Age-related loss of muscle mass and strength

Adaptations in mitochondrial quality control and interactions with innate immune signaling within skeletal muscle: A narrative review

Skeletal muscle health and function are essential determinants of metabolic health, physical performance, and overall quality of life. The quality of skeletal muscle is heavily dependent on the complex mitochondrial reticulum that contributes toward its unique adaptability. It is now recognized that mitochondrial perturbations can activate various innate immune pathways, such as the nucleotide-binding oligomerization domain (NOD)-like receptor protein 3 (NLRP3) inflammasome complex by propagating inflammatory signaling in response to damage-associated molecular patterns (DAMPs). The NLRP3 inflammasome is a multimeric protein complex and is a prominent regulator of innate immunity and cell death by mediating the activation of caspase-1, pro-inflammatory cytokines interleukin-1β and interleukin-18 and pro-pyroptotic protein gasdermin-D. While several studies have begun to demonstrate the relationship between various mitochondrial DAMPs (mtDAMPs) and NLRP3 inflammasome activation, the influence of various metabolic states on the production of these DAMPs and subsequent inflammatory profile remains poorly understood. This narrative review aimed to address this by highlighting the effects of skeletal muscle use and disuse on mitochondrial quality mechanisms including mitochondrial biogenesis, fusion, fission and mitophagy. Secondly, this review summarized the impact of alterations in mitochondrial quality control mechanisms following muscle denervation, aging, and exercise training in relation to NLRP3 inflammasome activation. By consolidating the current body of literature, this work aimed to further the understanding of innate immune signaling within skeletal muscle, which can highlight areas for future research and therapeutic strategies to regulate NLRP3 inflammasome activation during divergent metabolic conditions.

β-hydroxy-β-methylbutyrate Attenuates Age-Dependent Loss of Flight Ability and Extends Lifespan in Drosophila

β-hydroxy-β-methylbutyrate (HMB) has been shown to enhance muscle function and strength in older humans and rodents after periods of consumption extending for several weeks. We investigated the feasibility of utilizing Drosophila as a model organism to study the biological effects of HMB on aging muscle when consumed throughout adult life. Using flight ability as an index of flight muscle function, we found that HMB attenuates the age-dependent decline in flight ability. Male and female flies fed a diet supplemented with 10 mg/mL HMB had significantly higher flight scores from median age until the onset of flight senescence than control flies fed a standard diet. HMB supplementation also resulted in improved flight scores in males before median age and delayed the onset of flight senescence in females. Notably, the consumption of HMB throughout adult life increased the rate of survival and extended lifespan. The effect on lifespan did not result from changes in food consumption or body weight. Old flies on the HMB-supplemented diet retained a higher proportion of flight muscle mitochondria whose morphology resembled that of young flies than the control diet group. Together, these results suggest that HMB attenuates the age-dependent decline in flight ability and prolongs lifespan by enhancing muscle health.

The effect of advanced age and stool modification on reaching distance in sitting

[Purpose] Reaching is an important functional ability. We investigated the effect of advanced age and stool modification on sitting reach distance. [Participants and Methods] Twenty-four participants (twelve older adults 70 ± 4 years and twelve young adults 29 ± 4 years) reached forward and laterally while sitting on an adjustable stool with 0°, 10° forward, 10° backward, 10° right or 10° left inclination of the seat, with and without footrest and front, back or side leg support. [Results] The outcome of this exploratory study revealed that young adults reached farther than older adults across all the directions of reach and seat conditions. While the inclined seat was utilized, both young and older adults reached farthest in the forward direction. Additional leg supports allowed to reach further; however, older adults were not able to reach in the forward direction as far as young adults. When reaching in the lateral direction, leg support had minimal effect on the reach distance. [Conclusion] Age affects the sitting functional reach ability. Future research should focus on investigating the efficiency of interventions to enhance performance of functional tasks in sitting older adults.

Sarcopenic obesity and osteoporosis: Research progress and hot spots

Sarcopenic obesity (SO) and osteoporosis (OP) are associated with aging and obesity. The pathogenesis of SO is complex, including glucolipid and skeletal muscle metabolic disorders caused by inflammation, insulin resistance, and other factors. Growing evidence links muscle damage to bone loss. Muscle-lipid metabolism disorders of SO disrupt the balance between bone formation and bone resorption, increasing the risk of OP. Conversely, bones also play a role in fat and muscle metabolism. In the context of aging and obesity, the comprehensive review focuses on the effects of mechanical stimulation, mesenchymal stem cells (MSCs), chronic inflammation, myokines, and adipokines on musculoskeletal, at the same time, the impact of osteokines on muscle-lipid metabolism were also analyzed. So far, exercise combined with diet therapy is the most effective strategy for increasing musculoskeletal mass. A holistic treatment of musculoskeletal diseases is still in the preliminary exploration stage. Therefore, this article aims to improve the understanding of musculoskeletal -fat interactions in SO and OP, explores targets that can provide holistic treatment for SO combined with OP, and discusses current limitations and challenges. We hope to provide relevant ideas for developing specific therapies and improving disease prognosis in the future.

Effects of Different Resistance Training Frequencies on Body Composition, Muscular Strength, Muscle Quality, and Metabolic Biomarkers in Sarcopenic Older Women

ABSTRACT

Dos Santos, VR, Antunes, M, dos Santos, L, Nascimento, MA, Pina, FLC, Carneiro, NH, Trindade, MCC, Venturini, D, Barbosa, DS, and Cyrino, ES. Effects of different resistance training frequencies on body composition, muscular strength, muscle quality, and metabolic biomarkers in sarcopenic older women. J Strength Cond Res 38(9): e521-e528, 2024-Resistance training (RT) can ameliorate outcomes related to sarcopenia by promoting beneficial changes in muscular strength, skeletal muscle mass (SMM), and muscle quality. This study compared the effects of 12 weeks of RT performed 2 and 3 sessions a week on body composition, muscular strength, muscle quality, and metabolic biomarkers in sarcopenic older women. Thirty-four sarcopenic older women (>60 years) were randomly assigned to perform a whole-body RT program, either 2 (G2X, n = 18) or 3 (G3X, n = 16) sessions a week during 12 weeks (8 exercises, single set of 10-15 repetitions). Body composition, muscular strength, muscle quality, and metabolic biomarkers were assessed before and after the intervention. Both groups increased (p < 0.05) 1 repetition maximum total muscular strength (G2X = +20.4% and G3X = +21.0%), SMM (G2X = +4.0% and G3X = +7.0%), and improved muscle quality (G2X = +16.7% and G3X = +13.6%), with no differences between groups (p > 0.05). No change over time was found for IGF-1 and testosterone (p > 0.05). Our results suggest that 12 weeks of RT performed at a lower weekly frequency is as effective as a higher frequency in improving muscular strength, SMM, and muscle quality in sarcopenic older women.

Different resistance training volumes on strength, functional fitness, and body composition of older people: A systematic review with meta-analysis

Aging causes several changes in the body, reducing strength and muscle mass, which leads to a decline in function. Resistance training (RT) is used to counteract these changes. However, there is still ongoing debate about the optimal volume of RT in the context of aging. We systematically reviewed articles that assessed the impact of different volumes of RT on muscular strength, functional fitness, and body composition of older people. We conducted a systematic search in the PubMed/MEDLINE, Scopus, Embase, Web of Science, Cochrane Library, LILACS, PEDro, and Google Scholar databases, using keywords related to the older population and various RT volumes. We performed meta-analyses for each outcome separately using intervention time in weeks for subgroup analyses. We employed random effects models for all meta-analyses and expressed the results as standardized mean differences (Hedges' g). We included 31 studies, encompassing a total of 1.744 participants. The sample size ranged from 18 to 376, with an average size of 56 participants. Participants' ages ranged from 60 to 83 years. On average, HV-RT (High-Volume Resistance Training) induced significant adaptations in muscle strength of the upper limbs (g = 0.36; 95 % CI = 0.11-0.61) and lower limbs (g = 0.41; 95 % CI = 0.23-0.59), with superiority more pronounced after 12 weeks of training. Regarding functional fitness, there was a tendency favoring HV-RT (g = 0.41; 95 % CI = 0.23-0.59). Thus, HV-RT outperforms LV-RT (Low-Volume Resistance Training) in enhancing muscle strength, particularly in longer interventions with independent older adults.

Motor Performance and Skill Acquisition in Oral Motor Training With Exergames: A Pilot Study

Objective

To investigate the effects of oral-motor training with exergames on motor performance and motor skill acquisition in two different age groups.

Methods

Thirty-two healthy participants were recruited in the current pilot study and divided equally into two groups (Gen Z and Baby Boomers) according to their age. A pair of electromyographic (EMG) electrodes were placed on the participants’ masseter muscles. The EMG device communicated via Bluetooth with a mobile video game in response to the electromyographic activity of the masseter muscles during clenching. During the experimental session, participants were asked to play a video game in five blocks of 5 min each, with a 3-min break between each time block. The goal of the game was to collect as many coins (game points) as possible and to dodge/avoid upcoming obstacles (game life). Motor performance was assessed by performance scores and the number of game lives. Skill acquisition was measured by task efficiency (ratio of performance scores and number of game lives) across time blocks.

Results

The results of the study showed significantly lower performance scores (p < 0.001), a higher number of game lives (p < 0.001), and lower task efficiency in the Baby Boomer group compared to the Gen Z group. Specifically, the results showed that there was a significant difference in task efficiency between the first and second, third and fourth, fourth- and fifth-time blocks in the Gen Z group (p < 0.002). However, there was only a significant difference between first- and second-time blocks in the Baby Boomer group (p = 1.012), suggesting that skill acquisition in the Baby Boomer group did not change significantly over the course of the time blocks.

Conclusion

The study showed higher motor performance and superior motor skill acquisition with novel exergame training in the Gen Z group compared to the Baby Boomer group. The results of the study indicate that there is an improvement in oral motor skills with short-term training, yet the differences in oral motor skills between the two groups are still evident. The Baby Boomer group, unlike the Gen Z group, did not show robust improvement in task efficiency over the course of the series.

Functional changes in decidual mesenchymal stem/stromal cells are associated with spontaneous onset of labour

Ageing and parturition share common pathways, but their relationship remains poorly understood. Decidual cells undergo ageing as parturition approaches term, and these age-related changes may trigger labour. Mesenchymal stem/stromal cells (MSCs) are the predominant stem cell type in the decidua. Stem cell exhaustion is a hallmark of ageing, and thus ageing of decidual MSCs (DMSCs) may contribute to the functional changes in decidual tissue required for term spontaneous labour. Here, we determine whether DMSCs from patients undergoing spontaneous onset of labour (SOL-DMSCs) show evidence of ageing-related functional changes compared with those from patients not in labour (NIL-DMSCs), undergoing Caesarean section. Placentae were collected from term (37-40 weeks of gestation), SOL (n = 18) and NIL (n = 17) healthy patients. DMSCs were isolated from the decidua basalis that remained attached to the placenta after delivery. DMSCs displayed stem cell-like properties and were of maternal origin. Important cell properties and lipid profiles were assessed and compared between SOL- and NIL-DMSCs. SOL-DMSCs showed reduced proliferation and increased lipid peroxidation, migration, necrosis, mitochondrial apoptosis, IL-6 production and p38 MAPK levels compared with NIL-DMSCs (P < 0.05). SOL- and NIL-DMSCs also showed significant differences in lipid profiles in various phospholipids (phosphatidylethanolamine, phosphatidylglycerol, phosphatidylinositol, phosphatidylserine), sphingolipids (ceramide, sphingomyelin), triglycerides and acyl carnitine (P < 0.05). Overall, SOL-DMSCs had altered lipid profiles compared with NIL-DMSCs. In conclusion, SOL-DMSCs showed evidence of ageing-related reduced functionality, accumulation of cellular damage and changes in lipid profiles compared with NIL-DMSCs. These changes may be associated with term spontaneous labour.

Association of muscular fitness with rehospitalization for heart failure with reduced ejection fraction

BACKGROUND

Limited information is available regarding the prognostic potential of muscular fitness parameters in heart failure (HF) with reduced ejection fraction (HFrEF).

HYPOTHESIS

We aimed to investigate the predictive potential of knee extensor muscle strength and power on rehospitalization and evaluate the correlation between exercise capacity and muscular fitness in patients newly diagnosed with HFrEF.

METHODS

Ninety nine patients hospitalized with a new diagnosis of HF were recruited (64 men; aged 58.7 years [standard deviation (SD), 13.2 years]; 32.3% ischemic; ejection fraction, 28% [SD, 8%]). The inclusion criteria were left ventricular ejection fraction <40% and sufficient clinical stability to undergo exercise testing. Aerobic exercise capacity was measured with cardiopulmonary exercise testing. Knee extensor maximal voluntary isometric contraction (MVIC) and muscle power (MP) were measured using the Baltimore therapeutic equipment system. The clinical outcome was HF rehospitalization.

RESULTS

Over a mean follow-up period of 1709 ± 502 days, 39 patients were rehospitalized due to HF exacerbation. HF rehospitalization was more probable for patients with diabetes and lower oxygen uptake at peak exercise (peak VO₂ ), knee extensor MVIC, and MP. The Kaplan-Meier survival analysis revealed significantly different cumulative HF rehospitalization rates according to the tertiles of peak VO₂ (P = 0.005) and MP (P = 0.002). Multivariable Cox proportional hazard model showed that the lowest tertiles of peak VO₂ (hazard ratio (HR), 6.26; 95% confidence interval (CI), 1.93-20.27); and MP (HR, 5.29; 95% CI, 1.05-26.53) were associated with HF rehospitalization. Knee extensor muscle power was an independent predictor for rehospitalization in patients with HFrEF.

CONCLUSION

Knee extensor muscle power was an independent predictor for rehospitalization in patients with HFrEF.

Ageing in human parturition: impetus of the gestation clock in the decidua†

Despite sharing many common features, the relationship between ageing and parturition remains poorly understood. The decidua is a specialized lining of endometrial tissue, which develops in preparation for pregnancy. The structure and location of the decidua support its role as the physical scaffold for the growing embryo and placenta, and thus, it is vital to sustain pregnancy. Approaching term, the physical support properties of the decidua are naturally weakened to permit parturition. In this review, we hypothesize that the natural weakening of decidual tissue at parturition is promoted by the ageing process. Studies of the ageing-related functional and molecular changes in the decidua at parturition are reviewed and classified using hallmarks of ageing as the framework. The potential roles of decidual mesenchymal stem/stromal cell (DMSC) ageing in labor are also discussed because, although stem cell exhaustion is also a hallmark of ageing, its role in labor is not completely understood. In addition, the potential roles of extracellular vesicles secreted by DMSCs in labor, and their parturition-related miRNAs, are reviewed to gain further insight into this research area. In summary, the literature supports the notion that the decidua ages as the pregnancy progresses, and this may facilitate parturition, suggesting that ageing is the probable impetus of the gestational clocks in the decidua. This conceptual framework was developed to provide a better understanding of the natural ageing process of the decidua during parturition as well as to encourage future studies of the importance of healthy ageing for optimal pregnancy outcomes.

Sinensetin regulates age-related sarcopenia in cultured primary thigh and calf muscle cells

Background

Sarcopenia, the decline of skeletal muscle tissue attributed to primary aging is a major concern in older adults. Flavonoids might have potential benefits by modulating the regulation of satellite cells, thus preventing muscle loss. Sinensetin (SIN), a citrus methylated flavone with anti-inflammatory and anti-proliferative activity, can enhance lipolysis. The objective of the present study was to investigate whether SIN might have sarcopenia-suppressing effect on satellite cells from thigh and calf muscle tissues of young and old rats.

Methods

Primary muscle cells were obtained from thigh and calf tissues of young and old group rats by dissection. Obtained satellite cells were incubated with indicated concentrations of SIN (50 and 100 μM) treated and untreated condition in differentiation medium. Morphological changes of cells were examined using a phase-contrast microscope. Protein expression levels of myoD and myogenin were analyzed by Western blot. Cells treated with or without SIN under differentiation condition were also immunocytochemically stained for myogenin and 4′,6-diamidino-2-phenylindole (DAPI).

Results

Morphologically, the differentiation extracted satellite cells was found to be more evident in SIN treated group of aged rat′s cells than that in SIN untreated group. Expression levels of myoD and myogenin proteins involved in myogenesis were increased upon treatment with SIN.

Conclusions

Collectively, our results indicate that SIN can alleviate age-related sarcopenia by increasing differentiation rate and protein levels of myoD and myogenin.

Strengthening the Brain-Is Resistance Training with Blood Flow Restriction an Effective Strategy for Cognitive Improvement?

Aging is accompanied by a decrease in physical capabilities (e.g., strength loss) and cognitive decline. The observed bidirectional relationship between physical activity and brain health suggests that physical activities could be beneficial to maintain and improve brain functioning (e.g., cognitive performance). However, the exercise type (e.g., resistance training, endurance training) and their exercise variables (e.g., load, duration, frequency) for an effective physical activity that optimally enhance cognitive performance are still unknown. There is growing evidence that resistance training induces substantial brain changes which contribute to improved cognitive functions. A relative new method in the field of resistance training is blood flow restriction training (BFR). While resistance training with BFR is widely studied in the context of muscular performance, this training strategy also induces an activation of signaling pathways associated with neuroplasticity and cognitive functions. Based on this, it seems reasonable to hypothesize that resistance training with BFR is a promising new strategy to boost the effectiveness of resistance training interventions regarding cognitive performance. To support our hypothesis, we provide rationales of possible adaptation processes induced by resistance training with BFR. Furthermore, we outline recommendations for future studies planning to investigate the effects of resistance training with BFR on cognition.

Effects of home-based tele-exercise on sarcopenia among community-dwelling elderly adults: Body composition and functional fitness

OBJECTIVES

This study aims to develop a form of tele-exercise that would enable real-time interactions between exercise instructors and community-dwelling elderly people and to investigate its effects on improvement of sarcopenia-related factors of body composition and functional fitness among the elderly.

DESIGN

Randomized, controlled trial, with a 12-week intervention period.

SETTING

Community-dwelling senior citizens in Gangseo-gu, Seoul, South Korea.

PARTICIPANTS

The participants were 23 elderly individuals (tele-exercise group: 11, control group: 12), aged 69 to 93years.

INTERVENTION

The tele-exercise program was developed utilizing a 15-in. all-in-one PC and video conferencing software (Skype™), with broadband Internet connectivity. The tele-exercise group performed supervised resistance exercise at home for 20-40min a day three times per week for 12weeks. The remote instructor provided one-on-one instruction to each participant during the intervention. The control group maintained their lifestyles without any special intervention.

MEASUREMENTS

The sarcopenia-related factors of body composition and functional fitness were examined prior to, as well as following, a 12-week intervention period. The data were analyzed with a two-way repeated measures ANOVA.

RESULTS

There were significant improvements in lower limb muscle mass (p=0.017), appendicular lean soft tissue (p=0.032), total muscle mass (p=0.033), and chair sit-and-reach length (p=0.019) for the tele-exercise group compared to the control group. No group×time interaction effects were detected for the 2-min step, chair stand, and time effects (p<0.05).

CONCLUSION

Video conferencing-based supervised resistance exercise had positive effects on sarcopenia-related factors such as total-body skeletal muscle mass, appendicular lean soft tissue, lower limb muscle mass, and the chair sit-and-reach scores among community-dwelling elderly adults. These results imply that tele-exercise can be a new and effective intervention method for increasing skeletal muscle mass and the physical functioning of the lower limbs from the perspective of sarcopenia improvement among the elderly.

Exercise does not enhance aged bone's impaired response to artificial loading in C57Bl/6 mice

Bones adapt their structure to their loading environment and so ensure that they become, and are maintained, sufficiently strong to withstand the loads to which they are habituated. The effectiveness of this process declines with age and bones become fragile fracturing with less force. This effect in humans also occurs in mice which experience age-related bone loss and reduced adaptation to loading. Exercise engenders many systemic and local muscular physiological responses as well as engendering local bone strain. To investigate whether these physiological responses influence bones' adaptive responses to mechanical strain we examined whether a period of treadmill exercise influenced the adaptive response to an associated period of artificial loading in young adult (17-week) and old (19-month) mice. After treadmill acclimatization, mice were exercised for 30 min three times per week for two weeks. Three hours after each exercise period, right tibiae were subjected to 40 cycles of non-invasive axial loading engendering peak strain of 2250 με. In both young and aged mice exercise increased cross-sectional muscle area and serum sclerostin concentration. In young mice it also increased serum IGF1. Exercise did not affect bone's adaptation to loading in any measured parameter in young or aged bone. These data demonstrate that a level of exercise sufficient to cause systemic changes in serum, and adaptive changes in local musculature, has no effect on bone's response to loading 3h later. This study provides no support for the beneficial effects of exercise on bone in the elderly being mediated by systemic or local muscle-derived effects rather than local adaptation to altered mechanical strain.

Effects of age and hindlimb immobilization and remobilization on fast troponin T precursor mRNA alternative splicing in rat gastrocnemius muscle

Fast skeletal muscle troponin T (TNNT3) is an important component of the skeletal muscle contractile machinery. The precursor mRNA (pre-mRNA) encoding TNNT3 is alternatively spliced, and changes in the pattern of TNNT3 splice form expression are associated with alterations in thin-filament calcium sensitivity and force production during muscle contraction and thereby regulate muscle function. Interestingly, during aging, the muscle force/cross-sectional area is reduced, suggesting that loss of mass does not completely account for the impaired muscle function that develops during the aging process. Therefore, in this study, we tested the hypothesis that age and changes in muscle loading are associated with alterations in Tnnt3 alternative splicing in the rat gastrocnemius muscle. We found that the relative abundance of several Tnnt3 splice forms varied significantly with age among 2-, 9-, and 18-month-old rats and that the pattern correlated with changes in body mass rather than muscle mass. Hindlimb immobilization for 7 days resulted in dramatic alterations in splice form relative abundance such that the pattern was similar to that observed in lighter animals. Remobilization for 7 days restored the splicing pattern toward that observed in the nonimmobilized limb, even though muscle mass had not yet begun to recover. In conclusion, the results suggest that Tnnt3 pre-mRNA alternative splicing is modulated rapidly (i.e., within days) in response to changes in the load placed on the muscle. Moreover, the results show that restoration of Tnnt3 alternative splicing to control patterns is initiated prior to an increase in muscle mass.

Intense Walking Exercise Affects Serum IGF-1 and IGFBP3

Background

Insulin-like growth factor (IGF-1) is associated with chronic diseases such as diabetes, cardiovascular disease, and hypertension, as well as muscle dysfunction. Previous studies of exercise interventions yield controversial results regarding plasma IGF-1, IGFBP3, and IGF-1/IGFBP3 ratio. In this study, we examined whether 100 km walking exercise affects serum levels of IGF-1 and IGFBP3 and IGF-1/IGFBP3 ratio. We also investigated several metabolic-related blood parameters before and after walking.

Methods

Participants were 14 healthy middle aged men (41.0 ± 6.78 years of age). We assessed body composition and measured metabolic-related blood indicators, such as such as lipid profiles, glucose, renal and hepatic metabolic bio-markers before and after a 100 km walking race. Blood samples from all participants were taken before and immediately after the walkathon. We also analyzed serum levels of IGF-1 and IGFBP3, and calculated the IGF-1/IGFBP3 ratio.

Results

After participants completed a 100 km walking race, some of their metabolic profiles were markedly changed. Serum levels of IGF-1 and IGFBP3 were significantly decreased, and therefore the IGF-1/IGFBP3 ratio also decreased before and after 100 km of walking.

Conclusion

Our results indicate that intense walking exercise affects serum levels of IGF-1 and IGFBP3 as well as metabolic bio-markers including high density cholesterol, glucose and triglycerides.

Influence of ageing and essential amino acids on quantitative patterns of troponin T alternative splicing in human skeletal muscle

Ageing is associated with a loss of skeletal muscle performance, a condition referred to as sarcopenia. In part, the age-related reduction in performance is due to a selective loss of muscle fiber mass, but mass-independent effects have also been demonstrated. An important mass-independent determinant of muscle performance is the pattern of expression of isoforms of proteins that participate in muscle contraction (e.g., the troponins). In the present study, we tested the hypothesis that ageing impairs alternative splicing of the pre-mRNA encoding fast skeletal muscle troponin T (TNNT3) in human vastus lateralis muscle. Furthermore, we hypothesized that resistance exercise alone or in combination with consumption of essential amino acids would attenuate age-associated effects on TNNT3 alternative splicing. Our results indicate that ageing negatively affects the pattern of TNNT3 alternative splicing in a manner that correlates quantitatively with age-associated reductions in muscle performance. Interestingly, whereas vastus lateralis TNNT3 alternative splicing was unaffected by a bout of resistance exercise 24 h prior to muscle biopsy, ingestion of a mixture of essential amino acids after resistance exercise resulted in a significant shift in the pattern of TNNT3 splice form expression in both age groups to one predicted to promote greater muscle performance. We conclude that essential amino acid supplementation after resistance exercise may provide a means to reduce impairments in skeletal muscle quality during ageing in humans.

Does the heel-rise test explain functional capacity in venous insufficiency?

Introduction Individuals with chronic venous insufficiency (CVI) have muscle pump dysfunction and reduced functionality. However, studies are inconsistent in proving whether a particular test can assess muscle functional capacity. Therefore, the aim of this study was to evaluate whether the heel-rise test (HRT) is able to explain functional capacity in patients with CVI. Materials and methods Subjects with CVI aged between 20 and 59 years old were selected for this study. All participants were classified by means of the Clinical Anatomy Etiology Pathophysiology Classification of Chronic Venous Disease (CEAP). The HRT and the shuttle walk test (SWT) were performed. Descriptive statistics, Spearman correlation, linear models and regression variance analysis (one-way ANOVA) were used for data analysis. Significance was set at alpha ≤ 5%. Results 79 subjects were included in the study (38.79 ± 1.34 years). The HRT was able to explain functional capacity only in individuals aged between 50-59 years (R2 = 0.60, p = 0.0001). The heel-rise test was not sensitive to detect differences between the CEAP classes analyzed (p > 0.05). Conclusion The HRT was able to explain functional capacity in individuals aged between 50-59 years, and it can be applied in clinical practice for the functional evaluation of patients with CVI with mild severity in this age range.

Pretreatment with mechano-growth factor E peptide protects bone marrow mesenchymal cells against damage by fluid shear stress

Improper fluid shear stress (FSS) can cause serious damages to bone marrow mesenchymal stem cells (MSCs). Mechano-growth factor (MGF) E peptide pretreatment was proposed to protect MSCs against FSS damage in this study. MSCs were exposed to FSS for 30 min after they were pretreated with MGF E peptide for 24 h. Then, the effects of MGF E peptide on the viability, proliferation and cell apoptosis of MSCs were investigated. MGF E peptide pretreatment could recover the cellular metabolic activity of MSCs reduced by 72 dyne cm(-2) FSS and had a synergistic effect with FSS on the cellular metabolic viability of MSCs under 24 and 72 dyne cm(-2) FSS. These results suggested that MGF E peptide pretreatment could be an effective method for the protection of FSS damage in bone tissue engineering.

Muscle atrophy, voluntary activation disturbances, and low serum concentrations of IGF-1 and IGFBP-3 are associated with weakness in people with chronic stroke

BACKGROUND

The muscle weakness that is exhibited poststroke is due to a multifactorial etiology involving the central nervous system and skeletal muscle changes. Insulinlike growth factor 1 (IGF-1) and IGF binding protein 3 (IGFBP-3) have been described as biomarkers of neuromuscular performance in many conditions. However, no information about these biomarkers is available for people with chronic hemiparesis.

OBJECTIVE

The purpose of this study was to investigate possible factors involved in muscle weakness, such as IGF-1 and IGFBP-3 serum concentrations, muscle volume, and neuromuscular performance of the knee flexors and extensors, in people with chronic hemiparesis poststroke.

DESIGN

This was a cross-sectional study.

METHODS

A cross-sectional study was performed on 14 individuals poststroke who were paired with healthy controls. Mobility, function, balance, and quality of life were recorded as outcome measures. Knee flexor and extensor muscle volumes and neuromuscular performance were measured using nuclear magnetic resonance imaging, dynamometry, and electromyography. The serum concentrations of IGF-1 and IGFBP-3 were quantified by enzyme-linked immunosorbent assay (ELISA).

RESULTS

The hemiparetic group had low serum concentrations of IGF-1 (25%) and IGFBP-3 (40%); reduced muscle volume in the vastus medialis (32%), vastus intermedius (29%), biceps femoris (16%), and semitendinosus and semimembranosus (12%) muscles; reduced peak torque, power, and work of the knee flexors and extensors; and altered agonist and antagonist muscle activation compared with controls.

CONCLUSIONS

Low serum concentrations of IGF-1 and IGFBP-3, deficits in neuromuscular performance, selective muscle atrophy, and decreased agonist muscle activation were found in the group with chronic hemiparesis poststroke. Both hemorrhagic and ischemic stroke were considered, and the data reflect a chronic poststroke population with good function.

An overview of structure, mechanical properties, and treatment for age-related tendinopathy

Tendons transfer tensile loads from muscle to bone, which enable joint motions and stabilize joints. Tendons sustain large mechanical loads in vivo and as a result, tendons were frequently injured. Aging has been confirmed as a predisposing factor of tendinopathy and bad recovery quality following tendon repair. Current treatment methods are generally not effective and involve either symptomatic relief with non-steroidal antiinflammatory drugs and physical therapy or surgery when conservative treatments failed. The limitation in treatment options is due to our incomplete knowledge of age-related tendinopathy. Studies over the past decades have uncovered a number of important mechanical and cellular changes of aging tendon. However, the basis of aging as a major risk factor for tendon injury and impaired tendon healing remained poorly understood. The objectives of this review are to provide an overview of the current knowledge about the aging-associated changes of structure, mechanical properties and treatment in tendon and highlight causes and therapies for age-related tendinopathy.

Sonic hedgehog therapy in a mouse model of age-associated impairment of skeletal muscle regeneration

Sonic hedgehog (Shh) is a morphogen regulating muscle development during embryogenesis. We have shown that the Shh pathway is postnatally recapitulated after injury and during regeneration of the adult skeletal muscle and regulates angiogenesis and myogenesis after muscle injury. Here, we demonstrate that in 18-month-old mice, there is a significant impairment of the upregulation of the Shh pathway that physiologically occurs in the young skeletal muscle after injury. Such impairment is even more pronounced in 24-month-old mice. In old animals, intramuscular therapy with a plasmid encoding the human Shh gene increases the regenerative capacities of the injured muscle, in terms of Myf5-positive cells, regenerating myofibers, and fibrosis. At the molecular level, Shh treatment increases the upregulation of the prototypical growth factors, insulin-like growth factor-1 and vascular endothelial growth factor. These data demonstrate that Shh increases regeneration after injury in the muscle of 24-month-old mice and suggest that the manipulation of the Shh pathway may be useful for the treatment of muscular diseases associated with aging.

Interaction between Muscle and Bone

The clinical significance of sarcopenia and osteoporosis has increased with the increase in the population of older people. Sarcopenia is defined by decreased muscle mass and impaired muscle function, which is related to osteoporosis independently and dependently. Numerous lines of clinical evidence suggest that lean body mass is positively related to bone mass, which leads to reduced fracture risk. Genetic, endocrine and mechanical factors affect both muscle and bone simultaneously. Vitamin D, the growth hormone/insulin-like growth factor I axis and testosterone are physiologically and pathologically important as endocrine factors. These findings suggest the presence of interactions between muscle and bone, which might be very important for understanding the physiology and pathophysiology of sarcopenia and osteoporosis. Muscle/bone relationships include two factors: local control of muscle to bone and systemic humoral interactions between muscle and bone. As a putative local inducer of muscle ossification, we found Tmem119, a parathyroid hormone-responsive osteoblast differentiation factor. Moreover, osteoglycin might be one of the muscle-derived humoral bone anabolic factors. This issue may be important for the development of novel drugs and biomarkers for osteoporosis and sarcopenia. Further research will be necessary to clarify the details of the linkage of muscle and bone.

Low-dose baclofen therapy raised plasma insulin-like growth factor-1 concentrations, but not into the normal range in a predictable and sustained manner in men with chronic spinal cord injury

OBJECTIVE

To evaluate, whether once-daily oral baclofen administration increases and/or sustains plasma insulin-like growth factor-1 (IGF-1) concentration in 11 men with chronic spinal cord injury (SCI) and IGF-1 deficiency (i.e. <250 ng/ml).

DESIGN

Prospective, open-label, dose titration study. Baclofen was administered at 20 mg/day for 8 weeks; then increased to 40 mg/day for another 8 weeks. Plasma IGF-1 and self-reported side effects were measured at baseline and every other week for the duration of the study.

RESULTS

The subjects were 43 ± 12 years old, had duration of injury of 20 ± 12 years; eight subjects had a complete motor injury, and eight had paraplegia. Nine of 11 subjects completed the 20 mg/day treatment and 5 subjects completed the 40 mg/day treatment. Plasma IGF-1 levels improved with each baclofen dose; however, only one subject increased from baseline and remained above the targeted physiological range of 250 ng/ml throughout treatment. A significant increase in IGF-1concentration was observed between baseline and week 2 (154 ± 63 vs. 217 ± 69 ng/ml; P < 0.05), weeks 8 and 10 (188 ± 95 vs. 228 ± 93 ng/ml; P < 0.05), and weeks 8 and 16 (188 ± 95 vs. 259 ± 92 ng/ml; P < 0.05). No serious side effects were observed at 20 mg/day; the 40 mg/day dose was less well tolerated.

CONCLUSION

Baclofen was not effective at sustaining plasma IGF-1 concentrations in the physiological range in men with chronic SCI.

SIRT1 regulates differentiation of mesenchymal stem cells by deacetylating β-catenin

Mesenchymal stem cells (MSCs) are multi-potent cells that can differentiate into osteoblasts, adipocytes, chondrocytes and myocytes. This potential declines with aging. We investigated whether the sirtuin SIRT1 had a function in MSCs by creating MSC specific SIRT1 knock-out (MSCKO) mice. Aged MSCKO mice (2.2 years old) showed defects in tissues derived from MSCs; i.e. a reduction in subcutaneous fat, cortical bone thickness and trabecular volume. Young mice showed related but less pronounced effects. MSCs isolated from MSCKO mice showed reduced differentiation towards osteoblasts and chondrocytes in vitro, but no difference in proliferation or apoptosis. Expression of β-catenin targets important for differentiation was reduced in MSCKO cells. Moreover, while β-catenin itself (T41A mutant resistant to cytosolic turnover) accumulated in the nuclei of wild-type MSCs, it was unable to do so in MSCKO cells. However, mutating K49R or K345R in β-catenin to mimic deacetylation restored nuclear localization and differentiation potential in MSCKO cells. We conclude that SIRT1 deacetylates β-catenin to promote its accumulation in the nucleus leading to transcription of genes for MSC differentiation.

Estimation of the efficacy of inertial training in older women

This study aimed to estimate the efficacy of inertial training in older women using the Inertial Training and Measurement System (ITMS), an original device. Forty-five active women age 53-74 yr performed inertial training with 2 different loads (0 or 5 kg) 3 times weekly for 4 wk. Training sessions consisted of exercises involving the shoulder muscles of the dominant and nondominant arms. The maximal torque and power developed by the dominant and nondominant arms in the 0-kg and 5-kg groups were significantly greater after 4 wk of inertial training (with the exception of torque for the nondominant arm in the 5-kg group; p > .05). Thus, short-term training using the ITMS is efficacious and can be used in older women to improve strength and power. However, ITMS training-induced changes in older women are greater after application of smaller external loads.