Sarcopenia and Muscle Aging: A Brief Overview

The effect of biocide chloromethylisothiazolinone/methylisothiazolinone (CMIT/MIT) mixture on C2C12 muscle cell damage attributed to mitochondrial reactive oxygen species overproduction and autophagy activation

The mixture of 5-chloro-2-methyl-4-isothiazolin-3-one and 2-methyl-4-isothiazolin-3-one (CMIT/MIT) is a biocide widely used as a preservative in various commercial products. This biocide has also been used as an active ingredient in humidifier disinfectants in South Korea, resulting in serious health effects among users. Recent evidence suggests that the underlying mechanism of CMIT/MIT-initiated toxicity might be associated with defects in mitochondrial functions. The aim of this study was to utilize the C2C12 skeletal muscle model to investigate the effects of CMIT/MIT on mitochondrial function and relevant molecular pathways associated with skeletal muscle dysfunction. Data demonstrated that exposure to CMIT/MIT during myogenic differentiation induced significant mitochondrial excess production of reactive oxygen species (ROS) and a decrease in intracellular ATP levels. Notably, CMIT/MIT significantly inhibited mitochondrial oxidative phosphorylation (Oxphos) and reduced mitochondrial mass at a lower concentration than the biocide amount, which diminished the viability of myotubes. CMIT/MIT induced activation of autophagy flux and decreased protein expression levels of myosin heavy chain (MHC). Taken together, CMIT/MIT exposure produced damage in C2C12 myotubes by impairing mitochondrial bioenergetics and activating autophagy. Our findings contribute to an increased understanding of the underlying mechanisms associated with CMIT/MIT-induced adverse skeletal muscle health effects.

The role of chronic low-grade inflammation in the development of sarcopenia: Advances in molecular mechanisms

With the exacerbation of global population aging, sarcopenia has become an increasingly recognized public health issue. Sarcopenia, characterized by a progressive decline in skeletal muscle mass, strength, and function, significantly impacts the quality of life in the elderly. Herein, we explore the role of chroniclow-gradeinflammation in the development of sarcopenia and its underlying molecular mechanisms, including chronic inflammation-associated signaling pathways, immunosenescence, obesity and lipid infiltration, gut microbiota dysbiosis and intestinal barrier disruption, and the decline of satellite cells. The interplay and interaction of these molecular mechanisms provide new perspectives on the complexity of the pathogenesis of sarcopenia and offer a theoretical foundation for the development of future therapeutic strategies.

The BET inhibitor JQ1 targets fat metabolism and counteracts obesity

INTRODUCTION

Obesity, one of the most frequent health problems in the adult population, is a condition characterized by excessive white adipose tissue accumulation and accompanied by the increased risk to develop other disorders such as type II diabetes, cardiovascular disorders, physical disability, frailty and sarcopenia. Total fat mass frequently increases during aging, often coexisting with sarcopenia, thus resulting in an emerging condition defined sarcopenic obesity (SO). Our previous data demonstrated the relevant role of the bromo and extra-terminal domain (BET) proteins inhibitor JQ1 in attenuating inflammation and fibrosis in sarcopenic mice. Moreover, we preliminarily observed that JQ1 administration markedly reduces white adipose tissue mass, suggesting a potential role of BET proteins on visceral fat deposition during aging.

OBJECTIVES

Starting from those observations, the aim of this study was to investigate the ability of JQ1 to reduce adiposity in a chronic diet-induced obesity (DIO) mouse model mimicking the human metabolic syndrome.

METHODS

Male C57BL/6J mice were divided in subgroups, either fed a standard diet or a high fat diet for 22 or 12 weeks, treated over the last 14 days with JQ1 or with vehicle.

RESULTS

The results showed that JQ1 administration reduces fat mass, preserving skeletal muscle mass and function. A direct JQ1 lipolytic effect was demonstrated on mature adipocyte cultures. JQ1-mediated loss of adipose tissue mass was not associated with systemic inflammation or with lipid accumulation in muscle and liver. JQ1 administration did not impinge on skeletal muscle metabolism and oxidative capability, as shown by the lack of significant impact on mitochondrial mass and biogenesis.

CONCLUSION

In conclusion, the current data highlight a potential benefit of JQ1 administration to counteract obesity, suggesting epigenetic modulation as a prospective target in the treatment of obesity and sarcopenic obesity, despite the underlying multiorgan molecular mechanism is still not completely elucidated.

Intramuscular administration of fractalkine modulates mitochondrial properties and promotes fast glycolytic phenotype

A newly categorized myokine called fractalkine (CX3CL1) has been associated with divergent conditions such as obesity, tissue inflammation, and exercise. CX3CL1 works through specific membrane-bound receptors (CX3CR1) found in various tissues including skeletal muscles. Studies indicate CX3CL1 induces muscles to uptake energy substrates thereby improving glucose utilization and countering diabetes. Here, we tested if the administration of purified CX3CL1 directly into mice skeletal muscles affects its histoarchitecture, mitochondrial activity, and expression of metabolic proteins. We analyzed four muscles: two upper-limb (quadriceps, hamstrings) and two lower-limb (tibialis anterior, gastrocnemius), contralateral leg muscles were taken as controls. The effects of CX3CL1 treatment on histoarchitecture, mitochondrial activity, and expression of metabolic proteins in muscles were characterized. We used histochemical staining succinate dehydrogenase (SDH)/cytochrome c oxidase (COX), myosin ATPase, alkaline phosphatase (ALP) to evaluate the mitochondrial activity, fiber types, and vascularization in the muscles, respectively. Western blotting was used to evaluate the expression of proteins associated with mitochondrial metabolism (OXPHOS), glycolysis, and vascularization. Overall, this study indicates CX3CL1 primarily modulates mitochondrial metabolism and shifts substrate preference toward glucose in the skeletal muscle. Evidence also supports that CX3CL1 stimulates the relative composition of fast fiber types, influencing selection of energy substrates in the skeletal muscle.

Prospective Intervention Strategies Between Skeletal Muscle Health and Mitochondrial Changes During Aging

Sarcopenia is a geriatric condition characterized by a decrease in skeletal muscle mass and function, significantly impacting both quality of life and overall health. Mitochondria are the main sites of energy production within the cell, and also produce reactive oxygen species (ROS), which maintain mitochondrial homeostasis-mitophagy (clearing damaged mitochondria); mitochondrial dynamics, which involve fusion and fission to regulate mitochondrial morphology; mitochondrial biogenesis, which ensures the functionality and homeostasis of mitochondria. Sarcopenia is linked to mitochondrial dysfunction, suggesting that muscle mitochondrial function therapy should be investigated. Extrinsic therapies are extensively examined to identify new treatments for muscular illnesses including sarcopenia. Changes in muscle physiology and lifestyle interventions, such as pharmacological treatments and exercise, can modulate mitochondrial activity in older adults. This PubMed review encompasses the most significant mitophagy and sarcopenia research from the past five years. Animal models, cellular models, and human samples are well covered. The review will inform the development of novel mitochondria-targeted therapies aimed at combating age-related muscle atrophy.

A microbiota-derived metabolite, 3-phenyllactic acid, prolongs healthspan by enhancing mitochondrial function and stress resilience via SKN-1/ATFS-1 in C. elegans

The mechanisms underlying the impact of probiotic supplementation on health remain largely elusive. While previous studies primarily focus on the discovery of novel bioactive bacteria and alterations in the microbiome environment to explain potential probiotic effects, our research delves into the role of living Lactiplantibacillus (formerly known as Lactobacillus) and their conditioned media, highlighting that only the former, not dead bacteria, enhance the healthspan of Caenorhabditis elegans (C. elegans). To elucidate the underlying mechanisms, we conduct transcriptomic profiling through RNA-seq analysis in C. elegans exposed to GTB1, a strain of Lactiplantibacillus plantarum or 3-phenyllactic acid (PLA), mimicking the presence of key candidate metabolites of GTB1 and evaluating healthspan. Our findings reveal that PLA treatment significantly extends the healthspan of C. elegans by promoting energy metabolism and stress resilience in a SKN-1/ATFS-1-dependent manner. Moreover, PLA-mediated longevity is associated with a novel age-related parameter, the Healthy Aging Index (HAI), introduced in this study, which comprises healthspan-related factors such as motility, oxygen consumption rate (OCR), and ATP levels. Extending the relevance of our work to humans, we observe an inverse correlation between blood PLA levels and physical performance in patients with sarcopenia, when compared to age-matched non-sarcopenic controls. Our investigation thus sheds light on the pivotal role of the metabolite PLA in probiotics-mediated enhancement of organismal healthspan, and also hints at its potential involvement in age-associated sarcopenia. These findings warrant further investigation to delineate PLA's role in mitigating age-related declines in healthspan and resilience to external stressors.

Perindopril erbumine-entrapped ultradeformable liposomes alleviate sarcopenia via effective skin delivery in muscle atrophy mouse model

Sarcopenia is a pertinent challenge in the super-aged societies causing reduced functional performance, poor quality of life and increased morbidity. In this study, the potential of perindopril erbumine-loaded ultradeformable liposomes (PE-UDLs) against sarcopenia was investigated. PE-UDLs were prepared by thin-film hydration and extrusion method using egg yolk L-α-phosphatidylcholine (EPC) as a lipid bilayer former and Tween 80 or sodium deoxycholate as an edge activator. Owing to the smallest particle size (75.0 nm) and the highest deformability (54.2) and entrapment efficiency (35.7 %), PE-UDLs with EPC to Tween 80 ratio of 8:2 was selected as the optimized formulation. The optimized PE-UDLs showed substantially higher cumulative amount of drug permeated and permeation rate across the rat skin compared to PE solution (485.7 vs. 50.1 µg and 13.4 vs. 2.3 µg/cm2/h, respectively). Topically applied PE-UDLs successfully ameliorated the effects of lipopolysaccharide (LPS)-induced sarcopenia in mice by improving body weight changes, grip strength and muscle weight. Furthermore, PE-UDLs reduced the shrinkage of muscle fibers as demonstrated by higher cross-sectional area than PE solution. PE-UDLs also increased the expression of myosin heavy chain (MHC) protein and reduced the expression of muscle atrophy F-box (Atrogin-1) and muscle ring-finger protein-1 (MuRF1), thereby improving muscles atrophy. In conclusion, these results demonstrate the therapeutic potential of PE-UDLs against sarcopenia.

FAPs orchestrate homeostasis of muscle physiology and pathophysiology

As a common clinical manifestation, muscle weakness is prevalent in people with mobility disorders. Further studies of muscle weakness have found that patients with muscle weakness present with persistent muscle inflammation, loss of muscle fibers, fat infiltration, and interstitial fibrosis. Therefore, we propose the concept of muscle microenvironment homeostasis, which explains the abnormal pathological changes in muscles through the imbalance of muscle microenvironment homeostasis. And we identified an interstitial progenitor cell FAP during the transition from normal muscle microenvironment homeostasis to muscle microenvironment imbalance caused by muscle damage diseases. As a kind of pluripotent stem cell, FAPs do not participate in myogenic differentiation, but can differentiate into fibroblasts, adipocytes, osteoblasts, and chondrocytes. As a kind of mesenchymal progenitor cell, it is involved in the generation of extracellular matrix, regulate muscle regeneration, and maintain neuromuscular junction. However, the muscle microenvironment is disrupted by the causative factors, and the abnormal activities of FAPs eventually contribute to the complex pathological changes in muscles. Targeting the mechanisms of these muscle pathological changes, we have identified appropriate signaling targets for FAPs to improve and even treat muscle damage diseases. In this review, we propose the construction of muscle microenvironmental homeostasis and find the key cells that cause pathological changes in muscle after homeostasis is broken. By studying the mechanism of abnormal differentiation and apoptosis of FAPs, we found a strategy to inhibit the abnormal pathological changes in muscle damage diseases and improve muscle regeneration.

An immunohistochemical evaluation of fast twitch muscle formation induced by repeated administration of flavan 3-ols in mice

Flavan-3-ols (FL) are poorly bioavailable astringent polyphenols that induce hyperactivation of the sympathetic nervous system. The aim of this study was to investigate the effects of repeated oral administration of FL on mice hindlimb skeletal muscle using immunohistochemical techniques. C57BL/6J male mice were orally administered 50 mg/kg of FL for a period of 2 weeks, and bromideoxyuridine (BrdU) was administered intraperitoneally 3 days prior to the dissection. The soleus and extensor digitorum longus (EDL) were excised and prepared for frozen sections. Myosin heavy chain (MHC) antibodies were used to classify muscle types, in addition, muscle cross-sectional areas (CSA) were measured. We observed a shift in the peak of CSA in the soleus muscle and to a larger extent in the EDL. In addition, a distinct shift toward fast muscle was detected, documented by a reduction in type I and an increase in type IIb in the soleus muscle, whereas in the EDL, we observed a decline in type IIa and an expansion in type IIb. Incorporation of BrdU into cells was significantly increased in all skeletal muscles, with a significant increase in cells co-expressing pair box 7 (Pax7), a marker of differentiation, as observed in the EDL. Given the evidence that β2-adrenergic receptors in skeletal muscles regulate differentiation and size, we measured plasma catecholamine (CA) concentrations following a single differentiation of FL. A single oral dose of FL was observed to significantly increase plasma CA. These findings indicate that catecholamines secreted into the bloodstream from the adrenal gland following oral administration of FL may influence skeletal muscle size and type via β2-receptors.

Sphingolipid metabolites as potential circulating biomarkers for sarcopenia in men

BACKGROUND

Sarcopenia is an age-related progressive loss of muscle mass and function. Sarcopenia is a multifactorial disorder, including metabolic disturbance; therefore, metabolites may be used as circulating biomarkers for sarcopenia. We aimed to investigate potential biomarkers of sarcopenia using metabolomics.

METHODS

After non-targeted metabolome profiling of plasma from mice of an aging mouse model of sarcopenia, sphingolipid metabolites and muscle cells from the animal model were evaluated using targeted metabolome profiling. The associations between sphingolipid metabolites identified from mouse and cell studies and sarcopenia status were assessed in men in an age-matched discovery (72 cases and 72 controls) and validation (36 cases and 128 controls) cohort; women with sarcopenia (36 cases and 36 controls) were also included as a discovery cohort.

RESULTS

Both non-targeted and targeted metabolome profiling in the experimental studies showed an association between sphingolipid metabolites, including ceramides (CERs) and sphingomyelins (SMs), and sarcopenia. Plasma SM (16:0), CER (24:1), and SM (24:1) levels in men with sarcopenia were significantly higher in the discovery cohort than in the controls (all P < 0.05). There were no significant differences in plasma sphingolipid levels for women with or without sarcopenia. In men in the discovery cohort, an area under the receiver-operating characteristic curve (AUROC) of SM (16:0) for low muscle strength and low muscle mass was 0.600 (95% confidence interval [CI]: 0.501-0.699) and 0.647 (95% CI: 0.557-0.737). The AUROC (95% CI) of CER (24:1) and SM (24:1) for low muscle mass in men was 0.669 (95% CI: 0.581-0.757) and 0.670 (95% CI: 0.582-0.759), respectively. Using a regression equation combining CER (24:1) and SM (16:0) levels, a sphingolipid (SphL) score was calculated; an AUROC of the SphL score for sarcopenia was 0.712 (95% CI: 0.626-0.798). The addition of the SphL score to HGS significantly improved the AUC from 0.646 (95% CI: 0.575-0.717; HGS only) to 0.751 (95% CI: 0.671-0.831, P = 0.002; HGS + SphL) in the discovery cohort. The predictive ability of the SphL score for sarcopenia was confirmed in the validation cohort (AUROC = 0.695, 95% CI: 0.591-0.799).

CONCLUSIONS

SM (16:0), reflecting low muscle strength, and CER (24:1) and SM (16:0), reflecting low muscle mass, are potential circulating biomarkers for sarcopenia in men. Further research on sphingolipid metabolites is required to confirm these results and provide additional insights into the metabolomic changes relevant to the pathogenesis and diagnosis of sarcopenia.

Irisin in degenerative musculoskeletal diseases: Functions in system and potential in therapy

Degenerative musculoskeletal diseases are a class of diseases related to the gradual structural and functional deterioration of muscles, joints, and bones, including osteoarthritis (OA), osteoporosis (OP), sarcopenia (SP), and intervertebral disc degeneration (IDD). As the proportion of aging people around the world increases, degenerative musculoskeletal diseases not only have a multifaceted impact on patients, but also impose a huge burden on the medical industry in various countries. Therefore, it is crucial to find key regulatory factors and potential therapeutic targets. Recent studies have shown that irisin plays an important role in degenerative musculoskeletal diseases, suggesting that it may become a key molecule in the prevention and treatment of degenerative diseases of the musculoskeletal system. Therefore, this review provides a comprehensive description of the release and basic functions of irisin, and summarizes the role of irisin in OA, OP, SP, and IDD from a cellular and tissue perspective, providing comprehensive basis for clinical application. In addition, we summarized the many roles of irisin as a key information molecule in bone-muscle-adipose crosstalk and a regulatory molecule involved in inflammation, senescence, and cell death, and proposed the interesting possibility of irisin in degenerative musculoskeletal diseases.

The recent development, application, and future prospects of muscle atrophy animal models

Muscle atrophy, characterized by the loss of muscle mass and function, is a hallmark of sarcopenia and cachexia, frequently associated with aging, malignant tumors, chronic heart failure, and malnutrition. Moreover, it poses significant challenges to human health, leading to increased frailty, reduced quality of life, and heightened mortality risks. Despite extensive research on sarcopenia and cachexia, consensus in their assessment remains elusive, with inconsistent conclusions regarding their molecular mechanisms. Muscle atrophy models are crucial tools for advancing research in this field. Currently, animal models of muscle atrophy used for clinical and basic scientific studies are induced through various methods, including aging, genetic editing, nutritional modification, exercise, chronic wasting diseases, and drug administration. Muscle atrophy models also include in vitro and small organism models. Despite their value, each of these models has certain limitations. This review focuses on the limitations and diverse applications of muscle atrophy models to understand sarcopenia and cachexia, and encourage their rational use in future research, therefore deepening the understanding of underlying pathophysiological mechanisms, and ultimately advancing the exploration of therapeutic strategies for sarcopenia and cachexia.

Effects and mechanisms of APP and its cleavage product Aβ in the comorbidity of sarcopenia and Alzheimer's disease

Sarcopenia and AD are both classic degenerative diseases, and there is growing epidemiological evidence of their comorbidity with aging; however, the mechanisms underlying the biology of their commonality have not yet been thoroughly investigated. APP is a membrane protein that is expressed in tissues and is expressed not only in the nervous system but also in the NMJ and muscle. Deposition of its proteolytic cleavage product, Aβ, has been described as a central component of AD pathogenesis. Recent studies have shown that excessive accumulation and aberrant expression of APP in muscle lead to pathological muscle lesions, but the pathogenic mechanism by which APP and its proteolytic cleavage products act in skeletal muscle is less well understood. By summarizing and analyzing the literature concerning the role, pathogenicity and pathological mechanisms of APP and its cleavage products in the nervous system and muscles, we aimed to explore the intrinsic pathological mechanisms of myocerebral comorbidities and to provide new perspectives and theoretical foundations for the prevention and treatment of AD and sarcopenia comorbidities.

Experimental models as a tool for research on sarcopenia: A narrative review

Sarcopenia is a musculoskeletal disorder related to muscle mass and function; as the worldwide population ages, its growing prevalence means a decline in quality of life and an increased burden for public health systems. As sarcopenia is a reversible condition, its early diagnosis is of utmost importance. Consensus definitions and diagnosis protocols for sarcopenia have been evolving for a long time, and the identification of molecular pathways subjacent to sarcopenia is a growing research area. The use of liquid biopsies to identify circulating molecules does not provide information about specific regulatory pathways or biomarkers in relevant tissue, and the use of skeletal muscle biopsies from older people has many limitations. Complementary tools are therefore necessary to advance the knowledge of relevant molecular aspects. The development of experimental models, such as animal, cellular, or bioengineered tissue, together with knock-in or knock-out strategies, could therefore be of great interest. This narrative review will explore experimental models of healthy muscle and aged muscle cells as a tool for research on sarcopenia. We will summarize the literature and present relevant experimental models in terms of their advantages and disadvantages. All of the presented approaches could potentially contribute to the accurate and early diagnosis, follow-up, and possible treatment of sarcopenia.

Exploring the Relationship Between Gut Microbiota and Sarcopenia Based on Gut-Muscle Axis

Sarcopenia, as a disease characterized by progressive decline of quality, strength, and function of muscles, has posed an increasingly significant threat to the health of middle-aged and elderly individuals in recent years. With the continuous deepening of studies, the concept of gut-muscle axis has attracted widespread attention worldwide, and the occurrence and development of sarcopenia are believed to be closely related to the composition and functional alterations of gut microbiota. In this review, combined with existing literatures and clinical reports, we have summarized the role and impacts of gut microbiota on the muscle, the relevance between gut microbiota and sarcopenia, potential mechanisms of gut microbiota in the modulation of sarcopenia, potential methods to alleviate sarcopenia by modulating gut microbiota, and relevant advances and perspectives, thus contributing to adding more novel knowledge to this research direction and providing certain reference for future related studies.

Body Composition and Senescence: Impact of Polyphenols on Aging-Associated Events

Aging is a dynamic and progressive process characterized by the gradual accumulation of cellular damage. The continuous functional decline in the intrinsic capacity of living organisms to precisely regulate homeostasis leads to an increased susceptibility and vulnerability to diseases. Among the factors contributing to these changes, body composition-comprised of fat mass and lean mass deposits-plays a crucial role in the trajectory of a disability. Particularly, visceral and intermuscular fat deposits increase with aging and are associated with adverse health outcomes, having been linked to the pathogenesis of sarcopenia. Adipose tissue is involved in the secretion of bioactive factors that can ultimately mediate inter-organ pathology, including skeletal muscle pathology, through the induction of a pro-inflammatory profile such as a SASP, cellular senescence, and immunosenescence, among other events. Extensive research has shown that natural compounds have the ability to modulate the mechanisms associated with cellular senescence, in addition to exhibiting anti-inflammatory, antioxidant, and immunomodulatory potential, making them interesting strategies for promoting healthy aging. In this review, we will discuss how factors such as cellular senescence and the presence of a pro-inflammatory phenotype can negatively impact body composition and lead to the development of age-related diseases, as well as how the use of polyphenols can be a functional measure for restoring balance, maintaining tissue quality and composition, and promoting health.

Exploring SGLT-2 inhibitors and sarcopenia in FAERS: a post-marketing surveillance study

BACKGROUND

The sodium-dependent glucose transporters 2 inhibitors (SGLT-2i) is associated with body weight loss but the composition of the losing weight remains unclear.

RESEARCH DESIGN AND METHODS

Disproportionality analyses, including the reporting odds ratio (ROR), the proportional reporting ratio (PRR), the Bayesian confidence propagation neural network (BCPNN), and the multi- item gamma Poisson shrinker (MGPS) algorithms, were employed to quantify the signals of SGLT-2i-associated musculoskeletal and connective tissue disorders AEs.

RESULTS

The search retrieved a total of 3,206 cases of musculoskeletal and connective tissue disorder-related AEs during the reporting period. This included 1,061 cases for Canagliflozin, 1,052 cases for Dapagliflozin, 1,074 cases for Empagliflozin, and 19 cases for Ertugliflozin. Fifteen preferred terms (PTs) with significant disproportionality were retained. No musculoskeletal and connective tissue system-related AE signals were reported for Ertugliflozin. We identified a risk of muscle necrosis with Canagliflozin use, a risk of sarcopenia with Dapagliflozin use, and a chance of muscle atrophy with Dapagliflozin and Empagliflozin prescriptions. Most cases occurred within the first month after SGLT-2i initiation, and AEs can persist beyond 360 days of use.

CONCLUSIONS

Our study identified potential new musculoskeletal and connective tissue disorder-related AE signals associated with SGLT-2 inhibitors.

Effects of household solid fuel use on sarcopenia in middle-aged and older adults: evidence from a nationwide cohort study

Background

Household solid fuel use is common in global households and has been linked to changes in handgrip strength and muscle mass. However, whether household solid fuel use results in sarcopenia over time is not well elaborated.

Methods

This study employed data from the 2011-2015 China Health and Retirement Longitudinal Study (CHARLS) that recruited 4,932 participants ≥45 years. The Cox proportional hazards regression model was conducted to estimate the impact of household solid fuel use for cooking and heating on sarcopenia development. The analysis was further stratified based on geographic position. Mediation analysis was employed to estimate the potential mediating effects of cognitive function and depressive symptoms associated with household solid fuel use and sarcopenia.

Results

Over the 4-year follow-up, 476 cases of sarcopenia were reported (9.65%), with 254 in males (10.82%) and 222 in females (8.59%). Cooking and heating with solid fuels increased the risk of sarcopenia (Cooking: HR 1.401, 95% CI 1.138-1.724; Heating: HR 1.278, 95% CI 1.040-1.571). Crop residue/wood burning correlated with higher sarcopenia risk (Cooking: 1.420, 95% CI 1.147-1.758; Heating: 1.318, 95% CI 1.062-1.635). Switching to clean cooking fuels significantly reduced sarcopenia risk (HR 0.766, 95% CI 0.599-0.979). Heating with solid fuels was associated with higher sarcopenia risk only in southern China (HR 1.375, 95% CI 1.102-1.715). Additionally, cognitive function and depressive symptoms partially mediated the link between household solid fuel use and sarcopenia.

Conclusion

Household use of solid fuels is associated with an increased risk of sarcopenia. Restricting the use of solid fuels and focusing on cognitive function and depressive symptoms in solid fuel users can help decrease sarcopenia development.

Particulate matter 2.5 accelerates aging: Exploring cellular senescence and age-related diseases

Exposure to Particulate matter 2.5 (PM2.5) accelerates aging, causing declines in tissue and organ function, and leading to diseases such as cardiovascular, neurodegenerative, and musculoskeletal disorders. PM2.5 is a major environmental pollutant and an exogenous pathogen in air pollution that is now recognized as an accelerator of human aging and a predisposing factor for several age-related diseases. In this paper, we seek to elucidate the mechanisms by which PM2.5 induces cellular senescence, such as genomic instability, telomere attrition, epigenetic alterations, loss of proteostasis, and mitochondrial dysfunction, and age-related diseases. Our goal is to increase awareness among researchers within the field of the toxicity of environmental pollutants and to advocate for personal and public health initiatives to curb their production and enhance population protection. Through these endeavors, we aim to promote longevity and health in older adults.

Vascular Impairment, Muscle Atrophy, and Cognitive Decline: Critical Age-Related Conditions

The triad of vascular impairment, muscle atrophy, and cognitive decline represents critical age-related conditions that significantly impact health. Vascular impairment disrupts blood flow, precipitating the muscle mass reduction seen in sarcopenia and the decline in neuronal function characteristic of neurodegeneration. Our limited understanding of the intricate relationships within this triad hinders accurate diagnosis and effective treatment strategies. This review analyzes the interrelated mechanisms that contribute to these conditions, with a specific focus on oxidative stress, chronic inflammation, and impaired nutrient delivery. The aim is to understand the common pathways involved and to suggest comprehensive therapeutic approaches. Vascular dysfunctions hinder the circulation of blood and the transportation of nutrients, resulting in sarcopenia characterized by muscle atrophy and weakness. Vascular dysfunction and sarcopenia have a negative impact on physical function and quality of life. Neurodegenerative diseases exhibit comparable pathophysiological mechanisms that affect cognitive and motor functions. Preventive and therapeutic approaches encompass lifestyle adjustments, addressing oxidative stress, inflammation, and integrated therapies that focus on improving vascular and muscular well-being. Better understanding of these links can refine therapeutic strategies and yield better patient outcomes. This study emphasizes the complex interplay between vascular dysfunction, muscle degeneration, and cognitive decline, highlighting the necessity for multidisciplinary treatment approaches. Advances in this domain promise improved diagnostic accuracy, more effective therapeutic options, and enhanced preventive measures, all contributing to a higher quality of life for the elderly population.

New insights into the function of the NLRP3 inflammasome in sarcopenia: mechanism and therapeutic strategies

Sarcopenia is one of the most common skeletal muscle disorders and is characterized by infirmity and disability. While extensive research has focused on elucidating the mechanisms underlying the progression of sarcopenia, further comprehensive insights into its pathogenesis are necessary to identify new preventive and therapeutic approaches. The involvement of inflammasomes in sarcopenia is widely recognized, with particular emphasis on the NLRP3 (NLR family pyrin domain containing 3) inflammasome. In this review, we aim to elucidate the underlying mechanisms of the NLRP3 inflammasome and its relevance in sarcopenia of various etiologies. Furthermore, we highlight interventions targeting the NLRP3 inflammasome in the context of sarcopenia and discuss the current limitations of our knowledge in this area.

Impact of Gut Microbiota on Aging and Frailty: A Narrative Review of the Literature

Aging is a natural, complex, and individual process that focuses on the progressive decay of the body and a decrease in cell function that begins in approximately the sixth decade of life and ends with death. Current scientific evidence shows that the aging process is mostly related to genetic load and varies because of the environment. Therefore, aging can be adjusted through the intervention of factors that control homeostasis in genetic, biochemical, and immunological processes, including those involving the gut microbiota. Indeed, the diversity of the gut microbiota decreases during aging, based on the presence of modifications in the hormonal, immunological, and operational processes of the gastrointestinal tract. These modifications lead to a state of dysbiosis. However, altering bacterial communities remains complicated due to the great diversity of factors that influence their modification. Alterations caused by the aging process are known to foster dysbiosis and correspond to conditions that determine the degree of frailty in senior citizens. Consequently, the microbial structure can be used as a biomarker for geriatric care in the promotion of healthy aging.

Muscle-specific PGC-1α modulates mitochondrial oxidative stress in aged sarcopenia through regulating Nrf2

BACKGROUND

Aged sarcopenia is characterized by loss of skeletal muscle mass and strength, and mitochondrial dysregulation in skeletal myocyte is considered as a major factor. Here, we aimed to analyze the effects of peroxisome proliferator-activated receptor gamma coactivator-1 alpha (PGC-1α) on mitochondrial reactive oxygen species (ROS) and nuclear factor erythroid 2-related factor 2 (Nrf2) in aged skeletal muscles.

METHODS

C2C12 cells were stimulated by 50 μM 7β-hydroxycholesterol (7β-OHC) to observe the changes of cellular ROS, mitochondrial ROS, and expression of PGC-1α and Nrf2. Different PGC-1α expression in cells was established by transfection with small interfering RNA (siRNA) or plasmids overexpressing PGC-1α (pEX-3-PGC-1α). The effects of different PGC-1α expression on cellular ROS, mitochondrial ROS and Nrf2 expression were measured in cells. Wild type (WT) mice and PGC-1α conditional knockout (CKO) mice were used to analyze the effects of PGC-1α on aged sarcopenia and expression of Nrf2 and CD38 in gastrocnemius muscles. Diethylmaleate, a Nrf2 activator, was used to analyze the connection between PGC-1α and Nrf2 in cells and in mice.

RESULTS

In C2C12 cells, the expressions of PGC-1α and Nrf2 were declined by the 7β-OHC treatment or PGC-1α silence. Moreover, PGC-1α silence increased the harmful ROS and decreased the Nrf2 protein expression in the 7β-OHC-treated cells. PGC-1α overexpression decreased the harmful ROS and increased the Nrf2 protein expression in the 7β-OHC-treated cells. Diethylmaleate treatment decreased the harmful ROS in the 7β-OHC-treated or PGC-1α siRNA-transfected cells. At the same age, muscle-specific PGC-1α deficiency aggravated aged sarcopenia, decreased Nrf2 expression and increased CD38 expression in gastrocnemius muscles compared with the WT mice. Diethylmaleate treatment improved the muscle function and decreased the CD38 expression in the old two genotypes.

CONCLUSIONS

Our study demonstrated that PGC-1α modulated mitochondrial oxidative stress in aged sarcopenia through regulating Nrf2.

Dietary Protein and Physical Exercise for the Treatment of Sarcopenia

Sarcopenia is a multifactorial age-related disorder that causes a decrease in muscle mass, strength, and function, leading to alteration of movement, risk of falls, and hospitalization. This article aims to review recent findings on the factors underlying sarcopenia and the strategies required to delay and counteract its symptoms. We focus on molecular factors linked to ageing, on the role of low-grade chronic and acute inflammatory conditions such as cancer, which contributes to the onset of sarcopenia, and on the clinical criteria for its diagnosis. The use of drugs against sarcopenia is still subject to debate, and the suggested approaches to restore muscle health are based on adequate dietary protein intake and physical exercise. We also highlight the difference in the amount and quality of amino acids within animal- and plant-based diets, as studies have often shown varying results regarding their effect on sarcopenia in elderly people. In addition, many studies have reported that non-pharmacological approaches, such as an optimization of dietary protein intake and training programs based on resistance exercise, can be effective in preventing and delaying sarcopenia. These approaches not only improve the maintenance of skeletal muscle function, but also reduce health care costs and improve life expectancy and quality in elderly people.

The Combination of Lactoferrin and Creatine Ameliorates Muscle Decay in a Sarcopenia Murine Model

BACKGROUND

Sarcopenia is an age-related condition characterized by progressive loss of muscle mass, strength, and function. The occurrence of sarcopenia has a huge impact on physical, psychological, and social health. Therefore, the prevention and treatment of sarcopenia is becoming an important public health issue.

METHOD

35 six-week-old male C57BL/6 mice were randomly divided into five groups, one of which served as a control group, while the rest of the groups were constructed as a model of sarcopenia by intraperitoneal injection of D-galactose. The intervention with lactoferrin, creatine, and their mixtures, respectively, was carried out through gavage for 8 weeks. Muscle function was assessed based on their endurance, hanging time, and grip strength. The muscle tissues were weighed to assess the changes in mass, and the muscle RNA was extracted for myogenic factor expression and transcriptome sequencing to speculate on the potential mechanism of action by GO and KEGG enrichment analysis.

RESULT

The muscle mass (lean mass, GAS index), and muscle function (endurance, hanging time, and grip strength) decreased, and the size and structure of myofiber was smaller in the model group compared to the control group. The intervention with lactoferrin and creatine, either alone or combination, improved muscle mass and function, restored muscle tissue, and increased the expression of myogenic regulators. The combined group demonstrated the most significant improvement in these indexes. The RNA-seq results revealed enrichment in the longevity-regulated pathway, MAPK pathway, focal adhesion, and ECM-receptor interaction pathway in the intervention group. The intervention group may influence muscle function by affecting the proliferation, differentiation, senescence of skeletal muscle cell, and contraction of muscle fiber. The combined group also enriched the mTOR-S6K/4E-BPs signaling pathway, PI3K-Akt signaling pathway, and energy metabolism-related pathways, including Apelin signaling, insulin resistance pathway, and adipocytokine signaling pathway, which affect energy metabolism in muscle.

CONCLUSIONS

Lactoferrin and creatine, either alone or in combination, were found to inhibit the progression of sarcopenia by influencing the number and cross-sectional area of muscle fibers and muscle protein synthesis. The combined intervention appears to exert a more significant effect on energy metabolism.

Differences in Type 2 Fiber Composition in the Vastus Lateralis and Gluteus Maximus of Patients with Hip Fractures

BACKGRUOUND

Aging leads to sarcopenia, which is characterized by reduced muscle mass and strength. Many factors, including altered muscle protein turnover, diminished neuromuscular function, hormonal changes, systemic inflammation, and the structure and composition of muscle fibers, play a crucial role in age-related muscle decline. This study explored differences in muscle fiber types contributing to overall muscle function decline in aging, focusing on individuals with hip fractures from falls.

METHODS

A pilot study at Chungnam National University Hospital collected muscle biopsies from hip fracture patients aged 20 to 80 undergoing surgical treatment. Muscle biopsies from the vastus lateralis and gluteus maximus were obtained during hip arthroplasty or internal fixation. Handgrip strength, calf and thigh circumference, and bone mineral density were evaluated in individuals with hip fractures from falls. We analyzed the relationships between each clinical characteristic and muscle fiber type.

RESULTS

In total, 26 participants (mean age 67.9 years, 69.2% male) were included in this study. The prevalence of sarcopenia was 53.8%, and that of femoral and lumbar osteoporosis was 19.2% and 11.5%, respectively. Vastus lateralis analysis revealed an age-related decrease in type IIx fibers, a higher proportion of type IIa fibers in women, and an association between handgrip strength and type IIx fibers in men. The gluteus maximus showed no significant correlations with clinical parameters.

CONCLUSION

This study identified complex associations between age, sex, handgrip strength, and muscle fiber composition in hip fracture patients, offering insights crucial for targeted interventions combating age-related muscle decline and improving musculoskeletal health.

Telomere Length is Associated with the Prevalence, Persistence, and Incidence of Sarcopenia

BACKGROUND

Telomere length (TL) shortening has been identified as a marker of aging and associated with adverse health outcomes, but evidence of its association with sarcopenia is inconclusive.

AIMS

Estimate the cross-sectional and prospective associations between TL and sarcopenia.

METHODS

We used data from Waves 3 and 4 (2017, 2021) of the Study on Global Aging and Adult Health in Mexico (SAGE-Mexico). The cross-sectional sample consisted of 1,738 adults aged 50 and older, and the longitudinal sample consisted of 1,437. Relative TL was determined by real-time quantitative polymerase chain reaction (qPCR) on DNA extracted from saliva samples and quantified as the telomere/single-copy gene (T/S) ratio. Sarcopenia was defined according to the European Working Group on Sarcopenia in Older People (EWGSOP2).

RESULTS

The mean salivary TL was 1.50 T/S units (95% CI: 1.49-1.52). The baseline prevalence of sarcopenia was 13.3% (95% CI: 9.8-16.8%). The incidence and persistence of sarcopenia were 6.8% (95% CI: 5.0-9.5%) and 7.0% (95% CI: 5.1-9.6%), respectively. The results showed that a one standard deviation decrease in TL was cross-sectionally associated with higher odds of sarcopenia (OR = 1.31; 95% CI: 1.03-1.67) and prospectively with a higher incidence (RRR = 1.55; 95% CI: 1.06-2.25) and persistence (RRR = 1.50; 95% CI: 1.01-2.24) of sarcopenia.

CONCLUSIONS

Older adults with shorter TL had higher rates of incident and persistent sarcopenia. Implementation of interventions to delay the decline of TL in older adults is warranted. Further translational studies are needed to elucidate the effects of exercise or diet on DNA repair in the telomeric region and their associations with sarcopenia.

A randomized, controlled clinical trial demonstrates improved owner-assessed cognitive function in senior dogs receiving a senolytic and NAD+ precursor combination

Age-related decline in mobility and cognition are associated with cellular senescence and NAD + depletion in dogs and people. A combination of a novel NAD + precursor and senolytic, LY-D6/2, was examined in this randomized controlled trial. Seventy dogs with mild to moderate cognitive impairment were enrolled and allocated into placebo, low or full dose groups. Primary outcomes were change in cognitive impairment measured with the owner-reported Canine Cognitive Dysfunction Rating (CCDR) scale and change in activity measured with physical activity monitors. Fifty-nine dogs completed evaluations at the 3-month primary endpoint, and 51 reached the 6-month secondary endpoint. There was a significant difference in CCDR score across treatment groups from baseline to the primary endpoint (p = 0.02) with the largest decrease in the full dose group. No difference was detected between groups using in house cognitive testing. There were no significant differences between groups in changes in measured activity. The proportion of dogs that improved in frailty and owner-reported activity levels and happiness was higher in the full dose group than other groups, however this difference was not significant. Adverse events occurred equally across groups. All groups showed improvement in cognition, frailty, and activity suggesting placebo effect and benefits of trial participation. We conclude that LY-D6/2 improves owner-assessed cognitive function over a 3-month period and may have broader, but more subtle effects on frailty, activity and happiness as reported by owners.

Association between the systemic immune-inflammation index and sarcopenia: a systematic review and meta-analysis

BACKGROUND

Sarcopenia is associated with increased morbidity and mortality. The systemic immune-inflammation index (SII) has been correlated to a variety of disorders. The present study conducted a systematic review and meta-analysis to investigate the relationship between SII and sarcopenia.

METHODS

A literature search was performed in Web of Science, PubMed, Embase, Cochrane Library, CINAHL, China National Knowledge Infrastructure, Chinese Biomedical Literature Database, Wanfang Database, and VIP Chinese Science and Technology Database, from inception to March 2024. Then, the literature quality was assessed. After the heterogeneity test, a random effects or fixed effects model was applied to establish the forest plot, and investigate the relationship between SII and sarcopenia. Then, the sensitivity analysis and publication bias were examined.

RESULTS

Nine articles, which included 18,634 adults, were analyzed. Sarcopenic adults had higher SII levels, when compared to non-sarcopenic adults (standardized mean difference [SMD] = 0.66, 95% confidence interval [CI] = 0.22 - 0.19, p = 0.003). The high SII level was associated to the increased risk of sarcopenia (odds ratio = 1.52, 95% CI = 1.09-2.13, p = 0.01). In addition, the subgroup analysis revealed that the SII levels were higher in the sarcopenic group, when compared to the non-sarcopenic group, in elderly adults, as well as in adults with or without gastrointestinal disorders. The analysis was robust with a low risk of publication bias.

CONCLUSIONS

SII is closely associated to sarcopenia. Sarcopenic adults had elevated SII levels. The high SII level increased the risk of sarcopenia. Large scale multi-center prospective studies are required to validate these study findings.

Establishing an optimal diagnostic criterion for respiratory sarcopenia using peak expiratory flow rate

BACKGROUND

The skeletal muscle changes as aging progresses, causing sarcopenia in the older adult population, which affects the respiratory muscles' mass, strength, and function. The optimal cut-off point of peak expiratory flow rate (PEFR) for respiratory sarcopenia (RS) diagnosis in accordance with sarcopenia identification is needed.

AIM

To establish an optimal cut-off point of PEFR for RS diagnosis in community-dwelling Asian older women.

METHODS

Sarcopenia diagnostic indicators were evaluated according to the Asian Working Group for Sarcopenia 2019 (AWGS) criteria. The respiratory parameters composed of respiratory muscle strength and respiratory function were evaluated by assessing maximal inspiratory pressure (MIP), percent predicted forced vital capacity (Pred FVC), and PEFR.

RESULTS

A total of 325 community-dwelling older women were included in this study. PEFR was negatively associated with RS (OR: 0.440; 95% CI: 0.344-0.564). The area under the curve (AUC) of PEFR was 0.772 (p < 0.001). The optimal cut-off point of PEFR for RS diagnosis was 3.4 l/s (sensitivity, 63.8%; specificity, 77.3%). Significant differences were found between the robust, possible sarcopenia, sarcopenia, and RS groups in terms of both sarcopenia diagnostic indicators and respiratory parameters (p < 0.05).

CONCLUSIONS

The cut-off point of PEFR can be used as a reasonable standard for RS diagnosis. This study finding can serve as a cornerstone for developing concrete criteria of RS in older women, supporting clinical judgment, which is crucial for providing appropriate treatment through accurate diagnosis.

Intermittent glucocorticoid treatment improves muscle metabolism via the PGC1α/Lipin1 axis in an aging-related sarcopenia model

Sarcopenia burdens the older population through loss of muscle energy and mass, yet treatments to functionally rescue both parameters are lacking. The glucocorticoid prednisone remodels muscle metabolism on the basis of frequency of intake, but its mechanisms in sarcopenia are unknown. We found that once-weekly intermittent prednisone administration rescued muscle quality in aged 24-month-old mice to a level comparable to that seen in young 4-month-old mice. We discovered an age- and sex-independent glucocorticoid receptor transactivation program in muscle encompassing peroxisome proliferator-activated receptor γ coactivator 1 α (PGC1α) and its cofactor Lipin1. Treatment coordinately improved mitochondrial abundance through isoform 1 and muscle mass through isoform 4 of the myocyte-specific PGC1α, which was required for the treatment-driven increase in carbon shuttling from glucose oxidation to amino acid biogenesis. We also probed myocyte-specific Lipin1 as a nonredundant factor coaxing PGC1α upregulation to the stimulation of both oxidative and anabolic effects. Our study unveils an aging-resistant druggable program in myocytes for the coordinated rescue of energy and mass in sarcopenia.

Gut microbiota-generated metabolites: missing puzzles to hosts' health, diseases, and aging

The gut microbiota, an intricate community of bacteria residing in the gastrointestinal system, assumes a pivotal role in various physiological processes. Beyond its function in food breakdown and nutrient absorption, gut microbiota exerts a profound influence on immune and metabolic modulation by producing diverse gut microbiota-generated metabolites (GMGMs). These small molecules hold potential to impact host health via multiple pathways, which exhibit remarkable diversity, and have gained increasing attention in recent studies. Here, we elucidate the intricate implications and significant impacts of four specific metabolites, Urolithin A (UA), equol, Trimethylamine N-oxide (TMAO), and imidazole propionate, in shaping human health. Meanwhile, we also look into the advanced research on GMGMs, which demonstrate promising curative effects and hold great potential for further clinical therapies. Notably, the emergence of positive outcomes from clinical trials involving GMGMs, typified by UA, emphasizes their promising prospects in the pursuit of improved health and longevity. Collectively, the multifaceted impacts of GMGMs present intriguing avenues for future research and therapeutic interventions. [BMB Reports 2024; 57(5): 207-215].

Temporal Muscle Thickness: A Practical Approximation for Assessing Muscle Mass in Older Adults

OBJECTIVE

Ongoing research has evidenced the importance of muscle measurement in predicting adverse outcomes. Measurement of other muscles is promising in current research. This study aimed to determine the correlation between temporal muscle thickness (TMT) and appendicular lean soft tissue (ALSTI) in older adults.

DESIGN

Cross-sectional study.

SETTINGS AND PARTICIPANTS

Single cohort gathered in Gothenburg, Sweden, consisting of individuals born in 1944 (n = 1203).

METHODS

We studied 657 magnetic resonance images to measure TMT. Comparisons of TMT with dual-energy X-ray absorptiometry ALSTI (kg/m2) as a reference standard were performed. Finally, TMT associations with cognition evaluated using the Mini-Mental State Examination (MMSE), gait speed, and handgrip strength were explored with linear regressions.

RESULTS

The correlation between TMT and ALSTI was weak yet significant (r = 0.277, P < .001). TMT exhibited significant associations with MMSE (estimate = 0.168, P = .002), gait speed (estimate = 1.795, P < .001), and ALSTI (estimate = 0.508, P < .001). These associations varied when analyzed by sex. In women, TMT was significantly associated with gait speed (estimate = 1.857, P = .005) and MMSE (estimate = 0.223, P = .003). In men, TMT scores were significantly correlated with ALSTI scores (estimate = 0.571, P < .001).

CONCLUSION AND IMPLICATIONS

Repurposing head images can be an accessible alternative to detect muscle mass and ultimately detect sarcopenia. These studies have the potential to trigger interventions or further evaluation to improve the muscle and overall health of individuals. However, additional research is warranted before translating these findings into clinical practice.

Moderate dietary restriction delays the onset of age-associated sarcopenia in Caenorhabditis elegans due to reduced myosin UNC-54 degradation

Sarcopenia, a gradual decrease in skeletal muscle mass and strength, is a major component of frailty in the elderly, with age, (lack of) exercise and diet found to be the major risk factors. The nematode Caenorhabditis elegans is an important model of sarcopenia. Although many studies describe loss of muscle function in ageing C. elegans, surprisingly few report on the loss of muscle mass. Here, in order to quantify loss of muscle mass under various dietary restriction (DR) conditions, we used an internal GFP standard to determine levels of the major body wall muscle myosin (UNC-54) in transgenic unc-54::gfp worms over their lifespan. Myosin density linearly increased during the first week of adulthood and there was no significant effect of DR. In contrast, an exponential decrease in myosin density was seen during the second week of adulthood, with reduced rates of myosin loss for mild and medium DR compared to control. UNC-54 turnover rates, previously determined using pulse-labelling methods, correspond well with the t1/2 value found here for UNC-54-GFP using fluorescence (control t1/2 = 12.0 days), independently validating our approach. These data indicate that sarcopenia is delayed in worms under mild and medium DR due to a reduced rate of myosin UNC-54 degradation, thereby maintaining protein homeostasis.

D-galactose might mediate some of the skeletal muscle hypertrophy-promoting effects of milk-A nutrient to consider for sarcopenia?

Sarcopenia is a process of progressive aging-associated loss of skeletal muscle mass (SMM) recognized as a serious global health issue contributing to frailty and increased all-cause mortality. Exercise and nutritional interventions (particularly intake of dairy products and milk) demonstrate good efficacy, safety, and broad applicability. Here, we propose that at least some of the well-documented favorable effects of milk and milk-derived protein supplements on SMM might be mediated by D-galactose, a monosaccharide present in large quantities in milk in the form of disaccharide lactose (milk sugar). We suggest that ingestion of dairy products results in exposure to D-galactose in concentrations metabolized primarily via the Leloir pathway with the potential to (i) promote anabolic signaling via maintenance of growth factor (e.g., insulin-like growth factor 1 [IGF-1]) receptor mature glycosylation patterns; and (ii) provide extracellular (liver glycogen) and intracellular substrates for short (muscle glycolysis) and long-term (muscle glycogen, intramyocellular lipids) energy availability. Additionally, D-galactose might optimize the metabolic function of skeletal muscles by increasing mitochondrial content and stimulating glucose and fatty acid utilization. The proposed potential of D-galactose to promote the accretion of SMM is discussed in the context of its therapeutic potential in sarcopenia.

Circulating lumican as a potential biomarker for osteosarcopenia in older adults

In vitro and animal experiments demonstrated that lumican exerts anabolic effects on bone and muscle by stimulating osteoblastogenesis, suppressing osteoclastogenesis and increasing myogenesis. However, the relationship between circulating lumican and musculoskeletal phenotypes in humans remains unclear. We aimed to analyze the relationship between serum lumican levels and osteosarcopenia in older adults. Blood samples were collected from 134 participants (age: 65 years and older) who underwent comprehensive assessment of bone and muscle phenotypes. Osteoporosis and sarcopenia were diagnosed based on World Health Organization and Asian consensus guidelines, respectively. Osteosarcopenia was defined as the simultaneous presence of osteoporosis and sarcopenia. After adjusting for sex, age, and body mass index, older adults with osteosarcopenia had 20.2 % lower serum lumican levels than those without (P = 0.010). The odds ratio (OR) for osteosarcopenia per standard deviation decrease in serum lumican level was 4.17 (P = 0.003). Consistently, higher serum lumican levels were correlated with higher bone mass at all measured sites (P = 0.004 to 0.045) and higher grip strength (P = 0.023). Furthermore, participants in the lowest tertile (T1) had 7.56-fold higher OR for osteosarcopenia (P = 0.024) than those in the highest lumican tertile (T3). In conclusion, these findings clinically validate previous experimental data showing the musculoskeletal protective effects of lumican and suggest that blood lumican levels could be used as a potential biomarker to assess the risk of not only osteosarcopenia but also osteoporosis or sarcopenia in older adults.

Undernutrition in obese older adults by fat percentage

OBJECTIVE

The prevalence of obesity by fat percentage has seen a steady increase in older adults in recent years, secondary to increases in fat mass in body composition, even in healthy aging. Malnutrition is a common geriatric syndrome with serious clinical outcomes. Increases in fat mass and waist circumference with healthy aging should not prevent the risk of malnutrition from being masked. Malnutrition is often ignored in obese older people due to low BMI cut-off values in many screening tests. The present study seeks to raise awareness of the need to assess the frequency of undernutrition and related factors in obese older adults.

METHODS

The data of 2013 community-dwelling patients aged ≥ 60 years who applied to a university geriatrics outpatient clinic between April 2012 and November 2022 were analyzed retrospectively, of which 296 were found to be obese based on fat percentage and were included in the study. Demographic data and the presence of any geriatric syndromes were obtained retrospectively from the patient files, functional status was assessed using the KATZ Activities of Daily Living (ADL) Scale and the LAWTON-BRODY Instrumental Activities of Daily Living Scale (IADL); frailty was screened using FRAIL-scale; and the sample was assessed for malnutrition using the Mini Nutritional Assessment-Short Form (MNA-SF), with undernutrition defined as an MNA-SF score of [Formula: see text] The patients' fat percentage and weight were measured using a bioimpedance analyzer. Fatty obesity was defined using the Zoico methodology (fat percentage [Formula: see text] 27.3% for males, [Formula: see text] 40.7% for females)[Formula: see text] handgrip strength (HGS) was measured using a hand dynamometer, and probable sarcopenia was defined as low HGS based on regional cut-off values (35 kg for males, 20 kg for females).

RESULTS

The mean age of the 296 fatty obese older adults (102 males/194 females) was 74.4 + 6.5 years, and the median fat was 42.2% (27.4-59.5). Undernutrition was detected in 19.6% of the patients based on MNA-SF screening. A univariate analysis revealed age, sex, educational status, daily physical activity status, depression, difficulty in swallowing, chewing difficulty, probable sarcopenia, number of chronic diseases, and IADL to be associated with undernutrition, while a multivariate logistic regression analysis revealed depression [OR = 3.662, 95% CI (1.448-9.013), p = 0.005] and daily physical activity status [OR:0.601, 95% CI (0.417-0.867), p = 0.006] to be independently associated with malnutrition in obese older adults based on fat percentage.

CONCLUSION

 The present study clarifies the significance of undernutrition in obese older adults also in our country, and recommends undernutrition screening to be carried out, by fat percentage, on obese older adults, especially with depression and low daily physical activity.

Interactions between mitochondrial dysfunction and other hallmarks of aging: Paving a path toward interventions that promote healthy old age

Current research on human aging has largely been guided by the milestone paper "hallmarks of aging," which were first proposed in the seminal 2013 paper by Lopez-Otin et al. Most studies have focused on one aging hallmark at a time, asking whether the underlying molecular perturbations are sufficient to drive the aging process and its associated phenotypes. More recently, researchers have begun to investigate whether aging phenotypes are driven by concurrent perturbations in molecular pathways linked to not one but to multiple hallmarks of aging and whether they present different patterns in organs and systems over time. Indeed, preliminary results suggest that more complex interactions between aging hallmarks must be considered and addressed, if we are to develop interventions that successfully promote healthy aging and/or delay aging-associated dysfunction and diseases. Here, we summarize some of the latest work and views on the interplay between hallmarks of aging, with a specific focus on mitochondrial dysfunction. Indeed, this represents a significant example of the complex crosstalk between hallmarks of aging and of the effects that an intervention targeted to a specific hallmark may have on the others. A better knowledge of these interconnections, of their cause-effect relationships, of their spatial and temporal sequence, will be very beneficial for the whole aging research field and for the identification of effective interventions in promoting healthy old age.

Higher Plasma Stromal Cell-Derived Factor 1 Is Associated with Lower Risk for Sarcopenia in Older Asian Adults

BACKGRUOUND

Despite the protective effects of stromal cell-derived factor 1 (SDF-1) in stimulating muscle regeneration shown in experimental research, there is a lack of clinical studies linking circulating SDF-1 concentrations with muscle phenotypes. In order to elucidate the role of SDF-1 as a potential biomarker reflecting human muscle health, we investigated the association of plasma SDF-1 levels with sarcopenia in older adults.

METHODS

This cross-sectional study included 97 community-dwelling participants who underwent a comprehensive geriatric assessment at a tertiary hospital in South Korea. Sarcopenia was defined by specific cutoff values applicable to the Asian population, whereas plasma SDF-1 levels were determined using an enzyme immunoassay.

RESULTS

After accounting for sex, age, and body mass index, participants with sarcopenia and low muscle mass exhibited plasma SDF-1 levels that were 21.8% and 18.3% lower than those without these conditions, respectively (P=0.008 and P=0.009, respectively). Consistently, higher plasma SDF-1 levels exhibited a significant correlation with higher skeletal muscle mass index (SMI) and gait speed (both P=0.043), and the risk of sarcopenia and low muscle mass decreased by 58% and 55% per standard deviation increase in plasma SDF-1 levels, respectively (P=0.045 and P=0.030, respectively). Furthermore, participants in the highest SDF-1 tertile exhibited significantly higher SMI compared to those in the lowest tertile (P=0.012).

CONCLUSION

These findings clinically corroborate earlier experimental discoveries highlighting the muscle anabolic effects of SDF- 1 and support the potential role of circulating SDF-1 as a biomarker reflecting human muscle health in older adults.

Familial Correlation and Heritability of Hand Grip Strength in Korean Adults (Korea National Health and Nutrition Examination Survey 2014 to 2019)

BACKGRUOUND

The onset and progression of sarcopenia are highly variable among individuals owing to genetic and environmental factors. However, there are a limited number of studies measuring the heritability of muscle strength in large numbers of parent-adult offspring pairs. We aimed to investigate the familial correlation and heritability of hand grip strength (HGS) among Korean adults.

METHODS

This family-based cohort study on data from the Korea National Health and Nutrition Examination Survey (2014 to 2019) included 5,004 Koreans aged ≥19 years from 1,527 families. HGS was measured using a digital grip strength dynamometer. Familial correlations of HGS were calculated in different pairs of relatives. Variance component methods were used to estimate heritability.

RESULTS

The heritability estimate of HGS among Korean adults was 0.154 (standard error, 0.066). Correlation coefficient estimates for HGS between parent-offspring, sibling, and spouse pairs were significant at 0.07, 0.10, and 0.23 (P<0.001, P=0.041, and P<0.001, respectively). The total variance in the HGS phenotype was explained by additive genetic (15.4%), shared environmental (11.0%), and unique environmental (73.6%) influences. The odds of weak HGS significantly increased in the offspring of parents with weak HGS (odds ratio [OR], 1.69-3.10; P=0.027-0.038), especially in daughters (OR, 2.04-4.64; P=0.029-0.034).

CONCLUSION

HGS exhibits a familial correlation and significant heritable tendency in Korean adults. Therefore, Asian adults, especially women, who have parents with weak HGS, need to pay special attention to their muscle health with the help of healthy environmental stimuli.

Predicted lean body mass trajectories, and cancer risk and cancer-specific and all-cause mortality: A prospective cohort study

BACKGROUND

Although many studies have investigated the association between body composition, cancer risk and mortality, predicting these risks through a single body composition measurement undoubtedly increases the limitations of the study. Few studies have explored the association between the trajectory of changes in body composition and the risk of cancer and death. We aimed to explore the association of predicted lean mass trajectories with cancer risk, cancer-specific mortality and all-cause mortality.

METHODS

The participants in this study were all from the Kailuan cohort, a prospective, periodic, resurvey cohort study initiated in 2006. Latent mixture modelling was used to identify predicted lean mass trajectories for 2006-2010. The hazard ratios (HRs) and 95% confidence intervals (95% CIs) of the Cox proportional hazard models were used to describe the association between predicted lean mass trajectories and cancer risk and cancer-specific and all-cause mortality during follow-up (2010-2021).

RESULTS

A total of 44 374 participants (average age, 53.01 ± 11.41 years, 78.99% men and 21.01% women) were enrolled in this study. Five distinct trajectories were identified: low-stable (n = 12 060), low-increasing (n = 8027), moderately stable-decreasing (n = 4725), moderately stable-increasing (n = 8053) and high-stable (n = 11 509). During the 11-year follow-up period, 2183 cancer events were recorded. After adjusting for age, predicted fat mass in 2010, sex, BMI, sedentary, physical activity, smoke, alcohol use, salt consumption, high-fat diet, high-sensitivity C-reactive protein, serum creatinine, family history of tumour, hypertension, diabetes mellitus, compared with the low-stable group, participants in the low-increasing group (HR = 0.851, 95% CI, 0.748-0.969), moderately stable-increasing group (HR = 0.803, 95% CI, 0.697-0.925) and high-stable group (HR = 0.770, 95% CI, 0.659-0.901) had a lower cancer risk, but not in the moderately stable-decreasing group (HR = 0.864, 95% CI, 0.735-1.015). Compared with the low-stable group, the risk of cancer-specific mortality was reduced by 25.4% (8.8-38.9%), 36.5% (20.3-49.4%) and 35.4% (17.9-49.2%), and the risk of all-cause mortality was reduced by 24.2% (16.9-30.8%), 37.0% (30.0-43.2%) and 47.4% (41.0-53.1%) in the low-increasing, moderately stable-increasing group and high-stable groups, respectively.

CONCLUSIONS

Predicted lean mass trajectories may be closely associated with cancer risk and cancer-specific and all-cause mortality. Regular monitoring of body composition is necessary.

Zebrafish as an Emerging Model for Sarcopenia: Considerations, Current Insights, and Future Directions

Sarcopenia poses a significant challenge to public health and can severely impact the quality of life of aging populations. Despite extensive efforts to study muscle degeneration using traditional animal models, there is still a lack of effective diagnostic tools, precise biomarkers, and treatments for sarcopenia. Zebrafish models have emerged as powerful tools in biomedical research, providing unique insights into age-related muscle disorders like sarcopenia. The advantages of using zebrafish models include their rapid growth outside of the embryo, optical transparency during early developmental stages, high reproductive potential, ease of husbandry, compact size, and genetic tractability. By deepening our understanding of the molecular processes underlying sarcopenia, we may develop novel diagnostic tools and effective treatments that can improve the lives of aging individuals affected by this condition. This review aims to explore the unique advantages of zebrafish as a model for sarcopenia research, highlight recent breakthroughs, outline potential avenues for future investigations, and emphasize the distinctive contributions that zebrafish models offer. Our research endeavors to contribute significantly to address the urgent need for practical solutions to reduce the impact of sarcopenia on aging populations, ultimately striving to enhance the quality of life for individuals affected by this condition.

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.

Influence of sarcopenia on postoperative complications in patients undergoing autologous microsurgical breast reconstruction: an inverse probability of treatment weighting analysis

Background

Sarcopenia is characterized by the loss of skeletal muscle mass and power. Preoperative sarcopenia may be associated with an increased risk of postoperative complications after autologous free-flap breast reconstruction surgery; however, this relationship is controversial.

Objectives

This study aimed to determine whether preoperative sarcopenia is associated with a high complication rate in patients undergoing autologous free-flap breast reconstruction.

Methods

Patients who underwent autologous free-flap breast reconstruction at our hospital between 2019 and 2021 were included in the study. Data on significant complications requiring surgical intervention were retrospectively collected from the medical records. Sarcopenia was defined as having a skeletal muscle index value <41 cm2/m2. The skeletal muscle index was calculated by dividing the sum of the psoas and iliopsoas muscle areas at the level of the third lumbar vertebra by the patient's height in meters squared. The relationship between preoperative sarcopenia and postoperative complications was investigated using an inverse probability of treatment weighting (IPTW) analysis.

Results

Among the 203 participants, 90 (44.33%) had preoperative sarcopenia. The general patient characteristics were similar between the sarcopenia and non-sarcopenia groups after IPTW adjustment. Sarcopenia did not significantly increase the risk of flap failure or emergency surgery related to breast reconstruction before IPTW adjustment. However, after IPTW adjustment, the rates of recipient site infection and hematoma were significantly higher in participants with sarcopenia than in those without sarcopenia (p < 0.001 and p = 0.014, respectively).

Conclusion

Preoperative sarcopenia may influence certain complications of autologous free-flap breast reconstruction surgery.

Glucocorticoid intermittence coordinates rescue of energy and mass in aging-related sarcopenia through the myocyte-autonomous PGC1alpha-Lipin1 transactivation

Sarcopenia burdens the elderly population through loss of muscle energy and mass, yet treatments to functionally rescue both parameters are missing. The glucocorticoid prednisone remodels muscle metabolism based on frequency of intake, but its mechanisms in sarcopenia are unknown. We found that once-weekly intermittent prednisone rescued muscle quality in aged 24-month-old mice to levels comparable to young 4-month-old mice. We discovered an age- and sex-independent glucocorticoid receptor transactivation program in muscle encompassing PGC1alpha and its co-factor Lipin1. Treatment coordinately improved mitochondrial abundance through isoform 1 and muscle mass through isoform 4 of the myocyte-specific PGC1alpha, which was required for the treatment-driven increase in carbon shuttling from glucose oxidation to amino acid biogenesis. We also probed the myocyte-specific Lipin1 as non-redundant factor coaxing PGC1alpha upregulation to the stimulation of both oxidative and anabolic capacities. Our study unveils an aging-resistant druggable program in myocytes to coordinately rescue energy and mass in sarcopenia.

Non-alcoholic fatty liver disease in women - Current knowledge and emerging concepts

Non-alcoholic fatty liver disease (NAFLD) is a major cause of liver disease worldwide, affecting up to 30% of adults. Progression to non-alcoholic steatohepatitis (NASH) is a key risk factor for cirrhosis, hepatocellular carcinoma and cardiovascular events. Alterations in reproductive hormones are linked to the development and/or progression of NAFLD/NASH in women. Women with polycystic ovary syndrome and those with oestrogen deficiency are at increased risk of NAFLD/NASH, with higher mortality rates in older women compared to men of similar ages. NAFLD/NASH is currently the leading indication for liver transplantation in women without hepatocellular carcinoma. Therefore, a better understanding of NAFLD in women is needed to improve outcomes. In this review, we discuss the hormonal and non-hormonal factors that contribute to NAFLD development and progression in women. Furthermore, we highlight areas of focus for clinical practice and for future research.

Multidisciplinary approach to sarcopenia: a narrative review

Sarcopenia is a condition in which muscle mass and strength are decreased and muscle function is impaired. It is an indicator of frailty and loss of independence in older adults. It is also associated with increased physical disability, which increases the risk of falls. As a multifactorial disease, sarcopenia is caused by a combination of factors including aging, hormonal changes, nutritional deficiencies, and physical inactivity. Understanding the underlying pathophysiology of sarcopenia and identifying its different causes is critical to developing effective prevention and treatment strategies. This review summarizes the pathophysiology, consequences, diagnostic methods, and multidisciplinary approaches to sarcopenia.

Stromal vascular fraction in the treatment of myositis

Muscle regeneration is a physiological process that converts satellite cells into mature myotubes under the influence of an inflammatory environment progressively replaced by an anti-inflammatory environment, with precise crosstalk between immune and muscular cells. If the succession of these phases is disturbed, the immune system can sometimes become auto-reactive, leading to chronic muscular inflammatory diseases, such as myositis. The triggers of these autoimmune myopathies remain mostly unknown, but the main mechanisms of pathogenesis are partially understood. They involve chronic inflammation, which could be associated with an auto-reactive immune response, and gradually with a decrease in the regenerative capacities of the muscle, leading to its degeneration, fibrosis and vascular architecture deterioration. Immunosuppressive treatments can block the first part of the process, but sometimes muscle remains weakened, or even still deteriorates, due to the exhaustion of its capacities. For patients refractory to immunosuppressive therapies, mesenchymal stem cells have shown interesting effects but their use is limited by their availability. Stromal vascular fraction, which can easily be extracted from adipose tissue, has shown good tolerance and possible therapeutic benefits in several degenerative and autoimmune diseases. However, despite the increasing use of stromal vascular fraction, the therapeutically active components within this heterogeneous cellular product are ill-defined and the mechanisms by which this therapy might be active remain insufficiently understood. We review herein the current knowledge on the mechanisms of action of stromal vascular fraction and hypothesise on how it could potentially respond to some of the unmet treatment needs of refractory myositis.

Metallosis after Hip Arthroplasty Damages Skeletal Muscle: A Case Report

Good musculoskeletal quality dramatically influences the outcome of an arthroplasty operation in geriatric patients, as well as is a key element for optimal osseointegration. In this context, metallosis is a complication associated with the type of prosthesis used, as implants with a chromium-cobalt interface are known to alter the bone microarchitecture and reduce the ratio of muscle to fat, resulting in lipid accumulation. Therefore, the aim of our study was to investigate possible muscle changes by histological, morphometric, and immunohistochemical analyses in a patient undergoing hip replacement revision with elevated blood and urinary concentrations of chromium and cobalt. Interestingly, the muscle tissue showed significant structural changes and a massive infiltration of adipose tissue between muscle fibers in association with an altered expression pattern of important biomarkers of musculoskeletal health and oxidative stress, such as myostatin and NADPH Oxidase 4. Overall, our results confirm the very serious impact of metallosis on musculoskeletal health, suggesting the need for further studies to adopt a diagnostic approach to identify the cause of metallosis early and eliminate it as part of the prosthesis revision surgery.

Normative reference values, determinants and regression equations for the incremental shuttle walk test (ISWT) in healthy Asian population aged 21 to 80 years

BACKGROUND

The validated Incremental Shuttle Walk Test (ISWT) is widely used for evaluating maximal exercise capacity, with the distance-walked (IWSD) as the primary outcome. However, there are no normative reference values (NRV) and reference equations to predict ISWD for the Singaporean population.

OBJECTIVES

This study aims to establish the NRV and reference equations for ISWD in healthy Singaporeans aged 21 to 80 and investigate the determining variables during ISWT.

METHODS

This cross-sectional study recruited community-dwelling healthy subjects aged 21-80 from the community via convenience sampling. Each subject completed two trials of the ISWT according to the standard protocol. Variables measured during the trials included ISWD, pre-and post-test heart rate (HR), oxygen saturation, blood pressure (BP), modified Borg's dyspnoea score and Borg's rate of perceived exertion (RPE).

RESULTS

199 healthy Singaporean (females = 114, males = 85) participated in the study. The overall median ISWD was 660.0 metres (m) [interquartile range (IQR):440.0-850.0]. The age-stratified mean ISWD ranged from 430.0 m (IQR:350.0-450.0) (aged 60-80) to 480.0 m (IQR:438.0-650.0) (aged 40-59) to 780.0 m (IQR:670.0-960.0) (aged 21-39). Gender, age, weight, height and HR change (highest post-test HR minus pre-test HR) were the most significant variables (p < 0.001). IWSD (m) = 651.4(Height, m) +89.7(Gender, male = 1; female = 0) -6.31(Age, years) -3.61(Weight, kilograms) +2.54(HR change, beats per minute); R2 = 0.741. Previously published ISWT reference equations cannot accurately predict the ISWD in the Singaporean population.

CONCLUSIONS

This study investigated the ISWD NRV and established reference equations for healthy Singaporeans aged 21-80. The information would be beneficial in setting performance benchmarks to guide physical assessment, intervention and rehabilitation.