The developmental origins of sarcopenia: from epidemiological evidence to underlying mechanisms

Identifying Risk Factors for Presarcopenia in Early Middle Age

OBJECTIVE

This study aimed to determine whether risk factors for presarcopenia can be identified in a sample of early middle-aged men and women.

DESIGN

Prospective study.

SETTING

Longitudinal data from the Dunedin Multidisciplinary Health and Development Study were used to investigate the relationship between presarcopenia at age 45 years and selected early markers at ages 26, 32, and 38 years.

PARTICIPANTS

Longitudinal data from N=899 participants from the Dunedin Multidisciplinary Health and Development Study.

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

Presarcopenia was defined as low relative appendicular lean mass index assessed by dual energy x-ray absorptiometry and low strength assessed by grip strength. Logistic regressions were used to describe the association between selected markers and presarcopenia at age 45 years.

RESULTS

Multivariate logistic regression revealed that a higher body mass index (BMI) at ages 26, 32, and 38 years was associated with lower likelihood of presarcopenia at age 45 years in both men and women (odds ratio [OR] range, 0.46-0.64). Higher age-normative grip strength at age 38 years in both men and women (OR range, 0.88-0.92) was also associated with lower likelihood for presarcopenia. Lastly, lower self-perceived physical fitness level in men at age 38 years was associated with an increased likelihood of presarcopenia at age 45 years (OR, 9.35; 95% confidence interval, 3.28-26.70).

CONCLUSIONS

BMI and strength were associated with lower likelihood of presarcopenia during middle age. A higher likelihood of presarcopenia was associated with sex-specific lower self-perceived physical fitness. These modifiable biomarkers may serve as targets for clinical screening and early intervention aimed at slowing or preventing progression to sarcopenia in old age.

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.

The Effect of Family Wealth on Physical Function Among Older Adults in Mpumalanga, South Africa: A Causal Network Analysis

Objectives: The aging of the South African population could have profound implications for the independence and overall quality of life of older adults as life expectancy increases. While there is evidence that lifetime socio-economic status shapes risks for later function and disability, it is unclear whether, and how, the wealth of family members shapes these outcomes. We investigated the relationship between outcomes activities of daily living (ADL), grip strength, and gait speed, and the household wealth of non-coresident family members. Methods: Using data from Health and Aging in Africa: A Longitudinal Study of an INDEPTH Community in South Africa (HAALSI) and the Agincourt Health and Demographic Surveillance System (AHDSS), we examined the relationship between physical function and household and family wealth in the 13 preceding years. HAALSI is a cohort of 5,059 adults who were 40 years or older at baseline in 2014. Using auto-g-computation-a recently proposed statistical approach to quantify causal effects in the context of a network of interconnected units-we estimated the effect of own and family wealth on the outcomes of interest. Results: We found no evidence of effects of family wealth on physical function and disability. Conclusion: Further research is needed to assess the effect of family wealth in early life on physical function and disability outcomes.

A Systematic Temporal Assessment of Changes in Tendon Stiffness Following Rotator Cuff Repair

OBJECTIVES

How the material properties of the human supraspinatus tendon change following arthroscopic rotator cuff repair is undetermined. Shear wave elastography ultrasound is a relatively new, noninvasive measure of tissue stiffness. We aimed to evaluate any temporal changes in stiffness and/or thickness of supraspinatus tendons in humans following primary arthroscopic rotator cuff repair.

METHODS

Shear wave elastography was performed at three predetermined regions by a single sonographer at 1-, 6-, 12-, 24-, and 52 weeks postoperatively in 50 consecutive single-row inverted mattress primary arthroscopic rotator cuff repairs. One-way ANOVA with Tukey's correction and Spearman's correlation tests was performed.

RESULTS

Of 50 patients, two retore by 1-week and were excluded. Two patients retore at 6 weeks, two at 12 weeks, and one at 24 weeks. The mean tendon stiffness in 48 patients at the tendon footprint increased by 21% (1.32 m/s) at 6 months (P < .001), with the lateral tendon stiffening before the medial tendon. Tendon thickness decreased by 11% (0.6 mm) at 6 weeks (P = .008), then stabilized to 24 weeks. Tendons that were less elastographically stiff at 1 week were more likely to be thinner at 6-weeks (r = .38, P = .010).

CONCLUSIONS

The data supports the hypothesis that rotator cuff tendons repaired using the single-row inverted-mattress technique take 6 weeks to heal to bone. Unlike in other tendons, there was no hypertrophic healing response. Prior to 6 weeks, the tendon may stretch/thin-out, particularly if its material properties, as assessed by shear wave elastography, are inferior. The material properties of the tendon improved at the tendon insertion site first, then medially out to 12 months post-repair.

High-intensity interval aerobic and resistance training to counteract low relative lean soft tissue mass in middle age: A randomized controlled trial

BACKGROUND

Age-related loss of skeletal muscle mass and function begins in early middle age, yet research to date has focused on older individuals, limiting our understanding of interventions earlier in the lifespan. To date, no high-intensity interval training studies have been conducted in middle-aged adults with low relative lean soft tissue mass.

METHODS

Eighty-two middle-aged adults (40-50 years of age) with low appendicular lean soft tissue mass index confirmed with dual energy x-ray absorptiometry (DXA) were randomly allocated (1:1) to group-based, 20-week, three times a week, high-intensity aerobic and resistance training (HIART) program or 60-min education session (Control). The primary outcome was change in total lean soft tissue mass measured by DXA. Secondary outcomes included cardiorespiratory fitness, physical function (handgrip strength, gait speed, 30-seconds sit-to-stand, quadriceps strength and muscle quality). Measures were obtained at baseline (0 weeks), mid-intervention (10 weeks) and post-intervention (20 weeks).

RESULTS

Mean age in HIART was 44.8 (SD 3.2) and 45.4 (SD 2.9) in Control group. The majority of the participants were female with 88 % in HIART and 83 % in Control group. Mean BMI in HIART was 25.8 kg/m² (SD 3.5) and 26.4 kg/m² (SD 4.1) Control group. Intention to treat analysis showed that post-intervention, HIART increased significantly more total lean soft tissue mass (0.8 kg, 95%CI 0.15, 1.46), appendicular lean soft tissue mass index (0.2 kg/m², 95%CI 0.09, 0.33), peak oxygen uptake (5.18 mL/min/kg, 2.97 to 7.39 95%CI), grip strength (2.2 kg, 95%CI 0.09, 4.32), and 30-s sit-to-stand (1.3 times, 95%CI 0.43, 2.12) with significantly greater reductions in body fat percentage (-1.1 %, 95%CI -2.03, -0.10) and maximum gait speed (-0.2 m/s, 95 % CI -0.34, -0.03) compared Control.

CONCLUSION

The HIART program is an effective exercise intervention to increase total lean soft tissue mass in middle-aged adults with low relative lean soft tissue mass compared to a waitlist control group.

Association of sarcopenia with important health conditions among community-dwelling Asian women

This study aimed to examine sarcopenia prevalence using the Asian Working Group for Sarcopenia 2019 (AWGS) and the Foundation for the National Institutes of Health (FNIH) definitions, and their associations with important health conditions affecting midlife Singaporean women. Muscle mass and function were objectively assessed in 1201 healthy community-dwelling subjects aged 45-69 years under the Integrated Women's Health Program (IWHP). Dual-energy X-ray absorptiometry (DXA), handgrip strength and the Short Physical Performance Battery (SPPB) were measured, and the relationship between sarcopenia with hypertension, type 2 diabetes (T2DM), osteoporosis, depression/anxiety, and urinary incontinence were examined using binary logistic regression models. Sarcopenia prevalence was 18.0% and 7.7% by the AWGS and FNIH criteria respectively. Osteoporosis (aOR: 1.74, 95% CI: 1.02, 2.94) and T2DM (aOR: 1.98, 95% CI: 1.14, 3.42) was positively associated with AWGS- and FNIH-defined sarcopenia respectively, while hypertension was not, after adjustment for age, ethnicity, education levels and menopausal status. A negative percent agreement of 95.6% suggests good agreement between the criteria in the absence of sarcopenia. Even though they represent a single concept, sarcopenia by either criterion differed in their relationships with diabetes and osteoporosis, suggesting the need for further rationalization of diagnostic criteria.

A prediction model for skeletal muscle evaluation and computed tomography-defined sarcopenia diagnosis in a predominantly overweight cohort of patients with head and neck cancer

PURPOSE

This study investigates the feasibility of computed tomography (CT)-defined sarcopenia assessment using a prediction model for estimating the cross-sectional area (CSA) of skeletal muscle (SM) in CT scans at the third lumbar vertebra (L3), using measures at the third cervical level (C3) in a predominantly overweight population with head and neck cancer (HNC).

METHODS

Analysis was conducted on adult patients with newly diagnosed HNC who had a diagnostic positron emission tomography-CT scan. CSA of SM in CT images was measured at L3 and C3 in each patient, and a predictive formula developed using fivefold cross-validation and linear regression modelling. Correlation and agreement between measured CSA at L3 and predicted values were evaluated using intraclass correlation coefficients (ICC) and Bland-Altman plot. The model's ability to identify sarcopenia was investigated using Cohen's Kappa (k).

RESULTS

A total of 109 patient scans were analysed, with 64% of the cohort being overweight or obese. The prediction model demonstrated high level of correlation between measured and predicted CSA measures (ICC 0.954, r = 0.916, p < 0.001), and skeletal muscle index (SMI) (ICC 0.939, r = 0.883, p < 0.001). Bland-Altman plot showed good agreement in SMI, with mean difference (bias) = 0.22% (SD 8.65, 95% CI - 3.35 to 3.79%), limits of agreement (- 16.74 to 17.17%). The model had a sensitivity of 80.0% and specificity of 85.0%, with moderate agreement on sarcopenia diagnosis (k = 0.565, p = 0.004).

CONCLUSION

This model is effective in predicting lumbar SM CSA using measures at C3, and in identifying low SM in a predominately overweight group of patients with HNC.

Muscle fat infiltration but not muscle cross-sectional area is independently associated with bone mineral density at the lumbar spine

OBJECTIVE

Although sarcopenia and osteoporosis are inter-related conditions that are common with advancing age, few studies have explored relationships between muscle quality and bone mineral density (BMD). We investigated age- and sex-specific paraspinal muscle fat infiltration (MFI), muscle cross-sectional area (CSA), and spine volumetric BMD (vBMD) in healthy Chinese adults.

METHODS

605 healthy adults aged 20-59 years (340 women, mean age 39.2 years; 265 men, mean age 38.8 years) had axial T2WI MRI imaging of the lumbar spine and CSA (cm2) and MFI (%) were measured in the psoas and multifidus and erector spinae (MF-ES) muscles (L3-L4). MFI measurements were calibrated against a region of interest in an adjacent area of subcutaneous pure fat. L2-L4 vBMD was measured by quantitative CT. Age- and sex-specific subgroups were compared using the Mann-Whitney test. Multiple regression was used to test independent associations of MFI and CSA with vBMD.

RESULTS

Females had lower CSA and higher MFI than males in both the psoas and MF-ES muscles (p < 0.001). In females and males, MF-ES MFI increased with age (p < 0.001) and in females age-related increases were observed for the psoas muscles (p < 0.05). Greater fat infiltration of the MS-ES muscle unit was associated with lower vBMD in both sexes (p < 0.001) but not with CSA. Following adjustment for demographic variables and CSA, MS-ES MFI remained predictive of vBMD (β = -0.408 to -0.157, p < 0.001).

CONCLUSION

We have demonstrated that, independent of CSA and demographic variables, MFI of the MF-ES muscles is predictive of lower lumbar spine vBMD in both sexes.

ADVANCES IN KNOWLEDGE

This is the first study to demonstrate that, independent of muscle size and demographic variables, MFI of the paraspinal MF-ES muscles is predictive of lower lumbar spine vBMD in both sexes.

Protein interventions augment the effect of resistance exercise on appendicular lean mass and handgrip strength in older adults: a systematic review and meta-analysis of randomized controlled trials

BACKGROUND

Increased protein intake is suggested as a strategy to slow or reverse the loss of muscle mass and strength observed in sarcopenia, but results from studies that directly tested this possibility have been inconsistent.

OBJECTIVES

We assessed the evidence on the effects of whole protein supplementation or higher-protein diets, without the use of amino acids or supplements known to stimulate hypertrophy, alone or in combination with resistance exercise (RE) interventions, on lean body mass (LBM) and strength in older adults.

METHODS

A systematic search was conducted using PubMed, Medline, Web of Science, and Cochrane CENTRAL databases from January 1990 to July 2021. Randomized controlled trials that assessed the effects of protein supplementation and/or higher-protein dietary interventions in older adults (mean age ≥50 y) on total LBM, appendicular lean mass (ALM), and handgrip (HG) and knee extension (KE) strength were included.

RESULTS

Twenty-eight studies were identified. In pooled analysis, compared with lower protein controls, protein supplementation did not have a significant positive effect on total LBM [weighted mean difference in change (WMD): 0.34; 95% CI: -0.21, 0.89; I2 = 90.01%], ALM (WMD: 0.4; 95% CI: -0.01, 0.81; I2 = 90.38%), HG strength (WMD: 0.69; 95% CI: -0.69, 2.06; I2 = 94.52%), or KE strength (WMD: 1.88; 95% CI: -0.6, 4.35; I2 = 95.35%). However, in interventions that used also RE, statistically significant positive effects of protein were observed for ALM (WMD: 0.54; 95% CI: 0.03, 1.05; I2 = 89.76%) and HG (WMD: 1.71; 95% CI: 0.12, 3.30; I2 = 88.71%). Meta-regression revealed no significant association between age, per-meal protein dose, duration, and baseline protein intake with change in any outcome. Subgroup analysis revealed the statistically significant effects on ALM occurred only in sarcopenic/frail populations (WMD: 0.88; 95% CI: 0.51, 1.25; I2 = 79.0%). Most studies (n = 22) had some risk of bias.

CONCLUSIONS

In older adults performing RE, increased protein intake leads to greater ALM and HG strength compared with lower protein controls. Without RE, protein has no additional benefit on changes in total LBM, ALM, or HG strength.

Clinical Significance of Serum Zinc Levels on the Development of Sarcopenia in Cirrhotic Patients

BACKGROUND/AIM

Sarcopenia increases the mortality in patients with cirrhosis. Approximately 60% of zinc is accumulated in skeletal muscle. We aimed to determine the role of subclinical zinc deficiency on sarcopenia development in patients with cirrhosis.

PATIENTS AND METHODS

We enrolled 151 patients with cirrhosis and divided them into the group with normal serum zinc levels (Group N: 80-130 μg/dl; n=38) and group with subclinical zinc deficiency (Group D: <80 μg/dl; n=113). The risk factors for sarcopenia were then investigated.

RESULTS

Group D had more sarcopenia cases than Group N (31.0% vs. 13.2%). In group D, HGS exhibited a weakly positive but significant correlation with serum zinc levels (R=0.287, p=0.00212), serum zinc levels negatively correlated with both ammonia and myostatin levels (R=-0.254, p=0.0078; R=-0.33, p<0.01), and low zinc levels were independently associated with sarcopenia development.

CONCLUSION

Patients with cirrhosis showing subclinical zinc deficiency have a significantly higher risk of developing sarcopenia.

A Combination of Serum Biomarkers in Elderly Patients with Sarcopenia: A Cross-Sectional Observational Study

BACKGROUND

The pathogenesis of sarcopenia in the elderly has not yet been fully understood. This study aimed to explore the relationship between sarcopenia and several serum biomarkers in elderly population.

METHODS

It was an observational cross-sectional study of data collected from 70 patients. According to the criteria of the Asian Working Group for Sarcopenia (AWGS), subjects were divided into the sarcopenia group and nonsarcopenic group. We compared age, body mass index (BMI), biochemical indexes, smoking status, underlying disease, muscle mass, handgrip strength (HS), gait speed (GS), skinfold thickness, muscle thickness, and IL-6, IL-10, IL-17A, and TNF-α levels between these groups.

RESULTS

Of the 70 subjects, 35 patients were diagnosed with sarcopenia. The number of men was higher than that of women in both groups. The patients with sarcopenia were older and had lower BMI and muscle thickness but higher SARC-F questionnaire scores. However, the difference in smoking status and skinfold thickness between these two groups were not statistically significant. Higher IL-6, IL-17A, and TNF-α levels were observed in participants with sarcopenia (P < 0.05). Patients with sarcopenia had a lower IL-10 level. Positive associations were present between the severity of sarcopenia and IL-6, IL-17A, and TNF-α levels, while there was an inverse correlation between the presence of sarcopenia and IL-10 level.

CONCLUSIONS

Our research found that in sarcopenic elderly subjects, the serum levels of several biomarkers, such as IL-6, IL-17A, and TNF-α, were higher than those in nonsarcopenic elderly persons. Further studies are needed to explore the possible molecular mechanisms and discover new therapeutic targets.

Sarcopenia: What a Surgeon Should Know

Sarcopenia is an increasingly frequent syndrome characterized by generalized and progressive loss of muscle mass, reduction in muscle strength, and resultant functional impairment. This condition is associated with increased risk of falls and fractures, disability, and increased risk of death. When a sarcopenic patient undergoes major surgery, it has a higher risk of complications and postoperative mortality because of less resistance to surgical stress. It is not easy to recognize a sarcopenic patient preoperatively, but this is essential to evaluate the correct risk to benefit ratio. The role of sarcopenia in surgical patients has been studied for both oncological and non-oncological surgery. For correct surgical planning, data about sarcopenia are essential to design a correct tailored treatment.

Sarcopenia during COVID-19 lockdown restrictions: long-term health effects of short-term muscle loss

The COVID-19 pandemic is an extraordinary global emergency that has led to the implementation of unprecedented measures in order to stem the spread of the infection. Internationally, governments are enforcing measures such as travel bans, quarantine, isolation, and social distancing leading to an extended period of time at home. This has resulted in reductions in physical activity and changes in dietary intakes that have the potential to accelerate sarcopenia, a deterioration of muscle mass and function (more likely in older populations), as well as increases in body fat. These changes in body composition are associated with a number of chronic, lifestyle diseases including cardiovascular disease (CVD), diabetes, osteoporosis, frailty, cognitive decline, and depression. Furthermore, CVD, diabetes, and elevated body fat are associated with greater risk of COVID-19 infection and more severe symptomology, underscoring the importance of avoiding the development of such morbidities. Here we review mechanisms of sarcopenia and their relation to the current data on the effects of COVID-19 confinement on physical activity, dietary habits, sleep, and stress as well as extended bed rest due to COVID-19 hospitalization. The potential of these factors to lead to an increased likelihood of muscle loss and chronic disease will be discussed. By offering a number of home-based strategies including resistance exercise, higher protein intakes and supplementation, we can potentially guide public health authorities to avoid a lifestyle disease and rehabilitation crisis post-COVID-19. Such strategies may also serve as useful preventative measures for reducing the likelihood of sarcopenia in general and in the event of future periods of isolation.

High-Intensity Interval Aerobic Resistance Training to Counteract Low Relative Appendicular Lean Soft Tissue Mass in Middle Age: Study Protocol for a Randomized Controlled Trial

BACKGROUND

Sarcopenia is the age-related loss of skeletal muscle mass and function and may exist in early middle age. Previous research in this area has focused on resistance training in older individuals; however, there is a lack of intervention trials in middle-aged adults with low relative appendicular lean soft tissue mass who may be at risk for sarcopenia in older age.

OBJECTIVE

This randomized controlled trial aims to determine the effects of a high-intensity interval aerobic resistance training intervention on appendicular lean soft tissue mass in middle-aged adults with low relative appendicular lean soft tissue mass.

METHODS

We will conduct a 40-week, single-blinded randomized controlled trial in 84 middle-aged adults with low appendicular lean soft tissue mass in the wider Dunedin area, New Zealand. We will randomly allocate participants to receive either a group-based, 20-week high-intensity interval aerobic resistance training intervention program or a single, 60-minute education session on current exercise recommendations. After the first 20 weeks, both groups will be given a 20-week home program. The study will assess primary and secondary outcome measures, including body composition (regional and whole-body lean soft tissue mass, fat mass, percentage body fat, measured by dual x-ray absorptiometry), blood biomarkers (cortisol, creatinine, C-reactive protein, lipid profile, hemoglobin), physical fitness (maximum oxygen consumption, blood pressure), physical activity (accelerometry), physical function (handgrip strength, sit-to-stand, gait speed, quadriceps strength), and self-reported questionnaires (health outcomes, self-efficacy, perceived enjoyment of physical activity, and multifactorial lifestyle), at baseline, 20 weeks, and 40 weeks. Physical function and self-reported questionnaires will also be measured at 10 weeks. We will assess the primary outcome measure, total body lean soft tissue mass, at baseline, 20 weeks, and 40 weeks. Analyses will be performed using intention-to-treat principles, comparing the outcomes resulting from the intervention, using linear mixed models.

RESULTS

We obtained ethical approval for this study from The University of Otago Human Ethics Committee on December 10, 2018. Participant recruitment started on February 11, 2019 and was completed on May 14, 2019. Data collection started on February 25, 2019 and was completed on February 28, 2020. We expect to publish the results in January 2021.

CONCLUSIONS

High-intensity interval aerobic resistance training is a time-efficient form of exercise, enabling busy middle-aged adults to meet physical activity recommendations while maximizing training results. The findings can inform the development of future prevention-focused interventions aimed at counteracting the high prevalence of sarcopenia in the aging population.

TRIAL REGISTRATION

Australian New Zealand Clinical Trials Registry (ACTRN12618001778279); https://tinyurl.com/y555z6fz.

INTERNATIONAL REGISTERED REPORT IDENTIFIER (IRRID)

DERR1-10.2196/22989.

Preliminary report; Comparison of the circadian rest-activity rhythm of elderly Japanese community-dwellers according to sarcopenia status

We investigated in a preliminarily study the circadian rest-activity rhythm of elderly Japanese community-dwellers according to sarcopenia status based upon the 2019 updated classification criteria of the Asian Working Group for Sarcopenia. A total of 30 participants were recruited from a single rehabilitation center in northern Japan between July and November 2019. The rest-activity rhythm of those with and without sarcopenia was assessed for 7 consecutive 24 h spans by wrist actigraphy in free-living condition and gait performance in the clinic. As group phenomena, the circadian activity rhythm of the sarcopenia cohort (N = 11) was of significantly lower amplitude and more fragmented than the non-sarcopenia cohort (N = 19). The nonparametric circadian rest activity (RAR) parameters of intra-daily variability (IV), relative amplitude (RA), most active 10-h span (M10), and the least active 5-h span (L5), but not interdaily stability (IS), of the sarcopenia group, were all significantly worse than those of the non-sarcopenia group. Gait performance for the sarcopenia group correlated strongly with the fragmentation and altered amplitude of the RAR. These preliminary findings motivated future longitudinal investigation both to improve the detection of sarcopenia in community dwelling elderly and to inform novel preventive or rehabilitative strategies.

Dysregulated homeostatic pathways in sarcopenia among frail older adults

Sarcopenia, a core feature of the physical frailty syndrome, is characterized by multisystem physiological dysregulation. No study has explored qualitatively the hierarchical network of relationships among different dysregulated pathways involved in the pathogenesis of sarcopenia. We used 40 blood biomarkers belonging to community‐dwelling prefrail and frail older persons to derive measures of multiple physiological pathways, and structural equation modeling to generate path network models of the multisystem physiological dysregulations associated with muscle mass and function (MMF). Insulin–leptin signaling and energy regulation, anabolic sex steroid regulation (testosterone, leptin), and tissue oxygenation (hemoglobin, red cell count) appear to be primary mediating factors exerting direct influences on MMF. There was additionally secondary mediatory involvement of myocyte‐ and adipocyte‐derived cytokines, hypothalamic pituitary adrenal (HPA) stress hormones (cortisol, DHEAS), glomerular function, and immune cell regulatory and inflammatory cytokines and glycoproteins. We conclude that within a hierarchical network of multisystem physiological dysregulations in sarcopenia, dysregulated anabolic and catabolic pathways via sex steroids and insulin–leptin dual signaling and tissue hypoxemia are primary physiological dysregulations responsible for sarcopenia and frailty.

Correlates of Level and Loss of Grip Strength in Later Life: Findings from the English Longitudinal Study of Ageing and the Hertfordshire Cohort Study

Characterisation of grip strength (GS) using isometric dynamometry is central to the definition of sarcopenia. Determinants of low GS include: older age, shorter stature, low physical activity, poor nutrition, socioeconomic disadvantage and multimorbidity. Less is known about risk factors for accelerated loss of GS. We investigated determinants of level and 8-year loss of GS in 3703 men and women (aged 52-82 years) in the English Longitudinal Study of Ageing (ELSA). Four hundred and forty-one men and women (aged 59-71 years) who participated in a 10-year follow-up of the Hertfordshire Cohort Study (HCS) were used for replication. Variables were harmonised between cohorts. Change in GS was characterised using mixed-effects models in ELSA and a residual change approach in HCS and analysed for men and women combined. Men in ELSA and HCS had higher average levels of GS at baseline, and accelerated rates of loss, compared with women. In ELSA, older age, shorter stature and multimorbidity were correlated with lower level, and accelerated rate of loss, of GS in both sexes (accelerated loss of 0.04 (95% CI 0.00-0.08) standard deviation scores per additional morbidity after multivariable adjustment). Socioeconomic disadvantage, low level of physical activity and poorer self-reported health were also correlated with low GS level, but not loss rate, after multivariable adjustment. Analysis in HCS yielded similar results. Our results identify multimorbidity as a modifiable determinant of loss of muscle strength in later life, and raise the possibility that developmental influences may impact on rate of involutional decline in muscle strength.

Evaluation of Intradialytic Hypertension Using Bioelectrical Impedance Combined With Echocardiography in Maintenance Hemodialysis Patients

Although intra-dialytic hypertension (IDH) has been noted in clinical settings for many years, its pathogenesis remains unclear. In this cross-sectional study, we analyzed IDH incidence in our center and the correlation between postdialysis volume state and IDH. One hundred thirty-one maintenance hemodialysis (MHD) patients were enrolled in our study, and bioelectrical impedance (BIA) and echocardiography (ECG) were recorded. In addition, demographic data were collected, and laboratory examinations were conducted. The patients were grouped into four groups according to the change in systolic blood pressure (SBP) between predialysis and postdialysis. The incidence of IDH was 10.7%. The proportion of extracellular water to total body weight (ECW/TW), as evaluated by BIA, was significantly higher in the IDH group than in the other three groups both in pre-and post-dialysis. In particular, postdialysis SBP was highest in the highest tertile interval of ECW/TW. In addition, among the four groups, left ventricular volume (LVV) was highest in the IDH group. Binary logistic analyses revealed that predialysis SBP, postdialysis ECW/TW and LVV were independent risk factors of intradialytic hypertension. When predicting IDH, the AUC of the ROC curve was higher for ECW/TW combined with LVV (0.752, 95% CI 0.613-0.896) than for either LVV or ECW/TW alone. Our study further showed that post-dialysis volume expansion is an important factor for the development of IDH.

Poor maternal nutrition and accelerated postnatal growth induces an accelerated aging phenotype and oxidative stress in skeletal muscle of male rats

‘Developmental programming’, which occurs as a consequence of suboptimal in utero and early environments, can be associated with metabolic dysfunction in later life, including an increased incidence of cardiovascular disease and type 2 diabetes, and predisposition of older men to sarcopenia. However, the molecular mechanisms underpinning these associations are poorly understood. Many conditions associated with developmental programming are also known to be associated with the aging process. We therefore utilized our well-established rat model of low birth weight and accelerated postnatal catch-up growth (termed ‘recuperated’) in this study to establish the effects of suboptimal maternal nutrition on age-associated factors in skeletal muscle. We demonstrated accelerated telomere shortening (a robust marker of cellular aging) as evidenced by a reduced frequency of long telomeres (48.5-8.6 kb) and an increased frequency of short telomeres (4.2-1.3 kb) in vastus lateralis muscle from aged recuperated offspring compared to controls. This was associated with increased protein expression of the DNA-damage-repair marker 8-oxoguanine-glycosylase (OGG1) in recuperated offspring. Recuperated animals also demonstrated an oxidative stress phenotype, with decreased citrate synthase activity, increased electron-transport-complex activities of complex I, complex II-III and complex IV (all markers of functional mitochondria), and increased xanthine oxidase (XO), p67^phox and nuclear-factor kappa-light-chain-enhancer of activated B-cells (NF-κB). Recuperated offspring also demonstrated increased antioxidant defense capacity, with increased protein expression of manganese superoxide dismutase (MnSOD), copper-zinc superoxide dismutase (CuZnSOD), catalase and heme oxygenase-1 (HO1), all of which are known targets of NF-κB and can be upregulated as a consequence of oxidative stress. Recuperated offspring also had a pro-inflammatory phenotype, as evidenced by increased tumor necrosis factor-α (TNFα) and interleukin-1β (IL1β) protein levels. Taken together, we demonstrate, for the first time to our knowledge, an accelerated aging phenotype in skeletal muscle in the context of developmental programming. These findings may pave the way for suitable interventions in at-risk populations.

Summary: Muscle of ‘developmentally programmed’ rat offspring demonstrated accelerated aging and oxidative stress, which could explain why some individuals are at greater risk of developing age-associated muscular dysfunction than others.

Limited and excess protein intake of pregnant gilts differently affects body composition and cellularity of skeletal muscle and subcutaneous adipose tissue of newborn and weanling piglets

AIM

This study investigated whether dietary protein intake less (50%) or greater (250%) than requirements throughout gestation differently affects offspring body composition and cellular properties of skeletal muscle and subcutaneous adipose tissue (SCAT).

METHODS

Primiparous gilts were fed iso-energetic diets containing adequate (22 AP), high (21 HP), or low (19 LP) protein contents. Newborn (n = 166) and weanling piglets cross-fostered to sows fed a standard diet (day 28; n = 83) were examined by morphological, biochemical, histological, and molecular analyses of the body, SCAT, and semitendinosus, longissimus, biceps femoris muscles.

RESULTS

Lowered birth weight (BW) in response to the HP and LP diets (p < 0.01) resulted from decreases in all body constituents in LP, and mainly from reduced body fat in HP piglets (p < 0.05). In the light BW class within litters, HP piglets exhibited a greater percentage of muscle tissue (p < 0.05) than LP piglets. Less SCAT mass in HP and LP piglets resulted from reduced (p < 0.05) number, but not the size of adipocytes. The LP diet adversely affected myogenesis and muscular differentiation derived from less (p < 0.01) primary and secondary myofibers, lower creatine kinase activity (p < 0.05), less IGF2 mRNA (p < 0.10), and greater expression of the embryonic myosin heavy chain isoform (p < 0.01). Catch-up growth of LP but not HP pigs until day 28 increased body fat (p = 0.01). Despite compensated muscle growth in LP piglets, the deficit in myofiber number remained.

CONCLUSION

Poor intrauterine environment by limited and excess protein supply retards fetal growth, but only limited protein supply impairs myogenesis, persistently restricts muscle growth potential, and favors obesity at infancy.