Live strong and prosper: the importance of skeletal muscle strength for healthy ageing

Lean Mass, Muscle Strength, and Muscle Quality in Retired Rugby Players: The UK Rugby Health Project

Although athletes from sports such as rugby have greater lean mass and strength during their playing careers, little is known about these characteristics post-retirement. Therefore, this study investigated lean mass, strength, and muscle quality in retired elite and amateur rugby players and non-contact athletes. Retired elite male rugby players (n=42, 43.9±10.3 y; 101.1±13.4 kg; 1.82±0.09 m), amateur rugby players (n=46, 48.0±10.5 y; 98.9±16.6 kg; 1.79±0.07 m) and non-contact athletes (n=30, 51.3±12.5 y; 91.3±13.4 kg; 1.79±0.07 m) received one total body dual-energy X-ray absorptiometry assessment of appendicular lean mass (ALM) and ALM index (ALMI). Grip strength was measured, and muscle quality (grip strength/unit of arm lean mass) was calculated. Sarcopenia was identified as ALMI<7.23 kg/m² and handgrip strength<37.2 kg. Total lean mass, ALM and grip strength were greater in the elite rugby compared to amateur rugby and non-contact groups (p<0.01). There were no significant differences in muscle quality or sarcopenia prevalence. Retired elite rugby players had greater lean mass and grip strength than amateur rugby and non-contact athletes, although muscle quality was similar. The greater lean mass and strength might reflect genetic influences or previous participation in a highly physical sport.

Targeted proteomics of appendicular skeletal muscle mass and handgrip strength in black South Africans: a cross-sectional study

Although appendicular skeletal muscle mass (ASM) and handgrip strength (HGS) are key components of sarcopenia, their underlying biological mechanisms remain poorly understood. We aimed to investigate associations of circulating biomarkers with ASM and HGS in middle-aged black South Africans. This study consisted of 934 black South Africans (469 men and 465 women, aged 41-72 years) from the Middle-aged Soweto cohort. Linear regression models were used to examine relationships between 182 biomarkers (measured with proximity extension assay) and dual-energy X-ray absorptiometry-measured ASM and dynamometer-measured HGS. Age, height, sex, smoking, alcohol, food insecurity, physical activity, visceral adipose tissue, HIV and menopausal status were included as confounders. Regression models showing sex-interactions were stratified by sex. The Benjamini-Hochberg false discovery rate (FDR) was used to control for multiple testing, and FDR-adjusted P values were reported. In the total sample, 10 biomarkers were associated with higher ASM and 29 with lower ASM (P < 0.05). Out of these 39 biomarkers, 8 were also associated with lower HGS (P < 0.05). MMP-7 was associated with lower HGS only (P = 0.011) in the total sample. Sex-interactions (P < 0.05) were identified for 52 biomarkers for ASM, and 6 for HGS. For men, LEP, MEPE and SCF were associated with higher ASM (P < 0.001, = 0.004, = 0.006, respectively), and MEPE and SCF were also associated with higher HGS (P = 0.001, 0.012, respectively). Also in men, 37 biomarkers were associated with lower ASM (P < 0.05), with none of these being associated with lower HGS. Furthermore, DLK-1 and MYOGLOBIN were associated with higher HGS only (P = 0.004, 0.006, respectively), while GAL-9 was associated with lower HGS only (P = 0.005), among men. For women, LEP, CD163, IL6, TNF-R1 and TNF-R2 were associated with higher ASM (P < 0.001, = 0.014, = 0.027, = 0.014, = 0.048, respectively), while IGFBP-2, CTRC and RAGE were associated with lower ASM (P = 0.043, 0.001, 0.014, respectively). No biomarker was associated with HGS in women. In conclusion, most biomarkers were associated with ASM and not HGS, and the associations of biomarkers with ASM and HGS displayed sex-specificity in middle-aged black South Africans. Proteomic studies should examine ASM and HGS individually. Future research should also consider sexual dimorphism in the pathophysiology of sarcopenia for development of sex-specific treatment and diagnostic methods.

Uncovering the effects of gender affirming hormone therapy on skeletal muscle and epigenetics: protocol for a prospective matched cohort study in transgender individuals (the GAME study)

INTRODUCTION

Gender affirming hormone therapy (GAHT) is increasingly used by transgender individuals and leads to shifts in sex hormone levels. Skeletal muscle is highly responsive to hormone activity, with limited data on the effects of GAHT on different human tissues. Here, we present the protocol for the GAME study (the effects of Gender Affirming hormone therapy on skeletal Muscle training and Epigenetics), which aims to uncover the effects of GAHT on skeletal muscle 'omic' profiles (methylomics, transcriptomics, proteomics, metabolomics) and markers of skeletal muscle health and fitness.

METHODS AND ANALYSIS

This study is a prospective age-matched cohort study in transgender adults commencing GAHT (n=80) and age-matched individuals not commencing GAHT (n=80), conducted at Austin Health and Victoria University in Victoria, Australia. Assessments will take place prior to beginning GAHT and 6 and 12 months into therapies in adults commencing GAHT. Age-matched individuals will be assessed at the same time points. Assessments will be divided over three examination days, involving (1) aerobic fitness tests, (2) muscle strength assessments and (3) collection of blood and muscle samples, as well as body composition measurements. Standardised diets, fitness watches and questionnaires will be used to control for key confounders in analyses. Primary outcomes are changes in aerobic fitness and muscle strength, as well as changes in skeletal muscle DNA methylation and gene expression profiles. Secondary outcomes include changes in skeletal muscle characteristics, proteomics, body composition and blood markers. Linear mixed models will be used to assess changes in outcomes, while accounting for repeated measures within participants and adjusting for known confounders.

ETHICS AND DISSEMINATION

The Austin Health Human Research Ethics Committee (HREC) and Victoria University HREC granted approval for this study (HREC/77146/Austin-2021). Findings from this project will be published in open-access, peer-reviewed journals and presented to scientific and public audiences.

TRIAL REGISTRATION NUMBER

ACTRN12621001415897; Pre-results.

Impact of ski geometry data and standing height ratio on the ACL injury risk and its use for prevention in recreational skiers

OBJECTIVES

To evaluate the impact of ski geometry data and standing height ratio on anterior cruciate ligament (ACL) injury risk of male and female recreational skiers.

METHODS

A retrospective questionnaire-based, case-control study of ACL-injured and uninjured recreational skiers was conducted during six consecutive winter seasons. Ski geometry data (ski length, side-cut radius, widths of the tip, waist and tail) were recorded from each participant's skis. Standing heights at the front and rear components of the ski binding were measured with a digital sliding calliper, and the standing height ratio between the front and rear was calculated.

RESULTS

A total of 1817 recreational skiers participated in this study, of whom 392 (21.6%) sustained an ACL injury. Multiple logistic regression analysis indicates a higher age, a lower skill level and riskier behaviour as independent individual risk factors associated with an ACL injury. An increase in ski length, tip width of the ski, standing height at the rear ski binding component, and in standing height ratio were found to be independent equipment-related risk factors for an ACL injury.

CONCLUSION

Reduced ski length, narrower ski tip width, lower rear standing height and a lower standing height ratio (ie, rear component of the ski binding is more elevated compared with the front component) were associated with a reduced likelihood for ACL injury. When buying or renting skis, these parameters could be considered to reduce the likelihood of ACL injury in recreational skiers.

Canine Mobility Maintenance and Promotion of a Healthy Lifestyle

This article highlights the recommendations and considerations for maintaining a healthy canine lifestyle. A key component of a healthy lifestyle is the enhancement and optimization of mobility. Mobility is essential in maintaining a high quality of life and involves the interplay of a dog's structure, posture, body condition score, physical exercise, and a healthy human-animal bond throughout a dog's lifetime.

Factors Associated with Handgrip Strength Among Older Adults in Malaysia

Purpose

Handgrip strength (HGS) is indicative of overall physical health among older adults. A decrease in HGS may be associated with an increased risk of disease. The aim of this study is to determine the factors associated with HGS among older adults in Malaysia.

Patients and Methods

One thousand two hundred four (1204) participants from urban and rural areas in Selangor state, Malaysia, were recruited. Sociodemographic and health-related conditions were gathered through a comprehensive face-to-face interview, followed by HGS assessments by a handgrip dynamometer. Subsequently, multiple linear regression was used to test the main association with the HGS.

Results

A total of 691 participants (57.4%) were male, and 513 (42.6%) were female. Males had a mean HGS of 30.0 (SD 7.53) kg, and females had a mean HGS of 19.4 (SD 5.28) kg. Males’ handgrip strength was significantly reduced with increasing age, physically inactive, and diabetes (all at the level p<0.001) after adjusting for social-demographic characteristics and health-related variables. Meanwhile, for females, the HGS was significantly decreased with age (p<0.001), physically inactive (p<0.001) and hypertension (p=0.03). However, female HGS was positively related to BMI (p<0.001).

Conclusion

The study contributed to a better understanding of factors associated with HGS, and thus, the HGS is recommended as a section in the health evaluation among high-risk older adults as the strategy of disease control and prevention.

Combined effects of handgrip strength and sensory impairment on the prevalence of cognitive impairment among older adults in Korea

Older adults commonly experience concurrent lower handgrip strength and sensory impairment. However, previous studies have analyzed the individual effects of either handgrip strength or sensory impairment on cognitive impairment. To address this gap, this study investigated the combined effects of handgrip strength and sensory impairment on cognitive impairment among older adults. In total, 2930 participants aged 65 and older were analyzed using 2014–2018 data from the Korean Longitudinal Study of Aging. Participants underwent assessments of handgrip strength (grip dynamometer), sensory impairment (self-reported responses), and cognitive impairment (Korean version of the Mini-Mental State Examination). Low handgrip strength, compared to normal handgrip strength, was associated with cognitive impairment. In participants with low handgrip strength, vision and hearing impairment were associated with cognitive impairment (odds ratio [OR] 1.36, 95% confidence interval [CI] 1.06–1.75; OR 2.58, 95% CI 1.77–3.78, respectively) compared to those with normal handgrip strength. Participants with low handgrip strength and dual sensory impairment had the highest OR for cognitive impairment (OR 3.73, 95% CI 2.65–5.25). Due to the strong association of low handgrip strength and dual sensory impairment with cognitive impairment, people living with low handgrip strength and dual sensory impairment should be classified as a high-risk group for cognitive impairment and should be prioritized for interventions.

Influencing factors for the decline of limb muscle strength and the association with all-cause mortality: evidence from a nationwide population-based cohort study

BACKGROUND

The decline of muscle strength, a typical characteristic of sarcopenia, greatly affects aging-related health outcomes; however, prospective data on influencing factors and mortality in the Chinese population are relatively sparse.

AIMS

We investigated the influencing factors for the declined limb muscle strength and the association with all-cause mortality among the elderly Chinese individuals aged ≥ 65 years in a large long-term prospective cohort study.

METHODS

We used data from the China Health and Retirement Longitudinal Study (CHARLS). Logistic regression analyses were performed to investigate the influencing factors of declined limb muscle strength. Cox proportional hazard models were used to analyze the impact on all-cause mortality, whose performance was evaluated by train-test cross-validation.

RESULTS

The prevalences of declined upper and lower limb strength, which were defined by low hand grip strength (HS) and gait speed (GS), respectively, were 34.4% and 59.7%. The declined HS was significantly associated with older age (p < 0.001), female (p < 0.001), lower educational level (p < 0.001), lower BMI (p < 0.001), and combined with chronic diseases (p = 0.001). Moreover, the declined limb muscle strength was correlated with all-cause mortality (HR: 1.13, 95% CI 1.03-1.21 for HS; HR: 1.09, 95% CI 1.04-1.15 for GS), according to a multi-adjusted model with moderate predictive ability (C-index: 0.714, AUC of 7 year follow-up: 0.716).

CONCLUSIONS

The decline of limb muscle strength was prevalent among elderly Chinese individuals and had a strong impact on all-cause mortality. Identification of key populations and tailored interventions on their influencing factors should be implemented in further research.

Acute normobaric hypoxia blunts contraction-mediated mTORC1- and JNK-signaling in human skeletal muscle

Aim

Hypoxia has been shown to reduce resistance exercise‐induced stimulation of protein synthesis and long‐term gains in muscle mass. However, the mechanism whereby hypoxia exerts its effect is not clear. Here, we examine the effect of acute hypoxia on the activity of several signalling pathways involved in the regulation of muscle growth following a bout of resistance exercise.

Methods

Eight men performed two sessions of leg resistance exercise in normoxia or hypoxia (12% O₂) in a randomized crossover fashion. Muscle biopsies were obtained at rest and 0, 90,180 minutes after exercise. Muscle analyses included levels of signalling proteins and metabolites associated with energy turnover.

Results

Exercise during normoxia induced a 5‐10‐fold increase of S6K1^Thr389 phosphorylation throughout the recovery period, but hypoxia blunted the increases by ~50%. Phosphorylation of JNK^{Thr183/Tyr185} and the JNK target SMAD2^{Ser245/250/255} was increased by 30‐ to 40‐fold immediately after the exercise in normoxia, but hypoxia blocked almost 70% of the activation. Throughout recovery, phosphorylation of JNK and SMAD2 remained elevated following the exercise in normoxia, but the effect of hypoxia was lost at 90‐180 minutes post‐exercise. Hypoxia had no effect on exercise‐induced Hippo or autophagy signalling and ubiquitin‐proteasome related protein levels. Nor did hypoxia alter the changes induced by exercise in high‐energy phosphates, glucose 6‐P, lactate or phosphorylation of AMPK or ACC.

Conclusion

We conclude that acute severe hypoxia inhibits resistance exercise‐induced mTORC1‐ and JNK signalling in human skeletal muscle, effects that do not appear to be mediated by changes in the degree of metabolic stress in the muscle.

The m6A methyltransferase METTL3 regulates muscle maintenance and growth in mice

Skeletal muscle serves fundamental roles in organismal health. Gene expression fluctuations are critical for muscle homeostasis and the response to environmental insults. Yet, little is known about post-transcriptional mechanisms regulating such fluctuations while impacting muscle proteome. Here we report genome-wide analysis of mRNA methyladenosine (m⁶A) dynamics of skeletal muscle hypertrophic growth following overload-induced stress. We show that increases in METTL3 (the m⁶A enzyme), and concomitantly m⁶A, control skeletal muscle size during hypertrophy; exogenous delivery of METTL3 induces skeletal muscle growth, even without external triggers. We also show that METTL3 represses activin type 2 A receptors (ACVR2A) synthesis, blunting activation of anti-hypertrophic signaling. Notably, myofiber-specific conditional genetic deletion of METTL3 caused spontaneous muscle wasting over time and abrogated overload-induced hypertrophy; a phenotype reverted by co-administration of a myostatin inhibitor. These studies identify a previously unrecognized post-transcriptional mechanism promoting the hypertrophic response of skeletal muscle via control of myostatin signaling.

Muscle undergoes hypertrophy and atrophy in response to physiological stimuli or in pathological conditions, which is partially controlled through altered gene expression. Here the authors report that m⁶A methyltransferase METTL3 and mRNA m⁶A post-transcriptional modifications as a mechanism that regulates muscle hypertrophy and atrophy via myostatin signalling in mice.

Preliminary evidence of differential expression of myogenic and stress factors in skeletal muscle of older adults with low muscle strength

The age-related loss of muscle strength and mass, or sarcopenia, is a growing concern in the ageing population. Yet, it is not fully understood which molecular mechanisms underlie sarcopenia. Therefore, the present study compared the protein expression profile, such as catabolic, oxidative, stress-related and myogenic pathways, between older adults with preserved (8 ♀ and 5 ♂; 71.5 ±2.6 years) and low muscle strength (6 ♀ and 5 ♂; 78.0±5.0 years). Low muscle strength was defined as chair stand test time >15 seconds and/or handgrip strength <16kg (women) or <27kg (men) according the EWGSOP2 criteria. Catabolic signaling (i.e. FOXO1/3a, MuRF1, MAFbx, LC3b, Atg5, p62) was not differentially expressed between both groups, whereas the mitochondrial marker COX-IV, but not PGC1α and citrate synthase, was lower in the low muscle strength group. Stress factors CHOP and p-ERK1/2 were higher (~1.5-fold) in older adults with low muscle strength. Surprisingly, the inflammatory marker p-p65NF-κB was ~7-fold higher in older adults with preserved muscle strength. Finally, expression of myogenic factors (i.e. Pax7, MyoD, desmin; ~2-fold) was higher in adults with low muscle strength. To conclude, whereas the increased stress factors might reflect the age-related deterioration of tissue homeostasis, e.g. due to misfolded proteins (CHOP), upregulation of myogenic markers in the low strength group might be an attempt to compensate for the gradual loss in muscle quantity and quality. These data might provide valuable insights in the processes that underlie sarcopenia.

NOT JUST CALORIC RESTRICTION: A COMPLEX APPROACH TO PROLONG LIFESPAN AND IMPROVE QUALITY OF LIFE

Aging is an urgent healthcare issue in view of the rapid growth of the proportion of older persons. Searching for reliable aging biomarkers and prolonging lifespan are increasingly important scientific directions. Experimental gerontology helps to explore fundamental facts which are not always applicable in clinical scenarios. As an example, caloric restriction is one of the key interventions that prolongs laboratory animals’ lifespan and ameliorates some, but not all, aging biomarkers in humans. Consequences of overeating such as obesity, insulin resistance, type 2 diabetes, and metabolic syndrome are taking their toll with aging, making caloric restriction a hot topic in gerontology and geriatrics. Nevertheless, caloric restriction is not widely applicable in view of poor adherence to and limitations of strict diets. Drugs mimicking caloric restrictions, the so-called caloric restriction mimetics, are developed to overcome these limitations. Caloric restriction alone is not a panacea since metabolic pathways are complex and not responsive to a single intervention. Fasting and exercising are additional options for reducing effects of excessive intake of calories. Arguably, physical activity significantly improves the quality of life at old age and delays the onset of overt insulin resistance and associated diseases. Thus, developing optimal fasting and exercising schemes is becoming increasingly important. Such interventions are confounded by a number of factors, including circadian and other biorhythms and baseline metabolic activity. It is justifiable to test fasting and exercising in experimental animals to reveal numerous confounding factors. A hypothesis in this article points to the role of complex interventions such as moderate and balanced diet, intermittent fasting, and physical exercise adjusted to circadian rhythms for prolonging life and improving quality of life. The hypothesis may shed light on fundamental mechanisms of aging and perspectives of anti-aging drug therapies.

Potential Benefits of a Minimal Dose Eccentric Resistance Training Paradigm to Combat Sarcopenia and Age-Related Muscle and Physical Function Deficits in Older Adults

The ability of older adults to perform activities of daily living is often limited by the ability to generate high mechanical outputs. Therefore, assessing and developing maximal neuromuscular capacity is essential for determining age-related risk for functional decline as well as the effectiveness of therapeutic interventions. Interventions designed to enhance neuromuscular capacities underpinning maximal mechanical outputs could positively impact functional performance in daily life. Unfortunately, < 10% of older adults meet the current resistance training guidelines. It has recently been proposed that a more “minimal dose” RT model may help engage a greater proportion of older adults, so that they may realize the benefits of RT. Eccentric exercise offers some promising qualities for such an approach due to its efficiency in overloading contractions that can induce substantial neuromuscular adaptations. When used in a minimal dose RT paradigm, eccentric-based RT may be a particularly promising approach for older adults that can efficiently improve muscle mass, strength, and functional performance. One approach that may lead to improved neuromuscular function capacities and overall health is through heightened exercise tolerance which would favor greater exercise participation in older adult populations. Therefore, our perspective article will discuss the implications of using a minimal dose, submaximal (i.e., low intensity) multi-joint eccentric resistance training paradigm as a potentially effective, and yet currently underutilized, means to efficiently improve neuromuscular capacities and function for older adults.

A 12-Week Randomized Double-Blind Placebo-Controlled Clinical Trial, Evaluating the Effect of Supplementation with a Spinach Extract on Skeletal Muscle Fitness in Adults Older Than 50 Years of Age

The aim of a 12-week randomized double-blind placebo-controlled study was to assess the effect of daily supplementation with a natural extract of Spinacia oleracea L. (4 × 500 mg capsules/day; total 2 g per day) combined with a moderate-intensity training program (1 h session/3 times a week) on skeletal muscle fitness in adults over 50 years of age. Muscle strength assessed by isokinetic and isometric dynamometry improved significantly in the experimental (n = 23) and the placebo (n = 22) groups, but the magnitude of improvement was higher in the experimental group, with between-group differences in almost all variables, including isokinetic at 60° s⁻¹ in knee extension, peak torque (p < 0.007); total work per repetition maximum (p < 0.009); isokinetic at 180°s⁻¹ in knee extension, peak torque (p < 0.002); total work (p < 0.007); total work per repetition maximum (p < 0.005); average power (p < 0.027); isometric in knee extension, peak torque (p < 0.005); and average peak torque (p < 0.002). Similar findings were observed for muscle quality. Changes in quality of life (SF-36) were not found, except for improvements in the role physical (p < 0.023) and role emotional (p < 0.001) domains, likely as a result of the physical training sessions. A nutritional survey did not revealed changes in dietary habits. No adverse events were recorded. In subjects over 50 years of age, moderate-intensity strength training combined with daily supplementation for 12 weeks with a natural extract of Spinacia oleracea L. improved muscle-related variables and muscle quality. Maintaining muscle health is a key component of healthy aging.

T1ρ imaging as a non-invasive assessment of collagen remodelling and organization in human skeletal muscle after ligamentous injury

Dysregulation and fibrosis of the extracellular matrix (ECM) in skeletal muscle is a consequence of injury. Current ECM assessment necessitates muscle biopsies to evaluate alterations to the muscle ECM, which is often not practical in humans. The goal of this study was to evaluate the potential of a magnetic resonance imaging sequence that quantifies T1ρ relaxation time to predict ECM collagen composition and organization. T1ρ imaging was performed and muscle biopsies obtained from the involved and non-involved vastus lateralis muscle on 27 subjects who had an anterior cruciate ligament (ACL) tear. T1ρ times were quantified via monoexponential decay curve fitted to a series of T1ρ-weighted images. Several ECM indices, including collagen content and organization, were obtained using immunohistochemistry and histochemistry in addition to hydroxyproline. Model selection with multiple linear regression was used to evaluate the relationships between T1ρ times and ECM composition. Additionally, the ACL-deficient and healthy limb were compared to determine sensitivity of T1ρ to detect early adaptations in the muscle ECM following injury. We show that T1ρ relaxation time was strongly associated with collagen unfolding (t = 4.093, P = 0.0007) in the ACL-deficient limb, and collagen 1 abundance in the healthy limb (t = 2.75, P = 0.014). In addition, we show that T1ρ relaxation time is significantly longer in the injured limb, coinciding with significant differences in several indices of collagen content and remodelling in the ACL-deficient limb. These results support the use of T1ρ to evaluate ECM composition in skeletal muscle in a non-invasive manner. KEY POINTS: Dysregulation and fibrotic transformation of the skeletal muscle extracellular matrix (ECM) is a common pathology associated with injury and ageing. Studies of the muscle ECM in humans have necessitated the use of biopsies, which are impractical in many settings. Non-invasive MRI T1ρ relaxation time was validated to predict ECM collagen composition and organization with aligned T1ρ imaging and biopsies of the vastus lateralis in the healthy limb and anterior cruciate ligament (ACL)-deficient limb of 27 subjects. T1ρ relaxation time was strongly associated with collagen abundance and unfolding in the ACL-deficient limb, and T1ρ relaxation time was strongly associated with total collagen abundance in the healthy limb. T1ρ relaxation time was significantly longer in the ACL-deficient limb, coinciding with significant increases in several indices of muscle collagen content and remodelling supporting the use of T1ρ to non-invasively evaluate ECM composition and pathology in skeletal muscle.

Inflammatory markers are associated with quality of life, physical activity, and gait speed but not sarcopenia in aged men (40-79 years)

BACKGROUND

Age-related chronic low-grade inflammation (inflammaging) is one of the proposed mechanisms behind sarcopenia. However, findings regarding inflammatory markers in sarcopenic older adults are conflicting. This study aimed to determine the association between inflammatory markers, prevalent as well as incident sarcopenia, sarcopenia-defining parameters, quality of life (QoL), and physical activity in middle-aged and older men.

METHODS

Men aged 40-79 years (mean 59.66 ± 11.00y) were recruited from population registers in eight European centres for participation in the European Male Aging study (EMAS). Subjects were assessed at baseline (2003-2005) and again after a median follow-up of 4.29 years. In 2577 participants, associations between baseline inflammatory markers [high-sensitive C-reactive protein (hs-CRP), white blood cell count (WBC), albumin] and baseline physical activity (PASE) and QoL (SF-36) were analysed. In the Leuven and Manchester cohort (n = 447), data were available on muscle mass (whole-body dual X-ray absorptiometry) and strength. In this subgroup, cross-sectional associations between baseline inflammatory markers and sarcopenia-defining parameters (handgrip strength, chair stand test, appendicular lean mass, and gait speed) and prevalent sarcopenia were examined. In a further subgroup (n = 277), associations with knee extensor strength were explored. Longitudinally, predictive value of baseline inflammation on functional decline, physical activity, QoL, and incident sarcopenia was examined. Subgroup analyses were performed in subgroups with chronic inflammation and stratified by age. Linear and logistic regressions were used, adjusted for age, body mass index, centre, and smoking.

RESULTS

At baseline, hs-CRP and WBC were negatively associated with PASE score (hs-CRP: β = -7.920, P < 0.001; and WBC: β = -4.552, P < 0.001) and the physical component score of SF-36 (hs-CRP: β = -1.025, P < 0.001; and WBC: β = -0.364, P < 0.001). Baseline WBC levels were negatively associated with gait speed (β = -0.013; P = 0.025), quadriceps isometric 90° (β = -5.983; P = 0.035) and isokinetic 60°/s peak torque/body weight (β = -5.532; P = 0.027). The prevalence of sarcopenia at baseline was 18.1% (n = 81). Of those without sarcopenia at baseline, 64 (18.6%) satisfied criteria for sarcopenia at follow-up. There were no significant associations between baseline inflammatory markers and either prevalent or incident sarcopenia, or change in level of sarcopenia-defining parameters between baseline and follow-up.

CONCLUSIONS

In middle-aged and older men, hs-CRP and WBC were negatively associated with QoL and PASE scores, while WBC was negatively associated with gait speed and knee strength. Associations with hs-CRP remained significant in all ages, whereas WBC levels were only associated with PASE, gait speed and knee strength in older adults (60-79 years). Baseline inflammatory markers (hs-CRP, WBC and albumin) did not predict functional decline, decline in physical activity, decreased QoL or incident sarcopenia.

Current Thoughts of Notch's Role in Myoblast Regulation and Muscle-Associated Disease

The evolutionarily conserved signaling pathway Notch is unequivocally essential for embryogenesis. Notch’s contribution to the muscle repair process in adult tissue is complex and obscure but necessary. Notch integrates with other signals in a functional antagonist manner to direct myoblast activity and ultimately complete muscle repair. There is profound recent evidence describing plausible mechanisms of Notch in muscle repair. However, the story is not definitive as evidence is slowly emerging that negates Notch’s importance in myoblast proliferation. The purpose of this review article is to examine the prominent evidence and associated mechanisms of Notch’s contribution to the myogenic repair phases. In addition, we discuss the emerging roles of Notch in diseases associated with muscle atrophy. Understanding the mechanisms of Notch’s orchestration is useful for developing therapeutic targets for disease.

Nuclei isolation methods fail to accurately assess the subcellular localization and behaviour of proteins in skeletal muscle

AIM

Subcellular fractionation is often used to determine the subcellular localization of proteins, including whether a protein translocates to the nucleus in response to a given stimulus. Examining nuclear proteins in skeletal muscle is difficult because myonuclear proteins are challenging to isolate unless harsh treatments are used. This study aimed to determine the most effective method for isolating and preserving proteins in their native state in skeletal muscle.

METHODS

We compared the ability of detergents, commercially available kit-based and K⁺ -based physiological methodologies for isolating myonuclear proteins from resting samples of human muscle by determining the presence of marker proteins for each fraction by western blot analyses.

RESULTS

We found that following the initial pelleting of nuclei, treatment with 1% Triton-X 100, 1% CHAPS or 0.5% Na-deoxycholate under various ionic conditions resulted in the nuclear proteins being either resistant to isolation or the proteins present behaving aberrantly. The nuclear proteins in brain tissue were also resistant to 1% Triton-X 100 isolation. Here, we demonstrate aberrant behaviour and erroneous localization of proteins using the kit-based method. The aberrant behaviour was the activation of Ca²⁺ -dependent protease calpain-3, and the erroneous localization was the presence of calpain-3 and troponin I in the nuclear fraction.

CONCLUSION

Our findings indicate that it may not be possible to reliably determine the translocation of proteins between subcellular locations and the nucleus using subcellular fractionation techniques. This study highlights the importance of validating subcellular fractionation methodologies using several subcellular-specific markers and solutions that are physiologically relevant to the intracellular milieu.

Therapeutic Potential of Mitophagy-Inducing Microflora Metabolite, Urolithin A for Alzheimer's Disease

Mitochondrial dysfunction including deficits of mitophagy is seen in aging and neurodegenerative disorders including Alzheimer’s disease (AD). Apart from traditionally targeting amyloid beta (Aβ), the main culprit in AD brains, other approaches include investigating impaired mitochondrial pathways for potential therapeutic benefits against AD. Thus, a future therapy for AD may focus on novel candidates that enhance optimal mitochondrial integrity and turnover. Bioactive food components, known as nutraceuticals, may serve as such agents to combat AD. Urolithin A is an intestinal microbe-derived metabolite of a class of polyphenols, ellagitannins (ETs). Urolithin A is known to exert many health benefits. Its antioxidant, anti-inflammatory, anti-atherogenic, anti-Aβ, and pro-mitophagy properties are increasingly recognized. However, the underlying mechanisms of urolithin A in inducing mitophagy is poorly understood. This review discusses the mitophagy deficits in AD and examines potential molecular mechanisms of its activation. Moreover, the current knowledge of urolithin A is discussed, focusing on its neuroprotective properties and its potential to induce mitophagy. Specifically, this review proposes potential mechanisms by which urolithin A may activate and promote mitophagy.

Effect of Caloric Restriction on Aging: Fixing the Problems of Nutrient Sensing in Postmitotic Cells?

The review discusses the role of metabolic disorders (in particular, insulin resistance) in the development of age-related diseases and normal aging with special emphasis on the changes in postmitotic cells of higher organisms. Caloric restriction helps to prevent such metabolic disorders, which could probably explain its ability to prolong the lifespan of laboratory animals. Maintaining metabolic homeostasis is especially important for the highly differentiated long-lived body cells, whose lifespan is comparable to the lifespan of the organism itself. Normal functioning of these cells can be ensured only upon correct functioning of the cytoplasm clean-up system and availability of all required nutrients and energy sources. One of the central problems in gerontology is the age-related disruption of glucose metabolism leading to obesity, diabetes, metabolic syndrome, and other related pathologies. Along with the adipose tissue, skeletal muscles are the main consumers of insulin; hence the physical activity of muscles, which supports their energy metabolism, delays the onset of insulin resistance. Insulin resistance disrupts the metabolism of cardiomyocytes, so that they fail to utilize the nutrients to perform their functions even being surrounded by a nutrient-rich environment, which contributes to the development of age-related cardiovascular diseases. Metabolic pathologies also alter the nutrient sensitivity of neurons, thus disrupting the action of insulin in the central nervous system. In addition, there is evidence that neurons can develop insulin resistance as well. It has been suggested that affecting nutritional sensors (e.g., AMPK) in postmitotic cells might improve the state of the entire multicellular organism, slow down its aging, and increase the lifespan.

Association of Adherence to a Mediterranean Diet with Excess Body Mass, Muscle Strength and Physical Performance in Overweight or Obese Adults with or without Type 2 Diabetes: Two Cross-Sectional Studies

Overweight and obesity in older adults is associated with disability and is exacerbated by the presence of type 2 diabetes (T2DM). There is emerging evidence that adherence to a Mediterranean diet (MedDiet) reduces adiposity and attenuates physical disability. These cross-sectional studies explored the associations of adherence to a MedDiet with body mass index (BMI), adiposity, muscle strength, and physical performance in older adults without diabetes and in middle-aged or older adults with T2DM. MedDiet adherence was assessed using the Mediterranean Diet Adherence Screener. Fat mass and percent body fat were assessed by dual energy X-ray absorptiometry. Muscle strength was assessed using hand-grip strength, while physical performance was assessed using the Short Physical Performance Battery and gait speed. A total of n = 87 participants with T2DM (T2DM sample: 71.2 ± 8.2 years, BMI: 29.5 ± 5.9) and n = 65 participants without diabetes (non-T2DM sample: 68.7 ± 5.6 years, BMI: 33.7 ± 4.9) were included in these analyses. In the T2DM sample, when controlled for age, gender, and appendicular lean mass index, adherence to a MedDiet was inversely associated with BMI, fat mass, and percent body fat. However, this was no longer maintained in the fully adjusted models. Although, adherence to a MedDiet was positively associated with gait speed (β = 0.155; p = 0.050) independent of all covariates used. Adherence to a MedDiet may be a suitable dietary strategy for preserving lower body physical function in middle-aged and older adults with T2DM. However, these findings should be further investigated using well-designed randomised controlled trials and prospective cohort studies with a wider range of adherence scores to investigate temporal associations.

Weight Pulling: A Novel Mouse Model of Human Progressive Resistance Exercise

This study describes a mouse model of progressive resistance exercise that utilizes a full-body/multi-joint exercise (weight pulling) along with a training protocol that mimics a traditional human paradigm (three training sessions per week, ~8–12 repetitions per set, 2 min of rest between sets, approximately two maximal-intensity sets per session, last set taken to failure, and a progressive increase in loading that is based on the individual’s performance). We demonstrate that weight pulling can induce an increase in the mass of numerous muscles throughout the body. The relative increase in muscle mass is similar to what has been observed in human studies, and is associated with the same type of long-term adaptations that occur in humans (e.g., fiber hypertrophy, myonuclear accretion, and, in some instances, a fast-to-slow transition in Type II fiber composition). Moreover, we demonstrate that weight pulling can induce the same type of acute responses that are thought to drive these long-term adaptations (e.g., the activation of signaling through mTORC1 and the induction of protein synthesis at 1 h post-exercise). Collectively, the results of this study indicate that weight pulling can serve as a highly translatable mouse model of progressive resistance exercise.

Transient activation of mTORC1 signaling in skeletal muscle is independent of Akt1 regulation

The regulation of cellular protein synthesis is a critical determinant of skeletal muscle growth and hypertrophy in response to an increased workload such as resistance exercise. The mechanistic target of rapamycin complex 1 (mTORC1) and its upstream protein kinase Akt1 have been implicated as a central signaling pathway that regulates protein synthesis in the skeletal muscle; however, the precise molecular regulation of mTORC1 activity is largely unknown. This study employed germline Akt1 knockout (KO) mice to examine whether upstream Akt1 regulation is necessary for the acute activation of mTORC1 signaling in the plantaris muscle following mechanical overload. The phosphorylation states of S6 kinase 1, ribosomal protein S6, and eukaryotic translation initiation factor 4E‐binding protein 1 which show the functional activity of mTORC1 signaling, were significantly increased in the skeletal muscle of both wildtype and Akt1 KO mice following an acute bout (3 and 12 hr) of mechanical overload. Akt1 deficiency did not affect load‐induced alteration of insulin‐like growth factor‐1 (IGF‐1)/IGF receptor mRNA expression. Also, no effect of Akt1 deficiency was observed on the overload‐induced increase in the gene expressions of pax7 and myogenic regulatory factor of myogenin. These observations show that the upstream IGF‐1/Akt1 regulation is dispensable for the acute activation of mTORC1 signaling and regulation of satellite cells in response to mechanical overload.

A Coordinated Multi-study Analysis of the Longitudinal Association Between Handgrip Strength and Cognitive Function in Older Adults

OBJECTIVE

Handgrip strength, an indicator of overall muscle strength, has been found to be associated with slower rate of cognitive decline and decreased risk for cognitive impairment and dementia. However, evaluating the replicability of associations between aging-related changes in physical and cognitive functioning is challenging due to differences in study designs and analytical models. A multiple-study coordinated analysis approach was used to generate new longitudinal results based on comparable construct-level measurements and identical statistical models and to facilitate replication and research synthesis.

METHODS

We performed coordinated analysis on 9 cohort studies affiliated with the Integrative Analysis of Longitudinal Studies of Aging and Dementia (IALSA) research network. Bivariate linear mixed models were used to examine associations among individual differences in baseline level, rate of change, and occasion-specific variation across grip strength and indicators of cognitive function, including mental status, processing speed, attention and working memory, perceptual reasoning, verbal ability, and learning and memory. Results were summarized using meta-analysis.

RESULTS

After adjustment for covariates, we found an overall moderate association between change in grip strength and change in each cognitive domain for both males and females: Average correlation coefficient was 0.55 (95% CI = 0.44-0.56). We also found a high level of heterogeneity in this association across studies.

DISCUSSION

Meta-analytic results from nine longitudinal studies showed consistently positive associations between linear rates of change in grip strength and changes in cognitive functioning. Future work will benefit from the examination of individual patterns of change to understand the heterogeneity in rates of aging and health-related changes across physical and cognitive biomarkers.

Endurance training alleviates MCP-1 and TERRA accumulation at old age in human skeletal muscle

Both oxidative stress and telomere transcription are up-regulated by acute endurance exercise in human skeletal muscle. Whether and how life-long exercise training influences the antioxidant system response at transcriptional level and TERRA expression is unknown, especially during aging. Response to acute endurance exercise was investigated in muscle biopsies of 3 male subjects after 45 min of cycling. MCP-1 and SOD1 mRNA levels increased up to, 15-fold and 63%, respectively, after the cycling session while the mRNA levels of SOD2 were downregulated by 25%. The effects of chronic endurance exercise and aging were tested in the blood and muscle of 34 male subjects divided into four groups: young (YU) or old (OU) untrained, young (YT) or old (OT) trained cyclists. Long-term endurance training limited the age-dependent elevation in SOD1 (OT vs OU, -26%, P = 0.03) and the decline in SOD2 mRNA levels (OU vs YU, -41%, P = 0.04). A high endurance training status alleviated the age-related increase in the aging biological marker MCP-1 in plasma (OU vs YU, +48%, P = 0.005). Similar results were observed for telomeric transcription as the age-associated increase in 16p TERRA levels (OU vs YU, +39%, P = 0.001) was counteracted by a high endurance training status (OT vs OU, -63%, P = 0.0005). In conclusion, as MCP-1, we propose that the age-related TERRA accumulation might represent a novel biological marker of aging. Those aging-related increase expression might be alleviated by a high endurance training status. Whether those biological markers of aging are linked to an elevation of oxidative stress is still an open question. Therefore, whether the positive adaptations provided by endurance training indeed reduce oxidative stress, including at telomeres, and whether TERRA plays any role in this, need to be further investigated.

Maintaining proteostasis under mechanical stress

Cell survival, tissue integrity and organismal health depend on the ability to maintain functional protein networks even under conditions that threaten protein integrity. Protection against such stress conditions involves the adaptation of folding and degradation machineries, which help to preserve the protein network by facilitating the refolding or disposal of damaged proteins. In multicellular organisms, cells are permanently exposed to stress resulting from mechanical forces. Yet, for long time mechanical stress was not recognized as a primary stressor that perturbs protein structure and threatens proteome integrity. The identification and characterization of protein folding and degradation systems, which handle force-unfolded proteins, marks a turning point in this regard. It has become apparent that mechanical stress protection operates during cell differentiation, adhesion and migration and is essential for maintaining tissues such as skeletal muscle, heart and kidney as well as the immune system. Here, we provide an overview of recent advances in our understanding of mechanical stress protection.

Effects of 1 Year of Lifestyle Intervention on Institutionalized Older Adults

The socio-economic and health consequences of our ageing population are well documented, with older adults living in long-term care facilities amongst the frailest possessing specific and significant healthcare and social care needs. These needs may be exacerbated through the sedentary behaviour which is prevalent within care home settings. Reducing sedentary time can reduce the risk of many diseases and improve functional health, implying that improvements in health may be gained by simply helping older adults substitute time spent sitting with time spent standing or in light-intensity ambulation. This study identified the impact of 1 year of lifestyle intervention in a group of older adults living in a long-term care setting in Italy. One hundred and eleven older adults (mean age, 82.37 years; SD = 10.55 years) participated in the study. Sixty-nine older adults were in the intervention group (35 without severe cognitive decline and 34 with dementia) and 42 older adults were in the control group. Data on physical functioning, basic activities of daily living (BADL) and mood were collected 4 times, before, during (every four months) and after the 1 year of intervention. The lifestyle intervention focused on improving the amount of time spent every week in active behaviour and physical activity (minimum 150 min of weekly activities). All participants completed the training program and no adverse events, related to the program, occurred. The intervention group showed steady and significant improvements in physical functioning and a stable situation in BADL and mood following the intervention in older adults with and without dementia, whilst the control group exhibited a significant decline over time. These results suggest that engagement in a physical activity intervention may benefit care home residents with and without dementia both physically and mentally, leading to improved social care and a reduced burden on healthcare services.

Handgrip strength as a moderator of the influence of age on olfactory impairment in US adult population ≥ 40 years of age

The aim of this study was to determine whether handgrip strength attenuates the negative relationship between age and olfactory function in a representative US population sample 40 years old and over. A cross-sectional study was performed with 2861 adults from the US National Health and Nutrition Examination Survey NHANES (2013–2014). An 8-item odor identification test was applied to determine olfactory function. Muscle strength was determined through a handgrip dynamometer (defined as the sum of the largest handgrip strength reading from right and left hands). Moderation analysis was performed to test whether the association between age and olfactory impairment was moderated by handgrip strength. Moderation analysis highlighted two regions of significance: the first region was found at < 56.6 kg, indicating that the adverse influence of age on olfactory function may be greater for the participants in this area; the second region was found at ≥ 56.6 kg, indicating that the negative impact of age on olfactory function disappeared for adults who were above this estimate point. In conclusion, handgrip strength, a general indicator of muscle strength, moderates the relationship between age and olfactory ability in a US adult population aged 40 years and older. Our findings are clinically relevant, since they emphasize the importance of muscular fitness in adulthood and old age by diminishing the deleterious effect of aging on olfactory performance.

Sports Medicine and Rehabilitation in Working Dogs

Canine sports medicine and rehabilitation recently have evolved to embody the optimization of performance, injury prevention, and mitigation of musculoskeletal degeneration. This article discusses the diverse factors and considerations of working dog wellness and injury prevention and the importance of recognizing normal and abnormal posture and anatomic structure for performance evaluation and early indication of musculoskeletal injury. The importance of a canine physical fitness program is highlighted and the need for a 4-phase recovery plan to determine if a working dog can safely return to work after injury discussed.

Effects of early-life exposure to Western diet and voluntary exercise on adult activity levels, exercise physiology, and associated traits in selectively bred High Runner mice

Exercise behavior is under partial genetic control, but it is also affected by numerous environmental factors, potentially including early-life experiences whose effects persist into adulthood. We studied genetic and early-life environmental effects on wheel-running behavior in a mouse model that includes four replicate high runner (HR) lines selectively bred for increased voluntary wheel running as young adults and four non-selected control (C) lines. In a full factorial design, mice from each line were granted wheel access or not and administered either standard or Western diet (WD) from weaning (3 weeks old) to 6 weeks of age (sexual maturity). In addition to acute effects, after a washout period of 8 weeks (∼6 human years) in which all mice had standard diet and no wheel access, we found both beneficial and detrimental effects of these early-life exposures. During the first week of treatments, WD increased distance run by 29% in C mice and 48% in HR mice (significant Diet × Linetype interaction), but diet effects disappeared by the third week. Across the three weeks of juvenile treatment, WD significantly increased fat mass (with lean mass as a covariate). Tested as adults, early-life exercise increased wheel running of C mice but not HR mice in the first week. Early-life exercise also reduced adult anxiety-like behavior and increased adult fasted blood glucose levels, triceps surae mass, subdermal fat pad mass, and brain mass, but decreased heart ventricle mass. Using fat mass as a covariate, early-life exercise treatment increased adult leptin concentration. In contrast, early-life WD increased adult wheel running of HR mice but not C mice. Early-life WD also increased adult lean mass and adult preference for Western diet in all groups. Surprisingly, early-life treatment had no significant effect on adult body fat or maximal aerobic capacity (VO2max). No previous study has tested for combined or interactive effects of early-life WD and exercise. Our results demonstrate that both factors can have long-lasting effects on adult voluntary exercise and related phenotypes, and that these effects are modulated by genetic background. Overall, the long-lasting effects of early-life exercise were more pervasive than those of WD, suggesting critical opportunities for health intervention in childhood habits, as well as possible threats from modern challenges. These results may be relevant for understanding potential effects of activity reductions and dietary changes associated with the obesity epidemic and COVID-19 pandemic.

Farmed Mussels: A Nutritive Protein Source, Rich in Omega-3 Fatty Acids, with a Low Environmental Footprint

The world’s ever-growing population presents a major challenge in providing sustainable food options and in reducing pressures on the Earth’s agricultural land and freshwater resources. Current estimates suggest that agriculture contributes ~30% of global greenhouse gas (GHG) emissions. Additionally, there is an increased demand for animal protein, the production of which is particularly polluting. Therefore, the climate-disrupting potential of feeding the planet is likely to substantially worsen in the future. Due to the nutritional value of animal-based protein, it is not a simple solution to recommend a wholesale reduction in production/consumption of animal proteins. Rather, employing strategies which result in the production of low carbon animal protein may be part of the solution to reduce the GHGs associated with our diets without compromising diet quality. We suggest that farmed mussels may present a partial solution to this dilemma. Mussel production has a relatively low GHG production and does not put undue pressure on land or fresh water supplies. By drawing comparisons to other protein sources using the Australian Food and Nutrient Database and other published data, we demonstrate that they are a sustainable source of high-quality protein, long-chain omega-3 fatty acids, phytosterols, and other key micronutrients such as B-12 and iron. The aim of this review is to summarise the current knowledge on the health benefits and potential risks of increasing the consumption of farmed mussels.

How important is current physical fitness for future quality of life? Results from an 8-year longitudinal study on older adults

INTRODUCTION

A vast amount of research has focused on the effects of physical fitness (PF) on mortality, with little research evaluating the effects of PF on future expected health related quality of life (HRQoL).

AIM

To evaluate how current PF influences future HRQoL measured in a prospective 8-year study in older adults.

METHODS

A total of 617 (157 males) older adults (>65y) participated in the study. PF was assessed with the EXERNET battery in 2008-2009 (baseline) and 2016-2017 (follow-up). HRQoL was assessed using the EQ-5D-3L questionnaire in both evaluations. PF tertiles were developed from baseline PF variables: FIT (highest PF values), REGULAR and UNFIT (lowest PF values) taking into account age and sex. Follow-up HRQoL values were compared to sex and age-specific expected values. Logistic regressions were performed to test differences between PF tertiles regarding future expected quality of life. Linear regressions were developed to test whether baseline PF could predict future HRQoL scores.

RESULTS

The FIT group showed higher probabilities of an improved HRQoL when compared to the UNFIT group. All PF variables seemed to be important at some point of the study except upper extremities flexibility. Aerobic endurance was the variable that showed to be significant for most of the HRQoL predictions.

CONCLUSION

PF influences future HRQoL in older adults who accordingly should try to remain fit to maintain an increased age-adjusted HRQoL.

Body Protein Sparing in Hibernators: A Source for Biomedical Innovation

Proteins are not only the major structural components of living cells but also ensure essential physiological functions within the organism. Any change in protein abundance and/or structure is at risk for the proper body functioning and/or survival of organisms. Death following starvation is attributed to a loss of about half of total body proteins, and body protein loss induced by muscle disuse is responsible for major metabolic disorders in immobilized patients, and sedentary or elderly people. Basic knowledge of the molecular and cellular mechanisms that control proteostasis is continuously growing. Yet, finding and developing efficient treatments to limit body/muscle protein loss in humans remain a medical challenge, physical exercise and nutritional programs managing to only partially compensate for it. This is notably a major challenge for the treatment of obesity, where therapies should promote fat loss while preserving body proteins. In this context, hibernating species preserve their lean body mass, including muscles, despite total physical inactivity and low energy consumption during torpor, a state of drastic reduction in metabolic rate associated with a more or less pronounced hypothermia. The present review introduces metabolic, physiological, and behavioral adaptations, e.g., energetics, body temperature, and nutrition, of the torpor or hibernation phenotype from small to large mammals. Hibernating strategies could be linked to allometry aspects, the need for periodic rewarming from torpor, and/or the ability of animals to fast for more or less time, thus determining the capacity of individuals to save proteins. Both fat- and food-storing hibernators rely mostly on their body fat reserves during the torpid state, while minimizing body protein utilization. A number of them may also replenish lost proteins during arousals by consuming food. The review takes stock of the physiological, molecular, and cellular mechanisms that promote body protein and muscle sparing during the inactive state of hibernation. Finally, the review outlines how the detailed understanding of these mechanisms at play in various hibernators is expected to provide innovative solutions to fight human muscle atrophy, to better help the management of obese patients, or to improve the ex vivo preservation of organs.

Comparison of blood flow restriction devices and their effect on quadriceps muscle activation

OBJECTIVES

Blood flow restriction training (BFRT) provides an alternative approach to traditional strength training. The purpose of this study was to determine differences in quadriceps muscle activation, subject reported pain, and perceived exertion between three exercise conditions: low-load resistance BFRT with (1) regulated and (2) standardized devices, and (3) high-load resistance exercise without BFRT.

DESIGN

Randomized cross over study.

SETTING

XX University Biomechanics laboratory.

PARTICIPANTS

Thirty-four healthy subjects (18 male/16 female) each completed three randomized sessions of knee extensions using Delfi's Personalized Tourniquet System (R) at 30% of 1 repetition maximum (1RM), the B-Strong™ device (S) at 30% 1RM, and high-load resistance exercise (HL) at 80% 1RM.

MAIN OUTCOME MEASURES

Quadriceps EMG activity, numeric pain rating scale (NPRS), and perceived exertion (OMNI-RES) were recorded.

RESULTS

Average and peak EMG were greater in HL sessions than both S and R (p < .001). NPRS was greater in the R sessions compared to both S (p < .001) and HL (p < .001). OMNI-RES was greater in the R sessions compared to S (p < .02) and HL (p < .001). No differences (p > .05) in average or peak EMG activation were found between S and R sessions.

CONCLUSIONS

Quadriceps EMG amplitude was greater during high-load resistance exercise versus low-load BFR exercise and there were no differences in EMG findings between BFRT devices.

Full characterisation of knee extensors' function in ageing: effect of sex and obesity

BACKGROUND/OBJECTIVES

Muscle function is a marker of current and prospective health/independence throughout life. The effects of sex and obesity (OB) on the loss of muscle function in ageing remain unresolved, with important implications for the diagnosis/monitoring of sarcopenia. To characterise in vivo knee extensors' function, we compared muscles torque and power with isometric and isokinetic tests in older men (M) and women (W), with normal range (NW) of body mass index (BMI) and OB.

SUBJECTS/METHODS

In 70 sedentary older M and W (69 ± 5 years), NW and OB (i.e. BMI < 30 kg m^-2 and ≥30 kg m^-2, respectively) we tested the right knee's extensor: (i) isometric torque at 30°, 60°, 75° and 90° knee angles, and (ii) isokinetic concentric torque at 60, 90, 150, 180 and 210° s^-1 angular speeds. Maximal isometric T-angle, maximal isokinetic knee-extensor torque-velocity, theoretical maximal shortening velocity, maximal power, optimal torque and velocity were determined in absolute units, normalised by body mass (BM) and right leg lean mass (LLM_R) and compared over sex, BMI categories and angle or angular speeds by three-way ANOVA.

RESULTS

In absolute units, relative to BM and LLM_R, sex differences were found in favour of M for all parameters of muscle function (main effect for sex, p < 0.05). OB did not affect either absolute or relative to LLM_R isometric and isokinetic muscle function (main effect for BMI, p > 0.05); however, muscle function indices, when adjusted for BM, were lower in both M and W with OB compared to NW counterparts (p < 0.05).

CONCLUSIONS

We confirmed sex differences in absolute, relative to BM and LLM_R muscle function in favour of men. While overall muscle function and muscle contractile quality is conserved in individuals with class I OB, muscle function normalised for BM, which defines the ability to perform independently and safely the activities of daily living, is impaired in comparison with physiological ageing.

Relationship between dietary factors and S-Klotho plasma levels in young sedentary healthy adults

OBJECTIVE

To study the associations of dietary factors with S-Klotho plasma levels in young adults. We also aimed to study whether body composition and cardiometabolic risk factors affected the association between dietary factors and S-Klotho plasma levels.

METHODS

A total of 139 young adults took part in this study. Dietary factors were measured using a food frequency questionnaire and three non-consecutive 24 h recalls. S-Klotho plasma levels were measured by immunosorbent assay. Body composition was measured by DXA.

RESULTS

We observed a direct association of ethanol intake and S-Klotho plasma levels in women. An inverse association was also observed between the dietary inflammatory index (DII) with S-Klotho plasma levels in all sample. No mediation effects of body composition or cardiometabolic risk factors were observed in the relationship between alcohol and S-Klotho plasma levels. Lean mass index (LMI) and uric acid levels mediated the relationship between DII and S-Klotho plasma levels.

CONCLUSION

A pro-inflammatory dietary pattern was inversely associated with S-Klotho plasma levels in young adults, which was partially mediated by LMI and uric acid levels.

High-Intensity Functional Training: Molecular Mechanisms and Benefits

High-intensity interval training (HIIT) and strength exercise are known to improve health markers, such as cardiovascular health, metabolic health, and cognitive function, as well as to reduce all-cause mortality. High-Intensity Functional Training (HIFT) is a training paradigm derived from both HIIT and strength exercise to elicit greater muscle recruitment than repetitive aerobic exercises, thereby improving both cardiovascular fitness and strength parameters. Herein, we provide a focused review of the known molecular mechanisms that underlie the beneficial effects of HIFT on cardiovascular, metabolic, and cognitive functions.

Effects of Antidiabetic Drugs on Muscle Mass in Type 2 Diabetes Mellitus

BACKGROUND

When considering the administration of glucagon-like peptide-1 receptor agonists (GLP-1RAs), sodium-glucose cotransporter-2 (SGLT2) inhibitors, or metformin, it is important to understand their weight loss effect as well as the degree of muscle loss caused by each drug in clinical practice.

OBJECTIVE

To comparatively examine the effects of GLP-1RAs and oral antidiabetic drugs, including SGLT2 inhibitors and metformin, on muscle mass and body weight in patients with type 2 diabetes via a network meta-analysis of randomized controlled trials.

METHODS

We included randomized controlled trials evaluating the effects of antidiabetic drugs on muscle mass and body weight. Mean difference (MD) and 95% confidence intervals (CIs) were calculated using a random-effects network meta-analysis.

RESULTS

Of the studies identified, 18 randomized controlled trials (1, 363 subjects) satisfied the eligibility criteria. In all studies, the effects of these drugs on fat-free mass (FFM) were evaluated. Therefore, FFM, which is used as an alternative index of muscle mass, was included in the study. Semaglutide (MD: -1.68, 95% CI: -2.84 to -0.52), dapagliflozin (-0.53, -0.93 to -0.13), and canagliflozin (-0.90, -1.73 to -0.07) showed a significant decrease in FFM compared with the placebo. Metformin did not show a significant decrease in FFM compared with the placebo. When compared with the placebo, semaglutide, dapagliflozin, ipragliflozin, and canagliflozin showed a significant weight loss.

CONCLUSION

Although semaglutide, dapaglifrozin, and canagliflozin have a large weight loss effect, it is important to pay attention to muscle loss because a decrease in FFM was observed.

Exercise and Nutrition for Healthy AgeiNg (ENHANce) project - effects and mechanisms of action of combined anabolic interventions to improve physical functioning in sarcopenic older adults: study protocol of a triple blinded, randomized controlled trial

Background

The Exercise and Nutrition for Healthy AgeiNg (ENHANce) project aims to assess the combined effects of exercise and nutritional interventions to prevent loss of skeletal muscle mass and function with ageing, and to determine the underlying mechanisms of action.

Methods

One hundred eightycommunity-dwelling sarcopenic individuals (≥ 65 years) are allocated in a randomized controlled trial (RCT) in a 1:1 ratio into five groups for a 12-week intervention period, followed by a 12-week follow-up period: 1) exercise intervention +protein placebo +omega-3 fatty acids placebo; 2) protein +omega-3 fatty acids placebo; 3) exercise intervention +protein +omega-3 fatty acids placebo; 4) exercise intervention +protein +omega-3 fatty acids; 5) protein placebo +omega-3 fatty acids placebo. All interventions are in line with recommendations of expert groups such as the American College of Sports Medicine and the PROT-AGE study group and individualized to the physical capabilities and nutritional intake of each participant. Sarcopenia is diagnosed by the assessment of gait speed, handgrip strength (Jamar handheld dynamometer), chair stand test and muscle mass (DXA) according to the European Working Group on Sarcopenia in Older People (EWGSOP2) criteria. Participants, researchers and statisticians are blinded to omega-3 fatty acids and protein treatment. Compliance to the exercise program, protein and omega-3 fatty acids interventions is objectively measured, by monitoring movement by an activity monitor, determining nitrogen content in urine and analyzing the fatty acid composition of the red blood cell membrane. The primary outcome of the RCT is the change in Short Physical Performance Battery (SPPB) score. Secondary endpoints are, among others, changes in muscle mass, strength and function, objective compliance to interventions, changes in muscle and blood biomarkers related to sarcopenia, cognition, quality of life and falls.

Discussion

This RCT in well-defined sarcopenic older adults assesses the effects of combined anabolic interventions, including the additive effects of omega-3 fatty acids supplements, compared to single or placebo interventions. Compliance with the exercise intervention and with the intake of nutritional supplements is measured objectively. Also, blood and muscle samples will be used to explore the underlying determinants that contribute to the mechanism of action of anabolic interventions.

Trial registration

Clinicaltrials.gov: NCT03649698, retrospectively registered at 28 August 2018, first participant was randomized 16 February 2018.

Targeting Mitophagy in Alzheimer's Disease

Mitochondria perform many essential cellular functions including energy production, calcium homeostasis, transduction of metabolic and stress signals, and mediating cell survival and death. Maintaining viable populations of mitochondria is therefore critical for normal cell function. The selective disposal of damaged mitochondria, by a pathway known as mitophagy, plays a key role in preserving mitochondrial integrity and quality. Mitophagy reduces the formation of reactive oxygen species and is considered as a protective cellular process. Mitochondrial dysfunction and deficits of mitophagy have important roles in aging and especially in neurodegenerative disorders such as Alzheimer's disease (AD). Targeting mitophagy pathways has been suggested to have potential therapeutic effects against AD. In this review, we aim to briefly discuss the emerging concepts on mitophagy, molecular regulation of the mitophagy process, current mitophagy detection methods, and mitophagy dysfunction in AD. Finally, we will also briefly examine the stimulation of mitophagy as an approach for attenuating neurodegeneration in AD.

Exploring the Impact of Obesity on Skeletal Muscle Function in Older Age

Sarcopenia is of important clinical relevance for loss of independence in older adults. The prevalence of obesity in combination with sarcopenia ("sarcopenic-obesity") is increasing at a rapid rate. However, whilst the development of sarcopenia is understood to be multi-factorial and harmful to health, the role of obesity from a protective and damaging perspective on skeletal muscle in aging, is poorly understood. Specifically, the presence of obesity in older age may be accompanied by a greater volume of skeletal muscle mass in weight-bearing muscles compared with lean older individuals, despite impaired physical function and resistance to anabolic stimuli. Collectively, these findings support a potential paradox in which obesity may protect skeletal muscle mass in older age. One explanation for these paradoxical findings may be that the anabolic response to weight-bearing activity could be greater in obese vs. lean older individuals due to a larger mechanical stimulus, compensating for the heightened muscle anabolic resistance. However, it is likely that there is a complex interplay between muscle, adipose, and external influences in the aging process that are ultimately harmful to health in the long-term. This narrative briefly explores some of the potential mechanisms regulating changes in skeletal muscle mass and function in aging combined with obesity and the interplay with sarcopenia, with a particular focus on muscle morphology and the regulation of muscle proteostasis. In addition, whilst highly complex, we attempt to provide an updated summary for the role of obesity from a protective and damaging perspective on muscle mass and function in older age. We conclude with a brief discussion on treatment of sarcopenia and obesity and a summary of future directions for this research field.

Associations of combined genetic and epigenetic scores with muscle size and muscle strength: a pilot study in older women

BACKGROUND

Inter-individual variance in skeletal muscle is closely related to genetic architecture and epigenetic regulation. Studies have examined genetic and epigenetic relationships with characteristics of ageing muscle separately, while no study has combined both genetic and epigenetic profiles in ageing muscle research. The aim of this study was to evaluate the association between combined genetic and methylation scores and skeletal muscle phenotypes in older women.

METHODS

Forty-eight older Caucasian women (aged 65-79 years) were included in this study. Biceps brachii thickness and vastus lateralis anatomical cross-sectional area (ACSA_VL ) were measured by ultrasonography. Maximum isometric elbow flexion (MVC_EF ) and knee extension (MVC_KE ) torques were measured by a customized dynamometer. The muscle-driven genetic predisposition score (GPS_SNP ) was calculated based on seven muscle-related single nucleotide polymorphisms (SNPs). DNA methylation levels of whole blood samples were analysed using Infinium MethylationEPIC BeadChip arrays. The DNA methylation score was calculated as a weighted sum of methylation levels of sarcopenia-driven CpG sites (MS_SAR ) or an overall gene-wise methylation score (MS_SNP , the mean methylation level of CpG sites located in muscle-related genes). Linear regression models were built to study genetic and epigenetic associations with muscle size and strength. Three models were built with both genetic and methylation scores: (1) MS_SAR  + GPS_SNP , (2) MS_SNP  + GPS_SNP , and (3) gene-wise combined scores which were calculated as the ratio of the SNP score to the mean methylation level of promoters in the corresponding gene. Additional models with only a genetic or methylation score were also built. All models were adjusted for age and BMI.

RESULTS

MS_SAR was negatively associated with ACSA_VL , MVC_EF , and MVC_KE and explained 10.1%, 35.5%, and 40.1% of the variance, respectively. MS_SAR explained more variance in these muscular phenotypes than GPS_SNP , MS_SNP , and models including both genetic and methylation scores. MS_SNP and GPS_SNP accounted for less than 8% and 5% of the variance in all muscular phenotypes, respectively. The genotype and methylation level of CNTF was positively related to MVC_KE (P = 0.03) and explained 12.2% of the variance. The adjusted R² and Akaike information criterion showed that models with only a MS_SAR performed the best in explaining inter-individual variance in muscular phenotypes.

CONCLUSIONS

Our results improve the understanding of inter-individual variance in muscular characteristics of older women and suggest a possible application of a sarcopenia-driven methylation score to muscle strength estimation in older women while the combination with a genetic score still needs to be further studied.

Influence of Fermented Red Clover Extract on Skeletal Muscle in Early Postmenopausal Women: A Double-Blinded Cross-Over Study

Objective: To investigate effects of supplementation with a fermented red clover (RC) extract on signaling proteins related to muscle protein synthesis and breakdown at rest and in response to a resistance exercise bout. Methods: Ten postmenopausal women completed a double-blinded cross-over trial with two different intervention periods performed in random order: (A) RC extract twice daily for 14 days, and (B) placebo drink twice daily for 14 days. The intervention periods were separated by a two-week washout period. After each intervention period a muscle tissue sample was obtained before and three hours after a one-legged resistance exercise bout. Muscle strength was assessed before and after each intervention period. Results: Protein expression of FOXO1 and FOXO3a, two key transcription factors involved in protein degradation, were significantly lower and HSP27, a protein involved in cell protection and prevention of protein aggregation was significantly higher following RC extract compared to placebo. No significant treatment × time interaction was observed for muscle protein expression in response to exercise. However, p-mTOR, p-p70S6k and HSP90 protein content were significantly increased in response to exercise in both groups. Conclusions: This study demonstrates that RC extract supplementation downregulates molecular markers of muscle protein degradation compared to placebo in postmenopausal women.

Elevated plasma lactate levels via exogenous lactate infusion do not alter resistance exercise-induced signaling or protein synthesis in human skeletal muscle

Lactate has been implicated as a potential signaling molecule. In myotubes, lactate incubation increases mechanistic target of rapamycin complex 1 (mTORC1)- and ERK-signaling and induces hypertrophy, indicating that lactate could be a mediator of muscle adaptations to resistance exercise. However, the potential signaling properties of lactate, at rest or with exercise, have not been explored in human tissue. In a crossover design study, 8 men and 8 women performed one-legged resistance exercise while receiving venous infusion of saline or sodium lactate. Blood was sampled repeatedly, and muscle biopsies were collected at rest and at 0, 90, and 180 min and 24 h after exercise. The primary outcomes examined were intracellular signaling, fractional protein synthesis rate (FSR), and blood/muscle levels of lactate and pH. Postexercise blood lactate concentrations were 130% higher in the Lactate trial (3.0 vs. 7.0 mmol/L, P < 0.001), whereas muscle levels were only marginally higher (27 vs. 32 mmol/kg dry wt, P = 0.003) compared with the Saline trial. Postexercise blood pH was higher in the Lactate trial (7.34 vs. 7.44, P < 0.001), with no differences in intramuscular pH. Exercise increased the phosphorylation of mTOR^S2448 (∼40%), S6K1^T389 (∼3-fold), and p44^T202/T204 (∼80%) during recovery, without any differences between trials. FSR over the 24-h recovery period did not differ between the Saline (0.067%/h) and Lactate (0.062%/h) trials. This study does not support the hypothesis that blood lactate levels can modulate anabolic signaling in contracted human muscle. Further in vivo research investigating the impact of exercised versus rested muscle and the role of intramuscular lactate is needed to elucidate its potential signaling properties.

The Association of Grip Strength with Depressive Symptoms among Middle-Aged and Older Adults with Different Chronic Diseases

Low grip strength has been associated with an increase in depressive symptoms, independent of age group or gender, although the literature has not investigated this association among different chronic diseases. The present study aims to investigate the association of grip strength and depressive symptoms among middle-aged and older adults with different chronic diseases. A cross-section of data from the Survey of Health, Ageing, and Retirement in Europe wave 6 (collected in 2015) was analysed. Grip strength was measured by a handgrip dynamometer, and the European Depression Symptoms 12-item scale (EURO-D) was used to assess depressive symptoms. Multivariable logistic regression analysis was conducted. Those in the high strength tertile had 42% (95% confidence interval: 0.50, 0.71; p < 0.005) and 41% (95% confidence interval: 0.50, 0.70; p < 0.001) lower odds of depressive symptoms in the ‘no disease’ and in the ‘metabolic diseases’ groups of participants, respectively, compared with those in the lower strength tertile. No statistically significant relationship between grip strength and depression was observed in the ‘arthritis diseases’ group of participants. The association of grip strength with depressive symptoms must consider, besides gender and age group, the chronic conditions that an individual could have.

Diurnal Differences in Human Muscle Isometric Force In Vivo Are Associated with Differential Phosphorylation of Sarcomeric M-Band Proteins

We investigated whether diurnal differences in muscle force output are associated with the post-translational state of muscle proteins. Ten physically active men (mean ± SD; age 26.7 ± 3.7 y) performed experimental sessions in the morning (08:00 h) and evening (17:00 h), which were counterbalanced in order of administration and separated by at least 72 h. Knee extensor maximal voluntary isometric contraction (MVIC) force and peak rate of force development (RFD) were measured, and samples of vastus lateralis were collected immediately after exercise. MVIC force was greater in the evening (mean difference of 67 N, 10.2%; p < 0.05). Two-dimensional (2D) gel analysis encompassed 122 proteoforms and discovered 6 significant (p < 0.05; false discovery rate [FDR] = 10%) diurnal differences. Phosphopeptide analysis identified 1693 phosphopeptides and detected 140 phosphopeptides from 104 proteins that were more (p < 0.05, FDR = 22%) phosphorylated in the morning. Myomesin 2, muscle creatine kinase, and the C-terminus of titin exhibited the most robust (FDR < 10%) diurnal differences. Exercise in the morning, compared to the evening, coincided with a greater phosphorylation of M-band-associated proteins in human muscle. These protein modifications may alter the M-band structure and disrupt force transmission, thus potentially explaining the lower force output in the morning.

The Genetic Effect on Muscular Changes in an Older Population: A Follow-Up Study after One-Year Cessation of Structured Training

Older adults lose muscle mass and strength at different speeds after the cessation of physical exercise, which might be genotype related. This study aimed to explore the genetic association with changes in muscle mass and strength one year after the cessation of structured training in an older population. Participants (n = 113, aged between 61 and 81 years) who performed one-year of combined fitness (n = 44) or whole-body vibration (n = 69) training were assessed one year after the cessation of the training. Whole-body skeletal muscle mass and knee strength were measured. Data-driven genetic predisposition scores (GPSs) were calculated and analysed in a general linear model with sex, age, body mass index and post-training values of skeletal muscle mass or muscle strength as covariates. Forty-six single nucleotide polymorphisms (SNPs) from an initial 170 muscle-related SNPs were identified as being significantly linked to muscular changes after cessation. Data-driven GPSs and over time muscular changes were significantly related (p < 0.01). Participants with higher GPSs had less muscular declines during the cessation period while data-driven GPSs accounted for 26–37% of the phenotypic variances. Our findings indicate that the loss of training benefits in older adults is partially genotype related.

Transcriptional Changes Involved in Atrophying Muscles during Prolonged Fasting in Rats

Food deprivation resulting in muscle atrophy may be detrimental to health. To better understand how muscle mass is regulated during such a nutritional challenge, the current study deciphered muscle responses during phase 2 (P2, protein sparing) and phase 3 (P3, protein mobilization) of prolonged fasting in rats. This was done using transcriptomics analysis and a series of biochemistry measurements. The main findings highlight changes for plasma catabolic and anabolic stimuli, as well as for muscle transcriptome, energy metabolism, and oxidative stress. Changes were generally consistent with the intense use of lipids as fuels during P2. They also reflected increased muscle protein degradation and repressed synthesis, in a more marked manner during P3 than P2 compared to the fed state. Nevertheless, several unexpected changes appeared to be in favor of muscle protein synthesis during fasting, notably at the level of the phosphatidylinositol-3-kinase (PI3K)/protein kinase B (AKT)/mammalian target of rapamycin (mTOR) signaling pathway, transcription and translation processes, and the response to oxidative stress. Such mechanisms might promote protein sparing during P2 and prepare the restoration of the protein compartment during P3 in anticipation of food intake for optimizing the effects of an upcoming refeeding, thereby promoting body maintenance and survival. Future studies should examine relevance of such targets for improving nitrogen balance during catabolic diseases.