Mitochondrial pathways and sarcopenia in the geroscience era

Sarcopenia is associated with structural, ultrastructural, and molecular abnormalities of skeletal muscle. Mitochondrial dysfunction is a pivotal factor involved in muscle aging and sarcopenia. Mitochondrial bioenergetics are significantly reduced in muscles of older adults which is associated with whole-body aerobic capacity, muscle strength, and physical performance. Transcriptional profiling of muscle samples from older adults also revealed inverse correlations between gene expression patterns of autophagy and mitophagy and muscle volume and physical performance. This is in line with the proposition that mitochondrial quality control (MQC) processes are key to organellar and tissue health. MQC encompasses mitochondrial biogenesis, dynamics, and mitophagy. The latter has recently been included among the hallmarks of aging and alterations in MQC have been associated with chronic sterile inflammation as well as muscle atrophy and dysfunction. Several biomarkers spanning MQC, inflammation, metabolism, intercellular communication, and gut microbiota have been linked to sarcopenia. Findings from these initial studies hold promise to inform geroscience-based research in the field of sarcopenia by offering a plausible biological framework for developing gerotherapeutics and monitoring their effects.

The role of mitochondria in cytokine and chemokine signalling during ageing

Ageing is accompanied by a persistent, low-level inflammation, termed "inflammageing", which contributes to the pathogenesis of age-related diseases. Mitochondria fulfil multiple roles in host immune responses, while mitochondrial dysfunction, a hallmark of ageing, has been shown to promote chronic inflammatory states by regulating the production of cytokines and chemokines. In this review, we aim to disentangle the molecular mechanisms underlying this process. We describe the role of mitochondrial signalling components such as mitochondrial DNA, mitochondrial RNA, N-formylated peptides, ROS, cardiolipin, cytochrome c, mitochondrial metabolites, potassium efflux and mitochondrial calcium in the age-related immune system activation. Furthermore, we discuss the effect of age-related decline in mitochondrial quality control mechanisms, including mitochondrial biogenesis, dynamics, mitophagy and UPRmt, in inflammatory states upon ageing. In addition, we focus on the dynamic relationship between mitochondrial dysfunction and cellular senescence and its role in regulating the secretion of pro-inflammatory molecules by senescent cells. Finally, we review the existing literature regarding mitochondrial dysfunction and inflammation in specific age-related pathological conditions, including neurodegenerative diseases (Alzheimer's and Parkinson's disease, and amyotrophic lateral sclerosis), osteoarthritis and sarcopenia.

LC/MS-Based Untargeted Lipidomics Reveals Lipid Signatures of Sarcopenia

Sarcopenia, a multifactorial systemic disorder, has attracted extensive attention, yet its pathogenesis is not fully understood, partly due to limited research on the relationship between lipid metabolism abnormalities and sarcopenia. Lipidomics offers the possibility to explore this relationship. Our research utilized LC/MS-based nontargeted lipidomics to investigate the lipid profile changes as-sociated with sarcopenia, aiming to enhance understanding of its underlying mechanisms. The study included 40 sarcopenia patients and 40 control subjects matched 1:1 by sex and age. Plasma lipids were detected and quantified, with differential lipids identified through univariate and mul-tivariate statistical analyses. A weighted correlation network analysis (WGCNA) and MetaboAna-lyst were used to identify lipid modules related to the clinical traits of sarcopenia patients and to conduct pathway analysis, respectively. A total of 34 lipid subclasses and 1446 lipid molecules were detected. Orthogonal partial least squares discriminant analysis (OPLS-DA) identified 80 differen-tial lipid molecules, including 38 phospholipids. Network analysis revealed that the brown module (encompassing phosphatidylglycerol (PG) lipids) and the yellow module (containing phosphati-dylcholine (PC), phosphatidylserine (PS), and sphingomyelin (SM) lipids) were closely associated with the clinical traits such as maximum grip strength and skeletal muscle mass (SMI). Pathway analysis highlighted the potential role of the glycerophospholipid metabolic pathway in lipid me-tabolism within the context of sarcopenia. These findings suggest a correlation between sarcopenia and lipid metabolism disturbances, providing valuable insights into the disease's underlying mechanisms and indicating potential avenues for further investigation.

Research Progress on the Effect and Mechanism of Exercise Intervention on Sarcopenia Obesity

With the increasingly severe situation of obesity and population aging, there is growing concern about sarcopenia obesity (SO). SO refers to the coexistence of obesity and sarcopenia, which imposes a heavier burden on individuals and society compared to obesity or sarcopenia alone. Therefore, comprehending the pathogenesis of SO and implementing effective clinical interventions are vital for its prevention and treatment. This review uses a comprehensive literature search and analysis of PubMed, Web of Science, and CNKI databases, with search terms including "Sarcopenic obesity", "exercise", "cytokines", "inflammation", "mitochondrial quality control", and "microRNA", covering relevant studies published up to July 2024. The results indicate that the pathogenesis of SO is complex, involving mechanisms like age-related changes in body composition, hormonal alterations, inflammation, mitochondrial dysfunction, and genetic and epigenetic factors. Regarding exercise interventions for SO, aerobic exercise can reduce fat mass, resistance exercise can increase skeletal muscle mass and strength, and combined exercise can achieve both, making it the optimal intervention for SO. The potential mechanisms by which exercise may prevent and treat SO include regulating cytokine secretion, inhibiting inflammatory pathways, improving mitochondrial quality, and mediating microRNA expression. This review emphasizes the effectiveness of exercise interventions in mitigating sarcopenic obesity through comprehensive analysis of its multifactorial pathogenesis and the mechanistic insights into exercise's therapeutic effects. Understanding these mechanisms informs targeted therapeutic strategies aimed at alleviating the societal and individual burdens associated with SO.

Bidirectional Relationships between Sarcopenia and Pelvic Floor Disorders

Sarcopenia and pelvic floor disorders (PFDs) are prevalent and often cooccurring conditions in the aging population. However, their bidirectional relationship and underlying mechanisms remain underexplored. This narrative review aims to elucidate this relationship by exploring potential causative interplays, shared pathophysiological mechanisms, and common risk factors. A comprehensive literature search was conducted to identify relevant studies focusing on epidemiological associations, interaction mechanisms, and implications for patient care. While epidemiological studies demonstrate associations between sarcopenia and PFDs, our findings reveal a cyclical relationship where sarcopenia may exacerbate PFDs through mechanisms such as decreased muscle strength and mobility. Conversely, the presence of PFDs often leads to reduced physical activity due to discomfort and mobility issues, which in turn exacerbate the muscle atrophy associated with sarcopenia. Additionally, shared risk factors such as physical inactivity, nutritional deficiencies, metabolic syndrome, and menopausal hormonal changes likely contribute to the onset and progression of both conditions. These interactions underscore the importance of concurrently integrated care approaches that address both conditions. Effective management requires comprehensive screening, the recognition of contributing factors, and tailored exercise regimens supported by a multidisciplinary approach. Future research should focus on longitudinal studies tracking disease progression and evaluating the efficacy of multidisciplinary care models in optimizing patient outcomes.

Delineating the contribution of ageing and physical activity to changes in mitochondrial characteristics across the lifespan

Ageing is associated with widespread physiological changes prominent within all tissues, including skeletal muscle and the brain, which lead to a decline in physical function. To tackle the growing health and economic burdens associated with an ageing population, the concept of healthy ageing has become a major research priority. Changes in skeletal muscle mitochondrial characteristics have been suggested to make an important contribution to the reductions in skeletal muscle function with age, and age-related changes in mitochondrial content, respiratory function, morphology, and mitochondrial DNA have previously been reported. However, not all studies report changes in mitochondrial characteristics with ageing, and there is increasing evidence to suggest that physical activity (or inactivity) throughout life is a confounding factor when interpreting age-associated changes. Given that physical activity is a potent stimulus for inducing beneficial adaptations to mitochondrial characteristics, delineating the influence of physical activity on the changes in skeletal muscle that occur with age is complicated. This review aims to summarise our current understanding and knowledge gaps regarding age-related changes to mitochondrial characteristics within skeletal muscle, as well as to provide some novel insights into brain mitochondria, and to propose avenues of future research and targeted interventions. Furthermore, where possible, we incorporate discussions of the modifying effects of physical activity, exercise, and training status, to purported age-related changes in mitochondrial characteristics.

Association of low muscle mass with cognitive function and mortality in USA seniors: results from NHANES 1999-2002

BACKGROUND

Sarcopenia and cognitive impairment have been linked in prior research, and both are linked to an increased risk of mortality in the general population. Muscle mass is a key factor in the diagnosis of sarcopenia. The relationship between low muscle mass and cognitive function in the aged population, and their combined impact on the risk of death in older adults, is currently unknown. This study aimed to explore the correlation between low muscle mass and cognitive function in the older population, and the relationship between the two and mortality in older people.

METHODS

Data were from the National Health and Nutrition Examination Survey 1999-2002. A total of 2540 older adults aged 60 and older with body composition measures were included. Specifically, 17-21 years of follow-up were conducted on every participant. Low muscle mass was defined using the Foundation for the National Institute of Health and the Asian Working Group for Sarcopenia definitions: appendicular lean mass (ALM) (< 19.75 kg for males; <15.02 kg for females); or ALM divided by body mass index (BMI) (ALM: BMI, < 0.789 for males; <0.512 for females); or appendicular skeletal muscle mass index (ASMI) (< 7.0 kg/m2 for males; <5.4 kg/m2 for females). Cognitive functioning was assessed by the Digit Symbol Substitution Test (DSST). The follow-up period was calculated from the NHANES interview date to the date of death or censoring (December 31, 2019).

RESULTS

We identified 2540 subjects. The mean age was 70.43 years (43.3% male). Age-related declines in DSST scores were observed. People with low muscle mass showed lower DSST scores than people with normal muscle mass across all age groups, especially in the group with low muscle mass characterized by ALM: BMI (60-69 years: p < 0.001; 70-79 years: p < 0.001; 80 + years: p = 0.009). Low muscle mass was significantly associated with lower DSST scores after adjusting for covariates (ALM: 43.56 ± 18.36 vs. 47.56 ± 17.44, p < 0.001; ALM: BMI: 39.88 ± 17.51 vs. 47.70 ± 17.51, p < 0.001; ASMI: 41.07 ± 17.89 vs. 47.42 ± 17.55, p < 0.001). At a mean long-term follow-up of 157.8 months, those with low muscle mass were associated with higher all-cause mortality (ALM: OR 1.460, 95% CI 1.456-1.463; ALM: BMI: OR 1.452, 95% CI 1.448-1.457); ASMI: OR 3.075, 95% CI 3.063-3.088). In the ALM: BMI and ASMI-defined low muscle mass groups, participants with low muscle mass and lower DSST scores were more likely to incur all-cause mortality ( ALM: BMI: OR 0.972, 95% CI 0.972-0.972; ASMI: OR 0.957, 95% CI 0.956-0.957).

CONCLUSIONS

Low muscle mass and cognitive function impairment are significantly correlated in the older population. Additionally, low muscle mass and low DSST score, alone or in combination, could be risk factors for mortality in older adults.

Multi-Modal Prehabilitation in Thoracic Surgery: From Basic Concepts to Practical Modalities

Over the last two decades, the invasiveness of thoracic surgery has decreased along with technological advances and better diagnostic tools, whereas the patient's comorbidities and frailty patterns have increased, as well as the number of early cancer stages that could benefit from curative resection. Poor aerobic fitness, nutritional defects, sarcopenia and "toxic" behaviors such as sedentary behavior, smoking and alcohol consumption are modifiable risk factors for major postoperative complications. The process of enhancing patients' physiological reserve in anticipation for surgery is referred to as prehabilitation. Components of prehabilitation programs include optimization of medical treatment, prescription of structured exercise program, correction of nutritional deficits and patient's education to adopt healthier behaviors. All patients may benefit from prehabilitation, which is part of the enhanced recovery after surgery (ERAS) programs. Faster functional recovery is expected in low-risk patients, whereas better clinical outcome and shorter hospital stay have been demonstrated in higher risk and physically unfit patients.

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

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

Pathophysiological changes of muscle after ischemic stroke: a secondary consequence of stroke injury

Sufficient clinical evidence suggests that the damage caused by ischemic stroke to the body occurs not only in the acute phase but also during the recovery period, and that the latter has a greater impact on the long-term prognosis of the patient. However, current stroke studies have typically focused only on lesions in the central nervous system, ignoring secondary damage caused by this disease. Such a phenomenon arises from the slow progress of pathophysiological studies examining the central nervous system. Further, the appropriate therapeutic time window and benefits of thrombolytic therapy are still controversial, leading scholars to explore more pragmatic intervention strategies. As treatment measures targeting limb symptoms can greatly improve a patient's quality of life, they have become a critical intervention strategy. As the most vital component of the limbs, skeletal muscles have become potential points of concern. Despite this, to the best of our knowledge, there are no comprehensive reviews of pathophysiological changes and potential treatments for post-stroke skeletal muscle. The current review seeks to fill a gap in the current understanding of the pathological processes and mechanisms of muscle wasting atrophy, inflammation, neuroregeneration, mitochondrial changes, and nutritional dysregulation in stroke survivors. In addition, the challenges, as well as the optional solutions for individualized rehabilitation programs for stroke patients based on motor function are discussed.

Restoring Mitochondrial Function and Muscle Satellite Cell Signaling: Remedies against Age-Related Sarcopenia

Sarcopenia has a complex pathophysiology that encompasses metabolic dysregulation and muscle ultrastructural changes. Among the drivers of intracellular and ultrastructural changes of muscle fibers in sarcopenia, mitochondria and their quality control pathways play relevant roles. Mononucleated muscle stem cells/satellite cells (MSCs) have been attributed a critical role in muscle repair after an injury. The involvement of mitochondria in supporting MSC-directed muscle repair is unclear. There is evidence that a reduction in mitochondrial biogenesis blunts muscle repair, thus indicating that the delivery of functional mitochondria to injured muscles can be harnessed to limit muscle fibrosis and enhance restoration of muscle function. Injection of autologous respiration-competent mitochondria from uninjured sites to damaged tissue has been shown to reduce infarct size and enhance cell survival in preclinical models of ischemia-reperfusion. Furthermore, the incorporation of donor mitochondria into MSCs enhances lung and cardiac tissue repair. This strategy has also been tested for regeneration purposes in traumatic muscle injuries. Indeed, the systemic delivery of mitochondria promotes muscle regeneration and restores muscle mass and function while reducing fibrosis during recovery after an injury. In this review, we discuss the contribution of altered MSC function to sarcopenia and illustrate the prospect of harnessing mitochondrial delivery and restoration of MSCs as a therapeutic strategy against age-related sarcopenia.

Effects and potential mechanisms of exercise and physical activity on eye health and ocular diseases

In the field of eye health, the profound impact of exercise and physical activity on various ocular diseases has become a focal point of attention. This review summarizes and elucidates the positive effects of exercise and physical activities on common ocular diseases, including dry eye disease (DED), cataracts, myopia, glaucoma, diabetic retinopathy (DR), and age-related macular degeneration (AMD). It also catalogues and offers exercise recommendations based on the varying impacts that different types and intensities of physical activities may have on specific eye conditions. Beyond correlations, this review also compiles potential mechanisms through which exercise and physical activity beneficially affect eye health. From mitigating ocular oxidative stress and inflammatory responses, reducing intraocular pressure, enhancing mitochondrial function, to promoting ocular blood circulation and the release of protective factors, the complex biological effects triggered by exercise and physical activities reveal their substantial potential in preventing and even assisting in the treatment of ocular diseases. This review aims not only to foster awareness and appreciation for how exercise and physical activity can improve eye health but also to serve as a catalyst for further exploration into the specific mechanisms and key targets through which exercise impacts ocular health. Such inquiries are crucial for advancing innovative strategies for the treatment of eye diseases, thereby holding significant implications for the development of new therapeutic approaches.

What role do extracellular vesicles play in developing physical frailty and sarcopenia? : A systematic review

BACKGROUND

Frailty and sarcopenia are typical geriatric conditions with a complex pathophysiology. Extracellular vesicles (EVs) are key regulators of age-related diseases, but the mechanisms underlying physical frailty, sarcopenia, and EVs are not well understood.

METHODS

A systematic literature review was conducted to examine the evidence supporting an association between EVs and physical frailty and/or sarcopenia by searching the electronic databases, including the Cochrane Library, PubMed, and Embase, from January 2000 to January 2021.

RESULTS

A total of 216 cross-sectional studies were retrieved, and after the removal of 43 duplicate records, the title and abstract of 167 articles were screened, identifying 6 relevant articles for full-text review. Of the studies five met the inclusion criteria, and heterogeneity among studies was high. There is controversy regarding whether frailty and/or sarcopenia are related to circulating EV levels; however, the cargo of EVs has been associated with frailty and sarcopenia in various ways, such as microRNAs, mitochondrial-derived vesicles (MDVs), and protein cargoes.

CONCLUSION

Recent studies, although limited, depicted that EVs could be one of the underlying mechanisms of frailty and/or sarcopenia. There is a possibility that physical frailty and sarcopenia may have specific EV concentrations and cargo profiles; however, further research is required to fully understand the mechanisms and identify potential biomarkers and early preventative strategies for physical frailty and sarcopenia.

Hallmarks of ageing in human skeletal muscle and implications for understanding the pathophysiology of sarcopenia in women and men

Ageing is a complex biological process associated with increased morbidity and mortality. Nine classic, interdependent hallmarks of ageing have been proposed involving genetic and biochemical pathways that collectively influence ageing trajectories and susceptibility to pathology in humans. Ageing skeletal muscle undergoes profound morphological and physiological changes associated with loss of strength, mass, and function, a condition known as sarcopenia. The aetiology of sarcopenia is complex and whilst research in this area is growing rapidly, there is a relative paucity of human studies, particularly in older women. Here, we evaluate how the nine classic hallmarks of ageing: genomic instability, telomere attrition, epigenetic alterations, loss of proteostasis, deregulated nutrient sensing, mitochondrial dysfunction, cellular senescence, stem cell exhaustion, and altered intercellular communication contribute to skeletal muscle ageing and the pathophysiology of sarcopenia. We also highlight five novel hallmarks of particular significance to skeletal muscle ageing: inflammation, neural dysfunction, extracellular matrix dysfunction, reduced vascular perfusion, and ionic dyshomeostasis, and discuss how the classic and novel hallmarks are interconnected. Their clinical relevance and translational potential are also considered.

Ubiquitin-proteasome pathway in skeletal muscle atrophy

Skeletal muscles underpin myriad human activities, maintaining an intricate balance between protein synthesis and degradation crucial to muscle mass preservation. Historically, disruptions in this balance-where degradation overshadows synthesis-have marked the onset of muscle atrophy, a condition diminishing life quality and, in grave instances, imperiling life itself. While multiple protein degradation pathways exist-including the autophagy-lysosome, calcium-dependent calpain, and cysteine aspartate protease systems-the ubiquitin-proteasome pathway emerges as an especially cardinal avenue for intracellular protein degradation, wielding pronounced influence over the muscle atrophy trajectory. This paper ventures a panoramic view of predominant muscle atrophy types, accentuating the ubiquitin-proteasome pathway's role therein. Furthermore, by drawing from recent scholarly advancements, we draw associations between the ubiquitin-proteasome pathway and specific pathological conditions linked to muscle atrophy. Our exploration seeks to shed light on the ubiquitin-proteasome pathway's significance in skeletal muscle dynamics, aiming to pave the way for innovative therapeutic strategies against muscle atrophy and affiliated muscle disorders.

A bibliometric analysis of inflammation in sarcopenia from 2007 to 2022

OBJECTIVE

In recent years, the impact of inflammation regulation on the progression of sarcopenia has garnered significant attention in research. However, there has been a lack of bibliometric analysis on the literature pertaining to inflammation in sarcopenia. This study was designed for the purpose of exploring the current research trends in this field as well as general situations and hot spots through bibliometric analysis.

METHODS

Searches were performed on the Web of Science Core Collection for articles related to inflammation in sarcopenia from 2007 to 2022, and selected in compliance with PRISMA guidelines. A variety of data were analyzed and visualized using VOSviewer and CiteSpace, including countries, institutions, authors, keywords, journals, and publications.

RESULTS

1833 articles were obtained in the last 16 years in all. The number of publications and citations increased from 2007 to 2022, with a notable rise occurring after 2016. Based on the results, the United States, the University of Melbourne, Nutrients, and Marzetti Emanuele were the most productive countries, institutions, journals, and authors, respectively. The primary keywords were oxidative stress and insulin resistance, and the burst detection analysis of keywords found that there is a possibility that future research will focus on "Inflammatory Bowel Disease".

CONCLUSION

This is the first bibliometric analysis of inflammation in sarcopenia. The interaction between oxidative stress, insulin resistance and inflammation in sarcopenia is regarded as the current research priorities. As sarcopenia becomes more prevalent, a focus will be placed on determining the molecular mechanisms and therapeutic targets for regulating inflammation to intervene in sarcopenia.

Mitochondria Transplantation from Stem Cells for Mitigating Sarcopenia

Sarcopenia is defined as the age-related loss of muscle mass and function that can lead to prolonged hospital stays and decreased independence. It is a significant health and financial burden for individuals, families, and society as a whole. The accumulation of damaged mitochondria in skeletal muscle contributes to the degeneration of muscles with age. Currently, the treatment of sarcopenia is limited to improving nutrition and physical activity. Studying effective methods to alleviate and treat sarcopenia to improve the quality of life and lifespan of older people is a growing area of interest in geriatric medicine. Therapies targeting mitochondria and restoring mitochondrial function are promising treatment strategies. This article provides an overview of stem cell transplantation for sarcopenia, including the mitochondrial delivery pathway and the protective role of stem cells. It also highlights recent advances in preclinical and clinical research on sarcopenia and presents a new treatment method involving stem cell-derived mitochondrial transplantation, outlining its advantages and challenges.

Sarcopenia Diagnosis and Management in Hematological Malignancies and Differences with Cachexia and Frailty

Sarcopenia is a geriatric syndrome characterized by a progressive loss of systemic muscle mass and decreased muscle strength or physical function. Several conditions have a role in its pathogenesis, significantly impacting adverse outcomes such as falls, functional decline, frailty, disability, multiple hospitalizations, and mortality. In the oncological setting, sarcopenia is associated with an increased risk of treatment toxicity, postoperative complications, and a higher mortality rate related to other causes (e.g., pneumonia). In the hematological field, even more so, sarcopenia predicts toxicity and response to treatments. In patients with hematologic malignancy, low muscle mass is associated with adverse outcomes and is a predictor of overall survival and non-relapse mortality. Therefore, it is essential to correctly recognize sarcopenia, evaluate the risk factors and their impact on the patient's trajectory, and effectively treat sarcopenia. Sarcopenia is a reversible condition. The most effective intervention for reversing it is physical exercise combined with nutrition. The objective of clinical assessment focused on sarcopenia is to be able to carry out a "tailor-made treatment".

Exploring molecular mechanisms underlying the pathophysiological association between knee osteoarthritis and sarcopenia

Objectives

Accumulating evidence indicates a strong link between knee osteoarthritis (KOA) and sarcopenia. However, the mechanisms involved have not yet been elucidated. This study primarily aims to explore the molecular mechanisms that explain the connection between these 2 disorders.

Methods

The gene expression profiles for KOA and sarcopenia were obtained from the Gene Expression Omnibus database, specifically from GSE55235, GSE169077, and GSE1408. Various bioinformatics techniques were employed to identify and analyze common differentially expressed genes (DEGs) across the 3 datasets. The techniques involved the analysis of Gene Ontology and pathways to enhance understanding, examining protein-protein interaction (PPI) networks, and identifying hub genes. In addition, we constructed the network of interactions between transcription factors (TFs) and genes, the co-regulatory network of TFs and miRNAs for hub genes, and predicted potential drugs.

Results

In total, 14 common DEGs were found between KOA and sarcopenia. Detailed information on biological processes and signaling pathways of common DEGs was obtained through enrichment analysis. After performing PPI network analysis, we discovered 4 hub genes (FOXO3, BCL6, CDKN1A, and CEBPB). Subsequently, we developed coregulatory networks for these hub genes involving TF-gene and TF-miRNA interactions. Finally, we identified 10 potential chemical compounds.

Conclusions

By conducting bioinformatics analysis, our study has successfully identified common gene interaction networks between KOA and sarcopenia. The potential of these findings to offer revolutionary understanding into the common development of these 2 conditions could lead to the identification of valuable targets for therapy.

TT3, a More Practical Indicator for Evaluating the Relationship Between Sarcopenia and Thyroid Hormone in the Euthyroid Elderly Compared with FT3

BACKGROUND AND AIMS

Sarcopenia is a common disease in the elderly, and the thyroid hormone (TH) might participate in the pathogenesis of sarcopenia. However, the results of previous studies were not completely consistent. We performed this study to investigate the association between THs and sarcopenia in a Chinese elderly euthyroid population.

SUBJECTS AND METHODS

A total of 309 Chinese elderly euthyroid subjects with an average age of 85.19 ± 7.8 years were enrolled. Participants were divided into four groups (non-sarcopenia, possible sarcopenia, sarcopenia and serve sarcopenia) according to the consensus update of AWGS in 2019. Serum levels of TT3, FT3, TT4, FT4, TSH, rT3 and TBG were measured. Muscle mass was measured by multifrequency bioelectrical impedance analysis, hand grip (HG) was represented by spring-type dynamometer, and gait speed (GS) was determined by 6-metre walk test. The FRAIL scale was used to assess frailty.

RESULTS

Compared to the non-sarcopenia group, the sarcopenia group showed a significant increase in age and FRIAL score, while FT3 and TT3 levels decreased significantly. Partial correlation analysis (adjusted by age, gender and the scores of FRIAL scale) indicated that FT3, TT3 and TSH had significant positive correlations with HG, and there also was a significant positive correlation between TT3 and GS. In addition, after adjusting for age, gender, BMI, ALT, sCr, and score on the FRAIL scale, the multivariate linear regression analysis showed that TT3 was positively associated with muscle strength and negatively associated with sarcopenia risk.

CONCLUSION

There is an association between the low TT3 level and sarcopenia. Therefore, maintaining higher T3 concentrations within the normal range appears to be beneficial for sarcopenia in the elderly. In addition, due to the fluctuation of FT3, TT3 is a more stable and practical indicator to evaluate the relationship between sarcopenia and thyroid hormone in the elderly euthyroid population.

A Narrative Review of Non-Pharmacological Strategies for Managing Sarcopenia in Older Adults with Cardiovascular and Metabolic Diseases

This narrative review examines the mechanisms underlying the development of cardiovascular disease (CVD) and metabolic diseases (MDs), along with their association with sarcopenia. Furthermore, non-pharmacological interventions to address sarcopenia in patients with these conditions are suggested. The significance of combined training in managing metabolic disease and secondary sarcopenia in type II diabetes mellitus is emphasized. Additionally, the potential benefits of resistance and aerobic training are explored. This review emphasises the role of nutrition in addressing sarcopenia in patients with CVD or MDs, focusing on strategies such as optimising protein intake, promoting plant-based protein sources, incorporating antioxidant-rich foods and omega-3 fatty acids and ensuring sufficient vitamin D levels. Moreover, the potential benefits of targeting gut microbiota through probiotics and prebiotic fibres in sarcopenic individuals are considered. Multidisciplinary approaches that integrate behavioural science are explored to enhance the uptake and sustainability of behaviour-based sarcopenia interventions. Future research should prioritise high-quality randomized controlled trials to refine exercise and nutritional interventions and investigate the incorporation of behavioural science into routine practices. Ultimately, a comprehensive and multifaceted approach is essential to improve health outcomes, well-being and quality of life in older adults with sarcopenia and coexisting cardiovascular and metabolic diseases.

"Diet for the prevention and management of sarcopenia"

Sarcopenia is a geriatric condition characterized by a progressive loss of skeletal muscle mass and strength, with an increased risk of adverse health outcomes (e.g., falls, disability, institutionalization, reduced quality of life, mortality). Pharmacological remedies are currently unavailable for preventing the development of sarcopenia, halting its progression, or impeding its negative health outcomes. The most effective strategies to contrast sarcopenia rely on the adoption of healthier lifestyle behaviors, including adherence to high-quality diets and regular physical activity. In this review, the role of nutrition in the prevention and management of sarcopenia is summarized. Special attention is given to current "blockbuster" dietary regimes and agents used to counteract age-related muscle wasting, together with their putative mechanisms of action. Issues related to the design and implementation of effective nutritional strategies are discussed, with a focus on unanswered questions on the most appropriate timing of nutritional interventions to preserve muscle health and function into old age. A brief description is also provided on new technologies that can facilitate the development and implementation of personalized nutrition plans to contrast sarcopenia.

Augmented temperature fluctuation aggravates muscular atrophy through the gut microbiota

Large temperature difference is reported to be a risk factor for human health. However, little evidence has reported the effects of temperature fluctuation on sarcopenia, a senile disease characterized by loss of muscle mass and function. Here, we demonstrate that higher diurnal temperature range in humans has a positive correlation with the prevalence of sarcopenia. Fluctuated temperature exposure (10-25 °C) accelerates muscle atrophy and dampens exercise performance in mid-aged male mice. Interestingly, fluctuated temperature alters the microbiota composition with increased levels of Parabacteroides_distasonis, Duncaniella_dubosii and decreased levels of Candidatus_Amulumruptor, Roseburia, Eubacterium. Transplantation of fluctuated temperature-shaped microbiota replays the adverse effects on muscle function. Mechanically, we find that altered microbiota increases circulating aminoadipic acid, a lysine degradation product. Aminoadipic acid damages mitochondrial function through inhibiting mitophagy in vitro. And Eubacterium supplementation alleviates muscle atrophy and dysfunction induced by fluctuated temperature. Our results uncover the detrimental impact of fluctuated temperature on muscle function and provide a new clue for gut-muscle axis.

Post-translational regulation of muscle growth, muscle aging and sarcopenia

Skeletal muscle makes up 30-40% of the total body mass. It is of great significance in maintaining digestion, inhaling and exhaling, sustaining body posture, exercising, protecting joints and many other aspects. Moreover, muscle is also an important metabolic organ that helps to maintain the balance of sugar and fat. Defective skeletal muscle function not only limits the daily activities of the elderly but also increases the risk of disability, hospitalization and death, placing a huge burden on society and the healthcare system. Sarcopenia is a progressive decline in muscle mass, muscle strength and muscle function with age caused by environmental and genetic factors, such as the abnormal regulation of protein post-translational modifications (PTMs). To date, many studies have shown that numerous PTMs, such as phosphorylation, acetylation, ubiquitination, SUMOylation, glycosylation, glycation, methylation, S-nitrosylation, carbonylation and S-glutathionylation, are involved in the regulation of muscle health and diseases. This article systematically summarizes the post-translational regulation of muscle growth and muscle atrophy and helps to understand the pathophysiology of muscle aging and develop effective strategies for diagnosing, preventing and treating sarcopenia.

The Link between Mitochondrial Dysfunction and Sarcopenia: An Update Focusing on the Role of Pyruvate Dehydrogenase Kinase 4

Sarcopenia, defined as a progressive loss of muscle mass and function, is typified by mitochondrial dysfunction and loss of mitochondrial resilience. Sarcopenia is associated not only with aging, but also with various metabolic diseases characterized by mitochondrial dyshomeostasis. Pyruvate dehydrogenase kinases (PDKs) are mitochondrial enzymes that inhibit the pyruvate dehydrogenase complex, which controls pyruvate entry into the tricarboxylic acid cycle and the subsequent adenosine triphosphate production required for normal cellular activities. PDK4 is upregulated in mitochondrial dysfunction-related metabolic diseases, especially pathologic muscle conditions associated with enhanced muscle proteolysis and aberrant myogenesis. Increases in PDK4 are associated with perturbation of mitochondria-associated membranes and mitochondrial quality control, which are emerging as a central mechanism in the pathogenesis of metabolic disease-associated muscle atrophy. Here, we review how mitochondrial dysfunction affects sarcopenia, focusing on the role of PDK4 in mitochondrial homeostasis. We discuss the molecular mechanisms underlying the effects of PDK4 on mitochondrial dysfunction in sarcopenia and show that targeting mitochondria could be a therapeutic target for treating sarcopenia.

Dynapenic Abdominal Obesity as a Risk Factor for Metabolic Syndrome in Individual 50 Years of Age or Older: English Longitudinal Study of Ageing

OBJECTIVES

To analyse whether dynapenic abdominal obesity is a risk factor for Metabolic syndrome (MetS) and its components in individuals 50 years of age or older.

DESIGN

A longitudinal study was conducted with an eight-year follow-up.

SETTING

Representative sample of community-dwelling participants of the English Longitudinal Study of Ageing (ELSA).

PARTICIPANTS

3,952 individuals free of MetS at baseline.

MEASUREMENTS

Dynapenic abdominal obesity was defined based on waist circumference (> 102 cm for men and > 88 cm for women) and grip strength (< 26 kg for men and < 16 kg for women). The participants were classified as non-abdominally obese/non-dynapenic (NAO/ND - reference group), abdominally obese/non-dynapenic (AO/ND), non-abdominally obese/dynapenic (NAO/D) and abdominally obese/dynapenic (AO/D). The outcome was the incidence of MetS based on the presence of three or more of the following criteria: hypertriglyceridemia, hyperglycaemia, low HDL cholesterol, arterial hypertension or body mass index ≥ 30 kg/m2 throughout eight-year follow-up. Additionally, the incidence of each component of MetS was also analyzed. Poisson regression models were run and controlled for sociodemographic, behavioural and clinical variables.

RESULTS

The mean age of the participants was 65 years and 55% were women. The prevalence of AO/ND, NAO/D and AO/D were 35.3, 4.3 and 2.2%, respectively. At the end of follow-up 558 incident cases of MetS were recorded. The adjusted model demonstrated that although abdominal obesity was a risk factor for MetS (IRR: 2.26; 95% CI: 1.87 - 2.73), the IRR was greater in AO/D individuals (IRR: 3.34; 95% CI: 2.03 - 5.50) compared with ND/NAO group. Furthermore, ND/AO was a risk factor for incidence of hypertriglyceridemia (IRR: 1.27; 95% CI: 1.06 - 1.52), hyperglycaemia (IRR: 1.41; 95% CI: 1.18 - 1.69), low HDL cholesterol (IRR: 1.70; 95% CI: 1.32 - 2.19) and BMI ≥ 30 kg/m2 (IRR: 2.58; 95% CI: 2.04 - 3.26) while D/AO was a risk factor for hyperglycaemia (IRR: 1.78; 95% CI: 1.02 - 3.10), low HDL cholesterol (IRR: 2.36; 95% CI: 1.10 - 5.08), and BMI ≥ 30 kg/m2 (IRR: 2.79; 95% CI: 1.38 - 5.62).

CONCLUSIONS

Dynapenic abdominal obesity increases the risk of MetS, with a higher IRR compared to obesity alone. The understanding of this synergic action could guide specific clinical strategies, enabling the prevention of metabolic changes that can lead to cardiovascular disease, disability and death.

A single-set functional training program increases muscle power, improves functional fitness, and reduces pro-inflammatory cytokines in postmenopausal women: A randomized clinical trial

Introduction: Aging can be associated with reduced muscle power, functional decline, and increased plasma concentrations of proinflammatory cytokines. Functional training (FT) can improve muscle power, functional fitness and reduce plasma cytokines. However, the functional training optimal volume required to produce these adaptations must be clarified. Our study analyzed the effects of multiple-set functional training (MSFT) and single-set functional training (SSFT) on postmenopausal women's muscle power, functional fitness, and inflammatory profile. Methods: Forty-three women were randomly allocated into three groups: multiple-set functional training (n = 16, age 64.13 ± 5.17), single-set functional training (n = 14, age 63.79 ± 4.88), and control group (CG, n = 13, age 64.62 ± 5.44). The bench press and squat exercises evaluated upper and lower limb muscle power. The following tests assessed functional fitness: putting on and taking off a T-shirt, gallon-jug shelf-transfer, standing up and walking around the house, five times sit-to-stand, and 400-m walk. Plasma cytokine (TNF-α, IL-6, and IL 10) concentrations were measured by flow cytometry. Results: Single-set functional training and multiple-set functional training increased upper and lower limbs muscle power and improved functional fitness, except for the putting on and taking off a T-shirt test. Multiple-set functional training reduced TNF-α and IL-6, while single-set functional training reduced only TNF-α. IL-10 was unaffected by exercise. Discussion: Single-set functional training and multiple-set functional training, therefore, promoted similar muscle power and functional fitness improvements over 24 weeks. Multiple-set functional training was more effective than single-set functional training, reducing both TNF and IL-6, while single-set functional training only decreased TNF-α.

From mitochondria to sarcopenia: role of 17β-estradiol and testosterone

Sarcopenia, characterized by a loss of muscle mass and strength with aging, is prevalent in older adults. Although the exact mechanisms underlying sarcopenia are not fully understood, evidence suggests that the loss of mitochondrial integrity in skeletal myocytes has emerged as a pivotal contributor to the complex etiology of sarcopenia. Mitochondria are the primary source of ATP production and are also involved in generating reactive oxygen species (ROS), regulating ion signals, and initiating apoptosis signals in muscle cells. The accumulation of damaged mitochondria due to age-related impairments in any of the mitochondrial quality control (MQC) processes, such as proteostasis, biogenesis, dynamics, and mitophagy, can contribute to the decline in muscle mass and strength associated with aging. Interestingly, a decrease in sex hormones (e.g., 17β-estradiol and testosterone), which occurs with aging, has also been linked to sarcopenia. Indeed, 17β-estradiol and testosterone targeted mitochondria and exhibited activities in regulating mitochondrial functions. Here, we overview the current literature on the key mechanisms by which mitochondrial dysfunction contribute to the development and progression of sarcopenia and the potential modulatory effects of 17β-estradiol and testosterone on mitochondrial function in this context. The advance in its understanding will facilitate the development of potential therapeutic agents to mitigate and manage sarcopenia.

Ginsenoside Rb1 Prevents Oxidative Stress-Induced Apoptosis and Mitochondrial Dysfunction in Muscle Stem Cells via NF-κB Pathway

Sarcopenia, featured by the progressive loss of skeletal muscle function and mass, is associated with the impaired function of muscle stem cells (MuSCs) caused by increasing oxidative stress in senescent skeletal muscle tissue during aging. Intact function of MuSCs maintains the regenerative potential as well as the homeostasis of skeletal muscle tissues during aging. Ginsenoside Rb1, a natural compound from ginseng, exhibited the effects of antioxidation and against apoptosis. However, its effects of restoring MuSC function during aging and improving age-related sarcopenia remained unknown. In this study, we investigated the role of Rb1 in improving MuSC function and inhibiting apoptosis by reducing oxidative stress levels. We found that Rb1 inhibited the accumulation of reactive oxygen species (ROS) and protected the cells from oxidative stress to attenuate the H₂O₂-induced cytotoxicity. Rb1 also blocked oxidative stress-induced apoptosis by inhibiting the activation of caspase-3/9, which antagonized the decrease in mitochondrial content and the increase in mitochondrial abnormalities caused by oxidative stress via promoting the protein expression of genes involved in mitochondrial biogenesis. Mechanistically, it was proven that Rb1 exerted its antioxidant effects and avoided the apoptosis of myoblasts by targeting the core regulator of the nuclear factor-kappa B (NF-κB) signal pathway. Therefore, these findings suggest that Rb1 may have a beneficial role in the prevention and treatment of MuSC exhaustion-related diseases like sarcopenia.

Contribution of muscle satellite cells to sarcopenia

Sarcopenia, a disorder characterized by age-related muscle loss and reduced muscle strength, is associated with decreased individual independence and quality of life, as well as a high risk of death. Skeletal muscle houses a normally mitotically quiescent population of adult stem cells called muscle satellite cells (MuSCs) that are responsible for muscle maintenance, growth, repair, and regeneration throughout the life cycle. Patients with sarcopenia are often exhibit dysregulation of MuSCs homeostasis. In this review, we focus on the etiology, assessment, and treatment of sarcopenia. We also discuss phenotypic and regulatory mechanisms of MuSC quiescence, activation, and aging states, as well as the controversy between MuSC depletion and sarcopenia. Finally, we give a multi-dimensional treatment strategy for sarcopenia based on improving MuSC function.

Effect of Physical Activity/Exercise on Oxidative Stress and Inflammation in Muscle and Vascular Aging

Functional status is considered the main determinant of healthy aging. Impairment in skeletal muscle and the cardiovascular system, two interrelated systems, results in compromised functional status in aging. Increased oxidative stress and inflammation in older subjects constitute the background for skeletal muscle and cardiovascular system alterations. Aged skeletal muscle mass and strength impairment is related to anabolic resistance, mitochondrial dysfunction, increased oxidative stress and inflammation as well as a reduced antioxidant response and myokine profile. Arterial stiffness and endothelial function stand out as the main cardiovascular alterations related to aging, where increased systemic and vascular oxidative stress and inflammation play a key role. Physical activity and exercise training arise as modifiable determinants of functional outcomes in older persons. Exercise enhances antioxidant response, decreases age-related oxidative stress and pro-inflammatory signals, and promotes the activation of anabolic and mitochondrial biogenesis pathways in skeletal muscle. Additionally, exercise improves endothelial function and arterial stiffness by reducing inflammatory and oxidative damage signaling in vascular tissue together with an increase in antioxidant enzymes and nitric oxide availability, globally promoting functional performance and healthy aging. This review focuses on the role of oxidative stress and inflammation in aged musculoskeletal and vascular systems and how physical activity/exercise influences functional status in the elderly.

Molecular Mechanisms Underlying Intensive Care Unit-Acquired Weakness and Sarcopenia

Skeletal muscle is a highly adaptable organ, and its amount declines under catabolic conditions such as critical illness. Aging is accompanied by a gradual loss of muscle, especially when physical activity decreases. Intensive care unit-acquired weakness is a common and highly serious neuromuscular complication in critically ill patients. It is a consequence of critical illness and is characterized by a systemic inflammatory response, leading to metabolic stress, that causes the development of multiple organ dysfunction. Muscle dysfunction is an important component of this syndrome, and the degree of catabolism corresponds to the severity of the condition. The population of critically ill is aging; thus, we face another negative effect-sarcopenia-the age-related decline of skeletal muscle mass and function. Low-grade inflammation gradually accumulates over time, inhibits proteosynthesis, worsens anabolic resistance, and increases insulin resistance. The cumulative consequence is a gradual decline in muscle recovery and muscle mass. The clinical manifestation for both of the above conditions is skeletal muscle weakness, with macromolecular damage, and a common mechanism-mitochondrial dysfunction. In this review, we compare the molecular mechanisms underlying the two types of muscle atrophy, and address questions regarding possible shared molecular mechanisms, and whether critical illness accelerates the aging process.

Adipose improves muscular atrophy caused by Sirtuin1 deficiency by promoting mitochondria synthesis

Muscular dysplasia is a common muscle disease, but its pathological mechanism is still unclear. Adipose is originally identified as a highly conservative and widely expressed anti-obesity gene, and our previous study has reported that Adipose is also a positive regulator of myogenesis. Considering the vital role of during muscle development, this study was to demonstrate a potential relationship between Sirtuin1 and Adipose and clarified the mechanism by which Adipose regulated muscle development. Our results showed that the muscle fiber cross-sectional area and myosin heavy chain protein level were significantly reduced in Sirtuin1^+/- mice. Moreover, the longitudinal section of muscle fibers was obviously irregular. Sirtuin1 knockdown significantly reduced the expression levels of Adipose and its upstream transcriptional regulator Kruppel like factor 15 and notably inhibited the AMP-activated protein kinase α-peroxisome proliferator-activated receptor gamma coactivator 1α signaling pathway in skeletal muscle. However, Adipose over-expression activated this signaling pathway and promoted mitochondrial biosynthesis in C2C12 myoblasts. Adipose over-expression also enhanced glucose absorption of C2C12 cells, suggesting the increased needs for cells for metabolic substrates. In C2C12 cells with hydrogen peroxide treatment, Adipose over-expression repressed hydrogen peroxide-elicited apoptosis and mitochondrial loss, while Sirtuin1-specific inhibitor dramatically weakened these roles of Adipose. Taken together, our findings reveal that Adipose rescues the adverse effects of Sirtuin1 deficiency or hydrogen peroxide on muscle development by activating the AMP-activated protein kinase α- peroxisome proliferator-activated receptor gamma coactivator 1α pathway to promote mitochondria synthesis, which provides theoretical basis for developing new therapeutic targets against some muscle diseases.

Pathophysiological mechanisms explaining the association between low skeletal muscle mass and cognitive function

Low skeletal muscle mass is associated with cognitive impairment and dementia in older adults. This review describes the possible underlying pathophysiological mechanisms: systemic inflammation, insulin metabolism, protein metabolism, and mitochondrial function. We hypothesize that the central tenet in this pathophysiology is the dysfunctional myokine secretion consequent to minimal physical activity. Myokines, such as fibronectin type III domain containing 5/irisin and cathepsin B, are released by physically active muscle and cross the blood–brain barrier. These myokines upregulate local neurotrophin expression such as brain-derived neurotrophic factor (BDNF) in the brain microenvironment. BDNF exerts anti-inflammatory effects that may be responsible for neuroprotection. Altered myokine secretion due to physical inactivity exacerbates inflammation and impairs muscle glucose metabolism, potentially affecting the transport of insulin across the blood–brain barrier. Our working model also suggests other underlying mechanisms. A negative systemic protein balance, commonly observed in older adults, contributes to low skeletal muscle mass and may also reflect deficient protein metabolism in brain tissues. As a result of age-related loss in skeletal muscle mass, decrease in the abundance of mitochondria and detriments in their function lead to a decrease in tissue oxidative capacity. Dysfunctional mitochondria in skeletal muscle and brain result in the excessive production of reactive oxygen species, which drives tissue oxidative stress and further perpetuates the dysfunction in mitochondria. Both oxidative stress and accumulation of mitochondrial DNA mutations due to aging drive cellular senescence. A targeted approach in the pathophysiology of low muscle mass and cognition could be to restore myokine balance by physical activity.

NAD+ centric mechanisms and molecular determinants of skeletal muscle disease and aging

The nicotinamide adenine dinucleotide (NAD+) is an essential redox cofactor, involved in various physiological and molecular processes, including energy metabolism, epigenetics, aging, and metabolic diseases. NAD+ repletion ameliorates muscular dystrophy and improves the mitochondrial and muscle stem cell function and thereby increase lifespan in mice. Accordingly, NAD+ is considered as an anti-oxidant and anti-aging molecule. NAD+ plays a central role in energy metabolism and the energy produced is used for movements, thermoregulation, and defense against foreign bodies. The dietary precursors of NAD+ synthesis is targeted to improve NAD+ biosynthesis; however, studies have revealed conflicting results regarding skeletal muscle-specific effects. Recent advances in the activation of nicotinamide phosphoribosyltransferase in the NAD+ salvage pathway and supplementation of NAD+ precursors have led to beneficial effects in skeletal muscle pathophysiology and function during aging and associated metabolic diseases. NAD+ is also involved in the epigenetic regulation and post-translational modifications of proteins that are involved in various cellular processes to maintain tissue homeostasis. This review provides detailed insights into the roles of NAD+ along with molecular mechanisms during aging and disease conditions, such as the impacts of age-related NAD+ deficiencies on NAD+-dependent enzymes, including poly (ADP-ribose) polymerase (PARPs), CD38, and sirtuins within skeletal muscle, and the most recent studies on the potential of nutritional supplementation and distinct modes of exercise to replenish the NAD+ pool.

Correlation between musculoskeletal mass and perfusion in patients with gastrointestinal malignancy: a preliminary study based on quantitative CT and CT perfusion

BACKGROUND

To investigate the correlation between musculoskeletal mass and perfusion using quantitative computer tomography (QCT) and CT perfusion (CTP) in patients with gastrointestinal malignancy.

METHODS

In this prospective study, 96 patients (mean age 66 years, range 25-90; 63.5% male) with gastrointestinal malignancy underwent QCT and CTP between May 2019 and February 2021. Bone mineral density (BMD) and body composition [perivertebral muscular mass index (PMI), skeletal muscular mass index (SMI) and muscular fat fraction] were evaluated through QCT. Musculoskeletal perfusion parameters were measured by CTP. Differences in these parameters between (or among) two (or three) groups (grouped by BMD, SMI, and TNM staging) were analyzed.

RESULTS

There were significant differences in PMI and muscular fat fraction among normal (n = 30), osteopenia (n = 43), and osteoporosis (n = 23) groups (both P < 0.001). Blood flow (r = 0.336, P = 0.001; adjusted for age and gender, r = 0.383, P < 0.001), blood volume (r = 0.238, P = 0.011; adjusted for age and gender, r = 0.329, P = 0.001), and flow extraction product (r = 0.217, P = 0.034; adjusted for age and gender, r = 0.320, P = 0.002) vaules of vertebral perfusion showed positive correlation with BMD. However, the relationships between PMI and perfusion parameters of perivertebral muscle were not significant. No significant differences were found in musculoskeletal mass and perfusion parameters between different TNM staging.

CONCLUSIONS

The changes of bone mass and perivertebral muscular mass in patients with gastrointestinal malignancy are synchronous. Decreased vertebral bone mass is accompanied with reduced perivertebral muscular mass, increased muscular fat, and decreased bone perfusion. However, the changes of perfusion in vertebra and perivertebral muscles are asynchronous. Musculoskeletal mass and perfusion have no correlation with TNM staging of the patients with gastrointestinal malignancy.

TRIAL REGISTRATION

SHSY-IEC-4.1/20-242/01 (Registered 09-12-2020, Retrospectively registered).

Exercise Therapy for People With Sarcopenic Obesity: Myokines and Adipokines as Effective Actors

Sarcopenic obesity is defined as a multifactorial disease in aging with decreased body muscle, decreased muscle strength, decreased independence, increased fat mass, due to decreased physical activity, changes in adipokines and myokines, and decreased satellite cells. People with sarcopenic obesity cause harmful changes in myokines and adipokines. These changes are due to a decrease interleukin-10 (IL-10), interleukin-15 (IL-15), insulin-like growth factor hormone (IGF-1), irisin, leukemia inhibitory factor (LIF), fibroblast growth factor-21 (FGF-21), adiponectin, and apelin. While factors such as myostatin, leptin, interleukin-6 (IL-6), interleukin-8 (IL-8), and resistin increase. The consequences of these changes are an increase in inflammatory factors, increased degradation of muscle proteins, increased fat mass, and decreased muscle tissue, which exacerbates sarcopenia obesity. In contrast, exercise, especially strength training, reverses this process, which includes increasing muscle protein synthesis, increasing myogenesis, increasing mitochondrial biogenesis, increasing brown fat, reducing white fat, reducing inflammatory factors, and reducing muscle atrophy. Since some people with chronic diseases are not able to do high-intensity strength training, exercises with blood flow restriction (BFR) are newly recommended. Numerous studies have shown that low-intensity BFR training produces the same increase in hypertrophy and muscle strength such as high-intensity strength training. Therefore, it seems that exercise interventions with BFR can be an effective way to prevent the exacerbation of sarcopenia obesity. However, due to limited studies on adipokines and exercises with BFR in people with sarcopenic obesity, more research is needed.

The role and therapeutic potential of stem cells in skeletal muscle in sarcopenia

Sarcopenia is a common age-related skeletal muscle disorder featuring the loss of muscle mass and function. In regard to tissue repair in the human body, scientists always consider the use of stem cells. In skeletal muscle, satellite cells (SCs) are adult stem cells that maintain tissue homeostasis and repair damaged regions after injury to preserve skeletal muscle integrity. Muscle-derived stem cells (MDSCs) and SCs are the two most commonly studied stem cell populations from skeletal muscle. To date, considerable progress has been achieved in understanding the complex associations between stem cells in muscle and the occurrence and treatment of sarcopenia. In this review, we first give brief introductions to sarcopenia, SCs and MDSCs. Then, we attempt to untangle the differences and connections between these two types of stem cells and further elaborate on the interactions between sarcopenia and stem cells. Finally, our perspectives on the possible application of stem cells for the treatment of sarcopenia in future are presented. Several studies emerging in recent years have shown that changes in the number and function of stem cells can trigger sarcopenia, which in turn leads to adverse influences on stem cells because of the altered internal environment in muscle. A better understanding of the role of stem cells in muscle, especially SCs and MDSCs, in sarcopenia will facilitate the realization of novel therapy approaches based on stem cells to combat sarcopenia.

Mitochondrial Quality Control in Sarcopenia: Updated Overview of Mechanisms and Interventions

Sarcopenia is a common geriatric disorder characterized by decreased muscle strength, low muscle mass and poor physical performance. This aging-related skeletal muscle deterioration leads to adverse outcomes and severely impairs the quality of life of patients. The accumulation of dysfunctional mitochondria with aging is an important factor in the occurrence and progression of sarcopenia. Mitochondrial quality control (MQC) fundamentally ensures the normal mitochondrial functions and is comprised of four main parts: proteostasis, biogenesis, dynamics and autophagy. Therefore, any pathophysiologic factors compromising the quality control of homeostasis in the skeletal muscle may lead to sarcopenia. However, the specific theoretical aspects of these processes have not been fully elucidated. Current therapeutic interventions using nutritional and pharmaceutical treatments show a modest therapeutic efficacy; however, only physical exercise is recommended as the first-line therapy for sarcopenia, which can ameliorate skeletal muscle deficiency by maintaining the homeostatic MQC. In this review, we summarized the known mechanisms that contribute to the pathogenesis of sarcopenia by impairing normal mitochondrial functions and described potential interventions that mitigate sarcopenia through improving MQC.

Skeletal muscle depletion predicts death in severe community-acquired pneumonia patients entering ICU

BACKGROUND

Sarcopenia, or skeletal muscle depletion, was common in the elderly and often led to a poor prognosis of diseases. The area of the psoas muscle in abdominal computed tomography (CT) is the most common used for diagnosing sarcopenia. However, patients with pneumonia routinely only undergo chest CT.

OBJECTIVES

This study aimed to determine whether paraspinal muscle area (PMA) obtained by chest CT can predict death for community-acquired pneumonia (SCAP) patients entering intensive care unit (ICU).

METHODS

This study enrolled 208 SCAP patients admitted to ICU after undergoing chest CT. PMA, paraspinal muscle radiodensity (PMD), and lean paraspinal muscle area (LPMA) were calculated on chest CT images. The main outcome was mortality during hospitalization. Logistic regression, receiver operating characteristic (ROC) curve, and Kaplan-Meier curves were used to evaluate forecasting effectiveness.

RESULTS

The primary outcome occurred in 76 (36.53%) patients. In multivariate logistic regression, PMA, lactic dehydrogenase (LDH), invasive mechanical ventilation (IMV), red blood cell (RBC) and age≥ 65 years were independent risk factors predicting death during hospitalization (adjusted Odds Ratio [OR]: 0.886, 1.002, 3.178, 0.612 and 2.003, respectively). The area under curve (AUC) of PMA to predict death was 0.720 (P< 0.001). During hospitalization, the median survival time of high-PMA (51.00 days) and low-PMA groups (20.00 days) was statistically significant (P< 0.001).

CONCLUSION

Lower PMA was associated with an increased risk of death for SCAP patients admitted to the ICU. In other words, PMA may help early identify adverse prognosis of SCAP patients admitted to ICU.

Redox Signaling and Sarcopenia: Searching for the Primary Suspect

Sarcopenia, the age-related decline in muscle mass and function, derives from multiple etiological mechanisms. Accumulative research suggests that reactive oxygen species (ROS) generation plays a critical role in the development of this pathophysiological disorder. In this communication, we review the various signaling pathways that control muscle metabolic and functional integrity such as protein turnover, cell death and regeneration, inflammation, organismic damage, and metabolic functions. Although no single pathway can be identified as the most crucial factor that causes sarcopenia, age-associated dysregulation of redox signaling appears to underlie many deteriorations at physiological, subcellular, and molecular levels. Furthermore, discord of mitochondrial homeostasis with aging affects most observed problems and requires our attention. The search for the primary suspect of the fundamental mechanism for sarcopenia will likely take more intense research for the secret of this health hazard to the elderly to be unlocked.

The Impact of Glucose-Lowering Drugs on Sarcopenia in Type 2 Diabetes: Current Evidence and Underlying Mechanisms

The age-related decrease in skeletal muscle mass together with the loss of muscle power and function is defined sarcopenia. Mounting evidence suggests that the prevalence of sarcopenia is higher in patients with type 2 diabetes mellitus (T2DM), and different mechanisms may be responsible for this association such as impaired insulin sensitivity, chronic hyperglycemia, advanced glycosylation end products, subclinical inflammation, microvascular and macrovascular complications. Glucose-lowering drugs prescribed for patients with T2DM might impact on these mechanisms leading to harmful or beneficial effect on skeletal muscle. Importantly, beyond their glucose-lowering effects, glucose-lowering drugs may affect per se the equilibrium between protein anabolism and catabolism through several mechanisms involved in skeletal muscle physiology, contributing to sarcopenia. The aim of this narrative review is to provide an update on the effects of glucose-lowering drugs on sarcopenia in individuals with T2DM, focusing on the parameters used to define sarcopenia: muscle strength (evaluated by handgrip strength), muscle quantity/quality (evaluated by appendicular lean mass or skeletal muscle mass and their indexes), and physical performance (evaluated by gait speed or short physical performance battery). Furthermore, we also describe the plausible mechanisms by which glucose-lowering drugs may impact on sarcopenia.

Mitochondrial DNA variants in inclusion body myositis characterized by deep sequencing

Muscle pathology in inclusion body myositis (IBM) typically includes inflammatory cell infiltration, muscle fibers with rimmed vacuoles and cytochrome c oxidase (COX)‐deficient fibers. Previous studies have revealed clonal expansion of large mitochondrial DNA (mtDNA) deletions in the COX‐deficient muscle fibers. Technical limitations have prevented complete investigations of the mtDNA deletions and other mtDNA variants. Detailed characterization by deep sequencing of mtDNA in muscle samples from 21 IBM patients and 10 age‐matched controls was performed after whole genome sequencing with a mean depth of mtDNA coverage of 46,000x. Multiple large mtDNA deletions and duplications were identified in all IBM and control muscle samples. In general, the IBM muscles demonstrated a larger number of deletions and duplications with a mean heteroplasmy level of 10% (range 1%‐35%) compared to controls (1%, range 0.2%‐3%). There was also a small increase in the number of somatic single nucleotide variants in IBM muscle. More than 200 rearrangements were recurrent in at least two or more IBM muscles while 26 were found in both IBM and control muscles. The deletions and duplications, with a high recurrence rate, were mainly observed in three mtDNA regions, m.534‐4429, m.6330‐13993, and m.8636‐16072, where some were flanked by repetitive sequences. The mtDNA copy number in IBM muscle was reduced to 42% of controls. Immunohistochemical and western blot analyses of IBM muscle revealed combined complex I and complex IV deficiency affecting the COX‐deficient fibers. In conclusion, deep sequencing and quantitation of mtDNA variants revealed that IBM muscles had markedly increased levels of large deletions and duplications, and there were also indications of increased somatic single nucleotide variants and reduced mtDNA copy numbers compared to age‐matched controls. The distribution and type of variants were similar in IBM muscle and controls indicating an accelerated aging process in IBM muscle, possibly associated with chronic inflammation.

An Examination of Lactobacillus paracasei GKS6 and Bifidobacterium lactis GKK2 Isolated from Infant Feces in an Aged Mouse Model

Supplementary which could maintain normal physiological mechanisms and functions while aging has drawn our attention due to the population aging in recent years. Probiotics have been believed with desirable properties such as antioxidation and anti-inflammatory for delaying the aging process. However, the age-related experiments conducted in the mammalian models with probiotics were few. In this study, we demonstrated the effects of administration of probiotics Lactobacillus paracasei GKS6 (GKS6) and Bifidobacterium lactis GKK2 (GKK2), respectively, at the dosage of 5.0 × 10⁹ cfu/kg BW/day for fourteen weeks in senescence-accelerated mouse prone 8 (SAMP8) mice. The three-month-old SAMP8 mice were divided into three groups: control, mice fed with GKS6, and mice fed with GKK2. There were ten females and ten males in each group. The SAMP8 mice fed with probiotics GKS6 and GKK2 showed a significantly lower degree of aging followed by Takeda's grading method on the eleventh week of the experiment. The GKK2 group showed significantly increased forelimb grip strength in male SAMP8 mice and muscle fiber number in both genders. Compared to the control, both GKS6 and GKK2 presented a significant increase in liver superoxide dismutase and catalase activities. In addition, a significant decrease in the levels of liver thiobarbituric acid-reactive substances was observed in the probiotics group. These results suggested that probiotics GKS6 and GKK2 could act as antioxidants in delaying the process of aging and preventing age-related muscle loss.

Measuring Exercise Capacity and Physical Function in Adult and Older Mice

The inability of older adults to maintain independence is a consequence of sarcopenia and frailty. In order to identify the molecular mechanisms responsible for decreased physical function, it will be critical to utilize a small animal model. The main purpose of this study was to develop a composite Comprehensive Functional Assessment Battery (CFAB) of well-validated tests to determine physical function and exercise capacity in 3 age groups of male C57BL/6 mice (6 months old, n = 29; 24 months old, n = 24; 28+ months old, n = 28). To measure physical function in mice, we used rotarod (overall motor function), grip meter (forelimb strength), treadmill (endurance), inverted cling (strength/endurance), voluntary wheel running (volitional exercise and activity rate), and muscle performance with in vivo contractile physiology (dorsiflexor torque). We hypothesized that CFAB would be a valid means to assess the physical function of a given mouse across the life span. In addition, we proposed that CFAB could be used to determine relationships between different parameters associated with sarcopenia. We found that there was an overall age-related significant decline (p < .05) in all measurements, and the CFAB score demonstrated that some individual mice (the upper quartile) retained the functional capacity of average mice 1 cohort younger. We conclude that the CFAB is a powerful, repeatable, and noninvasive tool to assess and compare physical function and assess complex motor task ability in mice, which will enable researchers to easily track performance at the individual mouse level.

The role of novel motor unit magnetic resonance imaging to investigate motor unit activity in ageing skeletal muscle

Sarcopenia is a progressive and generalized disease, more common in older adults, which manifests as a loss of muscle strength and mass. The pathophysiology of sarcopenia is still poorly understood with many mechanisms suggested. Age associated changes to the neuromuscular architecture, including motor units and their constituent muscle fibres, represent one such mechanism. Electromyography can be used to distinguish between different myopathies and produce counts of motor units. Evidence from electromyography studies suggests that with age, there is a loss of motor units, increases to the sizes of remaining units, and changes to their activity patterns. However, electromyography is invasive, can be uncomfortable, does not reveal the exact spatial position of motor units within muscle and is difficult to perform in deep muscles. We present a novel diffusion-weighted magnetic resonance imaging technique called 'motor unit magnetic resonance imaging (MUMRI)'. MUMRI aims to improve our understanding of the changes to the neuromuscular system associated with ageing, sarcopenia and other neuromuscular diseases. To date, we have demonstrated that MUMRI can be used to detect statistically significant differences in fasciculation rate of motor units between (n = 4) patients with amyotrophic lateral sclerosis (mean age ± SD: 53 ± 15) and a group of (n = 4) healthy controls (38 ± 7). Patients had significantly higher rates of fasciculation compared with healthy controls (mean = 99.1/min, range = 25.7-161.0 in patients vs. 7.7/min, range = 4.3-9.7 in controls; P < 0.05. MUMRI has detected differences in size, shape, and distribution of single human motor units between (n = 5) young healthy volunteers (29 ± 2.2) and (n = 5) healthy older volunteers (65.6 ± 14.8). The maximum size of motor unit territories in the older group was 12.4 ± 3.3 mm and 9.7 ± 2.7 mm in the young group; P < 0.05. MUMRI is an entirely non-invasive tool, which can be used to detect physiological and pathological changes to motor units in neuromuscular diseases. MUMRI also has the potential to be used as an intermediate outcome measure in sarcopenia trials.

Circulating Mitochondrial-Derived Vesicles, Inflammatory Biomarkers and Amino Acids in Older Adults With Physical Frailty and Sarcopenia: A Preliminary BIOSPHERE Multi-Marker Study Using Sequential and Orthogonalized Covariance Selection - Linear Discriminant Analysis

Physical frailty and sarcopenia (PF&S) is a prototypical geriatric condition characterized by reduced physical function and low muscle mass. The multifaceted pathophysiology of this condition recapitulates all hallmarks of aging making the identification of specific biomarkers challenging. In the present study, we explored the relationship among three processes that are thought to be involved in PF&S (i.e., systemic inflammation, amino acid dysmetabolism, and mitochondrial dysfunction). We took advantage of the well-characterized cohort of older adults recruited in the “BIOmarkers associated with Sarcopenia and Physical frailty in EldeRly pErsons” (BIOSPHERE) study to preliminarily combine in a multi-platform analytical approach inflammatory biomolecules, amino acids and derivatives, and mitochondrial-derived vesicle (MDV) cargo molecules to evaluate their performance as possible biomarkers for PF&S. Eleven older adults aged 70 years and older with PF&S and 10 non-sarcopenic non-frail controls were included in the analysis based on the availability of the three categories of biomolecules. A sequential and orthogonalized covariance selection—linear discriminant analysis (SO-CovSel–LDA) approach was used for biomarkers selection. Of the 75 analytes assayed, 16 had concentrations below the detection limit. Within the remaining 59 biomolecules, So-CovSel–LDA selected a set comprising two amino acids (phosphoethanolamine and tryptophan), two cytokines (interleukin 1 receptor antagonist and macrophage inflammatory protein 1β), and MDV-derived nicotinamide adenine dinucleotide reduced form:ubiquinone oxidoreductase subunit S3 as the best predictors for discriminating older people with and without PF&S. The evaluation of these biomarkers in larger cohorts and their changes over time or in response to interventions may unveil specific pathogenetic pathways of PF&S and identify new biological targets for drug development.

Physical activity and exercise: Strategies to manage frailty

Frailty, a consequence of the interaction of the aging process and certain chronic diseases, compromises functional outcomes in the elderly and substantially increases their risk for developing disabilities and other adverse outcomes. Frailty follows from the combination of several impaired physiological mechanisms affecting multiple organs and systems. And, though frailty and sarcopenia are related, they are two different conditions. Thus, strategies to preserve or improve functional status should consider systemic function in addition to muscle conditioning. Physical activity/exercise is considered one of the main strategies to counteract frailty-related physical impairment in the elderly. Exercise reduces age-related oxidative damage and chronic inflammation, increases autophagy, and improves mitochondrial function, myokine profile, insulin-like growth factor-1 (IGF-1) signaling pathway, and insulin sensitivity. Exercise interventions target resistance (strength and power), aerobic, balance, and flexibility work. Each type improves different aspects of physical functioning, though they could be combined according to need and prescribed as a multicomponent intervention. Therefore, exercise intervention programs should be prescribed based on an individual's physical functioning and adapted to the ensuing response.

Role of Age-Related Mitochondrial Dysfunction in Sarcopenia

Skeletal muscle aging is associated with a significant loss of skeletal muscle strength and power (i.e., dynapenia), muscle mass and quality of life, a phenomenon known as sarcopenia. This condition affects nearly one-third of the older population and is one of the main factors leading to negative health outcomes in geriatric patients. Notwithstanding the exact mechanisms responsible for sarcopenia are not fully understood, mitochondria have emerged as one of the central regulators of sarcopenia. In fact, there is a wide consensus on the assumption that the loss of mitochondrial integrity in myocytes is the main factor leading to muscle degeneration. Mitochondria are also key players in senescence. It has been largely proven that the modulation of mitochondrial functions can induce the death of senescent cells and that removal of senescent cells improves musculoskeletal health, quality, and function. In this review, the crosstalk among mitochondria, cellular senescence, and sarcopenia will be discussed with the aim to elucidate the role that the musculoskeletal cellular senescence may play in the onset of sarcopenia through the mediation of mitochondria.