Age-related Muscle Mass Research Articles

The Theoretical and Practical Research of Traditional Chinese Medicine in the Prevention and Treatment of Sarcopenia

Sarcopenia, as an age-related skeletal muscle mass and strength decline in the elderly syndrome, seriously affects the quality of life of patients. In recent years, with the aggravation of aging in China, the incidence of sarcopenia is gradually increasing. The research on sarcopenia in traditional Chinese medicine is also deepening, and relatively rich experience and results have been achieved. This paper summarizes and expounds the theoretical research and intervention methods of traditional Chinese medicine for sarcopenia by combing the relevant literature. The purpose of this paper is to discuss the current status of its theoretical research and to look forward to the future development trend, so that the etiology and mechanism of sarcopenia in TCM can be further explored and the treatment plan can be optimized, and more possibilities for the treatment of sarcopenia in TCM can be provided in the future research.

Effect of high plant protein/peptide nutrition supplementation on knee osteoarthritis in older adults with sarcopenia: A randomized, double-blind, placebo-controlled trial

Background & AimsSkeletal muscle is an important contributor to joint health. Previous studies have shown that age-related muscle mass and strength loss are closely associated with the development of knee osteoarthritis. The objective of this study is to investigate whether a high plant protein/peptide nutrition supplementation can alleviate knee osteoarthritis by improving muscle mass and strength. MethodsThis randomized, double-blind, placebo-controlled trial that included participants aged 50–70 years diagnosed with knee osteoarthritis and sarcopenia was conducted in China from February 2022 to September 2022 (ChiCTR2200056415). Participants were randomized to receive a 12-week high plant protein/peptide nutrition supplementation or a placebo twice daily, with one serving each after breakfast and lunch, respectively. The primary outcome analyzed using intention-to-treat analysis was difference in Short Physical Performance Battery (SPPB) from baseline to week 12 between the two groups. The secondary outcomes included changes in muscle mass, strength, symptom and imaging of knee osteoarthritis, body composition, biochemical parameters, and health quality scores. ResultsAfter 12 weeks, a total of 124 participants (38.7% male) completed the trial and were included in the final analysis. Over the 12-week follow-up, the experimental group showed a significant improvement in the SPPB total score (1.03, 95% CI, 0.69 to 1.38, P < 0.0001) compared with the placebo group. Grip strength (2.83 kg, 95% CI, 2.13–3.53, P < 0.0001) and skeletal muscle mass index (0.66 kg/m2, 95% CI, 0.45–0.86, P < 0.0001) were also significantly increased in the experimental group compared with the placebo group. The mean change in Western Ontario and McMaster Universities Osteoarthritis Index total score was −3.95 points (95% CI, −5.02 to −2.89, P < 0.0001) in the experimental group and 0.23 points (95% CI, −0.17 to 0.63, P = 0.253) in the placebo group. Additionally, within the experimental group, nine participants experienced an improvement in osteophyte magnetic resonance imaging results, while no improvement was observed in the placebo group. The experimental group also exhibited significant improvements in health quality compared with the placebo group as assessed by Short Form 36, the World Health Organization Quality of Life Brief Scale, and the Chalder Fatigue Scale. No serious adverse event was reported during the trial. ConclusionOral supplementation with high levels of plant protein/peptides can alleviate symptoms of osteoarthritis in elderly individuals with minor and mild knee osteoarthritis and sarcopenia. The improvement may be attributed to the enhancement of muscle mass, strength, and physical performance.

Sex differences in physical functioning among older adults: cross-sectional results from the OUTDOOR ACTIVE study

BackgroundMaintaining good functional ability is a key component of healthy ageing and a basic requirement for carrying out activities of daily living, staying independent, and delaying admission to a nursing home. Even though women have a higher life expectancy and slower age-related muscle mass loss than men, they often show a higher prevalence of limitations in physical functioning. However, the reasons behind these sex differences are still unclear. Therefore, the aims of this study were to investigate sex differences among older adults regarding physical functioning and to study which factors are explaining these sex differences.MethodsCross-sectional data from participants of the OUTDOOR ACTIVE study residing in Bremen, Germany, aged 65 to 75 years, were included in the analyses. Physical functioning was assessed via a self-administered questionnaire using the SF-36 10-item Physical Functioning Scale. Social, lifestyle, and health-related factors were also assessed using the questionnaire. Physical activity was measured objectively using wrist-worn accelerometers over seven consecutive days. Descriptive analyses with absolute and relative frequencies, means and standard deviations, as well as T-tests and chi-square tests were carried out. To test for associations between sex, physical functioning, and several individual factors, linear regressions were performed.ResultsData of 2 141 participants (52.1% female) were included in the study. Women and men showed statistically significant differences in physical functioning, with men perceiving fewer limitations than women. On average, women had a physical functioning score of 81.4 ± 19.3 and men 86.7 ± 17.0. Linear regression showed a statistically significant negative association between physical functioning score and sex (β: -0.15, 95% CL: -0.19, -0.10). The association remained statistically significant when adding individual factors to the model. All factors together were only able to explain 51% of the physical functioning-sex association with health indicators and the presence of chronic diseases being the most influential factors.ConclusionsWe found sex differences in physical functioning, with older women having more limitations than older men. The results showed that health-related factors and chronic diseases played the biggest roles in the different physical functioning scores of women and men. These findings contribute to future longitudinal, more in-depth research.Trial registrationGerman Clinical Trials Register DRKS00015117 (Date of registration 17-07-2018).

Distribution Dynamics and Proposed Determinants: Exploring Morphological, Clinical Laboratory, and Lifestyle Factors in the Coexistence of Age-Related Skeletal Muscle Mass L oss and Obesity among Y oung Men: A Nationwide Cross-Sectional Study

Distribution Dynamics and Proposed Determinants: Exploring Morphological, Clinical Laboratory, and Lifestyle Factors in the Coexistence of Age-Related Skeletal Muscle Mass L oss and Obesity among Y oung Men: A Nationwide Cross-Sectional Study

Greater myofibrillar protein synthesis following weight-bearing activity in obese old compared with non-obese old and young individuals

The mechanisms through which obesity impacts age-related muscle mass regulation are unclear. In the present study, rates of integrated myofibrillar protein synthesis (iMyoPS) were measured over 48-h prior-to and following a 45-min treadmill walk in 10 older-obese (O-OB, body fat[%]: 33 ± 3%), 10 older-non-obese (O-NO, 20 ± 3%), and 15 younger-non-obese (Y-NO, 13 ± 5%) individuals. Surface electromyography was used to determine thigh muscle “activation”. Quadriceps cross-sectional area (CSA), volume, and intramuscular thigh fat fraction (ITFF) were measured by magnetic resonance imaging. Quadriceps maximal voluntary contraction (MVC) was measured by dynamometry. Quadriceps CSA and volume were greater (muscle volume, Y-NO: 1182 ± 232 cm3; O-NO: 869 ± 155 cm3; O-OB: 881 ± 212 cm3, P < 0.01) and ITFF significantly lower (m. vastus lateralis, Y-NO: 3.0 ± 1.0%; O-NO: 4.0 ± 0.9%; O-OB: 9.1 ± 2.6%, P ≤ 0.03) in Y-NO compared with O-NO and O-OB, with no difference between O-NO and O-OB in quadriceps CSA and volume. ITFF was significantly higher in O-OB compared with O-NO. Relative MVC was lower in O-OB compared with Y-NO and O-NO (Y-NO: 5.5 ± 1.6 n·m/kg−1; O-NO: 3.9 ± 1.0 n·m/kg−1; O-OB: 2.9 ± 1.1 n·m/kg−1, P < 0.0001). Thigh muscle “activation” during the treadmill walk was greater in O-OB compared with Y-NO and O-NO (Y-NO: 30.5 ± 13.5%; O-NO: 35.8 ± 19.7%; O-OB: 68.3 ± 32.3%, P < 0.01). Habitual iMyoPS did not differ between groups, whereas iMyoPS was significantly elevated over 48-h post-walk in O-OB (+ 38.6 ± 1.2%·day−1, P < 0.01) but not Y-NO or O-NO (+ 11.4 ± 1.1%·day−1 and + 17.1 ± 1.1%·day−1, respectively, both P > 0.271). Equivalent muscle mass in O-OB may be explained by the muscle anabolic response to weight-bearing activity, whereas the age-related decline in indices of muscle quality appears to be exacerbated in O-OB and warrants further exploration.

The prevalence of low muscle mass associated with obesity in the USA

BackgroundSarcopenia is defined as age-related low muscle mass and function, and can also describe the loss of muscle mass in certain medical conditions, such as sarcopenic obesity. Sarcopenic obesity describes loss of muscle and function in obese individuals; however, as sarcopenia is an age-related condition and obesity can occur in any age group, a more accurate term is obesity with low lean muscle mass (OLLMM). Given limited data on OLLMM (particularly in those aged < 65 years), the purpose of this study was to estimate the prevalence of OLLMM in adults aged ≥ 20 years in the USA.MethodsData from the National Health and Nutrition Examination Survey (NHANES) 2017–2018 and 1999–2006 were used. OLLMM was defined as an appendicular lean mass, adjusted for body mass index (BMI), cut-off point < 0.789 for males and < 0.512 for females, measured by dual-energy X-ray absorptiometry (DXA). DXA was only measured in individuals 20–59 years old in NHANES 2017–2018; we therefore utilized logistic regression models to predict OLLMM from NHANES 1999–2006 for those aged ≥ 60 years. The prevalence of OLLMM was estimated overall, and by sex, age, race/ethnicity, and clinical subgroup (high BMI, prediabetes, type 2 diabetes mellitus [T2DM], non-alcoholic fatty liver disease [NAFLD] with fibrosis, or post-bariatric surgery). Prevalence estimates were extrapolated to the USA population using NHANES sampling weights.ResultsWe estimated that, during 2017–2018, 28.7 million or 15.9% of the USA population had OLLMM. The prevalence of OLLMM was greater in older individuals (8.1%, aged 20–59 years vs 28.3%, aged ≥ 60 years), highest (66.6%) in Mexican-American females aged ≥ 60 years, and lowest (2.6%) in non-Hispanic Black males aged 20–59 years. There was a higher prevalence of OLLMM in adults with prediabetes (19.7%), T2DM (34.5%), NAFLD with fibrosis (25.4%), or post-bariatric surgery (21.8%), compared with those without each condition.ConclusionsOverall, the burden of OLLMM in the USA is substantial, affecting almost 30 million adults. The prevalence of OLLMM increased with age, and among those with prediabetes, T2DM, NAFLD with fibrosis, or post-bariatric surgery. A unified definition of OLLMM will aid diagnosis and treatment strategies.

Proprioception and Geriatric Low Back Pain.

Proprioception is a deep sensation that perceives the position of each part of the body, state of movement and muscle contraction, and resistance and mass applied to the body. Proprioceptive feedback influences movement and positional accuracy, resulting in key somatosensory functions for human postural control. Proprioception encompasses signals received from proprioceptors located in the skin, subcutaneous tissue, muscles, tendons, and joint capsules, commonly known as mechanoreceptors. The muscle spindle, a crucial proprioceptor, is stretched during eccentric contraction of muscle, thus generating an action potential on afferent fibers to convey a proprioceptive information to the sensorimotor cortex in the brain. For exercise therapy in patients with locomotor disease, proprioception serves an essential function for motor control; thus, this should be considered to obtain effective muscle output. As postural control is achieved by proprioceptive function according to the balance between the lower limb and trunk, relative proprioceptive weighting ratio can help clarify proprioceptive control using muscle response to mechanical vibration. The absence of proprioceptive information congruent with motor intention activates cortical center monitoring incongruence of sensation, leading to pathological pain. Therapeutic procedures may aim to restore the integrity of cortical information processing in musculoskeletal chronic pain. Poor proprioception is one of the main causes of decreased postural balance control in elderly patients with low back pain (LBP). It has been hypothesized that proprioception of the lower limbs deteriorates with age-related muscle mass loss (sarcopenia), which increases the proprioceptive burden on the lumbar spine. Accurate diagnosis of the proprioceptive function is important for establishing a treatment procedure for proprioceptive recovery, and further prospective research is required to clarify the relationship between proprioception and LBP improvement.

1200-P: The Prevalence of Obesity-Associated Loss of Lean Muscle Mass

Sarcopenia, originally defined as age-related low muscle mass and function, has also been used to describe the loss of muscle mass and quality among certain populations, such as sarcopenic obesity (SO) . SO refers to loss of muscle and function in obese subjects; however, given age is not a factor in SO, we classified SO as obesity with low lean muscle mass (OLLMM) . Given the paucity of data in OLLMM, the purpose was to describe the prevalence of OLLMM in the US. Data from NHANES 2017-2018 were used to estimate the prevalence of OLLMM in adults ≥20 yrs of age. OLLMM was defined as DEXA-assessed low appendicular lean mass, adjusted for BMI (men &amp;lt;0.789, women &amp;lt;0.512) and obesity (body fat%: men &amp;gt;25%, women &amp;gt;35%) . Since DEXA was only measured in those aged 20-59 in NHANES 2017-2018, we utilized logistic regression models to predict OLLMM from NHANES 1999-20for those ≥60 yrs. The prevalence of OLLMM was estimated overall, by sex, age group, and diabetes status (prediabetes and T2DM) . We extrapolated results to the US using NHANES sampling weights. Of the 4174 adults (representing 181M US adults) , we identified 827 (28.8M, 15.9% of the US pop.) with OLLMM. Older adults had higher prevalence of OLLMM as did those with prediabetes and T2DM (Figure 1) . The prevalence of OLLMM in the US is high. While the prevalence of OLLMM was higher with age, its prevalence was also high in diabetics, regardless of age. Clinicians should monitor for OLLMM among obese T2DM patients. Disclosure D.J. Murdock: Employee; Regeneron Pharmaceuticals Inc. Stock/Shareholder; Regeneron Pharmaceuticals Inc. N. Wu: Employee; Regeneron Pharmaceuticals Inc. Stock/Shareholder; Regeneron Pharmaceuticals Inc. D.J. Glass: Employee; Regeneron Pharmaceuticals Inc. Stock/Shareholder; Regeneron Pharmaceuticals Inc. J.S. Grimsby: Employee; Regeneron Pharmaceuticals Inc. Stock/Shareholder; Regeneron Pharmaceuticals Inc. R.A. Calle: Employee; Regeneron Pharmaceuticals Inc. Stock/Shareholder; Regeneron Pharmaceuticals Inc. S. Donahue: Employee; Regeneron Pharmaceuticals Inc. Stock/Shareholder; Regeneron Pharmaceuticals Inc. M. Sleeman: Employee; Regeneron Pharmaceuticals Inc. Stock/Shareholder; Regeneron Pharmaceuticals Inc. R.J. Sanchez: Employee; Regeneron Pharmaceuticals Inc. Stock/Shareholder; Regeneron Pharmaceuticals Inc. Funding Supported by Regeneron Pharmaceuticals, Inc.

Implication of Exercise for Healthy Longevity in Older People

As the aging population is increasing substantially worldwide, extending the healthy life expectancy of older people has become a challenging issue. The structure and function of skeletal muscle decline with age, and this change has been shown to be involved in the development of various adverse health outcomes. In recent years, sarcopenia, a disease that is associated with age-related skeletal muscle mass loss and muscle weakness, has been attracting attention, and disuse muscle atrophy is also an important condition. For these diseases, it is recommended to increase exercise and physical activity, especially resistance exercise. In addition to conducting further research, it is necessary to widely disseminate information regarding the significance of exercise and physical activity as cost-effective interventions to the general public as well as health care professionals.

Cardiac troponin T and autoimmunity in skeletal muscle aging.

Age-related muscle mass and strength decline (sarcopenia) impairs the performance of daily living activities and can lead to mobility disability/limitation in older adults. Biological pathways in muscle that lead to mobility problems have not been fully elucidated. Immunoglobulin G (IgG) infiltration in muscle is a known marker of increased fiber membrane permeability and damage vulnerability, but whether this translates to impaired function is unknown. Here, we report that IgG1 and IgG4 are abundantly present in the skeletal muscle (vastus lateralis) of ~ 50% (11 out of 23) of older adults (&gt; 65years) examined. Skeletal muscle IgG1 was inversely correlated with physical performance (400m walk time: r = 0.74, p = 0.005; SPPB score: r = - 0.73, p = 0.006) and muscle strength (r = - 0.6, p = 0.05). In a murine model, IgG was found to be higher in both muscle and blood of older, versus younger, C57BL/6 mice. Older mice with a higher level of muscle IgG had lower motor activity. IgG in mouse muscle co-localized with cardiac troponin T (cTnT) and markers of complement activation and apoptosis/necroptosis. Skeletal muscle-inducible cTnT knockin mice also showed elevated IgG in muscle and an accelerated muscle degeneration and motor activity decline with age. Most importantly, anti-cTnT autoantibodies were detected in the blood of cTnT knockin mice, old mice, and older humans. Our findings suggest a novel cTnT-mediated autoimmune response may be an indicator of sarcopenia.

Transgenic Expression of Bmp3b in Mesenchymal Progenitors Mitigates Age-Related Muscle Mass Loss and Neuromuscular Junction Degeneration.

Skeletal muscle is a vital organ for a healthy life, but its mass and function decline with aging, resulting in a condition termed sarcopenia. The etiology of sarcopenia remains unclear. We recently demonstrated that interstitial mesenchymal progenitors are essential for homeostatic muscle maintenance, and a diminished expression of the mesenchymal-specific gene Bmp3b is associated with sarcopenia. Here, we assessed the protective function of Bmp3b against sarcopenia by generating conditional transgenic (Tg) mice that enable a forced expression of Bmp3b specifically in mesenchymal progenitors. The mice were grown until they reached the geriatric stage, and the age-related muscle phenotypes were examined. The Tg mice had significantly heavier muscles compared to control mice, and the type IIB myofiber cross-sectional areas were preserved in Tg mice. The composition of the myofiber types did not differ between the genotypes. The Tg mice showed a decreasing trend of fibrosis, but the degree of fat infiltration was as low as that in the control mice. Finally, we observed the preservation of innervated neuromuscular junctions (NMJs) in the Tg muscle in contrast to the control muscle, where the NMJ degeneration was conspicuous. Thus, our results indicate that the transgenic expression of Bmp3b in mesenchymal progenitors alleviates age-related muscle deterioration. Collectively, this study strengthens the beneficial role of mesenchymal Bmp3b against sarcopenia and suggests that preserving the youthfulness of mesenchymal progenitors may be an effective means of combating sarcopenia.

Influence of Age and Individual Differences on Mouthfeel Perception of Whey Protein-Fortified Products: A Review.

Protein needs are considered to increase with age, with protein consumption being associated with many positive outcomes. Protein-fortified products are often used to improve nutritional status and prevent age-related muscle mass loss in older adults. Accordingly, older adults are commonly provided with products fortified with whey protein; however, such products can cause mouthdrying, limiting consumption and product enjoyment. Currently, the extent to which age and individual differences (e.g., saliva, oral health, food oral processing) influence the perception of whey protein-derived mouthdrying is relatively unclear. Previous research in this area has mainly focused on investigating mouthdrying, without taking into account individual differences that could influence this perception within the target population. Therefore, the main focus of this review is to provide an overview of the relevant individual differences likely to influence mouthfeel perception (specifically mouthdrying) from whey protein-fortified products, thereby enabling the future design of such products to incorporate better the needs of older adults and improve their nutritional status. This review concludes that age and individual differences are likely to influence mouthdrying sensations from whey protein-fortified products. Future research should focus more on the target population and individual differences to maximise the benefits from whey protein fortification.

Impaired pulse pressure amplification, augmentation index, and arterial stiffness are associated with reduced limb lean mass in overweight and obese postmenopausal women.

The age-related muscle mass loss has been associated with increased arterial stiffness (brachial-ankle pulse wave velocity, baPWV) and wave reflection (augmentation index, AIx). In healthy individuals, pulse pressure (PP) is lower in the aorta compared to the brachial artery (PP amplification, PPA). Postmenopausal women experience elevated aortic stiffness leading to increased AIx and aortic PP causing reduced PPA, an independent predictor of cardiovascular mortality. It is unknown whether appendicular skeletal muscle index (ASMI), arm (ArmLM) or leg lean mass (LegLM) are negatively associated with PPA. The purpose of this study was to investigate the associations between vascular function (PPA, AIx, and baPWV) and lean mass (ASMI, ArmLM, and LegLM) in postmenopausal women. The study was performed in 93 postmenopausal women (48-71years; BMI: 30±7kg/m2). PPA (brachial/aortic PP), aortic AIx, and baPWV were measured. ArmLM and LegLM were measured by dual-energy X-ray absorptiometry. ASMI was calculated as (ArmLM+LegLM)/Ht2. Associations between vascular and lean mass measures were analyzed by multiple linear regression. PPA was associated with ASMI (β=0.29, p=.016) and LegLM (β=0.25, p=.028) after adjustment for age, height, systolic pressure, strength, and heart rate. AIx was associated with ASMI (β=-0.27, p=.011), ArmLM (β=-0.25, p=.023), and LegLM (β=-0.22, p=.026), while baPWV was associated with reduced ASMI (β=-0.23, p=.043) and ArmLM (β=-0.23, p=.045), but not with LegLM (β=-0.19, p=.074) after full adjustment. Our findings indicate that impaired pulsatile hemodynamics (PPA and AIx) are negatively associated with ASMI and LegLM, while arterial stiffness is negatively associated with ASMI and ArmLM. Thus, vascular dysfunction may be implicated in muscle mass loss in overweight and obese postmenopausal women.

Estimation of skeletal muscle mass by bioimpedance and differences among skeletal muscle mass indices for assessing sarcopenia

It is crucial to assess age-related muscle mass changes and derived indices differences in geriatric medicine. We aimed to develop and validate four bioimpedance analysis (BIA) prediction equations against dual-energy X-ray absorptiometry (DEXA) and magnetic resonance image (MRI) in estimating skeletal muscle mass and to compare the differences among skeletal muscle mass indices, cutoff values, and corresponding prevalence rates of low muscle mass for assessing sarcopenia in Chinese adults. We measured the height (Ht), weight (Wt), appendicular lean mass (ALM) or skeletal muscle mass (ASM), total lean body mass (LBM) or skeletal muscle mass (TSM) obtained using DEXA or MRI, and a multi-frequency BIA (BCA II;50, 250kHz), in 371 adults aged 18.0-87.0 years. We also collected gender, age, Ht, Wt, and impedance indexes (Ht2/R50, Ht2/R250, R50/Ht2, R250/Ht2) from 30,500 adults aged 18-96 years living in China. Multiple regression analyses were used to derive four prediction equations by BIA, and double cross-validation techniques and Bland-Altman analyses were used to test agreement. Various muscle mass indices and prevalence rates were depicted by line plots in regard to age trends. Satisfactory results were found in the four prediction models as they had the larger R2 (0.833-0.930) values and low SEE (1.409-2.335kg) values. The predictive variables included impedance indexes (Ht2/R50, R50/Ht2, R250/Ht2), gender, age, Wt, and Ht. The corresponding prevalence rates of low muscle mass exhibited significant differences according to the various muscle mass indices adjusted for Ht, Wt, or body mass index (BMI), in addition to the cutoff values based on two standard deviations (2SD) of young people or the lower 20% of the study group. The BIA equations have the potential to be applied as a practical method of quantifying skeletal muscle mass in Chinese adults. However, the operational methods that are most appropriate for determining the degree of low muscle mass that actually contributes to sarcopenia remains inconclusive.

Nutritional Supplements to Support Resistance Exercise in Countering the Sarcopenia of Aging.

Skeletal muscle plays an indispensable role in metabolic health and physical function. A decrease in muscle mass and function with advancing age exacerbates the likelihood of mobility impairments, disease development, and early mortality. Therefore, the development of non-pharmacological interventions to counteract sarcopenia warrant significant attention. Currently, resistance training provides the most effective, low cost means by which to prevent sarcopenia progression and improve multiple aspects of overall health. Importantly, the impact of resistance training on skeletal muscle mass may be augmented by specific dietary components (i.e., protein), feeding strategies (i.e., timing, per-meal doses of specific macronutrients) and nutritional supplements (e.g., creatine, vitamin-D, omega-3 polyunsaturated fatty acids etc.). The purpose of this review is to provide an up-to-date, evidence-based account of nutritional strategies to enhance resistance training-induced adaptations in an attempt to combat age-related muscle mass loss. In addition, we provide insight on how to incorporate the aforementioned nutritional strategies that may support the growth or maintenance of skeletal muscle and subsequently extend the healthspan of older individuals.

Molecular and Cellular Aspects of Sarcopenia, Muscle Healthy Aging and Physical Conditioning in the Elderly

During aging, the skeletal muscle tissue is one of the most affected, undergoing loss of mass and function, a process defined as sarcopenia. This age-related muscle mass and function decline, dependent on many factors, predispose individuals to decreased mobility, reduced muscle power and increased risk of falls. Several factors at the cellular and molecular level affect muscle aging, synergizing with each other. At present, it is broadly accepted that Reactive Oxygen Species (ROS) play a primary role in the aging process, especially in those tissues like skeletal muscle, where the generation of free radicals is more pronounced as a consequence of the high consumption of oxygen. Recently, several studies have highlighted the involvement of muscle stem cells (satellite cells, SCs) in the progression of sarcopenia, showing a concomitant regression of activity and number of these cells. At a sub-cellular level, the main processes correlated with sarcopenia are the alteration of protein synthesis and mitochondrial dysfunction. Attempts to slow down or revert sarcopenia are essentially based on three approaches: use of supplements, pharmaceutical therapies and physical activity. In brief, it seems that appropriate physical exercise training protocols could be capable of slowing down and sometimes reversing the sarcopenic process. This finding is the consequence of a beneficial action of physical exercise on mitochondria and/or on the regenerative process led by SCs with different effects on the basis of training characteristics. Furthermore, according to a recent hypothesis, early strength training should be considered as public health advice.

Molecular and Functional Networks Linked to Sarcopenia Prevention by Caloric Restriction in Rhesus Monkeys.

Caloric restriction (CR) improves survival in nonhuman primates and delays the onset of age-related morbidities including sarcopenia, which is characterized by the age-related loss of muscle mass and function. A shift in metabolism anticipates the onset of muscle-aging phenotypes in nonhuman primates, suggesting a potential role for metabolism in the protective effects of CR. Here, we show that CR induced profound changes in muscle composition and the cellular metabolic environment. Bioinformatic analysis linked these adaptations to proteostasis, RNA processing, and lipid synthetic pathways. At the tissue level, CR maintained contractile content and attenuated age-related metabolic shifts among individual fiber types with higher mitochondrial activity, altered redox metabolism, and smaller lipid droplet size. Biometric and metabolic rate data confirm preserved metabolic efficiency in CR animals that correlated with the attenuation of age-related muscle mass and physical activity. These data suggest that CR-induced reprogramming of metabolism plays a role in delayed aging of skeletal muscle in rhesus monkeys.

Short Communication: Low Muscle Mass Is Associated with Osteoporosis in Older Adults Living with HIV.

Sarcopenia, age-related low muscle mass and function, is a well-established independent risk factor for bone fracture in the geriatric population but is understudied in older people living with HIV (PLWH). The objective of this cross-sectional study was to investigate in older PLWH the relationship between muscle mass and bone mineral density (BMD). Sedentary PLWH who were ≥50 years of age, receiving antiretroviral therapy, and enrolled in an exercise intervention trial were included. Established definitions for sarcopenia and osteopenia/osteoporosis were applied to muscle mass data and BMD collected by dual-energy X-ray absorptiometry before exercise training. Participants were 93% male and 33% Caucasian race with median age 61 years, and median CD4 lymphocytes 707 cells/μL. The majority (64%) were overweight and obese by body mass index. Appendicular skeletal muscle index (ASMI) correlated with BMD at the femoral neck (r = 0.49, p < .01), total hip (r = 0.54, p < .01), and lumbar spine (r = 0.48, p < .05). Low BMD at the femoral neck was present in 39% (26% osteopenia, 13% osteoporosis). ASMI was lower among those with low BMD compared with normal BMD (p = .02). Low muscle mass measured by ASMI is associated with low BMD in clinically stable older PLWH. Detailed body composition assessment may help guide lifestyle recommendations to prevent bone fractures in older PLWH.

Effects of Leucine-Enriched Whey Protein Supplementation on Physical Function in Post-Hospitalized Older Adults Participating in 12-Weeks of Resistance Training Program: A Randomized Controlled Trial.

Age-related strength and muscle mass loss is further increased after acute periods of inactivity. To avoid this, resistance training has been proposed as an effective countermeasure, but the additional effect of a protein supplement is not so clear. The aim of this study was to examine the effect of a whey protein supplement enriched with leucine after resistance training on muscle mass and strength gains in a post-hospitalized elderly population. A total of 28 participants were included and allocated to either protein supplementation or placebo supplementation following resistance training for 12 weeks (2 days/week). Physical function (lower and upper body strength, aerobic capacity and the Short Physical Performance Battery (SPPB) test), mini nutritional assessment (MNA) and body composition (Dual X-ray Absorptiometry) were assessed at baseline and after 12 weeks of resistance training. Both groups showed improvements in physical function after the intervention (p < 0.01), but there were no further effects for the protein group (p > 0.05). Muscle mass did not improve after resistance training in either group (p > 0.05). In conclusion, 12 weeks of resistance training are enough to improve physical function in a post-hospitalized elderly population with no further benefits for the protein-supplemented group.

Dual Role of Reactive Oxygen Species in Muscle Function: Can Antioxidant Dietary Supplements Counteract Age-Related Sarcopenia?

Sarcopenia is characterized by the progressive loss of skeletal muscle mass and strength. In older people, malnutrition and physical inactivity are often associated with sarcopenia, and, therefore, dietary interventions and exercise must be considered to prevent, delay, or treat it. Among the pathophysiological mechanisms leading to sarcopenia, a key role is played by an increase in reactive oxygen and nitrogen species (ROS/RNS) levels and a decrease in enzymatic antioxidant protection leading to oxidative stress. Many studies have evaluated, in addition to the effects of exercise, the effects of antioxidant dietary supplements in limiting age-related muscle mass and performance, but the data which have been reported are conflicting. In skeletal muscle, ROS/RNS have a dual function: at low levels they increase muscle force and adaptation to exercise, while at high levels they lead to a decline of muscle performance. Controversial results obtained with antioxidant supplementation in older persons could in part reflect the lack of univocal effects of ROS on muscle mass and function. The purpose of this review is to examine the molecular mechanisms underlying the dual effects of ROS in skeletal muscle function and the analysis of literature data on dietary antioxidant supplementation associated with exercise in normal and sarcopenic subjects.