Sarcopenia

Effects of physical inactivity behavior during COVID-19 pandemic on physical fitness, body composition, inflammatory cytokine, and immunocytes in older adults: A retrospective and prospective study

The prolonged period of COVID-19 has ingrained physical inactivity as a habit, leading to a reluctance to move. This has resulted in a decline in physical fitness and the loss of a healthy body composition. While this trend is particularly noticeable among the older adults, its impact on the immune cell defense system, which is crucial for minimizing viral infections, remains unclear. This study aimed to investigate the physical fitness, body composition, cytokines and immunocytes of older adults who engaged in physical activity (PA) before the COVID-19 pandemic but had to stop it due to the lockdown. A total of 172 older adults aged 61 to 85 years participated in this study: 90 in non-PA group (NPAG, 34 men and 56 women), and 82 in PA group (PAG, 29 men and 53 women). Physical inactivity was 45.13 ± 5.67 weeks in the NPAG and 1.70 ± 0.43 weeks in the PAG. Although there was no significant difference in calorie intake, PA volume showed a significant decrease in NPGA (P < 0.001). VO₂max, strength, and sit-ups decreased in NPAG, whereas they maintained or increased in PAG (Ps < 0.001). NPAG experienced an increase in fat mass (∼33.0 %), along with a decrease in muscle mass (∼10.4 %), but PAG showed slight increases (∼1.1 % vs. ∼1.5 %, Ps < 0.001). Interleukin-6 (∼38.9 %), tumor necrosis factor-α (∼38.3 %), and C-reactive protein (∼33.6 %) increased, whereas immunocytes decreased in NPAG (Ps < 0.001). In contrast, those in PAG showed the opposite phenomenon. This study indicates that even during the COVID-19 situation, maintaining active PA in the older adults helps retain beneficial physical fitness and body composition, reduces inflammatory factors, and contributes to preserving or enhancing the function of immunocytes.

Harnessing immunomodulation to combat sarcopenia: current insights and possible approaches

Sarcopenia is a complex age-associated syndrome of progressive loss of muscle mass and strength. Although this condition is influenced by many factors, age-related changes in immune function including immune cell dynamics, and chronic inflammation contribute to its progression. The complex interplay between the immune system, gut-muscle axis, and autophagy further underscores their important roles in sarcopenia pathogenesis. Immunomodulation has emerged as a promising strategy to counteract sarcopenia. Traditional management approaches to treat sarcopenia including physical exercise and nutritional supplementation, and the emerging technologies of biophysical stimulation demonstrated the importance of immunomodulation and regulation of macrophages and T cells and reduction of chronic inflammation. Treatments to alleviate low-grade inflammation in older adults by modulating gut microbial composition and diversity further combat sarcopenia. Furthermore, some pharmacological interventions, nano-medicine, and cell therapies targeting muscle, gut microbiota, or autophagy present additional avenues for immunomodulation in sarcopenia. This narrative review explores the immunological underpinnings of sarcopenia, elucidating the relationship between the immune system and muscle during ageing. Additionally, the review discusses new areas such as the gut-muscle axis and autophagy, which bridge immune system function and muscle health. Insights into current and potential approaches for sarcopenia management through modulation of the immune system are provided, along with suggestions for future research directions and therapeutic strategies. We aim to guide further investigation into clinical immunological biomarkers and identify indicators for sarcopenia diagnosis and potential treatment targets to combat this condition. We also aim to draw attention to the importance of considering immunomodulation in the clinical management of sarcopenia.

Decreased Neuromuscular Function and Muscle Quality along with Increased Systemic Inflammation and Muscle Proteolysis Occurring in the Presence of Decreased Estradiol and Protein Intake in Early to Intermediate Post-Menopausal Women

Menopause causes a reduction in estradiol (E2) and may be associated with neuromuscular degeneration. Compared to pre-menopausal (PRE-M) women, this study sought to determine dietary protein intake and whether lower levels of circulating E2 in post-menopausal women (POST-M) were occurring alongside increased levels of biomarkers of axonal and neuromuscular junction degeneration (NMJ), inflammation, muscle protein degradation, and reduced indices of muscle quality and performance. Employing a cross-sectional design, PRE-M (n = 6) and POST-M (n = 6) dietary analysis data were collected and participants then donated a blood and urine sample followed by assessments for body composition, motor unit activation, and muscle performance. Independent group t-tests were performed to determine differences between groups (p ≤ 0.05). In POST-M women, E2, motor unit activity, muscle quality, and muscle performance were significantly less than those for PRE-M women; however, the levels of c-terminal fragment of agrin, tumor necrosis factor-α, and urinary titin were significantly greater (p < 0.05). POST-M women were also shown to be ingesting fewer total calories and less protein than PRE-M (p < 0.05). Reduced E2 and dietary protein intake in POST-M women occurs in conjunction with increased levels of biomarkers of NMJ degradation, inflammation, and muscle proteolysis, which may be associated with reduced motor unit activation and muscle quality.

Advances in nutritional supplementation for sarcopenia management

Sarcopenia is a syndrome characterized by a decline in muscular mass, strength, and function with advancing age. The risk of falls, fragility, hospitalization, and death is considerably increased in the senior population due to sarcopenia. Although there is no conclusive evidence for drug treatment, resistance training has been unanimously recognized as a first-line treatment for managing sarcopenia, and numerous studies have also pointed to the combination of nutritional supplementation and resistance training as a more effective intervention to improve quality of life for people with sarcopenia. People with both malnutrition and sarcopenia have a higher mortality rate, so identifying people at risk of malnutrition and intervening early is extremely important to avoid sarcopenia and its associated problems. This article provides important information for dietary interventions in sarcopenia by summarizing the discoveries and developments of nutritional supplements such as protein, leucine, β-hydroxy-β-methylbutyric acid, vitamin D, vitamin C, vitamin E, omega-3 fatty acids, creatine, inorganic nitrate, probiotics, minerals, collagen peptides, and polyphenols in the management of sarcopenia.

Association of dietary and lifestyle inflammation scores with muscle strength and muscle endurance among Tehranian adults

Diet and lifestyle as modifiable factors play an effective role in muscle strength and muscle endurance. In addition, inflammatory reactions may have an association with the etiology of a a lower muscle strength and muscle endurance. We aimed to investigate the association of dietary and lifestyle inflammation scores (DLIS) with muscle strength and muscle endurance in a sample of Iranian adults. In this cross-sectional study, 270 adults aged 20 to 59 years (55.9% female) were selected. The dietary intakes were collected using a 168-item semi-quantitative food frequency questionnaire. The DLIS was calculated using the dietary inflammatory score (DIS), and lifestyle inflammatory score (LIS). Muscle endurance and muscle strength were measured by a digital-handgrip-dynamometer. Multivariate adjusted means for muscle strength and endurance across quartiles of the DIS, LIS, and DLIS were determined by the ANCOVA test. Multiple linear regression analysis was used to evaluate the association between inflammation scores (i.e., DIS, LIS, and DLIS), and muscle strength, muscle endurance. The DLIS ranged between -2.94 and 3.09. The adjusted P-value of muscle strength of the right hand (MSR) along quartiles of DIS was significantly lower (P = 0.024). MSR (β: -1.19; P-value: 0.020) and mean muscle strength (MMS) (β: -0.95; P-value: 0.047) had significant association with DIS. MSR (β: -0.85; P-value: 0.050) had a marginally significant association with DLIS. Overall, we found that a high adherence to a pro-inflammatory diet might be associated to a lower muscle strength. However, a lifestyle with greater inflammatory potential was not related to any components of muscle endurance. Further studies with prospective designs are needed to confirm the present findings in further details.

Shared and Divergent Epigenetic Mechanisms in Cachexia and Sarcopenia

Significant loss of muscle mass may occur in cachexia and sarcopenia, which are major causes of mortality and disability. Cachexia represents a complex multi-organ syndrome associated with cancer and chronic diseases. It is often characterized by body weight loss, inflammation, and muscle and adipose wasting. Progressive muscle loss is also a hallmark of healthy aging, which is emerging worldwide as a main demographic trend. A great challenge for the health care systems is the age-related decline in functionality which threatens the independence and quality of life of elderly people. This biological decline can also be associated with functional muscle loss, known as sarcopenia. Previous studies have shown that microRNAs (miRNAs) play pivotal roles in the development and progression of muscle wasting in both cachexia and sarcopenia. These small non-coding RNAs, often carried in extracellular vesicles, inhibit translation by targeting messenger RNAs, therefore representing potent epigenetic modulators. The molecular mechanisms behind cachexia and sarcopenia, including the expression of specific miRNAs, share common and distinctive trends. The aim of the present review is to compile recent evidence about shared and divergent epigenetic mechanisms, particularly focusing on miRNAs, between cachexia and sarcopenia to understand a facet in the underlying muscle wasting associated with these morbidities and disclose potential therapeutic interventions.

Association between total protein intake and low muscle mass in Korean adults

Background

Adults with low muscle mass have a poor prognosis. Studies that examined the association between total protein intake and low muscle mass among adults are limited. Thus, we investigated the association between total protein intake and low muscle mass among Korean adults aged ≥19 years.

Methods

We included 15,995 adults (6528 male and 9467 female) aged ≥19 years from the Korea National Health and Nutrition Examination Surveys (2008–2011). We divided the participants into groups according to protein intake quartile: Q1, Q2, Q3 and Q4 groups. The odds ratios (ORs) and 95% confidence intervals (CIs) of low muscle mass according to protein intake were analysed via multivariable logistic regression analysis. Stratified analyses according to sex, age and comorbidities were also performed.

Results

Of the participants, 3.8% had weight-adjusted low muscle mass. The prevalence rates of low muscle mass were 1.5, 3.0, 3.9 and 7.2% in the Q4, Q3, Q2 and Q1 groups, respectively (p < 0.001). Compared with the Q4 group, the Q1 group had the highest ORs for low muscle mass, followed by the Q2 and Q3 groups (Model 5; OR, 95% CI: 2.03, 1.36–3.02 for Q3; 2.44, 1.64–3.61 for Q2; and 4.32, 2.89–6.45 for Q4) after adjusting for confounding variables (p for trend < 0.001). The associations between protein intake and low muscle mass were stronger in younger individuals, men, individuals without hypertension, those with diabetes mellitus and those without dyslipidemia.

Conclusions

The prevalence of low muscle mass in Korean adults significantly increased with lower protein intake. Nutrition education for proper protein intake is also important for adults.

Trial registration

Retrospectively registered.

Detraining Effects of COVID-19 Pandemic on Physical Fitness, Cytokines, C-Reactive Protein and Immunocytes in Men of Various Age Groups

Background and Objectives: Since the start of the COVID-19 pandemic caused by severe acute respiratory syndrome coronavirus II, levels of physical inactivity have become more severe and widespread than ever before. Physical inactivity is known to have a negative effect on the human body, but the extent to which reduced physical fitness has effected immune function before and after the current pandemic has not yet been uncovered. The aim of this study was to investigate the detraining effects of the COVID-19 confinement period on physical fitness, immunocytes, inflammatory cytokines, and proteins in various age groups. The participants of this study included sixty-four male adults who did not exercise during the pandemic, although they had exercised regularly before. Materials and Methods: Participants were classified by age group, which included the 20s group (20s’G, n = 14), 30s group (30s’G, n = 12), 40s group (40s’G, n = 12), 50s group (50s’G, n = 12), and 60s group (60s’G, n = 14). Results: Regarding body composition, muscle mass significantly decreased, whereas fat mass, fat percentage, and waist/hip ratio significantly increased in most groups. Cardiopulmonary endurance and strength significantly decreased in all groups, while muscle endurance and flexibility decreased in some groups compared to the pre-COVID-19 pandemic. This study confirmed the immunocytopenia and enhanced inflammation due to physical inactivity during the COVID-19 pandemic, and a greater detrimental decrease mainly after the age of 50. Conclusion: This study confirmed a decrease in physical fitness after the start of the COVID-19 pandemic, characterized by an increase in fat mass and a decrease in muscle mass, thereby increasing cytokines and reducing immunocytes in the body. While social distancing is important during the pandemic, maintaining physical fitness should also be a top priority.

Exercise Dosage in Reducing the Risk of Dementia Development: Mode, Duration, and Intensity-A Narrative Review

Senile dementia, also known as dementia, is the mental deterioration which is associated with aging. It is characterized by a decrease in cognitive abilities, inability to concentrate, and especially the loss of higher cerebral cortex function, including memory, judgment, abstract thinking, and other loss of personality, even behavior changes. As a matter of fact, dementia is the deterioration of mental and intellectual functions caused by brain diseases in adults when they are mature, which affects the comprehensive performance of life and work ability. Most dementia cases are caused by Alzheimer’s disease (AD) and multiple infarct dementia (vascular dementia, multi-infarct dementia). Alzheimer’s disease is characterized by atrophy, shedding, and degenerative alterations in brain cells, and its occurrence is linked to age. The fraction of the population with dementia is smaller before the age of 65, and it increases after the age of 65. Since women live longer than men, the proportion of women with Alzheimer’s disease is higher. Multiple infarct dementia is caused by a cerebral infarction, which disrupts blood supply in multiple locations and impairs cerebral cortex function. Researchers worldwide are investigating ways to prevent Alzheimer’s disease; however, currently, there are no definitive answers for Alzheimer’s prevention. Even so, research has shown that we can take steps to reduce the risk of developing it. Prospective studies have found that even light to moderate physical activity can lower the risk of dementia and Alzheimer’s disease. Exercise has been proposed as a potential lifestyle intervention to help reduce the occurrence of dementia and Alzheimer’s disease. Various workout modes will be introduced based on various physical conditions. In general, frequent exercise for 6–8 weeks lessens the risk of dementia development.

Prevalence of sarcopenia and clinical implications in patients with newly diagnosed rheumatoid arthritis

OBJECTIVE

The aim of this study was to determine the frequency of sarcopenia at the time of diagnosis in patients with rheumatoid arthritis (RA), assessing disease activity and factors that may be associated with sarcopenia and observe effects of treatment on sarcopenia.

METHOD

A prospective study was conducted with patients who have newly diagnosed RA. Patients were evaluated twice, at the time of diagnosis and 3 mo after the initiation of treatment. Demographic data, anthropometric measurements, disease activity scores, and sarcopenia status were recorded. Sarcopenia was evaluated with grip strength and bioelectric impedance. The results were compared with healthy volunteers.

RESULTS

The age at onset of RA was 50.6 ± 14.6 y. Handgrip strength (P < 0.001), skeletal muscle mass (P = 0.009), and skeletal muscle mass index (P = 0.032) were reduced in patients with RA but not in the control group. The frequency of sarcopenia in RA at onset of diagnosis was 31.5%. There was a significant decrease in the rate of sarcopenia after 3 mo of treatment (31.5 versus 8.7%; P = 0.046).

CONCLUSION

Sarcopenia was found in approximately one-third of the patients with newly diagnosed RA in our study. With treatment, sarcopenia improved significantly. Patients with RA should be evaluated in terms of sarcopenia in addition to evaluating joint and extraarticular findings at the time of diagnosis. Early detection and treatment planning may improve quality of life.

Deterioration of nuclear morphology and architecture: A hallmark of senescence and aging

The metazoan nucleus is a highly structured organelle containing several well-defined sub-organelles. It is the largest organelle inside a cell taking up from one tenth to half of entire cell volume. This makes it one of the easiest organelles to identify and study under the microscope. Abnormalities in the nuclear morphology and architecture are commonly observed in an aged and senescent cell. For example, the nuclei enlarge, loose their shape, appear lobulated, harbour nuclear membrane invaginations, carry enlarged/fragmented nucleolus, loose heterochromatin, etc. In this review we discuss about the age-related changes in nuclear features and elaborate upon the molecular reasons driving the change. Many of these changes can be easily imaged under a microscope and analysed in silico. Thus, computational image analysis of nuclear features appears to be a promising tool to evaluate physiological age of a cell and offers to be a legitimate biomarker. It can be used to examine progression of age-related diseases and evaluate therapies.

Animal protein intake reduces risk of functional impairment and strength loss in older adults

BACKGROUND & AIMS

Protein intake has been shown to lower risk of aging-related functional decline. The goal of this study was to assess long-term effects of weight-adjusted animal (AP) and plant protein (PP) intakes on aging-related change in functional status and grip strength.

METHODS

Framingham Offspring Study participants (n = 1896, 891 men and 1005 women), ≥age 50, were followed for an average of 14.4 years. Protein intake derived from two sets of 3-day diet records (exams 3 and 5) was expressed as both weight-adjusted intake (from residuals) and per kilogram of body weight (g/kg/d). Seven tasks from two standardized assessments (Nagi and the Rosow-Breslau scales) were selected to determine functional status at exams 5-9. Functional impairment was defined as failure to complete (or having a lot of difficulty completing) a given task. Grip strength was assessed by dynamometer at exams 7-9.

RESULTS

Participants with higher (vs. lower) weight-adjusted intakes of AP and PP maintained higher functional scores (p = 0.001 and p < 0.001, respectively). After accounting for baseline skeletal muscle mass (SMM) and physical activity, only AP was linked with lower risks of functional impairment. Higher AP intake among sedentary individuals led to 29% (95% CI: 0.51-1.00) reduced risks of impairment; among subjects with lower SMM, higher AP was associated with 30% (95% CI: 0.49-0.98) reduced risks. Physical activity and SMM were independently associated with reduced risks of functional impairment, regardless of protein intake. Finally, higher AP intake led to 34% and 48% greater preservation of grip strength in men (p = 0.012) and women (p = 0.034). Results were similar for protein intake expressed as g/kg/d.

CONCLUSIONS

Higher AP intake and higher levels of physical activity and SMM were independently associated with lower risks of functional impairment and greater preservation of grip strength in adults over the age of 50 years.

Sarcopenia: A Contemporary Health Problem among Older Adult Populations

Sarcopenia, a geriatric disease characterized by a progressive loss of skeletal muscle mass and loss of muscle function, constitutes a rising, often undiagnosed health problem. Its prevalence in the elderly population is largely considered variable, as it ranges from 5% to 50% depending on gender, age, pathological conditions as well as diagnostic criteria. There is no one unified approach of treatment or assessment, which makes sarcopenia even harder to assess. There is a pressing need to provide better diagnosis, diagnostics, prevention, and individualized health care. Physical activity and nutrition are the main studied ways to prevent sarcopenia, and they also offer better outcomes. This review aims to report the prevalence of sarcopenia in older adults, its etiology, prevention, and treatment techniques.

Perioperative nutritional supplementation and skeletal muscle mass in older hip-fracture patients

Older people with hip fractures are often malnourished at the time of fracture, which can have substantial influence on mortality and clinical outcomes, as well as functional outcome and quality of life. A close relationship between protein intake and muscle maintenance has been demonstrated. Skeletal muscle weakness is an independent risk factor for falls and fall-related injuries in the elderly and is an independent marker of prognosis. However, the effect of perioperative nutritional interventions on outcomes in elderly hip-fracture patients remains controversial. In this narrative review, an overview is presented of the existing literature on nutritional status and sarcopenia in elderly hip-fracture patients, clinical outcomes, and the effects of nutritional intervention on outcome and rehabilitation in this patient group.

Efficacy of Nutritional Interventions as Stand-Alone or Synergistic Treatments with Exercise for the Management of Sarcopenia

Sarcopenia is an age-related and accelerated process characterized by a progressive loss of muscle mass and strength/function. It is a multifactorial process associated with several adverse outcomes including falls, frailty, functional decline, hospitalization, and mortality. Hence, sarcopenia represents a major public health problem and has become the focus of intense research. Unfortunately, no pharmacological treatments are yet available to prevent or treat this age-related condition. At present, the only strategies for the management of sarcopenia are mainly based on nutritional and physical exercise interventions. The purpose of this review is, thus, to provide an overview on the role of proteins and other key nutrients, alone or in combination with physical exercise, on muscle parameters.

A randomized controlled trial of exercise to prevent muscle mass and functional loss in elderly hemodialysis patients: Rationale, study design, and baseline sample

Background

Elderly maintenance hemodialysis (MHD) patients exhibit muscle wasting and impaired physical function. This trial determines whether MHD patients benefit from a 12-week home-based exercise program, protein supplementation, or both.

Design

and Methods: This is a randomized, blinded controlled trial involving 60 elderly MHD patients with impaired exercise capacity and function. Patients are randomized into either a homebased exercise program or normal care over a 12-week period. Measures at baseline include peak VO₂, strength and body composition as well as cognitive and disease-specific questionnaires. Muscle biopsies are obtained and analyzed for protein signaling, expression of IGF-1, androgen receptors, and myostatin.

Results

At baseline, patient characteristics in the exercise and normal care groups were similar by age, gender and anthropomorphic measures. Peak VO₂ was impaired (14.7 ± 3.3 ml/kg/min), representing 55 ± 14% of the age-predicted value. Six-minute walk distance was 322 ± 71 m, and the mean 1-min sit to stand test was 18 ± 8 repetitions, representing 69 ± 16% and 55 ± 22% of the age-predicted values, respectively. Indices of muscle function, including upper and lower body and hand grip strength all indicate marked impairment. Quality of life (QoL) using the SF36, the Beeson cognitive test, and KDQOL all suggest marked impairments compared to age-expected reference values for non-MHD patients.

Conclusions

Patients undergoing MHD exhibit markedly reduced physical function and QoL. Thus, there are potentially significant gains to be made through a program of aerobic and resistance exercise. We anticipate this trial will demonstrate that home-based exercise improves cardiopulmonary function, protein signaling and QoL, and increases muscle mass, strength, and body composition.

Immunotherapy in Older Adults: A Checkpoint to Palliation?

The excitement about immunotherapy is justified. Patients with advanced disease and limited life expectancy before immune checkpoint inhibitors are now having prolonged and sometimes complete responses to treatment; however, most patients do not respond to checkpoint inhibitors. The hope for a meaningful response with only a limited risk of high-grade toxicity generated a prognostic dilemma for patients with advanced cancers and their treating oncologists. Older adults with advanced cancers are at the intersection of multiple biologic and clinical factors that can influence the efficacy of immunotherapy. Treating physicians should take all of these elements into account when considering treatment options for an older adult with advanced disease. Oncologists should have an honest conversation with their patients regarding the uncertainty around the clinical profile of checkpoint inhibitors. Early high-quality goals of care discussions can help manage expectations of older adults with advanced cancer treated with immunotherapy. We review in this paper select clinical characteristics that are important to consider when evaluating an older adult for checkpoint inhibitor therapy. In addition, we discuss strategies to optimize goals of care discussion given the increasing complexity of prognostication in the immunotherapy era.

Association between sarcopenia and erectile dysfunction in males with type II diabetes mellitus

BACKGROUND

The prevalence rates for both sarcopenia and erectile dysfunction (ED) gradually increase in middle-aged and elderly diabetic male population and they impair physical functioning, sexual functioning, and quality of life. The aim of the present study was to evaluate the sarcopenia in patients with diabetic ED.

METHODS

The study included 98 male patients with type II diabetes mellitus (DM) aged 18-80 years. Blood chemistry and hormone levels were obtained. The International Index of Erectile Function (IIEF-5) questionnaire was administered to the patients. The patients were divided into three groups according to the IIEF-5 score; a score of 5-10 points indicated severe ED, a score of 11-20 indicated moderate ED, and a score of 21-25 points indicated no ED. The muscle mass, handgrip strength, timed up and go test, upper mid-arm circumference, calf circumference, and body mass index were obtained. The statistical analysis was performed using MedCalc Statistical Software version 12.7.7. All parameters were compared between the three groups.

RESULTS

Of 98 patients included in the study, 84 patients had severe sarcopenia, 13 had moderate sarcopenia, while only one patient had normal muscle mass. The mean age was 56.59 ± 11.46 years. When patients were divided into three groups according to IIEF-5 score, 38 had severe ED, 39 had moderate ED, and 21 had no ED. There was a significant difference between the three groups in terms of handgrip strength, timed up and go test scores, upper mid-arm circumference, and calf circumference (p < .05 for all).

CONCLUSIONS

Although muscle mass remains unchanged, muscle strength and physical performance decrease in diabetic ED patients. Diabetic patients with severe and moderate ED have lower muscle strength and physical performance.

Mechanisms Underlying Metabolic Syndrome-Related Sarcopenia and Possible Therapeutic Measures

Although there are several reviews that report the interrelationship between sarcopenia and obesity and insulin resistance, the relation between sarcopenia and the other signs that compose the metabolic syndrome (MetS) has not been extensively revised. Here, we review the mechanisms underlying MetS-related sarcopenia and discuss the possible therapeutic measures proposed. A vicious cycle between the loss of muscle and the accumulation of intramuscular fat might be associated with MetS via a complex interplay of factors including nutritional intake, physical activity, body fat, oxidative stress, proinflammatory cytokines, insulin resistance, hormonal changes, and mitochondrial dysfunction. The enormous differences in lipid storage capacities between the two genders and elevated amounts of endogenous fat having lipotoxic effects that lead to the loss of muscle mass are discussed. The important repercussions of MetS-related sarcopenia on other illnesses that lead to increased disability, morbidity, and mortality are also addressed. Additional research is needed to better understand the pathophysiology of MetS-related sarcopenia and its consequences. Although there is currently no consensus on the treatment, lifestyle changes including diet and power exercise seem to be the best options.

Skeletal Muscles Do Not Undergo Apoptosis During Either Atrophy or Programmed Cell Death-Revisiting the Myonuclear Domain Hypothesis

Skeletal muscles are the largest cells in the body and are one of the few syncytial ones. There is a longstanding belief that a given nucleus controls a defined volume of cytoplasm, so when a muscle grows (hypertrophy) or shrinks (atrophy), the number of myonuclei change accordingly. This phenomenon is known as the “myonuclear domain hypothesis.” There is a general agreement that hypertrophy is accompanied by the addition of new nuclei from stem cells to help the muscles meet the enhanced synthetic demands of a larger cell. However, there is a considerable controversy regarding the fate of pre-existing nuclei during atrophy. Many researchers have reported that atrophy is accompanied by the dramatic loss of myonuclei via apoptosis. However, since there are many different non-muscle cell populations that reside within the tissue, these experiments cannot easily distinguish true myonuclei from those of neighboring mononuclear cells. Recently, two independent models, one from rodents and the other from insects, have demonstrated that nuclei are not lost from skeletal muscle fibers when they undergo either atrophy or programmed cell death. These and other data argue against the current interpretation of the myonuclear domain hypothesis and suggest that once a nucleus has been acquired by a muscle fiber it persists.

Effects of 8-week kettlebell training on body composition, muscle strength, pulmonary function, and chronic low-grade inflammation in elderly women with sarcopenia

OBJECTIVES

To examine the effect of kettlebell training on body composition, muscle strength, pulmonary function, and chronic low-grade inflammatory markers among elderly people with sarcopenia.

DESIGN

Randomized controlled trial.

SETTING

Community center and research center.

PARTICIPANTS

A total of 33 elderly women with sarcopenia (aged 65-75 years) were recruited.

INTERVENTION

The participants were randomly assigned to a kettlebell training (KT) group or a control (CON) group. The KT group received an 8-week training intervention involving 60-min sessions twice a week, whereas the CON group members continued their daily lifestyles without participating in any exercise training. Four weeks of detraining were organized to observe the retention effect of the training program on the KT group.

MEASUREMENTS

The participants' body composition, muscle strength, pulmonary function, and chronic low-grade inflammatory markers were measured and analyzed before training (at Week 0, W0), after 8 weeks of training (at Week 8, W8), and after 4 weeks of detraining (at Week 12, W12).

RESULTS

In the KT group, appendicular skeletal muscle mass (ASM) and the sarcopenia index measured at W8 and W12 were significantly higher than those at W0(p = .004; p = .005). At W8 and W12, the sarcopenia index was significantly higher in the KT group than the CON group(p = .020; p = .019). In the CON group, the skeletal muscle mass levels measured at W8 and W12 were significantly lower than that at W0(p = .029; p = .005), and the ASM and the sarcopenia index measured at W8 were significantly lower than those at W0(p = .037; p = .036). Additionally, the measured left handgrip strength(p = .006), back strength(p = .011; p = .018), and peak expiratory flow (PEF) (p = .008; p = .006) were significantly higher in the KT group than the CON group at W8 and W12. At W8, the measured right handgrip strength was significantly higher in the KT group than the CON group(p = .043). In the KT group, the back strength and PEF levels measured at W8 and W12 were significantly higher than those at W0(p = .000; p = .004), and the left and right handgrip strength levels at W8 were significantly higher than those at W0(p = .004; p = .013). By contrast, in the CON group, the left(p = .004; p = .006)and right(p = .002; p = .004)handgrip strength levels and PEF(p = .018; p = .012) measured at W8 and W12 were significantly lower than those at W0. Moreover, compared with the high-sensitivity C-reactive protein (hs-CRP) levels measured at W0, those measured at W8 and W12 were significantly lower in the KT group(p = .006; p = .013)but significantly higher in the CON group(p = .005; p = .009). There was no significant difference in hs-CRP, IL-6, TNF-α between the KT and CON group.

CONCLUSION

For elderly people with sarcopenia, participating in kettlebell training significantly increases the sarcopenia index, grip strength, back strength, and PEF. In addition, the retention effect of the training program continued after 4 weeks of detraining.

Comparison between Dual-Energy X-ray Absorptiometry and Bioelectrical Impedance Analyses for Accuracy in Measuring Whole Body Muscle Mass and Appendicular Skeletal Muscle Mass

We evaluate the accuracy of whole body muscle mass (WBMM) and appendicular skeletal muscle mass (ASMM) assessed by bioelectrical impedance analysis (BIA) using an InBody770 machine (InBody, Seoul, Korea) referenced to dual-energy X-ray absorptiometry (DXA) in 507 people (mean age 63.7 ± 10.8 years, body mass index (BMI) 25.2 ± 3.5 kg/m²). Mean WBMMs measured by BIA and DXA were 49.3 ± 6.6 kg and 46.8 ± 6.5 kg in men and 36.1 ± 4.7 kg and 34.0 ± 4.8 kg in women, respectively. The respective effect sizes and 95% confidence intervals (CIs) for the difference were 2.49 (2.22⁻2.76) for men, and 2.12 (1.91⁻2.33) for women. Mean ASMMs measured by BIA and DXA were 22.1 ± 3.3 kg and 19.9 ± 3.2 kg in men, and 15.3 ± 2.5 kg and 13.5 ± 2.2 kg in women, respectively. The respective effect sizes and 95% CIs for the difference were 2.26 (2.10⁻2.41) for men and 1.75 (1.65⁻1.87) for women. The BIA clearly overestimated WBMM by 2.28 kg and ASMM by 1.97 kg compared with DXA. Using BMI, gender, and fat percentage, we derive equations that improved the residuals to.

Gender difference in the effects of interleukin-6 on grip strength - a systematic review and meta-analysis

Background

Aging sarcopenia characterized by low muscle mass with low muscle strength affects men and women differently. The contribution of interleukin-6 (IL-6) to sarcopenia has been suggested based on a negative correlation between plasma IL-6 and muscle function described by some studies. However, no consensus regarding clinically relevant cut-off criteria has been reached. Another question arises whether pooling male and female data is an accurate way to determine the predictive value of IL-6 in sarcopenia. The present meta-analysis was designed to assess: (1) whether plasma IL-6 in aged populations in fact correlates negatively to muscle strength; (2) whether such a correlation exists both in men and in women; and (3) whether plasma IL-6 shows a gender difference in old age.

Methods

We applied the preferred reporting items for systematic review and meta-analysis protocols (PRISMA). We searched PubMed and Embase for papers that reported data on individuals over 65 without inflammatory diseases. We extracted either separate male and female data on plasma IL-6 along with at least one muscle parameter or correlation coefficient between plasma IL-6 and these parameters. Random effect models calculated with DerSimonian and Laird weighting methods were applied to analyze correlation coefficients and gender difference in plasma IL-6. Egger’s test was used to assess the small study effect.

Results

Twenty articles out of 468 records identified were suitable for analyses. Plasma IL-6 correlates negatively with grip strength in mixed populations and also separately in men [− 0.25 with 95% confidence interval (CI): − 0.48, − 0.02] and in women (− 0.14 with 95% CI: − 0.24, − 0.03). However, contrary to expectations, men with better muscle condition have higher plasma IL-6 than women of similar age with worse muscle condition (plasma IL-6 male–female difference: 0.25 pg/mL with 95% CI: 0.15, 0.35).

Conclusion

This is the first study to demonstrate that a higher predictive IL-6 cut-off level should be determined for aging sarcopenia in men than in women.

Electronic supplementary material

The online version of this article (10.1186/s12877-018-0798-z) contains supplementary material, which is available to authorized users.

Phrenic motor neuron loss in aged rats

Sarcopenia is the age-related reduction of muscle mass and specific force. In previous studies, we found that sarcopenia of the diaphragm muscle (DIAm) is evident by 24 mo of age in both rats and mice and is associated with selective atrophy of type IIx and IIb muscle fibers and a decrease in maximum specific force. These fiber type-specific effects of sarcopenia resemble those induced by DIAm denervation, leading us to hypothesize that sarcopenia is due to an age-related loss of phrenic motor neurons (PhMNs). To address this hypothesis, we determined the number of PhMNs in young (6 mo old) and old (24 mo old) Fischer 344 rats. Moreover, we determined age-related changes in the size of PhMNs, since larger PhMNs innervate type IIx and IIb DIAm fibers. The PhMN pool was retrogradely labeled and imaged with confocal microscopy to assess the number of PhMNs and the morphometry of PhMN soma and proximal dendrites. In older animals, there were 22% fewer PhMNs, a 19% decrease in somal surface area, and a 21% decrease in dendritic surface area compared with young Fischer 344 rats. The age-associated loss of PhMNs involved predominantly larger PhMNs. These results are consistent with an age-related denervation of larger, more fatigable DIAm motor units, which are required primarily for high-force airway clearance behaviors. NEW & NOTEWORTHY Diaphragm muscle sarcopenia in rodent models is well described in the literature; however, the relationship between sarcopenia and frank phrenic motor neuron (MN) loss is unexplored in these models. We quantify a 22% loss of phrenic MNs in old (24 mo) compared with young (6 mo) Fischer 344 rats. We also report reductions in phrenic MN somal and proximal dendritic morphology that relate to decreased MN heterogeneity in old compared with young Fischer 344 rats.

The prevalence of musculoskeletal symptoms in the construction industry: a systematic review and meta-analysis

PURPOSE

Although individual studies have reported high prevalence of musculoskeletal symptoms (MSS) among construction workers, no systematic review has summarized their prevalence rates. Accordingly, this systematic review/meta-analysis aimed to synthesize MSS prevalence in different construction trades, gender and age groups, which may help develop specific ergonomic interventions.

METHODS

Nine databases were searched for articles related to the research objective. Two reviewers independently screened citations, extracted information and conducted quality assessment of the included studies. Meta-analyses were conducted on clinical and statistical homogenous data.

RESULTS

Thirty-five out of 1130 potential citations were included reporting diverse types of period prevalence and case definitions. Only the 1-year prevalence rates of MSS (defined as at least one episode of pain/MSS in the last year) at nine anatomical regions had sufficient homogeneous data for meta-analysis. Specifically, the 1-year prevalence of MSS was 51.1% for lower back, 37.2% for knee, 32.4% for shoulder, 30.4% for wrist, 24.4% for neck, 24.0% for ankle/foot, 20.3% for elbow, 19.8% for upper back, and 15.1% for hip/thigh. Female workers demonstrated a higher prevalence of MSS while there was insufficient information on the prevalence of trade-specific or age-related MSS. The quality assessments revealed that many included studies estimated prevalence solely based on self-reported data, and did not report non-respondents' characteristics.

CONCLUSIONS

Lumbar, knee, shoulder, and wrist MSS are the most common symptoms among construction workers. Future studies should standardize the reporting of period prevalence of MSS in different construction trades to allow meta-analyses and to develop relevant MSS prevention program.

Cushing's syndrome: a model for sarcopenic obesity

PURPOSE

Obesity and its metabolic impairments are discussed as major risk factors for sarcopenia leading to sarcopenic obesity. Cushing's syndrome is known to be associated with obesity and muscle atrophy. We compared Cushing's syndrome with matched obese controls regarding body composition, physical performance, and biochemical markers to test the hypothesis that Cushing's syndrome could be a model for sarcopenic obesity.

METHODS

By propensity score matching, 47 controls were selected by body mass index and gender as obese controls. Fat mass and muscle mass were measured by bioelectrical impedance analysis. Muscle function was assessed by chair rising test and hand grip strength. Biochemical markers of glucose and lipid metabolism and inflammation (hsCRP) were measured in peripheral blood.

RESULTS

Muscle mass did not differ between Cushing's syndrome and obese controls. However, Cushing's syndrome patients showed significantly greater chair rising time (9.5 s vs. 7.3 s, p = 0.008) and significantly lower hand grip strength (32.1 kg vs. 36.8 kg, p = 0.003). Cushing's syndrome patients with impaired fasting glucose have shown the highest limitations in hand grip strength and chair rising time.

CONCLUSIONS

Similar to published data in ageing medicine, Cushing's syndrome patients show loss of muscle function that cannot be explained by loss of muscle mass. Impaired muscle quality due to fat infiltration may be the reason. This is supported by the observation that Cushing's syndrome patients with impaired glucose metabolism show strongest deterioration of muscle function. Research in sarcopenic obesity in elderly is hampered by confounding comorbidities and polypharmacy. As Cushing's syndrome patients are frequently free of comorbidities and as Cushing's syndrome is potentially curable we suggest Cushing's syndrome as a clinical model for further research in sarcopenic obesity.

The effects of exercise on muscle strength, body composition, physical functioning and the inflammatory profile of older adults: a systematic review

PURPOSE OF REVIEW

This systematic review reports the most recent literature regarding the effects of physical exercise on muscle strength, body composition, physical functioning and inflammation in older adults. All articles were assessed for methodological quality and where possible effect size was calculated.

RECENT FINDINGS

Thirty-four articles were included - four involving frail, 24 healthy and five older adults with a specific disease. One reported on both frail and nonfrail patients. Several types of exercise were used: resistance training, aerobic training, combined resistance training and aerobic training and others. In frail older persons, moderate-to-large beneficial exercise effects were noted on inflammation, muscle strength and physical functioning. In healthy older persons, effects of resistance training (most frequently investigated) on inflammation or muscle strength can be influenced by the exercise modalities (intensity and rest interval between sets). Muscle strength seemed the most frequently used outcome measure, with moderate-to-large effects obtained regardless the exercise intervention studied. Similar effects were found in patients with specific diseases.

SUMMARY

Exercise has moderate-to-large effects on muscle strength, body composition, physical functioning and inflammation in older adults. Future studies should focus on the influence of specific exercise modalities and target the frail population more.

Preoperative sarcopenia determinants in pancreatic cancer patients

BACKGROUND & AIMS

Recent studies report that muscle depletion can impair short and long-term results after abdominal surgery. The aim of the present study is to quantify sarcopenia rate in patients undergoing pancreatic resection for cancer and to identify possible determinants of muscle waste.

METHODS

Total abdominal muscle area (TAMA) and visceral fat area (VFA) were measured by preoperative CT scan imaging at the level of the third lumbar vertebra in 273 patients undergoing pancreas resection for cancer. Demographics, preoperative parameters, and cancer stage were prospectively collected in our Institutional electronic database. An adjusted regression model was used to identify independent predictors for low TAMA.

RESULTS

176 (64.5%) patients were sarcopenic, with only 52 of them showing weight loss > 10%. Patients with cancer stage II and III had lower TAMA compared to patients with stage I (p = 0.002). The magnitude of weight loss was inversely correlated with VFA (p = 0.001), while no correlation with TAMA was found. Multivariate analysis showed that cancer stage was an independent predictor of low TAMA. Patients aged over 75 had the highest probability of having both low TAMA (p = 0.031) and high VFA (p < 0.0001).

CONCLUSIONS

Most of patients undergoing oncologic pancreatic surgery are sarcopenic. Cancer stage was an independent determinant of sarcopenia while nutritional factors seem less important. An age of over 75 years was significantly correlated with both muscle compartment depletion and visceral fat increase.

Osteosarcopenia is more than sarcopenia and osteopenia alone

BACKGROUND

Sarcopenia and osteopenia/osteoporosis show a high prevalence in old age and incur a high risk for falls, fractures, and further functional decline. Physical performance and bone metabolism in patients suffering from the so-called osteosarcopenia-the combination of sarcopenia and osteopenia-are currently still unknown.

AIMS

This study investigates physical performance and bone metabolism in osteosarcopenic, prefrail, community-dwelling older adults.

METHODS

68 prefrail adults between 65 and 94 years were assigned to four groups according to mean DXA results: osteosarcopenic [low T-score and low appendicular lean mass (aLM)], sarcopenic (low aLM), osteopenic (low T-score), and controls. Multiple linear regression analysis, adjusted for age, gender, physical activity, and 25-OH-vitamin D3 serum level, was used to identify the influence of being osteosarcopenic, sarcopenic, or osteopenic on physical performance (hand grip, chair rise test, sit-to-stand power, gait speed, SPPB) and serum markers for increased bone turnover [osteocalcin, β-crosslaps and procollagen type 1 amino-terminal propeptide (P1NP)].

RESULTS

Only osteosarcopenic participants showed significantly reduced hand grip strength, increased chair rising time, and STS power time as well as significantly increased bone turnover markers.

DISCUSSION

Due to low physical performance and high bone turnover, older adults with osteosarcopenia have to be regarded as the most at-risk population for fractures and further functional decline.

CONCLUSIONS

Up-to-date osteoporosis and post-fracture management of older persons should aim at both, bone and muscle.

Age-related sarcopenia and its pathophysiological bases

Age-related loss of the skeletal muscle and its function is known as sarcopenia. Definition and diagnostic criteria for sarcopenia have been outlined as consensus statements from several study groups, including usual gait speed, grip strength, and skeletal muscle mass. Whereas underlying mechanisms and pathophysiology of sarcopenia remains to be clarified, recent studies have suggested that chronic inflammatory status as well as lifestyle-related factors in older individuals might contribute to the process and progress of sarcopenia.

The Association between Total Protein and Vegetable Protein Intake and Low Muscle Mass among the Community-Dwelling Elderly Population in Northern Taiwan

Sarcopenia, highly linked with fall, frailty, and disease burden, is an emerging problem in aging society. Higher protein intake has been suggested to maintain nitrogen balance. Our objective was to investigate whether pre-sarcopenia status was associated with lower protein intake. A total of 327 community-dwelling elderly people were recruited for a cross-sectional study. We adopted the multivariate nutrient density model to identify associations between low muscle mass and dietary protein intake. The general linear regression models were applied to estimate skeletal muscle mass index across the quartiles of total protein and vegetable protein density. Participants with diets in the lowest quartile of total protein density (<13.2%) were at a higher risk for low muscle mass (odds ratio (OR) 3.03, 95% confidence interval (CI) 1.37–6.72) than those with diets in the highest quartile (≥17.2%). Similarly, participants with diets in the lowest quartile of vegetable protein density (<5.8%) were at a higher risk for low muscle mass (OR 2.34, 95% CI 1.14–4.83) than those with diets in the highest quartile (≥9.4%). Furthermore, the estimated skeletal muscle mass index increased significantly across the quartiles of total protein density (p = 0.023) and vegetable protein density (p = 0.025). Increasing daily intakes of total protein and vegetable protein densities appears to confer protection against pre-sarcopenia status.

Accuracy of the Timed Up and Go test for predicting sarcopenia in elderly hospitalized patients

OBJECTIVES

The ability of the Timed Up and Go test to predict sarcopenia has not been evaluated previously. The objective of this study was to evaluate the accuracy of the Timed Up and Go test for predicting sarcopenia in elderly hospitalized patients.

METHODS

This cross-sectional study analyzed 68 elderly patients (≥60 years of age) in a private hospital in the city of Salvador-BA, Brazil, between the 1st and 5th day of hospitalization. The predictive variable was the Timed Up and Go test score, and the outcome of interest was the presence of sarcopenia (reduced muscle mass associated with a reduction in handgrip strength and/or weak physical performance in a 6-m gait-speed test). After the descriptive data analyses, the sensitivity, specificity and accuracy of a test using the predictive variable to predict the presence of sarcopenia were calculated.

RESULTS

In total, 68 elderly individuals, with a mean age 70.4±7.7 years, were evaluated. The subjects had a Charlson Comorbidity Index score of 5.35±1.97. Most (64.7%) of the subjects had a clinical admission profile; the main reasons for hospitalization were cardiovascular disorders (22.1%), pneumonia (19.1%) and abdominal disorders (10.2%). The frequency of sarcopenia in the sample was 22.1%, and the mean length of time spent performing the Timed Up and Go test was 10.02±5.38 s. A time longer than or equal to a cutoff of 10.85 s on the Timed Up and Go test predicted sarcopenia with a sensitivity of 67% and a specificity of 88.7%. The accuracy of this cutoff for the Timed Up and Go test was good (0.80; IC=0.66-0.94; p=0.002).

CONCLUSION

The Timed Up and Go test was shown to be a predictor of sarcopenia in elderly hospitalized patients.

Associations between low back pain, urinary incontinence, and abdominal muscle recruitment as assessed via ultrasonography in the elderly

BACKGROUND

Low back pain (LBP) and urinary incontinence (UI) are highly prevalent among elderly individuals. In young adults, changes in trunk muscle recruitment, as assessed via ultrasound imaging, may be associated with lumbar spine stability.

OBJECTIVE

To assess the associations between LBP, UI, and the pattern of transversus abdominis (TrA), internal (IO), and external oblique (EO) muscle recruitment in the elderly as evaluated by ultrasound imaging.

METHOD

Fifty-four elderly individuals (mean age: 72±5.2 years) who complained of LBP and/or UI as assessed by the McGill Pain Questionnaire, Incontinence Questionnaire-Short Form, and ultrasound imaging were included in the study. The statistical analysis comprised a multiple linear regression model, and a p-value <0.05 was considered significant.

RESULTS

The regression models for the TrA, IO, and EO muscle thickness levels explained 2.0% (R2=0.02; F=0.47; p=0.628), 10.6% (R2=0.106; F=3.03; p=0.057), and 10.1% (R2=0.101; F=2.70; p=0.077) of the variability, respectively. None of the regression models developed for the abdominal muscles exhibited statistical significance. A significant and negative association (p=0.018; β=-0.0343) was observed only between UI and IO recruitment.

CONCLUSION

These results suggest that age-related factors may have interfered with the findings of the study, thus emphasizing the need to perform ultrasound imaging-based studies to measure abdominal muscle recruitment in the elderly.

Effects of PTEN on the longevity of cultured human umbilical vein endothelial cells: the role of antioxidants

Ageing is a major cause of illness, disease and mortality, mainly due to the shortening of telomeres, resulting in cells undergoing senescence and apoptosis. Increasing autophagy and the levels of antioxidants removes oxidants that cause DNA and telomere damage, thus reducing the rate at which telomeres shorten, resulting in a longer cellular lifespan. Phosphatase and tensin homolog (PTEN) has been shown to increase the lifespan of organisms by upregulating pathways involved in DNA damage repair, autophagy/antioxidants. The aim of this study was to investigate the effects of the overexpression of PTEN on the longevity of human cell cultures by examining the increase in antioxidant potential. Human umbilical vein endothelial cell (HUVEC) cultures were transfected with PTEN plasmids using lipofectamine. An assay was performed to quantify the protein levels of PTEN and the antioxidant potential of the cell cultures. The cell cultures were maintained until senescence occurred in order to determine longevity. The results of each assay were then compared and correlated with each other and with the longevity of the cells. The transfected cultures showed a significant increase in PTEN protein levels, total antioxidant potential and longevity (all P-values <0.001) compared with the non-transfected cell cultures. The correlation coefficient between cell longevity and PTEN levels was 0.8727; and the correlation coefficient between cell longevity and antioxidant potential was 0.6564. The successful transfection of PTEN led to an increase in PTEN levels, antioxidant potential and an increased cellular longevity. This study demonstrates that there is a potential for PTEN to be used to extend human longevity. This can lay the foundation for further studies to be carried out on humans involving PTEN and longevity.

Low serum selenium level is associated with low muscle mass in the community-dwelling elderly

OBJECTIVES

Elderly persons with low muscle mass (LMM) or sarcopenia are prone to frailty and functional decline. This study aimed to investigate the relationship between serum selenium level and skeletal muscle mass in community-dwelling elderly.

DESIGN

Cross-sectional observational study.

SETTING AND PARTICIPANTS

A total of 327 elderly Taipei citizens (mean age 71.5 ± 4.7 years) were recruited from the community.

MEASUREMENTS

Skeletal muscle mass was measured by bioelectrical impedance analysis. LMM was defined by low skeletal muscle index (SMI: muscle mass (kg)/[height (m)](2)). All participants were further divided into quartiles by serum selenium level and the risk for LMM among these quartiles was examined using multivariate logistic regression analyses. Estimated serum selenium levels for the LMM group vs the normal group and estimated SMI in the quartiles of serum selenium were computed by least square method in linear regression models.

RESULTS

The estimated mean (±standard deviation) of serum selenium level was significantly lower in the LMM group compared with the normal group after adjusting for confounders (1.01 ± 0.03 μmol/L vs 1.14 ± 0.02 μmol/L, P < .001). After adjusting for age, sex, lifestyle, and physical and metabolic factors, the odds ratios (95% confidence interval, P value) of LMM in the bottom, second, and third selenium quartile groups were 4.62 (95% CI 2.11-10.10, P < .001), 2.30 (95% CI 1.05-5.03, P < .05) and 1.51 (95% CI 0.66-3.46, P = .327), respectively, compared with the top quartile group of serum selenium level. The least square mean of SMI increased with the quartiles of serum selenium (P < .001).

CONCLUSIONS

This is the first study to demonstrate that low serum selenium is independently associated with low muscle mass in the elderly. The causality and underlying mechanism between selenium and low muscle mass or sarcopenia warrant further research.

Secreted protein acidic and rich in cysteine internalization and its age-related alterations in skeletal muscle progenitor cells

Aging causes phenotypic changes in skeletal muscle progenitor cells (Skm-PCs), such as reduced myogenesis and increased adipogenesis due to alterations in their environment or niche. Secreted protein acidic and rich in cysteine (SPARC), which is secreted into the niche of Skm-PCs, inhibits adipogenesis and promotes myogenesis. We have previously reported that Skm-PC responsiveness to SPARC declines with age, although the mechanism underlying this decline is unknown. In this study, we found that SPARC is internalized by Skm-PCs and that this uptake increases with age. Internalization is dependent on integrin-α5, a cell surface SPARC-binding molecule, and clathrin-mediated endocytosis. We also demonstrated that internalized SPARC is transported to Rab7-positive endosomes. Skm-PCs from old rats exhibited increased clathrin expression and decreased Rab7 expression exclusively in MyoD-negative cells. In loss-of-function analyses, clathrin knockdown increased the anti-adipogenic effect of SPARC, whereas Rab7 knockdown reduced it, indicating that alterations in SPARC internalization may mediate the age-related decline in its anti-adipogenic effect. These results provide insights into age-related SPARC resistance in Skm-PCs, which may lead to sarcopenia.

Forum on bone and skeletal muscle interactions: summary of the proceedings of an ASBMR workshop

Annual costs are enormous for musculoskeletal diseases such as osteoporosis and sarcopenia and for bone and muscle injuries, costing billions annually in health care. Although it is clear that muscle and bone development, growth, and function are connected, and that muscle loads bone, little is known regarding cellular and molecular interactions between these two tissues. A conference supported by the National Institutes of Health (NIH) and the American Society for Bone and Mineral Research (ASBMR) was held in July 2012 to address the enormous burden of musculoskeletal disease. National and international experts in either bone or muscle presented their findings and their novel hypotheses regarding muscle-bone interactions to stimulate the exchange of ideas between these two fields. The immediate goal of the conference was to identify critical research themes that would lead to collaborative research interactions and grant applications focusing on interactions between muscle and bone. The ultimate goal of the meeting was to generate a better understanding of how these two tissues integrate and crosstalk in both health and disease to stimulate new therapeutic strategies to enhance and maintain musculoskeletal health.

Loss of SPARC in mouse skeletal muscle causes myofiber atrophy

INTRODUCTION

The expression of secreted protein acidic and rich in cysteine (SPARC) in skeletal muscle decreases with age. Here, we examined the role of SPARC in skeletal muscle by reducing its expression.

METHODS

SPARC expression was suppressed by introducing short interfering RNA (siRNA) into mouse tibialis anterior muscle. Myofiber diameter, atrogin1, and muscle RING-finger protein 1 (MuRF1) expression, and tumor necrosis factor-α (TNFα) and transforming growth factor-β (TGFβ) signaling were then analyzed.

RESULTS

Reduced SPARC expression caused decreases in the diameter of myofibers, especially fast-type ones, accompanied by upregulation of atrogin1, but not MuRF1, at 10 days after siRNA transfection. The expression of TNFα and TGFβ and the phosphorylation status of p38 were not affected by SPARC knockdown, whereas Smad3 phosphorylation was increased at 2 days after siRNA transfection.

CONCLUSIONS

The loss of SPARC not only upregulates atrogin1 expression but also enhances TGFβ signaling, which may in turn cause muscle atrophy.

Sarcopenia: definition, epidemiology, and pathophysiology

The epidemiological trends that characterize our generation are the aging of the population. Aging results in a progressive loss of muscle mass and strength called sarcopenia, which is Greek for 'poverty of flesh'. Sarcopenia could lead to functional impairment, physical disability, and even mortality. Today, sarcopenia is a matter of immense public concern for aging prevention. Its prevalence continues to rise, probably as a result of increasing elderly populations all over the world. This paper addressed the definition and epidemiology of sarcopenia and its underlying pathophysiology. In addition, we summarized the abundant information available in the literature related to sarcopenia, together with results from Korean sarcopenic obesity study (KSOS) that we performed.

Impact of nutrition on muscle mass, strength, and performance in older adults

Muscle strength plays an important role in determining risk for falls, which result in fractures and other injuries. While bone loss has long been recognized as an inevitable consequence of aging, sarcopenia-the gradual loss of skeletal muscle mass and strength that occurs with advancing age-has recently received increased attention. A review of the literature was undertaken to identify nutritional factors that contribute to loss of muscle mass. The role of protein, acid-base balance, vitamin D/calcium, and other minor nutrients like B vitamins was reviewed. Muscle wasting is a multifactorial process involving intrinsic and extrinsic alterations. A loss of fast twitch fibers, glycation of proteins, and insulin resistance may play an important role in the loss of muscle strength and development of sarcopenia. Protein intake plays an integral part in muscle health and an intake of 1.0-1.2 g/kg of body weight per day is probably optimal for older adults. There is a moderate [corrected] relationship between vitamin D status and muscle strength. Chronic ingestion of acid-producing diets appears to have a negative impact on muscle performance, and decreases in vitamin B12 and folic acid intake may also impair muscle function through their action on homocysteine. An adequate nutritional intake and an optimal dietary acid-base balance are important elements of any strategy to preserve muscle mass and strength during aging.

Acquired myopathy/dystrophies

Diseases of muscle may be congenital or acquired. They cause muscle weakness without sensory loss. The onset, distribution, and clinical course help to differentiate the type of muscle disorder. The diagnostic workup may include laboratory examination, electrodiagnostic studies, and muscle biopsy. A definitive diagnosis leads to better decision making with regard to treatment, genetic education, prognosis, functional expectations, and the impact of exercise on muscle function.

Troponin T nuclear localization and its role in aging skeletal muscle

Troponin T (TnT) is known to mediate the interaction between Tn complex and tropomyosin (Tm), which is essential for calcium-activated striated muscle contraction. This regulatory function takes place in the myoplasm, where TnT binds Tm. However, recent findings of troponin I and Tm nuclear translocation in Drosophila and mammalian cells imply other roles for the Tn-Tm complex. We hypothesized that TnT plays a nonclassical role through nuclear translocation. Immunoblotting with different antibodies targeting the NH2- or COOH-terminal region uncovered a pool of fast skeletal muscle TnT3 localized in the nuclear fraction of mouse skeletal muscle as either an intact or fragmented protein. Construction of TnT3-DsRed fusion proteins led to the further observation that TnT3 fragments are closely related to nucleolus and RNA polymerase activity, suggesting a role for TnT3 in regulating transcription. Functionally, overexpression of TnT3 fragments produced significant defects in nuclear shape and caused high levels of apoptosis. Interestingly, nuclear TnT3 and its fragments were highly regulated by aging, thus creating a possible link between the deleterious effects of TnT3 and sarcopenia. We propose that changes in nuclear TnT3 and its fragments cause the number of myonuclei to decrease with age, contributing to muscle damage and wasting.

Resistance exercise improves hippocampus-dependent memory

It has been demonstrated that resistance exercise improves cognitive functions in humans. Thus, an animal model that mimics this phenomenon can be an important tool for studying the underlying neurophysiological mechanisms. Here, we tested if an animal model for resistance exercise was able to improve the performance in a hippocampus-dependent memory task. In addition, we also evaluated the level of insulin-like growth factor 1/insulin growth factor receptor (IGF-1/IGF-1R), which plays pleiotropic roles in the nervous system. Adult male Wistar rats were divided into three groups (N = 10 for each group): control, SHAM, and resistance exercise (RES). The RES group was submitted to 8 weeks of progressive resistance exercise in a vertical ladder apparatus, while the SHAM group was left in the same apparatus without exercising. Analysis of a cross-sectional area of the flexor digitorum longus muscle indicated that this training period was sufficient to cause muscle fiber hypertrophy. In a step-through passive avoidance task (PA), the RES group presented a longer latency than the other groups on the test day. We also observed an increase of 43 and 94% for systemic and hippocampal IGF-1 concentration, respectively, in the RES group compared to the others. A positive correlation was established between PA performance and systemic IGF-1 (r = 0.46, P < 0.05). Taken together, our data indicate that resistance exercise improves the hippocampus-dependent memory task with a concomitant increase of IGF-1 level in the rat model. This model can be further explored to better understand the effects of resistance exercise on brain functions.