and amongst EZH2 target genes (all P ≤ 0.05). Furthermore, treatment of human primary myoblasts with the EZH2 inhibitor GSK343 inhibitor led to an increase in PAX7 expression (P ≤ 0.05), decreased myotube fusion (P = 0.043), and an increase in ATP production (P = 0.008), with alterations in the DNA methylation of genes involved in oxidative phosphorylation and myogenesis.

CONCLUSIONS

These findings show that differences in the muscle methylome are associated with sarcopenia and individual measures of muscle mass, strength, and function in older individuals. This suggests that changes in the epigenetic regulation of genes may contribute to impaired muscle function in later life.

Mitochondrial oxidative capacity and NAD+ biosynthesis are reduced in human sarcopenia across ethnicities

The causes of impaired skeletal muscle mass and strength during aging are well-studied in healthy populations. Less is known on pathological age-related muscle wasting and weakness termed sarcopenia, which directly impacts physical autonomy and survival. Here, we compare genome-wide transcriptional changes of sarcopenia versus age-matched controls in muscle biopsies from 119 older men from Singapore, Hertfordshire UK and Jamaica. Individuals with sarcopenia reproducibly demonstrate a prominent transcriptional signature of mitochondrial bioenergetic dysfunction in skeletal muscle, with low PGC-1α/ERRα signalling, and downregulation of oxidative phosphorylation and mitochondrial proteostasis genes. These changes translate functionally into fewer mitochondria, reduced mitochondrial respiratory complex expression and activity, and low NAD+ levels through perturbed NAD+ biosynthesis and salvage in sarcopenic muscle. We provide an integrated molecular profile of human sarcopenia across ethnicities, demonstrating a fundamental role of altered mitochondrial metabolism in the pathological loss of skeletal muscle mass and function in older people.

The Hertfordshire Cohort Study: an overview

The Hertfordshire Cohort Study is a nationally unique study of men and women born in the English county of Hertfordshire in the early part of the 20 ^th century. Records that detail their health in infancy and childhood have been preserved, their sociodemographic, lifestyle, medical and biological attributes have been characterised in later life, and routinely collected data on their hospital use and mortality have been acquired. This paper provides an overview of the study since its inception in the 1980s, including its methods, findings, and plans for its future.

Exercising Bioengineered Skeletal Muscle In Vitro: Biopsy to Bioreactor

The bioengineering of skeletal muscle tissue in-vitro has enabled researchers to more closely mimic the in-vivo skeletal muscle niche. The three-dimensional (3-D) structure of the tissue engineered systems employed to date enable the generation of highly aligned and differentiated myofibers within a representative biological matrix. The use of electrical stimulation to model concentric contraction, via innervation of the myofibers, and the use of mechanical loading to model passive lengthening or stretch has begun to provide a manipulable environment to investigate the cellular and molecular responses following exercise mimicking stimuli in-vitro. Currently available bioreactor systems allow either electrical stimulation or mechanical loading to be utilized at any given time. In the present manuscript, we describe in detail the methodological procedures to create 3-D bioengineered skeletal muscle using both cell lines and/or primary human muscle derived cells from a tissue biopsy, through to modeling exercising stimuli using a bioreactor that can provide both electrical stimulation and mechanical loading simultaneously within the same in-vitro system.

Associations Between Objectively Measured Physical Activity, Body Composition and Sarcopenia: Findings from the Hertfordshire Sarcopenia Study (HSS)

Regular physical activity (PA) is associated with reduced risk of the development and progression of musculoskeletal, metabolic and vascular disease. However, PA declines with age and this can contribute to multiple adverse outcomes. The aims of this study were to describe the relationship between accelerometer-determined PA, body composition and sarcopenia (the loss of muscle mass and function with age). Seven-day PA was measured using the GENEactiv accelerometer among 32 men and 99 women aged 74-84 years who participated in the Hertfordshire Sarcopenia Study. We measured mean daily acceleration and minutes/day spent in non-sedentary and moderate-to-vigorous physical activity (MVPA) levels. Body composition was measured by dual-energy X-ray absorptiometry, muscle strength by grip dynamometry and function by gait speed. Sarcopenia was defined according to the EWGSOP diagnostic algorithm. Men and women spent a median (inter-quartile range) of 138.8 (82, 217) and 186 (122, 240) minutes/day engaging in non-sedentary activity but only 14.3 (1.8, 30.2) and 9.5 (2.1, 18.6) min in MVPA, respectively. Higher levels of PA were associated with reduced adiposity, faster walking speed and decreased risk of sarcopenia. For example, a standard deviation (SD) increase in mean daily acceleration was associated with an increase in walking speed of 0.25 (95% CI 0.05, 0.45) SDs and a reduction in the risk of sarcopenia of 35% (95% CI 1, 57%) in fully adjusted analyses. PA was not associated with hand grip strength. Community-dwelling older adults in this study were largely sedentary but there was evidence that higher levels of activity were associated with reduced adiposity and improved function. PA at all intensity levels in later life may help maintain physical function and protect against sarcopenia.

Muscle Mass, Muscle Morphology and Bone Health Among Community-Dwelling Older Men: Findings from the Hertfordshire Sarcopenia Study (HSS)

Sarcopenia and osteoporosis are associated with poor health outcomes in older people. Relationships between muscle and bone have typically been reported at a functional or macroscopic level. The aims of this study were to describe the relationships between muscle morphology and bone health among participants of the Hertfordshire Sarcopenia Study (HSS). 105 older men, mean age 72.5 (SD 2.5) years, were recruited into the HSS. Whole body lean mass as well as appendicular lean mass, lumbar spine and femoral neck bone mineral content (BMC) and bone mineral density (BMD) were obtained through dual-energy X-ray absorptiometry scanning. Percutaneous biopsy of the vastus lateralis was performed successfully in 99 participants. Image analysis was used to determine the muscle morphology variables of slow-twitch (type I) and fast-twitch (type II) myofibre area, myofibre density, capillary and satellite cell (SC) density. There were strong relationships between whole and appendicular lean body mass in relation to femoral neck BMC and BMD (r ≥ 0.43, p < 0.001). Type II fibre area was associated with both femoral neck BMC (r = 0.27, p = 0.01) and BMD (r = 0.26, p = 0.01) with relationships robust to adjustment for age and height. In unadjusted analysis, SC density was associated with whole body area (r = 0.30, p = 0.011) and both BMC (r = 0.26, p = 0.031) and area (r = 0.29, p = 0.017) of the femoral neck. We have demonstrated associations between BMC and changes in muscle at a cellular level predominantly involving type II myofibres. Interventions targeted at improving muscle mass, function and quality may improve overall musculoskeletal health. Larger studies that include women are needed to explore these relationships further.

Learning from older peoples' reasons for participating in demanding, intensive epidemiological studies: a qualitative study

Background

Recruitment rates of older people in epidemiological studies, although relatively higher than in clinical trials, have declined in recent years. This study aimed to explore motivating factors and concerns among older participants in an intensive epidemiological study (Hertfordshire Sarcopenia Study - HSS) and identify those that could aid future recruitment to epidemiological studies and clinical trials.

Methods

Participants of the HSS fasted overnight and travelled several hours each way to the research facility at an English hospital for extensive diet/lifestyle questionnaires and investigations to assess muscle including blood tests and a muscle biopsy. We conducted semi-structured interviews with 13 participants (ten women) at the research facility in May–October 2015. The interviews were audio-taped, transcribed verbatim, coded and analysed thematically by three researchers.

Results

We identified personal motives for participation (potential health benefit for self and family; curiosity; comparing own fitness to others; socialising). Altruistic motives (benefit for other people; belief in importance of research) were also important. Participants voiced a number of external motives related to the study uniqueness, organisation and safety record; family support; and just ‘being asked’. Anxiety about the biopsy and travel distance were the only concerns and were alleviated by smooth and efficient running of the study.

Conclusions

Personal and altruistic reasons were important motivators for these older people to participate in demanding, intensive research. They valued belonging to a birth cohort with previous research experience, but personal contact with the research team before and after consent provided reassurance, aided recruitment to HSS and could be readily replicated by other researchers.

Any fears or concerns related to certain aspects of a demanding, intensive study should ideally be explored at an early visit to establish a good relationship with the research team.

Sarcopenia and frailty: new challenges for clinical practice

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

Does skeletal muscle have an 'epi'-memory? The role of epigenetics in nutritional programming, metabolic disease, aging and exercise

Skeletal muscle mass, quality and adaptability are fundamental in promoting muscle performance, maintaining metabolic function and supporting longevity and healthspan. Skeletal muscle is programmable and can ‘remember’ early‐life metabolic stimuli affecting its function in adult life. In this review, the authors pose the question as to whether skeletal muscle has an ‘epi’‐memory? Following an initial encounter with an environmental stimulus, we discuss the underlying molecular and epigenetic mechanisms enabling skeletal muscle to adapt, should it re‐encounter the stimulus in later life. We also define skeletal muscle memory and outline the scientific literature contributing to this field. Furthermore, we review the evidence for early‐life nutrient stress and low birth weight in animals and human cohort studies, respectively, and discuss the underlying molecular mechanisms culminating in skeletal muscle dysfunction, metabolic disease and loss of skeletal muscle mass across the lifespan. We also summarize and discuss studies that isolate muscle stem cells from different environmental niches in vivo (physically active, diabetic, cachectic, aged) and how they reportedly remember this environment once isolated in vitro. Finally, we will outline the molecular and epigenetic mechanisms underlying skeletal muscle memory and review the epigenetic regulation of exercise‐induced skeletal muscle adaptation, highlighting exercise interventions as suitable models to investigate skeletal muscle memory in humans. We believe that understanding the ‘epi’‐memory of skeletal muscle will enable the next generation of targeted therapies to promote muscle growth and reduce muscle loss to enable healthy aging.

Human Vastus Lateralis Skeletal Muscle Biopsy Using the Weil-Blakesley Conchotome

Percutaneous muscle biopsy using the Weil-Blakesley conchotome is well established in both clinical and research practice. It is a safe, effective and well tolerated technique. The Weil-Blakesley conchotome has a sharp biting tip with a 4 - 6 mm wide hollow. It is inserted through a 5 - 10 mm skin incision and can be maneuvered for controlled tissue penetration. The tip is opened and closed within the tissue and then rotated through 90 -180° to cut the muscle. The amount of muscle obtained following repeated sampling can vary from 20 mg to 290 mg which can be processed for both histology and molecular studies. The wound needs to be kept dry and vigorous physical activity kept to a minimum for approximately 72 hr although normal levels of activity can restart immediately following the procedure. This procedure is safe and effective when close attention is paid to the selection of subjects, full asepsis and post procedure care.  Both right and left vastus lateralis are suitable for biopsy dependent on participant preference.

Skeletal muscle morphology in sarcopenia defined using the EWGSOP criteria: findings from the Hertfordshire Sarcopenia Study (HSS)

Background

Sarcopenia is defined as the loss of muscle mass and function with age and is associated with decline in mobility, frailty, falls and mortality. There is considerable interest in understanding the underlying mechanisms. Our aim was to characterise muscle morphology changes associated with sarcopenia among community dwelling older men.

Methods

One hundred and five men aged 68–76 years were recruited to the Hertfordshire Sarcopenia Study (HSS) for detailed characterisation of muscle including measures of muscle mass, strength and function. Muscle tissue was obtained from a biopsy of the vastus lateralis for 99 men and was processed for immunohistochemical studies to determine myofibre distribution and area, capillarisation and satellite cell (SC) density.

Results

Six (6 %) men had sarcopenia as defined by the European Working Group on Sarcopenia in Older People (EWGSOP) criteria. These men had lower SC density (1.7 cells/mm² vs 3.8 cells/mm², p = 0.06) and lower SC/fibre ratio (0.02 vs 0.06, p = 0.06) than men without sarcopenia. Although men with sarcopenia tended to have smaller myofibres and lower capillary to fibre ratio, these relationships were not statistically significant.

Conclusion

We have shown that there may be altered muscle morphology parameters in older men with sarcopenia. These results have the potential to help identify cell and molecular targets for therapeutic intervention. This work now requires extension to larger studies which also include women.

Sarcopenia and frailty: new challenges for clinical practice

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

Skeletal muscle cells possess a 'memory' of acute early life TNF-α exposure: role of epigenetic adaptation

Sufficient quantity and quality of skeletal muscle is required to maintain lifespan and healthspan into older age. The concept of skeletal muscle programming/memory has been suggested to contribute to accelerated muscle decline in the elderly in association with early life stress such as fetal malnutrition. Further, muscle cells in vitro appear to remember the in vivo environments from which they are derived (e.g. cancer, obesity, type II diabetes, physical inactivity and nutrient restriction). Tumour-necrosis factor alpha (TNF-α) is a pleiotropic cytokine that is chronically elevated in sarcopenia and cancer cachexia. Higher TNF-α levels are strongly correlated with muscle loss, reduced strength and therefore morbidity and earlier mortality. We have extensively shown that TNF-α impairs regenerative capacity in mouse and human muscle derived stem cells [Meadows et al. (J Cell Physiol 183(3):330-337, 2000); Foulstone et al. (J Cell Physiol 189(2):207-215, 2001); Foulstone et al. (Exp Cell Res 294(1):223-235, 2004); Stewart et al. (J Cell Physiol 198(2):237-247, 2004); Al-Shanti et al. (Growth factors (Chur, Switzerland) 26(2):61-73, 2008); Saini et al. (Growth factors (Chur, Switzerland) 26(5):239-253, 2008); Sharples et al. (J Cell Physiol 225(1):240-250, 2010)]. We have also recently established an epigenetically mediated mechanism (SIRT1-histone deacetylase) regulating survival of myoblasts in the presence of TNF-α [Saini et al. (Exp Physiol 97(3):400-418, 2012)]. We therefore wished to extend this work in relation to muscle memory of catabolic stimuli and the potential underlying epigenetic modulation of muscle loss. To enable this aim; C2C12 myoblasts were cultured in the absence or presence of early TNF-α (early proliferative lifespan) followed by 30 population doublings in the absence of TNF-α, prior to the induction of differentiation in low serum media (LSM) in the absence or presence of late TNF-α (late proliferative lifespan). The cells that received an early plus late lifespan dose of TNF-α exhibited reduced morphological (myotube number) and biochemical (creatine kinase activity) differentiation vs. control cells that underwent the same number of proliferative divisions but only a later life encounter with TNF-α. This suggested that muscle cells had a morphological memory of the acute early lifespan TNF-α encounter. Importantly, methylation of myoD CpG islands were increased in the early TNF-α cells, 30 population doublings later, suggesting that even after an acute encounter with TNF-α, the cells have the capability of retaining elevated methylation for at least 30 cellular divisions. Despite these fascinating findings, there were no further increases in myoD methylation or changes in its gene expression when these cells were exposed to a later TNF-α dose suggesting that this was not directly responsible for the decline in differentiation observed. In conclusion, data suggest that elevated myoD methylation is retained throughout muscle cells proliferative lifespan as result of early life TNF-α treatment and has implications for the epigenetic control of muscle loss.

Lean mass, muscle strength and gene expression in community dwelling older men: findings from the Hertfordshire Sarcopenia Study (HSS)

Sarcopenia is associated with adverse health outcomes. This study investigated whether skeletal muscle gene expression was associated with lean mass and grip strength in community-dwelling older men. Utilising a cross-sectional study design, lean muscle mass and grip strength were measured in 88 men aged 68-76 years. Expression profiles of 44 genes implicated in the cellular regulation of skeletal muscle were determined. Serum was analysed for circulating cytokines TNF (tumour necrosis factor), IL-6 (interleukin 6, IFNG (interferon gamma), IL1R1 (interleukin-1 receptor-1). Relationships between skeletal muscle gene expression, circulating cytokines, lean mass and grip strength were examined. Participant groups with higher and lower values of lean muscle mass (n = 18) and strength (n = 20) were used in the analysis of gene expression fold change. Expression of VDR (vitamin D receptor) [fold change (FC) 0.52, standard error for fold change (SE) ± 0.08, p = 0.01] and IFNG mRNA (FC 0.31; SE ± 0.19, p = 0.01) were lower in those with higher lean mass. Expression of IL-6 (FC 0.43; SE ± 0.13, p = 0.02), TNF (FC 0.52; SE ± 0.10, p = 0.02), IL1R1 (FC 0.63; SE ± 0.09, p = 0.04) and MSTN (myostatin) (FC 0.64; SE ± 0.11, p = 0.04) were lower in those with higher grip strength. No other significant changes were observed. Significant negative correlations between serum IL-6 (R = -0.29, p = 0.005), TNF (R = -0.24, p = 0.017) and grip strength were demonstrated. This novel skeletal muscle gene expression study carried out within a well-characterized epidemiological birth cohort has demonstrated that lower expression of VDR and IFNG is associated with higher lean mass, and lower expression of IL-6, TNF, IL1R1 and myostatin is associated with higher grip strength. These findings are consistent with a role of proinflammatory factors in mediating lower muscle strength in community-dwelling older men.

Sarcopenia

Sarcopenia, the loss of muscle mass and function with age, is highly relevant to clinical practice as it has been associated with a wide range of ageing outcomes including disability and shorter survival times. As such it is now a major focus for research and drug discovery. There has been recent progress in the development of consensus definitions for the diagnosis of sarcopenia, taking the form of measurements of muscle mass and strength or physical performance. These definitions form potential inclusion criteria for use in trials, although the optimum choice of outcome measures is less clear. Prevalence estimates using these new definitions vary, although they suggest that sarcopenia is a common (approximately 13% from one study) clinical problem in older people. A range of lifestyle factors have been investigated in regard to the development of this condition, and progressive resistance training is the most well-established intervention so far. There is also marked research interest in the role of diet, although so far the value of supplementation is less clear. Other potential treatments for sarcopenia include the angiotensin-converting enzyme inhibitors, with some evidence that they can improve physical performance in older people. Future research directions include an increased understanding of the molecular and cellular mechanisms of sarcopenia and the use of a life course approach to explore the possibility of earlier intervention and prevention.

Prevalence of sarcopenia in community-dwelling older people in the UK using the European Working Group on Sarcopenia in Older People (EWGSOP) definition: findings from the Hertfordshire Cohort Study (HCS)

INTRODUCTION

sarcopenia is associated with adverse health outcomes. The aim of this study was to describe the prevalence of sarcopenia in community-dwelling older people in the UK using the European Working Group on Sarcopenia in Older People (EWGSOP) consensus definition.

METHODS

we applied the EWGSOP definition to 103 community-dwelling men participating in the Hertfordshire Sarcopenia Study (HSS) using both the lowest third of dual-energy X-ray absorptiometry (DXA) lean mass (LM) and the lowest third of skin-fold-based fat-free mass (FFM) as markers of low muscle mass. We also used the FFM approach among 765 male and 1,022 female participants in the Hertfordshire Cohort Study (HCS). Body size, physical performance and self-reported health were compared in participants with and without sarcopenia.

RESULTS

the prevalence of sarcopenia in HSS men (mean age 73 years) was 6.8% and 7.8% when using the lowest third of DXA LM and FFM, respectively. DXA LM and FFM were highly correlated (0.91, P < 0.001). The prevalence of sarcopenia among the HCS men and women (mean age 67 years) was 4.6% and 7.9%, respectively. HSS and HCS participants with sarcopenia were shorter, weighed less and had worse physical performance. HCS men and women with sarcopenia had poorer self-reported general health and physical functioning scores.

CONCLUSIONS

this is one of the first studies to describe the prevalence of sarcopenia in UK community-dwelling older people. The EWGSOP consensus definition was of practical use for sarcopenia case finding. The next step is to use this consensus definition in other ageing cohorts and among older people in a range of health-care settings.

Mortality as an adverse outcome of sarcopenia

Sarcopenia has an important impact in elderly. Recently the European Working Group on Sarcopenia in Older People (EWGSOP) defined sarcopenia as the loss of muscle mass plus low muscle strength or low physical performance. Lack of clinical sounding outcomes (ie external validity), is one of the flaws of this algorithm. The aim of our study was to determine the association of sarcopenia and mortality in a group of Mexican elderly. A total of 345 elderly were recruited in Mexico City, and followed up for three years. The EWGSOP algorithm was integrated by: gait speed, grip strength and calf circumference. Other covariates were assessed in order to test the independent association of sarcopenia with mortality. Of the 345 subjects, 53.3% were women; with a mean age of 78.5 (SD 7) years. During the three year follow-up a total of 43 (12.4%) subjects died. Age, cognition, ADL, IADL, health self-perception, ischemic heart disease and sarcopenia were associated in the bivariate analysis with survival. Negative predictive value for sarcopenia regarding mortality was of 90%. Kaplan-Meier curves along with their respective log-rank test were significant for sarcopenia. The components of the final Cox-regression multivariate model were age, ischemic heart disease, ADL and sarcopenia. Adjusted HR for age was 3.24 (CI 95% 1.55-6.78 p 0.002), IHD 5.07 (CI 95% 1.89-13.59 p 0.001), health self-perception 5.07 (CI 95% 1.9-13.6 p 0.001), ADL 0.75 (CI 95% 0.56-0.99 p 0.048) and sarcopenia 2.39 (CI 95% 1.05-5.43 p 0.037).

Mass spectrometry-based proteomic analysis of middle-aged vs. aged vastus lateralis reveals increased levels of carbonic anhydrase isoform 3 in senescent human skeletal muscle

The age-related loss of skeletal muscle mass and associated progressive decline in contractile strength is a serious pathophysiological issue in the elderly. In order to investigate global changes in the skeletal muscle proteome after the fifth decade of life, this study analysed total extracts from human vastus lateralis muscle by fluorescence difference in-gel electrophoresis. Tissue specimens were derived from middle-aged (47-62 years) vs. aged (76-82 years) individuals and potential changes in the protein expression profiles were compared between these two age groups by a comprehensive gel electrophoresis-based survey. Age-dependent alterations in the concentration of 19 protein spots were revealed and mass spectrometry identified these components as being involved in the excitation-contraction-relaxation cycle, muscle metabolism, ion handling and the cellular stress response. This indicates a generally perturbed protein expression pattern in senescent human muscle. Increased levels of mitochondrial enzymes and isoform switching of the key contractile protein, actin, support the idea of glycolytic-to-oxidative and fast-to-slow transition processes during muscle aging. Importantly, the carbonic anhydrase (CA)3 isoform displayed an increased abundance during muscle aging, which was independently verified by immunoblotting of differently aged human skeletal muscle samples. Since the CA3 isoform is relatively muscle-specific and exhibits a fibre type-specific expression pattern, this enzyme may represent an interesting new biomarker of sarcopenia. Increased levels of CA are indicative of an increased demand of CO₂-removal in senescent muscle, and also suggest age-related fibre type shifting to slower-contracting muscles during human aging.

Exercício resistido em idosos frágeis: uma revisão da literatura

INTRODUÇÃO: A síndrome da fragilidade, bastante comum em pessoas de idade avançada, consiste em um conjunto de sinais e sintomas no qual estão presentes critérios como perda de peso corporal não intencional em um ano (aproximadamente 5%), diminuição na velocidade da marcha, níveis baixos de atividade física, exaustão subjetiva e diminuição de força muscular. Os consequentes efeitos dessas mudanças relacionadas à idade, que incluem sarcopenia, disfunção imunológica e desregulação neuroendócrina, aumentam a vulnerabilidade do organismo ao estresse, reduzindo a habilidade de adaptar, compensar ou modular esses estímulos. Diferentes intervenções têm sido propostas para atenuar esse processo, sendo o exercício resistido (ER) uma das opções estudadas. OBJETIVO: Realizar uma revisão bibliográfica averiguando os efeitos dos ER na fisiopatologia da síndrome da fragilidade. MATERIAIS E MÉTODOS: Foi realizada uma revisão bibliográfica do período de 2004 a 2010, por meio das bases de dados LILACS, MEDLINE e PubMed. RESULTADOS: Por meio das análises dos estudos, foram observadas alterações nos sistemas hormonal e imune, atuando de forma sistêmica na reversão ou minimização dos efeitos da sarcopenia exercendo influência positiva na síndrome da fragilidade. CONCLUSÃO: O ER deve ser indicado como opção terapêutica para idosos frágeis ou pré-frágeis que não apresentem contraindicações para realização desta modalidade de exercício.

Physical activity, exercise, and sarcopenia - future challenges

BACKGROUND

Numerous studies have demonstrated that the etiology of sarcopenia is multi-causal and very complex process. The degradation of muscle mass leads to a loss of strength, later on to a decreased functional status, impaired mobility, a higher risk of falls, and eventually an increased risk of mortality. Present guidelines state that physical inactivity or a decreased physical activity level is a part of the underlying mechanisms of sarcopenia and therefore physical activity can be seen as an important factor to reverse or modify the development of sarcopenia.

TOPIC

Results in the area of physical activity and aging have not always been homogeneous. The inconsistent findings in this research area are related to the different understanding of terms and underlying constructs along with different population, type of intervention, or measurement methods. These aspects will be discussed in the paper. With regard to the formulated future role of physical activity this article will discuss in addition different barriers and challenges in the prevention and treatment of sarcopenia. A multitude of studies shows that structured exercise programs including progressive resistance or power training have positive effects on sarcopenia and sarcopenia-related outcomes but less or inconclusive information is available for the transfer to functional outcomes.

CONCLUSIONS

Both physical activities and exercise have shown to decrease risk of sarcopenia and onset of functional limitations in older persons. Unfortunately the cohort of older persons is the one with the highest percentage of individuals classified as inactive or sedentary. Therefore motivating older persons to increase their physical activity level as well as providing safe access to exercise programs seems to be a mandatory task.

Physical activity and sarcopenia

Physical activity can be a valuable countermeasure to sarcopenia in its treatment and prevention. In considering physical training strategies for sarcopenic subjects, it is critical to consider personal and environmental obstacles to access opportunities for physical activity for any patient with chronic disease. This article presents an overview of current knowledge of the effects of physical training on muscle function and the physical activity recommended for sarcopenic patients. So that this countermeasure strategy can be applied in practice, the authors propose a standardized protocol for prescribing physical activity in chronic diseases such as sarcopenia.

Developmental influences, muscle morphology, and sarcopenia in community-dwelling older men

BACKGROUND

Sarcopenia is associated with disability, morbidity, and mortality. Lower birth weight is associated with reduced muscle mass and strength in older people, suggesting that developmental influences are important in sarcopenia. However, underlying mechanisms are unknown. Our objective was to determine whether low birth weight is associated with altered skeletal muscle morphology in older men.

METHODS

Ninety-nine men with historical records of birth weight (≤3.18 kg and ≥3.63 kg), aged 68-76 years, consented for detailed characterization of muscle, including a biopsy of the vastus lateralis. Tissue was processed for immunohistochemical studies and analyzed to determine myofibre density, area, and score.

RESULTS

Muscle fibre score (fibres kilograms per square millimeter) was significantly reduced in those with lower birth weight: 1.5 × 10(3) vs 1.7 × 10(3), p = .04 unadjusted; p = .09 adjusted for age, height, and physical activity. In addition, there was a trend for reduced myofibre density (fibres per square millimeter) in those with lower birth weight: total fibre density: 176 vs 184, type I myofibre density: 77 vs 80, and type II myofibre density: 99 vs 105. Types I and II myofibre areas (square micrometers) were larger in those with lower birth weight: type I: 4903 vs 4643 and type II: 4046 vs 3859. However, none of these differences were statistically significant.

CONCLUSIONS

This is the first study showing that lower birth weight is associated with a significant decrease in muscle fibre score, suggesting that developmental influences on muscle morphology may explain the widely reported associations between lower birth weight and sarcopenia. However, the study may have been underpowered and did not include women supporting replication in larger cohorts of older men and women.